Modification to the Automatic Ionization Chamber

The automatic ionization chamber has been described previously [1,2]. It has proven quite reliable in service and has many desirable features, especially for balloon-borne equipment. A disadvantage has been that the time of discharge was dependent upon the potential applied to the quartz fiber. Thus, during the comparison of the instrument to be used with the standards, careful measurement of the potential used on the standards was required. Furthermore, care was required to make sure that the battery used during the flight remained constant in potential. It has now been found that the time between rechargings can be made nearly independent of the potential of the fiber by inserting a metal conductor inside and insulating it from the outer conductor surrounding the quartz fiber, and making the potential of this inner conductor the same as that of the fiber

Ionization experiment

Mariner space probe ionization chamber and Geiger counter experiments on galactic radiation entering solar syste

Techniques Useful in Evacuating and Pressurizing Metal Chambers

The aforementioned problems arose in connection with the automatic ionization chamber described previously (1). It was fund that the functioning of these instruments was more consistent if the ion chamber was baked at 350°C for several hours and then filled with pure argon. This procedure resulted in the elimination of organic impurities from the inner surfaces. The impurities, settling on the gold-coated quartz fiber and the collector, apparently altered the contact, resulting in some uncertainty in the recharging. The baking procedure has completely curved this difficulty

Ecoenzymes as Indicators of Compost to Suppress Rhizoctonia solani

Reports of disease suppression by compost are inconsistent likely because there are no established standards for feedstock material, maturity age for application, and application rate. The overall goal of the study was to evaluate a suite of biological indicators for their ability to predict disease suppression. Indicators included both commercial available methods for compost stability (Solvita™, respiration) and metrics of soil ecology not yet adopted by the compost industry (e.g., ecoenzymes, nematode community index). Damping-off by Rhizoctonia solani on radish was chosen as a model system given its global importance, competitiveness affected by carbon quality, and lack of disease management options for organic production. Biological indicators were evaluated for their ability to consistently differentiate among curing process, maturity, and feedstock material as a function of disease severity of a seedling bioassay and a compost extract assay to test competition with R. solani growth. Compost processed as vermicompost and anaerobic digestate were more suppressive against R. solani than windrow or aerated static pile. Mature composts were more suppressive than immature components. Feedstocks containing dairy manure and/or hardwood bark tended to have suppressive qualities. In contrast, poultry manure-based components were conducive to disease. Microbial ecoenzymes active on chitin and cellulose and nematode community indices were better predictors of disease suppressiveness than microbial respiration. These indicators are quicker than plant bioassays and could be adopted as tools to certify commercial products

Extensions and block decompositions for finite-dimensional representations of equivariant map algebras

Suppose a finite group acts on a scheme $X$ and a finite-dimensional Lie algebra $\mathfrak{g}$. The associated equivariant map algebra is the Lie algebra of equivariant regular maps from $X$ to $\mathfrak{g}$. The irreducible finite-dimensional representations of these algebras were classified in previous work with P. Senesi, where it was shown that they are all tensor products of evaluation representations and one-dimensional representations. In the current paper, we describe the extensions between irreducible finite-dimensional representations of an equivariant map algebra in the case that $X$ is an affine scheme of finite type and $\mathfrak{g}$ is reductive. This allows us to also describe explicitly the blocks of the category of finite-dimensional representations in terms of spectral characters, whose definition we extend to this general setting. Applying our results to the case of generalized current algebras (the case where the group acting is trivial), we recover known results but with very different proofs. For (twisted) loop algebras, we recover known results on block decompositions (again with very different proofs) and new explicit formulas for extensions. Finally, specializing our results to the case of (twisted) multiloop algebras and generalized Onsager algebras yields previously unknown results on both extensions and block decompositions.Comment: 41 pages; v2: minor corrections, formatting changed to match published versio

Saturn S-IVB Continuous Vent System for Propellent Control During Parking Orbit

Cryogenic propellant tanks coasting in space must be vented periodically to prevent excessive pressure. This requires that the liquid be settled with auxiliary ullaging rockets prior to venting to ensure minimum propellant loss. Other problems associated with blowdown of saturated liquids, such as surface level rise and boilover, are severe. The S-IVB, third stage of the Saturn Launch Vehicle, eliminates these problems during the earth parking orbit by continuously venting the liquid hydrogen tank. The boiloff gas is vented in the aft direction providing a continuous settling thrust on the propellants. The philosophy behind the system design is explored and critical components in the design are examined. Evaluation of system performance on several flights is presented

The patch-clamp technique in the study of secretion.

One of the basic cellular functions of virtually every cell type is the exocytotic release of molecules synthesized, stored and packaged into intracellular vesicles or granules. Over decades much effort has been concentrated on elucidating the chain of events leading to exocytosis. Unfortunately, the nature of the process that ultimately induces membrane fusion is not known, nor has it been established definitively whether or not the final steps in the secretory cascade are identical in different cells. Although the fusion between vesicle and plasma membrane has been neatly documented by electron micrographs, it was only recently that the technique of time-resolved membrane capacitance measurement has provided a more detailed insight into mechanistic aspects of exocytosis, both in terms of the fusion event and the steps involved in stimulus-secretion coupling

Ozone Depletion from Nearby Supernovae

Estimates made in the 1970's indicated that a supernova occurring within tens of parsecs of Earth could have significant effects on the ozone layer. Since that time, improved tools for detailed modeling of atmospheric chemistry have been developed to calculate ozone depletion, and advances have been made in theoretical modeling of supernovae and of the resultant gamma-ray spectra. In addition, one now has better knowledge of the occurrence rate of supernovae in the galaxy, and of the spatial distribution of progenitors to core-collapse supernovae. We report here the results of two-dimensional atmospheric model calculations that take as input the spectral energy distribution of a supernova, adopting various distances from Earth and various latitude impact angles. In separate simulations we calculate the ozone depletion due to both gamma-rays and cosmic rays. We find that for the combined ozone depletion roughly to double the ``biologically active'' UV flux received at the surface of the Earth, the supernova must occur at <8 pc. Based on the latest data, the time-averaged galactic rate of core-collapse supernovae occurring within 8 pc is ~1.5/Gyr. In comparing our calculated ozone depletions with those of previous studies, we find them to be significantly less severe than found by Ruderman (1974), and consistent with Whitten et al. (1976). In summary, given the amplitude of the effect, the rate of nearby supernovae, and the ~Gyr time scale for multicellular organisms on Earth, this particular pathway for mass extinctions may be less important than previously thought.Comment: 24 pages, 4 Postscript figures, to appear in The Astrophysical Journal, 2003 March 10, vol. 58

What is the best macrolide for atypical pneumonia?

Erythromycin, clarithromycin, and azithromycin are equally effective in treating pneumonia caused by Mycoplasma pneumoniae or Chlamydophila (formerly Chlamydia) pneumoniae (strength of recommendation [SOR]: B, small head-to-head trials). Macrolide choice can be based on other considerations--cost, side effects, and effectiveness against other suspected pathogens (SOR: C, expert opinion)