After stars formed in the early Universe, their ultraviolet light is expected, eventually, to have penetrated the primordial hydrogen gas and altered the excitation state of its 21-centimetre ...hyperfine line. This alteration would cause the gas to absorb photons from the cosmic microwave background, producing a spectral distortion that should be observable today at radio frequencies of less than 200 megahertz. Here we report the detection of a flattened absorption profile in the sky-averaged radio spectrum, which is centred at a frequency of 78 megahertz and has a best-fitting full-width at half-maximum of 19 megahertz and an amplitude of 0.5 kelvin. The profile is largely consistent with expectations for the 21-centimetre signal induced by early stars; however, the best-fitting amplitude of the profile is more than a factor of two greater than the largest predictions. This discrepancy suggests that either the primordial gas was much colder than expected or the background radiation temperature was hotter than expected. Astrophysical phenomena (such as radiation from stars and stellar remnants) are unlikely to account for this discrepancy; of the proposed extensions to the standard model of cosmology and particle physics, only cooling of the gas as a result of interactions between dark matter and baryons seems to explain the observed amplitude. The low-frequency edge of the observed profile indicates that stars existed and had produced a background of Lyman-α photons by 180 million years after the Big Bang. The high-frequency edge indicates that the gas was heated to above the radiation temperature less than 100 million years later.
We report constraints on the global 21 cm signal due to neutral hydrogen at redshifts 14.8 ≥ z ≥ 6.5 . We derive our constraints from low-foreground observations of the average sky brightness ...spectrum conducted with the EDGES High-band instrument between 2015 September 7 and October 26. Observations were calibrated by accounting for the effects of antenna beam chromaticity, antenna and ground losses, signal reflections, and receiver parameters. We evaluate the consistency between the spectrum and phenomenological models for the global 21 cm signal. For tanh-based representations of the ionization history during the epoch of reionization, we rule out, at ≥ 2 significance, models with duration of up to Δ z = 1 at z 8.5 and higher than Δ z = 0.4 across most of the observed redshift range under the usual assumption that the 21 cm spin temperature is much larger than the temperature of the cosmic microwave background during reionization. We also investigate a "cold" intergalactic medium (IGM) scenario that assumes perfect Ly coupling of the 21 cm spin temperature to the temperature of the IGM, but that the latter is not heated by early stars or stellar remants. Under this assumption, we reject tanh-based reionization models of duration Δ z 2 over most of the observed redshift range. Finally, we explore and reject a broad range of Gaussian models for the 21 cm absorption feature expected in the First Light era. As an example, we reject 100 mK Gaussians with duration (full width at half maximum) Δ z ≤ 4 over the range 14.2 ≥ z ≥ 6.5 at ≥ 2 significance.
Approximately 10% of active galactic nuclei exhibit relativistic jets, which are powered by the accretion of matter onto supermassive black holes. Although the measured width profiles of such jets on ...large scales agree with theories of magnetic collimation, the predicted structure on accretion disk scales at the jet launch point has not been detected. We report radio interferometry observations, at a wavelength of 1.3 millimeters, of the elliptical galaxy M87 that spatially resolve the base of the jet in this source. The derived size of 5.5 ± 0.4 Schwarzschild radii is significantly smaller than the innermost edge of a retrograde accretion disk, suggesting that the M87 jet is powered by an accretion disk in a prograde orbit around a spinning black hole.
We present new constraints on parameters of cosmic dawn and the epoch of reionization derived from the EDGES High-Band spectrum (90-190 MHz). The parameters are probed by evaluating global 21 cm ...signals generated with the recently developed Global21cm tool. This tool uses neural networks trained and tested on ∼30,000 spectra produced with semi-numerical simulations that assume the standard thermal evolution of the cosmic microwave background and the intergalactic medium. From our analysis, we constrain at 68% (1) the minimum virial circular velocity of star-forming halos to Vc < 19.3 km s−1, (2) the X-ray heating efficiency of early sources to fX > 0.0042, and (3) the low-energy cutoff of the X-ray spectral energy distribution to min < 2.3 keV. We also constrain the star formation efficiency (f*), the electron scattering optical depth (τe), and the mean-free path of ionizing photons (Rmfp). We recompute the constraints after incorporating into the analysis four estimates for the neutral hydrogen fraction from high-z quasars and galaxies, and a prior on τe from Planck 2018. The largest impact of the external observations is on the parameters that most directly characterize reionization. Specifically, we derive the combined 68% constraints τe < 0.063 and Rmfp > 27.5 Mpc. The external observations also have a significant effect on Vc due to its degeneracy with τe, while the constraints on f*, fX, and min, remain primarily determined by EDGES.
In nanoparticle (NP)-mediated drug delivery, liposomes are the most widely used drug carrier, and the only NP system currently approved by the FDA for clinical use, owing to their advantageous ...physicochemical properties and excellent biocompatibility. Recent advances in liposome technology have been focused on bioconjugation strategies to improve drug loading, targeting, and overall efficacy. In this review, we highlight recent literature reports (covering the last five years) focused on bioconjugation strategies for the enhancement of liposome-mediated drug delivery. These advances encompass the improvement of drug loading/incorporation and the specific targeting of liposomes to the site of interest/drug action. We conclude with a section highlighting the role of bioconjugation strategies in liposome systems currently being evaluated for clinical use and a forward-looking discussion of the field of liposomal drug delivery.
