Seeding of supercooled polyethylene with extended chain crystals

Seeding of supercooled polyethylene with extended chain crystal

Modeling the physical properties in the ISM of the low-metallicity galaxy NGC4214

We present a model for the interstellar medium of NGC4214 with the objective to probe the physical conditions in the two main star-forming regions and their connection with the star formation activity of the galaxy. We used the spectral synthesis code Cloudy to model an HII region and the associated photodissociation region (PDR) to reproduce the emission of mid- and far-infrared fine-structure cooling lines from the Spitzer and Herschel space telescopes for these two regions. Input parameters of the model, such as elemental abundances and star formation history, are guided by earlier studies of the galaxy, and we investigated the effect of the mode in which star formation takes place (bursty or continuous) on the line emission. Furthermore, we tested the effect of adding pressure support with magnetic fields and turbulence on the line predictions. We find that this model can satisfactorily predict (within a factor of ~2) all observed lines that originate from the ionized medium ([SIV] 10.5um, [NeIII] 15.6um, [SIII] 18.7um, [SIII] 33.5um, and [OIII] 88um), with the exception of [NeII] 12.8um and [NII] 122um, which may arise from a lower ionization medium. In the PDR, the [OI] 63um, [OI] 145um, and [CII] 157um lines are matched within a factor of ~5 and work better when weak pressure support is added to the thermal pressure or when the PDR clouds are placed farther away from the HII regions and have covering factors lower than unity. Our models of the HII region agree with different evolutionary stages found in previous studies, with a more evolved, diffuse central region, and a younger, more compact southern region. However, the local PDR conditions are averaged out on the 175 pc scales that we probe and do not reflect differences observed in the star formation properties of the two regions.Comment: accepted for publication in A&

DCAL Data Archive and Management Policy

The DCAL Data Archiving and Management Policy outlines the goals of the Deafness Cognition and Language Research Centre (DCAL) at University College London to preserve and share research datasets in a manner that maximises their long-term ethical research use and value. The policy reflects UCL best research practise guidelines - as well as best practice guidelines from the Economic and Social Research Council (ESRC), DCAL’s funder from 2006 to 2016 - ensuring that research data is effectively and appropriately handled, organised, documented, and enhanced

Modeling laser wakefield accelerators in a Lorentz boosted frame

Modeling of laser-plasma wakefield accelerators in an optimal frame of reference \cite{VayPRL07} is shown to produce orders of magnitude speed-up of calculations from first principles. Obtaining these speedups requires mitigation of a high-frequency instability that otherwise limits effectiveness in addition to solutions for handling data input and output in a relativistically boosted frame of reference. The observed high-frequency instability is mitigated using methods including an electromagnetic solver with tunable coefficients, its extension to accomodate Perfectly Matched Layers and Friedman's damping algorithms, as well as an efficient large bandwidth digital filter. It is shown that choosing the frame of the wake as the frame of reference allows for higher levels of filtering and damping than is possible in other frames for the same accuracy. Detailed testing also revealed serendipitously the existence of a singular time step at which the instability level is minimized, independently of numerical dispersion, thus indicating that the observed instability may not be due primarily to Numerical Cerenkov as has been conjectured. The techniques developed for Cerenkov mitigation prove nonetheless to be very efficient at controlling the instability. Using these techniques, agreement at the percentage level is demonstrated between simulations using different frames of reference, with speedups reaching two orders of magnitude for a 0.1 GeV class stages. The method then allows direct and efficient full-scale modeling of deeply depleted laser-plasma stages of 10 GeV-1 TeV for the first time, verifying the scaling of plasma accelerators to very high energies. Over 4, 5 and 6 orders of magnitude speedup is achieved for the modeling of 10 GeV, 100 GeV and 1 TeV class stages, respectively

