Origin for electrochemically driven phase transformation in the oxygen electrode for a solid oxide cell.

The next generation of fuel cells, electrolyzers, and batteries requires higher power, faster kinetics, and larger energy density, which necessitate the use of compositionally complex oxides to achieve multifunctionalities and activity. These compositionally complex oxides may change their phases and structures during an electrochemical process-a so-called "electrochemically driven phase transformation." The origin for such a phase change has remained obscure. The aim of this paper is to present an experimental study and a theoretical analysis of phase evolution in praseodymium nickelates. Nickelate-based electrodes show up to 60 times greater phase transformation during operation when compared with thermally annealed ones. Theoretical analysis suggests that the presence of a reduced oxygen partial pressure at the interface between the oxygen electrode and the electrolyte is the origin for the phase change in an oxygen electrode. Guided by the theory, the addition of the electronic conduction in the interface layer leads to the significant suppression of phase change while improving cell performance and performance stability.

Layer Control of Magneto-Optical Effects and Their Quantization in Spin-Valley Splitting Antiferromagnets.

Magneto-optical effects (MOE), interfacing the fundamental interplay between magnetism and light, have served as a powerful probe for magnetic order, band topology, and valley index. Here, based on multiferroic and topological bilayer antiferromagnets (AFMs), we propose a layer control of MOE (L-MOE), which is created and annihilated by layer-stacking or an electric field effect. The key character of L-MOE is the sign-reversible response controlled by ferroelectric polarization, the Néel vector, or the electric field direction. Moreover, the sign-reversible L-MOE can be quantized in topologically insulating AFMs. We reveal that the switchable L-MOE originates from the combined contributions of spin-conserving and spin-flip interband transitions in spin-valley splitting AFMs, a phenomenon not observed in conventional AFMs. Our findings bridge the ancient MOE to the emergent realms of layertronics, valleytronics, and multiferroics and may hold immense potential in these fields.

Mechanistic Insights into Surfactant-Modulated Electrode-Electrolyte Interface for Steering H2O2 Electrosynthesis.

Electrocatalytic reactions taking place at the electrified electrode-electrolyte interface involve processes of proton-coupled electron transfer. Interfacial protons are delivered to the electrode surface via a H2O-dominated hydrogen-bond network. Less efforts are made to regulate the interfacial proton transfer from the perspective of interfacial hydrogen-bond network. Here, we present quaternary ammonium salt cationic surfactants as electrolyte additives for enhancing the H2O2 selectivity of the oxygen reduction reaction (ORR). Through in situ vibrational spectroscopy and molecular dynamics calculation, it is revealed that the surfactants are irreversibly adsorbed on the electrode surface in response to a given bias potential range, leading to the weakening of the interfacial hydrogen-bond network. This decreases interfacial proton transfer kinetics, particularly at high bias potentials, thus suppressing the 4-electron ORR pathway and achieving a highly selective 2-electron pathway toward H2O2. These results highlight the opportunity for steering H2O-involved electrochemical reactions via modulating the interfacial hydrogen-bond network.

Crystal Thermal Transport in Altermagnetic RuO_{2}.

We demonstrate the emergence of a pronounced thermal transport in the recently discovered class of magnetic materials-altermagnets. From symmetry arguments and first-principles calculations performed for the showcase altermagnet, RuO_{2}, we uncover that crystal Nernst and crystal thermal Hall effects in this material are very large and strongly anisotropic with respect to the Néel vector. We find the large crystal thermal transport to originate from three sources of Berry's curvature in momentum space: the Weyl fermions due to crossings between well-separated bands, the strong spin-flip pseudonodal surfaces, and the weak spin-flip ladder transitions, defined by transitions among very weakly spin-split states of similar dispersion crossing the Fermi surface. Moreover, we reveal that the anomalous thermal and electrical transport coefficients in RuO_{2} are linked by an extended Wiedemann-Franz law in a temperature range much wider than expected for conventional magnets. Our results suggest that altermagnets may assume a leading role in realizing concepts in spin caloritronics not achievable with ferromagnets or antiferromagnets.

Obesity Paradox in Patients with Acute Coronary Syndrome: Is Malnutrition the Answer?

