Article
Chemistry, Multidisciplinary
Muhammad Bilal Hanif, Guru Karthikeyan Thirunavukkarasu, Viktoriia Liapun, Hryhorii Makarov, Maros Gregor, Tomas Roch, Tomas Plecenik, Karol Hensel, Marcel Sihor, Olivier Monfort, Martin Motola
Summary: This study presents an environmentally friendly synthesis of TiO2 nanotube (TNT) layers and demonstrates their photocatalytic performance and HO radical production rate. The best preparation condition was using AgNO3 as the electrolyte, which resulted in TNT layers with suitable morphological features and crystal structure.
Article
Chemistry, Physical
Kaihang Zhang, Yuanzheng Zhang, Su Liu, Xin Tong, Junfeng Niu, Dong Wang, Junchen Yan, Zhaoyang Xiong, John Crittenden
Summary: In this study, a MnOx-TiO2 NTAs anode was prepared by compositing narrow bandgap manganese oxide (MnOx) with TiO2 nanotube arrays (TiO2 NTAs). Electrochemical characterizations revealed that increasing the composited concentration of MnOx improved the conductivity and reduced the oxygen evolution potential, thus enhancing the electrochemical activity of the MnOx-TiO2 NTAs anode. Moreover, the optimal degradation rate of benzoic acid (BA) was achieved by adjusting the MnOx concentration and degradation voltage. These quantitative results are of great significance for the design and application of high-performance materials for electrochemical advanced oxidation processes (EAOPs).
GREEN ENERGY & ENVIRONMENT
(2023)
Article
Chemistry, Physical
Maryam Karimi-Shamsabadi, Mohsen Behpour
Summary: In this study, STS/TNAs and ATS/TNAs hybrid photocatalysts were prepared and characterized, with STS/TNAs showing superior photocatalytic activity for BB41 dye degradation. Optimization of S3TS3/TNAs catalyst resulted in the best photodegradation performance.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2021)
Article
Chemistry, Physical
Huiling Yan, Rong Wang, RuiXi Liu, Ting Xu, Jing Sun, Lizhi Liu, Jianlong Wang
Summary: The CeO2/TiO2 nanotube arrays heterojunction shows excellent antibacterial effects in photocatalytic disinfection, maintaining a high sterilization efficiency even after multiple cycles.
APPLIED CATALYSIS B-ENVIRONMENTAL
(2021)
Article
Engineering, Chemical
Chaorui Xue, Ruizhi Xue, Ruirui Huang, Xiangqian Fan, Huinian Zhang, Wenjing Zheng, Ying Li, Ning Li, Qing Chang, Shengliang Hu
Summary: The performance of interfacial solar-driven water evaporation (ISDWE) technology was enhanced by anodized TiO2 nanotube film and applied voltage on Ti mesh. The water evaporation rate increased from 1.20 kg·m- 2·h-1 to 2.48 kg·m- 2·h-1. The hydrophilic and nanoporous nature of TiO2 nanotube film improved the solar absorptivity and wettability of Ti mesh, thereby reducing the water evaporation enthalpy and achieving a water evaporation rate of 1.98 kg·m- 2·h-1. The applied voltage also enhanced the salt-resistance property of Ti mesh coated with TiO2 nanotube film.
SEPARATION AND PURIFICATION TECHNOLOGY
(2023)
Article
Engineering, Environmental
Chengze Yu, Fan Zhang, Kai Wang, Tianlie Luo, Chengzhi Zhou
Summary: Artificial sweeteners, particularly aspartame, have raised concerns due to their widespread use and ecological toxicity. This study investigated the efficient decomposition of aspartame using a Ti3+ self-doped TiO2 nanotube arrays electrode. The results showed that electrocatalysis was highly effective in degrading aspartame, with potential for removing artificial sweeteners from wastewater.
JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING
(2022)
Article
Engineering, Chemical
Bingrui Ma, Shuaishuai Xin, Yanjun Xin, Xiaoming Ma, Chunlei Zhang, Mengchun Gao, Fei Ma, Yumiao Ma
Summary: BiOBr modified TiO2 nanotube arrays photoelectrodes showed higher PEC degradation efficiency for p-chloronitrobenzene. Hydroxyl radical and photogenerated holes were the main active species responsible for degradation. However, the coexistence of dissolved anions and humic acid could decline p-CNB removal rate.
