Atomic dynamics of electrified solid-liquid interfaces in liquid-cell TEM.

Electrified solid-liquid interfaces (ESLIs) play a key role in various electrochemical processes relevant to energy1-5, biology6 and geochemistry7. The electron and mass transport at the electrified interfaces may result in structural modifications that markedly influence the reaction pathways. For example, electrocatalyst surface restructuring during reactions can substantially affect the catalysis mechanisms and reaction products1-3. Despite its importance, direct probing the atomic dynamics of solid-liquid interfaces under electric biasing is challenging owing to the nature of being buried in liquid electrolytes and the limited spatial resolution of current techniques for in situ imaging through liquids. Here, with our development of advanced polymer electrochemical liquid cells for transmission electron microscopy (TEM), we are able to directly monitor the atomic dynamics of ESLIs during copper (Cu)-catalysed CO2 electroreduction reactions (CO2ERs). Our observation reveals a fluctuating liquid-like amorphous interphase. It undergoes reversible crystalline-amorphous structural transformations and flows along the electrified Cu surface, thus mediating the crystalline Cu surface restructuring and mass loss through the interphase layer. The combination of real-time observation and theoretical calculations unveils an amorphization-mediated restructuring mechanism resulting from charge-activated surface reactions with the electrolyte. Our results open many opportunities to explore the atomic dynamics and its impact in broad systems involving ESLIs by taking advantage of the in situ imaging capability.

Unveiling Corrosion Pathways of Sn Nanocrystals through High-Resolution Liquid Cell Electron Microscopy.

Unveiling materials' corrosion pathways is significant for understanding the corrosion mechanisms and designing corrosion-resistant materials. Here, we investigate the corrosion behavior of Sn@Ni3Sn4 and Sn nanocrystals in an aqueous solution in real time by using high-resolution liquid cell transmission electron microscopy. Our direct observation reveals an unprecedented level of detail on the corrosion of Sn metal with/without a coating of Ni3Sn4 at the nanometric and atomic levels. The Sn@Ni3Sn4 nanocrystals exhibit "pitting corrosion", which is initiated at the defect sites in the Ni3Sn4 protective layer. The early stage isotropic etching transforms into facet-dependent etching, resulting in a cavity terminated with low-index facets. The Sn nanocrystals under fast etching kinetics show uniform corrosion, and smooth surfaces are obtained. Sn nanocrystals show "creeping-like" etching behavior and rough surfaces. This study provides critical insights into the impacts of coating, defects, and ion diffusion on corrosion kinetics and the resulting morphologies.

Visualizing Facets Asymmetry Induced Directional Movement of Cadmium Chloride Nanomotor.

Nanomotors in solution have many potential applications. However, it has been a significant challenge to realize the directional motion of nanomotors. Here, we report cadmium chloride tetrahydrate (CdCl2·4H2O) nanomotors with remarkable directional movement under electron beam irradiation. Using in situ liquid phase transmission electron microscopy, we show that the CdCl2·4H2O nanoparticle with asymmetric surface facets moves through the liquid with the flat end in the direction of motion. As the nanomotor morphology changes, the speed of movement also changes. Finite element simulation of the electric field and fluid velocity distribution around the nanomotor assists the understanding of ionic self-diffusiophoresis as a driving force for the nanomotor movement; the nanomotor generates its own local ion concentration gradient due to different chemical reactivities on different facets.

Solid-liquid-gas reaction accelerated by gas molecule tunnelling-like effect.

Solid-liquid-gas reactions are ubiquitous and are encountered in both nature and industrial processes1-4. A comprehensive description of gas transport in liquid and following reactions at the solid-liquid-gas interface, which is substantial in regard to achieving enhanced triple-phase reactions, remains unavailable. Here, we report a real-time observation of the accelerated etching of gold nanorods with oxygen nanobubbles in aqueous hydrobromic acid using liquid-cell transmission electron microscopy. Our observations reveal that when an oxygen nanobubble is close to a nanorod below the critical distance (~1 nm), the local etching rate is significantly enhanced by over one order of magnitude. Molecular dynamics simulation results show that the strong attractive van der Waals interaction between the gold nanorod and oxygen molecules facilitates the transport of oxygen through the thin liquid layer to the gold surface and thus plays a crucial role in increasing the etching rate. This result sheds light on the rational design of solid-liquid-gas reactions for enhanced activities.

Observation of Surface Ligands-Controlled Etching of Palladium Nanocrystals.

