Voronoi Particle Merging Algorithm for PIC Codes

We present a new particle-merging algorithm for the particle-in-cell method. Based on the concept of the Voronoi diagram, the algorithm partitions the phase space into smaller subsets, which consist of only particles that are in close proximity in the phase space to each other. We show the performance of our algorithm in the case of the two-stream instability and the magnetic shower.Comment: 11 figure

The Canonical Nuclear Many-Body Problem as an Effective Theory

Recently it was argued that it might be possible treat the conventional nuclear structure problem -- nonrelativistic point nucleons interacting through a static and rather singular potential -- as an effective theory in a shell-model basis. In the first half of this talk we describe how such a program can be carried out for the simplest nuclei, the deuteron and 3He, exploiting a new numerical technique for solving the self-consistent Bloch-Horowitz equation. Some of the properties of proper effective theories are thus illustrated and contrasted with the shell model. In the second half of the talk we use these examples to return to a problem that frustrated the field three decades ago, the possibility of reducing the effective interactions problem to perturbation theory. We show, by exploiting the Talmi integral expansion, that hard-core potentials can be systematically softened by the introduction of a series of contact operators familiar from effective field theory. The coefficients of these operators can be run analytically by a renormalization group method in a scheme-independent way, with the introduction of suitable counterterms. Once these coefficients are run to the shell model scale, we show that the renormalized coefficients contain all of the information needed to evaluate perturbative insertions of the remaining soft potential. The resulting perturbative expansion is shown to converge in lowest order for the simplest nucleus, the deuteron.Comment: Latex, 12 pages, 2 figures Talk presented at the International Symposium on Nuclei and Nucleons, held in honor of Achim Richter Typos corrected in this replacemen

Optical processing for landmark identification

A study of optical pattern recognition techniques, available components and airborne optical systems for use in landmark identification was conducted. A data base of imagery exhibiting multisensor, seasonal, snow and fog cover, exposure, and other differences was assembled. These were successfully processed in a scaling optical correlator using weighted matched spatial filter synthesis. Distinctive data classes were defined and a description of the data (with considerable input information and content information) emerged from this study. It has considerable merit with regard to the preprocessing needed and the image difference categories advanced. A optical pattern recognition airborne applications was developed, assembled and demontrated. It employed a laser diode light source and holographic optical elements in a new lensless matched spatial filter architecture with greatly reduced size and weight, as well as component positioning toleranced

Investigation into jaundice in farmed catfish (Pangasianodon hypophthalmus, Sauvage) in the Mekong Delta, Vietnam

Disease outbreaks continue to be a major problem in the sustainable development of the aquaculture industry. Clinical outbreaks can negatively impact on the welfare of the fish and the economic gain derived from this industry. Jaundice observed as a yellow colouration in the abdominal skin, sclera of the eyes and fin bases is a significant health problem affecting the Vietnamese freshwater catfish industry. This study was designed to investigate jaundice of farmed catfish, Pangasianodon hypophthalmus using several complementary approaches. These included clinical investigations and identification of potential aetiological agents as well as epidemiological analyses to identify farm-based risk factors for this economically devastating condition occurring in the catfish farms of the Mekong Delta. The results of this survey demonstrated that the jaundice was not linked to a single geographical location as affected fish were found widely distributed throughout the five main production areas. Nor was any association found between any weight groupings, feed type or feeding regime applied in the affected farms. The highest prevalence occurred between June to October and fish mortalities ranged from 1 to 10% in the study sites. The duration of this condition was significantly correlated (P < 0.05) to mortality but not to total farm area, depth of pond, stocking density, or amount of water exchanged. The number of fish ponds affected was not as high in the large-scale farms compared to the small-scale farms. The results from the clinical description study showed that the affected fish were suffering a form of jaundice or icterus. Histological examination revealed a number of serious pathologies in the affected fish. Spleenomegaly was associated with the loss of cell structure and connective tissue and the haematopoietic tissue had large areas of necrosis. In the liver, histological changes consisted of vasculitis and multifocal to diffuse hepatocellular necrosis. The presence of haemosiderin was observed in melano-macrophage centres in the spleen and kidney of jaundiced fish. No single pathogen was identified in the jaundiced fish. Myxosporean infection was found in both apparently normal fish and jaundiced fish. However, there was a definite tendency for jaundiced fish to be more heavily infected. Histopathological examination found several changes that could not be ascribed to specific aetiological factors and presume that both groups (jaundiced alone and myxosporean-affected jaundiced fish) have similar lesions. The results of this study would suggest that the parasite identified as M. pangasii was not a primary pathogen associated with the haemolytic jaundice. Neither were the gills myxosporeans associated with the haemolytic jaundice and they may be considered more as a nuisance rather than as primary pathogens in farmed P. hypophthalmus in the Mekong Delta, Vietnam. Univariate analysis of the whole dataset showed several variables were significantly associated with the haemolytic jaundice. However, none of the variables achieved lasting statistical relevance in multivariable models. In conclusion, this study identified a haemolytic jaundice condition affecting farmed P. hypophthalmus in Vietnam, but no single aetiological agent or farm based risk factor was identified with this condition. Several priority areas for further work were identified and include a prospective, longitudinal cohort study to identify further the risk factors associated with the clinical jaundice condition

