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Search Results: 1 - 10 of 463732 matches for " Stephanie A. Moeckel-Cole "
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Effects of Atorvastatin on Resting and Peak Exercise Blood Pressure among Normotensive Men and Women
Amanda L. Zaleski,Marianne L. Mentch,Linda S. Pescatello,Beth A. Taylor,Jeffrey A. Capizzi,Adam S. Grimaldi,Priscilla M. Clarkson,Stephanie A. Moeckel-Cole,Stuart R. Chipkin,Justin Keadle,Charles Michael White,Paul D. Thompson
Cholesterol , 2014, DOI: 10.1155/2014/720507
Abstract: Statins are the most widely prescribed and effective medication for reducing low density lipoprotein cholesterol. Statins may also lower resting blood pressure (BP); however, results are inconsistent. We sought to determine if the maximum dose of atorvastatin reduces resting BP and the peak systolic BP (SBP) achieved on a graded exercise stress test (GEST) among a large sample of 419 healthy men (48%) and women (52%). Subjects (419, ?yr) were double-blinded and randomized to 80?mgd?1 of atorvastatin () or placebo () for 6?mo. Among the total sample, there were no differences in resting BP (SBP, ; diastolic BP [DBP], ; mean arterial pressure (); or peak SBP on a GEST ()) over 6?mo, regardless of drug treatment group. However, among women on atorvastatin, resting SBP/DBP (?mmHg, ?mmHg, ) and peak SBP on a GEST (?mmHg, ) were lower versus men. Atorvastatin lowered resting BP 3-4?mmHg and peak SBP on a GEST ~7?mmHg more among women than men over 6?mo of treatment. The inconsistent findings regarding the antihypertensive effects of statins may be partially explained by not accounting for sex effects. 1. Introduction Statins are the most commonly prescribed and effective medication for reducing low density lipoprotein (LDL) cholesterol and, consequently, lowering cardiovascular disease (CVD) risk [1]. Interestingly, statins may produce other nonlipid, pleiotropic health benefits that may additionally lower CVD risk [2–8]. For example, they may decrease resting blood pressure (BP), which could have a substantial public health impact because hypertension affects one in three U.S. adults and one billion people worldwide [9, 10] and is a major risk factor for heart disease, stroke, congestive heart failure, and kidney disease [11, 12]. Indeed, a recent review has shown that statins lower systolic blood pressure (SBP) up to 8.0?mmHg in patients with dyslipidemia and normal BP; 6.0?mmHg in patients without dyslipidemia and with hypertension; and 13.7?mmHg in patients with dyslipidemia and hypertension [2]. However, other reports have reported no effect of statins on resting BP, and thus results are inconsistent regarding the influence of statin therapy on resting BP [13–15]. These inconsistencies could be attributable to a very small effect of statins on resting BP, such that the benefits of statins on BP may only be apparent during conditions in which BP is augmented, such as exercise. Although a hypertensive response to exercise is predictive of developing future hypertension and increases CVD risk, to the best of our knowledge the effect of statins on the peak
First-pass perfusion CMR two days after infarction predicts severity of functional impairment six weeks later in the rat heart
Daniel J Stuckey, Carolyn A Carr, Stephanie J Meader, Damian J Tyler, Mark A Cole, Kieran Clarke
Journal of Cardiovascular Magnetic Resonance , 2011, DOI: 10.1186/1532-429x-13-38
Abstract: In isolated perfused rat hearts, contrast agent infusion gave uniform signal enhancement throughout the myocardium. Occlusion of the left anterior descending coronary artery significantly reduced the rate of signal enhancement in anterior regions of the heart, demonstrating that the first-pass method was sensitive to perfusion deficits. In vivo measurements of myocardial morphology, function, perfusion and viability were made at 2 and 8 days after infarction. Morphology and function were further assessed using cine-MRI at 42 days. The perfusion delay was larger in rat hearts that went on to develop greater functional impairment, demonstrating that first-pass CMR can be used as an early indicator of infarct severity. First-pass CMR at 2 and 8 days following infarction better predicted outcome than cardiac ejection fraction, end diastolic volume or end systolic volume.First-pass CMR provides a predictive measure of the severity of myocardial impairment caused by infarction in a rodent model of heart failure.Non-invasive, in vivo measurements of cardiac morphology, viability and function have revolutionised our understanding of cardiac disease [1-3]. In combination, echocardiography, angiography, PET, SPECT, CT and CMR can be used to measure wall and valve motion, cavity volumes, aortic and coronary blood flows, tissue perfusion and cardiac metabolism [1-5]. CMR offers excellent soft tissue contrast, coupled with high temporal and spatial resolution, allowing accurate measurement of cavity volumes, wall thickness and ejection fraction. Further, infarct size and transmurality, measured using CMR shortly after systemic infusion of the contrast agent gadolinium-diethylenetriaminepentaacetate (DTPA), strongly correlates with progression to heart failure and patient mortality [2,5-8]. MR imaging of the first-pass of a bolus infusion of Gd-DTPA has become a standard clinical method for identifying under-perfused regions of the human heart and accurately predicts the severity
Does sub-cluster merging accelerate mass segregation in local star formation?
