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Spin-Noise-Detected Two-Dimensional Nuclear Magnetic Resonance at Triple Sensitivity
No full textA major breakthrough in speed and sensitivity of 2D spin-noise-detected NMR is achieved owing to a new acquisition and processing scheme called double block usage (DBU) that utilizes each recorded noise block in two independent cross-correlations. The mixing, evolution, and acquisition periods are repeated head-to-tail without any recovery delays and well-known building blocks of multidimensional NMR (constant-time evolution and quadrature detection in the indirect dimension as well as pulsed field gradients) provide further enhancement and artifact suppression. Modified timing of the receiver electronics eliminates spurious random excitation. We achieve a threefold sensitivity increase over the original snHMQC (spin-noise-detected heteronuclear multiple quantum correlation) experiment (K. Chandra etal., J. Phys. Chem. Lett. 2013, 4, 3853) and demonstrate the feasibility of spin-noise-detected long-range correlation
Metal-Free S-Arylation of Cysteine Using Arenediazonium Salts
No full textA mild chemoselective method for S-arylation of cysteine has been developed in an open-flask procedure under metal-free conditions using arenediazonium salts in methanol
Modeling of a hybrid electric heavy duty vehicle to assess energy recovery using a thermoelectric generator
No full textConventional internal combustion engines exhibit efficiency in the range of 30%-40%. A significant portion of the remaining energy is dissipated as exhaust heat, some of which can be recovered using thermoelectric generators to reduce fuel consumption and CO2 emissions. The current study evaluates the benefits of using thermoelectric electric generators in hybrid electric vehicles over a prescribed drive-cycle. Specifically, a hybrid electric bus was first modeled over a realistic urban drive-cycle. Engine operating parameters such as torque and speed were extracted and provided as inputs to an engine simulation model. A virtual thermoelectric generator was then modeled using the Matlab/Simulink architecture to evaluate the quantity of energy that can be recovered based on inputs from the engine simulation model. Simulations were carried out to accurately assess the amount of fuel savings achieved due to the use of the thermoelectric generators system. From the analysis, it was observed that a fuel saving of 7.2% and 6.5% can be achieved with the use of Skutterudite and Silicon Germanium-based thermoelectric generator systems, respectively. It was also observed that the additional weight of the thermoelectric generator system had a negligible effect on the fuel consumption. (C) 2018 Elsevier Ltd. All rights reserved
Solomon W. Golomb-Mathematician, Engineer, and Pioneer
No full textIn this paper, we present some fundamental concepts and theoretical advances attributable to Solomon Golomb, together with the history and applications of this paper to communications, coding, and cryptography, along with some long-standing conjectures. Examples include the first engineering problem relating to feedback shift-register sequences that Sol Golomb was asked to solve in the mid-1950s. This paper covers m-sequences and Golomb's three randomness postulates, the cross-correlation of m-sequences, the exp-Golomb code, the Golomb ruler, Costas arrays, Golomb invariants, polyominoes, the distribution of prime numbers, and irreducible polynomials
Ferrocene conjugated copper(II) complexes of terpyridine and traditional Chinese medicine (TCM) anticancer ligands showing selective toxicity towards cancer cells
No full textSix novel mixed-ligand copper(II) complexes, namely, Cu(R-tpy)(L)]NO3 (1-6), where R-tpy is 4-phenyl-2,2:6,2-terpyridine (Ph-tpy; 1-3) and 4-ferrocenyl-2,2:6,2-terpyridine (Fc-tpy; 4-6), L is the bidentate O,O donor monoanion of plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone; plum in 1, 4), chrysin (5,7-dihydroxyflavone; chry in 2, 5) and curcumin (bis(4-hydroxy-3-methoxyphenyl)-1,6-diene-3,5-dione; curc in 3, 6) have been synthesized and characterized and their in vitro cytotoxicity against cancer cells is evaluated. The energy optimized structures and the frontier orbitals of the complexes have been obtained from the DFT calculations. Complexes 4-6 with a conjugated ferrocenyl moiety and TCM anticancer ligands, namely, plum (in 4), chry (in 5) and curc (in 6) showed potent cytotoxicity giving respective IC50 values of 1.2M, 0.62M and 0.21M in HeLa and 2.0M and 1.0M and 0.34M in MCF-7 cancer cells while being much less toxic to MCF-10A normal cells (IC50: 8.3-17.1M). In contrast, complexes 1-3 with a conjugated phenyl moiety were appreciably less toxic to HeLa cells with respective IC50 values of 10.4M, 8.1M and 5.5M when compared with their ferrocenyl analogues 4-6. Mechanistic studies using Hoechst staining and Annexin-V-FITC assays on cancer cells revealed an apoptotic pathway of cell death induced by the complexes. Fluorescence imaging study showed that complex 6 having curcumin as ligand localized primarily in the mitochondria of HeLa cells. Thus, we demonstrate in this study that ferrocene conjugation to copper(II) complexes of TCM anticancer ligands significantly increases the selectivity and cytotoxicity of the resulting complexes towards cancer cells over normal cells
Synthesis and electrochemical performance of Li2VxMn1-xO3 positive electrode for lithium batteries
