Thermal Equation of State of Cubic Silicon Carbide at High Pressures.

We have performed in situ X-ray diffraction measurements of cubic silicon carbide (SiC) with a zinc-blende crystal structure (B3) at high pressures and temperatures using multi-anvil apparatus. The ambient volume inferred from the compression curves is smaller than that of the starting material. Using the 3rd-order Birch-Murnaghan equation of state and the Mie-Grüneisen-Debye model, we have determined the thermoelastic parameters of the B3-SiC to be K0=228±3 GPa, K0',=4.4±0.4, q=0.27±0.37, where K0, K0' and q are the isothermal bulk modulus, its pressure derivative and logarithmic volume dependence of the Grüneisen parameter, respectively. Using the 3rd-order Birch-Murnaghan EOS with the thermal expansion coefficient, the thermoelastic parameters have been found as K0=221±3 GPa, K0',=5.2±0.4, α0=0.90±0.02 ⋅ 10-5 ⋅ K-1, where α0 is the thermal expansion coefficient at room pressure and temperature. We have determined that paired B3-SiC - MgO calibrants can be used to estimate pressure and temperature simultaneously in ultrahigh-pressure experiments up to 60 GPa.

Assessing perceived stress in medical personnel: in search of an appropriate scale for the bengali population.

BACKGROUND: The occurrence of stress and stress related anxiety and depression in medical personnel are being increasingly reported in literature. The perceived stress scale (PSS) is the most widely used psychological instrument for measuring the perception of stress. It is needed to assess perceived stress in our population using appropriately translated version of PSS. The objectives of study were to prepare a Bengali version of PSS-10 and to establish its psychometric properties in the study population. MATERIALS AND METHODS: The study was conducted in a teaching hospital among medical students and interns (N=37). The translated Bengali version and the original English version of PSS-10 were separately handed over to the individual subjects. The scores were compared across different subgroups and psychometric properties of the translated version were assessed using SPSS 16. RESULTS: Internal consistency of PSS English (α=0.79) and Bengali (α=0.80) was satisfactory. Intra-rater reliability was adequate (κ>0.5) for most of the items, but showed an inadequate value (κ<0.5) for four items on the scale. After deleting these four items from the Bengali version, a new six-item PSS in Bengali was derived that showed good internal consistency (α=0.699). CONCLUSION: This new version needs to be validated in a larger study population. Perceived stress score using PSS-10 was considerably high in our study population, although there was no significant difference between the subgroups (male/female, intern/student).

Caenorhabditis elegans mutants resistant to attachment of Yersinia biofilms.

The detailed composition and structure of the Caenorhabditis elegans surface are unknown. Previous genetic studies used antibody or lectin binding to identify srf genes that play roles in surface determination. Infection by Microbacterium nematophilum identified bus (bacterially unswollen) genes that also affect surface characteristics. We report that biofilms produced by Yersinia pestis and Y. pseudotuberculosis, which bind the C. elegans surface predominantly on the head, can be used to identify additional surface-determining genes. A screen for C. elegans mutants with a biofilm absent on the head (Bah) phenotype identified three novel genes: bah-1, bah-2, and bah-3. The bah-1 and bah-2 mutants have slightly fragile cuticles but are neither Srf nor Bus, suggesting that they are specific for surface components involved in biofilm attachment. A bah-3 mutant has normal cuticle integrity, but shows a stage-specific Srf phenotype. The screen produced alleles of five known surface genes: srf-2, srf-3, bus-4, bus-12, and bus-17. For the X-linked bus-17, a paternal effect was observed in biofilm assays.