Sedimentology and isotope geochemistry of transitional evaporitic environments within arid continental settings : from erg to saline lakes

This research was supported by grants to RPP from the AAPG (Gustavus E. Archie Memorial Grant) and by the European Union’s Horizon 2020 research and innovation programme (Grant 678812 to M.W.C.).Arid continental basins typically contain a spectrum of coeval environments that coexist and interact from proximal to distal. Within the distal portion, aeolian ergs often border playa, or perennial, desert lakes, fed by fluvial incursions or elevated groundwaters. Evaporites are common features in these dryland, siliciclastic dominant settings. However, sedimentary controls upon evaporite deposition are not widely understood, especially within transitional zones between coeval clastic environments that are dominantly controlled by larger scale allocyclic processes, such as climate. The sulphur (δ34S) and oxygen (δ18O, Δ17O) isotope systematics of evaporites can reveal cryptic aspects of sedimentary cycling and sulphate sources in dryland settings. However, due to the lack of sedimentological understanding of evaporitic systems, isotopic data can be easily misinterpreted. This work presents detailed sedimentological and petrographic observations, coupled with δ34S, δ18O and Δ17O data, for the early Permian Cedar Mesa Sandstone Formation (western USA). Depositional models for mixed evaporitic / clastic sedimentation, which occurs either in erg-marginal or lacustrine-marginal settings, are presented to detail the sedimentary interactions present in terms of climate variations that control them. Sedimentological and petrographical analysis of the evaporites within the Cedar Mesa Sandstone Formation reveal a continental depositional environment and two end member depositional models have been developed: erg-margin and lake-margin. The δ34S values of gypsum deposits within the Cedar Mesa Sandstone Formation are consistent with late Carboniferous to early Permian marine settings. However, a marine interpretation is inconsistent with sedimentological and petrographic evidence. Consequently, δ34S, δ18O and Δ17O values are probably recycled and do not reflect ocean-atmosphere values at the time of evaporite precipitation. They are most likely derived from the weathering of older marine evaporites in the hinterland. Thus, the results demonstrate the need for a combination of both sedimentological and geochemical analysis of evaporitic systems to better understand their depositional setting and conditions.PostprintPeer reviewe

Mindfulness meditation in the treatment of substance use disorders and preventing future relapse: neurocognitive mechanisms and clinical implications

Substance use disorders (SUDs) are a pervasive public health problem with deleterious consequences for individuals, families, and society. Furthermore, SUD intervention is complicated by the continuous possibility of relapse. Despite decades of research, SUD relapse rates remain high, underscoring the need for more effective treatments. Scientific findings indicate that SUDs are driven by dysregulation of neural processes underlying reward learning and executive functioning. Emerging evidence suggests that mindfulness training can target these neurocognitive mechanisms to produce significant therapeutic effects on SUDs and prevent relapse. The purpose of this manuscript is to review the cognitive, affective, and neural mechanisms underlying the effects of mindfulness-based interventions (MBIs) on SUDs. We discuss the etiology of addiction and neurocognitive processes related to the development and maintenance of SUDs. We then explore evidence supporting use of MBIs for intervening in SUDs and preventing relapse. Finally, we provide clinical recommendations about how these therapeutic mechanisms might be applied to intervening in SUDs and preventing relapse.National Institute of Health (NIH) award to ELG (R01DA042033

The Variation of Mechanical Properties of M300 Maraging Steel Manufactured with Varying Process Parameters in Laser Powder Bed Fusion

Laser power bed fusion (L-PBF) is a type of additive manufacturing (AM) that uses layers of powdered metal and a laser to manufacture a part in a layer-by-layer fashion. L-PBF uses a variety of process parameters that ultimately determine the overall quality and mechanical properties of a print. The ability to alter parameters allows for the utilization of various metals in this form of AM. Maraging 300 steel (M300) is a material of particular interest due to its combined tensile strength and high strength-to-weight ratio. By using an assortment of parameters and comparing the resulting mechanical properties it can be determined which process parameters result in a more favorable part to be used in a variety of applications. A favorable process parameter set was selected for future use. This study aims to determine which process parameters result in the best overall mechanical properties of M300 manufactured using L-PBF.Mechanical Engineerin

Effects Due to Variations in Thermal Properties of Maraging Steel for Finite Element Modeling of the WAAM Process

