Gamma measurements with the 4pi BaF2 detector for the FRANZ facility

The current performance of a 4π barium fluoride gamma detector consisting of 41 modules is evaluated. It will be used to measure neutron capture events in different samples that are exposed to a neutron beam that is expected to contain up to 10^7 neutrons/(cm^2 sec). The capture cross-sections acquired in this experiment will be relevant to a multitude of different areas, for example to s-process studies, or accelerator-driven systems. The detector array was re-mounted after having been moved from Karlsruhe to Frankfurt and in the course of this process, the detector modules have been checked for their current detection properties. Every module consists of a BaF2 crystal, a photomultiplier tube connected to the crystal by sillicon oil and a voltage divider to drive the PMT, so each of them is already an individual gamma detector. Using Cobalt-60 and Caesium-137 test sources the energy resolution and - more importantly - the time resolution of every module has been determined; the results are presented in this work and compared to previous data taken at the time the detector was built initially in the mid-1980s.Für astrophysikalische Experiment soll ein aus 41 Modulen zusammengesetzter 4pi-Barium-Fluorid Gamma-Detektor Verwendung finden, dessen messtechnische Eigenschaften im Rahmen dieser Arbeit ermittelt wurden. Für verschiedene Isotope, die einem Strahl mit bis zu 10^7 Neutronen/(cm^2 sec) ausgesetzt werden, sollen Neutroneneinfangsquerschnitte gemessen werden. Die so ermittelten Querschnitte sind für zahlreiche Forschungsschwerpunkte interessant, darunter Verbesserungen der Modelle für den s-Prozess oder sog. Accelerator-driven Systems, bei denen durch einen Beschleuniger ein unterkritischer Reaktor auf kritischem Niveau gehalten wird. Das Detektor-Array wurde neu zusammengesetzt, nachdem es in Einzelteilen von Karlsruhe nach Frankfurt gebracht wurde. Während dieses Umzuges wurden die einzelnen Module, die jeweils aus einem BaF2-Kristall, einem Photomultiplier und einem die PMT versorgenden Spannungsteiler bestehen, auf ihre momentanen Eigenschaften überprüft. Um die Energie- und, wichtiger noch, die Zeitauflösung zu ermitteln, wurden Cobalt-60- und Caesium-137-Quellen benutzt; in dieser Arbeit werden die Ergebnisse vorgestellt und mit Daten verglichen, die bereits in den 1980er Jahren für diesen Detektor in Karlsruhe ermittelt wurden

Getting Feasible Variable Estimates From Infeasible Ones: MRF Local Polytope Study

This paper proposes a method for construction of approximate feasible primal solutions from dual ones for large-scale optimization problems possessing certain separability properties. Whereas infeasible primal estimates can typically be produced from (sub-)gradients of the dual function, it is often not easy to project them to the primal feasible set, since the projection itself has a complexity comparable to the complexity of the initial problem. We propose an alternative efficient method to obtain feasibility and show that its properties influencing the convergence to the optimum are similar to the properties of the Euclidean projection. We apply our method to the local polytope relaxation of inference problems for Markov Random Fields and demonstrate its superiority over existing methods.Comment: 20 page, 4 figure

An Experimental Investigation of the Disparity between WTA and WTP for Lotteries

In this paper we experimentally investigate the disparity between willingness-to-accept (WTA) and willingness-to-pay (WTP) for risky lotteries. The direction of the income effect is reversed by endowing subjects with the highest price of a lottery when asking the WTP question. Our results show that the income effect is too small to be the only source of the disparity. Since the disparity concentrates on a subsample of subjects, parametric and nonparametric tests of the WTA-WTP ratio may lead to contradictory results. The disparity is significantly reduced when background risk is introduced. That is, putting subjects always into a risky position could improve the contingent valuation method which is often concerned with the assessment of risky situations such as health risks, automobile safety, etc. --WTA-WTP disparity,lotteries,background risk,contingent valuation

Probabilistic Intra-Retinal Layer Segmentation in 3-D OCT Images Using Global Shape Regularization

