Geometry Optimization of Crystals by the Quasi-Independent Curvilinear Coordinate Approximation

The quasi-independent curvilinear coordinate approximation (QUICCA) method [K. N\'emeth and M. Challacombe, J. Chem. Phys. {\bf 121}, 2877, (2004)] is extended to the optimization of crystal structures. We demonstrate that QUICCA is valid under periodic boundary conditions, enabling simultaneous relaxation of the lattice and atomic coordinates, as illustrated by tight optimization of polyethylene, hexagonal boron-nitride, a (10,0) carbon-nanotube, hexagonal ice, quartz and sulfur at the $\Gamma$-point RPBE/STO-3G level of theory.Comment: Submitted to Journal of Chemical Physics on 7/7/0

A GENERIC MODEL FOR KNOWLEDGE BASES

A knowledge base system is a database system with logical, temporal and topological structures together with operations on these structures. vVe provide the necessary mathematical concepts for modeling such a system. These are parametrized hierarchical relations, logic functions, hierarchies of variables with their hierarchical control operators, and neighborhood/similarity structures. These concepts are then applied to define a model of a knowledge module. By composition of knowledge modules we obtain the knowledge system model

Lying Your Way to Better Traffic Engineering

To optimize the flow of traffic in IP networks, operators do traffic engineering (TE), i.e., tune routing-protocol parameters in response to traffic demands. TE in IP networks typically involves configuring static link weights and splitting traffic between the resulting shortest-paths via the Equal-Cost-MultiPath (ECMP) mechanism. Unfortunately, ECMP is a notoriously cumbersome and indirect means for optimizing traffic flow, often leading to poor network performance. Also, obtaining accurate knowledge of traffic demands as the input to TE is elusive, and traffic conditions can be highly variable, further complicating TE. We leverage recently proposed schemes for increasing ECMP's expressiveness via carefully disseminated bogus information ("lies") to design COYOTE, a readily deployable TE scheme for robust and efficient network utilization. COYOTE leverages new algorithmic ideas to configure (static) traffic splitting ratios that are optimized with respect to all (even adversarially chosen) traffic scenarios within the operator's "uncertainty bounds". Our experimental analyses show that COYOTE significantly outperforms today's prevalent TE schemes in a manner that is robust to traffic uncertainty and variation. We discuss experiments with a prototype implementation of COYOTE

Surveying viruses on ornamental trees and shrubs in two Hungarian botanical gardens and an arboretum

In Hungary the most common disease of fruit trees causing the most severe damages is Plum pox virus (PPV). This is why it is important to know other woody host plants that can be considered as source of infection. National surveys have been carried out since 2002 for revealing the distribution of PPV on ornamental and wild Prunus species.From 2005 this work has been extended to studying other viruses on other woody plants. In two botanical gardens and an arboretum we selected plants (species and varieties) showing virus symptoms among various thousands of woody plants and submitted them to indexing on woody and herbaceous indicators, as well as to testing with ELISA for the presence of the following 11 viruses occurring on woody plants: PPV, Prune dwarf virus (PDV), Prunus necrotic ringspot virus (PNRSV), Cherry leafroll virus (CLRV), Apple stem pitting virus (ASPV), Apple stem grooving virus (ASGV), Apple mosaic virus (ApMV), Apple chlorotic leafspot virus (ACLSV), Strawberry latent ringspot virus (SLRV), Tomato black ring virus (TBRV) and Arabis mosaic virus (ArMV).Up to now, in 28 plant species and varieties, PPV, PDV, PNRSV, CLRV and ASPV have been detected so far. The presence of PPV was found in 9 species/varieties, such as Prunus cerasifera ’Pendula’, P. cerasifera ’Pissardii’, P. glandulosa, P. glandulosa ‘Alba Plena’, P. glandulosa ’Sinensis’, P. japonica, P. sogdiana, P. tomentosa (from Tibet) and P. x blireana.Seventeen species/varieties were found to be infected with PDV: Lonicera caucasica, L. maackii, L. sachalinensis, Prunus mume ’Omoi-no-mama’, P. salicina (from China), P. spinosa ’Plena’, P. spinosa ’Purpurea’, P. serrulata ’Amanogawa’, P. serrulata ’Ichiyo’, P. serrulata ’Pink Perfection’, P. serrulata ’Taihaku’, P. serrulata ’Yedo-sakura’, P. subhirtella ’Plena’, P. tenella, P. yedoensis, P. yedoensis ’Moerheimii’ and Syringa yunnanensis. Certain species/varieties infected with PDV were positive also for CLRV, such as P. spinosa ’Purpurea’, P. yedoensis, P. yedoensis ’Moerheimii’, P. subhirtella ’Plena’, P. serrulata ’Yedo-sakura’ and to ASPV: P. subhirtella ’Plena’ and P. serrulata ’Yedo-sakura’. PNRSV was detected in P. cerasifera ’ Nigra ’ and ’Hollywood’. The difference of symptoms provoked by PDV on herbaceous hosts suggests that various strains of this virus affect hosts, mainly yellow mottle disease described as a separate strain by Ramaswamy and Posnette on ornamental cherries in 1972. Molecular studies are in progress to confirm the above results. Keywords: ornamental trees and shrubs, virus symptoms, ELISA, Prunus, Lonicera, Syring

Twinning of cubic diamond explains reported nanodiamond polymorphs

The unusual physical properties and formation conditions attributed to h-, i-, m-, and n-nanodiamond polymorphs has resulted in their receiving much attention in the materials and planetary science literature. Their identification is based on diffraction features that are absent in ordinary cubic (c-) diamond (space group: Fd-3m). We show, using ultra-high-resolution transmission electron microscope (HRTEM) images of natural and synthetic nanodiamonds, that the diffraction features attributed to the reported polymorphs are consistent with c-diamond containing abundant defects. Combinations of {113} reflection and rotation twins produce HRTEM images and d-spacings that match those attributed to h-, i-, and m-diamond. The diagnostic features of n-diamond in TEM images can arise from thickness effects of c-diamonds. Our data and interpretations strongly suggest that the reported nanodiamond polymorphs are in fact twinned c-diamond. We also report a new type of twin ( rotational), which can give rise to grains with dodecagonal symmetry. Our results show that twins are widespread in diamond nanocrystals. A high density of twins could strongly influence their applications