MD Ksenija Vucurovic
email: vksenija@yahoo.com

MD b , Clémentine Dupont-Gaudin

Delphine Raucher-Chéné

MD PhD Arthur Kaladjian

PhD Christine-Vanessa Cuervo-Lombard

MD PhD Delphine Raucher Chéné

Fibromyalgia patients make scarce reference to pain in self-defining memories

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

1

Fibromyalgia patients make scarce reference to pain in self-defining memories 1. INTRODUCTION Chronic pain is a highly disabling medical condition that occurs in over 10% of the general population [START_REF] King | The epidemiology of chronic pain in children and adolescents revisited: a systematic review[END_REF]. Chronic pain may have detrimental effects on one's sense of self, particularly if the underlying mechanisms are not well understood and are therefore difficult to control. While nociceptive or neuropathic chronic pain mechanisms are well understood nowadays, pain conditions involving centralized sensitization are still challenging for physicians. Fibromyalgia (FM) can be regarded as a prototypical central chronic pain disorder [START_REF] Häuser | Fibromyalgia[END_REF] that occurs in 2-4% of the general population. It is characterized by widespread pain, chronic fatigue, unrefreshing sleep, cognitive dysfunction and somatic symptoms [START_REF] Wolfe | revisions to the 2010/2011 fibromyalgia diagnostic criteria[END_REF].

It is significantly more prevalent in women than in men [START_REF] Häuser | Fibromyalgia[END_REF], and induces severe painrelated disability, including difficulties in daily physical functioning and decreased quality of life. Pain perception seems to be at the centre of patients' current selfunderstanding and has severe negative consequences for their wellbeing. Even though an FM diagnosis can have a negative and long-lasting impact on sense of self, no study has yet been conducted on the subject.

Fibromyalgia, self and memory

Over the past 25 years, a growing number of studies have suggested that the way people remember personal past events is predictive of their psychological functioning [START_REF] Sumner | The mechanisms underlying overgeneral autobiographical memory: an evaluative review of evidence for the CaR-FA-X model[END_REF]. Memory processes that specifically contribute to the construction of personal identity, such as autobiographical memory, have never been studied in patients with FM. Autobiographical memories are transitory mental constructions generated from an autobiographical knowledge base held at different levels of specificity [START_REF] Conway | The cocktail party phenomenon revisited: the importance of working memory capacity[END_REF][START_REF] Conway | The construction of autobiographical memories in the self-memory system[END_REF]. By explicitly referring to the self, recent models of autobiographical memory provide a new conceptual frame that underlines the close reciprocal relationships between personal identity and a particular type of memory called self-defining memories (SDMs) [START_REF] Singer | An experimental investigation of specificity and generality in memory narratives[END_REF]. SDMs have been the subject of many studies over the past 20 years [START_REF] Werner-Seidler | Characteristics of self-defining memory in depression vulnerability[END_REF].

Autobiographical memories incorporate facts, knowledge about the self, and recollections of personal experiences. They reflect individuals' most enduring concerns (achievement, intimacy, spirituality, etc.) and/or unresolved conflicts [START_REF] Singer | Self-defining memories, scripts, and the life story: narrative identity in personality and psychotherapy: healthy narrative identity[END_REF][START_REF] Houle | Networks of self-defining memories as a contributing factor to emotional openness[END_REF].

SDMs relate to the relationship between autobiographical memory and self-identity, and can thus be distinguished from other autobiographical memory processes insofar as they are associated with the senses of personal identity and continuity in one's individual history. SDMs are vivid, emotionally intense and well-rehearsed autobiographical memories concerning the central goals, values and conflicts of an individual's life. According to the biopsychosocial model of FM occurrence and evolution developed by Eich et al. [START_REF] Eich | The role of psychosocial factors in fibromyalgia syndrome[END_REF], the way in which individuals remember selfrelevant memories, particularly those referring to painful events, could help to precipitate and/or perpetuate the illness [START_REF] Van Liew | A longitudinal analysis of pain experience and recall in fibromyalgia[END_REF]. However, in order to understand the precise impact of memory-related intrusions on an individual's self-identity [START_REF] Knez | Place and the self: an autobiographical memory synthesis[END_REF][START_REF] Mutlutürk | Remembering and telling self-consistent and selfdiscrepant memories[END_REF],

we need to understand the relationship between memory and self.

Even though autobiographical memory has never been explored in FM, we have data from disorders (e.g., affective and chronic pain disorders) sharing psychopathological features with FM that reveal overgeneral autobiographical memory recall in these populations [START_REF] Lemogne | Episodic autobiographical memory in depression: specificity, autonoetic consciousness, and self-perspective[END_REF][START_REF] Liu | Overgeneral autobiographical memory in patients with chronic pain[END_REF][START_REF] Meyer | Pain can produce systematic distortions of autobiographical memory[END_REF]. We therefore set out to identify the factors that potentially interact with or affect SDM recall in FM, drawing on the CaR-FA-X model developed by Williams [18]. This model theorizes the mechanisms behind overgeneral autobiographical memory. Williams [START_REF] Williams | Capture and rumination, functional avoidance, and executive control (CaRFAX): Three processes that underlie overgeneral memory[END_REF] delineated three main processes: capture and rumination, functional avoidance, and impaired executive control. This model was further consolidated by empirical data reviewed by Sumner [START_REF] Sumner | The mechanisms underlying overgeneral autobiographical memory: an evaluative review of evidence for the CaR-FA-X model[END_REF]. Capture and rumination processes, highly prevalent in affective disorders, refer to the disruption of cognitive resources during self-relevant information searches. Previous studies of SDMs in affective disorders have suggested that psychological distress, particularly depression and anxiety, affects SDM recall [START_REF] Lemogne | Episodic autobiographical memory in depression: specificity, autonoetic consciousness, and self-perspective[END_REF]. Moreover, depression, anxiety, catastrophizing thoughts, neuroticism and proneness to negative interpretation of life events have been described as more prevalent in patients with FM than in those with other chronic pain conditions [START_REF] Borg | Pain-related mood influences pain perception differently in fibromyalgia and multiple sclerosis[END_REF][START_REF] Piccinni | Subthreshold mood symptoms in patients with fibromyalgia and rheumatoid arthritis[END_REF] or healthy individuals [START_REF] Vural | Evaluation of personality profile in patients with fibromyalgia syndrome and healthy controls[END_REF][START_REF] Novo | A meta-analysis of studies with the Minnesota Multiphasic Personality Inventory in fibromyalgia patients[END_REF]. By analogy with SDM studies in affective disorders, we assumed that psychological distress in patients with FM can affect their SDM recall. Functional avoidance refers to the passive avoidance of traumatic-event retrieval as a means of affect regulation. A history of childhood adversity, physical or psychological abuse or neglect, and trauma-related psychopathology have been described as predisposing factors in FM [START_REF] Weissbecker | Childhood trauma and diurnal cortisol disruption in fibromyalgia syndrome[END_REF][START_REF] Sluka | Neurobiology of fibromyalgia and chronic widespread pain[END_REF] and correlated with symptom severity [START_REF] Lee | Fibromyalgia and childhood abuse: exploration of stress reactivity as a developmental mediator[END_REF][START_REF] Amital | Posttraumatic stress disorder, tenderness, and fibromyalgia syndrome: are they different entities?[END_REF]. Moreover, it has been suggested that the functional avoidance of pain is the main mechanism behind overgeneral autobiographical recall in chronic pain conditions other than FM [START_REF] Liu | Overgeneral autobiographical memory in patients with chronic pain[END_REF][START_REF] Meyer | Pain can produce systematic distortions of autobiographical memory[END_REF].

Nevertheless, Meyer et al. [START_REF] Meyer | Pain can produce systematic distortions of autobiographical memory[END_REF] postulated that it is current pain, rather than chronic pain per se, that induces a lack of specificity in autobiographical memory. Thus, pain severity appears to be a relevant factor that can affect or interact with SDM recall in patients. Finally, impaired executive control, especially deficits in the inhibition of irrelevant information [START_REF] Piolino | Reduced specificity of autobiographical memory and aging: do the executive and feature binding functions of working memory have a role?[END_REF], limits the ability to conduct successful autobiographical retrieval. Patients with FM report cognitive dysfunction as one of their core symptoms. These cognitive complaints can be divided into two categories: subjective cognitive dysfunction, known as fibrofog [START_REF] Kravitz | Fibrofog and fibromyalgia: a narrative review and implications for clinical practice[END_REF], and objective cognitive dysfunction documented by impaired performance on standardized neuropsychological tests [START_REF] Gelonch | Executive function in fibromyalgia: comparing subjective and objective measures[END_REF].

Compared with healthy controls, patients with FM underperform on cognitive tests of attention [START_REF] Cherry | Physical performance as a predictor of attention and processing speed in fibromyalgia[END_REF], verbal fluency [START_REF] Kratz | Development and initial validation of a brief self-report measure of cognitive dysfunction in fibromyalgia[END_REF], executive function [START_REF] Gelonch | Executive function in fibromyalgia: comparing subjective and objective measures[END_REF], and social cognition [START_REF] Tella | Theory of mind and emotional functioning in fibromyalgia syndrome: an investigation of the relationship between social cognition and executive function[END_REF].

Cognitive inhibition tasks indicate impaired processing speed in FM [START_REF] Veldhuijzen | Intact cognitive inhibition in patients with fibromyalgia but evidence of declined processing speed[END_REF][START_REF] Martinsen | Fibromyalgia patients had normal distraction related pain inhibition but cognitive impairment reflected in caudate nucleus and hippocampus during the Stroop Color Word Test[END_REF], along with reduced task-related subcortical activation [START_REF] Martinsen | Fibromyalgia patients had normal distraction related pain inhibition but cognitive impairment reflected in caudate nucleus and hippocampus during the Stroop Color Word Test[END_REF]. Based on the CaR-FA-X model, cognitive inhibition has been identified as the executive function that most affects SDM characteristics [START_REF] Stewart | A prospective investigation of rumination and executive control in predicting overgeneral autobiographical memory in adolescence[END_REF]. Therefore, our review of the literature allowed us to identify the most plausible confounding factors that may affect SDM recall, namely severity of current or mean pain, depression, anxiety, reduced cognitive inhibition ability, and medication use.

SDMs provide key information about cognitive-affective-motivational representations of self, helping us to understand how future actions may be guided by past experiences [START_REF] Blagov | Four dimensions of self-defining memories (specificity, meaning, content, and affect) and their relationships to self-restraint, distress, and repressive defensiveness[END_REF]. These memories influence other current cognitive functions and productions, and may be valuable predictors of adaptation to long-term illness [START_REF] Nourkova | On the advantage of autobiographical memory pliability: implantation of positive self-defining memories reduces trait anxiety[END_REF].

Therefore, characterizing the phenomenology of SDMs in patients with FM not only has the potential to enhance our understanding of predisposing and/or perpetuating factors of the illness, but could also be used to improve clinical interventions in this population.

