Standardisierung im E-Learning oder Vom schleichenden Untergang der Didaktik

Die Autoren diskutieren die Vor- und Nachteile einer Standardisierung von E-Learning Formaten. Ähnlich wie der Standard Rich Text zum Datenaustausch von Textdateien standardisiert wurde, können Lerneinheiten (learning objects) als standardisierte, wieder verwendbare Objekte gespeichert und vielseitig eingesetzt werden. Eine Möglichkeit besteht im Ablegen in zentralen Pools in Hochschulen, wo sie in unterschiedliche Plattformen eingebunden werden. Die Autoren stellen in Frage, ob hierbei wegen der Fokussierung auf Effizienz und Atomisierung von Information mediendidaktische Überlegungen vernachlässigt werden und der Begriff des Wissens reduziert wird auf abrufbare Informationen. In einem Exkurs verdeutlichen sie die Problematik am Beispiel von Studierenden der Medizin, die über ein gutes Faktenwissen verfügen, häufig aber Schwierigkeiten bei der Anwendung haben. In diesem Zusammenhang stellen sie die Kliniksimulation "Prometheus" vor, die wegen ihrer Handlungsorientierung die Studierenden zur Expertise anleiten soll

Chemical composition of modern and fossil Hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation: 1. major and minor element variation [Discussion paper]

Bioapatite in mammalian teeth is readily preserved in continental sediments and represents a very important archive for reconstructions of environment and climate evolution. This project intends to provide a detailed data base of major, minor and trace element and isotope tracers for tooth apatite using a variety of microanalytical techniques. The aim is to identify specific sedimentary environments and to improve our understanding on the interaction between internal metabolic processes during tooth formation and external nutritional control and secondary alteration effects. Here, we use the electron microprobe, to determine the major and minor element contents of fossil and modern molar enamel, cement and dentin from hippopotamids. Most of the studied specimens are from different ecosystems in Eastern Africa, representing modern and fossil lakustrine (Lake Kikorongo, Lake Albert, and Lake Malawi) and modern fluvial environments of the Nile River system. Secondary alteration effects in particular FeO, MnO, SO3 and F concentrations, which are 2 to 10 times higher in fossil than in modern enamel; secondary enrichments in fossil dentin and cement are even higher. In modern and fossil enamel, along sections perpendicular to the enamel-dentin junction (EDJ) or along cervix-apex profiles, P2O5 and CaO contents and the CaO/P2O5 ratios are very constant (StdDev ~1 %). Linear regression analysis reveals very tight control of the MgO (R2∼0.6), Na2O and Cl variation (for both R2>0.84) along EDJ-outer enamel rim profiles, despite large concentration variations (40 % to 300 %) across the enamel. These minor elements show well defined distribution patterns in enamel, similar in all specimens regardless of their age and origin, as the concentration of MgO and Na2O decrease from the enamel-dentin junction (EDJ) towards the outer rim, whereas Cl displays the opposite variation. Fossil enamel from hippopotamids which lived in the saline Lake Kikorongo have a much higher MgO/Na2O ratio (∼1.11) than those from the Neogene fossils of Lake Albert (MgO/Na2O∼0.4), which was a large fresh water lake like those in the western Branch of the East African Rift System today. Similarly, the MgO/Na2O ratio in modern enamel from the White Nile River (∼0.36), which has a Precambrian catchment of dominantly granite and gneisses and passes through several saline zones, is higher than that from the Blue Nile River, whose catchment is the Neogene volcanic Ethiopian Highland (MgO/Na2O∼0.22). Thus, particularly MgO/Na2O might be a sensitive fingerprint for environments where river and lake water have suffered strong evaporation. Enamel formation in mammals takes place at successive mineralization fronts within a confined chamber where ion and molecule transport is controlled by the surrounding enamel organ. During the secretion and maturation phases the epithelium generates different fluid composition, which in principle, should determine the final composition of enamel apatite. This is supported by co-linear relationships between MgO, Cl and Na2O which can be interpreted as binary mixing lines. However, if maturation starts after secretion is completed the observed element distribution can only be explained by recrystallization of existing and addition of new apatite during maturation. Perhaps the initial enamel crystallites precipitating during secretion and the newly formed bioapatite crystals during maturation equilibrate with a continuously evolving fluid. During crystallization of bioapatite the enamel fluid becomes continuously depleted in MgO and Na2O, but enriched in Cl which results in the formation of MgO, and Na2O-rich, but Cl-poor bioapatite near the EDJ and MgO- and Na2O-poor, but Cl-rich bioapatite at the outer enamel rim. The linkage between lake and river water composition, bioavailability of elements for plants, animal nutrition and tooth formation is complex and multifaceted. The quality and limits of the MgO/Na2O and other proxies have to be established with systematic investigations relating chemical distribution patterns to sedimentary environment and to growth structures developing as secretion and maturation proceed during tooth formation

