The AEPEX CubeSat Mission: Quantifying Energetic Particle Precipitation through Bremsstrahlung X-Ray Imaging

Fundamental gaps exist in the understanding and observation of energetic particle precipitation (EPP),a solar-terrestrial coupling mechanism that is vital for climatelogical modeling of the atmosphere and magnetosphere. The Atmospheric Effects of Precipitation through Energetic X-rays (AEPEX) mission is a 6U CubeSat that will measure energetic electron spectra and X-ray images in order to quantify the spatial scales and amount of energy input into the atmosphere, and therefore lost from the magnetosphere, via EPP. AEPEX includes two instruments; AEPEX’s FIRE (Focused Investigations of Relativistic Electron) instrument (AFIRE), a TRL 9 electron detector previously flown on the FIREBIRD mission; and the Atmospheric X-ray Imaging Spectrometer (AXIS), an instrument being developed at CU Boulder that will take novel images and spectra of 50–300 keV X-ray photons. This work describes the AEPEX mission overview, the detailed design and operation of AXIS, and initial test and calibration results

Pepper Mild Mottle Virus, a Plant Virus Associated with Specific Immune Responses, Fever, Abdominal Pains, and Pruritus in Humans

Background: Recently, metagenomic studies have identified viable Pepper mild mottle virus (PMMoV), a plant virus, in the stool of healthy subjects. However, its source and role as pathogen have not been determined. Methods and Findings: 21 commercialized food products containing peppers, 357 stool samples from 304 adults and 208 stool samples from 137 children were tested for PMMoV using real-time PCR, sequencing, and electron microscopy. Anti-PMMoV IgM antibody testing was concurrently performed. A case-control study tested the association of biological and clinical symptoms with the presence of PMMoV in the stool. Twelve (57%) food products were positive for PMMoV RNA sequencing. Stool samples from twenty-two (7.2%) adults and one child (0.7%) were positive for PMMoV by real-time PCR. Positive cases were significantly more likely to have been sampled in Dermatology Units (p<10−6), to be seropositive for anti-PMMoV IgM antibodies (p = 0.026) and to be patients who exhibited fever, abdominal pains, and pruritus (p = 0.045, 0.038 and 0.046, respectively). Conclusions: Our study identified a local source of PMMoV and linked the presence of PMMoV RNA in stool with a specific immune response and clinical symptoms. Although clinical symptoms may be imputable to another cofactor, including spicy food, our data suggest the possibility of a direct or indirect pathogenic role of plant viruses in humans

Toll-like Receptor 7-Dependent Loss of B Cell Tolerance in Pathogenic Autoantibody Knockin Mice

SummarySystemic lupus erythematosus (SLE) is characterized by the production of autoantibodies that are frequently directed against nucleic acid-associated antigens. To better understand how B cells reactive with such antigens are regulated, we generated a model system in which heavy and light chain genes encoding 564 immunoglobulin have been targeted to the heavy and light chain loci of the nonautoimmune C57BL/6 mouse strain. This antibody recognizes RNA, single-stranded DNA, and nucleosomes. We show that B cells expressing this immunoglobulin were activated, producing class-switched autoantibody in vivo despite the apparently normal induction of anergy. This autoantibody production was largely dependent on Toll-like receptor 7 (TLR7). We further show that production of these autoantibodies was sufficient to cause kidney pathology in these mice. These results demonstrate that the particular threat of nucleic acid-containing autoantigens lies in their ability to bind both antigen receptor and TLR7

The AEPEX Mission: Imaging Energetic Particle Precipitation Into Earth’s Upper Atmosphere

Radiation belt electron fluxes can be enhanced during geomagnetic storms by two orders of magnitude; subsequently, these fluxes decay back to nominal levels in a few days. Precipitation into the upper atmosphere is a primary loss mechanism for these electrons, particularly during the decay phase. Upon impacting the upper atmosphere, these electrons create new ionization, leading to a chemical response that increases NOx and HOx and destroys ozone. Quantifying both radiation belt loss and the impact on the atmosphere requires an accurate estimate of the flux, energy spectrum, and spatial and temporal scales of precipitation. The NASA-funded Atmospheric Effects of Precipitation through Energetic X-rays (AEPEX) Cube-Sat mission is designed to quantify these parameters of radiation belt precipitation by measuring the bremsstrahlung X-rays created during the precipitation process, using a new instrument called the Atmospheric X-ray Imaging Spectrometer (AXIS). Hard X-rays (50-300 keV) emitted by Earth’s atmosphere have previously been measured from high-altitude balloons and satellites, but have never been imaged from space. The AXIS instrument will image the X-ray fluxes produced by the atmosphere, providing measurements of spatial scales, along with the X-ray flux and spectrum, using off-the-shelf pixelated detector modules and coded aperture optics. A solid-state energetic particle detector, with heritage from the FIREBIRD Cube Sat mission, will measure the precipitating electron energy spectrum, which is used to constrain the inversion from X-ray fluxes to electron fluxes. The AEPEX spacecraft is a 6U CubeSat, currently being built by the University of Colorado Boulder. It includes a custom-designed structure and a custom spacecraft bus consisting of an electrical power system, command and data handling, flight software, and instrument interface electronics designed by the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder. The system also includes custom-designed doubly-deployable solar panels. The mission will be launched into ahigh-inclination orbit to ensure coverage of high latitudes; launch is scheduled for early 2024

Fractalkine Expression Induces Endothelial Progenitor Cell Lysis by Natural Killer Cells

