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A total of 126 ejaculates, 21 from each of six bucks comprising three Beetal and three Sirohi bucks, collected by artificial vagina were used to study various semen characteristics. The semen characteristics viz., ejaculate volume, mass activity, initial sperm motility, live sperm, sperm concentration, sperm number per ejaculate, cold shock resistance index, live intact acrosome and sperm abnormalities were studied by conventional methods. The overall mean values of different characteristics of fresh semen in Beetal and Sirohi bucks for ejaculate volume, mass activity, initial sperm motility, live sperm, sperm concentration, sperm number per ejaculate, cold shock resistance index, live intact acrosome, head abnormalities, mid piece abnormalities, tail abnormalities and sperm with proximal and distal cytoplasmic droplet were 1.08 ± 0.05 and 1.18 ± 0.04 ml, 3.71+ and 3.92+, 82.94 ± 0.73 and 84.60 ± 0.61 per cent, 85.57 ± 0.52 and 86.03 ± 0.48 per cent, 3356.73 ± 83.06 and 3176.94 ± 53.92 million per ml, 3595.17 ± 122.08 and 3669.00 ± 126.42 million, 6.72 ± 0.22 and 6.77 ± 0.20 per cent, 85.18 ± 0.39 and 84.05 ± 0.41 per cent, 1.65 ± 0.13 and 1.50 ± 0.12 per cent, 0.25 ± 0.02 and 0.30 ± 0.03 per cent, 2.73 ± 0.18 and 2.53 ± 0.13 per cent, 0.43 ± 0.03 and 0.48 ± 0.04 per cent and 0.86 ± 0.12 and 0.61 ± 0.04 per cent respectively. The different semen characteristics did not differ significantly between breeds; however, the differences between bucks within the breed were significant for ejaculate volume, live intact acrosome, mid piece abnormalities, tail abnormalities and sperm with distal cytoplasmic droplet.

For large-scale graphene applications, such as the production of polymer-graphene nanocomposites, exfoliated graphene oxide (GO) and its reduced form (rGO) are presently considered to be very suitable starting materials, showing enhanced chemical reactivity with respect to pristine graphene, in addition to suitable electronic properties (i.e., tunable band gap). Among other chemical processes, a suitable way to obtain surface decoration of graphene is through a direct one-step Diels-Alder (DA) reaction, e.g. through the use of dienophile or diene moieties. However, the feasibility and extent of decoration largely depends on the specific graphene microstructure that in the case of rGO sheets is not easy to control and generally presents a high degree of inhomogeneity owing to various on-plane functionalization (e.g., epoxide and hydroxyl groups) or in-plane lattice defects. In an effort to gain some insights into the covalent functionalization of variably reduced GO samples, we present a combined experimental and theoretical study on the DA cycloaddition reaction of maleimide, a dienophile functional unit well-suited for chemical conjugation of polymers and macromolecules. In particular, we considered both mildly and strongly reduced GOs. Using thermogravimetry, Raman and X-Ray photoelectron spectroscopy, and elemental analysis we show evidence of variable chemical reactivity of rGO as a function of the residual oxygen content. Moreover, from quantum mechanical calculations carried out at the DFT level on different graphene reaction sites, we provide a more detailed molecular view to interpret experimental findings and to assess the reactivity series of different graphene modifications. This journal is

Grimme's dispersion-corrected density functional theory (DFT-D) methods have emerged among the most practical approaches to perform accurate quantum mechanical calculations on molecular systems ranging from small clusters to microscopic and mesoscopic samples, i.e., including hundreds or thousands of molecules. Moreover, DFT-D functionals can be easily integrated into popular ab initio molecular dynamics (MD) software packages to carry out first-principles condensed-phase simulations at an affordable computational cost. Here, starting from the well-established D3 version of the dispersion-correction term, we present a simple protocol to improve the accurate description of the intermolecular interactions of molecular clusters of growing size, considering acetonitrile as a test case. Optimization of the interaction energy was performed with reference to diffusion quantum Monte Carlo calculations, successfully reaching the same inherent accuracy of the latter (statistical error of ∼0.1 kcal/mol per molecule). The refined DFT-D3 model was then used to perform ab initio MD simulations of liquid acetonitrile, again showing significant improvements toward available experimental data with respect to the default correction.

