1,595 research outputs found
Comment on "Role of heavy meson exchange in near threshold N N --> d pi"
In a recent paper by C. J. Horowitz (Phys. Rev. C {\bf 48}, 2920 (1993)) a
heavy meson exchange is incorporated into threshold NN --> d pi to enhance the
grossly underestimated cross section. However, that calculation uses an
unjustified assumption on the initial and final momenta, which causes an
overestimate of this effect by a factor of 3--4. I point out that the inclusion
of the Delta(1232) isobar increases the cross section significantly even at
threshold.Comment: 7 pages, figures by fax or mail from [email protected]
An update on the status of wet forest stream-dwelling frogs of the Eungella region
Eungella’s wet forests are home to a number of stream-breeding frogs including three species endemic to the Eungella region: the Eungella dayfrog (Taudactylus eungellensis), Eungella tinkerfrog (T. liemi), and northern gastric brooding frog (Rheobatrachus vitellinus). During the mid-1980s, T. eungellensis and R. vitellinus suffered dramatic population declines attributable to amphibian chytridiomycosis, a disease caused by the amphibian chytrid fungus (Batrachochytrium dendrobatidis or Bd). While surveys in the late 1980s failed to locate T. eungellensis or R. vitellinus, populations of the former were located on a handful of streams surveyed by researchers in the mid-to-late 1990s. Between January 2000 and November 2015, additional surveys targeting these and other wet forest frog species were conducted at 114 sites within Eungella National Park and adjoining areas of State Forest. During these surveys, we located T. eungellensis at many more sites than surveys in the 1990s. Abundances of T. eungellensis at these sites were typically low, however, and well below abundance levels prior to declines in the mid-1980s. As with surveys in the 1990s, T. eungellensis was scarce at high-elevation sites above 600 metres altitude. Numbers of this species do not appear to have increased significantly since the mid-1990s, suggesting recovery of T. eungellensis populations is occurring slowly, at best. In contrast with T. eungellensis, T. liemi was frequently recorded at high-elevation sites, albeit at low densities. As with previous surveys, surveys during 2000–2015 were unsuccessful in locating R. vitellinus. Further frog surveys and monitoring (including disease surveillance) are needed to better assess the status of stream frogs at Eungella, and to understand the influence of Bd on the abundance and distribution of threatened stream-dwelling frogs at Eungella
Post-discharge follow-up of stroke patients at Groote Schuur Hospital - a prospective study
A survey of 59 stroke patients was undertaken between 3 and 6 months after the event to determine whether a weekly stroke round would improve the rate of referral for rehabilitation. Comparison with a previous survey at Groote Schuur Hospital showed a marked improvement (40% for physiotherapy and 10% for occupational therapy v. 76% and 50% respectively). A comparison of referral rates between younger « 65 years old) and older patients (> 65 years old) revealed a significantly higher rate of referral among the younger patients. Attendance for both groups was low (approx. 7 sessions per 3 months). Social work was an important requirement and 60% of all patients expressed a need for more help. Social needs of older and younger patients differ. Despite the improved referral rate the rehabilitation of stroke patients is unsatisfactory, mainly because of transport difficulties. Methods should be investigated to establish rehabilitation centres in the community to overcome this impasse
Glueballs and k-strings in SU(N) gauge theories : calculations with improved operators
We test a variety of blocking and smearing algorithms for constructing
glueball and string wave-functionals, and find some with much improved overlaps
onto the lightest states. We use these algorithms to obtain improved results on
the tensions of k-strings in SU(4), SU(6), and SU(8) gauge theories. We
emphasise the major systematic errors that still need to be controlled in
calculations of heavier k-strings, and perform calculations in SU(4) on an
anisotropic lattice in a bid to minimise one of these. All these results point
to the k-string tensions lying part-way between the `MQCD' and `Casimir
Scaling' conjectures, with the power in 1/N of the leading correction lying in
[1,2]. We also obtain some evidence for the presence of quasi-stable strings in
calculations that do not use sources, and observe some near-degeneracies
between (excited) strings in different representations. We also calculate the
lightest glueball masses for N=2, ...,8, and extrapolate to N=infinity,
obtaining results compatible with earlier work. We show that the N=infinity
