Human Capital and Economic Growth in OECD Countries

The results of the PISA 2000 study renewed the interest in the contribution of human capital to economic growth. So far the exploration of large country comparisons delivered rather mixed results. Concentrating on those OECD member countries which participated in PISA 2000, this paper uses panel data estimation techniques to refine this analysis. Estimation results reveal a positive impact of the human capital stock on economic growth suggesting that an increase in the average schooling years by one year yields a rise in the GDP growth rate of about 0.5 percentage points. However, when taking possible endogeneity into account in an instrumental variables approach, these conclusions on the impact of the level of human capital on economic growth is demonstrated to be rather fragile.Human capital accumulation, Convergence, Fixed-effects estimation, Instrumental variable estimation

Returns to Education in Europe – Detailed Results from a Harmonized Survey

We use the European Community Household Panel, a harmonized data set covering the countries of the European Union, to provide detailed estimates of the returns to education. Our results can be summarized as follows. Firstly, average returns to education have been mostly stable during the second half of the 1990s and are highest in Portugal and Ireland and lowest in the UK and Italy. Secondly, returns to schooling are significantly negatively related to the educational attainment of the population. Thirdly, for most countries we find significant cohort effects and these are in general uniform across countries implying lower returns to education for younger cohorts. Fourthly, in most countries schooling exerts a significantly stronger impact on wages at the top of the wage distribution, aggravating within-group inequality. Finally, we provide evidence that the more pronounced the difference in returns to education along the wage distribution, the higher the average return to education.Returns to schooling, cohort effects, quantile regression

Investment, Internal Funds and Public Banking in Germany

Previous studies argued that low investment-cash flow sensitivities of German firms may be caused by dominance of public banking.The paper addresses this topic and applies a unique accounting dataset of German firms. Results from a dynamic panel data approach show that the dependence of investment spending on internal funds does not significantly differ between firms attached to savings banks, cooperative banks or commercial banks. Thus, the importance of the public banking sector in Germany may not explain the rather low dependence of firms on internal funds and public ownership of borrowers seems not essential to reduce financing constraints.Investment, Relationship Banking, Panel Data,GMM

Characterizing Movements of the U.S. Current Account Deficit

It is unclear whether the exceptionally highU.S. current account deficit can be sustained for a prolonged period. In this paper we approach the topic whether a gradual adjustment or a pronounced reduction of the deficit is likely to occur. We therefore characterize the dynamics of the current account deficit movements by a three-regime Markov-Switching model. Our finding is that it is possible to distinguish a regime of a strong increasing deficit, a just slightly increasing deficit and a regime of a deficit reduction. Furthermore we find that movements of the deficit are asymmetric.Whereas expansions of the current account deficit are long lasting, reductions of the deficit are rather short. This implies that a pronounced reduction is not likely to occur. Secondly we try to uncover determinants of regime shifts of the current account. Applying ordered Logit models we conclude that a combination of U.S. inflation, U.S. investment and share prices predicts pronounced changes in the current account deficit quite reliably.Markov-Switching Model, Ordered Logit, Indicators

Molecular biological investigations for detection, epidemiological studies and differentiation of avian poxviruses

