Pierre-Louis Hénaux

PhD Pierre Jannin
email: pierre.jannin@univ-rennes1.fr

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

Dr Pierre-Louis Henaux
email: pierre-louis.henaux@etudiant.univ-rennes1.fr

Non-technical skills in Neurosurgery : a systematic review of the literature

Keywords: Technical Skills, Neurosurgery, Interpersonal Skills, Cognitive Skills, Patient Safety

Background

Undesirable events in the neurosurgery operating theatre are surprisingly less often the result of a technical error than of a dysfunction linked to non-technical skills (NTS). The essential aim of our study was a systematic literature study published on NTS in neurosurgery. The secondary objective was identification of a list of NTS more specific to neurosurgery in order to define on that basis the training needs of neurosurgery trainees.

Methods

MEDLINE and

The Cochrane Database of Systematic Reviews were searched according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) statement.

Research initially identified 2132 articles. 21 were eligible for systematic study. Data were extracted from the articles regarding study design, sample size, NTS assessed, assessment tools and the key results were collected.

Results

Interpersonal skills (communication, teamwork), cognitive skills (decision making, situation awareness) and personal resource factors (coping with stress or fatigue) were specifically identified. No article used assessment tools such as NOTECHS, NOTSS or OTAS. They were carried out in a real environment in 11 cases, in a simulated environment in 9 cases and during theoretical teaching in 1 case.

Conclusions

Very few studies have been carried out concerning neurosurgical NTS, despite increasing numbers of articles over the last few years on NTS in other domains of surgery. Society today is concentrating more and more on the quality and safety of medical care.

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application of NTS assessment tools is therefore essential in order to provide assistance in the training of future neurosurgeons.

INTRODUCTION

Neurosurgery is a discipline requiring knowledge of numerous hyperspecialist domains such as vascular, tumoral, malformation, degenerative and spinal pathologies. As well as this declarative knowledge of neurosurgical pathologies and their associated indications for operation , the surgeon has to acquire technical skills both in accordance with good practice and under ongoing development, for example microsurgery, computer-assisted surgery [START_REF] Alaraj | Role of cranial and spinal virtual and augmented reality simulation using immersive touch modules in neurosurgical training[END_REF][START_REF] Chan | Virtual reality simulation in neurosurgery: technologies and evolution[END_REF][START_REF] De Ribaupierre | Construction of a 3-D anatomical model for teaching temporal lobectomy[END_REF][START_REF] Fargen | Simulator based angiography education in neurosurgery: results of a pilot educational program[END_REF][START_REF] Filho | Quality assessment of a new surgical simulator for neuroendoscopic training[END_REF][START_REF] Haji | Needs assessment for simulation training in neuroendoscopy: a Canadian national survey[END_REF][START_REF] Malone | Simulation in neurosurgery: a review of computer-based simulation environments and their surgical applications[END_REF] and robotics [START_REF] Nathoo | Robotics and neurosurgery[END_REF] . Even with perfect mastery of this knowledge and of the technical skills (TS) involved, a certain number of undesirable events (UE) are to be observed in the neurosurgery operating theatre [START_REF] Ladak | Redefining "wrong site surgery" and refining the surgical pause and checklist: taking surgical safety to another level[END_REF][START_REF] Mitchell | Side errors in neurosurgery[END_REF][START_REF] Walcott | Infection following operations on the central nervous system: deconstructing the myth of the sterile field[END_REF][START_REF] Wong | Patterns in neurosurgical adverse events: endovascular neurosurgery[END_REF][START_REF] Wong | Patterns in neurosurgical adverse events: open cerebrovascular neurosurgery[END_REF][START_REF] Wong | Patterns in neurosurgical adverse events: cerebrospinal fluid shunt surgery[END_REF][START_REF] Wong | Patterns in neurosurgical adverse events: intracranial neoplasm surgery[END_REF][START_REF] Wong | Patterns in neurosurgical adverse events and proposed strategies for reduction[END_REF] . These events may have irreversible consequences involving serious functional deficits or even life-threatening situations [START_REF] Ajlan | The human factor and safety attitudes in neurosurgical operating rooms[END_REF][START_REF] Arora | Factors compromising safety in surgery: stressful events in the operating room[END_REF] . Surprisingly, they are less often the result of a technical error than of a dysfunction linked to non-technical skills (NTS) [START_REF] Hull | The Impact of Nontechnical Skills on Technical Performance in Surgery: A Systematic Review[END_REF] . This relationship between NTS and UE has led the surgical community to explore in greater depth safety and quality issues with increasing numbers of publications on NTS over the last few years. NTS can be divided into two groups according to the taxonomy developed by Yule et al. [START_REF] Yule | Non-technical skills for surgeons in the operating room: a review of the literature[END_REF] . The first includes interpersonal skills : communication, leadership, teamwork, briefing, planning and preparation, resource management, requests for advice and feedback, attitudes to pressure, stress and fatigue. The second group covers cognitive skills including awareness of the situation, mental disposition, risk assessment, anticipation of problems, decision-making, adaptation strategies, flexibility or workload. In real conditions, interpersonal skills and cognitive skills may be involved simultaneously. For example, poor communication between the surgeon and the anesthesiologist during an unexpected haemorrhage in the operating theatre (NTS involved: communication and situational awareness) may have life-threatening consequences. Publications on this subject still rely for the moment on non-standardized methods.

NTS assessment is rendered problematical by a methodology difficult to put into practice (necessitating robust psychometric testing) involving multiple variables which are themselves not easily controlled [START_REF] Sharma | Non-technical skills assessment in surgery[END_REF][START_REF] Arora | Objective structured assessment of debriefing: bringing science to the art of debriefing in surgery[END_REF][START_REF] Arora | Self vs expert assessment of technical and non-technical skills in high fidelity simulation[END_REF][START_REF] Hull | Assessment of stress and teamwork in the operating room: an exploratory study[END_REF][START_REF] Hull | Training faculty in nontechnical skill assessment: national guidelines on program requirements[END_REF][START_REF] Mitchell | Evaluation of the Scrub Practitioners' List of Intraoperative Non-Technical Skills system[END_REF][START_REF] Mitchell | Development of a behavioural marker system for scrub practitioners' non-technical skills (SPLINTS system)[END_REF][START_REF] Russ | Measuring safety and efficiency in the operating room: development and validation of a metric for evaluating task execution in the operating room[END_REF][START_REF] Russ | Observational teamwork assessment for surgery: feasibility of clinical and nonclinical assessor calibration with short-term training[END_REF][START_REF] Yule | Development of a rating system for surgeons' non-technical skills[END_REF] . However, it is certain that NTS exercise a positive or negative influence on TS depending on whether or not they are applied [START_REF] Hull | The Impact of Nontechnical Skills on Technical Performance in Surgery: A Systematic Review[END_REF] . The safety and quality of care is a universal and

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increasing preoccupation among the population [START_REF] Ladak | Redefining "wrong site surgery" and refining the surgical pause and checklist: taking surgical safety to another level[END_REF][START_REF] Ajlan | The human factor and safety attitudes in neurosurgical operating rooms[END_REF][START_REF] Fallah | The "SAAFE" neurosurgical sign-out[END_REF][START_REF] Hull | Building global capacity for patient safety: a training program for surgical safety research in developing and transitional countries[END_REF][START_REF] Lau | Creating a culture of safety within operative neurosurgery: the design and implementation of a perioperative safety video[END_REF][START_REF] Muzumdar | Safety in the operating room: neurosurgical perspective[END_REF] : surgeons have taken this into account and, as in other sensitive domains such as the army [START_REF] Ferroli | Application of an aviation model of incident reporting and investigation to the neurosurgical scenario: method and preliminary data[END_REF] or navy, they are beginning to develop "firewall" tools such as checklists [START_REF] Ladak | Redefining "wrong site surgery" and refining the surgical pause and checklist: taking surgical safety to another level[END_REF][START_REF] Haynes | A Surgical Safety Checklist to Reduce Morbidity and Mortality in a Global Population[END_REF][START_REF] Silva-Freitas | Establishment of a modified surgical safety checklist for the neurosurgical patient: Initial experience in 400 cases[END_REF][START_REF] Mcconnell | Surgical checklists: A detailed review of their emergence, development, and relevance to neurosurgical practice[END_REF][START_REF] Rahmathulla | Surgical briefings, checklists, and the creation of an environment of safety in the neurosurgical intraoperative magnetic resonance imaging suite[END_REF][START_REF] Zuckerman | Neurosurgical checklists: a review[END_REF] . These NTS, still ill-defined, are only just beginning to emerge in surgeon training objectives and are even less present in the confidential world of neurosurgery 25,41- 54 .

The essential aim of our study was a systematic study of the literature published on NTS in the neurosurgical domain. The secondary objective was identification, from the existing literature, of a list of NTS more specific to neurosurgery in order to define on that basis the training needs of neurosurgery trainees.

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MATERIAL AND METHODS

We conducted a systematic review following the PRISMA statement [START_REF] Liberati | The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate healthcare interventions: explanation and elaboration[END_REF] . Ethics committee approval was not required for our research protocol. We did not register our review protocol in the PROS-PERO database.

Using the databases PubMed-MEDLINE and The Cochrane Database of Systematic Reviews, we combined two A and B categories using the Boolean operator "AND", Category A was the following : Adaptation, Psychologic OR Adjustment, Psychological OR Behavior, Adaptive OR Coping Behavior OR Coping Skills OR Psychological Adaptation OR Psychological Adjustment OR skills, Category B was: neurosurgery OR neurosurgical procedures. We defined the following limits: publication date between January 1980 and December 2018 ; articles concerning studies on humans, excluding those on animals ; publications in English and French. The final research was carried out on 2 nd January 2019. The lists of article references included were also researched to find other references such as grey literature (unpublished studies with limited distribution, for example conference abstracts) and published studies not identified using our initial search strategy. This led us to add 2 articles for which we made a complete assessment of the text. We assessed the collected quotations, sifting through the titles and abstracts to identify the pertinent articles on the basis of the following predefined inclusion criteria :

3) Data on training needs OR teaching OR simulation systems including robotics. These criteria were chosen to identify the articles specifically examining NTS in neurosurgery, the resulting training needs and the integration of these skills to simulation systems.

The data was extracted from the articles concerned using a structured data résumé (Figure 1), to ensure coherent assessment of each article. Using this method, details of the study design, the size of the sample, the NTS assessed, the assessment tools and the key results were collected.

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RESULTS

Selection of articles

The diagram summarizing the research strategy is shown in Figure 2.

Research initially identified 2132 articles. In all, 21 articles were eligible for systematic study.

