The effect of water on intergranular mass transport: new insights from diffusion-controlled reaction rims in the MgO–SiO2 system     

E. Gardés  B. Wunder  K. Marquardt  W. Heinrich 《Contributions to Mineralogy and Petrology》2012,164(1):1-16

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CAD assessment of the posture and range of motion of <Emphasis Type="Italic">Kentrosaurus aethiopicus</Emphasis> H<Emphasis Type="SmallCaps">ennig</Emphasis> 1915     

Heinrich Mallison 《Swiss Journal of Geoscience》2010,103(2):211-233

A computer aided design analysis using high-resolution laser scans of the bones of the stegosaur Kentrosaurus aethiopicus Hennig 1915 from the Late Jurassic Tendaguru Formation indicates that in the habitual walking pose the forelimbs were probably held erect, and that strong humeral flexion and abduction mainly occurred in a defensive stance. Rapid gaits with unsupported phases could not be used. The neck allowed sufficient lateral flexion to guarantee good sight in all directions including posteriorly. The tail covered an arch of roughly 180° and had sufficient range to be used as a weapon. Possibly, the animal could accomplish tail blows against specific targets in sight. Also, a tripodal pose is suggested to have been possible, roughly doubling the maximum vertical feeding height of Kentrosaurus.  相似文献   

Orientation Distribution Within a Single Hematite Crystal     

Ralf Hielscher  Helmut Schaeben  Heinrich Siemes 《Mathematical Geosciences》2010,42(4):359-375

While crystallography conventionally presumes that a single crystal carries a unique crystallographic orientation, modern experimental techniques reveal that a single crystal may exhibit an orientation distribution. However, this distribution is largely concentrated; it is extremely concentrated when compared with orientation distributions of polycrystalline specimen. A case study of a deformation experiment with a single hematite crystal is presented, where the experimental deformation induced twining, which in turn changed a largely concentrated unimodal “parent” orientation distribution into a multimodal orientation distribution with a major mode resembling the parent mode and three minor modes corresponding to the progressive twining. The free and open source software MTEX for texture analysis was used to compute and visualize orientations density functions from both integral orientation measurements, i.e. neutron diffraction pole intensity data, and individual orientation measurements, i.e. electron back scatter diffraction data. Thus it is exemplified that MTEX is capable of analysing orientation data from largely concentrated orientation distributions.  相似文献   

Immigration and community development in New York City   总被引：1，自引：0，他引：1  

James DeFilippis  Benjamin Faust 《Urban geography》2013,34(8):1196-1214

Community development corporations play a central role in the provision of affordable housing and social services in the contemporary American welfare state. This organizational form, however, emerged in the distinctive, historical political-economic context of the Black Power Movement and America's Great Society. American cities are now very different places, transformed by immigration from spaces of Black–White separation to much more heterogeneous and diverse spaces. In this article, our central question is whether, and how, these vital service organizations are incorporating immigrants into their work. We find that the answer varies, and such variations indicate differential access, or “differential citizenship”—in the urban structure of the contemporary American welfare state.  相似文献   

Boltzmann Equilibrium of Endothermic Heavy Nuclear Synthesis in the Universe and a Quark Relation to the Magic Numbers     

Heinrich Hora  George H. Miley  Frederick Osman 《Astrophysics and Space Science》2005,298(1-2):247-253

As laser–plasma interactions access ever-increasing ranges of plasma temperatures and densities, it is interesting to consider whether they will some day shed light on questions concerning nuclear synthesis. One such open question is the process of endothermic nuclear synthesis for elements with A > 60, thought to have taken place at a point in time during the big bang, or currently in supernovae. We present an explanation based on a Boltzmann equilibrium condition, in combination with the change of the Fermi-statistics from the relativistic branch for hadrons from higher than nuclear densities to the lower density subrelativistic branch. The Debye length confinement of nuclei breaks down at the relativistic change, thus leading to the impossibility of nucleation of the quark-gluon state at higher than nuclear densities. Taking the increment for the proton number Z as Z′ = 10 of the measured standard abundance distribution (SAD) of the elements for a Boltzmann probability for heavy element synthesis, a sequence 3 ⁿ was found with the exponent n for the sequence of the magic numbers. The jump between the magic numbers 20 and 28 does not need then the usual spin-orbit explanation.  相似文献   

The first dinosaur tracksite from Xinjiang, NW China (Middle Jurassic Sanjianfang Formation, Turpan Basin)——a preliminary report     

Oliver WINGS  Rico SCHELLHORN  Heinrich MALLISON  Ben THUY  Wenhao WU  Ge SUN 《世界地质(英文版)》2007,10(2)

A new dinosaur tracksite was discovered in a steeply inclined sandstone layer of the Middle Jurassic Sanjianfang Formation in the Shanshan area of the Turpan Basin. The site is the first record of dinosaur footprints from Xinjiang Province in northwestern China. More than 150 tridactyl theropod dinosaur footprints are preserved as positive hyporeliefs on the lower bedding plane of a fine-grained sandstone body. Most of the footprints are isolated and appear to be randomly distributed. Some show well defined phalangeal pads, heels and rarely indistinct impressions of the distal part of the metatarsus. Two distinct morphotypes are present: a larger type with relatively broad pads shows similarities to Changpeipus and Megalosauripus, and a slightly smaller, slender and gracile type which is similar to Grallator, Eubrontes and Anchisauripus. In both morphotypes, digit III is the longest with a length between 11.4 and 33.6 cm. A single imprint shows prominent scratches, probably formed during slipping of the track maker.  相似文献   

