An investigation of pipeline materials for continuous hyperpolarized 129Xe gas spectroscopy

In order to establish a continuous hyperpolarized xenon-129 (HP-129Xe) gas delivery system for MR imaging, the effect of the metallic materials in the gas pipeline on the signal intensity was investigated. In the gas pipeline, an appropriate surface is needed to minimize wall relaxation by the HP-129Xe gas caused by the interaction between the HP gas and the surface, which can lead to signal loss. Although Pyrex glass is a popular material for the HP gas chamber, it is fragile under heat or physical stress. In this study, five stainless steel tubes (STs) prepared with different surface film-forming processes were examined. The MR signal intensities of HP-129Xe gas that passed through each tube were then compared. The film passivated by iron fluoride maintained the highest level of hyperpolarization, whereas that passivated by chromium oxide maintained the lowest. A ST with an appropriate passive film may be a useful alternative to a Pyrex glass pipeline.     

Local magnetic fields in the Mo layer of Mo/Fe multilayer

Using time-differential perturbed-angular-correlation technique, hyperfine fields at ⁹⁹Tc (←⁹⁹Mo) in the Mo layers in polyimide/Fe (10 nm)/[Mo (t _Mo)/Fe (2.0 nm)]₁₂₀, where t _Mo is in the range between 0.4 and 1.5 nm, were measured at room temperature. The values of the magnetic hyperfine field at the Mo/Fe interface were extracted. Its dependence on the Mo layer thickness suggests that the oscillatory interlayer exchange coupling is due to conduction electron spin polarization in the Mo layer, which in turn is produced via an RKKY-type mechanism.     

Composite bonded magnets with controlled anisotropy directions prepared by viscous deformation technique

When a radially anisotropic rare earth bonded magnet for a rotor with a high (BH)_max value is magnetized multi-polarly, its flux distributes rectangularly and increases a cogging torque. In order to overcome this difficulty, we newly developed highly dense Sm₂Fe₁₇N₃ and Nd₂Fe₁₄B-based composite bonded magnets with continuously controlled anisotropy directions by using a viscous deformation technique.     

Functionalization of ultradispersed diamond for DNA detection

Carbon nanotubes have been synthesized by catalytic chemical vapour deposition of acetylene diluted with argon using three different catalysts, namely, nickel formate, cobalt formate and ferrocene. The synthesis was carried out at 700°C in a quartz reactor for 30 minutes. Thermal analysis was carried out in order to determine the yield of the nanotube. It was found that the deposit contains 86% nanotube, with nickel-based catalyst, which was the maximum. The yield of nanotube was 71 times that of the nickel loading. The TEM images reveal helical type of nanotubes with iron catalyst while cobalt and nickel catalysts yielded straight nanotubes. This technique can be explored for the bulk production of carbon nanotube in an economic way.     

2‐Arylsilacyclobutane as a Latent Carbanion Reacting with CO2

An electronically neutral 2‐arylsilacyclobutane generates a nucleophilic carbanion at room temperature through cleavage of the benzylic C?Si bond when simply dissolved in polar aprotic solvents such as N,N‐dimethylformamide (DMF). The nucleophilic species is capable of capturing carbon dioxide to furnish a silalactone. The carboxylation reaction is unique in that no additional activating agents are required.     

Photocatalyzed ortho‐Alkylation of Pyridine N‐Oxides through Alkene Cleavage

A photocatalyzed reaction of pyridine N‐oxides with alkenes gives ortho‐alkylated pyridines with cleavage of the carbon–carbon double bond. Benzyl and secondary alkyl groups are incorporated at the ortho position of pyridines in one pot.     

Thermal-expansion-derived lattice instability in La2CuO4

We present results for the thermal expansion, (T), of both polycrystalline and single crystalline La₂CuO₄. Our results demonstrate the existence of an anomaly in (T) aroundT=35 K which is clearly intrinsic and most likely due to a lattice instability.