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With the aim of temperature diagnostic, femtosecond time-resolved CARS (coherent anti-Stokes Raman spectroscopy) is applied to probe H2 in H2–N2 mixtures. In a first part, a Lorentzian profile is used to model the femtosecond CARS response. A difference between the experimental broadening and the expected one is observed in the collision regime. The observed broadening increases strongly in an inhomogeneous way with respect to the perturber concentration. This is of considerable importance for temperature measurements. In a second part, we show that in the collision regime, this inhomogeneous broadening is due to the speed dependence of the collisional parameters and the memory effects of the radiator speed. A new modelization of the time-resolved CARS response taking into account the speed memory effects is presented and applied to the temperature diagnostic in H2–N2 mixtures. The numerical results are in good agreement with experiments. [ABSTRACT FROM AUTHOR]

Electronic band structures dictate the mechanical, optical and electrical properties of crystalline solids. Their experimental determination is therefore crucial for technological applications. Although the spectral distribution in energy bands is routinely measured by various techniques1, it is more difficult to access the topological properties of band structures such as the quantized Berry phase, γ, which is a gauge-invariant geometrical phase accumulated by the wavefunction along an adiabatic cycle2. In graphene, the quantized Berry phase γ = π accumulated by massless relativistic electrons along cyclotron orbits is evidenced by the anomalous quantum Hall effect4,5. It is usually thought that measuring the Berry phase requires the application of external electromagnetic fields to force the charged particles along closed trajectories3. Contradicting this belief, here we demonstrate that the Berry phase of graphene can be measured in the absence of any external magnetic field. We observe edge dislocations in oscillations of the charge density ρ (Friedel oscillations) that are formed at hydrogen atoms chemisorbed on graphene. Following Nye and Berry6 in describing these topological defects as phase singularities of complex fields, we show that the number of additional wavefronts in the dislocation is a real-space measure of the Berry phase of graphene. Because the electronic dispersion relation can also be determined from Friedel oscillations7, our study establishes the charge density as a powerful observable with which to determine both the dispersion relation and topological properties of wavefunctions. This could have profound consequences for the study of the band-structure topology of relativistic and gapped phases in solids. The Berry phase of graphene is measured in the absence of an applied magnetic field by observing dislocations in the Friedel oscillations formed at a hydrogen atom adsorbed on graphene. [ABSTRACT FROM AUTHOR]

Background: The few studies assessing long-term effects of educational interventions on antibiotic prescription have produced conflicting results.Objectives: Our aim was to assess the effects after 4.5 years of an interactive educational seminar designed for GPs and focused on antibiotic therapy in respiratory tract infections (RTIs). The seminar was expected to decrease antibiotic prescriptions for any diagnosis.Methods: We conducted a randomized controlled parallel-group trial in a Paris suburb (France), with GPs as the randomization unit and prescriptions as the analysis unit. The intervention occurred in September 2004 and the final assessment in March 2009. Among 203 randomized GPs, 168 completed the study, 70 in the intervention group and 98 in the control group. Intervention GPs were randomized to attending only a 2-day interactive educational seminar on evidence-based guidelines about managing RTIs or also 1 day of problem-solving training. The primary outcome was the percentage of change in the proportion of prescriptions containing an antibiotic for any diagnosis in 2009 versus 2004. An intention-to-treat sensitivity analysis was performed using multiple imputation.Results: After 4.5 years, absolute changes in the primary outcome measure were -1.1% (95% confidence interval: -2.2 to 0.0) in the intervention group and +1.4% (0.3-2.6) in the control group, yielding an adjusted between-group difference of -2.2% (-2.7 to -1.7; P < 0.001). Both intervention modalities had significant effects, and multiple imputation produced similar results.Conclusions: A single, standardized and interactive educational seminar targeting GPs significantly decreased antibiotic use for RTIs after 4.5 years. [ABSTRACT FROM AUTHOR]

The fundamental properties of valleys are recently attracting growing attention due to electrons in new and topical materials possessing this degree-of-freedom and recent proposals for valleytronics devices. In silicon MOSFETs, the interest has a longer history since the valley degree of freedom had been identified as a key parameter in the observation of the controversial "metallic behaviour" in two dimensions. However, while it has been recently demonstrated that lifting valley degeneracy can destroy the metallic behaviour, little is known about the role of intervalley scattering. Here, we show that the metallic behaviour can be observed in the presence of strong intervalley scattering in silicon on insulator (SOI) quantum wells. Analysis of the conductivity in terms of quantum corrections reveals that interactions are much stronger in SOI than in conventional MOSFETs, leading to the metallic behaviour despite the strong intervalley scattering. [ABSTRACT FROM AUTHOR]

