Correction-to-scaling exponents for two-dimensional self-avoiding walks

We study the correction-to-scaling exponents for the two-dimensional self-avoiding walk, using a combination of series-extrapolation and Monte Carlo methods. We enumerate all self-avoiding walks up to 59 steps on the square lattice, and up to 40 steps on the triangular lattice, measuring the mean-square end-to-end distance, the mean-square radius of gyration and the mean-square distance of a monomer from the endpoints. The complete endpoint distribution is also calculated for self-avoiding walks up to 32 steps (square) and up to 22 steps (triangular). We also generate self-avoiding walks on the square lattice by Monte Carlo, using the pivot algorithm, obtaining the mean-square radii to ~0.01% accuracy up to N = 4000. We give compelling evidence that the first non-analytic correction term for two-dimensional self-avoiding walks is Delta_1 = 3/2. We compute several moments of the endpoint distribution function, finding good agreement with the field-theoretic predictions. Finally, we study a particular invariant ratio that can be shown, by conformal-field-theory arguments, to vanish asymptotically, and we find the cancellation of the leading analytic correction.Comment: LaTeX 2.09, 56 pages. Version 2 adds a renormalization-group discussion near the end of Section 2.2, and makes many small improvements in the exposition. To be published in the Journal of Statistical Physic

Ontologies for the study of neurological disease

We have begun work on two separate but related ontologies for the study of neurological diseases. The first, the Neurological Disease Ontology (ND), is intended to provide a set of controlled, logically connected classes to describe the range of neurological diseases and their associated signs and symptoms, assessments, diagnoses, and interventions that are encountered in the course of clinical practice. ND is built as an extension of the Ontology for General Medical Sciences — a high-level candidate OBO Foundry ontology that provides a set of general classes that can be used to describe general aspects of medical science. ND is being built with classes utilizing both textual and axiomatized definitions that describe and formalize the relations between instances of other classes within the ontology itself as well as to external ontologies such as the Gene Ontology, Cell Ontology, Protein Ontology, and Chemical Entities of Biological Interest. In addition, references to similar or associated terms in external ontologies, vocabularies and terminologies are included when possible. Initial work on ND is focused on the areas of Alzheimer’s and other diseases associated with dementia, multiple sclerosis, and stroke and cerebrovascular disease. Extensions to additional groups of neurological diseases are planned. The second ontology, the Neuro-Psychological Testing Ontology (NPT), is intended to provide a set of classes for the annotation of neuropsychological testing data. The intention of this ontology is to allow for the integration of results from a variety of neuropsychological tests that assay similar measures of cognitive functioning. Neuro-psychological testing is an important component in developing the clinical picture used in the diagnosis of patients with a range of neurological diseases, such as Alzheimer’s disease and multiple sclerosis, and following stroke or traumatic brain injury. NPT is being developed as an extension to the Ontology for Biomedical Investigations

I-WALK: An Innovative Approach to Community Walkability

One way of combating rising obesity rates and decreasing physical activity levels among children is to promote active transportation to and from schools. The award-winning I-WALK program provides a comprehensive framework for addressing community walkability and related infrastructure. The program uses a unique and innovative methodology that combines volunteer data collection workshops; classroom-based teacher tallies; and a dynamic Web-based survey that brings parents and children together to discuss school transportation issues. The program\u27s success demonstrates the benefits of coalition-building and community-based participatory research approaches to designing healthy and safe local environments

Matter-gravity couplings and Lorentz violation

The gravitational couplings of matter are studied in the presence of Lorentz and CPT violation. At leading order in the coefficients for Lorentz violation, the relativistic quantum hamiltonian is derived from the gravitationally coupled minimal Standard-Model Extension. For spin-independent effects, the nonrelativistic quantum hamiltonian and the classical dynamics for test and source bodies are obtained. A systematic perturbative method is developed to treat small metric and coefficient fluctuations about a Lorentz-violating and Minkowski background. The post-newtonian metric and the trajectory of a test body freely falling under gravity in the presence of Lorentz violation are established. An illustrative example is presented for a bumblebee model. The general methodology is used to identify observable signals of Lorentz and CPT violation in a variety of gravitational experiments and observations, including gravimeter measurements, laboratory and satellite tests of the weak equivalence principle, antimatter studies, solar-system observations, and investigations of the gravitational properties of light. Numerous sensitivities to coefficients for Lorentz violation can be achieved in existing or near-future experiments at the level of parts in 10^3 down to parts in 10^{15}. Certain coefficients are uniquely detectable in gravitational searches and remain unmeasured to date.Comment: 59 pages two-column REVTe

