814 research outputs found
Mode competition in a system of two parametrically driven pendulums with nonlinear coupling
This paper is part three in a series on the dynamics of two coupled, parametrically driven pendulums. In the previous parts Banning and van der Weele (1995) and Banning et al. (1997) studied the case of linear coupling; the present paper deals with the changes brought on by the inclusion of a nonlinear (third-order) term in the coupling. Special attention will be given to the phenomenon of mode competition.\ud
\ud
The nonlinear coupling is seen to introduce a new kind of threshold into the system, namely a lower limit to the frequency at which certain motions can exist. Another consequence is that the mode interaction between 1¿ and 2ß (two of the normal motions of the system) is less degenerate, causing the intermediary mixed motion known as MP to manifest itself more strongly
Strings in extremal BTZ black holes
We study the spectrum of the worldsheet theory of the bosonic closed string
in the massless and extremal rotating BTZ black holes. We use a hyperbolic
Wakimoto representation of the SL(2,R) currents to construct vertex operators
for the string modes on these backgrounds. We argue that there are tachyons in
the twisted sector, but these are not localised near the horizon. We study the
relation to the null orbifold in the limit of vanishing cosmological constant.
We also discuss the problem of extending this analysis to the supersymmetric
case.Comment: 20 pages, no figure
Haematology and clinical chemistry values for harbour seals (Phoca vitulina) fed environmentally contaminated herring remain within normal ranges
Abstract: Twenty-two young harbour seals (Phoca vitulina) were fed herring from either the relatively unpolluted Atlantic Ocean or the heavily polluted Baltic Sea as part of a 2½-year immunotoxicological study. Blood samples taken at regular intervals were analyzed for routine haematology and clinical chemistry. Minimal differences between the two groups were observed in these parameters over the course of the experiment. Of the 20 clinical chemistry parameters analyzed, slight differences were found in serum levels of urea, creatinine, magnesium, and cholesterol. In haematology profiles, red blood cell counts and haematocrit values were higher in seals fed Baltic herring, but these differences diminished over time. Neutrophil counts were also higher in this group of seals, especially during the second half of the feeding study. Factors affecting haematological and clinical chemistry parameters within feeding groups included gender, age, and season. The data collected demonstrate a relative insensitivity of clinical chemistry parameters to the effects of chronic exposure to environmental contaminants accumulated through the food chain, but suggest the induction of clear alterations in differential white blood cel
Relative immunocompetence of the newborn harbour seal, phoca vitulina
The immune system of many mammalian species is not fully developed at birth, with newborns obtaining temporary immunological protection from maternal antibodies. Little is known of the immune system of the harbour seal, and developmental aspects of its immune system have not been systematically studied. We collected blood and milk samples from nine free-ranging mother-pup pairs throughout the lactation period on Sable Island, Canada, in an effort to characterise developmental aspects of the immune system of this newborn pinniped. Pup lymphocytes responded stronger to the mitogens concanavalin A, phytohaemagglutinin, and pokeweed mitogen tha
The Diabetes Remission Clinical Trial (DiRECT): protocol for a cluster randomised trial
Background:
Despite improving evidence-based practice following clinical guidelines to optimise drug therapy, Type 2 diabetes (T2DM) still exerts a devastating toll from vascular complications and premature death. Biochemical remission of T2DM has been demonstrated with weight loss around 15kg following bariatric surgery and in several small studies of non-surgical energy-restriction treatments. The non-surgical Counterweight-Plus programme, running in Primary Care where obesity and T2DM are routinely managed, produces >15 kg weight loss in 33 % of all enrolled patients. The Diabetes UK-funded Counterpoint study suggested that this should be sufficient to reverse T2DM by removing ectopic fat in liver and pancreas, restoring first-phase insulin secretion.
