A novel flow cytometric protocol for assessment of yeast cell adhesion

Microbial adhesion is a field of recognized relevance and, as such, an impressive array of tools has been developed to understand its molecular mechanisms and ultimately for its quantification. Some of the major limitations found within these methodologies concern the incubation time, the small number of cells analyzed, and the operator's subjectivity. To overcome these aspects, we have developed a quantitative method to measure yeast cells' adhesion through flow cytometry. In this methodology, a suspension of yeast cells is mixed with green fluorescent polystyrene microspheres (uncoated or coated with host proteins). Within 2 h, an adhesion profile is obtained based on two parameters: percentage and cells-microsphere population's distribution pattern. This flow cytometry protocol represents a useful tool to quantify yeast adhesion to different substrata in a large scale, providing manifold data in a speedy and informative manner.

Efeitos tridimensionais no escoamento em torno de cilindros confinados

Mestrado em Engenharia Química

Computing the phase diagram of binary mixtures: A patchy particle case study

We investigate the phase behaviour of 2D mixtures of bi-functional and three-functional patchy particles and 3D mixtures of bi-functional and tetra-functional patchy particles by means of Monte Carlo simulations and Wertheim theory. We start by computing the critical points of the pure systems and then we investigate how the critical parameters change upon lowering the temperature. We extend the successive umbrella sampling method to mixtures to make it possible to extract information about the phase behaviour of the system at a fixed temperature for the whole range of densities and compositions of interest. (C) 2013 AIP Publishing LLC.

Magnetic and plagioclase linear fabric discrepancy in dykes: a new way to define the flow vector using magnetic foliation

In basaltic dykes the magnetic lineation K1 (maximum magnetic susceptibility axis) is generally taken to indicate the flow direction during solidification of the magma. This assumption was tested in Tertiary basaltic dykes from Greenland displaying independent evidence of subhorizontal flow. The digital processing of microphotographs from thin sections cut in (K1, K2) planes yields the preferred linear orientation of plagioclase, which apparently marks the magma flow lineation. In up to 60% of cases, the angular separation between K1 and the assumed flow direction is greater than 45degrees. This suggests that the uncorroborated use of magnetic lineations in dykes is risky. A simple geometrical method is proposed to infer the flow vector from AMS in dykes based solely on magnetic foliations.

Particle agglomeration study in rf silane plasmas: In situ study by polarization-sensitive laser light scattering

To determine self-consistently the time evolution of particle size and their number density in situ multi-angle polarization-sensitive laser light scattering was used. Cross-polarization intensities (incident and scattered light intensities with opposite polarization) measured at 135 degrees and ex situ transmission electronic microscopy analysis demonstrate the existence of nonspherical agglomerates during the early phase of agglomeration. Later in the particle time development both techniques reveal spherical particles again. The presence of strong cross-polarization intensities is accompanied by low-frequency instabilities detected on the scattered light intensities and plasma emission. It is found that the particle radius and particle number density during the agglomeration phase can be well described by the Brownian free molecule coagulation model. Application of this neutral particle coagulation model is justified by calculation of the particle charge whereby it is shown that particles of a few tens of nanometer can be considered as neutral under our experimental conditions. The measured particle dispersion can be well described by a Brownian free molecule coagulation model including a log-normal particle size distribution. (C) 1996 American Institute of Physics.

The influence of the blood pressure on the venous cerebral flow measured by magnetic susceptibility (SWI) technique

Susceptibility Weighted Image (SWI) is a Magnetic Resonance Imaging (MRI) technique that combines high spatial resolution and sensitivity to provide magnetic susceptibility differences between tissues. It is extremely sensitive to venous blood due to its iron content of deoxyhemoglobin. The aim of this study was to evaluate, through the SWI technique, the differences in cerebral venous vasculature according to the variation of blood pressure values. 20 subjects divided in two groups (10 hypertensive and 10 normotensive patients) underwent a MRI system with a Siemens® scanner model Avanto of 1.5T using a synergy head coil (4 channels). The obtained sequences were T1w, T2w-FLAIR, T2* and SWI. The value of Contrast-to-Noise Ratio (CNR) was assessed in MinIP (Minimum Intensity Projection) and Magnitude images, through drawing free hand ROIs in venous structures: Superior Sagittal Sinus (SSS) Internal Cerebral Vein (ICV) and Sinus Confluence (SC). The obtained values were presented in descriptive statistics-quartiles and extremes diagrams. The results were compared between groups. CNR shown higher values for normotensive group in MinIP (108.89 ± 6.907) to ICV; (238.73 ± 18.556) to SC and (239.384 ± 52.303) to SSS. These values are bigger than images from Hypertensive group about 46 a.u. in average. Comparing the results of Magnitude and MinIP images, there were obtained lower CNR values for the hypertensive group. There were differences in the CNR values between both groups, being these values more expressive in the large vessels-SSS and SC. The SWI is a potential technique to evaluate and characterize the blood pressure variation in the studied vessels adding a physiological perspective to MRI and giving a new approach to the radiological vascular studies.

