A A Shiryaev
email: shiryaev@phyche.ac.ru

F V Kaminsky

W Ludwig

D A Zolotov

A V Buzmakov

S V Titkov

Texture and genesis of polycrystalline varieties of diamond based on phase-contrast and diffraction contrast tomography

Keywords: carbonado, yakutite, cryptocrystalline diamond, texture, phase-contrast tomography, Diffraction-contrast tomography

Structural peculiarities of several types of cryptocrystalline diamond varieties: carbonado, impact-related yakutite and cryptocrystalline diamond aggregates from kimberlite were studied using Infrared spectroscopy, X-ray diffraction contrast (DCT -Diffraction Contrast Tomography) and phase contrast tomography (PCT). It is shown that the porosity of the carbonado and kimberlitic cryptocrystalline aggregates is similar being in range of 5-10 vol%, possibly indicating similar formation mechanism(s), whereas that of yakutite is essentially zero. Crystallographic texture is observed for some carbonado samples. It is suggested that at least partially the texture is explained by deformation-related bands. Infrared spectroscopy reveals presence of hydrous and, probably, of hydrocarbon species in carbonado.

INTRODUCTION

Several types of natural polycrystalline diamonds are known [START_REF] Jeynes | Natural polycrystalline diamond[END_REF][START_REF] Sunagawa | Morphology of natural, synthetic diamond crystals[END_REF][START_REF] Yu | Mineralogy of Diamond[END_REF]. They span a range from simple aggregates such as boart and diamondite with various grain sizes and whose formation mechanism is likely similar to that of single crystals, to cryptocrystalline varieties such as carbonado and yakutite. Carbonado is a very peculiar and enigmatic variety of natural diamond. It is a black or dark-brown, cryptocrystalline, porous diamond aggregate [START_REF] Kaminsky | Carbonado and yakutite: properties and possible genesis[END_REF] of undetermined origin. Morphological and mineralogical properties of carbonado differ considerably from those of diamond single crystals and polycrystalline aggregates related to kimberlites and lamproites. Primary source(s) of carbonado remains elusive; they are found only in placer deposits in Brazil, Central African Republic, Russian Far East, and possibly Venezuela [START_REF] Kaminsky | Carbonado and yakutite: properties and possible genesis[END_REF]. One of the peculiarities of carbonado, in addition to mineral inclusions typical for crustal conditions, is its microstructure: it is composed of diamond micro-grains (crystallites) with sizes ranging from 0.5-1 to several tens of micrometers [START_REF] Magee | Constrains from luminescence on the history and origin of carbonado[END_REF][START_REF] De | Chemical heterogeneity in carbonado, an enigmatic polycrystalline diamond[END_REF][START_REF] Petrovsky | Morphology and defects of diamond grains in carbonado: clues to carbonado genesis[END_REF]. Grain boundaries between crystallites often form zigzag-like pattern, and overall have some similarities with sintered diamonds. In the same time, some of fine-crystalline polycrystals (fine-grained and cryptocrystalline boart, diamondite) from kimberlite pipes [START_REF] Jeynes | Natural polycrystalline diamond[END_REF][START_REF] Kaminskiy | Bort with garnet from the Mir pipe, Yakutia[END_REF][START_REF] Titkov | Geochemistry and genesis of carbonado from Yakutian diamond deposits[END_REF][START_REF] Spetsius | Diamonds of Yakutia: Photographic Evidence for their Origin[END_REF][START_REF] Sobolev | Polycrystalline diamond aggregates from the Mir kimberlite pipe, Yakutia: Evidence for mantle metasomatism[END_REF], from Avacha volcano, Kamchatka [START_REF] Kaminsky | Carbonado-like diamond from the Avacha active volcano in Kamchatka, Russia[END_REF] and yakutitea Popigai crater impact ejecta (Orlov and Kaminskiy 1981;[START_REF] Titkov | Shapeless dark diamonds (yakutites) from the placers of the Siberian platform and criteria of their impact origin[END_REF][START_REF] Yelisseyev | Yakutites: Are they impact diamonds from the Popigai crater?[END_REF] exhibit features similar to classical carbonado from Brazil and Central Africa. Contradictory observations, such as coexistence of highly reduced and oxidized mineral inclusions, have given rise to numerous hypotheses concerning the genesis of carbonado, ranging from deep mantle horizons [START_REF] Nadolinny | Observation and interpretation of paramagnetic defects in Brazilian and Central African carbonados[END_REF][START_REF] Petrovsky | Morphology and defects of diamond grains in carbonado: clues to carbonado genesis[END_REF] to near-surface conditions [START_REF] Kaminsky | Origin of polycrystalline carbonado diamond aggregates[END_REF].

Studies of carbonado structure are numerous and were performed using transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) [START_REF] Trueb | Carbonado: a microstructural study[END_REF][START_REF] Moriyoshi | The microstructure of natural polycrystal diamond, carbonado, and ballas[END_REF][START_REF] De | Microstructural observations of polycrystalline diamond: a contribution to the carbonado conundrum[END_REF][START_REF] Chen | Microstructure of tough polycrystalline natural diamond[END_REF][START_REF] Sautter | Petrogenesis of mineral micro-inclusions in an uncommon carbonado[END_REF][START_REF] Ishibashi | Hydrous fluid as the growth media of natural polycrystalline diamond, carbonado: implication from IR spectra and microtextural observations[END_REF][START_REF] Kaminsky | Internal texture and syngenetic inclusions in carbonado[END_REF], X-ray absorption tomography [START_REF] Ketcham | New textural evidence on the origin of carbonado diamond: an example of 3-D petrography using X-ray computed tomography[END_REF], neutron diffraction and transmission Kikuchi diffraction analysis [START_REF] Piazolo | Carbonado revisited: Insights from neutron diffraction analysis, high resolution orientation analysis and numerical simulations[END_REF]. EBSD demonstrated that the grain size distribution in several studied carbonado samples is indeed broad (1-55 µm), but is largely unimodal with a peak around 5-15 µm. In the same time, absence of a clear peak in the grain size distribution was found in Ishibashi et al., (2016, and references therein). Neutron diffraction allows investigation of bulk samples and provides statistics for thousands of grains against hundreds of grains in EBSD case, but due to lower fluence, is limited to relatively large grains. Both EBSD and neutron diffraction confirmed lack of crystallographic preferred orientation of crystallites in carbonado, although most grains exhibit locally significant internal plastic deformation [START_REF] Piazolo | Carbonado revisited: Insights from neutron diffraction analysis, high resolution orientation analysis and numerical simulations[END_REF], confirming earlier TEM results [START_REF] Trueb | Carbonado: a microstructural study[END_REF][START_REF] De | Microstructural observations of polycrystalline diamond: a contribution to the carbonado conundrum[END_REF]. On the other hand, X-ray absorption tomography demonstrated a preferred orientation of mineral inclusions and pores in a carbonado specimen [START_REF] Ketcham | New textural evidence on the origin of carbonado diamond: an example of 3-D petrography using X-ray computed tomography[END_REF]. Crystallographic texture of yakutite and mutual crystallographic orientation of diamond and its hexagonal polytypelonsdaleitewere addressed by X-ray diffraction in considerable detail [START_REF] Kharlashina | Textures of natural lonsdaleite-bearing diamonds[END_REF]Sokhor and Futergendler, 1975, respectively). Despite all these works, unambiguous scenario of carbonado formation is still lacking. In this contribution we characterize structural peculiarities of several cryptocrystalline diamond varieties: carbonado from Central African Republic, impact-related yakutite, and cryptocrystalline diamond aggregates from Yakutia using relatively novel techniques of diffraction contrast tomography (DCT) and phase contrast tomography (PCT). In addition, infrared (IR) spectroscopy in reflection and Attenuated Total Reflection (ATR) modes were used to extract information on nitrogen aggregation state and some inclusions. On this basis, we attempt to constrain mechanisms of formation of these polycrystalline varieties of diamond.

SAMPLES AND TECHNIQUES

Samples

The samples analyzed in this work are three Central-African grains (CAR-1, 2 and 3) collected from Ubangi River placer deposit, which were studied by [START_REF] Kaminsky | Internal texture and syngenetic inclusions in carbonado[END_REF] and [START_REF] Piazolo | Carbonado revisited: Insights from neutron diffraction analysis, high resolution orientation analysis and numerical simulations[END_REF]. They contain syngenetic inclusions of apatite, sulfides FeS and FeS2, SiO2, TiO2, Si-Ti-Al-Mg-Fe-Ca-K-O silicate, iron oxide, Ca-Mg-Sr carbonate, and various quench phases. According to [START_REF] Kaminsky | Internal texture and syngenetic inclusions in carbonado[END_REF] such inclusion suites might indicate crustal origin.

