A Quantitative Comparison between 1D and 3D Source Inversion Methodologies: Application to the Middle East

We present a quantitative comparison between seismic moment tensor (MT) inversion solutions using 1D and 3D synthetic seismograms at two frequency bands for events in the Middle East, to assess the effects of 3D models on source studies. Complex geology associated with the active continental convergent margin leads to a scarcity of reliable, available data, necessitating a thorough examination of solution stability and robustness to assure an accurate description of sources with well‐characterized source parameters. Solutions were calculated for 195 events (Mw \u3e 5.5) using a full‐waveform MT inversion matching both phase and amplitude. Seismic data processed at two frequency bands compares short‐ and long‐period performance for 1D and 3D synthetic seismograms. An improvement in fit between data and synthetics is seen using 3D over 1D synthetic seismograms, especially for complex body‐wave propagation and surface‐wave dispersion. At short periods, 3D synthetics provide a more robust solution compared with 1D, showing a reduction in error of the source mechanism. The percentage of double‐couple components increases with the addition of 3D structure and suggests the percentage of non‐double‐couple components is a result of poorly constrained Earth structure. Event solutions contained in the catalog (Ⓔ Table S1 in the electronic supplement to this paper) have an average cross‐correlation value of 0.87, with good amplitude ratios, and are improved (i.e., increased variance reduction) yet consistent with longer period solutions from the Global Centroid Moment Tensor (CMT) catalog

Apparent Role for \u3cem\u3eBorrelia burgdorferi\u3c/em\u3e LuxS During Mammalian Infection

The Lyme disease spirochete, Borrelia burgdorferi, controls protein expression patterns during its tick-mammal infection cycle. Earlier studies demonstrated that B. burgdorferi synthesizes 4,5-dihydroxy-2,3-pentanedione (autoinducer-2 [AI-2]) and responds to AI-2 by measurably changing production of several infection-associated proteins. luxS mutants, which are unable to produce AI-2, exhibit altered production of several proteins. B. burgdorferi cannot utilize the other product of LuxS, homocysteine, indicating that phenotypes of luxS mutants are not due to the absence of that molecule. Although a previous study found that a luxS mutant was capable of infecting mice, a critical caveat to those results is that bacterial loads were not quantified. To more precisely determine whether LuxS serves a role in mammalian infection, mice were simultaneously inoculated with congenic wild-type and luxS strains, and bacterial numbers were assessed using quantitative PCR. The wild-type bacteria substantially outcompeted the mutants, suggesting that LuxS performs a significant function during mammalian infection. These data also provide further evidence that nonquantitative infection studies do not necessarily provide conclusive results and that regulatory factors may not make all-or-none, black-or-white contributions to infectivity

RNA-Seq of \u3cem\u3eBorrelia burgdorferi\u3c/em\u3e in Multiple Phases of Growth Reveals Insights into the Dynamics of Gene Expression, Transcriptome Architecture, and Noncoding RNAs

Borrelia burgdorferi, the agent of Lyme disease, differentially expresses numerous genes and proteins as it cycles between mammalian hosts and tick vectors. Insights on regulatory mechanisms have been provided by earlier studies that examined B. burgdorferi gene expression patterns during cultivation. However, prior studies examined bacteria at only a single time point of cultivation, providing only a snapshot of what is likely a dynamic transcriptional program driving B. burgdorferi adaptations to changes during culture growth phases. To address that concern, we performed RNA sequencing (RNA-Seq) analysis of B. burgdorferi cultures at early-exponential, mid-exponential, and early-stationary phases of growth. We found that expression of nearly 18% of annotated B. burgdorferi genes changed significantly during culture maturation. Moreover, genome-wide mapping of the B. burgdorferi transcriptome in different growth phases enabled insight on transcript boundaries, operon structures, and identified numerous putative non-coding RNAs. These RNA-Seq data are discussed and presented as a resource for the community of researchers seeking to better understand B. burgdorferi biology and pathogenesis

X-ray Evaluation of the Marshall Grazing Incidence X-Ray Spectrometer (MaGIXS) Nickel-Replicated Mirrors

