The krathis lake, one century of evolution.

A riverbed swamp in the Krathis River, N. Peloponnese, is studied and analyzed geomorphologicaly. Our analysis is also based on sedimentological, geochemical, palaeontological and radiometric dating data which enabled the investigation of the possible relationship between the studied swamp and the 1913 Tsivlos landslide. Sedimentological analysis showed that the current sedimentation is dominated by fine grain material and occasional coarse-grained beds. Micropalaeontological analysis indicated that the deeper layers of the core are barren, while the upper ones contain fresh water ostracods suggesting hydrodynamically a progressively more stable environment. In accordance, radiocarbon C14 and 137Cs dating showed a progressively decreasing sedimentation rate over the last fifty years. The results of this study show that the Tsivlos landslide is not the only cause for the formation of the modern swamp. Tectonic movements in the area seem to play a decisive role causing uplift and subsidence in the area near an active fault.

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Solubilization of Charged Porphyrins in Interpolyelectrolyte Complexes: A Computer Study

Polymers ◽

10.3390/polym13040502 ◽

2021 ◽

Vol 13 (4) ◽

pp. 502

Author(s):

Karel Šindelka ◽

Zuzana Limpouchová ◽

Karel Procházka

Keyword(s):

Dissipative Particle Dynamics ◽

Water Soluble ◽

Coarse Grained ◽

Core Shell ◽

Computer Study ◽

Interpolyelectrolyte Complex ◽

The Core ◽

Porphyrin Derivatives ◽

Oppositely Charged ◽

Positively Charged

Using coarse-grained dissipative particle dynamics (DPD) with explicit electrostatics, we performed (i) an extensive series of simulations of the electrostatic co-assembly of asymmetric oppositely charged copolymers composed of one (either positively or negatively charged) polyelectrolyte (PE) block A and one water-soluble block B and (ii) studied the solubilization of positively charged porphyrin derivatives (P+) in the interpolyelectrolyte complex (IPEC) cores of co-assembled nanoparticles. We studied the stoichiometric mixtures of 137 A10+B25 and 137 A10−B25 chains with moderately hydrophobic A blocks (DPD interaction parameter aAS=35) and hydrophilic B blocks (aBS=25) with 10 to 120 P+ added (aPS=39). The P+ interactions with other components were set to match literature information on their limited solubility and aggregation behavior. The study shows that the moderately soluble P+ molecules easily solubilize in IPEC cores, where they partly replace PE+ and electrostatically crosslink PE− blocks. As the large P+ rings are apt to aggregate, P+ molecules aggregate in IPEC cores. The aggregation, which starts at very low loadings, is promoted by increasing the number of P+ in the mixture. The positively charged copolymers repelled from the central part of IPEC core partially concentrate at the core-shell interface and partially escape into bulk solvent depending on the amount of P+ in the mixture and on their association number, AS. If AS is lower than the ensemble average ⟨AS⟩n, the copolymer chains released from IPEC preferentially concentrate at the core-shell interface, thus increasing AS, which approaches ⟨AS⟩n. If AS>⟨AS⟩n, they escape into the bulk solvent.

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On the formation and stability of fermionic dark matter halos in a cosmological framework

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3986 ◽

2020 ◽

Author(s):

Carlos R Argüelles ◽

Manuel I Díaz ◽

Andreas Krut ◽

Rafael Yunis

Keyword(s):

Black Hole ◽

Dark Matter ◽

Space Distribution ◽

Coarse Grained ◽

Dark Matter Halos ◽

The Core ◽

The Galaxy ◽

Gravitating Systems ◽

The Given ◽

First Time

Abstract The formation and stability of collisionless self-gravitating systems is a long standing problem, which dates back to the work of D. Lynden-Bell on violent relaxation, and extends to the issue of virialization of dark matter (DM) halos. An important prediction of such a relaxation process is that spherical equilibrium states can be described by a Fermi-Dirac phase-space distribution, when the extremization of a coarse-grained entropy is reached. In the case of DM fermions, the most general solution develops a degenerate compact core surrounded by a diluted halo. As shown recently, the latter is able to explain the galaxy rotation curves while the DM core can mimic the central black hole. A yet open problem is whether this kind of astrophysical core-halo configurations can form at all, and if they remain stable within cosmological timescales. We assess these issues by performing a thermodynamic stability analysis in the microcanonical ensemble for solutions with given particle number at halo virialization in a cosmological framework. For the first time we demonstrate that the above core-halo DM profiles are stable (i.e. maxima of entropy) and extremely long lived. We find the existence of a critical point at the onset of instability of the core-halo solutions, where the fermion-core collapses towards a supermassive black hole. For particle masses in the keV range, the core-collapse can only occur for Mvir ≳ E9M⊙ starting at zvir ≈ 10 in the given cosmological framework. Our results prove that DM halos with a core-halo morphology are a very plausible outcome within nonlinear stages of structure formation.

