Development of a Millimeter-Wave Electron-Spin-Resonance Measurement System for Ultralow Temperatures and Its Application to Measurements of Copper Pyrazine Dinitrate

We have developed a millimeter-wave electron-spin-resonance (ESR) measurement system using a ³He-⁴He dilution refrigerator for the ultralow-temperature range below 1 K. The currently available frequency range is 125–130 GHz. This system is based on a Fabry-Pérot-type resonator (FPR) that is composed of two mirrors. The frequency can be changed by adjusting the distance between the mirrors using a piezoelectric actuator installed at the bottom of the resonator. A homodyne detection system with an InSb detector is built into the low-temperature section of the ³He-⁴He dilution refrigerator; this system provides high sensitivity. Using this system, we performed ESR measurements on a Heisenberg quantum-spin chain—copper pyrazine dinitrate, Cu(C₄H₄N₂)(NO₃)₂—over the temperature range from 6.6 down to 0.25 K. The ESR lines change continuously with decreasing temperature. Our results suggest that the ESR spectrum of copper pyrazine dinitrate may be useful as a temperature sensor for the very low-temperature range.     

Dynamic nuclear self-polarization of Ⅲ-Ⅴ semiconductors

Ⅲ-Ⅴ semiconductors exhibit dynamic nuclear self-polarization (DYNASP) owing to the contact hyperfine interaction (HFI) between optically excited conduction electrons and lattice nuclei.In the self-polarization process at a low temperature,electron spin state and the nuclear polarization (magnetization) exchange a positive feedback,increasing energy splitting of the conduction electron states,thereby a large nuclear polarization.This phenomenon was theoretically predicted previously for conduction electrons excited linearly and elliptically polarized light.The polarization of the conduction electrons was represented by a parameter α in a formula for nuclear polarization (Eq.(9) in Ref.[1]);however,the effect of external magnetic fields on the nuclear polarization was not considered.Therefore,this study introduces this effect by further extending the previous studies.Herein,α'represents the combination of the effects of elliptically polarized electrons and an external magnetic field,which is used in the equations presented in previous studies.When α'=0,a large nuclear polarization is obtained below critical temperature Tc,but no polarization occurs above Tc.When α'＞ 0,the nuclear polarization is enhanced above Tc.Below Tc,the nuclear polarization follows a hysteresis curve when α'is partially manipulated by adjusting the degree of the polarization of the exciting laser.     

Measurement of axial neutral density profiles in a microwave discharge ion thruster by laser absorption spectroscopy with optical fiber probes

In order to reveal the physical processes taking place within the "μ10" microwave discharge ion thruster, internal plasma diagnosis is indispensable. However, the ability of metallic probes to access microwave plasmas biased at a high voltage is limited from the standpoints of the disturbance created in the electric field and electrical isolation. In this study, the axial density profiles of excited neutral xenon were successfully measured under ion beam acceleration by using a novel laser absorption spectroscopy system. The target of the measurement was metastable Xe I 5p(5)((2)P(0) (3/2))6s[3/2](0) (2) which absorbed a wavelength of 823.16 nm. Signals from laser absorption spectroscopy that swept a single-mode optical fiber probe along the line of sight were differentiated and converted into axial number densities of the metastable neutral particles in the plasma source. These measurements revealed a 10(18) m(-3) order of metastable neutral particles situated in the waveguide, which caused two different modes during the operation of the μ10 thruster. This paper reports a novel spectroscopic measurement system with axial resolution for microwave plasma sources utilizing optical fiber probes.     

A sonic spray interface for the mass analysis of highly charged ions from protein solutions at high flow rates

We have improved the sonic spray interface to enable the analysis of multiply charged ions of protein from a solution at a flow rate of 1 mL/min using a conventional liquid chromatograph/mass spectrometer. In this interface, we added a multihole plate in front of the sampling orifice of a mass spectrometer. This plate does not have a hole coaxial to the sampling orifice but has small holes around the central region of the plate. The plate reduces the density of the solvent molecules in the sprayed gas introduced into the vacuum region through the sampling orifice from the atmosphere and prevents the ions from being solvated and becoming charged droplets due to the cooling that follows adiabatic expansion of the sprayed gas. With this improvement, multiply charged ions whose charge distribution ranged from 11+ to 16+ were analyzed from a 1 μM cytochrome c solution at a high flow rate of 1 mL/min without using a splitter.     

