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Dynamic Features (dynamic + feature)

Distribution by Scientific Domains

Chemistry	29%
Medical Sciences	11%
Information Science and Computing	11%
Engineering	11%
Earth and Environmental Science	11%

Selected Abstracts

Synthesis and Dynamic Features of (Chloro)zirconocene Cations Stabilised by Pendant (Diarylphosphanyl)alkyl and (Dimethylamino)alkyl Substituents at Their Cyclopentadienyl Ring Systems

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2003
Steve Döring
Abstract Treatment of the substituted (diarylphosphanyl)methyl group-4 metallocene complexes [(C5H4,CR1R2,PAr2)2ZrCl2] (2: R1/R2 = CH3/CH3, H/CH3, H/aryl) with Li[B(C6F5)4] in dichloromethane solution results in chloride ligand abstraction (with LiCl precipitation) to yield the complexes [(C5H4,CR1R2,PAr2)2Zr,Cl+] (5), with both phosphanyl groups internally coordinated to the metal centre. Three possible diastereoisomers are observed in the case of 5c (R1 = H; R2 = CH3), while bulkier R2 substituents give higher selectivities. The thermally induced (reversible) cleavage of the Zr,phosphane linkage results in dynamic NMR behaviour. Gibbs activation energies of ,G,(298 K) = 14.8 ± 0.5 and 14.5 ± 0.5 kcal/mol were obtained for these intramolecular equilibration processes in the complexes trans - 5d (R1 = H; R2 = Ph) and trans - 5e (R1 = H; R2 = ferrocenyl), respectively. Treatment of the substituted (dimethylamino)methyl metallocene complexes [(C5H4,CR1R2,NMe2)2ZrCl2] (6a, 6b) with Li[B(C6F5)4] proceeds analogously to yield the cation systems [{C5H4,C(CH3)2,NMe2}2ZrCl+] (12a) and [{C5H4,CH(CH3),NMe2}2ZrCl+] (12b, three possible diastereoisomers). Both complexes have their pairs of amino groups coordinated to the metal centre. The complexes exhibit dynamic NMR spectra. Selective equilibration of the diastereotopic N(CH3)A(CH3)B resonances of complex 12a is observed [,G,(233 K) = 11.5 ± 0.2 kcal/mol], whereas the adjacent C(CH3)A(CH3)B methyl groups remain diastereotopic. The dynamic equilibration of the latter was observed at a markedly higher temperature [,G,(333 K) = 17.3 ± 0.2 kcal/mol]. Treatment of [{C5H4,C(CH3)2,NMe2}CpZrCl2] (10) with Li[B(C6F5)4] resulted in the formation of complex [{C5H4,C(CH3)2,NMe2}CpZr,Cl+] (11), which shows the internal ,N(CH3)A(CH)B equilibration proceeding with a markedly higher activation barrier [,G,(333 K) = 17.6 ± 0.2 kcal/mol] than in 12a, and a stereochemical memory effect indicative of solvent coordination to the metal centre of the resulting highly electrophilic chlorozirconocene cation intermediate. Complex 11 was characterised by an X-ray crystal structure analysis, which shows the internal Zr,amine coordination. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

You Go This Way and I'll Go That Way: Developmental Changes in Infants' Detection of Correlations among Static and Dynamic Features in Motion Events

CHILD DEVELOPMENT, Issue 3 2002
David H. Rakison
Four experiments utilizing the habituation procedure examined 10- to 18-month-olds' ability to detect and encode correlations among features in a motion event (N= 136). Infants were habituated to two events in which objects,with distinct parts and a distinct body,moved across a screen along a rectilinear or curvilinear motion path. Infants were then tested with one familiar event and three events in which one feature of the object (parts, body, or motion path) was presented in a novel combination with the other features. The results of the experiments revealed that 10-month-olds process independently static features in an event, but do not process correlations among dynamic features; whereas 14-month-olds detect the correlation between an object's parts and its motion trajectory, but only when the movement of parts is correlated with the motion of the object. Further, the data show that 18-month-olds detect correlations between all three features when the parts of the object move, but they detect only the relation between parts and motion path when the parts do not move. It is proposed that infants develop representations for the static and dynamic properties of objects through a sensitive perceptual system that detects individual features, whole objects, and movement properties, and a domain-general associative learning mechanism that encodes independent features and correlations among features. [source]

