Molecular structures of kerogen control hydrocarbon production in unconventional reservoirs. Significant progress has been made in developing model representations of various kerogen structures. ...These models have been widely used for the prediction of gas adsorption and migration in shale matrix. However, using density functional perturbation theory (DFPT) calculations and vibrational spectroscopic measurements, we here show that a large gap may still remain between the existing model representations and actual kerogen structures, therefore calling for new model development. Using DFPT, we calculated Fourier transform infrared (FTIR) spectra for six most widely used kerogen structure models. The computed spectra were then systematically compared to the FTIR absorption spectra collected for kerogen samples isolated from Mancos, Woodford and Marcellus formations representing a wide range of kerogen origin and maturation conditions. Limited agreement between the model predictions and the measurements highlights that the existing kerogen models may still miss some key features in structural representation. A combination of DFPT calculations with spectroscopic measurements may provide a useful diagnostic tool for assessing the adequacy of a proposed structural model as well as for future model development. This approach may eventually help develop comprehensive infrared (IR)-fingerprints for tracing kerogen evolution.
Numerous experimental investigations indicated that expansive clays such as montmorillonite can intercalate CO2 preferentially into their interlayers and therefore potentially act as a material for ...CO2 separation, capture, and storage. However, an understanding of the energy–structure relationship during the intercalation of CO2 into clay interlayers remains elusive. Here, we use metadynamics molecular dynamics simulations to elucidate the energy landscape associated with CO2 intercalation. Our free energy calculations indicate that CO2 favorably partitions into nanoconfined water in clay interlayers from a gas phase, leading to an increase in the CO2/H2O ratio in clay interlayers as compared to that in bulk water. CO2 molecules prefer to be located at the centers of charge-neutral hydrophobic siloxane rings, whereas interlayer spaces close to structural charges tend to avoid CO2 intercalation. The structural charge distribution significantly affects the amount of CO2 intercalated in the interlayers. These results provide a mechanistic understanding of CO2 intercalation in clays for CO2 separation, capture, and storage.
Granular salt is likely to be used as backfill material and a seal system component within geologic salt formations serving as a repository for long-term isolation of nuclear waste. Pressure from ...closure of the surrounding salt formation will promote consolidation of granular salt, eventually resulting in properties comparable to native salt. Understanding dependence of consolidation processes on stress state, moisture availability, temperature, and time is important for demonstrating sealing functions and long-term repository performance. This study characterizes laboratory-consolidated granular salt by means of microstructural observations. Granular salt material from mining operations was obtained from the bedded Salado Formation hosting the Waste Isolation Pilot Plant and the Avery Island salt dome. Laboratory test conditions included hydrostatic consolidation of jacketed granular salt with varying conditions of confining isochoric stress to 38 MPa, temperature to 250 °C, moisture additions of 1% by weight, time duration, and vented and non-vented states. Resultant porosities ranged between 1% and 22%. Optical and scanning electron microscopic techniques were used to ascertain consolidation mechanisms. From these investigations, samples with 1% added moisture or unvented during consolidation, exhibit clear pressure solution processes with tightly cohered grain boundaries and occluded fluid pores. Samples with only natural moisture content consolidated by a combination of brittle, cataclastic, and crystal plastic deformation. Recrystallization at 250 °C irrespective of moisture conditions was also observed. The range and variability of conditions applied in this study, combined with the techniques used to display microstructural features, are unique, and provide insight into an important area of governing deformation mechanism(s) occurring within salt repository applications.
•Granular salt consolidation is dependent on temperature, stress, moisture, and time.•Small amounts of moisture show consolidation by pressure-solution-redeposition.•Consolidation processes were not impeded by pore pressure.•Recrystallization seen at consolidation temperatures of 250 °C.
Two‐phase fluid flow properties underlie quantitative prediction of water and gas movement, but constraining these properties typically requires multiple time‐consuming laboratory methods. The ...estimation of two‐phase flow properties (van Genuchten parameters, porosity, and intrinsic permeability) is illustrated in cores of vitric nonwelded volcanic tuff using Bayesian parameter estimation that fits numerical models to observations from spontaneous imbibition experiments. The uniqueness and correlation of the estimated parameters is explored using different modeling assumptions and subsets of the observed data. The resulting estimation process is sensitive to both moisture retention and relative permeability functions, thereby offering a comprehensive method for constraining both functions. The data collected during this relatively simple laboratory experiment, used in conjunction with a numerical model and a global optimizer, result in a viable approach for augmenting more traditional capillary pressure data obtained from hanging water column, membrane plate extractor, or mercury intrusion methods. This method may be useful when imbibition rather than drainage parameters are sought, when larger samples (e.g., including heterogeneity or fractures) need to be tested that cannot be accommodated in more traditional methods, or when in educational laboratory settings.
Core Ideas
Mass imbibed and wetting front elevation data were collected during spontaneous imbibition.
Markov chain Monte Carlo optimizer matches two‐phase flow models to observations.
Mass and wetting front data were both required for unique model parameter estimation.
An approach sensitive to both moisture retention and relative permeability functional forms was used.
Markov chain Monte Carlo approach highlights correlations and uncertainties in results.
Buprenorphine can be used to treat maternal opioid use disorder effectively and decrease obstetrical risks. Compared with the use of other medications to treat opioid use disorder, the use of ...buprenorphine results in improved neonatal outcomes; however, its use is associated with higher rates of treatment attrition. Initiation of buprenorphine, termed “induction,” is a high-risk time for treatment dropout and can require repeated attempts.
