Granulometric Analysis of the Exotic Sandstones in and around Moreh and Chandel, Chandel District, Manipur

Chaotic assemblage of conglomerate, gritstone, sandstone, shale, limestone, chert and ophiolitic derivatives occurs along the western contact of Nagaland-Manipur ophiolite belt in N-S to NNE-SSW trending direction. This assemblage is known as sedimentary melange and extends for about 200 km from north-east of Chokla in Nagaland to the south of Moreh in Manipur. Sandstones being the dominant litho-unit among the sedimentary mélange have been selected for the present study. These sandstones occur as floating bodies intermingling with both Disangs and ophiolite, hence the term exotic sandstone is used. Analysis of grain size data of these exotic sandstones in and around Moreh and Chandel, Chandel district reveals that all the samples show unimodal distribution. Cumulative curves suggest saltation and suspension are the major mode of transportation of these sediments. Mean values ranging from 1.40 ? to 3.29 ? suggest medium to very fine sand size. Standard deviation values (0.20 to 1.10) suggest that these sediments are very well sorted to moderately sorted and indicate fluctuating energy conditions during the time of deposition. The values of skewness range from -0.88 to 0.19 and 76.31% of the samples are negatively skewed, indicating high energy condition during the time of deposition of the sediments. Bivariate plots suggest that sediments were deposited both in fluvial and near shore environments. Discriminant function analysis reveals that exotic sandstones of the present study area were deposited under diverse condition

Theoretical analysis of acoustic stop bands in two-dimensional periodic scattering arrays

This paper presents a theoretical analysis of the recently reported observation of acoustic stop bands in two-dimensional scattering arrays (Robertson and Rudy, J. Acoust. Soc. Am. {\bf 104}, 694, 1998). A self-consistent wave scattering theory, incorporating all orders of multiple scattering, is used to obtain the wave transmission. The band structures for the regular arrays of cylinders are computed using the plane wave expansion method. The theoretical results compare favorably with the experimental data.Comment: 18 pages, 4 page

Acoustic Attenuation by Two-dimensional Arrays of Rigid Cylinders

In this Letter, we present a theoretical analysis of the acoustic transmission through two-dimensional arrays of straight rigid cylinders placed parallelly in the air. Both periodic and completely random arrangements of the cylinders are considered. The results for the sound attenuation through the periodic arrays are shown to be in a remarkable agreement with the reported experimental data. As the arrangement of the cylinders is randomized, the transmission is significantly reduced for a wider range of frequencies. For the periodic arrays, the acoustic band structures are computed by the plane-wave expansion method and are also shown to agree with previous results.Comment: 4 pages, 3 figure

Viscoelastic response of sonic band-gap materials

A brief report is presented on the effect of viscoelastic losses in a high density contrast sonic band-gap material of close-packed rubber spheres in air. The scattering properties of such a material are computed with an on-shell multiple scattering method, properties which are compared with the lossless case. The existence of an appreciable omnidirectional gap in the transmission spectrum, when losses are present, is also reported.Comment: 5 pages, 4 figures, submitted to PR

ESBL, MBL AND AMP C-β LACTAMASES PRODUCED BY SUPERBUGS: AN EMERGING THREAT TO CLINICAL THERAPEUTICS

Objectives: The present study was undertaken to determine the prevalence of multi drug resistant (MDR) and multiple β-lactamase producing Pseudomonas aeruginosa isolates in lower respiratory tract infection (LRTI) patients at a tertiary care hospital in India.Methods: A total of 80 consecutive, non-duplicate isolates of P. aeruginosa were studied for the presence of class A or B β-lactamase. Antibiotic susceptibility tests and PCR amplification of genes encoding class A (PER-1 and CTX-M 1, 2, 9) and class B β-lactamases (blaVIM-2, blaIMP-1 and blaSIM-1) were performed.Results: Out of 80 P. aeruginosa isolates, 65% (52/80) of the isolates were MDR with 34 being Metallo-β-lactamase (MBL) producers, 23 were extended spectrum β-lactamase (ESBL) producers and 21 were positive for AmpC production. The cross-class resistance rates to other antibiotics was significantly higher in class A and B β-lactamase producers than in non-producers (P<0.05 for fluoroquinolone, aztreonam, ceftazidime and meropenem). Combined disk test (CDT) for MBL highest sensitivity and specificity compared to PCR. Combined disk method (CDM) for ESBL co-related well with PCR (sensitivity and specificity).Conclusion: This study reports the validation of a simple and accurate MBL and ESBL detection method which can be easily integrated into the daily routine of a clinical laboratory.Â