The yakutite sample was collected in a contemporary placer of the Olenyok River in Yakutia. It is a dark-gray irregular pebble with rounded surfaces, ~9 mm in size. The studied sample contains approximately 25-30 % of lonsdaleite admixture and has significantly smaller crystallite sizes (0.1-1 µm) than carbonado.

In addition, three samples of cryptocrystalline diamond aggregates from Yakutian kimberlites previously characterised by [START_REF] Titkov | Geochemistry and genesis of carbonado from Yakutian diamond deposits[END_REF] were also investigated. These samples contain micron-size inclusions of native Fe, Cr, Ni, rutile, sphalerite, pentlandite, muscovite, zircon-xenotime solid solutions and also epigenetic anatase, florensite, kaolinite and goetite. Debye rings in electron diffraction patterns indicate that significant fraction of diamond grains in these samples were below 1 μm. REE patterns determined by bulk neutron activation analysis correspond to typical kimberlites. Electron Paramagnetic resonance shows presence of the P1 (single substitutional nitrogen or the C-defect) and the W15 (single nitrogen with a vacancy, i.e., NV -) paramagnetic centers.

Methods

Infrared (IR) spectroscopy of micro-and nanocrystalline materials is often complicated

by strong light scattering on grain boundaries and other imperfections, if characteristic distance between the defects becomes comparable with the wavelength of the probing radiation. Most IR studies of diamond concentrate on bands corresponding to the diamond lattice (~5 µm) and to nitrogen defects (7-20 µm). As indicated above, an average carbonado sample contains grains of widely different sizes, but significant fraction may be smaller than these values. In addition, many carbonado samples contain numerous strongly absorbing inclusions. To overcome some of the difficulties, we have employed Attenuated Total Reflections (ATR) technique for investigation of the carbonado. Application of the ATR spectroscopy requires very good physical contact between the sample surface and the ATR crystal. IR spectra were acquired using Ge crystal with a tip diameter of 150 microns for two samples, however the acquisition was unsuccessful for the third one. IR spectra of polycrystalline diamonds were recorded using Diffuse reflectance attachment, the samples were placed on gold mirrors.

X-ray Diffraction contrast tomography (DCT) and phase contrast tomography (PCT)

were performed at the ID11 beamline of European Synchrotron Radiation Source. The DCT approach is based on acquisition of large number of 2D diffraction patterns separated by small angular distance, identification of grains, matching of Friedel pairs for every discernible grain and subsequent reconstruction of their shape and orientation. For detailed reviews of experimental protocol and evaluation procedure see [START_REF] Ludwig | Three-dimensional grain mapping by x-ray diffraction contrast tomography and the use of Friedel pairs in diffraction data analysis[END_REF] and [START_REF] Reischig | Advances in X-ray diffraction contrast tomography: flexibility in the setup geometry and application to multiphase materials[END_REF].

Despite relatively high energy of X-rays (40 keV) small lattice parameter of diamond required acquisition of the diffraction patterns in wide angular range which forced us to use small sample-to-detector distance. Irregular shape of the samples further complicated the experiment and we had to limit the investigated volume to apexes of the samples.

Phase contrast tomography differs from more widely employed absorption tomography in significantly higher sensitivity to grain boundaries, cracks etc. The pixel size of Freelon camera employed in the current study was 0.7 µm. Whole samples were studied.

Since extraction of porosity from the tomographic images can be performed by various algorithms with somewhat different results, we provide a brief description of the procedure used by us (see also [START_REF] Soille | Morphological Image Analysis: Principles and Applications[END_REF]. The treatment was performed using MATLAB Image Processing Toolbox. The first operation requires segmentation of every slice. To achieve this on the first step binarisation of the slices was performed. The imfill function was employed to equalize voids inside the sample with the background. Filtration with the imerode function with circular size of 2 pixels was employed to reduce noise. To select the total volume of the object smoothing using morphological closing operation was performed employing 10-pixel circular disk in the imerode.

Remaining unfilled domains were again treated using the imfill function. The mask obtained using this approach is a binary image, which allows robust calculation of the total volume. Similar procedure was used to separate inclusions of foreign phases and filled pores, but on the first step adaptive threshold filtration (function adaptthresh) and subsequent inversion of the binary mask were employed.

The approach described above was applied to all tomographic slices, which allowed extracting relative fractions of the pores and inclusions for every slice. One-dimensional median filtration was used for smoothing.

RESULTS

Infrared spectroscopy

FTIR spectra of the carbonado samples are shown in Fig. 1; for every sample, several spots were analysed. No bands related to diamond lattice or to nitrogen defects are observed. However, this is not surprising due to the micro-nanocrystalline nature of carbonado and such situation was earlier encountered both for natural carbonado (e.g., [START_REF] Ishibashi | Hydrous fluid as the growth media of natural polycrystalline diamond, carbonado: implication from IR spectra and microtextural observations[END_REF] and for several types of synthetic analogues [START_REF] Shiryaev | Spectroscopic study of defects and inclusions in bulk poly-and nanocrystalline diamond aggregates[END_REF]. In one-phonon region of the spectra broad peaks with maxima at 900, 1000 and 1030 cm -1 , presumably due to inclusions, are observed. Several other prominent features are present in all spectra: a strong doublet at 2920 cm -1 and broad bands centered at 1650 and 3200-3600 cm -1 . The first doublet is due to C-H bonds in methylene groups and might represent contamination, which has survived chemical cleaning preceding the IR study. However, keeping in mind presence of hydrocarbons in carbonado (Kaminsky et al., 1985) these bands may be related to such species. Two other bands are clearly related to vibrations of OH-groups and molecular water. Observation of these bands is in line with previous reports [START_REF] Magee | Constrains from luminescence on the history and origin of carbonado[END_REF][START_REF] Ishibashi | Hydrous fluid as the growth media of natural polycrystalline diamond, carbonado: implication from IR spectra and microtextural observations[END_REF] and is explained by presence of hydrous minerals and fluid microinclusions.

The polycrystalline diamond aggregates from Yakutian kimberlites were not polished and were investigated in diffuse reflectance mode. Their spectra differ from those of carbonado by presence of obvious diamond lattice bands and nitrogen defects represented by dominating Cdefects with some admixture of A-defects. Such spectra are typical for diamonds subjected to moderate annealing. Strong absorption bands due to water and OH-species are also present.

Phase contrast tomography

Representative tomographic slices from the studied samples are shown in Fig. 2. One can immediately recognize differences between the impact-related yakutite specimen from one side and carbonado and cryptocrystalline diamond aggregate. The yakutite contains only several cracks and is a dense material otherwise. We note here that examination of flaky impact-related diamonds from the Popigai crater itself (unpublished) also showed homogeneous internal structure. In the same time, the cryptocrystalline samples from Central Africa and Yakutia are clearly heterogeneous and contain both pores and inclusions. Some inclusions fill pores completely, some preserve open space. The inclusions could be connected to cracks, but in many cases they are fully surrounded by diamond matrix (see also [START_REF] Ketcham | New textural evidence on the origin of carbonado diamond: an example of 3-D petrography using X-ray computed tomography[END_REF]. The carbonado samples from African placers and cryptocrystalline aggregates from Yakutian kimberlites show significant similarities in geometry, sizes and spatial distribution of the pores.

The only marked difference is significantly lower concentration of inclusions in the latter case.

Image analysis of the slices was performed in order to estimate the relative pore fraction (Fig. 3), see Methods section for details. For some samples the contrast matrix/pore was too weak for reliable analysis, therefore Figure 3 shows results only for samples CAR2 and diamondites. The fraction of the pores is approx. 5-7% and all four samples are qualitatively similar.

X-ray diffraction contrast tomography

The studied yakutite specimen differs from the other samples by showing pronounced texture (see also [START_REF] Kharlashina | Textures of natural lonsdaleite-bearing diamonds[END_REF] and is not analysed further. One of the carbonado samples and all cryptocrystalline aggregates from Yakutia showed almost continuous Debye rings indicating very small grain sizes. Unfortunately, in such cases analysis of individual grains becomes impossible. Eventually this task can be solved by using a smaller X-ray beam and by scanning the sample. A 3D visualization of grains in two carbonado sample is shown in Fig. 4.

Projections of Orientation Distribution Functions (ODF) on several crystallographic planespole figures -are shown in Fig. 5. For CAR-1 624 grains were analysed, for CAR-2 -1100. In addition only the grains smaller than several arbitrary size thresholds were also plotted, but resulting pole figures are very similar to those obtained for the complete grains set.

Examination of the pole figures clearly show existence of a preferential orientation of diamond grains in [111]. A smaller grain fraction is oriented in [110]. Examination of spatial arrangement of the [110]-oriented grains in individual slices show that at least in some cases these grains form bands (Fig. 6).

