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Search Results: 1 - 10 of 4514 matches for " Rachel Kennedy "
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Constraining the WDM Particle Mass with Milky Way Satellites
Rachel Kennedy,Carlos Frenk,Shaun Cole,Andrew Benson
Physics , 2013, DOI: 10.1093/mnras/stu719
Abstract: Well-motivated particle physics theories predict the existence of particles (such as sterile neutrinos) which acquire non-negligible thermal velocities in the early universe. These particles could behave as warm dark matter (WDM) and generate a small-scale cutoff in the linear density power spectrum which scales approximately inversely with the particle mass. If this mass is of order a keV, the cutoff occurs on the scale of dwarf galaxies. Thus, in WDM models the abundance of small galaxies, such as the satellites that orbit in the halo of the Milky Way, depends on the mass of the warm particle. The abundance also scales with the mass of the host galactic halo. We use the \galform semi-analytic model of galaxy formation to calculate the properties of galaxies in universes in which the dark matter is warm. Using this method, we can compare the predicted satellite luminosity functions to the observed data for the Milky Way dwarf spheroidals, and determine a lower bound on the thermally produced WDM particle mass. This depends strongly on the value of the Milky Way halo mass and, to some extent, on the baryonic physics assumed; we examine both of these dependencies. For our fiducial model we find that for a particle mass of 3.3 keV (the 2$\sigma$ lower limit found by Viel et al. from a recent analysis of the Lyman-$\alpha$ forest) the Milky Way halo mass is required to be $> 1.4 \times 10^{12}$ \msun. For this same fiducial model, we also find that all WDM particle masses are ruled out (at 95% confidence) if the halo of the Milky Way has a mass smaller than $1.1 \times 10^{12}$ \msun, while if the mass of the Galactic halo is greater than 1.8 $\times 10^{12}$ \msun, only WDM particle masses larger than 2 keV are allowed.
An antibody present in everybody that attacks malaria infected erythrocytes  [PDF]
James Kennedy
Journal of Biomedical Science and Engineering (JBiSE) , 2013, DOI: 10.4236/jbise.2013.67A1001
Abstract: These malaria targeting antibodies are band 3 antibodies and they recognize a special configuration of a molecule called band 3 that is present on erythrocytes. The special band 3 configuration is present on the surface of senescent erythrocytes, malaria infected erythrocytes, the erythrocytes of certain hemoglobinnopathies such as sickle cell disease and on the erythrocytes of some metabolic disorders such as G6PD. Note that these hemoglobinopathies and metabolic disorders all aid in the survival of falciparum malaria to such an extent that their incidence is increased in falciparum endemic areas [1-3]. Though there are many adhesive molecules involved in the pathology of falciparum malaria and sickle cell anemia, the focus here is on the band 3 molecules.
Improved Image Fusion in PET/CT Using Hybrid Image Reconstruction and Super-Resolution
John A. Kennedy,Ora Israel,Alex Frenkel,Rachel Bar-Shalom,Haim Azhari
International Journal of Biomedical Imaging , 2007, DOI: 10.1155/2007/46846
Abstract: Purpose. To provide PET/CT image fusion with an improved PET resolution and better contrast ratios than standard reconstructions. Method. Using a super-resolution algorithm, several PET acquisitions were combined to improve the resolution. In addition, functional PET data was smoothed with a hybrid computed tomography algorithm (HCT), in which anatomical edge information taken from the CT was employed to retain sharper edges. The combined HCT and super-resolution technique were evaluated in phantom and patient studies using a clinical PET scanner. Results. In the phantom studies, 3 mmF18-FDG sources were resolved. PET contrast ratios improved (average: 54%, range: 45%–69%) relative to the standard reconstructions. In the patient study, target-to-background ratios also improved (average: 34%, range: 17%–47%). Given corresponding anatomical borders, sharper edges were depicted. Conclusion. A new method incorporating super-resolution and HCT for fusing PET and CT images has been developed and shown to provide higher-resolution metabolic images.
Colonization-Competition Tradeoffs as a Mechanism Driving Successional Dynamics in Ectomycorrhizal Fungal Communities
Peter G. Kennedy, Logan M. Higgins, Rachel H. Rogers, Marjorie G. Weber
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0025126
Abstract: Colonization-competition tradeoffs have been shown to be important determinants of succession in plant and animal communities, but their role in ectomycorrhizal (ECM) fungal communities is not well understood. To experimentally examine whether strong spore-based competitors remain dominant on plant root tips as competition shifts to mycelial-based interactions, we investigated the mycelial competitive interactions among three naturally co-occurring ECM species (Rhizopogon occidentalis, R. salebrosus, and Suillus pungens). Each species was grown alone and in all pair-wise combinations on P. muricata seedlings in experimental microcosms and culture assays. Competitive outcomes were assessed from ECM root tip colonization, soil mycelial abundance, and mycelial growth in culture. In the microcosm experiment, we observed a clear competitive hierarchy of R. salebrosus>R. occidentalis>S. pungens. Competitive effects were also apparent in the culture assays, however, no similar hierarchy was present. These results contrast with our previous findings from spore-based competition, suggesting that ECM competitive outcomes can be life-stage dependent. The differing competitive abilities observed here also showed general correspondence with patterns of ECM succession in Pinus muricata forests, indicating that competitive interactions may significantly influence temporal patterns of ECM community structure.
