抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

The chemistry of graphene oxide is discussed in this critical review Particular emphasis is directed toward the synthesis of graphene oxide, as well as its structure Graphene oxide as a substrate for a variety of chemical transformations, including its reduction to graphene-like materials, is also discussed This review will be of value to synthetic chemists interested in this emerging field of materials science, as well as those investigating applications of graphene who would find a more thorough treatment of the chemistry of graphene oxide useful in understanding the scope and limitations of current approaches which utilize this material (91 references)

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The chemistry of graphene oxide

An improved method for the preparation of graphene oxide (GO) is described. Currently, Hummers’ method (KMnO4, NaNO3, H2SO4) is the most common method used for preparing graphene oxide. We have found that excluding the NaNO3, increasing the amount of KMnO4, and performing the reaction in a 9:1 mixture of H2SO4/H3PO4 improves the efficiency of the oxidation process. This improved method provides a greater amount of hydrophilic oxidized graphene material as compared to Hummers’ method or Hummers’ method with additional KMnO4. Moreover, even though the GO produced by our method is more oxidized than that prepared by Hummers’ method, when both are reduced in the same chamber with hydrazine, chemically converted graphene (CCG) produced from this new method is equivalent in its electrical conductivity. In contrast to Hummers’ method, the new method does not generate toxic gas and the temperature is easily controlled. This improved synthesis of GO may be important for large-scale production of GO as well as the ...

https://www.researchgate.net/file.PostFileLoader.html?id=54ca19b4cf57d79a768b4618&assetKey=AS%3A273691751976961%401442264606356

Improved Synthesis of Graphene Oxide

There is intense interest in graphene in fields such as physics, chemistry, and materials science, among others. Interest in graphene's exceptional physical properties, chemical tunability, and potential for applications has generated thousands of publications and an accelerating pace of research, making review of such research timely. Here is an overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.

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Graphene and Graphene Oxide: Synthesis, Properties, and Applications

The richness of optical and electronic properties of graphene attracts enormous interest. Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability. So far, the main focus has been on fundamental physics and electronic devices. However, we believe its true potential lies in photonics and optoelectronics, where the combination of its unique optical and electronic properties can be fully exploited, even in the absence of a bandgap, and the linear dispersion of the Dirac electrons enables ultrawideband tunability. The rise of graphene in photonics and optoelectronics is shown by several recent results, ranging from solar cells and light-emitting devices to touch screens, photodetectors and ultrafast lasers. Here we review the state-of-the-art in this emerging field.

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Graphene photonics and optoelectronics

ALLENDE. P. R. Heck, M. J. Pellin, A. M. Davis, D. Isheim, D. N. Seidman, J. Hiller, A. Mane, J. Elam, M. R. Savina, T. Stephan, F. J. Stadermann, X. Zhao, T. L. Daulton, C. Floss, S. Amari, Robert A. Pritzker Center for Meteoritics and Polar Studies, Dept. of Geology, The Field Museum, 1400 S. Lake Shore Drive, Chicago IL, USA, prheck@fieldmuseum.edu. Chicago Center for Cosmochemistry, Dept. of the Geophysical Sciences, Univ. of Chicago, Chicago, IL, USA. Materials Science Division, Argonne National Laboratory, Argonne, IL, USA. Enrico Fermi Institute, Univ. of Chicago, Chicago, IL, USA. Northwestern Univ. Center for Atom-Probe Tomography, Dept. of Materials Science & Engineering, Northwestern Univ., Evanston, IL, USA. Energy Systems Division, Argonne National Laboratory, Argonne, IL, USA. Laboratory for Space Sciences, Physics Dept., Center for Materials Innovation, Washington Univ., St. Louis, MO, USA.

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Atom-Probe Tomographic Analyses of Meteoritic Nanodiamond Residue from Allende

VOLATILE ELEMENT FRACTIONATION IN THE INNER SOLAR SYSTEM. P. A. Bland, D. Rost, E. P. Vicenzi, F. J. Stadermann, C. Floss, M. Fries, A. Steele, G. K. Benedix, M. R. Lee, L. E. Watt and A. T. Kearsley; IARC, Dept Earth Sci. & Eng., Imperial College London, South Kensington Campus, London SW7 2AZ, UK, p.a.bland@imperial.ac.uk; Dept. Mineralogy, Natural History Museum, Cromwell Road, London SW7 5BD, UK; Dept. Mineral Sci., National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA; Laboratory for Space Sci. & Dept Physics, CB 1105, Washington University, Saint Louis, MO 63130, USA; Geophys. Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road, Washington, D.C. 20015, USA; Dept. Earth & Planetary Sci., Washington University, Saint Louis, MO 63130, USA; Div. Earth Sci., University of Glasgow, Lilybank Gardens, Glasgow G12 8QQ, UK.

