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Synthesis of Superclean Graphene

Xiaoting Liu, Jincan Zhang, Heng Chen, Zhongfan Liu
2021 Wuli huaxue xuebao  
Graphene has attracted enormous interest in both academic and industrial fields, owing to its unique, extraordinary properties and significant potential applications. Various methods have been developed to synthesize high-quality graphene, among which chemical vapor deposition (CVD) has emerged as the most encouraging for scalable graphene film production with promising quality, controllability, and uniformity. However, a gap still exists between ideal graphene, having remarkable properties,
more » ... the currently available CVD-derived graphene films. To close this gap, numerous studies in the past decade have been devoted to decreasing defect density, grain boundaries, and wrinkles, and increasing the controllability of layer thickness and doping of graphene. Significant recent advances in this regard were the discovery of the inevitable contamination of graphene surface during high-temperature CVD growth and the synthesis of superclean graphene, representing a new growth frontier in CVD graphene research. Surface contamination of graphene is a major hurdle in probing its intrinsic properties, and strongly hinders its applications, for instance, in electrical and photonic devices. In this review, we aim to provide comprehensive knowledge on the inevitable contamination of CVD graphene and current synthesis strategies for preparing superclean graphene films, and an outlook for the future mass production of high-quality superclean graphene films. First, we focus on surface contamination formation, e.g. amorphous carbon, during the high-temperature CVD growth process of graphene. After introducing evidence to confirm the origin of surface contamination, the formation mechanism of the amorphous carbon is thoroughly discussed. Meanwhile, the influence of the intrinsic cleanness of graphene on the peeling and transfer quality is also revealed. Second, we summarize the state-of-the-art superclean growth strategies and classify them into direct-growth approaches and post-growth treatment approaches. For the former, modification of the CVD gas-phase reactions, for example, using metal-vapor-assisted methods or cold-wall CVD, is effective in inhibiting the formation of amorphous carbon. For the latter, both chemical and physical cleaning methods are employed to eliminate amorphous carbon without damaging the graphene, e.g. selective etching of as-formed amorphous carbon using CO2, and removal of amorphous carbon from the graphene surface using a lint roller based on interfacial force control. Third, we summarize the outstanding electrical, optical, and thermal properties of superclean graphene. Superclean graphene exhibits high carrier mobility, low contact resistance, high transparency, and high thermal conductivity, further highlighting the significance of superclean graphene growth. Finally, future opportunities and challenges for the industrial production of high-quality superclean graphene are discussed.
doi:10.3866/pku.whxb202012047 fatcat:vxoqnaato5ee5imo6a32w6atom

Oral contraception following abortion

Yan Che, Xiaoting Liu, Bin Zhang, Linan Cheng
2016 Medicine  
96 Zhang Ying-hui, 2013 Surgical 105 a, c 97 Yan Wei-wei, 2013 Surgical 320 i, j 98 Feng Ming-yue, 2012 Surgical 160 c, e 99 Sun Guang-fan, 2013 Surgical 1000 a, c, d, i, j 100 Liu  ...  a, c, d 106 Lei Y, 2011 Surgical 240 a, c 107 Meng Xia, 2011 Surgical 120 a, c, d 108 Yi Jing-qiu, 2014 Surgical 200 a, c, f, g 109 Zheng Chun-qin, 2014 Surgical 198 a, c, j 110 Liu  ... 
doi:10.1097/md.0000000000003825 pmid:27399060 pmcid:PMC5058789 fatcat:dprtja2ib5gevb2bj2hbdwcyhy

Clustering via Content-Augmented Stochastic Blockmodels [article]

