959 resultados para Discrepancy principle


Relevância:

20.00% 20.00%

Publicador:

Resumo:

The long-term mean properties of the global climate system and those of turbulent fluid systems are reviewed from a thermodynamic viewpoint. Two general expressions are derived for a rate of entropy production due to thermal and viscous dissipation (turbulent dissipation) in a fluid system. It is shown with these expressions that maximum entropy production in the Earth s climate system suggested by Paltridge, as well as maximum transport properties of heat or momentum in a turbulent system suggested by Malkus and Busse, correspond to a state in which the rate of entropy production due to the turbulent dissipation is at a maximum. Entropy production due to absorption of solar radiation in the climate system is found to be irrelevant to the maximized properties associated with turbulence. The hypothesis of maximum entropy production also seems to be applicable to the planetary atmospheres of Mars and Titan and perhaps to mantle convection. Lorenz s conjecture on maximum generation of available potential energy is shown to be akin to this hypothesis with a few minor approximations. A possible mechanism by which turbulent fluid systems adjust themselves to the states of maximum entropy production is presented as a selffeedback mechanism for the generation of available potential energy. These results tend to support the hypothesis of maximum entropy production that underlies a wide variety of nonlinear fluid systems, including our planet as well as other planets and stars

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We have shown that the mobility tensor for a particle moving through an arbitrary homogeneous stationary flow satisfies generalized Onsager symmetry relations in which the time-reversal transformation should also be applied to the external forces that keep the system in the stationary state. It is then found that the lift forces, responsible for the motion of the particle in a direction perpendicular to its velocity, have different parity than the drag forces.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In this paper we consider a general action principle for mechanics written by means of the elements of a Lie algebra. We study the physical reasons why we have to choose precisely a Lie algebra to write the action principle. By means of such an action principle we work out the equations of motion and a technique to evaluate perturbations in a general mechanics that is equivalent to a general interaction picture. Classical or quantum mechanics come out as particular cases when we make realizations of the Lie algebra by derivations into the algebra of products of functions or operators, respectively. Later on we develop in particular the applications of the action principle to classical and quantum mechanics, seeing that in this last case it agrees with Schwinger's action principle. The main contribution of this paper is to introduce a perturbation theory and an interaction picture of classical mechanics on the same footing as in quantum mechanics.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

There is a need for more efficient methods giving insight into the complex mechanisms of neurotoxicity. Testing strategies including in vitro methods have been proposed to comply with this requirement. With the present study we aimed to develop a novel in vitro approach which mimics in vivo complexity, detects neurotoxicity comprehensively, and provides mechanistic insight. For this purpose we combined rat primary re-aggregating brain cell cultures with a mass spectrometry (MS)-based metabolomics approach. For the proof of principle we treated developing re-aggregating brain cell cultures for 48h with the neurotoxicant methyl mercury chloride (0.1-100muM) and the brain stimulant caffeine (1-100muM) and acquired cellular metabolic profiles. To detect toxicant-induced metabolic alterations the profiles were analysed using commercial software which revealed patterns in the multi-parametric dataset by principal component analyses (PCA), and recognised the most significantly altered metabolites. PCA revealed concentration-dependent cluster formations for methyl mercury chloride (0.1-1muM), and treatment-dependent cluster formations for caffeine (1-100muM) at sub-cytotoxic concentrations. Four relevant metabolites responsible for the concentration-dependent alterations following methyl mercury chloride treatment could be identified using MS-MS fragmentation analysis. These were gamma-aminobutyric acid, choline, glutamine, creatine and spermine. Their respective mass ion intensities demonstrated metabolic alterations in line with the literature and suggest that the metabolites could be biomarkers for mechanisms of neurotoxicity or neuroprotection. In addition, we evaluated whether the approach could identify neurotoxic potential by testing eight compounds which have target organ toxicity in the liver, kidney or brain at sub-cytotoxic concentrations. PCA revealed cluster formations largely dependent on target organ toxicity indicating possible potential for the development of a neurotoxicity prediction model. With such results it could be useful to perform a validation study to determine the reliability, relevance and applicability of this approach to neurotoxicity screening. Thus, for the first time we show the benefits and utility of in vitro metabolomics to comprehensively detect neurotoxicity and to discover new biomarkers.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This handbook describes the peer review methodology that was applied at the GODIAC project fi eld studies1. The peer review evaluation method as initiated by Otto Adang in the Netherlands and further developed in a European football context (Adang & Brown, 2008) involves experienced police offi cers cooperating with researchers to perform observational fi eld studies to identify good practices and learning points for public order management. The handbook builds on the GODIAC seminars and workshops, for the fi eld study members, which took place in September 2010, January 2012 and January 2013. The handbook has been discussed in the project group and in the steering committee. It is primarily written for the GODIAC fi eld study members as background material for understanding the fi eld study process and for clarifying the different responsibilities that enable active participation in the fi eld study. The handbook has been developed during the project period and incorporates learning points and developments of the peer review method. The handbook aims at promoting the use of fi eld studies for evaluation of policing major events.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The volume is divided into two parts; the fi rst deals with issues related to the police, and the second addresses issues related to demonstrators and protesters. We hope that this volume will provide further insight into issues associated with policing at major events and shed light on the complexity of the organisations, motives, and strategies in play whenever protester groups are involved.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This report summarises the fi eld study results of the project ’Good practice for dialogue and communication as strategic principles for policing political manifestations in Europe’ (GODIAC).1 The overall idea was to integrate operative police work, research and training within the fi eld and to build international and institutional networks, ensuring and recognising the responsibilities of the organisers. The purpose of the GODIAC project was to contribute to the development of a European approach to policing political manifestations.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Despite the increase of animal and plant introductions worldwide and the strong augmentation of the reptile trade, few invasive snake populations have been studied. Dice snakes (Natrix tessellata) were introduced to the shores of Lake Geneva (Switzerland) in the early 1920s, and are now well established. This region of introduction was previously inhabited by Viperine snakes (N. maura). Ever since these two species have been under monitoring (which began in 1996) the Viperine snake population has shown drastic decline. We examine here the possibility of trophic competition by analysing diet composition, prey size and trophic niche overlap. Spatial distribution is also assessed in order to address the question of spatial competitive exclusion. We found very similar diets, and thus a high trophic niche overlap, indicating no partitioning of the trophic resource. No arguments in favour of spatial competitive exclusion were found. Our study suggests that trophic competition may occur between the two natricines and that it may give an explanation for the drastic decline of the Viperine snake in this area. Other pathways potentially playing a role in the exclusion of the Viperine snake are discussed.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

