Barbara Resta
email: barbara.resta@unibg.it

Stefano Dotti
email: stefano.dotti@unibg.it

Roberto Pinto
email: roberto.pinto@unibg.it

Paolo Gaiardelli
email: paolo.gaiardelli@unibg.it

A Decision Making Process for Sustainability in the Textile Sector

Keywords: Life Cycle Management (LCM), Life Cycle Assessment (LCA), Sustainability, Textile, Decision making process

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

The increasing concern about industrial pollution, waste problem, effects of global warming, and water scarcity has led to the need of approaches, methods, and tools for measuring and reducing the environmental impact of textile products and processes, from fiber sourcing to end product [START_REF] Lakhal | Comparing conventional and certified organic cotton supply chains: the case of Mali[END_REF]. In particular, the negative impacts associated with this sector can be grouped in four main categories [START_REF] Allwood | Well Dressed? The Present and Future Sustainability of Clothing and Textiles in the United Kingdom[END_REF]: i) energy use in laundry, in the production of primary materials (especially man-made fibers), and in yarn manufacturing of natural fibers; ii) use of toxic chemicals which may harm human health and the environment; iii) release of chemicals in water -especially in wet pretreatment, dyeing, finishing and laundry; and iv) solid waste arising from yarn manufacturing of natural fibers, making up, and disposal of products at the end of their life. Despite the awareness of the relevance of this topic for the entire textile industry, the concept of environmental sustainability still must be assessed and transformed into business practices [START_REF] Caniato | Environmental sustainability in fashion supply chains: an exploratory case based research[END_REF].

As argued by Waite [START_REF] Waite | Sustainable textiles: the role of bamboo and a comparison of bamboo textile properties[END_REF], a life cycle thinking is one of the approaches that can support companies in making the textile industry more sustainable and less damaging to the environment, while at the same time remaining competitive. To this extent, the Life Cycle Assessment (LCA) [START_REF] Rebitzer | Life cycle assessment -Part 1: Framework, goal & scope definition, inventory analysis, and applications[END_REF] is one of the analytical methodologies that support the quantitative assessment of the environmental impacts of products, processes and services. Even though life cycle assessments currently available in the textile sector address numerous environmental issues, they do not properly consider the economic impacts of the decisions that, on the contrary, represent the main aim of private sector managers [START_REF] Norris | Integrating life-cycle cost analysis and LCA[END_REF]. Hence, there is a need of investigating how LCA can be integrated with other management practices in order to encompass more aspects of the decisionmaking process.

In this paper, we develop a decision making process based on LCA that incorporates economic analyses, adopting a continuous improvement approach. This process helps the companies operating in the textile industry to measure, monitor and improve their performance in order to achieve, at the same time, economic and environmental advantages, both in the long-and short-term.

The remainder of the paper is organized as follows. Section 2 presents the theoretical background of the paper, focusing on Life Cycle Management (LCM) and LCA. Section 3 describes the development of a decision making process for the textile sector based on LCA, while Section 4 introduces an application to a real case. A discussion of the results precedes the final conclusions (Section 5).

Literature review

Life Cycle Management (LCM) is defined as "an integrated framework of concepts, techniques and procedures to address environmental, economic, technological and social aspects of products and organizations to achieve continuous environmental improvement from a life-cycle perspective" [START_REF] Hunkeler | Life Cycle Management -Definitions, Case Studies and Corporate Applications[END_REF], from raw material extraction, through manufacturing, to consumption and finally to ultimate disposal [START_REF]European Commission: Making sustainable consumption and production a reality: A guide for business and policy makers to life cycle thinking and assessment[END_REF]. Within this framework, Life Cycle Assessment (LCA) is one of the most prominent methodology [START_REF]UNEP: Why Take A Life Cycle Approach?[END_REF] for the systematic evaluation of the potential environmental aspects of a product or service system through all stages of its life cycle. It can assist in [START_REF]Life Cycle Management: How Business Uses it to Decrease Footprint, Create Opportunities and Make Value Chains More Sustainable[END_REF]: i) identifying opportunities to improve the environmental performance of products at various points in their life cycle; ii) informing decision-makers in industry, government or non-governmental organizations (e.g., for the purposes of strategic planning, priority setting, and product or process design or redesign); iii) selecting relevant indicators of environmental performance; and iv) marketing (e.g., implementing an eco-labeling scheme, making an environmental claim, or producing an environmental product declaration).

Both the public sector and many business associations and industrial companies already use the life-cycle approach in the framework of sustainability. Within the textile sector, several LCA results were contributed from many areas like cotton growing, spinning, weaving and finishing, laundering and integrated life cycles, as analyzed by Nieminen et al. [START_REF] Nieminen | EU COST Action 628: life cycle assessment (LCA) of textile products, eco-efficiency and definition of best available technology (BAT) of textile processing[END_REF]. The key objective of these LCAs is to select the most appropriate strategies for a product or a process to reduce its environmental impacts [START_REF] Brezet | Ecodesign -a promising approach to sustainable production and consumption[END_REF]. Although environmental issues are important, it is crucial to consider in the decision-making process also business strategies and economic consequences, especially when considering private industry applications.

However, since LCA is a decision supporting methodological framework [START_REF] Rebitzer | Life cycle assessment -Part 1: Framework, goal & scope definition, inventory analysis, and applications[END_REF] rather than a decision making methodology, economic aspects of the decisions are within the scope of LCA methodology, and are not properly addressed by existing LCA tools. This traditional separation of life cycle environmental assessment from economic analysis has limited the influence and relevance of LCA for decision making, and left uncharacterized the important relationships and trade-offs between the economic and environmental performance [START_REF] Norris | Integrating life-cycle cost analysis and LCA[END_REF]. Therefore, LCA results should be handled together with other criteria (e.g., economic aspects) in the decision-making process in order to utilize the outcomes in the final decision context [START_REF] Choi | A Framework for the Integration of Environmental and Business Aspects Toward Sustainable Product Development[END_REF].

In order to consider both environmental and economic aspects, a new decision making process based on a LCA approach, integrated with economic consideration, is proposed in this paper.

Development of the process

Through the identification of the critical elements in managing primary and support processes and facility infrastructures, combined with the definition of a set of indicators to measure and control environmental performances, the proposed decision making process aims at supporting a textile firm to: i) evaluate its environmental performance with a dynamic perspective; ii) identify "hotspots", that are activities and/or infrastructures that could be improved or changed in order to reduce environmental impact, save money in the short as well as in the long term; iii) drive investments for sustainability; and iv) increase a sustainable image. The proposed model, depicted in Figure 1, is built on the technical framework for the Life Cycle Assessment methodology that has been standardized by the International Standards Organization [START_REF]Environmental management-life cycle assessment-principles and framework[END_REF].

Goal and Scope Definition

Goal of the project is the integration of a traditional business model with sustainable principles to get environmental, economic and competitive benefits. By making the workplace healthier and working activities safer, also social sustainability can be obtained as a direct consequence. As for the system boundaries, the textile production chain as defined in [START_REF] Fletcher | Sustainable fashion and textiles: design journeys[END_REF] is addressed, including yarn, fabric and product manufacturing (spinning, weaving, knitting, cutting, making and trimming) as well as finishing processes (desizing, scouring, bleaching, dyeing, printing, printing and finishing).

Inventory analysis

Through the support of a panel of experts, from both academia and industry, 14 semistructured interviews in 6 companies operating in the textile production chain were conducted. Each of the 14 interviews, carried out by two or three researchers, lasted between one and two hours and was recorded and subsequently transcribed. Inform-ants included the Plant Manager, shop floor supervisors and workers, and representatives from Manufacturing and Quality function. Additionally, direct observation (e.g., plant tours) was also used as data collection method. As result, the main processes and facility features were identified. Both primary and support activities [START_REF] Porter | Competitive Advantage. Creating and Sustaining Superior Performance[END_REF] were considered. Then, for each single process/facility feature, inputs (materials, water, and energy), outputs (environmental releases in the form of air emissions, water emissions or solid waste) and resources (including tools and equipment that support the processes execution) were identified and coded. The main result of this phase was a comprehensive textile inventory matrix, containing 152 inputs, 128 outputs and 64 resources.

Impact assessment phase

In accordance with the GRI standards [START_REF]Sustainability Reporting Framework: Guidelines[END_REF] the environmental performance areas were identified, considering an operative as well as a strategic perspective: material consumption, energy consumption, water consumption, and waste production (operative areas); environmental protection expenses and innovation and training (strategic areas). Then, for each area, a set of Key Performance Indicators (KPIs) was proposed.

They were used as a basis for a Sustainable Textile Scorecard, that enables managers to clarify their sustainable strategy and translate it into action. A performance target can also be defined for each KPI and used as a reference value to sustain continuous improvement. The strategic performance areas measure the innovation level and the culture for sustainability of the company, while the operative KPIs support the identification of the criticalities, as described in the follows.

Regarding the operative KPIs, a prioritization strategy was then needed to identify the "hotspots", defined as the elements within the system that contribute most to the environmental impact. Consequently the different input/output values should be characterized into a common equivalence unit that can be compared and eventually summed to provide an overall impact. Among the impact categories defined by the ISO standard [START_REF]Environmental management-life cycle assessment-principles and framework[END_REF], the Global Warming was considered as the most representative. Hence, the characterization formula proposed by Heijungs et al. [START_REF] Heijungs | Improvement of LCA characterization factors and LCA practise for metals[END_REF], and adapted by Forster et al. [START_REF] Forster | Changes in atmospheric constituents and in radiative forcing[END_REF], was selected:

= * (1)
where EI s is the environmental impact associated to substance s (input or output), GWPs the global warming potential (characterization factor) for substance s calculated in terms of carbon dioxide (CO 2 ) equivalent, and Qs the quantity of substance s.