Populations studied

12 articles concerned analysis of neurosurgery residents [START_REF] Pettit | Neurosurgery resident leadership development: an innovative approach[END_REF][START_REF] Cusimano | An analysis of attrition from Canadian neurosurgery residency programs[END_REF][START_REF] Selden | A National Fundamentals Curriculum for Neurosurgery PGY1 Residents: The 2010 Society of Neurological Surgeons Boot Camp Courses[END_REF][START_REF] Ganju | The effect of call on neurosurgery residents' skills: implications for policy regarding resident call periods[END_REF][START_REF] Ciporen | Crisis Management Simulation: Establishing a Dual Neurosurgery and Anesthesia Training Experience[END_REF][START_REF] Khan | Nurturing the Next Generation of Neurosurgeons: How Important Are Nontechnical Skills?[END_REF][START_REF] Haji | Teaching for the Transition: the Canadian PGY-1 Neurosurgery 'Rookie Camp[END_REF][START_REF] Hunt | Commentary: An Introduction to Leadership Self-Assessment at the Society of Neurological Surgeons Post-Graduate Year 1 Boot Camp: Observations and Commentary[END_REF][START_REF] Brandman | Needs Assessment for Incoming PGY-1 Residents in Neurosurgical Residency[END_REF][START_REF] Tanweer | Neurosurgical decision making: personal and professional preferences[END_REF][START_REF] Harnof | Simulation-based interpersonal communication skills training for neurosurgical residents[END_REF][START_REF] Morineau | Decision Making During Preoperative Surgical Planning[END_REF] . 12 others studied senior neurosurgeons [START_REF] Lau | Creating a culture of safety within operative neurosurgery: the design and implementation of a perioperative safety video[END_REF][START_REF] Ferroli | Application of an aviation model of incident reporting and investigation to the neurosurgical scenario: method and preliminary data[END_REF][START_REF] Khan | Nurturing the Next Generation of Neurosurgeons: How Important Are Nontechnical Skills?[END_REF][START_REF] Tanweer | Neurosurgical decision making: personal and professional preferences[END_REF][START_REF] Morineau | Decision Making During Preoperative Surgical Planning[END_REF][START_REF] Oszvald | Team time-out" and surgical safety-experiences in 12,390 neurosurgical patients[END_REF][START_REF] Mclaughlin | Impact of the Time-Out Process on Safety Attitude in a Tertiary Neurosurgical Department[END_REF][START_REF] Pathak | Ideal ward round making in neurosurgical practice[END_REF][START_REF] Couat | A prospective video-based observational and analytical approach to evaluate management during brain tumour surgery at a university hospital[END_REF][START_REF] Fargen | Enhanced staff communication and reduced near-miss errors with a neurointerventional procedural checklist[END_REF][START_REF] Michinov | Assessing neurosurgical nontechnical skills: an exploratory study of a new behavioural marker system[END_REF][START_REF] Sakamoto | Comparative Prospective Study of Microvascular Anastomosis Training by Self-Learning or with Expert Instruction[END_REF] and 3 others directors of training (also senior neurosurgeons) [START_REF] Cusimano | An analysis of attrition from Canadian neurosurgery residency programs[END_REF][START_REF] Khan | Nurturing the Next Generation of Neurosurgeons: How Important Are Nontechnical Skills?[END_REF][START_REF] Brandman | Needs Assessment for Incoming PGY-1 Residents in Neurosurgical Residency[END_REF] . Six others dealt with the whole team of a neurosurgery operating theatre [START_REF] Ferroli | Application of an aviation model of incident reporting and investigation to the neurosurgical scenario: method and preliminary data[END_REF][START_REF] Oszvald | Team time-out" and surgical safety-experiences in 12,390 neurosurgical patients[END_REF][START_REF] Mclaughlin | Impact of the Time-Out Process on Safety Attitude in a Tertiary Neurosurgical Department[END_REF][START_REF] Couat | A prospective video-based observational and analytical approach to evaluate management during brain tumour surgery at a university hospital[END_REF][START_REF] Fargen | Enhanced staff communication and reduced near-miss errors with a neurointerventional procedural checklist[END_REF][START_REF] Michinov | Assessing neurosurgical nontechnical skills: an exploratory study of a new behavioural marker system[END_REF] and one article studied the whole team of a neurosurgery department [START_REF] Lau | Creating a culture of safety within operative neurosurgery: the design and implementation of a perioperative safety video[END_REF] .

Study designs

7 were experimental studies [START_REF] Ganju | The effect of call on neurosurgery residents' skills: implications for policy regarding resident call periods[END_REF][START_REF] Ciporen | Crisis Management Simulation: Establishing a Dual Neurosurgery and Anesthesia Training Experience[END_REF][START_REF] Haji | Teaching for the Transition: the Canadian PGY-1 Neurosurgery 'Rookie Camp[END_REF][START_REF] Hunt | Commentary: An Introduction to Leadership Self-Assessment at the Society of Neurological Surgeons Post-Graduate Year 1 Boot Camp: Observations and Commentary[END_REF][START_REF] Harnof | Simulation-based interpersonal communication skills training for neurosurgical residents[END_REF][START_REF] Morineau | Decision Making During Preoperative Surgical Planning[END_REF][START_REF] Sakamoto | Comparative Prospective Study of Microvascular Anastomosis Training by Self-Learning or with Expert Instruction[END_REF] , 7 were surveys [START_REF] Pettit | Neurosurgery resident leadership development: an innovative approach[END_REF][START_REF] Cusimano | An analysis of attrition from Canadian neurosurgery residency programs[END_REF][START_REF] Selden | A National Fundamentals Curriculum for Neurosurgery PGY1 Residents: The 2010 Society of Neurological Surgeons Boot Camp Courses[END_REF][START_REF] Khan | Nurturing the Next Generation of Neurosurgeons: How Important Are Nontechnical Skills?[END_REF][START_REF] Brandman | Needs Assessment for Incoming PGY-1 Residents in Neurosurgical Residency[END_REF][START_REF] Tanweer | Neurosurgical decision making: personal and professional preferences[END_REF][START_REF] Mclaughlin | Impact of the Time-Out Process on Safety Attitude in a Tertiary Neurosurgical Department[END_REF] , 5 were interventional studies [START_REF] Lau | Creating a culture of safety within operative neurosurgery: the design and implementation of a perioperative safety video[END_REF][START_REF] Ferroli | Application of an aviation model of incident reporting and investigation to the neurosurgical scenario: method and preliminary data[END_REF][START_REF] Oszvald | Team time-out" and surgical safety-experiences in 12,390 neurosurgical patients[END_REF][START_REF] Pathak | Ideal ward round making in neurosurgical practice[END_REF][START_REF] Fargen | Enhanced staff communication and reduced near-miss errors with a neurointerventional procedural checklist[END_REF] , and 2 were observational studies [START_REF] Couat | A prospective video-based observational and analytical approach to evaluate management during brain tumour surgery at a university hospital[END_REF][START_REF] Michinov | Assessing neurosurgical nontechnical skills: an exploratory study of a new behavioural marker system[END_REF] .

Environment

These studies were carried out :

in a real environment in 11 cases : 10 in the operating theatre [START_REF] Lau | Creating a culture of safety within operative neurosurgery: the design and implementation of a perioperative safety video[END_REF][START_REF] Ferroli | Application of an aviation model of incident reporting and investigation to the neurosurgical scenario: method and preliminary data[END_REF][START_REF] Cusimano | An analysis of attrition from Canadian neurosurgery residency programs[END_REF][START_REF] Khan | Nurturing the Next Generation of Neurosurgeons: How Important Are Nontechnical Skills?[END_REF][START_REF] Brandman | Needs Assessment for Incoming PGY-1 Residents in Neurosurgical Residency[END_REF][START_REF] Oszvald | Team time-out" and surgical safety-experiences in 12,390 neurosurgical patients[END_REF][START_REF] Mclaughlin | Impact of the Time-Out Process on Safety Attitude in a Tertiary Neurosurgical Department[END_REF][START_REF] Couat | A prospective video-based observational and analytical approach to evaluate management during brain tumour surgery at a university hospital[END_REF][START_REF] Fargen | Enhanced staff communication and reduced near-miss errors with a neurointerventional procedural checklist[END_REF][START_REF] Michinov | Assessing neurosurgical nontechnical skills: an exploratory study of a new behavioural marker system[END_REF] , 1 in a neurosurgery department [START_REF] Lau | Creating a culture of safety within operative neurosurgery: the design and implementation of a perioperative safety video[END_REF] , and 4 in consultation [START_REF] Cusimano | An analysis of attrition from Canadian neurosurgery residency programs[END_REF][START_REF] Khan | Nurturing the Next Generation of Neurosurgeons: How Important Are Nontechnical Skills?[END_REF][START_REF] Brandman | Needs Assessment for Incoming PGY-1 Residents in Neurosurgical Residency[END_REF][START_REF] Pathak | Ideal ward round making in neurosurgical practice[END_REF] ,

in a simulated environment in 9 cases [START_REF] Selden | A National Fundamentals Curriculum for Neurosurgery PGY1 Residents: The 2010 Society of Neurological Surgeons Boot Camp Courses[END_REF][START_REF] Ganju | The effect of call on neurosurgery residents' skills: implications for policy regarding resident call periods[END_REF][START_REF] Ciporen | Crisis Management Simulation: Establishing a Dual Neurosurgery and Anesthesia Training Experience[END_REF][START_REF] Haji | Teaching for the Transition: the Canadian PGY-1 Neurosurgery 'Rookie Camp[END_REF][START_REF] Hunt | Commentary: An Introduction to Leadership Self-Assessment at the Society of Neurological Surgeons Post-Graduate Year 1 Boot Camp: Observations and Commentary[END_REF][START_REF] Tanweer | Neurosurgical decision making: personal and professional preferences[END_REF][START_REF] Harnof | Simulation-based interpersonal communication skills training for neurosurgical residents[END_REF][START_REF] Morineau | Decision Making During Preoperative Surgical Planning[END_REF][START_REF] Sakamoto | Comparative Prospective Study of Microvascular Anastomosis Training by Self-Learning or with Expert Instruction[END_REF] ,

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Non-technical surgical skills assessed

Interpersonal NTS were specifically assessed in 9 studies [START_REF] Lau | Creating a culture of safety within operative neurosurgery: the design and implementation of a perioperative safety video[END_REF][START_REF] Pettit | Neurosurgery resident leadership development: an innovative approach[END_REF][START_REF] Cusimano | An analysis of attrition from Canadian neurosurgery residency programs[END_REF][START_REF] Haji | Teaching for the Transition: the Canadian PGY-1 Neurosurgery 'Rookie Camp[END_REF][START_REF] Hunt | Commentary: An Introduction to Leadership Self-Assessment at the Society of Neurological Surgeons Post-Graduate Year 1 Boot Camp: Observations and Commentary[END_REF][START_REF] Harnof | Simulation-based interpersonal communication skills training for neurosurgical residents[END_REF][START_REF] Pathak | Ideal ward round making in neurosurgical practice[END_REF][START_REF] Couat | A prospective video-based observational and analytical approach to evaluate management during brain tumour surgery at a university hospital[END_REF][START_REF] Sakamoto | Comparative Prospective Study of Microvascular Anastomosis Training by Self-Learning or with Expert Instruction[END_REF] .

