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Open Access Publications from the University of California

Scholarly Works (48 results)

  • Article
California Journal of Politics and Policy, Volume 13, Issue 1 (2021)
    Cover page: Providing Access to Justice in the Midst of a Pandemic
    • Thesis
    • Peer Reviewed
    UC Berkeley Electronic Theses and Dissertations (2019)

    Regions facing water scarcity are expanding their water portfolios to augment supplies and meet future demand. Direct potable reuse, the deliberate introduction of advanced treated municipal wastewater into a drinking water treatment facility or distribution system, has gained considerable traction in the United States in recent years. The high concentrations of pathogens and chemical contaminants in municipal wastewater necessitates a high degree of treatment to meet drinking water standards and protect public health. Therefore, in potable reuse systems, municipal wastewater is typically treated by conventional wastewater treatment processes (e.g., sedimentation and activated sludge) followed by “advanced” treatment processes (e.g., microfiltration, reverse osmosis, and advanced oxidation). To date, the main research focus on microbial water quality in potable reuse systems has been quantifying the removal of pathogens (primarily enteric viruses and protozoa) present in municipal wastewater. While essential, this research does not provide insight into how advanced treatment alters the entire microbial community or the potential for microbial growth in treated water. Moreover, the management of microbial risk and water quality in distribution systems remains poorly studied in the context of direct potable reuse.

    In this dissertation, improved microbial monitoring methods were applied to two advanced wastewater treatment facilities and a lab-scale simulated direct potable reuse distribution systems to evaluate the impact of advanced treatment on microbial numbers, viability, and growth potential in direct potable reuse systems. Microbial water quality through the treatment and distribution systems was evaluated by measuring changes in total and potentially viable prokaryotic cells, total and intracellular ATP, organic carbon, several primary and opportunistic pathogens, and two antibiotic resistance genes. Enhanced microbial analysis methods such as flow cytometry for cell counts, ATP analysis, and dead-end ultrafiltration for quantitative PCR analyses were applied and evaluated as research tools and/or routine monitoring methods for potable reuse systems.

    Through this work I showed that the introduction of advanced treated water into a drinking water distribution system holds the potential for improving microbial water quality, but growth during the distribution of advanced treated water must still be properly managed. The microbial water quality of drinking water distribution systems may improve following the introduction of advanced treated water by a lower potential for microbial growth, lower microbial viability, and greater stability of a chlorine residual during simulated distribution. Specifically, chlorine residual decay and the numbers of potentially viable cells (i.e., intact cell counts measured by flow cytometry) were lower in distribution systems fed with advanced-treated water as compared to those fed with 100% conventional water. The prevalence of the opportunistic pathogens Legionella pnuemophila and Mycobacterium avium complex were unaffected by the use of advanced treated water. Furthermore, assimilable organic carbon concentrations (i.e., a common metric for microbial growth potential) in advanced treated water was similar to or less than values reported for finished and distributed drinking waters in the United States. The transportation, conditioning, and storage of reverse osmosis permeate without a chlorine residual resulted in large increases in microbial numbers, but no more than those typically seen in drinking water with a degraded residual. The relative abundance of sul1 remained unchanged by the handling of RO permeate, leading to high increases in absolute sul1 gene counts. Regardless, the application and maintenance of a chlorine residual substantially suppressed microbial numbers during distribution of advanced treated water; however, the passage of ammonia through advanced treatment could cause significant variability in the performance of chlorine disinfection.

    I also demonstrated the utility of flow cytometry, ATP analysis, and dead-end ultrafiltration (to concentrate water for quantitative PCR analyses) as informative research and monitoring methods for potable reuse systems. In particular, these tools were used to successfully quantify microbial cells in matrices with low biomass (e.g., reverse osmosis permeate) with relatively good precision. Furthermore, flow cytometry and ATP analysis showed promise as routine/continuous tools to monitor the performance of treatment processes such as microfiltration, reverse osmosis, and chlorination. These tools also provided additional insights into how the chlorine residual impacted microbial viability (e.g., changes in intact cell counts) in simulated distribution systems.

