Fundamental aspects of noise in analog-hardware neural networks.

We study and analyze the fundamental aspects of noise propagation in recurrent as well as deep, multilayer networks. The motivation of our study is neural networks in analog hardware; yet, the methodology provides insight into networks in general. Considering noisy linear nodes, we investigate the signal-to-noise ratio at the network's outputs, which determines the upper limit of computational precision. We consider additive and multiplicative noise, which can be purely local as well as correlated across populations of neurons. This covers the chief internal-perturbations of hardware networks, and noise amplitudes were obtained from a physically implemented neural network. Analytically derived descriptions agree exceptionally well with numerical data, enabling clear identification of the components critical for management and mitigation of noise. We find that analog neural networks are surprisingly robust, in particular, against noisy neurons. Their uncorrelated perturbations are almost fully suppressed, while correlated noise can accumulate. Our work identifies notoriously sensitive points while highlighting a surprising robustness of such computational systems.

[Teacher sick leave: Prevalence, duration, reasons and covariates]. / Congés-maladie des enseignants : fréquence, durées, raisons et facteurs associés.

BACKGROUND: Absences from work have considerable social and economic impact. In the education sector, the phenomenon is particularly worrying since teacher sick leave has an impact on the overall performance of the education system. Yet, available data are scarce. METHODS: In April-June 2013, 2653 teachers responded to a population-based postal survey on their quality of life (enquête Qualité de vie des enseignants, MGEN Foundation/Ministry of education, response rate 53 %). Besides questions on work environment and health, teachers were asked to describe their eventual sick leave(s) since the beginning of the school year: duration, type and medical reasons. Self-reported information was reinforced by administrative data from ministerial databases and weighted to be extrapolated to all French teachers. Tobit models adjusted for individual factors of a private nature were used to investigate different occupational risk factors of teacher sick leave, taking into account both the estimated effect on the probability of sick leave and the length of it. RESULTS: More than one in three teachers (36 %) reported having had at least one day of sick leave since the beginning of the school year. Respiratory/ENT diseases were the leading reason for sick leave (37 %). However, and because sick leave duration depended on the underlying health problem, such diseases came in third place among justifications of sick leave days (14 %), far behind musculoskeletal problems (27 %) and neurological and psychological disorders (25 %). Tobit models suggested that some occupational factors significantly associated with the risk of sick leave may represent promising preventive targets, including high psychological demand, workplace violence and unfavorable socio-environmental context. CONCLUSION: Our study provides objective evidence about the issue of sick leave among French teachers, highlighting the usefulness of implementing actions to minimize its weight. To this end, the study findings point-out the importance of considering not only the probability of sick leave, but also its duration.

Single-shot ultrafast laser processing of high-aspect-ratio nanochannels using elliptical Bessel beams.

Ultrafast lasers have revolutionized material processing, opening a wealth of new applications in many areas of science. A recent technology that allows the cleaving of transparent materials via non-ablative processes is based on focusing and translating a high-intensity laser beam within a material to induce a well-defined internal stress plane. This then enables material separation without debris generation. Here, we use a non-diffracting beam engineered to have a transverse elliptical spatial profile to generate high-aspect-ratio elliptical channels in glass of a dimension 350 nm×710 nm and subsequent cleaved surface uniformity at the sub-micron level.

High aspect ratio micro-explosions in the bulk of sapphire generated by femtosecond Bessel beams.

Femtosecond pulses provide an extreme degree of confinement of light matter-interactions in high-bandgap materials because of the nonlinear nature of ionization. It was recognized very early on that a highly focused single pulse of only nanojoule energy could generate spherical voids in fused silica and sapphire crystal as the nanometric scale plasma generated has energy sufficient to compress the material around it and to generate new material phases. But the volumes of the nanometric void and of the compressed material are extremely small. Here we use single femtosecond pulses shaped into high-angle Bessel beams at microjoule energy, allowing for the creation of very high 100:1 aspect ratio voids in sapphire crystal, which is one of the hardest materials, twice as dense as glass. The void volume is 2 orders of magnitude higher than those created with Gaussian beams. Femtosecond and picosecond illumination regimes yield qualitatively different damage morphologies. These results open novel perspectives for laser processing and new materials synthesis by laser-induced compression.

Mapping human risk of infection with Borrelia burgdorferi sensu lato, the agent of Lyme borreliosis, in a periurban forest in France.

