Unternehmer - Fakten und Fiktionen. Historisch-biografische Studien

The essays in this volume examine successful entrepreneurs from different industries and time periods. They show that at least in terms of Schumpeter`s model, entrepreneurship must be regarded as an individual quality, for no specific defining characteristic can be found, including social background, that suggests the existence of a specific ´entrepreneurial` type

Design of a Test Rig and its Testing Methods for Rotation and Expansion Performing Assemblies in Parabolic Trough Collector Power Plants

The present master’s thesis deals with the design of a new test rig for the investigation of durability and failure mechanisms of flexible pipe connections – so called Rotation and Expansion Performing Assemblies (REPAs) –, which are utilized in Parabolic Trough Collector power plants. Said assemblies compensate for the motion of the absorber tubes relative to the fixed piping of the header connection. The work focusses on the test rig’s design in view of a realistic simulation of all loads a REPA is exposed to in commercial applications. To achieve this, all possible requirements of the components, which are supposed to endure a lifetime of up to 30 years in power plants, are depicted. A literature research is carried out in order to investigate and evaluate existing test rigs for REPAs or their single components. By means of the findings, a specification sheet is derived. The test rig is composed of two main assemblies. On the one hand, a Kinematics Unit is used to reproduce the cyclic rotational and translational motions of a Parabolic Trough Collector. On the other hand, an HTF cycle (Heat Transfer Fluid cycle) conduces to set up pressure, temperature and flow rate circulating through the test specimens. The main part of the thesis contributes to the integration of the externally designed Kinematics Unit into the HTF cycle – taking into consideration realistic operation conditions and a complete and precise measurement of all parameters. Special emphasis is put on an accurate acquisition of the mechanical loads the test objects have to cope with. As a result of this work, a test rig is erected enabling realistic endurance tests of two serially connected REPAs in less than three months. The hydraulic properties are adjustable in terms of mass flow (6−60 m3/h), pressure (up to 40 bars) and temperature (up to 450 °C). The investigations can be tailored to customized applications of the REPA concept (Ball Joint Assemblies or Rotary Flex Hose Assemblies) and the collector geometry (e.g. focal length)

Modeling of the glottal flow derivative waveform with application to speaker identification

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 102-107).by Michael David Plumpe.M.S

Las estrategias de crecimiento de la industria química alemana en España, 1880-1936: exportación e inversión directa

Editada en la Fundación Empresa PúblicaEn este trabajo se reconstruyen y examinan las dos grandes estrategias de crecimiento de las empresas químicas alemanas en España entre 1880 y 1936: la exportación y la inversión directa. Ambas fueron, en todo el mundo, importantes vías de transferencia tecnológica especialmente después de la Primera Guerra Mundial. Para averiguar por qué en la industria química española los efectos modemizadores del primer mversor mundial fueron tan escasos, se abordan dos tareas: 1) valorar la estratega de las firmas alemanas en España a la luz de las desplegadas en todo el mundo, y 2) analizar las medidas que las empresas y la Administración españolas aplicaron para defender el mercado nacional y fomentar el surgmuento y la consolidación de la industria química española.This paper reconstructs and examines the growth strategies displayed by the German chemical industry in Spain between 1880 and 1936: exports and direct investment. Elsewhere both became instrumental for the transfer of technology and managerial skills, particularly after World War I. In order to understand why the effects of the fírst world chemical investor were so poor on the Spanish industry, the German strategies are analyzed in the light of those followed elsewhere. Furthermore, those policies applied both by the Spanish firms and Administration to encourage the rise and development of the local industry are also examined.Publicad

Tis21 Expression Marks Not Only Populations of Neurogenic Precursor Cells but Also New Postmitotic Neurons in Adult Hippocampal Neurogenesis

During embryonic cortical development, expression of Tis21 is associated with cell cycle lengthening and neurogenic divisions of progenitor cells. We here investigated if the expression pattern of Tis21 also correlates with the generation of new neurons in the adult hippocampus. We used Tis21 knock-in mice expressing green fluorescent protein (GFP) and studied Tis21-GFP expression together with markers of adult hippocampal neurogenesis in newly generated cells. We found that Tis21-GFP 1) was absent from the radial glia–like putative stem cells (type-1 cells), 2) first appeared in transient amplifying progenitor cells (type-2 and 3 cells), 3) did not colocalize with markers of early postmitotic maturation stage, 4) was expressed again in maturing neurons, and 5) finally decreased in mature granule cells. Our data show that, in the course of adult neurogenesis, Tis21 is expressed in a phase additional to the one of the embryonic neurogenesis. This additional phase of expression might be associated with a new and different function of Tis21 than during embryonic brain development, where no Tis21 is expressed in mature neurons. We hypothesize that this function is related to the final functional integration of the newborn neurons. Tis21 can thus serve as new marker for key stages of adult neurogenesis

