Search results for "Number"
showing 10 items of 3939 documents
Stability of melt flow due to a traveling magnetic field in a closed ampoule
2004
The linear three-dimensional instability of the flow due to a low frequency traveling magnetic field in a regular cylinder is studied numerically for height-to-diameter ratios in the range [0.5:2.5]. The first instability has the form of an azimuthal wave with wave numbers between 1 and 6 depending on the aspect ratio. It is shown that the flow is stable if the Reynolds number is below 290. Even stronger stationary flows may be obtained in a flattened cylinder.
Quantum dynamical study of the O(1D) + CH4→ CH3+ OH atmospheric reaction
2014
Time independent quantum mechanical (TIQM) scattering calculations have been carried out for the O((1)D) + CH4(X(1)A1) → CH3(X(2)A2″) + OH(X(2)Π) atmospheric reaction, using an ab initio ground potential energy surface where the CH3 group is described as a pseudo-atom. Total and state-to-state reaction probabilities for a total angular momentum J = 0 have been determined for collision energies up to 0.5 eV. The vibrational and rotational state OH product distributions show no specific behavior. The rate coefficient has been calculated by means of the J-shifting approach in the 10-500 K temperature range and slightly depends on T at ordinary temperatures (as expected for a barrierless reacti…
Anomalies from the phenomenological and geometrical points of view
2008
Chiral anomalies are reviewed according to three different points of view: the usual approach together with some phenomenological implications, the algebraic approach, and, in the end and more detailed, the geometric approach. In particular, the topological approach of the Atiyah-Singer is extended in a way which allows the treatment of all chiral anomalies within the geometric (equivariant) point of view.
Bag models and hadron structure
2008
We review the fundamental ideas leading to the basic assumptions behind the bag model description of hadron structure and explore in some detail the so called MIT bag model. We discuss the relevance of chiral symmetry and incorporate it in a bag model scheme by adding a pion field. We show perturbative techniques of calculating gluonic and pionic effects. We discuss the consequences of the solitonic nature of the hedgehog solution of the pion field and introduce the skyrmion bag model. We end up by drawing some conclusions of our study and discussing recent developments in this area.
Layered composite based on halloysite and natural polymers: a carrier for the pH controlled release of drugs
2019
We have prepared new biohybrid materials based on halloysite nanotubes and natural polymers (alginate and chitosan) for the controlled and sustained release of bioactive species. A functional nanoarchitecture has been designed allowing us to generate a layered tablet with a chitosan/halloysite nanocomposite film sandwiched between two alginate layers. The assembly of the raw components and the final structure of the hybrid tablet have been highlighted by the morphological and wettability properties of the prepared materials. Since the biohybrid has been designed as a smart carrier, halloysite nanotubes have been first loaded with a model drug (sodium diclofenac). The effect of the tablet th…
Decision Under Uncertainty: An Experimental View
2010
This work (experimental research) is based on Prospect theory, which was developed by D. Kahneman and A. Tversky in 1979. This is one the most quoted and best-documented point of view in economic psychology. First of all, it replaces, once again, the notion of utility with value. But value is defined in terms of gains and losses and this, according with an irrational human tendency to be less willing to gamble with profits than with losses. So, we discover the great importance of these assumptions in the field of risk individual decision-making. n experimental study was conducted to examine the influence of elaboration and the way in which alternatives are phased on decision. Subjects were …
Porous fractal gels: secondary effects in SEC
1992
Abstract The fractal nature of porous silica gels, Spherosil XOA 200 and of a Lichrospher mixture, has been tested through size exclusion chromatography of polystyrene in pure and mixed eluents. Fractal parameters, D f and L , depend on eluent with D f values close to 2.0 for Spherosil and higher than 2.0 for Lichrospher. D f and L changes with eluent have been related to secondary separation effects and partition and adsorption contributions have been evaluated.
Peak deconvolution in one-dimensional chromatography using a two-way data approach.
2002
A deconvolution methodology for overlapped chromatographic signals is proposed. Several single-wavelength chromatograms of binary mixtures, obtained in different runs at diverse concentration ratios of the individual components, were simultaneously processed (multi-batch approach), after being arranged as two-way data. The chromatograms were modelled as linear combinations of forced peak profiles according to a polynomially modified Gaussian equation. The fitting was performed with a previously reported hybrid genetic algorithm with local search, leaving all model parameters free. The approach yielded more accurate solutions than those found when each experimental chromatogram was fitted in…
A theoretical plate model accounting for slow kinetics in chromatographic elution.
2011
The chromatographic elution has been studied from different perspectives. However, in spite of the simplicity and evident deficiencies of the plate model proposed by Martin and Synge, it has served as a basis for the characterization of columns up-to-date. This approach envisions the chromatographic column as an arbitrary number of theoretical plates, each of them consisting of identical repeating portions of mobile phase and stationary phase. Solutes partition between both phases, reaching the equilibrium. Mobile phase transference between the theoretical plates is assumed to be infinitesimally stepwise (or continuous), giving rise to the mixing of the solutions in adjacent plates. This yi…
Extraktionschromatographische trennung der freien uroporphyrinisomere i und iii und deren simultane quantitative bestimmung
1968
Abstract Separation and simultaneous quantitative determination of the free uroporphyrin isomers I and III by means of extraction chromatography Separation and quantitative determination of the uroporphyrin isomers I and III in the acid from can be performed simultaneously in the partition system tri-n-butylphosphate/I N hydrochloric acid using columns with a large number of theoretical plates (N) = 300-450). The eluent is passed through a flow cuvette and the transmission is recorded continuously. The transmission peaks of the isomers are digitized and transformed into extinction values. By integrating the extinction peaks, the amount of the uroporphyrins can be evaluated from the correspo…