ZnO based thermopower wave sources

Exothermic chemical reactions of nitrocellulose are coupled onto thermoelectric zinc oxide (ZnO) layers to generate self-propagating thermopower waves resulting in highly oscillatory voltage output of the order of 500 mV. The peak specific power obtained from ZnO based sources is approximately 0.5 kW kg(-1).     

The magnetic properties across the martensitic transition in the Co38Ni34Al28 alloy

The magnetic properties of the Co₃₈Ni₃₄Al₂₈ alloy have been studied. The alloy exhibits a first order austenite-martensite phase transition in the temperature region between 155 and 247 K. A strain of 0.07% is produced across this phase transition. The Arrott plots obtained from the isothermal magnetic field dependence of magnetization indicate the presence of spontaneous magnetization both in the austenite and martensite phases, confirming the ferromagnetic character of the alloy up to room temperature. The temperature dependence of the high field magnetization indicates the presence of spin wave excitations, spin wave excitation gap and spin wave-spin wave interactions in the martensite phase. The magnetic anisotropy energy constant for the Co₃₈Ni₃₄Al₂₈ alloy is estimated both with the help of the standard law of approach to saturation of magnetization, and also from the field dependence of magnetization using the field for technical saturation of magnetization. The temperature dependences of these energy terms are compared. The estimated values of the magnetic anisotropy constant seem to be in agreement with the magnitude of the spin wave excitation gap estimated from the temperature dependence of high field magnetization.     

An efficient TDMA-based variable interval multichannel MAC protocol for vehicular networks

Vehicular Adhoc NETworks (VANETs) are the key to the future of intelligent transportation systems. An efficient MAC protocol is of greater importance to meet the strict deadlines of safety related applications in VANETs. This work introduces a novel TDMA-based variable interval multichannel MAC protocol (TM-MAC) for VANETs. TM-MAC employs TDMA along with variable interval multichannel scheduling for providing a reliable and efficient broadcast service over a lossy wireless medium. TM-MAC reduces transmission collisions thus making Control CHannel (CCH) more reliable and provides high throughput over Service CHannel (SCH) via maximum channel utilization. The scheduling strategy ensures that vehicles are assigned a slot instantaneously. Moreover there is a reduction of almost 50 % in number of vehicles incurring merging collisions when compared with VeMAC (Omar et al. in IEEE Trans Mob Comput 12(9):1724–1736, 2013), an existing and recently proposed TDMA based MAC protocol. This reduction in merging collisions increased the packet delivery ratio by almost 25 % when compared with VeMAC. Extensive simulations which were done over a realistic city scenario connote the superiority of TM-MAC over existing schemes for a wide range of traffic conditions.     

Stability-indicating liquid chromatography method development and validation for impurity profiling of montelukast sodium in bulk drug and tablet dosage form

Montelukast sodium (MLS) is a leukotriene receptor antagonist drug used in the treatment of asthma, bronchospasm, allergic rhinitis and urticaria. A reversed-phase high performance liquid chromatography method was developed to separate, identify and quantitative determination of MLS and its eight known organic impurities in tablet dosage form using a C₁₈ column and mobile phases consisting of a gradient mixture of pH 2.5 phosphate buffer and acetonitrile. The stability-indicating character of the developed method was proven using stress testing (1 m HCl at 80°C/30 min, 1 m NaOH at 80°C/30 min, H₂O at 80°C/30 min, 3% H₂O₂ at 25°C/1 min, dry heat at 105°C/10 h and UV–vis light/4 days) and was validated for specificity, quantitation limit, linearity, precision, accuracy and robustness. For MLS and its eight known impurities, the quantitation limits, linearity and recoveries were 0.015–0.03 μg/ml, correlation coefficient > 0.997 (R² > 0.995) and 85.5–107.0%, respectively. The developed chromatographic method is suitable for impurity profiling and also for assay determination of MLS in bulk drugs and pharmaceutical formulations. The mass values (m/z) of newly formed degradation products (DP1 and DP2) of montelukast sodium were identified using liquid chromatography–mass spectrometry.     

Nonradiative Energy Transfer through Distributed Bands in Piezochemically Synthesized Cesium and Formamidinium Lead Halide Perovskites

Repeated absorption of emitted photons, also called photon recycling, in large crystals and thick films of perovskites leads to delayed photoluminescence (PL) and decrease of PL intensity. The role of distinct band gaps, which act as donors and acceptors of energy, and nonradiative energy transfer on such delayed, low intensity emission is yet to be rationalized. Here we report delayed emission by nonradiative energy transfer across a distribution of energy states in close-packed crystallites of cesium lead bromide CsPbBr₃, formamidinium lead bromide FAPbBr₃, or the mixed halide FAPb(BrI)₃ perovskite synthesized in the form of thick pellets by the piezochemical method. The PL lifetime of the bromide-rich domain in the mixed halide pellet is considerably decreased when compared with a pure FAPbBr₃ pellet. Here the domains with higher bromide composition act as the energy donor, whereas the iodide-rich domains are the acceptors. Time-resolved PL measurements of CsPbBr₃, FAPbBr₃, and the mixed halide FAPb(BrI)₃ perovskite pellets help us to clarify the role of nonradiative energy transfer on photon recycling.     

Synthesis of 9-Deoxynanaomycin,a Methyl Ester via 1,2-Ketone Transposition

The title compound, methyl trans 1-methyl-5,10-dioxo-3,4,5,10-tetrahydro-1H-naphthol[2,3-c] pyran-3-yl-acetate has been synthesised using the key intermediate, 1-(1,4-dimethoxy-2-naphthyl)-2-oxo-4-acetoxybutane, prepared through 1,2-ketone transposition of the 1-(1,4-dimethoxy-2-naphthyl)-4-acetoxy-1-butanone.     

Intracellularly grown gold nanoislands as SERS substrates for monitoring chromate,sulfate and nitrate localization sites in remediating bacteria biofilms by Raman chemical imaging

Understanding the chemical composition of biofilm matrices is vital in different fields of biology such as surgery, dental medicine, synthetic grafts and bioremediation. The knowledge of biofilm development, composition, active reduction sites and remediation efficacy will help in the development of effective solutions and evaluation of remediating approaches prior to implementation. Surface-enhanced Raman spectroscopy (SERS) based imaging is an invaluable tool to obtain an understanding of the remediating efficacy of microorganisms and its role in the formation of organic and inorganic compounds in biofilms. We demonstrate for the first time, the presence of chromate, sulfate, nitrate and reduced trivalent chromium in soil biofilms. In addition, we demonstrate that SERS imaging was able to validate two observations made by previous studies on chromate/sulfate and chromate/nitrate interactions in Shewanella oneidensis MR-1 biofilms. Additionally, we show a detailed Raman mapping based evidence of the existence of chromate–sulfate competition for cellular entry. Subsequently, we use Raman mapping to study the effect of nitrate on chromate reduction. The findings presented in this paper are among the first to report – detection of multiple metallic ions in bacterial biofilms using intracellular SERS substrates. Such a detailed characterization of biofilms using gold nanoislands based SERS mapping substrate can be extended to study cellular localization of other metallic ions and chemical species of biological and toxicological significance and their effect on reduction reactions in bacterial biofilms.     

Optical tweezer for micro and nano scale rheology of biomaterials

Since the first proposal and demonstration of an optical trap to hold micron sized particles by Ashkin in 1986, optical tweezer-based techniques for control and manipulation of particles has seen tremendous progress and enabled the exploration of the structure and dynamics of materials at the nano length scale. In biophysical applications, these techniques have enabled a range of activities from measurements of very small forces (at sub-pN levels) at operation within cells thus assisting in the elucidation of intracellular transport mechanisms, to obtaining elastic parameters of biomolecules. The techniques have helped in gaining insights on the viscoelastic properties at micro and nano length scales of a range of soft materials such as colloids, polymer melts, bio membranes etc.