Approach for calibrated measurement of the frequency response for characterization of compliant interface elements on vibration test benches

In vibration tests, the behavior of the structure depends on its mechanical boundary conditions, which are represented in physical tests by connecting elements with mechanical properties. Adjustable impedance elements are machine elements fulfilling the task of an adjustable connection on a vibration test bench and therefore represent a variety of properties. Their mechanical properties must be known over wider ranges than comparable compliant structures tested in the literature. This paper is dedicated to vibration testing of the adjustable impedance elements themselves, taking the influences of fixtures and measuring devices of the test bench into account. Different approaches for measuring the frequency response functions are applied to freely vibrating masses at a hydraulic and an electrodynamic test bench. Mass cancellation and the frequency-dependent measurement systems function have shown their usefulness in characterizing the biodynamic response of hand–arm models before. This measurement method is extended to be transferable to machine elements to obtain reliable results under a wider range of test conditions. The necessity for dynamically calibrated measurement of the frequency response functions is demonstrated for different free vibration masses and for two compliant elements on two different test benches to provide results over a wide range of test conditions

Chinesische Einflüsse auf die Lexik der Bahasa Indonesia

Der Autor zeichnet den chinesischen Einfluss auf die Bahasa Indonesia nach. Er listet chinesische Lehnwörter im heutigen Indonesisch auf, gibt Etymologien an und erörtert ihren Assimilationsprozess. Die meisten dieser Entlehnungen haben ihren Ursprung nicht in P'u-t'ung-hua, sondern in den Dialekten der der südöstlichen Küstenprovinzen Chinas: Chekiang, Fukien und Kwangtung. Vor allem der Dialekt von Süd-Fukien, auch bekannt als Amoy-Chinesisch, hatte großen Einfluss auf die Sprachgewohnheiten der malaiisch sprechenden chinesischen Siedler auf dem indonesischen Archipel. Bahasa Indonesia hat viele dieser Wörter übernommen, die heute in der gesprochenen Sprache der Republik weit verbreitet sind. der heutigen gesprochenen Sprache der Republik Indonesien.The author traces Chinese influence on the Bahasa Indonesia. He lists Chinese loanwords in present-day Indonesian giving etymologies and discussing their assimilation process. The majority of these loans have their origins not in P’u-t’ung-hua but in the dialects of the South Eastern coastal provinces of China: Chekiang, Fukien and Kwangtung. Especially the dialect of Southern Fukien, also known as Amoy Chinese, had great impact on the language habit of Malay-spenking Chinese settlers in the Indonesian archipelago. Bahasa Indonesia has absorbed a lot of these words which are now being widely used in the present-day spoken language of the Republic of Indonesia

Chemical composition of modern and fossil hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation : part 2, alkaline earth elements as tracers of watershed hydrochemistry and provenance