Then, the operative KPIs can be assessed in terms of CO 2 emissions using the following formula:

= ∑ ∈ = ∑ * ∈ ( 2
)
where S i is the set of the substances that refer to the calculation of KPI i .

Interpretation

Based on the results from the Inventory analysis and I can be then created by ranking the environmental criticality (in terms lent), thus identifying the most critical elements (process, input or out ferent classes of solutions facility structures and equipment management and waste disposal, including reuse, recycling and re Since the aim of this decision making process is to combine environmental and economic benefits, the environmental impact, ment returns and cash flow impact. ture all relevant and significant on the Total Cost Assessment (TCA the solution has an impact need to be iden tional capital budgeting techniques except that it benefits associated with each alternative savings. In accordance ered: i) direct costs; ii) ble costs. Once all the financial tools familiar to many businesses for rating each investment are then used to select the best option. defined in the Impact assessment phase, new critical indicators are id solutions could be proposed

An empirical application

In this section the application of the decision making company (hereafter referred to as TexCo) ing fabrics for a wide range of end uses and markets was limited to hospital cotton bed lines as they represent for the company. Data was collected through semi audits performed by the authors was then discussed with a panel of experts, who supported the tial solutions to implement in order to reduce the company's impact on the enviro ment.

Firstly, the processes and facility features associated to the company's b were selected from the comprehensive inventory matrix. For each proces

Interpretation of results

Based on the results from the Inventory analysis and Impact assessment, a priority list can be then created by ranking the environmental criticality (in terms of CO the most critical elements (process, input or output). T ferent classes of solutions can be identified to decrease the environmental impact equipment; ii) organizational solutions; and iii) material supply management and waste disposal, including reuse, recycling and recovery.

Since the aim of this decision making process is to combine environmental and he identified solutions, potentially advantageous to mitigate the environmental impact, are then assessed with financial tools, to evaluate their ment returns and cash flow impact. In particular, the financial analysis must also ca all relevant and significant environmental costs related to the alternatives Total Cost Assessment (TCA) method [START_REF] Epstein | Improving environmental management with full environmental cost accounting[END_REF], the environmental costs the solution has an impact need to be identified and estimated. TCA is similar to trad tional capital budgeting techniques except that it attempts to include all costs and benefits associated with each alternative, including environmental expenditure accordance with Curkovica and Sroufe [START_REF] Curkovic | Total quality environmental management and total cost assessment: An exploratory study[END_REF], four tiers of costs are con ; ii) hidden costs; iii) contingent liability costs; and iv) l Once all the cost and savings that accompany each solution are identified, financial tools familiar to many businesses for rating each investment are then used to select the best option. By constantly collecting data and calculating the indicators defined in the Impact assessment phase, new critical indicators are identified and new could be proposed by applying a continuous improvement approach.

Fig. 1. The decision making process

An empirical application

In this section the application of the decision making process to an Italian textile (hereafter referred to as TexCo) is presented. TexCo is specialized in finis for a wide range of end uses and markets. The application of the model tal cotton bed lines as they represent the most profitable Data was collected through semi-structured interviews and several audits performed by the authors and their research groups. The gathered information was then discussed with a panel of experts, who supported the definition of the pote tial solutions to implement in order to reduce the company's impact on the enviro Firstly, the processes and facility features associated to the company's b the comprehensive inventory matrix. For each proces mpact assessment, a priority list of CO 2 equiva-Three diftal impact: i) ; ii) organizational solutions; and iii) material supply Since the aim of this decision making process is to combine environmental and , potentially advantageous to mitigate the ate their investmust also capalternatives. Based , the environmental costs on which TCA is similar to tradito include all costs and , including environmental expenditures and are considless tangiidentified, financial tools familiar to many businesses for rating each investment are then used to collecting data and calculating the indicators entified and new continuous improvement approach.

to an Italian textile is specialized in finishof the model t profitable market structured interviews and several . The gathered information the potential solutions to implement in order to reduce the company's impact on the environ-Firstly, the processes and facility features associated to the company's business the comprehensive inventory matrix. For each process/facility feature, inputs, outputs and resources were measured. Afterwards the operative KPIs were assessed in terms of CO 2 emissions. The "Gas Consumption" KPI was recognized as the most critical, since it was responsible for the major contribution to CO 2 emissions. The inputs/outputs/resources, which were directly linked to gas consumption, were "Gas" (Input) and "Singeing machine", "Desizing machine", "Scouring machine", "Mercerizing machine" and "Bleaching machine" (Resources). Consequently, the analysis was focused on five operative processes (Singeing, Desizing, Scouring, Mercerizing and Bleaching) and on one facility feature (Heating System), which were directly connected with the aforementioned input. Since 40% of the total gas consumption was imputable to bleaching process, the solutions proposed were addressed to improve its environmental sustainability. In particular, a panel of experts proposed the introduction of a peracid bleach for the bleaching process. The use of peracetic acid can accelerate the reaction rate and shorten bleaching time at relatively low temperature, which can reduce both the environmental burden and the production cost. Its applicability was tested through laboratory experiments, while its advantages were evaluated through environmental and economic analyses.

Basically, the technical solution under analysis is characterized by a lower operating temperature and, consequently, a lower gas consumption (from 0.125 Nm 3 /kg to 0.077 Nm 3 /kg). On the contrary, compared to a traditional bleaching process, this solution requires higher quantity of chemical composites (+ 2g/l of TAED, + 0.5 g/l of soda and +2.5 g/l of peroxide). Such technical specifications were directly obtained from the supplier of peracetic acid. No investments in new machines or technologies are required. Considering the four tiers of costs [START_REF] Curkovic | Total quality environmental management and total cost assessment: An exploratory study[END_REF], the solution under analysis impacts on direct costs only. The best chemical formulation, characterised by the fulfilment of the required qualitative parameters at the lowest consumption of chemical substances, was defined through more than 30 experimental trials.

The cost analysis revealed savings for the bleaching costs (Table 1). Environmentally, equivalent CO 2 emissions savings of around 40% were gained. Moreover, additional aspects were analysed to comprehensively quantify the environmental and economic implications of introducing this operational solution. As for cycle time, no significant improvements were registered. Regarding the waste production, the quantity of COD (Chemical Oxygen Demand) in the waste water from the peracid bleaching process decreased by 12% compared to the initial situation.

Conclusions

Sustainability is gaining more and more relevance on the manager's agenda since it can positively contribute to the firm's value creation process. The benefits are numerous and range from cost reduction, through risk management and business innovation, to revenue and brand value growth. In the textile sector, several companies are starting to pave the way towards sustainability through a number of different approaches.

In such a context, this paper proposes a decision making process to help textile companies in fulfilling environmental, economic and competitive benefits. The model, which has been built on the LCA methodology, supports the identification of opportunities for preventing pollution and for reducing resource consumption through a systematic analysis. Summarizing, the model provides a management system able to support managers to: i) monitor and evaluate its environmental performances with a dynamic perspective; ii) identify which activity and/or infrastructure needs to be improved or changed in order to reduce the environmental impact, enabling cost savings in both the short-and long-term; iii) define strategies for sustainability and foster the sustainable development of a company; and iv) increase a sustainable image. As demonstrated by the pilot case study that has been used to illustrate and analyse the applicability and consistency of the model, the solution proposed and implemented has enabled significant economic and environmental savings through a lower resource utilization.

To conclude, this paper can be considered as a basis for further research. In particular, in order to overcome the limitations of this work, some possible directions are hereafter pointed out. First of all, the proposed Sustainable Textile Scorecard can be extended considering other relevant aspects and KPIs. Moreover, as shown in the empirical application, there could be solutions that entail a higher consumption of chemicals, whose environmental impact could go beyond the Global Warming category. Therefore, future investigations can be carried out to analyse the introduction of other additional impact categories which can be useful to represent environmental sustainability with a wider perspective. Finally, social costs are not included in the model, but could be considered as potential further extensions.

Table 1 .

 1 Economic and environmental costs and savings

		Additional costs	Savings	Costs or savings/year
		(per kg of fabric)	(per kg of fabric)	(742.500 kg)
	Gas consumption		0,020208 €/kg
	Chemical composites		---
	-Soda	0,00148 €/kg	---
	-Peroxide	0,00925 €/kg	---
	-TAED	0,00400€/kg	---
	Total	0,01473 €/kg		4.067,4 €


Barnett J., Gril J., Saranpää P. (2014)Introduction, in: The Biology of Reaction Wood, Springer Series in Wood Science, Springer (pub), Gardiner B., Barnett J., Saranpää P., Gril J (eds), p. 1-11.

The Biology of Reaction Wood

Chapter 1. Introduction J. R. Barnett, Joseph Gril, Pekka Saranpää "The rings on the cross-section of the branch of a tree show the number of its years, and the greater or smaller width of these rings show which years were wetter and which drier. They also show the direction in which the branch was turned, for the part that was turned towards the north grows thicker than that turned towards the south so that the centre of the stem is nearer to the bark that faces south than to that on the north side." Leonardo da Vinci.

Leonardo published his observations of stem asymmetry in his notes for a treatise on painting without any attempt at explanation. It must represent one of the earliest references to reaction wood in the literature, although there can be no doubt that carpenters and joiners had long been intuitively aware of its effects on the working and mechanical properties of timber. With the passage of time our understanding of why and how it is formed in the tree has increased, providing a scientific basis for folk knowledge, but despite extensive research, much remains to be explained.

