150 research outputs found
Critical behavior of weakly-disordered anisotropic systems in two dimensions
The critical behavior of two-dimensional (2D) anisotropic systems with weak
quenched disorder described by the so-called generalized Ashkin-Teller model
(GATM) is studied. In the critical region this model is shown to be described
by a multifermion field theory similar to the Gross-Neveu model with a few
independent quartic coupling constants. Renormalization group calculations are
used to obtain the temperature dependence near the critical point of some
thermodynamic quantities and the large distance behavior of the two-spin
correlation function. The equation of state at criticality is also obtained in
this framework. We find that random models described by the GATM belong to the
same universality class as that of the two-dimensional Ising model. The
critical exponent of the correlation length for the 3- and 4-state
random-bond Potts models is also calculated in a 3-loop approximation. We show
that this exponent is given by an apparently convergent series in
(with the central charge of the Potts model) and
that the numerical values of are very close to that of the 2D Ising
model. This work therefore supports the conjecture (valid only approximately
for the 3- and 4-state Potts models) of a superuniversality for the 2D
disordered models with discrete symmetries.Comment: REVTeX, 24 pages, to appear in Phys.Rev.
Magnetic critical behavior of two-dimensional random-bond Potts ferromagnets in confined geometries
We present a numerical study of 2D random-bond Potts ferromagnets. The model
is studied both below and above the critical value which discriminates
between second and first-order transitions in the pure system. Two geometries
are considered, namely cylinders and square-shaped systems, and the critical
behavior is investigated through conformal invariance techniques which were
recently shown to be valid, even in the randomness-induced second-order phase
transition regime Q>4. In the cylinder geometry, connectivity transfer matrix
calculations provide a simple test to find the range of disorder amplitudes
which is characteristic of the disordered fixed point. The scaling dimensions
then follow from the exponential decay of correlations along the strip. Monte
Carlo simulations of spin systems on the other hand are generally performed on
systems of rectangular shape on the square lattice, but the data are then
perturbed by strong surface effects. The conformal mapping of a semi-infinite
system inside a square enables us to take into account boundary effects
explicitly and leads to an accurate determination of the scaling dimensions.
The techniques are applied to different values of Q in the range 3-64.Comment: LaTeX2e file with Revtex, revised versio
Fairy tale tourism: the architectural projection mapping of magically real and irreal festival lightscapes
This paper explores how established light festivals such as the Fête des Lumières in Lyon and Lumiere in Durham were first conceived by Robert-Houdin as illusory illuminations in the Loire in the 1950s. The research investigates the concept of spectacles as inversions of reality; re-situating light works within authenticity theory by exploring their manipulation of magical reality and irreality. The research uses the authors’ experience of event design to assess different interactions of light with the tri-dimensional architectural canvas, suggesting three classifications of animated projection mapping events: architecturally passive, architecturally physically active and architecturally metaphysically active. Each category has implications for how spectators perceive these installations. Architecturally passive events may use fairy tale content, evoking atavistic and affective responses, the ‘skinning’ of buildings with magical reality is designed to evoke perceptual duality, and the wobbling unfolding of irreality may ultimately create a state of ‘illuminated flow.
