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Search Results: 1 - 10 of 136668 matches for " Richard T. Chapman "
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Impact of Genetic Polymorphisms of SLC2A2, SLC2A5, and KHK on Metabolic Phenotypes in Hypertensive Individuals
MyPhuong T. Le, Maximilian T. Lobmeyer, Marcus Campbell, Jing Cheng, Zhiying Wang, Stephen T. Turner, Arlene B. Chapman, Eric Boerwinkle, John G. Gums, Yan Gong, Richard J. Johnson, Julie A. Johnson
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0052062
Abstract: Objective In the past few decades, consumption of added sugars has increased dramatically. Studies have linked high sugar intake with increased risk for a number of diseases. Importantly, fructose, a component of sugar, has been linked with the development of features of metabolic syndrome. This study determined if single nucleotide polymorphisms in genes involved in fructose transport (solute carrier family 2 facilitated glucose transporter, member 2 (SLC2A2) and solute carrier family 2 facilitated glucose/fructose transporter, member 5 (SLC2A5)) and metabolism (ketohexokinase (KHK)) affect inter-individual variability in metabolic phenotypes, such as increased serum uric acid levels. Materials/Methods The influence of SLC2A2, SLC2A5, and KHK SNPs on metabolic phenotypes was tested in 237 European Americans and 167 African Americans from the Pharmacogenomic Evaluation and Antihypertensive Responses (PEAR) study. Using baseline untreated fasting data, associations were considered significant if p≤0.005. These SNPs were then evaluated for potential replication (p≤0.05) using data from the Genetic Epidemiology of Responses to Antihypertensives (GERA) studies. Results SLC2A5 rs5438 was associated with an increase in serum uric acid in European American males. However, we were unable to replicate the association in GERA. The minor allele of SLC2A2 rs8192675 showed an association with lower high-density lipoproteins in European Americans (A/A: 51.0 mg/dL, A/G: 47.0 mg/dL, G/G: 41.5 mg/dL, p = 0.0034) in PEAR. The association between rs8192675 and lower high-density lipoproteins was replicated in the combined European American GERA study samples (A/A: 47.6 mg/dL, A/G: 48.6 mg/dL, G/G: 41.9 mg/dL, p = 0.0315). Conclusions The association between SLC2A2 rs8192675 and high-density lipoproteins suggests the polymorphism may play a role in influencing high-density lipoproteins and thus metabolic risk of cardiovascular disease.
Spin, the Classical Theory  [PDF]
Richard T. Hammond
Journal of Modern Physics (JMP) , 2012, DOI: 10.4236/jmp.2012.31001
Abstract: With the development of local gauge theories of gravitation, it became evident that intrinsic spin was an integral part of the theory. This gave spin a classical formulation that predicted the existence of a new kind of field, the torsion field. To date only one class of experiments has been developed to detect this field, a search for a long range dipole force. In this article, the torsion equations are de-coupled from the curved space of general relativity derived from basic principles using vector calculus and the theory of electromagnetism as a guide. The results are written in vector form so that they are readily available to experimentalists, paving the way for new kinds of experiments.
Probing the structure and dynamics of molecular clusters using rotational wavepackets
Gediminas Galinis,Cephise Cacho,Richard T. Chapman,Andrew M. Ellis,Marius Lewerenz,Luis G. Mendoza Luna,Russell S. Minns,Mirjana Mladenovic,Arnaud Rouzée,Emma Springate,I. C. Edmond Turcu,Mark J. Watkins,Klaus von Haeften
Physics , 2014, DOI: 10.1103/PhysRevLett.113.043004
Abstract: The chemical and physical properties of molecular clusters can heavily depend on their size, which makes them very attractive for the design of new materials with tailored properties. Deriving the structure and dynamics of clusters is therefore of major interest in science. Weakly bound clusters can be studied using conventional spectroscopic techniques, but the number of lines observed is often too small for a comprehensive structural analysis. Impulsive alignment generates rotational wavepackets, which provides simultaneous information on structure and dynamics, as has been demonstrated successfully for isolated molecules. Here, we apply this technique for the firsttime to clusters comprising of a molecule and a single helium atom. By forcing the population of high rotational levels in intense laser fields we demonstrate the generation of rich rotational line spectra for this system, establishing the highly delocalised structure and the coherence of rotational wavepacket propagation. Our findings enable studies of clusters of different sizes and complexity as well as incipient superfluidity effects using wavepacket methods.
