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.

Glacier response in the European Alps to Heinrich Event 1 cooling: the Gschnitz stadial

Abstract: The Gschnitz stadial was a period of regionally extensive glacier advance in the European Alps that lies temporally between the breakdown of the Last Glacial Maximum piedmont lobes and the beginning of the Bolling warm interval. Moraines of the Gschnitz stadial are found in medium to small catchments, are steep-walled and blocky, and reflect a snowline lowering of 650- 700 m in comparison to the Little Ice Age reference snowline. 10 Be surface exposure dating of boulders from the moraine at the type locality at Trins (Gschnitz valley, Tyrol, Austria) shows that it stabilised no later than 15 400 � 1400 yr ago. The overall morphological situation and the long reaction time of the glacier suggest that the climatic downturn lasted about 500 � 300 yr, indicating that the Gschnitz cold period began approximately 15 900 � 1400 yr ago, if not somewhat earlier. This is consistent with published radiocarbon dates that imply that the stadial occurred sometime between 15 400 14 C yr BP (18 020-19 100 cal. yr) and 13 250 14 C yr BP (15 360-16 015 cal. yr). A palaeoclimatic interpretation of the Gschnitz glacier based on a simple glacier flow model and statistical glacier-climate models shows that precipitation was about one-third of modern-day precipitation and summer temperatures were about 10 K lower than today. In comparison, during the Younger Dryas, precipitation in this area was only about 10% less and Ts (summer temperature) was only 3.5-4 K lower than modern values. Based on the age of the moraine and the cold and dry climate at that time, we suggest that the Gschnitz stadial was the response of Alpine glaciers to cooling of the North Atlantic Ocean associated with Heinrich Event 1. Copyright 2005 John Wiley & Sons, Ltd.

3D Imaging of Catalyst Support Corrosion in Polymer Electrolyte Fuel Cells

Abstract: During the lifetime of a polymer electrolyte fuel cell, the pore structure of the Pt/C catalyst layer may change as a result of carbon corrosion. Three-dimensional visualization of porosity changes is important to understand the origin of fuel cell performance deterioration. A focused ion beam/scanning electron microscopy (FIB/SEM) approach was adopted together with electron tomographic studies to visualize the three-dimensional pore structure of a Pt/C catalyst. In the case of pristine catalyst layers, the pores form an interconnected network. After 1000 start-up/shut-down cycles, severe carbon corrosion leads to a collapse of the support structure. The porosity of the degraded catalyst layer shrinks drastically, resulting in a structure of predominantly isolated pores. These porosity changes hinder the mass transport in the catalyst layer, consequently leading to a substantial loss of fuel cell performance. FIB/SEM serial sectioning and electron tomography allows three-dimensional imaging of the catalys...

CO2 Splitting via Two-Step Solar Thermochemical Cycles with Zn/ZnO and FeO/Fe3O4 Redox Reactions II: Kinetic Analysis

Abstract: Two-step thermochemical cycles for splitting CO2 with Zn/ZnO and FeO/Fe3O4 redox pairs using concentrated solar energy are considered. Thermogravimetric-based kinetic analyses were performed for the reduction of CO2 to CO with Zn and FeO. Both reactions are characterized by an initial fast interface-controlled regime followed by a slow diffusion-controlled regime, which are described using a shell−core kinetic model. In the interface-controlled regime, a power rate law is applied with apparent activation energies 113.7 and 73.4 kJ mol−1, and corresponding reaction orders 0.339 and 0.792, for the Zn/CO2 and FeO/CO2 systems, respectively. In the diffusion-controlled regime, limited by the ion mobility through the oxide shells, the apparent activation energies are 162.3 kJ mol−1 for Zn/CO2 and 106.4 kJ mol−1 for FeO/CO2. Additional reaction mechanisms above the Zn melting point for Zn/CO2 reactions are postulated.