Probability-Changing Cluster Algorithm for Potts Models

We propose a new effective cluster algorithm of tuning the critical point automatically, which is an extended version of Swendsen-Wang algorithm. We change the probability of connecting spins of the same type, $p = 1 - e^{- J/ k_BT}$, in the process of the Monte Carlo spin update. Since we approach the canonical ensemble asymptotically, we can use the finite-size scaling analysis for physical quantities near the critical point. Simulating the two-dimensional Potts models to demonstrate the validity of the algorithm, we have obtained the critical temperatures and critical exponents which are consistent with the exact values; the comparison has been made with the invaded cluster algorithm.Comment: 4 pages including 5 eps figures, RevTeX, to appear in Phys. Rev. Let

Coupling of capillary RBC flow failure with neuronal depolarization

RBC (oxygen-carrier) behaviour in the cerebrocortical microvasculature during K^+^-induced cortical spreading depression (CSD) was examined in urethane-anesthetized male Wistar rats (n=10). The movements of FITC-labeled RBCs in single capillaries in the cortical region were traced with a high-speed camera laser scanning confocal fluorescence microscope and analyzed with Matlab domain software, KEIO-IS2, to obtain the velocities of all labeled RBCs appearing in local capillaries during CSD wave propagation. We found that CSD induced periodic decreases in both RBC number and velocity until RBCs halted or disappeared for 3.3 +/- 2.3 s, and then RBC flow was restored. The RBC flow stall was statistically significant (P < 0.05). During capillary flow failure in association with CSD spread, systemic arterial blood pressure remained unchanged. We conclude that RBCs are transiently sieved and stalled in capillaries during neuronal depolarization, and we suggest that this neuro-capillary coupling involves a hemorheological (viscosity-related) mechanism

Depolarization increases cellular light transmission

Application of optical methods to human brain tissue in vivo, e.g., measuring oxyhemoglobin and deoxyhemoglobin concentration changes with near-infrared spectroscopy (NIRS), requires the a priori assumption that background optical properties remain unchanged during measurements1,2. However, fundamental knowledge about light scattering by brain cells per se remains sparse; many factors influence light transmission changes through living brain tissue, bringing into question what is being measured. We have observed slow wave-ring spreads of light transmission changes on the rat cerebral cortex during potassium-induced cortical spreading depression (CSD) and ascribed them to squeezing-out of blood from capillaries by swollen brain cells3,4. However, in rat hippocampal slices, where no blood components were involved, similar light transmission changes were observed during K+-induced CSD and ascribed to cell swelling and dendritic beading5,6,7. Here we show that two-dimensional light scattering changes occur through suspensions of osmotically swollen (depolarized) red blood cells, apparently arising from light scattering changes at the less curved, swollen surface of the steep electrochemical gradient coupled with water activity difference across the plasmic membrane. These optical property changes are likely to be relevant to interpretation of photometry or spectroscopy findings of brain tissue in vivo, where neurons are polarizing and depolarizing during brain function

A Statistical Classification on a Mixture Distribution of Intelligence Quotients and Severe Mental Retardation

Main content of this paper is to classify IQ individuals into two categories of normal and abnormal groups. It is too difficult to divide IQ individuals into two groups of normal IQ group and abnormal group because of sparse number of cases with mental retardation. Therefore, we examined a normality of 1673 IQ individuals, but a significant difference was noted for the IQ data. The lowest three mentally retarded cases of less than or equal to 59 IQ score were excluded, the IQ data then fitted to a normal distribution well. The critical value which minimizes the probability of classification is obtained on the basis on an approximate technique with regard to normality. An approximate probability of misclassification for individuals at random from mixture of two normal populations is 25.5%

Finite-size Scaling of Correlation Ratio and Generalized Scheme for the Probability-Changing Cluster Algorithm

We study the finite-size scaling (FSS) property of the correlation ratio, the ratio of the correlation functions with different distances. It is shown that the correlation ratio is a good estimator to determine the critical point of the second-order transition using the FSS analysis. The correlation ratio is especially useful for the analysis of the Kosterlitz-Thouless (KT) transition. We also present a generalized scheme of the probability-changing cluster algorithm, which has been recently developed by the present authors, based on the FSS property of the correlation ratio. We investigate the two-dimensional quantum XY model of spin 1/2 with this generalized scheme, obtaining the precise estimate of the KT transition temperature with less numerical effort.Comment: 4 pages, RevTeX4, to appear in Phys. Rev. B, Rapid Communication

Interaction of a Relativistic Magnetized Collisionless Shock with a Dense Clump

The interactions between a relativistic magnetized collisionless shock and dense clumps have been expected to play a crucial role on the magnetic field amplification and cosmic-ray acceleration. We investigate this process by two-dimensional Particle-In-Cell (PIC) simulations for the first time, where the clump size is much larger than the gyroradius of downstream particles. We also perform relativistic magnetohydrodynamic (MHD) simulations for the same condition to see the kinetic effects. We find that particles escape from the shocked clump along magnetic field lines in the PIC simulations, so that the vorticity is lower than that in the MHD simulations. Moreover, in both the PIC and MHD simulations, the shocked clump quickly decelerates because of the Lorentz contraction. Owing to the escape and the deceleration, the shocked clump cannot amplify the downstream magnetic field in relativistic collisionless shocks. This large-scale PIC simulation opens a new window to understand large-scale behaviors in collisionless plasma systems

Effect of a Nitric Oxide Donor on Intracellular Cytokine Production in Normal Human Peripheral Lymphocytes

It has been recently suggested that nitric oxide (NO) plays an important role in modulating immune responses including helper T (Th) cell differentiation. To investigate the effect of NO on cytokine production in T cells, we examined in vitro the percentage of interferon (IFN)-γ and interleukin (IL)-4 producing cells by the intracellular cytokine staining method with flow cytometry. The percentage of IFN-γ and IL-4 producing cells reached maximal value 8 h after stimulation by phorbol 12-myristate 13-acetate (PMA) and ionomycin. When an NO donor, sodium nitroprusside (SNP), was co-incubated with PMA and ionomycin for 8 h, nitrite levels increased in a dose dependent manner for SNP (P = 0.007; Friedman test). The percentage of IFN-γ producing cells was diminished in consequence of the increasing doses of SNP (P = 0.002; Friedman test). While the percentage of IL-4 producing cells tended to be diminished by SNP, this difference, however, was statistically not significant (P = 0.062; Friedman test). Therefore, we have suggested that NO might affect Th cell differentiation through inhibition of Th1-cytokine production and might cause a Th2 cell predominant state