4,938 research outputs found
Magneto-optical Trapping of Cadmium
We report the laser-cooling and confinement of Cd atoms in a magneto-optical
trap, and characterize the loading process from the background Cd vapor. The
trapping laser drives the 1S0-1P1 transition at 229 nm in this two-electron
atom and also photoionizes atoms directly from the 1P1 state. This
photoionization overwhelms the other loss mechanisms and allows a direct
measurement of the photoionization cross section, which we measure to be
2(1)x10^(-16)cm^(2) from the 1P1 state. When combined with nearby laser-cooled
and trapped Cd^(+) ions, this apparatus could facilitate studies in ultracold
interactions between atoms and ions.Comment: 8 pages, 11 figure
Surface aided polarization reversal in small ferroelectric particles
Author name used in this publication: H. L. W. ChanAuthor name used in this publication: F. G. Shin2002-2003 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Dr. Martin Hillenbrand to Receive University of Dayton Distinguished Alumnus Award
News release announcing the University of Dayton will Award Assistant Secretary of State for European Affairs, Dr. Martin Hillenbrand, with the Distinguished Alumnus Award
A comprehensive ovine model of blood transfusion
Background: The growing awareness of transfusion-associated morbidity and mortality necessitates investigations into the underlying mechanisms. Small animals have been the dominant transfusion model but have associated limitations. This study aimed to develop a comprehensive large animal (ovine) model of transfusion encompassing: blood collection, processing and storage, compatibility testing right through to post-transfusion outcomes. Materials and methods: Two units of blood were collected from each of 12 adult male Merino sheep and processed into 24 ovine-packed red blood cell (PRBC) units. Baseline haematological parameters of ovine blood and PRBC cells were analysed. Biochemical changes in ovine PRBCs were characterized during the 42-day storage period. Immunological compatibility of the blood was confirmed with sera from potential recipient sheep, using a saline and albumin agglutination cross-match. Following confirmation of compatibility, each recipient sheep (n = 12) was transfused with two units of ovine PRBC. Results: Procedures for collecting, processing, cross-matching and transfusing ovine blood were established. Although ovine red blood cells are smaller and higher in number, their mean cell haemoglobin concentration is similar to human red blood cells. Ovine PRBC showed improved storage properties in saline-adenine-glucose-mannitol (SAG-M) compared with previous human PRBC studies. Seventy-six compatibility tests were performed and 17·1% were incompatible. Only cross-match compatible ovine PRBC were transfused and no adverse reactions were observed. Conclusion: These findings demonstrate the utility of the ovine model for future blood transfusion studies and highlight the importance of compatibility testing in animal models involving homologous transfusions
Properties of Regge Trajectories
Early Chew-Frautschi plots show that meson and baryon Regge trajectoies are
approximately linear and non-intersecting. In this paper, we reconstruct all
Regge trajectories from the most recent data. Our plots show that meson
trajectories are non-linear and intersecting. We also show that all current
meson Regge trajectories models are ruled out by data.Comment: 30 pages, latex, 18 figures, to be published in Physical Review
Lessons to be learned from the coherent photoproduction of pseudoscalar mesons
We study the coherent photoproduction of pseudoscalar mesons---particularly
of neutral pions---placing special emphasis on the various sources that put
into question earlier nonrelativistic-impulse-approximation calculations. These
include: final-state interactions, relativistic effects, off-shell ambiguities,
and violations to the impulse approximation. We establish that, while
distortions play an essential role in the modification of the coherent cross
section, the uncertainty in our results due to the various choices of
optical-potential models is relatively small (of at most 30%). By far the
largest uncertainty emerges from the ambiguity in extending the many
on-shell-equivalent representations of the elementary amplitude off the mass
shell. Indeed, relativistic impulse-approximation calculations that include the
same pionic distortions, the same nuclear-structure model, and two sets of
elementary amplitudes that are identical on-shell, lead to variations in the
magnitude of the coherent cross section by up to factors of five. Finally, we
address qualitatively the assumption of locality implicit in most
impulse-approximation treatments, and suggest that the coherent reaction
probes---in addition to the nuclear density---the polarization structure of the
nucleus.Comment: Manuscript is 27 pages long and includes 11 eps figure
A motivational intervention for patients with COPD in primary care: Qualitative evaluation of a new practitioner role.
Methods: Qualitative study using patient and practice staff informants. We audio-recorded interviews with 29 patients offered the intervention (three had declined it or withdrawn) and 13 practice staff (GPs, nurses and administrators). Analysis used a constant comparative approach. Background: Long-term conditions such as chronic obstructive pulmonary disease (COPD) are growing challenges for health services. Psychosocial co-morbidity is associated with poorer quality of life and greater use of health care in these patients but is often un-diagnosed or inadequately treated in primary care, where most care for these patients is provided. We developed a brief intervention, delivered by 'liaison health workers' (LHWs), to address psychosocial needs in the context of an integrated approach to physical and mental health. We report a qualitative study in which we characterize the intervention through the experience of the patients receiving it and examine how it was incorporated into primary care. Results: Most patients were enthusiastic about the LHWs, describing the intervention as mobilizing their motivation for self-management. By contrast with other practitioners, patients experienced the LHWs as addressing their needs holistically, being guided by patient needs rather than professional agendas, forming individual relationships with patients and investing in patients and their capacity to change. Practices accommodated and accepted the LHWs, but positioned them as peripheral to and separate from the priority of physical care. Conclusions: Despite being a short-term intervention, patients described it as having enduring motivational benefits. The elements of the intervention that patients described map onto the key features of motivating interventions described by Self-Determination Theory. We suggest that the LHWs motivated patients to self-management by: (i) respecting patients' competence to decide on needs and priorities; (ii) forming relationships with patients as individuals; and (iii) fostering patients' sense of autonomy. While truly integrated primary care for patients with long-term conditions such as COPD remains elusive, existing practice staff might adopt elements of the LHWs' approach to enhance motivational change in patients with long-term conditions such as COPD
Balancing Minimum Spanning and Shortest Path Trees
This paper give a simple linear-time algorithm that, given a weighted
digraph, finds a spanning tree that simultaneously approximates a shortest-path
tree and a minimum spanning tree. The algorithm provides a continuous
trade-off: given the two trees and epsilon > 0, the algorithm returns a
spanning tree in which the distance between any vertex and the root of the
shortest-path tree is at most 1+epsilon times the shortest-path distance, and
yet the total weight of the tree is at most 1+2/epsilon times the weight of a
minimum spanning tree. This is the best tradeoff possible. The paper also
describes a fast parallel implementation.Comment: conference version: ACM-SIAM Symposium on Discrete Algorithms (1993
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