Masses and Radii of the Nuclei with N>=Z in an Alpha-Cluster Model

In the framework of a recently developed alpha-cluster model a nucleus is represented as a core (alpha-cluster liquid drop with dissolved excess neutron pairs in it) and a nuclear molecule on its surface. From analysis of experimental nuclear binding energies one can find the number of alpha-clusters in the molecule and calculate the nuclear charge radii. It was shown that for isotopes of one Z with growing A the number of alpha-clusters in the molecule decreases to three, which corresponds to the nucleus 12C for even Z and 15N for odd Z, and the specific density of the core binding energy \rho grows and reaches its saturation value. In this paper it is shown that the value \rho=2.55 MeV/fm^3 explains the particular number of excess neutrons in stable nuclei.Comment: 7 pages, 3 eps figures, submitted as a contribution to the Proceedings of the International Conference, Messina, Italy, October 5-9, 200

Non-invasive detection of charge-rearrangement in a quantum dot in high magnetic fields

We demonstrate electron redistribution caused by magnetic field on a single quantum dot measured by means of a quantum point contact as non-invasive detector. Our device which is fabricated by local anodic oxidation allows to control independently the quantum point contact and all tunnelling barriers of the quantum dot. Thus we are able to measure both the change of the quantum dot charge and also changes of the electron configuration at constant number of electrons on the quantum dot. We use these features to exploit the quantum dot in a high magnetic field where transport through the quantum dot displays the effects of Landau shells and spin blockade. We confirm the internal rearrangement of electrons as function of the magnetic field for a fixed number of electrons on the quantum dot.Comment: 4 pages, 5 figure

Generation of high-power subpicosecond pulses at 155 nm

Subpicosecond vacuum-ultraviolet radiation at 155 nm with pulse energies above 0.2 mJ has been obtained by near-resonant four-wave difference-frequency mixing in a Xe gas jet. Laser fields for the mixing process have been generated by a short-pulse KrF dye excimer laser system and a Raman converter. The process permits tuning in a broad vacuum-ultraviolet range and can be scaled up to higher output energies

A 40th deg and order gravitational field model for Mars

Understanding the origin and evolution of major photographic features on Mars, such as the hemispheric dichotomy and Tharsis rise, will require improved resolution of that planet's gravitational and topographic fields. The highest resolution gravity model for Mars published to date was derived from Doppler tracking data from the Mariner 9 and Viking 1 and 2 spacecraft, and is of 18th degree and order. That field has a maximum spatial resolution of approx. 600 km, which is comparable to that of the best topographic model. The resolution of previous gravity models was limited not by data density, but rather by the computational resources available at the time. Because this restriction is no longer a limitation, the Viking and Mariner data sets were reanalyzed and a gravitational field was derived complete to the 40th degree and order with a corresponding maximum spatial resolution of 300 km where the data permit

Ursachen von Stromsperren in Privathaushalten : empirische Ergebnisse aus der Allgemeinen Sozialberatung

In diesem Aufsatz wird untersucht, welche Merkmale Haushalte aufweisen, denen Stromsperren (Unterbrechungen der Stromversorgung wegen Zahlungsrückständen) angedroht wurden bzw. bei denen sie umgesetzt wurden und welche Bedeutung diese Merkmale relativ zueinander haben. Dazu wird erstmals ein Datensatz aus der Beratungspraxis des Deutschen Caritasverbandes mittels multipler logistischer Regression ausgewertet. Die empirische Untersuchung zeigt, dass Stromsperren und ihre Androhung häufig auftreten, wenn ein Haushalt bereits bestehende Schulden hat. Haushalte, die Grundsicherungsleistungen beziehen, sind überdurchschnittlich oft von der Androhung bzw. Umsetzung einer Stromsperre betroffen. Im Gegensatz zur Androhung einer Stromsperre kommt es überproportional häufig zur tatsächlichen Umsetzung einer Stromsperre, wenn die Betroffenen über ein besonders geringes Bildungsniveau verfügen sowie in Ein-Personen-Haushalten. Insgesamt stützen die Ergebnisse die These, dass die Problematik der Stromsperren einer herkömmlichen Verschuldungsproblematik ähnlich ist. Gegenmaßnahmen sollten daher nicht alleine auf das Einkommen oder die Stromkosten der Haushalte fokussieren, sondern müssen auch kognitive und psychologische Faktoren adressieren, die mit Ver- bzw. Überschuldung einhergehen

Nuclear mass form factors from coherent photoproduction of π0\pi^0 mesons

Data for coherent photoproduction of $\pi^0$ mesons from nuclei ($^{12}$C, $^{40}$Ca, $^{93}$Nb, $^{nat}$Pb), recently measured with the TAPS detector at the Mainz MAMI accelerator, have been analyzed in view of the mass form factors of the nuclei. The form factors have been extracted in plane wave approximation of the $A(\gamma ,\pi^0)A$ reaction and corrected for final state interaction effects with the help of distorted wave impulse approximations. Nuclear mass rms-radii have been calculated from the slope of the form factors for $q^2\to 0$. Furthermore, the Helm model (hard sphere form factor folded with Gaussian) was used to extract diffraction radii from the zeroes of the form factor and skin thicknesses from the position and height of its first maximum. The diffraction radii from the Helm model agree with the corresponding charge radii obtained from electron scattering experiments within their uncertainties of a few per cent. The rms-radii from the slope of the form factors are systematically lower by up to 5% for PWIA and up to 10% for DWIA. Also the skin thicknesses extracted from the Helm model are systematically smaller than their charge counter parts.Comment: Accepted for publication in Eur. Phys. J.