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Search Results: 1 - 10 of 419514 matches for " M. Eric Brewer Jr. "
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Penile Rehabilitation Therapy with PDE-V Inhibitors Following Radical Prostatectomy: Proceed with Caution
M. Eric Brewer Jr.,Edward D. Kim
Advances in Urology , 2009, DOI: 10.1155/2009/852437
Abstract: Penile rehabilitation therapy following radical prostatectomy is a much debated topic. Erectile dysfunction is still a significant contributor to postoperative morbidity following radical prostatectomy, despite meticulous nerve-sparing technique. Secondary smooth muscle changes in the penis have been identified as the underlying causes of penile atrophy, veno-occlusive dysfunction, and fibrosis. Initial observations that intracavernous injection therapies used on a regular basis postoperatively resulted in improvements in the return of spontaneous erectile function led to the development of penile rehabilitation protocols. Chronic dosing of PDE-V inhibitors is now commonly used by urologists after radical prostatectomy. Despite the current enthusiasm of penile rehabilitation therapy, current scientific evidence with clinical trials is still limited.
A Long-Period Totally Eclipsing Binary Star at the Turnoff of the Open Cluster NGC 6819 Discovered with Kepler
Eric L. Sandquist,Robert D. Mathieu,Karsten Brogaard,Soren Meibom,Aaron M. Geller,Jerome A. Orosz,Katelyn E. Milliman,Mark W. Jeffries Jr,Lauren N. Brewer,Imants Platais,Frank Grundahl,Hans Bruntt,Soeren Frandsen,Dennis Stello
Physics , 2012, DOI: 10.1088/0004-637X/762/1/58
Abstract: We present the discovery of the totally eclipsing long-period (P = 771.8 d) binary system WOCS 23009 in the old open cluster NGC 6819 that contains both an evolved star near central hydrogen exhaustion and a low-mass (0.45 Msun) star. This system was previously known to be a single-lined spectroscopic binary, but the discovery of an eclipse near apastron using data from the Kepler space telescope makes it clear that the system has an inclination that is very close to 90 degrees. Although the secondary star has not been identified in spectra, the mass of the primary star can be constrained using other eclipsing binaries in the cluster. The combination of total eclipses and a mass constraint for the primary star allows us to determine a reliable mass for the secondary star and radii for both stars, and to constrain the cluster age. Unlike well-measured stars of similar mass in field binaries, the low-mass secondary is not significantly inflated in radius compared to model predictions. The primary star characteristics, in combination with cluster photometry and masses from other cluster binaries, indicates a best age of 2.62+/-0.25 Gyr, although stellar model physics may introduce systematic uncertainties at the ~10% level. We find preliminary evidence that the asteroseismic predictions for red giant masses in this cluster are systematically too high by as much as 8%.
WOCS 40007: A Detached Eclipsing Binary near the Turnoff of the Open Cluster NGC 6819
Mark W. Jeffries, Jr.,Eric L. Sandquist,Robert D. Mathieu,Aaron M. Geller,Jerome A. Orosz,Katelyn E. Milliman,Lauren N. Brewer,Imants Platais,Karsten Brogaard,Frank Grundahl,Soeren Frandsen,Aaron Dotter,Dennis Stello
Physics , 2013, DOI: 10.1088/0004-6256/146/3/58
Abstract: We analyze extensive BVR_cI_c time-series photometry and radial-velocity measurements for WOCS 40007 (Auner 259; KIC 5113053), a double-lined detached eclipsing binary and a member of the open cluster NGC 6819. Utilizing photometric observations from the 1-meter telescope at Mount Laguna Observatory and spectra from the WIYN 3.5-meter telescope, we measure precise and accurate masses (~1.6% uncertainty) and radii (~0.5%) for the binary components. In addition, we discover a third star orbiting the binary with a period greater than 3000 days using radial velocities and Kepler eclipse timings. Because the stars in the eclipsing binary are near the cluster turnoff, they are evolving rapidly in size and are sensitive to age. With a metallicity of [Fe/H]=+0.09+/-0.03, we find the age of NGC 6819 to be about 2.4 Gyr from CMD isochrone fitting and 3.1+/-0.4 Gyr by analyzing the mass-radius (M-R) data for this binary. The M-R age is above previous determinations for this cluster, but consistent within 1 sigma uncertainties. When the M-R data for the primary star of the additional cluster binary WOCS 23009 is included, the weighted age estimate drops to 2.5+/-0.2 Gyr, with a systematic uncertainty of at least 0.2 Gyr. The age difference between our CMD and M-R findings may be the result of systematic error in the metallicity or helium abundance used in models, or due to slight radius inflation of one or both stars in the WOCS 40007 binary.
