A finite deformation nonlinear thermo-elastic model that mimics plasticity during monotonic loading

We present and study a nonlinear thermo-elastic constitutive model that under monotonic loading closely reproduces the response seen in plasticity, showing the initial stiff elastic response, kneeing as if yielding, and then showing response resembling post-yield hardening. The proposed large deformation thermo-elastic response model is constructed based on four physically identifiable mechanical parameters, that are closely related to the parameters used to construct plasticity models, thermal expansion parameters and two thermodynamic parameters. The four mechanical parameters are the initial elastic shear and bulk moduli, the yield point in shear, the hardening slope in shear. The thermodynamic parameters are the heat capacity at a reference temperature and its rate of change with changes of temperature. The model can be considered an alternate to deformation plasticity models currently used and, as such, can be used as a lightweight substitute for plasticity modeling in certain analysis. Since the proposed model is thermodynamically based, not only thermal effects are integrated into the model, but also the stress is calculated in terms of the applied deformation, allowing the model to be integrated with other models when conducting numerical analysis. We study the response of the proposed model under simple shear, uniaxial extension, confined compression, partially-confined compression, and biaxial extension. We incorporate the elastic model into ABAQUS using its UMAT subroutine for solid elements and using UHYPER for shell elements. We compare the large deformation response from the proposed elastic model with J2-plasticity, and with plasticity and deformation plasticity models implemented in ABAQUS. The model in most cases compares very favorably to all such models. This comparison is done for both homogeneous and non-homogeneous problems including the case of a cantilever beam under tip loading. We show that for the problems that it applies to, the models run in approximately one tenth the computational time and with one tenth the number of iterations needed to conduct the analysis using the plasticity model in ABAQUS.     

DNA interaction, superoxide scavenging and cytotoxicity studies on new copper(II) complexes derived from a tridentate ligand

The copper complexes [Cu(Pyimpy)(H₂O)](ClO₄)₂ (1), [Cu(Pyimpy)₂](ClO₄)₂ (2), [Cu(Pyimpy)(Cl)₂]·2H₂O (3·2H₂O), [Cu(Pyimpy)(N₃)(ClO₄)]₂ (4) and [Cu(Pyimpy)(SCN)(ClO₄)]₂ (5) were synthesized and characterized by spectroscopic techniques, crystal structures and electrochemical studies (Pyimpy: (2-((2-phenyl-2-(pyridin-2-l)hydrazono)methyl)pyridine)). The superoxide scavenging activity of the two water soluble complexes 1 and 3 was examined. DNA interaction studies by UV-Vis absorption spectral changes during a titration experiment indicated the generation of new species. These small molecule SOD mimics exhibited excellent DNA cleavage activity in the presence of H₂O₂ as well as 2-mercaptoethanol. Complexes 1-5 exhibited better cytotoxicity compared to CuCl₂·2H₂O and the ligand Pyimpy, and showed more potency than cisplatin for MCF-7, PC-3 and HEK-293 cells. Complex 3 exhibited the highest potency for MCF-7, PC-3 and HEK-293 cells compared to the other complexes.     

Synthesis and structural characterization of pincer type bicyclic diacyloxy- and diazaselenuranes

Synthesis and structural characterization of a new class of pincer type bicyclic diacyloxy- and diazaselenuranes is reported. The reaction of dimethyl 2-bromo-5-tert-butylisophthalate (28) with sodium benzeneselenolate affords the corresponding monoselenide, dimethyl 5-tert-butyl-2-(phenylselanyl)isophthalate (29). Reduction of 29 with LiAlH(4) provides 5-tert-butyl-2-(phenylselanyl)-1,3-phenylene)dimethanol 31. Oxidation of 29 or its hydrolyzed derivative, 5-tert-butyl-2-(phenylselanyl)isophthalic acid (30), with H(2)O(2) results in the formation of bicyclic diacyloxyselenurane (25). The reaction of 30 with aniline using the DCC coupling reaction gives 5-tert-butyl-N(1),N(3)-diphenyl-2-(phenylselanyl)isophthalamide (38). Reaction of 38 with H(2)O(2) leads to the formation of the corresponding bicyclic diazaselenurane (27) via selenoxide intermediate 39. Compounds 25, 27, 29 and 31 were characterized by single crystal X-ray crystallography. The structural aspects of the pincer type bicyclic chalcogenuranes are investigated using experimental and computational studies and compared with the related systems.     