Cognitive NTS were specifically evaluated in 9 studies [START_REF] Cusimano | An analysis of attrition from Canadian neurosurgery residency programs[END_REF][START_REF] Ganju | The effect of call on neurosurgery residents' skills: implications for policy regarding resident call periods[END_REF][START_REF] Ciporen | Crisis Management Simulation: Establishing a Dual Neurosurgery and Anesthesia Training Experience[END_REF][START_REF] Tanweer | Neurosurgical decision making: personal and professional preferences[END_REF][START_REF] Morineau | Decision Making During Preoperative Surgical Planning[END_REF][START_REF] Oszvald | Team time-out" and surgical safety-experiences in 12,390 neurosurgical patients[END_REF][START_REF] Mclaughlin | Impact of the Time-Out Process on Safety Attitude in a Tertiary Neurosurgical Department[END_REF][START_REF] Fargen | Enhanced staff communication and reduced near-miss errors with a neurointerventional procedural checklist[END_REF][START_REF] Michinov | Assessing neurosurgical nontechnical skills: an exploratory study of a new behavioural marker system[END_REF] . Finally, neurosurgery NTS were assessed overall in 6 studies without differentiation between the two types [START_REF] Ferroli | Application of an aviation model of incident reporting and investigation to the neurosurgical scenario: method and preliminary data[END_REF][START_REF] Selden | A National Fundamentals Curriculum for Neurosurgery PGY1 Residents: The 2010 Society of Neurological Surgeons Boot Camp Courses[END_REF][START_REF] Ciporen | Crisis Management Simulation: Establishing a Dual Neurosurgery and Anesthesia Training Experience[END_REF][START_REF] Khan | Nurturing the Next Generation of Neurosurgeons: How Important Are Nontechnical Skills?[END_REF][START_REF] Brandman | Needs Assessment for Incoming PGY-1 Residents in Neurosurgical Residency[END_REF][START_REF] Fargen | Enhanced staff communication and reduced near-miss errors with a neurointerventional procedural checklist[END_REF] .

Assessment tools and key results of each study

None of the articles selected used assessment tools such as NOTECHS, NOTSS or OTAS, all of which have all been established as valid in the literature concerning assessment of NTS in surgery.

Studies in a real environment

Neurosurgery interns complained of lack of teaching on behaviour and interpersonal relations in a questionnaire designed by Cusimano et al. [START_REF] Cusimano | An analysis of attrition from Canadian neurosurgery residency programs[END_REF] given to a population of 30 interns. Open questions with content analysis and double-scale quantification were carried out both among neurosurgery interns and among heads of teaching programmes. These revealed a positive correlation between excessive workload and voluntary withdrawal, and between dismissal and interpersonal skills during the neurosurgery internship. According to Pathak et al. [START_REF] Pathak | Ideal ward round making in neurosurgical practice[END_REF] Senior neurosurgeons demonstrated good productivity and flexibility, but appeared to have difficulty in remaining objective and making themselves understood in consultation. This study was carried out during neurosurgery consultations, and the sample included 12 senior neurosurgeons with at least 10 years' experience.

The surgeon was assessed by an outside observer using an assessment scale including : productivity, flexibility, objectivity and comprehensibility. Fargen et al. [START_REF] Fargen | Enhanced staff communication and reduced near-miss errors with a neurointerventional procedural checklist[END_REF] studied the effect of the introduction of a checklist for neurointerventional procedures in neurovascular pathology. 71 procedures were carried out 4 weeks before the introduction of the checklist and 60 others 4 weeks after it. The checklist brought about a significant improvement in communication within the team and a significant reduction in the number of undesirable events. Ferroli et al. [START_REF] Ferroli | Application of an aviation model of incident reporting and investigation to the neurosurgical scenario: method and preliminary data[END_REF] assessed a notification system inspired by aviation and applied to the neurosurgical domain. The entire team of a

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neurosurgery department participated in the study and reported incidents occurring in the service.

14 incidents were reported and analyzed. 9 were due to human factors and 3 to questions of organization. Lau et al. [START_REF] Lau | Creating a culture of safety within operative neurosurgery: the design and implementation of a perioperative safety video[END_REF] assessed and installed a safety education video in a neurosurgery department. It had been made over several months by a multidisciplinary team including neurosurgeons, anaesthetists, nurses and professionals from the quality and video domains. This team ensured that all the safety parameters involved in a neurosurgical procedure were collected and formalized in video format. McLaughlin et al. [START_REF] Mclaughlin | Impact of the Time-Out Process on Safety Attitude in a Tertiary Neurosurgical Department[END_REF] examined the interest of establishing a checklist before the beginning of an operation. 98,9% of those questioned judged this to be in the interest of the patient's safety, and 97,8% thought it increased team spirit. All members of the team judged that the surgeon should be present at the time of the checklist and according 76,3% thought that the surgeon should carry it out in person. Osvald et al. [START_REF] Oszvald | Team time-out" and surgical safety-experiences in 12,390 neurosurgical patients[END_REF] studied the impact of the introduction of a checklist in a neurosurgery operating theatre. 8795 surgical procedures were carried out without checklist between January 2007 and December 2010, with two error reports : one procedure on the wrong side of the skull and one at the wrong level on the lumbar verterbrae. Between January 2011 and June 2012 no errors of side or level were reported. Couat et al. [START_REF] Couat | A prospective video-based observational and analytical approach to evaluate management during brain tumour surgery at a university hospital[END_REF] through an observational study of the operating theatre using video analysis and ethographical methods, demonstrated that 33% of errors committed in the operating theatre were at least partly caused by poor communication or organisation management. Michinov et al. [START_REF] Michinov | Assessing neurosurgical nontechnical skills: an exploratory study of a new behavioural marker system[END_REF] in an operating theatre observational study of deep brain stimulation showed that explicit coordination, awareness of the situation and leadership are the NTS most involved in deep brain stimulation by the neurosurgeon. What is more, these aspects of behaviour differ according to the time of operation and the other members of the theatre team with whom the surgeon is communicating. Brandman et al. [START_REF] Brandman | Needs Assessment for Incoming PGY-1 Residents in Neurosurgical Residency[END_REF] also used a survey which underlined the fact that heads of programmes considered NTS more important than did the interns, with an emphasis on the disclosure of bad news. Interns focussed more on obtaining the patients' consent.

Both heads of programmes and interns considered the communication of red flags as critical. The survey carried out by Khan et al. [START_REF] Khan | Nurturing the Next Generation of Neurosurgeons: How Important Are Nontechnical Skills?[END_REF] made it clear that according to interns the current environment

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does not leave enough place for the teaching of NTS. For them NTS appears more important than it does for their tutors, both quantitatively and qualitatively. Teachers judge that too much teaching time is spent on NTS, and students think the contrary.

Studies in a simulated environment

Sakamoto et al. [START_REF] Sakamoto | Comparative Prospective Study of Microvascular Anastomosis Training by Self-Learning or with Expert Instruction[END_REF] carried out an experimental study on 5th-year medical students which showed that expert feedback improved technical performance in surgical anastomosis, without lengthening operating time. Trainees with feedback achieved higher scores than neurosurgeons. Tanweer et al. [START_REF] Tanweer | Neurosurgical decision making: personal and professional preferences[END_REF] demonstrated through a survey that neurosurgical decision-making is essentially similar from both the patient's and the neurosurgeon's point of view. Morineau et al. [START_REF] Morineau | Decision Making During Preoperative Surgical Planning[END_REF] showed a significant association between expert decision-making and conflict reduction and management of conflict control based on knowledge essentially contributed by experts. Harnof et al. [START_REF] Harnof | Simulation-based interpersonal communication skills training for neurosurgical residents[END_REF] in an experimental study of neurosurgical interns in simulated interviews with patients and their families showed the realistic qualities of the actors and their efficiency in NTS communication training. Haji et al. [START_REF] Haji | Teaching for the Transition: the Canadian PGY-1 Neurosurgery 'Rookie Camp[END_REF] showed the importance of simulation in the teaching of teamwork, communication, dealing with pressure, stress and fatigue to first-year neurosurgery interns. Hunt et al. [START_REF] Hunt | Commentary: An Introduction to Leadership Self-Assessment at the Society of Neurological Surgeons Post-Graduate Year 1 Boot Camp: Observations and Commentary[END_REF] , also using simulation, demonstrated that leadership and teamwork are essential for a successful career in neurosurgery.

Training camps improved the trainee's awareness of his own behaviour and motivation. Threequarters of participants understood how to apply this in daily life. Ganju et al. specifically studied the effects of fatigue on neurosurgery interns [START_REF] Ganju | The effect of call on neurosurgery residents' skills: implications for policy regarding resident call periods[END_REF] . They subjected 7 neurosurgery interns to 4 sessions of 6 pre-and post-duty surgical exercises in a simulated environment. Fatigue appeared to reduce performance to a certain extent, particularly in "day after duty" interns. Memory and attention were the functions most impaired. Fluidity of gesture and operation duration were also affected by fatigue. Selden et al. [START_REF] Selden | A National Fundamentals Curriculum for Neurosurgery PGY1 Residents: The 2010 Society of Neurological Surgeons Boot Camp Courses[END_REF] carried out an opinion poll on 186 neurosurgery interns following practical and theoretical teaching of multiple NTS, in a simulated environment. The teaching of NTS received 100% approval from trainee neurosurgeons, particularly the sections on leadership. Finally, Ciporen et al. [START_REF] Ciporen | Crisis Management Simulation: Establishing a Dual Neurosurgery and Anesthesia Training Experience[END_REF] in an experimental study on interns in neurosurgery and anaesthetics showed no

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significant difference in NTS between the two groups. Understanding information and dealing with pressure were important elements. Leadership was more obvious among the neurosurgical interns, but not significantly so. The anaesthetist interns were better at collecting information and considering different options.

Study during theoretical teaching

Pettit et al. [START_REF] Pettit | Neurosurgery resident leadership development: an innovative approach[END_REF] formalized. However, the much more abundant literature on the subject in other surgical disciplines offers the possibility of interpolation with the neurosurgical domain.

Methodological limits of existing studies in neurosurgery

The methodology of the studies selected after our research did not offer a high standard of proof.