The last major work on this topic was the Magnum Opus of [START_REF] Timell | Compression Wood in Gymnosperms[END_REF], which summarised current ideas on compression wood in gymnosperms. No equivalent work has, however, been produced dealing with tension wood, its counterpart in angiosperm dicotyledonous trees. This reflects to some extent the fact that hitherto, tension wood has been of less commercial importance, although this is now changing with the breeding and development of fast-growing temperate-hardwood species. This book is intended to bring the reader up-to-date with progress in research into reaction wood, particularly with reference to tension wood, but also the developments in compression wood research since the publication of Timell's definitive work.

What is reaction wood?

Reaction wood has been defined by the Committee on Nomenclature of the International Association of Wood Anatomists [START_REF] Iawa | Multilingual Glossary of Terms used in Wood Anatomy[END_REF] as "Wood with more or less distinctive anatomical characters, formed typically in parts of leaning or crooked stems and in branches and tending to restore the original position, if this has been disturbed. It is divided into two types: tension wood in dicotyledons and compression wood in conifers". The Committee further defines compression wood as "Reaction wood formed typically on the lower sides of branches and leaning or crooked stems of coniferous trees and characterized anatomically by heavily lignified tracheids that are rounded in transverse section and bear spiral wall checks; zones of compression wood are typically denser and darker than the surrounding tissue". Tension wood is: "Reaction wood formed typically on the upper sides of branches and leaning or crooked stems of dicotyledonous trees and characterized anatomically by lack of cell wall lignification and often by the presence of an internal gelatinous layer in the fibres".

As might be expected, and as will become clear in this book, there are many examples of variations in detail from these necessarily succinct definitions. For example in the case of so-called mild compression wood, cell walls may lack spiral wall checks and not necessarily be rounded, while the gelatinous layer is not present in tension wood of many species. The Oxford English Dictionary provides several definitions of the word "reaction" several of which encompass the nature and function of the term when used in conjunction with wood. Perhaps the two most appropriate are: "The response made by a system or an organ to an external stimulus" and "A movement towards a reversal of an existing tendency or state of things………or desire to return, to a previous condition of affairs". The first definition is appropriate to the formation of reaction wood, while the second is appropriate to its function in the tree.

Briefly, reaction wood is formed in response to mechanical stress experienced by a tree. Its formation can work to restore vertical growth (gravitropy) in main stems, providing the stem is not already too thick to make this possible. It can be used also to incline stems in order to move the canopy in towards light (heliotropy). In the case of a branch, reaction wood formation is carefully controlled to balance its continuously increasing weight, either as a buttress in the case of compression wood in gymnosperms, or as a cantilever, in the case of tension wood in angiosperm dicotyledons, thereby maintaining the branches pre-ordained orientation and the architecture of the tree. It is noteworthy that reaction wood in a branch does not tend to force the branch into a vertical alignment unless the dominance of the apical shoot is lost. However, reaction wood is required to change the orientation of a lateral branch to the vertical in the event of damage to or loss of the leading shoot. Compression wood and tension wood sectors in the stem are always associated with local growth stresses which are very different from the normal tensile stress state common to gymnosperms and angiosperms: compressive stress in the case of compression wood, very high tensile stress in the case of tension wood.

There are, however, as will become apparent, variations on the theme. For example, compression wood may form around the entire growth ring in straight vertical fastgrowing conifer stems. This may be a result of almost continual movement in the wind of the long, recently formed apical internodes, which are highly flexible owing to the high microfibril angle in the S2 layer in the juvenile tracheids. Also, gelatinous fibres of the type normally associated with tension wood are sometimes found distributed randomly in vertical stems of fast-growing hybrid aspen. These phenomena might be explained by the existence of extraordinary growth stresses in fast growing trees or by some variation in the level of growth regulators. Some workers have observed cases in which the "normal" pattern of reaction wood formation was not found. For instance, Höster and Liese (1966) described compression wood in angiosperm species whose main axial elements were tracheids, observations confirmed by [START_REF] Yoshizawa | Distribution of guaiacyl and syringyl lignins in normal and compression wood of Buxus microphylla var. Insularis Nakai[END_REF] and Baillères et al. (1977). In contrast, [START_REF] Jacquiot | Note sur la présence de trachéides à parois gélatineuses dans des bois résineux[END_REF] described gelatinous fibres in coniferous wood.

Historical Background

The reason why branches and many tree stems are elliptical in cross section, with growth rings having different widths on opposite sides, and pith located to the side of the narrower growth rings, was already a subject of investigation in the nineteenth century. It was noted that in conifers growing on mountain slopes more growth occurred on the side of the stem facing the slope. Attempts were made to explain this in terms of nutrient distribution to the cambium, in that nutrients moved preferentially to areas to stimulate growth. [START_REF] Büsgen | The Structure and Life of Forest Trees[END_REF], pointed out that in fact the opposite was the case, as suggested by [START_REF] Cotta | Naturbeobachtungen über die Bewegung und Funktion des Saftes[END_REF], in that growth stimulates the movement of nutrients to where they are required. They suggested that this process was set in motion by stimuli which at that time were unknown. They also noted that in Germany, where south-west and west winds predominate, conifer stems take on an elliptical form with the long axis of the ellipse parallel to the wind direction and greatest growth on the leeward side of the stem. Similarly they noted that in leaning conifer stems, greatest growth occurred on the lower side. Thus the tree presents its least flexible profile to the prevailing stress. It was also noted that those roots aligned with the direction of the stress, whether wind or gravitational pull, also developed an elliptical profile. They proposed that this helped to prevent the stem from falling over. [START_REF] Hartig | Über das Vorkommen von Reaktionsgewebe in Wurzeln und Ästen der Dikotyledonen[END_REF] with spruce and Raadorsky (1925) with Helianthus induced elliptical stem form by rocking the experimental plant from side to side. [START_REF] Büsgen | The Structure and Life of Forest Trees[END_REF] interpreted this to mean that eccentric growth in branches and leaning stems was caused by mechanical stimulation. The fact that this response was also found by [START_REF] Hartig | Über das Vorkommen von Reaktionsgewebe in Wurzeln und Ästen der Dikotyledonen[END_REF] in a fallen spruce stem supported by the ground and therefore not under any bending stress, led to the view that the force of gravity played the most important part in the eccentricity of branches.

The facts that in conifers, reaction wood is produced on the underside of leaning stems and branches under compressive stress, and that it has a reddish hue, led to its being referred to in the German literature as Druckholz (pressure wood) or Rotholz (red wood). These terms were supplanted by the name compression wood as it was believed to be formed as a result of the tissue being under a compressive load. In contrast, reaction wood produced in angiosperm dicots, which is formed in tissues under tensile stress, and which is light in colour was referred to as tension wood or Weissholz (white wood). As [START_REF] Dadswell | Formation of red wood in conifers[END_REF] pointed out, the latter name is confusing as it was also used to describe wood formed in conifers on the opposite side of the stem to Rotholz. The terms compression wood and tension wood eventually acquired universal acceptance as reflecting the stress conditions under which they are usually formed.

However, there are circumstances in which tension wood can form in tissues under compressive stress and vice versa. Experiments by [START_REF] Dadswell | Formation of red wood in conifers[END_REF] in which they bent conifer twigs into vertical loops (Figure 1), demonstrated that compression wood formed on the lower side of the twigs at both the top of the loop (where the developing wood was under pressure) and the bottom (where it was under tension). [START_REF] Jaccard | Exzentisches Dickenwachstum un anatomisches-histologisches Differenzierung des Holzes[END_REF] repeated the experiment and found that in angiosperm saplings tension wood always formed on the upper side of the top and bottom of the loop. This, coupled with the discovery of auxin and its effects as a growth regulator which moves basipetally in tissues under the influence of gravity, led to the proposition that auxin accumulation on the lower side of conifer branches and leaning stems stimulated compression wood formation, while depletion of auxin from the upper side in angiosperms led to tension wood formation. The work of [START_REF] Wershing | Seedlings as experimental material in the study of "redwood" in conifers[END_REF], who found that external applications of auxin induced compression wood formation, lent support to this view. Conversely, [START_REF] Nečesaný | Effect of β-indoleacetic acid on the formation of reaction wood[END_REF] found that the application of auxin to the upper side of an angiosperm branch inhibited tension wood formation, while [START_REF] Lachaud | Xylogénèse chez les Dicotylédones arborescentes. V. Formation du bois de tension et transport de l'acide indole acétique tritié chez le Hêtre[END_REF] applied tritiated auxin to loops made in the manner of [START_REF] Jaccard | Exzentisches Dickenwachstum un anatomisches-histologisches Differenzierung des Holzes[END_REF] and found that it moved to the lower side of the loop while tension wood formed on the upper side. This effect was most pronounced when the loop was still attached to the plant, no movement of auxin taking place in a detached loop.

In essence this theory was accepted until questioned by [START_REF] Boyd | Basic causes of differentiation of tension wood and compression wood[END_REF], who felt that reaction wood formation was stimulated by stress, rather than auxin concentration changes. His view was supported by [START_REF] Wilson | Distribution of endogenous indole-3-acetic acid and compression wood formation in reoriented branches of Douglas fir[END_REF] following measurement of auxin levels in bent branches of Douglas fir made using gas chromatography-mass spectroscopy. It was found that auxin levels were higher on the upper side of these branches even though compression wood was formed on the lower side. [START_REF] Sundberg | Effect of indole-3-acetic acid transport inhibitors N-1-naphthylphthalamic acid and morphactin on endogenous IAA dynamics in relation to compression wood formation in 1-year-oldPinus sylvestris shoots[END_REF] measured auxin concentrations with a relatively high degree of resolution in the cambium of tilted pine stems and also found no difference in auxin distribution between tilted and control stems.