X-ray observations of astronomical objects provides diagnostics not available in any other wavelength regime, however the capability of making these observation at a high spatial resolution has proven challenging. Recently, NASA Marshall Space Flight Center (MSFC) has made good progress in employing computer numerical control (CNC) polishing techniques on electroless nickel mandrels as part of our replicated grazing incidence optics program. CNC polishing has afforded the ability to deterministically refine mandrel figure, thereby improving mirror performance. The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a MSFC-led sounding rocket instrument that is designed to make the first ever soft x-ray spectral observations of the Sun spatially resolved along a narrow slit. MaGIXS incorporates some of the first mirrors produced at MSFC using this polishing technique. Here we present the predicted mirror performance obtained from metrology, after completion of CNC polishing, as well as the results of X-ray tests performed on the MaGIXS telescope mirror before and after mounting

Fossil slabs attached to unsubducted fragments of the Farallon plate

As the Pacific–Farallon spreading center approached North America, the Farallon plate fragmented into a number of small plates. Some of the microplate fragments ceased subducting before the spreading center reached the trench. Most tectonic models have assumed that the subducting oceanic slab detached from these microplates close to the trench, but recent seismic tomography studies have revealed a high-velocity anomaly beneath Baja California that appears to be a fossil slab still attached to the Guadalupe and Magdalena microplates. Here, using surface wave tomography, we establish the lateral extent of this fossil slab and show that it is correlated with the distribution of high-Mg andesites thought to derive from partial melting of the subducted oceanic crust. We also reinterpret the high seismic velocity anomaly beneath the southern central valley of California as another fossil slab extending to a depth of 200 km or more that is attached to the former Monterey microplate. The existence of these fossil slabs may force a reexamination of models of the tectonic evolution of western North America over the last 30 My

Toward Realistic Nonstationarity of Semidiurnal Baroclinic Tides in a Hydrodynamic Model

Semidiurnal baroclinic tide sea surface height (SSH) variance and semidiurnal nonstationary variance fraction (SNVF) are compared between a hydrodynamic model and altimetry for the low‐ to middle‐latitude global ocean. Tidal frequencies are aliased by ∼10‐day altimeter sampling, which makes it impossible to unambiguously identify nonstationary tidal signals from the observations. In order to better understand altimeter sampling artifacts, the model was analyzed using its native hourly outputs and by subsampling it in the same manner as altimeters. Different estimates of the semidiurnal nonstationary and total SSH variance are obtained with the model depending on whether they are identified in the frequency domain or wave number domain and depending on the temporal sampling of the model output. Five sources of ambiguity in the interpretation of the altimetry are identified and briefly discussed. When the model and altimetry are analyzed in the same manner, they display qualitatively similar spatial patterns of semidiurnal baroclinic tides. The SNVF typically correlates above 80% at all latitudes between the different analysis methods and above 60% between the model and altimetry. The choice of analysis methodology was found to have a profound effect on estimates of the semidiurnal baroclinic SSH variance with the wave number domain methodology underestimating the semidiurnal nonstationary and total SSH variances by 68% and 66%, respectively. These results produce a SNVF estimate from altimetry that is biased low by a factor of 0.92. This bias is primarily a consequence of the ambiguity in the separation of tidal and mesoscale signals in the wave number domain.Key PointsHydrodynamic models incorporating mesoscale dynamics and tides are beginning to resolve stationary and nonstationary baroclinic tidesThe ratio of nonstationary to total semidiurnal variance computed from altimetry and HyCOM simulations agrees at low and middle latitudesComparisons of analysis methodologies show that total and nonstationary semidiurnal variances are underestimated in altimetry on averagePeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152034/1/jgrc23624_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152034/2/jgrc23624.pd

