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General Assumptions (general + assumption)
Selected AbstractsThe geometry and motion of nematode sperm cellsCYTOSKELETON, Issue 6 2009Evgeny Demekhin Abstract The nematode sperm cell crawls by recycling major sperm protein (MSP) from dimers into subfilaments, filaments, and filament complexes, as a result of thermal writhing in the presence of hydrophobic patches. Polymerization near leading edges of the cell intercolates MSP dimers onto the tips of growing filament complexes, forcing them against the cell boundary, and extending the cytoskeleton in the direction of motion. Strong adhesive forces attach the cell to the substrate in the forward part of the lamellipod, while depolymerization in the rearward part of the cell breaks down the cytoskeleton, contracting the lamellipod and pulling the cell body forward. The movement of these cells, then, is caused by coordinated protrusive, adhesive and contractile forces, spatially separated across the lamellipod. This paper considers a phenomenological model that tracks discrete elements of the cytoskeleton in curvilinear coordinates. The pseudo-two dimensional model primarily considers protrusion and rotation of the cell, along with the evolution of the cell boundary. General assumptions are that pH levels within the lamellipod regulate protrusion, contraction and adhesion, and that growth of the cytoskeleton, over time, is perpendicular to the evolving cell boundary. The model follows the growth and contraction of a discrete number of MSP fiber complexes, since they appear to be the principle contributors for force generation in cell boundary protrusion and contraction, and the backbone for the dynamic geometry and motion. Cell Motil. Cytoskeleton 2009. © 2009 Wiley-Liss, Inc. [source] Adult neurogenesis in the central olfactory pathway in the absence of receptor neuron turnover in Libinia emarginataEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2005Jeremy M. Sullivan Abstract Life-long neurogenesis is a characteristic feature of the olfactory pathways of a phylogenetically diverse array of animals. In both vertebrates and invertebrates, the life-long addition of olfactory interneurons in the brain occurs in parallel with the continuous proliferation of olfactory receptor neurons in the olfactory organ. It has been proposed that these two processes are related functionally, with new olfactory interneurons being added to accommodate the new olfactory receptor neurons added in the periphery. While this has not been tested directly because the two processes are not readily separable, this question can be addressed in the olfactory pathway of the crab, Libinia emarginata. Unlike most decapod crustaceans, which moult and grow throughout life, L. emarginata has a terminal, maturational moult after which animals become anecdysic (stop moulting). Because the addition of new receptor neurons in crustaceans is associated with moulting, a comparison of neurogenesis in immature and mature L. emarginata provides an opportunity to examine the interdependence of central and peripheral neurogenesis in the olfactory pathway. This study demonstrates that the continuous addition of olfactory receptor neurons in L. emarginata ceases at the terminal moult but that proliferation and differentiation of olfactory interneurons in the brain continues in mature animals. Contrary to the general assumption, therefore, continuous neurogenesis in the central olfactory pathway of this species does not occur as part of a process involving the coregulation of central and peripheral neurogenesis. These findings suggest that peripheral neurogenesis is not a requirement for continuous neurogenesis in the central olfactory pathway. [source] The Geysers geothermal field: results from shear-wave splitting analysis in a fractured reservoirGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2005Maya Elkibbi SUMMARY Clear shear-wave splitting (SWS) is observed in 1757 high signal-to-noise ratio microearthquake seismograms recorded by two high density seismic arrays in the NW and the SE Geysers geothermal fields in California. The Geysers reservoir rocks within the study area are largely composed of lithic, low-grade metamorphism, well-fractured metagraywackes which commonly lack schistosity, warranting the general assumption that shear-wave splitting here is induced solely by stress-aligned fracturing in an otherwise isotropic medium. The high quality of observed shear-wave splitting parameters (fast shear-wave polarization directions and time delays) and the generally good data spatial coverage provide an unprecedented opportunity to demonstrate the applicability and limitations of the shear-wave splitting approach to successfully detect fracture systems in the shallow crust based on SWS field observations from a geothermal reservoir. Results from borehole stations in the NW Geysers indicate that polarization orientations range between N and N60E; while in the SE Geysers, ground surface stations show polarization directions that are generally N5E, N35E-to-N60E, N75E-to-N85E, and N20W-to-N55W. Crack orientations obtained from observed polarization orientations are in good agreement with independent field evidence, such as cracks in geological core data, tracer tests, locally mapped fractures, and the regional tectonic setting. Time delays range typically between 8 and 40 ms km,1, indicating crack densities well within the norm of fractured reservoirs. The sizeable collection of high resolution shear-wave splitting parameters shows evidence of prevalent vertical to nearly