306 research outputs found
Real Time Optical Receiver Project
The goals for the Real Time Optical Receiver project are to Infuse Consultative Committee for Space Data Systems High Photon Efficiency standard into missions, such as Artemis and to provide a real time ground receiver solution (fiber device, detector, real time FPGA-based receiver) that is: (1) Scalable: data rate, atmosphere conditions, telescope aperture, etc., and (2) Uses COTS components when available and work with companies to move custom parts to COTS
A New Model For Including Galactic Winds in Simulations of Galaxy Formation II: Implementation of PhEW in Cosmological Simulations
Although galactic winds play a critical role in regulating galaxy formation,
hydrodynamic cosmological simulations do not resolve the scales that govern the
interaction between winds and the ambient circumgalactic medium (CGM). We
implement the Physically Evolved Wind (PhEW) model of Huang et al. (2020) in
the GIZMO hydrodynamics code and perform test cosmological simulations with
different choices of model parameters and numerical resolution. PhEW adopts an
explicit subgrid model that treats each wind particle as a collection of clouds
that exchange mass, metals, and momentum with their surroundings and evaporate
by conduction and hydrodynamic instabilities as calibrated on much higher
resolution cloud scale simulations. In contrast to a conventional wind
algorithm, we find that PhEW results are robust to numerical resolution and
implementation details because the small scale interactions are defined by the
model itself. Compared to conventional wind simulations with the same
resolution, our PhEW simulations produce similar galaxy stellar mass functions
at but are in better agreement with low-redshift observations at because PhEW particles shed mass to the CGM before escaping
low mass halos. PhEW radically alters the CGM metal distribution because PhEW
particles disperse metals to the ambient medium as their clouds dissipate,
producing a CGM metallicity distribution that is skewed but unimodal and is
similar between cold and hot gas. While the temperature distributions and
radial profiles of gaseous halos are similar in simulations with PhEW and
conventional winds, these changes in metal distribution will affect their
predicted UV/X-ray properties in absorption and emission.Comment: 23 pages, 17 figures, MNRAS accepte
Few-Mode Fiber Coupled Superconducting Nanowire Single-Photon Detectors for Photon Efficient Optical Communications
The NASA Glenn Research Center's development of a high-photon efficiency real-time optical communications ground receiver has added superconducting nanowire single-photon detectors (SNSPDs) coupled with few-mode fibers (FMF). High data rate space-to-ground optical communication links require enhanced ground receiver sensitivity to reduce spacecraft transmitter constraints, and therefore require highly efficient coupling from fiber to detector. In the presence of atmospheric turbulence the received optical wave front can be severely distorted introducing higher-order spatial mode components to the received signal. To reduce mode filtering and mismatch loss and the resulting degradations to detector coupling efficiency, we explore the use of few-mode fiber coupling to commercial single-pixel SNSPDs. Graded index 20-m few-mode fibers allow the commercial single pixel SNSPD's active area to couple with equal efficiency as single mode fibers. Here we determine detector characteristics such as count rate, detection efficiency, dark counts, and jitter, as well as detection efficiencies for higher-order fiber spatial modes. Additionally, we assess the laboratory performance of the detectors in an optical system which emulates future deep space optical communications links
Bell Inequality Experiment for a High Brightness Time-Energy Entangled Source
A periodically poled MgO doped LiNbO3 (MgO:LN) non-degenerate photon pair source is utilized for spontaneous parametric down-conversion of 532 nm photons into time-energy entangled pairs of 800 and 1600 nm photons. The entangled photons are separated using previously detailed sorting optics, such that each wavelength is independently directed through one of two modified Mach-Zehnder interferometers also known as a Franson interferometer after which they are fiber-optically guided to high-efficiency photon detectors. Output from the detectors is sent to a high resolution time tagger, where coincidences between the entangled photons are recorded. By varying the length of the long path in one Mach-Zehnder interferometer, it is possible to observe high visibility sinusoidal fringes in the measured coincidence rates (while no variation is seen in single photon detection rates). These fringes due to interference between the photon probability amplitudes are indicative of a violation of the Bell inequality, and confirm inconsistencies with local hidden variable theory for the correlations of the time-energy entangled photon pairs
Bell Inequality Experiment for a High Brightness Time-Energy Entangled Source
A periodically poled MgO - doped LiNbO3 (MgO:LN) non-degenerate photon pair source is utilized for spontaneous parametric down-conversion of 532-nanometer photons into time-energy entangled pairs of 800- and 1600-nanometer photons. The entangled photons are separated using previously detailed sorting optics, such that each wavelength is independently directed through one of two modified Mach-Zehnder interferometers - also known as a Franson interferometer - after which they are fiber-optically guided to high-efficiency photon detectors. Output from the detectors is sent to a high resolution time tagger, where coincidences between the entangled photons are recorded. By varying the length of the long path in one Mach-Zehnder interferometer, it is possible to observe high visibility sinusoidal fringes in the measured coincidence rates (while no variation is seen in single photon detection rates). These fringes - due to interference between the photon probability amplitudes - are indicative of a violation of the Bell inequality, and confirm inconsistencies with local hidden variable theory for the correlations of the time-energy entangled photon pairs