BACKGROUND: Obesity paradox has been reported in patients with cardiovascular disease, showing an inverse association between obesity as defined by BMI (in kg/m2) and prognosis. Nutritional status is associated with systemic inflammatory response and affects cardiovascular disease outcomes. OBJECTIVES: This study sought to examine the influence of obesity and malnutrition on the prognosis of patients with acute coronary syndrome (ACS). METHODS: This study included consecutive patients diagnosed with ACS and underwent coronary angiogram between January 2009 and February 2023. At baseline, patients were categorized according to their BMI as follows: underweight (<18), normal weight (18-24.9), overweight (25.0-29.9), and obese (>30.0). We assessed the nutritional status by Prognostic Nutritional Index (PNI). Malnutrition was defined as a PNI value of <38. RESULTS: Of the 21,651 patients with ACS, 582 (2.7%) deaths from any cause were observed over 28.7 months. Compared with the patient's state of normal weight, overweight, and obesity were associated with decreased risk of all-cause mortality. Malnutrition was independently associated with poor survival (hazards ratio: 2.64; 95% CI: 2.24, 3.12; P < 0.001). In malnourished patients, overweight and obesity showed a 39% and 72% reduction in the incidence of all-cause mortality, respectively. However, in nourished patients, no significant reduction in the incidence of all-cause mortality was observed (all P > 0.05). CONCLUSIONS: Obesity paradox appears to occur in patients with ACS. Malnutrition may be a significant independent risk factor for prognosis in patients with ACS. The obesity paradox is influenced by the status of malnutrition.

High-Density Dynamic Bonds Cross-Linked Hydrogel with Tissue Adhesion, Highly Efficient Self-Healing Behavior, and NIR Photothermal Antibacterial Ability as Dressing for Wound Repair.

Multifunctional hydrogels with tissue adhesion, self-healing behavior, and antibacterial properties have potential in wound healing applications. However, their inefficient self-healing behavior and antibacterial agents can cause long-term cytotoxicity and drug resistance, considerably limiting their clinical use. Herein, we reported a PDA@LA hydrogel constructed by introducing polydopamine nanoparticles (PDA-NPs) into a high-density dynamic bonds cross-linked lipoic acid (LA) hydrogel that was formed by the polymerization of LA. Because of its rich carboxyl groups, the LA hydrogel could adhere firmly to various tissues. Owing to the high-density dynamic bonds, the cut LA hydrogel exhibited highly inefficient self-healing behavior and recovered to its uncut state after self-healing for 10 min. After the introduction of the PDA-NPs, the hydrogel was able to heat up to more than 40 °C to kill approximately 100% of the Escherichia coli and Staphylococcus aureus under near-infrared (NIR) laser, thus resisting wound infections. Because no toxic antibacterial agent was used, the PDA@LA hydrogel caused mild long-term cytotoxicity or drug resistance. Consequently, the adhesive, highly efficient self-healing, and NIR photothermal antibacterial PDA@LA hydrogel exhibits considerable potential for clinical use.

Serum bile acid profiles are associated with heart failure with preserved ejection fraction in patients with metabolic dysfunction-associated fatty liver disease: An exploratory study.

AIM: To analyse the association between serum bile acid (BA) profile and heart failure (HF) with preserved ejection fraction (HFpEF) in patients with metabolic dysfunction-associated fatty liver disease (MAFLD). METHODS: We enrolled 163 individuals with biopsy-proven MAFLD undergoing transthoracic echocardiography for any indication. HFpEF was defined as left ventricular ejection fraction >50% with at least one echocardiographic feature of HF (left ventricular diastolic dysfunction, abnormal left atrial size) and at least one HF sign or symptom. Serum levels of 38 BAs were analysed using ultra-performance liquid chromatography coupled with tandem mass spectrometry. RESULTS: Among the 163 patients enrolled (mean age 47.0 ± 12.8 years, 39.3% female), 52 (31.9%) and 43 (26.4%) met the HFpEF and pre-HFpEF criteria, and 38 serum BAs were detected. Serum ursodeoxycholic acid (UDCA) and hyocholic acid (HCA) species were lower in patients with HFpEF and achieved statistical significance after correction for multiple comparisons. Furthermore, decreases in glycoursodeoxycholic acid and tauroursodeoxycholic acid were associated with HF status. CONCLUSIONS: In this exploratory study, specific UDCA and HCA species were associated with HFpEF status in adults with biopsy-confirmed MAFLD.

