Growth of undoped and Te doped InSb crystals by vertical directional solidification technique

We have successfully grown high mobility undoped and Te doped InSb crystals of size 10–12 mm dia. and 60 mm length under inert argon atmosphere in closed quartz ampoules, by vertical directional solidification (VDS) technique. The crystals showed predominantly (220) orientation along the growth axis. The surface defects, such as voids were reduced drastically by selecting proper lowering rate, rotational speed and cone angle of the ampoule. The high mobility and quality crystals were obtained with the ampoule conical angle less than 20°, lowering rate 5mm/h, and rotational speed 10 rpm.     

Sanguinarine and ellipticine cytotoxic alkaloids isolated from well-known antitumor plants. Intracellular targets of their action

Common molecular and cellular targets for alkaloids sanguinarine and ellipticine, isolated from well-known antitumor plants (as well as from their various natural and synthetic derivatives), have been studied and described. Sanguinarine and ellipticine are characterized by significant biological activities including a high antitumor potential. Among the important targets of their action the following are to be noted. 1. DNA and other double helical polynucleotides. Due to the ability of DNA-intercalation sanguinarine, ellipticine and some of their derivatives can modify the double helical structures and topological forms of polynucleotides. The results of these modifications in intercalative complexes manifest themselves in the inhibition of numerous enzymatic reactions, dependent on the structures and topological forms of DNA and other polynucleotides. 2. ATP synthesis in mitochondria. Most of DNA-intercalators, including sanguinarine and ellipticine, belong to a group of penetrating (hydrophobic) cations, which are accumulated near the external side of inner mitochondrial membranes during the membrane energization. They neutralize negative charges, arising just as the inner mitochondrial membranes become energized. By this neutralization of membrane charges the ATP synthesis in inhibited and the oxidative phosphorylation renders to be uncoupled. All studied DNA-intercalators under certain conditions uncouple the mitochondrial oxidative phosphorylation. Apparent correlation between the agents' ability for DNA-intercalation and for mitochondrial ATP synthesis inhibition seems to be determined by the importance for both types of reactions of molecule hydrophobicity and positive charges. 3. Cholinesterase systems. Sanguinarine, ellipticine and some of their derivatives, like other DNA-intercalators studied, inhibit also the enzymatic activities of cholinesterase systems due to hydrophobicity and positive charges of their molecules. 4. Sanguinarine (and chelerythrine), are also capable of inhibiting the biological activity of SH-dependent enzymes and proteins. Due to the reactivity of iminium groups in sanguinarine and chelerythrine molecules with nucleophilic reagents, e.g. thiol groups of enzymes and other proteins, the activities of SH-enzymes and proteins are inhibited. In particular, sanguinarine and chelerythrine inhibit enzymatic activity of some SH-dependent ATPases, including membrane-bound cation-transport ATPases. The earlier accumulated experience of the application in medicine of plant saps and extracts containing these alkaloids, and of the treatment of many diseases (including benign and malignant tumors) by isolated alkaloids may be explained, to a certain extent, by the inhibition of activities of the above mentioned cellular targets. The selective toxicity of these alkaloids for the number of transformed cells can be explained in the same manner.     

Risk factors in dengue shock syndrome

Despite a growing body of evidence predominantly, but not exclusively, from Thailand suggesting that the risk of developing dengue shock syndrome (DSS) is greatest following an anamnestic dengue infection, particularly if the most recent infection was with dengue 2 virus, there continues to be debate about the justification for these claims. This report describes a five-year, prospective study in two townships (suburbs) in Yangon (Rangoon) Myanmar (Burma) in which attempts were made to confirm the data from an earlier prospective study in Thailand and to address some of the criticism of earlier studies. This investigation found the incidence of anamnestic dengue infections in DSS patients to be significantly higher than in the community from which they were drawn and a significantly higher risk of developing DSS following an anamnestic infection (particularly with dengue 2 virus) than following a primary infection with any serotype.     

A MODEL FOR THE COMBINED EFFECTS OF STRESS RATIO AND GRAIN SIZE ON THE LEFM FATIGUE THRESHOLD CONDITION

A long-crack, fatigue-threshold model which explains and predicts the commonly observed effects of stress ratio, R, and grain size, d, on δK₀, is proposed. The inclusion of a grain-size-effect is an extension of a recently proposed model that examined the effect of the R ratio. The extended model is based on the hypothesis that near-threshold, crack growth involves two micro-mechanical processes of fracture; K_max-controlled submicroscopic cleavage, which predominates when the defect concentration is small, and δK-controlled reversed shear which predominates when the defect concentration is large, both processes occurring in a critically stressed volume, V_c, ahead of the crack tip. Defect concentration in V_c is reduced by a low value of R and a coarse grain size and is increased by a high value of R and a fine grain size. Good agreement is shown to exist between predicted and experimental curves of δK₀ versus R and δK₀ versus grain size for several steels and aluminium alloys. In particular, δK₀ is shown to have an upper and a lower bound value for a material. The model may be used as an alternative procedure for obtaining quick, approximate but conservative estimates of δK₀ for practical design applications.     

Determination of uranium in fertilisers using fission track method

Trace contents of uranium in various commercial fertilizers e.g. ureas, superphosphates, diammonium phosphates have been determined using fission track etch technique. The uranium content in ureas varies from .05 to 1.3 mg kg^–1 whereas in superphosphates it varies linearly with phosphate content.     

Surface modification of polyacrylonitrile staple fibers via alkaline hydrolysis for superabsorbent applications

The alkaline hydrolysis of polyacrylonitrile staple fibers was investigated for evaluation as superabsorbent materials. Studies were performed to analyze the hydrolysis of fibers and the quantification of the developed functional groups, such as carboxyl and amide groups as well as changes in the nitrile content by means of Micro‐ATR. Dyeing of the samples with methylene blue was carried out to monitor the carboxyl groups formed during the hydrolysis. A gradual decrease in the nitrile groups and built up of the carboxyl and the amide groups was observed during the hydrolysis. Microscopic investigation carried out to investigate the surface structure of hydrolyzed fibers. Hydrolysis led to surface nonhomogeneity and erosion that was dependent on the hydrolysis conditions. The fibers showed good water retention behavior, making them superabsorbent materials. The dyeing showed more intense coloration in the surface region of the modified fibers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3127–3133, 2004