Abstract We present JWST MIRI Medium Resolution Spectrograph (MRS) observations of the β Pictoris system. We detect an infrared excess from the central unresolved point source from 5 to 7.5 μ m which ...is indicative of dust within the inner ∼7 au of the system. We perform point-spread function (PSF) subtraction on the MRS data cubes and detect a spatially resolved dust population emitting at 5 μ m. This spatially resolved hot dust population is best explained if the dust grains are in the small grain limit (2 π a ≪ λ ). The combination of unresolved and resolved dust at 5 μ m could suggest that dust grains are being produced in the inner few astronomical units of the system and are then radiatively driven outwards, where the particles could accrete onto the known planets in the system, β Pictoris b and c. We also report the detection of an emission line at 6.986 μ m that we attribute to Ar ii . We find that the Ar ii emission is spatially resolved with JWST and appears to be aligned with the dust disk. Through PSF-subtraction techniques, we detect β Pictoris b at the 5 σ level in our MRS data cubes and present the first mid-infrared spectrum of the planet from 5 to 7 μ m. The planet’s spectrum is consistent with having absorption from water vapor between 5 and 6.5 μ m. We perform atmosphere model grid fitting of the spectra and photometry of β Pictoris b and find that the planet’s atmosphere likely has a substellar C/O ratio.
THE ARCTIC SYSTEM REANALYSIS, VERSION 2 Bromwich, D. H.; Wilson, A. B.; Bai, L. ...
Bulletin of the American Meteorological Society,
04/2018, Letnik:
99, Številka:
4
Journal Article
Recenzirano
The Arctic is a vital component of the global climate, and its rapid environmental evolution is an important element of climate change around the world. To detect and diagnose the changes occurring ...to the coupled Arctic climate system, a state-of-the-art synthesis for assessment and monitoring is imperative. This paper presents the Arctic System Reanalysis, version 2 (ASRv2), a multiagency, university-led retrospective analysis (reanalysis) of the greater Arctic region using blends of the polar-optimized version of the Weather Research and Forecasting (Polar WRF) Model and WRF three-dimensional variational data assimilated observations for a comprehensive integration of the regional climate of the Arctic for 2000–12. New features in ASRv2 compared to version 1 (ASRv1) include 1) higher-resolution depiction in space (15-km horizontal resolution), 2) updated model physics including subgrid-scale cloud fraction interaction with radiation, and 3) a dual outer-loop routine for more accurate data assimilation. ASRv2 surface and pressure-level products are available at 3-hourly and monthly mean time scales at the National Center for Atmospheric Research (NCAR). Analysis of ASRv2 reveals superior reproduction of near-surface and tropospheric variables. Broadscale analysis of forecast precipitation and site-specific comparisons of downward radiative fluxes demonstrate significant improvement over ASRv1. The high-resolution topography and land surface, including weekly updated vegetation and realistic sea ice fraction, sea ice thickness, and snow-cover depth on sea ice, resolve finescale processes such as topographically forced winds. Thus, ASRv2 permits a reconstruction of the rapid change in the Arctic since the beginning of the twenty-first century–complementing global reanalyses. ASRv2 products will be useful for environmental models, verification of regional processes, or siting of future observation networks.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this letter, we present the performance of a 100 μm × 400 μm × 40 nm W Transition-Edge Sensor with a critical temperature of 40 mK. This device has a noise equivalent power of 1.5×10-18 W/Hz, in a ...bandwidth of 2.6 kHz, indicating a resolution for Dirac delta energy depositions of 40 ± 5 meV (rms). The performance demonstrated by this device is a critical step toward developing a O(100) meV threshold athermal phonon detector for low-mass dark matter searches.
Trends in Silicates in the β Pictoris Disk Lu, Cicero X.; Chen, Christine H.; Sargent, B. A. ...
The Astrophysical journal,
07/2022, Letnik:
933, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
While
β
Pic is known to host silicates in ring-like structures, whether the properties of these silicate dust vary with stellocentric distance remains an open question. We re-analyze the
β
...Pictoris debris disk spectrum from the Spitzer Infrared Spectrograph (IRS) and a new Infrared Telescope Facility Spectrograph and Imager spectrum to investigate trends in Fe/Mg ratio, shape, and crystallinity in grains as a function of wavelength, a proxy for stellocentric distance. By analyzing a re-calibrated and re-extracted spectrum, we identify a new 18
μ
m forsterite emission feature and recover a 23
μ
m forsterite emission feature with a substantially larger line-to-continuum ratio than previously reported. We find that these prominent spectral features are primarily produced by small submicron-sized grains, which are continuously generated and replenished from planetesimal collisions in the disk and can elucidate their parent bodies’ composition. We discover three trends about these small grains: as stellocentric distance increases, (1) small silicate grains become more crystalline (less amorphous), (2) they become more irregular in shape, and (3) for crystalline silicate grains, the Fe/Mg ratio decreases. Applying these trends to
β
Pic’s planetary architecture, we find that the dust population exterior to the orbits of
β
Pic b and c differs substantially in crystallinity and shape. We also find a tentative 3–5
μ
m dust excess due to spatially unresolved hot dust emission close to the star. From our findings, we infer that the surfaces of large planetesimals are more Fe-rich and collisionally processed closer to the star but more Fe-poor and primordial farther from the star.
