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OALib Journal期刊

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Derivative-free methods for nonlinear programming with general lower-level constraints
Diniz-Ehrhardt, M. A.;Martínez, J. M.;Pedroso, L. G.;
Computational & Applied Mathematics , 2011, DOI: 10.1590/S1807-03022011000100003
Abstract: augmented lagrangian methods for derivative-free continuous optimization with constraints are introduced in this paper. the algorithms inherit the convergence results obtained by andreani, birgin, martínez and schuverdt for the case in which analytic derivatives exist and are available. in particular, feasible limit points satisfy kkt conditions under the constant positive linear dependence (cpld) constraint qualification. the form of our main algorithm allows us to employ well established derivative-free subalgorithms for solving lower-level constrained subproblems. numerical experiments are presented.
Otimiza??o da produ??o de álcool de mandioca
Curvelo-Santana, José Carlos;Ehrhardt, Daniela Diniz;Tambourgi, Elias Basile;
Ciência e Tecnologia de Alimentos , 2010, DOI: 10.1590/S0101-20612010000300007
Abstract: the objective of this study was the optimization of the manioc root starch hydrolysis by α-amylase from a. niger and alcohol production from this starch syrup. hydrolysis assays were performed at ph 4.8, the starch concentration and the temperature varied from 7 to 22 g.l-1, and 30 to 59.1 oc, respectively. the starch contents during the syrup fermentation were 2.2 and 5%. the results of the starch hydrolysis showed that the hydrolysis time was between 20-200 minutes, the rsm analysis showed a decrease in the starch yield at the average concentration and above of 70% at high temperatures, and the optimal conditions were found at temperature between 55-59.1 oc and concentration between 7.9-10 or 20-22 g.l-1; conditions at which 80% of the starch was hydrolyzed. the best fermentation condition was obtained for the must containing 5% of starch. the final fermentation composition obtained was of 0.68 g.l-1 art and 0.572 g.l-1 ar. after the fermentation process, an alcohol yield of 45% was obtained showing that this process is a very good alternative for sugar-alcohol industries.
Commentary on "Expansions for Eigenfunctions and Eigenvalues of large-n Toeplitz Matrices"
Torsten Ehrhardt
Papers in Physics , 2010, DOI: 10.4279/pip.020004
Abstract: A Commentary on the paper by L. P. Kadanoff [Pap. Phys. 2, 020003 (2010)]. Received: 29 September 2010, Accepted: 4 October 2010; Edited by: A. G. Green; DOI: 10.4279/PIP.020004
Dyson's constant in the asymptotics of the Fredholm determinant of the sine kernel
Torsten Ehrhardt
Mathematics , 2004,
Abstract: We prove that the asymptotics of the Fredholm determinant of $I-K_\alpha$, where $K_\alpha$ is the integral operator with the sine kernel $\sin(x-y)/(x-y)/\pi$ on the interval $[0,\alpha]$ is given by a formula which was conjectured by F.J. Dyson. The first and second order asymptotics as well as the higher order asymptotics except for the constant term have already been proved. In this paper we thus determine the constant term.
Dyson's constants in the asymptotics of the determinants of Wiener-Hopf-Hankel operators with the sine kernel
Torsten Ehrhardt
Mathematics , 2006, DOI: 10.1007/s00220-007-0239-x
Abstract: In this paper we are going to prove two asymptotic formulas for determinants det(I-K_s), as s goes to infinity, where K_s are the Wiener-Hopf-Hankel operators acting on L^2[0,s] with the kernels K(x-y)+K(x+y) and K(x-y)-K(x+y), respectively, and K(t):=sin(t)/(\pi*t). These formulas were conjectured by Dyson. The identification of the constant term in the asymptotics was an open problem for a long time.
Invertibility of Toeplitz + Hankel Operators and Singular Integral Operators with Flip - The case of smooth generating functions
Torsten Ehrhardt
Mathematics , 2000,
Abstract: It is well known that a Toeplitz operator is invertible if and only if its symbols admits a canonical Wiener-Hopf factorization, where the factors satisfy certain conditions. A similar result holds also for singular integral operators. More general, the dimension of the kernel and cokernel of Toeplitz or singular integral operators which are Fredholm can be expressed in terms of the partial indices of an associated Wiener-Hopf factorization problem. In this paper we establish corresponding results for Toeplitz + Hankel operators and singular integral operators with flip under the assumption that the generating functions are sufficiently smooth. We are led to a slightly different factorization problem, in which so-called characteristic pairs instead of the partial indices appear. These pairs provide the relevant information about the dimension of the kernel and cokernel and thus answer the invertibility problem.
The asymptotics a Bessel-kernel determinant which arises in Random Matrix Theory
Torsten Ehrhardt
Mathematics , 2010,
Abstract: In Random Matrix Theory the local correlations of the Laguerre and Jacobi Unitary Ensemble in the hard edge scaling limit can be described in terms of the Bessel kernel (containing a parameter $\alpha$). In particular, the so-called hard edge gap probabilities can be expressed as the Fredholm determinants of the corresponding integral operator restricted to the finite interval [0, R]. Using operator theoretic methods we are going to compute their asymptotics as R goes to infinity under certain assumption on the parameter $\alpha$.
Concentration by membrane separation processes of a medicinal product obtained from pineapple pulp
Lopes, Francisco Luiz Gumes;Severo Júnior, Jo?o Baptista;Souza, Roberto Rodrigues de;Ehrhardt, Daniela Diniz;Santana, José Carlos Curvelo;Tambourgi, Elias Basile;
Brazilian Archives of Biology and Technology , 2009, DOI: 10.1590/S1516-89132009000200024
Abstract: the concentration of pineapple juice is needed to retain the bromelain activity and to standardize the composition and proteolytic activity. thus, this work aimed to obtain a pure bromelain extract from the ananas comosus l. merril juice by membrane separation process. a 22 experimental planning was used to study the influence of ph and transmembrane pressure on the activity recovery by micro-filtration using a plain membrane. in second step, this enzyme was purified by the ultra-filtration using a 10 kda millipore kit. the best operation condition to bromelain concentration using the plain membrane was at ph 7.5 and transmembrane pressure of 0.05 bar, while 85% of bromelain activity was recovered. ultra-filtration retained 100% of proteolytic activity and concentrated in 10 fold the bromelain extract. sds-page electrophoresis showed that the ultra-filtrated had high purity and the bromelain from a. comosus pulp had a molecular weight of 24.5 kda.
RNA Interference Is Responsible for Reduction of Transgene Expression after Sleeping Beauty Transposase Mediated Somatic Integration
Christina Rauschhuber, Anja Ehrhardt
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035389
Abstract: Background Integrating non-viral vectors based on transposable elements are widely used for genetically engineering mammalian cells in functional genomics and therapeutic gene transfer. For the Sleeping Beauty (SB) transposase system it was demonstrated that convergent transcription driven by the SB transposase inverted repeats (IRs) in eukaryotic cells occurs after somatic integration. This could lead to formation of double-stranded RNAs potentially presenting targets for the RNA interference (RNAi) machinery and subsequently resulting into silencing of the transgene. Therefore, we aimed at investigating transgene expression upon transposition under RNA interference knockdown conditions. Principal Findings To establish RNAi knockdown cell lines we took advantage of the P19 protein, which is derived from the tomato bushy stunt virus. P19 binds and inhibits 21 nucleotides long, small-interfering RNAs and was shown to sufficiently suppress RNAi. We found that transgene expression upon SB mediated transposition was enhanced, resulting into a 3.2-fold increased amount of colony forming units (CFU) after transposition. In contrast, if the transgene cassette is insulated from the influence of chromosomal position effects by the chicken-derived cHS4 insulating sequences or when applying the Forg Prince transposon system, that displays only negligible transcriptional activity, similar numbers of CFUs were obtained. Conclusion In summary, we provide evidence for the first time that after somatic integration transposon derived transgene expression is regulated by the endogenous RNAi machinery. In the future this finding will help to further improve the molecular design of the SB transposase vector system.
Strontium disodium hexathiodiphosphate(IV) octahydrate
Claus Ehrhardt,Mimoza Gjikaj
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810025316
Abstract: The crystal structure of SrNa2(P2S6)·8H2O is isotypic with that of its calcium analogue. The asymmetric unit consists of one Sr2+ cation (2 symmetry), two Na+ cations (2 and overline{1} symmetry, respectively), one-half of a centrosymmetric (P2S6)4 anion with a staggered confirmation and four water molecules. The crystal structure is built up from layers of cations and anions extending parallel to (101). Each SrO8 polyhedron is connected via edge-sharing to two NaO4S2 octahedra and to one NaO2S4 octahedron. The NaO4S2 octaedra are, in turn, connected with two (P2S6)4 anions through common corners. Adjacent layers are held together by several O—H...S hydrogen-bonding interactions.
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