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"Oman, Jason"
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Characterization of quantitative trait loci controlling genetic variation for preharvest sprouting in synthetic backcross-derived wheat lines
Aegilops lauschii, the wild relative of wheat, has stronger seed dormancy, a major component of preharvest sprouting resistance (PHSR), than bread wheat. A diploid Ae. lanschii accession (AUS18836) and a tetraploid (Triticum lurgidum L. ssp. durum, var. Altar84) wheat were used to construct a synthetic wheat (Syn37). The genetic architecture of PHS was investigated in 277 BC1F7 synthetic backcross lines (SBLs) derived from Syn37/2*Janz (resistant/susceptible). The SBLs were evaluated in three environments over 2 years and PHS was assessed by way of three measures: the germination index (GI), which measures grain dormancy, the whole spike assay (SI), which takes into account all spike morphology, and counted visually sprouted seeds ant: of 200 (VI). Grain color was measured using both Chroma Meter- and NaOH-based approaches. QTL for PHSR and grain color were mapped and their additive and epistatic effects as well as their interactions with environment were estimated by a mixed linear-model approach. Single-locus analysis following composite interval mapping revealed four QTL for GI, two QTL for SI, and four QTL for VI on chromosomes 3DL and 4AL. The locus QPhs.dpiv-3D.1 on chromosome 3DL was tightly linked to the red grain color (RGC) at a distance of 5 cM. The other locus on chromosome 3D, QPhs.dpiv-3D.2 was independent: of RGC lochs. Two-locus analysis detected nine QTL with main effects and 18 additive X additive interactions for GI, SI, and VI. Two of the nine main effects QTL and two epistatic QTL showed significant interactions with environments. Both additive and epistatic effects contributed to phenotypic variance in PHSR and the identified markers are potential candidates for marker-assisted selection of favorable alleles at multiple loci. SBLs derived front Ae. lauschii proved to be a promising tool to dissect, introgress, and pyramid different PHSR genes into adapted wheat genetic backgrounds. The enhanced expression of PI IS resistance in SBLs enabled us to develop white PHS-resistant wheat germplasm Prom the red-grained Ae. lauschii accession.
Journal Article
Adsorption and photochemistry of 1,3-butadiene on HOPG(0001)
The adsorption and photochemistry of 1,3-butadiene (C 4H6) on HOPG(0001) at <85 K was studied using temperature-programmed desorption (TPD) and electron energy loss spectroscopy (EELS). Butadiene weakly adsorbs on HOPG, the monolayer (ML) exhibiting first order desorption with a maximum desorption rate at 129 K and a corresponding desorption energy of 32 kJ/mol. Multilayer butadiene showed zero order desorption with a maximum desorption rate at 105 K and a desorption energy of 28.5 kJ/mol. Irradiation of the C4H6/HOPG(0001) surface (1 and 3 monolayers of C4H6) with UV photons (193 nm, 248 nm, and 351 nm) at 100 mJ/pulse resulted in molecular photodesorption of the adsorbed butadiene layers. The cross section for photodesorption was calculated at each wavelength for both coverages. For 1 monolayer coverage, the cross-sections were 3.3 × 10−20 cm2, 2.4 × 10 −20 cm2, and 1.2 × 10−20 cm2 for 193 nm, 248 nm, and 351 nm, respectively. The 3 monolayer cross-sections were 1.1 × 10−17 cm2, 6.3 × 10−18 cm2, and 1.8 × 10−18 cm2 for 193 nm, 248 nm, and 351 nm, respectively. It was found the photodesorption mechanism could be described by a simple thermal process. The photo-processes occurring in both 1 and 3 ML C4H6(ad)/HOPG were also investigated at lower photon fluences of ≤10 mJ/pulse. Under these conditions, there was no detectable photodesorption or condensed phase photochemistry.
