9,537 research outputs found
Three-dimensional magnetostatic models of the large-scale corona
A special class of magnetostatic equilibria is described, which are mathematically simple and yet sufficiently versatile so as to fit any arbitrary normal magnetic flux prescribed at the photosphere. With these solutions, the corona can be modeled with precisely the same mathematically simple procedure as has previously been done with potential fields. The magnetostatic model predicts, in addition to the coronal magnetic field, the three dimensional coronal density which can be compared with coronagraph observations
Corrections to deuterium hyperfine structure due to deuteron excitations
We consider the corrections to deuterium hyperfine structure originating from
the two-photon exchange between electron and deuteron, with the deuteron
excitations in the intermediate states. In particular, the motion of the two
intermediate nucleons as a whole is taken into account. The problem is solved
in the zero-range approximation. The result is in good agreement with the
experimental value of the deuterium hyperfine splitting.Comment: 7 pages, LaTe
Wolf-Rayet and LBV Nebulae as the Result of Variable and Non-Spherical Stellar Winds
The physical basis for interpreting observations of nebular morphology around
massive stars in terms of the evolution of the central stars is reviewed, and
examples are discussed, including NGC 6888, OMC-1, and eta Carinae.Comment: To be published in the Proceedings of IAU Colloquium 169 on Variable
and Non-Spherical Stellar Winds in Luminous Hot Stars, ed. B. Wolf
(Springer-Verlag, Berlin, Heidelberg). 7 pages, including 5 figures. A
full-resolution version of fig 4 is available in the version at
http://www.mpia-hd.mpg.de/theory/preprints.html#maclo
Low-energy interaction of composite spin-half systems with scalar and vector fields
We consider a composite spin-half particle moving in spatially-varying scalar
and vector fields. The vector field is assumed to couple to a conserved charge,
but no assumption is made about either the structure of the composite or its
coupling to the scalar field. A general form for the piece of the spin-orbit
interaction of the composite with the scalar and vector fields which is
first-order in momentum transfer and second-order in the fields is
derived.Comment: 10 pages, RevTe
Error Voltage Components in Quantitative Voltage Contrast Measurement Systems
This paper presents the results of computer simulation studies into the respective contributions of the potential barrier, the off-normal incidence injection of secondary electrons (SEs) into the retarding field and analyser geometry on Types I and II local field error voltages for a practical 20 mm wide planar retarding field energy analyser. Results show that the error voltage component due to the off-normal incidence injection effect of SEs into the retarding field dominates the Type I local field error. For type II LFE, the error voltage component due to analyser geometry effect is the higher contributing factor. The presence of a neighbouring electrode voltage tends to draw SEs away from the central axis of the energy analyser, thus causing the electron trajectories to be more sensitive to the influence of the analyser geometry
Linking and causality in globally hyperbolic spacetimes
The linking number is defined if link components are zero homologous.
Our affine linking invariant generalizes to the case of linked
submanifolds with arbitrary homology classes. We apply to the study of
causality in Lorentz manifolds. Let be a spacelike Cauchy surface in a
globally hyperbolic spacetime . The spherical cotangent bundle
is identified with the space of all null geodesics in
Hence the set of null geodesics passing through a point gives an
embedded -sphere in called the sky of Low observed
that if the link is nontrivial, then are causally
related. This motivated the problem (communicated by Penrose) on the Arnold's
1998 problem list to apply link theory to the study of causality. The spheres
are isotopic to fibers of They are nonzero
homologous and is undefined when is closed, while is well defined. Moreover, if is not an
odd-dimensional rational homology sphere. We give a formula for the increment
of \alk under passages through Arnold dangerous tangencies. If is
such that takes values in and is conformal to having all
the timelike sectional curvatures nonnegative, then are causally
related if and only if . We show that in
nonrefocussing are causally unrelated iff can be deformed
to a pair of -fibers of by an isotopy through skies. Low
showed that if (\ss, g) is refocussing, then is compact. We show that the
universal cover of is also compact.Comment: We added: Theorem 11.5 saying that a Cauchy surface in a refocussing
space time has finite pi_1; changed Theorem 7.5 to be in terms of conformal
classes of Lorentz metrics and did a few more changes. 45 pages, 3 figures. A
part of the paper (several results of sections 4,5,6,9,10) is an extension
and development of our work math.GT/0207219 in the context of Lorentzian
geometry. The results of sections 7,8,11,12 and Appendix B are ne
Composite, multilayer and three-dimensional substrate supported tin-based electrodeposits from methanesulphonic acid
Docosahexaenoic Acid supplementation, vascular function and risk factors for cardiovascular disease: a randomized controlled trial in young adults
A high consumption of omega-3 long-chain polyunsaturated fatty acids, and particularly docosahexaenoic acid (DHA), has been suggested to reduce the risk of cardiovascular disease (CVD). However, while DHA supplementation may have benefits for secondary prevention, few studies have investigated the role of DHA in the primary prevention of CVD. Here, we tested the hypothesis that DHA supplementation improves endothelial function and risk factors for CVD
Community pharmacists' opinions of their role in administering non-prescription medicines in an emergency
Objective: To obtain community pharmacistsâ opinions of their role in administering Pharmacy (S2) and Pharmacist Only (S3) Medicines in a medical emergency. These medicines can only be sold in a pharmacy and are not available for self-selection by patients. Whilst qualified pharmacy assistants can supply S2 medicines, pharmacists must be directly involved in the supply of S3 medicines. Setting: Community pharmacies in South East Queensland, Australia. Method: A survey of 151 Gold Coast and Toowoomba community pharmacists was conducted during October 2009. Main outcome measures: Pharmacists were asked their opinions as to whether the administration of S2 and S3 medicines should fall within their scope of practice, whether they had administered S2 and S3 medicines in a medical emergency in the past and if clarification of this role was required. Results: The study achieved a 30% (n = 45) response rate and demonstrated similar results regarding whether pharmacists should administer salbutamol (22/44), adrenaline (23/42), glyceryl trinitrate (22/43) and aspirin (18/36) in a medical emergency. The majority (36/43) believed that role clarification was required. Pharmacists were more likely to administer an S3 medicine in a medical emergency when they considered potential outcomes first, had no easy access to a doctor and the patient could not administer the medicine they carried with them themselves (40/45).Conclusion: Community pharmacists have direct access to S2 and S3 medicines that could be required in the management of a variety of medical emergencies. This study demonstrates that some pharmacists have administered S2 and S3 medicines in an emergency situation. However, there are currently no clear guidelines for pharmacists when faced with a medical emergency other than to act within their professional competence. To promote patient safety through the appropriate use of S2 and S3 medicines in the event of a medical emergency, additional training of pharmacists on the administration of these readily accessible medicines is needed. Clarification of the role of pharmacists in an emergency situation is required
An implicit method for radiative transfer with the diffusion approximation in SPH
An implicit method for radiative transfer in SPH is described. The diffusion
approximation is used, and the hydrodynamic calculations are performed by a
fully three--dimensional SPH code. Instead of the energy equation of state for
an ideal gas, various energy states and the dissociation of hydrogen molecules
are considered in the energy calculation for a more realistic temperature and
pressure determination. In order to test the implicit code, we have performed
non--isothermal collapse simulations of a centrally condensed cloud, and have
compared our results with those of finite difference calculations performed by
MB93. The results produced by the two completely different numerical methods
agree well with each other.Comment: 25 pages, 9 figure
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