Different Topologies (different + topology)

Distribution by Scientific Domains

Selected Abstracts

Topology Design of Truss Structures in a Multicriteria Environment

Won-Sun Ruy
As an analogy of the general design process, this article presents a novel design approach that could generate structural design alternatives having different topologies and then select the optimal structures from them together with simultaneously determining the optimal design variables related to geometry and member size subjected to a multiple objective design environment. For this purpose, a specialized genetic algorithm, called StrGA_DeAl+MOGA, that can handle the design alternatives and multicriteria problems very effectively is developed for the optimal structural design. To validate the developed method, plain-truss design problems are considered as illustrative examples. To begin with, the promising topologies are generated under the name of "design alternatives" with consideration of the given multiobjective environment. Based on the selected topology of truss structures, the sizing or geometric optimization process starts to determine the optimal design parameters. Three-bar and ten-bar truss problems are treated in the article to test the concept and methodology. [source]

Hardware implementation of CNN architecture-based test bed for studying synchronization phenomenon in oscillatory and chaotic networks

Ákos Tar
Abstract A 3D modular cellular nonlinear network (CNN) architecture-based test bed, with four-neighbor connectivity, used to study synchronization phenomena in oscillatory and chaotic networks is designed. The architecture is implemented as hardware panels including a standalone robust Chua's circuit kit. The details of electronic implementation along with several test cases of connecting Chua's circuits in different topologies are provided. Test cases are adequately supported by oscilloscope traces. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Synthesis of symmetric and asymmetric singly terminated elliptic ladder filters for multiplexing applications

José R. Montejo-Garai
Abstract An extension of the Cauer ladder development for synthesizing singly terminated filters with symmetric and asymmetric responses is presented. Basically, a driving-point immittance including reactive constant elements is carried out in such a way that provides the transmission zeros. The reactive constant elements are introduced into the synthesis for two reasons. The first is to consider the possibility of the asymmetric position of transmission zeros in the real frequency axis. The second one is to obtain canonical forms, i.e. networks with the minimum number of elements in the case of symmetrical responses. To validate the proposed method, a filter with asymmetrical response has been synthesized, comparing different topologies for its use in multiplexers. This fact is illustrated with a Ku-band elliptic response diplexer designed in H-plane rectangular waveguide. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009. [source]

Nanoparticles of CdCl2 with closed cage structures

Reshef Tenne
Nanoparticles of various layered compounds having a closed cage or nanotubular structure, designated also inorganic fullerene-like (IF) materials, have been reported in the past. In this work IF -CdCl2 nanoparticles were synthesized by two methods. In one technique, a high temperature evaporation and subsequent condensation of dried cadmium chloride powder was used. In the other method, electron beam irradiation of the source powder led to its recrystallization into closed nanoparticles with a nonhollow core. The two methods are shown to produce nanoparticles of different topologies. While mostly spherical nested structures are obtained from the high temperature process, polyhedra with hexagonal or elongated rectangular characters are obtained by the electron beam induced process. The analysis also shows that, while the source (dried) powder is orthorhombic cadmium chloride monohydrate, the crystallized IF cage consists of the anhydrous 3R polytype which is not stable as bulk material in ambient atmosphere. Consistent with previous observations, this study shows that the seamless structure of the IF materials can stabilize phases, which are otherwise unstable in ambient conditions. [source]

Limited tendency of ,-helical residues to form disulfide bridges: a structural explanation

Alfonso De Simone
Abstract Disulfide bridges have an enormous impact on the structure of a large number of proteins and polypeptides. Understanding the structural basis that regulates their formation may be important for the design of novel peptide-based molecules with a specific fold and stability. Here we report a statistical analysis of the relationships between secondary structure and disulfide bond formation, carried out using a large database of protein structures. Our analyses confirm the observation sporadically reported in previous investigations that cysteine residues located in ,-helices display a limited tendency to form disulfide bridges. The very low occurrence of the disulfide bond in all ,-chains compared to all ,-chains indicates that this property is also evident when proteins with different topologies are investigated. Taking advantage of the large database that endorsed the analysis on relatively rare motifs, we demonstrate that cysteine residues embedded in 310 helices present a good tendency to form disulfide bonds. This result is somewhat surprising since 310 helices are commonly assimilated into ,-helices. A plausible structural explanation for the observed data has been derived combining analyses of disulfide bond sequence separation and of the length of the different secondary structure elements. Copyright © 2006 European Peptide Society and John Wiley & Sons, Ltd. [source]

Distinguishing Linear from Star-Branched Polystyrene Solutions with Fourier-Transform Rheology

