In vitro selection of bacteriophage Q beta ribonucleic acid variants resistant to ethidium bromide
Bacteriophage Q beta ribonucleic acid variants, considering fluorescence determination of replication inhibition by ethidium bromide
Orgel, L. E.↗
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Vibrational analysis of the infrared and Raman spectra of oxalyl bromide in the crystalline and fluid states
IR and Raman spectra vibrational analysis of crystalline and fluidic oxalyl bromide, explaining observations by two geometrical isomers existence
Baglin, F. G.↗
Photodissociation of methyl chloride and methyl bromide in the atmosphere
Methyl chloride (CH3Cl) and methyl bromide (CH3Br) have been suggested to be significant sources of the stratospheric halogens. The breakup of these compounds in the stratosphere by photodissociation or reaction with OH releases halogen atoms which catalytically destroy ozone. Experimental results are presented for ultraviolet photoabsorption cross sections of CH3Cl and CH3Br. Calculations are presented of loss rates for the methyl halides due to photodissociation and reaction with OH and of mixing ratios of these species in the stratosphere.
Robbins, D. E.↗
Long-duration high-efficiency operation of a continuously pulsed copper laser utilizing copper bromide as a lasant
A copper laser utilizing copper bromide as a lasant and neon as the buffer gas has been operated at an average laser power of between 16 and 19.5 W for a period of 68 h. Lasing was attained at a pulsing rate of 16.7 kHz in a quartz discharge tube 2.5-cm in diameter with an electrode separation of 200 cm. The laser energy/pulse and peak power/pulse corresponding to an average power of 19.5 W are 1.2 mJ and 30 kW, respectively. The ratio of laser power at 510.6 and 578.2 nm varied from 3.9 to 1.1 corresponding to a total average laser power of 4 and 18 W, respectively. The highest wall plug and capacitor efficiency measured during 68 h of operation were 0.7 and 1.1%, respectively.
Chen, C. J.↗
Morphological and functional manifestations of rat adrenal-cortex response to sodium bromide administration under hypodynamic stress
Functional and morphological manifestations of adrenal cortex response to hypodynamia (2-hr immobilization on an operating table) under the influence of bromine preparations were studied. The sodium bromide was administered intraperitoneally in 100, 250, and 500 mg/kg doses once and repeatedly during ten days. The adrenal gland was evaluated functionally by ascorbic acid and cholesterol content and morphologically by coloring it with hematoxylin-eosin and Sudans for lipid revealing at freezing. Results are displayed in two tables and microphotographs. They are summarized as follows: the bromine weakens the functional state of the adrenal cortex in intact rats, causing changes similar to those under stress. During immobilization combined with preliminary bromine administration, a less pronounced stress reaction is noticeable.
Kirichek, L. T.↗
Water vapor resistance of plasma-polymerized coatings on potassium bromide windows
Plasma-polymerized tetrafluoroethylene (PPTFE) coated potassium bromide IR window are shown to possess better resistance to moisture than either ethylene or chlorotrifluoroethylene. The PPTFE-coated windows tolerated an upper limit relative humidity of about 80% at 297 K, without visible damage to either window or coating, over a period of 24 hours. Elemental analysis of the bulk, and photoelectron spectroscopy of the coating surface, showed that PPTFE coatings deposited downstream of the internal plasma reactor electrodes contained less atmospheric oxygen than coatings deposited between the electrodes; perhaps accounting for the improved moisture resistance.
Wydeven, T.↗
Ultraviolet quantum detection efficiency of potassium bromide as an opaque photocathode applied to microchannel plates
The quantum detection efficiency (QDE) of potassium bromide as a photocathode applied directly to the surface of a microchannel plate over the 250-1600 A wavelength range has been measured. The contributions of the photocathode material in the channels and on the interchannel web to the QDE have been determined. Two broad peaks in the QDE centered at about 450 and about 1050 A are apparent, the former with about 50 percent peak QDE and the latter with about 40 percent peak QDE. The photoelectric threshold is observed at about 1600 A, and there is a narrow QDE minimum at about 750 A which correlates with 2X the band gap energy for KBr. The angular variation of the QDE from 0 to 40 deg to the channnel axis has also been examined. The stability of Kbr with time is shown to be good with no significant degradation of QDE at wavelengths below 1216 A over a 15-day period in air.
