Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 161
Filtrar
1.
IEEE Trans Biomed Eng ; PP2021 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-34613905

RESUMO

OBJECTIVE: In this paper, Keypoint Localization Region-based CNN (KL R-CNN) is proposed, which can simultaneously accomplish the guidewire detection and endpoint localization in a unified model. METHODS: KL R-CNN modifies Mask R-CNN by replacing the mask branch with a novel keypoint localization branch. Besides, some settings of Mask R-CNN are also modified to generate the keypoint localization results at a higher detail level. At the same time, based on the existing metrics of Average Precision (AP) and Percentage of Correct Keypoints (PCK), a new metric named AP PCK is proposed to evaluate the overall performance on the multi-guidewire endpoint localization task. Compared with existing metrics, AP PCK is easy to use and its results are more intuitive. RESULTS: Compared with existing methods, KL R-CNN has better performance when the threshold is loose, reaching a mean AP PCK of 90.65% when the threshold is 9 pixels. CONCLUSION: KL R-CNN achieves the state-of-the-art performance on the multi-guidewire endpoint localization task and has application potentials. SIGNIFICANCE: KL R-CNN can achieve the localization of guidewire endpoints in fluoroscopy images, which is a prerequisite for computer-assisted percutaneous coronary intervention. KL R-CNN can also be extended to other multi-instrument localization tasks.

2.
Nano Lett ; 21(19): 8043-8050, 2021 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-34550704

RESUMO

Two-dimensional (2D) trigonal selenium (t-Se) has become a new member in 2D semiconducting nanomaterial families. It is composed of well-aligned one-dimensional Se atomic chains bonded via van der Waals (vdW) interaction. The contribution of this unique anisotropic nanostructure to its mechanical properties has not been explored. Here, for the first time, we combine experimental and theoretical analyses to study the anisotropic mechanical properties of individual 2D t-Se nanosheets. It was found that its fracture strength and Young's modulus parallel to the atomic chain direction are much higher than along the transverse direction, which was attributed to the weak vdW interaction between Se atomic chains as compared to the covalent bonding within individual chains. Additionally, two distinctive fracture modes along two orthogonal loading directions were identified. This work provides important insights into the understanding of anisotropic mechanical behaviors of 2D semiconducting t-Se and opens new possibilities for future applications.


Assuntos
Nanoestruturas , Selênio , Anisotropia , Módulo de Elasticidade , Humanos
3.
Sci Total Environ ; 792: 148493, 2021 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-34465043

RESUMO

Dissolved organic matter (DOM) in wet weather overflows (WWFs) of storm drainage systems mainly originates from anthropogenic sources, such as paved runoff, illegally discharged domestic sewage and the retained sediment. This study provides a promising method to quantitatively apportion the WWF DOM of storm drainage systems using degradation potential index (DPI) and end member mixing (EMM) model. DPI is derived from excitation-emission matrix parallel factor analysis (EEM-PARAFAC), which can endow the end members and itself of WWF DOM with numerical features, and thus help quantify the source contributions of WWF DOM in EMM model. Findings show that (1) DPI was a reliable tool in the quantitative source apportionment of WWF DOM, owing to its features of small variance within source and large variances between sources; (2) DPI combined with EMM model could help identify the factors that induce significant impacts on the source contributions of WWF DOM, such as the storm pumping discharge and antecedent dry days in our case study; (3) the identified factors could guide the development of effective strategies for WWF DOM control, e.g. sediment management in our case.