The formation of polycyclic aromatic hydrocarbons (PAHs) in high temperature environments is an ongoing area of research due to the mismatch between the experimental and simulated concentration profiles of PAHs in several flames. In this work, the role of methyl radicals in the growth of PAHs is identified by developing a detailed reaction mechanism for the conversion of phenanthrene to pyrene by methyl radicals. The reaction energetics are obtained through quantum calculations using B3LYP and M06-2X functionals along with 6-311++G(d,p) basis set, and are used to compare the competing channels for pyrene formation. The transition state theory is used to determine the reaction kinetics. Through kinetic simulations, the most preferred path for pyrene formation from phenanthrene is determined. To quantify the contribution of the newly found reactions in PAH growth in the presence of other competing PAH mechanisms, the reactions are merged with a recently developed and well-validated mechanism for C 1 C 4 hydrocarbons with detailed PAH chemistry. Three premixed laminar aliphatic flames were simulated with the updated mechanism. It was observed that the new reactions did not appreciably influence the computed profiles of phenanthrene and pyrene. Through the rate-of-production analysis, it was found that the phenanthrene radicals created through H-abstraction were more susceptible to attack by C 2 H 2 than by methyl radicals. The indirect role of methyl radicals in PAH formation and growth is shown.

Resonantly stabilized radicals, such as propargyl, cyclopentadienyl, benzyl, and indenyl, play a vital role in the formation and growth of polycyclic aromatic hydrocarbons (PAHs) that are soot precursors in engines and flames. Pyrene is considered to be an important PAH, as it is thought to nucleate soot particles, but its formation pathways are not well known. This paper presents a reaction mechanism for the formation of four-ring aromatics, pyrene and fluoranthene, through the combination of benzyl and indenyl radicals. The intermediate species and transition structures involved in the elementary reactions of the mechanism were studied using density functional theory, and the reaction kinetics were evaluated using transition state theory. The barrierless addition of benzyl and indenyl to form the adduct, 1-benzyl-1H-indene, was found to be exothermic with a reaction energy of 204.2 kJ mol−1. The decomposition of this adduct through H-abstraction and H2-loss was studied to determine the possible products. The rate-of-production analysis was conducted to determine the most favourable reactions for pyrene and fluoranthene formation. The premixed laminar flames of toluene, ethylbenzene, and benzene were simulated using a well-validated hydrocarbon fuel mechanism with detailed PAH chemistry after adding the proposed reactions to it. The computed and experimentally observed species profiles were compared to determine the effect of the new reactions for pyrene and fluoranthene formation on their concentration profiles. The role of benzyl and indenyl combination in PAH formation and growth is highlighted.

Recently, the formation of the dimeric stibahousene molecule, bis(stibahousene), has been reported. In line with the report, the formation of dimeric housene molecules with N, P, and As is examined in light of density functional theory. Moreover, the extension of the study from dimeric to tetrameric and hexameric molecules (N, P, As, and Sb) is also performed. The study supports the formation of such polymeric housene analogues.

The role of resonantly stabilized radicals such as propargyl, cyclopentadienyl and benzyl in the formation of aromatic hydrocarbons such as benzene and naphthalene in the high temperature environments has been long known. In this work, the possibility of benzyl recombination to form three-ring aromatics, phenanthrene and anthracene, is explored. A reaction mechanism for it is developed, where reaction energetics are calculated using density functional theory (B3LYP functional with 6-311++G(d,p) basis set) and CBS-QB3, while temperature-dependent reaction kinetics are evaluated using transition state theory. The mechanism begins with barrierless formation of bibenzyl from two benzyl radicals with the release of 283.2 kJ mol(-1) of reaction energy. The further reactions involve H-abstraction by a H atom, H-desorption, H-migration, and ring closure to gain aromaticity. Through mechanism and rate of production analyses, the important reactions leading to phenanthrene and anthracene formation are determined. Phenanthrene is found to be the major product at high temperatures. Premixed laminar flame simulations are carried out by including the proposed reactions for phenanthrene formation from benzyl radicals and compared to experimentally observed species profiles to understand their effects on species concentrations.

