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  • 1
    Language: English
    In: Analytical chemistry, 03 January 2012, Vol.84(1), pp.224-31
    Description: MicroRNAs (miRNAs) play important roles in a wide range of biological processes, and their aberrant expressions are associated with various diseases. Here we develop a rapid, highly sensitive, and specific miRNA assay based on the two-stage exponential amplification reaction (EXPAR) and a single-quantum-dot (QD)-based nanosensor. The two-stage EXPAR involves two templates and two-stage amplification reactions under isothermal conditions. The first template enables the amplification of miRNA, and the second template enables the conversion of miRNA to the reporter oligonucleotide. Importantly, different miRNAs can be converted to the same reporter oligonucleotides, which can hybridize with the same set of capture and reporter probes to form sandwich hybrids. These sandwich hybrids can be assembled on the surface of 605 nm emission QDs (605QDs) to form the 605QD/reporter oligonucleotide/Cy5 complexes, where the 605QD functions as both a fluorescence resonance energy transfer donor and a target concentrator. Upon excitation with a wavelength of 488 nm, distinct Cy5 signals can be observed in the presence of target miRNA. This assay is highly sensitive and specific with a detection limit of 0.1 aM and can even discriminate single-nucleotide differences between miRNA family members. Moreover, in combination with the specific templates, this method can be applied for multiplex miRNA assay by simply using the same set of capture and reporter probes. This highly sensitive and specific assay has potential to become a promising miRNA quantification method in biomedical research and clinical diagnosis.
    Keywords: Quantum Dots ; Micrornas -- Analysis
    ISSN: 00032700
    E-ISSN: 1520-6882
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  • 2
    Language: English
    In: Clinical Chemistry, June, 2011, Vol.57(6), p.928(2)
    Description: In the past decade, more than 150 000 publications have documented thousands of newly discovered candidate biomarkers representing hundreds of millions of dollars in research investment, yet only about 100 biomarkers have demonstrated potential clinical utility. Additionally, although large-scale and high-throughput technologies such as proteomics and genomics have held special promise for the discovery of novel biomarkers that can be used clinically, these promises have yet to be fulfilled. In a recent article in Nature (1), Dr. George Poste, the chief scientist at the Complex Adaptive Systems Initiative and Regents Professor of Health Innovation at Arizona State University, argues that “the dismal patchwork of fragmented research on disease-associated biomarkers should be replaced by a coordinated ‘big science’ approach.” Highlights of this article are summarized below. Major components …
    Keywords: Biological Markers
    ISSN: 0009-9147
    E-ISSN: 15308561
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  • 3
    Language: English
    In: Environmental Pollution, July, 2013, Vol.178, p.463(11)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.envpol.2013.03.052 Byline: Yan Zhang Abstract: Urban metabolism analysis has become an important tool for the study of urban ecosystems. The problems of large metabolic throughput, low metabolic efficiency, and disordered metabolic processes are a major cause of unhealthy urban systems. In this paper, I summarize the international research on urban metabolism, and describe the progress that has been made in terms of research methodologies. I also review the methods used in accounting for and evaluating material and energy flows in urban metabolic processes, simulation of these flows using a network model, and practical applications of these methods. Based on this review of the literature, I propose directions for future research, and particularly the need to study the urban carbon metabolism because of the modern context of global climate change. Moreover, I recommend more research on the optimal regulation of urban metabolic systems. Author Affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Beijing Normal University, Xinjiekouwai Street No. 19, Beijing 100875, China Article History: Received 6 November 2012; Revised 30 March 2013; Accepted 30 March 2013
    Keywords: Pollution Control -- Physiological Aspects ; Pollution Control -- Analysis ; Ecosystems -- Physiological Aspects ; Ecosystems -- Analysis
    ISSN: 0269-7491
    Source: Cengage Learning, Inc.
