It has been known for more than a decade that phonons can produce an off-diagonal thermal conductivity in the presence of a magnetic field. Recent studies of thermal Hall conductivity, κ_{xy}, in a ...variety of contexts, however, have assumed a negligibly small phonon contribution. We present a study of κ_{xy} in quantum paraelectric SrTiO_{3}, which is a nonmagnetic insulator and find that its peak value exceeds what has been reported in any other insulator, including those in which the signal has been qualified as "giant." Remarkably, κ_{xy}(T) and κ(T) peak at the same temperature and the former decreases faster than the latter at both sides of the peak. Interestingly, in the case of La_{2}CuO_{4} and α-RuCl_{3}, κ_{xy}(T) and κ(T) peak also at the same temperature. We also studied KTaO_{3} and found a small signal, indicating that a sizable κ_{xy}(T) is not a generic feature of quantum paraelectrics. Combined to other observations, this points to a crucial role played by antiferrodistortive domains in generating κ_{xy} of this solid.
Fabricating ultrathin two-dimensional (2D) covalent organic framework (COF) nanosheets (NSs) in large scale and high yield still remains a great challenge. This limits the exploration of the unique ...functionalities and wide range of application potentials of such materials. Herein, we develop a scalable general bottom-up approach to facilely synthesize ultrathin (<2.1 nm) imine-based 2D COF NSs (including COF-366 NSs, COF-367 NSs, COF-367-Co NSs, TAPB-PDA COF NSs, and TAPB-BPDA COF NSs) in large scale (>100 mg) and high yield (>55%), via an imine-exchange synthesis strategy through adding large excess amounts of 2,4,6-trimethylbenzaldehyde into the reaction system under solvothermal conditions. Impressively, visualization of the periodic pore lattice for COF-367 NSs by a scanning tunneling microscope (STM) clearly discloses the ultrathin 2D COF nature. In particular, the ultrathin COF-367-Co NSs isolated are subject to the heterogeneous photocatalyst for CO2-to-CO conversion, showing excellent efficiency with a CO production rate as high as 10 162 μmol g–1 h–1 and a selectivity of ca. 78% in aqueous media under visible-light irradiation, far superior to corresponding bulk materials and comparable with the thus far reported state-of-the-art visible-light driven heterocatalysts.
Abstract
During the past two decades, it has been established that a non-trivial electron wave-function topology generates an anomalous Hall effect (AHE), which shows itself as a Hall conductivity ...non-linear in magnetic field. Here, we report on an unprecedented case of field-linear AHE. In Mn
3
Sn, a kagome magnet, the out-of-plane Hall response, which shows an abrupt jump, was discovered to be a case of AHE. We find now that the in-plane Hall response, which is perfectly linear in magnetic field, is set by the Berry curvature of the wavefunction. The amplitude of the Hall response and its concomitant Nernst signal exceed by far what is expected in the semiclassical picture. We argue that magnetic field induces out-of-plane spin canting and thereafter gives rise to nontrivial spin chirality on the kagome lattice. In band structure, we find that the spin chirality modifies the topology by gapping out Weyl nodal lines unknown before, accounting for the AHE observed. Our work reveals intriguing unification of real-space Berry phase from spin chirality and momentum-space Berry curvature in a kagome material.
Osteosarcoma is the most common primary bone tumor in children and adolescents. Unfortunately, osteosarcoma treatments often fail due to the development of chemoresistance, of which the underlying ...molecular mechanisms still remain unclear. In this study, we demonstrated that HSP90AA1 gene is responsible for drug resistance in osteosarcoma through an autophagy-related mechanism.
shRNAs were transfected into osteosarcoma cells for knockdown of HSP90AA1 gene. Stable HSP90AA1 overexpressing osteosarcoma cell lines were obtained by lentivirus infection. mRNA and protein expressions of HSP90AA1 in osteosarcoma cells were tested by quantitative real-time PCR and western blot, respectively. Autophagy of osteosarcoma cells was detected by western blot of LC3, transmission electron microscopy and fluorescence microscope. mRFP-GFP-LC3 lentiviral transfection was also performed to detect autophagic flux. NOD/SCID mices were inoculated with MG-63 tumor cells transfected with HSP90AA1 specific shRNA. TUNEL and LC3 staining were performed to detect apoptosis and autophagy of resected tumor tissues.
