11,284 research outputs found
Destruction of chain-superconductivity in YBa_2Cu_4O_8 in a weak magnetic field
We report measurements of the temperature dependent components of the
magnetic penetration depth {\lambda}(T) in single crystal samples of
YBa_2Cu_4O_8 using a radio frequency tunnel diode oscillator technique. We
observe a downturn in {\lambda}(T) at low temperatures for currents flowing
along the b and c axes but not along the a axis. The downturn in {\lambda}_b is
suppressed by a small dc field of ~0.25 T. This and the zero field anisotropy
of {\lambda}(T) likely result from proximity induced superconducting on the CuO
chains, however we also discuss the possibility that a significant part of the
anisotropy might originate from the CuO2 planes.Comment: 5 page
Eighth Amendment Challenges to the Length of a Criminal Sentence: Following the Supreme Court “From Precedent to Precedent”
Defendant A was convicted twice previously of felonies and sentenced to prison for fraudulent use of a credit card (28.36). Upon his third felony conviction for obtaining money by false pretenses ($120.75), he received a mandatory life sentence under a state recidivist statute
Nestling diet, secondary sexual traits and fitness in the zebra finch
We examined the effect of nestling diet quality on a suite of physiological, morphological and life-history
traits in adult male zebra finches,Taeniopygia guttata. Compared with birds reared on a supplemented diet,
nestlings reared on a seed-only diet showed a reduced rate of growth and reduced cell-mediated immune function as measured by an in vivo response to aT lymphocyte-dependent mitogen. There were no differences between birds reared on the two diets in any of the following adult traits: body size, primary sexual traits (testes mass, numbers of stored sperm, sperm function, velocity and morphology), secondary sexual traits (beak colour and song rate), serological traits or immunological traits. The only differences we detected were a lower body mass and a greater proportion of individuals with plumage abnormalities among those reared on a seed-only diet (this latter effect was transient). The fact that male zebra finches reared on a seed-only diet were, as adults, virtually indistinguishable from those reared on a supple-
mented diet, despite having reduced growth and immune function as nestlings, demonstrates that they
subsequently compensated through the di¡erential allocation of resources. Our results indicate that differ-
ential allocation is costly in terms of fitness since birds reared on a seed-only diet experienced a significantly greater mortality rate than those reared on a supplemented diet. This in turn suggests the existence of a trade-of between the development of traits important for reproduction, such as primary and secondary sexual traits and longevity
Feasibility of a chemical poison loop system
Chemical poison loop system for reactivity control of tungsten water moderated rocket reacto
Quantized charge pumping through a quantum dot by surface acoustic waves
We present a realization of quantized charge pumping. A lateral quantum dot
is defined by metallic split gates in a GaAs/AlGaAs heterostructure. A surface
acoustic wave whose wavelength is twice the dot length is used to pump single
electrons through the dot at a frequency f=3GHz. The pumped current shows a
regular pattern of quantization at values I=nef over a range of gate voltage
and wave amplitude settings. The observed values of n, the number of electrons
transported per wave cycle, are determined by the number of electronic states
in the quantum dot brought into resonance with the fermi level of the electron
reservoirs during the pumping cycle.Comment: 8 page
New insights on Saturn's formation from its nitrogen isotopic composition
The recent derivation of a lower limit for the N/N ratio in
Saturn's ammonia, which is found to be consistent with the Jovian value,
prompted us to revise models of Saturn's formation using as constraints the
supersolar abundances of heavy elements measured in its atmosphere. Here we
find that it is possible to account for both Saturn's chemical and isotopic
compositions if one assumes the formation of its building blocks at 45 K
in the protosolar nebula, provided that the O abundance was 2.6 times
protosolar in its feeding zone. To do so, we used a statistical thermodynamic
model to investigate the composition of the clathrate phase that formed during
the cooling of the protosolar nebula and from which the building blocks of
Saturn were agglomerated. We find that Saturn's O/H is at least 34.9
times protosolar and that the corresponding mass of heavy elements (43.1
\Mearth) is within the range predicted by semi-convective interior models.Comment: Accepted for publication in Astrophysical Journal Letter
Exoplanet atmospheres with EChO: spectral retrievals using EChOSim
We demonstrate the effectiveness of the Exoplanet Characterisation
Observatory mission concept for constraining the atmospheric properties of hot
and warm gas giants and super Earths. Synthetic primary and secondary transit
spectra for a range of planets are passed through EChOSim (Waldmann & Pascale
2014) to obtain the expected level of noise for different observational
scenarios; these are then used as inputs for the NEMESIS atmospheric retrieval
code and the retrieved atmospheric properties (temperature structure,
composition and cloud properties) compared with the known input values,
following the method of Barstow et al. (2013a). To correctly retrieve the
temperature structure and composition of the atmosphere to within 2 {\sigma},
we find that we require: a single transit or eclipse of a hot Jupiter orbiting
a sun-like (G2) star at 35 pc to constrain the terminator and dayside
atmospheres; 20 transits or eclipses of a warm Jupiter orbiting a similar star;
10 transits/eclipses of a hot Neptune orbiting an M dwarf at 6 pc; and 30
transits or eclipses of a GJ1214b-like planet.Comment: 13 pages, 15 figures, 1 table. Accepted by Experimental Astronomy.
The final publication will shortly be available at Springer via
http://dx.doi.org/10.1007/s10686-014-9397-
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