Influence of third-order dispersion on the propagation of incoherent light in optical fibers

We study the influence of third-order dispersion effects on the propagation of an incoherent nonlinear wave in an optical fiber system. The wave spectrum is shown to exhibit a highly asymmetric deformation characterized by a lateral spectral shoulder and the subsequent formation of an unexpected constant spectral pedestal. A kinetic approach to the problem reveals the existence of an invariant that explains in detail the essential properties of such asymmetric spectral evolution of the wave.

Masking technique for coating thickness control on large and strongly curved aspherical optics

We discuss a method to control the coating thickness deposited onto large and strongly curved optics by ion beam sputtering. The technique uses an original design of the mask used to screen part of the sputtered materials. A first multielement mask is calculated from the measured two-dimensional coating thickness distribution. Then, by means of an iterative process, the final mask is designed. By using such a technique, it has been possible to deposit layers of tantalum pentoxide having a high thickness gradient onto a curved substrate 500 mm in diameter. Residual errors in the coating thickness profile are below 0.7%.

Toxin mixture in cyanobacterial blooms--a critical comparison of reality with current procedures employed in human health risk assessment

Cyanobacteria are the oldest life forms on earth known to produce a broad spectrum of secondary metabolites. The functions/advantages of most of these secondary metabolites (peptides and alkaloids) are unknown, however, some of them have adverse effects in humans and wildlife, especially when ingested, inhaled or upon dermal exposure. Surprisingly, some of these cyanobacteria are ingested voluntarily. Indeed, for centuries mankind has used cyanobacteria as a protein source, primarily Spirulina species. However, recently also Aphanizomenon flos-aquae are used for the production of so called blue green algae supplements (BGAS), supposedly efficacious for treatment of various diseases and afflictions. Unfortunately, traces of neurotoxins and protein phosphatases (inhibiting compounds) have been detected in BGAS, making these health supplements a good example for human exposure to a mixture of cyanobacterial toxins in a complex matrix. The discussion of this and other possible exposure scenarios, e.g. drinking water, contact during recreational activity, or consumption of contaminated food, can provide insight into the question of whether or not our current risk assessment schemes for cyanobacterial blooms and the toxins contained therein suffice for protection of human health.

Biofilms of As(III)-oxidising bacteria: formation and activity studies for bioremediation process development

The formation and activity of an As(III)-oxidising biofilm in a bioreactor, using pozzolana as bacterial growth support, was studied for the purpose of optimising fixed-bed bioreactors for bioremediation. After 60 days of continuous functioning with an As(III)-contaminated effluent, the active biofilm was found to be located mainly near the inflow rather than homogeneously distributed. Biofilm development by the CAsO1 bacterial consortium and by Thiomonas arsenivorans was then studied both on polystyrene microplates and on pozzolana. Extra-cellular polymeric substances (EPS) and yeast extract were found to enhance bacteria attachment, and yeast extract also appears to increase the kinetics of biofilm formation. Analysis of proteins, sugars, lipids and uronic acids indicate that sugars were the main EPS components. The specific As(III)-oxidase activity of T. arsenivorans was higher (by ninefold) for planktonic cells than for sessile ones and was induced by As(III). All the results suggest that the biofilm structure is a physical barrier decreasing As(III) access to sessile cells and thus to As(III)-oxidase activity induction. The efficiency of fixed-bed reactors for the bioremediation of arsenic-contaminated waters can be thus optimised by controlling different factors such as temperature and EPS addition and/or synthesis to increase biofilm density and activity.

Generation of a flat-top laser beam for gravitational wave detectors by means of a nonspherical Fabry-Perot resonator

We have tested a new kind of Fabry-Perot long-baseline optical resonator proposed to reduce the thermal noise sensitivity of gravitational wave interferometric detectors--the "mesa beam" cavity--whose flat top beam shape is achieved by means of an aspherical end mirror. We present the fundamental mode intensity pattern for this cavity and its distortion due to surface imperfections and tilt misalignments, and contrast the higher order mode patterns to the Gauss-Laguerre modes of a spherical mirror cavity. We discuss the effects of mirror tilts on cavity alignment and locking and present measurements of the mesa beam tilt sensitivity.

Cytomégalovirus néonatal et allaitement maternel chez le nouveau-né prématuré. Quelles propositions?

