Fluorescence imaging microscopy studies on single molecule diffusion and photophysical dynamics

Within the last years, e.g. by investigating the fluorescence of single molecules in biological cells, remarkable progress has been made in cell biology extending conventional ensemble techniques concerning temporal / spatial resolution and the detection of particle subpopulations [82]. In addition to employing single fluorophores as "molecular beacons" to determine the position of biomolecules, single molecule fluorescence studies allow to access the photophysical dynamics of genetically encoded fluorescent proteins itself. However, in order to gain statistically consistent results, e.g. on the mobility behavior or the photophysical properties, the fluorescence image sequences have to be analyzed in a preferentially automated and calibrated (non-biased) way. In this thesis, a single molecule fluorescence optical setup was developed and calibrated and experimental biological in-vitro systems were adapted to the needs of single molecule imaging. Based on the fluorescence image sequences obtained, an automated analysis algorithm was developed, characterized and its limits for reliable quantitative data analysis were determined. For lipid marker molecules diffusing in an artifcial lipid membrane, the optimum way of the single molecule trajectory analysis of the image sequences was explored. Furthermore, effects of all relevant artifacts (specifically low signal-to-noise ratio, finite acquisition time and high spot density, in combination with photobleaching) on the recovered diffusion coefficients were carefully studied. The performance of the method was demonstrated in two series of experiments. In one series, the diffusion of a fluorescent lipid probe in artificial lipid bilayer membranes of giant unilamellar vesicles was investigated. In another series of experiments, the photoconversion and photobleaching behavior of the fluorescent protein Kaede-GFP was characterized and protein subpopulations were identified

Financial Risk Aversion and Household Asset Diversification

This paper explores the relationship between risk attitude and asset diversification in household portfolios. We first examine the impact of manifested risk aversion on the total number of distinct assets held in a portfolio (naive diversification). The second part of the paper focuses on a more sophisticated strategy of diversification and asks whether financial theory is compatible with observed diversification patterns. Based on the German Socioeconomic Panel which provides unique measures of individual propensity for taking risk, the results of the regression analysis show that, along with some socioeconomic characteristics, the propensity for taking investment risk is an important predictor of a household's diversification strategy. However, some of our findings are strongly at odds with what the concept of mean-variance utility suggests.household finances, diversification, financial portfolio

Private Households Display Strong Aversion to Investment Risk

The broadest possible diversification of investments is considered an important strategy for minimizing investment risk. Most households in Germany do distribute their financial assets over several types of investment. However, investment behavior is only partially consistent with the overall readiness for risk-taking reported by heads of households. This is demonstrated by a current empirical study based on data from the Socio-Economic Panel Study (SOEP). The probability of diversification does tend to rise according to the degree of risk aversion, yet not when it comes to a "fully diversified investment basket." With a higher fear of risk, the tendency to fill a portfolio with every kind of investment falls. Clearly, households make decisions in keeping with a principle propagated by Keynes: security and liquidity come first. The readiness to invest in riskier assets rises with the number of secure investments already in place in the portfolio.Household finances, Diversification, Financial portfolio

Financial Risk Aversion and Household Asset Diversification

This paper explores the relationship between risk attitude and asset diversification in household portfolios. We first examine the impact of manifested risk aversion on the total number of distinct assets held in a portfolio (naive diversification). The second part of the paper focuses on a more sophisticated strategy of diversification and asks whether financial theory is compatible with observed diversification patterns. Based on the German Socioeconomic Panel which provides unique measures of individual propensity for taking risk, the results of the regression analysis show that, along with some socioeconomic characteristics, the propensity for taking investment risk is an important predictor of a household's diversification strategy. However, some of our findings are strongly at odds with what the concept of mean-variance utility suggests.Household finances, diversification, financial portfolio

Individual Risk Attitudes and the Composition of Financial Portfolios: Evidence from German Household Portfolios

This paper explores the relationship between the self-declared risk aversion of private investors and their propensity to hold incomplete portfolios of financial assets. The analysis is based on household survey data from the German Socioeconomic Panel (SOEP) that provides a reliable measure of individual attitudes toward financial risk. Our findings suggest that more risk averse households tend to hold incomplete portfolios consisting mainly of a few risk-free assets. We also find that the propensity to acquire additional assets is highly dependent on whether liquidity and safety needs are met.This is the postprint of an article published in the Quarterly Review of Economics and Finance 52 (2012), 1, p. 1-14, available online at: http://dx.doi.org/10.1016/j.qref.2011.10.00