A pan-European valuation of the extent, causes and cost of escape events from sea cage fish farming

As part of an EU funded 7th Framework project, Prevent Escape, a programme of research was undertaken to document the extent, size and knowledge of the causes of escapes from marine fin fish farms in Europe over a three year period. Escape incidents were identified and assessed through questionnaires across the 6 countries (Ireland, UK, Norway, Spain, Greece, and Malta), and other data supplied by the Norwegian Fisheries Directorate and the Scottish Aquaculture Research Forum. A total of 8,922,863 fish were reported to have escaped from 242 incidents. Of these over 5 million occurred in two catastrophic escape incidents. Sea bream accounted for the highest number of escapes at 76.7% followed by Atlantic salmon at 9.2%. Of the 113 Atlantic salmon escape events, almost 75% were due to structure failure or operational error. Almost 50% of cod escape incidents were due to biological causes e.g. biting of nets. The nominal costs of escapes as calculated by value at point of first sale were very substantial, estimated at approximately €47.5 million per annum on average over the study period. Of this €42.8 million was for annual cost of losses of sea bass and sea bream in the Mediterranean and €4.7 million for losses of salmon in northern Europe.peer-reviewe

Aspiration therapy for the treatment of obesity: 4-year results of a multicenter randomized controlled trial.

BackgroundThe AspireAssist is the first Food and Drug Administration-approved endoluminal device indicated for treatment of class II and III obesity.ObjectivesWe earlier reported 1-year results of the PATHWAY study. Here, we report 4-year outcomes.SettingUnited States-based, 10-center, randomized controlled trial involving 171 participants with the treatment arm receiving Aspiration Therapy (AT) plus Lifestyle Therapy and the control arm receiving Lifestyle Therapy (2:1 randomization).MethodsAT participants were permitted to continue in the study for an additional year up to a maximum of 5 years providing they maintained at least 10% total weight loss (TWL) from baseline at each year end. For AT participants who continued the study, 5 medical monitoring visits were provided at weeks 60, 68, 76, 90, and 104 and thereafter once every 13 weeks up to week 260. Exclusion criteria were a history of eating disorder or evidence of eating disorder on a validated questionnaire. Follow-up weight, quality of life, and co-morbidities were compared with the baseline levels. In addition, rates of serious adverse event, persistent fistula, withdrawal, and A-tube replacement were reported. All analyses were performed using a per-protocol analysis.ResultsOf the 82 AT participants who completed 1 year, 58 continued to this phase of the trial. Mean baseline body mass index of these 58 patients was 41.6 ± 4.5 kg/m2. At the end of first year (at the beginning of the follow-up study), these 58 patients had a body mass index of 34.1 ± 5.4 kg/m2 and had achieved an 18.3 ± 8.0% TWL. On a per protocol basis, patients experienced 14.2%, 15.3%, 16.6%, and 18.7% TWL at 1, 2, 3, and 4 years, respectively (P < .01 for all). Forty of 58 patients (69%) achieved at least 10% TWL at 4 years or at time of study withdrawal. Improvements in quality of life scores and select cardiometabolic parameters were also maintained through 4 years. There were 2 serious adverse events reported in the second through fourth years, both of which resolved with removal or replacement of the A tube. Two persistent fistulas required surgical repair, representing approximately 2% of all tube removals. There were no clinically significant metabolic or electrolytes disorders observed, nor any evidence for development of any eating disorders.ConclusionsThe results of this midterm study have shown that AT is a safe, effective, and durable weight loss alternative for people with class II and III obesity and who are willing to commit to using the therapy and adhere to adjustments in eating behavior

