Have Superheavy Elements been Produced in Nature?

We discuss the possibility whether superheavy elements can be produced in Nature by the astrophysical rapid neutron capture process. To this end we have performed fully dynamical network r-process calculations assuming an environment with neutron-to-seed ratio large enough to produce superheavy nuclei. Our calculations include two sets of nuclear masses and fission barriers and include all possible fission channels and the associated fission yield distributions. Our calculations produce superheavy nuclei with A ~ 300 that however decay on timescales of days.Comment: 12 pages, 11 figure

A hot mini-Neptune in the radius valley orbiting solar analogue HD 110113

We report the discovery of HD 110113 b (TESS object of interest-755.01), a transiting mini-Neptune exoplanet on a 2.5-d orbit around the solar-analogue HD 110113 (Teff = 5730 K). Using TESS photometry and High Accuracy Radial velocity Planet Searcher (HARPS) radial velocities gathered by the NCORES program, we find that HD 110113 b has a radius of 2.05 ± 0.12 R⊕ and a mass of 4.55 ± 0.62 M⊕. The resulting density of $2.90^{+0.75}_{-0.59}$ g cm-3 is significantly lower than would be expected from a pure-rock world; therefore HD 110113 b must be a mini-Neptune with a significant volatile atmosphere. The high incident flux places it within the so-called radius valley; however, HD 110113 b was able to hold on to a substantial (0.1-1 per cent) H-He atmosphere over its ∼4 Gyr lifetime. Through a novel simultaneous Gaussian process fit to multiple activity indicators, we were also able to fit for the strong stellar rotation signal with period 20.8 ± 1.2 d from the RVs and confirm an additional non-transiting planet, HD 110113 c, which has a mass of 10.5 ± 1.2 M⊕ and a period of $6.744^{+0.008}_{-0.009}$ d

Mass determinations of the three mini-Neptunes transiting TOI-125

Stars and planetary system

TOI-431/HIP 26013: a super-Earth and a sub-Neptune transiting a bright, early K dwarf, with a third RV planet

Stars and planetary system

TOI-431/HIP 26013: A super-Earth and a sub-Neptune transiting a bright, early K dwarf, with a third RV planet

We present the bright (Vmag = 9.12), multiplanet system TOI-431, characterized with photometry and radial velocities (RVs). We estimate the stellar rotation period to be 30.5 ± 0.7 d using archival photometry and RVs. Transiting Exoplanet Survey Satellite (TESS) objects of Interest (TOI)-431 b is a super-Earth with a period of 0.49 d, a radius of 1.28 ± 0.04 R, a mass of 3.07 ± 0.35 M, and a density of 8.0 ± 1.0 g cm-3; TOI-431 d is a sub-Neptune with a period of 12.46 d, a radius of 3.29 ± 0.09 R, a mass of 9.90+1.53-1.49 M, and a density of 1.36 ± 0.25 g cm-3. We find a third planet, TOI-431 c, in the High Accuracy Radial velocity Planet Searcher RV data, but it is not seen to transit in the TESS light curves. It has an Msin i of 2.83+0.41-0.34 M, and a period of 4.85 d. TOI-431 d likely has an extended atmosphere and is one of the most well-suited TESS discoveries for atmospheric characterization, while the super-Earth TOI-431 b may be a stripped core. These planets straddle the radius gap, presenting an interesting case-study for atmospheric evolution, and TOI-431 b is a prime TESS discovery for the study of rocky planet phase curves

Validierung von Reaktionsmechanismen fuer die Gasphasenchemie der Troposphaere Abschlussbericht

