Influência das espécies ativas na absorção de intersticiais durante a carbonitretação a plasma do TI

Physical-chemical properties of Ti are sensible to the presence of interstitial elements. In the case of thermochemical treatments plasma assisted, the influence of different active species is not still understood. In order to contribute for such knowledge, this work purposes a study of the role played by the active species atmosphere into the Ar N2 CH4 carbonitriding plasma. It was carried out a plasma diagnostic by OES (Optical Emission Spectroscopy) in the z Ar y N2 x CH4 plasma mixture, in which z, y and x indexes represent gas flow variable from 0 to 4 sccm (cm3/min). The diagnostic presents abrupt variations of emission intensities associated to the species in determined conditions. Therefore, they were selected in order to carry out the chemical treatment and then to investigate their influences. Commercial pure Ti disks were submitted to plasma carbonitriding process using pre-established conditions from the OES measurements while some parameters such as pressure and temperature were maintained constant. The concentration profiles of interstitial elements (C and N atoms) were determined by Resonant Nuclear Reaction Analysis (NRA) resulting in a depth profile plots. The reactions used were 15N(ρ,αγ)12C and 12C(α,α)12C. GIXRD (Grazing Incidence X-Ray Diffraction) analysis was used in order to identify the presence of phases on the surface. Micro-Raman spectroscopy was used in order to qualitatively study the carbon into the TiCxN1 structure. It has been verified which the density species effectively influences more the diffusion of particles into the Ti lattice and characteristics of the layer formed than the gas concentration. High intensity of N2 + (391,4 nm) and CH (387,1 nm) species promotes more diffusion of C and N. It was observed that Hα (656,3 nm) species acts like a catalyzer allowing a deeper diffusion of nitrogen and carbon into the titanium lattice.

Diagnóstico das espécies ativas do plasma usado em tratamentos termoquímicos do titânio

Plasma diagnostics by Optical Emission Spectroscopy were performed for electrical discharge in three gas mixture respecting the combinations z N2 y Ar x H2, z N2 y Ar x O2 e z N2 y Ar x CH4, in which the indexes z and y systematically vary from 1 to 4 and x varies from 0 to 4, every one has dimension SCCM, resulting in 80 combinations. From the all obtained spectrums, the species CH (387,1 nm), N2+ (391,4 nm), Hβ (486,1 nm), Hα (656,3 nm), Ar (750,4 nm), O (777,4 nm) e O (842,6 nm) were analyzed because of their abundance and importance on the kinetic of reaction from the plasma to surface, besides their high dependences on the gases flows. Particularly interesting z, y and x combinations were chosen in order to study the influence of active species on the surface modification during the thermochemical treatment. From the mixtures N2 Ar O2 e N2 Ar CH4 were chosen three peculiar proportions which presented luminous intensity profile with unexpected maximum or minimum values, denominated as plasma anomaly. Those plasma concentrations were utilized as atmosphere of titanium treatment maintaining constant the control parameters pressure and temperature. It has been verified a relation among luminous intensity associated to N2+ and roughness, nanohardness and O atoms diffusion into the crystalline lattice of treated titanium and it has been seen which those properties becomes more intense precisely in the higher points found in the optical profile associated to the N2+ specie. Those parameters were verified for the mixture which involved O2 gas. For the mixture which involves CH4 gas, the relation was determinate by roughness, number of nitrogen and carbon atoms diffused into the titanium structure which presented direct proportionality with the luminous intensity referent to the N2+ and CH. It has been yet studied the formation of TiCN phases on the surface which presented to be essentially directly proportional to the increasing of the CH specie and inversely proportional to the increasing of the specie N2+

Influência das espécies ativas na absorção de intersticiais durante a carbonitretação a plasma do TI

Physical-chemical properties of Ti are sensible to the presence of interstitial elements. In the case of thermochemical treatments plasma assisted, the influence of different active species is not still understood. In order to contribute for such knowledge, this work purposes a study of the role played by the active species atmosphere into the Ar N2 CH4 carbonitriding plasma. It was carried out a plasma diagnostic by OES (Optical Emission Spectroscopy) in the z Ar y N2 x CH4 plasma mixture, in which z, y and x indexes represent gas flow variable from 0 to 4 sccm (cm3/min). The diagnostic presents abrupt variations of emission intensities associated to the species in determined conditions. Therefore, they were selected in order to carry out the chemical treatment and then to investigate their influences. Commercial pure Ti disks were submitted to plasma carbonitriding process using pre-established conditions from the OES measurements while some parameters such as pressure and temperature were maintained constant. The concentration profiles of interstitial elements (C and N atoms) were determined by Resonant Nuclear Reaction Analysis (NRA) resulting in a depth profile plots. The reactions used were 15N(ρ,αγ)12C and 12C(α,α)12C. GIXRD (Grazing Incidence X-Ray Diffraction) analysis was used in order to identify the presence of phases on the surface. Micro-Raman spectroscopy was used in order to qualitatively study the carbon into the TiCxN1 structure. It has been verified which the density species effectively influences more the diffusion of particles into the Ti lattice and characteristics of the layer formed than the gas concentration. High intensity of N2 + (391,4 nm) and CH (387,1 nm) species promotes more diffusion of C and N. It was observed that Hα (656,3 nm) species acts like a catalyzer allowing a deeper diffusion of nitrogen and carbon into the titanium lattice.

