Effect of pH on the precipitation of hydroxyapatite on silica gels

Silica-HAp composites have been produced with particle size ranging from several nm to few μm, through control of the pH of the solution, which also controls morphology. A calcium ions reservoir has been made available as a Ca/EDTA soluble complex allowing the production of HAp at low temperature and short periods of time (hours). The presence of silica seems to promote the formation of HAp under these conditions. Electronic Publication     

Cellular Uptake, DNA Binding and Apoptosis Induction of Cytotoxic Trans-[PtCl(2)(N,N-dimethylamine)(Isopropylamine)] in A2780cisR Ovarian Tumor Cells

Trans-[PtCl(2)(N,N-dimethylamine)(isopropylamine)] is a novel trans-platinum compound that shows cytotoxic activity in several cisplatin resistant cell lines. The aim of this paper was to analyse, by means of molecular cell biology techniques and total reflection X-ray fluorescence (TXRF), the cytotoxic activity, the induction of apoptosis, the cellular uptake and the DNA binding of trans-[PtCl(2)(N,N-dimethylamine)(isopropylamine)] in the cisplatin resistant cell line A2780cisR. The results show that this drug is more cytotoxic and induces a higher amount of apoptotic cells than cisplatin in A2780cisR cells. However, the intracellular accumulation and extent of binding to DNA of trans-[PtCl(2)(N,N-dimethylamine)( isopropylamine)] is lower than that of cis-DDP. Moreover, trans-[PtCl(2)(N,N-dimethylamine)(isopropylaminae)] is partially inactivated by intracellular levels of glulathione. The result suggest that circumvention of ciplatin resistance by trans-[PtCl(2)(N,N-dimethylamine)(isopropylamine)] in A2780cisR cells might be related with the ability of this drug to induce apoptosis.     

Dynamics of [Ca2+] in the endoplasmic reticulum and cytoplasm of intact HeLa cells. A comparative study

We have measured the [Ca2+] in the endoplasmic reticulum ([Ca2+]er) of intact HeLa cells at both 22 degrees C and 37 degrees C using endoplamsic reticulum-targeted, low Ca2+ affinity aequorin reconstituted with coelenterazine n. Aequorin consumption was much slower at 22 degrees C, and this allowed performing a much longer study of the dynamics of [Ca2+]er. The steady-state [Ca2+]er (500-600 microM) was not modified by the temperature, although both the rates of pumping and leak were decreased at 22 degrees C. The behavior of both [Ca2+]er and cytoplasmic [Ca2+] ([Ca2+]c) after the addition of increasing concentrations of agonists and/or Ca2+-ATPase inhibitors, or following incubation in Ca2+-free medium were compared. We show that agonists induce a fast but relatively small decrease in [Ca2+]er, which is enough to produce a sharp increase in [Ca2+]c. Termination of Ca2+ release is controlled by feedback inhibition of the inositol 1,4,5-trisphosphate receptors by [Ca2+]c, a mechanism that appears to be designed to release the minimum amount of Ca2+ necessary to produced the required [Ca2+]c signal. We also show that Ca2+ release is inhibited progressively when [Ca2+]er decreases below a threshold of about 150 microM, even in the absence of Ca2+ pumping or -Ca2+-c increase. This effect is consistent with a regulation of the inositol 1,4,5-trisphosphate-gated channels by [Ca2+]er.     

Cs Promoted Triglyceride Transesterification Over MgO Nanocatalysts

The influence of Cs on the structure and basicity of nanocrystalline MgO was assessed via electron microscopy, CO₂ chemisorption, XRD and XPS. Caesium incorporation via co-precipitation under supercritical conditions generates Cs₂Mg(CO₃)₂ nanocrystallites with an enhanced density and strength of surface base sites. Wet impregnation proved less effective for modifying MgO nanocrystals. A strong synergy between Cs and Mg components in the co-precipitated material dramatically enhanced the rate of tributyrin transesterification with methanol relative to undoped MgO and homogeneous Cs₂CO₃ catalysts. On-stream deactivation of Cs-doped MgO reflects heavy surface carbon deposition and loss of the high activity Cs₂Mg(CO₃)₂ phase due to limited Cs dissolution.     