Nickolas Moeckel,Ian A. Bonnell
Physics , 2009, DOI: 10.1111/j.1365-2966.2009.15499.x
Abstract: The nearest site of massive star formation in Orion is dominated by the Trapezium subsystem, with its four OB stars and numerous companions. The question of how these stars came to be in such close proximity has implications for our understanding of massive star formation and early cluster evolution. A promising route toward rapid mass segregation was proposed by McMillan et al. (2007), who showed that the merger product of faster-evolving sub clusters can inherit their apparent dynamical age from their progenitors. In this paper we briefly consider this process at a size and time scale more suited for local and perhaps more typical star formation, with stellar numbers from the hundreds to thousands. We find that for reasonable ages and cluster sizes, the merger of sub-clusters can indeed lead to compact configurations of the most massive stars, a signal seen both in Nature and in large-scale hydrodynamic simulations of star formation from collapsing molecular clouds, and that sub-virial initial conditions can make an un-merged cluster display a similar type of mass segregation. Additionally, we discuss a variation of the minimum spanning tree mass-segregation technique introduced by Allison et al. (2009).
Limits on initial mass segregation in young clusters
Nickolas Moeckel,Ian A. Bonnell
Physics , 2009, DOI: 10.1111/j.1365-2966.2009.14813.x
Abstract: Mass segregation is observed in many star clusters, including several that are less than a few Myr old. Timescale arguments are frequently used to argue that these clusters must be displaying primordial segregation, because they are too young to be dynamically relaxed. Looking at this argument from the other side, the youth of these clusters and the limited time available to mix spatially distinct populations of stars can provide constraints on the amount of initial segregation that is consistent with current observations. We present n-body experiments testing this idea, and discuss the implications of our results for theories of star formation. For system ages less than a few crossing times, we show that star formation scenarios predicting general primordial mass segregation are inconsistent with observed segregation levels.
Primordial triples and collisions of massive stars
Nickolas Moeckel,Ian A. Bonnell
Physics , 2013,
Abstract: Massive stars are known to have a high multiplicity, with examples of higher order multiples among the nearest and best studied objects. In this paper we study hierarchical multiple systems (an inner binary as a component of a wider binary) of massive stars in a clustered environment, in which a system with a size of 100--1000 au will undergo many close encounters during the short lifetime of a massive star. Using two types of N-body experiment we determine the post-formation collision probabilities of these massive hierarchies. We find that, depending on the specifics of the environment, the hierarchy, and the amount of time that is allowed to pass, tens of percent of hierarchies will experience a collision, typically between the two stars of the inner binary. In addition to collisions, clusters hosting a hierarchical massive system produce high velocity runaways at an enhanced rate. The primordial multiplicity specifics of massive stars appear to play a key role in the generation of these relatively small number events in cluster simulations, complicating their use as diagnostics of a cluster's history.
