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Search Results: 1 - 10 of 525388 matches for " David M. O’Sullivan "
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Electromyographic analysis of the three subdivisions of gluteus medius during weight-bearing exercises
Kieran O'Sullivan, Sharon M Smith, David Sainsbury
Sports Medicine, Arthroscopy, Rehabilitation, Therapy & Technology , 2010, DOI: 10.1186/1758-2555-2-17
Abstract: A single session, repeated-measures design. The activity of each GM subdivision was measured in 15 pain-free subjects using surface electromyography (sEMG) during three weight-bearing exercises; wall squat (WS), pelvic drop (PD) and wall press (WP). Muscle activity was expressed relative to maximum voluntary isometric contraction (MVIC). Differences in muscle activation were determined using one-way repeated measures ANOVA with post-hoc Bonferroni analysis.The activation of each GM subdivision during the exercises was significantly different (interaction effect; p < 0.001). There were also significant main effects for muscle subdivision (p < 0.001) and for exercise (p < 0.001). The exercises were progressively more demanding from WS to PD to WP. The exercises caused significantly greater activation of the middle and posterior subdivisions than the anterior subdivision, with the WP significantly increasing the activation of the posterior subdivision (all p < 0.05).Posterior GM displayed higher activation across all three exercises than both anterior and middle GM. The WP produced the highest %MVIC activation for all GM subdivisions, and this was most pronounced for posterior GM. Clinicians may use these results to effectively progress strengthening exercises for GM in the rehabilitation of lower extremity injuries.The primary role of gluteus medius (GM) is to stabilise the pelvis and control femoral motion during dynamic lower extremity motion [1-3]. Clinically, dysfunction of GM has been implicated in numerous musculoskeletal disorders including low back pain, patellofemoral pain syndrome and numerous other lower limb injuries [1,4-6]. Addressing dysfunction of hip muscles such as GM can significantly improve lower limb kinematics, assist in injury prevention, improve athletic performance and result in decreased pain [2,5-10].Gluteus medius attaches to the entire length of the iliac crest, the external ilium between the posterior and anterior gluteal lines, the glut
The impact of sloshing on the intra-group medium and old radio lobe of NGC 5044
Ewan O'Sullivan,Laurence P. David,Jan M. Vrtilek
Physics , 2013, DOI: 10.1093/mnras/stt1926
Abstract: We present temperature and abundance maps of the central 125 kpc of the NGC 5044 galaxy group, based an a deep XMM-Newton observation. The abundance map reveals an asymmetrical abundance structure, with the centroid of the highest abundance gas offset ~22 kpc northwest of the galaxy centre, and moderate abundances extending almost twice as far to the southeast than in any other direction. The abundance distribution is closely correlated with two previously-identified cold fronts and an arc--shaped region of surface brightness excess, and it appears that sloshing, induced by a previous tidal encounter, has produced both the abundance and surface brightness features. Sloshing dominates the uplift of heavy elements from the group core on large scales, and we estimate that the southeast extension (the tail of the sloshing spiral) contains at least 1.2x10^5 solar masses more iron than would be expected of gas at its radius. Placing limits on the age of the encounter we find that if, as previously suggested, the disturbed spiral galaxy NGC 5054 was the perturber, it must have been moving supersonically when it transited the group core. We also examine the spectral properties of emission from the old, detached radio lobe southeast of NGC 5044, and find that they are consistent with a purely thermal origin, ruling out this structure as a significant source of spectrally hard inverse-Compton emission.
