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The super massive binary system, η Car, experienced periastron passage in the summer of 2014. We observed the star twice around the maximum (forb =0.97, 2014 June 6) and just before the minimum (ϕorb =0.99, 2014 July 28) of its wind-wind colliding (WWC) X-ray emis-sion using the XMM-Newton and NuSTAR observatories, the latter of which is equipped with extremely hard X-ray (>10 keV) focusing mirrors. In both observations, NuSTAR detected the thermal X-ray tail up to 40-50 keV. The hard slope is consistent with an electron tem- perature of ∼6 keV, which is significantly higher than the ionization temperature (kT ∼4 keV) measured from the Fe K emission lines, assuming collisional equilibrium plasma. The spectrum did not show a hard power-law component above this energy range, unlike earlier detections with INTEGRAL and Suzaku. In the second NuSTAR observation, the X-ray flux above 5 keV declined gradually in ∼1 day. This result suggests that the WWC apex was gradually hidden behind the optically thick primary wind around conjunction.
I address uncertainties on the spatial distribution and mass of the dust formed in η Carinae's Homunculus nebula with data being combined from several space- and ground-based facilities spanning near-infrared to sub-mm wavelengths, in terms of observational constraints and modeling. Until these aspects are better understood, the mass loss history and mechanisms responsible for η Car's enormous eruption(s) remain poorly constrained.
Eta Carinae
(2015)
Since Augusto Damineli's demonstration in 1996 that Eta Carinae is a binary with a 5.52 year period, many innovative observations and increasingly advanced three-dimensional models have led to considerable insight on this massive system that ejected at least ten, possibly forty, solar masses in the nineteenth century. Here we present a review of our current understanding of this complex system and point out continuing puzzles.
We study the interaction of line-driven winds from massive stars with the magnetic field rooted in these stars by carrying out numerical simulations using the Nirvana MHD code in 2D in spherical polar coordinates. The code's adaptive mesh refinement feature allows high spatial resolution across the whole simulation box. We study both O and Wolf-Rayet stars for a range of magnetic field strengths from weak to strong as measured by the confinement parameter. For weak fields our simulations show that the initially dipolar field opens up far away from the star and a thin disk-like structure forms in the equatorial plane of the magnetic field. For stronger fields the disk is disrupted close to the stellar surface and closed field lines persist at low latitudes. For very strong fields a pronounced magnetosphere forms where the gas is forced to move along the field lines and eventually falls back to the stellar surface.
In the last decades, stellar atmosphere codes have become a key tool in understanding massive stars, including precise calculations of stellar and wind parameters, such as temperature, massloss rate, and terminal wind velocity. Nevertheless, for these models the hydrodynamic equation is not solved in the wind. Motivated by the results of the CAK theory, the models typically use a beta velocity law, which however turns out not to be adequate for stars with very strong winds, and treat the mass-loss rate as a free parameter. In a new branch of the Potsdam Wolf-Rayet model atmosphere (PoWR) code, we solve the hydrodynamic equation consistently throughout the stellar atmosphere. The PoWR code performs the calculation of the radiative force without approximations (e.g. Sobolev). We show the impact of hydrodynamically consistent modelling on OB and WR stars in comparison to conventional models and discuss the obtained velocity fields and their impact on the observed spectral lines.
The Wolf-Rayet (WR) phenomenon is widespread in astronomy. It involves classical WRs, very massive stars (VMS), WR central stars of planetary nebula CSPN [WRs], and supernovae (SNe). But what is the root cause for a certain type of object to turn into an emission-line star? In this contribution, I discuss the basic aspects of radiation-driven winds that might reveal the ultimate difference between WR stars and canonical O-type stars. I discuss the aspects of (i) self-enrichment via CNO elements, (ii) high effective temperatures (Tₑff), (iii) an increase in the helium abundance (Y ), and finally (iv) the Eddington factor Γₑ. Over the last couple of years, we have made a breakthrough in our understanding of Γₑ -dependent mass loss, which will have far-reaching consequences for the evolution and fate of the most massive stars in the Universe. Finally, I discuss the prospects for studies of the WR phenomenon in the highest redshift Lyα and He ii emitting galaxies.
Wolf-Rayet stars are important sources for the enrichment of the ISM with nuclear processed elements, UV photons and momentum. They are descendants of high-mass stars for which short lifetimes and transition times can hamper the spectral classification of the stars in their different evolutionary phases. The expanded stellar atmospheres of Wolf-Rayet stars can show spectra which seem inconsistent with the anticipated underlying evolution phase, for example in late hydrogen-burning WN stars and Of/WN transition stars. We present a sequence of synthetic spectra of the Potsdam Wolf-Rayet models based on the latest Geneva stellar evolution models. This will visualize the changes in stellar spectra over a full stellar lifetime. Direct comparison with observed stellar spectra, as well as the evolution of diagnostic line ratios will improve the connection of spectral classification and evolution phase.
Macroclumping in WR 136
(2015)
Macroclumping proved to resolve the discordance between different mass-loss rate diagnostics for O-type stars, in particular between Hα and the P v resonance lines. In this paper, we report first results from a corresponding investigation for WR stars. We apply our detailed 3-D Monte Carlo (MC) line formation code to the P v resonance doublet and show, for the Galactic WNL star WR136, that macroclumping is require to bring this line in accordance with the mass-loss rate derived from the emission-line spectrum.
We present results from our near-infrared spectroscopy with VLT/ISAAC of four, massive eclipsing binary systems in the young, heavily reddened, massive Danks clusters. We derive accurate fundamental parameters and the distance to these massive systems, which comprise of OIf+, WR and O-type stars. Our goal is to increase the sample of well-studied WR stars and constrain their physics by comparison with evolutionary models.
A detailed and comprehensive study of the Wolf-Rayet stars of the nitrogen sequence (WN
stars) in the Small Magellanic Cloud (SMC) and the Large Magellanic Cloud (LMC) is presented.
We derived the fundamental stellar and wind parameters for more than 100 massive stars, encompassing almost the whole WN population in the Magellanic Clouds (MCs). The observations are fitted with synthetic spectra, using the PotsdamWolf-Rayet model atmosphere
code (PoWR). For this purpose, large grids of line-blanket models for different metallicities have been calculated, covering a wide range of stellar temperatures, mass-loss rates, and hydrogen abundances. Our comprehensive sample facilitates statistical studies of the WN properties in the MCs without selection bias. To investigate the impact of the low LMC metallicity and the even lower SMC metallicity, we compare our new results to previous analyses of the Galactic WN population and the late type WN stars from M31. Based on these studies we derived an empirical relation between the WN mass-loss rates and the metallicity. Current stellar evolution tracks, even when accounting for rotationally induced mixing, partly fail to reproduce the observed ranges of luminosities and initial masses.
