Accumulation of silver nanoparticles by cultured primary brain astrocytes

Silver nanoparticles (AgNP) are components of various food industry products and are frequently used for medical equipment and materials. Although such particles enter the vertebrate brain, little is known on their biocompatibility for brain cells. To study the consequences of an AgNP exposure of brain cells we have treated astrocyte-rich primary cultures with polyvinylpyrrolidone (PVP)-coated AgNP. The incubation of cultured astrocytes with micromolar concentrations of AgNP for up to 24 h resulted in a time- and concentration-dependent accumulation of silver, but did not compromise the cell viability nor lower the cellular glutathione content. In contrast, the incubation of astrocytes for 4 h with identical amounts of silver as AgNO(3) already severely compromised the cell viability and completely deprived the cells of glutathione. The accumulation of AgNP by astrocytes was proportional to the concentration of AgNP applied and significantly lowered by about 30% in the presence of the endocytosis inhibitors chloroquine or amiloride. Incubation at 4?°C reduced the accumulation of AgNP by 80% compared to the values obtained for cells that had been exposed to AgNP at 37?°C. These data demonstrate that viable cultured brain astrocytes efficiently accumulate PVP-coated AgNP in a temperature-dependent process that most likely involves endocytotic pathways.     

Schottky barrier-based silicon nanowire pH sensor with live sensitivity control

We demonstrate a pH sensor based on ultrasensitive nanosize Schottky junctions formed within bottom-up grown dopant-flee arrays of assembled silicon nanowires. A new measurement concept relying on a continuous gate sweep is presented, which allows the straightforward determination of the point of maximum sensitivity of the device and allows sensing experiments to be performed in the optimum regime. Integration of devices into a portable fluidic system and an electrode isolation strategy affords a stable environment and enables long time robust FET sensing measurements in a liquid environment to be carried out. Investigations of the physical and chemical sensitivity of our devices at different pH values and a comparison with theoretical limits are also discussed. We believe that such a combination of nanofabrication and engineering advances makes this Schottky barrier-powered silicon nanowire lab-on-a-chip platform suitable for efficient biodetection and even for more complex biochemical analysis.     

积跬步以至千里——德国法兰克福城市绿带发展史与"慢营建"实践

城市绿色开放空间可以改善城市生态环境、提高居民生活质量,是营造城市意象与梳理城市结构的关键元素,其重要性得到越来越多的认同.然而绿地生态系统的有机性与城市自身的复杂性决定了绿色开放空间的营建不仅需要综合性规划设计,更需要一套完整的基于地方背景的长期建设与维护方案,才能保证绿色空间与城市的共同生长.德国法兰克福虽作为欧洲金融中心而闻名,但其高质量的城市生态环境才是其可持续发展的基础.本文追溯法兰克福城市核心绿色空间即城市绿带的发展建设史,从规划设计、管理结构、法律法规和实施保障等多个角度,展示其基于长期大量小型项目等"慢营建"策略对城市生态空间意象与居民绿色认知的塑造,分析这种实施策略的适用背景与优势劣势,指出其对我国城市绿色空间建设的重要借鉴意义.     

Quantification of extreme thermal gradients during in situ transmission electron microscope heating experiments

Studies on materials affected by large thermal gradients and rapid thermal cycling are an area of increasing interest, driving the need for real time observations of microstructural evoultion under transient thermal conditions. However, current in situ transmission electron microscope (TEM) heating stages introduce uniform temperature distributions across the material during heating experiments. Here, a methodology is described to generate thermal gradients across a TEM specimen by modifying a commercially available MEMS-based heating stage. It was found that a specimen placed next to the metallic heater, over a window, cut by FIB milling, does not disrupt the overall thermal stability of the device. Infrared thermal imaging (IRTI) experiments were performed on unmodified and modified heating devices, to measure thermal gradients across the device. The mean temperature measured within the central viewing area of the unmodified device was 3–5% lower than the setpoint temperature. Using IRTI data, at setpoint temperatures ranging from 900 to 1,300°C, thermal gradients at the edge of the modified window were calculated to be in the range of 0.6 × 10⁶ to 7.0 × 10⁶°C/m. Additionally, the Ag nanocube sublimation approach was used, to measure the local temperature across a FIB-cut Si lamella at high spatial resolution inside the TEM, and demonstrate “proof of concept” of the modified MEMS device. The thermal gradient across the Si lamella, measured using the latter approach was found to be 6.3 × 10⁶°C/m, at a setpoint temperature of 1,000°C. Finally, the applicability of this approach and choice of experimental parameters are critically discussed.     