Doxorubicin, cisplatin, and methotrexate, which are commonly used in chemotherapy, each induced HSP90AA1 upregulation in human osteosarcoma cells. Suppression of HSP90AA1 restored the sensitivity of osteosarcoma cells to chemotherapy both in vivo and in vitro. Mechanism study indicated that autophagy is responsible for the chemoresistance in osteosarcoma cells. HSP90AA1 increased drug resistance by inducing autophagy and inhibiting apoptosis. Suppression of HSP90AA1 diminished autophagic protection in response to chemotherapy in osteosarcoma cells. Moreover, HSP90AA1 promotes autophagy through PI3K/Akt/mTOR pathway and inhibits apoptosis through JNK/P38 pathway.
We showed that chemotherapy agents can induce HSP90AA1 expression in osteosarcoma cells. And HSP90AA1, acting as an important regulator of autophagy, is a critical factor in the development of osteosarcoma chemoresistance both in vitro and in vivo. HSP90AA1 provides a novel therapeutic target for improving osteosarcoma treatment.
The origin of phonon thermal Hall Effect (THE) observed in a variety of insulators is yet to be identified. Here, we report on the observation of a thermal Hall conductivity in a non-magnetic ...elemental insulator, with an amplitude exceeding what has been previously observed. In black phosphorus (BP), the longitudinal (κ
), and the transverse, κ
, thermal conductivities peak at the same temperature and at this peak temperature, the κ
/κ
/B is ≈ 10
-10
T
. Both these features are shared by other insulators displaying THE, despite an absolute amplitude spreading over three orders of magnitude. The absence of correlation between the thermal Hall angle and the phonon mean-free-path imposes a severe constraint for theoretical scenarios of THE. We show that in BP a longitudinal and a transverse acoustic phonon mode anti-cross, facilitating wave-like transport across modes. The anisotropic charge distribution surrounding atomic bonds can pave the way for coupling between phonons and the magnetic field.
Microalgae are the important part of carbon cycle in the nature, and they could utilize the carbon resource in water and soil efficiently. The abilities of microalgae to mitigate CO
2
emission and ...produce oil with a high productivity have been proven. Hence, this third-generation biodiesel should be popularized. This review firstly introduce the basic characteristics and application fields of microalgae. Then, the influencing parameters and recent advanced technologies for the microalgae biodiesel production have been discussed. In influencing parameters for biodiesel production section, the factors of microalgae cultivation, lipid accumulation, microalgae harvesting, and lipid extraction have been summarized. In recent advanced technologies for biodiesel production section, the microalgae cultivation systems, lipid induction technologies, microalgae harvesting technologies, and lipid extraction technologies have been reviewed. This review aims to provide useful information to help future development of efficient and commercially viable technology for microalgae-based biodiesel production.
The production of ammonia (NH3) from molecular dinitrogen (N2) under ambient conditions is of great significance but remains as a great challenge. Using first-principles calculations, we have ...investigated the potential of using a transition metal (TM) atom embedded on defective MXene nanosheets (Ti3–x C2O y and Ti2–x CO y with a Ti vacancy) as a single-atom electrocatalyst (SAC) for the nitrogen reduction reaction (NRR). The Ti3–x C2O y nanosheet with Mo and W embedded, and the Ti2–x C2O y nanosheet with Cr, Mo, and W embedded, can significantly promote the NRR while suppressing the competitive hydrogen evolution reaction, with the low limiting potential of −0.11 V for W/Ti2–x C2O y . The outstanding performance is attributed to the synergistic effect of the exposed Ti atom and the TM atom around an extra oxygen vacancy. The polarization charges of the active center are reasonably tuned by the embedded TM atoms, which can optimize the binding strength of key intermediate *N2H. The good feasibility of preparing such TM SACs on defective MXenes and the high NRR selectivity with regard to the competitive HER suggest new opportunities for driving NH3 production by MXene-based SAC electrocatalysts under ambient conditions.
