The Effect of Sulfates Concentration in Sulfated Zirconia (SZ) Catalysts n-Heptane Isomerization

Abstract

Interest in new catalysts for alkanes isomerization, such as sulfated zirconia, has been increasing in the last years. These catalysts, due to their superacid character, have a good activity for this reaction but undergo a rapid deactivation. For sulfated zirconia catalysts, the effect of sulfates concentration on the activity and stability for alkanes isomerization is not clear. In this work, Pt/sulfated zirconia catalysts with different sulfates content were prepared by the impregnation method; characterized by X-ray diffraction, high-resolution Raman spectroscopy, infrared spectroscopy, and BET surface area; and evaluated in an experimental system for n-heptane isomerization.     

Dextrin‐ and Conducting‐Polymer‐Containing Biocomposites: Properties and Behavior as Cellular Matrix

Both α‐cyclodextrin and linear dextrin are used to prepare biocomposites with poly(3,4‐ethylenedioxythiophene). Materials are prepared electrochemically in aqueous solution. Comparison with the pure polymer indicates that the electroactivity and electrostability decrease with the incorporation of the dextrins while the electrical conductivity is retained. The different properties of the two biocomposites suggest that the linear dextrin is mainly located at the surface, whereas the cyclodextrin is homogeneously distributed in the polymeric matrix. Cell adhesion and proliferation assays indicate that the cellular activity is significantly higher in the dextrin‐containing biocomposites.

     

A Conducting Polymer/Protein Composite with Bactericidal and Electroactive Properties

Lysozyme, an enzyme with bactericidal activity over Gram‐positive bacteria cells, is incorporated into PEDOT to prepare films with high biological and electrochemical activity. Two different strategies are used: (1) PEDOT films are coated with a layer of enzyme, which was adsorbed on the surface; and (2) the lysozyme is added to the polymerization medium used for the preparation of the conducting polymer. The enzyme adsorbed at the surface of the polymer produces a biphasic system that retains the electrochemical properties of the conducting polymer but is not able to protect against bacterial growth. In contrast, the addition of lysozyme to the polymerization medium results in a homogeneous composite with high bactericidal and electrochemical activities.

     

Site-specific fabrication and epitaxial conversion of functional oxide nanodisk arrays

Nanodisk arrays of technologically important magnetic (CoFe(2)O(4)) and ferroelectric (BaTiO(3)) oxides are fabricated on diverse substrates with well-defined size and separation using the soft-eBL approach. We demonstrate that below a certain pattern size, the as-deposited amorphous nanodisks can be readily converted into dense, single-crystal form that exhibit cube-on-cube heteroepitaxy with respect to the underlying single-crystal substrate. Such single-crystal disks show well-defined truncated-pyramid morphology that is consistent with Wulff construction. The mechanism of morphology development with the pattern size change is discussed. Localized characterization of the crystallinity, chemical composition, and magnetic behavior of the CFO nanodisk patterns are carried out using analytical transmission electron microscopy and magnetic force microscopy. Such solution-based epitaxial conversion of patterned arrays of multifunctional oxides has potential for viable cost-effective technological applications.     

Application of multilayered particles formed by poly(3,4‐ethylenedioxythiophene) and poly(N‐methylpyrrole) as anti‐corrosive additives of conventional organic coatings

Multilayered systems containing 3 or 5 layers of poly(3,4‐ethylenedioxythiophene) and poly(N‐methylpyrrole) have been prepared using a layer‐by‐layer electrodeposition technique. These multilayered systems have been found to present very high electroactivities suggesting that their performance as anti‐corrosive additive of conventional organic coatings (paints) could be even better than that of single‐component conducting polymers. The performance of the prepared multilayered systems as anti‐corrosive additives of epoxy paints has been checked. For this purpose, accelerated corrosion tests were performed using an aggressive solution medium. Analysis of the corroded area indicates that the addition of a low concentration (0.2% w/w) of these multilayered systems to the paint formulation enhances significantly the corrosion protection imparted by the coating.     

