Untersuchung innen und außen berippter, rohrförmiger, gasgekühlter Brennelemente

Die vorliegende Arbeit liefert einen Beitrag zur Entwicklung eines rohrförmigen innen und außen gekühlten Brennelementes für den Reaktortyp Natururan/Graphit/Gas. An sieben hierfür geeigneten Hüllrohren mit Längs-, Quer- und Pfeilrippen wurden mittlere und örtliche Wärmeübergangszahlen und mittlere Druckverlustbeiwerte gemessen. Die Untersuchungen erfolgten bezüglich Kühlgas, Druck, Temperatur, Massenstrom und Heizleistung unter Reaktorbedingungenim Hochdruckgaskreislauf des Instituts für Reaktorbauelemente. Die Aufteilung des Kühlgasmassenstromes in einen turbulenten inneren und äußeren Teilstrom wurde theoretisch berechnet und experimentell überprüft. Zur Beurteilung der einzelnen Rippenformen wurden in einer Rechnung Wärmeleistung, Gebläseleistung, Uran-, Rippenrohr- und Gastemperatur für einen vereinfachten Reaktorkühlkanal mit Originalabmessungen bestimmt. Die höchste Wärmeleistung wird unter Einhaltung aller Grenzen erreicht, wenn das Uranrohr außen und innen mit Pfeilrippenrohren umhüllt wird. Eine nur 11 % geringere Wärmeleistung wird erzielt, wenn das Uranrohr innen mit einem Längsrippenrohr umhüllt wird. Berücksichtigt man, daß beim Längsrippenrohr die erforderliche Gebläseleistung niedriger und die Herstellungskosten bedeutend geringer sind als beim Pfeilrippenrohr, so erkennt man, daß auch Längsrippenrohre als Innenhüllrohre durchaus geeignet sind

Fabrication of bismuth nanowires with a silver nanocrystal shadowmask

We fabricated bismuth (Bi) nanowires with low energy electron beam lithography using silver (Ag) nanocrystal shadowmasks and a subsequent chlorine reactive ion etching. Submicron-size metal contacts on the single Bi nanowire were successfully prepared by in situ focused ion beam metal deposition for transport measurements. The temperature dependent resistance measurements on the 50 nm wide Bi nanowires showed that the resistance increased with decreasing temperature, which is characteristic of semiconductors and insulators

The Willingness to Pay for Job Amenities: Evidence from Mothers' Return to Work

This study is the first to estimate mother's marginal willingness to pay (MWP) for job amenities directly. Its identification strategy relies on German maternity leave length. The key aspect of the maternal leave framework is that mothers can decide whether and when to return to their guaranteed job. Thus, in contrast to previous studies that analyze the job search of employed workers, this framework allows us to overcome the limitation of not observing the wage/amenity offer process. A theoretical model of the leave length decision is derived from a random utility approach. Using data from the German Socio-Economic Panel and the Qualification and Career Survey, this model is estimated by a discrete duration method. The MWP for amenities can be inferred through the estimated elasticities of the leave length with respect to the amenities and the wage. The results provide evidence that mothers are willing to sacrifice a significant fraction of their wage to reduce hazards (22%) and to enjoy a flexible working schedule (36-56%)

Women's job quality across family life stages: An analysis of female employees across 27 European countries

There is little empirical evidence on how working conditions affect women’s employment and fertility choices, despite a number of studies on the impact of individual-level and institutional factors. The article addresses this gap by examining how family life stages are related to particular aspects of job quality among employed women in 27 European countries. The central argument of the analysis is that high-quality jobs are conducive to both transitions to motherhood and employment after childbirth as women select into these roles. Accordingly, mothers of young children, if employed, are expected to have relatively better quality jobs. Four dimensions of job quality are considered: job security, career progression, working time and intrinsic job quality. The results indicate that mothers with young children are more likely to hold high-quality jobs than women at other life stages with respect to working time quality and job security, but with some variation across countries for job security. The findings highlight the importance of high-quality jobs for women’s fertility decisions and labour market attachment after childbirth, with implications for European employment policy

Intra-Household Work Timing: The Effect on Joint Activities and the Demand for Child Care

This study examines whether couples time their work hours and how this work timing influences child care demand and the time that spouses jointly spend on leisure, household chores, and child care. By using an innovative matching strategy, this study identifies the timing of work hours that cannot be explained by factors other than the partners' potential to communicate about the timing of their work. The main findings are that couples with children create less overlap in their work times and this effect is more pronounced the younger the children. We find evidence for a togetherness preference of spouses, but only for childless couples. Work timing also influences the joint time that is spent on household chores, but the effect is small. Finally, work timing behaviour affects the demand for informal child care, but not the demand for formal child care

Pregnancy postponement and childlessness leads to chronic hypervascularity of the breasts and cancer risk

Epidemiologists have established that women with small families, and particularly nulliparae, are prone to develop breast cancer later in life. We report that physiological mammary hypervascularity may be an intermediate reason against the background that breast-core vascularity is normal in pregnancy but pathological in the vascularisation of cancer. We examined breast ‘core’ vascularity in nulliparae during their potential reproductive life and in parous women after their last birth but before their menopause. Fifty clinically normal pre-menopausal non-pregnant women (100 breasts) were studied daily for one ‘luteal positive’ menstrual cycle. Their parity history varied from zero to five babies. Under controlled domestic conditions each wore a special electronic thermometric bra to automatically record breast ‘core’ temperature changes as a measure of mammary tissue blood flow. In the nulliparae there was a rise of breast vascularity throughout reproductive life. In the parous women, a year or so after each birth, breast vascularity was reset at a lower level than before the pregnancy; thereafter, as in nulliparae, there was progressive increase in mammary vascularity until the menopause

The pains of desistance

Desistance is generally presented in a positive light, with themes of ‘making good’ and generativity recurring in the literature. This article reports on two qualitative studies exploring the desistance journeys of two different groups of ex-offenders, drawing attention to the pains of this process. It examines the possible consequences of these ‘pains of desistance’ and how they are linked to three spheres of desistance: act-desistance; identity desistance; and relational desistance. The attempt to achieve act-desistance often led to the pain of isolation for our interviewees, while the clash between the need to achieve identity desistance and a lack of relational desistance (especially on the meso- and macro-levels) meant that they suffered the pain of goal failure. The pains of isolation and goal failure combined to lead to the further pain of hopelessness. Those interviewed were indeed ‘going straight’, but taking this path led many to a limited and often diminished life

Capacitive energy storage from -50 to 100 °C using an ionic liquid electrolyte

Relying on redox reactions, most batteries are limited in their ability to operate at very low or very high temperatures. While performance of electrochemical capacitors is less dependent on the temperature, present-day devices still cannot cover the entire range needed for automotive and electronics applications under a variety of environmental conditions. We show that the right combination of the exohedral nanostructured carbon (nanotubes and onions) electrode and a eutectic mixture of ionic liquids can dramatically extend the temperature range of electrical energy storage, thus defying the conventional wisdom that ionic liquids can only be used as electrolytes above room temperature. We demonstrate electrical double layer capacitors able to operate from -50 to 100 °C over a wide voltage window (up to 3.7 V) and at very high charge/discharge rates of up to 20 V/s