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OBJECTIVES: To conduct an in-depth study on the spatial distribution of traffic conflicts in the continuous merging areas of cross-river bridges and ensure public transportation safety. METHODS: First, we utilized drone aerial photography to collect videos of vehicle movements. Using the YOLOv7 object detection algorithm and the Strong SORT multi-object tracking algorithm, we extracted high-precision vehicle trajectory time-series data. Next, based on the motion characteristics of traffic entities, we proposed using Deceleration Rate (DR) to describe rear-end conflicts and Lane Change Speed (LCS) to describe lane-changing conflicts. Additionally, we employed the K-means clustering method to determine the threshold values for minor, moderate, and severe levels of rear-end and lane-changing conflicts. Finally, based on the obtained trajectory data, the values of traffic conflicts are calculated and their severity is classified. A heat map of the spatial distribution of vehicle conflicts in continuous merging zones is then created to study the spatial distribution patterns of traffic conflicts. RESULTS: The threshold values for minor, moderate, and severe levels of rear-end conflicts are determined to be 3.06 m/s2, 5.36 m/s2, and 8.04 m/s2, respectively. For lane-changing conflicts, the thresholds are 1.13 m/s, 2.07 m/s, and 3.45 m/s. The spatial distribution of traffic conflicts exhibits a "first increase, then decrease, and then increase again" trend. CONCLUSIONS: The study identifies the critical areas of traffic conflicts in the continuous merging zones of cross-river bridges. The research results provide a novel approach for acquiring traffic data in these areas and offer a reliable quantitative method for assessing safety risks on these road segments. This provides a theoretical basis for proposing targeted traffic safety management strategies.
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Hydrogen bonds profoundly influence the fundamental chemical, physical and biological properties of molecules and materials. Owing to their relatively weaker interactions compared to other chemical bonds, hydrogen bonds alone are generally insufficient to induce substantial changes in electrical properties, thus imposing severe constraints on their applications in related devices. Here we report a metal-insulator transition controlled by hydrogen bonds for an organic-inorganic (1,3-diaminopropane)0.5SnSe2 superlattice that exhibits a colossal on-off ratio of 107 in electrical resistivity. The key to inducing the transition is a change in the amino group's hydrogen-bonding structure from dynamic to static. In the dynamic state, thermally activated free rotation continuously breaks and forms transient hydrogen bonds with adjacent Se anions. In the static state, the amino group forms three fixed-angle positions, each separated by 120°. Our findings contribute to the understanding of electrical phenomena in organic-inorganic hybrid materials and may be used for the design of future molecule-based electronic materials.
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The surface of three-dimensional materials provides an ideal and versatile platform to explore quantum-confined physics. Here, we systematically investigate the electronic structure of Na-intercalated CrTe2, a van der Waals antiferromagnet, using angle-resolved photoemission spectroscopy and ab initio calculations. The measured band structure deviates from the calculation of bulk NaCrTe2 but agrees with that of ferromagnetic monolayer CrTe2. Consistently, we observe unexpected exchange splitting of the band dispersions, persisting well above the Néel temperature of bulk NaCrTe2. We argue that NaCrTe2 features a quantum-confined 2D ferromagnetic state in the topmost surface layer due to strong ferromagnetic correlation in the CrTe2 layer. Moreover, the exchange splitting and the critical temperature can be controlled by surface doping of alkali-metal atoms, suggesting the feasibility of tuning the surface ferromagnetism. Our work not only presents a simple platform for exploring tunable 2D ferromagnetism but also provides important insights into the quantum-confined low-dimensional magnetic states.
