Massive star evolution : rotation, winds, and overshooting vectors in the Mass-Luminosity plane I. A calibrated grid of rotating single star models

We aim to constrain massive star evolution models using the unique testbed eclipsing binary HD166734 with new grids of MESA stellar evolution models, adopting calibrated prescriptions of overshooting, mass loss, and rotation. We introduce a novel tool: the "mass-luminosity plane" or "M-L plane", as an equivalent to the traditional HR diagram, utilising it to reproduce the testbed binary HD166734 with newly calibrated MESA stellar evolution models for single stars. We can only reproduce the Galactic binary system with an enhanced amount of core overshooting (alpha = 0.5), mass loss, and rotational mixing. We can utilise the gradient in the M-L plane to constrain the amount of mass loss to 0.5 - 1.5 times the standard Vink et al. 2001 prescriptions, and we can exclude extreme reduction or multiplication factors. The extent of the vectors in the M-L plane leads us to conclude that the amount of core overshooting is larger than is normally adopted in contemporary massive star evolution models. We furthermore conclude that rotational mixing is mandatory to get the nitrogen abundance ratios between the primary and secondary components to be correct (3:1) in our testbed binary system. Our calibrated grid of models, alongside our new M-L plane approach, present the possibility of a widened main sequence due to an increased demand for core overshooting. The increased amount of core overshooting is not only needed to explain the extended main sequence, but the enhanced overshooting is also needed to explain the location of the upper-luminosity limit of the red supergiants. Finally, the increased amount of core overshooting has -- via the compactness parameter -- implications for supernova explodibility.Comment: Revised version, 14 pages, 19 figures, accepted for publication by Astronomy & Astrophysic

Quality interoperability within digital libraries: the DL.org perspective

Quality is the most dynamic aspect of DLs, and becomes even more complex with respect to interoperability. This paper formalizes the research motivations and hypotheses on quality interoperability conducted by the Quality Working Group within the EU-funded project DL.org (<a href="http://www.dlorg.eu">http://www.dlorg.eu/</a>). After providing a multi-level interoperability framework – adopted by DL.org - the authors illustrate key-research points and approaches on the way to the interoperability of DLs quality, grounding them in the DELOS Reference Model. By applying the DELOS Reference Model Quality Concept Map to their interoperability motivating scenario, the authors subsequently present the two main research outcomes of their investigation - the Quality Core Model and the Quality Interoperability Survey

Gapped tunneling spectra in the normal state of Pr2−x_{2-x}Cex_xCuO4_4

We present tunneling data in the normal state of the electron doped cuprate superconductor Pr$_{2-x}$Ce$_x$CuO$_4$ for three different values of the doping $x$. The normal state is obtained by applying a magnetic field greater than the upper critical field, $H_{c2}$ for $T < T_c$. We observe an anomalous normal state gap near the Fermi level. From our analysis of the tunneling data we conclude that this is a feature of the normal state density of states. We discuss possible reasons for the formation of this gap and its implications for the nature of the charge carriers in the normal and the superconducting states of cuprate superconductors.Comment: 7 pages ReVTeX, 11 figures files included, submitted to PR

The distribution of extremal points of Gaussian scalar fields

We consider the signed density of the extremal points of (two-dimensional) scalar fields with a Gaussian distribution. We assign a positive unit charge to the maxima and minima of the function and a negative one to its saddles. At first, we compute the average density for a field in half-space with Dirichlet boundary conditions. Then we calculate the charge-charge correlation function (without boundary). We apply the general results to random waves and random surfaces. Furthermore, we find a generating functional for the two-point function. Its Legendre transform is the integral over the scalar curvature of a 4-dimensional Riemannian manifold.Comment: 22 pages, 8 figures, corrected published versio

Role of oxygen in the electron-doped superconducting cuprates

We report on resistivity and Hall measurements in thin films of the electron-doped superconducting cuprate Pr$_{2-x}$Ce$_{x}$CuO$_{4\pm\delta}$. Comparisons between x = 0.17 samples subjected to either ion-irradiation or oxygenation demonstrate that changing the oxygen content has two separable effects: 1) a doping effect similar to that of cerium, and 2) a disorder effect. These results are consistent with prior speculations that apical oxygen removal is necessary to achieve superconductivity in this compound.Comment: 5 pages, 5 figure

The investigation of vertebral injury sustained during aircrew ejection. Phase 2a - Basic science experimental design and investigation of dynamic characteristics of vertebral columns considered as an engineering structure Annual report, 1 Nov. 1966 - 31 Oct. 1967

Dynamic strength studies on human vertebrae for correlation with data on effects of forcible ejection from disabled aircraf

Hall effect in cobalt-doped TiO2−δ_{2-\delta}

We report Hall effect measurements on thin films of cobalt-doped TiO$_{2-\delta}$. Films with low carrier concentrations (10$^{18}$ - 10$^{19}$) yield a linear behavior in the Hall data while those having higher carrier concentrations (10$^{21}$ - 10$^{22}$) display anomalous behavior near zero field. In the entire range of carrier concentration, n-type conduction is observed. The appearance of the anomalous behavior is accompanied by a possible structural change from rutile TiO$_{2}$ to Ti_[n}O$_{2n-1}$ Magneli phase(s)

Study of a small solar probe /sunblazer/. part ii- spacecraft and payload design progress report, jul. 1, 1964 - jun. 30, 1965

Design considerations for Sunblazer solar probe and payloa