Bioactivity of porous biphasic calcium phosphate enhanced by recombinant human bone morphogenetic protein 2/silk fibroin microsphere

To prepare a bioactive bone substitute, which integrates biphasic calcium phosphate (BCP) and rhBMP-2/silk fibroin (SF) microsphere, and to evaluate its characteristics. Hydroxyapatite and β-tricalcium phosphate were integrated with a ratio of 60–40 %. RhBMP-2/SF (0.5 μg/1 mg) microsphere was prepared, and its rhBMP-2-release kinetics was assed. After joining pore-forming agent (Sodium chloride, NaCl), porous BCP/rhBMP-2/SF were manufactured, and its characteristics and bioactivity in vitro were evaluated. Mean diameter of rhBMP-2/SF microsphere was 398.7 ± 99.86 nm, with a loading rate of 4.53 ± 0.08 %. RhBMP-2 was released in a dual-phase pattern, of which fast-release (nearly half of protein released) focused on the initial 3 days, and slow-release sustained more than 28 days. With the increase in concentration of NaCl, greater was porosity and pore size, but smaller mechanical strength of BCP/rhBMP-2/SF. Material with 150 % (w/v) NaCl had an optimal performance, with a porosity of 78.83 %, pore size of 293.25 ± 42.77μm and mechanical strength of 31.03 MPa. Proliferation of human placenta-derived mesenchymal stem cells (hPMSCs) on leaching extract medium was similar to the normal medium (P = 0.89), which was better than that on control group (P = 0.03). Activity of alkaline phosphatase on BCP/rhBMP-2/SF surface was higher than on pure BCP at each time point except at 1 day (P < 0.05). RhBMP-2 has a burst release on early times and a sustaining release on later times. BCP/rhBMP-2/SF with 150 % (w/v) pore-forming agent has excellent porosity, pore size and mechanical strength. The biomaterial induces proliferation and differentiation hPMSCs effectively.     

CMOS影像传感器的信噪比分析

本文使用像素密度归一化方法,对比分析了市场主流厂家生产的多系列数码相机产品中CMOS影像传感器的控噪水平。结论是：2009年尼康推出的采用瑞萨代工传感器的D3S在噪声控制方面达到了顶峰。之后的4年, CMOS控噪技术的发展似乎遇到了瓶颈,各厂商转而在提升像素密度方面大力进取。     

冰箱冷凝器的节能效应及热力分析

通过建立冰箱箱壁式冷凝器和冰箱风冷式冷凝器的传热和流动压降理论数模,计算得出在相同环境条件,制冷量和体积容量相同的两台冰箱因冷凝换热形式的改变而引起的能效差异。结果显示：翅片管风冷式冷凝器替代自然对流箱壁式冷凝器后,无论从节能上还是经济节约上来说都具有较大的优势。     

One‐Step Formation of a Single Atomic‐Layer Transistor by the Selective Fluorination of a Graphene Film

In this study, the scalable and one‐step fabrication of single atomic‐layer transistors is demonstrated by the selective fluorination of graphene using a low‐damage CF₄ plasma treatment, where the generated F‐radicals preferentially fluorinated the graphene at low temperature (<200 °C) while defect formation was suppressed by screening out the effect of ion damage. The chemical structure of the C–F bonds is well correlated with their optical and electrical properties in fluorinated graphene, as determined by X‐ray photoelectron spectroscopy, Raman spectroscopy, and optical and electrical characterizations. The electrical conductivity of the resultant fluorinated graphene (F‐graphene) was demonstrated to be in the range between 1.6 kΩ/sq and 1 MΩ/sq by adjusting the stoichiometric ratio of C/F in the range between 27.4 and 5.6, respectively. Moreover, a unique heterojunction structure of semi‐metal/semiconductor/insulator can be directly formed in a single layer of graphene using a one‐step fluorination process by introducing a Au thin‐film as a buffer layer. With this heterojunction structure, it would be possible to fabricate transistors in a single graphene film via a one‐step fluorination process, in which pristine graphene, partial F‐graphene, and highly F‐graphene serve as the source/drain contacts, the channel, and the channel isolation in a transistor, respectively. The demonstrated graphene transistor exhibits an on‐off ratio above 10, which is 3‐fold higher than that of devices made from pristine graphene. This efficient transistor fabrication method produces electrical heterojunctions of graphene over a large area and with selective patterning, providing the potential for the integration of electronics down to the single atomic‐layer scale.     

Surface Supported Gold–Organic Hybrids: On‐Surface Synthesis and Surface Directed Orientation

The surface‐assisted synthesis of gold–organic hybrids on Au (111) and Au (100) surfaces is repotred by thermally initiated dehalogenation of chloro‐substituted perylene‐3,4,9,10‐tetracarboxylic acid bisimides (PBIs). Structures and surface‐directed alignment of the Au–PBI chains are investigated by scanning tunnelling microscopy in ultra high vacuum conditions. Using dichloro‐PBI as a model system, the mechanism for the formation of Au–PBI dimer is revealed with scanning tunnelling microscopy studies and density functional theory calculations. A PBI radical generated from the homolytic C‐Cl bond dissociation can covalently bind a surface gold atom and partially pull it out of the surface to form stable PBI‐Au hybrid species, which also gives rise to the surface‐directed alignment of the Au–PBI chains on reconstructed Au (100) surfaces.     

Controllable and Facile Fabrication of Gold Nanostructures for Selective Metal‐Assisted Etching of Silicon

A method with the combination of organic‐vapor‐assisted polymer swelling and nanotransfer printing (nTP) is used to manufacture desirable patterns consisting of gold nano‐clusters on silicon wafers for Au‐assisted etching of silicon. This method remarkably benefits to the size control and regional selection of the deposited Au. By tuning the thickness of the Au films deposited on the polydimethylsiloxane (PDMS) stamps, along with the swelling of PDMS stamps in acetone atmosphere, the Au films are cracked into diverse nanostructures. These nanostructures are covalently transferred onto silicon substrates in a large scale and enable to accelerate the chemical etching of silicon. The etched areas are composed of porous structures which can be readily distinguished from the surroundings on optical microscope. PDMS stamps and the Au clusters provide the control over the feature of the etched areas and the porous silicon, respectively. The silicon surfaces with patterned porous features offer a platform for exploiting new functional templates, for example, they present a diversity of antireflective and fluorescent performance.     

Two‐Dimensional Periodic Relief Gratings as a Versatile Platform for Label‐Free Specific DNA Detection

In this study, nanopillar arrays of silicon oxide are fabricated through a process involving very‐large‐scale integration, for use as two‐dimensional periodic relief gratings (2DPRGs) on silicon surfaces. Oligonucleotides are successively immobilized on the pillar surface, allowing the system to be used as an optical detector specific for the targeted single‐stranded DNAs (ssDNAs). The surfaces of the oligonucleotides‐modified 2DPRGs undergo insignificant structural changes, but upon hybridizing with target ssDNA, the 2DPRGs undergo dramatic changes in terms of their pillar scale. Binding of the oligonucleotides to the 2DPRG occurs in a way that allows them to retain their function and selectively bind the target ssDNA. The performance of the sensor is evaluated by capturing the target ssDNA on the 2DPRGs and measuring the effective refractive index (n_eff). The binding of the target ssDNA species to the 2DPRGs results in a color change from pure blue to red, observable by the naked eye along an angle of 15–20°. Moreover, effective medium theory is used to calculate the filling factors inside the 2DPRGs and, thereby, examine the values of n_eff during the structural changes of the 2DPRGs. Accordingly, these new films have potential applications as label‐free optical biosensors.