Evaluation of nitric oxide scavenging activity of certain spices in vitro: a preliminary study

The plant extracts of some commonly used spices were examined for their possible regulatory effect on nitric oxide (NO) levels using sodium nitroprusside as a NO donor in vitro. Most of the extracts tested demonstrated direct scavenging of NO and exhibited significant activity and the potency of scavenging activity was in the following order: Foeniculum vulgare (aqueous) > Citrus limettiodes > Murraya koenigii (seed, aqueous) > Murraya koenigii (leaf, aqueous) > Curcuma aromatica (aqueous) > Murraya koenigii (leaf, dichloromethane:methanol) > Mentha arvensis (chloroform) > Mentha arvensis (aqueous) > Curcuma longa > Gingko biloba > Foeniculum vulgare (dichloromethane:methanol) > Zingiber officinale (aqueous) > Curcuma aromatica (ethanolic) > Murraya koenigii (seed, dichloromethane:methanol). All the evaluated extracts exhibited a dose-dependent NO scavenging activity. The aqueous extract of Foeniculum vulgare showed a greatest NO scavenging effect of 79.75% at 62.5 microg/mL as compared to the positive control, Gingko biloba where 36.22% scavenging was observed at similar concentration. The present results suggest that these spices might be potent and novel therapeutic agents for scavenging of NO and the regulation of pathological conditions caused by excessive generation of NO and its oxidation product, peroxynitrite.     

Oscillating two-phase flow in an elastic tube

Summary Analytical expressions of dust and fluid velocities have been obtained for small amplitude waves having large wave length. Equations giving the wave-velocity and its damping factor have been derived. Corresponding graphs for various values of dust parameters and elasticity of the wall of the thin walled tube have been drawn. It is found that both the wave-velocity and its damping factor decrease with the increase in mass-concentration of dust and also they increase with the increase in Poisson's ratio of the wall of the tube.

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Schwingende Zweiphasenströmung in einem elastischen Rohr

Zusammenfassung Analytische Ausdrücke der Staub- und Flüssigkeitsgesch windigkeiten werden für kleine Amplituden von Wellen mit großer Wellenlänge erhalten. Gleichungen für die Geschwindigkeit der Welle und ihr Dämpfungsverhalten werden hergeleitet und zugehörige Diagramme für verschiedene Werte des Staubparameters und der Wandelastizität des dünnwandigen Rohres erhalten. Es wird gefunden, daß sowohl die Wellengeschwindigkeit als auch der Dämpfungsfaktor mit zumehmender Massenkonzentration des Staubs abnehmen und daß sie mit der Poissonzahl der Rohrwand zunehmen.

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With 3 Figures

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On leave from Bolpur College, Bolpur, West Bengal, India.     

New cavity perturbation technique for microwave measurement of dielectric constant

A new cavity perturbation technique is presented for microwave measurement of dielectric constant, which uses a modified cylindrical reentrant cavity. Though suitable for only low dielectric constants, the method has the advantages, (a) sample area does not appear in the calculations, (b) only the ratio of frequency shifts due to two samples of same area and different thickness is involved, and (c) calibration of the measuring system with known dielectric is not necessary.     

Kinetics of niobium carbide precipitation in a low carbon austenitic steel

An examination has been made of the kinetics of niobium carbide precipitation in a 18-10-1 austenitic stainless steel in the temperature range 650 to 750° C. Electrical resistance-time plots, thin film electron microscopy and hardness measurements have been employed to follow the ageing sequence. In these alloys the carbides precipitate on undissociated dislocations and in association with stacking faults; these processes are diffusion controlled and have an activation energy of ～318 kJ mol^?1. Prior to the reaction beginning a clear incubation period existed, e.g. ～30 h at 650° C and 20 min at 750° C. During the first 10% transformation the carbide nucleation rate increases and the associated faults nucleate and grow rapidly. The carbide nucleation rate appears to peak around this level and then falls away gradually to zero around 70% transformation. At this latter stage fault growth ceases, and transformation continues by a carbide growth process. The age-hardening peak occurs much beyond the end of the reaction by which time precipitate coarsening is in evidence. The precise effect mechanical deformation has upon stacking fault formation depends to a major extent on the niobium supersaturation in the quenched alloy.     

Electron tunnelling in semiconductor heterostructures

A theory of electron tunnelling in GaAsGa_1?xAl_xAsGaAs heterostructures is presented. The theory takes into account the different non-parabolic energy dispersion relations in the two materials. Calculated values of allowed energy levels are also presented for structures used in earlier experiments. Results of optical absorption experiments are found to agree with theory within 1 meV, but the results of double-barrier tunnelling experiments differ from theory by a factor of about 1.5.     