CAPITAL,LABOUR SUBSTITUTION AND ENDOGENOUS FLUCTUATIONS: A MONOPOLISTIC COMPETITION APPROACH WITH VARIABLE MARKUP,

THE JAPANESE ECONOMIC REVIEW, Issue 3 2009
THOMAS SEEGMULLER
This paper analyses an overlapping generations model with endogenous product diversity where strategic interactions between producers are introduced; it examines how they affect the stability properties of the steady state. Because of free entry, strategic interactions between producers imply a new dynamic feature, markup variability, promoting indeterminacy and endogenous cycles. Indeed, in contrast to the model without strategic interaction, endogenous fluctuations can occur when the substitution between the production factors, capital and labour, is not too weak, but in accordance with empirical estimates. [source]

Most readily usable methods to measure ocular blood flow

ACTA OPHTHALMOLOGICA, Issue 2009
K GUGLETA
Purpose SIS Lecture. Methods Literature search. Results Ocular Blood Flow Research Association (OBFRA, recently merged with another organization - ISOCO, into one single Association for Ocular CDirculation - AOC) made a significant contribution to standardization of the blood flow measuring techniques in the field of ophthalmology. A consens was reached on the number of OBF measurements techniques that occured in the past decades. Particular emphasis was placed on the basic technology, specific parameters and interpretation, accuracy and reproducibility, field of clinical applications. Open questions were extensively discussed, limits of each technique clearly postulated. and a consensus statement put together for each of the technique involved. It encompassed techniques like color Doppler imaging, laser Doppler flowmetry (continuous as well as scanning LDF), laser Doppler velocimetry, Retinal Vessel Analyzer, combination of the vessel diameter measurement and the LDV, laser interferometry of the fundus pulsations amplitude, retinal oxymetry, measurements of the pulsatile component of the blood flow, blue field entoptic method and the newest - Doppler OCT. Conclusion There is no overwhelming measuring technique able to cover all the aspects of the research and the daily clinical routine. Various parameters and various vascular beds are involved, which makes the interpretation of the obtained results strenuous. Of particular importance is the capability of OBF measuring techniques to capture one dynamic feature of ocular circulation - its ability to regulate and to response to various challenges. It is widely believed that not the constantly reduced blood flow, but rather the lack of regulation thereof, leads to prevalent ocular diseases. [source]

PLANNING IN REACTIVE ENVIRONMENTS

COMPUTATIONAL INTELLIGENCE, Issue 4 2007
A. Milani
The diffusion of domotic and ambient intelligence systems have introduced a new vision in which autonomous deliberative agents operate in environments where reactive responses of devices can be cooperatively exploited to fulfill the agent's goals. In this article a model for automated planning in reactive environments, based on numerical planning, is introduced. A planner system, based on mixed integer linear programming techniques, which implements the model, is also presented. The planner is able to reason about the dynamic features of the environment and to produce solution plans, which take into account reactive devices and their causal relations with agent's goals by exploitation and avoidance techniques, to reach a given goal state. The introduction of reactive domains in planning poses some issues concerning reasoning patterns which are briefly depicted. Experiments of planning in reactive domains are also discussed. [source]

Semi-Automatic Time-Series Transfer Functions via Temporal Clustering and Sequencing

COMPUTER GRAPHICS FORUM, Issue 3 2009
Jonathan Woodring
Abstract When creating transfer functions for time-varying data, it is not clear what range of values to use for classification, as data value ranges and distributions change over time. In order to generate time-varying transfer functions, we search the data for classes that have similar behavior over time, assuming that data points that behave similarly belong to the same feature. We utilize a method we call temporal clustering and sequencing to find dynamic features in value space and create a corresponding transfer function. First, clustering finds groups of data points that have the same value space activity over time. Then, sequencing derives a progression of clusters over time, creating chains that follow value distribution changes. Finally, the cluster sequences are used to create transfer functions, as sequences describe the value range distributions over time in a data set. [source]