This study aimed to evaluate the effect of multiple buprenorphine induction attempts on maternal and neonatal outcomes.
This was a retrospective cohort study of all pregnant patients who underwent sublingual buprenorphine induction for the treatment of opioid use disorder from June 18, 2018, to January 1, 2021, at 3 tertiary care centers. Patients who required only 1 attempt for successful buprenorphine induction were compared with those who required multiple attempts but ultimately were successful in the treatment initiation during pregnancy, confirmed by urine drug screening. The primary outcome was nonprescribed opioid use at the time of delivery. The secondary outcomes included obstetrical and neonatal outcomes associated with opioid use disorder. Background characteristics were compared using Fisher exact, chi-square, Mann-Whitney U, and Student t tests. The outcomes were compared using multivariable logistic regression, and time to delivery after initiation of prenatal care was compared between groups using Kaplan-Meier curves and a Cox proportional-hazards model.
Overall, 63 patients undergoing buprenorphine induction during pregnancy were included, with 38 (60.3%) patients with 1 attempt and 25 patients (39.7%) with multiple attempts. There was no statistical difference between the 2 groups in terms of background characteristics. Compared with a single successful attempt, multiple attempts at buprenorphine induction were associated with a significantly increased odds of nonprescribed opioid use at the time of delivery (76.0% vs 15.8%; adjusted odds ratio, 30.00; 95% confidence interval, 5.50–163.90), increased risk of preterm birth (48.0% vs 15.8%; adjusted hazard ratio, 3.24; 95% confidence interval, 1.17–8.95), and decreased rate of breastfeeding at both maternal discharge (24.0% vs 78.9%; adjusted odds ratio, 0.06; 95% confidence interval, 0.00–0.30) and infant discharge (24.0% vs 55.3%; adjusted odds ratio, 0.23; 95% confidence interval, 0.10–0.80).
Requiring multiple attempts for buprenorphine induction significantly increases the odds of nonprescribed opioid use at the time of delivery and preterm birth and decreases the odds of breastfeeding. As the buprenorphine induction process may affect obstetrical outcomes for patients induced during pregnancy, investigating the techniques that increase the likelihood of successful induction is crucially needed to improve outcomes in patients with maternal opioid use disorder.
There is a growing need for disposal of high‐level nuclear waste. To reduce uncertainty associated with brine availability to repository excavations in salt formations, a collaboration between ...Sandia, Los Alamos, and Lawrence Berkeley National Laboratories is performing a series of borehole‐scale coupled process tests. Here, we report on the first round of the Brine Availability Test in Salt (BATS) project, a “shakedown” experiment called Phase 1s. Experimental testing included placing a resistive heater, a 260‐W radiative heater, and a 750‐W radiative heater within previously drilled horizontal boreholes at the Waste Isolation Pilot Plant (WIPP) while monitoring temperature and water inflow. The experiments successfully achieved the targeted temperature of 120 °C when using the 750‐W radiative heater. Simulations using FEHM (Finite Element Heat and Mass transfer code) and TOUGH‐FLAC (Transport Of Unsaturated Groundwater and Heat–Fast Lagrangian Analysis of Continua) were able to accurately predict the coupled thermo–hydro–mechanical–chemical response of salt, matching the observed temperature and brine production. Due to the extremely low permeability of salt, these systems take many years to reach steady state when perturbed by mining activities. Long‐term numerical simulations are used to develop the initial pressure and saturation conditions. The inclusion of a damaged rock zone with higher permeability around the borehole also affects the saturation and pressure distributions and plays an important role in dissipating the potential for thermal pressurization. Knowledge gained from this round of experimentation and simulation will be used to conduct the next BATS project experiment in new boreholes at WIPP.
This study was a partial replication of past studies in which a preperformance routine was found to have significant effects on the expressive performance of individual singers. In these studies, a ...psychologist taught participants how to identify in themselves a self-protective mindset and then taught them a preperformance routine that fostered a mindset more conducive to optimal expressive performance. In the present study, classroom teachers provided a similar intervention and follow-up lessons to members of 3 junior high choirs (N = 132). A research design comparing 4 testing occasions identified differences attributed to the intervention. Results indicated a positive effect on Overall Expressiveness (p < .001) and on the subcategories Dynamics (p = .006), Tone (p < .001), Articulation (p = .005), and Performance Factors (p < .001). Retention was significant regarding Overall Expressiveness as well (p = .004). Implications are that (a) mindset-oriented instruction may help singers put into play expressive skills and understandings that were previously fettered by a self-protective mindset, (b) mindset instruction may be effectively provided by classroom teachers, and (c) follow-up lessons are helpful for retaining an optimal performance mindset.
During the Spring 2020 semester, universities transitioned to online instruction to slow the spread of COVID-19. During this time, mathematics support/tutoring centers also moved their services ...online. We discuss best practices for online tutoring from the literature and the shared experiences of 28 tutoring center leaders who transitioned to online tutoring during the pandemic. We recommend tutoring centers offer both synchronous video conferencing with shared white boards and an asynchronous or text-based option to increase flexibility and alleviate issues of access. Tutors should be trained to utilize the chosen technology and to adapt their communication to the new environment.
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