Traveling length and minimal traveling time for flow through percolation networks with long-range spatial correlations

We study the distributions of traveling length l and minimal traveling time t through two-dimensional percolation porous media characterized by long-range spatial correlations. We model the dynamics of fluid displacement by the convective movement of tracer particles driven by a pressure difference between two fixed sites (''wells'') separated by Euclidean distance r. For strongly correlated pore networks at criticality, we find that the probability distribution functions P(l) and P(t) follow the same scaling Ansatz originally proposed for the uncorrelated case, but with quite different scaling exponents. We relate these changes in dynamical behavior to the main morphological difference between correlated and uncorrelated clusters, namely, the compactness of their backbones. Our simulations reveal that the dynamical scaling exponents for correlated geometries take values intermediate between the uncorrelated and homogeneous limiting cases

Reduced salivary flow and colonization by mutans streptococci in children with Down syndrome

OBJECTIVES: Although individuals with Down syndrome have considerable oral disease, the prevalence of dental caries in this group is low. The present study aimed to compare known risk factors for dental caries development in children with Down syndrome and a matched population (siblings). In both populations, the number of acidogenic microorganisms, such as mutans streptococci, lactobacilli and Candida species, and the paraffin-stimulated pH, flow rate and IgA concentration in whole saliva were evaluated and compared. METHOD: Saliva was collected, and the caries index was evaluated in 45 sibling pairs aged between 6 and 18 years old. The salivary IgA concentration was determined by immunoturbidimetry. Salivary mutans streptococci, lactobacilli and Candida species were quantified on mitis salivarius agar containing bacitracin and 20% sucrose, rogosa agar supplemented with glacial acetic acid and sabouraud agar supplemented with chloramphenicol, respectively. RESULTS: Down syndrome children had a higher caries-free rate (p<0.05) and lower salivary mutans streptococci counts (p<0.03) compared to their siblings. Similar numbers of lactobacilli and Candida species were found in both groups. Salivary flow rates were 36% lower in Down syndrome children compared to their siblings (p<0.05). The salivary pH did not differ between Down syndrome children and controls. The Down syndrome children had an IgA secretion rate 29% lower than that of their siblings, but this difference was not statistically significant. CONCLUSIONS: In conclusion, the lower number of mutans streptococci in the saliva may be one of the factors contributing to the lower caries rate observed in Down syndrome children, despite evidence of hyposalivation

On Aharonov-Casher bound states

In this work bound states for the Aharonov-Casher problem are considered. According to Hagen's work on the exact equivalence between spin-1/2 Aharonov-Bohm and Aharonov-Casher effects, is known that the $\boldsymbol{\nabla}\cdot\mathbf{E}$ term cannot be neglected in the Hamiltonian if the spin of particle is considered. This term leads to the existence of a singular potential at the origin. By modeling the problem by boundary conditions at the origin which arises by the self-adjoint extension of the Hamiltonian, we derive for the first time an expression for the bound state energy of the Aharonov-Casher problem. As an application, we consider the Aharonov-Casher plus a two-dimensional harmonic oscillator. We derive the expression for the harmonic oscillator energies and compare it with the expression obtained in the case without singularity. At the end, an approach for determination of the self-adjoint extension parameter is given. In our approach, the parameter is obtained essentially in terms of physics of the problem.Comment: 11 pages, matches published versio

Future environmental and agricultural impacts of Brazil's Forest Code

The role of improving the enforcement of Brazil's Forest Code in reducing deforestation in the Amazon has been highlighted in many studies. However, in a context of strong political pressure for loosening environmental protections, the future impacts of a nationwide implementation of the Forest Code on both environment and agriculture remain poorly understood. Here, we present a spatially explicit assessment of Brazil's 2012 Forest Code through the year 2050; specifically, we use a partial equilibrium economic model that provides a globally consistent national modeling framework with detailed representation of the agricultural sector and spatially explicit land-use change. We test for the combined or isolated impacts of the different measures of the Forest Code, including deforestation control and obligatory forest restoration with or without environmental reserve quotas. Our results show that, if rigorously enforced, the Forest Code could prevent a net loss of 53.4 million hectares (Mha) of forest and native vegetation by 2050, 43.1 Mha (81%) of which are in the Amazon alone. The control of illegal deforestation promotes the largest environmental benefits, but the obligatory restoration of illegally deforested areas creates 12.9 Mha of new forested area. Environmental reserve quotas further protect 5.8 Mha of undisturbed natural vegetation. Compared to a scenario without the Forest Code, by 2050, cropland area is only reduced by 4% and the cattle herd by 8%. Our results show that compliance with the Forest Code requires an increase in cattle productivity of 56% over four decades, with a combination of a higher use of supplements and an adoption of semi-intensive pasture management. We estimate that the enforcement of the Forest Code could contribute up to 1.03 PgCO&lt;sub&gt;2&lt;/sub&gt;e to the ambitious GHG emissions reduction target set by Brazil for 2030

