Canonical decompositions of 3-manifolds

We describe a new approach to the canonical decompositions of 3-manifolds along tori and annuli due to Jaco-Shalen and Johannson (with ideas from Waldhausen) - the so-called JSJ-decomposition theorem. This approach gives an accessible proof of the decomposition theorem; in particular it does not use the annulus-torus theorems, and the theory of Seifert fibrations does not need to be developed in advance.Comment: 20 pages. Published copy, also available at http://www.maths.warwick.ac.uk/gt/GTVol1/paper3.abs.htm

Determination of Vacant Lattice Sites in Aluminium Alloys by X-ray Diffraction Technique

THE study of the structure of metals and alloys is very important because this affords the possibility of developing new alloys with improved properties to be useful for meeting service requirements. Theories based on ideal crystals fail miserably when applied to real crystals of the metals and alloys, for example the calculated Yield strength and breaking strength of ideal crystals are 100 to 10,000 times more than the observed strength of real crystals. The reason is that the crystals contain many haws and irregularities, so it is felt that a detailed knowledge of vacant lattice sites in alloys will be useful, because of their effects on physical and mechanical properties. The object of this investigation is to find out the effect of copper on the lattice parameter and vacant lattice sites in aluminium

The Role of Wet-Tensile Strength of Foundry Sands in the Surface Finish of Aluminium Sand Casting

0NE of the most striking features of industrial deve-lopment during the past decade has been the rapid growth in the use of aluminium and it, alloys in the form of castings. To obtain sound casting has always been a prob-lem for the foundry engineer, as the qualities required of it moulding sand are in some measure contradictory and a compromise must be made. Thus permeability is favoured by a low clay content and coarse particle size, whereas a smooth finish calls for a line sand with a higher clay content.Similarly, green strength is impr- oved by the addition of clay up to a certain point but permeability is reduced. Further permeability and green strength depend largely on the moisture content. These conventional green properties do not allow conclusions of sand properties on casting conditions 1 2, because all these are tested at room temperature, where temper-ature and material distributions are uniform inside the moulding sand. To overcome the above difficulties a new concept of Wet-Tensile Strength has been developed recently in the Foundry institute of Rhcinsch- West falischen Technischen Hoehschule Aachen (West Germany. It shows a very good correlation with the scabbing tendency of moulding materials and has been found to be of practical importance in order to control the quality of' aluminium castings in the foundr

The Relation of Pilot Plants to Full Scale Operation

The author's chief interest in pilot plants is as a means of practical instruction. At the Banaras Hindu University a number of pilot plants have been installed so as to impart some practical Idea of metallurgical processes to final year students. These pilot plants include a sintering plant, several small size cupolas, an LD converter, a basic lined side blown converter, indirect arc furnace & high frequency electric furnaces. The latest addition to this range of pilot plants is a small scalp Edwards vacuum melting unit. In addition to their use for instructional purposes, it is hoped, as candidates present themselves, that these plants will be more fully employed in post- graduate res-earch, which it is felt will be of considerable importance to the development of the iron & steel industry in India. Post-graduate research, which it is felt will be of consi-derable importance to the development of the iron and steel industry in India. Post-graduate work of this nature must play an important role in the provision of thoroughly trained personnel for the rapidly growing industry in India

The Creation of Defects with Core Condensation

Defects in superfluid 3He, high-Tc superconductors, QCD colour superfluids and cosmic vortons can possess (anti)ferromagnetic cores, and their generalisations. In each case there is a second order parameter whose value is zero in the bulk which does not vanish in the core. We examine the production of defects in the simplest 1+1 dimensional scalar theory in which a second order parameter can take non-zero values in a defect core. We study in detail the effects of core condensation on the defect production mechanism.Comment: 9 pages, 7 figures, small corrections, 2 references added, final version to be published in PR

Oxidative Stress in Lead and Cadmium Toxicity and Its Amelioration

Oxidative stress has been implicated to play a role, at least in part, in pathogenesis of many disease conditions and toxicities in animals. Overproduction of reactive oxygen species and free radicals beyond the cells intrinsic capacity to neutralize following xenobiotics exposure leads to a state of oxidative stress and resultant damages of lipids, protein, and DNA. Lead and cadmium are the common environmental heavy metal pollutants and have widespread distribution. Both natural and anthropogenic sources including mining, smelting, and other industrial processes are responsible for human and animal exposure. These pollutants, many a times, are copollutants leading to concurrent exposure to living beings and resultant synergistic deleterious health effects. Several mechanisms have been explained for the damaging effects on the body system. Of late, oxidative stress has been implicated in the pathogenesis of the lead- and cadmium-induced pathotoxicity. Several ameliorative measures to counteract the oxidative damage to the body system aftermath or during exposure to these toxicants have been assessed with the use of antioxidants. The present review focuses on mechanism of lead- and cadmium-induced oxidate damages and the ameliorative measures to counteract the oxidative damage and pathotoxicity with the use of supplemented antioxidants for their beneficial effects

Fractional boundary value problems: Analysis and numerical methods

This is the author's PDF of an article published in Fractional calculus and applied analysis 2011. The original publication is available at www.springerlink.comThis journal article discusses nonlinear boundary value problems.Fundacao para a Ciencia e Tecnologi

Radiative absorption enhancements by black carbon controlled by particle-to-particle heterogeneity in composition.