Selective adsorption of ligands on nanocrystal surfaces can affect oxidative etching. Here, we report the etching of palladium nanocrystals imaged using liquid cell transmission electron microscopy. The adsorption of surface ligands (i.e., iron acetylacetonate and its derivatives) and their role as inhibitor molecules on the etching process were investigated. Our observations revealed that the etching was dominated by the interplay between palladium facets and ligands and that the etching exhibited different pathways at different concentrations of ligands. At a low concentration of iron acetylacetonate (0.1 mM), rapid etching primarily at {100} facets led to a concave structure. At a high concentration (1.0 mM), the etch rate was decreased owing to a protective film of iron acetylacetonate on the {100} facets and a round nanoparticle was achieved. Ab initio calculations showed that the differences in adsorption energy of inhibitor molecules on palladium facets were responsible for the etching behavior.

Tailoring atomic 1T phase CrTe2forin situfabrication.

Controllable tailoring and understanding the phase-structure relationship of the 1T phase two-dimensional (2D) materials are critical for their applications in nanodevices. Thein situtransmission electron microscope (TEM) could regulate and monitor the evolution process of the nanostructure of 2D material with atomic resolution. In this work, a controllably tailoring 1T-CrTe2nanopore is carried out by thein situTEM. A preferred formation of the 1T-CrTe2border structure and nanopore healing process are studied at the atomic scale. The controllable tailoring of the 1T phase nanopore could be achieved by regulating the transformation of two types of low indices of crystal faces {101¯0} and {112¯0} at the nanopore border. Machine learning is applied to automatically process the TEM images with high efficiency. By adopting the deep-learning-based image segmentation method and augmenting the TEM images specifically, the nanopore of the TEM image could be automatically identified and the evaluation result of DICE metric reaches 93.17% on test set. This work presents the unique structure evolution of 1T phase 2D material and the computer aided high efficiency TEM data analysis based on deep learning. The techniques applied in this work could be generalized to other materials for controlled nanostructure regulation and automatic TEM image analyzation.

Expression of the PTEN/FOXO3a/PLZF signalling pathway in pancreatic cancer and its significance in tumourigenesis and progression.

Pancreatic cancer (PC) is one of the most lethal gastrointestinal malignancies. The PTEN/AKT signalling pathway is closely related to the tumourigenesis and progression of PC. The downstream effectors, FOXO3a, PLZF and VEGF, are reported to be involved in angiogenesis, lymph node metastasis and poor survival in PC. By using tissue microarrays and immunohistochemistry, we found, that PTEN, FOXO3a and PLZF expression was significantly decreased in PC specimens compared with that in chronic pancreatitis (CP) specimens, while VEGF expression was significantly increased. Furthermore, the expression of PTEN was positively correlated with that of FOXO3a and PLZF but negatively correlated with that of VEGF. Our results suggest that the PTEN/FOXO3a/PLZF signalling pathway may negatively regulate VEGF expression in PC. Through clinical analysis of 69 PC patients, PTEN, FOXO3a and PLZF expression was found to be significantly decreased in specimens from PC patients with lymph node metastasis and poor prognosis, while VEGF expression was significantly increased. Taken together, these reaults suggest that the PTEN/FOXO3a/PLZF signalling pathway may be capable of inhibiting growth and metastasis in PC by regulating VEGF-mediated angiogenesis, which requires further in vivo and in vitro studies and can potentially be a therapeutic target for PC.

Anomalous Shape Evolution of Ag2O2 Nanocrystals Modulated by Surface Adsorbates during Electron Beam Etching.

An understanding of nanocrystal shape evolution is significant for the design, synthesis, and applications of nanocrystals with surface-enhanced properties such as catalysis or plasmonics. Surface adsorbates that are selectively attached to certain facets may strongly affect the atomic pathways of nanocrystal shape development. However, it is a great challenge to directly observe such dynamic processes in situ with a high spatial resolution. Here, we report the anomalous shape evolution of Ag2O2 nanocrystals modulated by the surface adsorbates of Ag clusters during electron beam etching, which is revealed through in situ transmission electron microscopy (TEM). In contrast to the Ag2O2 nanocrystals without adsorbates, which display the near-equilibrium shape throughout the etching process, Ag2O2 nanocrystals with Ag surface adsorbates show distinct facet development during etching by electron beam irradiation. Three stages of shape changes are observed: a sphere-to-a cube transformation, side etching of a cuboid, and bottom etching underneath the surface adsorbates. We find that the Ag adsorbates modify the Ag2O2 nanocrystal surface configuration by selectively capping the junction between two neighboring facets. They prevent the edge atoms from being etched away and block the diffusion path of surface atoms. Our findings provide critical insights into the modulatory function of surface adsorbates on the shape control of nanocrystals.

