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Twist Accumulation in Conformal Field Theory: A Rigorous Approach to the Lightcone Bootstrap
No full textWe prove that in any unitary CFT, a twist gap in the spectrum of operator product expansion (OPE) of identical scalar quasiprimary operators (i.e. ϕ×ϕ) implies the existence of a family of quasiprimary operators Oτ,ℓ with spins ℓ→∞ and twists τ→2Δ_ϕ in the same OPE spectrum. A similar twist-accumulation result is proven for any two-dimensional Virasoro-invariant, modular-invariant, unitary CFT with a normalizable vacuum and central charge c>1, where we show that a twist gap in the spectrum of Virasoro primaries implies the existence of a family of Virasoro primaries O_(h,h̅) with h→∞ and h̅→(c−1)/24 (the same is true with h and h¯ interchanged). We summarize the similarity of the two problems and propose a general formulation of the lightcone bootstrap
The nature of an ultra-faint galaxy in the cosmic dark ages seen with JWST
No full textIn the first billion years after the Big Bang, sources of ultraviolet (UV) photons are believed to have ionized intergalactic hydrogen, rendering the Universe transparent to UV radiation. Galaxies brighter than the characteristic luminosity L* (refs. 1,2) do not provide enough ionizing photons to drive this cosmic reionization. Fainter galaxies are thought to dominate the photon budget; however, they are surrounded by neutral gas that prevents the escape of the Lyman-α photons, which has been the dominant way to identify them so far. JD1 was previously identified as a triply-imaged galaxy with a magnification factor of 13 provided by the foreground cluster Abell 2744 (ref. 3), and a photometric redshift of z ≈ 10. Here we report the spectroscopic confirmation of this very low luminosity (≈0.05 L*) galaxy at z = 9.79, observed 480 Myr after the Big Bang, by means of the identification of the Lyman break and redward continuum, as well as multiple ≳4σ emission lines, with the Near-InfraRed Spectrograph (NIRSpec) and Near-InfraRed Camera (NIRCam) instruments. The combination of the James Webb Space Telescope (JWST) and gravitational lensing shows that this ultra-faint galaxy (M_(UV) = −17.35)—with a luminosity typical of the sources responsible for cosmic reionization—has a compact (≈150 pc) and complex morphology, low stellar mass (10^(7.19) M_⊙) and subsolar (≈0.6 Z_⊙) gas-phase metallicity
Did nutrient-rich oceans fuel Earth’s oxygenation?
No full textPhosphorus (P) availability exerts a strong influence on primary productivity in global oceans. However, its abundance and role as a limiting nutrient prior to the start of the Great Oxygenation Event (GOE) 2.45–2.32 Ga is unclear. Low concentrations of seawater P have been proposed to explain the apparent delay between the early appearance of oxygen-producing Cyanobacteria and the onset of atmospheric oxygenation. We report evidence for seawater precipitation of Ca-phosphate nanoparticles in 2.46–2.40 Ga iron formations deposited on a marine shelf, including shallow-water facies, immediately prior to the onset of the GOE. Our modeling shows that the co-precipitation of Ca-phosphate and ferrous silicate (greenalite) required ferruginous seawater with dissolved P concentrations many orders of magnitude higher than in today’s photic zone. If correct, it follows that P availability is unlikely to have suppressed the expansion of Cyanobacteria prior to the GOE. A reservoir of P-rich surface water shortly before 2.40 Ga could ultimately have triggered a rapid rise in atmospheric oxygen by fueling a sharp increase in primary productivity and organic-carbon burial. We speculate that the enigmatic Lomagundi positive carbon-isotope excursion, recorded in 2.32–2.06 Ga shallow-water carbonates, may mark a key step in the transition toward a modern biosphere of high biological productivity controlled by nutrient availability
Lubricated Interfaces Enabling Simultaneous Pulsatile and Continuous Chemical Release Modes
No full textThe release of chemicals following either pulsatile or continuous release modes is important for various potential applications, including programmed chemical reactions, mechanical actuation, and treatments of various diseases. However, the simultaneous application of both modes in a single material system has been challenging. Here, two chemical loading methods are reported in a liquid-crystal-infused porous surface (LCIPS) that enables both a pulsatile and continuous release of chemicals simultaneously. Specifically, chemicals loaded in the porous substrate exhibit a liquid crystal (LC) mesophase-dependent continuous release, whereas the chemicals dissolved in micrometer-sized aqueous droplets dispersed in the LC surface follow a pulsatile release activated by a phase transition. Moreover, the loading method of distinct molecules can be controlled to program their release mode. Finally, the pulsatile and continuous release of two distinct bioactive small molecules, tetracycline and dexamethasone, are demonstrated which display antibacterial and immunomodulatory activities for applications such as chronic wound healing and biomedical implant coating
