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Semiparametric quantile-difference estimation for length-biased and right-censored data

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Science China Mathematics 2019年第9期62卷 1823-1838页

作者： yutao liu Shucong Zhang Yong Zhou School of Statistics and Mathematics Central University of Finance and EconomicsBeijing100081China School of Statistics and Management Shanghai University of Finance and EconomicsShanghai200433China Key Laboratory of Advanced Theory and Application in Statistics and Data Science(MOE) Institute of Statistics and Interdisciplinary Sciences and School of StatisticsEast China Normal UniversityShanghai200241China

Prevalent cohort studies frequently involve length-biased and right-censored data, a fact that has drawn considerable attention in survival analysis. In this article, we consider survival data arising from lengthbiased sampling, and propose a new semiparametric-model-based approach to estimate quantile differences of failure time. We establish the asymptotic properties of our new estimators theoretically under mild technical conditions, and propose a resampling method for estimating their asymptotic variance. We then conduct simulations to evaluate the empirical performance and efficiency of the proposed estimators, and demonstrate their application by a real data analysis.

关键词： quantile differences length-biased sampling right-censored proportional hazards model

Risk factors for ventilator-associated pneumonia among patients undergoing major oncological surgery for head and neck cancer

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Frontiers of Medicine 2017年第2期11卷 239-246页

作者： yutao liu Yaxia Di Shuai Fu Department of Oral and Maxillofacial Surgery Children's Hospital Chongqing Medical University Chongqing 400014 China Department of Research and Administration Services Qujing No.1 Hospital Qujing 655000 China Department of Oral Surgery Dental Hospital Kunming Medical University Kunming 650031 China

Patients undergoing major oncological surgery for head and neck cancer （SHNC） have a particularly high risk of nosocomial infections. We aimed to identify risk factors for ventilator-associated pneumonia （VAP） in patients undergoing SHNC. The study included 465 patients who underwent SHNC between June 2011 and June 2014. The rate of VAP, risk factors for VAP, and biological aspects of VAP were retrospectively evaluated. The incidence of VAP was 19.6~0 （n = 95） in patients who required more than 48 h of mechanical ventilation. Staphylococcus （37.7%）, Enterobacteriaceae （32.1%）, Pseudomonas （20.8%）, and Haemophilus （16.9~） were the major bacterial species that caused VAP. The independent risk factors for VAP were advanced age, current smoking status, chronic obstructive pulmonary disease, and a higher simplified acute physiology score system II upon admission. Tracheostomy was an independent protective factor for VAP. The median length of stay in the ICU for patients who did or did not develop VAP was 8.0 and 6.5 days, respectively （P = 0.006）. Mortality among patients who did or did not develop VAP was 16.8% and 8.4%, respectively （P 〈 0.001）. The potential economic impact of VAP was high because of the significantly extended duration of ventilation. A predictive regression model was developed with a sensitivity of 95.3% and a specificity of 69.4%. VAP is common in patients who are undergoing SHNC and who require more than 48 h of mechanical ventilation. Therefore, innovative preventive measures should be developed and applied in this high-risk population.

关键词： ventilator-associated pneumonia (VAP) pneumonia risk factors surgery for head and neck cancer (SHNC)

MULTI-GRANULARITY EVOLUTION ANALYSIS OF SOFTWARE USING COMPLEX NETWORK THEORY

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Journal of Systems Science & Complexity 2011年第6期24卷 1068-1082页

作者： Weifeng PAN Bing LI yutao MA Jing liu State Key Laboratory of Software Engineering Wuhan University Wuhan 430072 China School of Computer Science and Information Engineering Zhejiang Gongshang University Hangzhou 310018 China School of Computer Wuhan University Wuhan 430072 China Complex Networks Research Center Wuhan University Wuhan 430072 China

Software systems are a typical kind of man-made complex systems. Understanding their evolutions can lead to better software engineering practices. In this paper, the authors use complex network theory as a tool to analyze the evolution of object-oriented （OO） software from a multi-granularity perspective. First, a multi-granularity software networks model is proposed to represent the topological structures of a multi-version software system from three levels of granularity. Then, some parameters widely used in complex network theory are applied to characterize the software networks. By tracing the parameters＇ values in consecutive software systems, we have a better understanding about software evolution. A case study is conducted on an open source OO project, Azureus, as an example to illustrate our approach, and some underlying evolution characteristics are uncovered. These results provide a different dimension to our understanding of software evolutions and also are very useful for the design and development of OO software systems.

关键词： Complex networks multi-granularity software evolution software system.

