Optical and structural characterization of ultrananocrystalline diamond/hydrogenated amorphous carbon composite films deposited via coaxial arc plasma

Ultrananocrystalline diamond/hydrogenated amorphous carbon composite films were deposited in the ambient of hydrogen by coaxial arc plasma deposition. The film compositions and chemical bonding structures were investigated by X-ray diffraction, X-ray photoemission and hydrogen forward scattering spectroscopies. The sp³/(sp²+sp³) ratio and hydrogen content in the film were estimated to be 64% and 35?at.%, respectively. The optical parameters and the optical dispersion profile were determined by using a variable angle spectroscopic ellipsometer at 55°, 65° and 75° angle of incidence in the photon energy range of 0.9–5?eV. Combinations of multiple Gaussian, and Tauc-Lorentz or Cody-Lorentz dispersion functions are used to reproduce the experimental data. Results of ellipsometry showed a refractive index of approximately 2.05 (at 2eV) and optical band gap of 1.63?eV. The imaginary part of dielectric function exhibited a peak at 3.8?eV, which has assigned to π-π* electron transitions. Furthermore, Electron spin resonance measurements implied the existence of dangling bonds, which might have a partial contribution to the optical absorption properties of the deposited films. A correlation between optical parameters and structural profile of the deposited films is discussed.     

Solvent-Free Synthesis,In Vitro and In Silico Studies of Novel Potential 1,3,4-Thiadiazole-Based Molecules against Microbial Pathogens

A new series of 1,3,4-thiadiazoles was synthesized by the reaction of methyl 2-(4-hydroxy-3-methoxybenzylidene) hydrazine-1-carbodithioate (2) with selected derivatives of hydrazonoyl halide by grinding method at room temperature. The chemical structures of the newly synthesized derivatives were resolved from correct spectral and microanalytical data. Moreover, all synthesized compounds were screened for their antimicrobial activities using Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, Bacillus subtilis, Staphylococcus aureus, and Candida albicans. However, compounds 3 and 5 showed significant antimicrobial activity against all tested microorganisms. The other prepared compounds exhibited either only antimicrobial activity against Gram-positive bacteria like compounds 4 and 6, or only antifungal activity like compound 7. A molecular docking study of the compounds was performed against two important microbial enzymes: tyrosyl-tRNA synthetase (TyrRS) and N-myristoyl transferase (Nmt). The tested compounds showed variety in binding poses and interactions. However, compound 3 showed the best interactions in terms of number of hydrogen bonds, and the lowest affinity binding energy (−8.4 and −9.1 kcal/mol, respectively). From the in vitro and in silico studies, compound 3 is a good candidate for the next steps of the drug development process as an antimicrobial drug.     

Microbial Transformation of Isolongifolen‐4‐one

The microbial transformation of (+)‐isolongifolen‐4‐one ( 4 ) by a number of fungi by means of a standard two‐stage fermentation technique afforded (7R)‐12‐hydroxyisolongifolen‐4‐one ( 5 ), (7S)‐13‐hydroxyisolongifolen‐4‐one ( 6 ), (11R)‐11‐hydroxyisolongifolen‐4‐one ( 7 ), (10R)‐10‐hydroxyisolongifolen‐4‐one ( 8 ), and (9R)‐9‐hydroxyisolongifolen‐4‐one ( 9 ) (Scheme). All five metabolites were found to be new, and metabolites 6 and 9 showed potent tyrosinase inhibitory activity (Table 1). The metabolites and their derivatives were characterized on the basis of spectroscopic and single‐crystal X‐ray‐diffraction techniques.     

Bivariate Sarmanov Phase-Type Distributions for Joint Lifetimes Modeling

Methodology and Computing in Applied Probability - In this paper, we are interested in the dependence between lifetimes based on a joint survival model. This model is built using the bivariate...     

Chromatographic methods development,validation and degradation characterization of the antithyroid drug Carbimazole

The current paper reports the development and validation of stability‐indicating HPLC and HPTLC methods for the separation and quantification of main impurity and degradation product of Carbimazole. The structures of the degradation products formed under stress degradation conditions, including hydrolytic and oxidative, photolytic and thermal conditions, were characterized and confirmed by MS and IR analyses. Based on the characterization data, the obtained degradation product from hydrolytic conditions was found to be methimazole—impurity A of Carbimazole as reported by the British Pharmacopeia and the European Pharmacopeia. A stability‐indicating HPLC method was carried out using a Zorbax Eclipse Plus CN column (150 × 4.6 mm i.d, 5 μm particle size) and a mobile phase composed of acetonitrile–0.05 m KH₂PO₄ (20: 80, v/v) in isocratic elution, at a flow rate of 1 mL/min. The method was proved to be sensitive for the determination down to 0.5% of Carbimazole impurity A. Additionally, a stability‐indicating chromatographic HPTLC method was achieved using cyclohexane–ethanol (9:1, v/v) as a developing system on HPTLC plates F₂₅₄ with UV detection at 225 nm. The proposed HPLC and HPTLC methods were successfully applied to Carbimazole^® tablets with mean percentage recoveries of 100.12 and 99.73%, respectively.     

Synoxazolidinone C; a bicyclic member of the synoxazolidinone family with antibacterial and anticancer activities

Synoxazolidinone C is a new member of the synoxazolidinone family of compounds which are dibrominated guanidinium 4-oxazolidinones isolated from the sub-Arctic ascidian Synoicum pulmonaria. The compound was isolated along with synoxazolidinones A and B from the same ascidian extract. Spectroscopic methods revealed that the synoxazolidinone C differed from the other synoxazolidinones by an unprecedented bicyclic partial structure, containing an additional pyrrolidine ring. Synoxazolidinone C exhibited both antibacterial and anticancer activities.     

A Microfluidic Approach to Chemically Driven Assembly of Colloidal Particles at Gas–Liquid Interfaces

Bubbling up : Dissolution of CO₂ bubbles in a suspension of colloidal particles chemically induces the assembly of particles on the surface of shrunken bubbles, and thus yields rapid continuous formation of a colloidal armor. This approach maintains the high colloidal stability of particles in bulk, has increased productivity, and allows the formation of bubbles with precisely controlled dimensions.

     

Modeling of nonlinear viscoelastic contact problems with large deformations

Contact problems are one of the most important engineering problems. These problems become much more tedious when one of the contacting bodies behaves nonlinear viscoelasticity and large deformations. This paper presents an incremental-iterative finite element model for the analysis of two dimensional quasistatic frictionless contact problems. Nonlinear viscoelastic behavior and large deformations are considered. The Schapery’s single-integral creep model with stress-dependent properties is used for nonlinear viscoelasticity. The constitutive equations are transformed into an incremental form resulting in a recursive relationship. Thereby, the need to store the entire strain histories is eliminated, except that from the previous time increment. The updated Lagrangian formulation is used to model the material and geometrical nonlinearities. Also, the Lagrange multiplier method is adopted to enforce the contact constraints. The converged solution is obtained using the Newton–Raphson iterative technique. The developed model has been verified with the previously published works and found a good agreement with them. To demonstrate the efficient capability of the developed computational model, three contact problems with different nature are analyzed.