Tokyo University of Science

About: Tokyo University of Science is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Catalysis & Thin film. The organization has 15800 authors who have published 24147 publications receiving 438081 citations. The organization is also known as: Tōkyō Rika Daigaku & Science University of Tokyo.

Asymmetric Diels–Alder Reactions of α,β‐Unsaturated Aldehydes Catalyzed by a Diarylprolinol Silyl Ether Salt in the Presence of Water

Abstract: The Diels–Alder reaction is a powerful synthetic method for the construction of regioand stereochemically defined cyclohexane frameworks. There are several catalytic enantioselective methods, and MacMillan and co-workers developed the first Diels–Alder reaction involving an organocatalyst, which proceeds by a LUMO-lowering activation mechanism. Since then several asymmetric Diels–Alder reactions involving organocatalysts have been reported. Our group and that of Jørgensen developed a diarylprolinol silyl ether as an effective organocatalyst in 2005, and this type of catalyst has since been employed widely in several asymmetric reactions. Recently, we found that diarylprolinol silyl ether 1 combined with CF3CO2H is an effective Diels–Alder catalyst in toluene. In contrast, water has attracted a lot of interest as a reaction medium in current organic chemistry because of its unique properties. In the Diels–Alder reaction, for instance, the reaction is accelerated “in water” (homogeneous dilute conditions) and “on water” (biphasic conditions). We reported the positive effect of water on diastereoand enantioselectivities for the asymmetric aldol reaction in the presence of water. Palomo et al. and Ma and co-workers reported the enantioselective Michael reaction catalyzed by dialkyland diphenylprolinol silyl ethers, respectively in the presence of water. Some organocatalyzed reactions are known to be affected by dissolved water, and on the basis of our interest in reactions in the presence of water, we have examined the enantioselective Diels–Alder reaction by using diarylprolinol silyl ether as an organocatalyst. Although Northrup and MacMillan and Ogilvie and co-workers reported the asymmetric Diels–Alder reaction in the presence of water, we developed a green and practical procedure that does not require an organic solvent, even for the purification step. We also observed an interesting phenomenon, namely the positive effect of water on the rate and enantioselectivity of the reaction, which is different from that of the “on water” reaction and will be described herein. First, we chose the model reaction between cinnamaldehyde and cyclopentadiene, which we had found to be promoted by a combination of 1 (Figure 1) and CF3CO2H in

Cosmology in generalized Proca theories

Abstract: We consider a massive vector field with derivative interactions that propagates only the 3 desired polarizations (besides two tensor polarizations from gravity) with second-order equations of motion in curved space-time. The cosmological implications of such generalized Proca theories are investigated for both the background and the linear perturbation by taking into account the Lagrangian up to quintic order. In the presence of a matter fluid with a temporal component of the vector field, we derive the background equations of motion and show the existence of de Sitter solutions relevant to the late-time cosmic acceleration. We also obtain conditions for the absence of ghosts and Laplacian instabilities of tensor, vector, and scalar perturbations in the small-scale limit. Our results are applied to concrete examples of the general functions in the theory, which encompass vector Galileons as a specific case. In such examples, we show that the de Sitter fixed point is always a stable attractor and study viable parameter spaces in which the no-ghost and stability conditions are satisfied during the cosmic expansion history.

Particle toxicology and health - where are we?

Abstract: Particles and fibres affect human health as a function of their properties such as chemical composition, size and shape but also depending on complex interactions in an organism that occur at various levels between particle uptake and target organ responses. While particulate pollution is one of the leading contributors to the global burden of disease, particles are also increasingly used for medical purposes. Over the past decades we have gained considerable experience in how particle properties and particle-bio interactions are linked to human health. This insight is useful for improved risk management in the case of unwanted health effects but also for developing novel medical therapies. The concepts that help us better understand particles’ and fibres’ risks include the fate of particles in the body; exposure, dosimetry and dose-metrics and the 5 Bs: bioavailability, biopersistence, bioprocessing, biomodification and bioclearance of (nano)particles. This includes the role of the biomolecule corona, immunity and systemic responses, non-specific effects in the lungs and other body parts, particle effects and the developing body, and the link from the natural environment to human health. The importance of these different concepts for the human health risk depends not only on the properties of the particles and fibres, but is also strongly influenced by production, use and disposal scenarios. Lessons learned from the past can prove helpful for the future of the field, notably for understanding novel particles and fibres and for defining appropriate risk management and governance approaches.

Detection of uranium and chemical state analysis of individual radioactive microparticles emitted from the Fukushima nuclear accident using multiple synchrotron radiation X-ray analyses.

Abstract: Synchrotron radiation (SR) X-ray microbeam analyses revealed the detailed chemical nature of radioactive aerosol microparticles emitted during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, resulting in better understanding of what occurred in the plant during the early stages of the accident. Three spherical microparticles (∼2 μm, diameter) containing radioactive Cs were found in aerosol samples collected on March 14th and 15th, 2011, in Tsukuba, 172 km southwest of the FDNPP. SR-μ-X-ray fluorescence analysis detected the following 10 heavy elements in all three particles: Fe, Zn, Rb, Zr, Mo, Sn, Sb, Te, Cs, and Ba. In addition, U was found for the first time in two of the particles, further confirmed by U L−edge X-ray absorption near-edge structure (XANES) spectra, implying that U fuel and its fission products were contained in these particles along with radioactive Cs. These results strongly suggest that the FDNPP was damaged sufficiently to emit U fuel and fission products outside the con...