    Overall, this body of work contributes to a better understanding of engineered water systems and will ultimately inform more comprehensive water quality monitoring strategies for water treatment systems. Further work is needed to characterize microbial water quality in different types of advanced treatment trains, and utilities that implement direct potable reuse should use conventional and improved monitoring methods to evaluate full-scale distribution systems before and after the introduction of advanced-treated water.

      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2013)
      The stereoselective Rauhut-Currier (RC) reaction catalyzed by a cysteine derivative has been explored computationally with density functional theory (M06-2X). Both methanethiol and a chiral cysteine derivative were studied as nucleophiles. The complete reaction pathway involves rate-determining elimination of the thiol catalyst from the Michael addition product. The stereoselective Rauhut-Currier reaction, catalyzed by a cysteine derivative as a nucleophile, has also been studied in detail. This reaction was experimentally found to be extremely sensitive to the reaction conditions, such as the number of water equivalents and the effect of potassium counterion. The E1cB process for catalyst elimination has been explored computationally for the eight possible stereoisomers. The effect of explicit water solvation and the presence of counterion (either K(+) or Na(+) ) has been studied for the lowest energy enantiomer pair (1S, 2R, 3S)/(1R, 2S, 3R).
        Cover page: The Roles of Counterion and Water in a Stereoselective Cysteine‐Catalyzed Rauhut–Currier Reaction: A Challenge for Computational Chemistry
        • Article
        • Peer Reviewed
        Faculty Publications (2010)
        A system for the shipboard measurement of air-sea CO2 fluxes by eddy covariance was developed and tested. The system was designed to reduce two major sources of experimental uncertainty previously reported. First, the correction for in situ water vapor fluctuations (the “Webb” correction) was reduced by 97% by drying the air sample stream. Second, motion sensitivity of the gas analyzer was reduced by using an open-path type sensor that was converted to a closed-path configuration to facilitate drying of the air stream. High-quality CO2 fluxes were obtained during 429 14 min flux intervals during two cruises in the North Atlantic. The results suggest that the gas analyzer resolved atmospheric CO2 fluctuations well below its RMS noise level. This noise was uncorrelated with the vertical wind and therefore filtered out by the flux calculation. Using climatological data, we estimate that the techniques reported here could enable high-quality measurements of air-sea CO2 flux over much of the world oceans.
        • 1 supplemental file
        Cover page: Ship-based measurement of air-sea CO <sub>2</sub> exchange by eddy covarianceCreative Commons 'BY' version 4.0 license
        • Article
        • Peer Reviewed
        UC Irvine Previously Published Works (2007)
        Forest gaps may provide conduits that preferentially vent moist, CO2-rich subcanopy air to the atmosphere. We measured the above-canopy fluxes of momentum, sensible heat (H), CO2, and water vapor (Et), and the vertical profiles of CO2 and water vapor, from two 67-m meteorological towers in a selectively logged Brazilian rainforest. The logging removed ∼3.5 trees ha-1, and increased the incidence of gaps by a factor of 3 over nearby undisturbed forest. One tower was located in an intact patch of forest within the selectively logged area; the other was 400 m upwind in a large gap created by the logging. During daytime the subcanopy air in the intact patch of forest had more CO2, more water vapor, and was cooler than the air at comparable altitudes in the gap. Meanwhile, the daytime CO2 flux was less negative (reduced CO2 uptake) above the gap than above the intact forest, the daytime Et was greater above the gap than the intact forest, and the daytime H was lower above the gap than the intact forest. These patterns cannot be explained fully by the local loss of canopy gas exchange in the gap, but are consistent with the horizontal transport into the gap, and subsequent vertical transport out of the gap, of high-CO2, humid, cool air from the forest understory. The understory was drier and warmer during daytime after the logging, which would be expected to increase flammability. Further measurement and modeling efforts are needed to better understand the effect of canopy gaps on the local CO2 and energy exchange, as well as the flux footprint. © 2006 Elsevier B.V. All rights reserved.
          Cover page: The effect of canopy gaps on subcanopy ventilation and scalar fluxes in a tropical forestCreative Commons 'BY' version 4.0 license
          • Article
          • Peer Reviewed
          UC Berkeley Previously Published Works (2017)