Few of them used specific statistical tests. We found no articles using specific surgery NTS assessment methods whose robustness and validity had been demonstrated in the literature. The 3 principal scales currently used for objective assessment of NTS are the OTAS (Observational Teamwork Assessment for Surgery) [START_REF] Hull | Observational teamwork assessment for surgery: content validation and tool refinement[END_REF] , the NOTECHS (NonTECHnical Skills) [START_REF] Sharma | Non-technical skills assessment in surgery[END_REF] and the NOTSS (Non Technical Skills for Surgeons) [START_REF] Yule | Surgeons' Nontechnical Skills in the Operating Room: Reliability Testing of the NOTSS Behavior Rating System[END_REF] . The OTAS [START_REF] Hull | Observational teamwork assessment for surgery: content validation and tool refinement[END_REF] essentially assesses the work of the team on the basis of 5 criteria : communication, leadership, cooperation, coordination and surveillance. The NOTECHS [START_REF] Sharma | Non-technical skills assessment in surgery[END_REF] classifies NTS in 4 categories : leadership and management, teamwork and cooperation, problem-solving, and decision-making and awareness of the situation. A score of 5 points is given for each category with a scale from 1 (very low) to 5 (very high). The NOTSS corresponds to interviews with consultant surgeons who show five main categories of NTS (awareness of the situation, decision-making, management tasks, leadership, communication and team spirit). Within each category there are 2 or 3 NTS elements depending on the surgical speciality, leading to a score covering 14 separate elements of skill. In some studies all the NTS are assessed together and in others only one or a few of the skills are examined. These factors make it difficult to interpret the results of all these studies. The ideal solution would be an overarching assessment scale with proportionally divided sub-sections to allow all the parameters of the NTS to

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be taken into account. Ten of these studies were carried out in a simulated environment or during teaching. The 11 others were done in a simulated environment, in the operating theatre or in consultation. There exist no studies comparing neurosurgery NTS in a simulated environment with a real environment such as the operating theatre. The scope of the evaluation of these NTS proposed here focused on the healthcare activity in real or simulated environment but does not include all the NTS required in this profession.

The methodological heterogeneity of the studies included in our work made it impossible to assess risk of bias in individual studies, summary measures, synthesis of results, risk of bias across studies and additional analysis as suggested in the PRISMA statement.

Literature on surgical NTS

Although there are numerous synonyms in the literature describing surgical NTS, the 4 essential domains most often described are communication, decision-making, leadership and teamwork 19- 21,73-80 . There also exists a subdivision of surgical NTS into two major groups : cognitive skills and interpersonal skills [START_REF] Yule | Non-technical skills for surgeons in the operating room: a review of the literature[END_REF] .

Several specific skills among the interpersonal NTS have been studied separately, in particular stress [START_REF] Arora | Factors compromising safety in surgery: stressful events in the operating room[END_REF] . Stress can apparently have both positive and negative effects. A moderate level of stress [START_REF] Hull | Assessment of stress and teamwork in the operating room: an exploratory study[END_REF] results in improved performance through increase in concentration. It can however endanger levels of performance when it becomes overwhelming. Pressure gives similar results to stress in a majority of cases. Surprisingly, fatigue (through sleep loss particularly post-duty) [START_REF] Ganju | The effect of call on neurosurgery residents' skills: implications for policy regarding resident call periods[END_REF] can bring about contradictory results. Some studies clearly show a slowdown in task performance, clumsiness and even numbers of supplementary errors, and difficulty in concentrating. Other studies highlight

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contrary conclusions, with more rapid procedure time, better gesture ergonomy and fewer errors. An element of disinhibition is probably the reason for this, with fewer conflicts in a fatigue situation, and more pragmatic attitudes. Therefore, assessment in stress or fatigue conditions is very important in order to have objective data on this topic. There is a major issue in the context of the respect of the weekly working hours imposed by the European directives, while at the same time neurosurgery is impaired by an insufficient surgical demography in France.

Interpersonal communication [START_REF] Fargen | Enhanced staff communication and reduced near-miss errors with a neurointerventional procedural checklist[END_REF] and communication with the patient are among the least studied areas in the literature. Most articles highlight the beneficial effects of feedback from a more experienced surgeon in terms of quality, gesture ergonomy, operation time and numbers of errors. In the rest of the literature NTS are analysed as a whole [START_REF] Ajlan | The human factor and safety attitudes in neurosurgical operating rooms[END_REF][START_REF] Hull | The Impact of Nontechnical Skills on Technical Performance in Surgery: A Systematic Review[END_REF][START_REF] Yule | Non-technical skills for surgeons in the operating room: a review of the literature[END_REF][START_REF] Sharma | Non-technical skills assessment in surgery[END_REF][START_REF] Arora | Objective structured assessment of debriefing: bringing science to the art of debriefing in surgery[END_REF][START_REF] Arora | Self vs expert assessment of technical and non-technical skills in high fidelity simulation[END_REF][START_REF] Hull | Assessment of stress and teamwork in the operating room: an exploratory study[END_REF][START_REF] Russ | Observational teamwork assessment for surgery: feasibility of clinical and nonclinical assessor calibration with short-term training[END_REF][START_REF] Hull | Observational teamwork assessment for surgery: content validation and tool refinement[END_REF][START_REF] Yule | Surgeons' Nontechnical Skills in the Operating Room: Reliability Testing of the NOTSS Behavior Rating System[END_REF][START_REF] Parker | The Surgeons' Leadership Inventory (SLI): a taxonomy and rating system for surgeons' intraoperative leadership skills[END_REF][START_REF] Neil-Dwyer | Mechanisms to improve teamworking in neurosurgery[END_REF][START_REF] Pauley | Surgeons' intraoperative decision making and risk management[END_REF][START_REF] Yule | Surgeons' non-technical skills[END_REF][START_REF] Yule | Development of a rating system for surgeons' non-technical skills[END_REF][START_REF] Parker | Towards a model of surgeons' leadership in the operating room[END_REF][START_REF] Parker | Surgeons' leadership in the operating room: an observational study[END_REF] , using scales to examine the different skills. Overall, a close link is shown to exist between teamwork and the number of undesirable events occurring in the operating theatre. These articles underline the necessity for maximum communication among the whole team before, during and after a surgical procedure in order to reduce the risk of errors [START_REF] Ajlan | The human factor and safety attitudes in neurosurgical operating rooms[END_REF][START_REF] Russ | Measuring safety and efficiency in the operating room: development and validation of a metric for evaluating task execution in the operating room[END_REF][START_REF] Hull | Building global capacity for patient safety: a training program for surgical safety research in developing and transitional countries[END_REF][START_REF] Lau | Creating a culture of safety within operative neurosurgery: the design and implementation of a perioperative safety video[END_REF][START_REF] Muzumdar | Safety in the operating room: neurosurgical perspective[END_REF][START_REF] Ferroli | Application of an aviation model of incident reporting and investigation to the neurosurgical scenario: method and preliminary data[END_REF][START_REF] Fargen | Enhanced staff communication and reduced near-miss errors with a neurointerventional procedural checklist[END_REF][START_REF] Sekhar | Teamwork mentality in neurosurgical teams to improve patient safety[END_REF] .

Repercussions and prospects

The utility of a good knowledge of NTS and of their assessment was demonstrated in the work of Hull et al in 2012 [START_REF] Hull | The Impact of Nontechnical Skills on Technical Performance in Surgery: A Systematic Review[END_REF] . NTS appear to have a positive influence on TS : they apparently improve the quality of care and patient outcome by improving safety and efficiency in the operating theatre. This study was carried out on a panel of several different types of specialist surgery.

Good mastery of NTS in neurosurgery has obvious pedagogical implications. A better understanding and definition of these skills in each specialist surgical domain, particularly in neurosurgery, would enable those responsible for teaching to identify more clearly the training

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needs for surgeons in that domain. The next step would be inclusion of NTS as specific subjects in educational programmes [START_REF] Hull | Training faculty in nontechnical skill assessment: national guidelines on program requirements[END_REF][START_REF] Long | Competency-based residency training: the next advance in graduate medical education[END_REF][START_REF] Heros | Neurosurgical education: the "other" competencies. The 2003 presidential address[END_REF][START_REF] Kabwama | Opportunities to improve undergraduate neurosurgery career interest, knowledge and skills: lessons from the BAPRAS undergraduate courses[END_REF][START_REF] Kaufman | Teaching surgeons to operate--principles of psychomotor skills training[END_REF][START_REF] Selden | A National Fundamentals Curriculum for Neurosurgery PGY1 Residents: The 2010 Society of Neurological Surgeons Boot Camp Courses[END_REF][START_REF] Morineau | Decision Making During Preoperative Surgical Planning[END_REF] . This is beginning to be done in the United States by the Accreditation Council for Graduate Medical Education (ACGME) [START_REF] Mazzola | Efficacy of neurosurgery resident education in the new millennium: the 2008 Council of State Neurosurgical Societies post-residency survey results[END_REF] Confining learning of these skills exclusively to one or another particular stage of the learning process seems unduly simplistic. Placing the acquisition of these skills at the beginning of internship training would be more valuable, since these are general skills which can be applied from the outset of daily surgical activity. They do not necessarily require previous specific declarative knowledge such as complex anatomical elements, which could represent a technical obstacle for a young resident operating, for example, on a brain tumour in a difficult location. It also appears more logical for students to acquire these skills as early as possible to optimize patient safety, for the same reason as they learn basic technical skills (for example, how to hold an instrument properly).

It is also essential to include NTS in CPD, since acquisition of these skills is not yet systematic in early training. Surgery, and neurosurgery in particular, is often taught by mentoring, the main teaching tool being the role model. In spite of many hours spent in the operating theatre or with patients, a neurosurgery intern may at times find it difficult to understand the difficulties facing the surgeon and the cognitive conflicts he experiences [START_REF] Morineau | Decision Making During Preoperative Surgical Planning[END_REF] . On the other hand, the surgeon may have difficulty in transmitting the skills he has learnt by experience, which seem natural to him since he cannot formalize them and make them explicit. Understanding NTS more clearly, formalizing them and rendering them explicit, will greatly improve the training of young neurosurgeons by helping them to identify problems at an early stage, so as to optimize patient safety [START_REF] Mb | What Every Graduating Resident Needs to Know About Quality Improvement and Patient Safety: A Content Analysis of 26 Sets of ACGME Milestones[END_REF] and accelerate their learning curve.

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NTS are also an important subject in the research domain. Initially, applying recognised measuring scales (NOTECHS, NOTSS, OTAS) to neurosurgery could render it possible to pursue the study of their feasability and assess their reliability and variability in a specific context. Neurosurgery is a complex and specific surgical discipline which nonetheless shares similar difficulties and NTS with other surgical specialties, while retaining its own particular aspects. Studying NTS in neurosurgery opens the possibility of enriching the taxonomy in this domain. The concepts of morbidity and mortality within neurosurgical procedures are of extreme importance. Many operations may carry a risk of life-threatening consequences or of life-changing functional handicaps. They involve cognitive conflicts which are difficult for the surgeon to manage, the more so as the procedure often takes place in the context of an emergency. One example is a patient's recovery from anaesthesia after an operation for cranio-cerebral pathology. Several different scenarios are possible : 1) A patient without preoperative neurological signs may on recovery present new disabilities which may or may not disappear (induced handicap) ; 2) A patient with no preoperative vigilance disorders may not recover consciousness after anaesthesia and risks falling into a chronic coma state ; 3)

Fortunately in the majority of cases the patient recovers consciousness without new disabilities, or with an improvement compared to preoperative neurological signs. It can easily be understood that in these different situations stress management, risk assessment and pressure are not the same.

Stress management continues until the patient's recovery from anaesthesia ; it does not end when the surgical procedure is finished.

