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921.
Hector Garcia‐Seisdedos Jos A. Villegas Emmanuel D. Levy 《Angewandte Chemie (International ed. in English)》2019,58(17):5514-5531
Mutations and changes in a protein's environment are well known for their potential to induce misfolding and aggregation, including amyloid formation. Alternatively, such perturbations can trigger new interactions that lead to the polymerization of folded proteins. In contrast to aggregation, this process does not require misfolding and, to highlight this difference, we refer to it as agglomeration. This term encompasses the amorphous assembly of folded proteins as well as the polymerization in one, two, or three dimensions. We stress the remarkable potential of symmetric homo‐oligomers to agglomerate even by single surface point mutations, and we review the double‐edged nature of this potential: how aberrant assemblies resulting from agglomeration can lead to disease, but also how agglomeration can serve in cellular adaptation and be exploited for the rational design of novel biomaterials. 相似文献
922.
This work describes a novel physics-based deflation preconditioner approach for solving porous media flow problems characterized by highly heterogeneous media. The approach relies on high-conductivity block solutions after rearranging the linear system coefficients into high-conductive and low condutive blocks from a given physically driven threshold value. This rearranging relies on the Hoshen-Kopelman (H-K) algorithm that is commonly used to determine percolation clusters. The resulting preconditioner may alternatively be combined with a deflation preconditioning stage. The proposed approach is coined as a physics-based 2-stage deflation preconditioner (P2SDP). Numerical experiments on different permeability distributions reveal that P2SDP is a powerful means to solve pressure systems when compared to more conventional algebraic approaches such as the incomplete Cholesky factorization. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
923.
Ross E. Falcon G.A. Rochau J.E. Bailey J.L. Ellis A.L. Carlson T.A. Gomez M.H. Montgomery D.E. Winget E.Y. Chen M.R. Gomez T.J. Nash 《High Energy Density Physics》2013,9(1):82-90
We present an experimental platform for measuring hydrogen Balmer emission and absorption line profiles for plasmas with white dwarf (WD) photospheric conditions (Te ~1 eV, ne ~1017 cm?3). These profiles will be used to benchmark WD atmosphere models, which, used with the spectroscopic method, are responsible for determining fundamental parameters (e.g., effective temperature, mass) for tens of thousands of WDs. Our experiment, performed at the Z Pulsed Power Facility at Sandia National Laboratories, uses the large amount of X-rays generated from a z-pinch dynamic hohlraum to drive plasma formation in a gas cell. The platform is unique compared to past hydrogen line profile experiments in that the plasma is radiation-driven. This decouples the heating source from the plasma to be studied in the sense that the radiation temperature causing the photoionization is independent of the initial conditions of the gas. For the first time we measure hydrogen Balmer lines in absorption at these conditions in the laboratory for the purpose of benchmarking Stark-broadened line shapes. The platform can be used to study other plasma species and to explore non-LTE, time-dependent collisional-radiative atomic kinetics. 相似文献
924.
In this work an analysis of the electronic origin of relativistic effects on the isotropic dia- and paramagnetic contributions to the nuclear magnetic shielding sigma(X) for noble gases and heavy atoms of hydrogen halides is presented. All results were obtained within the 4-component polarization propagator formalism at different level of approach [random-phase approximation (RPA) and pure zeroth-order approximation (PZOA)], by using a local version of the DIRAC code. From the fact that calculations of diamagnetic contributions to sigma within RPA and PZOA approaches for HX(X=Br,I,At) and rare-gas atoms are quite close each to other and the finding that the diamagnetic part of the principal propagator at the PZOA level can be developed as a series [S(Delta)], it was found that there is a branch of negative-energy "virtual" excitations that contribute with more than 98% of the total diamagnetic value even for the heavier elements, namely, Xe, Rn, I, and At. It contains virtual negative-energy molecular-orbital states with energies between -2 mc2 and -4 mc2. This fact can explain the excellent performance of the linear response elimination of small component (LR-ESC) scheme for elements up to the fifth row in the Periodic Table. An analysis of the convergency of S(Delta) and its physical implications is given. It is also shown that the total contribution to relativistic effects of the innermost orbital (1s1/2) is by far the largest. For the paramagnetic contributions results at the RPA and PZOA approximations are similar only for rare-gas atoms. On the other hand, if the mass-correction contributions to sigma(p) are expressed in terms of atomic orbitals, a different pattern is found for 1s1/2 orbital contributions compared with all other s-type orbitals when the whole set of rare-gas atoms is considered. 相似文献
925.
