How to Mix Molecules with Mathematics

In this paper we develop two methods to calculate thermodynamic properties of mixtures. Starting point are the basic assumptions that also form the basis for the COSMO-RS model. In this approach, the individual molecules are represented by their geometrical shape with an electrical charge density on their surfaces. Next, the surface is split up into surface segments each with its own charge. In COSMO-RS a strong reduction is introduced by treating the segments as if they are completely independent. In the present study we take into account that the coupling between two patches is essentially dependent on the charge distribution on neighboring segments and on the local geometrical structure of the surface. Two approaches are followed. The first one points out how the model equations, which comprise the optimization of the entropy and conservation of internal energy, can efficiently be solved in general, thus also if the dependency between segments and the local geometry is included in the expression for the coupling energy between segments. In the second method the configuration with maximal entropy and prescribed energy is sought via simulation. Successive molecular configurations of the mixture are simulated and updated via a genetic algorithm to optimize the entropy. The second method is more time consuming but very general

Nofs ta' kelma

Ġabra ta’ poeżiji u proża li tinkludi: Alla kbir bla qies! ta’ R. M. B. – Tantum ergo – Lil kewkba feġġa – Għajjiena le xebagħna ta’ Ros. Briffa – Sliem ta’ Dun Karm – Kewkba ta’ Dun Karm – Nofs ta’ kelma ta’ A. C.N/

Development and Implementation of a Flipped-Classroom Delivery in Engineering Computing and Analysis for First Year Engineering Students

University of Wollongong recently undertook a major restructure of its academic and professional units, after the appointment of a new Vice Chancellor in 2012. As a result, the previous 11 faculties have been merged and rationalised into five new faculties. The Faculty of Engineering and the Faculty of Informatics merged to become the Faculty of Engineering and Information Sciences (EIS), consisting of six schools representing a total of 13 disciplines. Following the restructuring, EIS made the decision to develop a new common first year curriculum for all engineering undergraduate programs, spanning nine disciplines, they being; civil, mining, environmental, electrical, computer, telecommunications, mechanical, materials and mechatronic engineering. The process of developing the new first year subjects was undertaken in 2014 by a Task and Finish (T&F) group aiming for full implementation at the commencement of 2015. Through consultation with key stakeholders from each discipline area, as well as teaching teams from existing first year programs, five new engineering subjects were to be created, to coexist with the unaltered physics and mathematics subjects. The T&F group met regularly over the course of 2014, where they initially tasked with identifying the key mastery skills that all engineering students should have developed by the end of their first year of full time study. These skills were then grouped into themes, leading to the creation of the five new subjects. The final role of the T&F group was to report back to the Heads of School who would then assign key personnel to develop the curriculum content for each new subject. This paper will focus on the development of one of those newly created subjects, ENGG105 Engineering Computing and Analysis, which adopted the flipped-classroom approach to deliver the subject content

Precise absolute astrometry from the VLBA imaging and polarimetry survey at 5 GHz

We present in this paper accurate positions of 857 sources derived from the astrometric analysis of 16 eleven-hour experiments from the Very Long Baseline Array imaging and polarimetry survey at 5 GHz (VIPS). Among observed sources, positions of 430 objects were not determined before at a milliarcsecond level of accuracy. For 95% of the sources the uncertainty of their positions range from 0.3 to 0.9 mas, with the median value of 0.5 mas. This estimate of accuracy is substantiated by the comparison of positions of 386 sources that were previously observed in astrometric programs simultaneously at 2.3/8.6 GHz. Surprisingly, the ionosphere contribution to group delay was adequately modeled with the use of the total electron contents maps derived from GPS observations and only marginally affected estimates of source coordinates.Comment: Accepted for publication by the Astronomical Journal. 7 pages, 2 tables, 4 figures. Submission contains an ascii file with the catalogue. You can get the catalogue by downloading the source of this paper and extracting file table2.tx

L'usage des systèmes d'informations électroniques en recherche scientifique : le cas de la neurophysiologie.

