The hydrogen molecule H2\rm{H}_{2} 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 $\theta$ with respect to the direction of a uniform constant magnetic field ${\bf B}$, for $B=0,\, 0.1,\, 0.175$ and $0.2\,$a.u. Three inclinations $\theta=0^\circ,\,45^\circ,\,90^\circ$ are studied in detail with emphasis to the ground state $1_g$. Diamagnetic and paramagnetic susceptibilities are calculated (for $\theta=45^\circ$ for the first time), they are in agreement with the experimental data and with other calculations. For $B=0,\, 0.1$ and $0.2\,$a.u. potential energy curves $E$ vs $R$ are built for each inclination, they are interpolated by simple, two-point Pad\'e approximant $Pade[2/6](R)$ 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 $B \leq B_{cr}=0.178\,$a.u. corresponds always to the parallel configuration, $\theta=0$, thus, it is a $^1\Sigma_g$ state. The state $1_g$ remains bound for any magnetic field, becoming metastable for $B > B_{cr}$, while for $B_{cr} < B < 12$\,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 H3+{\rm H}_3^+ hydrogen molecular ion

Three simple $7-, (7+3)-, 10-$parametric trial functions for the ${\rm H}_3^+$ 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 $\sim\exp{(\gamma r_{12})}$, where $\gamma$ is a variational parameter. The Born-Oppenheimer energy is found to be $E=-1.340 34, -1.340 73, -1.341 59$\,a.u., respectively, for optimal equilateral triangular configuration of protons with the equilibrium interproton distance $R=1.65$\,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 $(li, e)$ and molecular type $(li, li, e)$, $(li, \alpha, e)$ and $(li, p, e)$ are studied in the presence of a strong magnetic field $B \leq 10^{7}$ 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 ${\rm LiH}^{3+}$, ${\rm LiHe}^{4+}$ and ${\rm Li}_{2}^{5+}$ can exist for sufficiently strong magnetic fields $B \gtrsim 10^{4}$ a.u. and that ${\rm Li}_{2}^{5+}$ 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: CeCu2_2Si2_2 versus YbRh2_2Si2_2

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 CeCu$_2$Si$_2$, 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 CeCu$_2$Si$_2$. In YbRh$_2$Si$_2$, superconductivity appears to be suppressed at $T\gtrsim~10$ mK by AF order ($T_N$ = 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 $T_A$ 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 $T_c$ = 2 mK. Like the pressure - induced QCP in CeRhIn$_5$, the magnetic field - induced one in YbRh$_2$Si$_2$ 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-$T$ unconventional heavy - fermion superconductors and other families of unconventional superconductors with higher $T_c$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

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