Compact femtosecond electron diffractometer with 100 keV electron bunches approaching the single-electron pulse duration limit

We present the design and implementation of a highly compact femtosecond electron diffractometer working at electron energies up to 100 keV. We use a multi-body particle tracing code to simulate electron bunch propagation through the setup and to calculate pulse durations at the sample position. Our simulations show that electron bunches containing few thousands of electrons per bunch are only weakly broadened by space-charge effects and their pulse duration is thus close to the one of a single-electron wavepacket. With our compact setup we can create electron bunches containing up to 5000 electrons with a pulse duration below 100 femtoseconds on the sample. We use the diffractometer to track the energy transfer from photoexcited electrons to the lattice in a thin film of titanium. This process takes place on the timescale of few-hundred femtoseconds and a fully equilibrated state is reached within one picosecond.Comment: 5 pages, 3 figure

Produktivitätseffekte betrieblicher Zusatzleistungen

In der vorliegenden Arbeit werden die Produktivitätswirkungen von fünf unterschiedlichen Formen betrieblicher Zusatzleistungen analysiert. Als Datensatz wird das IAB-Betriebspanel aus dem Jahr 2000 verwendet. Im Ergebnis bestätigt diese Arbeit die Anreiztheorien, welche einen positiven Einfluss betrieblicher Zusatzleistungen auf die Produktivität eines Betriebes unterstellen. Werden die Leistungsformen in ihrer Summe analysiert, so kann ein positiver Zusammenhang zwischen Existenz betrieblicher Zusatzleistungen und Produktivität nachgewiesen werden. Allerdings gilt dies bei separater Betrachtung nicht für jede Leistungsform. Es zeigt sich, dass die verwendete Schätzmethodik keinen Einfluss auf dieses Ergebnis hat, wenngleich deutlich wird, dass gewisse Schätzprobleme bestehen, die bei einer empirischen Untersuchung nicht vernachlässigt werden dürfen.This paper investigates the productivity effects of five different forms of employee benefits. The data being used is the IAB-Establishment Panel from the year 2000. As a result, the study verifies incentive theories according to which fringe benefits affect a firm's productivity in a positive manner. Analyzing the sum of all fringe benefits, a positive relationship between the existence of employee benefits and firm-level productivity is found. However, this is not the case for each single form of employee benefits. Even though the used methodology of estimation has no impact on the result itself, it becomes apparent that problems of estimation exist, which should be taken into account

Produktivitätseffekte betrieblicher Zusatzleistungen

This paper analyses the productivity effects of five different types of employee benefits. The IAB establishment panel for the year 2000 is used as the data set. The results of the study largely confirm the incentive theories which assume that fringe benefits have a positive impact on a firm's productivity. It is shown that the estimation methodology used influences this result. If existing selection biases are corrected, then the difference in productivity between firms with and without fringe benefits is smaller than in the OLS estimate. In addition to this, in some cases the difference in productivity is no longer significant after the selection adjustment. Furthermore differences are found between individual types of employee benefits

Modulation of cell-matrix adhesions to affect mechanotransduction

In cultured fibroblasts three types of cell-matrix adhesion with specific cellular localization and protein composition can be distinguished: focal complexes, focal adhesions and fibrillar adhesions. The formation of fibrillar adhesions is known to be required for fibronectin fibrillogenesis. However, little is known about specific signaling from these adhesion sites. Previous experiments showed that ILK (integrin-linked kinase) knockout fibroblasts are defective in RhoA-dependent responses to cyclic strain. In addition these cells did not form fibrillar adhesions and did not assemble fibronectin. We therefore speculated that pericellular fibronectin and the fibrillar adhesions are important to activate the RhoA/ROCK pathway by mechanical stress. To test this hypothesis, we generated fibronectin knockdown fibroblasts and analyzed their ability to activate specific RhoA dependent responses to cyclic strain in the absence and presence of exogenous fibronectin. Normal fibroblasts seeded on vitronectin in fibronectin-depleted medium deposited their own fibronectin matrix and in response to cyclic strain, activated RhoA, formed stress fibers, translocated MAL (megakaryocytic leukemia protein) to the nucleus, and induced tenascin-C. By contrast, these responses were suppressed in fibronectin knockdown or knockout cells grown under identical conditions. Interestingly, on vitronectin substrate, fibronectin-deficient cells lacked integrin á5â1-positive fibrillar adhesions. However, when fibronectin-deficient fibroblasts were plated on exogenous fibronectin, their defects in adhesions and mechanotransduction were restored. Studies with fibronectin fragments indicated that both, the RGD-synergy site and the adjacent heparin-binding region were required for full activity in mechanotransduction, but not its ability to self-assemble. In contrast to RhoA-mediated responses, activation of Erk1/2 and PKB/Akt by cyclic strain was not affected in fibronectin-deficient cells. Our results indicate that activation of the RhoA/ROCK pathway by mechanical stress originates from fibrillar adhesions connected to fibronectin in the extracellular matrix. In a second project we tried to get more insight in signaling by focal complexes. These cellmatrix adhesions are the first to be formed by adhering fibroblasts. They are clearly smaller than more mature focal adhesions and are uniquely found at the cell border of lamellipodia. Using patterns with square-shaped, RGD-coupled gold dots of a limited size, we attempted to inhibit maturation of focal complexes into focal adhesions. Indeed, on RGD-coated goldsquares smaller than 1ìm, cells uniquely formed focal complexes indicated by low recruitment of á5 integrin. Cells formed excessive amounts of lamellipodia and assembled actin only into a fine meshwork. However, on squares equal or larger than 1 ìm cells exhibited focal adhesions, spread normally and assembled actin into thick fibers. Our results show that at the level of focal complexes cell adhesion maturation can be inhibited by restricting size. In addition, according to the lamellipodia which are seen with cells on patterns smaller than 1 ìm, let suggest increased Rac signaling deriving from these focal complexes

