φ meson production in NA60

NA60 is a fixed-target experiment at the CERN SPS which measured dimuon production in nucleus–nucleus and proton–nucleus collisions. The experiment collected muon pair samples of unprecedented quality in heavy-ion experiments. This paper presents a high quality measurement of the p_T distribution of the φ meson, covering a broad p_T window. The data were collected in 2003 in In-In collisions at 158 GeV per nucleon. The results, presented as a function of centrality, were studied against several possible sources of systematic effects and proved to be fairly stable. We show that the inverse m_T slope measured in In-In collisions, in the φ→μμ decay channel, depends significantly on the range used to perform the fit. When the fit is performed at low transverse momentum, the effective inverse slope increases from peripheral to central collisions, as measured by other experiments. We finally show that our measurement for In-In is compatible with the overall systematics of T slope versus mass, measured in different collision systems by the NA49 experiment PACS 25.75.Nq; 25.75.-q; 25.75.Dw; 14.40.Cs; 12.38.Mh     

Understanding the loading dependence of self-diffusion in carbon nanotubes

The influence of flexible walls on the self-diffusion of CH4 in an isolated single walled carbon nanotube, as an example, is studied by molecular dynamics simulations. By simulating the carbon nanotube as a flexible framework we demonstrate that the flexibility has a crucial influence on self-diffusion at low loadings. We show how this influence can be incorporated in a simulation of a rigid nanotube by using a Lowe-Andersen thermostat which works on interface-fluid collisions. The reproduction of the results of a flexible carbon nanotube by a rigid nanotube simulation is excellent.     

On the evaluation of elasto-plastic strains measured with strain gages

The analysis of plane-stress conditions using strain gages is feasible even when the deformations of the materials are in the elasto-plastic range. The calculation of stresses from the measured strain values is based on an analysis which requires knowledge of the stress-strain curve of the material as obtained from a uniaxial tensile test. In this paper, the practical procedure of such an analysis is described together with the application of a nomograph to allow a simplified evaluation to be made of the results of measurements. A numerical example is also given.     

Selektive spektralphotometrische Uranbestimmung

A simple, versatile spectrophotometric uranium determination was developed, which is not disturbed by over 60 cations and about 20 anions investigated. A separation with triphenylarsinoxide is first performed. The uranium extracted is then transferred by a simple method to the 8-hydroxyquinoline-complex and measured spectrophotometrically. Larger quantities of uranium can be directly measured in the extract. Further experiments with other reagents as a substitute for 8-hydroxyquinoline are described.     

Hochselektive spektralphotometrische

Ohne Zusammenfassung     

Selektive spektralphotometrische Spurenbestimmung von Thorium mit Arsenazo III nach Extraktionstrennung

Zusammenfassung Thorium wird durch Extraktion mit Triphenylarsinoxid in CHCl₃ und Rückextraktion mit 4 M HCl auf ein kleines Volumen konzentriert. Die Endbestimmung erfolgt spektralphotometrisch als Arsenazo-III-Komplex bei 660 nm in Mikroküvetten. Auf diese Weise konnte vor allem die Bestimmung von Spurenmengen Th wesentlich verbessert werden. 7 ng Th sind in bis zu 200 ml Ausgangslösung noch bestimmbar. Untersuchungen mit über 60 Kationen und etwa 20 Anionen zeigten, daß diese in weiten Grenzen nicht stören. U⁶⁺ wird zwar auch mitextrahiert, gibt aber in der salzsauren Rückextraktionslösung mit Arsenazo III einen etwa 15mal weniger lichtabsorbierenden Farbkomplex. Da aber Uran von den getesteten Kationen trotzdem am meisten stört und in Analysenproben das Th oft begleitet, werden weitere einfache Maßnahmen gezeigt, die einen bis zu 5000fachen Überschuß an Uran erlauben. Es wurde gefunden, daß auch die Seltenen Erden nicht stören und die zum Test verwendeten Seltenen Erd-Chemikalien Th enthalten. Bestimmungen in Standardgesteinen und Zementproben bestätigen die Anwendbarkeit der Methode.

---

Selective spectrophotometric trace determination of thorium by arsenazo III following pre-concentration by extraction

Summary Thorium is concentrated to a small volume by extraction with triphenylarsine oxide in chloroform and back extraction with 4M HCl. The spectrophotometric determination is then carried out in a micro cuvette using the absorption of the arsenazo III complex at 660 nm. By this procedure a sensitivity of 7 ng of Th in 200 ml solution can be achieved. About 60 cations and 20 anions were found not to cause interferences in a wide concentration range. The most disturbing element is U⁶⁺ which is coextracted, but leads to an arsenazo complex, which absorbs light at 660 nm about 15 times less than the Th complex. By simple measures, up to 5000 times higher U contents, as to Th, can be tolerated. Also the rare earths do not disturb the Th determination and it was found, that most rare earths chemicals, which were used for the tests, contained Th. The reliability of the method was confirmed by the analysis of standard rocks and by comparing the Th analyses of concrete samples with those obtained by neutron activation analysis.

Für die Überprüfung des Manuskriptes möchte ich Herrn Dr. P. Baertschi herzlich danken.