There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

Shape-engineerable and highly densely packed single-walled carbon nanotubes and their application as super-capacitor electrodes

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Gallium nitride (GaN) and its allied binaries InN and AIN as well as their ternary compounds have gained an unprecedented attention due to their wide-ranging applications encompassing green, blue, violet, and ultraviolet (UV) emitters and detectors (in photon ranges inaccessible by other semiconductors) and high-power amplifiers. However, even the best of the three binaries, GaN, contains many structural and point defects caused to a large extent by lattice and stacking mismatch with substrates. These defects notably affect the electrical and optical properties of the host material and can seriously degrade the performance and reliability of devices made based on these nitride semiconductors. Even though GaN broke the long-standing paradigm that high density of dislocations precludes acceptable device performance, point defects have taken the center stage as they exacerbate efforts to increase the efficiency of emitters, increase laser operation lifetime, and lead to anomalies in electronic devices. The p...

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Luminescence properties of defects in GaN

Carbon nanotubes are unique tubular structures of nanometer diameter and large length/diameter ratio. The nanotubes may consist of one up to tens and hundreds of concentric shells of carbons with adjacent shells separation of ∼0.34 nm. The carbon network of the shells is closely related to the honeycomb arrangement of the carbon atoms in the graphite sheets. The amazing mechanical and electronic properties of the nanotubes stem in their quasi-one-dimensional (1D) structure and the graphite-like arrangement of the carbon atoms in the shells. Thus, the nanotubes have high Young’s modulus and tensile strength, which makes them preferable for composite materials with improved mechanical properties. The nanotubes can be metallic or semiconducting depending on their structural parameters. This opens the ways for application of the nanotubes as central elements in electronic devices including field-effect transistors (FET), single-electron transistors and rectifying diodes. Possibilities for using of the nanotubes as high-capacity hydrogen storage media were also considered. This report is intended to summarize some of the major achievements in the field of the carbon nanotube research both experimental and theoretical in connection with the possible industrial applications of the nanotubes.

Carbon nanotubes: properties and application

Polarized micro-Raman spectroscopy has been performed on spatially separated single-wall carbon nanotubes (SWNTs) in the form of individual nanotubes or thin ropes of only a few SWNTs. Different from bulk samples, the Raman spectra are composed of well-resolved peaks which allow a direct comparison of experimental data with theoretical calculations. Orientation-dependent measurements reveal maximum intensity of all Raman modes when the nanotubes are aligned parallel to the polarization of the incident laser light. The angular dependences clearly deviate from the selection rules predicted by theoretical studies. These differences are attributed to depolarization effects caused by the strongly anisotropic geometry of the nanotubes and to electronic resonance effects for excitation at 633 nm.

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Polarized Raman Spectroscopy on Isolated Single-Wall Carbon Nanotubes

LaMnO(3) was studied by synchrotron x-ray diffraction, optical spectroscopies, and transport measurements under pressures up to 40 GPa. The cooperative Jahn-Teller (JT) distortion is continuously reduced with increasing pressure. There is strong indication that the JT effect and the concomitant orbital order are completely suppressed above 18 GPa. The system, however, retains its insulating state to approximately 32 GPa, where it undergoes a bandwidth-driven insulator-metal transition. Delocalization of electron states, which suppresses the JT effect but is insufficient to make the system metallic, appears to be a key feature of LaMnO(3) at 20-30 GPa.

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Pressure-induced quenching of the Jahn-Teller distortion and insulator-to-metal transition in LaMnO(3).

We study the spectral response of optical metamaterials consisting of gold split-ring resonators. We utilize reflection spectroscopy in the near infrared region at normal incidence in the experiments. Our theoretical modeling is based on rigorous diffraction theory. We perform a comprehensive analysis of the dependence of the features of both the electric and the oscillating-circuit resonance on the geometry of the metamaterial. We show that theory and experiment are in good agreement.

Resonances of split-ring resonator metamaterials in the near infrared

The laser host material yttrium orthovanadate ${\mathrm{YVO}}_{4}$ with a tetragonal zircon-type structure has been studied by angle-dispersive powder x-ray diffraction in a diamond anvil cell up to $26\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ $(T=300\phantom{\rule{0.3em}{0ex}}\mathrm{K})$. In situ diffraction confirms that the compound undergoes a nonreversible transformation to a scheelite-type structure at a pressure of $8.5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. The equations of state of the zircon and scheelite phases and changes in internal structural parameters are reported. The effect of pressure on the distorted tetrahedral and dodecahedral coordinations of the V and Y ions, respectively, is discussed.

Structural properties of the zircon- and scheelite-type phases of YVO 4 at high pressure

The pressure-volume relation of sodium is measured up to 100 GPa using high-resolution angle-dispersive synchrotron x-ray diffraction. At a pressure of 65(1) GPa Na is found to undergo a structural phase transition from a body-centered to a face-centered-cubic modification. Total-energy calculations of Na under pressure are performed using the full-potential linearized augmented plane-wave method. The calculated pressure-volume relations and the bcc-fcc transition pressure are compared to the experimental results.

Ingo Loa

Papers

Polarized Raman Spectroscopy on Isolated Single-Wall Carbon Nanotubes

Pressure-induced quenching of the Jahn-Teller distortion and insulator-to-metal transition in LaMnO(3).

Resonances of split-ring resonator metamaterials in the near infrared

Structural properties of the zircon- and scheelite-type phases of YVO 4 at high pressure

Sodium under pressure: bcc to fcc structural transition and pressure-volume relation to 100 GPa