Micro- and nanostructured Al2O3 surfaces for controlled vascular endothelial and smooth muscle cell adhesion and proliferation

The effect of the micro- and nanotopography on vascular cell-surface interaction is investigated using nano- and microstructured Al₂O₃ as model substrate. Two different nanostructured Al₂O₃ surfaces composed of low density (LD) and high density (HD) nanowires (NWs) were synthesized by chemical vapour deposition (CVD) and commercially available microstructured Al₂O₃ plates were used for comparison. A clear diverging response of human umbilical vein endothelial cells (HUVEC) and human umbilical vein smooth muscle cells (HUVSMC) was observed on these nano- and microstructured surfaces. LD Al₂O₃ NWs seem to enhance the proliferation of HUVECs selectively. This selective control of the cell-surface interaction by topography may represent a key issue for the future stent material design.     

A quantitative metallographic assessment of the evolution of porosity during processing and creep in single crystal Ni‐base super alloys

The present work reviews previous research on the evolution of porosity. It presents new results from a detailed study on the evolution of porosity during casting, heat treatment and creep of a single crystal Ni‐base superalloy subjected to uniaxial tensile creep at 1050 °C and 160 MPa in [001] and [110] directions. A quantitative metallographic study was performed on carefully polished metallographic cross sections, monitoring sampling fields of 4500 × 1000 µm² using the back scatter contrast of an analytical scanning electron microscope; evolutions of pore sizes and pore form factors were analyzed and all important details which were previously revealed in a synchrotron study could be reproduced. In addition, it was observed that micro cracks form at larger cast pores. They interlink and thus initiate final rupture. The [110] tensile creep tests showed lower rupture strains than the [001] experiments. In agreement with earlier work, this can be rationalized on the basis of aligned porosity along primary dendrites.     

Silicondioxide electret films prepared by the sol-gel process

Sol-gel silica electret films were coated on silicon substrates by a spin coating technique. The process of preparing the films is described and the electret behavior of the films is discussed. The films were corona charged at room temperature. Then, isothermal decay of the surface potential at room temperature and open-circuit thermally stimulated discharge (TSD) experiments were carried out. The results showed that the main peak of the TSD current spectra was situated at ~250°C and charge deposited in the film indicated good stability for the negative charged sample. After storage at room temperature for 50 days, the surface potential of the sample still retained at ~90% of the initial value. The authors found activation energies of 1.3 and 0.7 eV for negative and positive corona charged samples. Experimental results suggest that the sol-gel process could be useful in electret and electronic technique applications     

A place called HOPE: group psychotherapy for adolescents of parents with HIV/AIDS

Intraoperative ultrasound, whether during celiotomy or laparoscopy, plays an important role in assisting the surgeon in directing appropriate therapy for intra-abdominal diseases, particularly primary or metastatic malignancies involving the liver and primary malignancies of the pancreas and upper gastrointestinal tract. It is the most sensitive imaging technique for detecting small intraparenchymal lesions of the liver, pancreas, and other solid organs. Owing to its increased sensitivity over all commonly used preoperative imaging studies, it is responsible for changing the intraoperative treatment plan of these tumors in a significant percentage of cases. This is particularly true with respect to resectability. In the era of laparoscopic surgery, it replaces the surgeon's inability to palpate the liver and other organs during surgery. As surgeons use a laparoscopic approach with increasing frequency to treat intra-abdominal disease, they will have an increasing need to master the use of intraoperative ultrasound in order to render optimal care to their patients.     