Prospecting in late-type dwarfs: a calibration of infrared and visible spectroscopic metallicities of late-K and M dwarfs spanning 1.5 dex
Andrew W. Mann,John M. Brewer,Eric Gaidos,Sebastien Lepine,Eric J. Hilton
Physics , 2012, DOI: 10.1088/0004-6256/145/2/52
Abstract: Knowledge of late K and M dwarf metallicities can be used to guide planet searches and constrain planet formation models. However, the determination of metallicities of late-type stars is difficult because visible wavelength spectra of their cool atmospheres contain many overlapping absorption lines, preventing the measurement of equivalent widths. We present new methods, and improved calibrations of existing methods, to determine metallicities of late-K and M dwarfs from moderate resolution (1300 < R < 2000) visible and infrared spectra. We select a sample of 112 wide binary systems that contain a late-type companion to a solar-type primary star. Our sample includes 62 primary stars with previously published metallicities, as well as 50 stars with metallicities determined from our own observations. We use our sample to empirically determine which features in the spectrum of the companion are best correlated with the metallicity of the primary. We derive metallicity calibrations for different wavelength ranges, and show that it is possible to get metallicities reliable to < 0.10 dex using either visible, J, H, or K band spectra. Our calibrations are applicable to dwarfs with metallicities of -1.04 < [Fe/H]< +0.56 and spectral types from K7 to M5. Lastly, we use our sample of wide binaries to test and refine existing calibrations to determine M dwarf metallicities. We find that the zeta parameter, which measures the ratio of TiO can CaH bands, is correlated with [Fe/H] for super-solar metallicities, and zeta does not always correctly identify metal-poor M dwarfs. We also find that existing calibrations in the K and H band are quite reliable for stars with [Fe/H] > -0.5, but are less useful for more metal-poor stars.
A theory of algebraic cocycles
Eric M. Friedlander,H. Blaine Lawson Jr.
Mathematics , 1992,
Abstract: We introduce the notion of an algebraic cocycle as the algebraic analogue of a map to an Eilenberg-MacLane space. Using these cocycles we develop a ``cohomology theory" for complex algebraic varieties. The theory is bigraded, functorial, and admits Gysin maps. It carries a natural cup product and a pairing to $L$-homology. Chern classes of algebraic bundles are defined in the theory. There is a natural transformation to (singular) integral cohomology theory that preserves cup products. Computations in special cases are carried out. On a smooth variety it is proved that there are algebraic cocycles in each algebraic rational $(p,p)$-cohomology class.
