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Now showing items 145 - 160 of 297

  • Advanced Biotechnology for Cell Cryopreservation

    Jing Yang   Lei Gao   Min Liu   Xiaojie Sui   Yingnan Zhu   Chiyu Wen   Lei Zhang  

    Cell cryopreservation has evolved as an important technology required for supporting various cell-based applications,such as stem cell therapy,tissue engineering,and assisted reproduction.Recent times have witnessed an increase in the clinical demand of these applications,requiring urgent improvements in cell cryopreservation.However,cryopreservation technology suffers from the issues of low cryopreservation efficiency and cryoprotectant(CPA) toxicity.Application of advanced biotechnology tools can significantly improve post-thaw cell survival and reduce or even eliminate the use of organic solvent CPAs,thus promoting the development of cryopreservation.Herein,based on the different cryopreservation mechanisms available,we provide an overview of the applications and achievements of various biotechnology tools used in cell cryopreservation,including trehalose delivery,hydrogel-based cell encapsulation technique,droplet-based cell printing,and nanowarming,and also discuss the associated challenges and perspectives for future development.
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  • Frequency-Dependent Changes of Local Resting Oscillations in Sleep-Deprived Brain

    Lei Gao   Lijun Bai   Yuchen Zhang   Xi-jian Dai   Rana Netra   Youjiang Min   Fuqing Zhou   Chen Niu   Wanghuan Dun   Hong-han Gong   Ming Zhang  

    Sleep deprivation (SD) adversely affects brain function and is accompanied by frequency dependent changes in EEG. Recent studies have suggested that BOLD fluctuations pertain to a spatiotemporal organization with different frequencies. The present study aimed to investigate the frequency-dependent SD-related brain oscillatory activity by using the amplitude of low-frequency fluctuation (ALFF) analysis. The ALFF changes were measured across different frequencies (Slow-4: 0.027-0.073 Hz; Slow-5: 0.01-0.027 Hz; and Typical band: 0.01-0.08 Hz) in 24 h SD as compared to rested wakeful during resting-state fMRI. Sixteen volunteers underwent two fMRI sessions, once during rested wakefulness and once after 24 h of SD. SD showed prominently decreased ALFF in the right inferior parietal lobule (IPL), bilateral orbitofrontal cortex (OFC) and dorsolateral prefrontal cortex (DLPFC), while increased ALFF in the visual cortex, left sensorimotor cortex and fusiform gyrus. Across the Slow-4 and Slow-5, results differed significantly in the OFC, DLPFC, thalamus and caudate in comparison to typical frequency band; and Slow-4 showed greater differences. In addition, negative correlations of behavior performance and ALFF patterns were found mainly in the right IPL across the typical frequency band. These observations provided novel insights about the physiological responses of SD, identified how it disturbs the brain rhythms, and linked SD with frequency-dependent alterations in amplitude patterns.
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  • TotalProf: a fast and accurate retargetable source code profiler

    Lei Gao   Jia Huang   Jianjiang Ceng   Rainer Leupers   Gerd Ascheid   Heinrich Meyr  

    Profilers play an important role in software/hardware design; optimization; and verification. Various approaches have been proposed to implement profilers. The most widespread approach adopted in the embedded domain is Instruction Set Simulation (ISS) based profiling; which provides uncompromised accuracy but limited execution speed. Source code profilers; on the contrary; are fast but less accurate. This paper introduces TotalProf; a fast and accurate source code cross profiler that estimates the performance of an application from three aspects: First; code optimization and a novel virtual compiler backend are employed to resemble the course of target compilation. Second; an optimistic static scheduler is introduced to estimate the behavior of the target processor's datapath. Last but not least; dynamic events; such as cache misses; bus contention and branch prediction failures; are simulated at runtime. With an abstract architecture description; the tool can be easily retargeted in a performance characteristics oriented way to estimate different processor architectures; including DSPs and VLIW machines. Multiple instances of TotalProf can be integrated with SystemC to support heterogeneous Multi-Processor System-on-Chip (MPSoC) profiling. With only about a 5 to 15% error rate introduced to the major performance metrics; such as cycle count; memory accesses and cache misses; a more than one Giga-Instruction-Per-Second (GIPS) execution speed is achieved.
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  • Latent Tuberculosis Infection and Occupational Protection among Health Care Workers in Two Types of Public Hospitals in China

