916 resultados para theoretical study
Resumo:
A story-stem paradigm was used to assess interpretation bias in preschool children. Data were available for 131 children. Interpretation bias, behavioural inhibition (BI) and anxiety were assessed when children were aged between 3 years 2 months and 4 years 5 months. Anxiety was subsequently assessed 12-months, 2-years and 5-years later. A significant difference in interpretation bias was found between participants who met criteria for an anxiety diagnosis at baseline, with clinically anxious participants more likely to complete the ambiguous story-stems in a threat-related way. Threat interpretations significantly predicted anxiety symptoms at 12-month follow-up, after controlling for baseline symptoms, but did not predict anxiety symptoms or diagnoses at either 2-year or 5- year follow-up. There was little evidence for a relationship between BI and interpretation bias. Overall, the pattern of results was not consistent with the hypothesis that interpretation bias plays a role in the development of anxiety. Instead, some evidence for a role in the maintenance of anxiety over relatively short periods of time was found. The use of a story-stem methodology to assess interpretation bias in young children is discussed along with the theoretical and clinical implications of the findings.
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Clinical evidence suggests that a persistent search for solutions for chronic pain may bring along costs at the cognitive, affective, and behavioral level. Specifically, attempts to control pain may fuel hypervigilance and prioritize attention towards pain-related information. This hypothesis was investigated in an experiment with 41 healthy volunteers. Prioritization of attention towards a signal for pain was measured using an adaptation of a visual search paradigm in which participants had to search for a target presented in a varying number of colored circles. One of these colors (Conditioned Stimulus) became a signal for pain (Unconditioned Stimulus: electrocutaneous stimulus at tolerance level) using a classical conditioning procedure. Intermixed with the visual search task, participants also performed another task. In the pain-control group, participants were informed that correct and fast responses on trials of this second task would result in an avoidance of the Unconditioned Stimulus. In the comparison group, performance on the second task was not instrumental in controlling pain. Results showed that in the pain-control group, attention was more prioritized towards the Conditioned Stimulus than in the comparison group. The theoretical and clinical implications of these results are discussed.
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What are the microfoundations of dynamic capabilities that sustain competitive advantage in a highly volatile environment, such as a transition economy? We explore the detailed nature of these dynamic capabilities along with their antecedents by tracing the sequence of their development based on a longitudinal case study of an organization subject to an external context of radical transition — the Russian oil company, Yukos. Our rich qualitative data indicate two distinct types of dynamic capabilities that are pivotal for organizational transformation. Adaptation dynamic capabilities relate to routines of resource exploitation and deployment, which are supported by acquisition, internalization and dissemination of extant knowledge, as well as resource reconfiguration, divestment and integration. Innovation dynamic capabilities relate to the creation of completely new capabilities via exploration and path-creation processes, which are supported by search, experimentation and risk taking, as well as project selection, funding and implementation. Second, we find that sequencing the two types of dynamic capabilities, helped the organization both to secure short-term competitive advantage, and to create the basis for long-term competitive advantage. These dynamic capability constructs advance theoretical understanding of what dynamic capabilities are, whilst their sequencing explains how firms create, leverage and enhance them over time.
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Tests of the new Rossby wave theories that have been developed over the past decade to account for discrepancies between theoretical wave speeds and those observed by satellite altimeters have focused primarily on the surface signature of such waves. It appears, however, that the surface signature of the waves acts only as a rather weak constraint, and that information on the vertical structure of the waves is required to better discriminate between competing theories. Due to the lack of 3-D observations, this paper uses high-resolution model data to construct realistic vertical structures of Rossby waves and compares these to structures predicted by theory. The meridional velocity of a section at 24° S in the Atlantic Ocean is pre-processed using the Radon transform to select the dominant westward signal. Normalized profiles are then constructed using three complementary methods based respectively on: (1) averaging vertical profiles of velocity, (2) diagnosing the amplitude of the Radon transform of the westward propagating signal at different depths, and (3) EOF analysis. These profiles are compared to profiles calculated using four different Rossby wave theories: standard linear theory (SLT), SLT plus mean flow, SLT plus topographic effects, and theory including mean flow and topographic effects. Our results support the classical theoretical assumption that westward propagating signals have a well-defined vertical modal structure associated with a phase speed independent of depth, in contrast with the conclusions of a recent study using the same model but for different locations in the North Atlantic. The model structures are in general surface intensified, with a sign reversal at depth in some regions, notably occurring at shallower depths in the East Atlantic. SLT provides a good fit to the model structures in the top 300 m, but grossly overestimates the sign reversal at depth. The addition of mean flow slightly improves the latter issue, but is too surface intensified. SLT plus topography rectifies the overestimation of the sign reversal, but overestimates the amplitude of the structure for much of the layer above the sign reversal. Combining the effects of mean flow and topography provided the best fit for the mean model profiles, although small errors at the surface and mid-depths are carried over from the individual effects of mean flow and topography respectively. Across the section the best fitting theory varies between SLT plus topography and topography with mean flow, with, in general, SLT plus topography performing better in the east where the sign reversal is less pronounced. None of the theories could accurately reproduce the deeper sign reversals in the west. All theories performed badly at the boundaries. The generalization of this method to other latitudes, oceans, models and baroclinic modes would provide greater insight into the variability in the ocean, while better observational data would allow verification of the model findings.
