Two-dimensional multiarray formation of hepatocyte spheroids on a microfabricated PEG-brush surface

A two-dimensional microarray of ten thousand (100 x 100) hepatocyte heterospheroids, underlaid with endothelial cells, was successfully constructed with 100 microm spacing in an active area of 20 x 20 mm on microfabricated glass substrates that were coated with poly(ethylene glycol) brushes. Cocultivation of hepatocytes with endothelial cells was essential to stabilize hepatocyte viability and liver-specific functions, allowing us to obtain hepatocyte spheroids with a diameter of 100 microm, functioning as a miniaturized liver to secret albumin for at least one month. The most important feature of this study is that these substrates are defined to provide an unprecedented control of substrate properties for modulating cell behavior, employing both surface engineering and synthetic polymer chemistry. The spheroid array constructed here is highly useful as a platform of tissue and cell-based biosensors and detects a wide variety of clinically, pharmacologically, and toxicologically active compounds through a cellular physiological response.     

Transferred-electron negative-resistance amplifier

It has experimentally been shown that the travelling domain oscillations in an n type GaAs bulk element can be suppressed by applying externally a large microwave-signal electric field. A computer calculation indicates a possibility of amplifying the signal when the element mounted in a stripline is subject to such a relatively large microwave signal.     

Rheological interpretation of heat generation associated with fatigue of polycarbonate

Temperature change was measured of polycarbonate under monotonically increasing tensile and pulsating tensile loads. In the former case, the specimen temperature began to rise when an appreciable amount of viscoelastic strain was noticed on the stress—strain diagram. The rise, θ_v, could be formulated as a function of the viscoelastic strain, εv: In fatigue tests, the average temperature began to rise immediately after the decrease due to the thermoelastic effect. The amount of the heat generation, σ, was nearly constant for each cycle throughout the fatigue process and has a relation to the fatigue life, N_f, (α? a)·N_f = constant, where a is another adjustable constant. From a rheological aspect of dissipation energy, the equation is transformed to a relation between the viscoelastic strain and the fatigue life as εV^1/2 · N_f = constant, which is similar to the one for metals given by Manson and Coffin.⁶ The temperature rise in the fatigue was also related to the viscoelastic strain. The relation is of the same form as for static tension but less by a factor of one order.     

Effects of rice cleaning and cooking process on the residues of flutolanil,fenobucarb, silafluofen and buprofezin in rice

We studied the effect of cleaning and cooking on the residues of flutolanil, fenobucarb, silafluofen and buprofezin in rice. The rice had been sprayed in a paddy field in Wakayama city, with 3 kinds of pesticide application protocols: spraying once at the usual concentration of pesticides, repeated spraying (3 times) with the usual concentration of pesticides and spraying once with 3 times the usual concentration of pesticides. The residue levels of pesticide decreased during the rice cleaning process. Silafluofen, which has a higher log Pow value, remained in the hull of the rice. Fenobucarb, which has a lower log Pow value, penetrated inside the rice. The residue concentration of pesticide in polished rice was higher than that in pre-washed rice processed ready for cooking. During the cooking procedure, the reduction of pesticides in polished rice was higher than that in brown rice.     

Simple determination of residual anticoccidial drugs (diclazuril and nicarbazin) in chicken tissues by HPLC

A simple and rapid determination of anticoccidial drug residues, diclazuril (DCZ) and nicarbazin (NCZ), in chicken tissues has been developed. DCZ and NCZ were extracted with acetonitrile from chicken liver, muscle, and fat. The extract was rinsed with n-hexane saturated with acetonitrile and then evaporated. The residue was dissolved in 1.4 mL of acetonitrile-methanol (1:1), then 1.0 mL of n-hexane saturated with acetonitrile-methanol (1:1) was added, and the mixture was partitioned by the addition of 0.6 mL of water. DCZ and NCZ in the aqueous layers were determined by HPLC on an Xterra RP-18 column with acetonitrile-0.5% ammonium acetate containing 0.01 mol/L tetra-n-butylammonium hydrogen sulfate (43:57) as the mobile phase. The mean recoveries (n = 5) of DCZ and NCZ spiked in chicken tissues at the maximum residue levels were 92.0-95.6% (CV 2.4-3.0%) and 87.3-89.4% (CV 1.7-2.8%), respectively. The detection limits of DCZ and NCZ were 0.01 and 0.004 microgram/g, respectively.     

