@article{2684, abstract = {Calcium-activated potassium channels have been shown to be critically involved in neuronal function, but an elucidation of their detailed roles awaits identification of the microdomains where they are located. This study was undertaken to unravel the precise subcellular distribution of the large-conductance calcium-activated potassium channels (called BK, KCa1.1, or Slo1) in the somatodendritic compartment of cerebellar Purkinje cells by means of postembedding immunogold cytochemistry and SDS-digested freeze-fracture replica labeling (SDS-FRL). We found BK channels to be unevenly distributed over the Purkinje cell plasma membrane. At distal dendritic compartments, BK channels were scattered over the plasma membrane of dendritic shafts and spines but absent from postsynaptic densities. At the soma and proximal dendrites, BK channels formed two distinct pools. One pool was scattered over the plasma membrane, whereas the other pool was clustered in plasma membrane domains overlying subsurface cisterns. The labeling density ratio of clustered to scattered channels was about 60:1, established in SDS-FRL. Subsurface cisterns, also called hypolemmal cisterns, are subcompartments of the endoplasmic reticulum likely representing calciosomes that unload and refill Ca2+ independently. Purkinje cell subsurface cisterns are enriched in inositol 1,4,5-triphosphate receptors that mediate the effects of several neurotransmitters, hormones, and growth factors by releasing Ca2+ into the cytosol, generating local Ca2+ sparks. Such increases in cytosolic [Ca2+] may be sufficient for BK channel activation. Clustered BK channels in the plasma membrane may thus participate in building a functional unit (plasmerosome) with the underlying calciosome that contributes significantly to local signaling in Purkinje cells.}, author = {Walter Kaufmann and Ferraguti, Francesco and Fukazawa, Yugo and Kasugai, Yu and Ryuichi Shigemoto and Laake, Petter and Sexton, Joseph A and Ruth, Peter and Wietzorrek, Georg and Knaus, Hans G and Storm, Johan F and Ottersen, Ole P}, journal = {Journal of Comparative Neurology}, number = {2}, pages = {215 -- 230}, publisher = {Wiley-Blackwell}, title = {{Large-conductance calcium-activated potassium channels in Purkinje cell plasma membranes are clustered at sites of hypolemmal microdomains}}, doi = {10.1002/cne.22066}, volume = {515}, year = {2009}, } @article{2685, abstract = {Conduction velocity (CV) of myelinated axons has been shown to be regulated by oligodendrocytes even after myelination has been completed. However, how myelinating oligodendrocytes regulate CV, and what the significance of this regulation is for normal brain function remain unknown. To address these questions, we analyzed a transgenic mouse line harboring extra copies of the myelin proteolipid protein 1 (plp1) gene (plp1tg/- mice) at 2 months of age. At this stage, the plp1tg/- mice have an unaffected myelin structure with a normally appearing ion channel distribution, but the CV in all axonal tracts tested in the CNS is greatly reduced. We also found decreased axonal diameters and slightly abnormal paranodal structures, both of which can be a cause for the reduced CV. Interestingly the plp1tg/- mice showed altered anxiety-like behaviors, reduced prepulse inhibitions, spatial learning deficits and working memory deficit, all of which are schizophrenia-related behaviors. Our results implicate that abnormalities in the neuron-glia interactions at the paranodal junctions can result in reduced CV in the CNS, which then induces behavioral abnormalities related to schizophrenia.}, author = {Tanaka, Hisataka and Ma, Jianmei and Tanaka, Kenji F and Takao, Keizo and Komada, Munekazu and Tanda, Koichi and Suzuki, Ayaka and Ishibashi, Tomoko and Baba, Hiroko and Isa, Tadashi and Ryuichi Shigemoto and Ono, Katsuhiko and Miyakawa, Tsuyoshi and Ikenaka, Kazuhiro}, journal = {Journal of Neuroscience}, number = {26}, pages = {8363 -- 8371}, publisher = {Society for Neuroscience}, title = {{Mice with altered myelin proteolipid protein gene expression display cognitive deficits accompanied by abnormal neuron-glia interactions and decreased conduction velocities}}, doi = {10.1523/JNEUROSCI.3216-08.2009}, volume = {29}, year = {2009}, } @article{2686, abstract = {Channelrhodopsin-2 (ChR2), one of the archea-type rhodopsins from green algae, is a potentially useful optogenetic tool for restoring vision in patients with photoreceptor degeneration, such as retinitis pigmentosa. If the ChR2 gene is transferred to retinal