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331.
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333.
R. Shashidhar B. P. Gaber S. Krishna Prasad S. Chandrasekhar 《Molecular Crystals and Liquid Crystals》2013,570(1-4):153-160
We have carried out a detailed pressure study of the three phase transitions observed in hydrated dimyristoyl phosphatidylcholine (DMPC) containing 95% by weight of water. The P-T diagram shows a Gel III-Gel II-Gel I triple point at 3.5 kbar, 41[ddot]C. It is found that the Gel III phase can be obtained by pressure-annealing the sample for about 12 hours at room temperature. 相似文献
334.
A toric arrangement is a finite collection of codimension-1 subtori in a torus. These subtori stratify the ambient torus into faces of various dimensions. Let f i denote the number of i-dimensional faces; these so-called face numbers satisfy the Euler relation ∑ i (-1) i f i = 0. However, not all tuples of natural numbers satisfying this relation arise as face numbers of some toric arrangement. In this paper we focus on toric arrangements in a 2-dimensional torus and obtain a characterization of their face numbers. In particular we show that the convex hull of these face numbers is a cone. 相似文献
335.
Decanuclear Ln10 Wheels and Vertex‐Shared Spirocyclic Ln5 Cores: Synthesis,Structure, SMM Behavior,and MCE Properties
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Dr. Sourav Das Dr. Atanu Dey Dr. Subrata Kundu Sourav Biswas Dr. Ramakirushnan Suriya Narayanan Dr. Silvia Titos‐Padilla Dr. Giulia Lorusso Dr. Marco Evangelisti Prof. Enrique Colacio Prof. Vadapalli Chandrasekhar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(47):16955-16967
The reaction of a Schiff base ligand (LH3) with lanthanide salts, pivalic acid and triethylamine in 1:1:1:3 and 4:5:8:20 stoichiometric ratios results in the formation of decanuclear Ln10 (Ln=Dy( 1 ), Tb( 2 ), and Gd ( 3 )) and pentanuclear Ln5 complexes (Ln=Gd ( 4 ), Tb ( 5 ), and Dy ( 6 )), respectively. The formation of Ln10 and Ln5 complexes are fully governed by the stoichiometry of the reagents used. Detailed magnetic studies on these complexes ( 1 – 6 ) have been carried out. Complex 1 shows a SMM behavior with an effective energy barrier for the reversal of the magnetization (Ueff)=16.12(8) K and relaxation time (τo)=3.3×10?5 s under 4000 Oe direct current (dc) field. Complex 6 shows the frequency dependent maxima in the out‐of‐phase signal under zero dc field, without achieving maxima above 2 K. Complexes 3 and 4 show a large magnetocaloric effect with the following characteristic values: ?ΔSm=26.6 J kg?1 K?1 at T=2.2 K for 3 and ?ΔSm=27.1 J kg?1 K?1 at T=2.4 K for 4 , both for an applied field change of 7 T. 相似文献
336.
Dinne Naresh Kumar Reddy Kothapalli Bannoth Chandrasekhar Yaddanapudi Sesha Siva Ganesh Srikanth Sharathchandra Gorantla Siddabathuni Ramanjaneyulu K. Shiva Kumar 《合成通讯》2013,43(4):513-523
A greener approach for the synthesis of 3-arylmethyl/diarylmethyl indoles has been achieved via a PMA-SiO2-mediated three-component reaction (the aza-Friedel–Crafts reaction) involving indoles, aldehydes, and N,N-disubstituted anilines in PEG-400. A variety of indole derivatives were prepared by using this operationally simple and straightforward methodology in acceptable yields. 相似文献
337.
A new one-pot version of the titled reaction involves heating a mixture of a carbonyl compound, a phenylhydrazine, and the cation exchange resin Amberlite IR 120 in refluxing ethanol. A variety of enolizable aldehydes, and ketones and several substituted phenylhydrazines could thus be converted to the corresponding indoles in excellent yields (70–88%). Reaction times were typically 6–10 h, with the resin being then filtered off and the product isolated after minimal workup. 相似文献
338.
