3,716 research outputs found
On the psychological determinants of fertility: a panorama of concepts and approaches, and evidence from eastern Germany
In this paper we study the transition to parenthood, analyzing data from three waves of a psychological longitudinal survey from Rostock, eastern Germany. We apply hazard regressions in order to predict the timing of first births of 117 men and 124 women born in 1970 and 1971. Subjects, who were in their 20s during the 1990s, made their family decisions during the most turbulent times of societal transformation in eastern Germany following unification. We hypothesized a crucial relevance of personality traits, coping-styles, and other psychological variables for the prediction of fertility in this context. Results for men show that dispositional self-actualization and internal control-styles as well as a tendency to social withdrawal decrease the probability of fatherhood. For women, dispositional emotional stability and mental health decrease the probability of motherhood, whereas a tendency toward rationalization increases it. We discuss findings in light of the gender-specific life-span development of people’s personality and control behavior.Germany (Neue Bundesländer), fertility determinants, first birth, life span, psychology
Price indices and unit value indices in German foreign trade statistics
There is presently an international discussion among statistical institutes, reserve banks etc. about the feasibility of replacing true price indices of exports and imports by unit value indices. For the very few countries, such as Germany, providing both indices on a monthly basis this would mean to give up a (costly) compilation of P-indices. The paper shows that this would be unwise. It aims at exploring the still not well understood methodological differences of both types of indices, and it is also reporting some empirical results of a research project in cooperation with the German Bundesbank.unit value indices; foreign trade statistics
The Interpretation of Unit Value Indices - Unit Value Indices as Proxies for Price Indices
The unit value index (UVI) as compiled in Germany for exports and imports is compared with two other indices, viz. an index of Drobisch which unfortunately is likewise known as "unit value index" and the "normal" Laspeyres price index (PI) of exports and imports. The UVI may be viewed as a Paasche index compiled in two stages where unit values instead of prices are used in the low level aggregation stage. Unit values are average prices referring to an ag-gregate of (more or less homogeneous) commodities. The focus of the paper is on the decom-position of the discrepancy between UVIs and PIs (the "unit value bias") into a (well known) Laspeyres (or substitution) effect or "L-effect" and a structural component or "S-effect" due to substituting unit values for prices. It is shown that amount and sign of S depends on the corre-lation between the change of quantities of those goods that are included in the aggregate and their respective base period prices. By contrast to L the correlation between quantity and price movement is not relevant for S. This paper is a revised version of my contribution to the 11th Ottawa Group Meeting in Neuchatel (Switzerland) 27th to 29th May 2009 http://www.ottawagroup2009.ch/Price index, unit value index, unit values, axioms, foreign trade statistics, Bortkiewicz, Drobisch.
Secondary wind dispersal enhances long-distance dispersal of an invasive species in urban road corridors
Roads contribute to habitat fragmentation and function as dispersal barriers for many organisms. At the same time many nonnative plant species are associated with road systems, a relationship that has been explained by the availability of disturbed habitats along roadsides and traffic-mediated dispersal of species. By studying secondary wind dispersal (SWD) over paved ground in an urban road corridor, we add the perspective of corridor-specific, but traffic-independent dispersal processes to the complex dispersal systems along roads. We analyzed (1) the seed shadow of an invasive tree Ailanthus altissima along a sidewalk subsequent to a strong wind and (2) the movements of painted samaras of this species released at ground level at the same site to identify the functioning of SWD. For the first experiment, we searched for samaras in the vicinity of an isolated tree three days after a strong wind. For the second experiment, we tracked the movement of the released samaras repeatedly over a period of 9–11 days, approximated probability-distance functions to the frequency distribution of samaras along the transect for different times after release, and related nearby measured wind data to changes in dispersal kernels. Single samaras from an isolated tree formed a seed shadow that extended for a distance of up to 456 m, and fragments of fruit clusters traveled up to 240 m. Forty-two percent of the sampled samaras were moved >100 m. The second experiment revealed that painted samaras released on the ground were moved up to 150 m over the pavement. Dispersal distances increased with time after seed release. A wider distribution of diaspores over the transect was significantly related to higher wind sums. Habitat shifts to safe sites for germination occurred during SWD, and different types of pavement influenced these processes. Smooth-surfaced pavement enhanced SWD, while cobbles with irregular surfaces slowed down or terminated SWD. During the observation period, 17% of released samaras accumulated in patches with a planted tree. Some were recaptured within the median strip and thus must have been lifted and moved over four lanes of heavy traffic. Our results suggest that impervious surfaces within road corridors can function as powerful avenues of wind-mediated long-distance dispersal and may counteract fragmentation of urban habitats. This also offers a functional explanation for the invasion success of Ailanthus at isolated urban sites
