Giant Complex Modulus Reduction of κ‐Carrageenan Magnetic Gels

Summary: Effects of magnetization on the complex modulus of κ‐carrageenan magnetic gels have been investigated. The magnetic gel was made of a natural polymer, κ‐carrageenan, and a ferromagnetic particle, barium ferrite. The complex modulus of the magnetic gel was investigated by dynamic viscoelastic measurements with a compressional strain. It was first observed that the magnetic gels showed giant storage modulus reduction ≈10⁷ Pa before and after magnetization. The reduction was nearly independent of the frequency, and it increased with increasing the volume fraction of the ferrite. The maximum reduction in the storage modulus reached 14.9 MPa which corresponds to 76.5% of the modulus before magnetization. It was also found that the change in the modulus was nearly independent of a magnetization direction. Magnetism and morphology of the magnetic gels were also presented.

Strain dependence of the storage modulus at 1 Hz for κ‐carrageenan gel (□) and its magnetic gel before (○) and after (•) magnetization (ϕ = 0.39). The geometry of magnetization and strain directions is perpendicular.     

Intramolecular hydrosilation of acetylenes: Regioselective functionalization of homopropargyl alcohols

Platinum-catalyzed intramolecular hydrosilation of hydrodimethylsilyl ethers of homopropargyl alcohols proceeds regioselectively in a 5-exo-dig mode. The resulting vinylsilanes can be transformed into 3-alkanon-1-ol and 3-bromo-3-alken-1-ol derivatives by H₂O₂ oxidation and bromine cleavage, respectively.     

Anthraquinone-Based Oligomer as a Long Cycle-Life Organic Electrode Material for Use in Rechargeable Batteries

An anthraquinone (AQ)-based dimer and trimer linked by a triple bond (−C≡C−) were newly synthesized as active materials for the positive electrode of rechargeable lithium batteries. These synthesized oligomers exhibited an initial discharge capacity of about 200 mAh g⁻¹ with an average voltage of 2.2–2.3 V versus Li_(C.E.). These capacity values are similar to that of the AQ-monomer, reflecting the two-electron transfer redox per AQ unit. Regarding their cycling stability, the capacity of the monomer electrode quickly decreased; however, the electrodes of the prepared oligomers showed an improved cycling performance. In particular, the discharge capacities of the trimer remained almost constant for 100 cycles. A theoretical calculation revealed that the intermolecular binding energy can be increased to the level of a weak covalent bonding by oligomerization, which would be beneficial to suppress the dissolution of the organic active materials into the electrolyte solutions. These results show that the cycle-life of organic active materials can be extended without lowering the discharge capacity by the oligomerization of the redox active molecule unit.     

Intensive optimization and evaluation of global DNA methylation quantification using LC-MS/MS

Analytical and Bioanalytical Chemistry - DNA methylation is a typical epigenetic phenomenon. Numerous methods for detecting global DNA methylation levels have been developed, among which LC-MS/MS...     

Asymptotic Stability of N-Solitary Waves of the FPU Lattices

We study stability of N-solitary wave solutions of the Fermi-Pasta-Ulam (FPU) lattice equation. Solitary wave solutions of the FPU lattice equation cannot be characterized as critical points of conservation laws due to the lack of infinitesimal invariance in the spatial variable. In place of standard variational arguments for Hamiltonian systems, we use an exponential stability property of the linearized FPU equation in a weighted space which is biased in the direction of motion. The dispersion of the linearized FPU equation balances the potential term for low frequencies, whereas the dispersion is superior for high frequencies.We approximate the low frequency part of a solution of the linearized FPU equation by a solution to the linearized Korteweg-de Vries (KdV) equation around an N-soliton solution. We prove an exponential stability property of the linearized KdV equation around N-solitons by using the linearized Bäcklund transformation and use the result to analyze the linearized FPU equation.     

