Mechanical properties of organic matter in shales mapped at the nanometer scale     

《Marine and Petroleum Geology》2015

The mechanical properties of organic matter strongly affect the way shales deform and fracture. However, the way organic matter responds to mechanical stresses is poorly understood, representing a critical obstacle to assessing oil and gas production in shale formations. Little is known about the mechanical properties of organic matter in fine grained rocks primarily because it often occupies tiny nanometer-scale voids between the mineral grains which cannot be accessed using standard mechanical testing techniques. Here, we use a new atomic force microscopy technique (PeakForce QNM™) to map the mechanical properties of organic and inorganic components at the nanometer scale. We find that the method is able to distinguish between different phases such as pyrite, quartz, clays, and organic matter. Moreover, within the organic component Young's modulus values ranged from 0 to 25 GPa; in 3 different samples – all of which come from thermally mature Type II/III source rocks in the dry gas window – a modal value of 15–16 GPa was measured, with additional peaks measured at ≤10 GPa. In addition, the maps suggest that some porous organic macerals possess a soft core surrounded by a harder outer shell 50–100 nm thick. Thus, our results demonstrate that the method represents a powerful new petrographic tool with which to characterize the mechanical properties of organic-rich sedimentary rocks.  相似文献   

Fluctuations in isothermal spheres     

Joseph Katz  Isao Okamoto 《Monthly notices of the Royal Astronomical Society》2000,317(1):163-169

Isolated isothermal spheres of N gravitationally interacting points with equal mass are believed to be stable when density contrasts do not exceed 709. That stability limit does not, however, take into consideration fluctuations of temperature near the onset of instability. These are important when N is finite.
Here we correlate global mean quadratic temperature fluctuations with the onset of instability. We show that such fluctuations trigger instability when the density contrast reaches a value near 709×exp(−3.3 N ^−1/3). These lower values of limiting density contrasts are significantly smaller than 709 when N is not very large, and this suggests (i) that numerical calculations with small N may not reflect correctly the onset of core collapse in clusters with large N , and (ii) that a greater number of globular clusters than is normally believed may already be in an advanced stage of core collapse, because most of the observed globular clusters with parameters that fit quasi-isothermal configurations are close to marginal stability.  相似文献   

Two ways of biasing galaxy formation     

Paolo Catelan  Cristiano Porciani  Marc Kamionkowski 《Monthly notices of the Royal Astronomical Society》2000,318(3):L39-L44

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Charged meteoric smoke as ice nuclei in the mesosphere: Part 1—A review of basic concepts     

J. Gumbel  L. Megner 《Journal of Atmospheric and Solar》2009,71(12):1225-1235

The role of meteoric smoke as condensation nuclei for mesospheric ice has recently been challenged by model simulations on the global transport of meteoric material. At the same time a considerable fraction of smoke particles is charged in the mesosphere. This has significant effects on nucleation processes as it can remove the Kelvin barrier. We suggest that in particular nucleation on negatively charged smoke is likely to be a dominant mechanism for mesospheric ice formation. This is in contrast to nucleation on positive ion clusters as the latter is largely hampered by efficient ion/electron recombination. Surprisingly, the large potential of nucleation on charged smoke has so far not been considered in mesospheric ice models. A challenging question concerns the fraction of mesospheric smoke that is actually charged. An improved understanding of mesospheric charging and nucleation will require laboratory experiments on nuclei in the transition regime between molecular and particulate sizes.  相似文献   

Sinuosity evolution along an incising channel: New insights from the Jordan River response to the Dead Sea level fall     

Elad Dente  Nadav G. Lensky  Efrat Morin  Thomas Dunne  Yehouda Enzel 《地球表面变化过程与地形》2019,44(3):781-795

The geomorphic evolution of the Jordan River in recent decades indicates that interaction between incision and high-magnitude floods controls sinuosity changes under increasing mouth gradients during base-level fall. The evolution of the river was analyzed based on digital elevation models, remotely sensed imagery, hydrometric data, and a hydraulic model. The response varies along the river. Near the river mouth, where incision rate is high and a deep channel forms, overbank flooding is less likely. There, large floods exert high shear stress within the confined channel, increasing sinuosity. Upstream, near the migrating knickzone channel gradients also increase, incision is more moderate and floods continue to overtop the banks, favoring meander chute cutoffs. The resulting channel has a downstream well-confined meandering segment and an upstream low-sinuosity segment. These new insights regarding spatial differences along an incising channel can improve interpretations of the evolution of ancient planforms and floodplains that responded to base-level decline. © 2018 John Wiley & Sons, Ltd.  相似文献   

Environmental influences on dark matter haloes and consequences for the galaxies within them     

Gerard Lemson  Guinevere Kauffmann 《Monthly notices of the Royal Astronomical Society》1999,302(1):111-117

