Paul Nobre

Alice Ferrando

Gwenaël Gaborit

Raphaël Sablong

Olivier Beuf

RF endoluminal coil with NMR electro-optical conversion

Intro (145/150w)

Higher spatial resolution MRI of the colon wall could lead to diagnosis and characterization of colon cancer at an earlier stage thus increasing the five years survival rate. Endoluminal coils increase the image spatial resolution at close proximity of the loop coil, therefore allowing a better analysis of the colon wall [START_REF] Dorez | Endoluminal high-resolution MR imaging protocol for colon walls analysis in a mouse model of colitis[END_REF] . Nonetheless, the coaxial cable connecting the coil to the MR system causes safety issues 2 , as the excitation radiofrequency magnetic field B1 induces currents in the galvanic connexion leading to a local increase of the SAR. This unwanted effect can be avoided by using optical fiber instead of metallic cable [START_REF] Saniour | Active optical-based detuning circuit for receiver endoluminal coil[END_REF] . For that purpose, the NMR signal must be converted into light signals and converted back in electrical signal to be digitalized and reconstructed by the MR system. This work presents the first MR images obtained on a preclinical MR system after electro optical conversion using Pockel's effect.

Methods (260/350w)

Endoluminal coils previously designed and built for mouse colon imaging were used [START_REF] Dorez | Endoluminal high-resolution MR imaging protocol for colon walls analysis in a mouse model of colitis[END_REF] . The coil loop was 40mm in length and 1.6mm in width and was operating at 200.29 MHz corresponding to the proton frequency for the 4.7T preclinical MRI scanner used (Bruker, Germany). The endoluminal receiver RF output signal of the coil was connected to a MAXN-LN-20 (IXblue, France) used as electro-optical converter. The variations of the electrical field change the polarization of the 1550nm linearly polarized laser going through the crystal by Pockel's effect. An eoSense system (Kapteos, France) was used as the opto-electronic converter. To asses SNR, a cylindrical tube was filled with saline solution doped with nickel sulphate (1.25 g/L of NiSO4 + 5 g/L of NaCl) in order to reduce T1-value. The coil was inserted inside the tube and sealed. A 72mm inner diameter birdcage coil (Rapid Biomedical, Rimpar, Germany) was used as transmit coil. The figure 1 represents the optical transmission chain. MSME sequence with TR/TE 650/14ms was performed with optical conversion and compared with galvanic connexions and a quadrature 32mm inner diameter birdcage coil dedicated to mouse.

Results (96/100w)

As predicted, the surface coil with galvanic connexion depicts a considerable gain in SNR compared to the volume coil. As seen in the figure 2, SNR profiles obtained with the galvanic transmission chain is 20 times better that the optic one. However, there is a clear correlation between both SNR profiles. Despite the fact that achieved EO conversion do not reach the targeted SNR, the SNR in the area of interest (close proximity of the loop) is still higher than with the dedicated volume coil (figure 3).

Discussion (130/150w)

As predicted, the SNR obtained with the galvanic connexion endoluminal coil has an excellent SNR close to the loop coil (target colon area), making it a good objective reference. The proof of concept of the conversion chain based on Pockel's effect was demonstrated. Beside the fact the image is noisier, the figure 4c depict a similar image in shape than figure 4b. The SNR of the optical coil is however significantly inferior to the galvanic one but above the SNR obtained with the volume at the wall of the phantom. One lead could be to improve the linearity of the converter. It depends on the operating point defined by a voltage offset, which was notstudied in depth for this test. Secondly, the bandwidth of the electro-optical converter was not optimal for this application and the geometry of the crystal should be the subject of further improvements. Developing application-specific converter with suited bandwidth and operating point could improve significantly the SNR.

Conclusion (95/100w)

The concept of EO conversion based on a bulk crystal using Pockel's effect was demonstrated with an endoluminal coil for colon mouse. The next step is the improvements of the SNR and to add an efficient optical-based decoupling circuit as already demonstated [START_REF] Saniour | Electro-optic probe for real time assessments of RF electric field produced in an MRI scanner: Feasibility tests at 3 and 4.7 Tesla[END_REF] . This, in addition to monitoring the induced currents with an optoelectronic Electrical field probe [START_REF] Saniour | Electro-optic probe for real time assessments of RF electric field produced in an MRI scanner: Feasibility tests at 3 and 4.7 Tesla[END_REF] would pave the way to in vivo testing.

Figures

  Figures

Fig. 1 .

 1 Fig. 1. Diagram of optical conversion chain. Inside the MRI from left to right is the emission coil, the phantom mimicking the mouse's colon and the endoluminal coil. Outside are the converters and the processing MR console to reconstruct the images.

Fig. 2 .

 2 Fig. 2. Comparison of the local SNR profiles for the endoluminal coil with galvanic cable (in cyan) and with optical fiber (in blue).

Fig. 3 .

 3 Fig.3. SNR profiles obtained with 32 mm inner diameters quadrature birdcage coil (in cyan) and endoluminal coil with optical fiber. While the volume coil has higher average SNR, the endoluminal is almost 2 times better at the expected location of wall.

Fig. 4 .

 4 Fig. 4. Images of the saline solution tube obtained with the different coils. For reference, the outer diameter of the tube is 1.6mm

Acknowledgements

This work was funded by the AURA region iand performed within the scope of LABEX PRIMES (ANR-11-LABX-0063). Experiments were performed on the PILoT facility, part of the France Life Imaging infrastructure (ANR-11-INBS-0006).

Summary of Main Findings (220/250c)

This experiment showed that coaxial cables used with endoluminal coils could be replaced with optical fiber. Both conversions (opto-electronic and electro-optic) must be specific to the application in order to preserve the gain in SNR from the endoluminal coil.


est destinée au dépôt

  Figure 1.

  Figure 2.

  Figure 4.

Table 1 .

 1 Rhythm parameters (means values ± SEM) of core temperature (Tc) and locomotor activity (LA) determined from profiles of Tc and LA registered in adult and aged mouse lemurs under short photoperiod during the 9 days of exposures to 25 °C and to 12 °C. Parameters abbreviations are described in the text.

	p=0.32	p=0.007
	90
	80
	25°C	12°C


F 1 Aujard

Jérémy Terrien
email: terrien@mnhn.fr

Daily rhythms of core temperature and locomotor activity indicate different adaptive strategies to cold exposure in adult and aged mouse lemurs acclimated to a summer-like photoperiod

Keywords:

Daily variations in core temperature (Tc) within the normothermic range imply thermoregulatory processes that are essential for optimal function and survival. Higher susceptibility towards cold exposure in older animals suggests these processes are disturbed with age. In the mouse lemur, a long-day breeder, we tested whether aging affected circadian rhythmicity of Tc and locomotor activity (LA) and energy balance under long-day conditions when exposed to cold. Adult (N = 7) and aged (N = 5) mouse lemurs acclimated to LD14/10 were exposed to 10-day periods at 25 and 12°C. Tc and LA rhythms were recorded by telemetry, and caloric intake (CI), body mass changes, and plasma IGF-1 were measured.

During exposure to 25°C, both adult and aged mouse lemurs exhibited strong daily variations in Tc. Aged animals exhibited lower levels of nocturnal LA and nocturnal and diurnal Tc levels in comparison to adults. Body mass and IGF-1 levels remained unchanged with aging.

Under cold exposure, torpor bout occurrence was never observed whatever the age category.

Adult and aged mouse lemurs maintained their Tc in a normothermic range and a positive energy balance. All animals exhibited an increase in CI and a decrease in IGF-1 in response to cold. The decrease in IGF-1 was delayed in aged mouse lemurs compared to adults.

Moreover, both adult and aged animals responded to cold exposure by increasing their diurnal LA compared to those under Ta = 25°C. However, aged animals exhibited a strong decrease in nocturnal LA and Tc, whereas cold effects were only slight in adults. The temporal organization and amplitude of daily phase of low Tc were particularly well preserved under cold exposure in both age groups. Sexually active mouse lemurs exposed to cold seemed thus to prevent torpor exhibition and temporal disorganization of daily rhythms of Tc, even during aging. However, although energy balance was not impaired with age in mouse lemurs after cold exposure, aging was associated with lower LA and Tc during the night and delayed decrease in IGF-1. This might reflect that adaptive strategies to cold exposure differ with age in mouse lemurs acclimated to a summer-like photoperiod.

