Chemistry Commons^™

Mechanistic Rationale For Toxic Aerosol Formation From Vaping And Dabbing With A Focus On Ketene Formation From Semi-Synthetic Cannabinoids, Kaelas Ryan Munger

Dissertations and Theses

Cannabis vaping is a relatively new route of administration that is increasingly common among youth and young adults. Cannabis vaping has been associated with cases of acute lung injury, especially among youth, and most often involves the heating and aerosolization of high-potency products having cannabinoid concentrations of ~ 50 % - 98 % w/w. Proponents argue that vaping is safer than smoking due to the characteristically lower temperatures and fewer plant materials. However, the extreme cannabinoid concentrations, along with non-natural formulations having undisclosed additives, require studies of the health effects of these products. Despite the popularity of cannabis concentrate vaping, …

A Comparison Of Shear Bond Strength Of Denture Teeth To Denture Base Using Different Means Of Retention: An In Vitro Pilot Study, Dima Taha El Baba, Paul Boulos

International Arab Journal of Dentistry

Objectives: The objective of this work is to evaluate the shear bond strength between denture base resin and three different acrylic artificial denture teeth. The latter was subjected to three different surface modifications on the ridge lap area and compared to unmodified acrylic artificial denture teeth.

Methods: In this experimental in vitro study, twenty-four maxillary central incisor acrylic teeth were used from each of three manufacturers; namely Major®, Ivoclar® and Myerson®. The teeth were additionally divided into four test groups with six specimens in each: a control group, a chemical retention group, a mechanical retention group, and a …

Data From: Nek4 Suppresses Cell Proliferation In Bt20 Triple-Negative Breast Cancer Cells By Diminishing Expression Of Cell Cycle Genes, While Its Depletion Mitigates Proliferation In Other Cell Lines, Amanda Ashley

Chemistry & Biochemistry: Datasets

No abstract provided.

An Experiment In Electron Paramagnetic Resonance Spectroscopy For Undergraduate Labs In Physical Chemistry Or Physical Biochemistry, Evan A. Old, Matthew C. Rehak, Jefferson C. Thompson, Herbert J. Sipe Jr.

TeachEPR Submissions

We report a biochemically based EPR experiment for undergraduate laboratories that will serve as instruction for learning EPR sample preparation, spectral observation, and spectral analysis. There is a current lack of EPR instructional experiments that present complex spectra in which computational analysis may be required. The biochemical oxidation system of horse radish peroxidase (HRP) activated by H₂O₂ acts on 2,6-di-t-butyl-4-hydroxyanisole (DTBHA) to form phenoxyl radicals. This experiment produces moderately complex spectra of moderately long-lived radicals using relatively small amounts of readily available reactants. Spectrum analysis and simulation is accomplished using software freely available on-line. If desired, EPR …

The Next Frontier In The Study Of Noncovalent Bonding: Transition Metals, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

As work continues unabated in the study of noncovalent bonding, particularly σ-hole bonds, new challenges have emerged as the participation of transition metals in interactions of this sort is fast becoming appreciated. While there are certain similarities with the halogen, chalcogen, etc, bonds, in which the main group elements participate, there are certain unique properties of these metal atoms that must be analyzed before a complete understanding can be attained. As one example, these atoms tend to act simultaneously as both electron donors and acceptors, a synergistic action that amplifies the overall bond strength. Ideas are expressed in this paper …

The Influence Of Defects: Oxidation Of Non-Planar Transition Metal Model Catalysts, Maxwell Gillum

Dissertations

Metal-catalyzed oxidation reactions are a major application of heterogeneous catalysis and are a widely applied synthetic route for the production of chemicals and reagents essential to modern society. However, as the intricacies of heterogeneous surface catalysis are slowly being unraveled, minute details of the catalytic environment have been revealed to play outsized roles in the catalytic activity of the surface. The experiments herein further investigate the interplay between surface geometry and the formation oxygen-induced surface structures. Understanding how defects influence surface reactivity is a necessary step in gaining the ability to accurately model heterogeneous catalytic environments. Two different aspects of …

High-Capacity, Reversible, And Energy-Efficient Water Vapor Sorption By Hierarchical Micro-To-Macroporous Carbon Aerogels From Polybenzoxazine And Polybenzodiazine, Vaibhav A. Edlabadkar, Rushi U. Soni, Stephen Y. Owusu, A. B.M.Shaheen Ud Doulah, Nicholas Leventis, Chariklia Sotiriou-Leventis

