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111.
Igor Dubenko Tapas Samanta Arjun Kumar Pathak Alexandr Kazakov Valerii Prudnikov Shane Stadler Alexander Granovsky Arcady Zhukov Naushad Ali 《Journal of magnetism and magnetic materials》2012
The studies of magnetocaloric properties, phase transitions, and phenomena related to magnetic heterogeneity in the vicinity of the martensitic transition (MT) in Ni–Mn–In and Ni–Mn–Ga off-stoichiometric Heusler alloys are summarized. The crystal structure, magnetocaloric effect (MCE), and magnetotransport properties were studied for the following alloys: Ni50Mn50−xInx, Ni50−xCoxMn35In15, Ni50Mn35−xCoxIn15, Ni50Mn35In14Z (Z=Al, Ge), Ni50Mn35In15−xSix, Ni50−xCoxMn25+yGa25−y, and Ni50–xCoxMn32−yFeyGa18. It was found that the magnetic entropy change, ΔS, associated with the inverse MCE in the vicinity of the temperature of the magneto-structural transition, TM, persists in a range of (125-5) J/(kg K) for a magnetic field change ΔH=5 T. The corresponding temperature varies with composition from 143 to 400 K. The MT in Ni50Mn50−xInx (x=13.5) results in a transition between two paramagnetic states. Associated with the paramagnetic austenite-paramagnetic martensite transition ΔS=24 J/(kg K) was detected for ΔH=5 T at T=350 K. The variation in composition of Ni2MnGa can drastically change the magnetic state of the martensitic phase below and in the vicinity of TM. The presence of the martensitic phase with magnetic moment much smaller than that in the austenitic phase above TM leads to the large inverse MCE in the Ni42Co8Mn32−yFeyGa18 system. The adiabatic change of temperature (ΔTad) in the vicinity of TC and TM of Ni50Mn35In15 and Ni50Mn35In14Z (Z=Al, Ge) was found to be ΔTad=−2 K and 2 K for ΔH=1.8 T, respectively. It was observed that |ΔTad|≈1 K for ΔH=1 T for both types of transitions. The results on resistivity, magnetoresistance, Hall resistivity in some In-based alloys are discussed. 相似文献
112.
113.
Dr. Joy Debnath Prof. Swagata Dasgupta Prof. Tanmaya Pathak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(6):1618-1627
Ribonuclease A (RNase A) serves as a convenient model enzyme in the identification and development of inhibitors of proteins that are members of the ribonuclease superfamily. This is principally because the biological activity of these proteins, such as angiogenin, is linked to their catalytic ribonucleolytic activity. In an attempt to inhibit the biological activity of angiogenin, which involves new blood vessel formation, we employed different dinucleosides with varied non‐natural backbones. These compounds were synthesized by coupling aminonucleosides with dicarboxylic acids and amino‐ and carboxynucleosides with an amino acid. These molecules show competitive inhibition with inhibition constant (Ki) values of (59±3) and (155±5) μM for RNase A. The compounds were also found to inhibit angiogenin in a competitive fashion with corresponding Ki values in the micromolar range. The presence of an additional polar group attached to the backbone of dinucleosides was found to be responsible for the tight binding with both proteins. The specificity of different ribonucleolytic subsites were found to be altered because of the incorporation of a non‐natural backbone in between the two nucleosidic moieties. In spite of the replacement of the phosphate group by non‐natural linkers, these molecules were found to selectively interact with the ribonucleolytic site residues of angiogenin, whereas the cell binding site and nuclear translocation site residues remain unperturbed. Docked conformations of the synthesized compounds with RNase A and angiogenin suggest a binding preference for the thymine–adenine pair over the thymine–thymine pair. 相似文献
114.
An acid-catalyzed hydroarylation reaction of vinyl indoles is reported, which tolerates a wide range of heterocycles as the exogenous nucleophile such as indoles, pyrroles, and indolizines. The method rapidly accesses the biologically relevant bisindolylmethane scaffold in good to excellent yields. Evaluation of the biological activity of several synthesized analogues reveals cytotoxic activity against and selectivity for the MCF-7 breast cancer cell line. 相似文献
115.
Atul Kumar C.P. Paul A.K. Pathak P. Bhargava L.M. Kukreja 《Optics & Laser Technology》2012,44(3):555-565
We simulated the temperature distribution and single track geometry in Laser Rapid Manufacturing (LRM) of metal structures using two dimensional FEM with a finer modeling approach. This approach involved the calculation of excessive enthalpies above melting point for all nodal points in the process domain and using those for the computation of local track height at every node along the track width on the substrate. Laser power, laser beam size with its spatial profile, scan speed, powder feed rate and powder stream diameter with its flow distribution were taken as user-defined input parameters to simulate the single track geometry during LRM. The simulated results were experimentally verified. The percentage errors in simulated and corresponding experimental track heights along the normalized track width were calculated and compared with those of other existing models. With our modeling approach, the localized errors in predicting track geometries were found to be the least. This model is capable of dynamically predicting the temperatures and track geometry at various user-defined input parameters. 相似文献
116.
