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1.
We report some properties of the maximum eigenvalues of the reciprocal distance matrix and the reverse Wiener matrix of a connected graph, in particular, various lower and upper bounds, and the Nordhaus–Gaddum‐type results for them. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008  相似文献   

2.
On Harary index     
We report lower and upper bounds for the Harary index of a connected (molecular) graph, and, in particular, upper bounds of triangle- and quadrangle-free graphs. We also give the Nordhaus–Gaddum-type result for the Harary index. Dedicated to the memory of Professor Frank Harary (1921–2005), the late grandmaster of both graph theory and chemical graph theory.  相似文献   

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4.
Let G be a graph with n vertices and d i is the degree of its ith vertex (d i is the degree of v i). In this article, we compute the redefined first Zagreb index, redefined second Zagreb index, redefined third Zagreb index, augmented Zagreb index of graphs carbon nanocones CNC k[n], and nanotori [C4C6C8(p,q)]. Also, compute the multiplicative redefined first Zagreb index, multiplicative redefined second Zagreb index, multiplicative redefined third Zagreb index, multiplicative augmented Zagreb index of carbon nanocones CNC k[n], and nanotori [C4C6C8(p,q)].  相似文献   

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A method for resolution enhancement of a.c. polarograms (voltammograms) is presented. The method is based on deconvolution using fast Fourier transforms. Overlapped a.c. polarograms are mathematically narrowed and sharpened, retaining the peak position and linear proportionality of the sharpened peak height with concentration. The advantages and limitations of the method are demonstrated on simulated and experimental a.c. polarograms. The same approach is applicable to related techniques such as. differential pulse and square-wave polarography.  相似文献   

7.
The notion of the chemical structure matrix (CSM) is introduced. The columns of the CSM represent the numbers of occurrences of different subgraphs in molecular graphs and are treated as vectors in a linear space. Any topological indices and physicochemical properties can also be treated as vectors in the same linear space. The QSPR problem is formally reduced to the search for linear correlations between vectors. A simple procedure for solving the problem is proposed. A novel method for establishing QSAR is outlined. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1447–1453, September, 2006.  相似文献   

8.
Entries of the topological distance matrix are shown to be functions of entries of the reduced distance matrix, which has a smaller size. The latter entries are expressed through a minimum number m of independent parameters (m ≤ 2n − 3). The expanded distance matrices, whose sum constitutes the reduced matrix, are defined. The reduced vectors have lower degeneracy than the corresponding vectors proposed by Randić as molecular codes. Nondegenerate sets of reduced-matrix entries are proposed as molecular codes.  相似文献   

9.
The method to derive the rate matrix K of a chemical reaction in a direct and straightforward way is here completed with the introduction of a new rule due to the application of the detailed balance principle. This principle let us discover a further characteristic of the rate matrices for cyclic reactions, a characteristic that can be used both to check the validity of the rate matrix and to improve the mechanical method used to derive the structure of these matrices in a straightforward way.  相似文献   

10.
Imaging mass spectrometry is a powerful technique for the molecular analysis of tissue sections. As in many analytical methods, sample preparation is one of the main and most important steps to obtain results of good quality. Usually, the matrix concentration and solvent composition in different studies are taken for granted without any further consideration. In our studies, we aimed to find how matrix concentration and a type of solvent influence the signal. Moreover, we also aimed to find the relationship between these parameters, how they influence the spectra, and how they influence obtained ion maps. In our experiments, we used SunCollect®, which is a commercially available wet-interface system for matrix deposition. We decided to choose two matrix concentrations (2,5-dihydroxybenzoic acid [DHB]: 15 and 25 mg/mL; 9-aminoacridine [9AA]: 7 and 5 mg/mL) and two different water solutions of solvents in two different percentages for the matrices (DHB: 50% and 70% of methanol [MeOH] and acetonitrile [ACN]; 9AA 70% and 50% of ethanol [EtOH] and MeOH). In the end, the influence of these parameters on obtained spectra and ion maps was assessed.  相似文献   

