Several significant events of a geological nature occurred approximately 800 ka before the present: (1) Australasian tektite fall (AA), (2) Brunhes-Matuyama geomagnetic reversal (BMR), (3) mid-Pleistocene changes in i...Several significant events of a geological nature occurred approximately 800 ka before the present: (1) Australasian tektite fall (AA), (2) Brunhes-Matuyama geomagnetic reversal (BMR), (3) mid-Pleistocene changes in ice age cycles. Add to these the undated fault system (4) in the South-West (SW) of the South China Sea (SCS). Here we offer a unified cause for all four of these in (5), an impact in the SCS of a large, massive cosmic object, likely a comet, obliquely coming from the SW at an extremely shallow angle, striking the Sunda shelf yet unexploded with the shock of its compressed air bow wave, and causing the continual shelf and slope to collapse, resulting in the fault system (4), then traveling almost tangentially to the surface, exploding at impact with the sea surface, ejecting the tektites (1), creating the formation underlying the later atolls of Spratlies Archipelago (6), Nansha Islands in Chinese, & causing the BMR (2). An explanation of event (3) was Richard Muller’s hypothesis of planet Earth passing through an interplanetary dust cloud periodically due to ecliptic precession. Here we hypothesize this cloud actually is a belt of Australasian tektites ejected into space at super-orbital velocities that Earth encounters about every 100 ka.展开更多
A transformation of the electron states—say those enclosed in a potential box—into the de Broglie waves done in the paper, enabled us to calculate the energy change between two quantum levels as a function of the sp...A transformation of the electron states—say those enclosed in a potential box—into the de Broglie waves done in the paper, enabled us to calculate the energy change between two quantum levels as a function of the specific heat and difference of the temperature between the states. In consequence, the energy difference and that of entropy between the levels could be examined in terms of the appropriate classical parameters. In the next step, the time interval necessary for the electron transition between the levels could be associated with the classical electrodynamical parameters like the electric resistance and capacitance connected with the temporary formation of the electric cell in course of the transition. The parameters characterizing the mechanical inertia of the electron were next used as a check of the electrodynamical formulae referring to transition.展开更多
Mn_(3)Si_(2)Te_(6) is a ferrimagnetic nodal-line semiconductor with colossal angular magnetoresistance at ambient pressure.In this work,we investigated the effect of hydrostatic pressure on its electrical transport pr...Mn_(3)Si_(2)Te_(6) is a ferrimagnetic nodal-line semiconductor with colossal angular magnetoresistance at ambient pressure.In this work,we investigated the effect of hydrostatic pressure on its electrical transport properties,magnetic transition,and crystal structure by measuring resistivity,DC and AC magnetic susceptibility,and XRD under various pressures up to~20 GPa.Our results confirmed the occurrence of pressure-induced structural transition at P_(c)≈10–12 GPa accompanied by a concurrent drop of room-temperature resistance in Mn_(3)Si_(2)Te_(6).In the low-pressure phase at PP_(c),the sample exhibits a metallic behavior in the whole temperature range and its resistivity exhibits a kink anomaly at T_(M),characteristic of critical scattering around a magnetic transition.Recovery of the Raman spectrum upon decompression indicated that pressure-induced structural transition is reversible without amorphization under hydrostatic pressure conditions.Our present work not only resolves some existing controversial issues but also provides new insights into pressure-driven diverse behaviors of Mn_(3)Si_(2)Te_(6).展开更多
A longstanding discrepancy between theoretical predictions and experimental observations on the highpressurestructural transformations of lanthanum mononitride(LaN)has posed challenges for understandingthe behavior of...A longstanding discrepancy between theoretical predictions and experimental observations on the highpressurestructural transformations of lanthanum mononitride(LaN)has posed challenges for understandingthe behavior of heavy transition metal mononitrides.Here,we systematically investigate the structural evolutionof LaN under high pressure using first-principles calculations combined with angle-dispersive synchrotron X-raydiffraction,identifying the phase transition sequence and corresponding phase boundaries.Analyses of energetics,kinetic barriers,and lattice dynamics reveal distinct mechanisms driving these transitions.These results clarifythe structural stability of LaN and offer guidance for studying other heavy transition metal mononitrides withcomplex electronic behavior under extreme conditions.展开更多
In the context of climate change,the acceleration of the global water cycle has led to the emergence of abrupt transitions between drought and flood events,presenting a new challenge for flood and drought disaster mit...In the context of climate change,the acceleration of the global water cycle has led to the emergence of abrupt transitions between drought and flood events,presenting a new challenge for flood and drought disaster mitigation.Abrupt transitions between drought and flood refer to a phenomenon in which an extreme drought event quickly shifts to an extreme flood event,or vice versa,within a relatively short time span.This phenomenon disrupts the traditional spatiotemporal distribution patterns of water-related disasters,reflecting not only the extreme unevenness in the distribution of water resources but also the rapid alternation of the water cycle's evolution(He et al.,2016).Moreover,due to its suddenness,extremity,and complexity,it poses severe threats to human societies and ecosystems.Scientifically addressing abrupt transitions between drought and flood has thus become a new challenge in flood and drought disaster prevention.展开更多