Diagnóstico das espécies ativas do plasma usado em tratamentos termoquímicos do titânio

Plasma diagnostics by Optical Emission Spectroscopy were performed for electrical discharge in three gas mixture respecting the combinations z N2 y Ar x H2, z N2 y Ar x O2 e z N2 y Ar x CH4, in which the indexes z and y systematically vary from 1 to 4 and x varies from 0 to 4, every one has dimension SCCM, resulting in 80 combinations. From the all obtained spectrums, the species CH (387,1 nm), N2+ (391,4 nm), Hβ (486,1 nm), Hα (656,3 nm), Ar (750,4 nm), O (777,4 nm) e O (842,6 nm) were analyzed because of their abundance and importance on the kinetic of reaction from the plasma to surface, besides their high dependences on the gases flows. Particularly interesting z, y and x combinations were chosen in order to study the influence of active species on the surface modification during the thermochemical treatment. From the mixtures N2 Ar O2 e N2 Ar CH4 were chosen three peculiar proportions which presented luminous intensity profile with unexpected maximum or minimum values, denominated as plasma anomaly. Those plasma concentrations were utilized as atmosphere of titanium treatment maintaining constant the control parameters pressure and temperature. It has been verified a relation among luminous intensity associated to N2+ and roughness, nanohardness and O atoms diffusion into the crystalline lattice of treated titanium and it has been seen which those properties becomes more intense precisely in the higher points found in the optical profile associated to the N2+ specie. Those parameters were verified for the mixture which involved O2 gas. For the mixture which involves CH4 gas, the relation was determinate by roughness, number of nitrogen and carbon atoms diffused into the titanium structure which presented direct proportionality with the luminous intensity referent to the N2+ and CH. It has been yet studied the formation of TiCN phases on the surface which presented to be essentially directly proportional to the increasing of the CH specie and inversely proportional to the increasing of the specie N2+

COMBUSTION INITIATION BY ELECTRICAL-DISCHARGE-INDUCED PLASMA IN LEAN AND DILUTE METHANE-AIR MIXTURE: EXPERIMENTAL AND MODELING INVESTIGATION

This dissertation represents experimental and numerical investigations of combustion initiation trigged by electrical-discharge-induced plasma within lean and dilute methane air mixture. This research topic is of interest due to its potential to further promote the understanding and prediction of spark ignition quality in high efficiency gasoline engines, which operate with lean and dilute fuel-air mixture. It is specified in this dissertation that the plasma to flame transition is the key process during the spark ignition event, yet it is also the most complicated and least understood procedure. Therefore the investigation is focused on the overlapped periods when plasma and flame both exists in the system. Experimental study is divided into two parts. Experiments in Part I focuses on the flame kernel resulting from the electrical discharge. A number of external factors are found to affect the growth of the flame kernel, resulting in complex correlations between discharge and flame kernel. Heat loss from the flame kernel to code ambient is found to be a dominant factor that quenches the flame kernel. Another experimental focus is on the plasma channel. Electrical discharges into gases induce intense and highly transient plasma. Detailed observation of the size and contents of the discharge-induced plasma channel is performed. Given the complex correlation and the multi-discipline physical/chemical processes involved in the plasma-flame transition, the modeling principle is taken to reproduce detailed transitions numerically with minimum analytical assumptions. Detailed measurement obtained from experimental work facilitates the more accurate description of initial reaction conditions. The novel and unique spark source considering both energy and species deposition is defined in a justified manner, which is the key feature of this Ignition by Plasma (IBP) model. The results of numerical simulation are intuitive and the potential of numerical simulation to better resolve the complex spark ignition mechanism is presented. Meanwhile, imperfections of the IBP model and numerical simulation have been specified and will address future attentions.

