Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution

We present deep echelle spectrophotometry of the brightest emission-line knots of the star-forming galaxies He 2-10, Mkn 1271, NGC 3125, NGC 5408, POX 4, SDSS J1253-0312, Tol 1457-262, Tol 1924-416 and the HII region Hubble V in the Local Group dwarf irregular galaxy NGC 6822. The data have been taken with the Very Large Telescope Ultraviolet-Visual Echelle Spectrograph in the 3100-10420 {\AA} range. We determine electron densities and temperatures of the ionized gas from several emission-line intensity ratios for all the objects. We derive the ionic abundances of C$^{2+}$ and/or O$^{2+}$ from faint pure recombination lines (RLs) in several of the objects, permitting to derive their C/H and C/O ratios. We have explored the chemical evolution at low metallicities analysing the C/O vs. O/H, C/O vs. N/O and C/N vs. O/H relations for Galactic and extragalactic HII regions and comparing with results for halo stars and DLAs. We find that HII regions in star-forming dwarf galaxies occupy a different locus in the C/O vs. O/H diagram than those belonging to the inner discs of spiral galaxies, indicating their different chemical evolution histories, and that the bulk of C in the most metal-poor extragalactic HII regions should have the same origin than in halo stars. The comparison between the C/O ratios in HII regions and in stars of the Galactic thick and thin discs seems to give arguments to support the merging scenario for the origin of the Galactic thick disc. Finally, we find an apparent coupling between C and N enrichment at the usual metallicities determined for HII regions and that this coupling breaks in very low-metallicity objects.Comment: 27 pages, 12 figures, Accepted for publication in Monthly Notices of the Royal Astronomical Societ

Spin Pumping and Inverse Spin Hall Effect in Platinum: The Essential Role of Spin-Memory Loss at Metallic Interfaces

Through combined ferromagnetic resonance, spin-pumping and inverse spin Hall effect experiments in Co|Pt bilayers and Co|Cu|Pt trilayers, we demonstrate consistent values of spin diffusion length $\ell_{\rm sf}^{\rm Pt}=3.4\pm0.4$ nm and of spin Hall angle $\theta_{\rm SHE}^{\rm Pt}=0.051\pm0.004$ for Pt. Our data and model emphasize on the partial depolarization of the spin current at each interface due to spin-memory loss. Our model reconciles the previously published spin Hall angle values and explains the different scaling lengths for the ferromagnetic damping and the spin Hall effect induced voltage.Comment: 6 pages, 3 figures (main text) and 8 pages supplementary. Published with small modifications in Phys. Rev. Let

Determinación de proteínas en hojas de Citrus. I. Métodos e interferencias

The Folin-Lowry, UV absortion and Kjeldalh methods, for protein determination using ox albumine as standard, are studied. This last method only as a comparative one. For the Folin-Lowry method the cahbration curves and the corresponding regression equations are stabHshed. At the same time the interferences produced by different solvents and buffers are studied, so as its usefulness to extract vegetal protein

Determinación de proteínas en hojas de Citrus. II. Extracción, fraccionamiento y cuantificación

The extraction conditions for the chloroplastic and citoplasmic proteins of the Vema lemon tree leaves physiologically normáis are estudiad, chosing disgregation methods and extractants. For the citoplasmic proteins, tris-glycine-glucose (TGG) is selected as extractant (eluent), being stablished the action of each one of their components and the optimum pH. Likewise, it is tested that the adition to the buffer solution of different protective substances relatives to the formation of protein-quinone complex, do not improve the bioffer quality. The sedimentations conditions for chloroplasts are the foUowing: 6000 X g during 45 minutes using as the more appropiate extractein (eluent) for the chloroplastic protein, the sodium dodecil sulphate at a concentration of 0,5 %. A fractionation of the citoplasmic proteins, using amonium sulphate and trichloroacetic acid (TCA) is made. The chloroplastic proteins are divided at the same time in soluble and insoluble

Experimental evidences of a large extrinsic spin Hall effect in AuW alloy

We report an experimental study of a gold-tungsten alloy (7% at. W concentration in Au host) displaying remarkable properties for spintronics applications using both magneto-transport in lateral spin valve devices and spin-pumping with inverse spin Hall effect experiments. A very large spin Hall angle of about 10% is consistently found using both techniques with the reliable spin diffusion length of 2 nm estimated by the spin sink experiments in the lateral spin valves. With its chemical stability, high resistivity and small induced damping, this AuW alloy may find applications in the nearest future

Determination of the spin Hall angle, spin mixing conductance and spin diffusion length in Ir/CoFeB for spin-orbitronic devices

Iridium is a very promising material for spintronic applications due to its interesting magnetic properties such as large RKKY exchange coupling as well as its large spin-orbit coupling value. Ir is for instance used as a spacer layer for perpendicular synthetic antiferromagnetic or ferrimagnet systems. However, only a few studies of the spintronic parameters of this material have been reported. In this paper, we present inverse spin Hall effect - spin pumping ferromagnetic resonance measurements on CoFeB/Ir based bilayers to estimate the values of the effective spin Hall angle, the spin diffusion length within iridium, and the spin mixing conductance in the CoFeB/Ir bilayer. In order to have reliable results, we performed the same experiments on CoFeB/Pt bilayers, which behavior is well known due to numerous reported studies. Our experimental results show that the spin diffusion length within iridium is 1.3 nm for resistivity of 250 n$\Omega$.m, the spin mixing conductance $g_{eff}^{\uparrow \downarrow}$ of the CoFeB/Ir interface is 30 nm$^{-2}$, and the spin Hall angle of iridium has the same sign than the one of platinum and is evaluated at 26% of the one of platinum. The value of the spin Hall angle found is 7.7% for Pt and 2% for Ir. These relevant parameters shall be useful to consider Ir in new concepts and devices combining spin-orbit torque and spin-transfer torque.Comment: 8 pages, 4 figure