783 research outputs found
Light third-generation squarks from flavour gauge messengers
We study models of gauge-mediated supersymmetry breaking with a gauged
horizontal SU(3)_F symmetry acting on the quark superfields. If SU(3)_F is
broken non-supersymmetrically by F-term vacuum expectation values, the massive
gauge bosons and gauginos become messengers for SUSY breaking mediation. These
gauge messenger fields induce a flavour-dependent, negative contribution to the
soft masses of the squarks at one loop. In combination with the soft terms from
standard gauge mediation, one obtains large and degenerate first- and
second-generation squark masses, while the stops and sbottoms are light. We
discuss the implications of this mechanism for the superparticle spectrum and
for flavour precision observables. We also provide an explicit realization in a
model with simultaneous SUSY and SU(3)_F breaking.Comment: 25 pages, 7 figure
Optimum Experimental Design for the Identification of Gaussian Disorder Mobility Parameters in Charge Transport Models of Organic Semiconductors
This thesis treats optimum experimental design for the parameter estimation problem
of mobility parameters in charge transport models of organic semiconductors. The
models consist of the van Roosbroeck system, a quasi-electrochemical potential
defining equation, and the Extended Gaussian Disorder Model and the Extended
Correlated Disorder Model both describing the mobility. The arising problems are
very ill-conditioned. The essential points of this work are:
âą The robust numerical solution of the model equations w.r.t. varying parameters,
control parameters, boundary values and initial guesses for iterative methods.
âą The computation of exact derivatives up to order two, which are necessary for
the optimum experimental design problem. This includes derivatives of the
model functions and implicitly given derivatives of the solution.
The Scharfetter-Gummel scheme is applied to the spatial discretization in one dimension,
whereas in two dimensions bilinear finite elements are used. The numerical
simulation of the discretized equations is done by a hybrid simulation method consisting
of Gummelâs method with a special, problem-adapted stabilization term, a
contraction based damping strategy, and a full step Newton method in the end for
quadratic convergence near the solution. These strategies are independent of the
spatial discretization and are applied to the simulation of a polymer nano-chain
attached to the cathode. The simulation of the one dimensional problems are used
for the optimum experimental design. The derivatives are computed with automatic
differentiation exactly up to machine precision. Therefor we use software tools for
the computation of the derivatives of the model functions and solve tangential and
adjoint equations of the problem for the parameters and control parameters. With
optimum experimental design we plan experiments for newest organic materials, like
NRS-PPV and a-NPD. The confidence region of the parameters are reduced by a
factor of 100 for NRS-PPV
The Drosophila blood-brain barrier: development and function of a glial endothelium
The efficacy of neuronal function requires a well-balanced extracellular ion homeostasis and a steady supply with nutrients and metabolites. Therefore, all organisms equipped with a complex nervous system developed a so-called blood-brain barrier, protecting it from an uncontrolled entry of solutes, metabolites or pathogens. In higher vertebrates, this diffusion barrier is established by polarized endothelial cells that form extensive tight junctions, whereas in lower vertebrates and invertebrates the blood-brain barrier is exclusively formed by glial cells. Here, we review the development and function of the glial blood-brain barrier of Drosophila melanogaster. In the Drosophila nervous system, at least seven morphologically distinct glial cell classes can be distinguished. Two of these glial classes form the blood-brain barrier. Perineurial glial cells participate in nutrient uptake and establish a first diffusion barrier. The subperineurial glial cells form septate junctions, which block paracellular diffusion and thus seal the nervous system from the hemolymph. We summarize the molecular basis of septate junction formation and address the different transport systems expressed by the blood-brain barrier forming glial cells
Temperature dependent study of the spin dynamics of coupled YFeO/GdFeO/Pt trilayers
In this study, we investigate the dynamic response of a YFeO
(YIG)/ GdFeO (GdIG)/ Pt trilayer system by measurements of the
ferromagnetic resonance (FMR) and the pumped spin current detected by the
inverse spin Hall effect. This trilayer system offers the unique opportunity to
investigate the spin dynamics of the ferrimagnetic GdIG, close to its
compensation temperature. We show that our trilayer acts as a highly tunable
spin current source. Our experimental results are supported by micro-magnetic
simulations. As the detected spin current in the top Pt layer is distinctly
dominated by the GdIG layer, this gives the unique opportunity to investigate
the excitation and dynamic properties of GdIG while comparing it to the
broadband FMR absorption spectrum of the heterostructure
Oxygenation effect of interventional lung assist in a lavage model of acute lung injury: a prospective experimental study