Lyme borreliosis is a major zoonosis in Europe, with estimates of over 26,000 cases per year in France alone. The etiological agents are spirochete bacteria that belong to the Borrelia burgdorferi sensu lato (s. l.) complex and are transmitted by hard ticks among a large range of vertebrate hosts. In Europe, the tick Ixodes ricinus is the main vector. In the absence of a vaccine and given the current difficulties to diagnose and treat chronic Lyme syndromes, there is urgent need for prevention. In this context, accurate information on the spatial patterns of risk of exposure to ticks is of prime importance for public health. The objective of our study was to provide a snapshot map of the risk of human infection with B. burgdorferi s. l. pathogens in a periurban forest at a high resolution, and to analyze the factors that contribute to variation in this risk. Field monitoring took place over three weeks in May 2011 in the suburban Sénart forest (3,200ha; southeast of Paris), which receives over 3 million people annually. We sampled ticks over the entire forest area (from 220 forest stands with a total area of 35,200m(2)) and quantified the density of questing nymphs (DON), the prevalence of infection among nymphs (NIP), and the density of infected nymphs (DIN), which is the most important predictor of the human risk of Lyme borreliosis. For each of these response variables, we explored the relative roles of weather (saturation deficit), hosts (abundance indices of ungulates and Tamias sibiricus, an introduced rodent species), vegetation and forest cover, superficial soil composition, and the distance to forest roads. In total, 19,546 questing nymphs were collected and the presence of B. burgdorferi s. l. was tested in 3,903 nymphs by qPCR. The mean DON was 5.6 nymphs per 10m(2) (standard deviation=10.4) with an average NIP of 10.1% (standard deviation=0.11). The highest DIN was 8.9 infected nymphs per 10m(2), with a mean of 0.59 (standard deviation=0.6). Our mapping and modeling revealed a strong heterogeneity of risk within the forest. The highest risk was found in the eastern part of the forest and localized patches in the northwestern part. Lyme borreliosis risk was positively associated with stands of deciduous trees (mainly oaks) and roe deer abundance. Contrary to expectations, DIN actually increased with distance from the point of introduction of T. sibiricus (i.e., DIN was higher in areas with potentially lower abundances of T. sibiricus). Thus, despite the fact that T. sibiricus is an important reservoir host for B. burgdorferi s. l., our study found that other explanatory factors played a more important role in determining the density of infected ticks. Precise mapping of the risk of exposure to Lyme borreliosis in a highly visited forest represents an important tool for targeting prevention and control measures, as well as making the general public and local health officials aware of the risks.

Spatiotemporal structure of femtosecond Bessel beams from spatial light modulators.

We numerically investigate the spatiotemporal structure of Bessel beams generated with spatial light modulators (SLMs). Grating-like phase masks enable the spatial filtering of undesired diffraction orders produced by SLMs. Pulse front tilt and temporal broadening effects are investigated. In addition, we explore the influence of phase wrapping and show that the spatiotemporal structure of SLM-generated femtosecond Bessel beams is similar to Bessel X-pulses at short propagation distance and to subluminal pulsed Bessel beams at long propagation distance.

Arbitrary nonparaxial accelerating periodic beams and spherical shaping of light.

We report the observation of arbitrary accelerating beams (ABs) designed using a nonparaxial description of optical caustics. We use a spatial light modulator-based setup and techniques of Fourier optics to generate circular and Weber beams subtending over 95 deg of arc. Applying a complementary binary mask also allows the generation of periodic ABs taking the forms of snake-like trajectories, and the application of a rotation to the caustic allows the first experimental synthesis of optical ABs upon the surface of a sphere in three dimensions.

Sending femtosecond pulses in circles: highly nonparaxial accelerating beams.

We use caustic beam shaping on 100 fs pulses to experimentally generate nonparaxial accelerating beams along a 60° circular arc, moving laterally by 14 µm over a 28 µm propagation length. This is the highest degree of transverse acceleration reported to our knowledge. Using diffraction integral theory and numerical beam propagation simulations, we show that circular acceleration trajectories represent a unique class of nonparaxial diffraction-free beam profile which also preserves the femtosecond temporal structure in the vicinity of the caustic.

Arbitrary accelerating micron-scale caustic beams in two and three dimensions.

We generate arbitrary convex accelerating beams by direct application of an appropriate spatial phase profile on an incident Gaussian beam. The spatial phase calculation exploits the geometrical properties of optical caustics and the Legendre transform. Using this technique, accelerating sheet caustic beams with parabolic profiles (i.e. Airy beams), as well as quartic and logarithmic profiles are experimentally synthesized from an incident Gaussian beam, and we show compatibility with material processing applications using an imaging system to reduce the main intensity lobe at the caustic to sub-10 micron transverse dimension. By applying additional and rotational spatial phase, we generate caustic-bounded sheet and volume beams, which both show evidence of the recently predicted effect of abrupt autofocussing. In addition, an engineered accelerating profile with femtosecond pulses is applied to generate a curved zone of refractive index modification in glass. These latter results provide proof of principle demonstration of how this technique may yield new degrees of freedom in both nonlinear optics and femtosecond micromachining.

