Nodal surfaces of helium atom eigenfunctions

Using a rapidly convergent composite basis of Frankowski-Pekeris and Frankowski functions, we have accurately calculated the nodal surfaces of low-lying excited states of the helium atom to investigate Bressanini and Reynolds\u2019 conjecture D. Bressanini and P. J. Reynolds, Phys. Rev. Lett. 95, 110201 2005 that these nodal surfaces are rigorously independent of the interelectronic angle 12. We find that in fact there is a slight dependence of the nodal surfaces on 12, but it is so small that the assumption of strict independence may well yield extremely useful approximations in fixed-node quantum Monte Carlo calculations. We explain how Kato\u2019s cusp conditions determine the qualitative features of these nodal surfaces, which can accurately be modeled using the familiar ansatz of a symmetric or antisymmetric linear combination of products of hydrogenic orbitals, with some adjustments of the parameters. We explain why a similar near independence of the nodal surfaces on the angular variables can be expected for the ground and singly excited states of the lithium atom, but generally not for larger atoms

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

The Road to Bethlehem

It is a balmy summer evening and Central Coast Adventist School is preparing to open their gates. Everything is ready for the ‘hordes’ about to stream through the gates. Camels are saddled, farm animals are in their pens, tax collectors are out in force and the Roman soldiers are ready to maintain order. As the sounds of the marketplace are heard beyond the gates and the aromas of curries, burgers, hot chips and baked potatoes are wafting through the air, it is clearly not a regular school day

Cooling Strategies for Greenhouses in Summer: Control of Fogging by Pulse Width Modulation

The possibilities for improving the control of greenhouse fogging systems, were studied by comparing several combinations of ventilation cooling techniques, shade screening and low-pressure fogging. The study was divided into three parts: experiments, modelling and simulations. In the first part of the paper, ten combinations of five cooling techniques were tested during the summers of 2002 and 2003 in a 132m2 greenhouse with a steel structure and a single-layer methacrylate cover located in Madrid, Spain. An analysis of variance of the climatic parameters was carried out to determine which combinations produced significant differences in inside temperature or relative humidity. Comparing the values for the inside to outside temperature difference, the combination of a shade screen and above-screen fogging achieved a difference in temperature almost the same as that for under-screen fogging, but the relative humidity was significantly lower. In the second part of the study a dynamic model was developed (2002) and validated (2003). The mean absolute error obtained for inside temperature was similar in the fit and the validation and it was less than 1.5 1C in both cases. The model was used to simulate the inside air temperature for a fog system working without shading, and above and under a shade screen. Control algorithms were developed for reducing system water consumption. In the three cases a simple on/off control with a fixed fogging cycle was compared with a pulse width modulation (PWM) strategy, in which the duration of the fogging pulse was increased as a function of inside temperature. The strategies with PWM applied to the fog system were able to reduce water consumption by 8–15% with respect to the strategies with a fixed fogging cycle

Quantum Monte Carlo calculations of the one-body density matrix and excitation energies of silicon

Quantum Monte Carlo (QMC) techniques are used to calculate the one-body density matrix and excitation energies for the valence electrons of bulk silicon. The one-body density matrix and energies are obtained from a Slater-Jastrow wave function with a determinant of local density approximation (LDA) orbitals. The QMC density matrix evaluated in a basis of LDA orbitals is strongly diagonally dominant. The natural orbitals obtained by diagonalizing the QMC density matrix resemble the LDA orbitals very closely. Replacing the determinant of LDA orbitals in the wave function by a determinant of natural orbitals makes no significant difference to the quality of the wave function's nodal surface, leaving the diffusion Monte Carlo energy unchanged. The Extended Koopmans' Theorem for correlated wave functions is used to calculate excitation energies for silicon, which are in reasonable agreement with the available experimental data. A diagonal approximation to the theorem, evaluated in the basis of LDA orbitals, works quite well for both the quasihole and quasielectron states. We have found that this approximation has an advantageous scaling with system size, allowing more efficient studies of larger systems.Comment: 13 pages, 4 figures. To appear in Phys. Rev.

Incidental learning in a multisensory environment across childhood

Multisensory information has been shown to modulate attention in infants and facilitate learning in adults, by enhancing the amodal properties of a stimulus. However, it remains unclear whether this translates to learning in a multisensory environment across middle childhood, and particularly in the case of incidental learning. One hundred and eighty-one children aged between 6 and 10 years participated in this study using a novel Multisensory Attention Learning Task (MALT). Participants were asked to respond to the presence of a target stimulus whilst ignoring distractors. Correct target selection resulted in the movement of the target exemplar to either the upper left or right screen quadrant, according to category membership. Category membership was defined either by visual-only, auditory-only or multisensory information. As early as 6 years of age, children demonstrated greater performance on the incidental categorization task following exposure to multisensory audiovisual cues compared to unisensory information. These findings provide important insight into the use of multisensory information in learning, and particularly on incidental category learning. Implications for the deployment of multisensory learning tasks within education across development will be discussed

Reproducibility of fixed-node diffusion Monte Carlo across diverse community codes : The case of water–methane dimer

Fixed-node diffusion quantum Monte Carlo (FN-DMC) is a widely trusted many-body method for solving the Schrödinger equation, known for its reliable predictions of material and molecular properties. Furthermore, its excellent scalability with system complexity and near-perfect utilization of computational power make FN-DMC ideally positioned to leverage new advances in computing to address increasingly complex scientific problems. Even though the method is widely used as a computational gold standard, reproducibility across the numerous FN-DMC code implementations has yet to be demonstrated. This difficulty stems from the diverse array of DMC algorithms and trial wave functions, compounded by the method’s inherent stochastic nature. This study represents a community-wide effort to assess the reproducibility of the method, affirming that yes, FN-DMC is reproducible (when handled with care). Using the water–methane dimer as the canonical test case, we compare results from eleven different FN-DMC codes and show that the approximations to treat the non-locality of pseudopotentials are the primary source of the discrepancies between them. In particular, we demonstrate that, for the same choice of determinantal component in the trial wave function, reliable and reproducible predictions can be achieved by employing the T-move, the determinant locality approximation, or the determinant T-move schemes, while the older locality approximation leads to considerable variability in results. These findings demonstrate that, with appropriate choices of algorithmic details, fixed-node DMC is reproducible across diverse community codes—highlighting the maturity and robustness of the method as a tool for open and reliable computational science

Litigation, Mediation and the Psychology of Divorce

The adversary legal system has frequently been criticized by the mental health professions as poorly designed to meet the psychological needs of families. This article explores why that criticism is true. Successful adjustment to divorce by couples and their children requires the completion of critical psychological and practical tasks early in the divorce. In particular, the noninitiating spouse must come to terms with the fact of divorce and control the intense emotions that accompany the decision to divorce. The norms and values of the legal system and the perceptions and behaviors of the lawyers interfere with completion of the psychological tasks and retard adaptation. Mediation is viewed as an appropriate model for supporting the completion of successful divorce. </jats:p