Finite element (FE) thermal simulations of the wire arc additive manufacturing (WAAM) process have been widely used to predict the temperature history of as-built parts. Temperature-dependent thermal properties like density, conductivity, specific heat, and latent heat are required to accurately simulate the solidus to liquidus transition seen in the heat affected zone. Current research has shown that thermal properties measured experimentally or simulated using material database software can be used for thermal modeling; however, there has been no direct comparison shown to determine which is most appropriate for WAAM modeling. The focus of this research is to compare the temperature variation of the FE thermal simulations with experimentally measured and computer-generated properties for M250 grade maraging steel. The thermal history for thin wall builds are compared with differing temperature-dependent thermal properties to examine the relationship between thermal properties and history. It was shown that constant values at room temperature result in an increased thermal response for WAAM thermal simulations and linearized properties decreased the temperature when both were compared with the experimental thermal property inputs. Further work needs to be performed before determining the most appropriate source for thermal properties (wrought, wire, as-built, or material database), but it can be concluded that the form of material does affect the thermal response for maraging grade 250 steel.Mechanical Engineerin

Low-speed instrumented drill press for bone screw insertion

Screw insertion torque is a widely used/effective method for quantifying fixation strength in orthopedic implant research for different screw geometries, implantation sites, and loads. This work reports the construction of an open-source instrumented benchtop screw insertion device for a total cost of $7545 ($492 + $7053 for equipped sensors), as well as validation of the device and an example use-application. The insertion device is capable of recording the axial load, rotational speed, and applied torque throughout the screw insertion process at 10 samples per second, as demonstrated in the validation test. For this combination of bone analog (20 PCF Sawbones©), screw, and loading, the resolution of the torque sensor was 25% of the maximum measured torque; a different model torque sensor would be required to meet ASTM F543-17, which specifies a resolution of 10% of the maximum torque. This system is optimized for fastener insertion at speeds of 120 rpm or less and axial loading up to 50 N

Towards an Open-Source, Preprocessing Framework for Simulating Material Deposition for a Directed Energy Deposition Process

This work focuses on the development of an open-source framework to simulate material deposition for arbitrary geometries with respect to desired process parameters during a directed energy deposition (DED) process. This framework allows the flexibility to define the element activation criteria used in conjunction with Abaqus. A Python script was developed to extract toolpath coordinates from G-code and implement an element activation sequence that is unique to a specific CAD drawing. This is important for simulating the additive manufacturing construction of complex geometries because the thermal history of the component is dependent on laser path, which has a significant effect on residual stresses and distortion. The results of varying the element activation criteria are compared with simulated temperature profiles.Mechanical Engineerin

Examining the GPU Acceleration Speed-Up for Finite Element Modeling of Additive Manufacturing

Using a graphics processing unit (GPU) in addition to a central processing unit (CPU) has demonstrated promise for the acceleration of processing-intensive operations such as finite element (FE) simulations. Commercial FE solvers have begun to utilize GPU acceleration for classical multi-physics applications, but the speed-up for additive manufacturing (AM) simulations is not well understood. There is a significant need for GPU acceleration for metal-based AM FE simulations, which are computationally expensive because of the high mesh densities and the large number of time increments employed. This study examines the efficacy of GPU acceleration for Abaqus AM simulations, where benchmark simulations using a sequentially coupled FE thermo- mechanical model are run both with and without GPU acceleration. The speed-up is compared across the AM process for the thermal and mechanical analysis. In this study, GPU acceleration provided the ability to decrease simulation runtime by two-to-four times on 4-8 CPU cores, and one-to-two times on 16-32 CPU cores.Mechanical Engineerin

Investigating the Relationship Between In-Process Quality Metrics and Mechanical Response in the L-PBF Process

Laser powder bed fusion (L-PBF) additive manufacturing is a process that utilizes a high- powered laser to build near net-shaped parts in a layer-by-layer fashion using metal powder as the feedstock material. Traditionally, the analysis of L-PBF produced parts has relied solely on post- build characterization to understand the relationship between the printing process and the final mechanical properties. Recent developments of in-process quality assurance systems, such as Sigma Additive Solutions’ PrintRite3D, can measure in-process thermal signatures and melt pool disturbances in real-time. This research aims to examine the relationship between process parameters (e.g., scan strategy, scanning speed, and layer thickness) and in-process quality metrics (IPQMs) captured by the PrintRite3D system on a Renishaw AM400. The mechanical response of multiple part geometries (NIST residual stress bridges, single-arched bridges) and build materials (Ti6Al4V) includes residual stress deflection and hardness; the results are compared with the IPQMs.Mechanical Engineerin