A DFT study of substrate effect on the magnetism of V(001) surface

The effect of isoelectric transition metals (TM) Nb and Ta on the magnetism of the V(001) surface is investigated from first principles using Density functional theory (DFT), with the generalized gradient approximation (GGA). Ferromagnetic (FM) moments of 2.5 μ_B and 2.2 μ_B are obtained for the relaxed surface V monolayer (ML) in the V/Nb(001) and the V/Ta(001) systems respectively, at T = 0 K. The values are almost twice of those obtained with Mo and W of group VIB and can be attributed to the comparatively smaller bandwidths of the substrates Nb and Ta. Small induced magnetic moments are present on the Nb and Ta interfacial layers, which are coupled anti-ferromagnetically with the V ML.     

A 2‐Tyr‐1‐carboxylate Mononuclear Iron Center Forms the Active Site of a Paracoccus Dimethylformamidase

N,N‐dimethyl formamide (DMF) is an extensively used organic solvent but is also a potent pollutant. Certain bacterial species from genera such as Paracoccus, Pseudomonas, and Alcaligenes have evolved to use DMF as a sole carbon and nitrogen source for growth via degradation by a dimethylformamidase (DMFase). We show that DMFase from Paracoccus sp. strain DMF is a halophilic and thermostable enzyme comprising a multimeric complex of the α₂β₂ or (α₂β₂)₂ type. One of the three domains of the large subunit and the small subunit are hitherto undescribed protein folds of unknown evolutionary origin. The active site consists of a mononuclear iron coordinated by two Tyr side‐chain phenolates and one carboxylate from Glu. The Fe³⁺ ion in the active site catalyzes the hydrolytic cleavage of the amide bond in DMF. Kinetic characterization reveals that the enzyme shows cooperativity between subunits, and mutagenesis and structural data provide clues to the catalytic mechanism.     

Developments in quantum information processing by nuclear magnetic resonance: Use of quadrupolar and dipolar couplings

Use of dipolar and quadrupolar couplings for quantum information processing (QIP) by nuclear magnetic resonance (NMR) is described. In these cases, instead of the individual spins being qubits, the 2 ⁿ energy levels of the spin-system can be treated as an n-qubit system. It is demonstrated that QIP in such systems can be carried out using transition-selective pulses, in CH₃CN, ¹³CH₃CN, ⁷Li (I=3/2) and ¹³³Cs (I=7/2), oriented in liquid crystals yielding 2 and 3 qubit systems. Creation of pseudopure states, implementation of logic gates and arithmetic operations (half-adder and subtractor) have been carried out in these systems using transition-selective pulses.     

Functionalized SWNT/polymer nanocomposites for dramatic property improvement

In this paper, we present results for polymer nanocomposites of poly‐ (methyl methacrylate) (PMMA) and amide‐functionalized SWNTs. The results demonstrate that even at very low loadings, 1 wt % (0.5 vol %), the mechanical and electrical properties are significantly improved. The improvement over PMMA properties exceeds the theoretical bounds for composites with the same volume fraction loading of randomly oriented, straight, individually dispersed nanotubes. The modeling and experimental results thus suggest that the nanotube bundles are well dispersed in the polymer matrix, that the functionalization significantly improves interaction with polymer, and that the interphase formed has improved mechanical properties over that of the matrix material. Loss modulus results indicate a significant difference between functionalized and nonfunctionalized tubes in the composite. Functionalized tubes result in a composite in which relaxation mechanisms are shifted by 30 °C from that of the matrix material, indicating extensive interphase regions and absence of PMMA with bulk properties. Unfunctionalized composites demonstrate a broadening of relaxation modes, but still retain the signature of bulk PMMA properties. These data suggest a morphological difference with a discrete interphase layer in unfunctionalized composites and a fully transformed matrix in the case of functionalization. This difference is consistent with electrical and mechanical property data. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2269–2279, 2005     

Estimating energy consumption of transport modes in India using DEA and application to energy and environmental policy

Energy is consumed both by passenger and freight traffic, and it is generally not possible to apportion energy consumption exclusively to either of the traffic without making restrictive assumptions on the energy consumption norms of vehicles. The use of data envelopment analysis (DEA) has been suggested earlier in the literature for comparing energy efficiencies without requiring any such restrictive assumptions. In this paper, the applicability of DEA is further extended to estimate energy consumption of rail and/or road transport that would result in a pre-specified DEA efficiency. Using this new approach, effects of capturing some modal split in favour of rail transport on future energy consumption and emissions of carbon dioxide are presented in the paper via a scenario analysis. It is shown that if rail could capture 50% modal share in the years 2005–2006 and 2020–2021, it would save nearly 35% energy consumption and emissions compared to the situation when existing patterns of modal split are allowed to continue without policy intervention.     