Marine mammals can play important ecological roles in aquatic ecosystems, and their presence can be key to community structure and function. Consequently, marine mammals are often considered ...indicators of ecosystem health and flagship species. Yet, historical population declines caused by exploitation, and additional current threats, such as climate change, fisheries bycatch, pollution and maritime development, continue to impact many marine mammal species, and at least 25% are classified as threatened (Critically Endangered, Endangered or Vulnerable) on the IUCN Red List. Conversely, some species have experienced population increases/recoveries in recent decades, reflecting management interventions, and are heralded as conservation successes. To continue these successes and reverse the downward trajectories of at-risk species, it is necessary to evaluate the threats faced by marine mammals and the conservation mechanisms available to address them. Additionally, there is a need to identify evidence-based priorities of both research and conservation needs across a range of settings and taxa. To that effect we: (1) outline the key threats to marine mammals and their impacts, identify the associated knowledge gaps and recommend actions needed; (2) discuss the merits and downfalls of established and emerging conservation mechanisms; (3) outline the application of research and monitoring techniques; and (4) highlight particular taxa/populations that are in urgent need of focus.
We present a new analysis of previously published SuperCDMS data using a profile likelihood framework to search for sub-GeV dark matter (DM) particles through two inelastic scattering channels: ...bremsstrahlung radiation and the Migdal effect. By considering these possible inelastic scattering channels, experimental sensitivity can be extended to DM masses that are undetectable through the DM-nucleon elastic scattering channel, given the energy threshold of current experiments. We exclude DM masses down to 220 MeV/c2 at 2.7 x 10-30 cm2 via the bremsstrahlung channel. The Migdal channel search provides overall considerably more stringent limits and excludes DM masses down to 30 MeV/ c2 at 5.0 x 10-30 cm2.
Nonnative species are often perceived to cause the decline or impede management and recovery of native species, yet the ability to quantify the ecological impacts of nonnative species is often ...difficult. Disentangling the consequences of other stressors (e.g., habitat loss, climate change) and nonnative invasions on native fish communities might be accomplished by a thorough understanding of spatial and temporal variation in nonnative fish behavior and physiological rates of prey consumption mediated by environmental conditions. We examined the potential predatory and competitive threat of nonnative channel catfish (
Ictalurus punctatus
) on a native fish community in the San Juan River, New Mexico, Colorado, and Utah by examining how diet composition and prey intake varied across diel, seasonal, and annual temporal scales over a broad spatial extent (152 km). Prey intake rate and diet composition did not differ across diel temporal scales, but shifted across seasonal and annual scales as well as longitudinally. Estimated consumption of prey by the entire channel catfish population varied between 9.3 dry kg/ha/yr in 2019 and 16.5 dry kg/ha/yr in 2018 with consumption dominated by nonnative terrestrial plants (57.9%; mainly nonnative Russian olive seeds), aquatic invertebrates (13.4%), and aquatic plants (9.0%). The probability of prey in the diet of channel catfish was largely predicted by factors influencing their availability in the system, highlighting the opportunistic feeding strategy of channel catfish. Native fish were consistent in the diet spatially but increased with higher water turbidity and in larger catfish, and despite their relatively low proportion of total prey consumed (2.6%) the impact of this number depends on population sizes of the nonnative predator and native prey. Opportunistic feeding across a wide range of prey items likely allows catfish to sustain high abundances in this system, increasing the potential for negative interaction with native fishes. However, this foraging strategy is dominated by nonnative Russian olive seeds, which may also reduce predatory and competitive interactions with native fishes.
Objectives This study was designed to assess the effects on resource utilization of routine coronary computed tomographic angiography (CCTA) in triaging chest pain patients in the emergency ...department (ED). Background The routine use of CCTA for ED evaluation of chest pain is feasible and safe. Methods We conducted a retrospective multivariate analysis of data from two risk-matched cohorts of 894 ED patients presenting with chest pain to assess the impact of CCTA versus standard evaluation on admissions rate, length of stay, major adverse cardiovascular event rates, recidivism rates, and downstream resource utilization. Results The overall admission rate was lower with CCTA (14% vs. 40%; p < 0.001). Standard evaluation was associated with a 5.5-fold greater risk for admission (odds ratio OR: 5.53; p < 0.001). Expected ED length of stay with standard evaluation was about 1.6 times longer (OR: 1.55; p < 0.001). There were no differences in the rates of death and acute myocardial infarction within 30 days of the index visit between the two groups. The likelihood of returning to the ED within 30 days for recurrent chest pain was 5 times greater with standard evaluation (OR: 5.06; p = 0.022). Standard evaluation was associated with a 7-fold greater likelihood of invasive coronary angiography without revascularization (OR: 7.17; p < 0.001), while neither group was significantly more likely to receive revascularization (OR: 2.06; p = 0.193). The median radiation dose with CCTA was 5.88 mSv (n = 1039; confidence interval: 5.2 to 6.4). Conclusions The routine use of CCTA in ED evaluation of chest pain reduces healthcare resource utilization.
Representation of female surgical residents has slowly increased, but underrepresented in medicine (URiM) representation remains disappointingly low. National residency matching reports suggest that ...meaningful research experience improves surgical residency match success - therefore, formal funding opportunities and early mentorship for URiM medical students. In this study, we catalog medical student (MS) funding opportunities (funding type, eligibility by year, mission, compensation, length of commitment, number of awardees, and dollar investment amount per student) from 7 surgical departments (general surgery, thoracic surgery, vascular surgery, plastic surgery, otorhinolaryngology, orthopedic surgery, neurosurgery) within 196 US medical schools and 20 professional surgical educational organizations through manually searching web pages. We recorded 146 surgical funding opportunities from medical school surgical departments and 16 surgical funding opportunities from professional organizations. Overall, we find that medical institutions' surgical departments and professional surgical educational organizations may not be effectively utilizing recruitment strategies in MS funding opportunities.
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