The Galactic Center (GC) hosts three of the most massive WR rich, resolved young clusters in the Local Group as well as a large number of apparently isolated massive stars. Therefore, it constitutes a test bed to study the star formation history of the region, to probe a possible top-heavy scenario and to address massive star formation (clusters vs isolation) in such a dense and harsh environment. We present results from our ongoing infrared spectroscopic studies of WRs and other massive stars at the Center of the Milky Way.
The enigmatic oxygen-sequence Wolf-Rayet stars represent a rare stage in the evolution of massive stars. Their properties can provide unique constraints on the pre-supernova evolution of massive stars. This work presents the results of a quantitative spectroscopic analysis of the known single WO stars, with the aim to obtain the key stellar parameters and deduce their evolutionary state.X-Shooter spectra of the WO stars are modeled using the line-blanketed non-local thermal equilibrium atmosphere code cmfgen. The obtained stellar parameters show that the WO stars are very hot, with temperatures ranging from 150 kK to 210 kK. Their chemical composition is dominated by carbon (>50%), while the helium mass fraction is very low (down to 14%). Oxygen mass fractions reach as high as 25%. These properties can be reproduced with dedicated evolutionary models for helium stars, which show that the stars are post core-helium burning and very close to their eventual supernova explosion. The helium-star masses indicate initial masses or approximately 40 - 60M⊙.Thus, WO stars represent the final evolutionary stage of stars with estimated initial masses of 40 - 60M⊙. They are post core-helium burning and may explode as type Ic supernovae within a few thousand years.
The Westerlund 1 (Wd1) cluster hosts a rich and varied collection of massive stars. Its dynamical youth and the absence of ongoing star formation indicate a coeval population. As such, the simultaneous presence of both late-type supergiants and Wolf-Rayet stars has defied explanation in the context of single-star evolution. Observational evidence points to a high binary fraction, hence this stellar population offers a robust test for stellar models accounting for both single-star and binary evolution. We present an optical to near-IR (VLT & NTT) spectroscopic analysis of 22 WR stars in Wd 1, delivering physical properties for the WR stars.
We discuss how these differ from the Galactic field population, and how they may be reconciled with the predictions of single and binary evolutionary models.
As part of our ongoing Wolf-Rayet (WR) Magellanic Cloud survey, we have discovered 13 new WRs. However, the most exciting outcome of our survey is not the number of new WRs, but their unique characteristics. Eight of our discoveries appear to belong to an entirely new class of WRs. While one might naively classify these stars as WN3+O3V binaries, such a pairing is unlikely. Preliminary CMFGN modeling suggests physical parameters similar to early-type WNs in the Large Magellanic Cloud except with mass-loss rates three to five times lower and slightly higher temperatures. The evolution status of these stars remains an open question.
Before GAIA improves the HIPPARCOS survey, direct determination of the distance via parallax is only possible for γ Vel, but the analysis of the cluster or association to which WR stars are associated can give distances with a 50% to a 10% accuracy. The list of Galactic clusters, associations and clusters/association candidates has grown significantly in the last decade with the numerous deep, high resolution surveys of the Milky Way. In this work, we revisit the fundamental parameters of known clusters with WR stars, and we present the search for new ones. All our work is based on the catalogs from the VVV (from the VISTA telescope) and the UKIDS (from the UKIRT telescope) near infrared surveys. Finally, the relations between the fundamental parameters of clusters with WR stars are explored.
The emission-line dominated spectra of Wolf-Rayet stars are formed in expanding layers of their atmosphere, i.e. in their strong stellar wind. Adequate modeling of such spectra has to face a couple of difficulties. Because of the supersonic motion, the radiative transfer is preferably formulated in the co-moving frame. The strong deviations from local thermodynamical equilibrium (LTE) require to solve the equations of statistical equilibrium for the population numbers, accounting for many hundred atomic energy levels and thousands of line transitions. Moreover, millions of lines from iron-group elements must be taken into account for their blanketing effect. Model atmospheres of the described kind can reproduce the observed WR spectra satisfyingly, and have been widely applied for corresponding spectral analyses.
Because most massive stars have been or will be affected by a companion during the course of their evolution, we cannot afford to neglect binaries when discussing the progenitors of supernovae and GRBs. Analyzing linear polarization in the emission lines of close binary systems allows us to probe the structures of these systems' winds and mass flows, making it possible to map the complex morphologies of the mass loss and mass transfer structures that shape their subsequent evolution. In Wolf-Rayet (WR) binaries, line polarization variations with orbital phase distinguish polarimetric signatures arising from lines that scatter near the stars from those that scatter far from the orbital plane. These far-scattering lines may form the basis for a "binary line-effect method" of identifying rapidly rotating WR stars (and hence GRB progenitor candidates) in binary systems.
In this paper, I review observational evidence from spectroscopy and polarimetry for the presence of small and large scale structure in the winds of Wolf-Rayet (WR) stars. Clumping is known to be ubiquitous in the winds of these stars and many of its characteristics can be deduced from spectroscopic time-series and polarisation lightcurves. Conversely, a much smaller fraction of WR stars have been shown to harbour larger scale structures in their wind (∼ 1/5) while they are thought to be present is the winds of most of their O-star ancestors. The reason for this difference is still unknown.
Professional and amateur astronomers around the world contributed to a 4-month long campaign in 2013, mainly in spectroscopy but also in photometry, interferometry and polarimetry, to observe the first 3 Wolf-Rayet stars discovered: WR 134 (WN6b), WR 135 (WC8) and WR 137 (WC7pd+O9). Each of these stars are interesting in their own way, showing a variety of stellar wind structures. The spectroscopic data from this campaign were reduced and analyzed for WR 134 in order to better understand its behavior and long-term periodicity in the context of CIRs in the wind. We will be presenting the results of these spectroscopic data, which include the confirmation of the CIR variability and a time-coherency of ∼ 40 days (half-life of ∼ 20 days).
For some years now, spectroscopic measurements of massive stars in the amateur domain have been fulfilling professional requirements. Various groups in the northern and southern hemispheres have been established, running successful professional-amateur (ProAm) collaborative campaigns, e.g., on WR, O and B type stars. Today high quality data (echelle and long-slit) are regularly delivered and corresponding results published. Night-to-night long-term observations over months to years open a new opportunity for massive-star research. We introduce recent and ongoing sample campaigns (e.g. ∊ Aur, WR 134, ζ Pup), show respective results and highlight the vast amount of data collected in various data bases. Ultimately it is in the time-dependent domain where amateurs can shine most.
We highlight the basic physics that allows fundamental parameters, such as the effective
temperature, luminosity, abundances, and mass-loss rate, of Wolf-Rayet (W-R) stars to be
determined. Since the temperature deduced from the spectrum of a W-R star is an ionization
temperature, a detailed discussion of the ionization structure of W-R winds, and how it is set, is given. We also provide an overview of line and continuum formation in W-R stars. Mechanisms that contribute to the strength of different emission lines, such as collisional excitation, radiative recombination, dielectronic recombination, and continuum uorescence, are discussed.