The work performed by the French consortium ASMA (Fournier et al 1991a[START_REF] Thibaut | Mechanics of wood and trees: some new highlights for an old story[END_REF] demonstrated that reaction wood is not a consequence of stresses acting on a zone in the tree but rather, its role is to generate specific levels of stress when and where they are needed. The fact that while the main stem of the tree produces reaction wood in an apparent attempt to maintain as vertical an alignment as possible, while branches produce it to maintain a particular orientation has led to the suggestion that the stress imposed by gravitational force does not of itself stimulate reaction wood formation. Rather it is the tree's perception of the effect of the gravitational force in displacing the stem or branch from its pre-ordained alignment that provokes the response.

Recent developments in this area are described in Chapters 4 and 5.

Structure of reaction wood.

The anatomical and structural features of reaction wood are usually described by comparison with so-called normal wood. The latter term actually refers to wood which has those properties most desired by the timber industry, for example, straight grain, high density, high bending strength and uniform shrinkage without distortion on drying. Interestingly there appears to be no definition of normal wood and it is A B C D noteworthy that the IAWA glossary in its definitions of reaction wood, tension wood and compression wood avoids the use of comparatives.

Those features usually associated with what authors refer to as normal wood and which are responsible for the desirable characteristics of good timber are determined by the anatomical structure of the wood and the structure of fibre (hardwoods) and tracheid (softwood) walls. In particular, tracheids and fibres have the classical threelayered secondary wall (Figure 2) with the microfibril angle in the S2 layer being small, resulting in a high modulus of elasticity. In reacting to gravity-induced displacement of the stem or branch, the tree produces fibres or tracheids whose structure differs to a greater or lesser extent from this "ideal". These variations and other differences in reaction wood will be discussed in more detail in Chapter 2.

In brief, compression wood is a darker colour than normal wood, the tracheids are more rounded in cross-section with the result that intercellular spaces are formed. They are also shorter than normal wood tracheids in the same tree. Cell walls of compression wood tracheids are normally thicker than those of normal wood tracheids in the same part of the tree. This coupled with the greater proportion of lignin in the cell wall makes the wood denser, more impermeable and stronger in compression. The microfibril angle in the S2 layer is larger, which reduces the tensile strength, modulus of elasticity and increases the brittleness of the wood, making it unsuitable for uses in which it is likely to experience high stresses. The larger microfibril angle also means that the wood has a higher longitudinal shrinkage on drying, but a lower transverse shrinkage. This explains the distortion on drying of pieces of wood containing both normal and compression wood. In severe cases the S3 wall layer is absent and the S2 layer contains splits which lie parallel to the microfibril angle.

The structure of tension wood fibres is less clear-cut than that of compression wood tracheids. Tension wood fibres are longer than those in normal wood and have been found to contain a lower proportion of lignin than normal wood, giving it a whiter appearance. They are most commonly described as lacking an S3 layer and having variable amounts of the S2 remaining, inside which is a gelatinous layer composed mainly of hydrated cellulose microfibrils [START_REF] Norberg | Physical and chemical properties of the gelatinous layer in tension wood fibre of aspen (Populus tremulaL)[END_REF] oriented almost parallel to the long axis of the fibre. This gives the wood a glistening gelatinous appearance when wet. Variations on this theme have been reported, however. For example [START_REF] Faruya | The chemical composition of the gelationous layer from the tension wood of Populus euroamericana[END_REF] reported the presence of a gelatinous layer in fibres of Populus euroamericana which had retained their S3 layer, while [START_REF] Côté | A contribution to the ultractructure of tension wood fibres[END_REF] reported an S3 layer inside a gelatinous layer. More and more variations on the structure of tension wood fibres are being reported, with numerous species apparently lacking a gelatinous layer in their fibre walls.

These structural variations, which are adapted to the mechanical role the fibres and tracheids must fulfil, are of course, a normal response by the tree to enhance its chances of survival, either by helping to maintain the upward movement of the crown by the shortest possible route, by restoring verticality of trees partially uprooted by wind, or by maintaining the optimum branch architecture for efficient light capture. As such, for the tree, making reaction wood is as normal as making the normal wood beloved of the timber merchant, engineer, carpenter or joiner. The use of the term normal for the latter carries the implication that reaction wood is abnormal, and by extension that it is of no value. However, trees as we know them could not have evolved without reaction wood, a fact which needs to be borne in mind by those working to improve wood quality.

The formation of reaction wood demonstrates that the tree is capable of fine tuning the structure of its fibre or tracheid walls to generate growth stress. It does this by adjusting the proportions and arrangement of its major wall components, cellulose, hemicellulose and lignin. The structure and composition of the cell wall in reaction wood forms the subject of Chapter 3.

How Reaction Wood Works

It is now well known that reaction wood effects stem reorientation by generating a long lasting flexure momentum (Alméras et al 2005). This is linked to asymmetry between wood production (new ring) on the two sides of the wooden axis: asymmetry of generated growth stress and often asymmetry of ring width. But it is not yet well understood how growth stress level is tuned during cell differentiation.

Various theories have been put forward, but none has so far proved satisfactory. [START_REF] Brodski | Callose in compression wood tracheids[END_REF] proposed that the water in the developing S2 layer of the compression wood tracheid wall was replaced during maturation by a compound, laricinan, and that this insertion provided the force needed to push the stem upright. [START_REF] Boyd | Significance of laricinan in compression wood tracheids[END_REF] published a convincing argument against such a role for laricinan. The tensional effect of gelatinous layer of tension wood fibres is also difficult to explain. When gelatinous fibres are severed, the gelatinous layer may be observed to detach itself from the other wall layers and contract. This is despite the fact that its major component is cellulose microfibrils with their major axis parallel to the direction of shrinkage. As the microfibrils are highly crystalline they would not be expected to shrink in this way. Current thinking on these topics is covered in Chapter 5.

Why is Reaction Wood so important?

It is precisely those properties which enable reaction wood to carry out its function in the tree that render it a problem for the timber industry. When [START_REF] Jaccard | Exzentisches Dickenwachstum un anatomisches-histologisches Differenzierung des Holzes[END_REF] cut loops in which reaction wood had formed, the curvature immediately changed as internal stresses were released (Figure 1). In the case of the gymnosperm loop, in which compression wood had formed on the convex side of the lower curve, and the concave side of the upper curve, the effect of cutting the loop was to increase the radius of curvature of the lower section, and decrease the radius of curvature of the upper section Thus the compression wood appeared to have been exerting a positive pressure prior to release. In the case of the angiosperm loop, where tension wood formed on the upper sides of the loop, the effect was the opposite, with release prompting a shortening of the tension wood side. These movements illustrate the phenomena associated with growth stress release during wood processing, further amplified by drying-induced deformations. The commercial significance of such effects is enormous, since timber containing reaction wood cannot be used where dimensional stability is required.

Other problems associated with compression wood include the difficulty of working the hard timber. [START_REF] Büsgen | The Structure and Life of Forest Trees[END_REF] commented that it is very difficult to drive a nail into it. It is also brittle and prone to brash compression failure. The higher levels of lignin also increase costs for the pulp and paper industry since lignin is expensive to remove and was hitherto difficult to dispose of. However, increasing pressure on non-renewable natural resources mean that research is now looking into utilisation of this abundant waste product.

Tension wood suffers from similar problems of dimensional stability and is also difficult to work. The gelatinous fibres tear rather than cut, giving a wood surface containing tension wood a woolly appearance. On the other hand, the lower levels of lignin might be considered advantageous for the pulp industry. The problems created by reaction wood for industry are discussed in Chapters 6, 8 and 9.

If reaction wood were present in wood in only small amounts, these problems might be ameliorated. However, the fact that tree growth takes place subject to environmental pressures means that trees constantly have to make some reaction wood to brace themselves against the wind, to correct for windthrow and to support branches at the optimum angle. Even those trees which are perfect in form (from the forester's and timber merchant's point of view), with straight and vertical stems, may contain significant amounts of reaction wood. Vertical growth may only be achieved by constant corrections of tendencies to lean under the influence of wind, whose direction may change from day to day. For this reason it is essential that we have the tools for identification of reaction wood. It is not always easy to do this, and methods for doing so are reviewed in Chapter 7.

The evolution of reaction wood was an essential step in the evolution of trees. Without it, tall trees could not exist and there would be no timber of any size for industry to use. It is certain therefore, that the wood-based industries will have to live with reaction wood and allow for its behaviour. However, it is possible to reduce the levels of reaction wood by careful forest management and it may be possible to reduce the levels to the minimum required for successful tree growth through focussed tree breeding. These and other commercial issues are discussed in Chapter 9.

In a world where pressure on forests is increasing as demand for wood for traditional purposes is added to by demand from new uses such as biofuel, it is essential that we grow trees with high quality wood while optimising biomass production. This means that we need to find ways of keeping the amount of reaction wood in timber to a minimum compatible with the safety of the tree. In addition we should be actively seeking ways of using reaction wood and ensuring that wastage is kept to a minimum. This book provides the best scientific understanding of the formation, function and behaviour of reaction wood, which will help achieve these goals.

Figure 1 :

 1 Figure 1: Diagram after Jaccard 1938. Diagrammatic representations of A: Loop made in a conifer stem. Compression wood is shown as a thicker line on the lower sides of the upper and lower parts of the loop. B: Loop made in a woody dicotyledon stem. Tension wood is shown as a thicker line on the upper sides of the upper and lower parts of the loop. C and D: The effect of cutting the loops is similar in each case suggesting compression wood acts by pushing, while tension wood by pulling against the normal wood.

