Initial Softening in Some Aluminium Base Precipitation Hardening Alloys

It has been reported by previous workers that some extent of softening is observed before setting in of the usual hardening process when ageing is carried out on the AI-Cu- and AI-Mg precipitation hardening alloys. The possible reason for the initial softening has been sugg-ested as relief of thermal strain. Present work was undertaken to make systematic study of initial softening in certain Al-Cu and Al-Mg alloys. The phenomenon. of initial softening was studied as a funct-ion of solute concentration, quenching medium, and temperature of ageing. Hardness measurements were carried out to follow the process of softening and relief of thermal strain was studied by analysing X-ray line profile

Initial softening in some Aluminium base precipitation hardening Alloys

IT has been reported by previous workers1'2 that some extent of softening is observed before setting in of the usual hardening process when ageing is carried out on the Al-Cu and Al-Mg precipitation hardening alloys. The possible reason for the initial softening has been suggested as relief of thermal strain. No experimental evidence in support of this postulate has been reported so far

Deep neck space infections: comparison of outcomes between diabetic and non-diabetic patients

Background: The objective of the study was to study the clinical presentation, microbiological profile, treatment protocol of deep neck space infections in diabetics and non diabetics.Methods: This was a prospective study conducted on 76 patients (diabetics and non diabetics) admitted in the Department of Otorhinolaryngology, TD Medical college, Alappuzha over a period of 18 months from January 2012 to June 2013.Results: The age distribution was 15-75 years. Male to female ratio was 2:1. Fever, pain, neck swelling and odynophagia were the common symptoms with dyspnoea and chest pain indicative of complications. The most common etiology was odontogenic (68.4%) followed by tonsillopharyngeal infection and foreign bodies. No etiological factor was found in 34.2%. The commonest site was submandibular space (64.2%) followed by parapharyngeal space (26.6%). Abscess was present in majority needing surgical drainage. The most common organism isolated was streptococcus viridans (37.5%). Preponderance of klebsiella species was noted in diabetics. Streptococcus showed susceptibility to pencillin (83.33%), ampicillin (92%), cefotaxime (60.526%). Klebsiella showed susceptibility to gentamicin (42.3%) and ciprofloxacin (28.57%). The complication rate was more in diabetics (34.21%). Contrast enhanced CT was done in cases suspected to have complication. The mean hospital stay was longer in diabetics (19.6 days) than non diabetics (6.4 days).Conclusions: Deep neck space infection still remains life threatening if not heeded promptly. Senescence and diabetes demand surgical intervention and meticulous glycemic control to prevent complications. Judicious use of antimicrobials and timely radiological and surgical interventions have come a long way in the management and in providing a cure to this dreaded condition

Lack of Peripherally Induced Tolerance to Established Skin Allografts in Immunologically Reconstituted Scid Mice

The mechanism by which the antigen-specific immune system distinguishes between foreign antigens (toward which it mounts an immune response) and self-antigens (of which it is tolerant) is not completely understood. Studies using “superantigens” and transgenic mice have allowed investigations into some of the mechanisms of clonal deletion, anergy, and peripheral tolerance. In the present report, we have attempted to develop a new model system to investigate the possible mechanism(s) of peripheral tolerance to allografts. In this system, skin grafts from C57BL/6J (B6; H-2b mice are grafted onto T- and B-lymphocyte-deficient C.B-17-scid/scid (H-2d; hereafter referred to as scid) mice. Because of their lack of functional lymphocytes, the scid mice readily accept the allogeneic skin grafts. After the allografts healed, the scid mice were reconstituted with T-cell-deficient fetal liver from coisogeneic C.B-17-∤/∤ mice or bone marrow from weanling congenitally athymic BALB/c-nu/nu (H-2d; hereafter referred to as nude) mice. Upon immunological reconstitution, the scid mice reiected the established B6 skin allografts, suggesting that an immune system developing in the presence of an intact peripheral skin allograft fails to develop tolerance to the peripheral allograft. This model system may be useful for the study of the mechanisms required for the induction of peripheral tolerance

Effect of natural convection on oscillating flow in a pipe with cryogenic temperature difference across the ends