The development of luminescent radicals withα-type transition properties is significant for advancing the understanding of luminescence mechanisms and photophysical properties in radical-based systems.Here,we present...The development of luminescent radicals withα-type transition properties is significant for advancing the understanding of luminescence mechanisms and photophysical properties in radical-based systems.Here,we present a straightforward strategy for acquiring stable luminescent radicals withα-type transition by directly decorating bis(2,4,6-trichlorophenyl)methyl radicals(BTM)-based luminescent radicals with strong electron acceptors.This approach effectively narrows the energy gap between the singly occupied molecular orbital(SOMOα)and lowest doubly unoccupied molecular orbital(LUMOα)(ΔE_(SOMOα→LOMOα)),enabling a transform of luminescent radicals from the conventionalβ-type transition to the rareα-type transition upon D_(0)→D_(1)excitation process.Theα-type transition was experimentally validated through the fabrication of organic light-emitting diodes(OLEDs)incorporating appropriate host materials.The result also expands the selection of available host materials for OLED devices exploiting radicals as emitters,as more host materials with higher highest occupied molecular orbital(HOMO)can now be considered.This work not only establishes a rational molecular design strategy for luminescent radicals withα-type transition but also provides valuable insights to guide future research in radical-based optoelectronic materials.展开更多
This letter presents a method for probing the attosecond time delay between two radiatively resonant transitions from Fano structures,which arise from interference between the extreme ultraviolet free induction decay(...This letter presents a method for probing the attosecond time delay between two radiatively resonant transitions from Fano structures,which arise from interference between the extreme ultraviolet free induction decay(XFID)emission and high-order harmonics.The ellipticity dependence of the Ne^(+)XFID yield confirms that the ionic excited-state populations originate from inelastic recollision between tunneling electrons and parent ions.Subsequent extraction of relative phases from Fano structures enables the determination of the time delay(~22 as)between the two decay pathways.This work provides an experimental approach to probe the attosecond time delay between different XFID channels and contributes to a deeper understanding of the tunneling-plusrescattering model in strong laser fields.展开更多
Elucidating the relationship between spin excitations and fermiology is essential for clarifying the pairing mechanism in iron-based superconductors(FeSCs).Here,we report inelastic neutron scattering results on the ho...Elucidating the relationship between spin excitations and fermiology is essential for clarifying the pairing mechanism in iron-based superconductors(FeSCs).Here,we report inelastic neutron scattering results on the hole overdoped Ba_(0.4)K_(0.6)Fe_(2)As_(2) near a Lifshitz transition,where the electron pocket at M point is nearly replaced by four hole pockets.In the normal state,the spin excitations is observed at incommensurate wave vectors with a chimney-like dispersion.By cooling down to the superconducting state,a neutron spin resonance mode emerges with a peak energy of Er=14-15 meV,weakly modulated along the L-direction.The incommensurability notably increases at low energies,giving rise to downward dispersions of the resonance mode.This behavior contrasts sharply with the upward dispersions of resonance observed in optimally doped Ba_(0.67)K_(0.33)Fe_(2)As_(2) contributed by the hole to electron scattering,but resembles those in KFe_(2)As_(2) and KCa_(2)Fe_(4)As_(4)F_(2) where the fermiology is dominated by hole pockets.These results highlight the critical role of electronic structure modifications near the Fermi level,especially in governing interband scattering under imperfect nesting conditions,which fundamentally shape the spin dynamics of FeSCs.展开更多
Non-iterative analysis of indentation results allows for the detection of phase transitions under load and their transition energy. The closed algebraic equations have been deduced on the basis of the physically found...Non-iterative analysis of indentation results allows for the detection of phase transitions under load and their transition energy. The closed algebraic equations have been deduced on the basis of the physically founded normal force ?depth3/2 relation. The precise transition onset position is obtained by linear regression of the FN = kh3/2 plot, where k is the penetration resistance, which also provides the axis cuts of both polymorphs of first order phase transitions. The phase changes can be endothermic or exothermic. They are normalized per μN or mN normal load. The analyses of indentation loading curves with self-similar diamond indenters are used as validity check of the loading curves, also from calibration standards that exhibit previously undetected phase-transitions and are thus incorrect. The phase-transition energies for fused quartz are determined from the loading curves from instrument provider handbooks. The anisotropic behavior of phase transition energies is studied for the first time. Quartz is a useful test object. The reasons for the packing-dependent differences are discussed on the basis of the local crystal structure under and around the inserting tip.展开更多
Phase transitions,as one of the most intriguing phenomena in nature,are divided into first-order phase transitions(FOPTs)and continuous ones in current classification.While the latter shows striking phenomena of scali...Phase transitions,as one of the most intriguing phenomena in nature,are divided into first-order phase transitions(FOPTs)and continuous ones in current classification.While the latter shows striking phenomena of scaling and universality,the former has recently also been demonstrated to exhibit scaling and universal behavior within a mesoscopic,coarse-grained Landau-Ginzburg theory.Here we apply this theory to a microscopic model-the paradigmatic Ising model,which undergoes FOPTs between two ordered phases below its critical temperature-and unambiguously demonstrate universal scaling behavior in such FOPTs.These results open the door for extending the theory to other microscopic FOPT systems and experimentally testing them to systematically uncover their scaling and universal behavior.展开更多
The ductile-to-brittle transition temperature(DBTT)of high strength steels can be optimized by tailoring microstructure and crystallographic orientation characteristics,where the start cooling temperature plays a key ...The ductile-to-brittle transition temperature(DBTT)of high strength steels can be optimized by tailoring microstructure and crystallographic orientation characteristics,where the start cooling temperature plays a key role.In this work,X70 steels with different start cooling temperatures were prepared through thermo-mechanical control process.The quasi-polygonal ferrite(QF),granular bainite(GB),bainitic ferrite(BF)and martensite-austenite constituents were formed at the start cooling temperatures of 780℃(C1),740℃(C2)and 700℃(C3).As start cooling temperature decreased,the amount of GB decreased,the microstructure of QF and BF increased.Microstructure characteristics of the three samples,such as high-angle grain boundaries(HAGBs),MA constituents and crystallographic orientation,also varied with the start cooling temperatures.C2 sample had the lowest DBTT value(−86℃)for its highest fraction of HAGBs,highest content of<110>oriented grains and lowest content of<001>oriented grains parallel to TD.The high density of{332}<113>and low density of rotated cube{001}<110>textures also contributed to the best impact toughness of C2 sample.In addition,a modified model was used in this paper to quantitatively predict the approximate DBTT value of steels.展开更多
