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Alles auf Anfang!
(2019)
Im Zuge der Bologna-Reform ist an Hochschulen vieles in Bewegung gekommen. Studium und Lehre sind stärker ins Blickfeld gerückt. Dabei kommt der Studieneingangsphase besondere Bedeutung zu, werden doch hier die Weichen für ein erfolgreiches Studium gestellt. Deshalb ist es verständlich, dass die Hauptanstrengungen der Hochschulen auf den Studieneingang gerichtet sind – ganz nach dem Motto: „Auf den Anfang kommt es an!“. Konsens herrscht dahingehend, dass der Studieneingang neu zu gestalten ist, doch beim „Wie?“ gibt es unterschiedliche Antworten. Zugleich wird immer deutlicher, dass eine wirksame Neugestaltung der Eingangsphase nur mit einer umfassenden Reform des Studiums gelingen kann.
Ziel des vierten Bandes der Potsdamer Beiträge zur Hochschulforschung ist es, eine Zwischenbilanz der Debatte zum Studieneingang zu ziehen. Auf der Basis empirischer Studien werden unterschiedliche Perspektiven auf den Studieneingang eingenommen und Empfehlungen zur Optimierung des Studieneingangs abgeleitet. Die zahlreichen Untersuchungsergebnisse Potsdamer Forschergruppen werden durch weitere nationale sowie internationale Perspektiven ergänzt. Der Band richtet sich an alle, die sich für die Entwicklung an Hochschulen interessieren.
Seismic scattering and absorption of oceanic lithospheric S waves in the Eastern North Atlantic
(2021)
The scattering and absorption of high-frequency seismic waves in the oceanic lithosphere is to date only poorly constrained by observations. Such estimates would not only improve our understanding of the propagation of seismic waves, but also unravel the small-scale nature of the lithosphere and its variability. Our study benefits from two exceptional situations: (1) we deployed over 10 months a mid-aperture seismological array in the central part of the Eastern North Atlantic in 5 km water depth and (2) we could observe in total 340 high-frequency (up to 30 Hz) Po and So arrivals with tens to hundreds of seconds long seismic coda from local and regional earthquakes in a wide range of backazimuths and epicentral distances up to 850 km with a travel path in the oceanic lithosphere. Moreover, the array was located about 100 km north of the Gloria fault, defining the plate boundary between the Eurasian and African plates at this location which also allows an investigation of the influence of an abrupt change in lithospheric age (20 Ma in this case) on seismic waves. The waves travel with velocities indicating upper-mantle material. We use So waves and their coda of pre-selected earthquakes to estimate frequency-dependent seismic scattering and intrinsic attenuation parameters. The estimated scattering attenuation coefficients are between 10(-4) and 4 x 10(-5) m(-1) and are typical for the lithosphere or the upper mantle. Furthermore, the total quality factors for So waves below 5 Hz are between 20 and 500 and are well below estimates from previous modelling for observations in the Pacific Ocean. This implies that the Atlantic Ocean is more attenuative for So waves compared to the Pacific Ocean, which is inline with the expected behaviour for the lithospheric structures resulting from the slower spreading rates in the Atlantic Ocean. The results for the analysed events indicate that for frequencies above 3 Hz, intrinsic attenuation is equal to or slightly stronger than scattering attenuation and that the So-wave coda is weakly influenced by the oceanic crust. Both observations are in agreement with the proposed propagation mechanism of scattering in the oceanic mantle lithosphere. Furthermore, we observe an age dependence which shows that an increase in lithospheric age is associated with a decrease in attenuation. However, we also observe a trade-off of this age-dependent effect with either a change in lithospheric thickness or thermal variations, for example due to small-scale upwellings in the upper mantle in the southeast close to Madeira and the Canaries. Moreover, the influence of the nearby Gloria fault is visible in a reduction of the intrinsic attenuation below 3 Hz for estimates across the fault. This is the first study to estimate seismic scattering and absorption parameters of So waves for an area with several hundreds of kilometres radius centred in the Eastern North Atlantic and using them to characterize the nature of the oceanic lithosphere.
Marine seismology usually relies on temporary deployments of stand alone seismic ocean bottom stations (OBS), which are initialized and synchronized on ship before deployment and re-synchronized and stopped on ship after recovery several months later. In between, the recorder clocks may drift and float at unknown rates. If the clock drifts are large or not linear and cannot be corrected for, seismological applications will be limited to methods not requiring precise common timing. Therefore, for example, array seismological methods, which need very accurate timing between individual stations, would not be applicable for such deployments.
We use an OBS test-array of 12 stations and 75 km aperture, deployed for 10 months in the deep sea (4.5-5.5 km) of the mid-eastern Atlantic. The experiment was designed to analyse the potential of broad-band array seismology at the seafloor. After recovery, we identified some stations which either show unusual large clock drifts and/or static time offsets by having a large difference between the internal clock and the GPS-signal (skew).
