Vibrational-mechanical properties of the highly-mismatched Cd1-xBexTe semiconductor alloy: experiment and ab initio calculations.

The emerging CdTe-BeTe semiconductor alloy that exhibits a dramatic mismatch in bond covalency and bond stiffness clarifying its vibrational-mechanical properties is used as a benchmark to test the limits of the percolation model (PM) worked out to explain the complex Raman spectra of the related but less contrasted Zn1-xBex-chalcogenides. The test is done by way of experiment ([Formula: see text]), combining Raman scattering with X-ray diffraction at high pressure, and ab initio calculations ([Formula: see text] ~ 0-0.5; [Formula: see text]~1). The (macroscopic) bulk modulus [Formula: see text] drops below the CdTe value on minor Be incorporation, at variance with a linear [Formula: see text] versus [Formula: see text] increase predicted ab initio, thus hinting at large anharmonic effects in the real crystal. Yet, no anomaly occurs at the (microscopic) bond scale as the regular bimodal PM-type Raman signal predicted ab initio for Be-Te in minority ([Formula: see text]~0, 0.5) is barely detected experimentally. At large Be content ([Formula: see text]~1), the same bimodal signal relaxes all the way down to inversion, an unprecedented case. However, specific pressure dependencies of the regular ([Formula: see text]~0, 0.5) and inverted ([Formula: see text]~1) Be-Te Raman doublets are in line with the predictions of the PM. Hence, the PM applies as such to Cd1-xBexTe without further refinement, albeit in a "relaxed" form. This enhances the model's validity as a generic descriptor of phonons in alloys.

Gut microbiota composition during a 12-week intervention with delayed-release dimethyl fumarate in multiple sclerosis - a pilot trial.

INTRODUCTION: Patients with multiple sclerosis may have a distinct gut microbiota profile. Delayed-release dimethyl fumarate is an orally administered drug for relapsing-remitting multiple sclerosis, which has been associated with gastrointestinal side-effects in some patients. OBJECTIVES: The purpose of this study was to determine if dimethyl fumarate alters the abundance and diversity of commensal gut bacteria, and if these changes are associated with gastrointestinal side-effects. METHODS: Thirty-six patients with relapsing-remitting multiple sclerosis received either dimethyl fumarate (n = 27) or an injectable multiple sclerosis disease-modifying therapy (glatiramer acetate or interferons, n = 9) for 12 weeks. Stool samples were collected at baseline, two and 12 weeks. We included 165 healthy individuals as controls. RESULTS: At baseline, 16 microbial genera were altered in multiple sclerosis patients compared with healthy controls. In the dimethyl fumarate-treated patients (n = 21) we observed a trend of reduced Actinobacteria (p = 0.03, QFDR = 0.24) at two weeks, mainly driven by Bifidobacterium (p = 0.06, QFDR = 0.69). At 12 weeks, we observed an increased abundance of Firmicutes (p = 0.02, QFDR = 0.09), mostly driven by Faecalibacterium (p = 0.01, QFDR = 0.48). CONCLUSIONS: This pilot study did not detect a major effect of dimethyl fumarate on the gut microbiota composition, but we observed a trend towards normalization of the low abundance of butyrate-producing Faecalibacterium after 12 weeks treatment. The study was underpowered to link microbiota to gastrointestinal symptoms.

Defect-induced ultimately fast volume phonon-polaritons in the wurtzite Zn0.74Mg0.26Se mixed crystal.

Volume-phonon-polaritons (VPP's) propagating at a light-in-vacuum-like speed are identified in the wurtzite-type Zn0.74Mg0.26Se mixed crystal by near-forward Raman scattering. Their detection is selective to both the laser energy and the laser polarization, depending on whether the ordinary (n0) or extraordinary (ne) refractive index is addressed. Yet, no significant linear birefringence (n0 [Formula: see text] ne) is observed by ellipsometry. The current access to ultrafast VPP's is attributed to the quasi-resonant Raman probing of an anomalous dispersion of n0 due to impurity levels created deep in the optical band gap by oriented structural defects. The resonance conditions are evidenced by a dramatic enhancement of the Raman signals due to the polar modes. Hence, this work reveals a capacity for the lattice defects' engineering to "accelerate" the VPP's of a mixed crystal up to light-in-vacuum-like speeds. This is attractive for ultrafast signal processing in the terahertz range. On the fundamental side we provide an insight into the VPP's created by alloying ultimately close to the center of the Brillouin zone.

