Reevaluation of the role of nuclear uncertainties in experiments on atomic parity violation with isotopic chains

In light of new data on neutron distributions from experiments with antiprotonic atoms [ Trzcinska {\it et al.}, Phys. Rev. Lett. 87, 082501 (2001)], we reexamine the role of nuclear-structure uncertainties in the interpretation of measurements of parity violation in atoms using chains of isotopes of the same element. With these new nuclear data, we find an improvement in the sensitivity of isotopic chain measurements to ``new physics'' beyond the standard model. We compare possible constraints on ``new physics'' with the most accurate to date single-isotope probe of parity violation in the Cs atom. We conclude that presently isotopic chain experiments employing atoms with nuclear charges Z < 50 may result in more accurate tests of the weak interaction.Comment: 6 pages, 1 fig., submitted to Phys. Rev.

Comparison of two non-primitive methods for path integral simulations: Higher-order corrections vs. an effective propagator approach

Two methods are compared that are used in path integral simulations. Both methods aim to achieve faster convergence to the quantum limit than the so-called primitive algorithm (PA). One method, originally proposed by Takahashi and Imada, is based on a higher-order approximation (HOA) of the quantum mechanical density operator. The other method is based upon an effective propagator (EPr). This propagator is constructed such that it produces correctly one and two-particle imaginary time correlation functions in the limit of small densities even for finite Trotter numbers P. We discuss the conceptual differences between both methods and compare the convergence rate of both approaches. While the HOA method converges faster than the EPr approach, EPr gives surprisingly good estimates of thermal quantities already for P = 1. Despite a significant improvement with respect to PA, neither HOA nor EPr overcomes the need to increase P linearly with inverse temperature. We also derive the proper estimator for radial distribution functions for HOA based path integral simulations.Comment: 17 pages, latex, 6 postscript figure

Dysmorphism of urinary red blood cells—Value in diagnosis

Dysmorphism of urinary red blood cells—Value in diagnosis. To aid investigation into the clinical problem of hematuria, assessment of abnormalities in the shape of red cells in the urine (dysmorphism) is gaining popularity in nephrology. However, there is uncertainty in the literature regarding both the number of red blood cells (RBC) in normal urine, as well as the quantification of dysmorphism. We have shown that in normal urine (N = 27) the number of RBC is less than 2,000/ml as assessed by scanning electron microscopy of filtered urine specimens from normal volunteers without known renal disease, which compared to less than 1,000/ml by centrifugation and phase contrast microscopy of the same specimen. To determine whether dysmorphism of urinary red blood cells was a significant predictor of glomerular disease we compared the number of dysmorphic cells in the urine of patients with biopsy proven glomerulonephritis (GN), before and immediately after renal biopsy. We also compared the number of dysmorphic cells in patients with glomerulonephritis to those with lower urinary tract bleeding. Renal biopsy caused significant dysmorhpic hematuria, indicating that dysmorphism suggests renal rather than glomerular bleeding. Although patients with GN had significantly more dysmorphic urinary RBC when compared to those with lower tract urinary bleeding, the overlap was such that one could only be confident of renal hematuria if they accounted for greater than 75% of the total number of RBC. Non renal hematuria is present if number of dysmorphic cells is less than 17% of total RBC. Thus dysmorphism of urinary RBC is a useful diagnostic tool, but only if strict criteria established for each laboratory are adhered to

Hydrogen-Helium Mixtures at High Pressure

The properties of hydrogen-helium mixtures at high pressure are crucial to address important questions about the interior of Giant planets e.g. whether Jupiter has a rocky core and did it emerge via core accretion? Using path integral Monte Carlo simulations, we study the properties of these mixtures as a function of temperature, density and composition. The equation of state is calculated and compared to chemical models. We probe the accuracy of the ideal mixing approximation commonly used in such models. Finally, we discuss the structure of the liquid in terms of pair correlation functions.Comment: Proceedings article of the 5th Conference on Cryocrystals and Quantum Crystals in Wroclaw, Poland, submitted to J. Low. Temp. Phys. (2004

Superconducting Coherence and the Helicity Modulus in Vortex Line Models

We show how commonly used models for vortex lines in three dimensional superconductors can be modified to include k=0 excitations. We construct a formula for the k=0 helicity modulus in terms of fluctuations in the projected area of vortex loops. This gives a convenient criterion for the presence of superconducting coherence. We also present Monte Carlo simulations of a continuum vortex line model for the melting of the Abrikosov vortex lattice in pure YBCO.Comment: 4 pages RevTeX, 2 eps figures included using eps

Identifying genotype specific elevated-risk areas and associated herd risk factors for bovine tuberculosis spread in British cattle

Bovine tuberculosis (bTB) is a chronic zoonosis with major health and economic impact on the cattle industry. Despite extensive control measures in cattle and culling trials in wildlife, the reasons behind the expansion of areas with high incidence of bTB breakdowns in Great Britain remain unexplained. By balancing the importance of cattle movements and local transmission on the observed pattern of cattle outbreaks, we identify areas at elevated risk of infection from specific Mycobacterium bovis genotypes. We show that elevated-risk areas (ERAs) were historically more extensive than previously understood, and that cattle movements alone are insufficient for ERA spread, suggesting the involvement of other factors. For all genotypes, we find that, while the absolute risk of infection is higher in ERAs compared to areas with intermittent risk, the statistically significant risk factors are remarkably similar in both, suggesting that these risk factors can be used to identify incipient ERAs before this is indicated by elevated incidence alone. Our findings identify research priorities for understanding bTB dynamics, improving surveillance and guiding management to prevent further ERA expansion

Stability of the lattice formed in first-order phase transitions to matter containing strangeness in protoneutron stars

Well into the deleptonization phase of a core collapse supernova, a first-order phase transition to matter with macroscopic strangeness content is assumed to occur and lead to a structured lattice defined by negatively charged strange droplets. The lattice is shown to crystallize for expected droplet charges and separations at temperatures typically obtained during the protoneutronstar evolution. The melting curve of the lattice for small spherical droplets is presented. The one-component plasma model proves to be an adequate description for the lattice in its solid phase with deformation modes freezing out around the melting temperature. The mechanical stability against shear stresses is such that velocities predicted for convective phenomena and differential rotation during the Kelvin-Helmholtz cooling phase might prevent the crystallization of the phase transition lattice. A solid lattice might be fractured by transient convection, which could result in anisotropic neutrino transport. The melting curve of the lattice is relevant for the mechanical evolution of the protoneutronstar and therefore should be included in future hydrodynamics simulations.Comment: accepted for publication in Physical Review