A Discussion of IGS Solutions and Their Impact on Geodetic and Geophysical Applications

The International Association of Geodesy officially established the International GPS Service (IGS) on Janaury 1, 1994. Its prime objective is to provide support and a rerefence system for a wide variety of scientific and practical applications involving GPS. To fulfill its role the IGS also generates, in addition to its fundamental products (orbital/staion positions and consistent Earth orientation parameters), additional reference-system products providing the necessary infrastructure, standards, and means of calibrations for timing and various atmospheric applications of GPS. The generation and efficient application of IGS products and their impact on a number of positioning and atmospheric applications, including low earth orbit satellites, is reviewed and discussed. @ 1998 John Wiley & Sons, Inc.     

The Bayesian approach to an internally consistent thermodynamic database: theory, database, and generation of phase diagrams

An internally consistent thermodynamic dataset has been derived for 148 endmember phases (145 solids and 3 fluids) comprising the elements Li, Na, K, Be, Mg, Ca, Ti, Cr, Mn, Fe, Zn, Al, Si, C, H, and O. This has been achieved by simultaneous treatment of phase property (like standard enthalpy of formation, standard entropy, molar heat capacity, molar volume, thermal expansivity, bulk modulus etc.) and reaction reversal data by the Bayesian method. The theory underlying the approach, and the computational methods involved, are briefly outlined. (For the benefit of readers unfamiliar with inference statistics, the basic concepts of the Bayes method are also presented in such a way that they can be grasped intuitively.) Although not yet addressed, this method can be extended to refine the thermodynamic mixing properties of crystalline solutions. The sources of the input data, culled from the literature, are summarized in the Appendix. The resulting database is succinctly documented in this paper. It includes the enthalpies of formation and entropies, their uncertainties, and the correlation among them. The database allows calculation of P-T, T-X _CO2, P-X _CO2, and T-f _O2 sections, with error propagation into the computed phase diagrams on a routine basis. A user-friendly computer program has been written to generate such phase diagrams. It is public domain software. The software and the thermodynamic database (which includes a complete documentation of the thermodynamic data above and beyond those listed (Table 2, here) may be downloaded from the web site http://homepage.ruhr-uni-bochum.de/niranjan.chatterjee/Index.htm. Examples of computed phase diagrams are given to illustrate the quality of the data and the capabilities of the software. Received: 11 March 1998 / Accepted: 11 June 1998     

Mercury colonial footprint in Darién Gulf sediments,Colombia

The mercury (Hg) deposition history in the Darién Gulf is reconstructed from three sediment cores spanning up to 1,000 years. Knowledge on the contribution to global Hg budget from the Caribbean is limited. Patterns of water circulation, sediment deposition rates, cataclysmic atmospheric inputs, and post-depositional migration have been considered in Hg trapping in the seabed. The sediment delivery rates to the coastal zone over the Late Holocene have increased from 0.2 to 1 cm year^?1 owing to anthropogenic influence. This alteration took the form of geological effects, like coastal morphology change, that played a major role in Hg downcore signal preservation. Natural background Hg levels in Southern Caribbean sediments (77.0 μg kg^?1) are up to three times higher than preindustrial signals at other latitudes, because of volcanic contributions from the Pacific ring of fire. Enrichment factors rose from 0.9 to 1.5 (70.1–113.5 μg kg^?1) within profiles related to Hg usage since Spanish colonial times between the calendar years 1550 and 1811.     

Trends in extremes of temperature, dew point, and precipitation from long instrumental series from central Europe

For the analysis of trends in weather extremes, we introduce a diagnostic index variable, the exceedance product, which combines intensity and frequency of extremes. We separate trends in higher moments from trends in mean or standard deviation and use bootstrap resampling to evaluate statistical significances. The application of the concept of the exceedance product to daily meteorological time series from Potsdam (1893 to 2005) and Prague–Klementinum (1775 to 2004) reveals that extremely cold winters occurred only until the mid-20th century, whereas warm winters show upward trends. These changes were significant in higher moments of the temperature distribution. In contrast, trends in summer temperature extremes (e.g., the 2003 European heatwave) can be explained by linear changes in mean or standard deviation. While precipitation at Potsdam does not show pronounced trends, dew point does exhibit a change from maximum extremes during the 1960s to minimum extremes during the 1970s.     

Planetary transit observations at the University Observatory Jena: XO‐1b and TrES‐1

We report on observations of transit events of the transiting planets XO‐1b and TrES‐1 with a 25 cm telescope of the University Observatory Jena. With the transit timings for XO‐1b from all 50 available XO, SuperWASP, Transit Light Curve (TLC)‐Project‐ and Exoplanet Transit Database (ETD)‐data, including our own I ‐band photometry obtained in March 2007, we find that the orbital period is P = (3.941501 ± 0.000001) d, a slight change by ∼3 s compared to the previously published period. We present new ephemeris for this transiting planet. Furthermore, we present new R ‐band photometry of two transits of TrES‐1. With the help of all available transit times from literature this allows us to refine the estimate of the orbital period: P = (3.0300722 ± 0.0000002) d. Our observations will be useful for future investigations of timing variations caused by additional perturbing planets and/or stellar spots and/or moons (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)