A5086581047- Isotope Analysis in Ecology
- Atmospheric Ozone and Climate
- Atmospheric and Environmental Gas Dynamics
- Marine and coastal ecosystems
- Geology and Paleoclimatology Research
- Atmospheric chemistry and aerosols
- Methane Hydrates and Related Phenomena
- Paleontology and Stratigraphy of Fossils
- Spectroscopy and Laser Applications
- Groundwater and Isotope Geochemistry
- Marine Biology and Ecology Research
- Hydrocarbon exploration and reservoir analysis
- Oceanographic and Atmospheric Processes
- Astro and Planetary Science
- Advanced Chemical Physics Studies
- Geological and Geochemical Analysis
- Catalytic Processes in Materials Science
- Cryospheric studies and observations
- Scientific Measurement and Uncertainty Evaluation
- Avian ecology and behavior
- Analytical Chemistry and Sensors
- Geochemistry and Elemental Analysis
- Polar Research and Ecology
- Atomic and Subatomic Physics Research
- Marine animal studies overview
Terasaki Foundation
2025
Rice University
2015-2023
Planetary Science Institute
2014-2015
University of California, Los Angeles
2011-2015
Southern California Earthquake Center
2011-2015
University of Southern California
2011-2015
California Institute of Technology
2008-2011
Northwestern University
2009
Montana State University
2009
Oberlin College
2003-2005
The geochemistry of multiply substituted isotopologues ('clumped-isotope' geochemistry) examines the abundances in natural materials molecules, formula units or moieties that contain more than one rare isotope (e.g. (13)C(18)O(16)O, (18)O(18)O, (15)N(2), (13)C(18)O(16)O(2) (2-)). Such species form basis carbonate clumped-isotope thermometry and undergo distinctive fractionations during a variety processes, but initial reports have provided few details their analysis. In this study, we...
Abstract The oxygen and hydrogen isotopic composition in snow ice have long been utilized to reconstruct past temperatures of polar regions, under the assumption that post‐depositional processes such as sublimation do not fractionate snow. In low‐accumulation (<0.01 m yr −1 ) areas near McMurdo Dry Valleys Antarctica, surface samples exceptionally low deuterium excess values (d‐excess ≡ δD – 8*δ 18 O)—sometimes negative −5‰—an uncommon phenomenon is fully understood. Here we use both an...
Of the six stable isotopic variants of O 2 , only three are measured routinely. Observations natural variations in 16 18 O/ and 17 ratios have led to insights atmospheric, oceanographic, paleoclimate research. Complementary measurements exceedingly rare might therefore broaden our understanding oxygen cycling. Here we describe a method measure these multiply substituted isotopologues . Its accuracy is demonstrated by measuring effects for Knudsen diffusion electrolysis laboratory that...
Offshore tropical river plumes are associated with areas of high N 2 fixation (diazotrophy) and biological carbon drawdown. Episodic blooms the diatom Hemiaulus hauckii its diazotrophic cyanobacterial symbiont Richelia intracellularis believed to dominate that drawdown, but mechanism is not well understood. We report primary productivity these diatom‐diazotroph assemblages (DDAs) in offshore plume Amazon River using simultaneous measurements O /Ar ratios triple‐isotope composition dissolved...
[1] The oxygen triple-isotope composition of dissolved O2 provides an integrative method to estimate the rates Gross Photosynthetic Production (GPP) in upper ocean, and combined with estimates Net Community (NCP) yields net-to-gross (NCP/GPP) production ratios. However, derivations GPP from measurements have involved some mathematical approximations. We derive exact expression for calculating GPP, show that small errors associated approximations result a relative error up ∼38% ∼50% N/G. In...
The abundances of molecules containing more than one rare isotope have been applied broadly to determine formation temperatures natural materials. These applications "clumped" isotopes rely on the assumption that isotope-exchange equilibrium is reached, or at least approached, during those In a closed-system terrarium experiment, we demonstrate biological oxygen (O2) cycling drives clumped-isotope composition O2 away from isotopic equilibrium. Our model system suggests unique signatures are...
Abstract The Arosa Zone, Central Alps, represents a Cretaceous to Paleogene fossil subduction interface from paleodepths of 10 >35 km. Metasedimentary schists directly below preserved seismogenic zone exhibit viscous (foliations, folds, and lineations) brittle (crack‐seal quartz ± calcite veins) deformation features. Si‐in‐phengite barometry published temperature estimates yield metamorphism conditions 0.8–0.9 GPa 300–350°C for an albite‐rich pelitic schist 0.9 420°C calcite‐rich...
Isotope ratio measurements have become extremely precise in recent years, with many approaching parts-per-million (ppm) levels of precision. However, seemingly innocuous errors signal baselines, which exist only when gas enters the instrument, might lead to significant errors. These "pressure-baseline" (PBL) offsets may a variety origins, such as incoherent scattering analyte, isobaric interferences, or electron ablation from walls flight tube. They are probably present all but...
Abstract The movement of tropical cyclones (TCs), particularly around the time landfall, can substantially affect resulting damage. Recently, trends in TC translation speed and likelihood stalled TCs such as Harvey have received significant attention, but findings remained inconclusive. Here, we examine how June-September steering wind landfalling Texas change future under anthropogenic climate change. Using several large-ensemble/multi-model datasets, find pronounced regional variations...
Upper-atmospheric chemistry and biological N 2 cycling engage in a planetary-scale tug-of-war seen 15 of air.
Abstract Background: Clinical resistance to immunotherapy remains a significant challenge in cancer treatment, with many patients requiring combination therapies achieve optimal therapeutic outcomes. Tumor cells often evade immune detection by down-regulating Major Histocompatibility Complex (MHC)-I or Human Leukocyte Antigen (HLA) expression, effectively escaping T-cell-mediated immunity. However, this loss may enhance tumors susceptible Natural Killer (NK) cells, which are capable of...
The stratospheric CO(2) oxygen isotope budget is thought to be governed primarily by the O((1)D)+CO(2) exchange reaction. However, there increasing evidence that other important physical processes may occurring standard isotopic tools have been unable identify. Measuring distribution of exceedingly rare isotopologue (16)O(13)C(18)O, in concert with (18)O and (17)O abundances, provides sensitivities these additional and, thus, a valuable test current models. We identify large unexpected...
The precise mass dependence of respiratory O2 consumption underpins the "oxygen triple-isotope" approach to quantifying gross primary productivity in modern and ancient environments. Yet, physical-chemical origins key 18O/16O 17O/16O covariations observed during respiration have not been tied theory; thus, remains empirical. First-principles calculations on enzyme active-site models suggest that changes O–O bond strength upon electron transfer strongly influence isotopic fractionation....
Abstract The abundances of 18 O and 17 in the atmosphere were recently found to be enriched relative stochastic distribution isotopes 2 . enrichment is believed arise from O( 3 P ) + isotope exchange reactions, which reorder a that favors bonds between heavy isotopes. Theoretical predictions laboratory experiments suggest reordered should reflect internal isotopic equilibrium, but test this hypothesis for complete isotopologue system has not yet been realized. Here we use simple...
Kinetics studies of the OH-initiated oxidation 2-butyne, propyne, and acetylene were conducted at 100 Torr 298 K using turbulent flow chemical ionization mass spectrometry. The major products identified, with aid supporting electronic structure thermodynamics calculations, a general mechanism for alkynes is proposed. product branching ratio product-forming rate constants 2-butyne-OH adduct + O(2) reaction experimentally determined as well. atmospheric implications kinetics results are discussed.