Different methods of intervention to improve safety in operating theatres have been appearing over the last few years, particularly since 2009 with the Surgical Safety Checklist [START_REF] Haynes | A Surgical Safety Checklist to Reduce Morbidity and Mortality in a Global Population[END_REF] . Other specific checklists have been developed in neurosurgical specialist areas such as vascular neurosurgery or deep brain stimulation [START_REF] Zuckerman | Neurosurgical checklists: a review[END_REF] . In terms of public health, surgical errors are responsible for a significant increase in morbidity, a deterioration in the quality of life and increased expenditure 10,12- 17,28,33,34,36,38,86 . These checklists have been developed [START_REF] Haynes | A Surgical Safety Checklist to Reduce Morbidity and Mortality in a Global Population[END_REF][START_REF] Silva-Freitas | Establishment of a modified surgical safety checklist for the neurosurgical patient: Initial experience in 400 cases[END_REF][START_REF] Mcconnell | Surgical checklists: A detailed review of their emergence, development, and relevance to neurosurgical practice[END_REF][START_REF] Rahmathulla | Surgical briefings, checklists, and the creation of an environment of safety in the neurosurgical intraoperative magnetic resonance imaging suite[END_REF][START_REF] Zuckerman | Neurosurgical checklists: a review[END_REF] in order to reduce the number of avoidable errors, with the constant purpose of improving the quality of care and the safety of 9

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Study characteristics 18 For each study, present characteristics for which data were extracted (e.g., study size, PICOS, follow-up period) and provide the citations.

10-13

Risk of bias within studies 19 Present data on risk of bias of each study and, if available, any outcome level assessment (see item 12).

NC

Results of individual studies 20 For all outcomes considered (benefits or harms), present, for each study: (a) simple summary data for each intervention group (b) effect estimates and confidence intervals, ideally with a forest plot.

10-13

Synthesis of results 21 Present results of each meta-analysis done, including confidence intervals and measures of consistency.

NC

Risk of bias across studies 22 Present results of any assessment of risk of bias across studies (see Item 15).

NC

Additional analysis 23 Give results of additional analyses, if done (e.g., sensitivity or subgroup analyses, meta-regression [see Item 16]).

NC

DISCUSSION

Summary of evidence 24 Summarize the main findings including the strength of evidence for each main outcome; consider their relevance to key groups (e.g., healthcare providers, users, and policy makers).

114

Limitations 25 Discuss limitations at study and outcome level (e.g., risk of bias), and at review-level (e.g., incomplete retrieval of identified research, reporting bias). For more information, visit: www.prisma-statement.org.

14-15

NC: non considered

1 )

 1 Data concerning NTS OR interpersonal behaviour OR leadership OR teamwork OR planning and preparation OR feedback OR stress and pressure OR fatigue OR cognitive skills OR anticipation of problems OR decision-making OR flexibility OR adaptation strategies

DISCUSSION

  used an opinion poll on theoretical teaching of one hour per month given to 11 neurosurgery interns. Pre-tests and post-tests revealed both quantitative and qualitative improvements in knowledge concerning leadership.This systematic review of the literature on NTS is to our knowledge the first which specifically concerns neurosurgery. Analysis of these skills is scattered through the literature, and they are frequently assessed individually without use of an up-to-date unified domain taxonomy. Articles reporting on the assessment of one or several NTS appear very limited in number(21). Specific training needs are difficult to define for the moment since these NTS have not yet been properly

  . The ACGME indicated for each of the specialties the "milestones" to be achieved by residents in training in each of the six "core competencies" required in the training course. Those dedicated to neurosurgery are particularly detailed in the March 2018 version of these recommendations 84 . Including NTS learning in neurosurgery can be envisaged at two points in the training period : during internship (initial training) and/or as ongoing education in the context of continuing professional development (CPD).

  review of the literature, it appears that very few studies have been carried out concerning neurosurgical NTS, in spite of increasing numbers of articles over the last few years on NTS in other domains of surgery. Moreover, this literature is very diverse in comparison with studies on TS. The complexity of the methodology required to ensure robust assessment tools is probably the reason for this disparity. Society today is concentrating more and more on the quality and safety of medical care, particularly in the domain of neurosurgery. The development and application of these assessment tools is therefore essential. They will also provide important and still underestimated assistance in the training of future neurosurgeons, thus ensuring that all the skills necessary to the profession are effectively transmitted.

Figure 1 Figure 2 and

 12 Figure 1 Résumé of structured data for article analysis

  Risk of bias across studies15 Specify any assessment of risk of bias that may affect the cumulative evidence (e.g., publication bias, selective reporting within studies).NCAdditional analyses 16 Describe methods of additional analyses (e.g., sensitivity or subgroup analyses, meta-regression), if done, indicating which were pre-specified.NCRESULTSStudy selection 17 Give numbers of studies screened, assessed for eligibility, and included in the review, with reasons for exclusions at each stage, ideally with a flow diagram.

Conclusions 26 20 FUNDINGFunding 27

 262027 Provide a general interpretation of the results in the context of other evidence, and implications for future research. Describe sources of funding for the systematic review and other support (e.g., supply of data); role of funders for the systematic review.

21 From:

 21 Moher D, Liberati A, Tetzlaff J, Altman DG, The PRISMA Group (2009). Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRISMA Statement. PLoS Med 6(7): e1000097. doi:10.1371/journal.pmed1000097

Table 1 .

 1 Characteristics of the studies assessing non-technical skills in neurosurgery

		Year
	First author	of public	Population	Type of study	Environment	Non-technical skills assessed	Tools for assessment	Key results
		ation
			Teaching
	Cusimano 44 1999	hospital neurosurgeon s and interns in	Qualitative	Real	Interpersonal skills and workload	Qualitative analysis of questionnaires Double scale content analysis	Positive correlation between excess workload and voluntary withdrawal and between dismissal and interpersonal skills during the neurosurgery internship
			neurosurgery
	Pathak 67	2000	Professors of neurosurgery	Intervention al study	Real environment and consultations	Leadership	External observation scale for patterns of leadership and language	Good productivity and flexibility, moderate objectivity and comprehensibility
			Neurosurgery				Number of conflicts and checks	Significant link between the expert
	Morineau 64 2009	interns, registrars and	Experimenta l study	Simulation Decision-making	reported by each neurosurgeon Skills /Rule / Knowledge	undertaking tasks and checking of conflicts, Regulation of conflict control
			professors				approach	essentially based on experts' knowledge
	Pettit 43	2011	Neurosurgery interns	Survey	Theoretical teaching	Leadership	Opinion poll	Training in the importance of leadership and the means to develop it.
	Ganju 56	2012	Neurosurgery inters	Semi-experimenta l study	Simulation	Dealing with fatigue, cognitive skills	Fluidity of gestures, time taken and cognitive errors	No significant reduction in skills during simulated surgical procedures after on-call service.
			Professors of
	Selden 54	2012	neurosurgery and first-year neurosurgery	Survey	Simulation	Multiple non-technical skills	Opinion poll	Teaching appreciated by interns for the improvement of their knowledge and their technical and non-technical skills .
			interns

Funding sources

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Disclosure

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Analysis of perioperative safety video

The perioperative safety video improves safety in the operating theatre and raises the team's awareness of safety issues

Disclosure-Conflict of Interest

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.


Zhihao Wu

Yinsheng Xu

Dongfeng Qi

Qiuhua Nie

Xianghua Zhang

Progress in preparation and applications of Te-As-Se chalcogenide glasses and fibers

Keywords: TAS glasses, MIR applications, FEWS, Fiber sensing

Te-As-Se (TAS) chalcogenide (ChG) glasses are suitable candidates for mid-infrared (MIR) applications. In this work, the formation, preparation of highpurity glasses and optical fibers, and the applications of TAS fibers were systematically reviewed. In this review, the thermal, optical properties as well as the fiber performance parameters of TAS glasses were summarized. Finally, the progress of TAS fibers in MIR applications, especially for sensor applications such as food monitoring and medical diagnostic were described in detail.

Introduction

Chalcogenide (ChG) glasses are composed IVA group elements (S, Se, Te), and added with heavy elements such as Ge, As and Sb, as shown in Fig. 1(a). Compared with traditional silicate glass, ChG glasses have many prominent features including ultra-wide infrared transmission range (up to 25 μm, Fig. 1(b)), lower phonon energy (<350 cm -1 ), higher linear refractive index n 0 (2.0-3.5) and nonlinear refractive index (100 to 1000 times higher than those of silicate glasses), ultra-fast optical response time (<100 fs), excellent resistance to corrosion in atmospheric environment and tunable composition for different applications [START_REF] Tao | Infrared fibers[END_REF][START_REF] Anashkina | Development of As-Se tapered suspended-core fibers for ultra-broadband mid-IR wavelength conversion[END_REF]. With the above superior performance, ChG glasses have been applied to infrared lens for night vision, phase change memories, electrolytes for batteries, waveguide devices for all-optical signal processing, photoresists for lithography and some new optoelectronic devices [START_REF] Adam | Chalcogenide glasses[END_REF][START_REF] Lan | Integrated flexible chalcogenide glass photonic devices[END_REF]. Besides, ChG glasses are suitable for drawing fibers. ChG fibers have low intrinsic losses, favorable bendability, stable chemical properties, high nonlinear coefficients and ultra-wide infrared transmission range (up to ~26 μm). The ChG fibers have significant applications in the laser delivery [START_REF] Sato | Multihundred-watt CO laser power delivery through chalcogenide glass fibers[END_REF][START_REF] Sincore | High power single-mode delivery of midinfrared sources through chalcogenide fiber[END_REF], transmission of thermal image [START_REF] Suto | Chalcogenide fiber bundle for 3D spectroscopy[END_REF][START_REF] Zhang | High-resolution chalcogenide fiber bundles for infrared imaging[END_REF][START_REF] Qi | High-resolution chalcogenide fiber bundles for longwave infrared imaging[END_REF], MIR supercontinuum (SC) generation [START_REF] Petersen | Mid-infrared supercontinuum covering the 1.4-13.3 μm molecular fingerprint region using ultrahigh NA chalcogenide step-index fibre[END_REF][START_REF] Zhao | Mid-infrared supercontinuum covering 2.0-16 μm in a low-loss telluride single-mode fiber[END_REF][START_REF] Zhang | Ultrabroadband and coherent mid-infrared supercontinuum generation in Te-based chalcogenide tapered fiber with all-normal dispersion[END_REF] and infrared sensing [START_REF] Chahal | Fiber evanescent wave spectroscopy based on IR fluorescent chalcogenide fibers[END_REF][START_REF] Sharma | Simulation and performance evaluation of fiber optic sensor for detection of hepatic malignancies in human liver tissues[END_REF][START_REF] Velmuzhov | Fiber sensor on the basis of Ge 26 As 17 Se 25 Te 32 glass for FEWS analysis[END_REF] since covering the molecular fingerprint region of 3-13 μm MIR bands. To be drawn to a fiber, the glass is required to possess the good thermal stability. Usually, the difference of T x and T g larger than 120 o C is the minimum value to avoid crystallization during the drawing process. Until now, ChG fibers such as As-S, As-Se, Ge-As-Se, Ge-Ga-Sb-S (Se), etc are successfully fabricated. Among numerous ChG glasses, TAS glasses have been widely investigated since their excellent thermal stability for drawing fibers and broad transmittance in the MIR [START_REF] Yang | Effect of Physical Aging Conditions on the Mechanical Properties of Te 2 As 3 Se 5 (TAS) Glass Fibers[END_REF][START_REF] Brandová | Thermo-structural characterization of (As 2 Se 3 ) 100-x -(As 2 Te 3 ) x glasses for infrared optics[END_REF][START_REF] Wu | 1.8-13 μm supercontinuum generation by pumping at normal dispersion regime of As-Se-Te glass fiber[END_REF]. TAS fibers have low transmission losses in the 2-18 μm bands, especially in the range of 2-12 μm, which is an ideal medium for detecting fingerprint region molecules [START_REF] Bureau | Chalcogenide optical fibers for mid-infrared sensing[END_REF][START_REF] Shiryaev | Infrared fibers based on Te-As-Se glass system with low optical losses[END_REF].

