About

Conrad M. Davis is a visiting faculty member with a background in taxation and accounting. He holds a Master of Science in Taxation from Golden Gate University and a Bachelor of Science in Agricultural Science and Management from the University of California-Davis. Davis is the Partner-in-Charge of the Tax Practice at a firm in Sacramento, California, with more than 28 years of experience providing tax compliance and consulting services to closely held businesses, particularly in the food and food production industries. He works closely with clients to understand their business goals and collaborates with auditors to deliver effective tax services. His professional affiliations include the California Society of Certified Public Accountants, where he has served as Past Chair, the American Institute of Certified Public Accountants, the Association of Certified Fraud Examiners, and the National Association of Accountants for Cooperatives, where he has served as Past President.

Research topics

• Computer Science
• Artificial Intelligence
• Real-time computing
• Embedded system
• Risk analysis (engineering)
• Veterinary medicine
• Pathology
• Medicine
• Virology
• Human–computer interaction
• Engineering
• Biology

Selected publications

• Volatile organic compound analysis of Humboldt Penguin (Spheniscus humboldti) preen oil: a pilot study

  Journal für Ornithologie · 2026-04-15

  articleSenior author
  PublisherDOI

• Evaluation of lung oxidative stress and inflammatory state using exhaled breath condensate analysis in early-life arsenic exposure

  Journal of Breath Research · 2025-09-09 · 1 citations

  articleOpen access

  Abstract Millions of people worldwide are exposed to environmental arsenic in drinking water, resulting in both malignant and nonmalignant diseases. Interestingly, early life exposure by itself is sufficient to produce higher incidences of these diseases later in life. Based on the delayed onset of disease, we hypothesized that early life arsenic exposure would also induce long-term alterations in the metabolic profile. The objective of this study was to examine metabolomic biomarkers in exhaled breath condensate (EBC) of individuals exposed to arsenic in drinking water early in life, but not later. One hundred and fifty subjects (75 males and 75 females) were initially recruited from Antofagasta, Chile, some of whom were exposed to high water arsenic levels (⩾870 µ g l −1 ; HighAE group), and others, low water arsenic levels (⩽110 µ g l −1 ; LowAE group) early in life (1958–1970). EBC samples were collected for targeted and untargeted metabolomic biomarker analysis. The results showed significantly shorter individuals and reduced pulmonary functions (forced vital capacity, FVC and forced expiratory volume in 1 s, FEV 1 ) in both males and females in the high-arsenic groups. Males exposed to high arsenic levels also had reduced red blood cell concentrations, as well as higher concentrations of the oxidative stress metabolites 8-OH-2dG and 8-iso-PGF2 α . Females in the high-arsenic group showed reductions in 8-OH-2dG. Untargeted analysis revealed metabolomic markers that differentiated the HighAE group from the LowAE group, with a subgroup of markers whose concentrations were proportional to the level of arsenic exposure. Targeted and untargeted analyses of EBC using liquid chromatography–mass spectrometry indicated that adults exposed to high arsenic levels in drinking water in utero and during early childhood retained a modified metabolic profile 47 years after the end of exposure.

  PublisherDOI

• Breath analysis for health monitoring and clinical applications

  European Respiratory Society eBooks · 2025-04-01 · 1 citations

  book-chapter

  Breath composition can now be measured in real time, offering a dynamic and noninvasive view of physiological and biochemical processes occurring in the human body. However, despite many decades of research in the field, clinical use of breath analysis remains limited. Within the breath community, there is no consensus on the exact reasons, but the lack of standardised protocols for breath sampling and analysis, the influence of extrinsic and intrinsic confounders as well as misconceptions in appropriately designing and conducting studies are thought to play a major role. Here, we present a snapshot of the research field, starting with the rationale and origins of breath components, followed by a discussion of the state-of-the-art technologies for breath sampling and analysis, and concluding with present clinical applications, limitations and perspectives.

  PublisherDOI

• OpenDMS: An Open-Source Approach to Differential Mobility Spectrometry

  Analytical Chemistry · 2025-06-19 · 3 citations

  articleOpen accessSenior authorCorresponding

  Differential mobility spectrometry (DMS) is a powerful gas-phase chemical analysis technique that separates ions based on their differential mobility in an asymmetric electric field, offering high sensitivity and rapid analysis crucial for fields such as proteomics, metabolomics, and environmental monitoring. Despite its advantages, the widespread adoption of DMS technology has been hindered by the high cost, proprietary nature, and lack of flexibility of commercial systems. In this study, we introduce OpenDMS, an open-source differential mobility spectrometry system designed to be accessible, customizable, and cost-effective. OpenDMS is constructed using readily available components with fully documented designs and open-source software for data processing and visualization. We demonstrate the system's performance through detailed dispersion plots and sensitivity analyses, achieving a theoretical limit of detection of 38 ppt and a resolving power of 1.57 at 10 ppb and 836 SV for an ethylbenzene monomer. The ability to interchange ionization sources, such as plasma and UV ionization, highlights the system's versatility. Importantly, we demonstrate that doping is compatible with the OpenDMS with the use of acetone shifting the DMMP monomer peak. By providing an open-source platform, OpenDMS aims to provide a solid foundation for access to DMS technology, fostering innovation and collaboration within the scientific community and accelerating advancements in various scientific fields.

