Electro-gravimetric recovery of silver from aqueous solutions and its precursors

A simple electrolytic cell was used for electrochemical recovery of silver from aqueous solutions containing 100 mg/L Ag(I). Two different sets of electrodes were applied to find the enhanced recovery of silver. Rocks and ores samples were processed through fire assay method and acid digestion. A set of electrodes comprised of stainless steel anode and aluminum cathode gave maximum recovery (96.5%) of silver. This simple, robust, environment friendly and highly sensitive method was effectively applied to various ores and rock samples. The developed method with slight modifications can also be applied for the recovery of other metals. KEY WORDS: Boulangerite ore, Deposition, Electrolytic cell, Electrodes, Recovery, Silver Bull. Chem. Soc. Ethiop. 2016, 30(2), 165-174DOI: http://dx.doi.org/10.4314/bcse.v30i2.

Interplay of the exciton and electron-hole plasma recombination on the photoluminescence dynamics in bulk GaAs

We present a systematic study of the exciton/electron-hole plasma photoluminescence dynamics in bulk GaAs for various lattice temperatures and excitation densities. The competition between the exciton and electron-hole pair recombination dominates the onset of the luminescence. We show that the metal-to-insulator transition, induced by temperature and/or excitation density, can be directly monitored by the carrier dynamics and the time-resolved spectral characteristics of the light emission. The dependence on carrier density of the photoluminescence rise time is strongly modified around a lattice temperature of 49 K, corresponding to the exciton binding energy (4.2 meV). In a similar way, the rise-time dependence on lattice temperature undergoes a relatively abrupt change at an excitation density of 120-180x10^15 cm^-3, which is about five times greater than the calculated Mott density in GaAs taking into account many body corrections.Comment: 15 pages, 7 figures, submitted to Phys. Rev.

Optimizing photon indistinguishability in the emission from incoherently-excited semiconductor quantum dots

Most optical quantum devices require deterministic single-photon emitters. Schemes so far demonstrated in the solid state imply an energy relaxation which tends to spoil the coherent nature of the time evolution, and with it the photon indistinguishability. We focus our theoretical investigation on semiconductor quantum dots embedded in microcavities. Simple and general relations are identified between the photon indistinguishability and the collection efficiency. The identification of the key parameters and of their interplay provides clear indications for the device optimization

Air Pollution Modelling to Predict Maximum Ground Level Concentration for Dust from a Palm Oil Mill Stack

The study is to model emission from a stack to estimate ground level concentration from a palm oil mill. The case study is a mill located in Kuala Langat, Selangor. Emission source is from boilers stacks. The exercise determines the estimate the ground level concentrations for dust to the surrounding areas through the utilization of modelling software. The surround area is relatively flat, an industrial area surrounded by factories and with palm oil plantations in the outskirts. The model utilized in the study was to gauge the worst-case scenario. Ambient air concentrations were garnered calculate the increase to localized conditions.Keywords: emission, modelling, palm oil mill, particulate, POM

LearnSDN: optimizing routing over multimedia-based 5G-SDN using machine learning

With the advent of 5G networks and beyond, there is an increasing demand to leverage Machine Learning (ML) capabilities and develop new and innovative solutions that could achieve efficient use of network resources and improve users' Quality of Experience (QoE). One of the key enabling technologies for 5G networks is Software Defined Networking (SDN) as it enables fine-grained monitoring and control of the network. Given the variety of dynamic networking conditions within 5G-SDN environments and the diversity of routing algorithms, an intelligent control of these strategies should exist to maximize the Quality of Service (QoS) provisioning of multimedia traffic with more stringent requirements without penalizing the performance of the background traffic. This paper proposes LearnSDN, an innovative ML-based solution that enables QoS provisioning over multimedia-based 5G-SDN environments. LearnSDN uses ML to learn the most convenient routing algorithm to be employed on the background traffic based on the dynamic network conditions in order to cater for the QoS requirements of the multimedia traffic. The performance of the proposed LearnSDN solution is evaluated under a realistic emulation-based SDN environment. The results indicate that LearnSDN outperforms other state-of-the-art solutions in terms of QoS provisioning, PSNR and MOS

Fritz John Type Duality in Nondifferentiable Continuous Programming with Equality and Inequality Constraints

