New Mexico Institute of Mining and Technology
  • Socorro, New Mexico, United States
Recent publications
This paper is concerned with periodic measures of fractional stochastic reaction-diffusion equations with variable time delay defined on unbounded domains. We first prove the existence of periodic measures of the Markov process associated with the equation by showing the weak compactness of distribution laws of a family of solutions based on the uniform estimates and the equicontinuity of solutions in probability. We then establish the regularity of periodic measures and prove the tightness of the set of all periodic measures of the equation for small noise intensity. As a result, any sequence of periodic measures possesses at least one limit point, and we further prove every such limit must be a periodic measure of the corresponding limiting system. Finally, under further assumptions on the nonlinear terms, we establish the uniqueness and the exponential mixing property of periodic measures in the sense of Wasserstein metric. All the results of the paper are also valid for invariant measures of the corresponding autonomous version of the stochastic equation with constant time delay. The idea of uniform tail estimates of solutions in probability is employed to overcome the difficulty introduced by the non-compactness of Sobolev embeddings on unbounded domains.
The mid-Proterozoic (ca. 1850–850 Ma) is a peculiar period of Earth history in many respects: ophiolites and passive margins of this age are rare, whereas anorthosite and A-type granite suites are abundant; metamorphic rocks typically record high thermobaric (temperature/pressure) ratios, whereas ultrahigh pressure (UHP) rocks are rare; and the abundance of economic mineral deposits features rare porphyry Cu-Au and abundant Ni-Cu and Fe-oxide Cu-Ag (IOCG) deposit types. These collective observations have been used to propose that a stagnant-lid, or single-lid, tectonic regime operated at this time, between periods of plate tectonics in the Paleoproterozoic and Neoproterozoic. In our reappraisal of the mid-Proterozoic geological record, we not only assess the viability of the single-lid hypothesis for each line of evidence, but also that of the plate tectonic alternative. We find that evidence for the single-lid hypothesis is equivocal in all cases, whereas for plate tectonics the evidence is equivocal or supporting. We therefore find no reason to abandon a plate tectonic model for the mid-Proterozoic time period. Instead, we propose that the peculiarities of this enigmatic interval can be reconciled through the combination of two processes working in tandem: secular mantle cooling and the exceptionally long tenure and incomplete breakup of Earth's first supercontinent, where both of these phenomena had a dramatic effect on lithospheric behaviour and its resulting imprint in the geological record.
Coastal wetlands of the Laurentian Great Lakes are diverse and productive ecosystems that provide many ecosystem services, but are threatened by anthropogenic factors, including nutrient input, land-use change, invasive species, and climate change. In this study, we examined one component of wetland ecosystem structure – phytoplankton biomass – using the proxy metric of water column chlorophyll-a measured in 514 coastal wetlands across all five Great Lakes as part of the Great Lakes Coastal Wetland Monitoring Program. Mean chlorophyll-a concentrations increased from north-to-south from Lake Superior to Lake Erie, but concentrations varied among sites within lakes. To predict chlorophyll-a concentrations, we developed two random forest models for each lake – one using variables that may directly relate to phytoplankton biomass (“proximate” variables; e.g., dissolved nutrients, temperature, pH) and another using variables with potentially indirect effects on phytoplankton growth (“distal” variables; e.g., land use, fetch). Proximate and distal variable models explained 16–43% and 19–48% of variation in chlorophyll-a, respectively, with models developed for lakes Erie and Michigan having the highest amount of explanatory power and models developed for lakes Ontario, Superior, and Huron having the lowest. Land-use variables were important distal predictors of chlorophyll-a concentrations across all lakes. We found multiple proximate predictors of chlorophyll-a, but there was little consistency among lakes, suggesting that, while chlorophyll-a may be broadly influenced by distal factors such as land use, individual lakes and wetlands have unique characteristics that affect chlorophyll-a concentrations. Our results highlight the importance of responsible land-use planning and watershed-level management for protecting coastal wetlands.
