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Novel device to collect deep-sea porewater in situ: A focus on benthic carbonate chemistry
No full textWe have designed, built, tested, and deployed a novel device to extract porewater from deep-sea sediments in situ, constructed to work with a standard multicorer. Despite the importance of porewater measurements for numerous applications, many sampling artifacts can bias data and interpretation during traditional porewater processing from shipboard-processed cores. A well-documented artifact occurs in deep-sea porewater when carbonate precipitates during core recovery as a function of temperature and pressure changes, while porewater is in contact with sediment grains before filtration, thereby lowering porewater alkalinity and dissolved inorganic carbon (DIC). Here, we present a novel device built to obviate these sampling artifacts by filtering porewater in situ on the seafloor, with a focus near the sediment–water interface on cm-scale resolution, to obtain accurate porewater profiles. We document 1–10% alkalinity loss in shipboard-processed sediment cores compared to porewater filtered in situ, at depths of 1600–3200 m. We also show that alkalinity loss is a function of both weight % sedimentary CaCO₃ and water column depth. The average ratio of alkalinity loss to DIC loss in shipboard-processed sediment cores relative to in situ porewater is 2.2, consistent with the signal expected from carbonate precipitation. In addition to collecting porewater for defining natural profiles, we also conducted the first in situ dissolution experiments within the sediment column using isotopically labeled calcite. We present evidence of successful deployments of this device on and adjacent to the Cocos Ridge in the Eastern Equatorial Pacific across a range of depths and calcite saturation states
Response to Commentary on development of the "molecular microscope (MMDx) assay for heart transplant rejection surveillance: SCVP journal club"
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Deep Orbital Search for Additional Planets in the HR 8799 System
No full textThe HR 8799 system hosts four massive planets orbiting 15 and 80 au. Studies of the system's orbital stability and its outer debris disk open the possibility of additional planets, both interior to and exterior to the known system. Reaching a sufficient sensitivity to search for interior planets is very challenging due to the combination of bright quasi-static speckle noise close to the stellar diffraction core and relatively fast orbital motion. In this work, we present a deep L-band imaging campaign using NIRC2 at Keck comprising 14 observing sequences. We further re-reduce archival data for a total of 16.75 hr, one of the largest uniform data sets of a single direct imaging target. Using a Bayesian modeling technique for detecting planets in images while compensating for plausible orbital motion, we then present deep limits on the existence of additional planets in the HR 8799 system. The final combination shows a tentative candidate, consistent with 4–7 M_jup at 4–5 au, detected with an equivalent false-alarm probability better than 3σ. This analysis technique is widely applicable to archival data and to new observations from upcoming missions that revisit targets at multiple epochs
Bridging the divide in energy policy research: Empirical evidence from global collaborative networks
No full textEnergy research seeking to influence policy in low- and middle-income countries (LMICs) is often funded by – and conceptualised by authors in – institutions from higher income countries (HICs). Research agendas and policy recommendations determined in HICs potentially yield the most influence on policymaking in LMICs. This risks leaving a multidimensional gap in how LMICs frame, evidence and enact policies. This paper is the first to provide quantitative evidence to geographical imbalances in energy policy research, and to shed light into the fact that research proposing energy policy coupled with development objectives to LMICs is dominated by HICs researchers. We find that the latter not only publish more articles proposing energy policy to LMICs, but also are more cited when doing so. We reach these findings by analysing the spatial dynamics of energy research on LMICs through a multi-method approach using bibliometric, network science and regression-based techniques. We established a framework using a sample of 6,636 papers from the Web of Science database, journal impact data from Scimago Journal Ranking and country economic data from the World Bank. Results show the existence of a cycle of imbalances across research practices. Most scientific articles recommending energy policy for LMICs have a primary author based in a HIC, funded by a HIC institution. The number of citations articles receive increases with the GDP of the country of primary author. Funders support authors based in countries of the same income band or higher. We recommend revising research practices and funding policies to place local actors and knowledge at the heart of energy policy research, enabling high-impact policymaking in LMICs
A 2.0 GS/s Two-Stage Quad-Channel Digital Downconverter for a 380 GHz Spaceborne Atmospheric H₂O Monitoring Instrument
No full textThis brief presents a quad-channel 2.0 GS/s digital downconverter (DDC) chip in 65nm CMOS that supports the NASA Stratospheric Water Inventory and Tomography by Convective Hydration (SWITCH) spaceborne instrument. The presented DDC chipset provides a wide input bandwidth and allows the transmitted 380 GHz signals to be channelized to perform the atmospheric measurements. The prototype DDC chip is implemented in a 65nm CMOS technology and consumes 177mW of DC power
Topics in Shear Flow (version 2.0): References Consulted
No full textA collection of draft files of reference lists, assembled roughly in order of the chapters of the book "Topics in Shear Flow" (v 2.0) by Donald Coles. The lists date from 1999 or earlier. A few additional references found with the book manuscript which are cited therein but not included in these lists are added at the end. Some sources appear in more than one section while others were ultimately not cited in the book
Comprehensive coverage of particle acceleration and kinetic feedback from the stellar mass black hole V404 Cygni
