1,931 research outputs found
Comment on "New Experimental Limit for the Electric Dipole Moment of the Neutron"
A new limit for the neutron electric dipole moment has been recently
reported. This new limit is obtained by combining the result from a previous
experiment with the result from a more recent experiment that has much worse
statistical accuracy. We show that the old result has a systematic error
possibly four times greater than the new limit, and under the circumstances,
averaging of the old and new results is statistically invalid. The conclusion
is that it would be more appropriate to quote two independent but mutually
supportive limits as obtained from each experiment separately.Comment: 7 pages, 2 figure
Prosopis pods as human food, with special reference to Kenya
Several legume tree and shrub species of the genus Prosopis from South and Central America have been distributed around the dry regions of the world over the past 200 years. The first documented introduction of Prosopis in Kenya was in 1973, since when it has spread widely, adversely affecting natural habitats, rangelands and cultivated areas. P. juliflora is the most common naturalised species in Kenya, but P. pallida also occurs. In contrast to their undesirable effects as invasive weeds, many Prosopis species are valuable multipurpose resources in their native range, providing timber, firewood, livestock feed, human food, shade, shelter and soil improvement. The pods, which are high in sugars, carbohydrates and protein, have been a historic source of food for human populations in North and South America providing flour and other edible products. However, this indigenous knowledge has not followed the Prosopis trees and the fruit are unused or provide only fodder for livestock in most of Africa and Asia. Although Prosopis will not easily be eradicated in Kenya, a degree of control may be achieved through intensive utilisation of tree products and by improved management. In 2005, a project was launched in Kenya to develop income-generating activities using Prosopis. A workshop in 2006 explored the possibility of producing locally-acceptable food from Prosopis flour. Taste tests and feedback on the different recipes indicated that all of the food made with 20% Prosopis flour had a pleasant taste. Preliminary analyses of Prosopis flour samples from Kenya indicate good nutritional properties, but also the presence of aflatoxins and Ochratoxin A. Further study is required to determine toxin levels in freshly harvested pods, and in pods and flour after various periods of storage, and to develop appropriate harvesting and storage methods to maximise nutritional benefit and minimise risk to human health.Keywords: Aflatoxin, human food, Kenya, Ochratoxin A, Prosopi
The Casimir Problem of Spherical Dielectrics: Numerical Evaluation for General Permittivities
The Casimir mutual free energy F for a system of two dielectric concentric
nonmagnetic spherical bodies is calculated, at arbitrary temperatures. The
present paper is a continuation of an earlier investigation [Phys. Rev. E {\bf
63}, 051101 (2001)], in which F was evaluated in full only for the case of
ideal metals (refractive index n=infinity). Here, analogous results are
presented for dielectrics, for some chosen values of n. Our basic calculational
method stems from quantum statistical mechanics. The Debye expansions for the
Riccati-Bessel functions when carried out to a high order are found to be very
useful in practice (thereby overflow/underflow problems are easily avoided),
and also to give accurate results even for the lowest values of l down to l=1.
Another virtue of the Debye expansions is that the limiting case of metals
becomes quite amenable to an analytical treatment in spherical geometry. We
first discuss the zero-frequency TE mode problem from a mathematical viewpoint
and then, as a physical input, invoke the actual dispersion relations. The
result of our analysis, based upon the adoption of the Drude dispersion
relation at low frequencies, is that the zero-frequency TE mode does not
contribute for a real metal. Accordingly, F turns out in this case to be only
one half of the conventional value at high temperatures. The applicability of
the Drude model in this context has however been questioned recently, and we do
not aim at a complete discussion of this issue here. Existing experiments are
low-temperature experiments, and are so far not accurate enough to distinguish
between the different predictions. We also calculate explicitly the
contribution from the zero-frequency mode for a dielectric. For a dielectric,
this zero-frequency problem is absent.Comment: 23 pages, LaTeX, 7 ps figures; expanded discussion, especially in
Sec. 5. To appear in Phys. Rev.
Temperature correction to the Casimir force in cryogenic range and anomalous skin effect
Temperature correction to the Casimir force is considered for real metals at
low temperatures. With the temperature decrease the mean free path for
electrons becomes larger than the field penetration depth. In this condition
description of metals with the impedance of anomalous skin effect is shown to
be more appropriate than with the permittivity. The effect is crucial for the
temperature correction. It is demonstrated that in the zero frequency limit the
reflection coefficients should coincide with those of ideal metal if we demand
the entropy to be zero at T=0. All the other prescriptions discussed in the
literature for the term in the Lifshitz formula give negative entropy. It
is shown that the temperature correction in the region of anomalous skin effect
is not suppressed as it happens in the plasma model. This correction will be
important in the future cryogenic measurements of the Casimir force.Comment: 12 pages, 2 figures, to be published in Phys. Rev.