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Submarine lava deltas of the 2018 eruption of Kīlauea volcano

Bulletin of Volcanology ◽

10.1007/s00445-020-01424-1 ◽

2021 ◽

Vol 83 (4) ◽

Author(s):

S. Adam Soule ◽

Michael Zoeller ◽

Carolyn Parcheta

Keyword(s):

Grain Size ◽

Pore Pressure ◽

Mechanistic Model ◽

Large Fraction ◽

Volcanic Hazards ◽

Lava Flows ◽

Coarse Grained ◽

Fine Grained ◽

Fine Grain ◽

Delta Formation

AbstractHawaiian and other ocean island lava flows that reach the coastline can deposit significant volumes of lava in submarine deltas. The catastrophic collapse of these deltas represents one of the most significant, but least predictable, volcanic hazards at ocean islands. The volume of lava deposited below sea level in delta-forming eruptions and the mechanisms of delta construction and destruction are rarely documented. Here, we report on bathymetric surveys and ROV observations following the Kīlauea 2018 eruption that, along with a comparison to the deltas formed at Pu‘u ‘Ō‘ō over the past decade, provide new insight into delta formation. Bathymetric differencing reveals that the 2018 deltas contain more than half of the total volume of lava erupted. In addition, we find that the 2018 deltas are comprised largely of coarse-grained volcanic breccias and intact lava flows, which contrast with those at Pu‘u ‘Ō‘ō that contain a large fraction of fine-grained hyaloclastite. We attribute this difference to less efficient fragmentation of the 2018 ‘a‘ā flows leading to fragmentation by collapse rather than hydrovolcanic explosion. We suggest a mechanistic model where the characteristic grain size influences the form and stability of the delta with fine grain size deltas (Pu‘u ‘Ō‘ō) experiencing larger landslides with greater run-out supported by increased pore pressure and with coarse grain size deltas (Kīlauea 2018) experiencing smaller landslides that quickly stop as the pore pressure rapidly dissipates. This difference, if validated for other lava deltas, would provide a means to assess potential delta stability in future eruptions.

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Yield Stress Model for Natural Debris Flows in Presence of Fine and Coarse–Grained Sediments

Water ◽

10.3390/w13131865 ◽

2021 ◽

Vol 13 (13) ◽

pp. 1865

Author(s):

Leonardo Schippa

Keyword(s):

Yield Stress ◽

Debris Flows ◽

Rheological Behaviour ◽

Coarse Fraction ◽

Coarse Grained ◽

Stress Model ◽

Coarse Sediment ◽

Fine Grain ◽

Sediment Fraction ◽

Coarse To Fine

When dealing with natural geo–hazards, it is important to understand the influence of sediment sorting on debris flows. The presence of coarse fraction is one of the aspects which affects the rheological behaviour of natural viscous granular fluid mixtures. In this paper, experiments on reconstituted debris flow mixtures with different coarse–to–fine sediment ratios are considered. Such mixtures behave just as non–Newtonian yield stress fluids and their rheological behaviour is largely affected by the presence of coarse fraction. Experimental results demonstrate that yield stress is very sensitive not only to bulk sediment concentration but also to coarse sediment fraction. A novel yield stress model is presented. It accounts for an empirical grading function depending on the coarse–to–fine grain content. The yield stress model performed satisfactorily in comparison with the experiments, showing that it is almost independent of the coarse–to–fine grain fraction in case of dominant coarse sediment content.