Chemistry Faculty Research & Creative Works

Quantitative, reversible water vapor sorption is in rising demand for applications ranging from home appliances to atmospheric water harvesting. However, most sorbents suffer from low water-uptake capacities, nonreusability, and especially high regeneration temperatures. This study addresses this challenge by introducing polybenzoxazine- (PBO) and polybenzodiazine-derived (PBDAZ) carbon aerogels as reversible high-capacity desiccants. PBO and PBDAZ aerogels were prepared from structurally related monomers via HCl-catalyzed ring opening polymerization. Both types of aerogels were first aromatized at 200–240 °C under air or O2 and then were carbonized at 800 °C under Ar. These as-prepared carbon aerogels were further etched at 1000 °C under …

Synergetic Adsorptive Mechanisms, Reusability And Cost Evaluations Of Green Fabricated Hybrid Barium Cobalt Nanocomposites For Methylene Blue And Lead Removal From Wastewater, Titus Chinedu Egbosiuba, Chibuike Christogonus Njoku, Ijeoma Jacinta Ani, Godwin Ifeanyi Ogbuehi, Abdulkareem Omeiza Yusuf, Abiodun Azeez Saka, Ugochukwu Ewuzie, Ebuka Emmanuel Ezennajiego, Blessing Onyinye Okafor, Walter Chibuike Anene, Cecilia Chika Unegbu, Florence Acha, Monday Uchenna Okoronkwo

Chemical and Biochemical Engineering Faculty Research & Creative Works

Barium nanoparticles (BaNPs), cobalt nanoparticles (CoNPs), and hybrid barium-cobalt nanocomposites (BaCoNCs) were synthesized using an eco-friendly green technique with Anacardium occidentale leaf extract for sequestration of methylene blue (MB) dye and lead (Pb (II)) ions from industrial wastewater. The nanoparticles and nanocomposites were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), high-resolution scanning electron microscopy (HRSEM), and Brunauer-Emmett-Teller (BET) analysis to assess their functional groups, crystalline structure, morphology, and surface properties, confirming successful synthesis. Batch adsorption studies showed that optimal pollutant removal occurred at pH values of 8 for MB and 5 for Pb(II), with a contact time …

Cysteine Oxidation Of A Redox Hub Within Complex I Can Facilitate Electron Transport Chain Supercomplex Formation, Runtai Chen, Seyed Amirhossein Tabatabaei Dakhili, Rokas Gerulskis, Yuan Yuan Zhao, Steven Lockhart, Lusine Tonoyan, Arno G. Siraki, Guocheng Huang, Adam Kinnaird, Darren H. Freed, Shelley D. Minteer, Evangelos D. Michelakis, John R. Ussher

Chemistry Faculty Research & Creative Works

The mitochondrial electron transport chain (ETC) is a four complex unit that could be considered the most essential infrastructure within the mitochondria, as it primarily functions to generate the mitochondrial membrane potential (ΔΨm), which can then be utilized for ATP synthesis or heat production. Another important aspect of ETC function is the generation of mitochondrial reactive oxygen species (mtROS), which are essential physiologic signaling mediators that can be toxic to the cell if their levels become too high. Currently, it remains unresolved how a highly utilized and functioning ETC can sense excessive mtROS generation and adapt, to enhance ΔΨm. Here, …

Comprehensive Review Of In Vitro Approaches For Environmental Heavy Metal Exposure, Manas Warke, Madeline English, Camila Padilla, Lexie Gasco, Wendy Leisner, Rupali Datta, Smitha Rao

Michigan Tech Publications

Heavy metals are ubiquitous environmental pollutants, contaminating air, soil, and water via the erosion of natural deposits, as well as originating from anthropogenic sources, such as agriculture, industries, transportation, and landfills. The increasing utilization of heavy metals over the years, combined with the persistent nature of metals in the environment poses a direct threat to human and environment health. Although regulatory limits have been established for toxic metals, assessing the associated health risks using real-life exposure scenarios remains challenging. In this review, we summarize the development and use of in vitro models based two- and three-dimensional cell culture systems, focusing …

Validation And Proposed Expansion Of The Data-Driven D Region Model, Kevin M. Watson

