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Useful Properties (useful + property)
Selected AbstractsBarycentric Coordinates on SurfacesCOMPUTER GRAPHICS FORUM, Issue 5 2010Raif M. Rustamov This paper introduces a method for defining and efficiently computing barycentric coordinates with respect to polygons on general surfaces. Our construction is geared towards injective polygons (polygons that can be enclosed in a metric ball of an appropriate size) and is based on replacing the linear precision property of planar coordinates by a requirement in terms of center of mass, and generalizing this requirement to the surface setting. We show that the resulting surface barycentric coordinates can be computed using planar barycentric coordinates with respect to a polygon in the tangent plane. We prove theoretically that the surface coordinates properly generalize the planar coordinates and carry some of their useful properties such as unique reconstruction of a point given its coordinates, uniqueness for triangles, edge linearity, similarity invariance, and smoothness; in addition, these coordinates are insensitive to isometric deformations and can be used to reconstruct isometries. We show empirically that surface coordinates are shape-aware with consistent gross behavior across different surfaces, are well-behaved for different polygon types/locations on variety of surface forms, and that they are fast to compute. Finally, we demonstrate effectiveness of surface coordinates for interpolation, decal mapping, and correspondence refinement. [source] Rapid and easy semi-quantitative evaluation method for diacylglycerol and inositol-1,4,5-trisphosphate generation in orexin receptor signallingACTA PHYSIOLOGICA, Issue 3 2010M. E. Ekholm Abstract Aim:, Fluorescent protein-based indicators have enabled measurement of intracellular signals previously nearly inaccessible for studies. However, indicators showing intracellular translocation upon response suffer from serious limitations, especially the very time-consuming data collection. We therefore set out in this study to evaluate whether fixing and counting cells showing translocation could mend this issue. Methods:, Altogether three different genetically encoded indicators for diacylglycerol and inositol-1,4,5-trisphosphate were transiently expressed in Chinese hamster ovary cells stably expressing human OX1 orexin receptors. Upon stimulation with orexin-A, the cells were fixed with six different protocols. Results:, Different protocols showed clear differences in their ability to preserve the indicator's localization (i.e. translocation after stimulus) and its fluorescence, and the best results for each indicator were obtained with a different protocol. The concentration,response data obtained with cell counting are mostly comparable to the real-time translocation and biochemical data. Conclusion:, The counting method, as used here, works at single time point and looses the single-cell-quantitative aspect. However, it also has some useful properties. First, it easily allows processing of a 100- to 1000-fold higher cell numbers than real-time imaging producing statistically consistent population-quantitative data much faster. Secondly, it does not require expensive real-time imaging equipment. Fluorescence in fixed cells can also be quantitated, though this analysis would be more time-consuming than cell counting. Thirdly, in addition to the quantitative data collection, the method could be applied for identifying responsive cells. This might be very useful in identification of e.g. orexin-responding neurones in a large population of non-responsive cells in primary cultures. [source] Paraxial ray methods for anisotropic inhomogeneous mediaGEOPHYSICAL PROSPECTING, Issue 1 2007Tijmen Jan Moser ABSTRACT A new formalism of surface-to-surface paraxial matrices allows a very general and flexible formulation of the paraxial ray theory, equally valid in anisotropic and isotropic inhomogeneous layered media. The formalism is based on conventional dynamic ray tracing in Cartesian coordinates along a reference ray. At any user-selected pair of points of the reference ray, a pair of surfaces may be defined. These surfaces may be arbitrarily curved and oriented, and may represent structural interfaces, data recording surfaces, or merely formal surfaces. A newly obtained factorization of the interface propagator matrix allows to transform the conventional 6 × 6 propagator matrix in Cartesian coordinates into a 6 × 6 surface-to-surface paraxial matrix. This matrix defines the transformation of paraxial ray quantities from one surface to another. The redundant non-eikonal and ray-tangent solutions of the dynamic ray-tracing system in Cartesian coordinates can be easily eliminated from the 6 × 6 surface-to-surface paraxial matrix, and it can be reduced to 4 × 4 form. Both the 6 × 6 and 4 × 4 surface-to-surface paraxial matrices satisfy useful properties, particularly the symplecticity. In their 4 × 4 reduced form, they can be used to solve important boundary-value problems of a four-parametric system of paraxial rays, connecting the two surfaces, similarly as the well-known surface-to-surface matrices in isotropic media in ray-centred coordinates. Applications of such boundary-value problems include the two-point eikonal, relative geometrical spreading, Fresnel zones, the design of migration operators, and more. [source] On the discretization of problems involving periodic planar tilingsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 8 2001André Bénard Abstract Features related to the discretization of problems characterized by simple periodic tilings using cells of various shapes are discussed. Various cell geometries that tile the plane periodically are considered. Equivalent problems are identified, where the discretization can take place on a parallelogram, regardless of the shape of the original cell. These equivalent problems also suggest a numbering of