INTRODUCTION

Daily variations in core temperature within the normothermic range imply thermoregulatory processes that are essential for optimal function and survival. The circadian rhythmicity in core temperature (Tc) is the result of both intrinsic circadian variations in heat production and heat loss, and interactions of heat generating behaviors, such as locomotor activity (LA) or adapted postures (for review, see [START_REF] Van Someren | Circadian and age-related modulation of thermoreception and temperature regulation: mechanisms and functional implications[END_REF]. Its expression is under the control of the central circadian pacemaker which generates the endogenous rhythmicity and allows effective synchronization to the light dark cycle [START_REF] Dardente | Molecular circadian rhythms in central and peripheral clocks in mammals[END_REF]. Thermoregulatory processes are seasonally dependent [START_REF] Lovegrove | Seasonal thermoregulatory responses in mammals[END_REF], suggesting that the seasonal breeding state could interfere with Tc levels. In long-day breeders, acclimatization to a long photoperiod induces entrance into reproductive state with an increase in gonadal steroid hormones, which are well known for their thermogenic action [START_REF] Hampl | Steroids and thermogenesis[END_REF]. This may partially explain why many mammals, such as European [START_REF] Wollnik | Seasonal and daily rhythms of body temperature in the European hamster (Cricetus cricetus) under semi-natural conditions[END_REF] and golden hamsters [START_REF] Jefimow | Seasonal changes in the thermoregulation of laboratory golden hamsters during acclimation to seminatural outdoor conditions[END_REF]) exhibit higher Tc during the summer than winter. The influence of seasonal acclimatization on thermoregulatory mechanisms has also been demonstrated in voles [START_REF] Zubidat | Thermoregulatory and endocrine responses to light pulses in short-day acclimated social voles (Microtus socialis)[END_REF].

Thus, the sexually active state could allow animals to cope with low ambient temperatures (Ta) and to efficiently prevent hypothermia. In fact, cold exposure interferes with circadian rhythmicity in Tc by inducing modulations in thermoregulatory processes. This implies hormonal changes [START_REF] Larrouy | La Thermorégulation[END_REF]. More specifically, Insulin-like Growth Factor type 1 (IGF-1) has been proposed to act in cold-induced thermogenesis processes in the rat [START_REF] Duchamp | Transient upregulation of IGF-I gene expression in brown adipose tissue of cold-exposed rats[END_REF][START_REF] Yamashita | Is insulin-like growth factor I involved in brown adipose tissue enlargement?[END_REF].

With age, there are evidences of a decrease in the robustness of circadian rhythmicity in Tc (for review, see [START_REF] Van Someren | Circadian and age-related modulation of thermoreception and temperature regulation: mechanisms and functional implications[END_REF][START_REF] Weinert | The circadian rhythm of core temperature: effects of physical activity and aging[END_REF]. More, aging is associated with an increased prevalence of death caused by hypothermia [START_REF] Stocks | Human physiological responses to cold exposure[END_REF][START_REF] Ward | Hypothermia: a natural cause of death[END_REF]. However, data on daily Tc and LA rhythms during continuous exposure to cold are scarce [START_REF] Palkova | Effect of ambient temperature on the circadian activity rhythm in common marmosets, Callithrix j. jacchus (primates)[END_REF][START_REF] Rensing | Temperature effect on entrainment, phase shifting, and amplitude of circadian clocks and its molecular bases[END_REF][START_REF] Tokura | Effects of temperature on the circadian rhythm of pig-tailed macaques Macaca nemestrina[END_REF] and do not address the question of age-related disturbances. Thus, the reasons why some aged individuals become more sensitive to cold exposure are not entirely clear.

Considering that aging induces changes in many hormonal factors [START_REF] Ferrari | Neuroendocrine features in extreme longevity[END_REF][START_REF] Vermeulen | Dehydroepiandrosterone sulfate and aging[END_REF], seasonal variations in hormones might also be disturbed with aging (Vom [START_REF] Saal | Natural History and Mechanisms of Reproductive Aging in Humans, Laboratory Rodents, and Other Selected Vertebrates[END_REF], with lower capacities for photoperiod-induced adjustments. IGF-1 secretion is influenced by photoperiod in golden hamsters [START_REF] Laartz | Diurnal, photoperiodic, and age-related changes in plasma growth hormone levels in the golden hamster[END_REF] and primates [START_REF] Ganzhorn | Adaptations to seasonality: Some Primate and Nonprimate Examples[END_REF] and is also modified with aging [START_REF] Sherlock | Aging and the growth hormone/insulin like growth factor-I axis[END_REF]. Such endocrine processes could directly or indirectly contribute to age-related impaired thermoregulatory responses towards cold exposure. Based on these published findings and to the lack of study on the role of reproductive state on cold resistance, we explored whether age-associated Tc decrease in response to cold are preserved in a sexually active non-human primate, i.e., the mouse lemur (Microcebus murinus).

Microcebus murinus is a small nocturnal primate (body weight: 60 -90 g) originating from Madagascar. The life span of this species is about 8 yrs in captivity [START_REF] Perret | Change in photoperiodic cycle affects life span in a prosimian primate (Microcebus murinus)[END_REF]. In thermoneutral conditions, mouse lemurs exhibit robust daily rhythms in Tc, particularly characterized by a phase of low Tc (assimilated as a drop to a minimal Tc followed by an increase in Tc) during the first half of the light period (Perret & Aujard, 2001). Daily exposure to light for longer than 12 h promotes sustained behavioral and reproductive activity [START_REF] Perret | Environmental and social determinants of sexual function in the male lesser mouse lemur (Microcebus murinus)[END_REF]. Entrance into the reproductive state appears to protect normothermia maintenance in the mouse lemur. For example, when testing behavioral thermoregulatory responses, adult animals under LD14/10 did not need to select warm environments to efficiently maintain normothermia. Furthermore, the effects of a moderate food deprivation, known to induce a decrease in Tc, were minimal in adult mouse lemurs exposed to LD14/10 [START_REF] Giroud | Chronic food shortage and seasonal modulations of daily torpor and locomotor activity in the grey mouse lemur (Microcebus murinus)[END_REF]. In contrast, aged animals always chose the warmest ambient temperatures during the behavioral test. Such differences in adaptive strategies between young adults and aged mouse lemurs highlight subtle changes in thermoregulatory capacities that were undetected when studying daily rhythms of Tc in reference Ta (25°C). Indeed, a marked rhythm of Tc is maintained in aged animals with, however, a delayed time of occurrence of minimal Tc with age [START_REF] Aujard | Attenuated effect of increased daylength on activity rhythm in the old mouse lemur, a non-human primate[END_REF]. Finally, aging is also associated in the mouse lemur with a decrease in amplitude of the seasonal variations in body mass, gonadal hormones [START_REF] Aujard | Age-related effects on reproductive function and sexual competition in the male prosimian primate, Microcebus murinus[END_REF], melatonin [START_REF] Aujard | Artificially accelerated aging by shortened photoperiod alters early gene expression (Fos) in the suprachiasmatic nucleus and sulfatoxymelatonin excretion in a small primate, Microcebus murinus[END_REF], and DHEA-S (Perret & Aujard, 2005, 2006). Based on these findings, age-related effects on thermoregulatory responses towards cold were investigated by monitoring daily Tc and LA rhythms, body mass, caloric intake, and plasma IGF-1 in sexually active mouse lemurs.

METHODS

Animals and housing conditions:

All the gray mouse lemurs studied were males, born in the laboratory breeding colony of Brunoy (MNHN, France, license approval N° A91.114.1) and were pathogen free. General conditions of captivity were maintained constant: Ta (24 -26°C) and relative humidity (55%).

Food (including fresh fruits and a milky mixture) and water were available ad libitum. In captivity, seasonal variations of physiological functions can be entrained by alternating 6month periods of summer-like long photoperiod (14 h of light/day) and winter-like short photoperiod (10 h of light/day) under artificial light (fluorescent tubes during the day and dim red light during the night). In the present study, male mouse lemurs were studied during the long-day season (LD14/10), at least two months after the onset of the summer-like photoperiod. This ensured stabilization of the physiological status of the animals. Long days correspond to the mating season (high testosterone levels and large testis size), associated with high levels of activity and significant body mass decrease. General conditions of captivity were applied and animals were maintained in social groups before and after experimenting. In the breeding colony of the Brunoy laboratory, analysis of survival from 254 male mouse lemurs determined the mean life span (mean ± SEM)to be 6.0 ± 0.2 yrs, the mean life span of the 10% of longest lived animals to be 10.0 ± 0.2 yrs, and the observed maximal survival duration to be 12.0 yrs. In the present study, randomly chosen adults (N = 7; mean age ± SEM: 1.6 ± 0.3 yrs, range: 1.0 -2.4 yrs) and aged mouse lemurs (N = 5; mean age ± SEM: 7.4 ± 0.2 yrs, range: 6.4 -8.3 yrs) were used throughout all experiments. All experiments were carried out in accordance with the European Communities Council Directive (86/609/EEC) and the ethical standards of the journal [START_REF] Portaluppi | Ethical and methodological standards for laboratory and medical biological rhythm research[END_REF]. All efforts were made to minimize nociception.

Core temperature and locomotor activity recording: Animals were maintained in climate chambers (Sanyo incubator MIR-253), in which air was filtered and light was provided by cool fluorescent lamps. Mouse lemurs were acclimated to the experimental device for 10 days at Ta = 25°C. They were then studied for 10 days at the reference Ta of 25°C and then exposed to a cold environment (10 days at 12°C). Core temperature (Tc) was measured using a telemetric device: a 2.5 g transmitter (TA10TA-F20, Data Science Co. Ltd, Minnesota, USA) was implanted under general anesthesia (Valium, 2mg/100g i.m.; Ketamine Imalgem, 10mg/100g i.p.) in the visceral cavity of the animals.

Calibrations for each transmitter were provided by the manufacturer. Experiments were performed after at least 2 weeks of recovery. Mouse lemurs were isolated in individual cages provided with branches and a wooden nest. A receiving plate (RPC-1, Data Science Co Ltd, Minnesota, USA) localized in the cage permitted the recording of data sent by the transmitter. Tc (in °C) was recorded every 10 min and locomotor activity (LA in arbitrary units a.u.) was continuously recorded and summed within this interval by two antennas located in the receptor plate and detecting vertical and horizontal movements (X-Y coordinate system, Dataquest Lab Pro v. 3.0, Data Science Co. Ltd, Minnesota, USA).

The following parameters were analyzed: mean Tc during the active nocturnal phase (Tc night ), mean Tc during the resting diurnal phase (Tc day ), minimal Tc value (Tc min ), time of occurrence of Tc min (H min ), and time of onset of Tc drop (H decr ). The last two parameters were expressed in minutes relative to lights on and determined day after day on graphic determination. H decr was determined each day as the first time point after which at least 3 successive bins of Tc decrease occurred. Similarly, H min was determined each day as the time point occurring at least after 30 min of decrease and preceding at least 30 min of Tc increase.

Consequently, Tc min corresponded to the Tc value pointed at the H min time point. Tc min , H decr , and H min were representative parameters of the daily phase of low Tc. Finally, LA values were averaged during the nocturnal active phase (LA night ) and the diurnal resting phase (LA day ).

Actograms were also generated using Clocklab software (Actimetrics Inc., Evanston, IL). LA onset and offset (in min) were defined as the time of occurrence of the first or last (respectively) 3 successive bins when activity was greater or lower (respectively) than LA day .

LA onset and offset were calculated in reference to the time of lights-off and lights-on, respectively. The duration of the LA active phase (alpha, in min) corresponded to the time duration between LA onset and offset values. For all temporal parameters, phase advances were expressed by positive values and phase delays by negative values in reference to their respective reference points. All telemetric parameters were averaged for each thermal exposure.

Body mass, caloric intake: Before the experiment, body mass (BM) of adult (mean ± SEM: 80.4 ± 4.9 g) and aged mouse lemurs (mean ± SEM: 97.1 ± 8.7 g) did not differ significantly (one-way ANOVA, F 1, mass gain (BMG) was calculated as a mean ratio (in g/day) during the whole exposures.

Animals were routinely fed ad libitum on a diet including fresh banana (393 kJ/100g) and a homemade milky mixture containing baby cereals, eggs, and milk (435 kJ/100g). Daily caloric intake (CI) was calculated by subtracting the remaining food from the total food mass given. CI was expressed in kJ according to the Diem table [START_REF] Diem | Les vitamines liposolubles[END_REF] and normalized to the BM of the animal (kJ/day*100g BM). The evaporation-related loss was taken into account in the calculation of CI [START_REF] Seguy | Changes in olfactory inputs modify the energy balance response to short days in male gray mouse lemurs[END_REF] to ensure reliable comparisons between 25 and 12°C, since evaporative loss varied between the two Tas.

Plasma IGF-1 levels:

To assess the IGF-1 response to thermal stress, blood was taken from animals 3 h before the beginning of the nocturnal phase at the reference Ta of 25°C and then 2 days (short-term response) and 9 days (long-term response) after the beginning of cold exposure. About 100 μl of blood was drawn from the saphenous vein into heparinized tubes without anesthesia. After centrifugation, plasma was immediately collected and preserved at -20°C until the radioimmunoassay, which was performed according to the manufacturer instructions (Immunotech IGF-I IRMA; Beckman Coulter, Paris, France). Intra-and between-series variation rates were <7% and the minimal detectable value was 2 ng/ml. To avoid any potential influence of animal handling on Tc values, the telemetric data corresponding to the 4 h after the blood samples were removed. Plasma IGF-1 is expressed in ng/ml. IGF-1 is known to co-vary with BM since it influences body composition, particularly body fat [START_REF] Engstrom | Effects of gastric bypass on the GH/IGF-I axis in severe obesity -and a comparison with GH deficiency[END_REF][START_REF] Onder | Body mass index, free insulin-like growth factor I, and physical function among older adults: results from the ilSIRENTE study[END_REF]; therefore, BM was included in all statistical models analyzing IGF-1.

Statistical analysis

All dependent variables were analyzed with Linear Mixed Effect models (LME), built with the "nlme" function [START_REF] Pinheiro | nlme: linear and nonlinear mixed effects models[END_REF]. All dependent variables were checked for normality with the residuals of the models. Non-normal variables were transformed to reach normality, i.e., log-transformation for LA night , H min , and Tc night and square-root transformation for LA onset and alpha. To take into account inter-individual variability, the effect of individual identity was declared as a random effect. In addition, since the same individuals were used at 12 and 25°C, we allowed inter-individual variation to depend on temperature by declaring the slope of the effect of Ta as a random factor. Statistical models that included the additive effects of age (two levels, adult versus old) and Ta (two levels, 12 and 25°C) and their interaction were constructed. Significance of effects were assessed by F-tests [START_REF] Bolker | Generalized linear mixed models: a practical guide for ecology and evolution[END_REF] with software R Version 2.6.0 (R Development [START_REF] Development Core | R: a language and environment for statistical computing[END_REF].

RESULTS

Effects of age and Ta on energy balance and IGF-1 levels:

Energy balance was studied by quantifying CI, BMG, and plasma IGF-1 levels. CI was affected by cold exposure, independently of age (Figure 1A). Adult animals ingested on average 138 ± 12 kJ/day*100g BM at 25°C and 183 ± 7 kJ/day*100g BM at 12°C (33% increase from 25°C to 12°C). Aged animals exhibited an increase of 14% in CI after cold exposure, from 131 ± 22 kJ/day*100g BM at 25°C to 149 ± 30 kJ/day*100g BM at 12°C. BM remained stable throughout the experiment without significant effects of age or Ta exposure (Figure 1B), although the decrease in BMG between 25 and 12°C was close to significance.

When taking into account variations in BM, IGF-1 was affected by an interaction between age and Ta effects (Figure 2). IGF-1 levels were similar at both ages at 25°C, but they were differently modified after cold exposure. The IGF-1 level decreased from 878 ± 70 ng/ml to 685 ± 68 ng/ml after 2 days of cold exposure in adult animals, whereas such a decrease was only observed after 9 days in aged animals (from 944 ± 131 to 808 ± 109 ng/ml). Therefore, the IGF-1 level was higher in aged than in adult animals at the beginning of cold exposure, but it was similar at the end of the 10-day cold exposure (Figure 2).

Effects of age and cold exposure on Tc and LA rhythms parameters:

LA daily rhythms, for both age groups during both exposures to 25 and 12°C, are represented in Figure 3. The LA night level significantly differed by interaction between age and Ta effects (Figure 3 & Table 1). At 25°C, aged animals exhibited a lower LA than adults during both the nocturnal and diurnal phases (Table 1). After cold exposure, adult animals slightly decreased their nocturnal activity compared to 25°C, whereas a 39% decrease occurred in aged animals between 25 and 12°C (Figure 3). Therefore, the LA night level remained lower in aged compared to the young adult animals at 12°C as observed at 25°C. Cold exposure induced a 2.1-fold increase in LA day in adult animals, whereas a 1.5-fold increase was observed between 25 and 12°C in aged animals. In addition, a 10% lengthening of LA alpha was observed in both young adult and aged animals between 25 and 12°C (Table 1). This effect of cold exposure was due to a strong phase advance in LA onset in both adult and aged mouse lemurs at 12°C, whereas LA offset was not affected by age or cold exposure.

The nocturnal organization of LA was also modulated in both age groups in response to cold.