Instantons and unitarity in quantum cosmology with fixed four-volume

We find a number of complex solutions of the Einstein equations in the so-called unimodular version of general relativity, and we interpret them as saddle points yielding estimates of a gravitational path integral over a space of almost everywhere Lorentzian metrics on a spacetime manifold with topology of the "no-boundary" type. In this setting, the compatibility of the no-boundary initial condition with the definability of the quantum measure reduces reduces to the normalizability and unitary evolution of the no-boundary wave function \psi. We consider the spacetime topologies R^4 and RP^4 # R^4 within a Taub minisuperspace model with spatial topology S^3, and the spacetime topology R^2 x T^2 within a Bianchi type I minisuperspace model with spatial topology T^3. In each case there exists exactly one complex saddle point (or combination of saddle points) that yields a wave function compatible with normalizability and unitary evolution. The existence of such saddle points tends to bear out the suggestion that the unimodular theory is less divergent than traditional Einstein gravity. In the Bianchi type I case, the distinguished complex solution is approximately real and Lorentzian at late times, and appears to describe an explosive expansion from zero size at T=0. (In the Taub cases, in contrast, the only complex solution with nearly Lorentzian late-time behavior yields a wave function that is normalizable but evolves nonunitarily, with the total probability increasing exponentially in the unimodular "time" in a manner that suggests a continuous creation of new universes at zero volume.) The issue of the stability of these results upon the inclusion of more degrees of freedom is raised.Comment: 32 pages, REVTeX v3.1 with amsfonts. (v2: minor typos etc corrected.

Cluster Hybrid Monte Carlo Simulation Algorithms

We show that addition of Metropolis single spin-flips to the Wolff cluster flipping Monte Carlo procedure leads to a dramatic {\bf increase} in performance for the spin-1/2 Ising model. We also show that adding Wolff cluster flipping to the Metropolis or heat bath algorithms in systems where just cluster flipping is not immediately obvious (such as the spin-3/2 Ising model) can substantially {\bf reduce} the statistical errors of the simulations. A further advantage of these methods is that systematic errors introduced by the use of imperfect random number generation may be largely healed by hybridizing single spin-flips with cluster flipping.Comment: 16 pages, 10 figure

Haptoglobin Phenotype, Preeclampsia Risk and the Efficacy of Vitamin C and E Supplementation to Prevent Preeclampsia in a Racially Diverse Population

Haptoglobin's (Hp) antioxidant and pro-angiogenic properties differ between the 1-1, 2-1, and 2-2 phenotypes. Hp phenotype affects cardiovascular disease risk and treatment response to antioxidant vitamins in some non-pregnant populations. We previously demonstrated that preeclampsia risk was doubled in white Hp 2-1 women, compared to Hp 1-1 women. Our objectives were to determine whether we could reproduce this finding in a larger cohort, and to determine whether Hp phenotype influences lack of efficacy of antioxidant vitamins in preventing preeclampsia and serious complications of pregnancy-associated hypertension (PAH). This is a secondary analysis of a randomized controlled trial in which 10,154 low-risk women received daily vitamin C and E, or placebo, from 9-16 weeks gestation until delivery. Hp phenotype was determined in the study prediction cohort (n = 2,393) and a case-control cohort (703 cases, 1,406 controls). The primary outcome was severe PAH, or mild or severe PAH with elevated liver enzymes, elevated serum creatinine, thrombocytopenia, eclampsia, fetal growth restriction, medically indicated preterm birth or perinatal death. Preeclampsia was a secondary outcome. Odds ratios were estimated by logistic regression. Sampling weights were used to reduce bias from an overrepresentation of women with preeclampsia or the primary outcome. There was no relationship between Hp phenotype and the primary outcome or preeclampsia in Hispanic, white/other or black women. Vitamin supplementation did not reduce the risk of the primary outcome or preeclampsia in women of any phenotype. Supplementation increased preeclampsia risk (odds ratio 3.30; 95% confidence interval 1.61-6.82, p<0.01) in Hispanic Hp 2-2 women. Hp phenotype does not influence preeclampsia risk, or identify a subset of women who may benefit from vitamin C and E supplementation to prevent preeclampsia