6,301 research outputs found
A disorder analysis of the Ising model
Lattice studies of monopole condensation in QCD are based on the construction
of a disorder parameter, a creation operator of monopoles which is written in
terms of the gauge fields. This procedure is expected to work for any system
which presents duality. We check it on the Ising model in 2d, which is exactly
solvable. The output is an amusing exercise in statistical mechanics.Comment: 14 pages, 3 figure
Vanishing conductivity of quantum solitons in polyacetylene
Quantum solitons or polarons are supposed to play a crucial role in the
electric conductivity of polyacetylene, in the intermediate doping regime. We
present an exact fully quantized calculation of the quantum soliton
conductivity in polyacetylene and show that it vanishes exactly. This is
obtained by applying a general method of soliton quantization, based on
order-disorder duality, to a Z(2)-symmetric complex extension of the TLM
dimerization effective field theory. We show that, in this theory,
polyacetylene solitons are sine-Gordon solitons in the phase of the complex
field.Comment: To appear in J. Phys. A: Math. Theor., 15 page
Monopole Condensation and Color Confinement
New evidence is discussed of monopole condensation in the vacuum of SU(2) and
SU(3) gauge theories. Monopoles defined by different abelian projections do
condense in the transition to the confined phase and show the same behavior.
For SU(2) critical indices are determined by finite size scaling analysis and
the results agree with the 3d Ising Model, as expected.Comment: LATTICE98(confinement),3 pages,4 figure
A matrix model for the topological string II: The spectral curve and mirror geometry
In a previous paper, we presented a matrix model reproducing the topological
string partition function on an arbitrary given toric Calabi-Yau manifold.
Here, we study the spectral curve of our matrix model and thus derive, upon
imposing certain minimality assumptions on the spectral curve, the large volume
limit of the BKMP "remodeling the B-model" conjecture, the claim that
Gromov-Witten invariants of any toric Calabi-Yau 3-fold coincide with the
spectral invariants of its mirror curve.Comment: 1+37 page
Progress in understanding colour confinement
New results from lattice are presented,which demonstrate that monopoles
condense in the vacuum of confined phase of QCD, which is thus a dual
superconductor. Monopoles defined by different abelian projections appear to be
physically equivalent.Comment: 5 pages,4 figures. Presented by A.Di Giacomo at QCD98 Montpellier
July199
Statistics of non-linear stochastic dynamical systems under L\'evy noises by a convolution quadrature approach
This paper describes a novel numerical approach to find the statistics of the
non-stationary response of scalar non-linear systems excited by L\'evy white
noises. The proposed numerical procedure relies on the introduction of an
integral transform of Wiener-Hopf type into the equation governing the
characteristic function. Once this equation is rewritten as partial
integro-differential equation, it is then solved by applying the method of
convolution quadrature originally proposed by Lubich, here extended to deal
with this particular integral transform. The proposed approach is relevant for
two reasons: 1) Statistics of systems with several different drift terms can be
handled in an efficient way, independently from the kind of white noise; 2) The
particular form of Wiener-Hopf integral transform and its numerical evaluation,
both introduced in this study, are generalizations of fractional
integro-differential operators of potential type and Gr\"unwald-Letnikov
fractional derivatives, respectively.Comment: 20 pages, 5 figure
Impact of DEL22q11, trisomy 21, and other genetic syndromes on surgical outcome of conotruncal heart defects
Objective: Genetic syndromes occur in more than 20% of patients with conotruncal heart defects. We investigated
the impact of genetic syndromes on the surgical outcome of conotruncal anomalies in infancy.
Methods: This retrospective study reviews the outcome of 787 patients (median age 6.3 months) who underwent
primary (598) or staged (189) repair of a conotruncal defect between 1992 and 2007.
Results: Proven genetic syndrome was diagnosed in 211 patients (26.8%), including del22q11 (91 patients), trisomy
21 (29 patients), VACTERL (18 patients), and other syndromes (73 patients). Primary repair was accomplished
in 80.9% of nonsyndromic patients and 74.4% of syndromic patients (P ÂĽ .18) Fifteen-year
cumulative survival was 84.3% 2.3% in nonsyndromic patients and 73.2% 4.2% in syndromic patients
(P<.001). Primary and staged repair allowed similar 15-year survival (81.4% 4.5% vs 79.1% 5.1%,
P ÂĽ .8). Freedom from noncardiac cause of death was significantly lower in syndromic patients (P ÂĽ .0056). Fifteen-
year Kaplan–Meier survival was 87.6% 3.9% for del22q11, 95.8% 4.1% for trisomy 21, 56.8%
6.3% for VACTERL, and 62.3% 12.7% for patients with other syndromes (P ÂĽ .022). Total intensive care
unit stay was 10.8 4.9 days in syndromic patients and 5.1 1.7 days in nonsyndromic patients (P<.001). Freedom
from reintervention 15 years after repair was 79.6% 4.9%in nonsyndromic patients and 62.4% 7.4%in
syndromic patients (P ÂĽ .007).
