ALBERT

Notes: Abstract Some Ar II transition probabilities were measured absolutely using a tungsten ribbon lamp as a calibration standard. The plasma was produced by a conical Theta-pinch. Gas mixtures of H∶Ar and He∶Ar were used to exclude inhomogeneity of the layer as a possible source of error. Electron densities and temperatures were determined by measuring Hydrogen and Helium line profiles respectively, and line to continuum intensity ratios. The measured values can be compared with results of earlier experiments and with newer theoretical calculations. The agreement between the results of this experiment and the theoretical values is satisfactory.

Notes: Abstract A homogeneous and thermal plasma was produced by a modified T-tube. In a shot to shot analysis the lines of several multiplets of singly ionized Nitrogen were investigated as to their Starkeffect. Densities were determined by comparing the measured halfwidths of some neutral Helium-lines with the well established theory of Starkbroadening of these lines. The temperature followed from the relative intensities of the measured Helium- and Nitrogenlines assuming partial thermal equilibrium. The results of this experiment deviate from previous measurements ofDay et al. as well as from the theory of Starkbroadening in isolated lines of the heavier elements byGriem. It is shown (1) that the broadening in N II is a rough factor of two larger than theoretically expected, (2) that linebroadening in N II is proportional to the density, (3) that the Stark broadened lines follow dispersion profiles to the distance of several halfwidths from the line center.

Notes: Abstract Experimental results concerning the density-dependent relative populations of two energetically different states of the singly ionized Oxygenatom are compared to theory. Opposed to the latter, the experiment gave relative populations consistent with the thermodynamic equilibrium assumption down to electron densities of 1016(cm−3). The plasma was produced by a modifiedT-tube and the measured effect may be a peculiarity of the particular plasma investigated. The conclusion may be drawn that the plasma radiates in thermal equilibrium at much lower densities than theoretically expected. If a theoretical estimate ofGriem may be assumed formally correct, a correction factor of the order of ten can be applied. This granted, even the states of doubly ionized species may be assumed to be populated as in thermal equilibrium at densities exceeding 1017(cm−3).

Notes: Abstract According to two different theories the 4686å-line of ionized Helium should be blue-shifted by measurable amounts. In the attempt of a precision measurement of the effect under several different plasma conditions no displacement could be found within the experimental accuracy of ±0.3å. A previous measurement is discussed.

Notes: Abstract It is shown that by solely measuring intensities without explicit knowledge of the plasmatemperature or density absolute transition probabilities in the higher ions can be obtained. To do this one procures a mixture of Helium with the testgas and uses Helium as the “thermometergas” by determining the relative intensities of chosen He I and He II transitions. This measurement, however, is not used to determine an actual temperature but rather to deduce directly the relative populations in the test-gas-ions. This becomes possible if for certain levels a combination of ionization- and exitation potentials results in the same value for Helium and the testgas. An experimental test has been performed with Oxygen as an example and absolute O III-oszillator strength are quoted.

Notes: Zusammenfassung Die Eigenschaften synthetischer Fasern hängen von ihrer Molekül- und Faserstruktur ab. Moleküllänge, Moleküllängenverteilung, die Statistik der Anordnung von Monomeren bei der Copolymerisation und die Steifheit des Moleküles sowie die Beweglichkeit von Molekülteilen im festen Zustand beeinflussen die Orientierbarkeit und die Kristallisation der Fasern und damit vor allem die mechanischen Eigenschaften und das thermische Umwandlungsverhalten. Im Anschluß an eine Darstellung der Fasermodelle wird eine Reihe von Fragen zur Veränderung der Faserstruktur bei der Faser-Herstellung, -Verarbeitung und bei ihrem Gebrauch diskutiert. Einige Beispiele zeigen, daß jede meßbare Fasereigenschaft von einer ganzen Reihe von Strukturparametern abhängt, bzw. daß jeder Strukturparameter eine Reihe von Fasereigenschaften bestimmt. Dabei gehen die Strukturparameter mit unterschiedlichem Gewicht und abhängig vom Wege, auf dem sie erreicht werden, in die Fasereigenschaften ein.

Notes: Abstract The intensities of the stronger N III-transitions in the visible range of the spectrum are determined by an experimental method, insensitive to the precise knowledge of the temperature, density, and chemical composition of the plasma. By linking to known N II-values absolute N III transition probabilities are obtained. In the comparison of the two spectra LTE-relations may be used due to the opacity of the plasma in the resonance transitions of N III. The experiment is carried out in a modifiedT-tube as well as in a longer duration high current discharge and also by the photoelectric as well as by the photographic method of detection. The fair agreement of the results obtained with varied apparatus and measuring methods adds to the reliability of the results.

Notes: Summary Photo-depolarizers and diffusion currents caused by photoreaction are of some interest from the analytical point of view. Mostly investigated are free radicals, which are able to exchange electrons with the electrode surface after photogeneration or immediately after excitation. In the case of photochemical forward-reaction of the radicals the quantum requirement may be measured by means of the photoreaction-caused oxidation current, especially with ketyls.

Notes: The electrochemical possibilities for investigation of nucleic acids with high molecular weight are restricted to the determination of the adsorption behavior. According to our experience the alternating current polarography (Breyer-polarography) is mainly appropriate for the characterization of changes in the secondary structure of DNA. The Breyer-polarogram shows the alternating current of the dropping electrode in dependence on their potential which varied from 0-2 v. negative against the normal calomel electrode (NCE). By addition of native DNA to the supporting electrolyte (buffer solution) the current drops down in the range of adsorption between 0 and 1 v. At 1.16 v. against NCE the desorption takes place together with the formation of a rounded desorption peak. The investigation was carried out in phosphate buffer solution 0.1m with 0.075m NaCl or in a phosphate buffer 0.18m with 0.03m NaCl. In the pH range above pH 8 NaOH was added to realize the higher pH values. A calf thymus DNA sample having a mean molecular weight of about 18 million was used. The concentration of DNA was 5 × 10-3-1 × 10-1 wt.-%. The polarographic measurements were performed with an a.c./d.c.-polarograph “GWP 564” from Akademiewerkstätten für Forschungsbedarf der Deutschen Akademie der Wissenschaften zu Berlin (DAW). The denaturation of the double helix causes a sharp desorption peak at negative potentials of the alternating current polarogram. This new criterion for the helix-coil transition is due to formation of unpaired bases. These nearly free bases undergo a specific adsorption and the desorption takes place within a narrow potential range. Nevertheless, at present time an electron transfer to particular bases cannot be excluded at special conditions. The increase of the sharp peak permits to estimate: (a) the melting curve of the double helix in agreement with spectroscopic measurements; (b) the photolysis of the double helix; (c) the strand separation in acid and alkaline solution. In the alkaline range the sharp peak increases and reaches its maximum at pH 〉 12. In the acid range, however, no sharp peak is observed and the rounded desorption peak decreases. Therefore, the best way of following the conformation changes is to measure the current difference between the curves of the solutions with and without DNA at electrocapillary-zero-potential. On the classical d.c.-polarogram one can measure small current steps only, which may be caused mainly by capacity changes. Moreover, the scission of the molecule by ultrasonic action can be followed. In this case the rounded peak of DNA increases but the sharp peak does not appear. Similar alternating current polarograms are obtained with poly-A in the native state, because helical and unordered regions coexist in the same molecule. The very rapid indication of these structure changes allows one to carry out kinetic measurements at a fixed potential with this method.