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

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Thermoelectric materials, which can generate electricity from waste heat or be used as solid-state Peltier coolers, could play an important role in a global sustainable energy solution. Such a development is contingent on identifying materials with higher thermoelectric efficiency than available at present, which is a challenge owing to the conflicting combination of material traits that are required. Nevertheless, because of modern synthesis and characterization techniques, particularly for nanoscale materials, a new era of complex thermoelectric materials is approaching. We review recent advances in the field, highlighting the strategies used to improve the thermopower and reduce the thermal conductivity.

/pdf/complex-thermoelectric-materials-59e25n2qme.pdf

Complex thermoelectric materials.

Fuel cells convert chemical energy directly into electrical energy with high efficiency and low emission of pollutants. However, before fuel-cell technology can gain a significant share of the electrical power market, important issues have to be addressed. These issues include optimal choice of fuel, and the development of alternative materials in the fuel-cell stack. Present fuel-cell prototypes often use materials selected more than 25 years ago. Commercialization aspects, including cost and durability, have revealed inadequacies in some of these materials. Here we summarize recent progress in the search and development of innovative alternative materials.

Materials for fuel-cell technologies

http://ma.ecsdl.org/content/MA2006-01/24/850.full.pdf

Proton Conducting Oxides for Fuel Cell Applications

Solid acid proton conductors: from laboratory curiosities to fuel cell electrolytes.

Highly preferred oriented lead barium titanate thin films using acetylacetone as chelating agent in a sol-gel process

CsH2PO4 has garnered interest as a proton-conducting electrolyte due to its exceptional conductivity at intermediate temperatures (228–300 °C) at which it adopts a cubic structure with a high degree of disorder. Here, through a study of mixtures of CsH2PO4 (CDP) and CsH5(PO4)2, the cubic phase was discovered to form solid solutions of composition [Cs1–xHx]H2PO4, with x extending to at least 2/9. A phase diagram of the composition space (1–x)CsH2PO4 – xH3PO4, 0 ≤ x ≤ 2/9 was developed through thermal analysis, high-temperature in situ X-ray diffraction experiments, and variable-temperature NMR spectroscopy. At temperatures above about 90 °C, monoclinic, stoichiometric CDP exists in equilibrium with Cs7(H4PO4)(H2PO4)8. These two phases displayed eutectoid behavior, with a eutectoid reaction temperature and composition of 155 °C and x = 0.18, respectively, to form cubic [Cs1–xHx]H2PO4. The structural studies revealed, rather remarkably, that the cubic phase accommodates vacancies on the cation site that are charge-balanced by excess protons, where the latter are chemically associated with phosphate groups. The conductivities of cubic phases of various compositions, measured by impedance spectroscopy, are comparable to that of CDP. The excellent proton conductivities of off-stoichiometric, cubic [Cs1–xHx]H2PO4 at temperatures well below the superprotonic transition of stoichiometric CDP present the opportunity to extend the low-temperature operating limit of CDP-based devices. More generally, the off-stoichiometric phase behavior demonstrated here introduces a new approach for the modification of superprotonic solid acid compounds. 

Phase Behavior and Superprotonic Conductivity in the System (1–x)CsH2PO4 – xH3PO4: Discovery of Off-Stoichiometric α-[Cs1–xHx]H2PO4

The use of ceria-based inverse opals as a catalyst system for the thermochemical production of fuels from sunlight offers the potential of improved fuel production kinetics over materials with random porosity. Quantitative methods for characterizing ordered porosity are lacking, thus limiting the ability to predict the lifetime of ordered structures at elevated temperatures. In the present work, Fourier transform image analysis was used to determine the effect of composition and temperature on ordered porosity for a series of CeO_2-ZrO_2 inverse opals having pore sizes ranging from 300 nm to 1 μm. An order parameter, γ, derived from the image analysis, was applied to scanning electron microscopy images and used to determine the degree of order in the inverse opal. The thermal stability studies indicate that loss of ordered porosity is highly dependent on temperature and that gas cycling effects have a minor effect on periodicity. A minimum Zr content of 20 at.% is necessary to retain periodicity for annealing up to 1000°C with pore diameters larger than 1 μm. These results show that CeO_2-ZrO_2 inverse opals can be used at higher temperatures than previously thought for efficient thermochemical hydrogen production without loss of the benefits associated with ordered porosity.

High-temperature structural stability of ceria-based inverse opals

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