Estimations of subgraph positions in molecular graphs and their common subgraph peculiarities

Some questions emerged from electronic data processing of molecular structures (graphs) and its fragments have been considered in this work. Quantitative estimations of subgraph positions in molecular graphs are presented and some properties of their maximal common subgraphs are described.     

Semiglobal simplex optimization and its application to determining the preferred solvation sites of proteins

The classical simplex method is extended into the Semiglobal Simplex (SGS) algorithm. Although SGS does not guarantee finding the global minimum, it affords a much more thorough exploration of the local minima than any traditional minimization method. The basic idea of SGS is to perform a local minimization in each step of the simplex algorithm, and thus, similarly to the Convex Global Underestimator (CGU) method, the search is carried out on a surface spanned by local minima. The SGS and CGU methods are compared by minimizing a set of test functions of increasing complexity, each with a known global minimum and many local minima. Although CGU delivers substantially better success rates in simple problems, the two methods become comparable as the complexity of the problems increases. Because SGS is generally faster than CGU, it is the method of choice for solving optimization problems in which function evaluation is computationally inexpensive and the search region is large. The extreme simplicity of the method is also a factor. The SGS method is applied here to the problem of finding the most preferred (i.e., minimum free energy) solvation sites on a streptavidin monomer. It is shown that the SGS method locates the same lowest free energy positions as an exhaustive multistart Simplex search of the protein surface, with less than one-tenth the number of minizations. The combination of the two methods, i.e.. multistart simplex and SGS, provides a reliable procedure for predicting all potential solvation sites of a protein.     

PERI-INTERACTIONS IN NAPHTHALENES, 21. SUBSTITUENT EFFECTS IN (8-DIMETHYLAMINO-NAPHTH-1-YL)- AND [2-DIMETHYLAMINO-METHYL)PHENYL] - PHOSPHINES ON THE 31P-NMR SIGNAL POSITIONS

Abstract

Contrary to claims in the literature, the ³¹P NMR signal positions of ortho-dimethylaminomethyl-substituted triarylphosphines do not provide evidence for hypercoordination at phosphorus; the observed highfield shifts relative to triphenylphosphine are rather due to the ortho-effect. In (8-dimethylamino-naphth-1-yl)phosphines, the signal positions similar to that of triphenylphosphine are the result of the highfield ortho-effect and a lowfield peri-substituent effect of about the same magnitude whose nature remains to be explored.     

APU故障智能诊断系统设计

针对高旋环境下测试困难、测量精度低这一问题,提出了一种能在高旋环境下实现轴向减速装置,以达到稳定的良好的测试环境。该装置通过驱动仓内大量程陀螺仪测得的转速反馈给控制系统,控制系统输出控制信号来控制伺服电机,同时电机捷联内筒仓,使其相对外部转动方向反向旋转,实现轴向减速。实验结果表明,该装置可在高旋弹药飞行过程中提供稳定测试环境,从而得到更精准的姿态解算结果,为高旋环境下的测试提供了新的思路,具有广阔的应用前景。     

Influence of vent positions on smoke clearance from a room

Results of solutions to the equations governing the clearance of smoke in laminar and in turbulent flow from a single rectilinear room are presented fof five different vent arrangements. These results show that the average smoke concentration in the room decreases in an approximately exponential manner with time at a rate that depdends much more on room geometry (vent positions in the present case) than on whether the flow is laminar or turbulent. The benefit of this observation is that, provided the clearance air jet is disrupted by impingement on a solid surface within the room, the analysis of smoke movement can for many practical purposes be limited to consideration of laminar flow only. An exceptional case is when the jet is allowed to take a straight line path between the inlet and outlet vents. Here in the absence of the large scale eddies caused by jet impingement, the smaller scale eddies of turbulent flow become relatively important as a mixing mechanism and give higher clearance rates than in laminar flow. Even so, this type of geometry is best avoided. The appearance of the jet is shown in a graphic presentation of the numerical results for laminar flow.     

污泥的超声破解实验研究

本文在测量超声破解污泥试验所用反应器声场的基础上,主要研究了复频超声作用下,超声频率和换能器位置对污泥破解效果的影响。在此基础上采用两个同相换能器,以污泥滤液COD、NH₃-N、TP的增量,首次研究了复频超声破解污泥的效果,且详细探讨了影响复频超声破解污泥的影响因素（不同频率组合、不同功率组合、不同时间组合）。实验结果与理论分析符合较好,从而说明超声是一种有效的破解污泥的方法,进而对超声处理污泥的规律进行研究,这将为超声处理污泥提供一定的实验基础。     

The ν5 and 2ν9 bands of the N isotopic species of nitric acid (H15NO3): Line positions and intensities