J. Massey Cashore, Xiaoting Zhao, Alexander A. Alemi, Yujia Liu, Peter I. Frazier
2015 arXiv   pre-print
Much of the data being created on the web contains interactions between users and items. Stochastic blockmodels, and other methods for community detection and clustering of bipartite graphs, can infer latent user communities and latent item clusters from this interaction data. These methods, however, typically ignore the items' contents and the information they provide about item clusters, despite the tendency of items in the same latent cluster to share commonalities in content. We introduce
more » ... ntent-augmented stochastic blockmodels (CASB), which use item content together with user-item interaction data to enhance the user communities and item clusters learned. Comparisons to several state-of-the-art benchmark methods, on datasets arising from scientists interacting with scientific articles, show that content-augmented stochastic blockmodels provide highly accurate clusters with respect to metrics representative of the underlying community structure.
arXiv:1505.06538v1 fatcat:xfbxro2khnc7jka4sczk7xyy5i

Scale-Sensitive Feature Reassembly Network for Pedestrian Detection

Xiaoting Yang, Qiong Liu
2021 Sensors  
Serious scale variation is a key challenge in pedestrian detection. Most works typically employ a feature pyramid network to detect objects at diverse scales. Such a method suffers from information loss during channel unification. Inadequate sampling of the backbone network also affects the power of pyramidal features. Moreover, an arbitrary RoI (region of interest) allocation scheme of these detectors incurs coarse RoI representation, which becomes worse under the dilemma of small pedestrian
more » ... lative scale (PRS). In this paper, we propose a novel scale-sensitive feature reassembly network (SSNet) for pedestrian detection in road scenes. Specifically, a multi-parallel branch sampling module is devised with flexible receptive fields and an adjustable anchor stride to improve the sensitivity to pedestrians imaged at multiple scales. Meanwhile, a context enhancement fusion module is also proposed to alleviate information loss by injecting various spatial context information into the original features. For more accurate prediction, an adaptive reassembly strategy is designed to obtain recognizable RoI features in the proposal refinement stage. Extensive experiments are conducted on CityPersons and Caltech datasets to demonstrate the effectiveness of our method. The detection results show that our SSNet surpasses the baseline method significantly by integrating lightweight modules and achieves competitive performance with other methods without bells and whistles.
doi:10.3390/s21124189 fatcat:o3glrsk5mrb4fl2bs6k53c7fsq

p, p′-Dichlorodiphenyldichloroethylene Induces Colorectal Adenocarcinoma Cell Proliferation through Oxidative Stress

Li Song, Jianxin Liu, Xiaoting Jin, Zhuoyu Li, Meirong Zhao, Weiping Liu, Chunming Liu
2014 PLoS ONE  
p, p'-Dichlorodiphenyldichloroethylene (DDE), the major metabolite of Dichlorodiphenyltrichloroethane (DDT), is an organochlorine pollutant and associated with cancer progression. The present study investigated the possible effects of p,p'-DDE on colorectal cancer and the involved molecular mechanism. The results indicated that exposure to low concentrations of p,p'-DDE from 10 210 to 10 27 M for 96 h markedly enhanced proliferations of human colorectal adenocarcinoma cell lines. Moreover,
more » ... DDE exposure could activate Wnt/b-catenin and Hedgehog/Gli1 signaling cascades, and the expression level of c-Myc and cyclin D1 was significantly increased. Consistently, p,p'-DDE-induced cell proliferation along with upregulated c-Myc and cyclin D1 were impeded by b-catenin siRNA or Gli1 siRNA. In addition, p,p'-DDE was able to activate NADPH oxidase, generate reactive oxygen species (ROS) and reduce GSH content, superoxide dismutase (SOD) and calatase (CAT) activities. Treatment with antioxidants prevented p,p'-DDE-induced cell proliferation and signaling pathways of Wnt/b-catenin and Hedgehog/Gli1. These results indicated that p,p'-DDE promoted colorectal cancer cell proliferation through Wnt/b-catenin and Hedgehog/Gli1 signalings mediated by oxidative stress. The finding suggests an association between p,p'-DDE exposure and the risk of colorectal cancer progression.
doi:10.1371/journal.pone.0112700 pmid:25386960 pmcid:PMC4227882 fatcat:nctpiyyfd5f3plixv5rladpfty

