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- Rojas, Cristian R., 1980-, et al.
(författare)
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Equivalence between Transfer-Matrix and Observed-State Feedback Control
- 2006
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Ingår i: IEE Proceedings - Control Theory and Applications. - : Institution of Engineering and Technology (IET). - 1350-2379 .- 1359-7035. ; 153:2, s. 147-155
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Tidskriftsartikel (refereegranskat)abstract
- An observed-state feedback is built for a given multiple input-multiple Output (MIMO) control loop, where the controller is specified in transfer-matrix form. This contribution solves for the first time, for MIMO systems, the classical problem of finding a feedback gain and an observer gain such that the observed-state feedback control loop has the same sensitivity as that provided by a one-degree-of-freedom classical control loop.
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| 4. |
- Schut, J, et al.
(författare)
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Glass transition temperature prediction of polymers through the mass-per-flexible-bond principle
- 2007
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 48:20, s. 6115-6124
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Tidskriftsartikel (refereegranskat)abstract
- A semi-empirical method based on the mass-per-flexible-bond (M/f) principle was used to quantitatively explain the large range of glass transition temperatures (T-g) observed in a library of 132 L-tyrosine derived homo, co- and terpolymers containing different functional groups. Polymer class specific behavior was observed in T-g vs. M/f plots, and explained in terms of different densities, steric hindrances and intermolecular interactions of chemically distinct polymers. The method was found to be useful in the prediction of polymer T-g. The predictive accuracy was found to range from 6.4 to 3.7 K, depending on polymer class. This level of accuracy compares favorably with (more complicated) methods used in the literature. The proposed method can also be used for structure prediction of polymers to match a target T-g value, by keeping the thermal behavior of a terpolymer constant while independently choosing its chemistry. Both applications of the method are likely to have broad applications in polymer and (bio)material science.
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- Han, Shizhong, et al.
(författare)
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Evaluation of imputation-based association in and around the integrin-alpha-M (ITGAM) gene and replication of robust association between a non-synonymous functional variant within ITGAM and systemic lupus erythematosus (SLE)
- 2009
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 18:6, s. 1171-1180
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Tidskriftsartikel (refereegranskat)abstract
- We recently identified a novel non-synonymous variant, rs1143679, at exon 3 of the ITGAM gene associated with systemic lupus erythematosus (SLE) susceptibility in European-Americans (EAs) and African-Americans. Using genome-wide association approach, three other studies also independently reported an association between SLE susceptibility and ITGAM or ITGAM-ITGAX region. The primary objectives of this study are to assess whether single or multiple causal variants from the same gene or any nearby gene(s) are involved in SLE susceptibility and to confirm a robust ITGAM association across nine independent data sets (n = 8211). First, we confirmed our previously reported association of rs1143679 (risk allele 'A') with SLE in EAs (P = 1.0 x 10(-8)) and Hispanic-Americans (P = 2.9 x 10(-5)). Secondly, using a comprehensive imputation-based association test, we found that ITGAM is one of the major non-human leukocyte antigen susceptibility genes for SLE, and the strongest association for EA is the same coding variant rs1143679 (log(10)Bayes factor=20, P = 6.17 x 10(-24)). Thirdly, we determined the robustness of rs1143679 association with SLE across three additional case-control samples, including UK (P = 6.2 x 10(-8)), Colombian (P = 3.6 x 10(-7)), Mexican (P = 0.002), as well as two independent sets of trios from UK (P(TDT) = 1.4 x 10(-5)) and Mexico (P(TDT) = 0.015). A meta-analysis combing all independent data sets greatly reinforces the association (P(meta) = 7.1 x 10(-50), odds ratio = 1.83, 95% confidence interval = 1.69-1.98, n = 10 046). However, this ITGAM association was not observed in the Korean or Japanese samples, in which rs1143679 is monomorphic for the non-risk allele (G). Taken together along with our earlier findings, these results demonstrate that the coding variant, rs1143679, best explains the ITGAM-SLE association, especially in European- and African-derived populations, but not in Asian populations.
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- Menéndez, M., et al.