SEPARATION AND PURIFICATION TECHNOLOGY
(2021)
Article
Chemistry, Physical
Xinxia Yang, Yang Guo, Feng Cao, Hui Xu, Yifan Liu, Liangjun Yin, Chunhong Mu, Xian Jian
Summary: Plasma-modified FSA catalysts were used to efficiently convert acetylene into CNT arrays with a carbon conversion rate of up to 97.2%. The growth mechanism analysis confirmed the growth mode of CNT arrays and predicted the maximum theoretical yield, offering a solution for large-scale production of CNT arrays.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Chemistry, Multidisciplinary
David L. White, Brian A. Day, Zidao Zeng, Zachary M. Schulte, Noah R. Borland, Nathaniel L. Rosi, Christopher E. Wilmer, Alexander Star
Summary: The hybridization of a 2-D metal organic framework with single-walled carbon nanotubes has allowed for discrimination of carbohydrates based on molecular size. Liquid gated field-effect transistor devices show improved differentiation capabilities for carbohydrates of varying sizes. Molecular Dynamics calculations reveal decreased ion diffusivity in the presence of different sugars, supporting the proposed sensing mechanism of gate capacitance reduction with carbohydrate molecules in the pores.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2021)
Article
Environmental Sciences
Yen -Ping Peng, En-Xian Zhang, Chia -Hung Chen, Wu -Xing Chen
Summary: In this study, iron was deposited onto titanium dioxide nanotube arrays (TNAs) using the impregnation method to enhance its photocatalytic ability. The results showed that the iron modification successfully attached iron nanoparticles evenly to the TNAs, resulting in improved degradation of trichloroethylene (TCE) in a photoelectrochemical (PEC) system. The Fe-TNAs exhibited red-shifted absorption wavelength and reduced recombination of photo-generated electron-hole pairs, leading to enhanced TCE degradation.
Article
Environmental Sciences
Weibin Huang, Yue Huang, Bobin Tang, Yuanhang Fu, Chunhui Guo, Jinzhong Zhang
Summary: In this study, a blue TiO2 nanotube arrays anode on porous titanium substrate (Ti-porous/blue TiO2 NTA) was successfully fabricated and used for the electro-chemical oxidation of carbamazepine (CBZ) in aqueous solution. The anode showed larger electroactive surface area, better electrochemical performance, and higher center dot OH generation ability compared to the Ti-plate substrate. The removal efficiency of CBZ reached 99.75% after 60 min with low energy consumption.
Article
Electrochemistry
Christian L. Conrad, Welman C. Elias, Sergi Garcia-Segura, Michael A. Reynolds, Michael S. Wong
Summary: Highly ordered TiO2 nanostructures, known as nanotube arrays (NTAs), have potential applications in energy, chemical sensing, and biomedical fields. The prevailing synthesis method, titanium anodization, can be improved by modulating electrolyte conductivity to achieve accelerated growth rates. Regulating solution conductivity within a desired range allows for the fabrication of NTAs at faster rates.
Article
Chemistry, Physical
Bowen Gao, Mingxuan Sun, Wen Ding, Zhipeng Ding, Wenzhu Liu
Summary: A series of gamma-graphyne/TiO2 nanotube array heterostructures were synthesized by a simple and environmentally friendly method. The modified heterostructures showed improved performance in photoelectrocatalytic degradation and nitrogen fixation, indicating great potential for applications in photoelectrochemical and photoelectrocatalytic processes.
APPLIED CATALYSIS B-ENVIRONMENTAL
(2021)
Article
Engineering, Environmental
Jianhui Xu, Yufeng Liu, Dan Li, Chunhui Zhang, Xin Fu, Yunfei Zhang, Pengxu Wang, Jincheng Lu, Shenggui Chen, Lei Li
Summary: Electrocatalytic technology is used for the activation of peroxymonosulfate (PMS) for acetaminophen (ACT) degradation and detoxification. The study provides evidence that PMS activation on the cathode is mainly triggered by superoxide radical (O2-). Factors affecting ACT degradation in the EC/PMS system were evaluated and optimal kinetic constant and lowest energy consumption were determined.
JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING
(2023)
Article
Chemistry, Physical
Yukun Chang, Yanhui Chen, Zicong Yang, Jinshu Wang, Hongyi Li
Summary: In this study, PtCo nanoparticles were encapsulated in bamboo-like highly ordered TiO2 nanotubes (PtCo/TNTs/Ti) using an electrochemical method. The obtained PtCo/TNTs/Ti electrode showed a large electrochemical active area and mass activity, which was 3.6 times and 7.5 times higher than that of traditional Pt/TNTs/Ti and PtC electrodes, respectively. Lattice strain was identified as an important factor for improving catalytic performance.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Environmental Sciences
Ling Xiao, Chi Zhang, Gang Wang, Dongsheng Guan, Renduo Zhang, Yujuan Chen, Jun Dai
ENVIRONMENTAL POLLUTION
(2020)
Correction
Biochemistry & Molecular Biology
Dongsheng Guan, Yingxia Li, Yinglin Cui, Yanke Guo, Ning Dong, Ge Li, Yun Dai, Liang Ji
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
(2021)
Article
Agronomy
Chenxi Yu, Dongsheng Guan, Wang Gang, Duo Lou, Long Wei, Yi Zhou, Jianxiang Feng
Summary: Mangrove ecosystems play a crucial role in mitigating climate change by sequestering and storing carbon. The study found that ecosystem carbon stocks vary among mangrove stands of different ages, with vegetation biomass contributing more to carbon stock as the stand ages, while soil carbon stock shows the opposite trend. Additionally, the annual accumulation rate of ecosystem carbon stocks decreases with mangrove stand chronology.
Article
Oncology
Kun Wang, Dongsheng Guan, Xu Zhao, Dongge Qiao, Yanhua Yang, Yinglin Cui
ANNALS OF TRANSLATIONAL MEDICINE
(2020)
Article
Chemistry, Physical
Wangwang Xu, Congli Sun, Na Wang, Xiaobin Liao, Kangning Zhao, Guang Yao, Qiangchao Sun, Hongwei Cheng, Ying Wang, Xionggang Lu
Summary: This study developed an advanced cathode material Sn1.5V2O7(OH)(2)center dot 3.3H(2)O for ZIBs, showing excellent cycling life and rate capability. The tetravalent tin ions were found to have a strong beneficial effect on the battery performance of layered-structure cathode materials, indicating potential for further research in multi-valent rechargeable batteries.
Article
Agronomy
Gang Wang, Chenxi Yu, Minerva Singh, Dongsheng Guan, Yanmei Xiong, Rongbao Zheng, Rongbo Xiao
Summary: Mangrove plantations have high potential for biomass carbon sequestration, but their effects on soil organic carbon accumulation are unclear. Biomass increment and SOC accumulation are unsynchronized with mangrove plantation development, with monospecific plantations potentially not significantly accelerating SOC sequestration in the early stage. Multi-specific plantations may facilitate SOC accumulation more effectively than monospecific plantations.
Article
Forestry
Chunyu Shen, Nannan Shi, Shenglei Fu, Wanhui Ye, Lei Ma, Dongsheng Guan
Summary: The study revealed that forest fragmentation significantly reduces aboveground biomass storage in forest fragments, along with lower species richness and abundance. Additionally, the increase in average DBH with decreasing patch size is a distinctive feature in fragmented stands.
Article
Geosciences, Multidisciplinary
Yasong Zhang, Chenxi Yu, Junjie Xie, Shuntao Du, Jianxiang Feng, Dongsheng Guan
Summary: Despite having higher vegetation and fine root biomass, the exotic Sonneratia apetala does not significantly increase soil organic carbon storage compared to native mangroves. Lower C:N ratio and soil salinity in S. apetala can promote fine root decomposition rate, offsetting the carbon accumulation advantage related to higher fine root biomass. Restoration of mangrove is effective in enhancing soil carbon stock, but the use of exotic S. apetala should be decreased or avoided, especially in Natural Reserves.
