ALBERT

Description: Binary supermassive black holes (BSBHs) are expected to be a generic byproduct from hierarchical galaxy formation. The final coalescence of BSBHs is thought to be the loudest gravitational wave (GW) siren, yet no confirmed BSBH is known in the GW-dominated regime. While periodic quasars have been proposed as BSBH candidates, the physical origin of the periodicity has been largely uncertain. Here we report discovery of a periodicity (P=1607±7 days) at 99.95% significance (with a global p-value of ∼10−3 accounting for the look elsewhere effect) in the optical light curves of a redshift 1.53 quasar, SDSS J025214.67−002813.7. Combining archival Sloan Digital Sky Survey data with new, sensitive imaging from the Dark Energy Survey, the total ∼20-yr time baseline spans ∼4.6 cycles of the observed 4.4-yr (restframe 1.7-yr) periodicity. The light curves are best fit by a bursty model predicted by hydrodynamic simulations of circumbinary accretion disks. The periodicity is likely caused by accretion rate modulation by a milli-parsec BSBH emitting GWs, dynamically coupled to the circumbinary accretion disk. A bursty hydrodynamic variability model is statistically preferred over a smooth, sinusoidal model expected from relativistic Doppler boost, a kinematic effect proposed for PG1302−102. Furthermore, the frequency dependence of the variability amplitudes disfavors Doppler boost, lending independent support to the circumbinary accretion variability hypothesis. Given our detection rate of one BSBH candidate from circumbinary accretion variability out of 625 quasars, it suggests that future large, sensitive synoptic surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time may be able to detect hundreds to thousands of candidate BSBHs from circumbinary accretion with direct implications for Laser Interferometer Space Antenna.

Description: We report a natural wind cycle, the Antarctic Centennial Wind Oscillation (ACWO), whose properties explain milestones of climate and human civilization, including contemporary global warming. We explored the wind/temperature relationship in Antarctica over the past 226 millennia using dust flux in ice cores from the European Project for Ice Coring in Antarctica (EPICA) Dome C (EDC) drill site as a wind proxy and stable isotopes of hydrogen and oxygen in ice cores from EDC and ten additional Antarctic drill sites as temperature proxies. The ACWO wind cycle is coupled 1:1 with the temperature cycle of the Antarctic Centennial Oscillation (ACO), the paleoclimate precursor of the contemporary Antarctic Oscillation (AAO), at all eleven drill sites over all time periods evaluated. Such tight coupling suggests that ACWO wind cycles force ACO/AAO temperature cycles. The ACWO is modulated in phase with the millennial-scale Antarctic Isotope Maximum (AIM) temperature cycle. Each AIM cycle encompasses several ACWOs that increase in frequency and amplitude to a Wind Terminus, the last and largest ACWO of every AIM cycle. This historic wind pattern, and the heat and gas exchange it forces with the Southern Ocean (SO), explains climate milestones including the Medieval Warm Period and the Little Ice Age. Contemporary global warming is explained by venting of heat and carbon dioxide from the SO forced by the maximal winds of the current positive phase of the ACO/AAO cycle. The largest 20 human civilizations of the past four millennia collapsed during or near the Little Ice Age or its earlier recurrent homologs. The Eddy Cycle of sunspot activity oscillates in phase with the AIM temperature cycle and therefore may force the internal climate cycles documented here. Climate forecasts based on the historic ACWO wind pattern project imminent global cooling and in ~4 centuries a recurrent homolog of the Little Ice Age. Our study provides a theoretically-unified explanation of contemporary global warming and other climate milestones based on natural climate cycles driven by the Sun, confirms a dominant role for climate in shaping human history, invites reconsideration of climate policy, and offers a method to project future climate.

Description: Salt marshes provide important services to coastal ecosystems in the southeastern United States. In many locations, salt marsh habitats are threatened by coastal development and erosion, necessitating large-scale monitoring. Assessing vegetation height across the extent of a marsh can provide a comprehensive analysis of its health, as vegetation height is associated with Above Ground Biomass (AGB) and can be used to track degradation or growth over time. Traditional methods to do this, however, rely on manual measurements of stem heights that can cause harm to the marsh ecosystem. Moreover, manual measurements are limited in scale and are often time and labor intensive. Unoccupied Aircraft Systems (UAS) can provide an alternative to manual measurements and generate continuous results across a large spatial extent in a short period of time. In this study, a multirotor UAS equipped with optical Red Green Blue (RGB) and multispectral sensors was used to survey five salt marshes in Beaufort, North Carolina. Structure-from-Motion (SfM) photogrammetry of the resultant imagery allowed for continuous modeling of the entire marsh ecosystem in a three-dimensional space. From these models, vegetation height was extracted and compared to ground-based manual measurements. Vegetation heights generated from UAS data consistently under-predicted true vegetation height proportionally and a transformation was developed to predict true vegetation height. Vegetation height may be used as a proxy for Above Ground Biomass (AGB) and contribute to blue carbon estimates, which describe the carbon sequestered in marine ecosystems. Employing this transformation, our results indicate that UAS and SfM are capable of producing accurate assessments of salt marsh health via consistent and accurate vegetation height measurements.

Description: Stratocumulus clouds have a distinctive structure composed of a combination of lumpy cellular structures and thin elongated regions, resembling canyons or slits. The elongated slits are referred to as “spiderweb” structure to emphasize their interconnected nature. Using very high resolution large-eddy simulations (LES), it is shown that the spiderweb structure is generated by cloud-top evaporative cooling. Analysis of liquid water path (LWP) and cloud liquid water content shows that cloud-top evaporative cooling generates relatively shallow slits near the cloud top. Most of liquid water mass is concentrated near the cloud top, thus cloud-top slits of clear air have a large impact on the entire-column LWP. When evaporative cooling is suppressed in the LES, LWP exhibits cellular lumpy structure without the elongated low-LWP regions. Even though the spiderweb signature on the LWP distribution is negligible, the cloud-top evaporative cooling process significantly affects integral boundary layer quantities, such as the vertically integrated turbulent kinetic energy, mean liquid water path, and entrainment rate. In a pair of simulations driven only by cloud-top radiative cooling, evaporative cooling nearly doubles the entrainment rate.

