250 research outputs found

    Efeitos da flexibilização da regulamentação sobre o mercado de transporte aéreo no Brasil

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    O Governo brasileiro implantou um processo gradual de flexibilização do mercado de Transporte Aéreo doméstico a partir de 1990, depois de anos de regulamentação rígida. Este trabalho visa analisar quais efeitos que a flexibilização trouxe ao mercado brasileiro, a partir da resposta a duas perguntas básicas: o mercado brasileiro é oligopolizado, requerendo uma regulamentação atuante ou possui características que permitam evoluir a um ambiente competitivo; e se os usuários e o País foram beneficiados pela flexibilização introduzida a partir de 1990. Informações sobre eficiência das empresas aéreas, freqüências, custos, níveis de segurança foram reunidas e comparadas aos valores correspondentes do mercado norteamericano (que e referência para qualquer processo de desregulamentação/flexibilização em Transporte Aéreo no mundo) e também dos mercados canadense e australiano (dois países com mercados semelhantes ao brasileiro e que desregulamentaram seus mercados recentemente). Incluem-se também análises sobre a existência de algumas particularidades no mercado de aviação regional no Brasil e modelagem econométrica, comparando parâmetros de demanda para períodos anteriores e posteriores à flexibilização. Apesar do curto período decorrido desde o início da flexibilização, algumas tendências podem ser verificadas. As freqüências de vôos aumentaram destacadamente, houve um aumento discreto no nível de competição do mercado, os níveis de segurança não foram afetadas até o momento em função da liberalização, e pode-se perceber algum acréscimo no nível de eficiência das empresas. A fixação, por partes das empresas, de tarifas e política de descontos semelhantes demonstra a tendência oligopolista do mercado. A regulamentação ainda vigente introduziu uma distorção de mercado, ao permitir que as companhias regionais competissem com as nacionais nos pares origem-destino mais importantes do país, e reservando às primeiras a operação nos aeroportos urbanos. A modelagem econométrica apresentou um notável aumento na demanda das companhias regionais após 1990, enquanto que a demanda das empresas nacionais e do total doméstico não acompanhou nem mesmo o crescimento do PIB no período como ocorria no período regulamentado. Resumindo, a flexibilização do mercado brasileiro de Transporte Aéreo já trouxe alguns benefícios aos usuários, contudo, há ainda muitas restrições impedindo que o mercado evolua para uma situação competitiva, como por exemplo, a diferenciação hoje existente entre companhias nacionais e regionais.After years of tight regulation, up to 1990, Brazilian Governrnent adopted a gradual process of liberalization of the domestic airline industry. This research intends to verify whjch effects this liberalization has brought to the Brazilian domestic airline market, by answering two main questions, if the Brazilian market is an oligopoly, requiring regulation or it can develop to a competitive environment, and if passengers and the country itself have perceived any advantage after 1990 due to the liberalization. lnformation about airline efficiency, costs, frequencies, safety records and entry barriers are collected and compared with correspondent values from the U.S. market (wruch is a benchmark for any deregulation/liberalization ofairline industry in the world) and also from Canada and Australia (both of them deregulated their markets recently and share similarities with the Brazilian industry). Furthermore, some particularities of Brazilian regional market and econometric modeling comparing demand parameters prior and after market liberalization are also included. Despite the short period elapsed since the beginning of the process, some tendencies can be distinguished. Frequencies rised remarkably, a modest increase in competition levei might be noticed, safety leveis were not affected up to now by the liberalization, and there has been some improvement in airline efficiency. Common price deterrnination and discount policy testifies a trend to an oligopoly. Remaining regulatory issues introduced a distortion to the market by allowing regional airlines to compete with trunk in most important city pairs, reserving urban airport operations to the former. The econometric modeling depicts a vigorous grow in regional market demand after 1990, wrulst the trunk and domestic markets not even followed the GDP grow as they formerly did. To sum up, the liberalization o f Brazilian airline market has already introduced some advantages to the consumers, however, too many constraints are still preventing the market to develop naturally, e.g., the dichotomy between regional and trunk

    Study of polypropylene surface modification by air dielectric barrier discharge operated at two different frequencies

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    AbstractIn this work, air dielectric barrier discharge (DBD) operating at the line frequency (60Hz) or at frequency of 17kHz was used to improve the wetting properties of polypropylene (PP). The changes in the surface hydrophilicity were investigated by contact angle measurements. The plasma-induced chemical modifications of PP surface were studied by X-ray photoelectron spectroscopy (XPS) and Fourier-transformed infrared spectroscopy (FTIR). The polymer surface morphology and roughness before and after the DBD treatment were analyzed by atomic force microscopy (AFM). To compare the plasma treatment effect at different frequencies the variation of the contact angle is presented as a function of the deposited energy density. The results show that both DBD treatments leaded to formation of water-soluble low molecular weight oxidized material (LMWOM), which agglomerated into small mounts on the surface producing a complex globular structure. However, the 60Hz DBD process produced higher amount of LMWOM on the PP surface comparing to the 17kHz plasma treatment with the same energy dose. The hydrophilic LMWOM is weakly bounded to the surface and can be easily removed by polar solvents. After washing the DBD-treated samples in de-ionized water their surface roughness and oxygen content were reduced and the PP partially recovered its original wetting characteristics. This suggested that oxidation also occurred at deeper and more permanent levels of the PP samples. Comparing both DBD processes the 17kHz treatment was found to be more efficient in introducing oxygen moieties on the surface and also in improving the PP wetting properties

