• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 259
  • 81
  • 63
  • 34
  • 14
  • 13
  • 6
  • 6
  • 5
  • 4
  • 3
  • 3
  • 2
  • 2
  • 2
  • Tagged with
  • 557
  • 91
  • 78
  • 75
  • 69
  • 68
  • 59
  • 55
  • 55
  • 46
  • 41
  • 39
  • 37
  • 37
  • 35
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Multidimensional Born velocity inversion: single wide band point source

January 1984 (has links)
Cengiz Esmersoy, Michael L. Oristaglio, Bernard C. Levy. / Bibliography: p. 16-18. / "November, 1984."
62

Multidimensional Born inversion with a wide-band plane wave source

January 1985 (has links)
Cengiz Esmersoy, Bernard C. Levy. / "June 1985." / Bibliography: leaves 23-24.
63

Structure and break-up of one-neutron halo nuclei

Cross, Brian January 1995 (has links)
This thesis concerns the use of nuclear reactions to study the structure of neutron-rich light nuclei. Emphasis is placed on 11Be which has been identified as a nucleus with a single neutron halo and which offers a simple 2-body case for detailed analysis. Comparisons are made with experimental data for the break-up of 11Be on gold, titanium and beryllium targets. As a prelude to more detailed work a simple elastic break-up model calculation, using the Distorted Wave Born Approximation (DWBA), is attempted. The resulting theoretical cross-sections show good agreement with the shape of the experimental data but cannot predict the absolute magnitude. A major part of the break-up work is a more accurate model using the post-form DWBA. The formulation is built up from basic scattering theory and includes details of employing the Zero Range Approximation and the Vincent and Fortune method of integration. A Finite Range Correction is also applied. Cross-section calculations for a gold target agree closely with experiment but a problem arises for lighter targets. Here the Coulomb potential must be excluded from the calculation to obtain a result that matches the experimental data. A method for the calculation of inelastic break-up is presented which only requires a small modification to the methods used for elastic break-up. As it suffers from the same light target problem only calculations for a gold target give an inclusive cross-section, produced from the elastic and inelastic contributions, which matches the experimental data satisfactorily. To overcome the light target problem a full recoil calculation is introduced. Arguments and analysis are produced to show that this method is too demanding of both computing time and storage for practicable implementation. Future calculations are proposed using an analytical method for Coulomb break-up.
64

On the separation of nuclear and electronic motions in molecular scattering states

Gerber, R. B. January 1968 (has links)
No description available.
65

The Association of Vitamin D Supplementation with Type I Diabetes in New Born and Pregnant Mothers: A systematic Review

Sarmadnia, Newsha, Slack, Marion, Herrier, Richard January 2013 (has links)
Class of 2013 Abstract / Specific Aims: To assess whether vitamin D supplementation is associated with a reduced risk of type I diabetes in infants. Methods: This study was a systematic review using Pubmed, Google Scholar and reference lists of retrieved articles. Only randomized controlled trials and prospective observational studies were considered for this study. Data were extracted and organized into tables. The data were organized into three categories; study characteristics, patient characterisitics and study outcomes. The main outcomes were association of type I diabetes with vitamin D deficiency and identify the proper dose of vitamin D in pediatric population. Main Results: A total of 3 randomized controlled trials and 2 prospective observational studies were found that met the inclusion criteria; retrospective studies and case control studies were excluded. Combining all studies, no association was seen between vitamin D supplement and control group. Most of the randomized control studies have not shown a statistically significant association between Hb A1C, C-Peptide and vitamin D level with type I diabetes. The Gabbay et al. study showed that vitamin D serum concentrations (25(OH)D3) in the cholecalciferol and placebo groups were not significant at 6 ( P= 0.93),12( P= 0.81), and 18 (P= 0.53) months of follow up. The vitamin D concentration was increased during the 6 months period compared to baseline value (Basal: 26.34ng/ml vs 6 months: 60.88 ng/mL; P <001). Also, Bizzarri et al. study showed that at 6, 12, and 24 months the A1C and insulin usage in both calcitrol and placebo groups were not different. On the other hand, the observational study by Vojtková et al. showed that two thirds of children with type I diabetes had insufficient vitamin D concentration and lower Z score of lumbar spine. Also, the Fronczak observational study showed that maternal Intake of vitamin D via food was significant in decrease of IA-2 autoantibodies in offspring ( HR=0.37;95%Cl 0.17-0.78). Variety of different dosage of vitamin D supplement has been used in primary literatures. The data from Wicklow and Hypponen et al. used 2000IU/d that decreased risk of type I diabetes in diabetes type I. Conclusion: Reported studies did not have consistent conclusion for association of type I diabetes and vitamin D. The data from the randomized clinical trials have shown that vitamin D supplementation can increase serum vitamin D >30 ng/ml but none support the use of vitamin D in prevention of type I diabetes. Given the lack of data to support the use of vitamin D to reduce the risk of type I diabetes, vitamin D supplementation should be used to supplement vitamin D levels in children not exposed to adequate sunlight. There is no clear recommendation dose for treatment and prevention of vitamin D supplementation for pediatric patients. Therefore, monitoring and routine measurements of vitamin D by physician can play an important role. More randomized control trials with large sample would be needed to answer all of the unknown questions regarding the dosage of vitamin D supplement.
66