Adaptive Fabrication of Electrochemical Chips with a Paste-Dispensing 3D Printer.

Electrochemical (EC) detection is a powerful tool supporting simple, low-cost, and rapid analysis. Although screen printing is commonly used to mass fabricate disposable EC chips, its mask is relatively expensive. In this research, we demonstrated a method for fabricating three-electrode EC chips using 3D printing of relatively high-viscosity paste. The electrodes consisted of two layers, with carbon paste printed over silver/silver chloride paste, and the printed EC chips were baked at 70 °C for 1 h. Engineering challenges such as bulging of the tubing, clogging of the nozzle, dripping, and local accumulation of paste were solved by material selection for the tube and nozzle, and process optimization in 3D printing. The EC chips demonstrated good reversibility in redox reactions through cyclic voltammetry tests, and reliably detected heavy metal ions Pb(II) and Cd(II) in solutions using differential pulse anodic stripping voltammetry measurements. The results indicate that by optimizing the 3D printing of paste, EC chips can be obtained by maskless and flexible 3D printing techniques in lieu of screen printing.

Spin-Chirality-Driven Quantum Anomalous and Quantum Topological Hall Effects in Chiral Magnets.

The quantum anomalous Hall effect (QAHE) is a highly researched topic in condensed matter physics due to its ability to enable dissipationless transport. Previous studies have mainly focused on the ferromagnetic QAHE, which arises from the combination of collinear ferromagnetism and two-dimensional (2D) Z2 topological insulator phases. In our study, we demonstrate the emergence of the spin-chirality-driven QAHE and the quantum topological Hall effect (QTHE) by sandwiching a 2D Z2 topological insulator between two chiral kagome antiferromagnetic single-layers synthesized experimentally. The QAHE is surprisingly realized with fully compensated noncollinear antiferromagnetism in contrast to conventional collinear ferromagnetism. The Chern number can be regulated periodically with the interplay between vector- and scalar-spin chiralities, and the QAHE emerges even without spin-orbit coupling, indicating the rare QTHE. Our findings open a new avenue for realizing antiferromagnetic quantum spintronics based on the unconventional mechanisms from chiral spin textures.

Catalytic Hydroconversion of Model Compounds over Ni/NiO@NC Nanoparticles.

The conversion of lignite into aromatic compounds by highly active catalysts is a key strategy for lignite valorization. In this study, Ni/NiO@NC nanocomposites with a high specific surface area and a vesicular structure were successfully prepared via a facile sol-gel method. The Ni/NiO@NC catalysts exhibited excellent catalytic activity for the catalytic hydroconversion (CHC) of benzyloxybenzene (as lignite-related modeling compounds) under mild conditions (120 °C, 1.5 MPa H2, 60 min). The possible mechanism of the catalytic reaction was investigated by analyzing the type and content of CHC reaction products at different temperatures, pressures, and times. More importantly, the magnetic catalyst could be conveniently separated by a magnet after the reaction, and it maintained high catalytic efficiency after six reuses. This study provides an efficient and recyclable catalyst for the cleavage of >CH-O bonds in lignite, thereby offering another way for improved utilization of lignite.

Organic-Inorganic Hybrid Crystal-Assisted Etching of Nickel Foam for the Collectively Exhaustive Electrochemical Performance of Oxygen Evolution Reaction.

In this work, an organic-inorganic hybrid crystal, violet-crystal (VC), was used to etch the nickel foam (NF) to fabricate a self-standing electrode for the water oxidation reaction. The efficacy of VC-assisted etching manifests the promising electrochemical performance towards the oxygen evolution reaction (OER), requiring only ~356 and ~376 mV overpotentials to reach 50 and 100 mA cm-2 , respectively. The OER activity improvement is attributed to the collectively exhaustive effects arising from the incorporation of various elements in the NF, and the enhancement of active site density. Furthermore, the self-standing electrode is robust, exhibiting a stable OER activity after 4,000 cyclic voltammetry cycles, and ~50 h. The anodic transfer coefficients (αa ) show that the first electron transfer step is the rate-determining step on the surface of NF-VCs-1.0 (NF etched by 1 g of VCs) electrode, while the chemical step involving dissociation following the first electron transfer step is identified as the rate-limiting step in other electrodes. The lowest Tafel slope value observed in the NF-VCs-1.0 electrode indicates the high surface coverage of oxygen intermediates and more favorable OER reaction kinetics, as confirmed by high interfacial chemical capacitance and low charge transport/interfacial resistance. This work demonstrates the importance of VCs-assisted etching of NF to activate the OER, and the ability to predict reaction kinetics and rate-limiting step based on αa values, which will open new avenues to identify advanced electrocatalysts for the water oxidation reaction.

