Determination of absorption length of CO2 and high power diode laser radiation for ordinary Portland cement and its influence on the depth of melting

The laser beam absorption lengths of CO2 and a high power diode laser (HPDL) radiation for concrete have been determined. By employing Beer-Lambert’s law the absorption lengths for concrete of CO2 and a HPDL radiation were 47022 m and 17715 m respectively. Indeed, this was borne out somewhat from a cross-sectional analysis of the melt region produced by both lasers which showed melting occurred to a greater depth when the CO2 laser was used

ac hopping admittance in spinel manganate negative temperature coefficient thermistor electroceramics

In this work, the ac admittance of a thick film nickel manganate spinel negative temperature coefficient thermistor ceramic system containing a glass phase is investigated. The dominating relaxation process is a grain boundary (GB) effect and has been investigated comprehensively. We present double-logarithmic plots of the specific admittance σ' vs ω and (σ'/σ_(dc)) vs ω, and specific impedance z vs −z"/ω and [(ρ_(dc)/z')−1] vs ω, in order to characterize GB charge transport. Using the complex admittance notation (σ*), an unusually low Jonscher exponent of frequency ~0.007 was obtained and the GB relaxation displayed close to ideal behavior

The van Hove distribution function for Brownian hard spheres: dynamical test particle theory and computer simulations for bulk dynamics

We describe a test particle approach based on dynamical density functional theory (DDFT) for studying the correlated time evolution of the particles that constitute a fluid. Our theory provides a means of calculating the van Hove distribution function by treating its self and distinct parts as the two components of a binary fluid mixture, with the `self' component having only one particle, the `distinct' component consisting of all the other particles, and using DDFT to calculate the time evolution of the density profiles for the two components. We apply this approach to a bulk fluid of Brownian hard spheres and compare to results for the van Hove function and the intermediate scattering function from Brownian dynamics computer simulations. We find good agreement at low and intermediate densities using the very simple Ramakrishnan-Yussouff [Phys. Rev. B 19, 2775 (1979)] approximation for the excess free energy functional. Since the DDFT is based on the equilibrium Helmholtz free energy functional, we can probe a free energy landscape that underlies the dynamics. Within the mean-field approximation we find that as the particle density increases, this landscape develops a minimum, while an exact treatment of a model confined situation shows that for an ergodic fluid this landscape should be monotonic. We discuss possible implications for slow, glassy and arrested dynamics at high densities.Comment: Submitted to Journal of Chemical Physic

Dynamics in inhomogeneous liquids and glasses via the test particle limit

We show that one may view the self and the distinct part of the van Hove dynamic correlation function of a simple fluid as the one-body density distributions of a binary mixture that evolve in time according to dynamical density functional theory. For a test case of soft core Brownian particles the theory yields results for the van Hove function that agree quantitatively with those of our Brownian dynamics computer simulations. At sufficiently high densities the free energy landscape underlying the dynamics exhibits a barrier as a function of the mean particle displacement, shedding new light on the nature of glass formation. For hard spheres confined between parallel planar walls the barrier height oscillates in-phase with the local density, implying that the mobility is maximal between layers, which should be experimentally observable in confined colloidal dispersions.Comment: 4 pages, 3 figure

Epidemiology of HPV in HIV-Positive and HIV-Negative Fertile Women in Cameroon, West Africa

Background. HPV types vary by country and HIV status. There are no data on the prevalent HPV genotypes from Cameroon. Methods. We conducted a cross-sectional, observational study on 65 Cameroonian women. Samples were sent for HPV genotyping and Thin Prep analyses. Results. 41 out of 61 samples tested (67.2%) had HPV subtypes detected. The most common high risk types encountered were: 45 (24.6%) and 58 (21.5%). HIV-positive women were more likely to test positive for any HPV (P = .014), have more than one HPV subtype (P = .003), and to test positive for the high risk subtypes (P = .007). Of those with high risk HPV, HIV-positive women were more likely to have Thin Prep abnormalities than HIV-negative women (P = .013). Conclusions. Oncogenic HPV subtypes 45 and 58 were more prevalent than those subtypes carried in the quadrivalent vaccine. Further studies are needed to assess whether the current vaccine will be effective in this region

Boundary Homogenization and Capture Time Distributions of Semipermeable Membranes with Periodic Patterns of Reactive Sites

We consider the capture dynamics of a particle undergoing a random walk in a half- space bounded by a plane with a periodic pattern of absorbing pores. In particular, we numerically measure and asymptotically characterize the distribution of capture times. Numerically we develop a kinetic Monte Carlo (KMC) method that exploits exact solutions to create an efficient particle- based simulation of the capture time that deals with the infinite half-space exactly and has a run time that is independent of how far from the pores one begins. Past researchers have proposed homogenizing the surface boundary conditions, replacing the reflecting (Neumann) and absorbing (Dirichlet) boundary conditions with a mixed (Robin) boundary condition. We extend previous work to asymptotically determine the leakage parameter for the mixed boundary condition for arbitrary periodic pore configurations in the dilute fraction limit. In this asymptotic limit, we pose and solve an optimization problem for the Bravais lattice which maximizes the capture rate of the absorbing pores, finding the hexagonal lattice to be the global maximum

Testing forecast rationality for measures of central tendency

Rational respondents to economic surveys may report as a point forecast any measure of the central tendency of their (possibly latent) predictive distribution, for example the mean, median, mode, or any convex combination thereof. We propose tests of forecast rationality when the measure of central tendency used by the respondent is unknown. We overcome an identification problem that arises when the measures of central tendency are equal or in a local neighborhood of each other, as is the case for (exactly or nearly) symmetric distributions. As a building block, we also present novel tests for the rationality of mode forecasts. We apply our tests to survey forecasts of individual income, Greenbook forecasts of U.S. GDP, and random walk forecasts for exchange rates. We find that the Greenbook and random walk forecasts are best rationalized as mean, or near-meanforecasts, while the income survey forecasts are best rationalized as mode forecasts