Plain Language Summary The charge distribution within the horizontal charge region may have a more significant effect on the extension of the lightning channel. At present, it is still difficult to directly observe the charge structure of thunderstorm clouds, especially the horizontal charge structure. Also, the morphological study of the channel is not perfect due to the limitations of observation and data acquisition. Therefore, there is currently a lack of understanding of how lightning channel morphology reveals developmental characteristics and charge structure. In the paper, the relationship between the lightning channel morphology, developmental characteristics, and charge structure was investigated for the first time based on Lightning mapping array localization data, and the spatial distribution of the lightning fractal dimension (FD) was obtained. It is found that, compared to regions with unidirectional extended channels, regions with more channel branches or direction change of channel development have a larger FD and a higher power density, where horizontal channel development is accelerated. These correspondence features reflect the inhomogeneous presence of pocket charge, which provides a new method to use lightning morphology information to reveal the characteristics of charge level distribution within thunderstorm clouds.
Plain Language Summary We present a method for automated identification of two distinct types of electrical activity from explosive volcanic eruptions. Explosive eruptions produce lightning, just like thunderstorms. In addition, they also produce small (<4 m) spark‐like electrical discharges at the vent of a volcano, which are called vent discharges. These vent discharges occur for relatively long durations compared to the duration of a typical lightning flash (seconds vs. hundreds of milliseconds) and are thus easily distinguishable in very high frequency (30–300 MHz) electric field measurements. We use logistic regression to classify an electric field impulse as either being part of a lightning flash or a vent discharge. The classifier uses the number of peaks in the electric field signal in 1 ms time windows before and after an electric field impulse. The accuracy of the classifier is 97.9%. We explain that the classifier could be used on a low‐power lightning sensor to automatically identify that an explosive eruption had occurred. We discuss how this capability would enable a new era of volcanic lightning monitoring that would allow for new research into understanding the physical mechanisms of vent discharges to learn how they can be used during the response to an eruption.
Cytonuclear coevolution is a common feature among plants, which coordinates gene expression and protein products between the nucleus and organelles. Consequently, lineage-specific differences may result in incompatibilities between the nucleus and cytoplasm in hybrid taxa. Allopolyploidy is also a common phenomenon in plant evolution. The hybrid nature of allopolyploids may result in cytonuclear incompatibilities, but the massive nuclear redundancy created during polyploidy affords additional avenues for resolving cytonuclear conflict (i.e., cytonuclear accommodation). Here we evaluate expression changes in organelle-targeted nuclear genes for six allopolyploid lineages that represent four genera (i.e., Arabidopsis, Arachis, Chenopodium, and Gossypium) and encompass a range in polyploid ages. Because incompatibilities between the nucleus and cytoplasm could potentially result in biases toward the maternal homoeolog and/or maternal expression level, we evaluate patterns of homoeolog usage, expression bias, and expression-level dominance in cytonuclear genes relative to the background of non-cytonuclear expression changes and to the diploid parents. Although we find subsets of cytonuclear genes in most lineages that match our expectations of maternal preference, these observations are not consistent among either allopolyploids or categories of organelle-targeted genes. Our results indicate that cytonuclear expression evolution may be subtle and variable among genera and genes, likely reflecting a diversity of mechanisms to resolve nuclear-cytoplasmic incompatibilities in allopolyploid species.
Modulating crucial biological processes such as gene regulation, aging, and relationship to globally important human health issues such as cancer has significantly brought considerable attention to G-quadruplex over the past few decades. As the impact of G-quadruplex emerges on so many biological roles, cancer prognosis and pathogenesis have not been fully understood, and selective small molecular binders with suitable chemical, photophysical and biological properties are potentially applicable biophysical tools for tracking G-quadruplex functions. The chemical properties include suitable water solubility, liphophilicity, etc., and the photophysical properties include excitation, emission, stoke-shift, lifetime, quantum yield, and measurable, selective changes of former photophysical parameters within the ideal spectral window upon interaction with the target. The biological properties include; toxicity, cellular infiltration, and selective binding with G-quadruplex over non-specific targets (e.g., duplex DNA, RNA, non-specific biomolecules etc.) in the complex cellular matrix. The development of G-quadruplex-selective probes, therefore, continues to be an important but challenging task for molecular therapeutic, diagnostic, imaging, and sensing applications. In this review, we have classified and summarized several classes of probes; carbocyanine, porphyrins, ethidium, carbazoles, acridines, tripodal or tetrapodal probes, pyrimidine carboxamides, tianguleniums, anthraquinones, polyaromatic hydrocarbons, BODIPY dyes, berberines, acetones and their derivatives for the variation of selectivity, photophysical, and biological properties with respect to the structural modifications, which ultimately provide helpful guidance for designing novel probes with optimal characteristics.
