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771.
[structure: see text] Transesterification of 2-hydroxypropyl-p-nitrophenyl phosphate in the presence of 0.092 M HClO4 is 50-5000 times faster in acetonitrile, 1,4-dioxane, methanol, ethanol, N,N-dimethylformamide, or dimethyl sulfoxide than in water. This demonstrates the importance of tuning the microenvironments in designing synthetic nucleases. 相似文献
772.
Curro NJ Hammel PC Suh BJ Hücker M Büchner B Ammerahl U Revcolevschi A 《Physical review letters》2000,85(3):642-645
We report Cu and La nuclear magnetic resonance measurements in the title compound that reveal an inhomogeneous glassy behavior of the spin dynamics. A low temperature peak in the La spin lattice relaxation rate and the "wipeout" of Cu intensity both arise from these slow electronic spin fluctuations that reveal a distribution of activation energies. Inhomogeneous slowing of spin fluctuations appears to be a general feature of doped lanthanum cuprate. 相似文献
773.
Large eddy simulation (LES)-based computational aeroacoustics techniques were applied to a static model of the human glottis, idealized here as a planar channel with an orifice, to study flow-acoustic interactions related to speech. Rigid models of both converging and diverging glottal passages, each featuring a 20 deg included angle and a minimal glottal diameter of 0.04 cm, with an imposed transglottal pressure of 15 cm H2O, were studied. The Favre-filtered compressible Navier-Stokes equations were integrated for this low-Mach-number flow using an additive semi-implicit Runge-Kutta method and a high-order compact finite-difference scheme with characteristic-based nonreflecting boundary conditions and a multiblock approach. Flow asymmetries related to the Coanda effect and transition to turbulence, as well as the far-field sound, were captured. Acoustic-analogy-based far-field sound predictions were compared with direct simulations and showed that dipole sources, arising from unsteady flow forces exerted on the glottal walls, are primarily responsible for the tonal sound observed in the divergent glottis case. 相似文献
774.
Chun SH Kim YS Choi HK Jeong IT Lee WO Suh KS Oh YS Kim KH Khim ZG Woo JC Park YD 《Physical review letters》2007,98(2):026601
Investigating the scaling behavior of annealed Ga1-xMnxAs anomalous Hall coefficients, we note a universal crossover regime where the scaling behavior changes from quadratic to linear. Furthermore, measured anomalous Hall conductivities in the quadratic regime when properly scaled by carrier concentration remain constant, spanning nearly a decade in conductivity as well as over 100 K in T_[C] and comparing favorably to theoretically predicated values for the intrinsic origins of the anomalous Hall effect. Both qualitative and quantitative agreements strongly point to the validity of new equations of motion including the Berry phase contributions as well as the tunability of the anomalous Hall effect. 相似文献
775.
Na+-Ca2+ exchanger (NCX) transports Ca2+ coupled with Na+ across the plasma membrane in a bi-directional mode. Ca2+ flux via NCX mediates osteogenic processes, such as formation of extracellular matrix proteins and bone nodules. However, it is not clearly understood how the NCX regulates cellular Ca2+ movements in osteogenic processes. In this study, the role of NCX in modulating Ca2+ content of intracellular stores ([Ca2+]ER) was investigated by measuring intracellular Ca2+ activity in isolated rat osteoblasts. Removal of extracellular Na+ elicited a transient increase of intracellular Ca2+ concentration ([Ca2+]i). Pretreatment of antisense oligodeoxynucleotide (AS) against NCX depressed this transient Ca2+ rise and raised the basal level of [Ca2+]i. In AS-pretreated cells, the expression and activity of alkaline phosphatase (ALP), an osteogenic marker, were decreased. However, the cell viability was not affected by AS-pretreatment. Suppression of NCX activity by the AS-pretreatment decreased ATP-activated Ca2+ release from intracellular stores and significantly enhanced Ca2+ influx via store operated calcium influx (SOCI), compared to those of S-pretreated or control cells. These results strongly suggest that NCX has a regulatory role in cellular Ca2+ pathways in osteoblasts by modulating intracellular Ca2+ content. 相似文献
776.
777.
We present a novel ultraviolet (UV)-curable mold that enables the formation of reversibly bonded nanocapillaries (500-50 nm) on a gold or silicon substrate. A sheet-type ( approximately 50 microm) polyethylene diacrylate (PEG-DA) mold was used for its rigiflex nature; it provides rigidity high enough for maintaining nanostructures (elastic modulus >70 MPa) and also flexibility good enough for intimate contact over a large area aided by weak electrostatic forces (zeta potential approximately -113.55 mW). The electrostatic charge is generated on a rigiflex PEG-DA mold upon peeling from an original engraved silicon master by mechanical friction, thereby assisting the formation of spontaneous contact with the gold or silicon substrate. 相似文献
778.
779.
Sterically modulated bis-imine ligands (L1-L3) were prepared by reacting 4,4′-methylene bis-(2,6-dialkyl aniline) and antipyrine-4-carboxaldehyde in a 1:2 stoichiometric ratio. The reactions of L1-L3 with dichloro(cycloocta-1.5-diene)palladium(II) [PdCl2(cod)] yield the corresponding binuclear palladium complexes with the general formula Pd2Cl4L (L = L1, L2, and L3). The binucleating ligands bind to the palladium ion via the lone pair on the imine nitrogen and amide oxygen atoms, resulting in a square-planar geometry around the metal center. All the palladium catalysts efficiently oligomerize ethylene to produce C4-C20 fractions at activities of up to 1308 kg-oligomer mol-Pd−1 bar−1 h−1 at 30 °C in combination with ethylaluminum sesquichloride. The formation of active sites by the change in geometry of the metal complexes could be traced using spectroscopic and electrochemical techniques. 相似文献
780.
Suh HJ Lee KS Kim SR Shin MH Park S Park S 《Journal of photochemistry and photobiology. B, Biology》2011,102(2):102-107
The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging effect and total phenolic contents were evaluated for the screening of singlet oxygen ((1)O(2)) quenching efficacy of various seed extracts from Rumex crispus L. The butanol and ethyl-acetate extracts displayed remarkable effect of DPPH as compared to positive control ascorbic acid. The concentrations (QC(50)) of butanol and ethyl-acetate extracts required to exert 50% reducing effect on (1)O(2) were found to be 116 and 82 μg mL(-1), respectively. Both extracts were also found to protect the in vitro biological system from the detrimental effect of (1)O(2) on type II photosensitization in Escherichia coli, red blood cell, lactate dehydrogenase and histidine. Among all the tested extracts, the ethyl-acetate and butanol extracts contained higher amount of total phenolic contents. The results suggest that our study may contribute to the development of new bioactive products with potential applications to reduce photo-produced oxidative stress involving reactive oxygen species in living organisms. 相似文献