Microthermoforming as a novel technique for manufacturing scaffolds in tissue engineering (CellChips)

The CellChip is a microstructured polymer scaffold, which favours a three-dimensional cultivation of cells within an array of cubic microcontainers. The manufacturing process used so far is microinjection moulding combined with laser-based perforation. In a first attempt to simplify the process, costly perforation was avoided by using commercially available, inexpensive microfiltration membranes for the bottom of the microcavities. Microthermoforming is a promising novel technique which allows the CellChip to be produced from thin film. Working pressures of approximately 4000 kPa were required for the adequate moulding of 50 microm thick films from three different polymers (polystyrene, polycarbonate, cyclo-olefin polymer). Integrating drafts and chamfers in micromoulds is not going to eliminate an uneven thickness profile, but reduces demoulding forces. Microthermoformed CellChips of polycarbonate were perforated by an ion track technique to guarantee a sufficient supply of medium and gases to the cells. The prestructured CellChips were irradiated with 1460 MeV xenon ions at a fluence of a few 10(6) ions/cm2. The tracks were etched in an aqueous solution of 5 N NaOH at 30 degrees C, which resulted in cylindrical pores approximately 2 microm in diameter. Microinjection-moulded, membrane-bonded and thermoformed CellChips were subjected to comparative examination for viability in a cell culture experiment with parenchymal liver cells (HepG2). The cells stayed viable over a period of more than 20 days. No significant differences in viability between injection-moulded, membrane-bonded, and thermoformed CellChips were observed.     

Making inferences about the location of hidden food: Social dog, causal ape.

Domestic dogs (Canis familiaris) and great apes from the genus Pan were tested on a series of object choice tasks. In each task, the location of hidden food was indicated for subjects by some kind of communicative, behavioral, or physical cue. On the basis of differences in the ecologies of these 2 genera, as well as on previous research, the authors hypothesized that dogs should be especially skillful in using human communicative cues such as the pointing gesture, whereas apes should be especially skillful in using physical, causal cues such as food in a cup making noise when it is shaken. The overall pattern of performance by the 2 genera strongly supported this social-dog, causal-ape hypothesis. This result is discussed in terms of apes' adaptations for complex, extractive foraging and dogs' adaptations, during the domestication process, for cooperative communication with humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Food security in high mountain regions: agricultural production and the impact of food subsidies in Ladakh,Northern India

The issues of food security and its specifics in high mountain regions are often neglected in national and international science and policy agendas. At the same time, local food systems have undergone significant transitions over the past two decades. Whereas subsistence agriculture still forms the economic mainstay in these regions, current dynamics are generally characterized by livelihood diversification with increased off-farm income opportunities and an expansion of external development interventions. A case study from Ladakh (Indian Himalayas) illustrates how changes of the political and socio-economic conditions have affected food security strategies of mountain households. In the cold, arid environment of Ladakh, where combined mountain agriculture is the dominant land use system, reduced importance of the subsistence base for staple foods is reflected in current consumption patterns. Seasonal shortfalls and low dietary diversity lead to micronutrient deficiencies, a phenomenon that has been described as “hidden hunger”. This paper describes determinants of the transition of the current food system, based on land-use analyses and quantitative and qualitative social research at the household, regional and national level. It shows how monetary income and governmental as well as non-governmental development interventions shape food security in this peripheral region. Focusing on the particular example of staple food subsidies through the Indian Public Distribution System, the paper illustrates and discusses how this national-level measure addresses food security and shows the implications for household strategies. Against the background of our findings we argue that tailor-made regional policies and programmes are needed to face the specific challenges in high mountain regions.     

Automation of Solubility Measurements on a Robotic Platform

Experimental investigation in the laboratory can be accelerated and supported by miniaturized automation techniques. In the design of unit operations, e.g., for crystallization and precipitation processes or for chromatographic separations where no solids should appear during the run, reliable solubility data are mandatory. The development and validation of a robotic routine for completely automated solubility measurements are introduced. The triple‐determination of automated solubility measurements of the model systems succinic acid and adipic acid/water have a relative standard deviation below 0.99 % and are comparable to literature and manual experiments. Data are generated with high precision and accuracy, and the experimental effort and the hands‐on time are reduced significantly to a few minutes necessary to prepare the platform since all subsequent pipetting and control steps are automated.     

