Methodische Beiträge zu Vogelstimmenexkursionen für Anfänger

Im Sommersemester 1987 nahmen etwa 100 Studierende an Vogelstimmenexkursionen für Anfänger teil. Dabei wurden in Kleingruppenorganisation unter Anleitung während zweistündiger Exkursionen Artdiagnosen von häufig gehörten Vogelgesängen erstellt und diese anschließend zu einem dichotomen Bestimmungsschlüssel verarbeitet. Der Lernzuwachs während der Exkursion wurde durch gezielte Befragungen, der Lernerfolg durch einen abschließenden Test erkundet. Die Teilnehmer konnten am Schluß im Durchschnitt zwei von drei gehörten Vogelgesängen aus dem Gedächtnis bestimmen. Der selbst erarbeitete Schlüssel war nur bei schwierigen Arten hilfreich, seine Erstellung dürfte aber den Lernprozeß gefördert haben.In summer 1987, about 100 students at Osnabrück University (Lower Saxony, Fed. Repulic of Germany) participated in a course devoted to the study of common bird songs. Sm all groups of up to 15 persons worked in the field during aseries of 2 hour excursions and were supervised by weil educated ornithologists. The aim of each excursion was to define a number of bird songs by species diagnoses after a given pattern. Subsequently, a dichotomie key was constructed from these diagnoses. The learning progress during the excursions was assessed by informal questioning. The final learning success was measured by a formal test. Participants were able to determine 2 out of 3 bird songs just by memory. The key was helpful with difficult species. Working with speciss diagnoses and construction of the key is presumed to have speeded up the learning process

Paid to quit

__Abstract__ Inspired by a recent observation about an online retail company, this paper explains why a firm may find it optimal to offer an exit bonus to recent hires so as to induce self-selection. We study a double adverse selection problem, in which the principal can neither observe agents’ commitment to the job nor their intrinsic motivation. A steep wage-tenure profile deters uncommitted agents from applying. An exit bonus can stimulate that –among the committed agents– those who discovered that they are not intrinsically motivated for the job discontinue employment with the principal. Our key findings are that offering an exit bonus increases profits when the first adverse selection problem is sufficiently severe compared to the second and that the exit bonus needs to come as a surprise for the agents in order to function well

The Web Data Commons Structured Data Extraction

More and more websites annotate their content using different markup formats. These annotations involve a large number of topics such as persons, events, products, hotels, organizations and cities. The purpose of embedding structured data in HTML pages is to make the content of those pages understandable to web applications. In this way, the retrieval and integration of data deriving from different web pages is greatly facilitated. The presented poster gives an overview of the Web Data Commons - structured data project for the year 2016. The Web Data Commons project extracts structured data from the web corpus provided by Common Crawl, the largest public web corpus, and offers the extracted data for public download. In order to process these huge amounts of data, Web Data Commons builds upon its Extraction Framework and the Amazon Web Services

Century-scale trends and seasonality in pH and temperature for shallow zones of the Bering Sea

No records exist to evaluate long-term pH dynamics in high-latitude oceans, which have the greatest probability of rapid acidification from anthropogenic CO2 emissions. We reconstructed both seasonal variability and anthropogenic change in seawater pH and temperature by using laser ablation high-resolution 2D images of stable boron isotopes (δ11B) on a long-lived coralline alga that grew continuously through the 20th century. Analyses focused on four multiannual growth segments. We show a long-term decline of 0.08 ± 0.01 pH units between the end of the 19th and 20th century, which is consistent with atmospheric CO2 records. Additionally, a strong seasonal cycle (∼0.22 pH units) is observed and interpreted as episodic annual pH increases caused by the consumption of CO2 during strong algal (kelp) growth in spring and summer. The rate of acidification intensifies from –0.006 ± 0.007 pH units per decade (between 1920s and 1960s) to –0.019 ± 0.009 pH units per decade (between 1960s and 1990s), and the episodic pH increases show a continuous shift to earlier times of the year throughout the centennial record. This is indicative of ecosystem shifts in shallow water algal productivity in this high-latitude habitat resulting from warming and acidification

Phase Field Modeling of Fast Crack Propagation

We present a continuum theory which predicts the steady state propagation of cracks. The theory overcomes the usual problem of a finite time cusp singularity of the Grinfeld instability by the inclusion of elastodynamic effects which restore selection of the steady state tip radius and velocity. We developed a phase field model for elastically induced phase transitions; in the limit of small or vanishing elastic coefficients in the new phase, fracture can be studied. The simulations confirm analytical predictions for fast crack propagation.Comment: 5 pages, 11 figure

Using Different Data Sources for New Findings in Visualization of Highly Detailed Urban Data

