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.

Atomic mechanism for dislocation emission from nanosized grain boundaries

Abstract: The present work deals with the atomic mechanism responsible for the emission of partial dislocations from grain boundaries (GB's) in nanocrystalline metals. It is shown that in 12 and 20 nm grain size samples GB's containing GB dislocations can emit a partial dislocation during deformation by local atomic shuffling and stress-assisted free volume migration. The free volume is often emitted or absorbed in a neighboring triple junction. It is further suggested that the degree of delocalization surrounding the grain boundary dislocation determines whether atomic shuffling can associate displacements into the Burgers vector necessary to emit a partial dislocation. Temporal analysis of atomic configurations during dislocation emission indicates that creation and propagation of the partial might be separate processes.

Carbon isotope discrimination indicates improving water-use efficiency of trees in northern Eurasia over the last 100 years

Abstract: We investigated the response of conifer trees in northern Eurasia to climate change and increasing CO2 over the last century by measuring the carbon isotope ratio in tree rings. Samples from Larix, Pinus and Picea trees growing at 26 high-latitude sites (59‐711N) from Norway to Eastern Siberia were analysed. When comparing the periods 1861‐1890 and 1961‐1990, the isotope discrimination and the ratio of the intercellular to ambient CO2 concentration (ci/ca) remained constant for trees growing in mild oceanic climate and under extremely cold and dry continental conditions. This shows a strong coordination of gas-exchange processes, consisting in a biochemical acclimation and a reduction of the stomatal conductance. The correlation for ci/ca between the two investigated periods was particularly strong for Larix (r 2 50.90) and Pinus (r 2 50.94), but less pronounced for Picea (r 2 50.47). Constant ci/ca under increasing CO2 in the atmosphere resulted in improved intrinsic water-use efficiency (Wi), the amount of water loss at the leaf level per unit carbon gain. We found that 125 out of 126 trees showed increasing Wi from 1861 to 1890 to 1961 to 1990, with an average improvement of

Advances in solid state photon detectors

Abstract: Semiconductor photodiodes were developed in the early `Forties approximately at the time when the photomultiplier tube became a commercial product (RCA 1939) Only in recent years, with the invention of the Geiger-mode avalanche photodiodes, have the semiconductor photo detectors reached sensitivity comparable to that of photomultiplier tubes The evolution started in the `Sixties with the p-i-n (PIN) photodiode, a very successful device, which is still used in many detectors for high energy physics and a large number of other applications like radiation detection and medical imaging The next step was the development of the avalanche photodiode (APD) leading to a substantial reduction of noise but not yet achieving single photon response The weakest light flashes that can be detected by the PIN diode need to contain several hundreds of photons An improvement of the sensitivity by 2 orders of magnitude was achieved by the development of the avalanche photodiode, a device with internal gain At the end of the millennium, the semiconductor detectors evolved with the Geiger-mode avalanche photodiode into highly sensitive devices, which have an internal gain comparable to the gain of photomultiplier tubes and a response to single photons A review of the semiconductor photo detector design and development, the properties and problems, some applications and a speculative outlook on the future evolution will be presented

Flavor physics of leptons and dipole moments

Abstract: This chapter of the report of the “Flavor in the era of the LHC” Workshop discusses the theoretical, phenomenological and experimental issues related to flavor phenomena in the charged lepton sector and in flavor conserving CP-violating processes. We review the current experimental limits and the main theoretical models for the flavor structure of fundamental particles. We analyze the phenomenological consequences of the available data, setting constraints on explicit models beyond the standard model, presenting benchmarks for the discovery potential of forthcoming measurements both at the LHC and at low energy, and exploring options for possible future experiments.

SoFi, an IGOR-based interface for the efficient use of the generalized multilinear engine (ME-2) for the source apportionment: ME-2 application to aerosol mass spectrometer data

Abstract: . Source apportionment using the bilinear model through a multilinear engine (ME-2) was successfully applied to non-refractory organic aerosol (OA) mass spectra collected during the winter of 2011 and 2012 in Zurich, Switzerland using the aerosol chemical speciation monitor (ACSM). Five factors were identified: low-volatility oxygenated OA (LV-OOA), semivolatile oxygenated OA (SV-OOA), hydrocarbon-like OA (HOA), cooking OA (COA) and biomass burning OA (BBOA). A graphical user interface SoFi (Source Finder) was developed at PSI in order to facilitate the testing of different rotational techniques available within the ME-2 engine by providing a priori factor profiles for some or all of the expected factors. ME-2 was used to test the positive matrix factorization (PMF) model, the fully constrained chemical mass balance (CMB) model, and partially constrained models utilizing a values and pulling equations. Within the set of model solutions determined to be environmentally reasonable, BBOA and SV-OOA factor mass spectra and time series showed the greatest variability. This variability represents the uncertainty in the model solution and indicates that analysis of model rotations provides a useful approach for assessing the uncertainty of bilinear source apportionment models.