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991.
Kevin Bläsing Dr. Jonas Bresien René Labbow Prof. Dr. Axel Schulz Dr. Alexander Villinger 《Angewandte Chemie (International ed. in English)》2018,57(29):9170-9175
A highly labile dimer of hydrogen cyanide, HCN???HCN, was extracted from liquid HCN by adduct formation with the bulky Lewis acid B(C6F5)3, affording HCN???HCN?B(C6F5)3, which was fully characterized. The influence of the solvent (HCN, CH2Cl2, and aromatic hydrocarbons) on the crystallization process was studied, revealing dimer formation when using HCN or CH2Cl2 as solvent, whereas aromatic hydrocarbons led to the formation of monomeric arene??HCN?B(C6F5)3 adducts, additionally stabilized by η6‐coordination of the aromatic ring system similar to well‐known half‐sandwich complexes. 相似文献
992.
Dr. Dirk Alpers Dr. Kevin P. Cole Prof. Dr. Corey R. J. Stephenson 《Angewandte Chemie (International ed. in English)》2018,57(37):12167-12170
The photocatalytic preparation of aminoalkylated heteroarenes from haloalkylamides via a 1,4‐aryl migration from nitrogen to carbon, conceptually analogous to a radical Smiles rearrangement, is reported. This method enables the substitution of amino groups in heteroaromatic compounds with aminoalkyl motifs under mild, iridium(III)‐mediated photoredox conditions. It provides rapid access to thienoazepinone, a pharmacophore present in multiple drug candidates for potential treatment of different conditions, including inflammation and psychotic disorders. 相似文献
993.
Separations of used nuclear fuel at the engineered scale have generally been completed using the Plutonium Uranium Redox Extraction (PUREX) process. The PUREX process uses tributyl phosphate (TBP) as an extractant to recover uranium and plutonium. While the TBP extractant has proven effective at recovering U and Pu at the engineered scale, TBP is potentially vulnerable to third phase formation and TBP degradation products (monobutyl and dibutyl phosphoric acids) which can complicate recovery of extracted metals from the organic phase. An alternative class of extractants, monoamides, has been considered for applications in thorium and uranium fuel cycles. When compared to TBP, monoamides tend to have higher separation factors for U or Pu from fission products, structural materials, and Th. This review summarizes the literature that explores actinide separations using monoamides by assessing the physiochemical properties between a broader library of branched and straight-chain monoamides than considered in previous reviews. An emphasis is placed on fine-tuning the selectivity of branched monoamides. 相似文献
994.
We study the nonlinear stability of general undercompressive viscous shock waves. Previously, the authors showed stability in a special case when the shock phase shift can be determined a priori from the total mass of the perturbation, using new pointwise methods. By examining time invariants associated with the linearized equations, we can now overcome a new difficulty in the general case, namely, nonlinear movement of the shock. We introduce a coordinate transformation suitable to treat this new aspect, and demonstrate our method by analyzing a model system of generic type. We obtain sharp pointwise bounds andL
p
behavior of the solution for allp, 1p. 相似文献
995.
In this paper, a network model of polymer melts is proposed in which network junction points move non-affinely. In this non-affine motion, junction points follow particle paths as seen by an observer rotating at the fluid element's net rigid-rotation rate. The speed at which junction points move is reduced as the network segments near their maximum extensions. In order to maintain a frame invariant model, it is necessary that the vorticity be decomposed into two portions, such that, =
R
+
D
. The deformational vorticity,
D
, arises from shear deformation and is frame invariant while the rigid vorticity,
R
, is frame dependent. A constitutive equation based on this finitely extensible network strand (FENS) motion is developed. The model illustrates how rotations that cause changes in the relative orientation of a fluid element with its surroundings can be incorporated into a constitutive equation using the deformational vorticity. The FENS model predicts a shear-thinning viscosity, and the Trouton viscosity predicted by the model is finite for all elongation rates. Finally, stochastic simulation results are presented to justify a mathematical approximation used in deriving the constitutive equation. 相似文献
996.
