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

Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

Tin dioxide is a widely used sensitive material for gas sensors. Many research and development groups in academia and industry are contributing to the increase of (basic) knowledge/(applied) know-how. However, from a systematic point of view the knowledge gaining process seems not to be coherent. One reason is the lack of a general applicable model which combines the basic principles with measurable sensor parameters. The approach in the presented work is to provide a frame model that deals with all contributions involved in conduction within a real world sensor. For doing so, one starts with identifying the different building blocks of a sensor. Afterwards their main inputs are analyzed in combination with the gas reaction involved in sensing. At the end, the contributions are summarized together with their interactions. The work presented here is one step towards a general applicable model for real world gas sensors.

Conduction Model of Metal Oxide Gas Sensors

The interaction of water with solid surfaces: Fundamental aspects

On the Controllable Soft-Templating Approach to Mesoporous Silicates

The dynamics of water molecules confined in MCM-41 was investigated by quasi-elastic neutron scattering. The measurement was performed for three water-filled MCM-41 samples with different pore sizes in the temperature range 200−300 K. The spectra were analyzed by using a model employed by Teixeria et al. in a study for bulk water. This model is composed of two motions of water molecules:  rotational and translational diffusions. For the translational diffusion, water molecules in MCM-41 are, on the whole, less mobile than those in bulk water, and the mobility is decreased by narrowing of the pore size. The residence time of translational diffusion of the confined water molecules shows the Arrhenius type of temperature dependence, which is in contrast to a non-Arrhenius behavior for bulk water. This implies that a growth of the hydrogen-bond network of water is hindered in a confined space by surface field. Spectra of MCM-41 sample having monolayer water were also measured and could be analyzed with a mode...

Neutron Scattering Study on Dynamics of Water Molecules in MCM-41

The thermal desorption spectra of ammonia, amines and pyridines chemisorbed on Cr2O3 as well as the infrared absorption spectra have been measured in order to elucidate the acidic properties of the surface. The adsorption of ammonia on the bare Cr2O3 surface at room temperature leads to the formation of two kinds of coordination species giving rise to desorption peaks at 443 and 543 K, and the bonding of the latter species to the surface is strengthened to cause a shift in the peak to 593 K when the adsorption temperature is raised to 473 K. Dimethylamine bonded to Lewis-acid sites on Cr2O3 causes the N—H bond-cleavage reaction when the sample is heated at 473 K. Pyridine is strongly held on the surface: half the pyridine molecules absorbed on Cr2O3 at room temperature remain on the surface even after evacuation at 773 K. The infrared study of these molecules suggests the formation of an α-pyridone-like complex.

Thermal desorption and infrared studies of ammonia, amines and pyridines chemisorbed on chromic oxide

The effect of confinement on the solid-liquid phase transitions of water was studied by using DSC and FT-IR measurements. Enthalpy changes upon melting of frozen water in MCM-41 and SBA-15 were determined as a function of pore size and found to decrease with decreasing pore size. The melting point also decreased almost monotonically with a decrease in pore size. Analysis of the Gibbs-Thomson relation on the basis of the thermodynamic data showed that there were two stages of interfacial free energy change after the constant region, i.e., below a pore size of 6.0 nm: a gradual decrease down to 3.4 nm and another decrease after a small jump upward. This fact demonstrates that the simple Gibbs-Thomson relation, i.e., a linear relation between the melting point change and the inverse pore size, is limited to the range not far from the melting point of bulk water. FT-IR measurements suggest that the decrease in enthalpy change and interfacial free energy change with decreasing pore size reflect the similarity of the structures of both liquid and solid phases of water in smaller pores at lower temperatures.

Enthalpy and interfacial free energy changes of water capillary condensed in mesoporous silica, MCM-41 and SBA-15.

Quasielastic neutron scattering (QENS) spectra of water-filled MCM-41 samples (pore diameters: 21.4 and 28.4 Angstrom) were measured over the temperature range 238-298 K and the momentum transfer range 0.31-0.99 A(-1) to investigate the dynamics of confined water molecules. The spectra, which consist mainly of contributions from the translational diffusion of water molecules, were analyzed by using the Lorentzian and the stretched exponential functions. Comparison of the fits indicated that the latter analysis is more reliable than the former one. The fraction of immobile water molecules located in the vicinity of the pore walls, which give an elastic component, was found to be 0.044-0.061 in both pores. The stretch exponent beta was determined as 0.66-0.80. It was shown that the translational diffusion of water molecules in the pores is decelerated by confinement and that the deceleration becomes marked with a decrease in pore size. The ratios of the translational diffusion coefficient D(T) of confined water to that of bulk water at room temperature were within a range of 0.47-0.63.

Neutron scattering study on dynamics of water molecules in MCM-41. 2. Determination of translational diffusion coefficient.

The state of water in room-temperature ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI+BF4−), has been investigated by measurements of absorption and desorption isotherms, attenuated total reflectance infrared (ATR-IR) spectroscopy, and 2H NMR relaxation method. The absorption enthalpies of water for the ionic liquid were estimated from the absorption isotherms. The enthalpies in the water mole fraction range of xw ≤ ∼0.5 are lower than the enthalpy of vaporization for bulk water, but become larger than the value for bulk with increasing mole fraction of absorbed water. The ATR-IR spectra for EMI+BF4−−water solutions in the range of 0.09 ≤ xw ≤ 0.34 have revealed that individual water molecules hydrogen-bonded to the anions predominate in the solutions at xw ≤ ∼0.2, while ∼30% of water molecules are hydrogen-bonded among them in the solutions at xw > ∼0.3. In addition, the activation energies for the rotational motion of a water molecule estimated from the 2H NMR relaxation rates have ind...

Shigeharu Kittaka

Papers

Neutron Scattering Study on Dynamics of Water Molecules in MCM-41

Thermal desorption and infrared studies of ammonia, amines and pyridines chemisorbed on chromic oxide

Enthalpy and interfacial free energy changes of water capillary condensed in mesoporous silica, MCM-41 and SBA-15.

Neutron scattering study on dynamics of water molecules in MCM-41. 2. Determination of translational diffusion coefficient.

Effect of Water on Structure of Hydrophilic Imidazolium-Based Ionic Liquid