A high-precision low-voltage bipolar current mirror circuit and its compensation for stability

A current mirror circuit is widely utilized as an important building block in analogue signal processing circuits. This paper describes a high-precision low voltage bipolar current mirror circuit. Well known current mirror circuits, such as a simple current mirror and a Wilson current mirror, have a trade-off between low-voltage operation and accuracy of the current gain. The accuracy of the proposed current mirror is high in spite of low current amplification factor (β) of transistors and large current output (or a large number of the multiple output). The current mirror circuit can operate at a 1V or less supply voltage. The high accuracy is realized by negative current feedback with high gain. Thus, the stability of the circuit and compensation methods are discussed. PSPICE simulation shows that the proposed current mirror circuit compensated using Miller components composed of a capacitor and a resistor is stable and can operate at a 1V supply voltage.     

Improvement in microstructure of SBT thin films

Abstract

Various attempts to improve the microstructure of SBT thin films were carried out. One was to employ ultra-thin BT film as a top layer on the conventional SBT thin film. After optimization of the BT top layer thickness, a very smooth SBT surface was successfully achieved. Particularly, the insulation break down field was improved to more than 1.0 MV/cm. Next we used UV exposure during the baking process. By optimizing the UV assisted process, surface morphology was successfully improved with fine grain microstructure. The break down field was improved to more than 1.0 MV/cm. Also, these two process combinations successfully lead to more reliable SBT thin films. The break down field was drastically improved to more than 1.2 MV/cm.     

Reduced Thermal Budget Process for SBT Thin Film in Planer Type Stack Cell FeRAMs

In order to reduce the thermal budget for SBT crystallization process in planer type stack cell FeRAMs, Rapid Thermal Anneal (RTA) based process for SBT thin film was investigated. Our new process is characterized by crystallization in RTA without any furnace annealing process, and includes a low temperature recovery annealing process (hereafter RTB (Reduced Thermal Budget) process). As a result of only 750C RTA for accumulated time of 60s without furnace annealing process, the sufficient ferroelectric properties were derived in comparison with that of conventional SBT thin film. In the RTB process, two approaches to improve the break down voltage were carried out. First, we used UV exposure during the baking process. By optimizing the UV assisted baking process, a high break down field due to smooth surface morphology was successfully obtained, resulting in break down field of more than 1.2 MV/cm. Secondly, ultra thin SBT films as a top few layer on the base SBT thin film were employed. After optimization of the ultra thin SBT layer thickness, a very smooth SBT surface was successfully achieved, resulting in improvement of the break down field of more than 1.1 MV/cm.     

Hydrodesulfurization activity of highly dispersed Co sulfide clusters prepared in zeolite cages

Zeolite-supported highly dispersed Co sulfide clusters are synthesized using Co(CO)₃ (NO) as a precursor. The amount of Co inCoS_x/zeolite anchored by a CVD technique increases as the Al/Si ratio of the zeolite increases, whereas the activity per Co atomdecreases for thiophene hydrodesulfurization (HDS). When an Na-exchanged USY zeolite is used, the Co sulfide catalyst shows a muchhigher HDS activity than a conventional Co—Mo/Al₂ O₃ catalyst. It is considered from XAFS and NO adsorption techniques that thehigh HDS activity of CoS_x/USY-Na is due to an extremely high dispersion of Co sulfide clusters. This revised version was published online in July 2006 with corrections to the Cover Date.     

Psychological Stress Exacerbates Inflammation of the Ileum via the Corticotropin-Releasing Hormone-Mast Cell Axis in a Mouse Model of Eosinophilic Enteritis

The effects of psychological stress on eosinophilic gastrointestinal disorders have not been elucidated. This study investigated the effects of psychological stress in a mouse model of eosinophilic enteritis (EoN). BALB/c mice were treated with ovalbumin (OVA) to create an EoN model and subjected to either water avoidance stress (WAS) or sham stress (SS). Microscopic inflammation, eosinophil and mast cell counts, mRNA expression, and protein levels of type 2 helper T cell (Th2) cytokines in the ileum were compared between groups. We evaluated ex vivo intestinal permeability using an Ussing chamber. A corticotropin-releasing hormone type 1 receptor (CRH-R1) antagonist was administered before WAS, and its effects were analyzed. WAS significantly increased diarrhea occurrence and, eosinophil and mast cell counts, and decreased the villus/crypt ratio compared to those in the SS group. The mRNA expression of CRH, interleukin IL-4, IL-5, IL-13, eotaxin-1, and mast cell tryptase β2 significantly increased, and the protein levels of IL-5, IL-13, and OVA-specific immunoglobulin E (IgE) also significantly increased in the WAS group. Moreover, WAS significantly increased the intestinal permeability. The CRH-R1 antagonist significantly inhibited all changes induced by WAS. Psychological stress exacerbated ileal inflammation via the CRH-mast cell axis in an EoN mouse model.     