The Impact of Enteric Contrast on Radiologist Confidence in Intravenously Enhanced MDCT of the Abdomen and Pelvis: A Randomized Controlled Trial  [PDF]
Christopher M. Garcia, Steven Boe, Bret Coughlin, David M. OSullivan, Douglas Moote, Michael T. O’Loughlin, Devika Jajoo, Steve Lee
Advances in Computed Tomography (ACT) , 2014, DOI: 10.4236/act.2014.32004
Abstract:

After Institutional Review Board approval, 109 patients ≥ 18 years old undergoing intravenously enhanced Computed Tomography (CT) of the abdomen and pelvis were prospectively enrolled and randomized into two arms. Patients with a history of inflammatory bowel disease, Crohn disease and ulcerative colitis were excluded. The control arm received routine enteric contrast and intravenous contrast. The experimental arm did not receive oral contrast, but received the standard dose of intravenous (IV) contrast. One of four experienced body radiologists reviewed the studies and rated his/her confidence on a scale of 1 (no confidence) to 10 (all confident findings have been made). Confidence levels were compared between groups. The 109 subjects were distributed 54 (49.5%) in the control arm and 55 (50.5%) in the experimental arm. The average confidence level in the control arm was 8.7 ± 0.9 versus 8.4 ± 1.1 in the experimental arm, which is not statistically significant (p value = 0.09). Among radiologists, the average confidence levels ranged from 6 - 10 in the control arm and 7 - 10 in the experimental arm. No examinations were repeated for technical considerations in either group. No studies were repeated in the experimental group in order to administer oral contrast. When each radiologist was compared to the others, there were no differences in confidence level between pairs in the control arm; however, there were statistically significant differences in confidence level among three pairs of radiologists for the experimental arm. There was no statistically significant difference in radiologist confidence level between intravenously enhanced abdomen and pelvis CTs with enteric contrast and without enteric contrast.

An XMM-Newton observation of the galaxy group MKW 4
E. O'Sullivan,J. M. Vrtilek,A. M. Read,L. P. David,T. J. Ponman
Physics , 2003, DOI: 10.1046/j.1365-2966.2003.07108.x
Abstract: We present an X-ray study of the galaxy group or poor cluster MKW 4. Working with XMM data we examine the distribution and properties of the hot gas which makes up the group halo. The inner halo shows some signs of structure, with circular or elliptical beta models providing a poor fit to the surface brightness profile. This may be evidence of large scale motion in the inner halo, but we do not find evidence of sharp fronts or edges in the emission. The temperature of the halo declines in the core, with deprojected spectral fits showing a central temperature of ~1.3 keV compared to ~3 keV at 100 kpc. In the central ~30 kpc of the group multi-temperature spectral models are required to fit the data, but they indicate a lack of gas at low temperatures. Steady state cooling flow models provide poor fits to the inner regions of the group and the estimated cooling time of the gas is long except within the central dominant galaxy, NGC 4073. Abundance profiles show a sharp increase in the core of the group, with mean abundance rising by a factor of two in the centre of NGC 4073. Fitting individual elements shows the same trend, with high values of Fe, Si and S in the core. We estimate that ~50% of the Fe in the central 40 kpc was injected by SNIa, in agreement with previous ASCA studies. Using our best fitting surface brightness and temperature models, we calculate the mass, gas fraction, entropy and mass-to-light ratio of the group. At 100 kpc (~0.1 virial radii) the total mass and gas entropy of the system (~2x10^13 Msol and ~300 keV cm^2) are quite comparable to those of other systems of similar temperature, but the gas fraction is rather low (~1%). We conclude that MKW 4 is a fairly relaxed group, which has developed a strong central temperature gradient but not a large-scale cooling flow.
