On the properties of the interstellar medium in extremely metal-poor blue compact dwarf galaxies: GMOS-IFU spectroscopy and SDSS photometry of the double-knot galaxy HS 2236+1344

The main goal of this study is to carry out a spatially resolved investigation of the warm interstellar medium (ISM) in the extremely metal-poor Blue Compact Dwarf (BCD) galaxy HS 2236+1344. Special emphasis is laid on the analysis of the spatial distribution of chemical abundances, emission-line ratios and kinematics of the ISM, and to the recent star-forming activity in this galaxy. This study is based on optical integral field unit spectroscopy data from Gemini Multi-Object Spectrograph at the Gemini North telescope and archival Sloan Digital Sky Survey images. The data were obtained in two different positions across the galaxy, obtaining a total 4 arcsec X 8 arcsec field which encompasses most of its ISM. Emission-line maps and broad-band images obtained in this study indicate that HS 2236+1344 hosts three Giant HII regions. Our data also reveal some faint curved features in the BCD periphery that might be due to tidal perturbations or expanding ionized-gas shells. The ISM velocity field shows systematic gradients along the major axis of the BCD, with its south-eastern and north-western half differing by ~80 km/s in their recessional velocity. The Ha and Hb equivalent width distribution in the central part of HS 2236+1344 is consistent with a very young (~3 Myr) burst. Our surface photometry analysis indicates that the ongoing starburst provides ~50% of the total optical emission, similar to other BCDs. It also reveals an underlying lower-surface brightness component with moderately red colors, which suggest that the galaxy has undergone previous star formation. We derive an integrated oxygen abundance of 12+log(O/H)=7.53\pm0.06 and a nitrogen-to-oxygen ratio of log(N/O)=-1.57\pm0.19. Our results are consistent, within the uncertainties, with a homogeneous distribution of oxygen and nitrogen within the ISM of the galaxy. (abridged)Comment: 15 pages, 16 figures, accepted for publication in A&

Low Temperature (ln2) And Uhv Mechanically Controllable Break Junction Setup To Study Quantum Electrical Transport Of Atomic-size Metal Nanowire

Reliable metal nanowire studies requires experimental stringent conditions, as clean samples and environment. In this sense, we have designed and built a dedicated instrument to study electrical transport properties of atomic-size metal contacts based on the mechanically controlled break junction technique, operating at ultra-high-vacuum conditions. Here we describe the chosen setup, its implementation and performance. © 2008 IOP Publishing Ltd.100PART 5Landauer, R., (1957) IBM J. Res. Dev., 1, p. 223Agrait, N., Yeyati, A.L., Van Ruitenbeek, J.M., (2003) Phys. Rep., 377, p. 81Rodrigues, V., Fuhrer, T., Ugarte, D., (2000) Phys. Rev. Lett., 85, p. 4124Hansen, K., Lægsgaard, E., Stensgaard, I., Besenbacher, F., (1997) Phys. Rev. B, 56, p. 2208De Heer, W.A., Frank, S., Ugarte, D., (1997) Z. Phys. B, 104, p. 469Rodrigues, V., Bettini, J., Rocha, A.R., Rego, L.G.C., Ugarte, D., (2002) Phys. Rev. B, 65, p. 153402Rego, L.G.C., Rocha, A.R., Rodrigues, V., Ugarte, D., (2003) Phys. Rev. B, 67, p. 045412Gonzalez, J.C., Rodrigues, V., Bettini, J., Rego, L.G.C., Rocha, A.R., Coura, P.Z., Dantas, S.O., Ugarte, D., (2004) Phys. Rev. Lett., 93, p. 126103Lagos, M., Rodrigues, V., Ugarte, D., (2007) J. Electron Spectroscopy and Related Phenomena, 20, pp. 156-158Rubio, G., Agraït, N., Vieira, S., (1996) Phys. Rev. Lett., 76, p. 2302Smit, R.H.M., Noat, Y., Untiedt, C., Lang, N.D., Van Hemert, M.C., Van Ruitenbeek, J.M., (2002) Nature, 419, p. 906VaLkering A, M.C., Mares, A.I., Untiedt, C., Gavan, K.B., Oosterkamp, T.H., Van Ruitenbeek, J.M., (2005) Review of Scientific Instruments, 76, p. 103903Zhou, C., Muller, C.J., Deshpande, M.R., Sleight, J.W., Reed, M.A., (1995) Appl. Phys. Lett., 67, p. 1160Hansen, K., Nielsen, S.K., Brandbyge, M., Lægsgaard, E., Stensgaard, I., Besenbacher, F., (2000) Appl. Phys. Lett., 77, p. 708Hakkinen, H., Barnett, R.N., Landman, U., (1999) J. Phys. Chem. B, 103, p. 8814Legoas, S.B., Rodrigues, V., Ugarte, D., Galvao, D.S., (2004) Phys. Rev. Lett., 93, p. 216103Novaes, F.D., Da Silva A, J.R., Fazzio, A., Da Silva, E.Z., (2005) J. Appl. Phys. A, 81, p. 1551Barnett, R.N., Hakkinen, H., Scherbakov, A.G., Landman, U., (2004) Nano Lett., p. 41845Hakkinen, H., Barnett, R.N., Scherbakov, A.G., Landman, U., (2000) J. Phys. Chem. B, 104, p. 9063Rodrigues, V., Bettini, J., Silva, P.C., Ugarte, D., (2003) Phys. Rev. Lett., 91, p. 096801Costa-Kramer, J.L., Garcia, N., Olin, H., (1997) Phys. Rev. B, 55, p. 1291