The amount of LA decreased in the middle of the night and increased around the periods of lights on and lights off into distinct early and late peaks of activity (Figure 3). Tc daily rhythms of both age groups during the exposures to 25 and 12°C, are represented in Figure 4. At each Ta (25 or 12°C), adult and aged animals exhibited robust daily rhythms of Tc, with high values during the nocturnal active phase and lower values during the diurnal resting phase. Daily rhythms of Tc throughout the 10 days of exposure to compared to young adults ones, except for the minimal levels of Tc that were not affected by age at 25°C (Table 2). Nocturnal Tc responses to cold exposure strongly differed according to the age category. Indeed, only a slight decrease in Tc night was observed in young adult animals after exposure to 12 compared to 25°C (Table 2). In contrast, in aged animals, Tc night strongly decreased by 0.8°C between mean values at 25 and 12°C (Figure 4). Mean values of Tc min were not significantly lowered, and neither adult nor aged animals exhibited torpor phases (i.e., Tc dropping <33°C). Tc min values ranged from 33.8 to 35.4°C in young adult mouse lemurs and from 33.2 and 35.8°C in aged animals at 12°C. However, during the day, levels of Tc remained lower in aged than in adult animals. The difference between the two ages was greatly accentuated by cold exposure. Moreover, the amplitude between the nocturnal and diurnal levels of Tc was lowered after cold exposure (F (1,11) = 8.96, p = 0.01), independently of age (F (1,11) = 0.10, p = 0.76). In fact, the difference between night and day decreased from 1.2 ± 0.1 to 1.0 ± 0.1°C in adult mouse lemurs, and from 1.2 ± 0.1 to 0.8 ± 0.1°C in aged animals.

Concerning the temporal organization of the daily phase of low Tc, H min was not significantly affected by age or cold exposure (Figure 5A). Tc min occurred in adult mouse lemurs -156 ± 36 min and -209 ± 30 min after lights-on at 25 and 12°C, respectively. Aged animals exhibited H min values of -198 ± 22 min and -280 ± 18 min at 25 and 12°C, respectively. In contrast, H decr was significantly lowered after cold exposure, whatever the age, and the Tc drop was thus delayed at 12°C compared to 25°C (Figure 5B). At 25 °C, H decr occurred 51 ± 14 min before lights-off in young adult animals and 68 ± 22 min before lights-off in aged mouse lemurs. After cold exposure, H decr was delayed in aged (44 ± 18 min) and in adult (47 ± 14 min) animals. No age effect could be detected at either 25 or 12°C.

DISCUSSION

Both young adult and aged mouse lemurs exhibited strong daily variations in Tc at 25°C as previously described [START_REF] Aujard | Behavioral thermoregulation in a non human primate: effects of age and photoperiod on temperature selection[END_REF][START_REF] Aujard | Attenuated effect of increased daylength on activity rhythm in the old mouse lemur, a non-human primate[END_REF]. In adult mouse lemurs under LD14/10, behavioral thermoregulation appeared to be less crucial for maintenance of normothermia than what was observed under LD 10/14 [START_REF] Aujard | Behavioral thermoregulation in a non human primate: effects of age and photoperiod on temperature selection[END_REF]. Thus, autonomic mechanisms and hormonal status of breeding season seemed sufficient to maintain normothermia under long-day exposure. This is corroborated by the fact that, in the present study, no torpor bout was observed at 25°C, whatever the age category, and that age effects on Tc and LA rhythms were only slight. Aged animals exhibited a decreased nocturnal LA as seen previously in mouse lemurs [START_REF] Aujard | Attenuated effect of increased daylength on activity rhythm in the old mouse lemur, a non-human primate[END_REF][START_REF] Cayetanot | Shortened seasonal photoperiodic cycles accelerate aging of the diurnal and circadian locomotor activity rhythms in a primate[END_REF] and in humans [START_REF] Huang | Age-associated difference in circadian sleep-wake and rest-activity rhythms[END_REF]. For the first time, the recording of daily rhythms was associated with a quantification of caloric intake (CI) and body mass variation in adult and aged animals. Interestingly, body mass stabilization was achieved by aged animals in a similar manner as in adult animals.

Moreover, there is some evidence of age-related decline in sexual endocrine function in the mouse lemur during the long-day season [START_REF] Aujard | Artificially accelerated aging by shortened photoperiod alters early gene expression (Fos) in the suprachiasmatic nucleus and sulfatoxymelatonin excretion in a small primate, Microcebus murinus[END_REF][START_REF] Aujard | Age-related effects on reproductive function and sexual competition in the male prosimian primate, Microcebus murinus[END_REF]Perret & Aujard, 2005, 2006). However, no significant effect of age on endocrine function was detected at 25°C in the present study, since IGF-1 level, which can be considered as a good biomarker for aging [START_REF] Kappeler | Biological aspects of longevity and ageing[END_REF], remained similar between adult and aged mouse lemurs. It would be interesting to test the effect of age on others hormones involved in energy balance to further define the ability of aged mouse lemurs to maintain energy balance and body temperature within a normothermic range at a Ta of 25°C under LD 14/10. Exposure to 12°C only induced slight variations in Tc in adult mouse lemurs. Diurnal and minimal Tc levels remained unchanged and only nocturnal Tc was significantly lowered between 25 and 12°C. Moreover, torpor bouts were not observed during the whole exposure at 12°C, in contrast to animals acclimated under LD10/14 [START_REF] Terrien | Effects of age on thermoregulatory responses during cold exposure in a nonhuman primate, Microcebus murinus[END_REF]. Gonadal hormonal status, particularly enhanced during the reproductive season, would thus allow protective normothermia and torpor avoidance. In the present study, mouse lemurs increased their caloric intake after cold exposure, as previously described in pigs [START_REF] Schenck | Interactive effects of thermal environment and dietary amino acid and fat levels on rate and efficiency of growth of pigs housed in a conventional nursery[END_REF].

In contrast with this species, body mass did not vary significantly in mouse lemurs, and this could be related to their stable energy balance in summer-like photoperiodic conditions. The concomitant increase in CI and diurnal LA suggest that adult animals strongly focus energy expenditure into the enhancement of LA to produce body heat and prevent Tc decrease. IGF-1 level decreased after cold exposure, and this may implicate IGF-1 in cold resistance through non-shivering thermogenesis (NST) process, as already described in mouse lemurs acclimated to LD10/14 [START_REF] Terrien | Effects of age on thermoregulatory responses during cold exposure in a nonhuman primate, Microcebus murinus[END_REF]. The daily organization of the Tc and LA rhythms appeared slightly disturbed in young adult mouse lemurs after cold exposure. In contrast with results observed in LD10/14, daily adjustments were manifested during the diurnal active phase.

Adult animals strongly anticipated lights-off, therefore extending their locomotor activity periods. In fact, adult animals delayed the beginning of the Tc drop at the end of the activity period, and minimized their activity during the early phase of diurnal Tc decrease. But from the second part of the day to the beginning of night, their activity progressively increased. The time of occurrence of the minimal Tc value was unaffected by exposure to 12°C. Daily rhythmicity remained highly present in adult mouse lemurs under LD14/10, as also observed in squirrels monkeys [START_REF] Robinson | Endogenous thermoregulatory rhythms of squirrel monkeys in thermoneutrality and cold[END_REF]. The sexually active state of mouse lemurs under summer-like photoperiod might enable a strong protection of Tc rhythm stability.

Age-related differences in Tc were also slight after cold exposure in mouse lemurs and appeared clearly minor compared to results observed under LD10/14 [START_REF] Terrien | Effects of age on thermoregulatory responses during cold exposure in a nonhuman primate, Microcebus murinus[END_REF]. In the present study, nocturnal Tc levels dropped between 25 and 12°C in association with a concomitant decrease in LA, probably reflecting the masking effect of LA on Tc. In aged animals, the increase in diurnal LA, combined with the decrease in nocturnal LA, led to a decreased amplitude of the daily rhythm in LA. In this manner, aged mouse lemurs could compensate diurnal costs of LA, allowing normothermia maintenance and torpor avoidance, by lowering the costs of LA during the night. Moreover, aged animals prevented energy imbalance and compensated energy expended by increasing their CI. These results revealed that aged mouse lemurs enhance LA-induced production of body heat with a lower propensity than young adults. This could explain the lower nocturnal and diurnal levels of Tc observed in aged animals compared to young adults at 12°C. Otherwise, it is commonly accepted that aging is associated with a decreased stabilization and synchronization in Tc rhythms [START_REF] Van Someren | Circadian and age-related modulation of thermoreception and temperature regulation: mechanisms and functional implications[END_REF][START_REF] Weinert | The circadian rhythm of core temperature: effects of physical activity and aging[END_REF]. In the present work, daily temporal organization in Tc rhythms were slightly modulated in aged mouse lemurs after cold exposure, as observed in adult animals. H decr occurred later in aged animals at 12 than at 25°C, which can be related to the delayed peak of LA observed at the end of the dark phase at such an ambient temperature. The time occurrence of minimal Tc was unaffected by cold exposure. Moreover, aged animals seemed to adapt their LA like the young adults did, by extending the LA duration to cope with Ta lowering. Finally, the decrease in plasma IGF-1 level observed after cold exposure occurred later in aged than in young adult mouse lemurs. It was not associated with a differential time-course of day-after-day variations in Tc levels between both ages, but it could lead to impaired responses towards extreme cold during aging.