Widespread missing super-emitters of nitrogen oxides across China inferred from year-round satellite observations
No full textNitrogen oxides (NOₓ ≡ NO + NO₂) play a central role in air pollution and are targeted for emission mitigation by environmental protection agencies globally. Unique challenges for mitigation are presented by super-emitters, typically with the potential to dominate localized NOₓ budgets. Nevertheless, identifying super-emitters still challenges emission mitigation, while the spatial resolution of emission monitoring rises continuously. Here we develop an efficient, super-resolution (1 × 1 km²) inverse model based on year-round TROPOMI satellite observations over China. Consequently, we resolve hundreds of super-emitters in virtually every corner of China, even in remote and mountainous areas. They are attributed to individual plants or parks, mostly associated with industrial sectors, like energy, petrochemical, and iron and steel industries. State-of-the-art bottom-up emission estimates (i.e., MEICv1.3 and HTAPv2), as well as classic top-down inverse methods (e.g., a CTM coupled with the Ensemble Kalman Filter), do not adequately identify these super-emitters. Remarkably, more than one hundred super-emitters are unambiguously missed, while the establishments or discontinuations of the super-emitters potentially lead to under- or over-estimates, respectively. Moreover, evidence shows that these super-emitters generally dominate the NOₓ budget in a localized area (e.g., equivalent to a spatial scale of a medium-sized county). Although our dataset is incomplete nationwide due to the undetectable super-emitters on top of high pollution, our results imply that super-emitters contribute significantly to national NOₓ budgets and thus suggest the necessity to address the NOₓ budget by revisiting super-emitters on a large scale. Integrating the results we obtain here with a multi-tiered observation system can lead to identification and mitigation of anomalous NOₓ emissions
Imaging suprathermal x-rays from a laboratory plasma jet using PIN-diode-based and scintillator-based 1D pinhole/coded aperture cameras
No full textA PIN-diode-based 1D x-ray camera and a scintillator-based 1D x-ray camera, both with a microsecond to submicrosecond time resolution, have been developed to perform time-resolved imaging of transient, low-intensity, suprathermal x-rays associated with magnetohydrodynamic instabilities disrupting a plasma jet. These cameras have a high detection efficiency over a broad x-ray band, a wide field of view, and the capability to produce > 50 time-resolved frames with a ≤ 1 μs time resolution. The x-ray images are formed by a pinhole or by a coded aperture placed outside a vacuum chamber in which the plasma jet is launched. The 1D imaging shows that the location of the x-ray source is either a few centimeters away from an inner disk electrode or near a spatially translatable metal frame that is 30–40 cm away from the electrode. Compared to a pinhole, a coded aperture increases the signal collection efficiency but also introduces unwanted artifacts
Trends in obesity prevalence and cardiometabolic risk factor control in US adults with diabetes, 1999-2020
No full textObjective: Trends in obesity prevalence and trends in control of cardiometabolic risk factors among National Health and Nutrition Examination Survey participants with diabetes from 1999 through 2020 were analyzed.
Methods: Adults who were 20 years or older and who reported having received a diagnosis of diabetes from a physician were included.
Results: The prevalence of overall obesity, obesity class II, and obesity class III increased from 46.9%, 14.1%, and 10.3% in 1999 to 2002 to 58.1%, 16.6%, and 14.8% in 2015 to 2020, respectively. The prevalence of participants who achieved glycemic control (HbA1c <7%) increased from 42.5% in 1999 to 2002 to 51.8% in 2007 to 2010, then decreased to 48.0% in 2015 to 2020. The prevalence of participants who achieved blood pressure control (<140/90 mmHg) or achieved non-high-density lipoprotein cholesterol control (<130 mg/dL) increased throughout the study periods. The prevalence of participants who met all three risk factor goals increased from 8.3% in 1999 to 2002 to 21.2% in 2011 to 2014 and then decreased to 18.5 in 2015 to 2020. Participants with obesity showed worsening glycemic control and lipid control than participants with normal weight.
