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Search Results: 1 - 10 of 160799 matches for " Charles B. Scott "
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Identifying Lenses with Small-Scale Structure. I. Cusp Lenses
Charles R. Keeton,B. Scott Gaudi,A. O. Petters
Physics , 2002, DOI: 10.1086/378934
Abstract: The inability of standard models to explain the flux ratios in many 4-image gravitational lenses has been cited as evidence for significant small-scale structure in lens galaxies. That claim has generally relied on detailed lens modeling, so it is both model dependent and somewhat difficult to interpret. We present a more robust and generic method for identifying lenses with small-scale structure. For a close triplet of images associated with a source near a cusp caustic, the sum of the signed magnifications should approximately vanish. We derive realistic upper bounds on the sum, and argue that lenses with flux ratios that significiantly violate the bounds can be said to have structure in the lens potential on scales smaller than the image separation. Five observed lenses have such flux ratio ``anomalies'': B2045+265, 1RXS J1131-1231, and SDSS J0924+0219 have strong anomalies; B0712+472 has a strong anomaly at optical/near-IR wavelengths and a marginal anomaly at radio wavelengths; and RX J0911+0551 appears to have an anomaly, but this conclusion is subject to uncertainties about octopole modes in early-type galaxies. Analysis of the cusp relation does not identify the known anomaly in B1422+231, so methods that are more sophisticated (and less generic) than the cusp relation may be necessary to uncover flux ratio anomalies in some systems. Although these flux ratio anomalies might represent milli- or micro-lensing, we cannot identify the cause; we can only conclude that the lenses have significant structure in the potential on scales smaller than the separation between the images. Additional arguments must be invoked to specify the nature of this small-scale structure. [Abridged]
A Case Study of Adopting Security Guidelines in Undergraduate Software Engineering Education  [PDF]
Yen-Hung Hu, Charles Scott
Journal of Computer and Communications (JCC) , 2014, DOI: 10.4236/jcc.2014.214003
Abstract: Security plays a large role in software development; simply without its existence the software would be vulnerable to many different types of attacks. Software security prevents leaks of data, alternation of data, and unauthorized access to data. Building a secure software involves a number of different processes but security awareness and implementation are the most important ones among them. To produce high quality software security engineers need to meet today’s cybersecurity demands, security awareness and implementation must be integrated in undergraduate computer science programming courses. In this paper, we demonstrate the importance of adopting security guidelines in undergraduate software engineering education. Thus, this paper focuses on integrating secure guidelines into existing applications to eliminate common security vulnerabilities. An assessment table, derived from several existing Java security guidelines, is developed to provide in depth critiques of the selected capstone project. Potential security vulnerabilities in the capstone project are identified and presented in a form showing the degree of threats against the three security characteristics: confidentiality, integrity, and availability addressed in the McCumber Cube model. Meanwhile, vulnerability density of the capstone project is calculated to demonstrate the performance of this research.
Fluorescence-based Sensing of 2,4,6-Trinitrotoluene (TNT) Using a Multi-channeled Poly(methyl methacrylate) (PMMA) Microimmunosensor
Paul T. Charles,Andre A. Adams,Peter B. Howell,Scott A. Trammell,Jeffrey R. Deschamps,Anne W. Kusterbeck
Sensors , 2010, DOI: 10.3390/s100100876
Abstract: Fluorescence immunoassays employing monoclonal antibodies directed against the explosive 2,4,6-trinitrotoluene (TNT) were conducted in a multi-channel microimmunosensor. The multi-channel microimmunosensor was prepared in poly (methyl methacrylate) (PMMA) via hot embossing from a brass molding tool. The multi-channeled microfluidic device was sol-gel coated to generate a siloxane surface that provided a scaffold for antibody immobilization. AlexaFluor-cadaverine-trinitrobenzene (AlexaFluor-Cad-TNB) was used as the reporter molecule in a displacement immunoassay. The limit of detection was 1-10 ng/mL (ppb) with a linear dynamic range that covered three orders of magnitude. In addition, antibody crossreactivity was investigated using hexahydro-1,3,5-triazine (RDX), HMX, 2,4-dinitrotoluene (DNT), 4-nitrotoluene (4-NT) and 2-amino-4,6-DNT.