Furthermore, this could be related to the impairment of hormonal status observed during aging [START_REF] Ferrari | Neuroendocrine features in extreme longevity[END_REF][START_REF] Vermeulen | Dehydroepiandrosterone sulfate and aging[END_REF] and could play a role in the circadian instability, however not really evidenced in the present study.

Conclusions and perspectives

Modulations of rhythm parameters were relative minor after cold exposure in LD14/10, even in aged animals. This might suggest the active reproductive state of animals protects circadian rhythmicity and prevents animals from Tc decrease when coping with low ambient temperatures and that this property is well preserved with age. However, additional experiments such as effects of castration or injection of testosterone during LD10/14 are necessary to determine if this process is only due to gonadal function. Finally, challenges in energy savings appeared strongly dependent on seasons, since the present results strongly differed from those observed under LD10/14 [START_REF] Aujard | Behavioral thermoregulation in a non human primate: effects of age and photoperiod on temperature selection[END_REF][START_REF] Terrien | Effects of age on thermoregulatory responses during cold exposure in a nonhuman primate, Microcebus murinus[END_REF]. In fact, the increase in diurnal LA, compensated with an increase in CI, appeared efficient to avoid Tc decrease below the normothermic level. However, even though energy balance was not impaired with age in mouse lemurs after cold exposure, aging was associated with lower LA and Tc levels during the night and delayed decrease in plasma IGF-1. This might reflect different adaptive strategies to cold exposure that vary by age in mouse lemurs acclimated to a summer-like photoperiod.

FIGURE CAPTIONS

Figure 1 :

 1 Figure 1: A. Mean (± SEM) body mass (BM) corrected caloric intake (CI in kJ/day*100g

Figure 2 :

 2 Figure 2: Mean (± SEM) levels of plasma IGF-1 (ng/ml) measured in young adult (N = 7) and

Figure 3 :

 3 Figure 3: Average daily profiles of locomotor activity (LA in arbitrary units a.u.) in adult (N =

Figure 4 :

 4 Figure 4: Time course of mean (± SEM) core temperature (Tc in °C) in adult (N = 7) and aged

Figure 5 :

 5 Figure 5: A. Time of minimal core temperature occurrence (H min in min) and B. of core

  Figure 1.

  Figure 2.

Figure 3 .

 3 Figure 3.

Figure 4 .

 4 Figure 4.

Figure 5 .

 5 Figure 5.

= 3.0, p = 0.11). BM was measured every 2 days throughout the experiment and the body

ACKNOWLEDGEMENTS

We would like to thank Pierre-Yves Henry for his help for statistical analysis. This work was carried out with the financial support of the "Institut de la Longévité et du Vieillissement », the « Fondation pour la Recherche Médicale (FRM) » and the « ANR-Agence Nationale de la Recherche -The French National Research Agency » under the « Programme National de Recherche en Alimentation et nutrition humaine », project « ANR-06-PNRA-010-01».


Benchekroun Tahar-Hakim
email: tahar-hakim.benchekroun@lecnam.net

Bounouar Mouad

Bearee Richard

Siadat Ali

Industry of the future, future of work: the case of collaborative robotics

Keywords: Industry of the future, Collaborative robotics, Design project management

This communication discusses the resulting changes in the field of design project management generated by the industry of the future and its promises, with a special focus on collaborative robotics. Among the guiding issues of this work, we will focus on the importance of including such an intention to cobotize some or all of the tasks initially assigned to human operators, during the strategic stakes of the design process and to instruct and support it by the potential contributions of a bottum up approach centered on the real activities, mobilized and deployed during the realization of the tasks which are objects of cobotization. This discussion is based on an industrial case study, aimed at assisting a finishing workstation (the last stage of a production process) for fragile mechanical parts used in the manufacture of metal parts for the aeronautics sector.

1

Introduction and methodology

Introduction

The emergence of new technologies presents a major challenge to the transformation of the work and activity of human operators. These technologies once again raise questions about the place of humans in the new work organizations, and about their potential impact on the work and activity of operators [START_REF] Benchekroun | Intervenir en ergonomie : analyser le travail pour le comprendre et transformer le travail pour le concevoir[END_REF][START_REF] Garrigou | Contributions et démarche de l'ergonomie dans les processus de conception[END_REF].

The appearance of robots that can share the same workspace with human operators (cobot(s)) [START_REF] Bounouar | Etat des lieux de la cobotique industrielle et de la conduite de projet associée In 16ème édition S-mart colloque (AIP-Primeca)[END_REF] generates multidisciplinary discussions related to the multi-stakeholder aspect of these new technological devices [START_REF] Bounouar | L'ergonomie, la robotique collaborative et le génie industriel: Vers une conception pluridisciplinaire des systèmes Humains-Robots[END_REF], including the nature of the new forms of human -cobot(s) interactions, called collaborative interactions, and the health and safety of users [START_REF] Safeea | Efficient Calculation of Minimum Distance Between Capsules and Its Use in Robotics[END_REF], the transformation of their work [START_REF] Thibault | L'ergonomie dans la conception de systèmes cobotiques[END_REF], its organization, the relationship to work and the collective, the new skills to be acquired and developed as well as the profitability of these investments (impact on the quality and productivity of the existing system) [START_REF] Quenehen | Process optimisation using collaborative robots -comparative case study[END_REF][START_REF] Bounouar | User centered design of a collaborative robotic system for an industrial recycling operation[END_REF].

In this sense and in order to contribute to the new classes of problems and debates raised by these emerging technologies, we present in this paper a brief feedback of a research-intervention study conducted in a French SME, interested in these new technological devices (cobots), with the aim of assisting manual finishing stations for fragile mechanical parts intended for the manufacture of technical devices in the aeronautical and other sectors. This research and development involve a multidisciplinary team of engineers and ergonomists with the main objective of carrying out a feasibility study to answer the following questions: how could the use of industrial cobotics provide a relevant, realistic and feasible response to the strategic issues of improving production performance, health (MSD risks) and working conditions? In which way does a mobilization and involvement approach of the operators concerned by the cobotization project, in particular through the analysis of their actual activities, represent an essential condition to succeed the design project?

Methodology

To address the issues and objectives outlined above, we have conducted an actionresearch project with a French SME. This project aimed to integrate a collaborative robotics solution for the refining workstations used to manufacture mechanical parts for the aeronautics sector with high quality, reliability and safety standards.

During this project, we sought to:

• Understand and analyze the strategic issues of the different stakeholders of the design project in order to contextualize the choice of this technology as an answer and solution to the issues of customer retention, the perspectives of modernization of the manufacturing equipments, a more efficient performance by reducing rejects, prevention of MSD risks and global work conditions improvement, etc.;

• To mobilize and involve the concerned operators, in particular by the precise analysis of the gestural refining activities, to model the operations of manipulation and refining of the cores; to investigate the possibilities of cobotisation of the refining operations to support the gestural activity and to reduce the hardship of these workstations.

All these steps are part of a mobilization process of the involved design project participants, including the refining operators, and required the setting up of a strategic monitoring group of the project.

2

Analysis and modeling of the refining activity

Analysis of the refining activity

Initially, the team focused on understanding the issues related to the finishing activity targeted by the cobotization project. The exploratory interviews conducted with members of management, local managers and finishing agents highlighted the following strategic dimensions:

-The strategic stakes of winning new shares of the product market, higher reliability of the produced products answering more and more strict specifications, etc.;

-The strategic stakes of increasing product market share, greater reliability of the produced products in response to the more and more demanding specifications, etc.;

-Quality and reliability requirements: A high product rejection rate is observed in the manufacturing process. This is due to customers' strict standards for aviation safety reasons.

