The influence of conjugate natural convective heat transfer on the temperature field in a monocrystalline sapphire tape in the Stepanov method

Natural convective heat transfer in the system “monocrystalline tape – environment – walls of the growth vessel”, geometrically similar to the simplified scheme of the upper part of the heat node in the Stepanov method, is studied numerically by the finite element method in the conjugate formulation. The calculations were performed with a Prandtl number equal to 0.68 (argon), in the range of Grashof numbers 1000 ≤ Gr ≤ 25000 and with a discrete set of tape lengths in the range from 1 to 5.

Enhanced crystalline perfection and fluorescence properties of p-terphenyl single crystals grown by the vertical Bridgman technique with a novel modified growth vessel

During the growth process of organic crystals, it is easy to induce thermal defects and impurities when using the conventional Bridgman technique. In the present study, a specially designed double-wall ampoule was used to solve this problem. High-quality p-terphenyl single crystals were successfully grown by the vertical Bridgman method with the improved ampoule. Powder X-ray diffraction analyses were performed to evaluate the crystallinity of the grown single crystals. Fluorescence spectrum studies show an enhancement of fluorescence properties due to the improvement in crystalline perfection.

Development of a Carbon-14 Bioseperation Technique for Cleanup of Nuclear Graphite

A preliminary study on the bioseperation of Carbon-14 was carried out using a mixed-culture of microorganisms obtained from the Pebble Bed Modular Reactor Company (PBMR). The culture demonstrated the ability to bioaccumulate radiocarbon-14 (C-14) from solution. The experiment consisting of a growth vessel and a biofilter connected in a closed loop. The biofilter was not installed for the purpose of treatment but rather as a method of isolation of microorganisms for further processing. Significant amounts of C-14 were detected in the trapped cells in the biofilter, significantly higher than in controls taken before adding carbon sources containing C-14. The microorganisms were grown under micro-aerobic conditions with graphite carbon and commercially purchased powdered carbon as the predominant supplied carbon sources. Small amounts of sucrose (500 mg/L) were added at 48 hour intervals to promote the growth of heterotrophic microorganisms. Additional work is required to determine the amount of C-14 escaping through gases produced as a product of metabolism (CO2 and CO) and the total carbon metabolized by the microorganisms in order to report with accuracy the degree of separation of C-14 from the C-14/C-12 mixture. A proof of concept study is underway to determine the C-14 mass balance, characterize the microorganisms in the reactor, and establish the presence or absence of processes that might have affected the preliminary observations.

Oxygen-Dependent Growth of the Sulfate-Reducing Bacterium Desulfovibrio oxyclinae in Coculture withMarinobacter sp. Strain MB in an Aerated Sulfate-Depleted Chemostat

ABSTRACT A chemostat coculture of the sulfate-reducing bacteriumDesulfovibrio oxyclinae and the facultatively aerobic heterotroph Marinobacter sp. strain MB was grown for 1 week under anaerobic conditions at a dilution rate of 0.05 h−1. It was then exposed to an oxygen flux of 223 μmol min−1by gassing the growth vessel with 5% O2. Sulfate reduction persisted under these conditions, though the amount of sulfate reduced decreased by 45% compared to the amount reduced during the initial anaerobic mode. After 1 week of growth under these conditions, sulfate was excluded from the incoming medium. The sulfate concentration in the growth vessel decreased exponentially from 4.1 mM to 2.5 μM. The coculture consumed oxygen effectively, and no residual oxygen was detected during either growth mode in which oxygen was supplied. The proportion of D. oxyclinae cells in the coculture as determined by in situ hybridization decreased from 86% under anaerobic conditions to 70% in the microaerobic sulfate-reducing mode and 34% in the microaerobic sulfate-depleted mode. As determined by the most-probable-number (MPN) method, the numbers of viable D. oxyclinae cells during the two microaerobic growth modes decreased compared to the numbers during the anaerobic growth mode. However, there was no significant difference between the MPN values for the two modes when oxygen was supplied. The patterns of consumption of electron donors and acceptors suggested that when oxygen was supplied in the absence of sulfate and thiosulfate, D. oxyclinaeperformed incomplete aerobic oxidation of lactate to acetate. This is the first observation of oxygen-dependent growth of a sulfate-reducing bacterium in the absence of either sulfate or thiosulfate. Cells harvested during the microaerobic sulfate-depleted stage and exposed to sulfate and thiosulfate in a respiration chamber were capable of anaerobic sulfate and thiosulfate reduction.