Extension of the operational lifetime of the proportional chambers in the HERMES spectrometer

Abstract The experience of the extension of the proportional chambers lifetime at the HERMES (DESY) experiment is presented. A non-invasive technique against the aging process while continuously operating the detectors in the gap of the HERMES spectrometer magnet was performed. It was found that adding 0.14% water to the 65%Ar+30%CO2+5%CF4 gas mixture perfectly cancelled the appearance of self-sustained current (Malter effect). The studies of the remedy for the lifetime extension were performed with the test prototypes of the original proportional chambers. For the complete recovery of the aged test proportional chambers a special training method was developed as well. Training of the aged proportional chamber at 80%CF4+20%CO2 mixture glow discharge with reversed high voltage demonstrated a complete recovery of the detector

Preparation and in vitro characterization of novel bioactive glass ceramic nanoparticles

SiO2-CaO-P2O5 ternary bioactive glass ceramic (BGC) nanoparticles with different compositions were prepared via a three-step sol-gel method. Polyethylene glycol was selected to be used as the surfactant to improve the dispersion of the nanoparticles. The morphology and composition of these BGC nanoparticles were observed by ESEM and EDX. All the BGC particles obtained in this method were about 20 nm in diameter. XRD analysis demonstrated that the different compositions can result in very different crystallinities for the BGC nanoparticles. Bioactivity tests in simulated body fluid solution (SBF), and degradability in phosphate buffer solution (PBS), were performed in vitro. SEM, EDX, and XRD were employed to monitor the surface variation of neat poly(L-lactic acid), PLLA, foam and PLLA/BGC porous scaffolds during incubation. The BGC nanoparticles with lower phosphorous and relative higher silicon content exhibited enhanced mineralization capability in SBF and a higher solubility in PBS medium. Such novel nanoparticles may have potential to be used in different biomedical applications, including tissue engineering or the orthopedic field.Contract grant sponsor: FCT; contract grant numbers: POCTI/FIS/61621/2004, SFRH/BPD/25828/2005, PTDC/QUI/69263/200

Rheological behavior of thermoreversible k-carrageenan/nanosilica gels

The rheological behavior of silica/κ-carrageenan nanocomposites has been investigated as a function of silica particle size and load. The addition of silica nanoparticles was observed to invariably impair the gelation process, as viewed by the reduction of gel strength and decrease of gelation and melting temperatures. This weakening effect is seen, for the lowest particle size, to become slightly more marked as silica concentration (or load) is increased and at the lowest load as particle size is increased. These results suggest that, under these conditions, the particles act as physical barriers to polysaccharide chain aggregation and, hence, gelation. However, for larger particle sizes and higher loads, gel strength does not weaken with size or concentration but, rather, becomes relatively stronger for intermediate particles sizes, or remains unchanged for the largest particles, as a function of load. This indicates that larger particles in higher number do not seem to increasingly disrupt the gel, as expected, but rather promote the formation of stable gel network of intermediate strength. The possibility of this being caused by the larger negative surface charge found for the larger particles is discussed. This may impede further approximation of neighboring particles thus leaving enough inter-particle space for gel formation, taking advantage of a high local polysaccharide concentration due to the higher total space occupied by large particles at higher loads.FCT - PTDC/QUI/67712/2006FEDE

Cellular uptake of magnetic nanoparticle is mediated through energy-dependent endocytosis in A549 cells

Biocompatible silica-overcoated magnetic nanoparticles containing an organic fluorescence dye, rhodamine B isothiocyanate (RITC), within a silica shell [50 nm size, MNP@SiO2(RITC)s] were synthesized. For future application of the MNP@SiO2(RITC)s into diverse areas of research such as drug or gene delivery, bioimaging, and biosensors, detailed information of the cellular uptake process of the nanoparticles is essential. Thus, this study was performed to elucidate the precise mechanism by which the lung cancer cells uptake the magnetic nanoparticles. Lung cells were chosen for this study because inhalation is the most likely route of exposure and lung cancer cells were also found to uptake magnetic nanoparticles rapidly in preliminary experiments. The lung cells were pretreated with different metabolic inhibitors. Our results revealed that low temperature disturbed the uptake of magnetic nanoparticles into the cells. Metabolic inhibitors also prevented the delivery of the materials into cells. Use of TEM clearly demonstrated that uptake of the nanoparticles was mediated through endosomes. Taken together, our results demonstrate that magnetic nanoparticles can be internalized into the cells through an energy-dependent endosomal-lysosomal mechanism

