Clear-sky biases in satellite infrared estimates of upper tropospheric humidity and its trends

We use microwave retrievals of upper tropospheric humidity (UTH) to estimate the impact of clear-sky-only sampling by infrared instruments on the distribution, variability and trends in UTH. Our method isolates the impact of the clear-sky-only sampling, without convolving errors from other sources. On daily time scales IR-sampled UTH contains large data gaps in convectively active areas, with only about 20-30 % of the tropics (30 S­ 30 N) being sampled. This results in a dry bias of about -9 %RH in the area-weighted tropical daily UTH time series. On monthly scales, maximum clear-sky bias (CSB) is up to -30 %RH over convectively active areas. The magnitude of CSB shows significant correlations with UTH itself (-0.5) and also with the variability in UTH (-0.6). We also show that IR-sampled UTH time series have higher interannual variability and smaller trends compared to microwave sampling. We argue that a significant part of the smaller trend results from the contrasting influence of diurnal drift in the satellite measurements on the wet and dry regions of the tropics

Understanding filter cake formation through electrical impedance measurements

An electrical impedance tomography technique for determining the solids concentration in solid/liquid mixtures has been used to analyse cake formation during the pressure leaf filtration of aqueous based mineral suspensions. The experimental data are interpreted through so-called ‘modern filtration theory’ which serves to highlight some of the difficulties that currently exist in the areas of both modelling and scale-up in solid/liquid separation

The importance of cake compressibility in deadend pressure filtration

Particulate suspensions were pressure filtered over a range of experimental conditions using a well controlled deadend leaf filter system. An electrical resistance measuring technique was incorporated in the system to obtain real time transient solids concentration profiles through the filtering suspensions/cakes. Data are shown which illustrate the use of the apparatus and the effects of some process variables and surface charge on cake compressibility. Three different diameter filter cells were used to obtain scale-up data and the need to correctly incorporate these scale-up parameters in filtration models is highlighted

Aspects of modelling in compressible filter cake formation

Solids concentrations through a solid/liquid mixture were determined using an electrical impedance measuring technique described previously. A number of pressure leaf filter experiments have been performed for two materials exhibiting a range of compressibility at differing applied filtration pressures, initial solids concentrations and surface charges. The paper indicates how such experimental data can be interpreted and modelled using both the classical and so-called ‘modern’ filtration theory. The need to enhance these models for compressible materials is highlighted with reference to the experimental data and the influential particulate and process parameters. Suggestions for the ways in which models can be improved are made

Compressible cake filtration

The formation of a compressible kaolin filter cake has been examined using an electrical conductivity technique that continuously monitors the local solids concentration with height and time during filtration. The relative importance of liquid drag, solids weight and velocity inside a filter cake during the cake forming process were studied, and their effect on the modelling approach of Tiller and Shirato considered. It is concluded that a more accurate representation of the cake concentration profile would result from an incremental simulation of the solid deposition process

Influence of particulate and process variables in compressible cake filtration

Data are reported on particulate and process variables which influence the formation of compressible filter cakes. Variables such as surface charge, particle size and size distribution, filtration pressure and solids concentration have been investigated. To obtain a greater insight into the filter cake behaviour, an electrical impedance imaging technique for determining the in-situ solids concentration in solid/liquid mixtures has been used. Pressure leaf filtration tests of wellcharacterised solids dispersed in aqueous media have been performed over a range of conditions to investigate the characteristics of compressibility. The majority of the results from these tests are shown through solids concentration profiles as functions of suspension/cake height and time, and specific cake resistance and porosity as functions of pressure. The dependence of the compressibility on surface charge and other variables has been found. Comparisons have been made with the Tiller/Shirato ‘modern’ filtration theory and the difficulties highlighted