Microbial Decontamination Study of Medicinal Plants by Plasma Treatment

In the present work the microbial decontamination of some medicinal plants by plasma treatment using oxygen gas or a mixture of oxygen and hydrogen peroxide was investigated. The efficiency of the decontamination process was analyzed by the count of heterotropic microorganisms and pathogenic research. The results showed a reduction in the microorganism number such as 3 and 4 logarithmic cycles for ginkgo and artichoke, while it was not efficient for samples containing hard and thick cells, and mucilage, such as guarana and chamomile.

HPLC-UV determination of metformin in human plasma for application in pharmacokinetics and bioequivalence studies

In this study, a simple, rapid and sensitive HPLC method with UV detection is described for determination of metformin in plasma samples from bioequivalence assays. Sample preparation was accomplished through protein precipitation with acetonitrile and chromatographic separation was performed on a reversed-phase phenyl column at 40 degrees C. Mobile phase consisted of a mixture of phosphate buffer and acetonitrile at flow rate of 1.0 ml/min. Wavelength was set at 236 nm. The method was applied to a bioequivalence study of two drug products containing metformin, and allowed determination of metformin at low concentrations with a higher throughput than previously described methods. (c) 2007 Elsevier B.V. All rights reserved.

Sterilization by pure oxygen plasma and by oxygen-hydrogen peroxide plasma: An efficacy study

Plasma is an innovative sterilization method characterized by a low toxicity to operators and patients, and also by its operation at temperatures close to room temperatures. The use of different parameters for this method of sterilization and the corresponding results were analyzed in this study. A low-pressure inductive discharge was used to study the plasma sterilization processes. Oxygen and a mixture of oxygen and hydrogen peroxide were used as plasma source gases. The efficacy of the processes using different combinations of parameters such as plasma-generation method, type of gas, pressure, gas flow rate, temperature, power, and exposure time was evaluated. Two phases were developed for the processes, one using pure oxygen and the other a mixture of gases. Bacillus subtilis var. niger ATCC 9372 (Bacillus atrophaeus) spores inoculated on glass coverslips were used as biological indicators to evaluate the efficacy of the processes. All cycles were carried out in triplicate for different sublethal exposure times to calculate the D value by the enumeration method. The pour-plate technique was used to quantify the spores. D values of between 8 and 3 min were obtained. Best results were achieved at high power levels (350 and 40oW) using pure oxygen, showing that plasma sterilization is a promising alternative to other sterilization methods. (c) 2007 Elsevier B.V. All rights reserved.

LC-MS-MS Identification and Determination of the Flavone-C-Glucoside Vicenin-2 in Rat Plasma Samples Following Intraperitoneal Administration of Lychnophora Extract

The flavone C-glucoside, vicenin-2, in semi-purified extracts of the leaves of Lychnophora ericoides was quantified in rat plasma samples using a method based on reversed-phase high performance liquid chromatography coupled to tandem mass spectrometry. Vicenin-2 was analyzed on a LiChrospher (R) RP18 column using an isocratic mobile phase consisting of a mixture of methanol: water (30:70, v/v) plus 2.0% glacial acetic acid at a flow rate of 0.8 mL min(-1). Genistein was used as internal standard. The mass spectrometer was operated in positive ionization mode and analytes were quantified by multiple reaction monitoring at m/z 595 > 457 for vicenin-2 and m/z 271 > 153 for internal standard. Prior to the analysis, each rat plasma sample was acidified with 200 mu L of 50 mmol L(-1) acetic acid solution and extracted by solid-phase extraction using a C18 cartridge. The absolute recoveries were reproducible and the coefficients of variation values were lower than 5.2%. The method was linear over the 12.5 - 1500 ng mL(-1) concentration range and the quantification limit was 12.5 ng mL(-1). Within-day and between-day assay precision and accuracy were studied at three concentration levels (40, 400 and 800 ng mL(-1)) and were lower than 15%. The developed and validated method seems to be suitable for analysis of vicenin-2 in plasma samples obtained from rats that receive a single i.p. dose of 200 mg kg(-1) vicenin-2 extract.

