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Isolation pyro valves fabricated from AISI 321 austenitic stainless steel are performance-critical components used in launch vehicle propulsion systems. These valves isolate the fuel and oxidizer separated by a thin membrane that will be severed during its operation. As a part of the qualification program, a set of pyro valves were tested at the operating temperature of 20 K. During post-test examination of the hardware, membrane separation was not observed in one of the pyro valves tested. The failed and successfully tested valves were analysed to understand the reason for the non-separation of the pyro valve membrane. The present work brings out the details of metallurgical and mechanical aspects of the failed as well as successfully tested isolation pyro valves.

The optimized molecular structure, vibrational wavenumbers, corresponding vibrational assignments of 2-[4-(4-phenylbutanamido)phenyl]-5-ethylsulphonyl-benzoxazole have been investigated experimentally and theoretically using Gaussian09 software. The wavenumbers were assigned by potential energy distribution and the frontier molecular orbital analysis is used to determine the charge transfer within the molecule. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. The MEP analysis shows that the negative electrostatic potential regions are mainly localized over the oxygen's of the carbonyl and sulfonyl groups and nitrogen atom of the benzoxazole ring and are possible sites for electrophilic attack and the positive regions are localized over the NH group as possible sites for nucleophilic attack. From the molecular docking study, the ligand binds at the active sites of the protein by weak non-covalent interactions most prominent of which are H-bonding, cation-π and sigma-π interactions.

Bearing damages in reaction/momentum wheels are detrimental to the life and performance of the spacecraft. The signature of performance degradation in spacecraft ball bearings includes an increase in the bearing friction as evidenced by the increase in wheel current with a simultaneous increase in the wheel bearing temperature. The potential source of the problem should be addressed to avoid the irreversible impact on mission life. This paper presents the details of metallurgical analysis conducted on AISI 440C ball bearings to address the issues which perhaps contribute to the above problem and suggest possible remedial measures to avoid the recurrence of such issues. During ground testing, surface distress/running tracks were noticed on the contact surfaces of the balls. Detailed metallurgical analysis revealed loss of hard/coarse primary carbides from the matrix. In a closed system, these particles once removed, can contaminate the lubricant and cause further surface distress and progressive damage to the contact surface.

IR and Raman spectra of 1-[3-(1H-imidazol-1-yl)propyl]-3-phenylthiourea (HIPPT) have been recorded in the solid phase and the vibrational wave numbers are calculated theoretically by B3LYP/6-31G(d,p) (6D, 7F) method. All the fundamental vibrational modes have been assigned using potential energy distribution values and the molecular structure was analyzed in terms of parameters like bond length, bond angles and dihedral angles. The ring breathing mode of the phenyl ring is observed at 1016 cm(-1) in the IR spectrum, 1014 cm(-1) in the Raman spectrum and at 1014 cm(-1) theoretically. The values of polarizability and hyperpolarizabilities were calculated and nonlinear optical properties are discussed. The HOMO-LUMO plot reveals the charge transfer possibilities in the molecule. The NBO analysis was computed and possible transitions were correlated with the electronic transitions. In the title compound, the imidazole ring and CH2 groups are tilted from each other and the thiourea group is tilted from the phenyl ring. Using MEP plot the electrophilic and nucleophilic regions are identified. Local reactivity properties were investigated by analysis of ALIE surfaces and Fukui functions. Oxidation and degradation properties were initially assessed by calculation of bond dissociation energies of all single acyclic bonds. Determination of atoms with pronounced interactions with water molecules was performed by calculation of radial distribution functions after molecular dynamics simulations. Chargehopping rates were calculated within Marcus semi-empiric approach, employing both DFT calculations and MD simulations. The molecular docking computational predictions were complemented by the in vitro antibacterial activity evaluation. (C) 2016 Elsevier B.V. All rights reserved.

Gelatin based electrospun nanofibers are promising candidates for tissue engineering and regenerative medicine due to properties like biocompatibility, non antigenicity, non-toxicity and structural resemblance with native extracellular matrix. In the present work, a new nanofibrous scaffold using amine functionalized gelatin is fabricated. Modified gelatin is also known by the name cationized gelatin as the amino group is getting protonated. Unlike gelatin, the cationized gelatin is soluble in water without forming gel at room temperature. Hence, electrospinning of cationized gelatin can be carried out using water as the solvent. The water stability of cationized gelatin nanofibers is improved by cross-linking with two novel cross-linking agents, namely a disaccharide (sucrose) and a polysaccharide (dextran). The resulting cationized gelatin nanofibers are evaluated for the mouse fibroblast and human osteoblast like cells attachment, adhesion and proliferation. The results demonstrate that the electrospun cationized gelatin nanofibers can be potential scaffold materials for tissue regenerations.