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Search Results: 1 - 10 of 262557 matches for " D. I. Glazier "
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Measurement of polarisation transfer in hyperon photoproduction at MAMI
T. C. Jude,D. I. Glazier,D. P. Watts
Physics , 2008, DOI: 10.1142/S0217751X09044188
Abstract: The photoproduction of K+ mesons is an important challenge to recent QCD based chiral perturbation theories in the strange quark sector and is an important constraint on the nucleon excitation spectrum. We present preliminary data from a new high precision measurement using the Crystal Ball detector. The measurement pioneers a new technique for tagging strangeness using detailed cluster analysis in segmented calorimeters which has potential wider application at present and future hadron physics facilities.
Comment on "Evidence for narrow resonant structures at $W\approx$ 1.68 GeV and $W\approx$ 1.72 GeV in real Compton scattering off the proton"
D. Werthmüller,L. Witthauer,D. I. Glazier,B. Krusche
Physics , 2015, DOI: 10.1103/PhysRevC.92.069801
Abstract: We comment on the statement by Kuznetsov et al. that the structure around W=1.72 GeV seen in the beam asymmetry in Compton scattering off the proton is not observed in the total cross section of $\eta$ photoproduction on the neutron.
Dependence of the $^{12}$C($\vecγ$,pd) reaction on photon linear polarisation
D. P. Watts,J. R. M. Annand,R. Beck,D. Branford,D. Glazier,P. Grabmayr,K. Livingston,I. J. D. Macgregor,J. C. Mcgeorge,R. O. Owens
Physics , 2005, DOI: 10.1016/j.physletb.2007.02.013
Abstract: The sensitivity of the $^{12}$C$(\vec{\gamma},pd)$ reaction to photon linear polarisation has been determined at MAMI, giving the first measurement of the reaction for a nucleus heavier than $^{3}$He. Photon asymmetries and cross sections were measured for $E_{\gamma}$=170 to 350 MeV. For $E_{\gamma}$ below the $\Delta$ resonance, reactions leaving the residual $^{9}$Be near its ground state show a positive asymmetry of up to 0.3, similar to that observed for $^{3}$He suggesting a similar reaction mechanism for the two nuclei.
Gender differences in mental health service utilization among respondents reporting depression in a national health survey  [PDF]
Katherine L. W. Smith, Flora I. Matheson, Rahim Moineddin, James R. Dunn, Hong Lu, John Cairney, Richard H. Glazier
Health (Health) , 2013, DOI: 10.4236/health.2013.510212
Abstract:

This study examined whether people who self-reported depression sought mental health treatment in the year after being interviewed, and how gender affected utilization. Depression data were obtained from the Canadian Community Health Survey (2000-01), and linked to medical records in Ontario (n = 24,677). Overall, women had higher rates of mental health service utilization, but there were no gender differences in rates of specialist care. The gender difference in mental health contact was greater for those without depression, as opposed to those with depression. Among those without depression, women were significantly more likely than men to use mental health services; however, rates were similar for women and men with depression. This finding suggests that men may be more likely than women to delay seeing a doctor for minor mental health concerns, but will seek help once a problem reaches a threshold.

