An equivalent algorithm for simulating thermal effects of magma intrusion problems in porous rocks

An equivalent algorithm is proposed to simulate thermal effects of the magma intrusion in geological systems, which are composed of porous rocks. Based on the physical and mathematical equivalence, the original magma solidification problem with a moving boundary between the rock and intruded magma is transformed into a new problem without the moving boundary but with a physically equivalent heat source. From the analysis of an ideal solidification model, the physically equivalent heat source has been determined in this paper. The major advantage in using the proposed equivalent algorithm is that the fixed finite element mesh with a variable integration time step can be employed to simulate the thermal effect of the intruded magma solidification using the conventional finite element method. The related numerical results have demonstrated the correctness and usefulness of the proposed equivalent algorithm for simulating the thermal effect of the intruded magma solidification in geological systems. (C) 2003 Elsevier B.V. All rights reserved.

Theoretical and numerical analyses of convective instability in porous media with temperature-dependent viscosity

Exact analytical solutions of the critical Rayleigh numbers have been obtained for a hydrothermal system consisting of a horizontal porous layer with temperature-dependent viscosity. The boundary conditions considered are constant temperature and zero vertical Darcy velocity at both the top and bottom of the layer. Not only can the derived analytical solutions be readily used to examine the effect of the temperature-dependent viscosity on the temperature-gradient driven convective flow, but also they can be used to validate the numerical methods such as the finite-element method and finite-difference method for dealing with the same kind of problem. The related analytical and numerical results demonstrated that the temperature-dependent viscosity destabilizes the temperature-gradient driven convective flow and therefore, may affect the ore body formation and mineralization in the upper crust of the Earth. Copyright (C) 2003 John Wiley Sons, Ltd.

Operational regimes for a simplified one-step artificial chaperone refolding method

The artificial chaperone method for protein refolding developed by Rozema et al. (Rozema, D.; Gellman, S. H. J. Am. Chem. Soc. 1995, 117 (8), 2373-2374) involves the sequential dilution of denatured protein into a buffer containing detergent (cetyltrimethylammonium bromide, CTAB) and then into a refolding buffer containing cyclodextrin WD). In this paper a simplified one-step artificial chaperone method is reported, whereby CTAB is added directly to the denatured solution, which is then diluted directly into a refolding buffer containing P-cyclodextrin (P-CD). This new method can be applied at high protein concentrations, resulting in smaller processing volumes and a more concentrated protein solution following refolding. The increase in achievable protein concentration results from the enhanced solubility of CTAB at elevated temperatures in concentrated denaturant. The refolding yields obtained for the new method were significantly higher than for control experiments lacking additives and were comparable to the yields obtained with the classical two-step approach. A study of the effect of beta-CD and CTAB concentrations on refolding yield suggested two operational regimes: slow stripping ( beta-CDXTABsimilar to1), most suited for higher protein concentrations, and fast stripping (beta-CD/CTABsimilar to2.7), best suited for lower protein concentrations. An increased chaotrope concentration resulted in higher refolding yields and an enlarged operational regime.

ANNA: A new prediction method for bioassessment programs

1. Cluster analysis of reference sites with similar biota is the initial step in creating River Invertebrate Prediction and Classification System (RIVPACS) and similar river bioassessment models such as Australian River Assessment System (AUSRIVAS). This paper describes and tests an alternative prediction method, Assessment by Nearest Neighbour Analysis (ANNA), based on the same philosophy as RIVPACS and AUSRIVAS but without the grouping step that some people view as artificial. 2. The steps in creating ANNA models are: (i) weighting the predictor variables using a multivariate approach analogous to principal axis correlations, (ii) calculating the weighted Euclidian distance from a test site to the reference sites based on the environmental predictors, (iii) predicting the faunal composition based on the nearest reference sites and (iv) calculating an observed/expected (O/E) analogous to RIVPACS/AUSRIVAS. 3. The paper compares AUSRIVAS and ANNA models on 17 datasets representing a variety of habitats and seasons. First, it examines each model's regressions for Observed versus Expected number of taxa, including the r(2), intercept and slope. Second, the two models' assessments of 79 test sites in New Zealand are compared. Third, the models are compared on test and presumed reference sites along a known trace metal gradient. Fourth, ANNA models are evaluated for western Australia, a geographically distinct region of Australia. The comparisons demonstrate that ANNA and AUSRIVAS are generally equivalent in performance, although ANNA turns out to be potentially more robust for the O versus E regressions and is potentially more accurate on the trace metal gradient sites. 4. The ANNA method is recommended for use in bioassessment of rivers, at least for corroborating the results of the well established AUSRIVAS- and RIVPACS-type models, if not to replace them.

Numerical modelling of chemical effects of magma solidification problems in porous rocks

The solidification of intruded magma in porous rocks can result in the following two consequences: (1) the heat release due to the solidification of the interface between the rock and intruded magma and (2) the mass release of the volatile fluids in the region where the intruded magma is solidified into the rock. Traditionally, the intruded magma solidification problem is treated as a moving interface (i.e. the solidification interface between the rock and intruded magma) problem to consider these consequences in conventional numerical methods. This paper presents an alternative new approach to simulate thermal and chemical consequences/effects of magma intrusion in geological systems, which are composed of porous rocks. In the proposed new approach and algorithm, the original magma solidification problem with a moving boundary between the rock and intruded magma is transformed into a new problem without the moving boundary but with the proposed mass source and physically equivalent heat source. The major advantage in using the proposed equivalent algorithm is that a fixed mesh of finite elements with a variable integration time-step can be employed to simulate the consequences and effects of the intruded magma solidification using the conventional finite element method. The correctness and usefulness of the proposed equivalent algorithm have been demonstrated by a benchmark magma solidification problem. Copyright (c) 2005 John Wiley & Sons, Ltd.

