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Numbers and space are two semantic primitives that interact with each other. Both recruit brain regions along the dorsal pathway, notably parietal cortex. This makes parietal cortex a candidate for the origin of numerical–spatial interaction. The underlying cognitive architecture of the interaction is still under scrutiny. Two classes of explanations can be distinguished. The early interaction approach assumes that numerical and spatial information are integrated into a single representation at a semantic level. A second approach postulates independent semantic representations. Only at the stage of response selection and preparation these two streams interact. In this study we used a numerical landmark task to identify the locus of the interaction between numbers and space. While lying in an MR scanner participants decided on the smaller of two numerical intervals in a visually presented number triplet. The spatial position of the middle number was varied; hence spatial intervals were congruent or incongruent with the numerical intervals. Responses in incongruent trials were slower and less accurate than in congruent trials. By combining across-vertex correlations (micro pattern) with a cluster analysis (macro pattern) we identified large-scale networks that were devoted to number processing, eye movements, and sensory–motor functions. Using support vector classification in different regions of interest along the intraparietal sulcus, the frontal eye fields, and supplementary motor area we were able to distinguish between congruent and incongruent trials in each of the networks. We suggest that the identified networks participate in the integration of numerical and spatial information and that the exclusive assumption of either an early or a late interaction between numerical and spatial information does not do justice to the complex interaction between both dimensions.
Sphingosine kinases (SK) catalyze the phosphorylation of proapoptotic sphingosine to the prosurvival factor sphingosine 1-phosphate (S1P), thereby promoting oncogenic processes. Breast (MDA-MB-231), lung (NCI-H358), and colon (HCT 116) carcinoma cells were transduced with shRNA to downregulate SK-1 expression or treated with a pharmacologic SK-1 inhibitor. The effects of SK-1 targeting were investigated by measuring the level of intracellular sphingosine, the activity of protein kinase C (PKC) and cell cycle regulators, and the mitotic index. Functional assays included measurement of cell proliferation, colony formation, apoptosis, and cell cycle analysis. Downregulation of SK-1 or its pharmacologic inhibition increased intracellular sphingosine and decreased PKC activity as shown by reduced phosphorylation of PKC substrates. In MDA-MB-231 cells this effect was most pronounced and reduced cell proliferation and colony formation, which could be mimicked using exogenous sphingosine or the PKC inhibitor RO 31-8220. SK-1 downregulation in MDA-MB-231 cells increased the number of cells with 4N and 8N DNA content, and similar effects were observed upon treatment with sphingosine or inhibitors of SK-1 or PKC. Examination of cell cycle regulators unveiled decreased cdc2 activity and expression of Chk1, which may compromise spindle checkpoint function and cytokinesis. Indeed, SK-1 kd cells entered mitosis but failed to divide, and in the presence of taxol also failed to sustain mitotic arrest, resulting in further increased endoreduplication and apoptosis. Our findings delineate an intriguing link between SK-1, PKC and components of the cell cycle machinery, which underlines the significance of SK-1 as a target for cancer therapy.
The experiments presented in my thesis were performed to resolve the following major questions: i. Initial experiments are based on the systematic characterization of the C-terminal domains of all 21 HSFs of Arabidopsis with respect to their transactivation potential as well as intracellular localization. This led to the identification of a signature motif for class A HSFs, that consists of an AHA motif (essential for activator potential), and a C-treminal NES (nuclear export signal). With this signature motif, we could identify homologues sequences of more than 90 HSFs in various plant species. ii. Analysis of developmental expression profiles of HSFs using AtGenExpress microarray data led to the identification of the unique expression of HsfA9 during late seed developmental stages. This was the starting point for the investigation of the regulation of HsfA9 as well as its function during seed development. iii. The seed specific transcription factor ABI3 was identified to be responsible for the regulation of HsfA9 by using knock out mutant lines and ectopically expressing transgenic lines for ABI3 gene. Furthermore, the importance of a RY/Sph motif, as binding site for ABI3 on HsfA9 promoter has been analyzed with transient GUS reporter assays. In addition, contribution of component(s) of ABA (abscisic acid) signaling cascade as a functional interacting partner of ABI3 on HsfA9 promoter has been shown and discussed. iv. The essential role of HsfA9 as master regulator for the expression of seed specific members of of HSP encoding genes and GolS1 was shown by analyzing transgenic plants ectopically expressing HsfA9 as well as, by carrying out transient GUS reporter assays. Correlating with this, transgenic plants with ectopic expression of HsfA9 showed a thermotolerent phenotype. Furthermore, a model where HsfA9 plays a key function for the regulation of seed expressed genes which might involved in providing dessication tolerance during seed maturation has been proposed.
The recently published experimental dependence of the J/psi suppression pattern in Pb+Pb collisions at the CERN SPS on the energy of zero degree calorimeter EZDC are analyzed. It is found that the data obtained within the minimum bias analysis (using theoretical Drell-Yan ) are at variance with the previously published experimental dependence of the same quantity on the transversal energy of neutral hadrons ET . The discrepancy is related to the moderate centrality region: 100 << Np << 200 (Np is the number of nucleon participants). This could result from systematic experimental errors in the minimum bias sample. A possible source of the errors may be contamination of the minimum bias sample by o -target interactions. The data obtained within the standard analysis (using measured Drell-Yan multiplicity) are found to be much less sensitive to the contamination.
The study of hidden charm production is an important part of the heavy ion program. The standard approach to this problem [1] assumes that c¯c bound states are created only at the initial stage of the reaction and then partially destroyed at later stages due to interactions with the medium [2, 3, 4].
Production of J/ψ mesons in heavy ion collisions is considered within the statistical coalescence model. The model is in agreement with the experimental data of the NA50 Collaboration for Pb+Pb collisions at 158 AGeV in a wide centrality range, including the so-called “anomalous” suppression domain. The model description of the J/ψ data requires, however, strong enhancement of the open charm production in central Pb+Pb collisions. This model prediction may be checked in the future SPS runs.
The quantum mechanical formula for Mayer s second cluster integral for the gas of relativistic particles with hard-core interaction is derived. The proper pion volume calculated with quantum mechanical formula is found to be an order of magnitude larger than its classical evaluation. The second cluster integral for the pion gas is calculated in quantum mechanical approach with account for both attractive and hard-core repulsive interactions. It is shown that, in the second cluster approximation, the repulsive -interactions as well as the finite width of resonances give important but almost canceling contributions. In contrast, an appreciable deviation from the ideal gas of pions and pion resonances is observed beyond the second clus- ter approximation in the framework of the Van der Waals excluded-volume model.
The equation of state for the pion gas is analyzed within the third virial approximation. The second virial coeffcient is found from the pi pi -scattering data, while the third one is considered as a free parameter. The proposed model leads to a first-order phase transition from the pion gas to a more dense phase at the temperature Tpt < 136 MeV. Due to relatively low temperature this phase transition cannot be related to the deconfinement. This suggests that a new phase of hadron matter hot pion liquid may exist.
The high E(T) drop of J / psi to Drell-Yan ratio from the statistical c anti-c coalescence model
(2002)
The dependence of the J/psi yield on the transverse energy ET in heavy ion collisions is considered within the statistical c¯c coalescence model. The model fits the NA50 data for Pb+Pb collisions at the CERN SPS even in the high-ET region (ET >< 100 GeV). Here ET -fluctuations and ET -losses in the dimuon event sample naturally create the celebrated drop in the J/psi to Drell-Yan ratio.