In the Claus process, the presence of aromatic contaminants such benzene, toluene, and xylenes (BTX), in the H2S feed stream has a detrimental effect on catalytic reactors, where BTX form soot particles and clog and deactivate the catalysts. Among BTX, xylenes are proven to be most damaging contaminant for catalysts. BTX oxidation in the Claus furnace, before they enter catalyst beds, provides a solution to this problem. A reaction kinetics study on m-xylene oxidation by SO2, an oxidant present in Claus furnace, is presented. The density functional theory is used to study the formation of m-xylene radicals (3-methylbenzyl, 2,6-dimethylphenyl, 2,4-dimethylphenyl, and 3,5-dimethylphenyl) through H-abstraction and their oxidation by SO2. The mechanism begins with SO2 addition on the radicals through an O-atom rather than the S-atom with the release of 180.0-183.1 kJ/mol of reaction energies. This exothermic reaction involves energy barriers in the range 3.9-5.2 kJ/mol for several m-xylene radicals. Thereafter, O-S bond scission takes place to release SO, and the O-atom remaining on aromatics leads to CO formation. Among four m-xylene radicals, the resonantly stabilized 3-methylbenzyl exhibited the lowest SO2 addition and SO elimination rates. The reaction rate constants are provided to facilitate Claus process simulations to find conditions suitable for BTX oxidation.

The main objective of this study is to provide an insight into the interactions involved during adsorption of the alcohols on β-CD composite nanostructured membrane. Interactions between β-cyclodex...

The presence of aromatics such as benzene, toluene, and xylene (BTX) as contaminants in the H2S gas stream entering Claus sulfur recovery units has a detrimental effect on catalytic reactors, where BTX forms soot particles and clogs and deactivates the catalysts. BTX oxidation, before they enter catalyst beds, can solve this problem. A theoretical investigation is presented on toluene oxidation by SO2. Density functional theory is used to study toluene radical (benzyl, o-methylphenyl, m-methylphenyl, and p-methylphenyl)–SO2 interactions. The mechanism begins with SO2 addition on the radical through one of the O atoms rather than the S atom. This exothermic reaction involves energy barriers of 4.8–6.1 kJ/mol for different toluene radicals. Thereafter, O–S bond scission takes place to release SO. The reaction rate constants are evaluated to facilitate process simulations. Among four toluene radicals, the resonantly stabilized benzyl radical exhibited lowest SO2 addition rate. A remarkable similarity between...

We studied the thermodynamic and kinetic aspects of guanine alkylation by five derivatives of formononetin nitrogen mustard using density functional theory (DFT). Investigation of the reactivity pattern of the aziridinium ion intermediates as well as drug-guanine adducts were performed using Density functional reactivity theory (DFRT). Aziridinium ion formation was observed to be endothermic, in contrast, the drug-guanine adduct formation was exothermic. A significant interaction of the aziridinium ion with guanine has been observed. The results illustrate the applicability of maximum hardness principle (MHP) and minimum electrophilicity principle (MEP).

Two tryptophan-based pyridine dicarboxamide ligands have been synthesised and characterised. 1H NMR studies indicated that these ligands are capable of coordinating to bromide anions through amide/indole NH and CH groups. Based on 1H NMR studies, we found that organic bromides selectively bind to with one of the ligands, as evidenced by complexation induced chemical shifts for the indole and amide NH resonances.

Reactivity of aziridinium ion and mono- as well as cross-linked adducts formed during alkylation of DNA (GC base pair) by nitrogen mustards were analysed, using density functional theory (DFT). DFT based global- and local reactivity descriptors were used to compare reactivity of the aziridinium ion intermediates and mono-adducts. Our results witnessed the inability of global reactivity parameters to explain higher reactivity of mustine. Out of the chosen set of seven drug molecules, propensity of cross-linked adduct formation by uracil mustard was observed to be highest compared to other family members. Electrophilic Fukui function was found to be useful in explaining the local reactivity pattern. Gibbs free energy of solvation for the second aziridinium ions were observed to be higher compared to that of the first aziridinium ions.

Reactivity/stability of the tricyclic aziridinium ion intermediate of the mustine drug molecule varies with the ∠NCC bond angle of the tricyclic ring during alkylation of guanine. A sharp variation in reactivity of the aziridinium ion intermediate is observed along the intrinsic reaction coordinate. Further, shifting of the lowest unoccupied molecular orbital towards the carbon centre that interacts with guanine is also observed. Thermochemical analysis shows that the alkylation reaction is exothermic and presence of polar solvent effect activation energy.

A density functional theory study is performed to understand the effect of discrete water molecules during Az+ ion formation in nitrogen mustards. A comparative study in gas phase, and implicit and explicit solvation models of three drug molecules (mustine, chlorambucil and melphalan) is reported. Noteworthy changes in the structure and C–N stretching frequencies of the transition states have been observed in the presence of explicit water molecules. Presence of explicit water molecules reduces the positive charge around the tricyclic Az+ ring, and hence stabilising it. Both activation energy and rate constants are seen to be significantly affected in the presence of discrete water molecules.

