Untersuchungen zum Einfluß der 1-Hydroxyethan-1,1-diphosphonsäure,HEDP, auf die Kristallisation von CaCO3 in Ca(HCO3)2-Lösungen

Studies about the Influence of 1-Hydroxyethane-1,1-diphosphonic Acid, HEDP, on the Crystallization of CaCO₃ in Ca(HCO₃)₂ Solutions When cleaned air at 40 °C is passed through solutions of Ca(HCO₃)₂ (4) mmol/l containing ≥5 μmol HEDP/1 x-ray-pure Vaterite crystallizes after a longer time. The reason of the delayed crystallization is not — as usual said in literature — a disturbed growth of the seed crystals of Calcite and Aragonite, but the changed conditions of the formation of crystal nuclei. This is demonstrated by measuring the scattered light, the pH-value and ionic balances. The most important factors of the stability of Ca(HCO₃)₂-solutions containing HEDP are characterized.     

Einige ergänzende Bemerkungen zur Beschreibung von Vorgängen in der klassischen Kontinuumsmechanik

Ohne Zusammenfassung     

High-Resolution Phase Doppler Particle Sizing based on Hilbert transform signal processing

A new phase Doppler anemometry (PDA) signal processing method based on a Hilbert transform algorithm is introduced and analysed. By generating a 90° phase-shifted burst signal in the time domain, the envelope of the Doppler burst can be determined. In addition, this envelope is approximated by a Gaussian exponential function. The difference of the maxima of these Gaussian approximations for two related PDA bursts gives an estimate of the time difference between these time shifted signals. With the introduction of this estimation method, the restriction to the [0,360°] interval resulting from conventional signal analysis may be avoided in many cases. To investigate the dependence on SNR, burst position, burst frequency and sampling rate, results of computer simulations are presented. The feasibility of the method is demonstrated briefly by experimental results. Phase differences of more than 2000° arising from the measurement of monodisperse droplets by a conventional PDA setup could be determined.     

Elektrochemische Untersuchungen am Ninhydrin

Zusammenfassung Bei der potentiostatischen zweilektronigen Reduktion des Ninhydrins wird eine der beiden nicht hydratisierten Ketogruppen durchreduziert. Bei pH-Werten oberhalb 4,5 lagert sich dieses benzoide Reduktionsprodukt in eine tautomere chinoide Verbindung um, die im pH-Bereich 4,5–8 ein Proton und ein Molekül Wasser, bei pH-Werten oberhalb 11 zwei Protonen abspaltet. Im Gegensatz zum farblosen benzoiden 2e-Reduktionsprodukt hat die einfach ionisierte chinoide Verbindung eine rote, die zweifach ionisierte chinoide eine blaue Farbe. Die elektroneutrale chinoide Verbindung unterhalb pH 4,5 its farblos und dehydratisiert.Oberhalb pH 9 dissoziiert von der hydratisierten mittleren Ketogruppe des Ninhydrins ein Proton ab (pKs=8,6), was bei hohen pH-Werten zur raschen Umwandlung in o-Carboxymandelsäure führt. Ninhydrin läßt sich zweielektronig oxydieren zur o-Carboxy-phenylglyoxylsäure.Mit 8 Abbildungen     

Elastic scattering of antiprotons on protons at 5 GeV/c evidence for a backward peak

Antiproton-proton elastic scattering has been measured at 5 GeV/c. A total of 30 000 events were observed in the angular range 17° < θ_cm < 136°, corresponding to 0.3 < −t < 7.7 (GeV/c²). In addition to the known dip at −t = 0.5 (GeV/c)², we observe a structure at about −t = 2 (GeV/c)² and a backward peak with a slope4.1 ± 0.6 (GeV/c)². The extrapolated differential cross-section at u = 0 is 1.3 ± 0.8 μb/(GeV/c)².     

Methods for the Numerical Calculation of the Plasma Potential from Measured Langmuir Probe Characteristics

In a previous paper the results of the Langmuir probe experiment carried out on board of two INTERKOSMOS satellites have been described. The experiences have shown that the usage of high quality algorithms for analyzing the current-voltage-characteristics is necessary to yield real physical parameters. The key problem is the determination of the plasma potential. This paper reviews the different methods to determine the plasma potential especially under the circumstances of computer application. The test of the well developed methods shows, that for the evaluation of the applied methods a number of different factors, discussed in the following sections of this paper, has to be taken into account. The used test data are model values or real measurements obtained by the satellite missions IK-10, IK-18 and BULGARIA-1300. The computer procedures have been realized as FORTRAN-subroutines for the BESM 6 and ES 1040.     

Anomalous hyperfine splitting of 57Fe in α-quartz

The hyperfine splitting of ⁵⁷Fe for substitutional Fe³⁺ in synthetic α-quartz was found to increase monotonically with increasing slope of the fine structure transitions exceeding the free ion value several times in highly anisotropic regions. A tentative explanation for this hitherto unreported effect is proposed.     

Neutron-proton charge exchange scattering between 190 MeV and 590 MeV

Differential cross sections of the np charge exchange scattering between 190 MeV and 590 MeV have been measured by detecting the scattered protons in an angular range of 0^° θ_lab 18^°. The cross section at 0^° as well as the logarithmic slope of the angular distribution are found to be almost energy independent, in contrast to previous experiments, but in agreement with recent LAMPF data.