The First Mesozoic Heterodactyl Bird from China   总被引：1，自引：1，他引：0  

ZHANG Zihui HOU Lianhai HASEGAWA Yoshikasu Jingmai O＇CONNOR Larry D. MARTIN Luis M. CHIAPPE 《《地质学报》英文版》2006,80(5):631-635

1 Introduction Enantiornithines were the dominant birds nearly worldwide throughout the entire span of the Cretaceous (Chiappe, 1995; Feduccia, 1996). The adaptive radiation of opposite birds is little known besides the disparity of rostral morphology in Boluochia (Zhou, 1995), Longipteryx (Zhang et al., 2001), Longirostravis ( Hou et al., 2004), and the presence of stomach contents that reflect a diversity of diets. Like the structure of rostrum, differentiation of the locomotor apparatu…  相似文献   

Raw material economies among prehistoric Hunter-Gatherers,Anta Montet-White and Steven Holen (editors), 1991, University of Kansas publications in anthropology 19, xiv + 415 pp., $30.00 (paperbound)     

Larry D. Banks 《Geoarchaeology》1992,7(5):488-490

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Comment on “a thermodynamic model for multicomponent melts,with application to the system CaOAl2O3SiO2” by Berman and Brown     

Larry M. Barron 《Geochimica et cosmochimica acta》1985,49(2):611-612

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An ellipse-based discrete element model for granular materials     

John M. Ting  Mahmood Khwaja  Larry R. Meachum  Jeffrey D. Rowell 《国际地质力学数值与分析法杂志》1993,17(9):603-623

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1891–1883 Ma Southern Bastar–Cuddapah mafic igneous events, India: A newly recognized large igneous province     

Jason E. French  Larry M. Heaman  Thomas Chacko  Rajesh K. Srivastava 《Precambrian Research》2008,160(3-4):308-322

A newly recognized remnant of a Paleoproterozoic Large Igneous Province has been identified in the southern Bastar craton and nearby Cuddapah basin from the adjacent Dharwar craton, India. High precision U–Pb dates of 1891.1 ± 0.9 Ma (baddeleyite) and 1883.0 ± 1.4 Ma (baddeleyite and zircon) for two SE-trending mafic dykes from the BD2 dyke swarm, southern Bastar craton, and 1885.4 ± 3.1 Ma (baddeleyite) for a mafic sill from the Cuddapah basin, indicate the existence of 1891–1883 Ma mafic magmatism that spans an area of at least 90,000 km² in the south Indian shield.This record of 1.9 Ga mafic/ultramafic magmatism associated with concomitant intracontinental rifting and basin development preserved along much of the south-eastern margin of the south Indian shield is a widespread geologic phenomenon on Earth. Similar periods of intraplate mafic/ultramafic magmatism occur along the margin of the Superior craton in North America (1.88 Ga Molson large igneous province) and in southern Africa along the northern margin of the Kaapvaal craton (1.88–1.87 Ga dolerite sills intruding the Waterberg Group). Existing paleomagnetic data for the Molson and Waterberg 1.88 Ga large igneous provinces indicate that the Superior and Kalahari cratons were at similar paleolatitudes at 1.88 Ga but a paleocontinental reconstruction at this time involving these cratons is impeded by the lack of a robust geological pin such as a Limpopo-like 2.0 Ga deformation zone in the Superior Province. The widespread occurrence of 1.88 Ga intraplate and plate margin mafic magmatism and basin development in numerous Archean cratons worldwide likely reflects a period of global-scale mantle upwelling or enhanced mantle plume activity at this time.  相似文献   

Sensitivity of Turbine-Height Wind Speeds to Parameters in Planetary Boundary-Layer and Surface-Layer Schemes in the Weather Research and Forecasting Model     

Ben Yang  Yun Qian  Larry K. Berg  Po-Lun Ma  Sonia Wharton  Vera Bulaevskaya  Huiping Yan  Zhangshuan Hou  William J. Shaw 《Boundary-Layer Meteorology》2017,162(1):117-142

We evaluate the sensitivity of simulated turbine-height wind speeds to 26 parameters within the Mellor–Yamada–Nakanishi–Niino (MYNN) planetary boundary-layer scheme and MM5 surface-layer scheme of the Weather Research and Forecasting model over an area of complex terrain. An efficient sampling algorithm and generalized linear model are used to explore the multiple-dimensional parameter space and quantify the parametric sensitivity of simulated turbine-height wind speeds. The results indicate that most of the variability in the ensemble simulations is due to parameters related to the dissipation of turbulent kinetic energy (TKE), Prandtl number, turbulent length scales, surface roughness, and the von Kármán constant. The parameter associated with the TKE dissipation rate is found to be most important, and a larger dissipation rate produces larger hub-height wind speeds. A larger Prandtl number results in smaller nighttime wind speeds. Increasing surface roughness reduces the frequencies of both extremely weak and strong airflows, implying a reduction in the variability of wind speed. All of the above parameters significantly affect the vertical profiles of wind speed and the magnitude of wind shear. The relative contributions of individual parameters are found to be dependent on both the terrain slope and atmospheric stability.  相似文献   