Reversal of Glial and Neurovascular Markers of Unhealthy Brain Aging by Exercise in Middle-Aged Female Mice
Caitlin S. Latimer, James L. Searcy, Michael T. Bridges, Lawrence D. Brewer, Jelena Popovi?, Eric M. Blalock, Philip W. Landfield, Olivier Thibault, Nada M. Porter
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0026812
Abstract: Healthy brain aging and cognitive function are promoted by exercise. The benefits of exercise are attributed to several mechanisms, many which highlight its neuroprotective role via actions that enhance neurogenesis, neuronal morphology and/or neurotrophin release. However, the brain is also composed of glial and vascular elements, and comparatively less is known regarding the effects of exercise on these components in the aging brain. Here, we show that aerobic exercise at mid-age decreased markers of unhealthy brain aging including astrocyte hypertrophy, a hallmark of brain aging. Middle-aged female mice were assigned to a sedentary group or provided a running wheel for six weeks. Exercise decreased hippocampal astrocyte and myelin markers of aging but increased VEGF, a marker of angiogenesis. Brain vascular casts revealed exercise-induced structural modifications associated with improved endothelial function in the periphery. Our results suggest that age-related astrocyte hypertrophy/reactivity and myelin dysregulation are aggravated by a sedentary lifestyle and accompanying reductions in vascular function. However, these effects appear reversible with exercise initiated at mid-age. As this period of the lifespan coincides with the appearance of multiple markers of brain aging, including initial signs of cognitive decline, it may represent a window of opportunity for intervention as the brain appears to still possess significant vascular plasticity. These results may also have particular implications for aging females who are more susceptible than males to certain risk factors which contribute to vascular aging.
A Natural Polymorphism in rDNA Replication Origins Links Origin Activation with Calorie Restriction and Lifespan
Elizabeth X. Kwan,Eric J. Foss,Scott Tsuchiyama,Gina M. Alvino,Leonid Kruglyak,Matt Kaeberlein,M. K. Raghuraman,Bonita J. Brewer,Brian K. Kennedy,Antonio Bedalov
PLOS Genetics , 2013, DOI: 10.1371/journal.pgen.1003329
Abstract: Aging and longevity are complex traits influenced by genetic and environmental factors. To identify quantitative trait loci (QTLs) that control replicative lifespan, we employed an outbred Saccharomyces cerevisiae model, generated by crossing a vineyard and a laboratory strain. The predominant QTL mapped to the rDNA, with the vineyard rDNA conferring a lifespan increase of 41%. The lifespan extension was independent of Sir2 and Fob1, but depended on a polymorphism in the rDNA origin of replication from the vineyard strain that reduced origin activation relative to the laboratory origin. Strains carrying vineyard rDNA origins have increased capacity for replication initiation at weak plasmid and genomic origins, suggesting that inability to complete genome replication presents a major impediment to replicative lifespan. Calorie restriction, a conserved mediator of lifespan extension that is also independent of Sir2 and Fob1, reduces rDNA origin firing in both laboratory and vineyard rDNA. Our results are consistent with the possibility that calorie restriction, similarly to the vineyard rDNA polymorphism, modulates replicative lifespan through control of rDNA origin activation, which in turn affects genome replication dynamics.
Prospecting in Ultracool Dwarfs: Measuring the Metallicities of Mid- and Late-M Dwarfs
Andrew W. Mann,Niall R. Deacon,Eric Gaidos,Megan Ansdell,John M. Brewer,Michael C. Liu,Eugene A. Magnier,Kimberly M. Aller
Physics , 2014, DOI: 10.1088/0004-6256/147/6/160
Abstract: Metallicity is a fundamental parameter that contributes to the physical characteristics of a star. However, the low temperatures and complex molecules present in M dwarf atmospheres make it difficult to measure their metallicities using techniques that have been commonly used for Sun-like stars. Although there has been significant progress in developing empirical methods to measure M dwarf metallicities over the last few years, these techniques have been developed primarily for early- to mid-M dwarfs. We present a method to measure the metallicity of mid- to late-M dwarfs from moderate resolution (R~2000) K-band (2.2 microns) spectra. We calibrate our formula using 44 wide binaries containing an F, G, K, or early M primary of known metallicity and a mid- to late-M dwarf companion. We show that similar features and techniques used for early M dwarfs are still effective for late-M dwarfs. Our revised calibration is accurate to 0.07 dex for M4.5-M9.5 dwarfs with -0.58<[Fe/H]<+0.56 and shows no systematic trends with spectral type, metallicity, or the method used to determine the primary star metallicity. We show that our method gives consistent metallicities for the components of M+M wide binaries. We verify that our new formula works for unresolved binaries by combining spectra of single stars. Lastly, we show that our calibration gives consistent metallicities with the Mann et al. (2013a) study for overlapping (M4-M5) stars, establishing that the two calibrations can be used in combination to determine metallicities across the entire M dwarf sequence.
