Studies of the protein and the energy metabolism in man during a wintering in Antarctica

During the 29th Soviet Antarctic Expedition in Novolazarevskaya from March 1984 to March 1985, the protein and energy metabolisms were studied in six expeditioners from the German Democratic Republic. The investigations were carried out at the beginning of the expedition (May), during the polar night (July) and during the polar day (December). The effect of a special stress situation (sledge trek in April 1984) was investigated in one subject. The stable nitrogen isotope ¹⁵N was used to study the protein metabolism. The assessment of the energy metabolism was based on the oxygen consumption, which was determined by means of a spirograph. In addition, the vital capacity, the breath minute volume, the blood pressure, etc. were measured. The following results were obtained: During the polar night, the utilisation of the dietary proteins and the whole body protein synthesis calculated by means of the ¹⁵N excretion of the total nitrogen in urine were greater (73.6±0.9 % and 3.48±0.17 g protein d^?1 kg^?1, n=3) than the respective values during the polar day (69.7±1.2, p<0.05, n=3 and 3.05±0.07, p<0.05, n=3) and at the beginning of the expedition (69.6±1.4, p<0.02, n=5 and 2.81±0.09, p<0.01, n=5). The lowest values (58.0 % and 2.43 g protein d^?1 kg^?1) were obtained in the subject after the trek. The resting metabolic rate (in kJ d^?1 m^?2) was decreased during the polar night (45.6±5.0, n=4) in comparison with the polar day (61.5±11.3, n=3) and the beginning of the expedition (52.3±9.6, n=4) with p<0.01 in both cases.     

Advances in nitrogen-15 use for environmental studies in the soil-plant system

Abstract

A review is being presented of the latest results in the use of nitrogen-15 in the soil-plant system. The literature covers the period from 1991 to early April 1993. The increase in environmentally related experiments shows that the stable nitrogen isotope technique, applied either as tracer or as the natural isotope tracing approach, is well suited particularly to ecosystem studies. This trend is supported by convenient analytical systems. An important challenge to scientists in the field of environmental research is to contrive ways and means of permitting the plants to utilize the available nitrogen in the soil more efficiently. Examples of research areas needing more attention are pointed out.     

Zur Probenchemie von Stickstoffverbindungen für die emissionsspektrometrische Isotopenanalyse des Stickstoffs

In einer Übersicht werden diewichtigsten Verfahren zurprobenchemischen Aufbereitung ¹⁵N-markierter Verbindungen wiedergegeben. Im Anschluß daran wird eine bewährte Mikormethode zur Probenchemie von Stickstoffverbindungen für die optische Isotopenanalyse des Stickstoffs beschrieben, die auf der Oxydation von Ammoniumchlorid mittels Natriumhypobromit zu N₂ beruht und Stickstoffmengen von etwa · 10^?6 Mol für eine Probe benötigt. Aufbau der Apparatur und Arbeitsweise werden eingehend erläutert.     

Trennung von Ammonium-, Nitrit- und Nitrat-Stickstoff für die 15N-Analytik

Die beschriebene Methode besteht aus einer Kombination der Ionenaustauschchromatographie mit der klassischen Wasserdampfdestillation. Die Trennung von Nitrit und Nitrat erfolgt dabei durch selektive Reduktion mittels Eisen-II-hydroxid und eines geeigneten Katalysators zu Ammoniak. Am Ende der Trennung liegt der Stickstoff der N-Verbindungen jeweils als Ammoniumchlorid vor, das direkt für die emissionsspektrometrische ¹⁵N-Analyse einsetzbar ist. Die vorgestellte Methode ist vorzugsweise gecignet für die Untersuchung der mikrobiellen Ammoniumoxydation (Nitrifikation) mittels der ¹⁵N-Tracertechnik.

The method described consists of a combination of the ion exchange chromatography with the common steam distillation. Nitrite and nitrate are separated by the selective reduction to ammonia using ferrous hydroxide and an appropriate catalyst. Ammonia liberated is titrated with standard hydrochloric acid and directly used as ammonium chloride for ¹⁵N analysis by an emission spectrometer. The method is suitable for the investigation of the microbial ammonia oxidation (nitrification) by means of the ¹⁵N tracer technique.     

Nuclear structure effects in the mass region aroundA=100, derived from experimentalQ β -values

The endpoint energies ofβ-transitions in 15 neuron-rich nuclei with mass numbers 101≦A≦106 have been measured with a plastic scintillator telescope in coincidence with a large Ge(Li)-detector at the on-line mass separator LOHENGRIN. From theQ _β -values obtained in these experiments, nuclear structure effects in this region of the nuclear chart are deduced. Finally, nuclear masses derived from theseQ _β -values are compared with the predictions of different theoretical mass calculations.     

The level scheme of 137Pr; evidence for prolate nuclear shape

The level scheme of ¹³⁷Pr was investigated by means of the γ-rays following the β-decay of ¹³⁷Nd as well as by prompt γ-rays accompanying (α, xn) reactions. We measured γ-ray single spectra, γγ coincidences (both in-beam and off-beam), angular distributions of prompt γ-rays and conversion electrons. About 100 γ-rays were assigned to the 38 min decay of ¹³⁷Nd most of which fit into a scheme of 26 deduced levels. From in-beam experiments we tentatively assigned an $\text{11}\text{2}$^? level which is the basis of a strong cascade of stretched E2 transitions with a probable level sequence of $\text{23}\text{2}$^? ?$\text{19}\text{2}$^? ?$\text{15}\text{2}$^? ?$\text{11}\text{2}$^?. The interpretation of this cascade in the framework of a strong coupling model indicates a prolate deformation of ¹³⁷Pr. Another indication for such a deformation was obtained from the very low energy (75 keV) of the first $\text{3}\text{2}$⁺ level which could not be interpreted in an intermediate coupling model, but is suggested by a Nilsson scheme.     

Cytosine analogues from substituted acetonitriles via Thorpe condensation

[reaction: see text] A Thorpe condensation is the key bond construction in a rapid and efficient synthesis of substituted cytosine derivatives from readily available starting materials.     

The new isotopes247Md,243Fm,239Cf,and investigation of the evaporation residues from fusion of206Pb,208Pb,and209Bi with40Ar

The evaporation residues produced in heavy ion fusion reactions between⁴⁰Ar and²⁰⁶Pb,²⁰⁸Pb, and²⁰⁹Bi, respectively, were investigated. They were separated in-flight using a velocity filter (SHIP) and identified after implantation into an array of position sensitive surface barrier detectors by measuring their decay characteristics. Three newα-emitting isotopes were found:²⁴⁷Md,²⁴³Fm, and²³⁹Cf.²⁴⁷Md was identified by correlation to its known daughter decay²⁴³Es, and²⁴³Fm and²³⁹Cf were observed as correlated decays. Moreover, all previously known deexcitation channels, characterized by spontaneous fission or byα decay, could be observed for the first time in one experimental setup. Our results for formation cross sections and decay characteristics are in agreement with known data.