Dual Geometric Worm Algorithm for Two-Dimensional Discrete Classical Lattice Models

We present a dual geometrical worm algorithm for two-dimensional Ising models. The existence of such dual algorithms was first pointed out by Prokof'ev and Svistunov \cite{ProkofevClassical}. The algorithm is defined on the dual lattice and is formulated in terms of bond-variables and can therefore be generalized to other two-dimensional models that can be formulated in terms of bond-variables. We also discuss two related algorithms formulated on the direct lattice, applicable in any dimension. These latter algorithms turn out to be less efficient but of considerable intrinsic interest. We show how such algorithms quite generally can be "directed" by minimizing the probability for the worms to erase themselves. Explicit proofs of detailed balance are given for all the algorithms. In terms of computational efficiency the dual geometrical worm algorithm is comparable to well known cluster algorithms such as the Swendsen-Wang and Wolff algorithms, however, it is quite different in structure and allows for a very simple and efficient implementation. The dual algorithm also allows for a very elegant way of calculating the domain wall free energy.Comment: 12 pages, 6 figures, Revtex

Bayesian model averaging with fixed and flexible priors: theory, concepts, and calibration experiments for rainfall-runoff modeling

This paper introduces for the first time the concept of Bayesian Model Averaging (BMA) with multiple prior structures, for rainfall‐runoff modeling applications. The original BMA model proposed by Raftery et al. (2005) assumes that the prior probability density function (pdf) is adequately described by a mixture of Gamma and Gaussian distributions. Here we discuss the advantages of using BMA with fixed and flexible prior distributions. Uniform, Binomial, Binomial‐Beta, Benchmark, and Global Empirical Bayes priors along with Informative Prior Inclusion and Combined Prior Probabilities were applied to calibrate daily streamflow records of a coastal plain watershed in the South‐East USA. Various specifications for Zellner's g prior including Hyper, Fixed, and Empirical Bayes Local (EBL) g priors were also employed to account for the sensitivity of BMA and derive the conditional pdf of each constituent ensemble member. These priors were examined using the simulation results of conceptual and semi‐distributed rainfall‐runoff models. The hydrologic simulations were first coupled with a new sensitivity analysis model and a parameter uncertainty algorithm to assess the sensitivity and uncertainty associated with each model. BMA was then used to subsequently combine the simulations of the posterior pdf of each constituent hydrological model. Analysis suggests that a BMA based on combined fixed and flexible priors provides a coherent mechanism and promising results for calculating a weighted posterior probability compared to individual model calibration. Furthermore, the probability of Uniform and Informative Prior Inclusion priors received significantly lower predictive error whereas more uncertainty resulted from a fixed g prior (i.e. EBL)

Dimension Spectra of Lines

This paper investigates the algorithmic dimension spectra of lines in the Euclidean plane. Given any line L with slope a and vertical intercept b, the dimension spectrum sp(L) is the set of all effective Hausdorff dimensions of individual points on L. We draw on Kolmogorov complexity and geometrical arguments to show that if the effective Hausdorff dimension dim(a, b) is equal to the effective packing dimension Dim(a, b), then sp(L) contains a unit interval. We also show that, if the dimension dim(a, b) is at least one, then sp(L) is infinite. Together with previous work, this implies that the dimension spectrum of any line is infinite

Dissipative Transport of a Bose-Einstein Condensate

We investigate the effects of impurities, either correlated disorder or a single Gaussian defect, on the collective dipole motion of a Bose-Einstein condensate of $^7$Li in an optical trap. We find that this motion is damped at a rate dependent on the impurity strength, condensate center-of-mass velocity, and interatomic interactions. Damping in the Thomas-Fermi regime depends universally on the disordered potential strength scaled to the condensate chemical potential and the condensate velocity scaled to the peak speed of sound. The damping rate is comparatively small in the weakly interacting regime, and the damping in this case is accompanied by strong condensate fragmentation. \textit{In situ} and time-of-flight images of the atomic cloud provide evidence that this fragmentation is driven by dark soliton formation.Comment: 14 pages, 20 figure

Application of SWAT Hydrologic Model for TMDL Development on Chapel Branch Creek Watershed, SC

