OALib Journal期刊

ISSN: 2333-9721




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匹配條件: “Michael Burgess” ,找到相關結果約45380條。
Soil Erosion Threatens Food Production
David Pimentel,Michael Burgess
Agriculture , 2013, DOI: 10.3390/agriculture3030443
Abstract: Since humans worldwide obtain more than 99.7% of their food (calories) from the land and less than 0.3% from the oceans and aquatic ecosystems, preserving cropland and maintaining soil fertility should be of the highest importance to human welfare. Soil erosion is one of the most serious threats facing world food production. Each year about 10 million ha of cropland are lost due to soil erosion, thus reducing the cropland available for world food production. The loss of cropland is a serious problem because the World Health Organization and the Food and Agricultural Organization report that two-thirds of the world population is malnourished. Overall, soil is being lost from agricultural areas 10 to 40 times faster than the rate of soil formation imperiling humanity’s food security.
The Rest-Frame Golenetskii Correlation via a Hierarchical Bayesian Analysis
J. Michael Burgess
Physics , 2015,
Abstract: Gamma-ray bursts (GRBs) are characterised by a strong correlation between the instantaneous luminosity and the spectral peak energy within a burst. This correlation, which is known as the hardness-intensity correlation or the Golenetskii correlation, not only holds important clues to the physics of GRBs but is thought to have the potential to determine redshifts of bursts. In this paper, I use a hierarchical Bayesian model to study the universality of the rest-frame Golenetskii correlation and in particular I assess its use as a redshift estimator for GRBs. I find that, using a power-law prescription of the correlation, the power-law indices cluster near a common value, but have a broader variance than previously reported ($\sim 1-2$). Furthermore, I find evidence that there is spread in intrinsic rest-frame correlation normalizations for the GRBs in our sample ($\sim 10^{51}-10^{53}$ erg s$^{-1}$). This points towards variable physical settings of the emission (magnetic field strength, number of emitting electrons, photospheric radius, viewing angle, etc.). Subsequently, these results eliminate the Golenetskii correlation as a useful tool for redshift determination and hence a cosmological probe. Nevertheless, the Bayesian method introduced in this paper allows for a better determination of the rest frame properties of the correlation, which in turn allows for more stringent limitations for physical models of the emission to be set.
On Spectral Evolution and Temporal Binning in Gamma-Ray Bursts
J. Michael Burgess
Physics , 2014, DOI: 10.1093/mnras/stu1925
Abstract: The understanding of the prompt $\gamma$-ray spectra of gamma-ray bursts (GRBs) is of great importance to correctly interpreting the physical mechanisms that produce the underlying event as well as the structure of the relativistic jet from which the emission emanates. Time-resolved analysis of these spectra is the main method of extracting information from the data. In this work, several techniques for temporal binning of GRB spectra are examined to understand the systematics associated with each with the goal of finding the best method(s) to bin lightcurves for analysis. The following binning methods are examined: constant cadence (CC), Bayesian blocks (BB), signal-to-noise (S/N) and Knuth bins (KB). I find that both the KB and BB methods reconstruct the intrinsic spectral evolution accurately while the S/N method fails in most cases. The CC method is accurate when the cadence is not too coarse but does not necessarily bin the data based on the true source variability. Additionally, the integrated pulse properties are investigated and compared to the time-resolved properties. If intrinsic spectral evolution is present then the integrated properties are not useful in identifying physical and cosmological properties of GRBs without knowing the physical emission mechanism and its evolution.
Are GRB Blackbodies an Artifact of Spectral Evolution?
J. Michael Burgess,Felix Ryde
Physics , 2014, DOI: 10.1093/mnras/stu2670
Abstract: The analysis of gamma-ray burst (GRB) spectra with multi-component emission models has become an important part of the field. In particular, multi-component analysis where one component is a blackbody representing emission from a photosphere has enabled both a more detailed understanding of the energy content of the jet as well as the ability to examine the dynamic structure of the outflow. While the existence of a blackbody-like component has been shown to be significant and not a byproduct of background fluctuations, it is very possible that it can be an artifact of spectral evolution of a single component that is being poorly resolved in time. Herein, this possibility is tested by simulating a single component evolving in time and then folding the spectra through the $Fermi$ detector response to generate time-tagged event Gamma-ray Burst Monitor (GBM) data. We then fit both the time integrated and resolved generated spectral data with a multi-component model using standard tools. It is found that in {\it time-integrated} spectra, a blackbody can be falsely identified due to the spectral curvature introduced by the spectral evolution. However, in time-resolved analysis defined by time bins that can resolve the evolution of the spectra, the significance of the falsely identified blackbody is very low. Additionally, the evolution of the artificial blackbody parameters does not match the recurring behavior that has been identified in the actual observations. These results reinforce the existence of the blackbody found in {\it time-resolved} analysis of GRBs and stress the point that caution should be taken when using time-integrated spectral analysis for identifying physical properties of GRBs.
Treating Imatinib-Resistant Leukemia: The Next Generation Targeted Therapies
Michael R. Burgess,Charles L. Sawyers
The Scientific World Journal , 2006, DOI: 10.1100/tsw.2006.184
Link-Prediction Enhanced Consensus Clustering for Complex Networks
Matthew Burgess,Eytan Adar,Michael Cafarella
Computer Science , 2015,
Abstract: Many real networks that are inferred or collected from data are incomplete due to missing edges. Missing edges can be inherent to the dataset (Facebook friend links will never be complete) or the result of sampling (one may only have access to a portion of the data). The consequence is that downstream analyses that consume the network will often yield less accurate results than if the edges were complete. Community detection algorithms, in particular, often suffer when critical intra-community edges are missing. We propose a novel consensus clustering algorithm to enhance community detection on incomplete networks. Our framework utilizes existing community detection algorithms that process networks imputed by our link prediction based algorithm. The framework then merges their multiple outputs into a final consensus output. On average our method boosts performance of existing algorithms by 7% on artificial data and 17% on ego networks collected from Facebook.
