Are the self-employed really jacks-of-all-trades? Testing the assumptions and implications of Lazear's theory of entrepreneurship with German data

Using a large representative German data set and various concepts of self-employment, this paper tests the 'jack-of-all-trades' view of entrepreneurship by Lazear (AER 2004). Consistent with its theoretical assumptions we find that self-employed individuals perform more tasks and that their work requires more skills than that of paid employees. In contrast to Lazear's assumptions, however, self-employed individuals do not just need more basic but also more expert skills than employees. Our results also provide only very limited support for the idea that human capital investment patterns differ between those who become self-employed and those ending up in paid employment. -- Unter Verwendung eines großen, repräsentativen Datensatzes für Deutschland und verschiedener Abgrenzungen der Selbständigkeit überprüft diese Arbeit die 'jack-of-all-trades'-Sicht des Unternehmertums von Lazear (AER 2004). In Übereinstimmung mit ihren theoretischen Annahmen finden wir, dass Selbständige mehr verschiedene Tätigkeiten ausüben und Kenntnisse aus mehr verschiedenen Gebieten benötigen als nicht-selbständige Arbeitnehmer. Im Gegensatz zu Lazear's Annahmen benötigen Selbständige allerdings nicht nur mehr Grundkenntnisse sondern auch mehr Fachkenntnisse als Nicht-Selbständige. Unsere Ergebnisse liefern zudem nur wenig Unterstützung für die Behauptung, dass sich die Muster der Humankapitalaneignung zwischen Selbstständigen und abhängig beschäftigten Arbeitnehmern sichtbar unterscheiden.entrepreneurship,self-employed,Germany

Are the self-employed really jacks-of-all-trades? Testing the assumptions and implications of Lazear's theory of entrepreneurship with German data

Using a large representative German data set and various concepts of self-employment, this paper tests the jack-of-all-trades view of entrepreneurship by Lazear (AER 2004). Consistent with its theoretical assumptions we find that self-employed individuals perform more tasks and that their work requires more skills than that of paid employees. In contrast to Lazear's assumptions, however, self-employed individuals do not just need more basic but also more expert skills than employees. Our results also provide only very limited support for the idea that human capital investment patterns differ between those who become self-employed and those ending up in paid employment. -- Unter Verwendung eines großen, repräsentativen Datensatzes für Deutschland und verschiedener Abgrenzungen der Selbständigkeit überprüft diese Arbeit die jack-of-all-trades-Sicht des Unternehmertums von Lazear (AER 2004). In Übereinstimmung mit ihren theoretischen Annahmen finden wir, dass Selbständige mehr verschiedene Tätigkeiten ausüben und Kenntnisse aus mehr verschiedenen Gebieten benötigen als nicht-selbständige Arbeitnehmer. Im Gegensatz zu Lazear's Annahmen benötigen Selbständige allerdings nicht nur mehr Grundkenntnisse sondern auch mehr Fachkenntnisse als Nicht-Selbständige. Unsere Ergebnisse liefern zudem nur wenig Unterstützung für die Behauptung, dass sich die Muster der Humankapitalaneignung zwischen Selbstständigen und abhängig beschäftigten Arbeitnehmern sichtbar unterscheiden.entrepreneurship,self-employed,Germany

Comment des objets changent de procenance.

