2,188 research outputs found
On the existence of an upper critical dimension for systems within the KPZ universality class
In this work we extend the etching model to dimensions. This permits us
to investigate its exponents behaviour on higher dimensions, to try to verify
the existence of an upper critical dimension for the KPZ equations, with our
results sugesting that is not an upper critical dimension for the etching
model
A Multiple Criteria Framework to Evaluate Bank Branch Potential Attractiveness
Remarkable progress has occurred over the years in the performance evaluation of bank branches. Even though financial measures are usually considered the most important in assessing branch viability, we posit that insufficient attention has been given to other factors that affect the branchesâ potential profitability and attractiveness. Based on the integrated used of cognitive maps and MCDA techniques, we propose a framework that adds value to the way that potential attractiveness criteria to assess bank branches are selected and to the way that the trade-offs between those criteria are obtained. This framework is the result of a process involving several directors from the five largest banks operating in Portugal, and follows a constructivist approach. Our findings suggest that the use of cognitive maps systematically identifies previously omitted criteria that may assess potential attractiveness. The use of MCDA techniques may clarify and add transparency to the way trade-offs are dealt with. Advantages and disadvantages of the proposed framework are also discussed.
Surface-ATRP of PEGMA onto polydimethyl siloxane for biomedical applications
Silicone rubber (poly(dimethyl siloxane; PDMS)), is extensively used for
biomedical implants due to its low toxicity, flexible processing techniques, long-term
endurance and good blood compatibility. However, the presence of low molecular weight
organic molecules and catalyst residues that cause host systemic inflammatory reactions.
The hydrophobic nature of PDMS also allows microbial adhesion followed by infection.
Hydrophilic PDMS surfaces would be of great value in inhibiting biofilm formation thus
prolonging the lifetime of the implants. This could be obtained by surface-initiated atom
transfer radical polymerization (ATRP). The robustness and versatility of ATRP allow the
preparation of functional bioactive surfaces, including antifouling, antibacterial, stimuliresponsive,
biomolecule-coupled and micropatterned surfaces.[1-3]
We aim at establishing the experimental conditions allowing the surface-grafting of
polyethylene glycol methacrylate (PEGMA) by surface attaching an initiator (1-
trichlorosilyl-2-(chloromethylphenyl)ethane) onto PDMS (Sylgard Âź 184). Here, cooper is
being used as a metal catalyst and 2,2'-Bipyridine as a ligant. Polymerizations are being
assayed in aqueous media.
The native smooth and transparent surface of the PDMS could be preserved following
polymerization (as confirmed by SEM). FTIR-ATR also showed the presence of PEGMA
polymer chains. By contact angle measurement, a change in the surface hydrophobicity
was observed, the values changing from 114Âș to 60Âș, following 30h polymerization.
Work is in progress to optimize the modification of PDMS by PEGMA surface-ATRP.
This implies following up the polymer chain growth kinetics, surface characterization by
XPS, FTIR-ATR, SEM and contact angle measurements. Static and dynamic microbial
adhesion, as well as biocompatibility studies are also envisaged
Die Optimierung von Poly(Dimethylsiloxan) fĂŒr biomedizinische Anwendungen durch oberflĂ€cheninitiierte Atom-Transferradikal-Polymerisation
Project BIOSURFA ref. PTDC/SAU-BEB/73498/200
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In situ degradation of YSZ and YSZ + Al2O3 electrolytes of sensors used in glass melting furnaces
This work reports on the degradation of pure YSZ and YSZ +10 wt% alumina composite electrolytes by exposure to the atmosphere of a heat recovery chamber of an industrial glass furnace, at a temperature around 1300 °C. Microstructural observations and impedance spectroscopy measurements were used to evaluate the corrosion effects. YSZ samples directly placed in the sidewalls and intimately exposed to the dusts and volatiles in the atmosphere show strong corrosion effects after short periods. These samples present large amounts of a glassy phase in the intergranular region, containing the same elements as the common batch with inclusion of volatile species from the fuel. At the same time, the average composition of YSZ grains remains almost unchanged. Effects on the electrical properties are obviously stronger in the intergranular response, as confirmed by changes in the typical relaxation frequency.
The protection of samples and/or their careful placement in the furnace strongly inhibit the corrosion process. The effectiveness of alumina addition to the YSZ electrolyte in increasing its corrosion resistance was only tested in protected samples, where the corrosion is less severe. For this reason, the expected benefits of this incorporation were found almost irrelevant
Purple corn (zea mays l.) pericarp hydroalcoholic extracts obtained by conventional processes at atmospheric pressure and by processes at high pressure
Extracts of Peruvian purple corn pericarp (Zea mays L.) were obtained: (1) via supercritical fluid extraction with CO2 as solvent and EtOH-H2O (70:30, v/v) as co-solvent, (2) via pressurized liquid extraction (PLE) with EtOH-H2O (70:30, v/v) and, (3) via two conventional extraction processes, stirred vessel and Soxhlet. The extraction yields and extract compositions were compared to each other. The parameters measured were the point-to-point extraction yield, the global extraction yield and composition of extracts regarding contents of total phenolics, total flavonoids, total anthocyanins and specific anthocyanins such as cyanidin-3-glucoside, peonidin-3-glucoside and pelargonidin-3-glucoside. Antioxidant activity by DPPH and in vitro antiproliferative activity were also evaluated considering seven cancer cell lines. High yields and higher contents of phenolic compounds, accompanied by a high antioxidant activity at 50 °C, were obtained for supercritical extraction at 60 °C. Antioxidant activity showed good correlation with the content of phenolic compounds, but there was no antiproliferative activity37237248COORDENAĂĂO DE APERFEIĂOAMENTO DE PESSOAL DE NĂVEL SUPERIOR - CAPESFUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULO - FAPESPSem informação12/51317-
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