Nitric acid (HNO₃) plays an important role in the Earth’s atmosphere as a reservoir molecule of NO_x species. It has a strong infrared signature at 11 μm which is one of the most commonly used for the infrared retrieval of this species in the atmosphere since this spectral region coincides with an atmospheric window. It is therefore essential to have high quality spectral parameters in this spectral region. For the H¹⁴NO₃ (main) isotopic species, the 11 μm bands were already the subject of numerous extensive studies which involve not only the ν₅ and 2ν₉ cold bands but also the first hot bands. The present work is the first high resolution Fourier transform analysis of the 11 μm bands for H¹⁵NO₃, which is the second most abundant isotopomer of nitric acid [a ≅ 0.00365(7)]. In this way, the analysis of the ν₅ and 2ν₉ cold bands centered at 871.0955 and 893.4518 cm⁻¹ was performed, and as for H¹⁴NO₃, these bands are significantly perturbed since rather strong resonances couple the 5¹ and 9² rotational levels. The theoretical model that we used to compute the line positions and line intensities is directly issued from the one which we used recently for H¹⁴NO₃ [A. Perrin, J. Orphal, J.-M. Flaud, S. Klee, G. Mellau, H. Mäder, D. Walbrodt, M. Winnewisser, J. Mol. Spectrosc. 228 (2004) 375-391]. Actually, for the H¹⁵NO₃ line positions, the Hamiltonian matrix accounts for the rather strong Fermi and the weaker Coriolis interactions linking the 5¹⇔9² rotational levels. Using this model which accounts correctly for the strong mixing of the 5¹ and 9² upper state energy levels, the ν₅ and 2ν₉ line intensities for H¹⁵NO₃ were satisfactorily computed using the ν₅ and 2ν₉ transition moment operators achieved previously for the ¹⁴N (main) isotopic species. In this way, the transfer of intensities from the ν₅ fundamental (and presumably strong) band to the 2ν₉ overtone (and presumably weak) band could be explained for H¹⁵NO₃ as it was done previously for the ¹⁴N (main) isotopic species. Finally, the position of the H¹⁵NO₃ν₅ + ν₉ − ν₉ hot band was identified at 875.245 cm⁻¹.     

Probing Absolute Electronic Energy Levels in Hg‐Doped CdTe Semiconductor Nanocrystals by Electrochemistry and Density Functional Theory

The absolute electronic energy levels in Hg‐doped CdTe semiconductor nanocrystals (CdHgTe NCs) with varying sizes/volumes and Hg contents are determined by using cyclic voltammetry (CV) measurements and density functional theory (DFT) ‐based calculations. The electrochemical measurements demonstrate several distinct characteristic features in the form of oxidation and reduction peaks in the voltammograms, where the peak positions are dependent on the volume of CdHgTe NCs as well as on their composition. The estimated absolute electronic energy levels for three different volumes, namely 22, 119 and 187 nm³ with 2.7±0.3 % of Hg content, show strong volume dependence. The volume‐dependent shift in the characteristic reduction and oxidation peak potential scan can be attributed to the alteration in the energetic band positions owing to the quantum confinement effect. Moreover, the composition (Cd/Hg=98.3/1.7 and 97.0/3.0) ‐dependent alteration in the electronic energy levels of CdHgTe NCs for two different samples with similar volumes (ca. 124±5 nm³) are shown. Thus obtained electronic energy level values of CdHgTe NCs as a function of volume and composition demonstrate good congruence with the corresponding absorption and emission spectral data, as well as with DFT‐based calculations. DFT calculations reveal that incorporation of Hg into CdTe NCs mostly affects the energy levels of conduction band edge, whereas the valence band edge remains almost unaltered.     

Recent advances in the structural determination of endohedral metallofullerenes

The structural determination of endohedral metallofullerenes has attracted special attention in disclosing the formation mechanism and developing new routes to bulk production. Recent advances in the theoretical and experimental studies are summarized with representative mono- and dimetallofullerenes such as M@C₈₂ (M=Ca, Sc, Y, and La), Sc₂@C₈₄, and La₂@C₈₀. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 232–239, 1998     

Distribution of selected monaural acoustical parameters in concert halls

Acoustical parameters calculated from impulse responses are often used to evaluate the characteristics of concert halls. Representative parameters are listed in the Annex of ISO 3382 and the methods of calculation and the minimum number of measurement positions are explained in detail. However, a method for selecting measurement positions is not discussed clearly, because there are wide variations in the characteristics of sound fields. This report provides basic data to solve this problem using spatial distribution characteristics of parameters in halls. Three large-scale measurement campaigns were conducted in which impulse responses were measured at 1427, 180, and 511 locations. Relatively large differences in the obtained parameters compared with well-known difference limens suggest that determining the distributions of parameter values is important. Contour maps are therefore used to display the distributions along with mean values.