Scattering of elastic waves by periodic arrays of spherical bodies

We develop a formalism for the calculation of the frequency band structure of a phononic crystal consisting of non-overlapping elastic spheres, characterized by Lam\'e coefficients which may be complex and frequency dependent, arranged periodically in a host medium with different mass density and Lam\'e coefficients. We view the crystal as a sequence of planes of spheres, parallel to and having the two dimensional periodicity of a given crystallographic plane, and obtain the complex band structure of the infinite crystal associated with this plane. The method allows one to calculate, also, the transmission, reflection, and absorption coefficients for an elastic wave (longitudinal or transverse) incident, at any angle, on a slab of the crystal of finite thickness. We demonstrate the efficiency of the method by applying it to a specific example.Comment: 19 pages, 5 figures, Phys. Rev. B (in press

First order antiferro-ferromagnetic transition in Fe49(Rh0.93Pd0.07)51 under simultaneous application of magnetic field and external pressure

The magnetic field-pressure-temperature (H-P-T) phase diagram for first order antiferromagnetic (AFM) to ferromagnetic (FM) transition in Fe49(Rh0.93Pd0.07)51 has been constructed using resistivity measurements under simultaneous application of magnetic field (up to 8 Tesla) and pressure (up to 20 kbar). Temperature dependence of resistivity ({\rho}-T) shows that with increasing pressure, the width of the transition and the extent of hysteresis decreases whereas with the application of magnetic field it increases. Consistent with existing literature the first order transition temperature (TN) increases with the application of external pressure (~ 7.3 K/ kbar) and decreases with magnetic field (~ - 12.8 K/Tesla). Exploiting these opposing trends, resistivity under simultaneous application of magnetic field and pressure is used to distinguish the relative effect of temperature, magnetic field and pressure on disorder broadened first order transition. For this a set of H and P values are chosen for which TN (H1, P1) = TN (H2, P2). Measurements for such combinations of H and P show that the temperature dependence of resistivity is similar i.e. the broadening (in temperature) of transition as well as extent of hysteresis remains independent of H and P. The transition width decreases exponentially with increasing temperature. Isothermal magnetoresistance measurement under various constant pressure show that even though the critical field required for AFM-FM transition depends on applied pressure, the hysteresis as well as transition width (in magnetic field) both remains independent of pressure, consistent with our conclusions drawn from {\rho}-T measurements.Comment: 10 pages, 6 figure

Broken time-reversal symmetry in cubic skutterudite-like superconductor Y3_3Ru4_4Ge13_{13}

The microscopic properties of superconducting cubic skutterudite-like material Y$_3$Ru$_4$Ge$_{13}$ are investigated using muon spin relaxation and rotation ($\mu$SR) measurements. Zero-field $\mu$SR measurements reveal the presence of a spontaneous internal field with a magnitude of $\approx$ 0.18~mT below the superconducting transition temperature, indicating broken time-reversal symmetry in the ground state. In line with previous experiments, transverse-field $\mu$SR measurements are consistent with a fully developed superconductivity gap in Y$_3$Ru$_4$Ge$_{13}$. Our observations point towards the relevance of electronic correlations beyond electron-phonon coupling as origin and indicate that spin-orbit coupling is likely not the key driving force behind the spontaneous breaking of time-reversal symmetry in this system.Comment: 7 pages, 3 figure