Lucky Spectroscopy, an equivalent technique to Lucky Imaging. Spatially resolved spectroscopy of massive close visual binaries using the William Herschel Telescope

CONTEXT: Many massive stars have nearby companions whose presence hamper their characterization through spectroscopy. AIMS: We want to obtain spatially resolved spectroscopy of close massive visual binaries to derive their spectral types. METHODS: We obtain a large number of short long-slit spectroscopic exposures of five close binaries under good seeing conditions, select those with the best characteristics, extract the spectra using multiple-profile fitting, and combine the results to derive spatially separated spectra. RESULTS: We demonstrate the usefulness of Lucky Spectroscopy by presenting the spatially resolved spectra of the components of each system, in two cases with separations of only ~0.3". Those are delta Ori Aa+Ab (resolved in the optical for the first time) and sigma Ori AaAb+B (first time ever resolved). We also spatially resolve 15 Mon AaAb+B, zeta Ori AaAb+B (both previously resolved with GOSSS, the Galactic O-Star Spectroscopic Survey), and eta Ori AaAb+B, a system with two spectroscopic B+B binaries and a fifth visual component. The systems have in common that they are composed of an inner pair of slow rotators orbited by one or more fast rotators, a characteristic that could have consequences for the theories of massive star formation.Comment: Accepted for publication in A&A, 7 page

Phase separation and valence instabilities in cuprate superconductors. Effective one-band model approach

We study the Cu-O valence instability (VI) and the related phase separation (PS) driven by Cu-O nearest-neighbor repulsion $U_{pd}$, using an effective extended one-band Hubbard model ($H_{eff}$) obtained from the extended three-bandHubbard model, through an appropriate low-energy reduction. $H_{eff}$ is solved by exact diagonalization of a square cluster with 10 unit cells and also within a slave-boson mean-field theory. Its parameters depend on doping for $U_{pd}\neq 0$ or on-site O repulsion $U_p\neq 0$. The results using both techniques coincide in that there is neither VI nor PS for doping levels $x<0.5$ if $U_{pd}\lesssim 2$ eV. The PS region begins for $U_{pd}\gtrsim 2$ eV at large doping $x>0.6$ and increases with increasing $U_{pd}$. The PS also increases with increasing on-site Cu repulsion $U_d$.Comment: 16 pages and 10 figures in postscript format, compressed with uufile

Stem cells "aclymatise" to regenerate the blood system.

How blood stem cells balance fate decisions between quiescence maintenance and differentiation during recovery from cancer treatment remains poorly understood. A recent study by Umemoto et al (2022) uncovers an unexpected linkage between metabolic and epigenetic regulation of haematopoiesis, suggesting new targets in haematopoietic regeneration, with possible implications in leukaemogenesis and therapy resistance

Stachorutes cabagnerensis sp. n., Collembola (Neanuridae) de la región central de España, y una aproximación preliminar a la filogenia del género

A new species of the genus Stachorutes, Stachorutes cabagnerensis n. sp., from central Spain is described. It is characterized by the presence of 6+6 eyes in the head, retinaculum 2+2 teeth, dentes with 5 hairs, and the absence of mucron. A phylogenetic analysis of this genus was attempted. Potential synapomorphies supporting the monophyly of Stachorutes are presented. One member of the genus (the Nearctic S. navajellus) appears as a basal form, phylogenetically distant from the remaining (Old World) species. There is evidence for a monophyletic infrageneric clade with the species S. dematteisi, S. jizuensis and S. sphagnophilus. However, more information is required for further phylogenetic resolution.Se describe una nueva especie del genero Stachorutes de la region central de España. Stachorutes cabagnerensis nov. sp. se caracteriza por la presencia de 6+6 ojos en la cabeza, retinaculum con 2+2 dientes y 5 sedas en cada rama del dentes; la furca carece de mucrón. Se ha efectuado un análisis filogenético. Las sinapomorfias potenciales establecen la monofilia del género. Una especie del mismo, S. navajellus, aparece como forma basal, filogenéticamente distante del resto de especies (Viejo Mundo). Se podría establecer un clado infragenérico con las especies S. dematteisi, S. jizuensis y S. sphagnophilus. Sin embargo, se precisa de mayor información para poder confirmarlo

1-(4-Chloro­phen­yl)-3-(2-meth­oxy­anilino)propan-1-one

In the title compound, C16H16ClNO2, the mol­ecule adopts a bowed conformation, with a dihedral angle of 39.9 (2)° between the aromatic rings. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds, generating C(6) chains propagating in [010]. Very weak aromatic π–π stacking is also observed [centroid–centroid distance = 4.040 (2) Å]

Two photon decay of neutral scalars below 1.5 GeV in a chiral model for bar{q}q and bar{q}bar{q}qq states

We study the two photon decay of neutral scalars below 1.5 GeV in the context of a recently proposed chiral model for bar{q}q and bar{q}bar{q}qq states. We find good agreement with experimental results for the a_{0}(980)->gamma gamma. Our calculations for f_{0}(980)->gamma gamma shows that further work is necessary in order to understand the structure of this meson. The model predicts Gamma(a_{0}(1450)->gamma gamma)=0.16+/-0.10KeV, Gamma(sigma->gamma gamma)=0.47+/-0.66 KeV, Gamma(f(1370)->gamma gamma)=0.07+/-0.15 KeV, Gamma(f(1500)->gamma gamma)=0.74+/-0.78 KeV.Comment: 6 pages, 1 figur

Optical properties of an effective one-band Hubbard model for the cuprates

We study the Cu and O spectral density of states and the optical conductivity of CuO_2 planes using an effective generalized one-band Hubbard model derived from the extended three-band Hubbard model. We solve exactly a square cluster of 10 unit cells and average the results over all possible boundary conditions, what leads to smooth functions of frequency. Upon doping, the Fermi energy jumps to Zhang-Rice states which are connected to the rest of the valence band (in contrast to an isolated new band in the middle of the gap). The transfer of spectral weight depends on the parameters of the original three-band model not only through the one-band effective parameters but also through the relevant matrix elements. We discuss the evolution of the gap upon doping. The optical conductivity of the doped system shows a mid-infrared peak due to intraband transitions, a pseudogap and a high frequency part related to interband transitions. Its shape and integrated weight up to a given frequency (including the Drude weight) agree qualitatively with experiments in the cuprates for low to moderate doping levels, but significant deviations exist for doping $x>0.3$.Comment: 11 pages (tex), 14 figures (ps