  PublisherDOI

• IABR Symposium 2021 meeting report: breath standardization, sampling, and testing in a time of COVID-19

  UNC Libraries · 2025-06-05

  articleOpen access

  Due to COVID-19 travel disruptions, the International Association of Breath Research hosted the planned 2021 Breath Summit virtually as a symposium with oral and poster presentations. The event was comprised of a week-long social media asynchronous online event for sharing research abstracts, posters and discussions. Subsequently, there were two days of real-time webinar platform interactions each featuring three technical presentations, open forum questions, answers, and commentary. The symposium was well attended and well received. It allowed the breath community to share new research and to reconnect with colleagues and friends. This report presents an overview of the topics presented and various salient discussion points.

  PublisherDOI

• Volatile organic compounds (VOCs) to monitor cell expansion and microbial contamination of mesenchymal stromal cells (MSCs): a preliminary study

  Journal of Breath Research · 2025-11-04

  articleOpen accessSenior authorCorresponding

  Abstract Several investigations have identified volatile organic compounds (VOCs) as potential biomarkers for the detection and identification of microbial contamination of metabolically active mammalian cell cultures. In this study, we showed that emitted VOCs discriminate between uncontaminated mesenchymal stromal cells (MSCs) and those contaminated with the bacterium Staphylococcus epidermidis or fungus Aspergillus Fumigatus separately, in vitro , using a methodology based on an adapted cell culture and thermal desorption–gas chromatography–mass spectrometry. In addition, we elucidated a set of discriminatory volatile compounds from the MSC cultures and media alone across a time series experiment. Partial least squares–discriminant analysis-variable importance in projection confirmed putative identifications of 18, 16, and 26 VOCs that showed relevant changes in a bacterial, fungal, and universal pathogen model, respectively, with an accuracy of 100% in the fungal model. Among these metabolites, octane, 2,5,6-trimethyl- overlapped between the three groups. Furthermore, a total of 15 VOCs were found most relevant to cell culture expansion over three days based on cluster analysis. This novel study goes a step further in identifying distinct VOC signatures of MSCs contaminated with S. epidermidis or A. fumigatus , and in monitoring MSCs proliferation over time. This pilot study shows preliminary results that indicate that VOC headspace analysis could serve as a suitable, rapid, non-invasive, and non-destructive tool for the metabolic and growth monitoring of MSCs in a dynamic cell culture bioreactor system.

  PublisherDOI

• A device for volatile organic compound (VOC) analysis from skin using heated dynamic headspace sampling

  Journal of Breath Research · 2025-04-15 · 1 citations

  articleOpen accessSenior author

  Human skin is an important source of volatile organic compounds (VOCs) offering noninvasive methods to gain clinical metabolite information. This work was focused on the development of a skin sampling device based on a dynamic headspace sampling method with the addition of temperature to increase VOC metabolite recovery. The device preconcentrates skin VOC emissions onto a sorbent substrate, which can either be preserved for offline analysis or attached to a real time sensor downstream. In this work, skin VOC samples were analyzed offline using thermal desorption-gas chromatography-mass spectrometry. A list of 10 common skin VOCs was pre-selected to optimize parameters of sampling time, sampling temperature, and sorbent selection. Overall, this study highlights an effective skin VOC sampling technology with a heating dimension (40 °C, rather than 30 °C or no heating) with a sampling time of 15 min (rather than 5 or 30 mins) and onto Tenax TA sorbent (rather than PDMS), which collectively increases the recovery of compounds with lower vapor pressure and decreases the observed variability in skin VOC measurements. Finally, a list of 79 skin VOC compounds were detected and identified within a cohort of 20 young, healthy volunteers.