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THE IDEAL DISTRIBUTION OF FARMERS: EXPLAINING THE EURO-AMERICAN SETTLEMENT OF UTAH

American Antiquity ◽

10.1017/aaq.2017.46 ◽

2017 ◽

Vol 83 (1) ◽

pp. 75-90 ◽

Cited By ~ 11

Author(s):

Peter M. Yaworsky ◽

Brian F. Codding

Keyword(s):

Population Density ◽

Ideal Free Distribution ◽

Negative Relationship ◽

Coarse Grained ◽

Distribution Model ◽

Test Model ◽

Fine Grained ◽

Fine Grain ◽

Model Predictions ◽

The Ideal

Explaining how and why populations settle a new landscape is central to many questions in American archaeology. Recent advances in settlement research have adopted predictions from the Ideal Free Distribution model (IFD). While tests of IFD predictions to date rely either on archaeologically derived coarse-grained diachronic data or ethnographically derived fine-grained synchronic data, here we provide the first test using historically derived data that is both fine-grained and diachronic. Fine-grain diachronic data allow us to test model predictions at a temporal scale in line with human settlement decisions and to validate proxies for application in archaeological contexts. To test model predictions pertaining to the relationship between population density and habitat quality, we use data from the historical settlement of Utah. The results demonstrate a negative relationship between population density and the quality of habitats occupied. These results are consistent with IFD predictions, suggesting that Euro-American settlement of Utah resulted from individuals attempting to maximize individual returns via agricultural productivity. Our results provide a quantitative and testable explanation for population dispersion over time and explain the spatial distribution of population density today. The results support predictions derived from a general theory of behavior, providing an explanatory framework for colonization events worldwide.

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Stratigraphy, stable isotopes and salinity in multi-year sea ice from the rift area, south George VI Ice Shelf, Antarctic Peninsula

Journal of Glaciology ◽

10.3189/s0022143000005797 ◽

1991 ◽

Vol 37 (127) ◽

pp. 357-367

Author(s):

J.-L. Tison ◽

E. M. Morris ◽

R. Souchez ◽

J. Jouzel

Keyword(s):

Stable Isotopes ◽

Sea Ice ◽

Fresh Water ◽

Large Scale ◽

Sea Water ◽

Ice Core ◽

Ice Shelf ◽

The Core ◽

Brackish Ice ◽

Ice Production

AbstractResults from a detailed profile in a 5.54 m multi-year sea-ice core from the rift area in the southern part of George VI Ice Shelf are presented. Stratigraphy, stable isotopes and Na content are used to investigate the growth processes of the ice cover and to relate them to melting processes at the bottom of the ice shelf.The thickest multi-year sea ice in the sampling area appears to be second-year sea ice that has survived one melt season. Combined salinity/stable-isotope analyses show large-scale sympathetic fluctuations that can be related to the origin of the parent water. Winter accretion represents half of the core length and mainly consists of frazil ice of normal sea-water origin. However, five major dilution events of sea water, with fresh-water input from the melting base of the ice shelf reaching 20% on two occasions, punctuate this winter accretion. Two of them correspond to platelet-ice production, which is often related to the freezing of ascending supercooled water from the bottom of the ice shelf.Brackish ice occurs between 450 and 530 cm in the core. It is demonstrated that this results from the freezing of brackish water (Jeffries and others, 1989) formed by mixing of normal sea water with melted basal shelf ice, with dilution percentages of maximum 80% fresh water.

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Research on the Low-Carbon Technology Innovation System of Petroleum Enterprises

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.521.810 ◽

2014 ◽

Vol 521 ◽

pp. 810-814

Author(s):

Jie Luo

Keyword(s):

Technological Innovation ◽

Technology Innovation ◽

Innovation System ◽

Decisive Role ◽

System Optimization ◽

System Construction ◽

Low Carbon ◽

The Core ◽

Enterprise Technology ◽

Core Activity

Technological innovation is the core activity of petroleum enterprises. Low-carbon technology innovation system construction and optimization play a decisive role for improving the ability of technological innovation and sustainable development. Based on analyzing the meaning of enterprise technology innovation system, detailed the structure of the low-carbon technology innovation system of petroleum enterprises, pointed out the direction and the main content of the low-carbon technology innovation system optimization, and provided a reference for Chinese petroleum enterprises to develop low-carbon technology innovation.