Claus process, consisting of a furnace and catalytic reactors, is used to recover sulfur from H2S found in raw natural gas and gases from refineries. This acid gas is accompanied by contaminants such as benzene, toluene, xylenes (collectively called BTX), other hydrocarbons, NH3, CO2, N2 and sulfur compounds having detrimental effect on catalytic reactors, where BTX form soot particles and sulfur-hydrocarbons, and clog and deactivate the catalysts. This work focuses on BTX oxidation by SO2 as a potential solution that can be carried out in a BTX destruction unit placed between Claus furnace and catalytic units. Density functional theory is used to study the interaction between BTX-radicals and SO2 and the stability of the intermediate species formed during the course of the mechanism. The rates of elementary reactions are evaluated using transition state theory. The pathways leading to the formation of important by-products such as CO, SO, S, CHO were obtained.

Department of Chemistry, Arya Vidyapeeth College, Guwahati-781 016, Assam, India E-mail : prdpbhatta@yahoo.com Manuscript received online 23 April 2013, accepted 26 August 2013 Thermodynamic and kinetic driving force for keto-enol tautomerism in guanine, guanine-cytosine and alkylated guanine has been studied in gas as well as in aqueous phase using density functional theory (DFT). Variation of DFT based reactivity descriptors were observed along the IRC pathway. Energy barrier of the tautomerism is of almost same magnitude in guanine and alkylated guanine. No significant lowering in energy barrier is observed in alkylated guanine signifying the absence of kinetic driving force for enol formation. Thermochemical analysis confirmed a small barrier. &nbsp

Department of Chemistry, Arya Vidyapeeth College, Guwahati-781 016, Assam, India E-mail : prdpbhatta@yahoo.com Manuscript received online 08 December 2012, accepted 24 January 2013 Reactivities of the aziridinium ion intermediates of six anticancer drugs belonging to the nitrogen mustard family are analysed using conceptual density functional theory based reactivity descriptors. Reactivity of the species is found to depend on dielectric of the solvent. Enthalpy, Gibbs energy and entropy of formation of aziridinium ions are analysed at different temperatures and solvents at 83LYP/6-31+G(d) level of theory. Further, the natural bond orbital (NBO) analysis is performed which seemed to be quite informative.

A DFT and ab initio quantum chemical study has been carried out at different theoretical levels to delve into the role of the cation-π interaction within the main group metal cations (Li(+), Na(+) and K(+)), substituted benzene and borazine. The effects of electron withdrawing and electron donating groups on these non-covalent forces of interaction were also studied. The excellent correlation between Hammett constants and binding energy values indicates that the cation-π interaction is influenced by both inductive and resonance effects. Electron donating groups (EDG) such as -CH3 and -NH2 attached to benzene at the 1, 3 and 5 position and the three boron atoms of borazine were found to strengthen these interactions, while electron withdrawing groups (EWG) such as -NO2 did the reverse. These results were further substantiated by topological analysis using the quantum theory of atoms in molecules (QTAIM). The polarized continuum model (PCM) and the discrete solvation model were used to elucidate the effect of solvation on the cation-π interaction. The size of the cations and the nature of the substituents were found to influence the enthalpy and binding energy of the systems (or complex). In the gas phase, the cation-π interaction was found to be exothermic, whereas in the presence of a polar solvent the interaction was highly endothermic. Thermochemical analysis predicts the presence of thermodynamic driving forces for borazine and benzene substituted with EDG. DFT based reactivity descriptors, such as global hardness (η), chemical potential (μ) and the electrophilicity index (ω) were used to elucidate the effect of the substituent on the reactivity of the cation-π complexes.

Claus process, consisting of a furnace and catalytic reactors, is used to recover sulfur from H 2 S found in raw natural gas and gases from refineries. H 2 S is accompanied by contaminants such as benzene, toluene, xylenes (collectively called BTX), other hydrocarbons, NH 3 , CO 2 , N 2 and sulfur compounds. Among these, BTX have attracted several research activities as they form soot and sulfur-hydrocarbons in catalytic units that clog and deactivate the catalysts. This work focusses on BTX oxidation by SO 2 as a potential solution that can be carried out in a BTX destruction unit placed between Claus furnace and catalytic units. To determine the extent of BTX destruction by SO 2 , reaction mechanisms are developed using density function theory. The rates of elementary reactions are evaluated using transition state theory. The pathways leading to the formation of CO and SO are obtained.