Theoretical Study of the Water–Gas Shift Reaction on a Au/Hematite Model Catalyst

Topics in Catalysis - Using the density functional theory, the mechanism of the water–gas shift reaction has been investigated employing a model catalyst formed by a Au5 cluster supported on...     

Nanocomposites of PBAT and cellulose nanocrystals modified by in situ polymerization and melt extrusion

Cellulose nanocrystals (CNC) were successfully grafted with a low molecular weight poly(butylene glutarate) through an in situ polymerization procedure. The grafting treatment decreased the CNC hydrophilic character and increased the onset of their thermal degradation by approximately 20°C, thus increasing the possibilities of CNC application. Composites of grafted and nongrafted CNC with a poly(butylene‐adipate‐co‐terephthalate) (PBAT) matrix were prepared by melt extrusion. The CNC addition led to an increase of 50% of the tensile elastic modulus of the PBAT. In addition, dynamic mechanical thermal analysis showed that the composite with CNC retained its high modulus even at temperatures far above the glass transition temperature of PBAT. At 60°C the storage modulus of the composite with CNC was approximately 200% higher than that of the pure PBAT. Thus, in this work, nanocomposites of improved properties were obtained through a combination of in situ polymerization and melt extrusion. POLYM. ENG. SCI., 56:1339–1348, 2016. © 2016 Society of Plastics Engineers     

Sorption of propylene and propane in polyurethane membranes containing silver nanoparticles

The preparation of a facilitated transport membrane of polyurethane (PU) containing silver nanoparticles is reported. The propylene and propane sorption was investigated aiming at the selective separation from C3s mixtures. The silver particles were photogenerated in situ into the polyurethane matrix using UV light radiation and silver triflate (AgCF₃SO₃) as precursor. The morphological properties of these membranes (PUAg) reveled great dispersion of silver particles, which size was smaller than 110 nm. The propylene solubility in PUAg resulted more than four times superior to the one for the pure PU membrane, revealing the high affinity between silver and propylene. Flory–Huggins theory was more accurate to describe the propylene sorption behavior in PUAg than Henry's model. The ideal solubility selectivity of PUAg membrane resulted 24.4, indicating that there is a good potential for an industrial application aiming at the separation of propylene/propane. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42916.     

Polyphenolic fractions improve the oxidative stability of microencapsulated linseed oil

The main objective of this study was to evaluate the effect of incorporating polyphenolic‐enriched fractions from murta leaves on the oxidative stability of linseed oil microencapsulated by spray drying. For this purpose, polyphenol‐enriched fractions from murta leaves were separated by gel permeation chromatography and chemically characterized. The oxidative stability of microencapsulated linseed oil (MLO) with antioxidants was evaluated in storage conditions at 25°C for 40 days. The antioxidant effects of the polyphenolic fractions and commercial antioxidants (BHT and trolox) on microencapsulated oil were evaluated by the value of conjugated dienes, peroxide, and p‐anisidine. In the initiation step of the oxidation, no significant oxidation delay (p>0.05) in MLO containing fractions F₆, F₈, or BHT and trolox was observed. However, in the termination step of the oxidation, the addition of fractions F₆, F₈, and BHT and trolox decreases significantly (p ≤ 0.05) the rancidity in MLO. Furthermore, the results of this study demonstrated the importance of the addition of natural antioxidants such as fractions of murta leaf extract in microencapsulated linseed oil to increase its resistance to oxidation. Practical applications: For incorporating linseed oil, a source of omega‐3 fatty acids, in the diet it is necessary to protect it against oxidative rancidity, the main cause of deterioration that affects food with a high unsaturated fat content. Microencapsulation is effective in retarding or suppressing the oxidation of unsaturated fatty acids and natural plants extracts are effective in inhibiting the lipid oxidation of microencapsulated oil. The use of process technology and a natural additive is expected to increase storage stability and enable its use in dry foods such as instant products. Linseed oil can be used in human nutrition as well as in animal feed as a replacement for fish oil.     