Our first aim was to compare the characteristics of patients' SDMs with those of healthy participants. The first broad assumption of this study was that patients with FM would provide overgeneral and less integrated SDMs, as described in the models of autobiographical recall in mood disorders and chronic pain. Given that a painful condition is reported as being central to their current self-concept, we expected these patients to report more memories of pain and physical concerns than the healthy controls. Finally, we statistically controlled our results for the most plausible confounding factors, namely psychological distress, pain severity, cognitive inhibition ability and medication use.

MATERIAL AND METHOD

Participants

Twenty-five patients (21 women) with a diagnosis of FM based on ACR 2010 criteria [START_REF] Häuser | Fibromyalgia[END_REF] by a rheumatologist, pain practitioner or general medicine physician, and 24 healthy controls (HC) without FM (20 women) matched for age, sex and education level, took part in the study. All patients with FM reported having pain for more than 6 months.

Our sample of patients with FM was predominantly female (84%). We decided to include men in the study because outpatients were consecutively recruited and enrolled in the study in naturalistic conditions that also included male patient management. Our sample was thus consistent with epidemiological studies reporting a higher prevalence of the disease in women, but also the existence, albeit to a lesser extent, of the FM diagnosis in men [START_REF] Häuser | Fibromyalgia[END_REF][START_REF] Yunus | The role of gender in fibromyalgia syndrome[END_REF]. Other authors have recruited similar patient samples with a proportion of women varying from 70% to 95% [START_REF] Üçeyler | Small fibre pathology in patients with fibromyalgia syndrome[END_REF][START_REF] Bartley | Experimental assessment of affective processing in fibromyalgia[END_REF].

HC were recruited by advertisement in social media and among employees of the university hospital, and were matched with patients for age, sex and education level.

There was no monetary compensation for participation in the study.

We did not include patients or controls aged under 18 or over 65 years, or affected by any other chronic pain or severe medical condition comprising central nervous system disorders, dyslexia or illiteracy, uncorrected hearing or sight problems. In addition, no individuals who took pain medication or reported any chronic pain were included in the control group.

All participants were native French speakers and none used alcohol or illicit psychoactive substances. They were interviewed individually in a quiet standardized environment. All procedures were clearly described to the participants in the form of both oral and written information, and during the interview we checked that they fully understood all the instructions they had received. This research was conducted in accordance with the Declaration of Helsinki and was approved by the local ethics committee. All participants gave their written informed consent before being included in the study.

Depression and anxiety assessment

The severity of depression symptoms was rated using a validated French-language version of the Beck Depression Inventory -Second Edition (BDI-II; [START_REF] Beck | Manual for Beck Depression Inventory II (BDI-II)[END_REF]), and participants' level of anxiety was assessed with a validated French-language version of the State-Trait Anxiety Inventory (STAI) [START_REF] Spielberger | STAI manual for the State-trait Anxiety Inventory[END_REF].

Mental flexibility and inhibition assessment

Mental flexibility was evaluated with the Trail Making Test (TMT) [START_REF] Tombaugh | Trail Making Test A and B: normative data stratified by age and education[END_REF]. In Part A, participants are required to connect a series of 25 circles containing numbers randomly arranged in a spatial array. This part requires attention, mental tracking, and visual searching. In Part B, participants are asked to alternate between connecting a series of circles containing numbers in increasing order and connecting a series of circles containing letters in alphabetic order. This part requires the additional process of set shifting, as participants must alternate between number and letter use. The dependent measure was the completion time (in seconds) for each part. We also calculated the difference in completion time between B and A, to gain a relatively pure indicator of set shifting [START_REF] Sánchez-Cubillo | Construct validity of the Trail Making Test: role of taskswitching, working memory, inhibition/interference control, and visuomotor abilities[END_REF].

The Stroop test is widely used to assess inhibitory function [START_REF] Stroop | Studies of interference in serial verbal reactions[END_REF][START_REF] Miyake | The unity and diversity of executive functions and their contributions to complex "frontal lobe" tasks: a latent variable analysis[END_REF]. Participants are asked to name as quickly and as accurately as possible the colour of the ink used to print rows of Xs (colour condition), to read colour words (word condition), and to name the ink colour of incongruous colour words (colour-word condition). It probes the speed of information processing (colour and word conditions) and the ability to inhibit a prepotent response tendency (colour-word condition). We also calculated an interference score [START_REF] Golden | Diagnosis and rehabilitation in clinical neuropsychology[END_REF] taking overall slowing into account.

Pain and symptom severity assessment

Pain intensity was assessed on a visual numerical scale (VNS) ranging from 0 (no pain) to 10 (maximum pain). We asked patients to report a measure of current pain, as well as the mean and maximum pain experienced during the week before the assessment. FM severity was assessed with the Fibromyalgia Symptom Scale (FSS) [START_REF] Häuser | Fibromyalgia[END_REF] combining a Widespread Pain Index (number of affected areas from 0 to 19) and a Symptom Severity Scale ranging from 0 (no problem) to 3 (severe symptoms) in four domains: fatigue, unrefreshing sleep, and cognitive and somatic symptoms. The total FSS score ranges from 0 to 31.

Medication use quantification

To quantify patients' painkiller consumption, we used the Medication Quantification Scale (MQS). This is an instrument for quantifying medication regimen use in chronic pain populations that was developed in 1992 and updated for the third and last time in

Self-defining memory assessment

Five SDMs were collected with the Self-Defining Questionnaire [START_REF] Singer | An experimental investigation of specificity and generality in memory narratives[END_REF], introduced by an oral definition of an SDM during a face-to-face interview. Participants were instructed to report events in their personal memory with the following specific attributes: 1) the event should have taken place at least 1 year earlier; 2) it should be important for the individual and vividly represented; 3) it should help the individual and others explain who he or she is as an individual; 4) it should be related to an important and enduring theme, issue, conflict, or concern in the individual's life, and be linked to other events on the same theme; 5) it should generate strong feelings, be they positive or a negative; and 6) it should be an event that participants had thought of many times. While listening to this definition, participants had a sheet of paper in front of them summing up the main points. Next, participants were asked to describe their five SDM events, providing a caption for each of them, their age at each occurrence, the people they were with, what happened, and how they and other people reacted to the event. They were asked to write a title or sentence summarizing each event, described with enough details to help a virtual friend visualize the scene and imagine precisely what the person or others felt. Participants then had to rate their emotional response when remembering the event on a 7-point scale ranging from -3 (very negative) to 3 (very positive), the personal importance of the SDM on a scale ranging from 1 (not important) to 7 (very important), and whether remembering this event allowed them to mentally relive it on a scale ranging from 0 (not at all) to 7(completely).

The content of each SDM was evaluated using the classification proposed by Thorne and McLean [START_REF] Thorne | Manual for coding events in self-defining memories[END_REF]. Contents were divided into seven categories: life-threatening event, recreation, relationship, achievement/mastery, guilt/shame, drug/alcohol abuse, and not classifiable. Independently of these categories, we also compared the participants' SDMs referring to physical or psychological pain (procedure similar to that used by Cuervo-Lombard et al. [START_REF] Cuervo-Lombard | Self-defining memories in recently detoxified alcohol-dependent patients[END_REF]). A memory was coded as specific if the event being described happened at a particular place and time and lasted less than a day. An event was considered to be integrated if the individual stepped back from the event narration and added a statement or comment indicating the personal significance of the event. SDMs were also coded for the presence or absence of tension, which was defined as an explicit reference to discomfort, disagreement, or unease during the narration of the event. The emotional valence (i.e., positive, neutral, or negative) and intensity (i.e., absolute value of the valence rating) of the affective response to each event were also rated on a scale ranging from -3 to +3. The event was coded as redemptive if the narration contained a clear and explicit transformation from a decidedly negative-affect state to a positive one. Conversely, an event was classified as contaminative if the memory narration contained an explicit transformation from a demonstrably positive affective state to a negative one. We counted the number of memories associated with redemption or contamination.

Two raters (CC-L & CD-G) independently scored each SDM according to the criteria proposed by Blagov and Singer [START_REF] Blagov | Four dimensions of self-defining memories (specificity, meaning, content, and affect) and their relationships to self-restraint, distress, and repressive defensiveness[END_REF] and Thorne and McLean [START_REF] Thorne | Manual for coding events in self-defining memories[END_REF]. In the few cases where their ratings differed, the SDM was discussed until agreement was reached.

The kappa interrater reliability coefficient was 0.97 for specificity, 0.97 for integrative meaning, 0.95 for content, 0.89 for both redemption and contamination, and 0.97 for tension.

Statistical analysis

Data were analysed using STATISTICA® version 13.0 for Windows.

Patients with FM were compared with HC on sociodemographic variables, symptom severity, cognitive scores and SDM scores, using independent t tests. To examine the influence of possible confounding factors on observed group differences for SDM characteristics, we calculated Pearson's correlation coefficients between the depression (BDI-II), anxiety (STAI), pain intensity (VNS), symptom severity (FSS), quantity of medication use (MQS) and executive function (TMT/Stroop) scores and SDM characteristics. When we found a statistically significant correlation, ran analyses of covariance (ANCOVAs) with group as the independent variable, mean SDM characteristics (i.e., specificity, integrative meaning, tension, redemption, contamination, emotional valence and intensity) as dependent variables, and correlated clinical parameters as covariates.

[INSERT TABLE 1 ABOUT HERE]

3. RESULTS

Participants' characteristics

Details of participants' sociodemographic characteristics and clinical scores are provided in Table 1. The groups did not differ on either age or years of formal education. Patients with FM scored significantly higher on the BDI-II and STAI than HC. The results of the executive function assessment showed that patients with FM performed more slowly than HC, but displayed comparable accuracy, on both the TMT and the Stroop test. The Stroop Interference score did not differ between groups.

[INSERT TABLE 2 ABOUT HERE]

Characteristics of SDMs

Details of the statistical analyses of SDM characteristics in both groups are provided in Table 2. Content classified as exploration/recreation was less common in FM than in HC, the opposite being true of relationship events. The proportion of memories concerning physical or psychological pain did not differ significantly between groups.

Patients provided less specific and less integrative meanings. Taken together, SDMs were generally characterized by higher tension and a more positive valence in HC than in FM. The intensity of negative memories was significantly higher in FM than in HC. The intensity of positive memories did not differ significantly between groups.

The proportion of redemptive events was lower in FM. The proportion of contaminative events was also lower in FM than HC, but the difference was not statistically significant. Participants' mean age at the time of the described event did not differ between groups.

There were no statistical correlations between the STAI-A (p s > 0.72), STAI-B (p s > 0.07), VNS (p s > 0.05), FSS (p s > 0.2), MQS (p s > 0.2), TMT-A (p s > 0.05), TMT-B (p s > 0.05), TMT (B-A) (p s > 0.09), and Stroop Interference (p s > 0.22) scores and the different characteristics of the SDMs described above. However, we found a negative correlation between the depression score (BDI-II) and SDM specificity (r = -0.31, p = 0.032). An ANCOVA with BDI-II score as the covariate, group as the independent variable, and SDM specificity as the dependent variable, did not change the statistical difference between groups, F(1, 46) = 5.18, p = 0.028.