No full textLithium excess manganese oxide, namely, Li2MnO3 is under investigations to improve its electrochemical performance as the next generation high capacity electrode material. Partial substitution of Mn by another metal is one of the ways to influence the properties of Li2MnO3. In the present study, vanadium is used to partially substitute Mn in various ratios. Li2VxMn1-xO3 (x = 0.1, 0.2, 0.3 and 0.4) samples are prepared by sol-gel method using stoichiometric ratios weights of Mn(CH3COO)(2)center dot 4H(2)O, Li2CO3 and NH4VO3. The crystalline phases are identified by X-ray diffraction. The particles morphology is studied with a scanning electron microscope. Furthermore, impedance measurements (EIS) are applied using frequency range between 10(6) and 10(-2) Hz. The optimum EIS is obtained with for the Li2V0.3Mn0.7O3 cell. Cyclic voltammetric measurements are carried out for the lithium manganate materials between 0.01 and 4.5 V versus Li+ with scan rate 0.1 mV s(-1). Also, galvanostatic charging and discharging cycling of the cells are achieved with the same potentials windows using charging and discharging current intensity of 10 mA g(-1) between 1.5 and 4.5 V versus Li+. It is observed that Li/Li2V0.3Mn0.7O3 cell has higher specific discharge capacity, 227 mAh g(-1) rather than the other cells
Spin-Noise-Detected Two-Dimensional Nuclear Magnetic Resonance at Triple Sensitivity
No full textA major breakthrough in speed and sensitivity of 2D spin-noise-detected NMR is achieved owing to a new acquisition and processing scheme called double block usage (DBU) that utilizes each recorded noise block in two independent cross-correlations. The mixing, evolution, and acquisition periods are repeated head-to-tail without any recovery delays and well-known building blocks of multidimensional NMR (constant-time evolution and quadrature detection in the indirect dimension as well as pulsed field gradients) provide further enhancement and artifact suppression. Modified timing of the receiver electronics eliminates spurious random excitation. We achieve a threefold sensitivity increase over the original snHMQC (spin-noise-detected heteronuclear multiple quantum correlation) experiment (K. Chandra etal., J. Phys. Chem. Lett. 2013, 4, 3853) and demonstrate the feasibility of spin-noise-detected long-range correlation
Observation of power-law behavior in temperature dependent conductivity of multiwall carbon nanotube/polystyrene composites
No full textFor last two decades, a pronounced temperature dependence of electrical conductivity (sigma) in the multiwall carbon nanotube (MWCNT) - based polymer composite (even above the percolation threshold) has been widely reported; the conduction mechanism has been understood by employing conventional models, namely variable range hopping and fluctuation induced tunneling. Herein, we report on the observation of a weak temperature dependence of sigma in the MWCNT/polystyrene composites above percolation threshold (0.7-7 wt %) at temperatures down to 1.4 K, with a conductivity ratio smaller than 3. The low temperature conductivity data follow power-law exhibiting two slope behavior, with exponent values beta(1) similar to 0.10-0.14 (at T > 5 K) and beta(2) similar to 0.23-0.36 (at T < 5 K). The observation of weak temperature dependence of sigma is attributed to high aspect ratio (more than 4000), achievement of high degree of dispersion, and excellent electrical properties of MWCNT as well as optimized composite processing. Further, all the samples exhibit negative magnetoresistance which can be explained within the framework of weak localization model. (C) 2018 Elsevier B.V. All rights reserved
Temperature-dependent layer breathing modes in two-dimensional materials
No full textRelative out-of-plane displacements of the constituent layers of two-dimensional materials give rise to unique low-frequency breathing modes. By computing the height-height correlation functions from molecular dynamics simulations, we show that the layer breathing modes (LBMs) can be mapped consistently to vibrations of a simple linear chain model. Our calculated thickness dependence of LBM frequencies for few-layer (FL) graphene and molybdenum disulfide (MoS2) are in excellent agreement with available experiments. Our results show a redshift of LBM frequency with an increase in temperature, which is a direct consequence of anharmonicities present in the interlayer interaction. We also predict the thickness and temperature dependence of LBM frequencies for FL hexagonal boron nitride. Our Rapid Communication provides a simple and efficient way to probe the interlayer interaction for layered materials and their heterostructures with the inclusion of anharmonic effects
Multistress Aging Studies on Polymeric Insulators
No full textPolymeric insulators are emerging as popular outdoor insulation for high voltage applications. However, environmental stresses along with prolonged electric discharges cause degradation to the promising properties of polymeric insulators. In present work, an attempt has been made to fabricate the experimental facility, study the multiple stresses (humidity, temperature, UV and electric stress) on HTV and LSR silicone based rubber insulators (SIR) to evaluate long-term performance under different climatic conditions. Leakage current waveforms were regularly monitored over the experimental duration of 1000 hours. Fourier transform infrared (FTIR) spectroscopy is utilized to assess the surface hydroxylation phenomenon observed on aged SIR. Salt layer is detected on all aged samples and it is found to govern the spray pattern on aged samples during wettability Class (WC) measurement. Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDAX) and Thermo-Gravimetric Analysis (TGA) are employed to analyze the elemental composition and thermal stability of SIR after aging. X-ray Diffraction (XRD) analysis is performed on fresh and aged samples to detect the structural changes and loss of ATH fillers before and after the experimentation. Also, the consequence of multistress aging of the tensile strength on SIR is evaluated