Effect-Directed Analysis of Municipal Landfill Soil Reveals Novel Developmental Toxicants in the Zebrafish Danio rerio

Effect-directed analysis (EDA) is an approach used to identify (unknown) contaminants in complex samples which cause toxicity, using a combination of biology and chemistry. The goal of this work was to apply EDA to identify developmental toxicants in soil samples collected from a former municipal landfill site. Soil samples were extracted, fractionated, and tested for developmental effects with an embryotoxicity assay in the zebrafish Danio rerio. Gas chromatograph mass selective detection (GC-MSD) chemical screening was used to reveal candidate developmental toxicants in fractions showing effects. In a parallel study, liquid chromatography-hybrid linear ion trap Orbitrap mass spectrometry was also applied to one polar subfraction (Hoogenboom et al. J. Chromatogr. A2009, 1216, 510-519). EDA resulted in the identification of a number of previously unknown developmental toxicants, which were confirmed to be present in soil by GC-MS. These included 11H-benzo[b]fluorene, 9-methylacridine, 4-azapyrene, and 2-phenylquinoline, as well as one known developmental toxicant (retene). This work revealed the presence of novel contaminants in the environment that may affect vertebrate development, which are not subject to monitoring or regulation under current soil quality assessment guidelines. © 2011 American Chemical Society

Sublimation of advanced tungsten alloys under DEMO relevant accidental conditions

Tungsten (W) is deemed as the main candidate for the first wall armor material of future fusion power plants such as DEMO. Advantages of W include a high melting point, low erosion yield, low tritium retention, and a high thermal conductivity. One issue concerning W is the oxidation resistance in case of a loss-of-coolant accident with simultaneous air ingress. The major challenge in such a scenario is to suppress the sublimation which is responsible for a release of radioactivity. This work studies an alloy containing tungsten (W), 12 weight % chromium (Cr), and 0.6 weight % yttrium (Y) in DEMO-relevant conditions: a temperature in the range of 1100 K to 1473 K in humid air. The sublimation rates are measured for the first time in humid air. Tungsten oxide sublimates at a rate of 1.4 × 10−4 mg cm−2 s−1 at 1273 K in humid air. At the same conditions the alloy suppresses sublimation by more than one order of magnitude as compared to that of pure W. This suppression is achieved due to the formation of a protective chromium oxide layer on the surface of the sample. Details about the protection mechanisms are presented and discussed. Testing is performed for up to 10 days

Tungsten–chromium–yttrium alloys as first wall armor material: Yttrium concentration, oxygen content and transmutation elements

Tungsten (W) is a prime candidate as first wall armor material of future fusion power plants as W withstands extreme particle, heat, and radiation loads without forming long-lived radioactive waste. The release of radioactive material from the reactor to the environment should be suppressed in case of an accident such as a loss of coolant (LOCA) with simultaneous air ingress into the vacuum vessel. W oxidizes and sublimates in case of a LOCA. Therefore, oxidation resistant tungsten, chromium, yttrium (W–Cr–Y) alloys are developed to provide intrinsic safety in case of such an accident.In this paper, the optimization of the yttrium (Y) concentration is presented on bulk samples compacted by field assisted sintering technology (FAST). W with 11.4 weight (wt)% Cr and 0.6 wt% Y appears to be an optimum regarding the oxidation resistance. Further, first preparations for industrial upscaling, which may increase the impurity level, are addressed. The oxygen (O) content is varied systematically. It is shown that a good oxidation resistance requires a low O level.The exposure of the material to fusion neutrons is another issue addressed on W–Cr–Y alloys. In a non-activated environment it is shown that 1 wt% rhenium (Re) dramatically changes the oxidation kinetics: at 1273 K the mass gain of W–Cr–Y–Re follows a cubic rate law while W–Cr–Y follows a linear rate law for two days. Further, the influence of the alloying elements on the neutron transport and transmutation of W is studied by simulating the exposure of spatially heterogeneous high-resolution models of the W–Cr–Y alloys to 14 MeV fusion neutrons

On Oxidation Resistance Mechanisms at 1273 K of Tungsten-Based Alloys Containing Chromium and Yttria

