TY - JOUR AB - We perform numerical simulations to study self-assembly of nanoparticles mediated by an elastic planar surface. We show how the nontrivial elastic response to deformations of these surfaces leads to anisotropic interactions between the particles resulting in aggregates having different geometrical features. The morphology of the patterns can be controlled by the mechanical properties of the surface and the strength of the particle adhesion. We use simple scaling arguments to understand the formation of the different structures, and we show how the adhering particles can cause the underlying elastic substrate to wrinkle if two of its opposite edges are clamped. Finally, we discuss the implications of our results and suggest how elastic surfaces could be used in nanofabrication. AU - Šarić, Anđela AU - Cacciuto, Angelo ID - 10389 IS - 18 JF - Soft Matter KW - condensed matter physics KW - general chemistry SN - 1744-683X TI - Soft elastic surfaces as a platform for particle self-assembly VL - 7 ER - TY - JOUR AB - We present experimentally derived potential curves 1?and spin-orbit interaction functions for the strongly perturbed AΣu+ 3?and bΠu states of the cesium dimer. The results are based on data from several sources. Laser-induced fluorescence Fourier transform spectroscopy (LIF FTS) was used some time ago in the Laboratoire Aimé Cotton primarily to study the XΣg+ state. More recent work at Tsinghua University provides information from moderate 3?resolution spectroscopy on the lowest levels of the bΠ0u± state as well as additional high-resolution data. From Innsbruck University, we have precision data obtained with cold Cs2 molecules. Recent data from Temple University was obtained using the optical-optical double resonance polarization spectroscopy technique, and finally, a group at the University of Latvia has added additional LIF FTS data. In the Hamiltonian matrix, we have used analytic potentials (the expanded Morse oscillator form) with both finite-difference (FD) coupled-channel and discrete variable representation (DVR) calculations of the term values. Fitted diagonal and off-diagonal spin-orbit functions are obtained and compared with ab initio results from Temple and Moscow State universities. AU - Bai, Jianmei AU - Ahmed, Ergin AU - Beser, Bediha AU - Guan, Yafei AU - Kotochigova, Svetlana AU - Lyyra, Marjatta AU - Ashman, Seth AU - Wolfe, Christopher AU - Huennekens, John AU - Xie, Feng AU - Li, Dan AU - Li, Li AU - Tamanis, Maris AU - Ferber, Ruvin AU - Drozdova, Anastasia AU - Pazyuk, Elena AU - Stolyarov, Andrey AU - Danzl, Johann G AU - Nägerl, Hanns AU - Bouloufa, Nadia AU - Dulieu, Olivier AU - Amiot, Claude AU - Salami, Houssam AU - Bergeman, Thomas ID - 1050 IS - 3 JF - Physical Review A - Atomic, Molecular, and Optical Physics TI - Global analysis of data on the spin-orbit-coupled A 1Σu+ and b 3Πu inf states of Cs2 VL - 83 ER - TY - JOUR AB - We produce an ultracold and dense sample of rovibronic ground state Cs 2 molecules close to the regime of quantum degeneracy, in a single hyperfine level, in the presence of an optical lattice. The molecules are individually trapped, in the motional ground state of an optical lattice well, with a lifetime of 8 s. For preparation, we start with a zero-temperature atomic Mott-insulator state with optimized double-site occupancy and efficiently associate weakly-bound dimer molecules on a Feshbach resonance. Despite extremely weak Franck-Condon wavefunction overlap, the molecules are subsequently transferred with >50% efficiency to the rovibronic ground state by a stimulated four-photon process. Our results present a crucial step towards the generation of Bose-Einstein condensates of ground-state molecules and, when suitably generalized to polar heteronuclear molecules such as RbCs, the realization of dipolar many-body quantum-gas phases in periodic potentials. AU - Nägerl, Hanns AU - Mark, Manfred AU - Haller, Elmar AU - Gustavsson, Mattias AU - Hart, Russell AU - Danzl, Johann G ID - 1048 IS - 1 JF - Journal of Physics: Conference Series TI - Ultracold and dense samples of ground-state molecules in lattice potentials VL - 264 ER - TY - JOUR AB - The present paper aims at finding optimal parameters for trapping of Cs 2 molecules in optical lattices, with the perspective of creating a quantum degenerate gas of ground-state molecules. We have calculated dynamic polarizabilities of Cs 2 molecules subject to an oscillating electric field, using accurate potential curves and electronic transition dipole moments. We show that for some particular wavelengths of the optical lattice, called "magic wavelengths", the polarizability of the ground-state molecules is equal to the one of a Feshbach molecule. As the creation of the sample of ground-state molecules relies on an adiabatic population transfer from weakly-bound molecules created on a Feshbach resonance, such a coincidence ensures that both the initial and final states are favorably trapped by the lattice light, allowing optimized transfer in agreement with the experimental