Impact of Accurate Photolysis Calculations on the Simulation of Stratospheric Chemistry

The interpretation of atmospheric measurements and the forecasting of the atmospheric composition require a hierarchy of accurate chemical transport and global circulation models. Here, the results of studies using Bremens Atmospheric Photochemical Model (BRAPHO) are presented. The focus of this study is given to the calculation of the atmospheric photolysis frequencies It is shown that the spectral high resolved simulation of the O₂ Schumann–Runge bands leads to differences in the order of 10% in the calculated O₂ photolysis frequency when compared with parameterizations used in other atmospheric models. Detailed treatment of the NO absorption leads to even larger differences (in the order of 50%) compared to standard parameterizations. Refraction leads to a significant increase in the photolysis frequencies at large solar zenith angles and, under polar spring conditions, to a significant change in the nighttime mixing ratio of some trace gases, e.g., NO₃. It appears that recent changes in some important rate constants significantly alter the simulated BrO_x- and HO_x-budgets in the mid-latitude stratosphere.     

Noble gases in chondrules and associated metal‐sulfide‐rich samples: Clues on chondrule formation and the behavior of noble gas carrier phases

Abstract— Chondrules are generally believed to have lost most or all of their trapped noble gases during their formation. We tested this assumption by measuring He, Ne, and Ar in chondrules of the carbonaceous chondrites Allende (CV3), Leoville (CV3), Renazzo (CR2), and the ordinary chondrites Semarkona (LL3.0), Bishunpur (LL3.1), and Krymka (LL3.1). Additionally, metalsulfide‐rich chondrule coatings were measured that probably formed from chondrule metal. Low primordial ²⁰Ne concentrations are present in some chondrules, while even most of them contain small amounts of primordial ³⁶Ar. Our preferred interpretation is that‐in contrast to CAIs‐the heating of the chondrule precursor during chondrule formation was not intense enough to expel primordial noble gases quantitatively. Those chondrules containing both primordial ²⁰Ne and ³⁶Ar show low presolar‐diamond‐like ³⁶Ar/²⁰Ne ratios. In contrast, the metal‐sulfide‐rich coatings generally show higher gas concentrations and Q‐like ³⁶Ar/²⁰Ne ratios. We propose that during metalsilicate fractionation in the course of chondrule formation, the Ar‐carrying phase Q became enriched in the metal‐sulfide‐rich chondrule coatings. In the silicate chondrule interior, only the most stable Ne‐carrying presolar diamonds survived the melting event leading to the low observed ³⁶Ar/²⁰Ne ratios. The chondrules studied here do not show evidence for substantial amounts of fractionated solar‐type noble gases from a strong solar wind irradiation of the chondrule precursor material as postulated by others for the chondrules of an enstatite chondrite.     

Imaging very high energy gamma-ray telescopes

The technique of γ-ray astronomy at very high energies (VHE:>?100 GeV) with ground-based imaging atmospheric Cherenkov telescopes is described, the H.E.S.S. array in Namibia serving as example. Mainly a discussion of the physical principles of the atmospheric Cherenkov technique is given, emphasizing its rapid development during the last decade. The present status is illustrated by two examples: the spectral and morphological characterization in VHE γ-rays of a shell-type supernova remnant together with its theoretical interpretation, and the results of a survey of the Galactic Plane that shows a large variety of non-thermal sources. The final part is devoted to an overview of the ongoing and future instrumental developments.     

Zur Rekonstruktion des Paläoklimas aus dem mikrofaziellen bild Mesozoischer Flachwasserkalke

Zusammenfassung Ein Vergleich der Faziestypen oberjurassischer Flachwasserkalke aus dem Ostpontischen Gebirge (NE-Türkei) mit den rezenten Karbonatsedimenten auf der Gro\en Bahama-Bank zeigt im wesentlichen Punkten übereinstimmung: Es treten die gleichen biomorphen und heteromorphen Sedimentkomponenten auf. Unter den Biogenen überwiegen die Kalkalgen und Foraminiferen (Milioliden). Es fehlen pelagische Faunenelemente. Die Faziestypen sind wie auf der Gro\en Bahama-Bank angeordnet: an den Rändern der Plattform gut sortierte Calcarenite und im Inneren der Plattform schlecht sortierte Schlickfazies.Die daraus zu folgernden gemeinsamen, klimaabhängigen Sedimentationsbedingungen beziehen sich auf Wasserströmung, Wassertemperatur und physikalisch-chemische Bedingungen. Somit gibt das mikrofazielle Bild einer Faziesgemeinschaft, wie sie für die Gro\e Bahama-Bank kennzeichnend ist, einen Hinweis auf tropisches Klima, Gezeitenströmung und Windbewegung.