Cinnamon and health

Cinnamon has been used as a spice and as traditional herbal medicine for centuries. The available in vitro and animal in vivo evidence suggests that cinnamon has anti-inflammatory, antimicrobial, antioxidant, antitumor, cardiovascular, cholesterol-lowering, and immunomodulatory effects. In vitro studies have demonstrated that cinnamon may act as an insulin mimetic, to potentiate insulin activity or to stimulate cellular glucose metabolism. Furthermore, animal studies have demonstrated strong hypoglycemic properties. However, there are only very few well-controlled clinical studies, a fact that limits the conclusions that can be made about the potential health benefits of cinnamon for free-living humans. The use of cinnamon as an adjunct to the treatment of type 2 diabetes mellitus is the most promising area, but further research is needed before definitive recommendations can be made.     

Rapid,Label-Free Screening of Diverse Biotransformations by Flow-Injection Mass Spectrometry

Mass spectrometry-based high-throughput screening methods combine the advantages of photometric or fluorometric assays and analytical chromatography, as they are reasonably fast (throughput ≥1 sample/min) and broadly applicable, with no need for labelled substrates or products. However, the established MS-based screening approaches require specialised and expensive hardware, which limits their broad use throughout the research community. We show that a more common instrumental platform, a single-quadrupole HPLC-MS, can be used to rapidly analyse diverse biotransformations by flow-injection mass spectrometry (FIA-MS), that is, by automated infusion of samples to the ESI-MS detector without prior chromatographic separation. Common organic buffers can be employed as internal standard for quantification, and the method provides readily validated activity and selectivity information with an analytical run time of one minute per sample. We report four application examples that cover a broad range of analyte structures and concentrations (0.1–50 mM before dilution) and diverse biocatalyst preparations (crude cell lysates and whole microbial cells). Our results establish FIA-MS as a versatile and reliable alternative to more traditional methods for screening enzymatic reactions.     

Reduction of 3‐Substituted 1‐Arylcyclobutanols

A useful and specific method for the the title reaction ( 1 → 2 ) involves treatment with NaBH₄ in CF₃COOH whereas other procedures from the literature yield hard‐toseparate mixtures. 1‐Arylcyclohexanols 3 give mainly cyclohexenes with borohydride/trifluoroacetic acid. Their reduction to compounds 4 ,however, is possible with MeSO₃H/NaBH₄.     

Dislocation-tuned electrical conductivity in solid electrolytes (9YSZ): A micro-mechanical approach

Tailoring the electrical conductivity of functional ceramics by introducing dislocations is a comparatively recent research focus, and its merits were demonstrated through mechanical means. Especially bulk deformation at high temperatures is suggested to be a promising method to introduce a high dislocation density. So far, however, controlling dislocation generation and their annihilation remains difficult. Although deforming ceramics generate dislocations on multiple length scales, dislocation annihilation at the same time appears to be the bottleneck to use the full potential of dislocations-tailoring the electrical conductivity. Here, we demonstrate the control over these aspects using a micromechanical approach on yttria-stabilized zirconia - YSZ. Targeted indentation well below the dislocation annihilation temperature resulted in extremely dense dislocation networks, visualized by chemical etching and electron channeling contrast imaging. Microcontact-impedance measurements helped evaluate the electrical response of operating individual slip systems. A significant conductivity enhancement is revealed in dislocation-rich regions compared to pristine ones in fully stabilized YSZ. This enhancement is mainly attributed to oxygen ionic conductivity. Thus, the possibility of increasing the conductivity is illustrated and provides a prospect to transfer the merits of dislocation-tuned electrical conductivity to solid oxygen electrolytes.