Optimization and validation of RP-HPLC-UV method with solid-phase extraction for determination of buparvaquone in human and rabbit plasma: application to pharmacokinetic study

A simple, sensitive and specific reversed-phase high-performance liquid chromatographic method with UV detection at 251 nm was developed for quantitation of buparvaquone (BPQ) in human and rabbit plasma. The method utilizes 250 microL of plasma and sample preparation involves protein precipitation followed by solid-phase extraction. The method was validated on a C18 column with mobile phase consisting of ammonium acetate buffer (0.02 m, pH 3.0) and acetonitrile in the ratio of 18:82 (v/v) at a flow rate of 1.1 mL/min. The calibration curves were linear (correlation coefficient>or=0.998) in the selected range. The method is specific and sensitive with limit of quantitation of 50 ng/mL for BPQ. The validated method was found to be accurate and precise in the working calibration range. Stability studies were carried out at different storage conditions and BPQ was found to be stable. Partial validation studies were carried out using rabbit plasma and intra- and inter-day precision and accuracy were within 7%. This method is simple, reliable and can be routinely used for preclinical pharmacokinetic studies for BPQ.     

Measurement of carbon-proton dipolar couplings in liquid crystals using DAPT

Dipolar couplings provide valuable information on order and dynamics in liquid crystals. For measuring heteronuclear dipolar couplings in oriented systems, a new separated local field experiment is presented here. The method is based on the dipolar assisted polarization transfer (DAPT) pulse sequence proposed recently (Chem. Phys. Lett. 2007, 439, 407) for transfer of polarization between two spins I and S. DAPT utilizes the evolution of magnetization of the I and S spins under two blocks of phase shifted BLEW-12 pulses on the I spin separated by a 90 degree pulse on the S spin. Compared to the rotating frame techniques based on Hartmann-Hahn match, this approach is easy to implement and is independent of any matching conditions. DAPT can be utilized either as a proton encoded local field (PELF) technique or as a separated local field (SLF) technique, which means that the heteronuclear dipolar coupling can be obtained by following either the evolution of the abundant spin like proton (PELF) or that of the rare spin such as carbon (SLF). We have demonstrated the use of DAPT both as a PELF and as a SLF technique on an oriented liquid crystalline sample at room temperature and also have compared its performance with PISEMA. We have also incorporated modifications to the original DAPT pulse sequence for (i) improving its sensitivity and (ii) removing carrier offset dependence.     

Structural and Electronic Properties of Two-Dimensional Materials: A Machine-Learning-Guided Prediction

The growing number of studies and interest in two-dimensional (2D) materials has not yet resulted in a wide range of material applications. This is a result of difficulties in getting the properties, which are often determined through numerical experiments or through first-principles predictions, both of which require lots of time and resources. Here we provide a general machine learning (ML) model that works incredibly well as a predictor for a variety of electronic and structural properties such as band gap, fermi level, work function, total energy and area of unit cell for a wide range of 2D materials derived from the Computational 2D Materials Database (C2DB). Our predicted model for classification of samples works extraordinarily well and gives an accuracy of around 99 %. We are able to successfully decrease the number of studied features by employing a strict permutation-based feature selection method along with the sure independence screening and sparsifying operator (SISSO), which further supports the design recommendations for the identification of novel 2D materials with the desired properties.     

o-Fluoranil chemistry: Diels-Alder versus hetero-Diels-Alder cycloaddition

The title quinone undergoes [4 + 2] cycloadditions in two ways, Diels-Alder on the ring and hetero-Diels-Alder by attack at the oxygens. The latter mode of reaction is strongly favored thermodynamically, but there is a kinetic bias favoring the normal Diels-Alder addition that often prevails, especially with cycloaddends that are not electron-rich.