Identifying an outbreak of a novel swine disease using test requests for porcine reproductive and respiratory syndrome as a syndromic surveillance tool
Terri L OSullivan, Robert M Friendship, David L Pearl, Beverly McEwen, Catherine E Dewey
BMC Veterinary Research , 2012, DOI: 10.1186/1746-6148-8-192
Abstract: Retrospective data were collected from the Animal Health Laboratory (AHL) at the University of Guelph, Guelph, Ontario Canada and were comprised of weekly counts of PRRSV ELISA and PRRSV PCR diagnostic tests requested by swine practitioners from 2000–2007. The results of the PRRSV ELISA and PRRSV PCRs were analysed separately in two models using logistic regression with the dependent variables being: the weekly probability of PRRSV ELISA positivity, and the weekly probability of PRRSV PCR positivity, respectively. The weekly probability of PRRSV PCR positivity decreased during the PVCAD outbreak (OR=0.66, P=0.01). The weekly probability of PRRSV ELISA positivity was not associated with the PCVAD outbreak.The results of this study showed that during the PCVAD outbreak in Ontario from December 2004-May 2006, the probability of a positive PRRSV PCR at the AHL decreased. We conclude that when a decrease in test positivity occurs for a known disease, it may suggest that a new disease agent is emerging in the population. Hence, monitoring the test results of commonly used first-order tests for a known disease (e.g. PRRSV) has the potential to be a unique form of syndromic data for the timely identification of novel disease outbreaks in swine populations.The information captured by veterinary diagnostic laboratories generates an immense database of animal health information and has contributed significantly to the collective knowledge of animal diseases. In addition to playing a role in determining disease etiology, the data are crucial in providing essential health information for disease monitoring and passive disease surveillance systems of livestock industries worldwide [1-3]. In response to the need for improving and implementing coordinated disease surveillance for Canadian livestock sectors, the Canadian Animal Health Surveillance Network (CAHSN) was established and veterinary diagnostic laboratory data contribute significantly to the network [4]. The use of laborat
A deep Chandra observation of the poor cluster AWM 4 - I. Properties of the central radio galaxy and its effects on the intracluster medium
Ewan O'Sullivan,Simona Giacintucci,Laurence P. David,Jan M. Vrtilek,Somak Raychaudhury
Physics , 2010, DOI: 10.1111/j.1365-2966.2010.16895.x
Abstract: Using observations from the Chandra X-ray Observatory and Giant Metrewave Radio Telescope, we examine the interaction between the intracluster medium and central radio source in the poor cluster AWM 4. In the Chandra observation a small cool core or galactic corona is resolved coincident with the radio core. This corona is capable of fuelling the active nucleus, but must be inefficiently heated by jet interactions or conduction, possibly precluding a feedback relationship between the radio source and cluster. A lack of clearly detected X-ray cavities suggests that the radio lobes are only partially filled by relativistic plasma. We estimate a filling factor of phi=0.21 (3 sigma upper limit phi<0.42) for the better constrained east lobe. We consider the particle population in the jets and lobes, and find that the standard equipartition assumptions predict pressures and ages which agree poorly with X-ray estimates. Including an electron population extending to low Lorentz factors either reduces (gamma_min=100) or removes (gamma_min=10) the pressure imbalance between the lobes and their environment. Pressure balance can also be achieved by entrainment of thermal gas, probably in the first few kiloparsecs of the radio jets. We estimate the mechanical power output of the radio galaxy, and find it to be marginally capable of balancing radiative cooling.
A deep Chandra observation of the poor cluster AWM4 - II. The role of the radio jets in enriching the intra-cluster medium
Ewan O'Sullivan,Simona Giacintucci,Laurence P. David,Jan M. Vrtilek,Somak Raychaudhury
Physics , 2010, DOI: 10.1111/j.1365-2966.2010.17812.x
Abstract: We use a Chandra observation of the poor cluster AWM4 to map the temperature and abundance of the intra-cluster medium, so as to examine the influence of the central radio galaxy on its environment. While the cluster core is generally enriched to near-solar abundances, we find evidence of super-solar abundances correlated with the radio jets, extending ~35 kpc from the core of the central dominant galaxy NGC 6051 along its minor axis. We conclude that the enriched gas has been transported out of the central galaxy through the action of the radio source. We estimate the excess mass of iron in the entrained gas to be ~1.4x10^6 Msol, and find that this can be produced in the core of NGC 6051 within the timescale of the AGN outburst. The energy required to transport this gas to its current location is ~4.5x10^57 erg, a significant fraction of the estimated total mechanical energy output of the AGN, though this estimate is dependent on the degree of enrichment of the uplifted gas. The larger near-solar abundance region is also compatible with enrichment by metals mixed outward from NGC 6051 over a much longer timescale.