Siegmund, Oswald H. W.↗
Effect of growth conditions on the quality of lead bromide crystals
Single crystals of pure and doped lead bromide were grown by the Bridgman method in different convective conditions. The convection level was varied by changing the thermal and solutal Rayleigh number. The homogeneity in refractive index, and hence the optical quality, was estimated by examining the optical distortion, birefringence interferograms, and laser scattering through the crystal. The optical quality of the crystal varied significantly with the variation of convection level during the crystal growth. The critical concentration of the solute was estimated for several values of growth velocity by numerical analysis at the thermal gradient of 20 K/cm.
Singh, N. B.↗
An investigation of the atmospheric sources and sinks of Methyl Bromide
Methyl Bromide (CH3Br) is a ubiquitous component of the atmosphere and has been implicated as an important player in the depletion of stratospheric ozone. Atmospheric CH3Br abundances, interhemispheric gradients, oceanic concentrations, man-made emissions, and removal processes have been analyzed and interpreted with the help of a simple box model and a 2D global photochemical model. Its calculated atmospheric lifetime (T) of 1.7-1.9 years, based on reaction with OH radicals, is consistent with a global source of 90-110 Gg (10 exp 9 g)/year. Consequences of a much shorter lifetime of 1.2 years, due to possible deposition/hydrolysis losses, are also considered. Available data are used to estimate a CH3Br source that is 35 percent (20-50 percent) man-made and 65 percent (80-50 percent) natural. Oceans are substantially supersaturated and provide the most important natural source of about 60 (40-80) Gg/year.
Singh, Hanwant B.↗
Locations of Bromide Ions in Tetragonal Lysozyme Crystals
Anions have been shown to play a dominant role in the crystallization of chicken egg-white lysozyme from salt solutions. Previous studies employing X-ray crystallography have found one chloride ion binding site in the tetragonal crystal form of the protein and four nitrate ion binding sites in the monoclinic form. In this study the anion positions in the tetragonal form were determined from the difference Fourier map obtained from lysozyme crystals grown in bromide and chloride solutions. Five possible anion-binding sites were found in this manner. Some of these sites were in pockets containing basic residues while others were near neutral, but polar, residues. The sole chloride ion binding site found in previous studies was confirmed, while four further sites were found which corresponded to the four binding sites found for nitrate ions in monoclinic crystals. The study suggests that most of the anion-binding sites in lysozyme remain unchanged even when different anions and different crystal forms of lysozyme are employed.
Lim, Kap↗
Location of Bromide Ions in Tetragonal Lysozyme Crystals
Anions have been shown to play a dominant role in the crystallization of chicken egg white lysozyme from salt solutions. Previous studies employing X-ray crystallography had found one chloride ion binding site in the tetragonal crystal form of the protein and four nitrate ion binding sites in the monoclinic form. In this study the anion positions in the tetragonal form were determined from the difference Fourier map obtained from lysozyme crystal grown in bromide and chloride solutions. Five possible anion binding sites were found in this manner. Some of these sites were in pockets containing basic residues while others were near neutral, but polar, residues. The sole chloride ion binding site found in previous studies was confirmed, while four of these sites corresponded to four binding sites found for nitrate ions in monoclinic crystals. The study suggests that most of the anion binding sites in lysozyme remain unchanged, even when different anions and different crystal forms of lysozyme are employed.
Lim, Kap↗
Flight Experiment to Study Double-Diffusive Instabilities in Silver-Dopped Lead Bromide Crystals
The main objective of the present program is to understand thermosolutal convection during crystal growth of PbBr2-AgBr alloys. This involves identification of the growth conditions for microgravity experiments delineating the microsegregation, observation of convecto-diffusive instabilities and comparison with theoretical models. The overall objectives can be summarized as follows: 1. Observe and study the double diffusive and morphological instabilities in controlled conditions and to compare with theoretically predicted convective and morphological instability curves. 2. Study the three-dimensional morphological instabilities and resulting cellular growth that occur near the onset of morphological instability in the bulk samples under purely diffusive conditions. 3. Understand the micro-and macro-segregation of silver dopant in lead bromide crystals in microgravity. 4. Provide basic data on convective behavior in alloy crystals grown by the commercially important Bridgman crystal growth process.