Assuntos
Esgotos , Tempo (Meteorologia) , Análise Fatorial , Espectrometria de Fluorescência
4.
Huan Jing Ke Xue ; 42(10): 4916-4924, 2021 Oct 08.
Artigo em Chinês | MEDLINE | ID: mdl-34581135

RESUMO

The accumulation of some harmful elements in plants from intensive production systems pose a serious threat to human health. In this study, seven heavy metals(Cu, Pb, Zn, Cr, Cd, As, and Hg) and their distribution characteristics in the crops, vegetables, and fruits were analyzed alongside single factor evaluation and Nemero index analysis. Combined with dietary recommended consumption data from the Chinese Nutrition Society, the dietary exposure of heavy metals were further analyzed, and a consequent safety risk assessment was conducted. A total of 673 crop, vegetable, and fruit samples were collected from typical intensive production systems in Hainan Province. The results showed that the content of Cu, As, and Hg in the 673 plant samples was below the value of the national food standard. The exceed rates of Pb, Zn, Cr, and Cd were 2.67%, 3.71%, 2.53%, and 3.71%, respectively. The heavy metal comprehensive pollution degree of six species of plants showed the trend of leafy vegetables > tuber crops > non-leafy vegetables > legume crops > fruits > cereals. In particular, Cr in leafy vegetables showed significantly higher hazard quotients(HQ) than that in other types, and exceeded 1, suggesting a high potential health risk via the ingestion of heavy metals through leafy vegetables. The relatively lower hazard index(HI) values of tuber crops, non-leafy vegetables, legume crops, fruits, and cereals suggest that these types of plants are more suitable for intensive production systems.


Assuntos
Metais Pesados , Poluentes do Solo , China , Grão Comestível/química , Monitoramento Ambiental , Frutas/química , Humanos , Metais Pesados/análise , Medição de Risco , Solo , Poluentes do Solo/análise , Verduras
5.
J Phys Condens Matter ; 33(49)2021 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-34479213

RESUMO

Two-dimensional (2D) materials have attracted broad interests and been extensively exploited for a variety of functional applications. Moreover, one-dimensional (1D) atomic crystals can also be integrated into 2D templates to create mixed-dimensional heterostructures, and the versatility of combinations provides 2D-1D heterostructures plenty of intriguing physical properties, making them promising candidate to construct novel electronic and optoelectronic nanodevices. In this review, we first briefly present an introduction of relevant fabrication methods and structural configurations for 2D-1D heterostructures integration. We then discuss the emerged intriguing physics, including high optical absorption, efficient carrier separation, fast charge transfer and plasmon-exciton interconversion. Their potential applications such as electronic/optoelectronic devices, photonic devices, spintronic devices and gas sensors, are also discussed. Finally, we provide a brief perspective for the future opportunities and challenges in this emerging field.

6.
Artigo em Inglês | MEDLINE | ID: mdl-34375531

RESUMO

Thin-film composite (TFC) membranes are attracting wide attention because their ultrathin selective layer usually corresponds to the higher membrane flux for pervaporation. However, the direct preparation of the TFC membranes on ceramic substrates confronted with the great difficulties because the larger pores on ceramic substrate surfaces are detrimental to the formation of an intact polyamide (PA) selective layer produced by interfacial polymerization (IP) reaction. Here, the integrated ZIF-L nanosheets were proposed to be used as an assistance interlayer for the first time to eliminate the existence of the pores of the ceramic support, and provides a better basis for the formation of an intact PA selective layer by IP reaction between TMC and ethylenediamine (EDA). The experimental data obtained in pervaporation (PV) show that the increased flux from 1.1 to 2.9 kg/m2h corresponds to the decreased separation factor from 396 to 110 when the feed concentration of ethanol decreases from 95 wt % to 80 wt % at 50 °C. In addition, the membrane flux increases from 0.8 to 2.5 kg/m2h with a change of the separation factor from 683 to 111 when the operational temperature varies from 30 to 60 °C. These results demonstrate the great potential of the fabricated TFC membranes in practical application for PV dehydration of organic solutions.