Creating mock catalogues of stellar haloes from cosmological simulations
Ben Lowing,Wenting Wang,Andrew Cooper,Rachel Kennedy,John Helly,Carlos Frenk,Shaun Cole
Physics , 2014, DOI: 10.1093/mnras/stu2257
Abstract: We present a new technique for creating mock catalogues of the individual stars that make up the accreted component of stellar haloes in cosmological simulations and show how the catalogues can be used to test and interpret observational data. The catalogues are constructed from a combination of methods. A semi-analytic galaxy formation model is used to calculate the star formation history in haloes in an N-body simulation and dark matter particles are tagged with this stellar mass. The tags are converted into individual stars using a stellar population synthesis model to obtain the number density and evolutionary stage of the stars, together with a phase-space sampling method that distributes the stars while ensuring that the phase-space structure of the original N-body simulation is maintained. A set of catalogues based on the $\Lambda$CDM Aquarius simulations of Milky Way mass haloes have been created and made publicly available on a website. Two example applications are discussed that demonstrate the power and flexibility of the mock catalogues. We show how the rich stellar substructure that survives in the stellar halo precludes a simple measurement of its density profile and demonstrate explicitly how pencil-beam surveys can return almost any value for the slope of the profile. We also show that localized variations in the abundance of particular types of stars, a signature of differences in the composition of stellar populations, allow streams to be easily identified.
Expression analysis of secreted and cell surface genes of five transformed human cell lines and derivative xenograft tumors
Robert A Stull, Roya Tavassoli, Scot Kennedy, Steve Osborn, Rachel Harte, Yan Lu, Cheryl Napier, Arie Abo, Daniel J Chin
BMC Genomics , 2005, DOI: 10.1186/1471-2164-6-55
Abstract: Three different analyses were performed: (1) A PCA-based linear discriminant analysis identified a 54 gene profile characteristic of all tumors, (2) Application of MANOVA (Pcorr < .05) to tumor data revealed a larger set of 149 differentially expressed genes. (3) After MANOVA was performed on data from individual tumors, a comparison of differential genes amongst all tumor types revealed 12 common differential genes. Seven of the 12 genes were identified by all three analytical methods. These included late angiogenic, morphogenic and extracellular matrix genes such as ANGPTL4, COL1A1, GP2, GPR57, LAMB3, PCDHB9 and PTGER3. The differential expression of ANGPTL4 and COL1A1 and other genes was confirmed by quantitative PCR.Overall, a comparison of the three analyses revealed an expression pattern indicative of late angiogenic processes. These results show that a xenograft model using multiple cell lines of diverse tissue origin can identify common tumorigenic cell surface or secreted molecules that may be important biomarker and therapeutic discoveries.The process of tumorigenesis has long been recognized to depend upon complex interactions of a tumor with its non-transformed tissue environment [1]. Beyond transformation and increased proliferation, many pathways are activated both in the growing tumor and its environment to culminate in an established solid tumor. For example, adhesive pathways are activated to enable transformed cells to aggregate and form a microtumor. Subsequently, microtumors must avoid destruction by the immune system and elicit vasculature formation for continued growth [2,3]. In support of these events, cell-matrix adhesion proteins, cell surface antigens, angiogenic factors and modulatory agents have been found differentially expressed in several experimental models of tumorigenesis [4-6] and in tumor biopsy samples relative to control tissues [7,8]. Experimental models with established tumorigenic human cell lines have compared the gene expre
Duration of Type 2 Diabetes and Very Low Density Lipoprotein Levels Are Associated with Cognitive Dysfunction in Metabolic Syndrome
Divya Yogi-Morren,Rachel Galioto,Sarah Elizabeth Strandjord,L. Kennedy,Pooja Manroa,John P. Kirwan,Sangeeta Kashyap,John Gunstad
Cardiovascular Psychiatry and Neurology , 2014, DOI: 10.1155/2014/656341
Abstract: Type 2 diabetes (T2D) is now recognized as an independent risk factor for accelerated cognitive decline and neurological conditions like Alzheimer’s disease. Less is known about the neurocognitive function of T2D patients with comorbid metabolic syndrome, despite their elevated risk for impairment. Computerized testing in 47 adults with T2D that met criteria for NCEP metabolic syndrome revealed that cognitive impairment was prevalent, including 13% in tests of memory, 50% in attention, and 35% in executive function. Partial correlations showed that longer duration of diabetes was associated with poorer performance on tests of basic attention ( ), working memory ( ), and executive function ( ). Strong associations between very low density lipoprotein and poor cognitive function also emerged, including tests of set shifting ( ) and cognitive inhibition ( ). Findings suggest that patients with T2D that meet criteria for metabolic syndrome are at high risk for cognitive impairment. Prospective studies should look to replicate these findings and examine the possible neuroprotective effects of lipid-lowering medication in this population. 