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Geometrical Properties (geometrical + property)
Selected AbstractsGeometrical properties of nodal surfaces of many-electron wave functionsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 10 2010Nikolai D. Chuvylkin Abstract Hypothesis of the exclusion of equipotential surfaces for many-electron wave functions (MWF) has been enunciated. This hypothesis clarifies the physical meaning of the Pauli exclusion principle and opens the way for future progress of new quantum-chemical methods for the construction of approximate MWFs differing from the traditional Hartree,Fock approximation. The equipotential surface exclusion principle has been tested on traditional representative "test systems" of quantum mechanics: the helium atom, the lithium atom, and the hydrogen molecule. Judging by the results of these tests, the use of the suggested approach can lead to a considerable increase in the efficiency of high-accuracy quantum-chemical calculations. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Robust fault detection and isolation for LPV systems under a sensitivity constraintINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 1 2009Saverio Armeni Abstract A novel fault detection and isolation (FDI) filter design method is proposed for linear parameter varying (LPV) systems. The LPV system description can be used to approximate the behavior of nonlinear systems and leads to simple nonlinear FDI designs. The main goal here is to obtain residual generator (RG) filters with enhanced fault transmission dc-gains and large ,, nuisance attenuation. This is achieved using bilinear matrix inequality techniques by exploiting the relevant geometrical properties of the affine LPV description. Finally, it is shown by a nonlinear example that the RG filters designed by the proposed method compare well with alternative approaches including direct nonlinear design methods. Copyright © 2008 John Wiley & Sons, Ltd. [source] Shape-understanding system: A system of expertsINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 10 2004Zbigniew Les A shape-understanding system (SUS) that is able to perform different tasks of shape analysis and recognition, based on the ability of the system to understand different concepts of shape at the different levels of cognition, is proposed. This system is an implementation of a shape-understanding method. The proposed method of shape understanding is based on the concept of possible classes of shapes. Possible classes of shape are based on shape models and are viewed as a hierarchical structure at different levels of description. At each level of description the different aspects of shape such as geometrical properties of shape, perceptual properties of figure, or meaningful properties of visual form are incorporated in the shape model. The shape-understanding system consists of different types of experts that perform different processing and reasoning tasks. © 2004 Wiley Periodicals, Inc. Int J Int Syst 19: 949,978, 2004. [source] Quantifying spatial heterogeneity in dynamic contrast-enhanced MRI parameter mapsMAGNETIC RESONANCE IN MEDICINE, Issue 2 2009Chris J. Rose Abstract Dynamic contrast-enhanced MRI is becoming a standard tool for imaging-based trials of anti-vascular/angiogenic agents in cancer. So far, however, biomarkers derived from DCE-MRI parameter maps have largely neglected the fact that the maps have spatial structure and instead focussed on distributional summary statistics. Such statistics,e.g., biomarkers based on median values,neglect the spatial arrangement of parameters, which may carry important diagnostic and prognostic information. This article describes two types of heterogeneity biomarker that are sensitive to both parameter values and their spatial arrangement. Methods based on Rényi fractal dimensions and geometrical properties are developed, both of which attempt to describe the complexity of DCE-MRI parameter maps. Experiments using simulated data show that the proposed biomarkers are sensitive to changes that distribution-based summary statistics cannot detect and demonstrate that heterogeneity biomarkers could be applied in the drug trial setting. An experiment using 23 DCE-MRI parameter maps of gliomas,a class of tumour that is graded on the basis of heterogeneity,shows that the proposed heterogeneity biomarkers are able to differentiate between low- and high-grade tumours. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source] Vertically aligned diamond nanowires: Fabrication, characterization, and application for DNA sensingPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2009Nianjun Yang Abstract In this review, we introduce a novel procedure to fabricate vertically aligned diamond nanowires with controlled geometrical properties like length and distance between wires by use of nanodiamond particles as a hard mask and by use of reactive ion etching. We summarize the characterizations of nanowires by atomic force microscopy and scanning tunneling microscopy as well as electrochemical techniques. In the last section, we show biofunctionalization of nucleic acid molecules on diamond nanowires using electrochemically bond nitrophenyl molecules as linker for deoxyribonucleic acid (DNA) sensing. The tip biofunctionalization and performance of as-prepared DNA sensors are discussed in detail. [source] A comparison between EAM interatomic potentials for Al and Ni: from bulk systems to nanowiresPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2006S. Peláez Abstract Two different kinds of interatomic potentials within the Embedded Atom Method (EAM) have been used to study several properties of selected crystalline structures and nanowire configurations (ordered and helical) for Al and Ni based systems. Reliability of these potentials has been explored when describing cohesive energy and geometrical properties of the systems under consideration as the atomic coordination number decreases. Results provide a criteria for stablishing the limits of validity of EAM potentials when applied to such systems as metallic ultra-narrow or single atom nanowires. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] An exact sinusoidal beam finite elementPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2008Zdzislaw Pawlak The purpose of the paper is to derive an efficient sinusoidal thick beam finite element for the static analysis of 2D structures. A two,node, 6,DOF curved, sine,shape element of a constant cross,section is considered. Effects of flexural, axial and shear deformations are taken into account. Contrary to commonly used curvilinear co,ordinates, a rectangular co,ordinates system is used in the present analysis. First, an auxiliary problem is solved: a symmetric clamped,clamped sinusoidal arch subjected to unit nodal displacements of both supports is considered using the flexibility method. The exact stiffness matrix for the shear,flexible and compressible element is derived. Introduction of two parameters "n" and "t" enables the identification of shear and membrane influences in the element stiffness matrix. Basing on the principle of virtual work a full set of 18 shape functions related to unit support displacements is derived (total rotations of cross,sections, tangential and normal displacements along the element). The functions are found analytically in the closed form. They are functions of one linear dimensionless coordinate of x,axis and depend on one geometrical parameter of sinusoidal arch, height/span ratio "c" and on physical and geometrical properties of the element cross,section. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fast and automated functional classification with MED-SuMo: An application on purine-binding proteinsPROTEIN SCIENCE, Issue 4 2010Olivia Doppelt-Azeroual Abstract Ligand,protein interactions are essential for biological processes, and precise characterization of protein binding sites is crucial to understand protein functions. MED-SuMo is a powerful technology to localize similar local regions on protein surfaces. Its heuristic is based on a 3D representation of macromolecules using specific surface chemical features associating chemical characteristics with geometrical properties. MED-SMA is an automated and fast method to classify binding sites. It is based on MED-SuMo technology, which builds a similarity graph, and it uses the Markov Clustering algorithm. Purine binding sites are well studied as drug targets. Here, purine binding sites of the Protein DataBank (PDB) are classified. Proteins potentially inhibited or activated through the same mechanism are gathered. Results are analyzed according to PROSITE annotations and to carefully refined functional annotations extracted from the PDB. As expected, binding sites associated with related mechanisms are gathered, for example, the Small GTPases. Nevertheless, protein kinases from different Kinome families are also found together, for example, Aurora-A and CDK2 proteins which are inhibited by the same drugs. Representative examples of different clusters are presented. The effectiveness of the MED-SMA approach is demonstrated as it gathers binding sites of proteins with similar structure-activity relationships. Moreover, an efficient new protocol associates structures absent of cocrystallized ligands to the purine clusters enabling those structures to be associated with a specific binding mechanism. Applications of this classification by binding mode similarity include target-based drug design and prediction of cross-reactivity and therefore potential toxic side effects. [source] River spacing and drainage network growth in widening mountain rangesBASIN RESEARCH, Issue 3 2006Sébastien Castelltort ABSTRACT Drainage networks in linear mountain ranges always display a particular geometrical organisation whereby the spacing between the major drainage basins is on average equal to half the mountain width (distance from the mountain front to the main drainage divide), independent of climate and tectonics. This relationship is valid for mountains having different widths and is thus usually thought to be maintained by drainage reorganisation during mountain belt widening. However, such large-scale systematic drainage reorganisation has never been evidenced. In this paper, we suggest an alternative explanation, namely that the observed drainage basin relationships are an inherent property of dendritic river networks and that these relationships are established on the undissected, lowland margins outside mountain ranges and are progressively incorporated and quenched into uplifted topography during range widening. Thus, we suggest that the large-scale geometry of drainage networks in mountain ranges is mainly antecedent to erosion. We propose a model in which the large-scale drainage geometry is controlled mainly by the geometrical properties of the undissected surfaces (in particular, the ratio of the regional slope to the local slope related to roughness) over which rivers are flowing before uplift, and is therefore independent of climate and tectonics. [source] Amphiphilic Organic Ion Pairs in Solution: A Theoretical StudyCHEMPHYSCHEM, Issue 10 2007Vincent Pradines Dr. Abstract The macroscopic manifestation of hydrophobic interactions for amphiphilic organic ion pairs (tetraalkylammonium,anion) has been shown experimentally by measuring their association constants and their affinity with the organic phase. Beyond a certain size, there is a direct relation between association constants and chain lengths in tetraalkylammonium ions. We propose to cast a bridge between these results and geometrical properties considered at the level of a single ion pair by means of quantum chemistry calculations performed on model systems: trimethylalkylammonium,pentyl sulfate instead of tetraalkylammonium,dodecyl sulfate. Two limiting cases are considered: head-to-head configurations, which yield an optimal electrostatic interaction between polar heads, and parallel configurations with a balance between electrostatic and hydrophobic interactions. All properties (geometries, complexation energies, and atomic charges) were obtained at the MP2 level of calculation, with water described by a continuum model (CPCM). Dispersion forces link hydrocarbon chains of tetraalkylammonium ions and pentyl sulfate, thus yielding (for the largest ion pairs) parallel configurations favored with respect to head-to-head geometries by solute,solvent electrostatic interactions. Given the small experimental association energies, we probe the accuracy limit of the MP2 and CPCM methods. However, clear trends are obtained as a function of chain length, which agree with the experimental observations. The calculated monotonic stabilization of ion pairs when the hydrocarbon chain increases in length is discussed in terms of electrostatic interactions (between ions and between ion pairs and water), dispersion forces, and cavitation energies. [source] | |||||||||||||