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排序方式: 共有229条查询结果,搜索用时 15 毫秒
31.
The summation of the small x-corrections to hard-scattering QCD amplitudes by collinear factorisation method is reconsidered and the K-factor is derived in leading ln?x approximation with a result differing from the corresponding expression by Catani and Hautmann (Nucl. Phys. B 427, 475, 1994). The significance of the difference is demonstrated in the examples of structure function F L and of exclusive vector meson electroproduction. The formulation covers the channels of non-vanishing conformal spin n paving the way for new applications. 相似文献
32.
Fukumoto K Kuch W Vogel J Romanens F Pizzini S Camarero J Bonfim M Kirschner J 《Physical review letters》2006,96(9):097204
The dynamics of magnetic domain wall motion in the FeNi layer of a FeNi/Al2O3/Co trilayer has been investigated by a combination of x-ray magnetic circular dichroism, photoelectron emission microscopy, and a stroboscopic pump-probe technique. The nucleation of domains and subsequent expansion by domain wall motion in the FeNi layer during nanosecond-long magnetic field pulses was observed in the viscous regime up to the Walker limit field. We attribute an observed delay of domain expansion to the influence of the domain wall energy that acts against the domain expansion and that plays an important role when domains are small. 相似文献
33.
Allodi MA Dunn ME Livada J Kirschner KN Shields GC 《The journal of physical chemistry. A》2006,110(49):13283-13289
It has been speculated that the presence of OH(H2O)n clusters in the troposphere could have significant effects on the solar absorption balance and the reactivity of the hydroxyl radical. We have used the G3 and G3B3 model chemistries to model the structures and predict the frequencies of hydroxyl radical/water clusters containing one to five water molecules. The reaction between hydroxyl radical clusters and methane was examined as a function of water cluster size to gain an understanding of how cluster size affects the hydroxyl radical reactivity. 相似文献
34.
Pickard FC Shepherd RL Gillis AE Dunn ME Feldgus S Kirschner KN Shields GC Manoharan M Alabugin IV 《The journal of physical chemistry. A》2006,110(7):2517-2526
We present a detailed theoretical study of geometries, electronic structure, and energies of transition states and intermediates completing the full Bergman cycloaromatization pathway of ortho-substituted enediynes with a focus on polar and steric contributions to the kinetics and thermodynamics of hydrogen abstraction. This study provides a rare unambiguous example of remote substitution that affects reactivity of a neutral reactive intermediate through an sigma framework. 相似文献
35.
Mironets O Meyerheim HL Tusche C Stepanyuk VS Soyka E Zschack P Hong H Jeutter N Felici R Kirschner J 《Physical review letters》2008,100(9):096103
Surface x-ray diffraction in combination with scanning tunneling microscopy and molecular dynamics calculations provide first quantitative evidence for unusually large relaxations in nanometer-sized Co islands deposited on Cu(001) at 170 K. These lead to sharply reduced interatomic Co distances as low as 2.36 A as compared to bulk Co (2.51 A) involving low symmetry Co adsorption sites. Our results prove the validity of the concept of mesoscopic mismatch which governs the strain relaxation of nanosized islands in general. 相似文献
36.
Justina Jovaišaitė Sven Kirschner Steponas Raišys Gediminas Kreiza Paulius Baronas Saulius Juršėnas Matthias Wagner 《Angewandte Chemie (International ed. in English)》2023,62(4):e202215071
Organic ultralong room temperature phosphorescence (RTP), or organic afterglow, is a unique phenomenon, gaining widespread attention due to its far-reaching application potential and fundamental interest. Here, two laterally expanded 9,10-dimesityl-dihydro-9,10-diboraanthracene (DBA) derivatives are demonstrated as excellent afterglow materials for red and blue-green light emission, which is traced back to persistent thermally activated delayed fluorescence and RTP. The lateral substitution of polycyclic DBA scaffold, together with weak transversal electron-donating mesityl groups, ensures the optimal molecular properties for (reverse) intersystem crossing and long-lived triplet states in a rigid poly(methyl methacrylate) matrix. The achieved afterglow emission quantum yields of up to 3 % and 15 %, afterglow lifetimes up to 0.8 s and 3.2 s and afterglow durations up to 5 s and 25 s (for red and blue-green emitters, respectively) are attributed to the properties of single molecules. 相似文献
37.
