To examine the effect of pore shape on freezing and melting temperatures of water, we measured X-ray diffraction patterns from water confined in four kinds of ordered mesoporous silicas with thin carbon films on the pore wall and three kinds of the inverse carbon replicas during freezing and melting processes. The melting temperature of the pore ice revealed a good correlation with the capillary condensation pressure of nitrogen at 77 K, whereas the freezing temperature of the pore water did not. This indicates that the experimental melting point represents an equilibrium solid-liquid phase transition temperature, whereas the experimental freezing point is controlled by a kinetic factor. The curvature effect of the solid-liquid interface adjacent to the pore wall did not appreciably affect the melting behavior of the pore ice. The melting point depression of the pore ice revealed an almost linear relationship with ln(p 0 /p) of the capillary condensation pressure of nitrogen at 77 K for various pores of different sizes and shapes. This strongly suggests that the reciprocal of ln(p 0 /p) for capillary condensation of nitrogen at 77 K gives a good measure of pore size, irrespective of the pore shapes, and the melting-point depression of the pore ice is almost proportional to the surface-to-volume ratio (S/V) of the pores confining it.
AbstractThe aim of this study was to determine parameters for estimating the internal exposure of all organs in mouse experiments from the radioactivity concentration in organs. The estimation of internal exposure rate conversion coefficients and absorbed fractions for 137Cs, 134Cs and 90Sr by the Particle and Heavy Ion Transport code System (PHITS) with a voxel-based mouse phantom is presented. The geometry of the voxel phantom is constructed from computer tomography images of a mouse 9 cm in length weighing 23.9 g. The voxel-based mouse phantom has the following organs: brain, skull, heart, lungs, liver, stomach, spleen, kidneys, bladder, testis and tissue (tissue and other organs). Gamma- and beta-rays from 137Cs, 134Cs and 90Sr sources in each source organ are generated and scored for every target organ. The internal exposure rate conversion coefficients and absorbed fractions are calculated from deposition energies in each target organ from each source organ and are used to generate an internal exposure rate conversion coefficient matrix and an absorbed fraction matrix. The absorbed fractions of beta-rays in the source organs are roughly 0.5–0.8 for 137Cs and 134Cs, and the absorbed fractions of gamma-rays are <0.04 for 137Cs and <0.03 for 134Cs. The internal exposure rate conversion coefficient matrix is defined using the absorbed fractions. The calculated internal exposure rate coefficient matrix is tested under a uniform radioactivity concentration of 1 Bq/kg for 137Cs, 134Cs and 90Sr. The estimated internal exposure rates in the mouse whole body for 137Cs, 134Cs and 90Sr are 3.28 × 10−3, 2.55 × 10−3 and 1.20 × 10−2 μGy/d, respectively. These values are very similar to those for an ellipsoid frog (31.4 g) and an ellipsoid crab egg mass (12.6 g) reported in ICRP Publication 108.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.