Trace Element Carrier Phases in Primitive Chondrite Matrix: Implications for Volatile Element Fractionation in the Inner Solar System

Extreme Uncorrelated 54Cr, 17O, and 18O Enrichments In Sub-Micron Orgueil Grains

Introduction: Presolar silicates are the newest addition to the presolar grain inventory. Abundant sub-micrometer silicate grains have been identified and characterized to date [e.g., 1–4]. Here we report results from searches for O-bearing presolar grains in the CO3 chondrite, ALHA77307. Experimental: The NanoSIMS was used to search for isotopically anomalous grains in a thin-section of ALHA77307 by rastering a primary Cs + beam of about 1 pA over 10×10 μm

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Presolar Silicate and Oxide Dust in ALH A77307

Introduction: Oxide and silicate grains have been identified by infrared (IR) spectroscopy to be a major component of the dust shells in O-rich Asymptotic Giant Branch (AGB) stars. Recently, such grains have also been identified in the laboratory through investigations of meteoritic presolar grains. Coordinated isotopic and elemental measurements of these presolar grains can enhance our understanding of dust formation processes in O-rich environments and also aid in the interpretation of IR spectra. The IR spectra of about half of all AGB stars exhibit a 13 μm feature [1]. A variety of phases have been proposed as its carrier including SiO2 whose extinction spectra similarly show a 13 μm peak [2]. Here we report on two silica grains identified in the primitive carbonaceous chondrite ALHA77307 [3], and explore the possibility that silica may be the carrier of the 13 μm feature associated with evolved stars. Experimental Methods: Phases with anomalous O-isotopic compositions were identified in a polished thin-section of ALHA77307 with the NanoSIMS 50. A primary Cs + beam of less than 1 pA was rastered over 10×10 μm 2 matrix areas. Secondary electrons as well as 12,13 C – and 16,17,18 O – secondary ions were collected in multi-collection mode, with total integration times of ~2 hours per area. Following the isotopic measurements, the elemental compositions of the Oanomalous grains were measured with the PHI 700 Scanning Auger Nanoprobe at electron beam settings of 10 keV and 0.25 nA. Elemental maps were acquired for selected grains. After the Auger Nanoprobe measurements, one of the silica grains found was measured by Transmission Electron Microscopy (TEM). The TEM sample was prepared by focused ion beam (FIB) extraction using the Nova NanoLab 600, and was then characterized in a 200 kV JEOL 2200FS TEM at the Naval Research Laboratory. Finally, an additional O-isotopic measurement of the extracted FIB section was done with the NanoSIMS at Washington University. Results: Our isotopic survey of ALHA77307 led to the identification of sixty-six presolar grains, two of which were later identified as likely silica grains. Figure 1 shows the O-isotopic compositions of these two silica grains as well as two similar grains identified in other studies [4, 5]. All four of the silica grains found to date are 17 O-rich, with near-solar 18 O/ 16 O ratios, and therefore can be classified as group 1 grains [6]. Outflows of low-mass AGB stars that have undergone first dredge-up are likely sources for group 1 grains. The identification as possible silica is based on Auger Nanoprobe data, which show that both grains have compositions consistent with SiO2 (O/Si = 2.2±0.3; Figure 2); Mg and Fe contents in the grains are below detection limits (< 3 at.%). Grain 21420 was extracted using the FIB technique and studied in the TEM. The measurements showed the presence of a 50×140 nm 2 Si-rich area, adjacent to a 300 nm Mgand Fe-bearing grain. NanoSIMS measurements on the extracted slice showed a solar Oisotopic composition for the Mgand Fe-bearing grain, but the size of the Si-rich region was insufficient for definitive structural or isotopic characterization. Three of the silica grains identified to date come from ALHA77307. Based on the data from this study, the abundance of presolar silica is 4 ppm and makes up ~4% of all presolar silicates found in this meteorite.

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Frank J. Stadermann

Papers

Atom-Probe Tomographic Analyses of Meteoritic Nanodiamond Residue from Allende

Trace Element Carrier Phases in Primitive Chondrite Matrix: Implications for Volatile Element Fractionation in the Inner Solar System

Extreme Uncorrelated 54Cr, 17O, and 18O Enrichments In Sub-Micron Orgueil Grains

Presolar Silicate and Oxide Dust in ALH A77307

The Origin of Presolar Silica Grains in AGB Stars