High aspect ratio taper-free microchannel fabrication using femtosecond Bessel beams.

We present a systematic study of femtosecond laser microchannel machining in glass using nondiffracting Bessel beams. In particular, our results identify a source and focusing parameter working window where high aspect ratio taper-free microchannels can be reproducibly produced without sample translation. With appropriate source parameters, we machine channels of 2 microm diameter and with aspect ratios up to 40. We propose the filamentation stability of the Bessel beam propagation as the critical factor underlying the controlled and reproducible results that have been obtained.

How surface composition of high milk proteins powders is influenced by spray-drying temperature.

High milk proteins powders are common ingredients in many food products. The surface composition of these powders is expected to play an essential role during their storage, handling and/or final application. Therefore, an eventual control of the surface composition by modifying the spray-drying temperature could be very useful in the improvement of powder quality and the development of new applications. For this purpose, the influence of five spray-drying temperatures upon the surface composition of the powders was investigated by X-ray photoelectron spectroscopy. The major milk proteins were studied: native micellar casein and native whey, both more or less enriched in lactose. The results show a surface enrichment in lipids for all the powders and in proteins for many powders. Whatever the drying temperature, lipids and proteins are preferentially located near the surface whereas lactose is found in the core. This surface enrichment is also highly affected by the spray-drying temperature. More lipids, more proteins and less lactose are systematically observed at the surface of powders spray-dried at lower outlet air temperatures. The nature of proteins is also found essential; surface enrichment in lipids being much stronger for whey proteins containing powders than for casein containing powders. Additionally, we found a direct correlation between the lipids surface concentration and the wetting ability for the 25 powders studied.

Surface nanoprocessing with nondiffracting femtosecond Bessel beams.

We demonstrate the application of nondiffracting Bessel beams for reproducible nanometric-scale feature patterning in glass. A femtosecond pulse zero-order Bessel beam with a central spot radius of 360 nm was used to write 500 nm radius nanocraters over a longitudinal positioning range exceeding 20 microm, with a variation in radius of less than 10%. The use of Bessel beams significantly reduces constraints on critical sample positioning in the nanoscale writing regime, enabling the use of femtosecond pulses for fast inscription of nanometer-scale features over large sample areas.

Optimization of the components concentrations of the lactoperoxidase system by RSM.

AIMS: The aim of this work was to use response surface methodology (RSM) approach, a statistical mathematical tool, to model effects and interactions of glucose oxidase (GOD), glucose, lactoperoxidase (LPO) and pH-values on the thiocyanate (SCN-) peroxidation, to determine the best concentrations of lactoperoxidase system (LP-s) components in order to obtain maximal SCN- peroxidation and so to enhance the LP-s antibacterial effects. METHODS AND RESULTS: Experimental design using RSM was used for modelling effects and interactions of GOD (28.5-142.5 IU l(-1)), glucose (0.55-11.11 mmol l(-1)), LPO (0-6284 IU l(-1)) concentrations, and pH-values (6.0-7.4) on thiocyanate peroxidation. A fixed SCN- concentration of 0.5 mmol l(-1) was used. Experiments were carried out at 4 or at 25 degrees C in 0.1 mol l(-1) phosphate buffer. Optimized concentrations for both temperatures (4 and 25 degrees C) were quite similar and were 85.5 IU l(-1) for GOD, 8 mmol l(-1) for glucose and 3927.5 IU l(-1) for LPO at an initial pH-value of 6.5. SCN- peroxidation was more efficient at 25 than at 4 degrees C. At 4 degrees C, no interaction between factors occurred. At 25 degrees C, thiocyanate peroxidation was affected by GOD/glucose, GOD/pH and LPO/pH. Thiocyanate peroxidation was mainly increased by glucose and LPO factors. The optimized system had a bacteriostatic effect on Listeria monocytogenes CIP 82110(T) and a strong bactericidal effect on Pseudomonas fluorescens CIP 6913(T). CONCLUSIONS: Appropriate combinations of LPO, GOD, glucose concentrations and pH-values allowed maximal thiocyanate peroxidation and enhanced the antibacterial effect of the LP-s. SIGNIFICANCE AND IMPACT OF THE STUDY: This optimization by RSM approach allowed a better understanding of the LP-s functioning, the description of the component impacts on the SCN- peroxidation, and the observation of different interactions between the factors. The antimicrobial efficiency of LP-s can be enhanced by better concentration ratios of the LP-s components.