ganglion cells (RGCs), which send visual information to the brain, the RGCs may be repurposed to act as photoreceptors. In this study, by using a transgenic rat expressing ChR2 specifically in the RGCs under the regulation of a Thy-1.2 promoter, we tested the possibility that direct photoactivation of RGCs could restore effective vision. Although the contrast sensitivities of the optomotor responses of transgenic rats were similar to those observed in the wild-type rats, they were enhanced for visual stimuli of low-spatial frequency after the degeneration of native photoreceptors. This result suggests that the visual signals derived from the ChR2-expressing RGCs were reinterpreted by the brain to form behavior-related vision.}, author = {Tomita, Hiroshi and Sugano, Eriko and Fukazawa, Yugo and Isago, Hitomi and Sugiyama, Yuka and Hiroi, Teru and Ishizuka, Toru and Mushiake, Hajime and Kato, Megumi and Hirabayashi, Masumi and Ryuichi Shigemoto and Yawo, Hiromu and Tamai, Makoto}, journal = {PLoS One}, number = {11}, publisher = {Public Library of Science}, title = {{Visual properties of transgenic rats harboring the channelrhodopsin-2 gene regulated by the thy-1.2 promoter}}, doi = {10.1371/journal.pone.0007679}, volume = {4}, year = {2009}, } @article{2703, abstract = {We consider N×N Hermitian random matrices with i.i.d. entries. The matrix is normalized so that the average spacing between consecutive eigenvalues is of order 1/N. We study the connection between eigenvalue statistics on microscopic energy scales η≪1 and (de)localization properties of the eigenvectors. Under suitable assumptions on the distribution of the single matrix elements, we first give an upper bound on the density of states on short energy scales of order η∼log N/N. We then prove that the density of states concentrates around the Wigner semicircle law on energy scales η≫N−2/3. We show that most eigenvectors are fully delocalized in the sense that their ℓp-norms are comparable with N1/p−1/2 for p≥2, and we obtain the weaker bound N2/3(1/p−1/2) for all eigenvectors whose eigenvalues are separated away from the spectral edges. We also prove that, with a probability very close to one, no eigenvector can be localized. Finally, we give an optimal bound on the second moment of the Green function. }, author = {László Erdös and Schlein, Benjamin and Yau, Horng-Tzer}, journal = {Annals of Probability}, number = {3}, pages = {815 -- 852}, publisher = {Institute of Mathematical Statistics}, title = {{Semicircle law on short scales and delocalization of eigenvectors for Wigner random matrices}}, doi = {10.1214/08-AOP421}, volume = {37}, year = {2009}, } @article{2757, abstract = {We propose a new approach for the study of the time evolution of a factorized N-particle bosonic wave function with respect to a mean-field dynamics with a bounded interaction potential. The new technique, which is based on the control of the growth of the correlations among the particles, leads to quantitative bounds on the difference between the many-particle Schrödinger dynamics and the one-particle nonlinear Hartree dynamics. In particular the one-particle density matrix associated with the solution to the N-particle Schrödinger equation is shown to converge to the projection onto the one-dimensional sub-space spanned by the solution to the Hartree equation with a speed of convergence of order 1/N for all fixed times.}, author = {László Erdös and Schlein, Benjamin}, journal = {Journal of Statistical Physics}, number = {5-6}, pages = {859 -- 870}, publisher = {Springer}, title = {{Quantum dynamics with mean field interactions: A new approach}}, doi = {10.1007/s10955-008-9570-7}, volume = {134}, year = {2009}, } @article{2758, abstract = {We consider N × N Hermitian random matrices with independent identical distributed entries. The matrix is normalized so that the average spacing between consecutive eigenvalues is of order 1/N. Under suitable assumptions on the distribution of the single matrix element, we prove that, away from the spectral edges, the density of eigenvalues concentrates around the Wigner semicircle law on energy scales n ≫ N -1 (log N) 8 . Up to the logarithmic factor, this is the smallest energy scale for which the semicircle law may be valid. We also prove that for all eigenvalues away from the spectral edges, the -tempℓ∞-norm of the corresponding eigenvectors is of order O(N -1/2), modulo logarithmic corrections. The upper bound O(N -1/2) implies that every eigenvector is completely delocalized, i.e., the maximum size of the components of the eigenvector is of the same order as their average size. In the Appendix, we include a lemma by J. Bourgain which removes one of our assumptions on the distribution of the matrix elements.