Cigarette Smoking and Alcohol Use among Adolescents and Young Adults with Asthma
Elizabeth Burgess Dowdell,Michael A. Posner,M. Katherine Hutchinson
Nursing Research and Practice , 2011, DOI: 10.1155/2011/503201
Abstract: Asthma is one of the most common, serious chronic diseases in pediatric and young adult populations. Health-risk behaviors, including cigarette smoking and alcohol use, may exacerbate chronic diseases and complicate their management. The aim of this study was to longitudinally analyze rates of cigarette smoking and alcohol use in adolescents and young adults who have asthma and those who do not have asthma. A secondary analysis of data from the National Longitudinal Study of Adolescent Health was undertaken. Individuals with asthma were found to exhibit increasing rates of cigarette smoking and alcohol use as they aged. When an adolescent with a chronic health issue begins health-risk-taking behaviors, behavior change interventions must be planned. Pediatric nurses, practitioners, and clinicians are uniquely positioned to assess for health-risk behaviors in youth with asthma and to intervene with plans of care that are tailored for the needs of this vulnerable population. 1. Introduction Risk-taking behaviors that can have lifelong implications are often begun in adolescence and young adulthood. Two common health-risk behaviors that are frequently initiated are cigarette smoking and the alcohol consumption. The long-term negative health consequences of these behaviors have been well documented, as has their prevalence in the general healthy adolescent population; however, what is beginning to emerge in the literature is that health-risk behaviors are also occurring among youth and adults with chronic health conditions, specifically asthma. This paper discusses the findings from a study that examined cigarette smoking and alcohol use in adolescents and young adults who have asthma and in those who do not have asthma. The sample was drawn through a secondary analysis of data from the National Longitudinal Study of Adolescent Health (Add Health) [1]. Our study addressed the following research questions:(1)How many adolescents and young adults with asthma are engaging in health-risk behaviors (e.g., smoking cigarettes and drinking alcohol)?(2)How do cigarette smoking and alcohol use rates and patterns change as adolescents with asthma age?(3)Are there differences in cigarette smoking and alcohol use behaviors between adolescents and young adults with asthma and those who do not have asthma? Asthma is a significant and growing public health problem in the United States, with the Centers for Disease Control and Prevention (CDC) estimating that about 7 million children under the age of 18 years are affected [2]. Asthma is considered the most common serious
Dispersal of Biofilms by Secreted, Matrix Degrading, Bacterial DNase
Reindert Nijland,Michael J. Hall,J. Grant Burgess
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0015668
Abstract: Microbial biofilms are composed of a hydrated matrix of biopolymers including polypeptides, polysaccharides and nucleic acids and act as a protective barrier and microenvironment for the inhabiting microbes. While studying marine biofilms, we observed that supernatant produced by a marine isolate of Bacillus licheniformis was capable of dispersing bacterial biofilms. We investigated the source of this activity and identified the active compound as an extracellular DNase (NucB). We have shown that this enzyme rapidly breaks up the biofilms of both Gram-positive and Gram-negative bacteria. We demonstrate that bacteria can use secreted nucleases as an elegant strategy to disperse established biofilms and to prevent de novo formation of biofilms of competitors. DNA therefore plays an important dynamic role as a reversible structural adhesin within the biofilm.
Threatened fertility and gonadal function after a polytraumatic, life-threatening injury
Ward Michael,Burgess Pamela,Williams Daniel,Herrforth Casey
Journal of Emergencies, Trauma and Shock , 2010,
Abstract: Trauma literature regarding management of genitalia trauma affecting future fertility and gonadal function in the face of coexisting life-threatening injuries is underdeveloped. We present a unique case that necessitated integrative management of a 24-year-old male who became entangled within the blades of a manure spreader and presented with life-threatening trauma in addition to severe genital trauma, including penile degloving, bilateral testicular avulsion and bilateral spermatic cord laceration. During the initial stabilization and surgical management, urology and plastic surgery were consulted to assess the urogenital injuries. Together, the surgical team orchestrated potentially life-saving interventions while successfully performing both a testicular sperm extraction and a testicular revascularization. Viable sperm was collected on the day of surgery and initial follow-up showed preserved sexual function and adequate perfusion to the testicle. This report presents a case and provides a review discussing the management of traumatic genital injuries and the importance of early involvement of surgical specialties in genitalia trauma to optimize future fertility and gonadal function. The literature search was performed in August 2008 using Medline for articles only in English, including any of the following terms: polytrauma, trauma, penis, testicle, degloving, avulsion, spermatic cord, laceration, fertility, reproduction or revascularization.
Power-counting and the Validity of the Classical Approximation During Inflation
C. P. Burgess,Hyun Min Lee,Michael Trott
Physics , 2009, DOI: 10.1088/1126-6708/2009/09/103
Abstract: We use the power-counting formalism of effective field theory to study the size of loop corrections in theories of slow-roll inflation, with the aim of more precisely identifying the limits of validity of the usual classical inflationary treatments. We keep our analysis as general as possible in order to systematically identify the most important corrections to the classical inflaton dynamics. Although most slow-roll models lie within the semiclassical domain, we find the consistency of the Higgs-Inflaton scenario to be more delicate due to the proximity between the Hubble scale during inflation and the upper bound allowed by unitarity on the new-physics scale associated with the breakdown of the semiclassical approximation within the effective theory. Similar remarks apply to curvature-squared inflationary models.

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