scholarly journals Floodplains and paleosols in the Wyoming Eocene sequence: implications for the taphonomy and paleoecology of faunas

1992 ◽  
Vol 6 ◽  
pp. 31-31
Author(s):  
Thomas M. Bown ◽  
Mary J. Kraus ◽  
Andres Aslan
Keyword(s):  
Large Scale ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Three Dimensional ◽  
Lateral Position ◽  
National Geographic Society ◽  
Faunal Turnover ◽  
Fossil Vertebrate ◽  
Willwood Formation ◽  
Crevasse Splay

The Willwood Fm. of the southern Bighorn Basin of Wyoming, U.S.A., comprises 700 m of lower Eocene alluvial molasse, nearly all of which contains relict pedogenic features. These rocks are grouped into pedofacies–alluvial sediment prisms, thick with immature paleosols proximal to streams and thinner with mature paleosols distally. Pedofacies are bounded by either trunk-stream channel or crevasse-splay deposits, which represent time-stratigraphic markers. The floodplain widths of the Willwood rivers varied from 15 to 20+ km. Paleosols occur throughout the Willwood Formation and the most mature paleosols required about 60 Ka to form whereas the least mature, required 0.5 to 1.0 Ka. Paleosol thicknesses vary from about 0.3–8.0 m and are directly related to net sediment accumulation rate (NSAR) and profile maturity. Pedofacies also reflect NSAR controls; pedofacies are continuously superposed, 15–35-m-thick, and represent time intervals of 30–60 Ka.In the earliest Eocene, paleosol maturity rose sharply, and NSAR plummeted (Fort Union Fm./Willwood Fm. contact), after which maturity gradually declined (and NSAR rose) throughout the early Eocene. This decline was punctuated by two episodes of severe decline, each corresponding with major increases in NSAR, increased tectonism, and episodes of faunal turnover (“Biohorizons” A and B). Above the biohorizons, species earlier tied to particular paleosol maturities were replaced by closely related though more generalized species with no marked paleosol preferences. Time-stratigraphic reconstruction of the Willwood Fm. shows that “Biohorizons” B and C record the same faunal event; B the extinctions, and C the immigrations.The 1,300 Willwood fossil vertebrate localities, which are distributed throughout the entire formation, occur in the surface horizons of cumulative alluvial paleosols. All fossil accumulations in paleosols are attritional and formed during pedogenesis. The most complete remains occur in immature paleosols, whereas the most abundant remains are found in mature paleosols. Within the large-scale Willwood ecologic setting, studies of discrete (m's to tens of m's thick) stratigraphic intervals suggest that the paleontology and sedimentology of these intervals can be significantly influenced by lateral differences in paleosol hydromorphy (soil wetness) and maturity (lateral position of a fossil-bearing paleosol with respect to an ancient river channel). These smaller-scale controls on fossil occurrences are important for distinguishing between real and apparent changes in faunal compositions over time and emphasize the value of three-dimensional stratigraphic analysis for interpreting paleontologic events.Supported by National Geographic Society grant 3985-89.

Global wind-induced change of deep-sea sediment budgets, new ocean production and CO 2 reservoirs ca . 3.3-2.35 Ma BP

1988 ◽  
Vol 318 (1191) ◽  
pp. 487-504 ◽  
Keyword(s):  
Large Scale ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Distribution Patterns ◽  
Trade Wind ◽  
Accumulation Rates ◽  
Deep Sea Sediment ◽  
Late Pliocene ◽  
High Productivity ◽  
Sediment Fraction

The late Pliocene phase of large-scale climatic deterioration about 3.2-2.4 Ma BP is well documented in a number of (benthic) δ 18 O records. To test the global implications of this event, we have mapped the distribution patterns of various sediment variables in the Pacific and Atlantic Oceans during two time slices, 3.4-3.18 and 2.43-2.33 Ma BP. The changes of bulk sedimentation and bulk sediment accumulation rates are largely explained by the variations of CaCO 3 -accumulation rates (and the accumulation rates of the complementary siliciclastic sediment fraction near continents in higher latitudes). During the late Pliocene, the CaCO 3 -accumulation rate increased along the equatorial Pacific and Atlantic and in the northeastern Atlantic, but decreased elsewhere. The accumulation rate of organic carbon (C org ) and net palaeoproductivity also increased below the high-productivity belts along the equator and the eastern continental margins. From these patterns we may conclude that (trade-) wind- induced upwelling zones and upwelling productivity were much enhanced during that time. This change led to an increased transfer of CO 2 from the surface ocean to the ocean deep water and to a reduction of evaporation, which resulted in an aridification of the Saharan desert belt as depicted in the dust sediments off northwest Africa.