A multi-target tracking algorithm based on Gaussian mixture model

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Journal of Systems Engineering and Electronics 2020年第3期31卷 482-487页

作者： SUN Lili CAO Yunhe WU Wenhua liu yutao National Laboratory of Radar Signal Processing Xidian UniversityXi’an 710071China Science and Technology on Communication Networks Laboratory Shijiazhuang 050081China

Since the joint probabilistic data association(JPDA)algorithm results in calculation explosion with the increasing number of targets,a multi-target tracking algorithm based on Gaussian mixture model(GMM)clustering is *** algorithm is used to cluster the measurements,and the association matrix between measurements and tracks is constructed by the posterior *** with the traditional data association algorithm,this algorithm has better tracking performance and less computational *** results demonstrate the effectiveness of the proposed algorithm.

关键词： multiple-target tracking Gaussian mixture model(GMM) data association expectation maximization(EM)algorithm

Is there an optimal time to initiate adjuvant chemotherapy to predict benefit of survival in non-small cell lung cancer?

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Chinese Journal of Cancer Research 2017年第3期29卷 263-271页

作者： yutao liu Xiaoyu Zhai Junling Li Zhiwen Li Di Ma Ziping Wang Department of Medical Oncology National Cancer Center/Cancer Hospital Chinese Academy of Medical Sciences and Peking Union Medical College Institute of Reproductive & Child Health Peking University Ministry of Health Key Laboratory of Reproductive Health Department of Epidemiology and Biostatistics School of Public Health Peking University Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing) Department of Thoracic Medical Oncology Peking University Cancer Hospital &Institute

Objective: Adjuvant chemotherapy (AC) after curative resection is known to improve the survival of patients with non-small cell lung cancer (NSCLC); however, few studies have reported the correlation between the time to initiation of AC (TTAC) and survival in NSCLC patients. Methods: The clinical data of 925 NSCLC patients who received curative resection and post-operative AC at the Cancer Hospital of Chinese Academy of Medical Sciences between 2003 and 2013 were retrospectively analyzed. TTAC was measured from the date of surgery to the initiation of AC. Disease-free survival (DFS) was defined as the duration from surgery to the time of tumor recurrence or last follow-up evaluation. The optimal cut-off value of TTAC was determined by maximally selected log-rank statistics. The DFS curve was estimated using the Kaplan-Meier method, and the Cox proportional hazards regression model was used to identify risk factors independently associated with DFS. Propensity score matching (PSM) was performed for survival analysis using the match data. Results: The optimal discriminating cut-off value of TTAC was set at d 35 after curative resection based on which the patients were assigned into two groups: group A ( 35 d). There was no significant difference in the DFS between the two groups (P=0.246), indicating that the TTAC is not an independent prognostic factor for DFS. A further comparison continued to show no significant difference in the DFS among 258 PSM pairs (P=0.283). Conclusions: There was no significant correlation between the TTAC and DFS in NSCLC patients. Studies with larger samples are needed to further verify this conclusion.

关键词： Non-small cell lung cancer (NSCLC) adjuvant chemotherapy time to adjuvant chemotherapy(TTAC) disease-free survival

Quantitative analysis of 3-dimensional root architecture based on image reconstruction and its application to research on phosphorus uptake in soybean

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Chinese Science Bulletin 2006年第19期51卷 2351-2361页

作者： ZHU Tong lin FANG Suqin LI Zhiyuan liu yutao LIAO Hong YAN Xiaolong Root Biology Center South China Agricultural University Guangzhou 510642 China Department of Computer Science South China Agricultural University Guangzhou 510642 China

Quantification of 3-dimensional (3-D) plant root architecture is one of the most important approaches to investigating plant root growth and its function in nutrient acquisition and utilization. However, no effective methods have been reported hitherto to quantify 3-D root architecture parameters, making it difficult to further study the 3-D characteris- tics of the root system and its function. In the present study, we created a rapid algorithm to reconstruct 3-D root system images based on the basic structural features of such linear objects as roots, using 2-D root images taken by digital CCD cameras at multi- viewing angles. This method is very effective in the reconstruction of plant root system images, thus enabling us to obtain the digital model of 3-D root architecture and its 3-D skeleton, based on which some major root architecture parameters can be calculated. Using this method, we were able to ac- quire 3-D parameters of soybean root architecture whose root diameter was more than 0.3 mm, includ- ing tap root length, total root length, average basal root angle, ratio of root width to root depth, percent- age distribution of root length in different layers and root distribution in different 3-D regions of the growth medium. We also quantitatively analyzed the rela- tionship between different root architecture parame-ters and such plant nutrition parameters as soybean biomass and phosphorus (P) uptake. Our study may provide a new tool in studying the growth and nutri- tional functions of plant root systems.