The main objective of this work is to investigate the evolution of massive stars, and the interplay between them and the ionized gas for a sample of local metal-poor Wolf-Rayet galaxies.
Optical integral field spectrocopy was used in combination with multi-wavelength radio data.
Combining optical and radio data, we locate Wolf-Rayet stars and supernova remnants across the Wolf-Rayet galaxies to study the spatial correlation between them. This study will shed light on the massive star formation and its feedback, and will help us to better understand
distant star-forming galaxies.
PopIII-star siblings in IZw18 and metal-poor WR galaxies unveiled from integral field spectroscopy
(2015)
Here, we highlight our recent results from the IFS study of Mrk178, the closest metal-poor WR galaxy, and of IZw18, the most metal-poor star-forming galaxy known in the local Universe. The IFS data of Mrk178 show the importance of aperture effects on the search for WR features, and the extent to which physical variations in the ISM properties can be detected. Our IFS data of IZw18 reveal its entire nebular HeIIλ4686-emitting region, and indicate for the very first time that peculiar, hot (nearly) metal-free ionizing stars (called here PopIII-star siblings) might hold the key to the HeII-ionization in IZw18.
The evolution of massive stars in very low metallicity galaxies is less well observationally
constrained than in environments more similar to the Milky Way, M33, or the LMC. We discuss
in this contribution the current state of our program to search for and characterize Wolf-Rayet stars (and other massive emission line stars) in low metallicity galaxies in the Local Volume.
Obtaining a complete census of massive, evolved stars in a galaxy would be a key ingredient for testing stellar evolution models. However, as the evolution of stars is also strongly dependent on their metallicity, it is inevitable to have this kind of data for a variety of galaxies with different metallicities. Between 2009 and 2011, we conducted the Magellanic Clouds Massive Stars and Feedback Survey (MSCF); a spatially complete, multi-epoch, broad- and narrow-band optical imaging survey of the Large and Small Magellanic Clouds. With the inclusion of shallow images, we are able to give a complete photometric catalog of stars between B ≈ 18 and B ≈ 19 mag.
These observations were augmented with additional photometric data of similar spatial res-
olution from UV to IR (e.g. from GALEX, 2MASS and Spitzer) in order to sample a large portion of the spectral energy distribution of the brightest stars (B < 16 mag) in the Magel- lanic Clouds. Using these data, were are able to train a machine learning algorithm that gives us a good estimate of the spectral type of tens of thousands of stars.
This method can be applied to the search for Wolf-Rayet-Stars to obtain a sample of candi- dates for follow-up observations. As this approach can, in principle, be adopted for any resolved galaxy as long as sufficient photometric data is available, it can form an effective alternative method to the classical strategies (e.g. He II filter imaging).
Detection and Characterization of Wolf-Rayet stars in M81 with GTC/OSIRIS spectra and HST images
(2015)
Here we investigate a sample of young star clusters (YSCs) and other regions of recent star formation with Wolf-Rayet (W-R) features detected in the relatively nearby spiral galaxy M81 by analysing long-slit (LS) and Multi-Object Spectroscopy (MOS) spectra obtained with the OSIRIS instrument at the 10.4-m Gran Telescopio Canarias (GTC). We take advantage of the synergy between GTC spectra and Hubble Space Telescope (HST) images to also reveal their spatial localization and the environments hosting these stars. We finally discuss and comment on the next steps of our study.
We summarize past and current surveys for WRs among the Local Group galaxies, empha- sizing both the why and how. Such studies are invaluable for helping us learn about massive star evolution, and for providing sensitive tests of the stellar evolution models. But for such surveys to be useful, the completeness limits must be well understood. We illustrate that point by following the “evolution” of the observed WC/WN ratio in nearby galaxies. We end by examining our new survey for WR stars in the Magellanic Clouds, which has revealed a new type of WN star, never before seen.
In this contribution we present some preliminary results obtained from a SOAR-Goodman optical spectroscopic survey aimed to confirm the OIf* - OIf*/WN nature of a sample of Galactic candidates that were previously confirmed as massive stars based on near-infrared spectra taken with OSIRIS at SOAR. With only a few of such stars known in the Galaxy to date, our study significantly contributes to improve the number of known Galactic O2If* stars, as well as almost doubling the number of known members of the galactic sample of the rare type OIf*/WN.
The total population of Wolf-Rayet (WR) stars in the Galaxy is predicted by models to be as many as ~6000 stars, and yet the number of catalogued WR stars as a result of optical surveys was far lower than this (~200) at the turn of this century. When beginning our WR searches using infrared techniques it was not clear whether WR number predictions were too optimistic or whether there was more hidden behind interstellar and circumstellar extinction. During the last decade we pioneered a technique of exploiting the near- and mid-infrared continuum colours for individual point sources provided by large-format surveys of the Galaxy, including 2MASS and Spitzer/GLIMPSE, to pierce through the dust and reveal newly discovered WR stars throughout the Galactic Plane. The key item to the colour discrimination is via the characteristic infrared spectral index produced by the strong winds of the WR stars, combined with dust extinction, which place WR stars in a relatively depopulated area of infrared colour-colour diagrams. The use of the Spitzer/GLIMPSE 8µm and, more recently, WISE 22µm fluxes together with cross-referencing with X-ray measurements in selected Galactic regions have enabled improved candidate lists that increased our confirmation success rate, achieved via follow-up infrared and optical spectroscopy. To date a total of 102 new WR stars have been found with many more
candidates still available for follow-up. This constitutes an addition of ~16% to the current
inventory of 642 Galactic WR stars. In this talk we review our methods and provide some
new results and a preliminary review of their stellar and interstellar medium environments. We provide a roadmap for the future of this search, including statistical modeling, and what we can add to star formation and high mass star evolution studies.
Although we all use the name Wolf-Rayet to refer to specific groups of stars, “Wolf-Rayet” per se is really an astrophysical phenomenon of fast-moving, hot plasma, normally expanding around a hot star. However, expediency demands that we follow established traditions by referring to three specific kinds of WR stars: (1) cWR, “classical” He-burning descendants of massive, O-type stars, presumably all of which pass through a WR stage; (2) WNh, the most massive and luminous hydrogen-rich main-sequence stars with strong winds; and (3) [WR], the central stars of some 15 % of Planetary Nebulae. Wolf-Rayet stars are the epitome of relatively stable stars with the highest mass-loss rates for their kind. It behooves us to understand the what, how and why of this circumstance, along with its manyfold and fascinating consequences.