Sin resume

Self assembled materials for solar cell application

In der vorliegenden Arbeit wurden Materialien und Aufbauten für Hybrid Solarzellen entwickelt und erforscht. rnDer Vergleich zweier bekannter Lochleitermaterialien für Solarzellen in einfachen Blend-Systemen brachte sowohl Einsicht zur unterschiedlichen Eignung der Materialien für optoelektronische Bauelemente als auch neue Erkenntnisse in Bereichen der Langzeitstabilität und Luftempfindlichkeit beider Materialien.rnWeiterhin wurde eine Methode entwickelt, um Hybrid Solarzelle auf möglichst unkomplizierte Weise aus kostengünstigen Materialien darzustellen. Die „Eintopf“-Synthese ermöglicht die unkomplizierte Darstellung eines funktionalen Hybridmaterials für die optoelektronische Anwendung. Mithilfe eines neu entwickelten amphiphilen Blockcopolymers, das als funktionelles Templat eingesetzt wurde, konnten mit einem TiO2-Precursor in einem Sol-Gel Ansatz verschiedene selbstorganisierte Morphologien des Hybridmaterials erhalten werden. Verschiedene Morphologien wurden auf ihre Eignung in Hybrid Solarzellen untersucht. Ob und warum die Morphologie des Hybridsystems die Effizienz der Solarzelle beeinflusst, konnte verdeutlicht werden. Mit der Weiterentwicklung der „Eintopf“-Synthese, durch den Austausch des TiO2-Precursors, konnte die Solarzelleneffizienz von 0.15 auf 0.4 % gesteigert werden. Weiterhin konnte die Übertragbarkeit des Systems durch den erfolgreichen Austausch des Halbleiters TiO¬2 mit ZnO bewiesen werden.rnNew materials and assemblies were designed and tested for hybrid solar cell application. A simple blending approach was used to prepare hybrid solar cells in a convenient, cheap and fast method. Nano crystalline TiO2 rods were blended with different hole conducting materials and tested in solar cell devices. Comparing their performance in photovoltaic devices, while experimental conditions are kept identical, showed that the choice of solvent and photovoltaic characterization conducted in inert atmosphere is of different influence for different hole conducting materials. External influences as long term stability were investigated.rnIn comparison to the blend approach a new one-pot approach was invented to prepare a nanostructured, multi-functional material with orthogonal properties. It consists of TiO2 as a functional metal oxide and a new amphiphilic block-copolymer poly(ethyleneoxide)-b-poly(triphenylamine) (PEO-b-PTPA) that was synthesized. The hybrid material was obtained within a single step via self assembly in solution. Therefore a method had to be found to obtain crystalline TiO2 under mild conditions. Within the materials synthesis the block-copolymer not only acts as a templating agent but also adds an electronic functionality to the resulting hybrid material. During the synthesis a variety of self assembled morphologies ranging from spheres to wires were created in a controlled fashion. The obtained morphology depends on the weight fraction of the polymer, solvent, TiO2 precursor and acid. Studying films on silicon wafers with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) a ternary phase diagram could be mapped whereas the crystallinity of TiO2 could be proved by high resolution-TEM. Different morphologies of this self assembled hybrid material were tested for solar cell application. Even for devices with layer thicknesses of the active material below 10 nm power conversion efficiencies up to 0.15 % at 1 sun and 1.5 AM were observed. The solar cell efficiency was increased with further development of the one-pot approach by changing the precursor. A polyethyleneglycole modified titanate was used as precursor in combination with the functional block copolymer PEO-b-PTPA. Again self-assembled network morphologies were obtained and tested in solar cell devices. While the formation of percolating networks is of general importance the solar cell performance was found to depend on the morphological design of the hybrid material. With the aid of conductive scanning force microscopy, it was proven to preserve a percolating network despite an increase of the active layer thickness. In combination with a special functionalized Ti-precursor hybrid bulk heterojunction solar cells having a maximum power conversion efficiency of 0.4 % at 1 sun and 1.5 AM were obtained.r

An integrated geological-geophysical approach to subsurface interface reconstruction of muon tomography measurements in high alpine regions

Muon tomography is an imaging technique that emerged in the last decades. The principal concept is similar to X-ray tomography, where one determines the spatial distribution of material densities by means of penetrating photons. It differs from this well-known technology only by the type of particle. Muons are continuously produced in the Earth’s atmosphere when primary cosmic rays (mostly protons) interact with the atmosphere’s molecules. Depending on their energies these muons can penetrate materials up to several hundreds of metres (or even kilometres). Consequently, they have been used for the imaging of larger objects, including large geological objects such as volcanoes, caves and fault systems. This research project aimed at applying this technology to an alpine glacier in Central Switzerland to determine its bedrock geometry, and if possible, to gain information on the bedrock erosion mechanism. To this end, two major experimental studies have been conducted with the aim to reconstruct bedrock geometries of two different glaciers. Given this framework, I present in this thesis my contribution to the project in which I worked for 5 years. Most of the technological know-how of muon tomography still lies within physics institutes who were the key drivers in the development of this method. As the geophysical/geological community is nowadays an important user of this technology, it is important that also non-physicists familiarise themselves with the theory and concepts behind muon tomography. This can be seen as an effective method to bring more geoscientists to utilize this new technology for their own research. The first part of this thesis is designed to tackle this problem with a review article on the principles of muon tomography and a guide to best practice. A second important aspect is the reconstruction of the bedrock topography given muon flux measurements at various locations. Many to-date reconstruction algorithms include supplementary geological information such as density and/or compositional measurements only on the side. A probabilistic framework was successfully set up that allows for such additional data to be included into the inversion. This may be used to better constrain the bedrock geometry. Moreover, this flexible framework allows also for the inclusion of modelling errors in the physical models which may result in a more reliable estimate of the mean and standard deviation of the bedrock position. The third article is concerned with the determination of the effect of rock composition on the muon flux measurements. Researchers in the community use a made-up rock, called “standard-rock” in their calculations. Hitherto, it was unclear in which geological settings this is a valid assumption and in which the induced error becomes too large. Simulations that use this fantasy rock are performed and compared to simulations that use a more realistic rock model. It was found that for felsic rocks the standard-rock approximation is valid over all thickness ranges, while for mafic rocks and limestones this can lead to a serious bias if the rock is thicker than 300m

