Quantum‐based models of charge‐dependent potential energy surfaces: Three‐state models

Quantum‐based models of how potential energies depend on charge are developed from a three‐state model, at the level of neglecting state‐to‐state overlap. The energy as a function of charge is defined as proposed previously (Valone and Atlas, J Chem Phys 2004, 120, 7262). With this definition, addition of a third state smooths the derivatives of the energy model with respect to charge at integer values of charge that are in the interior of the allowed charge range. These derivatives are related to the chemical potential. At the dissociation limit, this model converges to established limits. Another dependence is proposed that uses two different charges simultaneously. The concepts are illustrated, with calculations on an OH molecule. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Comparison of proton conduction in KTaO3 and SrZrO3

In the present paper, the authors focus on proton conduction pathways in a cubic perovskite KTaO(3) and an orthorhombic perovskite SrZrO(3). Density functional theory with a generalized gradient approximation is used to find proton binding sites. The nudged elastic band method is used to find transition states between minima. With this potential energy map of binding and transition states, adjacency matrices and their analogs identify four types of conduction paths in KTaO(3). Distortions from these paths are seen in SrZrO(3). In both cases, the lowest energy path has an intraoctahedral transfer rate-limiting barrier. A Fourier analysis of the OH stretch in ab initio molecular dynamics simulations revealed a strongly redshifted OH stretch in SrZrO(3) relative to KTaO(3). Hence, an orthorhombic system with a lowest energy conduction path limited by an intraoctahedral barrier can exhibit a redshifted OH stretch.     

Forced Degradation Study on Gliclazide and Application of Validated Stability-Indicating HPLC-UV Method in Stability Testing of Gliclazide Tablets

Forced degradation study on gliclazide was conducted under the conditions of hydrolysis, oxidation, dry heat and photolysis and an isocratic stability-indicating HPLC-UV method was developed and validated. All the seven degradation products (I–VII) formed under different conditions were optimally resolved on a C₁₈ column with mobile phase composed of 40% acetonitrile and 60% ammonium acetate solution (0.025 M, pH 3.5) at a flow rate of 0.25 mL min^?1 using 235 nm as detection wavelength. The method was linear between 5–500 μg mL^?1 drug concentrations. The %RSD of intra- and inter-day precision studies was <1 and <2% respectively. Excellent recoveries (99.81–100.97%) proved the method sufficiently accurate. Each peak resolved always with a resolution of >1.90 indicating the method to be rugged enough. The method was used to study the drug degradation behaviour under the forced conditions. Four degradation products (I–IV) were formed in 0.1 N HCl and water whereas only I and III were formed in 3% H₂O₂. Two new products V and VI in addition to I, III and IV were formed in 0.1 N NaOH. The drug was stable to thermal and photolytic decomposition. The degradation behaviour in water and 0.1 N NaOH was similar under dark and light conditions but a new product VII was formed in 0.01 N HCl in light. In general, the rate of degradation was accelerated by the light. The method was applied successfully in stability testing of gliclazide tablets.     

2‐(2‐Naphthyloxy)acetate derivatives. I. A new class of antiamnesic agents

The title compounds 1‐(2‐naphthyloxymethylcarbonyl)piperidine, C₁₇H₁₉NO₂, (I), and 3‐methyl‐1‐(2‐naphthyl­oxy­methyl­carbonyl)­piperidine, C₁₈H₂₁NO₂, (II), are potential antiamnesics. In (II), the methyl‐substituted piperidine ring is disordered over two conformations. The piperidine ring has a chair conformation in both compounds. In (I), the mol­ecules are linked by weak intermolecular C—H⃛O interactions to give networks represented by C(4), C(6) and (18) graph‐set motifs, while in (II), weak intermolecular C—H⃛O interactions generate (5), C(4) and C(7) graph‐set motifs. The dihedral angle between the naphthalene moiety and the piperidine ring is 33.83 (7)° in (I), while it is 31.78 (11) and 19.38 (19)° for the major and minor conformations, respectively, in (II).     

DeepNGlyPred: A Deep Neural Network-Based Approach for Human N-Linked Glycosylation Site Prediction

Protein N-linked glycosylation is a post-translational modification that plays an important role in a myriad of biological processes. Computational prediction approaches serve as complementary methods for the characterization of glycosylation sites. Most of the existing predictors for N-linked glycosylation utilize the information that the glycosylation site occurs at the N-X-[S/T] sequon, where X is any amino acid except proline. Not all N-X-[S/T] sequons are glycosylated, thus the N-X-[S/T] sequon is a necessary but not sufficient determinant for protein glycosylation. In that regard, computational prediction of N-linked glycosylation sites confined to N-X-[S/T] sequons is an important problem. Here, we report DeepNGlyPred a deep learning-based approach that encodes the positive and negative sequences in the human proteome dataset (extracted from N-GlycositeAtlas) using sequence-based features (gapped-dipeptide), predicted structural features, and evolutionary information. DeepNGlyPred produces SN, SP, MCC, and ACC of 88.62%, 73.92%, 0.60, and 79.41%, respectively on N-GlyDE independent test set, which is better than the compared approaches. These results demonstrate that DeepNGlyPred is a robust computational technique to predict N-Linked glycosylation sites confined to N-X-[S/T] sequon. DeepNGlyPred will be a useful resource for the glycobiology community.     

Pricing vulnerable European options with stochastic default barriers

CF Lo and KC Ku Institute of Theoretical Physics and Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong, China Email: cho-hoi_hui{at}hkma.gov.hk Received on 31 July 2006. Accepted on 15 March 2007. This paper develops a valuation model of European options incorporatinga stochastic default barrier, which extends a constant defaultbarrier proposed in the Hull–White model. The defaultbarrier is considered as an option writer's liability. Closed-formsolutions of vulnerable European option values based on themodel are derived to study the impact of the stochastic defaultbarriers on option values. The numerical results show that negativecorrelation between the firm values and the stochastic defaultbarriers of option writers gives material reductions in optionvalues where the options are written by firms with leverageratios corresponding to BBB or BB ratings.     

Studies of the thiadiazine, taurolidine-I. Identification of the molecular species present in aqueous solutions by (1)H- and (13)C-NMR spectroscopy

The equilibria in deuterium oxide solutions of the diamine, 4,4'-methylenebis(tetrahydro-1,2,4-thiadiazine-1,1-dioxide), were studied using highfield (1)H- and (13)C-NMR with the aid of solutions of tetrahydro-2H-1,2,4-thiadiazine-1,1-dioxide (taurultam), its two N-methyl detivatives and methylene glycol. Comparison of the (1)H-NMR spectrum of taurolidine with the one obtained from a mixture of taurultam and methylene glycol indicated that the same equilibria exists in both these solutions. It was concluded that taurolidine, taurultam and its 4-hydroxymethyl adduct and methylene glycol are the major components present. To facilitate the interpretation of the (13)C-spectra, (13)C-enriched methylene glycol was added to solutions of taurultam. The (13)C-studies confirmed the (1)H-NMR study.     

Effect of non-homogeneity on natural frequencies of vibration of elliptic plates

This paper presents the effect of non-homogeneity of the material of plate structures on the vibration frequencies. The non-homogeneity of the plate is characterized by taking a variety of combinations of linear as well as quadratic variations in the Young’s modulus and density of the material. Boundary characteristic orthogonal polynomials using Gram-Schmidt procedure have been employed in the Rayleigh Ritz method. The results have been included for the first few frequencies of the plate element for all the boundary conditions viz. clamped, simply supported and free. Related Tables and graphs are incorporated to show the effect of the non-homogeneity parameter on the frequencies of the vibration of elliptic and circular plates.