Mutualist-Provisioned Resources Impact Vector Competency

ABSTRACT Many symbionts supplement their host’s diet with essential nutrients. However, whether these nutrients also enhance parasitism is unknown. In this study, we investigated whether folate (vitamin B9) production by the tsetse fly (Glossina spp.) essential mutualist, Wigglesworthia, aids auxotrophic African trypanosomes in completing their life cycle within this obligate vector. We show that the expression of Wigglesworthia folate biosynthesis genes changes with the progression of trypanosome infection within tsetse. The disruption of Wigglesworthia folate production caused a reduction in the percentage of flies that housed midgut (MG) trypanosome infections. However, decreased folate did not prevent MG trypanosomes from migrating to and establishing an infection in the fly’s salivary glands, thus suggesting that nutrient requirements vary throughout the trypanosome life cycle. We further substantiated that trypanosomes rely on symbiont-generated folate by feeding this vitamin to Glossina brevipalpis, which exhibits low trypanosome vector competency and houses Wigglesworthia incapable of producing folate. Folate-supplemented G. brevipalpis flies were significantly more susceptible to trypanosome infection, further demonstrating that this vitamin facilitates parasite infection establishment. Our cumulative results provide evidence that Wigglesworthia provides a key metabolite (folate) that is “hijacked” by trypanosomes to enhance their infectivity, thus indirectly impacting tsetse species vector competency. Parasite dependence on symbiontderived micronutrients, which likely also occurs in other arthropod vectors, represents a relationship that may be exploited to reduce disease transmission. IMPORTANCE Parasites elicit several physiological changes in their host to enhance transmission. Little is known about the functional association between parasitism and microbiota-provisioned resources typically dedicated to animal hosts and how these goods may be rerouted to optimize parasite development. This study is the first to identify a specific symbiont-generated metabolite that impacts insect vector competence by facilitating parasite establishment and, thus, eventual transmission. Specifically, we demonstrate that the tsetse fly obligate mutualist Wigglesworthia provisions folate (vitamin B9) that pathogenic African trypanosomes exploit in an effort to successfully establish an infection in the vector’s MG. This process is essential for the parasite to complete its life cycle and be transmitted to a new vertebrate host. Disrupting metabolic contributions provided by the microbiota of arthropod disease vectors may fuel future innovative control strategies while also offering minimal nontarget effects

Baryon Decuplet to Octet Electromagnetic Transitions in Quenched and Partially Quenched Chiral Perturbation Theory

We calculate baryon decuplet to octet electromagnetic transition form factors in quenched and partially quenched chiral perturbation theory. We work in the isospin limit of SU(3) flavor, up to next-to-leading order in the chiral expansion, and to leading order in the heavy baryon expansion. Our results are necessary for proper extrapolation of lattice calculations of these transitions. We also derive expressions for the case of SU(2) flavor away from the isospin limit.Comment: 16 pages, 3 figures, revtex

Spectral decomposition of internal gravity wave sea surface height in global models

Two global ocean models ranging in horizontal resolution from 1/12° to 1/48° are used to study the space and time scales of sea surface height (SSH) signals associated with internal gravity waves (IGWs). Frequency‐horizontal wavenumber SSH spectral densities are computed over seven regions of the world ocean from two simulations of the HYbrid Coordinate Ocean Model (HYCOM) and three simulations of the Massachusetts Institute of Technology general circulation model (MITgcm). High wavenumber, high‐frequency SSH variance follows the predicted IGW linear dispersion curves. The realism of high‐frequency motions (>0.87  cpd) in the models is tested through comparison of the frequency spectral density of dynamic height variance computed from the highest‐resolution runs of each model (1/25° HYCOM and 1/48° MITgcm) with dynamic height variance frequency spectral density computed from nine in situ profiling instruments. These high‐frequency motions are of particular interest because of their contributions to the small‐scale SSH variability that will be observed on a global scale in the upcoming Surface Water and Ocean Topography (SWOT) satellite altimetry mission. The variance at supertidal frequencies can be comparable to the tidal and low‐frequency variance for high wavenumbers (length scales smaller than ∼50 km), especially in the higher‐resolution simulations. In the highest‐resolution simulations, the high‐frequency variance can be greater than the low‐frequency variance at these scales.Key PointsTwo high‐resolution ocean models compare well against data in frequency spectral density of dynamic heightSea surface height frequency‐horizontal wavenumber spectral densities show high variance along internal gravity wave dispersion curvesTwo high‐resolution ocean models give different estimates of variance in high‐frequency, high wavenumber phenomenaPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/139946/1/jgrc22465-sup-0002-2017JC013009-fs01.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139946/2/jgrc22465-sup-0003-2017JC013009-fs02.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139946/3/jgrc22465_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139946/4/jgrc22465.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139946/5/jgrc22465-sup-0007-2017JC013009-fs06.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139946/6/jgrc22465-sup-0009-2017JC013009-fs08.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139946/7/jgrc22465-sup-0004-2017JC013009-fs03.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139946/8/jgrc22465-sup-0005-2017JC013009-fs04.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139946/9/jgrc22465-sup-0006-2017JC013009-fs05.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139946/10/jgrc22465-sup-0001-2017JC013009-s01.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139946/11/jgrc22465-sup-0008-2017JC013009-fs07.pd