DISCUSSION

This work presents new results on structure of several types of polycrystalline diamonds with presumably different formation mechanisms. The impact-related sampleyakutiteclearly stands off the row possessing very dense structure without obvious inclusions. Clear differences between structures of natural and synthetic impact diamonds and carbonado rule out exotic but still popular hypotheses relating carbonado to meteorites and extraterrestrial bodies.

The principal new observation on carbonado is clearly revealed [111] texture in two samples, which were previously studied using EBSD [START_REF] Kaminsky | Internal texture and syngenetic inclusions in carbonado[END_REF] and neutron diffraction [START_REF] Piazolo | Carbonado revisited: Insights from neutron diffraction analysis, high resolution orientation analysis and numerical simulations[END_REF]. The difference between all these studies likely stems from significantly higher statistics of the current study (up to 1000 grains) and acquisition of grainspecific three-dimensional information. We note here that our investigation is limited to grains exceeding certain size, namely, larger than 3-4 pixels, i.e. 2-3 microns, since shape of smaller grains can not be resolved in the current experiment.

Textured polycrystals can be produced by several independent mechanisms such as: 1) Crystallization process in which faceted crystallites are precipitated in ordered arrangement relative to each other.

2) Recrystallisation process leading to preferential growth of some grains in the expense of heavily strained ones.

3) Deformation leading to formation of preferential orientation.

Of course, these mechanisms are not mutually contradictory and may operate simultaneously or in sequence. Lets consider these mechanisms in detail.

A crystallisation process may produce ordered aggregates in several circumstances and the simplest one is an ordered settling or formation of individual grains possessing similar morphology. Crystallization of carbonado at slowly changing carbon supersaturation was suggested, for example, by [START_REF] Petrovsky | Morphology and defects of diamond grains in carbonado: clues to carbonado genesis[END_REF] on the basis of gradual changes in morphology and surface features of large (>5 microns) diamond grains.

The recrystallisation process was suggested to operate in carbonado and diamondite in order to explain fine details of internal structure [START_REF] Rubanova | Deformation microstructures reveal a complex mantle history for polycrystalline diamond[END_REF][START_REF] Piazolo | Carbonado revisited: Insights from neutron diffraction analysis, high resolution orientation analysis and numerical simulations[END_REF], in particular, serrated grain boundaries. Whereas this approach adequately describes some features, it implies extensive atomic diffusion. It is known, however, that self-diffusion in diamond is extremely sluggish [START_REF] Koga | Diffusive relaxation of carbon and nitrogen isotope heterogeneity in diamond: a new thermochronometer[END_REF] and even fine compositional zoning remains largely intact at mantle temperatures for time scales of several billion years. Infra-red data for carbonado suggest that the annealing of carbonado was insignificant both in time and temperature, since N aggregation state is low [START_REF] Kagi | Infrared and Raman spectroscopic observations of Central African carbonado and implications for its origin[END_REF]this work). Moreover, in deformation processes when two orthogonal slip systems operate (pure shear), serration of grains is not uncommon, thus obviating the recrystallisation process. We note also that in case of submicron grains diamond can be reversibly deformed elastically without cracking or generation of dislocations [START_REF] Banerjee | Ultralarge elastic deformation of nanoscale diamond[END_REF]; this mechanism might also operate in some grains during the deformation of the carbonado specimen.

Nevertheless, these contradictions could be at least partially resolved if extensive plastic deformation is present. At high temperatures diamond can be deformed plastically and under confinement pressure of 6 GPa the plastic behavior is observed already at 900 ˚C [START_REF] Devries | Plastic deformation and "work-hardening" of diamond[END_REF]. This process is widespread in nature, manifested, for example, in presence of birefringence in absolute majority of natural diamonds. In the same time, recrystallisation kinetics of (sub)microscopic grains strongly depend on surface diffusion, which is generally faster than of the bulk. Whereas the nitrogen aggregation is largely driven by relaxation of local strain in diamond lattice on scale of several tens of lattice parameters and formation of a N pair (the A-defect) greatly reduce the strain [START_REF] Briddon | Theory of impurities in diamond[END_REF], the mass flow of carbon atoms in a significant strain field may be well-pronounced as demonstrated by bending of a single crystal diamond plate for 8 degrees [START_REF] Evans | Plastic bending of diamond plates[END_REF]. In addition, plastic deformation introduces vacancies, which promote atomic diffusion and are detected as NV/W15 defects in photoluminescence/EPR spectra of carbonado (of course some vacancies are also produced by irradiation from radioactive inclusions) [START_REF] Yu | Distinctive features of natural polycrystalline diamonds[END_REF][START_REF] Petrovsky | Morphology and defects of diamond grains in carbonado: clues to carbonado genesis[END_REF][START_REF] Titkov | Geochemistry and genesis of carbonado from Yakutian diamond deposits[END_REF].

It is interesting to note that in most cases deformation of a polycrystal leads to rotation of grains. In view of this our observation that the [110]-oriented grains appear to be distributed not completely randomly, but instead they likely form kind of bands (fig. 6).

Another interesting result of the current study is observation of close similarities between porous structure of sensu stricto carbonado and kimberlitic cryptocrystalline diamond aggregates. We note here that extensive porosity does not contradict to high formation pressures: for example, bulk poly-and nanocrystalline diamonds with abundant pores filled with water and other materials were obtained at pressures of up to 25 GPa and temperatures in excess of 2000 ˚C [START_REF] Shiryaev | Spectroscopic study of defects and inclusions in bulk poly-and nanocrystalline diamond aggregates[END_REF]. Whereas the "real" carbonado differs from the cryptocrystalline aggregates from kimberlites in appearance and composition of inclusions, these variations might be explained assuming much older ages of Brazilian and African carbonadoes and complex history of their secondary alteration. Indeed, already the inclusions in Brazilian carbonado are dated as 3 Ga [START_REF] Sano | Ion microprobe Pb-Pb dating of carbonado, polycrystalline diamond[END_REF], indicating that the carbonado matrix itself should be older.

Results of the current study are in line with several previous studies where carbonado formation was described as growth of individual diamond crystallites in confined environment at high carbon supersaturation, their sintering and/or intergrowth and subsequent deformation at a later stage [START_REF] Burgess | He, Ar and C isotopes in coated and polycrystalline diamonds[END_REF][START_REF] De | Chemical heterogeneity in carbonado, an enigmatic polycrystalline diamond[END_REF][START_REF] Devries | Evidence for plastic deformation in the natural polycrystalline diamond, framesite[END_REF]Magee and Taylor, 1998;[START_REF] Petrovsky | Morphology and defects of diamond grains in carbonado: clues to carbonado genesis[END_REF][START_REF] Piazolo | Carbonado revisited: Insights from neutron diffraction analysis, high resolution orientation analysis and numerical simulations[END_REF]. In some works presence of two (and even three) populations of diamond crystallites in a single carbonado specimen was suggested (Magee and Taylor, 1998;[START_REF] De | Chemical heterogeneity in carbonado, an enigmatic polycrystalline diamond[END_REF][START_REF] Rondeau | New columnar texture of carbonado: cathodoluminescence study[END_REF], although temporal and genetic relationships between them remain unspecified. In other cases, a single population is inferred from grain size distribution [START_REF] Ishibashi | Relationships between textural and photoluminescence spectral features of carbonado (natural polycrystalline diamond) and implications for its origin[END_REF][START_REF] Kaminsky | Internal texture and syngenetic inclusions in carbonado[END_REF]. It is very likely that both cases are possible, and the two extreme cases ("multiple" vs "single" population of grains) represent various steps of one general process, which presumably operated at mantle conditions. Even isotopic and chemical (amount of N) heterogeneity of diamond grains in individual carbonado samples can be explained in this framework, since surface properties of different growth sectors [START_REF] Zedgenizov | Directional chemical variations in diamond showing octahedral following cuboid growth[END_REF]Reutsky et al., 2017a) and variations in growth rate [START_REF] Reutsky | Effect of diamond growth rate on carbon isotope fractionation in Fe-Ni-C system[END_REF][START_REF] Reutsky | Evidence for large scale fractionation of carbon isotopes and of nitrogen impurity during crystallization of gem quality cubic diamonds from placers of North Yakutia[END_REF]) may lead to noticeable variations of C, N isotopic composition and N content even within a single diamond crystal.

CONCLUSIONS

We present results of investigation of samples representing different types of poly-and cryptocrystalline diamond varieties using novel X-ray and spectroscopic techniques. The impactrelated diamondyakutiteclearly differs from the carbonado and kimberlitic diamond aggregate, thus ruling out possibility of impact origin of the later diamond varieties. However, results for the carbonado and the kimberlitic cryptocrystalline aggregate are more difficult to compare. Whereas some of the featuressuch as porosity, are fairly similar, other properties, in particular grain size distribution and spectroscopically-active impurities, differ in a nonsystematic way. We show that the grain size distribution is not a very robust criterion to distinguish between the sensu stricto carbonado from CAR and carbonado-like samples from kimberlites.

