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Search Results: 1 - 10 of 239737 matches for " Gilbert Andrew R "
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Hard X-ray and ultraviolet emission during the 2011 June 7 solar flare
Andrew R. Inglis,Holly R. Gilbert
Physics , 2013, DOI: 10.1088/0004-637X/777/1/30
Abstract: The relationship between X-ray and UV emission during flares, particularly in the context of quasi-periodic pulsations, remains unclear. To address this, we study the impulsive X-ray and UV emission during the eruptive flare of 2011 June 7 utilising X-ray imaging from RHESSI and UV 1700A imaging from SDO/AIA. This event is associated with quasi-periodic pulsations in X-ray and possibly UV emission, as well as substantial parallel and perpendicular motion of the hard X-ray footpoints. The motion of the footpoints parallel to the flare ribbons is unusual; it is shown to reverse direction on at least two occasions. However, there is no associated short-timescale motion of the UV bright regions. Additionally, we find that the locations of the brightest X-ray and UV regions are different, particularly during the early portion of the flare impulsive phase, despite their integrated emission being strongly correlated in time. Correlation analysis of measured flare properties, such as the footpoint separation, flare shear, photospheric magnetic field and coronal reconnection rate, reveals that - in the impulsive phase - the 25 - 50 keV hard X-ray flux is only weakly correlated with these properties, in contrast to previous studies. We characterise this event in terms of long-term behaviour, where the X-ray nonthermal, thermal, and UV emission sources appear temporally and spatially consistent, and short-term behaviour, where the emission sources are inconsistent and quasi-periodic pulsations are a dominant feature requiring explanation. We suggest that the short timescale behaviour of hard X-ray footpoints, and the nature of the observed quasi-periodic pulsations, is determined by fundamental, as-yet unobserved properties of the reconnection region and particle acceleration sites. This presents a challenge for current three-dimensional flare reconnection models.
MRI structural findings in schizophrenia
Gilbert Andrew R,Keshavan Matcheri S
Revista Brasileira de Psiquiatria , 2001,
Predictions of the causal entropic principle for environmental conditions of the universe
Cline, James M.;Frey, Andrew R.;Holder, Gilbert
High Energy Physics - Phenomenology , 2007, DOI: 10.1103/PhysRevD.77.063520
Abstract: The causal entropic principle has been proposed as a superior alternative to the anthropic principle for understanding the magnitude of the cosmological constant. In this approach, the probability to create observers is assumed to be proportional to the entropy production \Delta S in a maximal causally connected region -- the causal diamond. We improve on the original treatment by better quantifying the entropy production due to stars, using an analytic model for the star formation history which accurately accounts for changes in cosmological parameters. We calculate the dependence of \Delta S on the density contrast Q=\delta\rho/\rho, and find that our universe is much closer to the most probable value of Q than in the usual anthropic approach and that probabilities are relatively weakly dependent on this amplitude. In addition, we make first estimates of the dependence of \Delta S on the baryon fraction and overall matter abundance. Finally, we also explore the possibility that decays of dark matter, suggested by various observed gamma ray excesses, might produce a comparable amount of entropy to stars.
Is VATS Bullectomy and Pleurectomy an Effective Method for the Management of Spontaneous Pneumothorax?  [PDF]
Ramzi A. Addas, Farid M. Shamji, Sudhir R. Sundaresan, Patrick James Villeneuve, Andrew J. E. Seely, Sebastien Gilbert, Donna E. Maziak
Open Journal of Thoracic Surgery (OJTS) , 2016, DOI: 10.4236/ojts.2016.63005
Abstract: Spontaneous pneumothorax, primary or secondary, is a common medical emergency for which specific indications for surgical intervention are well defined in selected patients. The traditional surgical approach has been by limited thoracotomy using axillary or posterolateral incision. With the advent of video-assisted minimally invasive technique in the last 20 years the traditional approach is infrequently used. The definitive operation to prevent recurrent pneumothorax by surgical approach requires bullectomy and parietal pleurectomy. The recurrence rate after the traditional open surgical approach has been low at <2%. On the other hand, video-assisted thoracoscopic surgery, although better tolerated has a higher recurrence rate at 5% [1]. Information on post-operative morbidity and mortality are lacking. For this reason, we have reviewed our experience at one institution on the outcome of the VATS approach. We found that prolonged post- operative air leak is the most common complication and cigarette smoking remains an important associated factor.
Analyzing the Impact of Gender on Depictions of Touch in Early Childhood Textbooks
Andrew Gilbert,Shané Williams
Early Childhood Research & Practice , 2008,
Abstract: Early childhood contexts often enact “common-sense identities” that create and sustain the notion that teachers of young children are expressly female and heterosexual. It has also been argued that touch is a key difference between men and women in early childhood classrooms. This exploratory study examined 10 early childhood textbooks to determine whether images depicting touch enacted these common-sense notions. To investigate whether implicit gendered messages existed within the texts, images displaying touch between teachers and children were grouped according to three main recurrent themes: teacher touching child, child touching teacher, and mutually negotiated contact. Findings indicated that, although the images of male teachers were positive, troubling patterns did emerge concerning the type and nature of men’s contact with children. These patterns worked to reaffirm larger patriarchal structures at play in schools and society while simultaneously painting women as more suitable to nurture young children. Furthermore, the texts provided clear messages to beginning teachers that acceptable types of touch were delineated by gender. The article concludes with a discussion of the implications of these findings for early childhood preservice teacher education.
