251 research outputs found
The group structure of non-Abelian NS-NS transformations
We study the transformations of the worldvolume fields of a system of
multiple coinciding D-branes under gauge transformations of the supergravity
Kalb-Ramond field. We find that the pure gauge part of these NS-NS
transformations can be written as a U(N) symmetry of the underlying Yang-Mills
group, but that in general the full NS-NS variations get mixed up non-trivially
with the U(N). We compute the commutation relations and the Jacobi identities
of the bigger group formed by the NS-NS and U(N) transformations.Comment: Latex, 11 pages. v2: Typos corrected; version to appear in JHEP
Fake supersymmetry versus Hamilton-Jacobi
We explain when the first-order Hamilton-Jacobi equations for black holes
(and domain walls) in (gauged) supergravity, reduce to the usual first-order
equations derived from a fake superpotential. This turns out to be equivalent
to the vanishing of a newly found constant of motion and we illustrate this
with various examples. We show that fake supersymmetry is a necessary condition
for having physically sensible extremal black hole solutions. We furthermore
observe that small black holes become scaling solutions near the horizon. When
combined with fake supersymmetry, this leads to a precise extension of the
attractor mechanism to small black holes: The attractor solution is such that
the scalars move on specific curves, determined by the black hole charges, that
are purely geodesic, although there is a non-zero potential.Comment: 20 pages, v2: Typos corrected, references adde
First results from the Solar Orbiter Heavy Ion Sensor
Context.
Aims. Solar Orbiter launched in February 2020 with the goal of revealing the connections between the Sun’s interior, atmosphere, and
the heliosphere. The Solar Orbiter Heavy Ion Sensor (HIS) is a time-of-flight ion mass spectrometer dedicated to measuring heavy
ions in the solar wind.
Methods. We present an overview of the first measurements of heavy ion composition from HIS, reviewing the methods used to
transform the spectra obtained on board into scientific data products and examining two solar wind case studies as well as the
statistical properties of the heavy ion composition observed by HIS. We also carried out a comparison with prior measurements of
heavy ions at L1.
Results. The HIS data set provides the first mass- and charge-resolved heavy ion measurements in the inner heliosphere.
Conclusions. These high temporal resolution data have the potential to transform our understanding of the connections between the
solar wind and its origin at the Sun, as well as the interaction between the solar wind and the environment around planets, comets,
and in the interstellar medium
Standard psychological consultations and follow up for women at increased risk of hereditary breast cancer considering prophylactic mastectomy
__Background:__ Women at increased (genetic) risk of breast cancer have to weigh the personal pros and cons of prophylactic mastectomy (PM) as an option to reduce their cancer risk. So far, no routine referral to a psychologist has been investigated for women considering PM.
Aim of this study was to asses:
1) the acceptance of the offer of a standard psychological consultation as part of pre-surgical decision-making in high-risk women,
2) reasons for PM and reasons for postponing it,
3) the need for additional psychological interventions, and factors associated, and
4) the frequency of psychiatric/psychological treatment history.
__Methods:__ During a 30 months period, women at high risk considering PM were offered a psychological consultation. The content of these, and follow-up, consultations were analyzed.
__Results:__ Most women (70 out of 73) accepted the psychological consultation, and 81% proceeded with PM. Main reasons for undergoing PM were to reduce anxiety about cancer, and to reduce the cancer risk. Uncertainty about surgery and the need for further information were the reasons given most frequently for postponing PM. Additional psychological support was given to 31% before and 14% after PM. The uptake of additional support was significantly higher in women with a BRCA1/2 mutation. A history of psychiatric/psychological treatment was present in 36%, mainly consisting of depression and grief after death of a mother.
