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1.
Artigo em Inglês | MEDLINE | ID: mdl-33006468

RESUMO

Metal-support interaction enhancement is critical in the fuel cell catalyst design and fabrication. Herein, taking the Pd@CeO2 system as an example, we revealed the substrate morphology coupling effect and the thermal annealing-induced Pd-O-Ce linkage enhancement in the improved catalytic capability for formic acid electrooxidation. Three well-defined CeO2 nanocrystals were employed to support Pd nanoparticles, and the best catalytic performance for formic acid oxidation and anti-CO poisoning ability was found on CeO2 plates because of the high oxygen vacancy, Ce3+, and more Pd-O-Ce linkages resulting from the more edge/corner defects. This interaction of Pd-O-Ce linkages could be largely enhanced by thermal annealing in the N2 atmosphere, as confirmed by a series of crystal structures, surface chemical state, and Raman analysis because the oxygen vacancies and lattice oxygen resulting from the oxygen atoms leaching from the CeO2 lattice would trap the mobile Pd nanocrystals by forming strengthened Pd-O-Ce linkages. Due to the high oxygen vacancy and strong Pd-O-Ce linkages, largely increased catalytic activity and stability, catalytic kinetics, and rapid charge transfer were found for all the thermal annealed Pd@CeO2 catalysts. A nearly 1.93-fold enhancement in the mass activity was achieved on the Pd@CeO2-plate catalysts demonstrating the significance of Pd-O-Ce linkage enhancement. The formation mechanism of Pd-O-Ce linkage was also probed, and a valid Pd-O-Ce linkage can only be formed in the inert atmosphere because of the reaction between metallic Pd and CeO2. This finding sheds some light on the more efficient catalyst interface construction and understanding for the fuel cell catalysis via metal-support interaction enhancement.

2.
Sci Total Environ ; 755(Pt 1): 142581, 2020 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-33039893

RESUMO

The low-level and intermediate-level radioactive waste is generally an alkaline solution with high concentration of sodium salts. Moreover, extra NaOH will be added into the matrices when the high content of mineral admixtures is used in the preparation of solidified cement matrices. This study mainly researches the influence of NaOH on the structure of C-S-H gels and the leaching rate of Sr2+ in the solidified cement matrices by isothermal conduction calorimetry, X-ray diffractometry, thermogravimetry, 29Si nuclear magnetic resonance, mercury intrusion porosimetry and inductively coupled plasma. The results show that the addition of NaOH accelerated the hydration of cement in the early age but decreased the normalized hydration heat until 28 days. Also, the fraction of total Ca(OH)2 decreased with the increasing content of NaOH. Moreover, NaOH promoted the formation of C-S-H gels along the main chain by increasing the mean chain length but decreased the Q3 sites. However, the addition of NaOH has optimized the pore structure through reducing the porosity and median pore diameter. At last, the cumulative leaching fraction of Sr2+ at the NaOH content of 10% decreased by 17.5% compared to the NaOH content of 0.82%. Based on the results, it can be concluded that NaOH enhanced the adsorption capacity of C-S-H gels to Sr2+ and improved the immobilization performance of solidified cement matrices.