Produktivitätseffekte betrieblicher Zusatzleistungen

In der vorliegenden Arbeit werden die Produktivitätswirkungen von fünf unterschiedlichen Formen betrieblicher Zusatzleistungen analysiert. Als Datensatz wird das IAB-Betriebspanel aus dem Jahr 2000 verwendet. Im Ergebnis bestätigt diese Arbeit die Anreiztheorien, welche einen positiven Einfluss betrieblicher Zusatzleistungen auf die Produktivität eines Betriebes unterstellen. Werden die Leistungsformen in ihrer Summe analysiert, so kann ein positiver Zusammenhang zwischen Existenz betrieblicher Zusatzleistungen und Produktivität nachgewiesen werden. Allerdings gilt dies bei separater Betrachtung nicht für jede Leistungsform. Es zeigt sich, dass die verwendete Schätzmethodik keinen Einfluss auf dieses Ergebnis hat, wenngleich deutlich wird, dass gewisse Schätzprobleme bestehen, die bei einer empirischen Untersuchung nicht vernachlässigt werden dürfen. -- This paper investigates the productivity effects of five different forms of employee benefits. The data being used is the IAB-Establishment Panel from the year 2000. As a result, the study verifies incentive theories according to which fringe benefits affect a firm?s productivity in a positive manner. Analyzing the sum of all fringe benefits, a positive relationship between the existence of employee benefits and firm-level productivity is found. However, this is not the case for each single form of employee benefits. Even though the used methodology of estimation has no impact on the result itself, it becomes apparent that problems of estimation exist, which should be taken into account.betriebliche Zusatzleistungen,Produktivität

Determinanten betrieblicher Zusatzleistungen

Die genauen Motive, warum Betriebe neben dem Lohn zusätzliche Leistungen gewähren, sind bis heute nicht geklärt. Auf der Basis des IAB-Betriebspanels aus dem Jahr 2000 untersucht die vorliegende Arbeit die existierenden Erklärungsansätze auf ihre empirische Evidenz. Dabei wird eine Vielzahl unterschiedlicher Leistungsformen sowohl einzeln als auch in ihrer Summe analysiert. Die Schätzergebnisse machen deutlich, dass sowohl Verhandlungs- als auch Anreiztheorien eine wichtige Rolle bei der Gewährung zusätzlicher betrieblicher Leistungen spielen. Die reine Substitution zwischen Lohn und zusätzlichen Leistungen findet keine Bestätigung. Betriebliche Zusatzleistungen scheinen auch nicht gewährt zu werden, um die Wettbewerbsposition des Unternehmens zu verbessern. -- The precise motives for firms granting fringe benefits are still not resolved. This paper investigates existing theories empirically using the IABEstablishment Panel data for the year 2000. Several different forms of fringe benefits are analyzed both separately and together. The estimation results show that bargaining theories as well as incentive theories play an important role in explaining the existence of fringe benefits. There is no evidence for the substitution of wages by fringe benefits. Likewise, employee benefits do not seem to be granted to enhance a firm?s competitive position.betriebliche Zusatzleistungen,Anreiztheorie,Verhandlungsansatz,Marktansatz,Wettbewerbsansatz

Produktivitätseffekte betrieblicher Zusatzleistungen (Productivity effects of employee benefits)

"This paper analyses the productivity effects of five different types of employee benefits. The IAB establishment panel for the year 2000 is used as the data set. The results of the study largely confirm the incentive theories which assume that fringe benefits have a positive impact on a firm's productivity. It is shown that the estimation methodology used influences this result. If existing selection biases are corrected, then the difference in productivity between firms with and without fringe benefits is smaller than in the OLS estimate. In addition to this, in some cases the difference in productivity is no longer significant after the selection adjustment. Furthermore differences are found between individual types of employee benefits." (Author's abstract, IAB-Doku) ((en))IAB-Betriebspanel, Arbeitsanreiz, Produktivitätseffekte, Gewinnbeteiligung, Weihnachtsgeld, Urlaubsgeld, Sonderzuwendung, Kapitalbeteiligung, Prämienlohn, Anreizsystem, Produktionsfunktion, betriebliche Alterssicherung