High niche diversity in Mesozoic pollinating lacewings

Qing Liu, Xiumei Lu, Qingqing Zhang, Jun Chen, Xiaoting Zheng, Weiwei Zhang, Xingyue Liu, Bo Wang
2018 Nature Communications  
The specific epithet 'liui' is in honour of the collector, Haoying Liu. Description. Holotype male (NIGP164471). Body length 12.00 mm; forewing length 26.0 mm, hind wing length 25.1 mm.  ...  Family Incertae sedis Genus Fiaponeura Lu, Zhang & Liu, 2016 (Supplementary Fig. 9 ) Type species. Fiaponeura penghiani Lu et al. 24 : 325 (monotypy). Revised diagnosis (from Lu et al. 24 ).  ... 
doi:10.1038/s41467-018-06120-5 pmid:30224679 pmcid:PMC6141599 fatcat:f5rsuxwgbrcvfcpypbfkczj67y

Effect of Gas-Phase Reaction on the CVD Growth of Graphene

Heng Chen, Jincan Zhang, Xiaoting Liu, Zhongfan Liu
2021 Wuli huaxue xuebao  
Chemical vapor deposition (CVD) is considered as the most promising method for the mass production of high-quality graphene films owing to its fine controllability, uniformity, and scalability. In the past decade, significant efforts have been devoted to exploring new strategies for growing graphene with improved quality. During the high-temperature CVD growth process of graphene, besides the surface reactions, gas-phase reactions play an important role in the growth of graphene, especially for
more » ... the decomposition of hydrocarbons. However, the effect of gas-phase reactions on the CVD growth of graphene has not been analyzed previously. To fill this gap, it is essential to systematically analyze the relationship between gas-phase reactions and the growth of graphene films. In this review article, we aim to provide comprehensive knowledge of the gas-phase reactions occurring in the CVD system during graphene growth and to summarize the typical strategies for improving the quality of graphene by modulating gas-phase reactions. After briefly introducing the elementary steps and basic concept of graphene growth, we focus on the gas-phase dynamics and reactions in the CVD system, which influence the decomposition of hydrocarbons, nucleation of graphene, and lateral growth of graphene nuclei, as well as the merging of adjacent graphene domains. Then, a systematic description of the mass transport process in gas phase is provided, including confirmation of the states of gas flow under different CVD conditions and introduction to the boundary layer, which is crucial for graphene growth. Furthermore, we discuss the possible reaction paths of carbon sources in the gas phase and the corresponding active carbon species existing in the boundary layer, based on which the main impact factors of gas-phase reactions are discussed. Representative strategies for obtaining graphene films with improved quality by modulating gas-phase reactions are summarized. Gas-phase reactions affect the crystallinity, cleanness, domain size, layer number, and growth rate of graphene grown on both metal and non-metal substrates. Therefore, we will separately review the detailed strategies, corresponding mechanisms, key parameters, and latest status regarding the quality improvement of graphene. Finally, a brief summary and proposals for future research are provided. This review can be divided into two parts: (1) gas-phase reactions occurring in the high-temperature CVD system, including the mass transport process and the reaction paths of hydrocarbons; and (2) the synthesis of high-quality graphene film via modulation of the gas-phase reaction, in order to improve the crystallinity, cleanness, domain size, layer number, and growth rate of graphene.
doi:10.3866/pku.whxb202101053 fatcat:yo5ojekstvasbk3fapbqf5pura

Response Inhibition in Smokers

Xin ZHAO, Xiaoting LIU, Xiangyi ZAN, Aibao ZHOU
2015 Advances in Psychological Science  
Recent studies have found that smoking affects individual response inhibition ability. Compared with non-smokers, smokers have higher false rates and longer reaction times in the Go/No Go task and Stop signal task. Although smokers have deficits in early response inhibition, there is no difference between smokers and non-smokers in conflict monitoring. In addition, the study also found that smokers' left thalamus, left middle frontal gyrus, and left anterior cingulate cortex have smaller grey
more » ... eas than found in non-smokers. Nicotine intake harms the prefrontal cortex and mesolimbic dopamine system, which leads to lower response inhibition ability in smokers. However, some studies have found that smoking does not affect response inhibition ability; these contradictory results may be due to experimental tasks and subject selection. Future research will feature the reaction to individual inhibition in different types of cigarette deprivations, the comparisons of response inhibition between smokers and other addicts (alcohol, drugs), the variance in smokers' response inhibition ability in the oddball, Go/No Go, and the Stop-Signal tasks, and interventions and response inhibition training for smokers.
doi:10.3724/sp.j.1042.2015.01031 fatcat:j7bsgsjfrngablfae6xyh6lq7a

Protective humoral and CD4+ T cellular immune responses of Staphylococcus aureus vaccine MntC in a murine peritonitis model

Wei Yu, Di Yao, Simiao Yu, Xintong Wang, Xiaoting Li, Mengyao Wang, Shuo Liu, Zhenyue Feng, Xiaoting Chen, Wanyu Li, Lizi Wang, Wei Liu (+5 others)
2018 Scientific Reports  
Staphylococcus aureus can cause different types of diseases from mild skin infections to life-threatening sepsis worldwide. Owing to the emergence and transmission of multidrug-resistant strains, developing an impactful immunotherapy especially vaccine control approach against S. aureus infections is increasingly encouraged and supported. S. aureus manganese transport protein C (MntC), which is a highly-conserved cell surface protein, can elicit protective immunity against S. aureus and
more » ... coccus epidermidis. In this study, we evaluated the humoral immune response and CD4 + T cell-mediated immune responses in a mouse peritonitis model. The results showed that MntC-specific antibodies conferred an essential protection for mice to reduce invasion of S. aureus, which was corroborated via the opsonophagocytic killing assay and passive immunization experiment in mice, and moreover MntC-induced Th17 played a remarkable part in preventing S. aureus infection since the MntC-induced protective immunity decreased after neutralization of IL-17 by antibody in vivo and the Th17 adoptive transferred-mice could partly resist S. aureus challenge. In conclusion, we considered that the MntC-specific antibodies and MntC-specific Th17 cells play cooperative roles in the prevention of S. aureus infection. Staphylococcus aureus is the most common pathogenic bacterium in humans and animals. It can cause multi-organ infection, pneumonia, pseudomembranous colitis and endocarditis, as well as life-threatening systemic diseases such as septicaemia, sepsis and peritonitis 1,2 . In the past, S. aureus-caused infection was commonly treated with vancomycin and methicillin antibiotics in clinical practice 3 . However, with the extensive use of antibiotics, many drug-resistant strains have appeared. In the face of the growing drug-resistance of S. aureus, development of an effective vaccine against this pathogen is particularly important. Recently researchers have carried out clinical trials of vaccines, including capsular polysaccharide vaccine, subunit vaccine and multivalent capsular polysaccharide with recombinant proteins vaccine. A study of capsular polysaccharide vaccine StaphVAX ™ , the bivalent S. aureus type 5 and 8 capsular polysaccharides (T5/T8) conjugate vaccine, failed to demonstrate vaccine efficacy in preventing S. aureus bacteraemia in end-stage renal disease patients receiving hemodialysis 4 . The V710 vaccine produced by Merck, that is a single conserved protein antigen IsdB, has failed in Phase III and II/III clinical trials 5 . Although a correlate of protection has not yet been established for a vaccine against S. aureus infection, one of the reasons for these failures is that we need to deepen and improve understanding of the mechanism of humoral immunity and protective cellular immune response to S. aureus infection. There is evidence that both humoral and cellular immunity are important in preventing staphylococcal diseases 6,7 , and recent research suggests that CD4 + T cells play an important role in clearing pathogenic bacteria. For example, immunocompromised individuals with reduced ability to produce functional antibodies, such as those with acquired immune deficiency syndrome 8 or defects in immunoglobulin production, have increased susceptibility to staphylococcal infections 9 . On the other hand, the help provided by CD4 + T cells is required to develop functional antibody responses. Moreover, cytokines secreted by T helper cells like IFN-γ and IL-17
doi:10.1038/s41598-018-22044-y pmid:29483570 pmcid:PMC5832154 fatcat:afy5ktjtlnazzp4wmnpnrs3smm

