New fossil assemblages from the Early Ordovician Fezouata Biota

The Fezouata Biota (Morocco) is an exceptionally well-preserved fossil community of Early Ordovician age and although its oldest units are comparable with Burgess Shale-type localities of the Cambrian Explosion, little attention has been paid to the younger units despite potential to reveal the conditions of the Ordovician Radiation. Herein, we describe a new middle to upper Floian Fezouata locality (Taichoute) encompassing an assemblage dominated by large bivalved euarthropods and giant filter-feeding radiodonts, which were transported and preserved in concretions associated with density-flow deposits. Taichoute captures the closing of the taphonomic window that characterizes exceptional fossil preservation during the Cambrian Explosion (i.e., carbonaceous compressions) as well as the faunal transition to assemblages dominated by typical Palaeozoic taxa.

Electrical and Optical Characterization Methodologies for Advanced Spark Ignition

Due to the high transiency and high voltage characteristics of spark ignition, precise measurements are in demand for efficient ignition in future clean combustion engines. The practical challenges of SI systems arise as the gaseous substances vary extensively in density, flow, and temperature. In this paper, a typical transistor coil ignition system with a current management module maintains the transient discharge condition for more credible measurements. Suitable apparatus with FPGA multi-task control systems are established to effectively control and stabilize the discharge current level and duration. The electrical waveforms and spark plasma patterns are correlated, via concurrent electric probing and shadowgraph imaging, under quiescent and flow conditions. The multi-task FPGA provides synchronization of ignition control and data acquisition. The empirical setup and analyzing methods of this work provide essential guidance for facilitating broader innovations in spark ignition, and for advancing the clean and efficient combustion in automotive and aviation engines.

Density Slopes in Variable Density Flow Modeling

Variable density flow (VDF) modeling is a valuable tool for assessing the potential impacts of global climate change and sea level rise on coastal aquifers. When using any of these modeling tools, a quantitative relationship is needed to compute the fluid density from salt concentration. A full understanding of the relationship between fluid density and solute concentration and the correct implementation of the equation of state are critical for variable density modeling. The works of Baxter and his colleagues in the early 20th century showed that fluid density could be linearly correlated to salt concentrations. A constant density slope of 0.7 is often assumed and applied. The assumption is reasonable when the salinity is less than 100‰. The density slope can also be defined from chloride concentration data with the assumption of a constant ratio (55%) between chloride and total dissolved solids (TDS). Field data from central Florida indicate that the chloride/TDS ratio can be as low as 5%. Therefore, TDS is the preferred water quality data for fluid density determination in variable density modeling. Other issues with density slope are also discussed, and some commonly used values of density slope are provided in this technical note.

Charge-Flow Profiles along Curvilinear Paths: A Flexible Scheme for the Analysis of Charge Displacement upon Intermolecular Interactions

The Charge-Displacement (CD) analysis has proven to be a powerful tool for a quantitative characterization of the electron-density flow occurring upon chemical bonding along a suitably chosen interaction axis. In several classes of interesting intermolecular interactions, however, an interaction axis cannot be straightforwardly defined, and the CD analysis loses consistency and usefulness. In this article, we propose a general, flexible reformulation of the CD analysis capable of providing a quantitative view of the charge displacement along custom curvilinear paths. The new scheme naturally reduces to ordinary CD analysis if the path is chosen to be a straight line. An implementation based on a discrete sampling of the electron densities and a Voronoi space partitioning is described and shown in action on two test cases of a metal-carbonyl and a pyridine-ammonia complex.

Efficient Stochastic Simulation of Seawater Intrusion, With Mixing, in Confined Coastal Aquifers

We present a high-efficiency method for simulating seawater intrusion (SWI), with mixing, in confined coastal aquifers based on uncoupled equations in the through-flow region of the aquifer. The flow field is calculated analytically and the tracer transport numerically, via spatial splitting along the principal directions (PD) of transport. Advection-dispersion processes along streamlines are simulated with the very efficient matched artificial dispersivity (MAD) method of Syriopoulou and Koussis and the system of discretized transverse-dispersion equations is solved with the Thomas algorithm. These concepts are embedded in the 2D-MADPD-SWI model, yielding comparable solutions to those of the uncoupled SWI equations with the state-of-the-art FEFLOW code, but faster, while 2D-MADPD-SWI achieves an at least hundredfold faster solution than a variable-density flow model. We demonstrate the utility of the 2D-MADPD-SWI model in stochastic Monte Carlo simulations by assessing the uncertainty on the advance of the 1,500 ppm TDS line (limit of tolerable salinity for irrigation) due to randomly variable hydraulic conductivity and freshwater flow rate.

Debris Capture Distribution in Deepwater Wells with Riser Filter Tool

In deepwater and ultra-deepwater wells, hydraulic debris removal, or the circulating of debris to surface, serves as the primary method of removing debris from the wellbore during the displacement of drilling fluid to completion fluid. In a standard cased hole completion, this operation typically takes place after the last liner has been set and before the completion is run. The likelihood of successful hydraulic debris removal is dependent on many factors such as debris particle size and density, flow rates and the resulting average annular velocity in the annulus, pipe movement, and the properties of the fluids circulated in the well. Mechanical debris extraction tools such as downhole filters and magnets are used to capture significant amounts of debris that are unable to be hydraulically removed from the wellbore. Versions of downhole filters and magnets that are run inside of casing and magnets run inside of the riser are common across the industry, however downhole filter tools run in the riser are less common and their use in these operations is not an industry standard. This paper examines a data set generated over two years containing more than 30 runs that include the use of a downhole filter tool run in the riser during wellbore clean out operations.