AREG is involved in scleral remodeling in form-deprivation myopia via the ERK1/2-MMP-2 pathway.

Previous studies have found that amphiregulin (AREG) may participate in eye elongation during the development of myopia, but the mechanism remains unclear. Here, we tested tear concentrations of AREG in adults and detected the role of AREG in scleral remodeling in form-deprivation myopia (FDM) in guinea pigs. We found the tear concentrations of AREG in myopes were significantly higher than those in emmetropes using enzyme-linked immunosorbent assay (ELISA). Tear concentrations of AREG were negatively correlated with spherical equivalent refraction and positively correlated with axial length (AL) and AL/corneal radii. We then used RNAi, DNA transfection and PD98059 treatments to determine the effects of AREG on extracellular signal-regulated kinase 1/2 (ERK1/2) and matrix metalloprotease-2 (MMP-2) in primary scleral fibroblasts (SFs). The hypothesis was further verified via loss- and gain-of-function experiments by intravitreal application of anti-AREG antibody (anti-AR) or AREG in form-deprivation eyes in guinea pigs. Immunofluorescence assay was used for cell type identification. Western-blot and q-PCR were used for the detection of relative expressions. Transmission electron microscopy was performed for posterior scleral observation. In vitro, we found AREG overexpression increased phospho-ERK1/2 and MMP-2 expression, while depletion of AREG inhibited their expressions. PD98059 (an effective ERK1/2 inhibitor) inhibited AREG-induced MMP-2 upregulation. In vivo, we found anti-AR treatments suppressed FDM by inhibiting scleral remodeling, while AREG treatments promoted FDM. Our results suggest that AREG in tear fluids can serve as a potential biomarker in myopes. AREG is involved in scleral remodeling through the ERK1/2-MMP-2 pathway. AREG is a potential target for myopia control.

The interaction between hyperuricemia and low-density lipoprotein cholesterol increases the risk of 1-year post-discharge all-cause mortality in ST-segment elevation myocardial infarction patients.

BACKGROUND AND AIMS: Hyperuricemia is a known risk factor for cardiovascular diseases, but little is known on whether the association between hyperuricemia and poor outcomes in ST-segment elevation myocardial infarction (STEMI) is modified by low-density lipoprotein cholesterol (LDL-c). This study aimed to investigate the effect of the interaction between hyperuricemia and LDL-c on the risk of 1-year post-discharge all-cause mortality in STEMI patients. METHODS AND RESULTS: A total of 1396 STEMI patients were included. Cox proportional hazards models were used to determine the association between hyperuricemia and 1-year all-cause mortality in the overall population and subgroups stratified based on LDL-c levels (<3.0 mmol/L or ≥3.0 mmol/L). Multivariate analysis indicated that hyperuricemia was associated with 1-year mortality (HR: 2.66; 95% CI: 1.30-5.47; p = 0.008). However, the prognostic effect of hyperuricemia was only observed in patients with LDL-c level ≥3.0 mmol/L (HR: 12.90; 95% CI: 2.98-55.77; p < 0.001), but not in those with LDL-c level <3.0 mmol/L (HR: 0.91, 95% CI: 0.30-2.79, p = 0.875). The interaction between hyperuricemia and LDL-c levels had a significant effect on 1-year mortality. CONCLUSION: Hyperuricemia was associated with increased 1-year post-discharge mortality in patients with LDL-c level≥ 3.0 mmol/L, but not in those with LDL-c level< 3.0 mmol/L.

Impact of closed management on gastrointestinal function and mental health of Chinese university students during COVID-19.