vertical fracture patterns in The Geysers field. At some locations, however, strong variations of SWS parameters with ray azimuth and incident angle within the shear-wave window of seismic stations indicate the presence of more complex fracture patterns in the subsurface. [source] Do northern riverine anadromous Arctic charr Salvelinus alpinus and sea trout Salmo trutta overwinter in estuarine and marine waters?JOURNAL OF FISH BIOLOGY, Issue 7 2008J. L. A. Jensen By use of acoustic telemetry, the present study showed that both riverine anadromous brown trout (sea trout) Salmo trutta and Arctic charr Salvelinus alpinus in a north Norwegian river descended the river within the first 4 months after spawning in late September and spent long parts of the remaining winter period in the estuary and also possibly partly in salt water. This contradicts the general assumption, based on studies of lake-dwelling populations, that both species, and in particular S. alpinus, overwinter and spend 9,11 months in fresh water at northern latitudes and the rest of the year in salt water. [source] Coagulation dynamics and platelet functions in obstructive jaundiced patientsJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 5 2009Tebessüm Çak Abstract Background:, All of the body systems are affected by increased levels of bilirubin. The aim of this study is to investigate the function of platelets and clotting dynamics in patients with obstructive jaundice. Methods:, Liver function tests, serum CRP, PT, PTT and hemogram were measured in 23 patients with obstructive jaundice. Thromboelastography (TEG) was done for the evaluation of coagulation dynamics, while platelet function assay (PFA 100) was used to evaluate platelet functions. Blood samples were obtained at two occasions, before the drainage and 3 weeks after the relief of the obstruction. Results:, Hypercoagulation was detected in 80% of patients. Maximum strength, elasticity, coagulation indices of the clot were correlated with increased concentrations of direct bilirubin. Although maximum strength of coagulum usually represents increased activity of platelet function, membrane closure times with PFA 100 were found to be prolonged in 30% of patients, reduced values were determined in 17% of patients. No demonstrable effect on coagulation parameters and platelet function were detected after drainage procedures regardless of modality. Conclusions:, Even though there is a general assumption about the increased bleeding tendency in obstructive jaundiced patients, we could not demonstrate reduced clotting activity by measuring with either PFA or TEG. On the contrary we observed tendency for hypercoagulation independent of increased prothrombin times. The most probable cause of this effect is the increased activity of fibrin polymers on platelet membrane. [source] Social networking: Communication revolution or evolution?BELL LABS TECHNICAL JOURNAL, Issue 2 2008Cheryl L. Coyle Social networks and the need to communicate are universal human conditions. A general assumption is that communication technologies help to increase and strengthen social ties. The Internet provides many social networking opportunities. But how do social networking sites affect individual relationships? Do people use social networking sites to expand their personal networks, to find people who have had similar experiences, to discuss a common hobby, for the potential of offline dating? Or, do people spend time on networking sites to deepen their existing personal networks and stay connected to old friends or distant family? What is the nature of the communications that transpire on social networking sites? Is it personal, emotional, private, and important; or trivial, informal, and public? We examined the literature on social networking sites and conducted our own studies of how students on American college campuses engage in social networking. © 2008 Alcatel-Lucent. [source] Monetary policy arithmetic: reconciling theory with evidenceCANADIAN JOURNAL OF ECONOMICS, Issue 1 2006Maxim Nikitin Existing budget arithmetic models of monetary policy cannot deliver superneutrality. In this paper, we conduct a budget arithmetic analysis of monetary policy using a money demand specification , money in the utility function , that is new to this literature. We find that one simple assumption about utility from money delivers superneutrality, while a more general assumption delivers departures from superneutrality in the direction consistent with the evidence. JEL classification: E60, E13 Arithmétique de la politique monétaire: arrimage de la théorie avec les faits., Les résultats empiriques montrent que, dans les pays à faible taux d'inflation, une chute permanente du taux d'inflation soit n'a aucun impact sur le stock de capital et la production (superneutralité) soit entraîne une chute modérée dans l'un et l'autre. Les modèles arithmétiques des budgets existants de la politique monétaire ne peuvent pas engendrer la superneutralité. Dans ce mémoire, on fait une analyse arithmétique de la politique monétaire en utilisant une spécification de la demande de monnaie qui est inédite. Il appert qu'un simple postulat à propos de l'utilité de la monnaie engendre la superneutralité, alors qu'un postulat plus général engendre certains écarts par rapport à la superneutralité dans des directions qui sont compatibles avec les faits observés. [source] The Essential Ingredients of Successful Sibling Relationships: An Emerging Framework for Advancing Theory and PracticeCHILD DEVELOPMENT PERSPECTIVES, Issue 2 2010Laurie Kramer Abstract, Although conflict