5,738 research outputs found

    Impact of Cosmic Rays on Population III Star Formation

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    We explore the implications of a possible cosmic ray (CR) background generated during the first supernova explosions that end the brief lives of massive Population III stars. We show that such a CR background could have significantly influenced the cooling and collapse of primordial gas clouds in minihaloes around redshifts of z ~ 15 - 20, provided the CR flux was sufficient to yield an ionization rate greater than about 10^-19 s^-1 near the center of the minihalo. The presence of CRs with energies less than approximately 10^7 eV would indirectly enhance the molecular cooling in these regions, and we estimate that the resulting lower temperatures in these minihaloes would yield a characteristic stellar mass as low as ~ 10 M_sun. CRs have a less pronounced effect on the cooling and collapse of primordial gas clouds inside more massive dark matter haloes with virial masses greater than approximately 10^8 M_sun at the later stages of cosmological structure formation around z ~ 10 - 15. In these clouds, even without CR flux the molecular abundance is already sufficient to allow cooling to the floor set by the temperature of the cosmic microwave background.Comment: MNRAS in press, 12 pages, 6 figure

    Affinity Programs and the Real Estate Brokerage Industry

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    This study surveys active real estate brokers obtaining information on involvement in affinity programs and referral/relocation networks. Some results regarding affinity involvement are: (a) 13% of respondents reported affinity affilliations, 75% reported no affiliations, and 12% indicated plans to become involved within the next year; (b) about half having affinity affiliations were involved with 2-4 groups; (c) affinity relationships were most often with membership organizations, corporations, and professional organizations; (d) the primary affinity benefits provided were commission reductions, special mortgage packages, and discounted closing services; (e) 38% of respondents reported an increase in profitability die tp affinity affiliation while 21% reported a decrease; and (f) 56% reported an increase in agent productivity. An empirical income model shows that affinity affiliation has a positive effect on broker income. The probit models shows that: (a) participation in affinity arrangements is more likely for larger firms and national franchises but is not sensitive to location; and (b) large firms are more likely to participate in a larger number of affinity relationships.

    A review of the supply of liquid propellants and other fluids in support of the Space Shuttle Program

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    In this study, over twenty significant liquid propellants and other fluids were reviewed as to their supply in support of the Space Shuttle Program (SSP), primarily at KSC. The uniqueness of most of the products, either by their application or production characteristics, present a variety of supply issues to contend with. Each, however, is critical to the success of the SSP. It becomes necessary to formulate, and maintain, a logistic approach to assure a continued availability of each product. For convenience, two categories were established. One, labeled limited-availability, represents those products wherein they are single sourced, have production restrictions and/or there has been a history of supply problems. The other, labeled universally-available, is characteristic of those having several sources and/or having little, if any, historical supply problems. This last category was not examined in depth. Through concepts of establishing stockpile inventories, multiple supply contracts, or other arrangements, the supply of liquid propellants and other fluids can be assured

    The elevation, slope, and curvature spectra of a wind roughened sea surface

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    The elevation, slope and curvature spectra are defined as a function of wave number and depend on the friction velocity. There are five wave number ranges of definition called the gravity wave-gravity equilibrium range, the isotropic turbulence range, the connecting range due to Leykin Rosenberg, the capillary range, and the viscous cutoff range. The higher wave number ranges are strongly wind speed dependent, and there is no equilibrium (or saturated) capillary range, at least for winds up to 30 meters/sec. Some properties of the angular variation of the spectra are also found. For high wave numbers, especially in the capillary range, the results are shown to be consistent with the Rayleigh-Rice backscattering theory (Bragg scattering), and certain properties of the angular variation are deduced from backscatter measurements

    Results of the 2007-2008 Illinois Hunter Harvest Survey

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    Grant/Contract No: W-112-R-17A random sample of 3,000 potential hunters was selected from among 2007 Illinois Habitat Stamp and hunting license purchasers. An 8-page questionnaire was successfully mailed to 2,906 of the 3,000 individuals. We received 1,625 returned questionnaires, 1,620 of which were usable, for a 56% response rate. Comparisons of harvest estimates from the 2006-2007 season to the 2007-2008 season suggest harvest decreased for 10 game animal categories (rabbit, quail, pheasant, dove, gray partridge, fox squirrel, gray squirrel, red fox, gray fox, and opossum), and increased for 3 categories (woodcock, raccoon, and coyote). License sales increased 0.4% from 282,000 sold for the 2006 season to 283,000 sold in the 2007 season. This represents a recovery in license sales of less than 1% since the lowest level on record (since 1938) in 2005. Low license sales may be related to increasing difficulty in finding land to hunt. Resident hunters pursuing deer (61%) and small game species (51%) reported little difficulty in gaining access to hunting lands. However, all other seasons were associated with more difficulty in accessing land. Efforts should be undertaken to ensure that hunters are aware of the locations of public hunting lands associated with these seasons. Few residents reported leasing land (4%) or hiring outfitters (1%) to access land.INHS Technical Report Prepared for Illinois Department of Natural Resources; Illinois Natural History Surve

    Government Role and the Interoperability Ecosystem

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    Measuring early numeracy of kindergarten students in a group setting

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    Early identification practices in assessment are crucial to preventing academic failure as well as identifying students at-risk for later learning disabilities. The PAM Early Numeracy Screening is a set of subscales designed to measure early numeracy in kindergarten students in a group setting. Given that the existing early numeracy measures are individually administered, the purpose of the current study was to explore the psychometric properties of the PAM Early Numeracy Screening. Correlational analysis was the primary research design used to investigate the evidence of reliability, criterion-related validity, and construct validity of the PAM Early Numeracy Screening. Criterion measures included the KeyMath-3 Diagnostic Assessment, Metropolitan Achievement Tests, Eighth Edition, Early Math Measures Study Teacher Rating of Students’ Math Proficiency, and the Early Numeracy Indicators. The sample consisted of 97 kindergarten students from a school district in the Greater New Orleans Metropolitan Area. Results support the PAM Early Numeracy Screening as a promising group administered measure of early numeracy in kindergarten. Implications for future research include investigating the internal structure of the subscales and exploring evidence of predictive validity of the subscales, specifically the Quantity Discrimination subscale to independently predict later math achievement
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