Post-transition Region Research Articles

Critical behavior of interfacial t-ZrO2 and other oxide features of zirconium alloy reaching critical transition condition

Transition of zirconium alloys during uniform corrosion is not expected but inevitable, since it accelerates the degradation of corrosion property. Up to now, proposed transition mechanisms have not clearly illustrated the critical behavior of interfacial t-ZrO2 and other oxide features under the critical transition condition. Therefore, study on the under-transition sample was carried out. Microscopically, the monoclinic stress increases after transition, strongly supporting the occurrence of transformation from t-ZrO2 to m-ZrO2. A sudden stress decrease in t-ZrO2 occurs in pre-transition region of the under-transition sample. This decrease might be attributed to formation of permeable paths which induce consumption of interfacial oxygen vacancies. This critical behavior possibly destabilizes the grown t-ZrO2 grains. And the post-transition regions will propagate after t-ZrO2 transformation. The transition region in the oxide consists of lateral cracks propagated transgranularly and large numbers of interconnected pores, both of which may originate from t-ZrO2 transformation. Current works suggest that three critical behaviors of t-ZrO2 induce oxide fracture and corrosion transition. The growth nature and evolution mechanism of t-ZrO2 are further illustrated. Even though t-ZrO2 layer similarly evolve as the ZrO suboxide layer, the unstable nature of t-ZrO2 indicates that it is severely affected by grain size, stress value and chemical composition.

KINERJA KEUANGAN DAERAH PASCA PERALIHAN BEA PEROLEHAN HAK ATAS TANAH DAN BANGUNAN

This study examined differences in the local government's financial performance before and after the transition from central tax BPHTB be local taxes? In general, this study aims to determine the contribution BPHTB to the PAD as a source of funding for the survival of each region in order to achieve local autonomy system. The samples used in this study is the district/city that has existed since autonomy BPHTB not be treated as 114 cities/districts. The realization of the study observation period is the period before the transition budget BPHTB (Year 2010) and after the transition BPHTB (Year 2011). The research data were statistically tested with a different test of two paired samples.
 The results show that the performance of local government in Java have differences before and after the transition BPHTB from the central government to local governments. This research can provide empirical evidence of the differences in the financial performance of the post-transition region from the center to the regions BPHTB especially Java. The results of this study can also be used as a reference in future studies with similar themes to consider several things. First, the use of samples that are not confined to the local government but the entire Indonesian island of Java. Second, adding the growth rate ie performance measurement. Third, review the compatibility ratio because in addition to operational expenditure and capital expenditure is no longer heading in the budget expenditure is financing and transfer.
 
 
 Keywords: Bea Perolehan Hak atas Tanah dan Bangunan, Financial Performance, Autonomous Region.

Change of chemical states of niobium in the oxide layer of zirconium–niobium alloys with oxide growth

The change of chemical states of niobium with oxide growth was examined in the oxide layers of Zr–2.5Nb around the first kinetic transition by the conversion electron yield – X-ray absorption near-edge structure measurements. The detailed depth profiles of niobium chemical states were obtained in both the pre- and the post-transition oxide layers of Zr–2.5Nb formed in water at 663 K for 40–280 d. The depth profiling revealed that the inner oxide layer remained protective to oxidizing species even though in the post-transition region and this excellent stability of barrierness would be attributed the suppression of hydrogen pickup.

Regional determinants of MNE’s location choice in post-transition economies

This article focuses on the impact of agglomeration and labour market factors on the location choice of MNEs in post-transition economies. We compare data from 33 regions in East Germany, the Czech Republic and Poland using a mixed logit model on a sample of 4,343 subsidiaries for the time period between 2000 and 2010. The results show that agglomeration advantages, such as sectoral specialization as well as a region’s economic and technological performance prove to be some of the most important pull factors for FDI in post-transition regions. With respect to access to labour, the results suggest that FDI in post-transition regions is (no longer) only dominated by efficiency seeking behaviour, but also by access to well-qualified labour.

A Comparison of Macroscopic Fracture Surface and Crack Growth Rate of Ti-6Al-4V

A comparison between crack growth rate (da/dN) vs. effective stress intensity range factor (ΔKeff) curve behavior and microscopic and macroscopic fracture surface of commercial Ti-6Al-4V alloy are presented. Three different regimes are correlated with characteristics measured on the fracture surfaces. Three regions can be observed in which part I is rough and darker than others parts known as pre-transition, part II is smooth and light known as transition region and part III is a little darker than part II known as post-transition region. In the present investigation the correlation of fatigue crack growth rate for Ti-6Al-4V and microstructure of fracture surface has been presented.

Ionic conduction and effect of immobile cation substitution in binary system (AgI)4/5–(PbI2)1/5

Samples of stoichiometry (AgI)4(PbI2)1−x (CdI2) x , (0 ≤ x ≤ 0.4), have been prepared and studied by electrical conductivity, X-ray powder diffraction and DSC techniques. The ionic conductivity of samples was found to increase with temperature, and an abrupt increase at phase transition temperature was observed. The Cd+2-doped samples exhibited lower phase transition temperature compared to that of the pure samples. The ionic conductivity decreases with an increase in Cd+2 content in pre-transition, while enhances in conductivity result in Cd+2 content samples of x ≤ 0.2 in the post-transition region. Different resources of investigation confirmed the solubility limit of Cd+2 in the high-temperature phase to be x = 0.2. The change in the ionic conductivity of Cd+2-doped samples is explained by the increase in the defect concentration and the free volume available in the lattice. The drop in phase transition temperature of Cd2+-doped systems is attributed to the lattice distortion and the increase in the defect–defect interaction.

Dimerization of Hsp90 Is Required for in Vivo Function

Heat shock protein 90 (Hsp90) plays a central role in signal transduction and has emerged as a promising target for anti-cancer therapeutics, but its molecular mechanism is poorly understood. At physiological concentration, Hsp90 predominantly forms dimers, but the function of full-length monomers in cells is not clear. Hsp90 contains three domains: the N-terminal and middle domains contribute directly to ATP binding and hydrolysis and the C domain mediates dimerization. To study the function of Hsp90 monomers, we used a single-chain strategy that duplicated the C-terminal dimerization domain. This novel monomerization strategy had the dual effect of stabilizing the C domain to denaturation and hindering intermolecular association of the ATPase domain. The resulting construct was predominantly monomeric at physiological concentration and did not function to support yeast viability as the sole Hsp90. The monomeric construct was also defective at ATP hydrolysis and the activation of a kinase and steroid receptor substrate in yeast cells. The ability to support yeast growth was rescued by the addition of a coiled-coil dimerization domain, indicating that the parental single-chain construct is functionally defective because it is monomeric.

Studies of Corrosion of Cladding Materials in Simulated BWR Environment using Impedance Measurements

Abstract In the present work, the corrosion of three Zircaloy-2 cladding materials have been studied in-situ in an autoclave using electrochemical impedance spectroscopy. Measurements were conducted in simulated boiling water reactor environment at temperatures up to 288°C, both in the pre-transition and the post-transition stage. In addition, impedance measurements were performed at room temperature on samples previously exposed to irradiation. This work clearly demonstrates that impedance spectroscopy can be used for in-situ studies of the corrosion of Zircaloy cladding materials in the pre-transition region at high temperatures. Oxide thickness, oxide conductivity, and effective donor density were successfully evaluated from the impedance data. Less information has been able to be gained from the impedance measurements in the post-transition region compared to the measurements in the pre-transition region. However, the thickness of the inner oxide layer, oxide conductivity, and oxide porosity were successfully evaluated from the impedance data. The measurements on irradiated samples of the same materials as investigated in autoclaves indicate that irradiation introduces defects in the oxide structure, resulting in a higher number of charge carriers and a more inhomogeneous oxide than produced under autoclave exposure.

Perchlorate-induced conformational transition of Staphylococcal nuclease: evidence for an equilibrium unfolding intermediate

The sodium perchlorate-induced conformational transition of Staphylococcal nuclease has been monitored by both circular dichroism (CD) and fluorescence spectroscopy. The perchlorate-induced transition is cooperative as observed by both spectroscopic signals. However, the protein loses only about one-third of its native far-UV CD signal at high perchlorate concentrations, indicating that a significant amount of secondary structure remains in the post-transition state. The remaining CD signal can be further diminished in a cooperative manner by the addition of the strong denaturant, urea. Near-UV CD spectra clearly show that the protein loses its tertiary structure in the perchlorate-induced denatured state. The perchlorate-induced transition curves were fit to the standard two-state model and the standard free energy change and m value of the transition are 2.3 kcal/mol and 1.8 kcal/(mol M), respectively. By comparison, the urea-induced unfolding of Staphylococcal nuclease (in the absence of perchlorate) yields an unfolding free energy change, Δ G 0,un, of 5.6 kcal/mol and an m value of 2.3 kcal/(mol M). Thus, the thermodynamic state obtained in the post-transition region of perchlorate-induced conformation transition has a significantly lower free energy change, a high content of secondary structure, and diminished tertiary structure. These results suggest that the perchlorate-induced denatured state is a partially folded equilibrium state. Whether this intermediate is relevant to the folding/unfolding path under standard conditions is unknown at this time.

