Controlling the charge transfer flow at the graphene/pyrene-nitrilotriacetic acid interface

The fabrication of highly efficient bio-organic nanoelectronic devices is still a challenge due to the difficulty in interfacing the biomolecular component to the organic counterparts. One of the ways to overcome this bottleneck is to add a self-assembled monolayer (SAM) in between the electrode and the biological material. The addition of a pyrene-nitrilotriacetic acid layer to a graphene metal electrode enhances the charge transfer within the device. Our theoretical calculations and electrochemical results show that the formation of a pyrene-nitrilotriacetic acid SAM enforces a direct electron transfer from graphene to the SAM, while the addition of the Ni2+ cation and imidazole reverses the charge transfer direction, allowing an atomic control of the electron flow, which is essential for a true working device. © 2018 The Royal Society of Chemistry

Bioavailability of metals species in water ecosystem

Koncentrace volných kovových iontů je často jen malou částí celkové koncentrace kovu v prostředí. Přes tento malý obsah, je ve většině případů koncentrace volných kovových iontů klíčovým faktorem při určování biodostupnosti a toxicity pro organizmus. Membránová technika Donnan se používá k měření koncentrace volných kovových iontů a v této diplomové práci je ověřena pro směsi kovů (Pb + Cu) při absenci a přítomnosti malých organických ligandů. Olovo a měď jsou environmentálně důležité kovy díky své toxicitě a rozdílným vazebným vlastnostem ve vztahu ke studovaným ligandům.The free metal ion concentration is often only a small fraction of the total metal concentration in the environment. Despite their small amount, in most of the circumstances the free metal ion concentration is the key factor in determining metal bioavailability and toxicity for the organisms. The Donnan membrane technique is able to measure the free metal ion concentration and in this thesis, it is validated for metal mixtures (Pb + Cu) in absence and presence of small organic ligand mixtures. Lead and copper are environmental relevant metals due to their toxic properties and different binding properties relative to the studied ligands.

Microbial demethylation of dimethylsulfoniopropionate and methylthiopropionate

As discussed in chapter 1 , there is an increased interest in the production of certain natural sulfur-containing flavor compounds or flavor precursors. Production of natural flavors is becoming increasingly important, because consumerts end to prefer natural compounds for health reasons. With the aid of extraction techniques it is possible to obtain flavors directly from plant material, but these methods are time consuming and expensive, because the most interesting flavors are present in only very low concentrations. A more recent method to produce flavors is based on a biotechnological approach where natural precursors, isolated mainly from plant material, can be convertedt o the desired flavor in a bioreactor with the aid of enzymes and/or microorganisms.

Hypochlorite Oxidation of Nitrilotriacetic Acid

The chemical degradation of nitrilotriacetic acid (NTA) by sodium hypochlorite is examined. Preliminary work indicates that NTA undergoes decarboxylation. In the second phase of this investigation (S92), the work was mainly concerned with the products from the reaction of NTA with hypochlorite. The product of decarboxylation has been found to be iminodiacetic acid. The decrease in concentration of hypochlorite per unit time was studied over a pH range of 7-14 and in the presence of lead, calcium, zinc, and copper ions

An evaluation of metal removal during wastewater treatment: The potential to achieve more stringent final effluent standards

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2011 Taylor & Francis.Metals are of particular importance in relation to water quality, and concern regarding the impact of these contaminants on biodiversity is being encapsulated within the latest water-related legislation such as the Water Framework Directive in Europe and criteria revisions to the Clean Water Act in the United States. This review undertakes an evaluation of the potential of 2-stage wastewater treatment consisting of primary sedimentation and biological treatment in the form of activated sludge processes, to meet more stringent discharge consents that are likely to be introduced as a consequence. The legislation, sources of metals, and mechanisms responsible for their removal are discussed, to elucidate possible pathways by which the performance of conventional processes may be optimized or enhanced. Improvements in effluent quality, achievable by reducing concentrations of suspended solids or biochemical oxygen demand, may also reduce metal concentrations although meeting possible requirements for the removal of copper my be challenging

Preparation of zinc-oxide and zinc-sulfide powders by controlled precipitation from aqueous-solution

Resumo não disponível..

Speciation and fate of copper in sewage treatment works with and without tertiary treatment: The effect of return flows

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2013 Taylor & Francis.The removal of metals from wastewaters is becoming an important issue, with new environmental quality standards putting increased regulatory pressure on operators of sewage treatment works. The use of additional processes (tertiary treatment) following two-stage biological treatment is frequently seen as a way of improving effluent quality for nutrients and suspended solids, and this study investigates the impact of how back washes from these tertiary processes may impact the removal of copper during primary sedimentation. Seven sites were studied, three conventional two-stage biological treatment, and four with tertiary processes. It was apparent that fluxes of copper in traditional return flows made a significant contribution to the load to the primary treatment tanks, and that<1% of this was in the dissolved phase. Where tertiary processes were used, back wash liquors were also returned to the primary tanks. These return flows had an impact on copper removal in the primary tanks, probably due to their aerobic nature. Returning such aerobic back wash flows to the main process stream after primary treatment may therefore be worth consideration. The opportunity to treat consolidated liquor and sludge flows in side-stream processes to remove toxic elements, as they are relatively concentrated, low volume flow streams, should also be evaluated

The DNA Binding Properties of the Parsley bZIP Transcription Factor CPRF4a Are Regulated by Light

The common plant regulatory factors (CPRFs) from parsley are transcription factors with a basic leucine zipper motif that bind to cis-regulatory elements frequently found in promoters of light-regulated genes. Recent studies have revealed that certain CPRF proteins are regulated in response to light by changes in their expression level and in their intracellular localization. Here, we describe an additional mechanism contributing to the light-dependent regulation of CPRF proteins. We show that the DNA binding activity of the factor CPRF4a is modulated in a phosphorylation-dependent manner and that cytosolic components are involved in the regulation of this process. Moreover, we have identified a cytosolic kinase responsible for CPRF4a phosphorylation. Modification of recombinant CPRF4a by this kinase, however, is insufficient to cause a full activation of the factor, suggesting that additional modifications are required. Furthermore, we demonstrate that the DNA binding activity of the factor is modified upon light treatment. The results of additional irradiation experiments suggest that this photoresponse is controlled by different photoreceptor systems. We discuss the possible role of CPRF4a in light signal transduction as well as the emerging regulatory network controlling CPRF activities in parsley