Einstein Gravity Explorer–a medium-class fundamental physics mission     

S. Schiller  G. M. Tino  P. Gill  C. Salomon  U. Sterr  E. Peik  A. Nevsky  A. Görlitz  D. Svehla  G. Ferrari  N. Poli  L. Lusanna  H. Klein  H. Margolis  P. Lemonde  P. Laurent  G. Santarelli  A. Clairon  W. Ertmer  E. Rasel  J. Müller  L. Iorio  C. Lämmerzahl  H. Dittus  E. Gill  M. Rothacher  F. Flechner  U. Schreiber  V. Flambaum  Wei-Tou Ni  Liang Liu  Xuzong Chen  Jingbiao Chen  Kelin Gao  L. Cacciapuoti  R. Holzwarth  M. P. Heß  W. Schäfer 《Experimental Astronomy》2009,23(2):573-610

The Einstein Gravity Explorer mission (EGE) is devoted to a precise measurement of the properties of space-time using atomic clocks. It tests one of the most fundamental predictions of Einstein’s Theory of General Relativity, the gravitational redshift, and thereby searches for hints of quantum effects in gravity, exploring one of the most important and challenging frontiers in fundamental physics. The primary mission goal is the measurement of the gravitational redshift with an accuracy up to a factor 10⁴ higher than the best current result. The mission is based on a satellite carrying cold atom-based clocks. The payload includes a cesium microwave clock (PHARAO), an optical clock, a femtosecond frequency comb, as well as precise microwave time transfer systems between space and ground. The tick rates of the clocks are continuously compared with each other, and nearly continuously with clocks on earth, during the course of the 3-year mission. The highly elliptic orbit of the satellite is optimized for the scientific goals, providing a large variation in the gravitational potential between perigee and apogee. Besides the fundamental physics results, as secondary goals EGE will establish a global reference frame for the Earth’s gravitational potential and will allow a new approach to mapping Earth’s gravity field with very high spatial resolution. The mission was proposed as a class-M mission to ESA’s Cosmic Vision Program 2015–2025.

S. SchillerEmail:

  相似文献   

Inter‐ and intra‐colonial genotypic diversity in hermatypic hydrozoans of the family Milleporidae          下载免费PDF全文

Maximilian Schweinsberg  Ralph Tollrian  Kathrin P. Lampert 《Marine Ecology》2017,38(1)

Genetic diversity is the basis for adaptation and therefore of primary scientific interest, especially in species that are threatened by anthropogenic challenges, e.g. climate change and/or pollution. Coral reefs are among the most threatened but also the most diverse ecosystems and have therefore been studied quite extensively. So far, most investigations have focused on scleractinian corals while the equally important reef builders, the hydrozoans, have been less considered. Here we provide the first study of genotypic variability as well as intra‐colonial genetic variability, the co‐occurrence of more than one genotype within a single colony, in Milleporidae based on microsatellites. We analysed two geographically distinct populations from the Millepora dichotoma complex, one from the Red Sea and one from the Great Barrier Reef. Additionally, a population of Millepora platyphylla was analysed from French Polynesia. We compared microsatellite multilocus genotypes and cytochrome c oxidase subunit I haplotypes for each of the three field sites to detect levels of genotypic diversity at the intra‐ and inter‐specific levels. Furthermore, we examined all species for the occurrence of intra‐colonial genetic variability, a recently described mechanism in scleractinian corals that might enhance the adaptive potential of sessile organisms. We found both species and all field sites to be genotypically variable. Twelve mitochondrial haplotypes and 27 multilocus microsatellite genotypes were identified. In addition, intra‐colonial genetic variability was detected in the M. dichotoma complex from the Great Barrier Reef as well as in M. platyphylla from French Polynesia. All of the intra‐colonial genetically variable colonies consisted of one main genotype and a second divergent genotype caused by somatic mutations (mosaicism). Our study proves that Milleporidae are genetically variable and that the phenomenon of intra‐colonial genetic variability also occurs in this important reef‐building family.  相似文献   

Transpiration by dryland oaks: studies in the south-western United States and Northern Israel     

Peter F. Ffolliott  Gerald J. Gottfried  Yehezkel Cohen  Gabriel Schiller 《Journal of Arid Environments》2003,55(4):595-605

Increased understanding of transpiration by dryland oaks in the woodlands of the south-western United States and northern Israel has been obtained from studies in the two countries. Transpiration was estimated in both studies by the heat pulse velocity (HPV) method in stands of Quercus emoryi, a drought-deciduous species growing in the south-western United States, and stands supporting Q. ithaburensis, a deciduous oak, and Q. calliprinos, an evergreen oak, in northern Israel. Estimates of daily transpiration rates by individual trees and annual transpiration amounts on a stand basis indicate that depending on the species and stand structure, 45–80% of the precipitation inputs to the stands sampled are represented by transpiration component of the respective hydrologic cycles.  相似文献   