Our study provides new evidence for deformation stage in history of carbonado, which is manifested in marked crystallographic texture of the studied samples.

Presence of significant amount of hydrous and possibly hydrocarbon species in carbonado and kimberlitic cryptocrystalline diamonds is inferred from infrared spectroscopy.

Fig. 1 .

 1 Fig. 1. FTIR spectra of carbonado samples CAR-1 and CAR-3 (A), and of cryptocrystalline diamond aggregate from Yakutian kimberlites (B).

Fig. 2 .

 2 Fig. 2. Representative slices from phase tomography reconstructions for the studied samples. Pixel size 0.7 μm, Scale bar corresponds to 200 μm. Bright areas are inclusions. Top -CAR1, Second row: CAR2, Third rowdiamondite 88 and 89, Bottomdiamondite 90 and yakutite.

Fig. 4 .Fig. 5 .

 45 Fig. 4. 3D vizualisation of grains in samples CAR1 and CAR2 obtained from X-ray diffraction contrast tomography. Flat top surface reflects polished surface.

Acknowledgements

This work was supported by the Ministry of Science and Higher Education of Russian Federation.

Part of analysis was performed within the State assignment FSRC «Crystallography and Photonics» RAS.


Dr Maxime Bretonnier
email: maxime.bretonnier@chu-rennes.fr

Estelle Michinov
email: estelle.michinov@univ-rennes2.fr

Xavier Morandi
email: xavier.morandi@chu-rennes.fr

Laurent Riffaud
email: laurent.riffaud@chu-rennes.fr

Interruptions in Surgery: a comprehensive review Interruptions in surgery

Keywords: surgery, interruptions, disruptions, safety 2

Background: Recent literature showed that analysis of interruptions can contribute to evaluating the care process in the operating room and thus understanding potential errors which may occur during surgical procedures. The aim of this comprehensive review was to summarize current knowledge on the description and impact of interruptions in surgery.

Material and methods:

A literature search was conducted according to a set of criteria in the databases MEDLINE, BASE, Cochrane's Library and PsycINFO.

Results: 41 articles were included. 2 main methodological approaches were found, observational in the OR, or controlled in an experimental simulated environment.

Interruptions in the OR were manifold and several classifications were used. The severity of interruptions differed according to the category of the interruptions. Interruptions were influenced by team familiarity and the expertise of the surgical team; high team familiarity and a high level of expertise decreased the frequency of interruptions. However, our literature search lacked controlled studies carried out in the OR. Interruptions seemed to increase the workload and stress of the surgical team and impair non-technical skills, but no clear evidence of this was advanced.

Conclusions: Interruptions are probably risk factors for errors in the operating room.

However, there is as yet no clear evidence of the association of interruption frequency with errors in the operating room. There is a need to define and target interruptions which should be reduced, by putting safeguards in place, thereby allowing those which could be beneficial and neglecting those with no potential consequences.

Introduction

In 1999, the United States Institute of Medicine published a report distinguishing medical errors as the 8th leading cause of death in that country (98,000 deaths a year). [START_REF]of health care in America. To err is human: building a safer health system[END_REF] Surgical disciplines are largely concerned by these errors and up to 66% of medical adverse effects, defined as the occurrence of an undesired effect after treatment, are related to a surgical procedure. [START_REF] Gawande | The incidence and nature of surgical adverse events in Colorado and Utah in 1992[END_REF][START_REF] Etchells | Patient safety in surgery: error detection and prevention[END_REF] Because of the increased risk of morbidity and mortality during a surgical procedure, investigations into quality and safety issues in the operating room (OR) were conducted. The OR is a complex work environment, this research therefore involved multidisciplinary teams including human factor, [START_REF] Shouhed | Integrating human factors research and surgery: a review[END_REF] psychologist, [START_REF] Li | A systematic review of the psychological literature on interruption and its patient safety implications[END_REF] management, [START_REF] Jett | Work interrupted: a closer look at the role of interruptions in organizational life[END_REF] and ergonomic [START_REF] Trafton | Task Interruptions[END_REF] researchers.

There exist effective tools to assess quality and safety in the OR: adverse event measurement allows identification of potential errors in the surgical process, [START_REF] Etchells | Patient safety in surgery: error detection and prevention[END_REF] workload and stress assessment by validated scales points out their negative impact on surgical performance. [START_REF] Wilson | Development and validation of a surgical workload measure: The Surgery Task Load Index (SURG-TLX)[END_REF][START_REF] Yu | Quantifying intraoperative workloads across the surgical team roles: room for better balance?[END_REF][START_REF] Arora | The impact of stress on surgical performance: A systematic review of the literature[END_REF] It is now accepted that errors resulting from adverse events are mainly secondary to a lack of non-technical skills (NTS). [START_REF] Shouhed | Integrating human factors research and surgery: a review[END_REF] NTS are divided into cognitive (situation awareness, mental readiness, assessing risks…) and interpersonal (communication, leadership, teamwork, planning…) skills. [START_REF] Yull | Non-technical skills for surgeons in the operating room: a review of the literature[END_REF] Interruptions are defined as incidents or occurrences preventing the worker from progressing in his primary task. [START_REF] Jett | Work interrupted: a closer look at the role of interruptions in organizational life[END_REF] They constitute a well-studied phenomenon in occupational psychology and management, and their analysis is essential to evaluate the care process in the OR and to understand errors arising during surgical procedures. In the particular context of surgery, an interruption can be defined as a deviation in the normal course of the surgical procedure or surgical workflow. Interruptions at the work place can be differentiated into several types: intrusions, breaks, distractions, discrepancies. [START_REF] Jett | Work interrupted: a closer look at the role of interruptions in organizational life[END_REF] They may have both positive and negative consequences but they are mainly described as harmful in the literature. They impair quality of work and well-being and increase workload and time of completion, [START_REF] Foroughi | Do interruptions affect the quality of work?[END_REF][START_REF] Keus Van De Poll | Effects of task interruption and background speech on word processed writing: effects on writing performance[END_REF][START_REF] Zijlstra | Temporal factors in mental work: Effects of interrupted activities[END_REF][START_REF] Eyrolle | The effects of interruptions in work activity: Field and laboratory results[END_REF] particularly if the work task is complex. [START_REF] Furnham | Music is as distracting as noise: the differential distraction of background music and noise on the cognitive test performance of introverts and extraverts[END_REF][START_REF] Gillie | What makes interruptions disruptive? A study of length, similarity, and complexity[END_REF][START_REF] Trafton | Preparing to resume an interrupted task: effects of prospective goal encoding and retrospective rehearsal[END_REF][START_REF] Li | A systematic review of the psychological literature on interruption and its patient safety implications[END_REF] However, the negative impact of interruptions is not obvious for repetitive tasks: they accelerate the achievement of the main task without damaging the quality of work. [START_REF] Trafton | Task Interruptions[END_REF][START_REF] Keus Van De Poll | Effects of task interruption and background speech on word processed writing: effects on writing performance[END_REF] The impact of interruptions also depends on the worker's expertise: interruptions cause a poorer quality of work and an increased completion time for a novice when compared to an expert. [START_REF] Jett | Work interrupted: a closer look at the role of interruptions in organizational life[END_REF][START_REF] Li | A systematic review of the psychological literature on interruption and its patient safety implications[END_REF] Interruptions in surgical procedures have been examined in numerous studies, both in the OR and in simulated environments. Information acquired from these studies needs to be analyzed and summarized, since their methodologies and results were heterogeneous. A systematic review was published in 2016, but this study focused solely on distractions: these only represent a portion of the interruptions, which is why this literature review included only 17 studies. [START_REF] Mentis | A systematic review of the effect of distraction on surgeon performance: directions for operating room policy and surgical training[END_REF] No other review on the description and impact of interruptions on surgical procedure has been published. Through this comprehensive review, we aimed to summarize current knowledge on the description and impact of interruptions on surgical procedures. We first described interruptions particularities in surgery and then focused our description on their consequences.

Particular emphasis has been placed on trying to understand how interruptions can impair NTS and potentially threaten safety in the OR.

Material and methods

We conducted a comprehensive review of the literature. Two investigators (first and second authors) independently carried out literature searches in the databases MEDLINE, BASE, Cochrane's Library, PsycINFO in December 2018, without restriction of date of publication. The following keywords were searched: "surg*" or "operating room*" or A c c e p t e d M a n u s c r i p t "operating theatre*" or "task" or "work" and "interrupt*" or "distract*" or "disrupt*". Articles whose titles and abstracts were related to interruptions in surgery were reviewed. Inclusion criteria were: studies published in English, retrospective and prospective studies, reviews, studies carried out in the OR or in a simulated environment, studies whose main or secondary outcomes were descriptions and evaluation of the impact of interruptions on the surgical procedure or the surgical team. Exclusion criteria were: studies focusing on interruptions of the anaesthetic team. After reading eligible articles, we checked the references of those selected in order to enlarge our research to other relevant articles. Each article fulfilling the inclusion criteria was included in our review, the validity of the studies was assessed by the two investigators and consensus between them was used to resolve any disagreement.