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  • 4
    Language: English
    In: Journal of Power Sources, 15 October 2011, Vol.196(20), pp.8413-8423
    Description: ► In this study, we developed a set of system-level model for a portable PEM fuel cell-battery system. ► This model can be used as a platform to optimize system design. ► A portable PEM fuel cell-battery power system with microcontroller has been built to demonstrate the functions of a PEM fuel cell power system. ► Also this system has been used to validate the system modeling and control algorithm. A portable proton exchange membrane (PEM) fuel cell–battery power system that uses hydrogen as fuel has a higher power density than conventional batteries, and it is one of the most promising environmentally friendly small-scale alternative energy sources. A general methodology of modeling, control and building of a proton exchange membrane fuel cell–battery system is introduced in this study. A set of fuel cell–battery power system models have been developed and implemented in the Simulink environment. This model is able to address the dynamic behaviors of a PEM fuel cell stack, a boost DC/DC converter and a lithium-ion battery. To control the power system and thus achieve proper performance, a set of system controllers, including a PEM fuel cell reactant supply controller and a power management controller, were developed based on the system model. A physical 100 W PEM fuel cell–battery power system with an embedded micro controller was built to validate the simulation results and to demonstrate this new environmentally friendly power source. Experimental results demonstrated that the 100 W PEM fuel cell–battery power system operated automatically with the varying load conditions as a stable power supply. The experimental results followed the basic trend of the simulation results.
    Keywords: Fuel Cell–Battery Hybrid Power System ; System Modeling ; System Control ; Power Management ; Portable Power System ; Experimental Study ; Engineering
    ISSN: 0378-7753
    E-ISSN: 1873-2755
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  • 5
    Language: English
    In: Chemical Engineering Science, 2012, Vol.69(1), pp.449-455
    Description: The paper deals with thermosolutal Marangoni convection, which can be formed with an electrically conducting fluid along a vertical surface in the presence of a magnetic field, heat generation and a first-order chemical reaction. In conformity to actuality, it is assumed that the surface tension varies linearly with both the temperature and concentration and that both interface temperature and concentration are quadratic functions of the interface arc length . The general governing partial differential equations are converted into nonlinear ordinary differential equations using unique similarity transformations. The analytical approximate solutions of similarity equations are firstly obtained by double-parameter transformation perturbation expansion method and Padé approximants technique. The effects of Hartmann number, heat generation coefficient and the chemical reaction coefficient on the velocity, temperature and concentration profiles as well as the wall velocity are presented and discussed. ► We establish mathematical model of MHD thermosolutal Marangoni convection. ► We obtain the similarity solutions of mathematical formulation. ► Increasing will increase temperature and concentration, but decrease velocity. ► Increasing will increase temperature and its boundary layer thickness. ► Increasing will decrease concentration and its boundary layer thickness.
    Keywords: Marangoni Convection ; Heat Transfer ; Laminar Flow ; Mass Transfer ; Perturbation Expansion ; Solutions ; Engineering
    ISSN: 0009-2509
    E-ISSN: 1873-4405
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  • 6
    Language: English
    In: Chemistry – A European Journal, 17 March 2014, Vol.20(12), pp.3288-3291
    Description: A complex dynamic system based on a network of multiple reversible reactions has been established. The network was applied to a dynamic systemic resolution protocol based on kinetically controlled lipase‐catalyzed transformations. This resulted in the formation of cyclized products, where two thiazolidinone compounds were efficiently produced from a range of potential transformations. : A dynamic system based on a network of multiple reversible reactions has been established (see scheme). The network was applied to a dynamic systemic resolution protocol based on two kinetically controlled lipase‐catalyzed transformations, in which two thiazolidinone compounds were efficiently formed from a range of potential transformations.
