Microstructure and electrical properties of zirconia and composite nanostructured ceramics sintered by different methods

The aim of this study is the preparation and characterization of dense cubic zirconia ceramics and zirconia nanocomposites (reinforced with 5 wt% alumina). The powders were obtained through sol–gel methods and densified using classical sintering and spark plasma sintering (SPS) methods. The obtained ceramics were characterized through X-ray diffraction, scanning electron microscopy and impedance spectroscopy at room and high temperature. The average grain size of cubic zirconia particles was found to be approximately 8 and 2.5 μm for the classical sintering and 99 nm for SPS. The alumina particles in composites have an average grain size of 0.7 μm for classical sintering and 53 nm for SPS ones. The total conductivity for nanocomposites sintered through both methods was also determined.     

Films and crystalline powder of BiI3 intercalated with ammonia

Intercalation, i.e. the insertion of guest species in a crystalline layered structure, is an efficient route for generating new materials with novel properties. Thin films and crystalline powder of BiI₃ layered semiconductor were intercalated by exposure to ammonia vapors at room temperature. The intercalated compound was studied by thermo-gravimetric analysis, differential scanning calorimetry, X-ray diffraction, UV–vis optical absorption, FTIR spectroscopy and Raman scattering. After exposure of BiI₃ to ammonia the formation of a new phase, BiI₃(NH₃)_3.83, was evidenced by thermal analysis. The intercalation process leads to a blue shift of the BiI₃ optical absorption edge by 0.5 eV. The appearance of new Raman lines at 135 and 353 cm^?1 in the Raman spectrum of intercalated BiI₃ is considered as an evidence of the chemical interaction between the ammonia molecules and BiI₃ lattice.     

Beitrag zum Problem der Wechselströme beliebiger Kurvenform

Ohne Zusammenfassung     

Magnetite nanoparticles for functionalized textile dressing to prevent fungal biofilms development

ABSTRACT: The purpose of this work was to investigate the potential of functionalized magnetite nanoparticles to improve the antibiofilm properties of textile dressing, tested in vitro against monospecific Candida albicans biofilms. Functionalized magnetite (Fe3O4/C18), with an average size not exceeding 20 nm, has been synthesized by precipitation of ferric and ferrous salts in aqueous solution of oleic acid (C18) and NaOH. Transmission electron microscopy, X-ray diffraction analysis, and differential thermal analysis coupled with thermo gravimetric analysis were used as characterization methods for the synthesized Fe3O4/C18. Scanning electron microscopy was used to study the architecture of the fungal biofilm developed on the functionalized textile dressing samples and culture-based methods for the quantitative assay of the biofilm-embedded yeast cells. The optimized textile dressing samples proved to be more resistant to C. albicans colonization, as compared to the uncoated ones; these functionalized surfaces-based approaches are very useful in the prevention of wound microbial contamination and subsequent biofilm development on viable tissues or implanted devices.     

Films and crystalline powder of PbI2 intercalated with ammonia and pyridine

Thin films and crystalline powder of PbI₂ intercalated with ammonia or pyridine have been studied by optical absorption, Raman scattering, photoluminescence, FTIR spectroscopy and thermo-gravimetric analysis. Ammonia intercalated PbI₂ shows an increased optical band gap, of about 0.6 eV, with an intense broad emission band peaking at about 2.3 eV as signature in the photoluminescence spectrum. The intercalation of PbI₂ with ammonia is noticed in the Raman spectrum by the appearance of new lines situated in low frequency range. The D_3d coordination geometry of Pb²⁺ in the PbI₂ crystal is reduced by compression to orthorhombic one, the distribution of the electronic states in valence band is also changed. Thus, the top of the valence band undergo a deformation inducing a weakness of the interaction between the lead and iodine ions within a layer. Also the PbI₂ intercalated with pyridine is featured by optical and vibration properties different that of pure crystalline powder. Finally, the intercalation of PbI₂ with different molecules changes the basic semiconducting properties of the crystal. Thermal analyses and infrared absorption spectra have been used to study the desorption of guests species from PbI₂ in order to evaluate the stability range and morphological changes with temperature.     

Phage typing, an accessible and useful method in the epidemiological surveillance of diphtheria

Within the framework of the measures for diphtheria prevention and control, phage typing of isolates is useful for epidemiological investigations in a disease focus and in general population. The identification of asymptomatic carriers of toxigenic C.diphtheriae and its eradication decrease the transmission rate of the disease. The study of the circulating phage types (6058) enabled us to demonstrate the frequency and distribution of the different phage types, toxigenic and nontoxigenic in Romania. With the current knowledge of the circulating phage types it can be concluded that imported cases of diphtheria have not occurred so far. The Romanian phage typing schemes are able to type isolates from overseas, sometimes through phage adaptation methods. Our phage typing schemes are also able to demonstrate any modifications in the phage sensitivity patterns of diphtheria.     

Intracellular Delivery of Doxorubicin by Iron Oxide-Based Nano-Constructs Increases Clonogenic Inactivation of Ionizing Radiation in HeLa Cells

In this study, we determined the potential of polyethylene glycol-encapsulated iron oxide nanoparticles (IONP_CO) for the intracellular delivery of the chemotherapeutic doxorubicin (IONP_DOX) to enhance the cytotoxic effects of ionizing radiation. The biological effects of IONP and X-ray irradiation (50 kV and 6 MV) were determined in HeLa cells using the colony formation assay (CFA) and detection of γH2AX foci. Data are presented as mean ± SEM. IONP were efficiently internalized by HeLa cells. IONP_CO radiomodulating effect was dependent on nanoparticle concentration and photon energy. IONP_CO did not radiosensitize HeLa cells with 6 MV X-rays, yet moderately enhanced cellular radiosensitivity to 50 kV X-rays (DMF_SF0.1 = 1.13 ± 0.05 (p = 0.01)). IONP_DOX did enhance the cytotoxicity of 6 MV X-rays (DMF_SF0.1 = 1.3 ± 0.1; p = 0.0005). IONP treatment significantly increased γH2AX foci induction without irradiation. Treatment of HeLa cells with IONP_CO resulted in a radiosensitizing effect for low-energy X-rays, while exposure to IONP_DOX induced radiosensitization compared to IONP_CO in cells irradiated with 6 MV X-rays. The effect did not correlate with the induction of γH2AX foci. Given these results, IONP are promising candidates for the controlled delivery of DOX to enhance the cytotoxic effects of ionizing radiation.