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Search Results: 1 - 10 of 10592 matches for " Matthew Bowser "
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Quasi-Kernels for Oriented Paths and Cycles  [PDF]
Stephen Bowser, Charles Cable
Open Journal of Discrete Mathematics (OJDM) , 2012, DOI: 10.4236/ojdm.2012.22010
Abstract: If D is a digraph, then K∈V(D) is a quasi-kernel of D if D[K]is discrete and for each y∈V(D)-K there is x∈K such that the directed distance from y to x is less than three. We give formulae for the number of quasi-kernels and for the number of minimal quasi-kernels of oriented paths and cycles.
Control of Male and Female Fertility by the Netrin Axon Guidance Genes
Gunnar Newquist, Jesse Hogan, Kirsti Walker, Matthew Lamanuzzi, Micah Bowser, Thomas Kidd
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0072524
Abstract: The netrin axon guidance genes have previously been implicated in fertility in C. elegans and in vertebrates. Here we show that adult Drosophila lacking both netrin genes, NetA and NetB, have fertility defects in both sexes together with an inability to fly and reduced viability. NetAB females produce fertilized eggs at a much lower rate than wild type. Oocyte development and ovarian innervation are unaffected in NetAB females, and the reproductive tract appears normal. A small gene, hog, that resides in an intron of NetB does not contribute to the NetAB phenotype. Restoring endogenous NetB expression rescues egg-laying, but additional genetic manipulations, such as restoration of netrin midline expression and inhibition of cell death have no effect on fertility. NetAB males induce reduced egg-laying in wild type females and display mirror movements of their wings during courtship. Measurement of courtship parameters revealed no difference compared to wild type males. Transgenic manipulations failed to rescue male fertility and mirror movements. Additional genetic manipulations, such as removal of the enabled gene, a known suppressor of the NetAB embryonic CNS phenotype, did not improve the behavioral defects. The ability to fly was rescued by inhibition of neuronal cell death and pan-neural NetA expression. Based on our results we hypothesize that the adult fertility defects of NetAB mutants are due to ovulation defects in females and a failure to properly transfer sperm proteins in males, and are likely to involve multiple neural circuits.
Absence of Functional Leptin Receptor Isoforms in the POUND (Leprdb/lb) Mouse Is Associated with Muscle Atrophy and Altered Myoblast Proliferation and Differentiation
Phonepasong Arounleut, Matthew Bowser, Sunil Upadhyay, Xing-Ming Shi, Sadanand Fulzele, Maribeth H. Johnson, Alexis M. Stranahan, William D. Hill, Carlos M. Isales, Mark W. Hamrick
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0072330
Abstract: Objective Leptin receptors are abundant in human skeletal muscle, but the role of leptin in muscle growth, development and aging is not well understood. Here we utilized a novel mouse model lacking all functional leptin receptor isoforms (POUND mouse, Leprdb/lb) to determine the role of leptin in skeletal muscle. Methods and Findings Skeletal muscle mass and fiber diameters were examined in POUND mice, and primary myoblast cultures were used to determine the effects of altered leptin signaling on myoblast proliferation and differentiation. ELISA assays, integrated pathway analysis of mRNA microarrays, and reverse phase protein analysis were performed to identify signaling pathways impacted by leptin receptor deficiency. Results show that skeletal muscle mass and fiber diameter are reduced 30–40% in POUND mice relative to wild-type controls. Primary myoblast cultures demonstrate decreased proliferation and decreased expression of both MyoD and myogenin in POUND mice compared to normal mice. Leptin treatment increased proliferation in primary myoblasts from muscles of both adult (12 months) and aged (24 months) wild-type mice, and leptin increased expression of MyoD and myogenin in aged primary myoblasts. ELISA assays and protein arrays revealed altered expression of molecules associated with the IGF-1/Akt and MAPK/MEK signaling pathways in muscle from the hindlimbs of mice lacking functional leptin receptors. Conclusion These data support the hypothesis that the adipokine leptin is a key factor important for the regulation of skeletal muscle mass, and that leptin can act directly on its receptors in peripheral tissues to regulate cell proliferation and differentiation.