The Role of the Communicative Approach in the Development of Terminology

The emergence of new terminology approaches does not mean that one approach should be used in preference to a previous one. These approaches suggest the structuring of terminology as a scientific research program, as described in Lakatos’s Methodology of Scientific Research Programmes. Specifically, we propose to explore the role of the Communicative Theory of Terminology in the development of the discipline. The heuristic of this approach, the set of rules intended to increase the probability of solving a problem within the discipline, will allow us to determine how the communicative approach contributes to the development of the research program.Du point de vue de la méthodologie du programme de recherche scientifique de Lakatos, l’émergence de nouvelles approches terminologiques ne signifie pas qu’on doive privilégier une approche plutôt qu’une autre. Ces approches doivent plutôt être vues comme celles qui structurent la terminologie comme programme de recherche scientifique. De façon spécifique, nous nous proposons d’explorer le rôle de la théorie communicative de la terminologie dans le développement de la discipline. L’heuristique de l’approche — l’ensemble de règles conçues pour augmenter les possibilités de résoudre un problème dans la discipline — nous permettra de déterminer comment l’approche communicative contribue au développement du programme de recherche terminologique

Les noms propres et leurs dérivés dans le vocabulaire de l’intelligence artificielle

Les noms propres et leurs dérivés dans le vocabulaire de l'intelligence artificielle – Cet article présente les résultats d'une étude qui porte sur un sujet relativement peu exploré par les terminologues, à savoir la part des noms propres et de leurs dérivés dans la formation des vocabulaires techniques et scientifiques. Nous nous intéressons en particulier dans cet article aux onomastismes qui font partie du vocabulaire de l'intelligence artificielle. L'article se divise en trois parties. Nous présentons tout d'abord les matrices morphosyntaxiques qui composent les onomastismes de l'intelligence artificielle. Nous étudions ensuite les unités terminologiques complexes onomastiques du point de vue du nom propre et de son réfèrent. Enfin, nous examinons ces mêmes unités du point de vue de leur déterminé.Proper Names and Their Derivatives in Artificial Intelligence Terminology – This article presents the results of a study on a topic which has received relatively little attention from terminologists: the place of proper names and their derived forms in the formation of scientific and technical terms. The study focusses on the field of artificial intelligence: the morphosyntactic patterns of onomastic forms used in the field; the complex onomastic terminological units seen from the point of view of the proper noun and its referent; and finally, these forms as examined from the point of view of their base unit

Speeding up simulations of relativistic systems using an optimal boosted frame

It can be computationally advantageous to perform computer simulations in a Lorentz boosted frame for a certain class of systems. However, even if the computer model relies on a covariant set of equations, it has been pointed out that algorithmic difficulties related to discretization errors may have to be overcome in order to take full advantage of the potential speedup. We summarize the findings, the difficulties and their solutions, and show that the technique enables simulations important to several areas of accelerator physics that are otherwise problematic, including self-consistent modeling in three-dimensions of laser wakefield accelerator stages at energies of 10 GeV and above.Comment: To be published in the proceedings of DPF-2009, Detroit, MI, July 2009, eConf C09072

Effects of Hyperbolic Rotation in Minkowski Space on the Modeling of Plasma Accelerators in a Lorentz Boosted Frame

Laser driven plasma accelerators promise much shorter particle accelerators but their development requires detailed simulations that challenge or exceed current capabilities. We report the first direct simulations of stages up to 1 TeV from simulations using a Lorentz boosted calculation frame resulting in a million times speedup, thanks to a frame boost as high as gamma=1300. Effects of the hyperbolic rotation in Minkowski space resulting from the frame boost on the laser propagation in the plasma is shown to be key in the mitigation of a numerical instability that was limiting previous attempts

Psychosis or Spiritual Emergency: The Potential of Developmental Psychopathology for Differential Diagnosis

This paper reviews the nosological systems in the field of psychology, comparing the classic medical model with a developmental approach to psychopathology and wellbeing. The argument is made that a developmental model offers greater refinement for distinguishing phenomenologically similar experiential states. Due to their substantial overt resemblance, a contrast between spiritual emergencies and pathological psychotic reactions is presented as an example. To make this comparison, the nature and etiology of psychotic disorders is reviewed, underscoring their developmental, as opposed to spontaneous, origins. This is followed by a brief overview of spirituality and its place in psychological wellbeing and development. Finally, the concept of spiritual emergency is presented, followed by a discussion of how a holistic, developmental understanding of psychological disorder and wellbeing can aid clinicians in differentiating psychotic experiences indicative of psychopathology from spiritual emergencies