The ALICE Transition Radiation Detector: status and perspectives for Run II

The ALICE Transition Radiation Detector contributes to the tracking, particle identification, and triggering capabilities of the experiment. It is composed of six layers of multi-wire proportional chambers, each of which is preceded by a radiator and a Xe/CO$_2$-filled drift volume. The signal is sampled in timebins of 100~ns over the drift length which allows for the reconstruction of chamber-wise track segments, both online and offline. The particle identification is based on the specific energy loss of charged particles and additional transition radiation photons, the latter being a signature for electrons. The detector is segmented into 18 sectors, of which 13 were installed in Run I. The TRD was included in data taking since the LHC start-up and was successfully used for electron identification and triggering. During the Long Shutdown 1, the detector was completed and now covers the full azimuthal acceptance. Furthermore, the readout and trigger components were upgraded. When data taking was started for \runii{}, their performance fulfilled the expectations

Triggering with the ALICE TRD

We discuss how a level-1 trigger, about 8 us after a hadron-hadron collision, can be derived from the Transition Radiation Detector (TRD) in A Large Ion Collider Experiment (ALICE) at the LHC. Chamber-wise track segments from fast on-detector reconstruction are read out with position, angle and electron likelihood. In the Global Tracking Unit up to 6 tracklets from a particle traversing the detector layers are matched and used for the reconstruction of transverse momentum and electron identification. Such tracks form the basis for versatile and flexible trigger conditions, e.g. single high-pt hadron, single high-pt electron, di-electron (J/Psi, Upsilon) and at least n close high-pt tracks (jet). The need for low-latency on-line reconstruction poses challenges on the detector operation. The calibration for gain (pad-by-pad) and drift velocity must be applied already in the front-end electronics. Due to changes in pressure and gas composition an on-line monitoring and feedback loop for these parameters is required. First experiences on the performance were gathered from triggering in cosmic and pp runs.Comment: 6 pages, 10 figure

Improving students' understanding of rotating frames of reference using videos from different perspectives

The concepts of the Coriolis and the centrifugal force are essential in various scientific fields and they are standard components of introductory physics lectures. In this paper we explore how students understand and apply concepts of rotating frames of reference in the context of an exemplary lecture demonstration experiment. We found in a $Predict-Observe-Explain$-setting, that after predicting the outcome prior to the demonstration, only one out of five physics students correctly reported the observation of the trajectory of a sphere rolling over a rotating disc. Despite this low score, a detailed analysis of distractors revealed significant conceptual learning during the observation of the experiment. In this context, we identified three main misconceptions and learning difficulties. First, the centrifugal force is only required to describe the trajectory if the object is coupled to the rotating system. Second, inertial forces cause a reaction of an object on which they act. And third, students systematically mix-up the trajectories in the stationary and the rotating frame of reference. Furthermore, we captured students' eye movements during the $Predict$ task and found that physics students with low confidence ratings focused longer on relevant task areas than confident students despite having a comparable score. Consequently, this metric is a helpful tool for the identification of misconceptions using eye tracking. Overall, the results help to understand the complexity of concept learning from demonstration experiments and provide important implications for instructional design of introductions to rotating frames of reference.Comment: 12 page

Vulnerability to Poverty and Vulnerability to Climate Change : Conceptual Framework, Measurement and Synergies in Policy

This paper attempts to compare the concepts and metrics related to vulnerability notion as used in the poverty literature with those in the filed of climate change. Such comparison could shed light on the understanding of the perceived and real differences between the two fields and also help to identify possible policy synergies between the climate change and poverty communities. The analysis shows that while vulnerability concepts in both the disciplines are defendable, broader policy relevant statements about vulnerability could be made if the analysis clearly identifies three primitives introduced in Ionescu et al. (2006) namely, the entity that is vulnerable, the stimulus due to which the entity is vulnerable, and the preference criteria on the outcome of concern. The analysis shows significant similarities between the two fields in terms of vulnerability measurement. The link between the vulnerability metrics in the two fields can be established through the introduction of sensitivity notion. The analysis also shows that the vulnerability metrics in both fields demand a stricter restriction (namely, complete reorder) on preference criteria on the outcome(s) of concern. The analysis identifies two issues that, if addressed, could create synergies between vulnerability assessments in the climate change and the poverty communities. First, the climate change community could benefit from exploring a notion analogous to that of poverty. In development policy, the notion of poverty enables one to recognise that there is a need to focus not only on people who are likely to become poor due to some exogenous input, but also on those who already are poor (and may become even poorer). Second, it would be interesting to explore the analogous concepts of mitigation and adaptive capacity in poverty research. Similar to their use in climate research and policy, the analysis of these concepts could lead to the more explicit consideration of the multidimensional nature of both causes and outcomes of poverty, as well as of the multiple time scales on which these occur.vulnerability, poverty, Climate change, Adaptation