Singh, N. B.↗
Methyl bromide: ocean sources, ocean sinks, and climate sensitivity
The oceans play an important role in the geochemical cycle of methyl bromide (CH3Br), the major carrier of O3-destroying bromine to the stratosphere. The quantity of CH3Br produced annually in seawater is comparable to the amount entering the atmosphere each year from natural and anthropogenic sources. The production mechanism is unknown but may be biological. Most of this CH3Br is consumed in situ by hydrolysis or reaction with chloride. The size of the fraction which escapes to the atmosphere is poorly constrained; measurements in seawater and the atmosphere have been used to justify both a large oceanic CH3Br flux to the atmosphere and a small net ocean sink. Since the consumption reactions are extremely temperature-sensitive, small temperature variations have large effects on the CH3Br concentration in seawater, and therefore on the exchange between the atmosphere and the ocean. The net CH3Br flux is also sensitive to variations in the rate of CH3Br production. We have quantified these effects using a simple steady state mass balance model. When CH3Br production rates are linearly scaled with seawater chlorophyll content, this model reproduces the latitudinal variations in marine CH3Br concentrations observed in the east Pacific Ocean by Singh et al. [1983] and by Lobert et al. [1995]. The apparent correlation of CH3Br production with primary production explains the discrepancies between the two observational studies, strengthening recent suggestions that the open ocean is a small net sink for atmospheric CH3Br, rather than a large net source. The Southern Ocean is implicated as a possible large net source of CH3Br to the atmosphere. Since our model indicates that both the direction and magnitude of CH3Br exchange between the atmosphere and ocean are extremely sensitive to temperature and marine productivity, and since the rate of CH3Br production in the oceans is comparable to the rate at which this compound is introduced to the atmosphere, even small perturbations to temperature or productivity can modify atmospheric CH3Br. Therefore atmospheric CH3Br should be sensitive to climate conditions. Our modeling indicates that climate-induced CH3Br variations can be larger than those resulting from small (+/- 25%) changes in the anthropogenic source, assuming that this source comprises less than half of all inputs. Future measurements of marine CH3Br, temperature, and primary production should be combined with such models to determine the relationship between marine biological activity and CH3Br production. Better understanding of the biological term is especially important to assess the importance of non-anthropogenic sources to stratospheric ozone loss and the sensitivity of these sources to global climate change.
NASA Discipline Exobiology↗
Laboratory Evaluation of Drop-in Solvent Alternatives to n-Propyl Bromide for Vapor Degreasing
Based on this limited laboratory study, solvent blends of trans-1,2 dichloroethylene with HFEs, HFCs, or PFCs appear to be viable alternatives to n-propyl bromide for vapor degreasing. The lower boiling points of these blends may lead to greater solvent loss during use. Additional factors must be considered when selecting a solvent substitute, including stability over time, VOC, GWP, toxicity, and business considerations.
Mitchell, Mark A.↗
Mount for a Larger Potassium Bromide Beamsplitter in a Cryogenic, Space Application
This paper describes an approach to mounting Potassium Bbromide (Kbr) optical elements that are expected to survive launch vibrations and a cryogenic environment.
potassium bromide RTV silicone cyrogenic optical m↗
Acid/alkali bromide secondary battery
Secondary electrochemical battery has been developed which has high energy/ weight density. Battery is rechargeable and works on reaction between hydrogen and bromine.
England, C.↗
X-ray photoelectron spectroscopy study of radiofrequency sputtered chromium bromide, molybdenum disilicide, and molybdenum disulfide coatings and their friction properties
Radiofrequency sputtered coatings of CRB2, MOSI2, and MOS2 were examined by X-ray photoelectron spectroscopy. The effects of sputtering target history, deposition time, RF power level, and substrate bias on film composition were studied. Friction tests were run on RF sputtered surfaces of 440-C steel to correlate XPS data with lubricating properties. Significant deviations from stoichiometry and high oxide levels for all three compounds were related to target outgassing. The effect of biasing on these two factors depended on the compound. Improved stoichiometry correlated well with good friction and wear properties.
Wheeler, D. R.↗