BACKGROUND: The innovative closed management of universities may have influenced the physical and mental health of students during the fourth stage of the COVID-19 pandemic in China. The study aimed to assess the gastrointestinal and mental health status of students in this stage and to explore the possible risk factors and mechanisms to provide a reference for future school responses to similar stressful events. METHOD: A multicenter, cross-sectional survey was administered to 598 college students from 10 Chinese universities. The study used the 7-item Generalized Anxiety Disorder Scale (GAD-7), 9-item Patient Health Questionnaire (PHQ-9), Fear of COVID-19 Scale (FCV-19 S), and the Diagnostic Tendency of Functional Bowel Disease Scale (DT-FBD) to evaluate anxiety, depression, fear of COVID-19 and likelihood of being diagnose diagnosed with functional bowel disease (FBD), respectively. RESULTS: A total of 516 college students completed the questionnaire. The proportions of students with more severe anxiety, more severe depression, greater fear of COVID-19, and a greater likelihood of being diagnosed with FBD were 49.8%, 57.0%, 49%, and 49%, respectively. These symptoms were significantly and positively correlated with the frequency of irregular sleep and eating (p < 0.05). Students in high-risk areas were more likely to experience anxiety and depression than students in areas with low/medium risk (odds ratio [OR] = 1.90, 95% confidence interval [CI]: 1.12-3.24, p = 0.017; OR = 2.14, 95% CI: 1.11-4.11, p = 0.022). A high likelihood of being diagnosed with FBD was positively associated with the severity of anxiety and depression symptoms and fear of COVID-19 (all p < 0.001). Moreover, mediation analysis revealed the following pathway in college students: fear of COVID-19 → depression and anxiety → poor diet → likelihood of being diagnosed with FBD. CONCLUSION: College students generally exhibited higher more severe anxiety and depression symptoms and psychological symptoms with a greater higher propensity likelihood of being to be diagnosed with FBD. Good lifestyle habits, especially adequate sleep and a regular diet, can alleviate these problems. In addition, appropriate psychological intervention is very important.

Helical Luttinger Liquid on the Edge of a Two-Dimensional Topological Antiferromagnet.

A boundary helical Luttinger liquid (HLL) with broken bulk time-reversal symmetry belongs to a unique topological class that may occur in antiferromagnets (AFM). Here, we search for signatures of HLL on the edge of a recently discovered topological AFM, MnBi2Te4 even-layer. Using a scanning superconducting quantum interference device, we directly image helical edge current in the AFM ground state appearing at its charge neutral point. Such a helical edge state accompanies an insulating bulk which is topologically distinct from the ferromagnetic Chern insulator phase, as revealed in a magnetic field driven quantum phase transition. The edge conductance of the AFM order follows a power law as a function of temperature and source-drain bias which serves as strong evidence for HLL. Such HLL scaling is robust at finite fields below the quantum critical point. The observed HLL in a layered AFM semiconductor represents a highly tunable topological matter compatible with future spintronics and quantum computation.

Insights into the Relationship between the Microstructure and the Catalytic Behavior of Fe2(MoO4)3 during the Ethanolysis of Naomaohu Coal.

Ethanolysis is an effective method to depolymerize weak bonds in lignite under mild conditions, which can result in the production of high-value-added chemicals. However, improving ethanolysis yield and regulating its resulting product distribution is a big challenge. Hence, exploiting highly active catalysts is vital. In this work, Fe2(MoO4)3 catalysts with zero-dimensional nanoparticles, one-dimensional (1D) nanorods, two-dimensional (2D) nanosheets, and three-dimensional (3D) nanoflower structures were successfully prepared and applied in the ethanolysis of Naomaohu coal. The results showed that for all samples, the yield of ethanol-soluble portions (ESP) was significantly improved. The highest yield was obtained for the Fe2(MoO4)3 nanorods, with an increase from 28.84% to 47.68%, and could be attributed to the fact that the Fe2(MoO4)3 nanorods had a higher number of exposed active (100) facets. In addition, the amounts of oxygen-containing compounds, such as ethers, esters, and phenols, increased significantly. The mechanism of ethanolysis catalyzed by the Fe2(MoO4)3 nanorods was also studied using phenylbenzyl ether (BOB) as a model compound. BOB was completely converted at 260 °C after 2 h. It is suggested that Fe2(MoO4)3 nanorods can effectively break the C-O bonds of coal macromolecules, thus promoting the conversion of coal.

Outcome and safety of intracardiac echocardiography guided left atrial appendage closure within zero-fluoroscopy atrial fibrillation ablation procedures.