DISCUSSION

The present study was designed to improve our understanding of how patients with FM define themselves and how pain is integrated into their self-identity. To our knowledge, this is the first study to have investigated SDMs in an FM population. In addition, we addressed the issue of psychological distress, pain severity, cognitive inhibitory function and medication use as potential confounding factors in patients' SDM recall. As expected, the patients with FM displayed greater psychological distress than HC. The assessment of executive function indicated slower overall performance among patients, but no impairment of cognitive inhibition. Rather than retrieve specific memories for events that occurred at a particular time and place and lasted less than a day, patients described memories that were summaries or categories of events that lasted more than a day, and these memories were more negative but less intense than those of HC. Patients' SDMs were less redemptive, less integrative, and thus contained less meaning making. By contrast, despite our initial hypothesis, patients did not report more pain-oriented memories than HC did, even though pain appeared to be the main organizer of their current existence.

Biased SDM recall and affective dysregulation in FM

Taken together, the decreased specificity and integration of patients' SDMs, together with the scant references to pain, suggest that functional avoidance is used as a means of adapting to the illness. According to Conway and Pleydell-Pearce [START_REF] Conway | The construction of autobiographical memories in the self-memory system[END_REF], retrieving memories of negative or painful events generates less emotional distress if those memories are less specific. Reduced specificity in autobiographical memory has been associated with less effective social problem-solving and difficulty imagining specific future events [START_REF] Mclean | The role of domain content in understanding identity development processes[END_REF]. Overgeneral autobiographic memory has been found to be predictive of both the onset and recurrence of depression and posttraumatic stress disorder [START_REF] Kleim | Reduced autobiographical memory specificity predicts depression and posttraumatic stress disorder after recent trauma[END_REF][START_REF] Sumner | Overgeneral autobiographical memory and chronic interpersonal stress as predictors of the course of depression in adolescents[END_REF], both highly prevalent in FM, as well as a worse course of depression [START_REF] Sumner | Overgeneral autobiographical memory as a predictor of the course of depression: a meta-analysis[END_REF]. Accordingly, difficulty activating specific memories, particularly memories referring to pain, could lead to maladaptive functioning in patients with FM, by leaving them less able to benefit from the cognitive and affective information available from vivid and detailed memories. Moreover, functional avoidance as a cognitive strategy and means of negative affect regulation has previously been identified as a vulnerability factor for other chronic pain conditions [START_REF] Liu | Overgeneral autobiographical memory in patients with chronic pain[END_REF][START_REF] Meyer | Pain can produce systematic distortions of autobiographical memory[END_REF]. Patients also provided less integrated SDMs than HC did, suggesting that they failed to take advantage of experiences regarded as self-defining when constructing and adjusting their current perceptions of self-identity and daily social life. Therefore, biased SDM recall and the use of functional avoidance (i.e., a mechanism that decreases patients' ability to effectively fight current pain) could be mutually reinforcing processes.

Future studies should test developmental aspects of the functional avoidance mechanism and its longitudinal relation to the self and memory in FM, in order to further improve our understanding of the disorder's precipitating factors.

A second possible explanation for the scant references to pain in patients' SDMs is the high prevalence of alexithymia that has recently been reported in a number of studies of the psychopathology of FM [START_REF] Tella | Alexithymia, not fibromyalgia, predicts the attribution of pain to anger-related facial expressions[END_REF][START_REF] Ghiggia | Alexithymia and depression in patients with fibromyalgia: when the whole is greater than the sum of its parts[END_REF][START_REF] Tella | Alexithymia and fibromyalgia: clinical evidence[END_REF][START_REF] Tella | Coping strategies and perceived social support in fibromyalgia syndrome: relationship with alexithymia[END_REF]. Alexithymia is a personality dimension defined as difficulty identifying and describing subjective feelings [START_REF] Taylor | Disorders in affect regulation: alexithymia in medical and psychiatric illness[END_REF], and it is highly prevalent in psychosomatic disorders [START_REF] Tella | Alexithymia and fibromyalgia: clinical evidence[END_REF]. Alexithymic individuals are prone to misinterpret the somatic manifestations of emotional arousal as the signs of the disease [START_REF] Lumley | The relationship of alexithymia to pain severity and impairment among patients with chronic myofascial pain: comparisons with self-efficacy, catastrophizing, and depression[END_REF]. Researchers have investigated the presence of alexithymia in patients with FM using a range of methods [START_REF] Tella | Alexithymia, not fibromyalgia, predicts the attribution of pain to anger-related facial expressions[END_REF][START_REF] Taylor | Disorders in affect regulation: alexithymia in medical and psychiatric illness[END_REF][START_REF] Sayar | Alexithymia and anger in patients with fibromyalgia[END_REF][START_REF] Steinweg | Fibromyalgia: unspeakable suffering, a prevalence study of alexithymia[END_REF][START_REF] Tuzer | Causal attributions and alexithymia in female patients with fibromyalgia or chronic low back pain[END_REF][START_REF] Castelli | Alexithymia and psychological distress in fibromyalgia: prevalence and relation with quality of life[END_REF]. Their findings suggest that patients have particular difficulty identifying feelings and the affective dimension of pain [START_REF] Lumley | The relationship of alexithymia to pain severity and impairment among patients with chronic myofascial pain: comparisons with self-efficacy, catastrophizing, and depression[END_REF][START_REF] Sayar | Alexithymia and anger in patients with fibromyalgia[END_REF][START_REF] Steinweg | Fibromyalgia: unspeakable suffering, a prevalence study of alexithymia[END_REF][START_REF] Tuzer | Causal attributions and alexithymia in female patients with fibromyalgia or chronic low back pain[END_REF][START_REF] Castelli | Alexithymia and psychological distress in fibromyalgia: prevalence and relation with quality of life[END_REF]. Recently, alexithymia per se was found to directly contribute to poor quality of life in FM, while depressive symptoms would rather have indirect impact [START_REF] Tesio | Alexithymia and Depression Affect Quality of Life in Patients With Chronic Pain: A Study on 205 Patients With Fibromyalgia[END_REF]. Thus, scarce reference to pain in the SDMs reported by patients with FM may reflect an inability to make sense of what happens during the illness at the most personal level. Moreover, alexithymia may disrupt patients' giving of meaning to SDMs related to pain, and impair awareness of and learning from these memories. Alexithymia is described as an emotional dysregulation trait [START_REF] Taylor | Recent developments in alexithymia theory and research[END_REF], and as such may play an intermediate role between biased SDM recall (particularly scarce reference to pain) and the psychopathology of FM, characterized by highly prevalent psychological distress. Tesio et al [START_REF] Tesio | Alexithymia and Depression Affect Quality of Life in Patients With Chronic Pain: A Study on 205 Patients With Fibromyalgia[END_REF] brought further evidence that poor psychosocial functioning in FM is related to alexithymia, so similar mechanisms could underpin SDM recall.

However, this hypothesis needs to be addressed in future studies examining SDMs and alexithymia in the same FM sample.

In addition, less redemptive SDMs with a more negative emotional valence, but paradoxically retrieved with less tension, constitute further evidence of affective dysregulation in FM. Redemptive SDMs are predictive of greater psychological wellbeing [START_REF] Liao | Young women in today's Taiwan: relation of identity status and redemptive narration to psychological well-being[END_REF], while autobiographical reasoning that transforms experience into an emotionally positive situation may be a basic psychological mechanism of appropriate affective adaptation [START_REF] Liao | Young women in today's Taiwan: relation of identity status and redemptive narration to psychological well-being[END_REF][START_REF] Lardi Robyn | Self-defining memories and selfdefining future projections in hypomania-prone individuals[END_REF]. Less emotionally intense positive memories and more vivid negative memories have been reported in depressed patients [START_REF] Neshat-Doost | Enhancing autobiographical memory specificity through cognitive training: an intervention for depression translated from basic science[END_REF][START_REF] Werner-Seidler | Characteristics of self-defining memory in depression vulnerability[END_REF].

Nevertheless, as major depressive disorder involves disturbances in both negative and positive memory processes [START_REF] Werner-Seidler | Characteristics of self-defining memory in depression vulnerability[END_REF], different mechanisms of affective dysregulation seem to be involved in FM. Consistent with our results, Van Middendorp et al. [START_REF] Van Middendorp | Emotions and emotional approach and avoidance strategies in fibromyalgia[END_REF] reported that negative affective experience was more disturbed than positive affective experience in patients with FM, while Rosello et al. [START_REF] Rosselló | Affective modulation of brain and autonomic responses in patients with fibromyalgia[END_REF] found multilevel deficits in affective modulation in their FM sample. Furthermore, an abnormal emotional autonomous nervous system response has been linked to higher experimental pain response in patients with FM [START_REF] Rosselló | Affective modulation of brain and autonomic responses in patients with fibromyalgia[END_REF], suggesting that a negative interpretation of past events is related to unclear emotional concepts [START_REF] Simplicio | Self-images in the present and future: role of affect and the bipolar phenotype[END_REF][START_REF] Seth | Interoceptive inference, emotion, and embodied self[END_REF] in patients and an inability to activate these concepts during the autobiographical recall of self-defining events.

Hence, when analysed via SDM characteristics, FM can best be described as an affective disorder with emotional dysregulation as the most prominent factor, affecting and interacting with autobiographical recall.

Clinical applications and future research

The ability to give meaning to important events in our lives is a critical function that allows SDMs to be integrated into a coherent representation of self and, as such, to guide our fulfilment of current and future goals. As discussed above, patients with FM seemed to avoid painful content when describing their SDMs, at both cognitive and affective levels of regulation. Therefore, new approaches in FM management, particularly in psychotherapy, based on how pain is integrated into self-identity, could be useful. These aspects of pain perception and self have not been specifically targeted in the field of psychotherapy for FM, even though a cognitive remediation approach called imagery rescripting has been found to be effective in reducing adverse SDMs in a nonclinical sample [START_REF] Çili | Impact of imagery rescripting on adverse self-defining memories and post-recall working selves in a non-clinical sample: a pilot study[END_REF]. A specific programme of autobiographical memory remediation could therefore help patients with FM cope better with current pain by targeting impaired meaning making from SDMs, and as such represents a potential new direction for clinical practice.

Future studies should more specifically address SDMs in chronic pain conditions with low affective dysregulation, in order to gauge the influence of FM as a chronic illness on different SDM characteristics independently of pain avoidance strategies.

