搭载人类自体干细胞的纤维支架及其在软组织再生中的应用

文章介绍了搭载人类自体干细胞的纤维支架技术及其在软组织再生中的应用优势。选用藻酸盐材料结合人体干细胞搭载关键技术制成的纤维支架,同时具有促进血管再生和触发成脂分化的能力。     

Chemical structure of autoignition in a turbulent lifted H2/N2 jet flame issuing into a vitiated coflow

In the present paper autoignition is studied as the main stabilization mechanism in turbulent lifted H₂/N₂ jet flames issuing into a vitiated hot coflow. The numerical study is performed using the joint scalar PDF approach with detailed chemistry in a two dimensional axisymmetric domain. The SSG Reynolds stress model is used as a turbulence model in the simulation. Chemical structure and characteristics of autoignition are investigated using various methods and parameters. Reaction rate analysis is made to analyze the ignition process at the flame base. The results show the occurrence of a chain branching reaction preceding thermal runaway, which boosts the chain branching process in the flame. This demonstrates the large impact of autoignition at the flame base on the stabilization of the lifted turbulent flame. Further investigation using the scatter-plots of scalars reveals the characteristics of the ignition. The relation between the behavior of temperature and of key intermediate species demonstrates the formation of OH through consumption of HO₂ at nearly isothermal conditions in a very lean-fuel mixture at the flame base. Flux analyses in the conservation equations of species are used to explore the impacts of mass transport on ignition process. Ignition is found to be mainly controlled by chemical features rather than the mixing processes near the flame base. Characteristics of autoignition are also investigated in terms of Damköhler number and progress variable.     

Influence of thermal ageing on the stability of polymer bulk heterojunction solar cells

A new approach is presented in order to improve the thermal stability of polymer: [6-6]-phenyl C₆₁ butyric acid methyl ester (PCBM) bulk heterojunction solar cells. The central idea in this approach is the use of a polymer with high glass transition temperature (T_g), well above the normal operating temperatures of the devices. In this paper, a PPV-derivative with a T_g of 150 °C was used as an electron donor and the thermal stability of the obtained solar cells was compared with solar cells based on the reference material poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV) with a T_g of 45 °C. The use of the material with higher glass transition temperature resulted in a significant improvement of the thermal stability of the photovoltaic parameters. Furthermore, a systematic transmission electron microscope (TEM) study demonstrates that the better thermal stability of performance coincides with a more stable active layer morphology. Both improvements are attributed to the reduced free movement of the electron donor material (PCBM) within the active layer of the solar cell.     

Kontextbasierte Kooperation für mobile Geschäftsanwendungen

Realistic requirements of mobile business applications often exceed the capabilities of their respective local environments. In order to overcome such restrictions of specific mobile devices, services, and resources, this contribution introduces the concept of context-based cooperation. It is based on mobile processes which enable applications to cross boundaries of individual systems and thereby allow combining both mobile and stationary resources in order to realize highly dynamic individual applications. This contribution presents an approach for realizing context-based cooperation built upon on a respective context management infrastructure and execution environment. It also identifies specific requirements and proposes related enhancements for mobile business applications.     

The acceptance of Tablet-PCs in classroom instruction: The teachers’ perspectives

Limited research has been conducted on the integration of Tablet-PCs in classroom instruction. This paper reports a qualitative study which investigates the acceptance of Tablet-PCs, seen as technological innovation, amongst teachers. The research approach intends to complement research on the acceptance of technology through a more detailed qualitative examination. Semi-structured interviews were conducted with 18 teachers during a pilot project introducing Tablet-PCs to classroom instruction at three different schools. The findings indicate diversity in the attitude of teachers towards the technology, but also with regards to the performance expectancy and the facilitating conditions.     

Identification of quasi-optimal regions in the design space using surrogate modeling

The use of Surrogate Based Optimization (SBO) is widely spread in engineering design to find optimal performance characteristics of expensive simulations (forward analysis: from input to optimal output). However, often the practitioner knows a priori the desired performance and is interested in finding the associated input parameters (reverse analysis: from desired output to input). A popular method to solve such reverse (inverse) problems is to minimize the error between the simulated performance and the desired goal. However, there might be multiple quasi-optimal solutions to the problem. In this paper, the authors propose a novel method to efficiently solve inverse problems and to sample Quasi-Optimal Regions (QORs) in the input (design) space more densely. The development of this technique, based on the probability of improvement criterion and kriging models, is driven by a real-life problem from bio-mechanics, i.e., determining the elasticity of the (rabbit) tympanic membrane, a membrane that converts acoustic sound wave into vibrations of the middle ear ossicular bones.