We test the approach of ambient noise cross-correlation to synchronize clocks of a deep water OBS array with km-scale interstation distances. We show that small drift rates and static time offsets can be resolved on vertical components with a standard technique. Larger clock drifts (several seconds per day) can only be accurately recovered if time windows of one input trace are shifted according to the expected drift between a station pair before the cross-correlation. We validate that the drifts extracted from the seismometer data are linear to first order. The same is valid for most of the hydrophones. Moreover, we were able to determine the clock drift at a station where no skew could be measured. Furthermore, we find that instable apparent drift rates at some hydrophones, which are uncorrelated to the seismometer drift recorded at the same digitizer, indicate a malfunction of the hydrophone.
Oceanic lithospheric S-wave velocities from the analysis of P-wave polarization at the ocean floor
(2016)
Our knowledge of the absolute S-wave velocities of the oceanic lithosphere is mainly based on global surface wave tomography, local active seismic or compliance measurements using oceanic infragravity waves. The results of tomography give a rather smooth picture of the actual S-wave velocity structure and local measurements have limitations regarding the range of elastic parameters or the geometry of the measurement. Here, we use the P-wave polarization (apparent P-wave incidence angle) of teleseismic events to investigate the S-wave velocity structure of the oceanic crust and the upper tens of kilometres of the mantle beneath single stations. In this study, we present an up to our knowledge new relation of the apparent P-wave incidence angle at the ocean bottom dependent on the half-space S-wave velocity. We analyse the angle in different period ranges at ocean bottom stations (OBSs) to derive apparent S-wave velocity profiles. These profiles are dependent on the S-wave velocity as well as on the thickness of the layers in the subsurface. Consequently, their interpretation results in a set of equally valid models. We analyse the apparent P-wave incidence angles of an OBS data set which was collected in the Eastern Mid Atlantic. We are able to determine reasonable S-wave-velocity-depth models by a three-step quantitative modelling after a manual data quality control, although layer resonance sometimes influences the estimated apparent S-wave velocities. The apparent S-wave velocity profiles are well explained by an oceanic PREM model in which the upper part is replaced by four layers consisting of a water column, a sediment, a crust and a layer representing the uppermost mantle. The obtained sediment has a thickness between 0.3 and 0.9 km with S-wave velocities between 0.7 and 1.4 km s(-1). The estimated total crustal thickness varies between 4 and 10 km with S-wave velocities between 3.5 and 4.3 km s(-1). We find a slight increase of the total crustal thickness from similar to 5 to similar to 8 km towards the South in the direction of a major plate boundary, the Gloria Fault. The observed crustal thickening can be related with the known dominant compression in the vicinity of the fault. Furthermore, the resulting mantle S-wave velocities decrease from values around 5.5 to 4.5 km s(-1) towards the fault. This decrease is probably caused by serpentinization and indicates that the oceanic transform fault affects a broad region in the uppermost mantle. Conclusively, the presented method is useful for the estimation of the local S-wave velocity structure beneath ocean bottom seismic stations. It is easy to implement and consists of two main steps: (1) measurement of apparent P-wave incidence angles in different period ranges for real and synthetic data, and (2) comparison of the determined apparent S-wave velocities for real and synthetic data to estimate S-wave velocity-depth models.
Receiver functions (RF) have been used for several decades to study structures beneath seismic stations. Although most available stations are deployed on shore, the number of ocean bottom station (OBS) experiments has increased in recent years. Almost all OBSs have to deal with higher noise levels and a limited deployment time (approximate to 1year), resulting in a small number of usable records of teleseismic earthquakes. Here we use OBSs deployed as midaperture array in the deep ocean (4.5-5.5km water depth) of the eastern mid-Atlantic. We use evaluation criteria for OBS data and beamforming to enhance the quality of the RFs. Although some stations show reverberations caused by sedimentary cover, we are able to identify the Moho signal, indicating a normal thickness (5-8km) of oceanic crust. Observations at single stations with thin sediments (300-400m) indicate that a probable sharp lithosphere-asthenosphere boundary (LAB) might exist at a depth of approximate to 70-80km which is in line with LAB depth estimates for similar lithospheric ages in the Pacific. The mantle discontinuities at approximate to 410km and approximate to 660km are clearly identifiable. Their delay times are in agreement with PREM. Overall the usage of beam-formed earthquake recordings for OBS RF analysis is an excellent way to increase the signal quality and the number of usable events.
Epigenetic modulations are a hypothesized link between environmental factors and the development of psychiatric disorders. Research has suggested that patients with depression or bipolar disorder exhibit higher methylation levels in the glucocorticoid receptor gene NR3C1. We aimed to investigate whether NR3C1 methylation changes are similarly associated with externalizing disorders such as aggressive behavior and conduct disorder. NR3C1 exon 1F methylation was analyzed in young adults with a lifetime diagnosis of an externalizing disorder (N = 68) or a depressive disorder (N = 27) and healthy controls (N = 124) from the Mannheim Study of Children at Risk. The externalizing disorders group had significantly lower NR3C1 methylation levels than the lifetime depressive disorder group (p = 0.009) and healthy controls (p = 0.001) This report of lower methylation levels in NR3C1 in externalizing disorders may indicate a mechanism through which the differential development of externalizing disorders as opposed to depressive disorders might occur.