•Integrating ESV into the evaluation of sustainable land use is applicable.•Six sustainability indicators based on ESV from two dimensions are valid.•Land use changes in fast-growing cities ...profoundly influence ESV.•ESV-based SLU evaluation results provide guidance for land use management.
Integrating ecosystem service value (ESV) into the evaluation system for sustainable land use (SLU) in fast-growing cities is an effective way to implement Sustainable Development Goals (SDGs) 15 and 11 of the United Nations' 2030 Agenda for Sustainable Development. Taking ESV as the intermediate parameter, six sustainability indicators were developed to evaluate SLU from two dimensions: sustainable land ecosystem services and economic development. These indicators are the total supply and demand index (RT) of ecosystem services, the potential supply and demand index (RP) of ecosystem services, the ecological cost index per unit of GDP (RC), the eco-economic coordination index (RD), the eco-economic equilibrium index (RE), and the ESV-based sustainable land use index (RS). Empirical research was conducted in Qingdao, a fast-growing city in eastern China, to verify the validity of the indicators. Five sets of Landsat TM/ETM/OLI remote sensing images from 1996, 2005, 2010, 2015, and 2017 were used to analyze the land use and ESV changes in Qingdao. The results indicate that land use changes in fast-growing cities significantly affect the ESV. The decrease in the area of ecological land and the expansion of construction land caused by rapid urbanization reduced ESV. The RC and RD of Qingdao were sustainable, while the RT and RP were unsustainable, and the RE showed volatility, which reduced the evaluation level of SLU in Qingdao from extremely strongly sustainable (L1) to moderately sustainable (L3). Thus, it is necessary to improve the ESV of Qingdao. Optimization strategies for promoting SLU in Qingdao are proposed based on the results, confirming that the evaluation provides guidance for land use management.
DNA G-quadruplexes (G4s) in vivo have been linked to cancer and other diseases such as neurological disorders. Nondestructive fast detection of endogenous DNA G4s can provide specific real-time ...information, which is of particular interest for clinic accurate diagnosis. However, tools to probe live-cell endogenous DNA G4s in real time are very limited. Herein, we report the design and development of a fluorescent molecule QIN for the real-time detection of endogenous DNA G4s in live cells with the aid of a new spiropyran in situ switching (SIS) strategy. The lipophilic spiropyran-linked QIN differs from the other probes in that it can enter live cells readily within 15 s and can be in situ induced by DNA G4s to adopt its charged open form, causing a large red shift in the fluorescent emission wavelength. Live-cell super-resolution fluorescent imaging suggests that the SIS-based probe has high photostability and can be applied for the accurate detection of DNA G4s in complex biosystems with very high sensitivity and selectivity.
SrTiO
, a quantum paralectric, displays a detectable phonon thermal Hall effect (THE). Here, we show that the amplitude of the THE is extremely sensitive to stoichiometry. It drastically decreases ...upon substitution of a tiny fraction of Sr atoms with Ca, which stabilizes the ferroelectric order. It drastically increases by an even lower density of oxygen vacancies, which turn the system to a dilute metal. The enhancement in the metallic state exceeds by far the sum of the electronic and the phononic contributions. We explain this observation as an outcome of three features: 1) Heat is mostly transported by phonons; 2) the electronic Hall angle is extremely large; and 3) there is substantial momentum exchange between electrons and phonons. Starting from Herring's picture of phonon drag, we arrive to a quantitative account of the enhanced THE. Thus, phonon drag, hitherto detected as an amplifier of thermoelectric coefficients, can generate a purely thermal transverse response in a dilute metal with a large Hall angle. Our results reveal a hitherto-unknown consequence of momentum-conserving collisions between electrons and phonons.
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