Spring-Like Pseudoelectroelasticity of Monocrystalline Cu2S Nanowire.

Prediction from the dual-phase nature of superionic conductors-both solid and liquid-like-is that mobile ions in the material may experience reversible extraction-reinsertion by an external electric field. However, this type of pseudoelectroelasticity has not been confirmed in situ, and no details on the microscopic mechanism are known. Here, we in situ monitor the pseudoelectroelasticity of monocrystalline Cu2S nanowires (NWs) using transmission electron microscopy (TEM). Specifically, we reveal the atomic scale details including phase transformation, migration and redox reactions of Cu+ ions, nucleation, growth, as well as spontaneous shrinking of Cu protrusion. Caterpillar-diffusion-dominated deformation is confirmed by the high-resolution transmission electron microscopy (HRTEM) observation and  ab initio calculation, which can be driven by either an external electric field or chemical potential difference. The observed spring-like behavior was creatively adopted for electric nanoactuators. Our findings are crucial to elucidate the mechanism of pseudoelectroelasticity and could potentially stimulate in-depth research into electrochemical and nanoelectromechanical systems.

Three New Highly Oxygenated Germacranolides from Carpesium Divaricatum and Their Cytotoxic Activity.

Three new highly oxygenated (2⁻4), and two known (1 and 5) germacranolides, were isolated from the whole plant of Carpesium divaricatum. The planar structures and relative configurations of the new compounds were determined by detailed spectroscopic analysis. The absolute configuration of 1 was established using the circular dichroism (CD) method and X-ray diffraction, and the stereochemistry of the new compounds 2⁻4 were determined using similar CD spectra with 1. The new compound 2 and the known compound 5 exhibited potent cytotoxicity against hepatocellular cancer (Hep G2) and human cervical cancer (HeLa) cells, superior to those of the positive control cis-platin.

Two new unsaturated fatty acids from the whole plant of Pothos chinensis.

Two new unsaturated fatty acids, (Z)-octadec-13-en-11-ynoic acid (1) and (Z)-octadec-16-en-12,14-diynoic acid (2), along with six known compounds were isolated from the whole plant of Pothos chinensis. The structures of these compounds were elucidated by detailed spectroscopic analysis, including 1D and 2D NMR data. Compound 2 showed moderate antibacterial activity against Staphylococcus aureus.

Bmi1 combines with oncogenic KRAS to induce malignant transformation of human pancreatic duct cells in vitro.

It is critical to understand the pathogenesis of preinvasive stages of pancreatic duct adenocarcinoma (PDAC) for developing novel potential diagnostic and therapeutic targets. The polycomb group family member B-lymphoma Moloney murine leukemia virus insertion region-1 (Bmi1) is overexpressed and involved in cancer progression in PDAC; however, its role in the multistep malignant transformation of human pancreatic duct cells has not been directly demonstrated. In this study, we stably expressed Bmi1 in a model of telomerase-immortalized human pancreatic duct-derived cells (HPNE) and showed that Bmi1 promoted HPNE cell proliferation, migration, and invasion but not malignant transformation. We then used mutant KRASG12D as a second oncogene to transform HPNE cells and showed that it further enhanced Bmi1-induced malignant potential. More importantly, coexpression of KRASG12D and Bmi1 caused anchorage-independent growth transformation in vitro but still failed to produce tumors in nude mice. Finally, we found that mutant KRASG12D induced HPNE-Bmi1 cells to undergo partial epithelial-mesenchymal transition (EMT) likely via upregulation of snail. Knockdown of KRASG12D significantly reduced the expression of snail and vimentin at both the messenger RNA (mRNA) and protein level and further impaired the anchorage-independent growth capability of invasive cells. In summary, our findings demonstrate that coexpression of Bmi1 and KRASG12D could lead to transformation of HPNE cells in vitro and suggest potential new targets for diagnosis and treatment of PDAC.

[Chemical investigation of triterpenoids from Dichrocephala benthamii].

The triterpenoids of Dichrocephala benthamii were investigated by means of silica gel, Sephadex LH-20 and semi-preparative HPLC. Nine triterpenoids were isolated from D. benthamii. By analysis of the EI-MS, NMR spectra and comparison to the data reported in literatures, the structures of these compounds were determined as ß-amyrin formiate (1), ß-amyrin acetate (2), ß-amyrenol (3), ß-amyrone (4), 3ß-hydroxy-olean-11, 13 (18)-diene (5) , Δ12-oleanene (6) , friedelin (7), dammaradienyl acetate (8), epi-friedeband (9), respectively. Compounds 1-8 were isolated for the first time form this genus, compound 9 was isolated for the first time from this plant, whereas ß-amyrin formiate (1) was a new natural product.

