Effect of Oversized Alloying Elements on Damage Rates and Recovery in Zirconium

2009 ◽  
Vol 1215 ◽  
Author(s):  
Valeriy Borysenko ◽  
Yuri Petrusenko ◽  
Dmitro Barankov

AbstractStudies were made into the influence of oversized rare-earth atoms on the processes of radiation defect accumulation and annealing in two-component zirconium alloys. Zr and Zr-X alloys (where X = Sc, Dy, Y, Gd and La) have been irradiated with 2 MeV electrons at 82 K. The radiation-induced resistivity has been measured in situ as a function of dose. As compared to unalloyed zirconium, the alloys have exhibited a decrease in the resistivity gain, this decrease being proportional to both the concentration and the size of dopant atoms. A possible explanation for the effect is offered. The difference between the recovery processes in zirconium and in its alloys has been studied. To this end, the irradiated specimens were subjected to isochronal annealing at temperatures between 82 and 350 K. It is shown that Dy, Y, Gd and La atoms trap interstitial atoms at stage I of the recovery. The dissociation of interstitial-impurity complexes takes place at stage II. In zirconium alloys with Dy, Y and Gd, splitting of recovery stage III into two substages has been revealed. The Zr-La alloy has not shown this splitting. Isothermal annealing data were used to determine the activation energies of recovery stages, and also to calculate the activation energy spectra for zirconium and its alloys. The oversized atoms of rare-earth metals are shown to interact effectively with both the interstitials and the vacancies in the zirconium matrix. This effect must be taken into account when developing new radiation-resistant Zr-base alloys or modifying the ones already existing.

2002 ◽  
Vol 719 ◽  
Author(s):  
W. Jiang ◽  
W. J. Weber ◽  
C. M. Wangxya

AbstractSingle crystal wafers of <0001>-oriented 6H-SiC were irradiated at different temperatures using a variety of ion species. The disorder on both the Si and C sublattices has been studied in situ using a combination of ion beam analyses in multiaxial channeling geometry. The fraction of the irradiation-induced defects surviving simultaneous recovery processes decreases with decreasing ion mass and with increasing irradiation temperature. Some of the Si and C defects are well aligned with the <0001> axis and the rate of C disordering is higher than that of Si disordering. Three recovery stages in Au2+-irradiated 6H-SiC have been identified.


1995 ◽  
Vol 10 (4) ◽  
pp. 981-985 ◽  
Author(s):  
N. Bordes ◽  
L.M. Wang ◽  
R.C. Ewing ◽  
K.E. Sickafus

Ion-irradiation induces amorphization in many intermetallics and ceramics, but spinel (MgAl2O4) is considered a “radiation resistant” ceramic. Spinel was irradiated with 1.5 MeV Kr+ at 20 K and observed in situ by transmission electron microscopy (TEM). The spinel remained crystalline to a high dose of 1 × 1016 ions/cm2, without any evidence of amorphization. Another spinel was preimplanted with Ne (400 keV and 50 keV). The microstructure revealed a still crystalline material with 8 nm interstitial loops. After irradiation with 1.5 MeV Kr+ (20 K), amorphization, a result of cation disordering, initiated at a dose of 1.7 × 1015 ions/cm2. At a dose of 1 × 1016 ions/cm2, the spinel was partially amorphous and the remaining crystalline domains disordered. These results show that spinel can be disordered and that amorphization can be triggered by the introduction of stable defects, followed by ion irradiation at low temperature.


Author(s):  
Charles W. Allen

Irradiation effects studies employing TEMs as analytical tools have been conducted for almost as many years as materials people have done TEM, motivated largely by materials needs for nuclear reactor development. Such studies have focussed on the behavior both of nuclear fuels and of materials for other reactor components which are subjected to radiation-induced degradation. Especially in the 1950s and 60s, post-irradiation TEM analysis may have been coupled to in situ (in reactor or in pile) experiments (e.g., irradiation-induced creep experiments of austenitic stainless steels). Although necessary from a technological point of view, such experiments are difficult to instrument (measure strain dynamically, e.g.) and control (temperature, e.g.) and require months or even years to perform in a nuclear reactor or in a spallation neutron source. Consequently, methods were sought for simulation of neutroninduced radiation damage of materials, the simulations employing other forms of radiation; in the case of metals and alloys, high energy electrons and high energy ions.