Enantioselective analysis of praziquantel and trans-4-hydroxypraziquantel in human plasma by chiral LC-MS/MS: Application to pharmacokinetics

A simple enantioselective method for the determination of praziquantel (PZQ) and trans-4-hydroxypraziquantel (4-OHPZQ) in human plasma was developed and validated by high-performance liquid chromatography/mass spectrometry. The plasma samples were prepared by liquid-liquid extraction using a mixture of methyl-tert-butylether/dichloromethane (2:1, v/v) as extraction solvent. The direct resolution of PZQ and 4-OHPZQ enantiomers was performed on a Chiralpak AD column using hexane-isopropanol (75:25, v/v) as the mobile phase. Diazepam was used as internal standard. The method described here is simple and reproducible. The quantitation limit of 1.25 ng/ml for each PZQ enantiomer and of 12.5 ng/ml for each 4-OHPZQ enantiomer permits the use of the method in studies investigating the kinetic disposition of a single dose of 1.5g racemic PZQ. Enantioselectivity in the kinetic disposition of PZQ and 4-OHPZQ was observed in the clinical study. with the demonstration of a higher proportion of the (+)-(S)-PZQ and (-)-(R)-4-OHPZQ enantiomers in plasma. (C) 2009 Elsevier B.V. All rights reserved.

Simultaneous Analysis of Tramadol, O-Desmethyltramadol, and N-Desmethyltramadol Enantiomers in Rat Plasma by High-Performance Liquid Chromatography-Tandem Mass Spectrometry: Application to Pharmacokinetics

Tramadol (T) is available as a racemic mixture of (+)-trans-T and (-)-trans-T. The main metabolic pathways are O-demethylation and N-demethylation, producing trans-O-desmethyltramadol (M1) and trans-N-desmethyltramadol (M2) enantiomers, respectively. The analgesic effect of T is related to the opioid activity of (+)-trans-T and (+)-M1 and to the monoaminergic action of (+/-)-trans-T. This is the first study using tandem mass spectrometry as a detection system for the simultaneous analysis of trans-T, M1, and M2 enantiomers. The analytes were resolved on a Chiralpak (R) AD column using hexane: ethanol (95.5:4.5, v/v) plus 0.1% diethylamine as the mobile phase. The quantitation limits were 0.5 ng/ml for trans-T and M1 and 0.1 ng/ml for M2. The method developed and validated here was applied to a pharmacokinetic study in rats. Male Wistar rats (n = 6 at each time point) received a single oral dose of 20 mg/kg racemic trans-T. Blood samples were collected up to 12 h after drug administration. The kinetic disposition of trans-T and M2 was enantioselective (AUC((+)/(-)) ratio = 4.16 and 6.36, respectively). The direction and extent of enantioselectivity in the pharmacokinetics of trans-T and M2 in rats were comparable to data previously reported for healthy volunteers, suggesting that rats are a suitable model for enantioselective studies of trans-T pharmacokinetics. Chirality 23: 287-293, 2011. (C) 2010 Wiley-Liss, Inc.

Determination of Cyclophosphamide Enantiomers in Plasma by LC-MS/MS: Application to Pharmacokinetics in Breast Cancer and Lupus Nephritis Patients

This article describes the enantioseleclive analysis of cyclophosphamide (CPA) in human plasma using LC-MS/MS. CPA enantiomers were extracted from plasma using a mixture of ethyl acetate and chloroform (75:25, v/v). The enantiomers were separated on a Chiralcel(R) OD-R column, with the mobile phase consisting of a mixture of acetonitrile and water (75:25, v/v) plus 0.2% formic acid. The protonaled ions and their respective product ions were monitored using two functions, 261 > 141 for CPA enantiomers and 189 > 104 for the internal standard (antipyrine). Recovery rates were higher than 95% and the quantification limit was 2.5-ng/ml plasma for both enantiomers. The coefficients of variation and the relative errors obtained for the validation of intra- and interassay precision and accuracy were less than 10%. The method was applied for the investigation of the enantioselective pharmacokinetics of CPA in a lupus nephritis patient treated with 1 g CPA infused over 2 h and in a breast cancer patient treated with 0.9 g infused over 1 h. No stereoselectivity in the pharmacokinetic parameters was observed for either patient. Clearance values of 2.63 and 2.93 l/h and of 3.36 and 3.61 l/h for (-)-(S) and (+)-(R)-CPA were obtained for the breast cancer and lupus nephritis patient., respectively. Chirality 21:383-389, 2009. (C) 2008 Wiley-Liss, Inc.