Measurement of infrastructure has highly evolved in the last years. Scanning systems became more precise and many methods were found to add and improve content created for the analysis of buildings and landscapes. Therefore the pure amount of data increased significantly and new algorithms had to be found to visualize these data for further exploration. Additionally many data types and formats originate from different sources, such as Dibits hybrid scanning systems delivering laser-scanned point clouds and photogrammetric texture images. These are usually analyzed separately. Combinations of different types of data are not widely used but might lead to new findings and improved data exploration. In our work we use different data formats like meshes, unprocessed point clouds and polylines in tunnel visualization to give experts a tool to explore existing datasets in depth with a wide variety of possibilities. The diverse creation of datasets leads to new challenges for preprocessing, out-of-core rendering and efficient fusion of this varying information. Interactive analysis of different formats of data also has to have several approaches and is usually difficult to merge into one application. In this paper we describe the challenges and advantages of the combination of different data sources in tunnel visualization. Large meshes with high resolution textures are merged with dense point clouds and additional measurements. Interactive analysis can also create additional information, which has to be integrated precisely to prevent errors and misinterpretation. We present the basic algorithms used for heterogeneous data formats, how we combined them and what advantages are created by our methods. Several datasets evolve over time. This dynamic is also considered in our visualization and analysis methods to enable change detection. For tunnel monitoring this allows to investigate the entire history of the construction project and helps to make better informed decisions in the preceding construction phases or for repairs. Several methods are merged like the data they are based on enabling new ways of data exploration. In analyzing this new approach to look at heterogeneous datasets we come to the conclusion that the combination of different sources leads to a better solution than the sum of its parts

Thermoelectric performance of classical topological insulator nanowires

There is currently substantial effort being invested into creating efficient thermoelectric nanowires based on topological insulator chalcogenide-type materials. A key premise of these efforts is the assumption that the generally good thermoelectric properties that these materials exhibit in bulk form will translate into similarly good or even better thermoelectric performance of the same materials in nanowire form. Here, we calculate thermoelectric performance of topological insulator nanowires based on Bi2Te3, Sb2Te3 and Bi2Se3 as a function of diameter and Fermi level. We show that the thermoelectric performance of topological insulator nanowires does not derive from the properties of the bulk material in a straightforward way. For all investigated systems the competition between surface states and bulk channel causes a significant modification of the thermoelectric transport coefficients if the diameter is reduced into the sub-10 um range. Key aspects are that the surface and bulk states are optimized at different Fermi levels or have different polarity as well as the high surface to volume ratio of the nanowires. This limits the maximum thermoelectric performance of topological insulator nanowires and thus their application in efficient thermoelectric devices

Paid to Quit

Inspired by a recent observation about an online retail company, this paper explains why a frm may fnd it optimal to ofer an exit bonus to recent hires so as to induce self-selection. We study a double adverse selection problem, in which the principal can neither observe agents’ commitment to the job nor their intrinsic motivation. A steep wage-tenure profle deters uncommitted agents from applying. An exit bonus can stimulate that—among the committed agents—those who discovered that they are not intrinsically motivated for the job discontinue employment with the principal. Our key fndings are that ofering an exit bonus increases profts when the frst adverse selection problem is sufciently severe compared to the second and that the exit bonus needs to come as a surprise for the agents in order to function well

Decreased renal function and associated factors in cities, towns and rural areas of Tanzania: a community-based population survey.

OBJECTIVES: Data on renal dysfunction in sub-Saharan Africa, comparing urban and rural areas, have not yet been reported. Therefore, we aimed to determine the distribution of low estimated glomerular filtration rates (eGFRs) in urban and rural Tanzania, to describe factors associated with low eGFR and to quantify fractions attributable to common risk factors. METHODS: We conducted a community-based survey of 1095 randomly selected Tanzanian adults (≥18 years). A structured questionnaire and examinations were used to document sociodemographic characteristics, diet, physical activity, anthropomorphic measurements and blood pressure. Blood tests were performed for HIV infection, diabetes mellitus and creatinine. eGFR was calculated using two equations recommended for African adults. RESULTS: Serum creatinine was available for 1043 participants: 170 in Mwanza city, 326 in district towns and 547 in rural areas. Mean age was 35.5 years and 54% were females. The prevalence of eGFR < 60 ml/min/1.73 m(2) in these 3 strata was 2.3% (95% CI = 0.8-6.6%), 7.5% (4.7-11.8%) and 7.4% (5.1-10.6%), respectively. When age standardised to the WHO world population, prevalences were 3.8%, 10.1% and 8.1%. Factors associated with low eGFR included district town residence, older age, greater wealth, less physical activity and hypertension. Only 21% of cases with eGFR < 60 ml/min/1.73 m(2) were attributable to HIV, hypertension or diabetes. CONCLUSIONS: Decreased renal function is common in Tanzania, particularly in district towns, and unique risk factors for kidney disease may exist in this population. Population-specific strategies for prevention, early diagnosis and treatment of kidney disease are needed for Africa