The spectrum of permutation orbifolds

We study the spectrum of permutation orbifolds of 2d CFTs. We find examples where the light spectrum grows faster than Hagedorn, which is different from known cases such as symmetric orbifolds. We also describe how to compute their partition functions using a generalization of Hecke operators.

     

Fractionation factors for stable isotopes of N and O during N2O reduction in soil depend on reaction rate constant

Nitrous oxide (N(2)O) is a major greenhouse gas that is mainly produced but also reduced by microorganisms in soils. We determined factors for N and O isotope fractionation during the reduction of N(2)O to N(2) in soil in a flow-through incubation experiment. The absolute value of the fractionation factors decreased with increasing reaction rate constant. Reaction rates constants ranged from 1.7 10(-4) s(-1) to 4.5 10(-3) s(-1). The minimum, maximum and median of the observed fractionation factors were for N -36.0 per thousand, -1.0 per thousand and -9.3 per thousand and for O -74.0 per thousand, -6.9 per thousand and -26.3 per thousand, respectively. The ratio of O isotope fractionation to N isotope fractionation was 2.4 +/- 0.3 and it was independent from the reaction rate constants. This leads us to conclude that fractionation factors are variables while their ratio in this particular reaction might be a constant.     

Process analysis of electroless nickel deposition baths using optical spectroscopies

Summary The analytical techniques of Vis-spectrophotometry and FTIR spectroscopy have been applied to the quantitative determination of important plating bath constituents of an electroless nickel-phosphorus electrolyte under realistic bath operation conditions. In combination with multivariate calibration methods (partial-least squares (PLS)- and principal component (PCR) regression) Ni²⁺, the reducing agent H₂PO ₂ ^– and its oxidation product HPO ₃ ^– could be directly determined even in the presence of other bath constituents like malic, lactic and adipic acids. For Ni²⁺, absorbance spectra in the 500–900 nm wavelength range were used to develop a PLS calibration model that allows to compensate matrix influences on the Ni²⁺ spectrum. PLS regression was carried out in the concentration range 0.5–6 g l^–1 Ni²⁺ with independently varying bath parameters (concentration of other bath constituents, pH and temperature). Evaluation of the model by predicting the concentrations of test samples which had been drawn from real process solutions of a Ni plating bath yielded a root-mean-squared error of 0.06 g l^–1. The metal concentration of the nickel electrolyte in a compact electroplating unit was monitored in-line by measuring spectra by means of a Vis-spectrometer adapted to the process via quartz glass fiber optical cables of 50 m length. A comparison of the in-line data with potentiometric off-line reference analyses showed good agreement of both data sets with a root mean-squared error of 0.15 g l^–1. The potential of FTIR spectroscopy for process analysis of plating bath solutions could be demonstrated by measuring off-line the concentrations of H₂PO ₂ ^– and HPO ₃ ^– . For these two components calibration samples containing all other main bath constituents were used to set up a PCR calibration model with IR spectra measured in the range from 850 to 1800 cm^–1 with an ATR trough technique. The data showed — within the error of the method of about 10% — generally a good accordance with the stoichiometry of the Ni²⁺/H₂PO ₂ ^– reduction process. The correlation of both parameters which was confirmed in these experiments could allow effective bath control with minimum analytical instrumentation, e.g. only a Vis-spectrophotometer.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

Neutronenaktivierungsanalytische Bestimmung von Neodym-148 in Spalterden

Zusammenfassung Neodym-148 wurde in Spalterden zum Zweck der Abbrandanalyse von bestrahlten Kernbrennstoffen neutronenaktivierungsanalytisch bestimmt. Nach ionenaustauschchromatographischer Trennung von anderen Lanthaniden haben wir das Spaltneodym in der thermischen Säule des FR 2 bestrahlt und die Gammaaktivität des Nd-149 ohne jede weitere chemische Aufarbeitung gemessen. Als Standardproben dienten bekannte Mengen Nd-148 (Reinisotop). Die chemische Ausbeute nach der Trennung bestimmten wir gammaspektroskopisch bei Verwendung von trägerarmem Nd-147 als Spike.

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Neutron activation analytical determination of neodymium-148 in cleaved earths

Summary Neodymium-148 was determined in cleaved earths for the purpose of consumption loss analysis of irradiated nuclear fuels employing neutron activation analysis. Following ion exchange Chromatographie separation of other lanthanides, the fission neodymium was irradiated in the thermal column of the FR 2 and the gamma activity of the neodymium-149 was measured without any additional chemical workup. Known amounts of Nd-148 (the pure isotope) were used as standard samples. The chemical yield after the separation was determined gamma spectrometrically using the carrier-poor Nd-147 as spike.

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Vorgetragen bei der Fachgruppentagung über radiochemische Arbeitsmethoden in Graz, September 1970.