observation. AU - Vexiau, Romain AU - Bouloufa, Nadia AU - Aymar, Mireille AU - Danzl, Johann G AU - Mark, Manfred AU - Nägerl, Hanns AU - Dulieu, Olivier ID - 1052 IS - 1-2 JF - European Physical Journal D TI - Optimal trapping wavelengths of Cs 2 molecules in an optical lattice VL - 65 ER - TY - JOUR AB - We demonstrate the temporal Talbot effect for trapped matter waves using ultracold atoms in an optical lattice. We investigate the phase evolution of an array of essentially non-interacting matter waves and observe matter-wave collapse and revival in the form of a Talbot interference pattern. By using long expansion times, we image momentum space with sub-recoil resolution, allowing us to observe fractional Talbot fringes up to tenth order. AU - Mark, Manfred AU - Haller, Elmar AU - Danzl, Johann G AU - Lauber, Katharina AU - Gustavsson, Mattias AU - Nägerl, Hanns ID - 1051 JF - New Journal of Physics TI - Demonstration of the temporal matter-wave Talbot effect for trapped matter waves VL - 13 ER - TY - JOUR AB - We perform precision measurements on a Mott-insulator quantum state of ultracold atoms with tunable interactions. We probe the dependence of the superfluid-to-Mott-insulator transition on the interaction strength and explore the limits of the standard Bose-Hubbard model description. By tuning the on-site interaction energies to values comparable to the interband separation, we are able to quantitatively measure number-dependent shifts in the excitation spectrum caused by effective multibody interactions. AU - Mark, Manfred AU - Haller, Elmar AU - Lauber, Katharina AU - Danzl, Johann G AU - Daley, Andrew AU - Nägerl, Hanns ID - 1053 IS - 17 JF - Physical Review Letters TI - Precision measurements on a tunable Mott insulator of ultracold atoms VL - 107 ER - TY - JOUR AB - We investigate local three-body correlations for bosonic particles in three dimensions and one dimension as a function of the interaction strength. The three-body correlation function g(3) is determined by measuring the three-body recombination rate in an ultracold gas of Cs atoms. In three dimensions, we measure the dependence of g(3) on the gas parameter in a BEC, finding good agreement with the theoretical prediction accounting for beyond-mean-field effects. In one dimension, we observe a reduction of g( 3) by several orders of magnitude upon increasing interactions from the weakly interacting BEC to the strongly interacting Tonks-Girardeau regime, in good agreement with predictions from the Lieb-Liniger model for all strengths of interaction. AU - Haller, Elmar AU - Rabie, Mahmoud AU - Mark, Manfred AU - Danzl, Johann G AU - Hart, Russell AU - Lauber, Katharina AU - Pupillo, Guido AU - Nägerl, Hanns ID - 1054 IS - 23 JF - Physical Review Letters TI - Three-body correlation functions and recombination rates for bosons in three dimensions and one dimension VL - 107 ER - TY - JOUR AB - Nuclear pore complexes (NPCs) assemble at the end of mitosis during nuclear envelope (NE) reformation and into an intact NE as cells progress through interphase. Although recent studies have shown that NPC formation occurs by two different molecular mechanisms at two distinct cell cycle stages, little is known about the molecular players that mediate the fusion of the outer and inner nuclear membranes to form pores. In this paper, we provide evidence that the transmembrane nucleoporin (Nup), POM121, but not the Nup107–160 complex, is present at new pore assembly sites at a time that coincides with inner nuclear membrane (INM) and outer nuclear membrane (ONM) fusion. Overexpression of POM121 resulted in juxtaposition of the INM and ONM. Additionally, Sun1, an INM protein that is known to interact with the cytoskeleton, was specifically required for interphase assembly and localized with POM121 at forming pores. We propose a model in which POM121 and Sun1 interact transiently to promote early steps of interphase NPC assembly. AU - Talamas, Jessica A. AU - HETZER, Martin W ID - 11094 IS - 1 JF - Journal of Cell Biology KW - Cell Biology SN - 0021-9525 TI - POM121 and Sun1 play a role in early steps of interphase NPC assembly VL - 194 ER - TY - JOUR AB - As the gatekeepers of the eukaryotic cell nucleus, nuclear pore complexes (NPCs) mediate all molecular trafficking between the nucleoplasm and the cytoplasm. In recent years, transport-independent functions of NPC components, nucleoporins, have been identified including roles in chromatin organization and gene regulation. Here, we summarize our current view of the NPC as a dynamic hub for the integration of chromatin regulation and nuclear trafficking and discuss the functional interplay between nucleoporins and the nuclear genome. AU - Liang, Yun AU - HETZER, Martin W ID - 11096 IS - 1 JF - Current Opinion in Cell Biology KW - Cell Biology SN - 0955-0674 TI - Functional interactions between nucleoporins and chromatin VL - 23 ER - TY - JOUR AU - HETZER, Martin W AU - Cavalli, Giacomo ID - 11095 IS - 3 JF - Current Opinion in Cell Biology KW - Cell Biology SN - 0955-0674 TI - Editorial