Finite-element analysis of rectangular plates with rectangular inserts

The present investigation deals with the stress distribution in the vicinity of rectangular inserts in finite rectangular plates. This problem is more complex due to the singularities at the corners of the inserts. In this paper, the finite-element technique is used to determine the deformations and, subsequently, the stresses. The paper treats the problem in a generalized form in the sense that the size and orientation of the insert are taken as variables. The finite rectangular plate is subjected to a uniform axial tensile load. The material of the plate and that of the insert are considered to be different. Element selections are made which are optimal with regard to accuracy and computational effort. The local element stresses which generate considerable discontinuity at the element nodes are plotted. Averaging process for the local stress calculations is discussed and these are compared with the results available¹ which are obtained by experimental techniques.     

Supramolecular homobimetallic <Emphasis Type="Italic">bis</Emphasis>-diorganotin(IV) complexes of ditopic oxygen nitrogen donor ligand: synthesis,spectroscopic characterization,crystal structure and biological screening

Six new homobimetallic bis-diorganotin(IV) complexes: [Me₂Sn]₂L (1), [Et₂Sn]₂L (2), [n-Bu₂Sn]₂L (3), [Ph₂Sn]₂L (4), [Oct₂Sn]₂L (5) and [n-BuClSn]₂L (6) (H ₄ L=N¹′, N⁶′-bis(2-hydroxybenzylidene)adipodihydrazide) have been synthesized and structurally characterized by means of elemental analysis, mass spectroscopy, FT-IR, NMR (¹H, ¹³C{¹H}, ¹¹⁹Sn) and single-crystal X-ray diffraction. Spectroscopic studies indicate coordination of the ligand to the diorganotin(IV) moieties via iminolic oxygen, nitrogen and phenolic oxygen atoms generating pentacoordinated tin centers. Single-crystal X-ray analysis of (1) revealed homobimetallic nature of complex with dimethyltin moieties oriented in trans-conformation. The ligand is non-planar with each Sn atom in a distorted square pyramidal coordination geometry. Packing diagrams suggest the essential role of C–H^…N and C–H^…O interactions in generating supramolecular assembly. The ligand and complexes were screened for in vitro antimicrobial activity and cytotoxicity. Compound (4) exhibits highest cytotoxicity.     

Laser-induced thermal stresses on steel surface

In laser heat treatment of steels, a thin surface layer of austenite forms during heating and subsequent phase change process in the cooling period. However, thermal stress develops due to high-temperature gradient attainment in the surface vicinity which in turn results in microcrack development at the surface. The present study is carried out to compute the temperature profiles due to step input pulse laser radiation and determine the resulting thermal stresses. The study is extended to include three-step input pulses having the same energy content. This provides the comparison for the influence of the pulse length on the resulting thermal stresses. To validate the theoretical predictions, an experiment is conducted to irradiate the AISI 4142 steel surface by an Nd–YAG laser. Microphotography and EDS analysis of the heated regions are carried out. It is found that considerable thermal stress is eveloped at the workpiece surface due to attainment of high-temperature gradient in this region. In addition, microcracks are observed at the surface of the irradiated spot.     

Reactivity of the Coordinated Hydroperoxo Ligand

The reactivity of the hydroperoxo complex [Co(CN)(5)OOH](3)(-) has been studied in aqueous solution. The complex undergoes acid-catalyzed aquation (k = 1.89(5) x 10(-)(2) s(-)(1), pK(a) = 5.21(4), T = 20 degrees C, I = 0.1 M). Assuming an I(d) mechanism, this allows the relative affinity for Co(III) to be deduced as H(2)O(2) < H(2)O < HO(2)(-) and implies H(2)O(2) to be a very weak ligand. At neutral pH the hydroperoxo complex effects efficient oxygen atom transfer to L-methionine to give an intermediate identified as [Co(CN)(5)(L-methionine S-oxide)](2)(-), which then dissociates to [Co(CN)(5)OH(2)](2)(-) and L-methionine S-oxide. The reaction is acid catalyzed and is proposed to take place via nucleophilic attack of sulfur on the proximal oxygen of the hydroperoxo ligand with concerted loss of water. The significance of these results for the interaction of hydrogen peroxide with labile metal ions is discussed.     

Low frequency electrostatic nonlinear structures in an inhomogeneous magnetized non-Maxwellian electron–positron–ion plasma

The properties of low frequency (coupled acoustic and drift wave) nonlinear structures including solitary waves and double layers in an inhomogeneous magnetized electron–positron–ion (EPI) nonthermal plasma with density and temperature inhomogeneities are studied in a simplified way. The nonlinear differential equation derived here for the study of double layers in the inhomogeneous EPI plasma resembles with the modified KdV equation in the stationary frame. But the method used for the derivation of nonlinear differential equation is simple and consistent to give both the stationary solitary waves and double layers. Further, the illustrations show that superthermality κ, drift velocity and temperature inhomogeneity have significant effects on the amplitude, width, and existence range of the structures.     