With the introduction of spectral-domain optical coherence tomography (OCT), resulting in a significant increase in acquisition speed, the fast and accurate segmentation of 3-D OCT scans has become evermore important. This paper presents a novel probabilistic approach, that models the appearance of retinal layers as well as the global shape variations of layer boundaries. Given an OCT scan, the full posterior distribution over segmentations is approximately inferred using a variational method enabling efficient probabilistic inference in terms of computationally tractable model components: Segmenting a full 3-D volume takes around a minute. Accurate segmentations demonstrate the benefit of using global shape regularization: We segmented 35 fovea-centered 3-D volumes with an average unsigned error of 2.46 $\pm$ 0.22 {\mu}m as well as 80 normal and 66 glaucomatous 2-D circular scans with errors of 2.92 $\pm$ 0.53 {\mu}m and 4.09 $\pm$ 0.98 {\mu}m respectively. Furthermore, we utilized the inferred posterior distribution to rate the quality of the segmentation, point out potentially erroneous regions and discriminate normal from pathological scans. No pre- or postprocessing was required and we used the same set of parameters for all data sets, underlining the robustness and out-of-the-box nature of our approach.Comment: Accepted for publication in Medical Image Analysis (MIA), Elsevie

Dissolved methane pluming mapping using Membrane Inlet Mass-Spectrometry (MIMS) at a blowout site in the North Sea

A blow out site in the North Sea (well 22/4-b, UK EEZ) in a water depth of 83 m, served as a test area to demonstrate MIMS as a powerful tool for the continuous measurement of dissolved methane simultaneously to the partial pressure of carbon dioxide, nitrogen and oxygen as well as other gases. A pump-CTD arrangement was used to generate a continuous water stream through a 2.5 cm thick tube to the ship laboratory and was analyzed using a membrane inlet quadrupole mass spectrometer (GAM 200, InProcessInstruments). The pump-CTD was further equipped with calibrated HydroC CH4/CO2 sensors. The MIMS measurements were conducted under fully controlled temperature conditions and were calibrated for CH4, N2, O2, and pCO2. The pump-CTD arrangement was towed along transects across the blow out and dissolved gas concentrations as well as physical water column data were synchronized and geo-referenced. The transects were repeated in three different depth layers, including a bottom layer of � 2 m above the sea floor, 60 m above the sea floor just below the thermocline and a third plane in 10 m water depth. During the tows water samples were taken for later onboard methane analysis and cross-calibration with the MIMS and HydroC data. After data selection under consideration of the tidal regime lateral and vertical plume dimensions of dissolved methane were constructed. Dissolved methane concentrations ranged between background and up to about 18�M. Below the thermocline, which represents an effective barrier for the vertical distribution of dissolved methane, methane distinctively spreads laterally. Only at locations were the gas bubble stream and concurrently advected water from below the thermocline reaches the sea surface enhanced methane emission into the atmosphere took place

PQCDSM-Logic in Maintenance (TPM) and Mountaineering

TPM is the foundation for JIT (Just in Time) and Lean Manufacturing and forms the basis of JIT or on-time delivery. The goal of TPM is to improve equipment effectiveness and optimize equipment performance, namely PQCDSM (Productivity, Quality, Cost and Delivery, Safety and health, environment, and Morale). Many producers have tried to transform their production system to a JIT or Lean production system with the aim of increasing productivity and quality, but thus far with little success. This contribution shows how trekking and climbing tours can be used to illustrate the application of PQCDSM-Logic in mountaineering and how this can be transferred to logistics and maintenance practice. The background is the author\u27s decades of experience with expeditions, trekking and climbing tours, TPM implementations and interviews with numerous experts. There are many similarities between the application of PQCDSM-Logic in mountaineering and in logistics and maintenance practice, which will help both in operational practice in industry and in high mountain tours, especially regarding safety in a changing environment. Presented is the extrapolation from mountain climbing to TPM and the importance of leadership for a successful (summit climbs and the like) transformation of the production system to a JIT or Lean production system