Conclusion: Del22q11 and trisomy 21 do not represent risk factors for mortality after repair of conotruncal anomalies,
whereas other syndromes adversely affect the surgical outcome for predominant noncardiac attrition.
Higher morbidity and lower mid-term freedom from reintervention can be predicted in syndromic patients
Recognition of facial emotion expressions and perceptual processes in 22q11.2 deletion syndrome
Background: Social cognition (SC) deficits and of its facial emotion expression (FEE) component have been described in 22q11.2 Deletion Syndrome (22q11.2DS), a high-risk for schizophrenia (SCZ) systemic genetic syndrome. Correlations between deficits in FEE skills and visual-spatial abilities in people with 22q11.2DS warrant investigation. Methods: The sample consisted of 37 patients with 22q11.2DS (DEL), 19 with 22q11.2DS and psychosis (DEL-SCZ), 23 with idiopathic SCZ, and 48 healthy controls. We assessed FEE through The Ekman 60 Faces test (EK-F60), visual-spatial skills with Raven's Standard Progressive Matrices, and symptom severity with the positive And negative syndrome scale. Statistics were conducted through multivariate analysis of variance and correlation analysis. Results: Patients with 22q11.2DS performed worse that the other groups in recognizing Surprise, Disgust, Rage, Fear, and Neutral expressions on the EK-F60. Recognition of Surprise and Disgust correlated positively with visual-spatial abilities in patients with 22q11.2DS; negative and cognitive symptoms correlated negatively with recognition of Sadness, Surprise, and Disgust. Conclusions: Patients with 22q11.2DS show impairments of both peripheral and central steps of the emotional recognition process, leading to SC deficits. The latter are present regardless of the presence of a full-blown psychosis
Additive value to clinical judgement of blood neutrophil gelatinase-associated lipocalin in diagnosis of acute kidney injury and prediction of mortality in patients hospitalized from the emergency department
High resolution computed tomography quantitation of emphysema is correlated with selected lung function values in stable COPD.
BACKGROUND:
The literature shows conflicting results when high-resolution computed tomography (HRCT) scores of emphysema were correlated with different indices of airflow obstruction.
OBJECTIVES:
We correlated HRCT scores of emphysema with different indices of airflow obstruction.
METHODS:
We performed HRCT of the chest in 59 patients, all smokers or ex-smokers, with stable chronic obstructive pulmonary disease of different severity [GOLD stages I-IV; mean age \ub1 SD 67.8 \ub1 7.3 years; pack/years 51.0 \ub1 34.6; percent predicted forced expiratory volume in 1 s (FEV(1)% predicted) 52.3 \ub1 17.6; post-bronchodilator FEV(1)% predicted 56.5 \ub1 19.1; FEV(1)/forced vital capacity (FVC) ratio 50.8 \ub1 10.2; post-bronchodilator FEV(1)/FVC ratio 51.6 \ub1 11.0; percent diffusion lung capacity for carbon monoxide (DLCO%) 59.2 \ub1 21.1; DLCO/percent alveolar volume (VA%) 54.5 \ub1 18.2; percent residual volume 163.0 \ub1 35.6; percent total lung capacity (TLC%) 113.2 \ub1 15; residual volume/TLC 1.44 \ub1 0.2]. All patients were in stable phase.
RESULTS:
The mean \ub1 SD visual emphysema score in all patients was 25.6 \ub1 25.4%. There was a weak but significant correlation between the percentage of pulmonary emphysema and numbers of pack/years (R = +0.31, p = 0.024). The percentage of emphysema was inversely correlated with the FEV(1)/FVC ratio before and after bronchodilator use (R = -0.44, p = 0.002, and R = -0.39, p = 0.005), DLCO% (R = -0.64, p = 0.0003) and DLCO/VA% (R = -0.68, p < 0.0001). A weak positive correlation was also found with TLC% (R = +0.28, p = 0.048). When patients with documented emphysema were considered separately, the best significant correlation observed was between DLCO/VA% and HRCT scan score (p = 0.007).
CONCLUSIONS:
These data suggest that in patients with stable chronic obstructive pulmonary disease of varying severity, the presence of pulmonary emphysema is best represented by the impaired gas exchange capability of the respiratory system
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