Where qualitative research meets demography: interdisciplinary explorations of conceptions on fatherhood in an extremely low fertility context
Recent demands to include psychological theories of decision-making and intention-formation in research on family formation coincide with calls for improving research on male fertility and fatherhood. In this paper, we address these notions and present findings from in-depth interviews with 30-year-old childless men from Eastern Germany on their desire for children. Our research is embedded in the societal situation of contemporary Eastern Germany, where birth rates have faced a historical low - the lowest in more than 10 years. We analyze fourteen interviews, using an analytical paradigm, which we derive from the contemporary social cognitive theory of intention-formation. The focus lies on the examination of male attitudes, values, motives, interests, goals, action beliefs, and self-concepts, and their connection to men´s intentions for parenthood.In conclusion, we compare our results with explanations that the Theory of Symbolic Self-Completion and the Theory of Reasoned Action give. We argue for the need to bring together psychological and sociological theorizing in this field.Germany (Neue Bundesländer), fertility decline, men, social psychology
Endangered Plants in Novel Urban Ecosystems Are Filtered by Strategy Type and Dispersal Syndrome, Not by Spatial Dependence on Natural Remnants
Understanding the contribution of cities to nature conservation is gaining increasing importance with a globally accelerating urbanization and requires insights into the mechanisms that underlie urban distribution patterns. While a considerable number of endangered plant species have been reported for cities, the spatial dependence of populations of these species on natural remnants versus anthropogenic ecosystems is critically understudied due to deficiencies in population distribution data. To which extent endangered species in anthropogenic ecosystems spatially rely on natural remnants is thus an open question. We used a unique dataset of 1,742 precisely mapped populations of 213 endangered plant species in the city of Berlin and related these point data to habitat patches that had been assigned to natural remnants, hybrid ecosystems and novel ecosystems according to the novel ecosystem approach. By applying point pattern analyses (Ripley’s K function, cross K function, cross pair correlation function) we unraveled the spatial dependence of the populations toward the different ecosystem types. Moreover, we tested how plant traits related to plant strategy and dispersal filter for species occurrence across ecosystems. Differentiating populations on anthropogenic sites revealed that populations in hybrid ecosystems spatially depended on natural remnants, but populations in novel ecosystems (i.e. more than a third of all populations) surprisingly didn’t. A conditional inference tree showed that endangered plant species in novel ecosystems are filtered for ruderal strategy type and wind dispersal syndrome, while competitive and stress-tolerant species were mainly confined to natural remnants. Our results highlight the importance of conserving natural remnants as habitats and seed sources of endangered plants. Yet novel urban ecosystems can support many populations of endangered plant species beyond the adjacency to natural remnants, with hybrid ecosystems likely acting as stepping stones. This indicates a specific contribution of urban ecosystems to biodiversity conservation. Since different filters modulate the species pools of different ecosystem types, novel urban ecosystems are not supposed to substitute fully the habitat functions of natural remnants. Our study thus highlights promising opportunities for involving the total range of urban ecosystem types into urban conservation approaches.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität BerlinBMBF, 01LC1501, BIBS-Verbund: Bridging in Biodiversity Science (BIBS
A programmable-load CMOS ring oscillator/inverter chain for propagation-delay measurements
A description is given of a test structure consisting of a combination of a ring oscillator and an inverter chain. The circuit can be used to carry out propagation delay measurements on two circuit types and under a number of load conditions. Full characterization only takes one test circuit. The elements of this structure are connected to a programmable load varying from a fan-in of 1 up to a fan-in of 15. In this way, the operating environment of the circuit can be simulated in hardware. The measurements can be carried out by means of a conventional automated digital measurement system providing AC and DC parametric measurement capabilities
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