Dissertation
Mapping hydroxyl variability throughout the global remote troposphere via synthesis of airborne and satellite formaldehyde observations
The hydroxyl radical (OH) fuels tropospheric ozone production and governs the lifetime of methane and many other gases. Existing methods to quantify global OH are limited to annual and global-to-hemispheric averages. Finer resolution is essential for isolating model deficiencies and building process-level understanding. In situ observations from the Atmospheric Tomography (ATom) mission demonstrate that remote tropospheric OH is tightly coupled to the production and loss of formaldehyde (HCHO), a major hydrocarbon oxidation product. Synthesis of this relationship with satellite-based HCHO retrievals and model-derived HCHO loss frequencies yields a map of total-column OH abundance throughout the remote troposphere (up to 70% of tropospheric mass) over the first two ATom missions (August 2016 and February 2017). This dataset offers unique insights on near-global oxidizing capacity. OH exhibits significant seasonality within individual hemispheres, but the domain mean concentration is nearly identical for both seasons (1.03 ± 0.25 × 106 cm−3), and the biseasonal average North/South Hemisphere ratio is 0.89 ± 0.06, consistent with a balance of OH sources and sinks across the remote troposphere. Regional phenomena are also highlighted, such as a 10-fold OH depression in the Tropical West Pacific and enhancements in the East Pacific and South Atlantic. This method is complementary to budget-based global OH constraints and can help elucidate the spatial and temporal variability of OH production and methane loss.
Journal Article
Opinion: Beyond global means – novel space-based approaches to indirectly constrain the concentrations of and trends and variations in the tropospheric hydroxyl radical (OH)
The hydroxyl radical (OH) plays a central role in tropospheric chemistry, as well as influencing the lifetimes of some greenhouse gases. Because of limitations in our ability to observe OH, we have historically relied on indirect methods to constrain its concentrations, trends, and variations but only as annual global or annual semi-hemispheric averages. Recent methods demonstrated the feasibility of indirectly constraining tropospheric OH on finer spatio-temporal scales using satellite observations as proxies for the photochemical drivers of OH (e.g., nitrogen dioxide, formaldehyde, isoprene, water vapor, ozone). We found that there are currently reasonable satellite proxies to constrain up to about 75 % of the global sources of tropospheric OH and up to about 50 % of the global sinks. With additional research and investment in observing various volatile organic compounds, there is potential to constrain an additional 10 % of the global sources and 30 % of the global sinks. We propose steps forward for the development of a comprehensive space-based observing strategy, which will improve our ability to indirectly constrain OH on much finer spatio-temporal scales than previously achieved. We discuss the strengths and limitations of such an observing strategy and potential improvements to current satellite instrument observing capabilities that would enable better constraint of OH. Suborbital observations (i.e., data collected from non-satellite platforms such as aircraft, balloons, and buildings) are required to collect information difficult to obtain from space and for validation of satellite-based OH estimates; therefore, they should be an integral part of a comprehensive observing strategy.
Journal Article
Visions of human futures in space and SETI
We discuss how visions for the futures of humanity in space and SETI are intertwined, and are shaped by prior work in the fields and by science fiction. This appears in the language used in the fields, and in the sometimes implicit assumptions made in discussions of them. We give examples from articulations of the so-called Fermi Paradox, discussions of the settlement of the Solar System (in the near future) and the Galaxy (in the far future), and METI. We argue that science fiction, especially the campy variety, is a significant contributor to the ‘giggle factor’ that hinders serious discussion and funding for SETI and Solar System settlement projects. We argue that humanity's long-term future in space will be shaped by our short-term visions for who goes there and how. Because of the way they entered the fields, we recommend avoiding the term ‘colony’ and its cognates when discussing the settlement of space, as well as other terms with similar pedigrees. We offer examples of science fiction and other writing that broaden and challenge our visions of human futures in space and SETI. In an appendix, we use an analogy with the well-funded and relatively uncontroversial searches for the dark matter particle to argue that SETI's lack of funding in the national science portfolio is primarily a problem of perception, not inherent merit.
