Structural analyses of blended Nafion/PVDF electrospun nanofibers.

A new type of polymer blend, prepared by electrospinning nanofibers containing the immiscible polymers polyvinylidene fluoride (PVDF, 10 wt%) and Nafion® perfluorosulfonic acid (90 wt%), has been characterized experimentally. The internal nanofiber morphology is unique and unlike a normal blend, with individual phase-separated and randomly distributed fibrils of Nafion and PVDF (∼2-7 nm in diameter) that are bundled together and aligned in the fiber axis direction (where the fiber diameter is ∼500 nm). This morphology is retained when fiber mats are hot-pressed into dense films. The physicochemical properties of the electrospun blended fibers are also highly unusual and unanticipated. As shown in this study, each polymer component influences the thermal and structural behavior of the other, especially in the dry state. Thus, dry composite polymer mats and membranes exhibit properties and attributes that are not observed for either pure PVDF or pure Nafion. Experimental results indicate that: (i) PVDF imparts conformational constraints on the polytetrafluoroethylene (PTFE) backbone chains of Nafion, resulting in an increased 21 helical conformation that effects Nafion's water uptake and thermal properties; and (ii) dipole-dipole interactions between PVDF polymer chains and Nafion make the ß-phase polymorph of PVDF much more stable at elevated temperatures. Such "reciprocal templating" in electrospun fibers may not be unique to Nafion and PVDF, thus the procedure represents a new method of creating nanostructured multi-component polymer materials with innovative features.

Experimental and molecular dynamics characterization of dense microemulsion systems: morphology, conductivity and SAXS.

Microemulsions are exciting systems that are promising as tuneable self-assembling templating reaction vessels at the nanoscale. Determination of the nano-structure of microemulsions is, however, not trivial, and there are fundamental questions regarding their design. We were able to reproduce experimental data for an important microemulsion system, sodium-AOT-n-heptane-water, using coarse-grained simulations involving relatively limited computational costs. The simulation allows visualization and deeper investigation of controversial phenomena such as bicontinuity and ion mobility. Simulations were performed using the Martini coarse-grained force field. AOT bonded parameters were fine-tuned by matching the geometry obtained from atomistic simulations. We investigated several compositions with a constant ratio of surfactant to oil while the water content was varied from 10 to 60% in weight. From mean square displacement calculation of all species, it was possible to quantify caging effects and ion mobility. Average diffusion coefficients were calculated for all charged species and trends in the diffusion coefficients were used to rationalize experimental conductivity data. Especially, the diffusion coefficient of charged species qualitatively matched the variation in conductivity as a function of water content. The scattering function was calculated for the hydrophilic species and up to 40% water content quantitatively matched the experimental data obtained from small angle X-ray scattering measurements. For higher water contents, discrepancies were observed and attributed to a nearby phase separation. In particular, bicontinuity of water and oil was computationally visualized by plotting the coordinates of hydrophilic beads. Equilibrated coarse-grained simulations were reversed to atomistic models in order both to compare ion mobility and to catch finer simulation details. Especially, it was possible to capture the intimate ion pair interaction between the sodium ion and the surfactant head group.

Investigating the genetic role of aquaporin4 gene in migraine.

Aquaporin4 (AQP4) has an important role in water homeostasis of human brain and a dysfunction of AQP4 could induce pathological conditions in neuronal activity. The purpose of our work was to evaluate the association of polymorphisms in the AQP4 gene with the risk and the clinical features of migraine. A total of 293 migraineurs and 249 controls were involved in the study. They were genotyped for four single nucleotide polymorphisms (SNPs) of AQP4 gene. No significant difference in the distribution of AQP4 genotypic and allelic frequencies between cases and controls was found. In addition, haplotype analysis did not show any significant difference. Comparison of the clinical features of the disease according to different AQP4 genotypes showed no significant difference. Our data do not support the hypothesis that the AQP4 gene could represent a genetic susceptibility factor for migraine.

Medicine in the time of Carracci: the cases of Domenico Lanzoni and Giuseppe Rosaccio.

