Let G be a graph with vertex set V (G) and edge set E(G) . The first and second multiplicative Zagreb indices of G are Π1 = ∏ x∈V (G) deg(x) 2 and Π2 = ∏ xy∈E(G) deg(x) deg(y) , respectively, where deg(v) is the degree of the vertex v . Let Tn be the set of trees with n vertices. We determine the elements of Tn , extremal w.r.t. Π1 and Π2 . AMS Mathematics Subject Classification (2000): 05C05, ...

To characterize molecule structures by using informationtheoretic techniques is an interesting and challenging problem in mathematical chemistry. However, most of the classical information indices are only defined for characterizing the skeletons of chemical graphs that correspond to unweighted graphs. This work presents a possible extension of an information measure that was recently developed...

Let G and H be graphs. The tensor product G⊗H of G and H has vertex set V (G ⊗ H) = V (G) × V (H) and edge set E(G ⊗ H) = {(a, b)(c, d)|ac ∈ E(G) and bd ∈ E(H)}. In this paper, some results on this product are obtained by which it is possible to compute the Wiener and Hyper Wiener indices of Kn ⊗G.

Let G be a simple connected graph in chemical graph theory and uν e = be an edge of G. The Randić index ( ) G χ and sum-connectivity ( ) G X of a nontrivial connected graph G are defined as the sum of the weights ν ud d 1 and ν u d d + 1 over all edges ν u e = of G, respectively. In this paper, we compute Randić ( ) G χ and sum-connectivity ( ) G X indices of V-phenylenic nanotubes and nanotori.

It is proved that the Wiener index of a weighted graph (G, w) can be expressed as the sum of the Wiener indices of weighted quotient graphs with respect to an arbitrary combination of Θ∗-classes. Here Θ∗ denotes the transitive closure of the Djoković-Winkler’s relation Θ. A related result for edge-weighted graphs is also given and a class of graphs studied in [19] is characterized as partial cu...

Let I(G) be a topological index of a graph. If I(G+ e) < I(G) (or I(G+ e) > I(G), respectively) for each edge e ∈ G, then I(G) decreases (or increases, respectively) with addition of edges. In this paper, we determine the extremal values of some topological indices which decrease or increase with addition of edges, and characterize the corresponding extremal graphs in bipartite graphs with a gi...

A new parameter, related to and easily determined from the structure of a benzenoid system and that of a phenylene – the number of inlets (r) – is introduced. The connectivity (Randi}) index of both benzenoid systems and phenylenes is then shown to depend solely on the number of vertices and on r. A simple relation is established between the connectivity index of a phenylene and of the correspo...

Measurement of vegetation photosynthetic activity from space has been an objective for the development of new techniques. Among the different existing techniques, passive fluorescence measurements, specific reflectance indices such as the PRI (Photochemical Reflectance Index), and derivative of high spectral resolution reflectance in the red-edge (680-750 nm) are the three methods than can be u...

The Hosoya index of a (molecular) graph is defined as the total number of the matchings, including the empty edge set, of this graph. Let Un,d be the set of connected unicyclic (molecular) graphs of order n with diameter d. In this paper we completely characterize the graphs from Un,d minimizing the Hosoya index and determine the values of corresponding indices. Moreover, the third smallest Hos...