Thorsten Neidhöfer
Abstract Summary: Fourier-Transform rheology (FT rheology) was used to study the influence of the degree of branching on the nonlinear relaxation behaviour of polystyrene solutions. The results were compared with those obtained under oscillatory shear and step-shear conditions. The different topologies could be distinguished using FT rheology where the other rheological measurements failed. Significant differences occurred under large amplitude oscillatory shear (LAOS) conditions as particularly reflected in the phase difference of the third harmonic, ,3, which could be related to strain-softening and strain-hardening behaviour. Currently, this work is extended towards different topologies in polyolefins (e.g. long chain branched). Phase difference ,3 as a function of the Deborah number De at ,0,=,2 for the polystyrene solutions measured at temperatures from 295 to 350.5 K. [source]

Phylogenetic reconstruction of Gram-positive organisms based on comparative sequence analysis of molecular chaperones from the ruminal microorganism Ruminococcus flavefaciens FD-1

Dionysios A. Antonopoulos
Abstract Primers designed on the basis of nucleotide sequences conserved in DnaK and GroEL from Gram-positive organisms were used to PCR amplify internal regions of the cognate genes from the anaerobic ruminal cellulolytic bacterium Ruminococcus flavefaciens FD-1. Genome walking was then utilized to elucidate the remainder of the sequences in addition to upstream and downstream regions. The full sequence of the gene encoding the GroES protein (groES) was found directly upstream from groEL. The deduced amino acid sequence of the groEL gene showed the highest homology with the amino acid sequence of the Clostridium thermocellum GroEL protein (72% amino acid identity). Similarly, translation of the groES nucleotide sequence showed highest homology to the C. thermocellum GroES protein (61% amino acid identity). Analysis of the upstream region of this chaperonin operon revealed a CIRCE regulatory element 45 bp upstream from the putative start of the groES ORF. The deduced amino acid sequence of the putative dnaK gene showed the highest homology with the amino acid sequence of the Clostridium acetobutylicum DnaK protein (68% amino acid identity). Phylogenetic analyses based on the translated sequences reiterate this relationship between R. flavefaciens and the Clostridia. However, when the nucleotide sequences of Gram-positive organisms are analyzed, a different topology occurs of the relationship between high- and low-G+C Gram-positive organisms to the 16S rRNA interpretation. [source]

Diversity in five goat populations of the Lombardy Alps: comparison of estimates obtained from morphometric traits and molecular markers