scholarly journals Re-evaluating <sup>14</sup>C dating accuracy in deep-sea sediment archives

Geochronology ◽  
2020 ◽  
Vol 2 (1) ◽  
pp. 17-31 ◽  
Author(s):  
Bryan C. Lougheed ◽  
Philippa Ascough ◽  
Andrew M. Dolman ◽  
Ludvig Löwemark ◽  
Brett Metcalfe
Keyword(s):  
Deep Sea ◽  
Large Scale ◽  
Accumulation Rate ◽  
Global Climate ◽  
Age Distribution ◽  
Sediment Accumulation ◽  
Depth Interval ◽  
Time Step ◽  
Deep Sea Sediment ◽  
14C Age

Abstract. The current geochronological state of the art for applying the radiocarbon (14C) method to deep-sea sediment archives lacks key information on sediment bioturbation. Here, we apply a sediment accumulation model that simulates the sedimentation and bioturbation of millions of foraminifera, whereby realistic 14C activities (i.e. from a 14C calibration curve) are assigned to each single foraminifera based on its simulation time step. We find that the normal distribution of 14C age typically used to represent discrete-depth sediment intervals (based on the reported laboratory 14C age and measurement error) is unlikely to be a faithful reflection of the actual 14C age distribution for a specific depth interval. We also find that this deviation from the actual 14C age distribution is greatly amplified during the calibration process. Specifically, we find a systematic underestimation of total geochronological error in many cases (by up to thousands of years), as well as the generation of age–depth artefacts in downcore calibrated median age. Even in the case of “perfect” simulated sediment archive scenarios, whereby sediment accumulation rate (SAR), bioturbation depth, reservoir age and species abundance are all kept constant, the 14C measurement and calibration processes generate temporally dynamic median age–depth artefacts on the order of hundreds of years – whereby even high SAR scenarios (40 and 60 cm kyr−1) are susceptible. Such age–depth artefacts can be especially pronounced during periods corresponding to dynamic changes in the Earth's Δ14C history, when single foraminifera of varying 14C activity can be incorporated into single discrete-depth sediment intervals. For certain lower-SAR scenarios, we find that downcore discrete-depth true median age can systematically fall outside the calibrated age range predicted by the 14C measurement and calibration processes, thus leading to systematically inaccurate age estimations. In short, our findings suggest the possibility of 14C-derived age–depth artefacts in the literature. Furthermore, since such age–depth artefacts are likely to coincide with large-scale changes in global Δ14C, which themselves can coincide with large-scale changes in global climate (such as the last deglaciation), 14C-derived age–depth artefacts may have been previously incorrectly attributed to changes in SAR coinciding with global climate. Our study highlights the need for the development of improved deep-sea sediment 14C calibration techniques that include an a priori representation of bioturbation for multi-specimen samples.

scholarly journals A Review on Additive Manufacturing Possibilities for Electrical Machines

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1940
Author(s):  
Muhammad Usman Naseer ◽  
Ants Kallaste ◽  
Bilal Asad ◽  
Toomas Vaimann ◽  
Anton Rassõlkin
Keyword(s):  
Additive Manufacturing ◽  
Large Scale ◽  
Three Dimensional ◽  
Electrical Machines ◽  
Electromagnetic Properties ◽  
Scale Production ◽  
Performance Parameters ◽  
Large Scale Production ◽  
One Step ◽  
Manufacturing Techniques

This paper presents current research trends and prospects of utilizing additive manufacturing (AM) techniques to manufacture electrical machines. Modern-day machine applications require extraordinary performance parameters such as high power-density, integrated functionalities, improved thermal, mechanical & electromagnetic properties. AM offers a higher degree of design flexibility to achieve these performance parameters, which is impossible to realize through conventional manufacturing techniques. AM has a lot to offer in every aspect of machine fabrication, such that from size/weight reduction to the realization of complex geometric designs. However, some practical limitations of existing AM techniques restrict their utilization in large scale production industry. The introduction of three-dimensional asymmetry in machine design is an aspect that can be exploited most with the prevalent level of research in AM. In order to take one step further towards the enablement of large-scale production of AM-built electrical machines, this paper also discusses some machine types which can best utilize existing developments in the field of AM.

