1,032 research outputs found
The upper-atmosphere extension of the ICON general circulation model (version: Ua-icon-1.0)
How the upper-atmosphere branch of the circulation contributes to and interacts with the circulation of the middle and lower atmosphere is a research area with many open questions. Inertia-gravity waves, for instance, have moved in the focus of research as they are suspected to be key features in driving and shaping the circulation. Numerical atmospheric models are an important pillar for this research. We use the ICOsahedral Non-hydrostatic (ICON) general circulation model, which is a joint development of the Max Planck Institute for Meteorology (MPI-M) and the German Weather Service (DWD), and provides, e.g., local mass conservation, a flexible grid nesting option, and a non-hydrostatic dynamical core formulated on an icosahedral-triangular grid. We extended ICON to the upper atmosphere and present here the two main components of this new configuration named UA-ICON: an extension of the dynamical core from shallow- to deep-atmosphere dynamics and the implementation of an upper-atmosphere physics package. A series of idealized test cases and climatological simulations is performed in order to evaluate the upper-atmosphere extension of ICON. © Author(s) 2019
Viewpoint: filovirus haemorrhagic fever outbreaks: much ado about nothing?
The recent outbreak of Marburg haemorrhagic fever in the Democratic Republic of Congo has put the filovirus threat back on the international health agenda. This paper gives an overview of Marburg and Ebola outbreaks so far observed and puts them in a public health perspective. Damage on the local level has been devastating at times, but was marginal on the international level despite the considerable media attention these outbreaks received. The potential hazard of outbreaks, however, after export of filovirus from its natural environment into metropolitan areas, is argued to be considerable. Some avenues for future research and intervention are explored. Beyond the obvious need to find the reservoir and study the natural history, public health strategies for a more timely and efficient response are urgently needed
Measurement of the charged pion mass using X-ray spectroscopy of exotic atoms
The transitions in pionic nitrogen and muonic oxygen were measured
simultaneously by using a gaseous nitrogen-oxygen mixture at 1.4\,bar. Due to
the precise knowledge of the muon mass the muonic line provides the energy
calibration for the pionic transition. A value of
(139.57077\,\,0.00018)\,MeV/c (\,1.3ppm) is derived for the
mass of the negatively charged pion, which is 4.2ppm larger than the present
world average
Nuclear effects in atomic transitions
Atomic electrons are sensitive to the properties of the nucleus they are
bound to, such as nuclear mass, charge distribution, spin, magnetization
distribution, or even excited level scheme. These nuclear parameters are
reflected in the atomic transition energies. A very precise determination of
atomic spectra may thus reveal information about the nucleus, otherwise hardly
accessible via nuclear physics experiments. This work reviews theoretical and
experimental aspects of the nuclear effects that can be identified in atomic
structure data. An introduction to the theory of isotope shifts and hyperfine
splitting of atomic spectra is given, together with an overview of the typical
experimental techniques used in high-precision atomic spectroscopy. More exotic
effects at the borderline between atomic and nuclear physics, such as parity
violation in atomic transitions due to the weak interaction, or nuclear
polarization and nuclear excitation by electron capture, are also addressed.Comment: review article, 53 pages, 14 figure
Modulating the polarization of broadband terahertz pulses from a spintronic emitter at rates up to 10 kHz
Reliable modulation of terahertz electromagnetic waveforms is important for many applications. Here, we rapidly modulate the direction of the electric field of linearly polarized terahertz electromagnetic pulses with 1â30 THz bandwidth by applying time-dependent magnetic fields to a spintronic terahertz emitter. Polarity modulation of the terahertz field with more than 99% contrast at a rate of 10 kHz is achieved using a harmonic magnetic field. By adding a static magnetic field, we modulate the direction of the terahertz field between angles of, for instance, â53° and 53° at kilohertz rates. We believe our approach makes spintronic terahertz emitters a promising source for low-noise modulation spectroscopy and polarization-sensitive techniques such as ellipsometry at 1â30 THz
Marburg hemorrhagic fever in Durba and Watsa, Democratic Republic of the Congo: clinical documentation, features of illness, and treatment
The objective of the present study was to describe day of onset and duration of symptoms of Marburg hemorrhagic fever (MHF), to summarize the treatments applied, and to assess the quality of clinical documentation. Surveillance and clinical records of 77 patients with MHF cases were reviewed. Initial symptoms included fever, headache, general pain, nausea, vomiting, and anorexia (median day of onset, day 1-2), followed by hemorrhagic manifestations (day 5-8+), and terminal symptoms included confusion, agitation, coma, anuria, and shock. Treatment in isolation wards was acceptable, but the quality of clinical documentation was unsatisfactory. Improved clinical documentation is necessary for a basic evaluation of supportive treatment
Deciphering a Marine Bone-Degrading Microbiome Reveals a Complex Community Effort
The marine bone biome is a complex assemblage of macro- and microorganisms; however, the enzymatic repertoire to access bone-derived nutrients remains unknown. The bone matrix is a composite material made up mainly of organic collagen and inorganic hydroxyapatite. We conducted field experiments to study microbial assemblages that can use organic bone components as nutrient source. Bovine and turkey bones were deposited at 69 m depth in a Norwegian fjord (Byfjorden, Bergen). Metagenomic sequence analysis was used to assess the functional potential of microbial assemblages from bone surface and the bone-eating worm Osedax mucofloris, which is a frequent colonizer of whale falls and known to degrade bone. The bone microbiome displayed a surprising taxonomic diversity revealed by the examination of 59 high-quality metagenome-assembled genomes from at least 23 bacterial families. Over 700 genes encoding enzymes from 12 relevant enzymatic families pertaining to collagenases, peptidases, and glycosidases putatively involved in bone degradation were identified. Metagenome-assembled genomes (MAGs) of the class Bacteroidia contained the most diverse gene repertoires. We postulate that demineralization of inorganic bone components is achieved by a timely succession of a closed sulfur biogeochemical cycle between sulfur-oxidizing and sulfur-reducing bacteria, causing a drop in pH and subsequent enzymatic processing of organic components in the bone surface communities. An unusually large and novel collagen utilization gene cluster was retrieved from one genome belonging to the gammaproteobacterial genus Colwellia
Adsorption and reaction of CO on (Pdâ)Al2O3 and (Pdâ)ZrO2: vibrational spectroscopy of carbonate formation
Îł-Alumina is widely used as an oxide support in catalysis, and palladium nanoparticles supported by alumina represent one of the most frequently used dispersed metals. The surface sites of the catalysts are often probed via FTIR spectroscopy upon CO adsorption, which may result in the formation of surface carbonate species. We have examined this process in detail utilizing FTIR to monitor carbonate formation on Îł-alumina and zirconia upon exposure to isotopically labelled and unlabelled CO and CO2. The same was carried out for well-defined Pd nanoparticles supported on Al2O3 or ZrO2. A water gas shift reaction of CO with surface hydroxyls was detected, which requires surface defect sites and adjacent OH groups. Furthermore, we have studied the effect of Cl synthesis residues, leading to strongly reduced carbonate formation and changes in the OH region (isolated OH groups were partly replaced or were even absent). To corroborate this finding, samples were deliberately poisoned with Cl to an extent comparable to that of synthesis residues, as confirmed by Auger electron spectroscopy. For catalysts prepared from Cl-containing precursors a new CO band at 2164 cmâ1 was observed in the carbonyl region, which was ascribed to Pd interacting with Cl. Finally, the FTIR measurements were complemented by quantification of the amount of carbonates formed via chemisorption, which provides a tool to determine the concentration of reactive defect sites on the alumina surface
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