12,115 research outputs found
Reflection above the barrier as tunneling in momentum space
Quantum mechanics predicts an exponentially small probability that a particle
with energy greater than the height of a potential barrier will nevertheless
reflect from the barrier in violation of classical expectations. This process
can be regarded as tunneling in momentum space, leading to a simple derivation
of the reflection probability.Comment: 7 pages, 3 figures, submitted to American Journal of Physics. Version
2: MIT preprint number added, typographical error in caption to Figure 2
correcte
SU(3) symmetry breaking in decay constants and electromagnetic properties of pseudoscalar heavy mesons
In this paper, the decay constants and mean square radii of pseudoscalar
heavy mesons are studied in the SU(3) symmetry breaking. Within the light-front
framework, the ratios and are individually
estimated using the hyperfine splittings in the and
states and the light quark masses, (), to
extract the wave function parameter . The values and are obtained, which are not only
chiefly determined by the ratio of light quark masses , but also
insensitive to the heavy quark masses and the decay constants
. The dependence of on with the
varied charm quark masses is also shown. In addition, the mean square radii are
estimated as well. The values and are obtained, and the sensitivities of on
the heavy and light quark masses are similar to those of the decay constants.Comment: 21 pages, 5 figures, 4 tables, some typos are corrected, version to
be published in Phys. Rev.
Fitting Together the HI Absorption and Emission in the SGPS
In this paper we study 21-cm absorption spectra and the corresponding
emission spectra toward bright continuum sources in the test region (326deg< l
< 333 deg) of the Southern Galactic Plane Survey. This survey combines the high
resolution of the Australia Telescope Compact Array with the full brightness
temperature information of the Parkes single dish telescope. In particular, we
focus on the abundance and temperature of the cool atomic clouds in the inner
galaxy. The resulting mean opacity of the HI, , is measured as a
function of Galactic radius; it increases going in from the solar circle, to a
peak in the molecular ring of about four times its local value. This suggests
that the cool phase is more abundant there, and colder, than it is locally.
The distribution of cool phase temperatures is derived in three different
ways. The naive, ``spin temperature'' technique overestimates the cloud
temperatures, as expected. Using two alternative approaches we get good
agreement on a histogram of the cloud temperatures, T(cool), corrected for
blending with warm phase gas. The median temperature is about 65 K, but there
is a long tail reaching down to temperatures below 20 K. Clouds with
temperatures below 40 K are common, though not as common as warmer clouds (40
to 100 K).
Using these results we discuss two related quantities, the peak brightness
temperature seen in emission surveys, and the incidence of clouds seen in HI
self-absorption. Both phenomena match what would be expected based on our
measurements of and T(cool).Comment: 50 pages, 20 figure
Promoting family inclusive practice in Home Treatment Teams
Purpose
Families play an instrumental role in helping their relatives experiencing mental health issues to stay well. This study aimed to evaluate the feasibility, acceptability and potential benefits of a bespoke one-day workshop for practitioners working with families in crisis.
Design
The study was an uncontrolled evaluation of a one-day workshop for Home Treatment Team practitioners (HTTs) using pre and post-workshop questionnaires.
Findings
Eighty three practitioners participated. Overall, there was strong agreement for the involvement of families in their relative’s care, which increased marginally following the workshop. There were significant changes in views about talking to family members without service user consent (p=0.001) and keeping them informed of their relative’s wellbeing (p=0.02).
Qualitative feedback indicated that participants enjoyed the interactive elements of the workshop, particularly the opportunity to practise skills. It encouraged participants to share knowledge and facilitate the integration of family work into their professional role.
Research and practical implications
Support for families can contribute to effective mediation of crisis and continuation of care; factors that are important in reducing admission rates and protecting relationships. Participants’ responses suggested that this one-day workshop offered a helpful introduction to a family approach at times of a mental health crisis, which could be routinely offered in HTTs.
Originality/value
A social systems perspective is at the heart of a successful HTT approach to managing mental health crises. This workshop offered a feasible means to address one element of the necessary conditions for family-focused practice; practitioner confidence to talk with families at times of crisis
Are Simple Real Pole Solutions Physical?
