Critical behavior of 3D Z(N) lattice gauge theories at zero temperature

Three-dimensional $Z(N)$ lattice gauge theories at zero temperature are studied for various values of $N$. Using a modified phenomenological renormalization group, we explore the critical behavior of the generalized $Z(N)$ model for $N=2,3,4,5,6,8$. Numerical computations are used to simulate vector models for $N=2,3,4,5,6,8,13,20$ for lattices with linear extension up to $L=96$. We locate the critical points of phase transitions and establish their scaling with $N$. The values of the critical indices indicate that the models with $N>4$ belong to the universality class of the three-dimensional $XY$ model. However, the exponent $\alpha$ derived from the heat capacity is consistent with the Ising universality class. We discuss a possible resolution of this puzzle. We also demonstrate the existence of a rotationally symmetric region within the ordered phase for all $N\geq 5$ at least in the finite volume.Comment: 25 pages, 4 figures, 8 table

The phase transitions in 2D Z(N) vector models for N>4

We investigate both analytically and numerically the renormalization group equations in 2D Z(N) vector models. The position of the critical points of the two phase transitions for N>4 is established and the critical index \nu\ is computed. For N=7, 17 the critical points are located by Monte Carlo simulations and some of the corresponding critical indices are determined. The behavior of the helicity modulus is studied for N=5, 7, 17. Using these and other available Monte Carlo data we discuss the scaling of the critical points with N and some other open theoretical problems.Comment: 19 pages, 8 figures, 10 tables; version to appear on Phys. Rev.

Long-term changes in the structure of a polychaete community on artificial habitats

A mediterranean polychaete community was studied for 10 years since the first settlement to examine community dynamics and to compare it with the model proposed by Hughes (1984) for benthic invertebrates. Cluster analysis (Q-mode) pointed out the presence of four main periods during the colonization process in agreement with edaphic changes produced by the colonization and disappearance of mussels. During this time the pattern of species abundance changed from a log series distribution (with few dominant species) towards a truncated log normal distribution (with many rare species) characteristic of a more complex community structure

Critical behavior of the compact 3d U(1) theory in the limit of zero spatial coupling

Critical properties of the compact three-dimensional U(1) lattice gauge theory are explored at finite temperatures on an asymmetric lattice. For vanishing value of the spatial gauge coupling one obtains an effective two-dimensional spin model which describes the interaction between Polyakov loops. We study numerically the effective spin model for N_t=1,4,8 on lattices with spatial extension ranging from L=64 to L=256. Our results indicate that the finite-temperature U(1) lattice gauge theory belongs to the universality class of the two-dimensional XY model, thus supporting the Svetitsky-Yaffe conjecture.Comment: 17 pages, 5 figures; two references added, a few comments included, title changed; version to appear on J. Stat. Mec

Colonization and disappearance of Mytilus galloprovincialis Lam. on an artificial habitat in the Mediterranean Sea

A Mytilus galloprovincialis population, settled on a new artificial habitat at 12 m depth in the Central Tyrrhenian Sea, was investigated for 10 years. The new substratum, located at a depth lower than the preferential range of the species, was colonized temporarily by mussels which reached very high densities and dominated the benthic community from their colonization until the third year. The length-frequency distribution analysis showed a progressively complex population structure with up to three cohorts. The yearly recruitments were observed once a year in spring. The growth curve provided a maximum length higher than that reported for shallow waters. Nevertheless, the gregarious habits of mussels and the reduced water movement caused edaphic modifications of the substratum, which was covered progressively by sediments and biodeposits (pseudofaeces). Consequently, the population structure was affected by a reduction of the newly recruited cohorts, and mussels disappeared after 5 years of colonization. This may be explained by the reduction in the substratum available for the first settlement (hydroid covering), as well as by the modification of the surface required for final settlement. (C) 1996 Academic Press Limite

Episode Based Payment Models and the Hospital Safety-net: An Evaluation of the Center for Medicare and Medicaid Services’ Comprehensive Joint Replacement Bundled Payment Program

