A computer-controlled multi-electrode switch

A computer-actuated switch was built to control, simultaneously, two automatic titration assemblies each consisting of an electrode pair and a burette, and using only one measuring device. This switch is modular, simple and versatile allowing easy adaptation and expansion; apart from its application in multiple-titration systems, this device can also be used for standard addition analysis and multi-component analysis using ion-selective electrodes (ISE). The repeatability as well as the accuracy of the measurements made with this switch were ensured using high-quality relays, and very high electrical insulation, attained through the use of two separate printed circuit boards (pcb) of good quality and careful design of these pcbs. This low-cost multi-electrode switch is controlled through the parallel port of a PC that collects the data via an inexpensive 12-bit ADC board (8-bit ISA type), and is easily programmable in any high-level language. This type of device allows the collection of a large amount of data in relatively short periods, which can be analysed later allowing the choice of the best compromise of time versus accuracy for the study of any particular system

A computer-controlled multi-electrode switch

A computer-actuated switch was built to control, simultaneously, two automatic titration assemblies each consisting of an electrode pair and a burette, and using only one measuring device. This switch is modular, simple and versatile allowing easy adaptation and expansion; apart from its application in multiple-titration systems, this device can also be used for standard addition analysis and multi-component analysis using ion-selective electrodes (ISE). The repeatability as well as the accuracy of the measurements made with this switch were ensured using high-quality relays, and very high electrical insulation, attained through the use of two separate printed circuit boards (pcb) of good quality and careful design of these pcbs. This low-cost multi-electrode switch is controlled through the parallel port of a PC that collects the data via an inexpensive 12-bit ADC board (8-bit ISA type), and is easily programmable in any high-level language. This type of device allows the collection of a large amount of data in relatively short periods, which can be analysed later allowing the choice of the best compromise of time versus accuracy for the study of any particular system

Influence of synthesis conditions on carbonate entrapment in perovskite SrSnO 3

Strontium stannate (SrSnO 3 ), a perovskite material, was synthesized by the polymeric precursor method, with different routes to eliminate organic matter. The utilization of pure oxygen for the elimination of organic matter changed the Raman spectra, especially in the low frequency region. Some peaks, which were previously assigned to the perovskite phase, were not noticed when the carbonate amount was lower. On the other hand, the profile of the IR spectra and XRD patterns did not change. These results suggest that carbonate may be present inside the perovskite lattice

“Healthy Life”: interaction of polyphenols with lipid bilayers and their effects in human cells

This work concerns the transversal project of the CQB thematic line: “Healthy Life: Molecular Interventions and Regulation Mechanisms”. Biologically active plant phytochemicals have a broad range of pharmacological effects including anticarcinogenic, antimicrobial, antioxidant, and anti-inflammatory activity. [1] Notwithstanding the possibility of having a specific target, phytochemicals must interact and permeate through cell membranes in the body. Indeed, it was suggested that those molecules insert into the membranes and thereby may have a promiscuous activity by changing structural properties of lipid bilayers. [2] Some well-known phenolic acids such as caffeic (CA), rosmarinic (RA) and chlorogenic (CGA) acids, whose identification in plant extracts has been achieved by CQB research groups, were selected to be addressed in first place. All the phenolic acids studied have low lipophilicity and among them, RA was the only one with a partition to biological membrane models measurable by fluorescence spectroscopy, as opposed to CA and CGA. Cyclic voltammetry measurements using an electrode modified with a supported lipid bilayer, also indicated a higher affinity of RA to lipid membranes. In addition, oxidation/reduction of the phenolic acids displayed higher reversibility in the lipid milieu than in the aqueous bulk. Indeed, the reduced form of phenolic acids was unstable in aqueous solution. In particular, in DMEM/F-12 cell culture media, a colour change observed after incubation with each compound could be reverted by the addition of a reducing agent. The higher reversibility of phenolic acids oxidation/reduction, once they were inserted in the lipid membrane, may contribute to the stability of the compounds and prevent the formation of degradation products. Molecular dynamics (MD) simulations are being performed to probe the location and orientation of these and other selected compounds in lipid bilayers. The influence of the phenolic acids in the cytoskeleton organization, both actin filaments and microtubules, of a human retinal pigment epithelial cell line (RPE1) was also investigated. All compounds induced concentration and time dependent effects, translated in structural alterations mainly at the cell periphery, and also in the perturbation of cell division. Moreover, it was not evident that these compounds induce apoptosis under the conditions tested. RA seemed to induce evident effects at earlier times and at lower concentrations, as compared to CA and CGA. This higher sensibility of RPE1 cells to RA correlates with the higher affinity of this compound to the lipid bilayer.info:eu-repo/semantics/publishedVersio

