Grain-size distribution of silicon carbide as a factor in the properties of electric heaters

Conclusions The variation of the proportion of the main fractions in the powders of green silicon carbide are a source of irregularity in the properties (porosity, pore structure, strength, and oxidation resistance) of silicon carbide electric heaters.The properties of the heaters can be improved by increasing and stabilizing the proportion of main fraction. It would be advisable to define the relevant norms in the standard for granular silicon carbide more precisely.Translated from Ogneupory, No. 4, pp. 46–51, April, 1977.     

On Enumerating Minimal Dicuts and Strongly Connected Subgraphs

We consider the problems of enumerating all minimal strongly connected subgraphs and all minimal dicuts of a given strongly connected directed graph G=(V,E). We show that the first of these problems can be solved in incremental polynomial time, while the second problem is NP-hard: given a collection of minimal dicuts for G, it is NP-hard to tell whether it can be extended. The latter result implies, in particular, that for a given set of points , it is NP-hard to generate all maximal subsets of contained in a closed half-space through the origin. We also discuss the enumeration of all minimal subsets of whose convex hull contains the origin as an interior point, and show that this problem includes as a special case the well-known hypergraph transversal problem. This research was supported by the National Science Foundation (Grant IIS-0118635). The third and fourth authors are also grateful for the partial support by DIMACS, the National Science Foundation’s Center for Discrete Mathematics and Theoretical Computer Science. Our friend and co-author, Leonid Khachiyan tragically passed away on April 29, 2005.     

Subchronic Toxicity of Copper Oxide Nanoparticles and Its Attenuation with the Help of a Combination of Bioprotectors

In the copper metallurgy workplace air is polluted with condensation aerosols, which a significant fraction of is presented by copper oxide particles <100 nm. In the scientific literature, there is a lack of their in vivo toxicity characterization and virtually no attempts of enhancing organism’s resistance to their impact. A stable suspension of copper oxide particles with mean (±SD) diameter 20 ± 10 nm was prepared by laser ablation of pure copper in water. It was being injected intraperitoneally to rats at a dose of 10 mg/kg (0.5 mg per mL of deionized water) three times a week up to 19 injections. In parallel, another group of rats was so injected with the same suspension against the background of oral administration of a “bio-protective complex” (BPC) comprising pectin, a multivitamin-multimineral preparation, some amino acids and fish oil rich in ω-3 PUFA. After the termination of injections, many functional and biochemical indices for the organism’s status, as well as pathological changes of liver, spleen, kidneys, and brain microscopic structure were evaluated for signs of toxicity. In the same organs we have measured accumulation of copper while their cells were used for performing the Random Amplification of Polymorphic DNA (RAPD) test for DNA fragmentation. The same features were assessed in control rats infected intraperitoneally with water with or without administration of the BPC. The copper oxide nanoparticles proved adversely bio-active in all respects considered in this study, their active in vivo solubilization in biological fluids playing presumably an important role in both toxicokinetics and toxicodynamics. The BPC proposed and tested by us attenuated systemic and target organs toxicity, as well as genotoxicity of this substance. Judging by experimental data obtained in this investigation, occupational exposures to nano-scale copper oxide particles can present a significant health risk while the further search for its management with the help of innocuous bioprotectors seems to be justified.     

PROCESSING HIGH EFFICIENCY CdTe SOLAR CELLS

High efficiency solar cells can be fabricated on CdTe films prepared by a wide variety of deposition techniques. Most of these methods yield CdTe layers that need to be subjected to post-deposition treatments before they can be utilized in high efficiency device fabrication. In some cases these treatments can be made an integral part of the film growth process so that a post-deposition step is not needed. This paper discusses the procedures that are commonly used in high efficiency CdTe solar cell fabrication and reports on a newly emerging technique that holds the promise of becoming a high-throughput industrial process for thin film photovoltaic module production.     

Insulin inhibits surfactant protein A and B gene expression in the H441 cell line

Brachytherapy, the direct application of a radioactive isotope into the tumor bed, delivers a high dose to the tumor as compared to the surrounding normal tissue. Interstitial brachytherapy, the placement of the isotope into a tumor bed where no lumen exists, has been described but is utilized infrequently in clinical practice. Endobronchial brachytherapy, the placement of the source within the airway lumen, as a boost to conventional external beam radiation has not yet demonstrated improved local tumor control or overall survival as compared to external beam alone in the definitive treatment of inoperable lung cancer. In the palliative setting, brachytherapy can provide prompt relief of obstructive symptoms and hemoptysis in the majority of patients.     

Factors influencing reduction in blood pressure and left ventricular mass in hypertensive type-1 diabetic patients using captopril or doxazosin for 6 months

The effect of doxazosin versus captopril on blood pressure, albuminuria, and left ventricular mass was studied in 33 hypertensive type-1 diabetic patients randomized to 6 months treatment with captopril (17 patients, mean daily dose 100 mg) or doxazosin (16 patients, mean daily dose 9 mg). Casual and 24-h ambulatory blood pressure (24hBP) were reduced from 163/95 to 144/83 mm Hg and 152/86 to 145/81 mm Hg, respectively, in the captopril group, and from 160/93 to 145/86 mm Hg and 156/86 to 147/79 mm Hg in the doxazosin group (all P < .05). The achieved 24hBP on treatment was positively associated with pretreatment levels of glycosylated hemoglobin (HbA1c) and plasma atrial natriuretic peptide (r = 0.53 and 0.59, respectively, both P < .01). Albuminuria did not change significantly in either group. Left ventricular hypertrophy was present in 13 patients (7 in the captopril and 6 in the doxazosin group). Left ventricular mass was reduced by an average of 27% and 23%, respectively, in these patients (both P < .01), but did not change significantly in patients without left ventricular hypertrophy. The reduction in left ventricular mass was positively associated with the presence of baseline left ventricular hypertrophy and inversely with dietary sodium intake and achieved casual blood pressure on treatment (R2 = 0.59, P < .001). We conclude that doxazosin and captopril used for 6 months are equally effective in reducing blood pressure and left ventricular hypertrophy in hypertensive type-1 diabetic patients; the antihypertensive effect is closely related to glycemic control; and dietary sodium intake and achieved casual blood pressure after treatment are independent determinants of the reduction in left ventricular mass seen in these patients.