1,050 research outputs found
Genericity of Cosmic Strings Formation in SUSY GUTs
The idea of GUT implies that the universe went through a series of phase
transitions during which topological defects are expected to form. We
investigate here the genericity of cosmic strings formation in realistic SUSY
GUTs models. We conclude that all acceptable symmetry breaking schemes produce
cosmic strings after the last inflationary phase. Generically, as they form at
the end of inflation, they have a mass of order of the GUT scale. Since
cosmological data coming from CMB measurements do not show evidence for such
strings, they constrain GUT scale physics.Comment: 4 pages, talk at the XXXIX Rencontres de Moriond (La Thuile, March
2004), to appear in the proceeding
Venous thromboembolism risk and prophylaxis prescription in surgical patients at a tertiary hospital in Eastern Cape Province, South Africa
Background. Venous thromboembolism (VTE) is a common complication during and after hospitalisation, and is regarded as the most common cause of preventable death in hospitalised patients worldwide. Despite its importance, there are few data on VTE risk and adherence to prophylaxis prescription guidelines in surgical patients from the South African (SA) public sector, especially from lowresource environments such as Eastern Cape Province.Objectives. To evaluate the risk and prescription of VTE prophylaxis to surgical patients at a tertiary government hospital in the Eastern Cape.Methods. A cross-sectional clinical audit of general surgical inpatients was performed on two dates during July and August 2017. Patients’ VTE risk was calculated by using the Caprini risk assessment model (RAM) and thromboprophylaxis prescription evaluated accordingly.Results. A total of 179 patients were included in the study, of whom 56% were male and 44% female. The average age was 45 (range 18 - 83) years. Of the total number of participants, 33% were elective cases and 67% were emergency admissions. With application of RAM, 77% of patients were at risk of VTE (Caprini score ≥2), with 81% of elective and 74% of emergency patients being at risk. The most prevalent risk factors for VTE were major surgery (34%), age 41 - 60 years (30%), age 61 - 74 years (20%) and sepsis during the previous month (27%). A contraindication to chemoprophylaxis was recorded in 30% of patients, with the most prevalent being renal dysfunction (40%), peptic ulcer disease (34%), active bleeding (17%), liver dysfunction (17%), coagulopathy (6%) and recent cerebral haemorrhage (6%). With regard to VTE risk profile and contraindications to chemoprophylaxis, the correct thromboprophylactic treatment was prescribed to 26% of at-risk patients, with 21% of elective and 27% of emergency admission patients receiving the correct therapy.Conclusions. Despite a high proportion of patients being at risk of VTE, the rate of adequate thromboprophylaxis prescription for surgical inpatients at Frere Hospital, East London, SA is very low. Increased availability of mechanical prophylaxis, as well as interventions to improve the rate of adequate prophylaxis prescription, needs to be evaluated for feasibility and effect in this hospital and other SA public hospitals
Scattering of cosmic strings by black holes: loop formation
We study the deformation of a long cosmic string by a nearby rotating black
hole. We examine whether the deformation of a cosmic string, induced by the
gravitational field of a Kerr black hole, may lead to the formation of a loop
of cosmic string. The segment of the string which enters the ergosphere of a
rotating black hole gets deformed and, if it is sufficiently twisted, it can
self-intersect chopping off a loop of cosmic string. We find that the formation
of a loop, via this mechanism, is a rare event. It will only arise in a small
region of the collision phase space, which depends on the string velocity, the
impact parameter and the black hole angular momentum. We conclude that
generically, the cosmic string is simply scattered or captured by the rotating
black hole.Comment: 11 pages, 2 figures, RevTe
D-term inflation in non-minimal supergravity
D-term inflation is one of the most interesting and versatile models of
inflation. It is possible to implement naturally D-term inflation within high
energy physics, as for example SUSY GUTs, SUGRA, or string theories. D-term
inflation avoids the -problem, while in its standard form it always ends
with the formation of cosmic strings. Given the recent three-year WMAP data on
the cosmic microwave background temperature anisotropies, we examine whether
D-term inflation can be successfully implemented in non-minimal supergravity
theories. We show that for all our choices of K\"ahler potential, there exists
a parameter space for which the predictions of D-term inflation are in