Proteomics reveals multiple routes to the osteogenic phenotype in mesenchymal stem cells
Kristin P Bennett, Charles Bergeron, Evrim Acar, Robert F Klees, Scott L Vandenberg, Bülent Yener, George E Plopper
BMC Genomics , 2007, DOI: 10.1186/1471-2164-8-380
Abstract: Direct component analysis in the gene ontology space identifies three components that account for 90% of the variance between hMSC, osteoblasts, and the four stimulated hMSC populations. The directed component maps the differentiation stages of the stimulated stem cell populations along the differentiation axis created by the difference in the expression profiles of hMSC and hOST. Surprisingly, hMSC treated with ECM proteins lie closer to osteoblasts than do hMSC treated with OS media. Additionally, the second component demonstrates that proteomic profiles of collagen I- and vitronectin-stimulated hMSC are distinct from those of OS-stimulated cells. A three-mode tensor analysis reveals additional focus proteins critical for characterizing the phenotypic variations between na?ve hMSC, partially differentiated hMSC, and hOST.The differences between the proteomic profiles of OS-stimulated hMSC and ECM-hMSC characterize different transitional phenotypes en route to becoming osteoblasts. This conclusion is arrived at via a three-mode tensor analysis validated using hMSC plated on laminin-5.Interest in human stem cells continues to grow amongst those interested in understanding fundamental mechanisms of development and disease progression and those interested in harnessing the differentiation potential of these cells to generate living replacements for damaged or diseased tissues. In both cases, the promise is the same: stem cells offer the potential to define and manipulate fundamental principles of cell and tissue behavior, which in turn will uncover a new set of therapeutic targets for correcting errors in cell and tissue function [1]. Human mesenchymal stem cells (hMSC) are a population of multipotent adult cells found within the bone marrow and periosteum [2] and capable of differentiating into as many as seven different cell types [3].One bottleneck in the development of hMSC-derived therapies is our incomplete understanding of the mechanisms governing hMSC differen
First-principles calculation of intrinsic defect formation volumes in silicon
Scott A. Centoni,Babak Sadigh,George H. Gilmer,Thomas J. Lenosky,Tomas Diaz de la Rubia,Charles B. Musgrave
Physics , 2005, DOI: 10.1103/PhysRevB.72.195206
Abstract: We present an extensive first-principles study of the pressure dependence of the formation enthalpies of all the know vacancy and self-interstitial configurations in silicon, in each charge state from -2 through +2. The neutral vacancy is found to have a formation volume that varies markedly with pressure, leading to a remarkably large negative value (-0.68 atomic volumes) for the zero-pressure formation volume of a Frenkel pair (V + I). The interaction of volume and charge was examined, leading to pressure--Fermi level stability diagrams of the defects. Finally, we quantify the anisotropic nature of the lattice relaxation around the neutral defects.
Cultural Heritage Assets: Rituals, Grinding Hollows and Other Socio-Cultural Practices in Simiyu Region, Tanzania  [PDF]
Charles B. Saanane
Natural Resources (NR) , 2016, DOI: 10.4236/nr.2016.74020
Abstract: This paper presents results from preliminary assessments in Ngasamo ward, Busega district in Simiyu region. The main objective was to assess cultural heritage assets in some areas of Bariadi district in Simiyu region. Specific objectives of the assessment are to identify tangible cultural heritage resources in Simiyu region; to identify intangible cultural heritage resources in Simiyu region; and to provide suggestions for pertinent protection, conservation and presentation of cultural heritage resources. The assessment was carried out through surveys that included documentation together with records for Global Positioning System (GPS) coordinates per surveyed locality; key informant interviews; and Focus Group Discussion. Results from the assessment revealed several worship areas that include immovable physical objects associated to ritual performance places. For example, wells like Luhuhi in Ilula village, Nkindwa biye tree in Ilula village, Magahi well in Isenge village, Isangijo hill at Isenge village, Dutwa well in Isenge village, Nyabusalu well in Igalukilo village and similar others are worship places that were revealed by informants. The assessment uncovered granite rock boulders that are being chopped off flakes for traditional medicine use in the area. Some cultural heritage sites have been identified such that a lot more needs to be explored in order to establish existence of other physical cultural heritage sites in Busega district, Bariadi district. For example, the grinding hollows, bao and the like are unique heritage resources. Such resources including undiscovered immovable archaeological objects would need presentation of sustainable preservation as well as conservation plans in line with Antiquities Acts, Antiquities Rules and Monuments of 1980 together with Cultural Heritage Policy of 2008.
