Biocompatible fluorescent silicon nanocrystals for single-molecule tracking and fluorescence imaging.

Fluorescence microscopy is used extensively in cell-biological and biomedical research, but it is often plagued by three major problems with the presently available fluorescent probes: photobleaching, blinking, and large size. We have addressed these problems, with special attention to single-molecule imaging, by developing biocompatible, red-emitting silicon nanocrystals (SiNCs) with a 4.1-nm hydrodynamic diameter. Methods for producing SiNCs by simple chemical etching, for hydrophilically coating them, and for conjugating them to biomolecules precisely at a 1:1 ratio have been developed. Single SiNCs neither blinked nor photobleached during a 300-min overall period observed at video rate. Single receptor molecules in the plasma membrane of living cells (using transferrin receptor) were imaged for ≥10 times longer than with other probes, making it possible for the first time to observe the internalization process of receptor molecules at the single-molecule level. Spatial variations of molecular diffusivity in the scale of 1-2 µm, i.e., a higher level of domain mosaicism in the plasma membrane, were revealed

Modeling and Simulation of Closed-Loop Supply Chains Considering Economic Efficiency

Part 2: Sustainable Supply ChainsInternational audienceThis study proposes a basic model of closed-loop supply chains which includes not only traditional forward supply chains for the generation of products but also reverse supply chains for the reuse of products in consideration of economic efficiency for MTO (Make to Order) companies. The model consists of four model components, i.e., clients, manufacturers, suppliers, and remanufacturers. A remanufacturer is added to the previous model of forward supply chains as a new model component which collects used products from clients and provides reusable parts to manufacturers. Remanufacturers as well as manufacturers and suppliers modify their schedules and negotiate with each other in order to determine suitable prices and delivery times of products. Remanufacturers stimulate clients to discard used products to meet the demand of reusable parts. They can increase the amount of reused products and reduce wastes by creating a balance between supply and demand of reusable parts