Impurity Effects on Quantum Depinning of Commensurate Charge Density Waves

We investigate quantum depinning of the one-dimensional (1D) commensurate charge-density wave (CDW) in the presence of one impurity theoretically. Quantum tunneling rate below but close to the threshold field is calculated at absolute zero temperature by use of the phase Hamiltonian within the WKB approximation. We show that the impurity can induce localized fluctuation and enhance the quantum depinning. The electric field dependence of the tunneling rate in the presence of the impurity is different from that in its absence.Comment: 14 pages with 13 figures. Submitted to J. Phys. Soc. Jp

Latitudinal variation of stochastic properties of the geomagnetic field

We explore the stochastic fractal qualities of the geomagnetic field from 210 mm ground-based magnetometers during quiet and active magnetospheric conditions. We search through 10 yr of these data to find events that qualify as quiet intervals, defined by Kp ≤ 1 for 1440 consecutive minutes. Similarly, active intervals require Kp ≥ 4 for 1440 consecutive minutes. The total for quiet intervals is ~ 4.3 x 10⁶ and 2 x 10⁸ min for active data points. With this large number of data we characterize changes in the nonlinear statistics of the geomagnetic field via measurements of a fractal scaling. A clear difference in statistical behavior during quiet and active intervals is implied through analysis of the scaling exponents; active intervals generally have larger values of scaling exponents. This suggests that although 210 mm data appear monofractal on shorter timescales, the scaling changes, with overall variability are more likely described as a multifractional Brownian motion. We also find that low latitudes have scaling exponents that are consistently larger than for high latitudes

Local Inhomogeneity Effects on Nucleation Process in a High External Bias

Quantum nucleation processes in the presence of local moderate inhomogeneities are studied theoretically at high biases. The quantum nucleation rate Gamma is calculated for one-dimensional systems in a form Gamma = A e^(-B/hbar) by using the `bounce' method. The bias-dependence of the exponent B is shown to be changed by inhomogeneities. This change is explained by the reduction of the effective spatial dimension of the system. By studying the system-size dependence of the prefactor A, the condition for the appearance of inhomogeneity effects is evaluated. Nucleation rates in thermal activation regimes are also calculated, and compared with quantum tunneling regimes. For higher-dimensional systems, it is shown that the local approximation of inhomogeneity does not hold, and that spatial profiles of inhomogeneity become important.Comment: 10 pages, 6 figure

Using the Guttman Scale to Define and Estimate Measurement Error in Items over Time: The Case of Cognitive Decline and the Meaning of “Points Lost”

We used a Guttman model to represent responses to test items over time as an approximation of what is often referred to as “points lost” in studies of cognitive decline or interventions. To capture this meaning of “point loss”, over four successive assessments, we assumed that once an item is incorrect, it cannot be correct at a later visit. If the loss of a point represents actual decline, then failure of an item to fit the Guttman model over time can be considered measurement error. This representation and definition of measurement error also permits testing the hypotheses that measurement error is constant for items in a test, and that error is independent of “true score”, which are two key consequences of the definition of “measurement error” –and thereby, reliability- under Classical Test Theory. We tested the hypotheses by fitting our model to, and comparing our results from, four consecutive annual evaluations in three groups of elderly persons: a) cognitively normal (NC, N = 149); b) diagnosed with possible or probable AD (N = 78); and c) cognitively normal initially and a later diagnosis of AD (converters, N = 133). Of 16 items that converged, error-free measurement of “cognitive loss” was observed for 10 items in NC, eight in converters, and two in AD. We found that measurement error, as we defined it, was inconsistent over time and across cognitive functioning levels, violating the theory underlying reliability and other psychometric characteristics, and key regression assumptions

Effect of Probiotic and Propolis in the EPS of Root Canal Bacteria Biofilm

Objective: This study aimed to evaluate the effects of Apis trigona ethanolic propolis and probiotic bacteria Lactobacillus acidophilus on the nucleic acid concentration in the extracellular polymeric substances (EPS) derived from biofilm of root canal bacteria. Materials and Methods: Clinical bacteria of the root canal were cultured with ethanolic extract of propolis (EEP; 10 or 0.1%) and L. acidophilus. After the formation of biofilm was observed in the monolayer bacterial culture under several conditions, the enzymatic treatment and nucleic acid quantification were sequentially performed. Statistical Analysis: Independent t-test and Mann–Whitney were performed following data normality to analyze the significant differences of the treatment effect on the nucleic acid concentration in EPS from the isolated biofilm. Results: The results showed that the nucleic acid concentration in EPS biofilm were not increased by coculture with L. acidophilus as probiotics. However, the treatment with 10% EEP could significantly increase nucleic acid concentration. Conclusion: This study suggested that the biosurfactants from probiotic bacteria L. acidophilus might be a promising candidate for endodontic treatment, arguably better than EEP in inhibiting biofilm maturation and complexity