Methoprene, an insect growth regulator, was complexed with beta-cyclodextrin, yielding a stable inclusion complex. TGA, X-ray powder diffraction and conformational analysis have been used to confirm the nature of this inclusion complex. The interaction between methoprene and beta-cyclodextrin was investigated by means of Molecular Mechanics. The results account for the formation of a 1:1 inclusion complex stabilised by Van der Waals forces and hydrogen bonds. The [methoprene-beta-cyclodextrin] complex included in smoke generating formulations and protected from thermal decomposition by the foaming agent azodicarbonamide was shown to be stable enough to release methoprene in fumes with good yields. The improved stabilty of the methoprene complex showed a correlation with increased biological activity against Musca domestica. 相似文献
926.
Stability of the Picard Bundle 总被引:2,自引:0,他引:2
Biswas I.; Brambila-Paz L.; Gomez T. L.; Newstead P. E. 《Bulletin London Mathematical Society》2002,34(5):561-568
Let X be a non-singular algebraic curve of genus g 2, n 2an integer, a line bundle over X of degree d > 2n(g 1) with (n,d) = 1 and M the moduli space of stable bundles ofrank n and determinant over X. It is proved that the Picardbundle W is stable with respect to the unique polarisation ofM. 2000 Mathematics Subject Classification 14H60, 14J60. 相似文献
927.
Ulmer PE Aniol KA Arenhövel H Chen JP Chudakov E Crovelli D Finn JM Fissum KG Gayou O Gomez J Hansen JO De Jager CW Jeschonnek S Jones MK Kuss M LeRose JJ Liang M Lindgren RA Malov S Meekins D Michaels R Mitchell J Perdrisat CF Punjabi V Roché R Sabatie F Saha A Suleiman R Todor L Wojtsekhowski BB 《Physical review letters》2002,89(6):062301
The 2H(e,e(')p)n cross section was measured in Hall A of the Thomas Jefferson National Accelerator Facility near the top of the quasielastic peak (x(Bj)=0.964) at a four-momentum transfer squared, Q(2)=0.665 (GeV/c) (2) (omega=0.368 GeV, W=2.057 GeV), and for recoil momenta up to 550 MeV/c. The measured cross section deviates by 1-2sigma from a state-of-the-art calculation at low recoil momenta. At high recoil momenta the cross section is well described by the same calculation; however, in this region, final-state interactions and interaction currents are predicted to be large, and alternative choices of nucleon-nucleon potential and nucleon current operator may result in significant spread in the calculations. 相似文献
928.
Gayou O Aniol KA Averett T Benmokhtar F Bertozzi W Bimbot L Brash EJ Calarco JR Cavata C Chai Z Chang CC Chang T Chen JP Chudakov E De Leo R Dieterich S Endres R Epstein MB Escoffier S Fissum KG Fonvieille H Frullani S Gao J Garibaldi F Gilad S Gilman R Glamazdin A Glashausser C Gomez J Gorbenko V Hansen JO Higinbotham DW Huber GM Iodice M de Jager CW Jiang X Jones MK Kelly JJ Khandaker M Kozlov A Kramer KM Kumbartzki G LeRose JJ Lhuillier D Lindgren RA Liyanage N Lolos GJ Margaziotis DJ 《Physical review letters》2002,88(9):092301
The ratio of the electric and magnetic form factors of the proton G(E(p))/G(M(p)), which is an image of its charge and magnetization distributions, was measured at the Thomas Jefferson National Accelerator Facility (JLab) using the recoil polarization technique. The ratio of the form factors is directly proportional to the ratio of the transverse to longitudinal components of the polarization of the recoil proton in the elastic e(-->)p---> e(-->)p reaction. The new data presented span the range 3.5< Q(2)< 5.6 GeV(2) and are well described by a linear Q(2) fit. Also, the ratio sqrt[Q(2)] F(2(p))/F(1(p)) reaches a constant value above Q(2) = 2 GeV(2). 相似文献
929.
930.