Video endoscopic inguinal lymphadenectomy (VEIL): minimally invasive resection of inguinal lymph nodes
Tobias-Machado, M.;Tavares, Alessandro;Molina Jr, Wilson R.;Forseto Jr, Pedro H.;Juliano, Roberto V.;Wroclawski, Eric R.;
International braz j urol , 2006, DOI: 10.1590/S1677-55382006000300012
Abstract: objectives: describe and illustrate a new minimally invasive approach for the radical resection of inguinal lymph nodes. surgical technique: from the experience acquired in 7 operated cases, the video endoscopic inguinal lymphadenectomy (veil) technique was standardized in the following surgical steps: 1) positioning of the inferior member extended in abduction, 2) introduction of 3 work ports distal to the femoral triangle, 3) expansion of the working space with gas, 4) retrograde separation of the skin flap with a harmonic scalpel, 5) identification and dissection of the long saphenous vein until the oval fossa, 6) identification of the femoral artery, 7) distal ligature of the lymph node block at the femoral triangle vertex, 8) liberation of the lymph node tissue up to the great vessels above the femoral floor, 9) distal ligature of the long saphenous vein, 10) control of the saphenofemoral junction, 11) final liberation of the surgical specimen and endoscopic view showing that all the tissue of the region was resected, 12) removal of the surgical specimen through the initial orifice, 13) vacuum drainage and synthesis of the incisions. comments: the veil technique is feasible and allows the radical removal of inguinal lymph nodes in the same limits of conventional surgery dissection. the main anatomic repairs of open surgery can be identified by the endoscopic view, confirming the complete removal of the lymphatic tissue within the pre-established limits. preliminary results suggest that this technique can potentially reduce surgical morbidity. oncologic follow-up is yet premature to demonstrate equivalence on the oncologic point of view.
Hippocampal CA1 Transcriptional Profile of Sleep Deprivation: Relation to Aging and Stress
Nada M. Porter, Julia H. Bohannon, Meredith Curran-Rauhut, Heather M. Buechel, Amy L. S. Dowling, Lawrence D. Brewer, Jelena Popovic, Veronique Thibault, Susan D. Kraner, Kuey Chu Chen, Eric M. Blalock
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0040128
Abstract: Background Many aging changes seem similar to those elicited by sleep-deprivation and psychosocial stress. Further, sleep architecture changes with age suggest an age-related loss of sleep. Here, we hypothesized that sleep deprivation in young subjects would elicit both stress and aging-like transcriptional responses. Methodology/Principal Findings F344 rats were divided into control and sleep deprivation groups. Body weight, adrenal weight, corticosterone level and hippocampal CA1 transcriptional profiles were measured. A second group of animals was exposed to novel environment stress (NES), and their hippocampal transcriptional profiles measured. A third cohort exposed to control or SD was used to validate transcriptional results with Western blots. Microarray results were statistically contrasted with prior transcriptional studies. Microarray results pointed to sleep pressure signaling and macromolecular synthesis disruptions in the hippocampal CA1 region. Animals exposed to NES recapitulated nearly one third of the SD transcriptional profile. However, the SD -aging relationship was more complex. Compared to aging, SD profiles influenced a significant subset of genes. mRNA associated with neurogenesis and energy pathways showed agreement between aging and SD, while immune, glial, and macromolecular synthesis pathways showed SD profiles that opposed those seen in aging. Conclusions/Significance We conclude that although NES and SD exert similar transcriptional changes, selective presynaptic release machinery and Homer1 expression changes are seen in SD. Among other changes, the marked decrease in Homer1 expression with age may represent an important divergence between young and aged brain response to SD. Based on this, it seems reasonable to conclude that therapeutic strategies designed to promote sleep in young subjects may have off-target effects in the aged. Finally, this work identifies presynaptic vesicular release and intercellular adhesion molecular signatures as novel therapeutic targets to counter effects of SD in young subjects.
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