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排序方式: 共有191条查询结果,搜索用时 15 毫秒
91.
Singh Shashank Oswal Mumtaz Behera B. R. Kumar Ashok Santra S. Acharya R. Singh K. P. 《Journal of Radioanalytical and Nuclear Chemistry》2020,323(3):1443-1449
Journal of Radioanalytical and Nuclear Chemistry - Elemental concentrations namely P, S, Cl, K, Ca, Sc, Ti, Mn, Fe, Cu, Zn, Rb, Br and Sr were determined using Particle Induced X-ray Emission... 相似文献
92.
93.
Kaittanis C Santra S Santiesteban OJ Henderson TJ Perez JM 《Journal of the American Chemical Society》2011,133(10):3668-3676
The target-induced clustering of magnetic nanoparticles is typically used for the identification of clinically relevant targets and events. A decrease in the water proton transverse NMR relaxation time, or T(2), is observed upon clustering, allowing the sensitive and accurate detection of target molecules. We have discovered a new mechanistically unique nanoparticle-target interaction resulting in a T(2) increase and demonstrate herein that this increase, and its associated r(2) relaxivity decrease, are also observed upon the interaction of the nanoparticles with ligands or molecular entities. Small molecules, proteins, and a 15-bp nucleic acid sequence were chemically conjugated to polyacrylic-acid-coated iron oxide nanoparticles, and all decreased the original nanoparticle r(2) value. Further experiments established that the r(2) decrease was inversely proportional to the number of ligands bound to the nanoparticle and the molecular weight of the bound ligand. Additional experiments revealed that the T(2)-increasing mechanism was kinetically faster than the conventional clustering mechanism. Most importantly, under conditions that result in T(2) increases, as little as 5.3 fmol of Bacillus anthracis plasmid DNA (pX01 and pX02), 8 pmol of the cholera toxin B subunit (Ctb), and even a few cancer cells in blood were detected. Transition from the binding to the clustering mechanism was observed in the carbohydrate-, Ctb-, and DNA-sensing systems, simply by increasing the target concentration significantly above the nanoparticle concentration, or using Ctb in its pentameric form as opposed to its monomer. Collectively, these results demonstrate that the molecular architectures resulting from the interaction between magnetic nanosensors and their targets directly govern water proton NMR relaxation. We attribute the observed T(2) increases to the bound target molecules partially obstructing the diffusion of solvent water molecules through the superparamagnetic iron oxide nanoparticles' outer relaxation spheres. Finally, we anticipate that this novel interaction can be incorporated into new clinical and field detection applications, due to its faster kinetics relative to the conventional nanoparticle-clustering assays. 相似文献
94.
A rapid, cascade reaction process has been developed to access biologically validated spiro-2,5-diketopiperazines. The facile and environmentally benign method capitalizes on commercially available starting reagents for a sequential Ugi/6-exo-trig aza-Michael reaction, water as a solvent, and microwave irradiation without any extraneous additives. 相似文献
95.
Acetylene cations [HCCH](+) produced in the A(2)Σ(g)(+) state by extreme ultraviolet (XUV) photoionization are investigated theoretically, based on a mixed quantum-classical approach. We show that the decay of the A(2)Σ(g)(+) state occurs via both ultrafast isomerization and nonradiative electronic relaxation. We find a time scale for hydrogen migration and electronic decay of about 60 fs, in good agreement with recent XUV-pump/XUV-probe time-resolved experiments on the same system [Phys. Rev. Lett. 105, 263002 (2010)]. Moreover, we predict an efficient vibrational energy redistribution mechanism that quickly transfers excess energy from the isomerization coordinates to slower modes in a few hundred femtoseconds, leading to a partial regeneration of acetylenelike conformations. 相似文献
96.
Savchuk Maria I. Kopchuk Dmitry S. Taniya Olga S. Nikonov Igor L. Egorov Ilya N. Santra Sougata Zyryanov Grigory V. Chupakhin Oleg N. Charushin Valery N. 《Journal of fluorescence》2021,31(4):1099-1111
Journal of Fluorescence - A PASE (pot, step, atom, economic) synthetic approach to 5-aryl-6-arylthio-2,2′-bipyridine and 6-arylthio-2,5-diarylpyridine ligands/fluorophores has been reported... 相似文献
97.
V. V. Parkar V. Jha S. Santra B. J. Roy K. Ramachandran A. Shrivastava K. Mahata A. Chatterjee S. Kailas 《Pramana》2009,72(2):363-373
The elastic scattering and the 6He angular distributions were measured in 7Li + 7Li reaction at two energies, E
lab = 20 and 25 MeV. FRDWBA calculations have been performed to explain the measured 6He data. The calculations were very sensitive to the choice of the optical model potentials in entrance and exit channels.
The one-step proton transfer was found to be the dominant reaction mechanism in 6He production.
相似文献
98.
Sulai IA Wu Q Bishof M Drake GW Lu ZT Mueller P Santra R 《Physical review letters》2008,101(17):173001
Two anomalously weak transitions within the 2(3)S_(1)--3(3)P_(J) manifolds in 3He have been identified. Their transition strengths are measured to be 1000 times weaker than that of the strongest transition in the same group. This dramatic suppression of transition strengths is due to the dominance of the hyperfine interaction over the fine-structure interaction. An alternative selection rule based on IS coupling (where the nuclear spin is first coupled to the total electron spin) is proposed. This provides qualitative understanding of the transition strengths. It is shown that the small deviations from the IS coupling model are fully accounted for by an exact diagonalization of the strongly interacting states. 相似文献
99.
R. N. Santra T. K. Chaki P. G. Mukunda G. B. Nando 《Journal of Thermal Analysis and Calorimetry》1995,44(6):1401-1415
Curing reactions of ethylene methyl acrylate (EMA) polydimethyl siloxane (PDMS) rubber blends have been investigated by differential
scanning calorimetry (DSC) and by Rheometry. The curing exoterms obtained from DSC curves have been analysed to derive the
kinetic parameters associated with the curing process. Crosslinking of EMA-PDMS rubber blends follow first order kinetics.
The effect of blend ratio and peroxide concentration on the crosslinking characteristics of the blends have also been investigated.
Department of Metallurgical Engineering 相似文献
100.