-Dimensions related to the employment, training and hiring of finishing operators, their overall cost and the insecurity of retaining them;

Modeling of the refining activity

After the strategic analysis phase, the team focused on the analysis of finishing activities. Observation campaigns equipped with audio and video tools were organized following a schedule consisting in observing the finishing activity of parts of different complexity (parts qualified by the workshop manager from complex to simple) by operators with different levels of experience (4 months, 5 years, 10 years and 17 years of experience). These observation campaigns were followed by exchanges and explanatory interviews with the observed operators, with the aim of understanding and analyzing their finishing activity. This phase made it possible to propose and validate (by the finishing operators) a characterization of the finishing gestural activity according to a view of the professional gestures not only from a biomechanical and physical point of view but extended to a greater complexity mobilizing the cognitive, collective and psychic dimensions. Such a conception of the professional gesture will make it possible to enrich the reflection and the choice of the technological solutions in the perspective of an allocation of the functions between the human and the cobot. An allocation of functions that takes into account the usefulness of the cobot and its integration in the course of the actions of the operators concerned, its participation in reducing the risks of Musculoskeletal disorders (MSD) related to the manipulation of parts and to preserve, or even develop new forms of efficient activities that produce meaning and recognition for the final users.

In order to go more deeply into this characterization, and inspired by the work of Chassaing [START_REF] Chassaing | Elaboration, structuration et réalisation des gestuelles de travail : les gestes dans l'assemblage automobile, et dans le coffrage des ponts d'autoroute[END_REF] and Benchekroun et al [START_REF] Benchekroun | Vitalité des activités et rationalité du Lean : deux études de cas[END_REF][START_REF] Benchekroun | Caractérisation pluridisciplinaire de l'activité en ergonomie[END_REF], gestural activity would be located, invested, constructed and developing:

-Situated as long as the gesture is permanently inscribed in changing and evolving contexts on the organizational, technological, spatio-temporal, historical, social and cultural levels; -The invested character of the gestural activity refers to its subjective dimension of the moment that it is singular and that everyone attaches values and meaning to it. The invested character of the gestural activity refers to its subjective dimension of the moment that it is singular and that each person attaches values and meaning to it. The gesture is not reduced to what is realized, it is also this activity that cannot be done and that risks being prevented; -The constructed and developmental character of gestural activity refers to the processes of training and learning on both the individual and collective levels. In these processes of construction and development, Weill-Fassina [START_REF] Clot | La fonction psychologique du travail[END_REF] gives an important place to reflexive activities which, according to her, can be spontaneously made by the subject, develop in the work group or be provoked by various forms of questioning or interviews.

On the basis of this characterization of the gestural activities of the finishing operators, we come to represent them according to the following model (Fig. 1):

Fig 1. The 4 squares scheme for the analyzed activity

This type of analysis made it possible to broaden the discussions and to develop the project on dimensions that had not been questioned until then, with a projection of the finishing operators on the part of their activity to be assisted possibly by a cobotic solution. If the right hand fulfils the essential role of finishing the part by filing, sanding, filling, using different finishing tools, operations considered to be the key role of the finishing operator, which valorize them and give a recognized brand image of the SME; the role of the left hand remains essential as long as it carries the piece, manipulates it to prepare and anticipate the actions of the right hand, but capitalizes on the complaints of all finishing operators in terms of pain, discomfort and potential risk of Musculo-skeletal disorders (MSD). They unanimously believe that if their work is to be helped and relieved, it must be through a solution to reduce the discomfort felt in the left hand and left shoulder (see Fig. 2 -Finishing work mobilizes knowledge about products, their destination, their complexity, their sensitivity, the different kind of methods and used tools, gestural finishing skills mobilizing precision, accuracy, detection of imperfections, caution not to break the products; the different uses made of the light source to support and anticipate the lighting and its quality on the different treatment areas, etc.;

-The left hand has an essential role in preparing the operations of the right hand and protecting the pieces -which are very fragile-from breakage by continuously adapting their position according to the operations to be carried out by the right hand, the orientation in relation to the light source, the effort exerted by the right hand, etc.

-Dimensions related to the health and hardship of the work: observation of significant solicitations of the upper limbs, in particular the hands, fingers and wrists. These solicitations are described as painful by the operators, particularly those of the left hand, which seems, to an outside observer, "not to be strongly solicited", etc.

Par un travail systématique d'observation, de traitement et d'analyse, nous avons identifié différents « patterns » de port et de manipulation des pièces par la main gauche. Ces patterns présentent les pièces à la lumière selon des plans longitudinaux et sagittaux rendant possible les opérations précisent, rapides et délicates de la main droite.

Discussion and perspectives

The analysis of the finishing activity in this case study has made it possible to direct the reflection of the finishing station' assistance (the objective of this case study) towards a more precise objective which is the assistance of the left hand (the hand that carries the parts during the finishing activity).

In fact, the analyses and modeling carried out have shown, the one hand, that it is this part of the gestural activity that causes the most pain to the finishing operators, especially if the parts are heavy or too small. On the other hand, the perceptivecognitive activity mobilized and the skills developed by the finishing operators constitute the central part of the finishing activity, and any intervention on this part will transform the central part of the finishing activity. With regard to the gestural activity of the right hand that performs the intervention on the parts to be finished (burr removal, polishing, drilling, turning the parts to be finished, etc.), the great variability of the operations performed makes it difficult to think about technological assistance paths. This assistance track was subsequently discussed with the finishing operators who expressed their curiosity and interest in seeing what a solution of this kind could look like, and that they were in favour of testing a prototype of this technological solution.

Based on the analyses carried out, the design team pointed out that a few constraints must be considered in this potential future system in order to ensure its goal of providing assistance without compromising too much on the quality and scrap rate of the manufactured parts, the productivity of the finishing department and the sense of this activity. These constraints are formalized below (see Table 1.). Currently a feasibility study is underway to propose technological directions that would be able to meet all the constraints related to the activity to be assisted. As the strategic analysis and activity analysis stages, this phase is conducted by a multidisciplinary team of robotics engineers and ergonomists. Potential technological approaches will be discussed with the finishing operators and the piloting committee to decide whether to go further in this assistance track or iterate to specify or modify the constraints to be fulfilled by the assistance system.

Conclusion

The development of collaborative robotics and the emergence of new technologies more generally will continue to transform production systems and the activities of human operators. These new technologies, although they present significant potential for the future, must be thought out and implemented with great caution. In fact, what is supposed to improve performance or improve working conditions represents at the same time a risk of disturbing the existing system, degrading productivity [START_REF] Chassaing | Elaboration, structuration et réalisation des gestuelles de travail : les gestes dans l'assemblage automobile, et dans le coffrage des ponts d'autoroute[END_REF] or even placing additional constraints on human operators [START_REF] Benchekroun | Vitalité des activités et rationalité du Lean : deux études de cas[END_REF].

To avoid undertaking unnecessary investments, it is necessary to verify the need in terms of these technologies and the presence of a real potential added value for the existing system (increased productivity, improved quality, reduced effort and hardship). A preliminary analysis of the strategic challenges and the real activity targeted is essential before starting the technical feasibility study of any new technology, especially technologies with high interactivity with humans, such as collaborative robotics.

Even after the emergence of potential technical solutions, they must be tested and evaluated to ensure their adequacy with the requirements of the activity being transformed. This transformation must not downgrade the activity of human operators; the dimensions related to the perception of this transformation, its acceptability and the meaning of the work of human operators must be at the heart of the design, evaluation and deployment processes of potential technological solutions.

Fig 2 .

 2 Fig 2. Schematization of the finishing gesture activity targeted by the cobotization project

Table 1 .

 1 Table of necessary constraints the future system must consider

	Constraint reference	Example
	Constraint 1	Ensuring parts carrying
	Constraint 2	Allow to carry a variety of parts
	Constraint 3	Allowing parts to be rotated and inclined smoothly
	Constraint 4	Allow to feel the forces applied on the parts (force feedback)
	Constraint 5	Do not damage or break the carried parts
	Constraint 6	Allows parts to be assembled and disassembled quickly and easily
	Constraint 7	Ensuring user safety & CE conformity (Machinery Directive)


Laurent Alleman

Note technique VERIFICATION DE LA QUALITE ET VEILLE

SYNTHESE

Comme chaque année, le LCSQA-IMT Lille Douai assure un rôle de conseil, de transfert de compétence et d'expertise vers les AASQA, soit directement ou par l'intermédiaire de groupe de travail dans le domaine de la mesure des polluants métalliques dans les particules atmosphériques. En 2020, ce travail inclut l'analyse de filtres vierges en fibre de quartz précommandés par les AASQA et achetés en lots par SynAir'GIE. Cette année, 2 lots de filtres en fibre de quartz QMA Whatman GE (1300 filtres) et 1 lot de filtres QAT-UP Palflex (825 filtres) ont été contrôlés et caractérisés chimiquement vis à vis de leurs teneurs en métaux et métalloïdes. Les 3 lots testés ont été validés car les teneurs des 4 métaux réglementés mesurés sur les filtres vierges testés étaient du même niveau que les lots des années précédentes.