Journal Article
THE SUPREME COURT'S THEORY OF PRIVATE LAW
In this Article, we revisit the clash between private law and the First Amendment in the Supreme Court's recent case, Snyder v. Phelps, using a private-law lens. We are scholars who write about private law as individual justice, a perspective that has been lost in recent years but is currently enjoying something of a revival. Our argument is that the Supreme Court's theory of private law has led it down a path that has distorted its doctrine in several areas, including the First Amendment—tort clash in Snyder. In areas that range from punitive damages to preemption, the Supreme Court has adopted a particular and dominant, but highly contested, theory of private law. It is the theory that private law is not private at all; it is part and parcel of government regulation, or \"public law in disguise.\" Part I is a brief overview of how that jurisprudential view came to be, as well as a sketch of a competing view of private law as individual justice. In Part II, we briefly trace the development of the doctrine surrounding the tension between the First Amendment and private law, particularly tort law, and how it helps lead to the view of private law as government regulation displayed in Snyder. We also point out how the intentional infliction of emotional distress tort, the main claim at issue in Snyder, is a particularly poor vehicle for the Court's theory of private law. A relatively recent tort, it was developed by scholars and judges as a means of redress for plaintiffs who had been wronged, but were left without a remedy. Part III presents the central claims of the Article. We argue that the conception of private law as government regulation in Snyder arises from a combination of (1) the doctrinal tools that judges use in First Amendment cases, (2) the unitary nature of the state-action doctrine, and (3) the influence of instrumentalism, specifically in obscuring the plaintiff's agency and the state interest in redress, and in privileging a particular view of compensation. In Part IV, we present some normative or prescriptive implications of our analysis, and then conclude.
Journal Article
Effects of urban-induced mutations on ecology, evolution and health
Increasing evidence suggests that urbanization is associated with higher mutation rates, which can affect the health and evolution of organisms that inhabit cities. Elevated pollution levels in urban areas can induce DNA damage, leading to de novo mutations. Studies on mutations induced by urban pollution are most prevalent in humans and microorganisms, whereas studies of non-human eukaryotes are rare, even though increased mutation rates have the potential to affect organisms and their populations in contemporary time. Our Perspective explores how higher mutation rates in urban environments could impact the fitness, ecology and evolution of populations. Most mutations will be neutral or deleterious, and higher mutation rates associated with elevated pollution in urban populations can increase the risk of cancer in humans and potentially other species. We highlight the potential for urban-driven increased deleterious mutational loads in some organisms, which could lead to a decline in population growth of a wide diversity of organisms. Although beneficial mutations are expected to be rare, we argue that higher mutation rates in urban areas could influence adaptive evolution, especially in organisms with short generation times. Finally, we explore avenues for future research to better understand the effects of urban-induced mutations on the fitness, ecology and evolution of city-dwelling organisms.
Pollution in urban areas causes higher rates of mutation than in unpolluted areas. This Perspective discusses the effects of these mutations on the health, evolutionary fitness and ecology of urban organisms.
Journal Article
Visions of Human Futures in Space and SETI
We discuss how visions for the futures of humanity in space and SETI are intertwined, and are shaped by prior work in the fields and by science fiction. This appears in the language used in the fields, and in the sometimes implicit assumptions made in discussions of them. We give examples from articulations of the so-called Fermi Paradox, discussions of the settlement of the Solar System (in the near future) and the Galaxy (in the far future), and METI. We argue that science fiction, especially the campy variety, is a significant contributor to the \"giggle factor\" that hinders serious discussion and funding for SETI and Solar System settlement projects. We argue that humanity's long-term future in space will be shaped by our short-term visions for who goes there and how. Because of the way they entered the fields, we recommend avoiding the term \"colony\" and its cognates when discussing the settlement of space, as well as other terms with similar pedigrees. We offer examples of science fiction and other writing that broaden and challenge our visions of human futures in space and SETI. In an appendix, we use an analogy with the well-funded and relatively uncontroversial searches for the dark matter particle to argue that SETI's lack of funding in the national science portfolio is primarily a problem of perception, not inherent merit.
Paper