In France, screening for cytomegalovirus infection (CMV) during pregnancy is not recommended in routine. The transmission of CMV through breastmilk from mothers to preterm infants is frequent (15-20%). The frequency of neuro-sensorial handicap related to congenital CMV infection in very preterm infants is not well documented. We report the case of a female infant born at 30 weeks of gestation. At 15 days, she developed cholestatic jaundice. Urine cultures were positive for CMV. Diagnostic procedure showed no other cause for jaundice. At 40 days, the infant presented with hepato-splenomegaly, purpura and abnormal skin color related to a symptomatic, secondary CMV infection, probably transmitted through breastmilk. Ganciclovir was begun for 21 days. At 12 months, she presents with normal development. This observation raises questions about breastfeeding in very preterm infants. Unexplained prematurity could reflect recent infection or reactivation in the mother. Thus, because of the well-known risks of prematurity on one hand, and CMV infection on the other, we suggest that detection of CMV seropositive mothers should be considered before allowing breastfeeding. If the mother has serologic evidence of recent infection or reactivation, freezing breastmilk at -20 degrees C for 3 days may be an option in order to reduce virolactia, especially during early lactation. This may reduce the risk of postnatal vertical virus transmission with minimal logistical difficulties and without interrupting breastfeeding.

Left size distortion (hyperschematia) after right brain damage

OBJECTIVE

To quantitate a size distortion involving the side of space contralateral to the lesion (contralesional) in two right-brain-damaged patients.

METHODS

We studied two right-brain-damaged patients with lesions sparing the occipital lobe and a mild left neglect on target cancellation or line bisection. The lesions involved the temporoparietal region (Patient 1) and the basal ganglia and the insula (Patients 1 and 2). Patients were given drawing tasks and tasks requiring perceptual and visuomotor judgments of horizontal extent.

RESULTS

In drawing objects such as a daisy both from memory and by copying, patients exhibited a disproportionate enlargement of the left-hand side of objects and added more left-sided petals to the drawn daisy. This pathologic behavior persisted when the patients were blindfolded and was likely to reflect a perceptual, rather than premotor, size distortion. In a task requiring the perceptual matching of two rectangles, patients underestimated the left-sided stimulus. In a visuomotor task requiring the reproduction of the horizontal extent of a segment, patients exhibited a hyperextension, when a leftward movement was required.

CONCLUSIONS

We showed a disordered representation of extrapersonal space, possibly involving a contralesional relaxation of the spatial medium. The deficit does not arise at the level of retinotopic coordinate frames and is independent of unilateral spatial neglect.

High-sensitivity optical monitoring of a micromechanical resonator with a quantum-limited optomechanical sensor

We experimentally demonstrate the high-sensitivity optical monitoring of a micromechanical resonator and its cooling by active control. Coating a low-loss mirror upon the resonator, we have built an optomechanical sensor based on a very high-finesse cavity (30 000). We have measured the thermal noise of the resonator with a quantum-limited sensitivity at the 10(-19) m/sqrt[Hz] level, and cooled the resonator down to 5 K by a cold-damping technique. Applications of our setup range from quantum optics experiments to the experimental demonstration of the quantum ground state of a macroscopic mechanical resonator.

Functional anatomy of the therapeutic effects of prism adaptation on left neglect

OBJECTIVE

To investigate the anatomic substrates underlying the beneficial effect of prism adaptation in five patients with persistent left neglect following right stroke.

METHODS

In a functional imaging PET study, we used a covariation analysis to examine linear changes of regional cerebral blood flow over sessions as a function of left neglect improvement.

RESULTS

The network of significant brain regions associated with improvement of left neglect performance produced by prism adaptation involved the right cerebellum, the left thalamus, the left temporo-occipital cortex, the left medial temporal cortex, and the right posterior parietal cortex.

CONCLUSION

Our results suggest that the realignment of visuomotor coordinates is processed by the cerebellum and that low level sensorimotor adaptation actively modulates cerebral areas, albeit now relying on intact cerebellocerebral connections. Hence, our data support the hypothesis that the beneficial effect of prism adaptation on the clinical presentation of left neglect derives from modulation of cortical regions implicated in spatial cognition.