During the 16th century and at the beginning of the 17th century the age-old competition between scholarly doctors and folk healers became more and more serious, creating a division between the two categories entrusted with treating population diseases. On one side there were the representatives who practiced medicine in an official capacity, and on the other, the "others", that is, the charlatans, the acrobats and female healers. Two representatives of these contrasting approaches of practicing medicine within the health profession during that historical period were two Italian doctors, Domenico Lanzoni and Giuseppe Rosaccio. Together, with their ties to the city of Bologna and the bolognese Carracci family of painters, they were able to describe in complete detail these two types of practices as medical sciences of the sixteenth and early seventeenth century.

Environmentally Friendly Carbon-Preserving Recovery of Noble Metals From Supported Fuel Cell Catalysts.

The dissolution of noble-metal catalysts under mild and carbon-preserving conditions offers the possibility of in situ regeneration of the catalyst nanoparticles in fuel cells or other applications. Here, we report on the complete dissolution of the fuel cell catalyst, platinum nanoparticles, under very mild conditions at room temperature in 0.1 M HClO4 and 0.1 M HCl by electrochemical potential cycling between 0.5-1.1 V at a scan rate of 50 mV s(-1) . Dissolution rates as high as 22.5 µg cm(-2) per cycle were achieved, which ensured a relatively short dissolution timescale of 3-5 h for a Pt loading of 0.35 mg cm(-2) on carbon. The influence of chloride ions and oxygen in the electrolyte on the dissolution was investigated, and a dissolution mechanism is proposed on the basis of the experimental observations and available literature results. During the dissolution process, the corrosion of the carbon support was minimal, as observed by X-ray photoelectron spectroscopy (XPS).

Effectiveness and safety of enteral vancomycin to control endemicity of methicillin-resistant Staphylococcus aureus in a medical/surgical intensive care unit.

A prospective trial was undertaken to assess the effectiveness and safety of enteral vancomycin in controlling methicillin-resistant Staphylococcus aureus (MRSA) in an endemic setting. Over the 49 month period patients aged >14 years were enrolled, following admission to a medical/surgical intensive care unit (ICU) and expected to require ventilation for three days or more. A total of 799 patients were included in the trial. Period one, 1 July 1996-30 April 1997, (N=140), was observational. During period two, 1 May 1997-30 September 1998, (N=258), surveillance samples were obtained. MRSA carriers were isolated and received enteral vancomycin. During period three, 1 October 1998-31 July 2000, (N=400), all ventilated patients were given selective digestive decontamination (SDD) with polymyxin E, tobramycin, amphotericin B and vancomycin and four days of intravenous cefotaxime. The primary endpoints were: (1) incidence of patients with diagnostic samples positive for MRSA acquired on the ICU; (2) incidence of patients with vancomycin-resistant enterococci (VRE) in surveillance or diagnostic samples; (3) incidence of patients with samples positive for S. aureus with intermediate sensitivity to glycopeptides (GISA). The incidence of patients with MRSA in diagnostic samples were 31%, 14%, and 2% in periods one, two and three, respectively (P<0.001). There was a VRE outbreak involving 13 patients during period three. VRE disappeared with no change in policy. GISA was not detected. These findings support the effectiveness and safety of enteral vancomycin in the control of MRSA.

[Epidemiology of parenteral nutrition during 5 years of follow-up by a nutrition team]. / Epidemiología de la nutrición parenteral a lo largo de cinco años de seguimiento por parte de un equipo de nutrición.

The purpose of this retrospective study is to ascertain the physiopathological characteristics of patients on parenteral nutrition (PN), the types of diet used and duration of treatment. Presentation of epidemiological results and evolution of 637 adults receiving PN after a five-year period of nutritional follow-up, conducted by a Nutrition Team (NT) in hospital. For the purpose of this study, we used the Follow-Up charts of all the patients treated with PN from 1986-1990. The results obtained lead us to affirm that most patients suffered a malignant gastrointestinal process, that the duration of the PN was reduced significantly during the five-year term, mainly using dietary protocols, and that there was a gradual increase in preparations of nutrient units subjected to controls compared to the total prepared by the Pharmacy Department.

High yield, controlled synthesis of graphitic networks from dense micro emulsions.

We report on the production of Carbon Nano Networks (CNNs) from dense microemulsions in which catalyst nanoparticles have been synthesized. CNNs are 3D carbon networks, consisting of branches and junctions, and are mesoporous, graphitic, and conductive being suitable as electrode materials.