Electrochemical behavior of tantalum in potassium hydroxide solutions

The electrochemical behavior of tantalum in various concentrations of KOH solutions (0.1 M - 10 M), was investigated using the evolution of the open circuit potential in time, cyclic voltammetry and ellipsometric measurements. Depending on KOH concentrations, the open circuit potential measurements have shown three distinct behaviors concerning oxide film formation on the electrode surface and its dissolution. The cyclic voltammetry measurements were performed in various potential ranges, from -1.4 to 8 V, different concentrations of KOH solutions (0.1-10 M) and sweep rates ranging from 0.005 V/s to 1 V/s. In the passive region, very stable passive films were formed, which reduction has not been possible during cathodic polarization even at highly concentrated KOH solutions. In the trans-passive region, the very strong peak at 1.65 V was monitored, which nature and chemical composition is still not well known

Advanced Electrochemical Technologies in Wastewater Treatment Part I: Electrocoagulation

This paper aims to provide an overview of electrochemical technologies in wastewater treatment. Part I focuses on the basic theory development and application of electro-coagulation. Electrocoagulation is advanced and innovative method which involves direct interaction between the ions of sacrificial metal anode and the pollutants in the water. The dissolved metal ions from sacrificial anode release in wastewater, coagulate with pollutant in wastewater in a manner similar to the traditionally one where chemicals are added for coagulation. The traditionally used chemicals, alum and ferric salts, liberate both, cations and anions. In electrocoagulation there is no supplemental addition of anions and therefore, no increase in salinity of the treated water. The quantity of sludge produced is smaller than that produced during chemical treatment. In the first part of the paper is given the importance for saving the fresh water and cleaning of wastewater using traditionally methods as: physical/mechanical methods, chemical methods and biological methods. In the second part the structure of colloids and traditional coagulation widely using in nowadays is presented. In the third part, an overview of detailed electrocoagulation theory, supported by literature survey for application in wastewater treatment plants, is given 

Advanced Electrochemical Technologies in Wastewater Treatment. Part II: Electro-Flocculation and Electro-Flotation

This paper aims to provide an overview of electrochemical technologies in wastewater treatment. First part was focuses on the development, basic theory and application of electro-coagulation whereas the second part is consecrated to the development, and application of electro-flocculation and electro-flotation. The basic designs of electrochemical units are also presented. An appropriately constructed single unit can be used to successively coagulate, flocculate and float the pollutants. The coagulated and flocculated pollutants could be removed easily by sedimentation/filtration or by capturing them with the bubbles generated on the electrodes and then floating them to the water surface. In wastewater treatment plants these three processes must be operated synergistically to effectively remove the pollutants

Electrochemical Passivation of Niobium in KOH Solutions

Electrochemical formation and dissolution of passive films on niobium surfaces were studied in various concentrations of KOH solutions using the open-circuit potential and potentiodynamic techniques. Potentiodynamic I/E profiles indicated that the electrolyte concentration strongly affects the active/passive transition, as well as the values of the passivation potentials and critical currents. At higher KOH solution concentrations, after passivation of the electrode surface in the first positive cyclic voltammetry scan, reactivation processes were monitored in the reverse scan. Formation of passive films is a diffusion-controlled process only for higher sweep rates. Cathodic pretreatment of niobium electrode affects the chemical structure and oxide composition of passive films. Corrosion measurements have shown that at higher KOH concentrations the passive film is rapidly attacked and the corrosion resistance of Nb electrode is drastically diminished

Boosting cross-border regions through better cross-border transport services. The European case

Cross-border regions are the laboratories of European integration. Daily interactions across European borders let citizens experience the benefits of the European Union (EU) internal market. Still, many border barriers continue to prevent individuals and organisations from exploiting the full-potential of European border regions and the benefits of a more integrated European territory. Amongst these barriers are the absence or inappropriate supply of cross-border public transport services. In this context, this paper presents potential policy tools to increase border permeability related to cross-border public transport as well as practical results from a few case-studies implemented across Europe.info:eu-repo/semantics/publishedVersio

On the use of dexamethasone-loaded liposomes to induce the osteogenic differentiation of human mesenchymal stem cells

Article first published online: 7 Oct. 2013Stem cells have received considerable attention by the scientific community because of their potential for tissue engineering and regenerative medicine. The most frequently used method to promote their differentiation is supplementation of the in vitro culture medium with growth/differentiation factors (GDFs). The limitations of that strategy caused by the short half-life of GDFs limit its efficacy in vivo and consequently its clinical use. Thus, the development of new concepts that enable the bioactivity and bioavailability of GDFs to be protected, both in vitro and in vivo, is very relevant. Nanoparticle-based drug delivery systems can be injected, protect the GDFs and enable spatiotemporal release kinetics to be controlled. Liposomes are well-established nanodelivery devices presenting significant advantages, viz. a high load-carrying capacity, relative safety and easy production, and a versatile nature in terms of possible formulations and surface functionalization. The main objective of the present study was to optimize the formulation of liposomes to encapsulate dexamethasone (Dex). Our results showed that the optimized Dex-loaded liposomes do not have any cytotoxic effect on human bone marrow-derived mesenchymal stem cells (hBMSCs). More importantly, they were able to promote an earlier induction of differentiation of hBMSCs into the osteogenic lineage, as demonstrated by the expression of osteoblastic markers, both phenotypically and genotypically. We concluded that Dex-loaded liposomes represent a viable nanoparticle strategy with enhanced safety and efficacy for tissue engineering and regenerative medicine.The authors thank the Portuguese Foundation for Science and Technology for a PhD grant (No. SFRH/BD/62465/2009, to N. S. Monteiro). This work was partly supported by the FIND and BIND Project (No. NMP4-SL-2009-229292) and the OsteoGraphy Project (No. PTDC/EME-MFE/2008)