Ipsidirectional impairment of prism adaptation after unilateral lesion of anterior cerebellum

In a patient with damage of the left cerebellar cortex (SCA territory), the authors tested four combinations of exposure to optical shift (leftward prisms, right hand; rightward prisms, right hand; leftward prisms, left (ataxic) hand; rightward prisms, left (ataxic) hand). He adapted to rightward but not leftward prisms, independent of which hand was used during exposure. This suggests a role of anterior cerebellar cortex in the computation or compensation of ipsidirectional visual error.

Resistance pattern and assessment of phenicol agents' minimum inhibitory concentration in multiple drug resistant Chryseobacterium isolates from fish and aquatic habitats

AIMS

To assess the susceptibility of Chryseobacterium isolates of fish and aquatic habitats to antimicrobial compounds. Special attention was paid to the resistance to chloramphenicol and florfenicol, a phenicol derivative recently licensed for use in veterinary medicine and fish farming.

METHODS AND RESULTS

Sixty-seven Chryseobacterium spp. isolates and reference strains, originating mainly from different aquatic habitats, were tested using the disk-diffusion method. In addition, agar dilution was used for assessing minimum inhibitory concentration of chloramphenicol and florfenicol. In spite of (i) conditions that hampered properly standardized experiments and (ii) the heterogeneity of the isolates resulting in some aberrant values in diffusion, correlation between the two methods was confirmed. Most of the isolates exhibited considerable multiresistance to most antimicrobial drug families, and many were clearly resistant to phenicols. Molecular investigations conducted on 10 strains selected for high resistance to florfenicol did not establish the existence of floR or cmlA genes currently reported in the literature as responsible for florfenicol resistance. Nevertheless, when an efflux pump inhibitor, phenyl-arginin-beta-naphthylamide, was combined with diffusion tests, drug susceptibility to florfenicol was restored, suggesting that Chryseobacterium's resistance to this molecule is under the control of efflux mechanisms.

CONCLUSIONS

Constitutive multiresistance to antibiotics is common in chryseobacteria isolated from the aquatic environment. Although no gene related to the floR family could be detected, efflux mechanisms could partly support the resistance to phenicols.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results explain the difficulty of treatment and clearly reflect the properties previously reported in Chryseobacterium isolates of human origin. Because several species have been involved in opportunistic infections in humans, the possible role of aquatic organisms as a source of infection should be considered.

Évaluation d’une campagne de formation des médecins généralistes et des médecins du travail au dépistage du mélanome dans le Haut-Rhin

INTRODUCTION

Dermatologists frequently provide training for general practitioners, but such training is not systematic and evaluation is rare.

MATERIALS AND METHODS

A training campaign for general practitioners and occupational physicians in melanoma screening was carried out in the Haut-Rhin Department of France in 2004. The 630 general practitioners and 120 occupational physicians in this geographic department received repeated mail together with materials (posters and booklets) for their waiting rooms, and they were invited to attend medical training sessions. The sessions consisted of 10 photographs for initial evaluation, provision of epidemiological information, training in identification of subjects at risk and diagnosis of pigmented lesions, with a further 10 photographs for evaluation at the end. The 20 evaluation photographs were randomly selected for each session from 40 photographs comprising 18 cases of melanomas, 14 of nevi, 4 of basal cell carcinomas and 4 of seborrheic keratoses. At the end of each session, the physicians returned 2 anonymous questionnaires containing their overall assessment of the campaign (Q1) and their answers concerning the 20 evaluation photographs (proposed diagnosis and management strategy) (Q2). The questionnaires were then analyzed. The 40 evaluation photographs were also tested on 47 dermatologists.

