Ion-beam processing of single crystal diamond using SOG mask

Various ion-beam etching characteristics of diamond and selectivity between diamond and spin-on-glass (SOG) were examined. The maximum selectivity of diamond and SOG was 12.7 in oxygen reactive ion-beam etching process at 100 V acceleration voltage. Using this etching condition and dot-shaped SOG mask, conical diamond field electron emitter arrays with 30 nm curvature radius, 2.58 μm base radius and 5.86 μm height were fabricated.     

Antireflection coating formed by plasma-enhanced chemical-vapor deposition for terahertz-frequency germanium optics

A method of manufacturing optical coatings for germanium optics used at terahertz frequencies has been developed. The various optical coatings used at terahertz frequencies are difficult to manufacture conventionally because these coatings must be as thick as several tens of micrometers, which is far thicker than those used in the optical region. One way to overcome this problem is to form a silicon oxide layer through plasma-enhanced chemical-vapor deposition, with silane (SiH4) as a source gas. Using this method, I formed 21-microm-thick silicon oxide films as antireflection (AR) layers for germanium optics and obtained low reflection at 1.7 THz (wavelength, lambda = 175 microm). This method is easily applied to large-aperture optics and micro-optics as well as to optics with a complex surface form. The AR coatings can also be formed for photoconductive detectors made from germanium doped with gallium at a low temperature (160 degrees C); this low temperature ensures that the doped impurities in the germanium do not diffuse. Fabrication of optical coatings upon substrates that have refractive indices of 3.84-11.7 may also be possible by control of the refractive indices of the deposited layers.     

Nepheline gradient solid solutions

Nepheline solid solutions having high thermal expansion coefficients ranging from 1.2 to 1.8×10⁻⁵°C⁻¹ were prepared from the systems NaAlSiO₄-LiAlSiO₄ and NaAlSi₄-KAlSiO₄. The thermal expansion coefficient decreased by substituting Li⁺ for Na⁺, and increased by substituting K⁺ for Na⁺. By forming a series of the nepheline solid solutions in a single ceramic body, a functionally gradient material with respect to thermal expansion was prepared. The thermal expansion coefficient should gradually vary with position according to the composition x in Na_1−x M_xAlSiCO₄ (M=Li and K).     

Inhomogeneous compression of PEMFC gas diffusion layer: Part I. Experimental

This paper presents a study on the effect of inhomogeneous compression of gas diffusion layer (GDL) caused by the channel/rib structure of flow-field plate. The experimentally evaluated properties are GDL intrusion into the channel, gas permeability, in-plane and through-plane bulk electric conductivities, and contact resistances at interfaces as a function of compressed thickness of GDL. It was found that the GDL is compressed very little under the channel whereas GDL under the rib is compressed to gasket thickness. The compression of GDL reduces gas permeability and contact resistance, and improves bulk conductivity. Hence, the inhomogeneous compression of GDL may lead into significant local variation of mass and charge transport properties in the GDL. These effects have been ignored in most of the published modeling studies. This contribution, part I, covers the experimental setup and measurement results, and a model which takes the inhomogeneous compression of GDL into account is presented in part II.     

Inhomogeneous compression of PEMFC gas diffusion layer: Part II. Modeling the effect

The effect of inhomogeneous compression of GDL on the mass and charge transfer in PEMFC is studied. The model utilizes experimentally evaluated GDL parameters as a function of thickness. The modeling results are compared with a conventional model that excludes the effects. As a result, it is shown that the inhomogeneous compression has a significant effect on the current density distribution because of the varying contact resistance between GDL and electrode. This also implies that there are possible hot spots occurring inside the electrode, and thus inhomogeneous compression can have significant effects on the lifetime and local performance of the cell. According to the achieved results, the inhomogeneous compression of GDL cannot be neglected.     

Inhibition by angiotensin II type 1 receptor antagonist of cardiac phenotypic modulation after myocardial infarction

