4,930 research outputs found

    Cutting edges at random in large recursive trees

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    We comment on old and new results related to the destruction of a random recursive tree (RRT), in which its edges are cut one after the other in a uniform random order. In particular, we study the number of steps needed to isolate or disconnect certain distinguished vertices when the size of the tree tends to infinity. New probabilistic explanations are given in terms of the so-called cut-tree and the tree of component sizes, which both encode different aspects of the destruction process. Finally, we establish the connection to Bernoulli bond percolation on large RRT's and present recent results on the cluster sizes in the supercritical regime.Comment: 29 pages, 3 figure

    Non-Uniformity of Pellets Coating, Effect on the Dose Release Profile andHow to Improve the Coating Process by Reducing the Electrostatic Charging of the Pellets

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    The aim of this work was to study the effect of several process parameters used during pellets coating in two wurster fluid beds of different scales on: a) the uniformity of pellets coating, and b) the presence of an initial burst in the release profile caused by the existence of a significant fraction of pellets having a very thin film coating. The pellets used in this work presented high insulating properties. The pellets were coated with extended release films made mainly of ethyl cellulose and it was shown that larger pellets had a thicker coating. The choice of the process parameters had a large effect on the amount of pellets that were subtracted from the coating process due to the buildup of electrostatic charges on the pellets. Using not too high fluidizing air flows, pellets of larger size, a smaller pellets load and humidified air to fluidize the pellets resulted in more uniform coatings and, consequently, in more favorable release profiles that did not present or presented a reduced initial burst release

    Non-Uniformity of Pellets Coating, Effect on the Dose Release Profile andHow to Improve the Coating Process by Reducing the Electrostatic Charging of the Pellets

    Get PDF
    The aim of this work was to study the effect of several process parameters used during pellets coating in two wurster fluid beds of different scales on: a) the uniformity of pellets coating, and b) the presence of an initial burst in the release profile caused by the existence of a significant fraction of pellets having a very thin film coating. The pellets used in this work presented high insulating properties. The pellets were coated with extended release films made mainly of ethyl cellulose and it was shown that larger pellets had a thicker coating. The choice of the process parameters had a large effect on the amount of pellets that were subtracted from the coating process due to the buildup of electrostatic charges on the pellets. Using not too high fluidizing air flows, pellets of larger size, a smaller pellets load and humidified air to fluidize the pellets resulted in more uniform coatings and, consequently, in more favorable release profiles that did not present or presented a reduced initial burst release

    Dipole-Quadrupole Theory of Surface Enhanced Infrared Absorption and Appearance of Forbidden Lines in the SEIRA Spectra of Symmetrical Molecules

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    The paper presents main aspects of the Dipole-Quadrupole theory of Surface Enhanced Infrared Absorption (SEIRA). It is pointed out the possibility of appearance of the lines, caused by totally symmetric vibrations transforming after the unit irreducible representation, which are forbidden in usual infrared absorption spectra in molecules with sufficiently high symmetry. Observation of such lines in the SEIRA spectra of diprotonated and ethylene, adsorbed on and on mordenites is pointed out. The results well agree with our ideas about surface enhanced optical processes, based on the conception of a strong quadrupole light-molecule interaction, which allows us to develop the SERS and SEHRS theories.Comment: 15 pages,3 figures, 1 tabl

    Localization of thioredoxin in the rat brain and functional implications

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    The immunoreactivity for thioredoxin, which catalyzes protein disulfide reductions, has previously been shown to exist in nerve cells and their axons. Here we demonstrate the localization of thioredoxin mRNA as revealed by in situ hybridization in the rat brain. The gene is expressed in nerve cells of a variety of brain regions, for example, the cerebral cortex, the piriform cortex, the medial preoptic area, the CA3/CA4 region of the hippocampal formation, the dentate gyrus, the paraventricular nucleus of the hypothalamus, the arcuate nucleus, the substantia nigra pars compacta, the locus coeruleus, the ependyma of the 4th ventricle, and the epithelial cells of the choroid plexus. This distribution implicates an important function in nerve cell metabolism, especially in regions with high energy demands and indicates a role of the choroid plexus in nerve cell protection from environmental influences. It was found that after mechanical injury induced by partial unilateral hemitransection the thioredoxin mRNA expression is upregulated in the lesioned area and spreads to the cortical hemispheres at the lesioned level. This induction suggests a function of thioredoxin in the regeneration machinery of the brain following mechanical injury and oxidative stress

    Mountain Plants of Northeastern Utah

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    Transient two-phase heat transfer and flow characteristics of liquid hydrogen

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    Single-phase and two-phase flow and forced convection transient boiling heat transfer by liquid and gaseous hydrogen for NERVA reacto

    Dust in the Ionized Medium of the Galaxy: GHRS Measurements of Al III and S III

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    We present interstellar absorption line measurements of the ions S III and Al III towards six stars using archival Goddard High Resolution Spectrograph data. The ions Al III and S III trace heavily depleted and non-depleted elements, respectively, in ionized gas. We use the photoionization code CLOUDY to derive the ionization correction relating N(Al III)/N(S III) to the gas-phase abundance [Al/S]_i in the ionized gas. For spectral types considered here, the corrections are small and independent of the assumed ionization parameter. Using the results of these photoionization models, we find [Al/S]_i = -1.0 in the ionized gas towards three disk stars. These values of [Al/S]_i (=[Al/H]_i) imply that Al-bearing grains are present in the ionized nebulae around these stars. If the WIM of the Galaxy is photoionized by OB stars, our data for two halo stars imply [Al/S]_i = -0.4 to -0.5 in the WIM and thus the presence of dust grains containing Al in this important phase of the ISM. While photoionization appears to be the most likely origin of the ionization for Al III and S III, we cannot rule out confusion from the presence of hot, collisionally ionized gas along two sightlines. We find that [Al/S]_i in the ionized gas along the six sightlines is anti-correlated with the electron density and average sightline neutral density. The degree of grain destruction in the ionized medium of the Galaxy is not much higher than in the warm neutral medium. The existence of grains in the ionized regions studied here has important implications for the thermal balance of these regions. (Abstract Abridged)Comment: 30 pages including 8 embedded tables and 8 embedded figures. Accepted for publication in the Astrophysical Journa
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