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21.
关于拼挤黎曼流形中具有平行平均曲率向量的子流形 总被引:3,自引:1,他引:3
徐慧群 《浙江大学学报(理学版)》1997,24(4):297-305
本文对一般拼挤黎受流形中的具有平行平均曲率向量的等距浸入子流形给出了一个积分不等式,推广了文献〔3].[6〕的结果. 相似文献
22.
Irena Zupanič Pajnič Carlo Previderè Tomaž Zupanc Martina Zanon Paolo Fattorini 《Electrophoresis》2022,43(13-14):1521-1530
The recent introduction of polymerase chain reaction (PCR)-massively parallel sequencing (MPS) technologies in forensics has changed the approach to allelic short tandem repeat (STR) typing because sequencing cloned PCR fragments enables alleles with identical molecular weights to be distinguished based on their nucleotide sequences. Therefore, because PCR fidelity mainly depends on template integrity, new technical issues could arise in the interpretation of the results obtained from the degraded samples. In this work, a set of DNA samples degraded in vitro was used to investigate whether PCR-MPS could generate “isometric drop-ins” (IDIs; i.e., molecular products having the same length as the original allele but with a different nucleotide sequence within the repeated units). The Precision ID GlobalFiler NGS STR panel kit was used to analyze 0.5 and 1 ng of mock samples in duplicate tests (for a total of 16 PCR-MPS analyses). As expected, several well-known PCR artifacts (such as allelic dropout, stutters above the threshold) were scored; 95 IDIs with an average occurrence of 5.9 IDIs per test (min: 1, max: 11) were scored as well. In total, IDIs represented one of the most frequent artifacts. The coverage of these IDIs reached up to 981 reads (median: 239 reads), and the ratios with the coverage of the original allele ranged from 0.069 to 7.285 (median: 0.221). In addition, approximately 5.2% of the IDIs showed coverage higher than that of the original allele. Molecular analysis of these artifacts showed that they were generated in 96.8% of cases through a single nucleotide change event, with the C > T transition being the most frequent (85.7%). Thus, in a forensic evaluation of evidence, IDIs may represent an actual issue, particularly when DNA mixtures need to be interpreted because they could mislead the operator regarding the number of contributors. Overall, the molecular features of the IDIs described in this work, as well as the performance of duplicate tests, may be useful tools for managing this new class of artifacts otherwise not detected by capillary electrophoresis technology. 相似文献
23.
Krzysztof Wolinski Robert Haacke James F. Hinton Peter Pulay 《Journal of computational chemistry》1997,18(6):816-825
We implemented our gauge-including atomic orbital (GIAO) NMR chemical shielding program on a workstation cluster, using the parallel virtual machine (PVM) message-passing system. On a modest number of nodes, we achieved close to linear speedup. This program is characterized by several novel features. It uses the new integral program of Wolinski that calculates integrals in vectorized batches, increases efficiency, and simplifies parallelization. The self-consistent field (SCF) step includes a multi-Fock algorithm, i.e., the simultaneous calculation of several Fock matrices with the same integral set, increasing the efficiency of the direct SCF procedure. The SCF diagonalization step, which is difficult to parallelize, has been replaced by pseudodiagonalization. The latter, widely used in semiempirical programs, becomes important in ab initio type calculations above a certain size, because the ultimate scaling of the diagonalization step is steeper than that of integral computation. Examples of the calculation of the NMR shieldings in large systems at the SCF level are shown. Parallelization of the density functional code is underway. © 1997 by John Wiley & Sons, Inc. J Comput Chem 18: 816–825, 1997 相似文献
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25.
Nicholas F. Chilton Russell P. Anderson Lincoln D. Turner Alessandro Soncini Keith S. Murray 《Journal of computational chemistry》2013,34(13):1164-1175
A new program, PHI, with the ability to calculate the magnetic properties of large spin systems and complex orbitally degenerate systems, such as clusters of d‐block and f‐block ions, is presented. The program can intuitively fit experimental data from multiple sources, such as magnetic and spectroscopic data, simultaneously. PHI is extensively parallelized and can operate under the symmetric multiprocessing, single process multiple data, or GPU paradigms using a threaded, MPI or GPU model, respectively. For a given problem PHI is been shown to be almost 12 times faster than the well‐known program MAGPACK, limited only by available hardware. © 2013 Wiley Periodicals, Inc. 相似文献
26.