    Keywords: Cyclization ; Dynamic Chemistry ; Enzymes ; Lipases ; Resolution
    ISSN: 0947-6539
    E-ISSN: 1521-3765
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  • 7
    In: Journal of the American Society for Information Science and Technology, June 2013, Vol.64(6), pp.1158-1172
    Description: Designing effective consumer health information systems requires deep understanding of the context in which the systems are being used. However, due to the elusive nature of the concept of context, few studies have made it a focus of examination. To fill this gap, we studied the context of consumer health information searching by analyzing questions posted on a social question and answer site: Yahoo! Answers. Based on the analysis, a model of context was developed. The model consists of 5 layers: demographic, cognitive, affective, situational, and social and environmental. The demographic layer contains demographic factors of the person of concern; the cognitive layer contains factors related to the current search task (specifically, topics of interest and information goals) and users' cognitive ability to articulate their needs. The affective layer contains different affective motivations and intentions behind the search. The situational layer contains users' perceptions of the current health condition and where the person is in the illness trajectory. The social and environmental layer contains users' social roles, social norms, and various information channels. Several novel system functions, including faceted search and layered presentation of results, are proposed based on the model to help contextualize and improve users' interactions with health information systems.
    Keywords: Information Seeking ; End User Searching ; User Attributes
    ISSN: 1532-2882
    E-ISSN: 1532-2890
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  • 8
    Language: English
    In: Analytical chemistry, 16 October 2012, Vol.84(20), pp.8846-52
    Description: Evaluation of plasma renin activity is essential to the assessment of renin-related diseases such as hypertension, congestive heart failure, and cancers. Here, we develop a single quantum dot (QD) based nanosensor for sensitive detection of renin activity. This single-QD-based nanosensor consists of a streptavidin-coated QD and multiple biotinylated and Cy5-labeled peptide substrates, which form a QD/substrate/Cy5 complex where fluorescence resonance energy transfer (FRET) occurs with the QD as the donor and Cy5 as the acceptor. The presence of renin leads to the cleavage of the substrate and the separation of Cy5 from the QD and consequently the decrease of FRET efficiency and the reduction of Cy5 counts. Through the measurement of Cy5 counts by total internal reflection fluorescence (TIRF) microscopy, the renin activity can be quantitatively evaluated at the single-molecule level. This single-QD-based nanosensor can measure not only the renin concentration, but also the enzymatic velocity and the Michaelis-Menten kinetic parameters, and has significant advantages of simplicity, low cost with minimum sample consumption, and high sensitivity with a detection limit of 25 pM. This single-QD-based nanosensor might be further applied to monitor a variety of important enzymatic biomarkers such as kinases and endonuleases.
    Keywords: Quantum Dots ; Enzyme Assays -- Methods ; Fluorescence Resonance Energy Transfer -- Methods ; Peptides -- Metabolism ; Renin -- Metabolism
    ISSN: 00032700
    E-ISSN: 1520-6882
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  • 9
    Language: English
    In: Journal of the American Chemical Society, 22 May 2013, Vol.135(20), pp.7458-61
    Description: Archimedean tilings are periodic polygonal tessellations that are created by placing regular polygons edge-to-edge around a vertex to fill the plane. Here we show that three- and four-arm DNA junction tiles with specifically designed arm lengths and intertile sticky-end interactions can be used to form sophisticated two-dimensional (2D) and three-dimensional (3D) tessellation patterns. We demonstrate two different complex Archimedean patterns, (3(3).4(2)) and (3(2).4.3.4), and the formation of 2D lattices, 3D tubes, and sealed polygon-shaped pockets from the tessellations. The successful growth of hybrid DNA tile motif arrays suggests that it maybe possible to generate 2D quasi-crystals from DNA building blocks.
    Keywords: DNA -- Chemistry ; Nanostructures -- Chemistry
    ISSN: 00027863
    E-ISSN: 1520-5126
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  • 10
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 24 March 2015, Vol.112(12), pp.E1402
    Description: Author contributions: F.C. and Y.-L.Z. wrote the paper.
    Keywords: Sciences (General);
    ISSN: 00278424
    E-ISSN: 1091-6490
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