Ramifications of Optical Pumping on the Interpretation of Time-Resolved Photoemission Experiments on Graphene
S?ren Ulstrup,Jens Christian Johannsen,Federico Cilento,Alberto Crepaldi,Jill A. Miwa,Michele Zacchigna,Cephise Cacho,Richard T. Chapman,Emma Springate,Felix Fromm,Christian Raidel,Thomas Seyller,Phil D. C. King,Fulvio Parmigiani,Marco Grioni,Philip Hofmann
Physics , 2015,
Abstract: In pump-probe time and angle-resolved photoemission spectroscopy (TR-ARPES) experiments the presence of the pump pulse adds a new level of complexity to the photoemission process in comparison to conventional ARPES. This is evidenced by pump-induced vacuum space-charge effects and surface photovoltages, as well as multiple pump excitations due to internal reflections in the sample-substrate system. These processes can severely affect a correct interpretation of the data by masking the out-of-equilibrium electron dynamics intrinsic to the sample. In this study, we show that such effects indeed influence TR-ARPES data of graphene on a silicon carbide (SiC) substrate. In particular, we find a time- and laser fluence-dependent spectral shift and broadening of the acquired spectra, and unambiguously show the presence of a double pump excitation. The dynamics of these effects is slower than the electron dynamics in the graphene sample, thereby permitting us to deconvolve the signals in the time domain. Our results demonstrate that complex pump-related processes should always be considered in the experimental setup and data analysis.
Observation of Ultrafast Free Carrier Dynamics in Single Layer MoS$_2$
Antonija Grubi?i? ?abo,Jill A. Miwa,Signe S. Gr?nborg,Jonathon M. Riley,Jens C. Johannsen,Cephise Cacho,Oliver Alexander,Richard T. Chapman,Emma Springate,Marco Grioni,Jeppe V. Lauritsen,Phil D. C. King,Philip Hofmann,S?ren Ulstrup
Physics , 2015, DOI: 10.1021/acs.nanolett.5b01967
Abstract: The dynamics of excited electrons and holes in single layer (SL) MoS$_2$ have so far been difficult to disentangle from the excitons that dominate the optical response of this material. Here, we use time- and angle-resolved photoemission spectroscopy for a SL of MoS$_2$ on a metallic substrate to directly measure the excited free carriers. This allows us to ascertain a direct quasiparticle band gap of 1.95 eV and determine an ultrafast (50 fs) extraction of excited free carriers via the metal in contact with the SL MoS$_2$. This process is of key importance for optoelectronic applications that rely on separated free carriers rather than excitons.
Inter-ELM pedestal evolution on MAST and impact of Resonant Magnetic Perturbations
R. Scannell,A. Kirk,I. T. Chapman
Physics , 2013, DOI: 10.1088/0741-3335/55/3/035013
Abstract: The peak pressure gradient in the pedestal (dPe/d{\psi}) on MAST varies little between edge localized modes (ELMs), although it varies between discharges due factors such as gas fuelling and plasma current. The pressure pedestal width in flux space on the high-field side (HFS), both during the inter-ELM period and amongst different plasma discharges is consistent with a scaling of . In flux space very similar dPe/d{\psi} and {\Delta}pe are observed on the HFS and low-field side (LFS) in single null configuration. This symmetry is broken by the application of resonant magnetic perturbations (RMPs). During ELM mitigation by application of RMPs changes in the edge transport barrier position and width are observed. These changes are dependent on the intensity of the RMP and on the toroidal location with respect to the RMP phase. An outward displacement of up to 30 mm and increase in the edge pedestal width of up to 50% with respect to the coils case off are observed. Increased particle transport causes a decrease in ne,ped, and hence Pe,ped, as is observed on other devices. The combination of an increase in {\Delta}pe on the LFS and decrease in Pe,ped results in significantly reduced LFS dPe/d{\psi} when these perturbations are applied to the plasma edge. A decrease in dPe/d{\psi} on the HFS is also observed due to RMP; however, this decrease is caused solely by the Pe,ped decrease whilst no expansion of {\Delta}pe on the HFS is observed.
Postoperative Pain Trajectories in Cardiac Surgery Patients
C. Richard Chapman,Ruth Zaslansky,Gary W. Donaldson,Amihay Shinfeld
Pain Research and Treatment , 2012, DOI: 10.1155/2012/608359
Abstract: Poorly controlled postoperative pain is a longstanding and costly problem in medicine. The purposes of this study were to characterize the acute pain trajectories over the first four postoperative days in 83 cardiac surgery patients with a mixed effects model of linear growth to determine whether statistically significant individual differences exist in these pain trajectories, and to compare the quality of measurement by trajectory with conventional pain measurement practices. The data conformed to a linear model that provided slope (rate of change) as a basis for comparing patients. Slopes varied significantly across patients, indicating that the direction and rate of change in pain during the first four days of recovery from surgery differed systematically across individuals. Of the 83 patients, 24 had decreasing pain after surgery, 24 had increasing pain, and the remaining 35 had approximately constant levels of pain over the four postoperative days. 1. Introduction Intense pain typically follows surgical procedures, and the control of postoperative pain is still a major challenge [1–9]. In 1998, nearly 32 million Americans underwent 41.5 million surgical procedures, and they spent on the average 5.1 days in hospital [10]. Nearly four decades ago, almost three-fourths of all patients reported moderate-to-severe pain following surgery [11], and one