Pressure-induced phonon freezing in the ZnSeS II-VI mixed crystal: phonon-polaritons and ab initio calculations.

Near-forward Raman scattering combined with ab initio phonon and bond length calculations is used to study the 'phonon-polariton' transverse optical modes (with mixed electrical-mechanical character) of the II-VI ZnSe1-x S x mixed crystal under pressure. The goal of the study is to determine the pressure dependence of the poorly-resolved percolation-type Zn-S Raman doublet of the three oscillator [1 × (Zn-Se), 2 × (Zn-S)] ZnSe0.68S0.32 mixed crystal, which exhibits a phase transition at approximately the same pressure as its two end compounds (~14 GPa, zincblende → rocksalt), as determined by high-pressure x-ray diffraction. We find that the intensity of the lower Zn-S sub-mode of ZnSe0.68S0.32, due to Zn-S bonds vibrating in their own (S-like) environment, decreases under pressure (Raman scattering), whereas its frequency progressively converges onto that of the upper Zn-S sub-mode, due to Zn-S vibrations in the foreign (Se-like) environment (ab initio calculations). Ultimately, only the latter sub-mode survives. A similar 'phonon freezing' was earlier evidenced with the well-resolved percolation-type Be-Se doublet of Zn1-x Be x Se (Pradhan et al 2010 Phys. Rev. B 81 115207), that exhibits a large contrast in the pressure-induced structural transitions of its end compounds. We deduce that the above collapse/convergence process is intrinsic to the percolation doublet of a short bond under pressure, at least in a ZnSe-based mixed crystal, and not due to any pressure-induced structural transition.

Microstructure and optical dispersion characterization of nanocomposite sol-gel TiO2-SiO2 thin films with different compositions.

Nanocomposite TiO2-SiO2 thin films with different compositions (from 0 to 100 mol% TiO2) were deposited by sol-gel dip-coating method on silicon substrate. Crystal structure, chemical bonding configuration, composition and morphology evolutions with composition were followed by Raman scattering, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy respectively. The refractive index and the extinction coefficient were derived in a broad band wavelength (250-900 nm) from spectroscopic ellipsometry data with high accuracy and correlated with composition and microstructure. Results showed an anatase structure for 100% TiO2 with a grain size in 6-10nm range. Whereas, the inclusion of SiO2 enlarges the optical band gap and suppresses the grain growth up to 4 nm in size. High TiO2 dispersion in SiO2 matrix was observed for all mixed materials. The refractive index (at λ=600 nm) increases linearly with composition from 1.48 (in 100% SiO2) to 2.22 (in 100% TiO2) leading to lower dense material, its dispersion being discussed in terms of the Wemple-DiDomenico single oscillator model. Hence, the optical parameters, such optical dispersion energies E0 and Ed, the average oscillators, strength S0 and wavelength λ0 and the ratio of the carrier concentration to the effective mass N/m(∗) have been derived. The analysis revealed a strong dependence on composition and structure. The optical response was also investigated in term of complex optical conductivity (σ) and both volume and surface energy loss functions (VELF and SELF).

Diphenyl diselenide and ascorbic acid changes deposition of selenium and ascorbic acid in liver and brain of mice.

Sodium selenite (Na2SeO3) is the selenium form used in the composition of dietary supplements, and diphenyl diselenide (PhSe)2 is an important intermediate in organic synthesis, which increases the risk of human exposure to this chemical in the workplace. These compounds have been reported to inhibit the cerebral and hepatic aminolevulinic acid dehydratase (ALA-D) in vitro, and now we show that ascorbic acid can reverse some alterations caused by in vivo selenium exposure, but not ALA-D inhibition. The effect of Na2SeO3 or (PhSe)2 and ascorbic acid on selenium distribution, total non-protein thiol, ascorbic acid content (liver and brain) and haemoglobin was also examined. Mice were exposed to 250 micromol/kg (PhSe)2, or 18.75 micromol/kg Na2SeO3 subcutaneously, and to ascorbic acid, twice a day, 1 mmol/kg intraperitonially, for 10 days. Hepatic ALA-D of mice treated with (PhSe)2 was inhibited about 58% and similar results were observed in the animals that received ascorbic acid supplementation (P<0.01, for (PhSe)2-treated and (PhSe)2+ascorbic acid-treated mice). The haemoglobin content decreased after treatment with (PhSe)2 (P<0.01). However, the haemoglobin content of the (PhSe)2+ascorbic acid group was significantly higher than in the (PhSe)2-treated mice (P<0.05), and similar to control (P>0.10). Ascorbic acid treatment decreased significantly the hepatic and cerebral deposition of Se in (PhSe)2-exposed mice (P<0.01). Hepatic non-protein thiol content was not changed by treatment with (PhSe)2, ascorbic acid or (PhSe)2+ascorbic acid. Hepatic content of ascorbic acid was twice that in mice that received (PhSe)2, independent of ascorbic acid treatment (P<0.001). The results of this study suggest that vitamin C may have a protective role in organodiselenide intoxication.

