查看更多>>摘要：Superconductivity transition temperature(Tc)marks the inception of a macroscopic quantum phase-coherent paired state in fermionic systems.For 2D superconductivity,the paired electrons condense into a coherent superfluid state at Tc,which is usually lower than the pairing temperature,between which intrinsic physics including Berezinskii-Kosterlitz-Thouless transition and pseudogap state are hotly debated.In the case of monolayer FeSe superconducting films on SrTiO3(001),although the pairing temperature(Tp)is revealed to be 65-83 Kby using spectroscopy characterization,the measured zero-resistance temperature(Tc0)is limited to 20 K.Here,we report significantly enhanced superconductivity in monolayer FeSe filmsby δ-doping of Eu or Al on SrTiO3(001)surface,in which T0 is enhanced by 12 K with a narrowed transition width ΔTc～8 K,compared with non-doped samples.Using scanning tunneling microscopy/spectroscopy measurements,we demonstrate lowered work function of theδ-doped SrTiO3(001)surface and enlarged superconducting gaps in the monolayer FeSe with improved morphology/electronic homogeneity.Our work provides a practical route to enhance 2D superconductivity by using interface engineering.
查看更多>>摘要：Despite the importance of ontogenetic data on early diverging euarthropods to our understanding of the ecology and evolution of past life,the data are distinctly lacking,as reconstructing life histories of fossil animals is often challenging.Here we report the growth trajectory of frontal appendages of the apex predator Amplectobelua symbrachiata,one of the most common radiodont arthropods from the early Cambrian Chengjiang biota(c.520 Ma)of China.Analysis of432 specimens(9.1-137.1 mm length;1.3-25.6 mm height)reveals that appendages grew isometrically,with an estimated maximum size of the whole animal of c.90 cm.Individuals grew rapidly compared to extant arthropods,as assessed using the electronic length-frequency analysis(ELEFAN)approach.Therefore,we show that the Cambrian apex predator A.symbrachiata was an extremely fast-growing arthropod,with an unusual life history strategy that formed as part of the escalatory'arms race'that shaped the Cambrian explosion over 500 Ma.
查看更多>>摘要：China is among the top nitrous oxide(N2O)-emitting countries,but existing national inventories do not provide full-scale emissions including both natural and anthropogenic sources.We conducted a four-decade(1980-2020)of comprehensive quantification of Chinese N2O inventory using empirical emission factor method for anthropogenic sources and two up-to-date process-based models for natural sources.Total N2O emissions peaked at 2287.4(1774.8-2799.9)Gg N2O yr-1 in 2018,and agriculture-developed regions,like the East,Northeast,and Central,were the top N2O-emitting regions.Agricultural N2O emissions have started to decrease after 2016 due to the decline of nitrogen fertilization applications,while,industrial and energetic sources have been dramatically increasing after 2005.N2O emissions from agriculture,industry,energy,and waste represented 49.3％,26.4％,17.5％,and 6.7％of the anthropogenic emissions in 2020,respectively,which revealed that it is imperative to prioritize N2O emission mitigation in agriculture,industry,and energy.Natural N2O sources,dominated by forests,have been steadily growing from 317.3(290.3-344.1)GgN2Oyr-1 in 1980 to 376.2(335.5-407.2)GgN2Oyr-1 in 2020.Our study produces a Full-scale Annual N2O dataset in China(FAN2020),providing emergent counting to refine the current national N2O inventories.
查看更多>>摘要：Organic vapors from biomass burning are a major source of secondary organic aerosols(SOAs).Previous smog chamber studies found that the SOA contributors in biomass-burning emissions are mainly volatile organic compounds(VOCs).While intermediate volatility organic compounds(IVOCs)are efficient SOA precursors and contribute a considerable fraction of biomass-burning emissions,their contribution to SOA formation has not been directly observed.Here,by deploying a newly-developed oxidation flow reactor to study SOA formation from wood burning,we find that IVOCs can contribute～70％of the formed SOA,i.e.＞2 times more than VOCs.This previously missing SOA fraction is interpreted to be due to the high wall losses of semi-volatile oxidation products of IVOCs in smog chambers.The finding in this study reveals that SOA production from biomass burning is much higher than previously thought,and highlights the urgent need for more research on the IVOCs from biomass burning and potentially other emission sources.
查看更多>>摘要：A digital coding metasurface is a platform connecting the digital space and electromagnetic wave space,and has therefore gained much attention due to its intriguing value in reshaping wireless channels and realizing new communication architectures.Correspondingly,there is an urgent need for electromagnetic information theory that reveals the upper limit of communication capacity and supports the accurate design of metasurface-based communication systems.To this end,we propose a macroscopic model and a statistical model of the digital coding metasurface.The macroscopic model uniformly accommodates both digital and electromagnetic aspects of the meta-atoms and predicts all possible scattered fields of the digital coding metasurface based on a small number of simulations or measurements.Full-wave simulations and experimental results show that the macroscopic model is feasible and accurate.A statistical model is further proposed to correlate the mutual coupling between meta-atoms with covariance and to calculate the entropy of the equivalent currents of digital coding metasurface.These two models can help reconfigurable intelligent surfaces achieve more accurate beamforming and channel estimation,and thus improve signal power and coverage.Moreover,the models will encourage the creation of a precoding codebook in metasurface-based direct digital modulation systems,with the aim of approaching the upper limit of channel capacity.With these two models,the concepts of current space and current entropy,as well as the analysis of information loss from the coding space to wave space,is established for the first time,helping to bridge the gap between the digital world and the physical world,and advancing developments of electromagnetic information theory and new-architecture wireless systems.
