New high-pressures vapor-liquid equilibrium data for the carbon dioxide + 2-methyl-2-propanol binary system

New vapor-liquid equilibria (VLE) data at 323.15, 333.15, 343.15, and 353.15 K and pressures up to 112.9 bar are reported for the carbon dioxide + 2-methyl-2-propanol system. The experimental method used in this work was a static analytical method with liquid and vapor phases sampling using a rapid online sampler injector (ROLSI?) coupled to a gas chromatograph (GC) for analysis. Measured VLE data and literature data for carbon dioxide + 2-methyl-2-propanol system were modeled with the Soave-Redlich-Kwong (SRK) cubic equation of state with classical van der Waals (two-parameter conventional mixing rule, 2PCMR) mixing rules. A single set of interaction parameters that lead to a correct phase behavior was used in this work to model the new VLE data and critical points of the mixtures in a wide range of temperature and pressure. The SRK prediction results were compared to the new data measured in this study and to available literature data.

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On the Unitary Binary Group

One consider the variety of the unitary binary group in n variables and it is shown that this algebraic variety is rational and it has n² parameters. Then it is given a parametrical rational representation of this variety.AMS Subject Classification (1991) 20G20     

Using color histograms and SPA-LDA to classify bacteria

In this work, a new approach is proposed to verify the differentiating characteristics of five bacteria (Escherichia coli, Enterococcus faecalis, Streptococcus salivarius, Streptococcus oralis, and Staphylococcus aureus) by using digital images obtained with a simple webcam and variable selection by the Successive Projections Algorithm associated with Linear Discriminant Analysis (SPA-LDA). In this sense, color histograms in the red–green–blue (RGB), hue-saturation-value (HSV), and grayscale channels and their combinations were used as input data, and statistically evaluated by using different multivariate classifiers (Soft Independent Modeling by Class Analogy (SIMCA), Principal Component Analysis-Linear Discriminant Analysis (PCA-LDA), Partial Least Squares Discriminant Analysis (PLS-DA) and Successive Projections Algorithm-Linear Discriminant Analysis (SPA-LDA)). The bacteria strains were cultivated in a nutritive blood agar base layer for 24 h by following the Brazilian Pharmacopoeia, maintaining the status of cell growth and the nature of nutrient solutions under the same conditions. The best result in classification was obtained by using RGB and SPA-LDA, which reached 94 and 100 % of classification accuracy in the training and test sets, respectively. This result is extremely positive from the viewpoint of routine clinical analyses, because it avoids bacterial identification based on phenotypic identification of the causative organism using Gram staining, culture, and biochemical proofs. Therefore, the proposed method presents inherent advantages, promoting a simpler, faster, and low-cost alternative for bacterial identification. Figure

Summary of the new proposed methodology for bacteria classification by using color histograms and SPA-LDA     

Isomerization of Safrole and Eugenol Under Microwave Irradiation

Abstract: Safrole and eugenol isomerization reactions were carried out under microwave irradiation at atmospheric pressure and homogeneous medium with various alcohols used as solvents and different base concentrations. The rate reaction enhancement shown was 2.3 to 13.2 times faster than conventional reflux.     

Chemical analysis of the semipurified extract of Paullinia cupana and evaluation of in vitro inhibitory effects against Helicobacter pylori

Abstract

Paullinia cupana Kunth, commonly known as guarana, is a native Brazilian plant species from the Amazon area that presents various biological effects, including antimicrobial action. The aim of this study was to chemically analyse the semipurified aqueous extract (AqF) of the plant and to evaluate the activity of crude (CE), ethyl-acetate (EAF), and AqF extracts against Helicobacter pylori. The chemical profile of AqF was determined based on solid analysis ¹³C-NMR, direct infusion mass spectrometry (ESI-MS), and MALDI-TOF. The ¹³C-NMR spectrum showed characteristics of flavan-3-ol and oligomeric proanthocyanidins. ESI-MS revealed the presence of procyanidin, caffeic acid and its derivatives. MALDI-TOF analysis detected procyanidins of up to 6 units and profisetinidins of up to 5 units. Whereas CE and EAF showed inhibitory activity against H. pylori, CE, EAF, and AqF presented not high inhibitory activity against urease. The results demonstrate the potential of P. cupana to control and prevent H. pylori infection.     

High-pressure phase equilibria in the (carbon dioxide + 1-hexanol) system

(Vapour + liquid) equilibria (VLE) and (vapour + liquid + liquid) equilibria (VLLE) data for the (carbon dioxide + 1-hexanol) system were measured at (293.15, 303.15, 313.15, 333.15, and 353.15) K. Phase behaviour measurements were made in a high-pressure visual cell with variable volume, based on the static-analytic method. The pressure range under investigation was between (0.6 and 14.49) MPa. The Soave–Redlich–Kwong (SRK) equation of state (EOS) with classical van der Waals mixing rules (two-parameters conventional mixing rule, 2PCMR), was used in a semi-predictive approach, in order to represent the complex phase behaviour (critical curve, LLV line, isothermal VLE, LLE, and VLLE) of the system. The topology of phase behaviour is reasonably well predicted.     

Fluid phase equilibria in the binary system trifluoromethane + 1-phenyloctane

Vapour–liquid, liquid–liquid and liquid–liquid–vapour equilibria in the binary system consisting of trifluoromethane (refrigerant R23) and 1-phenyloctane were determined in the temperature range T = 250–400 K and at pressures up to 15 MPa. The experiments were carried using a Cailletet apparatus according to the synthetic method. The investigated system exhibits type III phase behaviour according to the classification of van Konynenburg and Scott. Modelling of the equilibrium data was done with the Peng–Robinson (PR) and Soave–Redlich–Kwong (SRK) equations of state coupled with classical van der Waals mixing rules. In order to predict the global phase behaviour of the system, one single set of binary parameters was used. The topology of the phase behaviour was correctly reproduced.     

Copper-catalyzed intermolecular aminochlorination of alkenes

A copper-catalyzed radical and regioselective aminochlorination of alkenes using N-fluoro-benzenesulfonimide (NFSI) and TMSCl as nitrogen and chlorine sources respectively is reported.     

Influence of process parameters on microstructure and mechanical properties of starch-cellulose acetate/silver sulfadiazine matrices prepared by melt extrusion

Starch-cellulose acetate matrices containing silver sulfadiazine were produced using melt extrusion for application in drug delivery devices (DDDs). The influence of the extrusion parameters (screw speed and temperature) on the morphological and mechanical properties of the matrices was evaluated at three different levels. The microstructural characterization of all matrices showed that an increase in the screw speed enhances the porosity and drug dispersion, while an increase in the extrusion temperature decreases the pore diameter of the matrices. Mechanical results did not show significant differences between the elastic modulus values for the matrices; however, a faster screw speed led to higher ultimate strength and strain at failure values. Results obtained in the dynamic mechanical analysis showed that the glass transition and loss tangent (tan δ) peak values became higher with increasing screw speed and temperature.