Size Spectra as a tool to understand structures and processes of aquatic communities

Aquatische Gemeinschaften sind stark körpergrößenstrukturiert mit einer exponentiellen Abnahme der Häufigkeit der Individuen mit zunehmender Körpergröße, die als Größenspektrum (SS) bezeichnet wird. Körpergrößenbasierte Ansätze bieten eine einfache und kostengünstige Methode zur Beantwortung komplexer ökologischer Fragestellungen in aquatischer Forschung. Widersprüchliche Ergebnisse zu den wichtigsten Faktoren, die Größenspektren beeinflussen unterstreichen jedoch die Notwendigkeit weiterer Studien. Um einige dieser widersprüchlichen Schlussfolgerungen anzugehen, habe ich eine Reihe von Fragen in den Bereichen Limnologie und Korallenriffökologie untersucht. In dieser Dissertation wurden größenbasierte Ansätze wie SS verwendet, um zu untersuchen, (i) was die Größenverteilung von Zooplankton beeinflusst und ob Zooplankton-fressende Fische (topdown) oder Ressourcenverfügbarkeit und Umweltbedingungen (bottom-up) die SS der Zooplanktongemeinschaft bestimmen, (ii) ob traditionelle Schleppnetze oder moderne hydroakustische Methoden Fisch-SS zuverlässiger darstellen, und (iii) ob SS von Korallenriff- Fischgemeinschaften und die strukturelle Komplexität der Korallen bzw. deren Beziehung zueinander sich unter verschiedenen anthropogenen Stressoren verändert. Zuallererst konnte ich zeigen, dass weder Top-down- noch Bottom-up-Kräfte stark die Größenverteilung der Zooplanktongemeinschaft beeinflussten. Zooplankton SS scheinen robust gegenüber Prädationseffekten zu sein, aber ein empfindlicher Indikator für die Energieverfügbarkeit und Transfereffizienz im Nahrungsnetz des untersuchten Sees. Des Weiteren konnten meine Studien bestätigen, dass hydroakustische Methoden die SS von pelagischen Fischgemeinschaften zuverlässig darstellen, was sie zu einer kostengünstigen und minimalinvasiven Alternative zu traditionellen Fischentnahmemethoden macht. Ich konnte jedoch kein allgemeingültiges Muster hinsichtlich der Größenverteilung von Korallenrifffischen und der strukturellen Komplexität der Korallen in Beziehung zu unterschiedlichen anthropogenen Stressoren finden. Insgesamt zeigt die Dissertation das weite Anwendungsspektrum von SS, um Strukturen und Prozesse in aquatischen Gemeinschaften und Fischfangmethoden zu untersuchen. Die hohe Variabilität von Größenspektren und der Einfluss von Umweltbedingungen unterstreicht weiter die Wichtigkeit, Daten über einen langen Zeitraum einzubeziehen. Darüber hinaus unterstreichen die Ergebnisse dieser Arbeit auch die Grenzen der Anwendung von SS, da für die Beantwortung mancher ökologischer Fragestellungen artenspezifische Informationen, wie Lebensraum- und Nahrungspräferenzen benötigt werden.Aquatic communities are highly body-size structured with an exponential decline of abundance with increasing body size, which is referred to as the size spectrum (SS). The importance of body size as a principal and simplifying framework within aquatic communities, has led to a high number of theoretical and empirical studies on energy fluxes in food webs and predatorprey interactions using Size Spectra. These size-based approaches offer a rather simple and inexpensive method to answer complex ecological questions. However, conflicting findings on the key drivers of SS highlight the need for further studies. To address some of these conflicting conclusions, I investigated a range of questions within the fields of limnology and coral reef ecology. In this thesis size-based approaches such as SS were employed to explore (i) what drives zooplankton size distribution and whether zooplanktivorous fish (top-down) or resource availability and environmental condition (bottom-up) determine zooplankton community SS, (ii) whether traditional midwater trawling or modern hydroacoustic methods more reliably represent fish SS, and (iii) coral reef fish community SS and habitat structural complexity and their relationship across site-specific anthropogenic stressors. By analysing long term data, I first found that neither top-down or bottom-up forces drove the zooplankton community size distribution. Zooplankton SS seem robust against predation effects but a sensitive indicator for lake-wide energy availability and transfer efficiency in the food web. Then I found that hydroacoustic methods reliably represent pelagic fish community SS, making it a great alternative to traditional and more invasive fish removal sampling methods. Finally, I discovered that coral reef fish SS slope and structural complexity of the reef exhibited a significant negative relationship on two of the examined reef sites which are least exposed to anthropogenic disturbances. A consistent pattern of fish SS and reef complexity was missing, indicating that other environmental factors may also impact the assessed parameters. Overall, my studies show the range of applications of SS to effectively answer universal questions from trophic interactions and the importance of habitat characteristics in a community to a methodological comparison of fish sampling methods. The high variability of SS behaviour and the influence of environmental conditions further underlines the importance to include data on a large temporal scale. Community information, such as taxonomic identity and consideration of species-specific feeding and habitats preferences, for example, are still beneficial in some cases to answer ecologically questions extensively