3.
Blood ; 2020 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-33036022

RESUMO

In multiple myeloma (MM), frequent mutations of NRAS, KRAS, or BRAF are found in up to 50% of newly diagnosed patients. The majority of the NRAS, KRAS, and BRAF mutations occur in hotspots causing constitutive activation of the corresponding proteins. Thus targeting RAS mutation in MM will increase therapeutic efficiency and potentially overcome drug-resistance. We identified Germinal Center Kinase (GCK) as a novel therapeutic target in MM with RAS mutation. GCK knockdown in MM cells demonstrated in vitro and in vivo that silencing of GCK induces MM cell growth inhibition, associated with blocked MKK4/7-JNK phosphorylation and impaired degradation of IKZF1/3, BCL-6, and c-MYC. These effects were rescued by overexpression of an shRNA-resistant GCK, thereby excluding the potential off-target effects of GCK knockdown. In contrast, overexpression of shRNA-resistant GCK kinase-dead mutant (K45A) inhibited MM cell proliferation and failed to rescue the effects of GCK knockdown on MM growth inhibition, indicating that GCK kinase activity is critical for regulating MM cell proliferation and survival. Importantly, the higher sensitivity to GCK knockdown in RASMut cells suggests that targeting GCK is effective in multiple myeloma which harbors RAS mutations. In accordance with the effects of GCK knockdown, the GCK inhibitor TL4-12 dose-dependently downregulated IKZF1 and BCL-6 and led to MM cell proliferation inhibition accompanied by induction of apoptosis. Hereby our data identify GCK as a novel target in RASMut MM cells, providing a rationale to treat RAS mutations in MM. Furthermore, GCK inhibitors might represent an alternative therapy to overcome IMiD-resistance in MM.

4.
Bioorg Med Chem ; 28(22): 115735, 2020 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-33007552

RESUMO

Soluble epoxide hydrolase (sEH), a novel therapeutic target for neuropathic pain, is a largely cytosolic enzyme that degrades epoxy-fatty acids (EpFAs), an important class of lipid signaling molecules. Many inhibitors of sEH have been reported, and to date, the 1,3-disubstituted urea has the highest affinity reported for the sEH among the central pharmacophores evaluated. An earlier somewhat water soluble sEH inhibitor taken to the clinic for blood pressure control had mediocre potency (both affinity and kinetics) and a short in vivo half-life. We undertook a study to overcome these difficulties, but the sEH inhibitors carrying a 1,3-disubstituted urea often suffer poor physical properties that hinder their formulation. In this report, we described new strategies to improve the physical properties of sEH inhibitors with a 1,3-disubstituted urea while maintaining their potency and drug-target residence time (a complementary in vitro parameter) against sEH. To our surprise, we identified two structural modifications that substantially improve the potency and physical properties of sEH inhibitors carrying a 1,3-disubstituted urea pharmacophore. Such improvements will greatly facilitate the movement of sEH inhibitors to the clinic.

5.
Artigo em Inglês | MEDLINE | ID: mdl-33068774

RESUMO

BACKGROUND & AIMS: Alcohol-associated liver disease (ALD) is a significant cause of liver-related morbidity and mortality worldwide and with limited therapies. Soluble epoxide hydrolase (sEH; Ephx2) is a largely cytosolic enzyme that is highly expressed in the liver and is implicated in hepatic function, but its role in ALD has heretofore remained uncharted. METHODS: To decipher the role of hepatic sEH in ALD, we generated mice with liver-specific sEH disruption (Alb-Cre; Ephx2fl/fl). Alb-Cre; Ephx2fl/fl and control (Ephx2fl/fl) mice were subjected to an ethanol challenge using the chronic plus binge model of ALD and hepatic injury, inflammation, and steatosis evaluated under pair- and ethanol-fed states. Additionally, we investigated the capacity of pharmacological inhibition of sEH in the chronic plus binge mouse model. RESULTS: We observed elevation of hepatic sEH in mice upon ethanol consumption, suggesting that dysregulated hepatic sEH expression might be involved in ALD. Alb-Cre; Ephx2fl/fl mice presented efficient deletion of hepatic sEH with the corresponding attenuation in the sEH activity and alteration in the lipid epoxide/diol ratio. Consistently, hepatic sEH deficiency ameliorated ethanol-induced hepatic injury, inflammation, and steatosis. Additionally, targeted metabolomics identified lipid mediators that were significantly impacted by hepatic sEH deficiency. Moreover, hepatic sEH deficiency was associated with a significant attenuation of ethanol-induced hepatic endoplasmic reticulum and oxidative stress. Notably, pharmacological inhibition of sEH recapitulated the effects of hepatic sEH deficiency and abrogated injury, inflammation, and steatosis caused by ethanol feeding. CONCLUSIONS: These findings elucidated a role for sEH in ALD and validated a pharmacological inhibitor of this enzyme in a preclinical mouse model as a potential therapeutic approach.

