Endothelial cell-matrix interactions

Dynamic interactions between endothelial cells and components of their surrounding extracellular matrix are necessary for the invasion, migration, and survival of endothelial cells during angiogenesis. These interactions are mediated by matrix receptors that initiate intracellular signaling cascades in response to binding to specific extracellular matrix molecules. The interactions between endothelial cells and their environment are also modulated by enzymes that degrade different matrix components and thus enable endothelial invasion. Recent reports on gene targeting in mice have confirmed the role of two classes of matrix receptors, integrins and cell surface heparan sulfate proteoglycans, and a group of matrix degrading proteolytic enzymes, matrix metalloproteinases, in angiogenesis. The significance of endothelial cell-matrix interactions is further supported by several ongoing clinical trials that analyze the effects of drugs blocking this interaction on angiogenesis-dependent growth of human tumors.     

壹号住宅楼

建筑过程中砂雕玻璃和预制混凝土等材料的运用,在降低项目造价的同时,实现了实用与艺术效果的结合,同时多色彩的叠加增添了外观的活泼和生动性。     

赫尔辛基海员中心

精选理由在自然景观和元素的簇拥下,作为此地唯一的公共建筑物,它让远道而来的海员们休息和放松,结合其柔和的体量,将其定位为一个小型的多功能建筑。这里既有抚慰人心的精神食粮,也提供了咖啡     

Hepatocellular integrity during and after isoflurane and halothane anaesthesia in surgical patients

Subclinical disturbance in hepatocellular integrity, indicated by glutathione transferase Alpha (GSTA), has been associated with halothane, sevoflurane and propofol, but not with isoflurane anaesthesia. We anaesthetized 82 patients with isoflurane or halothane at 1 MAC for superficial surgery. GSTA concentration were measured with a sensitive time-resolved immunofluorometric assay in serum samples. GSTA concentrations increased from a baseline value of geometric mean 1.8 micrograms litre-1 (95% confidence intervals 1.4-2.2 micrograms litre-1) to a peak of 4.3 (3.3-5.7) micrograms litre-1 in the isoflurane group and from 2.1 (1.6-2.9) micrograms litre-1 to 6.2 (4.1-9.5) micrograms litre-1 in the halothane group. The change in GSTA was significant within groups but the difference between groups was not significant. Two patients exhibited an unexpectedly large increase in GSTA (peaks 370 and 620 micrograms litre-1) and a mild increase in alanine aminotransferase after halothane anaesthesia. We conclude that hepatocellular integrity was mildly disturbed after isoflurane and halothane anaesthesia but there was no difference between anaesthetics. Halothane anaesthesia may be associated with more advanced hepatocellular disturbance in some cases.     

Synthesis of γ-TiAl based alloy by mechanical alloying and reactive hot isostatic pressing

Elemental Ti-48Al-2Cr-2Nb powders were mechanically alloyed (MA) for 8 h and 45 h. The MA powders were then consolidated by reactive hot isostatic pressing (HIP). The microstructure of the HIPed materials consisted of equiaxed γ-TiAl and α₂-Ti₃Al phases. During the high-temperature annealing of the HIPed materials, the α₂-Ti₃-Al phase transformed into a lamellar structure consisting of alternating laths of α₂-Ti₃Al and γ-TiAl. It is suggested that a high content of interstitial elements together with the microalloying elements of niobium and/or chromium in MA powders raises α/(α + γ) transus to a higher temperature.     

Modelling of citral hydrogenation kinetics on an Ni/Al2O3 catalyst

The kinetics of citral hydrogenation in ethanol over an Ni/Al₂O₃ catalyst was studied in a slurry reactor operating at atmospheric pressure and at a temperature range of 60–77°C. Citronellal was the primary reaction product, whereas the amounts of unsaturated alcohols were very minor. Citronellol was the dominating product, generated mainly through the hydrogenation of the carbonyl group of citronellal. Based on the experimental data, a kinetic model was developed for hydrogenation. The model comprises competitive and rapid adsorption steps as well as rate-determining hydrogenation steps. The mass transfer limitation of hydrogen was included in the mathematical model. The kinetic parameters and the mass transfer parameter of hydrogen were estimated from the experimental data. A comparison of the model predictions with the experimental data revealed that the proposed kinetic approach gave a satisfactory reproduction of the data.     

Tissue reactions to bioabsorbable ciprofloxacin-releasing polylactide-polyglycolide 80/20 screws in rabbits’ cranial bone

The aim of this study was to assess tissue reactions to bioabsorbable self-reinforced ciprofloxacin-releasing polylactide/polyglycolide (SR-PLGA) 80/20 screws in rabbits' cranial bone. Two screws were implanted in each rabbit, one screw on either side of the sagittal suture (n = 28 rabbits). Animals were sacrificed after 2, 4, 8, 16, 24, 54 and 72 weeks, four animals per group. On histological examination the number of macrophages, giant cells, active osteoblasts and fibrous tissue layers were assessed and degradation of the screws was evaluated. At 2 weeks, the highest number of macrophages and giant cells were seen near the heads of the screws. After 4 and 8 weeks, the number of giant cells decreased but that of macrophages decreased from 16 weeks and on. Screws were surrounded by fibrous tissue capsule that progressively was growing in thickness by time. Active osteoblasts were seen around the shaft of the screws with the highest number seen at 4 weeks postoperatively. At 16 weeks, compact fragmentation of the screw heads was seen with macrophages seen inside the screw matrices. After 24 weeks, no polarization of the screws was seen. After one year, PLGA screws had been replaced by adipose tissue, fibrous tissue and "foamy macrophages" which had PLGA particles inside them. After 1(1/2) years, the amount of biomaterial remaining had decreased remarkably. The particles of biomaterial were inside "foamy macrophages." Ciprofloxacin-releasing SR-PLGA 80/20 screws elicited a mild inflammatory reaction but did not interfere with osteoblast activity. No complications were seen when implanted in cranial bone of rabbit.     

Radiation Resistance of Microelectronic Systems

The radiation resistance of microcircuit systems has been studied by testing separate microcircuits and using statistics based on known data of the transistor damage coefficients. The logic gates with bipolar transistors can be characterized by a transistor base transit time, tb, defined as tb=0.2/f? where f? is the alpha cutoff frequency. When tb? < 105ns/cm2 the separate gates almost certainly survive, failure almost certainly occuring when tb? > 107ns/cm2. The quantity ? is the fast neutron exposure of a reactor spectrum (E > 10 keV).     

Ultra-porous titanium oxide scaffold with high compressive strength

Highly porous and well interconnected titanium dioxide (TiO₂) scaffolds with compressive strength above 2.5 MPa were fabricated without compromising the desired pore architectural characteristics, such as high porosity, appropriate pore size, surface-to-volume ratio, and interconnectivity. Processing parameters and pore architectural characteristics were investigated in order to identify the key processing steps and morphological properties that contributed to the enhanced strength of the scaffolds. Cleaning of the TiO₂ raw powder removed phosphates but introduced sodium into the powder, which was suggested to decrease the slurry stability. Strong correlation was found between compressive strength and both replication times and solid content in the ceramic slurry. Increase in the solid content resulted in more favourable sponge loading, which was achieved due to the more suitable rheological properties of the ceramic slurry. Repeated replication process induced only negligible changes in the pore architectural parameters indicating a reduced flaw size in the scaffold struts. The fabricated TiO₂ scaffolds show great promise as load-bearing bone scaffolds for applications where moderate mechanical support is required.