Moreover, TAS fibers have excellent resistance to water, corrosion and electromagnetic interference. They could not only monitor and identify in-situ and long-distance real-time substances in harsh environments such as high temperature (around 100 o C), electromagnetic interference and toxic, but also realize the detection of special aqueous solutions, biological tissues [START_REF] Hocdé | Biological tissue infrared analysis by chalcogenide glass optical fiber spectroscopy[END_REF], liquids and gaseous substances with infrared characteristic absorption spectra, which has been attracted extensive attention in the fields of biochemistry, microbiology, medical diagnosis, etc [START_REF] Lucas | Chalcogenide glass sensors for bio-molecule detection[END_REF].

Although TAS glasses have been investigated for half a century, there is no detailed review that summarizes the glass forming, fiber drawing, and applications until now.

In this review, we retrospected the formation of TAS glasses first, followed by summary of glass purification technique, the thermal and optical properties of TAS glasses. Finally we introduced the research progress of TAS glasses and fibers in MIR applications and made a prospect.

Formation of TAS glasses

Formation and properties of TAS glasses

In 1976, Kotkata et al. first reported the TAS glasses [START_REF] Kotkata | Measurement of the electrical and thermal conductivity coefficients of As 2 Se 3 -As 2 Te 3 glassy alloys[END_REF]. Generally, ChG glasses were prepared by melt-quenching technique in the vacuumed ampoule ChG glasses [START_REF] Sun | Fabrication and characterization of multimaterial chalcogenide glass fiber tapers with high numerical apertures[END_REF][START_REF] Chubanov | High-purity glasses based on arsenic chalcogenides[END_REF][START_REF] Kanamori | Chalcogenide glass fibers for mid-infrared transmission[END_REF]. As shown in Fig. 2, TAS glass formation domain was relatively large, including As-Se, As-Te, Se-Te binary systems [START_REF] Bureau | Forming glasses from Se and Te[END_REF][START_REF] Borisova | Glassy Semiconductors[END_REF]. The As-Se binary system had better glass forming ability than that of As-Te and Se-Te. In the TAS ternary system, the glass forming domain was located in the Se-rich region, which was biased toward the As-Se side. with the heating rate of 2.5 K/min. When x= 0, 25, 30, 35, 40, there was an obvious crystallization peak; when x= 5, 10, 15, there was a weak crystallization phenomenon; when x=20, there was no crystallization. When the heating rate was 5 K/min, as shown in Table 1, no crystallization occurred in the compositions of x=10, 15, and 20.

When the heating rate was 10 K/min, the x=5, 10, 15, and 20 compositions did not undergo crystallizations as shown in Fig. 3(b). From the formula K gl = (T c -T g )/(T l -T c ) proposed by Hruby [START_REF] Hrubý | Evaluation of glass-forming tendency by means of DTA[END_REF], we know that the interval T c -T g is directly proportional to the glass-forming tendency and the T l -T c is indirectly proportional to the glass-forming tendency. Therefore, the TAS glasses of x=5, 10, and 15 compositions were relatively stable. At different heating rates (2.5, 5 and 10 K/min), only Te 20 As 40 Se 40 had no crystallization peak, indicating that this glass was most stable. μm, but poor mechanical properties. In contrast, the mechanical behavior of Ge 25 Sb 10 S 65 is improved, but the transmission is limited to 12 μm in the infrared.

Between these glasses, TAS glass is an interesting compromise for many applications, with correct mechanical properties and broad-enough transmission range for detection in the molecular fingerprint region. TeX glasses [START_REF] Snopatin | Highpurity chalcogenide glasses for fiber optics[END_REF] [START_REF] Lucas | The tellurium halide glasses[END_REF]. [35].

Glass E/GPa ρ/(g•cm -3 ) α/K -1 H v /(kg•mm -2 ) T g / o C

Impurity and purification of TAS glasses

The infrared transmission properties of ChG glasses are sensitive to impurities. The impurities in TAS glasses can be divided into two types. The first one is the impurity combined with the glass network or dissolved in the glass matrix. Such impurities usually absorb light selectively. In the fiber loss spectrum, the corresponding absorption peak size is determined by the corresponding impurity concentration, such impurities are mainly combined with H and O. The second one is different from the refractive index of glass, which exhibits scattering of light and then increases the loss of the entire infrared bands including holes, microcrystalline particles and solid inclusions such as SiO 2 , carbon, transition metal oxides, etc.

There are three types of impurity sources for TAS glasses [START_REF] Snopatin | Highpurity chalcogenide glasses for fiber optics[END_REF]. The first category is mainly from raw materials: commercial materials (Te, As, Se) have a purity of 5N (99.999%), thus impurities such as oxygen, molecular water, carbon, and transition metals in the raw materials should be removed as much as possible. Table 3 lists the melting point and purification methods of the raw materials. The second source is from the container for the synthesis of glass at a high temperature. Silica glass tubes are the main container material used for the synthesis of ChG glasses. Hydrogen and silicon dioxide impurities are introduced from the walls of the silica glass tubes. The impurities with high diffusion coefficients, especially hydrogen, can enter the TAS melts easily. It was found that hydrogen started to enter the TAS melts from the silica glass tubes, containing 100 ppm of hydrogen, beginning from 650 ℃. The temperature T dependence of a hydrogen entrance rate v (g•cm -2 •s -1 ) is described by the expression: lnv=-11.2-(15300/T), the range of T is 873~1023 K [START_REF] Snopatin | Highpurity chalcogenide glasses for fiber optics[END_REF]. The chemical interaction of ChG and impurities with silica glass tubes at high temperatures results in the formation of a thin layer on its surface. Owing to the difference in thermo-mechanical properties of the glass matrix and the layers, these layers can be separated from the silica glass tubes and enter the TAS melts to form heterogeneous inclusions, which were represented by αcristobalite impured with β-cristobalite [START_REF] Snopatin | Highpurity chalcogenide glasses for fiber optics[END_REF].

The third type of impurity source mainly comes from the reaction of residual gas in the air with TAS glass during vacuuming. Impurities embedded in the glass network include O-H, Se-H, H 2 O, As-H as well as N 2 , CO 2 and the like. The common impurities in TAS glasses and their corresponding absorption peak wavelengths were described in Ref. [START_REF] Snopatin | Highpurity chalcogenide glasses for fiber optics[END_REF]. Generally O-H, H 2 O, Se-H, and S-H bonds are relatively difficult to remove.

In addition, for the impurities commonly found in the above TAS glasses, impurity mass fraction can be calculated easily according to the Lambert-Beer law, I=I 0 exp(-εxL), where I and I 0 are the light fluxes of sample output and input, respectively, ε is the extinction coefficient, x is the impurity mass fraction, and L is the distance (here is the sample thickness). Table 4 shows the extinction coefficients that can be found for some known impurities.

Table 4. Extinction coefficients of impurities in TAS glasses. Reprinted with permission from Ref. [START_REF] Snopatin | Highpurity chalcogenide glasses for fiber optics[END_REF].

Impurities Extinction coefficient (dB/m) Se-H 1×10 -3 As 2 O 3 1.03×10 -3 Se-O 3.8×10 -4 CO 2 1.5×10 -2
For preparing TAS glasses with better performance, the key problem to be solved is to design the purification process to remove the impurities as much as possible.

Common oxygen getters such as Al (or Mg) and hydrogen getters such as TeCl 4 (or GaCl 3 , AlCl 3 ) were usually mixed and used together into the raw materials for distillation and purification to synthesize glasses. Table 5 shows the mass fraction of impurities measured by different methods [START_REF] Shiryaev | Recent progress in preparation of chalcogenide As-Se-Te glasses with low impurity content[END_REF]. The addition of AlCl designed the experimental apparatus as illustrated in Fig. 6 [START_REF] Hocdé | Chalcogens Based Glasses for IR Fiber Chemical Sensors[END_REF]. Firstly, the As and Se of 5N purity were heated and evaporated at 290 ℃ and 250 ℃ respectively during the vacuuming process to remove the oxide impurities and molecular water. Subsequently

As and Te were introduced into the double chambers tube together with Se. After sealed, the double chambers tube was heated with a temperature gradient furnace designed for melting the elements in the hot zone and then for purification of the melt by distillation into the cold zone. After resealed, the high purity glass was homogenized in a rocking furnace at 700 °C and then cooled down close to the T g (127 °C). At this temperature, the glass was annealed for several hours and slowly cooled to room temperature. Finally, the high purity TAS glasses were obtained. o C, causing it to remain in silica tube 1 during the subsequent distillation process.

Then, the heating temperature of the silica tube 1 was maintained, and the silica tube 2 was heated to condense the glass melt in the silica tube 3. After the second distillation, the silica tube 3 was sealed, melted and homogenized at 700 °C for 7 h.

Finally, high purity TAS glasses were obtained by quenching and annealing. Ref. [START_REF] Shiryaev | Infrared fibers based on Te-As-Se glass system with low optical losses[END_REF].

TAS glasses transmission and fiber loss

The short cut-off wavelength of ChG glasses are caused by electronic transitions, while the IR edge depends mainly on the lattice vibration of the material. The transmission spectrum of the purified glass is shown in Fig. 8 Désévédavy et al. drew TAS glass into microstructured fiber for the first time [START_REF] Désévédavy | Te-As-Se glass microstructured optical fiber for the middle infrared[END_REF].

Its cross-sectional view was shown in Fig. 10(a). Single mode transmission could be achieved with a loss of 9 dB/m@3.39 μm and 6 dB/m@9 μm, respectively. The predicted loss is expected to be reduced to 1 dB/m. The fiber loss would be up to 20-30 dB/m when the interstitials holes were collapsed [START_REF] Brilland | Interfaces impact on the transmission of chalcogenides photonic crystal fibres[END_REF]. [40].

The applications of TAS glasses

Fiber sensing

The types of fiber sensor mainly include reaction cell light absorption type sensing, sensitive film light reflection and scattering type sensing, fluorescence type sensing, phosphorescence type sensing and evanescent field response type sensing [START_REF] Ramakrishnan | Overview of fiber optic sensor technologies for strain/temperature sensing applications in composite materials[END_REF].