(författare)
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Grace : Development of Pd-zeolite composite membranes for hydrogen production by membrane reactor
- 2005
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Ingår i: Carbon Dioxide Capture for Storage in Deep Geologic Formations. - : Elsevier. - 9780080445700 ; , s. 341-364
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Pd–zeolite composite membranes have been prepared over the external surface of macroporous a-alumna tubular supports by secondary growth of zeolite layers followed by Pd modification. Pd nanoparticles (few nanometers in size) filtration and/or impregnation þ in situ reduction of an organic Pd precursor have been explored as deposition techniques devoted to enhance the H2 separation performance of the non-defect free A-type zeolite membranes. The Pd deposition aims toward the partial blockage of the non-selective intercrystalline pathways, which may account for a significant fraction of the total permeation flux. The Pd–zeolite composite substrates have been characterized by XRD, SEM and EDX. The study of the permeation properties of these substrates for single (N2) and binary mixtures (H2–CO2) before and after Pd modification, reveals some improvements in terms of H2 separation performance. The impregnation þ in situ reduction of palladium acetylacetonate solution (Pd(acac)2) carried out over KA zeolite membranes previously seeded with Pd nanoparticles appears as the most adequate among the tested methods. Separation factors for H2-CO2 binary mixtures up to 145 have been achieved, although further optimization is required to improve the H2 permeation fluxes (around 1028 mol H2/m2 s Pa).
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| 8. |
- Thuswaldner, Sophie, 1976-, et al.
(författare)
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Identification, expression, and functional analyses of a thylakoid ATP/ADP carrier from Arabidopsis
- 2007
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Ingår i: J Biol Chem. - 0021-9258 .- 1083-351X. ; 282:12, s. 8848-59
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Tidskriftsartikel (refereegranskat)abstract
- In plants the chloroplast thylakoid membrane is the site of light-dependent photosynthetic reactions coupled to ATP synthesis. The ability of the plant cell to build and alter this membrane system is essential for efficient photosynthesis. A nucleotide translocator homologous to the bovine mitochondrial ADP/ATP carrier (AAC) was previously found in spinach thylakoids. Here we have identified and characterized a thylakoid ATP/ADP carrier (TAAC) from Arabidopsis.(i) Sequence homology with the bovine AAC and the prediction of chloroplast transit peptides indicated a putative carrier encoded by the At5g01500 gene, as a TAAC. (ii) Transiently expressed TAAC-green fluorescent protein fusion construct was targeted to the chloroplast. Western blotting using a peptide-specific antibody together with immunogold electron microscopy revealed a major location of TAAC in the thylakoid membrane. Previous proteomic analyses identified this protein in chloroplast envelope preparations. (iii) Recombinant TAAC protein specifically imports ATP in exchange for ADP across the cytoplasmic membrane of Escherichia coli. Studies on isolated thylakoids from Arabidopsis confirmed these observations. (iv) The lack of TAAC in an Arabidopsis T-DNA insertion mutant caused a 30-40% reduction in the thylakoid ATP transport and metabolism. (v) TAAC is readily expressed in dark-grown Arabidopsis seedlings, and its level remains stable throughout the greening process. Its expression is highest in developing green tissues and in leaves undergoing senescence or abiotic stress. We propose that the TAAC protein supplies ATP for energy-dependent reactions during thylakoid biogenesis and turnover in plants.
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- Torres, Miguel F., et al.
(författare)
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Effect of ionic strength on the rheological behavior of aqueous cetyltrimethylammonium p-toluene sulfonate solutions
- 2007
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 307:1, s. 221-228
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Tidskriftsartikel (refereegranskat)abstract
- The influence of ionic environment on the rheological properties of aqueous cetyltrimethylammonium p-toluene sulfonate (CTAT) solutions has been studied under three different flow fields: simple shear, opposed-jets flow and porous media flow. Emphasis was placed in the experiments on a range of CTAT concentration in which wormlike micelles were formed. It is known that these solutions exhibit shear thickening in the semi-dilute regime, which has been explained in terms of the formation of shear-induced, cooperative structures involving wormlike micelles. In simple shear flow, the zero shear viscosity exhibits first an increase with salt addition followed by a decrease, while the critical shear rate for shear thickening increases sharply at low salt contents and tends to saturate at relatively high ionic strengths. The results are explained in terms of a competition between micellar growth induced by salt addition and changes in micellar flexibility caused by ionic screening effects. Dynamic light scattering results indicate that micelles grow rapidly upon salt addition but eventually achieve a constant size under static conditions. These observations suggest that the wormlike micelles continuously grow with salt addition, but, as they become more flexible due to electrostatic screening, the wormlike coils tend to adopt a more compact conformation. The trends observed in the apparent viscosities measured in porous media flows seem to confirm these hypotheses-but viscosity increases in the shear thickening region-and are magnified by micelle deformation induced by the elongational nature of the local flow in the pores. In opposed-jets flow, the solutions have a behavior that is close to Newtonian, which suggests that the range of strain rates employed makes the flow strong enough to destroy or prevent the formation of cooperative micellar structures. (c) 2006 Published by Elsevier Inc.
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