There is a growing recognition of the critical role of security governance in advancing democratic transition in the post-conflict environment.Despite such a recognition,the security sector reform concept has overshad...There is a growing recognition of the critical role of security governance in advancing democratic transition in the post-conflict environment.Despite such a recognition,the security sector reform concept has overshadowed the importance of the overarching strategic role of security governance in transition to democracy,particularly in Africa.This paper assesses the status and challenges facing security governance and how they thwarted the efforts to furthering the democratic transition in South Sudan.The paper shows a deterioration in security,safety and security governance outcomes since the independence of South Sudan in 2011 with such a trend unlikely to be abated in the near future without strategic interventions.Some of the challenges facing security governance in South Sudan include the legacies of some historical events including the“Big Tent Policy”,absence of strategic leadership,lack of overarching policy framework,impractical and tenuous security arrangements in the 2018 peace agreement,persistent postponement of the first elections,and dysfunctional justice sector.The paper provides some strategic and operational recommendations to improve security governance and advance democratic transition in South Sudan.These recommendations include formulation of an inclusive and people-centered national security policy,rigorous judicial reform,and early political agreement on new political infrastructure if conditions for holding the first national elections are not met in 2026.展开更多
ASEAN and China have built the most successful and dynamic model of regional cooperation in the Asia-Pacific region or even the whole world.Both are each other’s largest trading partners.China has maintained as ASEAN...ASEAN and China have built the most successful and dynamic model of regional cooperation in the Asia-Pacific region or even the whole world.Both are each other’s largest trading partners.China has maintained as ASEAN’s top trading partner for 16 consecutive years,and ASEAN has been China’s largest trading partner for five consecutive years.In 2024,the total bilateral trade volume approached 1 trillion US dollars,with a year-on-year increase of 7.8%.China is ASEAN’s second-largest source of foreign investment,and ASEAN is also an important source of foreign investment for China.Pragmatic cooperation between the two sides in various fields has been deepening continuously.展开更多
Due to the coexistence of compressibility,viscosity,and threedimensional effects,laminar flow is difficult to maintain for high-speed boundary layer on complex geometries.The unstable disturbance waves in the boundary...Due to the coexistence of compressibility,viscosity,and threedimensional effects,laminar flow is difficult to maintain for high-speed boundary layer on complex geometries.The unstable disturbance waves in the boundary layer are excited and rapidly increase during the receptivity process,so sufficiently large Reynolds stress causes the basic flow velocity profile to change,and the formation of turbulence is inevitable.展开更多
The authors regret<During the submission process,Hongxiang Zhang and Honggen Peng served as the first and the second corresponding author,respectively.The original manuscript submitted for this paper also listed tw...The authors regret<During the submission process,Hongxiang Zhang and Honggen Peng served as the first and the second corresponding author,respectively.The original manuscript submitted for this paper also listed two co-corresponding authors(Hongxiang Zhang and Honggen Peng).But the corresponding author of Honggen Peng was omitted in the final published manuscript.So,we apply to designate Honggen Peng(penghonggen@ncu.edu.cn)as the second co-corresponding author and the corresponding unit is“a,b">.展开更多
Plp1-lineage Schwann cells(SCs)of peripheral nerve play a critical role in vascular remodeling and osteogenic differentiation during the early stage of bone healing,and the abnormal plasticity of SCs would jeopardize ...Plp1-lineage Schwann cells(SCs)of peripheral nerve play a critical role in vascular remodeling and osteogenic differentiation during the early stage of bone healing,and the abnormal plasticity of SCs would jeopardize the bone regeneration.However,how Plp1-lineage cells respond to injury and initiate the vascularized osteogenesis remains incompletely understood.Here,by employing single-cell transcriptional profiling combined with lineage-specific tracing models,we uncover that Plp1-lineage cells undergoing injury-induced glia-to-MSCs transition contributed to osteogenesis and revascularization in the initial stage of bone injury.Importantly,our data demonstrated that the Sonic hedgehog(Shh)signaling was responsible for the transition process initiation,which was strongly activated by c-Jun/SIRT6/BAF170 complex-driven Shh enhancers.Collectively,these findings depict an injuryspecific niche signal-mediated Plp1-lineage cells transition towards Gli1+MSCs and may be instructive for approaches to promote bone regeneration during aging or other bone diseases.展开更多
Two-dimensional(2D)fully compensated collinear magnetic materials ofer signifcant advantages for spintronic applications,including robustness against magnetic feld perturbations,no stray felds,and ultrafast dynamics.A...Two-dimensional(2D)fully compensated collinear magnetic materials ofer signifcant advantages for spintronic applications,including robustness against magnetic feld perturbations,no stray felds,and ultrafast dynamics.Among these materials,fully compensated ferrimagnets are particularly promising due to their unique characteristics such as the magneto-optical efect,completely spin-polarized currents,and the anomalous Hall efect.We performed a structural search on 2D unconventional stoichiometric Cr-I crystals using a global optimization algorithm.The most stable CrI-P21/m monolayer is a fully compensated ferrimagnetic semiconductor with a band gap of 1.57 eV and a high magnetic transition temperature of 592 K.The spontaneous spin splitting in CrI-P21/m originates from the inequivalent local coordination environments of Cr^(1)and Cr^(2)ions,yielding a mismatch in their 3d orbitals splitting.Notably,carrier doping at a concentration of 0.01 electrons or holes per atom enables reversible spin polarization,generating a fully spin-polarized current in CrI-P21/m.This performance makes it a highly promising candidate for spintronic devices.Our fndings not only provide a structural paradigm for discovering fully compensated ferrimagnets but also open a new avenue for designing zero-moment magnetic materials with intrinsic spin splitting.展开更多
