Direct numerical simulation of gas transfer across the air-water interface driven by buoyant convection

A series of direct numerical simulations of mass transfer across the air-water interface driven by buoyancy-induced convection has been carried out to elucidate the physical mechanisms that play a role in the transfer of heat and atmospheric gases. The buoyant instability is caused by the presence of a thin layer of cold water situated on top of a body of warm water. In time, heat and atmospheric gases diff use into the uppermost part of the thermal boundary layer and are subsequently transported down into the bulk by falling sheets and plumes of cold water. Using a specifically-designed numerical code for the discretization of scalar convection and diffusion, it was possible to accurately resolve this buoyant instability induced transport of atmospheric gases into the bulk at a realistic Prandtl number (Pr = 6) and Schmidt numbers ranging from Sc = 20 to Sc = 500. The simulations presented here provided a detailed insight into instantaneous gas transfer processes. The falling plumes with highly gas-saturated fluid in their core were found to penetrate deep inside the bulk. With an initial temperature difference between the water surface and the bulk of slightly above 2 K peaks in the instantaneous heat flux in excess of 1600 W/m² were observed, proving the potential effectiveness of buoyant convective heat and gas transfer. Furthermore, the validity of the scaling law for the ratio of gas and heat transfer velocities K_L / H_L ∼ (Pr/Sc)^0:5 for the entire range of Schmidt numbers considered was confirmed. A good time-accurate approximation of K_L was found using surface information such as velocity fluctuations and convection cell size or surface divergence. A reasonable time-accuracy for the K_L estimation was obtained using the horizontal integral length scale and the root-mean-square of the horizontal velocity fluctuations in the upper part of the bulk.The German Research Foundation (DFG grant UH242/6-1). Additional funding by the Helmholtz Water Network

J0811+4730: the most metal-poor star-forming dwarf galaxy known

We report the discovery of the most metal-poor dwarf star-forming galaxy (SFG) known to date, J0811+4730. This galaxy, at a redshift z=0.04444, has a Sloan Digital Sky Survey (SDSS) g-band absolute magnitude M_g = -15.41 mag. It was selected by inspecting the spectroscopic data base in the Data Release 13 (DR13) of the SDSS. LBT/MODS spectroscopic observations reveal its oxygen abundance to be 12 + log O/H = 6.98 +/- 0.02, the lowest ever observed for a SFG. J0811+4730 strongly deviates from the main-sequence defined by SFGs in the emission-line diagnostic diagrams and the metallicity - luminosity diagram. These differences are caused mainly by the extremely low oxygen abundance in J0811$+$4730, which is ~10 times lower than that in main-sequence SFGs with similar luminosities. By fitting the spectral energy distributions of the SDSS and LBT spectra, we derive a stellar mass of M* = 10^6.24 - 10^6.29 Msun (statistical uncertainties only), and we find that a considerable fraction of the galaxy stellar mass was formed during the most recent burst of star formation.Comment: 12 pages, 5 figures, accepted for publication in MNRA

A Widespread, Clumpy Starburst in the Isolated Ongoing Dwarf Galaxy Merger dm1647+21

Interactions between pairs of isolated dwarf galaxies provide a critical window into low-mass hierarchical, gas-dominated galaxy assembly and the buildup of stellar mass in low-metallicity systems. We present the first VLT/MUSE optical IFU observations of the interacting dwarf pair dm1647+21, selected from the TiNy Titans survey. The H$\alpha$ emission is widespread and corresponds to a total unobscured star formation rate (SFR) of 0.44 M$_{\odot}$ yr$^{-1}$, 2.7 times higher than the SFR inferred from SDSS data. The implied specific SFR (sSFR) for the system is elevated by more than an order of magnitude above non-interacting dwarfs in the same mass range. This increase is dominated by the lower-mass galaxy, which has a sSFR enhancement of $>$ 50. Examining the spatially-resolved maps of classic optical line diagnostics, we find the ISM excitation can be fully explained by star formation. The velocity field of the ionized gas is not consistent with simple rotation. Dynamical simulations indicate that the irregular velocity field and the stellar structure is consistent with the identification of this system as an ongoing interaction between two dwarf galaxies. The widespread, clumpy enhancements in star formation in this system point to important differences in the effect of mergers on dwarf galaxies, compared to massive galaxies: rather than the funneling of gas to the nucleus and giving rise to a nuclear starburst, starbursts in low-mass galaxy mergers may be triggered by large-scale ISM compression, and thus be more distributed.Comment: Accepted for publication in ApJ. 11 pages, 5 figures, 1 table. Figures slightly degraded to meet arXiv size restrictions. For more information about TiNy Titans see https://lavinia.as.arizona.edu/~tinytitans

