A Study of Structure, Electric and Magnetic Properties of the New Layered Cobalt Oxides Sr2Y1-x Ca x Co2O7-z

The crystal structure of Sr ₂ Y _0.8 Ca _0.2 Co ₂ O ₆ is orthorhombic below 270 K (Immm, a = 3.84029(7) Å, b = 3.80691(6) Å and c = 19.4980(3) Å at 20 K), transformed from tetragonal (I4/mmm, a = 3.82765(6) Å and c = 19.5795(3) Å) at 295 K. The crystal structure distortion is accompanied by an anomalous temperature dependence of the degree of buckling of the CoO ₂ plane and is correlated with the development of anisotropic antiferromagnetic ordering of magnetic moments (2.93(2) _B per Co at 20 K). A magnetically glassy state below about 35 K and variable range hopping conduction below about 64 K for were found by magnetic susceptibility and electrical resistivity measurements.     

Photon conductivity of metallurgical slags of the three component system CaO-SiO2-Al2O3

The measuring method proposed by Keene and Quinn has been further developed to investigate 3-component slags of the system CaO-SiO₂-Al₂O₃ at temperatures of 800–1600°C in the wavelength range of 550 to 850 nm. The results are presented with the aid of the complex refraction index, which embodies all information on the optical properties of the slags investigated, including photon conductivity and thermal emissivity. Comparison of the photon conductivities determined shows good agreement with the corresponding values of various types of glass cited in literature. The discontinuous pattern of the phonon conductivity curve in the melting range of 40% CaO-40% SiO₂-20% Al₂O₃ slag, as already found by Gammal and Li, is also evident from the data of the present investigation.     

Weiterentwicklung des Ring-Kern-Verfahrens zur Messung von Eigenspannungen

Anwendung des Ring-Kern-Verfahrens zur Messung von Eigenspannungen in den Randschichten schwerer Schmiedestücke. Ableitung der Grundgleichungen für den Zusammenhang zwischen gemessenen Dehnungsänderungen und den zu ermittelnden Eigenspannungen bei gleichmäßiger und ungleichmäßiger Spannungsverteilung im Inneren. Näherungsverfahren und Vereinfachungen. Grenzwertbetrachtungen. Verbesserte Arbeitsweise bei der Durchführung der Messungen. Herstellung der Ringnut mit einem besonders gestalteten Kronenfräser. Ermittlung der Abklingfunktionen in Eichversuchen. Vereinfachte Auswertung mit Nomogrammen.     

n-Channel Si-gate process for MNOS EEPROM transistors

An n-channel Si-gate process has been developed to fabricate MNOS EEPROM transistors and fast logic circuits on one chip. The technology proposed involves low thermal oxidation temperatures ≤900°C after nitride deposition, two LOCOS process steps and application of self-aligned overlapped poly-Si contacts. The MNOS memory transistors obtained have been programmed by ±25 V pulses with a write time of t_w = 10 ms and an erase time of t_e = 100 ms.The retention data have been found to be dependent on nitride thickness and threshold voltage shift, but independent of channel length and channel doping. For devices with a nitride thickness of 30.5 nm the short-term decay rate of 0.6 V/(decade of time) has been determined. Endurance testing using up to 10⁷ pulses of ±25 V, 100 μs corresponding to approx. 10⁴ write/erase cycles showed no time dependence for the decay rate over the time of 10⁵ min in which retention measurements were made.     

Development of a hyphenated microanalytical system for the investigation of leaching kinetics of heavy metals in environmental samples

A fast and convenient method for on-line monitoring of the extraction of heavy metals from solid (environmental) matrixes was developed. By the incorporation of microcartridges filled with dried and pulverized solid samples into the conduits of a flow system and appropriate selection of the liquid flowing through the cartridge, information about the degree of leaching and in particular of the kinetics of the leaching process are obtained. The method was optimized for determination of different metals of environmental concern using in-line detection by FAAS and ICPMS.     

Effect of candicidin on cholesterol and bile acid metabolism in the rat

Sterol metabolism studies were carried out in rats maintained on a diet containing a polyene antibiotic, candicidin, (30 mg/kg/day) for 2-1/2 months. Compared to the controls, the candicidintreated animals had a smaller food intake and weight gain during this period. There was no difference between the 2 groups in serum cholesterol levels, biliary cholesterol or bile acid concentrations. However, in the experimental group, liver cholesterol content decreased by 27% and hepatic HMG-CoA reductase increased by 36%. Candicidin administration produced an 84% increase in neutral sterol output without change in bile acid output. Cholesterol absorption was reduced 80% by candicidin feeding. The weight of ventral prostate was reduced 33% by candicidin administration. Prostatic HMG-CoA reductase levels were 3 times higher than those of the liver, but enzyme activity was unchanged by candicidin treatment.     

Theory of mixing sections in single screw extruders

A discussion of the effect of deformation on mixing leads to reorientation of fluid interfaces as a proposed mechanism for special “mixing sections” in single screw extruders. Based on the kinematics of mixing it is shown how a mixing section can greatly decrease the amount of work necessary to accomplish extensive mixing through orienting the fluid more favorably for mixing by subsequent shear. Mathematical development quantitatively describes favored configurations of mixing sections. An upper bound for the mixing performance of a simple model of an extruder with special sections is shown to be similar to turbulent mixing. Based on this theory the key actions of the special sections are identified.     

Crystallization studies on phase-change optical recording media by use of a two-dimensional periodic mark array

We present the results of crystallization studies in thin-film samples of amorphous and crystalline Ge(x)Sb(y)Te(z). The experiments, conducted at moderately elevated temperatures, are based on measurements of the first-order diffraction efficiency from a two-dimensional periodic array of recorded marks. When the samples are slowly heated above room temperature, changes in the efficiencies of various diffracted orders give information about the on-going crystallization process within the sample. Two different compositions of the GeSbTe alloy are used in these experiments. Measurements on Ge(2)Sb(2.3)Te(5) films show crystallization dominated by nucleation. For the Sb-rich eutectic composition Ge-(SbTe), crystallization is found to be dominated by growth from crystalline boundaries. We also show that crystalline marks written by relatively high-power laser pulses are different in their optical properties from the regions crystallized by slow heating of the sample to moderate temperatures.