Discussion of the article by A. C. Lasaga and H. Ohmoto on “The Oxygen Geochemical Cycle: Dynamics and Stability,” Geochim. Cosmochim. Acta66, 361-381, 2002     

Heinrich D. Holland 《Geochimica et cosmochimica acta》2003,67(4):787-789

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Statistical downscaling in the arid central Andes: uncertainty analysis of multi-model simulated temperature and precipitation     

Maxime Souvignet  J��rgen Heinrich 《Theoretical and Applied Climatology》2011,106(1-2):229-244

Statistical downscaling is a technique widely used to overcome the spatial resolution problem of General Circulation Models (GCMs). Nevertheless, the evaluation of uncertainties linked with downscaled temperature and precipitation variables is essential to climate impact studies. This paper shows the potential of a statistical downscaling technique (in this case SDSM) using predictors from three different GCMs (GCGM3, GFDL and MRI) over a highly heterogeneous area in the central Andes. Biases in median and variance are estimated for downscaled temperature and precipitation using robust statistical tests, respectively Mann?CWhitney and Brown?CForsythe's tests. In addition, the ability of the downscaled variables to reproduce extreme events is tested using a frequency analysis. Results show that uncertainties in downscaled precipitations are high and that simulated precipitation variables failed to reproduce extreme events accurately. Nevertheless, a greater confidence remains in downscaled temperatures variables for the area. GCMs performed differently for temperature and precipitation as well as for the different test. In general, this study shows that statistical downscaling is able to simulate with accuracy temperature variables. More inhomogeneities are detected for precipitation variables. This first attempt to test uncertainties of statistical downscaling techniques in the heterogeneous arid central Andes contributes therefore to an improvement of the quality of predictions of climate impact studies in this area.  相似文献   

U–Pb dating, Hf-isotope characteristics and trace-REE-patterns of zircons from Medet porphyry copper deposit, Bulgaria: implications for timing, duration and sources of ore-bearing magmatism     

Irena Peytcheva  Albrecht von Quadt  Franz Neubauer  Martin Frank  Rossen Nedialkov  Christoph Heinrich  Strashimir Strashimirov 《Mineralogy and Petrology》2009,96(1-2):19-41

Precise U–Pb geochronology, Hf isotope compositions and trace element distributions in zircons are combined in the present study to define the timing and sources of the magmatism forming the Medet porphyry copper deposit, Bulgaria. ID-TIMS U–Pb-zircon dating demonstrates that ore-bearing magmatism extended for less than 1.12 Ma. As inferred from the field relationships, it started with the intrusion of a quartz-monzodiorite at 90.59?±?0.29 Ma followed by granodiorite porphyries at 90.47?±?0.30 and 90.27?±?0.60 Ma and by crosscutting aplite dykes at 90.12?±?0.36 Ma. These units were overprinted by potassic alteration and host economic copper-(Mo–Au) mineralization. The main magmatic–hydrothermal activity ceased after that, and a later quartz-granodiorite porphyry dyke, dated at 89.26?±?0.32 Ma, only contains an uneconomic quartz–pyrite mineralization. Assimilation of Lower Paleozoic rocks with a mantle to mantle–crust signature is characteristic of the fertile magma in the Medet deposit, as defined by positive ?-Hf values of the inherited zircons. The positive Ce-anomalies and the higher Eu/Eu* ratios of the zircons in the mineralized Cretaceous rocks of Medet deposit argue for crystallization from a generally more oxidized magma compared to the later quartz-granodiorite porphyry dyke. A change in paleostress conditions occurred during the intrusion of the Medet pluton and its dykes. The initial stage reveals E–W extension associated with N–S compression, whereas the younger granodiorite dyke was emplaced during subsequent N–S extension. The large-scale switch of the extensional stress regime during the mineralization was favourable for ore deposition by channelling the fluids and increasing the effective permeability.  相似文献   

On acceleration and motion of ions in corona and solar wind     

Johannes Geiss  Peter Hirt  Heinrich Leutwyler 《Solar physics》1970,12(3):458-483

Assuming a stationary, radial, spherically symmetric solar wind and a radial magnetic field direction in the vicinity of the sun, an equation of motion for ions heavier than protons in the solar wind is derived. The general properties of this equation are discussed and the results of numerical integrations are given. These results are based on the assumption of maxwellian velocity distribution functions for electrons, protons and ions, but the effects of first order deviations from such distributions are also presented and discussed. It is shown that dynamical friction, i.e. momentum transfer from protons to heavier ions accounts for the observed fact that heavier ions - if accelerated at all - normally reach the same velocity as the protons in the solar wind. Because of the non-linear relation between dynamical friction and proton-ion velocity difference a minimum proton flux is required to carry a certain ion species in the solar wind. Formulae comparing the minimum fluxes for different ions are given. It is shown that elements up to and beyond iron will be carried along in the solar wind as long as helium is carried along. Substantial isotopic fractionation is possible, in particular in the case of helium. The effects of ion motion and escape on abundances in the corona and in the outer convective zone of the sun are discussed.  相似文献