Endothelialization of Rationally Microtextured Surfaces with Minimal Cell Seeding Under Flow

The generation of a confluent and functional endothelium at the luminal surface of cardiovascular devices represents the ideal solution to avoid contact between blood and synthetic materials thus allowing the long‐term body integration of the implants. Due to the foreseen paucity of source cells in cardiovascular patients, surface engineering strategies to achieve full endothelialization, while minimizing the amount of endothelial cells required to seed the surface leading to prompt and full coverage with an endothelium are necessary. A stable endothelialization is the result of the interplay between endothelial cells, the flow‐generated walls shear stress and the substrate topography. Here a novel strategy is designed and validated based on the use of engineered surface textures combined with confined islands of seeded endothelial cells. Upon release of the confinement, the cell island populations are able to migrate on the texture and merge under physiological flow conditions to promptly generate a fully connected endothelium. The interaction between endothelial cells and surface textures supports the process of endothelialization through the stabilization of cell‐to‐substrate adhesions and cell‐to‐cell junctions. It is shown that with this approach, when ≈50% of a textured surface is initially covered with cell seeding, the time to full endothelialization compared to an untextured surface is almost halved, underpinning the viability and effectiveness of the method for the quick and stable coverage of cardiovascular implants.     

Bridging Artifacts and Actors: Expertise Sharing in Organizational Ecosystems

We synthesize findings from longitudinal case studies examining work practices in three different organizations and propose analytical and methodological frameworks to guide the design and implementation of technologies for expertise and knowledge management. We appropriate the concept of ecosystem to argue that we can create active and useful solutions for knowledge management through a focus on interaction between two mutually intertwined elements of an ecosystem—artifacts and actors. We show that in expertise and knowledge sharing systems domain knowledge and technological knowledge are complementary and we present evidence that small solutions can have far reaching effects. Finally, we make a case for full integration of IT developers as an element of expertise sharing ecosystem.     

Kinetics and regioselectivity of the Autoxidation of o-Substituted Isopropyl Aromatics

The relative chain propagation constants and the regioselectivities of the oxidations of o-cymene and 2-isopropyl-1,4-dimethylbenzene were determined by competitive oxidations of the hydrocarbons with cumene. As expected, the reactivity of the tertiary C H bond of the isopropyl group is considerably decreased by o-methyl groups. Also in α-isopropylnaphthalene a considerable decrease in the reactivity of the tertiary C H bond takes place. The decrease of the chain propagation constants effects a decrease of the oxidabilities of o-substituted isopropyl aromatics. In the case of the methyl isopropyl benzenes the increase of the chain termination constants by primary peroxy radicals must also be taken into consideration. This results in a decrease of the oxidabilities which can be observed even in p-cymene (in comparison with cumene).     

Low‐Temperature Spark Plasma Sintering of Pure Nano WC Powder

For the first time we have demonstrated the densification of high‐purity nanostructured (d_avg ≈ 60 nm) tungsten carbide by High Pressure Spark Plasma Sintering (HPSPS) in the unusually low temperature range of 1200°C–1400°C. The high‐pressure sintering (i.e., 300 MPa) produced dense material at a temperature as low as 1400°C. In comparison with more conventional sintering techniques, such as SPS (80 MPa) or hot isostatic pressing, HPSPS lowered the temperature required for full densification by 400°C–500°C. High Pressure Spark Plasma Sintering, even in absence of any sintering aid or grain growth inhibitor, retained a very fine microstructure resulting in a significant improvement in both hardness (2721 HV₁₀) and fracture toughness (7.2 MPa m^1/2).     

End Users at the Bazaar: Designing Next-Generation Enterprise Resource Planning Systems

The "bazaar" metaphor has developed a lasting popularity in software engineering, especially as software architectures have evolved from monoliths to service orientation. Nevertheless, the metaphor is limited because it doesn't consider end users, those who develop software for themselves. Introducing such an end user, the "prosumer," to the bazaar not only suggests a changing division of work in software development but also calls for different functionality and architectural choices. The authors evaluated changing software architectures from an end-user development (EUD) perspective, taking the case of enterprise resource planning (ERP) systems as traditionally monolithically designed systems moving toward service orientation. On the basis of the study's findings, which indicated problems with the systems' technical flexibility, the authors developed a tool set for fostering EUD activities. Their new architecture for ERP systems enables end users to create their own solutions.     

An active rc filter for pcm systems

An active RC low-pass filter using two high-gain amplifiers with bridge feedback is described which serves as terminating unit of a PCM system channel. Some conditions derived from telecommunication applications and effecting the choice of the filter structure are discussed in detail, and the principles guaranteeing imaginary zeros under the condition of absolute stability of the filter sections are explained. The measurement results confirm that, using the method described, the fairly severe requirements, particularly the high pass-band constancy demanded for units of telecommunication equipments, can be met at an economical cost.