High-power operation of quantum-dot semiconductor disk laser at 1180 nm

In this letter, we report on a high-power operation of an optically pumped quantum-dot semiconductor disk laser designed for emission at 1180 nm. As a consequence of the optimization of the operation conditions, a record-high continuous-wave output power exceeding 7 W is obtained for this wavelength at a heat-sink temperature of 2 °C. A wavelength tuning over a range of 37 nm is achieved using a birefringent filter inside the cavity

Self-mode-locked vertical-external-cavity surface-emitting laser

Ultrashort laser pulses from vertical-external-cavity surface-emitting lasers (VECSELs) have been receiving much attention in the semiconductor laser community since the first demonstration of sub-ps-pulsed devices more than a decade ago. Originally relying on semiconductor saturable-absorber mirrors for pulse formation, mode-locked operation has not only become accessible by using a variety of saturable absorbers, but also by using a saturable-absorber-free technique referred to as self-mode-locking (SML). Here, we highlight achievements in the field of SML-VECSELs with quantum-well and quantum-dot gain chips, and study the influence of a few VECSEL parameters on the assumed nonlinear lensing behavior in the system

Post-Darwinian longevity

Die Umweltbedingungen koennen die durchschnittliche Lebensdauer einer Spezies dramatisch beeinflussen. Die menschliche Lebenserwartung liegt heute in vielen Entwicklungslaender unter 50 Jahren, in frueheren Populationen lag sie unter 25 Jahren; japanische Frauen erreichen demgegenueber heute ein durchschnittliches Alter von 85 Jahren. Bienenkoeniginnen leben um ein vielfaches laenger als Arbeiterinnen, obgleich sie genetisch identisch sind. Die Varianz der Langlebigkeit wird hauptsaechlich durch die Ernaehrungsweise und beim Menschen durch ein Buendel von gesellschaftlichen Stressfaktoren bedingt. Das vorliegende Arbeitspapier versucht aus einer evolutionstheoretischen Perspektive, die Langlebigkeit in menschlichen Populationen zu erklaeren. Aus darwinistischer Sicht ist die post-reproduktive Phase eigentlich 'ueberfluessig'. Der dramatische Anstieg der menschlichen Lebenserwartung und die damit verbundene Gefahr der 'Ueberalterung' der Gesellschaften lassen sich aus biologischer Sicht durch einen 'Ueberlebensvorteil' erklaeren, und sei es auch nur,dass die aeltere Generation sich um den Nachwuchs der Kindergeneration kuemmert. (ICA)German title: Post-darwinistische LanglebigkeitAvailable from http://www.demogr.mpg.de/papers/working/wp-2002-043.pdf / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Decomposing change in life expectancy A bouquet of formulas in honour of Nathan Keyfitz's 90th birthday

'This article extends Nathan Keyfitz's research on continuous change in life expectancy over time. A new formula for decomposing such change is presented and proved. The formula separates change in life expectancy over time into two terms. The first term captures the general effect of reduction in death rates at all ages. The second term captures the effect of heterogeneity in the pace of improvement in mortality at different ages. The formula is extended to decompose change in life expectancy into age-specific and cause-specific components. The methods are applied to analyze changes in life expectancy in Sweden and Japan.' (author's abstract)Der Beitrag stellt eine Erweiterung der Untersuchungen von Nathan Keyfitz ueber den kontinuierlichen Wandel der Lebenserwartung im Zeitverlauf dar. Es wird eine neue Formel fuer die Analyse dieses Wandels entwickelt. Diese Formel zerlegt den Wandel der Lebenserwartung im Zeitverlauf in zwei Terme. Der erste Term beschreibt den allgemeinen Effekt einer Reduktion der Sterbequoten in allen Altersklassen. Der zweite Term beschreibt den Effekt der heterogenen Geschwindigkeit, mit der sich Verbesserungen der Mortalitaet in unterschiedlichen Altersklassen vollziehen. Eine Ausweitung der Formel erlaubt die Differenzierung des Wandels der Lebenserwartung in altersspezifische und ursachenspezifische Komponenten. Die Verfasser demonstrieren ihre Analysemethode am Beispiel Schwedens und Japans. (ICEUebers)German title: Die Analyse des Wandels in der Lebenserwartung: ein bunter Strauss von Formeln anlaesslich des 90. Geburtstags von Nathan KeyfitzAvailable from http://www.demogr.mpg.de/papers/working/wp-2002-042.pdf / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

The milli-Newton µHEMPT as Potential Main Thruster for Small Satellites

In the last years, small satellites become more important due to the continuing miniaturisation of key technology. Due to the constraining mass requirements of small satellites, electric propulsion with its high propellant-to-thrust ratio offers several advantages. Airbus DS in Friedrichshafen performs a downscaling of the HEMPT principle to the micro-Newton regime and additionally developed a mN-µHEMPT which can be operated towards 10 mN. The mN-µHEMPT performance was characterised by direct thrust measurement as well as an indirect thrust measurement using a retarding potential analyser and Faraday cup at the AirbusDS test facility

