69,177 research outputs found

    A two-dimensional mathematical model of non-linear dual-sorption

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    Background: Certain drugs, for example scopolamine and timolol, show non-linear kinetic behavior during permeation process. This non-linear kinetic behavior is due to two mechanisms; the first mechanism being a simple dissolution producing mobile and freely diffusible molecules and the second being an adsorption process producing non-mobile molecules that do not participate in the diffusion process. When such a drug is applied on the skin surface, the concentration of the drug accumulated in the skin and the amount of the drug eliminated into the blood vessel depend on the value of a parameter, C, the donor concentration. The present paper studies the effect of the parameter value, C, when the region of the contact of the skin with drug, is a line segment on the skin surface. To confirm that dual-sorption process gives an explanation to non-linear kinetic behavior, the characteristic features that are used in one-dimensional models are (1) prolongation of half-life if the plot of flux versus time are straight lines soon after the vehicle removal, (2) the decrease in half-life with increase in donor concentration. This paper introduces another feature as a characteristic to confirm that dual-sorption model gives an explanation to the non-linear kinetic behavior of the drug. This new feature is "the prolongation of half-life is not a necessary feature if the plots of drug flux versus time is a non-linear curve, soon after the vehicle removal"

    Aspects of F-Theory GUTs

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    The basic tools for model building in F-theory are reviewed and applied to the construction of SU(5) models. The flux mechanism for gauge symmetry breaking and doublet triplet splitting is analysed. A short account for the gauge coupling unification and the role of flux and Kaluza-Klein thresholds is also given.Comment: 37 pages. Based on Talk presented at Corfu 2011 Workshop "Fields and Strings: Theory - Cosmology - Phenomenology. September 14 - 18, 2011". (Prepared for the proceedings

    The Crisis over Kuwait, August 1990 - February 1991

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    The folic acid antagonists and their use is the treatment of acute leukemia

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    Thesis (M.D.)--Boston Universit

    D0-branes with non-zero angular momentum

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    In my talk I shall consider the mechanism of self-expansion of a system of N D0-branes into high-dimensional non-commutative world-volume investigated by Harmark and Savvidy. Here D2-brane is formed due to the internal angular momentum of D0-brane system. The idea is that attractive force of tension should be cancelled by the centrifugal motion preventing a D-brane system from collapse to a lower-dimensional one. I shall also present a new extended solution where a total of 9 space dimensions is used to embed a D0-brane system. In the last section, by performing linear analysis, the stability of the system is demonstrated.Comment: 10 pages, Latex, aipxfm.sty, fix2col.sty; Based on talk given at 10th Tohwa International Symposium on String Theory, Tohwa Univ., Fukuoka, (Japan), July 3-7, 200

    Extending the Electron Spin Coherence Time of Atomic Hydrogen by Dynamical Decoupling

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    We study the electron spin decoherence of encapsulated atomic hydrogen in octasilsesquioxane cages induced by the 1H and 29Si nuclear spin bath. By applying the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence we significantly suppress the low-frequency noise due to nuclear spin flip-flops up to the point where a maximum T2 = 56 us is observed. Moreover, dynamical decoupling with the CPMG sequence reveals the existence of two sources of high-frequency noise: first, a fluctuating magnetic field with the proton Larmor frequency, equivalent to classical magnetic field noise imposed by the 1H nuclear spins of the cage organic substituents, and second, decoherence due to entanglement between the electron and the inner 29Si nuclear spin of the cage

    The Federal Rules of Civil Procedure in the Context of Transnational Law

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    The development of exceptions in the Rules of Civil Procedure and federal statutes that apply only to litigants outside the US is explored. The Rules should not make exceptions on a blanket basis, as some proposals indicate
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