overview VL - 23 ER - TY - JOUR AB - Eukaryotic cell function depends on the physical separation of nucleoplasmic and cytoplasmic components by the nuclear envelope (NE). Molecular communication between the two compartments involves active, signal-mediated trafficking, a function that is exclusively performed by nuclear pore complexes (NPCs). The individual NPC components and the mechanisms that are involved in nuclear trafficking are well documented and have become textbook knowledge. However, in addition to their roles as nuclear gatekeepers, NPC components-nucleoporins-have been shown to have critical roles in chromatin organization and gene regulation. These findings have sparked new enthusiasm to study the roles of this multiprotein complex in nuclear organization and explore novel functions that in some cases appear to go beyond a role in transport. Here, we discuss our present view of NPC biogenesis, which is tightly linked to proper cell cycle progression and cell differentiation. In addition, we summarize new data suggesting that NPCs represent dynamic hubs for the integration of gene regulation and nuclear transport processes. AU - Capelson, M. AU - Doucet, C. AU - HETZER, Martin W ID - 11100 JF - Cold Spring Harbor Symposia on Quantitative Biology KW - Genetics KW - Molecular Biology KW - Biochemistry SN - 0091-7451 TI - Nuclear pore complexes: Guardians of the nuclear genome VL - 75 ER - TY - JOUR AB - Particle beams are important tools for probing atomic and molecular interactions. Here we demonstrate that particle beams also offer a unique opportunity to investigate interactions in macroscopic systems, such as granular media. Motivated by recent experiments on streams of grains that exhibit liquid-like breakup into droplets, we use molecular dynamics simulations to investigate the evolution of a dense stream of macroscopic spheres accelerating out of an opening at the bottom of a reservoir. We show how nanoscale details associated with energy dissipation during collisions modify the stream\'s macroscopic behavior. We find that inelastic collisions collimate the stream, while the presence of short-range attractive interactions drives structure formation. Parameterizing the collision dynamics by the coefficient of restitution (i.e., the ratio of relative velocities before and after impact) and the strength of the cohesive interaction, we map out a spectrum of behaviors that ranges from gaslike jets in which all grains drift apart to liquid-like streams that break into large droplets containing hundreds of grains. We also find a new, intermediate regime in which small aggregates form by capture from the gas phase, similar to what can be observed in molecular beams. Our results show that nearly all aspects of stream behavior are closely related to the velocity gradient associated with vertical free fall. Led by this observation, we propose a simple energy balance model to explain the droplet formation process. The qualitative as well as many quantitative features of the simulations and the model compare well with available experimental data and provide a first quantitative measure of the role of attractions in freely cooling granular streams. AU - Waitukaitis, Scott R AU - Grütjen, Helge AU - Royer, John AU - Jaeger, Heinrich ID - 112 IS - 5 JF - Physical Review E TI - Droplet and cluster formation in freely falling granular streams VL - 83 ER - TY - JOUR AB - Given only the URL of a Web page, can we identify its topic? We study this problem in detail by exploring a large number of different feature sets and algorithms on several datasets. We also show that the inherent overlap between topics and the sparsity of the information in URLs makes this a very challenging problem. Web page classification without a page’s content is desirable when the content is not available at all, when a classification is needed before obtaining the content, or when classification speed is of utmost importance. For our experiments we used five different corpora comprising a total of about 3 million (URL, classification) pairs. We evaluated several techniques for feature generation and classification algorithms. The individual binary classifiers were then combined via boosting into metabinary classifiers. We achieve typical F-measure values between 80 and 85, and a typical precision of around 86. The precision can be pushed further over 90 while maintaining a typical level of recall between 30 and 40. AU - Baykan, Eda AU - Henzinger, Monika H AU - Marian, Ludmila AU - Weber, Ingmar ID - 11673 IS - 3 JF - ACM Transactions on the Web KW - Topic classification KW - URL KW - ODP SN - 1559-1131 TI - A comprehensive study of features and algorithms for URL-based topic classification VL - 5 ER - TY - JOUR AB - We study a novel load balancing problem that arises in web search engines. The problem is a combination of an offline assignment problem, where files need to be (copied and) assigned to machines, and an online load balancing problem, where requests ask for specific files and need to be assigned to a corresponding machine, whose load is increased by this. We present simple deterministic algorithms for this problem and exhibit an interesting trade-off between the available space to make file copies and the obtainable makespan. We also give non-trivial lower bounds for a large class of deterministic algorithms and present a randomized algorithm that beats these bounds with high probability. AU - Dütting, Paul AU - Henzinger, Monika H AU - Weber, Ingmar ID - 11760 IS - 4 JF - Information Processing Letters SN - 0020-0190 TI - Offline file assignments for online load balancing VL - 111 ER - TY - CONF AB - The design of truthful auctions that approximate the optimal expected revenue is a central problem in algorithmic mechanism design. 