Development, characterization, and first application of a resonant laser secondary neutral mass spectrometry setup for the research of plutonium in the context of long-term nuclear waste storage.

Plutonium is a major contributor to the radiotoxicity in a long-term nuclear waste repository; therefore, many studies have focused on interactions of plutonium with the technical, geotechnical, and geological barriers of a possible nuclear waste storage site. In order to gain new insights into the sorption on surfaces and diffusion of actinides through these complex heterogeneous materials, a highly sensitive method with spatial resolution is required. Resonant laser secondary neutral mass spectrometry (Laser-SNMS) uses the spatial resolution available in time-of-flight secondary ion mass spectrometry (TOF-SIMS) in combination with the high selectivity, sensitivity, and low background noise of resonance ionization mass spectrometry (RIMS) and is, therefore, a promising method for the study and analysis of the geochemical behavior of plutonium in long-term nuclear waste storage. The authors present an approach with a combined setup consisting of a commercial TOF-SIMS instrument and a Ti:sapphire (Ti:Sa) laser system, as well as its optimization, characterization, and improvements compared to the original proof of concept by Erdmann et al. (2009). As a first application, the spatial distributions of plutonium and other elements on the surface of a pyrite particle and a cement thin section were measured by Laser-SNMS and TOF-SIMS, respectively. These results exemplify the potential of these techniques for the surface analysis of heterogeneous materials in the context of nuclear safety research.

Meta-analysis and single-center experience on the protective effect of negative suction drains on wound healing after stoma reversal.

BACKGROUND: Compromised wound healing following stoma reversal is a frequent problem. The use of negative suction drainage for reduction of complications remains controversial. METHODS: The patient database of our center was reviewed for patients with ileostomy reversal between 2007 and 2017. Risk factors for wound complications were analyzed using multivariate regression analysis. Systematic review and meta-analysis was performed. Ultimately, results of this study were integrated into meta-analysis to assess the effect of drainage placement on wound healing. RESULTS: In our institutional analysis, a total of 406 patients with ileostomy reversal were included (n = 240 (59.1%) with drainage vs. n = 166 (40.8%) without drainage). In multivariate analysis, body mass index (BMI) was a risk factor for wound complications (odds ratio (95% CI) 1.06 (1.02-1.12)). Patients with drainage needed significantly fewer interventions than those without drainage (17.1% vs. 28.9%, p = 0.005). Placement of drainage significantly reduced the risk of wound complications even in the group with elevated BMI (odds ratio (95% CI) 0.462 (0.28-0.76), p = 0.003). Meta-analysis identified 6 studies with a total of 1180 patients eligible for further analysis (2 prospectively randomized trials; 4 retrospective cohort studies). Overall analysis revealed a significantly beneficial effect of wound drainage following ileostomy reversal (RR (95% CI) 0.47 (0.34, 0.66); p < 0.0001). CONCLUSION: In our institutional analysis as well as meta-analysis, the use of subcutaneous suction drains was beneficial for prevention of wound healing complications following ostomy reversal. Drainage placement is especially valuable in high-risk situations such as in obese patients.

Aluminum Nanocrystals as a Plasmonic Photocatalyst for Hydrogen Dissociation.

Hydrogen dissociation is a critical step in many hydrogenation reactions central to industrial chemical production and pollutant removal. This step typically utilizes the favorable band structure of precious metal catalysts like platinum and palladium to achieve high efficiency under mild conditions. Here we demonstrate that aluminum nanocrystals (Al NCs), when illuminated, can be used as a photocatalyst for hydrogen dissociation at room temperature and atmospheric pressure, despite the high activation barrier toward hydrogen adsorption and dissociation. We show that hot electron transfer from Al NCs to the antibonding orbitals of hydrogen molecules facilitates their dissociation. Hot electrons generated from surface plasmon decay and from direct photoexcitation of the interband transitions of Al both contribute to this process. Our results pave the way for the use of aluminum, an earth-abundant, nonprecious metal, for photocatalysis.