Author(s):  
I. A. Rauf

To understand the electronic conduction mechanism in Sn-doped indium oxide thin films, it is important to study the effect of dopant atoms on the neighbouring indium oxide lattice. Ideally Sn is a substitutional dopant at random indium sites. The difference in valence (Sn4+ replaces In3+) requires that an extra electron is donated to the lattice and thus contributes to the free carrier density. But since Sn is an adjacent member of the same row in the periodic table, the difference in the ionic radius (In3+: 0.218 nm; Sn4+: 0.205 nm) will introduce a strain in the indium oxide lattice. Free carrier electron waves will no longer see a perfect periodic lattice and will be scattered, resulting in the reduction of free carrier mobility, which will lower the electrical conductivity (an undesirable effect in most applications).One of the main objectives of the present investigation is to understand the effects of the strain (produced by difference in the ionic radius) on the microstructure of the indium oxide lattice when the doping level is increased to give high carrier densities. Sn-doped indium oxide thin films were prepared with four different concentrations: 9, 10, 11 and 12 mol. % of SnO2 in the starting material. All the samples were prepared at an oxygen partial pressure of 0.067 Pa and a substrate temperature of 250°C using an Edwards 306 coating unit with an electron gun attachment for heating the crucible. These deposition conditions have been found to give optimum electrical properties in Sn-doped indium oxide films. A JEOL 2000EX transmission electron microscope was used to investigate the specimen microstructure.


2020 ◽  
Author(s):  
Chi-Toan Nguyen ◽  
Alistair Garner ◽  
Javier Romero ◽  
Antoine Ambard ◽  
Michael Preuss ◽  
...  

Author(s):  
Yu Wang ◽  
Jiantao Wang ◽  
Haiping Wang ◽  
Xinyu Yang ◽  
Liming Chang ◽  
...  

Objective: Accurate assessment of breast tumor size preoperatively is important for the initial decision-making in surgical approach. Therefore, we aimed to compare efficacy of mammography and ultrasonography in ductal carcinoma in situ (DCIS) of breast cancer. Methods: Preoperative mammography and ultrasonography were performed on 104 women with DCIS of breast cancer. We compared the accuracy of each of the imaging modalities with pathological size by Pearson correlation. For each modality, it was considered concordant if the difference between imaging assessment and pathological measurement is less than 0.5cm. Results: At pathological examination tumor size ranged from 0.4cm to 7.2cm in largest diameter. For mammographically determined size versus pathological size, correlation coefficient of r was 0.786 and for ultrasonography it was 0.651. Grouped by breast composition, in almost entirely fatty and scattered areas of fibroglandular dense breast, correlation coefficient of r was 0.790 for mammography and 0.678 for ultrasonography; in heterogeneously dense and extremely dense breast, correlation coefficient of r was 0.770 for mammography and 0.548 for ultrasonography. In microcalcification positive group, coeffient of r was 0.772 for mammography and 0.570 for ultrasonography. In microcalcification negative group, coeffient of r was 0.806 for mammography and 0.783 for ultrasonography. Conclusion: Mammography was more accurate than ultrasonography in measuring the largest cancer diameter in DCIS of breast cancer. The correlation coefficient improved in the group of almost entirely fatty/ scattered areas of fibroglandular dense breast or in microcalcification negative group.


2011 ◽  
Vol 286 (1-2) ◽  
pp. 32-47 ◽  
Author(s):  
Christopher M. Fisher ◽  
John M. Hanchar ◽  
Scott D. Samson ◽  
Bruno Dhuime ◽  
Janne Blichert-Toft ◽  
...  

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 924
Author(s):  
Laurence Blanchard ◽  
Arjan de Groot

Deinococcus bacteria are extremely resistant to radiation and able to repair a shattered genome in an essentially error-free manner after exposure to high doses of radiation or prolonged desiccation. An efficient, SOS-independent response mechanism to induce various DNA repair genes such as recA is essential for radiation resistance. This pathway, called radiation/desiccation response, is controlled by metallopeptidase IrrE and repressor DdrO that are highly conserved in Deinococcus. Among various Deinococcus species, Deinococcus radiodurans has been studied most extensively. Its genome encodes classical DNA repair proteins for error-free repair but no error-prone translesion DNA polymerases, which may suggest that absence of mutagenic lesion bypass is crucial for error-free repair of massive DNA damage. However, many other radiation-resistant Deinococcus species do possess translesion polymerases, and radiation-induced mutagenesis has been demonstrated. At least dozens of Deinococcus species contain a mutagenesis cassette, and some even two cassettes, encoding error-prone translesion polymerase DnaE2 and two other proteins, ImuY and ImuB-C, that are probable accessory factors required for DnaE2 activity. Expression of this mutagenesis cassette is under control of the SOS regulators RecA and LexA. In this paper, we review both the RecA/LexA-controlled mutagenesis and the IrrE/DdrO-controlled radiation/desiccation response in Deinococcus.


