Esterification of Acetic Acid with Butanol: Operation in a Packed Bed Reactive Distillation Column

The esterification reaction between acetic acid and butanol was investigated in a reactive distillation column. The thermodynamic aspects of considered system are discussed, equilibrium constant, vapor pressures and UNIQUAC interaction parameters were investigated. Reactive distillation experiments were carried out to provide high purity butyl acetate. For this purpose, a 2 m column with nonreactive and reactive zones filled with Amberlyst 15 and Raschig rings, were used in the experiments. Several operating conditions such as total feed flow rate, molar ratio of butanol to acetic acid, amount of catalyst and reboiler temperature and three different column configurations were realized experimentally. The experimental optimum values of these parameters obtained were 1.6 mol h–1, 1, 25 g and 383 K, respectively within the range of study. The butyl acetate purity of 82 % and acetic acid conversion of 80.5 % were obtained at the optimum operating conditions

A strange recursion operator for a new integrable system of coupled Korteweg - de Vries equations

A recursion operator is constructed for a new integrable system of coupled Korteweg - de Vries equations by the method of gauge-invariant description of zero-curvature representations. This second-order recursion operator is characterized by unusual structure of its nonlocal part.Comment: 12 pages, final versio

Variable Coefficient Third Order KdV Type of Equations

We show that the integrable subclassess of a class of third order non-autonomous equations are identical with the integrable subclassess of the autonomous ones.Comment: Latex file , 15 page

New evidence on taxes and portfolio choice

Identifying the effect of differential taxation on portfolio allocation requires exogenous variation in marginal tax rates. Marginal tax rates vary with income, but income surely affects portfolio choice directly. In systems of individual taxation – like Canada’s – couples with the same household income can face different effective tax rates on capital income when labor income is distributed differently within households. Using this source of variation we find statistically significant but economically modest responses to taxation. In a “placebo” test, using data from the U.S. (which has joint taxation), we find no effect of the intra-household distribution of labor income on portfolios

Emission-Line Fluxes of Northern Planetary Nebulae

We present long slit spectrophotometric emission line fluxes of bright and extended (<5 arcsec in diameter) Planetary Nebulae (PNe) selected from Acker et al. 1992 catalog with suitable equitorial coordinates for Northern hemisphere. In total, 17 PNe have been choosen and observed in 2008--2010. To measure absolute fluxes, broad slit sizes, ranging from 3.5\arcsec to 7.5\arcsec were used and thus equivalent widths of all observable emission line fluxes were also calculated. Among 17 PNe's observed, line flux measurements of 12 of them were made for the first time. This work also aims to extend the sky coverage of emission line flux standards in Northern hemisphere (Dopita & Hua 1997 - 52 PNe in Southern hemisphere; Wright et al. 2005 - 6 PNe in Northern hemisphere). Electron temperatures and densities, and chemical abundances of these PNe were also calculated in this work. These data is expected to lead the photometric or spectrometric further work for absolute emission line flux measurements needed for \hii regions, supernova remnants etc.Comment: 24 pages, 3 Figures, 21 Tables, Accepted for publication in Publications of the Astronomical Society of Australi

Quadrilateral meshes with provable angle bounds

In this paper, we present an algorithm that utilizes a quadtree data structure to construct a quadrilateral mesh for a simple polygonal region in which no newly created angle is smaller than 18.43∘(=arctan(13)) or greater than 171.86∘(=135∘+2arctan(13)). This is the first known result, to the best of our knowledge, on a direct quadrilateral mesh generation algorithm with a provable guarantee on the angles

Quadrilateral meshes with provable angle bounds

In this paper, we present an algorithm that utilizes a quadtree data structure to construct a quadrilateral mesh for a simple polygonal region in which no newly created angle is smaller than 18.43∘(=arctan(13)) or greater than 171.86∘(=135∘+2arctan(13)). This is the first known result, to the best of our knowledge, on a direct quadrilateral mesh generation algorithm with a provable guarantee on the angles

A new integrable generalization of the Korteweg - de Vries equation

A new integrable sixth-order nonlinear wave equation is discovered by means of the Painleve analysis, which is equivalent to the Korteweg - de Vries equation with a source. A Lax representation and a Backlund self-transformation are found of the new equation, and its travelling wave solutions and generalized symmetries are studied.Comment: 13 pages, 2 figure

Closed timelike curves and geodesics of Godel-type metrics

It is shown explicitly that when the characteristic vector field that defines a Godel-type metric is also a Killing vector, there always exist closed timelike or null curves in spacetimes described by such a metric. For these geometries, the geodesic curves are also shown to be characterized by a lower dimensional Lorentz force equation for a charged point particle in the relevant Riemannian background. Moreover, two explicit examples are given for which timelike and null geodesics can never be closed.Comment: REVTeX 4, 12 pages, no figures; the Introduction has been rewritten, some minor mistakes corrected, many references adde

Attributed relational graphs for cell nucleus segmentation in fluorescence microscopy Images

Cataloged from PDF version of article.More rapid and accurate high-throughput screening in molecular cellular biology research has become possible with the development of automated microscopy imaging, for which cell nucleus segmentation commonly constitutes the core step. Although several promising methods exist for segmenting the nuclei of monolayer isolated and less-confluent cells, it still remains an open problem to segment the nuclei of more-confluent cells, which tend to grow in overlayers. To address this problem, we propose a new model-based nucleus segmentation algorithm. This algorithm models how a human locates a nucleus by identifying the nucleus boundaries and piecing them together. In this algorithm, we define four types of primitives to represent nucleus boundaries at different orientations and construct an attributed relational graph on the primitives to represent their spatial relations. Then, we reduce the nucleus identification problem to finding predefined structural patterns in the constructed graph and also use the primitives in region growing to delineate the nucleus borders. Working with fluorescence microscopy images, our experiments demonstrate that the proposed algorithm identifies nuclei better than previous nucleus segmentation algorithms