The Corrosion of Carbon Steel under Deep Geologic Nuclear Waste Disposal Conditions

The proposed disposal scenario for high-level nuclear waste (spent fuel) in Canada is emplacement within a sealed, deep geological repository (DGR) located in either granitic rock or sedimentary clay. Disposal is based on a multi-barrier approach, with the primary barrier being a sealed container which could be either dual-walled with a copper shell over an inner carbon steel vessel for granitic rock or a single thick-walled steel container for sedimentary clay. This study focuses on the corrosion behaviour of A516 Gr70 carbon steel as well as the corrosion products formed in a variety of groundwater compositions and concentrations expected within a sedimentary clay DGR environment. In particular, the effects of groundwater anions such as Cl-, HCO3-/CO32-, and SO42- on the corrosion behaviour and corrosion product compositions and morphologies were studied. Several electrochemical and surface characterization techniques were employed to investigate the corrosion behaviour of the steel as well as the identities and morphologies of the subsequent corrosion products. It was shown that in the presence of trace levels of O2, Cl- is able to induce passivation of the steel surface by the catalytic conversion of Fe2+ to Fe3+ with passivation induced in this manner then leading to the initiation of breakdown sites. The addition of HCO3-/CO32- to highly concentrated Cl- solutions led to a competition between the catalytic formation of FeIII oxides and the stabilization of soluble Fe2+ by complexation with HCO3-/CO32-. In addition, an increase in the total carbonate concentration increased the breakdown potential by preventing the stabilization of pits by buffering the development of acidity required for propagation. In contrast, SO42- was shown not to interfere with the Cl--catalyzed oxidation to FeIII oxides in the presence of trace O2 but to have a significant effect on the breakdown potential, possibly due to its ability to be more strongly adsorbed to the FeIII surface. Electrochemical experiments performed under totally anaerobic conditions showed that an increase in [Cl-] promoted corrosion leading to an increased roughening of the steel surface. This was attributed to an acceleration of the cathodic reaction on exposed Fe3C bands from the pearlite structure. The addition of groundwater ions led to a suppression of the anodic kinetics due to the accumulation of CaCO3 crystals. Addition of HCO3-/CO32- to buffer the pH to 8.85 led to a significant decrease in the corrosion rate. This was attributed to the growth of a Fe3O4 barrier layer with additional protection provided by an outer layer of Fe2(OH)2CO3. Complementary long-term corrosion studies showed that an initial period of humid air exposure led to the formation of a γ-Fe2O3 layer which was subsequently reduced to Fe3O4 by galvanic coupling to steel dissolution over approximately the first 100 days of exposure. Corrosion occurred preferentially at pearlite grains due to the lower cathodic overpotential on the Fe3C lamellae. Addition of groundwater ions suppressed steel corrosion due to the rapid deposition of CaSO4 and CaCO3 crystals. High levels of Mg2+ were shown to promote the formation of aragonite, a polymorph of CaCO3 known to cause a reduction in steel corrosion rates. Finally, the addition of HCO3-/CO32- led to the rapid formation of Fe2(OH)2CO3, attributed to the initial γ-Fe2O3 layer whose reduction led to high [Fe2+] and the promotion of Fe2(OH)2CO3 deposition. However, thermodynamic transformation of Fe2(OH)2CO3 to FeCO3 appeared to induce some localized corrosion/pitting processes. The influence of H2O2 on steel corrosion under deaerated and totally anaerobic conditions was studied to determine whether radiolytic oxidants produced by the radiation fields in the fuel waste form would influence corrosion of the inside of a failed waste container. The interaction of the H2O2 with the steel was confirmed by the presence of FeIII-containing corrosion products. The results showed that continuous steel corrosion can be expected in an anaerobic environment but that passivation occurred in the deaerated experiment. However, passivation was attributed to the higher levels of dissolved O2 present and not the addition of H2O2 used as a surrogate for radiolytic oxidants. As such, active steel corrosion should be maintained inside a failed container and the soluble corrosion products (Fe2+ and H2) will be available to suppress fuel corrosion and radionuclide release

Meal delivery programs reduce the use of costly health care in dually eligible medicare and medicaid beneficiaries

Delivering food to nutritionally vulnerable patients is important for addressing these patients' social determinants of health. However, it is not known whether food delivery programs can reduce the use of costly health services and decrease medical spending among these patients. We sought to determine whether home delivery of either medically tailored meals or nontailored food reduces the use of selected health care services and medical spending in a sample of adults dually eligible for Medicare and Medicaid. Compared with matched nonparticipants, participants had fewer emergency department visits in both the medically tailored meal program and the nontailored food program. Participants in the medically tailored meal program also had fewer inpatient admissions and lower medical spending. Participation in the nontailored food program was not associated with fewer inpatient admissions but was associated with lower medical spending. These findings suggest the potential for meal delivery programs to reduce the use of costly health care and decrease spending for vulnerable patients

Ground-based walking training improves quality of life and exercise capacity in COPD