7.
Huan Jing Ke Xue ; 42(8): 3595-3603, 2021 Aug 08.
Artigo em Chinês | MEDLINE | ID: mdl-34309246

RESUMO

In late August 2020, a period of O3 pollution occurred in the main urban area of Chongqing and lasted for approximately 2 weeks (till early September). Ambient air samples, collected using Summa Canisters and DNPH sampling columns at three observation sites in the main urban area, were used to study the composition, photochemical reaction activity, and source apportionment of volatile organic compounds (VOCs) during the period of O3 pollution. The results showed that the mean volume fraction of TVOCs in the main urban area of Chongqing during the observation period was 45.08×10-9, and the components were ranked by volume fraction in the following order:OVOCs, alkanes, halohydrocarbons, alkenes, aromatics, and alkynes. Formaldehyde, ethylene, and acetone made up the higher volume fraction of VOCs, together accounting for more than 30% of TVOCs. OVOCs and alkenes contributed more to · OH loss rate (Li·OH) and ozone formation potential (OFP) and were the key VOCs components for ozone generation. The main active species in the OVOCs component were formaldehyde, acetaldehyde, and acrolein; the main active species in the alkene component were isoprene, ethylene, and n-butene. The ratio of xylene to ethylbenzene in VOCs was low, and they showed a significant correlation, indicating that the VOCs air mass in the main urban area was highly aging and affected by long-distance transmission from other areas. The source apportionment results of the PMF model showed five main sources of VOCs, namely secondary generation (27.67%), vehicle exhaust (26.56%), industrial emission (17.86%), plant (14.51%), and fossil fuel combustion (13.4%).


Assuntos
Poluentes Atmosféricos , Ozônio , Compostos Orgânicos Voláteis , Poluentes Atmosféricos/análise , China , Monitoramento Ambiental , Ozônio/análise , Emissões de Veículos/análise , Compostos Orgânicos Voláteis/análise
8.
Andrologia ; 53(9): e14122, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34319588

RESUMO

Radical prostatectomy, radiotherapy and active surveillance are three widely used treatment options for patients with low-risk prostate cancer, but the relative effects are controversial. We searched PubMed, Embase and Web of Science until June 2020, focusing on the studies comparing the effect of radical prostatectomy, radiotherapy and active surveillance in patients with low-risk prostate cancer. Through the random-effects model, dichotomous data were extracted and summarised by odds ratio with a 95% confidence interval. Twenty-two studies containing 185,363 participants were pooled for the comprehensive comparison. The Bayesian mixed network estimate demonstrated the cancer-specific mortality of radical prostatectomy was significantly lower than active surveillance (OR, 0.46; 95% CI 0.34-0.64) and external beam radiation therapy (OR, 0.66; 95% CI 0.46-0.96), but not brachytherapy (OR, 0.63; 95% CI 0.41-1.03). The brachytherapy demonstrated the best treatment ranking probability results in terms of all-cause mortality, while no significant difference was observed when compared with other three treatment modalities. Brachytherapy and radical prostatectomy were associated with a similar risk of cancer-specific mortality, and both of them were significantly superior to active surveillance and external beam radiation therapy; nevertheless, there was no significant difference among the aforementioned treatment methods in all-cause mortality.


Assuntos
Braquiterapia , Neoplasias da Próstata , Teorema de Bayes , Humanos , Masculino , Metanálise em Rede , Prostatectomia , Neoplasias da Próstata/radioterapia , Neoplasias da Próstata/cirurgia
9.
Nat Prod Res ; : 1-9, 2021 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-34142619

RESUMO

Two new sesquiterpenoid lactone derivatives, linderin A (1) and linderin B (2) comprising a sesquiterpenoid lactone and a methyl geranylhomogentisate moiety together with six known compounds were isolated from the roots of Lindera aggregata. Their chemical structures were elucidated using extensive spectroscopic analysis including 1 D, 2 D NMR, and HR-ESI-MS data and compared with previously reported data. The absolute configurations of 1 and 2 were assigned based on the electronic circular dichroism calculation. Compound 2 showed moderate anticoagulant activity.

