Variability and nature of the binary in the Red Rectangle Nebula

We present new observations of the central binary inside the Red Rectangle nebula. The detection of zinc in the optical spectrum confirms that the peculiar photospheric abundances are due to accretion of circumstellar gas. Grey brightness variations with the orbital period are observed. They are interpreted as being due to the variation of the scattering angle with orbital phase. The small orbital separation of the system is not compatible with previous normal evolution of the primary on the AGB. We point out the similarity of the orbital history of this and other similar systems with those of some close Barium stars and suggest that the nonzero eccentricity of the orbit is the result of tidal interaction with the circumbinary disk.Comment: 4 pages, 3 figures, A&A Letters accepte

An update to the surface ocean CO2 atlas (SOCAT version 2)

22 páginas, 9 figuras, 10 tablas.-- D. C. E. Bakker ... et al.-- This work is distributed under the Creative Commons Attribution 3.0 License.-- Proyecto CarbochangeThe Surface Ocean CO2 Atlas (SOCAT), an activity of the international marine carbon research community, provides access to synthesis and gridded fCO2 (fugacity of carbon dioxide) products for the surface oceans. Version 2 of SOCAT is an update of the previous release (version 1) with more data (increased from 6.3 million to 10.1 million surface water fCO2 values) and extended data coverage (from 1968–2007 to 1968–2011). The quality control criteria, while identical in both versions, have been applied more strictly in version 2 than in version 1. The SOCAT website (http://www.socat.info/) has links to quality control comments, metadata, individual data set files, and synthesis and gridded data products. Interactive online tools allow visitors to explore the richness of the data. Applications of SOCAT include process studies, quantification of the ocean carbon sink and its spatial, seasonal, year-to-year and longerterm variation, as well as initialisation or validation of ocean carbon models and coupled climate-carbon modelsSupport for SOCAT has been received from the University of East Anglia (UK), the Bjerknes Centre for Climate Research, the Geophysical Institute at the University of Bergen (Norway), the Climate Observation Division of the Climate Program Office of the US National Oceanic and Atmospheric Administration, the University of Washington, Oak Ridge National Laboratory (USA), PANGAEA ® Data Publisher for Earth and Environmental Data (Germany), the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (Germany), the National Institute for Environmental Studies (Japan), the Korean Institute of Ocean Science and Technology, the European Union projects CarboChange (FP7 264879) and GEO- CARBON (FP7 283080), the UK Ocean Acidification Research Programme (NE/H017046/1; funded by the Natural Environment Research Council, the Department for Energy and Climate Change and the Department for Environment, Food and Rural Affairs), the Research Council of Norway (CARBON-HEAT), the Scientific Committee on Oceanic Research (SCOR, US, OCE-0938349), the US National Science Foundation (OCE-1068958), Swedish Research Council projects (2009–2994; 2008–6228; 2009–2994) and the Swedish National Space Board (RESCUE project; REmote Sensing ocean Carbon UptakE).Peer reviewe

Infrared High-Resolution Spectroscopy of Post-AGB Circumstellar Disks. I. HR 4049 - The Winnowing Flow Observed?

High-resolution infrared spectroscopy in the 2.3-4.6 micron region is reported for the peculiar A supergiant, single-lined spectroscopic binary HR 4049. Lines from the CO fundamental and first overtone, OH fundamental, and several H2O vibration-rotation transitions have been observed in the near-infrared spectrum. The spectrum of HR 4049 appears principally in emission through the 3 and 4.6 micron region and in absorption in the 2 micron region. The 4.6 micron spectrum shows a rich 'forest' of emission lines. All the spectral lines observed in the 2.3-4.6 micron spectrum are shown to be circumbinary in origin. The presence of OH and H2O lines confirm the oxygen-rich nature of the circumbinary gas which is in contrast to the previously detected carbon-rich material. The emission and absorption line profiles show that the circumbinary gas is located in a thin, rotating layer near the dust disk. The properties of the dust and gas circumbinary disk and the spectroscopic orbit yield masses for the individual stars, M_AI~0.58 Msolar and M_MV~0.34 Msolar. Gas in the disk also has an outward flow with a velocity of $\gtrsim$ 1 km/s. The severe depletion of refractory elements but near-solar abundances of volatile elements observed in HR 4049 results from abundance winnowing. The separation of the volatiles from the grains in the disk and the subsequent accretion by the star are discussed. Contrary to prior reports, the HR 4049 carbon and oxygen isotopic abundances are typical AGB values: 12C/13C=6^{+9}_{-4} and 16O/17O>200.Comment: 42 pages, 14 figures, Accepted by Ap

Interplay of Peltier and Seebeck effects in nanoscale nonlocal spin valves

We have experimentally studied the role of thermoelectric effects in nanoscale nonlocal spin valve devices. A finite element thermoelectric model is developed to calculate the generated Seebeck voltages due to Peltier and Joule heating in the devices. By measuring the first, second and third harmonic voltage response non locally, the model is experimentally examined. The results indicate that the combination of Peltier and Seebeck effects contributes significantly to the nonlocal baseline resistance. Moreover, we found that the second and third harmonic response signals can be attributed to Joule heating and temperature dependencies of both Seebeck coefficient and resistivity.Comment: 4 pages, 4 figure

