@article{2741, abstract = {The Pauli operator describes the energy of a nonrelativistic quantum particle with spin 1/2 in a magnetic field and an external potential. A new Lieb-Thirring type inequality on the sum of the negative eigenvalues is presented. The main feature compared to earlier results is that in the large field regime the present estimate grows with the optimal (first) power of the strength of the magnetic field. As a byproduct of the method, we also obtain an optimal upper bound on the pointwise density of zero energy eigenfunctions of the Dirac operator. The main technical tools are: (i) a new localization scheme for the square of the resolvent of a general class of second order elliptic operators; (ii) a geometric construction of a Dirac operator with a constant magnetic field that approximates the original Dirac operator in a tubular neighborhood of a fixed field line. The errors may depend on the regularity of the magnetic field but they are uniform in the field strength.}, author = {László Erdös and Solovej, Jan P}, journal = {Annales Henri Poincare}, number = {4}, pages = {671 -- 741}, publisher = {Birkhäuser}, title = {{Uniform Lieb-Thirring inequality for the three-dimensional Pauli operator with a strong non-homogeneous magnetic field}}, doi = {10.1007/s00023-004-0180-x}, volume = {5}, year = {2004}, } @article{2742, abstract = {We consider a system of N weakly interacting fermions with a real analytic pair interaction. We prove that for a general class of initial data there exists a fixed time T such that the difference between the one particle density matrix of this system and the solution of the nonlinear Hartree equation is of order N−1 for any time t⩽T.}, author = {Elgart, Alexander and László Erdös and Schlein, Benjamin and Yau, Horng-Tzer}, journal = {Journal de Mathématiques Pures et Appliquées}, number = {10}, pages = {1241 -- 1273}, publisher = {Elsevier}, title = {{Nonlinear Hartree equation as the mean field limit of weakly coupled fermions}}, doi = {10.1016/j.matpur.2004.03.006}, volume = {83}, year = {2004}, } @article{2787, abstract = {The results of experimental and numerical investigations of the onset of oscillatory convection in a sidewall heated rectangular cavity of molten gallium are reported. Detailed comparisons are made between experimental observations and calculations from numerical simulations of a three-dimensional Boussinesq model. The onset of time-dependence takes place through supercritical Hopf bifurcations and the loci of critical points in the (Gr, Pr)-plane are qualitatively similar with excellent agreement between the frequencies of the oscillatory motion. This provides a severe test of the control of the experiment since the mode of oscillation is extremely sensitive to imperfections. Detailed numerical investigations reveal that there are a pair of Hopf bifurcations which exist on two asymmetric states which themselves arise at a subcritical pitchfork from the symmetric state. There is no evidence for this in the experiment and this qualitative difference is attributed to non-Boussinesq perturbations which increase with Gr. However, the antisymmetric spatial structure of the oscillatory state is robust and is present in both the experiment and the numerical model. Moreover, the detailed analysis of the numerical results reveals the origins of the oscillatory instability.}, author = {Björn Hof and Juel, Anne and Zhao, Li and Henry, Daniel and Ben Hadid, Hamda and Mullin, Tom P}, journal = {Journal of Fluid Mechanics}, pages = {391 -- 413}, publisher = {Cambridge University Press}, title = {{On the onset of oscillatory convection in molten gallium}}, doi = {10.1017/S0022112004000527}, volume = {515}, year = {2004}, } @article{2786, abstract = {Transition to turbulence in pipe flow is one of the most fundamental and longest- standing problems in fluid dynamics. Stability theory suggests that the flow remains laminar for all flow rates, but in practice pipe flow becomes turbulent even at moderate speeds. This transition drastically affects the transport efficiency of mass, momentum, and heat. On the basis of the recent discovery of unstable traveling waves in computational studies of the Navier-Stokes equations and ideas from dynamical systems theory, a model for the transition process has been suggested. We report experimental observation of these traveling waves in pipe flow, confirming the proposed transition scenario and suggesting that the dynamics associated with these unstable states may indeed capture the nature of fluid turbulence.