701 research outputs found
Coupling of Josephson flux-flow oscillators to an external RC load
We investigate by numerical simulations the behavior of the power dissipated
in a resistive load capacitively coupled to a Josephson flux flow oscillator
and compare the results to those obtained for a d.c. coupled purely resistive
load. Assuming realistic values for the parameters R and C, both in the high-
and in the low-Tc case the power is large enough to allow the operation of such
a device in applications.Comment: uuencoded, gzipped tar archive containing 11 pages of REVTeX text + 4
PostScript figures. To appear in Supercond. Sci. Techno
Primary thermometry triad at 6 mK in mesoscopic circuits
Quantum physics emerge and develop as temperature is reduced. Although
mesoscopic electrical circuits constitute an outstanding platform to explore
quantum behavior, the challenge in cooling the electrons impedes their
potential. The strong coupling of such micrometer-scale devices with the
measurement lines, combined with the weak coupling to the substrate, makes them
extremely difficult to thermalize below 10 mK and imposes in-situ thermometers.
Here we demonstrate electronic quantum transport at 6 mK in micrometer-scale
mesoscopic circuits. The thermometry methods are established by the comparison
of three in-situ primary thermometers, each involving a different underlying
physics. The employed combination of quantum shot noise, quantum back-action of
a resistive circuit and conductance oscillations of a single-electron
transistor covers a remarkably broad spectrum of mesoscopic phenomena. The
experiment, performed in vacuum using a standard cryogen-free dilution
refrigerator, paves the way toward the sub-millikelvin range with additional
thermalization and refrigeration techniques.Comment: Article and Supplementar
Molecular markers for chronic toxicity of marine pollutants in North Sea brown shrimp (<i>Crangon crangon</i> L.)
Electron quantum optics : partitioning electrons one by one
We have realized a quantum optics like Hanbury Brown and Twiss (HBT)
experiment by partitioning, on an electronic beam-splitter, single elementary
electronic excitations produced one by one by an on-demand emitter. We show
that the measurement of the output currents correlations in the HBT geometry
provides a direct counting, at the single charge level, of the elementary
excitations (electron/hole pairs) generated by the emitter at each cycle. We
observe the antibunching of low energy excitations emitted by the source with
thermal excitations of the Fermi sea already present in the input leads of the
splitter, which suppresses their contribution to the partition noise. This
effect is used to probe the energy distribution of the emitted wave-packets.Comment: 5 pages, 4 figure
Did the use of TBT-based antifouling paints cause severe damage to the common shrimp (<i>Crangon crangon</i>) population of the Southern Bight?
Excavation of the first stars
The external pollution of the first stars in the Galaxy is investigated. The
first stars were born in clouds composed of the pristine gas without heavy
elements. These stars accreted gas polluted with heavy elements while they
still remained in the cloud. As a result, it is found that they exhibit a
distribution with respect to the surface metallicity. We have derived the
actual form of this distribution function. This metallicity distribution
function strongly suggests that the recently discovered most metal-deficient
star HE0107-5240 with [Fe/H]=-5.3 was born as a metal-free star and accreted
gas polluted with heavy elements. Thus the heavy elements such as Fe in
HE0107-5240 must have been supplied from supernovae of later generations
exploding inside the cloud in which the star had been formed. The elemental
abundance pattern on the surface of stars suffering from such an external
pollution should not be diverse but exhibit the average pattern of numerous
supernovae. Future observations for a number of metal-deficient stars with
[Fe/H]<-5 will be able to prove or disprove this external pollution scenario.
Other possibilities to produce a star with this metallicity are also discussed.Comment: 4 pages, 5 figures, to appear in The Astrophysical Journal Letter
Feasibility of cheese production and whey valorization in the Adamawa Province of Cameroon
Problems associated with perishability and distribution of local milk and milk products by small-scale producers in the Adamawa province of Cameroon, justified development of an easy process for producing pressed-dough cheese and flavoured whey. Production from raw milk was technically profitable with mean cheese and flavoured whey yields of 8.9 and 85,6% (w/w), respectively. The cheese and whey comprise 50 and 45.7 % (w/w), respectively, of the milk initial dry matter and were highly appreciated by about 90% of panellists. The profitability of a small-scale production unit was established based on 562 kg of treated milk per month. An initial investment of about US 237, which gives a profit of 45.8%.Key words: Adamawa, milk, cheese, whey, feasibility, profitability
Species-richness patterns of the living collections of the world's botanic gardens: a matter of socio-economics?
Background and Aims The botanic gardens of the world are now unmatched ex situ collections of plant biodiversity. They mirror two biogeographical patterns (positive diversity-area and diversity-age relationships) but differ from nature with a positive latitudinal gradient in their richness. Whether these relationships can be explained by socio-economic factors is unknown. Methods Species and taxa richness of a comprehensive sample of botanic gardens were analysed as a function of key ecological and socio-economic factors using (a) multivariate models controlling for spatial autocorrelation and (b) structural equation modelling. Key Results The number of plant species in botanic gardens increases with town human population size and country Gross Domestic Product (GDP) per person. The country flora richness is not related to the species richness of botanic gardens. Botanic gardens in more populous towns tend to have a larger area and can thus host richer living collections. Botanic gardens in richer countries have more species, and this explains the positive latitudinal gradient in botanic gardens' species richness. Conclusions Socio-economic factors contribute to shaping patterns in the species richness of the living collections of the world's botanic garden
Mineral cloud and hydrocarbon haze particles in the atmosphere of the hot Jupiter JWST target WASP-43b
Context: Having a short orbital period and being tidally locked makes WASP-43b an ideal candidate for the James Webb Space Telescope (JWST) phase curve measurements. Phase curve observations of an entire orbit will enable the mapping of the atmospheric
structure across the planet, with different wavelengths of observation allowing different atmospheric depths to be seen.
Aims: We provide insight into the details of the clouds that may form on WASP-43b and their impact on the remaining gas phase, in
order to prepare the forthcoming interpretation of the JWST and follow-up data.
Methods: We follow a hierarchical modelling strategy. We utilise 3D GCM results as input for a kinetic, non-equilibrium model for
mineral cloud particles and for a kinetic model to study a photochemically-driven hydrocarbon haze component.
Results: Mineral condensation seeds form throughout the atmosphere of WASP-43b. This is in stark contrast to the ultra-hot Jupiters,
such as WASP-18b and HAT-P-7b. The dayside is not cloud free but it is loaded with few yet large mineral cloud particles in addition to
hydrocarbon haze particles of a comparable abundance. Photochemically driven hydrocarbon haze appears on the dayside, but it does
not contribute to the cloud formation on the nightside. The geometrical cloud extension differs across the globe due to the changing
thermodynamic conditions. Day and night differ by 6000 km in pressure scale height. As reported for other planets, the C/O is not
constant throughout the atmosphere and varies between 0.74 and 0.3. The mean molecular weight is approximately constant in a H2-
dominated WASP-43b atmosphere because of the moderate day/night-temperature differences compared to the super-hot Jupiters.
Conclusions: WASP-43b is expected to be fully covered in clouds which are not homogeneously distributed throughout the atmosphere. The dayside and the terminator clouds are a combination of mineral particles of locally varying size and composition as well
as of hydrocarbon hazes. The optical depth of hydrocarbon hazes is considerably lower than that of mineral cloud particles such that a
wavelength-dependent radius measurement of WASP-43b would be determined by the mineral cloud particles but not by hazes
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