PSI-Potsdam
(2023)
An der Universität Potsdam wird seit 2015 im Rahmen der „Qualitätsoffensive Lehrerbildung“ das Projekt „Professionalisierung – Schulpraktische Studien – Inklusion“ (PSI-Potsdam) durchgeführt und am Zentrum für Lehrerbildung und Bildungsforschung (ZeLB) koordiniert. Zur ersten Projektförderphase (2015-2018) erschien der Band „PSI-Potsdam – Ergebnisbericht zu den Aktivitäten im Rahmen der Qualitätsoffensive Lehrerbildung (2015-2018)“ zum Auftakt der Reihe „Potsdamer Beiträge zur Lehrerbildung und Bildungsforschung“.
Der vorliegende Band aus der gleichen Reihe gibt in den Kapiteln „Erhebungen“, „Lehrkonzepte“ und „Vernetzungen“ einen Überblick über alle Teilprojekte der zweiten Projektförderphase (2019-2023). Wissenschaftler:innen aus verschiedenen Fachdidaktiken, Fachwissenschaften sowie aus den Bildungswissenschaften und der Inklusionspädagogik haben im Rahmen des Projektes kooperiert. Sowohl praxisnahe Forschung als auch die Entwicklung neuer Lehrkonzepte sowie Strategien zur Vernetzung innerhalb der Lehrkräftebildung stehen im Fokus dieses Bandes. Die Praxisphasen, die im Rahmen des „Potsdamer Modells der Lehrerbildung“ eine zentrale Rolle spielen, wurden in einer großen Studie über alle Praxisphasen untersucht.
Der Band gibt interessante Einblicke in die Ergebnisse der Teilprojekte und Anregungen sowohl für die eigene Forschung als auch für Entwicklungsarbeit wie zum Beispiel die Entwicklung neuer Lehrkonzepte. Herausgegeben wird dieser Band von PD Dr. Jolanda Hermanns (Gesamtkoordinatorin PSI-Potsdam und Chemiedidaktikerin).
Improving our understanding of biodiversity and ecosystem functioning and our capacity to inform ecosystem management requires an integrated framework for functional biodiversity research (FBR). However, adequate integration among empirical approaches (monitoring and experimental) and modelling has rarely been achieved in FBR. We offer an appraisal of the issues involved and chart a course towards enhanced integration. A major element of this path is the joint orientation towards the continuous refinement of a theoretical framework for FBR that links theory testing and generalization with applied research oriented towards the conservation of biodiversity and ecosystem functioning. We further emphasize existing decision-making frameworks as suitable instruments to practically merge these different aims of FBR and bring them into application. This integrated framework requires joint research planning, and should improve communication and stimulate collaboration between modellers and empiricists, thereby overcoming existing reservations and prejudices. The implementation of this integrative research agenda for FBR requires an adaptation in most national and international funding schemes in order to accommodate such joint teams and their more complex structures and data needs.
In this receiver function study, we investigate the structure of the crust beneath six seismic broadband stations close to the Sunda Arc formed by subduction of the Indo-Australian under the Sunda plate. We apply three different methods to analyse receiver functions at single stations. A recently developed algorithm determines absolute shear-wave velocities from observed frequency-dependent apparent incidence angles of P waves. Using waveform inversion of receiver functions and a modified Zhu and Kanamori algorithm, properties of discontinuities such as depth, velocity contrast, and sharpness are determined. The combination of the methods leads to robust results. The approach is validated by synthetic tests. Stations located on Malaysia show high-shear-wave velocities (V (S)) near the surface in the range of 3.4-3.6 km s (-aEuro parts per thousand 1) attributed to crystalline rocks and 3.6-4.0 km s (-aEuro parts per thousand 1) in the lower crust. Upper and lower crust are clearly separated, the Moho is found at normal depths of 30-34 km where it forms a sharp discontinuity at station KUM or a gradient at stations IPM and KOM. For stations close to the subduction zone (BSI, GSI and PSI) complexity within the crust is high. Near the surface low V (S) of 2.6-2.9 km s (-aEuro parts per thousand 1) indicate sediment layers. High V (S) of 4.2 km s (-aEuro parts per thousand 1) are found at depth greater than 6 and 2 km at BSI and PSI, respectively. There, the Moho is located at 37 and 40 km depth. At station GSI, situated closest to the trench, the subducting slab is imaged as a north-east dipping structure separated from the sediment layer by a 10 km wide gradient in V (S) between 10 and 20 km depth. Within the subducting slab V (S) a parts per thousand aEuro parts per thousand 4.7 km s (-aEuro parts per thousand 1). At station BSI, the subducting slab is found at depth between 90 and 110 km dipping 20A degrees +/- 8A degrees in approximately N 60A degrees E. A velocity increase in similar depth is indicated at station PSI, however no evidence for a dipping layer is found.