This study was designed to determine the effect of ground-based walking training on health-related quality of life and exercise capacity in people with chronic obstructive pulmonary disease (COPD). People with COPD were randomised to either a walking group that received supervised, ground-based walking training two to three times a week for 8–10 weeks, or a control group that received usual medical care and did not participate in exercise training. 130 out of 143 participants (mean±SD age 69±8 years, forced expiratory volume in 1 s 43±15% predicted) completed the study. Compared to the control group, the walking group demonstrated greater improvements in the St George’s Respiratory Questionnaire total score (mean difference -6 points (95% CI -10– -2), p<0.003), Chronic Respiratory Disease Questionnaire total score (mean difference 7 points (95% CI 2–11), p<0.01) and endurance shuttle walk test time (mean difference 208 s (95% CI 104–313), p<0.001). This study shows that ground-based walking training is an effective training modality that improves quality of life and endurance exercise capacity in people with COPD

Evolution of the electronic structure with size in II-VI semiconductor nanocrystals

In order to provide a quantitatively accurate description of the band gap variation with sizes in various II-VI semiconductor nanocrystals, we make use of the recently reported tight-binding parametrization of the corresponding bulk systems. Using the same tight-binding scheme and parameters, we calculate the electronic structure of II-VI nanocrystals in real space with sizes ranging between 5 and 80 {\AA} in diameter. A comparison with available experimental results from the literature shows an excellent agreement over the entire range of sizes.Comment: 17 pages, 4 figures, accepted in Phys. Rev.

Prediction of pH Change in Processed Acidified Turnips

The acetic acid uptake by turnips was studied during an acidification process in containers. The process was successfully described by a Fickian diffusion, using a correlation for the buffer effect. Diffusion coefficients (0.629 to 3.99 × 10-9 m2/sec) and partition coefficients (0.8 to 1.1) were obtained by optimization of the fit between experimental and theoretical values, using the simplex method. The partition coefficient did not show an evident dependence on temperature, while diffusivity followed an Arrhenius type behavior. The relationship between acid concentration and pH was described using a cubic model with parameters independent of temperature. Results showed that the combination of these models describing the acid diffusion into the food and the buffering effects of the food allowed accurate prediction of pH evolution in the acidification process

Search for Single Top Production at LEP

Single top production in e+e- annihilations is searched for in data collected by the L3 detector at centre-of-mass energies from 189 to 209 GeV, corresponding to a total integrated luminosity of 634 pb-1. Investigating hadronic and semileptonic top decays, no evidence of single top production at LEP is obtained and upper limits on the single top cross section as a function of the centre-of-mass energy are derived. Limits on possible anomalous couplings, as well as on the scale of contact interactions responsible for single top production are determined

Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results

The chromosphere is a thin layer of the solar atmosphere that bridges the relatively cool photosphere and the intensely heated transition region and corona. Compressible and incompressible waves propagating through the chromosphere can supply significant amounts of energy to the interface region and corona. In recent years an abundance of high-resolution observations from state-of-the-art facilities have provided new and exciting ways of disentangling the characteristics of oscillatory phenomena propagating through the dynamic chromosphere. Coupled with rapid advancements in magnetohydrodynamic wave theory, we are now in an ideal position to thoroughly investigate the role waves play in supplying energy to sustain chromospheric and coronal heating. Here, we review the recent progress made in characterising, categorising and interpreting oscillations manifesting in the solar chromosphere, with an impetus placed on their intrinsic energetics.Comment: 48 pages, 25 figures, accepted into Space Science Review

Inotropic therapy in patients with advanced heart failure: a clinical consensus statement from the Heart Failure Association of the European Society of Cardiology

This clinical consensus statement reviews the use of inotropic support in patients with advanced heart failure. The current guidelines only support use of inotropes in the setting of acute decompensated heart failure with evidence of organ malperfusion or shock. However, inotropic support may be reasonable in other patients with advanced heart failure without acute severe decompensation. The clinical evidence supporting use of inotropes in these situations is reviewed. Particularly, patients with persistent congestion, systemic hypoperfusion, or advanced heart failure with need for palliation, and specific situations relevant to implantation of left ventricular assist devices or heart transplantation are discussed. Traditional and novel drugs with inotropic effects are discussed and use of guideline-directed therapy during inotropic support is reviewed. Finally, home inotropic therapy is described, and palliative care and end-of-life aspects are reviewed in relation to management of ongoing inotropic support (including guidance for maintenance and weaning of chronic inotropic therapy support). Cardiolog

TERT promoter mutations are highly recurrent in SHH subgroup medulloblastoma

Telomerase reverse transcriptase (TERT) promoter mutations were recently shown to drive telomerase activity in various cancer types, including medulloblastoma. However, the clinical and biological implications of TERT mutations in medulloblastoma have not been described. Hence, we sought to describe these mutations and their impact in a subgroup-specific manner. We analyzed the TERT promoter by direct sequencing and genotyping in 466 medulloblastomas. The mutational distributions were determined according to subgroup affiliation, demographics, and clinical, prognostic, and molecular features. Integrated genomics approaches were used to identify specific somatic copy number alterations in TERT promoter-mutated and wild-type tumors. Overall, TERT promoter mutations were identified in 21 % of medulloblastomas. Strikingly, the highest frequencies of TERT mutations were observed in SHH (83 %; 55/66) and WNT (31 %; 4/13) medulloblastomas derived from adult patients. Group 3 and Group 4 harbored this alteration in <5 % of cases and showed no association wit