Limitations and conclusion

Our study had several limitations. First, we had a small sample size, although as the participants were each asked to identify five SDMs, we obtained a total of 245 memories to analyse, thus increasing our data. In addition, many studies describing SDMs have been conducted with comparable sample sizes, and we achieved enough power to observe statistically significant differences between the groups. Second, we statistically controlled our results for the most plausible confounding factors (i.e., psychological distress, pain severity, cognitive inhibition ability and medication use) identified in a systematic literature review, and none could explain (either alone or in combination) impaired SDM recall in FM. Nevertheless, we cannot exclude the possibility that the mental fatigue described by patients [START_REF] Bar-On Kalfon | Cognitive functioning in fibromyalgia: the central role of effort[END_REF] interacted with the ability to provide optimum effort during SDM searching, and other cognitive and affective factors should also be addressed in future studies. In addition, other types of statistical analysis, such as multiple regression, would yield more information if our sample was larger. Third, our sample is consistent with prevalence of FM in women, so gender could influence SDMs characteristics, in particular emotional aspects of reported memories. Finally, the cross-sectional design of our study did not allow us to make any extrapolations about causality between FM and the characteristics of SDMs.

In conclusion, our results suggest that SDM recall is biased in patients with FM. Even though other mechanisms may be involved, we discussed functional avoidance and alexithymia as two potential factors for scant references to pain in patients' SDMs, which in turn are indicative of affective dysregulation in FM. In clinical practice, remediating the way in which pain is integrated into SDMs in FM may enhance our ability to mitigate its negative impact on patients' lives. and Dr Jean-Pierre Conce, Dr Ai-Thu Nguyen, Dr Frédérique Arndt and Dr Christine Chemla from the Pain Assessment and Treatment Unit.

  2005 by Harden et al.[START_REF] Harden | Medication Quantification Scale Version III: update in medication classes and revised detriment weights by survey of American Pain Society physicians[END_REF] as the MQS-III. The MQS score for an individual patient is calculated as the sum of scores derived by multiplying the detriment weight, determined by professional consensus of American Pain Association members, and the relative daily dosage of the pharmacological class for each pain-related medication. Scores relative to pharmacological classes and their detriment weights are detailed in Harden et al,[START_REF] Harden | Medication Quantification Scale Version III: update in medication classes and revised detriment weights by survey of American Pain Society physicians[END_REF].

  = patients with fibromyalgia; HC = healthy controls; M = mean value; SD = standard deviation; n = number; % = percentage; BDI = Beck Depression Inventory; STAI = State Trait Anxiety Inventory; TMT = Trail Making Test; VNS = Visual Numerical Scale (0-10); MQS-III = Medication Quantification Scale -third version; NSAI: nonsteroidal antiinflammatory drugs. * p < 0.05. ** p < 0.01. *** p < 0.001.

Table 1 :

 1

	Participants' characteristics
		FM		HC
		(n = 25)	(n = 24)
		M	(SD)	M	(SD)	t	P
	Age (years)	51.2 (7.8)	50.6	(7.6)	0.280	0.781
	Education level (years)	11.8 (1.4)	11.7	(1.7)	0.212	0.833
	BDI-II	29.2	(10.4)	6.1	(6.1)	9.442
	STAI
	-STAI-State	41.3	(16.8)	29.0	(9.6)	3.143
	-STAI-Trait	56.8	(11.2)	33.5	(9.2)	7.948
	TMT-A (time in seconds)	53.2	(21.9)	38.4	(7.4)	3.134
	TMT-A (n errors)	0.1	(0.3)	0	(0.0)	1.772
	TMT-B (time in s)	97.2	(50.3)	62.6	(8.7)	3.326
	TMT-B (n errors)	0.3	(0.1)	0.1	(0.4)	1.059
	TMT B-A (time in s)	44.1	(35.8)	22.2	(6.5)	2.680
	Stroop test
	Word (number)	94.3	(20.0)	109.8	(14.2)	1.991
	Colour (number)	64.8	(15.0)	76.9	(11.4)	1.708
	Colour-Word (number)	39.7	(10.0)	45.9	(9.7)	1.063
	Interference score	1.50	(6.3)	0.79	(5.8)	1.192
	Age at pain onset (years)	36.4	(12.0)	-	-
	VNS score
	-Current pain	5.5	(2.1)	-	-
	-Mean pain (/week)	7.5	(1.5)	-	-
	-Maximum pain (/week)	8.6	(1.4)	-	-
	Fibromyalgia Severity Score	24.7	(7.4)	-	-
	-Affected areas (n)	15.1	(4.3)	-	-
	-Fatigue	2.8	(0.5)	-	-
	-Unrefreshing sleep	2.4	(0.8)	-	-
	-Cognitive symptoms	2.2	(0.8)	-	-
	-Somatic symptoms	2.2	(1.0)	-	-
	MQS-III	17	(13.4)	-	-

Table 2

 2 Note. SDM = self-defining memory; FM = patients with fibromyalgia; HC = healthy controls; M = mean value; SD = standard deviation; n = number.

	: Detailed SDM characteristics
		FM		HC
		(n = 25)		(n = 24)
		M	(SD)	M	(SD)	t	P
	Thematic content (%)
	-Life-threatening events	30.4	(25.2)	27.5	(15.4)	0.48	0.631
	-Exploration/recreation	7.2	(12.7)	20.0	(23.6)	-2.38	0.022
	-Relationship events	47.2	(26.4)	31.7	(17.6)	2.41	0.020
	-Achievement events	8.0	(12.9)	7.5	(12.9)	0.14	0.893
	-Guilt theme	1.6	(5.5)	3.3	(9.6)	-0.78	0.441
	-Drug abuse	0.8	(4)	0.0	(0.0)	0.97	0.332
	-Non-classifiable events	4.8	(10.4)	10.0	(14.4)	-1.45	0.154
	Reference to pain (%)
	-Physical pain	8.0	(15.6)	8.0	(11.6)	-0.086	0.932
	-Psychological pain	12.0	(20.0)	20.0	(17.4)	-1.861	0.079
	Specificity (%)	32.8	(27.0)	60.8	(33.6)	-3.22	0.002
	Integrative meaning (%)	31.2	(23.9)	48.3	(33.8)	-2.06	0.045
	Tension (%)	20.0	(18.3)	36.7	(21.8)	-2.91	0.006
	Redemption (%)	2.4	(6.6)	9.2	(13.2)	-2.29	0.027
	Contamination (%)	3.2	(7.5)	4.2	(10.2)	-0.38	0.706
	Emotional valence	-0.03	(1.7)	0.90	(1.1)	-2.23	0.031
	Emotional intensity
	-Positive valence	2.60	(0.5)	2.66	(0.3)	0.50	0.618
	-Negative valence	2.69	(0.4)	2.44	(0.7)	1.54	0.131
	Age at SDM (years)	24.12	(12.1)	23.17	(16.1)	0.23	0.821

Acknowledgments

We would like to thank the study participants, together with the following physicians from Reims University Hospital for their invaluable help with patient recruitment: Dr Violaine Noel and Prof. Amélie Servettaz from the General Medicine Department,

Funding

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


Keywords: Nitric oxide, Engine Combustion Network (ECN), Spray and Combustion Characterization, Lift-Off Length, Ignition Delay

A New One Shot Engine (NOSE) was designed to simulate the thermodynamic conditions at High Pressure-High Temperature like an actual common-rail diesel engine in order to study the compression ignition of spray. The volume of the combustion chamber provided with large optical windows simplified the implementation of various optical diagnostics. The advantage of this kind of set-up in comparison to pre-burn or flue chambers is that the initial gas mixture can be well controlled in terms of species and mole fraction. The purpose of this work was to investigate the impact of nitric oxide (NO) on ignition delay (ID) for two fuels with different cetane numbers: nheptane, and n-dodecane. In the thermodynamic conditions chosen (60 bar and over 800-900 K), NO had a strong effect on ID, with increases in NO tending to reduce the ignition delay. Results showed that ID and Lift-Off Length (LOL) presented the same trend as a function of temperature and NO concentration. Experimentally, at 900 K the ignition of n-dodecane was promoted by NO up to 100 ppm, whilst higher NO levels did not further promote ignition and a stabilization of the value has been noticed. For n-heptane, stronger promoting effects were observed in the same temperature conditions: the ignition delays were monotonically reduced with up to 200 ppm NO addition. At a lower temperature (800 K) the inhibiting effect was observed for n-dodecane for [NO] greater than 40 ppm, whereas only a promoting effect was observed for n-heptane. The experimental results of LOL showed that NO shortened LOL in almost all cases, and this varied with both the NO concentration and the mixture temperature. Thus, fuels with shorter ignition delays produce shorter lift-off lengths.

Impact of nitric oxide on n-heptane and n-dodecane autoignition in a new high-pressure and high-temperature chamber Hugo Ajrouche a,* , Ob Nilaphai a , Camille Hespel a , Fabrice Foucher a a Univ. Orléans 2: [50 mm + 10 mm] x 2.2 words/mm x 2 column + (14 words in caption) = words Figure 3: [62 mm + 10 mm] x 2.2 words/mm x 2 column + (40 words in caption) = words Figure 4:

[37 mm + 10 mm] x 2.2 words/mm x 2 column + (42 words in caption) = words Figure 5:

[37 mm + 10 mm] x 2.2 words/mm x 2 column + (42 words in caption) = words Figure 6:

[37 mm + 10 mm] x 2.2 words/mm x 1 column + (49 words in caption) = words Figure 7:

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Figure (total): 2063 words

Color reproduction: online only (color figures are to be printed in gray scale)

Introduction

During the last decade, several new combustion chambers were developed to reach the thermodynamic conditions of current common-rail diesel engines [1][2][3], for example: Constant-Volume Preburnt (CVP) chamber, Constant-Pressure Flow (CPF) chamber, Rapid Compression Machine (RCM) or Optical Research Engine (ORE) [2,3]. Moreover, a new kind of RCM, called "Rapid Cycling Machine (RCYM)" [4,5], seems to be an interesting option to study spray in high pressure and high temperature conditions, due to the absence of combustion products as in the CVP and the possibility of covering a full range of diesel engine working conditions (up to 100 bar). The New One Shot Engine (NOSE) was designed to simulate these thermodynamic conditions at high pressure and high temperature [START_REF] Nilaphai | ILASS -Eur[END_REF][START_REF] Chiboub | 28th Conf. Liq. At. Spray Syst. ILASS-Europe 2017[END_REF] in order to study the diesel spray and combustion relevant to engines that use a moderate rate of Exhaust Gas Recirculation (EGR). The advantage of this kind of set-up in comparison to pre-burn or flue chambers is that the initial gas mixture can be well controlled in terms of species and mole fraction. For example, spray combustion can be achieved in a more realistic environment without H2O and CO2 or with species representing the burnt gases.

In piston engines, the reacting mixture always contains a certain amount of residual gases resulting from the incomplete combustion of species such as carbon monoxide (CO) and unburned hydrocarbons in the previous combustion cycle. One of these leftover combustion species is nitric oxide (NO) which has an impact on the autoignition kinetics. Some studies have reported that the appearance of small quantities of NO typically occurs inside the CVP at a concentration of a few dozen ppm after mixing with the fresh charge [START_REF] Nilaphai | ILASS -Eur[END_REF][START_REF] Chiboub | 28th Conf. Liq. At. Spray Syst. ILASS-Europe 2017[END_REF][START_REF] Roberts | [END_REF]. No studies are yet available confirming the absence of NO during premixed burn in this kind of chamber. However, the existence of these burnt products has been reported in few studies to have a significant impact on autoignition in SI engines [START_REF] Nilaphai | ILASS -Eur[END_REF][START_REF] Chiboub | 28th Conf. Liq. At. Spray Syst. ILASS-Europe 2017[END_REF][START_REF] Roberts | [END_REF] and HCCI engines [9][10][11][12][13]. Ignition delay (ID) is a key combustion property for fuels used in compression-ignition (CI) engines, and is commonly used as the metric for the validation of combustion simulations. A promoting effect of NO was often observed, particularly at high temperatures and low NO concentrations, whereas inhibiting effects have also been reported in other conditions [14][15][16].

