جستجوی مقالات مرتبط با کلیدواژه « first zagreb index » در نشریات گروه « شیمی »

The neighborhood first Zagreb index has recently been introduced for characterizing the topological structure of molecular graphs. In the present study, we characterize the graphs having minimum neighborhood first Zagreb index in the class of unicyclic/bicyclic graphs on vertices for every fixed integer n ≥ 5.

The aim of this paper is to give an upper and lower bounds for the first and second Zagreb indices of quasi bicyclic graphs. For a simple graph G, we denote M1(G) and M2(G), as the sum of deg2(u) overall vertices u in G and the sum of deg(u)deg(v) of all edges uv of G, respectively. The graph G is called quasi bicyclic graph if there exists a vertex x ∈ V (G) such that G−x is a connected bicyclic graph. The results mentioned in this paper, are mostly new or an improvement of results given by authors for quasi unicyclic graphs in [1].

Quantitative Structure-Property Relationship (QSPR) models for modeling and predicting thermodynamic properties such as the enthalpy of vaporization at standard condition (ΔH˚vap kJ mol-1) and normal temperature of boiling points (T˚bp K) of 57 mono and Polycyclic Aromatic Hydrocarbons (PAHs) have been investigated. The PAHs were randomly separated into 2 groups: training and test sets. A set of molecular descriptors was calculated for selected compounds using the Dragon software. The Genetic Algorithm (GA) method and backward stepwise regression were used to select the suitable descriptors. Multiple Linear Regression (MLR) technique was used to obtain a linear relationship between descriptors and chemical properties. The predictive ability of the GA-MLR models was implemented using squared cross-validation and external validation methods. The aforementioned results and discussion lead us to conclude that the training set models established by GA-MLR method have good correlation of thermodynamic properties, which means QSPR models could be efficiently used for estimating and predicting of the above mentioned properties of the mono and PAHs.

In this paper we give sharp upper bounds on the Zagreb indices and characterize all trees achieving equality in these bounds. Also, we give lower bound on first Zagreb coindex of trees.