Due to the characteristics and connectivity of today’s critical infrastructure systems, cyber-attacks on these systems are currently difficult to prevent in an efficient and sustainable manner. Prevention and mitigation strategies need accurate identification and evaluation of: system vulnerabilities, potential threats and attacks, and applicable hardening measures. Furthermore, the ability to prioritize hardening measures based on accurate assessments of risk is needed. In addition, the consideration of the availability, applicability, and cost of potential mitigation strategies is also needed. To address this challenge we created HESTIA: High-level and Extensible System for Training and Infrastructure risk Assessment. In this article we present a formal model of the HESTIA system. We then also present a formal verification of the HESTIA semantic model.
Uranium-bearing respirable dust can cause various health problems, such as cardiovascular and neurological disorders, cancers, immunosuppression, and autoimmunity. Exposure to elevated levels of uranium is linked to many such health...
Al2O3/ZrO2 systems with higher ZrO2 amounts (≥ 20wt%) are known to offer improved properties such as fracture toughness, but are restricted in their hardness, wear and strength performances. The incorporation of a third phase carbon nanostructure (such as CNTs and GN) to Al2O3/ZrO2 reinforced with low content ZrO2 (≤ 5wt%) has emerged as a novel process to overcome this property trade-off by exploring the remarkable mechanical properties of these hybrid nanocomposite systems. Therefore, in the current work, colloidal mixing followed by hot pressing process (@ 1600 °C) were used to consolidate monolith Al2O3, Al2O3/ZrO2, Al2O3/ZrO2/CNTs and Al2O3/ZrO2/GN nanocomposite structures using low ZrO2 content (4wt%) and optimum amounts of CNTs (2wt%) and GN (0.5wt%) as the hybrid reinforcement phases. Microhardness, fracture toughness and flexural strength properties were improved from 19GPa, ∼3MPa.m1/2 and 260MPa up to 24GPa, ∼7MPa.m1/2 and 374MPa respectively with hybrid additions of ZrO2/CNTs and ZrO2/GN to the monolith Al2O3. The primary source of the property enhancement in the hybrid nanocomposites was due to reduction in the matrix and ZrO2 grain sizes (decreased up to ∼78%), good interaction between reinforcement phases and combined mechanisms such as crack bridging and deflection, matrix grain wrapping and grain gluing by CNTs and GN. The wear rate of the parent Al2O3 was also improved from 9.71 × 10⁻⁵ mm³/N.m up to 0.81 × 10⁻⁵ mm³/N.m (showing ∼92% decrease) with ZrO2/CNTs and ZrO2/GN hybrid inclusions, which was attributed to the overall enhanced mechanical properties and wear resistant mechanisms during the dry sliding.
This study evaluates the chemo-mechanical influence of injected CO2 on the Morrow B sandstone reservoir and the upper Morrow shale caprock utilizing data from the inverted 5-spot pattern centered on Well 13-10A within the Farnsworth unit (FWU). This study also seeks to evaluate the integrity of the caprock and the long-term CO2 storage capability of the FWU. The inverted 5-spot pattern was extracted from the field-scale model and tuned with the available field observed data before the modeling work. Two coupled numerical simulation models were utilized to continue the study. First, a coupled hydro-geochemical model was constructed to simulate the dissolution and precipitation of formation minerals by modeling three intra-aqueous and six mineral reactions. In addition, a coupled hydro-geomechanical model was constructed and employed to study the effects of stress changes on the caprock’s porosity, permeability, and ground displacement. The Mohr–Coulomb circle and failure envelope were used to determine caprock failure. In this work, the CO2-WAG injection is followed by the historical field-observed strategy. During the forecasting period, a Water Alternating Gas (WAG) injection ratio of 1:3 was utilized with a baseline bottom-hole pressure constraint of 5500 psi for 20 years. A post-injection period of 1000 years was simulated to monitor the CO2 plume and its effects on the CO2 storage reservoir and caprock integrity. The simulation results indicated that the impacts of the geochemical reactions on the porosity of the caprock were insignificant as it experienced a decrease of about 0.0003% at the end of the 1000-year post-injection monitoring. On the other hand, the maximum stress-induced porosity change was about a 1.4% increase, resulting in about 4% in permeability change. It was estimated that about 3.3% of the sequestered CO2 in the formation interacted with the caprock. Despite these petrophysical property alterations and CO2 interactions in the caprock, the caprock still maintained its elastic properties and was determined to be far from its failure.
