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Search Results: 1 - 10 of 144387 matches for " B. Sheehy "
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The Quebec Pregnancy Cohort – Prevalence of Medication Use during Gestation and Pregnancy Outcomes
Anick Bérard, Odile Sheehy
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0093870
Abstract: Purpose We evaluated the potential and the validity of the Quebec Pregnancy Cohort (QPC) as a research tool in perinatal pharmacoepidemiology. Methods The QPC was built by linking four administrative databases: RAMQ (medical and pharmaceutical data), Med-Echo (hospitalizations), ISQ (births/deaths), and MELS (Ministry of Education data). A self-administered questionnaire was sent to a random sample of women to collect lifestyle information. The QPC includes data on all pregnancies of women covered by the Quebec provincial prescription drug insurance between 1998 and 2008. Date of entry in the QPC is the first day of pregnancy, and women are followed during and after pregnancy; children are followed after birth up until 2009. The prevalence of prescribed medications before, during and after pregnancy was compared between time-window. Pregnancy outcomes were also estimated among pregnancies ending with a live born infant. Results The QPC included 289,688 pregnancies of 186,165 women. Among them, 167,398 ended with a delivery representing 19.4% of all deliveries occurring in the Province of Quebec between 1998–2009. The total frequency of abortions was 35.9% in the QPC comparable to the 36.4% observed in the Province of Quebec. The prevalence of prescribed medication use was 74.6%, 59.0%, and 79.6% before, during and after pregnancy, respectively. Although there was a statistically significant decrease in the proportion of use once the pregnancy was diagnosed (p<.01), post-pregnancy prescribed medication use returned above the pre-pregnancy level. The prevalence of pregnancy outcomes found in the QPC were similar to those observed in the Province of Quebec. Conclusion The QPC is an excellent tool for the study of the risk and benefit of drug use during the perinatal period. This cohort has the advantage of including a validated date of beginning of pregnancy giving the possibility of assigning the exact gestational age at the time of maternal exposure.
Retention of Attosecond Pulse Structure in an HHG Seeded FEL Amplifier
B. W. J. McNeil,N. R. Thompson,D. J. Dunning,B. Sheehy
Physics , 2008,
Abstract: A model is presented which demonstrates that the attosecond pulse structure of a High Harmonic Generation (HHG) seed may be retained through to saturation in an FEL amplifier. At wavelengths of ~12nm a train of attosecond pulses of widths ~300 attoseconds with peak powers in excess of 1 GW are predicted from full 3D simulation. Methods for improving these results are discussed.
Critical illness-induced dysglycaemia: diabetes and beyond
Fang Smith, Ann M Sheehy, Jean-Louis Vincent, Douglas B Coursin
Critical Care , 2010, DOI: 10.1186/cc9266
Abstract: Type 2 diabetes is one of the greatest challenges facing healthcare professionals. The general population disease prevalence is approximately 2.8% worldwide [1]. In contrast, the most recent US National Health and Nutrition Examination Survey estimates that 12.9% of US ambulatory adults over 20 years of age have type 2 diabetes [2]. The prevalence of diabetes is expected to double over the next 30 years due to increased age, inactivity and obesity [1].Complicating this phenomenon is the knowledge that approximately 40% of patients with diabetes remain undiagnosed [2]. These patients cannot be treated, and are vulnerable to short-term and long-term complications [3-5]. The true prevalence of diabetes in hospitalised patients is not known, due to the heterogeneous patient population and limitations in diagnostic tests [6]. The prevalence in intensive care unit (ICU) patients is perhaps 25% or higher, depending on unit specialty and patient demographics [6].Adults with diabetes have at least double the annual mortality compared with adults without diabetes [7]. Paradoxically, several studies of hospitalised patients have demonstrated that hyperglycaemic individuals without known diabetes have significantly greater morbidity and mortality than either patients with known diabetes or those with normal glucose tolerance [8-11]. Hyperglycaemic patients without diabetes include those with undiagnosed diabetes, prediabetes (impaired fasting glucose and impaired glucose tolerance) or stress-induced hyperglycaemia (SIH) - defined as patients with elevated blood glucose that reverts to normal after illness subsides and counterregulatory hormone and inflammatory mediator surge abates [6]. Large, retrospective studies in critically ill adults have shown that hyper-glycaemic patients with diabetes have lower ICU and hospital mortality and shorter length of ICU stay than critically ill hyperglycaemic patients without diabetes [8-10]. This increased mortality in hyperglycaemic patien
Approximating Nearest Neighbor Distances
Michael B. Cohen,Brittany Terese Fasy,Gary L. Miller,Amir Nayyeri,Donald R. Sheehy,Ameya Velingker
Computer Science , 2015,
Abstract: Several researchers proposed using non-Euclidean metrics on point sets in Euclidean space for clustering noisy data. Almost always, a distance function is desired that recognizes the closeness of the points in the same cluster, even if the Euclidean cluster diameter is large. Therefore, it is preferred to assign smaller costs to the paths that stay close to the input points. In this paper, we consider the most natural metric with this property, which we call the nearest neighbor metric. Given a point set P and a path $\gamma$, our metric charges each point of $\gamma$ with its distance to P. The total charge along $\gamma$ determines its nearest neighbor length, which is formally defined as the integral of the distance to the input points along the curve. We describe a $(3+\varepsilon)$-approximation algorithm and a $(1+\varepsilon)$-approximation algorithm to compute the nearest neighbor metric. Both approximation algorithms work in near-linear time. The former uses shortest paths on a sparse graph using only the input points. The latter uses a sparse sample of the ambient space, to find good approximate geodesic paths.
