Coulomb dissociation of O-16 into He-4 and C-12

We measured the Coulomb dissociation of O-16 into He-4 and C-12 within the FAIR Phase-0 program at GSI Helmholtzzentrum fur Schwerionenforschung Darmstadt, Germany. From this we will extract the photon dissociation cross section O-16(alpha,gamma)C-12, which is the time reversed reaction to C-12(alpha,gamma)O-16. With this indirect method, we aim to improve on the accuracy of the experimental data at lower energies than measured so far. The expected low cross section for the Coulomb dissociation reaction and close magnetic rigidity of beam and fragments demand a high precision measurement. Hence, new detector systems were built and radical changes to the (RB)-B-3 setup were necessary to cope with the high-intensity O-16 beam. All tracking detectors were designed to let the unreacted O-16 ions pass, while detecting the C-12 and He-4

Coulomb dissociation of 16O into 4He and 12C

We measured the Coulomb dissociation of 16O into 4He and 12C at the R3B setup in a first campaign within FAIR Phase 0 at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt. The goal was to improve the accuracy of the experimental data for the 12C(a,?)16O fusion reaction and to reach lower center-ofmass energies than measured so far. The experiment required beam intensities of 109 16O ions per second at an energy of 500 MeV/nucleon. The rare case of Coulomb breakup into 12C and 4He posed another challenge: The magnetic rigidities of the particles are so close because of the same mass-To-charge-number ratio A/Z = 2 for 16O, 12C and 4He. Hence, radical changes of the R3B setup were necessary. All detectors had slits to allow the passage of the unreacted 16O ions, while 4He and 12C would hit the detectors' active areas depending on the scattering angle and their relative energies. We developed and built detectors based on organic scintillators to track and identify the reaction products with sufficient precision

Information Structure and Discourse Modelling

This dissertation investigates the interrelation between information structure and discourse structure. Information-structurally backgrounded material is here generally treated as being anaphoric in a very strict sense. It is argued that, apart from having more descriptive content, elements from the sentence background are not different from other types of anaphora: they are subject to the same locality restrictions and they must correspond to the same semantic types. The treatment of the sentence background as a monolithic and atomic unit is refuted. Instead it is argued that sentence backgrounds may be built up from smaller units which are linguistically realise as links and tails (in the sense of Vallduví, 1992). It is shown that links and tails play different roles with respect to the structure of discourse: linguistically realised links have to be bound by a discourse topic, while tails have to be bound by other salient referents within the discourse environment.Este trabajo investiga la interrelación entre la estructura informativa y la estructura del discurso. El material del trasfondo lingüístico (background) de la oración se trata como una serie de elementos anafóricos en sentido estricto. Aunque tengan más contenido descriptivo, comparten las mismas características con otros tipos de anáfora en términos de restricciones de localidad y del tipo semántico. Se rechaza un tratamiento del background de la oración como una unidad atómica. En este trabajo se argumenta que el background se puede construir a partir de elementos más fundamentales, llamados links y tails (siguiendo Vallduví, 1992). Links y tails juegan un papel muy distinto con respecto a la estructura del discurso: los constituyentes realizados como links tienen que estar ligados por un tópico discursivo, mientras que los constituyentes realizados como tails necesitan estar ligados por otros referentes discursivos que estén salientes en el entorno del discurso

Simplificación de textos en español: un estudio explorativo

La simplificación de textos tiene como objetivo la transformación de un texto en una versión equivalente que es mas fácil de leer. En este artículo presentamos un estudio de operaciones de simplificación de textos para el español. Este estudio tiene consecuencias importantes para el desarrollo de un sistema automático.Text simplification is the process of transforming a text into an equivalent which is more understandable for a target user. We focus on text simplification in the Spanish language and present a corpus-based study of simplification operations. The study has implications for the development of an automatic simplification system.The research described in this paper arises from a Spanish research project called Simplext: An automatic system for text simplification (http://www.simplext.es). Simplext is led by Technosite and partially funded by the Ministry of Industry, Tourism and Trade of the Government of Spain, by means of the National Plan of Scientific Research, Development and Technological Innovation (I+D+i), within strategic Action of Telecommunications and Information Society (Avanza Competitiveness, with file number TSI-020302-2010-84)

A second-order joint Eisner model for syntactic and semantic dependency parsing

We present a system developed for the CoNLL-2009 Shared Task (Hajic et al., 2009). We extend the Carreras (2007) parser to jointly annotate syntactic and semantic dependencies. This state-of-the-art parser factorizes the built tree in second-order factors. We include semantic dependencies in the factors and extend their score function to combine syntactic and semantic scores. The parser is coupled with an on-line averaged perceptron (Collins, 2002) as the learning method. Our averaged results for all seven languages are 71.49 macro F1, 79.11 LAS and 63.06 semantic F1.Peer ReviewedPostprint (published version

