Helmholtz-Type Equations of State for Hydrocarbon Refrigerant Mixtures of Propane/n-Butane, Propane/Isobutane, n-Butane/Isobutane, and Propane/n-Butane/Isobutane

Highly accurate thermodynamic property models for binary and ternary hydrocarbon mixtures containing propane, n-butane, and isobutane have been developed. In the present model, reliable equations of state explicit in Helmholtz free energy for these three hydrocarbons that have already been developed by the present authors have been adapted. The excess term used to represent the contribution of mixing was optimized for each binary mixture by using the available experimental thermodynamic property data including PTx, isochoric heat capacity, and saturation properties (bubble-point pressures, mole fractions in the vapor phase, and saturated vapor- and liquid-densities) as input data. A generalized correction for the three binary mixtures, besides the ideal mixing, consists of only four terms in its functional form, the structure of which was determined by simultaneous optimization to the input data for the three binary mixtures by employing a stepwise regression analysis. The bank of terms, that is a matrix of candidate terms applied for the regression, was carefully prepared through detailed observation of the nonideal mixing representation of the experimental data of the three binary mixtures. No additional adjustable parameters were used in the present model for the ternary propane/n-butane/isobutane mixture. Based on comparisons with the available experimental data and values from the developed equations of state, the present models for the three binary and the ternary hydrocarbon mixtures accurately represent most of the reliable experimental data. In addition, the graphical tests of the derived thermodynamic properties show that the models, including that for the ternary mixture, provide a physically sound representation of all the thermodynamic properties over the entire fluid phase.     

Strong induction of phytochelatin synthesis by zinc in marine green alga, Dunaliella tertiolecta

Synthesis of phytochelatins (PCs), heavy-metal-sequestering peptides, in the marine green alga, Dunaliella tertiolecta, was evaluated under various conditions of exposure to heavy metals. To investigate the effect of heavy metals on both PC synthesis and their upstream biosynthetic reactions, an ion-pair-HPLC system was developed in this study, by which PCs and their biosynthetic intermediates, cysteine (Cys), gamma-glutamylcysteine (gammaEC) and glutathione (GSH), could be determined simultaneously with high sensitivity. When the cells were exposed to Zn2+, the level of PCs was maximal at 200 microM and significantly higher than that obtained after exposure to 400 microM Cd2+, which is the strongest inducer of PC synthesis in higher plants in vivo and in vitro as well as in microalgae. The predominant PC subtype was PC4, followed by PC3 and PC5, whereas PC2, which is generally abundant in higher plants, has the lowest level among PC2 to PC5. These results suggest that the characteristics of PC synthase in D. tertiolecta including the requirement of heavy metals for its catalysis and substrate specificity towards GSH and PC(n) are considerably different from those in higher plants and other algae. While PC synthesis proceeded in the heavy-metal-treated cells, the level of GSH did not appreciably change. To maintain the same size of the GSH pool, GSH must be newly synthesized to balance the amount consumed for PC synthesis.     

Vacuum seal for a rectangular flange

A new vacuum seal for a rectangular flange used in r.f. equipments, was developed. The vacuum seal consists of a recess with a flat surface, machined into a rectangular flange, a rectangular metal gasket with a raised projection on one face, and a mating flange with a recess and raised projection. No leak greater than 1 × 10⁻¹⁰ Pa m³/s was found in leak tests, before and after baking cycles (100 °C, 12 h).     

An energy trading system with consideration of CO2 emissions

Abatement of CO₂ emission is one of the most important issues in the 21st century regarding preservation of the earth environment. This paper addresses a utility operations planning problem for distributed energy management systems (DEMSs), where we are to obtain optimal plans that minimize both costs and CO₂ emissions. A DEMS consists of multiple entities that seek their own economic profits. In this paper, we give a mathematical formulation of the utility operations planning problem for each entity, and propose an energy trading market, which utlizes a multi‐attribute auction protocol in order to deal with both a price and a CO₂ emission rate. Experimental results show that collaboration among entities through the market provides a more profitable plan for each entity and abatement of CO₂ emission is also achieved. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(4): 54–63, 2008; Published online in Wiley InterScience ( www.interscience.wiley. com ). DOI 10.1002/eej.20418     