The Structure of the Lens and Its Associations with the Visual Quality

Xiaoting Ruan, Zhenzhen Liu, Lixia Luo, Yizhi Liu
2020 BMJ Open Ophthalmology  
technology to measure the radius of anterior lens surface curvature (RAL) and found that the RAL decreases 57 µm per year, and the radius of curvature of the posterior lens decreases 17 µm per year. 11 Liu  ... 
doi:10.1136/bmjophth-2020-000459 pmid:33024825 pmcid:PMC7511618 fatcat:nwaijrkakjdjlbwcz4ws65o6ta

Pre‑treatment neutrophil‑to‑lymphocyte ratio predicts survival in patients with laryngeal cancer

Jintao Du, Jifeng Liu, Xinyuan Zhang, Xiaoting Chen, Rong Yu, Deying Gu, Jian Zou, Yafeng Liu, Shixi Liu
2017 Oncology Letters  
An increased neutrophil-to-lymphocyte ratio (NLR) is associated with poorer prognostic outcomes in numerous types of cancer. However, a small number of studies have demonstrated the prognostic role of NLR in patients with laryngeal cancer. The present study evaluated the association between NLR and survival outcomes in patients with laryngeal squamous cancer. All patients were scheduled for follow-up visits. The levels of cytokines from tumor tissues were analyzed by ELISA. A classification and
more » ... regression tree (CART) was used to determine the optimal cutoff values of NLR. The clinical features and NLR were determined using Kaplan-Meier analysis and Cox regression to analyze the survival outcomes and associated risks. Of the total 654 patients, 70 patients (70/654; 10.7%) failed to receive follow-up. Blood and biochemical parameters, including NLR, platelet-to-lymphocyte ratio and albumin-to-globulin ratio were associated with clinical characteristics of the patients, with the exception of histologic grade. Only one node with NLR at 3.18 divided patients into different categories, according to CART analysis. Survival analysis demonstrated that NLR at cutoff values subdivided patients into different survival outcomes (P<0.001). Subsequent to adjustments for age and other clinical features, NLR was identified to be an independent prognostic factor for overall survival and progression-free survival (P<0.05). Increased levels of cytokines, including IL-6 and IL-8, in tumor tissues were associated with NLR values. In summary, pre-treatment NLR was associated with the prognostic outcomes for patients with laryngeal cancer, and may assist to establish prognostic factors for these patients.
doi:10.3892/ol.2017.7501 pmid:29399193 pmcid:PMC5774534 fatcat:rwjxbdzwgjac3hbr4mzfm7s7ly

A Data-Driven Uncertainty Quantification Method for Stochastic Economic Dispatch [article]

Xiaoting Wang, Rong-Peng Liu, Xiaozhe Wang, Yunhe Hou, François Bouffard
2021 arXiv   pre-print
This letter proposes a data-driven sparse polynomial chaos expansion-based surrogate model for the stochastic economic dispatch problem considering uncertainty from wind power. The proposed method can provide accurate estimations for the statistical information (e.g., mean, variance, probability density function, and cumulative distribution function) for the stochastic economic dispatch solution efficiently without requiring the probability distributions of random inputs. Simulation studies on
more » ... n integrated electricity and gas system (IEEE 118-bus system integrated with a 20-node gas system are presented, demonstrating the efficiency and accuracy of the proposed method compared to the Monte Carlo simulations.
arXiv:2109.08195v1 fatcat:3jmbq5ao3nhwzfyv4dg5mi7lmq

Has Land Finance Increased Local Financial Risks in China?

