From a micro-polymeric pipe to a mini-polymeric pulsating heat pipe

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.In this work, a preliminary study related to the design and manufacturing of a micro polymeric pipe for micro heat exchangers was performed. Among possible polymeric materials, a thermoplastic copolyester elastomer composed of polybuthylene-terephthalate, as crystalline phase, and long glycol chains, as the amorphous one (Hytrel® 6356, Dupont) was selected, both unloaded and loaded with 7 % w/w carbon powder. A microextrusion process was set up to obtain microtubes and the thermo-mechanical characteristics of the produced pipes were studied. Thermal properties of extruded Hytrel® remained almost the same, in terms of melting temperature (Tm ≅ 208 °C) and enthalpy change of fusion (ΔH ≅ 45 mJ/mg), although the material was C-loaded. The thermomechanical tests performed on unloaded and C-loaded Hytrel® microtubes at 25 and 70 °C (possible working temperature) detected a considerable increase in the mechanical properties of C-loaded Hytrel®, compared to the unloaded one. In particular, a relevant improvement of the elastic modulus at 70 °C for the C-loaded microtubes was observed, demonstrating a better thermal stability at high temperature. Moreover, the fabrication of a micro heat exchanger prototype and prteliminary tests with different cooling fluids confirmed the possibility of using Hytrel® for electronic applications, as a good thermal exchange was evidenced.vk201

BeppoSAX observations of 3C 273

We present preliminary results of BeppoSAX AO1 observations of 3C 273 performed in January 1997. We also present a close comparison with data obtained during the satellite SVP, in July 1996. On average, the AO1 flux is about a factor 2 higher than the flux detected during the SVP, and roughly on the middle of the historical X-ray flux range. Power law fits with galactic absorption to all observations yield spectral indices in the range 1.53-1.6, with the spectrum extending from 0.2 to at least up to 200 keV without any significant slope change. The broad band spectrum appears basically featureless, marking a clear difference from the SVP data, where an absorption feature at low energy and a fluorescence iron emission line are present. The lack of cold/warm matter signatures in our data may indicate that, at this "high" level of luminosity, the featureless continuum produced in a relativistic jet overwhelms any thermal and/or reprocessing component, while the two components were at least comparable during the "low" state of July 1996.Comment: 1+4 pages, 3 ps inlined figures, espcrc2.sty. Proc. of the Conf. "The Active X-Ray Sky: Results from BeppoSAX and Rossi-XTE", Rome 21-24 October 199

New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

Eficiência na provisão de educação pública municipal: uma análise em três estágios dos municípios brasileiros

O artigo busca analisar as características municipais que afetam a eficiência dos municípios brasileiros na gestão educacional, consequência do processo de descentralização educacional na década de 90. As informações foram extraídas da Prova Brasil, Censo Escolar, Finbra e STN para 2005. Empregamos um procedimento em três estágios, cujo primeiro consiste no uso de modelos SBM (slacks based measure) no cálculo da eficiência no uso de insumos discricionários. Em seguida, controlamos pelos insumos não discricionários, resultando em um novo índice de eficiência. Finalmente, aplicamos as misturas finitas para analisar a heterogeneidade existente entre os diversos municípios em relação aos níveis de eficiência da gestão municipal. Os resultados mostram a não uniformidade de impactos demográficos, políticos e de recursos sobre a eficiência da gestão educacional entre os diversos grupos de municípios brasileiros. O aumento de democracia e recursos como o decorrente do Fundef, em geral, aumenta a eficiência da administração escolar municipal

Polyurethane Precursors

This article intends to provide a basic knowledge of polyurethanes (PUs) and their typologies, with particular reference to starting materials, both from a scientific and a commercial point of view. The possible types of PUs are described in short, together with their methods of production. Safety, ecological items, and recycling are considered as well. As a final point, the advantages of the use of PUs in composites production are highlighted, with an indication of the reinforced PU production processes

Fondamenti di Bioingegneria Chimica: non solo biomateriali. Seconda edizione

Per i suoi contenuti questo libro rappresenta un utile riferimento per chiunque desideri acquisire e conservare non solo le conoscenze di base dei Biomateriali e della Biocompatibilità, ma anche dei meccanismi fisiologici di difesa e riparo e dei concetti essenziali di Ingegneria dei Tessuti e di Biotecnologie. Una parte introduttiva (i primi 3 capitoli) riguarda i materiali, le loro proprietà e metodi di trasformazione ed è utile per coloro che non possiedono le conoscenze di base sulla ingegneria dei materiali e sulle varie classi di materiali. Gli argomenti significativi e specifici vengono affrontati nelle parti successive. Nella parte dedicata a Biomateriali e Biocompatibilità vengono presentate le problematiche relative all’utilizzo e alle applicazioni delle varie classi di materiali nel campo biomedicale, in particolare all’interno del corpo umano, le strutture e meccanismi alla base dei processi di difesa e riparo del nostro organismo e infine la fenomenologia dell’interazione tra ambiente biologico e biomateriale. L’ultima parte del libro riguarda due settori in forte espansione: l’Ingegneria dei tessuti e le Biotecnologie

Heparinizable segmented polyurethanes containing poly-amidoamine blocks

A poly-ether-urea-urethane was synthesized by copolymerization of 4,4'-diphenylmethanediisocyanate (MDI), propanediamine, and poly-oxytetra-methylene glycol (M.W. 1000). Two other corresponding copolymers were also synthesized by adding amino terminated poly-amidoamine macromonomers, purposely synthesized, so as to insert relatively small amounts (6 and 15 weight %) of two types of poly-amidoamine segments in the final product. Of the three copolymers several physicochemical and mechanical properties have been determined, and their heparin adsorption ability, blood compatibility, and cytotoxicity evaluate

New polymeric and oligomeric matrices as drug carriers

The preparation of polymeric derivatives of drugs, in which drug moieties are covalently linked to polymeric or oligomeric matrices, in such a way that they can be released at the site of action, is one of the most promising ways to achieve results which often can be hardly obtained by other means, such as, for instance, better adsorption by some ways of administration (e.g., oral administration), preferential localization in the body, and longer duration of activity. The aim of this review is to provide an up-to-date picture of the state of art in this field. The synthetic aspects of the preparation of polymeric derivatives of drugs will be discussed, with special emphasis on general methods. The main criteria for selecting a particular type of matrix, and a particular bond between drug and matrix, in order to achieve a given purpose, will be also discussed. The main pharmacological results so far obtained by this technique will be emphasize