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.     

Correlation between Thermal Expansion and Magnetic Characteristics of Fe-Ni Alloys in Fe_(1-x)Ni_x/Cu Superlattices

Thermal expansion behaviors of FeNi alloys were investigated by means of X-ray diffraction technique within a Fe1 -xNix/Cu superiattice structure. It was found that with a Ni concentration of x = 0.35, FeNi alloy layers showed the well-known Invar behavior, but for alloy layers with either lower or higher Ni concentrations, thermal expansion coefficients were larger. Based on results of magnetic measurements it is concluded that FeNi alloy layers with Ni concentrations lower than the Invar composition are in a superparamagnetic state which leads not only to low spontaneous magnetizations but also to large thermal expansions of the alloy layers.     

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.     

Gender differences in human sepsis

Severe tricuspid valve regurgitation and decreased pulmonary blood flow in neonatal Ebstein's anomaly with pulmonary atresia, may result in cardiac respiratory failure and hypoxemia. The poor natural course and lack of standard surgical treatment make treatment for neonatal Ebstein's anomaly very difficult. The Blalock-Taussig operation was performed for hypoxemia in Ebstein's anomaly associated with pulmonary atresia and severe tricuspid regurgitation on 36th day after birth. On the 63rd day after birth, tricuspid valve orifice closure and right atrium plication (Starnes procedure) were accomplished under cardiopulmonary bypass. Heart failure became controllable and the patient condition was satisfactory at one year after surgery.     

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.     

T wave alternans as a predictor of recurrent ventricular tachyarrhythmias in ICD recipients: prospective comparison with conventional risk markers

INTRODUCTION: The current standard for arrhythmic risk stratification is electrophysiologic (EP) testing, which, due to its invasive nature, is limited to patients already known to be at high risk. A number of noninvasive tests, such as determination of left ventricular ejection fraction (LVEF) or heart rate variability, have been evaluated as additional risk stratifiers. Microvolt T wave alternans (TWA) is a promising new risk marker. Prospective evaluation of noninvasive risk markers in low- or moderate-risk populations requires studies involving very large numbers of patients, and in such studies, documentation of the occurrence of ventricular tachyarrhythmias is difficult. In the present study, we identified a high-risk population, recipients of an implantable cardioverter defibrillator (ICD), and prospectively compared microvolt TWA with invasive EP testing and other risk markers with respect to their ability to predict recurrence of ventricular tachyarrhythmias as documented by ICD electrograms. METHODS AND RESULTS: Ninety-five patients with a history of ventricular tachyarrhythmias undergoing implantation of an ICD underwent EP testing, assessment of TWA, as well as determination of LVEF, baroreflex sensitivity, signal-averaged ECG, analysis of 24-hour Holter monitoring, and QT dispersion from the 12-lead surface ECG. The endpoint of the study was first appropriate ICD therapy for electrogram-documented ventricular fibrillation or tachycardia during follow-up. Kaplan-Meier survival analysis revealed that TWA (P < 0.006) and LVEF (P < 0.04) were the only significant univariate risk stratifiers. EP testing was not statistically significant (P < 0.2). Multivariate Cox regression analysis revealed that TWA was the only statistically significant independent risk factor. CONCLUSIONS: Measurement of microvolt TWA compared favorably with both invasive EP testing and other currently used noninvasive risk assessment methods in predicting recurrence of ventricular tachyarrhythmias in ICD recipients. This study suggests that TWA might also be a powerful tool for risk stratification in low- or moderate-risk patients, and needs to be prospectively evaluated in such populations.     

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.