Development of a technique for high resolution electron microscopic observation of nano-materials at elevated temperatures

A technique for high resolution transmission electron microscopic (TEM) observation of nano-materials at very high temperatures has been developed. A spirally wound tungsten wire, normally used as the heating element of a high resolution-high temperature-specimen heating holder, was coated with a thin carbon film and the carbon film was used as the substrate of nanometer-sized specimen. The carbon film was securely self-adhered on the heater and the form of the carbon film remained unchanged until the tungsten heater is heated to around 1173 K. Temperature distribution on the carbon film has been measured by observing the sublimation of ZnS particles. Behavior of gold atoms on a surface of gold nano-particles dispersed on the carbon film has been clearly observed at 773 K in a scanning transmission electron microscope (STEM).     

Microbioassay system for antiallergic drug screening using suspension cells retaining in a poly(dimethylsiloxane) microfluidic device

This article describes an antiallergic drug-screening system by the detection of histamine released from mast cells (suspension cells) on a multilayer microchip. In this study, the elastmeric material, poly(dimethylsiloxane) (PDMS), was employed to fabricate microchannels and microchambers. The microchip consists of two sections: a histamine-releasing one, which has a cell chamber, and a histamine-derivatizing one. Both were laminated to one microchip. Rat peritoneal mast cells were retained in the cell chamber (1.2 microL) with a filtering system using a cellulose nitrate membrane. This filtering system could easily retain suspension cells without cell damage. Mast cells were viable for a sufficient time to conduct the assay on the cell chamber. The cells were stimulated with a chemical release compound 48/80 (C48/80), and then histamine flowed into the lower layer, where it was derivatized to the fluorescent molecules with o-phthalaldehyde and its fluorescence was detected on the microchip. This flow system could detect the time course of the histamine release, and this microchip system required only 20 min for the assay. By this integrated system, 51 pmol of histamine released from 500 cells was detected, and the number of cells required for the assay was reduced to 1% compared with conventional bulk systems. By comparing the released histamine levels with and without drugs, their effect could be evaluated. The inhibition ratio of C48/80 induced-histamine release using an antiallergic drug, disodium cromoglicate (DSCG), was related to the concentration of DSCG. This flow system was applicable for antiallergy drug screening by rapid measurement of the inhibition of histamine release from a very small amount of mast cells.     

Fabrication of CNT-carbon composite microstructures using Si micromolding and pyrolysis

A fabrication method of carbon nanotube (CNT)-carbon composite microstructures has been developed. CNT-carbon composite microstructures with dimensions from 10 micrometers to several hundred micrometers have been fabricated by pyrolysis process from the patterned SU-8 photoresist mixed with 1 wt% of CNTs at temperature of ~600 °C under inert atmosphere. The resulting composite microstructures with a high aspect ratio of ~34 can be successfully fabricated by this novel fabrication method. This research provides a simple approach that is compatible with microfabrication technology and is capable of fabricating composite microstructures with reproducible shape and dimensions, at desired locations. This approach has potential for the further exploring of applications of composite micro/nano structures as functional units in various microdevices. Also the ultramicroindentation hardness of the CNT-carbon composite films was investigated by nanoindentation measurement.     

Glass capillaries based on a glass reflow into nano-trench for controlling light transmission

This paper reports the fabrication of Tempax glass capillaries based on a glass reflow into nano-trench for an optical modulator toward image sensing applications. The optical window consists of micrometer-order glass capillaries (porous solids) that can modulate the transmission light intensity by moving a liquid in and out of the porous solids. A high optical transmittance can be achieved due to refractive index matching when the liquid is penetrated into the porous solid. Otherwise, its light transmittance is low because of light reflection and scattering by air holes and capillary walls. The glass is completely filled into the nano-trench between silicon pillars under a high temperature process and assistance of enhancement of the surface wettability. Glass capillaries with depth of 8 μm, diameter of 1.2 μm, and the pitch of two capillaries of 2 μm have been achieved. The optical window integrated with an image sensor for an optical modulator is clearly demonstrated and a light modulation effect dependent on liquid penetration is observed.     

Mass detection using capacitive resonant silicon resonator employing LC resonant circuit technique

Capacitive resonant mass sensing using a single-crystalline silicon resonator with an electrical LC oscillator was demonstrated in ambient atmosphere. Using capacitive detection method, the detectable minimum mass of 1 x 10(-14) g was obtained in the self-oscillation of cantilever with a thickness of 250 nm. The noise amplitude of the sensor output corresponds to a vibration amplitude of 0.05 nm(Hz)(0.5) in the frequency domain compared with the actuation signal, which is equivalent to the detectable minimum capacitance variation of 2.4 x 10(-21) F. Using the capacitive detection method, mass/stress induced resonance frequency shift due to the adsorption of ethanol and moist vapor in a pure N(2) gas as a carrier is successfully demonstrated. These results show the high potential of capacitive silicon resonator for high mass/stress-sensitive sensor.     

Strengthening Effects at Dissimilar Metal Interfaces Created by Ultrasonic Additive Manufacturing

Metallurgical and Materials Transactions A - Ultrasonic additive manufacturing (UAM) technology can produce structural materials with complex geometries and embedded sensors. Under UAM-processing...     

Suppression of Lysophosphatidylcholine-Induced Human Aortic Smooth Muscle Cell Calcification by Protein Kinase A Inhibition

Lysophosphatidylcholine (lysoPtdCho) is produced mainly by the phospholipase A2-dependent hydrolysis of phosphatidylcholine (PtdCho) and can induce inflammatory activation and osteogenic gene expression in vascular smooth muscle cells. However, the mechanisms mediating these processes have not been fully elucidated. In this study, we investigated whether inhibition of protein kinase A (PKA) signaling suppressed lysoPtdCho-induced calcification of human aortic smooth muscle cells (HASMC). Calcium levels and alkaline phosphatase activity were significantly increased in HASMC treated with lysoPtdCho, but not PtdCho, compared with those in phosphate-buffered saline-treated HASMC. However, the addition of a PKA inhibitor (H-89) or PKA siRNA blocked lysoPtdCho-induced HASMC calcification. These results showed that lysoPtdCho could activate PKA-mediated HASMC calcification and that PKA may be a therapeutic target for lysoPtdCho-mediated vascular smooth muscle cell calcification.     

MEASUREMENT OF TRANSIENT THERMAL STRESSES USING THE 5-ELEMENT STRAIN GAGE

The transient thermal stresses on the 5-element strain gage are measured both for the disk and the circular plate with holes, and under a partial heating by molten metal on one face. The results are in good agreement with the theoretical solutions. The effects of the disk thickness and the interference with holes on the thermal stresses have been investigated.     

Effect of Environmental Temperature on the Fatigue Crack Propagation Behavior of Cemented Carbides

Cemented carbides have been utilized as high speed turning tools or heat-resistant tools. So, it is necessary to study fatigue crack propagation behavior of the cemented carbides under high temperature environment in order to understand, or to grasp their capabilities under such a severe environmental conditions. Many studies on static fatigue, on creep and on monotonic mechanical properties of the cemented carbides have been conducted under high temperature environment. However, studies on cyclic fatigue of the cemented carbides under the above environment are very few and limited. In the present study, cyclic fatigue tests were conducted on cemented carbides under high temperature environment. The tests were performed at two stress ratios, R = 0.1 and 0.5. In addition to these cyclic fatigue tests, static fatigue tests at R = 1 were also conducted to study more detail about the effects of cyclic stress, stress ratio and temperature on the fatigue crack propagation behavior of the cemented carbides.