Temperature gradient driven lasing and stimulated cooling

A laser can be understood as thermodynamic engine converting heat to a coherent single mode field close to Carnot efficiency. From this perspective spectral shaping of the excitation light generates a higher effective temperature on the pump than on the gain transition. Here, using a toy model of a quantum well structure with two suitably designed tunnel-coupled wells kept at different temperature, we study a laser operated on an actual spatial temperature gradient between pump and gain region. We predict gain and narrow band laser emission for a sufficient temperature gradient and resonator quality. Lasing appears concurrent with amplified heat flow and points to a new form of stimulated solid state cooling. Such a mechanism could raise the operating temperature limit of quantum cascade lasers by substituting phonon emission driven injection, which generates intrinsic heat, by an extended model with phonon absorption steps

Necessity and Opportunity Entrepreneurs and their Duration in Self-employment: Evidence from German Micro Data

Using data from the German Socio-Economic Panel Study (GSOEP), we analyze whether necessity entrepreneurs differ from opportunity entrepreneurs in terms of self-employment duration. Using univariate statistics, we find that opportunity entrepreneurs remain in self-employment longer than necessity entrepreneurs. However, after controlling for the entrepreneurs’ education in the professional area where they start their venture, this effect is no longer significant. We therefore conclude that the difference observed is not an original effect but rather is due to selection. We then go on to discuss the implications of our findings for entrepreneurship-policy making, and give suggestions to improve governmental start-up programs

Personalakquisition im Zeitalter des Internet : Surviving the Online War for Talent

Das vorliegende Arbeitspapier soll Unternehmen helfen, das Neue Medium Internet erfolgreich für die Personalakquisition einzusetzen. Neben einer umfassenden Darstellung der Möglichkeiten, welche sich Unternehmen online für diesen Aspekt des Personalmarketing bieten, erfahren auch die Belange der Arbeitsuchenden eine eingehende Betrachtung. So werden exemplarisch die Ergebnisse einer empirischen Untersuchung dargestellt, welche die Erfolgsfaktoren von Jobbörsen aus der Sicht von Bewerbern beleuchtet. Die Befunde der Studie liefern Unternehmen dabei wertvolle Implikationen für die Praxis: Zum einen lassen sich die ermittelten zentralen Determinanten des Erfolges von Jobbörsen zum großen Teil auf den eigenen personalbezogenen WWW-Auftritt von Unternehmen übertragen, zum anderen dienen die Ergebnisse der kritischen Evaluation von Jobbörsen-Anbietern im Sinne einer erfolgreichen Mediaselektion bei der Schaltung von Anzeigen

An Implementation of a Process-Oriented Cross-System Compliance Monitoring Approach in a SAP ERP and BI Environment

Compliance to regulatory demands has become a crucial matter for organizations. Non-observancemay lead to far-reaching consequences, e.g. damage to reputation, decline of credit rating or marketvalue, fraud and fines. The success of compliance management correlates with the frequency ofmonitoring and reporting and is affected by complex and often time-consuming manual validationtasks. To address this problem, organizations implement corresponding IT solutions. However, theoften heterogeneous system landscapes, the different information sources and their integrationrepresent major challenges.This paper presents an implementation of a novel process-oriented and cross-system compliancemonitoring approach. The approach is based on a model which provides for the annotation ofbusiness processes with internal controls, critical permissions and roles as well as an architecturewhich provides for the automatic detection, timely communication and deep analysis of controlexceptions. It solely relies on established standards (i.e. XACML, BPMN, COSO and SWRL) andexisting technologies. The implementation has been deployed in a productive SAP ERP and BIenvironment. It automatically converts access control data from the proprietary SAP model andpublishes control exceptions to the BI system. The effects and causes of these control exception can beappropriately analyzed using BI queries and reports

Determinanten des Erfolgs staatlich geförderter Existenzgründungen – eine empirische Untersuchung

Ein Großteil der Neugründungen in Deutschland ist auf staatliche Förderung von Existenzgründern zurückzuführen. Dieser Anteil hat sich nach Einführung des als „Ich-AG“ bekannten Existenzgründungszuschusses Anfang 2003 stark erhöht. Die Erfolgsfaktorenforschung hat diese Form von Gründungen bislang jedoch wenig untersucht. Im Rahmen einer großzahligen Befragung von geförderten Existenzgründern untersucht dieser Beitrag die Erfolgsdeterminanten solcher geförderter Existenzgründungen. Die Ergebnisse der Analyse zeigen, dass der Gewinn aus der Existenzgründung bei älteren Gründern und bei Gründern mit einer langen Phase der Arbeitslosigkeit vor der Gründung seltener beziehungsweise erst später zur Bestreitung des Lebensunterhalts ausreicht. Dies gilt auch für Franchisegründungen und für Gründungen durch Frauen. In Bezug auf Bildungsvariablen, Gründungserfahrung und Teamgründungen im Vergleich zu Einzelgründungen wurde kein Effekt gefunden. Vorhandene Branchenerfahrung wirkt sich hingegen positiv auf den Erfolg der Gründung aus, Gründungs- und Führungserfahrung dagegen nicht. Die Implikationen unserer Ergebnisse für die Entrepreneurship-Forschung sowie für die Entrepreneurship-Praxis werden diskutiert. Herausforderungen aus Sicht der Gründungspolitik werden aufgezeigt.A large number of new ventures in Germany are undertaken due to government aid. With the introduction of the “Ich-AG” or “me-plc” in January 2003, this share has increased strongly. Entrepreneurship research so far has said very little about the success and the determinants of success of these types of start-ups. With this study, we aim to close this gap. We analyze the success and the determinants of success of these new ventures in a large scale survey of founders that have received governmental aid for their start-up. Our results show that the income generated by the venture is less likely to cover the costs of living in particular for elderly founders and for those founders that have experienced a long period of unemployment before they started their venture. This finding is also true for new ventures founded by women as well as for franchise start-ups. As concerns formal education, founder experience, and the fact whether the venture is founded by a team or not no significant effects exist. Industry experience, however, has a significant positive effect on the success of the new venture whereas founding and management experience have no effect. We discuss the implications of our findings from a perspective of entrepreneurship research as well as from a perspective of governmental start-up policy