11.
We report some properties of the reciprocal molecular topological index RMTI of a connected graph, and, in particular, its relationship with the first Zagreb index M1. We also derive the upper bounds for RMTI in terms of the number of vertices and the number of edges for various classes of graphs, including K r+1 -free graphs with r ≥ 2, quadrangle-free graphs, and cacti. Additionally, we consider a Nordhaus-Gaddum-type result for RMTI.  相似文献   

12.
An Aufbau recursive algorithm, leading to the construction of molecular Quantum similarity matrices (QSM) with positive definite structure is described. As a consequence, Molecular Quantum Similarity measures optimization has to be restricted by a recursive constraint, related to the Euclidian norm of the QSM column elements in Quantum Object density tag reciprocal space.  相似文献   

13.
Summary Finite order expressions are derived for expectation values and transition matrix elements within the framework of the coupled cluster method.  相似文献   

14.
We find a necessary and sufficient conditions on a sequence
for the existence of an acyclic molecular graph G such that exactly m ij edges connect vertices of degree i and j. We use this result together with two additional results to make an algorithm that generates all the sequences
such that a molecular acyclic graph exists with exactly m ij edges connecting vertices of degree i and j. This algorithm is utilized to compare discriminative properties of the Zagreb index and the modified Zagreb index, and it is found that the modified Zagreb index is more discriminative then the Zagreb index.  相似文献   

15.
In a recent article Gopinathan and Jug have proposed a definition of atomic valency which had previously been given by Armstrong, Perkins and Stewart for closed shell molecules. The validity and interpretation of this definition for open shell systems is discussed. A new parameter for structural analysis, the free electron index, is presented.We want to acknowledge the computer time made available by Centro de Estudios Superiores para el Procesamiento de la Informatión (CESPI) de la Universidad National de La Plata and many useful suggestions made by the referees of this paper.  相似文献   

16.
The aim of this study was to examine two different synthetic routes for obtaining new hydrophilic matrices either by the modification of a synthetic matrix or by the copolymerization of hydrophilic monomers. First, the acrylic acid‐ethylene glycol dimethacrylate (AAc‐EGDMA) matrix, obtained from suspension with cyclohexane as the diluent at 70 °C after 2 h of reaction, was used as a base to be modified with TRIS(hydroxymethyl)aminomethane (TRIS). Experimental variables affecting the carbodiimide‐mediated amide‐bond development (i.e., the type of carbodiimide, reaction time, pH, and concentration of the matrix in the reaction medium) on the synthetic AAc‐EGDMA matrix with TRIS were studied. Second, the N‐acryloyl‐TRIS(hydroxymethyl)aminomethane‐ethylene glycol dimethacrylate (NAT‐EGDMA) matrix was obtained under the same experimental conditions as reported for AAc‐EGDMA. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 489–497, 2000  相似文献   

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18.
Using the unitary group approach it is shown that the amount of storage needed for the construction of symbolic CI matrix element lists for N-electron basis functions with large numbers of open shells and arbitrary multiplicities may substantially be reduced compared to methods currently available in the literature.  相似文献   

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20.
Experiments for the determination of mono-, di and tri-butyltin (MBT, DBT and TBT) by hydride generation/gas chromatography/atomic absorption spectrometry in various matrices (sediment, suspended matter, mussel, algae and water) have revealed that poor butyltin recoveries are obtained in sediments displaying high sulphur and hydrocarbon contents; very poor recoveries were also observed for TBT in sediments with high chlorophyll pigment contents as well as in algal samples. It was however not clear whether the hydride generatin was inhibited by these infering compounds, as was previously assumed in the case of hydrocarbons, or whether interferences affected the atomization rate. Further studies were performed to solve this problem in order to validate this method in the case of analyses of, for example, oil-contaminated sediment and algae. This paper presents the results obtained. It is concluded here that the poor recoveries were due to an inhibition of hydride generation rather than to interference at the atomization stage.  相似文献   

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