Paul Scherrer Institute

About: Paul Scherrer Institute is a facility organization based out in Villigen, Switzerland. It is known for research contribution in the topics: Neutron & Large Hadron Collider. The organization has 9248 authors who have published 23984 publications receiving 890129 citations. The organization is also known as: PSI.

Evolution of Asian aerosols during transpacific transport in INTEX-B

Abstract: . Measurements of aerosol composition were made with an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) on board the NSF/NCAR C-130 aircraft as part of the Intercontinental Chemical Transport Experiment Phase B (INTEX-B) field campaign over the Eastern Pacific Ocean. The HR-ToF-AMS measurements of non-refractory submicron aerosol mass are shown to compare well with other aerosol instrumentation in the INTEX-B field study. Two case studies are described for pollution layers transported across the Pacific from the Asian continent, intercepted 3–4 days and 7–10 days downwind of Asia, respectively. Aerosol chemistry is shown to be a robust tracer for air masses originating in Asia, specifically the presence of sulfate dominated aerosol is a distinguishing feature of Asian pollution layers that have been transported to the Eastern Pacific. We examine the time scales of processing for sulfate and organic aerosol in the atmosphere and show that our observations confirm a conceptual model for transpacific transport from Asia proposed by Brock et al. (2004). Our observations of both sulfate and organic aerosol in aged Asian pollution layers are consistent with fast formation near the Asian continent, followed by washout during lofting and subsequent transformation during transport across the Pacific. Our observations are the first atmospheric measurements to indicate that although secondary organic aerosol (SOA) formation from pollution happens on the timescale of one day, the oxidation of organic aerosol continues at longer timescales in the atmosphere. Comparisons with chemical transport models of data from the entire campaign reveal an under-prediction of organic aerosol mass in the MOZART model, but much smaller discrepancies with the GEOS-Chem model than found in previous studies over the Western Pacific. No evidence is found to support a previous hypothesis for significant secondary organic aerosol formation in the free troposphere.

Renewable Production of Methane from Woody Biomass by Catalytic Hydrothermal Gasification

Abstract: Production of synthetic natural gas (SNG) from wood by a catalytic hydrothermal process was studied in a laboratory batch reactor suitable for high feed concentrations (10−30 wt %) at 300−410 °C and 12−34 MPa with Raney nickel as the catalyst. A maximum methane yield of 0.33 (g of CH4)/(g of wood) was obtained, corresponding to the thermodynamic equilibrium yield. The carbon gasification efficiency was a function of the reaction time, and for reaction times long enough (∼90 min), complete gasification was achieved. At supercritical conditions, the remaining liquid phase always was tar-free, was colorless, and contained less than 2 wt % of the feed carbon. Analysis of the spent catalyst revealed a slight increase of carbonaceous deposits on the surface (15 atom % vs 10 atom % for the fresh catalyst).

Accumulation of biogenic and lithogenic material in the Pacific sector of the Southern Ocean during the past 40,000 years

Abstract: The 230Th-normalization technique was applied to surface sediments and down-core records from the Pacific sector of the Southern Ocean between 120°W and 170°W in order to reconstruct vertical rain rates, corrected for lateral redistribution of sediment. Preserved rain rates of opal, organic carbon and biogenic Ba all indicate that biological productivity south of the Antarctic Polar Front (APF) was much lower than today during the Last Glacial Maximum (LGM), probably in response to increased ice cover. However, by analogy with modern opal fluxes south of the ACC, we show that year-round ice cover is not a prerequisite for very low rates of opal accumulation. Available records from north of the APF indicate little to no change in opal export, in contrast to records from the Indian and Atlantic sectors, which show enhanced opal export north of the APF during the LGM. Glacial records from north of 66°S in the Pacific all show lithogenic fluxes that were greater than today, but significantly lower than lithogenic fluxes in the glacial Atlantic and Indian sectors. Together, these new records from the Pacific sector show that during the LGM the three basins of the Southern Ocean were significantly more differentiated than today. The observed inter-basin distribution of lithogenic fluxes and opal burial, and the presumed geographical distribution of increased dust input to the Southern Ocean during the LGM, are consistent with an Atlantic–Indian–Pacific gradient in the degree of iron-stimulated diatom productivity within the zone lying between the APF and the Subantarctic Front. Previous studies, which focused primarily on the Atlantic sector, may have overestimated the glacial increase in the strength of the biological pump in the Southern Ocean.

Direct observation of the spin texture in SmB6 as evidence of the topological Kondo insulator

Abstract: Topological Kondo insulators have been proposed as a new class of topological insulators in which non-trivial surface states reside in the bulk Kondo band gap at low temperature due to strong spin-orbit coupling. In contrast to other three-dimensional topological insulators, a topological Kondo insulator is truly bulk insulating. Furthermore, strong electron correlations are present in the system, which may interact with the novel topological phase. By applying spin- and angle-resolved photoemission spectroscopy, here we show that the surface states of SmB6 are spin polarized. The spin is locked to the crystal momentum, fulfilling time reversal and crystal symmetries. Our results provide strong evidence that SmB6 can host topological surface states in a bulk insulating gap stemming from the Kondo effect, which can serve as an ideal platform for investigating of the interplay between novel topological quantum states with emergent effects and competing orders induced by strongly correlated electrons.