  PublisherDOI

• VOC analysis for rapid, early detection of bacteria, mold, and mycoplasma in cell and tissue cultures

  SLAS DISCOVERY · 2025-10-01

  articleOpen access

  Identifying microbial contamination early in cell culture processing can save time, money, and reagents. However, standard strategies for performing contamination testing often take days, leaving production vulnerable to potential spread of bacteria, mold, and mycoplasma. Volatile organic compounds (VOCs) are released by every living organism. These VOCs are increasingly being used to identify cell pathologies, study cell metabolomics, and assess other biological processes. Often, gas chromatography with mass spectrometry (GC-MS) is used to perform these analyses. Here, we utilized gas chromatography with ion mobility spectrometry (GC-IMS) to detect bacteria, mold, and mycoplasma in both cell and tissue cultures. Traditional GC-MS was used to validate the detection of microbes in cell cultures using GC-IMS. In most cases, headspace samples were collected just two hours after inoculations. GC-IMS was able to detect as low as 10 CFU of 5 different industry standard microbes, including both bacteria and mold species. In addition, mycoplasma presence, which is notoriously difficult to test, was detectable at 24 h post-inoculation. GC-IMS is highly sensitive, has a small footprint, requires minimal training, and can provide results in as little as 20 min per sample. Combined, this makes it an ideal strategy for detecting contamination in cell and tissue production workflows. Such rapid detection could save substantial amounts of time, money, and valuable reagents, and reduce risks to patient safety.

  PublisherOA PDFDOI

• Harnessing breath biomarkers for pneumonia diagnosis and prognosis

  Expert Review of Respiratory Medicine · 2025-11-24

  articleOpen access

  INTRODUCTION: Pneumonia is a major cause of death and disability worldwide. A host of pathogens causes pneumonia, and pneumonia presents with a remarkable heterogeneity of clinical symptoms and signs and has varied outcomes. Current approaches to pneumonia diagnosis and risk stratification lack precision such that there is no universally agreed upon biomarker or scoring system. These limitations have prompted calls for novel, noninvasive, and more precise approaches to better diagnosing pneumonia and predicting outcomes. AREAS COVERED: We performed a comprehensive literature search through PubMed to identify studies reporting on breath biomarkers in pneumonia published up to 31 July 2025. This manuscript explores breath-based metabolomics as a novel approach to biomarker development in pneumonia. It describes breath collection methods, including devices available and types of breath samples for analysis. It reviews the potential role of exhaled breath analysis to expedite pneumonia diagnosis, monitor response to therapy, and predict clinical trajectory. EXPERT OPINION: Breath-based metabolomics could improve the recognition and management of pneumonia. It is a noninvasive, potentially continuous method that provides a direct window into the lung for novel insights into the underlying biology of pneumonia.

  PublisherOA PDFDOI

• Impacts of vaping and marijuana use on airway health as determined by exhaled breath condensate (EBC)

  Respiratory Research · 2025-02-21 · 4 citations

  articleOpen accessSenior author

  Across the United States, there is increased use of cannabis products and electronic delivery systems for cannabis products and nicotine, yet little is known about their impacts on lung health. We analyzed exhaled breath condensate of 254 participants who were non-users and users who used cannabis and tobacco products. The 132 participants reported using a product ("users") were distributed into cohorts of tobacco products and cannabis products, with some participants following into multiple cohorts. Targeted analysis of inflammatory oxylipins found up-regulation among persons using tobacco products, while cannabis users had concentrations closer to nonusers, and often down-regulated. Untargeted screening of 403 significant metabolites found tobacco users had similar breath profiles, and that cannabis users had a similar profile that was closer to the profile of nonusers. Metabolites were significantly higher in breath of people using combustion products (tobacco and cannabis) relative to nonusers, and significantly lower in e-device users (nicotine and THC). Our work demonstrates the relative impact of e-delivery systems and cannabis products compared to traditional cigarette smoking on lung metabolic profiles.

  PublisherOA PDFDOI

Recent grants

• IDBR: Portable monitoring device for off-gassed volatile plant metabolites

  NSF · $600k · 2013–2017

• Monitoring of disease-induced skin VOC patterns from handheld and wearable chemical sensors

  NIH · $4.6M · 2022–2027

• Portable GC detector for breath-based COVID diagnostics

  NIH · $898k · 2020–2024

• NIH Grant U01EB02200301

  NIH · $1.5M · 2020

• ENG-SEMICON: Meshed chemical sensor network for targeted monitoring of environmental VOCs of concern

  NSF · $400k · 2024–2027

Frequent coauthors

• Nicholas J. Kenyon

  VA Northern California Health Care System

  112 shared

• Mitchell M. McCartney

  VA Northern California Health Care System

  101 shared

• Michael Schivo

  University of California, Davis

  60 shared

• Alexander A. Aksenov

  59 shared

• Eva Borras

  University of California, Davis

  48 shared

• Alberto Pasamontes

  Universidad Rovira i Virgili

  46 shared

• Alexander G. Fung

  University of California, Davis

  44 shared

• Abhaya M. Dandekar

  University of California, Davis

  35 shared

Education

• Postdoctoral Fellowship (Joint: Physiology and Electrical Engineering), Physiology, Electrical Engineering

  Johns Hopkins University

  2001

• PhD, Biomedical Engineering

  University of Virginia

  1999

• MS, Biomedical Engineering

  University of Virginia

  1996