My case study of "Caroline"-a 26 year old presenting with depression, PTSD symptoms, and a history of sexual abuse as a teenager-represents a "third way" between (1) a strict adherence to a manualized treatment, and (2) a principle-guided therapy, in which the therapy follows particular theoretical concepts, but depends on the therapist's clinical judgement to flexibly apply them to the individual case. Specifically, in my therapy with Caroline (Kramer, 2009), I employed Foa and Rothbaum's (1998) cognitive-behavioral, "Prolonged Exposure" (PE) manual for PTSD, but deviated from it in certain ways based upon my evaluation of Caroline's individualized goals and reactions using Grawe and Caspar's "Plan Analysis," which is a cross-theoretical model for assessment and treatment planning. In their commentaries on my case study of Caroline, Caspar (2009) and Haldimann-Balli (see Appendix in Kramer, 2009) support my use of this third way. On the other hand, the other commentators-Muller (2009) and Hembree and Brinen (2009)-critique my handling of the case, arguing that strict adherence to the Foa and Rothbaum manual would have resulted in a more cost-effective therapy. In this article, I respond to the important issues raised by the four commentators.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Gas-liquid mass transfer is an important issue in the design and operation of many chemical unit operations. Despite its importance, the evaluation of gas-liquid mass transfer is not straightforward due to the complex nature of the phenomena involved. In this thesis gas-liquid mass transfer was evaluated in three different gas-liquid reactors in a traditional way by measuring the volumetric mass transfer coefficient (kLa). The studied reactors were a bubble column with a T-junction two-phase nozzle for gas dispersion, an industrial scale bubble column reactor for the oxidation of tetrahydroanthrahydroquinone and a concurrent downflow structured bed.The main drawback of this approach is that the obtained correlations give only the average volumetric mass transfer coefficient, which is dependent on average conditions. Moreover, the obtained correlations are valid only for the studied geometry and for the chemical system used in the measurements. In principle, a more fundamental approach is to estimate the interfacial area available for mass transfer from bubble size distributions obtained by solution of population balance equations. This approach has been used in this thesis by developing a population balance model for a bubble column together with phenomenological models for bubble breakage and coalescence. The parameters of the bubble breakage rate and coalescence rate models were estimated by comparing the measured and calculated bubble sizes. The coalescence models always have at least one experimental parameter. This is because the bubble coalescence depends on liquid composition in a way which is difficult to evaluate using known physical properties. The coalescence properties of some model solutions were evaluated by measuring the time that a bubble rests at the free liquid-gas interface before coalescing (the so-calledpersistence time or rest time). The measured persistence times range from 10 msup to 15 s depending on the solution. The coalescence was never found to be instantaneous. The bubble oscillates up and down at the interface at least a coupleof times before coalescence takes place. The measured persistence times were compared to coalescence times obtained by parameter fitting using measured bubble size distributions in a bubble column and a bubble column population balance model. For short persistence times, the persistence and coalescence times are in good agreement. For longer persistence times, however, the persistence times are at least an order of magnitude longer than the corresponding coalescence times from parameter fitting. This discrepancy may be attributed to the uncertainties concerning the estimation of energy dissipation rates, collision rates and mechanisms and contact times of the bubbles.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This paper aims at evaluating the compatibility of coercive climate policies with liberal neutrality. More precisely, it focuses on the doctrine of state neutrality as associated with the "harm principle". It argues that given the difficulty of attributing causal responsibilities for climate harms to individuals, the harm principle doesn't work in this case, at least if one endorses a liberal atomistic ontology. Furthermore, the definition of what constitutes climate harms implies making moral assumptions, which makes it impossible to justify climate policies in a neutral way. Finally, the paper shows another consequence of applying neutrality to the case of climate change, that is the risk of a shift from political forms of decision-making to technocracy. Focusing too much on liberty of choice may (paradoxically) be to the detriment of political freedom. The paper concludes that climate change is an intrinsically moral issue and that it should be the occasion of a political debate about our current values and lifestyles. It should not be reduced to a mere question of carbon metric.