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The pursuit of discovering new high-temperature superconductors that diverge from the copper-based model1-3 has profound implications for explaining mechanisms behind superconductivity and may also enable new applications4-8. Here our investigation shows that the application of pressure effectively suppresses the spin-charge order in trilayer nickelate La4Ni3O10-δ single crystals, leading to the emergence of superconductivity with a maximum critical temperature (Tc) of around 30 K at 69.0 GPa. The d.c. susceptibility measurements confirm a substantial diamagnetic response below Tc, indicating the presence of bulk superconductivity with a volume fraction exceeding 80%. In the normal state, we observe a strange metal behaviour, characterized by a linear temperature-dependent resistance extending up to 300 K. Furthermore, the layer-dependent superconductivity observed hints at a unique interlayer coupling mechanism specific to nickelates, setting them apart from cuprates in this regard. Our findings provide crucial insights into the fundamental mechanisms underpinning superconductivity, while also introducing a new material platform to explore the intricate interplay between the spin-charge order, flat band structures, interlayer coupling, strange metal behaviour and high-temperature superconductivity.
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The quest for high-performance piezoelectric materials has been synonymous with the pursuit of the morphotropic phase boundary (MPB), yet the full potential of MPBs remains largely untapped outside of the realm of ferroelectrics. In this study, we reveal a new class of MPB by creating continuous molecular-based solid solutions between centro- and noncentrosymmetric compounds, exemplified by (tert-butylammonium)1-x(tert-amylammonium)xFeCl4 (0 ≤ x ≤ 1), where the MPB is formed due to disorder of molecular cations. Near the MPB, we discovered an exceptionally sensitive nonlinear optical material in the centrosymmetric phase, capable of activation at pressures as low as 0.12-0.27 GPa, and producing tunable second-harmonic generation (SHG) signals from zero to 18.8 times that of KH2PO4 (KDP). Meanwhile, synchrotron diffraction experiments have unveiled a third competing phase (P212121) appearing at low pressure, forming a triple-phase point near the MPB, thereby providing insight into the mechanism underpinning the nonlinear optical (NLO) switch behavior. These findings highlight the opportunity to harness exceptional physical properties in symmetry-breaking solid solution systems by strategically designing novel MPBs.
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Moiré superlattices, consisting of rotationally aligned 2D atomically thin layers, provide a highly novel platform for the study of correlated quantum phenomena. However, reliable and efficient construction of moiré superlattices is challenging because of difficulties to accurately angle-align small exfoliated 2D layers and the need to shun wet-transfer processes. Here, efficient and precise construction of various moiré superlattices is demonstrated by picking up and stacking large-area 2D mono- or few-layer crystals with predetermined crystal axes, made possible by a gold-template-assisted mechanical exfoliation method. The exfoliated 2D layers are semiconductors, superconductors, or magnets and their high quality is confirmed by photoluminescence and Raman spectra and by electrical transport measurements of fabricated field-effect transistors and Hall devices. Twisted homobilayers with angle-twisting accuracy of ≈0.3°, twisted heterobilayers with sub-degree angle-alignment accuracy, and multilayer superlattices are precisely constructed and characterized by their moiré patterns, interlayer excitons, and second harmonic generation. The present study paves the way for exploring emergent phenomena in moiré superlattices.
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Emergent phenomena in exfoliated layered transition metal compounds have attracted much attention in the past several years. Especially, pursuing a ferromagnetic insulator is one of the exciting goals for stimulating a high-performance magnetoelectrical device. Here, we report the transition from a metallic to high-Tc semiconductor-like ferromagnet in thinned Fe3GaTe2, accompanied with competition among various magnetic interactions. As evidenced by critical exponents, Fe3GaTe2 is the first layered ferromagnet described by a 3D Ising model coupled with long-range interactions. An extra magnetic phase from competition between ferromagnetism and antiferromagnetism emerges at a low field below Tc. Upon reducing thickness, the Curie temperature (Tc) monotonically decreases from 342 K for bulk to 200 K for 1-3 nm flakes, which is the highest Tc reported as far as we know. Furthermore, a semiconductor-like behavior has been observed in such 1-3 nm flakes. Our results highlight the importance of Fe3GaTe2 in searching for ferromagnetic insulators, which may benefit spintronic device fabrication.