Quality assessment of studies was evaluated using the NIH Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. 21 Quality assessment was carried out by both first and second authors. This tool permitted the evaluation of key method points for the studies included, in particular the definition of the research question and the population studied, the justification of the sample size, the inclusion/exclusion criteria.

Results

The flow diagram of our literature search is displayed in Figure A. Our review included 41 studies dealing with interruptions and surgery.

Studies' methodology

Two main methodological approaches have been reported:

•An observational approach in a natural environment for 15 studies. [START_REF] Zheng | A quantitative study of disruption in the operating room during laparoscopic antireflux surgery[END_REF][START_REF] Lingard | Communication failures in the operating room: an observational classification of recurrent types and effects[END_REF][START_REF] Wiegmann | Disruptions in surgical flow and their relationship to surgical errors: An exploratory investigation[END_REF][START_REF] Sevdalis | Distracting communications in the operating theatre[END_REF][START_REF] Antoniadis | Identification and interference of intraoperative distractions and interruptions in operating rooms[END_REF][START_REF] Sevdalis | Impact of intraoperative distractions on patient safety: a prospective descriptive study using validated instruments[END_REF][START_REF] Gillespie | Interruptions and miscommunications in surgery: an observational study[END_REF][START_REF] Persoon | The effect of distractions in the operating room during endourological procedures[END_REF][START_REF] Weigl | The impact of intra-operative interruptions on surgeons' perceived workload: an observational study in elective general and orthopedic surgery[END_REF][START_REF] Wheelock | The impact of operating room distractions on stress, workload, and teamwork[END_REF][START_REF] Allers | Evaluation and impact of workflow interruptions during robot-assisted surgery[END_REF][START_REF] Weber | Effects of flow disruptions on mental workload and surgical performance in robotic-assisted surgery[END_REF][START_REF] Willett | The impact of distractions and interruptions during Cesarean Sections: a prospective study in a London teaching hospital[END_REF][START_REF] Yoong | Interruptions and distractions in the gynaecological operating theatre: irritating or dangerous?[END_REF][START_REF] Henaux | Relationships between expertise, crew familiarity and surgical workflow disruptions: an observational study[END_REF] The goals were to quantify and characterize interruptions according to their type and impact on the surgical team. Some studies evaluated correlations between interruptions and NTS performance, workload or stress. [START_REF] Weigl | The impact of intra-operative interruptions on surgeons' perceived workload: an observational study in elective general and orthopedic surgery[END_REF][START_REF] Wheelock | The impact of operating room distractions on stress, workload, and teamwork[END_REF] A c c e p t e d M a n u s c r i p t

•An experimental approach in a simulated environment for 15 studies. [START_REF] Szafranski | Distractions and surgical proficiency: an educational perspective[END_REF][START_REF] Pluyter | Do absorption and realistic distraction influence performance of component task surgical procedure?[END_REF][START_REF] Park | Effect of distraction on simulated anterior segment surgical performance[END_REF][START_REF] Goodell | Effects of cognitive distraction on performance of laparoscopic surgical tasks[END_REF][START_REF] Hsu | Experienced surgeons can do more than one thing at a time: effect of distraction on performance of a simple laparoscopic and cognitive task by experienced and novice surgeons[END_REF][START_REF] Weigl | Intraoperative disruptions, surgeon's mental workload, and technical performance in a full-scale simulated procedure[END_REF][START_REF] Moorthy | Objective evaluation of the effect of noise on the performance of a complex laparoscopic task[END_REF][START_REF] Miskovic | Randomized controlled trial investigating the effect of music on the virtual reality laparoscopic learning performance of novice surgeons[END_REF][START_REF] Feuerbacher | Realistic distractions and interruptions that impair simulated surgical performance by novice surgeons[END_REF][START_REF] Suh | The negative effect of distraction on performance of robot-assisted surgical skills in medical students and residents[END_REF][START_REF] Zheng | A quantitative study of disruption in the operating room during laparoscopic antireflux surgery[END_REF][START_REF] Murji | Evaluating the effect of distractions in the operating room on clinical decision-making and patient safety[END_REF][START_REF] Allers | Evaluation and impact of workflow interruptions during robot-assisted surgery[END_REF][START_REF] Sujka | Simulation-based testing of pager interruptions during laparoscopic cholecystectomy[END_REF][START_REF] Persoon | Effect of distraction on the performance of endourological tasks: a randomized controlled trial[END_REF] Comparisons were made between an experimental and a control group during surgical simulation were performed. For example, two groups carried out the same task, during which one of the two was interrupted (by a distraction or a secondary task). Judgment criteria varied: frequency of errors, time of realization, evaluation of workload, learning of technical gesture.

Other studies using different methodological approaches were published:

•Development and validation of interruption measurement tools useful for research were reported in 7 studies. [START_REF] Healey | A method for measuring work interference in surgical teams[END_REF][START_REF] Sevdalis | Annoyances, disruptions, and interruptions in surgery: the disruptions in surgery index (DiSI)[END_REF][START_REF] Morgan | Capturing intraoperative process deviations using a direct observational approach: the glitch method[END_REF][START_REF] Parker | Development and evaluation of an observational tool for assessing surgical flow disruptions and their impact on surgical performance[END_REF][START_REF] Healey | Measuring intra-operative interference from distraction and interruption observed in the operating theatre[END_REF][START_REF] Healey | Quantifying distraction and interruption in urological surgery[END_REF][START_REF] Seelandt | Assessing distractors and teamwork during surgery: developing an event-based method for direct observation[END_REF] These studies used interruption classifications, or interruption severity scores. One study developed a score which calculated the impact of interruptions reported by surgical staff after surgery. [START_REF] Sevdalis | Annoyances, disruptions, and interruptions in surgery: the disruptions in surgery index (DiSI)[END_REF] •2 retrospective observational studies were performed: they described interruptions reported by medical and paramedical staff. [START_REF] Lee | Evaluation of potential distractors in the urology operating room[END_REF][START_REF] Elfering | Workflow interruptions and failed action regulation in surgery personnel[END_REF] •One interventional study tested a measure of interruption reduction in the OR. [START_REF] Wright | Implementing no interruption zones in the perioperative environment[END_REF] Five phases of risk were defined during a surgical procedure (anesthesia induction, surgical briefing, specimen collection, final surgical counts and debriefing, anesthesia emergence). The staff was educated to reduce interruptions during these 5 phases.

Results showed a significant decrease in recorded noise level during these 5 phases after staff education.

•A systematic review of the impact of interruptions on surgical performance was published in 2016 including 17 articles. This study did not deal with the impact of interruptions on NTS. [START_REF] Mentis | A systematic review of the effect of distraction on surgeon performance: directions for operating room policy and surgical training[END_REF]

Categories of interruptions

A c c e p t e d M a n u s c r i p t

Table A summarized all the studies carried out in the OR whose primary or secondary objective was description of interruptions. Quality assessment of studies is reported.