RESULTS

Three hundred and fifty physicians - 278/630 general practitioners (44%) and 72/120 occupational physicians (60%) - attended 18 medical training sessions. Response levels for questionnaires Q1 and Q2 were 88% and 90% respectively. Almost all of the physicians involved considered the campaign to be warranted. At the end of the training sessions, 96% felt they were better equipped to identify subjects at risk for melanoma and 53% (58% of general practitioners and 39% of occupational physicians, p=0.03) felt they had greatly improved their ability to diagnose pigmented lesions. The median number of correct replies concerning the evaluation photographs increased from 6/10 to 7/10 between the initial evaluation photographs and the final evaluation photographs (p<0.0001), with no difference being seen between the general practitioners and occupational physicians. The median number of correct replies from the 47 dermatologists was 35/40 (8.75/10). The most striking improvement noted during the campaign concerned the ability to identify melanomas. The figure rose from an initial 59% at the start of the session (initial evaluation photographs) (versus 86% for the dermatologists) to 84% by the end of the session (final evaluation photographs) (p<0.0001). The management strategy proposed for photographs of melanoma (irrespective of the proposed diagnosis) was judged "appropriate" in 86% of cases at the start of the session versus 94% at the end of the session (p<0.001). Seborrheic keratosis was correctly identified in 43% of cases by the general practitioners/occupational physicians versus 75% by the dermatologists, and was confused with melanoma in 22% of cases by the general practitioners/occupational physicians versus 5% by the dermatologists. No improvement was seen during the training session in terms of the ability of the general practitioners/occupational physicians to correctly identify seborrheic keratosis. The majority of participants indicated their willingness to participate in the screening program and asked to receive information on melanoma on a regular basis.

DISCUSSION

This initial study shows the immediate impact of medical training sessions on general practitioners/occupational physicians to be important in terms of sensitization and moderate but significant in terms of improved diagnosis of pigmented lesions. The longer term impact, as well as the impact of the campaign on physicians not taking part in the medical training sessions, remains unknown. This study militates in favor of the involvement of general practitioners and occupational physicians in mass screening for melanoma in collaboration with dermatologists. The 2004 campaign in the Haut-Rhin Department also included information for the general public. The primary evaluation criterion of the campaign will be change in incidence of thick melanomas recorded by the departmental cancer registry.

Chronic stress reduces body fat content in both obesity-prone and obesity-resistant strains of mice

Unpredictable stressors have been used to assess the effect of stress on energy metabolism in obesity-prone (C57BL6J) and obesity-resistant (AJ) mice. Mice were exposed for 25 days to a stress protocol. Both strains of mice were divided into groups of control and stressed mice, which had access to either a high-fat or a high-carbohydrate diet. Twenty-four hours after the last session of stress, mice were sacrificed for blood and brain collections. Insulin, corticosterone, and glucose concentrations in plasma were measured, and expressions of corticotropin-releasing factor (CRF) in the paraventricular hypothalamic nucleus (PVH) and the central amygdala (CeA) were determined by in situ hybridization. Stressed mice in all groups had lower body fat contents than control mice, and all mice fed with the high-fat diet had heavier retroperitoneal and inguinal fat pads than mice fed with carbohydrate. CRF mRNA level in the CeA was lower in B6 mice than in AJ mice. Stressed mice had a lower expression of CRF in the CeA than control mice. In conclusion, chronic stress reduces body fat content in obesity-prone as well as in obesity-resistant mice.

Statistical list-mode image reconstruction for the high resolution research tomograph

We have investigated statistical list-mode reconstruction applicable to a depth-encoding high resolution research tomograph. An image non-negativity constraint has been employed in the reconstructions and is shown to effectively remove the overestimation bias introduced by the sinogram non-negativity constraint. We have furthermore implemented a convergent subsetized (CS) list-mode reconstruction algorithm, based on previous work (Hsiao et al 2002 Conf. Rec. SPIE Med. Imaging 4684 10-19; Hsiao et al 2002 Conf. Rec. IEEE Int. Symp. Biomed. Imaging 409-12) on convergent histogram OSEM reconstruction. We have demonstrated that the first step of the convergent algorithm is exactly equivalent (unlike the histogram-mode case) to the regular subsetized list-mode EM algorithm, while the second and final step takes the form of additive updates in image space. We have shown that in terms of contrast, noise as well as FWHM width behaviour, the CS algorithm is robust and does not result in limit cycles. A hybrid algorithm based on the ordinary and the convergent algorithms is also proposed, and is shown to combine the advantages of the two algorithms (i.e. it is able to reach a higher image quality in fewer iterations while maintaining the convergent behaviour), making the hybrid approach a good alternative to the ordinary subsetized list-mode EM algorithm.