An overview of the known Wolf-Rayet (WR) population of the Milky Way is presented, including a brief overview of historical catalogues and recent advances based on infrared photometric and spectroscopic observations resulting in the current census of 642 (vl.13 online catalogue). The observed distribution of WR stars is considered with respect to known star clusters, given that ≤20% of WR stars in the disk are located in clusters. WN stars outnumber WC stars at all galactocentric radii, while early-type WC stars are strongly biased against the inner Milky Way. Finally, recent estimates of the global WR population in the Milky Way are reassessed, with 1,200±100 estimated, such that the current census may be 50% complete. A characteristic WR lifetime of 0.25 Myr is inferred for an initial mass threshold of 25 M⊙.
A main limitation in the field of flood hydrology is the short time period covered by instrumental flood time series, rarely exceeding more than 50 to 100 years. However, climate variability acts on short to millennial time scales and identifying causal linkages to extreme hydrological events requires longer datasets. To extend instrumental flood time series back in time, natural geoarchives are increasingly explored as flood recorders. Therefore, annually laminated (varved) lake sediments seem to be the most suitable archives since (i) lake basins act as natural sediment traps in the landscape continuously recording land surface processes including floods and (ii) individual flood events are preserved as detrital layers intercalated in the varved sediment sequence and can be dated with seasonal precision by varve counting.
The main goal of this thesis is to improve the understanding about hydrological and sedimentological processes leading to the formation of detrital flood layers and therewith to contribute to an improved interpretation of lake sediments as natural flood archives. This goal was achieved in two ways: first, by comparing detrital layers in sediments of two dissimilar peri-Alpine lakes, Lago Maggiore in Northern Italy and Mondsee in Upper Austria, with local instrumental flood data and, second, by tracking detrital layer formation during floods by a combined hydro-sedimentary monitoring network at Lake Mondsee spanning from the rain fall to the deposition of detrital sediment at the lake floor.
Successions of sub-millimetre to 17 mm thick detrital layers were detected in sub-recent lake sediments of the Pallanza Basin in the western part of Lago Maggiore (23 detrital layers) and Lake Mondsee (23 detrital layers) by combining microfacies and high-resolution micro X-ray fluorescence scanning techniques (µ-XRF). The detrital layer records were dated by detailed intra-basin correlation to a previously dated core sequence in Lago Maggiore and varve counting in Mondsee. The intra-basin correlation of detrital layers between five sediment cores in Lago Maggiore and 13 sediment cores in Mondsee allowed distinguishing river runoff events from local erosion. Moreover, characteristic spatial distribution patterns of detrital flood layers revealed different depositional processes in the two dissimilar lakes, underflows in Lago Maggiore as well as under- and interflows in Mondsee. Comparisons with runoff data of the main tributary streams, the Toce River at Lago Maggiore and the Griesler Ache at Mondsee, revealed empirical runoff thresholds above which the deposition of a detrital layer becomes likely. Whereas this threshold is the same for the whole Pallanza Basin in Lago Maggiore (600 m3s-1 daily runoff), it varies within Lake Mondsee. At proximal locations close to the river inflow detrital layer deposition requires floods exceeding a daily runoff of 40 m3s-1, whereas at a location 2 km more distal an hourly runoff of 80 m3s-1 and at least 2 days with runoff above 40 m3s-1 are necessary. A relation between the thickness of individual deposits and runoff amplitude of the triggering events is apparent for both lakes but is obviously further influenced by variable influx and lake internal distribution of detrital sediment.
To investigate processes of flood layer formation in lake sediments, hydro-sedimentary dynamics in Lake Mondsee and its main tributary stream, Griesler Ache, were monitored from January 2011 to December 2013. Precipitation, discharge and turbidity were recorded continuously at the rivers outlet to the lake and compared to sediment fluxes trapped close to the lake bottom on a basis of three to twelve days and on a monthly basis in three different water depths at two locations in the lake basin, in a distance of 0.9 (proximal) and 2.8 km (distal) to the Griesler Ache inflow. Within the three-year observation period, 26 river floods of different amplitude (10-110 m3s-1) were recorded resulting in variable sediment fluxes to the lake (4-760 g m-2d-1). Vertical and lateral variations in flood-related sedimentation during the largest floods indicate that interflows are the main processes of lake internal sediment transport in Lake Mondsee. The comparison of hydrological and sedimentological data revealed (i) a rapid sedimentation within three days after the peak runoff in the proximal and within six to ten days in the distal lake basin, (ii) empirical runoff thresholds for triggering sediment flux at the lake floor increasing from the proximal (20 m3s-1) to the distal lake basin (30 m3s-1) and (iii) factors controlling the amount of detrital sediment deposition at a certain location in the lake basin. The total influx of detrital sediment is mainly driven by runoff amplitude, catchment sediment availability and episodic sediment input by local sediment sources. A further role plays the lake internal sediment distribution which is not the same for each event but is favoured by flood duration and the existence of a thermocline and, therewith, the season in which a flood occurred.
In summary, the studies reveal a high sensitivity of lake sediments to flood events of different intensity. Certain runoff amplitudes are required to supply enough detrital material to form a visible detrital layer at the lake floor. Reasonable are positive feedback mechanisms between rainfall, runoff, erosion, fluvial sediment transport capacity and lake internal sediment distribution. Therefore, runoff thresholds for detrital layer formation are site-specific due to different lake-catchment characteristics. However, the studies also reveal that flood amplitude is not the only control for the amount of deposited sediment at a certain location in the lake basin even for the strongest flood events. The sediment deposition is rather influenced by a complex interaction of catchment and in-lake processes. This means that the coring location within a lake basin strongly determines the significance of a flood layer record. Moreover, the results show that while lake sediments provide ideal archives for reconstructing flood frequencies, the reconstruction of flood amplitudes is a more complex issue and requires detailed knowledge about relevant catchment and in-lake sediment transport and depositional processes.
Diese Arbeit befasst sich mit der ganzheitlichen Betrachtung der Fluideigenschaften eines unterpermischen Reservoirs am Geothermie Forschungsstandort Groß Schönebeck (GrSk) bei Reservoirbedingungen und im Betrieb der Geothermieanlage. Die Untersuchungen zur Fluidherkunft ergeben, dass es sich um ein konnates Wasser meteorischen Ursprungs ohne den Einfluss der darüberliegenden Zechsteinwässer handelt. Die Ionen und Isotopenverhältnisse im Formationswasser gelöster Komponenten in GrSk belegen einen gemeinsamen Genesepfad mit Wässern anderer Rotliegend-Reservoire des Nordostdeutschen Beckens (NEGB). Die Isotopenverhältnisse von ⁸⁷Sr/⁸⁶Sr ≈ 0,7158 und von δ³⁴SV CDT ≈ 4,1 ‰ des Sulfats weisen auf die Anreicherung des Fluids mit schweren Isotopen durch die Fluid Gestein-Wechselwirkung mit Vulkaniten und Rotliegend Sandsteinen des Unteren Perms hin.