Varicella pneumonia in the adult. A review of 25 cases

OBJECTIVE: To study the clinical, therapeutic, and evolutive features in 25 patients with the diagnosis of varicella pneumonia (VP) in the last 15 years. PATIENTS AND METHODS: The diagnosis was established by clinical and radiologic criteria in the course of varicella infection. The antecedents of smoking habit, pregnancy, and underlying disease were evaluated. Hypoxemia was defined as a pO2 < or = 65 mmHg with a FiO2 of 0.21. RESULTS: Twenty-five patients (16 males and 9 women; mean age 31.5 years, range: 24-43 years) were included in the study. Ninety-two percent of patients were smokers of more than 20 cigarettes a day; five met criteria of simple chronic bronchitis, 3 were known carriers of human immunodeficiency virus (HIV) and one had a chronic liver disease caused by hepatitis C virus. In 16 patients (64%) there were no underlying diseases and none of the female patients was pregnant. Respiratory symptoms began from the first and seventh day after the skin rash, and the most common symptoms were cough (76%), dyspnea (48%), and chest pain (44%). In 22 patients an arterial gas determination was obtained and hypoxemia was documented in 8 patients (32%). Hypoxemia was greater and statistically significant in patients with underlying diseases (p < 0.01). Chest X-ray revealed an interstitial pattern predominantly at both bases. Intravenous acyclovir therapy was started in 19 patients (76%) with severe respiratory symptoms and/or underlying disease. Three patients (12%) were admitted to the Intensive Care Unit for mechanical ventilation. All patients had a favourable clinical course. CONCLUSIONS: Adult patients with symptoms of VP had a favourable clinical course with intravenous acyclovir, and the presence of hypoxemia was more commonly observed when underlying diseases were also present.     

Preliminary study of AP-64 cell line (Aedes pseudoscutellaris) for dengue-1 and -2 virus multiplication

We study a new arthropod cell line, AP-64, which was obtained from Aedes pseudoscutellaris larvae. The best growth and maintenance media are defined, testing the adequacy of dengue 1 and 2 viruses which become manifest by the appearance of the cytopathogenic effect as syncytiums. The immunofluorescence technique is applied to detect early multiplication of those viruses.     

Interfacial Fracture Phenomena in Ceramic Composite Directionally Solidified Eutectics with a Ductile Interphase

Interphase interfaces in Ni _x Co_{1− x} O/ZrO₂(CaO) directionally solidified eutectics (DSEs) are modified by selective chemical reduction of the Ni _x Co_{1− x} O oxide phase. Scanning electron microscopy studies of such Ni _x Co_{1− x} O/ZrO₂(CaO) DSEs show formation of a thin layer of metallic Ni(Co) interphase (∼100 nm) and interfacial porosity upon reduction at high temperatures. A significant change is observed in the mechanical behavior of the reduced Ni _x Co_{1− x} O/ZrO₂(CaO) DSEs compared with its pristine counterpart, which is largely attributed to the formation of metallic Ni(Co) interphases. Indentation fracture studies indicate that the presence of metallic interphases in the DSEs enhance the stress energy release mechanism through plastic deformation, interfacial delamination, crack arrest, and crack bridging across the metallic interphase after reduction.     

Controllable p-Type Doping of 2D WSe2 via Vanadium Substitution

Scalable substitutional doping of 2D transition metal dichalcogenides is a prerequisite to developing next-generation logic and memory devices based on 2D materials. To date, doping efforts are still nascent. Here, scalable growth and vanadium (V) doping of 2D WSe₂ at front-end-of-line and back-end-of-line compatible temperatures of 800 and 400 °C, respectively, is reported. A combination of experimental and theoretical studies confirm that vanadium atoms substitutionally replace tungsten in WSe₂, which results in p-type doping via the introduction of discrete defect levels that lie close to the valence band maxima. The p-type nature of the V dopants is further verified by constructed field-effect transistors, where hole conduction becomes dominant with increasing vanadium concentration. Hence, this study presents a method to precisely control the density of intentionally introduced impurities, which is indispensable in the production of electronic-grade wafer-scale extrinsic 2D semiconductors.