Article
Geosciences, Multidisciplinary
Gang Wang, Minerva Singh, Jiaqiu Wang, Ling Xiao, Dongsheng Guan
Summary: The study investigated the effects of climate, tidal range, and marine pollution on the spatial patterns of biomass and sediment organic carbon in China's mangrove forests. It was found that these factors play a crucial role in regulating the latitudinal variations in biomass and carbon content. Additionally, heavy metal pollution and suspended solid concentration were found to negatively impact carbon storage in the mangrove ecosystems.
Article
Chemistry, Multidisciplinary
Shelton Farai Kuchena, Ying Wang
Summary: The study introduces a new flexible full NH4+ ion battery with a concentrated hydrogel electrolyte, demonstrating significantly improved performance.
CHEMISTRY-A EUROPEAN JOURNAL
(2021)
Article
Biodiversity Conservation
Yasong Zhang, Ling Xiao, Dongsheng Guan, Yujuan Chen, Mikael Motelica-Heino, Yisheng Peng, Shing Yip Lee
Summary: This study investigated the impact of biotic and abiotic factors on the production and decomposition of mangrove fine roots on SOC accumulation, with findings showing that root production is mainly influenced by vegetation biomass while decomposition is negatively affected by soil salinity. Across the sea-land gradient, there were increases in POC and SOC, while DOC/SOC and MBC/SOC ratios decreased. Fine root production had the most significant impact on the ratio of SOC components among the multiple factors analyzed.
ECOLOGICAL INDICATORS
(2021)
Article
Biodiversity Conservation
Gang Wang, Yasong Zhang, Dongsheng Guan, Ling Xiao, Minerva Singh
Summary: Non-native Sonneratia apetala plantations are recommended for mangrove reforestation in China due to their rapid carbon accumulation, but monitoring data on carbon dynamics in mature planted mangroves is lacking. This study found that biomass increased significantly with mangrove growth, while SOC content remained stable. Longer-term monitoring is needed to further evaluate SOC accumulation in Sonneratia apetala plantations.
ECOLOGICAL INDICATORS
(2021)
Article
Electrochemistry
Ying Wang, Yehong Chen
Summary: A novel flexible zinc-ion battery has been developed with an optimized concentrated hydrogel electrolyte, showing enhanced performance at subzero temperatures. The hydrogel electrolytes, synthesized by mixing xanthan gum and aqueous ZnCl2 solution, can be tuned and optimized for maximized battery performance through various characterizations. This battery exhibits excellent electrochemical performance, mechanical durability, flexibility, and anti-freezing property, showing high potential for powering wearable electronics in cold environments or where safety is crucial.
ELECTROCHIMICA ACTA
(2021)
Article
Chemistry, Multidisciplinary
Minkang Wang, Tianhao Liao, Xinglong Zhang, Jinlong Cao, Shuangquan Xu, Hui Tang, Ying Wang
Summary: This study reports a novel and efficient ORR electrocatalyst with atomic FeNx sites and neighboring Fe2O3 nanoparticles embedded in carbon nanofibers. The catalyst shows a well-defined fibrous structure, large specific surface area, and uniformly distributed active sites, and exhibits excellent ORR performance in both alkaline and acidic media. Additionally, the catalyst shows high discharge voltage, excellent power density, and cycling durability in Zn-air batteries.
ADVANCED MATERIALS INTERFACES
(2022)
Article
Cell Biology
Xu Zhao, Dongge Qiao, Dongsheng Guan, Kun Wang, Yinglin Cui
Summary: This study found that Chrysophanol (CHR) prevented apoptosis, endoplasmic reticulum stress, and oxidative stress after intracerebral hemorrhage (ICH) by regulating the miR-320-5p/Wnt3a/beta-catenin pathway. This suggests that CHR could be a potential treatment for brain damage following ICH.
OXIDATIVE MEDICINE AND CELLULAR LONGEVITY
(2022)
Article
Chemistry, Multidisciplinary
Laetitia Bardet, Herve Roussel, Stefano Saroglia, Masoud Akbari, David Munoz-Rojas, Carmen Jimenez, Aurore Denneulin, Daniel Bellet
Summary: The thermal instability of silver nanowires leads to increased electrical resistance in AgNW networks. Understanding the relationship between structural and electrical properties of AgNW networks is crucial for their integration as transparent electrodes in flexible optoelectronics. In situ X-ray diffraction measurements were used to study the crystallographic evolution of Ag-specific Bragg peaks during thermal ramping, revealing differences in thermal and structural transitions between bare and SnO2-coated AgNW networks.