Spectral fuzzy classification: an application

Geographical information (including remotely sensed data) is usually imprecise, meaning that the boundaries between different phenomena are fuzzy. In fact, many classes in nature show internal gradual differences in species, health, age, moisture, as well other factors. If our classification model does not acknowledge that those classes are heterogeneous, and crisp classes are artificially imposed, a final careful analysis should always search for the consequences of such an unrealistic assumption. We consider the unsupervised algorithm presented by A. del Amo et al. (2000), and its application to a real image in Sevilla province (south Spain). Results are compared with those obtained from the ERDAS ISO-DATA classification program on the same image, showing the accuracy of our fuzzy approach. As a conclusion, it is pointed out that whenever real classes are natural fuzzy classes, with gradual transition between classes, then its fuzzy representation will be more easily understood, and therefore accepted by users     

Accelerated Aging in 3-mol%-Yttria-Stabilized Tetragonal Zirconia Ceramics Sintered in Reducing Conditions

The aging behavior of 3-mol%-yttria-stabilized tetragonal zirconia (3Y-TZP) ceramics sintered in air and in reducing conditions was investigated at 140°C in water vapor. It was observed by X-ray diffraction (XRD) that 3Y-TZP samples sintered in reducing conditions exhibited significantly higher tetragonal-to-monoclinic transformation than samples with similar density and average grain size values but obtained by sintering in air. This fact is explained by the increase of the oxygen vacancy concentration and by the presence at the grain boundary region of a new aggregate phase formed because of the exolution of Fe²⁺ ions observed by X-ray photoelectron spectroscopy.     

Antioxidant activity of several marine skin gelatins

Gelatins obtained from the skins of tuna and halibut, and from the tunics of jumbo flying squid were hydrolysed by Alcalase to produce antioxidant peptides. Hydrolysis yielded an increase in the antioxidant capacity of gelatins of around two-fold when measured by the Fe reducing capacity (FRAP) method and even more when measured by the ABTS radical scavenging method. When both squid and tuna gelatins were hydrolysed with different enzymes (collagenase, trypsin, pepsin), Alcalase and pepsin gave the hydrolysates with the highest and lowest ABTS radical scavenging ability, respectively. FRAP assay showed that the squid hydrolysates prepared using Alcalase were the most effective in reducing ferric ions, whereas trypsin gave rise to the tuna hydrolysates with the highest iron reducing ability. When the amino acid composition of the gelatins was related to the antioxidant properties, ABTS radical scavenging was observed to be negatively correlated to the total content of hydrophobic amino acids and imino acids in all the samples, while Fe reducing power (FRAP) was strongly correlated with Hyl and degree of hydroxylation.     

Characterization of phenoloxidase activity of carapace and viscera from cephalothorax of Norway lobster (Nephrops norvegicus)

The characterization of phenoloxidase activity was performed in both carapace and viscera extracts of Norway lobster. Phenoloxidase activity rose with increasing temperature up to 60 °C. The carapace enzymatic extract showed the highest themostability, retaining about 80% of maximum activity at 45 °C and 40% at 65 °C. On the other hand, both enzymatic extracts showed a single peak activity at neutral-slightly alkaline pH and were quite resistant to inactivation at alkaline pH (pH > 8), but phenoloxidase activity became unstable at pH lower than 5.5. The enzymatic extract obtained from viscera showed a higher affinity for catechol (K_M 5.97 mM) than carapace extract (K_M 19.40 mM). Both mono- and diphenoloxidase activities were found in carapace and viscera. Polyphenoloxidase and converted-hemocyanin into PPO-like enzyme could be the main responsible for these activities.     

Rural electrification systems based on renewable energy: The social dimensions of an innovative technology

Many areas in rural non-Western regions are installing electrification systems based on renewable energy. Although these projects are usually welcome, they sometimes fail. Explanations for failures often cite technical reasons. In this research, partly based on the results of the SOPRA_RE project, we focus on the users, studying the relationships between technology and society. By analysing potential sources of failures, we identify the root of the problem as how a new technology is received by the local society. In this paper we introduce dimensions that we consider to be especially important in the process of technology integration. We defend the importance of combining the technical outlook with the sociological one, based on the idea that the latter is often indispensable as a complementary element of technical explanations of system failures, which in turn provides a better basis for solving them. We use specific examples to bolster our insistence on the need to achieve convergence between the technical and the sociological outlooks.