Apollo 17 mission Report. Supplement 6: Calibration results for gamma ray spectrometer sodium iodide crystal

A major difficulty in medium energy gamma-ray remote sensing spectroscopy and astronomy measurements was the high rate of unwanted background resulting from the following major sources: (1) prompt secondary gamma-rays produced by cosmic-ray interactions in satellite materials; (2) direct charged-particle counts; (3) radioactivity induced in the detector materials by cosmic-ray and trapped protons; (4) radioactivity induced in detector materials by the planetary (e.g., earth or moon) albedo neutron flux; (5) radioactivity induced in the detector materials by the interaction of secondary neutrons produced throughout the spacecraft by cosmic-ray and trapped proton interactions; (6) radioactivity induced in spacecraft materials by the mechanisms outlined in 3, 4, and 5; and (7) natural radioactivity in spacecraft and detector materials. The purpose of this experiment was to obtain information on effects 3, 4, and 5, and from this information start developing calculational methods for predicting the background induced in the crystal detector in order to correct the Apollo gamma-ray spectrometer data for this interference

The influence of grazing on land surface climatological variables

Research accomplishments in empirical measurements, laboratory analyses, data analyses, and modeling are summarized. Publications are listed. Presentations made during the funding period are also listed

The influence of grazing on surface climatological variables of tallgrass prairie

Mass and energy exchange between most grassland canopies and the atmosphere are mediated by grazing activities. Ambient temperatures can be increased or decreased by grazers. Data have been assembled from simulated grazing experiments on Konza Prairie Research Natural Area and observations on adjacent pastures grazed by cattle show significant changes in primary production, nutrient content, and bidirectional reflectance characteristics as a function of grazing intensity. The purpose of this research was to provide algorithms that would allow incorporation of grazing effects into models of energy budgets using remote sensing procedures. The approach involved: (1) linking empirical measurements of plant biomass and grazing intensities to remotely sensed canopy reflectance, and (2) using a higher resolution, mechanistic grazing model to derive plant ecophysiological parameters that influence reflectance and other surface climatological variables

APPLICATION OF AN AVIAN BIOENERGETICS SIMULATION MODEL TO RED-WINGED BLACKBIRD - CROP RELATIONS

The impact of bird populations upon the properties or processes of ecosystems is mediated through patterns and magnitudes of energy flow. This impact may be either direct, by processing of large quantities of energy or nutrients, or indirect, through feedback control of other ecosystem rate processes or components. In either case, however, the impact is a result of the population dynamics and the pattern and magnitude of food consumption of the birds. Recent research by several groups points to a relatively small direct impact on birds on most natural ecosystems (Wiens 1973). Impact through feedback control, a more difficult relationship to study, is just beginning to receive close attention in a total systems framework. In managed ecosystems, however, where our interest is in either the bird population or its prey as an aesthetic or economic resource, the direct impacts are of considerable importance. These direct impacts are a reflection of prey consumption, which in turn is a result of the interactions of prey selection and energy demand. There is little field information available on either of these components for most bird populations, however, and we have therefore employed simulation modelling, coupled with existing information on dietary composition, to generate estimates of prey consumption rates and thus of potential impact. Our modelling tactic has been to stress generality and biological realism at the expense of precision (Levins 1966), since we are interested in models which are both robust and broadly applicable. Also, we recognize that the data base of the model is frequently imprecise, and it seems intuitively illogical to build extremely precise models for imprecise data inputs, even though this if often done

Pmp27 Promotes Peroxisomal Proliferation

Peroxisomes perform many essential functions in eukaryotic cells. The weight of evidence indicates that these organelles divide by budding from preexisting peroxisomes. This process is not understood at the molecular level. Peroxisomal proliferation can be induced in Saccharomyces cerevisiae by oleate. This growth substrate is metabolized by peroxisomal enzymes. We have identified a protein, Pmp27, that promotes peroxisomal proliferation. This protein, previously termed Pmp24, was purified from peroxisomal membranes, and the corresponding gene, PMP27, was isolated and sequenced. Prop27 shares sequence similarity with the Pmp30 family in Candida boidinii. Pmp27 is a hydrophobic peroxisomal membrane protein but it can be extracted by high pH, suggesting that it does not fully span the bilayer. Its expression is regulated by oleate. The function of Pmp27 was probed by observing the phenotype of strains in which the protein was eliminated by gene disruption or overproduced by expression from a multicopy plasmid. The strain containing the disruption (3B) was able to grow on all carbon sources tested, including oleate, although growth on oleate, glycerol, and acetate was slower than wild type. Strain 3B contained peroxisomes with all of the enzymes of β-oxidation. However, in addition to the presence of a few modestly sized peroxisomes seen in a typical thin section of a cell growing on oleate-containing medium, cells of strain 3B also contained one or two very large peroxisomes. In contrast, cells in a strain in which Pmp27 was overexpressed contained an increased number of normal-sized peroxisomes. We suggest that Pmp27 promotes peroxisomal proliferation by participating in peroxisomal elongation or fission.

A Dichotomy Theorem for Homomorphism Polynomials

In the present paper we show a dichotomy theorem for the complexity of polynomial evaluation. We associate to each graph H a polynomial that encodes all graphs of a fixed size homomorphic to H. We show that this family is computable by arithmetic circuits in constant depth if H has a loop or no edge and that it is hard otherwise (i.e., complete for VNP, the arithmetic class related to #P). We also demonstrate the hardness over the rational field of cut eliminator, a polynomial defined by B\"urgisser which is known to be neither VP nor VNP-complete in the field of two elements, if VP is not equal to VNP (VP is the class of polynomials computable by arithmetic circuit of polynomial size)