    Feng Zhou   Li Zhang   Lei Gao   Yibin Hao   Xianli Zhao   Jian-min Liu   Jie Lu   Xiangwei Li   Yu Yang   Junguo Chen   Ying Deng  

    OBJECTIVE To determine the impact factors of latent tuberculosis infection (LTBI) and the knowledge of TB prevention and treatment policy among health care workers (HCWs) in different types of hospitals and explore the strategies for improving TB prevention and control in medical institutions in China. METHODS A cross-sectional study was carried out to evaluate the risk of TB infection and personnel occupational protection among HCWs who directly engage in medical duties in one of two public hospitals. Each potential participant completed a structured questionnaire and performed a tuberculin skin test (TST). Factors associated with LTBI were identified by logistic regression analysis. RESULTS Seven hundred twelve HCWs completed questionnaires and 74.3% (n = 529) took the TST or had previous positive results. The TST-positive prevalence was 58.0% (n = 127) in the infectious disease hospital and 33.9% (n = 105) in the non-TB hospital. The duration of employment in the healthcare profession (6-10 years vs. ≤5 years [OR = 1.89; 95% CI = 1.10, 3.25] and >10 vs. ≤5 [OR = 1.80; 95% CI = 1.20, 2.68]), type of hospital (OR = 2.40; 95% CI = 1.59, 3.62), and ever-employment in a HIV clinic or ward (OR = 1.87; 95% CI = 1.08, 3.26) were significantly associated with LTBI. The main reasons for an unwillingness to accept TST were previous positive TST results (70.2%) and concerns about skin reaction (31.9%). CONCLUSION A high prevalence of TB infections was observed among HCWs working in high-risk settings and with long professional experiences in Henan Province in China. Comprehensive guidelines should be developed for different types of medical institutions to reduce TB transmission and ensure the health of HCWs.
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  • The efficacy and mechanism of apoptosis induction by hypericin-mediated sonodynamic therapy in THP-1 macrophages

    Xue-song Li   Lei Gao   Longbin Zheng   Jiayuan Y Kou   Xing Zhu   Yueqing Q Jiang   Zhaoyu Zhong   Juhua Dan   Haobo Xu   Yang Yang   Hong-xia Li   Sa Shi   Wenwu Cao   Yajun Zhao   Ye Tian   Liming Yang  

    PURPOSE To investigate the sonoactivity of hypericin (HY); together with its sonodynamic effect on THP-1 macrophages and the underlying mechanism. MATERIALS AND METHODS CCK-8 was used to examine cell viability. Confocal laser scanning microscopy was performed to assess the localization of HY in cells; reactive oxygen species (ROS) generation; and opening of the mitochondrial permeability transition pore (mPTP) after different treatments. Apoptosis was analyzed using Hoechst-propidium iodide and transmission electron microscopy. Mitochondrial membrane potential (ΔΨm) collapse was detected via fluorescence microscopy. Lipoprotein oxidation was determined in malondialdehyde (MDA) assays. Western blotting was conducted to determine the translocation of BAX and cytochrome C and the expression of apoptosis-related proteins. RESULTS HY was sublocalized among the nuclei and the mitochondria; endoplasmic reticulum; Golgi apparatus; and lysosome in the cytosol of THP-1 macrophages. Under low-intensity ultrasound irradiation; HY significantly decreased cell viability and induced apoptosis. Furthermore; greater ROS generation; higher MDA levels; and greater ΔΨm loss were observed in the sonodynamic therapy (SDT) group. Both ROS generation and MDA levels were significantly reduced by the ROS scavenger N-acetyl cysteine (NAC) and the singlet oxygen scavenger sodium azide. Most of the loss of ΔΨm was inhibited by pretreatment with NAC; sodium azide; and the mPTP inhibitor cyclosporin A (CsA). mPTP opening was induced upon SDT but was reduced by pretreatment with bongkrekic acid; 4;4'-diisothiocyanatostilbene-2;2'-disulfonic acid disodium; CsA; and NAC. Western blot analyses revealed translocation of BAX and cytochrome C; downregulated expression of Bcl-2; and upregulated expression of cleaved caspase-9; cleaved caspase-3; and cleaved poly(ADP-ribose) polymerase in the SDT group; which were reversed by NAC. CONCLUSION HY mediated SDT-induced apoptosis in THP-1 macrophages via ROS generation. Then; the proapoptotic factor BAX translocated from the cytosol to the mitochondria; increasing the ratio of BAX/Bcl-2; and the mPTP opened to release cytochrome C. This study demonstrated the great potential of HY-mediated SDT for treating atherosclerosis.
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  • "Pattern Inter-Domain Mapping Variation" Methodology and Application