is a frequent and dynamic interpersonal process in children's sibling relationships, ambivalence (i.e., combinations of, or shifts between, positive and negative behaviors and affects) may better characterize normative sibling interactions. Nonetheless, there is a general assumption that reducing conflict is the most effective mechanism for improving sibling relationships. This review argues that the focus on conflict as the predominant attribute of sibling relationships is misplaced and has served to overshadow research on other relationship processes; it has also handicapped the development of effective prevention and intervention tools. Strategies are presented for moving theory, research, and practice toward the identification and development of factors and social processes that promote prosocial forms of sibling engagement and manage conflict. Innovative strategies are needed on two fronts: to help young siblings set their relationship on a positive trajectory and to help them avoid or remediate conflictual interactions. [source] Adiabatic charge pumping in open quantum systemsCOMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 4 2004Joseph E. Avron We introduce a mathematical setup for charge transport in quantum pumps connected to a number of external leads. It is proved that under rather general assumption on the Hamiltonian describing the system, in the adiabatic limit, the current through the pump is given by a formula of Büttiker, Prêtre, and Thomas, relating it to the frozen S -matrix and its time derivative. © 2004 Wiley Periodicals, Inc. [source] Unnatural landscapes in ecology: generating the spatial distribution of brine spills,ENVIRONMETRICS, Issue 7 2005Henriette I. Jager Abstract Quantitative tools are needed to evaluate the ecological effects of increasing petroleum production. In this article, we describe two stochastic models for simulating the spatial distribution of brine spills on a landscape. One model uses general assumptions about the spatial arrangement of spills and their sizes; the second model distributes spills by siting rectangular well complexes and conditioning spill probabilities on the configuration of pipes. We present maps of landscapes with spills produced by the two methods and compare the ability of the models to reproduce a specified spill area. A strength of the models presented here is their ability to extrapolate from the existing landscape to simulate landscapes with a higher (or lower) density of oil wells. Published in 2005 by John Wiley & Sons, Ltd. [source] Ideology,Driven opinion formation in Europe: The case of attitudes towards the third sector in SwedenEUROPEAN JOURNAL OF POLITICAL RESEARCH, Issue 4 2001STAFFAN KUMLIN This paper uses attitudes towards the third sector in Sweden to test general assumptions about how citizens in West European political systems apply ideological schemas as shortcuts to political preferences. Attitudes towards the third sector are found to be affected by all ideological schemas reflected in the Swedish party system (state,market, Christian traditionalism, and growth,ecology). Contrary to what is implied by findings from America, these effects are very stable across socio,economic groups (especially those of the dominant statemarket schema). Similarly, no interaction effects of political sophistication could be traced, and the relative impact of the schemas remains the same regardless of whether or not the third sector is presented as an alternative to the welfare state. The implications of these findings for the nature of public opinion formation in ideologically clear and structured political systems are discussed. [source] Palsas in Härjedalen, Sweden: 1910 and 1998 ComparedGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 1 2000Tomas Nihlén In 1998 an area near Helagsfjället in Härjedalen was investigated in an attempt to relocate palsas discovered by the botanist Harry Smith in 1910. Several small palsa-like features with ice cores were detected. The palsas were found on an almost flat peat bog at 950 m, 3 km NW of Helagsfjället. Five clearly elevated mounds and some indistinct ones with palsa-like features were traced. The five mounds were about 0.6 m high and had an area of about 2 × 3 m. One of the mounds was examined in more detail. At a depth of 0.3 m in the peat an ice body with a hard ice core was found. This location is the most southerly area known with occurrence of palsa-like forms in Sweden at the present time. In spite of a warmer climate towards the latter part of this century, palsa-like features have survived in this area. The mean annual temperature barely fits the criterion for palsa formation while the mean annual precipitation is too high as compared with the general assumptions. The palsa formation is probably dependent on strong winds thinning out the snowcover. [source] Non-linear circuit modelling via nodal methodsINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 4 2005Ricardo Riaza Abstract We discuss in this paper several interrelated nodal methods for setting up the equations of non-linear, lumped electrical circuits. A rather exhaustive framework is presented, aimed at surveying different approaches and terminologies in a comprehensive manner. This framework includes charge-oriented, conventional, and hybrid systems. Special attention is paid to so-called augmented node analysis (ANA) models, which somehow articulate the tableau and modified node analysis (MNA) approaches to non-linear circuit modelling. We use a differential,algebraic formalism and, extending previous results proved in the MNA context, we