This study demonstrates that alkaline earth elements in enamel of hippopotamids, in particular Ba and Sr, are tracers for water provenance and hydrochemistry in terrestrial settings. The studied specimens are permanent premolar and molar teeth found in modern and fossil lacustrine sediments of the Western Branch of the East African Rift system (Lake Kikorongo, Lake Albert, and Lake Malawi) and from modern fluvial environments of the Nile River. Concentrations in enamel vary by two orders of magnitude for Ba (120–9336 μg g−1) as well as for Sr (9–2150 μg g−1). The variations are partially induced during post-mortem alteration and during amelogenesis, but the major contribution originates ultimately from the variable water chemistry in the habitats of the hippopotamids which is controlled by the lithologies and weathering processes in the watershed areas. Amelogenesis causes a distinct distribution of MgO, Ba and Sr in modern and fossil enamel, in that element concentrations increase along profiles from the outer rim towards the enamel–dentin junction by a factor of 1.3–1.9. These elements are well correlated in single specimens, thus suggesting that their distribution is determined by a common, single process, which can be described by closed system Rayleigh crystallization of bioapatite in vivo. Enamel from most hippopotamid specimens has Sr/Ca and Ba/Ca which are typical for herbivores. However, Ba/Sr ranges from 0.1 to 3 and varies on spatial and temporal scales. Thus, Sr concentrations and Ba/Sr in enamel differentiate between habitats having basaltic mantle rocks or Archean crustal rocks as the ultimate sources of Sr and Ba. This provenance signal is modulated by climate change. In Miocene to Pleistocene enamel from the Lake Albert region, Ba/Sr decreases systematically with time from 2 to 0.5. This trend can be correlated with changes in climate from humid to arid, in vegetation from C3 to C4 biomass as well as with increasing evaporation of the lake water. The most plausible explanation is that Ba mobility decreased with increasing aridification due to preferential deposition with clay and Fe-oxide-hydroxide or barite on the watershed of Lake Albert

Spatial decoupling of agricultural production and consumption: Quantifying dependences of countries on food imports due to domestic land and water constraints

In our globalizing world, the geographical locations of food production and consumption are becoming increasingly disconnected, which increases reliance on external resources and their trade. We quantified to what extent water and land constraints limit countries' capacities, at present and by 2050, to produce on their own territory the crop products that they currently import from other countries. Scenarios of increased crop productivity and water use, cropland expansion (excluding areas prioritized for other uses) and population change are accounted for. We found that currently 16% of the world population use the opportunities of international trade to cover their demand for agricultural products. Population change may strongly increase the number of people depending on ex situ land and water resources up to about 5.2 billion (51% of world population) in the SRES A2r scenario. International trade will thus have to intensify if population growth is not accompanied by dietary change towards less resource-intensive products, by cropland expansion, or by productivity improvements, mainly in Africa and the Middle East. Up to 1.3 billion people may be at risk of food insecurity in 2050 in present low-income economies (mainly in Africa), if their economic development does not allow them to afford productivity increases, cropland expansion and/or imports from other countries

Simulation modularer Produktarchitekturen durch modellbasierte Konfiguration

Im Zuge der Globalisierung sehen sich produzierende Unternehmen mit einem kontinuierlich anwachsenden Wettbewerbsdruck konfrontiert. Aufgrund dessen sehen sich viele Marktakteure zu einer intensivierten Spezialisierung gezwungen, um auf kunden-individuelle Anforderungen eingehen zu können. Einen möglichen Lösungsansatz zur Bewältigung dieser Herausforderung bietet der Ansatz der Modularisierung. Hier wird allerdings nicht konkret ein Baukasten definiert, vielmehr werden verschiedene Alternativen generiert. Die Entscheidung, welcher Baukasten schlussendlich implementiert wird, fällt meist aufgrund einiger weniger Einflussfaktoren sowie maßgeblich durch Expertenentscheidungen. An dieser Stelle setzt der vorliegende Beitrag an. Um ein quantifizierbares und ganzheitliches Kriterium zur Unter-stützung der Auswahl modularer Baukastensysteme zu bieten, wird eine multifaktorielle Simulation eingesetzt. Einer der maßgeblichen Aspekte derer ist die beidseitige Inbezugnahme von sowohl Kunden- als auch Unternehmensperspektive. Dies wird v.a. durch die Verwendung eines dynamischen Produktkonfigurationssystems ermöglicht. Um die zugrundeliegenden, teils komplexen Produktarchitekturen datentechnisch konsistent und pflegbar zu halten, wird zusätzlich der Einsatz einer modellbasierten Datenstruktur aufgezeigt. Die Verwendung des Model-Based Systems-Engineering (MBSE) Ansatzes hilf dabei, die vielschichtigen Zusammenhänge des Modulbaukastens in einer konsistenten und maschinenlesbaren Form auszudrücken. Somit kann das Konfigurationssystem produktunabhängig auf die Ontologie der zugrundeliegenden Datenstruktur zugreifen. Für die Baukastensimulation wird dieses Konfigurationssystem rekursiv für mehrere Kundenanfragen und alternative Baukästen eingesetzt, um anschließend mittels eines geometrisch-mathematischen Algorithmus ein multi-dimensionales Entscheidungskriterium hinsichtlich der Baukasten-performance zu generieren