Currently, TAS fiber sensor is mainly based on the principle of fiber evanescent wave spectroscopy (FEWS), that is, evanescent field response type sensing. Because of the spectral range cover the domain where are located the main IR signatures of molecules and biomolecules, TAS FEWS has been carried out to get some fruitful information in biology and medicine for early stage diagnosis or food safety [START_REF] Bureau | Development of chalcogenide glass fibers for mid-IR technologies[END_REF].

According to Snell's law, when the incident angle of light is bigger than the critical angle θ c , then total internal reflection (TIR) occurs at the interface between the fiber (unclad ) and air. The result of interaction with the reflected light is the generation of standing wave near the interface. In general, the phase of the light changes as it is reflected, the amplitude of the standing wave at the interface will be limited. The detailed explanation of Maxwell's equation shows that the standing wave is exponentially attenuated when it extends along the reflection cross section to a medium with a low refractive index, which called evanescent wave. A key parameter is the penetration depth (d p ) of the evanescent field for sensing detection [START_REF] Jiang | Engineering of a Ge-Te-Se glass fibre evanescent wave spectroscopic (FEWS) mid-IR chemical sensor for the analysis of food and pharmaceutical products[END_REF].

(

) 2 2 2 2 1 p sin π 2 n n d     1
where λ is the light wavelength, n 2 and n 1 are the refractive indices of the fiber and surrounding detection substance, respectively; θ is the angle of incidence of the wave in the fiber. The penetration of the evanescent wave increases linearly with the wavelength. When the optical fiber is in contact with the liquid to be tested, the infrared light is absorbed by the corresponding characteristic frequency chemical bond to exhibit a characteristic absorption spectrum. According to the absorption spectrum obtained by the contact of the evanescent wave on the surface of the fiber with the substance to be tested, it is extremely possible to detect the chemical substance and concentration, which does not destroy the substance itself and realizes remote sensing [START_REF] Cui | From selenium-to tellurium-based glass optical fibers for infrared spectroscopies[END_REF]. To improve the sensitivity of the FEWS detection and make the evanescent wave be more diffused into the sample, usually, the structure of the optical fiber is modfied. For example, the core-cladding and the tapered fibers as well as the single/multimode fibers combination, fiber bonding and other methods [START_REF] Bureau | Development of chalcogenide glass fibers for mid-IR technologies[END_REF]. The FEWS principle of normal fiber and tapered fiber set-up is shown in Fig. 11, respectively. The sensing zone in contact with the sample to be tested generally utilizes the tapered fiber, because the number of total internal reflections in the taper region is significantly increased, resulting that the sensitivity of the sensing can be effectively enhanced [START_REF] Jiang | An infrared fibre evanescent wave spectroscopic (FEWS) sensor using purified GeTeSe chalcogenide fibres[END_REF]. 12. TAS tapered fibers were both used as transmission and sensing elements. As shown in Fig. 13, the symmetry and asymmetry vibrations of CH 2 groups were successfully detected at 2853 cm -1 and 2926 cm -1 , respectively. Besides, the symmetrical and asymmetric vibrations of the Lucas et al. used TAS tapered fiber to place human lung cells with Triton X-100, and successfully detected infrared spectral changes caused by methyl and methylene hydrocarbons in the range of 2800-3000 cm -1 , which demonstrated the possibility of the ChG fibers for cell-based biosensors [START_REF] Lucas | Evaluation of toxic agent effects on lung cells by fiber evanescent wave spectroscopy[END_REF]. TAS fiber biosensors, small, simple and sensitive, can monitor various metabolic cells in situ, which can used for early diagnosis of tumors and cancers in medical fields. Therefore, it has extremely inclusive prospects in medicine and microbiology applications [START_REF] Bureau | Chalcogenide optical fibers for mid-infrared sensing[END_REF]. showing that several pollutants can be detected simultaneously. Reprinted with permission from Ref. [START_REF] Michel | Monitoring of pollutant in waste water by infrared spectroscopy using chalcogenide glass optical fibers[END_REF].

The research team in University of Rennes 1 committed to the research of fiber sensing for early disease diagnosis. In June 2011, DIAFIR was founded by an interdisciplinary team of researchers and engineers. Their product, fiber evanescent wave sensor, can be made great use of medical diagnosis shown in Fig. 17. TAS tapered fiber was used to collect information from serum. The system, equipped with an intuitive touch screen interface and a spectrum processing algorithm to directly diagnose the score, only requires a small detection source with 1 mm 2 of tissue or 10 μl of liquid sample (1 drop) [START_REF] Corvec | Fast and non-invasive medical diagnostic using mid infrared sensor: The AMNIFIR project[END_REF]. Thanks to timeliness and high sensitivity, it saves hospital stays through invasive and time-consuming surgery and helps doctors get more accurate results and better care for patients. Until now, the non-invasive test has been developed to diagnose the non-alcoholic steato-hepatitis (or NASH) and acute septic arthritis [START_REF] Anty | Mid-infrared spectroscopy has a high sensitivity and specificity for point-of-care diagnosis of non-alcoholic steato-hepatitis[END_REF][START_REF] Albert | A novel method for a fast diagnosis of septic arthritis using mid infrared and deported spectroscopy[END_REF]. Fig. 17. DIAFIR company's product in France: TAS fiber evanescent wave sensor

Laser delivery & light propagation

Kosolapav et al prepared a TAS microstructured hollow-core fiber shown in Fig. 18, which was firstly demonstrated that it was possible to use the TAS microstructured hollow-core fiber for propagating the 10.6 μm CO 2 -laser radiation. A further improvement of the technology and design of such fibers is expected to yield a reduction of the optical loss to below 1 dB/m. This TAS microstructured hollow-core fiber has great promise for the delivery of the СО 2 -laser radiation since the light is well limited at the fiber center.

Supercontinuum generation

The MIR SC generation spectra of ChG fibers, especially the ultra-broadband spectra covering 2-13 μm molecular fingerprint band, are expected to be developed new IR light sources [START_REF] Cimalla | Shear flow-induced optical inhomogeneity of blood assessed in vivo and in vitro by spectral domain optical coherence tomography in the 1.3 μm wavelength range[END_REF][START_REF] Petersen | Mid-infrared multispectral tissue imaging using a chalcogenide fiber supercontinuum source[END_REF]. TAS glasses have high nonlinear refractive index and wide MIR transmission [START_REF] Brandová | Thermo-structural characterization of (As 2 Se 3 ) 100-x -(As 2 Te 3 ) x glasses for infrared optics[END_REF], resulting that TAS glasses are more suitable for drawing fibers to obtain ultra-wide spectral conversion than binary sulfur arsenic compounds.

Until now, there are few reports on the SC spectra of TAS fibers. Anashkina et al.

proposed and optimized theoretically a SC laser source in the MIR using Te-As-Se/As-S step-index fiber and pumped by a center wavelength of 150 fs pulse femtosecond all-fiber laser system at 2 μm [START_REF] Anashkina | On the possibility of mid-IR supercontinuum generation in As-Se-Te/As-S core/clad fibers with all-fiber femtosecond pump source[END_REF]. Numerically simulated spectra extending from ~1 μm to >8 μm were demonstrated with pumping energy of 100 pJ.

Conclusion and Prospect

In conclusion, formation of Te-As-Se glasses, their thermal and optical properties, purification technology, the fiber preparation technology, as well as fiber sensing principle and the research progress in sensing applications were reviewed. Although the research of Te-As-Se glasses and fibers have been carried out for nearly half a century, there are still many problems to be solved: firstly, it is necessary to continuously improve the preparation and purification technology to reduce its loss, so as to improve light transmittance and the sensitivity in sensing research. Secondly, the commercial TAS fiber sensors have not appeared except DIAFIR company, therefore, it is necessary to increase its innovation and development with wide range of promotion and application. Finally, there is few TAS fibers report of SC spectrum pupmed by commercial laser, usually, large optical parametric amplifier (OPA) or optical parametric oscillator (OPO) is apply for pumping ChG fibers. Therefore, TAS fiber with proper waveguide dispersion should be designed, such as microstructure and tapered fibers, which makes zero dispersion wavelength blue shift and realize the broadband MIR SC generation.

Fig. 1 .

 1 Fig. 1. (a) The commonly used elements for forming chalcogenide glasses and (b)

Fig. 2 .

 2 Fig. 2. TAS glasses forming domain. Reprinted with permission from Ref. [27].

Fig. 3 .

 3 Fig. 3. DSC results for Te x As 40 Se 60-x glasses with heating rate of (a) 2.5 K/min,

T

  g : glass transition temperature, T c : onset of crystallization temperature, T p : peak of crystallization temperature, T s : solidus temperature, T l : liquidus temperature, ΔT=T c -T g , K gl = (T c -T g )/(T l -T c ); S=(T p -T c )(T c -T g )/T g . As the DSC results shown, the Te 20 As 40 Se 40 has good thermal stability which has been drawn to fiber. As shown in Fig. 4, the refractive indexes of Te 20 As 40 Se 40 and Te 18 As 40 Se 42 glasses can be close to 3, which was larger than that of silicate glasses.

Fig. 4 .

 4 Fig. 4. Refractive indices of fiber core (Te 20 As 40 Se 40 ) and cladding (Te 18 As 40 Se 42 ) and

  Experimental data also revealed the absence of Te-Te bonds even in the tellurium richest composition which let suppose a homogeneous repartition of tellurium atoms in the glassy network. Jóvári et al. researched the structure of Te 20 As 30 Se 50 glass by X-ray and neutron diffraction as well as extended X-ray absorption fine structure measurements at the As-, Se-, and Te K-edges[35]. The five datasets were modelled simultaneously by the reverse Monte Carlo simulation technique. Fig. 5 shows all the chemical bonds in Te 20 As 30 Se 50 glass network, which was a pyramid network structure. Experimental data could be fitted satisfactorily by allowing As-Se, As-Te and Se-Te bonds only. All atoms satisfy the 8-N rule (N As =3, N Se =N Te =2) and the affinity of As was much higher to Se than to Te. Chalcogen atoms preferentially bonded to As atom, and Se-Te bonds were formed only after saturating all valences of As.

Fig. 5 .

 5 Fig. 5. The atomic structures of Te 20 As 30 Se 50 . Reprinted with permission from Ref.

  3 can effectively remove hydrogen impurity (about 10 times reduction), and also reduce oxygen and silicon. The carbon mass fraction was almost unchanged, and the mass fraction of metal element impurities was determined by the raw materials and the purification process. Adding an appropriate amount of Al as oxygen getter can effectively reduce the oxygen absorption peak; however this way had a large disadvantage, which would significantly enhance the content of the Se-H peak. It was estimated that the mass fraction of hydrogen could from 0.5 to 4 ppm, when Al exceeds 1 ppm, the molecular H 2 O in the glasses network was effectively decomposed. Subsequently the decomposed oxygen and Al formed highly volatile substances, which were removed by distillation, resulting in forming Se-H peak by remaining hydrogen and Se elements.

