16,440 research outputs found
On the Efficient Calculation of a Linear Combination of Chi-Square Random Variables with an Application in Counting String Vacua
Linear combinations of chi square random variables occur in a wide range of
fields. Unfortunately, a closed, analytic expression for the pdf is not yet
known. As a first result of this work, an explicit analytic expression for the
density of the sum of two gamma random variables is derived. Then a
computationally efficient algorithm to numerically calculate the linear
combination of chi square random variables is developed. An explicit expression
for the error bound is obtained. The proposed technique is shown to be
computationally efficient, i.e. only polynomial in growth in the number of
terms compared to the exponential growth of most other methods. It provides a
vast improvement in accuracy and shows only logarithmic growth in the required
precision. In addition, it is applicable to a much greater number of terms and
currently the only way of computing the distribution for hundreds of terms. As
an application, the exponential dependence of the eigenvalue fluctuation
probability of a random matrix model for 4d supergravity with N scalar fields
is found to be of the asymptotic form exp(-0.35N).Comment: 21 pages, 19 figures. 3rd versio
Nonlinear dynamics of the interface of dielectric liquids in a strong electric field: Reduced equations of motion
The evolution of the interface between two ideal dielectric liquids in a
strong vertical electric field is studied. It is found that a particular flow
regime, for which the velocity potential and the electric field potential are
linearly dependent functions, is possible if the ratio of the permittivities of
liquids is inversely proportional to the ratio of their densities. The
corresponding reduced equations for interface motion are derived. In the limit
of small density ratio, these equations coincide with the well-known equations
describing the Laplacian growth.Comment: 10 page
The Economic Impact of Forming a European Company
Ever since 2004 companies located in Member States of the European Economic Area have been able to opt to incorporate in a supranational legal form, the Societas Europaea. We found that companies located in Member States where the Societas Europaea offers additional legal arbitrage opportunities benefit most. Moreover, our results show that the stock price reaction is positive when the decision to incorporate as an Societas Europaea involves moving the firm's registered office and that firms are moving to jurisdictions with significantly lower corporate tax rates. Finally, we found evidence of uncertainty at the registration date but not at the time of the shareholder meeting
Noncovalent complexation of amphotericin-B with Poly(α-glutamic acid).
A noncovalent complex of amphotericin B (AmB) and poly(α-glutamic acid) (PGA) was prepared to develop a safe and stable formulation for the treatment of leishmaniasis. The loading of AmB in the complex was in the range of ∼20-50%. AmB was in a highly aggregated state with an aggregation ratio often above 2.0. This complex (AmB-PGA) was shown to be stable and to have reduced toxicity to human red blood cells and KB cells compared to the parent compound; cell viability was not affected at an AmB concentration as high as 50 and 200 μg/mL respectively. This AmB-PGA complex retained AmB activity against intracellular Leishmania major amastigotes in the differentiated THP-1 cells with an EC50 of 0.07 ± 0.03-0.08 ± 0.01 μg/mL, which is similar to Fungizone (EC50 of 0.06 ± 0.01 μg/mL). The in vitro antileishmanial activity of the complex against Leishmania donovani was retained after storage at 37 °C for 7 days in the form of a solution (EC50 of 0.27 ± 0.03 to 0.35 ± 0.04 μg/mL) and for 30 days as a solid (EC50 of 0.41 ± 0.07 to 0.63 ± 0.25 μg/mL). These encouraging results indicate that the AmB-PGA complex has the potential for further development
Optimization of growth and extracellular glucoamylase production by Candida famata isolate
Candida famata was isolated from traditional Moroccan sourdough. It exhibited high glucoamylase and biomass production. Starch induces high glucoamylase production C. famata with maximum glucoamylase activity at 5 g/L. Glucose stimulates good production in biomass but strongly inhibitsglucoamylase production. Among the sources of nitrogen tested, yeast extract and the (NH4)2HPO4 gave maximum glucoamylase and biomass after 72 h of incubation in liquid medium at 30°C, pH 5 and 105 rpm
Pressure Driven Flow of Polymer Solutions in Nanoscale Slit Pores
Polymer solutions subject to pressure driven flow and in nanoscale slit pores
are systematically investigated using the dissipative particle dynamics
approach. We investigated the effect of molecular weight, polymer concentration
and flow rate on the profiles across the channel of the fluid and polymer
velocities, polymers density, and the three components of the polymers radius
of gyration. We found that the mean streaming fluid velocity decreases as the
polymer molecular weight or/and polymer concentration is increased, and that
the deviation of the velocity profile from the parabolic profile is accentuated
with increase in polymer molecular weight or concentration. We also found that
the distribution of polymers conformation is highly anisotropic and non-uniform
across the channel. The polymer density profile is also found to be
non-uniform, exhibiting a local minimum in the center-plane followed by two
symmetric peaks. We found a migration of the polymer chains either from or
towards the walls. For relatively long chains, as compared to the thickness of
the slit, a migration towards the walls is observed. However, for relatively
short chains, a migration away from the walls is observed.Comment: 11 pages, 13 figure
VoroCrust: Voronoi Meshing Without Clipping
Polyhedral meshes are increasingly becoming an attractive option with
particular advantages over traditional meshes for certain applications. What
has been missing is a robust polyhedral meshing algorithm that can handle broad
classes of domains exhibiting arbitrarily curved boundaries and sharp features.
In addition, the power of primal-dual mesh pairs, exemplified by
Voronoi-Delaunay meshes, has been recognized as an important ingredient in
numerous formulations. The VoroCrust algorithm is the first provably-correct
algorithm for conforming polyhedral Voronoi meshing for non-convex and
non-manifold domains with guarantees on the quality of both surface and volume
elements. A robust refinement process estimates a suitable sizing field that
enables the careful placement of Voronoi seeds across the surface circumventing
the need for clipping and avoiding its many drawbacks. The algorithm has the
flexibility of filling the interior by either structured or random samples,
while preserving all sharp features in the output mesh. We demonstrate the
capabilities of the algorithm on a variety of models and compare against
state-of-the-art polyhedral meshing methods based on clipped Voronoi cells
establishing the clear advantage of VoroCrust output.Comment: 18 pages (including appendix), 18 figures. Version without compressed
images available on https://www.dropbox.com/s/qc6sot1gaujundy/VoroCrust.pdf.
Supplemental materials available on
https://www.dropbox.com/s/6p72h1e2ivw6kj3/VoroCrust_supplemental_materials.pd
Mesoporous Functionalized Acid Catalysts And Their Use As Environmentally Friendly Catalysts In Esterification Of Glycerols For Monoglyceride Production.
Monoglycerides are valuable compounds with wide applications as emulsifiers in food, pharmaceutical and cosmetic industries. They can be produced by esterification of glycerols with fatty acids
Residual and Past Entropies of Concomitants from Lai And Xie Extensions of Case-II of Generalized Order Statistics and its Dual
In this article, we consider a new extensions of Morgenstern family is Lai and Xie extensions and discuss their concomitants for case-II of generalized order statistics and case-II of dual generalized order statistics. Additionally, recurrence relation between moments is found for the recommended models. We have also derived the expression for the joint distribution of concomitants for case-II of generalized order statistics and its dual. The residual and past entropies are shown last
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