}, author = {László Erdös and Schlein, Benjamin and Yau, Horng-Tzer}, journal = {Communications in Mathematical Physics}, number = {2}, pages = {641 -- 655}, publisher = {Springer}, title = {{Local semicircle law and complete delocalization for Wigner random matrices}}, doi = {10.1007/s00220-008-0636-9}, volume = {287}, year = {2009}, } @article{2759, abstract = {We consider the evolution of N bosons interacting with a repulsive short range pair potential in three dimensions. The potential is scaled according to the Gross-Pitaevskii scaling, i.e. it is given by N 2 V(N(x i - x j )). We monitor the behaviour of the solution to the N-particle Schrödinger equation in a spatial window where two particles are close to each other. We prove that within this window a short-scale interparticle structure emerges dynamically. The local correlation between the particles is given by the two-body zero energy scattering mode. This is the characteristic structure that was expected to form within a very short initial time layer and to persist for all later times, on the basis of the validity of the Gross-Pitaevskii equation for the evolution of the Bose-Einstein condensate. The zero energy scattering mode emerges after an initial time layer where all higher energy modes disperse out of the spatial window. We can prove the persistence of this structure up to sufficiently small times before three-particle correlations could develop.}, author = {László Erdös and Michelangeli, Alessandro and Schlein, Benjamin}, journal = {Communications in Mathematical Physics}, number = {3}, pages = {1171 -- 1210}, publisher = {Springer}, title = {{Dynamical formation of correlations in a Bose-Einstein condensate}}, doi = {10.1007/s00220-009-0828-y}, volume = {289}, year = {2009}, } @article{2760, author = {László Erdös and Schlein, Benjamin and Yau, Horng-Tzer}, journal = {Journal of the American Mathematical Society}, number = {4}, pages = {1099 -- 1156}, publisher = {American Mathematical Society}, title = {{Rigorous derivation of the gross-pitaevskii equation with a large interaction potential}}, doi = {10.1090/S0894-0347-09-00635-3}, volume = {22}, year = {2009}, } @article{2796, abstract = {As reported in a number of recent studies, turbulence in pipe flow is transient for Re<2000 and the flow eventually always returns to the laminar state. Generally, the lifetime of turbulence has been observed to increase rapidly with Reynolds number but there is currently no accord on the exact scaling behaviour. In particular, it is not clear whether a critical point exists where turbulence becomes sustained or if it remains transient. We here aim to clarify if these conflicting results may have been caused by the different experimental and numerical protocols used to trigger turbulence in these studies.}, author = {de Lózar, Alberto and Björn Hof}, journal = {Philosophical Transactions of the Royal Society A Mathematical Physical and Engineering Sciences}, number = {1888}, pages = {589 -- 599}, publisher = {Royal Society of London}, title = {{An experimental study of the decay of turbulent puffs in pipe flow}}, doi = {10.1098/rsta.2008.0199}, volume = {367}, year = {2009}, } @inproceedings{2797, abstract = {In pipe flow at low Reynolds number, decay of localized disturbances is observed. As the Reynolds number is increased, the question emerges whether the life time of these disturbances diverges at a finite Reynolds number or remains transient. In the current investigation we determine their life time quantitatively from pressure measurements, while in previous investigations the distance over which a structure survives has been determined. The obtained results confirm that the life time of localized disturbances does not diverge in the range of Reynolds numbers covered in the current experiment.}, author = {Kuik, Dirk J and Poelma, Christian and Björn Hof and Westerweel, Jerry}, pages = {145 -- 148}, publisher = {Springer}, title = {{Quantitative measurement of the life time of turbulence in pipe flow}}, doi = {10.1007/978-3-642-03085-7_36}, volume = {132}, year = {2009}, } @article{110, abstract = {In order to better understand magnetic reconnection and particle acceleration in solar flares, we compare the RHESSI hard X-ray (HXR) footpoint motions of three flares with a detailed study of the corresponding topology given by a Magnetic Charge Topology model. We analyze the relationship between the footpoint motions and topological spine lines and find that the examined footpoint sources move along spine lines. We present a three-dimensional topological model in which this movement can be understood. As reconnection proceeds, flux is transferred between the reconnecting domains, causing the separator to move. The movement of the separator\'s chromospheric ends, identified with the HXR footpoints, is along those spine lines on which the separator ends.