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The recent report of near-ambient superconductivity and associated color changes in pressurized nitrogen doped lutetium hydride has triggered worldwide interest and raised major questions about the nature and underlying physics of these latest claims. Here we report synthesis and characterization of high-purity nitrogen doped lutetium hydride LuH2±xNy. We find that pressure conditions have notable effects on Lu-N and Lu-NH chemical bonding and the color changes likely stem from pressure-induced electron redistribution of nitrogen/vacancies and interaction with the LuH2 framework. No superconducting transition is found in all the phases at temperatures 1.8-300 K and pressures 0-38 GPa. Instead, we identify a notable temperature-induced resistance anomaly of electronic origin in LuH2±xNy, which is most pronounced in the pink phase and may have been erroneously interpreted as a sign of superconducting transition. This work establishes key benchmarks for nitrogen doped lutetium hydrides, allowing an in-depth understanding of its novel pressure-induced phase changes.
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Here we report a low-temperature and vector-magnetic-field scanning tunneling microscopy/spectroscopy (STM/S) study on 3R-TaSe2. The sample surface was obtained by exfoliating a bulk 3R-TaSe2 single crystal in an ultrahigh-vacuum (UHV) chamber and then transferred in situ to STM. It was observed that the topmost layer shows a 3 × 3 charge density wave pattern at T = 4.2 K with metallic character in STS. The electronic characterization study by variable-temperature and magnetic field STS revealed that 3R-TaSe2 behaves as a type-II superconductor. More intriguingly, such superconductivity (SC) can survive under strong in-plane magnetic fields even up to 2.5 T and out-of-plane magnetic fields up to 0.7 T, exhibiting an anisotropic superconducting property. Temperature-dependent STS showed that 3R-TaSe2 undergoes a transition above 0.58 K. Our results may be important for understanding the intriguing SC properties of the 3R-phase van der Waals materials.
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All two-dimensional (2D) materials of group IV elements from Si to Pb are stabilized by carrier doping and interface bonding from substrates except graphene which can be free-standing. The involvement of strong hybrid of bonds, adsorption of exotic atomic species, and the high concentration of crystalline defects are often unavoidable, complicating the measurement of the intrinsic properties. In this work, we report the discovery of seven kinds of hitherto unreported bulk compounds (RO)nPb (R = rare earth metals, n = 1,2), which consist of quasi-2D Pb square nets that are spatially and electronically detached from the [RO]δ+ blocking layers. The band structures of these compounds near Fermi levels are relatively clean and dominantly contributed by Pb, resembling the electron-doped free-standing Pb monolayer. The R2O2Pb compounds are metallic at ambient pressure and become superconductors under high pressures with much enhanced critical fields. In particular, Gd2O2Pb (9.1 µB/Gd) exhibits an interesting bulk response of lattice distortion in conjunction with the emergence of superconductivity and magnetic anomalies at a critical pressure of 10 GPa. Our findings reveal the unexpected facets of 2D Pb sheets that are considerably different from their bulk counterparts and provide an alternative route for exploring 2D properties in bulk materials.
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The recently discovered kagome metals AV3Sb5 (A = Cs, Rb, K) exhibit a variety of intriguing phenomena, such as a charge density wave (CDW) with time-reversal symmetry breaking and possible unconventional superconductivity. Here, we report a rare non-monotonic evolution of the CDW temperature (TCDW) with the reduction of flake thickness approaching the atomic limit, and the superconducting transition temperature (Tc) features an inverse variation with TCDW. TCDW initially decreases to a minimum value of 72 K at 27 layers and then increases abruptly, reaching a record-high value of 120 K at 5 layers. Raman scattering measurements reveal a weakened electron-phonon coupling with the reduction of sample thickness, suggesting that a crossover from electron-phonon coupling to dominantly electronic interactions could account for the non-monotonic thickness dependence of TCDW. Our work demonstrates the novel effects of dimension reduction and carrier doping on quantum states in thin flakes and provides crucial insights into the complex mechanism of the CDW order in the family of AV3Sb5 kagome metals.