Dynamic Analysis of Vascular Morphogenesis Using Transgenic Quail Embryos
Yuki Sato,Greg Poynter,David Huss,Michael B. Filla,Andras Czirok,Brenda J. Rongish,Charles D. Little,Scott E. Fraser,Rusty Lansford
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0012674
Abstract: One of the least understood and most central questions confronting biologists is how initially simple clusters or sheet-like cell collectives can assemble into highly complex three-dimensional functional tissues and organs. Due to the limits of oxygen diffusion, blood vessels are an essential and ubiquitous presence in all amniote tissues and organs. Vasculogenesis, the de novo self-assembly of endothelial cell (EC) precursors into endothelial tubes, is the first step in blood vessel formation [1]. Static imaging and in vitro models are wholly inadequate to capture many aspects of vascular pattern formation in vivo, because vasculogenesis involves dynamic changes of the endothelial cells and of the forming blood vessels, in an embryo that is changing size and shape.
Maximum Running Speed of Captive Bar-Headed Geese Is Unaffected by Severe Hypoxia
Lucy A. Hawkes, Patrick J. Butler, Peter B. Frappell, Jessica U. Meir, William K. Milsom, Graham R. Scott, Charles M. Bishop
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0094015
Abstract: While bar-headed geese are renowned for migration at high altitude over the Himalayas, previous work on captive birds suggested that these geese are unable to maintain rates of oxygen consumption while running in severely hypoxic conditions. To investigate this paradox, we re-examined the running performance and heart rates of bar-headed geese and barnacle geese (a low altitude species) during exercise in hypoxia. Bar-headed geese (n = 7) were able to run at maximum speeds (determined in normoxia) for 15 minutes in severe hypoxia (7% O2; simulating the hypoxia at 8500 m) with mean heart rates of 466±8 beats min?1. Barnacle geese (n = 10), on the other hand, were unable to complete similar trials in severe hypoxia and their mean heart rate (316 beats.min?1) was significantly lower than bar-headed geese. In bar-headed geese, partial pressures of oxygen and carbon dioxide in both arterial and mixed venous blood were significantly lower during hypoxia than normoxia, both at rest and while running. However, measurements of blood lactate in bar-headed geese suggested that anaerobic metabolism was not a major energy source during running in hypoxia. We combined these data with values taken from the literature to estimate (i) oxygen supply, using the Fick equation and (ii) oxygen demand using aerodynamic theory for bar-headed geese flying aerobically, and under their own power, at altitude. This analysis predicts that the maximum altitude at which geese can transport enough oxygen to fly without environmental assistance ranges from 6,800 m to 8,900 m altitude, depending on the parameters used in the model but that such flights should be rare.
Criteria for Sample Selection to Maximize Planet Sensitivity and Yield from Space-Based Microlens Parallax Surveys
Jennifer C. Yee,Andrew Gould,Charles Beichman,Sebastiano Calchi Novati,Sean Carey,B. Scott Gaudi,Calen Henderson,David Nataf,Matthew Penny,Yossi Shvartzvald,Wei Zhu
Physics , 2015, DOI: 10.1088/0004-637X/810/2/155
Abstract: Space-based microlens parallax measurements are a powerful tool for understanding planet populations, especially their distribution throughout the Galaxy. However, if space-based observations of the microlensing events must be specifically targeted, it is crucial that microlensing events enter the parallax sample without reference to the known presence or absence of planets. Hence, it is vital to define objective criteria for selecting events where possible and to carefully consider and minimize the selection biases where not possible so that the final sample represents a controlled experiment. We present objective criteria for initiating observations and determining their cadence for a subset of events, and we define procedures for isolating subjective decision making from information about detected planets for the remainder of events. We also define procedures to resolve conflicts between subjective and objective selections. These procedures maximize planet sensitivity of the sample as a whole by allowing for planet detections even if they occur before satellite observations for objectively-selected events and by helping to trigger fruitful follow-up observations for subjectively-chosen events. This paper represents our public commitment to these procedures, which is a necessary component of enforcing objectivity on the experimental protocol.
Valuing Carbon Recycling through Ethanol: Zero Prices for Environmental Goods  [PDF]
Charles B. Moss, Andrew Schmitz
Theoretical Economics Letters (TEL) , 2014, DOI: 10.4236/tel.2014.43032
Abstract:

The Energy Independence and Security Act of 2007 imposes a Renewable Fuel Standard met through a combination of corn and cellulosic ethanol. A variety of rationales support this policy including the recycling of atmospheric carbon. This study examines the economic dimensions of this problem focusing on the role of zero prices for environmental goods and the use of an environmental equivalent. When environmental goods are taken into account, the optimal price policy cannot be defined with certainty.

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