Numbers of interruptions per hour varied from one study to another and ranged from 2.4/h to 114/h. However, classification of interruptions differed between studies. This rendered impossible the comparison of studies in terms of numbers of interruptions and categories observed. For example, some studies focused only on interruptions related to communication issues. [START_REF] Lingard | Communication failures in the operating room: an observational classification of recurrent types and effects[END_REF][START_REF] Sevdalis | Distracting communications in the operating theatre[END_REF] The most common categories of interruptions were: communication issues, [START_REF] Zheng | A quantitative study of disruption in the operating room during laparoscopic antireflux surgery[END_REF][START_REF] Sevdalis | Impact of intraoperative distractions on patient safety: a prospective descriptive study using validated instruments[END_REF][START_REF] Weigl | The impact of intra-operative interruptions on surgeons' perceived workload: an observational study in elective general and orthopedic surgery[END_REF][START_REF] Wheelock | The impact of operating room distractions on stress, workload, and teamwork[END_REF][START_REF] Weber | Effects of flow disruptions on mental workload and surgical performance in robotic-assisted surgery[END_REF][START_REF] Willett | The impact of distractions and interruptions during Cesarean Sections: a prospective study in a London teaching hospital[END_REF][START_REF] Henaux | Relationships between expertise, crew familiarity and surgical workflow disruptions: an observational study[END_REF][START_REF] Healey | Quantifying distraction and interruption in urological surgery[END_REF] telephone/beeper, [START_REF] Antoniadis | Identification and interference of intraoperative distractions and interruptions in operating rooms[END_REF][START_REF] Weigl | The impact of intra-operative interruptions on surgeons' perceived workload: an observational study in elective general and orthopedic surgery[END_REF][START_REF] Parker | Development and evaluation of an observational tool for assessing surgical flow disruptions and their impact on surgical performance[END_REF][START_REF] Healey | Measuring intra-operative interference from distraction and interruption observed in the operating theatre[END_REF][START_REF] Healey | Quantifying distraction and interruption in urological surgery[END_REF] entrances and exits, [START_REF] Antoniadis | Identification and interference of intraoperative distractions and interruptions in operating rooms[END_REF][START_REF] Persoon | The effect of distractions in the operating room during endourological procedures[END_REF][START_REF] Weigl | The impact of intra-operative interruptions on surgeons' perceived workload: an observational study in elective general and orthopedic surgery[END_REF][START_REF] Weber | Effects of flow disruptions on mental workload and surgical performance in robotic-assisted surgery[END_REF][START_REF] Willett | The impact of distractions and interruptions during Cesarean Sections: a prospective study in a London teaching hospital[END_REF] intrusions by outside personnel, [START_REF] Wiegmann | Disruptions in surgical flow and their relationship to surgical errors: An exploratory investigation[END_REF][START_REF] Wheelock | The impact of operating room distractions on stress, workload, and teamwork[END_REF] equipment issues, [START_REF] Sevdalis | Impact of intraoperative distractions on patient safety: a prospective descriptive study using validated instruments[END_REF][START_REF] Allers | Evaluation and impact of workflow interruptions during robot-assisted surgery[END_REF][START_REF] Healey | A method for measuring work interference in surgical teams[END_REF] work environment issues, [START_REF] Healey | A method for measuring work interference in surgical teams[END_REF][START_REF] Healey | Quantifying distraction and interruption in urological surgery[END_REF] movements around the monitors, [START_REF] Healey | A method for measuring work interference in surgical teams[END_REF][START_REF] Healey | Measuring intra-operative interference from distraction and interruption observed in the operating theatre[END_REF] procedural issues, [START_REF] Weber | Effects of flow disruptions on mental workload and surgical performance in robotic-assisted surgery[END_REF][START_REF] Healey | A method for measuring work interference in surgical teams[END_REF] distractions, [START_REF] Henaux | Relationships between expertise, crew familiarity and surgical workflow disruptions: an observational study[END_REF][START_REF] Morgan | Capturing intraoperative process deviations using a direct observational approach: the glitch method[END_REF] teamwork issues, [START_REF] Wiegmann | Disruptions in surgical flow and their relationship to surgical errors: An exploratory investigation[END_REF] and supervision/training. [START_REF] Allers | Evaluation and impact of workflow interruptions during robot-assisted surgery[END_REF]

Severity of interruptions

Severity or interference of interruptions was also studied. This was defined as the effect of interruptions on the surgical workflow, classified by the observer. Several scales were used to measure the interference or severity of interruptions: these are reported in Table A. The scales were established on the same principle in the majority of studies. Interference ranked from absence of impact on the workflow up to the complete cessation of the surgical procedure (an example of classification is shown in Table B). [START_REF] Sevdalis | Distracting communications in the operating theatre[END_REF][START_REF] Antoniadis | Identification and interference of intraoperative distractions and interruptions in operating rooms[END_REF][START_REF] Sevdalis | Impact of intraoperative distractions on patient safety: a prospective descriptive study using validated instruments[END_REF][START_REF] Persoon | The effect of distractions in the operating room during endourological procedures[END_REF][START_REF] Weigl | The impact of intra-operative interruptions on surgeons' perceived workload: an observational study in elective general and orthopedic surgery[END_REF][START_REF] Wheelock | The impact of operating room distractions on stress, workload, and teamwork[END_REF][START_REF] Weber | Effects of flow disruptions on mental workload and surgical performance in robotic-assisted surgery[END_REF][START_REF] Willett | The impact of distractions and interruptions during Cesarean Sections: a prospective study in a London teaching hospital[END_REF][START_REF] Yoong | Interruptions and distractions in the gynaecological operating theatre: irritating or dangerous?[END_REF][START_REF] Healey | A method for measuring work interference in surgical teams[END_REF][START_REF] Parker | Development and evaluation of an observational tool for assessing surgical flow disruptions and their impact on surgical performance[END_REF][START_REF] Healey | Measuring intra-operative interference from distraction and interruption observed in the operating theatre[END_REF][START_REF] Healey | Quantifying distraction and interruption in urological surgery[END_REF] Other studies used different methods to assess the interference of interruptions. Lingard et al. classified the observed effects of communication failures (detailed in Table A). [START_REF] Lingard | Communication failures in the operating room: an observational classification of recurrent types and effects[END_REF] Zheng et al. and Henaux et al. demonstrated a considerable increase in surgical procedure duration caused by interruptions. [START_REF] Zheng | A quantitative study of disruption in the operating room during laparoscopic antireflux surgery[END_REF][START_REF] Henaux | Relationships between expertise, crew familiarity and surgical workflow disruptions: an observational study[END_REF] A c c e p t e d

M a n u s c r i p t

Interruptions with the highest rates on scales of severity were: malfunction/shortage of equipment issues, [START_REF] Antoniadis | Identification and interference of intraoperative distractions and interruptions in operating rooms[END_REF][START_REF] Persoon | The effect of distractions in the operating room during endourological procedures[END_REF][START_REF] Weigl | The impact of intra-operative interruptions on surgeons' perceived workload: an observational study in elective general and orthopedic surgery[END_REF][START_REF] Wheelock | The impact of operating room distractions on stress, workload, and teamwork[END_REF][START_REF] Weber | Effects of flow disruptions on mental workload and surgical performance in robotic-assisted surgery[END_REF][START_REF] Healey | A method for measuring work interference in surgical teams[END_REF][START_REF] Parker | Development and evaluation of an observational tool for assessing surgical flow disruptions and their impact on surgical performance[END_REF][START_REF] Healey | Measuring intra-operative interference from distraction and interruption observed in the operating theatre[END_REF][START_REF] Healey | Quantifying distraction and interruption in urological surgery[END_REF] procedural issues (i.e. intrinsic to the surgical procedure), 29- 31,52,56,57 work environment issues, [START_REF] Antoniadis | Identification and interference of intraoperative distractions and interruptions in operating rooms[END_REF][START_REF] Healey | A method for measuring work interference in surgical teams[END_REF][START_REF] Healey | Measuring intra-operative interference from distraction and interruption observed in the operating theatre[END_REF] communication issues, [START_REF] Sevdalis | Impact of intraoperative distractions on patient safety: a prospective descriptive study using validated instruments[END_REF][START_REF] Persoon | The effect of distractions in the operating room during endourological procedures[END_REF][START_REF] Wheelock | The impact of operating room distractions on stress, workload, and teamwork[END_REF][START_REF] Healey | Quantifying distraction and interruption in urological surgery[END_REF] distractions 57 and changes of instruments. [START_REF] Zheng | A quantitative study of disruption in the operating room during laparoscopic antireflux surgery[END_REF][START_REF] Weber | Effects of flow disruptions on mental workload and surgical performance in robotic-assisted surgery[END_REF] The most severe interruptions were not the most frequent.

Timing of interruptions during the surgical procedure

Three studies presented data on the onset of interruptions during the intraoperative phase (from incision to closure). Their results were concordant as the majority of interruptions were observed at the beginning of the procedure. Antoniadis et al. showed that interruptions were significantly more frequent in the first quarter of the surgical procedure. [START_REF] Antoniadis | Identification and interference of intraoperative distractions and interruptions in operating rooms[END_REF] Morgan et al.

reported that their number was constant during the first 3 quarters and then decreased. [START_REF] Morgan | Capturing intraoperative process deviations using a direct observational approach: the glitch method[END_REF] Yoong et al. found that 90% of interruptions occurred during the first 30 minutes. [START_REF] Yoong | Interruptions and distractions in the gynaecological operating theatre: irritating or dangerous?[END_REF] Data concerning the precise phase of the surgical procedure were not specified.

Protagonists of interruptions

Seven studies performed in the OR described the groups of protagonists as the source or the target of interruptions. The OR staff was divided into 3 groups: "anesthesia" (anesthesiologist, nurse anesthetists), "surgical" (surgeon, assistant), "nurse" (scrub and circulating nurse). [START_REF] Sevdalis | Distracting communications in the operating theatre[END_REF][START_REF] Antoniadis | Identification and interference of intraoperative distractions and interruptions in operating rooms[END_REF][START_REF] Sevdalis | Impact of intraoperative distractions on patient safety: a prospective descriptive study using validated instruments[END_REF][START_REF] Gillespie | Interruptions and miscommunications in surgery: an observational study[END_REF][START_REF] Persoon | The effect of distractions in the operating room during endourological procedures[END_REF][START_REF] Wheelock | The impact of operating room distractions on stress, workload, and teamwork[END_REF][START_REF] Henaux | Relationships between expertise, crew familiarity and surgical workflow disruptions: an observational study[END_REF][START_REF] Healey | Measuring intra-operative interference from distraction and interruption observed in the operating theatre[END_REF] These studies led to the following conclusions:

•All groups could be a source or a target of interruptions •Proportions of different categories of interruptions depended on the source and the target •The degree of interference for the same category of interruption was not identical from one group to another •The surgical group was the most often targeted by interruptions.