A Fritz John type dual for a nondifferentiable continuous programming problem with equality and inequality constraints which represent many realistic situations is formulated using Fritz John type optimality conditions instead of Karush-Kuhn-Tucker type conditions and thus does not require a regularity condition. Various duality results under suitable generalized convexity assumptions are derived. A pair of Fritz John type dual continuous programming with natural boundary conditions rather than fixed end points is also presented. Finally, it is pointed that our duality results can be considered as dynamic generalizations of those of a nondifferentiable nonlinear programming problem in the presence of equality and inequality constraints recently treated in the literature

Coupling Transcriptional State to Large-Scale Repeat Expansions in Yeast

SummaryExpansions of simple DNA repeats cause numerous hereditary disorders in humans. Replication, repair, and transcription are implicated in the expansion process, but their relative contributions are yet to be distinguished. To separate the roles of replication and transcription in the expansion of Friedreich’s ataxia (GAA)n repeats, we designed two yeast genetic systems that utilize a galactose-inducible GAL1 promoter but contain these repeats in either the transcribed or nontranscribed region of a selectable cassette. We found that large-scale repeat expansions can occur in the lack of transcription. Induction of transcription strongly elevated the rate of expansions in both systems, indicating that active transcriptional state rather than transcription through the repeat per se affects this process. Furthermore, replication defects increased the rate of repeat expansions irrespective of transcriptional state. We present a model in which transcriptional state, linked to the nucleosomal density of a region, acts as a modulator of large-scale repeat expansions

Analysis of procainamide-derivatised heparan sulphate disaccharides in biological samples using hydrophilic interaction liquid chromatography mass spectrometry

Glycosaminoglycans (GAGs) are a family of linear heteropolysaccharides made up of repeating disaccharide units that are found on the surface and extracellular matrix of animal cells. They are known to play a critical role in a wide range of cellular processes including proliferation, differentiation and invasion. To elucidate the mechanism of action of these molecules, it is essential to quantify their disaccharide composition. Analytical methods that have been reported involve either chemical or enzymatic depolymerisation of GAGs followed by separation of non-derivatised (native) or derivatised disaccharide subunits and detection by either UV/fluorescence or MS. However, the measurement of these disaccharides is challenging due to their hydrophilic and labile nature. Here we report a pre-column LC-MS method for the quantification of GAG disaccharide subunits. Heparan sulphate (HS) was extracted from cell lines using a combination of molecular weight cutoff and anion exchange spin filters and digested using a mixture of heparinases I, II and III. The resulting subunits were derivatised with procainamide, separated using hydrophilic interaction liquid chromatography and detected using electrospray ionisation operated in positive ion mode. Eight HS disaccharides were separated and detected together with an internal standard. The limit of detection was found to be in the range 0.6–4.9 ng/mL. Analysis of HS extracted from all cell lines tested in this study revealed a significant variation in their composition with the most abundant disaccharide being the non-sulphated ∆UA–GlcNAc. Some structural functional relationships are discussed demonstrating the viability of the pre-column method for studying GAG biolog

Can quantification of Serum Glycans predict Pre-Eclampsia?

Objectives: To determine if concentrations of placental glycans and glycan components are altered in pre-eclamspia and to determine if serum levels can predict pre-eclampsia. Methods: Serum samples were collected from women in the third trimester of singleton pregnancy but before the onset of pre-eclampsia and also from women during unaffected pregnancies at the samegestational age. Tissues were collected from the basal plate of placentas collected at delivery following uncomplicated singleton pregnancy (term and preterm) and from pregnancies complicated by preeclampsia. Pre-eclampsia was diagnosed according to International Society for the Study of Hypertension in Pregnancy criteria. Glycan components were isolated using a combination of enzyme digestion, molecular weight filtration and ion exchange chromatography, and then derivatised prior to separation using hydrophilic interaction liquid chromatography. Components were detected using electrospray ionisation operated in positive ion mode with single ion monitoring. Results: Specific glycan components (designated glycan 1, 2 and 3) were significantly altered in the serum from women who went on to have preeclampsia compared to those who had an unaffected pregnancy. Interestingly, levels of the same biomarkers were also elevated in nulliparous versus multiparous pregnancy. Biomarkers were also significantly altered in placental tissues from pregnancies complicated by preeclampsia Conclusion: This study suggests that altered glycan levels may contribute to impaired placental development and that the glycome is a potential diagnostic target for pre-eclampsia, and possibly other disorders of pregnancy