Three-Dimensional Sedimentary Architecture of a Large, Mid-Channel Sand Braid Bar, Jamuna River, Bangladesh

2003 ◽  
Vol 73 (4) ◽  
pp. 516-530 ◽  
Author(s):  
J. L. Best ◽  
P. J. Ashworth ◽  
C. S. Bristow ◽  
J. Roden
Keyword(s):  
Three Dimensional ◽  
Sedimentary Architecture

Sedimentological characteristics and aeolian architecture of a plausible intermountain erg system in Southeast China during the Late Cretaceous

2020 ◽  
Vol 132 (11-12) ◽  
pp. 2475-2488
Author(s):  
Shuo Cao ◽  
Laiming Zhang ◽  
Chengshan Wang ◽  
Jing Ma ◽  
Jie Tan ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Three Dimensional ◽  
Small Scale ◽  
Southeast China ◽  
Climate Conditions ◽  
Aeolian Deposits ◽  
Intermountain Basin ◽  
Sedimentary Architecture ◽  
Hot Arid Climate ◽  
Near Future

Abstract Along with intensification of global warming, severe desertification has already impaired human sustainable development. In a near-future greenhouse world, the total area of desert will increase, and new types of desert may emerge. During the “greenhouse” Cretaceous, conventional large paleo-ergs developed in broad topographic basins, and many possible ergs developed in small-scale intermountain basins, which are unusual in near-modern times and less studied. A comprehensive study of their sedimentary architecture and mechanisms would refine our interpretation of desertification in a near-future “greenhouse” world. The Xinjiang Basin is a typical small-scale intermountain basin in Southeast China that formed >300 m of successive aeolian deposits during the early Late Cretaceous. In this study, we applied detailed facies and architecture analyses to the Tangbian Formation (K2t) in 16 outcrops throughout the Xinjiang Basin and reconstructed a three-dimensional sedimentary model for the intermountain ergs. We confirmed that the Tangbian Formation formed in a typical intermountain paleo-erg and summarized in detail the differences in sedimentary architecture between intermountain ergs and broad topographic ergs. We noticed that the “greenhouse” state during the Late Cretaceous seems to have been suitable for the development of ergs in intermountain basins due to the hot, arid climate conditions and penetrating winds with sufficient transport capacity. Therefore, we suggest that in addition to the ongoing expansion of broad topographic ergs, the emergence and development of intermountain ergs in a near-future “greenhouse” world would also contribute to global desert expansion and massive desertification.

scholarly journals Controls on mud distribution and architecture along the fluvial-to-marine transition

2020 ◽  
Author(s):  
Daniel Parsons ◽  
Wietse Van de Lageweg ◽  
Lisanne Braat ◽  
Maarten Kleinhans
Keyword(s):  
River Flow ◽  
Three Dimensional ◽  
Quantitative Information ◽  
System Stability ◽  
Relative Importance ◽  
Coastal System ◽  
Fluvial Processes ◽  
Coastal Systems ◽  
Sedimentary Architecture ◽  
Sedimentary Fill

<p>The interaction of marine (tides and waves) and fluvial processes determines the sedimentary fill of coastal systems in the fluvial-to-marine (FTM) transition zone. Despite frequent recognition of tidal and wave influence in modern and ancient systems, our understanding of the relative importance of marine processes and their impact on mud deposition, coastal system stability and sedimentary architecture is limited. This study combined subsurface field observations and numerical simulations to investigate the relative importance of river flow, tides, waves, and mud input in governing the sedimentary fill in funnel-shaped basins along the FTM transition. Model simulations show a self-forming bar-built estuary with dynamic channels and sandy bars flanked by mud flats, which is in agreement with trends observed in nature. From three-dimensional virtual sedimentary successions, statistical tendencies for mud distribution and thickness were derived for the spectrum of marine and fluvial processes, and these values provide quantitative information on the net-to-gross ratio and mud architecture. The relative influence of marine and fluvial processes leads to a predictable facies organization and architecture, with muddier and more heterogeneous sediments toward the flanks. For the first time, our simulations allow the sedimentary fill in basins along the FTM transition to be related explicitly to hydrodynamic conditions, providing new insights into the morphosedimentary evolution of coastal systems, with implications for system stability in the modern and sequence stratigraphy preserved in the ancient.</p>

The orbit of Pluto over a long interval of time

1966 ◽  
Vol 25 ◽  
pp. 227-229 ◽  
Author(s):  
D. Brouwer
Keyword(s):  
Periodic Orbit ◽  
Numerical Integration ◽  
Restricted Problem ◽  
Three Dimensional ◽  
The Third ◽  
Circular Restricted Problem ◽  
Resonance Relation

The paper presents a summary of the results obtained by C. J. Cohen and E. C. Hubbard, who established by numerical integration that a resonance relation exists between the orbits of Neptune and Pluto. The problem may be explored further by approximating the motion of Pluto by that of a particle with negligible mass in the three-dimensional (circular) restricted problem. The mass of Pluto and the eccentricity of Neptune's orbit are ignored in this approximation. Significant features of the problem appear to be the presence of two critical arguments and the possibility that the orbit may be related to a periodic orbit of the third kind.