The Star Formation Histories of Local Group Dwarf Galaxies III. Characterizing Quenching in Low-Mass Galaxies
Daniel R. Weisz,Andrew E. Dolphin,Evan D. Skillman,Jon Holtzman,Karoline M. Gilbert,Julianne J. Dalcanton,Benjamin F. Williams
Physics , 2015, DOI: 10.1088/0004-637X/804/2/136
Abstract: We explore the quenching of low-mass galaxies (10^4 < Mstar < 10^8 Msun) as a function of lookback time using the star formation histories (SFHs) of 38 Local Group dwarf galaxies. The SFHs were derived from analyzing color-magnitude diagrams of resolved stellar populations in archival Hubble Space Telescope/Wide Field Planetary Camera 2 imaging. We find: (1) Lower mass galaxies quench earlier than higher mass galaxies; (2) Inside of virial radius there is no correlation between a satellite's current proximity to a massive host and its quenching epoch; (3) There are hints of systematic differences in quenching times of M31 and Milky Way (MW) satellites, although the sample sample size and uncertainties in the SFHs of M31 dwarfs prohibit definitive conclusions. Combined with literature results, we qualitatively consider the redshift evolution (z=0-1) of the quenched galaxy fraction over ~7 dex in stellar mass (10^4 < Mstar < 10^11.5 Msun). The quenched fraction of all galaxies generally increases toward the present, with both the lowest and highest mass systems exhibiting the largest quenched fractions at all redshifts. In contrast, galaxies between Mstar ~ 10^8-10^10 Msun have the lowest quenched fractions. We suggest that such intermediate-mass galaxies are the least efficient at quenching. Finally, we compare our quenching times with predictions for infall times of low-mass galaxies associated with the MW. We find that some of the lowest-mass satellites (e.g., CVn II, Leo IV) may have been quenched before infall while higher mass satellites (e.g., Leo I, Fornax) typically quench ~1-4 Gyr after infall.
The Star Formation Histories of Local Group Dwarf Galaxies II. Searching For Signatures of Reionization
Daniel R. Weisz,Andrew E. Dolphin,Evan D. Skillman,Jon Holtzman,Karoline M. Gilbert,Julianne J. Dalcanton,Benjamin F. Williams
Physics , 2014, DOI: 10.1088/0004-637X/789/2/148
Abstract: We search for signatures of reionization in the star formation histories (SFHs) of 38 Local Group dwarf galaxies (10$^4$ $<$ M$_{\star}$ $<$ 10$^9$ M$_{\odot}$). The SFHs are derived from color-magnitude diagrams using archival Hubble Space Telescope/Wide Field Planetary Camera 2 imaging. Only five quenched galaxies (And V, And VI, And XIII, Leo IV, Hercules) are consistent with forming the bulk of their stars before reionization, when full uncertainties are considered. Observations of 13 of the predicted `true fossils' identified by Bovill & Ricotti show that only two (Hercules and Leo IV) indicate star formation quenched by reionization. However, both are within the virial radius of the Milky Way and evidence of tidal disturbance complicates this interpretation. We argue that the late-time gas capture scenario posited by Ricotti for the low mass, gas-rich, and star-forming fossil candidate Leo T is observationally indistinguishable from simple gas retention. Given the ambiguity between environmental effects and reionization, the best reionization fossil candidates are quenched low mass field galaxies (e.g., KKR 25).
The Star Formation Histories of Local Group Dwarf Galaxies I. Hubble Space Telescope / Wide Field Planetary Camera 2 Observations
Daniel R. Weisz,Andrew E. Dolphin,Evan D. Skillman,Jon Holtzman,Karoline M. Gilbert,Julianne J. Dalcanton,Benjamin F. Williams
Physics , 2014, DOI: 10.1088/0004-637X/789/2/147
Abstract: We present uniformly measured star formation histories (SFHs) of 40 Local Group dwarf galaxies based on color-magnitude diagram (CMD) analysis from archival Hubble Space Telescope imaging. We demonstrate that accurate SFHs can be recovered from CMDs that do not reach the oldest main sequence turn-off (MSTO), but emphasize that the oldest MSTO is critical for precisely constraining the earliest epochs of star formation. We find that: (1) the average lifetime SFHs of dwarf spheroidals (dSphs) can be approximated by an exponentially declining SFH with $\tau$ $\sim$ 5 Gyr; (2) lower luminosity dSphs are less likely to have extended SFHs than more luminous dSphs; (3) the average SFHs of dwarf irregulars (dIrrs), transition dwarfs (dTrans), and dwarf ellipticals (dEs) can be approximated by the combination of an exponentially declining SFH ($\tau$ $\sim$ 3-4 Gyr) for lookback ages $>$ 10-12 Gyr ago and a constant SFH thereafter; (4) the observed fraction of stellar mass formed prior to z=2 ranges considerably (80\% for galaxies with M $<$ 10$^5$ M$_{\odot}$ to 30\% for galaxies with M$>$10$^7$ M$_{\odot}$) and is largely explained by environment; (5) the distinction between "ultra-faint" and "classical" dSphs is arbitrary; (6) LG dIrrs formed a significantly higher fraction of stellar mass prior to z=2 than the SDSS galaxies from Leiter 2012 and the SFHs from the abundance matching models of Behroozi et al. 2013. This may indicate higher than expected star-formation efficiencies at early times in low mass galaxies. Finally, we provide all the SFHs in tabulated electronic format for use by the community.