On the relation of quark confinement and chiral symmetry breaking

We study the phase diagram of QCD with the help of order parameters for chiral symmetry breaking and quark confinement. We also introduce a new order parameter for the confinement phase transition, which is related to the quark density. It is easily accessible by different theoretical approaches, such as functional approaches or lattice simulations. Its relation to the Polyakov loop expectation value is discussed and the QCD phase diagram is analysed. Our results suggest a close relation between the chiral and the confinement phase transition.Comment: 5 pages, 3 figure

Improved Polyakov-loop potential for effective models from functional calculations

We investigate the quark backreaction on the Polyakov loop and its impact on the thermodynamics of quantum chromodynamics. The dynamics of the gluons generating the Polyakov-loop potential is altered by the presence of dynamical quarks. However, this backreaction of the quarks has not yet been taken into account in Polyakov-loop extended model studies. In the present work, we show within a 2+1 flavour Polyakov-quark-meson model that a quark-improved Polyakov-loop potential leads to a smoother transition between the low-temperature hadronic phase and the high-temperature quark-gluon plasma phase. In particular, we discuss the dependence of our results on the remaining uncertainties that are the critical temperature and the parametrisation of the Polyakov-loop potential as well as the mass of the sigma-meson.Comment: 19 pages, 25 figures; version published in Phys. Rev.

Transverse flow of nuclear matter in collisions of heavy nuclei at intermediate energies

The Quantum Molecular Dynamics Model (IQMD) is used to investigate the origin of the collective transverse velocity observed in heavy ion experiments. We find that there are three contributions to this effect: initial-final state correlations, potential interactions and collisions. For a given nuclear equation of state (eos) the increase of the transverse velocity with increasing beam energy is caused by the potential part. For a given beam energy the collective transverse velocity is independent of the nuclear eos but the relative contributions of potential and collisions differ. In view of the importance of the potential interactions between the nucleons it is not evident that the similarity of the radial velocities measured for fragments at beam energies below 1 AGeV and that for mesons at beam energies above 2 AGeV is more than accidental.Comment: 5 pages, 5 figures, revtex, OASIS ref PLB1700

Fiscal Investment Climate and the Cost of Capital in Germany

Measured in terms of the cost of capital, the investment climate in Germany currently ranks 24th Key Messages out of the 28 EU member states. However, this represents an improvement over the year 2000, when Germany ranked 27th. In fact, among the EU-28, Germany has seen the most significant decline in the cost of capital between 2000 and 2014, from 7.7% to 6.5%. This decline is mainly attributable to considerable reductions in the country’s corporate tax rate. The comprehensive corporate tax reforms enacted in 2001 and 2008 thus appear to have succeeded in improving the investment climate in Germany. Nevertheless, in comparison to most other EU member states, the cost of capital in Germany is still quite high. In order to further improve the investment climate in Germany, the (temporary) re-introduction of reduced-balance tax depreciation for movable fixed assets is currently being discussed. However, our analysis indicates that this would only slightly decrease the cost of capital from 6.5% to 6.3%. When we additionally account for the personal taxation of individual investors, a different picture emerges: The overall cost of capital in Germany currently amounts to 6.0%, and could be reduced considerably by taxing dividends and capital gains at lower rates than interest income

