2,647 research outputs found

    Massive Lyman Break Galaxies at z~3 in the Spitzer Extragalactic First Look Survey

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    We investigate the properties of 1088 Lyman Break Galaxies (LBGs) at z~3 selected from a ~2.63deg2subregionoftheFirstLookSurveyfieldusingthegroundbasedmulticolordataandtheSpitzerSpaceTelescopemidinfrareddataat38and24um.Withthewideareaandthebroadwavelengthcoverage,wesamplealargenumberofrareubanddropoutswhicharemassive(M>1011Msun),allowingustoperformastatisticalanalysisofthesesubsetsofLBGsthathavenotbeenstudiedindetail.Opticallybright(R(AB)<24.5mag)LBGsdetectedinmidinfrared(S3.6um>6uJy)resideatthemostmassiveanddustyendoftheLBGpopulation,withrelativelyhighandtight deg2 sub-region of the First Look Survey field using the ground-based multi-color data and the Spitzer Space Telescope mid-infrared data at 3--8 and 24 um. With the wide area and the broad wavelength coverage, we sample a large number of ``rare'' u-band dropouts which are massive (M* > 10^11 Msun), allowing us to perform a statistical analysis of these subsets of LBGs that have not been studied in detail. Optically bright (R(AB) < 24.5 mag) LBGs detected in mid-infrared (S_{3.6um} > 6 uJy) reside at the most massive and dusty end of the LBG population, with relatively high and tight M/L$ in rest-frame near-infrared. Most infrared-luminous LBGs (S_{24um} > 100 uJy) are dusty star-forming galaxies with star formation rates of 100--1000 Msun/yr, total infrared luminosity of > 10^12 Lsun. By constructing the UV luminosity function of massive LBGs, we estimate that the lower limit for the star formation rate density from LBGs more massive than 10^11 Msun at z~3 is > 3.3 x 10^-3 Msun/yr/Mpc^3, showing for the first time that the UV-bright population of massive galaxies alone contributes significantly to the global star formation rate density at z~3. When combined with the star formation rate densities at z < 2, our result reveals a steady increase in the contribution of massive galaxies to the global star formation from z=0 to z=3, providing strong support to the downsizing of galaxy formation.Comment: 15 pages, 13 figures. Accepted for publication in Ap

    Magnetic and Raman Based Method for Process Control During Fabrication of Carbon Nanotube Based Structures

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    A method of fabricating composite structures comprising carbon nanotubes. The method including providing a nanotube starting material, forming the composite structure with the nanotube starting material and monitoring at least a magnetic or Raman property of the composite structure while forming the composite structure

    Social and Environmental Predictors of Maternal Depression in Current and Recent Welfare Recipients

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74795/1/h0087688.pd

    In search of the optimal management strategy for Arabian oryx

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    Extirpated from the wild in 1972 by overhunting, Arabian oryx (Oryx leucoryx) were re-introduced in Saudi Arabia in March 1990; 17 oryx were released into Mahazat as-Sayd, a 2244 km2 fenced reserve in westcentral Arabia, which lies at the periphery of their historical home range. The population has increased to 346 animals. The National Commission for Wildlife Conservation and Development, and those that manage the herd, have recently asked, ‘What is the optimal management strategy to assure long-term persistence of the species, given the absence of immigration and predation?’ Food resources, determinants of rates of mortality and birth, covary with unpredictable rainfall in Mahazat as-Sayd. Using data-driven assumptions, we developed a computer model that evaluated the probability of extinction (Pex) under various management strategies: no intervention, removing a fixed number of animals each year, removing a fixed percentage of animals each year, and removing all individuals above a threshold. In addition, we explored the probability that oryx populations would decline below two thresholds, called the probability of quasi-extinction (Pq-ex) under various management schemes. Our analyses suggested that, without intervention, the oryx population had a high Pex. Removing 15% of the current population provided a low Pex, but this method also produced high values for Pq-ex and, as a by-product, wide fluctuations in population size (N). Although it required an assessment of both N and carrying capacity (K), the most successful management plan consisted of removing all oryx above 70% of K. Adoption of this plan resulted in low Pex, low Pq-ex, and smaller fluctuations in N. Our study may provide a useful model for evaluating management plans for a variety of threatened animal populations in desert ecosystems.Funding for this project was received from the National Wildlife Research Center, Taif, Saudi Arabia, and from the Columbus Zoo, Columbus, OH

    Athletic Performance at the National Basketball Association Combine After Anterior Cruciate Ligament Reconstruction.

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    BACKGROUND: Anterior cruciate ligament (ACL) injuries are significant injuries in elite-level basketball players. In-game statistical performance after ACL reconstruction has been demonstrated; however, few studies have reviewed functional performance in National Basketball Association (NBA)-caliber athletes after ACL reconstruction. PURPOSE: To compare NBA Combine performance of athletes after ACL reconstruction with an age-, size-, and position-matched control group of players with no previous reported knee injury requiring surgery. We hypothesized that there is no difference between the 2 groups in functional performance. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A total of 1092 NBA-caliber players who participated in the NBA Combine between 2000 and 2015 were reviewed. Twenty-one athletes were identified as having primary ACL reconstruction prior to participation in the combine. This study group was compared with an age-, size-, and position-matched control group in objective functional performance testing, including the shuttle run test, lane agility test, three-quarter court sprint, vertical jump (no step), and maximum vertical jump (running start). RESULTS: With regard to quickness and agility, both ACL-reconstructed athletes and controls scored an average of 11.5 seconds in the lane agility test and 3.1 seconds in the shuttle run test (P = .745 and .346, respectively). Speed and acceleration was measured by the three-quarter court sprint, in which both the study group and the control group averaged 3.3 seconds (P = .516). In the maximum vertical jump, which demonstrates an athlete\u27s jumping ability with a running start, the ACL reconstruction group had an average height of 33.6 inches while the controls averaged 33.9 inches (P = .548). In the standing vertical jump, the ACL reconstruction group averaged 28.2 inches while the control group averaged 29.2 inches (P = .067). CONCLUSION: In athletes who are able to return to sport and compete at a high level such as the NBA Combine, there is no significant difference in any combine performance test between players who have had primary ACL reconstruction compared with an age-, size-, and position-matched control group. CLINICAL RELEVANCE: Athletes with previous ACL reconstruction who are able to return to high-level professional basketball have equivalent performance measures with regard to speed, quickness, and jumping ability as those athletes who have not undergone knee surgery

    Models in the Design and Validation of Eddy Current Inspection for Cracking in the Shuttle Reaction Control System Thruster

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    A case study is presented for using models in eddy current NDE design for crack detection in Shuttle Reaction Control System thruster components. Numerical methods were used to address the complex geometry of the part and perform parametric studies of potential transducer designs. Simulations were found to show agreement with experimental results. Accurate representation of the coherent noise associated with the measurement and part geometry was found to be critical to properly evaluate the best probe designs

    Carbon nanotube-based sensor and method for detection of crack growth in a structure

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    A sensor has a plurality of carbon nanotube (CNT)-based conductors operatively positioned on a substrate. The conductors are arranged side-by-side, such as in a substantially parallel relationship to one another. At least one pair of spaced-apart electrodes is coupled to opposing ends of the conductors. A portion of each of the conductors spanning between each pair of electrodes comprises a plurality of carbon nanotubes arranged end-to-end and substantially aligned along an axis. Because a direct correlation exists between the resistance of a carbon nanotube and its strain, changes experienced by the portion of the structure to which the sensor is coupled induce a corresponding change in the electrical properties of the conductors, thereby enabling detection of crack growth in the structure
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