Association of late childbearing with healthy longevity among the oldest-old in China

'Statistical analysis of a large and unique longitudinal data set demonstrates that late childbearing after age 35 or 40 is significantly associated with survival and healthy survival among very old Chinese women and men. The association is stronger in oldest-old women than men. The estimates are adjusted for a variety of confounding factors of demographic characteristics, family support, social connections, health practices, and health conditions. Further analysis based on an extension of the Fixed Attribute Dynamics method shows that late childbearing is positively associated with long-term survival and healthy survival from ages 80-85 to 90-95 and 100-105. This association exists among oldest-old women and men, but, again, the effects are substantially stronger in women than men. We discuss four possible factors which may explain why late childbearing affects healthy longevity at advanced ages: (1) social factors; (2) biological changes caused by late pregnancy and delivery; (3) genetic and other biological characteristics; and (4) selection.' (author's abstract)Die statistische Analyse eines umfangreichen Laengsschnittdatensatzes zeigt, dass die Geburt von Kindern nach dem 35. oder 40. Lebensjahr in China signifikant mit der Gesundheit in sehr hohem Alter zusammenhaengt. Dieser Zusammenhang ist bei sehr alten Frauen staerker als bei Maennern. Moegliche Einfluesse von demographischen Faktoren, familialer Unterstuetzung, sozialen Beziehungen, Gesundheitsverhalten und Gesundheitszustand wurden beruecksichtigt. Die Geburt von Kindern im fortgeschrittenen Lebensalter haengt fuer die 80- bis 85jaehrigen, die 90- bis 95jaehrigen und die 100- bis 105jaehrigen positiv mit dem Erreichen eines hohen Alters und Gesundheit im Alter zusammen. Die Verfasser diskutieren vier Faktorenbuendel, die dieses Phaenomen erklaeren koennten: (1) soziale Faktoren, (2) biologische Veraenderungen auf Grund der spaeten Schwangerschaft und Geburt, (3) genetische oder biologische Charakteristika, (4) Selektion. (ICEUebers)German title: Der Zusammenhang einer spaeten Schwangerschaft mit gesunder Langlebigkeit bei sehr alten Menschen in ChinaAvailable from Max-Planck-Institut fuer demografische Forschung, Rostock (DE) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Taking advantage of tumor cell adaptations to hypoxia for developing new tumor markers and treatment strategies

Cancer cells in hypoxic areas of solid tumors are to a large extent protected against the action of radiation as well as many chemotherapeutic drugs. There are, however, two different aspects of the problem caused by tumor hypoxia when cancer therapy is concerned: One is due to the chemical reactions that molecular oxygen enters intoin therapeutically targeted cells. This results in a direct chemical protection against therapy by the hypoxic microenvironment which has little to do with cellular biological regulatory processes. This part of the protective effect of hypoxia has been known for more than half a century and has been studied extensively. However, in recent years more focus has been put into the other aspect of hypoxia, namely the effect of this microenvironmental condition on selecting cells with certain genetical pre-requisites that are negative with respect to patient prognosis. There are adaptive mechanisms, where hypoxia induces regulatory cascades in cells resulting in a changed metabolism or changes in extra cellular signalling. These processes may lead to changes in cellular intrinsic sensitivity to treatment irrespective of oxygenation and furthermore, may also have consequences for tissue organization. Thus, the adaptive mechanisms induced by hypoxia itself may have a selective effect on cells with a fine-tuned protection against damage and stress of many kinds. It therefore could be that the adaptive mechanisms may be taken advantage of for new tumor labelling/imaging and treatment strategies. One of the Achilles’ heels of hypoxia research has always been exact measurements of tissue oxygenation as well as control of oxygenation in biological tumor models. Thus, development of technology that can ease this control is vital in order to study mechanisms and perform drug development under relevant conditions. An integrated EU Framework project 2004-2009, termed Euroxy, demonstrates several pathways involved in transcription and translation control of the hypoxic cell phenotype and evidence of cross talk with responses to pH and redox changes. The carbon anhydrase isoenzyme CA IX was selected for further studies due to its expression on the surface of many types of hypoxic tumors. The effort has lead to marketable culture flaks with sensors and incubation equipment and the synthesis of new drug candidates against new molecular targets. New labelling/imaging methods for cancer diagnosing and imaging of hypoxic cancer tissue now are being tested in xeno-graft models and also are in early clinical testing while new potential anticancer drugs are undergoing tests using xenografted tumor cancers. The present paper describes the above results in individual consortium partner presentations