Theses and Dissertations

Predicting ionosphere effects on radio wave propagation is critical for communications and over-the-horizon radar systems. The D region is challenging to model for several reasons, one of which is chemical complexity. Ion density changes during sunrise/sunset introduce substantial uncertainty in electron density profiles (EDPs). The Data Driven D Region (D3R) model solves electron densities through an ion chemistry model and assimilates relevant space weather inputs. This study evaluates D3R against the Faraday International Reference Ionosphere (FIRI) and measurements using Very Low Frequency (VLF) propagation paths. Space weather event impacts on D3R EDPs are evaluated during the disturbed period from 8-12 …

Regioselective C-Allylation Of Indole With Potassium Allyltrifluoroborate In The Presence Of Pd-Catalyst, Milton Kumar Kundu

Tennessee State University Alumni Theses and Dissertations

Indole is a versatile heterocyclic scaffold renowned for its wide range of pharmacological activities and strong potential as a successful drug candidate. These attributes continue to inspire researchers to explore indole derivatives as promising leads in drug development. In this project, we report the development of a cross-coupling reaction of indoles and potassium allyltrifluoroborate to the corresponding 3-allylindoles in the presence of PdCl2(dtbpf) and PdCl2(dppf)CH2Cl2 catalyst under microwave heating, offering a rapid, regioselective, and high-yielding synthetic route. This methodology provides a valuable platform for generating structurally diverse indole-based compounds, which could serve as promising leads for further pharmacological evaluation and …

Root Exudates: The Rhizospheric Frontier For Advancing Sustainable Plant Protection, Muhammad Rahil Afzal, Misbah Naz, Youbo Yu, Lisha Yan, Peiyi Wang, Janaki Mohotti, Gefei Hao, Jing-Jiang Zhou, Zhou Chen, Libo Zhang, Qian Wang

Faculty Publications

Root exudates (REs), a diverse array of bioactive metabolites secreted by plant roots in response to environmental stimuli, serve as key mediators of rhizosphere ecology and plant defense responses, offering a promising avenue for sustainable pest management and eco-friendly plant protection. While earlier reviews primarily focus on root exudates in the context of general rhizosphere dynamics and plant-microbial interactions, critical knowledge gaps persist in REs-plant-pest tripartite interactions, the mechanistic basis of REs-mediated plant defense, and their practical integration with integrated pest management (IPM) frameworks. This review provides a synthesis of the latest literature on the biochemical diversity and functions of …

Characterizing The Excited States And Electronic Absorption Spectra Of Small Alkylperoxy (Ro2•) And Hydroperoxy (•Qooh) Radicals, Lily M. Guidry, Sofia E. Guidry, Tanima Barua, Barbara Marchetti, Michael F. Vansco, Tolga N.V. Karsili

Chemistry

Organic peroxy (ROO•) and hydroperoxy (•QOOH) radicals are key reactive intermediates that are formed via the oxidation of volatile organic compounds during combustion or in the Earth’s atmosphere. Their primary fate is continued unimolecular decay or bimolecular chemistry, the relative branching for which is heavily structure- and temperature-dependent. This article outlines a combined single- and multi-reference quantum chemical study to characterize the near-UV accessible electronically excited states of the prototypical ROO• and •QOOH intermediates, tert-butyl peroxy and hydroperoxy-tert-butyl radicals—the ground-state chemistries of which have been well studied both experimentally and computationally. Additionally, we simulate the electronic absorption profiles of these …

Quantification Of Terpenes In Various Commercial Cannabis Products By Gas Chromatography-Flame Ionization Detection And Gas Chromatography-Mass Spectrometry, Kaitlyn M. Ignaszak

Forensic Science Master's Projects

The goal of this research project was to identify and quantify the terpenes in five commercial cannabis products (dried bud, kief, two tinctures, and a pain cream) using gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). Terpene identification and quantification were conducted using GC-MS and GC-FID, with a standard sample containing 21 terpenes of known concentrations. To determine the most effective extraction conditions, three organic solvents (ethanol, acetonitrile, and ethyl acetate) were employed. Additionally, the effects of extraction time on terpene yield were investigated by analyzing aliquots collected at five different time intervals, ranging from one hour to …

Pd-Catalyzed Microwave Irradiated Cross-Coupling Of Carboxylic Acids And Amino Alcohols., Md Shahin Reza

Tennessee State University Alumni Theses and Dissertations

Amino esters are valuable pharmaceutical intermediates with anesthetic properties and applications as prodrugs. In this study, we have developed a new microwave-assisted method for the cross-coupling of aromatic carboxylic acids with amino alcohol using a palladium catalyst. This approach has enabled an efficient synthesis of amino esters, overcoming challenges such as side reactions and product separation.

