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.

Organic aerosol formation in urban and industrial plumes near Houston and Dallas, Texas

Abstract: [1] We present measurements of organic aerosol (OA) in urban plumes from Houston and Dallas/Fort Worth as well as in industrial plumes in the Houston area during TexAQS-2006. Consistent with the TexAQS-2000 study, measurements show greater amount of aerosol mass downwind of the industrial centers compared to urban areas. This is likely due to higher emission and processing of volatile organic compounds (VOCs) from the industrial sources along the Houston ship channel. Comparisons of the current measurements with observations from the northeastern (NE) United States indicate that the observed ratios of the enhancement above background in OA, ΔOA, to the enhancement above background in CO, ΔCO, downwind of urban centers of Houston and Dallas/Fort Worth are within a factor of 2 of the same values in plumes from urban areas in the NE United States. In the ship channel plumes, ΔOA/ΔCO exceeds that in the urban areas by factors ranging from 1.5 to 7. We use a chemical box model to simulate secondary organic aerosol (SOA) formation from anthropogenic and biogenic VOCs in different plumes using recently reported dependencies of SOA yields on VOC/NOx ratios. Modeled SOA to CO enhancement ratios are within a factor of 2 of measurements. The increase in SOA from biogenic VOCs (BVOCs) predicted by the chemical box model as well as by a separate analysis using a Lagrangian particle dispersion model (FLEXPART) is <0.7 μg per standard m3 (sm−3). We find no evidence for a substantial influence of BVOCs on OA formation in our measurements in Houston area.

A "magnetic" interatomic potential for molecular dynamics simulations

Abstract: We develop a semi-empirical many-body interatomic potential suitable for large scale molecular dynamics simulations of magnetic α-iron. The functional form of the embedding part of the potential is derived using a combination of the Stoner and the Ginzburg–Landau models. We show that it is the symmetry broken solutions of the Ginzburg–Landau model describing spontaneous magnetization of atoms that provide the link between magnetism and interatomic forces. We discuss a range of potential applications of the new method.

Coherent Nanotwins and Dynamic Disorder in Cesium Lead Halide Perovskite Nanocrystals

Abstract: Crystal defects in highy luminescent colloidal nanocrystals (NCs) of CsPbX3 perovskites (X = Cl, Br, I) are investigated. Here, using X-ray total scattering techniques and the Debye scattering equation (DSE), we provide evidence that the local structure of these NCs always exhibits orthorhombic tilting of PbX6 octahedra within locally ordered subdomains. These subdomains are hinged through a two-/three-dimensional (2D/3D) network of twin boundaries through which the coherent arrangement of the Pb ions throughout the whole NC is preserved. The density of these twin boundaries determines the size of the subdomains and results in an apparent higher-symmetry structure on average in the high-temperature modification. Dynamic cooperative rotations of PbX6 octahedra are likely at work at the twin boundaries, causing the rearrangement of the 2D or 3D network, particularly effective in the pseudocubic phases. An orthorhombic, 3D γ-phase, isostructural to that of CsPbBr3 is found here in as-synthesized CsPbI3 NCs.

A chemical sensor based on a micromechanical cantilever array for the identification of gases and vapors

Abstract: We have built and operated a novel setup for the characterization and identification of gases or vapors based on sequential position readout via a beam-deflection technique from a microfabricated array of eight cantilever-type sensors. Each of the cantilevers can be coated on one side with a dif- ferent sensor material to detect specific chemical interactions. We demonstrate that disturbances from vibrations and turbu- lent gas flow can be effectively removed in array sensors by taking difference signals with reference cantilevers. For ex- ample, H2 can be detected by its adsorption on a Pt-coated sensor because a change in surface stress causes a static bending of the sensor. The diffusion of various alcohols into polymethylmethacrylate induces resonance frequency shifts in a dynamic measuring mode and bending in the static mode, which allows one to distinguish between the various alcohols. Sensor devices for detection of gases and vapors via spe- cific coatings are gradually gaining importance in chemistry, materials science, and biochemistry owing to the increas- ing demand for detection of analytes at monolayer coverage. A field of increasing interest is the construction of so-called "electronic noses" capable of discerning different odors via a typical response pattern of the receptor layers to an analyte. Most devices currently applied involve square centimeter- sized detection areas and comparatively large gas volumes (typically 50- 1000 cm 3 ) resulting in relatively long response