Two genes involved in trichome morphogenesis: Localisation and putative function of STI and At-CLASP in A. thaliana.

Within the scope of this thesis two proteins were analysed whose mutant phenotype affects the branching of trichomes. at-clasp mutant plants posses unbranched trichomes and the strength of the phenotype depends on the allele used. Sterility is observed in the strongest alleles. Furthermore it was shown that the at-clasp mutant phenotype is temperature dependant. Growth conditions with temperatures up to 16°C are permissive for normal growth of all alleles. To determine the localisation of At-CLASP, fusions to fluorescent proteins were constructed. It was shown that At-CLASP is localised to microtubules. Contrary to the data from H. sapiens, At-CLASP localisation was not restricted to the +end of microtubules but marks filaments almost entirely. To understand the binding properties of At-CLASP to microtubules, it was dissected into two fragments. The C-terminal region of the protein was localised to the cell-cortex or the plasma membrane. In contrast, the N-terminal region was sufficient to mediate the binding to microtubules as this fragment was hardly distinguishable from the entire protein. Despite the altered localisation of At-CLASP compared to H. sapiens CLASP, several orthologs of H. sapiens CLASP interaction partners were identified in the A. thaliana genome. These putative A. thaliana binding partners were tested for interaction with At-CLASP in direct Yeast-Two-Hybrid experiments. However, no interactions were detected. One postulated function of CLASP from H. sapiens is the stabilisation of subsets of microtubules. To test a similar function of the A. thaliana protein, the rescue of the tfc-a mutant under an increased dosage of At-CLASP was analysed. Preliminary results suggest that a stabilizing function of At-CLASP might be evolutionary retained. Trichomes of strong stichel alleles are completely unbranched. To improve the understanding of STI function plants expressing GFP:STI fusions were analysed further. GFP:STI fusion proteins mark the tip of emerging trichomes. As soon as a trichomes becomes visible by means of morphological criteria, GFP:STI can be detected in the tip of trichomes. Trichomes that initiate the second branch showed GFP:STI signal even before the branch was visible. Plasmolysis experiments demonstrated that GFP:STI is likely localised to the plasma membrane. In order to get a closer insight into which part of the STI protein is responsible for its specific localization, fragments were analysed for showing a comparable localisation pattern. Fusions of parts of the STI protein with YFP could not reveal the likely present motif for the described localisation. Nevertheless one longer fragment S1/AS3 and one shorter fragment S3/AS3 showed a strong dominant negative effect when overexpressed in wild-type. To increase the understanding about the molecular function of STI, possible binding partners of GFP:STI were identified by an immunoprecipitation assay. Phospholipase Dα1 and one transcription factor of the MADS-box family were identified as candidates for interaction with STI. A. thaliana contains one gene (STI-HOM) which is very similar to STI. To test whether STI-HOM fulfils a comparable a role in trichome development T-DNA mutants were analysed. None of them showed a trichome phenotype. The analysis of a sti sti-hom double-mutant situation revealed no change in the sti mutant trichome phenotype. Promoter swapping experiments were performed to test whether both proteins are functionally exchangeable. However STI-HOM was not able to rescue the sti mutant trichome phenotype. Therefore STI and STI-HOM are likely functionally distinct

Bildungsforschung ohne kritische Theorie der Bildung? Ein Gutachten von Theodor W. Adorno zur Gründung eines (Max-Planck)„Instituts für Recht, Soziologie und Ökonomie der Bildung“ aus dem Jahre 1961

Der Autor kommentiert das Gutachten von Adorno zur Gründung des Max-Planck-Instituts für Bildungsforschung in Berlin. „Das Gutachten bietet eine willkommene Gelegenheit, sich angesichts des heute vorherrschenden mainstream von ‚Bildungsforschung‘ - und in PISA-Zeiten von ‚empirischer‘ zumal - noch einmal zu vergegenwärtigen, was der Anspruch von Bildungsforschung im Lichte der Kritischen Theorie der Bildung zu sein hätte. Es geht um das Problem der Verdinglichung, vor dem Adorno gewarnt hatte. Wenn Bildung (im Sinne des Wortes) festgestellt wird - als Bildungsgut, das erworben und besessen werden kann –, dann lassen sich definierte Bildungsprodukte messen und vergleichen, und wer dem aufsitzt, als was sie sich in Sachen ‚Bildung‘ ausgeben, ist ihrer Selbstideologisierung schon aufgesessen. Eben dies wollte Becker vermieden sehen.“ (DIPF/Orig.