6.
BMC Med ; 18(1): 268, 2020 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-33019943

RESUMO

BACKGROUND: Pulmonary arterial hypertension (PAH) is a fatal disease that results from cardio-pulmonary dysfunction with the pathology largely unknown. Insulin-like growth factor binding protein 2 (IGFBP2) is an important member of the insulin-like growth factor family, with evidence suggesting elevation in PAH patients. We investigated the diagnostic and prognostic value of serum IGFBP2 in PAH to determine if it could discriminate PAH from healthy controls and if it was associated with disease severity and survival. METHODS: Serum IGFBP2 levels, as well as IGF1/2 levels, were measured in two independent PAH cohorts, the Johns Hopkins Pulmonary Hypertension program (JHPH, N = 127), NHLBI PAHBiobank (PAHB, N = 203), and a healthy control cohort (N = 128). The protein levels in lung tissues were determined by western blot. The IGFBP2 mRNA expression levels in pulmonary artery smooth muscle cells (PASMC) and endothelial cells (PAEC) were assessed by RNA-seq, secreted protein levels by ELISA. Association of biomarkers with clinical variables was evaluated using adjusted linear or logistic regression and Kaplan-Meier analysis. RESULTS: In both PAH cohorts, serum IGFBP2 levels were significantly elevated (p < 0.0001) compared to controls and discriminated PAH from controls with an AUC of 0.76 (p < 0.0001). A higher IGFBP2 level was associated with a shorter 6-min walk distance (6MWD) in both cohorts after adjustment for age and sex (coefficient - 50.235 and - 57.336 respectively). Cox multivariable analysis demonstrated that higher serum IGFBP2 was a significant independent predictor of mortality in PAHB cohort only (HR, 3.92; 95% CI, 1.37-11.21). IGF1 levels were significantly increased only in the PAHB cohort; however, neither IGF1 nor IGF2 had equivalent levels of associations with clinical variables compared with IGFBP2. Western blotting shown that IGFBP2 protein was significantly increased in the PAH vs control lung tissues. Finally, IGFBP2 mRNA expression and secreted protein levels were significantly higher in PASMC than in PAEC. CONCLUSIONS: IGFBP2 protein expression was increased in the PAH lung, and secreted by PASMC. Elevated circulating IGFBP2 was associated with PAH severity and mortality and is a potentially valuable prognostic marker in PAH.

7.
Zool Res ; : 1-7, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-33058573

RESUMO

The restocking of the endangered Kanglang white minnow ( Anabarilius grahami) in Lake Fuxian, China, has been conducted for 13 years. However, few studies have reported on the effectiveness of the captive breeding and release of this species. Here, we investigated variations in morphology, including body shape and skeletal deformities, and genetic features among hatchery-born and recaptured A. grahami from Lake Fuxian. Results showed that current hatchery-reared fish displayed a stubbier body shape than their wild conspecifics from the 1980s. Furthermore, high skeletal deformity ratios were found in two aquafarms (Luchong, 50%; Haikou, 45.2%), and the release of malformed fish elevated the skeletal deformity rate of wild stocks found near the Lake Fuxian release sites (west coast, 19.0%; east coast, 12.5%). Based on variations in the cytochrome b (cyt b) gene, existing A. grahami populations showed relatively high haplotype diversity and low nucleotide diversity. Hatchery populations exhibited reduced genetic variations based on microsatellite markers and reintroduction led to markedly lower genetic diversity around the west coast release sites of Lake Fuxian. Analysis of molecular variance (AMOVA) of cyt b and microsatellite analysis showed that the greatest genetic variations were found within populations, and genetic distance and Bayesian clustering analysis showed that the 14 populations clustered into one group. Based on morphological and genetic tests, we discuss corresponding recommendations, including release size, feed formulations, breeding strategies, and release tags, to minimize potential risks and improve hatchery practices for better restocking of this species.

