Linearity performance comparison of cascode current source and single-device current source IDPs; analyses,simulations and measurements

The input differential pair (IDP) is usually a major source of nonlinear distortion in any op-amp. This is especially true if the input signal has a large common-mode component, as is the case when an op-amp functions as a unity-gain buffer or as part of a single-ended sample-hold (S/H) circuit. In this paper, we analyse the distortion of the commonly used cascode current source IDP structure and explain the sources of its nonlinear behaviour. Next, a special design technique is proposed which enhances the linearity of IDPs. The circuit uses a single device current source that has the same channel length while its width is double those of IDP devices. Theoretical analysis, as well as simulation and experimental results, is given to confirm the improved linearity of a unity gain buffer. Simulations predict improvements up to 20 dB. 15 dB total harmonic distortion (THD) reduction was also achieved for a 15 MHz input signal based on measurement of a test chip. The method is valuable as power supply voltages shrink, and the design offers extra voltage headroom at input.     

Novel diffusion control process using ultra thin buffer layer for MFIS memory

Abstract

MFIS structures having excellent clear interfaces and well-crystallized ferroelectric layer were successfully fabricated by a newly developed ultra thin metal buffer layer process on SiO₂/Si. We examined the effect of sputtered Zr or ZrO₂ ultra thin films as a buffer layer for Pb_xLa_1?xTiO₃ (PLT) growth. TEM observation revealed that the buffer layer formation process in which Zr oxidized after the metal deposition had advantages to produce MFIS structures. This method is also superior for the crystallization and the control of the orientation of PLT thin film on amorphous SiO₂. Especially, for buffer layer thicknesses below 10 nm, preferred c-axis oriented PLT thin films were grown. The I-V characteristics of MFIS-FET fabricated by the proposed method showed a clear memory window due to the remanent polarization of the ferroelectric thin film. This process is the most attractive candidate for realizing MFIS structure memory.     

Ultra-violet Absorption of Thermally Irradiated Gelatin

The effect of thermally irradiated gelatin at various pH's on the ultra-violet absorption at 257nm, the molecular weight and the amount of thermally coagulated material has been studied.

Decrease in pH of thermal irradiation leads to molecular weight decreases and ultra-violet absorption increases. The ultra-violet absorption correlates with the molecular weight of the thermally irradiated gelatin. At pH 3-4, however, irradiation leads to a very high ultra-violet absorption which is outside the regression line. The level of thermally coagulated material also increased in this pH range. It would seem that the ultra-violet absorption increase at pH 3-4 is related to the thermal coagulation reaction.     

Peak identification of L X-ray spectra of elemental Np and U

The L X-ray photons emitted by transuranic (TRU) elements are expected to be useful for developing nondestructive TRU monitors. Energy spectra of L X-rays emitted by ²⁴¹Am, ²³⁸Pu and ²³⁹Pu sources were measured by a transition edge sensor (TES) microcalorimeter, which allowed precise peak identification with high energy resolution. In the measurements using the TES microcalorimeter, the full width at half-maximum energy resolution was 62.6 eV at 17.222 keV for ²³⁹Pu source, 62.5 eV at 17.222 keV for ²³⁸Pu source and 60.9 eV at 17.751 keV for ²⁴¹Am source. This study demonstrates the separation of ²⁴¹Am and plutonium isotopes by L X-ray spectroscopy using a TES microcalorimeter.     

Operating results and simulations on a fuel cell for residential energy systems

This paper describes the performance evaluation of a polymer electrolyte fuel cell (PEFC) prototype and demonstration experiments of the electric power and domestic hot water system using it from a pragmatic view-point. Three types of demonstration experiments were carried out applying standard electric power and hot water demands. It was shown that the primary energy reduction rate of this system as compared to the conventional system reached up to 24% under double daily start and stop (DSS) operation. The amount of primary energy reduction in experiments using the energy demand of a household in Sapporo in winter exceeded the experimental results of the standard energy demand, demonstrating that the effects of the introduction of a fuel cell in cold regions could be considerable, in particular, during the winter season.     

亚硝酸钙阻锈剂的应用研究综述

阐述了亚硝酸钙对新鲜和硬化混凝土性质的影响,分析了亚硝酸离子对混凝土主钢筋腐蚀的阻锈机理,并总结了亚硝酸离子在不同混凝土环境下的阻锈效果,为亚硝酸钙阻锈剂的工程应用提供了理论基础和技术支持.     

