810 research outputs found
J-holomorphic curves in a nef class
Taubes established fundamental properties of holomorphic subvarieties in
dimension 4 in \cite{T1}. In this paper, we further investigate properties of
reducible holomorphic subvarieties. We offer an upper bound of the total
genus of a subvariety when the class of the subvariety is nef. For a
spherical class, it has particularly strong consequences. It is shown that, for
any tamed , each irreducible component is a smooth rational curve. We also
completely classify configurations of maximal dimension. To prove these results
we treat subvarieties as weighted graphs and introduce several combinatorial
moves.Comment: 30 pages. v2 Section 4.3 revised; minor changes elsewhere. v3
mistakes correcte
The Structure of Turbulence in Pulsatile Flow over Urban Canopies
The transport of energy, mass, and momentum in the atmospheric boundary layer
(ABL) is regulated by coherent structures. Although past studies have primarily
focused on stationary ABL flows, the majority of real-world ABL flows are
non-stationary, and a thorough examination of coherent structures under such
conditions is lacking. To fill this gap, this study examines the topological
changes in ABL turbulence induced by non-stationarity and their effects on
momentum transport. Results from a large-eddy simulation of pulsatile open
channel flow over an array of surface-mounted cuboids are examined with a focus
on the inertial sublayer, and contrasted to those from a corresponding constant
pressure gradient case. The analysis reveals that flow pulsation primarily
affects the ejection-sweep pattern. Inspection of the instantaneous turbulence
structures, two-point autocorrelations, and conditionally-averaged flow fields
shows that such a pattern is primarily influenced by the phase-dependent shear
rate. From a turbulence structure perspective, this influence is attributed to
the changes in the geometry of hairpin vortices. An increase (decrease) in the
shear rate intensifies (relaxes) the hairpin vortices, leading to an increase
(decrease) in the frequency of ejections and an amplification (reduction) of
their percentage contribution to the total momentum flux. Moreover, the size of
the hairpin vortex packets changes according to the hairpin vortices comprising
them, while the packet inclination remains unaltered during the pulsatile
cycle. Findings underscore the important impact of non-stationarity on the
structure of ABL turbulence and associated mechanisms supporting momentum
transport
A logistic regression model for microalbuminuria prediction in overweight male population
Background: Obesity promotes progression to microalbuminuria and increases the risk of chronic kidney disease. Current protocols of screening microalbuminuria are not recommended for the overweight or obese.

Design and Methods: A cross-sectional study was conducted. The relationship between metabolic risk factors and microalbuminuria was investigated. A regression model based on metabolic risk factors was developed and evaluated for predicting microalbuminuria in the overweight or obese.

Results: The prevalence of MA reached up to 17.6% in Chinese overweight men. Obesity, hypertension, hyperglycemia and hyperuricemia were the important risk factors for microalbuminuria in the overweight. The area under ROC curves of the regression model based on the risk factors was 0.82 in predicting microalbuminuria, meanwhile, a decision threshold of 0.2 was found for predicting microalbuminuria with a sensitivity of 67.4% and specificity of 79.0%, and a global predictive value of 75.7%. A decision threshold of 0.1 was chosen for screening microalbuminuria with a sensitivity of 90.0% and specificity of 56.5%, and a global predictive value of 61.7%.

Conclusions: The prediction model was an effective tool for screening microalbuminuria by using routine data among overweight populations
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