CONTEXTE

Depuis 2007, une surveillance est effectuée par l'ensemble des AASQA de façon continue ou ponctuelle, pour le Pb, As, Cd et Ni dans les PM10 en accord avec les Directives européennes en vigueur (2008/50/CE et 2004/107/CE modifiées par la Directive 2015/1480/CE). Les objectifs de l'IMT Lille Douai, au sein du LCSQA, sont : -d'assurer un rôle de conseil et de transfert de connaissances auprès des AASQA concernant l'analyse des métaux dans l'air ambiant notamment au travers de GT et CS ; -de procéder à des analyses et des études permettant de garantir la qualité des résultats ; -de participer activement aux travaux de normalisation français (AFNOR X43D) et européens (WG14, WG20, WG44) ; -de réaliser une veille technologique sur les nouvelles méthodes de prélèvement et d'analyse susceptibles d'optimiser les coûts et de facilité l'acquisition de données, tout en respectant les objectifs de qualité des directives ; -de participer à la valorisation des activités de surveillance et des études menées en collaborations avec les AASQA.

INTRODUCTION

Dans le cadre de sa politique de surveillance de la qualité de l'air, l'Union Européenne prévoit la surveillance de polluants particulaires (Directives 2008/50/CE et 2004/107/CE modifiées par la Directive 2015/1480/CE, ainsi que l'arrêté du 17 juillet 2019 modifiant l'arrêté du 19 avril 2017 relatif au dispositif national de surveillance de la qualité de l'air ambiant). La quatrième Directive fille de 2004 rend obligatoire la mesure des métaux As, Cd et Ni venant s'ajouter à celle du Pb dans les particules PM10 en suspension dans l'air ambiant. Cette mesure doit être réalisée suivant la méthode de référence NF EN 14902 (2005) ou suivant une méthode démontrée équivalente.

Sur le territoire français, la mesure des métaux dans les particules PM10 est réalisée par l'ensemble des AASQA, lors de prélèvements en continu ou ponctuels, dans le cadre de la surveillance réglementaire.

Dans ce contexte, le rôle du LCSQA-IMT Lille Douai inclut à la fois du développement métrologique (test de nouveaux supports de prélèvement et mise au point de méthodes de mesures), des travaux visant à assurer l'homogénéité et la justesse des mesures réalisées par les AASQA (conseils à l'AASQA, test et/ou distribution de filtres vierges en fibre de quartz, élaboration de filtres de tests impactés de PM10, campagnes de comparaison interlaboratoires tous les deux ou trois ans) mais aussi de la veille technologique (méthodologies et instrumentations), de la réflexion sur la stratégie de prélèvement et de la valorisation des mesures, notamment dans le cadre du programme CARA. En 2020, les travaux réalisés dans le cadre du LCSQA ont porté sur les actions suivantes :

FOURNITURES DE FILTRES VIERGES

Les particules PM10, réglementées au niveau européen, sont prélevées sur filtres avant d'être transportées au laboratoire pour l'analyse des métaux. La qualité des filtres vierges est donc un facteur important de la méthode de mesure car les teneurs en métaux cibles inclus dans leurs matrices en quartz peuvent générer un biais lors de l'analyse. Ce problème est particulièrement significatif pour le nickel, élément pour lequel les teneurs apportées par les médias filtrants peuvent parfois être du même ordre de grandeur que les teneurs dans les PM10 prélevées dans l'air ambiant (sites ruraux ou périurbains). Le rôle du LCSQA-IMT Lille Douai dans le choix des filtres s'articule autour de deux actions : (1) le contrôle et la validation de filtres en fibre de quartz fournis aux AASQA ;

(2) une veille auprès des différents fournisseurs concernant le type et la qualité des filtres disponibles sur le marché.

Contrôle des filtres

En prenant pour hypothèse (vérifiée jusqu'à présent) que la qualité des filtres est relativement homogène dans un même lot de fabrication, des contrôles de la teneur en métaux sont réalisés avant la mise en service de chaque nouveau lot de fabrication par les AAQSA. Ils sont effectués en prélevant de façon aléatoire dix filtres vierges d'un même numéro de lot qui sont préparés et analysés suivant les préconisations de la norme NF EN 14902 pour l'analyse des métaux dans les PM10 à savoir : solubilisation par minéralisation au four microondes à 220°C pendant 20 mn en milieu HNO3/H2O2 (3/1) puis analyse des métaux réglementés (As, Cd, Ni, Pb) par ICP-MS avec cellule de collision (gaz He) et/ou de réaction (gaz H2).

Contrôle de filtres en fibre de quartz

CONCLUSIONS

Les travaux réalisés en 2020 par le LCSQA-IMT Lille Douai ont porté notamment sur la validation de filtres vierges en fibre de quartz achetés par SynAir'GIE dans le cadre de son activité « achats groupés » puis transmis aux AASQA, permettant d'obtenir une assurance qualité des filtres utilisés pour la surveillance des métaux réglementés. L'utilisation de la centrale d'achat de SynAir'GIE permet de simplifier la procédure, de réduire les coûts et de maintenir l'assurance qualité rendue indispensable au vu des faibles teneurs en métaux actuellement mesurées dans l'air au niveau national. Les 3 nouveaux lots testés cette année ont été validés car les teneurs pour les 4 métaux réglementés mesurés sur les filtres vierges testés étaient du même niveau que les lots des années précédentes.

  IMT Lille Douai a acquis une expérience théorique et pratique de la mesure des métaux dans les particules atmosphériques en suspension dans l'air ambiant et les dépôts atmosphériques. De ce fait, une partie du travail consiste à transférer cette expertise vers les AASQA. Cet échange se fait :

	lots QMA Whatman GE -1300 filtres et 1 lot QAT-UP Palflex -825 filtres) ont été validés
	puis transmis auprès de 13 AASQA.
	• La participation à la CS « Anticipation », aux GT « Stratégie BC et PUF » et « Observatoires
	nationaux ».
	3. TRANSMISSION DES CONNAISSANCES
	Depuis 1999, grâce à des collaborations avec les AASQA, aux travaux menés dans le cadre de
	programmes de recherche (ANR, ADEME, PRIMEQUAL, ANSES …), à la participation aux
	groupes de travail européens sur les normes NF EN 14902 et EN 15841 ou AFNOR (NF X43-
	014) ainsi qu'aux essais de comparaison inter-laboratoires européens (EMEP, JRC, IRMM,
	NILU, NRC), le LCSQA--plus en amont, en participant aux groupes de travail français et européens sur la
		normalisation de la mesure des métaux dans l'air ambiant (WG14 : NF EN 14902)
		ou dans les retombées atmosphériques (GT X43D : X43-014 modifiée, WG 20 : EN
		15841) et sur la normalisation des méthodes d'évaluation des sources de PM
		(WG44 : Source apportionment).
	-	enfin, par la valorisation et la diffusion des travaux du LCSQA-IMT Lille Douai au
		travers de communications scientifiques : une publication issue des essais de
		terrains pour la norme EN 15841 est parue en 2010 dans Journal of Environmental
		Monitoring (Aas et al., 2010). Les résultats d'intercomparaison du JRC sur les
	• La transmission de connaissances techniques auprès des AASQA et des laboratoires métaux réglementés dans l'air ambiant ont été publiés en 2011 dans Atmospheric
	associés au travers d'échanges (email, téléphone).
	• La validation de filtres vierges en fibre de quartz fournis par SynAir'GIE. Les filtres ont été
	achetés par lots et leurs caractéristiques chimiques ont été contrôlées pour chaque lot
	sur un sous-échantillon de 10 filtres vierges. En 2020, 3 lots de filtres en fibre de quartz (2

de façon personnalisée, à travers des contacts téléphoniques et des échanges de courriels avec les AASQA et leurs laboratoires prestataires, tant pour les mesures sur les aérosols que sur les dépôts atmosphériques et incluant notamment la problématique de la gestion des blancs de filtre. -par une aide aux AASQA pour la sélection de laboratoires d'analyse. Un questionnaire et une procédure ont été rédigés à cet effet (rapport métaux LCSQA, annexe 2, 2009). Un kit de test (filtres, matériau de référence certifié) peut également être envoyé au laboratoire désigné dont les résultats d'analyse sont ensuite évalués par nos soins. -de façon plus générale, par la rédaction et l'implémentation du guide technique et méthodologique de l'analyse de l'As, Cd, Ni et Pb dans l'air ambiant (LCSQA : Guide Technique et Méthodologique de l'Analyse de l'Arsenic, Cadmium, Nickel et Plomb dans l'Air Ambiant, 2012). -par le transfert d'expertise dans le cadre des travaux du groupe de travail sur les incertitudes (concernant les métaux), du groupe de travail sur la caractérisation des PM (GT Carbone suie et Particules fines) et des Commissions de Suivi (CS « Métrologie » et CS « Anticipation »). Environment (Gerboles et al., 2011). Les travaux sur les échantillons CARA prélevés sur le site de Lens ont permis la publication d'un article sur l'identification des sources de PM10 dans la région Nord-Pas de Calais (Waked et al., 2014 ; Belis et al., Vérification de la qualité et veille technologique sur les filtres utilisés pour la mesure des métaux dans les PM10 4 2019), en Rhône Alpes (Srivastava et al., 2018) ou d'autres sites en France (Weber et al., 2019).