Assessing a numerical cellular braided-stream model with a physical model

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2005
Andrea B. Doeschl-Wilson
Abstract A. B. Murray and C. Paola (1994, Nature, vol. 371, pp. 54,57; 1997, Earth Surface Processes and Landforms, vol. 22, pp. 1001,1025) proposed a cellular model for braided river dynamics as an exploratory device for investigating the conditions necessary for the occurrence of braiding. The model reproduces a number of the general morphological and dynamic features of braided rivers in a simplified form. Here we test the representation of braided channel morphodynamics in the Murray,Paola model against the known characteristics (mainly from a sequence of high resolution digital elevation models) of a physical model of a braided stream. The overall aim is to further the goals of the exploratory modelling approach by first investigating the capabilities and limitations of the existing model and then by proposing modifications and alternative approaches to modelling of the essential features of braiding. The model confirms the general inferences of Murray and Paola (1997) about model performance. However, the modelled evolution shows little resemblance to the real evolution of the small-scale laboratory river, although this depends to some extent on the coarseness of the grid used in the model relative to the scale of the topography. The model does not reproduce the bar-scale topography and dynamics even when the grid scale and amplitude of topography are adapted to be equivalent to the original Murray,Paola results. Strong dependence of the modelled processes on local bed slopes and the tendency for the model to adopt its own intrinsic scale, rather than adapt to the scale of the pre-existing topography, appear to be the main causes of the differences between numerical model results and the physical model morphology and dynamics. The model performance can be improved by modification of the model equations to more closely represent the water surface but as an exploratory approach hierarchical modelling promises greater success in overcoming the identified shortcomings. Copyright © 2005 John Wiley & Sons, Ltd. [source]

NMR Study of L-Shaped (Quinoxaline)platinum(II) Complexes , Crystal Structure of [Pt(DMeDPQ)(bipy)](PF6)2

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2004
Enrico Rotondo
Abstract A 1H and 13C NMR study of nine PtII complexes of DMeDPQ [6,7-dimethyl-2,3-bis(2-pyridyl)quinoxaline] and BDPQ [2,3-bis(2-pyridyl)benzo[g]quinoxaline], and the crystal structure of one of them, are reported. The results are consistent with Cs symmetry of "L-shaped square-planar complexes". The rigid seven-membered chelated quinoxaline ligand holds the fused aromatic rings nearly perpendicular to the PtII coordination plane, generating the peculiar L-shaped structure. Ancillary ligands in the residual coordination sites are: a) bidentate flexible-planar 2,2,-bipyridine (bipy; complexes 1 and 2); b) bidentate rigid-planar dipyrido[3,2- a:2,3,- c]phenazine (dppz) or benzo[b]dipyrido[3,2- h:2,,3,- j]phenazine (bdppz; complexes 3,6); or c) 3-substituted monodentate pyridines (3-Rpy; complexes 7,9). The L-shaped geometry has been exploited to gain insight into the steric and dynamic features that regulate the noncovalent interactions of these square-planar complexes with DNA. We have shown previously, for [Pt(bipy)(n -Rpy)2]2+, that bipy twisting can be frozen out on the NMR timescale below 260 K. Preservation of the Cs symmetry at low temperature indicates a lack of bipy fluxionality within these L-shaped structures. The static butterfly-like symmetric orientation of the quinoxaline pyridyl rings accounts for the hampered twisting of Pt(bipy), which is otherwise assisted by the synchronous "windscreen wiper" conrotatory rocking of the ancillary pyridine rings. The L-geometry can also be used to monitor the ancillary n -Rpy rotation by NMR spectroscopy. The quasi-vertical quinoxaline pyridyl rings alignment leave room in the coordination plane for the crossing of the opposite pyridine rings, thereby reducing their rotational barriers about the Pt,N bond. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Thermodynamic and kinetic analyses for understanding sequence-specific DNA recognition

