Evaluation of true interlamellar spacing from microstructural observations

A method for evaluating true interlamellar spacing from micrographs is proposed for a multidomained lamellar structure. The microstructure of these materials is assumed to be composed of many domains with the lamellae aligned roughly parallel to each other within each domain and with the domains themselves randomly oriented relative to one another. An explicit expression for the distribution of apparent interlamellar spacing is derived assuming that the distribution of the true interlamellar spacing is Gaussian. The average interlamellar spacing is close to the peak interlamellar spacing observed in the distribution. The theoretical distributions are compared with experimental ones obtained by analyzing micrographs of PbTe–Sb2Te3 lamellar composites

Lattice thermal conductivity of self-assembled PbTe-Sb_2Te_3 composites with nanometer lamellae

In the system of PbTe and Sb_2Te_3, a metastable compound Pb_2Sb_6Te_(11) appears by solidification processing. It has been reported that this compound is decomposed into the two immiscible thermoelectric materials forming nanosized lamellar structure by heat treatments. The fraction transformed and the inter-lamellar spacing was systematically investigated. In this work, the thermal conductivities and the electrical resistivities have been measured as functions of annealing time through the transformation and the coarsening processes to clarify the effect of the fraction transformed and the inter-lamellar spacing. The thermal conductivity of Pb_2Sb_6Te_(11) is lower than that after the decomposition. The lattice part of the thermal conductivity of PbTe/Sb_2Te_3 lamellar samples decreases with decreasing inter-lamellar spacing. This is considered to be due to the coarsening of the microstructure

A Three Dimensional Lattice of Ion Traps

We propose an ion trap configuration such that individual traps can be stacked together in a three dimensional simple cubic arrangement. The isolated trap as well as the extended array of ion traps are characterized for different locations in the lattice, illustrating the robustness of the lattice of traps concept. Ease in the addressing of ions at each lattice site, individually or simultaneously, makes this system naturally suitable for a number of experiments. Application of this trap to precision spectroscopy, quantum information processing and the study of few particle interacting system are discussed.Comment: 4 pages, 4 Figures. Fig 1 appears as a composite of 1a, 1b, 1c and 1d. Fig 2 appears as a composite of 2a, 2b and 2

On stably free modules over affine algebras

We prove that stably free modules of rank d-1 over a smooth affine algebra of dimension d over an algebraically closed field k are free, provided (d-1)! is nonzero in k.Comment: Final version. To appear in Publ. Math. IHE

Dynamic crossover scaling in polymer solutions

The crossover region in the phase diagram of polymer solutions, in the regime above the overlap concentration, is explored by Brownian Dynamics simulations, to map out the universal crossover scaling functions for the gyration radius and the single-chain diffusion constant. Scaling considerations, our simulation results, and recently reported data on the polymer contribution to the viscosity obtained from rheological measurements on DNA systems, support the assumption that there are simple relations between these functions, such that they can be inferred from one another.Comment: 4 pages, 6 figures, 1 Table. Revised version to appear in Physical Review Letters. Includes supplemental material

Phonon density of states and heat capacity of La_(3−x)Te_4

The phonon density of states (DOS) of La_(3−x)Te_4 compounds (x=0.0,0.18,0.32) was measured at 300, 520, and 780 K, using inelastic neutron scattering. A significant stiffening of the phonon DOS and a large broadening of features were observed upon introduction of vacancies on La sites (increasing x). Heat-capacity measurements were performed at temperatures 1.85 ≤ T ≤ 1200 K and were analyzed to quantify the contributions of phonons and electrons. The Debye temperature and the electronic coefficient of heat capacity determined from these measurements are consistent with the neutron-scattering results, and with previously reported first-principles calculations. Our results indicate that La vacancies in La_(3−x)Te_4 strongly scatter phonons and this source of scattering appears to be independent of temperature. The stiffening of the phonon DOS induced by the introduction of vacancies is explained in terms of the electronic structure and the change in bonding character. The temperature dependence of the phonon DOS is captured satisfactorily by the quasiharmonic approximation