provide index-1 conditions for augmented systems, which are shown to be transferred to tableau models. This approach gives, in particular, precise conditions for the feasibility of certain state-space reductions. We work with very general assumptions on device characteristics; in particular, our approach comprises a wide range of resistive devices, going beyond voltage-controlled ones. Copyright © 2005 John Wiley & Sons, Ltd. [source] General linearized biexponential model for QSAR data showing bilinear-type distributionJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2005Peter Buchwald Abstract A major impediment of many QSAR-type analyses is that the data show a maximum or minimum and can no longer be adequately described by linear functions that provide unrivaled simplicity and usually give good description over more restricted ranges. Here, a general linearized biexponential (LinBiExp) model is proposed that can adequately describe data showing bilinear-type distribution as a function of not just often-employed lipophilicity descriptors (e.g., log P) but as a function of any descriptor (e.g., molecular volume). Contrary to Hansch-type parabolic models, LinBiExp allows the natural extension of linear models and fitting of asymmetrical data. It is also more general and intuitive than Kubinyi's model as it has a more natural functional form. It was obtained by a differential equation-based approach starting from very general assumptions that cover both static equilibriums and first-order kinetic processes and that involve abstract processes through which the concentration of the compound of interest in an assumed "effect" compartment is connected to its "external" concentration. Physicochemical aspects placing LinBiExp within the framework of linear free energy relationship (LFER) approaches are presented together with illustrative applications in various fields such as toxicity, antimicrobial activity, anticholinergic activity, and glucocorticoid receptor binding. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:2355-2379, 2005 [source] Multi-Scale Study of Sintering: A ReviewJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2006Eugene A. Olevsky An integrated approach, combining the continuum theory of sintering with a kinetic Monte-Carlo (KMC) model-based mesostructure evolution simulation is reviewed. The effective sintering stress and the normalized bulk viscosity are derived from mesoscale simulations. A KMC model is presented to simulate microstructural evolution during sintering of complex microstructures taking into consideration grain growth, pore migration, and densification. The results of these simulations are used to generate sintering stress and normalized bulk viscosity for use in continuum level simulation of sintering. The advantage of these simulations is that they can be employed to generate more accurate constitutive parameters based on most general assumptions regarding mesostructure geometry and transport mechanisms of sintering. These constitutive parameters are used as input data for the continuum simulation of the sintering of powder bilayers. Two types of bilayered structures are considered: layers of the same particle material but with different initial porosity, and layers of two different materials. The simulation results are verified by comparing them with shrinkage and warping during the sintering of bilayer ZnO powder compacts. [source] A Martingale Characterization of Consumption Choices and Hedging Costs with Margin RequirementsMATHEMATICAL FINANCE, Issue 3 2000Domenico Cuoco This paper examines optimal consumption and investment choices and the cost of hedging contingent claims in the presence of margin requirements or, more generally, of nonlinear wealth dynamics and constraints on the portfolio policies. Existence of optimal policies is established using martingale and duality techniques under general assumptions on the securities' price process and the investor's preferences. As an illustration, explicit solutions are provided for an agent with ,logarithmic' utility. A PDE characterization of the cost of hedging a nonnegative path-independent European contingent claim is also provided. [source] Convergence of phase field to phase relaxation models governed by an entropy equation with memoryMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 18 2006Gianni Gilardi Abstract The subject of the present paper consists in proving the convergence of a phase-field model, based on the entropy equation with memory, to phase relaxation. The well-posedness and the long-time behaviour of solutions for the non-linear and singular phase-field system have been recently shown by Bonetti et al. (Preprint IMATI-CNR, 2005; Discrete Contin. Dyn. Syst. Ser. B, in press). Here, we study the asymptotic behaviour of such solutions as the interfacial energy coefficient tends to zero. The limit problem is a phase relaxation problem with memory, which is new. We prove well-posedness results through convergence under rather general assumptions. However, the case of a quadratic non-linearity for the latent heat is excluded. Such a situation is dealt for the problem without memory in a generalized setting by introducing an ad hoc logarithm. Copyright © 2006 John Wiley & Sons, Ltd. [source] A rain water infiltration model with unilateral boundary condition: qualitative analysis and numerical simulationsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 17 2006I. Borsi Abstract We present a rigorous mathematical treatment of a model describing rain water infiltration through the vadose zone in case of runoff