Effects of Fe(II) and hydrogen peroxide interaction upon dissolving UO2 under geologic repository conditions

Iron redox cycling is supposed to be one of the major mechanisms that control the geochemical boundary conditions in the near field of a geologic repository for UO2 spent nuclear fuel. This work investigates the impact of reactions between hydrogen peroxide (H2O2) and iron (Fe2+/Fe3+) on UO2 dissolution. The reaction partners were contacted with UO2 in oxygen-free batch reactor tests. The interaction in absence of UO2 gives a stoichiometric redox reaction of Fe2+ and H2O2 when the reactants are present in equal concentration. Predomination of H202 results in its delayed catalytic decomposition. With UO2 present, its dissolution is controlled by either a slow mechanism (as typical for anoxic environments) or uranium peroxide precipitation, depending strongly on the reactant ratio. Uranium peroxide (UO4 x nH2O, m-studtite), detected on UO2 surfaces after exposure to H2O2, was not found on the surfaces exposed to solutions with stoichometric Fe(II)/ H2O2 ratios. This suggests that H2O2 was deactivated in redox reactions before a formation of UO4 took place. ESR measurements employing the spin trapping technique revealed only the DMPO-OH adduct within the first minutes after the reaction start (high initial concentrations of the OH radical); however, in the case of Fe(II) and H2O2 reacting at 10(-4) mol/L with UO2, dissolved oxygen and Fe2+ concentrations indicate the participation of further Fe intermediates and, therefore, Fenton redox activities.

Lactate is mainly fermented to butyrate by human intestinal microfloras but inter-individual variation is evident

AIM

To assess the role of lactate as a precursor for butyrate biosynthesis in human colonic microflora.

METHODS AND RESULTS

Three human faecal microfloras were incubated in vitro with media supplemented with 30 mmol l(-1) unenriched or 13C-enriched lactate. Lactate metabolism and short-chain fatty acid (SCFA) production were quantified. Lactate conversion to butyrate was investigated by gas chromatography-mass spectrometry and the pathways involved were identified by 13C nuclear magnetic resonance spectroscopy. All human faecal microfloras rapidly and completely fermented lactate, yielding approx. 19 mmol l(-1) total SCFAs. However, the SCFA composition varied markedly between microfloras. Butyrate was the main end-product for two microfloras but not for the third (60 and 61%vs 27% of the net concentration of SCFA produced respectively). The latter was typified by its ability to produce propionate as a major product (37%), and valerate (3%). 13C-Labelling showed that butyrate was produced through the acetyl-CoA pathway and that the three microfloras possessed significant differences in their metabolic pathways for lactate consumption.

CONCLUSIONS

In contrast to the ruminal microflora, the human intestinal microflora can utilize both d- and l-lactate as precursors for butyrate synthesis. Inter-individual variation is found.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study suggests that the butyrogenic capability of colonic prebiotics could be related to lactate availability. These findings will direct the development of selection strategies for the isolation of new butyrate-producing bacteria among the lactate-utilizing bacteria present in the human intestinal microfloras.

Preserved prism adaptation in bilateral optic ataxia: strategic versus adaptive reaction to prisms

To date the anatomical substrate(s) of prism adaptation remain(s) particularly debated, with two main candidates emerging from the literature: the posterior parietal cortex (PPC) and the cerebellum. The functional processes involved in the acquisition of the adaptive aftereffects also remain largely unknown. The main result shown here is that a patient with a bilateral optic ataxia can adapt to an optical deviation, which allows us to make a step forward on these two issues. First, it demonstrates that the corresponding part of the PPC is not a necessary substrate for prism adaptation. Second, since this patient exhibits deficit for fast visuo-motor guidance, it provides direct evidence for a dissociation between on-line visuo-motor control and visuo-motor plasticity. Since the intermanual transfer rate of adaptation is larger in this patient than in control subjects, the PPC may still have an influence on adaptation under normal conditions. We propose a model of the relative contribution of the PPC and the cerebellum during prism exposure, associating these two structures with the two interacting behavioural components of prism adaptation described by previous psychophysical experiments: the strategic component would be linked to the PPC and the adaptive component to the cerebellum. In this model, the strategic component enters in conflict with the development and the generalisation of the adaptive aftereffects. This idea is compatible with the fact that a lesion of the PPC increases the transfer rate and the generalisation of the adaptation, as is also observed in unilateral neglect.