INTRODUCTION: The aim of the study was to test the hypothesis that a pumpless arteriovenous extracorporeal membrane oxygenator (interventional lung assist (ILA)) does not significantly improve oxygenation in a lavage model of acute lung injury. METHODS: The study was designed as a prospective experimental study. The experiments were performed on seven pigs (48â60 kg body weight). The pigs were anesthetized and mechanically ventilated. Both femoral arteries and one femoral vein were cannulated and connected with ILA. Acute lung injury was induced by repeated bronchoalveolar lavage until the arterial partial pressure of O(2 )was lower than 100 Torr for at least 30 minutes during ventilation with 100% O(2). RESULTS: ILA was applied with different blood flow rates through either one or both femoral arteries. Measurements were repeated at different degrees of pulmonary gas exchange impairment with the pulmonary venous admixture ranging from 35.0% to 70.6%. The mean (± standard deviation) blood flow through ILA was 15.5 (± 3.9)% and 21.7 (± 4.9)% of cardiac output with one and both arteries open, respectively. ILA significantly increased the arterial partial pressure of O(2 )from 64 (± 13) Torr to 71 (± 14) Torr and 74 (± 17) Torr with blood flow through one and both femoral arteries, respectively. O(2 )delivery through ILA increased with extracorporeal shunt flow (36 (± 14) ml O(2)/min versus 47 (± 17) ml O(2)/min) and reduced arterialization of the inlet blood. Pulmonary artery pressures were significantly reduced when ILA was in operation. CONCLUSION: Oxygenation is increased by ILA in severe lung injury. This effect is significant but small. The results indicate that the ILA use may not be justified if the improvement of oxygenation is the primary therapy goal
Agronomic performance of interspecific Paspalum hybrids under nitrogen fertilization or mixed with legumes
Nitrogen supply and mixtures with legumes affect agronomic performance of pas- tures, and both practices can guide breeding decisions in Paspalum hybrids. The goals of this study were: (a) quantify herbage accumulation (HA), leaf accumulation (LA), cold tolerance, and N use efficiency (NUE) in P. plicatulum Ă P. guenoarum hybrids subjected to N fertilization or grown in a mixture with legumes; (b) compare the grassâlegume system to a grassâN fertilizer system; and (c) select the best hybrid for future cultivar releases. A randomized complete block design with three repli- cations and a split-plot treatment arrangement was used for 2 yr, with five N rates (0, 60, 120, 240, and 480 kg N haâ1) and a grassâlegume mixture [grass + white clover (Trifolium repens L.) + birdsfoot trefoil (Lotus corniculatus L.)] as whole plots, and six genotypes as subplots (hybrids: 1020133, 102069, 103084, 103061; and controls: P. guenoarum âAzulĂŁoâ and Megathyrsus maximus âAruanaâ). Higher N rates increased HA, LA, and cold tolerance. Higher NUE was obtained between 60 and 120 kg N haâ1. In the grassâlegume mixture HA was similar to the rates of 60 and 120 kg N haâ1. Hybrid 1020133 had HA similar to the controls, LA greater than Aruana, and greater cold tolerance and NUE at 60 kg N haâ1 than AzulĂŁo and Aruana. Hybrid 1020133 should be selected for further animal performance stud- ies. The agronomic performance of perennial pastures can be improved through N management, and NUE should be a selection criterion in forage breeding
COI1-dependent jasmonate signalling affects growth, metabolites production and cell wall protein composition in Arabidopsis
Background and Aims:
Cultured cell suspensions have been the preferred model to study the apoplast as well as to monitor metabolic and cell cycle-related changes. Previous work showed that methyl jasmonate (MeJA) inhibits leaf growth in a CORONATINE INSENSITIVE 1 (COI1)-dependent manner, with COI1 being the jasmonate (JA) receptor. Here, the effect of COI1 overexpression on the growth of stably transformed arabidopsis cell cultures is described.
Methods:
Time-course experiments were carried out to analyse gene expression, and protein and metabolite levels.
Key Results:
Both MeJA treatment and the overexpression of COI1 modify growth, by altering cell proliferation and expansion. DNA content as well as transcript patterns of cell cycle and cell wall remodelling markers were altered. COI1 overexpression also increases the protein levels of OLIGOGALACTURONIDE OXIDASE 1, BETA-GLUCOSIDASE/ENDOGLUCANASES and POLYGALACTURONASE INHIBITING PROTEIN2, reinforcing the role of COI1 in mediating defence responses and highlighting a link between cell wall loosening and growth regulation. Moreover, changes in the levels of the primary metabolites alanine, serine and succinic acid of MeJA-treated Arabidopsis cell cultures were observed. In addition, COI1 overexpression positively affects the availability of metabolites such as ÎČ-alanine, threonic acid, putrescine, glucose and myo-inositol, thereby providing a connection between JA-inhibited growth and stress responses.
Conclusions:
This study contributes to the understanding of the regulation of growth and the production of metabolic resources by JAs and COI1. This will have important implications in dissecting the complex relationships between hormonal and cell wall signalling in plants. The work also provides tools to uncover novel mechanisms co-ordinating cell division and post-mitotic cell expansion in the absence of organ developmental control
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