Kinky Brane Worlds

We present a toy model for five-dimensional heterotic M-theory where bulk three-branes, originating in 11 dimensions from M five-branes, are modelled as kink solutions of a bulk scalar field theory. It is shown that the vacua of this defect model correspond to a class of topologically distinct M-theory compactifications. Topology change can then be analysed by studying the time evolution of the defect model. In the context of a four-dimensional effective theory, we study in detail the simplest such process, that is the time evolution of a kink and its collision with a boundary. We find that the kink is generically absorbed by the boundary thereby changing the boundary charge. This opens up the possibility of exploring the relation between more complicated defect configurations and the topology of brane-world models.Comment: 31 pages, Latex, 6 eps-figure

Coronary artery bypass surgery in young adults: excellent perioperative results and long-term survival

OBJECTIVES: To analyse perioperative results, long-term survival and freedom from complications after coronary artery bypass grafting (CABG) in young adults. METHODS: A total of 163 patients, 40 years old or younger, had isolated CABG from January 1989 to December 2010. Pre- and perioperative demographic and clinical data were retrieved from a prospectively organised database. Follow-up data were obtained by letter or telephone interviews. The mean age of the patients was 37.6 ± 2.9 years and 146 were men (90%). Fifty-three patients (32.5%) had angina class III/IV; 106 (65.0%), previous myocardial infarction; and 23 (14.1%), impaired left ventricular function (ejection fraction <40%). Indication for surgery was 3-vessel disease in 101 cases (62.0%), 2-vessel disease in 30 (18.4%) and single-vessel disease in 32 (19.6%). The left main stem was affected in 16 patients (9.8%). The mean EuroSCORE II was 0.92 ± 0.71. A total of 417 grafts were constructed (mean 2.6 grafts/patient), 247 of which (59.2%) were arterial. RESULTS: There were no in-hospital deaths. The mean hospital stay was 7.1 ± 4.0 days. Four patients (2.5%) were lost to follow-up, which extended from 3 to 25 years (mean 15.1 ± 5.5 years). There were 22 late deaths, 72.7% of cardiac or unknown origin. The 5-, 10- and 20-year survival rates were 98.7 ± 10.9, 95.2 ± 1.8 and 79.4 ± 4.4%, respectively. Twenty-six patients (18.1%) had non-fatal cardiac adverse complications (myocardial infarct, percutaneous re-revascularization or class III/IV angina), for 5-, 10- and 20-year freedom from complications of 97.9 ± 1.2, 91.9 ± 2.5 and 65.7 ± 7.1%, respectively. Twenty-two patients (17.5%) needed re-revascularization, for 5-, 10- and 20-year freedom from re-revascularization of 97.6 ± 1.4, 91.9 ± 2.6 and 69.5 ± 6.7%, respectively. CONCLUSIONS: Despite the aggressive nature of coronary artery disease in young patients, perioperative death and morbidity rates are low, with good long-term survival and low rates of re-revascularization.info:eu-repo/semantics/publishedVersio

Elastic properties of carbon nanotubes and their heterojunctions

Comprehensive studies on the modelling and numerical simulation of the mechanical behaviour under tension, bending and torsion of single-walled carbon nanotubes and their heterojunctions are performed. It is proposed to deduce the mechanical properties of the carbon nanotubes heterojunctions from the knowledge of the mechanical properties of the single-walled carbon nanotubes, which are their constituent key unit

Predicting the critical density of topological defects in O(N) scalar field theories

O(N) symmetric $\lambda \phi^4$ field theories describe many critical phenomena in the laboratory and in the early Universe. Given N and $D\leq 3$, the dimension of space, these models exhibit topological defect classical solutions that in some cases fully determine their critical behavior. For N=2, D=3 it has been observed that the defect density is seemingly a universal quantity at T_c. We prove this conjecture and show how to predict its value based on the universal critical exponents of the field theory. Analogously, for general N and D we predict the universal critical densities of domain walls and monopoles, for which no detailed thermodynamic study exists. This procedure can also be inverted, producing an algorithm for generating typical defect networks at criticality, in contrast to the canonical procedure, which applies only in the unphysical limit of infinite temperature.Comment: 4 pages, 3 figures, uses RevTex, typos in Eq.(11) and (14) correcte