Differences in reactivity of oxide growth during the oxidation of Zircaloy-4 in water vapour before and after the kinetic transition

The oxidation of Zircaloy-4 by water vapour has been studied between 500 and 550 °C, the water vapour partial pressure ranging in 13–80 hPa, using isothermal and isobaric thermogravimetry, and calorimetry. During gravimetry experiments, sudden changes in temperature or water vapour pressure have also been performed. It results that the approximations of steady state and rate-limiting step are only valid before the kinetic transition. In the post-transition region, a significant influence of water vapour and hydrogen partial pressures has been found, contrarily to the kinetic behaviour before the transition (which is in this last case, in good agreement with a rate-limiting step of diffusion of oxygen vacancies). It comes out that the post-transition kinetic behaviour is definitely not the same as before the transition.

Long-term oxidation characteristics of oxygen-added modified Zircaloy-4 in 360°C water

The effect of oxygen on the long-term oxidation behavior of modified Zircaloy-4 (Zry-4) was investigated. The modified alloys were prepared by changing the chemical compositions of Zry-4; the tin content decreased from 0.5 wt% to zero while oxygen increased from 0.1 to 0.2 wt%, 0.1 wt% Nb was added and the amounts of Fe and Cr were kept to 0.1 and 0.2 wt%, respectively. The weight gain in water at 360°C for the 270 days exposure increased with increasing oxygen content from 0.1 to 0.2 wt%. In the case of the specimens containing 0.2 wt% oxygen, the tin free specimen showed a rate transition and a much higher weight gain compared to Zry-4. Raman spectroscopy showed that the tetragonal phase in the pre-transition region transformed to the monoclinic phase after the rate transition. Furthermore, this protective structure was changed to the non-protective cauliflower-like structure in the post-transition region.

Effects of oxygen partial pressure on oxidation of Zircaloy

The effects of oxygen partial pressure on the oxidation of Zircaloy-4 were examined at 773 K under the oxygen partial pressure between 0.1 and 2 × 10 −5 MPa to study the oxidation behavior of spent fuel during dry storage. The oxidation rate at first obeyed a cubic rate law, and changed to obey a linear rate law at almost the same weight gains even at different oxygen partial pressures. The oxidation rate during posttransition period showed p O 2 0.15 dependence. The dependency of the oxidation rate in the posttransition region agreed with the results of the oxygen diffusion coefficient in zirconium oxide measured by Keneshea and Douglass. Degradation of the protective oxide film of Zircaloy-4 under low oxygen partial pressures was not observed within the oxygen partial pressure range examined. The results of this experiment showed that the oxidation rate in air can be adopted to estimate the cladding oxidation rate during dry fuel storage in air and under low oxygen partial pressures.

Conformational stability and mechanism of folding of ribonuclease T1

Urea and thermal unfolding curves for ribonuclease T1 (RNase T1) were determined by measuring several different physical properties. In all cases, steep, single-step unfolding curves were observed. When these results were analyzed by assuming a two-state folding mechanism, the plots of fraction unfolded protein versus denaturant were coincident. The dependence of the free energy of unfolding, delta G (in kcal/mol), on urea concentration is given by delta G = 5.6 - 1.21 (urea). The parameters characterizing the thermodynamics of unfolding are: midpoint of the thermal unfolding curve, Tm = 48.1 degrees C, enthalpy change at Tm, delta Hm = 97 kcal/mol, and heat capacity change, delta Cp = 1650 cal/mol deg. A single kinetic phase was observed for both the folding and unfolding of RNase T1 in the transition and post-transition regions. However, two slow kinetic phases were observed during folding in the pre-transition region. These two slow phases account for about 90% of the observed amplitude, indicating that a faster kinetic phase is also present. The slow phases probably result from cis-trans isomerization at the 2 proline residues that have a cis configuration in folded RNase T1. These results suggest that RNase T1 folds by a highly cooperative mechanism with no structural intermediates once the proline residues have assumed their correct isomeric configuration. At 25 degrees C, the folded conformation is more stable than the unfolded conformations by 5.6 kcal/mol at pH 7 and by 8.9 kcal/mol at pH 5, which is the pH of maximum stability. At pH 7, the thermodynamic data indicate that the maximum conformational stability of 8.3 kcal/mol will occur at -6 degrees C.