查看更多>>摘要：The cell nucleus is the main site for the storage and replication of genetic material,and the synthesis of substances in the nucleus is rhythmic,regular and strictly regulated by physiological processes.However,whether exogenous substances,such as nanoparticles,can be synthesized in situ in the nucleus of live cells has not been reported.Here,we have achieved in-situ synthesis of CdSxSe1-x quantum dots(QDs)in the nucleus by regulation of the glutathione(GSH)metabolic pathway.High enrichment of GSH in the nucleus can be accomplished by the addition of GSH with the help of the Bcl-2 protein.Then,high-valence Se is reduced to low-valence Se by glutathione-reductase-catalyzed GSH,and interacts with the Cd precursor formed through Cd and thiol-rich proteins,eventually generating QDs in the nucleus.Our work contributes to a new understanding of the syntheses of substances in the cell nucleus and will pave the way for the development of advanced'supercells'.
查看更多>>摘要：Stereospecific recognition of chiral molecules plays a crucial role in biological systems.The μ-opioid receptor(MOR)exhibits binding affinity towards(-)-morphine,a well-established gold standard in pain management,while it shows minimal binding affinity for the(+)-morphine enantiomer,resulting in a lack of analgesic activity.Understanding how MOR stereoselectively recognizes morphine enantiomers has remained a puzzle in neuroscience and pharmacology for over half-a-century due to the lack of direct observation techniques.To unravel this mystery,we constructed the binding and unbinding processes of morphine enantiomers with MOR via molecular dynamics simulations to investigate the thermodynamics and kinetics governing MOR's stereoselective recognition of morphine enantiomers.Our findings reveal that the binding of(-)-morphine stabilizes MOR in its activated state,exhibiting a deep energy well and a prolonged residence time.In contrast,(+)-morphine fails to sustain the activation state of MOR.Furthermore,the results suggest that specific residues,namely D1142.50 and D1473.32,are deprotonated in the active state of MOR bound to(-)-morphine.This work highlights that the selectivity in molecular recognition goes beyond binding affinities,extending into the realm of residence time.
查看更多>>摘要：Carbyne,an elusive sp-hybridized linear carbon allotrope,has fascinated chemists and physicists for decades.Due to its high chemical reactivity and extreme instability,carbyne was much less explored in contrast to the sp2-hybridized carbon allotropes such as graphene.Herein,we report the on-surface synthesis of polyynic carbon chains by demetallization of organometallic polyynes on the Au(lll)surface;the longest one observed consists of～60 alkyne units(120 carbon atoms).The polyynic structure of carbon chains with alternating triple and single bonds was unambiguously revealed by bond-resolved atomic force microscopy.Moreover,an atomically precise polyyne,C14,was successfully produced via tip-induced dehalogenation and ring-opening of the decachloroanthracene molecule(C14Cl10)on a bilayer NaCl/Au(lll)surface at 4.7 K,and a band gap of 5.8 eV was measured by scanning tunnelling spectroscopy,in a good agreement with the theoretical HOMO-LUMO gap(5.48 eV).
查看更多>>摘要：Virus-like particle(VLP)vaccines had shown great potential during the COVID-19 pandemic,and was thought to be the next generation of antiviral vaccine technology due to viromimetic structures.However,the time-consuming and complicated processes in establishing a current recombinant-protein-based VLP vaccine has limited its quick launch to the out-bursting pandemic.To simplify and optimize VLP vaccine design,we herein report a kind of viromimetic polymer nanoparticle vaccine(VPNVax),with subunit receptor-binding domain(RBD)proteins conjugated to the surface of polyethylene glycol-b-polylactic acid(PEG-b-PLA)nanoparticles for vaccination against SARS-CoV-2.The preparation of VPNVax based on synthetic polymer particle and chemical post-conjugation makes it possible to rapidly replace the antigens and construct matched vaccines at the emergence of different viruses.Using this modular preparation system,we identified that VPNVax with surface protein coverage of 20％-25％had the best immunostimulatory activity,which could keep high levels of specific antibody titers over 5 months and induce virus neutralizing activity when combined with an aluminum adjuvant.Moreover,the polymer nano-vectors could be armed with more immune-adjuvant functions by loading immunostimulant agents or chemical chirality design.This VPNVax platform provides a novel kind of rapidly producing and efficient vaccine against different variants of SARS-CoV-2 as well as other viral pandemics.
查看更多>>摘要：Polysaccharide-based membranes with excellent mechanical properties are highly desired.However,severe mechanical deterioration under wet conditions limits their biomedical applications.Here,inspired by the structural heterogeneity of strong yet hydrated biological materials,we propose a strategy based on heterogeneous crosslink-and-hydration(HCH)of a molecule/nano dual-scale network to fabricate polysaccharide-based nanocomposites with robust wet mechanical properties.The heterogeneity lies in that the crosslink-and-hydration occurs in the molecule-network while the stress-bearing nanofiber-network remains unaffected.As one demonstration,a membrane assembled by bacterial cellulose nanofiber-network and Ca2+-crosslinked and hydrated sodium alginate molecule-network is designed.Studies show that the crosslinked-and-hydrated molecule-network restricts water invasion and boosts stress transfer of the nanofiber-network by serving as interfibrous bridge.Overall,the molecule-network makes the membrane hydrated and flexible;the nanofiber-network as stress-bearing component provides strength and toughness.The HCH dual-scale network featuring a cooperative effect stimulates the design of advanced biomaterials applied under wet conditions such as guided bone regeneration membranes.
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