High-efficiency hot-electron transport in GaInAs/InP hot electron transistor grown by OMVPE

Improved characteristics of the GaInAs/InP hot electron transistor (HET) fabricated by organo-metallic vapour phase epitaxy (OMVPE) are reported. The common-emitter current gain was 8 for the base thickness of 40 nm at 77 K. This result shows a promising potential for the heterostructure material system of GaInAs/InP for high-speed ballistic electron devices.<>     

GaInAs-GaInNAs-GaInAs intermediate layer structure for longwavelength lasers

Proposes two new structures, the GaInAs-GaInNAs intermediate layer (IML) and the GaInN_xAs graded wells, which show better optical properties than the commonly used GaInNAs-GaAs rectangular quantum-wells. A 1240-nm emitting IML laser has been achieved with a low-threshold current density (200 A/cm²/well) and a relatively high characteristic temperature (T_o=100 K). The IML structure is very promising for long wavelength GaAs-based laser applications     

In vitro selection of aptamers that bind to ribosome-inactivating toxins

Ribosome-inactivating proteins, such as ricin, pepocin and gypsophilin, catalyze the hydrolysis of a single N-glycosidic bond at a specific position in rRNAs. Aptamers targeting pepocin were selected from a random sequence RNA pool that spanned 30 positions. After 8 rounds, the anti-pepocin aptamers were sequenced and a conserved hairpin motif was identified. Interestingly, the selected motif is quite different from the toxin-binding domains of rRNAs.     

A 250-Mb/s/pin, 1-Gb double-data-rate SDRAM with a bidirectionaldelay and an interbank shared redundancy scheme

This paper describes three circuit technologies indispensable for high-bandwidth multibank DRAM's. (1) A clock generator based on a bidirectional delay (BDD) eliminates the output skew. The BDD measures the cycle time as the quantity charged or discharged of an analog quantity, and replicates it in the next cycle. This achieves a 0.18-mm ², two-cycle-lock clock generator operating from 25 to 167 MHz with a 30-ps resolution. (2) A quad-coupled receiver eliminates the internal skew caused by the difference between a rise input and a fall input by 40%. (3) An interbank shared redundancy scheme (ISR) with a variable unit redundancy (VUR) efficiently increases yield in multibank DRAM's. The ISR allows redundancy match circuits to be shared with two or more banks. The VUR allows the number of units replaced to be variable. These circuit technologies achieved a 250-Mb/s/pin, 8-bank, 1-Gb double-data-rate synchronous DRAM     

The pharmacokinetics of water-in-oil-in-water-type multiple emulsion of a new tacrolimus formulation

We developed a water-in-oil-in-water (W/O/W)-type multiple emulsion of a new tacrolimus formulation. A potential approach to avoid the complications of systemic immunosuppression and simultaneously enhance immunosuppressive efficacy is to deliver immunosuppressive agents locally to the site of the target organs. The W/O/W emulsion is dispersed oil drops containing smaller water droplets that allow the delivery of drugs preferentially to the reticuloendothelial system (RES). Since the liver and the spleen are primary components of the RES, and the brain and the kidney have a poor RES, we hypothesized that a W/O/W emulsion of tacrolimus would prossess the pharmacokinetic benefits of local immunosuppression. We evaluated this hypothesis in a rat model. The tacrolimus levels of whole blood, the liver, spleen, brain, and kidney in rats given intravenous emulsions of tacrolimus (W/O/W group) were compared with a group administered tacrolimus alone (T group). There were no significant differences between the pharmacokinetic parameters of W/O/W group and T group based on whole blood data. However, the W/O/W group had significantly decreased tacrolimus levels in the brain and kidney, and significantly increased levels in the liver and spleen compared with the T group. These data suggest that the W/O/W emulsion is applicable as an intravenous drug carrier for local immunosuppression.