Sector-zoned clinopyroxene is common in igneous rocks, but has been overlooked in the study of magmatic processes. Whilst concentric zoning is commonly used as a record of physicochemical changes in ...the melt feeding crystal growth, clinopyroxene is also highly sensitive to crystallisation kinetics. In sector-zoned crystals, the fidelity of compositional changes as recorders of magma history is dubious and the interplay between thermodynamic and kinetic controls remains poorly understood. Here we combine electron probe and laser ablation micro-chemical maps of titanaugite crystals from Mt. Etna (Sicily, Italy) to explore the origin of sector zoning at the major and trace element levels, and its implications for the interpretation of magmatic histories. Elemental maps afford the possibility to revisit sector zoning from a spatially controlled perspective. The most striking observation is a clear decoupling of elements into sectors vs. concentric zones within single crystals. Most notably, Al-Ti enrichments and Si-Mg depletions in the prism sectors {1 0 0}, {1 1 0} and {0 1 0} relative to the hourglass (or basal) sectors {−1 1 1} correlate with enrichments in rare earth elements and highly charged high field strength elements due to cation exchanges driven by kinetic effects. In contrast, transition metals (Cr, Ni, Sc) show little partitioning into sectors and strong enrichments in concentric zones following resorbed surfaces, interpreted as evidence of mafic recharge and magma mixing. Our results document that kinetic partitioning has minor effects on the compositional variations of cations with low charge relative to the ideal charge/radius of the structural site they occupy in the clinopyroxene lattice. We suggest that this may be due to a lower efficiency in charge balance mechanisms compared to highly charged cations. It follows that compatible metals such as Cr can be considered trustworthy recorders of mafic intrusions and eruption triggers even in sector-zoned crystals. We also observe that in alkaline systems where clinopyroxene crystallisation takes place at near-equilibrium conditions, sector zoning should have little effect on Na-Ca partitioning and in turn, on the application of experimentally calibrated thermobarometers. Our data show that whilst non-sector-zoned crystals form under relatively stagnant conditions, sector zoning develops in response to low degrees of undercooling, such as during slow magma ascent. Thus, we propose that the chemistry of sector-zoned crystals can provide information on magma history, eruption triggers, and possibly ascent rates.
Strong spin–orbit coupling, resulting in the formation of spin‐momentum‐locked surface states, endows topological insulators with superior spin‐to‐charge conversion characteristics, though the ...dynamics that govern it have remained elusive. Here, an all‐optical method is presented, which enables unprecedented tracking of the ultrafast dynamics of spin‐to‐charge conversion in a prototypical topological insulator Bi2Se3/ferromagnetic Co heterostructure, down to the sub‐picosecond timescale. Compared to pure Bi2Se3 or Co, a giant terahertz emission is observed in the heterostructure that originates from spin‐to‐charge conversion, in which the topological surface states play a crucial role. A 0.12 ps timescale is identified that sets a technological speed limit of spin‐to‐charge conversion processes in topological insulators. In addition, it is shown that the spin‐to‐charge conversion efficiency is temperature independent in Bi2Se3 as expected from the nature of the surface states, paving the way for designing next‐generation high‐speed optospintronic devices based on topological insulators at room temperature.
Ultrafast dynamics of spin‐to‐charge conversion in a prototypical topological insulator Bi2Se3/ferromagnetic Co heterostructure are presented using an all‐optical method. The observed 0.12 ps timescale sets a technological time limit of spin‐to‐charge conversion processes at the surface of topological insulators paving the way for designing next‐generation high‐speed optospintronic devices based on topological insulators at room temperature.
Relative to electron donors for bulk heterojunction organic solar cells (OSCs), electron acceptors that absorb strongly in the visible and even near‐infrared region are less well developed, which ...hinders the further development of OSCs. Fullerenes as traditional electron acceptors have relatively weak visible absorption and limited electronic tunability, which constrains the optical and electronic properties required of the donor. Here, high‐performance fullerene‐free OSCs based on a combination of a medium‐bandgap polymer donor (FTAZ) and a narrow‐bandgap nonfullerene acceptor (IDIC), which exhibit complementary absorption, matched energy levels, and blend with pure phases on the exciton diffusion length scale, are reported. The single‐junction OSCs based on the FTAZ:IDIC blend exhibit power conversion efficiencies up to 12.5% with a certified value of 12.14%. Transient absorption spectroscopy reveals that exciting either the donor or the acceptor component efficiently generates mobile charges, which do not suffer from recombination to triplet states. Balancing photocurrent generation between the donor and nonfullerene acceptor removes undesirable constraints on the donor imposed by fullerene derivatives, opening a new avenue toward even higher efficiency for OSCs.
High‐performance fullerene‐free single‐junction organic solar cells with power conversion efficiencies up to 12.5% are reported. Transient absorption spectroscopy reveals that exciting either the donor or acceptor component efficiently generates mobile charges, which do not suffer from recombination to triplet states.