A Pharmacogenetic Approach to Identify Mutant Forms of α-Galactosidase A that Respond to a Pharmacological Chaperone for Fabry Disease
Fabry disease is caused by mutations in the gene (GLA) that encodes α-galactosidase A (α-Gal A). The iminosugar AT1001 (GR181413A, migalastat hydrochloride, 1-deoxygalactonojirimycin) is a pharmacological chaperone that selectively binds and stabilizes α-Gal A, increasing total cellular levels and activity for some mutant forms (defined as “responsive”). In this study, we developed a cell-based assay in cultured HEK-293 cells to identify mutant forms of α-Gal A that are responsive to AT1001. Concentration-dependent increases in α-Gal A activity in response to AT1001 were shown for 49 (60%) of 81 mutant forms. The responses of α-Gal A mutant forms were generally consistent with the responses observed in male Fabry patient-derived lymphoblasts. Importantly, the HEK-293 cell responses of 19 α-Gal A mutant forms to a clinically achievable concentration of AT1001 (10 µM) were generally consistent with observed increases in α-Gal A activity in peripheral blood mononuclear cells from male Fabry patients orally administered AT1001 during Phase 2 clinical studies. This indicates that the cell-based responses can identify mutant forms of α-Gal A that are likely to respond to AT1001 in vivo. Thus, the HEK-293 cell-based assay may be a useful aid in the identification of Fabry patients with AT1001-responsive mutant forms. Hum Mutat 32:1–13, 2011. © 2011 Wiley-Liss, Inc
Using decision analysis to support proactive management of emerging infectious wildlife diseases
Despite calls for improved responses to emerging infectious diseases in wildlife, management is seldom considered until a disease has been detected in affected populations. Reactive approaches may limit the potential for control and increase total response costs. An alternative, proactive management framework can identify immediate actions that reduce future impacts even before a disease is detected, and plan subsequent actions that are conditional on disease emergence. We identify four main obstacles to developing proactive management strategies for the newly discovered salamander pathogen Batrachochytrium salamandrivorans (Bsal). Given that uncertainty is a hallmark of wildlife disease management and that associated decisions are often complicated by multiple competing objectives, we advocate using decision analysis to create and evaluate trade-offs between proactive (pre-emergence) and reactive (post-emergence) management options. Policy makers and natural resource agency personnel can apply principles from decision analysis to improve strategies for countering emerging infectious diseases
Growing up with cancer: Accommodating the effects of cancer into young people’s social lives.
Adolescence and young adulthood are transitional periods of rapid and dramatic personal change. Few events can cause as unpredictable and challenging alterations to this process as the onset of a serious illness, such as cancer. Although we know much about the physical and psychological consequences of having cancer at this time, we know little about the effect of cancer on young people’s relationships. We conducted interviews with 15 women and 12 men aged between 16 and 29 years, who had survived cancer. Our findings demonstrate that the experience of cancer and how it affects relationships is complex. It arrests young people’s development by increasing their dependence on parents, giving them life experiences unavailable to peers, and complicating the process of establishing new relationships. However, it also accelerates development by facilitating closer and more mature relationships with parents and giving young people wisdom and insight not shared by peers. Cancer profoundly shapes how young people conduct their relationships. These changes require ongoing accommodation by young people with cancer, their parents, peers, and new acquaintances
The future of zoonotic risk prediction
In the light of the urgency raised by the COVID-19 pandemic, global investment in wildlife virology is likely to increase, and new surveillance programmes will identify hundreds of novel viruses that might someday pose a threat to humans. To support the extensive task of laboratory characterization, scientists may increasingly rely on data-driven rubrics or machine learning models that learn from known zoonoses to identify which animal pathogens could someday pose a threat to global health. We synthesize the findings of an interdisciplinary workshop on zoonotic risk technologies to answer the following questions. What are the prerequisites, in terms of open data, equity and interdisciplinary collaboration, to the development and application of those tools? What effect could the technology have on global health? Who would control that technology, who would have access to it and who would benefit from it? Would it improve pandemic prevention? Could it create new challenges? This article is part of the theme issue 'Infectious disease macroecology: parasite diversity and dynamics across the globe'.Peer reviewe
Using decision analysis to support proactive management of emerging infectious wildlife diseases
Despite calls for improved responses to emerging infectious diseases in wildlife, management is seldom considered until a disease has been detected in affected populations. Reactive approaches may limit the potential for control and increase total response costs. An alternative, proactive management framework can identify immediate actions that reduce future impacts even before a disease is detected, and plan subsequent actions that are conditional on disease emergence. We identify four main obstacles to developing proactive management strategies for the newly discovered salamander pathogen Batrachochytrium salamandrivorans (Bsal). Given that uncertainty is a hallmark of wildlife disease management and that associated decisions are often complicated by multiple competing objectives, we advocate using decision analysis to create and evaluate trade-offs between proactive (pre-emergence) and reactive (post-emergence) management options. Policy makers and natural resource agency personnel can apply principles from decision analysis to improve strategies for countering emerging infectious diseases
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