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Short-chain fatty acids (SCFAs) like butyrate (BUT) largely influence vascular integrity and are closely associated with the onset and progression of cardiovascular diseases. However, their impact on vascular endothelial cadherin (VEC), a major vascular adhesion and signaling molecule, is largely unknown. Here, we explored the effect of the SCFA BUT on the phosphorylation of specific tyrosine residues of VEC (Y731, Y685, and Y658), which are reported to be critical for VEC regulation and vascular integrity. Moreover, we shed light on the signaling pathway engaged by BUT to affect the phosphorylation of VEC. Thereby, we used phospho-specific antibodies to evaluate the phosphorylation of VEC in response to the SCFA sodium butyrate in human aortic endothelial cells (HAOECs) and performed dextran assays to analyze the permeability of the EC monolayer. The role of c-Src and SCFA receptors FFAR2 and FFAR3 in the induction of VEC phosphorylation was analyzed using inhibitors and antagonists for c-Src family kinases and FFAR2/3, respectively, as well as by RNAi-mediated knockdown. Localization of VEC in response to BUT was assessed by fluorescence microscopy. BUT treatment of HAOEC resulted in the specific phosphorylation of Y731 at VEC with minor effects on Y685 and Y658. Thereby, BUT engages FFAR3, FFAR2, and c-Src kinase to induce phosphorylation of VEC. VEC phosphorylation correlated with enhanced endothelial permeability and c-Src-dependent remodeling of junctional VEC. Our data suggest that BUT, an SCFA and gut microbiota-derived metabolite, impacts vascular integrity by targeting VEC phosphorylation with potential impact on the pathophysiology and therapy of vascular diseases.
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Searching for functional square lattices in layered superconductor systems offers an explicit clue to modify the electron behavior and find exotic properties. The trigonal SnAs3 structural units in SnAs-based systems are relatively conformable to distortion, which provides the possibility to achieve structurally topological transformation and higher superconducting transition temperatures. In the present work, the functional As square lattice was realized and activated in Li0.6 Sn2 As2 and NaSnAs through a topotactic structural transformation of trigonal SnAs3 to square SnAs4 under pressure, resulting in a record-high Tc among all synthesized SnAs-based compounds. Meanwhile, the conductive channel transfers from the out-of-plane pz orbital to the in-plane px +py orbitals, facilitating electron hopping within the square 2D lattice and boosting the superconductivity. The reorientation of p-orbital following a directed local structure transformation provides an effective strategy to modify layered superconducting systems.
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OBJECTIVE: To explore the clinical effect of antibiotic artificial bone (Calcium phosphate) in the treatment of infection after internal fixation of tibial plateau fractures. METHODS: We retrospectively reviewed the clinical data of 32 patients with infection after internal fixation of tibial plateau fractures treating from March 2010 to October 2021. There were 18 males and 14 females, aged from 23 to 70 (average 49.66 ± 10.49), 19 cases of the left side and 13 cases of the right side. Among them, 7 cases were open fractures with initial injury and 25 cases were closed fractures. On the basis of thorough debridement and implanting antibiotic artificial bone, the internal fixation of 18 patients were tried to be preserved and the internal fixation of 14 patients were removed completely. In order to provide effective fixation, 14 patients also received external fixation. Postoperative wound healing, infection control, Hospital for Special Surgery knee scores (HSS), related inflammatory indicators and bone healing time were recorded and followed up. RESULTS: Thirty-two patients were followed up for 12 ~ 82 months (average 36.09 ± 19.47 months). The redness, swelling and pain of pin site occurred in 2 patients, which returned to normal after applying antibiotics and continuous dressing change. One patient retained the internal fixation during the first-stage operation. Redness and swelling of incision, subcutaneous undulation occurred after two months. In order to avoid the recurrence of infection, the internal fixation was removed completely and antibiotic artificial bone was filled again. The infection was controlled and fracture healed. Four patients' wounds could not be closed directly due to soft tissue defect and was covered with skin flap. After the first-stage operation, 12 patients received second-stage autologous iliac bone grafting due to residual bone defects and poor healing of the fracture end. The bone healing time was 4 ~ 16 months (average 7.31 ± 2.79 months). Inflammatory indicators including CRP, ESR, and WBC returned to normal levels within 2 ~ 10 weeks (average 4.97 ± 2.58 weeks). The HSS of all patients were 54 ~ 86 points (average 73.06 ± 8.44 points) at the last follow-up. CONCLUSION: Implantation of antibiotic artificial bone, retention or removal of internal fixation according to infection and fracture healing, application of external fixation timely is an effective method to treat infection after internal fixation of tibial plateau fractures, which can control infection effectively and promote functional recovery.
