Flow in the nose region and annular film around a Taylor bubble rising through vertical columns of stagnant and flowing Newtonian liquids

The flow in the nose region and in the annular film around individual Taylor bubbles rising through stagnant and co-current vertical columns of liquid were studied, employing particle image velocimetry (PIV) and pulsed shadowgraphy techniques (PST) at the same time. The combined techniques enabled simultaneous determination of the bubble shape and the velocity profiles in the liquid film. Experiments were performed with water and aqueous glycerol solutions in a wide range of viscosities , in an acrylic column of 32 mm ID.Values for the distance ahead of the nose in which the flow is disturbed by the presence of the bubble are presented for the conditions studied. The bubble shapes in the nose region are compared with Dumitrescu's shape for potential flow. The velocity profiles show that after the nose region the liquid begins to accelerate downwards, and at a certain distance from the bubble nose the velocity profile and the liquid film thickness stabilise. The liquid film acquires characteristics of a free-falling film. Values of the developing length and film thickness are reported for the experimental conditions studied. Average velocity profiles in the fully developed film are also presented. A critical Reynolds number of around 80 (based on the mean absolute velocity in the liquid film and on the film thickness) is reported for the transition from laminar to turbulent regime. Shear stress profiles (in the fully developed film) are also provided.The data reported are relevant for the validation of numerical codes in slug flow.     

Unbreakable solid-phase microextraction fibers obtained by sol-gel deposition on titanium wire

Solid-phase microextraction commercial fibers present a few drawbacks such as relatively low recommended operating temperature, instability and swelling in organic solvents, breakage of the fiber, stripping of coatings, and bending of the needle. Some of these problems have been obviated by covalent bonding of the polymer phase to the fused-silica substrate by sol-gel, but the easy breakage of the fiber remains a problem. In the present work, the known occurrence of titanol groups at the surface of titanium wire was exploited to produce sol-gel fibers supported on this unbreakable substrate. Scanning electron microscopy analysis revealed the film formation on titanium wire surface while temperature and solvent stability as well as durability tests showed that the sol-gel film was tightly attached to the substrate, thus suggesting covalent bonding. The use of this type of fiber is currently generalized in our laboratory without any breakage or stripping out incidents up to the moment.     

Evaluation of the influences of solution path length and additives concentrations on the solar photo-Fenton degradation of 4-chlorophenol using multivariate analysis

This study reports the photodegradation of 4-chlorophenol (4-CP) in aqueous solution by the photo-Fenton process using solar irradiation. The influence of solution path length, and Fe(NO(3))(3) and H(2)O(2) concentrations on the degradation of 4-CP is evaluated by response surface methodology. The degradation process was monitored by the removal of total organic carbon (TOC) and the release of chloride ion. The results showed a very important role of iron concentration either for TOC removal or dechlorination. On the other hand, a negative effect of increasing solution path length on mineralization was observed, which can be compensated by increasing the iron concentration. This permits an adjustment of the iron concentration according to the irradiation exposure area and path length (depth of a tank reactor). Under optimum conditions of 1.5 mM Fe(NO(3))(3), 20.0 mM H(2)O(2) and 4.5 cm solution path length, 17 min irradiation under solar light were sufficient to reduce a 72 mg CL(-1) solution of 4-CP by 91%.     

In vivo antitumoural activity and composition of an oil extract of Brazilian propolis

The present study aimed to evaluate in vivo and in vitro the antitumoural activity of a propolis extract obtained with edible vegetable oil and its fractions and also to investigate its chemical composition by LC–MS and LC–MS/MS. To evaluate the toxicological aspects related to the propolis extract treatment, hematological, biochemical, histopathological and morphological analyses of treated animals were performed. All propolis extracts showed an in vivo antitumour activity in the experimental model with a moderate toxicity effect at experimental exposure levels. The oil extract was as effective as the ethanolic extract at inhibiting tumour growth. In vitro assays showed that the whole oil extract produced better inhibition of tumour cells than its fractions. LC–MS and LC–MS/MS identified four phenolic acids and three flavonoids. The anticancer potential of the oil extract of propolis has been demonstrated and the edible vegetable oil was shown as an attractive alternative solvent to extract bioactive natural propolis components.     

Antibiofilm activity of the essential oil of citronella (Cymbopogon nardus) and its major component,geraniol, on the bacterial biofilms of Staphylococcus aureus

Food Science and Biotechnology - Medicinal plants with antimicrobial action have been investigated for uses against biofilms, among which, Cymbopogon nardus, citronella, stands out as a promising...     

ALATOP-RIA in the screening of atopy in a non Caucasian population

ALATOP is an "in vitro" radioimmunoassay screening test for atopy, previously validated in a caucasian population. The aim of the study was to assess the usefulness of a screening test of atopy in a non caucasian population. We select a non caucasian population (n = 208), from hospital immunoallergy consultations, Cape Verde Republic (Africa). It was determined the sensitivity, specificity and predictive values comparing with skin prick tests (SPT) results for the 208 patients, and with clinical data (Clin) in 115 patients. It was also determined the levels of total IgE, done by IRMA. RESULTS: Using different corrections factors, 0.85 gives the best results: ALATOP/SPT-Sensitivity-88.5% +/- 4.34; Specificity-73.8% +/- 8.41; Positive predictive value-66.9%; Negative predictive value-91.4%; Efficiency of the test-79.3%. ALATOP/CLIN-Sensitivity-95.2% +/- 3.89; Specificity-71.2% +/- 12.07; Positive predictive value-65.6%; Negative predictive value-96.2%; Efficiency of the test-80.0%. The mean values of total IgE were-406 IU/ml. CONCLUSIONS: The mean value of total IgE was significantly increased even in the ALATOP-/SPT-not saw in caucasian populations. The use of a different correction factor (0.85) for ALATOP, optimize the test, showing a good negative predictive value, but raises the question of adapted compositions of screening tests for different populations.     

A thin PANI and carrageenan–gold nanoparticle film on a flexible gold electrode as a conductive and low-cost platform for sensing in a physiological environment

In this work, we report the production of a layer-by-layer (LbL) film of gold nanoparticles stabilized with carrageenan (carr-AuNPs) interspersed with a conductive polyaniline (PANI) layer. Conventionally, PANI has poor electroactivity in physiological buffers, limiting its using in electrochemical biosensors. The films were prepared on low cost and easy to manufacture flexible gold electrodes (FEAu). Two adsorption sequences were tested for production of the films—PANI/carr-AuNP and carr-AuNP/PANI. The gold nanoparticle size and colloidal stability were characterized. The films were characterized by cyclic voltammetry, UV–visible spectroscopy and atomic force microscopy. The results showed the synergistic effects of the carr-AuNPs (120 nm) and PANI, which improved both the electrochemical response and the stability of the conductive polymer in physiological medium by three times. The presence of the carr-AuNPs in the film caused a significant increase in roughness of the FEAu-modified electrode compared to that of an unmodified electrode, resulting in an increased active electrode area. Studies of film growth by UV–Vis spectroscopy indicated that the deposition mechanisms of both films involved an auto-regulating adsorption process, with the same amount of material adsorbed in each coating step. The PANI/carr-AUNP film showed considerable improvement in stability and conductivity compared to PANI-only films in the physiological environment, which confers advantages for use as a biosensor.     

Analytical study of a solution-processed diode based on ZnO nanoparticles using multi-walled carbon nanotubes as Schottky contact

Journal of Materials Science: Materials in Electronics - The search for good electrodes processed by solution has interested several niches to produce printed solar cells, lighting emitting diodes,...