Niedriger Leitzins: Eine Chance in der Euro-Schuldenkrise

Seit vier Jahren kämpfen die Staaten des Euroraums gegen die Hinterlassenschaften der schweren Finanz- und Wirtschaftskrise an. Aber noch immer steigen die Schuldenquoten. Für die Krisenstaaten des Euroraums wurde zwar mit Rettungspaketen und Niedrigzinsen Zeit erkauft. Aber solange sich die anderen Einflussgrößen nicht positiver entwickeln, bleibt es ungewiss, ob die momentane Beruhigung der Euro-Verschuldungskrise nachhaltig ist. Zweifelsfrei stellt in dieser Situation die Niedrigzinspolitik der EZB eine Erleichterung dar. Zum einen ist die Zinslast für die meisten Eurostaaten in den letzten Jahren zurückgegangen. Dieser Effekt dämpft tendenziell das Wachstum der Schuldenquote. Zum anderen stärken die niedrigen Zinsen die Wirtschaft. Dies wiederum erhöht die Steuereinnahmen des Staates und verbessert den Primärsaldo. Niedrigzinsen haben auch bei der Rückführung der Schuldenquote in den USA eine große Rolle gespielt. Zwischen 1946 und 1953 konnten die USA ihren Schuldenstand ohne Schuldenschnitt fast halbieren. Negative Primärsalden, niedrige Wachstumsraten und die niedrige Inflationsrate lassen dies in der Euro-Schuldenkrise jedoch nicht zu. Deshalb scheinen Niedrigzinsen im Moment der einzige Hebel zu sein, mit dem die Schulden tragfähiger gemacht werden können. Nun kommt es darauf an, dass die Eurostaaten die Chance auch ergreifen.Member states of the euro area have been struggling with the legacies of the severe financial and economic crisis for four years now. But debt ratios are still rising. Negative primary balances, low growth, and low inflation do not allow for a recovery similar to the one in the US after the Second World War. Between 1946 and 1953, the US was able to almost halve its debt with no haircuts. The crisis countries of the euro area were able to buy time with bailout packages and low interest rates. But as long as the other influencing factors are not developing more positively, it remains uncertain whether the current stabilization of the euro debt crisis is sustainable. The ECB's low interest rate policy undoubtedly offers some relief in this situation. First, the interest burden for most countries in the euro area has declined in recent years. This effect has tended to stifle increases in the debt ratio. Second, low interest rates strengthen the economy. In turn, this increases government tax revenue and improves the primary balance. Low interest rates have also played an important role in driving down the debt ratio in the US. At the moment they appear to be the only lever in the euro area with which to make euro area countries' debt more sustainable. What matters now is that they seize this opportunity

Private Households Display Strong Aversion to Investment Risk

The broadest possible diversification of investments is considered an important strategy for minimizing investment risk. Most households in Germany do distribute their financial assets over several types of investment. However, investment behavior is only partially consistent with the overall readiness for risk-taking reported by heads of households. This is demonstrated by a current empirical study based on data from the Socio-Economic Panel Study (SOEP). The probability of diversification does tend to rise according to the degree of risk aversion, yet not when it comes to a "fully diversified investment basket." With a higher fear of risk, the tendency to fill a portfolio with every kind of investment falls. Clearly, households make decisions in keeping with a principle propagated by Keynes: security and liquidity come first. The readiness to invest in riskier assets rises with the number of secure investments already in place in the portfolio

Low base interest rates: An opportunity in the euro debt crisis

Member states of the euro area have been struggling with the legacies of the severe financial and economic crisis for four years now. But debt ratios are still rising. Negative primary balances, low growth, and low inflation do not allow for a recovery similar to the one in the US after the Second World War. Between 1946 and 1953, the US was able to almost halve its debt with no haircuts. The crisis countries of the euro area were able to buy time with bailout packages and low interest rates. But as long as the other influencing factors are not developing more positively, it remains uncertain whether the current stabilization of the euro debt crisis is sustainable. The ECB's low interest rate policy undoubtedly offers some relief in this situation. First, the interest burden for most countries in the euro area has declined in recent years. This effect has tended to stifle increases in the debt ratio. Second, low interest rates strengthen the economy. In turn, this increases government tax revenue and improves the primary balance. Low interest rates have also played an important role in driving down the debt ratio in the US. At the moment they appear to be the only lever in the euro area with which to make euro area countries' debt more sustainable. What matters now is that they seize this opportunity