Use of HPTLC to Establish the Chemotype of a Parasitic Plant,Dendrophthoe falcata (Linn. f.) Etting. (Loranthaceae), Growing on Different Substrates

JPC – Journal of Planar Chromatography – Modern TLC - Dendrophthoe falcata (Linn. f.) Etting. is a stem parasite commonly known as ‘Vanda’ in the Ayurvedic system of...     

Comparative studies on performance of radiation-induced and thermal cross-linked ion-exchange membrane for water electrolysis

Radiation-induced and thermal cross-linked sulfonated poly(ether sulfone) (SPS)–sulfonated poly(ether ether ketone) (SPK) composite ion-exchange membranes (SPS/SPK(γ) and SPS/SPK(T), respectively) were prepared. Their performances for water electrolysis were comparatively assessed. Thermal cross-linked membrane (SPS/SPK(T)) showed cross-linking of part functional groups (–SO₃H) and thus deterioration in membrane conductivity. While, radiation-induced cross-linked membrane (SPS/SPK(γ)) avoided any cross-linking between functional groups and thus conductivity. Electrolysis performances of these membranes were evaluated in comparison with Nafion117 membrane. Relatively low current efficiency (CE) for SPS/SPK and SPS/SPK(T) membranes was due to their high mass transfer (water) via electro-osmotic drag, which was negligible for SPS/SPK(γ) membrane. SPS/SPK(γ) membrane exhibited comparable stabilities and water splitting performance with Nafion117 membrane, which revealed its suitability as substitute for electrochemical applications.     

Performance analysis of traffic groomed optical network

In this paper we carry out the performance analysis of traffic groomed multilayer optical networks. It is seen that the number of wavelength channels required decreases as the wavelength grooming factor increases. We have evaluated blocking probability for different load and grooming factor. The performance of the network has been evaluated for different conditions; first for fixed number of links with grooming factor set to 3 and subsequently with increase in grooming factor up to 18 in steps. The load on each link is selected as 2, 5, 9, 12, 15 and 20 Erlangs and the blocking probability as function of number of optical channels has been evaluated. In this work the effect of number of wavelength channels, traffic load and grooming factor on network blocking probability has been studied. The investigation reveals that the blocking probability decreases with increase in wavelength channels. Similarly we found that the blocking probability increases with increase in traffic load which is quite evident. Further it is shown that when the grooming factor is increased to significant value (16), the number of wavelengths requirement (8) becomes relatively stable.     

Single-Atom Catalysis Using Chromium Embedded in Divacant Graphene for Conversion of Dinitrogen to Ammonia

Reduction of dinitrogen to ammonia under ambient conditions is a long-standing challenge. The few metal-based catalysts proposed have conspicuous disadvantages such as high cost, high energy consumption, and being hazardous to the environment. Single-atom catalysis has emerged as a new frontier in heterogeneous catalysis and metal atoms atomically dispersed on supports receive more and more attention owing to rapid advances in synthetic methodologies and computational modeling. Herein, we propose metal atoms embedded in divacant graphene as a catalyst for N₂ fixation based on density functional calculations. We systematically investigate the potential of using transition metal like Cr, Mn, Fe, Mo and Ru as catalysts and our study reveals that Cr embedded in graphene exhibit good catalytic activity for N₂ fixation. The synergy between the metal atoms and graphene surface provides a stable support to the metal center that has a high spin density to promote adsorption of N₂ and activation of its N≡N triple bond. Our study deciphers the mechanism of conversion of N₂ to ammonia following two possible reaction pathways, distal and enzymatic routes, via sequential protonation and reduction of activated N₂. The study provides a rational framework for conversion of dinitrogen to ammonia using single atom catalyst.