Incorporating physiologically relevant mobile phases in micellar liquid chromatography for the prediction of human intestinal absorption

Micellar liquid chromatography (MLC) is a popular method used in the determination of a compounds lipophilicity. This study describes the use of the obtained micelle/water partition coefficient (log Pmw) by such a method in the prediction of human intestinal absorption (HIA). As a result of the close resemblance of the novel composition of the micellar mobile phase to that of physiological intestinal fluid, prediction was deemed to be highly successful. The unique micellar mobile phase consisted of a mixed micellar mixture of lecithin and six bile salts, i.e. a composition matching that found in the human intestinal environment, prepared in ratios resembling those in the intestine. This is considered to be the first method to use a physiological mixture of biosurfactants in the prediction of HIA. As a result, a mathematical model with high predictive ability (R2PRED= 81 %) was obtained using multiple linear regression. The micelle/water partition coefficient (log Pmw) obtained from MLC was found to be a successful tool for prediction where the final optimum model included (log Pmw) and polar surface area (PSA) as key descriptors with high statistical significance for the prediction of HIA. This can be attributed to the nature of the mobile phase used in this study which contains the lecithin-bile salt complex, thus forming a bilayer system therefore mimicking absorption across the intestinal membrane

Polymer Networks Produced by Marine Diatoms in the Northern Adriatic Sea

Using high resolution molecular technique of atomic force microscopy, we address the extracellular polymer production of Adriatic diatom Cylindrotheca closterium analyzed at the single cell level and the supramolecular organization of gel phase isolated from the Northern Adriatic macroaggregates. Our results revealed that extracellular polysaccharides freshly produced by marine diatoms can self-assemble directly to form gel network characteristics of the macroscopic gel phase in the natural aquatorium. Based on the experiments performed with isolated polysaccharide fractions of C. closterium and of macroaggregates gel phase, we demonstrated that the polysaccharide self-assembly into gel network can proceed independent of any bacterial mediation or interaction with inorganic particles

Prospects of Nanotechnology in Clinical Immunodiagnostics

Nanostructured materials are promising compounds that offer new opportunities as sensing platforms for the detection of biomolecules. Having micrometer-scale length and nanometer-scale diameters, nanomaterials can be manipulated with current nanofabrication methods, as well as self-assembly techniques, to fabricate nanoscale bio-sensing devices. Nanostructured materials possess extraordinary physical, mechanical, electrical, thermal and multifunctional properties. Such unique properties advocate their use as biomimetic membranes to immobilize and modify biomolecules on the surface of nanoparticles. Alignment, uniform dispersion, selective growth and diameter control are general parameters which play critical roles in the successful integration of nanostructures for the fabrication of bioelectronic sensing devices. In this review, we focus on different types and aspects of nanomaterials, including their synthesis, properties, conjugation with biomolecules and their application in the construction of immunosensing devices. Some key results from each cited article are summarized by relating the concept and mechanism behind each sensor, experimental conditions and the behavior of the sensor under different conditions, etc. The variety of nanomaterial-based bioelectronic devices exhibiting novel functions proves the unique properties of nanomaterials in such sensing devices, which will surely continue to expand in the future. Such nanomaterial based devices are expected to have a major impact in clinical immunodiagnostics, environmental monitoring, security surveillance and for ensuring food safety

Production of {\pi}+ and K+ mesons in argon-nucleus interactions at 3.2 AGeV

First physics results of the BM@N experiment at the Nuclotron/NICA complex are presented on {\pi}+ and K+ meson production in interactions of an argon beam with fixed targets of C, Al, Cu, Sn and Pb at 3.2 AGeV. Transverse momentum distributions, rapidity spectra and multiplicities of {\pi}+ and K+ mesons are measured. The results are compared with predictions of theoretical models and with other measurements at lower energies.Comment: 29 pages, 20 figure