Determination of the bulk temperature from NOAA/AVHRR satellite data in a midlatitude lake     

Sabine Thiemann  Helmut Schiller   《International Journal of Applied Earth Observation and Geoinformation》2003,4(4):339-349

The spatial and temporal variability of the bulk temperature gives important insights into biological and hydrodynamic processes. However, standard algorithms for satellite data only provide information of the surface temperature. The comparison of current and new split-window coefficients applied on NOAA-14/AVHRR brightness temperatures of Lake Constance showed that a regional adaption was most promising. To derive the bulk temperature information, a priori progression from a weather station was included into the AVHRR analysis. Among the weather is data, the mean temperature of the three preceding days and the day of the year were the most relevant additional information. By a multiple regression approach the bulk temperature in the upper 4 m of Lake Constance could be determined with an accuracy of ±1.20 °C. The training of a neural network improved the determination of the bulk temperature to ±1.04 °C.An extended field campaign demonstrated that the algorithm is also applicable to other sensors with the same spectral band settings (in this case NOAA-16/AVHRR) with an acceptable error and that it is equally accurate over the entire lake.  相似文献   

Evaluation of the Salicylic Acid—Liquid Phase Scrubbing Technique to Monitor Atmospheric Hydroxyl Radicals     

R. A. Salmon  C. L. Schiller  G. W. Harris 《Journal of Atmospheric Chemistry》2004,48(1):81-104

A novel method has been examined for monitoring tropospheric hydroxyl radicals (OH), the most important oxidant in tropospheric chemistry. Aqueous phase salicylic acid reacts with atmospheric OH to produce 2,5-dihydroxy benzoic acid (2,5-DHBA) and other products. High Performance Liquid Chromatography (HPLC) is used to separate the post-reaction solution and the products are quantified using fluorescence detection. Unlike other methods, it has been reported to be inexpensive, portable and relatively simple. Although the sensitivity was sufficient to measure typical daytime OH concentrations of 0.04–0.4 ppt., the method was hindered by numerous interferences. Successive identification and elimination of these still resulted in a signal that was much larger than expected. Tests showed that this was not likely to be due to ozone, HO₂, NOx, H₂O₂, aerosols, light or bacteria. Experimental and numerical studies suggest that the interference could be due to methyl peroxy radicals. The effect of many other components in the atmosphere, both individual and combined, must also be tested before the method can be used reliably in the field. The validity of previous reports of ambient hydroxyl measurements using this technique is therefore brought into question.  相似文献   

Measurements of the HONO photodissociation constant     

K. J. Wall  C. L. Schiller  G. W. Harris 《Journal of Atmospheric Chemistry》2006,55(1):31-54

Measurements of the photodissociation constant for nitrous acid (j _HONO) were made at an urban site in Toronto, Canada, during the months of May–July 2005, using an optically thin actinometer. Operating details of the j _HONO monitor are reported, along with laboratory tests. Measurements of j _HONO were obtained for solar zenith angles ranging from 20–75^∘, under clear and cloudy skies. Maximum error estimates on j _HONO under clear skies range from 11% at sunrise, to 4% at solar noon, with a minimum detection limit of 5.7 × 10⁻⁴/sec for our actinometer. Measured clear-sky values of j _HONO were compared with values calculated by a four-stream discrete ordinate radiative transfer (RT) model (ACD TUV version 4.1), and were found to be within better than 10% agreement for solar zenith angles < 65^∘. For conditions of scattered cloud, enhancement and suppression of the j _HONO values occurred by as much as 16%–70%, and 59%–80%, respectively. The integrated band area of the nπ^∗ transition for gas-phase nitrous acid yields an oscillator strength, f = (1.06 ± 0.044)×10⁻³ (based on clear-sky data), 19.1% higher than the value reported by Bongartz et al. (1991).  相似文献   

Modeling of pile installation using contact mechanics and quadratic elements   总被引：1，自引：0，他引：1  

Kathrin A. Fischer  Daichao Sheng  Andrew J. Abbo 《Computers and Geotechnics》2007,34(6):449-461

In geotechnical engineering, numerical analysis of pile capacity is often performed in such a way that piles are modeled using only the geometry of their final position in the ground and simply loaded to failure. In these analyses, the stress changes caused by the pile installation are neglected, irrespective of the installation method. For displacement piles, which are either pushed or hammered into the ground, such an approach is a very crude simplification. To model the entire installation process of displacement piles a number of additional nonlinear effects need to be considered. As the soil adjacent to the pile is displaced significantly, small deformation theory is no longer applicable and a large deformation finite element formulation is required. In addition, the continuously changing interface between the pile and the soil has to be considered. Recently, large deformation frictional contact has been used to model the pile installation and cone penetration processes. However, one significant limitation of the analysis was the use of linear elements, which have proven to be less accurate than higher order elements for nonlinear materials such as soils.

This paper presents a large deformation frictional contact formulation which can be coupled consistently with quadratic solid elements. The formulation uses the so-called mortar-type discretisation of the contact surfaces. The performance of this contact discretisation technique is demonstrated by accurately predicting the stress transfer between the pile and the soil surfaces.  相似文献   

The surface energy balance and the mixing height in urban areas—activities and recommendations of COST-Action 715     

Martin Piringer  Sylvain Joffre  Alexander Baklanov  Andreas Christen  Marco Deserti  Koen De Ridder  Stefan Emeis  Patrice Mestayer  Maria Tombrou  Douglas Middleton  Kathrin Baumann-Stanzer  Aggeliki Dandou  Ari Karppinen  Jerzy Burzynski 《Boundary-Layer Meteorology》2007,124(1):3-24

The specific problems of determining and simulating the surface energy balance (SEB) and the mixing height (MH) over urban areas are examined. The SEB and MH are critical components of algorithms and numerical models for the urban boundary layer, though the constituent parts of the SEB and the MH are not routinely measured by national weather services. Parameterisations are thus needed in applications. In this investigation, several recently developed algorithms and models for estimating the SEB and MH were applied to new datasets and assessed. Results are discussed in terms of the need for spatial resolution and the parameters needed to describe the urban atmosphere. Limitations of models are identified and recommendations for further development and observations are given. Having identified gaps in knowledge, key findings from new urban experiments and numerical modelling for the SEB and MH are given. The diurnal cycle for the SEB is significantly different from rural conditions—urban heat storage is needed in urban parameterisations. The urban MH is increased over the rural MH, as shown by several numerical schemes and careful sodar analyses. This work has been carried out within the COST-715 Action “Meteorology applied to urban air pollution problems (1998–2004). COST 715 reached a consensus proposing representatively sited measurements of meteorological parameters and turbulent fluxes above roof-tops, and recognised that such data are needed to improve numerical models of the urban surface processes.  相似文献   

Performance of Aleppo pine (Pinus halepensis) provenances grown at the edge of the Negev desert: A review     

G. Schiller  N. Atzmon 《Journal of Arid Environments》2009,73(12):1051-1057

This paper reviews and summarizes the results of research projects conducted in the Aleppo pine provenance trial in the Yatir forest, located at the northern edge of the Israeli Negev desert, under semi-arid climate. Results show that to improve the sustainability of new Aleppo pine plantations at the edge of deserts, prospective seed sources (provenances) must be selected for heterozygosity on one hand, and for drought resistance and water-use efficiency on the other. Harsh environmental site conditions at the desert's edge provide an opportunity to exert heavy selection pressure among and within provenances of a priori drought-tolerant species. The survivors should be used as the seed source for new forest plantations aimed at combating desertification.  相似文献   

Imaging the Earth’s Interior: the Angular Distribution of Terrestrial Neutrinos     

Brian D. Fields  Kathrin A. Hochmuth 《Earth, Moon, and Planets》2006,99(1-4):155-181

Decays of radionuclides throughout the earth’s interior produce geothermal heat, but also are a source of antineutrinos; these geoneutrinos are now becoming observable in experiments such as KamLAND. The (angle-integrated) geoneutrino flux has been shown to provide a unique probe of geothermal heating due to decays, and an integral constraint on the distribution of radionuclides in the earth. In this paper, we calculate the angular distribution of geoneutrinos, which opens a window on the differential radial distribution of terrestrial radionuclides. We develop the general formalism for the neutrino angular distribution. We also present the inverse transformation which recovers the terrestrial radioisotope distribution given a measurement of the neutrino angular distribution. Thus, geoneutrinos not only allow a means to image the earth’s interior, but offer a direct measure of the radioactive earth, both revealing the earth’s inner structure as probed by radionuclides, and allowing a complete determination of the radioactive heat generation as a function of radius. Turning to specific models, we emphasize the very useful approximation in which the earth is modeled as a series of shells of uniform density. Using this multishell approximation, we present the geoneutrino angular distribution for the favored earth model which has been used to calculate the geoneutrino flux. In this model the neutrino generation is dominated by decays of potassium, uranium, and thorium in the earth’s mantle and crust; this leads to a very “peripheral” angular distribution, in which 2/3 of the neutrinos come from angles θ ≳ 60° away from the nadir. We note that a measurement of the neutrino intensity in peripheral directions leads to a strong lower limit to the central intensity. We briefly discuss the challenges facing experiments to measure the geoneutrino angular distribution. Currently available techniques using inverse beta decay of protons require a (for now) unfeasibly large number of events to recover with confidence the forward scattering signal from the background of subsequent elastic scatterings. Nevertheless, it is our hope that future large experiments, and/or more sensitive techniques, can resolve an image of the earth’s radioactive interior.  相似文献