6,296 research outputs found
Radiative and flavor-violating transitions of leptons from interactions with color-octet particles
It has been recently proposed that neutrino mass could originate from Yukawa
interactions of leptons with new colored particles. This raises the interesting
possibility of testing mass generation through copious production of those
particles at hadron colliders. A realistic assessment of it however should take
into account how large those interactions could be from available precision
results. In this work we make a systematic analysis to the flavor structure in
Yukawa couplings, provide a convenient parametrization to it, and investigate
the rare radiative and pure leptonic decays of the muon and tau leptons. For
general values of parameters the muon decays set stringent constraints on the
couplings, and all rare tau decays are far below the current experimental
sensitivity. However, there is room in parameter space in which the muon decays
could be significantly suppressed by destructive interference between colored
particles without generically reducing the couplings themselves. This is also
the region of parameters that is relevant to collider physics. We show that for
this part of parameter space some tau decays can reach or are close to the
current level of precision.Comment: 20 pages, 7 figure
Relating Neutrino Masses by dilepton modes of Doubly Charged Scalars
We study a model with Majorana neutrino masses generated through doubly
charged scalars at two-loop level. We give explicit relationships between the
neutrino masses and the same sign dilepton decays of the doubly charged
scalars. In particular, we demonstrate that at the tribimaximal limit of the
neutrino mixings, the absolute neutrino masses and Majorana phases can be
extracted through the measurements of the dilepton modes at colliders.Comment: 14 pages, 8 figures, references added, version to be published in PR
Quark-lepton mass unification at TeV scales
A scenario combining a model of early (TeV) unification of quarks and leptons
with the physics of large extra dimensions provides a natural mechanism linking
quark and lepton masses at TeV scale. This has been dubbed as early
quark-lepton mass unification by one of us (PQH) in one of the two models of
early quark-lepton unification, which are consistent with data, namely SU(4)_PS
\otimes SU(2)_L \otimes SU(2)_R \otimes SU(2)_H. In particular, it focused on
the issue of naturally light Dirac neutrino. The present paper will focus on
similar issues in the other model, namely SU(4)_PS \otimes SU(3)_L \otimes
SU(3)_H.Comment: Accepted for publication in PRD: The new version is in agreement with
the accepted manuscrip
The immunology of Takotsubo syndrome
Takotsubo syndrome (TTS) is a disorder characterized by transient cardiac dysfunction with ventricular regional wall motion abnormalities, primarily thought to be caused by the effects of a sudden catecholamine surge on the heart. Although the majority of patients exhibit prompt recovery of their cardiac dysfunction, TTS remains associated with increased mortality rates acutely and at long-term, and there is currently no cure for TTS. Inflammation has been shown to play a key role in determining outcomes in TTS patients, as well as in the early pathogenesis of the disorder. There are also cases of TTS patients that have been successfully treated with anti-inflammatory therapies, supporting the importance of the inflammatory response in TTS. In this article, we provide a comprehensive review of the available clinical and pre-clinical literature on the immune response in TTS, in an effort to not only better understand the pathophysiology of TTS but also to generate insights on the treatment of patients with this disorder
ASSESSMENT OF THE LINEFISHERY IN TWO URBAN ESTUARINE SYSTEMS IN KWAZULU-NATAL, SOUTH AFRICA
The recreational linefisheries in Durban Harbour and the Mgeni Estuary were surveyed using roving creel and access-point surveys during the period January–December 2000. In total, 3 351 shore-anglers and 652 boat-anglers were checked for catch-and-effort information, and 432 shore-anglers were interviewed using a demographic and socio-economic questionnaire. Durban Harbour had much higher angling effort than the Mgeni Estuary. Angling activity was higher on weekends (121 and 23 anglers per count for the harbour and Mgeni Estuary respectively) than during the week (34 and 9 anglers per count respectively). Total effort expended in Durban Harbour and the Mgeni Estuary shore-fisheries during 2000 was estimated to be 54 024 and 11 977 angler-outings respectively. Annual effort for the Durban Harbour boat-fishery for the same period was estimated to be 9 991 angler-outings. The flathead mullet Mugil cephalus was the most commonly harvested species in both Durban Harbour and the Mgeni Estuary shore-fisheries (25.2 and 68.1% respectively), and spotted grunter Pomadasys commersonnii (41.5%) was the most commonly harvested species in the Durban Harbour boat-fishery. Because of their small size, a large proportion (>63%) of the total fish catch at both localities was released. Mean catch per unit effort for the Durban Harbour boat-based fishery (0.11 fish angler-1 h-1 or 0.15 kg angler-1 h-1) was higher than that of the shore-based fishery (0.071 fish angler-1 h-1 or 0.034 kg angler-1 h-1). The questionnaire survey indicated that anglers had high site fidelity, considerable years of fishing experience (mean of 17.2 years for the harbour, 13.6 years for Mgeni) and high compliance with possession of fishing permits (86% harbour, 84% Mgeni). Although anglers generally supported the regulations currently applicable to the linefishery (>71% harbour, >77% Mgeni), the questionnaire results showed that specific nowledge for target species was poor (45–70% harbour, 29–60% Mgeni). The level of fisheries law enforcement (6.4% of harbour outings inspected, 7% Mgeni outings inspected) was poorer than in the previously studied KwaZulu-Natal marine shorefishery. Economic investment by participants in terms of angling equipment used in the shore-fisheries of the two systems was calculated to be > R10 million, and expenditure in terms of bait, travel and tackle costs was approximately R9 million per year.Afr. J. mar. Sci. 25: 111–13