tRNA Gene Identity Affects Nuclear Positioning
Chris D. M. Rodley, Dave A. Pai, Tyrone A. Mills, David R. Engelke, Justin M. O'Sullivan
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0029267
Abstract: The three-dimensional organization of genomes is dynamic and plays a critical role in the regulation of cellular development and phenotypes. Here we use proximity-based ligation methods (i.e. chromosome conformation capture [3C] and circularized chromosome confrmation capture [4C]) to explore the spatial organization of tRNA genes and their locus-specific interactions with the ribosomal DNA. Directed replacement of one lysine and two leucine tRNA loci shows that tRNA spatial organization depends on both tRNA coding sequence identity and the surrounding chromosomal loci. These observations support a model whereby the three-dimensional, spatial organization of tRNA loci within the nucleus utilizes tRNA gene-specific signals to affect local interactions, though broader organization of chromosomal regions are determined by factors outside the tRNA genes themselves.
Cold fronts and metal anisotropies in the X-ray cool core of the galaxy cluster Zw1742+3306
S. Ettori,F. Gastaldello,M. Gitti,E. O'Sullivan,M. Gaspari,F. Brighenti,L. David,A. C. Edge
Physics , 2013, DOI: 10.1051/0004-6361/201321107
Abstract: (Context) In recent years, our understanding of the cool cores of galaxy clusters has changed. Once thought to be relatively simple places where gas cools and flows toward the centre, now they are believed to be very dynamic places where heating from the central Active Galactic Nucleus (AGN) and cooling, as inferred from active star formation, molecular gas, and Halpha nebulosity, find an uneasy energetic balance. (Aims) We want to characterize the X-ray properties of the nearby cool-core cluster Zw1742+3306, selected because it is bright at X-ray (with a flux greater than 1e-11 erg/s/cm2 in the 0.1-2.4 keV band) and Halpha wavelengths (Halpha luminosity > 1e40 erg/s). (Methods) We used Chandra data to analyze the spatial and spectral properties of the cool core of Zw1742+3306, a galaxy cluster at z=0.0757 that emits in Halpha and presents the brightest central galaxy located in a diffuse X-ray emission with multiple peaks in surface brightness. (Results) We show that the X-ray cool core of the galaxy cluster Zw1742+3306 is thermodynamically very active with evidence of cold fronts and a weak shock in the surface brightness map and of an apparently coherent, elongated structure with metallicity greater than the value measured in the surrounding ambient gas by about 50 per cent. This anisotropic structure is 280 x 90 kpc2 and is aligned with the cold fronts and with the X-ray emission on larger scales. We suggest that all these peculiarities in the X-ray emission of Zw1742+3306 are either a very fine-tuned output of a sloshing gas in the cluster core or the product of a metal-rich outflow from the central AGN.
AGN Feedback in the Compact Group of Galaxies HCG 62 - as revealed by Chandra, XMM and GMRT data
M. Gitti,E. O'Sullivan,S. Giacintucci,L. P. David,J. M. Vrtilek,S. Raychaudhury,P. E. J. Nulsen
Physics , 2009, DOI: 10.1063/1.3293044
Abstract: As a part of an ongoing study of a sample of galaxy groups showing evidence for AGN/hot gas interaction, we report on the preliminary results of an analysis of new XMM and GMRT data of the X-ray bright compact group HCG 62. This is one of the few groups known to possess very clear, small X-ray cavities in the inner region as shown by the existing Chandra image. At higher frequencies (>1.4 GHz) the cavities show minimal if any radio emission, but the radio appears clearly at lower frequencies (<610 MHz). We compare and discuss the morphology and spectral properties of the gas and of the radio source. We find that the cavities are close to pressure balance, and that the jets have a "light" hadronic content. By extracting X-ray surface brightness and temperature profiles, we also identify a shock front located around 35 kpc to the south-west of the group center.
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