Figure 2 :

 2 Figure 2: Cell structure of normal (mature) wood, juvenile wood and compression wood (from Jozsa and Middleton 1994)


Higher Education institutions are increasingly interested in offering more flexible teaching and learning delivery methods that are often independent of place. Where foreign language learning is concerned, telecollaboration is gaining ground. This paper focuses on synchronous webconferencing-supported teaching and examines how different semiotic resources are used during lexical explanation sequences. The context is a telecollaborative exchange between Business students learning French and trainee teachers on a Master's programme in Teaching French as a Foreign Language. Using multimodal transcriptions of interaction data from two sessions, the sequential analysis provides access to different combinations of semiotic resources. These include using the visual mode to project active listening strategies and the complementary role of the text chat to secure common ground concerning the target item. The analysis sheds light on a 'thinking break' strategy employed by the trainees. Descriptive examples demonstrate how verbal explanations were accompanied, firstly, by deictic and iconic gestures and, secondly, by metaphoric gestures used to help forefront different properties of the target item. Finally, changes in gaze and proximity were observed as playing a role in interaction management and in signalling which verbal modality was forefronted. The study illustrates emerging pedagogical and multimodal communication strategies for 'doing vocabulary teaching'.

Introduction

A shift has been seen in the Computer-Assisted Language Learning (CALL) field from synchronous written technologies towards audiographic conferencing and both desktop videconferencing and webconferencing-supported technologies. Language teachers are frequently turning to these technologies to bring together geographically distant learners and trainee teachers in telecollaborative exchange projects. The synchronous nature of these technologies is seen as adding value to their interactions [START_REF] Levy | CALL dimensions. Options and issues in Computer-Assisted Language learning[END_REF]. This article contributes to a growing body of research that analyses synchronous interactions from a multimodal perspective, by exploring how trainee teachers during webconferencingsupported interactions allow for a focus on form whilst ensuring that this linguistic focus is context dependent and embedded within the ongoing interaction necessary for task completion. Focusing on the potential of the webcam and its combination with audio and text chat modalities, the study examines how participants manage different semiotic resources during lexical explanation sequences. The paper describes emerging pedagogical and multimodal communication strategies for 'doing vocabulary teaching.' [START_REF] Guichon | Multimodality and CALL[END_REF] argue that whilst any language learning activity is multimodal in nature, in CALL, technology plays a fundamental role in the meaning-making process through "the kinds of meaning which it facilitates or favours, and through the differential access to the means of production and reception which it provides" [START_REF] Kress | Reading Images: The Grammar of Visual Design[END_REF]: 233 cited in Guichon & Cohen, 2016:510).

CALL and multimodality

A social semiotic approach to multimodal communication regards the verbal mode as one amongst a multiplicity of modes that may, at different moments in an interaction, take superior, subordinate or integral roles. The approach is concerned with the choices made by a sign-maker [START_REF] Halliday | Language as Social Semiotic: The Social Interpretation of Language and Meaning[END_REF] regarding the combination and interactivity of different communication modes available to present a piece of information within the contextual constraints and potentials of the environment. It considers the social relations within the communication situation and studies the modes available to present information and how this is achieved through different forms of media [START_REF] Kress | Against arbitrariness: the social production of sign as a foundational issue in critical discourse analysis[END_REF][START_REF] Kress | Multimodality: A Social Semiotic Approach to Contemporary Communication[END_REF]. CALL environments may be synchronous or asynchronous. Although the communication modes (e.g. verbal, visual) may be the same in different environments, the nature of the dissemination technology (the medium) and its temporality (asynchronous / synchronous) and nature (static, dynamic, interactive) impact on the types of access that are offered for the presentation and comprehension of information (see [START_REF] Guichon | Multimodality and CALL[END_REF]. Within an environment, one mode may correspond to one modality (a specific form of communication related to a single mode), with its own grammar constraining interactions, or one mode can give rise to several modalities. For example, in the verbal mode, information may be communicated in the text chat modality or the audio modality. Consequently, an interaction may be multimodal because several modes are used and/or several modalities [START_REF] Chanier | Multimodalité et expression en langue étrangère dans une plateforme audio-synchrone[END_REF].

Concerning multimodal environments, Kress considers it vital to "understand the meaning potentials of the resources as precisely and explicitly as we can " (2003:24). This is true in CALL where research needs to assess the ways in which multimodal environments can support the pedagogical processes accepted as effective for language learning (Lamy, 2012) against the limitations on L2 learners' cognitive resources. [START_REF] Hauck | Telecollaboration in multimodal environments: the impact on task design and learner interaction[END_REF] stress that how teachers and material designers can use multimodal CMC settings to exploit communication opportunities and foster SLA is largely unanswered, potentially because only a small body of research examines the impact of the combined used of modes on interaction in online language classrooms. [START_REF] Hampel | Theoretical perspectives and new practices in audio-graphic conferencing for language learning[END_REF] describes, in particular, a need to investigate synchronous environments other than written text environments to examine whether the different communication modes can be used by different learner types to their advantage. Lamy, in advocating for CALL research to focus on multimodality, warns that if multimodal meaning resources in L2 studies of computermediated communication are not considered "we are in danger of missing out on explaining the nuances in the learning process" (2012b:121) and risk failing to exploit learning processes to the full.

Multimodality and language learning in videoconferencing environments

A small number of studies have been conducted to investigate the potential of online language learning interactions in videoconferencing environments from a multimodal perspective. Research to date has considered how different modes are used in online environments for specific purposes [START_REF] Guichon | Tutorat de langue par visioconférence : comment former aux régulations pédagogiques[END_REF][START_REF] Hampel | The use of videoconferencing to support multimodal interaction in an online language classroom[END_REF] or types of discourse [START_REF] Wang | Negotiation of meaning in desktop videoconferencing-supported distance language learning[END_REF]Guichon, Betrancourt & Prié, 2012), the effects of the webcam on multimodal interactive learning [START_REF] Develotte | The use of the webcam for teaching a foreign language in a desktop videoconferencing environment[END_REF][START_REF] Codreanu | Effects of webcams on multimodal interactive learning[END_REF][START_REF] Guichon | A semiotic perspective on webconferencing-supported language teaching[END_REF] and social presence [START_REF] Satar | Multimodal language learner interactions via desktop videoconferencing with a framework of social presence: Gaze[END_REF][START_REF] Guichon | The Impact Of The Webcam On An Online L2 Interaction[END_REF]. Task completion and learner proficiency have also been explored [START_REF] Wang | Task Design in Videoconferencing-Supported Distance Language Learning[END_REF]. Yamada and Akahori (2009) conducted an experimental study to examine the impact of the visual mode on self-repair by placing learners in different conditions: videoconferencing with both interlocutors' images; with only the partner's image or the learner's own image; without images. They concluded that communication was facilitated when the interlocutor's image was available. This had an effect on learners' perception of social presence and the consciousness of natural communication which led to more to self-corrections. [START_REF] Guichon | Managing written and oral negative feedback in a synchronous online teaching situation[END_REF] examined trainee teachers' feedback provision from a multimodal perspective. The researchers illustrated several strategies across different modalities often based on the trainee teachers' personal preferences and the desire to provide feedback in the text chat in order not to disrupt the communicative flow. The potential of the visual mode to signal incomprehension or the need for self-correction through gestures or facial expressions was barely exploited. The study highlights the need to train teachers in the skills needed to perform in multimodal environments so they do not become cognitively overloaded and in turn reduce feedback provision. [START_REF] Guichon | A semiotic perspective on webconferencing-supported language teaching[END_REF] examined the meaning-making potential of the webcam from a semiotic perspective by exploring how trainee teachers use its affordances to produce visual cues (communicative and extra-communicative gestures, proxemics) useful for mutual comprehension. The study found, firstly, that whilst a head and shoulders framing shot was favoured by the trainee teachers, there did not appear to be an optimal framing choice for desktop videoconferencing. Secondly, there was a loss between the number of gestures performed and those visible to the students. Thirdly, when audio and kinesic modalities were combined, communicative gestures that were framed, and held long enough to be perceived by the learners, were more likely to be valuable for mutual comprehension.

Although the above studies highlight the potentials of multimodal aspects of videoconferencing for language learning, the use of this synchronous technology does not come without challenges. With reference to online language learning and teaching contexts, [START_REF] Wang | Negotiation of meaning in desktop videoconferencing-supported distance language learning[END_REF] warns that the multimodality can put pressure and strain on users and [START_REF] Guichon | Managing written and oral negative feedback in a synchronous online teaching situation[END_REF] underline the difficulties of handling the interaction across several modalities, particularly regarding 'dual tasking' where two tasks in different modalities were put in competition in terms of the teachers' cognitive resources.

Lexical explanations during task-based interactions

One challenging aspect of online pedagogy that teachers face during task-based interactions in synchronous environments is how to extract new linguistic material, including lexical items, to allow for a focus on form whilst ensuring this focus is context-dependent and embedded within the ongoing interaction necessary for task completion. Mortensen (2011) describes how a spontaneous focus on lexical material can be analysed, from a conversation analysis perspective, in terms of repair [START_REF] Schegloff | The Preference for Self-Correction in the Organization of Repair in Conversation[END_REF], whereby the participants deal with a problem as it appears in the interaction. Either the teacher identifies a lexical item in his/her verbal turn as potentially problematic and provides an explanation, sometimes after asking the learners explicitly to state their (in)comprehension, or the lexical item is located and pointed out by the learners as problematic (other-initiated repair). Mortensen terms such sequences as "doing (vocabulary) teaching" (2011:136) to frame the pedagogical aspect as a social practice during which lexical explanations are constructed in and through the interaction, only diverting from the latter for a short 'side-sequence' (Fasel Lauzon, 2008:83) within the ongoing task accomplishment.