Long-Term Orientation and Relationship Lending: A Cross-Cultural Study on the Effect of Time Preferences on the Choice of Corporate Debt

We examine how time preferences impact the financing decision of firms. We hypothesize that the degree of long-term orientation in a country is positively related to the use of bank relationship lending. Based on a thorough theoretical investigation and an extensive empirical analysis using a large, worldwide dataset, we find strong support for our hypothesis on the role of time preferences for financial intermediation. Our results are robust to controlling for other determinants of the choice of debt financing as well as to applying alternative variables and different estimation methods. Firms in long-term orientation countries appear to prefer relationship bank financing, since it is usually available for the long run and will not be withdrawn quickly in response to adverse developments. This allows managers to preserve a more strategic view and pursue longer planning horizons.     

3D finite element modelling of multilateral junction wellbore stability

Wellbore failure can occur at different stages of operations. For example, wellbore collapse might happen during drilling and/or during production. The drilling process results in the removal of an already stressed rock material. If the induced stresses near the wellbore exceed the strength of rock, wellbore failure occurs. The production process also changes the effective stresses around the wellbore. Such changes in stresses can be significant for high drawdown pressures and can trigger wellbore failure. In this paper, the Mohr–Coulomb failure criterion with a hyperbolic hardening is used. The model parameters are identified from triaxial compression tests. The numerical simulations of laboratory tests showed that the model can reproduce the mechanical behaviour of sandstone. In addition, the simulations of multilateral junction stability experiments showed that the model was able to reproduce yielding and failure at the multilateral junction for different levels of applied stresses. Finally, a numerical example examining multilateral junction stability in an open borehole during drilling and production is presented. The results illustrate the development of a localized failure zone proximate to the area where two wellbore tracks join, particularly on the side with a sharp approaching angle, which would significantly increase the risk of wellbore collapse at the junction.     

The magic cup: Great apes and domestic dogs (Canis familiaris) individuate objects according to their properties.

Despite current interest in dog (Canis familiaris) cognition, very little is known about how dogs represent objects and how they compare with other species, such as the great apes. Therefore, we investigated how dogs and great apes (chimpanzees [Pan troglodytes], bonobos [Pan paniscus], orangutans [Pongo pygmaeus], gorillas [Gorilla gorilla]) individuate objects in a classical violation of expectation paradigm. We used a container (magic cup) with a double bottom that allowed us to change the type of food that subjects had seen being placed in the container. Using a 2 × 2 design, we varied whether subjects received a generally preferred food and whether the food was substituted (surprise trials) or not (baseline trials). Apes showed increased begging and looking behaviors and dogs showed increased smelling behavior. Both species stayed near the experimenter more frequently in the surprise trials compared with baseline trials. Both species reacted to positive (i.e., good food substituted for bad food) and negative (i.e., bad food substituted for good food) surprises. These results suggest that apes and dogs were able to individuate objects according to their properties or type in comparable ways. In addition, we looked for frustration and elation effects, but subjects' behaviors were not influenced by the food they saw and which they received in previous trials. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Manufacturing of dies from hardened tool steels by 3-axis micromilling

In this paper the results of an experimental investigation to analyze the machinability of a hardened, carbide-rich cold-work tool steel 1.2379 (approx. 62 HRC) with coated micro end-milling cutters are discussed. Fundamental experiments were performed to determine a cutting-parameter set, which enables an economic manufacturing of dies by 3-axis micromilling with commercially available cemented-carbide tools. The evaluation of the applicability of different tool types is conducted by analyzing the process forces, the tool wear, the surface quality, the material removal rate, and the entire chip volume. Design of experiments was used to significantly reduce the number of experiments and to model the active and passive forces. Concerning the design of tools for the micromilling of such difficult-to-machine materials, it is shown that cemented-carbide tools with robust cutting edges are applicable for this kind of machining. Furthermore, test microstructures were manufactured with the intention of validating the determined cutting-parameter set in combination with the selected tool types. In addition, the dimension and shape accuracy of the microstructures are analyzed.