Strain hardening during constrained deformation of metal foams - Effect of shear displacement

The crush bands that form during plastic deformation of closed-cell metal foams are often inclined at 11-20 degrees to the loading axis, allowing for shear displacement of one part of the foam with respect to the other. Such displacement is prevented by the presence of a lateral constraint. This was analysed in this study, which shows that resistance against shear by the constraint leads to the strain-hardening effect in the foam that has been reported in a recent experimental study. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Effect of rodents on seed fate of five hornbill-dispersed tree species in a tropical forest in north-east India

Hornbills are important dispersers of a wide range of tree species. Many of these species bear fruits with large, lipid-rich seeds that could attract terrestrial rodents. Rodents have multiple effects on seed fates, many of which remain poorly understood in the Palaeotropics. The role of terrestrial rodents was investigated by tracking seed fate of five horn bill-dispersed tree species in a tropical forest in north-cast India. Seeds were marked inside and outside of exclosures below 6-12 parent fruiting trees (undispersed seed rain) and six hornbill nest trees (a post-dispersal site). Rodent visitors and seed removal ere monitored using camera traps. Our findings suggest that several rodent species. especially two species of porcupine were major on-site seed predators. Scatter-hoarding was rare (1.4%). Seeds at hornbill nest trees had lower survival compared with parent fruiting trees, indicating that clumped dispersal by hornbills may not necessarily improve seed survival. Seed survival in the presence and absence of rodents varied with tree species. Some species (e.g. Polyalthia simiarum) showed no difference, others (e.g. Dysoxylum binectariferum) experienced up to a 64%. decrease in survival in the presence of rodents. The differing magnitude of seed predation by rodents can have significant consequences at the seed establishment stage.

Effect of cupric-isonicotinic acid hydrazide complex on avian myeloblastosis virus reverse transcriptase and its associated enzyme activities

Cupric complex of isonicotinic acid hydrazide inhibits DNA synthesis by avian myloblastosis virus reverse transcriptase. This inhibition occurs in the presence of either ribonucleotide or deoxyribonucleotide templates. The inhibition of reverse transcriptase by cupric-INH complex is considerably reduced when stored or proteolytically cleaved enzyme was used in the reaction. The complex also inhibits the reverse transciptase-associated RNase H activity. The cupric-isonicotinic acid hydrazide complex cleaves pBR 322 from I DNA into smaller molecules in the presence or absence of reverse transcriptase-associated endonuclease. However, in the presence of the enzyme the DNA is cleaved to a greater extent.

Effect of inclination on laminar film condensation

The effect of inclination on laminar film condensation over and under isothermal flat plates is investigated analytically. The complete set of Navier Stokes equations in two dimensions is considered. Analysed as a perturbation problem, the zero-order perturbation represents the boundary layer equations. First and second order perturbations are solved to bring about the leading edge effects. Corresponding velocity and temperature profiles are presented. The results show decrease in heat transfer with larger ∥inclinations∥ from the vertical. Comparison with experimental data of Gerstmann and Griffith indicates a closer agreement of the present results than the analytical results of the same authors.

Effect of antiserum to luteinizing hormone (LHAS) on the physiology of the epididymis and accessory glands in the albino rat

Rabbit antiserum specific to ovine luteinizing hormone free of contaminating antibodies to nonspecific proteins and FSH was administered to adult, intact rats at a dose of 0.1 and 0.2 ml/day for five days. LHAS had no effect on the weights of the epididymis but decreased their secretory activity to castrate level. Administration of 0.2 ml of LHAS or castration resulted in a marked and comparable reduction in the weights and secretory activity of the accessory glands. LHAS, even at a lower dose (0.1 ml/day), caused a significant reduction in the content of sialic acid in the vas deferons and Cowper's glands. These results are discussed in relation to the factors that regulate the functions of the epididymis and accessory glands.

Effect of ion temperature on propagation of ion-acoustic solitary waves of small amplitudes in collisionless plasma

By using a perturbation technique, the Korteweg-de Vries equation is derived for a mixture of warm-ion fluid and hot, isothermal electrons. Stationary solutions are obtained for this equation and are compared with the corresponding solutions for a mixture consisting of cold-ion fluid and hot, isothermal electrons.

Effect of surface resistance on gas absorption accompanied by a chemical reaction in a gas - liquid contactor

An analysis of gas absorption accompanied by chemical reaction in the presence of interfacial resistance is presented. The analysis indicates that the effect of interfacial resistance on interphase mass transfer is significantly higher in presence of a reaction compared to the pure absorption case. For fixed values of surface resistance and contact time, the difference between the amount of gas transferred across the interface with and without surface resistance increases as the value of reaction velocity increases. For ranges of contact time and surface resistance of practical relevance, the influence of surface resistance is too high to be neglected while designing gas-liquid contactors.

