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51.
We discuss a class of reversible, discrete approximations to Hamilton's equations for use in the hybrid Monte Carlo algorithm and derive an asymptotic formula for the step-size-dependent errors arising from this family of approximations. For lattice QCD with Wilson fermions, we construct several different updates in which the effect of fermion vacuum polarization is given a longer time step than the gauge field's self-interaction. On a 44 lattice, one of these algorithms with an optimal choice of step size is 30% to 40% faster than the standard leapfrog update with an optimal step size. 相似文献
52.
Spectroscopic studies of the adsorption of dimethyl sulfoxide, (CH3)2S = O, on Pt(111) have shown that the molecule is bound to the surface via the sulfur atom in an inverted pyramid configuration. A comparison of XPS and EELS data for the adsorbed multilayer and monolayer with XPS and infrared data on the complex PtCl2(DMSO)2 is consistent with sulfur bonding. In addition, we detect a considerable increase of the v(S=O) frequency in the DMSO monolayer with decreasing coverage, indicating a coverage dependent heat of adsorption. UPS data show that on adsorption to form a monolayer, the highest occupied molecular orbital of DMSO, presumably the sulfur “lone pair” orbital, shifts to a higher binding energy. These results show a remarkable similarity between DMSO bonding to a metal surface and bonding to a single Pt2+ species. 相似文献
53.
Proper identification of the cable’s resonant frequencies is critical to provide an accurate estimate of cable force. The
MUltiple SIgnal Classification (MUSIC) algorithm is implemented to estimate cable-stayed bridge cable tensions noninvasively from measured
cable motion. This algorithm performs eigenanalysis on the data sequence to estimate and eliminate noise contributions before
creating its frequency spectrum, providing a more robust estimation approach than traditional Fourier based frequency spectrums.
To aid in the selection of cable frequencies, a comprehensive finite difference cable model is simulated and compared to the
estimated MUSIC spectrums. 相似文献
54.
Sayuri Yonekawa Aaron M. Goodpaster Benjamin A. Abel Rodney G. Paulin Charles W. Sexton James S. Poole Bruce N. Storhoff Phillip E. Fanwick 《Journal of heterocyclic chemistry》2006,43(3):689-694
5‐Azido‐2‐methoxy‐1,3‐xylyl‐18‐crown‐5 has been prepared by reacting p‐toluenesulfonyl azide with the carbanion generated from the reaction of 5‐bromo‐2‐methoxy‐1,3‐xylyl‐18‐crown‐5 with n‐butyl lithium. The asymmetric N3 stretch of this product has been observed as a single band at 2110 cm?1 in dichloromethane solution. Addition of solid NaSCN, KSCN and CsSCN shifts this band to 2115, 2113 and 2112 cm?1, respectively. Computational studies of this azide at the B3LYP‐6‐31G* level in the presence and absence of Na+ predicted these bands to be at 2173 cm?1 and 2184 cm?1. For the salt‐containing solutions, additional bands were observed at 2066 cm?1, 2056 cm?1 and 2055 cm?1, respectively, which are in the range expected for CN stretches. The X‐ray structure of this azide has been determined. The terminal and internal N? N bond lengths were found to be 1.127(2) and 1.245(2) Δ, respectively, which is the usual pattern for aromatic azides. The crown ether is looped over the face of the aromatic ring resulting in an angle of 38.94° between the plane defined by the aromatic ring and that defined by the five ring oxygen atoms. In addition, the CH3 group is rotated out of the plane of the phenyl ring with C1‐C18‐O181‐C182 and C17‐C18‐O181‐C182 dihedral angles of 93.81(14)° and ‐90.54(14)°, respectively. 相似文献
55.
Background
The involvement of astrocyte water channel aquaporin-4 (AQP4) in autoimmune diseases of the central nervous system has been suggested following the identification of AQP4 autoantibodies in neuromyelitis optica, an inflammatory demyelinating disease. 相似文献56.
Mary E. Sexton Ami Okazaki Zhuowen Yu Alexis van Venrooy Jason R. Schmink William P. Malachowski 《Tetrahedron letters》2019,60(38):151057
Herein, we report the selective mono-γ-arylation of 7-methoxy-4-methylcoumarin under palladium-catalyzed conditions. The Buchwald G3 pre-catalyst in conjunction with either the Xantphos or N-Xantphos ligand proves to be highly reactive, engaging aryl iodides, bromides, chlorides, and triflates to effect the desired transformation. A wide range of functionality is tolerated, including the ability to activate heteroaryl halides in the transformation. The initial scope of aryl halides and limitations of this methodology are presented. 相似文献
57.
A fixed-time (integral) method is described for the enthalpimetric determination of enzyme activity. The method involves the determination of residual unreacted substrate after a fixed incubation time with the sample. Results are presented for the determination of cholinesterase in aqueous solution and in 0.1cm3 samples of reference sera using 30-min incubation periods. Results are correlated with a spectrophotometric procedure. A precision of 1.8% relative standard deviation is reported for serum assays. Preliminary data are also presented for the enthalpimetric determination of cholinesterase activity after immobilization onto non-porous glass beads by carbodiimide and glutaraldehyde coupling procedures. 相似文献
58.
High resolution electron energy loss vibrational spectroscopy was used to study the intermediate formed in the dehydration reaction for formic acid on Ni(110) and Ni(110)(4 × 5)C. On the carbided surface only the formate was observed. The frequencies of the asymmetric and symmetric OCO sketch indicated a monodentate configuration. On the clean surface a mixed adlayer of CO and HCOO formed. No losses expected for formic anhydride were observed. Lateral interactions between CO and HCOO appear to be responsible for the autocatalytic decomposition of the formate. 相似文献
59.
C.G. Olson J.H. Sexton D.W. Lynch A.J. Bevolo H.R. Shanks B.N. Harmon W.Y. Ching D.M. Wieliczka 《Solid State Communications》1985,56(1):35-37
The valence bands of epitaxial layers of A1N were studied by ultraviolet photoelectron spectroscopy and electron energy loss spectroscopy. A self-consistent band structure was calculated and the resultant density of states compared with the UPS spectra. Qualitative agreement was good, with discrepancies arising primarily from the neglect of dipole matrix elements. 相似文献
60.
Let pn be the nth prime. Then this paper is concerned with provingthe following result on the distribution of consecutive primes. The exponent of x in this theorem improves on the work of Heath-Brownwho proved (1) with exponent . Under the Riemann hypothesisone can prove (1) with exponent .The proof of the theorem startswith the Heath-BrownLinnik identity which leads to aformula giving the number of primes in an interval in termsof coefficients of certain Dirichlet series. I then estimatethe coefficients by using, among other things, the informationwhich can be gained from Montgomery's mean value theorem andHuxley's version of the Hal' asz lemma. Furthermore, by usingfamiliar sieve arguments I am able to discard some of the coefficientsallowing us to gain an improvement over the previous resultof Heath-Brown. 1991 Mathematics Subject Classification: 11N05. 相似文献