    Lei Gao   Zhong-Tuo Wang   Tong Li  

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  • The Perpendicular Magnetic Anisotropy of CoPt/Au Multilayer Films

    Tastuya Yokota   Lei Gao   R. Zhang   Leighann Nicholl   M. L. Yan   David J . Sellmyer   Sy-Hwang Liou  

    We have studied the magnetic properties of Au (2 nm)/Co50Pt50 (3 nm)/Au (2 nm) multilayer films prepared on amorphous Al2O3/Si and (0 0 1) MgO substrates. The as-deposited films on both substrates are magnetically soft with an FCC structure and exhibit a perpendicular anisotropy. After annealing at 500 °C; the sample on the Al2O3/Si substrate has become magnetically isotropic but the sample on the MgO substrate still has perpendicular anisotropy with FCT structure. This film deposited on the MgO substrate did not show a strong perpendicular anisotropy due to the diffusion of the Au and the (1 1 1) nucleation of initial Au layer. We can obtain a perpendicular anisotropy in the multilayer films without an initial Au layer on a (0 0 1) MgO substrate. After annealing at 400 °C; these films have L10 phase with (0 0 1) texture and strong perpendicular anisotropy.
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  • Dynamical resonant charge transfer of fast C<sup>−</sup>, O<sup>−</sup>, F<sup>−</sup> ions and water covered Si(111) surface

    Feifei Xiong   Lei Gao   Yuefeng Liu   Jianjie Lu   Pinyang Liu   Shunli Qiu   Xiyu Qiu   Yanling Guo   Ximeng Chen   Lin Chen  

    Abstract The experiment of 6.5–22.5 keV C − , O − and F − ions scattering on water covered Si(111) surface has been performed. It is found that the positive-ion fraction is very low and increases monotonically as a function of perpendicular exit velocity and exit angle. In particular, the negative-ion fraction increases monotonically with perpendicular exit velocity for specular scattering, and for a given incident energy the angle dependence of the fraction is nonmonotonic. We interpret the observed positive ions in terms of inelastic binary collision, and adopt a modified resonant charge transfer model to calculate the bell-shaped negative-ion fraction. We find that the neutral yield at short ion-surface distance is nonzero and obeys well an exponential dependence. It strongly indicates that a dynamical equilibrium for negative ion formation is never achieved at short distances, and the band gap effect on charge transfer can be neglected to a large extent in this relatively high energy region. Highlights • Positive and negative ion fractions are measured as a function of perpendicular exit velocity and exit angle. • A modified charge transfer model has been used to calculate negative ion fractions. • The comparison to previous work has been discussed.
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  • Drug nanocrystals: In vivo performances

    Lei Gao   Guiyang Liu   Jianli Ma   Xiaoqing Wang   Liang Zhou   Xiang Li  

    Over the past few decades, there has been a considerable research interest in drug nanocrystal system as a pharmaceutical approach for poorly soluble drugs. At the beginning lots of works have been done to study various technologies associated with production of drug nanocrystals and their in vitro physical and chemical properties, such as morphology, formulation composition, stabilities, crystalline structure and enhanced solubility and dissolution velocity. Recently, in vivo behaviors of the nanocrystals have been generally studied in animals (including human), and the results proved that drug nanocrystals could be used as a versatile formulation to alter and improve the pharmacokinetic, pharmacodynamic and targeting properties of poorly soluble drugs. In this paper, in vivo performances of drug nanocrystals exhibited in animals in different administration route were reviewed, and the advantages of drug nanocrystals in the aspect of safety, pharmacodynamics, pharmacokinetics and targeting delivery were discussed in detail. (C) 2012 Elsevier B.V. All rights reserved.
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  • Whistleblowing studies in accounting research: A review of experimental studies on the determinants of whistleblowing

