Productivity of Florida Springs: Second semi-annual report to the Biology Division, Office of Naval Research progress from February 1, 1953 to June 30, 1953

During this second six months emphasis has been laid on developing a complete understanding of the metabolism of the Silver Springs ecosystem as an example of a community apparently in a steady state. Variation in phosphates, uptake of nitrates, and importance of boron have been estimated. Fluctuation of some major elements has been estimated. Examination of stomach contents has permitted trophic classifications of dominant species and the standing crops have been estimated for these species by number and by dry weight. From these a pyramid of mass has been constructed. Special attention has been paid to bacteria using 3 methods for comparison of Silver Springs with lakes and estimation of the standing crop. The oxygen gradient method has been repeated at half hourly intervals. A carbon-dioxide gradient method has also been used to check the oxygen and to obtain a photosynthetic quotient. Black and light Bell jar experiments have been initiated to obtain checks on the other production measurement and to obtain a community respiration rate. An approximate balance has resulted from estimates of production , respiration , and downstream loss. A flow rate diagram has been constructed to clarify definitions of efficiency and their relationship to a steady state system. Mr. Sloan has statistically verified the increase of insect number and variety away from the boils and demonstrated the reliability of quantitative dipping for aquatic insects. Plans for the third half year include detained and comparative study of the dominant algae and further estimates of rates of growth of all community components. (29pp.

Productivity of Florida Springs: First annual (3rd semi-annual) report to Biology Branch, Office of Naval Research progress from January 1 to December 31, 1953

By means of new methods it has been possible to measure the overall community metabolism as well as the standing state community in Silver Springs. Photosynthetic rates have been determined by downstream gradient methods, transplantation growth plots, and bell jars diurnally and annually. Respiration rates have been estimated with bell jars. The downstream losses of particulate, and dissolved organic matter have been found to balance, the excess of photosynthesis over respiration. The community has thus been demonstrated to be in a constant temperature, steady state, somewhat comparable to a climax on land. Nitrate, phosphate, and major chemical constituents are essentially constant. There is an approximate constancy of standing crop of organisms although the production rates in summer are three times those in the winter. Some evidence suggests that there, are photoperiodic changes in reproduction rates in spite of constant temperature. Rates of protein syntehsis estimated from nitrate uptake downstream agree (1) with photosynthetic quotients obtained from carbon dioxide and oxygen uptake downstream and (2) with the nitrogen content of the community. The overall annual production of 50,000 lbs/acre is the greatest productivity we know of on land or sea. Such high figures seem reasonable with the flow of high nutrient, warm water and high light intensity over a dense periphyton community. Theoretical concepts of steady state thermodynamics have been applied to show that self maintaining open systems tend to adjust to high power and low efficiency output. The 3% photosynthetic efficiency observed in Silver Springs is in agreement with this principle. Pyramids of weight and pyramids of number have been determined including bacteria. These pyramids are similar to some in the literature. The contribution of an acre of a fertile stream annually is readily inferred from data obtained on downstream increase of bacteria, chlorophyll, and organic matter. In other springs, Mr. Sloan has related stability of insect populations to chlorinity and to gradients of stability of environmental factors. Dr. L.S. Whitford during the summer made an ecological and taxonomic study of the distribution of algae in 26 contrasting springs. From this lists and from analytical data on the chemostatic water in these springs one can infer culture conditions necessary for many species. (27 pages

Exoplanet Detection Techniques

We are still in the early days of exoplanet discovery. Astronomers are beginning to model the atmospheres and interiors of exoplanets and have developed a deeper understanding of processes of planet formation and evolution. However, we have yet to map out the full complexity of multi-planet architectures or to detect Earth analogues around nearby stars. Reaching these ambitious goals will require further improvements in instrumentation and new analysis tools. In this chapter, we provide an overview of five observational techniques that are currently employed in the detection of exoplanets: optical and IR Doppler measurements, transit photometry, direct imaging, microlensing, and astrometry. We provide a basic description of how each of these techniques works and discuss forefront developments that will result in new discoveries. We also highlight the observational limitations and synergies of each method and their connections to future space missions.Comment: 24 pages, 19 figures, PPVI proceedings. Appears as 2014, Protostars and Planets VI, Henrik Beuther, Ralf S. Klessen, Cornelis P. Dullemond, and Thomas Henning (eds.), University of Arizona Press, Tucson, 914 pp., p.715-73

Using Space Weather Variability in Evaluating the Environment Design Specifications for NASA'S Constellation Program

Spectral models of solar particle events and trapped radiation belts are necessary for the design requirements of total ionizing radiation dose, single event effects, and spacecraft charging. Space radiation and plasma environment specifications for hardware design are necessarily conservative to assure system robustness for a wide range of space environments

Using Space Weather Variability in Evaluating the Radiation Environment Design Specifications for NASA's Constellation Program

NASA's Constellation program, initiated to fulfill the Vision for Space Exploration, will create a new generation of vehicles for servicing low Earth orbit, the Moon, and beyond. Space radiation specifications for space system hardware are necessarily conservative to assure system robustness for a wide range of space environments. Spectral models of solar particle events and trapped radiation belt environments are used to develop the design requirements for estimating total ionizing radiation dose, displacement damage, and single event effects for Constellation hardware. We first describe the rationale using the spectra chosen to establish the total dose and single event design environmental specifications for Constellation systems. We then compare variability of the space environment to the spectral design models to evaluate their applicability as conservative design environments and potential vulnerabilities to extreme space weather event

Forage sorghum, 1981

"February 1982.""The Author: Harry C. Minor is an Associate Professor of Agronomy and State Extension Specialist, Carl G. Morris is a Senior Research Specialist, Richard E. Mattis is an Instructor of Agronomy and Assistant Superintendent, Bruce A. Burdick and Howard L. Mason are Research Specialists.

A Numbers Game:Ribosome Densities, Bacterial Growth, and Antibiotic-Mediated Stasis and Death

We postulate that the inhibition of growth and low rates of mortality of bacteria exposed to ribosome-binding antibiotics deemed bacteriostatic can be attributed almost uniquely to these drugs reducing the number of ribosomes contributing to protein synthesis, i.e., the number of effective ribosomes. We tested this hypothesis with Escherichia coli K-12 MG1655 and constructs that had been deleted for 1 to 6 of the 7 rRNA (rrn) operons. In the absence of antibiotics, constructs with fewer rrn operons have lower maximum growth rates and longer lag phases than those with more ribosomal operons. In the presence of the ribosome-binding “bacteriostatic” antibiotics tetracycline, chloramphenicol, and azithromycin, E. coli strains with 1 and 2 rrn operons are killed at a substantially higher rate than those with more rrn operons. This increase in the susceptibility of E. coli with fewer rrn operons to killing by ribosome-targeting bacteriostatic antibiotics is not reflected in their greater sensitivity to killing by the bactericidal antibiotic ciprofloxacin, which does not target ribosomes, but also to killing by gentamicin, which does. Finally, when such strains are exposed to these ribosome-targeting bacteriostatic antibiotics, the time before these bacteria start to grow again when the drugs are removed, referred to as the post-antibiotic effect (PAE), is markedly greater for constructs with fewer rrn operons than for those with more rrn operons. We interpret the results of these other experiments reported here as support for the hypothesis that the reduction in the effective number of ribosomes due to binding to these structures provides a sufficient explanation for the action of bacteriostatic antibiotics that target these structures