Effects of ozonized water and heat treatment on the papaya fruit epidermis

This study examined the effects of O₃ and hot water treatments on the epidermis of Golden papaya fruit. Heat treatments were applied in a hot water brushing (HWB) system. Papayas were brushed under a pressurized hot water rinse stage at 45, 55 and 65 °C for 60 s. In the HWB treatment, 4 ppm ozone was applied to the papayas for 1 or 2 min. The results show that ozone applications did not affect the fruit's cuticular surface, while heat treatments allowed natural fissures on the fruit epidermis to recover. Several crystalloid forms were identified on the epidermis of the papayas after the heat treatments. The predominant crystalloid forms on papayas are tubular and there is a positive response to temperature; the higher the temperature, the larger and more frequent the tubular crystalloids.     

FTIR spectroscopy characterization of poly (vinyl alcohol) hydrogel with different hydrolysis degree and chemically crosslinked with glutaraldehyde

In this work, poly (vinyl alcohol) (PVA) hydrogels with different degree of hydrolysis (DH) were prepared by chemical crosslinking with glutaraldehyde (GA). The nanostructure of the resulting hydrogels was investigated by Fourier Transform Infrared Spectroscopy (FTIR) and Synchrotron small-angle X-ray scattering characterization (SAXS). In vitro tests were performed by swelling ratio assays in different pH solutions. The infrared spectra of the crosslinked PVA showed absorption bands of the acetal bridges resulted from the reaction of the GA with the OH groups from PVA. Also the FTIR spectroscopy was used to determine the crystallinity of the PVA film based on the relative intensity of the vibration band at 1141 cm^− 1. The results have showed an increase of hydrogel crystallinity with higher DH of PVA. SAXS patterns have clearly indicated important modifications on the PVA semicrystalline structure when it was crosslinked by GA. The swelling ratio was significantly reduced by chemically crosslinking the PVA network. PVA-derived hydrogel with chemically modified network was found to be pH-sensitive, indicating a high potential to be used in drug delivery polymer system.     

Development and validation of a dissolution test for lodenafil carbonate based on in vivo data

Introduction: Lodenafil carbonate is a phosphodiesterase type 5 inhibitor used for the treatment of erectile dysfunction. Currently, there is no dissolution test reported for lodenafil carbonate and this drug is not listed in any pharmacopoeia.

Objective: The present study focused on the development and validation of a dissolution test for lodenafil carbonate tablets, using a simulated absorption profile based on in vivo data.

Methods: The appropriate conditions were determined after testing sink conditions. Different conditions as medium, surfactant concentration and rotation speed were evaluated. The percentage of dose absorbed was calculated by deconvolution, using the Wagner–Nelson method.

Results: According to the obtained results, the use of 0.1?M HCl?+?1.5% SLS (900?mL, at 37?+?0.5?°C) as the dissolution medium, paddles at 25?rpm were considered adequate. The samples were quantified by UV spectroscopy at 295?nm and the validation was performed according to international guidelines. The method showed specificity, linearity, accuracy and precision, within the acceptable range. Kinetics of drug release was better described by the first-order model.

Conclusion: The proposed dissolution test can be used for the routine quality control of lodenafil carbonate in tablets.     

The association of age, sex and helmet use with the risk of death for occupants of two-wheeled motor vehicles involved in traffic crashes in Spain

Background

This study was designed to separate the association of age, sex and helmet use with the risk of death for occupants of two-wheeled motor vehicles (TWMV) involved in crashes into its two theoretical components: severity of the crash and occupant resilience.

Methods

We analyzed the retrospective cohort comprising all 48 016 pairs of drivers and passengers aged 14 years or more in TWMV involved in crashes with victims in Spain from 1993 to 2007 recorded in the Spanish traffic crash registry. The outcome (death or survival), age, sex and helmet use was known for both occupants. Adjusted relative risks (RR) for the association of age, sex and helmet with the risk of death were calculated with Poisson regression models.

Results

Each 1-year increase in age was related with a 3% increase in the risk of death related with lower resilience. The severity-dependent RR of death was 1.84 for male sex and 0.86 for non-helmet use, and the resilience-dependent RR was 0.72 and 2.53, respectively.

Conclusions

The direction and magnitude of the association between age, sex and helmet use and the risk of death of an occupant of a TWMV involved in a crash changed depending on which component of risk was considered: crash severity or occupant resilience. Specifically, female sex and non-helmet use seemed to be associated with crashes of lower severity, but together with increased age they were also related with lower resilience to the energy released in the crash, and therefore with a higher risk of death after adjustment for crash severity. This should be taken into account when assessing the association of individual factors with the risk of death after a crash.