Author(s):  
Yu-Hsiang Wu ◽  
Elizabeth Stangl ◽  
Octav Chipara ◽  
Anna Gudjonsdottir ◽  
Jacob Oleson ◽  
...  

Abstract Background Ecological momentary assessment (EMA) is a methodology involving repeated surveys to collect in-situ self-reports that describe respondents' current or recent experiences. Audiology literature comparing in-situ and retrospective self-reports is scarce. Purpose To compare the sensitivity of in-situ and retrospective self-reports in detecting the outcome difference between hearing aid technologies, and to determine the association between in-situ and retrospective self-reports. Research Design An observational study. Study Sample Thirty-nine older adults with hearing loss. Data Collection and Analysis The study was part of a larger clinical trial that compared the outcomes of a prototype hearing aid (denoted as HA1) and a commercially available device (HA2). In each trial condition, participants wore hearing aids for 4 weeks. Outcomes were measured using EMA and retrospective questionnaires. To ensure that the outcome data could be directly compared, the Glasgow Hearing Aid Benefit Profile was administered as an in-situ self-report (denoted as EMA-GHABP) and as a retrospective questionnaire (retro-GHABP). Linear mixed models were used to determine if the EMA- and retro-GHABP could detect the outcome difference between HA1 and HA2. Correlation analyses were used to examine the association between EMA- and retro-GHABP. Results For the EMA-GHABP, HA2 had significantly higher (better) scores than HA1 in the GHABP subscales of benefit, residual disability, and satisfaction (p = 0.029–0.0015). In contrast, the difference in the retro-GHABP score between HA1 and HA2 was significant only in the satisfaction subscale (p = 0.0004). The correlations between the EMA- and retro-GHABP were significant in all subscales (p = 0.0004 to <0.0001). The strength of the association ranged from weak to moderate (r = 0.28–0.58). Finally, the exit interview indicated that 29 participants (74.4%) preferred HA2 over HA1. Conclusion The study suggests that in-situ self-reports collected using EMA could have a higher sensitivity than retrospective questionnaires. Therefore, EMA is worth considering in clinical trials that aim to compare the outcomes of different hearing aid technologies. The weak to moderate association between in-situ and retrospective self-reports suggests that these two types of measures assess different aspects of hearing aid outcomes.


2021 ◽  
Vol 13 (8) ◽  
pp. 4591
Author(s):  
Shuanglei Huang ◽  
Daishe Wu

The tremendous input of ammonium and rare earth element (REE) ions released by the enormous consumption of (NH4)2SO4 in in situ leaching for ion-adsorption RE mining caused serious ground and surface water contamination. Anaerobic ammonium oxidation (anammox) was a sustainable in situ technology that can reduce this nitrogen pollution. In this research, in situ, semi in situ, and ex situ method of inoculation that included low-concentration (0.02 mg·L−1) and high-concentration (0.10 mg·L−1) lanthanum (La)(III) were adopted to explore effective start-up strategies for starting up anammox reactors seeded with activated sludge and anammox sludge. The reactors were refrigerated for 30 days at 4 °C to investigate the effects of La(III) during a period of low-temperature. The results showed that the in situ and semi in situ enrichment strategies with the addition of La(III) at a low-concentration La(III) addition (0.02 mg·L−1) reduced the length of time required to reactivate the sludge until it reached a state of stable anammox activity and high nitrogen removal efficiency by 60–71 days. The addition of La(III) promoted the formation of sludge floc with a compact structure that enabled it to resist the adverse effects of low temperature and so to maintain a high abundance of AnAOB and microbacterial community diversity of sludge during refrigeration period. The addition of La(III) at a high concentration caused the cellular percentage of AnAOB to decrease from 54.60 ± 6.19% to 17.35 ± 6.69% during the enrichment and reduced nitrogen removal efficiency to an unrecoverable level to post-refrigeration.


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