Tristimulus measurements (CIELAB 76) of port wine colour

Tristimulus colour values were measured using the CIELAB 76 convention and compared with conventional measurements on 87 freshly-made and ageing single cultivar port wines from 5 sites for up to 6 years. There were high correlations between a* (redness) and A520nm, and saturation and colour density, and a high negative correlation between L* (Lightness) and colour density. There was little correlation between b* (yellowness) and A420nm; consequently hue angle did not correspond to tint. Amongst the tristimulus parameters, there were high correlations between L* or saturation and a*. In individual ports L* varied linearly but negatively with hue angle, but in the group of ports examined there was no significant relationship between L* and hue angle because of adc;litional variable phenolic browning depending upon cultivar. In model anthocyanin solutions increasing L* (by decreasing pigment concentration or increasing pH) caused a linear reduction in hue angle but an increase in tint; the latter was attributed to dissociation of associated anthocyanin molecules. Measurement of hue angle in ageing ports gives an indication of the relative occurrence of two competing ageing mechanisms, involving or not involving acetaldehyde. Hue angle is a more discriminating parameter for expressing the colour nuance of red wines than tint

Public exhibit for demonstrating the quantum of electrical conductance

We present a new robust setup that explains and demonstrates the quantum of electrical conductance for a general audience and which is continuously available in a public space. The setup allows users to manually thin a gold wire of several atoms in diameter while monitoring its conductance in real time. During the experiment, a characteristic step-like conductance decrease due to rearrangements of atoms in the cross-section of the wire is observed. Just before the wire breaks, a contact consisting of a single atom with a characteristic conductance close to the quantum of conductance can be maintained up to several seconds. The setup is operated full-time, needs practically no maintenance and is used on different educational levels

The colours, pigment and phenol contents of young port wines: Effects of cultivar, season and site

95 port wines were made under standard small scale conditions from grapes of 16 individual cultivars grown at 5 different sites in the Douro valley in northern Portugal during 1977-1983. Grape specific grayity and pH values were measured. The ports were analysed immediately after fortification for colour, pigment and phenol contents and pH. Cultivar variations were up to 12-fold in total pigments, 14-fold in colour density, but only 3.6-fold in total phenols . Seasonal vari ations were up to 2-fold in total pigments and colour density and 1.6-fold in total phenols . Because of seasonal effects and variation in the numbers of each cultivar examined, cultivar characteristics were compared by their mean values with reference to an arbitrarily chosen standard cultivar (Touriga Nacional). Statistical analysis confirmed that the variation in total pigments was affected much more by cultivar than by season. Souzão, Tinta da Barca and Touriga Nacional ports (all from Tua) were the most coloured and contained most pigments. Mourisco (Tua) and Tinta Cão (Baixo Corgo) were the least coloured and contained least pigments. Port colour was dependent principally on pigments content and pH, but small effects attributed to anthocyanin selfassociation and co-pigmentation were also discerned. Differences between sites were generally not significant, apart from some characteristics of Touriga Nacional from Pinhão compared with Tua and Vilariça. which were attributed to the particular strain of fruit at Pinhäo. Nevertheless, there was some indication that the inferior status of Baixo Corgo compared with Cima Corgo fruit may be attributed not only to its generally lower pigments content, but also to smaller percentages of the pigments being expressed in coloured forms

The Vector Meson Form Factor Analysis in Light-Front Dynamics

We study the form factors of vector mesons using a covariant fermion field theory model in $(3+1)$ dimensions. Performing a light-front calculation in the $q^+ =0$ frame in parallel with a manifestly covariant calculation, we note the existence of a nonvanishing zero-mode contribution to the light-front current $J^+$ and find a way of avoiding the zero-mode in the form factor calculations. Upon choosing the light-front gauge (\ep^+_{h=\pm}=0) with circular polarization and with spin projection $h=\uparrow\downarrow=\pm$, only the helicity zero to zero matrix element of the plus current receives zero-mode contributions. Therefore, one can obtain the exact light-front solution of the form factors using only the valence contribution if only the helicity components, $(h'h)=(++),(+-)$, and $(+0)$, are used. We also compare our results obtained from the light-front gauge in the light-front helicity basis (i.e. $h=\pm,0$) with those obtained from the non-LF gauge in the instant form linear polarization basis (i.e. $h=x,y,z$) where the zero-mode contributions to the form factors are unavoidable.Comment: 33 pages; typo in Eq.(15) is corrected; comment on Ref.[9] is corrected; version to appear in Phys. Rev.

The canonical structure of Podolsky's generalized electrodynamics on the Null-Plane

In this work we will develop the canonical structure of Podolsky's generalized electrodynamics on the null-plane. This theory has second-order derivatives in the Lagrangian function and requires a closer study for the definition of the momenta and canonical Hamiltonian of the system. On the null-plane the field equations also demand a different analysis of the initial-boundary value problem and proper conditions must be chosen on the null-planes. We will show that the constraint structure, based on Dirac formalism, presents a set of second-class constraints, which are exclusive of the analysis on the null-plane, and an expected set of first-class constraints that are generators of a U(1) group of gauge transformations. An inspection on the field equations will lead us to the generalized radiation gauge on the null-plane, and Dirac Brackets will be introduced considering the problem of uniqueness of these brackets under the chosen initial-boundary condition of the theory