Das im Formationswasser bei Reservoirbedingungen gelöste Gas (Gas/Wasser ≤ 2 bei STP) enthält Stickstoff (δ¹⁵NAir ≈ 0,6 ‰) und thermogenes Methan (δ¹³CV-PDB ≈ - 18 ‰) aus organischen Karbonablagerungen (Kerogen Typ - III Kohlen) hoher Reife. Die Isotopenverhältnisse der Edelgase belegen eine krustale Herkunft des Gasgemisches. Die berechnete Verweilzeit τ (⁴He) der Gase im Reservoir liegt zwischen 275 und 317 Ma und überschreitet damit bei gegebener Konzentration von Mutternukliden im Reservoirgestein das allgemein angenommene Zeitalter der Sedimentgruppe. Das lässt sich durch eine Zuwanderung von Gasen aus älteren Sedimentfolgen erklären.
Die Veränderungen der physikochemischen Fluidparameter während des Anlagenbetriebs sind hauptsächlich temperaturbedingt. Bei stabilen Produktionsbedingungen und einer Temperatur von ca. 100 °C stabilisieren sich auch die Fluideigenschaften. Bei In situ Bedingungen übertage beträgt die Dichte ρ = 1,1325 ± 0,0002 g ∙ mL⁻¹, das Redoxpotential Eh = -105,5 ± 1,3 mV und der pH = 6,61 ± 0,002. Die relative Zusammensetzung der Gasphase bei stabilen Produktionsbedingungen zeigt dagegen eine geringe Erhöhung des Stickstoffanteils sowie des Anteils der Kohlenwasserstoffe (Ethan, Propan, usw.) und Abnahme des relativen Methananteils im Laufe des Betriebs.
Die quantitative Untersuchung der sekundären mineralischen Ausfällungen im Fluid mittels sequentieller Extraktion zeigte, dass Schwermetalle als eine Hauptkomponente der Fluidfestphase größtenteils in Verbindung mit organischen Molekülen vorliegen. Experimente zum Einfluss organischer Verbindungen unterschiedlicher Substanzklassen auf eine Mobilisierung der Schwermetalle aus dem Reservoirgestein ergaben, dass die Verbindungen wie Fettsäuren und PAK (polyzyklische aromatische Kohlenwasserstoffe) die Freisetzung von Kupfer, Nickel, Chrom und Blei verhindern bzw. zu derer Immobilisierung beitragen. Im Gegensatz dazu wird die Mobilität von Zink in Anwesenheit von diesen Verbindungen erhöht. Niedermolekulare Monocarbonsäuren und stickstoffhaltige Heteroaromaten tragen, mit Ausnahme von Blei, zur Freisetzung bzw. Mobilisierung von Schwermetallen aus dem Reservoirgestein bei.
Die gewonnenen Erkenntnisse dieser Arbeit bestätigen das Risiko massiver Ausfällungen auf der kalten Seite der Geothermieanlage bei Inbetriebnahme des Kraftwerks, wenn keine an den Fluidchemismus angepassten Präventionsmethoden eingesetzt werden. Die Isotopenzusammensetzung der Fluidkomponenten sowie geringfügige Schwankungen der Gaszusammensetzung im kontinuierlichen Anlagenbetrieb lässt eine Kommunikation des unterpermischen Reservoirs mit dem darunter liegenden Oberkarbon vermuten, was eine nachträgliche Veränderung der Fluidzusammensetzung beim Dauerbetrieb der Anlage bedeuten kann.
Peak oil is forcing our society to shift from fossil to renewable resources. However, such renewable resources are also scarce, and they too must be used in the most efficient and sustainable way possible. Biorefining is a concept that represents both resource efficiency and sustainability. This approach initiates a cascade use, which means food and feed production before material use, and an energy-related use at the end of the value-added chain. However, sustainability should already start in the fields, on the agricultural side, where the industrially-used biomass is produced. Therefore, the aim of my doctoral thesis is to analyse the sustainable feedstock supply for biorefineries. In contrast to most studies on biorefineries, I focus on the sustainable provision of feedstock and not on the bioengineering processing of whatever feedstock is available.
Grasslands provide a high biomass potential. They are often inefficiently used, so a new utilisation concept based on the biorefining approach can increase the added value from grasslands. Fodder legumes from temporary and permanent grasslands were chosen for this study. Previous research shows that they are a promising feedstock for industrial uses, and their positive environmental impact is an important byproduct to promote sustainable agricultural production systems.
Green Biorefineries are a class of biorefineries that use fresh green biomass, such as grasses or fodder legumes, as feedstock. After fractionation, an organic solution (press juice) forms; this is used for the production of organic acids, chemicals and extracts, as well as fertilisers. A fibre component (press cake) is also created to produce feed, biomaterials and biogas. This thesis examines a specific value chain, using alfalfa and clover/grass as feedstock and generating lactic acid and one type of cattle feed from it. The research question is if biomass production needs to be adapted for the utilisation of fodder legumes in the Green Biorefinery approach. I have attempted to give a holistic analysis of cultivation, processing and utilisation of two specific grassland crops. Field trials with alfalfa and clover/grass at different study sites were carried out to obtain information on biomass quality and quantity depending on the crop, study site and harvest time. The fresh biomass was fractionated with a screw press and the composition of press juices and cakes was analysed. Fermentation experiments took place to determine the usability of press juices for lactic acid production. The harvest time is not of high importance for the quality of press juices as a fermentation medium. For permanent grasslands, late cuts, often needed for reasons of nature conservation, are possible without a major influence on feedstock quality. The press cakes were silaged for feed-value determination.
Following evidence that both intermediate products are suitable feedstocks in the Green Biorefinery approach, I developed a cost-benefit analysis, comparing different production scenarios on a farm. Two standard crop rotations for Brandenburg, producing either only market crops or market crops and fodder legumes for ruminant feed production, were compared to a system that uses the cultivated fodder legumes for the Green Biorefinery value chain instead of only feed production. Timely processing of the raw material is important to maintain quality for industrial uses, so on-site processing at the farm is assumed in Green Biorefinery scenario. As a result, more added value stays in the rural area. Two farm sizes, common for many European regions, were chosen to examine the influence of scale. The cost site of farmers has also been analysed in detail to assess which farm characteristics make production of press juices for biochemical industries viable. Results show that for large farm sizes in particular, the potential profits are high. Additionally, the wider spectrum of marketable products generates new sources of income for farmers.
The holistic analysis of the supply chain provides evidence that the cultivation processes for fodder legumes do not need to be adapted for use in Green Biorefineries. In fact, the new utilisation approach even widens the cultivation and processing spectrum and can increase economic viability of fodder legume production in conventional farming.