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We examine the effect of an in-plane magnetic field on the resistance of a 2-dimensional electron system confined in a silicon quantum well when the Fermi energy is tuned through the upper valley-subband edge while the electrons are otherwise valley-polarized. In contrast to previous experiments on valley-degenerate systems which only showed positive magnetoresistance, when the Fermi energy is at or near the upper valley-subband edge, the magnetoresistance is found to show a distinct negative contribution which is interpreted as being due to spin polarization of the upper valley-subband. [ABSTRACT FROM AUTHOR]

Convection-enhanced delivery using carboplatin in brainstem glioma models was reported to prolong survival. Functional impairment is of additional importance to evaluate the value of local chemotherapy. We established a neurological scoring system for the rat brainstem glioma model. In 46 male Fisher rats stereotactically 105 F-98 cells were implanted at 1.4-mm lateral to midline and at the lambdoid suture using guided screws. Following 4 days local delivery was performed using AlzetTM pumps (1 μl/h over 7 days) with either vehicle (5% dextrose) or carboplatin via one or two cannulas, respectively. All rats were subsequently tested neurologically using a specified neurological score. In 38 animals survival time was recorded. Representative MR imaging were acquired in eight rats, respectively, at day 12 after implantation. HE staining was used to evaluate tumor extension. Neurological scoring showed significantly higher impairment in the high dose carboplatin group during the treatment period. Survival was significantly prolonged compared to control animals in the high dose carboplatin-one cannula group as well as in both low dose carboplatin groups (18.6 ± 3 versus 26.3 ± 9, 22.8 ± 2, 23.6 ± 2 days; p < 0.05). Overall neurological grading correlated with survival time. MR imaging showed a focal contrast enhancing mass in the pontine brainstem, which was less exaggerated after local chemotherapy. Histological slices visualized decreased cellular density in treatment animals versus controls. Local chemotherapy in the brainstem glioma model showed significant efficacy for histological changes and survival. Our neurological grading enables quantification of drug and tumor-related morbidity as an important factor for functional performance during therapy. [ABSTRACT FROM AUTHOR]

Technical aspects of local chemotherapy in inoperable brainstem gliomas by convection-enhanced delivery (CED) are still under experimental considerations. In this study, we characterize the feasibility of multiple cannula placements in the rat brainstem. In 38 male Fisher rats, up to three guided screws were positioned in burr holes paramedian at 2.5 mm anterior and posterior to as well as at the lambdoid suture. Using Alzet™ pumps (1 μl/h flow rate over 7 days) either vehicle (5% dextrose) or 0.1 mg carboplatin was delivered via one, two, or three cannulas, respectively. During cannula insertion, electrocardiogram and respiratory rate was monitored. All rats were subsequently evaluated neurologically for 8 days. For drug distribution in coronal sections, the brain tissue concentration of platinum was measured. HE staining was used to evaluate the local site of drug delivery. Heart and respiratory rate remained within normal range during surgical procedure. Neurological scoring showed only mild neurological impairment in the groups receiving two or three cannulas, which resolved after vehicle delivery. However, after carboplatin delivery, this deficit remained unchanged. Drug distribution was more homogeneous in the three cannula group. Histological slices visualized edematous changes at the sight of cannula placement. The unilateral application of up to three cannulas in the brainstem of rats for local drug delivery studies is feasible. The remaining neurological deficit in carboplatin-treated animals underlines the need of low toxicity drugs for CED in the brainstem. [ABSTRACT FROM AUTHOR]

We report a non-monotonic and strongly temperature dependent magneto-resistance observed in clean quantum point contacts. At the same time the conductance of the point contact varies linearly with temperature. This unexpected behavior may be related to electron-electron interactions. [ABSTRACT FROM AUTHOR]

In the present work we study the electron transport properties of small (≈ 100 nm) ring interferometers fabricated by the local anodic oxidation of a AlGaAs/GaAs heteroatructures containing 2D electron gas. Owing to the small size of the rings the Aharonov­Bohm (AB) oscillations in them can be observed at temperatures as high as 9 K. It has been found that the temperature dependence of AB oscillations amplitude in these rings is sensitive to the modification of the microscopic potential realization resulting from thermal recycling of the structure. [ABSTRACT FROM AUTHOR]

