Lexical influences on disfluency production

no. PTA-030-2002-01229Natural spoken language is full of disfluency. Around 10% of utterances produced in everyday speech contain disfluencies such as repetitions, repairs, filled pauses and other hesitation phenomena. The production of disfluency has generally been attributed to underlying problems in the planning and formulation of upcoming speech. However, it remains an open question to what extent factors known to affect the selection and retrieval of words in isolation influence disfluency production during connected speech, and whether different types of disfluency are associated with difficulties at different stages of production. Previous attempts to answer these questions have largely relied on corpora of unconstrained, spontaneous speech; to date, there has been little direct experimental research that has attempted to manipulate factors that underlie natural disfluency production. This thesis takes a different approach to the study of disfluency production by constraining the likely content and complexity of speakers utterances while maintaining a context of naturalistic, spontaneous speech. This thesis presents evidence from five experiments based on the Network Task (Oomen & Postma, 2001), in addition to two related picture-naming studies. In the Network Task, participants described to a listener the route of a marker as it traverses a visually presented network of pictures connected by one or more paths. The disfluencies of interest in their descriptions were associated with the production of the picture name. The experiments varied the ease with which pictures in the networks could be named by manipulating factors known to affect lexical or pre-lexical processing: lexical access and retrieval were impacted by manipulations of picture-name agreement and the frequency of the dominant picture names, while visual and conceptual processing difficulty was manipulated by blurring pictures and through prior picture familiarisation. The results of these studies indicate that while general production difficulty does reliably increase the likelihood of disfluency, difficulties associated with particular aspects of lexical access and retrieval have dissociable effects on the likelihood of disfluency. Most notably, while the production of function word prolongations demonstrates a close relationship to lexical difficulties relating to the selection and retrieval of picture names, filled pauses tend to occur predominantly at the beginning of utterances, and appear to be primarily associated with message-level planning processes. Picture naming latencies correlated highly with the rates of observed hesitations, establishing that the likelihood of a disfluency could be attributed to the same lexical and pre-lexical processes that result in longer naming times. Moreover, acoustic analyses of a subset of observed disfluencies established that those disfluencies associated with more serious planning difficulties also tended to have longer durations, however they do not reliably relate to longer upcoming delays. Taken together, the results of these studies demonstrate that the elicitation of disfluency is open to explicit manipulation, and that mid-utterance disfluencies are related to difficulties during specific production processes. Moreover, the type of disfluency produced is not arbitrary, but may be related to both the type and location of the problem encountered at the point that speech is suspended. Through the further exploration of these relationships, it may be possible to use disfluency as an effective tool to study online language production processes

Intramolecular vibronic dynamics in molecular solids: C60

Vibronic coupling in solid C60 has been investigated with a combination of resonant photoemission spectroscopy (RPES) and resonant inelastic x-ray scattering (RIXS). Excitation as a function of energy within the lowest unoccupied molecular orbital resonance yielded strong oscillations in intensity and dispersion in RPES, and a strong inelastic component in RIXS. Reconciling these two observations establishes that vibronic coupling in this core hole excitation leads to predominantly inelastic scattering and localization of the excited vibrations on the molecule on a femtosecond time scale. The coupling extends throughout the widths of the frontier valence bands.

Resonant core spectroscopies of the charge transfer interactions between C60 and the surfaces of Au(111), Ag(111), Cu(111) and Pt(111)

