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Search Results: 1 - 10 of 637284 matches for " S?ren M?ller "
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Radial multipliers on amalgamated free products of II_1-factors
Sren Mller
Mathematics , 2013,
Abstract: Let $\mathcal{M}_i$ be a family of $\mathrm{II}_1$-factors, containing a common $\mathrm{II}_1$-subfactor $\mathcal{N}$, such that $[\mathcal{M}_i:\mathcal{N}] \in \mathbb{N}_0$ for all $i$. Furthermore, let $\phi \colon \mathbb{N}_0 \to \mathbb{C}$. We show that if a Hankel matrix related to $\phi$ is trace-class, then there exists a unique completely bounded map $M_\phi$ on the amalgamated free product of the $\mathcal{M}_i$ with amalgamation over $\mathcal{N}$, which acts as an radial multiplier. Hereby we extend a result of U. Haagerup and the author for radial multipliers on reduced free products of unital $C^*$- and von Neumann algebras.
The law of large numbers for the free multiplicative convolution
Uffe Haagerup,Sren Mller
Mathematics , 2012, DOI: 10.1007/978-3-642-39459-1_8
Abstract: In classical probability the law of large numbers for the multiplicative convolution follows directly from the law for the additive convolution. In free probability this is not the case. The free additive law was proved by D. Voiculescu in 1986 for probability measures with bounded support and extended to all probability measures with first moment by J. M. Lindsay and V. Pata in 1997, while the free multiplicative law was proved only recently by G. Tucci in 2010. In this paper we extend Tucci's result to measures with unbounded support while at the same time giving a more elementary proof for the case of bounded support. In contrast to the classical multiplicative convolution case, the limit measure for the free multiplicative law of large numbers is not a Dirac measure, unless the original measure is a Dirac measure. We also show that the mean value of \ln x is additive with respect to the free multiplicative convolution while the variance of \ln x is not in general additive. Furthermore we study the two parameter family (\mu_{\alpha,\beta})_{\alpha,\beta \ge 0} of measures on (0,\infty) for which the S-transform is given by S_{\mu_{\alpha,\beta}}(z) = (-z)^\beta (1+z)^{-\alpha}, 0 < z < 1.
Radial multipliers on reduced free products of operator algebras
Uffe Haagerup,Sren Mller
Mathematics , 2012, DOI: 10.1016/j.jfa.2012.08.008
Abstract: Let A_i be a family of unital C*-algebras, respectively, of von Neumann algebras and phi: N_0 \to C. We show that if a Hankel matrix related to phi is trace-class, then there exists a unique completely bounded map M_phi on the reduced free product of the A_i, which acts as an radial multiplier. Hereby we generalize a result of Wysocza\'nski for Herz-Schur multipliers on reduced group C*-algebras for free products of groups.
Effect of 1,25-dihydroxy-vitamin D3 in experimental sepsis
Sren Mller, Finn Laigaard, Klaus Olgaard, Claus Hemmingsen
International Journal of Medical Sciences , 2007,
Abstract: Background: In addition to the regulation of calcium homeostasis, vitamin D affects the cellular immune system, targets the TNF-α pathway and increases vasoconstrictor response to angiotensin II. We therefore examined the effect of 1,25-dihydroxy-vitamin D3 on coagulation and organ failure in experimental sepsis in the rat. Methods: Three series of placebo-controlled studies were conducted. All rats were pre-treated with daily SC injections of 1,25-dihydroxy-vitamin D3 100 ng/kg or placebo vehicle for 3 days. In study 1, sepsis was accomplished by abdominal surgery comprising a coecal ligation and puncture with a 1,2 mm needle, or sham surgery. In study 2, the rats had a single IP injection of lipopolysaccharide from E. Coli 0111:B4 (LPS) 8 mg/kg, or placebo. In study 3, an hour-long IV infusion of LPS 7 mg/kg, or placebo was given. Results: All three models of sepsis showed significant effects on coagulation and liver function with reduced thrombocyte count and prothrombin time together with elevated ALT and bilirubin (p<0.05) as compared to controls. In study 1, the vitamin D treated rats maintained normal platelet count, whereas the vehicle treated rats showed a significant reduction (p<0.05). This effect of vitamin D on platelets was not found in the LPS-treated groups. We found no significant differences between vitamin D and placebo-treated rats with regards to liver function. Conclusion: The present data suggest a positive modulating effect of 1,25-dihydroxy-vitamin D3 supplementation on sepsis-induced coagulation disturbances in the coecal ligation and puncture model. No such effect was found in LPS-induced sepsis.