The Role Of Water In Peptide Behavior And Peptide-Based Water-Responsive Crystals, Janel Jannette Rivera Cancel

Dissertations, Theses, and Capstone Projects

Water plays a crucial role in shaping the behavior and function of biomolecules across the liquid, supercooled, and glassy states. This thesis presents a dual approach combining computational simulations and experimental investigations to explore the influence of water on biomolecular systems, particularly peptide-based materials. We employ molecular dynamics simulations to study the hydration-dependent structural dynamics of homopolymer peptides. Simulations were carried out across a range of temperatures and pressures to analyze changes in hydration and structural stability, shedding light on the behavior of peptides under supercooled and glassy conditions. These studies are especially relevant for understanding biomolecular stability in cryopreservation. …

Linking Core Concepts And Competencies In General Chemistry Via Gowin’S Theory Of Learning And Vee Heuristic, Vijay Vyas, Scott A. Reid

Chemistry Faculty Research and Publications

The content in introductory science courses has often been criticized as “miles wide and inches deep”. In general chemistry, several revisions have focused on framing around a set of core or anchoring concepts, and we recently adapted the anchoring concepts content map (ACCM) of the American Chemical Society (ACS) to develop an anchoring concept-based curriculum for our general chemistry courses. In this article, we describe efforts to connect this curriculum with laboratory learning using Gowin’s theory of learning and the associated knowledge Vee heuristic. Within this framework, the laboratories themselves become events connecting the conceptual and methodological domains, …

On The Chlorobenzene-Ammonia Cluster Reaction: Entrance Channel Dynamics, 2cr2pi Spectroscopy, And Ion Imaging Of The Reaction Dynamics, Ronald Mutete, Damian Kokkin, Natan Fessahaye, Thomas R. Howell, Richard A. Loomis, Scott A. Reid

Chemistry Faculty Research and Publications

Prior studies of halobenzene–ammonia complexes have shown that the nature of the cationic intermediate (i.e., Wheland-type vs ion-radical) may play a key role in determining the reaction products. To probe this link, we report here the reaction dynamics of the chlorobenzene-ammonia 1:1 complex (PhCl···NH₃) using product ion imaging following two-color resonant two-photon ionization. A threshold value of 8.863 ± 0.008 eV was determined for the appearance of protonated aniline, which accompanies Cl atom loss and is the dominant product channel at energies near threshold. Scanning down to energies close to threshold, we find no evidence for a roaming …

Bodipy-Based Photocages For The Controlled Release Of Hydrogen Sulfide And Persulfides, Yanmei Li

Dissertations

Reactive sulfur species (RSS) such as hydrogen sulfide (H2S) and hydropersulfides (RSSH) are crucial mediators in a variety of physiological and pathological processes. Their regulatory roles span from maintaining cellular redox balance to influencing signaling pathways critical for homeostasis and stress responses. This dissertation investigates H2S and RSSH as biologically important molecules and explores the development of boron-dipyrromethene (BODIPY)-based photocages for its controlled, light-triggered release. Given H2S and RSSH's critical role in redox regulation and cellular protection, achieving spatiotemporal control over its delivery is essential for both therapeutic and research applications. BODIPY scaffolds offer favorable photophysical properties, including visible-light activation …

Development And Implementation Of Novel Mass Spectrometric Methods For Metabolism Studies In Drug Discoveries, Huifang Yao

Dissertations

The field of drug discovery has evolved significantly over the past few decades, with a growing emphasis on understanding the metabolic pathways and biotransformation processes that influence the pharmacokinetics and pharmacodynamics of drug candidates. Novel mass spectrometric methods have emerged as powerful tools in this domain, facilitating the comprehensive analysis of metabolic profiles and enabling the identification of metabolites with implications for safety, efficacy, and overall drug development. However, challenges remain in quantifying metabolic flux—an essential aspect of understanding drug action—particularly due to the limitations of traditional isotope kinetic assays, which often involve lengthy sample preparation and the use of …