Angular momentum evolution of bulge stars in disc galaxies in NIHAO

We study the origin of bulge stars and their angular momentum (AM) evolution in 10 spiral galaxies with baryonic masses above $10^{10}$M$_\odot$ in the NIHAO galaxy formation simulations. The simulated galaxies are in good agreement with observations of the relation between specific AM and mass of the baryonic component and the stellar bulge-to-total ratio ($B/T$). We divide the star particles at $z=0$ into disc and bulge components using a hybrid photometric/kinematic decomposition method that identifies all central mass above an exponential disc profile as the `bulge'. By tracking the bulge star particles back in time, we find that on average 95\% of the bulge stars formed {\it in situ}, 3\% formed {\it ex situ} in satellites of the same halo, and only 2\% formed {\it ex situ} in external galaxies. The evolution of the AM distribution of the bulge stars paints an interesting picture: the higher the final $B/T$ ratio, the more the specific AM remains preserved during the bulge formation. In all cases, bulge stars migrate significantly towards the central region, reducing their average galactocentric radius by roughly a factor 2, independently of the final $B/T$ value. However, in the higher $B/T$ ($\gtrsim0.2$) objects, the velocity of the bulge stars increases and the AM of the bulge is almost conserved, whereas at lower $B/T$ values, the velocity of the bulge stars decreases and the AM of bulge reduces. The correlation between the evolution of the AM and $B/T$ suggests that bulge and disc formation are closely linked and cannot be treated as independent processes.Comment: 17 pages, 16 Figures, 1 table; accepted for publication in MNRA

Affordable, Energy-Efficient Housing Design for Chile: Achieving Passivhaus Standard with the Chilean State Housing Subsidy

In Chile, it is estimated that the energy demand will continue to increase if substantial energy efficiency measures in housing are not taken. These measures are generally associated with technical and mainly economic difficulties. This paper aims to show the technical and economic feasibility of achieving Passivhaus standard house in Chile, considering the budget of the maximum state subsidy currently available (Chilean Unidad de Fomento (CLF) 2000 ≈ 81,000 USD). The design was simulated in the Passive House Planning Package software to determine if the house could be certified with the selected standard. At the same time, the value of all the items was quantified in order not to exceed the stipulated maximum budget for a house considered as affordable. It was shown that in terms of design it is possible to implement the Passivhaus standard given the current housing subsidy. The designed housing ensures a reduction of 85% in heating demand and a 60% reduction in CO2 emissions during the operation, compared to an average typical Chilean house

