4,992 research outputs found
Exact Markovian kinetic equation for a quantum Brownian oscillator
We derive an exact Markovian kinetic equation for an oscillator linearly
coupled to a heat bath, describing quantum Brownian motion. Our work is based
on the subdynamics formulation developed by Prigogine and collaborators. The
space of distribution functions is decomposed into independent subspaces that
remain invariant under Liouville dynamics. For integrable systems in
Poincar\'e's sense the invariant subspaces follow the dynamics of uncoupled,
renormalized particles. In contrast for non-integrable systems, the invariant
subspaces follow a dynamics with broken-time symmetry, involving generalized
functions. This result indicates that irreversibility and stochasticity are
exact properties of dynamics in generalized function spaces. We comment on the
relation between our Markovian kinetic equation and the Hu-Paz-Zhang equation.Comment: A few typos in the published version are correcte
Sorption kinetics for the removal of aldehydes from aqueous streams with extractant impregnated resins
The sorption kinetics for the removal aldehydes from aqueous solutions with Amberlite XAD-16 and MPP particles impregnated with Primene JM-T was investigated. A model, accounting for the simultaneous mass transfer and chemical reaction, is developed to describe the process. It is based on the analogy to the diffusion and reaction in a stagnant liquid sphere, but corrected for the porosity and particle properties influencing the diffusion. The developed model describes the kinetic behavior of the process in the low concentration region rather well. However, in the high concentration region, larger discrepancies are observed. Initially, the influence of the flow rate was investigated to eliminate the effect of the external mass transfer. The influence of the particle morphology was investigated for both physical and reactive sorption. Physical sorption experiments were used to determine the factor τ that takes the particle properties influencing the diffusion into account. It was shown that the diffusion is faster in XAD-16 than in MPP impregnated systems. Reaction rate constant kx was determined by fitting the model to the experimental data. Sorption of benzaldehyde appears to be significantly slower (kx ~ 10−4 l/mol s) than the sorption of pentanal (kx ~ 10−3 l/mol s) due to the slower chemical reaction. The influence of the particle size was investigated for the sorption of pentanal with XAD-16. It was observed that the particle size does influence the diffusion term, but does not have an effect on the reaction rate. On the other hand, the extractant loading influences the reaction rate slightly in the low concentration region, whereas the initial concentration of the solute has more pronounced effect
The AMC Linear Disability Score in patients with newly diagnosed Parkinson disease
Objective: The aim of this study was to examine the clinimetric properties of the AMC Linear Disability Score (ALDS), a new generic disability measure based on Item Response Theory, in patients with newly diagnosed Parkinson disease (PD).\ud
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Methods: A sample of 132 patients with PD was evaluated using the Hoehn and Yahr (H&Y), the Unified PD Rating Scale motor examination, the Schwab and England scale (S&E), the Short Form–36, the PD Quality of Life Questionnaire, and the ALDS.\ud
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Results: The internal consistency reliability of the ALDS was good ([alpha] = 0.95) with 55 items extending the sufficient item-total correlation criterion (r > 0.20). The ALDS was correlated with other disability measures (r = 0.50 to 0.63) and decreasingly associated with measures reflecting impairments (r = 0.36 to 0.37) and mental health (r = 0.23 to -0.01). With regard to know-group validity, the ALDS indicated that patients with more severe PD (H&Y stage 3) were more disabled than patients with mild (H&Y stage 1) or moderate PD (H&Y stage 2) (p < 0.0001). The ALDS discriminated between more or less severe extrapyramidal symptoms (p = 0.001) and patients with postural instability showed lower ALDS scores compared to patients without postural instability (p = < 0.0001). Compared to the S&E (score 100% = 19%), the ALDS showed less of a ceiling effect (5%).\ud
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Conclusion: The AMC Linear Disability Score is a flexible, feasible, and clinimetrically promising instrument to assess the level of disability in patients with newly diagnosed Parkinson disease
The effects of pulse stimulation on biota - Research in relation to ICES advice - Effects on dogfish
Onderzoek naar het welzijn van hondshaaien bij de vangst. Er is onderzocht of de methode van het gebruik van stroom wel diervriendelijk is. De conclusie is dat dit geen beletsel voor de diervriendelijkheid oplever
The effect of pulse stimulation on marine biota - Research in relation to ICES advice - Progress report on the effects on benthic invertebrates
In response to ecosystem related concerns about bottom trawling and particularly beam trawling that were raised by various scientists in the last decades of the previous century. Many studies were done in the 1970s and 1980s, but in spite of promising results commercial uptake was lacking. The development of pulse trawling was again taken up in the 1990s by a private company (Verburg:Holland Ltd.) in The Netherlands. Meanwhile questions about ecosystem effects of introducing pulse beam trawling in the Dutch flatfish fishery were raised by the European Scientific, Technical and Economic Committee for Fisheries (STECF) and the Inter: national Council for the Exploration of the Sea (ICES) and discussed at the meeting of the ICES Working Group on Fishing Technology and Fish Behaviour (WGFTFB) in 2006. These questions led to field strength measurements in situ onboard the commercial beam trawler, and research on the effects of pulse stimulation on cod (Gadus morhua L.), and elasmobranch fish
Industrial Separation Processes:Fundamentals
Separation processes on an industrial scale account for well over half of the capital and operating costs in the chemical industry. Knowledge of these processes is key for every student of chemical or process engineering. This book is ideally suited to university teaching, thanks to its wealth of exercises and solutions. The second edition boasts an even greater number of applied examples and case studies as well as references for further reading. - An authoritative introduction to industrial separation technology. - Contains exercises at the end of each subject as well as solutions. - Now with extended and updated examples and case studies
The effects of fiscal policy at the effective lower bound
We estimate the effects of government spending shocks during prolonged episodes of low interest rates, which we consider as proxy for the effective lower bound (ELB). Using a panel VAR model for 17 advanced countries, we find that both the government consumption and investment multipliers are significantly higher, and exceed unity, when interest rates are persistently low. Distinguishing between construction- and equipment-related government investments, we find that only the former raises output by significantly more when the ELB binds. This result can be explained by existing New Keynesian models featuring time-to-build constraints on government investment
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