decade ago, this had not changed [12]. More conservatively, an estimated 50–60% of postsurgical patients currently receive inadequate pain control [13]. Failure to control postoperative pain adequately contributes to postoperative morbidity and mortality and drives up the cost of care [14–19]. Pain can persist for a long while after surgery, extending discomfort and slowing rehabilitation [20]. Uncontrolled pain following surgery appears to be a risk factor for the development of chronic pain [10, 21, 22]. Thirty-five of 85 postthoracotomy patients still had pain after one year [23]. Eisenberg et al. contacted patients months after coronary artery bypass grafting [24]. They found that 56% of patients had pain, and 72% of patients reported that the pain interfered with their daily activities. Good pain control during recovery from surgery requires good pain measurement in the individual patient. Unfortunately, current pain measurement methods suffer from low precision due to unreliability in scores within individuals [25]. Moreover, patients vary systematically and few patients resemble the population average. Postoperative pain normally changes with variation in tissue trauma, it is process dependent, and
Association between adherence to calcium-channel blocker and statin medications and likelihood of cardiovascular events among US managed care enrollees
Richard H Chapman, Jason Yeaw, Craig S Roberts
BMC Cardiovascular Disorders , 2010, DOI: 10.1186/1471-2261-10-29
Abstract: A retrospective cohort study was conducted using administrative claims data from the IMS LifeLink: US Health Plan Claims database, identifying adults already taking CCB or statin (but not both) who had an index event of either initiating treatment with SPAA or adding CCB to statin (or vice versa) between April 1, 2004 to August 31, 2005. Inclusion criteria included age 18+ years, continuously enrolled for minimum of 6 months prior and 18 months following treatment initiation, >1 diagnosis of hypertension, and no prescription claims for SPAA or added CCB or statin for 6 months prior. Exclusion criteria included >1 claim with missing or invalid days supplied, age 65+ years and not enrolled in Medicare Advantage, or history of prior CV events, cancer diagnosis, or chronic renal failure. The primary outcome measure was the rate of CV events (myocardial infarction, heart failure, angina, other ischemic heart disease, stroke, peripheral vascular disease, or revascularization procedure) from 6 to 18 months following index date, analyzed at three levels: 1) all adherent vs. non-adherent patients, 2) SPAA vs. dual-pill patients (regardless of adherence level), and 3) adherent SPAA, adherent dual-pill, and non-adherent SPAA patients vs. non-adherent dual-pill patients.Of 1,537 SPAA patients, 56.5% were adherent at 6 months, compared with 21.4% of the 17,910 CCB/statin patients (p < 0.001). Logistic regression found SPAA patients more likely to be adherent (OR = 4.7, p < 0.001) than CCB/statin patients. In Cox proportional hazards models, being adherent to either regimen was associated with significantly lower risk of CV event (HR = 0.77, p = 0.003). A similar effect was seen for SPAA vs. CCB/statin patients (HR = 0.68, p = 0.02). In a combined model, the risk of CV events was significantly lower for adherent CCB/statin patients (HR = 0.79, p = 0.01) and adherent SPAA patients (HR = 0.61, p = 0.03) compared to non-adherent CCB/statin patients.Patients receiving SPAA rather tha
Recensiones
Varndell, Gill,Guilaine, Jean,Harrison, Richard J.,Chapman, Bob
Trabajos de Prehistoria , 2012,
Abstract:
Somatosensory test responses in children with growing pains
Pathirana S, Champion D, Jaaniste T, Yee A, Chapman C
Journal of Pain Research , 2011, DOI: http://dx.doi.org/10.2147/JPR.S24875
Abstract: matosensory test responses in children with growing pains Original Research (2492) Total Article Views Authors: Pathirana S, Champion D, Jaaniste T, Yee A, Chapman C Published Date December 2011 Volume 2011:4 Pages 393 - 400 DOI: http://dx.doi.org/10.2147/JPR.S24875 Shanthi Pathirana1, David Champion1,2, Tiina Jaaniste1, Anthony Yee2, Cindy Chapman1 1Department of Anesthesia and Pain Medicine, 2Department of Rheumatology, Sydney Children's Hospital, Randwick, New South Wales, Australia Purpose: To further the understanding of growing pains (GP), in particular, the nature of this pain disorder. Methods: This study included 33 children aged 5–12 years who met criteria for GP (cases) and 29 children without GP of similar age and sex (controls). Nineteen controls were siblings of cases. GP was diagnosed by standard consensus questionnaires. A questionnaire addressed characteristics of the pain and family history of GP. Evidence for peripheral neuropathic disorder was tested by somatosensory testing and provocation tests of peripheral nerves. Somatosensory testing by a blinded researcher involved threshold determination and/or response magnitude to nonpainful stimuli including touch, dynamic brush, cold, vibration, and deep pressure applied to limb and abdominal sites. Results: Distributional, temporal, and quality characteristics of the pain were in accordance with published descriptions. There was no indication of primary musculoskeletal disorder. No evidence was found that GP is a peripheral neuropathic pain syndrome. There were minor but statistically significantly increased responses to cutaneous cold, vibration, and to deep pressure stimuli in cases compared to controls, evident in a wider distribution than the symptomatic lower limbs. Conclusion: GP is a regional pain syndrome with evidence in this study of mild widespread disorder of somatosensory processing.
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