The Effect of Fluctuations on the QCD Critical Point in a Finite Volume

We investigate the effect of a finite volume on the critical behavior of the theory of the strong interaction (QCD) by means of a quark-meson model for two quark flavors. In particular, we analyze the effect of a finite volume on the location of the critical point in the phase diagram existing in our model. In our analysis, we take into account the effect of long-range fluctuations with the aid of renormalization group techniques. We find that these quantum and thermal fluctuations, absent in mean-field studies, play an import role for the dynamics in a finite volume. We show that the critical point is shifted towards smaller temperatures and larger values of the quark chemical potential if the volume size is decreased. This behavior persists for antiperiodic as well as periodic boundary conditions for the quark fields as used in many lattice QCD simulations.Comment: 9 pages, 2 figures, 1 tabl

"Vom Lesesaal zum Learning Center" - Ein neues Raum- und Benutzungskonzept an der UB Mannheim

Der traditionelle Lesesaal der Universitätsbibliothek Mannheim ist 2014 in ein modernes Learning-Center umgewandelt worden. Ziel war ein Lernort, an dem Studierende insbesondere für kooperatives, aber auch für informelles Lernen jederzeit eine optimal unterstützende und variable Umgebung mit modernster technischer Ausstattung vorfinden. Der Beitrag beschreibt, wie dies in Raumkonzept, Innenarchitektur, technischer Ausstattung und Serviceangebot umgesetzt worden ist

Sphingolipids in human synovial fluid : a lipidomic study

Articular synovial fluid (SF) is a complex mixture of components that regulate nutrition, communication, shock absorption, and lubrication. Alterations in its composition can be pathogenic. This lipidomic investigation aims to quantify the composition of sphingolipids (sphingomyelins, ceramides, and hexosyl- and dihexosylceramides) and minor glycerophospholipid species, including (lyso)phosphatidic acid, (lyso)phosphatidylglycerol, and bis(monoacylglycero)phosphate species, in the SF of knee joints from unaffected controls and from patients with early (eOA) and late (lOA) stages of osteoarthritis (OA), and rheumatoid arthritis (RA). SF without cells and cellular debris from 9 postmortem donors (control), 18 RA, 17 eOA, and 13 lOA patients were extracted to measure lipid species using electrospray ionization tandem mass spectrometry - directly or coupled with hydrophilic interaction liquid chromatography. We provide a novel, detailed overview of sphingolipid and minor glycerophospholipid species in human SF. A total of 41, 48, and 50 lipid species were significantly increased in eOA, lOA, and RA SF, respectively when compared with normal SF. The level of 21 lipid species differed in eOA SF versus SF from lOA, an observation that can be used to develop biomarkers. Sphingolipids can alter synovial inflammation and the repair responses of damaged joints. Thus, our lipidomic study provides the foundation for studying the biosynthesis and function of lipid species in health and most prevalent joint diseases

The gravitational cat on the Cauchy horizon

We show that the stress tensor of a real scalar quantum field on Reissner-Nordstr{\"o}m-deSitter spacetime exhibits correlations over macroscopic distances near the Cauchy horizon. These diverge as the Cauchy horizon is approached and are universal, i.e., state-independent. This signals a breakdown of the semi-classical approximation near the Cauchy horizon. We also investigate the effect of turning on a charge of the scalar field and consider the correlation of the stress tensor between the two poles of the Cauchy horizon of Kerr-de Sitter spacetime.Comment: 6 pages, 6 figure