This paper presents a novel implementation of an integral sliding-mode controller (ISMC) on a two-wheeled mobile robot (2 WMR). The 2 WMR consists of two wheels in parallel and an inverse pendulum, ...which is inherently unstable. It is the first time that the sliding-mode control method is employed for real-time control of a 2 WMR platform and several critical issues are addressed. First, the 2 WMR is underactuated, which uses only one actuator to achieve position control of the wheels while balancing the pendulum around the upright position. ISMC is suitable for control of the underactuated 2 WMR, because ISMC has an extra degree of freedom in control when sliding mode is achieved. In this paper, we utilize this extra degree of freedom to implement a linear nominal controller, which is found adequate in stabilizing the sliding manifold in a range around the equilibrium. Second, the 2 WMR system is in presence of both matched and unmatched uncertainties. The implemented ISMC, with an integral sliding surface and a switching term, is able to completely nullify the influence from the matched uncertainties. The implemented linear nominal controller stabilizes the sliding manifold that is subject to unmatched uncertainties. Third, references design are addressed when implementing ISMC on the 2 WMR. The effectiveness of ISMC is verified through intensive simulation and experiment results.
Microbially mediated anaerobic oxidation of methane (AOM) is a key process in the regulation of methane emissions to the atmosphere. Iron can serve as an electron acceptor for AOM, and it has been ...suggested that Fe(III)-dependent AOM potentially comprises a major global methane sink. Although it has been proposed that anaerobic methanotrophic (ANME) archaea can facilitate this process, their active metabolic pathways have not been confirmed. Here we report the enrichment and characterisation of a novel archaeon in a laboratory-scale bioreactor fed with Fe(III) oxide (ferrihydrite) and methane. Long-term performance data, in conjunction with the
C- and
Fe-labelling batch experiments, demonstrated that AOM was coupled to Fe(III) reduction to Fe(II) in this bioreactor. Metagenomic analysis showed that this archaeon belongs to a novel genus within family Candidatus Methanoperedenaceae, and possesses genes encoding the "reverse methanogenesis" pathway, as well as multi-heme c-type cytochromes which are hypothesised to facilitate dissimilatory Fe(III) reduction. Metatranscriptomic analysis revealed upregulation of these genes, supporting that this archaeon can independently mediate AOM using Fe(III) as the terminal electron acceptor. We propose the name Candidatus "Methanoperedens ferrireducens" for this microorganism. The potential role of "M. ferrireducens" in linking the carbon and iron cycles in environments rich in methane and iron should be investigated in future research.
Although the mechanism of DNA methylation‐mediated gene silencing is extensively studied, relatively little is known about how promoter methylated genes are protected from transcriptional silencing. ...SUVH1, an Arabidopsis Su(var)3‐9 homolog, was previously shown to be required for the expression of a few promoter methylated genes. By chromatin immunoprecipitation combined with sequencing, we demonstrate that SUVH1 binds to methylated genomic loci targeted by RNA‐directed DNA methylation. SUVH1 and its homolog SUVH3 function partially redundantly and interact with three DNAJ domain‐containing homologs, SDJ1, SDJ2, and SDJ3, thus forming a complex which we named SUVH‐SDJ. The SUVH‐SDJ complex components are co‐localized in a large number of methylated promoters and are required for the expression of a subset of promoter methylated genes. We demonstrate that the SUVH‐SDJ complex components have transcriptional activation activity. SUVH1 and SUVH3 function synergistically with SDJ1, SDJ2, and SDJ3 and are required for plant viability. This study reveals how the SUVH‐SDJ complex protects promoter methylated genes from transcriptional silencing and suggests that the transcriptional activation of promoter methylated genes mediated by the SUVH‐SDJ complex may play a critical role in plant growth and development.
DNA methylation within promoters typically leads to transcriptional silencing. But little is known about how genes with methylated promoters are protected from transcriptional silencing. This study identifies a protein complex which binds to methylated promoters and is required for transcriptional activation.
Organic materials featuring intramolecular through‐space charge transfer (TSCT) excited states are advantageous for efficient thermally activated delayed fluorescence (TADF), although the realization ...of multiple TSCT systems remains challenging. Herein, a rigid molecule with a three‐dimensional dislocated sandwich acceptor‐donor‐acceptor configuration has been developed by a linking biphenazine (2PXZ) donor and 2,4,6‐triphenyl‐1,3,5‐triazine (TRZ) acceptor through the twin‐locking of two spiro‐fluorene bridges. The twin‐locking construction with multiple TSCT effects suppresses the intramolecular rotations of various segments in 2PXZ‐2TRZ, leading to a small singlet‐triplet energy difference, a fast reverse intersystem crossing process, and high photoluminescence quantum yield. This material simultaneously possesses the capabilities of TADF and aggregation‐induced emission. The device employing 2PXZ‐2TRZ as a dopant displays an optimal external quantum efficiency of 27.1 % and a low efficiency roll‐off.