agreement with the measurements. The cosmic string contribution on the measured
temperature anisotropies is always dominant, unless the superpotential coupling
constant is fine tuned; a result already obtained for D-term inflation within
minimal supergravity. In conclusion, cosmic strings and their r\^ole in the
angular power spectrum cannot be easily hidden by just considering a non-flat
K\"ahler geometry.Comment: 29 pages, 9 figures; minor changes to match publihed versio
The interplay between high energy physics and cosmology: an example
Cosmology and high energy physics are two closely connected areas. In this
lecture I present an example of their rich interplay.Comment: Invited talk at the DPU workshop: The density fluctuations in the
Universe: Beyond the inflationary paradigm (Dimokritos, Athens 2004) (see
http://physics.ntua.gr/dpu/). 8 two column page
Fiche de lecture. Xavier-Laurent Petit, Itawapa
Note de lectureInternational audienc
Production of topological defects at the end of inflation
Hybrid inflation within supersymmetric grand unified theories, as well as
inflation through brane collisions within braneworld cosmological models, lead
to the formation of one-dimensional defects. Observational data, mainly from
the cosmic microwave background temperature anisotropies but also from the
gravitational wave background, impose constraints on the free parameters of the
models. I review these inflationary models and discuss the constraints from the
currently available data.Comment: 9 pages, Invited talk in the Conference "Challenges in Particle
Astrophysics" -- 6th Rencontres du Vietnam, Hanoi (Vietnam) 6-12 Aug. 200
Venous thromboembolism risk and prophylaxis prescription in surgical patients at a tertiary hospital in Eastern Cape Province, South Africa
Background. Venous thromboembolism (VTE) is a common complication during and after hospitalisation, and is regarded as the most common cause of preventable death in hospitalised patients worldwide. Despite its importance, there are few data on VTE risk and adherence to prophylaxis prescription guidelines in surgical patients from the South African (SA) public sector, especially from low-resource environments such as Eastern Cape Province.Objectives. To evaluate the risk and prescription of VTE prophylaxis to surgical patients at a tertiary government hospital in the Eastern Cape.Methods. A cross-sectional clinical audit of general surgical inpatients was performed on two dates during July and August 2017. Patients’ VTE risk was calculated by using the Caprini risk assessment model (RAM) and thromboprophylaxis prescription evaluated accordingly.Results. A total of 179 patients were included in the study, of whom 56% were male and 44% female. The average age was 45 (range 18 - 83) years. Of the total number of participants, 33% were elective cases and 67% were emergency admissions. With application of RAM, 77% of patients were at risk of VTE (Caprini score ≥2), with 81% of elective and 74% of emergency patients being at risk. The most prevalent risk factors for VTE were major surgery (34%), age 41 - 60 years (30%), age 61 - 74 years (20%) and sepsis during the previous month (27%). A contraindication to chemoprophylaxis was recorded in 30% of patients, with the most prevalent being renal dysfunction (40%), peptic ulcer disease (34%), active bleeding (17%), liver dysfunction (17%), coagulopathy (6%) and recent cerebral haemorrhage (6%). With regard to VTE risk profile and contraindications to chemoprophylaxis, the correct thromboprophylactic treatment was prescribed to 26% of at-risk patients, with 21% of elective and 27% of emergency admission patients receiving the correct therapy.Conclusions. Despite a high proportion of patients being at risk of VTE, the rate of adequate thromboprophylaxis prescription for surgical inpatients at Frere Hospital, East London, SA is very low. Increased availability of mechanical prophylaxis, as well as interventions to improve the rate of adequate prophylaxis prescription, needs to be evaluated for feasibility and effect in this hospital and other SA public hospitals
Direct amine-functionalisation of γ-Fe2O3nanoparticles
A novel and simple preparation of amine-modified γ-Fe2O3 nanoparticles is described. The presence of amine groups on the surface, instead of hydroxyl groups, will allow conjugation of biologically active molecules to the iron oxide nanoparticles without the need for a size increasing silica shell. Furthermore, the outer amine-layer increases the temperature of the γ-Fe2O3 to α-Fe2O3 structural transition in a similar way to previously reported cationic substitutions. This may suggest the formation of an oxide–nitride outer layer. Re-dispersion of the amine-modified γ-Fe2O3 nanoparticles led to the preparation of stable ferrofluids
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