Resumo:
Sea ice contains flaws including frictional contacts. We aim to describe quantitatively the mechanics of those contacts, providing local physics for geophysical models. With a focus on the internal friction of ice, we review standard micro-mechanical models of friction. The solid's deformation under normal load may be ductile or elastic. The shear failure of the contact may be by ductile flow, brittle fracture, or melting and hydrodynamic lubrication. Combinations of these give a total of six rheological models. When the material under study is ice, several of the rheological parameters in the standard models are not constant, but depend on the temperature of the bulk, on the normal stress under which samples are pressed together, or on the sliding velocity and acceleration. This has the effect of making the shear stress required for sliding dependent on sliding velocity, acceleration, and temperature. In some cases, it also perturbs the exponent in the normal-stress dependence of that shear stress away from the value that applies to most materials. We unify the models by a principle of maximum displacement for normal deformation, and of minimum stress for shear failure, reducing the controversy over the mechanism of internal friction in ice to the choice of values of four parameters in a single model. The four parameters represent, for a typical asperity contact, the sliding distance required to expel melt-water, the sliding distance required to break contact, the normal strain in the asperity, and the thickness of any ductile shear zone.
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We investigate in detail the initial susceptibility, magnetization curves, and microstructure of ferrofluids in various concentration and particle dipole moment ranges by means of molecular dynamics simulations. We use the Ewald summation for the long-range dipolar interactions, take explicitly into account the translational and rotational degrees of freedom, coupled to a Langevin thermostat. When the dipolar interaction energy is comparable with the thermal energy, the simulation results on the magnetization properties agree with the theoretical predictions very well. For stronger dipolar couplings, however, we find systematic deviations from the theoretical curves. We analyze in detail the observed microstructure of the fluids under different conditions. The formation of clusters is found to enhance the magnetization at weak fields and thus leads to a larger initial susceptibility. The influence of the particle aggregation is isolated by studying ferro-solids, which consist of magnetic dipoles frozen in at random locations but which are free to rotate. Due to the artificial suppression of clusters in ferrosolids the observed susceptibility is considerably lowered when compared to ferrofluids.
Resumo:
The lattice dynamics method is used to study the stability of the chain structures formed in electrorheological (ER) fluids. The appearance of the soft modes in the phonon dispersion of the structures indicates that the chains tend to distort and aggregate into thicker columns due to the electrostatic attractive forces and thermal generated forces between them. The results show that the stability of the chains relies on their width and the separation between them. The complete chain structures are more stable than the chains with defects. The results can be used to elucidate the densification phenomenon of the chains in the structuring process of ER fluids in the quiescent state.
Resumo:
Langevin dynamics simulations are used to investigate the equilibrium magnetization properties and structure of magnetic dipolar fluids. The influence of using different boundary conditions are systematically studied. Simulation results on the initial susceptibility and magnetization curves are compared with theoretical predictions. The effect of particle aggregation is discussed in detail by performing a cluster analysis of the microstructure.
Resumo:
We have investigated the chemisorption of CH3D and CD3H on Pt{11 0}-(1 2) by performing first-principles molecular dynamics simulations of the recombinative desorption of CH3D (from adsorbed methyl and deuterium) and of CD3H (from adsorbed trideuteromethyl and hydrogen). Vibrational analysis of the symmetry adapted internal coordinates of the desorbing molecules shows that excitation of the single C– D (C–H) bond in the parent molecule is strongly correlated with energy excess in the reaction coordinate. The results of the molecular dynamics simulations are consistent with observed mode- and bond-specific reactivity measurements for chemisorption of methane and its isotopomers on platinum and nickel surfaces.