    Lei Gao   Alisa G. Brink  

    Abstract We review and summarize accounting literature that examines whistleblowing in the accounting context. We organize our review around the five determinants of whistleblowing identified by Near and Miceli (1995). The first determinant is characteristics of the whistleblower. Studies related to this determinant examine whistleblowers’ personality characteristics, moral judgment, and demographic characteristics. Studies related to the second determinant, characteristics of the report recipient, examine characteristics of the individual or individuals who receive the report and characteristics of the reporting channel. The third determinant is characteristics of the wrongdoer. Studies in this area focus on the wrongdoer’s power and credibility. Fourth, accounting studies related to characteristics of the wrongdoing examine factors that affect the dependence of the organization on the wrongdoing and evidence credibility. Studies related to the final determinant, characteristics of the organization, examine organizational perceptions of the appropriateness of whistleblowing, organizational climate, and organizational structure. For each determinant, we first summarize and analyze the findings of prior research, and then we present suggestions for future accounting research in whistleblowing.
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  • MicroRNAs transcriptionally regulate promoter activity in Arabidopsis thaliana^FA

    Guodong Yang   Yuanyuan Li   Binjiang Wu   Kaiyue Zhang   Lei Gao   Chengchao Zheng  

    Micro RNAs(mi RNAs) are vital regulators that repress gene expression in the cytoplasm in two main ways: m RNA degradation and translational inhibition. Several animal studies have shown that mi RNAs also target promoters, thereby activating expression.Whether this mi RNA action also occurs in plants is unknown. In this study, we demonstrated that several mi RNAs regulate target promoters in Arabidopsis thaliana. For example, mi R5658 was predominantly present in the nucleus and activated the expression of AT3 G25290 directly by binding to its promoter. Our observations suggest that this mode of action may be a general feature of plant mi RNAs, and thus provide insight into the vital roles of plant mi RNAs in the nucleus.
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  • Potential targets and mechanism of Xingxiao Pill for the treatment of lung cancer were analyzed based on network pharmacology and molecular docking

    Xiang-Nan Zhou   Kai-Wen Hu   Zhi-Ming Li   Lei Gao   Tian Zhou  

    Objective: To analyze the potential targets and mechanism of Xingxiao Pill for the treatment of lung cancer based on network pharmacology and molecular docking, providing reference for the research and clinical development of Xingxiao Pill. Method: The main chemical constituents and their targets of Xingxiao Pill was obtained through BATMAN-TCM database. Effective compounds were screened based on SwissADME and their targets were predicted by SwissTargetPrediction. Main lung cancer targets were obtained and integrated through GeneCards, OMIM(OMIM-Gene-Map-Retrieval), TTD and DRUGBANK databases. The intersection targets of Xingxiao Pill for lung cancer were obtained by Venn. The String platform was used to obtain the intersection targets. The core targets of Xingxiao Pill for lung cancer were screened by BisoGenet3.0. The Metasacpe database was used to analyze the biological processes and pathways involved in intersection targets. Cytoscape3.7.2 software was used to construct the "active ingredients of Xingxiao Pill-targets-pathways" network. Finally, Autodock was used for molecular docking verification. Results: The core active components of Xingxiao Pill for the treatment of lung cancer were morin, testosterone, 17-Beta-Estradiol, alpha-Estradiol, muscone, commiferin, commisterone, octyl acetate, etc. The primary pathways mainly included PI3K/Akt, MTOR, MAPK signaling pathway and MicroRNAs in cancer, etc. It has been proved that the combination of testosterone and estradiol with AKT1, SIRT7 and MDM2 was stable and could be used as reference. Conclusion: This study preliminarily revealed the mechanism of Xingxiao Pill on treating lung cancer with multiple components, targets and pathways, providing some ideas and references for clinical application and basic research in the future.
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  • Genome-Wide Association Analyses Highlight the Potential for Different Genetic Mechanisms for Litter Size Among Sheep Breeds

    Song-Song Xu   Lei Gao   Xing-Long Xie   Yan-Ling Ren   Zhi-Qiang Shen   Feng Wang   Min Shen   Emma Eyϸórsdóttir   Jón H. Hallsson   Tatyana Kiseleva   Juha Kantanen   Meng-Hua Li  