10.
Nano Lett ; 2021 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-34018750

RESUMO

Here, we report a novel topotactic method to grow 2D free-standing perovskite using KNbO3 (KN) as a model system. Perovskite KN with monoclinic phase, distorted by as large as ∼6 degrees compared with orthorhombic KN, is obtained from 2D KNbO2 after oxygen-assisted annealing at relatively low temperature (530 °C). Piezoresponse force microscopy (PFM) measurements confirm that the 2D KN sheets show strong spontaneous polarization (Ps) along [101̅]pc direction and a weak in-plane polarization, which is consistent with theoretical predictions. Thickness-dependent stripe domains, with increased surface displacement and PFM phase changes, are observed along the monoclinic tilt direction, indicating the preserved strain in KN induces the variation of nanoscale ferroelectric properties. 2D perovskite KN with low symmetry phase stable at room temperature will provide new opportunities in the exploration of nanoscale information storage devices and better understanding of ferroelectric/ferroelastic phenomena in 2D perovskite oxides.

11.
J Mater Chem B ; 9(12): 2845-2853, 2021 03 28.
Artigo em Inglês | MEDLINE | ID: mdl-33704321

RESUMO

Photothermal therapy (PTT) is a promising strategy for cancer treatment. However, the development of highly efficient photothermal agents with excellent biosafety, particularly with low liver retention, is very meaningful for clinical applications, but it is also challenging. We herein prepared a pH-sensitive nanoagent (NanoPc3) by the self-assembly of a zinc(ii) phthalocyanine substituted with hexadeca-sulphonates linked by hydrazone bonds for photoacoustic imaging and PTT. Due to the highly negative surface potential (-30.80 mV in water), NanoPc3 could effectively escape the phagocytosis of the reticuloendothelial system and be rapidly cleared from normal tissues, leading to little accumulation in the liver and excellent biosafety. The highly negatively-charged NanoPc3 changed into nearly neutral nanoparticles (NanoPc3H) under slightly acidic conditions, resulting in enhanced cellular uptake and retention time in tumor tissues. Moreover, the tumor of H22 tumor-bearing mice treated with NanoPc3 almost disappeared, suggesting an outstanding photothermal antitumor effect. NanoPc3 also hardly showed skin phototoxicity under irradiation. Its excellent antitumor effect and biosafety make NanoPc3 highly promising in clinical applications. This work will provide a new strategy for the design of tumor-targeted photothermal nanoagents with high biosafety.


Assuntos
Antineoplásicos/farmacologia , Indóis/farmacologia , Nanopartículas/química , Terapia Fototérmica , Zinco/farmacologia , Animais , Antineoplásicos/síntese química , Antineoplásicos/química , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Ensaios de Seleção de Medicamentos Antitumorais , Células Hep G2 , Humanos , Concentração de Íons de Hidrogênio , Indóis/química , Neoplasias Hepáticas Experimentais/tratamento farmacológico , Neoplasias Hepáticas Experimentais/patologia , Camundongos , Estrutura Molecular , Zinco/química
12.
Environ Res ; 197: 111040, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33771510

RESUMO

The ceramic membrane has been widely used in the wastewater treatment based on the chemical resistance and superior separation performance. A robust and defect-free thin-film nanocomposite (TFN) nanofiltration (NF) membrane on the macroporous hollow fiber ceramic (HFC) substrate was novelly developed for heavy metals removal. Before interfacial polymerization (IP), the aqueous solution of graphene oxide (GO) grafted with ethylenediamine (EDA) was deposited on the HFC substrate by vacuum filtration. Then, a thin polyamide (PA) film was fabricated by EDA and 1,3,5-trimesoyl chloride (TMC), followed by heat treatment. The effects of GO content and EDA concentration on the performance of the NF membrane have been systematically investigated. The results showed that when the GO content was 0.015 mg·mL-1 and the EDA concentration was 0.75 wt.%, the as-prepared eGO3/PA-HFC membrane had a rejection rate of 94.12% for MgCl2 and a pure water flux of 18.03 L·m-2·h-1. Additionally, the removal ability of eGO3/PA-HFC membranes for heavy metal ions was satisfactory (93.33%, 92.73%, 90.45% and 88.35% for Zn2+, Cu2+, Ni2+ and Pb2+, respectively). The study explored further that it was efficient and stable for heavy metal ions removal during 30 h in the simulated tap water and mining wastewater, which indicated that the eGO/PA-HFC membrane has great application potential in wastewater treatment.