Recent studies have successfully demonstrated high-Tc superconductivity in bilayer nickelate La3Ni2O7.However,research on modulating the structural and transport characteristics of La3Ni2O7 films by applying“chemical...Recent studies have successfully demonstrated high-Tc superconductivity in bilayer nickelate La3Ni2O7.However,research on modulating the structural and transport characteristics of La3Ni2O7 films by applying“chemical”compressive pressure through cation substitution is still limited.Here,we address this issue in the La_(3−x)Nd_(x)Ni_(2)O_(7)(x=0,1.0,1.5,2.0,and 2.5)thin film samples.It was found that using Nd3+with a smaller radius instead of La3+can reduce the c-axis lattice constant and shift the metal-insulator transition(MIT)temperature TMIT.To probe the origin of the MIT at cryogenic temperatures,experimental measurements of magnetoresistance were conducted,and theoretical analysis was carried out using the Kondo model,Hikami-Larkin-Nagaoka equation,and other methods.The results indicate that as Nd doping rises,the contributions of the Kondo effect and two-dimensional weak localization(WL)first decrease and then increase.The total contribution of WL and the Kondo effect in the mid-doped La_(1.5)Nd_(1.5)Ni_(2)O_(7)sample was the smallest,which to some extent explains the changes in TMIT.The Kondo effect dominates in other La_(3−x)Nd_(x)Ni_(2)O_(7)(x=0,1.0,2.0,and 2.5)samples.This work demonstrates that cation doping has a significant impact on bilayer nickelates,providing experimental evidence for understanding the physical mechanism of the MIT in bilayer nickelates.展开更多
Clinical translation of tissue-engineered advanced therapeutic medicinal products is hindered by a lack of patient-dependent and independent in-process biological quality controls that are reflective of in vivo outcom...Clinical translation of tissue-engineered advanced therapeutic medicinal products is hindered by a lack of patient-dependent and independent in-process biological quality controls that are reflective of in vivo outcomes.Recent insights into the mechanism of native bone repair highlight a robust path dependence.Organoid-based bottom-up developmental engineering mimics this pathdependence to design personalized living implants scaffold-free,with in-build outcome predictability.Yet,adequate(noninvasive)quality metrics of engineered tissues are lacking.Moreover,insufficient insight into the role of donor variability and biological sex as influencing factors for the mechanism toward bone repair hinders the implementation of such protocols for personalized bone implants.Here,male and female bone-forming organoids were compared to non-bone-forming organoids regarding their extracellular matrix composition,transcriptome,and secreted proteome signatures to directly link in vivo outcomes to quality metrics.As a result,donor variability in bone-forming callus organoids pointed towards two distinct pathways to bone,through either a hypertrophic cartilage or a fibrocartilaginous template.The followed pathway was determined early,as a biological sexdependent activation of distinct progenitor populations.Independent of donor or biological sex,a cartilage-to-bone transition was driven by a common panel of secreted factors that played a role in extracellular matrix remodeling,mineralization,and attraction of vasculature.Hence,the secreted proteome is a source of noninvasive biomarkers that report on biological potency and could be the missing link toward data-driven decision-making in organoid-based bone tissue engineering.展开更多
Exosomes have shown good potential in ischemic injury disease treatments.However,evidence about their effect and molecular mechanisms in osteonecrosis of femoral head(ONFH)treatment is still limited.Here,we revealed t...Exosomes have shown good potential in ischemic injury disease treatments.However,evidence about their effect and molecular mechanisms in osteonecrosis of femoral head(ONFH)treatment is still limited.Here,we revealed the cell biology characters of ONFH osteonecrosis area bone tissue in single cell scale and thus identified a novel ONFH treatment approach based on M2 macrophages-derived exosomes(M2-Exos).We further show that M2-Exos are highly effective in the treatment of ONFH by modulating the phenotypes communication between neutrophil and endothelium including neutrophil extracellular traps formation and endothelial phenotype transition.Additionally,we identified that M2-Exos’therapeutic effect is attributed to the high content of miR-93-5p and constructed miR-93-5p overexpression model in vitro and in vivo based on lentivirus and adenoassociated virus respectively.Then we found miR-93-5p can not only reduce neutrophil extracellular traps formation but also improve angiogenic ability of endothelial cells.These results provided a new theoretical basis for the clinical application of ONFH therapeutic exosomes.展开更多
文摘Several significant events of a geological nature occurred approximately 800 ka before the present: (1) Australasian tektite fall (AA), (2) Brunhes-Matuyama geomagnetic reversal (BMR), (3) mid-Pleistocene changes in ice age cycles. Add to these the undated fault system (4) in the South-West (SW) of the South China Sea (SCS). Here we offer a unified cause for all four of these in (5), an impact in the SCS of a large, massive cosmic object, likely a comet, obliquely coming from the SW at an extremely shallow angle, striking the Sunda shelf yet unexploded with the shock of its compressed air bow wave, and causing the continual shelf and slope to collapse, resulting in the fault system (4), then traveling almost tangentially to the surface, exploding at impact with the sea surface, ejecting the tektites (1), creating the formation underlying the later atolls of Spratlies Archipelago (6), Nansha Islands in Chinese, & causing the BMR (2). An explanation of event (3) was Richard Muller’s hypothesis of planet Earth passing through an interplanetary dust cloud periodically due to ecliptic precession. Here we hypothesize this cloud actually is a belt of Australasian tektites ejected into space at super-orbital velocities that Earth encounters about every 100 ka.
