A self-validating numerical method for the matrix exponential

An algorithm is presented, which produces highly accurate and automatically verified bounds for the matrix exponential function. Our computational approach involves iterative defect correction, interval analysis and advanced computer arithmetic. The algorithm presented is based on the “scaling and squaring” scheme, utilizing Padé approximations and safe error monitoring. A PASCAL-SC program is reported and numerical results are discussed.     

Dephosphorization equilibria between pure molten iron and CaO-saturated FeOn–CaO–SiO2 and FeOn–CaO–Al2O3 slags

Metal-slag refining reactions have been investigated to determine dephosphorization equilibria in steelmaking using CaO-saturated slags, low in P₂O₅–content, based on the systems FeO_n–CaO–SiO₂ and FeO_n–CaO–Al₂O₃. Slag compositions have been optimized with respect to basicity and oxygen potential to achieve maximum partition ratios wt.%(P₂O₅)/wt.%[P] and minimum phosphorus contents in pure molten iron at 1550, 1600 and 1700°C. Both slag systems prove to be effective dephosphorizers. Optimal slag compositions are around 10 wt.% SiO₂ near the CaO–3CaO · SiO₂ double saturation in the case of FeO_n–CaO–SiO₂ slags and at Al₂O₃ contents tending to zero in the case of FeO_n–CaO–Al₂O₃ slags. Attempts were also made to present phosphate capacities C_PO4^3?, fractions of free oxygen ions x_O^2? and theoretical optical basicities Λ as a function of the FeO_n content of slags.     

The effect of antenatal corticosteroid prophylaxis in premature newborns with the use of surfactant therapy

The influence of new probiotics from bacilli i.e. biosporin and subalin on the functional activity of murine peritoneal macrophages was studied. After a single oral administration of the probiotics the maximum activation of the macrophages was observed in 4 hours. The activation level depended on both the dose and the probiotic. The highest value of the stimulation index was recorded with subalin. Analogous regularities were stated with parenteral administration of the probiotics. Some mechanisms of activation of peritoneal macrophages after oral administration of probiotics from live microbial cultures are discussed.     

Study of submicron deposits in polycrystalline materials using the internal-friction method

An internal friction method is proposed for investigating the kinetics of impurity deposits on grain surfaces in polycrystalline samples. The possibilities of the method have been tested on polycrystalline, gas-sensitive, tellurium-doped layers of tin dioxide. Fiz. Tekh. Poluprovodn. 31, 841–843 (July 1997)     

Copper bromide laser of 120-W average output power

A Ne-H₂-CuBr laser (λ510.6, 578.2 nm) is reported, which produced an average output power of 120 W at 2.5% efficiency (based on stored energy) and 100 W at 3% efficiency. These output power and efficiency figures are record values for copper bromide lasers. The sealed-off device produced maximum output power at a pulse recurrency frequency (PRF) of 17.5 kHz. Laser operating characteristics and electrical parameters are described     

Control of the aluminium-oxygen reaction in pure iron melts

Modified electrochemical oxygen sensors based on CaO-doped ZrO₂ and Y₂O₃-doped ThO₂ were developed and applied to study the aluminium-oxygen reaction in pure liquid iron with special regard to the provision of reliable experimental conditions and the attainment of true chemical equilibrium. The sensors represent valuable tools particularly for EMF long-term measurements over several hours. At 1600 °C, values of the constant and of the interaction parameters and were determined. When Fe-O-Al melts are covered with a slag phase at an activity a(Al₂O₃) < 1, e.g., CaO-saturated CaO-Al₂O₃ slag, the Al-O relationship in the iron may nevertheless be controlled by an equilibrium oxide phase at an activity a(Al₂O₃) = 1, presumably represented by inclusion particles consisting of pure Al₂O₃.     

Control of the chromium-oxygen reaction in pure iron melts

Oxygen activities in Fe-O-Cr melts, equilibrated with chromium oxide, were determined as a function of chromium content by EMF measurements using ZrO₂(CaO) plug-type sensors with a Cr-Cr₂O₃ reference. Plug-type sensors with or without Cr₂O₃ saturator were used in the experiments. From the experimental results values for the activity coefficient f_O and the interaction parameters and were evaluated. Raoultian chromium activity features a slight positive deviation from ideal solution behaviour in the temperature range from 1550 to 1650°C. Taking into account the calculated interaction parameters, the equilibrium constant K_Cr-O was redetermined at 1550 to 1650°C. In comparison with previous studies a better agreement was obtained with existing thermochemical data.