1,003 research outputs found
Three-State Anti-ferromagnetic Potts Model in Three Dimensions: Universality and Critical Amplitudes
We present the results of a Monte Carlo study of the three-dimensional
anti-ferromagnetic 3-state Potts model. We compute various cumulants in the
neighbourhood of the critical coupling. The comparison of the results with a
recent high statistics study of the 3D XY model strongly supports the
hypothesis that both models belong to the same universality class. From our
numerical data for the anti-ferromagnetic 3-state Potts model we obtain for the
critical coupling \coup_c=0.81563(3), and for the static critical exponents
and .Comment: 18pages + 3figures, KL-TH-94/5 , CERN-TH.7183/9
Tuberculosis—diagnosis, management, prevention, and control: summary of updated NICE guidance
Tuberculosis (TB) incidence in the UK remains high compared with other Western European countries. It disproportionately affects underserved groups, including homeless people, people in poor housing or affected by poverty, people with problem drug use, and people born in countries with a high incidence of TB. However, many cases are preventable with public health measures, and, when disease does occur, most people can be cured. This article summarises the updated recommendations on diagnosing, managing, and preventing TB from the National Institute for Health and Care Excellence (NICE). This guidance updates the 2011 clinical guideline and incorporates the public health guidance on the identification and management of TB in under-served groups
ULF foreshock under radial IMF: THEMIS observations and global kinetic simulation Vlasiator results compared
European Research Council Starting grant (200141-QuESpace). Grant Number: ST/K001051/1; German Research Foundation (DFG
Exploring the gap between dynamic and constraint-based models of metabolism
Systems biology provides new approaches for metabolic engineering through
the development of models and methods for simulation and optimization of
microbial metabolism. Here we explore the relationship between two modeling
frameworks in common use namely, dynamic models with kinetic rate
laws and constraint-based flux models. We compare and analyze dynamic
and constraint-based formulations of the same model of the central carbon
metabolism of E. coli. Our results show that, if unconstrained, the space
of steady states described by both formulations is the same. However, the
imposition of parameter-range constraints can be mapped into kinetically
feasible regions of the solution space for the dynamic formulation that is not readily transferable to the constraint-based formulation. Therefore, with partial kinetic parameter knowledge, dynamic models can be used to generate constraints that reduce the solution space below that identied by constraint-based models, eliminating infeasible solutions and increasing the accuracy of simulation and optimization methods.This research was supported by PhD Grants SFRH/BD/35215/2007 and SFRH/BD/25506/2005 from the Fundacao para a Ciencia e a Tecnologia (FCT) and the MIT-Portugal Program through the project "Bridging Systems and Synthetic Biology for the Development of Improved Microbial Cell Factories" (MIT-Pt/BS-BB/0082/2008)
Lateglacial to Holocene relative sea-level changes in the Stykkishólmur area, northern Snæfellsnes, Iceland
Comparatively little research has been undertaken on relative sea-level (RSL) change in western Iceland. This paper presents the results of diatom, tephrochronological and radiocarbon analyses on six isolation basins and two coastal lowland sediment cores from the Stykkishólmur area, northern Snæfellsnes, western Iceland. The analyses provide a reconstruction of Lateglacial to mid-Holocene RSL changes in the region. The marine limit is measured to 65–69 m above sea level (asl), with formation being estimated at 13.5 cal ka BP. RSL fall initially occurred rapidly following marine limit formation, until ca. 12.6 cal ka BP, when the rate of RSL fall decreased. RSL fell below present in the Stykkishólmur area during the early Holocene (by ca. 10 cal ka BP). The rates of RSL change noted in the Stykkishólmur area demonstrate lesser ice thicknesses in Snæfellsnes than Vestfirðir during the Younger Dryas, when viewed in the regional context. Consequently, the data provide an insight into patterns of glacio-isostatic adjustment surrounding Breiðafjörður, a hypothesized major ice stream at the Last Glacial Maximum
Modeling Accelerated Pick-up Ion Distributions at an Interplanetary Shock
The acceleration of interstellar pick-up ions as well as solar wind species
has been observed at a multitude of interplanetary (IP) shocks by different
spacecraft. The efficiency of injection of the pick-up ion component differs
from that of the solar wind, and is expected to be strongly enhanced at highly
oblique and quasi-perpendicular shock events, in accord with inferences from
{\it in situ} observations. This paper explores theoretical modeling of the
phase space distributions of accelerated ions obtained by the Ulysses mission
for the Day 292, 1991 shock associated with a corotating interaction region,
encountered before Ulysses' fly-by of Jupiter. A Monte Carlo simulation is used
to model the acceleration process, adapting a technique that has been
successfully tested on earlier IP shocks possessing minimal pick-up ion
presence. Phase space distributions from the simulation technique for various
low mass ions are compared with SWICS and HI-SCALE data to deduce values of a
``turbulence parameter'' that controls the efficiency of injection, and the
degree of cross-field diffusion. Acceptable fits are obtained for the and
populations using standard prescriptions for the pick-up ion
distribution; spectral data was only fit well for scenarios very
close to the Bohm diffusion limit. It is also found that the simulation
successfully accounts for the observation of energetic protons farther upstream
of the forward shock than lower energy pick-up protons, using the same
turbulence parameter that is required to achieve reasonable spectral fits.Comment: 15 pages, 2 embedded figures, Advances Space Research, in pres
Zinc-modified nanopolymers improve the quality of resin-dentin bonded interfaces
Introduction: Demineralized collagen fibers at the hybrid layer are susceptible to degradation. Remineralization may aid to
improve bond longevity.