30 years after Myerson’s characterization of Bayesian optimal auctions in single-parameter domains [8], characterizing but also providing efficient mechanisms for multi-parameter domains still remains a very important unsolved problem. Our work improves upon recent results in this area, introducing new techniques for tackling the problem, while also combining and extending recently introduced tools. In particular we give the first approximation algorithms for Bayesian auctions with multiple heterogeneous items when bidders have additive valuations, budget constraints and general matroid feasibility constraints. AU - Henzinger, Monika H AU - Vidali, Angelina ID - 11796 SN - 1611-3349 T2 - 19th Annual European Symposium on Algorithms TI - Multi-parameter mechanism design under budget and matroid constraints VL - 6942 ER - TY - CONF AB - Auctions are widely used on the Web. Applications range from internet advertising to platforms such as eBay. In most of these applications the auctions in use are single/multi-item auctions with unit demand. The main drawback of standard mechanisms for this type of auctions, such as VCG and GSP, is the limited expressiveness that they offer to the bidders. The General Auction Mechanism (GAM) of [1] is taking a first step towards addressing the problem of limited expressiveness by computing a bidder optimal, envy free outcome for linear utility functions with identical slopes and a single discontinuity per bidder-item pair. We show that in many practical situations this does not suffice to adequately model the preferences of the bidders, and we overcome this problem by presenting the first mechanism for piece-wise linear utility functions with non-identical slopes and multiple discontinuities. Our mechanism runs in polynomial time. Like GAM it is incentive compatible for inputs that fulfill a certain non-degeneracy requirement, but our requirement is more general than the requirement of GAM. For discontinuous utility functions that are non-degenerate as well as for continuous utility functions the outcome of our mechanism is a competitive equilibrium. We also show how our mechanism can be used to compute approximately bidder optimal, envy free outcomes for a general class of continuous utility functions via piece-wise linear approximation. Finally, we prove hardness results for even more expressive settings. AU - Dütting, Paul AU - Henzinger, Monika H AU - Weber, Ingmar ID - 11864 SN - 978-145030632-4 T2 - Proceedings of the 20th international conference on World wide web TI - An expressive mechanism for auctions on the web ER - TY - JOUR AB - Temperature data from three Automatic Weather Stations and twelve Temperature Loggers are used to investigate the spatiotemporal variability of temperature over a glacier, its main atmospheric controls, the suitability of extrapolation techniques and their effect on melt modeling. We use data collected on Juncal Norte Glacier, central Chile, during one ablation season. We examine temporal and spatial variability in lapse rates (LRs), together with alternative statistical interpolation methods. The main control over the glacier thermal regime is the development of a katabatic boundary layer (KBL). Katabatic wind occurs at night and in the morning and is eroded in the afternoon. LRs reveal strong diurnal variability, with steeper LRs during the day when the katabatic wind weakens and shallower LRs during the night and morning. We suggest that temporally variable LRs should be used to account for the observed change. They tend to be steeper than equivalent constant LRs, and therefore result in a reduction in simulated melt compared to use of constant LRs when extrapolating from lower to higher elevations. In addition to the temporal variability, the temperature-elevation relationship varies also in space. Differences are evident between local LRs and including such variability in melt modeling affects melt simulations. Extrapolation methods based on the spatial variability of the observations after removal of the elevation trend, such as Inverse Distance Weighting or Kriging, do not seem necessary for simulations of gridded temperature data over a glacier. AU - Petersen, L. AU - Pellicciotti, Francesca ID - 12651 IS - D23 JF - Journal of Geophysical Research: Atmospheres KW - Paleontology KW - Space and