Vibro-acoustic response and sound transmission loss analysis of functionally graded plates

This paper presents analytical studies on the vibro-acoustic and sound transmission loss characteristics of functionally graded material (FGM) plates using a simple first-order shear deformation theory. The material properties of the plate are assumed to vary according to power law distribution of the constituent materials in terms of volume fraction. The sound radiation due to sinusoidally varying point load, uniformly distributed load and obliquely incident sound wave is computed by solving the Rayleigh integral with a primitive numerical scheme. Displacement, velocity, acceleration, radiated sound power level, radiated sound pressure level and radiation efficiency of FGM plate for varying power law index are examined. The sound transmission loss of the FGM plate for several incidence angles and varying power law index is studied in detail. It has been found that, for the plate being considered, the sound power level increases monotonically with increase in power law index at lower frequency range (0–500 Hz) and a non-monotonic trend is appeared towards higher frequencies for both point and distributed force excitations. Increased vibration and acoustic response is observed for ceramic-rich FGM plate at higher frequency band; whereas a similar trend is seen for metal-rich FGM plate at lower frequency band. The dBA values are found to be decreasing with increase in power law index. The radiation efficiency of ceramic-rich FGM plate is noticed to be higher than that of metal and metal-rich FGM plates. The transmission loss below the first resonance frequency is high for ceramic-rich FGM plate and low for metal-rich FGM plate and further depends on the specific material property. The study has found that increased transmission loss can be achieved at higher frequencies with metal-rich FGM plates.     

Enantioselective synthesis of (S)-3,7-dimethyl-2-oxo-6-octene-1,3-diol: a Colorado potato beetle pheromone

The recent identification of a male-produced aggregation pheromone [(S)-3,7-dimethyl-2-oxo-6-octene-1,3-diol, (S)-CPB] offers a new tool for Colorado potato beetle (CPB) management. We developed a novel synthetic approach to produce CPB pheromone in seven steps and 46.54% overall yield. Grignard reaction, oxidation, and stereoselective methylation using organometallic reagent are the key steps in the commercially viable total synthesis, generating CPB pheromone in 98.6% enantiomeric purity and gram quantity.     

A convenient synthesis of 1,3,4-thiadiazole and 1,3,4-oxadiazole based peptidomimetics employing diacylhydrazines derived from amino acids

Synthesis of novel orthogonally protected 1,3,4-thiadiazole and 1,3,4-oxadiazole tethered dipeptide mimetics is described. Both the heterocycles are prepared via a set of diacylhydrazines derived from amino acids. 1,3,4-Thiadiazoles are synthesized by dehydrosulfurization using Lawesson’s reagent while 1,3,4-oxadiazoles are obtained by EDC mediated cyclodehydration.     

Binder melt: Quantification using SEM/EDS and its effects on composite solid propellant combustion

The present study reports the development of a novel technique to quantify binder melt on the surface of the propellant. Non-aluminized AP-HTPB propellants of 86% particulate loading are used to illustrate the technique. Elemental maps of unburnt and extinguished propellant surface are obtained using EDS (Energy Dispersive Spectroscopy). Overlap between the elements is identified and the elemental maps are processed to calculate AP and binder area exposed in unburnt and extinguished samples. The AP area exposed is found to be around 72.3% and 63.3% for unburnt and extinguished samples, respectively, indicating a reduction in AP exposed area with extinguished samples. This has been attributed to the binder melt discussed in literature but never quantified. Simulations have been carried out to analyze and understand the effects of this binder melt. A random packing algorithm is used to simulate propellant packs. Also, a methodology to account for binder melt layer is introduced and is used to capture AP exposed areas. Effect of binder melt in propellants with different solid loading and varying particle size is discussed. It is shown that fine AP particles are more prone to being covered by binder melt than the coarse AP particles. A possible explanation to the behavior of plateau burning propellants observed in literature has been provided through this analysis.     