A c c e p t e d M a n u s c r i p t

Factors related to interruptions

The occurrence of interruptions was mainly dependent on the following factors:

•Team familiarity, referring to a group of people used to working together, sharing a similar mental model. "Mental models can be defined as knowledge structures which allow individuals to describe, explain and predict events in their environment". [START_REF] Mathieu | The influence of shared mental models on team process and performance[END_REF] Sharing mental models allows a team to work efficiently and to adapt quickly to a situation. [START_REF] Mathieu | The influence of shared mental models on team process and performance[END_REF] It has been demonstrated that a high level of familiarity decreases the number of interruptions, [START_REF] Gillespie | Interruptions and miscommunications in surgery: an observational study[END_REF][START_REF] Henaux | Relationships between expertise, crew familiarity and surgical workflow disruptions: an observational study[END_REF][START_REF] Allers | Evaluation and impact of workflow interruptions during robot-assisted surgery[END_REF] improves the performance of the surgical team by decreasing the duration of the surgical procedure [START_REF] Elbardissi | Cumulative team experience matters more than individual surgeon experience in cardiac surgery[END_REF] and postoperative complications, [START_REF] Kurmann | Impact of team familiarity in the operating room on surgical complications[END_REF] and by promoting teamwork and communication. [START_REF] Maruthappu | The impact of team familiarity and surgical experience on operative efficiency: a retrospective analysis[END_REF] •Technology. Interruptions related to equipment problems represented the highest risk of significant impact on the surgical procedure. [START_REF] Antoniadis | Identification and interference of intraoperative distractions and interruptions in operating rooms[END_REF][START_REF] Persoon | The effect of distractions in the operating room during endourological procedures[END_REF][START_REF] Weigl | The impact of intra-operative interruptions on surgeons' perceived workload: an observational study in elective general and orthopedic surgery[END_REF][START_REF] Wheelock | The impact of operating room distractions on stress, workload, and teamwork[END_REF][START_REF] Weber | Effects of flow disruptions on mental workload and surgical performance in robotic-assisted surgery[END_REF][START_REF] Healey | A method for measuring work interference in surgical teams[END_REF][START_REF] Parker | Development and evaluation of an observational tool for assessing surgical flow disruptions and their impact on surgical performance[END_REF][START_REF] Healey | Measuring intra-operative interference from distraction and interruption observed in the operating theatre[END_REF][START_REF] Healey | Quantifying distraction and interruption in urological surgery[END_REF] Thus, a surgical procedure requiring many technological tools would be more likely to be exposed to interruptions responsible for serious interference.

•Expertise. This aspect was studied in experimental simulation studies comparing experts and novices during the performance of an interrupted task. These studies showed that experts were superior to novices in terms of accuracy in performing the secondary task [START_REF] Park | Effect of distraction on simulated anterior segment surgical performance[END_REF][START_REF] Hsu | Experienced surgeons can do more than one thing at a time: effect of distraction on performance of a simple laparoscopic and cognitive task by experienced and novice surgeons[END_REF][START_REF] Suh | The negative effect of distraction on performance of robot-assisted surgical skills in medical students and residents[END_REF] and in speed of execution. [START_REF] Suh | The negative effect of distraction on performance of robot-assisted surgical skills in medical students and residents[END_REF] One observational study carried out in the OR concluded that expertise of the dyad surgeon/scrub nurse decreased the length of interruptions. [START_REF] Henaux | Relationships between expertise, crew familiarity and surgical workflow disruptions: an observational study[END_REF]

Impact of interruptions

Interruptions altered quality and safety in the OR. Wiegmann et al. [START_REF] Wiegmann | Disruptions in surgical flow and their relationship to surgical errors: An exploratory investigation[END_REF] showed a correlation between interruptions and errors during 31 cardiothoracic surgeries. Several studies contribute to explaining this correlation. Wheelock et al. showed that interruptions were correlated with higher stress of the surgical team in 90 general surgeries. [START_REF] Wheelock | The impact of operating room distractions on stress, workload, and teamwork[END_REF] Weber et al.

A c c e p t e d

M a n u s c r i p t reported that interruptions were associated with higher workload and stress in 40 roboticassisted prostatectomies and Weigl et al. reported a correlation between interruptions and a higher workload in 56 general and orthopedic surgeries. [START_REF] Weigl | The impact of intra-operative interruptions on surgeons' perceived workload: an observational study in elective general and orthopedic surgery[END_REF][START_REF] Weber | Effects of flow disruptions on mental workload and surgical performance in robotic-assisted surgery[END_REF] Sevdalis et al. showed that intraoperative distracting communications were associated with deterioration of the use of a safety checklist in 19 urological surgeries. [START_REF] Sevdalis | Impact of intraoperative distractions on patient safety: a prospective descriptive study using validated instruments[END_REF] Healey et al. showed a relationship between better teamwork (measured by the Observational Teamwork Assessment for Surgery (OTAS))

and lower intraoperative interference of interruptions. [START_REF] Healey | A method for measuring work interference in surgical teams[END_REF] On the contrary, Allers et al. did not find a correlation between interruptions and workload, [START_REF] Allers | Evaluation and impact of workflow interruptions during robot-assisted surgery[END_REF] Yoong et al. reported the absence of correlation between interruptions and surgical complications. [START_REF] Yoong | Interruptions and distractions in the gynaecological operating theatre: irritating or dangerous?[END_REF] Several experimental studies in simulated environments were conducted. [START_REF] Szafranski | Distractions and surgical proficiency: an educational perspective[END_REF][START_REF] Pluyter | Do absorption and realistic distraction influence performance of component task surgical procedure?[END_REF][START_REF] Park | Effect of distraction on simulated anterior segment surgical performance[END_REF][START_REF] Goodell | Effects of cognitive distraction on performance of laparoscopic surgical tasks[END_REF][START_REF] Hsu | Experienced surgeons can do more than one thing at a time: effect of distraction on performance of a simple laparoscopic and cognitive task by experienced and novice surgeons[END_REF][START_REF] Weigl | Intraoperative disruptions, surgeon's mental workload, and technical performance in a full-scale simulated procedure[END_REF][START_REF] Moorthy | Objective evaluation of the effect of noise on the performance of a complex laparoscopic task[END_REF][START_REF] Miskovic | Randomized controlled trial investigating the effect of music on the virtual reality laparoscopic learning performance of novice surgeons[END_REF][START_REF] Feuerbacher | Realistic distractions and interruptions that impair simulated surgical performance by novice surgeons[END_REF][START_REF] Suh | The negative effect of distraction on performance of robot-assisted surgical skills in medical students and residents[END_REF][START_REF] Zheng | A quantitative study of disruption in the operating room during laparoscopic antireflux surgery[END_REF] These studies showed that both rate of errors and time of completion increased when the surgeons were interrupted during the main task accomplishment and the secondary task. Performance deterioration was greater for novices than for experienced surgeons. One study demonstrated a positive aspect of coping with interruptions during learning. [START_REF] Szafranski | Distractions and surgical proficiency: an educational perspective[END_REF] It compared the performance of two groups of novices after learning a surgical procedure on a simulator in the presence or absence of interruptions (noise and visual distraction). This study showed that the group trained in the interrupted condition was more efficient than the group trained without interruption when they were compared in real conditions.

