HYDRODYNAMIC CHROMATOGRAPHY: THREE DIMENSIONAL LAMINAR DISPERSION IN RECTANGULAR CONDUITS WITH TRANSVERSE FLOW

Experimental observations^1,9 indicate much poorer separations than are predicted by two dimensional theory. The purpose of this work is to explain these differences and suggest ways in which system performance can be improved.

The large effect of span-wise variation in axial velocity caused by side walls on hydrodynamic separations carried out in rectangular conduits with transverse flow is studied theoretically. As the aspect ratio increases, the steady stale retentivity (convection coefficient) approaches an asymptotic value obtained by neglecting side wall effects. However, the dispersion coefficient does not reduce to that for a flow with no side walls. Indeed, the asymptotic steady state dispersion coefficient is at least six times larger than that obtained by two dimensional theory which neglects side wall effects. As the transverse Peclet number increases, the effect of side walls on the dispersion coefficient becomes much larger.

The present three dimensional theoretical predictions, in contrast to two dimensional ones, are in good agreement with the experimental data of Caldwell, et al.⁹ and Kesner, et al.¹ on electrical field flow fractionation. The results indicate that side wall effects may be of major importance in hydrodynamic chromatography even when the aspect ratio is 70 or more.

The adverse effect of side walls may be avoided by having the membranes enclose thin annular regions rather than rectangular conduits. This should improve performance significantly.     

Formulation of four Katsevich algorithms in native geometry

We derive formulations of the four exact helical Katsevich algorithms in the native cylindrical detector geometry, which allow efficient implementation in modern computed tomography scanners with wide cone beam aperture. Also, we discuss some aspects of numerical implementation.     

Effects of the depth of NO and N2O productions in soil on their emission rates to the atmosphere: analysis by a simulation model

Many factors are concerned in the changing forms of nitrogen compounds in soil, so it is not easy to make precise models to simulate the concentration profiles of soil nitric oxide (NO) and nitrous oxide (N₂O) and their emission rates under various soil conditions. We prepared a simple mathematical simulation model based on soil concentration profiles of NO and N₂O. The profiles were measured at lysimeters filled with Andosol soil and fertilized with ammonium sulfate at rate of 200 kgNha^-1, incorporating to plow layer (Hirose & Tsuruta, 1996). In this model, diffusion of gases in soil followed Fick's law and the diffusion coefficient was adopted from Sallam et al. (1984). The gas production rate was set up at constant value in the site of gas production, and the gaseous consumption followed Michaelis-Menten kinetics. By changing only the depth of NO and N₂O production in soil in this model, we obtained the following results.(1) When the depth of gas production was set at near the soil surface (NO: 0–10 cm, N₂O: 0-8 cm), the emission rates of both gases corresponded with the results of the lysimeter-measurement.(2) When the depth of gas production was shifted down 10 cm deeper (NO: 10–20 cm, N₂O: 10-18 cm), the gas emission rate of NO decreased to 1.3% of (1), while that of N₂O was almost the same as (1).(3) In the case that the total intensity of produced gases was not changed from (1) or (2), but that the extent of gas productions expanded 3 times wider (NO: 0–30 cm, N₂O: 0–24 cm) than (1) or (2), the emission rates of NO and N₂O became 26% and 95% of (1), respectively.The above results suggest the possibility of mitigating NO emission by setting the site of gaseous production in deeper soil, e.g. by means of deep application of fertilizer.     

Efficient Conversion of D-Glucose to D-Fructose in the Presence of Organogermanium Compounds

