Fractal geometry of critical Potts clusters

Numerical simulations on the total mass, the numbers of bonds on the hull, external perimeter, singly connected bonds and gates into large fjords of the Fortuin-Kasteleyn clusters for two-dimensional q-state Potts models at criticality are presented. The data are found consistent with the recently derived corrections-to-scaling theory. However, the approach to the asymptotic region is slow, and the present range of the data does not allow a unique identification of the exact correction exponentsComment: 7 pages, 8 figures, Late

Percolation and spatial correlations in a two-dimensional continuum deposition model

We introduce a two-dimensional continuum deposition model of spatially extended objects, with an effective repulsive contact interaction between them represented by a parameter 0<~q<~1. For q=0, the deposited network is uniformly random, while for q=1 particles are not allowed to overlap. For 0<~q<1, we carry out extensive simulations on fibers, needles, and disks to study the dependence of the percolation threshold on q. We derive expressions for the threshold near q=0 and q=1 and find good qualitative agreement with the simulations. The deposited networks produced by the model display nontrivial density correlations near percolation threshold. These are reflected in the appropriate spatial correlation functions. We study such functions close to q=1 and derive an approximate expression for the pair distribution function.Peer reviewe

Exact and efficient discrete random walk method for time-dependent two-dimensional environments

We present an exact method for speeding up random walk in two-dimensional complicated lattice environments. To this end, we derive the discrete two-dimensional probability distribution function for a diffusing particle starting at the center of a square of linear size s. This is used to propagate random walkers from the center of the square to sites which are nearest neighbors to its perimeter sites, thus saving O(s2) steps in numerical simulations. We discuss in detail how this method can be implemented efficiently. We examine its performance in the diffusion limited aggregation model which produces fractal structures, and in a one-sided step-growth model producing compact, fingerlike structures. We show that in both cases, the square propagator method reduces the computational effort by a factor proportional to the linear system size as compared to standard random walk.Peer reviewe

Productivity of Stump Harvesting for Fuel

The productivity of harvesting stump and root wood was studied in Norway spruce (Picea abies) stands. The objective was to create productivity models (m3/E0h) for stump wood extraction, stump wood forwarding, and site preparation, in addition to identifying work phases and improvement opportunities in the extraction and forwarding chain. Productivity models were based on time studies with professional operators. The independent variables in stump wood extraction were stump diameter (cm) and the number of stumps per hectare. For forwarding, the independent variables were volume of stump wood removed (m3/ha) and forwarding distance (m). When removing 350 stumps per ha with an average diameter of 40 cm, productivity was estimated at 7.9 m3/E0h. Increasing the number of stumps removed from 350 to 800 stumps per ha, increased productivity to 10.8 m3/E0h. Forwarding productivity was 7.8 m3/E0hwithaforwardingdistanceof250mandaload size of 7.0 m3 when removing 60 m3 of stumps per ha

Interface dynamics and kinetic roughening in fractals

We consider the dynamics and kinetic roughening of single-valued interfaces in two-dimensional fractal media. Assuming that the local height difference distribution function of the fronts obeys Levý statistics with a well-defined power-law decay exponent, we derive analytic expressions for the local scaling exponents. We also show that the kinetic roughening of the interfaces displays anomalous scaling and multiscaling in the relevant correlation functions. For invasion percolation models, the exponents can be obtained from the fractal geometry of percolation clusters. Our predictions are in excellent agreement with numerical simulations.Peer reviewe

Porphyromonas gingivalis may interfere with conception in women

In this observational and prospective study, we investigated if microbiological and serological markers of periodontitis associated with conception in 256 non-pregnant women (Mage = 29.2 years; range 19-42 years). Clinical oral and gynecological examinations were performed, major periodontal pathogens in the saliva were detected, and serum and saliva antibodies against major periodontal pathogens were analyzed. The follow-up period for becoming pregnant was 12 months. Porphyromonas gingivalis was significantly (p = 0.032) more frequently detected in the saliva among those who did not become pregnant (8.3%) than among those who became pregnant (2.1%). The median levels of salivary P. gingivalis immunoglobulin A (IgA; p = 0.006) and IgG (p = 0.007) antibodies were higher among those who did not become pregnant compared to those who became pregnant. Hazard ratios (HR) for not becoming pregnant were HR = 3.75 (95% confidence interval [CI] 1.01-13.9; p = 0.048) if the subject was polymerase chain reaction-positive for P. gingivalis with high salivary antibodies against it, and HR = 1.62 (95% CI 1.03-2.54; p = 0.035) if she had high levels of serum P. gingivalis IgA and signs of periodontal infection. P. gingivalis associated with no success in getting pregnant.Peer reviewe

Effects of intensified silviculture on timber production and its economic profitability in boreal Norway spruce and Scots pine stands under changing climatic conditions

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Alueellinen metsähaketase vuonna 2030

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