Low-Cost Cutaneous Protoporphyrin Ix (Ppix) Detection (Cpd) Device For Follow-Up Monitoring Of Patients After Photodynamic Therapy, Md Asaduzzaman Rasel

Graduate Masters Theses

Background: Photodynamic Therapy (PDT) utilizes specific wavelengths of light to activate photosensitizing chemical compounds, known as photosensitizers, which induce the generation of cytotoxic reactive oxygen species (ROS) for the targeted destruction of cancer cells. Among various photosensitizers for PDT, Protoporphyrin IX (PpIX) is widely employed in oncology and dermatology due to its natural in situ generation via the metabolic conversion of 5- aminolevulinic acid (ALA), a non-phototoxic prodrug. Systemic administration of ALA after 3-6 hr drug delay leads to peak PpIX accumulation in tissues, facilitating therapeutic and diagnostic applications. However, PpIX can persist in the skin for 24–48 hours post-treatment, …

Effect Of Seasonal Variability In Methane Emissions And Iron Redox Chemistry At Terrestrial-Aquatic Interfaces, Hermes C. Ruiz

Master's Theses

Methane (CH₄) emissions at terrestrial–aquatic interfaces (TAIs) are significant contributors to the global carbon budget, yet the mechanisms driving methanogenesis remain poorly understood. Limited data exist on how seasonal variations and redox processes influence CH₄ fluxes in these dynamic ecosystems. This study addressed two questions: (1) How are CH₄ fluxes in riverine floodplains and adjacent hillslopes impacted by seasonal variations? (2) What roles do metal redox processes (e.g., iron (Fe)) play in regulating methanogenesis?

In-situ CH₄ flux and solid-phase Fe speciation were quantified in East River, CO, under flooded and drained conditions. Groundwater chemistry, gas flux, and soil physical properties …

Molecular Dynamics Simulations Of Liposomes: Structure, Dynamics, And Applications, Ehsan Khodadadi, Ehsaneh Khodadadi, Parth Chaturvedi, Mahmoud Moradi

Chemistry & Biochemistry Faculty Publications and Presentations

Liposomes are nanoscale, spherical vesicles composed of phospholipid bilayers, typically ranging from 50 to 200 nm in diameter. Their unique ability to encapsulate both hydrophilic and hydrophobic molecules makes them powerful nanocarriers for drug delivery, diagnostics, and vaccine formulations. Several FDA-approved formulations such as Doxil (R) (Baxter Healthcare Corporation, Deerfield, IL, USA), AmBisome (R) (Gilead Sciences, Inc., Foster City, CA, USA), and Onivyde (R) (Ipsen Biopharmaceuticals, Inc., Basking Ridge, NJ, USA) highlight their clinical significance. This review provides a comprehensive synthesis of how molecular dynamics (MD) simulations, particularly coarse-grained (CG) and atomistic approaches, advance our understanding of liposomal membranes. We …

Design And Optimization Of Anode Catalysts For Direct Ethanol Fuel Cells: Advances And Challenges In C-C Bond Activation And Selective Modulation Of The C1 Pathway, Kai-Chi Qin, Meng-Tian Huo, Yu Liang, Si-Yuan Zhu, Zi-Hao Xing, Jin-Fa Chang

Journal of Electrochemistry

Direct ethanol fuel cells (DEFCs) are a promising alternative to conventional energy sources, offering high energy density, environmental sustainability, and operational safety. Compared to methanol fuel cells, DEFCs exhibit lower toxicity and a more mature preparation process. Unlike hydrogen fuel cells, DEFCs provide superior storage and transport feasibility, as well as cost-effectiveness, significantly enhancing their commercial viability. However, the stable C–C bond in ethanol creates a high activation energy barrier, often resulting in incomplete electrooxidation. Current commercial platinum (Pt)- and palladium (Pd)-based catalysts demonstrate low C–C bond cleavage efficiency (

Effect Of Saccharin On Crystallization Behavior Of Electroless Cobalt Plating, Yu-Xin Luo, Jing-Jing Wang, Lu Wang, Zi-Yi Yan, Yi Ma, Xin Bo, Jing-Shuang Dang, Zeng-Lin Wang