Symmetry breaking in crossed magnetic and electric fields
C. Neumann,R. Ubert,S. Freund,E. Floethmann,B. Sheehy,K. H. Welge,M. R. Haggerty,J. B. Delos
Physics , 1997, DOI: 10.1103/PhysRevLett.78.4705
Abstract: We present the first observations of cylindrical symmetry breaking in highly excited diamagnetic hydrogen with a small crossed electric field, and we give a semiclassical interpretation of this effect. As the small perpendicular electric field is added, the recurrence strengths of closed orbits decrease smoothly to a minimum, and revive again. This phenomenon, caused by interference among the electron waves that return to the nucleus, can be computed from the azimuthal dependence of the classical closed orbits.
A Classroom Full of Gifts
Jemma Giddings,Lisa Sheehy
Mathematics Educator , 2000,
Polarized superfluids near their tricritical point
Daniel E. Sheehy
Physics , 2008, DOI: 10.1103/PhysRevA.79.033606
Abstract: We obtain a variety of predictions for the properties of population-imbalanced (or polarized) fermionic superfluids near their tricritical point. In the vicinity of the high-symmetry tricritical point, observable quantities such as the cloud shape, heat capacity, and local polarization should exhibit distinct behavior arising from the tricritical scaling laws, as well as logarithmic corrections to scaling reflecting the marginal nature of interactions.
Feynman path-integral approach to the QED3 theory of the pseudogap
Daniel E. Sheehy
Physics , 2002, DOI: 10.1142/S0217979203022842
Abstract: In this work the connection between vortex condensation in a d-wave superconductor and the QED$_3$ gauge theory of the pseudogap is elucidated. The approach taken circumvents the use of the standard Franz-Tesanovic gauge transformation, borrowing ideas from the path-integral analysis of the Aharonov-Bohm problem. An essential feature of this approach is that gauge-transformations which are prohibited on a particular multiply-connected manifold (e.g. a superconductor with vortices) can be successfully performed on the universal covering space associated with that manifold.
Microwave conductivity of a d-wave superconductor disordered by extended impurities: a real-space renormalization group approach
Daniel E. Sheehy
Physics , 2003, DOI: 10.1103/PhysRevB.68.054529
Abstract: Using a real-space renormalization group (RSRG) technique, we compute the microwave conductivity of a d-wave superconductor disordered by extended impurities. To do this, we invoke a semiclassical approximation which naturally accesses the Andreev bound states localized near each impurity. Tunneling corrections (which are captured using the RSRG) lead to a delocalization of these quasiparticles and an associated contribution to the microwave conductivity.
Fulde-Ferrell-Larkin-Ovchinnikov state of two-dimensional imbalanced Fermi gases
Daniel E. Sheehy
Physics , 2014, DOI: 10.1103/PhysRevA.92.053631
Abstract: The ground-state phase diagram of attractively-interacting Fermi gases in two dimensions with a population imbalance is investigated. We find the regime of stability for the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase, in which pairing occurs at finite wave vector, and determine the magnitude of the pairing amplitude $\Delta$ and FFLO wavevector $q$ in the ordered phase, finding that $\Delta$ can be of the order of the two-body binding energy. Our results rely on a careful analysis of the zero temperature gap equation for the FFLO state, which possesses nonanalyticities as a function of $\Delta$ and $q$, invalidating a Ginzburg-Landau expansion in small $\Delta$.
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