Meiting Hu, Xiaoting Liu, Ruibin Guo, Xiuting Li
2021 Sustainability  
(Xiaoting Liu); Visualization, M.H. and R.G.; Writing-original draft, M.H., X.L. (Xiaoting Liu) and R.G.; Writingreview and editing, M.H. and X.L. (Xiuting Li).  ...  (Xiaoting Liu) and R.G.; Methodology, X.L. (Xiaoting Liu) and X.L. (Xiuting Li); Project administration, X.L. (Xiuting Li); Supervision, X.L. (Xiuting Li); Validation, X.L.  ... 
doi:10.3390/su13115937 fatcat:z6lumemdbvcx7d3yptad32llfe

Transcriptomic responses of the marine cyanobacterium Prochlorococcus to viral lysis products [article]

Xiaoting Fang, Yaxin Liu, Yao Zhao, Yue Chen, Riyue Liu, Qi-Long Qin, Gang Li, Yu-Zhong Zhang, Wan Chan, Wolfgang Hess, Qinglu Zeng
2018 bioRxiv   pre-print
Yehui Tan 311 and Jiaxing Liu in the South China Sea Institute of Oceanology and Dr.  ...  Thus, our study might only 298 represent oceanic regions where Prochlorococcus cells are not severely nutrient-limited because 299 of rapid nutrient recycling (Vaulot et al., 1995; Liu et al., 1997).  ... 
doi:10.1101/394122 fatcat:uni7vijcpfgtph4aspgnurxry4

Heavy Metal Contamination of Agricultural Soils in Taiyuan, China

Yong LIU, Huifeng WANG, Xiaoting LI, Jinchang LI
2015 Pedosphere  
This article reviews the conditions of heavy metal contamination of China's soils. The article starts with a discussion of the official environmental standards of soils in China, in terms of heavy metal contamination, and the extent of that contamination. Then, the article discusses the geographic distribution of soil contamination, and the food safety impact. The problem in China is that the provinces with the highest rates of soil contamination are also provinces with the largest amount of
more » ... d production. This results in high contamination of food, with 13.86 % of grain produced in China being affected by heavy metal contamination. Hunan Province represents the worst conditions: it is responsible for 32.1 % of China's cadmium (Cd) emissions, 20.6 % of its arsenic (As) emissions, 58.7 % of its mercury (Hg) emissions, and 24.6 % of its lead (Pb) emissions. While Hunan Province produces about 15 % of the total rice output of the country, according to official data, 13 % of the total area of the province has been contaminated with waste and heavy metals from mines. In many areas, especially those closer to mines, the agricultural production exceeds the official food safety standards. Zusammenfassung Dieser Beitrag analysiert die Schwermetallkontamination von Böden in China. Es werden die offiziellen Boden-Umweltstandards Chinas sowie das Ausmaß und die Auswirkungen von Schwermetallkontaminationen auf die Lebensmittelproduktion Chinas diskutiert. Als Problem zeigt sich, dass die Provinzen, die den stärksten Bodenkontaminierungsgrad aufweisen, gleichzeitig die Provinzen mit der höchsten Lebensmittelproduktion sind. So sind z. B. 13,86 % des in China produzierten Weizens mit Schwermetallen kontaminiert. Eine besondere Rolle kommt hierbei der Provinz Hunan zu: Sie ist für 32,1 % der Cadmium-Emissionen (Cd) Chinas verantwortlich sowie für 20,6 % der Arsen-Emissionen (As), 58,7 % der Quecksilber-Emissionen (Hg) und 24,6 % der Blei-Emissionen (Pb). Rund 15 % der Reisproduktion Chinas findet in der Provinz Hunan statt. Allerdings sind offiziellen Daten zufolge 13 % der Böden Hunans mit vorrangig aus dem Bergbau stammenden Schwermetallen kontaminiert. In vielen Bergbau nahen Gebieten wird eine Agrarproduktion trotz des Überschreitens offizieller Umweltstandards durchgeführt.
doi:10.1016/s1002-0160(15)30070-9 fatcat:lvrq3dthurcornkgmdids4g5fy
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