Modellbasierte Design-Space-Exploration nicht-funktionaler Auslegungskriterien des Fahrzeugenergiebordnetzes

Diese Arbeit analysiert mit Hilfe einer modellbasierten Design Space Exploration (DSE) gleichzeitig den Einfluss mehrerer Freiheiten des Energieversorgungsnetzes auf die Bewertungskriterien Energieverbrauch und Gesamtbetriebskosten (Total Cost of Ownership, TCO) unter Berücksichtigung der Spannungsstabilität als Randbedingung. Statt nur einzelne Aspekte des Energieversorgungsnetzes zu optimieren wird so ein Systemoptimum gesucht. Die betrachteten Freiheiten sind die Topologie des Energieversorgungsnetzes sowie die Anzahl, Kapazität und Position der integrierten Batterien. Sowohl die Auswahl der Freiheiten im Entwurf als auch die Erweiterung der Bewertungskriterien Gewicht und Stückkosten hin zu Energieverbrauch und TCO beruhen dabei auf den Ergebnissen eines Experteninterviews. Außerdem wird eine Änderung der Informations- und Kommunikationstechnik im Fahrzeug hin zu einer Plattform mit systemweiter Trennung von Funktion und Hardware, um der wachsenden Vernetzung, Datenmenge und neuen Anforderungen wie Erweiterbarkeit gerecht zu werden, als Randbedingung der Entwürfe vorausgesetzt. Der Vorteil der generischen DSE ist die Möglichkeit, die Modelle flexibel anpassen zu können, um neben den genannten Freiheiten auch verschiedene Fahrzeugmodelle, Antriebsvarianten, Verbraucherkonfigurationen, Umgebungsbedingungen oder Randbedingungen des Entwurfs zu untersuchen. Die Ergebnisse der DSE demonstrieren, dass eine Umgestaltung der etablierten Stern- hin zu einer Bustopologie mit zwei Batterien trotz der Zunahme des Gewichts und der Stückkosten den Energieverbrauch und damit die Betriebskosten eines Verbrennungsfahrzeugs deutlich senkt und deshalb die TCO betrachtet wirtschaftlich sinnvoll ist. Zusätzlich dazu erhöht die damit erreichte fail-operational Auslegung mittels zweier unabhängiger Energiequellen die Sicherheit des Energieversorgungsnetzes. Aufgrund der fehlenden Emissionsstrafen und Steuern sowie der höheren Effizienz des Antriebsstranges haben die Materialkosten im Elektrofahrzeug einen höheren Einfluss auf die TCO, weshalb eine Umgestaltung nur für hohe Laufleistungen oder eine durchweg hohe Last der Nebenverbraucher in einer deutlichen Kostenreduktion resultiert

Effects of Activated Bt Transgene Products (Cry1Ab, Cry3Bb) on Immature Stages of the Ladybird Adalia bipunctata in Laboratory Ecotoxicity Testing

Insect-active Bacillus thuringiensis (Bt) proteins are expressed by several transgenic crop plants to control certain pests, but nontarget organisms such as ladybirds also can be exposed to these proteins in the field. We developed an improved ecotoxicity testing protocol and conducted feeding trials in a laboratory setting to test for possible adverse effects of different concentrations of microbially produced trypsin-activated Cry1Ab and Cry3Bb toxins on the coccinellid Adalia bipunctata. Larval/pupal mortality, development time, and overall body mass accumulation were recorded. Even at the lowest concentration (5 μg/ml), A. bipunctata larvae fed with the lepidopteran-active Cry1Ab toxin exhibited significantly higher mortality than the control group. In experiments with the coleopteran-active Cry3Bb, only a concentration of 25 μg/ml resulted in a marginally significantly higher mortality compared to the control. Both experiments revealed a slight decline in mortality at the highest concentration of 50 μg/ml, though this was statistically significant only in the Cry1Ab treatment. No differences were detected for development time and body mass of newly emerged adults. Dilutions of the expression vector pBD10—used as a control to exclude effects of the toxin production method—at concentrations between 10 and 100 μg/ml revealed no significant effects on either of the studied parameters. This suggests that the increased mortality of larvae in the toxin feeding trials was caused directly by the activated Bt toxins and raises questions regarding their commonly postulated specificity and their mode of action in A. bipunctata. Implications of the reported results for ladybird populations and their biological pest control functions in transgenic crop ecosystems are discusse