2008 S.C. Water Resources Conference - Addressing Water Challenges Facing the State and Regio

Low-Energy Electron-Track Imaging for a Liquid Argon Time-Projection-Chamber Telescope Concept using Probabilistic Deep Learning

The GammaTPC is an MeV-scale single-phase liquid argon time-projection-chamber gamma-ray telescope concept with a novel dual-scale pixel-based charge-readout system. It promises to enable a significant improvement in sensitivity to MeV-scale gamma-rays over previous telescopes. The novel pixel-based charge readout allows for imaging of the tracks of electrons scattered by Compton interactions of incident gamma-rays. The two primary contributors to the accuracy of a Compton telescope in reconstructing an incident gamma-ray's original direction are its energy and position resolution. In this work, we focus on using deep learning to optimize the reconstruction of the initial position and direction of electrons scattered in Compton interactions, including using probabilistic models to estimate predictive uncertainty. We show that the deep learning models are able to predict locations of Compton scatters of MeV-scale gamma-rays from simulated pixel-based data to better than 0.6 mm RMS error, and are sensitive to the initial direction of the scattered electron. We compare and contrast different deep learning uncertainty estimation algorithms for reconstruction applications. Additionally, we show that event-by-event estimates of the uncertainty of the locations of the Compton scatters can be used to select those events that were reconstructed most accurately, leading to improvement in locating the origin of gamma-ray sources on the sky

Carriage of Haemophilus influenzae in Cape Town children

Little is known about the epideIDiology of Haemophilus influenzae infections in South Africa. This study was designed to determine the prevalence, serotype distribution, antimicrobial susceptibility pattern and effect of age and hospitalisation on the carriage of H. influenzae in 322 Cape Town children.The overall and type b specific carriage rates in normal children (N =107) were 45,8% and 4,7% respectively. The yield following nasopharyngeal culture was twice that following throat culture (P < 0,001). Children hospitalised with tuberculosis (N =62) had significantly greater carriage rates, 66,1% and 37,1% respectively (P =0,02). Institutionalised mentally handicapped children (N =77) and children with tuberculosis attending an outpatient clinic (N =76) had lower carriage rates (P < 0,02). Antimicrobial resistance was a major problem only in children hospitalised with tuberculosis (rifampicin 100%, penicillin 43,9%, erythromycin 85,4%, co-trimoxazole 82,9%). This universal resistance to rifampicin has not been reported previously. There was no difference in the mean age of children with positive or negative cultures, with the exception of those hospitalised with tuberculosis. In this group children infected with type b were much younger (mean 19,7 months) than those with other and non-typeableinfections (32,1 months) and the non-infected(50,1 months) (P =0,04). Duration of hospitalisation or outpatient therapy in the patients with tuberculosis did not influence carriage rates.We conclude that carriage of H. influenzae in normal children is similar to that reported from other countries and that carriage, particularly of type b, in children hospitalised with tuberculosis was of significance and probably contributed to an outbreak of multi-resistant invasive H. influenzae disease in this group

X-Ray Absorption Studies of Strain in Epitaxial (Si-Ge) Atomic Layer Superlattice and Alloy Films

The Si 1s (K-shell) X-ray absorption spectra of a series of strained SixGe100-x alloy thin films and several {(Si)m(Ge)n}p atomic layer superlattices (ALS) grown epitaxially on Si(100) and Ge(100) substrates have been investigated using plane polarized synchrotron radiation. Polarization dependent components of the signal are attributed to anisotropic states associated with strain-induced tetragonal distortions. The sense of the polarization is shown to be identical for all compositions (x = 25 to 92) of SiGe alloys grown on Si(100) substrates. The opposite polarization dependence is found to occur for all SixGe100-x alloys (x = 12 to 50) grown on Ge(100) substrates. The polarization dependence and shape of the near edge spectral features of alloy and ALS samples which have similar (average) chemical composition are remarkably similar. A preliminary comparison of the alloy results with literature band structure calculations is made

Contemplative Science: An Insider's Prospectus

This chapter describes the potential far‐reaching consequences of contemplative higher education for the fields of science and medicine