A second-order joint Eisner model for syntactic and semantic dependency parsing

We present a system developed for the CoNLL-2009 Shared Task (Hajic et al., 2009). We extend the Carreras (2007) parser to jointly annotate syntactic and semantic dependencies. This state-of-the-art parser factorizes the built tree in second-order factors. We include semantic dependencies in the factors and extend their score function to combine syntactic and semantic scores. The parser is coupled with an on-line averaged perceptron (Collins, 2002) as the learning method. Our averaged results for all seven languages are 71.49 macro F1, 79.11 LAS and 63.06 semantic F1.Peer Reviewe

A second-order joint Eisner model for syntactic and semantic dependency parsing

We present a system developed for the CoNLL-2009 Shared Task (Hajic et al., 2009). We extend the Carreras (2007) parser to jointly annotate syntactic and semantic dependencies. This state-of-the-art parser factorizes the built tree in second-order factors. We include semantic dependencies in the factors and extend their score function to combine syntactic and semantic scores. The parser is coupled with an on-line averaged perceptron (Collins, 2002) as the learning method. Our averaged results for all seven languages are 71.49 macro F1, 79.11 LAS and 63.06 semantic F1.Peer Reviewe

CATCG : un sistema de análisis morfosintáctico para el catalán

CATCG es un sistema de análisis morfosintáctico superficial para el catalán, basado en el formalismo Constraint Grammar, que contiene tres herramientas básicas: un analizador morfológico, un etiquetador morfológico y un analizador sintáctico superficial.CATCG is a shallow parser for Catalan. It uses the Constraint Grammar formalism and contains three basic tools: a morphological analyser, a POS tagger and a shallow parser

Investigation of 54Fe(n,γ)55Fe and 35Cl(n, γ)36Cl reaction cross sections at keV energies by Accelerator Mass Spectrometry

Activations with neutrons in the keV energy range were routinely performed at the Karlsruhe Institute of Technology (KIT) in Germany in order to simulate stellar conditions for neutron-capture cross sections. A quasi-Maxwell-Boltzmann neutron spectrum of kT = 25 keV, being of interest for the astrophysical s-process, was produced by the 7Li(p,n) reaction utilizing a 1912 keV proton beam at the Karlsruhe Van de Graaff accelerator. Activated samples resulting in long-lived nuclear reaction products with half-lives in the order of yr 100 Myr were analyzed by Accelerator Mass Spectrometry (AMS). Comparison of the obtained reaction cross sections to literature data from previous Time-of-Flight (ToF) measurements showed that the selected AMS data are systematically lower than the ToF data. To investigate this discrepancy, 54Fe(n,γ)55Fe and 35Cl(n,γ)36Cl reaction cross sections were newly measured at the Frankfurt Neutron Source (FRANZ) in Germany. To complement the existing data, an additional neutron activation of 54Fe and 35Cl at a proton energy of 2 MeV was performed. The results will give implications for the stellar environment at kT = 90 keV, reaching the not yet experimentally explored high-energy s-process range. AMS measurements of the activated samples are scheduled

Investigation of 54Fe(n,γ)55Fe and 35Cl(n, γ)36Cl reaction cross sections at keV energies by accelerator mass spectrometry

Activations with neutrons in the keV energy range were routinely performed at the Karlsruhe Institute of Technology (KIT) in Germany in order to simulate stellar conditions for neutron-capture cross sections. A quasi-Maxwell-Boltzmann neutron spectrum of kT = 25 keV, being of interest for the astrophysical s-process, was produced by the 7Li(p,n) reaction utilizing a 1912 keV proton beam at the Karlsruhe Van de Graaff accelerator. Activated samples resulting in long-lived nuclear reaction products with half-lives in the order of yr 100 Myr were analyzed by Accelerator Mass Spectrometry (AMS). Comparison of the obtained reaction cross sections to literature data from previous Time-of-Flight (ToF) measurements showed that the selected AMS data are systematically lower than the ToF data. To investigate this discrepancy, 54Fe(n,γ)55Fe and 35Cl(n,γ)36Cl reaction cross sections were newly measured at the Frankfurt Neutron Source (FRANZ) in Germany. To complement the existing data, an additional neutron activation of 54Fe and 35Cl at a proton energy of 2 MeV was performed. The results will give implications for the stellar environment at kT = 90 keV, reaching the not yet experimentally explored high-energy s-process range. AMS measurements of the activated samples are scheduled