文摘A transformation of the electron states—say those enclosed in a potential box—into the de Broglie waves done in the paper, enabled us to calculate the energy change between two quantum levels as a function of the specific heat and difference of the temperature between the states. In consequence, the energy difference and that of entropy between the levels could be examined in terms of the appropriate classical parameters. In the next step, the time interval necessary for the electron transition between the levels could be associated with the classical electrodynamical parameters like the electric resistance and capacitance connected with the temporary formation of the electric cell in course of the transition. The parameters characterizing the mechanical inertia of the electron were next used as a check of the electrodynamical formulae referring to transition.
基金supported by the National Key R&D Program of China (Grant Nos. 2023YFA1406100, 2022YFA1403900, 2024YFA1408400, 2021YFA1400200, 2022YFA1403800, and 2023YFA1406500)the National Natural Science Foundation of China (Grant Nos. 12174424, 12025408, 11921004, U22A6005, and 12274459)+1 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences (Grant No. 2023007)the Chinese Academy of Sciences President’s International Fellowship Initiative (Grant No. 2024PG0003)。
文摘Mn_(3)Si_(2)Te_(6) is a ferrimagnetic nodal-line semiconductor with colossal angular magnetoresistance at ambient pressure.In this work,we investigated the effect of hydrostatic pressure on its electrical transport properties,magnetic transition,and crystal structure by measuring resistivity,DC and AC magnetic susceptibility,and XRD under various pressures up to~20 GPa.Our results confirmed the occurrence of pressure-induced structural transition at P_(c)≈10–12 GPa accompanied by a concurrent drop of room-temperature resistance in Mn_(3)Si_(2)Te_(6).In the low-pressure phase at PP_(c),the sample exhibits a metallic behavior in the whole temperature range and its resistivity exhibits a kink anomaly at T_(M),characteristic of critical scattering around a magnetic transition.Recovery of the Raman spectrum upon decompression indicated that pressure-induced structural transition is reversible without amorphization under hydrostatic pressure conditions.Our present work not only resolves some existing controversial issues but also provides new insights into pressure-driven diverse behaviors of Mn_(3)Si_(2)Te_(6).
基金supported by the Natural Science Foundation of China(Grant Nos.T2325013,12474004,and 52288102)the National Key Research and Development Program of China(Grant No.2021YFA1400503)the Program for Jilin University Science and Technology Innovative Research Team。
文摘A longstanding discrepancy between theoretical predictions and experimental observations on the highpressurestructural transformations of lanthanum mononitride(LaN)has posed challenges for understandingthe behavior of heavy transition metal mononitrides.Here,we systematically investigate the structural evolutionof LaN under high pressure using first-principles calculations combined with angle-dispersive synchrotron X-raydiffraction,identifying the phase transition sequence and corresponding phase boundaries.Analyses of energetics,kinetic barriers,and lattice dynamics reveal distinct mechanisms driving these transitions.These results clarifythe structural stability of LaN and offer guidance for studying other heavy transition metal mononitrides withcomplex electronic behavior under extreme conditions.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFC3209800)the National Natural Science Foundation of China(Grant No.52279011).
文摘In the context of climate change,the acceleration of the global water cycle has led to the emergence of abrupt transitions between drought and flood events,presenting a new challenge for flood and drought disaster mitigation.Abrupt transitions between drought and flood refer to a phenomenon in which an extreme drought event quickly shifts to an extreme flood event,or vice versa,within a relatively short time span.This phenomenon disrupts the traditional spatiotemporal distribution patterns of water-related disasters,reflecting not only the extreme unevenness in the distribution of water resources but also the rapid alternation of the water cycle's evolution(He et al.,2016).Moreover,due to its suddenness,extremity,and complexity,it poses severe threats to human societies and ecosystems.Scientifically addressing abrupt transitions between drought and flood has thus become a new challenge in flood and drought disaster prevention.
基金supported by the 2025 Jilin Province Doctoral Research Innovation Capability Enhancement Project(grant no.JJKH20250062BS)National Natural Science Foundation of China(grant no.51925303).