          Selective reactions on structures of high complexity can move beyond the mind's eye and proof-of-principle. Enhanced understanding of noncovalent interactions and their interdependence, revealed through analysis of multiple parameters, should accelerate the discovery of efficient reactions in highly complex molecular environments.
            Cover page: Pursuit of Noncovalent Interactions for Strategic Site-Selective Catalysis
            • Article
            • Peer Reviewed
            UC Berkeley Previously Published Works (2018)
            Glycosylated natural products and synthetic glycopeptides represent a significant and growing source of biochemical probes and therapeutic agents. However, methods that enable the aqueous glycosylation of endogenous amino acid functionality in peptides without the use of protecting groups are scarce. Here, we report a transformation that facilitates the efficient aqueous O-glycosylation of phenolic functionality in a wide range of small molecules, unprotected tyrosine, and tyrosine residues embedded within a range of complex, fully unprotected peptides. The transformation, which uses glycosyl fluoride donors and is promoted by Ca(OH)2, proceeds rapidly at room temperature in water, with good yields and selective formation of unique anomeric products depending on the stereochemistry of the glycosyl donor. High functional group tolerance is observed, and the phenol glycosylation occurs selectively in the presence of virtually all side chains of the proteinogenic amino acids with the singular exception of Cys. This method offers a highly selective, efficient, and operationally simple approach for the protecting-group-free synthesis of O-aryl glycosides and Tyr-O-glycosylated peptides in water.
              Cover page: Rapid phenolic O-glycosylation of small molecules and complex unprotected peptides in aqueous solvent
              • Article
              • Peer Reviewed
              Faculty Publications (2009)
              We report the first simultaneous eddy covariance flux measurements of CO2 and dimethylsulfide (DMS) over the open ocean for two North Atlantic cruises. After normalization for Schmidt number, the two gases give essentially identical gas transfer coefficients and wind speed dependences for the wind speed range 2–10 ms−1. The data indicate a linear relationship between the gas transfer coefficient and mean wind speed, with measured gas transfer coefficients slightly above the Wanninkhof (1992) parameterization, particularly at low wind speeds.
                Cover page: Air-sea gas exchange of CO <sub>2</sub> and DMS in the North Atlantic by eddy covarianceCreative Commons 'BY' version 4.0 license
                • Article
                • Peer Reviewed
                UC Berkeley Previously Published Works (2016)
                We report a synthetic glycosylation reaction between sucrosyl acceptors and glycosyl fluoride donors to yield the derived trisaccharides. This reaction proceeds at room temperature in an aqueous solvent mixture. Calcium salts and a tertiary amine base promote the reaction with high site-selectivity for either the 3'-position or 1'-position of the fructofuranoside unit. Because nonenzymatic aqueous oligosaccharide syntheses are underdeveloped, mechanistic studies were carried out in order to identify the origin of the selectivity, which we hypothesized was related to the structure of the hydroxyl group array in sucrose. The solution conformation of various monodeoxysucrose analogs revealed the co-operative nature of the hydroxyl groups in mediating both this aqueous glycosyl bond-forming reaction and the site-selectivity at the same time.
                  Cover page: Aqueous Glycosylation of Unprotected Sucrose Employing Glycosyl Fluorides in the Presence of Calcium Ion and Trimethylamine
                  • Article
                  • Peer Reviewed
                  UC Berkeley Previously Published Works (2019)
                  The site-selective acylation of a steroidal natural product 19-hydroxydehydroepiandrosterone catalyzed by 1,1'-Bi(2-napthol)-derived (BINOL) chiral phosphoric acids (CPA's) is described. Systematic variation and multivariate linear regression analysis reveal that the same steric parameters typically needed for high enantioselectivity with this class of CPAs are also required for site-selectivity in this case. Density functional theory calculations identify additional weak CH-π interactions as contributors to site discrimination. We further report a rare example of site-selective acylation of phenols through the evaluation of naringenin, a flavonoid natural product, using CPA catalysis. These results suggest that BINOL-derived CPA's may have broader applications in site-selective catalysis.
                    Cover page: Site-Selective Acylation of Natural Products with BINOL-Derived Phosphoric Acids
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