Bringing Structure into Summaries: Crowdsourcing a Benchmark Corpus of Concept Maps

Concept maps can be used to concisely represent important information and bring structure into large document collections. Therefore, we study a variant of multi-document summarization that produces summaries in the form of concept maps. However, suitable evaluation datasets for this task are currently missing. To close this gap, we present a newly created corpus of concept maps that summarize heterogeneous collections of web documents on educational topics. It was created using a novel crowdsourcing approach that allows us to efficiently determine important elements in large document collections. We release the corpus along with a baseline system and proposed evaluation protocol to enable further research on this variant of summarization.Comment: Published at EMNLP 201

Chloride binding to the anion transport binding sites of band 3. A 35Cl NMR study

Band 3 is an integral membrane protein that exchanges anions across the red cell membrane. Due to the abundance and the high turnover rate of the band 3 transport unit, the band 3 system is the most heavily used ion-transport system in a typical vertebrate organism. Here we show that 35Cl NMR enables direct and specific observation of substrate Cl- binding to band 3 transport sites, which are identified by a variety of criteria: (a) the sites are inhibited by 4,4'- dinitrostilbene -2,2'- disulfonate, which is known to inhibit competitively Cl- binding to band 3 transport sites; (b) the sites have affinities for 4,4'- dinitrostilbene -2,2'-disulfonate and Cl- that are quantitatively similar to the known affinities of band 3 transport sites for these anions; and (c) the sites have relative affinities for Cl-, HCO-3, F-, and I- that are quantitatively similar to the known relative affinities of band 3 transport sites for these anions. The 35Cl NMR assay also reveals a class of low affinity Cl- binding sites (KD much greater than 0.5 M) that are not affected by 4,4'- dinitrostilbene -2,2'- disulfonate. These low affinity sites may be responsible for the inhibition of band 3 catalyzed anion exchange that has been previously observed at high [Cl-]. In the following paper the 35Cl NMR assay is used to resolve the band 3 transport sites on opposite sides of the membrane, thereby enabling direct observation of the transmembrane recruitment of transport sites

The minimal structure containing the band 3 anion transport site. A 35Cl NMR study

35Cl NMR, which enables observation of chloride binding to the anion transport site on band 3, is used in the present study to determine the minimal structure containing the intact transport site. Removal of cytoskeletal and other nonintegral membrane proteins, or removal of the 40-kDa cytoskeletal domain of band 3, each leave the transport site intact. Similarly, cleavage of the 52-kDa transport domain into 17- and 35-kDa fragments by chymotrypsin leaves the transport site intact. Extensive proteolysis by papain reduces the integral red cell membrane proteins to their transmembrane segments. Papain treatment removes approximately 60% of the extramembrane portion of the transport domain and produces small fragments primarily in the range 3-7 kDa, with 5 kDa being most predominant. Papain treatment damages, but does not destroy, chloride binding to the transport site; thus, the minimal structure containing the transport site is composed solely of transmembrane segments. In short, the results are completely consistent with a picture in which the transport site is buried in the membrane where it is protected from proteolysis; the transmembrane segments that surround the transport site are held together by strong attractive forces within the bilayer; and the transport site is accessed by solution chloride via an anion channel leading from the transport site to the solution

Study of the Born-Oppenheimer Approximation for Mass-Scaling of Cold Collision Properties

Asymptotic levels of the A $^1\Sigma_u^+$ state of the two isotopomers $^{39}{\rm K}_2$ and $^{39}{\rm K}^{41}{\rm K}$ up to the dissociation limit are investigated with a Doppler-free high resolution laser-spectroscopic experiment in a molecular beam. The observed level structure can be reproduced correctly only if a mass dependent correction term is introduced for the interaction potential. The applied relative correction in the depth of the potential is $10^{-6}$, which is in the order of magnitude expected for corrections of the Born-Oppenheimer approximation. A similar change in ground state potentials might lead to significant changes of mass-scaled properties describing cold collisions like the s-wave scattering length.Comment: 8 pages, 6 figure

Highly Ordered Organic Layers and Wires

This thesis deals with the synthesis of highly ordered organic thin films and the characterization of the molecule-substrate interaction through spectroscopy and diffraction. Organic devices, such as organic light emitting diodes (OLEDs) and organic field effect transistors (OFETs) have become ubiquitous in modern times. The transistor and high frequency performance of such organic devices crucially depends on charge carrier mobility. In inorganic semiconductors, which are bonded covalently, the band masses are typically lower and their crystallinity higher in comparison to their organic counterparts. In a simple Drude model, the charge carrier mobility is inversely proportional to the effective charge carrier mass. The low effective mass and high crystallinity of inorganic semiconductors result in large carrier mobilities of up to 1E7 cm^2/Vs for GaAs at low temperatures. The large effective mass in van der Waals bonded organic materials and their poorer molecular order decrease the carrier mobility. This thesis addresses the limitations of the inherently low mobility and disorder in organic thin films in a twofold way. The first is the introduction of a novel synthesis method for graphene nanoribbons, which are covalently bonded long stripes of graphene. This new method, developed in this thesis, is based on laser induced photothermal heating. It allows for the synthesis of atomically precise graphene nanoribbons with a higher degree of control over the reaction than conventional methods and is shown to work in a multitude of different nanoribbon species. The growth takes place in an area that is solely governed by the spotsize of the incoming laser light (4 µm). This method has an advantage over present methods through the exact control of the growth kinetics with regards to chemical uniformity and local area distribution. Additionally, the physical properties and growth kinetics of photothermally grown graphene nanoribbons are investigated by means of Raman spectroscopy. In a second way, the growth of organic moire structures on a topological insulator is studied. We show the growth of C60 thin films on the topological insulator Bi4Te3 through electron diffraction and observe a moire pattern. This indicates very long range order in the form of a (4x4) on (9x9) superstructure that is observable on the entire 1x1 cm^2 sample surface. The growth of the structure is performed using molecular beam epitaxy (MBE) and chemical vapor deposition (CVD) in ultra-high vacuum (UHV) conditions and the properties of the interface are studied using low energy electron diffraction (LEED), angle resolved photoemission spectroscopy (ARPES) and density functional theory (DFT). We find that a C60 induced surface reconstruction and the softness of the underlying, layered topological insulator are responsible for the high order. The theoretical calculations find that the structure bonds mostly through physisorption and both the theory and band structure measurements show no perturbation of the electronic states of the topological insulator by the overlayer. Finally, we extend the concept of well ordered growth of organic thin films on topological insulators to superconducting alkali metal doped C60. These organic films are metallic at room temperature but turn into s-wave superconductors at a critical temperature of 28 K. The combination of this relatively high transition temperature in combination with the well defined growth opens up a new playground for both experimental and theoretical studies. The van der Waals bond nature of the interface protects the interface from alloying, which can be a problem for inorganic topological insulator--superconductor interfaces. We show a novel synthesis route for the growth of well ordered superconducting alkali metal doped fullerenes on the topological insulator Bi4Te3. The growth process is studied using LEED and ultra violet photoemission spectroscopy (UPS) and makes the phase pure synthesis of thin film Rb3C60 possible, which is crucial to avoid contamination through an insulating Rb6C60 phase. ARPES spectra confirm the intactness of the interface by measurements of both the Fermi surface of the topological insulator as well as the newly formed Rb3C60 metallic film