The computational complexity of the Chow form

We present a bounded probability algorithm for the computation of the Chow forms of the equidimensional components of an algebraic variety. Its complexity is polynomial in the length and in the geometric degree of the input equation system defining the variety. In particular, it provides an alternative algorithm for the equidimensional decomposition of a variety. As an application we obtain an algorithm for the computation of a subclass of sparse resultants, whose complexity is polynomial in the dimension and the volume of the input set of exponents. As a further application, we derive an algorithm for the computation of the (unique) solution of a generic over-determined equation system.Comment: 60 pages, Latex2

Managing strategies for organochlorine contaminated soils for a safe food production

Background: Organochlorine pesticides such as dieldrin, DDT and others are highly persistant pesticides, which were applied world wide against pests in horticulture, fruit and arable crops. Although they are forbidden since more than thirty years in the European Union (EU), the compounds remain still in soil. Several crops are known to accumulate these pesticides in eatable parts up to critical levels. For instance dieldrin is detected in high economic value crops such as cucumbers (Cucurbitaceae) and in tomatoes (Solanaceae). Besides plant type and climatic conditions, soil properties, e.g. pH and soil organic carbon content influence the pesticide uptake. In particular in labelled food and feed stuff production, such as organic farming according to EU Regulation (EEC) No. 2092/91, consumer expectations in safe, high quality food are extremely high. Since organic farming is prospering – more than 10% of vegetable production is certified organic in Switzerland – the organochlorine residues in organic food stuff have become a major issue for food control authorities. Enquires showed that imported food from EU countries was partly highly contaminated with organochlorine pesticides such as pumpkin seed and oil. Hence, the organochlorine problem in food stuff is expected to occur EU wide

Depth Profile of Optically Recorded Patterns in Light-Sensitive Liquid Crystal Elastomers

We investigated nonlinear absorption and photobleaching processes in a liquid crystal elastomer (LCE) doped with light-sensitive azobenzene moiety. A conventional one-dimensional holographic grating was recorded in the material with the use of two crossed UV laser beams and the angular dependence of the diffraction efficiency in the vicinity of the Bragg peak was analyzed. These measurements gave information on the depth to which trans to cis isomerisation had progressed into the sample as a function of the UV irradiation time. Using a numerical model that takes into account the propagation of writing beams and rate equations for the local concentration of the absorbing trans conformer, we computed the expected spatial distribution of the trans and cis conformers and the shape of the corresponding Bragg diffraction peak for different irradiation doses. Due to residual absorption of the cis conformers the depth of the recording progresses logarithmically with time and is limited by the thermal relaxation from the cis to trans conformation.Comment: 19 pages (incl. figs), 6 figure

Robust Convergence of Power Flow using Tx Stepping Method with Equivalent Circuit Formulation

Robust solving of critical large power flow cases (with 50k or greater buses) forms the backbone of planning and operation of any large connected power grid. At present, reliable convergence with applications of existing power flow tools to large power systems is contingent upon a good initial guess for the system state. To enable robust convergence for large scale systems starting with an arbitrary initial guess, we extend our equivalent circuit formulation for power flow analysis to include a novel continuation method based on transmission line (Tx) stepping. While various continuation methods have been proposed for use with the traditional PQV power flow formulation, these methods have either failed to completely solve the problem or have resulted in convergence to a low voltage solution. The proposed Tx Stepping method in this paper demonstrates robust convergence to the high voltage solution from an arbitrary initial guess. Example systems, including 75k+ bus test cases representing different loading and operating conditions for Eastern Interconnection of the U.S. power grid, are solved from arbitrary initial guesses.Interconnection of the U.S. power grid, are solved from arbitrary initial guesses

The Ruse of Reading: The Postcolonial Literary Marketplace and the Novels of Gina Apostol

This paper explores the politics of reading in the novelistic production of Gina Apostol in relation to Sarah Brouillette’s analysis of the postcolonial literary marketplace, Timothy Brennan’s critique of cosmopolitanism, and Gayatri Chakravorty Spivak’s tracking of the native informant in postcolonial discourse. In Brouillette’s work, postcolonial writers, unlike the Romantic author who disavows commercial popularity, are aware of the commodification of their work and interact with it, either through resistance or complicity. Cosmopolitanism for Brennan denotes an unequal flow of intellectual commodities between center and periphery instantiated in the consciousness of the migrant writer valorized in “international book markets because of their authentic native attachment to a specific Third World locale” (“Cosmopolitans and Celebrities” 3). Lastly, the native informant, in Spivak’s A Critique of Postcolonial Reason, is a postcolonial subject whose self-representation projects the ascendancy of liberal Western discourse while authenticating a homogenized identity for the ‘Other’

Autopoetics, Market Competence, and the Transnational Author

Although materialist analyses have critiqued the institutionalization of postcolonial studies and its emergence in global capitalism, only few have addressed the role of creative writing in standardizing migrant novelistic production to what Mark McGurl has designated as ‘program fiction’ whose trademark is the practice of “involuted self-reference”. In filling this gap, this paper looks into Gina Apostol’s writings and their reception by international audiences as exemplary of the cultural capital of program fiction. While Apostol’s autofictions/ficto-criticism points to the influence of creative writing in her novels — she studied under John Barth in the MFA program in Johns Hopkins University, this context is overlooked when metropolitan readers construe her work as postcolonial literature. I argue that Apostol’s textualist renderings of Philippine history is an act of ventriloquism whose metropolitan success is a symptom of the auratic authority of postcolonial studies in the First world literary marketplace

Thermally assisted interlayer magnetic coupling through Ba0.05Sr0.95TiO3 barriers

We report on the interlayer exchange coupling across insulating barriers observed on Ni80Fe20/Ba0.05Sr0.95TiO3/La0.66Sr0.33MnO3 (Py/BST0.05/LSMO) trilayers. The coupling mechanism has been analyzed in terms of the barrier thickness, samples' substrate, and temperature. We examined the effect of MgO (MGO) and SrTiO3 (STO) (001) single-crystalline substrates on the magnetic coupling and also on the magnetic anisotropies of the samples in order to get a deeper understanding of the magnetism of the structures. We measured a weak coupling mediated by spin-dependent tunneling phenomena whose sign and strength depend on barrier thickness and substrate. An antiferromagnetic (AF) exchange prevails for most of the samples and smoothly increases with the barrier thicknesses as a consequence of the screening effects of the BST0.05. The coupling monotonically increases with temperature in all the samples and this behavior is attributed to thermally assisted mechanisms. The magnetic anisotropy of both magnetic components has a cubic symmetry that in the case of permalloy is added to a small uniaxial component.Fil: Carreira, Santiago José. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Aviles Felix, Luis Steven. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sirena, Martin. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alejandro, Gabriela. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Steren, Laura Beatriz. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin