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Zero Order (zero + order)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Nanotemplating of Biodegradable Polymer Membranes for Constant-Rate Drug Delivery

ADVANCED MATERIALS, Issue 21 2010
Daniel A. Bernards
A nanoporous biodegradable polymer (polycaprolactone) is fabricated utilizing a zinc oxide nanotemplate (see figure). Chemical characterization verifies removal of the template, and preliminary tests on the cytotoxicity demonstrate basic biocompatibility. Diffusion of a model small molecule and a protein are shown to be first and zero order, respectively, indicating these nanoporous membranes may be useful for controlled release of protein-based therapeutics. [source]

Design and evaluation of compound metformin/glipizide elementary osmotic pump tablets

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 7 2005
Defang Ouyang
A simple elementary osmotic pump (EOP) system that could deliver metformin hydrochloride (MT) and glipizide (GZ) simultaneously for extended periods of time was developed in order to reduce the problems associated with multidrug therapy of type 2 non-insulin-dependent diabetes mellitus. In general, both highly and poorly water-soluble drugs are not good candidates for elementary osmotic delivery. However, MT is a highly soluble drug with a high dose (500 mg) while GZ is a water-insoluble drug with a low dose (5 mg) so it is a great challenge to pharmacists to provide satisfactory extended release of MT and GZ. In this paper sodium carbonate was used to modulate the solubility of GZ within the core and MT was not only one of the active ingredients but also the osmotic agent. The optimal EOP was found to deliver both drugs at a rate of approximately zero order for up to 10h in pH 6.8, independent of environment media. In-vivo evaluation was performed relative to the equivalent dose of conventional MT tablet and GZ tablet by a cross-study in six Beagle dogs. The EOP had a good sustained effect in comparison with the conventional product. The prototype design of the system could be applied to other combinations of drugs used for cardiovascular diseases, diabetes, etc. [source]

Pseudodifferential operators with compound non-regular symbols

MATHEMATISCHE NACHRICHTEN, Issue 9-10 2007
Yu. I. Karlovich
Abstract Let V (,) denote the Banach algebra of absolutely continuous functions of bounded total variation on ,. We study an algebra ,, of pseudodifferential operators of zero order with compound slowly oscillating V (,)-valued symbols (x, y) , a (x, y, ·) that satisfy a Lipschitz condition with respect to the spatial variables x, y , ,. Sufficient conditions for the boundedness and compactness of pseudodifferential operators with compound symbols on the Lebesgue spaces Lp(,), for p = 2 and 1 < p < ,, are obtained. A Fredholm criterion and an index formula for pseudodifferential operators A , ,, are presented. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Numerical analysis of interferograms for evaluation of tear film build-up time

OPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 3 2009
Dorota H. Szczesna
Abstract The lateral shearing interferometer was applied to the in vivo dynamic investigation of the external surface of the pre-corneal tear film after an eye blink. Sequences of interferograms were recorded at a sampling frequency of 25 Hz. Immediately after every eye blink, a bright pattern was observed under the interference fringes. This disappeared after a short time interval (around 0.5,2 s): smooth interference fringes were then observed, corresponding to the creation of a smooth anterior optical surface over the cornea. The purpose of this study is to describe in detail the kinetics of pre-corneal tear film stability and to propose quantitative measures of the stabilisation process in healthy eyes during the 3 s period after a blink. Two methods of quantitative assessment of the tear film build-up time are presented. The first is based upon the evaluation of the inhomogeneity of the background of the interferogram; the second evaluates the orientation of the structure of the background by the analysis of the zero order of the Fast Fourier Transform (FFT) spectrum. The quasi-vertically oriented bright line patterns observed in interferograms immediately after a blink and the mirror-symmetry of their tilts for right and left eyes indicate that the pattern is related to the wiping movements of the upper eyelids during the eye blink. [source]