Do Entrepreneurs Matter?

Publisher PD

Do entrepreneurs matter?

In the large literature on firm performance, economists have given little attention to entrepreneurs. We use the deaths of 500 entrepreneurs as a source of exogenous variation, and ask whether this variation can explain shifts in firm performance. Using longitudinal data, we find large and sustained effects of entrepreneurs at all levels of the performance distribution. Entrepreneurs strongly affect firm growth patterns of very young firms and for firms that have begun to mature. We do not find significant differences between small and larger firms, family and non-family firms, nor between firms located in urban and rural areas, but we do find stronger effects for founders with high human capital. Overall, the results suggest that an often overlooked factor - individual entrepreneurs - plays a large role in affecting firm performance

Contact angle of sessile drops in Lennard-Jones systems

Molecular dynamics simulation is used for studying the contact angle of nanoscale sessile drops on a planar solid wall in a system interacting via the truncated and shifted Lennard-Jones potential. The entire range between total wetting and dewetting is investigated by varying the solid--fluid dispersive interaction energy. The temperature is varied between the triple point and the critical temperature. A correlation is obtained for the contact angle in dependence of the temperature and the dispersive interaction energy. Size effects are studied by varying the number of fluid particles at otherwise constant conditions, using up to 150 000 particles. For particle numbers below 10 000, a decrease of the contact angle is found. This is attributed to a dependence of the solid-liquid surface tension on the droplet size. A convergence to a constant contact angle is observed for larger system sizes. The influence of the wall model is studied by varying the density of the wall. The effective solid-fluid dispersive interaction energy at a contact angle of 90 degrees is found to be independent of temperature and to decrease linearly with the solid density. A correlation is developed which describes the contact angle as a function of the dispersive interaction, the temperature and the solid density. The density profile of the sessile drop and the surrounding vapor phase is described by a correlation combining a sigmoidal function and an oscillation term

MODS2FRBROO

Der vorliegende Beitrag stellt ein Verfahren vor, wie bereits existierende bibliographische Daten in die CIDOC CRM/FRBROO-Umgebung übertragen werden können. Es handelt sich dabei um einen mehrstufigen XSLT-Prozess, der im MODS-Format vorliegende bibliographische Daten in ein FRBROO-konformes RDF umwandelt. Dazu werden die unterschiedlichen Publikationstypen in FRBROO identifiziert und modelliert. Für die Abbildung der einzelnen bibliographischen Kategorien aus dem verwendeten Austauschformat auf die FRBROO-Klassen wird auf Konzepte von RDA zurückgegriffen

Employees, Firm Size and Profitability of U.S. Manufacturing Industries

We examine the relation between firm size and profitability within 109 SIC four-digit manufacturing industries. Depending on our measure of profitability, we find that profitability increases at a decreasing rate and eventually declines in up to 47 of our industries. No relation between profitability and size is found in up to 52 of our industries. These two categories account for 97 of our 109 industries. Profitability continues to increase as firms become larger in up to 11 industries. Hence, the relation between size and profitability is industry specific. But, regardless of the shape of the size profitability function, we find that profitability is negatively correlated with the number of employees for firms of a given size measured in terms of total assets and sales. These results are puzzling in the context of work by others who report that common stock returns are negatively correlated with size when size is measured by the market value of a company or with the work of those who argue that size is a proxy for risk. Interpreted against these works, our findings may mean that large firms earn excess returns, that small firms fail to earn their cost of capital, or that accounting returns simply behave differently than market returns with respect to firm size

Acute cardiac inflammatory responses to postischemic reperfusion during cardiopulmonary bypass

Objectives: The investigation centers on whether there is a reperfusion-induced specific cardiac inflammatory reaction after bypass surgery. Background: Cardiopulmonary bypass (CPB) leads to systemic inflammation. Additionally, cardiac inflammation due to reperfusion could occur. Knowledge about nature and time course of this reaction might help to develop cardioprotective interventions. Methods: In 12 patients receiving coronary bypass grafts, arterial and coronary venous blood was obtained before onset of CPB, and 1, 5, 10, 25, 35 and 75 min after cardiac reperfusion. Plasma levels of IL6 and IL8 were measured by immunoassay. CD11b, CD41, and CD62 on blood cells were quantified by flow cytometry. Measurement of CD41, a platelet marker, on neutrophils and monocytes allowed detection of leukocyte–platelet microaggregates. Results: Transcardiac veno–arterial difference of IL6 rose in the 10th and 25th min of reperfusion (from 0 to 7 pg/ml; p<0.05), and after 75 min (15 pg/ml). IL8 did not change. CD11b on neutrophils (PMN) decreased transcardially to 95, 88 and 82% of the initial level in the 5th, 10th, and 75th min, respectively, suggesting sequestration of activated neutrophils. CD62 on platelets rose about 30% in the 75th min. Initially, leukocyte–platelet microaggregates were formed during coronary passage (+31% of the arterial level for PMN, +23% for monocytes). During reperfusion, coaggregates were retained (PMN: -1% and -7% in the 5th and 10th min, monocytes: -22%, -13% and -12% in the 1st, 5th and 10th min. Conclusions: During early reperfusion after aortic declamping, the coronary bed is already a source of proinflammatory stimuli and target for activated leukocytes, partly in conjunction with platelets. Mitigation of these phenomena might help to improve cardiac function after CPB especially in patients at risk

Zur kalibrierung von streuungsfaktoren für pfahlwiderstände nach eurocode EC 7-1

Bei der Ermittlung von Bemessungswerten für Pfahlwiderstände aus Ergebnissen von Pfahlprobebelastungen nach DIN EN 1997-1:2009-09 (Eurocode EC 7-1) werden die charakteristischen Pfahlwiderstände Rc;k über Streuungsfaktoren Xsi abgemindert. Die entsprechenden Beiwerte sind von der Art und Anzahl der Probebelastungen abhängig und berücksichtigen Unsicherheiten wie etwa Streuungen der Versuchsergebnisse, die durch Änderungen im Baugrund oder im Bauverfahren entstehen. Die in Eurocode EC 7-1 nunmehr gewählte Art der Ermittlung des Grenzwertes von Pfahlwiderständen unterscheidet sich deutlich von den bisherigen Regelungen DIN 1054:1976-11, die sich durch ihre langjährige Anwendung bei der Bemessung von Pfählen in der Praxis bewährt haben. Die DIN 1054:2005-01 ist zwar im Vorgriff auf den Eurocode EC 7-1 formal ähnlich vorgegangen, enthält aber vollkommen andere Zahlenwerte für die Sicherheitsbeiwerte gamma_p und die Streuungsfaktoren Xsi. In dem Beitrag werden die an der Universität Kassel durchgeführten Untersuchungen zur Ableitung der Streuungsfaktoren und Teilsicherheitsbeiwerte für Pfahlwiderstände aus Ergebnissen von Probebelastungen und Erfahrungswerten für den Eurocode EC 7-1 vorgestellt. Mit diesen Werten werden die Ergebnisse an das bisherige nationale Sicherheitsniveau der DIN 1054:1976-11 und DIN 1054:2005-01 angepasst bzw. überprüft. Als Ergebnis der hier vorgestellten vergleichenden Untersuchungen wird für die verschiedenen Versuchsarten der nationale Vorschlag für die Streuungsfaktoren und die Teilsicherheitsbeiwerte mitgeteilt und bewertet

Entrepreneur Death and Startup Performance

Peer reviewedPublisher PD