    Surface modification of polymeric materials by cold atmosphericplasma jet

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    In this work we report the surface modification of different engineering polymers, such as, polyethylene terephthalate (PET), polyethylene (PE) and polypropylene (PP) by an atmospheric pressure plasma jet (APPJ). It was operated with Ar gas using 10 kV, 37 kHz, sine wave as an excitation source. The aim of this study is to determine the optimal treatment conditions and also to compare the polymer surface modification induced by plasma jet with the one obtained by another atmospheric pressure plasma source the dielectric barrier discharge (DBD). The samples were exposed to the plasma jet effluent using a scanning procedure, which allowed achieving a uniform surface modification. The wettability assessments of all polymers reveal that the treatment leads to reduction of more than 40 degrees in the water contact angle (WCA). Changes in surface composition and chemical bonding were analyzed by x-ray photoelectron spectroscopy (XPS) and Fourier-Transformed Infrared spectroscopy (FTIR) that both detected incorporation of oxygen-related functional groups. Surface morphology of polymer samples was investigated by Atomic Force Microscopy (AFM) and an increase of polymer roughness after the APPJ treatment was found. The plasma-treated polymers exhibited hydrophobic recovery expressed in reduction of the O-content of the surface upon rinsing with water. This process was caused by the dissolution of low molecular weight oxidized materials (LMWOMs) formed on the surface as a result of the plasma exposure. (C) 2014 Elsevier B.V. All rights reserved

    Characterization and Optimization of a Conical Corona Reactor for Seed Treatment of Rapeseed

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    Plasma agriculture is a growing field that combines interdisciplinary areas with the aim of researching alternative solutions for increasing food production. In this field, plasma sources are used for the treatment of different agricultural goods in pre-and post-harvest. With the big variety of possible treatment targets, studied reactors must be carefully investigated and characterized for specific goals. Therefore, in the present study, a cone-shaped corona reactor working with argon was adapted for the treatment of small seeds, and its basic properties were investigated. The treatment of rapeseed using different voltage duty cycles led to an increase in surface wettability, possibly contributing to the accelerated germination (27% for 90% duty cycle). The discharge produced by the conical reactor was able to provide an environment abundant with reactive oxygen species that makes the process suitable for seeds treatment. However, operating in direct treatment configuration, large numbers of seeds placed in the reactor start impairing the discharge homogeneity

    Effect of Cold Atmospheric Plasma Jet Associated to Polyene Antifungals on Candida albicans Biofilms

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    The increasing incidence of antifungal resistance represents a great challenge in the medical area and, for this reason, new therapeutic alternatives for the treatment of fungal infections are urgently required. Cold atmospheric plasma (CAP) has been proposed as a promising alternative technique for the treatment of superficial candidiasis, with inhibitory effect both in vitro and in vivo. However, little is known on the association of CAP with conventional antifungals. The aim of this study was to evaluate the effects of the association between CAP and conventional polyene antifungals on Candida albicans biofilms. C. albicans SC 5314 and a clinical isolate were used to grow 24 or 48 h biofilms, under standardized conditions. After that, the biofilms were exposed to nystatin, amphotericin B and CAP, separately or in combination. Different concentrations of the antifungals and sequences of treatment were evaluated to establish the most effective protocol. Biofilms viability after the treatments was compared to negative control. Data were compared by One-way ANOVA and post hoc Tukey (5%). The results demonstrate that 5 min exposure to CAP showed more effective antifungal effect on biofilms when compared to nystatin and amphotericin B. Additionally, it was detected that CAP showed similar (but smaller in magnitude) effects when applied in association with nystatin and amphotericin B at 40 µg/mL and 60 µg/mL. Therefore, it can be concluded that the application of CAP alone was more effective against C. albicans biofilms than in combination with conventional polyene antifungal agents

    Cold Atmospheric Plasma Jet as a Possible Adjuvant Therapy for Periodontal Disease

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    Due to the limitations of traditional periodontal therapies, and reported cold atmospheric plasma anti-inflammatory/antimicrobial activities, plasma could be an adjuvant therapy to periodontitis. Porphyromonas gingivalis was grown in blood agar. Standardized suspensions were plated on blood agar and plasma-treated for planktonic growth. For biofilm, dual-species Streptococcus gordonii + P. gingivalis biofilm grew for 48 h and then was plasma-treated. XTT assay and CFU counting were performed. Cytotoxicity was accessed immediately or after 24 h. Plasma was applied for 1, 3, 5 or 7 min. In vivo: Thirty C57BI/6 mice were subject to experimental periodontitis for 11 days. Immediately after ligature removal, animals were plasma-treated for 5 min once-Group P1 (n = 10); twice (Day 11 and 13)-Group P2 (n = 10); or not treated-Group S (n = 10). Mice were euthanized on day 15. Histological and microtomography analyses were performed. Significance level was 5%. Halo diameter increased proportionally to time of exposure contrary to CFU/mL counting. Mean/SD of fibroblasts viability did not vary among the groups. Plasma was able to inhibit P. gingivalis in planktonic culture and biofilm in a cell-safe manner. Moreover, plasma treatment in vivo, for 5 min, tends to improve periodontal tissue recovery, proportionally to the number of plasma applications
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