The pore texture of raney-nickel determined by impedance measurements

The pore texture of Raney-nickel was determined by impedance measurements carried out over a wide frequency range. The impedance obtained could be characterized by three resistances, R, Re and Rt and one capacitor C. R is the high frequency limit of the electrode impedance, and is equal to the electrolyte resistance between the reference capillary-tip and the upper-surface of catalyst layer. Re is the electrolyte resistance through the cavity of catalyst layer. Rt is linked in parallel with the capacitor C.C value allows to evaluate the surface area of catalyst in contact with electrolyte provided that the double layer capacitance of nickel electrode per unit surface is known. R value, measured with and without catalyst layer allows to estimate its thickness, hence the total pore volume when the density of catalyst-metal is known. The Raney-nickel has a double pore-structure: the one related to micro-pores inside catalyst grain and the other to a heaping of grains. If the volumes of these two types of pore are known, the pore radius of micro-pore can be evaluated. Therefore, impedance measurements determine, in situ, the pore texture of Raney-nickel in liquid phase. Results were in good agreement with those determined in gas phase by current methods.     

Nuclear Waste Repository Characterization: A Spatial Estimation/Identification Approach

In this paper we consider the application of spatial estimation techniques to groundwater aquifer and geological borehole data. We investigate the adequacy of these techniques to reliably develop contour maps from various data sets. The estimator is developed theoretically in a simplified fashion using vector-matrix calculus. The practice of spatial estimation is discussed and the estimator is then applied to a groundwater aquifer system and a deep geological formation. It is shown that the various statistical models must first be identified from the data and evaluated before reasonable results can be expected.     

Rotational band identification: A model-based detection and estimation approach

Nuclear theory predicts that secondary minima develop in the nuclear potential energy surface of some nuclei as they are stretched or elongated. Some minima are deep enough to support quasistationary states. The states are metastable because the decay is inhibited by the required shape change. Detection of these metastable states and their associated rotational bands allows us to investigate nuclei at large deformations and test existing theoretical predictions. The identification of these difficult-to-locate structures will permit the detailed study of nuclei at extraordinarily high deformation, providing new insights into nuclear structure. We discuss the application of model-based image processing techniques to detect and enhance the nuclear rotational bands in noisy experimental measurements. The aim of the experiment is to identify the shape isomer by detecting the presence of the associated rotational band pattern. Unfortunately, the band signal is only ≈?1% or less of the amplitude of similar disturbance signals due to the nuclear states of normal deformation; thus the signal-to-noise ratio is quite poor. Thus it is necessary to investigate image processing techniques to detect and extract the predicted band pattern. Using a model-based approach, that is, characterizing a particular band by a simple mathematical model and incorporating it into an image processing scheme, we show that we are able to solve the band pattern detection and enhancement problems from both synthesized and measured experimental data.     

Pathological changes in the nucleus of Meynert in Alzheimer's and Parkinson's diseases

Combined neuropathological and neurochemical assessment of the nucleus of Meynert in senile dementia of Alzheimer type (SDAT) have demonstrated that the cholinergic biochemical activity, choline acetyltransferase, is more extensively reduced in the nucleus (over 90%) than the loss of putative cholinergic perikarya (35%). Acetylcholinesterase histochemical activity was however substantially retained in individual neurones in the nucleus although virtually absent from the neocortex in SDAT. These abnormalities are consistent with a primary degeneration of cholinergic axons projecting to the cortex and secondary loss of perikarya from the subcortical nucleus. In contrast, preliminary observations on cases of Parkinson's disease suggest that the neuronal loss from the nucleus of Meynert may be greater in this disease than in SDAT, and previous studies have not consistently demonstrated a reduction in cortical choline acetyltransferase activities in Parkinson's disease. These observations, together with major differences in the neuropathology of the nucleus in SDAT and Parkinson's disease (neurofibrillary tangle and Lewy body formation, respectively) suggest that the involvement of the cholinergic system may differ in the two disease processes.     

Effect of apolipoprotein E genotype on Alzheimer's disease neuropathology in a cohort of elderly Norwegians

A cohort of elderly Norwegians dying in nursing homes in the Oslo region have been genotyped for the Apolipoprotein E (ApoE) gene. Alzheimer's disease (AD) cortical neuropathology and clinical evidence of dementia were used to assign cases without evidence of other confounding neuropathology. Senile plaque (SP) and neurofibrillary tangle (NFT) densities in frontal, temporal and parietal cortex were then correlated with ApoE genotype to determine any relationship between ApoE genotype and AD pathology. Comparisons with ApoE epsilon 3, epsilon 4 and epsilon 2 allele dosage failed to show any significant effect on cortical SP densities in any cortical area. NFT densities were increased by epsilon 4 allele dosage in the frontal cortex but not in other cortical regions. A reduction was seen in cortical NFT densities with epsilon 2 allele, though again this was not consistently significant in any of the groups. The epsilon 3 allele failed to show any consistent effect on cortical NFT densities. Assessment by individual genotypes showed epsilon 2/3 < epsilon 2/4 < epsilon 3/3 < epsilon 3/4 < epsilon 4/4 which had highest cortical NFT densities in all areas. By genotype, SP densities were generally of the order epsilon 2/4 < epsilon 2/3 < epsilon 3/3 < epsilon 4/4 < epsilon 3/4 though in none of the groups was this significant. Duration of disease showed no consistent effect on neuropathological burden. ApoE genotype may have an effect on determining whether individuals suffer from AD and the age at onset of disease but may only have a minimal effect on pathology burden.     

X-ray absorption fine structure combined with X-ray fluorescence spectrometry. Improvement of spectral resolution at the absorption edges of 9-29 keV

X-ray absorption near-edge structure (XANES) suffers from core-hole lifetime broadening at a higher energy absorption edge, such as Sn K (29 keV, Gamma(K) = 8.49 eV). To overcome this problem, emitted Sn Kalpha1 fluorescence from sample was counted using high-energy-resolution fluorescence spectrometer in the XANES measurements. Experimental energy resolution (5.0 eV) was consistent with theoretical values based on the Rowland configuration of the spectrometer. The absorption edge became steeper compared to conventional spectra. The white-line peak due to Sn(II) species became remarkably sharper and more intense in the Sn Kalpha1-detecting Sn K-edge XANES for Pt-Sn/SiO2. To support the semiclassical theory of resonant Raman scattering for the explanation of observed elimination of lifetime width, more resolved XANES data at Cu K, Pb L3, and Sn K in this work were convoluted (filtered) with a Lorentzian of each core-hole lifetime width. The processed data resembled generally well corresponding XANES spectrum measured in transmission mode. The verification based on ab initio XANES calculations was also performed.     

An investigation into supporting collaboration over the Internet

This paper describes an investigation into the practical use of multi-media tools available on the Internet for the purpose of communication and collaboration between remotely located users. A prototype interface incorporating voice, text and graphics-based communication tools was developed according to the needs of a group of researchers. Experiments were conducted whereby the interface was used to carry out authentic tasks for the joint preparation of a research paper. The tasks involved simultaneous activity between researchers located in the UK and Australia where the time difference between the sites was 8.5 h. From the results of the investigation, issues that are relevant to multi-media tool design and what users can expect in practice from their use on the Internet were identified.