The Diabetes Remission Clinical Trial (DiRECT) was designed to determine whether a structured, intensive, weight management programme, delivered in a routine Primary Care setting, is a viable treatment for achieving durable normoglycaemia. Other aims are to understand the mechanistic basis of remission and to identify psychological predictors of response.
Methods/Design:
Cluster-randomised design with GP practice as the unit of randomisation: 280 participants from around 30 practices in Scotland and England will be allocated either to continue usual guideline-based care or to add the Counterweight-Plus weight management programme, which includes primary care nurse or dietitian delivery of 12-20weeks low calorie diet replacement, food reintroduction, and long-term weight loss maintenance. Main inclusion criteria: men and women aged 20-65years, all ethnicities, T2DM 0-6years duration, BMI 27-45 kg/m2. Tyneside participants will undergo Magnetic Resonance (MR) studies of pancreatic and hepatic fat, and metabolic studies to determine mechanisms underlying T2DM remission. Co-primary endpoints: weight reduction ≥ 15 kg and HbA1c <48 mmol/mol at one year. Further follow-up at 2 years.
Discussion:
This study will establish whether a structured weight management programme, delivered in Primary Care by practice nurses or dietitians, is a viable treatment to achieve T2DM remission. Results, available from 2018 onwards, will inform future service strategy
Closed string tachyons, flips and conifolds
Following the analysis of tachyons and orbifold flips described in
hep-th/0412337, we study nonsupersymmetric analogs of the supersymmetric
conifold singularity and show using their toric geometry description that they
are nonsupersymmetric orbifolds of the latter. Using linear sigma models, we
see that these are unstable to localized closed string tachyon condensation and
exhibit flip transitions between their two small resolutions (involving
2-cycles), in the process mediating mild dynamical topology change. Our
analysis shows that the structure of these nonsupersymmetric conifolds as
quotients of the supersymmetric conifold obstructs the 3-cycle deformation of
such singularities, suggesting that these nonsupersymmetric conifolds decay by
evolving towards their stable small resolutions.Comment: Latex, 22 pgs, 2 figs. v4: matches JHEP version, 29 pgs, 3 figures,
more elaborate Introduction, various clarifications adde
Supergravity Inflation on the Brane
We study N=1 Supergravity inflation in the context of the braneworld
scenario. Particular attention is paid to the problem of the onset of inflation
at sub-Planckian field values and the ensued inflationary observables. We find
that the so-called -problem encountered in supergravity inspired
inflationary models can be solved in the context of the braneworld scenario,
for some range of the parameters involved. Furthermore, we obtain an upper
bound on the scale of the fifth dimension, M_5 \lsim 10^{-3} M_P, in case the
inflationary potential is quadratic in the inflaton field, . If the
inflationary potential is cubic in , consistency with observational data
requires that .Comment: 6 pages, 1 figure, to appear in Phys. Rev.
On fluctuations of closed string tachyon solitons
We discuss fluctuations on solitons in the dilaton/graviton/tachyon system
using the low energy effective field theory approach. It is shown that closed
string solitons are free of tachyons in this approximation, regardless of the
exact shape of the tachyon potential.Comment: 13 pages, 1 figure, uses JHEP3.cl
Neutrino properties and the decay of the lightest supersymmetric particle
Supersymmetry with broken R-parity can explain the neutrino mass squared
differences and mixing angles observed in neutrino oscillation experiments. In
the minimal model, where R-parity is broken only by bilinear terms, certain
decay properties of the lightest supersymmetric particle (LSP) are correlated
with neutrino mixing angles. Here we consider charginos, squarks, gluinos and
sneutrinos being the LSP and calculate their decay properties in bilinear
R-parity breaking supersymmetry. Together with the decays of charged scalars
and neutralinos calculated previously this completes the proof that bilinear
R-parity breaking as the source of neutrino masses will be testable at future
colliders. Moreover, we argue that in case of GMSB, the decays of the NLSP can
be used to test the model.Comment: 15 pages, 8 figure
- …