文摘The development of luminescent radicals withα-type transition properties is significant for advancing the understanding of luminescence mechanisms and photophysical properties in radical-based systems.Here,we present a straightforward strategy for acquiring stable luminescent radicals withα-type transition by directly decorating bis(2,4,6-trichlorophenyl)methyl radicals(BTM)-based luminescent radicals with strong electron acceptors.This approach effectively narrows the energy gap between the singly occupied molecular orbital(SOMOα)and lowest doubly unoccupied molecular orbital(LUMOα)(ΔE_(SOMOα→LOMOα)),enabling a transform of luminescent radicals from the conventionalβ-type transition to the rareα-type transition upon D_(0)→D_(1)excitation process.Theα-type transition was experimentally validated through the fabrication of organic light-emitting diodes(OLEDs)incorporating appropriate host materials.The result also expands the selection of available host materials for OLED devices exploiting radicals as emitters,as more host materials with higher highest occupied molecular orbital(HOMO)can now be considered.This work not only establishes a rational molecular design strategy for luminescent radicals withα-type transition but also provides valuable insights to guide future research in radical-based optoelectronic materials.
基金supported by the National Natural Science Foundation of China(Grant Nos.12234020,12474281,12450403,and 12274461)the Science and Technology Innovation Program of Hunan Province(Grant No.2022RC1193).
文摘This letter presents a method for probing the attosecond time delay between two radiatively resonant transitions from Fano structures,which arise from interference between the extreme ultraviolet free induction decay(XFID)emission and high-order harmonics.The ellipticity dependence of the Ne^(+)XFID yield confirms that the ionic excited-state populations originate from inelastic recollision between tunneling electrons and parent ions.Subsequent extraction of relative phases from Fano structures enables the determination of the time delay(~22 as)between the two decay pathways.This work provides an experimental approach to probe the attosecond time delay between different XFID channels and contributes to a deeper understanding of the tunneling-plusrescattering model in strong laser fields.
基金supported by the National Key Research and Development Program of China(Grant Nos.2023YFA1406100,2018YFA0704200,2022YFA1403400 and 2021YFA1400400)the National Natural Science Foundation of China(Grant Nos.11822411 and 12274444)+2 种基金the Strategic Priority Research Program(B)of the CAS(Grant Nos.XDB25000000 and XDB33000000)K.C.Wong Education Foundation(GJTD-2020-01)AP by HBNI-RRCAT and MPCST under the FTYS program。
文摘Elucidating the relationship between spin excitations and fermiology is essential for clarifying the pairing mechanism in iron-based superconductors(FeSCs).Here,we report inelastic neutron scattering results on the hole overdoped Ba_(0.4)K_(0.6)Fe_(2)As_(2) near a Lifshitz transition,where the electron pocket at M point is nearly replaced by four hole pockets.In the normal state,the spin excitations is observed at incommensurate wave vectors with a chimney-like dispersion.By cooling down to the superconducting state,a neutron spin resonance mode emerges with a peak energy of Er=14-15 meV,weakly modulated along the L-direction.The incommensurability notably increases at low energies,giving rise to downward dispersions of the resonance mode.This behavior contrasts sharply with the upward dispersions of resonance observed in optimally doped Ba_(0.67)K_(0.33)Fe_(2)As_(2) contributed by the hole to electron scattering,but resembles those in KFe_(2)As_(2) and KCa_(2)Fe_(4)As_(4)F_(2) where the fermiology is dominated by hole pockets.These results highlight the critical role of electronic structure modifications near the Fermi level,especially in governing interband scattering under imperfect nesting conditions,which fundamentally shape the spin dynamics of FeSCs.
文摘Non-iterative analysis of indentation results allows for the detection of phase transitions under load and their transition energy. The closed algebraic equations have been deduced on the basis of the physically founded normal force ?depth3/2 relation. The precise transition onset position is obtained by linear regression of the FN = kh3/2 plot, where k is the penetration resistance, which also provides the axis cuts of both polymorphs of first order phase transitions. The phase changes can be endothermic or exothermic. They are normalized per μN or mN normal load. The analyses of indentation loading curves with self-similar diamond indenters are used as validity check of the loading curves, also from calibration standards that exhibit previously undetected phase-transitions and are thus incorrect. The phase-transition energies for fused quartz are determined from the loading curves from instrument provider handbooks. The anisotropic behavior of phase transition energies is studied for the first time. Quartz is a useful test object. The reasons for the packing-dependent differences are discussed on the basis of the local crystal structure under and around the inserting tip.
基金supported by the National Natural Science Foundation of China(Grant No.12175316).
文摘Phase transitions,as one of the most intriguing phenomena in nature,are divided into first-order phase transitions(FOPTs)and continuous ones in current classification.While the latter shows striking phenomena of scaling and universality,the former has recently also been demonstrated to exhibit scaling and universal behavior within a mesoscopic,coarse-grained Landau-Ginzburg theory.Here we apply this theory to a microscopic model-the paradigmatic Ising model,which undergoes FOPTs between two ordered phases below its critical temperature-and unambiguously demonstrate universal scaling behavior in such FOPTs.These results open the door for extending the theory to other microscopic FOPT systems and experimentally testing them to systematically uncover their scaling and universal behavior.