1. Introduction Type 2 diabetes (T2D) is a metabolic disorder characterized by peripheral insulin resistance and reduced insulin production. The resulting hyperglycemia can lead to both microvascular complications, such as neuropathy, nephropathy, and retinopathy, and macrovascular complications, such as cardiovascular disease and stroke [1]. In addition to these complications, a growing number of studies demonstrate that T2D also has adverse effects on the brain, including elevated risk for conditions such as stroke and dementia [2–7]. More recent work shows that cognitive impairment is found in people with T2D long prior to the onset of these conditions, with impairments on tasks of memory and executive function being likely [8–10]. A better understanding of these cognitive impairments has important clinical implications, as they have recently been linked to poorer disease self-management [11]. The mechanisms contributing to cognitive changes in T2D remain poorly understood. Several parameters, particularly hyperglycemia [12, 13], have been proposed as potential risk factors for cognitive decline in type 2 diabetics. In the Memory in Diabetes (MIND) substudy of the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial, for example, Launer et al. [14] found an association between glycated hemoglobin (HbA1c), a marker of chronic hyperglycemia, and lower cognitive function in patients with T2D. Despite this
Dark Matter Halo Merger Histories Beyond Cold Dark Matter: I - Methods and Application to Warm Dark Matter
Andrew J. Benson,Arya Farahi,Shaun Cole,Leonidas A. Moustakas,Adrian Jenkins,Mark Lovell,Rachel Kennedy,John Helly,Carlos Frenk
Physics , 2012, DOI: 10.1093/mnras/sts159
Abstract: We describe a methodology to accurately compute halo mass functions, progenitor mass functions, merger rates and merger trees in non-cold dark matter universes using a self-consistent treatment of the generalized extended Press-Schechter formalism. Our approach permits rapid exploration of the subhalo population of galactic halos in dark matter models with a variety of different particle properties or universes with rolling, truncated, or more complicated power spectra. We make detailed comparisons of analytically derived mass functions and merger histories with recent warm dark matter cosmological N-body simulations, and find excellent agreement. We show that, once the accretion of smoothly distributed matter is accounted for, coarse-grained statistics such as the mass accretion history of halos can be almost indistinguishable between cold and warm dark matter cases. However, the halo mass function and progenitor mass functions differ significantly, with the warm dark matter cases being strongly suppressed below the free-streaming scale of the dark matter. We demonstrate the importance of using the correct solution for the excursion set barrier first-crossing distribution in warm dark matter - if the solution for a flat barrier is used instead the truncation of the halo mass function is much slower, leading to an overestimate of the number of low mass halos.
Does the Behavioral Science Curriculum in a Private College Fit the Needs of the Job Market?  [PDF]
Rachel Pasternak
Creative Education (CE) , 2014, DOI: 10.4236/ce.2014.52016
Abstract:

The perception of knowledge as consumer goods appeared with the development of private education and reflects a marketing or consumer needs approach. The consumer-needs approach sees advantages in adapting higher education to the needs of the consumer. This article examines whether the behavioral science curriculum (scope, and content) in the private college is based on the approach of knowledge as consumer goods. In addition, what is the level of satisfaction expressed by the alumni of the course, i.e. those who completed the curriculum? The study used a multi-method approach, combining textual analysis of archived documents and an online questionnaire survey of 250 alumni. The results: the scope and contents of the curriculum were only partially affected by this approach. Nonetheless, the graduates were very satisfied with the curriculums contribution to their personal and professional skills and occupations.

Drones under International Law  [PDF]
Rachel Alberstadt
Open Journal of Political Science (OJPS) , 2014, DOI: 10.4236/ojps.2014.44023
Abstract: There is a notable absence of legal approaches to the discourse evaluating use of drones. Even when drones are discussed in a legal context, arguments assert that drones require a new legal regime to adapt to modern qualities and circumstances. In the alternative, this paper argues that drones compatibly fit into existing legal regimes, particularly international criminal law (ICL) and international humanitarian law (IHL) in accordance with general principles of international law. This paper argues that use of drones in armed conflict fits within existing laws governing use of force as the frameworks in use today. It demonstrates that ICL and IHL provide flexible guidelines appropriately suitable to particulars of drones, such as types and capabilities, but more importantly, they continue to provide legal governance applicable to drones as weapons. Legal uncertainty as to the use of drones is thus evaluated within the hypothetical exploration of drone usage culminating in a war crime before the International Criminal Court (ICC).
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