Assuntos
Grafite , Metais Pesados , Nanocompostos , Cerâmica
13.
IEEE Trans Med Imaging ; 40(8): 2002-2014, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-33788685

RESUMO

The real-time localization of the guidewire endpoints is a stepping stone to computer-assisted percutaneous coronary intervention (PCI). However, methods for multi-guidewire endpoint localization in fluoroscopy images are still scarce. In this paper, we introduce a framework for real-time multi-guidewire endpoint localization in fluoroscopy images. The framework consists of two stages, first detecting all guidewire instances in the fluoroscopy image, and then locating the endpoints of each single guidewire instance. In the first stage, a YOLOv3 detector is used for guidewire detection, and a post-processing algorithm is proposed to refine the guidewire detection results. In the second stage, a Segmentation Attention-hourglass (SA-hourglass) network is proposed to predict the endpoint locations of each single guidewire instance. The SA-hourglass network can be generalized to the keypoint localization of other surgical instruments. In our experiments, the SA-hourglass network is applied not only on a guidewire dataset but also on a retinal microsurgery dataset, reaching the mean pixel error (MPE) of 2.20 pixels on the guidewire dataset and the MPE of 5.30 pixels on the retinal microsurgery dataset, both achieving the state-of-the-art localization results. Besides, the inference rate of our framework is at least 20FPS, which meets the real-time requirement of fluoroscopy images (6-12FPS).


Assuntos
Intervenção Coronária Percutânea , Algoritmos , Cateterismo , Fluoroscopia , Humanos
14.
Cogn Neurodyn ; 15(1): 181-189, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33786088

RESUMO

Deep learning has achieved great success in areas such as computer vision and natural language processing. In the past, some work used convolutional networks to process EEG signals and reached or exceeded traditional machine learning methods. We propose a novel network structure and call it QNet. It contains a newly designed attention module: 3D-AM, which is used to learn the attention weights of EEG channels, time points, and feature maps. It provides a way to automatically learn the electrode and time selection. QNet uses a dual branch structure to fuse bilinear vectors for classification. It performs four, three, and two classes on the EEG Motor Movement/Imagery Dataset. The average cross-validation accuracy of 65.82%, 74.75%, and 82.88% was obtained, which are 7.24%, 4.93%, and 2.45% outperforms than the state-of-the-art, respectively. The article also visualizes the attention weights learned by QNet and shows its possible application for electrode channel selection.

15.
Small ; 17(17): e2007739, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33739614

RESUMO

2D organic crystals exhibit efficient charge transport and field-effect characteristics, making them promising candidates for high-performance nanoelectronics. However, the strong Fermi level pinning (FLP) effect and large Schottky barrier between organic semiconductors and metals largely limit device performance. Herein, by carrying out temperature-dependent transport and Kelvin probe force microscopy measurements, it is demonstrated that the introducing of 2D metallic 1T-TaSe2 with matched band-alignment as electrodes for F16 CuPc nanoflake filed-effect transistors leads to enhanced field-effect characteristics, especially lowered Schottky barrier height and contact resistance at the contact and highly efficient charge transport within the channel, which are attributed to the significantly suppressed FLP effect and appropriate band alignment at the nonbonding van der Waals (vdW) hetero-interface. Moreover, by taking advantage of the improved contact behavior with 1T-TaSe2 contact, the optoelectronic performance of F16 CuPc nanoflake-based phototransistor is drastically improved, with a maximum photoresponsivity of 387 A W-1 and detectivity of 3.7 × 1014 Jones at quite a low Vds of 1 V, which is more competitive than those of the reported organic photodetectors and phototransistors. The work provides an avenue to improve the electrical and optoelectronic properties of 2D organic devices by introducing 2D metals with appropriate work function for vdW contacts.

