Continuous precipitation of calcium sulfate dihydrate from waste sulfuric acid and lime

Precipitation of calcium sulfate dihydrate, gypsum, from (i) a pure sulfuric acid/lime suspension and (ii) a waste sulfuric acid/lime suspension in a continuous pilot plant in the temperature range from 40 °C to 80 °C was studied. It was observed that in the case of waste sulfuric acid with a high content of Mg²⁺ and Fe²⁺ ions, several hours after the beginning of the precipitation, partial dissolution of the product and modification of the crystals from needle‐ and plate‐like to agglomerated structures occurred. It is suggested that the secondary changes occur due to the increased concentration of Mg²⁺ and Fe²⁺ ions in the reactor. Below 60 °C, and above 70 °C plate‐like and needle‐like single crystals respectively were formed. The mean size (d₅₀) of the crystals was found to increase with increasing temperature and decrease with the initial concentration of lime. Gypsum produced between 70 °C and 80 °C is suitable for further processing for construction plaster. In a precipitation process with pure sulfuric acid only single perfect needle‐like crystals occurred. Copyright © 2005 Society of Chemical Industry     

Fast Recognition of Fibonacci Cubes

Fibonacci cubes are induced subgraphs of hypercubes based on Fibonacci strings. They were introduced to represent interconnection networks as an alternative to the hypercube networks. We derive a characterization of Fibonacci cubes founded on the concept of resonance graphs. The characterization is the basis for an algorithm which recognizes these graphs in O(mlog n) time. A. Vesel supported by the Ministry of Science of Slovenia under the grant 0101-P-297.     

Thermodynamic analysis of the refining of technical boron nitride

The efficiency of the process of refining technical boron nitride was assessed based on calculations of the chemical equilibrium in the B-N-O-C-Cl-H system. Three refining mixtures, CCl₄ + H₂, CCl₄ + NH₃ and CHCl₃ + NH₃, were considered. The analysis indicates that the use of ammonia-containing mixtures is more convenient, a lower residual oxygen content, lower contamination of the product by carbon and a better overall boron balance emerging. The calculations of the equilibrium composition of the solid phase enabled suitable technological conditions of the refining process (temperature and starting composition of the gaseous phase) to be established. The calculated results are compared with experimental data, and some observed differences are discussed.     

A variable gap penalty function and feature weights for protein 3-D structure comparisons

We have developed a variable gap penalty function for use inthe comparison program COMPARER which aligns protein sequenceson the basis of their 3-D structures. For deletions and insertions,components are a function of structural features of individualamino acid residues (e.g. secondary structure and accessibility).We have also obtained relative weights for different featuresused in the comparison by examining the equivalent residuesin weight matrices and in alignments for pairs of 3-D structureswhere the equivalences are relatively unambiguous. We have usedthe new parameters and the varible gap penalty function in COMPARERto align protein structures in the Brookhaven Data Bank. Thevariable gap penalty function is useful especially in avoidinggaps in secondary structure elements and the new feature weightsgive improved alignments. The alignments for both azurins andplastocyanins and N- and C-terminal lobes for aspartic proteinasesare discussed     

Using Discriminative Dimensionality Reduction to Visualize Classifiers

Neural Processing Letters - Albeit automated classifiers offer a standard tool in many application areas, there exists hardly a generic possibility to directly inspect their behavior, which goes...     

Workflows for Heliophysics

In this paper we describe how we have introduced workflows into the working practices of a community for whom the concept of workflows is very new, namely the heliophysics community. Heliophysics is a branch of astrophysics which studies the Sun and the interactions between the Sun and the planets, by tracking solar events as they travel throughout the Solar system. Heliophysics produces two major challenges for workflow technology. Firstly it is a systems science where research is currently developed by many different communities who need reliable data models and metadata to be able to work together. Thus it has major challenges in the semantics of workflows. Secondly, the problem of time is critical in heliophysics; the workflows must take account of the propagation of events outwards from the sun. They have to address the four dimensional nature of space and time in terms of the indexing of data. We discuss how we have built an environment for Heliophysics workflows building on and extending the Taverna workflow system and utilising the myExperiment site for sharing workflows. We also describe how we have integrated the workflows into the existing practices of the communities involved in Heliophysics by developing a web portal which can hide the technical details from the users, who can concentrate on the data from their scientific point of view rather than on the methods used to integrate and process the data. This work has been developed in the EU Framework 7 project HELIO, and is being disseminated to the worldwide Heliophysics community, since Heliophysics requires integration of effort on a global scale.     

Effect of the Mn/Fe Ratio on the Microstructure and Magnetic Properties in the Powder Form (Fe<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>2</Subscript>P System

The structure, morphology, and magnetic properties of the mechanically alloyed iron manganese phosphides (Fe_1?x Mn _x )₂P with 0.15 ≤ x ≤ 0.75 (Mn/Fe ratio = 0.17, 0.33, 0.66, and 3) have been studied by means of X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectrometry, and BS1 and BS2 magnetometry. The powder form (Fe_1?x Mn _x )₂P compounds exhibit multiphase structures that contain Fe(Mn)-type solid solution and Fe₂P-type, Mn₂P-type, Fe₃P-type, and MnP/FeP-type phosphides. The magnetization versus temperature reveals the existence of multiple magnetic phase transitions. The saturation magnetization, coercivity, and squarness M _r/M _s ratio values are discussed as a function of both the Mn content and the temperature. From the approach to saturation magnetization studies, several fundamental magnetic parameters were extracted. The local magnetic anisotropy constant K ₁ was determined.