Tungsten (W) is currently deemed the main candidate for the plasma-facing armor material of the first wall of future fusion reactors, such as DEMO. Advantages of W include a high melting point, high thermal conductivity, low tritium retention, and low erosion yield. However, was an accident to occur, air ingress into the vacuum vessel could occur and the temperature of the first wall could reach 1200K to 1450K due to nuclear decay heat. In the absence of cooling, the temperature remains in that range for several weeks. At these temperatures, the radioactive tungsten oxidizes and then volatilizes. Smart W alloys are therefore being developed. Smart alloys are supposed to preserve properties of W during plasma operation while suppressing tungsten oxide formation in case of an accident. This study focuses on investigations of thin film smart alloys produced by magnetron sputtering. These alloys provide an idealistic system with a homogeneous distribution of the elements W, chromium (Cr), and yttrium (Y) on an atomic scale. The recommended composition is W with 12 weight % of Cr and 0.5 weight % of Y. Passivation and a suppression of WO3 sublimation is shown. For the first time, the mechanisms yielding the improved oxidation resistance are analyzed in detail. A protective Cr2O3 layer forms at the surface. The different stages of the oxidation processes up to the failure of the protective function are analyzed for the first time. Using 18O as a tracer, it is shown for the first time that the oxide growth occurs at the surface of the protective oxide. The Cr is continuously replenished from the bulk of the sample, including the Cr-rich phase which forms during exposure at 1273K. A homogenous distribution of yttria within the W-matrix, which is preserved during oxidation, is a peculiarity of the analyzed alloy. Further, an Y-enriched nucleation site is found at the interface between metal and oxide. This nucleation sites are deemed to be crucial for the improved oxidation resistance

Subcutaneous Stimulation as Add-on Therapy to Spinal Cord Stimulation in Patients With Failed Back Surgery Syndrome Significantly Increases the Total Electrical Charge per Second: Aspects on Stimulation Parameters and Energy Requirements of the Implanted Neurostimulators

OBJECTIVE: In our previous multicenter randomized controlled trial, we demonstrated the clinical effectiveness of peripheral nerve field stimulation (PNFS) as add-on therapy to spinal cord stimulation (SCS) for the treatment of chronic back pain in patients with failed back surgery syndrome. To our knowledge, no previous study has investigated the effect of PNFS as an add-on to SCS on the energy consumption of the implanted neurostimulators. Therefore, in this study, we compared the specific stimulation parameters and energy requirements of a previously unreported group of patients with only SCS with those of a group of patients with SCS and add-on PNFS. We also investigated differences that might explain the need for PNFS in the treatment of chronic low back pain. MATERIALS AND METHODS: We analyzed 75 patients with complete sets of stimulation parameters, with 21 patients in the SCS-only group and 54 patients in the SCS + PNFS group. Outcome measures were average visual analog scale score, SCS parameters (voltage, frequency, and pulse width), SCS charge per second, and total charge per second. We analyzed baseline characteristics and differences between and within groups over time. RESULTS: Both groups had comparable patient characteristics at baseline and showed a significant decrease in back and leg pain. SCS charge per second did not significantly differ between the groups at baseline or at 12 months. The total charge per second was significantly higher in the active SCS + PNFS group than in the SCS-only group at baseline; in the SCS + PNFS group, this persisted for up to 12 months, and the SCS charge per second and total charge per second increased significantly over time. CONCLUSIONS: Our results show that add-on PNFS increases the total charge per second compared with SCS alone, as expected. However, further research is needed because our results do not directly explain why some patients require add-on PNFS to treat low back pain

Spinal Cord Stimulation With Additional Peripheral Nerve/Field Stimulation vs Spinal Cord Stimulation Alone on Back Pain and Quality of Life in Patients With Failed Back Surgery Syndrome

INTRODUCTION: Failed back surgery syndrome (FBSS) refers to new or persistent pain following spinal surgery for back or leg pain in a subset of patients. Spinal cord stimulation (SCS) is a neuromodulation technique that can be considered in patients with predominant leg pain refractory to conservative treatment. Patients with predominant low back pain benefit less from SCS. Another neuromodulation technique for treatment of chronic low back pain is subcutaneous stimulation or peripheral nerve field stimulation (PNFS). We investigated the effect of SCS with additional PNFS on pain and quality of life of patients with FBSS compared with that of SCS alone after 12 months. MATERIALS AND METHODS: This is a comparative study of patients with FBSS who responded to treatment with either SCS + PNFS or SCS only following a multicenter randomized clinical trial protocol. In total, 75 patients completed the 12-month follow-up: 21 in the SCS-only group and 54 in the SCS + PNFS group. Outcome measures were pain (visual analog scale), quality of life (36-Item Short Form Survey [SF-36]), anxiety and depression (Hospital Anxiety and Depression Scale [HADS]), overall health (EuroQol Five-Dimension [EQ-5D]), disability (Oswestry Disability Index [ODI]), and pain assessed by the McGill questionnaire. RESULTS: There were no significant differences in baseline characteristics between the two groups. Both groups showed a significant reduction in back and leg pain at 12 months compared with baseline measurements. No significant differences were found between the groups in effect on both primary (pain) and secondary parameters (SF-36, HADS, EQ-5D, ODI, and McGill pain). CONCLUSION: In a subgroup of patients with chronic back and leg pain, SCS alone provided similar long-term pain relief and quality-of-life improvement as PNFS in addition to SCS. In patients with refractory low back pain not responding to SCS alone, adding PNFS should be recommended. CLINICAL TRIAL REGISTRATION: The Clinicaltrials.gov registration number for the study is NCT01776749