A simulation study of sample size for multilevel logistic regression models
Rahim Moineddin, Flora I Matheson, Richard H Glazier
BMC Medical Research Methodology , 2007, DOI: 10.1186/1471-2288-7-34
Abstract: In this paper simulation studies are used to assess the effect of varying sample size at both the individual and group level on the accuracy of the estimates of the parameters and variance components of multilevel logistic regression models. In addition, the influence of prevalence of the outcome and the intra-class correlation coefficient (ICC) is examined.The results show that the estimates of the fixed effect parameters are unbiased for 100 groups with group size of 50 or higher. The estimates of the variance covariance components are slightly biased even with 100 groups and group size of 50. The biases for both fixed and random effects are severe for group size of 5. The standard errors for fixed effect parameters are unbiased while for variance covariance components are underestimated. Results suggest that low prevalent events require larger sample sizes with at least a minimum of 100 groups and 50 individuals per group.We recommend using a minimum group size of 50 with at least 50 groups to produce valid estimates for multi-level logistic regression models. Group size should be adjusted under conditions where the prevalence of events is low such that the expected number of events in each group should be greater than one.The idea that individual action is shaped by macro-level forces was evident in sociological theories of psychiatric illness and delinquency arising out of the Chicago School [1,2]. These theories suggest that while individual risk factors can affect individual health and delinquent behavior, so also can the structure of the social environment in which we live. It is only in the last 20 years that these theories could be truly tested, when statistical models were developed that allowed researchers to examine the additive and interactive effects of individual-level and contextual features that affect sociological outcomes at the individual level. In the last ten years the use of multilevel models has burgeoned in epidemiology. These models are hi
Does Malaria Affect Placental Development? Evidence from In Vitro Models
Alexandra J. Umbers, Danielle I. Stanisic, Maria Ome, Regina Wangnapi, Sarah Hanieh, Holger W. Unger, Leanne J. Robinson, Elvin Lufele, Francesca Baiwog, Peter M. Siba, Christopher L. King, James G. Beeson, Ivo Mueller, John D. Aplin, Jocelyn D. Glazier, Stephen J. Rogerson
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0055269
Abstract: Background Malaria in early pregnancy is difficult to study but has recently been associated with fetal growth restriction (FGR). The pathogenic mechanisms underlying malarial FGR are poorly characterized, but may include impaired placental development. We used in vitro methods that model migration and invasion of placental trophoblast into the uterine wall to investigate whether soluble factors released into maternal blood in malaria infection might impair placental development. Because trophoblast invasion is enhanced by a number of hormones and chemokines, and is inhibited by pro-inflammatory cytokines, many of which are dysregulated in malaria in pregnancy, we further compared concentrations of these factors in blood between malaria-infected and uninfected pregnancies. Methodology/Principal Findings We measured trophoblast invasion, migration and viability in response to treatment with serum or plasma from two independent cohorts of Papua New Guinean women infected with Plasmodium falciparum or Plasmodium vivax in early pregnancy. Compared to uninfected women, serum and plasma from women with P. falciparum reduced trophoblast invasion (P = .06) and migration (P = .004). P. vivax infection did not alter trophoblast migration (P = .64). The P. falciparum-specific negative effect on placental development was independent of trophoblast viability, but associated with high-density infections. Serum from P. falciparum infected women tended to have lower levels of trophoblast invasion promoting hormones and factors and higher levels of invasion-inhibitory inflammatory factors. Conclusion/Significance We demonstrate that in vitro models of placental development can be adapted to indirectly study the impact of malaria in early pregnancy. These infections could result in impaired trophoblast invasion with reduced transformation of maternal spiral arteries due to maternal hormonal and inflammatory disturbances, which may contribute to FGR by limiting the delivery of maternal blood to the placenta. Future prevention strategies for malaria in pregnancy should include protection in the first half of pregnancy.
First measurements of the ^16O(e,e'pn)^14N reaction
D. G. Middleton,J. R. M. Annand,C. Barbieri,P. Barneo,P. Bartsch,D. Bauman,J. Bermuth,D. Bosnar,H. P. Blok,R. Bohm,M. Ding,M. O. Distler,D. Elsner,J. Friedrich,C. Giusti,D. I. Glazier,P. Grabmayr,S. Grozinger,T. Hehl,J. Heim,W. H. A Hesselink,E. Jans,F. Klein,M. Kohl,L. Lapikas,I. J. D. MacGregor,I. Martin,J. C. McGeorge,H. Merkel,P. Merle,F. Moschini,U. Muller,Th. Pospischil,G. Rosner,H. Schmieden,M. Seimetz,A. Sule,H. de Vries,Th. Walcher,D. P. Watts,M. Weis,B. Zihlmann
Physics , 2007, DOI: 10.1140/epja/i2005-10314-9
Abstract: This paper reports on the first measurement of the ^16O(e,e'pn)^14N reaction. Data were measured in kinematics centred on a super-parallel geometry at energy and momentum transfers of 215 MeV and 316 MeV/c. The experimental resolution was sufficient to distinguish groups of states in the residual nucleus but not good enough to separate individual states. The data show a strong dependence on missing momentum and this dependence appears to be different for two groups of states in the residual nucleus. Theoretical calculations of the reaction using the Pavia code do not reproduce the shape or the magnitude of the data.