Purinergic signalling and immune cells

This review article provides a historical perspective on the role of purinergic signalling in the regulation of various subsets of immune cells from early discoveries to current understanding. It is now recognised that adenosine 5'-triphosphate (ATP) and other nucleotides are released from cells following stress or injury. They can act on virtually all subsets of immune cells through a spectrum of P2X ligand-gated ion channels and G protein-coupled P2Y receptors. Furthermore, ATP is rapidly degraded into adenosine by ectonucleotidases such as CD39 and CD73, and adenosine exerts additional regulatory effects through its own receptors. The resulting effect ranges from stimulation to tolerance depending on the amount and time courses of nucleotides released, and the balance between ATP and adenosine. This review identifies the various receptors involved in the different subsets of immune cells and their effects on the function of these cells

Interactions of selected flavonoids with NaDS micelles

International audienceCritical micelle concentrations (cmc) and degree of counterion dissociation (β) of sodium dodecyl sulphate micelles, in the presence of two flavonoids type additives, were determined at 298.15 ± 0.01 K using electrical conductivity. The dependences of the cmc on additive concentration follow a generalised type Setchenow equation and allowed the determination of Setchenow micellisation constants (K M ) for each solute. K M values revealed the high hydrophobicity of these compounds, and suggest that structural factors are determinant for the partition towards the micellar phase

Thermal and structural investigation of SnO2/Sb2O3 obtained by the polymeric precursor method

SnO2-based materials are used as sensors, catalysts and in electro-optical devices. This work aims to synthesize and characterize the SnO2/Sb2O3-based inorganic pigments, obtained by the polymeric precursor method, also known as Pechini method (based on the metallic citrate polymerization by means of ethylene glycol). The precursors were characterized by thermogravimetry (TG) and differential thermal analysis (DTA). After characterization, the precursors were heat-treated at different temperatures and characterized by X-ray diffraction. According to the TG/DTA curves basically two-step mass loss process was observed: the first one is related to the dehydration of the system; and the second one is representative to the combustion of the organic matter. Increase of the heat treatment temperature from 500 to 600 degrees C and 700 degrees C resulted higher crystallinity of the formed product

Efeito da adição de rejeito na redução de coração negro em cerâmicas vermelhas Effect of solid waste addition in the decrease of black core occurrence in red ceramic

Um dos problemas que afeta a indústria cerâmica é a elevada perda de produtos acabados, decorrente do próprio processamento, levando a trincas e peças fora de conformidade. Deste modo, é necessário o reaproveitamento desses resíduos, como forma de reduzir o impacto ambiental. Neste trabalho, os resíduos de duas indústrias de cerâmica vermelha foram moídos e adicionados à própria massa, levando, também, a um ganho econômico. As porcentagens variaram de 10% a 30%, em peso. As peças foram conformadas por extrusão e sinterizadas a 950 ºC e 1000 ºC. Os resultados obtidos mostram que a adição levou a uma melhoria nas propriedades das amostras, pois diminuem a possibilidade de ocorrência de coração negro, levando a peças mais uniformes e menos porosas<br>One of the problems of the ceramic industry is the high level of finished product loss, due to ceramic processing, leading to cracks and materials out of conformity. In this way it is necessary to recycle these solid wastes in order to reduce the environment impact. In this work, the solid waste of two red ceramic industries were milled and incorporated to the formulation of the industry, leading also to an economic gain. Incorporation percentages varied from 10% to 30 wt %. Samples were processed by extrusion and sintered at 950 ºC and 1000 ºC. The results indicate that the addition led to an improvement of sample properties, due to the decrease of black core formation, producing samples with higher uniformity and lower porosity