GENES TO CELLS, Issue 5 2000
Masayuki Oda
Thermodynamic and kinetic analyses of biomolecular interactions reveal details of the energetic and dynamic features of molecular recognition processes, and complement structural analyses of the free and complexed conformations. The recent improvements in both isothermal titration calorimetry and surface plasmon resonance sensoring provide powerful tools for analysing biomolecular interactions in thermodynamic and kinetic approaches. The thermodynamic and kinetic parameters obtained for binding between protein and DNA indicate the mechanism of specific DNA recognition, in the high-resolution structures of the protein,DNA complexes. The effects of temperature and ionic strength reflect the conformational changes of the protein and DNA molecules upon complex formation, including important contributions of water and solutes. When combined with mutational studies, the interactions can be reduced to several energetic contributions from individual contacts. These studies should be useful to determine general features of protein functions in genetic regulation. [source]

Towards analog implementations of PWL two-dimensional non-linear functions

INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 2 2005
Marco Storace
Abstract This paper deals with the circuit implementation of non-linear algebraic bivariate functions. The synthesis procedure is based on a piecewise-linear approximation technique and on a corresponding circuit architecture, whose basic element is a circuit block with the input/output function y(x) = max(0; x). Some known CMOS circuit structures that can be used to obtain such a block are considered, and their main advantages and drawbacks are pointed out. The static and dynamic features of both the single circuit block and the overall architecture for two-dimensional PWL functions are illustrated by way of examples. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Nonlinear simulation of mixers for assessing system-level performance

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2005
Nuno B. Carvalho
Abstract This article deals with nonlinear simulation methods intended to evaluate the impact of mixer nonidealities on the performance of a wireless system. Behavioral models capable of accurately describing the mixer's nonlinear dynamic features at the system level are currently unavailable. The possibility of using alternative circuit analysis techniques to reach this goal is discussed. After a brief review of existing mixer analysis methods, the focus is directed to the techniques amenable to efficiently handling periodic carriers modulated by complex stochastic signals. In particular, it is shown how multi-envelope transient methods coupled with a three-dimensional harmonic-balance engine can model a nonlinear dynamic mixer excited by a modulated RF signal accompanied by a strong adjacent channel interferer and with a local oscillator corrupted by phase noise. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. [source]

Force field-dependant structural divergence revealed during long time simulations of Calbindin d9k

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 9 2010
Elad Project
Abstract The structural and the dynamic features of the Calbindin (CaB) protein in its holo and apo states are compared using molecular dynamics simulations under nine different force fields (FFs) (G43a1, G53a6, Opls-AA, Amber94, Amber99, Amber99p, AmberGS, AmberGSs, and Amber99sb). The results show that most FFs reproduce reasonably well the majority of the experimentally derived features of the CaB protein. However, in several cases, there are significant differences in secondary structure properties, root mean square deviations (RMSDs), root mean square fluctuations (RMSFs), and S2 order parameters among the various FFs. What is more, in certain cases, these parameters differed from the experimentally derived values. Some of these deviations became noticeable only after 50 ns. A comparison with experimental data indicates that, for CaB, the Amber94 shows overall best agreement with the measured values, whereas several others seem to deviate from both crystal and nuclear magnetic resonance data. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 [source]

Sediment dynamics and pollutant mobility in rivers: An interdisciplinary approach

LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 1 2004
Ulrich Förstner
Abstract Characteristic dynamic features of sediment-related processes in rivers include dramatic effects of stormwater events on particle transport, rapid and far-reaching effects of sulphide oxidation during resuspension, and biological accumulation and potential release of toxic chemicals. Pollutant mobility is the net result of the stabilizing and mobilizing effects in both hydraulic and chemical fields. In practice, emphasis has to be given to fine-grained sediments and suspended matter as these materials exhibit large surface areas and high sorption capacities. Organic materials are highly reactive. Degradation of organic matter will induce oxygen depletion and might enhance formation of flocs and biofilms. Study of variations of sediment and water chemistry should predominantly include changes of pH and redox conditions, competition of dissolved ions and processes such as complexation by organic substances. Major questions relate to the potential reduction of sorption sites on minerals and degradation of organic carrier materials. All these processes will influence solution/solid equilibrium conditions and have to be studied prior to modelling the overall effects of pollutants on the water body and aquatic ecosystems. With respect to handling and remediation of contaminated river sediments, either in-place or excavated, a chemical and biological characterization of the material, of the (disposal) site and of the long-term processes is crucial. Passive techniques (e.g. in situ stabilization, subaqueous capping) provide economic advantages as there are no operation costs following their installation. However, the success of these ecological and geochemical engineering approaches is mainly based on an in-depth knowledge of the underlying processes. [source]