Charge transfer interactions between C60 and the metal surfaces of Ag(111), Cu(111), Au(111) and Pt(111) have been studied using synchrotron-based photoemission, resonant photoemission and X-ray absorption spectroscopies. By placing the X-ray absorption and valence band spectra on a common binding energy scale, the energetic overlap of the unoccupied molecular orbitals with the density of states of the underlying metal surface have been assessed in the context of possible charge transfer pathways. Resonant photoemission and resonant Auger data, measuring the valence region as a function of photon energy for C60 adsorbed on Au(111) reveals three constant high kinetic energy features associated with Auger-like core-hole decay involving an electron transferred from the surface to the LUMO of the molecule and electrons from the three highest occupied molecular orbitals, respectively and in the presence of ultra-fast charge transfer of the originally photoexcited molecule to the surface. Data for the C60/Ag(111) surface reveals an additional Auger-like feature arising from a core-hole decay process involving more than one electron transferred from the surface into the LUMO. An analysis of the relative abundance of these core-hole decay channels estimates that on average 2.4 $\pm$ 0.3 electrons are transferred from the Ag(111) surface into the LUMO. A core-hole clock analysis has also been applied to assess the charge transfer coupling in the other direction, from the molecule to the Au(111) and Ag(111) surfaces. Resonant photoemission and resonant Auger data for C60 molecules adsorbed on the Pt(111) and Cu(111) surfaces are shown to exhibit no super-Auger features, which is attributed to the strong modification of the unoccupied molecular orbitals arising from stronger chemical coupling of the molecule to the surface

Resonant Lifetime of Core-Excited Organic Adsorbates from First Principles

We investigate by first-principles simulations the resonant electron-transfer lifetime from the excited state of an organic adsorbate to a semiconductor surface, namely isonicotinic acid on rutile TiO$_2$(110). The molecule-substrate interaction is described using density functional theory, while the effect of a truly semi-infinite substrate is taken into account by Green's function techniques. Excitonic effects due to the presence of core-excited atoms in the molecule are shown to be instrumental to understand the electron-transfer times measured using the so-called core-hole-clock technique. In particular, for the isonicotinic acid on TiO$_2$(110), we find that the charge injection from the LUMO is quenched since this state lies within the substrate band gap. We compute the resonant charge-transfer times from LUMO+1 and LUMO+2, and systematically investigate the dependence of the elastic lifetimes of these states on the alignment among adsorbate and substrate states.Comment: 24 pages, 6 figures, to appear in Journal of Physical Chemistry

Ambient pressure x-ray photoelectron spectroscopy setup for synchrotron-based in situ and operando atomic layer deposition research

An ambient pressure cell is described for conducting synchrotron-based x-ray photoelectron spectroscopy (XPS) measurements during atomic layer deposition (ALD) processes. The instrument is capable of true in situ and operando experiments in which it is possible to directly obtain elemental and chemical information from the sample surface using XPS as the deposition process is ongoing. The setup is based on the ambient pressure XPS technique, in which sample environments with high pressure (several mbar) can be created without compromising the ultrahigh vacuum requirements needed for the operation of the spectrometer and the synchrotron beamline. The setup is intended for chemical characterization of the surface intermediates during the initial stages of the deposition processes. The SPECIES beamline and the ALD cell provide a unique experimental platform for obtaining new information on the surface chemistry during ALD half-cycles at high temporal resolution. Such information is valuable for understanding the ALD reaction mechanisms and crucial in further developing and improving ALD processes. We demonstrate the capabilities of the setup by studying the deposition of TiO2 on a SiO2 surface by using titanium(IV) tetraisopropoxide and water as precursors. Multiple core levels and the valence band of the substrate surface were followed during the film deposition using ambient pressure XPS.Peer reviewe