Oxidation of zircaloy cladding in air

Abstract Non-irradiated, stress-relieved Zircaloy-4 claddings were oxidized at 350, 400, 450 and 500 °C in air. Some samples were dipped in sea water, dried and heated. Weight gain measured as a function of time revealed that the oxidation has pre- and post-transition regions just like the reaction in high temperature steam and water, and that sea water salts enhanced the weight gain after the transition point. Optical microscopy was carried out on the post-test oxide layer and substrate metal structure. Rate constants of the oxidation were determined and proved to be close to those of the previous studies including the experiments in high temperature steam and water.

Sedimentation and viscosity of bacteriophage T7 DNA in presence of CH3HgOH

AbstractThe effects of increasing concentartions of methylmercuric hydroxide (CH3HgOH) on the rate of sedimentation, S0, and intrinsic viscosity, [η], of T7 DNA have been studied at 20°C in 0.005, 0.05, and 0.5M Na2SO4, respectively, whereby each salt solvent conatined, in addition, 0.005M sodium borate, pH 9.18, as a buffer. Both S0 and [η] are independent of organomercurial concentration as long as DNA remains native. Denaturation, brought about by the complexing of CH3HgOH with the polymer, produces large changes in S0 as wll as [η]. The sedimentation coefficient increases strongly with increasing oragnomercurial concentration once strand separation has occured. Experimental difficulties prevented measuring of [η] in the posttransition region. The data on S0 have been used, in combination with available information on the so‐called density increment (∂ρ/∂c2), to obtain information on the frictional properties of single‐stranded and methylmercurated T7 DNA. The frictional coefficient, defined as f′2 = M2(∂p/∂c2)/S0ηNA, where M2 is the molecular wieght of T7 DNA, c2 is the concentration of DNA in g/ml of solution, ηr the realtive viscosity of the salt solvents, and NA is Avogadro's number, was evaluated for all three salt media as a function of organomercurial concentration. f′2 of native T7 DNA was found not to be sensitive to changes in ionic strngth; but f′2 of single‐stranded and methylmercurated T7 DNA varied strongly with salt concentration. Since f′2 of single‐stranded T7 DNA was barely affected by organomercurial concentration at a given ionic strength, it is concluded that the dramatic variations of S0 with pM (pM ≡ ‐log[CH3HgOH]) observed in the posttransition zone reflect only changes in the thermodynamic interactions (“preferential interactions”) existing between DNA and the vatious other solution components, but not changes in the coil dimensions of the polymer.

Oxidation Behavior of Chromium Between 300° and 600°C

Oxidation kinetics of high purity polycrystalline Cr were measured at and . The reaction proceeded in two stages: an initial period of growth, in which the kinetics could be described with the Cabrera‐Mott theory, was followed by an abrupt transition to a lower growth rate and parabolic kinetics. The kinetic transition was accompanied by a change in diffraction pattern of the oxide from that characteristic of a random orientation of very fine grained to a pattern indicating a strongly preferred fiber texture. The oxide film formed in the pretransition region was flat whereas that formed in the posttransition region was composed of ridges and nodules separated by a very thin oxide film. Activation energies in both kinetic regions were much less than that found for self‐diffusion in . It is concluded that the rate‐controlling process throughout the reaction is metal transport via preferred pathways, such as grain boundaries, through the oxide film. In the pretransition region the density of such pathways is high, leading to uniform film thickening. In the posttransition region the density of such pathways is low, leading to localized transport and hence localized oxide growth.

The effects of radiation on the corrosion of some Zr alloys

Under certain circumstances reactor irradiation enhances the corrosion of Zircaloy 2 andof Zr-2 1/2% Nb alloy by 10-fold or more. The enhancement is most significant in the post-transition region and in the temperature range 250–350°C; in the pre-transition region Zr-2 1/2%Nb alloy sometimes shows a slight suppressing effect of radiation. The detailed corrosion behaviour and the internal surface area of the oxide depend, inter alia, on whether the corrodent is “gaseous” (i.e. steam or impure carbon dioxide) or “liquid” (i.e. water); mechanisms to account for these observations are discussed.