Intellectual deficits in first-episode schizophrenia: evidence for progressive deterioration.

The developmental processes leading to neuropsychological deficits in schizophrenia are poorly understood. Both early developmental defects and subsequent deterioration may occur. Intelligence test profiles are often used to estimate premorbid ability and deterioration from prior levels of functioning. These characteristics were assessed in samples of first-episode (n = 51) and chronic (n = 50) schizophrenic patients. Although the groups showed few differences on tests to estimate premorbid intellectual ability, the chronic group performed worse on measures considered sensitive to deterioration. Dextral (right-handed) patients tended to have better performance; this effect was marked in the first-episode sample, especially on verbal tests. Male patients showed more evidence of deterioration than female patients. Subgroups differing in the time course of premorbid social dysfunction also differed in intelligence test profiles, suggesting that estimates of social and cognitive deterioration may have concurrent validity. The results support the hypothesis that patients differ in the course of cognitive decline and suggest that deterioration of function may follow the onset of overt psychosis in some patients. Prospective longitudinal studies of first-episode schizophrenic patients could directly test this hypothesis.

Antipsychotic medication effects on neuropsychological functions.

The investigator of antipsychotic drug effects on neuropsychological functions faces a range of conceptual, methodological, and technical obstacles. Some of these hurdles are pointed out in a brief review of existing literature, and a more detailed consideration of instrumentation issues is presented. The need for hypothesis-driven assessment strategies is highlighted. Interpretive difficulties are posed by the polyfactorial nature of the most widely used neuropsychological tests, and emphasis is placed on the use and development of methods that enable isolation of specific neuropsychological constructs. Examples of this strategy are drawn from ongoing work in the Neuropsychology Unit of the Clinical Research Center for the Study of Schizophrenia at Hillside Hospital, where hypotheses about the behavioral site of action of dopamine agonists and antagonists are used to guide the construction of novel computerized tests.

Benefits and prognoses following 10 years of a fluoride mouthrinsing program.

This paper is based upon the mean annual amounts of fillings (filled surfaces) and the DMFS among 6/7- to 15/16-year-old children. Each age group comprised about 450 children. Cross-sectional recordings were available prior to the start of a caries-preventive program based on 2-weekly fluoride rinses. Cross-sectional and longitudinal DMFS recordings were different during the 10 years of observation. This indicates benefits exceeding the present 70% reduction in need for fillings and 50% improved caries prevalence. The ratio fillings needed for giving the DMFS score among 13- to 14-year-old children was found to improve from 1.60 to 1.16. Based on the cumulative amounts of fillings and the ratio of fillings/DMFS, a DMFS of 15 may be expected in 4 years among children 15-16 years old. This caries prevalence is not markedly different from DMFS recordings among Scandinavian children living in fluoride areas.

An approach to objective assessment of caries prophylactic measures in a dental health program.

In a retrospective survey the mean number of intact proximal surfaces on the first molars of 13-year-old children was found to increase from 2.6 to 4.8 following 7 years of a preventive program with fortnightly fluoride mouthrinsings (0.2% NaF). This improvement was significant and corresponded to a reduction of the totally filled surfaces from 30.0 to 16.6. Caries on the proximal surfaces on the first molars was assessed from bite-wing radiographs. Judged from interexaminer comparisons, the number of filled surfaces was a reliable parameter of the caries prevalence in 13-year-old children. In a group of 54 children aged 13 who participated in the preventive program, the caries experience on the proximal surfaces of the first molars was significantly associated with the total DMFS.