Conformation of Ribosomes from Escherichia Coli

1974 ◽  
Vol 32 ◽  
pp. 210-211
Author(s):  
M. Boublik ◽  
W. Hellmann ◽  
F. Jenkins
Keyword(s):  
Binding Sites ◽  
Ribosomal Proteins ◽  
Fluorescent Dyes ◽  
Protein Biosynthesis ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Dimensional Structure ◽  
Complete Understanding ◽  
And Function

The present knowledge of the three-dimensional structure of ribosomes is far too limited to enable a complete understanding of the various roles which ribosomes play in protein biosynthesis. The spatial arrangement of proteins and ribonuclec acids in ribosomes can be analysed in many ways. Determination of binding sites for individual proteins on ribonuclec acid and locations of the mutual positions of proteins on the ribosome using labeling with fluorescent dyes, cross-linking reagents, neutron-diffraction or antibodies against ribosomal proteins seem to be most successful approaches. Structure and function of ribosomes can be correlated be depleting the complete ribosomes of some proteins to the functionally inactive core and by subsequent partial reconstitution in order to regain active ribosomal particles.

Ultrastructural Investigations of the Contractile Filaments of Amoebae

1974 ◽  
Vol 32 ◽  
pp. 188-189
Author(s):  
P.L. Moore
Keyword(s):  
Cytoplasmic Streaming ◽  
Three Dimensional ◽  
Freeze Fracture ◽  
Amoeboid Movement ◽  
Different Types ◽  
Chemical Conditions ◽  
Complete Interpretation

Previous freeze fracture results on the intact giant, amoeba Chaos carolinensis indicated the presence of a fibrillar arrangement of filaments within the cytoplasm. A complete interpretation of the three dimensional ultrastructure of these structures, and their possible role in amoeboid movement was not possible, since comparable results could not be obtained with conventional fixation of intact amoebae. Progress in interpreting the freeze fracture images of amoebae required a more thorough understanding of the different types of filaments present in amoebae, and of the ways in which they could be organized while remaining functional.The recent development of a calcium sensitive, demembranated, amoeboid model of Chaos carolinensis has made it possible to achieve a better understanding of such functional arrangements of amoeboid filaments. In these models the motility of demembranated cytoplasm can be controlled in vitro, and the chemical conditions necessary for contractility, and cytoplasmic streaming can be investigated. It is clear from these studies that “fibrils” exist in amoeboid models, and that they are capable of contracting along their length under conditions similar to those which cause contraction in vertebrate muscles.

Structural organization of escherichia coli ribosomes as determined by immuno electron microscopy

1978 ◽  
Vol 36 (2) ◽  
pp. 166-167 ◽  
Author(s):  
G. Stöffler ◽  
R.W. Bald ◽  
J. Dieckhoff ◽  
H. Eckhard ◽  
R. Lührmann ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Escherichia Coli ◽  
Ribosomal Proteins ◽  
Structural Organization ◽  
Three Dimensional ◽  
Ribosomal Subunit ◽  
Spatial Arrangement ◽  
Small Subunit ◽  
Antibody Binding ◽  
Immuno Electron Microscopy

A central step towards an understanding of the structure and function of the Escherichia coli ribosome, a large multicomponent assembly, is the elucidation of the spatial arrangement of its 54 proteins and its three rRNA molecules. The structural organization of ribosomal components has been investigated by a number of experimental approaches. Specific antibodies directed against each of the 54 ribosomal proteins of Escherichia coli have been performed to examine antibody-subunit complexes by electron microscopy. The position of the bound antibody, specific for a particular protein, can be determined; it indicates the location of the corresponding protein on the ribosomal surface.The three-dimensional distribution of each of the 21 small subunit proteins on the ribosomal surface has been determined by immuno electron microscopy: the 21 proteins have been found exposed with altogether 43 antibody binding sites. Each one of 12 proteins showed antibody binding at remote positions on the subunit surface, indicating highly extended conformations of the proteins concerned within the 30S ribosomal subunit; the remaining proteins are, however, not necessarily globular in shape (Fig. 1).

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