Radiative falloff of a scalar field in a weakly curved spacetime without symmetries

We consider a massless scalar field propagating in a weakly curved spacetime whose metric is a solution to the linearized Einstein field equations. The spacetime is assumed to be stationary and asymptotically flat, but no other symmetries are imposed -- the spacetime can rotate and deviate strongly from spherical symmetry. We prove that the late-time behavior of the scalar field is identical to what it would be in a spherically-symmetric spacetime: it decays in time according to an inverse power-law, with a power determined by the angular profile of the initial wave packet (Price falloff theorem). The field's late-time dynamics is insensitive to the nonspherical aspects of the metric, and it is governed entirely by the spacetime's total gravitational mass; other multipole moments, and in particular the spacetime's total angular momentum, do not enter in the description of the field's late-time behavior. This extended formulation of Price's falloff theorem appears to be at odds with previous studies of radiative decay in the spacetime of a Kerr black hole. We show, however, that the contradiction is only apparent, and that it is largely an artifact of the Boyer-Lindquist coordinates adopted in these studies.Comment: 17 pages, RevTeX

Application Of The Hsu Model To Soybean Grain Hydration [aplicação Do Modelo De Hsu à Hidratação De Grãos De Soja]

A comparative analysis of the theoretical-experimental study, developed by Hsu on the hydration of Amsoy 71 soybean grain, was performed through several soaking experiments using CD 202 soybean at 10, 20, 30, 40, and 50 °C, measuring moisture content over time. The results showed that CD 202 soybean equilibrium moisture content, Xeq, does not depend on temperature and is 21% higher than that found by Hsu, suggesting that soybean cultivar exerts great influence on Xeq. The Hsu model was numerically solved and its parameters were adjusted by the least squares method, with maximum deviations of +/- 10% relative to the experimental values. The limiting step in the mass transfer process during hydration corresponds to water diffusion inside the grain, leading to radial moisture gradients that decrease over time and with an increase in temperature. Regardless of the soybean cultivar, diffusivity increases as temperature or moisture content increases. However, the values of this transport property for Amsoy 71 were superior to those of CD 202, very close at the beginning of hydration at 20 °C and almost three times higher at the end of hydration at 50 °C.301Adeyemi, I.A., Dry-milling of sorghum for ogi manufacture (1983) Journal of Cereal Science, 1 (3), pp. 221-227Ahromrit, A., Ledward, D.A., Niranjan, K., High pressure induced water uptake characteristics of Thai glutinous rice (2006) Journal of Food Engineering, 72 (3), pp. 225-233Barrozo, M.A.S., Calado, V.M.A., Calçada, L.A., Secagem de soja em leito deslizante e recirculação pneumática: Influência da umidificação artificial (1991) ENCONTRO SOBRE ESCOAMENTO EM MEIOS POROSOS, 1, pp. 327-337. , Campinas. Anais... São Paulo: UNICAMP, 1991Beckert, O.P., Miguel, M.H., Marcos Filho, J., Absorção de água e potencial fisiológico em sementes de soja de diferentes tamanhos (2000) Scientia Agrícola, 57 (4), pp. 671-675Calado, V.M.A., (1993) Modelagem E Simulação De Secadores Em Leitos Fixo E Deslizante, , Tese (Doutorado em Engenharia Química) - Universidade Federal doRio de Janeiro - UFRJ, Rio de JaneiroChopra, R., Prasad, D.N., Standardization of soaking conditions for soybean seeds/cotyledons for improved quality of soymilk (1994) Indian Journal of Animal Sciences, 64 (4), pp. 405-410Ciabotti, S., Características sensoriais e físicas de extratos e tofus de soja comum processada termicamente e livre de lipoxigenase (2007) Ciência E