__Conclusion:__ The uptake-rate of the standard psychological consultation indicates a high level of acceptability of this service for women deciding about PM. Since anxiety is one of the main reasons for considering PM, and depression and grief were present in a third, a standard consultation with a psychologist for high-risk women considering PM may be indicated. This may help them arrive at an informed decision, to detect and manage psychological distress, and to plan psychological support services
Minute ventilation of cyclists, car and bus passengers: an experimental study
<p>Abstract</p> <p>Background</p> <p>Differences in minute ventilation between cyclists, pedestrians and other commuters influence inhaled doses of air pollution. This study estimates minute ventilation of cyclists, car and bus passengers, as part of a study on health effects of commuters' exposure to air pollutants.</p> <p>Methods</p> <p>Thirty-four participants performed a submaximal test on a bicycle ergometer, during which heart rate and minute ventilation were measured simultaneously at increasing cycling intensity. Individual regression equations were calculated between heart rate and the natural log of minute ventilation. Heart rates were recorded during 280 two hour trips by bicycle, bus and car and were calculated into minute ventilation levels using the individual regression coefficients.</p> <p>Results</p> <p>Minute ventilation during bicycle rides were on average 2.1 times higher than in the car (individual range from 1.3 to 5.3) and 2.0 times higher than in the bus (individual range from 1.3 to 5.1). The ratio of minute ventilation of cycling compared to travelling by bus or car was higher in women than in men. Substantial differences in regression equations were found between individuals. The use of individual regression equations instead of average regression equations resulted in substantially better predictions of individual minute ventilations.</p> <p>Conclusion</p> <p>The comparability of the gender-specific overall regression equations linking heart rate and minute ventilation with one previous American study, supports that for studies on the group level overall equations can be used. For estimating individual doses, the use of individual regression coefficients provides more precise data. Minute ventilation levels of cyclists are on average two times higher than of bus and car passengers, consistent with the ratio found in one small previous study of young adults. The study illustrates the importance of inclusion of minute ventilation data in comparing air pollution doses between different modes of transport.</p
In vivo effects of antibodies from patients with anti-NMDA receptor encephalitis: further evidence of synaptic glutamatergic dysfunction
Background: A severe encephalitis that associates with auto-antibodies to the NR1 subunit of the NMDA receptor (NMDA-R) was recently reported. Patients' antibodies cause a decrease of the density of NMDA-R and synaptic mediated currents, but the in vivo effects on the extracellular glutamate and glutamatergic transmission are unknown. Methods. We investigated the acute metabolic effects of patients' CSF and purified IgG injected in vivo. Injections were performed in CA1 area of Ammon's horn and in premotor cortex in rats. Results: Patient's CSF increased the concentrations of glutamate in the extracellular space. The increase was dose-dependent and was dramatic with purified IgG. Patients' CSF impaired both the NMDA- and the AMPA-mediated synaptic regulation of glutamate, and did not affect the glial transport of glutamate. Blockade of GABA-A receptors was associated with a marked elevation of extra-cellular levels of glutamate following a pretreatment with patients' CSF. Conclusion: These results support a direct role of NMDA-R antibodies upon altering glutamatergic transmission. Furthermore, we provide additional evidence in vivo that NMDA-R antibodies deregulate the glutamatergic pathways and that the encephalitis associated with these antibodies is an auto-immune synaptic disorder. © 2010 Manto et al; licensee BioMed Central Ltd.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Is TEA an inhibitor for human Aquaporin-1?
Excessive water uptake through aquaporins can be life threatening, and disregulation of water permeability causes many diseases. Therefore, reversible aquaporin inhibitors are highly desired. In this paper, we identified the binding site for tetraethylammonium (TEA) of the membrane water channel aquaporin-1 by a combined molecular docking and molecular dynamics simulation approach. The binding site identified from docking studies was independently confirmed with an unbiased molecular dynamics simulation of an aquaporin tetramer embedded in a lipid membrane, surrounded by a 100-mM tetraethylammonium solution in water. A third independent assessment of the binding site was obtained by umbrella sampling simulations. These simulations, in addition, revealed a binding affinity of more than 17 kJ/mol, corresponding to an IC50 value of << 3 mM. Finally, we observed in our simulations a 50% reduction of the water flux in the presence of TEA, in agreement with water permeability measurements on aquaporin expressed in oocytes. These results confirm TEA as a putative lead for an aquaporin-1 inhibitor
Exploring the views of young women and their healthcare professionals on dietary habits and supplementation practices in adolescent pregnancy: a qualitative study
Background: Nutrition is a modifiable factor affecting foetal growth and pregnancy outcomes. Inadequate nutrition
is of particular concern in adolescent pregnancies with poor quality diet and competing demands for nutrients. The
aim of this study was to explore knowledge and understanding of nutrition advice during adolescent pregnancy,and identify barriers and facilitators to dietary change and supplementation use in this vulnerable population.
Methods: Semi-structured interviews were conducted with young women and key antenatal healthcare providers:
midwives, family nurses and obstetricians. Doncaster, Manchester and London were chosen as sites offering different models of midwifery care alongside referral to the Family Nurse Partnership programme.
Results: A total of 34 young women (adolescents aged 16–19 years) and 20 health professionals were interviewed.
Young women made small changes to their dietary intake despite limited knowledge and social constraints.
Supplementation use varied; the tablet format was identified by few participants as a barrier but forgetting to take them was the main reason for poor adherence. Health professionals provided nutrition information but
often lack the time and resources to tailor this appropriately. Young women’s prime motivator was a desire
to have a healthy baby; they wanted to understand the benefits of supplementation and dietary change in
those terms.
Conclusion: Pregnancy is a window of opportunity for improving nutrition but often constrained by social
circumstances. Health professionals should be supported in their role to access education, training and resources which
build their self-efficacy to facilitate change in this vulnerable population group beyond the routine care they provide
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