Denken in Kreisläufen:Lernerperspektiven zum Entwicklungszyklus von Blütenpflanzen

In unserer vergleichenden Querschnittstudie haben wir die Vorstellungen zum pflanzlichen Entwicklungszyklus von Schülerinnen und Schülern unterschiedlicher Schulstufen (Jgst. 1, 6, 8) sowie von Studierenden erhoben. Im Rahmen leitfadenstrukturierter Einzelinterviews sollten unterschiedliche Entwicklungsstadien einer einjährigen Blütenpflanze geordnet und das Vorgehen begründet werden. Zusätzlich wurden ergänzende Fragen zur Herkunft von Pflanzen und Samen gestellt. Die Ergebnisse der Studie zeigen, dass die meisten Probanden Schwierigkeiten hatten, die pflanzliche Entwicklung als Zyklus bzw. Spirale zu verstehen. Dies ließ sich nicht nur an der gestellten Reihenfolge, sondern vor allem an den Begründungen für die gewählte Reihe erkennen. Die Mehrheit der Untersuchten – auch der Erwachsenen – verfügt demnach nicht über ein tragfähiges Konzept zum pflanzlichen Entwicklungszyklus. Einen entscheidenden Einfluss zur Entwicklung eines tragfähigen Konzepts hat die eigene Vorerfahrung mit Säen von Samen: Es besteht ein hochsignifikanter Zusammenhang zwischen eigenen Erfahrungen mit dem Aussäen und dem Stellen der Reihe. Dies spricht für einen erfahrungsbasierten Ansatz als Ausgangspunkt für erfolgreichen Unterricht

Expense and benefit of neoadjuvant treatment in squamous cell carcinoma of the esophagus

BACKGROUND: The effectiveness of neoadjuvant treatment (NT) prior to resection of squamous cell carcinoma of the esophagus (SCCE) in terms of prolonged survival has not been proven by randomized trials. Facing considerable financial expenses and with concerns regarding the consumption of the patient's remaining survival time, this study aims to provide rationales for pretreating resection candidates. METHODS: From March 1986 to March 1999, patients undergoing resection for SCCE were documented prospectively. Since 1989, NT was offered to patients with mainly upper and middle third T3 or T4 tumors or T2 N1 stage who were fit for esophagectomy. Until 1993, NT consisted of chemotherapy. Since that time chemoradiation has also been applied. The parameters for expense and benefit of NT are costs, pretreatment time required, postoperative morbidity and mortality, clinical and histopathological response, and actuarial survival. RESULTS: Two hundred and three patients were treated, 170 by surgery alone and 33 by NT + surgery. Postoperative morbidity and mortality were 52% to 30% and 12% to 6%, respectively (p = n.s.). The response to NT was detected in 23 patients (70%). In 11 instances (33%), the primary tumor lesion was histopathologically eradicated. Survival following NT + surgery was significantly prolonged in node-positive patients with a median survival of 12 months to 19 months (p = 0.0193). The average pretreatment time was 113 ± 43 days, and reimbursement for NT to the hospital amounted to Euro 9.834. CONCLUSIONS: NT did not increase morbidity and mortality. Expenses for pretreatment, particularly time and costs, are considerable. However, taking into account that the results are derived from a non-randomized study, patients with regionally advanced tumor stages seem to benefit, as seen by their prolonged survival

Where Brain, Body and World Collide

The production cross section of electrons from semileptonic decays of beauty hadrons was measured at mid-rapidity (|y| < 0.8) in the transverse momentum range 1 < pt < 8 Gev/c with the ALICE experiment at the CERN LHC in pp collisions at a center of mass energy sqrt{s} = 7 TeV using an integrated luminosity of 2.2 nb^{-1}. Electrons from beauty hadron decays were selected based on the displacement of the decay vertex from the collision vertex. A perturbative QCD calculation agrees with the measurement within uncertainties. The data were extrapolated to the full phase space to determine the total cross section for the production of beauty quark-antiquark pairs

The Kobresia pygmaea ecosystem of the Tibetan highlands – Origin, functioning and degradation of the world's largest pastoral alpine ecosystem: Kobresia pastures of Tibet