BACKGROUND: Circulating CD34(+) cells, a population that includes endothelial progenitors, participate in the maintenance of endothelial integrity. Better understanding of the mechanisms that regulate their survival is crucial to improve their regenerative activity in cardiovascular and renal diseases. Chemokine-receptor cross talk is critical in regulating cell homeostasis. We hypothesized that cell surface expression of the chemokine fractalkine (FKN) could target progenitor cell injury by Natural Killer (NK) cells, thereby limiting their availability for vascular repair. METHODOLOGY/PRINCIPAL FINDINGS: We show that CD34(+)-derived Endothelial Colony Forming Cells (ECFC) can express FKN in response to TNF-α and IFN-γ inflammatory cytokines and that FKN expression by ECFC stimulates NK cell adhesion, NK cell-mediated ECFC lysis and microparticles release in vitro. The specific involvement of membrane FKN in these processes was demonstrated using FKN-transfected ECFC and anti-FKN blocking antibody. FKN expression was also evidenced on circulating CD34(+) progenitor cells and was detected at higher frequency in kidney transplant recipients, when compared to healthy controls. The proportion of CD34(+) cells expressing FKN was identified as an independent variable inversely correlated to CD34(+) progenitor cell count. We further showed that treatment of CD34(+) circulating cells isolated from adult blood donors with transplant serum or TNF-α/IFN-γ can induce FKN expression. CONCLUSIONS: Our data highlights a novel mechanism by which FKN expression on CD34(+) progenitor cells may target their NK cell mediated killing and participate to their immune depletion in transplant recipients. Considering the numerous diseased contexts shown to promote FKN expression, our data identify FKN as a hallmark of altered progenitor cell homeostasis with potential implications in better evaluation of vascular repair in patients

From Vampire to Apollo: William Blake's Ghosts of the Flea (c. 1819-20)

Varley’s Zodiacal Physiognomy and Blake’s Visionary Heads are the two mainstays of a project which involved séance-like meetings at Varley’s house. While the lights were still on, Varley’s guests would have listened to the stories about the flea. With The Ghost of a Flea in front of them, the recitals of the flea’s pompous speeches, combined with the fact that it was just a ghost who leered after human blood, Varley’s guests may have laughed very heartily, if not in front of him then behind his back. Each evening followed the same protocol. When the lights were off, Varley would call out a name and Blake would look around, suddenly exclaiming ‘There he is!’ and start drawing. The flea is the most striking of the Visionary Heads, though it is not the only head which exists in different versions. If appearance is elemental to any kind of judgement of one human being of another, then Blake deliberately confused Varley. By working up the sketch, he played on Varley’s expectations; he presented him with an extraordinary and very puzzling painting, The Ghost of a Flea. But why, if Blake could have chosen any monster, did he settle on the ghost of a flea

The AEPEX Mission: Imaging Energetic Particle Precipitation in the Atmosphere through its Bremsstrahlung X-ray Signatures

The Atmospheric Effects of Precipitation through Energetic X-rays (AEPEX) mission is a 6U CubeSat that will monitor energetic electron precipitation from the radiation belts into the upper atmosphere. The primary instrument will image energetic (50&ndash;300 keV) X-rays produced in the atmosphere by bremsstrahlung, providing a near-direct signature of electron precipitation. An energetic electron detector will measure the precipitating electron spectrum, while the X-ray observations will be used to determine the absolute flux. X-ray images will be produced with 10-s time resolution and 50&ndash;100 km spatial resolution. The 6U spacecraft uses flight heritage spacecraft bus subsystems, including the attitude determination and control, electrical power, and command &amp; data handling systems. AEPEX is designed to be operated from low-Earth orbit at ~500 km altitude with a high inclination in order to cover the outer radiation belt. AEPEX will be the first spacecraft mission to measure X-rays in the 50&ndash;300 keV energy range emitted by Earth&rsquo;s atmosphere in response to radiation belt precipitation, and the first to image that precipitation from above.</p

Border Insecurity: Reading Transnational Environments in Jim Lynch’s Border Songs

This article applies an eco-critical approach to contemporary American fiction about the Canada-US border, examining Jim Lynch’s portrayal of the British Columbia-Washington borderlands in his 2009 novel Border Songs. It argues that studying transnational environmental actors in border texts—in this case, marijuana, human migrants, and migratory birds—helps illuminate the contingency of political boundaries, problems of scale, and discourses of risk and security in cross-border regions after 9/11. Further, it suggests that widening the analysis of trans-border activity to include environmental phenomena productively troubles concepts of nature and regional belonging in an era of climate change and economic globalization. Cet article propose une lecture écocritique de la fiction étatsunienne contemporaine portant sur la frontière entre le Canada et les États-Unis, en étudiant le portrait donné par Jim Lynch de la région frontalière entre la Colombie-Britannique et Washington dans son roman Border Songs, paru en 2009. L’article soutient que l’étude, dans les textes sur la frontière, des acteurs environnementaux transnationaux – dans ce cas-ci, la marijuana, les migrants humains et les oiseaux migratoires – jette un jour nouveau sur la contingence des limites territoriales politiques, des problèmes d’échelle et des discours sur le risque et la sécurité des régions transfrontalières après les évènements du 11 septembre 2001. Il suggère également qu’en élargissant l’analyse de l’activité transfrontalière pour y inclure les phénomènes environnementaux, on brouille de façon productive les concepts de nature et d’appartenance régionale d’une époque marquée par les changements climatiques et la mondialisation de l’économie