EVALUATION OF PARTICIPATION IN AND MANAGEMENT OF THE TRANSKEI SHORE LINEFISHERY
Both roving creel and aerial surveys were used to quantify fishing effort along the former Transkei coast. A stratified random sampling procedure was used during shore patrols to assess catch and effort, and a questionnaire survey provided information on total fishing effort, fisher demographics and attitudes towards current regulations. A total of 13 field trips was undertaken, during which 341 fishers were interviewed and the catches of 760 fishers examined. In all, 175 patrols were undertaken, covering in all 1 117 km. Some 24 random aerial counts of shore-fishers were also carried out during the study. From the aerial surveys, average fisher density along the Transkei coast was estimated at 0.79 fishers km-1, with an estimated total fishing effort of 170 457 fisher-days year-1. Fisher densities were highest in spring (0.9 fishers km-1) and lowest during summer (0.5 fishers km-1). Fishers were most successful in winter (1.0 fish fisher-1 inspection-1) and least successful in summer (0.4 fish fisher-1 inspection-1). Catch rates amounted to 1.4 fish fisher-1 day-1, or 0.86 kg fisher-1 day-1, and the total catch was estimated at 147 tons year-1. The main target species were bronze bream Pachymetopon grande (22%), blacktail Diplodus sargus capensis (19%) and dusky kob Argyrosomus japonicus (18%). Numerically, the most important species in the catches were elf Pomatomus saltatrix (18%) and blacktail (16%). By mass, the most important species were bronze bream (26%) and dusky kob (18%). Knowledge and compliance of regulations currently governing the linefishery in the Transkei was exceptionally poor, although most fishers supported the principle of regulations. Better-enforced and larger marine protected areas, establishment of a fisher awareness programme and improved enforcement of fishing regulations are suggestions for improving the current management of the Transkei shore-fishery.Afr. J. mar. Sci. 25: 79–9
Tetramixing of vector and pseudoscalar mesons: A source of intrinsic quarks
The tetramixing of pseudoscalar mesons --- and
vector mesons --- are studied in the light-cone
constituent quark model, and such mixing of four mesons provides a natural
source for the intrinsic charm components of light mesons. By mixing
with the light mesons, the charmonium states and could decay
into light mesons more naturally, without introducing gluons or a virtual
photon as intermediate states. Thus, the introduction of light quark components
into is helpful to reproduce the new experimental data of
decays. The mixing matrices and the behaviors of the transition form
factors are also calculated and compared with experimental data.Comment: 20 pages, 10 figures. Version for publication in PR
Hawking radiation of Dirac particles via tunneling from Kerr black hole
We investigated Dirac Particles' Hawking radiation from event horizon of Kerr
black hole in terms of the tunneling formalism. Applying WKB approximation to
the general covariant Dirac equation in Kerr spacetime background, we obtain
the tunneling probability for fermions and Hawking temperature of Kerr black
hole. The result obtained by taking the fermion tunneling into account is
consistent with the previous literatures.Comment: 7 pages, no figures, to appear in CQ
AN ASSESSMENT OF THE RECREATIONAL AND COMMERCIAL SKIBOAT FISHERY IN THE TRANSKEI
A survey of the recreational and commercial skiboat linefishery in the Transkei was conducted from March 1997 to April 1999. Effort by commercial skiboats was substantially higher than by recreational skiboats, and catch rates on commercial boats were much higher than rates on recreational boats. Catch rates in the region were not greater than those in the adjoining provinces of KwaZulu-Natal and the Eastern Cape, but the mean size of fish caught on commercial skiboats in the southern Transkei was larger than that in either KwaZulu-Natal or the Eastern Cape. Total annual commercial catches estimated for the Transkei were substantially greater than those based on returns submitted by skippers to the National Marine Linefish System. Catches in the northern Transkei were more diverse than in the south, and catches from both regions contained a large number of endemic species. Northern Transkei catches were characterized by subtropical species, whereas those from the southern Transkei contained more warm-temperate species. In the northern region, subtropical species replaced warmtemperate ones during winter. Knowledge of fishing regulations by fishers was reasonable, but compliance was poor, mainly as a result of the low level of enforcement of regulations in this region, which needs to be improved if catches are to be sustained. Among other recommendations, the establishment of an effective marine reserve in the area is a priority; it would assist with the conservation of several species of endemic linefish.Afr. J. mar. Sci. 25: 61–7
- …