Objectives: The aim of the present study was to infiltrate zinc and calcium-loaded polymeric nanoparticles into demineralized
dentin to facilitate hybrid layer remineralization.
Materials and methods: Zinc or calcium-loaded polymeric nanoparticles were infiltrated into etched dentin, and Single Bond Adhesive was applied. Bond strength was tested after
24 h and 6 months storage. Nanomechanical properties, dyeassisted confocal laser microscopy, and Masson’s trichrome
staining evaluation were performed to assess for the hybrid layer morphology, permeability, and remineralization ability
after 24 h and 3 months. Data were analyzed by ANOVA and Student–Newman–Keuls multiple comparisons tests (p < 0.05).
Results: Immediate bond strength was not affected by nanoparticles infiltration (25 to 30 MPa), while after 6 months, bond strengths were maintained (22 to 24 MPa). After
3 months, permeability occurred only in specimens in which nanoparticles were not infiltrated. Dentin remineralization, at
the bottom of the hybrid layer, was observed in all groups.
After microscopy analysis, zinc-loaded nanoparticles were shown to facilitate calcium deposition throughout the entire
hybrid layer. Young’s modulus at the hybrid layer increased from 2.09 to 3.25 GPa after 3 months, in specimens with zinc nanoparticles; meanwhile, these values were reduced from
1.66 to 0.49 GPa, in the control group.
Conclusion: Infiltration of polymeric nanoparticles into demineralized dentin increased long-term bond strengths.
Zinc-loaded nanoparticles facilitate dentin remineralization within the complete resin–dentin interface.
Clinical relevance: Resin–dentin bond longevity and dentin remineralization at the hybrid layer were facilitated by zincloaded
nanoparticles.This work was supported by a grant, MINECO/FEDER MAT2014-52036-P
Construction and completion of flux balance models from pathway databases
Motivation: Flux balance analysis (FBA) is a well-known technique for genome-scale modeling of metabolic flux. Typically, an FBA formulation requires the accurate specification of four sets: biochemical reactions, biomass metabolites, nutrients and secreted metabolites. The development of FBA models can be time consuming and tedious because of the difficulty in assembling completely accurate descriptions of these sets, and in identifying errors in the composition of these sets. For example, the presence of a single non-producible metabolite in the biomass will make the entire model infeasible. Other difficulties in FBA modeling are that model distributions, and predicted fluxes, can be cryptic and difficult to understand
Quantum Fields and Extended Objects in Space-Times with Constant Curvature Spatial Section
The heat-kernel expansion and -regularization techniques for quantum
field theory and extended objects on curved space-times are reviewed. In
particular, ultrastatic space-times with spatial section consisting in manifold
with constant curvature are discussed in detail. Several mathematical results,
relevant to physical applications are presented, including exact solutions of
the heat-kernel equation, a simple exposition of hyperbolic geometry and an
elementary derivation of the Selberg trace formula. With regards to the
physical applications, the vacuum energy for scalar fields, the one-loop
renormalization of a self-interacting scalar field theory on a hyperbolic
space-time, with a discussion on the topological symmetry breaking, the finite
temperature effects and the Bose-Einstein condensation, are considered. Some
attempts to generalize the results to extended objects are also presented,
including some remarks on path integral quantization, asymptotic properties of
extended objects and a novel representation for the one-loop (super)string free
energy.Comment: Latex file, 122 page
An integrated network visualization framework towards metabolic engineering applications
Background
Over the last years, several methods for the phenotype simulation of microorganisms, under specified genetic and environmental conditions have been proposed, in the context of Metabolic Engineering (ME). These methods provided insight on the functioning of microbial metabolism and played a key role in the design of genetic modifications that can lead to strains of industrial interest. On the other hand, in the context of Systems Biology research, biological network visualization has reinforced its role as a core tool in understanding biological processes. However, it has been scarcely used to foster ME related methods, in spite of the acknowledged potential.
Results
In this work, an open-source software that aims to fill the gap between ME and metabolic network visualization is proposed, in the form of a plugin to the OptFlux ME platform. The framework is based on an abstract layer, where the network is represented as a bipartite graph containing minimal information about the underlying entities and their desired relative placement. The framework provides input/output support for networks specified in standard formats, such as XGMML, SBGN or SBML, providing a connection to genome-scale metabolic models. An user-interface makes it possible to edit, manipulate and query nodes in the network, providing tools to visualize diverse effects, including visual filters and aspect changing (e.g. colors, shapes and sizes). These tools are particularly interesting for ME, since they allow overlaying phenotype simulation results or elementary flux modes over the networks.
Conclusions
The framework and its source code are freely available, together with documentation and other resources, being illustrated with well documented case studies.This work is partially funded by ERDF - European Regional Development Fund through the COMPETE Programme (operational programme for competitiveness) and by National Funds through the FCT (Portuguese Foundation for Science and Technology) within project ref. COMPETE FCOMP-01-0124-FEDER-015079 and the FCT Strategic Project PEst-OE/EQB/LA0023/2013. The work of PV is funded by PhD grant ref. SFRH/BDE/51442/2011
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