Amino Acids as biomarkers in the SOD1G93A mouse model of ALS

AbstractThe development of therapies for Amyotrophic Lateral Sclerosis (ALS) has been hindered by the lack of biomarkers for both identifying early disease and for monitoring the effectiveness of drugs. The identification of ALS biomarkers in presymptomatic individuals might also provide clues to the earliest biochemical correlates of the disease. Previous attempts to use plasma metabolites as biomarkers have led to contradictory results, presumably because of heterogeneity in both the underlying genetics and the disease stage in the clinical population. To eliminate these two sources of heterogeneity we have characterized plasma amino acids and other metabolites in the SOD1G93A transgenic mouse model for ALS. Presymptomatic SOD1G93A mice have significant differences in concentrations of several plasma metabolites compared to wild type animals, most notably in the concentrations of aspartate, cystine/cysteine, and phosphoethanolamine, and in changes indicative of methylation defects. There are significant changes in amino acid compositions between 50 and 70days of age in both the SOD1G93A and wild type mice, and several of the age-related and disease-related differences in metabolite concentration were also gender-specific. Many of the SOD1G93A-related differences could be altered by treatment of mice with methionine sulfoximine, which extends the lifespan of this mouse, inhibits glutamine synthetase, and modifies brain methylation reactions. These studies show that assaying plasma metabolites can effectively distinguish transgenic mice from wild type, suggesting that one or more plasma metabolites might be useful biomarkers for the disease in humans, especially if genetic and longitudinal analysis is used to reduce population heterogeneity

Breakage characteristics of granulated food products for prediction of attrition during lean-phase pneumatic conveying

Pneumatic conveying is utilised in a variety of industries to convey food products exhibiting diverse handling characteristics. Attrition of particles caused by this conveying process can result in a number of undesirable outcomes such as loss in product quality or issues in subsequent handling processes. The ability to predict the breakage behaviour of particulate materials is desirable in both new system design and resolving issues in existing plants. This work considers two different particulate materials (Salt and Golden Breadcrumbs) across a range of particle sizes, and quantifies their breakage behaviour under varying impact conditions. Narrow size fractions of each material was degraded; material retained on 250 µm and 355 µm sieves for salt, and 500µm, 710µm and 1000 µm sieves for Golden Breadcrumbs. Velocity was found to be the most influential factor with respect to particle attrition. The results from the narrow size fraction tests were superimposed to form a simulated full size distribution breakage behaviour, which was then compared to the experimentally determined behaviour. A good agreement was found, however the proportion of material predicted for size fractions smaller than 355 µm for Golden Breadcrumbs and 180 µm for Salt was under-predicted. Recommendations for increasing accuracy of the prediction method are given

Tracking Black Holes in Numerical Relativity

This work addresses and solves the problem of generically tracking black hole event horizons in computational simulation of black hole interactions. Solutions of the hyperbolic eikonal equation, solved on a curved spacetime manifold containing black hole sources, are employed in development of a robust tracking method capable of continuously monitoring arbitrary changes of topology in the event horizon, as well as arbitrary numbers of gravitational sources. The method makes use of continuous families of level set viscosity solutions of the eikonal equation with identification of the black hole event horizon obtained by the signature feature of discontinuity formation in the eikonal's solution. The method is employed in the analysis of the event horizon for the asymmetric merger in a binary black hole system. In this first such three dimensional analysis, we establish both qualitative and quantitative physics for the asymmetric collision; including: 1. Bounds on the topology of the throat connecting the holes following merger, 2. Time of merger, and 3. Continuous accounting for the surface of section areas of the black hole sources.Comment: 14 pages, 16 figure

Complete null data for a black hole collision

We present an algorithm for calculating the complete data on an event horizon which constitute the necessary input for characteristic evolution of the exterior spacetime. We apply this algorithm to study the intrinsic and extrinsic geometry of a binary black hole event horizon, constructing a sequence of binary black hole event horizons which approaches a single Schwarzschild black hole horizon as a limiting case. The linear perturbation of the Schwarzschild horizon provides global insight into the close limit for binary black holes, in which the individual holes have joined in the infinite past. In general there is a division of the horizon into interior and exterior regions, analogous to the division of the Schwarzschild horizon by the r=2M bifurcation sphere. In passing from the perturbative to the strongly nonlinear regime there is a transition in which the individual black holes persist in the exterior portion of the horizon. The algorithm is intended to provide the data sets for production of a catalog of nonlinear post-merger wave forms using the PITT null code.Comment: Revised version, to appear in Phys. Rev. D. July 15 (2001), 41 pages, 11 figures, RevTeX/epsf/psfi