Numerical Methods for the QCD Overlap Operator:III. Nested Iterations

The numerical and computational aspects of chiral fermions in lattice quantum chromodynamics are extremely demanding. In the overlap framework, the computation of the fermion propagator leads to a nested iteration where the matrix vector multiplications in each step of an outer iteration have to be accomplished by an inner iteration; the latter approximates the product of the sign function of the hermitian Wilson fermion matrix with a vector. In this paper we investigate aspects of this nested paradigm. We examine several Krylov subspace methods to be used as an outer iteration for both propagator computations and the Hybrid Monte-Carlo scheme. We establish criteria on the accuracy of the inner iteration which allow to preserve an a priori given precision for the overall computation. It will turn out that the accuracy of the sign function can be relaxed as the outer iteration proceeds. Furthermore, we consider preconditioning strategies, where the preconditioner is built upon an inaccurate approximation to the sign function. Relaxation combined with preconditioning allows for considerable savings in computational efforts up to a factor of 4 as our numerical experiments illustrate. We also discuss the possibility of projecting the squared overlap operator into one chiral sector.Comment: 33 Pages; citations adde

Auswirkungen differenzierter ökologischer Bewirtschaftung von Ansaat- und Dauergrünland auf Futterangebot, Fressverhalten sowie Weideleistung und Schlachtreife von Ochsen und Färsen

Von 2004 bis 2006 wurde durch die Universität Halle-Wittenberg am ZTT Iden der LLFG Sachsen-Anhalt ein Versuch zur Weidemast von Rindern auf 26 ha extensiv ökologisch bewirtschaftetem Dauergrünland in zwei Düngungsstufen (0 und 70 kg N/ha) durchgeführt. Die jährlich zwei Versuchsherden bestanden aus je circa 30 Absetzern (Ochsen und Färsen) üblicher Gebrauchskreuzungen (2004; tragende HF-Färsen). Der Tierbesatz lag bei max. 1 - 1,4 GV/ha. Die Versuchsflächen (vier Koppeln/Herde) lagen auf drei, bezüglich Bodenart, Feuchtigkeit und Pflanzenbestand, unterschiedlichen Standorten. Die Artenzahl war vom vorhandenen Pflanzenbestand zu Versuchsbeginn abhängig. Ein Flächentyp (Ansaatgrünland, leichter Boden) zeigte sich äußerst problematisch hinsichtlich Pflanzenbestand und Ertrag. Im überständigen Aufwuchs wurden vorwiegend Blattmasse enthaltende Bestandesschichten bevorzugt und Stängel und Blüten verschmäht. Die Energiekonzentrationen und Verdaulichkeiten des aufgenommenen Futters lagen deutlich über denen im Mittel des Futterangebotes, wobei der Unterschied besonders gegen Ende einer Teilflächenbeweidung deutlich wurde. Die Tiere waren in der Lage, durch die Futterselektion sehr lange ein hohes Qualitätsniveau zu halten und somit rückläufige Qualitätsentwicklungen zu einem guten Teil auszugleichen. Die Alkanmethode erwies sich mit der Unterscheidung ledig nach Artengruppen und für Untersuchungen von teils überständigen Pflanzenaufwüchsen zur Ermittlung einer artengruppenspezifischen Futterselektion als ungeeignet. Bezüglich des Tierverhaltens konnten zwischen beiden Herden signifikante, geringfügige Unterschiede festgestellt werden. Die mittleren Lebendmassezunahmen lagen bei über 800g pro Tag und waren hinsichtlich der Düngungsvarianten nicht signifikant unterschiedlich. Die Schlachtkörper sowohl der Ochsen wurden mit U und R (Fleischigkeit) eingestuft. Bei über 80 % der Tiere wurde die angestrebte Fettklasse 3 erzielt