Dynamic Quality Control for Transform Domain Wyner-Ziv Video Coding
Sören Sofke,Fernando Pereira,Erika Müller
EURASIP Journal on Image and Video Processing , 2009, DOI: 10.1155/2009/978581
Abstract: Wyner-Ziv is an emerging video coding paradigm based on the Slepian-Wolf and Wyner-Ziv theorems where video coding may be performed by exploiting the temporal correlation at the decoder and not anymore at the encoder as in conventional video coding. This approach should allow designing low-complexity encoders, targeting important emerging applications such as wireless surveillance and visual sensor networks, without any cost in terms of RD performance. However, the currently available WZ video codecs do not allow controlling the target quality in an efficient way which is a major limitation for some applications. In this context, the main objective of this paper is to propose an efficient quality control algorithm to maintain a uniform quality along time in low-encoding complexity WZ video coding by dynamically adapting the quantization parameters depending on the desired target quality without any a priori knowledge about the sequence characteristics. This objective will be reached in the context of the so-called Stanford WZ video codec architecture which is currently the most used in the literature.
Dynamic Quality Control for Transform Domain Wyner-Ziv Video Coding
Sofke Sren,Pereira Fernando,Müller Erika
EURASIP Journal on Image and Video Processing , 2009,
Abstract: Wyner-Ziv is an emerging video coding paradigm based on the Slepian-Wolf and Wyner-Ziv theorems where video coding may be performed by exploiting the temporal correlation at the decoder and not anymore at the encoder as in conventional video coding. This approach should allow designing low-complexity encoders, targeting important emerging applications such as wireless surveillance and visual sensor networks, without any cost in terms of RD performance. However, the currently available WZ video codecs do not allow controlling the target quality in an efficient way which is a major limitation for some applications. In this context, the main objective of this paper is to propose an efficient quality control algorithm to maintain a uniform quality along time in low-encoding complexity WZ video coding by dynamically adapting the quantization parameters depending on the desired target quality without any a priori knowledge about the sequence characteristics. This objective will be reached in the context of the so-called Stanford WZ video codec architecture which is currently the most used in the literature.
Wind Turbine Model and Observer in Takagi-Sugeno Model Structure
Sren Georg,Matthias Müller,Horst Schulte
Computer Science , 2014, DOI: 10.1088/1742-6596/555/1/012042
Abstract: Based on a reduced-order, dynamic nonlinear wind turbine model in Takagi-Sugeno (TS) model structure, a TS state observer is designed as a disturbance observer to estimate the unknown effective wind speed. The TS observer model is an exact representation of the underlying nonlinear model, obtained by means of the sector-nonlinearity approach. The observer gain matrices are obtained by means of a linear matrix inequality (LMI) design approach for optimal fuzzy control, where weighting matrices for the individual system states and outputs are included. The observer is tested in simulations with the aero-elastic code FAST for the NREL 5 MW reference turbine, where it shows a stable behaviour both for IEC wind gusts and turbulent wind input.