An invariant in shock clustering and Burgers turbulence

1-D scalar conservation laws with convex flux and Markov initial data are now known to yield a completely integrable Hamiltonian system. In this article, we rederive the analogue of Loitsiansky's invariant in hydrodynamic turbulence from the perspective of integrable systems. Other relevant physical notions such as energy dissipation and spectrum are also discussed.Comment: 11 pages, no figures; v2: corrections mad

Clinical profile and outcome of patients with meningoencephalitis in a tertiary care hospital

Background: Encephalitis is an important cause of morbidity, mortality, and permanent neurologic sequelae globally. Causes are diverse and include viral and non-viral infections. In the emergency setting differentiating the bacterial from other causes such as viral, fungal, tubercular, toxic or autoimmune causes is extremely difficult. Although plenty of literature is available on meningitis, the clinic-etiological profile and outcome with meningoencephalitis remains not that well studied, except for in paediatric population. Methods: The present prospective observational study included 75 patients who presented with acute encephalitis syndrome in tertiary care hospital, Bengaluru. All patients were subjected to complete clinical evaluation and appropriate investigations to study the etiology, clinical profile and outcome in them. Results: Among 75 patients, majority of them were <60 years constituting about 73.2%, mean age being 49.14 years with female preponderance. 30 (40%) patients had viral meningoencephalitis where aetiology was confirmed in 15 patients, remaining were presumed to be of viral aetiology. 12 (16%) had tubercular meningitis and 8 (10.6%) had bacterial meningitis followed by cryptococcal meningitis 7 (9.3%). In about 18 (24%) patients, aetiology was not identified and were treated based on syndromic approach. The most common presentation was fever and altered sensorium. Thrombocytopenia was common among viral and bacterial aetiologies and those in unspecified etiological group. Mortality was highest among cryptococcal meningitis (71.4%) followed by tubercular (66.7%) and bacterial meningitis (62.5%). Conclusions: A large number of number of cases where aetiology cannot be identified maybe benefited by a syndromic approach and better diagnostic modalities

The influence of heat treatment on the microstructural, mechanical and corrosion behaviour of cold sprayed SS 316L coatings

The present study evaluates the response of cold sprayed SS 316L coatings on mild steel substrate to aqueous corrosion in a 0.1 N HNO3 solution as determined using polarization tests. The corrosion behaviour of the SS 316L coating was studied not only in the as-coated condition, but also after heat treatment at 400, 800 and 1,100 °C. Heat treatment reduced the porosity, improved inter-splat bonding, increased the elastic modulus and more importantly increased the corrosion resistance of the cold sprayed SS 316L coating

Genetic characterization of Vibrio cholerae strains by inter simple sequence repeat-PCR

The utility of inter simple sequence repeat-PCR (ISSR-PCR) assay in the characterization and elucidation of the phylogenetic relationship between the pathogenic and nonpathogenic isolates of Vibrio cholerae is demonstrated. A total of 45 V. cholerae strains including 15 O1 El Tor, nine O139 and 21 non-O1/non-O139 strains were analyzed using eight ISSR primers. These primers, which are essentially simple sequence repeats (SSR) with additional nonrepeat bases at the 5' or 3' end, amplify genomic regions interspersed between closely spaced SSRs. Neighbor-joining analysis showed that the strains belonging to the same serogroup clustered together with the exception of one O1 and two O139 strains. The absence of pathogenicity islands in these strains, as confirmed by PCR, suggested their non-O1/non-O139 origin. Thus the ISSR-PCR-based phylogeny was consistent with the classification of V. cholerae based on serological methods. A finer resolution of the clustering of the toxinogenic O1 El Tor and toxinogenic O139 subtypes was obtained by ISSR-PCR analysis as compared with the Enterobacterial Repetitive Intergenic Consensus sequences-based PCR analysis for the same set of strains. Thus, it is proposed that ISSR-PCR is an efficient tool in phylogenetic classification of prokaryotic genomes in general and diagnostic genotyping of microbial pathogens in particular