Planetary Science KW - Earth and Planetary Sciences (miscellaneous) KW - Atmospheric Science KW - Earth-Surface Processes KW - Geochemistry and Petrology KW - Soil Science KW - Water Science and Technology KW - Ecology KW - Aquatic Science KW - Forestry KW - Oceanography KW - Geophysics SN - 0148-0227 TI - Spatial and temporal variability of air temperature on a melting glacier: Atmospheric controls, extrapolation methods and their effect on melt modeling, Juncal Norte Glacier, Chile VL - 116 ER - TY - JOUR AB - Physically based hydrological models describe natural processes more accurately than conceptual models but require extensive data sets to produce accurate results. To identify the value of different data sets for improving the performance of the distributed hydrological model TOPKAPI we combine a multivariable validation technique with Monte Carlo simulations. The study is carried out in the snow and ice-dominated Rhonegletscher basin, as these types of mountainous basins are generally the most critical with respect to data availability and sensitivity to climate fluctuations. Each observational data set is used individually and in combination with the other data sets to determine a subset of best parameter combinations out of 10,000 Monte Carlos runs performed with randomly generated parameter sets. We validate model results against discharge, glacier mass balance, and satellite snow cover images for a 14 year time period (1994–2007). While the use of all data sets combined provides the best overall model performance (defined by the concurrent best agreement of simulated discharge, snow cover and mass balance with their respective measurements), the use of one or two variables for constraining the model results in poorer performance. Using only one data set for constraining the model glacier mass balance proved to be the most efficient observation leading to the best overall model performance. Our main result is that a combination of discharge and satellite snow cover images is best for improving model performance, since the volumetric information of discharge data and the spatial information of snow cover images are complementary. AU - Finger, David AU - Pellicciotti, Francesca AU - Konz, Markus AU - Rimkus, Stefan AU - Burlando, Paolo ID - 12649 IS - 7 JF - Water Resources Research SN - 0043-1397 TI - The value of glacier mass balance, satellite snow cover images, and hourly discharge for improving the performance of a physically based distributed hydrological model VL - 47 ER - TY - JOUR AB - We explore the robustness and transferability of parameterizations of cloud radiative forcing used in glacier melt models at two sites in the Swiss Alps. We also look at the rationale behind some of the most commonly used approaches, and explore the relationship between cloud transmittance and several standard meteorological variables. The 2 m air-temperature diurnal range is the best predictor of variations in cloud transmittance. However, linear and exponential parameterizations can only explain 30–50% of the observed variance in computed cloud transmittance factors. We examine the impact of modelled cloud transmittance factors on both solar radiation and ablation rates computed with an enhanced temperature-index model. The melt model performance decreases when modelled radiation is used, the reduction being due to an underestimation of incoming solar radiation on clear-sky days. The model works well under overcast conditions. We also seek alternatives to the use of in situ ground data. However, outputs from an atmospheric model (2.2 km horizontal resolution) do not seem to provide an alternative to the parameterizations of cloud radiative forcing based on observations of air temperature at glacier automatic weather stations. Conversely, the correct definition of overcast conditions is important. AU - Pellicciotti, Francesca AU - Raschle, Thomas AU - Huerlimann, Thomas AU - Carenzo, Marco AU - Burlando, Paolo ID - 12652 IS - 202 JF - Journal of Glaciology SN - 0022-1430 TI - Transmission of solar radiation through clouds on melting glaciers: A comparison of parameterizations and their impact on melt modelling VL - 57 ER - TY - CHAP AB - Streamflow is a hydrological variable measured at a defined river cross-section; it spatially integrates the runoff generating processes in the contributing watershed, including precipitation and air temperature. Trends in streamflow are progressive changes in the time series of streamflow that can be detected with statistical methods and their statistical significance can be assessed. Mountainous regions are particularly vulnerable to streamflow change because of their high specific runoff and the sensitivity to the distribution of precipitation and air temperature, and the processes of snow accumulation and melt. AU - Molnar, Peter AU - Burlando, Paolo AU - Pellicciotti, Francesca ED - Singh, Vijay ED - Singh, Pratap ED - Haritashya, Umesh ID - 12650 SN - 1388-4360 T2 - Encyclopedia of Snow, Ice and Glaciers TI - Streamflow Trends in Mountainous Regions ER -