Instability in the Molecular Dynamics Step of Hybrid Monte Carlo in Dynamical Fermion Lattice QCD Simulations

We investigate instability and reversibility within Hybrid Monte Carlo simulations using a non-perturbatively improved Wilson action. We demonstrate the onset of instability as tolerance parameters and molecular dynamics step sizes are varied. We compare these findings with theoretical expectations and present limits on simulation parameters within which a stable and reversible algorithm is obtained for physically relevant simulations. Results of optimisation experiments with respect to tolerance prarameters are also presented

Instability in the molecular dynamics step of a hybrid Monte Carlo algorithm in dynamical fermion lattice QCD simulations

We investigate instability and reversibility within Hybrid Monte Carlo simulations using a non-perturbatively improved Wilson action. We demonstrate the onset of instability as tolerance parameters and molecular dynamics step sizes are varied. We compare these findings with theoretical expectations and present limits on simulation parameters within which a stable and reversible algorithm is obtained for physically relevant simulations. Results of optimisation experiments with respect to tolerance prarameters are also presented.Comment: RevTeX, Some results here were presented at Vielat 99, Vienna, Austria, Sept 1999 22 Pages, 10 figures, to be submitted to PR

Investigating local policy drivers for alcohol harm prevention: a comparative case study of two local authorities in England

Background: The considerable challenges associated with implementing national level alcohol policies have encouraged a renewed focus on the prospects for local-level policies in the UK and elsewhere. We adopted a case study approach to identify the major characteristics and drivers of differences in the patterns of local alcohol policies and services in two contrasting local authority (LA) areas in England. Methods: Data were collected via thirteen semi-structured interviews with key informants (including public health, licensing and trading standards) and documentary analysis, including harm reduction strategies and statements of licensing policy. A two-stage thematic analysis was used to categorize all relevant statements into seven over-arching themes, by which document sources were then also analysed. Results: Three of the seven over-arching themes (drink environment, treatment services and barriers and facilitators), provided for the most explanatory detail informing the contrasting policy responses of the two LAs: LA1 pursued a risk-informed strategy via a specialist police team working proactively with problem premises and screening systematically to identify riskier drinking. LA2 adopted a more upstream regulatory approach around restrictions on availability with less emphasis on co-ordinated screening and treatment measures. Conclusion: New powers over alcohol policy for LAs in England can produce markedly different policies for reducing alcohol-related harm. These difference are rooted in economic, opportunistic, organisational and personnel factors particular to the LAs themselves and may lead to closely tailored solutions in some policy areas and poorer co-ordination and attention in others

Critical scaling of the a.c. conductivity for a superconductor above Tc

We consider the effects of critical superconducting fluctuations on the scaling of the linear a.c. conductivity, \sigma(\omega), of a bulk superconductor slightly above Tc in zero applied magnetic field. The dynamic renormalization- group method is applied to the relaxational time-dependent Ginzburg-Landau model of superconductivity, with \sigma(\omega) calculated via the Kubo formula to O(\epsilon^{2}) in the \epsilon = 4 - d expansion. The critical dynamics are governed by the relaxational XY-model renormalization-group fixed point. The scaling hypothesis \sigma(\omega) \sim \xi^{2-d+z} S(\omega \xi^{z}) proposed by Fisher, Fisher and Huse is explicitly verified, with the dynamic exponent z \approx 2.015, the value expected for the d=3 relaxational XY-model. The universal scaling function S(y) is computed and shown to deviate only slightly from its Gaussian form, calculated earlier. The present theory is compared with experimental measurements of the a.c. conductivity of YBCO near Tc, and the implications of this theory for such experiments is discussed.Comment: 16 pages, submitted to Phys. Rev.

Sensitivity and Specificity of Multiple Kato-Katz Thick Smears and a Circulating Cathodic Antigen Test for Schistosoma mansoni Diagnosis Pre- and Post-repeated-Praziquantel Treatment

Two Kato-Katz thick smears (Kato-Katzs) from a single stool are currently recommended for diagnosing Schistosoma mansoni infections to map areas for intervention. This ‘gold standard’ has low sensitivity at low infection intensities. The urine point-of-care circulating cathodic antigen test (POC-CCA) is potentially more sensitive but how accurately they detect S. mansoni after repeated praziquantel treatments, their suitability for measuring drug efficacy and their correlation with egg counts remain to be fully understood. We compared the accuracies of one to six Kato-Katzs and one POC-CCA for the diagnosis of S. mansoni in primary-school children who have received zero to ten praziquantel treatments. We determined the impact each diagnostic approach may have on monitoring and evaluation (M&E) and drug-efficacy findings