Chuan Li Marharyta Petukh Lin Li Emil Alexov 《Journal of computational chemistry》2013,34(22):1949-1960
Due to the enormous importance of electrostatics in molecular biology, calculating the electrostatic potential and corresponding energies has become a standard computational approach for the study of biomolecules and nano‐objects immersed in water and salt phase or other media. However, the electrostatics of large macromolecules and macromolecular complexes, including nano‐objects, may not be obtainable via explicit methods and even the standard continuum electrostatics methods may not be applicable due to high computational time and memory requirements. Here, we report further development of the parallelization scheme reported in our previous work (Li, et al., J. Comput. Chem. 2012, 33, 1960) to include parallelization of the molecular surface and energy calculations components of the algorithm. The parallelization scheme utilizes different approaches such as space domain parallelization, algorithmic parallelization, multithreading, and task scheduling, depending on the quantity being calculated. This allows for efficient use of the computing resources of the corresponding computer cluster. The parallelization scheme is implemented in the popular software DelPhi and results in speedup of several folds. As a demonstration of the efficiency and capability of this methodology, the electrostatic potential, and electric field distributions are calculated for the bovine mitochondrial supercomplex illustrating their complex topology, which cannot be obtained by modeling the supercomplex components alone. © 2013 Wiley Periodicals, Inc. 相似文献
27.
采用格子自洽场理论计算研究了受限于2个平行板间的对称星形共聚物AmBm(m=1,2,3,4,5)熔体形成的层状相结构.在给定的相互作用下(χNAB不变,χ为Flory-Huggins相互作用参数,NAB=(N?1)/m为单个聚合物分子中一对AB臂的总链节数目),针对平行板间距为体相周期的情况,系统考察了共聚物链长N和单个聚合物分子中A(或B)臂数目m对受限层结构细节及层取向的影响.由计算结果,当N或NAB不变时,受限层的归一化界面宽度随m的增大而减小.受限板为中性时,垂直层结构的单链自由能比平行层结构的低.随着板对共聚物中一种嵌段的选择作用Λ的增大,体系发生垂直层到平行层的转变,该转变为一阶相变.当m不变时,N越小,上述转变出现在越大的Λ值处,体系越容易保持垂直层结构.并且N越小,层状结构周期越小.当N或NAB不变时,m越大体系越容易保持垂直层结构.总之,星形共聚物的链长越短、臂数越多时,垂直层稳定的Λ区间越大、层状结构的界面宽度越小.这些结论可以指导刻蚀应用中对体系参数的选择. 相似文献
28.
A new form of charged particle energy analyser is proposed. It is broadly based on the 180° magnetic spectrograph, but is intended to detect charged particles moving out of the dispersion plane with a helical motion. The analyser has the capability to acquire charged particle energy spectra over a large energy range, similar to those acquired in Auger electron spectroscopy, ca. 2500 eV and large angular range, up to 90°, in parallel. These conditions are more favourable for surface analysis by electron spectroscopy at high vacuum, where for example an electron energy resolution of 0.2% to 0.5% is typical. Expressions showing how the landing positions of the charged particles on the detector vary as a function of energy and polar take off angle are determined as well as the conditions for optimum energy resolution at a range of polar take off angles. The equations reveal that in general, the device obtains the highest resolution at angles of revolution greater than 180°. The design is simple and could be easily put into practice using available material and technologies and be used to analyse the energies of electrons emitted from a sample placed in a scanning electron microscope. It can be made to function with a primary electron beam of any desired energy and could fit in to the small space between the sample and the end of an electron column. However, the device is difficult to retrofit into existing SEMs and ideally an SEM column needs to be designed to work in association with the analyser. The direction of the magnetic field of the analyser is coincident with the axis of the electron gun so that the primary beam is little influenced by the magnetic field and symmetry can be maintained in the primary beam electron column. Because the device is intended to acquire electron spectra in parallel, any movement of the primary beam on the sample because of a ramping field in the analyser is avoided. The field of view and the effect of the analyser upon the operation of the SEM are discussed. Spectra including elastic and Auger peaks reveal an energy resolution of ~4 eV at 900‐eV electron energy. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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The electrical interaction between two long, parallel cylinders each is covered by an ion-penetrable charged membrane immersed in an oil/water interface is investigated. The effects of contact angle, radius of cylinder, and membrane thickness on the electrical interaction force are examined. The results of numerical simulation reveal that the following conditions lead to a greater electrical interaction force: (i) a larger contact angle, i.e. a larger fraction of a cylinder in the oil phase; (ii) a larger cylinder radius; and (iii) a thinner membrane. For a fixed ionic strength, the electrical interaction force is insensible to the type of electrolytes in the water phase, in general. However, if two cylinders are close enough, then the higher the valence of counterions the greater the electrical interaction force. 相似文献