13,029 research outputs found
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
Starling curves and central venous pressure
Recent studies challenge the utility of central venous
pressure monitoring as a surrogate for cardiac preload.
Starting with Starling’s original studies on the
regulation of cardiac output, this review traces the
history of the experiments that elucidated the role of
central venous pressure in circulatory physiology.
Central venous pressure is an important physiologic
parameter, but it is not an independent variable that
determines cardiac output
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 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
Monitoring coherence between the macro and microcirculation in septic shock
Purpose of review
Currently, the treatment of patients with shock is focused on the clinical symptoms of shock. In the early
phase, this is usually limited to heart rate, blood pressure, lactate levels and urine output. However, as the
ultimate goal of resuscitation is the improvement in microcirculatory perfusion the question is whether these
currently used signs of shock and the improvement in these signs actually correspond to the changes in the
microcirculation.
Recent findings
Recent studies have shown that during the development of shock the deterioration in the macrocirculatory
parameters are followed by the deterioration of microcirculatory perfusion. However, in many cases the
restoration of adequate macrocirculatory parameters is frequently not associated with improvement in
microcirculatory perfusion. This relates not only to the cause of shock, where there are some differences
between different forms of shock, but also to the type of treatment.
Summary
The improvement in macrohemodynamics during the resuscitation is not consistently followed by subsequent
changes in the microcirculation. This may result in both over-resuscitation and under-resuscitation le
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
Cruise report hydro acoustic survey for blue whiting (Micromesistius poutassou) with R.V. Tridens, 17 March - 04 April 2008
This is the report of the Dutch part of the international North East Atlantic hydro acoustic survey for blue whiting. The survey is coordinated by ICES and has been executed annually. The purpose of the survey is to estimate the blue whiting stock of the North East Atlantic. The ICES uses this estimation is as a “tuning index” to assess the North East Atlantic blue whiting stock. The applied method was echo integration. By sailing transects over the survey area, the total acoustic cross-section can be calculated by surface area sampled. Trawling identified species composition of localized schools. The length composition of each species was determined. Blue whiting was examined on age and fecundity from which a split up stock structure was mad
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
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