5,652 research outputs found
Toroidal Vortices in Resistive Magnetohydrodynamic Equilibria
Resistive steady states in toroidal magnetohydrodynamics (MHD), where Ohm's
law must be taken into account, differ considerably from ideal ones. Only for
special (and probably unphysical) resistivity profiles can the Lorentz force,
in the static force-balance equation, be expressed as the gradient of a scalar
and thus cancel the gradient of a scalar pressure. In general, the Lorentz
force has a curl directed so as to generate toroidal vorticity. Here, we
calculate, for a collisional, highly viscous magnetofluid, the flows that are
required for an axisymmetric toroidal steady state, assuming uniform scalar
resistivity and viscosity. The flows originate from paired toroidal vortices
(in what might be called a ``double smoke ring'' configuration), and are
thought likely to be ubiquitous in the interior of toroidally driven
magnetofluids of this type. The existence of such vortices is conjectured to
characterize magnetofluids beyond the high-viscosity limit in which they are
readily calculable.Comment: 17 pages, 4 figure
Generalized XY Model
The methods of Lie algebras are used to construct and solve a generalization of the XY model
Spontaneous creation of non-zero angular momentum modes in tunnel-coupled two-dimensional degenerate Bose gases
We investigate the dynamics of two tunnel-coupled two-dimensional degenerate
Bose gases. The reduced dimensionality of the clouds enables us to excite
specific angular momentum modes by tuning the coupling strength, thereby
creating striking patterns in the atom density profile. The extreme sensitivity
of the system to the coupling and initial phase difference results in a rich
variety of subsequent dynamics, including vortex production, complex
oscillations in relative atom number and chiral symmetry breaking due to
counter-rotation of the two clouds.Comment: 7 pages, 5 figure
Investigating the persistence of tick-borne pathogens via the R0 model
In the epidemiology of infectious diseases, the basic reproduction number,R0, has a number of important applications, most
notably it can be used to predict whether a pathogen is likely to become established, or persist, in a given area. We used the
R0 model to investigate the persistence of 3 tick-borne pathogens; Babesia microti, Anaplasma phagocytophilum and Borrelia
burgdorferi sensu lato in an Apodemus sylvaticus-Ixodes ricinus system. The persistence of these pathogens was also
determined empirically by screening questing ticks and wood mice by PCR. All 3 pathogens behaved differently in response
to changes in the proportion of transmission hosts on which I. ricinus fed, the efficiency of transmission between the host and
ticks and the abundance of larval and nymphal ticks found on small mammals. Empirical data supported theoretical
predictions of the R0 model. The transmission pathway employed and the duration of systemic infection were also identified
as important factors responsible for establishment or persistence of tick-borne pathogens in a given tick-host system. The
current study demonstrates how the R0 model can be put to practical use to investigate factors affecting tick-borne pathogen
persistence, which has important implications for animal and human health worldwide
Informed consent and medical ordeal: a qualitative study
Background Informed consent is a mainstay of clinical practice, with both moral and legal force. Material disclosure about extreme treatments, however, is unlikely to convey the full impact of the experience of treatment. Informed consent may be flawed under such cir-cumstances.
Aims To compare expressed satisfaction with pre-treatment information to satisfaction af-ter experiencing autologous stem cell transplantation (ASCT) for recurrent lymphoma.
Methods A qualitative, narrative-based cohort study has been conducted in a Teaching hospital Bone Marrow Transplant unit at Westmead Hospital, Sydney, Australia. The cohort consisted of ten transplant recipients and nine of their nominated lay carers. The Outcome measure was satisfaction expressed in narrative interviews at the time of transplantation and three months later. We used discourse analytic techniques to examine the narratives.
Results Both patients and carers expressed high satisfaction with the information given by individual clinicians and by speakers at a formal Information Day held before transplanta-tion. At the first interview, neither patients nor carers commented much on the forthcom-ing ordeal of chemotherapy and bone marrow ablation, although all patients had under-gone previous chemotherapy. At the second interview, the ordeal dominated the narratives, and retrospective dissatisfaction with information was common.
Conclusions This study suggests that information about treatment theories and protocols can be satisfactorily communicated, but personal experience of suffering defies communi-cation. This finding has serious implications for the practices involved in obtaining informed consent and for the very notion of informed consent.
KEY WORDS
Autologous stem cell transplantation; haematological malignancies; extreme treatment; medical communication; informed consent
Informed consent and medical ordeal: a qualitative study
Background Informed consent is a mainstay of clinical practice, with both moral and legal force. Material disclosure about extreme treatments, however, is unlikely to convey the full impact of the experience of treatment. Informed consent may be flawed under such cir-cumstances. Aims To compare expressed satisfaction with pre-treatment information to satisfaction af-ter experiencing autologous stem cell transplantation (ASCT) for recurrent lymphoma. Methods A qualitative, narrative-based cohort study has been conducted in a Teaching hospital Bone Marrow Transplant unit at Westmead Hospital, Sydney, Australia. The cohort consisted of ten transplant recipients and nine of their nominated lay carers. The Outcome measure was satisfaction expressed in narrative interviews at the time of transplantation and three months later. We used discourse analytic techniques to examine the narratives. Results Both patients and carers expressed high satisfaction with the information given by individual clinicians and by speakers at a formal Information Day held before transplanta-tion. At the first interview, neither patients nor carers commented much on the forthcom-ing ordeal of chemotherapy and bone marrow ablation, although all patients had under-gone previous chemotherapy. At the second interview, the ordeal dominated the narratives, and retrospective dissatisfaction with information was common. Conclusions This study suggests that information about treatment theories and protocols can be satisfactorily communicated, but personal experience of suffering defies communi-cation. This finding has serious implications for the practices involved in obtaining informed consent and for the very notion of informed consent. KEY WORDS Autologous stem cell transplantation; haematological malignancies; extreme treatment; medical communication; informed consent
Response to exercise rehabilitation in smoking and nonsmoking patients with intermittent claudication
AbstractBackgroundThe purpose was to compare the changes in claudication pain, ambulatory function, daily physical activity, peripheral circulation, and health-related quality of life following a program of exercise rehabilitation in smoking and nonsmoking patients with peripheral arterial disease (PAD) limited by intermittent claudication.Methods and resultsThirty-nine smokers (63 ± 4 pack-year smoking history; mean ± SE) and 46 nonsmokers (former smokers who had a 51 ± 7 pack-year smoking history who quit 14 ± 2 years prior to investigation) completed the study. The 6-month exercise rehabilitation program consisted of intermittent treadmill walking to near maximal claudication pain 3 days per week, with progressive increases in walking duration and intensity during the program. Measurements were obtained on each patient before and after rehabilitation. Following exercise rehabilitation the smokers and nonsmokers had similar improvements in these measures, as initial claudication distance increased by 119% in the smokers (P < .001) and by 97% in the nonsmokers (P < .001), and absolute claudication distance increased by 82% (P < .001) and 59% (P < .001) in the smokers and nonsmokers, respectively. Furthermore, exercise rehabilitation improved (P < .05) ambulatory function, daily physical activity, peripheral circulation, and health-related quality of life in the smokers and nonsmokers.ConclusionExercise rehabilitation is an effective therapy to improve functional independence in both smoking and nonsmoking patients with PAD limited by intermittent claudication. Therefore, smokers with intermittent claudication are prime candidates for exercise rehabilitation because their relatively low baseline physical function does not impair their ability to regain lost functional independence to levels similar to nonsmoking patients with PAD
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