}, author = {Björn Hof and van Doorne, Casimir W and Westerweel, Jerry and Nieuwstadt, Frans T and Faisst, Holger and Eckhardt, Bruno and Wedin, Håkan and Kersweli, Richard R and Waleffe, Fabian}, journal = {Science}, number = {5690}, pages = {1594 -- 1598}, publisher = {American Association for the Advancement of Science}, title = {{Experimental observation of nonlinear traveling waves in turbulent pipe flow}}, doi = {10.1126/science.1100393}, volume = {305}, year = {2004}, } @article{2998, abstract = {The packaging of the genomic DNA into chromatin in the cell nucleus requires machineries that facilitate DNA-dependent processes such as transcription in the presence of repressive chromatin structures. Using co-immunoprecipitation we have identified in Arabidopsis thaliana cells the FAcilitates Chromatin Transcription (FACT) complex, consisting of the 120-kDa Spt16 and the 71-kDa SSRP1 proteins. Indirect immunofluorecence analyses revealed that both FACT subunits co-localize to nuclei of the majority of cell types in embryos, shoots and roots, whereas FACT is not present in terminally differentiated cells such as mature trichoblasts or cells of the root cap. In the nucleus, Spt16 and SSRP1 are found in the cytologically defined euchromatin of interphase cells independent of the status of DNA replication, but the proteins are not associated with heterochromatic chromocentres and condensed mitotic chromosomes. FACT can be detected by chromatin immunoprecipitation over the entire transcribed region (5′-UTR, coding sequence, 3′-UTR) of actively transcribed genes, whereas it does not occur at transcriptionally inactive heterochromatic regions and intergenic regions. FACT localizes to inducible genes only after induction of transcription, and the association of the complex with the genes correlates with the level of transcription. Collectively, these results indicate that FACT assists transcription elongation through plant chromatin.}, author = {Duroux, Meg and Houben, Andreas and Růžička, Kamil and Jirí Friml and Grasser, Klaus D}, journal = {Plant Journal}, number = {5}, pages = {660 -- 671}, publisher = {Wiley-Blackwell}, title = {{The chromatin remodelling complex FACT associates with actively transcribed regions of the Arabidopsis genome}}, doi = {10.1111/j.1365-313X.2004.02242.x}, volume = {40}, year = {2004}, } @article{2997, abstract = {Polar transport-dependent local accumulation of auxin provides positional cues for multiple plant patterning processes. This directional auxin flow depends on the polar subcellular localization of the PIN auxin efflux regulators. Overexpression of the PINOID protein kinase induces a basal-to-apical shift in PIN localization, resulting in the loss of auxin gradients and strong defects in embryo and seedling roots. Conversely, pid loss of function induces an apical-to-basal shift in PIN1 polar targeting at the inflorescence apex, accompanied by defective organogenesis. Our results show that a PINOID-dependent binary switch controls PIN polarity and mediates changes in auxin flow to create local gradients for patterning processes.}, author = {Jirí Friml and Yang, Xiong and Michniewicz, Marta and Weijers, Dolf and Quint, Ab and Tietz, Olaf and Benjamins, René and Ouwerkerk, Pieter B and Ljung, Karin and Sandberg, Göran and Hooykaas, Paul J and Palme, Klaus and Offringa, Remko}, journal = {Science}, number = {5697}, pages = {862 -- 865}, publisher = {American Association for the Advancement of Science}, title = {{A PINOID-dependent binary switch in apical-basal PIN polar targeting directs auxin efflux}}, doi = {10.1126/science.1100618}, volume = {306}, year = {2004}, } @article{2999, abstract = {Embryogenesis of flowering plants establishes a basic body plan with apical-basal, radial and bilateral patterns from the single-celled zygote. Arabidopsis embryogenesis exhibits a nearly invariant cell division pattern and therefore is an ideal system for studies of early plant development. However, plant embryos are difficult to access for experimental manipulation, as they develop deeply inside maternal tissues. Here we present a method for