210 research outputs found
The hydrogen molecule in inclined configuration in a weak magnetic field
Highly accurate variational calculations, based on a few-parameter,
physically adequate trial function, are carried out for the hydrogen molecule
\hh in inclined configuration, where the molecular axis forms an angle
with respect to the direction of a uniform constant magnetic field ,
for and a.u. Three inclinations
are studied in detail with emphasis to
the ground state . Diamagnetic and paramagnetic susceptibilities are
calculated (for for the first time), they are in agreement
with the experimental data and with other calculations. For and
a.u. potential energy curves vs are built for each inclination,
they are interpolated by simple, two-point Pad\'e approximant
with accuracy of not less than 4 significant digits. Spectra of rovibrational
states are calculated for the first time. It was found that the optimal
configuration of the ground state for a.u. corresponds
always to the parallel configuration, , thus, it is a
state. The state remains bound for any magnetic field, becoming
metastable for , while for \,a.u. the ground state
corresponds to two isolated hydrogen atoms with parallel spins.Comment: 31 pages, 11 Tables, 7 Figures (2 new), following referee's
suggestions parts 4,5,6 essentially rewritten, to be published at Journal of
Quantitative Spectroscopy and Radiative Transfe
A note about the ground state of the hydrogen molecular ion
Three simple parametric trial functions for the molecular ion are presented. Each of them provides subsequently the
most accurate approximation for the Born-Oppenheimer ground state energy among
several-parametric trial functions. These trial functions are chosen following
a criterion of physical adequacy and includes the electronic correlation in the
exponential form , where is a variational
parameter. The Born-Oppenheimer energy is found to be \,a.u., respectively, for optimal equilateral triangular
configuration of protons with the equilibrium interproton distance
\,a.u. The variational energy agrees in three significant digits (s.d.)
with most accurate results available at present as well as for major
expectation values.Comment: 12 pages, 1 figure, 3 table
Different Harvest Schedules to Prepare Deferred Forage from C4 Grasses in Córdoba, Argentina
From 1995 until 1999 a trial was done in the fields of the Universidad Nacional de Córdoba with four C4 forage grasses. These fields lie in the subtropical and semiarid region of Argentina. This research aimed to identify forage species that could be used as deferred forage for the drier and cooler winter season. Four species of C4 grasses were used: Rhodesgrass (Chloris gayana Kunth), Gatton (Panicum maximum), coloratum (Panicum coloratum) and digitgrass (Digitaria eriantha), respectively. Two growing periods were used: full season growth (FS) and half season regrowth (HS), in both cases the deferred forage was harvested three times: at the beginning, in the middle and at the end of the winter. This paper foccuses DM yields in kg/hectare (DM) and percentage of crude protein (CP). The HS yields less but shows better CP than the FS, therefore it may be a better forage in winter. Coloratum and digigrass seems to give better deferred forage than the other species
Optoelectronic Sensitization of Carbon Nanotubes by CdTe Nanocrystals
We investigate the photoconductance of single-walled carbon
nanotube-nanocrystalhybrids. The nanocrystals are bound to the nanotubes via
molecular recognition. We find that the photoconductance of the hybrids can be
adjusted by the absorption characteristics of the nanocrystals. In addition,
the photoconductance of the hybrids surprisingly exhibits a slow time constant
of about 1 ms after excitation of the nanocrystals. The data are consistent
with a bolometrically induced current increase in the nanotubes caused by
photon absorption in the nanocrystals
One-electron atomic-molecular ions containing Lithium in a strong magnetic field
The one-electron Li-containing Coulomb systems of atomic type and
molecular type , and are studied in
the presence of a strong magnetic field a.u. in the
non-relativistic framework. They are considered at the Born-Oppenheimer
approximation of zero order (infinitely massive centers) within the parallel
configuration (molecular axis parallel to the magnetic field). The variational
and Lagrange-mesh methods are employed in complement to each other. It is
demonstrated that the molecular systems , and
can exist for sufficiently strong magnetic fields a.u. and that can even be stable at
magnetic fields typical of magnetars.Comment: 22 pages, 9 figures, 4 table
Interplay between unconventional superconductivity and heavy-fermion quantum criticality: CeCuSi versus YbRhSi
In this paper the low-temperature properties of two isostructural canonical
heavy-fermion compounds are contrasted with regards to the interplay between
antiferromagnetic (AF) quantum criticality and superconductivity. For
CeCuSi, fully-gapped d-wave superconductivity forms in the vicinity of
an itinerant three-dimensional heavy-fermion spin-density-wave (SDW) quantum
critical point (QCP). Inelastic neutron scattering results highlight that both
quantum critical SDW fluctuations as well as Mott-type fluctuations of local
magnetic moments contribute to the formation of Cooper pairs in CeCuSi.
In YbRhSi, superconductivity appears to be suppressed at
mK by AF order ( = 70 mK). Ultra-low temperature measurements reveal a
hybrid order between nuclear and 4f-electronic spins, which is dominated by the
Yb-derived nuclear spins, to develop at slightly above 2 mK. The hybrid
order turns out to strongly compete with the primary 4f-electronic order and to
push the material towards its QCP. Apparently, this paves the way for
heavy-fermion superconductivity to form at = 2 mK. Like the pressure -
induced QCP in CeRhIn, the magnetic field - induced one in YbRhSi
is of the local Kondo-destroying variety which corresponds to a Mott-type
transition at zero temperature. Therefore, these materials form the link
between the large family of about fifty low- unconventional heavy - fermion
superconductors and other families of unconventional superconductors with
higher s, notably the doped Mott insulators of the cuprates, organic
charge-transfer salts and some of the Fe-based superconductors. Our study
suggests that heavy-fermion superconductivity near an AF QCP is a robust
phenomenon.Comment: 30 pages, 7 Figures, Accepted for publication in Philosophical
Magazin
Is angiotensin-(3–4) (Val-Tyr), the shortest angiotensin II-derived peptide, opening new vistas on the renin–angiotensin system?
Angiotensin-(3−4) (Ang-(3−4) or Val-Tyr) is the shorter angiotensin (Ang) II-derived peptide, formed through successive hydrolysis that culminates with the release of Val-Tyr as a dipeptide. It is formed both in plasma and in kidney from Ang II and Ang III, and can be considered a component of the systemic and organ-based renin–angiotensin system. It is potently antihypertensive in humans and rats, and its concerted actions on proximal tubule cells culminate in the inhibition of fluid reabsorption, hyperosmotic urinary excretion of Na+. At the renal cell signaling level, Ang-(3−4) counteracts Ang II-type 1 receptor-mediated responses by acting as an allosteric enhancer in Ang II-type 2 receptor populations that target adenosine triphosphate-dependent Ca2+ and Na+ transporters through a cyclic adenosine monophosphate-activated protein kinase pathway
Magnetostratigraphy of the Cretaceous/Tertiary boundary and early Paleocene sedimentary sequence from the Chicxulub Impact Crater
Superconductivity in Ce- and U-based "122" heavy-fermion compounds
This review discusses the heavy-fermion superconductivity in Ce- and U-based
compounds crystallizing in the body-centered tetragonal ThCr2Si2 structure.
Special attention will be paid to the theoretical background of these systems
which are located close to a magnetic instability.Comment: 12 pages, 9 figures. Invited topical review (special issue on "Recent
Developments in Superconductivity") Metadata and references update
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