Phase Of Intermediate Density Research Articles

Depositional and postdepositional processes of an oil-shale analog at the microstructure scale: The Lower Cretaceous Agrio Formation, Neuquén Basin, northern Patagonia

The Lower Cretaceous Agrio Formation is a source rock considered to be a possible unconventional reservoir. However, no detailed microstructure characterization of this hydrocarbon play has been performed. An exceptional oil-prone level is determined through outcrop information, petrography, x-ray diffraction, geochemical analysis, and x-ray micro–computed tomography (μCT). Microscopic studies reveal a lenticular fabric and calcareous nannofossils suggesting high carbonate productivity in the water column and algal-derived organic matter. The high organic matter content points to anoxic–euxinic conditions consistent with pyrite framboids, authigenic fluorapatite, and an elevated concentration of redox-sensitive elements. However, burrows reveal the activity of infaunal organisms, thus rejecting the idea of persistent bottom-water anoxia. The bioturbated, calcareous plankton and carbonate-rich mudstone represents accumulation in a distal outer ramp setting with calcareous plankton blooms and the co-occurrence of benthic microbial mats. Bottom currents, probably as a consequence of storm-related processes, were involved in detrital transport and oxygenation pulses. A three-dimensional (3-D)–microstructure reconstruction reveals three main μCT density-dependent phases: (1) a low-density phase composed of organic matter and calcite, (2) an intermediate-density phase dominated by calcite and minor organic matter, and (3) a high-density phase composed of authigenic minerals (pyrite, marcasite, and fluorapatite) and silt-sized detrital quartz and plagioclase. This analysis showed that burial diagenesis did not create enough pore space to be evaluated through μCT and that besides mineralogy, particle-size distribution, particle arrangement (sorting), and the local compaction degree affect the 3-D reconstructed structure. The analyzed sample is located toward the carbonaceous end member of the shale spectrum and exemplifies new approaches for the characterization of carbonate oil shales in the unit and similar deposits. From the perspective of unconventional exploration, the evaluation of depositional and postdepositional controls on the resultant microstructure might contribute to a better understanding of potential target intervals within the Agrio Formation.

The effect of on-ramp and off-ramp on the one dimensional road with open boundaries

The effect of one on-ramp (entry) and one off-ramp (exit) is investigated numerically in a one dimensional cellular automaton traffic flow model, with open boundary conditions, using parallel dynamics. Our aim in this paper is to study how the injection rates α and α0 and the extraction rates β and β0 act on the density and flux of cars in a one dimensional road. The priority of occupation at entry site i1 (removing at exit site i2) is attributed to the particle that entered (was absorbed) the chain. Phase diagrams in (β0, α0) and (β, α0) plans are established. For α = 0.1, they show three different topologies in the flow behaviour. The first one corresponds to the presence of four regions, by varying α0, namely low-density phase (LDP), intermediate-density phase (IDP), plateau current phase (PCP), and high-density phase (HDP). In the second topology, the intermediate-density phase disappears. The third topology presents only two regions, i.e., low- and high-density phases. For small values of α, the (IDP) and (PCP) disappear, respectively, by increasing β. When increasing α, the fourth topology, corresponding to one phase (HDP), appears for low values of β and β0.

Self-Organization in 2D Traffic Flow Model with Jam-Avoiding Drive

A stochastic cellular automaton (CA) model is presented to investigate the traffic jam by self-organization in the two-dimensional (2D) traffic flow. The CA model is the extended version of the 2D asymmetric exclusion model to take into account jam-avoiding drive. Each site contains either a car moving to the up, a car moving to the right, or is empty. A up car can shift right with probability p ja if it is blocked ahead by other cars. It is shown that the three phases (the low-density phase, the intermediate-density phase and the high-density phase) appear in the traffic flow. The intermediate-density phase is characterized by the right moving of up cars. The jamming transition to the high-density jamming phase occurs with higher density of cars than that without jam-avoiding drive. The jamming transition point p 2c increases with the shifting probability p ja . In the deterministic limit of p ja =1, it is found that a new jamming transition occurs from the low-density synchronized-shifting phase to the high-density moving phase with increasing density of cars. In the synchronized-shifting phase, all up cars do not move to the up but shift to the right by synchronizing with the move of right cars. We show that the jam-avoiding drive has an important effect on the dynamical jamming transition.

Ordered phases in concentrated DNA solutions

Aqueous solutions of concentrated DNA, a strong polyelectrolyte, in 1:1 electrolyte form liquid-crystalline phases analogous to those observed for other semi-rigid neutral polymers and weak polyelectrolytes. Phase transitions were examined in detail for DNA fragments with a contour length (500 Å) approximating the persistence length. These fragments form at least three lyotropic phases. The lowest density or “precholesteric” phase appears to be a nematic with a slight and easily variable twist. The intermediate density phase is a true cholesteric with a pitch of ≈2.1 μm. With increasing concentration the cholesteric phase unwinds prior to formation of the third, high density, columnar phase. Phase transition boundaries were determined as functions of DNA concentration from 10 to 300 mg/ml solvent, supporting electrolyte concentration from 0.01 to 1.0 M, and temperature from 20°C to 60°C. Critical concentrations for formation of anisotropic phase ( C i ) and disappearance of isotropic phase ( C a ) were only moderately dependent on temperature. C i , C a , and the pitch of the cholesteric phase were surprisingly insensitive to the supporting electrolyte concentration. The insensitivity can be most simply related to the high concentrations required for anisotropic phase formation by these rather short, highly charged rod-like DNA fragments. At high concentrations the DNA counterions contribute significantly to the effective ionic strength, hence overall charge screening, and the counterion atmosphere as monitored by 23Na NMR, appears to be perturbed by inter-rod interactions.

On the ground state of an interacting boson system

We prove that the interacting boson system has three phases within the Hartree-Bose approximation. The low-density phase is the usual Bose-Einstein condensate while the high-density phase corresponds to the state in which a larger fraction of Bose condensate particles are paired in one non-zero momentum state. In the intermediate-density phase all the particles are paired in a non-zero momentum state. It is observed that the ground state in the new phases is an infinitely degenerate state contrary to the non-degenerate Bose-Einstein condensate.