Effects of water content on magnesium deposition from a Grignard reagent-based tetrahydrofuran electrolyte

It is well known that water causes decomposition of Grignard reagents. When these reagents are used, water or moisture should be eliminated. However, it is possible that a very small amount of water, for example, trapped in the walls of the glassware used, can enter the system even in a well-controlled Ar glove box. Therefore, in this work, the effect of very low concentrations of water on Mg deposition from a Grignard reagent-based electrolyte was studied. It was shown that a minute amount of water, although insufficient to cause destruction of the Grignard reagent, affects the overpotential for Mg deposition, resulting in Mg deposits of different morphology. For reproducible and reversible Mg deposition and dissolution, it is desirable that the water content of the electrolyte is kept as low as possible and the electrolyte is left to stand for at least several hours after preparation.     

Stereoselective Synthesis and Physicochemical Properties of Liquid‐Crystal Compounds Possessing a trans‐2,5‐Disubstituted Tetrahydropyran Ring with Negative Dielectric Anisotropy

Three stereoselective syntheses and the physicochemical properties of trans,trans‐5‐(4‐ethoxy‐2,3‐difluorophenyl)‐2‐(4‐propylcyclohexyl)tetrahydropyran, which is an important liquid‐crystal compound with a large negative dielectric anisotropy (Δε=?7.3), are described. The key step in the construction of the trans‐2,5‐disubstituted tetrahydropyran ring in the first approach involved a benzylic cation mediated intramolecular olefin cyclization of a 2‐allyloxy‐1‐arylethanol derivative. The second method included the Et₂Zn‐induced 1,2‐aryl shift of a bromohydrin obtained from a hetero‐Diels–Alder reaction, followed by stereoselective bromination. The third approach utilized the hetero‐Diels–Alder reaction of trans‐4‐propylcyclohexanecarboxaldehyde and a 2‐aryl‐3‐(trimethylsilyl)oxy‐1,3‐butadiene, followed by stereoselective protonation. From results obtained by using a quantum chemical calculation method, the reason why the target compound shows a large negative Δε value is discussed.     

Influence of Surface Properties on SEM Observation for Carbon Nanotubes with Pretreatment Using Room Temperature Ionic Liquids

In this study, we observed hydrophobic or hydrophilic carbon nanotubes (CNTs) by scanning electron microscopy (SEM); the samples were pretreated with room temperature ionic liquids (RTILs) to impart electrical conductivity to their surfaces. When the amount of RTIL on the sample surface and the affinity between the RTIL and sample surface were tuned, suitable electroconductive thin layers were formed on the sample surfaces. The presence of these layers allowed high-quality SEM images to be observed at the nano level. Suitable pretreatments for CNT were achieved using dilute RTIL/ethanol solutions. By optimizing these conditions, we acquired SEM images that were similar in quality to those of samples subjected to the conventional pretreatment of metal sputtering. The highest resolution of the SEM images was less than 30 nm.     

Monte Carlo Simulation of Near Infrared Reflectance Spectroscopy in the Wavelength Range from 1000 nm to 1900 nm

We have calculated the characteristics of reflected near infrared light, which is incident on the skin surface, scattered in the skin tissue and detected, in the wavelength range from 1000 nm to 1900 nm. We have used a Monte Carlo method to calculate the propagation path, the average photon visit depth, the average photon path length, etc. for the cases of short source-detector distances, to which the isotropic scattering approximation cannot be applied. An experiment to validate the simulation results was also conducted using a liquid phantom.     

Detection of H2O2 released from TiO2 photocatalyst to air.

H2O2 generated and released from TiO2 photocatalysts to the gas phase was detected. A flow-through cell packed with TiO2-coated glass beads was irradiated with UV light, and the gas flowing out of the cell was flushed through a collecting solution containing 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulforic acid) diammonium salt (ABTS) and peroxidase. Oxidative coloration of ABTS was observed only in the absence of catalase, indicating the presence of H2O2 in the gas. The quantum yield of the H2O2 generation was estimated to be > 1 x 10(-7). The detected amount of H2O2 decreased as the TiO2 thickness decreased. H2O2 was not detected when dry air or nitrogen was used.