Subject(s)
Tibial Fractures , Tibial Plateau Fractures , Male , Female , Humans , Retrospective Studies , Tibial Fractures/diagnostic imaging , Tibial Fractures/surgery , Fracture Fixation, Internal/adverse effects , Fracture Healing , Treatment Outcome , Bone PlatesABSTRACT
The lunar soils evolution over time is mainly caused by space weathering that includes the impacts of varying-sized meteoroids and charged particles implantation of solar/cosmic winds as well. It has long been established that space weathering leads to the formation of outmost amorphous layers (50-200 nm in thickness) embedded nanophase iron (npFe0) around the mineral fragments, albeit the origin of the npFe0 remains controversial . The Chang'e-5 (CE-5) mission returned samples feature the youngest mare basalt and the highest latitude sampling site , providing an opportunity to seek the critical clues for understanding the evolution of soils under space weathering. Here, we report the surface microstructures of the major minerals including olivine, pyroxene, anorthite, and glassy beads in the lunar soil of CE-5. Unlike the previous observations, only olivine in all crystals is surrounded by a thinner outmost amorphous SiO2 layer (â¼10 nm thick) and embedded wüstite nanoparticles FeO (np-FeO, 3-12 nm in size) instead of npFe0. No foreign volatile elements deposition layer and solar flare tracks can be found on the surface or inside the olivine and other minerals. This unique rim structure has not been reported for any other lunar, terrestrial, Martian, or meteorite samples so far. The observation of wüstite FeO and the microstructures support the existence of an intermediate stage in space weathering for lunar minerals by thermal decomposition.
Subject(s)
Mars , Soil , Animals , Female , Horses , Silicon Dioxide , Extraterrestrial Environment , Minerals/chemistryABSTRACT
Superatomic crystals are a class of hierarchical materials composed of atomically precise clusters assembled via van der Waals or covalent-like interactions. Au6Te12Se8, an all-inorganic superatomic superconductor exhibiting superatomic-charge-density-wave (S-CDW), provides the first platform to study the response of its collective quantum phenomenon to the external pressure in superatomic crystals. We reveal a competition between S-CDW and superconductivity in an ultra-narrow pressure range. Distinct from conventional CDW ordering, S-CDW shows the lowest threshold (0.1 GPa) toward external pressure that is 1-2 orders of magnitude lower than other atomic compounds. Prominently, a second superconducting phase emerges above 7.3 GPa with a threefold enhancement in the transition temperature (Tc) to 8.5 K, indicating a switch of the conduction channel from the a- to b-axis. In situ synchrotron diffractions and theoretical calculations reveal a pressure-mediated mesoscopic slip of the superatoms and a 2D-3D transition of the Fermi surface topology, which well explains the observed dimensional crossover of conductivity and re-entrant superconductivity.
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Nodal-line superconductor NaAlSi with a transition temperature (Tc) of 7 K has attracted considerable attention in recent years, whereas its Ge counterpart, NaAlGe, does not superconduct down to the lowest temperature regardless of their similar atomic and electrical structures. To tackle this enigma, we resort to the growth of NaAlGe single crystal and characterize its ground state. Interestingly, when hole doped by oxidation or extracting Na, single-crystalline NaAlGe transforms from a semimetal/semiconductor to a superconductor (Tc=1.8â¼3.3 K) with zero resistivity and a diamagnetic shielding fraction over 100%, but without a thermodynamic response in heat capacity. Continuous x-ray diffraction reveals a transient new structure with a largercaxis, which is suggested to have arisen from the minor loss of Na and to be responsible for the emergence of the delicate superconductivity. Our findings place NaAlGe on an equal footing with NaAlSi and provide an alternative for studying the intriguing relationship between superconductivity and nodal-line topology.