A reaction mechanism calculated for the troposphere ist validated by comparison of field measurements and model calculations. The first step in this comparison concerns OH, a reactive and therefore short-lived molecule that is considered a key substance in the atmosphere. Comparison with ground-level measurements show that the model calculations overestimate atmospheric OH concentrations on average by 15 to 20%. This error propagates into the calculation of atmospheric CO and hydrocarbon decomposition rates. The first and rate-determining step in the decomposition of these substances is their reaction with OH. This similarly applies also to the formation of HNO_3 and H_2SO_4, which make a substantial contribution to anthropogenic acid production. (EF)Die Validierung eines Reaktionsmechanismus der Troposphaere wird durch Vergleich von Feldmessungen und Modellrechnungen durchgefuehrt. Der erste Schritt geschieht durch Vergleich fuer eine der wichtigsten Schluesselsubstanzen in der Atmosphaere, das reaktive und darum kurzlebige OH. Vergleiche mit Messungen in Bodennaehe, zeigen, dass die Modellrechnungen die atmosphaerische OH-Konzentration im Mittel um 15-20% ueberschaetzen. Dieser Fehler geht direkt in die Berechnung der atmosphaerischen Abbaurate von CO und der Kohlenwasserstoffe ein. Erster und geschwindigkeitsbestimmender Schritt des Abbaus ist die Reaktion mit OH. Aehnliches gilt fuer die Bildung von NO_3 und H_2SO_4, die einen erheblichen Beitrag zu anthropogen verursachten Saeureproduktion liefern. (EF)Available from TIB Hannover: F95B507+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Implementierung und Validierung der Gasphasenchemie von Isopren und seiner Abbauprodukte Abschlussbericht

Biogenic sources of hydrocarbons are a substantial contribution to the total emission of volatile organic compounds into the atmosphere. The most important single compound is isoprene, which is mostly emitted from deciduous trees with a source strength, that depends on the biologically active solar radiation and the ambient temperature. Due to its high reactivity the degradation contributes significantly to the oxidant formation during summer smog events in rural areas downwind of industrialized sites. Implementation of the tropospheric isoprene degradation in numerical chemistry and transport models is therefore necessary to assess and predict that influence correctly. We have compiled a reaction scheme that is based on the RADM2 gas-phase chemistry and that incorporates the reactions of isopreneand its degradation products from recent lab-kinetic data. Comparison of model calculations with field data from a summer smog event demonstrate good agreement for the diurnal cyles of ozone, formaldeyde, higher aldehydes, PAN, and peroxides. Small discrepancies are likely to be the result of hydrocarbons like terpenes that were not taken into account. (orig.)Biogene Quellen gasfoermiger Kohlenwasserstoffe tragen erheblich zur Gesamtemission von fluechtigen organischen Verbindungen in der Atmosphaere bei. Die wichtigste einzelne Substanz ist Isopren, das von Laubbaeumen abgegeben wird mit einer Quellstaerke, die von der biologisch aktiven Strahlung und der Temperatur abhaengt. Aufgrund seiner hohen Reaktivitaet traegt der Isoprenabbau zur Bildung von Photooxidantien in der laendlichen Umgebung von Ballungszentren waehrend Sommersmogereignissen erheblich bei. Wir haben einen Reaktionsmechanismus zusammengestellt, der auf der RADM2-Gasphasenchemie aufbaut und den Abbau von Isopren nach neuen laborkinetischen Daten enthaelt. Vergleiche von Modellrechnungen mit Feldmessungen fuer Ozon, Formaldehyd, hoehre Aldehyde, PAN und den Perioxiden zeigen gute Uebereinstimmung. Kleinere Diskrepanzen koennen auf die nicht beruecksichtigten Einfluesse von hoeheren Kohlenwasserstoffen wie den Terpenen zurueckgefuehrt werden. (orig.)Available from TIB Hannover: F97B239+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Measurements of atmospheric trace gas concentrations during the field campaign in Juelich 1988