Graph transformation systems are a powerful formal model to capture model transformations or systems with infinite state space, among others. However, this expressive power comes at the cost of rather limited automated analysis capabilities. The general case of unbounded many initial graphs or infinite state spaces is only supported by approaches with rather limited scalability or expressiveness. In this report we improve an existing approach for the automated verification of inductive invariants for graph transformation systems. By employing partial negative application conditions to represent and check many alternative conditions in a more compact manner, we can check examples with rules and constraints of substantially higher complexity. We also substantially extend the expressive power by supporting more complex negative application conditions and provide higher accuracy by employing advanced implication checks. The improvements are evaluated and compared with another applicable tool by considering three case studies.
In der vorliegenden Dissertation werden Migrationsdiskurse in der deutschen Grenzregion zu Polen im Vorfeld der EU-Erweiterung zum 1. Mai 2004 exemplarisch in drei deutschen Grenzstädten, der jeweils westliche Teil der ehemals gemeinsamen, seit 1945 durch eine nationalstaatliche Grenze mit dem jeweils zeitspezifischen Grenzregime geteilten, deutsch-polnischen Zwillingsstädte Frankfurt (Oder) – Słubice, Guben – Gubin und Görlitz – Zgorzelec, analysiert.
Ausgewählt wurde der Untersuchungsraum mit Blick auf die tiefgreifenden europäischen Transformationsprozesse seit den späten 1980er Jahren, die für die örtliche Bevölkerung gravierende lebensweltliche Strukturumbrüche zur Folge hatten. Die Region wurde mit der Vereinigung der beiden deutschen Staaten überdies zu einem zentralen Aktionsraum nationaler und internationaler Migrationspolitik; ihr wurde eine wichtige stellvertretende Funktion betreffend die Zutrittsregelung zugewiesen. Mit der EU-Erweiterung waren für die Region neuerliche, unmittelbare Veränderungen verbunden, die vor Ort gerade auch aufgrund damit (mutmaßlich) einhergehender Migration eher als Bedrohung denn als Chance gedeutet wurden.
Den diskurstheoretischen Hintergrund der Untersuchungen stellen in erster Linie die Arbeiten von Michel Foucault und die von Siegfried Jäger darauf aufruhend konzipierte Kritische Diskursanalyse bereit. Diskurs wird – grob vereinfacht – als Fluss von sozialen Wissensbeständen und Bewusstseinsinhalten durch die Zeit verstanden, der individuelles und kollektives Handeln von Menschen bestimmt; Diskurse sind der Ort, an dem (Be-)Deutungen von Menschen ausgehandelt, verändert und der Wirklichkeit zugewiesen werden. Der Forschungszugang versteht sich als Teil der Neuen Kulturgeographie, die konsequent nicht-essentialistisch und erkenntnistheoretisch nicht-fundamentalistisch ist.
Die Datenbasis der empirischen Analysen repräsentieren zwei Ebenen bzw. Teilsektoren des Diskurses. Zum einen die Berichterstattung der jeweils monopolartigen regionalen Tageszeitung in Frankfurt (Oder), Guben und Görlitz (Märkische Oderzeitung/Frankfurter Stadtbote, Lausitzer Rundschau/Lokalausgabe Guben, Sächsische Zeitung/Görlitzer Zeitung). Zum anderen ein Sample von insgesamt 17 Experteninterviews mit lokalen Funktionsträgern, die mit Blick auf ihr, an ihre spezifische professionelle und/oder ehrenamtliche Tätigkeit gebundenes, praxisgesättigtes Sonder- bzw. Insiderwissen zum Thema Migration ausgewählt und befragt wurden.
Die durchgeführten Analysen verdeutlichen unter anderem die Bedeutung diskurssemantischer Grundfiguren des deutschen Migrationsdiskurses im Sinne politisch und alltagskulturell konservierter migrationskritischer Vorstellungsinhalte und Bedeutungszuweisungen zu Kategorien des Fremden und Konstruktionen von Wir und/vs. Sie. Ebenso explizieren sie eine gravierende Diskrepanz zwischen dem lokalen Staat und der Lebenswelt der lokalen Bevölkerung.
Wolf-Rayet Stars
(2015)
Nearly 150 years ago, the French astronomers Charles Wolf and Georges Rayet described stars with very conspicuous spectra that are dominated by bright and broad emission lines. Meanwhile termed Wolf-Rayet Stars after their discoverers, those objects turned out to represent important stages in the life of massive stars.
As the first conference in a long time that was specifically dedicated to Wolf-Rayet stars, an international workshop was held in Potsdam, Germany, from 1.-5. June 2015. About 100 participants, comprising most of the leading experts in the field as well as as many young scientists, gathered for one week of extensive scientific exchange and discussions. Considerable progress has been reported throughout, e.g. on finding such stars, modeling and analyzing their spectra, understanding their evolutionary context, and studying their circumstellar nebulae. While some major questions regarding Wolf-Rayet stars still remain open 150 years after their discovery, it is clear today that these objects are not just interesting stars as such, but also keystones in the evolution of galaxies.
These proceedings summarize the talks and posters presented at the Potsdam Wolf-Rayet workshop. Moreover, they also include the questions, comments, and discussions emerging after each talk, thereby giving a rare overview not only about the research, but also about the current debates and unknowns in the field. The Scientific Organizing Committee (SOC) included Alceste Bonanos (Athens), Paul Crowther (Sheffield), John Eldridge (Auckland), Wolf-Rainer Hamann (Potsdam, Chair), John Hillier (Pittsburgh), Claus Leitherer (Baltimore), Philip Massey (Flagstaff), George Meynet (Geneva), Tony Moffat (Montreal), Nicole St-Louis (Montreal), and Dany Vanbeveren (Brussels).
Ingo Schwarz: „Uebrigens verbleibe ich mit besonderer Werthschätzung Euer gnädiger König“. Zum Briefwechsel Alexander von Humboldts mit Friedrich Wilhelm III. im September 1804
Giuseppe Buffon: The Franciscans in Cathay: memory of men and places. A Contribution for the genealogy of geographical knowledge of Alexander von Humboldt
Ottmar Ette: Icono-grafía, cali-grafía, auto-grafía. Sobre el arte de la visualización en los diarios del viaje americano de Alexander von Humboldt
Elisa Garrido: Arte, ciencia y cultura visual en el atlas pintoresco: Vista de la Plaza Mayor de Mexico
Thomas Heyd: Ascensión al Teide de Alexander von Humboldt
Karin Lundberg: Networking Knowledge: Considering Alexander von Humboldt’s Legacy in a New Shared Space in Education
Petra Werner: In der Naturgeschichte „etwas Höheres suchen“. Zu Humboldts Konzept der Pflanzengeographie
Über die Autoren
(2015)
Der Erwerb der südamerikanischen Reisetagebücher Alexander von Humboldts durch die Staatsbibliothek Preußischer Kulturbesitz war 2014 ein bedeutendes Ereignis. In einem ersten Schritt wertet der Artikel unveröffentlichte Teile der Tagebücher und Dokumente aus dem Nachlass aus, um den „Kosmos Humboldt´scher Interessen“ zum Thema Pflanzengeographie zu umreißen, darunter auch seine Überlegungen zum Einfluss von Mensch und Tier auf die Ausbreitung von Pflanzen und die Veränderung von Vegetation. Die Einsichten des Gelehrten zur Abhängigkeit Europas von der sogenannten „Neuen Welt“ hinsichtlich der Nahrungsmittel werden ebenso behandelt. So vertrat Humboldt in seinen Ausführungen zum Thema „Was sind Barbaren?“ die These, dass Isolierung von Menschen aus der Gemeinschaft, Elend, Nahrungsmangel, klimatische Ursachen usw. „die Spuren von Zivilisation vertilgen“. Er betonte, dass es nötig sein, in einem weltweiten Wettstreit intellektueller Kräfte die Ressourcenknappheit zu überwinden.