Serum trefoil factor 3 is a promising non-invasive biomarker for gastric cancer screening: a monocentric cohort study in China.

BACKGROUND: The search for better non-invasive biomarkers for gastric cancer remains ongoing. We investigated the predictive power of serum trefoil factor (TFF) levels as biomarkers for gastric cancer in comparison with the pepsinogen (PG) test. METHODS: Patients with gastric cancer, chronic atrophic gastritis (CAG) or chronic non-atrophic gastritis (CNAG), and healthy people were recruited. Serum concentrations of TFFs, PG I, and PG II, as well as the presence of antibodies against Helicobacter pylori, were measured by enzyme-linked immunosorbent assays (ELISA). Receiver operating characteristics (ROC) were used to compare the predictive powers of the selected factors. RESULTS: The serum concentrations of TFF1, TFF2, and TFF3 in the control groups were significantly lower than those in the gastric cancer group with the exception of TFF2 which was elevated in CAG. The area under the ROC curve for TFF3 was greater than that for the PG I/II ratio (0.81 vs 0.78). TFF3 also had a significantly higher predictive power for distinguishing gastric cancer than the PG test (odds ratio: 10.33 vs 2.57). Moreover, combining the serum TFF3 and PG tests for gastric cancer had better predictive power than either alone. CONCLUSIONS: Serum TFF3 may be a better predictor of gastric cancer than the PG test, while the combined testing of serum PG and TFF3 could further improve the efficacy of gastric cancer screening.

Combination of siRNA-directed Kras oncogene silencing and arsenic-induced apoptosis using a nanomedicine strategy for the effective treatment of pancreatic cancer.

The synergetic inhibitory effects on human pancreatic cancer by nanoparticle-mediated siRNA and arsenic therapy were investigated both in vitro and in vivo. Poly(ethylene glycol)-block-poly(L-lysine) were prepared to form siRNA-complexed polyplex and poly(ethylene glycol)-block-poly(DL-lactide) were prepared to form arsenic-encapsulated vesicle, respectively. Down-regulation of the mutant Kras gene by siRNA caused defective abilities of proliferation, clonal formation, migration, and invasion of pancreatic cancer cells, as well as cell cycle arrest at the G0/G1 phase, which substantially enhanced the apoptosis-inducing effect of arsenic administration. Consequently, co-administration of the two nanomedicines encapsulating siRNA or arsenic showed ideal tumor growth inhibition both in vitro and in vivo as a result of synergistic effect of the siRNA-directed Kras oncogene silencing and arsenic-induced cell apoptosis. These results suggest that the combination of mutant Kras gene silencing and arsenic therapy using nanoparticle-mediated delivery strategy is promising for pancreatic cancer treatment. FROM THE CLINICAL EDITOR: Treatment of pancreatic cancer remains a major challenge. These authors demonstrate a method that combines a siRNA-based Kras silencing with arsenic delivery to pancreatic cancer cells using nanoparticles, resulting in enhanced apoptosis induction in the treated cells.

Hydraulic-driven adaptable morphing active-cooling elastomer with bioinspired bicontinuous phases.

The active-cooling elastomer concept, originating from vascular thermoregulation for soft biological tissue, is expected to develop an effective heat dissipation method for human skin, flexible electronics, and soft robots due to the desired interface mechanical compliance. However, its low thermal conduction and poor adaptation limit its cooling effects. Inspired by the bone structure, this work reports a simple yet versatile method of fabricating arbitrary-geometry liquid metal skeleton-based elastomer with bicontinuous Gyroid-shaped phases, exhibiting high thermal conductivity (up to 27.1 W/mK) and stretchability (strain limit >600%). Enlightened by the vasodilation principle for blood flow regulation, we also establish a hydraulic-driven conformal morphing strategy for better thermoregulation by modulating the hydraulic pressure of channels to adapt the complicated shape with large surface roughness (even a concave body). The liquid metal active-cooling elastomer, integrated with the flexible thermoelectric device, is demonstrated with various applications in the soft gripper, thermal-energy harvesting, and head thermoregulation.

TNFR2 promotes pancreatic cancer proliferation, migration, and invasion via the NF-κB signaling pathway.