关键词：大豆根系图象再现磷效率定量分析

Methyl functionalization of trimesic acid in copper-based metal-organic framework for ammonia colorimetric sensing at high relative humidity

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Chinese Chemical Letters 2024年第6期35卷 211-215页

作者： Yuxin Wang Zhengxuan Song yutao liu Yang Chen Jinping Li Libo Li Jia Yao College of Chemical Engineering and Technology Shanxi Key Laboratory of Gas Energy Efficient and Clean UtilizationTaiyuan University of TechnologyTaiyuan 030024China Department of Gastroenterology Shanxi Bethune HospitalShanxi Academy of Medical SciencesTongji Shanxi HospitalThird Hospital of Shanxi Medical UniversityTaiyuan 030024China

Exhaled ammonia(NH_(3))can be used as a crucial biomarker of kidney and liver ***,the high humidity in the detection conditions remains a challenge for accurate detection by gas ***,a copper-based metal-organic framework(CH_(3)-Cu-BTC)with methyl(CH_(3)^(-))functionalization of trimesic acid was synthesized for NH_(3) colorimetric *** CH_(3)-Cu-BTC exhibited a strong response for 5 ppm NH_(3) with high selectivity under high relative humidity(75%RH).Density functional theory(DFT)simulations indicated that the NH_(3) molecules interacted more strongly with CH_(3)-Cu-BTC than H_(2)O molecules did,and the corresponding color switching was attributed to the lone-pair electron in NH_(3) changing the coordination environment of Cu^(2+)ions,leading to an obviously visible color switching response from ruby green to *** on the tailor-made pore chemistry,the precise detection of trace amounts of NH_(3) in exhaled air was realized through functionalized MOF *** strategy used in this study not only offers a new pathway for the rapid detection of low concentration NH_(3) under humid conditions,but also shows a method for early respiration diagnosis of kidney and liver diseases.

关键词： Metal-organic framework Ammonia sensing Naked-eye color switching High humidity Respiration diagnosis

Potential unreliability of ALK variant allele frequency in the efficacy prediction of targeted therapy in NSCLC

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Frontiers of Medicine 2023年第3期17卷 493-502页

作者： Wei Rao yutao liu Yan Li Lei Guo Tian Qiu Lin Dong Jianming Ying Weihua Li Department of Pathology National Cancer Center/National Clinical Research Center for Cancer/Cancer HospitalChinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing 100021China Department of Medical Oncology National Cancer Center/National Clinical Research Center for Cancer/Cancer HospitalChinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing 100021China

Anaplastic lymphoma kinase(ALK)is the most common fusion gene involved in non-small cell lung cancer(NSCLC),and remarkable response has been achieved with the use of ALK tyrosine kinase inhibitors(ALK-TKIs).However,the clinical efficacy is highly ***-existing intratumoral heterogeneity(ITH)has been proven to contribute to the poor treatment response and the resistance to targeted *** this work,we investigated whether the variant allele frequencies(VAFs)of ALK fusions can help assess ITH and predict targeted therapy *** the application of next-generation sequencing(NGS),7.2%(326/4548)of patients were detected to be ALK *** the basis of the adjusted VAF(adjVAF,VAF normalization for tumor purity)of four different threshold values(adjVAF<50%,40%,30%,or 20%),the association of ALK subclonality with crizotinib efficacy was ***,no statistical association was observed between median progression-free survival(PFS)and ALK subclonality assessed by adjVAF,and a poor correlation of adjVAF with PFS was found among the 85 patients who received first-line *** suggest that the ALK VAF determined by hybrid capture-based NGS is probably unreliable for ITH assessment and targeted therapy efficacy prediction in NSCLC.

关键词： ALK fusion next-generation sequencing fluorescence in situ hybridization immunohistochemistry variant allele frequency intratumoral heterogeneity targeted therapy

Effects of Er on the microstructure and properties of AZ31 magnesium alloy prepared via the EMS process

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Rare Metals 2010年第4期29卷 339-345页

作者： MA yutao,ZHANG Xingguo,liu Hongbin,and MENG Linggang School of Materials Science and Engineering,Dalian University of Technology,Dalian 116023,China School of Materials Science and Engineering Dalian University of Technology Dalian China

The effects of small amounts of the rare-earth element erbium on the microstructure and the mechanical properties of AZ31 magnesium alloy via the electromagnetic stirring （EMS） process have been studied. It has been shown that AZ31-Er alloys are mainly composed of α-Mg solid solution and β-Mg17TA112 phases. When the Er content reaches 0.12 wt.%, the characteristic peaks of A12Er can be observed. The micro- structure is obviously refined and the tensile strength of the AZ31-based alloy at ambient temperature is significantly improved by contents of 0.03 wt.% Er, especially the elongation （8= 19%）. More addition of Er obviously decreases the tensile strength and elongation of the AZ31-based alloy because of the grain coarsening and the reduction of β-Mg17A112 phases.

关键词： AZ31 magnesium alloy microstructure mechanical properties erbium