P. Crepaldi
Phenotypic and genetic variability were studied within and between the goat populations of Bionda dell'Adamello, Frisa, Orobica, Verzaschese and Val di Livo. These are populations reared for most of the year on pastures of the Lombardy Alps, numbering a minimum of 1000 and a maximum of 8000 individuals per breed. The first four are standardized breeds of recent formation; at present they are supported by the European Union measures for the conservation of rare breeds. On the basis of its visible genetic profile the Val di Livo goat may be classified as a primary population. Phenotypic variability was estimated on the basis of six somatic measurements on 60,140 adult goats per breed, whereas genetic variation was measured on the basis of 201 AFLP loci. The partition of the total molecular variation into the within and between breed components indicates that the majority of the molecular variability is conserved within populations, whereas only 8.8% can be attributed to between population variation. Morphometric and molecular marker data produced unrelated distance values and different topology of UPGMA clusters. It may be hypothesized that the morphometric originality of the Val di Livo goat is mostly determined by environmental factors and selection pressure rather than by different origin and genome evolution. Conversely Orobica seems to have diverged from the other breeds at the genome level, which may be explained by an undocumented Southern Italian origin. An objective evaluation of conservation priorities may in the near future be based on the integrated use of molecular markers and of information on quantitative traits and allelic variation with adaptive relevance. Diversité dans cinq populations de chèvres des Alpes lombardes: comparaisons entre estmations obtenues par des mesures somatiques et par des marqueurs moléculaires On a etudié la variabilité phénotypique et génétique entre et parmi les populations de chèvres Bionda dell'Adamello, Frisa, Orobica, Verzaschese et Val di Livo. Il s'agit de populations qui content entre 1000 et 8000 sujets, elevés pour la plus part de l'année sur les pâturages des Alpes de Lombardie. Les quatre premières, actuellement sauvegardées par des mesures communautaires, sont des races à standard recemment constituées. La chèvre de la Val di Livo peut être rangée parmi les races primaires. La diversité phénotypique a été montrée par un dendrogramme obtenus des distances euclidiennes calculées à partir de six mesures somatiques qui avaient été prises sur 60,140 chèvres adultes pour chaque race. La diversité génétique a été montrée par un dendrogramme bâti sur la matrice des distances de Nei obtenues des 201 marqueurs moléculaires AFLP, produits par 7 combinaisons de primers, sur 30 sujets pour chaque race. La décomposition de la variabilité génétique totale estimée par les données moléculaires a montré que la plus part de la variabilité est conservée parmi la population, tandis que seulement l,8,8% peut être imputé aux différences entre populations. Les données moléculaires et somatiques ont donné lieu à des distances qui ne sont pas corrélées et à des cluster avec une topologie nettement différente. La comparaison entre les deux approches permet d'avancer l'hypothèse que l'originalité somatique de la chèvre de la Val di Livo pourrait être due à des facteurs d'environnement et/ou à la pression de sélection plutôt qu'à des facteurs liés à l'évolution du genome. Au contraire ces derniers seraient responsables de l'originalité génétique de la race Orobica et confirmeraient des témoignages orals non documentés. Un choix objectif des ressources génétiques qui méritent d'être conservées pourra probablement se baser sur l'employ conjoint des marqueurs et de renseignements sur les caractères quantitatifs et sur les variantes alléliques des gènes qui ont une valeur adaptative. Diversität in fünf Ziegenpopulationen der lombardischen Alpen: Vergleich von Schätzungen auf der Basis morphologischer Eigenschaften und molekularer Marker Es wurden die phänotypische und genetische Variabilität innerhalb und zwischen Bionda dell'Adamello, Frisa, Orobica, Verzaschese und Val di Livo Ziegenpopulationen untersucht. Diese Populationen, mit Größen zwischen 1000 und 8000 Tieren, werden den größten Teil des Jahres auf Weiden der lombardischen Alpen gehalten. Die vier erstgenannten Populationen sind erst kürzlich standardisierte Rassen; gegenwärtig werden sie mit EU-Mitteln für die Erhaltung seltener Rassen, unterstützt. Auf der Basis des erkennbaren genetischen Profils muß die Rasse Val di Livo als eine Primärpopulation eingeordnet werden. Phänotypische Variabilität wurde auf der Basis von sechs Körpermaßen an 60,140 ausgewachsenen Ziegen je Rasse geschätzt, die genetische Variation wurde auf der Basis von 201 AFLP-Loci gemessen. Die Aufteilung der gesamten molekularen Varianz in Varianzkomponenten innerhalb und zwischen Populationen zeigt, daß der größte Teil der molekularen Variabilität innerhalb der Populationen auftritt, und nur 8,8% der Gesamtvarianz auf die Varianz zwischen den Populationen entfällt. Morphologische und molekulare Marker erzeugten unabhängige Distanzwerte und unterschiedliche upgma-Cluster. Es kann die Hypothese aufgestellt werden, daß die morphologische Einzigartigkeit der Val di Livo Ziege stärker auf Umwelteffekte und Selektionsdruck als auf eine unterschiedliche Herkunft oder genomische Evolution zurückzuführen ist. Dagegen scheint Orobica auf Genomebene von den anderen Rassen abzuweichen, was durch einen nicht dokumentierten süditalienischen Ursprung erklärt werden könnte. Eine objektive Bewertung von Prioritäten für Konservierungsmaßnahmen dürfte in Zukunft auf einen integrierten Gebrauch molekularer Marker, Informationen über quantitative Merkmale sowie der genetischen Variation bezüglich der Adaptationsfähigkeit basieren. [source]

Combined Pharmacophore Modeling, Docking, and 3D QSAR Studies of ABCB1 and ABCC1 Transporter Inhibitors

CHEMMEDCHEM, Issue 11 2009

Abstract Quinazolinones, indolo- and pyrrolopyrimidines with inhibitory effects toward ABCB1 (P-gp) and ABCC1 (MRP1) transporters were studied by pharmacophore modeling, docking, and 3D QSAR to describe the binding preferences of the proteins. The pharmacophore overlays between dual and/or highly selective inhibitors point to binding sites of different topology and physiochemical properties for MRP1 and P-gp. Docking of selective inhibitors into the P-gp binding cavity by the use of a structural model based on the recently resolved P-gp structure confirms the P-gp pharmacophore features identified, and reveals the interactions of some functional groups and atoms in the structures with particular protein residues. The 3D QSAR analysis of the dual-effect inhibitors allows satisfactory prediction of the selectivity index of the compounds and outlines electrostatics as most important for selectivity. The results from the combined modeling approach complement each other and could improve our understanding of the protein,ligand interactions involved, and could aid in the development of highly selective and potent inhibitors of P-gp and MRP1. [source]