Morphology,thermal and mechanical properties of PVC/MMT nanocomposites prepared by solution blending and solution blending + melt compounding

Two types of montmorillonite (MMT), natural sodium montmorillonite (Na-MMT) and organically modified montmorillonite (OMMT), in different amounts of 1, 2, 5, 10 and 25 phr (parts per hundred resin), were dispersed in rigid poly (vinyl chloride) by two different methods: solution blending and solution blending + melt compounding. The effects on morphology, thermal and mechanical properties of the PVC/MMT nanocomposites were studied by varying the amount of Na-MMT and OMMT in both methods. SEM and XRD analysis revealed that possible intercalated and exfoliated structures were obtained in all of the PVC/MMT nanocomposites. Thermogravimetric analysis revealed that PVC/Na-MMT nanocomposites have better thermal stability than PVC/OMMT nanocomposites and PVC. In general, PVC/MMT nanocomposites prepared by solution blending + melt compounding revealed improved thermal properties compared to PVC/MMT nanocomposites prepared by solution blending. Vicat tests revealed a significant decrease in Vicat softening temperature of PVC/MMT nanocomposites prepared by solution blending + melt compounding compared to unfilled PVC.     

Comparative Antimicrobial Activity of Silver Nanoparticles Obtained by Wet Chemical Reduction and Solvothermal Methods

The synthesis of nanoparticles from noble metals has received high attention from researchers due to their unique properties and their wide range of applications. Silver nanoparticles (AgNPs), in particular, show a remarkable inhibitory effect against microorganisms and viruses. Various methods have been developed to obtain AgNPs, however the stability of such nanostructures over time is still challenging. Researchers attempt to obtain particular shapes and sizes in order to tailor AgNPs properties for specific areas, such as biochemistry, biology, agriculture, electronics, medicine, and industry. The aim of this study was to design AgNPs with improved antimicrobial characteristics and stability. Two different wet chemical routes were considered: synthesis being performed (i) reduction method at room temperatures and (ii) solvothermal method at high temperature. Here, we show that the antimicrobial properties of the obtained AgNPs, are influenced by their synthesis route, which impact on the size and shape of the structures. This work analyses and compares the antimicrobial properties of the obtained AgNPs, based on their structure, sizes and morphologies which are influenced, in turn, not only by the type or quantities of precursors used but also by the temperature of the reaction. Generally, AgNPs obtained by solvothermal, at raised temperature, registered better antimicrobial activity as compared to NPs obtained by reduction method at room temperature.     

A new short-path distillation system applied to the reduction of cholesterol in butter and lard

A molecular distillation plant, built particularly to increase the separation efficiency and to obtain safer working conditions, was tested to remove cholesterol from anhydrous butter and lard. A preliminary experiment was carried out with butter to evaluate the fractionation obtained at temperatures between 190 and 250°C and residual pressures between 10⁻³ and 10⁻⁴ torr. A second experiment was carried out at 185°C and at the maximum operational vacuum, evaluating the fractionation achieved within a time scale between 30 and 180 min. Cholesterol was almost completely removed during the second hour with minimal loss of low-molecular weight triglycerides. An experiment was carried out with lard at 250°C and maximum achievable operational vacuum (10⁻⁴ Torr), lasting approximately 6 h, and cholesterol was removed almost completely during the second hour without significant modifications in the triglyceride composition. This situation remained constant throughout the duration of the test.     

Gel mechanical properties of milk whey protein–dextran conjugates obtained by Maillard reaction

The effect of Maillard reaction on the mechanical properties of whey protein isolate (WPI) heat-induced gels was evaluated. WPI and dextran (15–25 kDa) conjugates were obtained by controlled dry heating during storage at 60 °C and 63% relative humidity for 2, 5 and 9 days. Changes in browning intensity and content of free amino groups were used to estimate the Maillard reaction. A decrease in free amino groups of WPI was observed when increasing polysaccharide concentration and reaction time. An increase in both a* and b* CIE Lab colour parameters indicated the development of a reddish-brown colour, typical of the Maillard reaction. Uniaxial compression and stress relaxation tests were performed to measure the mechanical properties of mixed and conjugate gels. Maillard reaction significantly modified the mechanical properties of WPI/DX gels, and even prevented fracture when conjugate gels were subjected to 80% deformation in uniaxial compression test.     

