High retention of polarization in polycrystalline M/PZT/M capacitors in the presence of depolarization field near grain boundaries

Recently, we reported on the photovoltaic current observed in poled capacitors with polycrystalline Pb(ZrTi)O(3) (PZT) films, where (111)-oriented PZT grains are separated by an ultrathin semiconductor PbO phase. This photocurrent is driven by the depolarization field, which is generated by residual uncompensated polarization charge located on grain boundaries near electrodes. We showed that the photocurrent can serve as a criterion of existence of the depolarization field and demonstrated that this field is retained in the film for at least one year. Here, we present new experimental and numerical results which confirm the proposed conception of the photovoltaic effect. We study the photocurrent depending on the kind of electrodes, preliminary illumination in an open-circuit regime, and light intensity of LED, and give evidence of retention of the depolarization field in the films for at least for one and one-half years. The numerical study of the photovoltaic effect at extremely high photogeneration rate shows that total compensation of the polarization charge by photoexcited carriers in these structures is impossible. This photovoltaic effect can be used for nondestructive readout in ferroelectric memory.     

X-ray absorption fine structure investigations on heat-treated Cr-doped titania thin films

Chromium-doped titanium oxide thin films were investigated in the as-deposited state and after thermal treatment (723 K for 3 h in air). X-ray diffraction data revealed an improvement in film crystallinity induced by the thermal treatment. Extended X-ray absorption fine structure data revealed similar atomic neighboring around Cr atoms in both as-deposited and annealed samples. A lattice contraction of ~ 2% is observed in the annealed samples. The 67% enhancement of the amplitude of the Cr 1 s X-ray absorption fine structure pre-edge peak after thermal treatment, which is a sign of “dipole-forbidden” 1 s → 3 d transitions, suggests strong alteration in the number of Cr 3 d vacancies, in spite of similar Cr local environment in the two kinds of investigated samples. We discuss here the Cr⁺ → Cr⁴⁺ and Cr²⁺ → Cr⁶⁺ changes induced by thermal treatment, and/or the evolution in local structures without inversion center.Refractive index dispersion spectra in the visible wavelength domain allowed us to compute the values of the dispersion energy, the single-oscillator energy and the coordination number of Ti atoms in both as-deposited and annealed samples.     

Protein organization on the PHA inclusion cytoplasmic boundary

Biotransformation of ethanol by liver nuclei was studied. The formation of acetaldehyde was determined by GC/FID. The 1-hydroxyethyl (1HEt) formation was established by spin trapping of the radical with N-t-butyl-alpha-phenylnitrone (PBN) followed by GC/MS. Liver nuclei, free of endoplasmic reticulum, cytosol or mitochondria, were able to biotransform ethanol to acetaldehyde in the presence of NADPH under air. Only 22% activity was observed in the absence of the cofactor. Twenty-six percent of the NADPH-dependent activity and 47% of the NADPH-independent activity were observable under nitrogen. Aerobic biotransformation was inhibited by CO, SKF 525A, 4-methylpyrazole and by diethyldithiocarbamate. This suggests that CYP2E1 is involved in the process. However, the formation of acetaldehyde was able to proceed under a pure CO atmosphere. The lack of inhibitory effects of 2-mercapto-1-methylimidazol and thiobenzamide excludes the potential participation of the NADPH flavin monooxigenase system. The formation of hydroxyl radicals in the process is suggested by the partial inhibitory effect of 5 mM mannitol and 5 mM sodium benzoate and by the fact that the 1HEt was detected. The NADPH-dependent anaerobic ethanol biotransformation pathway was stimulated by FAD and inhibited to some extent by iron chelators. The relevance of a liver nuclear ethanol biotransformation, generating reactive metabolites, such as acetaldehyde and free radicals, nearby DNA, nuclear proteins and lipids is discussed.     

Application of annealing for extension of WWER vessel lives

The safe operation of nuclear power plants (NPP) is dependent upon the assurance that the reactor pressure vessel will not fail in a brittle manner when the effects of radiation embrittlement are taken into account. The recovery of the properties of the irradiated materials is an important way of extending the operating life of a reactor vessel. The intent of this paper is to demonstrate the efficiency of thermal annealing for the recovery of reactor vessel material properties and to present the implications for extended service life.In order to substantiate the application of annealing to the extensior of the service life of vessels, detailed investigations were conducted which involved thermal annealing temperature and time, fast neutron fluence, and metallurgical factors (i.e. impurity contents) on the recovery of properties after the annealing of irradiated materials. Similar studies were continued to determine predictive methods for radiation embrittlement after repeated annealings.In May 19876 the first pilot annealing of a commercial reactor vessel (Novo-Voronezhskaya, III, NPP) was performed. The development of the annealing equipment and investigations performed to test the annealing process proved successful, and an improved safe operation period for the reactor vessel was thus attained providing for an extended service life.     

Mechanical testing of plasma-sprayed coatings of ceramics

Mechanical tests have been performed on two types of plasma-sprayed ceramic coatings: magnesium zirconate (ZM) on aluminium alloy and chromium oxide (CO) on cast iron. Tensile strength, shear strength, energy relaxation rate and crack velocity have been determined. Results obtained with double-torsion tests show good agreement with those of double-cantilever-beam tests. Fracture always occurred in the ceramic for the ZM coating and at the interface for the CO one. Finally, acoustic emission monitoring carried out during bending tests was used to point out different types of emission, and to correlate them with micrographic examinations in order to identify some damaging processes.[/p]     

Entkohlungsreaktionen mit unruhigem Blasverhalten beim Aufblasen von Sauerstoff auf Fe-C-Schmelzen

Reaktionen in der Gasphase und an der Badoberfläche. Filmaufnahmen von pulsierenden Vorgängen. Entkohlungsreaktionen nach Art von Siedeverzügen. Ruhiges und unruhiges Blasverhalten. Abgas- und Brennflecktemperaturen. Kleinkonverter- und Induktionsofenversuche.     

Spatial distributions of residuals produced inside a spallation target

The spallation target model of an accelerator driven system (ADS), consisting of six 5 cm thick and 16 cm in diameter Pb segments, was constructed. Three sets of 17 Bi samples (1/2 inch in diameter and 1 mm thick) were placed in 3 Pb disc-shaped holders inside the target at 5, 10 and 15 cm from its front. After irradiation with 660 MeV proton beam gamma-spectra of radioisotopes produced in Bi were collected several times for each sample with the use of HPGe detectors in order to identify the radioisotopes and to determine their absolute activities. Their spatial distributions were then compared with respective values obtained in the calculations made with the use of FLUKA and/or MCNPX code. A fair agreement with the experiment has been observed.