Single crystal silicon is an excellent system to explore dynamic nuclear polarization (DNP), as it exhibits a continuum of properties from metallic to insulating as a function of doping concentration and temperature. At low doping concentrations DNP has been observed to occur via the solid effect, while at very high-doping concentrations an Overhauser mechanism is responsible. Here we report the hyperpolarization of (29)Si in n-doped silicon crystals, with doping concentrations in the range of (1-3)?× 10(17) cm(-3). In this regime exchange interactions between donors become extremely important. The sign of the enhancement in our experiments and its frequency dependence suggest that the (29)Si spins are directly polarized by donor electrons via an Overhauser mechanism within exchange-coupled donor clusters. The exchange interaction between donors only needs to be larger than the silicon hyperfine interaction (typically much smaller than the donor hyperfine coupling) to enable this Overhauser mechanism. Nuclear polarization enhancement is observed for a range of donor clusters in which the exchange energy is comparable to the donor hyperfine interaction. The DNP dynamics are characterized by a single exponential time constant that depends on the microwave power, indicating that the Overhauser mechanism is a rate-limiting step. Since only about 2% of the silicon nuclei are located within 1 Bohr radius of the donor electron, nuclear spin diffusion is important in transferring the polarization to all the spins. However, the spin-diffusion time is much shorter than the Overhauser time due to the relatively weak silicon hyperfine coupling strength. In a 2.35 T magnetic field at 1.1 K, we observed a DNP enhancement of 244 ± 84 resulting in a silicon polarization of 10.4 ± 3.4% following 2 h of microwave irradiation. 相似文献
339.
Ramakotaiah Mogili Kanchanamala Kanala Balasekhara R. Challa Babu R. Chandu Chandrasekhar K. Bannoth 《Chromatographia》2011,74(7-8):585-592
A simple, sensitive, selective, rapid, rugged, reproducible and specific liquid chromatography?Ctandem mass spectrometry (LC?CMS/MS) method was used for quantitative estimation of rizatriptan (RZ) in human plasma using rizatriptan-d 6 (RZD6) as internal standard (IS). Chromatographic separation was performed on Ascentis Express RP Amide C18, 50 × 4.6 mm, 2.7 ??m column with isocratic mobile phase composed of 10 mM ammonium formate:acetonitrile (20:80 v/v) at flow rate of 0.5 mL min?1. RZ and RZD6 were detected with proton adducts at m/z (amu) 270.2 ?? 201.2 and 276.1 ?? 207.1, respectively, in multiple reaction monitoring (MRM) positive mode. Liquid?Cliquid extraction was used and validated over a linear concentration range of 0.1?C100.0 ng mL?1 with correlation coefficient r 2 ?? 0.9981. The limit of quantification (LOQ) and limit of detection (LOD) were found to be 0.1 ng mL?1 and 12.5 fg, respectively. Intra- and inter-day precision were within 1.7?C3.1% and 2.8?C3.7%, and accuracy within 96.0?C101.7% and 99.7?C101.4% for RZ. Drug was found to be stable throughout three freeze?Cthaw cycles. The method was successfully employed for analysis of plasma samples following oral administration of RZ (10 mg) in 25 healthy Indian male human volunteers under fasting conditions. 相似文献
340.
Molecular transition-metal phosphonates 总被引:2,自引:0,他引:2
Chandrasekhar V Senapati T Dey A Hossain S 《Dalton transactions (Cambridge, England : 2003)》2011,40(20):5394-5418
Molecular transition-metal phosphonates are of relatively recent origin and can be assembled by several synthetic strategies. The nuclearity and the structure of the metal aggregates can be modulated by several factors including the stoichiometry of the reactants, nature of the metal precursor and the type of phosphonic acid used. This perspective summarizes some of the recent work carried out on copper(II)-, zinc(II)- and cadmium(II) phosphonates with particular emphasis on their synthesis and structure. 相似文献