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161.
Raghavendra Sagar 《Solid State Communications》2011,151(24):1949-1952
Ceramic solid solution of nanocrystalline barium zirconium titanate in the form of Ba(Zr0.52Ti0.48)O3 substituted by samarium (Sm3+) was prepared using the conventional solid state reaction method. The phase assemblage analyzed by the X-ray diffraction technique was fitted for cubic-crystal-symmetry. The change in the grain size depicted the influence of Sm3+ ions on the microstructure. The electrical behavior was studied in the temperature range from 323 to 773 K. The sintered samples exhibited a negative temperature coefficient of resistance (NTCR) and superior semiconducting behavior above 513 K. Addition of Sm3+ increased the room temperature resistivity of Ba(Zr0.52Ti0.48)O3 solid solution. The results obtained from the thermoelectric power measurement confirm electrons as the majority charge carriers. 相似文献
162.
Vijayavitthal T. Mathad Gorakshanath B. Shinde Sharad S. Ippar Navnath C. Niphade Raghavendra K. Panchangam Pravinchandra J. Vankawala 《合成通讯》2013,43(3):341-346
An efficient synthesis of 1-(naphthalen-1-yl)ethanamine ( RS -2) and its practical resolution to optically pure (1R)-(naphthalen-1-yl)ethanamine ( R -(+)-2), a key intermediate in the synthesis of cinacalcet hydrochloride (1), is described. The resolution of RS -2 using R-(?)-mandelic acid as a resolving agent in ethanol was established on an industrial scale to give pure R -(+)-2 with >99.8% ee after liberation of the amine from its mandelate salt. An efficient process for the racemization of undesired isomer S -(?)-2 is also provided to maximize the yield of desired enantiomer. 相似文献
163.
Barylyuk K Balabin RM Grünstein D Kikkeri R Frankevich V Seeberger PH Zenobi R 《Journal of the American Society for Mass Spectrometry》2011,22(7):1167-1177
The disappearance of the hydrophobic effect in the gas phase due to the absence of an aqueous surrounding raises a long-standing question: can noncovalent complexes that are exclusively bound by hydrophobic interactions in solution be preserved in the gas phase? Some reports of successful detection by mass spectrometry of complexes largely stabilized by hydrophobic effect are questionable by the presence of electrostatic forces that hold them together in the gas phase. Here, we report on the MS-based analysis of model supramolecular complexes with a purely hydrophobic association in solution, β-cyclodextrin, and synthetic adamantyl-containing ligands with several binding sites. The stability of these complexes in the gas phase is investigated by quantum chemical methods (DFT-M06). Compared with the free interaction partners, the inclusion complex between β-cyclodextrin and adamantyl-containing ligand is shown to be stabilized in the gas phase by ΔG = 9.6 kcal mol–1. The host–guest association is mainly enthalpy-driven due to strong dispersion interactions caused by a large nonpolar interface and a high steric complementarity of the binding partners. Interference from other types of noncovalent binding forces is virtually absent. The complexes are successfully detected via electrospray ionization mass spectrometry, although a high dissociation yield is also observed. We attribute this pronounced dissociation of the complexes to the collisional activation of ions in the atmospheric interface of mass spectrometer. The comparison of several electrospray-based ionization methods reveals that cold spray ionization provides the softest ion generation conditions for these complexes. 相似文献
164.
V. Raghavendra Reddy R. Rawat T. G. Reddy Ajay Gupta P. Y. Reddy K. Rama Reddy 《Hyperfine Interactions》2008,183(1-3):109-115
The structural changes of near-equiatomic α-FeCr alloys, ground in a vibratory mill in vacuum and in argon, were followed as a function of milling time. An amorphous phase forms in both cases but at a much faster rate when milling in argon than when milling in vacuum. Amorphisation by ball-milling of α-FeCr alloys is deduced to be an intrinsic phenomenon which is however speeded-up by oxygen. The amorphous phase crystallizes into a bcc Cr-rich phase and a bcc Fe-rich phase when annealed for short times. 相似文献
165.
The nonlinear response of light transmission characteristics of a liquid crystal (LC) spatial light modulator (SLM) is studied.
The results show that the device exhibits a wide range of variations with different control parameters and input settings.
Experiments were performed to obtain intensity modulation that is best described by either power-law or sigmoidal functions.
Based on the inverse transformation, an appropriate pre-processing scheme for electrically addressed input gray-scale images,
particularly important in several optical processing and imaging applications, is suggested. Further, the necessity to compensate
the SLM image nonlinearities in a volume holographic data storage and retrieval system is demonstrated. 相似文献
166.
Prashant Jain Chethan D. Shanthamurthy Shani Leviatan Ben-Arye Robert J. Woods Raghavendra Kikkeri Vered Padler-Karavani 《Chemical science》2021,12(10):3674
Achieving selective inhibition of chemokines with structurally well-defined heparan sulfate (HS) oligosaccharides can provide important insights into cancer cell migration and metastasis. However, HS is highly heterogeneous in chemical composition, which limits its therapeutic use. Here, we report the rational design and synthesis of N-unsubstituted (NU) and N-acetylated (NA) heparan sulfate tetrasaccharides that selectively inhibit structurally homologous chemokines. HS analogs were produced by divergent synthesis, where fully protected HS tetrasaccharide precursor was subjected to selective deprotection and regioselectively O-sulfated, and O-phosphorylated to obtain 13 novel HS tetrasaccharides. HS microarray and SPR analysis with a wide range of chemokines revealed the structural significance of sulfation patterns and NU domain in chemokine activities for the first time. Particularly, HT-3,6S-NH revealed selective recognition by CCL2 chemokine. Further systematic interrogation of the role of HT-3,6S-NH in cancer demonstrated an effective blockade of CCL2 and its receptor CCR2 interactions, thereby impairing cancer cell proliferation, migration and invasion, a step towards designing novel drug molecules. 相似文献
167.
168.
Atomic spectroscopy is the most popular approach to determine the presence of heavy metals in the environment. Heavy metals are potentially toxic and have various negative effects on many living organisms, including humans. With the rapid increase in the variety of industries and human activities, large amounts of heavy metals are released into the atmosphere, water, and soil. Heavy metal analysis of environmental samples is very important for determining the exposure limits. Environmental samples are highly complex matrices, and various sample preparation techniques have been developed for the extraction of heavy metals from them, including magnetic solid-phase extraction (MSPE). The use of MSPE in heavy metal analysis has recently gained significant attention owing to a number of advantages. MSPE technique overcomes main issues such as phase separation, handling, and column packing. The use of magnetic adsorbents in sample preparation has grown over the past few years, making MSPE a promising technique for sample preparation. The objective of this review article is to provide the latest applications of MSPE coupled with atomic spectroscopy for heavy metal determination in environmental samples. In addition, new magnetic adsorbents and their analytical merits are emphasized. 相似文献