Dynamic equilibrium sets atomic content of galaxies across cosmic time

We analyze 88 independent high-resolution cosmological zoom-in simulations of disk galaxies in the NIHAO simulations suite to explore the connection between the atomic gas fraction and angular momentum of baryons throughout cosmic time. The study is motivated by the analytic model of \citet{obreschkow16}, which predicts a relation between the atomic gas fraction $f_{\rm atm}$ and the global atomic stability parameter $q \equiv j\sigma / (GM)$, where $M$ and $j$ are the mass and specific angular momentum of the galaxy (stars+cold gas) and $\sigma$ is the velocity dispersion of the atomic gas. We show that the simulated galaxies follow this relation from their formation ($z\simeq4$) to present within $\sim 0.5$ dex. To explain this behavior, we explore the evolution of the local Toomre stability and find that $90\%$--$100\%$ of the atomic gas in all simulated galaxies is stable at any time. In other words, throughout the entire epoch of peak star formation until today, the timescale for accretion is longer than the timescale to reach equilibrium, thus resulting in a quasi-static equilibrium of atomic gas at any time. Hence, the evolution of $f_{\rm atm}$ depends on the complex hierarchical growth history primarily via the evolution of $q$. An exception are galaxies subject to strong environmental effects.Comment: 12 pages, 7 figures; accepted to Ap

MicroRNA-155 induction via TNF-α and IFN-γ suppresses expression of programmed death ligand-1 (PD-L1) in human primary cells

Programmed death ligand-1 (PD-L1) is a critical regulator of T cell function contributing to peripheral immune tolerance. Although it has been shown that posttranscriptional regulatory mechanisms control PD-L1 expression in cancer, it remains unknown whether such regulatory loops operate also in non-transformed cells. Here we studied PD-L1 expression in human dermal lymphatic endothelial cells (HDLECs), which play key roles in immunity and cancer. Treatment of HDLECs with the pro-inflammatory cytokines IFN-γ and TNF-α synergistically upregulated PDL1 expression. IFN-γ and TNF-α also affected expression of several microRNAs (miRNAs) that have the potential to suppress PD-L1 expression. The most highly upregulated miRNA following IFN-γ and TNF-α treatment in HDLECs was miR- 155, which has a central role in the immune system and cancer. Induction of miR-155 was driven by TNF-α, the effect of which was significantly enhanced by IFN-γ. The PD-L1 3'- UTR contains two functional miR-155 binding sites. Endogenous miR-155 controlled the kinetics and maximal levels of PD-L1 induction upon IFN-γ and TNF-α treatment. We obtained similar findings in dermal fibroblasts, demonstrating that the IFN-γ/TNF-α/miR-155/PD-L1 pathway is not restricted to HDLECs. These results reveal miR- 155 as a critical component of an inflammationinduced regulatory loop controlling PD-L1 expression in primary cells

Jet interactions with a giant molecular cloud in the Galactic centre and ejection of hypervelocity stars

The hypervelocity OB stars in the Milky Way Galaxy were ejected from the central regions some 10-100 million years ago. We argue that these stars, {as well as many more abundant bound OB stars in the innermost few parsecs,} were generated by the interactions of an AGN jet from the central black hole with a dense molecular cloud. Considerations of the associated energy and momentum injection have broader implications for the possible origin of the Fermi bubbles and for the enrichment of the intergalactic medium.Comment: 4 pages, 1 figure. Astronomy and Astrophysics Letters, in pres

Observation of the Smallest Metal Nanotube with Square-cross-section

Understanding the mechanical properties of nanoscale systems requires a range of measurement techniques and theoretical approaches to gather the relevant physical and chemical information. The arrangements of atoms in nanostructures and macroscopic matter can be different, principally due to the role of surface energy, but the interplay between atomic and electronic structure in association with applied mechanical stress can also lead to surprising differences. For example, metastable structures such as suspended chains of atoms and helical wires have been produced by the stretching of metal junctions. Here we report the spontaneous formation of the smallest possible metal nanotube with a square cross-section during the elongation of silver nanocontacts. Ab initio calculations and molecular simulations indicate that the hollow wire forms because this configuration allows the surface energy to be minimized, and also generates a soft structure capable of absorbing a huge tensile deformation

Intrinsic Stability Of The Smallest Possible Silver Nanotube.

Recently, Lagos et al. [Nature Nanotech. 4, 149 (2009)] reported the discovery of the smallest possible Ag nanotube with a square cross section. Ab initio density functional theory calculations strongly support that the stability of these hollow structures is structurally intrinsic and not the result of contamination by light atoms. We also report the first experimental observation of the theoretically predicted corrugation of the hollow structure. Quantum conductance calculations predict a unique signature of 3.6 G0 for this new family of nanotubes.10606550