Our current understanding of the gas phase chemistry of the lower troposphere is based on measurements of trace gas concentrations in the atmosphere, laboratory studies of gas phase reactions and model calculations of the relevant chemical processes. The ultimate validation of a reaction scheme can only be derived from a comparison of model results with experimental data from measurements in the atmosphere. In order to establish an extended and reliable experimental data set on which such a comparison could be based the Institut fuer Atmosphaerische Chemie of the Forschungszentrum Juelich (KFA) has been conducting field campaigns for a number of years. One such campaign took place in Juelich from May 9 - June 10 in 1988. Many of the relevant trace species were measured on a continuous basis together with photolysis frequencies and meteorological parameters. All measurements were ground based and included OH, O_3, NO, and NO_2, NO_y, HCHO, SO_2, CH_4, CO, non methane hydrocarbons up to C_5, peroxyacetylnitrate, and aldehydes. The photolysis frequencies of O_3 and NO_2 were also monitored, as were atmospheric temperature, relative humidity, wind speed, and wind direction. All quantities were measured in-situ except OH and SO_2, which were exclusively measured by a long path differential optical absorption technique. HCHO, NO_2, and O_3 were determined by in-situ and also by long-path-absorption methods for intercomparison. (orig./EF)SIGLEAvailable from TIB Hannover: RA 831(2731) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

A Comparison of Measured OH Concentrations with Model Calculations

The influence of chemical precursors and sunlight on the atmospheric OH abundance is investigated by a comparison of locally measured tropospheric OH with model calculations. The latter are based on the gas phase reaction mechanism of the regional acid deposition model (RADM2) which incorporates an explicit inorganic and a comprehensive organic chemistry. The experimental data were obtained in the planetary boundary layer during two sets of campaigns. In Deuselbach (1983) and Schauinsland (1984), rural conditions were encountered with NO x concentrations on the average of 2.2 and 0.9 ppb, respectively. This data set was already compared with model calculations based upon an older and less detailed chemical reaction scheme (Perner et al., 1987). Since then the experimental data were reanalyzed leading to modified measured OH concentrations and also to modified precursor concentrations. For a consistent comparison with the more recent campaigns in Jülich (1987 and 1988) we have redone the calculations. The modeled and measured OH concentrations of the campaigns in 1983 and 1984 correlate well with a coefficient of correlation of r = 0.73. The model overpredicts OH by about 20%. Under more polluted conditions in Jülich with average NO x concentrations of 4 ppb the correlation coefficient between experimental and modeled data are significantly smaller (r = 0.61). Possible reasons are the influence of not measured precursors, for example isoprene, and the inapplicability of a quasi‐steady state model under the spatially inhomogeneous conditions in Jülich. Again the model overpredicts the OH concentration by about 15%, which is somewhat smaller than for the rural case. The precision of the comparison is limited by the uncertainties of the chemical reaction rate constants

Measuring atmospheric composition change

Scientific findings from the last decades have clearly highlighted the need for a more comprehensive approach to atmospheric change processes. In fact, observation of atmospheric composition variables has been an important activity of atmospheric research that has developed instrumental tools (advanced analytical techniques) and platforms (instrumented passenger aircrafts, ground-based in situ and remote sensing stations, earth observation satellite instruments) providing essential information on the composition of the atmosphere. The variability of the atmospheric system and the extreme complexity of the atmospheric cycles for short-lived gaseous and aerosol species have led to the development of complex models to interpret observations, test our theoretical understanding of atmospheric chemistry and predict future atmospheric composition. The validation of numerical models requires accurate information concerning the variability of atmospheric composition for targeted species via comparison with observations and measurements. In this paper, we provide an overview of recent advances in instrumentation and methodologies for measuring atmospheric composition changes from space, aircraft and the surface as well as recent improvements in laboratory techniques that permitted scientific advance in the field of atmospheric chemistry. Emphasis is given to the most promising and innovative technologies that will become operational in the near future to improve knowledge of atmospheric composition. Our current observation capacity, however, is not satisfactory to understand and predict future atmospheric composition changes, in relation to predicted climate warming. Based on the limitation of the current European observing system, we address the major gaps in a second part of the paper to explain why further developments in current observation strategies are still needed to strengthen and optimise an observing system not only capable of responding to the requirements of atmospheric services but also to newly open scientific questions. © 2009 Elsevier Ltd. All rights reserved.SCOPUS: re.jinfo:eu-repo/semantics/publishe