Hadron production in central nucleus-nucleus collisions at chemical freeze-out

We analyze the experimental hadron yield ratios for central nucleus-nucleus collisions in terms of thermal model calculations over a broad energy range, $\sqrt{s_{NN}}$=2.7-200 GeV. The fits of the experimental data with the model calculations provide the thermal parameters, temperature and baryo-chemical potential at chemical freeze-out. We compare our results with the values obtained in other studies and also investigate more technical aspects such as a potential bias in the fits when fitting particle ratios or yields. Using parametrizations of the temperature and baryonic chemical potential as a function of energy, we compare the model calculations with data for a large variety of hadron yield ratios. We provide quantitative predictions for experiments at LHC energy, as well as for the low RHIC energy of 62.4 GeV. The relation of the determined parameters with the QCD phase boundary is discussed.Comment: 38 pages, 25 figures - accepted to Nucl. Phys. A; v2: update fits of 4pi data,update on NA44 data at top SPS, fits at top RHIC without resonances; v3: include fits of absolute yields (appendix). Model calculations and data files available at http://www-linux.gsi.de/~andronic/physics/s/s.htm

Elemental Abundances of Nearby Galaxies through High Signal-to-Noise XMM-Newton Observations of ULXs

(abridged) In this paper, we examined XMM Newton EPIC spectra of 14 ultra-luminous X-ray sources (ULXs)in addition to the XMM RGS spectra of two sources (Holmberg II X-1 and Holmberg IX X-1). We determined oxygen and iron abundances of the host galaxy's interstellar medium (ISM) using K-shell (O) and L-shell (Fe) X-ray photo-ionization edges towards these ULXs. We found that the oxygen abundances closely matched recent solar abundances for all of our sources, implying that ULXs live in similar local environments despite the wide range of galaxy host properties. Also, we compare the X-ray hydrogen column densities (n_H) for 8 ULX sources with column densities obtained from radio H I observations. The X-ray model n_H values are in good agreement with the H I n_H values, implying that the hydrogen absorption towards the ULXs is not local to the source (with the exception of the source M81 XMM1). In order to obtain the column density and abundance values, we fit the X-ray spectra of the ULXs with a combined power law and one of several accretion disk models. We tested the abundances obtained from the XSPEC models bbody, diskbb, grad, and diskpn along with a power law, finding that the abundances were independent of the thermal model used. We comment on the physical implications of these different model fits. We also note that very deep observations allow a breaking of the degeneracy noted by Stobbart et al. (2006) favoring a high mass solution for the absorbed grad + power law model.Comment: 18 pages, accepted to Ap

Mentoring, Training, and Scholarly Productivity Experiences of Cancer-Related Health Disparities Research Trainees: Do Outcomes Differ for Underrepresented Scientists?

The study aims to explore variation in scholarly productivity outcomes by underrepresented status among a diverse sample of researchers in a community-engaged training program. We identified 141 trainees from a web-based survey of researchers in the National Cancer Institute-funded, Community Networks Program Centers (CNPCs) (2011-2016). We conducted a series of multiple logistic regression models to estimate the effect of National Institutes of Health (NIH)-defined underrepresented status on four, self-reported, scholarly productivity outcomes in the previous 5 years: number of publications (first-authored and total) and funded grants (NIH and any agency). Sixty-five percent (n = 92) indicated NIH underrepresented status. In final adjusted models, non-NIH underrepresented (vs. underrepresented) trainees reported an increased odds of having more than the median number of total publications (> 9) (OR = 3.14, 95% CI 1.21-8.65) and any grant funding (OR = 5.10, 95% CI 1.77-14.65). Reporting ≥ 1 mentors (vs. none) was also positively associated (p < 0.05) with these outcomes. The CNPC underrepresented trainees had similar success in first-authored publications and NIH funding as non-underrepresented trainees, but not total publications and grants. Examining trainees' mentoring experiences over time in relation to scholarly productivity outcomes is needed