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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Jatobà (Hymenaea courbaril l.) has an extensive history of use by natives of tropical forests, its fruits are composed of essential oils, tannins, bitter substances, resinous materials and pectic, starch and sugars. The objective of this study was to evaluate the antimicrobial activity of the essential oil extracted from the peel of fruits of Hymenaea courbaril l. (OEHc) and its mechanism of action on OSSA reference strains S. aureus (S. aureus ATCC 6538P and S. aureus 14458). For the evaluation of antimicrobial activity antimicrobial potential were determined from OEHc Inhibitory Concentrations (MIC) and Minimum Lethal (CLM) from OEHc, the effect of time of exposure to OEHc, OXA and OEHc associations-OXA, OEHc modulator effect on activity of antibiotics (ATB) for clinical use, and the OEHc action on exponential and stationary phases of growth and in growth stationary phase in the presence of chloramphenicol. The OEHc action mechanism was verified by crystal violet uptake, release of genetic material, determination of potassium ion efflux and for assessing the microbial morphology by atomic force microscopy. It was also evaluated the action of sub-inibitÃrias concentrations of OEHc on expression of virulence factors (catalase, coagulase, DNAse, lipase, and hemolysin) and stability of antimicrobial activity of OEHc at different pH. OEHc inhibited the growth of S. aureus strains ATCC 6538P (CIM = CLM = 2.5 mg/mL) and S. aureus ATCC 14458 (CIM = 2.5 mg/mL; CLM = 5 mg/mL). The CLM from OEHc was able to derail the OSSA strains tested in 8 (S. aureus ATCC 6538P) and 24 hours (S. aureus ATCC 14458) and the CIM inhibited the growth of S. aureus ATCC 14458 until 48 hours of exposure. The modulatory action of the antibiotic activity of OEHc clinical use ranged with the ATB and with the strain tested. OEHc associations-OXA tested was found a predominance of synergistic effects and indifferent to the OSSA strains tested. The OEHc was able to reduce the number of viable cells at all stages microbial growth. Its greater efficiency in the presence of CLO suggests a mechanism of action independent of the cellular metabolism. The OEHc was able to promote the increased uptake of crystal violet, the release of genetic material and the efflux of potassium ions, causing also changes in bacterial morphology, suggesting that its target of action is the cell wrap. However, the inhibition of the expression of virulence factors can indicate the participation of other targets on OEHc action, as the synthesis of macromolecules. The antimicrobial activity of OEHc about strains OSSA is potentized in alkaline pH. The results show that the OEHc has a good antimicrobial activity on the species Gram-positive S. aureus, with action mechanisms mediated by the occurrence of damage in microbial wrap with loss of intracellular material and inhibition of the synthesis of macromolecules, revealing its synergistic modulator effect when associated with oxacillin and other antibiotics of clinical use. / O Jatobà (Hymenaea courbaril L.) possui um amplo histÃrico de utilizaÃÃo pelos indÃgenas de florestas tropicais, seus frutos sÃo compostos por Ãleos essenciais, taninos, substÃncias amargas, matÃrias resinosas e pÃcticas, amido e aÃÃcares. O objetivo deste estudo foi avaliar a atividade antimicrobiana do Ãleo essencial extraÃdo da casca de frutos da Hymenaea courbaril L. (OEHc) e o seu mecanismo de aÃÃo sobre cepas OSSA de referÃncia de S. aureus (S. aureus ATCC 6538P e S. aureus 14458). Para a avaliaÃÃo da atividade antimicrobiana foram determinados o potencial antimicrobiano do OEHc, as ConcentraÃÃes InibitÃria (CIM) e Letal MÃnimas (CLM) do OEHc, o efeito do tempo de exposiÃÃo ao OEHc, a OXA e as associaÃÃes OEHc-OXA, o efeito modulador do OEHc na atividade de antibiÃticos (ATB) de uso clÃnico, e a aÃÃo do OEHc na fases de crescimento exponencial e estacionÃrio e na fase de crescimento estacionÃrio na presenÃa de cloranfenicol. O mecanismo de aÃÃo do OEHc foi verificado por captaÃÃo do cristal violeta, liberaÃÃo de material genÃtico, dosagem do efluxo de Ãons potÃssio e pela avaliaÃÃo da morfologia microbiana por microscopia de forca atÃmica. TambÃm foi avaliada a aÃÃo de concentraÃÃes sub-inibitÃrias do OEHc na expressÃo de fatores de virulÃncia (catalase, coagulase, hemolisina, lipase e DNAse) e a estabilidade da atividade antimicrobiana do OEHc em diferentes pH. OEHc inibiu o crescimento das cepas de S. aureus ATCC 6538P (CIM = CLM = 2,5 mg/mL) e S. aureus ATCC 14458 (CIM = 2,5 mg/mL; CLM = 5 mg/mL). A CLM do OEHc foi capaz de inviabilizar as cepas OSSA testadas em 8 horas (S. aureus ATCC 6538P) e 24 horas (S. aureus ATCC 14458) e a CIM inibiu o crescimento de S. aureus ATCC 14458 atà 48h de exposiÃÃo. A aÃÃo moduladora do OEHc na atividade de antibiÃticos de uso clÃnico variou com o ATB e com a cepa testada. Para as associaÃÃes OEHc-OXA testadas foi encontrada uma predominÃncia de efeitos sinÃrgicos e indiferentes para as cepas OSSA testadas. O OEHc foi capaz de reduzir o nÃmero de cÃlulas viÃveis em todas as fases crescimento microbiano. Sua maior eficiÃncia na presenÃa de CLO sugere um mecanismo de aÃÃo independente do metabolismo celular. O OEHc foi capaz de promover o aumento da captaÃÃo do cristal violeta, da liberaÃÃo de material genÃtico e do efluxo de Ãons potÃssio, provocando tambÃm alteraÃÃes na morfologia bacteriana, sugerindo que seu alvo de aÃÃo seja o envoltÃrio celular. No entanto, a inibiÃÃo da expressÃo de fatores de virulÃncia pode indicar a participaÃÃo de outros alvos na aÃÃo do OEHc, como a sÃntese de macromolÃculas. A atividade antimicrobiana do OEHc sobre cepas OSSA à potencializada em pH alcalino. Os resultados encontrados mostram que o OEHc possui uma boa atividade antimicrobiana sobre a espÃcie Gram-positivo S. aureus, com mecanismos de aÃÃo mediados pela ocorrÃncia de danos no envoltÃrio microbiano com perda de material intracelular e inibiÃÃo da sÃntese de macromolÃculas, revelando seu efeito modulador sinÃrgico quando associados a oxacilina e outros antibiÃticos de uso clÃnico.