Stereoselective Analysis of Labetalol in Human Plasma by LC-MS/MS: Application to Pharmacokinetics

Labetalol is clinically available as a mixture of two racemates (four stereoisomers). The stereoisomer (R,R) has as main activity the beta(1)-antagonism and the stereoisomer (S,R) is highly selective for the alpha(1) adrenoceptor and is responsible for most of the alpha-blocker activity. In the present investigation, a method for the analysis of labetalol stereoisomers in human plasma was developed and applied to pharmacokinetic studies. Plasma samples (0.5 ml) were extracted with methyl tert-butyl ether at pH 9.5. The four labetalol stereoisomers were analyzed by LC-MS/MS on a Chirobiotic (R) V column using a mobile phase consisting of methanol, acetic acid, and diethylamine, with a recovery of more than 90% for all four. The quantitation limit was 0.5 ng/ml and linearity was observed at 250 ng/ml plasma for each stereoisomer. Studies of precision and accuracy presented coefficients of variation and percentage inaccuracy of less than 15%, indicating that the method is precise and accurate. The method was applied to the study of the kinetic disposition of labetalol over a period of 12 h after oral administration of a single 100 mg dose to a hypertensive pregnant woman. The clinical study revealed stereoselectivity in the pharmacokinetics of labetalol, with a lower plasma proportion for the active stereoisomers (R,R)-labetalol and (S,R)-labetalol. The stereoselectivity observed after oral administration is due to the hepatic metabolism and the first pass effect, with an AUC((R,R))/AUC((S,S)) ratio of 0.5. Chirality 21:738-744, 2009. (C) 2008 Wiley-Liss, Inc.

Treatment With a Growth Factor-Protein Mixture Inhibits Formation of Mineralized Nodules in Osteogenic Cell Cultures Grown on Titanium

Despite wide clinical application, the efficacy of platelet-rich plasma (PRP) for repairing bone defects and enhancing osseointegration of metal implants is still subject of debate. This study aimed to evaluate the effects of a well-defined PRP-like mixture containing platelet-derived growth factor-BB, transforming growth factor (TGF)-beta 1, TGF-beta 2, albumin, fibronectin, and thrombospondin [growth factors (GFs) + proteins] on the development of the osteogenic phenotype on titanium (Ti) in vitro. Human alveolar bone-derived osteoblastic cells were subcultured on Ti discs and exposed during the first 7 days to osteogenic medium supplemented with GFs + proteins and to osteogenic medium alone thereafter up to 14 days. Control cultures were exposed to only osteogenic medium. Dose-response experiments were carried out using rat primary calvarial cells exposed to GFs + proteins and 1:10 or 1:100 dilutions of the mixture. Treated human-derived cell cultures exhibited a significantly higher number of cycling cells at days 1 and 4 and of total cells at days 4 and 7, significantly reduced alkaline phosphatase (ALP) activity at days 4, 7, and 10, and no Alizarin red-stained areas (calcium deposits) at day 14, indicating an impairment in osteoblast differentiation. Although the 1:10 and 1:100 dilutions of the mixture restored the proliferative activity of rat-derived osteogenic cells to control levels and promoted a significant increase in ALP activity at day 10 compared with GFs + proteins, mineralized nodule formation was only observed with the 1:100 dilution (similar to 50% of the control). These results showed that a PRP-like protein mixture inhibits development of the osteogenic phenotype in both human and rat osteoblastic cell cultures grown on Ti. (J Histochem Cytochem 57:265-276, 2009)

Effects of a mixture of growth factors and proteins on the development of the osteogenic phenotype in human alveolar bone cell cultures

Strategies to promote bone repair have included exposure of cells to growth factor (GF) preparations from blood that generally include proteins as part of a complex mixture. This study aimed to evaluate the effects of such a mixture on different parameters of the development of the osteogenic phenotype in vitro. Osteoblastic cells were obtained by enzymatic digestion of human alveolar bone and cultured under standard osteogenic conditions until subconfluence. They were subcultured on Thermanox coverslips up to 14 days. Treated cultures were exposed during the first 7 days to osteogenic medium supplemented with a GFs + proteins mixture containing the major components found in platelet extracts [plate I et-derived growth factor-BB, transforming growth factor (TGF)-beta 1, TGF-beta 2, albumin, fibronectin, and thrombospondin] and to osteogenic medium alone thereafter. Control cultures were exposed only to the osteogenic medium. Treated cultures exhibited a significantly higher number of adherent cells from day 4 onward and of cycling cells at days 1 and 4, weak alkaline phosphatase (ALP) labeling, and significantly decreased levels of ALP activity and mRNA expression. At day 14, no Alizarin red-stained nodular areas were detected in cultures treated with GFs + proteins. Results were confirmed in the rat calvaria-derived osteogenic cell culture model. The addition of bone morphogenetic protein 7 or growth and differentiation factor 5 to treated cultures upregulated Runx2 and ALP mRNA expression, but surprisingly, ALP activity was not restored. These results showed that a mixture of GFs + proteins affects the development of the osteogenic phenotype both in human and rat cultures, leading to an increase in the number of cells, but expressed a less differentiated state.