We use the sky-average spectrum measured by EDGES High-band (90-190 MHz) to constrain parameters of early galaxies independent of the absorption feature at 78 MHz reported by Bowman et al. These ...parameters represent traditional models of cosmic dawn and the epoch of reionization produced with the 21cmFAST simulation code. The parameters considered are (1) the UV ionizing efficiency (ζ); (2) minimum halo virial temperature hosting efficient star-forming galaxies ( ); (3) integrated soft-band X-ray luminosity ( ); and (4) minimum X-ray energy escaping the first galaxies (E0), corresponding to a typical H i column density for attenuation through the interstellar medium. The High-band spectrum disfavors high values of and ζ, which correspond to signals with late absorption troughs and sharp reionization transitions. It also disfavors intermediate values of , which produce relatively deep and narrow troughs within the band. Specifically, we rule out (95% C.L.). We then combine the EDGES High-band data with constraints on the electron-scattering optical depth from Planck and the hydrogen neutral fraction from high-z quasars. This produces a lower degeneracy between ζ and than that reported by Greig & Mesinger using the Planck and quasar constraints alone. Our main result in this combined analysis is the estimate (95% C.L.). We leave the evaluation of 21 cm models using simultaneously data from EDGES Low- and High-band for future work.
ABSTRACT The EDGES High-Band experiment aims to detect the sky-average brightness temperature of the 21 cm signal from the epoch of reionization in the redshift range . To probe this redshifted ...signal, EDGES High-Band conducts single-antenna measurements in the frequency range 90-190 MHz from the Murchison Radio-astronomy Observatory in Western Australia. In this paper, we describe the current strategy for calibration of the EDGES High-Band receiver and report calibration results for the instrument used in the 2015-2016 observational campaign. We propagate uncertainties in the receiver calibration measurements to the antenna temperature using a Monte Carlo approach. We define a performance objective of 1 mK residual rms after modeling foreground subtraction from a fiducial temperature spectrum using a five-term polynomial. Most of the calibration uncertainties yield residuals of 1 mK or less at confidence. However, current uncertainties in the antenna and receiver reflection coefficients can lead to residuals of up to 20 mK even in low-foreground sky regions. These dominant residuals could be reduced by (1) improving the accuracy in reflection measurements, especially their phase, (2) improving the impedance match at the antenna-receiver interface, and (3) decreasing the changes with frequency of the antenna reflection phase.
Alterations in the normal developmental trajectory of amygdala resting state functional connectivity (rs-FC) have been associated with atypical emotional processes and psychopathology. Little is ...known, however, regarding amygdala rs-FC at birth or its relevance to outcomes. This study examined amygdala rs-FC in healthy, full-term (FT) infants and in very preterm (VPT) infants, and tested whether variability of neonatal amygdala rs-FC predicted internalizing symptoms at age 2 years.
Resting state fMRI data were obtained shortly after birth from 65 FT infants (gestational age GA ≥36 weeks) and 57 VPT infants (GA <30 weeks) at term equivalent. Voxelwise correlation analyses were performed using individual-specific bilateral amygdala regions of interest. Total internalizing symptoms and the behavioral inhibition, depression/withdrawal, general anxiety, and separation distress subdomains were assessed in a subset (n = 44) at age 2 years using the Infant Toddler Social Emotional Assessment.
In FT and VPT infants, the amygdala demonstrated positive correlations with subcortical and limbic structures and negative correlations with cortical regions, although magnitudes were decreased in VPT infants. Neonatal amygdala rs-FC predicted internalizing symptoms at age 2 years with regional specificity consistent with known pathophysiology in older populations: connectivity with the anterior insula related to depressive symptoms, with the dorsal anterior cingulate related to generalized anxiety, and with the medial prefrontal cortex related to behavioral inhibition.
Amygdala rs-FC is well established in neonates. Variability in regional neonatal amygdala rs-FC predicted internalizing symptoms at 2 years, suggesting that risk for internalizing symptoms may be established in neonatal amygdala functional connectivity patterns.
While social-emotional learning (SEL) is regularly identified as a top priority for student well-being and achievement, effective implementation will not happen on its own. That's what makes the SEL ...coach critical to success. Effective systems change happens with an SEL coach who has the skills to lead, communicate, analyze, train, collaborate, and innovate. Whether you are brand new to the position or have been an SEL coach for some time, this book will provide you with all the resources and ideas you need to take implementation to the next level. Jennifer Rogers shares the secrets to enriching your coaching skillset, including: (1) Data Collection--strategic monitoring of the implementation progress; (2) Training--engaging staff in learning and advocating for their needs; (3) Communication--listening actively, modeling, and summarizing; and (4) Team-Leading--creating an environment that is supportive and goal-focused. The lessons and examples in this book produce coaching competencies and qualities necessary to transform practices into processes, ideas into action plans, and goals into outcomes. Learn how to be a successful SEL implementor with this strategy-packed guidebook!
Near a black hole, differential rotation of a magnetized accretion disk is thought to produce an instability that amplifies weak magnetic fields, driving accretion and outflow. These magnetic fields ...would naturally give rise to the observed synchrotron emission in galaxy cores and to the formation of relativistic jets, but no observations to date have been able to resolve the expected horizon-scale magnetic-field structure. We report interferometric observations at 1.3-millimeter wavelength that spatially resolve the linearly polarized emission from the Galactic Center supermassive black hole, Sagittarius A*. We have found evidence for partially ordered magnetic fields near the event horizon, on scales of ~6 Schwarzschild radii, and we have detected and localized the intrahour variability associated with these fields.
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