Measurement of the Electric Form Factor of the Neutron at Q^2 = 0.3-0.8 (GeV/c)^2
D. I. Glazier,M. Seimetz,J. R. M. Annand,H. Arenh?vel,M. Ases Antelo,C. Ayerbe,P. Bartsch,D. Baumann,J. Bermuth,R. B?hm,D. Bosnar,M. Ding,M. O. Distler,D. Elsner,J. Friedrich,S. Hedicke,P. Jennewein,G. Jover Ma?as,F. H. Klein,F. Klein,M. Kohl,K. W. Krygier,K. Livingston,I. J. D. MacGregor,M. Makek,H. Merkel,P. Merle,D. Middleton,U. Müller,R. Neuhausen,L. Nungesser,M. Ostrick,R. Pérez Benito,J. Pochodzalla,Th. Pospischil,M. Potokar,A. Reiter,G. Rosner,J. Sanner,H. Schmieden,A. Süle,Th. Walcher,D. Watts,M. Weis
Physics , 2004, DOI: 10.1140/epja/i2004-10115-8
Abstract: The electric form factor of the neutron, G_En, has been measured at the Mainz Microtron by recoil polarimetry in the quasielastic D(e_pol,e'n_pol)p reaction. Three data points have been extracted at squared four-momentum transfers Q^2 = 0.3, 0.6 and 0.8 (GeV/c)^2. Corrections for nuclear binding effects have been applied.
A Multi-cell, Multi-scale Model of Vertebrate Segmentation and Somite Formation
Susan D. Hester ,Julio M. Belmonte,J. Scott Gens,Sherry G. Clendenon,James A. Glazier
PLOS Computational Biology , 2011, DOI: 10.1371/journal.pcbi.1002155
Abstract: Somitogenesis, the formation of the body's primary segmental structure common to all vertebrate development, requires coordination between biological mechanisms at several scales. Explaining how these mechanisms interact across scales and how events are coordinated in space and time is necessary for a complete understanding of somitogenesis and its evolutionary flexibility. So far, mechanisms of somitogenesis have been studied independently. To test the consistency, integrability and combined explanatory power of current prevailing hypotheses, we built an integrated clock-and-wavefront model including submodels of the intracellular segmentation clock, intercellular segmentation-clock coupling via Delta/Notch signaling, an FGF8 determination front, delayed differentiation, clock-wavefront readout, and differential-cell-cell-adhesion-driven cell sorting. We identify inconsistencies between existing submodels and gaps in the current understanding of somitogenesis mechanisms, and propose novel submodels and extensions of existing submodels where necessary. For reasonable initial conditions, 2D simulations of our model robustly generate spatially and temporally regular somites, realistic dynamic morphologies and spontaneous emergence of anterior-traveling stripes of Lfng. We show that these traveling stripes are pseudo-waves rather than true propagating waves. Our model is flexible enough to generate interspecies-like variation in somite size in response to changes in the PSM growth rate and segmentation-clock period, and in the number and width of Lfng stripes in response to changes in the PSM growth rate, segmentation-clock period and PSM length.
Contact-Inhibited Chemotaxis in De Novo and Sprouting Blood-Vessel Growth
Roeland M. H. Merks ,Erica D. Perryn,Abbas Shirinifard,James A. Glazier
PLOS Computational Biology , 2008, DOI: 10.1371/journal.pcbi.1000163
Abstract: Blood vessels form either when dispersed endothelial cells (the cells lining the inner walls of fully formed blood vessels) organize into a vessel network (vasculogenesis), or by sprouting or splitting of existing blood vessels (angiogenesis). Although they are closely related biologically, no current model explains both phenomena with a single biophysical mechanism. Most computational models describe sprouting at the level of the blood vessel, ignoring how cell behavior drives branch splitting during sprouting. We present a cell-based, Glazier–Graner–Hogeweg model (also called Cellular Potts Model) simulation of the initial patterning before the vascular cords form lumens, based on plausible behaviors of endothelial cells. The endothelial cells secrete a chemoattractant, which attracts other endothelial cells. As in the classic Keller–Segel model, chemotaxis by itself causes cells to aggregate into isolated clusters. However, including experimentally observed VE-cadherin–mediated contact inhibition of chemotaxis in the simulation causes randomly distributed cells to organize into networks and cell aggregates to sprout, reproducing aspects of both de novo and sprouting blood-vessel growth. We discuss two branching instabilities responsible for our results. Cells at the surfaces of cell clusters attempting to migrate to the centers of the clusters produce a buckling instability. In a model variant that eliminates the surface–normal force, a dissipative mechanism drives sprouting, with the secreted chemical acting both as a chemoattractant and as an inhibitor of pseudopod extension. Both mechanisms would also apply if force transmission through the extracellular matrix rather than chemical signaling mediated cell–cell interactions. The branching instabilities responsible for our results, which result from contact inhibition of chemotaxis, are both generic developmental mechanisms and interesting examples of unusual patterning instabilities.
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