Three mechanisms of hydrogen-induced dislocation pinning in tungsten

The high-flux deuterium plasma impinging on a divertor degrades the long-termthermo-mechanical performance of its tungsten plasma-facing components. A prime actor inthis is hydrogen embrittlement, a degradation phenomenon that involves the interactions between hydrogen and dislocations, the primary carriers of plasticity. Measuring such nanoscaleinteractions is still very challenging, which limits our understanding. Here, we demonstrate anexperimental approach that combines thermal desorption spectroscopy (TDS) andnanoindentation, allowing to investigate the effect of hydrogen on the dislocation mobility in tungsten. Dislocation mobility was found to be reduced after deuterium injection, which ismanifested as a ‘pop-in’ in the indentation stress-strain curve, with an average activation stressfor dislocation mobility that was more than doubled. All experimental results can be confidentlyexplained, in conjunction with experimental and numerical literature findings, by the simultaneous activation of three mechanisms responsible for dislocation pinning: (i) hydrogentrapping at pre-existing dislocations, (ii) hydrogen-induced vacancies, and (iii) stabilization ofvacancies by hydrogen, contributing respectively 38%, 52%, and 34% to the extra activationstress. These mechanisms are considered to be essential for the proper understanding and modeling of hydrogen embrittlement in tungsten

Attenuated total reflection infrared spectroscopy for studying adsorbates on planar model catalysts : CO adsorption on silica supported Rh nanoparticles

A sensitive method is presented for studying adsorption of gaseous species on metal surfaces in vacuum by attenuated total internal reflection Fourier transform IR spectroscopy (ATR). The method is illustrated by CO adsorption expts. on silica supported Rh nanoparticles. An exptl. setup and a procedure are described in detail to obtain a sensitivity of reflectance change of .apprx.5 * 10-5 absorbance units. Here, a silicon ATR crystal with a 50 nm layer of hydroxylated silica acts as the support for the Rh nanoparticles. These particles are easily prepd. by spincoat impregnation from a RhCl3 soln. followed by H2 redn. XPS before and after redn. shows that rhodium is reduced to Rh0 and that all chlorine is removed. At. force microscope images the distribution of the particles, which are 3-4 nm in height. When the crystal is exposed to pressures up to 1 mbar of CO, a gas which is inert to the silica support, the stretch vibration of linearly adsorbed CO on the Rh nanoparticles is detected at 2023 cm-1, while no bridged CO or geminal dicarbonyl species can be distinguished. The min. detectable coverage is estd. .apprx.0.005 CO per nm2 substrate area or .apprx.5 * 10-4 ML. [on SciFinder (R)

Clinical response following hypertension induction for clinical delayed cerebral ischemia following subarachnoid hemorrhage: A retrospective, multicenter, cohort study

BACKGROUND: Hypertension induction (HTI) is often used for treating delayed cerebral ischemia (DCI) following aneurysmal subarachnoid hemorrhage (aSAH); however, high-quality studies on its efficacy are lacking. We studied immediate and 3-/6-month clinical efficacy of HTI in aSAH patients with clinical DCI. METHODS: A retrospective, multicenter, comparative, observational cohort study in aSAH patients with clinical deterioration due to DCI, admitted to three tertiary referral hospitals in the Netherlands from 2015 to 2019. Two hospitals used a strategy of HTI (HTI group) and one hospital had no such strategy (control group). We calculated adjusted relative risks (aRR) using Poisson regression analyses for the two primary (clinical improvement of DCI symptoms at days 1 and 5 after DCI onset) and secondary outcomes (DCI-related cerebral infarction, in-hospital mortality, and poor clinical outcome [modified Rankin Scale 4-6] assessed at 3 or 6 months), using the intention-to-treat principle. We also performed as-treated and per-protocol analyses. RESULTS: The aRR for clinical improvement on day 1 after DCI in the HTI group was 1.63 (95% CI 1.17-2.27) and at day 5 after DCI 1.04 (95% CI 0.84-1.29). Secondary outcomes were comparable between the groups. The as-treated and per-protocol analyses yielded similar results. CONCLUSIONS: No clinical benefit of HTI is observed 5 days after DCI due to spontaneous reversal of DCI symptoms in patients treated without HTI. The 3-/6-month clinical outcome was similar for both groups. Therefore, these data suggest that one may consider to not apply HTI in aSAH patients with clinical DCI

Early postoperative MRI overestimates residual tumour after resection of gliomas with no or minimal enhancement