The Hanle effect with partial frequency redistribution. Construction of a frequency-dependent polarization matrix and numerical solution by a PALI method

The polarized approximate lambda iteration (PALI) technique developed for the weak field Hanle effect relies on the decomposition of the Stokes parameters I, Q and U into six cylindrically symmetrical components. It has been applied to complete and partial frequency redistribution with redistribution matrices in which frequency redistribution is decoupled from scattering polarization. For partial frequency redistribution, the decoupling is obtained by an adequate decomposition of the frequency space into several domains. By angle-averaging frequency-dependent terms in the exact weak field Hanle redistribution matrix for a normal Zeeman triplet, we construct a redistribution matrix with coupling between frequency redistribution and polarization and no domain decomposition. The coupling is contained in generalized frequency redistribution functions that depend on the magnetic field. The redistribution matrix is expanded in the Landi Degl’Innocenti spherical tensors for polarimetry and the Stokes parameters are decomposed into cylindrically symmetrical components. A PALI method is set up for the calculation of these components. The Stokes parameters are calculated for different simple atmospheric models. The positive Q direction corresponds to the linear polarization perpendicular to the solar limb. It is shown that the frequency space decomposition may induce large errors on Stokes U in the transition region between line core and line wings but can safely be used for Stokes I and Q, the errors staying less than 1% at all the frequencies.     

Calculation of spin-wave energy and the mean value of Hamiltonian in a noncollinear magnetic sublattice structure by the method of Green's functions

The contribution of this work is the extension of Green's function formalism to the case of noncollinear, canted, 6-sublattice magnetic structure. The external magnetic field was considered. The selfconsistent procedure for calculation of renormalized spin-wave energies and the mean value of the Hamiltonian was discussed on the basis of both Tyablikov's and Callen's decoupling approximations and it was shown that the use of Callen's decoupling requires a preliminary solution of the problem on the basis of simpler decoupling. The equations are analogous to the Callen's equation but the temperature dependent factor has a more general form and instead of an explicit equation for energy there is an implicit equation.     

Noncollinear magnetic structure in a random system of densely packed hard spheres

For an amorphous model system consisting of a random set of 100 identical hard sphere densely packed in a cube with periodical boundary conditions the energies of spiral magnetic structures are investigated. It is shown for a simple model with exponentially decaying antiferromagnetic interaction that a spiral structure may exist displaying a minimum energy. The wavevector of the spiral minimizing the interaction energy depends on the range of interaction: for the short range one the pitch of the spiral is twice as high as that for the longer range of interactions The calculated energies are compared with the interaction energies in s.c., f.c.c., and b.c.c. lattices. It is found that the energy gain in the topologically random system with respect to the magnetically disordered state may be higher than that corresponding to the antiferromagnetic arrangement in a crystal.One of the authors (S. K.) thanks Dr. J. L. Finney for a valuable discussion concerning the computer generation of the random set of hard spheres.     

Effect of jet plasma on T98G human brain cancer cells

Nonthermal plasma (an ionized gas) is emerging as a novel tool for the treatment of living tissues for biological and medical purposes. In this study we describe the effects of a nonthermal air jet plasma on the T98G brain cancer cell line. The results of this study reveal that the jet plasma inhibits brain cancer cell growth efficiently with the loss of clongenicity in the cells. The main goal of this study is to induce cell death in T98G cancer cells by the toxic effect of jet plasma.     

Synthesis of the C38–C54 spiroketal segment of halichondrin B

Stereoselective synthesis of the C38–C54 segment of a marine metabolite halichondrin B comprising KLM and N rings with a C44 spiroketal including 10 chiral centers is described. The salient features of the synthesis are Carreira’s addition, Sharpless asymmetric dihydroxylation and double alkylation of TosMIC strategy and double vinyl coupling reactions.     

Enhanced stability of G-quadruplexes from conformationally constrained aep-PNA backbone

Nucleic (DNA) acids having contiguous stretch of G sequence form quadruplex structure, which is very critical to control cell division. Recently the existence of G-quadruplex in RNA is also reported in presence of monovalent metal ion. PNA is a promising DNA analogue which binds strongly to DNA to form PNA:DNA duplex or PNA(2):DNA triplex. PNA also forms quadruplexes such G-quadruplex and i-motif in G and C-rich sequences respectively. aep-PNA containing a prolyl ring is one of several PNA analogues that provide rigidity and chirality in backbone and has binding affinity to natural DNA which is higher than that of PNA. Here we examine the ability of aep-PNA-G to form a quadruplex by UV, CD and mass spectroscopic techniques.