Artériographie diagnostique par voie transradiale

Seventy five arteriographies were performed via the transradial route using 5F 130cm - long catheter. Prior to puncture the radial artery was evaluated with Allen test. Satisfying quality examinations were obtained for the thoracic aorta, selective carotid arteries examinations, infra renal aorta, pelvic and legs arteries. The major advantages obtained for the technique were the very low rate complication and technical failure. Transradial route for arteriography is a reasonable alternative approach to transfemoral or brachial arteriography for out patient management (peripheral angiography) in case in which transfemoral route is not feasible but also with patients with important haemorragic-risks.

Does action make the link between number and space representation? Visuo-manual adaptation improves number bisection in unilateral neglect

If the visual world is artificially shifted by only 10 degrees, people initially experience difficulty in directing their actions toward visual goals, but then rapidly compensate the visual distortion. The consequence of such adaptation can be measured as visual and proprioceptive aftereffects, as well as by performance on pointing tasks without visual feedback. Recent work has shown that more cognitive deficits can be improved following prism adaptation in patients with unilateral neglect. Here we show that a short visuo-manual adaptation to prisms improves performance on a mental number-bisection task recently shown to be impaired in unilateral neglect. The association previously found between space and number representation (the mental number line) may thus be grounded in common action principles. Our results suggest that visuo-motor plasticity functionally links parietal areas involved in space and number representation.

Prospective, randomized, parallel-group trial to evaluate the effects of lactulose and polyethylene glycol-4000 on colonic flora in chronic idiopathic constipation

BACKGROUND

Although lactulose and polyethylene glycol are osmotic laxatives widely used in the treatment of chronic constipation, no study has been conducted to compare their actions on the colonic bacterial ecosystem, which has an important influence on host health.

AIM

To assess the effects of lactulose and polyethylene glycol on the composition and metabolic indices of the faecal flora in patients with chronic idiopathic constipation.

METHODS

Sixty-five patients with chronic idiopathic constipation were included in this controlled, multi-centre, randomized, parallel-group study. Participants received lactulose (Duphalac) or polyethylene glycol-4000 (Forlax) powders for the first week at a fixed dosage at night (20 g/day); in the second week, patients were given the option to vary the dose according to efficacy and tolerance (10-30 g/day); for the last 2 weeks, treatment was administered at a fixed dosage based on the results of the second week (10-30 g/day). Stools were recovered for bacteriological analysis at days -1, 21 and 28.

RESULTS

Clinical efficacy and tolerance were similar with both treatments. In the lactulose group, an increase in faecal bifidobacteria counts (P = 0.04) and beta-galactosidase activity (P < 0.001) was observed from day -1 to day 28, whereas, in the polyethylene glycol group, there was a decrease in total short-chain fatty acids (P = 0.02), butyrate (P = 0.04), acetate (P = 0.02) and faecal bacterial mass (P = 0.001). No differences were observed in stools with regard to the following parameters: counts of Lactobacillus, clostridial spores, Bacteroides and enterobacteria, pH, biliary acids and neutral sterol concentrations.

CONCLUSIONS

Both lactulose and polyethylene glycol are efficacious and well tolerated. However, although lactulose can be considered as a pre-biotic in constipated patients, polyethylene glycol produces signs of decreased colonic fermentation in the stool.

Sensorimotor effects on central space representation: prism adaptation influences haptic and visual representations in normal subjects

Prism adaptation improves visual and haptic manifestations of left neglect, and can induce a small but reliable simulation of left visual neglect in normal individuals. Here, we present two experiments in which the effects of prism adaptation on the representation of space were explored. In Experiment 1, normal subjects were required to locate the centre of a haptically explored circle, before and after adaptation to leftward displacing prisms. In Experiment 2, a visual circle centring task was used. In both tasks, prism adaptation induced a significant rightward shift of performance. In addition, in both experiments, three classical measures of visuo-manual adaptation were taken: the visual shift, the proprioceptive shift and the total shift. The effects found on the haptic and visual tasks did not correlate with any of these measures. This suggests that the effects of prism adaptation on the circle centring tasks did not depend directly on the sensorimotor consequences of the adaptation. These results imply that prism adaptation can affect noetic levels of space representation in normal subjects, supporting the hypothesis that this low-level sensorimotor intervention can exert a bottom-up structuring influence on higher levels of cognitive integration.