The purpose of this work was to study the influence of NO on ID for different fuels in NOSE.

Pure n-heptane and pure n-dodecane were the fuels used. First, to determine the ability of fuels to auto-ignite, the ignition delays of these fuels without NO were characterized and compared.

Experiments were conducted at the Spray A operating conditions of ECN in NOSE. The engine setup was also improved to extend conditions to different ambient temperatures (800 K and 850 K). To provide a homogeneous temperature field at 800 K or 900 K two specific compression ratios were tested 12.6 and 15 respectively. In the thermodynamic conditions chosen (60 bar and over 800-900 K), the effect of NO on ID and LOL was studied by adding 0-200 ppm NO to the engine intake. To

Experimental approach 2.1. Experimental facility

The NOSE set-up is based on a single-cylinder engine (155 mm bore diameter and 177.8 mm stroke),

driven by an electric motor (Figure 1). The speed of the electric motor is controlled as a function of the crank angle, so that the time for the compression stroke (40 ms), a plateau near the Top Dead Centre (TDC) (15 ms) and the expansion stroke are completely known during one rotation (Figure 2).

For each run, the engine is used during a single compression-expansion stroke. The original cylinder head was replaced by a dedicated chamber, designed by extending the combustion chamber to enable optical measurements and the study of Diesel sprays. There are 4 quartz windows, 25 mm thick, 25 mm wide, and 80 mm long to support several kinds of optical measurement. The operation of NOSE starts by setting the initial conditions such as initial pressure, initial temperature and gas composition at Bottom Dead Center (BDC). After creating a vacuum, different gases (N2, O2, Air and bottle of NO at 200 ppm mixed into N2) were injected into the chamber by using mass flow controller (Brooks instruments). The initial temperature was specified by controlling the water temperature around the liner and 4 heaters in the cylinder head, and the temperature of the injector was maintained at the same temperature as the cylinder head (90 ºC ± 0.5 ºC for all experiments). Two type-K thermocouples were placed inside the chamber and casing (near the injector) to measure the gas temperature inside the chamber and the casing temperature, respectively. A high pressure pneumatic pump (MAXIMATOR M189 DVE-HD) maintained the injection pressure around 1 500 bar (±20 bar) before injection. The injection pressure was measured by a piezo-electric pressure sensor (KISTLER Type 6533A11) with a charge amplifier. As this new device compresses ambient gases during only one cycle from BDC to TDC, it is called a "New One Shot Engine." The cylinder pressure, temperature inside the vessel, injector driving current, photomultiplier signal and crank angle were recorded as a function of time with a National Instrument CompactRIO at 250 kHz. A high response piezo-electric pressure sensor (KISTLER 7001) was installed at the chamber head and coupled with a charge amplifier (KISTLER 5011). All the fuel injection system, comprising the Common-Rail, injector, high pressure tube, and injector, are the same specification as ECN Spray A injection devices [17]. Further details about the chamber design, thermal characterization chamber, specification of the injection system, and data acquisition system were presented in our previous studies [START_REF] Nilaphai | ILASS -Eur[END_REF][START_REF] Ajrouche | Mounaïm-rousselle[END_REF][START_REF] Nilaphai | 28th Conf. Liq. At. Spray Syst. ILASS-Europe 2017[END_REF].

Spray condition

Spray-A condition (Table 1) was the chosen reference standard condition. The operating conditions (800 K and 900 K ambient gas temperature, about 60 bar cylinder pressure and 22.8 kg/m 3 ) are typical of the real operating conditions of engines that use a moderate rate of EGR. To achieve standard Spray-A conditions for the lower temperature (800 K), the CR was changed from 15:1 to 12.3:1 by modifying the metallic plate of the piston (see Figure 1-left), thus changing the volumetric compression ratio. The initial pressure at the BDC made it possible to achieve 800 K and 22.8 kg/m 3 at the end of compression. LOL is defined as the distance between the injector tip and the stabilized flame of the high temperature reaction zone [5,[START_REF] Nilaphai | ILASS -Eur[END_REF]. As is well known, at high temperature the chemiluminescence spectrum of OH* is centered at 310 nm, so OH* is a good indicator to measure the LOL. According to the methodology developed by [22], the LOL was determined as the gradient of the OH* intensity along the chemiluminescence image recorded by an ICCD Photron Fastcam APX I2 and a 60 mm f/3.5 UV lens and equipped with a 310 nm (FWHM10) band-pass filter (BFP). A long constant gating time of 449 µs was used to allow turbulent fluctuation in the LOL to reach an average as well as to provide an image of the quasi-steady mean LOL after the Start Of Injection (SOI) [22]. LOL was defined as the average distance between the injector tip and the first value above 50 % of the maximum intensity of each profile, following the ECN method [START_REF][END_REF].

Optical diagnostics

The Schlieren set-up, presented in Figure 1, is composed of a continuous white LED with a 1 mm pinhole, mirrors and collimating mirrors to reflect light through the test section in the NOSE chamber. A 6 mm pinhole was set up to record Schlieren light by the high speed camera (Phantom V1611). A 550 nm low-pass filter was added to limit emissions due to soot radiation. As can be seen in Figure 2, the measured pressure and temperature reach the requirement of the standard Spray-A condition around TDC at 900 K and 60 bar, so a required density of 22.8 kg/m 3 .

The results clearly show that the disparity of the values of temperature and pressure are lower than 1 % during the injection duration and confirm that NOSE can achieve a wide range of standard Spray-A conditions. SOI was defined here as the time between the start of injection current and the first injection image of the spray obtained by Schlieren visualization, usually called "hydraulic delay". To use the same criterion to define ID with both techniques, the results shown in this work were corrected by the hydraulic delay. The cool and main flame ignition delays were detected using the Schlieren images. OH* chemiluminescence was also used to detect the main flame ignition delay by using a Photomultiplier tube side-on and a band-pass filter of 307 nm. It was set up close to the window and positioned on the opposite side to the ICCD camera, as shown in Figure 1. and n-heptane (right) at 900 K with 15% O2.

Results and discussion

Ignition Delay

10

The ignition delays of the cool and the main flames are plotted as a function of NO concentration at 900 K (Figure 4, Figure 5) for n-heptane and n-dodecane fuels. The ID measured with both Schlieren and photomultiplier techniques are in good agreement, with a disparity below 5 %. When no NO was added, the ignition delays were found to be close to those determined by [17] in the same spray conditions. The ID followed the expected trend with respect to the fuel cetane number, decreasing with increasing cetane number and with increasing ambient temperature. The high temperature ID (hot flame) is preceded by the appearance of the cool flame in all cases (Figure 4). The ID of nheptane and n-dodecane decreased monotonically as the NO concentration was increased, in agreement with the conclusion by Chen et al. [24] where n-heptane ignition was promoted by NO up to 100 ppm in a rapid compression machine. and n-heptane (right) at 800 K with 15% O2.

NO had a direct impact on the detection of the cool flame. The difference observed in this work between cool and hot flame was constant (around 100 µs) with increasing NO. This constant value can be explained by the dynamism of turbulent cool flame propagation described by Dahms et al.

[25] which is not impacted by NO. At 800 K, the same tendencies were found for n-heptane (Figure 5). However, the cool and hot flame delays of the n-dodecane spray were not monotonic. From a concentration of 0 to 40 ppm of NO, the delays decreased then increased to reach a delay greater than without NO when the concentration of NO was greater than 100 ppm. Thus, at this operating condition, the effect of NO on the autoignition delay process of n-dodecane exhibited two different aspects: NO can both promote and inhibit ID, depending on the added concentration.

Figure 6 shows the normalized ignition delays of n-dodecane and n-heptane for two temperatures, 800 K and 900 K, as a function of percent of NO. For n-heptane, ID was monotonically shortened as more NO was added at the two temperatures. Thus, NO concentration had the same promoting effect and at 200 ppm the ID was reduced by 15 %. However, for n-dodecane at low temperature (800 K), NO slightly promoted total ignition at lower levels of addition. This promoting effect peaked at around 40 ppm of NO, after which the ID increased with further NO addition, thus the impact of NO was less significant ± 10 %. NO tends to increase the extent of oxidation for high-octane fuel components. However, for the low-octane component n-heptane and n-dodecane, NO has an inhibiting effect on hydrocarbon oxidation, particularly at low temperatures. In this work, this effect has been observed for n-dodecane. The different behaviors seen for n-dodecane and n-heptane could be explained by the dominant inhibiting impact of NO on n-dodecane at low temperatures, which is less significant for n-heptane. This behavior is further explained in terms of reaction kinetics in the NO chemistry.

Lift-off length

While the ignition delay characterizes the first ignition area of the spray, the LOL can be associated to a stationary regime where the flame is stabilized behind the liquid spray. For both temperatures, the LOL were plotted as a function of the NO concentration. The LOL for the n-heptane fuel was affected by NO and decreased linearly, though the effect on the LOL was found to be slightly less than for the cool and the main flame. However, whereas the NO concentration decreased the LOL for the n-dodecane spray at 900 K, a decrease then an increase of the LOL was found at 800 K. By considering a different combustion parameter and using another diagnostic, this result confirms the promoting and inhibiting effect of ID observed in the previous section. The promoting or the inhibiting effect of the NO is therefore similar to that of the cool and the main flame but with a lesser impact on the LOL.

Simulation

To understand the impact of NO on the ignition stages, a Senkin constant volume simulation was carried out using the same conditions as in the experiments (T=800 K and 900 K, O2=15% and P=60 bar) for a large range of equivalence ratios and for a wide range of NO concentrations. The simulation was performed for vaporization kinetics in the premixed case at constant volume. The PFR mechanism including the NO sub-mechanism from Dubreuil et al. [15] was used to simulate nheptane oxidation. For n-dodecane, the NO sub-mechanism from [15] was included in the mechanism from Mzé-Ahmed et al. [26]. The main flame delays were determined from the temperature histories.

The promoting and inhibiting effects are presented as the percentage of the ID when no NO is added.