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Cosmological parameters from cluster abundances, cosmic microwave background and IRAS     

S. L. Bridle  V. R. Eke  O. Lahav  A. N. Lasenby  M. P. Hobson  S. Cole  C. S. Frenk  J. P. Henry 《Monthly notices of the Royal Astronomical Society》1999,310(2):565-570

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Fluid-rock interaction and thermal evolution during thrusting of an Alpine metamorphic complex (Tinos island, Greece)     

A. Matthews  J. Lieberman  D. Avigad  Z. Garfunkel 《Contributions to Mineralogy and Petrology》1999,135(2-3):212-224

This study examines the fluid-rock interaction and thermal evolution along a thrust that juxtaposes calcite-rich marbles of high P-T metamorphic unit of the Attic-Cycladic Massif (Greece) on top of a lower-grade dolomite marble unit. The Tertiary thrust represents a major phase of tectonic movement related to the decompression of the Alpine orogen in the Hellenides. The stable isotope signatures of the thrust plane and adjacent sections of the footwall and hanging wall rocks are characterized by significant carbon and oxygen isotope depletions. The depletion is most pronounced in calcite, but is almost entirely missing in coexisting dolomite. The isotopic patterns in the thrust zone can be explained by the infiltration of an externally derived water-rich H₂O-CO₂-CH₄ fluid [X _C (=X _{CO 2}+X _{CH 4})<0.05] at water-rock ratios on the order of 0.1 to 0.5 by weight. The fluid-induced calcite recrystallization is viewed as an important rheological control during thrusting. The temperature evolution of the footwall, hanging wall and mylonitic tectonic contact was determined by calcite-dolomite solvus thermometry. Histograms of calcite-dolomite temperatures are interpreted as indicating a heating of the footwall dolomite marble during the thrusting of the hotter upper plate. Conversely, the hanging wall marble unit was cooled during the thrusting. The calcite-dolomite thermometry of the thrust plane gives temperatures intermediate between the initial temperatures of the lower and upper marble units, and this leads to the conclusion that conductive heat transfer rather than fluid infiltration controlled the thermal evolution during thrusting. Received: 14 April 1998 / Accepted: 9 December 1998  相似文献   

Quaternary Stratigraphy and Paleogeography of the Galilee Coastal Plain, Israel   总被引：1，自引：0，他引：1  

Dorit Sivan  Gedaliahu Gvirtzman  Eytan Sass 《Quaternary Research》1999,51(3):280

The Quaternary deposits in the Galilee coastal plain comprise alternating calcareous sandstone, red loam, dark clay, and uncemented sand. The calcareous sandstone in the lower part of the sequence represents a Pliocene to early Pleistocene marine transgression, and is covered unconformably by the late Quaternary sequence. The base of this sequence has an estimated age of 500,000 yr. It is covered unconformably by marine calcareous sandstone in the west, which represents the global high sea-level stand of isotope stage 7.1, and is known as one of the “Tyrrhenian” events in the Mediterranean area. The overlying members represent the low sea-level stand of stage 6, the first a red paleosol indicating a relatively wet phase and the second an eolianite unit representing a drier phase. The eolianite forms longitudinal, subparallel ridges that formed contemporaneously. The overlying marine sandstone, which contains one of the diagnostic fossils of the “Tyrrhenian” events, the gastropodStrombus buboniusLMK, accumulated during the global high stand of stage 5.5. The last glacial period left no sedimentary record. The Holocene is represented by a marine clay unit that is covered by sand. The present study establishes a complete and detailed chronostratigraphic sequence for an eastern Mediterranean beach, which contains the gastropodS. buboniusLMK.S. buboniuson the Galilee coast is attributed to stage 5.5 and, therefore, establishes an east–west Mediterranean correlation, which can be used for linking Mediterranean events to paleo-sea levels and global climate changes.  相似文献   

A case devoid of bias: Optical Redshift Survey voids versus IRAS voids     

H. El-Ad  T. Piran 《Monthly notices of the Royal Astronomical Society》2000,313(3):553-558

We present a comparison between the voids in two nearly all-sky redshift surveys: the Optical Redshift Survey (ORS) and the IRAS 1.2-Jy survey. While the galaxies in these surveys are selected differently and their populations are known to be biased relative to each other, the two void distributions are similar. We compare the spatial distribution of the two void populations and demonstrate the correlation between them. The voids also agree with regard to the overall void statistics a filling factor of 0.45 of the volume, an average void diameter and an average galaxy underdensity in the voids Our measurements of the underdensities of the voids in the two surveys enable us to estimate the relative bias in the voids between optical and IRAS samples. We find ( b _opt b _IRAS )^void1, showing that on average there is little or no biasing between the two void populations.  相似文献