of the excess water. The main feature of the mathematical problem emerging from the model lies on the boundary condition on the ground surface which is in the form of a unilateral constraint. Existence and uniqueness of a weak solution is proved under general assumptions. We present also the results of a numerical study comparing the proposed model with other models which approach in a different way the rain water infiltration problem. Copyright © 2006 John Wiley & Sons, Ltd. [source] XIV,Moral Non -Cognitivism and the Grammar of MoralityPROCEEDINGS OF THE ARISTOTELIAN SOCIETY (HARDBACK), Issue 1pt3 2009Michael Blome-Tillmann This paper investigates the linguistic basis for moral non-cognitivism, the view that sentences containing moral predicates do not have truth conditions. It offers a new argument against this view by pointing out that the view is incompatible with our best empirical theories about the grammatical encoding of illocutionary force potentials. Given that my arguments are based on very general assumptions about the relations between the grammar of natural languages and a sentence's illocutionary function, my arguments are broader in scope than the familiar semantic objections to non-cognitivism relating to the so-called Frege-Geach problem: even if a solution to the Frege-Geach problem has been found, my arguments still stand. [source] Mixed-effects models in psychophysiologyPSYCHOPHYSIOLOGY, Issue 1 2000Emilia Bagiella The current methodological policy in Psychophysiology stipulates that repeated-measures designs be analyzed using either multivariate analysis of variance (ANOVA) or repeated-measures ANOVA with the Greenhouse,Geisser or Huynh,Feldt correction. Both techniques lead to appropriate type I error probabilities under general assumptions about the variance-covariance matrix of the data. This report introduces mixed-effects models as an alternative procedure for the analysis of repeated-measures data in Psychophysiology. Mixed-effects models have many advantages over the traditional methods: They handle missing data more effectively and are more efficient, parsimonious, and flexible. We described mixed-effects modeling and illustrated its applicability with a simple example. [source] Identification and fine tuning of closed-loop processes under discrete EWMA and PI adjustmentsQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 6 2001Rong Pan Abstract Conventional process identification techniques of a open-loop process use the cross-correlation function between historical values of the process input and of the process output. If the process is operated under a linear feedback controller, however, the cross-correlation function has no information on the process transfer function because of the linear dependency of the process input on the output. In this paper, several circumstances where a closed-loop system can be identified by the autocorrelation function of the output are discussed. It is assumed that a proportional integral controller with known parameters is acting on the process while the output data were collected. The disturbance is assumed to be a member of a simple yet useful family of stochastic models, which is able to represent drift. It is shown that, with these general assumptions, it is possible to identify some dynamic process models commonly encountered in manufacturing. After identification, our approach suggests to tune the controller to a near-optimal setting according to a well-known performance criterion. Copyright © 2001 John Wiley & Sons, Ltd. [source] Short-term variation in the ecological status of a Mediterranean coastal lagoon (NE Iberian Peninsula) after a man-made change of hydrological regimeAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 7 2008Anna Badosa Abstract 1.The Ter Vell (NE Iberian Peninsula) is a eutrophic coastal lagoon that has been mostly flooded by excessive irrigation water during recent decades. During 2001 and 2002 the lagoon was subject to several water management actions, the main consequence of which was a change in the hydrological regime due to drastically reduced irrigation water inputs to the lagoon. 2.In order to comply with the Water Framework Directive, all the management actions in an ecosystem should be focused on protecting and, where necessary, improving its ecological status. 3.The aims of this study were (1) to analyse whether the hydrological change caused by management actions have affected the ecological status of the lagoon, and (2) to discuss the suitability of several physicochemical and biological indicators for the assessment of the ecological status in this kind of coastal ecosystem. 4.After the change in the hydrological regime, a general improvement of the ecological status was observed mainly as a result of the significant decrease in the nitrogen Trophic State Index and in the abundance of rotifer indicative of eutrophy, and in turn by the significant increase in the water quality index QAELS, based on crustaceans and insect assemblages. 5.Contradictory results emerged with regard to some of the indicators used. After the hydrological change, the increase in the phosphorus Trophic State Index was related with the fact that Mediterranean confined coastal ecosystems are typically P-enriched. In contrast with general assumptions, low diversity and richness of the zooplankton and the dominance of a few species have been related with an improvement of the ecological status after the hydrological change, when freshwater inputs were reduced and the lagoon became more confined. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||