factorisation of the Euclidean correlators that are used in such mass
calculations does not make the masses any less calculable at large N.Comment: 49 pages, 15 figure
SU(3) lattice gauge theory with a mixed fundamental and adjoint plaquette action: Lattice artefacts
We study the four-dimensional SU(3) gauge model with a fundamental and an
adjoint plaquette term in the action. We investigate whether corrections to
scaling can be reduced by using a negative value of the adjoint coupling. To
this end, we have studied the finite temperature phase transition, the static
potential and the mass of the 0^{++} glueball. In order to compute these
quantities we have implemented variance reduced estimators that have been
proposed recently. Corrections to scaling are analysed in dimensionless
combinations such as T_c/\sqrt{\sigma} and m_{0^{++}}/T_c. We find that indeed
the lattice artefacts in e.g. m_{0^{++}}/T_c can be reduced considerably
compared with the pure Wilson (fundamental) gauge action at the same lattice
spacing.Comment: 36 pages, 12 figure
Cultural intermediaries and the circuit of culture : the digital ambassadors project in Johannesburg, South Africa
Abstract: The question raised by Cheney and Christensen (2001) as to “what a non-Western, nonmanagerial and non-rationalist form of public relations will look like” (p.182), together with the call made by Gregory (2014) for public relations practitioners (PRPs) to be active social change agents, motivated this paper. The aim of this research is to follow a culture-centred approach and apply the circuit of culture (Curtin & Gaither, 2005) to investigate the meanings that young people (aged 18 to 34), as cultural intermediaries, ascribe to their participation in a digital empowerment project implemented by the City of Johannesburg, South Africa. This research forms part of a larger, ongoing multi-disciplinary research project..
Magnetoinductance of Josephson junction array with frozen vortex diffusion
The dependence of sheet impedance of a Josephson junction array on the
applied magnetic field is investigated in the regime when vortex diffusion
between array plaquettes is effectively frozen due to low enough temperature.
The field dependent contribution to sheet inductance is found to be
proportional to f*ln(1/f), where f<<1 is the magnitude of the field expressed
in terms of flux quanta per plaquette.Comment: 5 pages, no figure
Glueball production in radiative J/psi, Upsilon decays
Using a bound-state model of weakly bound gluons for glueballs made of two
gluons and a natural generalization of the perturbative QCD formalism for
exclusive hadronic processes, we present results for glueball production in
radiative J/psi, Upsilon decays into several possible glueball states,
including L \not= 0 ones. We perform a detailed phenomenological analysis,
presenting results for the more favored experimental candidates and for decay
angular distributions.Comment: RevTeX4, 26 pages, 11 eps figure
Positive pion absorption on 3He using modern trinucleon wave functions
We study pion absorption on 3He employing trinucleon wave functions
calculated from modern realistic NN interactions (Paris, CD Bonn). Even though
the use of the new wave functions leads to a significant improvement over older
calculations with regard to both cross section and polarization data, there are
hints that polarization data with quasifree kinematics cannot be described by
just two-nucleon absorption mechanisms.Comment: 14 pages, 6 figure
Magnetotunneling spectroscopy of mesoscopic correlations in two-dimensional electron systems
An approach to experimentally exploring electronic correlation functions in
mesoscopic regimes is proposed. The idea is to monitor the mesoscopic
fluctuations of a tunneling current flowing between the two layers of a
semiconductor double-quantum-well structure. From the dependence of these
fluctuations on external parameters, such as in-plane or perpendicular magnetic
fields, external bias voltages, etc., the temporal and spatial dependence of
various prominent correlation functions of mesoscopic physics can be
determined. Due to the absence of spatially localized external probes, the
method provides a way to explore the interplay of interaction and localization
effects in two-dimensional systems within a relatively unperturbed environment.
We describe the theoretical background of the approach and quantitatively
discuss the behavior of the current fluctuations in diffusive and ergodic
regimes. The influence of both various interaction mechanisms and localization
effects on the current is discussed. Finally a proposal is made on how, at
least in principle, the method may be used to experimentally determine the
relevant critical exponents of localization-delocalization transitions.Comment: 15 pages, 3 figures include
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