Simultaneous improvement in solvent permeability and deacidification of soybean oil by nanofiltration.

In this paper, soybean oil deacidification and hexane removal using laboratory scale solvent resistance nanofiltration membranes based technique is presented. Composite nanofiltration membranes made of different polymers poly(vinylideneflouride) (PVDF), polydimethylsiloxane (SI), polycarbonate (PC), and glycerol were tested to remove the hexane and free fatty acid (FFA) from soybean oil/hexane miscella (oil feed solution 10, 25, and 35% w/w) at 20 bar of transmembrane pressure and 30 °C, in a dead-end filtration set up. All membranes tested showed low fouling phenomena and high stability in the presence of hexane throughout the membrane pre-treatment and permeation procedure. The PVDF-10SI-1PC membrane showed the best performance achieving a miscella permeability of Lm = 6.8 × 10-6 L (h m bar)-1, oil and FFA sieving efficiency of ß(oil) = 0.21(80% of oil rejection) and ßFFA = 2.43 (27% of FFA removal), respectively, at oil feed concentration of 25%. Apart from these specific properties, the PVDF-10SI-1PC membrane presented excellent mechanical and chemical resistances and low reversible fouling. The results demonstrate that membrane technology can attain a high efficiency in the simultaneous solvent recovery and deacidification of oil/hexane miscella commonly processed in the soybean oil industry.

Influence of Pectin as a green polymer electrolyte on the transport properties of Chitosan-Pectin membranes.

Novel blend membranes have been prepared from Chitosan (CH), Pectin (PEC) and their mixtures. The obtained samples were cross-linked and sulfonated before characterization. The results show that CH/PEC membranes display structural changes on the chemical and physical properties as a function of composition. DSC analysis reveals an endothermic peak due to the scission of the ionic pairs between carboxylic groups and ammonium groups, which produces a strong change on physical properties such as methanol permeability and proton conductivity. The methanol permeability decreases with the amount of Pectin from (4.24±0.04)×10-6cm2/s for pure Chitosan membrane to (1.51±0.03)×10-6cm2/s for blend CH/PEC membranes when the amount of Pectin is 50% (v/v). The proton conductivities of the blend membranes follow a similar behavior. For a pure CH membrane the conductivity is 2.44×10-3S/cm, decreasing with pectin content until the composition 50/50 (v/v), in which the conductivity drops almost one order of magnitude.

NaOH treatment of chitosan films: Impact on macromolecular structure and film properties.

In this paper, we examine the significance of treatment with NaOH on chitosan (CH) film structure to obtain biodegradable materials for several applications. In order to determine the structure of the films, an analysis based on SEM, FTIR spectroscopy and X-ray diffraction data was performed. In addition, the consequences of this treatment were evaluated by swelling index measurements and mechanical testing. As result of FTIR and X-ray analysis, three effects were identified: the deprotonation and phosphate extraction, which allowed new hydrogen bonds to form, and a higher CH deacetylation. These studies also revealed that two hydrated and anhydrous polymorphs were present in the CH-NaOH films. Moreover, the new hydrogen bond and the reduction of N-acetyl groups produced films with a more compact and disordered structure, reducing their swelling characteristics and increasing their brittleness. The introduction of a mild NaOH treatment is a versatile tool to obtain chitosan films with interesting and tunable properties.

Fractional statistical theory of adsorption applied to protein adsorption.

Experimental adsorption isotherms of bovine serum albumin (BSA) adsorbed on sulfonated microspheres were described by means of two analytical models: the first is the well-known Langmuir-Freundlich model (LF), and the second, called fractional statistical theory of adsorption (FSTA), is a statistical thermodynamics model developed recently by Ramirez-Pastor et al. [Phys. Rev. Lett. 93 (2004) 186101]. The experimental data, obtained by Hu et al. [Biochem. Eng. J. 23 (2005) 259] for different concentrations of sulfonate group on the surface of the microspheres, were correlated by using a fitting algorithm based on least-squares statistics. The combination of LF and FSTA models, along with the choice of an adequate fitting procedure, allowed us to obtain several conclusions: (i) as previously reported in the literature, the maximum amount adsorbed increases as the amount of sulfonate group increases; (ii) the equilibrium constant does not appear as a sensitive parameter to the amount of sulfonate group on the surface of the microspheres; and (iii) the values of the fitting parameters obtained from FSTA may be indicative of a mismatch between the equilibrium separation of the intermolecular interaction and the distance between the adsorption sites. The exhaustive study presented here has shown that FSTA model is a good one considering the complexity of the physical situation, which is intended to be described and could be more useful in interpreting experimental data of adsorption of molecules with different sizes and shapes.

Contrast enhancement of electronic speckle pattern interferometry addition fringes.

The electronic speckle pattern interferometer in the double-pulse addition mode can be used to measure physical parameters in unstable environmental conditions. Owing to additive optical noise, however, the fringe patterns obtained have poor contrast. Some methods that use subtraction of addition double-pulsed fringe patterns improve fringe visibility but impose a limitation in measurement time ranges. To increase this range, to be limited by only the pulse separation, the contrast enhancement of double-pulsed addition-fringe patterns with a spatial filter based on local-standard-deviation measurements is investigated. Computer simulations and experimental results are presented.

Antiácido de alta potência versus cimetidina no tratamento da úlcera duodenal: comodidade posológica / High potency antacid versus cometidine in the treatment of duodenal ulcer: commodus psosology

Foram estudados 98 pacientes com úlcera péptica duodenal distribuídos de forma randômica em dois grupos. Um grupo recebeu antiácido liquido de alta potência (282,4mEq/dia) dividido em 4 tomadas durante 4 semanas e outro recebeu cimetidina (800 mg/dia) dividida em 2 tomadas por igual período. A potência antiácida da associaçäo líquida utilizada é de 7,06 mEq/ml. Todos os pacientes foram avaliados clinicamente no pré-tratamento e duas e quatro semanas após, com exames endoscópicos realizados na admissäo e após quatro semanas. A eficácia, considerada como cicatrizaçäo da úlcera duodenal associada a melhora da sintomatologia foi equivalente para ambos os tratamentos, näo havendo diferença estatisticamente significante. A tolerabilidade de ambas as drogas foi considerada boa