the equations that results in matrices with interesting and useful properties. Copyright © 2001 John Wiley & Sons, Ltd. [source] Thermally associating polypeptides designed for drug delivery produced by genetically engineered cellsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2007David S. Hart Abstract Thermally associating polymers, including gelatin, cellulose ethers (e.g., Methocels® and poloxamers (e.g., Pluronics®) have a long history of use in pharmacy. Over the past 20 years, significant advances in genetic engineering and the understanding of protein secondary and tertiary structures have been made. This has led to the development of a variety of polypeptides that do not occur naturally but can be expressed in recombinant cells and have useful properties that lend themselves to novel applications where current materials cannot perform. The most intensively studied motifs are derived from the consensus repeats of elastin and silk, as well as coiled-coil helices. Many of these designed polypeptides or ,artificial proteins' are thermally associating materials. This property can be exploited to develop solid dosage forms, injectable drug delivery systems, micro- or nanoparticle drug carriers, triggered or targeted release systems, or as a means of simplifying the purification process and thus reducing costs of production of these materials. This review focuses on the development and characterization of this novel class of biomaterials and examines their potential for pharmaceutical applications. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci [source] Thermochemistry and Crystallization of Glass-Forming Y-Substituted Sr-Analogues of Fresnoite (Sr2TiSi2O8)JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2010Tae-Jin Park Strontium titanosilicate (Sr2TiSi2O8) is the Sr-analogue of fresnoite (Ba2TiSi2O8). It may provide useful properties due to the unusual five-coordinate titanium in its structure. Sr2TiSi2O8 is also a possible oxide form for the immobilization of short-lived fission products in radioactive waste. Through , decay, strontium decays to yttrium and then to zirconium. Therefore, not only the stability of Sr-loaded waste forms but also that of a potential decay product series with charge-balance in a naturally occurring mineral or ceramic is of fundamental importance. To incorporate the reaction 3Sr2+=2Y3++vacancy in the fresnoite composition, Y-substituted Sr-analogues of fresnoite, (Sr2,xY2/3x)TiSi2O8 (x=0, 0.5, 0.75, 1, 1.25, and 1.5) were prepared by a high-temperature synthesis and were found to form glass upon cooling. The Y-end-member (Y1.33TiSi2O8, x=2) crystallized to a mixture of Y2TiSiO7, TiO2, and SiO2 upon quenching in air. The enthalpies of formation of Y-substituted Sr-fresnoite glasses were obtained from drop solution calorimetry in a molten lead borate (2PbO·B2O3) solvent at 702°C. The enthalpies of formation from constituent oxides were exothermic but become less so with increasing Y content. The enthalpy of vitrification of Sr2TiSi2O8 composition was measured to be 68.5 ± 6.2 kJ/mol. The thermodynamic stability of the Y-substituted Sr-analogue of crystalline fresnoite may become marginal with increasing yttrium content. Their ready glass formation, even in the absence of radiation, suggests that amorphous phases may dominate as the Sr- and Cs-containing waste forms decay. [source] Contractual agreements for coordination and vendor-managed delivery under explicit transportation considerationsNAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 5 2006egül Toptal Abstract We consider the coordination problem between a vendor and a buyer operating under generalized replenishment costs that include fixed costs as well as stepwise freight costs. We study the stochastic demand, single-period setting where the buyer must decide on the order quantity to satisfy random demand for a single item with a short product life cycle. The full order for the cycle is placed before the cycle begins and no additional orders are accepted by the vendor. Due to the nonrecurring nature of the problem, the vendor's replenishment quantity is determined by the buyer's order quantity. Consequently, by using an appropriate pricing schedule to influence the buyer's ordering behavior, there is an opportunity for the vendor to achieve substantial savings from transportation expenses, which are represented in the generalized replenishment cost function. For the problem of interest, we prove that the vendor's expected profit is not increasing in buyer's order quantity. Therefore, unlike the earlier work in the area, it is not necessarily profitable for the vendor to encourage larger order quantities. Using this nontraditional result, we demonstrate that the concept of economies of scale may or may not work by identifying the cases where the vendor can increase his/her profits either by increasing or decreasing the buyer's order quantity. We prove useful properties of the expected profit functions in the centralized and decentralized models of the problem, and we utilize these properties to develop alternative incentive schemes for win,win solutions. Our analysis allows us to quantify the value of coordination and, hence, to identify additional opportunities for the vendor to improve his/her profits by potentially turning a nonprofitable transaction into a profitable one through the use of an appropriate tariff schedule or a vendor-managed delivery contract. We demonstrate that financial gain associated with these opportunities is truly tangible under a vendor-managed delivery arrangement that potentially improves the centralized solution. Although we take the viewpoint of supply chain coordination and our goal is to provide insights about the effect of transportation considerations on the channel coordination objective and contractual agreements, the paper also contributes to the literature by analyzing and developing efficient approaches for solving the centralized problem with stepwise freight costs in the single-period setting. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006 [source] Hyperbranched macromolecules through donor-acceptor type copolymerization of allyl,vinylene bifunctional monomers,POLYMER INTERNATIONAL, Issue 10 2002O Rzaev, Zakir M Abstract Present review is an attempt to generalize and systematize the results accumulated in synthesis of cyclolinear and hyperbranched reactive macromolecules via radical alternating copolymerization of various bifunctional monomers containing donor and acceptor type double bonds. Synthesis of hyperbranched reactive macromolecules was carried out using complex-radical cyclocopolymerization of donor-acceptor type bifunctional monomers such as monoallyl ester of maleic acid (MAM), allyl acrylate (AA), allyl methacrylate (AM), allyl trans -cinnamate (AC), methylallylmaleate (MeAM), methylallylfumarate (MAF) and allyl-,-(N-maleimido)acetate (AMI), and maleic anhydride (MA) and styrene (St) as typical acceptor and donor comonomers, respectively. The kinetic parameters of these reactions, constants of cyclization, complex-formation and copolymerization, as well as the ratios of chain growth rates for the participation of monomeric charge transfer complexes and free monomers, were all determined. It was demonstrated that in the studied systems, copolymerizations predominantly proceed according to alternating mechanism with formation of macromolecules having cyclolinear structure in the steady-state and hyperbranched structure in the high conversion conditions. It was shown that formation of linear and hyperbranched macromolecules containing allyl or vinylene groups in the side chain occurs selectively carry out and depends on the nature of used comonomer. General schemes and proposed mechanism of hyperbranching and crosslinking reactions were also described. Some useful properties of synthesized reactive copolymers were discussed. © 2002 Society of Chemical Industry. [source] Hybrids of hybrids: nano-scale combinations of polyphosphazenes with other materialsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2010Harry R. Allcock Abstract Although more than 700 different polyphosphazenes are known, with a wide range of physical and chemical properties, a further expansion of materials properties can be accomplished by combining these macromolecules with other materials such as organic polymers, ceramics or semiconductors. These combinations lead to uses in the fields of biomedicine, energy generation and energy storage, and the formation of nano-particles such as micelles. This article is a review of recent developments in the author's laboratory to combine polyphosphazenes with other materials in order to generate new combinations of useful properties. Copyright © 2010 John Wiley & Sons, Ltd. [source] Response Surface Designs for Experiments in BioprocessingBIOMETRICS, Issue 2 2006Steven G. Gilmour Summary Many processes in the biological industries are studied using response surface methodology. The use of biological materials, however, means that run-to-run variation is typically much greater than that in many experiments in mechanical or chemical engineering and so the designs used require greater replication. The data analysis which is performed may involve some variable selection, as well as fitting polynomial response surface models. This implies that designs should allow the parameters of the model to be estimated nearly orthogonally. A class of three-level response surface designs is introduced which allows all except the quadratic parameters to be estimated orthogonally, as well as having a number of other useful properties. These subset designs are obtained by using two-level factorial designs in subsets of the factors, with the other factors being held at their middle level. This allows their properties to be easily explored. Replacing some of the two-level designs with fractional replicates broadens the class of useful designs, especially with five or more factors, and sometimes incomplete subsets can be used. It is very simple to include a few two- and four-level factors in these designs by excluding subsets with these factors at the middle level. Subset designs can be easily modified to include factors with five or more levels by allowing a different pair of levels to be used in different subsets. [source] Estimation of Nonlinear Models with Measurement ErrorECONOMETRICA, Issue 1 2004Susanne M. Schennach This paper presents a solution to an important econometric problem, namely the root n consistent estimation of nonlinear models with measurement errors in the explanatory variables, when one repeated observation of each mismeasured regressor is available. While a root n consistent estimator has been derived for polynomial specifications (see Hausman, Ichimura, Newey, and Powell (1991)), such an estimator for general nonlinear specifications has so far not been available. Using the additional information provided by the repeated observation, the suggested estimator separates the measurement error from the "true" value of the regressors thanks to a useful property of the Fourier transform: The Fourier transform converts the integral equations that relate the distribution of the unobserved "true" variables to the observed variables measured with error into algebraic equations. The solution to these equations yields enough information to identify arbitrary moments of the "true," unobserved variables. The value of these moments can then be used to construct any estimator that can be written in terms of moments, including traditional linear and nonlinear least squares estimators, or general extremum estimators. The proposed estimator is shown to admit a representation in terms of an influence function, thus establishing its root n consistency and asymptotic normality. Monte Carlo evidence and an application to Engel curve estimation illustrate the usefulness of this new approach. [source] | ||||||||||||||||