Mushy-Zone Rayleigh Number to Describe Macrosegregation and Channel Segregate Formation During Directional Solidification of Metallic Alloys

A recently defined mushy-zone Rayleigh number (R-aM) that includes side-branching contributions to the mushy-zone permeability has been examined for its correlation with the longitudinal macrosegregation and channel segregate formation. The Rayleigh number shows (1) a strong correlation between the extent of longitudinal macrosegregation and increase in the mushy-zone convection and (2) a good ability to predict the formation of channel segregates during directional solidification

Prototype Positive Control Wells for Malaria Rapid Diagnostic Tests: Prospective Evaluation of Implementation Among Health Workers in Lao People's Democratic Republic and Uganda.

Rapid diagnostic tests (RDTs) are widely used for malaria diagnosis, but lack of quality control at point of care restricts trust in test results. Prototype positive control wells (PCW) containing recombinant malaria antigens have been developed to identify poor-quality RDT lots. This study assessed community and facility health workers' (HW) ability to use PCWs to detect degraded RDTs, the impact of PCW availability on RDT use and prescribing, and preferred strategies for implementation in Lao People's Democratic Republic (Laos) and Uganda. A total of 557 HWs participated in Laos (267) and Uganda (290). After training, most (88% to ≥ 99%) participants correctly performed the six key individual PCW steps; performance was generally maintained during the 6-month study period. Nearly all (97%) reported a correct action based on PCW use at routine work sites. In Uganda, where data for 127,775 individual patients were available, PCW introduction in health facilities was followed by a decrease in antimalarial prescribing for RDT-negative patients ≥ 5 years of age (4.7-1.9%); among community-based HWs, the decrease was 12.2% (P < 0.05) for all patients. Qualitative data revealed PCWs as a way to confirm RDT quality and restore confidence in RDT results. HWs in malaria-endemic areas are able to use prototype PCWs for quality control of malaria RDTs. PCW availability can improve HWs' confidence in RDT results, and benefit malaria diagnostic programs. Lessons learned from this study may be valuable for introduction of other point-of-care diagnostic and quality-control tools. Future work should evaluate longer term impacts of PCWs on patient management

Alternative low-cost adsorbent for water and wastewater decontamination derived from eggshellwaste: an overview

As the current global trend towards more stringent environmental standards, technical applicability and cost-effectiveness became key factors in the selection of adsorbents for water and wastewater treatment. Recently, various low-cost adsorbents derived from agricultural waste, industrial by-products or natural materials, have been intensively investigated. In this respect, the eggshells from egg-breaking operations constitute significant waste disposal problems for the food industry, so the development of value-added by-products from this waste is to be welcomed. The egg processing industry is very competitive, with low profit margins due to global competition and cheap imports. Additionally, the costs associated with the egg shell disposal (mainly on landfill sites) are significant, and expected to continue increasing as landfill taxes increase. The aim of the present review is to provide an overview on the development of low-cost adsorbents derived from eggshell by-products

Removal of chromate by solvent impregnated resins (SIRs) stabilized by coating and chemical crosslinking. I. Batch-mode sorption studies

WOS: 000221113100002Solvent impregnated resins (SIRs) that are stabilized by coating with vinyl sulphone crosslinked poly(vinyl alcohol) have been employed for the removal of chromate ions from an aqueous solution at pH 4.0. Batch sorption studies have shown that both uncoated and coated SIRs containing Aliquat 336 are effective for the removal of chromate ions from aqueous solution when an optimum concentration of SIRs is used in the solution. A series of batch-mode sorption-elution studies was performed to compare uncoated and coated-crosslinked SIRs in cyclic operation. Elution of chromate from SIRs was quantitatively achieved with a mixed 1 M NaOH-1 M NaCl solution. The sorption performance of coated SIRs remained almost constant after seven sorption-washing-elution-washing cycles whilst a decrease in sorption performance of uncoated SIRs was observed. However, the kinetic performance of uncoated SIRs was more favourable for chromate removal. However, it was possible to attain rapid kinetics by decreasing the degree of crosslinking of the resin coating. In addition, pre-conditioning of coated resins using a mixed I M NaOH-NaCl solution prior to sorption considerably enhanced the kinetic performance of coated SIRs. (C) 2004 Elsevier B.V. All rights reserved

Stabilization of solvent impregnated resins (SIRs) by coating with water soluble polymers and chemical crosslinking

WOS: 000221113100001Solvent impregnated resins (SIRs) have been stabilized by the formation of a surface coating consisting of crosslinked poly(vinyl alcohol). Amberlite XAD-4 and vinyl sulphone respectively proved to be the most effective matrix and crosslinking agent for the protective layer in the preparation of SIRs containing Aliquat 336 reagent. The derived materials have been characterized in terms of Aliquat 336 content, amount of poly(vinyl alcohol), sulphur elemental content in the protective layer as well as operational stability. It has been found that the Aliquat 336 loading of impregnated XAD-4 is 0.82 mmol of extractant/g: this falls to 0.55 mmol of extractant/g after coating with a layer of vinyl sulphone crosslinked poly(vinyl alcohol). (C) 2004 Elsevier B.V. All rights reserved

Removal of Cr(VI) by solvent impregnated resins (SIR) containing aliquat 336

WOS: 000180657300011Solvent impregnated resins (SIR) have been prepared by a wet-impregnation technique using two different polymer matrices, Diaion HP-20 and HP-2MG. Diaion HP-20 possesses a hydrophobic styrene-divinylbenzene polymeric structure whereas HP-2MG is a hydrophilic methacrylic based polymer. Aliquat 336 was employed as the extractant and acetone as the solvent for impregnation. Batch sorption studies have shown that solvent impregnated resins containing Aliquat 336 can be effectively used for the removal of hexavalent chromium from aqueous solutions. The Langmuir adsorption isotherm gave a satisfactory fit of the equilibrium data. A kinetic study has been performed for SIR at two different concentrations of Cr(VI) (2 X 10(-4) and 4 X 10(-4) M). A finite-bath diffusion-control model with changing bulk concentration was used for sorption of Cr(VI) by SIR. Increasing the impregnation ratio from 0.5 to 1.0 (g Aliquat 336/g polymer adsorbent) increased the breakthrough capacity in a column-mode sorption study. The Cr(VI) bound by the SIR has been quantitatively desorbed using 0.1 M NaOH-0.1 M NaCl mixture. (C) 2002 Elsevier Science B.V. All rights reserved