基金Project(2018XK2301) supported by the Change-Zhu-Tan National Independent Innavation Demonstration Zone Special Program,China。
文摘The ductile-to-brittle transition temperature(DBTT)of high strength steels can be optimized by tailoring microstructure and crystallographic orientation characteristics,where the start cooling temperature plays a key role.In this work,X70 steels with different start cooling temperatures were prepared through thermo-mechanical control process.The quasi-polygonal ferrite(QF),granular bainite(GB),bainitic ferrite(BF)and martensite-austenite constituents were formed at the start cooling temperatures of 780℃(C1),740℃(C2)and 700℃(C3).As start cooling temperature decreased,the amount of GB decreased,the microstructure of QF and BF increased.Microstructure characteristics of the three samples,such as high-angle grain boundaries(HAGBs),MA constituents and crystallographic orientation,also varied with the start cooling temperatures.C2 sample had the lowest DBTT value(−86℃)for its highest fraction of HAGBs,highest content of<110>oriented grains and lowest content of<001>oriented grains parallel to TD.The high density of{332}<113>and low density of rotated cube{001}<110>textures also contributed to the best impact toughness of C2 sample.In addition,a modified model was used in this paper to quantitatively predict the approximate DBTT value of steels.
文摘There is a growing recognition of the critical role of security governance in advancing democratic transition in the post-conflict environment.Despite such a recognition,the security sector reform concept has overshadowed the importance of the overarching strategic role of security governance in transition to democracy,particularly in Africa.This paper assesses the status and challenges facing security governance and how they thwarted the efforts to furthering the democratic transition in South Sudan.The paper shows a deterioration in security,safety and security governance outcomes since the independence of South Sudan in 2011 with such a trend unlikely to be abated in the near future without strategic interventions.Some of the challenges facing security governance in South Sudan include the legacies of some historical events including the“Big Tent Policy”,absence of strategic leadership,lack of overarching policy framework,impractical and tenuous security arrangements in the 2018 peace agreement,persistent postponement of the first elections,and dysfunctional justice sector.The paper provides some strategic and operational recommendations to improve security governance and advance democratic transition in South Sudan.These recommendations include formulation of an inclusive and people-centered national security policy,rigorous judicial reform,and early political agreement on new political infrastructure if conditions for holding the first national elections are not met in 2026.
文摘ASEAN and China have built the most successful and dynamic model of regional cooperation in the Asia-Pacific region or even the whole world.Both are each other’s largest trading partners.China has maintained as ASEAN’s top trading partner for 16 consecutive years,and ASEAN has been China’s largest trading partner for five consecutive years.In 2024,the total bilateral trade volume approached 1 trillion US dollars,with a year-on-year increase of 7.8%.China is ASEAN’s second-largest source of foreign investment,and ASEAN is also an important source of foreign investment for China.Pragmatic cooperation between the two sides in various fields has been deepening continuously.
文摘Due to the coexistence of compressibility,viscosity,and threedimensional effects,laminar flow is difficult to maintain for high-speed boundary layer on complex geometries.The unstable disturbance waves in the boundary layer are excited and rapidly increase during the receptivity process,so sufficiently large Reynolds stress causes the basic flow velocity profile to change,and the formation of turbulence is inevitable.
文摘The authors regret<During the submission process,Hongxiang Zhang and Honggen Peng served as the first and the second corresponding author,respectively.The original manuscript submitted for this paper also listed two co-corresponding authors(Hongxiang Zhang and Honggen Peng).But the corresponding author of Honggen Peng was omitted in the final published manuscript.So,we apply to designate Honggen Peng(penghonggen@ncu.edu.cn)as the second co-corresponding author and the corresponding unit is“a,b">.
基金supported by the National Natural Science Foundation of China(grants 81970910 and 82370931)Jiangsu Province Capability Improvement Project through Science,Technology and Education-Jiangsu Provincial Research Hospital Cultivation Unit(YJXYYJSDW4)Jiangsu Provincial Medical Innovation Center(CXZX202227).
文摘Plp1-lineage Schwann cells(SCs)of peripheral nerve play a critical role in vascular remodeling and osteogenic differentiation during the early stage of bone healing,and the abnormal plasticity of SCs would jeopardize the bone regeneration.However,how Plp1-lineage cells respond to injury and initiate the vascularized osteogenesis remains incompletely understood.Here,by employing single-cell transcriptional profiling combined with lineage-specific tracing models,we uncover that Plp1-lineage cells undergoing injury-induced glia-to-MSCs transition contributed to osteogenesis and revascularization in the initial stage of bone injury.Importantly,our data demonstrated that the Sonic hedgehog(Shh)signaling was responsible for the transition process initiation,which was strongly activated by c-Jun/SIRT6/BAF170 complex-driven Shh enhancers.Collectively,these findings depict an injuryspecific niche signal-mediated Plp1-lineage cells transition towards Gli1+MSCs and may be instructive for approaches to promote bone regeneration during aging or other bone diseases.
基金supported by the Natural Science Foundation of Wenzhou Institute,University of Chinese Academy of Sciences(UCAS)(Grant No.WIUCASQD2023004)the National Natural Science Foundation of China(Grant Nos.12304006,12404265,and 12435001)+2 种基金the Natural Science Foundation of Shanghai,China(Grant No.23JC1401400)the Natural Science Foundation of Wenzhou(Grant No.L2023005)the Fundamental Research Funds for the Central Universities of East China University of Science and Technology。
文摘Two-dimensional(2D)fully compensated collinear magnetic materials ofer signifcant advantages for spintronic applications,including robustness against magnetic feld perturbations,no stray felds,and ultrafast dynamics.Among these materials,fully compensated ferrimagnets are particularly promising due to their unique characteristics such as the magneto-optical efect,completely spin-polarized currents,and the anomalous Hall efect.We performed a structural search on 2D unconventional stoichiometric Cr-I crystals using a global optimization algorithm.The most stable CrI-P21/m monolayer is a fully compensated ferrimagnetic semiconductor with a band gap of 1.57 eV and a high magnetic transition temperature of 592 K.The spontaneous spin splitting in CrI-P21/m originates from the inequivalent local coordination environments of Cr^(1)and Cr^(2)ions,yielding a mismatch in their 3d orbitals splitting.Notably,carrier doping at a concentration of 0.01 electrons or holes per atom enables reversible spin polarization,generating a fully spin-polarized current in CrI-P21/m.This performance makes it a highly promising candidate for spintronic devices.Our fndings not only provide a structural paradigm for discovering fully compensated ferrimagnets but also open a new avenue for designing zero-moment magnetic materials with intrinsic spin splitting.