8.
J Mater Chem B ; 2020 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-33034328

RESUMO

Incorporating poly(lactic-co-glycolic) acid (PLGA) microparticles into human mesenchymal stem cells (hMSC) aggregates has shown promising application prospects. However, the acidic degradation products and burst release of PLGA microparticles still need to be ameliorated. In this study, the PLGA/chitosan-heparin (P/C-h) composite microparticles were successfully fabricated by integrating the double emulsion and microfluidic technology through the precise manipulation of the emulsion composition and flow rate of the two-phase in a flow-focusing chip. The P/C-h microparticles were highly monodispersed with a diameter of 23.45 ± 0.25 µm and shell-core structure of the PLGA encapsulated C-h complex, which were suitable for the fabrication of hMSC aggregates. When the mass ratio of PLGA to the C-h complex was optimized to 2 : 1, the pH of the leach liquor of P/C-h microparticles remained neutral. Compared with those of PLGA microparticles, the cytotoxicity and the initial burst release (loaded FGF-2 and VEGF) were both significantly reduced in P/C-h microparticles. Furthermore, the survival, stemness, as well as secretion and migration abilities of cells in hMSC aggregates incorporating P/C-h microparticles were also enhanced. In summary, the P/C-h composite microparticles prepared by the droplet microfluidic technique support the optimal biological and functional profile of the hMSC aggregates, which may facilitate the clinical applications of MSC-based therapy.

9.
Medicina (Kaunas) ; 56(10)2020 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-33008007

RESUMO

Patients with cardiopulmonary failure may not be fully supported with typical configurations of extracorporeal membrane oxygenation (ECMO), either veno-arterial (VA) or veno-venous (VV). Veno-arterial-venous (VAV)-ECMO is a technique used to support the cardiopulmonary systems during periods of inadequate gas exchange and perfusion. In the severe case of coronavirus disease 2019 (COVID-19), which simultaneously affects the heart and lung, VAV-ECMO may improve a patient's recovery potential. We report the case of a 72-year-old woman with acute respiratory distress syndrome and circulatory failure following COVID-19, who was treated with VAV-ECMO.


Assuntos
Betacoronavirus , Infecções por Coronavirus/complicações , Infecções por Coronavirus/terapia , Oxigenação por Membrana Extracorpórea/métodos , Pneumonia Viral/complicações , Pneumonia Viral/terapia , Insuficiência Respiratória/etiologia , Insuficiência Respiratória/terapia , Idoso , Cuidados Críticos/métodos , Estado Terminal , Feminino , Humanos , Pandemias
10.
Artigo em Inglês | MEDLINE | ID: mdl-33053715

RESUMO

Various indicator systems have been developed to monitor and assess healthy cities. However, few of them contain spatially explicit indicators. In this study, we assessed four health determinants in Shenzhen, China, using both indicators commonly included in healthy city indicator systems and spatially explicit indicators. The spatially explicit indicators were developed using detailed building information or social media data. Our results showed that the evaluation results of districts and sub-districts in Shenzhen based on spatially explicit indicators could be positively, negatively, or not associated with the evaluation results based on conventional indicators. The discrepancy may be caused by the different information contained in the two types of indicators. The spatially explicit indicators measure the quantity of the determinants and the spatial accessibility of these determinants, while the conventional indicators only measure the quantity. Our results also showed that social media data have great potential to represent the high-resolution population distribution required to estimate spatially explicit indicators. Based on our findings, we recommend that spatially explicit indicators should be included in healthy city indicator systems to allow for a more comprehensive assessment of healthy cities.

