Intermolecular forces and fixed-node diffusion Monte Carlo: A brute force test of accuracies for He-2 and He-LiH

The accuracy of the fixed-node approximation and diffusion Monte Carlo method in computing the interaction energy of van der Waals systems was investigated. Tests were carried out by simulating the electronic structures of He-2 and He-LiH. These two systems were chosen as representative of two fundamentally different interactions, namely the weak dispersion forces in He-2 and the dipole/induced-dipole interaction in He-LiH. The results for both systems are in excellent agreement with "state of the art" calculations, thereby indicating a high accuracy for the fixed-node approximation. Also, our interaction energies for He-LiH indicate that the coupled cluster single double triple method [Taylor and Hinde, J. Chem. Phys. 111, 973 (1999)] gives an accurate prediction of the interaction potential for that system. (C) 2003 American Institute of Physics

Синтез ультрадисперсного кристаллического карбида кремния в гиперскоростной струе углерод-кремниевой электроразрядной плазмы

Наночастицы карбида кремния (SiC) могут использоваться для армирования материалов, создания наноструктурированной керамики, микроэлектромеханических систем. В работе представлены результаты плазмодинамического синтеза ультрадисперсных порошков карбида кремния. Этот метод был реализован путем синтеза в электроразрядной плазменной струе, создаваемой сильноточным импульсным коаксиальным магнитоплазменным ускорителем. Синтезированные продукты были проанализированы несколькими современными методами. Согласно результатам анализа, все продукты в основном состоят из кубического карбида кремния (b-SiC) с небольшим количеством непрореагировавших прекурсоров. Сравнение результатов экспериментов позволило сделать выводы о путях контроля фазового состава и дисперсности продукта.Silicon carbide (SiC) nanoparticles can be used for ceramics reinforcement, creation of nanostructured ceramics, microelectromechanical systems. The work presents the results of plasmadynamic synthesis of silicon carbide ultradipersed powders. This method was realized by the synthesis in an electrodischarge plasma jet generated by a high-current pulsed coaxial magnetoplasma accelerator. The synthesized products were analysed by several modern techniques. According to analysis results all the products mainly composed of cubic silicon carbide (b-SiC) with a small amount of unreacted precursors. Comparison of the results of experiments made it possible to draw conclusions on ways to control product phase composition and dispersion

“I drive outside of peak time to avoid traffic jams—Public transport is not attractive here.” Challenging discourses on travel to the University campus in Manila

One of the major narratives in transport policy internationally concerns the promotion of private versus public modes. The Global North has many examples where public transport, walking and cycling networks are well developed, yet examples from the Global South are less evident. There is a historical failure of replicating policies and practices from the Global North, particularly in perpetuating the highway building model, often unsuitable to the cultural contexts in the Global South. This paper examines individual attitudes and discourses concerning travel to De La Salle University campus, in Metro Manila, the Philippines. 42 participants are surveyed using Q methodology. Four discourses are developed, reflecting attitudes to growing automobility in Manila, public transport service provision, the difficulties of travelling in the city and the aspiration for increased comfort whilst travelling. Manila provides an example of the complexities in moving towards greater sustainable travel in the southeast Asian context where levels of private car usage are already high. It is hoped that a greater awareness of the problems of the current travel experiences might lead to us to seek different narratives, where transport systems can be developed which better serve social equity and environmental goals

Strategic vision for sustainable urban transport and mobility in Sierra Leone: Practical implementation constraints and opportunities

This document summarises the consensus that emerged during the T-SUM workshop ‘Future Freetown, Improving Mobility – from Vision to Implementation’ that took place on March 4th 2020 in Freetown, Sierra Leone. The participatory workshop was led by SLURC and UCL, with the support of Freetown City Council, the Ministry of Transport and Aviation, the Sierra Leone Road Safety Authority, the Sierra Leone Roads Authority, the Sierra Leone Road Transport Cooperation, the Sierra Leone Institution of Engineer, Fourah Bay College and the Directorate of Science Technology and Innovation. Circa 50 key stakeholders across sectors and representatives of the public participated

Explicitly correlated trial wave functions in Quantum Monte Carlo calculations of excited states of Be and Be-

We present a new form of explicitly correlated wave function whose parameters are mainly linear, to circumvent the problem of the optimization of a large number of non-linear parameters usually encountered with basis sets of explicitly correlated wave functions. With this trial wave function we succeeded in minimizing the energy instead of the variance of the local energy, as is more common in quantum Monte Carlo methods. We applied this wave function to the calculation of the energies of Be 3P (1s22p2) and Be- 4So (1s22p3) by variational and diffusion Monte Carlo methods. The results compare favorably with those obtained by different types of explicitly correlated trial wave functions already described in the literature. The energies obtained are improved with respect to the best variational ones found in literature, and within one standard deviation from the estimated non-relativistic limitsComment: 19 pages, no figures, submitted to J. Phys.

Predictive model of the dropout intention of Chilean university students

Dropping out of university studies is one of the current problems of Higher Education; the increased rates during the first year of the study programme is considerable around the world. Dropping out has negative social implications that are reflected at the personal, family, institutional, and educational levels. The aim of this study was to evaluate a predictive model considering the mediation of university social satisfaction and perceived academic performance within the relations between perceived social support, social self-efficacy and academic purposes with career satisfaction and dropout intention in Chilean university students. A non-experimental explanatory design of latent and observed variables was used. Structural equation analyses with Mplus software were performed. The sample consisted of 956 first year university students. The study complied with the ethical requirements for research with human subjects. As a result, a predictive model with adequate adjustment indexes was obtained. When evaluating the explanatory capacity through the coefficient of determination (R2), it was observed that it explains 38.9 and 27.4% of the variance of the dropout intention and career satisfaction, respectively. This percentage of explanation indicates a large effect size in Social Sciences; therefore, they are considered adequate predictive models. The mediation of university social satisfaction on the relationships between social support, social self-efficacy, and academic purposes with academic adjustment and dropout intention was, respectively, confirmed. The perception of academic performance has less influence on dropout intention and on career satisfaction among first-year students. The model obtained allows explaining the dropout intention and career satisfaction in first year students. In addition, it is composed of variables that can potentially be modified in the interaction of students and professors