Article
Chemistry, Multidisciplinary
Nathalia Cancino-Fuentes, Arnau Manasanch, Joana Covelo, Alex Suarez-Perez, Enrique Fernandez, Stratis Matsoukis, Christoph Guger, Xavi Illa, Anton Guimera-Brunet, Maria V. Sanchez-Vives
Summary: This study provides a comprehensive characterization of graphene-based solution-gated field-effect transistors (gSGFETs) for brain recordings, highlighting their potential clinical applications.
Article
Chemistry, Multidisciplinary
Sikandar Aftab, Hailiang Liu, Dhanasekaran Vikraman, Sajjad Hussain, Jungwon Kang, Abdullah A. Al-Kahtani
Summary: This study examines the effects of hybrid nanoparticles made of NiO@rGO and NiO@CNT on the active layers of polymer solar cells and X-ray photodetectors. The findings show that these hybrid nanoparticles can enhance the charge carrier capacities and exciton dissociation properties of the active layers. Among the tested configurations, the NiO@CNT device demonstrates superior performance in converting sunlight into electricity, and achieves the best sensitivity for X-ray detection.
Article
Chemistry, Multidisciplinary
Hyo Jung Shin, Seung Gyu Choi, Fengrui Qu, Min-Hee Yi, Choong-Hyun Lee, Sang Ryong Kim, Hyeong-Geug Kim, Jaewon Beom, Yoonyoung Yi, Do Kyung Kim, Eun-Hye Joe, Hee-Jung Song, Yonghyun Kim, Dong Woon Kim
Summary: This study investigates the role of SOX9 in reactive astrocytes following ischemic brain damage using a PLGA nanoparticle plasmid delivery system. The results demonstrate that PLGA nanoparticles can reduce ischemia-induced neurological deficits and infarct volume, providing a potential opportunity for stroke treatment.
Article
Chemistry, Multidisciplinary
Anurag Chaudhury, Koushik Debnath, Nikhil R. Jana, Jaydeep K. Basu
Summary: The study investigates the interaction between nanoparticles and cell membranes, and identifies key parameters, including charge, crowding, and membrane fluidity, that determine the adsorbed concentration and unbinding transition of nanoparticles.
Article
Chemistry, Multidisciplinary
Sina Sadeghi, Fazel Bateni, Taekhoon Kim, Dae Yong Son, Jeffrey A. Bennett, Negin Orouji, Venkat S. Punati, Christine Stark, Teagan D. Cerra, Rami Awad, Fernando Delgado-Licona, Jinge Xu, Nikolai Mukhin, Hannah Dickerson, Kristofer G. Reyes, Milad Abolhasani
Summary: In this study, an autonomous approach for the development of lead-free metal halide perovskite nanocrystals is presented, which integrates a modular microfluidic platform with machine learning-assisted synthesis modeling. This approach enables rapid and optimized synthesis of copper-based lead-free nanocrystals.
Article
Chemistry, Multidisciplinary
Zahir Abbas, Nissar Hussain, Surender Kumar, Shaikh M. Mobin
Summary: The rational construction of free-standing and flexible electrodes for electrochemical energy storage devices is an emerging research focus. In this study, a redox-active metal-organic framework (MOF) was prepared on carbon nanofibers using an in situ approach, resulting in a flexible electrode with high redox-active behavior and unique properties such as high flexibility and lightweight. The prepared electrode showed excellent cyclic retention and rate capability in supercapacitor applications. Additionally, it could be used as a freestanding electrode in flexible devices at different bending angles.