Tecnologia De Alimentos, 27 (3), pp. 643-648Coutinho, M.R., Modelagem e validação da hidratação de grãos de soja (2005) Ciência E Tecnologia De Alimentos, 25 (3), pp. 603-610Coutinho, M.R., Novo modelo de parâmetros concentrados aplicado à hidratação de grãos (2007) Ciência E Tecnologia De Alimentos, 27 (3), pp. 451-455Crank, J., (1975) The Mathematics of Diffusion, , 2 ed. London: Oxford University PressEngels, C., Modelling water diffusion during long-grain rice soaking (1986) Journal of Food Engineering, 5 (1), pp. 55-73Hsu, K.H., A diffusion model with a concentration-dependent diffusion coefficient for describing water movement in legumes during soaking (1983) Journal of Food Science, 48 (2), pp. 618-622+645Hsu, K.H., Effect of temperature on water diffusion in soybean (1983) Journal of Food Science, 48 (4), pp. 1364-1365INSTITUTO ADOLFO LUTZ - IAL. Normas analíticas do Instituto Adolfo Lutz. 3 ed. São Paulo, 1985. (v. 1)Klamczynska, B., Czuchajowska, Z., Baik, B., Composition, soaking, cooking properties and thermal characteristics of starch of chickpeas, wrinkled peas and smooth peas (2001) International Journal of Food Science and Technology, 36 (5), pp. 563-572Lo, W.Y.L., Soaking soybeans before extraction as it affects chemical composition and yield of soymilk (1968) Food Technology, 22 (9), pp. 1188-1190Long, F.A., Richman, D., Concentration gradients for diffusion of vapor in glassy polymers and their relation to time dependent diffusion phenomena (1960) Journal of The American Chemical Society, 82 (3), pp. 513-519Nelson, A.I., Steinberg, M.P., Wei, L.S., Illinois process for preparation of soymilk (1976) Journal of Food Science, 41 (1), pp. 57-61Pan, Z., Tangratanavalee, W., Characteristics of soybeans as affected by soaking conditions (2003) Lebensmittel-Wissenschaft Und-Technologie, 36 (1), pp. 143-151Peleg, M., An empirical model for the description of moisture sorption curves (1988) Journal of Food Science, 53 (4), pp. 1216-1219Singh, B.P.N., Kulshrestha, S.P., Kinetics of water sorption by soybean and pigeonpea grains (1987) Journal of Food Science, 52 (6), pp. 1538-1544Sopade, P.A., Obekpa, J.A., Modelling water absorption in soybean, cowpea and peanuts at three temperatures using Peleg's equation (1990) Journal of Food Science, 55 (4), pp. 1084-1087Wang, H.L., Hydration of whole soybeans affects solids losses and cooking quality (1979) Journal of Food Science, 44 (5), pp. 1510-151

Circular orbits of corotating binary black holes: comparison between analytical and numerical results

We compare recent numerical results, obtained within a ``helical Killing vector'' (HKV) approach, on circular orbits of corotating binary black holes to the analytical predictions made by the effective one body (EOB) method (which has been recently extended to the case of spinning bodies). On the scale of the differences between the results obtained by different numerical methods, we find good agreement between numerical data and analytical predictions for several invariant functions describing the dynamical properties of circular orbits. This agreement is robust against the post-Newtonian accuracy used for the analytical estimates, as well as under choices of resummation method for the EOB ``effective potential'', and gets better as one uses a higher post-Newtonian accuracy. These findings open the way to a significant ``merging'' of analytical and numerical methods, i.e. to matching an EOB-based analytical description of the (early and late) inspiral, up to the beginning of the plunge, to a numerical description of the plunge and merger. We illustrate also the ``flexibility'' of the EOB approach, i.e. the possibility of determining some ``best fit'' values for the analytical parameters by comparison with numerical data.Comment: Minor revisions, accepted for publication in Phys. Rev. D, 19 pages, 6 figure