With 450,000 km2 Kobresia (syn. Carex) pygmaea dominated pastures in the eastern Tibetan highlands are the world's largest pastoral alpine ecosystem forming a durable turf cover at 3000–6000 m a.s.l. Kobresia's resilience and competitiveness is based on dwarf habit, predominantly below-ground allocation of photo assimilates, mixture of seed production and clonal growth, and high genetic diversity. Kobresia growth is co-limited by livestock-mediated nutrient withdrawal and, in the drier parts of the plateau, low rainfall during the short and cold growing season. Overstocking has caused pasture degradation and soil deterioration over most parts of the Tibetan highlands and is the basis for this man-made ecosystem. Natural autocyclic processes of turf destruction and soil erosion are initiated through polygonal turf cover cracking, and accelerated by soil-dwelling endemic small mammals in the absence of predators. The major consequences of vegetation cover deterioration include the release of large amounts of C, earlier diurnal formation of clouds, and decreased surface temperatures. These effects decrease the recovery potential of Kobresia pastures and make them more vulnerable to anthropogenic pressure and climate change. Traditional migratory rangeland management was sustainable over millennia, and possibly still offers the best strategy to conserve and possibly increase C stocks in the Kobresia turf

The Kobresia pygmaea ecosystem of the Tibetan highlands – Origin, functioning and degradation of the world's largest pastoral alpine ecosystem

Kobresia pastures in the eastern Tibetan highlands occupy 450000 km2 and form the world’s largest pastoral alpine ecosystem. The main constituent is an endemic dwarf sedge, Kobresia pygmaea, which forms a lawn with a durable turf cover anchored by a felty root mat, and occurs from 3000 m to nearly 6000 m a.s.l. The existence and functioning of this unique ecosystem and its turf cover have not yet been explained against a backdrop of natural and anthropogenic factors, and thus its origin, drivers, vulnerability or resilience remain largely unknown. Here we present a review on ecosystem diversity, reproduction and ecology of the key species, pasture health, cycles of carbon (C), water and nutrients, and on the paleo-environment. The methods employed include molecular analysis, grazing exclusion, measurements with micro-lysimeters and gas exchange chambers, 13C and 15N labelling, eddy-covariance flux measurements, remote sensing and atmospheric modelling. The following combination of traits makes Kobresia pygmaea resilient and highly competitive: dwarf habit, predominantly below-ground allocation of photo assimilates, mixed reproduction strategy with both seed production and clonal growth, and high genetic diversity. Growth of Kobresia pastures is co-limited by low rainfall during the short growing season and livestock-mediated nutrient withdrawal. Overstocking has caused pasture degradation and soil deterioration, yet the extent remains debated. In addition, we newly describe natural autocyclic processes of turf erosion initiated through polygonal cracking of the turf cover, and accelerated by soil-dwelling endemic small mammals. The major consequences of the deterioration of the vegetation cover and its turf include: (1) the release of large amounts of C and nutrients and (2) earlier diurnal formation of clouds resulting in (3) decreased surface temperatures with (4) likely consequences for atmospheric circulation on large regional and, possibly global, scales. Paleo-environmental reconstruction, in conjunction with grazing experiments, suggests that the present grazing lawns of Kobresia pygmaea are synanthropic and may have existed since the onset of pastoralism. The traditional migratory rangeland management was sustainable over millennia and possibly still offers the best strategy to conserve, and possibly increase, the C stocks in the Kobresia turf, as well as its importance for climate regulation

Confidence and perceived competence of preservice teachers to implement biodiversity education in primary schools—four comparative case studies from Europe

This multinational research study was carried out between 2004 and 2006 in four teacher education institutions in Cyprus, England, Switzerland, and Germany. With the help of a written questionnaire, the confidence and perceived competence of preservice primary teachers (N = 690) to deliver biodiversity education in school were investigated. Data were triangulated with findings from a previous stage of the overall research project. Study participants' confidence to carry out certain outdoor activities in school increased with the number of similar experiences they had during their own secondary school education, and the more personal classroom experiences they had during their teacher education. A sound knowledge of local wild organisms strongly added to their confidence. However, preservice teachers' perceived competence, and thus motivation to implement biodiversity education later on in school, was related even more strongly to the extent of preparation they had received during their teacher education. The results indicate that teacher education programmes that focus exclusively on filling (biodiversity) knowledge gaps might fail to raise confidence and competence in their students to carry out biodiversity education in school. Programmes that have a higher possibility of attaining effectiveness in biodiversity education seek to strike a balance between background knowledge development, pedagogical content knowledge, and opportunities during teaching practice that leads to experiential gains in enacting meaningful activity sequences and engaging students in holistic educational innovations. Within such programmes, it would be fruitful to further explore the relationship between confidence, perceived competence, and actual teaching performance