3,777 research outputs found
Monel-shot and screen regenerators
Monel has been found to be ideal material for matrix of regenerators operating in temperature range of 325 K to 50 K. Two best shapes are as spheres or as wire mesh. For given size of regenerator, spherical shots are preferable for low-temperature operation. At high temperatures, mesh would be superior by virtue of its lower flow resistance
Evaluation of selected chemical processes for production of low-cost silicon, phase 2
Potential designs for an integrated fluidized-bed reactor/zinc vaporizer/SiCl4 preheater unit are being considered and heat-transfer calculations have been initiated on versions of the zinc vaporizer section. Estimates of the cost of the silicon prepared in the experimental facility have been made for projected capacities of 25, 50, 75, and 100 metric ton of silicon. A 35 percent saving is obtained in going from 25 metric ton/year to the 50 metric ton/year level. This analysis, coupled with the recognition that use of two reactors in the 50 metric ton/year version allows for continued operation (at reduced capacity) with one reactor shut down, has resulted in a recommendation for adoption of an experimental facility capacity of 50 metric ton/year or greater. At this stage, the change to a larger size facility would not increase the design costs appreciably. In the experimental support program, the effects of seed bed particle size and depth were studied, and operation of the miniplant with a new zinc vaporizer was initiated, revealing the need for modification of the latter
Evaluation of selected chemical processes for production of low-cost silicon
Plant construction costs and manufacturing costs were estimated for the production of solar-grade silicon by the reduction of silicon tetrachloride in a fluidized bed of seed particles, and several modifications of the iodide process using either thermal decomposition on heated filaments (rods) or hydrogen reduction in a fluidized bed of seed particles. Energy consumption data for the zinc reduction process and each of the iodide process options are given and all appear to be acceptable from the standpoint of energy pay back. Information is presented on the experimental zinc reduction of SiCl4 and electrolytic recovery of zinc from ZnCl2. All of the experimental work performed thus far has supported the initial assumption as to technical feasibility of producing semiconductor silicon by the zinc reduction or iodide processes proposed. The results of a more thorough thermodynamic evaluation of the iodination of silicon oxide/carbon mixtures are presented which explain apparent inconsistencies in an earlier cursory examination of the system
Evaluation of selected chemical processes for production of low-cost silicon phase 2. silicon material task, low-cost silicon solar array project
Progress from October 1, 1977, through December 31, 1977, is reported in the design of the 50 MT/year experimental facility for the preparation of high purity silicon by the zinc vapor reduction of silicon tetrachloride in a fluidized bed of seed particles to form a free flowing granular product
Chromospherically Active Stars. X. Spectroscopy and Photometry of HD 212280
The system HD 212280 is a chromospherically active double lined spectroscopic binary with an orbital period of 45.284 days and an eccentricity of 0.50. The spectrum is composite with spectral types of G8 IV and F5-8 V for the components. An estimated inclination of 78 +/- 8 deg results in masses of 1.7 and 1.4 solar mass for the G subgiant and mid-F star, respectively. The distance to the system is estimated to be 112 pc. Photometric observations obtained between 1987 November and 1992 June reveal that HD 212280 is a newly identified variable star with a V amplitude of about 0.15 mag and a mean period of 29.46 days. Our V data were divided into 11 sets and in all but one case two spots were required to fit the data. Lifetimes of 650 days and a minimum of 1350 days have been determined for two of the four spots. The differential rotation coefficient of 0.05 is relatively small. The age of the system is about 1.9 X 10 exp 9 yrs. The G subgiant is rotating slower than pseudosynchronously while the F-type star is rotating faster
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Preliminary site report for the 2005 ICDP-USGS deep corehole in the Chesapeake Bay impact crater
First report for the ICDP-USGS 1.7-km-deep corehole drilled into the central part of the Chesapeake Bay impact crater during 2005
Effects of Intraventricular Locus Coeruleus Transplants on Seizure Severity in Genetically Epilepsy-Prone Rats Following Depletion of Brain Norepinephrine
Audiogenic seizures (AGS) in genetically
epilepsy-prone rats (GEPR) of the moderateseizure
substrain (GEPR-3s) were investigated
to determine whether norepinephrine (NE)
depletion induced by 6-hydroxydopalnine (6-OHDA)
microinfusion into the locus coeruleus
(LC) could alter the efficacy of intraventricular
NE tissue grafts in promoting reductions in
seizure severity in AGS. GEPR-3s were
stereotaxically infused with 6-OHDA
(4μg/side/rat), or vehicle into the region of the
LC. Following 6-OHDA treatment all animals
were subjected to 3 AGS tests. GEPR-3s seizure
severities were increased in 39.5% of the
animals after microinfusion of 6-OHDA into the
region of the LC. Following the third AGS test,
each rat was stereotaxicaily implanted with 17
gestational day rat fetal tissue obtained from the
dorsal pons and containing the primordia of the
LC or with tissue obtained from the neocortex
or were sham-grafted. Subsequent to grafting,
rats were subjected to 3 additional AGS tests.
53% (10/19) of 6-OHDA treated GEPRs showed
a significant reduction in seizure severity
following transplantation of fetal LC tissue. In
contrast, only 20% (1/5) of GEPRs infused with
saline rather than 6-OHDA showed, a reduction
of seizure severity following fetal LC
transplantation. NE content in the cortex and
pons/medulla was decreased by 78% and 46%
respectively following 6-OHDA microinfusion
into the LC. Prominent grafts with numerous
TH positive neurons and neurites were present
within the third ventricle of grafted animals,
while cortex grafts contained no TH
immunostained structures. These findings
suggest that the efficacy of fetal LC tissue to
promote reductions in seizure severity in GEPRs
is increased following depletion of central NE by
microinfusion of 6-OHDA
Transcription factor distribution in Escherichia coli: studies with FNR protein
Using chromatin immunoprecipitation (ChIP) and high-density microarrays, we have measured the distribution of the global transcription regulator protein, FNR, across the entire Escherichia coli chromosome in exponentially growing cells. Sixty-three binding targets, each located at the 5′ end of a gene, were identified. Some targets are adjacent to poorly transcribed genes where FNR has little impact on transcription. In stationary phase, the distribution of FNR was largely unchanged. Control experiments showed that, like FNR, the distribution of the nucleoid-associated protein, IHF, is little altered when cells enter stationary phase, whilst RNA polymerase undergoes a complete redistribution
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