Uncertainties and assessments of chemistry-climate models of the stratosphere

In recent years a number of chemistry-climate models have been developed with an emphasis on the stratosphere. Such models cover a wide range of time scales of integration and vary considerably in complexity. The results of specific diagnostics are here analysed to examine the differences amongst individual models and observations, to assess the consistency of model predictions, with a particular focus on polar ozone. For example, many models indicate a significant cold bias in high latitudes, the “cold pole problem”, particularly in the southern hemisphere during winter and spring. This is related to wave propagation from the troposphere which can be improved by improving model horizontal resolution and with the use of non-orographic gravity wave drag. As a result of the widely differing modelled polar temperatures, different amounts of polar stratospheric clouds are simulated which in turn result in varying ozone values in the models. The results are also compared to determine the possible future behaviour of ozone, with an emphasis on the polar regions and mid-latitudes. All models predict eventual ozone recovery, but give a range of results concerning its timing and extent. Differences in the simulation of gravity waves and planetary waves as well as model resolution are likely major sources of uncertainty for this issue. In the Antarctic, the ozone hole has probably reached almost its deepest although the vertical and horizontal extent of depletion may increase slightly further over the next few years. According to the model results, Antarctic ozone recovery could begin any year within the range 2001 to 2008. The limited number of models which have been integrated sufficiently far indicate that full recovery of ozone to 1980 levels may not occur in the Antarctic until about the year 2050. For the Arctic, most models indicate that small ozone losses may continue for a few more years and that recovery could begin any year within the range 2004 to 2019. The start of ozone recovery in the Arctic is therefore expected to appear later than in the Antarctic

Ultra-fast intramolecular vibronic coupling revealed by RIXS and RPES maps of an aromatic adsorbate on TiO2(110)

Two-dimensional resonant inelastic x-ray scattering (RIXS) and resonant photoelectron spectroscopy (RPES) maps are presented for multilayer and monolayer coverages of an aromatic molecule (bi-isonicotinic acid) on the rutile TiO2(110) single crystal surface. The data reveals ultra-fast intramolecular vibronic coupling upon core-excitation from the N 1s orbital into the lowest unoccupied molecular orbital (LUMO) derived resonance. In the RIXS measurements this results in the splitting of the participator decay channel into a purely elastic line which disperses linearly with excitation energy, and a vibronic coupling channel at constant emission energy. In the RPES measurements the vibronic coupling results in a linear shift in binding energy of the participator channel as the excitation is tuned over the LUMO-derived resonance. Localisation of the vibrations on the molecule on the femtosecond timescale results in predominantly inelastic scattering from the core-excited state in both the physisorbed multilayer and the chemisorbed monolayer

High-coverage structures of carbon monoxide adsorbed on Pt(111) studied by high-pressure scanning tunneling microscopy

High-pressure scanning tunneling microscopy was used to study the room-temperature adsorption of CO on a Pt(111) single-crystal surface in equilibrium with the gas phase. The coverage was found to vary continuously, and over the entire range from 10(-6)-760 Torr pressure-dependent moire patterns were observed, characteristic of a hexagonal or nearly hexagonal CO overlayer. Two different pressure ranges can be distinguished: below 10(-2) Tort, the moire lattice vector is oriented along a 30degrees high-symmetry direction of the substrate, corresponding to a pressure-dependent rotation of the CO overlayer with respect to the (1 x 1) Pt surface lattice, while above 10(-2) Torr, the CO layer angle is independent of the pressure. This behavior is analyzed in terms of the interplay of the repulsive CO-CO interaction potential and the substrate potential

Identifying and managing patients at risk of severe allergic reactions to food: report from two iFAAM workshops

Food allergy affects a small but important number of children and adults. Much of the morbidity associated with food allergy is driven by the fear of a severe reaction, and fatalities continue to occur. Foods are the commonest cause of anaphylaxis. One of the aims of the European Union funded Integrated Approaches to Food Allergen and Allergy Risk Management (iFAAM) project was to improve the identification and management of children and adults at risk of experiencing a severe reaction. A number of interconnected studies within the project have focused on quantifying the severity of allergic reactions; the impact of food matrix, immunological factors on severity of reactions; the impact of co‐factors such as medications on the severity of reactions; utilising single dose challenges to understand threshold and severity of reactions; and community studies to understand the experience of patients suffering real‐life allergic reactions to food. Associated studies have examined population thresholds, and co‐factors such as exercise and stress. This paper summarises two workshops focused on the severity of allergic reactions to food. It outlines the related studies being undertaken in the project indicating how they are likely to impact on our ability to identify individuals at risk of severe reactions and improve their management