Chabazite Synthesis and Its Exchange with Ti,Zn, Cu,Ag and Au for Efficient Photocatalytic Degradation of Methylene Blue Dye

A chabazite-type zeolite was prepared by the hydrothermal method. Before ion exchange, the chabazite was activated with ammonium chloride (NH₄Cl). The ion exchange process was carried out at a controlled temperature and constant stirring to obtain ion-exchanged chabazites of Ti⁴⁺ chabazite (TiCHA), Zn²⁺ chabazite (ZnCHA), Cu²⁺ chabazite (CuCHA), Ag⁺ chabazite (AgCHA) and Au³⁺ chabazite (AuCHA). Modified chabazite samples were characterized by X-ray diffraction (XRD), scanning electron microscope equipped with energy-dispersive spectroscopy (SEM-EDS), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), N₂ adsorption methods and UV–visible diffuse reflectance spectroscopy (DRS). XRD results revealed that the chabazite structure did not undergo any modification during the exchange treatments. The photocatalytic activity of chabazite samples was evaluated by the degradation of methylene blue (MB) in the presence of H₂O₂ under ultraviolet (UV) light illumination. The photodegradation results showed a higher degradation efficiency of modified chabazites, compared to the synthesized chabazite. CuCHA showed an efficiency of 98.92% in MB degradation, with a constant of k = 0.0266 min⁻¹ following a first-order kinetic mechanism. Then, it was demonstrated that the modified chabazites could be used for the photodegradation of dyes.     

Preferred orientation of chopped fibers in polymer-based composites processed by selective laser sintering and fused deposition modeling: Effects on mechanical properties

The orientation of reinforcing fibers in polymer-based composites greatly affects their mechanical features. It is known that different orientations of continuous fibers in the stacked layers of a laminate play a crucial role in providing an isotropic mechanical behavior, while the alignment of chopped fibers in injection molding of composites results in a degree of anisotropy. Recent additive manufacturing techniques have offered a way of controlling the fiber orientation. This article aims to investigate the effect of fiber orientation on the mechanical properties of polyamide/carbon fiber composites processed by fused deposition modeling and selective laser sintering. Tensile samples which had different fibers and layer interface with respect to the sample axis (and therefore to the tensile load) were produced. Tensile tests were performed at different strain rates; the tensile properties and the fracture surface morphology were correlated with the processing method and the sample microstructure. The best strength and stiffness were observed when the fibers and the layer interfaces were parallel to the sample axis.     

Understanding the effect of polymer crystallinity on the electrical conductivity of exfoliated graphite nanoplatelet/polylactic acid composite films

Electrically conductive exfoliated graphite nanoplatelet (GNP) / polylactic acid (PLA) nanocomposite films were fabricated using a two-step, scalable melt compounding process. The effect of the polymer’s physical properties, such as crystallinity, on the mechanical and electrical properties of the composites were determined. The crystallization characteristics of PLA were altered significantly by altering the cooling rate during compression molding of the films. The crystallinity and crystal structure were investigated using differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), and polarized optical microscopy (POM). The mechanical and electrical properties were also examined as a function of PLA’s crystallinity dictated by the cooling rate during compression molding. The electrical conductivity was examined using impedance spectroscopy. For the same GNP content, the crystallinity increases by ~40 % and electrical conductivity increases by ~3 orders of magnitude with decreased cooling rate indicating a strong correlation between polymer physical properties and electrical conductivity of the polymer composites. This mechanism can be utilized to tailor the electrical conductivity of a given filler/polymer system by tuning the physical properties of the polymer, without altering the fillers’ characteristics or the processing method, which is the common approach used.     

Use of high-resolution 13C nuclear magnetic resonance spectroscopy for the screening of virgin olive oils

¹³C Nuclear magnetic resonance (NMR) spectra of 104 oil samples were obtained and analyzed in order to study the use of this technique for routine screening of virgin olive oils. The oils studied included the following: virgin olive oils from different cultivars and regions of Europe and north Africa, and refined olive, “lampante” olive, refined olive pomace, high-oleic sunflower, hazelnut, sunflower, corn, soybean, rapeseed, grapeseed, and peanut oils, as well as mixtures of virgin olive oils from different geographical origins and mixtures of 5–50% hazelnut oil in virgin olive oil. The analysis of the spectra allowed us to distinguish among virgin olive oils, oils with a high content of oleic acid, and oils with a high content of linoleic acid, by using stepwise discriminant analysis. This parametric method gave 97.1% correct validated classifications for the oils. In addition, it classified correctly all the hazelnut oil samples and the mixtures of hazelnut oil in virgin olive oil assayed. All of these results suggested that ¹³C NMR may be used satisfactorily for discriminating some specific groups of oils, but to obtain 100% correct classifications for the different oils and mixtures, more information than that obtained from the direct spectra of the oils is needed.     