11.
J Clin Pharmacol ; 2020 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-33078430

RESUMO

Pharmacological target-mediated drug disposition (TMDD) represents a special source of nonlinear pharmacokinetics, and its occurrence in large-molecule compounds has been well recognized because numerous protein drugs have been reported to have TMDD due to specific binding to their pharmacological targets. Although TMDD can also happen in small-molecule compounds, it has been largely overlooked. In this mini-review, we summarize the occurrence of TMDD that we discovered recently in a series of small-molecule soluble epoxide hydrolase (sEH) inhibitors. Our journey started with an accidental discovery of target-mediated kinetics of 1-(1-propanoylpiperidin-4-yl)-3-[4-(trifluoromethoxy)phenyl]urea (TPPU), a potent sEH inhibitor, in a pilot clinical study. To confirm what we observed in humans, we conducted a series of mechanism experiments in animals, including pharmacokinetic experiments using sEH knockout mice as well as in vivo displacement experiments with co-administration of another potent sEH inhibitor. Our mechanism studies confirmed that the TMDD of TPPU is due to its pharmacological target sEH. We further expanded our evaluation to various other sEH inhibitors and found that TMDD is a class effect of this group of small-molecule sEH inhibitors. In addition to summarizing the occurrence of TMDD in sEH inhibitors, in this mini-review we also highlighted the importance of recognizing TMDD of small-molecule compounds and its impact in clinical development as well as using pharmacometric modeling in facilitating quantitative understanding of TMDD.

12.
Cancer Res ; 2020 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-33067268

RESUMO

Although B cell acute lymphoblastic leukemia (ALL) is the most common malignancy in children and while highly curable, it remains a leading cause of cancer-related mortality. The outgrowth of tumor subclones carrying mutations in genes responsible for resistance to therapy has led to a Darwinian model of clonal selection. Previous work has indicated that alterations in the epigenome might contribute to clonal selection yet the extent to which the chromatin state is altered under the selective pressures of therapy is unknown. To address this, we performed chromatin immunoprecipitation, gene expression analysis, and enhanced reduced representation bisulfite sequencing on a cohort of paired diagnosis and relapse samples from individual patients who all but one relapsed within 36 months of initial diagnosis. The chromatin state at diagnosis varied widely among patients: while the majority of peaks remained stable between diagnosis and relapse, yet a significant fraction were either lost or newly gained with some patients showing few differences and others showing massive changes of the epigenetic state. Evolution of the epigenome was associated with pathways previously linked to therapy resistance as well as novel candidate pathways through alterations in pyrimidine biosynthesis and downregulation of polycomb repressive complex 2 targets. Three novel, relapse-specific super-enhancers were shared by a majority of patients including one associated with S100A8, the top upregulated gene seen at relapse in childhood B-ALL. Overall, our results support a role of the epigenome in clonal evolution and uncover new candidate pathways associated with relapse.

13.
Nat Commun ; 11(1): 5035, 2020 10 07.
Artigo em Inglês | MEDLINE | ID: mdl-33028823

RESUMO

Aliphatic α,ω-dicarboxylic acids (DCAs) are a class of useful chemicals that are currently produced by energy-intensive, multistage chemical oxidations that are hazardous to the environment. Therefore, the development of environmentally friendly, safe, neutral routes to DCAs is important. We report an in vivo artificially designed biocatalytic cascade process for biotransformation of cycloalkanes to DCAs. To reduce protein expression burden and redox constraints caused by multi-enzyme expression in a single microbe, the biocatalytic pathway is divided into three basic Escherichia coli cell modules. The modules possess either redox-neutral or redox-regeneration systems and are combined to form E. coli consortia for use in biotransformations. The designed consortia of E. coli containing the modules efficiently convert cycloalkanes or cycloalkanols to DCAs without addition of exogenous coenzymes. Thus, this developed biocatalytic process provides a promising alternative to the current industrial process for manufacturing DCAs.