Nativity Status and Patient Perceptions of the Patient-Physician Encounter: Results From the Commonwealth Fund 2001 Survey on Disparities in Quality of Health Care

Dallo, Florence J., Borrell, Luisa N., Williams, Stacey L. 01 February 2008 (has links)
Background: Although racial and ethnic differences in healthcare have been extensively documented in the United States, little attention has been paid to the quality of health care for the foreign-born population in the United States. Objectives: This study examines the association between patient perceptions of the patient-physician interaction and nativity status. Research Design: Cross-sectional telephone survey. Subjects: A total of 6674 individuals (US-born ≤ 5156; foreign-born ≤ 1518) 18 years of age and older. Measures: Seven questions measuring the quality of patient-physician interactions. Results: Of the 7 outcome variables examined in the unadjusted logistic regression model, only 2 remained statistically significant in the fully adjusted model. For both the total sample and for Asians only, compared with US-born, foreign-born individuals were at greater odds [total sample, odds ratio (OR) ≤ 1.43; 95% confidence interval (CI) ≤ 1. 01ĝ€"2.04; Asians, OR ≤ 3.25; 95% CI ≤ 1.18ĝ€"8.95] of reporting that their physician did not involve them in their care as much as they would have liked. Compared with US-born Asians, foreign-born Asians were at greater odds of reporting that their physician did not spend as much time with them as they would have liked (OR ≤ 4.19; 95% CI ≤ 1.68ĝ€"10.46). Discussion: Findings from our study suggest that we should not only track disparities by race and ethnicity but also by nativity status.
67

Racial and Ethnic Disparities in Patient-Physician Interactions for US- and Foreign-Born Individuals

Dallo, Florence, Borrell, L. N., Williams, Stacey L. 01 March 2008 (has links)
No description available.
68

The Born-Oppenheimer approximation in scattering theory

Kargol, Armin 02 March 2006 (has links)
We analyze the Schrödinger equation i𝜖 ¬<sup>2</sup>â /â tΨ = H(𝜖)Ψ, where H(â ¬) = - f24 Î x + h(X) is the hamiltonian of a molecular system consisting of nuclei with masses of order 𝜖¬<sup>-4</sup> and electrons with masses of order 1. The Born-Oppenheimer approximation consists of the adiabatic approximation to the motion of electrons and the semiclassical approximation to the time evolution of nuclei. The quantum propagator associated with this Schrödinger Equation is exp(-itH(â ¬)/â ¬<sup>2</sup>). We use the Born-Oppenheimer method to find the leading order asymptotic expansion in â ¬ to exp(_it~(t:»Ψ, i.e., we find Ψ(t) such that: (1) We show that if H(𝜖) describes a diatomic Molecule with smooth short range potentials, then the estimate (1) is uniform in time; hence the leading order approximation to the wave operators can be constructed. We also comment on the generalization of our method to polyatomic molecules and to Coulomb systems. / Ph. D.
69

Born-Oppenheimer Expansion for Diatomic Molecules with Large Angular Momentum

Hughes, Sharon Marie 14 November 2007 (has links)
Semiclassical and Born-Oppenheimer approximations are used to provide uniform error bounds for the energies of diatomic molecules for bounded vibrational quantum number n and large angular momentum quantum number l. Specifically, results are given when (l + 1) < κ𝛜⁻³/². Explicit formulas for the approximate energies are also given. Numerical comparisons for the H+₂ and HD+ molecules are presented. / Ph. D.
70

The Born-Oppenheimer Approximation for Triatomic Molecules with Large Angular Momentum in Two Dimensions

Bowman, Adam Shoresworth 12 January 2011 (has links)
We study the Born-Oppenheimer approximation for a symmetric linear triatomic molecule in two space dimensions. We compute energy levels up to errors of order ε⁵, uniformly for three bounded vibrational quantum numbers n₁, n₂, and n₃; and nuclear angular momentum quantum numbers â ≤ kε<sup>-3/4</sup> for k > 0. Here the small parameter ε is the fourth root of the ratio of the electron mass to an average nuclear mass. / Master of Science

Page generated in 0.0752 seconds