For n-heptane, NO decreased the ignition delay regardless of the equivalence ratio when the concentration was less than 50 ppm. After 50 ppm at 800 K, a plateau was reached for an equivalence ratio greater than 1 and the promoting effect of NO increased for a lean equivalence ratio. At 900 K, the promoting effect was more constant but always greater for a lean equivalence ratio. From Figure 8, at 200 ppm of NO, the delay was found to be 87% of the delay without NO for both temperatures. That means that, at 800 K, ID occurs when the equivalence ratio is leaner than at 900 K. The ignition delay predictions from simulation show that at 800 K, the ignition of n-dodecane was promoted by NO up to 200 ppm, whilst higher NO levels did not further promote ignition. However, at poor region, higher NO levels had an inhibiting effect on n-dodecane ignition. At the higher temperature, NO promoted the ignition delay in all cases. According to the kinetic modeling, the acceleration of the low-temperature reactions resulting in a reduction of the low temperature heat

  measure ID, different techniques such as Schlieren visualization and OH* chemiluminescence were used to analyze the cool flame and the high temperature ignition (hot flame). The Lift-Off Length (LOL) was measured by OH* chemiluminescence images. The observed influence of NO addition on ID and LOL was analyzed. The related chemical reasons responsible for the effects are then discussed.

Figure 1 :

 1 Figure 1: The NOSE chamber: cross-section (left) and experimental scheme of the optical set-ups (right).

Figure 2 :

 2 Figure 2: Average thermodynamic measurement results and zoom caption of 10 superimposed pressure and temperature curves.

Figure 3 :

 3 Figure 3: The series of Schlieren images and post-processed images during cool flame and hot flame events (left) and validation of the ignition delay criterion on Schlieren images by the OH* chemiluminescence collected by a Photomultiplier at 900 K on n-dodecane (right).

Figure 4 :

 4 Figure 4: Comparison of ignition delay obtained from the cool and hot flame to those obtained from the photomultiplier as a function of percent of NO in the new one shot engine for n-dodecane (left)

Figure 5 :

 5 Figure 5: Comparison of ignition delay obtained from the cool and hot flame to those obtained from the photomultiplier as a function of percent of NO in the new one shot engine for n-dodecane (left)

Figure 6 :

 6 Figure 6: Normalized ignition delay with respect to ignition delay without NO as a function of percent of NO in the new one shot engine for n-dodecane (circles) and n-heptane (crosses) at 900 K (dashed line) and 800 K (solid line). NO additions from 0 ppm to 200 ppm.

Figure 7 :

 7 Figure 7: Normalized lift-off length with respect to lift-off length without NO as a function of percent of NO in the new one shot engine for n-dodecane (circles) and n-heptane (crosses) at 900 K (dashed line) and 800 K (solid line). NO additions from 0 ppm to 200 ppm.

Figure 8 :

 8 Figure 8: Normalized ignition delay with respect to ignition delay without NO as a function of percent of NO for different equivalence ratios at 900 K (dashed line) and 800 K (solid line) for ndodecane (left) and n-heptane (right). NO additions from 0 ppm to 1000 ppm.

  Figure captions:

Figure 1 :

 1 Figure 1: The NOSE chamber: cross-section (left) and experimental scheme of the optical set-ups (right).

Figure 2 :

 2 Figure 2: Average thermodynamic measurement results and zoom caption of 10 superimposed pressure and temperature curves.

Figure 3 :

 3 Figure 3: The series of Schlieren images and post-processed images during cool flame and hot flame events (left) and validation of the ignition delay criterion on Schlieren images by the OH* chemiluminescence collected by a Photomultiplier at 900 K on n-dodecane (right).

Figure 4 :

 4 Figure 4: Comparison of ignition delay obtained from the cool and hot flame to those obtained from the photomultiplier as a function of percent of NO in the new one shot engine for n-dodecane (left) and n-heptane (right) at 900 K with 15% O2.

Figure 5 :

 5 Figure 5: Comparison of ignition delay obtained from the cool and hot flame to those obtained from the photomultiplier as a function of percent of NO in the new one shot engine for n-dodecane (left)and n-heptane (right) at 800 K with 15% O2.

Figure 6 :

 6 Figure 6: Normalized ignition delay with respect to ignition delay without NO as a function of percent of NO in the new one shot engine for n-dodecane (circles) and n-heptane (crosses) at 900 K (dashed line) and 800 K (solid line). NO additions from 0 ppm to 200 ppm.

Figure 7 :

 7 Figure 7: Normalized lift-off length with respect to lift-off length without NO as a function of percent of NO in the new one shot engine for n-dodecane (circles) and n-heptane (crosses) at 900 K (dashed line) and 800 K (solid line). NO additions from 0 ppm to 200 ppm.

Figure 8 :

 8 Figure 8: Normalized ignition delay with respect to ignition delay without NO as a function of percent of NO for different equivalence ratios at 900 K (dashed line) and 800 K (solid line) for ndodecane (left) and n-heptane (right). NO additions from 0 ppm to 1000 ppm.

5954 words Main text: 2929 words (MSWord 2010 word count) References: (30 references

  , INSA CVL, PRISME, EA 4229F45072 Orléans, France

	Corresponding and Contact Author:
	Hugo AJROUCHE
	Université d'Orléans-Laboratoire PRISME
	Polytech Orléans
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	Phone: +33-02-38-49-47-28
	Fax.: +33-02-38-41-73-83

Email: hugo.ajrouche@univ-orleans.fr Colloquium Topic Area: Spray, Droplet, and Supercritical Combustion Total paper length (method 1): + 2) x (2.3 line/reference) x (7.6 words/line) = 559 words Figure 1: [63 mm + 10 mm] x 2.2 words/mm x 2 column + (14 words in caption) = words Figure

Table 1

 1

	:	(11 + 2 lines) x (7.6 words/line) x (1 columns) = 99 words
	Table 2:	(18 + 2 lines) x (7.6 words/line) x (2 columns) = 304 words

Table (total): 403 words

Submitted for consideration to the 37 th International Symposium on Combustion, the Convention Centre Dublin, Ireland, 29 July-3 August 2018.

Table 1 .

 1

	Standard Spray-A operating conditions of ECN [20].
		Parameter		Value
	Ambient gas temperature 800 and 900 K
	Ambient gas pressure		about 60 bar
	Ambient gas density		22.8 kg/m 3
	Ambient gas velocity		Near-quiescent, less than 1 m/s
	Fuel injection pressure		150 MPa (1 500 bar)
	Fuel			n-dodecane (Cetane number = 80 [21], Boiling
				temperature =489 K) and n-heptane (Cetane
				number = 56 [21], Boiling temperature =372 K)
	Fuel	temperature	at	363 K (90°C)
	nozzle
	Injection duration		1.5 ms

Table 2

 2 summarizes the optical set-ups for the different techniques needed to characterize macroscopic combustion parameters, following the ECN recommendations to ensure accurate experimental results. LOL was measured by OH* chemiluminescence images, and ID from high speed Schlieren images, and the OH* chemiluminescence temporal signal recorded by the photomultiplier as shown in Figure 1.

	Table 2.
	Summary of the optical set-ups
	Parameters	Lift-Off Length	Ignition Delay
	Optical Technique OH*Chemiluminescence	Schlieren	OH*Chemiluminescence
	Camera/Detector	Photron -APX-I2	Phantom-V1611	Newport Photomultiplier
				tube 70680
	Sensor type	Intensified-CMOS	CMOS	-
	Light source	-	LED (white) with 1	-
			mm pinhole
	Lens	UV 60 mm f/3.5	-	-
	Mirrors	-	2 Parabolic Mirrors 34	-
			inch
	Pin hole	-	6 mm	-
	Filter	BPF 310 nm , FWHM	LPF ≤ 550 nm (Asahi	BPF 307 nm, FWHM 10
		10 nm(Asahi ZBPA310)	XVS0550)	nm (Ealing 35-7939)
	Frame speed	2 kHz	39 kHz	-
	Exposure time	499 µs	5 µs	-
	Image size	512 x 1024 pix²	1024 x 400 pix²	-
	Magnification	18.2 pix/mm	12.3 pix/mm	-
	Repetitions	10 tests	10 tests	10 tests

Acknowledgements

The authors acknowledge the French National Research Agency (contract ANR-14-CE22-0015-01) for financial support to the ECN-France project and Region Centre Val de Loire (CPER 2007(CPER -2013 Energies du Futur) and FEDER for financial support to build the experimental set-up.

release delay is due to the production of active species through reactions involving NO, as already demonstrated under plug-flow and jet-stirred reactor conditions [27,28]: NO + HO2 = NO2 + OH and NO + RO2 = NO2 + RO. The NO+RO2 reactions are less pronounced or influential than the NO+HO2 reaction, as demonstrated in the literature [28,29]. At high NO concentrations, the inhibiting process, via: NO + OH + M = HONO + M and ROOH + NO = RO + HONO, becomes an increasingly important competitor that could even significantly delay low-temperature ignition, as demonstrated before [30].

Summary and conclusions

A new experimental set-up was designed and improved to guarantee high quality results based on Spray A conditions. At the thermodynamic conditions chosen (60 bar over 800-900 K), the ignition delays of n-heptane and n-dodecane in varying amounts of NO (0-200 ppm) were measured in a rapid cycling machine NOSE. The consistency of the data obtained from ID and LOL indicates a good level of repeatability and outlines a global agreement with the ECN dataset for 0 ppm of NO.

Experimental results showed that NO advanced ignition in most cases. NO had a strong effect on ID, with increases in NO tending to reduce the ignition delay at 900 K. The effect of NO on the autoignition delay process of n-dodecane exhibited two different aspects at 800 K: NO can both promote and inhibit the ignition delays, depending on the NO concentration added. Results obtained show that ID and LOL present the same trend as a function of temperature and NO concentration. Fuels with shorter ignition delays generally produce shorter lift-off lengths. In following work, the effect of different species in the ambient gases will be studied to assess their impact on combustion development and soot production/oxidation. Additionally, the influence of the droplet size distribution on ID will be performed by laser diffraction analysis.


T D A Ly

S Edouard

Sekene Badiaga

Herve Tissot-Dupont

Van Thuan Hoang

Vincent Pommier De Santi

Philippe Brouqui

Didier Raoult

VITROME Philippe Gautret
email: philippe.gautret@club-internet.fr

Tran Duc

Anh Ly

Epidemiology of respiratory pathogen carriage in the homeless population within two shelters in Marseille, France, 2015-2017: cross sectional 1-day surveys

Keywords: homeless, respiratory pathogen carriage, respiratory symptoms and signs, quantitative polymerase chain reaction (qPCR), quantitative reverse transcription polymerase

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

Introduction

Given their lack of customary and regular access to a conventional dwelling or residence, homeless people reside in the street and/or in shelters. The challenge of poor environmental conditions, poor physical state, smoking habit, alcohol abuse or illicit drug consumption significantly impairs their health status. Behind the frequent association with mental disease and unintentional injuries, homeless people are also predisposed to infectious diseases, especially respiratory infections such as tuberculosis and pneumonia [START_REF] Raoult | Infections in the homeless[END_REF]. A high prevalence of chronic respiratory diseases was recorded in the homeless, including bronchitis, asthma and chronic obstructive pulmonary disease [START_REF] Usatine | Health care for the homeless: a family medicine perspective[END_REF]. Respiratory diseases are frequently associated with death among homeless individuals [START_REF] Hwang | Risk factors for death in homeless adults in Boston[END_REF]. Pulmonary tuberculosis is frequent in the homeless population and has been extensively studied [START_REF] Vries | Barriers and facilitators to the uptake of tuberculosis diagnostic and treatment services by hard-toreach populations in countries of low and medium tuberculosis incidence: a systematic review of qualitative literature[END_REF][START_REF] Beijer | Changes over time in the risk of hospitalization for physical diseases among homeless men and women in Stockholm: A comparison of two cohorts[END_REF].