Kohler A Bertrand D Martens H Hannesson K Kirschner C Ofstad R 《Analytical and bioanalytical chemistry》2007,389(4):1143-1153
In this paper we present an algorithm for analysing sets of FTIR microscopic images of tissue sections. The proposed approach
allows one to investigate sets of many FTIR tissue images both with respect to sample information (variation from image to
image) and spatial variations of tissues (variation within the image). The algorithm is applied to FTIR microscopy images
of beef loin muscles containing myofibre and connective tissue regions. The FTIR microscopy images are taken of sub-samples
from five different beef loin muscles that were aged for four different lengths of time. The images were investigated regarding
variation due to the ageing length and due to the homogeneity of the connective tissue regions. The presented algorithm consists
of the following main elements: (1) pre-processing of the spectra to overcome large quality differences in FTIR spectra and
differences due to scatter effects, (2) identification of connective tissue regions in every image, (3) labelling of every
connective tissue spectrum with respect to its location in the connective tissue region, and (4) analysis of variations in
the FTIR microscopic images in regard to ageing time and pixel position of the spectra in the connective tissue region. Important
spectral parameters characterising collagen and proteoglycan structure were determined.
Figure Effective optical path length estimated by EMSC 相似文献
38.
Gaussian-3 and MP2/aug-cc-pVnZ methods have been used to calculate geometries and thermochemistry of CS(2)(H2O)n, where n=1-4. An extensive molecular dynamics search followed by optimization using these two methods located two dimers, six trimers, six tetramers, and two pentamers. The MP2/aug-cc-pVDZ structure matched best with the experimental result for the CS(2)(H2O) dimer, showing that diffuse functions are necessary to model the interactions found in this complex. For larger CS(2)(H2O)n clusters, the MP2/aug-cc-pVDZ minima are significantly different from the MP2(full)6-31G* structures, revealing that the G3 model chemistry is not suitable for investigation of sulfur containing van der Waals complexes. Based on the MP2/aug-cc-pVTZ free energies, the concentration of saturated water in the atmosphere and the average amount of CS(2) in the atmosphere, the concentrations of these clusters are predicted to be on the order of 10(5) CS(2)(H2O) clusters.cm(-3) and 10(2) CS(2)(H2O)(2) clusters.cm(-3) at 298.15 K. The MP2/aug-cc-pVDZ scaled harmonic and anharmonic frequencies of the most abundant dimer cluster at 298 K are presented, along with the MP2/aug-cc-pVDZ scaled harmonic frequencies for the CS(2)(H(2)O)(n) structures predicted to be present in a low-temperature molecular beam experiment. 相似文献
39.
Identification of small-molecule targets remains an important challenge for chemical genetics. We report an approach for target identification and protein discovery based on functional suppression of chemical inhibition in vitro. We discovered pirl1, an inhibitor of actin assembly, in a screen conducted with cytoplasmic extracts. Pirl1 was used to partially inhibit actin assembly in the same assay, and concentrated biochemical fractions of cytoplasmic extracts were added to find activities that suppressed pirl1 inhibition. Two activities were detected, separately purified, and identified as Arp2/3 complex and Cdc42/RhoGDI complex, both known regulators of actin assembly. We show that pirl1 directly inhibits activation of Cdc42/RhoGDI, but that Arp2/3 complex represents a downstream suppressor. This work introduces a general method for using low-micromolar chemical inhibitors to identify both inhibitor targets and other components of a signaling pathway. 相似文献
40.
V.S. Stepanyuk D.I. Bazhanov A.N. Baranov W. Hergert A.A. Katsnelson P.H. Dederichs J. Kirschner 《Applied Physics A: Materials Science & Processing》2001,72(4):443-446
Structural relaxations in small Co islands on the Cu(001) surface are investigated performing atomistic calculations. We demonstrate
that the strain relief at the metal interface in the early stages of heteroepitaxy is more complicated than suggested by simple
considerations based on the small mismatch between the Co and Cu bulk metals. We found that the strain distribution in the
surface region near the islands varies strongly on an atomic scale. The effect of strain on the shape of the Co islands is
revealed. Diffusion on the top of strained islands and edge diffusion are considered.
Received: 10 April 2000 / Accepted: 15 May 2000 / Published online: 7 March 2001 相似文献