Structural change associated with the incommensurate-normal phase transition in akermanite, Ca2MgSi2O7, at high pressure     

Hexiong Yang  Robert M. Hazen  Robert T. Downs  Larry W. Finger 《Physics and Chemistry of Minerals》1997,24(7):510-519

The structural changes associated with the incommensurate (IC)-normal (N) phase transition in akermanite have been studied with high-pressure single-crystal X-ray diffraction up to 3.79?GPa. The IC phase, stable at room pressure, transforms to the N phase at ～1.33?GPa. The structural transformation is marked by a small but discernable change in the slopes of all unit-cell parameters as a function of pressure. It is reversible with an apparent hysteresis and is classified as a tricritical phase transition. The linear compressibility of the a and c axes are 0.00280(10) and 0.00418(6)?GPa^?1 for the IC phase, and 0.00299(11) and 0.00367(8)?GPa^?1 for the N phase, respectively. Weighted volume and pressure data, fitted to a second-order Birch-Murnaghan equation of state (K′≡4.0), yield V₀=307.4(1)?ų and K₀=100(3)?GPa for the IC phase and V₀=307.6(2)?ų and K₀=90(2)?GPa for the N phase. No significant discontinuities in Si–O, Mg–O and Ca–O distances were observed across the transition, except for the Ca–O1 distance, which is more compressible in the IC phase than in the N phase. From room pressure to 3.79?GP the volume of the [SiO₄] tetrahedron is unchanged (2.16?ų), whereas the volumes of the [MgO₄] and [CaO₈] polyhedra decrease from 3.61 to 3.55(1)?ų and 32.8 to 30.9(2)?ų, respectively. Intensities of satellite reflections are found to vary linearly with the isotropic displacement parametr of Ca and the librational amplitude of the [SiO₄] tetrahedron. At room pressure, there is a mismatch between the size of the Ca cations and the configuration of tetrahedral sheets, which appears to be responsible for the formation of the modulated structure; as pressure increases, the misfit is diminished through the relative rotation and distortion of [MgO₄] and [SiO₄] tetrahedra and the differential compression of individual Ca–O distances, concurrent with a displacement of Ca along the (110) mirror plane toward the O1 atom. We regard the high-pressure normal structure as a result of the elimination of microdomains in the modulated structure.  相似文献   

The downside risk of climate change in California’s Central Valley agricultural sector     

Michael Hanemann  Susan Stratton Sayre  Larry Dale 《Climatic change》2016,134(1-2):15-28

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Geomorphology,acoustic backscatter,and processes in Santa Monica Bay from multibeam mapping   总被引：2，自引：0，他引：2  

Gardner JV  Dartnell P  Mayer LA  Hughes Clarke JE 《Marine environmental research》2003,56(1-2):15-46

Santa Monica Bay was mapped in 1996 using a high-resolution multibeam system, providing the first substantial update of the submarine geomorphology since the initial compilation by Shepard and Emery [(1941) Geol. Soc. Amer. Spec. Paper 31]. The multibeam mapping generated not only high-resolution bathymetry, but also coregistered, calibrated acoustic backscatter at 95 kHz. The geomorphology has been subdivided into six provinces; shelf, marginal plateau, submarine canyon, basin slope, apron, and basin. The dimensions, gradients, and backscatter characteristics of each province is described and related to a combination of tectonics, climate, sea level, and sediment supply. Fluctuations of eustatic sea level have had a profound effect on the area; by periodically eroding the surface of Santa Monica plateau, extending the mouth of the Los Angeles River to various locations along the shelf break, and by connecting submarine canyons to rivers. A wetter glacial climate undoubtedly generated more sediment to the rivers that then transported the increased sediment load to the low-stand coastline and canyon heads. The trends of Santa Monica Canyon and several bathymetric highs suggest a complex tectonic stress field that has controlled the various segments. There is no geomorphic evidence to suggest Redondo Canyon is fault controlled. The San Pedro fault can be extended more than 30 km to the northwest by the alignment of a series of bathymetric highs and abrupt changes in direction of channel thalwegs.  相似文献   

Measurement of sediment resuspension rates in Long Island Sound   总被引：1，自引：0，他引：1  

Henry Bokuniewicz  Larry McTiernan  Wayne Davis 《Geo-Marine Letters》1991,11(3-4):159-161

Resuspension rates have been measured on Long Island Sound sediments (New York/Connecticut, USA) under an oscillating grid, using a flume, and in place, using high frequency acoustics, transmissometers, and sediment traps. Despite differences, the results compare favorably. The methods all provide an order-of-magnitude estimate of the resuspension rate and increases under storm conditions can be estimated.  相似文献