Minichromosome formation in Chlorella cells irradiated with electron beams

Three minichromosomes, miniP7, miniB7, and miniK4 of 800 kbp, 450 kbp, and 550 kbp, respectively, were obtained from Chlorella vulgaris chromosome I by electron-beam irradiation. Two of them were structurally characterized: MiniP7 was formed by the deletion of an internal 180 kbp close to the right end of chromosome I. The 180-kbp region with a small interspersed nuclear element (SINE)-like element on its left terminus was translocated to another chromosome, leaving a footprint-like structure on miniP7. MiniB7 was a hybrid of chromosome I and another chromosome, retaining the left telomere and the centromere of chromosome I. The centromeric repetitive elements served as a rearrangement point in the miniB7 formation. These examples showed the complicated mechanisms involved in the minichromosome formation. The minichromosomes thus obtained can be useful for isolating the fundamental structural elements of a chromosome. Moreover, they may serve as starting materials or a vector to generate artificial chromosomes carrying useful genes.     

Enhanced enzyme activity and enantioselectivity of lipases in organic solvents by crown ethers and cyclodextrins

Lipases from Candida rugosa (CRL) and Pseudomonas cepacia (PCL) were co-lyophilized with cyclic oligoethers including four crown ethers and nine cyclodextrins (CyDs), and their transesterification activity and enantioselectivity in organic solvents were evaluated. The PCL co-lyophilized with each additive showed simultaneously enhanced enzyme activity and enantioselectivity when compared to the native lipase lyophilized from buffer alone; in contrast, such enhancement was not observed for the co-lyophilized CRL. Among the cyclic oligoethers examined, permethylated betaCyD (Me1.78betaCyD), as the most suitable additive, was used for the optimization of both the co-lyophilized PCL preparation and reaction conditions by determining the effects of varying the additive/lipase ratio, aqueous pH, the nature of organic solvents, and temperature. The initial rate determined for the transesterification between racemic 2,2-dimethyl-1,3-dioxolane-4-methanol and vinyl butyrate in diisopropyl ether at 30 degrees C increased by up to 17-fold and the enantioselectivity represented by E could be doubled. While there was an inverse correlation between temperature and enantioselectivity, with the Me1.78betaCyD-PCL co-lyophilizate, the reaction rate even at 0 degrees C was much higher than that at higher temperatures in the native PCL-catalyzed reaction. Hence, this method seems to be of practical use for the large-scale production of optically active compounds.     

Effects of Processing Parameters on the Deposition of Yttria Partially Stabilized Zirconia Coating During Suspension Plasma Spray

The process–microstructure relationship in suspension plasma spray (SPS) of yttria partially stabilized zirconia (YSZ) has been studied experimentally. An ethanol‐based suspension with a powder loading of 25 wt% was plasma sprayed with radial injection under four different plasma conditions, to examine the effects of plasma gas composition (Ar/He ratio), secondary gas (Ar/He and Ar/H₂), and the nozzle diameter of the plasma gun. The suspension feeding rate was optimized firstly and coatings were prepared for microstructural observation. Capturing of in‐flight particles into water as well as collection of splats formed on heated flat metal substrates were utilized in order to better understand the more complicated intermediate process steps in SPS. It was found that a plasma jet with higher momentum allowed a higher suspension flow rate and both columnar and deep vertically cracked structure could be created depending on the plasma parameters as well as the substrate surface roughness.     

Lipid Composition and Antioxidant Capacity Evaluation in Tilapia Fillets Supplemented with a Blend of Oils and Vitamin E

Since the nutritional value of farm‐raised fish fillets is directly related to the diet provided, we supplemented the diet of Tilapia (Oreochromis niloticus) with a blend of chia (Salvia hispanica L.) oil, tung (Aleurites fordii) oil, and conjugated linoleic acid (CLA) to evaluate the effects on the fatty acid composition. Vitamin E was also added to the diet to improve the antioxidant capacity of tilapia fillets. We observed an increase in α‐linolenic acid content (from 6.56 to 19.03 mg g^?1 of total lipids), as well as the incorporation of CLA and conjugated linolenic acid (CLnA) isomers in the fillets. The addition of vitamin E resulted in the antioxidant capacity improvement of the fillets and higher values were found after 15 feeding days (39.25 µmol TE g^?1 in the Ferric Reducing Ability Power assay). Supplementation proved to be an excellent tool to improve the nutritional value of fish fillets.