Estimation of mixing index and contact number by spot sampling of a mixture in an incompletely mixed state

There are two approaches to the determination of the mixing index based on the contact number. One is based on coordination number sampling, and the other on spot sampling. In this work, the estimation of the mixing index and that of the contact number by spot sampling of a mixture in an incompletely mixed state are examined. General expressions have been derived for the precision of the estimation of the population mean contact number and that for the contact number.     

Electrode heat balances of electrochemical cells: application to NaCl electrolysis

This paper deals with a method of estimating single electrode heat balances during the electrolysis of molten NaCl-ZnCl₂ in a cell using a-alumina diaphragm. By measuring the thermoelectric power of the thermogalvanic cells: (T) Na/-alumina/NaCl-ZnCl₂/-alumina/Na(T+dT) and (T) C,Cl₂/NaCl-ZnCl₂/Cl₂,C(T+dT) the single electrode Peltier heat for sodium deposition and for chlorine evolution at 370° C were estimated to be –0.026±0.001 JC^–1 and+0.614±0.096 J C^–1, respectively.     

Molecular orbital study of pyrolytic carbons based on small cluster models

Molecular orbital calculations are applied to the Raman scattering and ESR of pyrolytic carbons on the basis of small cluster models. The E_2g and A_1g modes of C-C stretching vibrations of coronene, hexabenzocoronene, and circumcoronene, which belong to D_6h carbon clusters, are shown to appear around the 1550 cm⁻¹ and 1360 cm⁻¹ bands, respectively. The unpaired electrons observed in pyrolytic carbons are attributed to the bond-alternation defects on odd-numbered carbon clusters that are more easily mobile than those of trans-polyacetylene.     

The modulated structure formed by isothermal ageing in ZrO2-5.2 mol % Y2O3 alloy

The modulated structure produced by isothermal ageing of ZrO₂-5.2 mol % Y₂O₃ alloy was examined mainly by electron microscopy. It was found that the modulated structure was formed at ageing temperatures between 1400 and 1600° C, but not at 1700° C. The structure is developed by spinodal decomposition, which produces compositional fluctuation in the elastically soft 111 direction in cubic zirconia. The hardness increase caused by the development of modulated structure during ageing is larger than the hardening by precipitation of tetragonal phase in the cubic matrix.Graduate Student, Tohoku Univerisy, Sendai, Japan.     

Excretion of deoxynivalenol and its metabolite in milk, urine, and feces of lactating dairy cows

Corn contaminated with deoxynivalenol was added to the diets of three dairy cows for 5 d and milk, urine, and 3 d following feeding of the diets. Dietary concentrations of deoxynivalenol averaged 66 mg/kg. Following exposure to deoxynivalenol, unconjugated deepoxydeoxynivalenol, a metabolite of deoxynivalenol, was present in milk at concentrations up to 26 ng/ml. Deoxynivalenol was not detected in the milk. Approximately 20% of the deoxynivalenol fed was recovered in the urine and feces in the unconjugated forms as deepoxydeoxynivalenol (96%) and deoxynivalenol (4%). After incubating urine with beta-glucuronidase, the concentration of unconjugated deepoxydeoxynivalenol increased by 7 to 15-fold whereas unconjugated deoxynivalenol increased 1.6 to 3-fold. Detectable concentrations of unconjugated deepoxydeoxynivalenol were found in urine and feces up to 72 h after the last oral exposure. Thus, urine and feces are the diagnostic specimens of choice for the determination of deoxynivalenol exposure in cows. Feeding deoxynivalenol-contaminated diets for 5 d did not alter feed intake or milk production nor were the milk concentrations of calcium, phosphorus, sodium, potassium, magnesium, or nitrogen altered.     

RK‐Slim: embedded Runge–Kutta without the excess baggage

Computationally demanding scientific simulations require numerical integration of large systems of ordinary differential equations (ODEs) in real time. Runge–Kutta (RK) methods with step‐size control are frequently employed because they are accurate and have short execution times. Computational step sizes can be increased while maintaining accuracy if the error generated during each time step is below a predetermined threshold. However, if the error exceeds the threshold, the time step must be re‐computed using a smaller step‐size. In practice, the re‐computation is unnecessary for most equations in the system because violations of the error tolerance are localized and occur in just a few equations. We present an efficient and accurate method for solving ODEs that exploits these observations on step‐size by eliminating many unnecessary computations in embedded RK methods. We demonstrate how our new method can be a valuable tool for practitioners in the field through simulations with real‐world data. Copyright © 2011 John Wiley & Sons, Ltd.     

Durability characteristics of the hydration of magnesium oxide under repetitive reaction

The durability of the magnesium oxide/water reaction system under repetitive reaction conditions was examined experimentally to demonstrate the operability of a magnesium oxide/water chemical heat pump. Changes in the reactivity in the hydration of magnesium oxide, which was the most sensitive process in the repetitive reaction, were measured at hydration temperatures from 90–170°C and pressures from 31.2–70.1 kPa. A lower temperature and a higher pressure for the hydration reaction were effective in maintaining reactivity. The effect of different reaction conditions experienced during repetitive cycles to the standard repetitive cycle was discussed. From microscopic observations, nucleation in primary particles of the material induced by the structure change during repetitive reaction was an important factor in the enhancement of durability.     

High-Tc dc SQUID cooled by pulse-tube cooler and corrosion measurements

We developed an YBCO high-Tc dc superconducting quantum interference device (SQUID) system cooled by a pulse-tube cooler. To stabilize and control the operating temperature of SQUID, a temperature controlling method, using dc SQUID itself as the temperature sensor, was developed. With the temperature controller, the temperature fluctuation could be reduced to about 50 mK and the dc SQUID magnetometer could keep locking for over 8 h. Using this dc SQUID magnetometer, we did some corrosion measurements in shielding. The field produced by the corrosion of aluminum plate with one side immersed in corrosion solution could be successfully detected.