纳米晶Ag—Cu合金的结构

用Ｘ－射线衍射，维氏显微硬度测量等方法研究了在惰性气体中蒸发Ａｇ－Ｃｕ母合金，然后原位加压成型得到的纳米晶Ａｇ－Ｃｕ合金，实验结果表明，ｎ－Ａｇ３７Ｃｕ６３合金由富根，富铜固溶体组成，点阵参数随退火温度的变化表明，它们是快速冷却超粒子时产生的孢和固溶全，样品的维氏显显镀昌粒的长大而减小，遵循Ｈａｌｌ－Ｐｅｔｃｈ关系。     

Integrating context-free and context-dependent attentional mechanisms for gestural object reference

We present a vision system for human-machine interaction based on a small wearable camera mounted on glasses. The camera views the area in front of the user, especially the hands. To evaluate hand movements for pointing gestures and to recognise object references, an approach to integrating bottom-up generated feature maps and top-down propagated recognition results is introduced. Modules for context-free focus of attention work in parallel with the hand gesture recognition. In contrast to other approaches, the fusion of the two branches is on the sub-symbolic level. This method facilitates both the integration of different modalities and the generation of auditory feedback.Published online: 5 October 2004Robert Rae: Now at PerFact Innovation, Lampingstr. 8, 33615 Bielefeld, Germany     

Empirically Verified Thermodynamic Model of Gate Capacitance and Threshold Voltage of Nanoelectronic MOS Devices With Applications to HfO2 and ZrO2 Gate Insulators

A thermodynamic variational model derived by minimizing the Helmholtz free energy of the MOS device is presented. The model incorporates an anisotropic permittivity tensor and accommodates a correction for quantum-mechanical charge confinement at the dielectric/substrate interface. The energy associated with the fringe field that is adjacent to the oxide is of critical importance in the behavior of small devices. This feature is explicitly included in our model. The model is verified using empirical and technology-computer-aided-design-generated capacitance-voltage data obtained on MOS devices with ZrO₂, HfO₂, and SiO₂ gate insulators. The model includes considerations for an interfacial low-k interface layer between the silicon substrate and the high-k dielectric. This consideration enables the estimation of the equivalent oxide thickness. The significance of sidewall capacitance effects is apparent in our modeling of the threshold voltage (V_th) for MOS capacitors with effective channel length at 30 nm and below. In these devices, a variation in high-k permittivity produces large differences in V_th. This effect is also observed in the variance of V_th, due to dopant fluctuation under the gate.     

Reduced myofibroblast differentiation on femtosecond laser treated 316LS stainless steel

In-stent restenosis is a common complication after stent surgery which leads to a dangerous wall narrowing of a blood vessel. Laser assisted patterning is one of the effective methods to modify the stent surface to control cell–surface interactions which play a major role in the restenosis. In this current study, 316LS stainless steel substrates are structured by focusing a femtosecond laser beam down to a spot size of 50 μm. By altering the laser induced spot density three distinct surfaces (low density (LD), medium density (MD) and high density (HD)) were prepared. While such surfaces are composed of primary microstructures, due to fast melting and re-solidification by ultra-short laser pulses, nanofeatures are also observed as secondary structures. Following a detailed surface characterization (chemical and physical properties of the surface), we used a well-established co-culture assay of human microvascular endothelial cells and human fibroblasts to check the cell compatibility of the prepared surfaces. The surfaces were analyzed in terms of cell adherence, proliferation, cell morphology and the differentiation of the fibroblast into the myofibroblast, which is a process indicating a general fibrotic shift within a certain tissue. It is observed that myofibroblast proliferation decreases significantly on laser treated samples in comparison to non-treated ones. On the other hand endothelial cell proliferation is not affected by the surface topography which is composed of micro- and nanostructures. Such surfaces may be used to modify stent surfaces for prevention or at least reduction of restenosis.     

Entwicklung einer leistungsstarken Mikrorektifikationsapparatur für analytische und präparative Anwendungen

In this contribution it is reported about the realization of efficient micro rectification equipment (MRA), which can be operated intermittently or continuously and be used both for analytical as well as for preparative separations of mixtures of liquid substances. Different binary systems were separated. A theoretical separation stage number of 12 was obtained together with a height equivalent to one theoretical plate of 1.08 cm. Compared to the state of microtechnology this can be regarded as an excellent progress.