In Marseille, there are an estimated 1500 homeless individuals including more than 800 sleeping in the street and approximately 600 living temporarily at the 2 main shelters of the city [6]. Infectious diseases are frequent among Marseille's sheltered homeless people, including lice and Bartonella quintana infection, hepatitis E and C, Tropheryma whipplei infection, skin infections and respiratory tract infections [START_REF] Badiaga | Preventing and Controlling Emerging and Reemerging Transmissible Diseases in the Homeless[END_REF]. A 50% rate of respiratory symptoms and signs was observed in this population, in winter 2005 [START_REF] Badiaga | Contribution of a shelter-based survey for screening respiratory diseases in the homeless[END_REF]. About 8.7% carried at least one respiratory virus, with rhinovirus being the most frequent when sampled during the winters of 2010-2011 [START_REF] Thiberville | Respiratory viruses within homeless shelters in Marseille, France[END_REF]. These preliminary finding demonstrated that respiratory infections might be frequent among sheltered homeless people in Marseille, warranting further investigation.

We described socio-demographic characteristics, underlying chronic medical conditions and addictions, clinical respiratory symptoms and signs, and prevalence of respiratory viruses and bacteria (other than Mycobacterium tuberculosis) in the homeless population in 2 shelters of Marseille over the 2015-2017 period of time and investigated potential risk factors.

The main objective of the study was the assessment of risk factors for respiratory tract infection symptoms and signs in sheltered homeless people during the French winter season, including pathogen carriage. We hypothesize that carriage of viral pathogens may be associated with clinical signs and symptoms since it is admitted that the vast majority of respiratory infections in adults are caused by rhinoviruses, coronaviruses and influenza viruses [START_REF] Green | Clinical Utility of On-Demand Multiplex Respiratory Pathogen Testing among Adult Outpatients[END_REF]; whereas carriage of bacterial pathogens may not necessarily be associated with clinical signs and symptoms since bacterial microorganisms that are potential aetiological agents of respiratory tract infections are also part of the resident microbiome [START_REF] Prat | Bacteria in the respiratory tract-how to treat? Or do not treat?[END_REF]. The secondary objective was to investigate the possible association between viral-bacterial cocarriage or dual bacterial infections and respiratory symptoms and signs, since the pathogenic role of respiratory viruses in virus-bacteria co-infected patients remains unclear [START_REF] Voiriot | Viralbacterial coinfection affects the presentation and alters the prognosis of severe community-acquired pneumonia[END_REF] and because interspecies interactions in patients infected with several respiratory bacteria is suspected [START_REF] Lewnard | Epidemiological Markers for Interactions Among Streptococcus pneumoniae , Haemophilus influenzae , and Staphylococcus aureus in Upper Respiratory Tract Carriage[END_REF].

Methods

Study population and data collection. Ethical approvals were obtained from the Institutional

Review Board and Ethics Committee of Marseille (2010-A01406-33). Cross sectional one-day surveys were organized on February 17, 2015, March 7-10, 2016 and February 6-8, 2017 in 2 shelters (A and B) in Marseille, France, housing 600 homeless persons, for the night only, with a high turnover. Shelter A has a special (day-night) unit with a 35-bed capacity, dedicated to high-risk sedentary homeless people who are characterized by a high level of poverty, poor hygiene, alcoholism and mental illness. Adult homeless people were recruited on a voluntary basis. A medical doctor administrated a standardized questionnaire addressing demographics, chronic medical conditions, chronic respiratory disease (CRDs) status (defined as suffering from one of the following conditions: asthma, chronic obstructive pulmonary disease, occupational lung diseases and pulmonary hypertension), substance abuse, vaccination status, symptoms and signs (cough, expectoration, rhinorrhea, dyspnea, sore throat, sibilants, rhonchi, crackles, headache, myalgia, conjunctivitis, fever) at enrollment and physically examined the participants. All patients signed an informed consent. The homeless people screened were offered treatment or further evaluation based on the symptom assessment, since qPCR data were obtained long after the surveys were done.

Respiratory specimens. Nasal and pharyngeal swabs were collected from each participant, transferred to Sigma-Virocult® medium and stored at -80°C. The DNA and RNA extractions were concurrently performed using the EZ1 Advanced XL (Qiagen, German) with the Virus Mini Kit v2.0 (Qiagen) according to the manufacturer's recommendation. All quantitative real-time PCR (qPCR) reactions were performed using a C1000 Touch™ Thermal Cycle (Bio-Rad, USA). Negative control (PCR mix + sterilized water) and positive control (DNA from bacterial strain or RNA from viral strain) were included in each run. Positive results of bacteria or virus amplification were defined as those with a cycle threshold (CT) value ≤35.

Patients having at least one nasal or pharyngeal positive sample were considered positive cases.

Identification of respiratory bacteria. Real-time PCR amplifications were carried out by using LightCycler® 480 Probes Master kit (Roche diagnostics, France) according to the manufacturer's recommendations. The SHD gene of Haemophilus influenzae, phoE gene of Klebsiella pneumoniae, NucA gene of Staphylococcus aureus, and lytA gene of Streptococcus pneumoniae were detected with internal controls T4 phage as previously described [START_REF] Ninove | RNA and DNA Bacteriophages as Molecular Diagnosis Controls in Clinical Virology: A Comprehensive Study of More than 45,000 Routine PCR Tests[END_REF][START_REF] Memish | Mass gathering and globalization of respiratory pathogens during the 2013 Hajj[END_REF] Identification of respiratory viruses: One-step duplex qRT-PCR amplifications by HCoV/HPIV-R Gene Kit (REF: 71-045, Biomerieux®, France) were used for the detection of human coronavirus (HCoV) and human para-influenzavirus (HPIV), according to the manufacturer's recommendations. One-step simplex real-time qRT-PCR amplifications were performed by using Multiplex RNA Virus Master Kit (Roche diagnostics, France) for influenza A (FLUA), influenza B (FLUB), human rhinovirus (HRV), human metapneumovirus (HMPV), human respiratory syncytial virus (HRSV) and internal controls MS2 phage [START_REF] Ninove | RNA and DNA Bacteriophages as Molecular Diagnosis Controls in Clinical Virology: A Comprehensive Study of More than 45,000 Routine PCR Tests[END_REF]. HCoV positive samples were further screened for HCoV-HKU1, HCoV-NL63, HCoV-229E, and HCoV-OC43 [START_REF] Thiberville | The Viral Etiology of an Influenza-like Illness During the 2009 Pandemic[END_REF].

Statistical analysis

Statistical analysis was conducted using STATA software (version 11.1). Differences in the proportions (percentages and odds ratio (OR) with 95% confidence interval (CI) estimations) were tested by Pearson's chi-square or Fisher's exact tests when appropriate. Two-tailed tests were used for comparisons. Univariate analysis was used to examine unadjusted associations between multiple factors (demographic, chronic medical condition), respiratory symptoms or physical finding and prevalence of respiratory pathogen carriages. A p value <0.05 was considered statistically significant. Only the variables with a prevalence ≥ 5.0% were considered for statistical analysis. Variables with p values of <0.2 from the univariate analysis were included in the multivariate analysis. Analysis of multicollinearity among the independent variables was performed using the phi coefficient to test for correlation among binary variables; and for pairs of variables that were highly correlated (Absolute value of correlation coefficient >0.7), only one variable was entered into the multivariate model.

Multivariable logistic regression (created by step-wise regression) was used to determine factors associated with respiratory symptoms and signs. Log likelihood Ratio Tests were performed to determine these multivariable modeling.

Results

Since only 2 women were identified, they were excluded. Of the 479 male individuals who answered the questionnaire and signed consent forms, 477 patients agreed to undergo nasal or pharyngeal sampling. About 11550 qPCR reactions were performed.

Characteristics and clinical status of the homeless participants

The socio-demographic characteristics, substance abuse, chronic disease and clinical features of participants are shown in Table 1 and Figure 1. The population was characterized by middleaged males (43.6 ± 16 years old) of North African origin, with a relatively high proportion of chronic homelessness (more than one year) reported by 37.2% of individuals and with a 61.2% prevalence of tobacco smoking. About 8% reported suffering from CRDs. The prevalence rate of at least one respiratory symptom or sign was of 35.3% with cough, rhinorrhea and dyspnea as the most frequent symptoms. Most symptomatic individuals (70.8%, 119 out of 168) were smoking tobacco or suffering from CRDs.

Prevalence of respiratory pathogens by real-time PCR

We evidenced a high prevalence of respiratory carriage of bacteria (65.6%, 313 of 477), notably, the proportion of individuals colonized by H. influenzae in nasal and/or pharyngeal swabs was of 58.7% (n=280) and that of S. pneumoniae was of 12.4% (n=59). Fifty-one patients (10.8%) were also tested positive for at least one virus by qRT-PCR. When comparing nasal and pharyngeal sampling sites, we found that H. influenzae was significantly more frequently detected in pharyngeal samples compared to nasal samples, while the prevalence of S. aureus and HRV in nasal samples was significantly higher than in pharyngeal samples (shown in Table 2). Co-infections were frequently observed with the most frequent being H. influenzae-virus and H. influenzae-S. pneumoniae co-infections (Table 1).

Association between demographics, chronic medical conditions, respiratory pathogen carriage and clinical findings according to respiratory symptoms and signs in univariate analysis and multivariate analysis

Respiratory symptom and signs prevalence significantly increased with the duration of homelessness (Table 1). The prevalence of symptoms and signs was higher in individuals ≥ 50 years of age, suffering from chronic respiratory diseases and in individuals born in France but was lower in individuals born in Sub-Saharan Africa. Among migrants, the symptom and sign prevalence was significantly higher in those visiting their country of origin compared to others.

Individuals carrying at least one virus, S. pneumoniae or H. influenzae-S. pneumoniae coinfection were more likely to present with at least one respiratory symptom or sign. In the multivariate analysis, only individuals experiencing chronic homelessness (OR=1.77 3). Overall, individuals carrying at least one virus were more likely to present with cough, expectoration, rhinorrhea and sore throat. Carriage of S. pneumoniae was associated with cough (Table 4).