Conclusions: There were increasing trends in prevalence of obesity, blood pressure control, and lipid control from 1999 to 2002 to 2015 to 2020. Participants with obesity showed worsening glycemic control and lipid control than normal-weight participants
Extending ensemble Kalman filter algorithms to assimilate observations with an unknown time offset
No full textData assimilation (DA), the statistical combination of computer models with measurements, is applied in a variety of scientific fields involving forecasting of dynamical systems, most prominently in atmospheric and ocean sciences. The existence of misreported or unknown observation times (time error) poses a unique and interesting problem for DA. Mapping observations to incorrect times causes bias in the prior state and affects assimilation. Algorithms that can improve the performance of ensemble Kalman filter DA in the presence of observing time error are described. Algorithms that can estimate the distribution of time error are also developed. These algorithms are then combined to produce extensions to ensemble Kalman filters that can both estimate and correct for observation time errors. A low-order dynamical system is used to evaluate the performance of these methods for a range of magnitudes of observation time error. The most successful algorithms must explicitly account for the nonlinearity in the evolution of the prediction model
Ozone- and Hydroxyl Radical-Mediated Oxidation of Pharmaceutical Compounds Using Ni-Doped Sb–SnO₂ Anodes: Degradation Kinetics and Transformation Products
No full textElectrochemical oxidation provides a versatile technique for treating wastewater streams onsite. We previously reported that a two-layer heterojunction Ni–Sb–SnO₂ anode (NAT/AT) can produce both ozone (O₃) and hydroxyl radical (•OH). In this study, we explore further the applicability of NAT/AT anodes for oxidizing pharmaceutical compounds using carbamazepine (CBZ) and fluconazole (FCZ) as model probe compounds. Details of the oxidation reaction kinetics and subsequent reaction products are investigated in the absence and presence of chloride (Cl⁻) and sulfate (SO₄²⁻). In all cases, faster or comparable degradation kinetics of CBZ and FCZ are achieved using the double-layered NAT/AT anode coupled with a stainless steel (SS) cathode in direct comparison to an identical setup using a boron-doped diamond anode. Production of O₃ on NAT/AT enhances the elimination of both parent compounds and their transformation products (TPs). Very fast CBZ degradation is observed during NAT/AT-SS electrolysis in both NaClO₄ and NaCl electrolytes. However, more reaction products are identified in the presence of Cl⁻ than ClO₄⁻ (23 TPs vs 6). Rapid removal of FCZ is observed in NaClO₄, while the degradation rate is retarded in NaCl depending on the [Cl⁻]. In SO₄²⁻-containing electrolytes, altered reaction pathways and transformation product distributions are observed due to sulfate radical generation. SO₄·⁻ oxidation produces fewer hydroxylated products and promotes the oxidation of aldehydes to carboxylic acids. Similar trend in treatment performance is observed in mixtures of CBZ and FCZ with other pharmaceutical compounds in latrine wastewater and secondary WWTP effluent
Kepler-102: Masses and Compositions for a Super-Earth and Sub-Neptune Orbiting an Active Star
No full textRadial velocity (RV) measurements of transiting multiplanet systems allow us to understand the densities and compositions of planets unlike those in the solar system. Kepler-102, which consists of five tightly packed transiting planets, is a particularly interesting system since it includes a super-Earth (Kepler-102d) and a sub-Neptune-sized planet (Kepler-102e) for which masses can be measured using RVs. Previous work found a high density for Kepler-102d, suggesting a composition similar to that of Mercury, while Kepler-102e was found to have a density typical of sub-Neptune size planets; however, Kepler-102 is an active star, which can interfere with RV mass measurements. To better measure the mass of these two planets, we obtained 111 new RVs using Keck/HIRES and Telescopio Nazionale Galileo/HARPS-N and modeled Kepler-102's activity using quasiperiodic Gaussian process regression. For Kepler-102d, we report a mass upper limit M_d < 5.3 M_⊕ (95% confidence), a best-fit mass M_d = 2.5 ± 1.4 M_⊕, and a density ρ_d = 5.6 ± 3.2 g cm⁻³, which is consistent with a rocky composition similar in density to the Earth. For Kepler-102e we report a mass Mₑ = 4.7 ± 1.7 M_⊕ and a density ρₑ = 1.8 ± 0.7 g cm⁻³. These measurements suggest that Kepler-102e has a rocky core with a thick gaseous envelope comprising 2%–4% of the planet mass and 16%–50% of its radius. Our study is yet another demonstration that accounting for stellar activity in stars with clear rotation signals can yield more accurate planet masses, enabling a more realistic interpretation of planet interiors