Detection of the heavy Higgs boson at $γγ$ colliders
David Bowser-Chao,Kingman Cheung
Physics , 1993, DOI: 10.1103/PhysRevD.48.89
Abstract: We consider the possibility of detecting a heavy Higgs boson ($m_H>2m_Z$) in proposed $\gamma\gamma$ colliders through the semi-leptonic mode $\gamma\gamma \rightarrow H \rightarrow ZZ \rightarrow q\bar q \ell^+\ell^-$. We show that due to the non-monochromatic nature of the photon beams produced by the laser-backscattering method, the resultant cross section for Higgs production is much smaller than the on-resonance cross section and generally {\it decreases} with increasing collider energy. Although continuum $ZZ$ production is expected to be negligible, we demonstrate the presence of and calculate sizeable backgrounds from $\gamma\gamma\rightarrow \ell^+\ell^-Z,\,q\bar qZ$, with $Z\rightarrow q\bar q,\,\ell^+\ell^-$, respectively, and $\gamma\gamma\rightarrow t\bar t\rightarrow b\bar b\ell^+\ell^-\nu\bar\nu$. This channel may be used to detect a Higgs of mass $m_H$ up to around 350~GeV at a 0.5~TeV $e^+e^-$ collider, assuming a nominal yearly luminosity of 10--20~fb$^{-1}$.
A Comparison of the Use of Binary Decision Trees and Neural Networks in Top Quark Detection
David Bowser-Chao,Debra L. Dzialo
Physics , 1992, DOI: 10.1103/PhysRevD.47.1900
Abstract: The use of neural networks for signal vs.~background discrimination in high-energy physics experiment has been investigated and has compared favorably with the efficiency of traditional kinematic cuts. Recent work in top quark identification produced a neural network that, for a given top quark mass, yielded a higher signal to background ratio in Monte Carlo simulation than a corresponding set of conventional cuts. In this article we discuss another pattern-recognition algorithm, the binary decision tree. We have applied a binary decision tree to top quark identification at the Tevatron and found it to be comparable in performance to the neural network. Furthermore, reservations about the "black box" nature of neural network discriminators do not apply to binary decision trees; a binary decision tree may be reduced to a set of kinematic cuts subject to conventional error analysis.
Cystatin C: A Candidate Biomarker for Amyotrophic Lateral Sclerosis
Meghan E. Wilson,Imene Boumaza,David Lacomis,Robert Bowser
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0015133
Abstract: Amyotrophic lateral sclerosis (ALS) is a fatal neurologic disease characterized by progressive motor neuron degeneration. Clinical disease management is hindered by both a lengthy diagnostic process and the absence of effective treatments. Reliable panels of diagnostic, surrogate, and prognostic biomarkers are needed to accelerate disease diagnosis and expedite drug development. The cysteine protease inhibitor cystatin C has recently gained interest as a candidate diagnostic biomarker for ALS, but further studies are required to fully characterize its biomarker utility. We used quantitative enzyme-linked immunosorbent assay (ELISA) to assess initial and longitudinal cerebrospinal fluid (CSF) and plasma cystatin C levels in 104 ALS patients and controls. Cystatin C levels in ALS patients were significantly elevated in plasma and reduced in CSF compared to healthy controls, but did not differ significantly from neurologic disease controls. In addition, the direction of longitudinal change in CSF cystatin C levels correlated to the rate of ALS disease progression, and initial CSF cystatin C levels were predictive of patient survival, suggesting that cystatin C may function as a surrogate marker of disease progression and survival. These data verify prior results for reduced cystatin C levels in the CSF of ALS patients, identify increased cystatin C levels in the plasma of ALS patients, and reveal correlations between CSF cystatin C levels to both ALS disease progression and patient survival.