Filtres vierges en fibre de quartz Whatman QMA -lot 17009593

  Jusqu'en 2018, ces filtres étaient financés par le LCSQA, puis en 2019, du fait des restrictions budgétaires les AASQA ont acheté elles-mêmes les filtres pour leur consommation propre et envoyé un lot de 10 filtres vierges à tester par le LCSQA-IMT Lille Douai avant de les mettre en circulation dans leur région.En 2020, SynAir'GIE a proposé aux AASQA de procéder à un achat groupé de ces filtres (Whatman GE ou Pall) dont elles avaient besoin auprès de fournisseurs dans le cadre de son activité « achats groupés » mais hors marchés publics (après appel de fonds auprès des AASQA partenaires). Les lots de filtres achetés en début d'année par SynAir'GIE ont été analysés et validés à partir d'un échantillon aléatoire de 10 filtres pour chacun des lots par le LCSQA-IMT Lille Douai (moyenne des blancs et calculs de limite de détection/quantification). Les lots ainsi validés ont ensuite été envoyés par le LCSQA-IMT Lille Douai et facturés par SynAir'GIE aux AASQA qui les ont commandés.Les filtres en quartz sont à utiliser uniquement pour des prélèvements hebdomadaires afin de limiter les problèmes de contamination (valeur de blanc non négligeable pour le Ni notamment, issu de la matrice quartz, voir données dans les tableaux ci-après). Au cours de l'année 2020, nous avons validé les filtres en quartz de 47 mm de diamètre provenant de la marque Whatman GE (2 lots de fabrication QMA) et de la marque Pall (1 lot de fabrication QAT-UP). Les teneurs moyennes des 4 éléments ciblés sont rappelées, par numéro de lot dans les tableaux 1 à 3.

	Tableau 1 : As	Cd	Ni	Pb
	Teneur (ng/filtre)	0,14	0,07	28,2	3,2
	LD tech. (ng/filtre)	0,05	0,04	0,04	0,04
	LD méth. (ng/filtre)	0,22	0,56	11,4	1,6
	Tableau 2 :
	Au final, cette solution s'est avérée au global plus onéreuse car la quantité de filtres achetés
	par chaque AASQA est faible et cela démultiplie les analyses avec des délais également
	rallongés. Par ailleurs, cette procédure ne permettait plus d'avoir une homogénéité des
	supports sur l'ensemble de la France, indispensable pour les métaux à faibles teneurs dans
	l'air.

Depuis de nombreuses années, l'IMT Lille Douai assure, dans le cadre du LCSQA, l'estimation du niveau de blanc des filtres en fibre de quartz de 47 mm utilisés pour la mesure des métaux réglementés.

Filtres vierges en fibre de quartz Whatman QMA -lot 17031634 As Cd Ni Pb Teneur (ng/filtre)

		0,16	0,11	56,2	2,6
	LD tech. (ng/filtre)	0,05	0,04	0,04	0,04
	LD méth. (ng/filtre)	0,3	0,37	23,0	1,1
	Tableau 3 :

Filtres vierges en fibre de quartz Pall QAT-UP -lot 20756

  Les analyses en V, Cu, Mn, Co, Cr, Zn Sb, Se, Sn et Tl ont également été effectuées sur ces lots de filtres mais ne sont données qu'à titre indicatif (Tableaux 4 à 6) car cela concerne des éléments non réglementés dans l'air ambiant. En effet, la méthode utilisée (NF EN 14902 : 2005 avec mélange HNO3/H2O2) n'a pas été validée au niveau européen pour ces éléments, notamment dans le cas du Cr (taux de récupération trop faible < 70% et blancs parfois élevés par rapport aux concentrations dans les PM10). Des travaux précédents du LCSQA-IMT Lille Douai (rapport LCSQA, 2014) ont toutefois montré qu'à l'exception du Cr, ces éléments étaient mesurables et l'application de la norme EN 14902 permettait d'obtenir des critères de qualité comparables aux métaux réglementés.

	Tableau 4 :
		As	Cd	Ni	Pb
	Teneur (ng/filtre)	0,16	<LDtech.	47,3	1,5
	LD tech. (ng/filtre)	0,05	0,04	0,04	0,04
	LD méth. (ng/filtre)	0,21	0,02	49,1	1,2

Filtres vierges en fibre de quartz Whatman QMA -lot 17009593

		V	Cu	Mn	Co	Cr	Zn	Sb	Se	Sn	Tl
	Teneur (ng/filtre)	0,6	7,7	10,7	0,9	167	190	2,0	<LDtech	3,7	<LDtech
	LD tech. (ng/filtre)	0,02	0,29	0,2	0,01	0,5	13	0,02	0,6	0,2	0 008
	LD méth. (ng/filtre)	0,2	2,4	4,4	0,5	31,4	534	0,7	0,3	1,7	0 005
		Tableau 5 :

Filtres vierges en fibre de quartz Whatman QMA -lot 17031634

		V	Cu	Mn	Co	Cr	Zn	Sb	Se	Sn	Tl
	Teneur (ng/filtre)	0,8	14,9	16,5	3,1	232	151	4,8	<LDtech	3,7	<LDtech
	LD tech. (ng/filtre)	0,03	0,29	0,2	0,01	0,5	13	0,02	0,6	0,2	0 008
	LD méth. (ng/filtre)	0,4	8,4	11,3	2.0	66,7	550	1,7	0,4	0,6	0 003
		Tableau 6 :

Filtres vierges en fibre de quartz Pall QAT-UP -lot 20756

  Les limites de détection méthodologique (LDméth.) et technique ou analytique (LDtech.) sont calculées respectivement à partir de l'analyse d'une série de dix filtres vierges (incluant donc la procédure de minéralisation de ces filtres) et de dix blancs d'acide (incluant la variabilité analytique) suivant la formule générale : LD = 3 x  avec  l'écart-type calculé à partir de la moyenne des dix mesures de concentrations. La LDméth. reflète surtout les variations des teneurs en élément contenu dans les filtres vierges.

	Tableau 7 :
		V	Cu	Mn	Co	Cr	Zn	Sb	Se	Sn	Tl
	Teneur (ng/filtre)	0,5	3,1	16,5	0,9	202	27	10,4	<LDtech	2,0	<LDtech
	LD tech. (ng/filtre)	0,02	0,29	0,2	0,01	0,5	13	0,02	0,6	0,2	0 008
	LD méth. (ng/filtre)	1,6	11,1	20,8	1,4	148	16	4,1	0,2	2,3	0 004
	Vérification de la qualité et veille technologique sur les filtres utilisés pour la mesure des métaux
	dans les PM10									7

Valeurs cibles et seuils d'évaluation inférieur (SEI ou LAT) de la directive et concentrations moyennes françaises (AASQA) dans l'air ambiant en site urbain de fond (2000 -2005) exprimés en ng/filtre pour des prélèvements hebdomadaires (168 m 3 )

  Prelevement et analyse des métaux dans les particules en suspension dans l'air ambiant, 2007.Dans le tableau 7, les valeurs cibles des 1 ère et 4 ème directives ont été multipliées par 168 (volume d'une semaine de prélèvement à 1 m 3 /h) pour être exprimées en ng/filtre et non pas en ng/m 3 . Ces teneurs sont très inférieures (d'un facteur 10 à 100) au Seuil d'Evaluation Inférieur (SEI ou LAT) ou aux teneurs moyennes urbaines françaises pour des prélèvements hebdomadaires. Elles sont toutefois plus variables et plus proches des valeurs moyennes mesurées en France en site urbain de fond (Tableau 7) dans le cas du Nickel, ce qui montre l'importance du respect des procédures de gestion et de stockage des filtres neufs.

		As	Cd	Ni	Pb
	Valeurs cibles	1008	840	3360	84000
	LAT (Seuil min.)	403	336	1680	42000
	* Valeurs moyennes en France (ng/filtre)	118±67	67±34	538±218	3746±3360

* Rapport LCSQA.