1,801 research outputs found
Analytical and experimental study of two concentric cylinders coupled by a fluid gap
From a structural point of view a liquid coolant type nuclear reactor consists of a heavy steel vessel containing the core and related mechanical components and filled with a hot fluid. This vessel is protected from the severe environment of the core by a shielding structure, the thermal liner, which is usually a relatively thin steel cylinder concentric with the reactor vessel and separated from it by a gap filled with the coolant fluid. This arrangement leads to a potential vibration problem if the fundamental frequency, or one of the higher natural vibration frequencies, of this liner system is close to the frequency of some vibration source present in the reactor vessel. The shell rigidly clamped at its base and free at the top was investigated since it is a better description of the conditions encountered in typical reactor designs
Nitrosourea-misonidazole combination chemotherapy: effect on KHT sarcomas, marrow stem cells and gut.
C3H/HeJ mice bearing i.m. transplanted KHT sarcomas were treated with varying doses of either 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) or 2-[3-(2-chloroethyl)-3-nitrosoureido]-D-glucopyranose (chlorozotocin; CHLZ) as single agents or in combination with 1 mg/g of the chemical radiosensitizer, misonidazole (MISO). Using an in vivo-in vitro tumour-excision assay, the administration of MISO simultaneously with or 3 h after low doses of BCNU (less than 20 mg/kg) was found to give a dose-modification factor (DMF) of approximately 1.65 relative to BCNU alone. At higher doses of BCNU, there was less enhancement of cell kill. The DMF for tumour growth delay was likewise dependent on BCNU dose, continuously decreasing with increasing BCNU dose. In contrast, the anti-tumour activity of CHLZ, assessed by both clonogenic cell survival and tumour-growth delay, was not significantly enhanced by the addition of MISO. The enhancement of gastrointestinal toxicity and haematotoxicity by BCNU-MISO combinations was assessed by LD50/7 and CFU-S assays, respectively. MISO enhanced BCNU marrow toxicity by a factor of 1.2-1.3, whilst gut toxicity was enhanced by a factor of approximately 1.2
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Design guide for single circular cylinder in turbulent crossflow. [LMFBR]
A design procedure is proposed for predicting the dynamic structural response of a circular cylinder in turbulent crossflow. The procedure is based on recently obtained data for a stationary, rigid cylinder and on existing information. The procedure is not applicable to conditions where the wake vortex shedding frequency locks into a structural natural frequency. This report is self-contained in that all the information and structural analysis methods employed in the procedure are reviewed and developed. Also, an example is given to illustrate the use of the method for a typical reactor component. The calculated responses are found to be very small
In vivo response of KHT sarcomas to combination chemotherapy with radiosensitizers and BCNU.
Female C3H/HeJ mice bearing intramuscularly transplanted KHT sarcomas were treated with a single dose of 1,3-bis (2-chloroethyl)-1-nitrosourea (BCNU, 30 mg/kg, i.p.) alone or in combination with a single dose of misonidazole (MISO, 1.0 mg/g, i.p.) or its desmethylated metabolite Ro-05-9963 (2.0 mg/g, i.p.). The effectiveness of drug therapy was assessed by a tumour growth-delay assay (i.e. measuring the median time required for tumours to grow to treatment size x 4). The relative efficacy of administering the nitroimidazoles in various schedules ranging from 12 h before to 12 h after BCNU administration also was evaluated. Untreated control KHT tumours grew to the initial size x 4 in a median time of 4 days. No significant growth delay was seen in mice treated with either nitroimidazole alone, whilst treatment with BCNU alone produced a median growth delay of 7 days. Combination chemotherapy with 9963 administration 3 h after BCNU significantly increased the median tumour growth delay to 9 days. However, no significant growth delay was produced in any of the other combinations of these agents. The median growth delay was significantly reduced to 5 days when MISO was administered 3 h before BCNU, whereas MISO administered simultaneously 3,6, or 12 h after BCNU significantly enhanced delays ( 9 days). These results indicate that both MISO and 0063 may be combined with conventional therapeutic agents, in this particular case a nitrosourea, to produce an enhanced tumour response. The production of such a response appears to be nitroimidazole as well as schedule dependent
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Leakage-flow-induced vibration of a tube-in-tube slip joint
The susceptibility of a cantilevered tube conveying water to self-excitation by leakage flow through a slip joint is assessed experimentally. The slip joint is formed by inserting a smaller, rigid tube into the free end of the cantilevered tube. Variations of the slip joint annular gaps and engagement lengths are tested, and several mechanisms for self-excitation are described
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Tube crossflow force measurements
A transducer has been designed and verified which has the potential for measuring lift and drag forces on circular rods in turbulent cross flow. The transducer is currently being used to obtain data
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Leakage flow-induced vibrations for variations of a tube-in-tube slip joint
Variations in the design of a specific slip joint separating two cantilevered, telescoping tubes conveying water were studied to determine their effect upon the leakage flow-induced vibration self-excitation mechanism known to exist for the original slip joint geometry. The important parameters controlling the self-excitation mechanism were identified, which, along with previous results, allowed the determination of a comprehensive set of design rules to avoid unstable vibrations. This was possible even though a new self-excitation mechanism was found when the engagement of the two tubes was small. 9 refs
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