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Browsing Artículos de conferencia by browse.metadata.categoria "Matemática física y química"
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- ItemAcrylamide reduction in potato chips by using commercial asparaginase in combination with conventional blanching(Elsevier Science BV, 2011) Pedreschi Plasencia, Franco Wilfredo; Mariotti Celis, María Salomé; Granby, Kit; Risum, JorgenIn this research acrylamide reduction in potato chips was investigated in relation to blanching and asparaginase immersion treatments before final frying. Potatoes slices (Verdi variety, diameter: 40 mm, thickness: 2.0 mm) were fried at 170 degrees C for 5 min (final moisture content of similar to 2.0 g/100 g). Prior to frying, potato slices were treated in one of the following ways: (i) Rinsing in distilled water (control I); (ii) Rinsing in distilled water plus blanching in hot water at 85 degrees C for 3.5 min; (iii) Rinsing in distilled water plus immersion in an asparaginase solution (10000 ASNU/L) at 50 degrees C for 20 min; (iv) Rinsing in distilled water plus blanching in hot water at 85 degrees C for 3.5 min plus immersion in an asparaginase solution (10000 ASNU/L) at 50 degrees C for 20 min; (v) Rinsing in distilled water plus blanching in hot water at 85 degrees C for 3.5 min plus immersion in distilled water at 50 degrees C for 20 min (control II). Blanching in hot water (ii) was almost as effective as asparaginase potato immersion (iii) in order to diminish acrylamide formation in potato chips (acrylamide reduction was similar to 17% of the initial acrylamide concentration). When potato slices were blanched before asparaginase immersion, the acrylamide content of the resultant potato chips was reduced considerably by almost 90%. We have demonstrated that blanching of potato slices plus asparaginase treatment is an effective combination for acrylamide mitigation during frying. It seems to be that blanching provokes changes in the microstructure of potato tissue leading to an easier and more effective diffusion of asparaginase. (C) 2011 Elsevier Ltd. All rights reserved.
- ItemAlgebraic Reconstruction of Source and Attenuation in SPECT Using First Scattering Measurements(Springer, 2018) Cueva, Evelyn; Osses Alvarado, Axel Esteban; Quintana Fresno, Juan Carlos; Tejos Núñez, Cristián Andrés; Courdurier Bettancourt Matias Alejandro; Irarrazaval Mena, PabloHere we present an Algebraic Reconstruction Technique (ART) for solving the identification problem in Single Photon Emission Computed Tomography (SPECT). Traditional reconstruction for SPECT is done by finding the radiation source, nevertheless the attenuation of the surrounding tissue affects the data. In this context, ballistic and first scattering information are used to recover source and attenuation simultaneously. Both measurements are related with the Attenuated Radon Transform and a Klein-Nishina angular type dependency is considered for the scattering. The proposed ART algorithm allow us to obtain good reconstructions of both objects in a few number of iterations.
- ItemEquilibrium Dynamics in Market Games with Exchangeable and Divisible Resources(2024) Correa, José; Harks, Tobias; Schedel, Anja; Verschae Tannenbaum Jose ClaudioWe study a market game with n ≥ 2 players competing over m ≥ 1 divisible resources of different finite capacities. Resources are traded via the proportional sharing mechanism, where players are price-anticipating, meaning that they can influence the prices with their bids. Additionally, each player has an initial endowment of the resources which are sold at market prices. Although the players’ total profit functions may be discontinuous in the bids, we prove existence and uniqueness of pure Nash equilibria of the resulting market game. Then, we study a discrete dynamic arising from repeatedly taking the (unique) equilibrium resource allocation as initial endowments for the next market game. We prove that the total utility value of the dynamic converges to either an optimal allocation value (maximizing total utility over the allocation space) or to a restricted optimal allocation value, where the restriction is defined by fixing some tight resources which are exclusively allocated to a single player. As a corollary, it follows that for strictly concave utility functions, the aggregated allocation vector of the dynamic converges to the unique (possibly restricted) optimal aggregated allocation, and for linear utility functions, we even get convergence of the dynamic to a (possibly restricted) optimal solution in the (non-aggregated) original allocation space.
- ItemFormation and Morphology of Single Phospholipid Bilayers Formed by Velocity-Controlled Dip-Coating(2018) Cisternas Fruns, Marcelo Andrés; Soto Arriaza, Marco Antonio; Retamal Ponce, Maria Jose; Moraga Alarcón, Nicolás Hernán; Catalán Lopez, Rodrigo Esteban; Volkmann, Ulrich Georg; Diaz, Diego; Corrales, Tomas P.
- ItemPractical implementation of test equating using r(Springer, 2020) Wiberg, Marie; González Burgos, Jorge AndrésTest equating methods are widely used in order to make comparable different test forms administered at different occasions to different test takers. Although software for test equating is currently available, in this paper we focus the attention on four different R packages which can facilitate test equating for researchers and test developers. This paper list the different R packages which are available at the moment. Examples are provided for the equate, equateIRT, kequate, and the SNSequate packages. Additional features of these packages are discussed as well.
- ItemPredictive validity under partial observability(Springer, 2020) Alarcón Bustamante, Eduardo Sebastián; San Martín, Ernesto; González Burgos, Jorge AndrésTo assess the predictive capacity of selection tests is a challenge because the response variable is observed only in selected individuals. In this paper we propose to evaluate the predictive capacity of selection tests through marginal effects under a partial identification approach. Identification bounds are defined for the marginal effects under monotonicity assumptions of the response variable. Theperformance of our method is assessed using a real data set from the university selection test applied in Chile and compared with the marginal effect of the traditional model used in Chile to evaluate the predictive capacity of the selection test.
- ItemQuantum transport across a slab of a type I Weyl Semimetal with a uniform concentration of torsion dislocation defects(2023) Bonilla Moreno, Daniel; Muñoz, EnriqueIn this work, we study the electronic transport in a Type I Weyl Semimetal slab with a uniform and diluted concentration of torsional dislocation defects. The defects have cylindrical geometry and are modeled as a pseudo-gauge field accounting for torsional strain and a repulsive delta-shell potential for the lattice mismatch effect. We give explicit forms for the retarded Green function in the presence of uniformly distributed scattering centers and the spectral density in terms of the relaxation time (imaginary part of the self-energy). The relaxation time is computed from the known scattering cross-section as a function of the phase shifts for the single-defect scattering problem. Finally, we use the Kubo formula to calculate electrical conductivity.
- ItemRepresenting Paths in Graph Database Pattern Matching(2023) Martens, Wim; Niewerth, Matthias; Popp, Tina; Rojas, Carlos; Vansummeren, Stijn; Vrgoc, DomagojModern graph database query languages such as GQL, SQL/PGQ, and their academic predecessor G-Core promote paths to first-class citizens in the sense that their pattern matching facility can return paths, as opposed to only nodes and edges. This is challenging for database engines, since graphs can have a large number of paths between a given node pair, which can cause huge intermediate results in query evaluation., We introduce the concept of path multiset representations (PMRs), which can represent multisets of paths exponentially succinctly and therefore bring significant advantages for representing intermediate results. We give a detailed theoretical analysis that shows that they are especially well-suited for representing results of regular path queries and extensions thereof involving counting, random sampling, and unions. Our experiments show that they drastically improve scalability for regular path query evaluation, with speedups of several orders of magnitude.