Discussion

The sheltered homeless population in our study was characterized by a high proportion of migrants of North African origin with a high prevalence of smoking habits and CRDs. We observed a high prevalence of respiratory symptoms and signs (35%) in line with the results of a survey conducted in Italy and The Netherlands [START_REF] Van Laere | Shelter-based convalescence for homeless adults in Amsterdam: a descriptive study[END_REF][START_REF] De Maio | Reaching out to the forgotten: providing access to medical care for the homeless in Italy[END_REF]. Dry or productive cough, rhinorrhea and dyspnea were the symptoms most frequently observed, suggesting that both upper and lower tract respiratory infections affect a significant proportion of sheltered homeless people during winter. We found relatively low rates of influenza virus infections. Cross sectional surveys took place when influenza was epidemic in the region of Marseille. Influenza vaccination rate in the homeless population screened in our surveys was in the same range in Marseille's overall population [19,20]. This result may indicate that the social isolation of homeless people might have a protective impact against community influenza virus transmission. One of the most important findings of this study is the very high prevalence of bacterial colonization by respiratory bacteria with H. influenzae (59%), and S. pneumoniae (13%), which were the most frequent. A high prevalence of H. influenzae carriage (70%) was also observed by direct PCR, in healthy infants from the Western region of Gambia [START_REF] Kwambana | Early acquisition and high nasopharyngeal co-colonisation by Streptococcus pneumoniae and three respiratory pathogens amongst Gambian new-borns and infants[END_REF] and a rate of 40.9% was reported among children aged ≤6 years in day-care centers in eastern France [START_REF] Talon | Antibiotic susceptibility and genotypic characterization of Haemophilus influenzae strains isolated from nasopharyngeal specimens from children in day-care centers in eastern France[END_REF]. In surveys conducted among healthy adults in the Australian Aboriginal population, the prevalence of non-typeable H. influenzae reached approximately 22.9% when culturing nasopharyngeal samples [START_REF] Mackenzie | Epidemiology of nasopharyngeal carriage of respiratory bacterial pathogens in children and adults: crosssectional surveys in a population with high rates of pneumococcal disease[END_REF]. A 2.3% H. influenzae nasal prevalence was observed in Marseille's individuals originating from North-Africa by qPCR in 2013 [START_REF] Van Laere | Shelter-based convalescence for homeless adults in Amsterdam: a descriptive study[END_REF], however, the survey was conducted in October, which may account for a lower prevalence, as shown in another healthy Italian children population [START_REF] Marchisio | Seasonal variations in nasal pharyngeal carriage of respiratory pathogene in healthy Italian children attenting day-care or school[END_REF]. K. pneumoniae naso-pharyngeal carriage rates have been reported to range from 3 to 15%, which is in agreement with our results [START_REF] Martin | Colonization, Infection, and the Accessory Genome of Klebsiella pneumoniae[END_REF]. This bacterium is known to be frequently multidrug-resistant [START_REF] Martin | Colonization, Infection, and the Accessory Genome of Klebsiella pneumoniae[END_REF] and further studies on drug resistance in bacteria isolated from homeless people would be of interest.

We identified chronic homelessness, chronic respiratory diseases and visiting countries of origin for migrants as independent risk factors for respiratory symptoms and signs. We found a strong association between virus or S. pneumoniae carriage and respiratory symptoms and signs, reinforcing the need to increase vaccination rates in this population.

Additionally, data obtained in this study emphasizes the difference between the microbial communities of the nose and throat, indicating the need for both nasal and pharyngeal swabs sampling in future studies to better assess upper respiratory microbiological carriage.

Our study has several limitations. The first is that we did not use a control group for evaluation of background carriage in the healthy adult population. The second limitation is that our survey took place in winter, so we could not have an overview about seasonal variations of carriage in the homeless, whereas it was demonstrated to have impacted the airway microbial community in adults and children [START_REF] Marchisio | Seasonal variations in nasal pharyngeal carriage of respiratory pathogene in healthy Italian children attenting day-care or school[END_REF][START_REF] Abdullahi | The descriptive epidemiology of Streptococcus pneumoniae and Haemophilus influenzae nasopharyngeal carriage in children and adults in Kilifi District, Kenya[END_REF]. Future studies will be conducted at least twice a year (in winter and in summer). The questionnaire design did not allow a clear distinction between acute (short-term) and chronic (going on) respiratory symptoms which needs to be considered in further studies. Finally, the level of precariousness of the homeless was limited to the duration of homelessness and more detailed information should be recorded in future studies.

In summary, we confirm the high prevalence of respiratory symptoms and signs in sheltered homeless people associated with a high level of bacterial carriage in the respiratory tract.

Several risk factors for respiratory symptoms and signs were identified, allowing a better identification of individuals at higher risk on whom to base targeted preventive interventions, including notably vaccination against influenza and S. pneumoniae infections. Such an approach has proven effective in identifying individuals at higher risk for body lice in the same population [START_REF] Ly | Changing Demographics and Prevalence of Body Lice among Homeless Persons, Marseille, France[END_REF] and the results of our study will benefit to homeless people in the future. Abbreviations: CRDs, chronic respiratory diseases.

  [1.11-2.83], p=0.017), those visiting their country of origin (OR=1.68 [1.04-2.71], p=0.035), those suffering from chronic respiratory diseases (OR=5.27 [2.24-12.41], p<0.0001), and those carrying at least one virus (OR=2.40 [1.21-4.74], p=0.012) or S. pneumoniae (OR=2.32 [1.18-5.3], p=0.014) remained associated with an increased prevalence of respiratory symptoms and signs (Table

Figure 1 .

 1 Figure 1. Prevalence of clinical signs and symptoms over the 2015-2017 period (N=479

Table 1 . Risk factors for respiratory disease: univariate analysis 320

 1 Year of study was not included in the analysis, given that no intervention could be done based on this criterion.

	Characteristics	Total (N)	At least one respiratory symptom or sign N (%)	No respiratory symptom and no sign N (%)	Univariate analysis Odds ratio (95%CI), p-value
	Total		168 (35.3)	308(64.3)
	Year of study*
	2015	125 (26.1)	37 (29.6)	88 (70.4)
	2016	156 (32.6)	74 (47.4)	82 (52.6)
	2017	198 (41.3)	57 (29.2)	138 (70.8)
	Shelter
	A	311 (64.9)	107 (35.2)	201 (65.3)	0.93 [0.63-1.38], p=0.73
	B	168 (35.1)	61 (36.3)	107 (63.7)	Ref
	Age
	Mean age (SD)	43.6±16 years	NA
	Age range	18-84 years	NA
	≤50 years of age	318 (66.8)	98 (30.8)	220 (69.2)	Ref
	>50 years of age	158 (33.2)	69 (44.2)	87 (55.8)	1.78 [1.20-2.64], p=0.004
	Birthplace
	France (mainland)	71 (14.8)	39 (54.9)	32 (45.1)	Ref
	France (overseas territories)	1 (0.2)	0 (0)	1 (100)	NA
	North Africa	300 (62.6)	100 (33.4)	199 (66.6)	0.41 [0.25-0.70], p=0.001
	Sub-Saharan Africa	43 (9.0)	7 (16.3)	36 (83.7)	0.16 [0.63-0.41], p<0.0001
	East Europe	35 (7.3)	13 (39.4)	20 (60.6)	0.53 [0.23-1.24], p=0.14
	West Europe	9 (1.9)	2 (22.2)	7 (77.8)	0.23 [0.04-1.21], p=0.08
	Asia	20 (4.2)	7 (35.0)	13 (65.0)	0.44 [0.16-1.24], p=0.12
	Other	0 (0)			NA
	Mean duration of residence in France (SD)	9.88 (0-25.4)	NA	NA
	Range of duration of residence in France	0-65 years	NA	NA
	≥ 1 year	220 (55.3)	79 (35.9)	141 (64.1)	1.52 [0.99-2.32], p=0.06
	< 1 year	178 (44.7)	48 (27.0)	130 (73.0)	Ref
	Visit to country of origin since immigration	126 (31.9)	51 (40.5)	75 (59.5)	1.76 [1.13-2.74], p=0.012
	No visits to country of origin since immigration	269 (68.1)	75 (27.9)	194 (72.1)	Ref
	Mean duration of homelessness (SD)	2.66 years (0-7.8)	NA	NA
	Range of duration of homelessness	0-52 years

Abbreviations: SD, standard deviation; NA, not applicable, Ref, Reference category *

Table 2 . Prevalence (%) of bacteria and viruses detected by qPCR

 2 473 patients had both nasal and pharyngeal sampling; 3 patients had only nasal swabs and 1 patient had only pharyngeal swabs. Patients having at least one nasal or pharyngeal positive sample were considered positive cases.

	Respiratory pathogen		Positive carriage
		Nasal	Pharyngeal	p-value	Nasal or
		specimen,	specimen,		pharyngeal,
		N (%)	N (%)		N (%)
	Total	476 (100)*	474 (100)*		477 (100)*
	Bacteria	105 (22.1)	280 (59.1)	<0.0001	313 (65.6)
	Haemophilus influenzae	46 (9.8)	266 (56.4)	<0.0001	280 (58.7)
	Klebsiella pneumoniae	17 (3.5)	20 (4.2)	0.61	35 (7.3)
	Staphylococcus aureus	28 (5.9)	12 (2.5)	<0.001	35 (7.3)
	Streptococcus pneumoniae	33 (7.0)	36 (7.6)	0.69	59 (12.4)
	Virus	34 (7.1)	24 (5.1)	0.18	51 (10.8)
	Influenza A	4 (0.8)	4 (1.0)	-	7 (1.5)
	Influenza B	4 (0.8)	6 (1.3)	-	7 (1.5)
	Human rhinovirus	20 (4.3)	7 (1.5)	<0.001	25 (5.3)
	Human respiratory syncytial virus	1 (0.2)	2 (0.4)	-	3 (0.6)
	Human metapneumovirus	0 (0)	0 (0)	-	0 (0)
	Human coronavirus	5 (1.1)	5 (1.1)	0.99	10 (2.1)
	HCoV-HKU1	0 (0)	1 (0.2)	-	1 (0.2)
	HCoV-E229	3 (0.6)	1 (0.2)	-	4 (0.8)
	HCoV-NL63	1 (0.2)	0 (0)	-	1 (0.2)
	HCoV-OC43	1 (0.2)	3 (0.6)	-	4 (0.8)
	Human para-influenza virus	0 (0)	1 (0.2)	-	1 (0.2)

*

Table 4 . Association between respiratory pathogen carriage and clinical findings in univariate analysis according to respiratory symptoms and signs

 4

	Respiratory		Odds ratio (95%CI), p-value
	pathogen	Cough	Expectoration a	Rhinorrhea a	Dyspnea	Sore throat
	Streptococcus
	pneumoniae

Acknowledgments

We thank our co-workers at the University Hospital Institute (IHU) who assisted us in recruiting, interviewing and examining participants and collecting samples, as well as Youssoupha Touré for his support in statistical analysis, Annick Abeille, Céline Gazin for excellent technical assistance and Pr. Rémi Charrel for his support in typing HCoV.

Funding

This work was supported by the French Government under the « Investissements d'avenir » (Investments for the Future) program managed by the Agence Nationale de la Recherche (ANR, fr: National Agency for Research), (Reference: Méditerranée Infection 10-IAHU-03)

Potential conflicts of interest

No reported conflicts of interest.