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No description available.

The development of more fundamental knowledge of the tribology of the cam and follower mechanism calls for a more comprehensive theoretical analysis and experimental investigation than has been previously reported. A mixed lubrication analysis has been applied to the problem to give an estimation of the nominal minimum film thickness and friction force associated with the contact in such mechanisms. The analysis showed that the roughness height and the distribution of the roughness between the two contacting surfaces had important effects on the lubrication performance of the contact. A full numerical transient EHL analysis was carried out allowing the normal velocity to vary along the conjunction. This revealed that local squeeze film velocity provided an increased damping effect which contributed to the persistence of the minimum film thicknesses in the two zero entraining velocity regions. An approximate technique for determining the minimum film thickness of a transient EHD line contact associated with rough surfaces was developed and applied to the mixed lubrication analysis of a four-power polynomial cam and non-rotating flat faced follower arrangement. The results demonstrated that under certain circumstances mixed lubrication predominated in the conjunction of the cam and follower with the surfaces being separated by an EHL film on the cam flanks. Existing experimental apparatus was improved to test the effects of altering the bulk temperature and camshaft rotational speed by measuring the friction torque and electrical resistivity across the contact. By adopting advanced techniques for data sampling and processing the instantaneous friction torque was successfully obtained with the camshaft rotational speed exceeding (2000 rpm). The wear characteristics were also examined. The bulk temperature showed a mild effect on the wear characteristics of the cam and follower as it was increased from (75° C) to (105° C), whilst, a substantial influence was found as the temperature was further increased to (120°C). Increasing the bulk temperature caused an increase in both the friction torque and power loss o f the valve train, but this increase was not considerable. Based upon the theoretical analyses and experimental observations, a theoretical model for evaluating the tribological performance of the valve train was developed. A multi-aspect comparison between theoretical and experimental results was made. The excellent agreement between theoretical and experimental results showed that the model provided a reliable prediction o f the tribological characteristics of the cam/flat faced follower. Three critical portions of the cycle could be identified — one over the cam nose and two in the vicinity of the zero entraining velocity regions. The minimum separation between the cam and follower occurred near the falling flank of the cam.

Lubricating oils subjected to the operating conditions in an automobile engine degrade by many routes. The most important of these routes is oxidation, which at room temperature and atmospheric pressure is almost immeasurably slow. The performance of a new oil formulation is ultimately assessed by the use of a standard engine test. Such engine tests are very expensive and time consuming, which makes the use of an initial screening test a necessity. Screening tests are used to eliminate any oils that would fail the full engine test, thereby saving considerable amounts of time and money. In the present research the concern has been to compare two screening tests for the analysis of antioxidants based on differential scanning calorimetry (DSQ and cyclic voltammetry (CV). The two techniques have been applied to the analysis the of the antioxidants, dioctyldiphenyl amine (DODPA) and Topanol '0' in three base oils. DSC is a commonly used technique in which the time to oxidation is measured when the sample is maintained at a constant temperature in a high pressure atmosphere of oxygen. CV has not been used widely to examine lubricating oils and the present work has included the development of reliable experimental techniques for the two types of antioxidants. The results obtained for both freshly prepared oil formulations and those partially oxidised clearly reveal the different nature of the tests. DSC is a non specific technique with respect to the antioxidant and leads to an indication of the overall oxidative stability of the oil blend, whereas the voltammogram obtained in CV is specific to certain groups of antioxidant. The value of the current flowing through the circuit reaches a maximum value at a potential specific to and dependant on the concentration of the additive being analysed. A kinetic analysis of an antioxidant by CV leads to information about the diffusion coefficient of the molecule and the rate of electron transfer at the electrode surface. It was found that the electrochemically oxidised species of the amine antioxidant underwent a chemical reaction to produce an electro-inactive species over the potential range studied. The kinetic data for this reaction was obtained but their relevance to the oxidation of an oil in an engine environment is doubtful, whereas the results obtained by DSC are probably more applicable. The kinetic data obtained from isothermal DSC curves were employed in a combined kinetic scheme to model the shapes of DSC curves.

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