University of Cologne

About: University of Cologne is a education organization based out in Cologne, Germany. It is known for research contribution in the topics: Population & Gene. The organization has 32050 authors who have published 66350 publications receiving 2210092 citations. The organization is also known as: Universität zu Köln & Universitatis Coloniensis.

Growth of graphene on Ir(111)

Abstract: Catalytic decomposition of hydrocarbons on transition metals attracts a renewed interest as a route toward high-quality graphene prepared in a reproducible manner. Here we employ two growth methods for graphene on Ir(111), namely room temperature adsorption and thermal decomposition at 870–1470 K (temperature programmed growth (TPG)) as well as direct exposure of the hot substrate at 870–1320 K (chemical vapor deposition (CVD)). The temperature- and exposure-dependent growth of graphene is investigated in detail by scanning tunneling microscopy. TPG is found to yield compact graphene islands bounded by C zigzag edges. The island size may be tuned from a few to a couple of tens of nanometers through Smoluchowski ripening. In the CVD growth, the carbon in ethene molecules arriving on the Ir surface is found to convert with probability near unity to graphene. The temperature-dependent nucleation, interaction with steps and coalescence of graphene islands are analyzed and a consistent model for CVD growth is developed.

Regional Differences in Current Density and Rate-Dependent Properties of the Transient Outward Current in Subepicardial and Subendocardial Myocytes of Human Left Ventricle

Abstract: Background Recordings of outward currents in human ventricular myocytes revealed the presence of a large calcium-insensitive transient outward current. This current has been suggested to contribute significantly to regional electrophysiological heterogeneity in myocardial cells and tissue of several animal species and to cause electrical gradients across the ventricular wall. Methods and Results The patch-clamp technique was used to record action potentials and outward currents in myocytes enzymatically isolated from thin subepicardial and subendocardial layers of human nonfailing and failing left ventricle. In all subepicardial cells studied, a calcium-insensitive transient outward current (Ito1) could be recorded with large density (10.6±1.08 pA/pF at 40 mV), whereas current density of Ito1 in subendocardial cells was fourfold smaller (2.63±0.31 pA/pF, P<.0001, nonfailing myocardium). In failing hearts, the density of Ito1 was significantly smaller in subepicardial cells (7.81±0.53 pA/pF, P=.012) but no...

Molecular line emission in NGC 1068 imaged with ALMA: I. An AGN-driven outflow in the dense molecular gas

Abstract: Aims. We investigate the fueling and the feedback of star formation and nuclear activity in NGC 1068, a nearby (D = 14 Mpc) Seyfert 2 barred galaxy, by analyzing the distribution and kinematics of the molecular gas in the disk. We aim to understand if and how gas accretion can self-regulate.Methods. We have used the Atacama Large Millimeter Array (ALMA) to map the emission of a set of dense molecular gas (n(H2) ' 1056 cm3) tracers (CO(3-2), CO(6-5), HCN(4-3), HCO+(4-3), and CS(7-6)) and their underlying continuum emission in the central r ∼ 2 kpc of NGC 1068 with spatial resolutions ∼0:3000:500 (∼20-35 pc for the assumed distance of D = 14 Mpc). Results. The sensitivity and spatial resolution of ALMA give an unprecedented detailed view of the distribution and kinematics of the dense molecular gas (n(H2) ≈ 1056cm3) in NGC 1068. Molecular line and dust continuum emissions are detected from a r ∼ 200 pc off-centered circumnuclear disk (CND), from the 2.6 kpc-diameter bar region, and from the r ∼ 1:3 kpc starburst (SB) ring. Most of the emission in HCO+, HCN, and CS stems from the CND. Molecular line ratios show dramatic order-of-magnitude changes inside the CND that are correlated with the UV/X-ray illumination by the active galactic nucleus (AGN), betraying ongoing feedback. We used the dust continuum fluxes measured by ALMA together with NIR/MIR data to constrain the properties of the putative torus using CLUMPY models and found a torus radius of 20+6 10 pc. The Fourier decomposition of the gas velocity field indicates that rotation is perturbed by an inward radial flow in the SB ring and the bar region. However, the gas kinematics from r ∼ 50 pc out to r ∼ 400 pc reveal a massive (Mmol ∼ 2:7+0:9 1:2 × 107 M) outflow in all molecular tracers. The tight correlation between the ionized gas outflow, the radio jet, and the occurrence of outward motions in the disk suggests that the outflow is AGN driven. Conclusions. The molecular outflow is likely launched when the ionization cone of the narrow line region sweeps the nuclear disk. The outflow rate estimated in the CND, dM=dt ∼ 63+21 37 M yr1, is an order of magnitude higher than the star formation rate at these radii, confirming that the outflow is AGN driven. The power of the AGN is able to account for the estimated momentum and kinetic luminosity of the outflow. The CND mass load rate of the CND outflow implies a very short gas depletion timescale of ≤1 Myr. The CND gas reservoir is likely replenished on longer timescales by efficient gas inflow from the outer disk. © ESO 2014.