PURPOSE: Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignant disease with low overall survival; chemotherapy and immunotherapy have limited efficacy. Tumor necrosis factor receptor 2 (TNFR2), a type II transmembrane protein, contributes to the development and progression of several tumors. In this study, we elucidated the effect and molecular mechanisms of TNFR2. METHOD: We used The Cancer Genome Atlas and the Genotype-Tissue Expression database to compare the expression of the TNFR2 gene between normal and malignant pancreatic tissue. Using immunohistochemical staining, we divided the patients into high and low-expression groups, then investigated clinicopathologic data and survival curves of pancreatic cancer patients. We measured TNFR2 protein expression in PANC-1 and ASPC-1 pancreatic cancer cells subjected to TNFR2 small interfering RNA or negative control treatment. We performed proliferation, invasion, and migration assays to study the biological effects of TNFR2 in PDAC. The molecular mechanisms were validated using western blotting. RESULTS: TNFR2 was more highly expressed in PDAC cells and tissues than controls. Abundant expression of TNFR2 was associated with aggressive clinicopathologic characteristics and poor outcomes. Overexpression of TNFR2 promoted PDAC cell proliferation, migration, and invasion in vitro. Mechanistically, TNFR2 binds to TNF-α and activates the NF-κB signaling pathway. CONCLUSION: TNFR2 is a prognostic marker that facilitates the proliferation, migration, and invasion of PDAC via the NF-κB signaling pathway. TNFR2 may become a therapeutic target.

A new acylated flavonol glycoside from the aerial parts of Cardamine tangutorum.

A new acylated flavonol glycoside, kaempferol-3-O-ß-D-(2-feruloylglucopyranosyl) (1 → 6)-[ß-D-glucopyranosyl(1 → 2)]-ß-D-glucopyranoside, named tangutorumoside A (1), together with 12 known compounds, was isolated from 50% acetone extract of Cardamine tangutorum. Their structures were elucidated by NMR and MS experiments. In addition, compound 1 could promote the proliferation of splenic lymphocytes and thymic lymphocytes with ConA in vitro.

Application value and safety of NIPPV combined with routine clearance in the treatment of stroke-associated pneumonia in elderly patients.

OBJECTIVE: To investigate the application value and safety of NIPPV (noninvasive positive pressure ventilation) combined with routine clearance in elderly patients with stroke-associated pneumonia (SAP). METHODS: Altogether 88 elderly SAP patients treated in our hospital from January 2021 to January 2022 were retrospectively evaluated. Among them, 48 cases treated with NIPPV and routine clearance were regarded as an experimental group (EG), and 40 with routine clearance alone were enrolled to a control group (CG). The sputum clearance rate and CPIS score were compared. The safety of NIPPV was evaluated. The clearance treatment cost, hospitalization time and expenses, and the changes of inflammatory factors (IL-6, TNF-α, C-reactive protein (CRP)) were compared before and after treatment. The efficacy of airway clearance after treatment and the risk factors affecting the severity of infection was assessed. RESULTS: The sputum clearance rate in the EG was higher than that in the CG (P < 0.05). After treatment, the CPIS score of EG was lower (P < 0.05). The hospitalization time and expenses of CG were higher. After treatment, the serum inflammatory factors in CG were higher (P < 0.05), while the clinical efficacy of EG was higher (P < 0.05). Treatment plan, course of disease and diabetes are risk factors for postoperative infection. CONCLUSION: NIPPV combined with routine clearance is effective for elderly SAP patients, which can shorten the hospitalization time and reduce the expenses.

Electron Tomography Reveals Porosity Degradation Spatially on Individual Pt-Based Nanocatalysts.

Probing porosity evolution is essential to understand the degradation mechanism of electrocatalytic activity. However, spatially dependent degradation pathways for porous catalysts remain elusive. Here, we reveal the multiple degradation behaviors of individual PtCu3 nanocatalysts spatially by three-dimensional (3D) electron tomography. We demonstrate that the surface area-volume ratio (SVR) of cycled porous particles decreases linearly rather than reciprocally with particle size. Additionally, an improved SVR (about 3-fold enhancement) results in increased oxygen reduction reaction (ORR) efficiency at the early stage. However, in the subsequent cycles, the degradation of catalytic activity is due to the excessive growth of pores, the reduction of reaction sites, and the chemical segregation of Cu atoms. The spatial porosity evolution model of nanocatalysts is applicable for a wide range of catalytic reactions, providing a critical insight into the degradation of catalyst activity.