Journal of Electrochemistry

In the process of electroless cobalt plating, the saccharin additive can significantly change the surface morphology, texture orientation, and conductivity of the cobalt coating layer. When the amount of saccharin was 3 mg·L^–1, the cobalt coating transformed from disordered large grains to a honeycomb structure, with a preferred orientation of (002) facet on hexagonal close-packed (HCP) cobalt crystals. The resistivity of the cobalt film decreased to 14.4 μΩ·cm, and further decreased to 10.7 μΩ·cm after the annealing treatment. When the concentration of saccharin was increased, the grain size was gradually refined and a “stone forest” structure was observed, …

Superhydrophilic Porous Coooh Nano-Architecture With Abundant Oxygen Vacancies For Enhanced Urea Electrooxidation At Ampere-Level Current Densities, Wen-Jing Lv, Xiao-Man Tang, Xue-Tong Wang, Wen-Cai Liu, Jian-Wen Zhu, Guo-Jing Wang, Yuan-Zhi Zhu

Journal of Electrochemistry

The conversion of urea-containing wastewater into clean hydrogen energy has gained increasing attention. However, challenges remain, particularly with sluggish catalytic kinetics and limited long-term stability of urea oxidation reaction (UOR). Herein, we report the loosely porous CoOOH nano-architecture (CoOOH LPNAs) with hydrophilic surface and abundant oxygen vacancies (O_v) on carbon fiber paper (CFP) by electrochemical reconstruction of the CoP nanoneedles precursor. The resulting three-dimensional electrode exhibited an impressively low potential of 1.38 V at 1000 mA·cm⁻² and excellent durability for UOR. Furthermore, when tested in an anion exchange membrane (AEM) electrolyzer, it required only 1.53 V at …

Structure Regulation Engineering For Biomass-Derived Carbon Anodes Enabling High-Rate Dual-Ion Batteries, Rui Zhou, Rui Liu, Yun-Nuo Li, Si-Jie Jiang, Tian-Tian Jing, Yan-Song Xu, Fei-Fei Cao

Journal of Electrochemistry

Dual-ion batteries (DIBs) usually use carbon-based materials as electrodes, showing advantages in high operating voltage, potential low cost, and environmental friendliness. Different from conventional “rocking chair” type secondary batteries, DIBs perform a unique working mechanism, which employ both cation and anion taking part in capacity contribution at an anode and a cathode, respectively, during electrochemical reactions. Graphite has been identified as a suitable cathode material for anion intercalation at high voltages (> 4.8 V) with fast reaction kinetics. However, the development of DIBs is being hindered by dynamic mismatch between a cathode and an anode due to sluggish Li^{+ …}

Anionic Azo Dyes: Wastewater Pollutants As Functionalizing Agents For Porous Polycarbonate Membranes Aiding In Water Decolorization, Alan Jarrett Messinger, Isabella S. Mays, Brennon Craigo, Jeffrey Joering, Sean P. Mcbride

Physics Faculty Research

Efficient water decolorization techniques are vital for ensuring fresh water for future generations. Azo dyes are used heavily in the textile industry and are a challenge to remove from industrial wastewater. This research expands on recent innovative work where anionic azo dyes themselves were used to functionalize track-etched porous polycarbonate filtration membranes with decolorized water obtained as a byproduct. The objective of this research is to determine whether the observed dye rejection is dependent on the magnitude of the intrinsic charge of the dye molecule or on its structure, using two selectively chosen anionic azo dye series during functionalization. The …

Effects Of Ambient Temperature On Nox Emissions From Heavy-Duty Diesel Vehicles Measured In Utah, Amber L. Gurecki Allen, Darrell B. Sonntag, Gary A. Bishop

Fuel Efficiency Automobile Test Publications

This study investigates the effects of ambient temperature on NOx (NO + NO2) emissions from model year 2011 and later heavy-duty (HD) diesel vehicles. Emission measurements were collected in Perry, Utah, using the Fuel Efficiency Automobile Test (FEAT) remote sensing device. Data were limited to model year 2011 and later to focus on vehicles likely equipped with selective catalytic reduction (SCR) systems, which control tailpipe NOx emissions and are shown to be temperature sensitive. HD diesel vehicles measured in the winter of 2020 had consistently higher NOx emissions than those measured in the summer of 2023, most significantly for vehicles …