The Multiple Strategies of an Insect Herbivore to Overcome Plant Cyanogenic Glucoside Defence
Stefan Pentzold, Mika Zagrobelny, Pernille S?lvh?j Roelsgaard, Birger Lindberg Mller, Sren Bak
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0091337
Abstract: Cyanogenic glucosides (CNglcs) are widespread plant defence compounds that release toxic hydrogen cyanide by plant β-glucosidase activity after tissue damage. Specialised insect herbivores have evolved counter strategies and some sequester CNglcs, but the underlying mechanisms to keep CNglcs intact during feeding and digestion are unknown. We show that CNglc-sequestering Zygaena filipendulae larvae combine behavioural, morphological, physiological and biochemical strategies at different time points during feeding and digestion to avoid toxic hydrolysis of the CNglcs present in their Lotus food plant, i.e. cyanogenesis. We found that a high feeding rate limits the time for plant β-glucosidases to hydrolyse CNglcs. Larvae performed leaf-snipping, a minimal disruptive feeding mode that prevents mixing of plant β-glucosidases and CNglcs. Saliva extracts did not inhibit plant cyanogenesis. However, a highly alkaline midgut lumen inhibited the activity of ingested plant β-glucosidases significantly. Moreover, insect β-glucosidases from the saliva and gut tissue did not hydrolyse the CNglcs present in Lotus. The strategies disclosed may also be used by other insect species to overcome CNglc-based plant defence and to sequester these compounds intact.
A Scatter-Based Prototype Framework and Multi-Class Extension of Support Vector Machines
Robert Jenssen,Marius Kloft,Alexander Zien,Sren Sonnenburg,Klaus-Robert Müller
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0042947
Abstract: We provide a novel interpretation of the dual of support vector machines (SVMs) in terms of scatter with respect to class prototypes and their mean. As a key contribution, we extend this framework to multiple classes, providing a new joint Scatter SVM algorithm, at the level of its binary counterpart in the number of optimization variables. This enables us to implement computationally efficient solvers based on sequential minimal and chunking optimization. As a further contribution, the primal problem formulation is developed in terms of regularized risk minimization and the hinge loss, revealing the score function to be used in the actual classification of test patterns. We investigate Scatter SVM properties related to generalization ability, computational efficiency, sparsity and sensitivity maps, and report promising results.
454 pyrosequencing based transcriptome analysis of Zygaena filipendulae with focus on genes involved in biosynthesis of cyanogenic glucosides
Mika Zagrobelny, Karsten Scheibye-Alsing, Niels Jensen, Birger Mller, Jan Gorodkin, Sren Bak
BMC Genomics , 2009, DOI: 10.1186/1471-2164-10-574
Abstract: Comparisons of the Z. filipendulae transcriptome with the sequenced genomes of Bombyx mori, Drosophila melanogaster, Tribolium castaneum, Apis mellifera and Anopheles gambiae indicate a high coverage of the Z. filipendulae transcriptome. 11% of the Z. filipendulae transcriptome sequences were assigned to Gene Ontology categories. Candidate genes for enzymes functioning in the biosynthesis of cyanogenic glucosides (cytochrome P450 and family 1 glycosyltransferases) were identified based on sequence length, number of copies and presence/absence of close homologs in D. melanogaster, B. mori and the cyanogenic butterfly Heliconius. Examination of biased codon usage, GC content and selection on gene candidates support the notion of cyanogenesis as an "old" trait within Ditrysia, as well as its origins being convergent between plants and insects.Pyrosequencing is an attractive approach to gain access to genes in the biosynthesis of bio-active natural products from insects and other organisms, for which the genome sequence is not known. Based on analysis of the Z. filipendulae transcriptome, promising gene candidates for biosynthesis of cyanogenic glucosides was identified, and the suitability of Z. filipendulae as a model system for cyanogenesis in insects is evident.The advent of new sequencing technologies opens up the opportunity to engage in genomics in non-model organisms, and to study model systems aimed at specific interactions in a biological context. In this paper, we have taken a genomics approach to unravel co-adaptation within a plant-insect interaction at the molecular level, investigating the refined metabolic interactions between the six-spot burnet moth, Zygaena filipendulae, and its host plant bird's-foot trefoil, Lotus corniculatus.Plants and insects have co-evolved for the last ~400 million years. A key driving component in these interactions is the ability to produce and handle bioactive natural products. The dogma is that plants produce low molecular
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