Influence of the Polymeric Matrix and Thermal Treatment on the Properties of Polyolefin‐Graphite Nanosheets Nanocomposites

Homo and copolymers of metallocenic poly(propylene) with 1‐hexene and 1‐octadecene are used to prepare nanocomposites via melt mixing by using graphite nanosheets (GNSs) as filler. Different amounts of GNSs are used in order to study the influence of the filler on the thermal, mechanical, and electrical properties of nanocomposites. Significant changes have been observed in the crystallization temperature (T_c) of the nanocomposites. Thermogravimetric analysis shows improvement in thermal stability. Young's modulus and elongation at break of the nanocomposites are depended on the type of the matrix and the amount of GNSs. Materials with high flexibility are obtained in the cases of matrices based on copolymers even at high filler loading. Nanocomposites have become a semiconductor material reaching conductivity of 10^?4 S cm^?1. Two different thermal treatments have been applied in the preparation of the films by compression molding. X‐ray diffraction analysis shows the existence of polymorphism according to the thermal treatment applied.

     

Natural antioxidants produced in oxidized lipid/amino acid browning reactions

1-Substituted pyrroles (1 and2) and1-substituted 2-(1′-hydroxypropyl)pyrroles (3–5) were produced in reactions between a lipid peroxidation product, 4,5(E)-epoxy-2(E)-heptenal, and the amino acid lysine. The antioxidative activity of compounds1–5 was studied. Oxidative stability was evaluated in refined soybean oil containing compounds1–5, butylated hydroxytoluene (BHT),n-propyl gallate orl-lysine, at concentrations of 50–200 ppm. Oils were either oxidized at 60°C and oxidation products determined by the thiobarbituric acid-reactive substances assay, or they were oxidized at 110°C by the Rancimat method. Although both methods gave similar results, greater differences were observed at 60°C than at 110°C. Addition of compounds1–5,l-lysine, BHT, and propyl gallate significantly (P<0.01) protected the oil against oxidation. The effectiveness order found was:l-lysine << compounds3–4 < compounds1–2 < compound5 ≈ BHT << propyl gallate.     

Expression of Aquaglyceroporins in Spermatozoa from Wild Ruminants Is Influenced by Photoperiod and Thyroxine Concentrations

This work identified the presence of AQPs in frozen-thawed sperm of wild ruminants and assessed the influence of the interaction between photoperiod and thyroxine on AQP expression, and on testosterone secretion. Thyroxine and melatonin were administered to ibexes. In a second experiment, performed in mouflons, circulating thyroxine was reduced via treatment with propylthiouracil (PTU), and an artificial long day (LD) photoperiod established. In the ibexes, the melatonin treatment increased the blood plasma testosterone concentration, reduced the cryoresistance ratio (CR) for sperm viability and the presence of an intact acrosome, and increased the percentage of sperm with AQP7 in the acrosome and of AQP3 and AQP10 in the midpiece. In the mouflons, neither the PTU treatment, the LD, nor the combination of both affected the CR of any sperm variable. The percentage of sperm with AQP3 increased in the post-acrosome region but decreased in the tail in the LD+PTU group. The percentage of sperm with AQP10 in the principal piece and endpiece was lower in the PTU+LD group than in the control and LD groups. The influence of photoperiod/melatonin on AQP expression might be indirectly exerted through changes in the testosterone concentration, and thus ultimately affect sperm cryoresistance.     

PCR-based methodology for the authentication of grouper (Epinephelus marginatus) in commercial fish fillets

In an attempt to authenticate commercial frauds in fish fillets of grouper (Epinephelus marginatus) by being substituted with those of Nile perch (Lates niloticus) and wreck fish (Polyprion americanus), a polymerase chain reaction (PCR) method, based on the design of specific primers of these species was explored here. The oligonucleotides, which were designed from the 12S ribosomal RNA gene, generated PCR fragments of 100, 138 and 169 bp length for grouper, wreck fish and Nile perch respectively. The specificity of the primers was tested against more than 50 different fish species. Moreover, in this work 70 commercial fish fillets samples were analysed by this methodology; 58 out of them confirmed to be incorrectly labelled. The results suggest that this method may be a reliable tool for the detection of grouper adulteration. Also, this technique may help implementation of traceability systems in the seafood industry.     

Gay-related stress and emotional distress among gay, lesbian and bisexual youths: A longitudinal examination.

The longitudinal relations between gay-related stress (i.e., gay-related stressful events, negative attitudes toward homosexuality, and discomfort with homosexuality) and emotional distress (i.e., anxious symptoms, depressive symptoms, and conduct problems) were examined at 3 assessment periods (baseline, 6 months, and 12 months) among 140 gay, lesbian, and bisexual (GLB) youths. Although some findings were consistent with the hypothesis that stress would be associated with subsequent distress among GLB youths, the larger number of nonsignificant relations and the presence of relations between distress and subsequent gay-related stress indicate that the hypothesis was unsupported. The authors discuss the potential reasons for the lack of hypothesized relations and offer suggestions for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physical aging of poly(diethylene glycol‐p,p′bibenzoate)

The structure of a quenched sample of a liquid crystalline polyester, poly(diethylene glycol‐p,p′‐bibenzoate) (PDEB), and its physical aging was studied by microhardness methods (MH), wide‐angle X‐ray scattering (WAXS), and positron annihilation lifetime spectroscopy (PALS). It was established that the smectic layers in the liquid crystalline domain are oriented parallel to the sample plane. Physical aging leads to an increase of either the Vickers microhardness, directly related to the elastic modulus of the material, or the total microhardness, which includes all the components of the overall deformation. These mechanical changes are due to a decrease in the sizes of nanopores and the consequential increase of the density of the disordered phase. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2363–2368, 2002