Nacre tablet thickness records formation temperature in modern and fossil shells

Nacre, the iridescent outer lining of pearls and inner lining of many mollusk shells, is composed of periodic, parallel, organic sheets alternating with aragonite (CaCO_3) tablet layers. Nacre tablet thickness (TT) generates both nacre's iridescence and its remarkable resistance to fracture. Despite extensive studies on how nacre forms, the mechanisms controlling TT remain unknown, even though they determine the most conspicuous of nacre's characteristics, visible even to the naked eye. Thermodynamics predicts that temperature (T) will affect both physical and chemical components of biomineralized skeletons. The chemical composition of biominerals is well-established to record environmental parameters, and has therefore been extensively used in paleoclimate studies. The physical structure, however, has been hypothesized but never directly demonstrated to depend on the environment. Here we observe that the physical TT in nacre from modern and fossil shallow-water shells of the bivalves Pinna and Atrina correlates with T as measured by the carbonate clumped isotope thermometer. Based on the observed TT vs. T correlation, we anticipate that TT will be used as a paleothermometer, useful to estimate paleotemperature in shallow-water paleoenvironments. Here we successfully test the proposed new nacre TT thermometer on two Jurassic Pinna shells. The increase of TT with T is consistent with greater aragonite growth rate at higher T, and with greater metabolic rate at higher T. Thus, it reveals a complex, T-dependent biophysical mechanism for nacre formation

Systematic Computational and Experimental Investigation of Lithium-Ion Transport Mechanisms in Polyester-Based Polymer Electrolytes

Understanding the mechanisms of lithium-ion transport in polymers is crucial for the design of polymer electrolytes. We combine modular synthesis, electrochemical characterization, and molecular simulation to investigate lithium-ion transport in a new family of polyester-based polymers and in poly(ethylene oxide) (PEO). Theoretical predictions of glass-transition temperatures and ionic conductivities in the polymers agree well with experimental measurements. Interestingly, both the experiments and simulations indicate that the ionic conductivity of PEO, relative to the polyesters, is far higher than would be expected from its relative glass-transition temperature. The simulations reveal that diffusion of the lithium cations in the polyesters proceeds via a different mechanism than in PEO, and analysis of the distribution of available cation solvation sites in the various polymers provides a novel and intuitive way to explain the experimentally observed ionic conductivities. This work provides a platform for the evaluation and prediction of ionic conductivities in polymer electrolyte materials

Bestimmung des anthropogenen und natuerlichen Anteils am Ozon im Mitteleuropaeischen Raum aus meteorologischer Sicht. Ein Beitrag zu dem EUROTRAC Unterprojekt TOR Abschlussbericht

To evaluate the question, to which extent tropospheric ozone is of natural (stratospheric) origin, measurements of ozone were interpreted with the aid of metereological data. Our research focused on the mechanisms in connection with cold front passages and the impact of stratospheric ozone. The effect of cold front passages on the near-ground ozone concentration was analysed for six ground-based stations in Germany during the years 1990, 1991 and 1992. Much of the ozone transport from the lowermost stratosphere into the troposphere at mid-latitudes is believed to occur in connection with tropopause fold events. An algorithm has been developed to determine the occurence of tropopause folds by an analysis of ozone soundings together with meterological parameters. In agreement with the large number of cold fronts and strong storms in 1990 the number of folds increased. The ozone flux from the stratosphere to the troposphere over Central Europe caused by tropopause folds are on average 2 to 15x10"1"0 molecules cm"-"2 s"-"1. (orig./KW)Um einen Beitrag zur Beantwortung der Frage zu liefern, welcher Anteil des troposphaerischen Ozons stratosphaerischen Ursprungs ist, wurden Ozonmessungen mit Hilfe rein meteorologischer Daten interpretiert. Dabei konzentrierten wir uns auf die Mechanismen in Zusammenhang mit Kaltfrontdurchgaengen und dem Eintrag von stratosphaerischem Ozon. Die Auswirkung von Kaltfrontdurchgaengen auf die bodennahe Ozonkonzentration wurde an sechs Stationen in Deutschland fuer die Jahre 1990, 1991 und 1992 untersucht. Ein grosser Teil des Ozontransportes aus der unteren Stratosphaere in die Troposphaere erfolgt in den mittleren Breiten durch Tropopausenfaltungen. Diese sind durch eine Schicht erhoehter Ozonkonzentrationen, geringer Feuchtewerte und hoher Werte der potentiellen Vorticity in der Troposphaere erkennbar, zusaetzlich durch hohe Windstaerken, die die Naehe des Jets anzeigen. Darauf aufbauend wurde ein Algorithmus entwickelt, der unter Verwendung von vertikalen Ozonsondierungen und meterologischer Daten, Faltungen auffindet. In Uebereinstimmung mit der erhoehten Anzahl von Kaltfronten und kraeftigen Stuermen fanden sich im Jahr 1990 auch deutlich mehr Faltungen als in den uebrigen Jahren. (orig./KW)SIGLEAvailable from TIB Hannover: F96B2033+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Meteorologische Interpretation von Ozon-Messungen. Ein Beitrag zu dem EUROTRAC Unterprojekt TOR Abschlussbericht ueber die wissenschaftlichen Ergebnisse 1990-1994

To evaluate the question, to which extent tropospheric ozone is of natural origin or anthropogenic produced, measruements of ozone were interpreted with the aid of meteorological data. This research focuses on the mechanism in connection with cold front passages, the advection of air masses enriched with pollutants, and the impact of stratospheric ozone. Within a statistical study the long range transport of VOC emissions and their influence on ground-based ozone concentrations were analysed for 11 stations during 1990 using a simple model based on the calculations of trajectories coupled with an emission inventory for VOC. The part of the ozone concentration produced by pollutants long-range transferred to the stations were estimated by regression calculations. The mean flow of air masses over Europe has a large eastward component up to 70% which partly explains the increasing ozone concentrations from Northwest to Southeast Europe. Emission sources in the west of stations are responsible for 20-50% of long-range transported pollution. The analysis of the influence of long-range transported pollutants on ozone suggests that the ozone budget is more controlled by the variability of radiation than by that of longe-range transported VOC emissions. (orig./KW)SIGLEAvailable from TIB Hannover: F95B2306+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman