Theoretical models of stellar evolution predict that most of the lithium inside a star is destroyed as the star becomes a red giant. However, observations reveal that about 1% of red giants are ...peculiarly rich in lithium, often exceeding the amount in the interstellar medium or predicted from the big bang. With only about 150 lithium-rich giants discovered in the past four decades, and no distinguishing properties other than lithium enhancement, the origin of lithium-rich giant stars is one of the oldest problems in stellar astrophysics. Here we report the discovery of 2330 low-mass (1-3 M ) lithium-rich giant stars, which we argue are consistent with internal lithium production that is driven by tidal spin-up by a binary companion. Our sample reveals that most lithium-rich giants have helium-burning cores ( ), and that the frequency of lithium-rich giants rises with increasing stellar metallicity. We find that while planet accretion may explain some lithium-rich giants, it cannot account for the majority that have helium-burning cores. We rule out most other proposed explanations for the origin of lithium-rich giants. Our analysis shows that giants remain lithium-rich for only about two million years. A prediction from this lithium depletion timescale is that most lithium-rich giants with a helium-burning core have a binary companion.
Patients with systemic lupus erythematosus (SLE) suffer frequent infections that account for significant morbidity and mortality. T cell cytotoxic responses are decreased in patients with SLE, yet ...the responsible molecular events are largely unknown. We find an expanded CD8CD38high T cell subset in a subgroup of patients with increased rates of infections. CD8CD38high T cells from healthy subjects and patients with SLE display decreased cytotoxic capacity, degranulation, and expression of granzymes A and B and perforin. The key cytotoxicity-related transcription factors T-bet, RUNX3, and EOMES are decreased in CD8CD38high T cells. CD38 leads to increased acetylated EZH2 through inhibition of the deacetylase Sirtuin1. Acetylated EZH2 represses RUNX3 expression, whereas inhibition of EZH2 restores CD8 T cell cytotoxic responses. We propose that high levels of CD38 lead to decreased CD8 T cell-mediated cytotoxicity and increased propensity to infections in patients with SLE, a process that can be reversed pharmacologically.
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•Expanded CD8CD38high T cells in SLE patients identify patients with infections•CD8CD38high T cells express decreased amounts of cytotoxic molecules•CD38 decreases NAD+ and SIRT1 activity and releases the activity of EZH2•Inhibition of EZH2 restores the degranulation capacity of CD8CD38high T cells
Katsuyama et al. find that an expanded CD8CD38high T cell population in SLE patients is linked to infections. CD8CD38high T cells display decreased cytotoxic capacity by suppressing the expression of related molecules through an NAD+/Sirtuin1/EZH2 pathway. EZH2 inhibitors increase cytotoxicity offering a means to mitigate infection rates in SLE.
Given that energy (exciton) migration in natural photosynthesis primarily occurs in highly ordered porphyrin-like pigments (chlorophylls), equally highly ordered porphyrin-based metal–organic ...frameworks (MOFs) might be expected to exhibit similar behavior, thereby facilitating antenna-like light-harvesting and positioning such materials for use in solar energy conversion schemes. Herein, we report the first example of directional, long-distance energy migration within a MOF. Two MOFs, namely F-MOF and DA-MOF that are composed of two Zn(II) porphyrin struts 5,15-dipyridyl-10,20-bis(pentafluorophenyl)porphinatozinc(II) and 5,15-bis4-(pyridyl)ethynyl-10,20-diphenylporphinatozinc(II), respectively, were investigated. From fluorescence quenching experiments and theoretical calculations, we find that the photogenerated exciton migrates over a net distance of up to ∼45 porphyrin struts within its lifetime in DA-MOF (but only ∼3 in F-MOF), with a high anisotropy along a specific direction. The remarkably efficient exciton migration in DA-MOF is attributed to enhanced π-conjugation through the addition of two acetylene moieties in the porphyrin molecule, which leads to greater Q-band absorption intensity and much faster exciton-hopping (energy transfer between adjacent porphyrin struts). The long distance and directional energy migration in DA-MOF suggests promising applications of this compound or related compounds in solar energy conversion schemes as an efficient light-harvesting and energy-transport component.
Abstract
We examine the production of energetic neutral atoms (ENAs) in solar flares and coronal mass ejection (CME)-driven shocks and their subsequent propagation to 1 au. Time profiles and fluence ...spectra of solar ENAs at 1 au are computed for two scenarios: (1) ENAs are produced downstream at CME-driven shocks, and (2) ENAs are produced at large-scale post-flare loops in solar flares. Both the time profiles and fluence spectra for these two scenarios are vastly different. Our calculations indicate that we can use solar ENAs as a new probe to examine the underlying acceleration process of solar energetic particles (SEPs) and to differentiate the two acceleration sites: large loops in solar flares and downstream of CME-driven shocks, in large SEP events.
In the era of state socialism under Mao, land in China was treated as a means of production and was allocated administratively by the state free of charge. To accommodate the interests of foreign ...investors without violating the socialist principle of public ownership, the Chinese state has, since the 1980s, separated land use rights from land ownership and opened up a new market track for the conveyance of land use rights to commercial users. The result has been a distinct dual-track land system in the new political economy, characterized by significant asymmetry for arbitrage. Discrepancy between the state's intention and actual outcome has been a consequence of the internal diversity of power relations concerning land development. Our data analysis reveals that the loss of farmland to nonagricultural developments has slowed down in recent years, that the state's intention to increase land use efficiency has been severely compromised by the socialist legacy, and that illegal activities are pervasive. The Chinese socialist state is better seen as a dynamic, complex, heterogeneous, and self-conflictual institutional ensemble in and through which the forces and interests of different levels of the state are contested, negotiated, and mediated.
Abstract
Glansreginin A has been reported to be an indicator of the quality of walnuts (
Juglans
spp.). However, bioactive properties of glansreginin A have not been adequately explored. In the ...present study, we quantified concentrations of glansreginin A in black walnuts (
Juglans nigra
) using high performance liquid chromatography-tandem mass spectrometry (HPLC–MS/MS) and performed an array of in vitro bioassays to characterize biological activities (e.g., antibacterial, antioxidant, anticancer capacities) of this compound. Results from HPLC–MS/MS analysis indicated that glansreginin A was presented in all 12 black cultivars examined and its contents were variable among black walnut cultivars, ranged from 6.8 mg/kg (Jackson) to 47.0 mg/kg (Hay). Glansreginin A possessed moderate antibacterial activities against Gram-positive pathogens (
Staphylococcus aureus
and
Bacillus anthracis
). This compound exhibited no antioxidant activities, did not induce the activity of antioxidant response element signaling pathways, and exerted no antiproliferative effects on tumorigenic alveolar epithelial cells and non-tumorigenic lung fibroblast cells.
Optical metamaterials, engineered to exhibit electromagnetic properties not found in natural materials, may enable new light-based applications including cloaking and optical computing. While there ...have been significant advances in the fabrication of two-dimensional metasurfaces, planar structures create nontrivial angular and polarization sensitivities, making omnidirectional operation impossible. Although three-dimensional (3D) metamaterials have been proposed, their fabrication remains challenging. Here, we use colloidal crystal engineering with DNA to prepare isotropic 3D metacrystals from Au nanocubes. We show that such structures can exhibit refractive indices as large as ∼8 in the mid-infrared, far greater than that of common high-index dielectrics. Additionally, we report the first observation of multipolar Mie resonances in metacrystals with well-formed habits, occurring in the mid-infrared for submicrometer metacrystals, which we measured using synchrotron infrared microspectroscopy. Finally, we predict that arrays of metacrystals could exhibit negative refraction. The results present a promising platform for engineering devices with unnatural optical properties.
Abstract We report on the annual variation of quiet-time suprathermal heavy ion spectral indices for C through Fe in the energy range 0.3–1.28 MeV nuc −1 during Solar Cycle 23's rising phase through ...Solar Cycle 24's declining phase. These Advanced Composition Explorer/Ultra-Low Energy Isotope Spectrometer measurements cover 1998–2019. We show that the average quiet-time suprathermal spectral index across species is γ = 2.5 ± 0.3. Such observations may imply that quiet-time suprathermals are the result of a superposition of various underlying acceleration and transport processes that accelerate suprathermal ions. As such, they may be remnants of particles from discrete events like large and impulsive solar energetic particle events along with corotating interaction regions that have decayed in intensity.
During MESSENGER's third flyby of Mercury, the magnetic field in the planet's magnetic tail increased by factors of 2 to 3.5 over intervals of 2 to 3 minutes. Magnetospheric substorms at Earth are ...powered by similar tail loading, but the amplitude is lower by a factor of approximately 10 and typical durations are approximately 1 hour. The extreme tail loading observed at Mercury implies that the relative intensity of substorms must be much larger than at Earth. The correspondence between the duration of tail field enhancements and the characteristic time for the Dungey cycle, which describes plasma circulation through Mercury's magnetosphere, suggests that such circulation determines the substorm time scale. A key aspect of tail unloading during terrestrial substorms is the acceleration of energetic charged particles, but no acceleration signatures were seen during the MESSENGER flyby.
Solar wind energy transfer to planetary magnetospheres and ionospheres is controlled by magnetic reconnection, a process that determines the degree of connectivity between the interplanetary magnetic ...field (IMF) and a planet's magnetic field. During MESSENGER's second flyby of Mercury, a steady southward IMF was observed and the magnetopause was threaded by a strong magnetic field, indicating a reconnection rate approximately 10 times that typical at Earth. Moreover, a large flux transfer event was observed in the magnetosheath, and a plasmoid and multiple traveling compression regions were observed in Mercury's magnetotail, all products of reconnection. These observations indicate that Mercury's magnetosphere is much more responsive to IMF direction and dominated by the effects of reconnection than that of Earth or the other magnetized planets.
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