The purpose of this study was to examine the cardiac phenotype and remodeling after myocardial infarction and the effect of the angiotensin II type 1 (AT1) receptor antagonist (TCV-116) on the gene expression. Myocardial infarction in rats was produced by ligation of the coronary artery. TCV-116 (10 mg/kg/day) was administered orally to rats from 1 day after myocardial infarction. At 1, 2 and 3 weeks after myocardial infarction, blood pressure and heart rate were measured, and the heart was removed. The left ventricle was measured for infarct size and weight, and then the total RNA from the non-ischemic left ventricle was extracted. mRNAs in the non-ischemic left ventricle were measured by Northern blot analysis. The weight of the non-ischemic left ventricle was significantly increased 3 weeks after infarction. This was completely prevented by TCV-116 treatment. mRNA levels for beta-myosin heavy chain (beta-MHC), atrial natriuretic polypeptide (ANP), collagen types I and III and transforming growth factor-beta 1 (TGF-beta 1) in the non-ischemic left ventricle were increased by a factor of 3.0, 6.7, 7.9, 4.0 and 1.4 (P < 0.01), respectively, 1 week after infarction. There was no increase in alpha-skeletal actin mRNA at 1 and 2 weeks, but it was increased by a factor of 2.9 (P < 0.05) at 3 weeks. On the other hand, there was no change in alpha-MHC mRNA during the 3 weeks. TCV-116 significantly suppressed the increased gene expression of beta-MHC and alpha-skeletal actin in the non-ischemic myocardium at all time points, and also suppressed the expression of ANP at 2 and 3 weeks. However, TCV-116 failed to inhibit the expression of collagen I and III mRNAs at 1 and 3 weeks. These results show that myocardial infarction causes a rapid shift of myocytes to fetal phenotype and a rapid activation of collagen genes in the non-ischemic myocardium. AT1 receptor may be responsible for the phenotypic modulation of myocytes following myocardial infarction.     

Seeding effects on solidification behavior of cocoa butter and dark chocolate. I. Kinetics of solidification

Effects of seeding of fat crystals on the crystallization kinetics of cocoa butter and dark chocolate were examined with a rotational viscometer. The seed crystals employed were cocoa butter, 1,3-distearoyl-2-oleoylglycerol (SOS), 1,3-dibehenoyl-2-oleoylglycerol (BOB) and 1,2,3-tristearoylglycerol (SSS). The seed powders were prepared by pulverization below —50°C, the dimensions being in a range from 20–70 μm. Particular attention was paid to the influence of polymorphism of the seed crystal. We found that all of the above seed materials accelerated the crystallization, the degree of acceleration being in a following order; SOS (β ₁) > cocoa butter (Form V) > SOS (a mixture ofβ’ andβ ₂) > BOB (β ₂) > BOB (pseudo-β’) > SSS (β). Precise measurements of the crystallization kinetics showed that the most influential factors in the seeding effects are the physical properties of the seed materials—above all, thermodynamic stability, and similarity in the crystal structure to cocoa butter are the most determinative.     

Application study of a high‐temperature superconducting fault current limiter for electric power system

Using high‐temperature superconductors, a superconducting fault current limiter (SFCL) was fabricated and tested. The superconductor and a vacuum interrupter serving as a commutation switch were connected in parallel with a bypass coil. When a fault occurs and excessive current flows, the superconductor is first quenched and the current is transferred to the bypass coil because of the voltage drop of the superconductor. At the same time, since a magnetic field is generated by the current flowing in the bypass coil, the commutation switch is immediately driven by an electromagnetic repulsion plate connected to the driving rod of the vacuum interrupter (VI), and the superconductor is separated from this circuit. Using the test model, we were able to separate the superconductor from the circuit by the movement of the VI within a half current cycle and to transfer all current to the bypass coil. Since the operation of the commutation switch is included in the current limiting operation of this test model, it will be a useful circuit in the development of SFCL in the future. Moreover, since it can make the energy consumption of the superconductor small during the fault state due to the realization of a high‐speed switch with simple composition, the burden on the superconductor is reduced compared with the conventional resistive type of SFCL and it is considered that the flexibility of SFCL design is increased. Cooperation with a circuit breaker was also considered; trial calculations of the parameters and energy of operation were conducted and a discussion of the installation of the SFCL in an electric power system is presented. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(4): 20–29, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20265     

A non-radioisotopic human natural killer cell assay using rhodamine-123 fluorescent dye as labelling probe

A non-radioisotopic method for assessment of human natural killer (NK) cell activity in peripheral blood mononuclear cells (PBMC) was established by labelling K562 erythroleukemia target cells with a fluorescent dye, rhodamine-123 (Rh-123). The labelling and assay conditions were determined for minimizing spontaneous release (SR). In order to investigate whether NK activity assessed by measuring Rh-123 release agrees with the activity determined by a 51Cr release assay, the NK activity of PBMC was measured simultaneously by both assay methods. Statistical analysis demonstrates that NK activities determined by Rh-123 release correlate well with those measured by 51Cr release. The Rh-123 release assay under the conditions determined was found to be applicable to measurement of the enhanced NK activity resulting from pretreatment of effector leukocytes with interferon-alpha. It is concluded that the Rh-123 release assay with use of K-562 labelled target cells is practical for the assessment of human NK activity in laboratories where use of radioisotopes is not permitted or undesirable.