Deckblatt-Impressum Inhaltsverzeichnis Verzeichnis der Abkürzungen Literatur Ziel der Arbeit Material und Methoden Ergebnisse Diskussion Zusammenfassung Summary Literaturverzeichnis Publikationsliste Anhang Danksagung SelbständigkeitserklärungAls Ziel der vorliegenden Arbeit wurde eine Polymerasekettenreaktion (PCR) als molekularbiologisches System zum routinemäßigen Nachweis und zur Differenzierung aviärer Pockenviren etabliert. Durch Untersuchungen von Hühnerpockenimpfstoff (HP-B) und Probenmaterial, in dem mittels konventioneller Diagnostikverfahren Geflügel-pockenvirus nachgewiesen worden war, wurde dieses Nachweisverfahren hinsichtlich seiner Spezifität überprüft. Es zeigte sich, dass hühnerpockenvirus-spezifische DNA nach gelelektrophoretischer Auftrennung der PCR-Produkte eindeutig durch eine Bande von 578 bp nachgewiesen werden konnte. Die Untersuchungen anderer aviärer Viren führten hingegen zu negativen Ergebnissen. Die Bestimmung der Sensitivität erfolgte mittels Auftrennung der PCR-Produkte durch Gelelektrophorese. Hühnerpockenvirus-spezifische DNA konnte ab einer Menge von 150 Genomäquivalenten nachgewiesen werden. Im Vergleich wurde die Sensitivität auch mittels Dot Blot-Verfahren überprüft. Hier zeigte sich eine Nachweisgrenze ab 75 Genomäquivalenten. Die Sensitivität des etablierten Verfahrens mit Gelelektrophorese der PCR-Produkte erscheint jedoch ausreichend, und durch die einfache sowie schnellere Anwendung vorteilhaft für die Routinediagnostik zu sein. Anhand der etablierten PCR und des im Rahmen der Geflügelpockendiagnostik von 2001 bis 2003 eingesandten Probenmaterials wurden Pockenvirusinfektionen in Geflügelbeständen unter epidemiologischen Gesichtspunkten untersucht. Es konnte am Anfang des Untersuchungszeitpunktes ein deutlicher Anstieg an Geflügel-pockeninfektionen beobachtet werden, der im Zusammenspiel mit weiteren Faktoren, insbesondere in der Einstellung der prophylaktischen Pockenimpfung in den letzten 20 Jahren, begründet sein könnte. Seit dem Jahr 2002 zeigte sich bei erneuter Intensivierung der Impfung eine wieder abnehmende Tendenz an Infektionen. Des Weiteren wurde die PCR in Kombination mit der Restriktionsenzymanalyse (REA) als ein molekularbiologisches System zur Differenzierung verschiedener Avipockenvirusspezies verwandt. Unter Verwendung eines Primerpaares konnte mittels PCR avipockenvirus-spezifische DNA in 53 Avipockenvirusstämmen und -isolaten von zwölf Vogelarten aus acht Ordnungen nachgewiesen werden. Mittels REA unter Verwendung der Enzyme EcoRV und NlaIII konnten die acht Ordnungen der verschiedenen Vogelarten weitgehend sechs spezifischen Spaltbildern zugeordnet werden. Die Stämme und Isolate von Hühnern sowie Puten (Ordnung Phasianiformes), Tauben und Strauß (Ordnungen Columbiformes und Struthioniformes), Falken (Ordnung Falconiformes) und Agaporniden (Ordnung Psittaciformes) führten jeweils zu einem spezifischen Spaltbild. Schwierigkeiten zeigten sich nur bei Isolaten von Vogelarten der Ordnung Passeriformes. Während die Isolate einer Rabenkrähe, eines Hakengimpels und von drei Kanarienvögeln sowie zwei Sperlingen zu einem Sperlingsvögel -spezifischen Spaltbild führten, zeigten sich zwei Abweichungen: bei Untersuchung der Kanarienpockenvirus-Stämme KP-1-V557 und KP-1 sowie eines Kanarienvogelisolates ergab sich durch eine zusätzliche EcoRV-Spaltstelle ein weiteres Spaltbild, und die Untersuchung von zwei Sperlingsisolaten führten zu dem Spaltbild, welches spezifisch für die Stämme und Isolate der Ordnung Phasianiformes war. Die Infektion von Sperlingen durch Geflügelpockenvirus (FWPV) wird in der Arbeit diskutiert. Darüber hinaus führten die Isolate des Triels (Ordnung Charadriformes) und des Habichts (Ordnung Accipitriformes) ebenfalls zu dem Sperlingsvögel -spezifischen Spaltbild. Zehn Pockenvirussolate und zwei -stämme wurden darüber hinaus sequenziert und phylogenetisch analysiert. Die Ergebnisse der REA wurden durch die phylogenetische Analyse bestätigt.The aim of the present study was to establish a polymerase chain reaction (PCR) as molecular biological tool for routine diagnosis and differentiation of avian poxviruses. For testing the specificity of this PCR, fowlpox vaccine (FWPV HP-B) and samples from which fowlpox viruses were diagosed by conventional methods, were investigated. FWPV specific DNA was detected by amplifying a 578 bp fragment within the FWPV 4 b core protein gene. Examination of other avian viruses in this PCR revealed negative results. The agarose gel electrophoresis of PCR products was used for ascertaining the sensitivity of the PCR. FWPV specific DNA could be detected from a minimal amount of 150 copies of the genome. In comparison, the sensitivity was also ascertained by dot blot hybridization. With this technique a minimal amount of 75 copies of the genome could be detected. The sensitivity of the established PCR combined with agarose gel electrophoresis of PCR products seems to be sufficient and, because of its simple and rapid application superior to routine diagnosis. The established PCR was used to examine all samples, submitted for fowlpox virus diagnosis to the Institute of Poultry Diseases of the Free University Berlin between 2001 to 2003. After a distinctive increase of FWPV-outbreaks at the beginning of the investigations, a decrease was observed in 2002. Since the vaccination against fowlpox was not routinely used in the past, and after observation of several outbreaks till 2001, intensive vaccinations of poultry flocks were applied and resulted in distinct decrease in the numbers of cases in 2002. Futher, PCR in combination with restriction enzyme analysis (REA) was used as a molecular biological tool for differentiation of various avian poxviruses. With one primer set, it was possible to detect the DNA of 53 avian poxvirus strains or isolates from twelve bird species out of eight orders. REA of PCR products using EcoRV and NlaIII allowed to differentiate these eight orders into six different restriction patterns in most cases. All investigated strains and isolates of fowl and turkey (order phasianiformes), pigeon and ostrich (orders columbiformes and struthioniformes), falcon (order falconiformes), and agapornis (order psittaciformes) had specific restriction patterns and were distinguishable from each other. Problems only occured with poxvirus isolates from birds of the order of passeriformes. Isolates of a carrion crow, a pine grosbeak, three canary-birds and two sparrows had an identical restriction pattern ( passeriformes-pattern ) but there were two exceptions: the canarypox virus strains KP-1-V557 and KP-1 as well as one isolate from a canary-bird showed a different restriction pattern, because of one additional EcoRV site in the PCR fragment, and the investigation of two isolates of sparrows had an identical pattern to strains and isolates of the order phasianiformes. The infections of sparrows by FWPV will be discussed in this work. In addition to the problem mentioned above, the isolates of a stone curlew (order charadriformes) and of a hawk (order accipitriformes) also showed the passeriformes-pattern . Nucleotide sequence analysis and phylogenetic analysis of amplified fragments of ten isolates and two strains confirmed the results obtained by REA

