25,399 research outputs found
Relativistic corrections to the Pionium Lifetime
Next to leading order contributions to the pionium lifetime are considered
within non-relativistic effective field theory. A more precise determination of
the coupling constants is then needed in order to be consistent with the
relativistic pion-pion scattering amplitude which can be obtained from chiral
perturbation theory. The relativistic correction is found to be 4.1% and
corresponds simply to a more accurate value for the non-relativistic decay
momentum.Comment: 5 pages, Latex. Includes corrections based on a more precise matching
to the pion-pion scattering amplitude from chiral perturbation theor
Time-Periodic Solutions of the Einstein's Field Equations II
In this paper, we construct several kinds of new time-periodic solutions of
the vacuum Einstein's field equations whose Riemann curvature tensors vanish,
keep finite or take the infinity at some points in these space-times,
respectively. The singularities of these new time-periodic solutions are
investigated and some new physical phenomena are found. The applications of
these solutions in modern cosmology and general relativity can be expected.Comment: 10 pages, 1 figur
Include medical ethics in the Research Excellence Framework
The Research Excellence Framework of the Higher Education
Funding Council for England is taking place in 2013, its three
key elements being outputs (65% of the profile), impact (20%),
and âquality of the research environmentâ (15%). Impact will
be assessed using case studies that âmay include any social,
economic or cultural impact or benefit beyond academia that
has taken place during the assessment period.â1
Medical ethics in the UK still does not have its own cognate
assessment panelâfor example, bioethics or applied
ethicsâunlike in, for example, Australia. Several researchers
in medical ethics have reported to the Institute of Medical Ethics
that during the internal preliminary stage of the Research
Excellence Framework several medical schools have decided
to include only research that entails empirical data gathering.
Thus, conceptual papers and ethical analysis will be excluded.
The arbitrary exclusion of reasoned discussion of medical ethics
issues as a proper subject for medical research unless it is based
on empirical data gathering is conceptually mistaken. âEmpirical
ethicsâ is, of course, a legitimate component of medical ethics
research, but to act as though it is the only legitimate component
suggests, at best, a partial understanding of the nature of ethics
in general and medical ethics in particular. It also mistakenly
places medicine firmly on only one side of the
science/humanities âtwo culturesâ divide instead of in its rightful
place bridging the divide.
Given the emphasis by the General Medical Council on medical
ethics in properly preparing âtomorrowâs doctors,â we urge
medical schools to find a way of using the upcoming Research
Excellence Framework to highlight the expertise residing in
their ethicist colleagues. We are confident that appropriate
assessment will reveal work of high quality that can be shown
to have social and cultural impact and benefit beyond academia,
as required by the framework
New Results for Diffusion in Lorentz Lattice Gas Cellular Automata
New calculations to over ten million time steps have revealed a more complex
diffusive behavior than previously reported, of a point particle on a square
and triangular lattice randomly occupied by mirror or rotator scatterers. For
the square lattice fully occupied by mirrors where extended closed particle
orbits occur, anomalous diffusion was still found. However, for a not fully
occupied lattice the super diffusion, first noticed by Owczarek and Prellberg
for a particular concentration, obtains for all concentrations. For the square
lattice occupied by rotators and the triangular lattice occupied by mirrors or
rotators, an absence of diffusion (trapping) was found for all concentrations,
except on critical lines, where anomalous diffusion (extended closed orbits)
occurs and hyperscaling holds for all closed orbits with {\em universal}
exponents and . Only one point on these critical lines can be related to a
corresponding percolation problem. The questions arise therefore whether the
other critical points can be mapped onto a new percolation-like problem, and of
the dynamical significance of hyperscaling.Comment: 52 pages, including 18 figures on the last 22 pages, email:
[email protected]
Radiative corrections to the Casimir force and effective field theories
Radiative corrections to the Casimir force between two parallel plates are
considered in both scalar field theory of one massless and one massive field
and in QED. Full calculations are contrasted with calculations based on
employing ``boundary-free'' effective field theories. The difference between
two previous results on QED radiative corrections to the Casimir force between
two parallel plates is clarified and the low-energy effective field theory for
the Casimir effect in QED is constructed.Comment: 17 pages, revte
Phonon self-energy corrections to non-zero wavevector phonon modes in single-layer graphene
Phonon self-energy corrections have mostly been studied theoretically and
experimentally for phonon modes with zone-center (q = 0) wave-vectors. Here,
gate-modulated Raman scattering is used to study phonons of a single layer of
graphene (1LG) in the frequency range from 2350 to 2750 cm-1, which shows the
G* and the G'-band features originating from a double-resonant Raman process
with q \not= 0. The observed phonon renormalization effects are different from
what is observed for the zone-center q = 0 case. To explain our experimental
findings, we explored the phonon self-energy for the phonons with non-zero
wave-vectors (q \not= 0) in 1LG in which the frequencies and decay widths are
expected to behave oppositely to the behavior observed in the corresponding
zone-center q = 0 processes. Within this framework, we resolve the
identification of the phonon modes contributing to the G* Raman feature at 2450
cm-1 to include the iTO+LA combination modes with q \not= 0 and the 2iTO
overtone modes with q = 0, showing both to be associated with wave-vectors near
the high symmetry point K in the Brillouin zone
Squamous Cell Carcinoma in a Heel Ulcer in a Patient With Diabetes
A technique for measuring B-H curves of grain-oriented silicon steel along arbitrary directions has been developed. As the control of waveform is not necessary in this technique, it is possible to measure B-H curves up to high flux densities which are required for calculating flux distribution using the finite element method</p
Spin Hall Effect in Doped Semiconductor Structures
In this Letter we present a microscopic theory of the extrinsic spin Hall
effect based on the diagrammatic perturbation theory. Side-jump (SJ) and
skew-scattering (SS) contributions are explicitly taken into account to
calculate the spin Hall conductivity, and we show their effects scale as
, with
being the transport relaxation time. Motivated by recent experimental work we
apply our theory to n- and p-doped 3D and 2D GaAs structures, obtaining
where is the spin Hall
(charge) conductivity, which is in reasonable agreement with the recent
experimental results of Kato \textit{et al}. [Science \textbf{306}, 1910
(2004)] in n-doped 3D GaAs system.Comment: 5 pages, 2 figure
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