D-Glucose and D-fructose are isomers of commonly consumed monosaccharides. The ratio of conversion of D-glucose to D-fructose by glucose isomerase (xylose isomerase) is not more than 50 %. However, addition of an equimolar ratio of the organogermanium compound poly-trans-[(2-carboxyethyl)germasesquioxane] (Ge-132) or its derivative increases the conversion ratio to 80 %. In contrast, use of the Lobry de Bruyn–Alberda van Ekenstein transformation with heating results in a lower conversion ratio, less than 30 %, whereas addition of an equimolar concentration of Ge-132 or its derivative to this reaction mixture increases the ratio to 73 %. Therefore, in this study, we aimed to further analyze the affinity between organogermanium compounds (i.e., Ge-132 and its derivatives) and sugar using ¹H-nuclear magnetic resonance (NMR) spectrometry. For the dimethyl derivative of Ge-132, the complex formation ratios at 0.25 M (mixing ratio 1:1) were 19 and 74 % for D-glucose and D-fructose, respectively. Additionally, the complex formation constants between monosaccharides and Ge-132 were 1.2 and 46 M^-1 for D-glucose and D-fructose, respectively. The complex formation capacity was approximately 40-fold higher for D-fructose than for D-glucose. Therefore, we concluded that the high affinity for the product of isomerization may promote isomerization, and that promotion of sugar isomerization using organogermanium compounds is an effective method for conversion of D-glucose to D-fructose.     

Universal Strategy for Efficient Electron Injection into Organic Semiconductors Utilizing Hydrogen Bonds

Molecular n‐dopants that can lower the electron injection barrier between organic semiconductors and electrodes are essential in present‐day organic electronics. However, the development of stable molecular n‐dopants remains difficult owing to their low ionization potential, which generally renders them unstable. It is shown that the stable bases widely used in organic synthesis as catalysts can lower the electron injection barrier similar to that in conventional n‐doping in organic optoelectronic devices. In contrast to conventional n‐doping, which is based on the electron transfer from dopants with low ionization potential, the reduction of the injection barrier caused by adding bases is determined by the formation of hydrogen bonds between the hosts and the bases, providing energy‐level‐independent electron injection. The observation of the efficient electron injection induced by hydrogen bonding affords new perspectives on the method for controlling the behavior of electrons unique to organic semiconductors.     

Bipartite modular multiplication with twice the bit-length of multipliers

This paper presents a new technique to compute 2ℓ-bit bipartite multiplications with ℓ-bit bipartite multiplication units. Low-end devices such as smartcards are usually equipped with crypto-coprocessors for accelerating the heavy computation of modular multiplications; however, security standards such as NIST and EMV have declared extending the bit length of RSA cryptosystem to resist mathematical attacks, making the multiplier quickly outdated. Therefore, the double-size techniques have been studied this decade to extend the life expectancy of such multipliers. This paper proposes new double-size techniques based on the multipliers implementing either classical or Montgomery modular multiplications, or even both simultaneously (bipartite modular multiplication), in which case one can potentially compute modular multiplications twice faster. Furthermore, in order to get a more realistic estimation than the other works, this paper considers not only the cost of the multiplication, but also the cost of the other arithmetic instructions. In our estimation, the proposal provides comparable results for classical multiplier and Montgomery multiplier, and is the only available method for the bipartite multiplier. A preliminary version of this paper was presented at the 12th Australasian Conference on Information Security and Privacy, ACISP’07.     

新型抗辐照氧化物弥散强化（ODS）型铁素体不锈钢辐照损伤特性研究

研制了一种具有低肿用蒿强度的氧化物弥散强化型铁素体钢Ｆｅ－Ｃｒ－Ｗ－Ｔｉ－Ｙ２Ｏ３，并对其抗辐照损伤行为进行了系统研究。电子辐照表明，Ｙ２Ｏ３弥散氧化物质点在所研究的辐照下是稳定的，在辐过程中形成ｂ＝ａ〈１００〉和ｂ＝ａ／２〈１１１〉两种类型的位错环。     

An experimental study of the characteristics of a Darrieus turbine for tidal power generation

The Darrieus turbine was initially developed for wind turbines. An example of its application to water turbines is found in the Darrieus turbine installed in a duct for low head power generation, but no example is known of its application in a natural water channel. The authors have developed a Darrieus turbine that is suitable for tidal current power generation with the aim of establishing tidal current power generation technology through demonstrations in test channels and oceans. The efficiency of tidal current power generation is influenced by the characteristics of the turbine. The characteristics of the Darrieus turbine are mainly affected by the solidity and the number of blades. The Darrieus turbine was tested in test channels to find the most suitable values for the rotor solidity and the number of blades. This paper describes and examines those test results. © 2000 Scripta Technica, Electr Eng Jpn, 132(3): 38–47, 2000