Aerodynamic Feeding 4.0: A New Concept for Flexible Part Feeding

In modern production environments, the need for flexible handling systems constantly increases due to increasing uncertainties, shorter product life cycles and higher cost pressure. Part feeding systems are vital to modern handling systems, but conventional solutions are often characterized by low flexibility, high retooling times, and complex design. Therefore, in previous research, multiple approaches towards aerodynamic feeding technology were developed. Using air instead of mechanical chicanes to manipulate workpieces, aerodynamic feeding systems can achieve high feeding rates while at the same time being very flexible and reliable. Still, the complexity of the workpieces that can be oriented relies on the number of aerodynamic actuators used in the system. Previously developed systems either used one nozzle with a constant air jet or one nozzle and an air cushion, allowing a maximum of two orientation changes. This work presents a new concept for an aerodynamic feeding system with higher flexibility (with regard to the workpiece geometry) and drastically reduced retooling times compared to conventional feeding systems. In contrast to previous implementations of aerodynamic feeding systems, using only one air nozzle or an air cushion, the new concept uses multiple, individually controllable air nozzles. Using a simulation-based approach, the orientation process is divided into several basic rotations - from a random initial orientation to the desired end orientation - each performed by a distinct nozzle. An optimization algorithm is then used to determine an optimal layout of the air nozzles, enabling the feeding system to feed any desired workpiece, regardless of the initial orientation. With the proposed concept, high flexibility, low retooling times and relatively low costs are expected, setting up aerodynamic feeding as an enabler for changeable production environments

Investment, Internal Funds and Public Banking in Germany

Previous studies argued that low investment-cash flow sensitivities of German firms may be caused by dominance of public banking.The paper addresses this topic and applies a unique accounting dataset of German firms. Results from a dynamic panel data approach show that the dependence of investment spending on internal funds does not significantly differ between firms attached to savings banks, cooperative banks or commercial banks. Thus, the importance of the public banking sector in Germany may not explain the rather low dependence of firms on internal funds and public ownership of borrowers seems not essential to reduce financing constraints

Satellite to model comparisons of volcanic ash emissions in the North Pacific

Thesis (Ph.D.) University of Alaska Fairbanks, 2013To detect, analyze and predict the movement of volcanic ash in real time, dispersion models and satellite remote sensing data are important. A combination of both approaches is discussed here to enhance the techniques currently used to quantify volcanic ash emissions, based on case studies of the eruptions of the Kasatochi (Alaska, USA, 2008), Mount Redoubt (Alaska, USA, 2009) and Sarychev Peak (Russia, 2009) volcanoes. Results suggest a quantitative approach determining masses from satellite images can be problematic due to uncertainties in knowledge of input values, most importantly the ground surface temperature required in the mass retrieval. Furthermore, a volcanic ash transport and dispersion model simulation requires its own set of accurate input parameters to forecast an ash cloud's future location. Such input parameters are often difficult to assess, especially in real time volcano monitoring, and default values are often used for simplification. The objective of this dissertation is to find a quantitative comparison technique to apply to satellite and volcanic ash transport and dispersion models that reduces the inherent uncertainty in the results. The binary 'Ash -- No Ash' approach focusing on spatial extent rather than absolute masses is suggested, where the ash extent in satellite data is quantitatively compared to that in the dispersion model's domain. In this technique, neither satellite data nor dispersion model results are regarded as the truth. The Critical Success Index (CSI) as well as Model and Satellite Excess values (ME and SE, respectively) are introduced as comparison tools. This approach reduces uncertainties in the analysis of airborne volcanic ash and, due to the reduced list of input parameters and assumptions in satellite and model data, the results will be improved. This decreased complexity of the analysis, combined with a reduced error as the defined edge of ash cloud is compared in each method rather than defined threshold or mass loading, will have important implications for real time monitoring of volcanic ash emissions. It allows for simpler, more easily implemented operational monitoring of volcanic ash movements.Chapter 1. Introduction -- Chapter 2. Qualitative comparison of Mount Redoubt 2009 volcanic clouds using the PUFF and WRF-Chem dispersion models and satellite remote sensing data -- Chapter 3. Qualitative analysis of input parameters for satellite-based quantification of airborne volcanic ash -- Chapter 4. Quantitative comparison of volcanic ash observations in satellite-based remote sensing data and WRF-chem model simulations -- Chapter 5. Improvements on volcanic ash quantification in the Puff Volcanic Ash Tracking and Dispersion Satellite Thermal Infrared Remote Sensing Data -- Chapter 6. Conclusions