USING PRESCRIPTION DRUG MONITORING DATA TO INFORM POPULATION LEVEL ANALYSIS OF OPIOID ANALGESIC UTILIZATION

Increased opioid analgesic (OA) prescribing has been associated with increased risk of prescription opioid diversion, misuse, and abuse. States established prescription drug monitoring programs (PDMPs) to collect and analyze electronic records for dispensed controlled substances to reduce prescription drug abuse and diversion. PDMP data can be used by prescribers for tracking patient’s history of controlled substance prescribing to inform clinical decisions. The studies in this dissertation are focused on the less utilized potential of the PDMP data to enhance public health surveillance to monitor OA prescribing and co-prescribing and association with opioid overdose mortality and morbidity. Longitudinal analysis of OA prescribing and evaluation of the effect of recent policies and opioid prescribing guidelines require consensus measures for OA utilization and computational tools for uniform operationalization by researchers and agencies. Statistical macros and computational tools for OA utilization measures were developed and tested with Kentucky PDMP data. A set of covariate measures using mortality and morbidity surveillance data were also developed as proxy measures for prevalence of painful conditions justifying OA utilization, and availability of heroin and medication treatment for opioid use disorder. A series of epidemiological studies used the developed OA measures as outcomes, and adjusted for time-varying socio-demographic and health care utilization covariates in population-averaged statistical models to assess longitudinal trend and pattern changes in OA utilization in Kentucky in recent years. The first study, “Trends and Patterns of OA Prescribing: Regional and Rural-Urban Variations in Kentucky from 2012 to 2015,” shows significant downward trends in rates of residents with OA prescriptions. Despite the significant decline over time, and after accounting for prevalence of injuries and cancer, the rate of dispensed OA prescriptions among residents in Kentucky Appalachian counties remained significantly higher than the rest of the state. The second study, “Population-Level Measures for High-Risk OA Prescribing: Longitudinal Trends and Relationships with Pain-Associated Conditions,” shows significant reduction in high-risk OA prescribing (e.g., high daily dosage, long-term use, concurrent prescriptions for OA and benzodiazepines) from 2012 to 2016, significantly positive associations between high-risk OA prescribing and cancer mortality rates with no substantial change in the association magnitude over time, and declining strengths of positive associations between high-risk OA prescribing and acute traumatic injuries or chronic non-cancer pain over the study period. The third study, “A Reciprocal Association between Longitudinal Trends of Buprenorphine/Naloxone Prescribing and High-Dose OA Prescribing,” indicates a significant reciprocal relationship between high-dose OA prescribing and buprenorphine/ naloxone prescribing, and a clinically meaningful effect of buprenorphine/naloxone prescribing on reducing OA utilization. The results from the studies advanced the understanding of the epidemiology of opioid use and misuse in Kentucky, and identified actionable risk and protective factors that can inform policy, education, and drug overdose prevention interventions. The developed operational definition inventory and computational tools could stimulate further research in Kentucky and comparative studies in other states

Three-fermion problems in optical lattices

We present exact results for the spectra of three fermionic atoms in a single well of an optical lattice. For the three lowest hyperfine states of Li6 atoms, we find a Borromean state across the region of the distinct pairwise Feshbach resonances. For K40 atoms, nearby Feshbach resonances are known for two of the pairs, and a bound three-body state develops towards the positive scattering-length side. In addition, we study the sensitivity of our results to atomic details. The predicted few-body phenomena can be realized in optical lattices in the limit of low tunneling.Comment: 4 pages, 4 figures, minor changes, to appear in Phys. Rev. Let

Beyond-the-Standard-Model matrix elements with the gradient flow

At the Forschungszentrum Juelich (FZJ) we have started a long-term program that aims to determine beyond-the-Standard-Model (BSM) matrix elements using the gradient flow, and to understand the impact of BSM physics in nucleon and nuclear observables. Using the gradient flow, we propose to calculate the QCD component of key beyond the Standard Model (BSM) matrix elements related to quark and strong theta CP violation and the strange content within the nucleon. The former set of matrix elements impacts our understanding of Electric Dipole Moments (EDMs) of nucleons and nuclei (a key signature of BSM physics), while the latter contributes to elastic recoil of Dark Matter particles off nucleons and nuclei. If successful, these results will lay the foundation for extraction of BSM observables from future low-energy, high-intensity and high-accuracy experimental measurements.Comment: 7 pages, 2 figures, presented at the 32nd International Symposium on Lattice Field Theory (Lattice 2014). Correct version of proceedings. Different wording of few paragraphs and different notation on few formulas. Added 1 referenc