Unique Solutions to Hartree-Fock Equations for Closed Shell Atoms

In this paper we study the problem of uniqueness of solutions to the Hartree and Hartree-Fock equations of atoms. We show, for example, that the Hartree-Fock ground state of a closed shell atom is unique provided the atomic number $Z$ is sufficiently large compared to the number $N$ of electrons. More specifically, a two-electron atom with atomic number $Z\geq 35$ has a unique Hartree-Fock ground state given by two orbitals with opposite spins and identical spatial wave functions. This statement is wrong for some $Z>1$, which exhibits a phase segregation.Comment: 18 page

Boundaries of Semantic Distraction: Dominance and Lexicality Act at Retrieval

Three experiments investigated memory for semantic information with the goal of determining boundary conditions for the manifestation of semantic auditory distraction. Irrelevant speech disrupted the free recall of semantic category-exemplars to an equal degree regardless of whether the speech coincided with presentation or test phases of the task (Experiment 1) and occurred regardless of whether it comprised random words or coherent sentences (Experiment 2). The effects of background speech were greater when the irrelevant speech was semantically related to the to-be-remembered material, but only when the irrelevant words were high in output dominance (Experiment 3). The implications of these findings in relation to the processing of task material and the processing of background speech is discussed

A parallel cellular automata Lattice Boltzmann Method for convection-driven solidification

This article presents a novel coupling of numerical techniques that enable three-dimensional convection-driven microstructure simulations to be con- ducted on practical time scales appropriate for small-size components or experiments. On the microstructure side, the cellular automata method is efficient for relatively large-scale simulations, while the lattice Boltzmann method provides one of the fastest transient computational fluid dynamics solvers. Both of these methods have been parallelized and coupled in a single code, allowing resolution of large-scale convection-driven solidification problems. The numerical model is validated against benchmark cases, extended to capture solute plumes in directional solidification and finally used to model alloy solidification of an entire differentially heated cavity capturing both microstructural and meso-/macroscale phenomena

A Range of Earth Observation Techniques for Assessing Plant Diversity

AbstractVegetation diversity and health is multidimensional and only partially understood due to its complexity. So far there is no single monitoring approach that can sufficiently assess and predict vegetation health and resilience. To gain a better understanding of the different remote sensing (RS) approaches that are available, this chapter reviews the range of Earth observation (EO) platforms, sensors, and techniques for assessing vegetation diversity. Platforms include close-range EO platforms, spectral laboratories, plant phenomics facilities, ecotrons, wireless sensor networks (WSNs), towers, air- and spaceborne EO platforms, and unmanned aerial systems (UAS). Sensors include spectrometers, optical imaging systems, Light Detection and Ranging (LiDAR), and radar. Applications and approaches to vegetation diversity modeling and mapping with air- and spaceborne EO data are also presented. The chapter concludes with recommendations for the future direction of monitoring vegetation diversity using RS

Fisch oder Karpfen? Lexikale Aktivierung von Benennungsalternativen bei der Objektbenennung

Die vorliegende Arbeit beschäftigt sich in erster Linie mit Prozessen, die dem Formulierungsprozess, genauer gesagt dem lexikalen Zugriff zugeordnet werden können. Es wird genauer auf die unterschiedlichen Vorhersagen von diskreten und nicht-diskreten Modellen des lexikalen Zugriffs eingegangen sowie auf empirische Evidenz für diese unterschiedlichen Modellvorstellungen

Distractor Modality Can Turn Semantic Interference Into Semantic Facilitation in the Picture-Word Interference Task: Implications for Theories of Lexical Access in Speech Production

Item does not contain fulltextA number of recent studies have questioned the idea that lexical selection during speech production is a competitive process. One type of evidence against selection by competition is the observation that in the picture-word interference task semantically related distractors may facilitate the naming of a picture, whereas the selection by competition account predicts them to interfere. In the experiments reported in this article, the authors systematically varied, for a given type of semantic relation-that is, basic-level distractors (e.g., fish) during subordinate-level naming (e.g., carp)-the modality in which distractor words were presented (auditory vs. visual) and the proportion of response-congruent trials (i.e., trials allowing for the correct naming response to be derived from both the distractor and the target). With auditory distractors, semantic interference was obtained irrespective of the proportion of response-congruent trials (low in Experiment 1, high in Experiment 2). With visual distractors, no semantic effect was obtained with a low proportion of response-congruent trials (Experiment 3), whereas a semantic facilitation effect was obtained with a high proportion of response-congruent trials (Experiment 4). The authors propose that two processes contribute to semantic effects observed in the picture-word interference paradigm, namely selection by competition (leading to interference) and response congruency (leading to facilitation). Whether facilitation due to response congruency overrules the interference effect because of competition depends on the relative strength of these two processes

Semantic and phonological activation in noun and pronoun production

2

Utterance format affects phonological priming in the picture-word task: implications for models of phonological encoding in speech production

Item does not contain fulltextPicture-word experiments investigating the production of multiword utterances with distractors that are phonologically related to words in noninitial position have yielded inconsistent results, ranging from facilitation to inhibition. A comparison of these studies is complicated by differences in detail. In parallel to the empirical inconsistencies, different theoretical accounts of phonological encoding in speech production have been provided. In the present article, the authors propose a unitary account, which can in principle account for facilitation, null effects, and inhibition. It assumes a graded activation pattern of the elements within the scope of phonological advance planning. The account is tested in an experiment varying utterance format while keeping all other aspects constant. The results are consistent with the proposed unitary account

Is There Semantic Interference in Delayed Naming?

Item does not contain fulltextThe semantic interference effect in the picture-word interference task is interpreted as an index of lexical competition in prominent speech production models. Janssen, Schirm, Mahon, and Caramazza (2008) challenged this interpretation on the basis of experiments with a novel version of this task, which introduced a task-switching component. Participants either named the picture or read the word, depending on the word's color. Janssen et al. reported semantic interference in picture naming, regardless of whether the word appeared simultaneously with the picture (immediate naming) or 1,000 ms after the picture (delayed naming). Because picture name retrieval is completed in less than 1,000 ms, the finding in delayed naming was taken as evidence against the lexical competition account. In 3 sets of experiments conducted in German and English, we tested for semantic effects in Janssen et al.'s task-switching version and in the standard picture-word interference task. Using identical materials, we obtained sizeable interference effects in the standard task (Experiments 2, 4, and 6) but no effects in the task-switching version (Experiments 1, 3, and 5). When the word reading trials of the task-switching version were replaced with no-go trials (Experiment 7), semantic interference reemerged in immediate naming but was still absent in delayed naming. The experiments question the reliability of Janssen et al.'s critical finding and suggest that theoretical inferences about the origin of semantic effects in the standard picture-word interference task based on results from the task-switching version used by Janssen et al. are difficult to draw.17 p