El cinema soviético y el segundo plan quinquenal

Liss, G. (1932). El cinema soviético y el segundo plan quinquenal. Nuestro cinema. (6):171-174. http://hdl.handle.net/10251/42819.Importación Masiva171174

340 years of atmospheric circulation characteristics reconstructed from an eastern Antarctic Peninsula ice core

Copyright @ 2006 American Geophysical Union (AGU)Precipitation delivery mechanisms for Dolleman Island (DI), located off the east coast of the Antarctic Peninsula, are investigated using reanalysis and back trajectory data. The Southern Annular Mode (SAM) and ENSO are both shown to influence precipitation delivery and event size. Precipitation delivery variability is compared against the interannual variation of chemical data from two DI ice cores. Nitrate concentration in the cores is strongly linked with the ratio of easterly to westerly back trajectories arriving at DI, as described by a Cross-Peninsula Index (CPI) defined in this paper. This CPI is used subsequently to reconstruct the atmospheric circulation characteristics for the 340-year ice core record. The analysis highlights a period of increased easterlies during 1720–1780 and an increase in westerlies for 1950–1980, the latter concomitant with a positive SAM trend and western Peninsula warming. The reconstruction also reveals periods when polynyas may have been present in the Weddell Sea

Measuring the Pressure in the Superficial Inferior Epigastric Vein to Monitor for Venous Congestion in Deep Inferior Epigastric Artery Perforator Breast Reconstructions: A Pilot Study

During deep inferior epigastric artery perforator (DIEP) flap dissection, we noted that in many cases the superficial vein on the ipsilateral side of the flap was engorged and tense, and in others, it was empty. This led us to believe that the pressure is increased as the result of preferential outflow through the superficial vein in some cases, which could result in venous congestion of the flap if this vessel was not anastomosed. To test this hypothesis, we measured the venous pressure in the superficial venous system before and after flap dissection. The pressure in the superficial inferior epigastic vein of a DIEP flap was measured in 26 consecutive flaps to investigate the correlation between the pressure and venous congestion of the flap. The first measurement was performed at the beginning of the dissection, and the second measurement was taken after the flap had been completely raised on a single perforator. The mean increase in pressure after flap dissection was 10.6 mm Hg (mu = 10.6; range -1 to 31; O +/- 7.0 mm Hg). Clinical signs of venous congestion were observed in one case. In this case, the increase in venous pressure was with 31 mm Hg, also the highest. Although the results of this report are preliminary, they indicate that the pressure in the superficial vein of DIEP flaps might be of predictive value for venous congestion

Cognitive Information Processing

Contains reports on four research projects.Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA28-043-AMC-02536(E)National Institutes of Health (Grant 1 PO1 GM-14940-01

Estimating oceanic primary production using vertical irradiance and chlorophyll profiles from ocean gliders in the North Atlantic

An autonomous underwater vehicle (Seaglider) has been used to estimate marine primary production (PP) using a combination of irradiance and fluorescence vertical profiles. This method provides estimates for depth-resolved and temporally evolving PP on fine spatial scales in the absence of ship-based calibrations. We describe techniques to correct for known issues associated with long autonomous deployments such as sensor calibration drift and fluorescence quenching. Comparisons were made between the Seaglider, stable isotope (13C), and satellite estimates of PP. The Seaglider-based PP estimates were comparable to both satellite estimates and stable isotope measurements

Ultracold-neutron infrastructure for the gravitational spectrometer GRANIT

The gravitational spectrometer GRANIT will be set up at the Institut Laue Langevin. It will profit from the high ultracold neutron density produced by a dedicated source. A monochromator made of crystals from graphite intercalated with potassium will provide a neutron beam with 0.89 nm incident on the source. The source employs superthermal conversion of cold neutrons in superfluid helium, in a vessel made from BeO ceramics with Be windows. A special extraction technique has been tested which feeds the spectrometer only with neutrons with a vertical velocity component v < 20 cm/s, thus keeping the density in the source high. This new source is expected to provide a density of up to 800 1/cm3 for the spectrometer.Comment: accepted for publication in Proceedings International Workshop on Particle Physics with Slow Neutron