Backbone dynamics of the human MIA protein studied by 15N NMR relaxation: Implications for extended interactions of SH3 domains

PROTEIN SCIENCE, Issue 3 2003
Raphael Stoll
MIA, melanoma inhibitory activity; NMR, nuclear magnetic resonance Abstract The melanoma inhibitory activity (MIA) protein is a clinically valuable marker in patients with malignant melanoma as enhanced values diagnose metastatic melanoma stages III and IV. Here, we report the backbone dynamics of human MIA studied by 15N NMR relaxation experiments. The folded core of human MIA is found to be rigid, but several loops connecting ,-sheets, such as the RT-loop for example, display increased mobility on picosecond to nanosecond time scales. One of the most important dynamic features is the pronounced flexibility of the distal loop, comprising residues Asp 68 to Ala 75, where motions on time scales up to milliseconds occur. Further, significant exchange contributions are observed for residues of the canonical binding site of SH3 domains including the RT-loop, the n-Src loop, for the loop comprising residues 13 to 19, which we refer to as the"disulfide loop", in part for the distal loop, and the carboxyl terminus of human MIA. The functional importance of this dynamic behavior is discussed with respect to the biological activity of several point mutations of human MIA. The results of this study suggest that the MIA protein and the recently identified highly homologous fibrocyte-derived protein (FDP)/MIA-like (MIAL) constitute a new family of secreted proteins that adopt an SH3 domain-like fold in solution with expanded ligand interactions. [source]

Computational Fluid Dynamics Analysis of Blade Tip Clearances on Hemodynamic Performance and Blood Damage in a Centrifugal Ventricular Assist Device

ARTIFICIAL ORGANS, Issue 5 2010
Jingchun Wu
Abstract An important challenge facing the design of turbodynamic ventricular assist devices (VADs) intended for long-term support is the optimization of the flow path geometry to maximize hydraulic performance while minimizing shear-stress-induced hemolysis and thrombosis. For unshrouded centrifugal, mixed-flow and axial-flow blood pumps, the complex flow patterns within the blade tip clearance between the lengthwise upper surface of the rotating impeller blades and the stationary pump housing have a dramatic effect on both the hydrodynamic performance and the blood damage production. Detailed computational fluid dynamics (CFD) analyses were performed in this study to investigate such flow behavior in blade tip clearance region for a centrifugal blood pump representing a scaled-up version of a prototype pediatric VAD. Nominal flow conditions were analyzed at a flow rate of 2.5 L/min and rotor speed of 3000 rpm with three blade tip clearances of 50, 100, and 200 µm. CFD simulations predicted a decrease in the averaged tip leakage flow rate and an increase in pump head and axial thrust with decreasing blade tip clearances from 200 to 50 µm. The predicted hemolysis, however, exhibited a unimodal relationship, having a minimum at 100 µm compared to 50 µm and 200 µm. Experimental data corroborate these predictions. Detailed flow patterns observed in this study revealed interesting fluid dynamic features associated with the blade tip clearances, such as the generation and dissipation of tip leakage vortex and its interaction with the primary flow in the blade-blade passages. Quantitative calculations suggested the existence of an optimal blade tip clearance by which hydraulic efficiency can be maximized and hemolysis minimized. [source]

Hybrid Automaton Model and Control of Hybird Systems

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2001
Wei Zhang
A hybrid automaton model is proposed in this paper for hybrid systems. The model, with particular emphasis on process control applications, is based on the dynamic features of hybrid systems. It takes into account the discrete dynamics of hybrid systems in particular and can clearly separate the controller from the closed-loop system. The definition of controllability of hybird systems with respect to the marked regions is also given. An analyzing algorithm and sufficient and necessary condition for controllability based on the hybrid automaton model are discussed. At the same time, the property of the loops in the trajectory of the closed-loop plant is studied. Finally, the synthesis scheme for a hybrid controller is given. In this scheme, the controller consists of two parts, the discrete supervisor and the continuous regulator. The closed-loop plant with the controller is state-controllable. [source]