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The dependence of the work function of rare earth metals on their electron structure
No full textThe work function primarily depends on the electron structure of the analysed material. Having in mind the importance of rare earth metals in advanced electronics, in this paper the dependence of the work function of rare earth metals on their electron structure has been analysed. It is shown that dependencies of work functions on the number of electrons of the most stable f(7) and f(14) configurations can be established for the series CeSm and GdTm
Grain growth during sintering of batio3 with lif
No full textThe sintering behavior of BaTiO3 with LiF showed that it was possible to sinter barium titanate at temperatures below 1000 degrees C. Different combinations of the sintering powders were prepared by adding 1 to 5 w% LiF and sintering at the temperature of 950 degrees C for 20 hours. The grain growth of LiF fluxed BaTiO3 was studied, and electron microscopy was used to investigate and characterize the microstructure of the samples. The dielectric constant and dielectric losses were determined. It was shown that the composition of the liquid phase formed during this process had a prominent influence on the grain growth and on the formation of BaTiO3 with better dielectric properties
A study of lignin formation at the molecular level by scanning tunneling microscopy
Full text linkA scanning tunneling microscope (STM) was used to observe the temporal formation and organization of dehydrogenative polymer (DHP) synthesized from coniferyl alcohol. The images obtained elucidate this structure for the first time. The structure of DHP, as seen from STM images, shows long-range order. It appears that DHP consists of building units or modules assembled into larger assemblies called supermodules. Supermodules are interconnected into the overall lattice-like polymer structure with or without spherical regions. One module consists of about 20 monomers, while the supermodule contains about 500 monomers. Calculated molecular weights for modules and supermodules agree with DHP molecular weight distribution peaks. Samples prepared at two different pH values, 6.4 and 7.6, have the same characteristics. The results presented demonstrate that the process of lignification, even in in vitro conditions, is highly ordered, and as such contribute to our understanding of the structure of lignin, a significant constitutive and functional element of cell walls
Effects of the air pollutant SO2 on leaves: Inhibition of sulfite oxidation in the apoplast by ascorbate and of apoplastic peroxidase by sulfite
No full textAfter SO2 has entered leaves of spinach (Spinacia oleracea) through open stomata and been hydrated in the aqueous phase of cell walls, the sulfite formed can be oxidized to sulfate by an apoplastic peroxidase that is normally involved in phenol oxidation. The oxidation of sulfite is competitive with the oxidation of phenolics. During sulfite oxidation, the peroxidase is inhibited. In the absence of ascorbate, which is a normal constituent of the aqueous phase of the apoplast, peroxidative sulfite oxidation facilitates fast additional sulfite oxidation by a radical chain reaction. By scavenging radicals, ascorbate inhibits chain initiation and sulfite oxidation. Even after exposure of leaves to high concentrations of SO2, which inhibited photosynthesis, the redox state of ascorbate remained almost unaltered in the apoplastic space of the leaves. It is concluded that the oxidative detoxification of SO2 in the apoplast outside the cells is slow. Its rate depends on the rate of apoplastic hydrogen peroxide generation and on the steady-state apoplastic concentrations of phenolics and sulfite. The affinity of the peroxidase for phenolics is higher than that for sulfite
Kinetic study of stress‐induced luminescence from different tissues
No full textAbstract— Exponential decay of the stress‐induced luminescence from different tissues was resolved into the first order reaction components and appropriate rate constants were determined from the reaction half‐times. Kinetic analysis shows that luminescence decays generally through three parallel pseudo‐first order reactions which can be affected independently. The same order of magnitude (even very close numerical values) of the rate constants of luminescent reactions induced by different chemical and physical stimuli in different organisms suggests that a common mechanism is included in their luminescence. Analysis of the secondary kinetics appearing in the particular cases of the luminescence decay, as well as kinetic analysis of the stress‐induced radical decay measured by electron paramagnetic resonance, show that activated forms of oxygen and peroxy‐radicals have a central role in the luminescence emission
A pool of nonpolysomal globin mRNAs in globin deficient reticulocytes of the anemic Belgrade rat
No full textIn anemia of the Belgrade rat ( b b) reticulocytes contain less than half of the normal amount of mRNA for seven adult rat globin chains. cDNA hybridization measurements of the relative sizes of polysomal and nonpolysomal pools of globin mRNAs in these cells show that 45% of all globin mRNA molecules are not used at any given time in protein synthesis. This implies a translational control which ensures a production of globin chains in a correct ratio despite a severe mRNA unbalance