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Mesoscale Simulation of the Structure of Star Acrylated Poly(ethylene glycol-co-lactide) Hydrogels

MRS Proceedings ◽

10.1557/opl.2012.100 ◽

2012 ◽

Vol 1418 ◽

Author(s):

Seyed Sina Moeinzadeh ◽

Esmaiel Jabbari

Keyword(s):

Ethylene Glycol ◽

Volume Fraction ◽

Equations Of Motion ◽

Dissipative Particle Dynamics ◽

Random Force ◽

Dynamics Simulation ◽

Coarse Grained ◽

Poly Ethylene Glycol ◽

The Core ◽

Poly Ethylene

ABSTRACTIn this work the microstructures of star acrylated poly(ethylene glycol-co-lactide) (SPELA) with different LA:EG ratios in the aqueous solution have been simulated via Dissipative Particle Dynamics (DPD) approach at the mesoscale. The system components were coarse-grained into different beads (set of atoms) which moved according to the Newton’s equations of motion integrated via a modified Velocity-Verlet algorithm. The force acting on each bead, in a specific cutoff distance (rc), was divided into a conservative force (FC), random force (FR), dissipative force (FD), bond force (FS) and bond angle force (FE). The repulsion parameters of the conservative force (αij) were calculated from the solubility parameter of the beads, each of which were extracted from an atomistic molecular dynamics simulation (MD). Simulations showed the formation of micelles with lactide and acrylate beads occupied the core and hydrophilic ethylene oxide segments extending through the water to form the corona. The micelles showed an increasing trend in size and decreasing trend in number density with increase in LA:EG ratio. Results showed that the acrylate density decreased from the center of the micelles to the core surface although the overall amount of acrylates increased due to the increase in volume. Furthermore, the running integration number of acrylate-water beads showed decreasing accessibility of acrylates to water with increasing PLA volume fraction.

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The Influence of Processing on Microstructural Development, Tensile Response and Fracture Behavior of Aluminum Alloy 5083

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.410.175 ◽

2011 ◽

Vol 410 ◽

pp. 175-186 ◽

Cited By ~ 1

Author(s):

Troy D. Topping ◽

Ying Li ◽

Enrique J. Lavernia ◽

K. Manigandan ◽

T.S. Srivatsan

Keyword(s):

Aluminum Alloy ◽

Fracture Behavior ◽

Tensile Deformation ◽

Coarse Grained ◽

Microstructural Development ◽

Deformation Kinetics ◽

Aluminum Alloy 5083 ◽

Fine Grain ◽

Deformation And Fracture ◽

Specific Influence

In this paper, the specific influence of quasi-isostatic forging and rolling of cryomilled powder on microstructural development and resultant tensile deformation and fracture behavior of aluminum alloy 5083 is highlighted and comparison made with the coarse grained counterpart. The specific influence and contribution of strain hardening to enhancing strength of the ultra-fine grain microstructure of the aluminum alloy is presented and discussed. It is shown that the capability of the ultra fine grain microstructure to recover strength through the mechanism of work hardening is quite similar to the conventionally processed counterpart. The influence and role of intrinsic microstructural features in governing tensile deformation and fracture behavior is elaborated upon. The viable microscopic mechanisms governing final fracture behavior is discussed in light of the competing and mutually interactive influences of nature of loading, intrinsic microstructural effects, and deformation kinetics. Key Words: aluminum alloy 5083, processing, microstructure, tensile properties, fracture

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Lake Sediments from the Kashmir Himalayas: Inverted 14C Chronology and Its Implications

Radiocarbon ◽

10.1017/s0033822200063839 ◽

1992 ◽

Vol 34 (3) ◽

pp. 561-565 ◽

Cited By ~ 13

Author(s):

Sheela Kusumgar ◽

D. P. Agrawal ◽

Narendra Bhandari ◽

R. D. Deshpande ◽

Alok Raina ◽

...

Keyword(s):

Magnetic Susceptibility ◽

Lake Sediments ◽

Sedimentation Rate ◽

Catchment Area ◽

Inversion Layer ◽

The Core ◽

Manasbal Lake ◽

Mineral Magnetic ◽

Lake Deposits

We have measured 14C, 210Pb and 137Cs profiles in two representative cores from Manasbal Lake, Kashmir, India. The sedimentation rate derived from 210Pb and 137Cs in the upper part of the core is in the range of 3.4 to 5.5 mm yr−1. In contrast, 14C ages show an inversion at depths >20 cm. These results are attributed to the erosion of the ubiquitous 10–20-m-thick loess mantle, based on the similarity of 14C ages of the inversion layer in the sediments and the paleosols present in the catchment area. Frequency-dependent mineral magnetic susceptibility (χfd), carbon to nitrogen ratios and pigment concentrations in the profile show a significant amount of allochthonous component in the lake deposits and support the conclusion that the 14C dates do not reflect the chronology of the in-situ lake sedimentation but episodic deposition of the surrounding loess. Thus, 14C serves as a useful tracer to understand source components of the sediments.

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