We consider exact solutions generated by the inverse scattering technique,
also known as the soliton transformation. In particular, we study the class of
simple real pole solutions. For quite some time, those solutions have been
considered interesting as models of cosmological shock waves. A coordinate
singularity on the wave fronts was removed by a transformation which induces a
null fluid with negative energy density on the wave front. This null fluid is
usually seen as another coordinate artifact, since there seems to be a general
belief that that this kind of solution can be seen as the real pole limit of
the smooth solution generated with a pair of complex conjugate poles in the
transformation. We perform this limit explicitly, and find that the belief is
unfounded: two coalescing complex conjugate poles cannot yield a solution with
one real pole. Instead, the two complex conjugate poles go to a different
limit, what we call a ``pole on a pole''. The limiting procedure is not unique;
it is sensitive to how quickly some parameters approach zero. We also show that
there exists no improved coordinate transformation which would remove the
negative energy density. We conclude that negative energy is an intrinsic part
of this class of solutions.Comment: 13 pages, 3 figure
The role of caking in optimising the performance of a concertinaed ceramic filtration membrane
Membrane filtration is a process of separating particles from fluids. Over time, particles are trapped within the membrane structure and on the membrane surface, forming a cake. In this paper, we develop a mathematical model for the transient blocking dynamics in a concertinaed filtration device composed of angled porous membranes and dead-ends. We examine how the inclusion of particles affects the flow dynamics, and we uncover potential inaccuracies in relying on flux–throughput curves to distinguish between caking and internal blocking dynamics. Moreover, we show that optimal filtration performance strongly depends on both the performance metric and the membrane configuration. Finally, to optimise the use of membrane area, we introduce a method for deriving a non-uniform permeance that ensures constant initial cake growth
Neutrino current in a gravitational plane wave collision background
The behaviour of a massless Dirac field on a general spacetime background
representing two colliding gravitational plane waves is discussed in the
Newman-Penrose formalism. The geometrical properties of the neutrino current
are analysed and explicit results are given for the special Ferrari-Ibanez
solution.Comment: 17 pages, 6 Postscript figures, accepted by International Journal of
Modern Physics
Billiard algebra, integrable line congruences, and double reflection nets
The billiard systems within quadrics, playing the role of discrete analogues
of geodesics on ellipsoids, are incorporated into the theory of integrable
quad-graphs. An initial observation is that the Six-pointed star theorem, as
the operational consistency for the billiard algebra, is equivalent to an
integrabilty condition of a line congruence. A new notion of the
double-reflection nets as a subclass of dual Darboux nets associated with
pencils of quadrics is introduced, basic properies and several examples are
presented. Corresponding Yang-Baxter maps, associated with pencils of quadrics
are defined and discussed.Comment: 18 pages, 8 figure
Particle Propagation on a Circle with a Point Interaction
We study a particle propagation on a circle in the presence of a point
interaction. We show that the one-particle Feynman kernel can be written into
the sum of reflected and transmitted trajectories which are weighted by the
elements of the n-th power of the scattering matrix evaluated on a line with a
point interaction. As a by-product we find three-parameter family of trace
formulae as a generalization of the Poisson summation formula.Comment: 21 pages, 12 figure
Online gaming addiction: the role of sensation seeking, self-control, neuroticism, aggression, state anxiety and trait anxiety
Research into online gaming has steadily increased over the last decade, although relatively little research has examined the relationship between online gaming addiction and personality factors. This study examined the relationship between a number of personality traits (sensation seeking, self-control, aggression, neuroticism, state anxiety, and trait anxiety) and online gaming addiction. Data were collected over a 1-month period using an opportunity sample of 123 university students at an East Midlands university in the United Kingdom. Gamers completed all the online questionnaires. Results of a multiple linear regression indicated that five traits (neuroticism, sensation seeking, trait anxiety, state anxiety, and aggression) displayed significant associations with online gaming addiction. The study suggests that certain personality traits may be important in the acquisition, development, and maintenance of online gaming addiction, although further research is needed to replicate the findings of the present study
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