Multiplex real-time PCR for the detection and differentiation of equid gammaherpesvirus 2 and 5

Equid gammaherpesvirus 2 (EHV-2) and 5 (EHV-5) are widely distributed in the equines. Although their pathogenic potential is not yet fully understood, they appear to play a role in disease patterns like equine multinodular pulmonary fibrosis. In this study, a multiplex real-time PCR (rtPCR) was designed to detect DNA of the glycoprotein H (EHV-2) and E11 gene (EHV-5). Analytical specificity was determined by testing DNA of other herpesviruses by SYBR Green rtPCR and melting curve analysis, as well as Sanger sequencing of positive field samples. Analytical sensitivity was assessed by standard curve generation of serial plasmid dilutions containing the respective target gene. Melting curves and BLAST analysis of the sequences indicated specific detection of the viruses. The lower limit of detection of the singleplex rtPCR was 40 and 29 DNA copies per reaction for EHV-2 and EHV-5, respectively. Comparison of the Ct values of a selection of positive field samples showed only minimal differences between the singleplex and the multiplex assay. The here described multiplex rtPCR protocol allows sensitive and specific detection of EHV-2 and EHV-5. It represents a convenient and rapid tool for future studies to investigate the clinical relevance of EHV-2 and EHV-5 in more detail

The traveling repairman problem

Diese Magisterarbeit gibt einen Überblick über das Traveling Repairman Problem (TRP), das eine Spezialform des Problems des Handlungsreisenden (Traveling Salesman Problem – TSP) darstellt. Beide Modelle werden benutzt, um die Tour eines Handlungsreisenden zu planen, der in einer vorgegebenen Zeitspanne eine bestimmte Anzahl von Kunden besuchen soll. Während das TSP sich darauf konzentriert, die Länge der Tour zu minimieren, versucht das TRP, die Summe der Wartezeiten der Kunden so gering wie möglich zu halten. Der Hauptteil der Arbeit beschäftigt sich mit der Definition und den Varianten des TRP und beschreibt mögliche Modelle und Verfahren, mit deren Hilfe diese zu lösen sind. Dabei werden zuerst die Problemstellungen definiert und dann die mathematischen Formulierungen bzw. die Algorithmen dargestellt. Zu Beginn der Arbeit werden das TSP und das TRP näher definiert und kurz anhand eines Beispiels illustriert (in Kapitel 2). Danach werden das allgemeine TRP und einige Lösungsverfahren dazu näher erläutert (in Kapitel 3). Im Hauptteil werden zuerst einige Variationen des TRP mit einem einzelnen Repairman und Algorithmen zur Lösung dieser Modelle beschrieben (in Kapitel 4). Dann werden das TRP mit mehreren Repairmen sowie einige Spezialformen hierzu erläutert (in Kapitel 5). Zusätzlich werden in dieser Arbeit Anwendungsmöglichkeiten beschrieben, von denen zwei genauer untersucht werden (in Kapitel 6). Schließlich werden noch einige Basisbegriffe und Lösungsmethoden erläutert (in Kapitel 7)

The Regret Elements Scale: Distinguishing the affective and cognitive components of regret