Size reduction in crystal grains in LiNb0.5Ta0.5O3 thin films by controlling nucleation density during thermal plasma spray chemical vapor deposition

Two approaches were applied to thermal plasma spray chemical vapor deposition (TPS CVD) in order to reduce crystal grain size or/and surface roughness of LiNb_0.5Ta_0.5O₃ thin films while retaining the advantages of this method, such as high deposition rate. The first method consists of a two-step deposition, where the nucleation density is controlled in the first step and the film with high crystallinity is deposited in the second step. The surface roughness and grain size could be reduced from 1 nm to 7.7 nm, and from 200-350 nm to 120-180 nm, respectively. In the second approach, employing a one-step TPS CVD process, the conventional precursor was substituted by a double-alkoxide precursor and grain size in the deposited films could be reduced to 50-80 nm. Both approaches adopted in this work permitted to reduce the optical propagation loss.     

Analytical Model for Redistribution Profile of Ion-Implanted Impurities During Solid-Phase Epitaxy

We evaluated the redistribution profiles of ion-implanted impurities during solid-phase epitaxy using Rutherford backscattering spectrometry (RBS). RBS data revealed that the As concentration changes only near the moving amorphous/crystal interface. We derived an analytical model for the redistribution profiles using a segregation coefficient m between amorphous and crystalline Si, introduced a parameter of reaction length l that is the distance where impurities were exchanged, and obtained good agreement with experimental data with an m value of 3 and an l value of 1 nm for As. Furthermore, we applied our model to P and B redistribution profiles and obtained good agreement with corresponding m value of 4 and l value of 1 nm for P and m value of 0.3 and l value of 1 nm for B     

Low-Force Electric Contact Processes on Cu Electrodes

A contact process between large-scale integration (LSI) pads and test probes at low contact force is a key to developing a probe card with smaller pitch and higher pin count. In this paper, we report on the characteristics of low-force contact methods on Cu electrodes. One is the fritting process, in which an electric breakdown is utilized to break the surface oxide, and the other is the heating treatment in hydrogen gas aimed at deoxidizing the surface Cu oxide. Conventional tungsten needle probes were used as testing probes, and contact resistances at low contact force of 1-5 mN were measured. Contact resistances smaller than 1 Omega were obtained by the fritting processes, in which the voltage and the current were 10 V and 280-320 mA, respectively. A deoxidization process at over 260degC was found to be effective for decreasing the contact resistance. The X-ray photoelectron spectroscopy (XPS) was utilized to investigate the surface state of hydrogen-treated Cu, and the deoxidization of Cu₂O to Cu was observed in samples treated at 260degC, while no change was found in that at 150degC.     

Steady-State Characteristics of a Current-Source Inverter/Double-Wound Synchronous Machine System for AC Power Supply

A detailed steady-state analysis of a novel dc-to-ac conversion system used as an ac power source in dc electric railway coaches is presented. This system consists of a current-source inverter, a double-wound synchronous machine, a position sensor, and a control circuit. An equivalent circuit convenient for predicting the steady-state behavior of the system is first derived. Based on this equivalent circuit, the output voltage waveforms are then examined. It is shown that the voltage waveforms are nearly sinusoidal except that narrow spikes are superposed on them during commutation of the thyristors. As to armature reaction in the double-wound synchronous machine, it is shown that a remarkable direct reaction appears which affects the voltage regulation of the system. Finally, a method for keeping the output voltage and frequency constant is discussed.