BACKGROUND: Simultaneous atrial fibrillation (AF) catheter ablation and left atrial appendage closure (LAAC) are sometimes recommended for both rhythm control and stroke prevention. However, the advantages of intracardiac echocardiography (ICE) guidance for this combined procedure have been scarcely reported. We aim to evaluate the clinical outcomes and safety of ICE-guided LAAC within a zero-fluoroscopy catheter ablation procedure. METHODS AND RESULTS: From April 2019 to April 2020, 56 patients with symptomatic AF underwent concomitant catheter ablation and LAAC. ICE with a multi-angled imaging protocol mimicking the TEE echo windows was used to guide LAAC. Successful radiofrequency catheter ablation and LAAC were achieved in all patients. Procedure-related adverse event rate was 3.6%. During the 12-month follow-up, 75.0% of patients became free of arrhythmia recurrences and oral anticoagulants were discontinued in 96.4% of patients. No ischemic stroke occurred despite two cases of device-related thrombosis versus an expected stroke rate of 4.8% based on the CHA2 DS2 -VASc score. The overall major bleeding events rate was 1.8%, which represented a relative reduction of 68% versus an expected bleeding rate of 5.7% based on the HAS-BLED score of the patient cohort. The incidence of iatrogenic atrial septal defect secondary to single transseptal access dropped from 57.9% at 2 months to 4.2% at 12 months TEE follow-up. CONCLUSION: The combination of catheter ablation and LAAC under ICE guidance was safe and effective in AF patients with high stroke risk. ICE with our novel protocol was technically feasible for comprehensive and systematic assessment of device implantation.

Metabolic dysfunction-associated fatty liver disease and implications for cardiovascular risk and disease prevention.

The newly proposed term "metabolic dysfunction-associated fatty liver disease" (MAFLD) is replacing the old term "non-alcoholic fatty liver disease" (NAFLD) in many global regions, because it better reflects the pathophysiology and cardiometabolic implications of this common liver disease. The proposed change in terminology from NAFLD to MAFLD is not simply a single-letter change in an acronym, since MAFLD is defined by a set of specific and positive diagnostic criteria. In particular, the MAFLD definition specifically incorporates within the classification recognized cardiovascular risk factors. Although convincing evidence supports a significant association between both NAFLD and MAFLD, with increased risk of CVD morbidity and mortality, neither NAFLD nor MAFLD have received sufficient attention from the Cardiology community. In fact, there is a paucity of scientific guidelines focusing on this common and burdensome liver disease from cardiovascular professional societies. This Perspective article discusses the rationale and clinical relevance for Cardiologists of the newly proposed MAFLD definition.

Disorder- and Topology-Enhanced Fully Spin-Polarized Currents in Nodal Chain Spin-Gapless Semimetals.

Recently discovered high-quality nodal chain spin-gapless semimetals MF_{3} (M=Pd, Mn) feature an ultraclean nodal chain in the spin up channel residing right at the Fermi level and displaying a large spin gap leading to a 100% spin polarization of transport properties. Here, we investigate both intrinsic and extrinsic contributions to anomalous and spin transport in this class of materials. The dominant intrinsic origin is found to originate entirely from the gapped nodal chains without the entanglement of any other trivial bands. The side-jump mechanism is predicted to be negligibly small, but intrinsic skew scattering enhances the intrinsic Hall and Nernst signals significantly, leading to large values of respective conductivities. Our findings open a new material platform for exploring strong anomalous and spin transport properties in magnetic topological semimetals.

Achieving Superhydrophobic Surfaces via Air-Assisted Electrospray.

Superhydrophobic surface is an enabling technology in numerous emerging and practical applications such as self-cleaning, anticorrosion, antifouling, anti-icing coatings, and oil-water separation. Here, we report a facile air-assisted electrospray approach to achieve a superhydrophobic surface by systematically studying spray conditions and the chemistry of a coating precursor solution consisting of silicon dioxide nanoparticles, polyacrylonitrile, and N,N-dimethylformamide. The wettability behavior of the surface was analyzed with contact angle measurement and correlated with surface structures. The superhydrophobic coating exhibits remarkable water and oil repellent characteristics, as well as good robustness against abrasion and harsh chemical conditions. This air-assisted electrospray technique has shown great control over the coating process and properties and thus can be potentially used for various advanced industrial applications for self-cleaning and anticorrosion surfaces.