Standards for residual tumour measurement after resection of gliomas with no or minimal enhancement have not yet been established. In this study residual volumes on early and late postoperative T2-/FLAIR-weighted MRI are compared. A retrospective cohort included 58 consecutive glioma patients with no or minimal preoperative gadolinium enhancement. Inclusion criteria were first-time resection between 2007 and 2009 with a T2-/FLAIR-based target volume and availability of preoperative, early (<48 h) and late (1-7 months) postoperative MRI. The volumes of non-enhancing T2/FLAIR tissue and diffusion restriction areas were measured. Residual tumour volumes were 22% smaller on late postoperative compared with early postoperative T2-weighted MRI and 49% smaller for FLAIR-weighted imaging. Postoperative restricted diffusion volume correlated with the difference between early and late postoperative FLAIR volumes and with the difference between T2 and FLAIR volumes on early postoperative MRI. We observed a systematic and substantial overestimation of residual non-enhancing volume on MRI within 48 h of resection compared with months postoperatively, in particular for FLAIR imaging. Resection-induced ischaemia contributes to this overestimation, as may other operative effects. This indicates that early postoperative MRI is less reliable to determine the extent of non-enhancing residual glioma and restricted diffusion volumes are imperativ

Radiological progression of cerebral metastases after radiosurgery: assessment of perfusion MRI for differentiating between necrosis and recurrence

To assess the capability of perfusion MRI to differentiate between necrosis and tumor recurrence in patients showing radiological progression of cerebral metastases treated with stereotactic radiosurgery (SRS). From 2004 to 2006 dynamic susceptibility-weighted contrast-enhanced perfusion MRI scans were performed on patients with cerebral metastasis showing radiological progression after SRS during follow-up. Several perfusion MRI characteristics were examined: a subjective visual score of the relative cerebral blood volume (rCBV) map and quantitative rCBV measurements of the contrast-enhanced areas of maximal perfusion. For a total of 34 lesions in 31 patients a perfusion MRI was performed. Diagnoses were based on histology, definite radiological decrease or a combination of radiological and clinical follow-up. The diagnosis of tumor recurrence was obtained in 20 of 34 lesions, and tumor necrosis in 14 of 34. Regression analyses for all measures proved statistically significant (χ2 = 11.6–21.6, P < 0.001–0.0001). Visual inspection of the rCBV map yielded a sensitivity and specificity of 70.0 respectively 92.9%. The optimal cutoff point for maximal tumor rCBV relative to white matter was 2.00 (improving the sensibility to 85.0%) and 1.85 relative to grey matter (GM), improving the specificity to 100%, with a corresponding sensitivity of 70.0%. Perfusion MRI seems to be a useful tool in the differentiation of necrosis and tumor recurrence after SRS. For the patients displaying a rCBV-GM greater than 1.85, the diagnosis of necrosis was excluded. Salvage treatment can be initiated for these patients in an attempt to prolong survival

MRSA prevalence in european healthcare settings: a review

<p>Abstract</p> <p>Background</p> <p>During the past two decades, methicillin-resistant <it>Staphylococcus aureus </it>(MRSA) has become increasingly common as a source of nosocomial infections. Most studies of MRSA surveillance were performed during outbreaks, so that results are not applicable to settings in which MRSA is endemic. This paper gives an overview of MRSA prevalence in hospitals and other healthcare institutions in non-outbreak situations in Western Europe.</p> <p>Methods</p> <p>A keyword search was conducted in the Medline database (2000 through June 2010). Titles and abstracts were screened to identify studies on MRSA prevalence in patients in non-outbreak situations in European healthcare facilities. Each study was assessed using seven quality criteria (outcome definition, time unit, target population, participants, observer bias, screening procedure, swabbing sites) and categorized as 'good', 'fair', or 'poor'.</p> <p>Results</p> <p>31 observational studies were included in the review. Four of the studies were of good quality. Surveillance screening of MRSA was performed in long-term care (11 studies) and acute care (20 studies). Prevalence rates varied over a wide range, from less than 1% to greater than 20%. Prevalence in the acute care and long-term care settings was comparable. The prevalence of MRSA was expressed in various ways - the percentage of MRSA among patients (range between 1% and 24%), the percentage of MRSA among <it>S. aureus </it>isolates (range between 5% and 54%), and as the prevalence density (range between 0.4 and 4 MRSA cases per 1,000 patient days). The screening policy differed with respect to time points (on admission or during hospital stay), selection criteria (all admissions or patients at high risk for MRSA) and anatomical sampling sites.</p> <p>Conclusions</p> <p>This review underlines the methodological differences between studies of MRSA surveillance. For comparisons between different healthcare settings, surveillance methods and outcome calculations should be standardized.</p