G. Fiorentini R. W. Kavanagh C. Rolfs 《Zeitschrift für Physik A Hadrons and Nuclei》1995,350(4):289-301
A summer institute was convened at the Gran Sasso Laboratory (Italy), 27. June to 7. July 1994, in part to explore the advantages of an accelerator laboratory deep underground, particularly for crucial nuclear-astrophysics measurements presently limited at low energies by cosmic-ray backgrounds. Here we review specific reactions identified as needing further study in a low-background environment, and outline suitable facilities to carry out such studies.The authors would like to thank P. Aguer, C. Angulo, R.E. Azuma, R.N. Boyd, C. Broggini, E. Cecil, P. Corvisiero, C. Czerski, P. Descouvemont, H. Dzitko, U. Greife, J.W. Hammer, F. Käppeler, J. Kiener, J. Lambert, Ch. Leclerc-Willain, Th. Paradellis, W.S. Rodney, T. Shoppa, A. Shotter, E. Somorjai, F. Terrasi, H.P. Trautvetter, M. Wiescher and other colleagues for their contributions and discussions during the summer insitute, which are in part included in this report. 相似文献
997.
Ramaswamy Nilakantan Norman Bauman Kevin S. Haraki 《Journal of computer-aided molecular design》1997,11(5):447-452
We present some new ideas for characterizing and comparing largechemical databases. The comparison of the contents of large databases is nottrivial since it implies pairwise comparison of hundreds of thousands ofcompounds. We have developed methods for categorizing compounds into groupsor series based on their ring-system content, using precalculatedstructure-based hashcodes. Two large databases can then be compared bysimply comparing their hashcode tables. Furthermore, the number of distinctring-system combinations can be used as an indicator of database diversity.We also present an indepen- dent technique for diversity assessment calledthe saturation diversity approach. This method is based on picking as manymutually dissimilar compounds as possible from a database or a subsetthereof. We show that both methods yield similar results. Since the twomethods measure very different properties, this probably says more about theproperties of the databases studied than about the methods. 相似文献
998.
Harper SM Neil LC Day IJ Hore PJ Gardner KH 《Journal of the American Chemical Society》2004,126(11):3390-3391
Phototropins are light-activated kinases from plants that utilize light-oxygen-voltage (LOV) domains as blue light photosensors. Illumination of these domains leads to the formation of a covalent linkage between the protein and an internally bound flavin chromophore, destabilizing the surrounding protein and displacing an alpha-helix from its surface. Here we use a combination of spectroscopic tools to monitor the kinetic processes that spontaneously occur in the dark as the protein returns to the noncovalent ground state. Using time-resolved two-dimensional (2D) NMR methods, we measured the rate of this process at over 100 independent sites throughout the protein, establishing that regeneration of the dark state occurs cooperatively within a 1.6-fold range of observed rates. These data agree with other spectroscopic measurements of the kinetics of protein/FMN bond cleavage and global conformational changes, consistent with these processes experiencing a common rate-limiting step. Arrhenius analyses of the temperature dependence of these rates suggest that the transition state visited during this regeneration has higher energy than the denatured form of this protein domain despite the fact that there is no global unfolding of the domain during this process. 相似文献
999.
Alpha-1-acid glycoprotein (AGP) is a plasma glycoprotein produced by the liver that undergoes increased production and altered glycosylation in several physiological and pathological conditions including rheumatoid arthritis. To date, although present in the synovial fluid of rheumatoid arthritis patients, there has been no evidence for the separate extra-hepatic production of AGP. This study indicates that there could be a localized production of AGP in rheumatoid synovial fluid by demonstrating that the glycosylation patterns of AGP differed between the serum and synovial fluid in the same rheumatoid patient. Serum AGP was largely composed of fucosylated tri- and tetra-antennary oligosaccharide chains while the synovial fluid contained mainly bi-antennary chains that were fucosylated to a lesser extent. This structural heterogeneity of glycosylation resulted in functional diversity; serum but not synovial AGP is able to inhibit binding to the cell adhesion molecule E-selectin through expression of antigen sialyl Lewis X. 相似文献
1000.
DNA-based photonic logic gates: AND,NAND, and INHIBIT 总被引:4,自引:0,他引:4
Saghatelian A Völcker NH Guckian KM Lin VS Ghadiri MR 《Journal of the American Chemical Society》2003,125(2):346-347
Conventional microprocessors use elementary logic gates to perform complex computational tasks. Mimicking such computational processes using purely molecular systems has been limited in most cases by the lack of design generality or potential addressability of existing molecular logic gates. Herein we report that by employing the universal recognition properties of DNA simple photonic logic gates can be created that are capable of AND, NAND, and INHIBIT logic operations. 相似文献