Application of RNAi to Genomic Drug Target Validation in Schistosomes
Alessandra Guidi?,Nuha R. Mansour?,Ross A. Paveley?,Ian M. Carruthers?,rémy Besnard?,Andrew L. Hopkins?,Ian H. Gilbert,Quentin D. Bickle
PLOS Neglected Tropical Diseases , 2015, DOI: 10.1371/journal.pntd.0003801
Abstract: Concerns over the possibility of resistance developing to praziquantel (PZQ), has stimulated efforts to develop new drugs for schistosomiasis. In addition to the development of improved whole organism screens, the success of RNA interference (RNAi) in schistosomes offers great promise for the identification of potential drug targets to initiate drug discovery. In this study we set out to contribute to RNAi based validation of putative drug targets. Initially a list of 24 target candidates was compiled based on the identification of putative essential genes in schistosomes orthologous of C. elegans essential genes. Knockdown of Calmodulin (Smp_026560.2) (Sm-Calm), that topped this list, produced a phenotype characterised by waves of contraction in adult worms but no phenotype in schistosomula. Knockdown of the atypical Protein Kinase C (Smp_096310) (Sm-aPKC) resulted in loss of viability in both schistosomula and adults and led us to focus our attention on other kinase genes that were identified in the above list and through whole organism screening of known kinase inhibitor sets followed by chemogenomic evaluation. RNAi knockdown of these kinase genes failed to affect adult worm viability but, like Sm-aPKC, knockdown of Polo-like kinase 1, Sm-PLK1 (Smp_009600) and p38-MAPK, Sm-MAPK p38 (Smp_133020) resulted in an increased mortality of schistosomula after 2-3 weeks, an effect more marked in the presence of human red blood cells (hRBC). For Sm-PLK-1 the same effects were seen with the specific inhibitor, BI2536, which also affected viable egg production in adult worms. For Sm-PLK-1 and Sm-aPKC the in vitro effects were reflected in lower recoveries in vivo. We conclude that the use of RNAi combined with culture with hRBC is a reliable method for evaluating genes important for larval development. However, in view of the slow manifestation of the effects of Sm-aPKC knockdown in adults and the lack of effects of Sm-PLK-1 and Sm-MAPK p38 on adult viability, these kinases may not represent suitable drug targets.
Receptive Anal Intercourse and HIV Infection  [PDF]
Gilbert R. Lavoie, John F. Fisher
World Journal of AIDS (WJA) , 2017, DOI: 10.4236/wja.2017.74023
Objective: Inform the public that receptive anal intercourse (RAI) is a key transmission route of the human immunodeficiency virus (HIV) epidemic in the United States. Method: The role of receptive anal intercourse (RAI) in this epidemic will be examined using the following approach: 1) Risk comparison of HIV transmission via RAI to the other major routes of transmission. 2) HIV transmission risks of RAI using some of the present risk reduction techniques. 3) HIV infection via anal intercourse among male youth. 4) HIV infection via anal intercourse among women. Results: Of the major transmission routes of HIV, receptive anal intercourse has the highest transmission risk for acquiring HIV infection. RAI is 2 times the risk of needle-sharing during injection drug use (IDU) and 17 times the risk of receptive vaginal intercourse. The estimated per act probability of acquiring HIV from an infected source by the exposure route of RAI is high in most circumstances: 1) Condoms alone only partially reduce the high risk of RAI. With the addition of pre-exposure prophylaxis (PrEP), the risk is further reduced. 2) When one or both partners are infected with a sexually transmitted disease (STD), even with condom use, the risks are very high. With the addition of PrEP the risks are reduced, but RAI still carries significant risks. 3) With exposure to acute HIV (high viral load) the risks of RAI are very high and remain significant even with condom use and PrEP. Anal intercourse often begins in adolescence; both genders are at risk. Conclusion: Public knowledge of the high transmission risks of receptive anal intercourse may likely result in a downward trend of new HIV infections and contribute to ending the epidemic.
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