A systematic review of patient and health system characteristics associated with late referral in chronic kidney disease
<p>Abstract</p> <p>Background</p> <p>To identify patient and health system characteristics associated with late referral of patients with chronic kidney disease to nephrologists.</p> <p>Methods</p> <p>MEDLINE, CENTRAL, and CINAHL were searched using the appropriate MESH terms in March 2007. Two reviewers individually and in duplicate reviewed the abstracts of 256 articles and selected 18 observational studies for inclusion. The reasons for late referral were categorized into patient or health system characteristics. Data extraction and content appraisal were done using a prespecified protocol.</p> <p>Results</p> <p>Older age, the existence of multiple comorbidities, race other than Caucasian, lack of insurance, lower socioeconomic status and educational levels were patient characteristics associated with late referral of patients with chronic kidney disease. Lack of referring physician knowledge about the appropriate timing of referral, absence of communication between referring physicians and nephrologists, and dialysis care delivered at tertiary medical centers were health system characteristics associated with late referral of patients with chronic kidney disease. Most studies identified multiple factors associated with late referral, although the relative importance and the combined effect of these factors were not systematically evaluated.</p> <p>Conclusion</p> <p>A combination of patient and health system characteristics is associated with late referral of patients with chronic kidney disease. Overall, being older, belonging to a minority group, being less educated, being uninsured, suffering from multiple comorbidities, and the lack of communication between primary care physicians and nephrologists contribute to late referral of patients with chronic kidney disease. Both primary care physicians and nephrologists need to engage in multisectoral collaborative efforts that ensure patient education and enhance physician awareness to improve the care of patients with chronic kidney disease.</p
A functional AT/G polymorphism in the 5'-untranslated region (UTR) of SETDB2 in the IgE locus on human chromosome 13q14
The immunoglobulin E (IgE)-associated locus on human chromosome 13q14 influencing asthma-related traits contains the genes PHF11 and SETDB2. SETDB2 is located in the same linkage disequilibrium region as PHF11 and polymorphisms within SETDB2 have been shown to associate with total serum IgE levels. In this report, we sequenced the 15 exons of SETDB2 and identified a single previously ungenotyped mutation (AT/G, rs386770867) in the 5′-untranslated region of the gene. The polymorphism was found to be significantly associated with serum IgE levels in our asthma cohort (P=0.0012). Electrophoretic mobility shift assays revealed that the transcription factor Ying Yang 1 binds to the AT allele, whereas SRY (Sex determining Region Y) binds to the G allele. Allele-specific transcription analysis (allelotyping) was performed in 35 individuals heterozygous for rs386770867 from a panel of 200 British families ascertained through probands with severe stage 3 asthma. The AT allele was found to be significantly overexpressed in these individuals (P=1.26 × 10(−21)). A dual-luciferase assay with the pGL3 luciferase reporter gene showed that the AT allele significantly affects transcriptional activities. Our results indicate that the IgE-associated AT/G polymorphism (rs386770867) regulates transcription of SETDB2
Aspirin induces cell death and caspase-dependent phosphatidylserine externalization in HT-29 human colon adenocarcinoma cells
The induction of cell death by aspirin was analysed in HT-29 colon carcinoma cells. Aspirin induced two hallmarks of apoptosis: nuclear chromatin condensation and increase in phosphatidylserine externalization. However, aspirin did not induce either oligonucleosomal fragmentation of DNA, decrease in DNA content or nuclear fragmentation. The effect of aspirin on Annexin V binding was inhibited by the caspase inhibitor Z-VAD.fmk, indicating the involvement of caspases in the apoptotic action of aspirin. However, aspirin did not induce proteolysis of PARP, suggesting that aspirin does not increase nuclear caspase 3-like activity in HT-29 cells. This finding may be related with the ‘atypical’ features of aspirin-induced apoptosis in HT-29 cells. © 1999 Cancer Research Campaig
Suppression of GATA-3 Nuclear Import and Phosphorylation: A Novel Mechanism of Corticosteroid Action in Allergic Disease
Peter Barnes and colleagues show that corticosteroids have a potent inhibitory effect on GATA-3 via two interacting mechanisms that suppress Th2 cytokine expression. This novel mechanism of corticosteroid action may help explain the efficacy of corticosteroids in allergic diseases
Renal replacement therapy in acute kidney injury: controversy and consensus
Renal replacement therapies (RRTs) represent a cornerstone in the management of severe acute kidney injury. This area of intensive care and nephrology has undergone significant improvement and evolution in recent years. Continuous RRTs have been a major focus of new technological and treatment strategies. RRT is being used increasingly in the intensive care unit, not only for renal indications but also for other organ-supportive strategies. Several aspects related to RRT are now well established, but others remain controversial. In this review, we review the available RRT modalities, covering technical and clinical aspects. We discuss several controversial issues, provide some practical recommendations, and where possible suggest a research agenda for the future
Micromechanical Properties of Injection-Molded Starch–Wood Particle Composites
The micromechanical properties of injection molded starch–wood particle composites were investigated as a function of particle content and humidity conditions.
The composite materials were characterized by scanning electron microscopy and X-ray diffraction methods. The microhardness
of the composites was shown to increase notably with the concentration of the wood particles. In addition,creep behavior under the indenter and temperature dependence
were evaluated in terms of the independent contribution of the starch matrix and the wood microparticles to the hardness value. The influence of drying time on the density
and weight uptake of the injection-molded composites was highlighted. The results revealed the role of the mechanism of water evaporation, showing that the dependence of water uptake and temperature was greater for the starch–wood composites than for the pure starch sample. Experiments performed during the drying process at 70°C indicated that
the wood in the starch composites did not prevent water loss from the samples.Peer reviewe
- …