}, author = {Des Jardins, Angela and Canfield, Richard and Longcope, Dana and Fordyce, Crystal and Waitukaitis, Scott R}, journal = {The Astrophysical Journal}, number = {2}, pages = {1628 -- 1636}, publisher = {IOP Publishing Ltd.}, title = {{Reconnection in three dimensions: The role of spines in three eruptive flares}}, doi = {10.1088/0004-637X/693/2/1628}, volume = {693}, year = {2009}, } @article{111, abstract = {Thin streams of liquid commonly break up into characteristic droplet patterns owing to the surface-tension-driven PlateauRayleigh instability 1-3. Very similar patterns are observed when initially uniform streams of dry granular material break up into clusters of grains4-6, even though flows of macroscopic particles are considered to lack surface tension7,8. Recent studies on freely falling granular streams tracked fluctuations in the stream profile9, but the clustering mechanism remained unresolved because the full evolution of the instability could not be observed. Here we demonstrate that the cluster formation is driven by minute, nanoNewton cohesive forces that arise from a combination of van der Waals interactions and capillary bridges between nanometre-scale surface asperities. Our experiments involve high-speed video imaging of the granular stream in the co-moving frame, control over the properties of the grain surfaces and the use of atomic force microscopy to measure grain-grain interactions. The cohesive forces that we measure correspond to an equivalent surface tension five orders of magnitude below that, of ordinary liquids. We find that, the shapes of these weakly cohesive, non-thermal clusters of macroscopic particles closely resemble droplets resulting from thermally induced rupture of liquid nanojets 10-12.}, author = {Royer, John and Evans, Daniel and Oyarte, Loreto and Guo, Qiti and Kapit, Eliot and Möbius, Matthias and Waitukaitis, Scott R and Jaeger, Heinrich}, journal = {Nature}, number = {7250}, pages = {1110 -- 1113}, publisher = {Nature Publishing Group}, title = {{High-speed tracking of rupture and clustering in freely falling granular streams}}, doi = {10.1038/nature08115}, volume = {459}, year = {2009}, } @article{11103, abstract = {Over the last decade, the nuclear envelope (NE) has emerged as a key component in the organization and function of the nuclear genome. As many as 100 different proteins are thought to specifically localize to this double membrane that separates the cytoplasm and the nucleoplasm of eukaryotic cells. Selective portals through the NE are formed at sites where the inner and outer nuclear membranes are fused, and the coincident assembly of ∼30 proteins into nuclear pore complexes occurs. These nuclear pore complexes are essential for the control of nucleocytoplasmic exchange. Many of the NE and nuclear pore proteins are thought to play crucial roles in gene regulation and thus are increasingly linked to human diseases.}, author = {HETZER, Martin W and Wente, Susan R.}, issn = {1534-5807}, journal = {Developmental Cell}, keywords = {Developmental Biology, Cell Biology, General Biochemistry, Genetics and Molecular Biology, Molecular Biology}, number = {5}, pages = {606--616}, publisher = {Elsevier}, title = {{Border control at the nucleus: Biogenesis and organization of the nuclear membrane and pore complexes}}, doi = {10.1016/j.devcel.2009.10.007}, volume = {17}, year = {2009}, } @article{11105, abstract = {Nuclear-pore complexes (NPCs) are large protein channels that span the nuclear envelope (NE), which is a double membrane that encloses the nuclear genome of eukaryotes. Each of the typically 2,000–4,000 pores in the NE of vertebrate cells is composed of multiple copies of 30 different proteins known as nucleoporins. The evolutionarily conserved NPC proteins have the well-characterized function of mediating the transport of molecules between the nucleoplasm and the cytoplasm. Mutations in nucleoporins are often linked to specific developmental defects and disease, and the resulting phenotypes are usually interpreted as the consequences of perturbed nuclear transport activity. However, recent evidence suggests that NPCs have additional functions in chromatin organization and gene regulation, some of which might be independent of nuclear transport. Here, we review the transport-dependent and transport-independent roles of NPCs in the regulation of nuclear function and gene expression.