Black carbon (BC) absorbs solar radiation, leading to a strong but uncertain warming effect on climate. A key challenge in modeling and quantifying BC's radiative effect on climate is predicting enhancements in light absorption that result from internal mixing between BC and other aerosol components. Modeling and laboratory studies show that BC, when mixed with other aerosol components, absorbs more strongly than pure, uncoated BC; however, some ambient observations suggest more variable and weaker absorption enhancement. We show that the lower-than-expected enhancements in ambient measurements result from a combination of two factors. First, the often used spherical, concentric core-shell approximation generally overestimates the absorption by BC. Second, and more importantly, inadequate consideration of heterogeneity in particle-to-particle composition engenders substantial overestimation in absorption by the total particle population, with greater heterogeneity associated with larger model-measurement differences. We show that accounting for these two effects-variability in per-particle composition and deviations from the core-shell approximation-reconciles absorption enhancement predictions with laboratory and field observations and resolves the apparent discrepancy. Furthermore, our consistent model framework provides a path forward for improving predictions of BC's radiative effect on climate

Učinak antioksidanata askorbinske kiseline, lmetionina i α tokoferola zasebno ili u kombinaciji s kelatom na srčano tkivo štakora izloženih olovu.

An experiment was conducted using 42 IVRI 2CQ rats to evaluate the effects of three antioxidants, ascorbic acid, l methionine or α tocopherol alone, or chelator CaNa2EDTA alone or along with antioxidant α tocopherol, on lead accumulation, status of lipid peroxidation, and of copper and zinc concentration in cardiac tissue of lead-treated rats. Lead was given intraperitoneally as 1% lead acetate solution at the dose rate of 1mg of Pb2+/kg body mass for a period of 30 days. The lead was then withdrawn and the lead-exposed rats (n=36) were randomly divided into six groups, six lead-treated rats in each group. A further six rats were given no treatment, including lead exposure, to serve as negative controls. The rats were sacrificed under light anaesthesia one day after one week of treatment with antioxidant ascorbic acid, l-methionine or α tocopherol or with chelator CaNa2EDTA alone or along with antioxidant α tocopherol. Blood samples were collected and heart was quickly excised. Mean lead concentration in cardiac tissue was significantly higher in the lead-treated group, even after its withdrawal for a period of seven days (5.02 ± 1.06 vs. 0.40 ± 0.09 μg/gm). The treatment with chelator plus antioxidant α tocopherol lowered the cardiac lead burden but the level remained significantly higher than that of the negative control. There was a non-significant increase in lipid peroxide levels in the cardiac tissue of lead-exposed untreated rats and either of the antioxidants lowered the lipid peroxide level, but the differences between the different treatment groups remained statistically comparable at P>0.05. The mean concentration of copper and zinc in cardiac tissue remained statistically comparable among the different treatment groups.U pokusu su korištena 42 štakora IVRI 2CQ. Cilj je bio utvrditi učinke antioksidanata askorbinske kiseline, l-metionina i α tokoferola na nakupljanje olova, peroksidaciju lipida te koncentraciju bakra i cinka u srčanom tkivu nakon davanja olova. Osim toga, isti pokazatelji analizirani su nakon aplikacije kelata CaNa2EDTA zasebno, odnosno u kombinaciji s α tokoferolom. Olovo je aplicirano intraperitonealno u obliku 1% otopine olovnoga acetata, u dozi od 1 mg Pb2+ na kilogram tjelesne mase tijekom razdoblja od 30 dana. Nakon prestanka davanja olova, štakori (n = 36) su slučajnim odabirom razdijeljeni u šest skupina po šest jedinki u svakoj skupini. Prva skupina bila je izložena samo učincima olova, a pet skupina su osim olova primile navedene antioksidante, kelat ili njegovu kombinaciju s α tokoferolom. Dodatnih šest štakora u 7. skupini nisu bili izloženi olovu, antioksidantu ili kelatu te su poslužili kao negativna kontrola. Štakori su žrtvovani u laganoj anesteziji nakon sedmodnevnog dobivanja olova odnosno antioksidanta i kelata. Uzeti su uzorci krvi, a odmah po žrtvovanju izvađeno je srce. Srednja vrijednost koncentracije olova u srčanom tkivu bila je statistički značajno viša u skupini štakora koji su dobivali olovo, čak i nakon prekida sedmodnevnog davanja (5,02 ± 1,06 prema 0,40 ± 0,09 μg/g). Liječenje kelatom u kombinaciji s α tokoferolom smanjilo je razinu olova u srčanom mišiću, ali je ona i dalje ostala značajno viša u odnosu na negativnu kontrolu. Nije utvrđeno statistički značajno povećanje razine peroksidacije lipida u srčanom tkivu štakora izloženih samo djelovanju olova. Ni jedan antioksidant nije smanjio razinu peroksidacije lipida, a i srednje koncentracije bakra odnosno cinka nisu se statistički značajno (P>0,05) razlikovale između skupina različito tretiranih štakora