Description: The clinical behavior of thyroid cancers is seen to reflect inherent transcriptional activities of mutated genes and trophic effects on tumors of circulating pituitary thyrotropin (TSH). The thyroid hormone, L-thyroxine (T4), has been shown to stimulate proliferation of a large number of different forms of cancer. This activity of T4 is mediated by a cell surface receptor on the extracellular domain of integrin αvβ3. In this brief review, we describe what is known about T4 as a circulating trophic factor for differentiated (papillary and follicular) thyroid cancers. Given T4′s cancer-stimulating activity in differentiated thyroid cancers, it was not surprising to find that genomic actions of T4 were anti-apoptotic. Transduction of the T4-generated signal at the integrin primarily involved mitogen-activated protein kinase (MAPK). In thyroid C cell-origin medullary carcinoma of the thyroid (MTC), effects of thyroid hormone analogues, such as tetraiodothyroacetic acid (tetrac), include pro-angiogenic and apoptosis-linked genes. Tetrac is an inhibitor of the actions of T4 at αvβ3, and it is assumed, but not yet proved, that the anti-angiogenic and pro-apoptotic actions of tetrac in MTC cells are matched by T4 effects that are pro-angiogenic and anti-apoptotic. We also note that papillary thyroid carcinoma cells may express the leptin receptor, and circulating leptin from adipocytes may stimulate tumor cell proliferation. Transcription was stimulated by leptin in anaplastic, papillary, and follicular carcinomas of genes involved in invasion, such as matrix metalloproteinases (MMPs). In summary, thyroid hormone analogues may act at their receptor on integrin αvβ3 in a variety of types of thyroid cancer to modulate transcription of genes relevant to tumor invasiveness, apoptosis, and angiogenesis. These effects are independent of TSH.

Description: Waterbirds may facilitate pathogen transport in rice fields from autumn to winter. This study investigated pathogen dynamics in two types of rice fields, those considered conventionally managed and a low-external-input-sustainable-agriculture (LEISA) rice system in the Mississippi Alluvial Valley, winter 2017–2018. In each system, fields were (1) left unflooded or (2) flooded from November to March. Fecal indicator and pathogenic bacteria (enterococci, Clostridium perfringens, Escherichia coli, Salmonella spp., and Campylobacter spp.) were quantified in soil before and after winter flooding, and bird fecal matter estimated on both farm types. Water samples were tested for enterococci, C. perfringens and E. coli before fields were drained. The LEISA flooded fields had greater detections of C. perfringens in the soil than conventional non-flooded fields. There was an observed decreasing trend of C. perfringens detection associated with lower bird abundances among treatment groups. All observed pathogen levels in both systems were below EPA standards. Results suggest that long-term waterbird stopovers can influence pathogen indicators in soil, but not at levels to threaten human and environmental health standards. Future studies should focus on long-term monitoring of pathogen introduction in rice fields that harbor wintering waterfowl or other waterbirds.

Description: Uranium is naturally found in the environment as a radioactive metal element with high concentrations in the Southwestern US. In this region is the Navajo Nation, which spans approximately 69,930 square kilometers. A decay product of uranium is radon gas, a lung carcinogen that has no color, odor, or taste. Radon gas may pass from soil into homes; and, indoor accumulation has been associated with geographical location, seasonality, home construction materials, and home ventilation. A home and indoor radon survey was conducted from November 2014 through May 2015, with volunteers who reported residence on the Navajo Nation. Home geolocation, structural characteristics, temperature (°C) during radon testing, and elevation (meters) were recorded. Short-term indoor radon kits were used to measure indoor radon levels. 51 homes were measured for indoor radon levels, with an arithmetic mean concentration of 60.5 Becquerels per cubic meter (Bq/m3) (SD = 42.7). The mean indoor radon concentrations (Bq/m3) by house type were: mobile, 29.0 (SD = 22.9); wood, 58.6 (SD = 36.0); hogan, 74.0 (SD = 0.0); homes constructed of cement and wood, 82.6 (SD = 3.5); and homes constructed of concrete and cement, 105.7 (SD = 55.8). A key observation is that house construction type appears to be associated with the mean home indoor radon concentration. This observation has been published in that the basic structural make-up of the home may affect home ventilation and therefore indoor radon concentration levels.

Description: Experiments have been performed to demonstrate that ultrasound in the 100–400 kHz frequency range can be used to propagate signals through various types of industrial insulation. This is despite the fact that they are highly attenuating to ultrasonic signals due to scattering and viscoelastic effects. The experiments used a combination of piezocomposite transducers and pulse compression processing. This combination allowed signal-to-noise levels to be enhanced so that signals reflected from the surface of an insulated and cladded steel pipe could be obtained.

Description: We observed the flare stars AD Leonis, Wolf 424, EQ Pegasi, EV Lacertae, and UV Ceti for nearly 135 h. These stars were observed between 63 and 83 MHz using the interferometry mode of the Long Wavelength Array. Given that emission from flare stars is typically circularly polarized, we used the condition that any significant detection present in Stokes I must also be present in Stokes V at the same time in order for us to consider it a possible flare. Following this, we made one marginal flare detection for the star EQ Pegasi. This flare had a flux density of 5.91 Jy in Stokes I and 5.13 Jy in Stokes V, corresponding to a brightness temperature 1.75 × 1016(r/r*)−2 K.