In the first instance, the teacher either tests the learner's lexical knowledge by asking a known-information question1 to determine whether he is able to display his knowledge of the lexical item, or explicitly asks the learner whether he understands the lexical item. This leads either to a learner explanation to which the teacher may react; a signal of comprehension to which the teacher may follow up on by asking a display question; or a signal of incomprehension that prompts a teacher explanation to which, in turn, the learner reacts.

The protypical teaching sequence that is associated with other-initiated repair, when a learner does not understand an element in the teacher's turn, is often described by a ternary model [START_REF] Gulich | Pour une ethnométhodologie linguistique. Description des séquences conversationnelles explicatives[END_REF] in which a lexical difficulty is manifested either explicitly or implicitly by the learner and managed by the teacher through an explanatory reaction to resolve the problem, which in turn the learner ratifies.

Although these models offer a clear starting point for examining lexical explanations in pedagogical contexts, real-time interaction between learners and teachers may not be as clear as these models indicate because when "discourse is stripped down to its lowest common denominator, that is, that of text […] the 'reality' of the discourse situation is lost during this process" [START_REF] Knight | Multimodality and Active Listenership[END_REF]2) including the multimodal properties of the interaction. A multimodal analysis of lexical explanations may reveal aspects of the learning sequence that would not appear if examining the verbal mode alone and may help to better understand how trainee teachers interact with and use the multimodal constituents of webconferencing-based platforms to identify strategies that could be explicitly taught during teacher training.

Multimodal analyses of lexical explanations

Several studies from the Gesture Studies field conducted in classroom environments and under experimental conditions have included a multimodal perspective while examining foreign language teachers' lexical explanations. The research suggests that learners receive considerable input in nonverbal form that is salient for second language acquisition because it modifies and makes verbal input more comprehensible [START_REF] Lazaraton | Gesture and speech in the vocabulary explanations of one ESL teacher. A microanalystic inquiry[END_REF]. [START_REF] Faraco | Gesture and the Negotiation of Meaning in a Second Language Classroom[END_REF] illustrated how facial signs can project lexical difficulties and make visual the different stages of the cognitive activity of the learner confronting difficulty whilst [START_REF] Tellier | Découvrir le pouvoir de ses mains : La gestuelle des futurs enseignants de langue[END_REF] show that illustrative iconic gestures to clarify and disambiguate meaning are more often used with language-learners than with native speakers. However, in CALL, few studies have examined spontaneous lexical explanations in webconferencing-based interactions from a multimodal perspective. They have examined lexical explanations within the wider context of instructional regulations that also included instructions and feedback [START_REF] Guichon | Tutorat de langue par visioconférence : comment former aux régulations pédagogiques[END_REF] or peer scaffolding [START_REF] Cappellini | Co-construction des routines d'étayage dans un tandem franco-chinois par visioconférence[END_REF]. [START_REF] Guichon | Tutorat de langue par visioconférence : comment former aux régulations pédagogiques[END_REF] conducted a content analysis of interactions between trainee teachers of French and American learners of French that took place over an eight-week period via a desktop videoconferencing platform. They identified different pedagogical strategies used by the trainees. Whilst some immediately offered lexical explanations, others used inference strategies that included eliciting examples, peer explanations, or associating the text chat and audio modalities to facilitate understanding. [START_REF] Cappellini | Co-construction des routines d'étayage dans un tandem franco-chinois par visioconférence[END_REF] examined a teletandem exchange between Chinese students of French and Master's students at the Language faculty of a French University. His qualitative study underlined different visual strategies during the manifestation phase, including changes in posture and head movements alongside facial mimics of incomprehension. Also, the use of the text chat modality appeared only partway through the interactions (fourth session) during the core phase of explanations.

In line with these two studies, this paper proposes a "multimodal analysis" of one aspect of synchronous online pedagogy and explores the orchestration of different semiotic resources during both during trainee-initiated and learner-initiated (unplanned) lexical explanations.

Methodology Pedagogical Context, Participants and Ethics

This study draws on interaction data from a telecollaborative exchange involving 18 Business undergraduates in their third semester of learning French at Dublin City University and 12 trainee teachers on a Master's programme in Teaching French as a Foreign Language at Université Lyon 2. For the Master's students, the exchange formed part of an optional module in online teaching. For the Dublin City University undergraduates, the exchange was one element of a 12-week blended French for Business module with level B1.2 of the Common European Framework of Reference for Languages as its minimum exit level (Council of Europe, 2001). The exchange was aligned with module outcomes that included understanding spoken language on topics related to professions, work placements and job applications and applying for an internship through French. This was pursued by most learners six months after the exchange.

The six-week telecollaborative exchange ran in autumn 2013. Participants met for weekly 40-minute online sessions in the webconferencing platform Visu [START_REF] Bétrancourt | Assessing the use of a Trace-Based Synchronous Tool for distant language tutoring[END_REF]. Following an introductory session, each online session was designed by two trainees and was thematic, focusing on Business French. Topics included preparing for an internship, project management, pitching a project, interviews, labour law. Although this paper focuses on the synchronous sessions, these interactions were part of a larger circular learning design that included debriefing sessions where trainees shared extracts from past interactions for collective exploration, and multimodal reports that offered asynchronous feedback to the learners after each session (detailed in [START_REF] Guichon | A semiotic perspective on webconferencing-supported language teaching[END_REF].

Groups were formed randomly by both course lecturers. Gender, teaching experience, and language level were not taken into account. Because of differently sized groups, most trainees worked with two learners whilst two trainees had one-to-one sessions.

This study focuses on interaction data from the third and fourth synchronous sessions of the exchange for three of the exchange groups. The topic for session three was 'preparing for an internship in Reims.' Participants engaged in an interview role play for an internship at a town council related to events marketing. Session four centred upon project management. Learners took on the role of a fast-food chain's employees who were meeting their manager to suggest new ideas for a children's birthday party formula.

The Visu platform was chosen for the web-conferencing interactions because it was specifically designed for synchronous language teaching-learning. Interactions were influenced by its functionalities (Table 1).

Audio

Full duplex (several speakers can speak simultaneously) Participants connected to Visu from university language labs using individual computers and headsets. Learners working in the same group were physically separated in the lab.

Participation in the research study was voluntary: not all participants involved in the pedagogical exchange gave permission. Prior to data collection, approval from Dublin City University's ethics committee was gained. To preserve anonymity, participants' names have been changed and, when requested, participants' images have been converted to line drawings.

Research Design

The ISMAEL corpus (Guichon et al. 2014) comprises the interaction data of six sessions for seven trainee-learner groups. This study uses data from sessions three and four for three of the exchange groups (Table 2). The rationale for selecting these sessions was that the trainees had gained some online teaching experience and established social relationships with the learners. At the time, the lengthy process of extracting the webcam videos from the Visu database and aligning them in one video file that could be imported into the transcription software ELAN [START_REF] Sloetjes | Annotation by category -ELAN and ISO DCR[END_REF] had been completed for these three groups. The spoken interaction had also been transcribed using the conventions given in Appendix A. Using the timestamps created in Visu, the parallel text chat logs were synchronized with these transcriptions. The first step in the analysis process was to identify lexical explanations in the data. This collection was identified in two ways: lexical explanations that followed display questions (e.g. can you explain what x means?) or questions to evaluate comprehension (do you understand the word x?) and had therefore been anticipated as potentially problematic by the trainees, and unplanned explanations that followed a learner's affirmation that he had encountered a comprehension problem as shown through prototypic phrases (e.g. what is x? what does x mean?). The sequences were isolated from the trainee or learner question until the turn in which a learner either asserted verbally or co-verbally his understanding/reception or in which a transition to a new activity was observed. Across the six sessions studied, there were 14 lexical explanation sequences in total of which only four were initiated by the learners.

Secondly, co-verbal acts used in each lexical explanation sequence were annotated in ELAN.

In the data, these included gestures, actions, proxemics, head movements and changes in gaze.

McNeill's (1992) schema that categorises gestures as iconic (representations of an action or object), metaphoric (illustrating an abstract concept), deictic (pointing gestures at concrete or abstract spaces) and beats (movements to accompany the rhythm of the discourse) was used to annotate gestures. Kendon's 1982 category of emblems, referring to culturally specific gestures was also included. Actions that contributed to the communication, such as writing something down or typing, were also annotated, but extra-communicative actions such as a participant pushing his hair behind his ear were not.

To annotate head movements, the distinctions offered by [START_REF] Altorfer | Measurement and meaning of head movements in everyday face-to-face communicative interaction[END_REF] between rotational (shaking the head), lateral (tilting the head) and sagittal (nodding) movements were used. Changes in proxemics, when a participant moved closer to or further away from the webcam were annotated. Gaze was annotated as being directed towards the screen, towards the keyboard, outside of the webcam frame and pensive (outside of the webcam frame with gaze directed upwards). Moments when participants' eyes were closed were also annotated.

Analysis

The following sequential analysis offers descriptive illustrations of different strategies used during the opening, explanation and closing phases of student-and teacher-initiated lexical explanation sequences.