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OBJECTIVE: To explore the clinical effect of antibiotic artificial bone implantation and external fixation in the treatment of infection after intramedullary nail fixation. METHODS: We retrospectively reviewed the clinical data of patients with infection after intramedullary nail fixation treated from March 2010 to August 2020. There were 27 males and 6 female, aged from 12 to 67 years (average 42.27 years), 18 cases on the left side and 15 cases on the right side. Among them, 20 cases were open fractures with initial injury and 13 cases were closed fractures. All patients were treated with intramedullary nail removal, local debridement, antibiotic artificial bone implantation and external fixation. Because of bone defects, 19 patients underwent secondary autologous cancellous bone grafting after infection control. Postoperative wound healing, related inflammatory indicators, fixation time, and bone healing time were recorded and followed up. RESULTS: The 33 patients were followed up with period of 10 ~ 98 months (average 62.7 months). One patients failed to control the infection effectively after treatment, so received antibiotics artificial bone implantation again. Two patients also received antibiotic artificial bone implants again due to the recurrence of the infection. After treatment, infection was controlled and the fracture healed well. One patient received vacuum sealing drainage (VSD) due to persistent postoperative exudation, and five patients were also cured successfully after continuous dressing. Two patients had sinus tract after surgery, and the wound was cured by continuous dressing change. Nineteen patients received autogenous iliac bone grafts for healing due to bone defects ranging from 3 to 6.5 cm (average 4.15 cm) after infection control. The external fixation time of 33 patients ranged from 4 to 16 months (average 7.79 months), the bone healing time ranged from 4 to 13 months (average 6.67 months), and the related inflammatory indexes returned to normal within 2-8 weeks (average 4.48 weeks). CONCLUSION: Antibiotic artificial bone implantation and external fixation is an effective method for the treatment of infection after intramedullary nail fixation.
Subject(s)
External Fixators , Fracture Fixation, Intramedullary , Adolescent , Adult , Aged , Anti-Bacterial Agents/therapeutic use , Bone Nails , Child , External Fixators/adverse effects , Female , Fracture Fixation , Fracture Fixation, Intramedullary/adverse effects , Fracture Healing , Humans , Male , Middle Aged , Retrospective Studies , Treatment Outcome , Young AdultABSTRACT
Pyroelectrics are a class of polar compounds that output electrical signals upon changes in temperature. With the rapid development of flexible electronics, organic pyroelectrics are highly desired. However, most organics suffer from low pyroelectric coefficients or low working temperatures. To date, the realization of superior pyroelectric performance in all-organics has remained a challenge. Here, we report the discovery of amantadine formate, an all-organic pyroelectric with ultrahigh voltage figures of merit (F v), surpassing those of all other known organics and commercial triglycine sulfate, LiTaO3 as well around room temperature. The key to the high F v is attributed to large pyroelectric coefficients in a favorable temperature range resulting from a ferroelectric-paraelectric phase transition of second order at 327 K, small dielectric constant, and moderate heat capacity. In addition, amantadine formate is relatively lightweight, soft, transparent, low-cost, and non-toxic, adding value to its potential applications in flexible electronics. Our results demonstrate that a new type of pyroelectrics can exist in organic compounds.
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The recently discovered layered kagome metals AV_{3}Sb_{5} (A=K, Rb, and Cs) with vanadium kagome networks provide a novel platform to explore correlated quantum states intertwined with topological band structures. Here we report the prominent effect of hole doping on both superconductivity and charge density wave (CDW) order, achieved by selective oxidation of exfoliated thin flakes. A superconducting dome is revealed as a function of the effective doping content. The superconducting transition temperature (T_{c}) and upper critical field in thin flakes are significantly enhanced compared with the bulk, which are accompanied by the suppression of CDW. Our detailed analyses establish the pivotal role of van Hove singularities in promoting correlated quantum orders in these kagome metals. Our experiments not only demonstrate the intriguing nature of superconducting and CDW orders, but also provide a novel route to tune the carrier concentration through both selective oxidation and electric gating. This establishes CsV_{3}Sb_{5} as a tunable 2D platform for the further exploration of topology and correlation among 3d electrons in kagome lattices.