Locking a large polycyclic aromatic hydrocarbon (PAH) by two spirofluorene groups has led to a rigid dislocated sandwich acceptor‐donor‐acceptor (A‐D‐A) configuration that exhibits multiple through‐space charge transfer (TSCT). This emitter shows both efficient thermally activated delayed fluorescence (TADF) and aggregation‐induced emission (AIE).
In this paper, we study unmanned aerial vehicle (UAV) aided internet of things (IoT) networks, where UAVs facilitate data transmission of IoT devices. We focus on uplink transmission from IoT devices ...to base station (BS). Multiple UAVs are employed as UAV relays between IoT devices and BS to enhance received signal strength at BS. Specifically, IoT devices periodically detect wireless channel quality between IoT devices and BS, as well as that among IoT devices. Based on the wireless channel quality, we propose a distributed user cluster (UC) algorithm to cluster IoT devices as multiple UCs. One IoT device in a UC, which is named cluster head (CH), is selected to connect to the BS and gather uplink signals of IoT devices. If the wireless channel quality between CH and BS is good, a direct connection between CH and the BS can be built. Otherwise, UAVs are divided into multiple UAV cooperative relay clusters (CRCs). The UAVs in a CRC are located between a specific CH and BS to relay uplink signals. We then formulate a system optimization model to minimize system power consumption, where UAV deployment and transmission power of UAV are jointly optimized. We solve this optimization problem by dual decomposition method. By extensive simulations, we demonstrate the effectiveness of the proposed algorithm. We also reveal several interesting insights for practical UAV aided IoT networks.
Trimethylated histone H3 lysine 27 (H3K27me3) is a repressive histone marker that regulates a variety of developmental processes, including those that determine flowering time. However, relatively ...little is known about the mechanism of how H3K27me3 is recognized to regulate transcription. Here, we identified BAH domain‐containing transcriptional regulator 1 (BDT1) as an H3K27me3 reader. BDT1 is responsible for preventing flowering by suppressing the expression of flowering genes. Mutation of the H3K27me3 recognition sites in the BAH domain disrupted the binding of BDT1 to H3K27me3, leading to de‐repression of H3K27me3‐enriched flowering genes and an early‐flowering phenotype. We also found that BDT1 interacts with a family of PHD finger‐containing proteins, which we named PHD1–6, and with CPL2, a Pol II carboxyl terminal domain (CTD) phosphatase responsible for transcriptional repression. Pull‐down assays showed that the PHD finger‐containing proteins can enhance the binding of BDT1 to the H3K27me3 peptide. Mutations in all of the PHD genes caused increased expression of flowering genes and an early‐flowering phenotype. This study suggests that the binding of BDT1 to the H3K27me3 peptide, which is enhanced by PHD proteins, is critical for preventing early flowering.
BAH DOMAIN‐CONTAINING TRANSCRIPTIONAL REGULATOR 1 (BDT1) functions as a histone H3K27me3 reader. A group of PHD finger‐containing proteins interact with BDT1 and enhance BDT1 binding to H3K27me3. BDT1 and the PHD finger‐containing proteins associate with H3K27me3‐enriched flowering genes and repress their transcription, thereby preventing early flowering.
According to the report from the Chinese Center for Disease Control and Prevention, the prevalence of human immunodeficiency virus (HIV) infection exceeded 1.2 million individuals by the year 2022, ...with an annual increase of about 80000 cases. The overall prevalence of hepatitis B surface antigen among individuals co-infected with HIV reached 13.7%, almost twice the rate of the general population in China. In addition to the well-documented susceptibility to opportunistic infections and new malignancies, HIV infected patients frequently experience liver-related organ damage, with the liver and kidneys being the most commonly affected. This often leads to the development of end-stage liver and kidney diseases. Therefore, organ transplantation has emerged as an important part of active treatment for HIV infected patients. However, the curative effect is not satisfactory. HIV infection has been considered a contraindication for organ transplantation. Until the emergence of highly active anti-retroviral therapy in 1996, the once intractable replication of retrovirus was effectively inhibited. With prolonged survival, the failure of important organs has become the main cause of death among HIV patients. Therefore, transplant centers worldwide have resumed exploration of organ transplantation for HIV-infected individuals and reached a positive conclusion. This study provides an overview of the current landscape of HIV-positive patients receiving liver transplantation (LT) in mainland China. To date, our transplant center has conducted LT for eight end-stage liver disease patients co-infected with HIV, and all but one, who died two months postoperatively due to sepsis and progressive multi-organ failure, have survived. Comparative analysis with hepatitis B virus-infected patients during the same period revealed no statistically significant differences in acute rejection reactions, cytomegalovirus infection, bacteremia, pulmonary infections, acute kidney injury, new-onset cancers, or vascular and biliary complications.
PDF