Nanoparticles from a Gold Complex with Sulfite Ion as Ligand: Preparation and Characterization

Gold colloidal nanoparticles (GNPs) were prepared by reducing a complex of Au⁺. Na₃Au(SO₃)₂ with sodium citrate. The procedure provides control of the dimension of nanoparticles produced, which is a function of reaction time and concentration of reactants. The nanoparticles were separated by centrifugation and their characteristics and dimensions were studied using UV-Vis and IR spectroscopy and transmission electronic microscopy (TEM).     

Growth in temperament and parenting as predictors of adjustment during children's transition to adolescence.

The author examined relations among demographic risk (income, maternal education, single-parent status), growth in temperament (fear, irritability, effortful control), and parenting (rejection, inconsistent discipline) across 3 years and the prediction of children's adjustment problems in a community sample (N=190; ages 8-12 years at Time 1). Family income was related to higher initial levels of fear, irritability, rejection, and inconsistency and lower effortful control but was not related to changes in these variables. Higher initial rejection predicted increases in child fear and irritability. Higher initial fear predicted decreases in rejection and inconsistency. Higher initial irritability predicted increases in inconsistency, and higher initial effortful control predicted decreases in rejection. When growth of parenting and temperament were considered simultaneously, increases in effortful control and decreases in fear and irritability predicted lower Time 3 internalizing and externalizing problems. Increases in rejection and inconsistent discipline predicted higher Time 3 externalizing, although sometimes the effect appeared to be indirect through temperament. The findings suggest that temperament and parenting predict changes in each other and predict adjustment during the transition to adolescence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

In vitro desaturation of 1-14C linoleic acid in Novikoff hepatoma

The lipid fatty acid pattern of normal liver, host liver, and Novikoff hepatoma was determined by gas liquid chromatography, and Δ6-desaturase activity for linoleic acid was measured in the microsomal fractions. The results showed that, in Novikoff hepatoma, there is a correlation between the low content of arachidonic acid and the low activity of Δ6-desaturase, a key enzyme in the biosynthetic pathway of this acid.     

Magnetization and Curie Temperature of Ilmenite–Hematite Ceramics

The morphology, structure, and magnetic properties of the magnetic semiconductor ceramic Ilmenite–Hematite (IH), (1− x )FeTiO₃– x Fe₂O₃, were studied as a function of the composition x . The magnetic ordering temperatures that we observed were consistently higher than those reported previously and were, for most of the composition range, above room temperature. We rule out the formation of Fe clusters as the origin of the magnetic properties. These magnetic properties of IH ceramics, in combination with their semiconducting characteristics, render them promising for spin-electronic applications.     

Structure, orientation, and conformational changes in transmembrane domains of multidrug transporters

Multidrug transporter proteins promote the active transmembrane efflux of noxious drugs, thereby decreasing their accumulation in the intracellular medium and reducing their therapeutic efficiency. Expression of such proteins drastically reduces the efficiency of chemotherapeutic treatments against cancer and various infectious diseases. To overcome major difficulties related to the crystallization of membrane proteins, other experimental approaches have been developed to gain information on the structural changes involved in drug transport. We examine here and illustrate with a few examples how infrared and fluorescence spectroscopy can provide new insights into the structure of the membrane domains of multidrug transporters in particular. Such domains contain the drug-binding site(s) and mediate the passage of substrates across the cell membrane.     

Synthesis of BaTiO3 by soft chemistry routes

In this paper we report a comparison concerning the properties of BaTiO₃ (BTO) ceramics obtained by two soft chemical routes, modified Pechini method and thermal decomposition of oxalate-based precursor. XRD data show the formation of single phase BaTiO₃ with tetragonal symmetry when the polymeric citrate-based precursor was annealed at 850 °C, 2 h. In the case of oxalate based-precursor, longer thermal treatment is required to obtain BaTiO₃ free of any secondary phases. For BaTiO₃ powders prepared by modified Pechini method, TEM and SEM investigations revealed the obtaining of uniformly sized particles forming spherical agglomerates inside large, non-uniform and partially sintered aggregates. The powders synthesized via oxalate route show particles of various sizes, with the same tendency of spherical agglomerates formation, but unlike the modified Pechini synthesis, more uniform and smaller aggregates with well-defined hexagonal-like shape were noticed. The relative permittivity values of 6,478 and 5,088 at Curie temperatures of 127 and 130 °C and low dielectric losses (tan δ?=?0.012) at room temperature were obtained for ceramic samples synthesized via Pechini method and oxalate route, respectively.