Bone Tissue Engineering in Rat Calvarial Defects Using Induced Bone-like Tissue by rhBMPs from Immature Muscular Tissues In Vitro

This study aimed to induce bone-like tissue from immature muscular tissue (IMT) in vitro using commercially available recombinant human bone morphogenetic protein (rhBMP)-2, rhBMP-4, and rhBMP-7, and then implanting this tissue into a calvarial defect in rats to assess healing. IMTs were extracted from 20-day-old Sprague-Dawley (SD) fetal rats, placed on expanded polytetrafluoroethylene (ePTFE) with 10 ng/μL each of rhBMP-2, BMP-4, and BMP-7, and cultured for two weeks. The specimens were implanted into calvarial defects in 3-week-old SD rats for up to three weeks. Relatively strong radiopacity was observed on micro-CT two weeks after culture, and bone-like tissue, comprising osteoblastic cells and osteoids, was partially observed by H&E staining. Calcium, phosphorus, and oxygen were detected in the extracellular matrix using an electron probe micro analyzer, and X-ray diffraction patterns and Fourier transform infrared spectroscopy spectra of the specimen were found to have typical apatite crystal peaks and spectra, respectively. Furthermore, partial strong radiopacity and ossification were confirmed one week after implantation, and a dominant novel bone was observed after two weeks in the defect site. Thus, rhBMP-2, BMP-4, and BMP-7 differentiated IMT into bone-like tissue in vitro, and this induced bone-like tissue has ossification potential and promotes the healing of calvarial defects. Our results suggest that IMT is an effective tissue source for bone tissue engineering.     

Antisense Oligonucleotide Modified with Disulfide Units Induces Efficient Exon Skipping in mdx Myotubes through Enhanced Membrane Permeability and Nucleus Internalization

We have found that antisense oligonucleotides and siRNA molecules modified with repeat structures of disulfide units can be directly introduced into the cytoplasm and exhibit a suppressive effect on gene expression. In this study, we analyzed the mechanism of cellular uptake of these membrane-permeable oligonucleotides (MPONs). Time-course analysis by confocal microscopy showed that the uptake of MPONs from the plasma membrane to the cytoplasm reached 50 % of the total uptake in about 5 min. In addition, analysis of the plasma membrane proteins to which MPONs bind, identified several proteins, including voltage-dependent anion channel. Next, we analyzed the behavior of MPONs in the cell and found them to be abundant in the nucleus as early as 24 h after addition with the amount increasing further after 48 and 72 h. The amount of MPONs was 2.5-fold higher than that of unmodified oligonucleotides in the nucleus after 72 h. We also designed antisense oligonucleotides and evaluated the effect of MPONs on mRNA exon skipping using DMD model cells; MPONs caused exon skipping with 69 % efficiency after 72 h, which was three times higher than the rate of the control. In summary, the high capacity for intracytoplasmic and nuclear translocation of MPONs is expected to be useful for therapeutic strategies targeting exon skipping.     

Completely Chemically Synthesized Long DNA Can be Transcribed in Human Cells

Chemical ligation reaction of DNA is useful for the construction of long functional DNA using oligonucleotide fragments that are prepared by solid phase chemical synthesis. However, the unnatural linkage structure formed by the ligation reaction generally impairs the biological function of the resulting ligated DNA. We achieved the complete chemical synthesis of 78 and 258 bp synthetic DNAs via multiple chemical ligation reactions with phosphorothioate and haloacyl-modified DNA fragments. The latter synthetic DNA, coding shRNA for luciferase genes with a designed truncated SV promoter sequence, successfully induced the expected gene silencing effect in HeLa cells.     

A method for estimating the errors in many-light rendering with supersampling

Computational Visual Media - In many-light rendering, a variety of visual and illumination effects, including anti-aliasing, depth of field, volumetric scattering, and subsurface scattering, are...