Powersoh9970

The centre of the Milky Way hosts several high-energy processes that have strongly affected the inner regions of our Galaxy. Activity from the super-massive black hole at the Galactic Centre, which is coincident with the radio source Sagittarius A*, and stellar feedback from the inner molecular ring1 expel matter and energy from the disk in the form of a galactic wind2. Multiphase gas has been observed within this outflow, including hot highly ionized3,4 (temperatures of about 106 kelvin), warm ionized5,6 (104 to 105 kelvin) and cool atomic7,8 (103 to 104 kelvin) gas. However, so far there has been no evidence of the cold dense molecular phase (10 to 100 kelvin). Here we report observations of molecular gas outflowing from the centre of our Galaxy. This cold material is associated with atomic hydrogen clouds travelling in the nuclear wind8. The morphology and the kinematics of the molecular gas, resolved on a scale of about one parsec, indicate that these clouds are mixing with the warmer medium and are possibly being disrupted. The data also suggest that the mass of the molecular gas outflow is not negligible and could affect the rate of star formation in the central regions of the Galaxy. The presence of this cold, dense and high-velocity gas is puzzling, because neither Sagittarius A* at its current level of activity nor star formation in the inner Galaxy seems to be a viable source for this material.The rate of global-mean sea-level rise since 1900 has varied over time, but the contributing factors are still poorly understood1. Previous assessments found that the summed contributions of ice-mass loss, terrestrial water storage and thermal expansion of the ocean could not be reconciled with observed changes in global-mean sea level, implying that changes in sea level or some contributions to those changes were poorly constrained2,3. Recent improvements to observational data, our understanding of the main contributing processes to sea-level change and methods for estimating the individual contributions, mean another attempt at reconciliation is warranted. Here we present a probabilistic framework to reconstruct sea level since 1900 using independent observations and their inherent uncertainties. The sum of the contributions to sea-level change from thermal expansion of the ocean, ice-mass loss and changes in terrestrial water storage is consistent with the trends and multidecadal variability in observed sea level on both global and basin scales, which we reconstruct from tide-gauge records. Ice-mass loss-predominantly from glaciers-has caused twice as much sea-level rise since 1900 as has thermal expansion. Mass loss from glaciers and the Greenland Ice Sheet explains the high rates of global sea-level rise during the 1940s, while a sharp increase in water impoundment by artificial reservoirs is the main cause of the lower-than-average rates during the 1970s. The acceleration in sea-level rise since the 1970s is caused by the combination of thermal expansion of the ocean and increased ice-mass loss from Greenland. Our results reconcile the magnitude of observed global-mean sea-level rise since 1900 with estimates based on the underlying processes, implying that no additional processes are required to explain the observed changes in sea level since 1900.Owing to their ultralow thermal conductivity and open pore structure1-3, silica aerogels are widely used in thermal insulation4,5, catalysis6, physics7,8, environmental remediation6,9, optical devices10 and hypervelocity particle capture11. Thermal insulation is by far the largest market for silica aerogels, which are ideal materials when space is limited. One drawback of silica aerogels is their brittleness. read more Fibre reinforcement and binders can be used to overcome this for large-volume applications in building and industrial insulation5,12, but their poor machinability, combined with the difficulty of precisely casting small objects, limits the miniaturization potential of silica aerogels. Additive manufacturing provides an alternative route to miniaturization, but was "considered not feasible for silica aerogel"13. Here we present a direct ink writing protocol to create miniaturized silica aerogel objects from a slurry of silica aerogel powder in a dilute silica nanoparticle suspension (sol). The inks exhibit shear-thinning behaviour, owing to the high volume fraction of gel particles. As a result, they flow easily through the nozzle during printing, but their viscosity increases rapidly after printing, ensuring that the printed objects retain their shape. After printing, the silica sol is gelled in an ammonia atmosphere to enable subsequent processing into aerogels. The printed aerogel objects are pure silica and retain the high specific surface area (751 square metres per gram) and ultralow thermal conductivity (15.9 milliwatts per metre per kelvin) typical of silica aerogels. Furthermore, we demonstrate the ease with which functional nanoparticles can be incorporated. The printed silica aerogel objects can be used for thermal management, as miniaturized gas pumps and to degrade volatile organic compounds, illustrating the potential of our protocol.The liquid-liquid transition (LLT), in which a single-component liquid transforms into another one via a first-order phase transition, is an intriguing phenomenon that has changed our perception of the liquid state. LLTs have been predicted from computer simulations of water1,2, silicon3, carbon dioxide4, carbon5, hydrogen6 and nitrogen7. Experimental evidence has been found mostly in supercooled (that is, metastable) liquids such as Y2O3-Al2O3 mixtures8, water9 and other molecular liquids10-12. However, the LLT in supercooled liquids often occurs simultaneously with crystallization, making it difficult to separate the two phenomena13. A liquid-liquid critical point (LLCP), similar to the gas-liquid critical point, has been predicted at the end of the LLT line that separates the low- and high-density liquids in some cases, but has not yet been experimentally observed for any materials. This putative LLCP has been invoked to explain the thermodynamic anomalies of water1. Here we report combined in situ density, X-ray diffraction and Raman scattering measurements that provide direct evidence for a first-order LLT and an LLCP in sulfur.