Article
Chemistry, Multidisciplinary
Lishan Zhang, Xiaoting Zhang, Hui Ran, Ze Chen, Yicheng Ye, Jiamiao Jiang, Ziwei Hu, Miral Azechi, Fei Peng, Hao Tian, Zhili Xu, Yingfeng Tu
Summary: Photodynamic therapy (PDT) is a promising local treatment modality in cancer therapy, but its therapeutic efficacy is restricted by ineffective delivery of photosensitizers and tumor hypoxia. In this study, a phototactic Chlorella-based near-infrared (NIR) driven green affording-oxygen microrobot system was developed for enhanced PDT. The system exhibited desirable phototaxis and continuous oxygen generation, leading to the inhibition of tumor growth in mice. This study demonstrates the potential of using a light-driven green affording-oxygen microrobot to enhance photodynamic therapy.
Article
Chemistry, Multidisciplinary
Yujin Li, Jing Xu, Xinqi Luo, Futing Wang, Zhong Dong, Ke-Jing Huang, Chengjie Hu, Mengyi Hou, Ren Cai
Summary: In this study, hollow heterostructured materials were constructed using an innovative template-engaged method as cathodes for zinc-ion batteries. The materials exhibited fast Zn2+ transport channels, improved electrical conductivity, and controlled volume expansion during cycling. The designed structure allowed for an admirable reversible capacity and high coulombic efficiency.
Article
Chemistry, Multidisciplinary
Paritosh Mahato, Shashi Shekhar, Rahul Yadav, Saptarshi Mukherjee
Summary: This study comprehensively elucidates the role of the core and electrostatic surface of metal nanoclusters in catalytic reduction reactions. The electrostatic surface dramatically modulates the reactivity of metal nanoclusters.
Article
Chemistry, Multidisciplinary
Pei Liu, Mengdi Liang, Zhengwei Liu, Haiyu Long, Han Cheng, Jiahe Su, Zhongbiao Tan, Xuewen He, Min Sun, Xiangqian Li, Shuai He
Summary: This study demonstrates a simple and environmentally-friendly method for the synthesis of zinc oxide nanozymes (ZnO NZs) using wasted hop extract (WHE). The WHE-ZnO NZs exhibit exceptional peroxidase-like activity and serve as effective catalysts for the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). In addition, a straightforward colorimetric technique for detecting both H2O2 and glucose was developed using the WHE-ZnO NZs as peroxidase-like catalysts.
Article
Chemistry, Multidisciplinary
Hyunkyu Oh, Young Jun Lee, Eun Ji Kim, Jinseok Park, Hee-Eun Kim, Hyunsoo Lee, Hyunjoo Lee, Bumjoon J. Kim
Summary: Mesoporous carbon particles have unique structural properties that make them suitable as support materials for catalytic applications. This study investigates the impact of channel nanostructures on the catalytic activity of porous carbon particles (PCPs) by fabricating PCPs with controlled channel exposure on the carbon surface. The results show that PCPs with highly open channel nanostructures exhibit significantly higher catalytic activity compared to those with closed channel nanostructures.
Article
Chemistry, Multidisciplinary
Yunjie Lu, Zhaohui Li, Zewei Li, Shihao Zhou, Ning Zhang, Jianming Zhang, Lu Zong
Summary: A tough, long-lasting adhesive and highly conductive nanocomposite hydrogel (PACPH) was fabricated via the synergy of interfacial entanglement and adhesion group densification. PACPH possesses excellent mechanical properties, interfacial adhesion strength, and conductivity, making it a promising material for long-term monitoring of human activities and electrocardiogram signals.
Article
Chemistry, Multidisciplinary
Zichao Wei, Audrey Vandergriff, Chung-Hao Liu, Maham Liaqat, Mu-Ping Nieh, Yu Lei, Jie He
Summary: We have developed a simple method to prepare polymer-grafted plasmonic metal nanoparticles with pH-responsive surface-enhanced Raman scattering. By using pH-responsive polymers as ligands, the aggregation of nanoparticles can be controlled, leading to enhanced SERS. The pH-responsive polymer-grafted nanoparticles show high reproducibility and sensitivity in solution, providing a novel approach for SERS without the need for sample pre-concentration.
Article
Chemistry, Multidisciplinary
Melis Ozge Alas Colak, Ahmet Gungor, Merve Buldu Akturk, Emre Erdem, Rukan Genc
Summary: This research investigates the effect of functionalizing carbon dots with hydroxyl polymers on their performance as electrode materials in a supercapacitor. The results show that the functionalized carbon dots exhibit excellent electrochemical performance and improved stability.