Evaluation of hydrogen sorption models for AB5-type metal alloys by employing a gravimetric technique

This paper is concerned with hydrogen absorption and desorption in AB₅-type hydrogen storage metal alloys. We give a brief overview on models which have been proposed for hydrogen sorption in metals over the past decades. We choose three models based on different perspectives, i.e. thermodynamics, reaction kinetics, and mere observation (empiricism), and evaluate their applicability in order to describe the sorption behaviour. Additionally, we propose a model which is based on a cumulative distribution function. In order to evaluate the models, the hydrogen absorption and desorption isotherms of LaNi₅ and LaNi_4.5Co_0.5 are measured by means of a gravimetric technique. A nonlinear regression is performed to fit the models to experimental data. The computed model parameters are compared to values reported in the literature. The emphasis is given to the applicability of the models with respect to describing the non-ideality of the plateau region and the continuity/smoothness of phase transition regions.     

Seasonal optimal mix of wind and solar power in a future,highly renewable Europe

The renewable power generation aggregated across Europe exhibits strong seasonal behaviors. Wind power generation is much stronger in winter than in summer. The opposite is true for solar power generation. In a future Europe with a very high share of renewable power generation those two opposite behaviors are able to counterbalance each other to a certain extent to follow the seasonal load curve. The best point of counterbalancing represents the seasonal optimal mix between wind and solar power generation. It leads to a pronounced minimum in required stored energy. For a 100% renewable Europe the seasonal optimal mix becomes 55% wind and 45% solar power generation. For less than 100% renewable scenarios the fraction of wind power generation increases and that of solar power generation decreases.     

An Equal-Order DG Method for the Incompressible Navier-Stokes Equations

We introduce and analyze a discontinuous Galerkin method for the incompressible Navier-Stokes equations that is based on finite element spaces of the same polynomial order for the approximation of the velocity and the pressure. Stability of this equal-order approach is ensured by a pressure stabilization term. A simple element-by-element post-processing procedure is used to provide globally divergence-free velocity approximations. For small data, we prove the existence and uniqueness of discrete solutions and carry out an error analysis of the method. A series of numerical results are presented that validate our theoretical findings.     

Reconceptualizing feeding and feeding disorders in interpersonal context: The case for a relational disorder.

The feeding of young children is fundamentally a relational and multisystemic process. Successful treatment of clinically significant feeding problems involves careful assessment of the full range of influences on the feeding relationship and integrated treatment approaches. However, current diagnostic approaches to feeding disorders tend to be reductionistic, exclusively focused on the child as an individual, and overly concerned with exclusionary criteria. Criteria are proposed for "Feeding Disorder Between Parent and Child" that address these limitations and embrace the complexity of feeding problems. A multiaxial diagnosis that describes the child (including medical, developmental, and behavioral characteristics); the parent; the parent-child relationship; and the social and nutritional context of feeding will more accurately speak to treatment planning in this population. The proposed diagnostic criteria were developed and refined on the basis of the available literature and many years of treatment experience across the authors of this article. The proposed diagnosis will support the development and evaluation of treatment packages with components specifically targeted to issues of the child, parent, parent-child interaction, and the broader environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Energy Norm shape A Posteriori Error Estimation for Mixed Discontinuous Galerkin Approximations of the Stokes Problem

In this paper, we develop the a posteriori error estimation of mixed discontinuous Galerkin finite element approximations of the Stokes problem. In particular, we derive computable upper bounds on the error, measured in terms of a natural (mesh-dependent) energy norm. This is done by rewriting the underlying method in a non-consistent form using appropriate lifting operators, and by employing a decomposition result for the discontinuous spaces. A series of numerical experiments highlighting the performance of the proposed a posteriori error estimator on adaptively refined meshes are presented.Paul Houston - Funded by the EPSRC (Grant GR/R76615). Thomas P. Wihler - Funded by the Swiss National Science Foundation (Grant PBEZ2-102321). This revised version was published online in July 2005 with corrected volume and issue numbers.     

Conferring selectivity to chemical sensors via polymer side-chain selection: thermodynamics of vapor sorption by a set of polysiloxanes on thickness-shear mode resonators

Entropy of mixing is shown to be the driving interaction for the endothermic physisorption process of organic vapor partitioning into seven systematically side-chain-modified (polar, acidic, basic, polarizable side groups and groups interacting via H-bridges) polysiloxanes on thickness-shear mode resonators. Each sensor was exposed to seven analytes, selected for their diversity of functional groups. This systematic investigation of sorption yields benchmarking data on physisorption selectivity: response data and modeling reveal a direct correlation of partition coefficients with interactions between specific polymer side chains and analyte functional groups. Partition coefficients were determined for every polymer/analyte pairing over the 273-343 K range at 10 K intervals; from partition coefficient temperature dependence, overall absorption enthalpies and entropies were calculated. By subtracting the enthalpy and entropy of condensation for a given pure analyte, its mixing entropy (primarily combinatorial) and mixing enthalpy (associated with intermolecular interactions) with each polymer matrix were determined. These two crucial thermodynamic parameters determine the chemical selectivity patterns of the polymers for the analytes. Simple molecular modeling based on the polymer contact surface share of the modified side group or the introduced functional group reveals a direct correlation between the partition coefficients and the side-group variation.     

Characterization of hydrogen bonding in the complex of adenosine deaminase with a transition state analogue: a Raman spectroscopic study

The Raman spectra of purine ribonucleoside as well as a stable model compound (1-methoxyl-1,6-dihydropurine ribonucleoside), free in solution and bound into its complex with adenosine deaminase (ADA), have been studied by Raman difference spectroscopy. Using purine riboside analogues labeled with 15N1 or 13C6 and the theoretical frequency normal-mode analyses of these molecules using ab initio quantum mechanic methods, we have positively identified many of the Raman bands in the enzyme-bound inhibitor. The spectrum of the enzyme-bound inhibitor is consistent with the enzyme-catalyzed hydration of the purine base to yield 1-hydroxyl-1,6-dihydropurine ribonucleoside, as suggested earlier by X-ray crystallographic studies. In addition, the Raman data and subsequent vibrational analyses show that the binding-induced Raman spectral changes of the inhibitor can be modeled by the formation of a strong hydrogen bond to its N1-H bond. This hydrogen bond, apparently between the N1-H of the inhibitor and the Odelta1 of Glu217 in ADA, causes a substantial N1-H bending frequency increase of about 50-100 cm-1 compared to its solution value, and this results in an estimated enthalpy of the hydrogen bond of 4-10 kcal/mol. The relationship of transition state stabilization in the catalytic strategy of this efficient enzyme to such a bonding pattern is discussed.     

Evaluation of pavement surface texture significance and measurement techniques

It is generally agreed that the skid resistance of a pavement is controlled by the surface texture characteristics. Therefore, by measuring the relevant parameters describing texture, or by measuring a physical process dependent on texture, regression techniques can be used to relate skid resistance to the chosen texture parameter or process. Two scales of texture are of particular importance: microtexture (small-scale asperities) and macrotexture (largescale asperities).In this paper work performed at the Pennsylvania Transportation Institute at the Pennsylvania State University is described and is given in two parts: (1) a review of candidate macrotexture and microtexture measurement methods that can be made at highway speeds (at or above 65 km h^?1), which are presently used or have potential for use in pavement texture research, with a recommendation of the more promising methods for further development, and (2) a summary of the effects of pavement surface texture on skid resistance.