An experimental study of the two-, three-, and four-terminal resistance of a ballistic wire is carried out. The wire is fabricated on the basis of high-mobility 2D electron gas in an AlGaAs/GaAs heterojunction. Different behavior of mesoscopic fluctuations of multiterminal resistances is observed depending on the gate voltage and magnetic field. At B = 0.45 T, the four-terminal resistance drops almost to zero and features resembling a ballistic conductance quantization are observed. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

A submersible study of a fast spreading (12 cm yr) Mid-Ocean ridge segment (East Pacific Rise near 12°50′ N) led to the discovery of intense hydrothermal activity. Twenty four sites with active vents and sixty inactive hydrothermal deposits were found within a narrow graben averaging about 300 m in width along a 20 km long segment of the ridge crest. The graben is floored with fresh basaltic sheet flows including collapsed pits or lava lake structures. From both deep towed camera stations and manned submersible observations, it is estimated that the average spacing between the ridge axis hydrothermal deposits averaging in size 10-50 m in diameter lies between 100 to 200 m. The hydrothermal deposits found in the central graben are believed to have formed rapidly (on the order of a few decades). Detailed investigations of one active site have enabled us to witness the growth of an active chimney which increased its height by 40 cm in 5 days i.e. 8 cm per day. Extensive hydrothermal deposits were discovered on an off-axis seamount located 6 km East of the ridge axis. The hydrothermal deposits found on both the ridge axis and on the seamount are similar in composition and consist essentially of zinc, copper and iron mineral phases. Chemical studies conducted on the venting fluids (320°C) showed that the concentration of the dissolved major metal ions (Fe, Mn, and Zn) is about 0.10-0.13 gl. If we accept an average flow rate of 10ls based on visual observations the mass of metallic products spewing out from an active chimney must be about 100 kg per day. [ABSTRACT FROM AUTHOR]

Degradation of tetrachloroethene (perchloroethylene, PCE) was investigated by combining the metabolic abilities of anaerobic bacteria, capable of reductive dechlorination of PCE, with those of aerobic methanotrophic bacteria, capable of co-metabolic degradation of the less-chlorinated ethenes formed by reductive dechlorination of PCE. Anaerobic communities reductively dechlorinating PCE, trichloroethene (TCE) and dichloroethenes were enriched from various sources. The maximum rates of dechlorination observed for various chloroethenes in these batch enrichments were: PCE to TCE (341 μmol 1 day), TCE to cis-dichloroethene (159 μmol 1 day), cis-dichloroethene ethene to chloroethene (99 μmol 1 day) and trans-dichloroethene to chloroethene (22 μmol 1 day). A mixture of these enrichments was inoculated into an anoxic fixed-bed upflow column. In this colum PCE was converted mainly into cis-1,2-dichloroethene, small amounts of TCE and chloroethene, and chloride. Enrichments of aerobic methanotrophic bacteria were grown in an oxic fixed-bed downflow column. Less-chlorinated ethenes, formed in the anoxic column, were further metabolized in this oxic methanotrophic column. On the basis of analysis of chloride production and the disappearance of chlorinated ethenes it was demonstrated that complete degradation of PCE was possible by combining these two columns. Operation of the two-column system under various process conditions indicated that the sensitivity of the methanotrophic bacteria to chlorinated intermediates respresented the bottle-neck in the sequential anoxic/oxic degradation process of PCE. [ABSTRACT FROM AUTHOR]

bstract [ABSTRACT FROM AUTHOR]

We investigate the growth of the recently demonstrated composite material composed of vertically aligned carbon nanotubes capped by few graphene layers. We show that the carbon nanotubes grow epitaxially under the few graphene layers. By using a catalyst and gaseous carbon precursor different from those used originally we establish that such unconventional growth mode is not specific to a precise choice of catalyst-precursor couple. Furthermore, the composite can be grown using catalyst and temperatures compatible with complementary-metal-oxide-semiconductor processing (T<450 °C). [ABSTRACT FROM AUTHOR]

Presents the case of a woman who was admitted because of respiratory distress and hypoxia. Results of the physical examination; Description of a pulmonary thrombectomy performed on the patient; Incidence of tumor embolism among patients with carcinoma.

A letter to the editor is presented about delayed progressive visual loss.