Trainees' strategies to highlight the target lexical item

Trainee-initiated sequences (TIS)

Freq. In eight of the ten turns that comprised the openings of trainee-initiated sequences, the target lexical item occurred in a possible turn constructional unit final position (TCU, [START_REF] Sacks | A Simplest Systematics for the Organization of Turn-Taking for Conversation[END_REF] where turn-transfer from the trainee to the learner(s) is possible (Table 3). The trainees' turns are completed by the target item and followed by a pause that shows the possible completion of the turn constructional unit and offers learner(s) a turn-taking opportunity. Prosody appears to play a role in the highlighting the lexical item in its TCU final position -in all cases, the trainees either stress the target item, elongate the pauses between the individual words in the item or, compared to the preceding turns and even the question form itself, produce the item at a slower speed.

vous
Trainees also combined the audio and written modalities by providing the lexical item in the text chat (5 instances) or drawing attention to its written form in resources the learner had already opened (1 instance). This strategy was accompanied by gaze changes (see Figure 1). During the first TCU when the target item was pronounced, the trainee, Samia, shifts her gaze towards the keyboard, perhaps signalling that the pause before the display question comprised a change in direction of an ongoing turn rather than a transition relevance place2 (Figure 1, plate 2). When the text chat message appears, the trainee changes her gaze (Figure 1, plate 3), seemingly towards the message on the screen before completing her audio turn. In the pause following the display questions (Figure 1, plate 4), the trainee smiles, to signal the end of her turn and encourage her learners to take the floor. The trainee's gaze then changes towards the other side of the screen (Figure 1, plate 5) presumably towards the learners' webcam images. This gaze change could be to monitor the visual mode for cues that the learners understand the target item or could help signal her wish for speaker transition. In this example, the text chat modality provides a complementary role to the audio modality. Should there be any technical issues, the text chat allows participants to establish common ground concerning the lexical item in question. It also allows the trainee to model the language in writing and therefore provide the spelling of the item, in addition to the target pronunciation. As text chat is a less ephemeral modality (the message remains on the screen), this strategy allows the learners to return to what is written.

Trainee's active listenership strategies in the openings of learner-initiated sequences

In the four learner-initiated sequences, the learners explicitly state their incomprehension. In Figure 2, the learner-initiated sequence follows the trainee visually displaying the instructions and asking whether they understand the activity (does that make sense to you?) before telling them to start the interaction (okay I'm listening to you). The learner, Alannah, who asks for an explanation has her hands over her earphones. This is a posture she often adopts during the interactions, rather than a co-verbal gesture to suggest that this specific incomprehension of the target item stems from technical problems. Indeed the sequence opening is prompted by a visual display of the target item rather than the item being used in the audio modality as is the case in Figure 3. In this example, the learner, Sean, thins his lips just after the trainee's pronunciation of le bilan (the reminder) (Figure 3, plate 1) and changes posture, moving closer to the webcam during his clarification request (Figure 3, plate 2). These signs could be projective of his difficulty. [START_REF] Bavelas | Faces in dialogue[END_REF] describe, for example, how pressing lips together is a back-channel signal to show concern.

What is perceptible in the openings of the learner-initiated sequences is how trainees visually show their engaged response during learner requests. In Figure 2, the trainee moves closer to the webcam and shifts gaze to the left-hand side of her screen, presumably to her learner's webcam image. In Figure 3, the trainee moves slightly closer to the screen and smiles just after the learner pronounces the problematic lexical item. These active listenership strategies demonstrate trainees' responsive role in the interaction (see [START_REF] Tsuchiya | Listenership Behaviours in Intercultural Encounters[END_REF]. They could be considered as proxemic engaged-response tokens: rather than using verbal response tokens (e.g. mmm), the trainees foreground the visual mode to show their availability to deal with learner requests.

Setting up the explanations in learner-initiated sequences

Learner-initiated sequences

Freq.

X c'est quoi/

X what is it/ Four learner-initiated lexical explanation sequences were identified (Table 4). Before trainees begin an explanation they systematically check the target word in the learner's turn and often give themselves a short thinking break before proceeding.

Foregrounding the text chat was a strategy used to check the target lexical item (Figure 4). The trainee repeats the problematic item (Figure 4, plate 1), and begins to contextualize it before repeating the beginning of the composite noun. The learner, Alannah, expresses her understanding of goûter as being the homonym to the infinitive verb form through a direct translation (taste) and an acknowledgement that goûter d'anniversaire is the item causing difficulty. The trainee, Adèle, then announces a change as to which modality is foregrounded. A gaze and posture change (Figure 4, plate 3) contextualise the deictic (here) in the audio. This change prompts Alannah's gaze to move downwards presumably to read the text chat message (plural noun form goûters), demonstrating understanding that it is the noun form rather than the verb form that is unclear. Recurrently, once the participants confirmed the target word for which a learner had requested an explanation or the learners had shown their incomprehension of a vocabulary item following a display question, the trainees adopted thinking strategies before proceeding with the explanation. These strategies were communicated visually and verbally.

For example, after a confirmation check (Figure 5, plate 1), the trainee repeats the target item before a shift in gaze off-screen that is preceded by the hesitator uh:. [START_REF] Goodwin | Gesture and coparticipation in the activity of searching for a word[END_REF] describe, in L1 face-to-face interaction, that when a speaker displays hesitancy in a word-search episode, a prototypical action is to accompany a sound stretch with withdrawing gaze from the recipient and a characteristic 'thinking face' described by [START_REF] Bavelas | Hand and Facial Gestures in Conversational Interaction[END_REF] as a break in eye contact and an effortful facial expression. Here the trainee displays hesitancy in his utterance-formulation and difficulty in finding the relevant items to explain the lexical This action may aid the trainee to maintain a sense of coherence for himself and help in his thinking process (Codeanu & Combe-Celik, 2013) but will not go unnoticed during the interaction (see [START_REF] Guichon | A semiotic perspective on webconferencing-supported language teaching[END_REF], particularly if the thinking strategy involves changes in gaze and posture accompanied by gestures (Figure 6). In this example, the trainee is present on screen in the visual mode but momentarily absent in the interactional space as she changes her posture and gaze towards somebody who does not appear in the webcam view. During her thinking-out-loud process (Figure 6, plate 1) an off-screen interaction appears to begin in the face-to-face interactional space. The question (how can I explain birthday party) appears to be directed not to the trainee herself or her learners but to a peer. The trainee then performs a body-focused gesture (Figure 6, plates 2 & 3) prompting one learner (Alannah) to state her understanding of the base form (goûter) thus offering a starting point for the explanation. The trainee gaze shifts and shows visually that she is again present in the online interactional order.

Multimodal explanations

In the audio modality, trainees employed different strategies to define the lexical items (Table 5). For the trainee-initiated sequences, the co-elaboration of explanations was privileged. The data included three examples of substitution whereby a lexical item (synonym) or paraphrase was offered.

Learner-initiated sequences (SIS) Freq. Trainee-initiated sequences (TIS)

Freq. The verbal strategies used for lexical explanations in the data did not stand alone and were only part of what learners were presented with. Combination with the visual mode allowed trainees to use gestures to add important information -for example, to help contextualise the lexical item by using a situation to illustrate the problematic item, as demonstrated by Victor's explanation of 'retroplanning' (Figure 7).

Firstly, in the verbal mode the trainee suggests that, when you plan an event, you start from one point. He combines the verbal and visual modes to give a suggestion (today) and an abstract deictic gesture points towards today that the trainee wants to be a point of common understanding (Figure 4, plate 3). The trainee then demonstrates the pointing gesture moving to the abstract reference to which he points in Figure 4, plate 4 (the date of the event). Presuming that this reference is secured, Victor then reuses a deictic towards this reference, accompanied by the date of the event and explains through a moving gesture that you plan backwards. Victor proceeds by giving a further contextualised example (Figure 8). In the second contextualisation, the trainee reuses the common referent of an activity that needs to be planned through the use of deictic gestures that contextualise his utterances in the verbal mode (this this and this). However, these gestures are not clearly framed in the webcam image and are barely accessible to his learner (Figure 8, plate 2). The trainee restates that you need to plan backwards and reuses a pointing gesture towards the gestural space for which the reference was previously secured as referring to the date of the final event (Figure 7, plate 5 & Figure 8, plate 4) and a diagonal gesture expressed with backwards (Figure 8, plate 5). In this example, the deictic gesture is no longer used with a verbal reference to the date of the event as this is understood as having been secured (Figure 8, plate 4). Rather, this gesture gives extra information about where you should start. The trainee does not need to explicitly restate that this is the date of the event as this information is communicated through his abstract deictic gesture. This gesture adds important information to the second contextualisation that is not given in the verbal mode, and cohesion to the explanation by tying together thematically related parts of the verbal discourse that are temporarily separated within the explanation. The trainees also used iconic gestures, to represent an action or an object, in their lexical explanations. For example, in Figure 9, when explaining birthday party, the trainee code switches and tries to use the English (cake). This is accompanied by a questioning facial expression (Figure 9, plate 1), showing to her learners that she may not be very sure of her translation. She then tries to explain using a context but, realising this may by culturally specific, adopts a questioning intonation throughout her turn. Adèle proceeds by using a numeric gesture (four o'clock) to explain that children eat. She mimes this action with an iconic gesture illustrating the physical movement of eating (Figure 9, plate 3) before using another gesture that accompanies 'something' and illustrates the physical property of the item she is referring to as small. The trainee then checks learners' comprehension of her explanation. This is not done verbally. Instead, the trainee uses the visual mode to seek a response through a questioning gesture (both hands, palm upwards, Figure 9, plate 6) accompanied by a facial expression and directs her gaze towards the webcam images of the learners. These visual cues signal a turn shift and offer learners the possibility to take the floor.