14.
Water Res ; 188: 116470, 2020 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-33045638

RESUMO

Intense storms pose a serious threat to ecosystem functioning and services. However, the effects of typhoons (tropical cyclones) on the biogeochemical processes mediating risk of eutrophication in deep freshwater ecosystems remain unclear. Here, we conducted a three-year study to elucidate linkages between environmental change, stable isotopes and the stoichiometry of particulate organic matter (POM), and nutrient cycling (i.e., carbon, nitrogen and phosphorus) in a subtropical deep reservoir subjected to typhoon events. The typhoons significantly changed the nutrient levels in the deep waters as well as the thermocline position. Increased typhoon-driven organic matter input, algae sinking and heterotrophic decomposition interacted with each other to cause steep and prolonged increases of total nitrogen, ammonium nitrogen and total phosphorus in the bottom waters of the reservoir. Small-sized or pico-sized POM (i.e., 0.2-3 µm) showed a substantial increase in bottom waters, and it exhibited stronger response than large-sized POM (i.e., 3-20, 20-64, 64-200 µm) to the typhoons. Our results also indicated that typhoons boost the nutrient cycling in deep waters mainly through pico-sized POM.

15.
Biotechnol J ; : e2000119, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-33002294

RESUMO

Diels-Alder reaction is one of the most important transformations used in organic synthesis, with the ability to construct two new CC bonds and up to four chiral centers simultaneously. However, the biggest synthetic challenge in Diels-Alder reaction lies in controlling its regio-, diastereo-, and enantioselectivity. Using Stille cross-coupling and enzymatic Diels-Alder reaction as the key steps, the first chemoenzymatic total synthesis of artonin I is achieved in 30% overall yield over only seven steps. This enzymatic Diels-Alder reaction catalyzed by MaDA is featured with excellent endo- and enantioselectivity and high catalytic efficiency (kcat /KM = 362 ± 54 mm-1  s-1 ). These successful chemoenzymatic total syntheses of artonin I and dideoxyartonin I demonstrated the remarkable potential of the intermolecular Diels-Alderase MaDA in biocatalysis.

16.
Bioconjug Chem ; 2020 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-33040528

RESUMO

The serious threat of antibiotic-resistant bacterial infections has brought an urgent need for the development of new antibacterial nanomaterials. We encapsulate glutathione (GSH)-protected gold nanoclusters (AuNCs) in zeolitic imidazolate frameworks-8 (ZIF-8) and present their potential in antibacterial capabilities. Under white light irradiation, AuNCs-embedded ZIF-8 nanocomposites show assembly-enhanced emission and reactive oxygen species (ROS) generation. AuNCs@ZIF-8 exhibit almost complete inactivation of bacterial growth within 60 min of light irradiation. Scanning electron microscopic results show that AuNCs@ZIF-8 nanocomposites are captured by bacterial cells, and the leakage of alkaline phosphatase and nucleotides from bacteria demonstrate that the photoinduced ROS can easily destroy the bacterial surface and totally kill the bacteria. Herein, our antibacterial nanocomposites have photoenhanced bactericidal capability and show promising applications for sterilization.

17.
Med (N Y) ; 2020 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-33043313

RESUMO

Background: The coronavirus disease 2019 (COVID-19) is an emerged respiratory infectious disease with kidney injury as a part of the clinical complications. However, the dynamic change of kidney function and its association with COVID-19 prognosis are largely unknown. Methods: In this multicenter retrospective cohort study, we analyzed clinical characteristics, medical history, laboratory tests, and treatment data of 12,413 COVID-19 patients. The patient cohort was stratified according to the severity of the outcome into three groups: non-severe, severe, and death. Findings: The prevalence of elevated blood urea nitrogen (BUN), elevated serum creatinine (Scr), and decreased blood uric acid (BUA) at admission was 6.29%, 5.22%, 11.66%, respectively. The trajectories showed elevation of BUN level and Scr level, as well as a reduction of BUA level during 28 days after admission in death cases. Increased all-cause mortality risk was associated with elevated baseline levels of BUN and Scr, and decreased level of BUA. Conclusion: The dynamic changes of the three kidney function markers were associated with different severity and poor prognosis of COVID-19 patients. BUN showed close association and high potential for predicting adverse outcomes in COVID-19 patients for severity stratification and triage.