scholarly journals Vibration characteristics of triple-gear-rotor system in compressed air energy storage under variable torque load

2021 ◽  
Vol 104 (1) ◽  
pp. 003685042098705
Author(s):  
Xinran Wang ◽  
Yangli Zhu ◽  
Wen Li ◽  
Dongxu Hu ◽  
Xuehui Zhang ◽  
...  
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Element Model ◽  
Rotor System ◽  
Dynamic Responses ◽  
System Response ◽  
Rotating Speed ◽  
Torque Load ◽  
Set Up ◽  
Two Stages

This paper focuses on the effects of the off-design operation of CAES on the dynamic characteristics of the triple-gear-rotor system. A finite element model of the system is set up with unbalanced excitations, torque load excitations, and backlash which lead to variations of tooth contact status. An experiment is carried out to verify the accuracy of the mathematical model. The results show that when the system is subjected to large-scale torque load lifting at a high rotating speed, it has two stages of relatively strong periodicity when the torque load is light, and of chaotic when the torque load is heavy, with the transition between the two states being relatively quick and violent. The analysis of the three-dimensional acceleration spectrum and the meshing force shows that the variation in the meshing state and the fluctuation of the meshing force is the basic reasons for the variation in the system response with the torque load. In addition, the three rotors in the triple-gear-rotor system studied show a strong similarity in the meshing states and meshing force fluctuations, which result in the similarity in the dynamic responses of the three rotors.

scholarly journals Shell-crossing in a ΛCDM Universe

2020 ◽  
Vol 501 (1) ◽  
pp. L71-L75
Author(s):  
Cornelius Rampf ◽  
Oliver Hahn
Keyword(s):  
Dark Matter ◽  
Perturbation Theory ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Three Dimensional ◽  
Random Initial Data ◽  
Recursion Relations ◽  
Indispensable Tool ◽  
First Time ◽  
Very High

ABSTRACT Perturbation theory is an indispensable tool for studying the cosmic large-scale structure, and establishing its limits is therefore of utmost importance. One crucial limitation of perturbation theory is shell-crossing, which is the instance when cold-dark-matter trajectories intersect for the first time. We investigate Lagrangian perturbation theory (LPT) at very high orders in the vicinity of the first shell-crossing for random initial data in a realistic three-dimensional Universe. For this, we have numerically implemented the all-order recursion relations for the matter trajectories, from which the convergence of the LPT series at shell-crossing is established. Convergence studies performed at large orders reveal the nature of the convergence-limiting singularities. These singularities are not the well-known density singularities at shell-crossing but occur at later times when LPT already ceased to provide physically meaningful results.

scholarly journals Advancing Drug Discovery for Neurological Disorders Using iPSC-Derived Neural Organoids

2021 ◽  
Vol 22 (5) ◽  
pp. 2659
Author(s):  
Gianluca Costamagna ◽  
Giacomo Pietro Comi ◽  
Stefania Corti
Keyword(s):  
Drug Discovery ◽  
Drug Screening ◽  
Neural Development ◽  
Neurological Disorders ◽  
Large Scale ◽  
Three Dimensional ◽  
Induced Pluripotent Stem Cell ◽  
Cellular Level ◽  
Complex Data ◽  
Complex Data Sets

In the last decade, different research groups in the academic setting have developed induced pluripotent stem cell-based protocols to generate three-dimensional, multicellular, neural organoids. Their use to model brain biology, early neural development, and human diseases has provided new insights into the pathophysiology of neuropsychiatric and neurological disorders, including microcephaly, autism, Parkinson’s disease, and Alzheimer’s disease. However, the adoption of organoid technology for large-scale drug screening in the industry has been hampered by challenges with reproducibility, scalability, and translatability to human disease. Potential technical solutions to expand their use in drug discovery pipelines include Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) to create isogenic models, single-cell RNA sequencing to characterize the model at a cellular level, and machine learning to analyze complex data sets. In addition, high-content imaging, automated liquid handling, and standardized assays represent other valuable tools toward this goal. Though several open issues still hamper the full implementation of the organoid technology outside academia, rapid progress in this field will help to prompt its translation toward large-scale drug screening for neurological disorders.

Large-scale, three-dimensional tissue cytometry of the human kidney: a complete and accessible pipeline

2021 ◽  
Author(s):  
Michael J. Ferkowicz ◽  
◽  
Seth Winfree ◽  
Angela R. Sabo ◽  
Malgorzata M. Kamocka ◽  
...  
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Human Kidney
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