Networking knowledge
(2015)
Global citizenship and diversity are well-represented concepts in today’s higher education. Learning outcomes and competencies are designed to sensitize students to the many cultural backgrounds of U.S. learning institutions. Nevertheless, true globality, as represented through diverse discourses and perspectives of the world, still seems neglected in curricula and course assignments. This article explores the possibilities offered through a new shared space in education where different forms of networked knowledge and multifaceted perspectives can build a global platform of exchange in a diverse student population. The universal science concept described by Alexander von Humboldt at the beginning of the 19th Century illuminates this intertwined approach to knowledge of the world, which has the potential to positively impact contemporary curricula and course design. Von Humboldt’s writings emphasize inclusion and interplay among cultures and natural phenomena. By inviting our students to be active representatives of diverse discourses, these interconnecting links will become more transparent. In turn, productive forms of knowing about the world may enrich current learning objectives and thereby reflect a true global citizenship as it evolves in a new shared space of education. Keywords: global citizenship, plurality, diverse discourses, multicultural education.
En este breve ensayo propongo que en la ascensión al Teide Alexander von Humboldt pudo adquirir una perspectiva integral, que le sirvió como marco de comunicación científica para aunar la multitud de datos que se había dispuesto a recoger en su breve estancia en la isla. Más aun, de ahí en adelante este marco además le serviría para darle sentido de conjunto a las incontables y diversas informaciones que recogería en los restantes cinco años de viaje. Para poner en evidencia el enfoque de la visita a Tenerife de Humboldt, analizo su relato de la ascensión al Teide suponiendo que está estructurado según los relatos de viajes épicos y peregrinaciones.
Lo pintoresco se puede definir como un sentimiento que invita al espectador de una escena particular a reproducirla en un cuadro, algo que permitió a los viajeros del siglo XIX transportar las imágenes como posesiones, especialmente a través de la publicación de un Atlas Pittoresque. Cada una de esas imágenes es un testimonio de los viajes y sus historias cruzadas. Este es el caso de la lámina III, Vista de la Plaza Mayor de México, que forma parte de la obra Vues des Cordillères et Monuments des Peuples Indigènes de l’Amérique, una imagen que ilustra las redes de intercambio que se sucedían entre artistas y científicos a través de los viajes y expediciones.
En las pinturas que retratan al erúdito Alexander von Humboldt encontramos densos signos visuales las cuales simbolizan su vida científica. La imagen del Chimborazo, cuya cima Humboldt no había alcanzado, recuerda la función epistémica de lo inacabado en su obra, mientras que la carta, el globo y su postura típica remiten al central significado del movimiento y al “escribir de cara a las cosas”. La presencia de sus objetos de escritura en las imagenes llama la atención, ya que se puede entender como referencia al significado de los diarios del viaje americano escritos durante toda la vida. En aquellos se ponen de manifiesto los momentos centrales del Humboldtian Science. El carácter del work in progress y la relacionalidad consecuente de la representación muestran las constantes epistemológicas de esta ciencia así como la dimensión de lo corporal en los manuscritos.
The Franciscans in Cathay
(2015)
The study analyzes the process that leads to the elaboration of the thesis of a continuity between the Medieval Asia mission and the New World mission. This effort, undertaken by the Catholic historiography of the mission during the XIX century, is the result of the impulse provided by Alexander von Humboldt’s studies about the discovery of America (Examen critique). The data about the geography of Asia collected by the missionaries-travelers working in the territory between Karakorum and Khanbalik during the XIII e XIV century reaches Christopher Colombus with the mediation of Roger Bacon, whom Humboldt himself esteems as a true cultural mediator. The conclusion of the article tries to identify reasons and modalities of the secularization of the missionary concept, i.e. the shift from the ideal of the propagation of the Christian message to a prevailing interest for cartography and topography, transformations arranged by a late medieval historiography that introduces into martyrolagia the loca toponomastica.
Background African weakly-electric fishes of the family Mormyridae are able to produce and perceive weak electric signals (typically less than one volt in amplitude) owing to the presence of a specialized, muscle-derived electric organ (EO) in their tail region. Such electric signals, also known as Electric Organ Discharges (EODs), are used for objects/prey localization, for the identification of conspecifics, and in social and reproductive behaviour. This feature might have promoted the adaptive radiation of this family by acting as an effective pre-zygotic isolation mechanism. Despite the physiological and evolutionary importance of this trait, the investigation of the genetic basis of its function and modification has so far remained limited. In this study, we aim at: i) identifying constitutive differences in terms of gene expression between electric organ and skeletal muscle (SM) in two mormyrid species of the genus Campylomormyrus: C. compressirostris and C. tshokwe, and ii) exploring cross-specific patterns of gene expression within the two tissues among C. compressirostris, C. tshokwe, and the outgroup species Gnathonemus petersii. Results Twelve paired-end (100 bp) strand-specific RNA-seq Illumina libraries were sequenced, producing circa 330 M quality-filtered short read pairs. The obtained reads were assembled de novo into four reference transcriptomes. In silico cross-tissue DE-analysis allowed us to identify 271 shared differentially expressed genes between EO and SM in C. compressirostris and C.tshokwe. Many of these genes correspond to myogenic factors, ion channels and pumps, and genes involved in several metabolic pathways. Cross-species analysis has revealed that the electric organ transcriptome is more variable in terms of gene expression levels across species than the skeletal muscle transcriptome. Conclusions The data obtained indicate that: i) the loss of contractile activity and the decoupling of the excitation-contraction processes are reflected by the down-regulation of the corresponding genes in the electric organ’s transcriptome; ii) the metabolic activity of the EO might be specialized towards the production and turn-over of membrane structures; iii) several ion channels are highly expressed in the EO in order to increase excitability; iv) several myogenic factors might be down-regulated by transcription repressors in the EO.