Nous présentons les premiers résultats d'une enquête destinée à mieux connaître les pratiques de recherche d'information bibliographique et documentaire chez les chercheurs scientifiques. 64 chercheurs et étudiants doctorants en neurophysiologie ont répondu à un questionnaire portant sur les méthodes, les outils, et les objectifs des recherches d'information typiques dans leur activité. De plus, 11 personnes parmi les répondants ont participé à un entretien individuel semi structuré. Il en ressort que l'usage d'outils informatisés de recherche d'information bibliographique (RIB) est désormais pratique courante, au détriment des index et autres sources imprimées. Les principaux outils utilisés sont la base de données bibliographiques PubMed et le moteur de recherche Google, avec toutefois de nombreux autres outils plus spécifiques utilisés à titre complémentaire. Les répondants mentionnent des objectifs très variés, comme l'acquisition de connaissances nouvelles, mais aussi la recherche de techniques expérimentales, la veille documentaire, l'alimentation du débat scientifique, ou l'aide à l'enseignement. Les difficultés que rencontrent les experts en neurosciences intégratives dans l'exploitation des outils informatiques de RIB spécialisés semblent surtout liées à l'absence de formation des experts à ces outils. Les chercheurs définissent l'outil informatique de RIB « idéal » comme fiable et exhaustif, mais aussi rapide et facile à utiliser et apprendre . De fait, le facteur temps apparaît déterminant dans leur choix d'utilisation ou non d'un outil particulier. Cette étude ouvre la voie à des expériences plus spécifiques, qui porteront sur les stratégies cognitives des experts dans ce type de tâches

Kinematic Age Estimates for 4 Compact Symmetric Objects from the Pearson-Readhead Survey

Based on multi-epoch observations at 15 and 43 GHz with the Very Long Baseline Array (VLBA) we detect significant angular expansions between the two hot spots of 4 Compact Symmetric Objects (CSOs). From these relative motions we derive kinematic ages of between 300 and 1200 years for the radio emission. These ages lend support to the idea that CSOs are produced in a recent phase of activity. These observations also allow us to study the evolution of the hot spots dynamically in individual sources. In all 4 sources the hot spots are separating along the source axis, but in 1031+567 the tip of one hot spot appears to be moving almost orthogonally to the source axis. Jet components, seen in 3 of the 4 sources observed, are found to be moving relativistically outward from the central engines towards the more slowly moving hot spots.Comment: in press at ApJ for v. 541 Oct. 1, 2000, 23 page LaTeX document includes 6 postscript figure

Magnetic Fields in Quasar Cores II

Multi-frequency polarimetry with the Very Long Baseline Array (VLBA) telescope has revealed absolute Faraday Rotation Measures (RMs) in excess of 1000 rad/m/m in the central regions of 7 out of 8 strong quasars studied (e.g., 3C 273, 3C 279, 3C 395). Beyond a projected distance of ~20 pc, however, the jets are found to have |RM| < 100 rad/m/m. Such sharp RM gradients cannot be produced by cluster or galactic-scale magnetic fields, but rather must be the result of magnetic fields organized over the central 1-100 pc. The RMs of the sources studied to date and the polarization properties of BL Lacs, quasars and galaxies are shown to be consistent so far with the predictions of unified schemes. The direct detection of high RMs in these quasar cores can explain the low fractional core polarizations usually observed in quasars at centimeter wavelengths as the result of irregularities in the Faraday screen on scales smaller than the telescope beam. Variability in the RM of the core is reported for 3C 279 between observations taken 1.5 years apart, indicating that the Faraday screen changes on that timescale, or that the projected superluminal motion of the inner jet components samples a new location in the screen with time. Either way, these changes in the Faraday screen may explain the dramatic variability in core polarization properties displayed by quasars.Comment: Accepted to the ApJ. 27 pages, 9 figures including figure 6 in colo