We study hard-core lattice bosons in a magnetic field near half filling. The bare vortex hopping rate is extracted from exact diagonalizations of square clusters. We deduce a quantum melting of the vortex lattice above vortex density of 6.5x10(-3) per lattice site. The Hall conductivity reverses sign abruptly as the density crosses half filling, where its characteristic temperature scale vanishes. We prove that at precisely half filling, each vortex carries a spin-1/2 quantum number ("v spin"). Experimental implications of these results are discussed.
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http://dx.doi.org/10.1103/PhysRevLett.102.070403 | DOI Listing |
Radiat Environ Biophys
January 2025
Department of Physics, Yazd University, Yazd, Iran.
Polymer nanocomposites have been investigated as lightweight and suitable alternatives to lead-based clothing. The present study aims to fabricate flexible, lead-free, X-ray-shielding composites using a polyvinyl chloride (PVC) matrix and different nanostructures. Four different nanostructures containing impure tungsten oxide, tungsten oxide (WO), barium tungstate (BaWO), and bismuth tungstate (BiWO) were synthesized through various methods.
View Article and Find Full Text PDFBackground: It is increasingly recognized that policies played a role in mitigating or exacerbating health inequities during the COVID-19 pandemic. While US counties were particularly active in policymaking, limited work has characterized geographic and temporal variation in pandemic-era policymaking at the local level, a prerequisite for later studies examining the health effects of these policies. This paper fills this gap by characterizing county-level COVID-19-related policy trajectories over time using a novel national policy database and innovative methods.
View Article and Find Full Text PDFJ Family Med Prim Care
December 2024
Department of Family Medicine, Head Quarters Hospital, Cuddalore, Tamil Nadu, India.
Background: India is witnessing a significant increase in the prevalence of non-communicable diseases (NCDs), and addressing this requires a comprehensive and multi-faceted approach. The burden of NCDs puts a strain on the healthcare system, requiring an increased focus on preventive measures, early detection, and management of chronic conditions. Adopting a risk-based approach to cardiovascular diseases (CVDs) in resource-poor settings offers several economic and social advantages.
View Article and Find Full Text PDFMalar J
January 2025
Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland.
Background: Members of the Anopheles gambiae complex are major malaria vectors in sub-Saharan Africa. Their larval stages inhabit a variety of aquatic habitats in which, under natural circumstances, they are preyed upon by different taxa of aquatic macroinvertebrate predators. Understanding the potential impact of predators on malaria vector larval population dynamics is important for enabling integrated local mosquito control programmes with a stronger emphasis on biocontrol approaches.
View Article and Find Full Text PDFJ Phys Chem A
January 2025
Department of Chemistry, Queen's University, 90 Bader Lane, Kingston, Ontario K7L 3N6, Canada.
We report a new NMR method for treating two-site chemical exchange involving half-integer quadrupolar nuclei in a solution. The new method was experimentally verified with extensive Na ( = 3/2), K ( = 3/2), and Rb ( = 3/2) NMR results from alkali metal ions (Na, K, and Rb) in a solution over a wide range of molecular tumbling conditions. In the fast-motion limit, all allowed single-quantum NMR transitions for a particular quadrupolar nucleus are degenerate giving rise to one Lorentzian signal.
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