Travelling Waves for Gas-Solid Reactions

Sin resume

Rigorous derivation of a hyperbolic model for Taylor dispersion

In this paper we upscale the classical convection-diffusion equation in a narrow slit. We suppose that the transport parameters are such that we are in Taylor's regime i.e. we deal with dominant Peclet numbers. In contrast to the classical work of Taylor, we undertake a rigorous derivation of the upscaled hyperbolic dispersion equation. Hyperbolic effective models were proposed by several authors and our goal is to confirm rigorously the effective equations derived by Balakotaiah et al in recent years using a formal Liapounov - Schmidt reduction. Our analysis uses the Laplace transform in time and an anisotropic singular perturbation technique, the small characteristic parameter " being the ratio between the thickness and the longitudinal observation length. The Peclet number is written as Ce¿a, with a<2. Hyperbolic effective model corresponds to a high Peclet number close to the threshold value when Taylor's regime turns to turbulent mixing and we characterize it by supposing 4/3 <a <2. We prove that the difference between the dimensionless physical concentration and the effective concentration, calculated using the hyperbolic upscaled model, divided by e2¿a (the local Peclet number) converges strongly to zero in L2-norm. For Peclet numbers considered in this paper, the hyperbolic dispersion equation turns out to give a better approximation than the classical parabolic Taylor model

HORACE: software for the analysis of data from single crystal spectroscopy experiments at time-of-flight neutron instruments

The HORACE suite of programs has been developed to work with large multiple-measurement data sets collected from time-of-flight neutron spectrometers equipped with arrays of position-sensitive detectors. The software allows exploratory studies of the four dimensions of reciprocal space and excitation energy to be undertaken, enabling multi-dimensional subsets to be visualized, algebraically manipulated, and models for the scattering to simulated or fitted to the data. The software is designed to be an extensible framework, thus allowing user-customized operations to be performed on the data. Examples of the use of its features are given for measurements exploring the spin waves of the simple antiferromagnet RbMnF$_{3}$ and ferromagnetic iron, and the phonons in URu$_{2}$Si$_{2}$.Comment: 14 pages, 6 figure

Scale construction and evaluation in practice:A review of factor analysis versus item response theory applications

In scale construction and evaluation, factor analysis (FA) and item response theory (IRT) are two methods frequently used to determine whether a set of items reliably measures a latent variable. In a review of 41 published studies we examined which methodology – FA or IRT – was used, and what researchers’ motivations were for applying either method. Characteristics of the studies were compared to gain more insight into the practice of scale analysis. Findings indicate that FA is applied far more often than IRT. Many times it is unclear whether the data justify the chosen method because model assumptions are neglected. We recommended that researchers (a) use substantive knowledge about the items to their advantage by more frequently employing confirmatory techniques, as well as adding item content and interpretability of factors to the criteria in model evaluation; and (b) investigate model assumptions and report corresponding findings. To this end, we recommend more collaboration between substantive researchers and statisticians/psychometricians

The external effects of inner-city shopping centers:Evidence from the Netherlands

Shopping center redevelopment is inevitable to remain attractive for consumers. In this paper, we investigate the external effects of shopping center redevelopment on nearby residential property prices. Using a difference-in-difference empirical framework, we find the redevelopment has positive external effects on nearby property prices. We find the price of a property located next to a redeveloped shopping center increases by 1.43% on average just after redevelopment. Our results indicate that these positive external effects wear off rather rapidly across space and over time. This suggests that shopping center redevelopment plays a substantial, but limited, role in combating neighborhood deprivation

Genome-based prediction of common diseases: methodological considerations for future research

The translation of emerging genomic knowledge into public health and clinical care is one of the major challenges for the coming decades. At the moment, genome-based prediction of common diseases, such as type 2 diabetes, coronary heart disease and cancer, is still not informative. Our understanding of the genetic basis of multifactorial diseases is improving, but the currently identified susceptibility variants contribute only marginally to the development of disease. At the same time, an increasing number of companies are offering personalized lifestyle and health recommendations on the basis of individual genetic profiles. This discrepancy between the limited predictive value and the commercial availability of genetic profiles highlights the need for a critical appraisal of the usefulness of genome-based applications in clinical and public health care. Anticipating the discovery of a large number of genetic variants in the near future, we need to prepare a framework for the design and analysis of studies aiming to evaluate the clinical validity and utility of genetic tests. In this article, we review recent studies on the predictive value of genetic profiling from a methodological perspective and address issues around the choice of the study population, the construction of genetic profiles, the measurement of the predictive value, calibration and validation of prediction models, and assessment of clinical utility. Careful consideration of these issues will contribute to the knowledge base that is needed to identify useful genome-based applications for implementation in clinical and public health practice

Serum levels of interleukin-6 are not elevated in patients with Alzheimer's disease

Serum levels of interleukin-6 (IL-6) were determined in 97 patients with clinically diagnosed Alzheimer's disease and 79 age- and sex-matched control subject. Median serum levels of IL-6 did not differ significantly between Alzheimer patients (8.6 U/ml) and controls (8.2 U/ml). Median levels of serum IL-6 were similar for sporadic and familial patients. The concentration of IL-6 was not associated with the severity of the dementia or the duration of the disease since first symptoms. According to these observations there is no evidence for a significant elevation in serum IL-6 in Alzheimer's disease