Mitochondrial and plastid functions depend on coordinated expression of proteins encoded by genomic compartments that have radical differences in copy number of organellar and nuclear genomes. In polyploids, doubling of the nuclear genome may add challenges to maintaining balanced expression of proteins involved in cytonuclear interactions. Here, we use ribo-depleted RNA sequencing (RNA-seq) to analyze transcript abundance for nuclear and organellar genomes in leaf tissue from four different polyploid angiosperms and their close diploid relatives. We find that even though plastid genomes contain <1% of the number of genes in the nuclear genome, they generate the majority (69.9 to 82.3%) of messenger RNA (mRNA) transcripts in the cell. Mitochondrial genes are responsible for a much smaller percentage (1.3 to 3.7%) of the leaf mRNA pool but still produce much higher transcript abundances per gene compared to nuclear genome. Nuclear genes encoding proteins that functionally interact with mitochondrial or plastid gene products exhibit mRNA expression levels that are consistently more than 10-fold lower than their organellar counterparts, indicating an extreme cytonuclear imbalance at the RNA level despite the predominance of equimolar interactions at the protein level. Nevertheless, interacting nuclear and organellar genes show strongly correlated transcript abundances across functional categories, suggesting that the observed mRNA stoichiometric imbalance does not preclude coordination of cytonuclear expression. Finally, we show that nuclear genome doubling does not alter the cytonuclear expression ratios observed in diploid relatives in consistent or systematic ways, indicating that successful polyploid plants are able to compensate for cytonuclear perturbations associated with nuclear genome doubling.
Formation damage in drilling comes from drilling fluid invasion due to high differential pressure between a wellbore and the formation. This mechanism happens with fracture fluid invasion of multi-fractured horizontal wells in tight formations. Some multi-fractured wells show production rates and cumulative productions far lower than expected. Those damaged wells may sustain further impact such as well shutting due to unexpected events such as the COVID-19 outbreak and then experience a further reduction in cumulative production. This paper focuses on the root causes of formation damage of fractured wells and provides possible solutions to improve production. A simulation study was conducted using Computer Modelling Group software to simulate formation damage due to fracture fluid invasion and well shut-in. Simulation results revealed that the decrease in cumulative hydrocarbon production due to leak-off and shut-in of the simulated well could range from 20 to 41%, depending on different conditions. The results showed that the main causes are high critical water saturation of tight formations, low drawdown, and low residual proppant permeability under formation closure stress. The sensitivity analysis suggests two feasible solutions to mitigate formation damage: optimizing drawdown during production and optimized proppant pack permeability of the hydraulic fracturing process. Optimizing pressure drawdown is effective in fixing leak-off damage, but it does not mitigate shut-in damage. Formation damage due to shut-in should be prevented in advance by using an appropriate proppant permeability. These key findings enhance productivity and improve the economics of tight gas and shale oil formations.
Coal mine workers are continuously exposed to respirable coal mine dust (RCMD) in workplaces, causing severe lung diseases. RCMD characteristics and their relations with dust toxicity need further research to understand the adverse exposure effects to RCMD. The geographic clustering of coal workers’ pneumoconiosis (CWP) suggests that RCMD in the Appalachian region may exhibit more toxicity than other geographic regions such as the Rocky Mountains. This study investigates the RCMD characteristics and toxicity based on geographic location. Dissolution experiments in simulated lung fluids (SLFs) and in vitro responses were conducted to determine the toxicity level of samples collected from five mines in the Rocky Mountains and Appalachian regions. Dust characteristics were investigated using Fourier-transform infrared spectroscopy, scanning electron microscopy, the BET method, total microwave digestion, X-ray diffraction, and X-ray photoelectron spectroscopy. Inductively coupled plasma mass spectrometry was conducted to determine the concentration of metals dissolved in the SLFs. Finer particle sizes and higher mineral and elemental contents were found in samples from the Appalachian regions. Si, Al, Fe, Cu, Sr, and Pb were found in dissolution experiments, but no trends were found indicating higher dissolutions in the Appalachian region. In vitro studies indicated a proinflammatory response in epithelial and macrophage cells, suggesting their possible participation in pneumoconiosis and lung diseases development.