Theoretical Interpretation of Low-Mass Dileptons

An overview is given of chiral symmetry restoration at finite temperature and baryochemical potential. Within hadronic models of the vector correlator its implications for low-mass dilepton spectra in ultrarelativistic heavy-ion collisions are discussed.Comment: 12 pages LaTeX, incl. 12 ps-/eps-figures and espcrc1.st

e+e−e^+e^- production in pAp A reactions at SIS energies

Detailed predictions for dilepton production from $p A$ reactions at SIS energies are presented within a semi-classical BUU transport model that includes the off-shell propagation of vector mesons nonperturbatively and calculates the width of the vector mesons dynamically. Different scenarios of in-medium modifications of vector mesons, such as collisional broadening and dropping vector meson masses, are investigated and the possibilities for an experimental observation of in-medium effects in $p A$ reactions at 1--4 GeV are discussed for a variety of nuclear targets.Comment: 38 pages, LaTeX, including 20 postscript figures, to be published in Nucl. Phys.

Carbon Nanotube Network Ambipolar Field-Effect Transistors with 10(8) On/Off Ratio

Polymer wrapping is a highly effective method of selecting semiconducting carbon nanotubes and dispersing them in solution. Semi-aligned semiconducting carbon nanotube networks are obtained by blade coating, an effective and scalable process. The field-effect transistor (FET) performance can be tuned by the choice of wrapping polymer, and the polymer concentration modifies the FET transport characteristics, leading to a record on/off ratio of 108

The ρ\rho Spectral Function in a Relativistic Resonance Model

We calculate the spectral function $A_\rho$ of the $\rho$ meson in nuclear matter. The calculation is performed in the {\it low density} approximation, where the in-medium self energy $\Sigma_{med}$ is completely determined by the vacuum $\rho N$ forward scattering amplitude. This amplitude is derived from a relativistic resonance model. In comparison to previous non-relativistic calculations we find a much weaker momentum dependence of $\Sigma_{med}$, especially in the transverse channel. Special attention is paid to uncertainties in the model. Thus, we compare the impact of different coupling schemes for the $RN\rho$ interaction on the results and discuss various resonance parameter sets.Comment: 47 pages, 19 figures, some discussion and formulae added, minor typos removed, accepted for publication in Nuclear Physics

Dilepton Production from AGS to SPS Energies within a Relativistic Transport Approach

We present a nonperturbative dynamical study of $e^+e^-$ production in proton-nucleus and nucleus-nucleus collisions from AGS to SPS energies on the basis of the covariant transport approach HSD. For p + Be reactions the dilepton yield for invariant masses $M \leq 1.4$ GeV is found to be dominated by the decays of the $\eta, \rho, \omega$ and $\Phi$ mesons at all energies from 10 -- 450 GeV. For nucleus-nucleus collisions, however, the dilepton yield shows an additional large contribution from $\pi^+\pi^-$, $K^+K^-$ and $\pi \rho$ channels. Systematic studies are presented for the 'free' meson mass scenario in comparison to a 'dropping' meson mass scenario at finite baryon density. We find that for 'dropping' meson masses the invariant dilepton mass range 0.35 GeV $\leq M \leq$ 0.65 GeV is increased in comparison to the 'free' meson mass scenario and that the data of the CERES-collaboration for nucleus-nucleus collisions can be described much better within the 'dropping' mass scheme. We study in detail the contributions from the various dilepton channels as a function of the transverse momentum and rapidity of the lepton pair as well as a function of the charged particle multiplicity. Furthermore, various direct photon channels for S + Au at 200 GeV/u are computed and found to be well below the upper bounds measured by the WA80-collaboration.Comment: 38 pages, LaTeX, including 19 postscript figures, to appear in Nucl. Phys.

Perspectives of e+e−e^+e^- production in pp, pd and p Be reactions at SIS energies

We study dilepton production from pp, pd and p Be collisions from 1 - 5 GeV including the $\pi^0$, $\eta$, $\omega$ and $\Delta$ Dalitz decays, direct decays of vector mesons ($\rho$, $\omega$) as well as subthreshold $\rho$ production via baryonic resonances (e.g. $D_{13}(1520), P_{11}(1710)$). Our calculations compare rather well with the pp and pd data from the DLS Collaboration, however, overestimate slightly the 'old' p Be data from that group. Futhermore, detailed predictions for differential dilepton spectra at SIS energies are made with a high mass resolution that can be controlled experimentally by the HADES Collaboration in near future.Comment: 27 pages, LaTeX, including 13 postscript figures, to be published in Nucl. Phys.

e^+e^- production from pp reactions at BEVALAC energies

We have performed a detailed study of dilepton production from pp collisions including the subthreshold $\rho$ production via baryonic resonances (N(1520), N(1700)) in addition to the conventional dilepton sources as $\pi^0, \eta, \omega$ and $\Delta$ Dalitz decays and direct decays of vector mesons ($\rho, \omega$). The role of baryonic resonances in $\rho$ production from nucleon-nucleon collisions is studied in comparison to the DLS data which are well described.Comment: 19 pages, revtex, including 7 postscript figures, to be published in Nucl. Phys.