18.
Artigo em Inglês | MEDLINE | ID: mdl-33006928

RESUMO

Recently, super-harmonic ultrasound imaging technology has caused much attention due to its capability of distinguishing microvessles from the tissues surrounding them. However, the fabrication of a dual-frequency confocal transducer is still a challenge. In this work, 270µm PMN-PT single crystal 1-3 composite and 28µm PVDF thick film, acting as transmission layer and receiving layer, respectively, are integrated in a novel co-focusing structure. To realize delicate wave propagation control, microwave transmission line theory is introduced to design such structure. Two acoustic filter layers, 13µm copper layer and 39µm Epoxy 301 layer, are indispensable and should be added between two piezoelectric layers. Therefore, an acoustic issue can be overcome via an electrical method and the successful achievement of a dual-frequency (5MHz/30MHz) ultrasound transducer with confocal distance of 8mm can be realized. The super harmonic ultrasound imaging experiment is conducted using this kind of device. 3D image of 110µm diameter phantom tube injected with microbubbles can be obtained. These promising results demonstrate that this novel dual-frequency (5MHz/30MHz) confocal ultrasound transducer is potentially usable for microvascular medical imaging application in the future.

19.
Artigo em Inglês | MEDLINE | ID: mdl-32924420

RESUMO

The vital challenge of a layered manganese oxide cathode for sodium-ion batteries is its severe capacity degradation and sluggish ion diffusion kinetics caused by irreversible phase transitions. In response to this problem, the spinel-layered manganese-based composite with an intergrowth structure is ingeniously designed by virtue of an interesting spinel-to-layered transformation in the delithiated LiMn2O4 under Na+ insertion. This unique spinel-layered intergrowth structure is strongly confirmed by combining multiple structure analysis techniques. The layered component can provide more reversible capacity, while the spinel component is crucial for the stabilized crystal structure and accelerated ion diffusion kinetics. As an appealing cathode for sodium-ion batteries, the layered-spinel composite delivers a high reversible capacity of 180.9 mAh g-1, excellent cycling stability, and superior rate capability with 55.7 mAh g-1 at 12 C. Furthermore, the reaction mechanism upon Na+ extraction/insertion is revealed in detail by ex situ X-ray diffraction and X-ray photoelectron spectroscopy, indicating that Na+ ions can be accommodated by the layered structure at a low voltage and by the spinel at a high voltage. This study will provide a new idea for the rational design of an advanced cathode for sodium-ion batteries.

20.
J Colloid Interface Sci ; 582(Pt B): 1099-1106, 2020 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-32947095

RESUMO

The exploration of low cost electrocatalyst with comparable catalytic activity and kinetics to the expensive noble metal catalysts for hydrogen evolution reaction (HER) is still the most urgent challenge. Herein, a facile strategy to synthesize Ti3C2Tx MXene by ultrasonication with controlled N-doping is reported. The surface modification of MXene can be achieved by the formation of TiN chemical bonds at an optimized ultrasonic temperature, which will further enhance the HER activity. Specifically, at the ultrasonic temperature of 35 °C, the N-doped MXene (N-MXene-35) exhibits the highest concentration of TiN bond, delivering an extraordinary HER activity with an overpotential of 162 mV (vs. the reversible hydrogen electrode, RHE) at the current density of 10 mA cm-2 in acid media, which is 3.5 times lower than that of the pristine MXene (578 mV vs. RHE). As expected, the obtained N-MXene-35 affords the best HER electrocatalytic performance among the MXene or N-doped MXene electrode as so far reported.

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