No full textWe present analysis of comprehensive radio observations of the black hole V404 Cyg during its 2015 outburst. These data represent the best ever coverage of jet production and particle acceleration from any black hole. We report for the first time a clear and near-linear flux–rms correlation in the radio flux densities. Investigation of individual flares reveals in nearly all cases the peak corresponds to the transition from optically thick to thin to synchrotron emission, but an extended phase of particle acceleration is required in contrast to simple impulsive injection models. The largest radio flare is preceded by a phase of optical oscillations and followed one day later by a smaller but optically thin flare, likely due to ejecta interacting with the interstellar medium. Comparing the radio emission to contemporaneous X-ray and optical data, we find that the X-ray and radio measurements are correlated on all time-scales from seconds to one day. Correlation with the optical flux densities is weak at short time-scales, but becomes significant on time-scales greater than a few hours. We evaluate the physical conditions (size, magnetic field, and internal energy) associated with 86 individual radio flares, which in turn allows us to place a lower limit on the kinetic feedback over the 15 d of intense activity. If this energy was deposited locally to the source, as implied by the failure to detect jets on angular scales larger than milliarcsec, then we predict that a nova-like shell could have been formed
PHANGS–JWST First Results: The Dust Filament Network of NGC 628 and Its Relation to Star Formation Activity
No full textPHANGS–JWST mid-infrared (MIR) imaging of nearby spiral galaxies has revealed ubiquitous filaments of dust emission in intricate detail. We present a pilot study to systematically map the dust filament network (DFN) at multiple scales between 25 and 400 pc in NGC 628. MIRI images at 7.7, 10, 11.3, and 21 μm of NGC 628 are used to generate maps of the filaments in emission, while PHANGS–HST B-band imaging yields maps of dust attenuation features. We quantify the correspondence between filaments traced by MIR thermal continuum/polycyclic aromatic hydrocarbon (PAH) emission and filaments detected via extinction/scattering of visible light; the fraction of MIR flux contained in the DFN; and the fraction of H ii regions, young star clusters, and associations within the DFN. We examine the dependence of these quantities on the physical scale at which the DFN is extracted. With our highest-resolution DFN maps (25 pc filament width), we find that filaments in emission and attenuation are cospatial in 40% of sight lines, often exhibiting detailed morphological agreement; that ∼30% of the MIR flux is associated with the DFN; and that 75%–80% of the star formation in H ii regions and 60% of the mass in star clusters younger than 5 Myr are contained within the DFN. However, the DFN at this scale is anticorrelated with looser associations of stars younger than 5 Myr identified using PHANGS–HST near-UV imaging. We discuss the impact of these findings on studies of star formation and the interstellar medium, and the broad range of new investigations enabled by multiscale maps of the DFN
Modernizing Wildland Firefighting to Protect Our Firefighters: Report to the President
No full textThe linchpin of our country’s effort to combat wildfires is a dedicated corps of tens of thousands of state and federal wildland firefighters, who risk their lives to defend over 1.5 billion acres of fireprone land in the United States. Thousands of additional local firefighters are also called upon to protect communities at the wildland urban interface, areas that now collectively house nearly one-third of the U.S. population. PCAST aims to identify opportunities for science and technology to make the job of wildland firefighting safer and more effective. Progress in this arena can complement and amplify actions already taken by the Biden-Harris Administration to strengthen the firefighting workforce via enhancements to job salary and classification levels5 and the 14% increase in wildland
fire suppression and prevention funding included in the Fiscal Year (FY) 23 Omnibus Appropriations Law. Our recommendations highlight immediate needs that can be addressed with existing technology as well as strategic, long-term investments in new science and technology to ensure that our firefighters do not have to face tomorrow’s fires with yesterday’s tools.
Forest management and similar long-term investments in wildfire prevention are also critically essential to reducing the burden on firefighters in the future. But technology needed to improve wildfire response is ready to help today. Hence, in this report we have intentionally trained our focus on critical aspects of wildfire response that are stuck — technologically and organizationally — in the last century. Several actions recommended in this report can be taken immediately to support the needs of today’s wildland firefighters and vulnerable communities nationwide, as we also pursue the longer-term actions recommended here that can ensure an enduring focus on wildland firefighting science and technology development for decades to come
A Framework to Assess the Seismic Performance of Multiblock Tower Structures as Gravity Energy Storage Systems
No full textThis paper proposes a framework for seismic performance assessment of mutiblock tower structures designed to store renewable energy. To perform our assessment, we deployed, in tandem, physical and numerical models that were developed using appropriate scaling for Newtonian systems that interact via frictional contact. The approach is novel, breaking away from continuum structures for which Cauchy scaling and continuum mechanics are used to model systems. We show that our discontinuous approach is predictive and consistent. We demonstrate predictiveness by showing that the numerical models can reproduce with high fidelity the physical models deployed across two different scales. Consistency is demonstrated by showing that our models can be seamlessly compared across scales and without regard for whether the model is physical or numerical. The integrated theoretical-numerical-experimental approach provides a robust framework to study multiblock tower structures, and the results of our seismic performance assessments are promising. These findings may open the door for new analysis tools in structural mechanics, particularly those applied to gravity energy storage systems