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81.
Enhancing NMR Sensitivity of Natural‐Abundance Low‐γ Nuclei by Ultrafast Magic‐Angle‐Spinning Solid‐State NMR Spectroscopy
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Dr. Rongchun Zhang Yitian Chen Prof. Dr. Nair Rodriguez‐Hornedo Prof. Dr. Ayyalusamy Ramamoorthy 《Chemphyschem》2016,17(19):2962-2966
Although magic‐angle‐spinning (MAS) solid‐state NMR spectroscopy has been able to provide piercing atomic‐level insights into the structure and dynamics of various solids, the poor sensitivity has limited its widespread application, especially when the sample amount is limited. Herein, we demonstrate the feasibility of acquiring high S/N ratio natural‐abundance 13C NMR spectrum of a small amount of sample (≈2.0 mg) by using multiple‐contact cross polarization (MCP) under ultrafast MAS. As shown by our data from pharmaceutical compounds, the signal enhancement achieved depends on the number of CP contacts employed within a single scan, which depends on the T1ρ of protons. The use of MCP for fast 2D 1H/13C heteronuclear correlation experiments is also demonstrated. The significant signal enhancement can be greatly beneficial for the atomic‐resolution characterization of many types of crystalline solids including polymorphic drugs and nanomaterials. 相似文献
82.
N. Ramamoorthy D. V. S. Narasimhan R. S. Mani 《Isotopes in environmental and health studies》2013,49(7):246-249
Presently available 113mSn.113mIn generators use high specific activity 113Sn which cannot be produced in low and medium flux research reactors even with enriched 112Sn. This paper describes a method of preparing 112Sn.113mIn generators using ll3Sn of relatively low specific activity (2—3 Ci/g) obtained by irradiation of enriched 112Sn in CIRUS. In this modified procedure, 113SnCl4 is firmly adsorbed on hydrous zirconia from 3—4 M NaCl solutions of pH 1.3 to 1.5 and the elution of 113mIn is effected by dilute HCl. The generator yields 70% of the theoretically available ll3mIn activity. 113Sn breakthrough has been consistantly less than 0.01% of the 113mIn activity. Stable zirconium contamination in the eluate has been estimated to be less than 1 ppm. The performance characteristics of different varieties of hydrous zirconia have been studied to evaluate the optimum tin loading, indium elution and soluble zirconium contamination. Generators containing upto 700 mCi of tin-113 have been prepared yielding pure indium-113m suitable for medical use. 相似文献
83.
Constant current electrolysis of sodium octanoate produced Kolbe and non-Kolbe products. Dimer is the major product at Pt
anode and non-Kolbe products were formed on graphite anode. Influence of quantity of electricity, current density, and nature
of electrode was studied. Under optimized experimental conditions, butanoate, perfluorooctanoate, and perfluorobutanoate were
electrolyzed. Major and minor products were identified based on GC–MS spectra. Isomeric products are due to cationic rearrangement
by 1,2-hydride shift and selectivity among them are also rationalized. Anodic decarboxylation of perfluorobutanoate and perfluorooctanoates
gave Kolbe dimer on platinum electrode. The role of solvent and criteria for choice of radical or cationic pathway has been
discussed. 相似文献
84.
85.
S. Mohammad. Haji-Saeid M.H. Sampa A. Safrany S. Sabharwal N. Ramamoorthy 《Radiation Physics and Chemistry》2012,81(8):1040-1044
Radiation treatment, or a combination of radiation with conventional biological–chemical–physical processes, can help in the remediation of contaminated surfaces and in combating industrial chemical effluents and air pollution. The use of ionizing radiation as a powerful tool for inactivation of microbes is a valuable option to address likely threats from biohazard contamination that could be introduced either deliberately or inadvertently into areas where the public are exposed to, as well as for treatment of volatile organic compounds and similar hazardous chemical agents is an emerging development in tackling harmful pollutants. The role of the IAEA has been crucial both in supporting the development of local capabilities as well as in fostering international cooperation due to the multidisciplinary expertise required for achieving sustainable benefits. The IAEA is implementing Coordinated Research Projects, (CRP) thematic topical reviews of issues and challenges involved, and Technical Cooperation (TC) assistance in establishing and maintaining infrastructure in the MS. This paper will give an insight into the above mentioned IAEA activities, with examples of successes achieved through CRPs, as well as challenges on the road for broader dissemination of radiation processing technology for environmental remediation. 相似文献
86.
Misfolded proteins in Alzheimer's disease and type II diabetes 总被引:1,自引:0,他引:1
87.
Vyas PV Ray P Adhikary SK Shah BG Rangarajan R 《Journal of colloid and interface science》2003,257(1):127-134
Heterogeneous ion-exchange membranes (both cationic and anionic types) have been synthesized by solution casting techniques using polyvinyl chloride (PVC) as binder and ion-exchange resin (-300+400 mesh). The binder:resin ratio varied from 60:40 to 30:70. The transport behavior of the membranes has been evaluated chronopotentiometrically in sodium chloride (NaCl) solutions of different concentrations. The different parameters E(0) (potential drop across the membrane at the instant of application of current I), E(max) (maximum potential drop across the membrane after the application of current I), DeltaE (magnitude of the potential jump across the membrane at transition time tau), Itau(1/2), tau, etc., have been evaluated. The isoconductance points were determined and based on the microheterogeneous model proposed by Zabolotsky and Nikonenko (J. Membrane Sci. 79 (1993) 181) the distribution factors beta has been evaluated for both types of ion exchange membranes. The electroconductivity of the joint gel (kappa ) and pure gel phases (kappa ' ) has been determined. At any particular solution concentration the transport number as well as the permselectivity of membranes increases with increased resin content of the membrane. The microheterogeneity factor beta exhibits synchronization among the each set of four different membranes for both the cationic and anionic type. 相似文献
88.
89.
In this work, the principle of interferometry is used to assess the surface roughness of the machined surfaces. Interferometry produces an interference fringe pattern when two or more light waves interact with each other. It is one of the important tool for precision optical metrology and testing. Well-known advantages of the phase shifting interferometry include high measurement accuracy, rapid measurement, good result even with low contrast fringes and that the polarity of the wave front can be determined. In fringe projection techniques, a known optical fringe pattern is projected onto the surface of interest. The fringe pattern on the surface is perturbed in accordance with the profile of the test surface, thereby enabling direct derivation of surface profile.In this work, an attempt has been made to assess the surface roughness using a speckle fringe analysis method of five frame phase shift algorithm for machined surface (ground surface). As these fringes are too noisy, advanced filtering technique has been used so as to reduce noise and to get improved wrapped phase map from the phase shifted fringes. A phase unwrapping software has been developed using discrete cosine transform (DCT) to generate the three-dimensional (3-D) profiles. Finally, it is compared with Ra values measured using a mechanical stylus instrument, showing good agreement. 相似文献
90.