Pyridyl-based triazole-linked calix[4]arene conjugates, viz. L(1) and L(2), were synthesized and characterized. These two conjugates were shown to be selective and sensitive for Zn(2+) among the 12 metal ions studied in HEPES buffer medium by fluorescence, absorption, and visual color change with the detection limit of ~31 and ~112 ppb, respectively, by L(1) and L(2). Moreover, the utility of the conjugates L(1) and L(2) in showing the zinc recognition in live cells has also been demonstrated using HeLa cells as monitored by fluorescence imaging. The zinc complexes of L(1) and L(2) were isolated, and the structure of [ZnL(1)] has been established by single-crystal XRD and that of [ZnL(2)] by DFT calculations. TDDFT calculations were performed in order to demonstrate the electronic properties of receptors and their zinc complexes. The isolated zinc complexes, viz. [ZnL(1)] and [ZnL(2)], have been used as molecular tools for the recognition of anions on the basis of their binding affinities toward Zn(2+). [ZnL(2)] was found to be sensitive and selective toward phosphate-bearing ions and molecules and in particular to pyrophosphate (PPi) and ATP among the other 18 anions studied; however, [ZnL(1)] was not sensitive toward any of the anions studied. The selectivity has been shown on the basis of the changes observed in the emission and absorption spectral studies through the removal of Zn(2+) from [ZnL(2)] by PPi. Thus, [ZnL(2)] has been shown to detect PPi up to 278 ± 10 ppb at pH 7.4 in aqueous methanolic (1/2 v/v) HEPES buffer. 相似文献
117.
118.
Dessingou J Tabbasum K Mitra A Hinge VK Rao CP 《The Journal of organic chemistry》2012,77(3):1406-1413
The structurally characterized lower rim 1,3-di{4-antipyrine}amide conjugate of calix[4]arene (L) exhibits high selectivity toward Hg(2+) among other biologically important metal ions, viz., Na(+), K(+), Ca(2+), Mg(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), and Ag(+) as studied by fluorescence, absorption, and ESI MS. L acts as a sensor for Hg(2+) by switch-off fluorescence and exhibits a lowest detectable concentration of 1.87 ± 0.1 ppm. The complex formed between L and Hg(2+) is found to be 1:1 on the basis of absorption and fluorescence titrations and was confirmed by ESI MS. The coordination features of the mercury complex of L were derived on the basis of DFT computations and found that the Hg(2+) is bound through an N(2)O(2) extending from both the arms to result in a distorted octahedral geometry with two vacant sites. The nanostructural features such as shape and size obtained using AFM and TEM distinguishes L from its Hg(2+) complex and were different from those of the simple mercuric perchlorate. L is also suited to sense pyrimidine bases by fluorescence quenching with a minimum detection limit of 1.15 ± 0.1 ppm in the case of cytosine. The nature of interaction of pyrimidine bases with L has been further studied by DFT computational calculations and found to have interactions through a hydrogen bonding and NH-π interaction between the host and the guest. 相似文献
119.
P. N. Pathak Neelam Kumari D. R. Prabhu V. K. Manchanda 《Journal of solution chemistry》2012,41(3):410-421
Spectrophotometric investigations have been carried out on the disproportionation of Np(V) to form Np(IV) and Np(VI) in 1.1
mol⋅L−1 solutions of tributyl phosphate (TBP) and in N,N-dihexyl octanamide (DHOA) in n-dodecane medium. The Np(V) was found to coordinate with Np(IV) in 1.1 mol⋅L−1 TBP solution in n-dodecane to form a mixed valence “cation–cation” complex by bonding through an axial oxo group on Np(V). By contrast, this
interaction was less prominent in the case of 1.1 mol⋅L−1 DHOA solutions. The effect of 1-octanol, added as phase modifier, on the disproportionation behavior of Np(V) was also investigated.
An attempt was made to calculate the disproportionation/reduction rate constants for Np(V) under the conditions of these studies.
Absorbance measurements on the Np stripped from organic phases revealed the occurrence of Np(V) in the aqueous phase. 相似文献
120.
We present the results of a study of structural, electronic, and optical properties of the unpassivated and H-passivated GaN nanowires having diameters in the range of 3.29 to 18.33 Å grown along [001] direction by employing the first-principles pseudopotential method within density functional theory in the local density approximation. Two types of nanowires having hexagonal and triangular cross-sections have been investigated. The binding energy increases with the diameter of the nanowire because of a decrease in the relative number of the unsaturated surface bonds. The binding energies of the triangular cross-sectional nanowires are somewhat smaller than those of the hexagonal cross-sectional nanowires in accordance with the Wulff’s rule except the smallest diameter triangular cross-sectional nanowire, where the binding energy is comparable with the corresponding hexagonal cross-sectional nanowires. The band gap varies rapidly with the diameter of the nanowire in the case of the smaller diameter nanowires, and quite slowly for the larger diameter nanowires. After atomic relaxation, appreciable distortion occurs in the nanowires, where the chains of Ga- and N-atoms are curved in different directions. These distortions are reduced with the diameters of the nanowires. The optical absorption in the GaN nanowires is quite strong in the ultra-violet region but an appreciable absorption is also present in the visible region for the larger diameter nanowires. The present results indicate the possibility of engineering the properties of nanowires by manipulating their diameter and surface structure. The presently predicted smaller diameter GaN nanowire possessing the triangular cross-section should be observable in the experiments. 相似文献