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Using a combination of idealized radiative transfer simulations and a case study from the first field campaign of the Saharan Mineral Dust Experiment (SAMUM) in southern Morocco, this paper provides a systematic assessment of the limitations of the widely used Spinning Enhanced Visible and Infrared Imager (SEVIRI) red-green-blue (RGB) thermal infrared dust product. Both analyses indicate that the ability of the product to identify dust, via its characteristic pink coloring, is strongly dependent on the column water vapor, the lower tropospheric lapse rate, and dust altitude. In particular, when column water vapor exceeds ∼20–25 mm, dust presence, even for visible optical depths of the order 0.8, is effectively masked. Variability in dust optical properties also has a marked impact on the imagery, primarily as a result of variability in dust composition. There is a moderate sensitivity to the satellite viewing geometry, particularly in moist conditions. The underlying surface can act to confound the signal seen through variations in spectral emissivity, which are predominantly manifested in the 8.7μm SEVIRI channel. In addition, if a temperature inversion is present, typical of early morning conditions over the Sahara and Sahel, an increased dust loading can actually reduce the pink coloring of the RGB image compared to pristine conditions. Attempts to match specific SEVIRI observations to simulations using SAMUM measurements are challenging because of high uncertainties in surface skin temperature and emissivity. Recommendations concerning the use and interpretation of the SEVIRI RGB imagery are provided on the basis of these findings.
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This paper explores the idea that stakeholder proximity, that is, how much/little experience a stakeholder has with a focal organization, impacts the extent to which stakeholders rely on strategic group characteristics as an anchor when judging the reputation of higher education institutions. We synthesize theories from psychology (ie, cognitive categorization theory) and management (ie, strategic group theory) to explore how stakeholder proximity may influence the formation of organizational reputation. Specifically, we examine how the proximity of three key stakeholders (N=1,049; prospective students, parents of students and hiring managers of new graduates) influences the perceived strategic character and generalized favorability of three distinct groups of post-secondary institutions (research-intensive universities, teaching-intensive universities and career colleges). Our results suggest that high proximity stakeholders rely less on strategic group characteristics, while reputation at a strategic group level is suggested to have greater influence on stakeholders who have less direct experience of and low proximity to an organization. Interestingly, our findings reveal some consistent differences between perceptions of prospective students and hiring managers that pose important theoretical questions about the role and impact of direct experiences in the reputation-building process, while also suggesting that higher education institutions may benefit significantly from differentiated marketing strategies according to issues of proximity.
Resumo:
The paper provides a theoretical insight into bank regulation and the process of internationalisation by examining the concepts of regulatory push and market pull within the context of Japanese bank entry into London during the 1980s. Rugman and Verbeke's [(1998). Corporate strategy and international environmental policy. Journal of International Business Studies, 29(4), 819–833] Consistency of Home and Host Government Goals model is utilised to structure the discussion, which centres on a situation where there is a conflict of goals between multinational enterprises (MNEs) and the home government but goal alignment between MNEs and the host government. As such the paper examines a relatively under-researched aspect of internationalisation and concludes that in certain circumstances internationalisation can occur despite great ‘psychic distance’. The paper also argues that although bank regulation can lead to a conflict situation it can also be conducive to the development of a strong home base and the development of firm specific advantages.
Resumo:
We develop a new measurement scale to assess consumers’ brand likeability in firm-level brands. We present brand likeability as a multidimensional construct. In the context of service experience purchases, we find that increased likeability in brands results in: (1) greater amount of positive association; (2) increased interaction interest; (3) more personified quality; and (4) increased brand contentment. The four-dimensional multiple-item scale demonstrates good psychometric properties, showing strong evidence of reliability as well as convergent, discriminant and nomological validity. Our findings reveal that brand likeability is positively associated with satisfaction and positive word of mouth. The scale extends existing branding research, providing brand managers with a metric so that likeability can be managed strategically. It addresses the need for firms to act more likeably in an interaction-dominated economy. Focusing on likeability acts as a differentiator and encourages likeable brand personality traits. We present theoretical implications and future research directions on the holistic brand likeability concept.