Fig. 6 .Fig. 7 .

 67 Fig. 6. Experimental set-up used for the purification of the starting elements, Te, As,

Fig. 7 .

 7 Fig. 7. Set-up for preparing high purity Te-As-Se glasses: 1-silica glass tube with Te-

  (a), especially at 2-12 μm has excellent transmittance[START_REF] Hocdé | Chalcogens Based Glasses for IR Fiber Chemical Sensors[END_REF].Shiryaev et al. added 700 ppm Al to purify the glass preform and drawed the TAS fibers, the lowest losses of the unclad Te 25 As 40 Se 35 and Te 20 As 30 Se 50 fibers were 0.07 dB/m@7.3 μm and 0.04 dB/m@6.7 μm, respectively[20]. In 2006, their group prepared the single mode step-index (Te 18.6 As 39 Se 42.4 /Te 18.3 As 39 Se 42.7 ) glass fiber, the minimum loss was about 0.33 dB/m at 7.5 μm[37]. As shown in Fig. 8(b), the large loss peak in the range of 4-5 μm was mainly due to the influence of Se-H bond, and the loss peak at 6.3 μm was affected by H 2 O. Lv et al. reduced the C-O peak of the drawn TAS fiber from 1.4 dB/m to 1.1 dB/m by simultaneously improving the TAS glass purification and melting process[38]; the Se-H peak dropped from 1.4 dB/m to 0.9 dB/m; As-O peak decreased from 9.8 dB/m to 6 dB/m.

Fig. 8 .

 8 Fig. 8. (a) IR transmission spectrum of the Te 20 As 30 Se 50 glass, reprinted with

Fig. 9 .

 9 Fig. 9. (a) MIR transmission spectra of Te 20 As 40 Se 40 glass before and after

Fig. 10 (

 10 b) shows the fundamental mode transmission of 3.39 μm and Gaussian fitting, and the software simulation was basically consistent with the experimental results.

Fig. 10 .

 10 Fig. 10. (a) Microscope image of TAS microstructured fiber, the hole diameter d is

Fig. 11 .

 11 Fig. 11. Principle of FEWS: (a) Normal fiber, (b) Tapered fiber.

Fig. 12 .

 12 Fig. 12. The monitoring experiment of human lung cell. Reprinted with permission

Fig. 13 .

 13 Fig. 13. Infrared spectra of human lung cell recorded with the TAS glass fiber.

Fig. 14 .

 14 Fig. 14. (a)Detection of C=O band of acetone at different volumic percentages in

Fig. 15 .

 15 Fig. 15. Evolution of the absorbence of the C 2 Cl 4 line at 908 cm -1 for a length of

Fig. 16 .

 16 Fig. 16. (a) Spectra recorded near Paris in an industrial fallow land mainly polluted by

Fig. 18 .

 18 Fig. 18. Fiber cross-section photograph obtained by SEM. Reprinted with permission

Fig. 19 .

 19 Fig. 19. Optical scheme of the detection of the MIR signal coming from an exo-planet

  Recently, our group have been reported the broadest SC generation spectrum (1.8-13 μm with a 30 dB spectral flatness) by pumping the unclad Te 20 As 40 Se 40 fiber in the normal dispersion region at 5 μm femtosecond laser at different pump powers as shown in Fig. 20(a), which covers almost all the transparent range of the material. By pumping the Te 20 As 40 Se 40 /Te 18 As 40 Se 42 step-index fiber in the normal dispersion region at 5 μm, the SC spectrum covering 2.1-11.2 μm with a 40 dB flatness was recorded(Fig. 20(b))[18].

Fig. 20 .

 20 Fig. 20. Spectra of SC at different output power pumped for (a) an unclad

Table 1 .

 1 Temperature points and criteria of glass stability at heating rate of 5 K/min for As 40 Se 60-x Te x glasses. Reprinted with permission from Ref. [31]. compositions T g / o C T c / o C T p / o C T s / o C T l / o C ΔT/ o C K gl S/K As 40 Se 60 Te 5 As 40 Se 55 Te 10 As 40 Se 50 Te 15 As 40 Se 45 Te 20 As 40 Se 40 Te 25 As 40 Se 35 Te 30 As 40 Se 30 Te 35 As 40 Se 25 Te 40 As 40 Se 20

	178	322	356	376	387	145	2.23	10.9
	166	306	339	355	368	110	2.26	10.5
	158	-	-	-	-	-	-	-
	147	-	-	-	-	-	-	-
	144	-	-	-	-	-	-	-
	140	290	309	330	348	150	2.58	6.9
	130	245	271	297	313	115	1.69	7.4
	131	244	271	304	327	113	1.36	7.4
	132	246	277	309	336	114	1.28	8.5

Table 2 shows the mechanical properties and optical windows of the Te 20 As 40 Se 40 , TeX and Ge 25 Sb 10 S 65 glasses. TeX glasses, which are built up with Te, Se, and halide elements, show a broad optical transmission in the mid infrared from 2 to about 20

 2

Table 2 .

 2 Young's modulus E, density ρ, linear coefficient of thermal expansion α, micro hardeness H v , T g , and optical windows of the Te 20 As 40 Se 40 , Ge 25 Sb 10 S 65 and

2.2 Structure of TAS glasses Delaizir et al. investigated the atomic structure of chalcogenide glasses As 3 Se 7-x Te x

  As 3 Se 7-x or Te x As 2 Se 3-x induced breaking of Se-Se bonds and the formation of Te x AsSe 3-x pyramidal units.

							Optical
							windows/μm
	Te 20 As 40 Se 40	18.0	5.07	23×10 -6	146	144	2-16
	Ge 25 Sb 10 S 65	18.5	3.4	15.7×10 -6	155	320	2-11
	TeX glasses	8				60	2-20
	(0≤x≤3) and As 2 Se 3-x Te x (0≤x≤2.5) by Wide-Angle X-ray Scattering (WAXS), 77 Se
	NMR as well as Raman and infrared measurements for different compositions[34]. It
	was shown that the progressive introduction of tellurium in Te x

Table 3 .

 3 Melting points, boiling points and purification methods of TAS glasses raw

			materials.
	elements melting point/ o C boiling points/ o C	purification methods
	Te	450	988	zone melting, distillation invacuum or chemical etching
	As	817	615(sublimation)	sublimation in Ar stream or vacuum
	Se	217	685	distillation under vacuum, Ar or SeCl 2 gas

Table 5 .

 5 Impurity content (ppm wt.) in TAS glasses prepared by different methods.

		Reprinted with permission from Ref. [29].
	Impurities Direct synthesis Melting with Al	Melting with AlCl 3
	C	1	0.6	1
	O	20	0.2	0.6
	H	0.2	1	0.02
	Si	6	4	0.5
	Al	<0.4	<0.5	0.1
	Cu	<0.1	<0.1	<0.02
	Fe	1	0.8	<0.05
	Cr, Ni	<2	<2	<0.03
	Mg	0.5	<0.3	<0.01
	Sn, Cd	<0.4	<0.5	<0.3
	Mn	0.1	<0.1	<0.03
	Zn	<0.3	<0.3	<0.2
	Pb	<0.5	<0.7	<0.03

To further improve the purity, Hocdé and Shiryaev et al. ameliorated the glass preparation technology and obtained high-purity optical fiber preforms. Hocdé et al.

Acknowledgements

This work was partially supported by the Zhejiang Provincial Natural Science Foundation of China (LY18F050004), Open Research Fund of State Key Laboratory of Transient Optics and Photonics (SKLST201705), National Natural Science Foundation of China (61627815), and K.C. Wong Magna Fund in Ningbo University.


Blandine Gourcerol
email: b.gourcerol@brgm.fr

Guillaume Bertrand

Pauline Moreau

Isabelle Duhamel Achin

Philippe Négrel

Werner Warscheid

I Duhamel-Achin

Assessment of critical raw material potential from Cu-Au deposits through the European Ion4Raw project

Keywords:

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.


F França De Barros

C Taillebuis

M Manuel

H Bras

D Combes

François Lambert

M Beraneck

Central pattern generator-driven efference copy couples eye movements with forelimb locomotion in mice

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

Central pattern generator-driven efference copy couples eye movements with forelimb locomotion in mice F. França de Barros 1,5 , C. Taillebuis 1,5,6 , M. Manuel 2,5 , H. Bras 3 , D. Combes 4,6 , F. M. Lambert 4,6 , M. Beraneck 1,5 Eye movements during treadmill locomotion in precollicular premammillary decerebrated An example of a predictive motor e erence copy is the signal originating from the locomotor spinal CPG that is simultaneously responsible for tail ondulation as well as for driving eye movements during swimming in the Xenopus tadpole.

Study whether the CPG-driven predictive signal coupling eye movements to locomotion is preserved in mammals.

Credit: F.Lambert 1. Ex vivo: rhythmic coupled discharge was found between limb and abducens motor nerve activity during ctive locomotion events elicited by both electrical and pharmacological stimulation.

2. In vivo: in absecbe of visual and vestibular inputs, conjugated eye movements are coupled to locomotion were recorded, suggesting that the e erence copy particpiates in gaze stabilization during viogorus locomotion.

3. Anatomy: rabies virus injection revealed ipsilateral monosynaptic ascending spinal connection from the cervical with abducens motoneurons.

Conclusion Aim

Neuronal substrates of the spino-extraocular pathway

  UMR 8002, 2-SPPIN UMR 8003, CNRS, Paris, France; 3-INT UMR 7289, CNRS, Marseille, France; 4-INCIA UMR 5287, CNRS, Bordeaux, France; 5-Univ. de Paris, France; 6-Univ. Bordeaux, France

  extra-ocular activity is coupled to ctive locomotion Cervical C8 stimulation -Cervical CPG activation Ex vivo recordings of the eye's motor nuclei and locomotor CPGs in brainstem-spinal cord preparations of neonatal mice (Hz) Lumbar CPG activation Lumbar CPG activation Cervical CPG activation 2. Blocking the cervical locomotor network removes the spino-extraocular coupling 3. The cervical locomotor network is su cient to produce the spino-: treadmill induced a trot-like pattern. are neural replicas of motor outputs used to anticipate the sensory consequences of a self-generated motor action. They are responsible for the coordination of motor behaviors by generating intrinsic feed-forward signals that directly connect a local motor circuitry with another local circuitry involved in another motor behaviour.

  virus in the lateral rectus of adult mice: 1. Infected (RV + ) motorneurons (ChAT labelling) in the abducens nucleus(nVI) ipsilateral to the injection. 2. RV+ interneurons are present all along the cervical (7547µm ± 1798). 3. On average, 1 infected MN in the nVI a ects 6 INs in the cervical. 4. C7 shows an homogeneous bilateral infection; C2-C6 and C8 infected mostly ipsilaterally (68%).

s 4 Hz 4Hz

Acknowledgments

Work funded by the French entities: Agence Nationale de la Recherche (ANR) and the Centre National de la Recherche Scienti que (CNRS). We also thank Université de Paris and Bordeaux and the technical support provided by Patrice Jegouzo.