16.
Med Image Anal ; 70: 101920, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33676097

RESUMO

Intraoperative tracking of laparoscopic instruments is often a prerequisite for computer and robotic-assisted interventions. While numerous methods for detecting, segmenting and tracking of medical instruments based on endoscopic video images have been proposed in the literature, key limitations remain to be addressed: Firstly, robustness, that is, the reliable performance of state-of-the-art methods when run on challenging images (e.g. in the presence of blood, smoke or motion artifacts). Secondly, generalization; algorithms trained for a specific intervention in a specific hospital should generalize to other interventions or institutions. In an effort to promote solutions for these limitations, we organized the Robust Medical Instrument Segmentation (ROBUST-MIS) challenge as an international benchmarking competition with a specific focus on the robustness and generalization capabilities of algorithms. For the first time in the field of endoscopic image processing, our challenge included a task on binary segmentation and also addressed multi-instance detection and segmentation. The challenge was based on a surgical data set comprising 10,040 annotated images acquired from a total of 30 surgical procedures from three different types of surgery. The validation of the competing methods for the three tasks (binary segmentation, multi-instance detection and multi-instance segmentation) was performed in three different stages with an increasing domain gap between the training and the test data. The results confirm the initial hypothesis, namely that algorithm performance degrades with an increasing domain gap. While the average detection and segmentation quality of the best-performing algorithms is high, future research should concentrate on detection and segmentation of small, crossing, moving and transparent instrument(s) (parts).


Assuntos
Processamento de Imagem Assistida por Computador , Laparoscopia , Algoritmos , Artefatos
17.
Ecotoxicology ; 30(8): 1632-1643, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33420883

RESUMO

While expanded polystyrene (EPS) microplastics have been widely recognized as one of the most important components of plastic litter in the intertidal zones of the global ocean, our understanding of their environmental fate on island beaches is insufficient. In this study, we intended to reveal that the latest EPS microplastic pollution status on 5 island beaches in the Pearl River Estuary, China, by comprehensively assessing the abundance, distribution, size, surface texture and carrying capacity of heavy metals (Cd, As, Cr, Ni, Cu, Pb, Mn, Fe, Al). High level of EPS microplastic abundance ranged from 328 to 82,276 particles m-2 was found, with the highest abundance at Guishan Island and the lowest at Dong'ao Island. Spatial distribution of EPS microplastic abundance was significantly different among different islands. EPS microplastics in the size range of 1-2 mm were the most abundant. The content of heavy metals in EPS microplastics collected on the beaches was greater than that in the new EPS products. The average concentrations of heavy metals in EPS microplastics from 5 islands are Cd (0.27 ± 0.19 µg g-1), As (5.50 ± 3.84 µg g-1), Cr (14.9 ± 8.25 µg g-1), Cu (15.0 ± 7.66 µg g-1), Ni (17.2 ± 17.6 µg g-1), Pb (24.8 ± 7.39 µg g-1), Mn (730 ± 797 µg g-1), Fe (8340 ± 4760 µg g-1), and Al (9624 ± 6187 µg g-1), respectively. The correlation between heavy metals in EPS microplastics and sediments was better than that between heavy metals in EPS microplastics and seawater. The study results indicated that EPS microplastics could act as a carrier for the transport of heavy metals, which might pose a threat to biological and human health.


