Affordances, perceptual complexity, and the development of tool use.

Perceiving the affordance of a tool requires the integration of several complementary relationships among actor, tool, and target. Higher order affordance structures are introduced to deal with these forms of complex action from an ecological-realist point of view. The complexity of the higher order affordance structure was used to predict the difficulty of perceiving the tool function. Predictions were tested in 3 experiments involving children between 9 mo and 4 yrs old. In a classical tool use task dating back to W. K?hler (1921), a desirable target was obtained by using a hook as a tool. The relative positions of the hook and the target were systematically varied to obtain structures differing in complexity. The observed difficulty of the task was found essentially in accordance with the theoretical complexity of the higher order affordance structures involved in perceiving the tool function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Shared caregiving: Comparisons between home and child-care settings.

The experiences of 84 German toddlers (12–24 months old) who were either enrolled or not enrolled in child care were described with observational checklists from the time they woke up until they went to bed. The total amount of care experienced over the course of a weekday by 35 pairs of toddlers (1 member of each pair in child care, 1 member not) did not differ according to whether the toddlers spent time in child care. Although the child-care toddlers received lower levels of care from care providers in the centers, their mothers engaged them in more social interactions during nonworking hours than did the mothers of home-only toddlers, which suggests that families using child care provided different patterns of care than families not using child care. Child-care toddlers experienced high levels of emotional support at home, although they experienced less prompt responses to their distress signals. Mothers' ages were unrelated to the amounts of time toddlers spent with them, but older mothers initiated more proximity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Die Kopff?ule der Speisezwiebel

Ohne Zusammenfassungbedeutet mit Abbildungen     

The epidemiology of helicobacteriosis in humans; studies of the survival capacity of the microbe in food

In man suffering from diseases of the stomach and the duodenum (gastritis, ulcus, enteritis, neoplasms), Helicobacter pylori (H..pylori) is frequently detected in the mucous membrane of the stomach. Up to now the spread of this agent is not quite clear. Since the direct transmission in humans can be taken for granted, the following study was to find out whether and for how long the agent mentioned above is able to survive in selected food and whether an infection of the consumer by these contaminated food is possible. 376 samples of secretions from the udder of healthy cows and those with mastitis where tested for the presence of H. pylori along with 100 stomachs of chicken from different flocks. In no case H. pylori could be detected. H. pylori was inoculated in high concentrations into milk and some milk-products. From cooled milk samples the agent could still be reisolated after six days in a density up to 10(3) CFU/ml of milk. At room-temperature or 37 degrees C resp. the pathogen could be detected in milk for three to four days only. In yoghurt the agent kept viable for three hours only, whereas in kefir for 24 hours. Mean survival time of then hours was found in pH-neutral curd cheese. The incubation of H.pylori in sterile drip from chicken and in physiologic saline resulted in maximal survival time of at least 48 hours at room temperature. But in H.pylori-broth the number of microorganisms had dropped below the limit of detectability only after 72 hours. At refrigerator-temperature (7 degrees C) H. pylori could still be detected within these three media after 72 hours in high concentrations. In drip from chicken kept at-20 degrees C before thawing H. pylori showed a considerable survival time. After four weeks its number had only dropped by one to two log cycles, whereas in saline and in broth the agent could not be detected anymore after one week at the most. Experiments concerning tenacity showed: On culture-media with different pH-values the growth-optimum of H. pylori was between pH 6.1 and 7.3 H. pylori was suspended in melting water from chicken and brought in thin layers onto wooden board, plastic and ceramic tiles. The bacterium could be recultured from these surfaces only as long as these were moist. At room-temperature the bacterium could not be detected anymore on wood after 30 minutes, on plastic or ceramic tiles after 90 minutes. At refrigerator-temperature the administered suspensions dried more slowly, so that H. pylori survived longer, but it still could not be isolated anymore on wood after 240 minutes, on plastic or ceramic tiles after 300 minutes. The decimal reduction-time for H. pylori suspensions in broth were. 72 sec. at +50 degrees C 43 sec. at +52 degrees C 20 sec. at +55 degrees C 10 sec. at +57 degrees C 4 sec. at +60 degrees C from which data z = 7.9 +/- 0.01 degrees C can be calculated. From these experiments on can conclude, that in all probability fresh milk and chicken do not contain H. pylori and thus do not represent a source of infection for man. After contamination of slaughtered chicken within the abattoir or from milk and milk-products within dairy industry by insufficient hygiene-management of infected personnel it can not be excluded, that H. pylori gets into households by these foods. An infection of the consumer by this route is not very likely, but can not be excluded with complete certainly.     

Lithological controls influence river form in contrasting sub-catchments: The Scamander and Avenue Rivers,Tasmania

Bedrock influence on river channel form is difficult to assess, with many catchments dominated by glacial erosion and with blanketing sediments from both pluvial and fluvial sources. The Scamander catchment in Tasmania lacks glacial history and features two bedrock-confined sub-catchments of similar area and maximum flow length, but one dominated by Mathinna Group sedimentary rocks, and the other with large areas in granite lithology. Lithology types, stream network parameters and near stream slope angles were analysed using geographical information systems, and results of stream cross sections, channel form and planforms were compared for each lithology. Results showed that granite features low gradient, shallow streams with channel slope cross sections of <10°. Granite channels are irregular and dominated by large boulders that create channel roughness and resist incision. Weathering products of coarse quartz sand provide anchorages for in-channel vegetation. By contrast, sedimentary Mathinna Group rocks feature steeply incised trough-like channels, with near-channel hillslope gradients mostly between 30° and 50°. Rectangular blocks disintegrate to gravel cobbles on the channel bed, providing poor anchorage for vegetation. Mathinna lithology influences steep, low roughness channels, and stable, incised recurved meanders formed by river interaction with vertical layers of resistant rock. The resistant bedrock lithology is demonstrated in this study to influence varied river planforms, near-channel slope gradients, channel sediments and cross sections.