Low cycle fatigue behaviour of Ti-6Al-5Zr-0-5Mo-0-25Si alloy at room temperature

Low cycle fatigue (LCF) behaviour of the near α titanium alloy, Ti-6Al-5Zr-0.5Mo-0.25Si (LT26A), was investigated in the (a + β) as well as β treated conditions at room temperature. LCF tests were carried out under total strain controlled mode in the range of Δε_t/2: from ±0.60% to ±1.40%. The alloy shows cyclic softening in both the conditions. Also it exhibits dual slope Coffin-Manson (C-M) relationship in both the treated conditions.     

High temperature ceramic radomes (HTCR) – A review

An electromagnetically transparent, structurally robust and environmentally resistant enclosure of radar antenna for ground based systems to modern avionics in military aircraft and missiles is called as radome. Radome materials are classified based on: (i) type of function - surface-based or flight-mode and (ii) speed of operation - subsonic, supersonic to hypersonic. The desired properties of these materials are low dielectric constant and low loss factor in addition to its capacity to withstand the high temperature of operation. Composite laminates of glass or aramid fibre reinforced polymeric resins are radome material candidates for applications in subsonic range. However, ceramics are the only viable option for military aerospace applications such as a fighter jet travelling at Mach 3 or an advanced hypersonic missile speeding up to Mach 5. This review outlines the hand-full of ceramic materials already in application as radome materials like high-purity-alumina, pyroceram, slip-cast-fused-silica, their processing technology, electromagnetic and mechanical properties, advantages and disadvantages with respect to advanced military vehicles. Use of silicon nitride based radome materials, that has exceptional mechanical strength and thermal stability up to 1400 °C is illustrated with respect to reaction bonded silicon nitride, hot pressed silicon nitride, silicon oxynitride, sialon and their composites. Design of new generation radome materials was conceptualized and discussed as applicable to silicon nitride and related ceramics, wherein incorporation of varied degree of porosity improves electromagnetic properties, simultaneously, maintaining the required mechanical strength. Multilayer and graded porosity and its influence on electromagnetic properties were briefly discussed. Si₃N₄ ceramics having controlled porosity leading to optimum electromagnetic and mechanical properties produced through systematic processing is proposed as the futuristic high temperature radome material for supersonic applications.     

热处理,预应力和表面强化对微合金钢断裂韧性的影响

微合金钢在行业的各个领域中日益得到应用,而且能提供各种各样的显微组织。大量文献论述了它们显微组织和性能的关系。微合金钢具有优越的力学性能是因为有细晶粒度的显微组织和V、Ti和Nb等微合金元素的沉淀,导致改善屈服强度,也提高产品的抗拉强度和总伸长和夏比V形缺口冲击能量。热处理引起显微组织的变化,或者表面硬化或机械方式强化可能会形成残余应力状态,从而影响这些微合金钢的断裂韧性。正是在这样的背景下,目前的工作始于对轧制状态条件下没有任何热处理的低碳(0.19%)微合金钢准静态的初步实验,测定了断裂韧性(J1c)。这项研究进一步探讨了正火,喷丸加工和喷丸加工接着氰化对所研究的轧制态钢断裂韧性的影响。正火热处理、喷丸加工和喷丸加工接着氰化三种加工表明对起始断裂韧性有积极的影响。对比的结果表明,喷丸加工接着氰化使J1c增加2.7倍。因此喷丸加工接着氰化可能被视为对所研究的这类微合金钢在轧制态条件下的起始断裂韧性产生最积极的影响。虽然在线弹性断裂力学(LEFM)领域里,一般已知的起始断裂韧性是随屈服强度的增加而减少,但是所研究的微合金钢在正火时显示屈服强度和J1c同步提高。以显微组织的研究和应力深度分布为基础能解释所有这些观察到的正火,喷丸加工和氰化对起始断裂韧性的应响(弹塑性断裂力学)。     

Modeling the economics of testing: a DFT perspective

Decision-makers typically make test tradeoffs using models that mainly represent direct costs such as test generation time and tester use. Analyzing a test strategy's impact on other significant factors such as test quality and yield learning requires an understanding of the dynamic nature of the interdomain dependencies of test, manufacturing, and design. Our research centers on modeling the tradeoffs between these domains. To answer the DFT question, we developed the Carnegie Mellon University Test Cost Model, a DFT cost-benefit model, derived inputs to the model for various IC cases with different assumptions about volume, yield, chip size, test attributes, and so forth; and studied DFT's impact on these cases. We used the model to determine the domains for which DFT is beneficial and for which DFT should not be used. The model is a composite of simple cause-and-effect relationships derived from published research. It incorporates many factors affecting test cost, but we don't consider it a complete model. Our purpose is to illustrate the necessity of using such models in assessing the effectiveness of various test strategies