A industria da cortiça e o seu potencial de inovação

Este trabalho teve como objectivo a avaliação da actual situação da indústria corticeira, o levantamento de eventuais possibilidades de inovação e o estudo de um caso promissor. Como caso promissor, decidiu-se estudar o efeito da pirólise nos resíduos de cortiça. A análise da situação actual da indústria corticeira aponta para a procura de novos produtos no sentido de alargar o mercado e promover um melhor escoamento deste recurso natural. Apesar de todos os esforços efectuados até ao momento, verifica-se que a indústria vinícola continua a ser o principal mercado da cortiça. O avanço da tecnologia tem permitido o desenvolvimento de novos produtos, alguns ainda em fase de desenvolvimento, e aponta para um potencial de inovação a vários níveis: ao nível do processo de transformação, no sentido da sua optimização; ao nível do desenvolvimento de novos produtos dado o potencial já demonstrado pela cortiça em desenvolvimentos recentes; ao nível da valorização de resíduos como, por exemplo, a consolidação de processo de recuperação de taninos da água de cozedura, a obtenção de suberina e poliois do pó e aparas de cortiça e a pirólise das aparas e pó de cortiça. Como estudo de caso, efectuou-se o estudo do efeito da pirólise em resíduos de cortiça natural, para se poder conhecer as características dos produtos obtidos bem como as condições óptimas de operação. Neste fase inicial e optou-se por se analisar as propriedades parte sólida de modo a saber as alterações sofridas durante a pirólise e estas podem apresentar uma mais-valia para o mercado corticeiro. Para efectuar o respectivo trabalho, recorreu-se a um forno pirolítico horizontal tipo Splitz e utilizou-se cortiça natural com granulometria entre 2,88 e 4,00mm. A pirólise foi realizada entre a gama de temperaturas de 400 e 900ºC e para duas rampas de aquecimento de 5ºC/min e 10ºC/min. O estudo experimental revela que na gama de temperaturas entre os 600 e 800ºC é onde a carbonização do resíduo está completa, sendo para essa mesma gama de temperaturas que se verifica, no resíduo carbonoso, um maior teor de carbono. Relativamente às rampas de aquecimento estas não apresentam efeitos significativos nas massas e teores de carbono no resíduo carbonoso final. Verificouse também, que o teor de hidrogénio diminui com o aumento da temperatura. Conclui-se que a pirólise consegue degradar os resíduos de cortiça levando à libertação de compostos que poderão ser uma mais-valia.

Flow amperometric determination of carbofuran and fenobucarb

A simple, rapid, and precise amperometric method for quantification of N-methylcarbamate pesticides in water samples and phytopharmaceuticals is presented. Carbofuran and fenobucarb are the target analytes. The method is developed in flow conditions providing the anodic oxidation of phenolic-based compounds formed after alkaline hydrolysis. Optimization of instrumental and chemical variables is presented. Under the optimal conditions, the amperometric signal is linear for carbofuran and fenobucarb concentrations over the range of 1.0*10-7 to 1.0*10-5 molL-1, with a detection limit of about 2 ngmL-1. The amperometric method is successfully applied to the analysis of spiked environmental waters and commercial formulations. The proposed method allows 90 samples to be analysed per hour, using 500 mL of sample, and producing wastewaters of low toxicity. The proposed method permits determinations at the mgL 1 level and offers advantages of simplicity, accuracy, precision, and applicability to coloured and turbid samples, and automation feasibility.

Environmental impact caused by fungal and particle contamination of Portuguese swine

Social concerns for environmental impact on air, water and soil pollution have grown along with the accelerated growth of pig production. This study intends to characterize air contamination caused by fungi and particles in swine production, and, additionally, to conclude about their eventual environmental impact. Fiftysix air samples of 50 litters were collected through impaction method. Air sampling and particle matter concentration were performed in indoor and also outdoor premises. Simultaneously, temperature and relative humidity were monitored according to the International Standard ISO 7726 – 1998. Aspergillus versicolor presents the highest indoor spore counts (>2000 CFU/m3) and the highest overall prevalence (40.5%), followed by Scopulariopsis brevicaulis (17.0%) and Penicillium sp. (14.1%). All the swine farms showed indoor fungal species different from the ones identified outdoors and the most frequent genera were also different from the ones indoors. The distribution of particle size showed the same tendency in all swine farms (higher concentration values in PM5 and PM10 sizes). Through the ratio between the indoor and outdoor values, it was possible to conclude that CFU/m3 and particles presented an eventual impact in outdoor measurements.

