Applicability of the Photochemically Generated Pendant Benzoyl Peroxides in both “Grafting From” and “Grafting To” Techniques

Methyl methacrylate and styrene copolymers containing pendant benzil groups, such as 1-[4-(2-methacroyloxyethoxy)phenyl]-2-phenyl-1,2-ethanedione-co-methyl metacrylate (BzMA/MMA), 1-[4-(2-methacroyloxyethoxy)phenyl]-2-phenyl-1,2-ethanedione-co-styrene (BzMA/S), and 1-phenyl-2-(4-propenoylphenyl)-1,2-ethanedione-co-styrene (PCOCO/S), were prepared and used as precursors for photochemically generated pendant benzoyl peroxides. Decomposition of the pendant benzoyl peroxides was subsequently used in grafting processes. Either irradiation or a combination of irradiation with subsequent thermal treatment was adopted for grafting a thin layer of BzMA/MMA copolymer onto the surface of LDPE films. The grafting resulted in a significant decrease in contact angle of the film surface. The same activation strategy was successfully adopted to initiate the polymerisation of acrylic or methacrylic acids from the surface of styrene copolymer films containing the initiator precursor in the polymer side chains (BzMA/S and PCOCO/S). The successful surface grafting was proved by contact angles measurement as well as by infrared spectroscopic analysis

Vickers Hardness and Positron Annihilation Study of Eurofer97 and ODS Eurofer

This paper describes investigations of Eurofer97 and oxide dispersion strengthened version of this steel, in as received state and after annealing. Vickers hardness test was performed on the as received specimens and after annealing at various temperatures to obtain information about development of the strength of studied materials. After identifying the temperature region where significant changes of the strength take place we applied positron annihilation spectroscopy to probe the microstructural changes in ferritic/martensitic steels. An observation of phase transformation was observed in both steels at various temperatures indicating different behaviour of the base material and its strengthened version. All applied methods proved the importance of strengthening by oxides to improve properties of steels

Electric properties of anorthite ceramics prepared from illitic clay and oil shale ash

Electrical properties during firing of anorthite ceramic prepared from mixtures of illitic clay (from Northeastern Hungary) and fly ashes (obtained from circulating fluidized bed combustion – IA4 and pulverized firing – ID4) with high content of CaO were investigated. Mixtures were prepared with 60 wt% of illitic clay and 40 wt% of oil shale ash. The ashes were hydrated prior to mixing, to prevent the reaction of free lime with water during sample preparation. The mixtures were subjected to thermal and structural analyses to describe the processes induced by thermal treatment. The contraction of the IA4 and ID4 samples reached 1.8% and 2.5%, respectively, at 1100 °C, which is significantly lower than that of the illitic clay (7%). X-ray diffraction (XRD) analysis revealed a presence of diopside, gehlenite, cristobalite, and leucite minerals as additional mineral phases in the prepared anorthite ceramics. Measurement of AC conductivity showed that after the decomposition of the CaCO3 at ∼880 °C, Ca2+ ions became the dominant charge carriers, and the electrical current was carried by a hopping mechanism throughout the studied temperature region. The electrical conductivity and the relative dielectric constant of the ID4 sample was higher compared to that of the IA4 sample. The relative dielectric constant reached values of 6 (sample IA4) and 8 (sample ID4) at 140 °C (after drying)

Densitometric patterns of NADPH diaphorase staining in the spinal cord of dog

Mar ala, M., Densitometric patterns of NADPH diaphorase staining in the spinal cord of dog. Biologia, Bratislava, 56: 685-693, 2001; ISSN 0006-3088 (Biologia). ISSN 1335-6399 (Biologia. Section Cellular and Molecular Biology). Segmental and laminar distribution of NADPHd activity was studied in the normal spinal cord of the dog and basic densitometric patterns of somatic, fiber-like and punctuate, non-somatic NADPHd staining were described in the gray and white matter. Prominent NADPHd activity was noted in the superficial and deep dorsal horn, pericentral region, intermediolateral cell column, Lissauer's tract and in the vertical and horizontal limbs of the medial longitudinal bundle of the ventral column in the cervical and upper thoracic segments. Key words: densitometry, NADPH diaphorase, spinal cord, dog. Introduction The use of nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) histochemistry alone or combined with the nitric oxide synthase immunoreactivity (NOS-IR) allowed for a morphologically distinct and topographically precise localization of small neuronal pools synthesizing, releasing and transporting NOS, an enzyme responsible for nitric oxide (NO) synthesis. The discrete loci, nuclei or solitary NOS-IR neurons have been identified not only in the cortex, brain stem and spinal cord, but also in the peripheral nervous system (Vincent & Johanson, 1983; Immunocytochemistry of the neuronal nitric oxide synthase (nNOS) showed that the occurrence of this enzyme is almost completely homotopic with the localization of neurons stained for NADPHd In the present study an attempt was made to specify the differences of somatic, fiber-like, and punctuate NADPHd staining in the gray and white matter of the spinal cord in the normal dog, including different segments and layers using the densitometric analysis. Densitometric patterns of NADPHd positivity in the undamaged spinal cord may be helpful in experimental studies aimed at a causal interpretation of changes affecting the NOS-containing neuronal pools in various experimental and pathologic conditions. Material and methods Tissue sampling, sectioning, examination of sections and the performance of the densitometric analysis Adult dogs (n = 6) of both sexes weighing 12-18 kg were used in this study. The animals were deeply anesthetized with pentobarbital (50 mg/kg, i.v.) and perfused transcardially with saline followed by freshly prepared 4% paraformaldehyde +0.1% glutaraldehyde buffered with 1M sodium phosphate, pH = 7.4. Following perfusion fixation, the spinal cords were carefully dissected out and stored in toto in the same fixative for 3-4 hours. After postfixation, the spinal cord was divided into cervical, thoracic, lumbar, sacral and coccygeal segments, and each segment was then secondarily divided into three small blocks comprising the upper, middle, and lower segmental levels, respectively. Specimens were then cryoprotected in an ascending concentration of sucrose (15-30%) with the same phosphate buffer and stored overnight at 4 • C. Frozen transverse sections (50 µm thick) were cut from all segments studied and processed for NADPH-d activity by using a modified histochemical procedure The densitometric analysis was performed using transverse sections stained for NADPHd histochemistry. Precise loci identified in the gray and white matter on transverse sections were used for the assessment of the densitometric patterns in both compartments of the spinal cor

Hydrogen-induced microstructural changes of Pd films

The development of the microstructure in nanocrystalline, polycrystalline and epitaxial Pd films loaded with hydrogen is investigated. Structural changes in Pd films loaded with hydrogen were characterized by positron annihilation spectroscopy combined with electron microscopy and X-ray diffraction. It was found that hydrogen charging causes plastic deformation which leads to an increase of the defect density in all Pd films studied. Moreover, the formation of buckles was observed in nanocrystalline and polycrystalline Pd films loaded above a certain critical hydrogen concentration. Buckling leads to detachment of the film from the substrate and this is accompanied with in-plane stress relaxation and plastic deformation of the film