Interpreting ambiguous ‘trace’ results in Schistosoma mansoni CCA Tests: Estimating sensitivity and specificity of ambiguous results with no gold standard

Background The development of new diagnostics is an important tool in the fight against disease. Latent Class Analysis (LCA) is used to estimate the sensitivity and specificity of tests in the absence of a gold standard. The main field diagnostic for Schistosoma mansoni infection, Kato-Katz (KK), is not very sensitive at low infection intensities. A point-of-care circulating cathodic antigen (CCA) test has been shown to be more sensitive than KK. However, CCA can return an ambiguous ‘trace’ result between ‘positive’ and ‘negative’, and much debate has focused on interpretation of traces results. Methodology/Principle findings We show how LCA can be extended to include ambiguous trace results and analyse S. mansoni studies from both Côte d’Ivoire (CdI) and Uganda. We compare the diagnostic performance of KK and CCA and the observed results by each test to the estimated infection prevalence in the population. Prevalence by KK was higher in CdI (13.4%) than in Uganda (6.1%), but prevalence by CCA was similar between countries, both when trace was assumed to be negative (CCAtn: 11.7% in CdI and 9.7% in Uganda) and positive (CCAtp: 20.1% in CdI and 22.5% in Uganda). The estimated sensitivity of CCA was more consistent between countries than the estimated sensitivity of KK, and estimated infection prevalence did not significantly differ between CdI (20.5%) and Uganda (19.1%). The prevalence by CCA with trace as positive did not differ significantly from estimates of infection prevalence in either country, whereas both KK and CCA with trace as negative significantly underestimated infection prevalence in both countries. Conclusions Incorporation of ambiguous results into an LCA enables the effect of different treatment thresholds to be directly assessed and is applicable in many fields. Our results showed that CCA with trace as positive most accurately estimated infection prevalence

Estimation of changes in the force of infection for intestinal and urogenital schistosomiasis in countries with Schistosomiasis Control Initiative-assisted programmes

The last decade has seen an expansion of national schistosomiasis control programmes in Africa based on large-scale preventative chemotherapy. In many areas this has resulted in considerable reductions in infection and morbidity levels in treated individuals. In this paper, we quantify changes in the force of infection (FOI), defined here as the per (human) host parasite establishment rate, to ascertain the impact on transmission of some of these programmes under the umbrella of the Schistosomiasis Control Initiative (SCI)

TLR9 Agonist Protects Mice from Radiation-Induced Gastrointestinal Syndrome

Radiation-induced gastrointestinal syndrome (RIGS) is due to the clonogenic loss of crypt cells and villi depopulation, resulting in disruption of mucosal barrier, bacterial invasion, inflammation and sepsis. Intestinal macrophages could recognize invading bacterial DNA via TLR9 receptors and transmit regenerative signals to the neighboring crypt. We therefore investigated whether systemic administration of designer TLR9 agonist could ameliorate RIGS by activating TLR9.Male C57Bl6 mice were distributed in four experimental cohorts, whole body irradiation (WBI) (8.4-10.4 Gy), TLR9 agonist (1 mg/kg s.c.), 1 h pre- or post-WBI and TLR9 agonist+WBI+iMyd88 (pretreatment with inhibitory peptide against Myd88). Animals were observed for survival and intestine was harvested for histological analysis. BALB/c mice with CT26 colon tumors in abdominal wall were irradiated with 14 Gy single dose of whole abdominal irradiation (AIR) for tumor growth study.Mice receiving pre-WBI TLR9 agonist demonstrated improvement of survival after 10.4 Gy (p<0.03), 9.4 Gy (p<0.008) and 8.4 Gy (p<0.002) of WBI, compared to untreated or iMyd88-treated controls. Post-WBI TLR9 agonist mitigates up to 8.4 Gy WBI (p<0.01). Histological analysis and xylose absorption test demonstrated significant structural and functional restitution of the intestine in WBI+TLR9 agonist cohorts. Although, AIR reduced tumor growth, all animals died within 12 days from RIGS. TLR9 agonist improved the survival of mice beyond 28 days post-AIR (p<0.008) with significant reduction of tumor growth (p<0.0001).TLR9 agonist treatment could serve both as a prophylactic or mitigating agent against acute radiation syndrome and also as an adjuvant therapy to increase the therapeutic ratio of abdominal Radiation Therapy for Gastro Intestinal malignancies