Protein Synthesis in Mycobacterium tuberculosis H37Rv and the Effect of Streptomycin in Streptomycin-Susceptible and -Resistant Strains

An efficient in vitro amino acid-incorporating system from Mycobacterium tuberculosis H37Rv was standardized. Ribonucleic acid (RNA) isolated from phage-infected M. smegmatis cells served as natural messenger RNA and directed the incorporation of 14C-amino acids into protein. The effects of various antitubercular drugs and “known inhibitors” of protein synthesis on amino acid incorporation were studied. Antibiotics like chloramphenicol and tetracycline inhibited mycobacterial protein synthesis, though they failed to prevent the growth of the organism. This failure was shown to be due to the impermeability of mycobacteria to these drugs by use of “membrane-active” agents along with the antibiotics in growth inhibition studies. Several independent streptomycin-resistant mutants of M. tuberculosis H37Rv were isolated. Streptomycin inhibited the incorporation of 14C-amino acids into proteins by whole cells of a streptomycin-susceptible strain by more than 90%, whereas very little or no inhibition was observed in either high-level or low-level streptomycin-resistant strains.

Effect of vitamin A deprivation on the cholesterol side-chain cleavage enzyme activity of testes and ovaries of rats (Short Communication)

The cholesterol side-chain cleavage enzyme activity is decreased considerably at the mild stage of vitamin A deficiency in rat testes and ovaries and the decrease in activity becomes more pronounced with progress of deficiency. Supplementation of the deficient rats with retinyl acetate, but not retinoic acid, restores the enzyme activity to normal values. The cholesterol side-chain cleavage enzyme of adrenals is not affected by any of the above treatments.

Effect of Load on Dry Sliding Wear of Aluminum-Silicon Alloys

Aluminum-silicon alloy pins were slid against steel disks under nominally dry condition at a speed of 0.6 m s-1. Each pin was slid at a constant load for 5 min, the load being increased in suitable steps from 2 to 65 N. The results show the wear to increase almost monotonically with load, to be sensitive to the presence of silicon in the alloy, and to be insensitive to actual silicon content. The monotonic nature of wear rate-load characteristic suggests that one dominant wear mechanism prevails over the load range studied. Morphological studies of the pin surface and the debris support this contention and point to delamination as being the dominant mode of wear.

Effect of LHRH agonists and antagonists in male and female bonnet monkeys (Macaca Radiata)

A few analogues of LHRH have been tested in the adult bonnet monkeys using change in serum testosterone following LHRH injection as a parameter of response to LHRH. Of the four analogues tested in male monkeys, Buserelin was found to be the most potent one in increasing serum testosterone levels. Injection of the LHRH antagonist at 1600 h resulted in the abolition of the characteristic nocturnal surge of testosterone observed in adult bonnet monkeys maintained under regulated light conditions. Following administration of LHRH a/s during early pregnancy, serum chorionic gonadotropin levels decreased though the course of pregnancy was not affected. These results suggest that bonnet monkey can be successfully employed to test LHRH analogues.

Studies on nucleotidases in plants : Reversible denaturation of the crystalline mung bean nucleotide pyrophosphatase and the effect of adenylates on the native and renatured enzyme

The crystalline mung bean nucleotide pyrophosphatase was inhibited nonlinearly by AMP, one of the products of the reaction. The partially inactive enzyme was specifically reactivated by ADP, and V at maximal activation was the same as that of the native enzyme. ATP was a linear, noncompetitive inhibitor. The kinetic evidence suggested that ADP and ATP might not be reacting at the same site as AMP. The electrophoretic mobility of the enzyme was increased by AMP, whereas ADP and ATP were without effect. The enzyme was denatured on treatment with urea or guanidine hydrochloride. The renatured and the native enzyme had the same pH (9.4) and temperature (49 °C) optimum. The Km (0.2 mImage ) and V (3.2) of the native enzyme increased on renaturation to 1.8 mImage and 8.0, respectively. In addition, renaturation resulted in desensitization of the enzyme to inhibition by low concentrations of AMP. Renaturation did not affect the reactivation of the apoenzyme by Zn2+.

Surface treatments for pistons and their effect on engine performance

Surface treatment alters the frictional behaviour of pistons in I.C. engines and can be used to improve engine performance. Surface treatments applied to aluminium alloy pistons of a high speed diesel engine and their effect on the engine performance are described. Certain piston surface treatments improve engine performance and also reduce the run-in period.

The effect of solar activity on temperatures in the equatorial mesosphere

A study of the response of neutral temperatures in the equatorial mesosphere to variations in solar activity has been carried out by investigating the correlation between the 10.7 cm solar radio flux and temperatures obtained from a series of 51 rocket soundings conducted over Thumba, India (8°N, 77°E) during the period December 1970–December 1971. A strong positive correlation between these two parameters has been obtained, indicating mesospheric heating effects caused by day-to-day variations in solar EUV emission. The correlation analysis indicates that this response persists over several days and that the peak correlation between the temperatures and the F10.7 index occurs with a time lag of less than 24 hr.

Zeeman effect of nuclear quadrupole resonance in 1-chloro-2,4-dinitrobenzene

The Zeeman effect of NQR was studied in 1-chloro-2,4-dinitrobenzene. A low value of the asymmetry parameter (0.10) was obtained. Four physically inequivalent field gradients were located and their orientations in the crystallographic abc system were determined using symmetry considerations. From these data the orientations of the molecules in the unit cell were determined. The results agree well with the two-dimensional x-ray structural data. The bond characters of the C[Single Bond]Cl bond were calculated, and the values compare well with those generally obtained for C[Single Bond]Cl bonds in chlorine derivatives of benzene. ©1973 The American Institute of Physics.