The heat and mass transfer characteristics of a simple shear flow over a surface covered with staggered herringbone structures are numerically investigated using the lattice Boltzmann method. Two flow motions are identified. The first is a spiral flow oscillation above the herringbone structures that advects heat and mass from the top plane to herringbone structures. The second is a flow recirculation in the grooves between the ridges that advects heat and mass from the area around the tips of the structures to their side walls and the bottom surfaces. These two basic flow motions couple together to form a complex transport mechanism. The results show that when advective heat and mass transfer takes effect at relatively large Reynolds and Schmidt numbers, the dependence of the total transfer rate on Schmidt number follows a power law, with the exponent being the same as that in the Dittus-Boelter equation for turbulent heat transfer. As Reynolds number increases, the dependence of the total transfer rate on Reynolds number also approaches a power law, and the exponent is close to that in the Dittus-Boelter equation.
Following the 15 January 2022 Hunga Tonga‐Hunga Ha'apai eruption, several trace gases measured by the Aura Microwave Limb Sounder (MLS) displayed anomalous stratospheric values. Trajectories and radiance simulations confirm that the H2O, SO2, and HCl enhancements were injected by the eruption. In comparison with those from previous eruptions, the SO2 and HCl mass injections were unexceptional, although they reached higher altitudes. In contrast, the H2O injection was unprecedented in both magnitude (far exceeding any previous values in the 17‐year MLS record) and altitude (penetrating into the mesosphere). We estimate the mass of H2O injected into the stratosphere to be 146 ± 5 Tg, or ∼10% of the stratospheric burden. It may take several years for the H2O plume to dissipate. This eruption could impact climate not through surface cooling due to sulfate aerosols, but rather through surface warming due to the radiative forcing from the excess stratospheric H2O.
Aerosol particles dynamically evolve in the atmosphere by physicochemical interactions with sunlight, trace chemical species, and water. Current modeling approaches fix properties such as aerosol refractive index, introducing spatial and temporal errors in the radiative impacts. Further progress requires a process-level description of the refractive indices as the particles age and experience physicochemical transformations. We present two multivariate modeling approaches of light absorption by brown carbon (BrC). The initial approach was to extend the modeling framework of the refractive index at 589 nm (nD), but that result was insufficient. We developed a second multivariate model using aromatic rings and functional groups to predict the imaginary part of the complex refractive index. This second model agreed better with measured spectral absorption peaks, showing promise for a simplified treatment of BrC optics. In addition to absorption, organic functionalities also alter the water affinity of the molecules, leading to a hygroscopic uptake and increased light absorption, which we show through measurements and modeling.
The smart meter data of the advanced metering infrastructure (AMI) can be tampered by electricity thieves with advanced digital instruments or cyber attacks to reduce their electricity bills, which causes devastating financial losses to utilities. A novel unsupervised data-driven method for electricity theft detection in AMI is proposed in this article. The method incorporates observer meter data, wavelet-based feature extraction, and fuzzy c-means (FCM) clustering. A new anomaly score is developed based on the degree of cluster membership information produced by FCM clustering to differentiate normal and fraudulent users. We perform an ablation study to investigate the impact of key components of the proposed method on the performance using a publicly available smart meter dataset. The results show that all key components of the proposed method contribute significantly to the performance improvement. The proposed method is compared with a set of baselines including state-of-the-art methods using smart meter data of both business users and residential users. The comparison results indicate that the proposed method achieves significantly better detection performance than all baseline methods. We also show that the proposed method maintains a good performance when the detection time frame is reduced from 30 to 20 days.
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987 members
Snezna Rogelj
  • Department of Biology
Ronald J Thomas
  • Langmuir Laboratory for Atmospheric Research
Deep Choudhuri
  • Department of Materials Engineering
Ivan Avramidi
  • Department of Mathematics
Brian Borchers
  • Department of Mathematics
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Head of institution
Dr. Stephen Wells
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www.nmt.edu
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575-835-5434