Electrospun fibers for vaginal administration of tenofovir disoproxil fumarate and emtricitabine in the context of topical pre-exposure prophylaxis

Women are particularly vulnerable to sexual HIV-1 transmission. Oral pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate and emtricitabine (TDF/FTC) is highly effective in avoiding new infections in men, but protection has only been shown to be moderate in women. Such differences have been associated, at least partially, to poor drug penetration of the lower female genital tract and the need for strict adherence to continuous daily oral intake of TDF/FTC. On-demand topical microbicide products could help circumvent these limitations. We developed electrospun fibers based on polycaprolactone (PCL fibers) or liposomes associated to poly(vinyl alcohol) (liposomes-in-PVA fibers) for the vaginal co-delivery of TDF and FTC, and assessed their pharmacokinetics in mice. PCL fibers and liposomes-in-PVA fibers were tested for morphological and physico chemical properties using scanning electron microscopy, differential scanning calorimetry and X-ray diffrac tometry. Fibers featured organoleptic and mechanical properties compatible with their suitable handling and vaginal administration. Fluorescent quenching of mucin in vitro – used as a proxy for mucoadhesion – was intense for PCL fibers, but mild for liposomes-in-PVA fibers. Both fibers were shown safe in vitro and able to rapidly release drug content (15–30 min) under sink conditions. Liposomes-in-PVA fibers allowed increasing genital drug concentrations after a single intravaginal administration when compared to continuous daily treatment for five days with 25-times higher oral doses. For instance, the levels of tenofovir and FTC in vaginal lavage were around 4- and 29-fold higher, respectively. PCL fibers were also superior to oral treatment, although to a minor extent (approximately 2-fold higher drug concentrations in lavage). Vaginal tissue drug levels were generally low for all treatments, while systemic drug exposure was negligible in the case of fibers. These data suggest that proposed fibers may provide an interesting alternative or an ancillary option to oral PrEP in women.This work was financed by Programa Gilead GÉNESE (refs. PGG/ 046/2015) and Portuguese funds through FCT - Fundação para a Ciência e a Tecnologia/Ministério da Ciência, Tecnologia e Ensino Superior in the framework of the project “Institute for Research and Innovation in Health Sciences” UID/BIM/04293/2019. The work was also financed by FCT in the framework of the Strategic Funding UID/FIS/04650/2019 and in the ambit of the project POCI-01-0145-FEDER-032651 and PTDC/NAN-MAT/326512017, co-financed by the FEDER, through COMPETE 2020, under PORTUGAL 2020, and FCT. Marlene Lúcio thanks FCT and ERDF for doctoral position Ref. CTTI-150/18-CF(1) in the ambit of the project CONCERT (POCI-01-0145-FEDER-032651 and PTDC/NAN-MAT/326512017)

Nanoparticle-based bioactive agent release systems for bone and cartilage tissue engineering

The inability to deliver bioactive agents locally in a transient but sustained manner is one of the challenges on the development of bio-functionalized scaffolds for tissue engineering (TE) and regenerative medicine. The mode of release is especially relevant when the bioactive agent is a growth factor (GF), because the dose and the spatiotemporal release of such agents at the site of injury are crucial to achieve a successful outcome. Strategies that combine scaffolds and drug delivery systems have the potential to provide more effective tissue regeneration relative to current therapies. Nanoparticles (NPs) can protect the bioactive agents, control its profile, decrease the occurrence and severity of side effects and deliver the bioactive agent to the target cells maximizing its effect. Scaffolds containing NPs loaded with bioactive agents can be used for their local delivery, enabling site-specific pharmacological effects such as the induction of cell proliferation and differentiation, and, consequently, neo-tissue formation. This review aims to describe the concept of combining NPs with scaffolds, and the current efforts aiming to develop highly multi-functional bioactive agent release systems, with the emphasis on their application in TE of connective tissues.POLARIS (REGPOT-CT2012-316331-POLARIS), RL3 – TECT – NORTE-01-0124-FEDER-000020, co-financed by North Portugal Regional Operational Programme (ON.2 – O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF), the OsteoGraphy (PTDC/EME-MFE/2008) and MaxBone (PTDC/SAU-ENB/115179/2009) project

Ellipsometric study of passive and anodic oxide films formed on Ti and Nb electrodes

Electrochemical formation of passive films and active/passive transition on Ti and Nb metal surfaces in various concentrations of H2SO4 and KOH solutions was investigated using potentiostatic and cyclic voltammetry methods. By simultaneous electrochemical and in-situ ellipsometric measurements the coefficients of film thickness growth of passive films in the potential region from -1.5 V to 4 V were determined. Results indicate the strong influence of the concentration and electrolyte nature to the active/passive transitions and stability of passive films. The influence of cathodic pre-treatment on the passive films dissolution and appearance of the reactivation peaks during the reverse potential cycling were shown. By multiple cycle sequences in which the final anodic potential was gradually enlarged, the barrier properties of passive films on investigated electrodes were confirmed. The electrochemical and ellipsometric data showed that the passive films formed on Nb electrode are more resistant that passive films formed on Ti electrode, especially in higher concentrations of investigated aggressive solutions