Second Zagreb and Sigma Indices of Semi and Total Transformations of Graphs

The study of structure-property relations including the transformations of molecules is of utmost importance in correlations with corresponding physicochemical properties. The graph topological indices have been used effectively for such study and, in particular, bond-based indices play a vital role. The bond-additive topological indices of a molecular graph are defined as a sum of edge measures over all edges in which edge measures can be computed based on degrees, closeness, peripherality, and irregularity. In this study, we provide the mathematical characterization of the transformation of a structure that can be accomplished by the novel edge adjacency and incidence relations. We derive the exact expressions of bond type indices such as second Zagreb, sigma indices, and their coindices of total transformation and two types of semitransformations of the molecules which in turn can be used to characterize the topochemical and topostructural properties.

System Analysis and Control of the Influence of a Mixed Type of Chemical Bond in Substances and Materials on their Structure and Properties

Nowadays, a lot of information on structure and properties of a wide variety of substances and materials has been accumulated. Yet, there is a lack of systemic universal approaches to assessing their structure and properties, including developing the effective approaches for monitoring and analysing various materials. It is of special interest in this respect to assess the effects of the chemical bond type on structure and properties of substances and materials. However, searching for necessary data on the effects of chemical bonds on structure of substances and materials is a rather laborious process. The authors, relying on the intermediate nature of chemical bonds of compounds of elements in any metallic and non-metallic material, as well as the system of chemical bonds and compounds developed by them in the form of a “Chemical Triangle”, produced an algorithm for creating a computer programme. It implies systematising of the database on the effect of chemical bond type on its length and energy, structure and various physicochemical and mechanical properties of homo-and heteronuclear compounds and materials. Development of such a specialised computer programme greatly simplifies this process, providing more efficient analysis and control of materials.

Noncovalent Bonds through Sigma and Pi-Hole Located on the Same Molecule. Guiding Principles and Comparisons

Over the last years, scientific interest in noncovalent interactions based on the presence of electron-depleted regions called σ-holes or π-holes has markedly accelerated. Their high directionality and strength, comparable to hydrogen bonds, has been documented in many fields of modern chemistry. The current review gathers and digests recent results concerning these bonds, with a focus on those systems where both σ and π-holes are present on the same molecule. The underlying principles guiding the bonding in both sorts of interactions are discussed, and the trends that emerge from recent work offer a guide as to how one might design systems that allow multiple noncovalent bonds to occur simultaneously, or that prefer one bond type over another.

EFFECTS OF CROSSLINK BOND TYPE OF IIR-BASED WASTE RUBBER POWDER ON THE EPDM-ASSISTED DEVULCANIZATION REACTION

ABSTRACT Isobutylene–isoprene rubber (IIR)–based waste rubber powder (WRP) present in WRP/ethylene–propylene–diene monomer (EPDM) blends was devulcanized through a stress-induced reaction by increasing the screw rotation speed in the presence of subcritical ethanol. The effects of crosslink bond type (which was cured using phenolic resin, sulphur, or zinc oxide) of WRP and the screw rotation speed on devulcanization were investigated. The results showed that the Mooney viscosity and gel content of the devulcanized blends (DWRP/EPDM) decreased with an increase in the screw rotation speed, and the optimal screw rotation speed maximized the molecular weight (Mη) of sols and enhanced the mechanical properties of the revulcanized material. The optimal screw rotation speed for the phenolic resin-cured WRP1 and zinc oxide-cured WRP3 was 500 r min−1 and that for sulphur-cured WRP2 was 300 r min−1. At the optimal screw rotation speed, crosslink bonds severely fractured, and the main chain structure remained relatively intact. The 1H-NMR spectra of the sol in the devulcanized blends (DWRP/EPDM) confirmed that the content of the alpha and double-bond protons of sols are the highest at the optimal screw rotation speed, and many promoting agent (480) molecules penetrate and participate in devulcanization. Scanning electron microscopy images indicated that the size of the unfused gel particles in the mixed-revulcanized materials of IIR/(DWRP1/EPDM), IIR/(DWRP2/EPDM), and BIIR/(DWRP3/EPDM) was the smallest at the optimal screw rotation speed.

