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Browsing by Author "Lamadrid, Hector M."

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    Effect of water activity on rates of serpentinization of olivine
    Lamadrid, Hector M.; Rimstidt, J. Donald; Schwarzenbach, Esther M.; Klein, Frieder; Ulrich, Sarah; Dolocan, Andrei; Bodnar, Robert J. (Nature, 2017-07-14)
    The hydrothermal alteration of mantle rocks (referred to as serpentinization) occurs in submarine environments extending from mid-ocean ridges to subduction zones. Serpentinization affects the physical and chemical properties of oceanic lithosphere, represents one of the major mechanisms driving mass exchange between the mantle and the Earth’s surface, and is central to current origin of life hypotheses as well as the search for microbial life on the icy moons of Jupiter and Saturn. In spite of increasing interest in the serpentinization process by researchers in diverse fields, the rates of serpentinization and the controlling factors are poorly understood. Here we use a novel in situ experimental method involving olivine micro-reactors and show that the rate of serpentinization is strongly controlled by the salinity (water activity) of the reacting fluid and demonstrate that the rate of serpentinization of olivine slows down as salinity increases and H₂O activity decreases.
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    Molecular preservation in mammoth bone and variation based on burial environment
    Colleary, Caitlin; Lamadrid, Hector M.; O'Reilly, Shane S.; Dolocan, Andrei; Nesbitt, Sterling J. (2021-01-29)
    Biomolecules preserved in fossils are expanding our understanding of the biology and evolution of ancient animals. Molecular taphonomy seeks to understand how these biomolecules are preserved and how they can be interpreted. So far, few studies on molecular preservation have considered burial context to understand its impact on preservation or the potentially complementary information from multiple biomolecular classes. Here, we use mass spectrometry and other analytical techniques to detect the remains of proteins and lipids within intact fossil mammoth bones of different ages and varied depositional setting. By combining these approaches, we demonstrate that endogenous amino acids, amides and lipids can preserve well in fossil bone. Additionally, these techniques enable us to examine variation in preservation based on location within the bone, finding dense cortical bone better preserves biomolecules, both by slowing the rate of degradation and limiting the extent of exogenous contamination. Our dataset demonstrates that biomolecule loss begins early, is impacted by burial environment and temperature, and that both exogenous and endogenous molecular signals can be both present and informative in a single fossil.
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    Shift in the Raman symmetric stretching band of N-2, CO2, and CH4 as a function of temperature, pressure, and density
    Sublett, D. Matthew, Jr.; Sendula, Eszter; Lamadrid, Hector M.; Steele-MacInnis, Matthew; Spiekermann, Georg; Burruss, Robert C.; Bodnar, Robert J. (2020-03)
    The Raman spectra of pure N-2, CO2, and CH4 were analyzed over the range 10 to 500 bars and from -160 degrees C to 200 degrees C (N-2), 22 degrees C to 350 degrees C (CO2), and -100 degrees C to 450 degrees C (CH4). At constant temperature, Raman peak position, including the more intense CO2 peak (nu+), decreases (shifts to lower wave number) with increasing pressure for all three gases over the entire pressure and temperature (PT) range studied. At constant pressure, the peak position for CO2 and CH4 increases (shifts to higher wave number) with increasing temperature over the entire PT range studied. In contrast, N-2 first shows an increase in peak position with increasing temperature at constant pressure, followed by a decrease in peak position with increasing temperature. The inflection temperature at which the trend reverses for N-2 is located between 0 degrees C and 50 degrees C at pressures above similar to 50 bars and is pressure dependent. Below similar to 50 bars, the inflection temperature was observed as low as -120 degrees C. The shifts in Raman peak positions with PT are related to relative density changes, which reflect changes in intermolecular attraction and repulsion. A conceptual model relating the Raman spectral properties of N-2, CO2, and CH4 to relative density (volume) changes and attractive and repulsive forces is presented here. Additionally, reduced temperature-dependent densimeters and barometers are presented for each pure component over the respective PT ranges. The Raman spectral behavior of the pure gases as a function of temperature and pressure is assessed to provide a framework for understanding the behavior of each component in multicomponent N-2-CO2-CH4 gas systems in a future study.