the culture of zygotic Arabidopsis embryos in vitro. The technique omits excision of the embryo by culturing the entire ovule, thus greatly facilitating the time and effort involved. It enables external manipulation of embryo development and culture from the earliest developmental stages up to maturity. Administration of various chemical treatments as well as the use of different molecular markers is demonstrated together with standard techniques for visualizing gene expression and protein localization in in vitro cultivated embryos. The presented set of techniques allows for so far unavailable molecular physiology approaches in the study of early plant development.}, author = {Sauer, Michael and Jirí Friml}, journal = {Plant Journal}, number = {5}, pages = {835 -- 843}, publisher = {Wiley-Blackwell}, title = {{In vitro culture of Arabidopsis embryos within their ovules}}, doi = {10.1111/j.1365-313X.2004.02248.x}, volume = {40}, year = {2004}, } @inproceedings{3208, abstract = {A new technique for proving the adaptive indistinguishability of two systems, each composed of some component systems, is presented, using only the fact that corresponding component systems are non-adaptively indistinguishable. The main tool is the definition of a special monotone condition for a random system F, relative to another random system G, whose probability of occurring for a given distinguisher D is closely related to the distinguishing advantage ε of D for F and G, namely it is lower and upper bounded by ε and (1+ln1), respectively. A concrete instantiation of this result shows that the cascade of two random permutations (with the second one inverted) is indistinguishable from a uniform random permutation by adaptive distinguishers which may query the system from both sides, assuming the components’ security only against non-adaptive one-sided distinguishers. As applications we provide some results in various fields as almost k-wise independent probability spaces, decorrelation theory and computational indistinguishability (i.e., pseudo-randomness).}, author = {Maurer, Ueli M and Krzysztof Pietrzak}, pages = {410 -- 427}, publisher = {Springer}, title = {{Composition of random systems: When two weak make one strong}}, doi = {10.1007/978-3-540-24638-1_23}, volume = {2951}, year = {2004}, } @inbook{3587, author = {Ulrich, Florian and Heisenberg, Carl-Philipp J}, booktitle = {Fish development and genetics : the zebrafish and medaka models}, editor = {Korzh, Vladimir and Gong, Zhiyuan}, pages = {39 -- 86}, publisher = {World Scientific Publishing}, title = {{Gastrulation in zebrafish}}, volume = {2}, year = {2004}, } @article{3617, abstract = {The coalescent process can describe the effects of selection at linked loci only if selection is so strong that genotype frequencies evolve deterministically. Here, we develop methods proposed by Kaplan, Darden, and Hudson to find the effects of weak selection. We show that the overall effect is given by an extension to Price's equation: the change in properties such as moments of coalescence times is equal to the covariance between those properties and the fitness of the sample of genes. The distribution of coalescence times differs substantially between allelic classes, even in the absence of selection. However, the average coalescence time between randomly chosen genes is insensitive to the current allele frequency and is affected significantly by purifying selection only if deleterious mutations are common and selection is strong (i.e., the product of population size and selection coefficient, Ns > 3). Balancing selection increases mean coalescence times, but the effect becomes large only when mutation rates between allelic classes are low and when selection is extremely strong. Our analysis supports previous simulations that show that selection has surprisingly little effect on genealogies. Moreover, small fluctuations in allele frequency due to random drift can greatly reduce any such effects. This will make it difficult to detect the action of selection from neutral variation alone.}, author = {Nicholas Barton and Etheridge, Alison M}, journal = {Genetics}, number = {2}, pages = {1115 -- 1131}, publisher = {Genetics Society of America}, title = {{The effect of selection on genealogies}}, doi = {10.1534/genetics.166.2.1115}, volume = {166}, year = {2004}, }