Manufacture of organic transistors on large‐area flexible substrate using direct imaging exposure system by wet process suitable for roll‐to‐roll production

Organic thin‐film transistors (OTFTs) can be fabricated via a wet process and have exceptionally high flexibility. Therefore, production using the roll‐to‐roll (RtoR) method is expected. We succeeded in developing a new OTFT wet fabrication process adaptable to the RtoR process. Utilizing the electroless plating method for wiring formation, all materials can be formed in a wet process and can be patterned using the photolithography process. In addition, we succeeded in fabricating OTFT on an A4‐type flexible substrate using RtoR direct imaging exposure system.     

Synthesis of Silicon Nitride by a Combustion Reaction under High Nitrogen Pressure

Fine Si₃N₄ powders were prepared by the combustion reaction of an Si powder compact undez 10 MPa nitrogen pressure. Addition of Si₃N₄ powder to the starting Si promoted conversion of the reactants to homogeneous Si₃N₄ particles. Submicrometer SisN₄powders with a uniform size distribution around 0.5 μm were obtained from a 1.8Si-0.4Si₃N₄ mixture (molar ratio); they were free of residual Si.     

Oxidative stability of sardine and mackerel lipids with reference to synergism between phospholipids and α-tocopherol

Relationships between oxidative stability and the compositions of sardine and mackerel lipids were investigated in view of possible synergism between phospholipids andα-tocopherol (α-Toc). The total lipids extracted from viscera were highly susceptible to autoxidation, compared with lipids of white and red muscles and of skin. This seemed to be due to lower concentrations ofα-Toc and phosphatidylethanolamine (PE) in the tissue, but not to the level of polyunsaturated fatty acids. The synergistic effect of PE withα-Toc seemed to be slightly affected by the degree of unsaturation of its fatty acyl chains. The synergistic ability ofO-phosphoethanolamine, the base moiety of PE, was higher than that ofO-phosphoserine.O-Phosphocholine was only slightly effective. During the induction period of autoxidation, theα-Toc level decreased rapidly, and rapid lipid oxidation began only afterα-Toc was almost exhausted.     

A new approach for simulating aerodynamic vibrations of structures in a wind tunnel—development of an experimental system by means of hybrid vibration technique

The present paper describes a newly proposed technique for simulating aerodynamic vibration of structures, which is referred to as the hybrid vibration technique or HVT. This technique is a combination of step-by-step computer calculation and measurement of the aerodynamic force acting on a model structure in a wind tunnel test. Even though the HVT can be applied effectively, problems still exist with respect to obtaining accurate simulations. These problems include response delay in controlling the model behavior and the inertia force component present in the measured aerodynamic force. Techniques for compensating for response delay and for eliminating inertia force from measured aerodynamic force are applied to a developed system based on HVT simulations of aerodynamic vibration of elastic structures and structures exhibiting elasto-plastic behavior are performed by means of the newly developed system. The effectiveness of the techniques for compensating for the response delay and eliminating the inertia force can be confirmed from the results of the simulations. In addition, the possibility and applicability of HVT is indicated.     

Effect of static pressure on intracellular pH of adhesive Chinese hamster ovary cells

The effect of static pressure on the intracellular pH of the Chinese hamster ovary (CHO) cell line DR1000L4N was investigated. In cultivation of CHO cells at 0.9 MPa, two distinct populations were observed in the histogram of a flow cytometer, while single population was observed in cultivation at 0.1 MPa. The intracellular pH of the major population at 0.9 MPa was markedly lower than that of the single population at 0.1 MPa.     

New π-conjugated polymers containing oxazole in the main chain: Optical and electrochemical properties

Oxazole-containing π-conjugated polymers, an alternating copolymer of 9,9-dioctylfluorene-2,7-diyl and 2,5-bis(p-phenylene)oxazole (P(Flu-DPOxz)) and an alternating copolymer of 2,5-dialkoxy-p-phenylene and 2,5-bis(p-phenylene(oxazole)) (P(ROPh-DPOxz)), have been synthesized by Pd-catalyzed organometallic polycondensation. They were soluble in organic solvents, and had number average molecular weights of 18?600 and 24?700, respectively, in GPC analysis. P(Flu-DPOxz) and P(ROPh-DPOxz) showed UV-vis absorption peaks at about 380 nm in CHCl₃. Powder XRD patterns and UV-vis data of the polymers indicated that the polymer solid was amorphous. The polymers were photoluminescent both in chloroform and in solid. In chloroform, the emission peak appeared at about 420 nm with a high quantum yield of about 70%. The polymers were electrochemically active, and electrochemical data revealed that the oxazole unit behaved as a moderate electron-accepting unit.