Determinanten des Erfolgs staatlich geförderter Existenzgründungen – eine empirische Untersuchung

Ein Großteil der Neugründungen in Deutschland ist auf staatliche Förderung von Existenzgründern zurückzuführen. Dieser Anteil hat sich nach Einführung des als „Ich-AG“ bekannten Existenzgründungszuschusses Anfang 2003 stark erhöht. Die Erfolgsfaktorenforschung hat diese Form von Gründungen bislang jedoch wenig untersucht. Im Rahmen einer großzahligen Befragung von geförderten Existenzgründern untersucht dieser Beitrag die Erfolgsdeterminanten solcher geförderter Existenzgründungen. Die Ergebnisse der Analyse zeigen, dass der Gewinn aus der Existenzgründung bei älteren Gründern und bei Gründern mit einer langen Phase der Arbeitslosigkeit vor der Gründung seltener beziehungsweise erst später zur Bestreitung des Lebensunterhalts ausreicht. Dies gilt auch für Franchisegründungen und für Gründungen durch Frauen. In Bezug auf Bildungsvariablen, Gründungserfahrung und Teamgründungen im Vergleich zu Einzelgründungen wurde kein Effekt gefunden. Vorhandene Branchenerfahrung wirkt sich hingegen positiv auf den Erfolg der Gründung aus, Gründungs- und Führungserfahrung dagegen nicht. Die Implikationen unserer Ergebnisse für die Entrepreneurship-Forschung sowie für die Entrepreneurship-Praxis werden diskutiert. Herausforderungen aus Sicht der Gründungspolitik werden aufgezeigt.A large number of new ventures in Germany are undertaken due to government aid. With the introduction of the “Ich-AG” or “me-plc” in January 2003, this share has increased strongly. Entrepreneurship research so far has said very little about the success and the determinants of success of these types of start-ups. With this study, we aim to close this gap. We analyze the success and the determinants of success of these new ventures in a large scale survey of founders that have received governmental aid for their start-up. Our results show that the income generated by the venture is less likely to cover the costs of living in particular for elderly founders and for those founders that have experienced a long period of unemployment before they started their venture. This finding is also true for new ventures founded by women as well as for franchise start-ups. As concerns formal education, founder experience, and the fact whether the venture is founded by a team or not no significant effects exist. Industry experience, however, has a significant positive effect on the success of the new venture whereas founding and management experience have no effect. We discuss the implications of our findings from a perspective of entrepreneurship research as well as from a perspective of governmental start-up policy.Entrepreneurship; Self-employment; Necessity Entreptreneurship; Entrepreneurship Policy; Determinants of Success

Routes to multiphoton double ionization in combined extreme ultraviolet and infrared laser pulses

Xenon multiphoton double ionization pathways are studied in a reaction microscope using a pump-probe arrangement of extreme ultraviolet high harmonic and infrared laser radiation. The momentum of photoelectrons is recorded in coincidence with singly or doubly charged ions. Among all possible routes to multiphoton double ionization, sequential processes using ionic excited states as intermediate steps are clearly identified

Laser Induced Non-Sequential Double Ionization Investigated at and Below the Threshold for Electron Impact Ionization

We use correlated electron–ion momentum measurements to investigate laserinduced non-sequential double ionization of Ar and Ne. Light intensities are chosen in a regime at and below the threshold where, within the rescattering model, electron impact ionization of the singly charged ion core is expected to become energetically forbidden. Yet we find Ar2+ ion momentum distributions and an electron–electron momentum correlation indicative of direct impactionization. Within the quasistatic model this may be understood by assuming that the electric field of the light wave reduces the ionization potential of the singly charged ion core at the instant of scattering. The width of the projection of the ion momentum distribution onto an axis perpendicular to the light beam polarization vector is found to scalewiththe square root of the peak electric field strength in the light pulse. A scaling like this is not expected from the phase space available after electron impact ionization. It may indicate that the electric field at the instant of scattering is usually different fromzero and determines the transverse momentum distribution. A comparison of our experimental results with several theoretical results is give

Interference in strong-field ionization of a two-centre atomic system

Strong-field photoionization of argon dimers by a few-cycle laser pulse is investigated using electron-ion coincidence momentum spectroscopy. The momentum distribution of the photoelectrons exhibits interference due to the emission from the two atomic argon centres, in analogy with a Young's doubleslit experiment. However, a simulation of the dimer photoelectron momentum spectrum based on the atomic spectrum supplemented with a theoretically derived interference term leads to distinct deviations from the experimental result. The deviations may have their origin in a complex electron dynamics during strong-field ionization of the Ar2 dimer. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft