van der Waals interactions of the benzene dimer: towards treatment of polycyclic aromatic hydrocarbon dimers

Although density functional theory (DFT) in principle includes even long-range interactions, standard implementations employ local or semi-local approximations of the interaction energy and fail at describing the van der Waals interactions. We show how to modify a recent density functional that includes van der Waals interactions in planar systems [Phys. Rev. Lett. 91, 126402 (2003)] to also give an approximate interaction description of planar molecules. As a test case we use this modified functional to calculate the binding distance and energy for benzene dimers, with the perspective of treating also larger, flat molecules, such as the polycyclic aromatic hydrocarbons (PAH).Comment: 7 pages, 2 figures (3 figure files) submitted to Materials Science and Engineering

Effect of \u3ci\u3eBeauveria Bassiana\u3c/i\u3e on Underground Stages Of the Colorado Potato Beetle, \u3ci\u3eLeptinotarsa Decemlineata\u3c/i\u3e (Coleoptera: Chrysomelidae)

Tests were conducted to determine the effect of the fungus Beauveria bassiana (B.b.) on underground of the Colorado potato beetle (CPB), Leptinotarsa decemlineata. Two levels of B.h., g/m2 and 75 g/m2 , were suspended in water and sprinkled over the surface of the ground in cages to which CPB were added, either as overwintering adults or as 4th instar larvae of the 15t generation. Efficacy of treatments was determined by counting emerged adults. Neither level of B .b. increased mortality in overwintering adults. The highest level of B.h. caused a significant decline in emergence of adults from the 1st generation 4th instars. The 7.5 g/m2 treatment level did not significantly differ from control treatments

A Model Third Grade Science Curriculum for Use in a Magnet School

The purpose of this project was to design and develop a model third grade magnet school science curriculum that would give students an opportunity for hands-on, experiential learning. To accomplish this purpose, current research and literature on magnet schools, magnet science curricula, elementary science curricula, experiential learning and multiple intelligences were reviewed. Additionally, information and materials from selected magnet elementary schools around the Yakima Valley were obtained and analyzed. Finally, student learning objectives, performance criteria, learning activities, teaching strategies and instructional materials were adapted and developed

Deep levels in a-plane, high Mg-content MgxZn1-xO epitaxial layers grown by molecular beam epitaxy

Deep level defects in n-type unintentionally doped a-plane MgxZn1−xO, grown by molecular beam epitaxy on r-plane sapphire were fully characterized using deep level optical spectroscopy (DLOS) and related methods. Four compositions of MgxZn1−xO were examined with x = 0.31, 0.44, 0.52, and 0.56 together with a control ZnO sample. DLOS measurements revealed the presence of five deep levels in each Mg-containing sample, having energy levels of Ec − 1.4 eV, 2.1 eV, 2.6 V, and Ev + 0.3 eV and 0.6 eV. For all Mg compositions, the activation energies of the first three states were constant with respect to the conduction band edge, whereas the latter two revealed constant activation energies with respect to the valence band edge. In contrast to the ternary materials, only three levels, at Ec − 2.1 eV, Ev + 0.3 eV, and 0.6 eV, were observed for the ZnO control sample in this systematically grown series of samples. Substantially higher concentrations of the deep levels at Ev + 0.3 eV and Ec − 2.1 eV were observed in ZnO compared to the Mg alloyed samples. Moreover, there is a general invariance of trap concentration of the Ev + 0.3 eV and 0.6 eV levels on Mg content, while at least and order of magnitude dependency of the Ec − 1.4 eV and Ec − 2.6 eV levels in Mg alloyed samples

Storage of correlated patterns in a perceptron

We calculate the storage capacity of a perceptron for correlated gaussian patterns. We find that the storage capacity $\alpha_c$ can be less than 2 if similar patterns are mapped onto different outputs and vice versa. As long as the patterns are in general position we obtain, in contrast to previous works, that $\alpha_c \geq 1$ in agreement with Cover's theorem. Numerical simulations confirm the results.Comment: 9 pages LaTeX ioplppt style, figures included using eps

Double diamond phase in pear-shaped nanoparticle systems with hard sphere solvent

The mechanisms behind the formation of bicontinuous nanogeometries, in particular in vivo, remain intriguing. Of particular interest are the many systems where more than one type or symmetry occurs, such as the Schwarz’ diamond surface and Schoen’s gyroid surface; a current example are the butterfly nanostructures often based on the gyroid, and the beetle nanostructures often based on the diamond surface. Here, we present a computational study of self-assembly of the bicontinuous Pn3m diamond phase in an equilibrium ensemble of pear-shaped particles when a small amount of a hard-sphere ‘solvent’ is added. Our results are based on previous work that showed the emergence of the gyroid Ia3d phase in a pure system of pear-shaped particles (Schönhöfer et al 2017 Interface Focus 7 20160161), in which the pear-shaped particles form an interdigitating bilayer reminiscent of a warped smectic structure. We here show that the addition of a small amount of hard spherical particles tends to drive the system towards the bicontinuous Pn3m double diamond phase, based on Schwarz diamond minimal surface. This result is consistent with the higher degree of spatial heterogeneity of the diamond minimal surface as compared to the gyroid minimal surface, with the hard-sphere ‘solvent’ acting as an agent to relieve packing frustration. However, the mechanism by which this relief is achieved is contrary to the corresponding mechanism in copolymeric systems; the spherical solvent tends to aggregate within the matrix phase, near the minimal surface, rather than within the labyrinthine channels. While it may relate to the specific form of the potential used to approximate the particle shape, this mechanism hints at an alternative way for particle systems to both release packing frustration and satisfy geometrical restrictions in double diamond configurations. Interestingly, the lattice parameters of the gyroid and the diamond phase appear to be commensurate with those of the isometric Bonnet transform

3-d Lattice QCD Free Energy to Four Loops

We compute the expansion of the 3-d Lattice QCD free energy to four loop order by means of Numerical Stochastic Perturbation Theory. The first and second order are already known and are correctly reproduced. The third and fourth order coefficients are new results. The known logarithmic divergence in the fourth order is correctly identified. We comment on the relevance of our computation in the context of dimensionally reduced finite temperature QCD.Comment: 8 pages, 3 figures, latex typeset with JHEP3.cl

Cygnus X-2: the Descendant of an Intermediate-Mass X-Ray Binary

The X-ray binary Cygnus X-2 (Cyg X-2) has recently been shown to contain a secondary that is much more luminous and hotter than is appropriate for a low-mass subgiant. We present detailed binary-evolution calculations which demonstrate that the present evolutionary state of Cyg X-2 can be understood if the secondary had an initial mass of around 3.5 M_sun and started to transfer mass near the end of its main-sequence phase (or, somewhat less likely, just after leaving the main sequence). Most of the mass of the secondary must have been ejected from the system during an earlier rapid mass-transfer phase. In the present phase, the secondary has a mass of around 0.5 M_sun with a non-degenerate helium core. It is burning hydrogen in a shell, and mass transfer is driven by the advancement of the burning shell. Cyg X-2 therefore is related to a previously little studied class of intermediate-mass X-ray binaries (IMXBs). We suggest that perhaps a significant fraction of X-ray binaries presently classified as low-mass X-ray binaries may be descendants of IMXBs and discuss some of the implications