Broadband supercontinuum interferometer for high-resolution profilometry.

In this paper, it is shown that a white light supercontinuum source generated in an air-silica microstructured optical fiber pumped with picosecond pulses offers the possibility to improve fringes visibility in interferometric acquisitions. Consequently, this source combined with a spectral interferometer, reaches high-resolution profilometric measurements. Phase calculation based on seven point algorithm can perform theoretically a subnanometer resolution. This method provides a one line profile of large surfaces from the analysis of a single shot image, without any mechanical scanning.

Imaging through a scattering medium with an interferential spectrometer by selection of an amplitude modulation correlator.

Low-coherence interferometric systems provide three-dimensional imaging through scattering media by measurement of the object's temporal response. An optical correlator is presented that allows direct recording of the signal issued from the object under reflection. The filtering technique enhances the image visibility and allows one to obtain an image with a good signal-to-noise ratio. The performance of two particular imaging systems, point-to-point and vertical-slice imaging, is discussed with an object comprising two cover plates that are attached.

[Imagination of women with breast cancer. About the etiologic theories of 10 patients]. / Vécu fantasmatique et imaginaire des femmes atteintes de cancer du sein. A propos des théories étiologiques de 10 patientes.

The announcement of the diagnosis of a breast cancer causes a rupture in the continuity of life of the patients. For women with such a potentially mortal illness, the development of an etiologic theory, falling under a subjective appropriation of the disease, allows them to face the traumatism of the diagnostic and the course of the cancer itself. These theories, often spontaneous, sometimes supported by the psychologist's work, are a great ally for the somatician in the therapy of those women.

Multiple splice variants of the pituitary adenylate cyclase-activating polypeptide type 1 receptor detected by RT-PCR in single rat pituitary cells.

Alternative splicing of the rat type 1 pituitary adenylate cyclase-activating polypeptide (PACAP) receptor (PVR1) produces variants that couple either to both adenylyl cyclase (AC) and phospholipase C (PLC) (PVR1 short, PVR1 hop, PVR1 hiphop), or to AC alone (PVR1 hip). We have previously shown that populations of clonal alphaT3-1 gonadotrophs express PVR1 hop and PVR1 short mRNAs, whereas clonal GH4C1 somatotrophs do not. Here we have used the single cell RT-PCR technique to investigate whether normal rat gonadotrophs and somatotrophs express PVR1 mRNA, whether a single cell co-expresses multiple splice variant forms, and whether differential PVR1 mRNA expression correlates with differences in PACAP-stimulated Ca2+ signalling. We found that individual rat gonadotrophs expressed mRNA either for PVR1 hop, for PVR1 short, or co-expressed the two forms. Although we found no differences between the splice variant(s) expressed and the characteristics of PACAP-stimulated Ca2+ responses, the expression of PVR1 mRNA is consistent with the known PACAP stimulation of the PLC system in gonadotrophs. Individual rat somatotrophs also expressed PVR1 hop or PVR1 short (but not PVR1 hip) mRNAs although these forms were never co-expressed. The expression of PVR1 mRNA in somatotrophs can explain in part the activation by PACAP of the AC system in such cells. In conclusion, the single cell RT-PCR technique was used to demonstrate expression of multiple PVR1 splice variants in single identified pituitary cells. These findings open up important questions on the role of alternative splicing in cell biology.

[Trimetazidine and degenerative deafness. Effect on hearing and integration]. / Trimétazidine et surdités dégénératives. Effets sur l'audition et l'intégration.

This study was conducted in order to assess the activity of trimetazidine dosed at 60 mg/day in patients presenting degenerative loss of hearing. Ten centers participated in this multicenter double-blind placebo-controlled trial which spanned 6 months. Included were 251 patients (118 women, 133 men) presenting with pure perception bilateral symmetrical deafness concerning predominantly the acute frequency range. 228 patients terminated the study, including 115 in the trimetazidine group and 113 in the placebo group. The evolution over a 6-month treatment period was significantly better with trimetazidine as regards the following parameters: audibility as assessed by pure-tone audiometry, namely at the acute frequency range (p = 0.002), intelligibility as assessed by speech audiometry (p = 0.008), subjective evaluation of hearing loss and its impact on the patient's social life. Results confirm the value of trimetazidine hearing loss management, based on clinical, subjective criteria as well as audiometric ones. Parameters reflecting best trimetazidine's efficacy were intelligibility and the psychological/behavioral impact of the impairment, allowing for better social integration of the subject.