Convexity deficit of benzenoids

In 2012, a family of benzenoids was introduced by Cruz, Gutman, and Rada, which they called convex benzenoids. In this paper we introduce the convexity deficit, a new topological index intended for benzenoids and, more generally, fusenes. This index measures by how much a given fusene departs from convexity. It is defined in terms of the boundary-edges code. In particular, convex benzenoids are exactly the benzenoids having convexity deficit equal to 0. Quasi-convex benzenoids form the family of non-convex benzenoids that are closest to convex, i.e., they have convexity deficit equal to 1. Finally, we investigate convexity deficit of several important families of benzenoids

A Huckel Molecular Orbital Study of Some Aromatic Hydrocarbons

Abstract Not Provided

Nenad Trinajstić – Pioneer of Chemical Graph Theory

We present a brief overview of many contributions of Nenad Trinajstić to Chemical Graph Theory, an important and fast developing branch of Theoretical Chemistry. In addition, we outline briefly the various activities of Trinajstić within the chemical community of Croatia. As can be seen, his scientific work has been very productive and has not abated despite the hostilities towards the Chemical Graph Theory in certain chemical circles over the past 30 years. On the contrary, Trinajstić continued, widened the areas of his research interest, which started with investigating the close relationship between Graph Theory and HMO, and demonstrated the importance of Chemical Graph theory for chemistry. In more than one way he has proven the opponents of Chemical Graph Theory wrong, though some continue to fail to recognize the importance of Graph Theory in Chemistry

Two essays in computational optimization: computing the clar number in fullerene graphs and distributing the errors in iterative interior point methods

Fullerene are cage-like hollow carbon molecules graph of pseudospherical sym- metry consisting of only pentagons and hexagons faces. It has been the object of interest for chemists and mathematicians due to its widespread application in various fields, namely including electronic and optic engineering, medical sci- ence and biotechnology. A Fullerene molecular, Γ n of n atoms has a multiplicity of isomers which increases as N iso ∼ O(n 9 ). For instance, Γ 180 has 79,538,751 isomers. The Fries and Clar numbers are stability predictors of a Fullerene molecule. These number can be computed by solving a (possibly N P -hard) combinatorial optimization problem. We propose several ILP formulation of such a problem each yielding a solution algorithm that provides the exact value of the Fries and Clar numbers. We compare the performances of the algorithm derived from the proposed ILP formulations. One of this algorithm is used to find the Clar isomers, i.e., those for which the Clar number is maximum among all isomers having a given size. We repeated this computational experiment for all sizes up to 204 atoms. In the course of the study a total of 2 649 413 774 isomers were analyzed.The second essay concerns developing an iterative primal dual infeasible path following (PDIPF) interior point (IP) algorithm for separable convex quadratic minimum cost flow network problem. In each iteration of PDIPF algorithm, the main computational effort is solving the underlying Newton search direction system. We concentrated on finding the solution of the corresponding linear system iteratively and inexactly. We assumed that all the involved inequalities can be solved inexactly and to this purpose, we focused on different approaches for distributing the error generated by iterative linear solvers such that the convergences of the PDIPF algorithm are guaranteed. As a result, we achieved theoretical bases that open the path to further interesting practical investiga- tion

The topology of fullerenes

Fullerenes are carbon molecules that form polyhedral cages. Their bond structures are exactly the planar cubic graphs that have only pentagon and hexagon faces. Strikingly, a number of chemical properties of a fullerene can be derived from its graph structure. A rich mathematics of cubic planar graphs and fullerene graphs has grown since they were studied by Goldberg, Coxeter, and others in the early 20th century, and many mathematical properties of fullerenes have found simple and beautiful solutions. Yet many interesting chemical and mathematical problems in the field remain open. In this paper, we present a general overview of recent topological and graph theoretical developments in fullerene research over the past two decades, describing both solved and open problems. WIREs Comput Mol Sci 2015, 5:96–145. doi: 10.1002/wcms.1207 Conflict of interest: The authors have declared no conflicts of interest for this article. For further resources related to this article, please visit the WIREs website

Electrochemical studies in aluminum chloride melts Semiannual status report, 15 Aug. 1970 - 14 Feb. 1971

Experimental and computerized electrochemical measurements in fused sodium aluminum chloride

Health effects of occupational exposure to asphalt

"The information in this document assesses the health hazards associated with occupational exposure to asphalt. Chapter 2 presents information about the uses of asphalt and the number of workers potentially exposed to asphalt during paving and roofing operations and during the manufacturing of asphalt roofing products. Chapter 3 describes the chemical and physical properties of asphalt, production methods, similarities and differences between paving and roofing asphalts and asphalt-based paints, and the representativeness of field- and laboratory-generated asphalt fumes. Chapter 4 discusses exposure monitoring methods extent of worker exposure, and estimates of biological responses in asphalt-exposed workers. Subsequent chapters describe the effects of exposure to asphalt and asphalt fumes on humans and animals, conclusions, recommendations, and needed research." - NIOSHTIC-2"December 2000."Evaluations, conclusions, and recommendations of NIOSH in regard to exposure to asphalt--See Executive summary, p. viii-xii.Also available via the World Wide Web.Includes bibliographical references (p. 101-114)

Stimuli-responsive materials: developing integrated opto-molecular systems as sensors and actuators in micro-fluidic devices

Micro-fluidic platforms have been conferred with inherent optical sensing capabilities by coating the walls of micro-fluidic channels or micro-capillaries with stimuli-responsive materials. These adaptive materials respond optically to environmental stimuli, such as changes in pH, solvent polarity, the presence of certain metal ions and light. This approach confers sensing capabilities along the entire length of the coated micro-channel or micro-capillary. Adaptive coatings based on two types of materials are presented: 1. Conductive polymer polyaniline - The optical properties of these coatings respond to changes in the pH of the solution that is passing through the micro- channel or micro-capillary, and therefore can be used for dynamic pH monitoring (pH 2-8) or for aqueous ammonia sensing. 2. Photochromic spiropyrans - Photoswitchable coatings based on spiropyran are used to photo-detect solvents of different polarity when passing through the micro-capillary in continuous flow. This sensing behaviour can be switched on/off remotely using light. Finally, it is reported, for the first time, the potential of using spiropyran as a pH pump in fluidic channels for photo-activated chemopropulsion of organic droplets and the solvato-morphological control of self-assembled micro-structures based on spiropyran