Episode Based Payment Models and the Hospital Safety-net: An Evaluation of the Center for Medicare and Medicaid Services’ Comprehensive Joint Replacement Bundled Payment Program By John Anthony Gravina Advisor: Alexis Pozen, Ph.D. Introduction: Payments for Healthcare services are increasingly being tied to clinical quality, patient experience, health outcomes, and efficiency through value-based payment arrangements (VBP). VBP presents a potential opportunity to reduce healthcare expenditures by requiring providers to take on financial risk associated with the cost and quality of care, therefore aligning payment incentives with the goals of providing higher quality and efficient care. As of 2020, 80 percent of Medicare payments had some link to value. As the shift from paying for volume of services to paying for value has progressed, focus has shifted to payment models, including episode-based payment models, that not only tie payment to clinical quality and patient outcomes but do so while encouraging efficiency and provider integration across multiple providers along the continuum of care. Episode-based payment models have demonstrated the ability to reduce Medicare payments to providers without harming measures of healthcare quality, but there is concern that these models may disadvantage safety-net providers and the vulnerable patients that they serve. The following study examines the impact of a mandatory Medicare episode-based payment program, the Comprehensive Care for Joint Replacement (CJR) program, on average price-standardized episode payments, and whether that impact is different for safety-net providers. Methods: Medicare claims data from the Limited Data Set (LDS) standard analytical files (SAFs) from 2011-2018 were used to construct longitudinal episodes of care for lower extremity joint replacement patients beginning with discharge for LEJR and extending 90 days post-discharge. A difference in differences (DID) approach was used to estimate whether the change in price-standardized payments for applicable services post implementation of the CJR program in episodes originating at participating facilities was significantly different in comparison to those originating at non-participating facilities. Two-part logistic-linear DID models were used to estimate the change in payments separately for each category of services. Analyses were then stratified by the safety-net burden of the anchor hospital, measured using the percent of total inpatient days for Medicaid patients, the percent of Medicare inpatient days for patients receiving supplemental security income, and the disproportionate share hospital patient percentage. Analyses controlled for patient characteristics, characteristics of the hospital providing the LEJR, along with MSA and Hospital level fixed effects. Results: Average price standardized episode spending decreased 3.5% (p Conclusion: These finding provide further evidence in support of episode-based payment models as an effective method to generate reduced payments to providers of LEJR services. This evidence comes at a crucial time, as Medicare, along with its advisors, the Medicare Payment Advisory Commission, are currently engaged in planning the future of episode-based payment models within the Medicare program. Importantly, safety-net burden was not found to impact the ability to generate payment reductions in an episode-based payment model. The findings presented related to the ability of safety-net providers to generate payment reductions are also timely and provide needed evidence at a time in which Medicare, Medicare Payment Advisory Commission and The Innovation Center plan for the future of alternative payment models in the Medicare program

Genome-wide quantitative analysis of DNA methylation from bisulfite sequencing data

Summary: Here we present the open-source R/Bioconductor software package BEAT (BS-Seq Epimutation Analysis Toolkit). It implements all bioinformatics steps required for the quantitative high-resolution analysis of DNA methylation patterns from bisulfite sequencing data, including the detection of regional epimutation events, i.e. loss or gain of DNA methylation at CG positions relative to a reference. Using a binomial mixture model, the BEAT package aggregates methylation counts per genomic position, thereby compensating for low coverage, incomplete conversion and sequencing errors. Availability and implementation: BEAT is freely available as part of Bioconductor at www.bioconductor.org/packages/devel/bioc/html/BEAT.html. The package is distributed under the GNU Lesser General Public License 3.0. Contact: [email protected] Supplementary information: Supplementary data are available at Bioinformatics online

Critical behavior of the compact 3d U(1) gauge theory on isotropic lattices

We report on the computation of the critical point of the deconfinement phase transition, critical indices and the string tension in the compact three dimensional U(1) lattice gauge theory at finite temperatures. The critical indices govern the behavior across the deconfinement phase transition in the pure gauge U(1) model and are generally expected to coincide with the critical indices of the two-dimensional XY model. We studied numerically the U(1) model for N_t=8 on lattices with spatial extension ranging from L=32 to L=256. Our determination of the infinite volume critical point on the lattice with N_t=8 differs substantially from the pseudo-critical coupling at L=32, found earlier in the literature and implicitly assumed as the onset value of the deconfined phase. The critical index $\nu$ computed from the scaling of the pseudo-critical couplings with the extension of the spatial lattice agrees well with the XY value $\nu$=1/2. On the other hand, the index $\eta$ shows large deviation from the expected universal value. The possible reasons of such behavior are discussed in details.Comment: 15 pages, 7 figures; version accepted for publication on J. Stat. Mech