Ultimate Molecular Theory of Sweet Taste

More than thirty years ago, I proposed a theory about sweet and bitter molecules’ recognition by protein helical structures. Unfortunately the papers could not go to public platform until now. The sweet and bitter taste theory is updated and presented in separated papers1,2. The sweet taste theory conveys that sweet molecules are recognized by receptor protein helical structures and the recognition process is a dynamic action, in which the sweet receptor protein helix has a torsion-spring-like oscillation between helical structures of 3.6 and 3 amino acids per turn. To help this kind of oscillation, there are two kinds of hydrogen donor and hydrogen acceptor DH-B entities for both receptor and sweet molecules: H-bond or non-H-bond. The distances between DH and B could be up to ~ 8.5 Å. The receptor H-bond type DH-B entities are the NH-O pairs forming H-bonds in protein helices; the receptor non-H-bond type DH-B entities are the ones from two pairs of NH-Os forming H-bonds which are about one turn away. To facilitate this kind of movement, the interaction of DH-Bs of a sweet molecule with those of sweet receptor, through a pair of complementary hydrogen bonds, must have hydrogen bond complementarities, which means Hbond type of ligands’ DH-Bs reacts on non-H-bond type of receptor’s O-NHs, and vice versa. As the oscillation may have different extent, it translates to sweet intensity. As recognition sites are only associated with a small fraction – helix structure of whole sweet receptor, multiple binding sites or multiple receptors are well expected.

Ultimate Molecular Theory of Sweet Taste

More than thirty years ago, I proposed a theory about sweet and bittermolecules’ recognition by protein helical structures. Unfortunately the paperscould not go to public platform until now. The sweet and bitter taste theory isupdated and presented in separated papers1,2. The sweet taste theory conveysthat sweet molecules are recognized by receptor protein helical structures andthe recognition process is a dynamic action, in which the sweet receptor proteinhelix has a torsion-spring-like oscillation between helical structures of 3.6 and 3amino acids per turn. To help this kind of oscillation, there are two kinds ofhydrogen donor and hydrogen acceptor DH-B entities for both receptor andsweet molecules: H-bond or non-H-bond. The distances between DH and Bcould be up to ~ 8.5 Å. The receptor H-bond type DH-B entities are the NH-Opairs forming H-bonds in protein helices; the receptor non-H-bond type DH-Bentities are the ones from two pairs of NH-Os forming H-bonds which are aboutone turn away. To facilitate this kind of movement, the interaction of DH-Bs of asweet molecule with those of sweet receptor, through a pair of complementaryhydrogen bonds, must have hydrogen bond complementarities, which means Hbondtype of ligands’ DH-Bs reacts on non-H-bond type of receptor’s O-NHs, andvice versa. As the oscillation may have different extent, it translates to sweetintensity. As recognition sites are only associated with a small fraction – helixstructure of whole sweet receptor, multiple binding sites or multiple receptors arewell expected.

“Chemical Triangle” as a modern intellectual basis for digital systematization of energy characteristics of substances

It was shown that sustainable power and mechanical engineering relies primarily on chemical transformation of matter, since a chemical substance (in the form of homo- and heteronuclear compounds of elements) is the most accessible type of substance on Earth. As a result, low-, oligo- and high-molecular and non-molecular (metallic and ionic) chemicals and products (fuels, polymers, alloys, glasses, etc.) are primary raw materials for production of thermal and electrical energy, as well as materials needed for alternative energy production. It was noted that the main drawback of the modern expert system for assessing the energy properties of substances used as fuels is not taking into account the influence of the chemical bond type on its energy and energy characteristics of fuels in general. It was shown that the solution to this problem is possible through the use of the unified model of chemical bond of elements, which considers any chemical bond as an overlay (resonance) of a 100% covalent bond with either metal or metal and ionic components, with a subsequent assessment of the effect of each of them on total energy of the mixed bond. This model is the fundamental basis of the System of chemical bonds and compounds (SCBC) in the form of the “Chemical Triangle”. The possibility of using the “Chemical Triangle” as a modern intellectual basis for digital systematization and creation of a database of energy characteristics of various substances based on homo- and heteronuclear compounds of elements was shown. A computer database was developed to assess the complex impact of composition and chemical bond type on its energy characteristics, structure and properties of substances and materials.

Persistent, Historic Factors Correlated with Airport Bond Returns

The factors that are associated with returns on airport bonds are explored, using a proxy for an airport bond portfolio with the S&P Municipal Bond Airport Index. Six spread-based factors representing the tax status, term length, credit quality, bond type, infrastructure, and insurance status of airport bonds provide the independent variables. Five models are developed to test for bonds’ risk exposure to these characteristics and to analyze how these exposures for airport bonds differ from those of general transportation bonds or municipal bonds. Over 90% of the variation in returns on the airport index is explained by these factors. When determining risk premiums on airport bonds relative to other transportation bonds, investors appear to consider the bond type and infrastructure factors as being most relevant. However, when transportation bonds are compared with other municipal bonds, all factors except the insurance factor act as risk premiums. The component of airport bond returns not associated with these factors is partially explained by monthly changes in jet fuel prices and enplanements across all U.S. airports. These results can help airport bond issuers to evaluate the relative costs of raising funds through debt issues, and understand the trends in the bond market that are more strongly associated with prices and expected returns in the airport bond sector. Hedges against fuel price, enplanement changes, or both, may also be actions that airport bond issuers could consider outside of traditional financial planning practices to manage trends in the bond markets.