}, author = {Capelson, Maya and HETZER, Martin W}, issn = {1469-3178}, journal = {EMBO reports}, keywords = {Genetics, Molecular Biology, Biochemistry}, number = {7}, pages = {697--705}, publisher = {EMBO}, title = {{The role of nuclear pores in gene regulation, development and disease}}, doi = {10.1038/embor.2009.147}, volume = {10}, year = {2009}, } @article{11106, abstract = {Formation of the nuclear envelope (NE) around segregated chromosomes occurs by the reshaping of the endoplasmic reticulum (ER), a reservoir for disassembled nuclear membrane components during mitosis. In this study, we show that inner nuclear membrane proteins such as lamin B receptor (LBR), MAN1, Lap2β, and the trans-membrane nucleoporins Ndc1 and POM121 drive the spreading of ER membranes into the emerging NE via their capacity to bind chromatin in a collaborative manner. Despite their redundant functions, decreasing the levels of any of these trans-membrane proteins by RNAi-mediated knockdown delayed NE formation, whereas increasing the levels of any of them had the opposite effect. Furthermore, acceleration of NE formation interferes with chromosome separation during mitosis, indicating that the time frame over which chromatin becomes membrane enclosed is physiologically relevant and regulated. These data suggest that functionally distinct classes of chromatin-interacting membrane proteins, which are present at nonsaturating levels, collaborate to rapidly reestablish the nuclear compartment at the end of mitosis.}, author = {Anderson, Daniel J. and Vargas, Jesse D. and Hsiao, Joshua P. and HETZER, Martin W}, issn = {1540-8140}, journal = {Journal of Cell Biology}, keywords = {Cell Biology}, number = {2}, pages = {183--191}, publisher = {Rockefeller University Press}, title = {{Recruitment of functionally distinct membrane proteins to chromatin mediates nuclear envelope formation in vivo}}, doi = {10.1083/jcb.200901106}, volume = {186}, year = {2009}, } @article{11107, abstract = {Nucleocytoplasmic transport occurs exclusively through nuclear pore complexes (NPCs) embedded in pores formed by inner and outer nuclear membrane fusion. The mechanism for de novo pore and NPC biogenesis remains unclear. Reticulons (RTNs) and Yop1/DP1 are conserved membrane protein families required to form and maintain the tubular endoplasmic reticulum (ER) and the postmitotic nuclear envelope. In this study, we report that members of the RTN and Yop1/DP1 families are required for nuclear pore formation. Analysis of Saccharomyces cerevisiae prp20-G282S and nup133Δ NPC assembly mutants revealed perturbations in Rtn1–green fluorescent protein (GFP) and Yop1-GFP ER distribution and colocalization to NPC clusters. Combined deletion of RTN1 and YOP1 resulted in NPC clustering, nuclear import defects, and synthetic lethality with the additional absence of Pom34, Pom152, and Nup84 subcomplex members. We tested for a direct role in NPC biogenesis using Xenopus laevis in vitro assays and found that anti-Rtn4a antibodies specifically inhibited de novo nuclear pore formation. We hypothesize that these ER membrane–bending proteins mediate early NPC assembly steps.}, author = {Dawson, T. Renee and Lazarus, Michelle D. and HETZER, Martin W and Wente, Susan R.}, issn = {1540-8140}, journal = {Journal of Cell Biology}, keywords = {Cell Biology}, number = {5}, pages = {659--675}, publisher = {Rockefeller University Press}, title = {{ER membrane–bending proteins are necessary for de novo nuclear pore formation}}, doi = {10.1083/jcb.200806174}, volume = {184}, year = {2009}, } @article{11108, abstract = {In dividing cells, nuclear pore complexes (NPCs) disassemble during mitosis and reassemble into the newly forming nuclei. However, the fate of nuclear pores in postmitotic cells is unknown. Here, we show that NPCs, unlike other nuclear structures, do not turn over in differentiated cells. While a subset of NPC components, like Nup153 and Nup50, are continuously exchanged, scaffold nucleoporins, like the Nup107/160 complex, are extremely long-lived and remain incorporated in the nuclear membrane during the entire cellular life span. Besides the lack of nucleoporin expression and NPC turnover, we discovered an age-related deterioration of NPCs, leading to an increase in nuclear permeability and the leaking of cytoplasmic proteins into the nucleus. Our finding that nuclear “leakiness” is dramatically accelerated during aging and that a subset of nucleoporins is oxidatively damaged in old cells suggests that the accumulation of damage at the NPC might be a crucial aging event.