Hydrothermal synthesis and in situ surface modification of boehmite nanoparticles in supercritical water

In situ surface modification of boehmite (AlOOH) nanoparticles during hydrothermal synthesis in supercritical water was examined by adding CH₃(CH₂)₄CHO and CH₃(CH₂)₅NH₂ as modifier reagents to the reactants. Changes in surface properties of the nanoparticles by surface modification was observed by FTIR, dispersion in solvents and TEM analyses, which demonstrated that reagents chemically binded onto the surface of the AlOOH nanoparticles. The results of SEM and TEM pictures show that the surface modification affects crystal growth and reduces the particle size and changes the morphology of the particles.     

Supercritical hydrothermal synthesis of organic-inorganic hybrid nanoparticles

We have developed supercritical hydrothermal synthesis method of metal oxide nanoparticles where metal salt aqueous solution is mixed with high temperature water to rapidly increase the temperature of the metal salt solution and thus reduce the reactions and crystallizations during the heating up period. By using this method, we succeeded in the continuous and rapid production of metal oxide nanocrystals. A new method proposes to synthesize organic-inorganic fused materials based on the methods of supercritical hydrothermal synthesis. By introducing organic materials in a reaction atmosphere of supercritical hydrothermal synthesis, we successfully synthesized metal oxide nanoparticles whose surface was modified with organic materials. In supercritical state, water and organic materials form a homogeneous phase, which provides an excellent reaction atmosphere for the organic modification of nanoparticles. Modification with bio-materials including amino acids was also possible. By changing organic modifiers, particle morphology and crystal structure were changed. This organic surface modification provides a various unique characteristics for the nanoparticles: Dispersion of nanoparticles in aqueous solutions, organic solvents or in liquid polymers can be controlled by selecting hydrophilic or hydrophobic modifiers.     

Analysis and modeling of char particle combustion with heat and multicomponent mass transfer

A char combustion model suitable for a large-scale boiler/gasifier simulation, which considers the variation of physical quantities in the radial direction of char particles, is developed and examined. The structural evolution within particles is formulated using the basic concept of the random pore model while simultaneously considering particle shrinkage. To reduce the computational cost, a new approximate analytical boundary condition is applied to the particle surface, which is approximately derived from the Stefan–Maxwell equations. The boundary condition showed reasonably good agreement with direct numerical integration with a fine grid resolution by the finite difference method under arbitrary conditions. The model was applied to combustion in a drop tube furnace and showed qualitatively good agreement with experiments, including for the burnout behavior in the late stages. It is revealed that the profiles of the oxygen mole fraction, conversion, and combustion rate have considerably different characteristics in small and large particles. This means that a model that considers one total conversion for each particle is insufficient to describe the state of particles. Since our char combustion model requires only one fitting parameter, which is determined from information on the internal geometry of char particles, it is useful for performing numerical simulations.     

Kinetic arrest behavior in martensitic transformation of NiCoMnSn metamagnetic shape memory alloy

High-field magnetic measurements were carried out in order to investigate behaviors of field-induced reverse martensitic transformation and kinetic arrest of NiCoMnSn metamagnetic shape memory alloy. In the thermomagnetization curves, it was confirmed that the reverse martensitic transformation temperature decreases 67 K by applying magnetic field of 5 T, while in the magnetic field cooling process under 5 T, martensitic transformation does not occur down to low temperatures. Equilibrium magnetic field, defined from the critical magnetic fields of the metamagnetic evidence in the magnetization curves, exhibits almost constant below about 100 K, suggesting that the entropy change becomes zero, which is considered to cause kinetic arrest behavior.     

Hydrothermal synthesis of surface-modified iron oxide nanoparticles

We synthesized surface-modified iron oxide nanoparticles in aqueous phase by heating an aqueous solution of iron sulfate (FeSO₄) at 473 K with a small amount of either n-decanoic acid (C₉H₁₉COOH) or n-decylamine (C₁₀H₂₁NH₂), which is not miscible with water at room temperature. Transmission electron microscopy showed that the addition of n-decanoic acid or decylamine changed the shape of the obtained nanoparticles. X-ray diffraction spectra revealed that the synthesized nanoparticles were in α-Fe₂O₃ or Fe₃O₄ phase while Fourier transform infrared spectroscopy and thermogravimetry indicated the existence of an organic layer on the surface of the nanoparticles. In the synthetic condition, decreased dielectric constant of water at higher temperature increased the solubility of n-decanoic acid or n-decylamine in water to promote the reaction between the surface of iron oxide nanoparticles and the organic reagents. After the synthesis, the used organic modifiers separated from the aqueous phase at room temperature, which may help the environmentally benign synthesis of surface-modified metal oxide nanoparticles.     