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Comparing the facies of the upper Jurassic limestones in the Eastern Pontian Mountain Range (NE-Turkey) and the recent carbonate sediments on the Bahama Banks we can see a conformity in the main features of the sediments: there are the same biomorphous and heteromorphous components; calcareous algae and foraminifera prevail among the skeletal components. Within the fauna there are no pelagic elements. The distribution of the facies corresponds with the recent example on the Great Bahama Bank: on the border of the platform we find well sorted calcarenites and to the central part of the platform the unsorted mud facies follows. These common features both in the recent sediments and in the ancient sediments show us the common conditions of sedimentation depending on the climate: the movement and temperature of the sea water and the physical and chemical conditions of sedimentation. Therefore studying the microfacies of shallow water limestones we can get a detailed knowledge about the climate of the past.

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Résumé Une comparaison des faciès des calcaires d'eau peu profonde du Jurassique supérieur, qui viennent de la région de la mer Noire (NE-Turquie), avec des sédiments carbonates actuels dans le Banc Grand des Bahamas corresponde en substance: on y trouve les mÊmes elements sédimentaires biomorphes et héteromorphes; les Algues calcaires et les Foraminifères (Miliolidae) prédominent parmi les organismes; ils manquent des éléments faunistiques pélagiques. La disposition des faciès corresponde à l'exemple actuel du Banc Grand des Bahamas: des calcarenites bien classifiés se trouvent aux bords du banc suivit dans le centre du banc d'un faciès boue plus mal classifié. Les conditions sédimentaires communes et climatiques conclurent du précédent, se rapportent à la température de mer, le courant de mer et les conditions sédimentaires physiques-chimiques. Par conséquent le microfaciès d'un communauté de faciès, comparable avec les sédiments actuels du Banc Grand des Bahamas, indique un climat tropique, le courant de marée et le courant de mer influencé par le vent, qui existent pendant la sédimentation de ces calcaires d'eau peu profonde.

     

On the construction of a comprehensive general catalogue of star positions

The procedures that would lead to the construction of a comprehensive general catalogue of star positions are outlined and discussed. Attention is drawn to the problems faced by a definitive reduction of the Astrographic Catalogue. The importance and necessity of the repetition of the original work in this connection are stressed. This would provide at present—barring the development of revolutionary new and fast techniques—the only chance for the very desirable wholesale computation of the proper motions of all stars down to about 13 ^m .Presented at the Symposium Star Catalogues, Positional Astronomy and Celestial Mechanics, held in honor of Paul Herget at the U.S. Naval Observatory, Washington, November 30, 1978.     

The effectiveness of bycatch reduction devices on crab pots at reducing capture and mortality of diamondback terrapins (Malaclemys terrapin) in Florida

Diamondback terrapins (Malaclemys terrapin) drown in blue crab (Callinectes sapidus) pots throughout their range. The objectives of this study were to test if bycatch mortality of diamondback terrapins in commercial crab pots is reduced by using bycatch reduction devices (BRDs) and to determine if BRDs affect crab catch in Florida by comparing sex, size, and number of blue crabs captured in standard crab pots with those captured in pots equipped with BRDs. We fished 15 standard crab pots (controls) and 15 crab pots with bycatch reduction devices (experimentals) for 10-d periods at two sites per year from 2002 through 2005. Study sites were located in eight Florida counties with one sample period per county. Pots were checked daily and baited on alternate days. We determined sex and size of captured terrapins and blue crabs to evaluate if BRDs affected the size of either species. Thirty-seven terrapins were caught in control pots and four in experimentals. Eleven terrapins were small enough that they would not have been prevented from entering either pot treatment, but we found that 73.2% of the terrapins in this study could have been prevented from entering crab pots with functional BRDs. There were no significant differences between the sex, measurements, or number of legal-sized crabs captured in control and experimental pots at any of the study sites. We recommend that the Florida Fish and Wildlife Conservation Commission devise and adopt regulations that require the use of 4.5×12 cm BRDs on all commercial and recreational crab pots in Florida without delay.     

Über den Bleigehalt des Kaolins von Hirschau-Sehnaittenbaeh und die Bleierzlagerstätte von Freihung in der Oberpfalz

Zusammenfassung Der Bleigehalt des Hirschau-Schnaittenbacher Kaolins (ca. 0.1% Pb) wird aus dem Entstehungszyklus der kaohnhaltigen Buntsandstein-Arkosen hergeleitet. Die Bleierzlagerstätte von Freihung kann als örtliche Konzentration des Bleigehaltes der Trias-Arkosen gedeutet werden.Herrn Professor Dr. Dr. h. c.C. W. Correns zum 70. Geburtstag gewidmet.     

Rigorous computation of proper motions and their effects on star positions

New rigorous formulas are given for the computation of the effects of proper motions and radial velocities on star positions, and for the transformation of proper motion components and radial velocities from one epoch to another. These expressions depend explicitly only on the values of the star's coordinates and distance, proper motion components and radial velocity, at the initial epoch.