}, author = {D'Angelo, Maximiliano A. and Raices, Marcela and Panowski, Siler H. and HETZER, Martin W}, issn = {0092-8674}, journal = {Cell}, keywords = {General Biochemistry, Genetics and Molecular Biology}, number = {2}, pages = {284--295}, publisher = {Elsevier}, title = {{Age-dependent deterioration of nuclear pore complexes causes a loss of nuclear integrity in postmitotic cells}}, doi = {10.1016/j.cell.2008.11.037}, volume = {136}, year = {2009}, } @inproceedings{11752, abstract = {We propose a model which suggests that structural martensitic transitions are related to significant changes in the electronic structure, and are effected by high-magnetic fields. The magnetic field dependence is considered unusual as many influential investigations of martensitic transitions have emphasized that the structural transitions are primarily lattice dynamical and are driven by the entropy due to the phonons. We provide a theoretical framework which can be used to describe the effect of high magnetic field on the transition and lattice dynamics in which the field dependence originates from the dielectric constant. The model is compared with some recent experimental results.}, author = {Yang, Xiaodong and Riseborough, Peter S and Modic, Kimberly A and Fisher, R A and Oppeil, C P and Finlayson, T R and Cooley, J C and Smith, J L and Goddard, P A and Silhanek, A V and Lashley, J C}, booktitle = {Journal of Physics: Conference Series}, issn = {1742-6596}, location = {Karlsruhe, Germany}, number = {3}, publisher = {IOP Publishing}, title = {{Influence of magnetic fields on structural martensitic transitions}}, doi = {10.1088/1742-6596/200/3/032062}, volume = {200}, year = {2009}, } @inproceedings{11799, abstract = {We study the problem of matching bidders to items where each bidder i has general, strictly monotonic utility functions u i,j (p j ) expressing her utility of being matched to item j at price p j . For this setting we prove that a bidder optimal outcome always exists, even when the utility functions are non-linear and non-continuous. Furthermore, we give an algorithm to find such a solution. Although the running time of this algorithm is exponential in the number of items, it is polynomial in the number of bidders.}, author = {Dütting, Paul and Henzinger, Monika H and Weber, Ingmar}, booktitle = {5th International Workshop on Internet and Network Economics}, isbn = {9783642108402}, issn = {1611-3349}, location = {Rome, Italy}, pages = {575--582}, publisher = {Springer Nature}, title = {{Bidder optimal assignments for general utilities}}, doi = {10.1007/978-3-642-10841-9_58}, volume = {5929}, year = {2009}, } @inproceedings{11905, abstract = {Given only the URL of a web page, can we identify its topic? This is the question that we examine in this paper. Usually, web pages are classified using their content, but a URL-only classifier is preferable, (i) when speed is crucial, (ii) to enable content filtering before an (objection-able) web page is downloaded, (iii) when a page's content is hidden in images, (iv) to annotate hyperlinks in a personalized web browser, without fetching the target page, and (v) when a focused crawler wants to infer the topic of a target page before devoting bandwidth to download it. We apply a machine learning approach to the topic identification task and evaluate its performance in extensive experiments on categorized web pages from the Open Directory Project (ODP). When training separate binary classifiers for each topic, we achieve typical F-measure values between 80 and 85, and a typical precision of around 85. We also ran experiments on a small data set of university web pages. For the task of classifying these pages into faculty, student, course and project pages, our methods improve over previous approaches by 13.8 points of F-measure.}, author = {Baykan, Eda and Henzinger, Monika H and Marian, Ludmila and Weber, Ingmar}, booktitle = {18th International World Wide Web Conference}, isbn = {978-1-60558-487-4}, location = {New York, NY, United States}, pages = {1109--1110}, publisher = {Association for Computing Machinery}, title = {{Purely URL-based topic classification}}, doi = {10.1145/1526709.1526880}, year = {2009}, }