Assuntos
Metais Pesados , Poluentes Químicos da Água , China , Conservação dos Recursos Naturais , Monitoramento Ambiental , Estuários , Sedimentos Geológicos , Humanos , Metais Pesados/análise , Microplásticos , Plásticos , Poliestirenos/análise , Rios , Poluentes Químicos da Água/análise
18.
Adv Mater ; 33(6): e2000581, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32725672

RESUMO

In van der Waals (vdWs) materials and heterostructures, the interlayers are bonded by weak vdWs interactions due to the lack of dangling bonds. The vdWs gap at the homo- or heterointerface provides great freedom to enrich the tunability of electronic structures by external intercalation of foreign ions or atoms at the interface, leading to the discovery of new physics and functionalities. Herein, the recent progress on electrochemical intercalation of foreign species into atomically thin vdWs materials for structural phase transition and device applications is reviewed and future opportunities are discussed. First, several kinds of electrochemical intercalation platforms to achieve the intercalation in vdWs materials and heterostructures are introduced. Next, the in situ characterization of electrochemical intercalation dynamics by state-of-the-art techniques is summarized, including optical techniques, scanning probe techniques, and electrical transport. Moreover, particular attention is paid on the experimentally reported phase transition and multifunctional applications of intercalated devices. Finally, future applications and challenges of intercalation in vdWs materials and heterostructures are proposed, including the intrinsic intercalation mechanism of solid ion conductors, exact identification of intercalated foreign species by near-field optical techniques, and the tunability of intercalation kinetics for ultrafast switching.

19.
Chemosphere ; 265: 129023, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33246708

RESUMO

Enhanced coagulation has been widely used in storm tanks to remove heavy metal ions (HMs) from combined sewer overflows (CSOs), but faces challenges on removing the HMs bound to dissolved organic matter (DOM) with small molecular weight (MW). DOM ubiquitously existing in CSOs generally contains a large distribution range of MW, which can significantly impact the MW distribution of HMs by complexing reaction, thereby adding uncertainties for the removal efficiency of coagulation. Therefore, realizing the potential MW distribution of the HMs bound to CSO-DOM is greatly important for cost-effectively removing HMs from CSOs in the coagulation process. This paper presents a comprehensive approach of ultrafiltration, fluorescence quenching titration, excitation-emission matrix parallel factor analysis, complexation model, and two-dimensional correlation fluorescence spectroscopy for exploring the MW-based complexing characteristics between Cu(II) ions and CSO-DOM components. Results show that: (1) Cu(II) ions that bound to the CSO-DOM were mainly distributed in the MW range of <5 kDa, which makes them very difficult to be removed from CSOs by coagulation technique. (2) Concentration effect and molecular composition exerted great impacts on the MW distribution of the Cu(II) ions bound to CSO-DOM. (3) The humic-like component of terrestrial origin with the MW range of 100 kDa∼0.45 µm possessed high binding stability, capacity, and priority with Cu(II) ions, and they could be used at a high concentration to promote the removal efficiency of coagulation for Cu(Ⅱ) ions of CSOs by competitive complexation and inter-molecular bridging.


Assuntos
Metais Pesados , Análise Fatorial , Substâncias Húmicas/análise , Íons , Espectrometria de Fluorescência
20.
Chemosphere ; 263: 127995, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297034

RESUMO

Catalytic membrane plays an important role in environmental remedy. In this study, we reported an Ag coated membrane (PAN-Si-Cu-Ag) with a high catalytic activity to reduce 4-nitrophenol (4-NP) and methyl orange (MO) from water. The best performance is 99% reduction degree and 280 L m-2.h-1.bar-1 flux for (4-NP) reduction at 4-NP: NaBH4 = 1:50 (mM) during a 12-h filtration. The reduction degree for MO is above 90% and the flux is about 230 L m-2·h-1·bar-1, which is almost the best report till now. The Ag coated membrane was prepared by metal displacement-epitaxial growth on silica covalent grafted PAN membrane (PAN-Si). Silica atoms were used as linker to ensure the good adhesion between polymer and metal NPs, the loss amount of Ag NPs from the coated catalytic membrane is loss about 2 µg/cm2 after one month storage. Cheap metal NPs were firstly reduced on the surface of PAN-Si membrane and then used to displace Ag ions. Thus the obtained catalytic membrane showed a very high loading (28%). Finally, the catalytic filtration mechanism of 4-NP was distinguished by Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and adsorption measurement.


Assuntos
Nanopartículas Metálicas , Prata , Catálise , Nitrofenóis
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...