Regret is one of the most common emotions, but researchers generally measure it in an ad-hoc, unvalidated fashion. Three studies outline the construction and validation of the Regret Elements Scale (RES), which distinguishes between an affective component of regret, associated with maladaptive affective outcomes, and a cognitive component of regret, associated with functional preparatory outcomes. The present research demonstrates the RES’s relationship with distress (Study 1), appraisals of emotions (Study 2), and existing measures of regret (Study 3). We further demonstrate the RES’s ability to differentiate regret from other negative emotions (Study 2) and related traits (Study 3). The scale provides both a new theoretical perspective on regret, and a tool for researchers interested in measuring post-decisional regret

Fully automated dried blood spot sample handling and extraction for BoHV-1 antibody testing by ELISA

This study is the first proof of concept of the DBS technology for Bovine alphaherpesvirus 1 (BoHV-1) antibody detection by ELISA after fully automated DBS extraction. DBS were prepared from nine BoHV-1 seropositive plasma samples spiked with erythrocytes. Spots were extracted automatically on a DBS-MS 500 HCT autosampler, as well as manually using a 3.2 mm puncher. DBS were equally prepared from 20 bovine seronegative EDTA-blood samples and extracted automatically. Extracts were tested in a commercial BoHV-1 antibody ELISA and results were compared with those from liquid plasma. Eight seropositive DBS samples were additionally tested in the ELISA after storage for four weeks at different conditions. After automated extraction all DBS samples yielded qualitatively correct results and were in full accordance with those obtained from liquid plasma. Automated extraction using a 6 mm extraction head was more sensitive than a 4 mm head. Stability of DBS was highest at - 20 °C and decreased with increasing temperature. Even after four weeks at 37 °C, most seropositive samples yielded a positive result in the ELISA. The minimal invasiveness, biosafety, and simplicity of DBS collection together with automated extraction represents an interesting, high-throughput compatible alternative to liquid blood samples for BoHV-1 monitoring or eradication programs

Relationship between tectonic overpressure, deviatoric stress, driving force, isostasy and gravitational potential energy

We present analytical derivations and 2-D numerical simulations that quantify magnitudes of deviatoric stress and tectonic overpressure (i.e. difference between the pressure, or mean stress, and the lithostatic pressure) by relating them to lateral variations in the gravitational potential energy (GPE). These predictions of tectonic overpressure and deviatoric stress associated with GPE differences are independent of rock rheology (e.g. viscous or elastic) and rock strength. We consider a simple situation with lowlands and mountains (plateau). We use a numerical two-layer model consisting of a crust with higher Newtonian viscosity than that in the mantle, and also a three-layer model in which the two-layer lithosphere overlies a much less viscous asthenosphere. Our results (1) explain why estimates for the magnitude of stresses in Tibet, previously published by different authors, vary by a factor of two, (2) are applied to test the validity of the thin sheet approximation, (3) show that the magnitude of the depth-integrated tectonic overpressure is equal to the magnitude of the depth-integrated deviatoric stress if depth-integrated shear stresses on vertical and horizontal planes within the lithosphere are negligible (the thin sheet approximation) and (4) show that under thin sheet approximation tectonic overpressure is required to build and support continental plateaus, such as in Tibet or in the Andes, even if the topography and the crustal root are in isostatic equilibrium. Under thin sheet approximation, the magnitude of the depth-integrated tectonic overpressure is equal to the depth-integrated horizontal deviatoric stress, and both are approximately 3.5 × 1012 N m−1 for Tibet. The horizontal driving force per unit length related to lateral GPE variations around Tibet is composed of the sum of both tectonic overpressure and deviatoric stress, and is approximately 7 × 1012 N m−1. This magnitude exceeds previously published estimates for the force per unit length required to fold the Indo-Australian Plate south of India, and hence the uplift of the Tibetan plateau could have folded the Indian Plate. We also discuss the mechanical conditions that are necessary to achieve isostasy, for which the lithostatic pressure is constant at a certain depth. The results show that tectonic overpressure can exist at a certain depth even if all deviatoric stresses are zero at this depth, because this tectonic overpressure is related to horizontal gradients of vertical shear stresses integrated across the entire depth of the lithosphere. The magnitude of the depth-integrated tectonic overpressure of 3.5 × 1012 N m−1 implies that the pressure estimated from observed mineral assemblages in crustal rocks is likely significantly different from the lithostatic pressure, and pressure recorded by crustal rocks is not directly related to depth. In case of significant weakening of the entire lithosphere by any mechanism our analytical and numerical studies provide a simple estimation of tectonic overpressure via variations in GP