Figure 9: Use of iconic gestures A further multimodal strategy used by the trainees in their explanations was to use the text chat to send a hyperlink to an image. Figure 10 illustrates this strategy. The trainee, Victor, is explaining the lexical item 'mind map' (carte mentale). The sequence was trainee-initiated and occurred during the instruction-giving stage of an activity. As discussed previously, the trainee uses both a verbal and visual hesitator (Figure 10, plate 1) before proceeding with his explanation. The trainee suggests that he might have preferred to offer a direct translation to his learner -perhaps deeming this as cognitively less challenging -as he states his inability to use this strategy (I don't know at all what it is in English). The trainee proceeds with a verbal explanation and privileges a formal definition (it's a table which allows you to summarise information). This is accompanied by a metaphoric gesture (Figure 10, plate 2). It is barely visible in the webcam image but the trainee moves both hands, palms facing each other together. It appears that the gesture is for the trainee himself and helps him to forefront the 'summarising' property of an online mind map that he then uses in the verbal mode. Perhaps in response to there being no change in the facial expression of his learner, Victor then decides to send the learner a link to the mind map image that he had prepared for the activity. The change in which verbal modality is foregrounded is announced (I'll send you a mindmap) perhaps to explain why the trainee's gaze has moved from being directed towards the webcam downwards towards the right-hand corner of his screen. This does not engender a change in gaze on behalf of the learner. Potentially this is what prompts the trainee to explicitly announce the modality used (in the text chat, Figure 10 plate 5). As he does so, the learner's gaze shifts and he then changes posture away from his webcam whilst we see a movement of his right arm, seemingly towards his mouse. Whilst the audio modality was mainly used by the learners to acknowledge the trainees' explanations during the closing phases of learner-initiated sequences, the data analysis shows that these were accompanied visually by both sagittal head movements and facial expressions (Figure 11). However, the data also exemplifies a visual strategy used by the learners to mark the end of the lexical explanation side sequences before continuing with the main task. Learners move proxemically away from the webcam either during or just following the verbal acknowledgement, as if to mark the end of the side sequence within the interaction concerning the task. The closing sequences were also characterised by the trainees asking one of the learners who had acknowledged the explanation to (re)explain to his/her peer. However, this did not always allow the trainee to check the learner had understood. The data shows instances of the learner, although remaining in the visual mode, moving out of the interactional order and using the face-to-face classroom environment to complete this trainee request (Figure 12). In other instances, the learners were asked the translation of the item or for some information about the use of an equivalent term in English, for example whether the formal/informal second-person singular pronoun existed. The requests were accompanied in the visual mode by pensive gaze directed outside of the webcam frame.

Conclusion and Perspectives

Prior work has documented lexical explanations from a conversation analysis approach in face-to-face settings and has described protypical teaching sequences for both teacher and student-initiated explanations by a ternary model. However, the multimodal reality of the interaction situation is lost in this approach and nuances in the learning process may be overlooked. Whilst multimodal studies into synchronous environments other than written text environments are rare, potentially due to the demands of data capture as well as multimodal transcription, a growing body of research examines webconferencing-based environments from this perspective. Although some research has explored lexical explanations in this context, the topic has been focused upon within the wider context of instructional regulations or peer scaffolding. This qualitative study concentrated on three trainee teachers' lexical explanations during two sessions of a telecollaborative exchange and examined the different strategies employed during student-and teacher-initiated lexical explanations across the visual mode and text chat and audio modalities. The synchronous interactions provide access to emerging pedagogical and multimodal communication strategies for 'doing vocabulary teaching'. The data illustrated that in the openings of such sequences, the visual mode was used to project active listening strategies during student-initiated sequences whilst in teacher-initiated sequences, the audio modality was used to highlight target items in the TCU final position and the text chat provided a complementary role to help establish common ground concerning the target item. Shifts from the audio to text chat were signalled through gaze shifts which aided conversation management and allowed the trainees to either maintain an ongoing turn or signal the end of a turn.

Analysis of the visual mode in combination with the audio modality shed light on a 'thinking break' between the opening and explanation components of the sequence that trainees used to maintain a sense of coherence. There appears to be a continuum concerning the explicitness of this strategy that ranges from employing a pensive facial expression with gaze off screen and a verbal hesitator to the trainee momentarily removing him/herself from the interactional order. The synchronous nature of the environment requires trainees to offer unplanned, spontaneous explanations and this strategy, which introduces a pause in the interaction, may be one means to avoid cognitive overload.

Trainees employed a range of verbal strategies in their lexical explanations. These were accompanied, firstly, by deictic and iconic gestures that, if made visible in the webcam view for the learners, had a complementary role in their explanations and, secondly, by metaphoric gestures that helped foreground different properties of the lexical item in order to include them in a verbal explanation. The text chat modality was also employed to send hyperlinks to images but again, if used, this change in modality in the verbal mode was always signalled to learners in the visual mode and, if visual cues were not noticed by learners, in the audio modality. In addition, the data showed different strategies employed in the closing phases of the sequence: firstly, the combination of the audio modality and visual mode by learners to acknowledge the explanation offered; and, secondly, a change in learner proximity to the webcam that appears to signal the end of the side-sequence focusing on form and, by indicating a wish to return to the main theme, to offer the trainees indications of how to manage the continuation of the interaction.

The analysis conducted sheds light on trainee teachers' abilities to exploit different communication modes for the specific pedagogical purpose of lexical explanations. Although it provides descriptions of the combination of different communication modes in synchronous interaction for lexical explanations, it does not cover how the multimodal activities are received by the other participants as the interaction unfolds. Indeed a limitation of this study is that it does not include stimulated recall data. Due to the ecological nature of the corpus, where specific research questions stemmed from initial viewings of the data and did not govern its collection, combined with the demands of multimodal transcription, the researcher was confronted with the issue of no longer having access to the participants once the research question had been identified. One way to overcome this would be to employ eye-tracking data collection techniques during the initial synchronous data collection. This would advance our understanding of how participants 'read' the different multimodal interaction and whether modes are read simultaneously or different channels are foregrounded in reception [START_REF] O'rourke | Eyetracking in CALL: present and future[END_REF]Stickler & Shi, 2015). Given that each group in the telecollaborative exchange followed the same lesson plan, additional research on the same corpus has been conducted by other research team members to isolate a collection of lexical explanation sequences that focus on the same target item in order to conduct a comparative analysis of how different trainees manage the same teaching moment [START_REF] Holt | Conduire des explications lexicales[END_REF].

As Internet access by different learner populations improves, Higher Education institutions are increasingly interested in offering more flexible teaching and learning delivery methods that are often independent of place. Webconferencing-supported language teaching opens up possibilities of bringing together native speakers and learners of the target language and foreground synchronous interaction skills in distance learning. As the mediation of this language learning is through ever more sophisticated platforms, training online language teachers to become aware of the range of semiotic resources available to support different pedagogical practices, including the provision of lexical explanations, appears increasingly important.

Figure 1 :

 1 Figure 1: Text chat modality and gaze changes

Figure 2 :

 2 Figure 2: Changes in screen proximity

Figure 3 :

 3 Figure 3: Active listenership

Figure 4 :

 4 Figure 4: Checking target word

Figure 5 :

 5 Figure 5: Thinking face

Figure 7 :

 7 Figure 7: Deictic gestures during a contextualization

Figure 8 :

 8 Figure 8: Gesturing to previously secured references

Figure 10 :

 10 Figure 10: Text chat to send images

Figure

  Figure 11: Acknowledgement strategies

Figure 12 :

 12 Figure 12: Peer explanations in a different interactional order

Table 1 :

 1 Functionalities of Visu

	Text chat	No private channels available
	Video images (via	Large pictures of interlocutors and thumbnail images of
	webcam)	individual
	Markers	Personal notes that can be placed on the session
		timeline by trainees
	Multimedia activity	Notes, images, videos, hypermedia links that can be pre-
	resources	prepared by the trainees before the sessions
	Automatic recording Automatic recording of sessions (allowing trainees later
		re-viewing for training purposes)

Table 2 :

 2 Data extent

	Trainee		Victor	Samia	Adèle
	Learners		Liam	Sean & Angela	Alannah &
					Catriona
	Session length and number of verbal	Session 3	29min18s 656	31min55s 177	33min03s 1018
	turns	Session 4	34min00s 958	35min21s 783	34min28 2116

Table 3 :

 3 Types of teacher-initiated sequencesIn trainee-initiated sequences, trainees' turns are formulated to frame the target lexical item (Table3). The display questions that open the sequences follow a pause and comprise a change in direction of an ongoing turn constructional unit containing the target item (examples 1-2).

		3
	do you know what X is
	tu connais X	1
	do you know X
	et X c'est quoi alors Student_name/	1
	and X so what is it Student_name/
	est-ce que tu connais + description/	1
	do you know + description/
	est-ce que tu connais l'expression X	1
	do you know the expression X

savez/ tu sais ce que c'est X you know what X is 3 est-ce que vous savez / tu sais ce que c'est X

Table 4 :

 4 Types of learner-initiated sequences

	1

Table 5 :

 5 Verbal strategies

		1	co-elaboration (learner suggestion 	4
	substitution		refinement)
	translation + contextualisation	1	substitution	3
	hypernym + translation	1	formal definition	2
	formal definition	1	contextualisation	1

Also termed display questions. These are typically questions to which the questioner already knows the answer.

Transition relevance places are junctures in interaction where transition to another speaker is a possible next action. The transition may, but need not, occur (see[START_REF] Sacks | A Simplest Systematics for the Organization of Turn-Taking for Conversation[END_REF].

Acknowledgements

The author is grateful to the ASLAN project (ANR-10-LABX-0081) of Université de Lyon, for its financial support within the program "Investissements d'Avenir" (ANR-11-IDEX-0007) of the French government operated by the National Research Agency (ANR). This research was also supported by the Ulysses programme funded jointly by the Irish Research Council and the French Ministry of Foreign Affairs. Thanks to reviewers for their comments on the initial version of this paper.

Appendices