Escaping stars from young low-N clusters
Carsten Weidner,Ian A. Bonnell,Nickolas Moeckel
Physics , 2010, DOI: 10.1111/j.1365-2966.2010.17567.x
Abstract: With the use of N-body calculations the amount and properties of escaping stars from low-N (N = 100 and 1000) young embedded star clusters prior to gas expulsion are studied over the first 5 Myr of their existence. Besides the number of stars also different initial radii and binary populations are examined as well as virialised and collapsing clusters. It is found that these clusters can loose substantial amounts (up to 20%) of stars within 5 Myr with considerable velocities up to more than 100 km/s. Even with their mean velocities between 2 and 8 km/s these stars will still be travelling between 2 and 30 pc during the 5 Myr. Therefore can large amounts of distributed stars in star-forming regions not necessarily be counted as evidence for the isolated formation of stars.
Optimizing production of serially diluted compounds and distribution to multiple targets
Cole O. Harris,Stephanie L. Schweiker
Journal of Analytical Methods in Chemistry , 2001, DOI: 10.1155/s1463924601000220
Abstract: The need for a multiple-target compound selectivity programme led to the establishment of a single robotic system that produces a compound's serial dilution and its distribution to multiple replicate assay plates. A Genesis RSP 150 integrated into a Zymate Laboratory Automation System XP produced the serial dilutions, and the subsequent replicate assay plates were produced quickly and accurately by an efficient use of the carousels and rapid plate. Currently, this process allows for the production of over 200 serial dilution assay plates in a workday.
The rapid dispersal of low-mass virialised clusters
Nickolas Moeckel,Christopher Holland,Cathie J. Clarke,Ian A. Bonnell
Physics , 2012, DOI: 10.1111/j.1365-2966.2012.21494.x
Abstract: Infant mortality brought about by the expulsion of a star cluster's natal gas is widely invoked to explain cluster statistics at different ages. While a well studied problem, most recent studies of gas expulsion's effect on a cluster have focused on massive clusters, with stellar counts of order $10^4$. Here we argue that the evolutionary timescales associated with the compact low-mass clusters typical of the median cluster in the Solar neighborhood are short enough that significant dynamical evolution can take place over the ages usually associated with gas expulsion. To test this we perform {\it N}-body simulations of the dynamics of a very young star forming region, with initial conditions drawn from a large-scale hydrodynamic simulation of gravitational collapse and fragmentation. The subclusters we analyse, with populations of a few hundred stars, have high local star formation efficiencies and are roughly virialised even after the gas is removed. Over 10 Myr they expand to a similar degree as would be expected from gas expulsion if they were initially gas-rich, but the expansion is purely due to the internal stellar dynamics of the young clusters. The expansion is such that the stellar densities at 2 Myr match those of YSOs in the Solar neighborhood. We argue that at the low-mass end of the cluster mass spectrum, a deficit of clusters at 10s of Myr does not necessarily imply gas expulsion as a disruption mechanism.
The 2MASS Color-Magnitude Diagram of the Center of the Sagittarius Dwarf Galaxy: Photometric Measurements of a Surprisingly High Mean Metallicity
A. A. Cole
Physics , 2001, DOI: 10.1086/323723
Abstract: We present the Two Micron All Sky Survey (2MASS) (J-K, K) color-magnitude diagram for the region within 1 degree of the center of the Sagittarius dwarf spheroidal galaxy. Using the slope of the red giant branch (RGB), we determine a mean metallicity for the main stellar population of [Fe/H] = -0.5 +/-0.2. The Sagittarius RGB possesses a blue tail that overlaps with the foreground Milky Way giant branch, and suggests that approximately 1/3 of the RGB is more metal-poor than [Fe/H] = -1. Direct comparison to the Large Magellanic Cloud confirms the metal-rich nature of the bulk of the Sagittarius population. Our result is marginally consistent with the even higher metallicities determined from high-resolution spectroscopy.
Solutions associated with the point symmetries of the hyperbolic Ernst equation
Sebastian Moeckel
Physics , 2013,
Abstract: The continuous point symmetry algebra of the hyperbolic Ernst equation is presented. In a second step the corresponding group transformations are considered. Accordingly, the solutions of the hyperbolic Ernst equation that are invariant under Lie point symmetries, are constructed from the related invariant surface conditions. Furthermore, all these solutions are revealed to be related to solutions of the Euler-Poisson-Darboux equation by a simple coordinate transformation. The parallels of these results to coordinate transformations, which are important in the context of colliding plane wave space times, are pointed out.
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