Detailed heat transfer and friction factor characteristics in a rectangular duct with alternate solid and converging-slit ribs

Liquid crystal thermography and pressure drop measurements have been carried out to study the heat transfer and frictional characteristics in a rectangular duct with solid ribs (C1), converging slit-ribs (C2), and alternate solid-slit ribs (C3) mounted transversely on the bottom wall, where C2 carries a continuous converging-slit in the flow direction. Effect of rib configurations, and rib pitch to height ratios (6, 8, 10, and 12) has been investigated at Re of 9400, 26160, 42500, and 58850. Results show that converging-slit considerably enhances the heat transfer rate in the downstream vicinity, and help in obviating the local hot spot formation.

Abbreviations: LCT: Liquid crystal thermography; HTC: Heat transfer coefficient; LHI: Laser holographic interferometry; NST: Naphthalene sublimation technique; IR: Infrared; TPF: Thermo-hydraulic performance; PIV: Particle image velocimetry.     

Laser consecutive pulse heating in relation to melting: influence of duty cycle on melting

Laser consecutive pulse heating of steel and titanium is considered and the influence of consecutive pulse duty cycle on the melting process is examined. A model study is introduced to accommodate the phase change process while an experiment is carried out to measure the size of the melting region along the irradiated surface. The simulations are repeated for three duty cycles. It is found that the sizes of melt and mushy zones are influenced by the duty cycle; in which case, radial distribution of temperature is modified significantly for low duty cycle as compared to for high duty cycle.     

Jasminum sambac: A Potential Candidate for Drug Development to Cure Cardiovascular Ailments

Jasminum sambac (L.) is a South Asian folkloric medicinal plant that has traditionally been used to treat cardiovascular problems. The current investigation was meticulously organized to explore the pharmacological foundation for the medicinal uses of J. sambac pertaining to cardiovascular ailments and to investigate the core mechanisms. Mechanistic investigation revealed that crude leaf extract of J. sambac produced ex-vivo vasorelaxant effects in endotheliumintact aorta ring preparation and hypotensive effect was recorded via pressure and force transducers coupled to the Power Lab Data Acquisition System. Moreover; J. sambac showed cardioprotective effects against adrenaline -induced left ventricular hypertrophy in rabbits observed hemodynamic. CK-MB, LDH, troponin, CRP, ALT, AST, ALP levels were shown to be lower in the myocardial infarction model, as were necrosis, oedema, and inflammatory cell recruitment in comparison to control. J. sambac has shown good antioxidant potential as well as prolonged the noradrenaline induced platelet adhesion. The vasorelaxant and cardioprotective effects in both in vivo and ex vivo experiments, which are enabled by activation of muscarinic receptor and/or releasing the nitric oxide and by reducing the adrenaline, induced oxidative stress, justifying its usage in cardiovascular disorders.     

Laser heating of semi-infinite solid with consecutive pulses: Influence of materaial properties on temperature field

The heating of solid surfaces using consecutive laser pulses is studied and the temperature field inside slabs with different thermal properties is predicted. A Gaussian beam intensity distribution is assumed at the irradiated surface and axisymmetric heating situation is accommodated in the numerical simulations. The materials selected include titanium, stainless steel, tantalum, nickel, and aluminum. A control volume approach is introduced to discretize the governing equation of heat transfer. It is found that temperature rise in the early heating period is higher than that in the later heating period. The temperature difference between two consecutive pulses is higher in the heating cycle than that corresponding to the cooling cycle of the consecutive pulses.     

Band gap anomaly in ternary chalcopyrite semiconductors,the role of p-d hybridization

Summary The anomalous reductions in the energy band gap of the chalcopyrite semiconductors as compared to their relative binary analogs are estimated quantitatively by using a simple relation that involves quantum defect electronegativity scale and the average principal quantum number. The chemical and the structural contribution to this anomaly is discussed in details and it is shown that the relation can be easily extended to explain the variation in the band gap of some cross-substitutional alloys.

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Riassunto Le anomale riduzioni del gap di energia nei semiconduttori a struttura calcopirite rispetto ai loro analoghi binari sono stimate quantitativamente usando una semplice relazione che implica l’uso della scala delle elettronegatività e il numero quantico principale medio. Il contributo chimico e strutturale a questa anomalia è discusso ed è mostrato che la relazione può essere agevolmente estesa per spiegare la variazione del gap in alcune soluzioni solide.

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Резюме Количественно оцениваются аномальные уменьшения ширины запрещенной зоны в полупроводниках халькопирита, по сравнению с бинарными аналогами. Подробно обсуждается химичекий и структурный вклад в эту аномалию. Показывается, что предложенный подход можно легко обобщить для объяснения изменения ширины запрещенной зоны в некоторых кросс-замещенных сплавах.