Although eye movements during reading are modulated by cognitive processing demands, they also reflect visual sampling of the input, and possibly preparation of output for speech or the inner voice. By simultaneously recording eye movements and the voice during reading aloud, we obtained an output measure that constrains the length of time spent on cognitive processing. Here we investigate the dynamics of the eye-voice span (EVS), the distance between eye and voice. We show that the EVS is regulated immediately during fixation of a word by either increasing fixation duration or programming a regressive eye movement against the reading direction. EVS size at the beginning of a fixation was positively correlated with the likelihood of regressions and refixations. Regression probability was further increased if the EVS was still large at the end of a fixation: if adjustment of fixation duration did not sufficiently reduce the EVS during a fixation, then a regression rather than a refixation followed with high probability. We further show that the EVS can help understand cognitive influences on fixation duration during reading: in mixed model analyses, the EVS was a stronger predictor of fixation durations than either word frequency or word length. The EVS modulated the influence of several other predictors on single fixation durations (SFDs). For example, word-N frequency effects were larger with a large EVS, especially when word N-1 frequency was low. Finally, a comparison of SFDs during oral and silent reading showed that reading is governed by similar principles in both reading modes, although EVS maintenance and articulatory processing also cause some differences. In summary, the EVS is regulated by adjusting fixation duration and/or by programming a regressive eye movement when the EVS gets too large. Overall, the EVS appears to be directly related to updating of the working memory buffer during reading.
Physical fitness is an important marker of health that enables people to carry out activities of daily living with vigour and alertness but without undue fatigue and with sufficient reserve to enjoy active leisure pursuits and to meet unforeseen emergencies. Especially, due to scientific findings that the onset of civilization diseases (e.g., obesity, cardiovascular disease) begins in childhood and that physical fitness tracks (at least) into young adulthood, the regular monitoring and promotion of physical fitness in children is risen up to a public health issue. In relation to the evaluation of a child’s physical fitness over time (i.e., development) the use of longitudinally-based percentile values is of particular interest due to their underlined dedication of true physical fitness development within subjects (i.e., individual changes in timing and tempo of growth and maturation). Besides its genetic determination (e.g., sex, body height), physical fitness is influenced by factors that refer to children’s environment and behaviour. For instance, disparities in physical fitness according to children’s living area are frequently reported concerning the fact that living in rural areas as compared to urban areas seems to be more favourable for children’s physical fitness. In addition, cross-sectional studies found higher fitness values in children participating in sports clubs as compared to non-participants. However, up to date, the observed associations between both (i.e., living area and sports club participating) and children’s physical fitness are unresolved concerning a long-term effect. In addition, social inequality as determined by the socioeconomic status (SES) extends through many areas of children’s life. While evidence indicates that the SES is inversely related to various indices of child’s daily life and behaviour like educational success, nutritional habits, and sedentary- and physical activity behaviour, a potential relationship between child’s physical fitness and the SES is hardly investigated and indicated inconsistent results.
The present thesis addressed three objectives: (1) to generate physical fitness percentiles for 9- to 12- year-old boys and girls using a longitudinal approach and to analyse the age- and sex-specific development of physical fitness, (2) to investigate the long-term effect of living area and sports club participation on physical fitness in third- to sixth-grade primary school students, and (3) to examine associations between the SES and physical fitness in a large and representative (i.e., for a German federal state) sample of third grade primary school students.
Methods
(i/ii) Healthy third graders were followed over four consecutive years (up to grade 6), including annually assessment of physical fitness and parental questionnaire (i.e., status of sports club participation and living area). Six tests were conducted to estimate various components of physical fitness: speed (50-m sprint test), upper body muscular power (1-kg ball push test), lower body muscular power (triple hop test), flexibility (stand-and-reach test), agility (star agility run test), and cardiorespiratory fitness (CRF) (9-min run test). (iii) Within a cross-sectional study (i.e., third objective), physical fitness of third graders was assessed by six physical fitness tests including: speed (20-m sprint test), upper body muscular power (1-kg ball push test), lower body muscular power (standing long jump [SLJ] test), flexibility (stand-and-reach test), agility (star agility run test), and CRF (6-min run test). By means of questionnaire, students reported their status of organized sports participation (OSP).
Results
(i) With respect to percentiles of physical fitness development, test performances increased in boys and girls from age 9 to 12, except for males’ flexibility (i.e., stable performance over time). Girls revealed significantly better performance in flexibility, whereas boys scored significantly higher in the remaining physical fitness tests. In girls as compared to boys, physical fitness development was slightly faster for upper body muscular power but substantially faster for flexibility. Generated physical fitness percentile curves indicated a timed and capacity-specific physical fitness development (curvilinear) for upper body muscular power, agility, and CRF. (ii) Concerning the effect of living area and sports club participation on physical fitness development, children living in urban areas showed a significantly faster performance development in physical fitness components of upper and lower body muscular power as compared to peers from rural areas. The same direction was noted as a trend in CRF. Additionally, children that regularly participated in a sports club, when compared to those that not continuously participated in a sports club demonstrated a significantly faster performance development in lower body muscular power. A trend of faster performance development in sports club participants occurred in CRF too. (iii) Regarding the association of SES with physical fitness, the percentage of third graders that achieved a high physical fitness level in lower body muscular power and CRF was significantly higher in students attending schools in communities with high SES as compared to middle and low SES, irrespective of sex. Similar, students from the high SES-group performed significantly better in lower body muscular power and CRF than students from the middle and/or the low SES-group.
Conclusion
(i) The generated percentile values provide an objective tool to estimate childrenʼs physical fitness within the frame of physical education (e.g., age- and sex-specific grading of motor performance) and further to detect children with specific fitness characteristics (low fit or high fit) that may be indicative for the necessity of preventive health promotion or long term athlete development. (ii) It is essential to consider variables of different domains (e.g., environment and behavior) in order to improve knowledge of potential factors which influence physical fitness during childhood. In this regard, the present thesis provide a first input to clarify the causality of living area and sports club participation on physical fitness development in school-aged children. Living in urban areas as well as a regular participation in sports clubs positively affected children´s physical fitness development (i.e., muscular power and CRF). Herein, sports club participation seems to be a key factor within the relationship between living area and physical fitness. (iii) The findings of the present thesis imply that attending schools in communities with high SES refers to better performance in specific physical fitness test items (i.e., muscular power, CRF) in third graders. Extra-curricular physical education classes may represent an important equalizing factor for physical activity opportunities in children of different SES backgrounds. In regard to strong evidence of a positive relationship between physical fitness - in particular muscular fitness/ CRF - and health, more emphasis should be laid on establishing sports clubs and extra-curricular physical education classes as an easy and attractive means to promote fitness-, and hence health- enhancing daily physical activity for all children (i.e. public health approach).