    Reproduction is an important trait in sheep breeding as well as in other livestock. However, despite its importance the genetic mechanisms of litter size in domestic sheep (Ovis aries) are still poorly understood. To explore genetic mechanisms underlying the variation in litter size, we conducted multiple independent genome-wide association studies in five sheep breeds of high prolificacy (Wadi, Hu, Icelandic, Finnsheep, and Romanov) and one low prolificacy (Texel) using the Ovine Infinium HD BeadChip, respectively. We identified different sets of candidate genes associated with litter size in different breeds: BMPR1B, FBN1, and MMP2 in Wadi; GRIA2, SMAD1, and CTNNB1 in Hu; NCOA1 in Icelandic; INHBB, NF1, FLT1, PTGS2, and PLCB3 in Finnsheep; ESR2 in Romanov and ESR1, GHR, ETS1, MMP15, FLI1, and SPP1 in Texel. Further annotation of genes and bioinformatics analyses revealed that different biological pathways could be involved in the variation in litter size of females: hormone secretion (FSH and LH) in Wadi and Hu, placenta and embryonic lethality in Icelandic, folliculogenesis and LH signaling in Finnsheep, ovulation and preovulatory follicle maturation in Romanov, and estrogen and follicular growth in Texel. Taken together, our results provide new insights into the genetic mechanisms underlying the prolificacy trait in sheep and other mammals, suggesting targets for selection where the aim is to increase prolificacy in breeding projects.
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  • Transapical transcatheter device closure of relapse left ventricular diverticulum: a novel minimally invasive technique for reoperation

    Weizhi Zhang   Lei Gao   Yifeng Yang   Tianli Zhao  

    We describe a novel minimally invasive technique, transapical transcatheter device closure of relapse left ventricular diverticulum (LVD) under transesophageal echocardiography (TEE) guidance. The patient previously underwent LVD primary repair and mitral valvular replacement. The anatomical characteristics of the relapse LVD and its adjacent structures are detailedly delineated by echocardiography. The relapse LVD is then managed by transapical transcatheter device closure under TEE guidance. This novel minimally invasive technique is not only limited in relapse LVD, but also could be extensively applied in other cardiac reoperation, such as perivalvular leak closure after valvular replacement.
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  • Type - specific detection of 30 oncogenic human papiloma viruses 1 by genotyping both E 6 and L 1 genes . 2 3 Running head : 4 Type - specific detection of 30

    Junping Peng   Lei Gao   Junhua Guo   Ting Wang   Ling Wang   Qing Yao   Haijun Zhu   Qi Jin  

    9 1 MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen 10 Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, 11 Beijing, P. R. China 12 2 Sequenom, Beijing, P. R. China 13 Department of Vascular and Endocrine Surgery, Xijing Hospital, Fourth Military 14 Medical University; Xi'an, Shaanxi Province, P. R. China 15 * Corresponding author: Qi Jin. Mailing address: No.6, Rongjing Eastern Street, BDA, 16 Beijing, China. Phone: ;86-10-67877732. Fax: ;86-10-67877736. E-mail: 17 zdsys@vip.sina.com 18 † These authors contributed equally to this work. 19
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  • Using Mobile Extensions to Support Disconnected Services

    Mike Dahlin   Bharat Chandra   Lei Gao   Amjad-Ali Khoja   Amol Nayate   Asim Razzaq   Anil Sewani  

    This paper examines the design and implementation of mobile extensions; a distributed operating system abstraction for supporting disconnected access to dynamic distributed services. The goal of mobile extensions is to make it as easy for service providers to deploy services that make use of caching; hoarding; asynchronous messaging; and application-level adaptation to cope with mobility; network failures; and server failures. We identify resource management as a crucial problem in this environment and develop a novel popularity-based resource management policy and demonstrate that under web service workloads it allocates resources nearly as efficiently as traditional schedulers; while under workloads with more aggressive resource users; it provides much stronger performance isolation. Overall; we find that for the four web service workloads we study; mobile extensions can reduce failures by as much as a factor of 5.9 to a factor of 16.7 for those applications able to provide tolerable service when disconnected.
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