基金supported by the Natural Science Foundation of Guangdong Province of China(Grant No.2025A1515011071)the National Natural Science Foundation of China(Grant Nos.92065110,11974048,and 12074334)the Beijing Municipal Natural Science Foundation Key Research Topics(Grant No.Z230006)。
文摘Recent studies have successfully demonstrated high-Tc superconductivity in bilayer nickelate La3Ni2O7.However,research on modulating the structural and transport characteristics of La3Ni2O7 films by applying“chemical”compressive pressure through cation substitution is still limited.Here,we address this issue in the La_(3−x)Nd_(x)Ni_(2)O_(7)(x=0,1.0,1.5,2.0,and 2.5)thin film samples.It was found that using Nd3+with a smaller radius instead of La3+can reduce the c-axis lattice constant and shift the metal-insulator transition(MIT)temperature TMIT.To probe the origin of the MIT at cryogenic temperatures,experimental measurements of magnetoresistance were conducted,and theoretical analysis was carried out using the Kondo model,Hikami-Larkin-Nagaoka equation,and other methods.The results indicate that as Nd doping rises,the contributions of the Kondo effect and two-dimensional weak localization(WL)first decrease and then increase.The total contribution of WL and the Kondo effect in the mid-doped La_(1.5)Nd_(1.5)Ni_(2)O_(7)sample was the smallest,which to some extent explains the changes in TMIT.The Kondo effect dominates in other La_(3−x)Nd_(x)Ni_(2)O_(7)(x=0,1.0,2.0,and 2.5)samples.This work demonstrates that cation doping has a significant impact on bilayer nickelates,providing experimental evidence for understanding the physical mechanism of the MIT in bilayer nickelates.
基金financed by the Hercules Foundation(project AKUL/13/47)funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 874837+2 种基金supported by the Flemish Government(department of Economy,Science and Innovation)through the Regenerative Medicine Crossing Borders(http://www.regmedxb.com)initiativeImages were recorded on a Zeiss LSM 780-SP Mai Tai HP DS(Cell and Tissue Imaging Cluster(CIC),Supported by Hercules AKUL/11/37 and FWO G.0929.15 to Pieter Vanden Berghe,University of Leuvensupported by Interne Fondsen KU Leuven/Internal Funds KU Leuven grant numbers C24M/22/058.
文摘Clinical translation of tissue-engineered advanced therapeutic medicinal products is hindered by a lack of patient-dependent and independent in-process biological quality controls that are reflective of in vivo outcomes.Recent insights into the mechanism of native bone repair highlight a robust path dependence.Organoid-based bottom-up developmental engineering mimics this pathdependence to design personalized living implants scaffold-free,with in-build outcome predictability.Yet,adequate(noninvasive)quality metrics of engineered tissues are lacking.Moreover,insufficient insight into the role of donor variability and biological sex as influencing factors for the mechanism toward bone repair hinders the implementation of such protocols for personalized bone implants.Here,male and female bone-forming organoids were compared to non-bone-forming organoids regarding their extracellular matrix composition,transcriptome,and secreted proteome signatures to directly link in vivo outcomes to quality metrics.As a result,donor variability in bone-forming callus organoids pointed towards two distinct pathways to bone,through either a hypertrophic cartilage or a fibrocartilaginous template.The followed pathway was determined early,as a biological sexdependent activation of distinct progenitor populations.Independent of donor or biological sex,a cartilage-to-bone transition was driven by a common panel of secreted factors that played a role in extracellular matrix remodeling,mineralization,and attraction of vasculature.Hence,the secreted proteome is a source of noninvasive biomarkers that report on biological potency and could be the missing link toward data-driven decision-making in organoid-based bone tissue engineering.
基金the support of the National Natural Science Foundation of China (Grant No.82272503)Natural Science Foundation of Zhejiang Province (Grant No. LQN25H060006)
文摘Exosomes have shown good potential in ischemic injury disease treatments.However,evidence about their effect and molecular mechanisms in osteonecrosis of femoral head(ONFH)treatment is still limited.Here,we revealed the cell biology characters of ONFH osteonecrosis area bone tissue in single cell scale and thus identified a novel ONFH treatment approach based on M2 macrophages-derived exosomes(M2-Exos).We further show that M2-Exos are highly effective in the treatment of ONFH by modulating the phenotypes communication between neutrophil and endothelium including neutrophil extracellular traps formation and endothelial phenotype transition.Additionally,we identified that M2-Exos’therapeutic effect is attributed to the high content of miR-93-5p and constructed miR-93-5p overexpression model in vitro and in vivo based on lentivirus and adenoassociated virus respectively.Then we found miR-93-5p can not only reduce neutrophil extracellular traps formation but also improve angiogenic ability of endothelial cells.These results provided a new theoretical basis for the clinical application of ONFH therapeutic exosomes.