Sulfadiazine-potentiometric sensors for flow and batch determinations of sulfadiazine in drugs and biological fluids

New PVC membrane electrodes for the determination of sulfadiazine (SDZ) are presented. The electrodes are fabricated with conventional and tubular configurations with a graphite-based electrical contact, and no internal reference solution. The selective membranes consist of bis(triphenylphosphoranilidene)ammonium·SDZ (electrode A), tetraoctylammonium bromide (electrode B), or iron(II)-phthalocyanine (FePC) (electrode C) electroactive materials dispersed in a PVC matrix of o-nitrophenyl octyl ether (o-NPOE) plasticizer. The sensors A, B, and C displayed linear responses over the concentration ranges 1.0*10-2 – 1.0*10–5, 1.0*10–2 – 7.5*10–6, and 3.2*10–2 – 7.0* 10–6 mol l–1 (detection limits of 1.09, 2.04 and 0.87 mg ml–1) with anionic slopes of –57.3 ± 0.1, –46.7 ± 0.5, and –65.1 ± 0.2 mV decade–1, respectively. No effect from pH was observed within 4.0 – 5.5, 4.8 – 10, and 4.5 – 8, respectively, and good selectivity was found. The sensors were applied to the analysis of pharmaceuticals and biological fluids in steady state and in flow conditions.

New biomimetic sensors for the determination of tetracycline in biological samples: batch and flow mode operations

New potentiometric membrane sensors with cylindrical configuration for tetracycline (TC) are described based on the use of a newly designed molecularly imprinted polymer (MIP) material consisting of 2-vinylpyridine as a functional monomer in a plasticized PVC membrane. The sensor exhibited significantly enhanced response towards TC over the concentration range 1.59 10 5–1.0 10 3 mol L 1 at pH 3–5 with a lower detection limit of 1.29 10 5 mol L 1. The response was near-Nernstian, with average slopes of 63.9 mV decade 1. The effect of lipophilic salts and various foreign common ions were tested and were found to be negligible. The possibility of applying the proposed sensor to TC determination in spiked biological fluid samples was demonstrated.

Direct electroanalytical determination of fluvastatin in a pharmaceutical dosage form: batch and flow analysis

The reduction of luvastatin (FLV) at a hanging mercury-drop electrode (HMDE) was studied by square-wave adsorptive-stripping voltammetry (SWAdSV). FLV can be accumulated and reduced at the electrode, with a maximum peak current intensity at a potential of approximately 1.26V vs. AgCl=Ag, in an aqueous electrolyte solution of pH 5.25. The method shows linearity between peak current intensity and FLV concentration between 1.0 10 8 and 2.7 10 6 mol L 1. Limits of detection (LOD) and quantification (LOQ) were found to be 9.9 10 9 mol L 1 and 3.3 10 8 mol L 1, respectively. Furthermore, FLV oxidation at a glassy carbon electrode surface was used for its hydrodynamic monitoring by amperometric detection in a flow-injection system. The amperometric signal was linear with FLV concentration over the range 1.0 10 6 to 1.0 10 5 mol L 1, with an LOD of 2.4 10 7 mol L 1 and an LOQ of 8.0 10 7 mol L 1. A sample rate of 50 injections per hour was achieved. Both methods were validated and showed to be precise and accurate, being satisfactorily applied to the determination of FLV in a commercial pharmaceutical.

Flow injection electrochemical determination of apomorphine

Few analytical methods are currently available for determination of apomorphine, the active substance of a new oral formulation used in the treatment of erectile dysfunction. In this way a flow injection electrochemical method (FIA-EC) was developed for its quantification and applied to pharmaceutical dosage forms. Based in previous findings regarding the stability of apomorphine in borate buffer and after optimization of several analytical parameters a single channel flow injection manifold was set up that enables the determination of this drug over the concentration range of 3 to 16 µmol L-1 with a detection limit of 0.5 µmol L-1 at a sampling rateof 90 h-1. The simplicity and rapidity of the FIA-EC method used, its reproducibility and sensitivity make it suitable for quality control of pharmaceutical preparations of apomorphine intended for clinical use and research.

Citrate selective electrodes for the flow injection analysis of soft drinks, beers and pharmaceutical products

Aiming the establishment of simple and accurate readings of citric acid (CA) in complex samples, citrate (CIT) selective electrodes with tubular configuration and polymeric membranes plus a quaternary ammonium ion exchanger were constructed. Several selective membranes were prepared for this purpose, having distinct mediator solvents (with quite different polarities) and, in some cases, p-tert-octylphenol (TOP) as additive. The latter was used regarding a possible increase in selectivity. The general working characteristics of all prepared electrodes were evaluated in a low dispersion flow injection analysis (FIA) manifold by injecting 500µl of citrate standard solutions into an ionic strength (IS) adjuster carrier (10−2 mol l−1) flowing at 3ml min−1. Good potentiometric response, with an average slope and a repeatability of 61.9mV per decade and ±0.8%, respectively, resulted from selective membranes comprising additive and bis(2-ethylhexyl)sebacate (bEHS) as mediator solvent. The same membranes conducted as well to the best selectivity characteristics, assessed by the separated solutions method and for several chemical species, such as chloride, nitrate, ascorbate, glucose, fructose and sucrose. Pharmaceutical preparations, soft drinks and beers were analyzed under conditions that enabled simultaneous pH and ionic strength adjustment (pH = 3.2; ionic strength = 10−2 mol l−1), and the attained results agreed well with the used reference method (relative error < 4%). The above experimental conditions promoted a significant increase in sensitivity of the potentiometric response, with a supra-Nernstian slope of 80.2mV per decade, and allowed the analysis of about 90 samples per hour, with a relative standard deviation <1.0%.