Interplay of magnetic order and Jahn-Teller distortion in a model with strongly correlated electron system
The Hubbard model has been employed successfully to understand many aspects
of correlation driven physical properties, in particular, the magnetic order in
itenerant electron systems. In some systems such as Heusler alloys, manganites
etc., it is known that, in addition to magnetic order, distortion induced by
Jahn-Teller(J-T) effect also exists. In this paper, based on two-fold
degenerate Hubbard model, the influence of magnetic order on J-T distortion is
investigated. The electron correlation is treated using a spectral density
approach and J-T interaction is added to the model. We find that magnetic order
and structural distortion coexist at low temperature for a certain range of
electron correlation strength , J-T coupling strength and band
occupation . At T=0, for a given and , magnetic order is present but
distortion appears only for a larger than a critical value. We also studied
the temperature dependence of lattice strain and magnetization choosing a
close to the critical value.Comment: 12 pages, 5 Figures. Physica- B 405 1701-1705 (2010
The Magnetic Casimir Effect
The Casimir effect results from alterations of the zero-point electromagnetic
energy introduced by boundary-conditions. For ferromagnetic layers separated by
vacuum (or a dielectric) such boundary-conditions are influenced by the
magneto-optical Kerr effect. We will show that this gives rise to a long-range
magnetic interaction and discuss the effect for two different configurations
(magnetization parallel and perpendicular to the layers). Analytical
expressions are derived for two models and compared to numerical calculations.
Numerical calculations of the effect for Fe are also presented and the
possibility of an experimental observation of the Casimir magnetic interaction
is discussed
Neutron-Electron EDM Correlations in Supersymmetry and Prospects for EDM Searches
Motivated by recent progress in experimental techniques of electric dipole
moment (EDM) measurements, we study correlations between the neutron and
electron EDMs in common supersymmetric models. These include minimal
supergravity (mSUGRA) with small CP phases, mSUGRA with a heavy SUSY spectrum,
the decoupling scenario and split SUSY. In most cases, the electron and neutron
EDMs are found to be observable in the next round of EDM experiments. They
exhibit certain correlation patterns. For example, if d_n ~ 10^{-27} e cm is
found, d_e is predicted to lie in the range 10^{-28}-10^{-29} e cm.Comment: 16 pages,12 figures. To appear in JHEP. A note on stability of the
correlations added in Conclusions; refs. and footnotes adde
Evaluating public involvement in research design and grant development: Using a qualitative document analysis method to analyse an award scheme for researchers
Background
A regional Research Design Service, funded by the National Institute for Health Research, introduced a small grant in 2008, to support public involvement (often known as patient and public involvement [PPI]) activities during the development of applications for research funding. Successful applicants are requested to submit a report detailing how the grant money was used, including a description of the aims and outcomes of the public involvement activities. The purpose of this study was to analyse the content of these reports. We aimed to find out what researcher views and experiences of public involvement activities were, and what lessons might be learned.
Methods
We used an innovative method of data analysis, drawing on group participatory approaches, qualitative content analysis, and Framework Analysis to sort and label the content of the reports. We developed a framework of categories and sub-categories (or themes and sub-themes) from this process.
Results
Twenty five documents were analysed. Four main themes were identified in the data: the added value of public involvement; planning and designing involvement; the role of public members; and valuing public member contributions. Within these themes, sub-themes related to the timing of involvement (prior to the research study/intended during the research study), and also specific benefits of public involvement such as: validating ideas; ensuring appropriate outcomes; ensuring the acceptability of data collection methods/tools and advice regarding research processes. Other sub-themes related to: finding and approaching public members; timing of events; training/support; the format of sessions; setting up public involvement panels: use of public contributors in analysis and interpretation of data; and using public members to assist with dissemination and translation into practice.
Conclusions
The analysis of reports submitted by researchers following involvement events provides evidence of the value of public involvement during the development of applications for research funding, and details a method for involving members of the public in data analysis which could be of value to other researchers The findings of the analysis indicate recognition amongst researchers of the variety in potential roles for public members in research, and also an acknowledgement of how involvement adds value to studies
Lateral projection as a possible explanation of the nontrivial boundary dependence of the Casimir force
We find the lateral projection of the Casimir force for a configuration of a
sphere above a corrugated plate. This force tends to change the sphere position
in the direction of a nearest corrugation maximum. The probability distribution
describing different positions of a sphere above a corrugated plate is
suggested which is fitted well with experimental data demonstrating the
nontrivial boundary dependence of the Casimir force.Comment: 5 pages, 1 figur
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