High-throughput sequencing of Astrammina rara: Sampling the giant genome of a giant foraminiferan protist
Andrea Habura, Yubo Hou, Andrew A Reilly, Samuel S Bowser
BMC Genomics , 2011, DOI: 10.1186/1471-2164-12-169
Abstract: 454 sequence analysis was performed on a library derived from whole genome amplification of microdissected nuclei of the Antarctic foraminiferan Astrammina rara. Xenogenomic sequence, which was shown not to be of eukaryotic origin, represented only 12% of the sample. The first foraminiferal examples of important classes of genes, such as tRNA genes, are reported, and we present evidence that sequences of mitochondrial origin have been translocated to the nucleus. The recovery of a 3' UTR and downstream sequence from an actin gene suggests that foraminiferal mRNA processing may have some unusual features. Finally, the presence of a co-purified bacterial genome in the library also permitted the first calculation of the size of a foraminiferal genome by molecular methods, and statistical analysis of sequence from different genomic sources indicates that low-complexity tracts of the genome may be endoreplicated in some stages of the foraminiferal life cycle.These data provide the first window into genomic organization and genetic control in these organisms, and also complement and expands upon information about foraminiferal genes based on EST projects. The genomic data obtained are informative for environmental and cell-biological studies, and will also be useful for efforts to understand relationships between foraminiferans and other protists.The Foraminifera are an abundant and widespread group of marine protists, noted for their ability to construct fossilizable shells or "tests". Some foraminiferans, such as members of the planktonic genus Globigerina, are so abundant that their empty tests dominate the biotic material in about 35% of the Earth's seafloor [1]; half of the CaCO3 deposited in the deep ocean is in the form of foraminiferal tests [2]. The early-evolving groups within the Foraminifera possess either nonmineralized organic tests, or agglutinated tests built from materials gathered from the environment [3]. Because foraminiferans are large and predatory p
Diving for the Sedimentary Record of Multiyear Sea Ice
Molly Fritz Miller,Samuel S. Bowser,Sally E. Walker
Oceanography , 2012,
Abstract: How is sediment transported to the seafloor along coastlines where the sea ice rarely melts? Are there distinctive characteristics of the resulting deposits that label them as accumulating in this setting that is so sensitive to climate change?
From Puffins to Plankton: A DNA-Based Analysis of a Seabird Food Chain in the Northern Gulf of Maine
A. Kirsten Bowser, Antony W. Diamond, Jason A. Addison
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0083152
Abstract: The predator-prey interactions within food chains are used to both characterize and understand ecosystems. Conventional methods of constructing food chains from visual identification of prey in predator diet can suffer from poor taxonomic resolution, misidentification, and bias against small or completely digestible prey. Next-generation sequencing (NGS) technology has become a powerful tool for diet reconstruction through barcoding of DNA in stomach content or fecal samples. Here we use multi-locus (16S and CO1) next-generation sequencing of DNA barcodes on the feces of Atlantic puffin (Fratercula arctica) chicks (n=65) and adults (n=64) and the stomach contents of their main prey, Atlantic herring (Clupea harengus, n=44) to investigate a previously studied food chain. We compared conventional and molecular-derived chick diet, tested the similarity between the diets of puffin adults and chicks, and determined whether herring prey can be detected in puffin diet samples. There was high variability in the coverage of prey groups between 16S and CO1 markers. We identified more unique prey with our 16S compared to CO1 barcoding markers (51 and 39 taxa respectively) with only 12 taxa identified by both genes. We found no significant difference between the 16S-identified diets of puffin adults (n=17) and chicks (n=41). Our molecular method is more taxonomically resolved and detected chick prey at higher frequencies than conventional field observations. Many likely planktonic prey of herring were detected in feces from puffin adults and chicks, highlighting the impact secondary consumption may have on the interpretation of molecular dietary analysis. This study represents the first simultaneous molecular investigation into the diet of multiple components of a food chain and highlights the utility of a multi-locus approach to diet reconstruction that is broadly applicable to food web analysis.
Detecting an Intermediate Mass Charged Higgs at $γγ$ Colliders
David Bowser-Chao,Kingman Cheung,Scott Thomas
Physics , 1993, DOI: 10.1016/0370-2693(93)91631-V
Abstract: The detection of an intermediate mass charged Higgs boson at $\gamgam$ colliders via the modes $\gamgam \to H^+ H^- \to \nu \tau^+ \bar{\nu} \tau^-,~ c \bar{s} \bar{c} s,~$ and $ \nu \tau^+ \bar{c}s + c \bar{s} \bar{\nu} \tau^-$ is considered. $W^+ W^-$ boson pair production is the dominant background for these modes. The three modes may be used in a complementary fashion to detect a charged Higgs boson. The mixed leptonic-hadronic mode may be used to determine the charged Higgs mass by reconstructing the invariant hadronic mass. The sensitivity of Br$(H^+ \rightarrow c\bar s,\,\nu \tau^+)$ on the discovery limit of the charged Higgs boson is also discussed.
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