1,727 research outputs found
Immunofluorescent Localization of RuBPCase in Degraded C\u3csub\u3e4\u3c/sub\u3e Grass Tissue
Digestion-resistant tissues found in C4 grasses may allow soluble protein to escape rumen degradation. The objective of this study was to use immunofluorescent localization to follow loss of ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBPCase) from switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerardii Vitman) parenchyma bundle sheath cells (BSC) during rumen degradation. Fluorescent signal was observed from switchgrass and big bluestem BSC through 24 and 16 h in situ digestion, respectively, and from BSC associated with both intact tissue fragments, and isolated vascular bundles in omasal digesta and fecal material from steers (Bos tarus L.) grazing switchgrass. Immunofluorescent localization demonstrated that in certain C4 grasses (i) parenchyma BSC can protect RuBPCase from degradation through 24-h in situ incubation, (ii) BSC containing RuBPCase can exit the rumen prior to degradation, and (iii) protein protected by BSC can escape degradation in the whole gastrointestinal tract and be excreted
Nuclear Reaction Rates in a Plasma
The problem of determining the effects of the surrounding plasma on nuclear
reaction rates in stars is formulated ab initio, using the techniques of
quantum statistical mechanics. We derive a result that expresses the complete
effects of Coulomb barrier penetration and of the influence of the surrounding
plasma in terms of matrix elements of well defined operators. We find that
possible "dynamical screening" effects that have been discussed in the
literature are absent. The form of our results suggests that an approach that
relies on numerical calculations of the correlation functions in a classical
Coulomb gas, followed by construction of an effective two body potential and a
quantum barrier penetration calculation, will miss physics that is as important
as the physics that it includes.Comment: 66 pages, revtex, Errors Fixed, Explanation Adde
Quasi-particle Density in Sr2RuO4 Probed by means of the Phonon Thermal Conductivity
The thermal conductivity of Sr2RuO4 along the least conducting direction
perpendicular to the RuO2 plane has been studied down to 0.3 K. In this
configuration the phonons remain the dominant heat carriers down to the lowest
temperature, and their conductivity in the normal state is determined by the
scattering on conduction electrons. We show that the phonon mean free path in
the superconducting state is sensitive to the density of the quasi-particles in
the bulk. An unusual magnetic field dependence of the phonon thermal
conductivity is ascribed to the anisotropic superconducting gap structure in
Sr2RuO4.Comment: 14 pages, 6 eps figures, Latex. This article corresponds to the
reference 25 of Phys. Rev. Lett. vol.86 page2649-2652 (2001) and
cond-mat/010449
Andreev Reflections in Micrometer-Scale Normal-Insulator-Superconductor Tunnel Junctions
Understanding the subgap behavior of Normal-Insulator-Superconductor (NIS)
tunnel junctions is important in order to be able to accurately model the
thermal properties of the junctions. Hekking and Nazarov developed a theory in
which NIS subgap current in thin-film structures can be modeled by multiple
Andreev reflections. In their theory, the current due to Andreev reflections
depends on the junction area and the junction resistance area product. We have
measured the current due to Andreev reflections in NIS tunnel junctions for
various junction sizes and junction resistance area products and found that the
multiple reflection theory is in agreement with our data
Superconducting Gap Structure of Spin-Triplet Superconductor Sr_2RuO_4 Studied by Thermal Conductivity
To clarify the superconducting gap structure of the spin-triplet
superconductor Sr_2RuO_4, the in-plane thermal conductivity has been measured
as a function of relative orientations of the thermal flow, the crystal axes,
and a magnetic field rotating within the 2D RuO_2 planes. The in-plane
variation of the thermal conductivity is incompatible with any model with line
nodes vertical to the 2D planes and indicates the existence of horizontal
nodes. These results place strong constraints on models that attempt to explain
the mechanism of the triplet superconductivity.Comment: 5 pages, 4 figures, to be published in Phys. Rev. Let
The rarity of terrestrial gamma-ray flashes
We report on the first search for Terrestrial Gamma-ray Flashes (TGFs) from altitudes where they are thought to be produced. The Airborne Detector for Energetic Lightning Emissions (ADELE), an array of gamma-ray detectors, was flown near the tops of Florida thunderstorms in August/September 2009. The plane passed within 10 km horizontal distance of 1213 lightning discharges and only once detected a TGF. If these discharges had produced TGFs of the same intensity as those seen from space, every one should have been seen by ADELE. Separate and significant nondetections are established for intracloud lightning, negative cloud-to-ground lightning, and narrow bipolar events. We conclude that TGFs are not a primary triggering mechanism for lightning. We estimate the TGF-to-flash ratio to be on the order of 10^(−2) to 10^(−3) and show that TGF intensities cannot follow the well-known power-law distribution seen in earthquakes and solar flares, due to our limits on the presence of faint events
Nonmonotonous Magnetic Field Dependence and Scaling of the Thermal Conductivity for Superconductors with Nodes of the Order Parameter
We show that there is a new mechanism for nonmonotonous behavior of magnetic
field dependence of the electronic thermal conductivity of clean
superconductors with nodes of the order parameter on the Fermi surface. In
particular, for unitary scatterers the nonmonotony of relaxation time takes
place. Contribution from the intervortex space turns out to be essential for
this effect even at low temperatures. Our results are in a qualitative
agreement with recent experimental data for superconducting UPt_3. For
E_{2u}-type of pairing we find approximately the scaling of the thermal
conductivity in clean limit with a single parameter x=T/T_c\sqrt{B_{c2}/B} at
low fields and low temperatures, as well as weak low-temperature dependence of
the anisotropy ratio K_{zz}/K_{yy} in zero field. For E_{1g}-type of pairing
deviations from the scaling are more noticeable and the anisotropy ratio is
essentially temperature dependent.Comment: 37 pages, 8 Postscript figures, REVTE
Constraints on planet X/Nemesis from Solar System's inner dynamics
We put full 3D constraints on a putative planet X by using the dynamics of
the inner planets of the solar system. In particular, we compute the mimium
distance of X as a function of its heliocentric latitude and longitude for
different values of its mass.Comment: LaTex, MNRAS macros. 12 pages, 4 figures, 3 tables. To appear in
Monthly Notices of the Royal Astronomical Society (MNRAS). Some typos fixe
Magnetic field - temperature phase diagram of quasi-two-dimensional organic superconductor lambda-(BETS)_2 GaCl_4 studied via thermal conductivity
The thermal conductivity kappa of the quasi-two-dimensional (Q2D) organic
superconductor lambda-(BETS)_2 GaCl_4 was studied in the magnetic field H
applied parallel to the Q2D plane. The phase diagram determined from this bulk
measurement shows notable dependence on the sample quality. In dirty samples
the upper critical field H_{c2} is consistent with the Pauli paramagnetic
limiting, and a sharp change is observed in kappa(H) at H_{c2 parallel}. In
contrast in clean samples H_{c2}(T) shows no saturation towards low
temperatures and the feature in kappa(H) is replaced by two slope changes
reminiscent of second-order transitions. The peculiarity was observed below ~
0.33T_c and disappeared on field inclination to the plane when the orbital
suppression of superconductivity became dominant. This behavior is consistent
with the formation of a superconducting state with spatially modulated order
parameter in clean samples.Comment: 10 pages, 8 figures, new figure (Fig.5) and references added, title
change
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