Discussion

Observation and impact of interruptions

There were two main methodological approaches identified in this review. The first one was observational in a natural environment. This approach showed that interruptions were commonly observed in the OR and in various specialties, the frequency of interruptions ranged from 2.4/h to 114/h. The classification of interruptions and their severity differed from A c c e p t e d M a n u s c r i p t one study to another as mentioned in the results section. This heterogeneity made it difficult to compare studies. However, similar categories of interruptions were most frequently observed, the results being comparable from one study to another. These observational studies made it possible to define an image of the most frequent interruptions (such as communication issues or distractions) and of the most severe (such as equipment or procedural issues). Several studies carried out in a natural environment evaluated the impact of interruptions on the quality and safety of surgical procedures. Some studies showed that interruptions increased the workload, [START_REF] Weigl | The impact of intra-operative interruptions on surgeons' perceived workload: an observational study in elective general and orthopedic surgery[END_REF][START_REF] Weber | Effects of flow disruptions on mental workload and surgical performance in robotic-assisted surgery[END_REF] stress [START_REF] Wheelock | The impact of operating room distractions on stress, workload, and teamwork[END_REF] or risk of errors. [START_REF] Wiegmann | Disruptions in surgical flow and their relationship to surgical errors: An exploratory investigation[END_REF] However, other studies found no correlation between interruptions and workload or complications. [START_REF] Allers | Evaluation and impact of workflow interruptions during robot-assisted surgery[END_REF][START_REF] Yoong | Interruptions and distractions in the gynaecological operating theatre: irritating or dangerous?[END_REF] Several factors were also found to have an impact on interruptions: team familiarity which reduces numbers of interruptions and promotes team work and communication, [START_REF] Gillespie | Interruptions and miscommunications in surgery: an observational study[END_REF][START_REF] Henaux | Relationships between expertise, crew familiarity and surgical workflow disruptions: an observational study[END_REF][START_REF] Allers | Evaluation and impact of workflow interruptions during robot-assisted surgery[END_REF][START_REF] Hart | Nasa-Task Load Index (NASA-TLX); 20 Years Later[END_REF] expertise which reduces the frequency of interruptions. [START_REF] Henaux | Relationships between expertise, crew familiarity and surgical workflow disruptions: an observational study[END_REF] The second methodological approach was experimental in a simulated environment.

These studies enabled comparison of performance of surgeons in an interrupted situation with those in a non-interrupted situation (control group). This approach made it possible to measure the impact of interruptions more precisely than those realized in a natural environment. It demonstrated a negative impact of interruptions with an increase in error rates and time of task completion. [START_REF] Szafranski | Distractions and surgical proficiency: an educational perspective[END_REF][START_REF] Pluyter | Do absorption and realistic distraction influence performance of component task surgical procedure?[END_REF][START_REF] Park | Effect of distraction on simulated anterior segment surgical performance[END_REF][START_REF] Goodell | Effects of cognitive distraction on performance of laparoscopic surgical tasks[END_REF][START_REF] Hsu | Experienced surgeons can do more than one thing at a time: effect of distraction on performance of a simple laparoscopic and cognitive task by experienced and novice surgeons[END_REF][START_REF] Weigl | Intraoperative disruptions, surgeon's mental workload, and technical performance in a full-scale simulated procedure[END_REF][START_REF] Moorthy | Objective evaluation of the effect of noise on the performance of a complex laparoscopic task[END_REF][START_REF] Miskovic | Randomized controlled trial investigating the effect of music on the virtual reality laparoscopic learning performance of novice surgeons[END_REF][START_REF] Feuerbacher | Realistic distractions and interruptions that impair simulated surgical performance by novice surgeons[END_REF][START_REF] Suh | The negative effect of distraction on performance of robot-assisted surgical skills in medical students and residents[END_REF][START_REF] Zheng | A quantitative study of disruption in the operating room during laparoscopic antireflux surgery[END_REF] A study carried out in a simulated environment demonstrated a potential beneficial effect of interruptions in the context of surgery learning, with better surgical performance of trainees who had been trained in simulated programs with interruptions. [START_REF] Szafranski | Distractions and surgical proficiency: an educational perspective[END_REF]

Quality appraisal and limitations of included studies

We used a quality assessment tool to evaluate the quality of the included studies. This tool was useful even though it was initially designed for observational cohort and crosssectional studies. It allowed us to evaluate key methodological points for each study. We A c c e p t e d M a n u s c r i p t observed several important methodological limitations. First, studies frequently included a limited number of procedures, as detailed in Table A, which is a strong limitation when statistical analysis is carried out for comparisons between groups. Second, there were no sample size justification, which is a limitation when the objective is to observe a significant statistical difference between groups. Third, data (interruptions) were extracted by observers from live surgical procedures. The surgical team, being observed, may be led to modify their behavior and cause distortion of the observation. Finally, observational studies were heterogeneous as regards the type of surgical settings and the definition of interruptions. It follows that results of observational study in one particular OR can hardly be generalized to other OR.

Propositions for future research

Studies conducted in a real operating room are valuable in order to assess the actual impact of interruptions on a trained team. However, many confounding factors should be measured to reduce the risk of misinterpretation. A solution could be to perform prospective studies with a control group, which would make it possible to assess more precisely the impact of interruptions on the surgical procedure with measurement of team familiarity and expertise. The study of the timing of interruptions during the surgical procedure should also be further studied as it was only examined in three studies. [START_REF] Antoniadis | Identification and interference of intraoperative distractions and interruptions in operating rooms[END_REF][START_REF] Yoong | Interruptions and distractions in the gynaecological operating theatre: irritating or dangerous?[END_REF][START_REF] Morgan | Capturing intraoperative process deviations using a direct observational approach: the glitch method[END_REF] This question is of importance, as it could lead to specific education of the OR team about phases of the surgical procedure which should not be interrupted (during the closing phase when the count is made by the OR nurses for example).

From an educational point of view, as interruptions are frequently seen in real environments, the development of simulated training programs would certainly be more effective if it included interruptions or settings corresponding to a real OR environment (OR noise, various interruptions). [START_REF] Szafranski | Distractions and surgical proficiency: an educational perspective[END_REF]

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Last but not least, our review showed that no study has specifically evaluated the potential positive aspect of interruptions in surgery. In the work psychology literature, some interruptions were found to have potentially beneficial effect on workers. [START_REF] Jett | Work interrupted: a closer look at the role of interruptions in organizational life[END_REF][START_REF] Trafton | Task Interruptions[END_REF][START_REF] Keus Van De Poll | Effects of task interruption and background speech on word processed writing: effects on writing performance[END_REF] We suggest that future research should be done to explore this point. As we learn from the data of work psychology research, potential beneficial interruptions may exist in the OR: contradictions (another surgeon interrupts a colleague and gives advice on the surgical case), breaks and some distractions (alarms which alert the teams to potentially serious problem, music or caseirrelevant communication which could promote team bonding and decrease workload). Thus, we can hypothesize that some interruptions could have a beneficial impact on the care process in the OR by permitting information exchange within the surgical team but also with external members, and by promoting the well-being of the OR team.

Conclusions

Interruptions during a surgical procedure are diverse and several classifications have been used in the literature. Interruptions are probably risk factors for errors in the OR but the evidence of the link between their number and these errors is not clear. The concept of interruption of surgical procedures needs to be defined more precisely: potentially beneficial interruptions must be separated from those that have a negative impact. This approach could make it possible to target only negative interruptions which should be reduced by safeguards, and leave aside those with no potential consequences.

Interference of interruptions

interruptions per hour

Categories of interruptions

Equipment, work environment, procedure: 38 %

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A c c e p t e d M a n u s c r i p t

Nine-point ordinal scale (table B)

Teamwork measured by Observational Teamwork Assessment for Surgery (OTAS) [START_REF] Hull | Observational teamwork assessment for surgery: content validation and tool refinement[END_REF] Movement in front of or behind monitor: 23% CIC: 15%

External staff interruption: 13%

Other: <5%

High interference categories

Equipment, environment, procedure

3

 3

52 Fair

 52 Fig. A Flow diagram of the literature search

Fair Observation of 48 25 A 8 Performance measured by 2 questionsFrequency of interruptions was correlated with higher stress 27 A c c e p t e d M a n u s c r i p t

 48258227 general and vascular surgeries Observation of failed case-relevant communications and their effect on the surgical team Equipment, procedure-related communication, patientirrelevant communication, and medically irrelevant communication: between 4 and 5 How productive have you been in your work during the operation? How do you evaluate the quality of your work during the operation? Weigl et al. 30 Good Observation of 56 general and orthopaedic surgeries Observation of interruptions and degree of interference of interruptions on the surgical team Impact of interruptions and workload External staff entering, exiting or initiating CIC CIC within the OR team Acoustic (telephone, mobile phones, pagers, radio, and external noises)

Acknowledgements

The authors thank Deirdre McKeown for revising the English style.

Disclosure

The authors report no proprietary or commercial interest in any product mentioned or concept discussed in this article. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Authors Quality Assessment 21

Type and objective of the study Classification(s) used Main results

Allers et al. [START_REF] Allers | Evaluation and impact of workflow interruptions during robot-assisted surgery[END_REF] Fair Observation of 10 robot assisted radical prostatectomies Observation of interruptions and relations with team familiarity and workload

Classification of interruptions

Equipment/technology Supervision/training Procedure specific

Procedure unrelated

Team familiarity score

Workload measured by NASA TLX [START_REF] Hart | Nasa-Task Load Index (NASA-TLX); 20 Years Later[END_REF] No correlation between interruptions and workload

Negative correlation between interruptions and team familiarity

Categories of interruptions

Equipment/technology: 56%