T helper 2-dominant antilymphoma immune response is associated with fatal outcome

The precise role of the endogenous immune system in modulating cancer development remains unclear. Tumor cells are generally thought to be nonimmunogenic because they are of 'self' origin. However, tumor-reactive lymphocytes can be isolated from patients with many types of cancer. It is unclear what role these lymphocytes play and why they fail to protect the host. Using a murine B-cell leukemia/lymphoma (BCL1) model, we showed the development of a vigorous antitumor T-cell response in the tumor-susceptible host. Specific T-cell responses against BCL1 developed as early as day 4. However, the nature of this nonprotective response is different from the protective response produced in a major histocompatibility complex-matched tumor-resistant host. Susceptible hosts developed a T helper 2 (Th2)-dominant response, whereas resistant hosts developed a Th1-dominant response to BCL1. Cytolytic activity against BCL1 developed in both resistant and susceptible hosts, but in the susceptible host, this response was weaker and delayed compared with that in the resistant host. Thus, tumor susceptibility does not necessarily mean the absence of an antitumor immune response. Rather, the nature of the antitumor immune response is critical in determining clinical outcome.     

Temperature control for the expansion of artificial DNA motif

The DNA, which forms a double helical conformation by the highly selective base-pairing rule with the width of 2 nm, is one of the polymers utilized as a template for nanoparticle assembly. Then, holiday junction structure, where two different DNA double strands intersect and replace each complement strand, is an important artificial motif for forming two-dimensional mesh-like DNA morphology. In this study, the two-dimensional sheet with the mesh-like conformation is formed and the growth of the DNA morphology is controlled by changing the temperature in the formation process. The influence of the cooling procedure on the formation process of the two-dimensional DNA sheet is observed by atomic force microscope, and the formation of double strands in the process is traced by absorption spectra. The spectroscopic results demonstrate that the two-dimensional DNA sheet is strongly dependent on the correlation between the applied cooling process and the melting temperature of double helical conformation, and that the growth of the two-dimensional DNA sheet can be manipulated by the cooling procedure. Further, we will show the size control of the DNA sheet by mixing the designed DNA which inhibits the growth of the DNA sheet.     

Magnetic properties and phase diagram of Ni50Mn50−xGax ferromagnetic shape memory alloys

We present the magnetic properties and the magnetic phase diagram of Ni₅₀Mn_50?xGa_x ferromagnetic shape memory alloys across a wide concentration range. Martensitic transformation, intermediate transformation, B2–L2₁ order–disorder transformation, Néel and Curie temperatures are determined for the prepared samples. The martensitic transformation temperature decreases with increasing Ga concentration and bends two times when crossing the Curie temperature and the intermediate-phase transformation temperature. Spontaneous magnetization and its composition dependence were also investigated. Composition dependence of the transformation temperatures and the spontaneous magnetization in the martensite phase of Ni₅₀Mn_50?xGa_x are compared with those of Ni₅₀Mn_50?xIn_x and Ni₅₀Mn_50?xSn_x, revealing a similarity in the NiMn-based alloy systems.     

Zinc oxide-coated plasmonic chip modified with a bispecific antibody for sensitive detection of a fluorescent labeled-antigen

A plasmonic biosensor chip of silver-coated PMMA grating with a zinc oxide (ZnO) overlayer is fabricated for surface plasmon field-enhanced fluorescence (SPF) detection of Cy5-labeled green fluorescent protein (GFP). A bispecific antibody (anti-GFP x anti-ZnO antibody) prepared in our lab is densely immobilized on the sensor chip for GFP detection. The sensitivity of the plasmonic biosensors is improved due to densely packed antibodies and ZnO-coating that suppresses nonspecific protein adsorption and fluorescent quenching. With the ZnO-coated plasmonic chip, Cy5-labeled GFP of 10 pM can be detected through SPF. This sensitivity is 100 higher compared with the normal fluorescent detection on a ZnO-coated glass slide.