Euclidean distances as measures of speaker similarity including identical twin pairs: a forensic investigation using source and filter voice characteristics

AbstractThere is a growing consensus that hybrid approaches are necessary for successful speaker characterization in Forensic Speaker Comparison (FSC); hence this study explores the forensic potential of voice features combining source and filter characteristics. The former relate to the action of the vocal folds while the latter reflect the geometry of the speaker’s vocal tract. This set of features have been extracted from pause fillers, which are long enough for robust feature estimation while spontaneous enough to be extracted from voice samples in real forensic casework. Speaker similarity was measured using standardized Euclidean Distances (ED) between pairs of speakers: 54 different-speaker (DS) comparisons, 54 same-speaker (SS) comparisons and 12 comparisons between monozygotic twins (MZ). Results revealed that the differences between DS and SS comparisons were significant in both high quality and telephone-filtered recordings, with no false rejections and limited false acceptances; this finding suggests that this set of voice features is highly speaker-dependent and therefore forensically useful. Mean ED for MZ pairs lies between the average ED for SS comparisons and DS comparisons, as expected according to the literature on twin voices. Specific cases of MZ speakers with very high ED (i.e. strong dissimilarity) are discussed in the context of sociophonetic and twin studies. A preliminary simplification of the Vocal Profile Analysis (VPA) Scheme is proposed, which enables the quantification of voice quality features in the perceptual assessment of speaker similarity, and allows for the calculation of perceptual–acoustic correlations. The adequacy of z-score normalization for this study is also discussed, as well as the relevance of heat maps for detecting the so-called phantoms in recent approaches to the biometric menagerie

Spatial Learning Depends on Both the Addition and Removal of New Hippocampal Neurons

The role of adult hippocampal neurogenesis in spatial learning remains a matter of debate. Here, we show that spatial learning modifies neurogenesis by inducing a cascade of events that resembles the selective stabilization process characterizing development. Learning promotes survival of relatively mature neurons, apoptosis of more immature cells, and finally, proliferation of neural precursors. These are three interrelated events mediating learning. Thus, blocking apoptosis impairs memory and inhibits learning-induced cell survival and cell proliferation. In conclusion, during learning, similar to the selective stabilization process, neuronal networks are sculpted by a tightly regulated selection and suppression of different populations of newly born neurons

Disc1 variation leads to specific alterations in adult neurogenesis

Disrupted in schizophrenia 1 (DISC1) is a risk factor for a spectrum of neuropsychiatric illnesses including schizophrenia, bipolar disorder, and major depressive disorder. Here we use two missense Disc1 mouse mutants, described previously with distinct behavioural phenotypes, to demonstrate that Disc1 variation exerts differing effects on the formation of newly generated neurons in the adult hippocampus. Disc1 mice carrying a homozygous Q31L mutation, and displaying depressive-like phenotypes, have fewer proliferating cells while Disc1 mice with a homozygous L100P mutation that induces schizophrenia-like phenotypes, show changes in the generation, placement and maturation of newly generated neurons in the hippocampal dentate gyrus. Our results demonstrate Disc1 allele specific effects in the adult hippocampus, and suggest that the divergence in behavioural phenotypes may in part stem from changes in specific cell populations in the brain

Differential Regulation of the Variations Induced by Environmental Richness in Adult Neurogenesis as a Function of Time: A Dual Birthdating Analysis

Adult hippocampal neurogenesis (AHN) augments after environmental enrichment (EE) and it has been related to some of the anxiolytic, antidepressant and neuroprotective effects of EE. Indeed, it has been suggested that EE specifically modulates hippocampal neurogenic cell populations over the course of time. Here we have used dual-birthdating to study two subpopulations of newborn neuron in mice (Mus musculus): those born at the beginning and at the end of enrichment. In this way, we demonstrate that while short-term cell survival is upregulated after an initial 1 week period of enrichment in 2 month old female mice, after long-term enrichment (2 months) neither cell proliferation nor the survival of the younger newly born cell populations are distinguishable from that observed in non-enriched control mice. In addition, we show that the survival of older newborn neurons alone (i.e. those born at the beginning of the enrichment) is higher than in controls, due to the significantly lower levels of cell death. Indeed, these parameters are rapidly adjusted to the sudden cessation of the EE conditions. These findings suggest both an early selective, long-lasting effect of EE on the neurons born in the initial stages of enrichment, and a quick response when the environment again becomes impoverished. Therefore, EE induces differential effects on distinct subpopulations of newborn neurons depending on the age of the immature cells and on the duration of the EE itself. The interaction of these two parameters constitutes a new, specific regulation of these neurogenic populations that might account for the long-term enrichment's behavioral effects