The design of planar gradient coils. Part I: A winding path correction method

In this work a new approach for designing planar gradient coils is outlined for the use in an existing MRI apparatus. A technique that allows for gradient field corrections inside the diameter-sensitive volume is deliberated. These corrections are brought about by making changes to the wire paths that constitute the coil windings, and hence, is called the path correction method. The existing well-known target held method is used to gauge the performance of a typical gradient coil. The gradient coil design methodology is demonstrated for planar openable gradient coils that can be inserted into an existing MRI apparatus. The path corrected gradient coil is compared to the coil obtained using the target field method. It is shown that using a wire path correction with optimized variables, winding patterns that can deliver high magnetic gradient field strengths and large imaging regions can be obtained.

Improved method for counting virus and virus like particles

An improved method for counting virus and virus like particles by electron microscopy (EM) was developed. The procedure involves the determination of the absolute concentration of pure or semi-pure particles once deposited evenly on EM grids using either centrifugation or antibody capture techniques. The counting of particles was done with a Microfiche unit which enlarged approximately 50 x the image of particles on a developed negative film which had been taken at a relatively low magnification (2500 x) by EM. Initially, latex particles of a known concentration were counted using this approach, to prove the accuracy of the technique. The latex particles were deposited evenly on an EM grid using centrifugation (Modified Beckmen EM-90 Airfuge technique). Subsequently, recombinant Bluetongue virus (BTV) core-like particles (CLPs) captured by a Monoclonal antibody using a hovel sample loading method were counted by the Microfiche unit method and by a direct EM method. Comparison of the simplified counting method developed with a conventional method, showed good agreement. The method is simple, accurate, rapid, and reproducible when used with either pure particles or with particles from crude cell culture extracts.

Improved comparison plot method for pore structure characterization of MCM-41

MCM-41 samples of various pore dimensions are synthesized. Plotting of nitrogen adsorption data at 77 K versus the statistical film thickness (comparison plot) reveals three distinct stages, with a characteristic of two points of inflection. The steep intermediate stage caused by capillary condensation occurred in the highly uniform mesopores. From the slopes of the sections before and after the condensation, the surface area of the mesopores is calculated. The linear portion of the last section is extrapolated to the adsorption axis of the comparison plot, and this intercept is used to obtain the volume of the mesopores. From the surface area and pore volume, average mesopore diameter is calculated, and the value thus obtained is in good agreement with the pore dimension obtained from powder X-ray diffraction measurements. The principle of the calculation as well as problems associated are discussed in detail.

Turbulent spots in boundary layers in a free-piston shock-tunnel flow

In this paper, experiments to detect turbulent spots in the transitional boundary layers, formed on a flat plate in a free-piston shock tunnel how, are reported. Experiments indicate that thin-film heat-transfer gauges are suitable for identifying turbulent-spot activity and can be used to identify parameters such as the convection rate of spots and the intermittency of turbulence.

Pore structure characterisation of pillared clays using a modified MP method

The data of nitrogen adsorption on pillared clays (PILC) are converted to comparison plots (t-plots) to derive their pore size distribution (PSD). As in the MP method, the surface area of a group of pores having similar pore sizes is calculated from the slopes of tangent lines at two succeeding points on a comparison plot. By the modified MP method in this work, the tangent line is extrapolated to the adsorption axis on the t-plot, and the difference between intercepts is used to obtain the volume of the group of pores. From the information of surface area and pore volume, the average width of the pore group can be calculated and hence the PSDs of PILCs are obtained by carrying out such calculation procedures from high to low t. With this method, PSDs of several pillared clays are calculated over a wide pore size range, from micropores to mesopores. It is found that the modified MP method could result in the underestimation of the width of ultramicropores due to the enhancement in adsorption energy in these pores. Nevertheless, the method can be very useful in calculating the surface area and pore volume, as well as a mean width of these pores. For super-micropores and mesopores, pore size can also be underestimated, due to deviation of the pore shape from a slit. The principles of the improved MP method, as well as problems associated with it are thoroughly discussed in this paper. In general, this modified method provides practically meaningful results which are consistent with the pore dimension obtained from powder X-ray diffraction measurements, but involves no complicated theoretical treatment or assumptions.

A method for drug infusion into the lateral median eminence and arcuate nucleus of sheep

The role of catecholamines in the control of the GnRH pulse generator is unclear as studies have relied on the use of peripheral or intracerebroventricular injections, which lack specificity in relation to the anatomical site of action. Direct brain site infusions have been used, however, these are limited by the ability to accurately target small brain regions. One such area of interest in the control of GnRH is the median eminence and arcuate nucleus within the medial basal hypothalamus. Here we describe a method of stereotaxically targeting this area in a large animal (sheep) and an infusion system to deliver drugs into unrestrained conscious animals. To test our technique we infused the dopamine agonist, quinpirole or vehicle into the medial basal hypothalamus of ovariectomised ewes. Quinpirole significantly suppressed LH pulsatility only in animals with injectors located close to the lateral median eminence. This in vivo result supports the hypothesis that dopamine inhibits GnRH secretion by presynaptic inhibition in the lateral median eminence. Also infusion of quinpirole into the medial basal hypothalamus suppressed prolactin secretion providing in vivo evidence that is consistent with the hypothesis that there are stimulatory autoreceptors on tubero-infundibular dopamine neurons. (C) 1997 Elsevier Science B.V.