The effect of natural convection on the oscillatory flow in an open-ended pipe driven by a timewise sinusoidally varying pressure at one end and subjected to an ambient-to-cryogenic temperature difference across the ends, is numerically studied. Conjugate effects arising out of the interaction of oscillatory flow with heat conduction in the pipe wall are taken into account by considering a finite thickness wall with an insulated exterior surface. Two cases, namely, one with natural convection acting downwards and the other, with natural convection acting upwards, are considered. The full set of compressible flow equations with axissymmetry are solved using a pressure correction algorithm. Parametric studies are conducted with frequencies in the range 5–15 Hz for an end-to-end temperature difference of 200 and 50 K. Results are obtained for the variation of velocity, temperature, Nusselt number and the phase relationship between mass flow rate and temperature. It is found that the Rayleigh number has a minimal effect on the time averaged Nusselt number and phase angle. However, it does influence the local variation of velocity and Nusselt number over one cycle. The natural convection and pressure amplitude have influence on the energy flow through the gas and solid

CFD analysis of high frequency miniature pulse tube refrigerators for space applications with thermal non-equilibrium model

High frequency, miniature, pulse tube cryocoolers are extensively used in space applications because of their simplicity. Parametric studies of inertance type pulse tube cooler are performed with different length-to-diameter ratios of the pulse tube with the help of the FLUENT® package. The local thermal non-equilibrium of the gas and the matrix is taken into account for the modeling of porous zones, in addition to the wall thickness of the components. Dynamic characteristics and the actual mechanism of energy transfer in pulse are examined with the help of the pulse tube wall time constant. The heat interaction between pulse tube wall and the oscillating gas, leading to surface heat pumping, is quantified. The axial heat conduction is found to reduce the performance of the pulse tube refrigerator. The thermal non-equilibrium predicts a higher cold heat exchanger temperature compared to thermal equilibrium. The pressure drop through the porous medium has a strong non-linear effect due to the dominating influence of Forchheimer term over that of the linear Darcy term at high operating frequencies. The phase angle relationships among the pressure, temperature and the mass flow rate in the porous zones are also important in determining the performance of pulse tube refrigerator

White spot syndrome virus (WSSV) infection in tiger shrimp Penaeus monodon: A non-lethal histopathological rapid diagnostic method using paraffin and frozen sections

White spot syndrome virus (WSSV) infection was induced in tiger shrimp, Penaeus monodon, under laboratory conditions, and histopathological changes in subcuticular epithelial cells of the eye stalk and pleopod were studied sequentially at different time post-challenge. Routine histological techniques using paraffin embedded tissues, as well as frozen tissues, were used to document WSSV infection. Histological manifestations such as cellular hypertrophy in the subcuticular epithelial cells of the eyestalk and pleopod could be detected as early as 18 h postinfection (p.i.) before the manifestation of clinical signs of the diseas

Use of restriction fragment length polymorphisms (RFLPs) to distinguish between nematodes of pathogenic significance

The availability of restriction fragment length polymorphisms (RFLPs) would be useful for studying the extent of diversity among morpholgically indistinguishable populations of filarial parasites. Such polymorphisms may be useful in correlating various physiological and clinical differences with parasite heterogeneity. In order to identify such RFLPs, we isolated DNA from microfilaria of 6 filarial species (Acanthocheilonema viteae, Brugia malayi, Brugia pahangi, Dirofilaria immitis, Litomosoides carinii and Setaria digitatum), digested the DNA with several restriction endonucleases, prepared Southern blots and probed with 32P-labelled DSA probes. The patterns of fragments generated using two restriction endonucleases, Mbo I and Taq I, in combination with two probes, rDNA from the free-living soil nematode Caenorhabditis elegans, and pBM103, an anonymous DNA probe from B. malayi, unequivocally distinguish between all 6 of the species. To ensure that the differences we observed between the species represent true interspecies variation rather than fortuitous individual variations we analysed DNA from several individual B. malayi and B. pahangi worms. The individual B. malayi worms demonstrated restriction profiles that were invariant, as did the individual B. pahangi worms, demonstrating that the differences we observed were true interspecies variations