共查询到20条相似文献，搜索用时 31 毫秒
1.
Ying Wang Guoxing You Peipei Chen Jianjun Li Gan Chen Bo Wang Penglong Li Dong Han Hong Zhou Lian Zhao 《Biomicrofluidics》2016,10(2)
The mechanical properties of red blood cells (RBCs) are critical to the rheological and hemodynamic behavior of blood. Although measurements of the mechanical properties of RBCs have been studied for many years, the existing methods, such as ektacytometry, micropipette aspiration, and microfluidic approaches, still have limitations. Mechanical changes to RBCs during storage play an important role in transfusions, and so need to be evaluated pre-transfusion, which demands a convenient and rapid detection method. We present a microfluidic approach that focuses on the mechanical properties of single cell under physiological shear flow and does not require any high-end equipment, like a high-speed camera. Using this method, the images of stretched RBCs under physical shear can be obtained. The subsequent analysis, combined with mathematic models, gives the deformability distribution, the morphology distribution, the normalized curvature, and the Young''s modulus (E) of the stored RBCs. The deformability index and the morphology distribution show that the deformability of RBCs decreases significantly with storage time. The normalized curvature, which is defined as the curvature of the cell tail during stretching in flow, suggests that the surface charge of the stored RBCs decreases significantly. According to the mathematic model, which derives from the relation between shear stress and the adherent cells'' extension ratio, the Young''s moduli of the stored RBCs are also calculated and show significant increase with storage. Therefore, the present method is capable of representing the mechanical properties and can distinguish the mechanical changes of the RBCs during storage. The advantages of this method are the small sample needed, high-throughput, and easy-use, which make it promising for the quality monitoring of RBCs. 相似文献
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Jian Gou Bingyu Xia Xuguang Wang Peng Cheng Andrew Thye Shen Wee Wenhui Duan Yong Xu Kehui Wu Lan Chen 《国家科学评论(英文版)》2022,9(2)
Creating and manipulating multiple charge states of solitary defects in semiconductors is of essential importance for solitary defect electronics, but is fundamentally limited by Coulomb''s law. Achieving this objective is challenging, due to the conflicting requirements of the localization necessary for the sizable band gap and delocalization necessary for a low charging energy. Here, using scanning tunneling microscopy/spectroscopy experiments and first-principles calculations, we realized exotic quinary charge states of solitary defects in two-dimensional intermetallic semiconductor Sn2Bi. We also observed an ultralow defect charging energy that increases sublinearly with charge number rather than displaying the usual quadratic behavior. Our work suggests a promising route for constructing multiple defect-charge states by designing intermetallic semiconductors, and opens new opportunities for developing quantum devices with charge-based quantum states. 相似文献
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Yuying Gao Feng Cheng Weina Fang Xiaoguo Liu Shengyang Wang Wei Nie Ruotian Chen Sheng Ye Jian Zhu Hongyu An Chunhai Fan Fengtao Fan Can Li 《国家科学评论(英文版)》2021,8(6)
A key issue for redox reactions in plasmon-induced photocatalysis, particularly for water oxidation, is the concentration of surface-accumulating charges (electrons or holes) at a reaction site for artificial photosynthesis. However, where plasmonic charge accumulated at a catalyst''s surface, and how to improve local charge density at active sites, remains unknown because it is difficult to identify the exact spatial location and local density of the plasmon-induced charge, particularly with regard to holes. Herein, we show that at the single particle level, plasmon-coupling-induced holes can be greatly accumulated at the plasmonic Au nanoparticle dimer/TiO2 interface in the nanogap region, as directly evidenced by the locally enhanced surface photovoltage. Such an accumulation of plasmonic holes can significantly accelerate the water oxidation reaction (multi-holes involved) at the interfacial reaction site, with nearly one order of magnitude enhancement in photocatalytic activities compared to those of highly dispersed Au nanoparticles on TiO2. Combining Kelvin probe force microscopy and theoretical simulation, we further clarified that the local accumulated hole density is proportional to the square of the local near-field enhancement. Our findings advance the understanding of how charges spatially distribute in plasmonic systems and the specific role that local charge density at reaction sites plays in plasmonic photocatalysis. 相似文献
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When quasiparticles move in condensed matters, the texture of their internal quantum structure as a function of position and momentum can give rise to Berry phases that have profound effects on the material’s properties. Seminal examples include the anomalous Hall and spin Hall effects from the momentum-space Berry phases in homogeneous crystals. Here, we explore a conjugate form of the electron Berry phase arising from the moiré pattern: the texture of atomic configurations in real space. In homobilayer transition metal dichalcogenides, we show that the real-space Berry phase from moiré patterns manifests as a periodic magnetic field with magnitudes of up to hundreds of Tesla. This quantity distinguishes moiré patterns from different origins, which can have an identical potential landscape, but opposite quantized magnetic flux per supercell. For low-energy carriers, the homobilayer moirés realize topological flux lattices for the quantum-spin Hall effect. An interlayer bias can continuously tune the spatial profile of the moiré magnetic field, whereas the flux per supercell is a topological quantity that can only have a quantized jump observable at a moderate bias. We also reveal the important role of the non-Abelian Berry phase in shaping the energy landscape in small moiré patterns. Our work points to new possibilities to access ultra-high magnetic fields that can be tailored to the nanoscale by electrical and mechanical controls. 相似文献
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本文研究了碳排放目标下我国能源结构的优化问题。论文运用碳夹点方法识别能源消费瓶颈,并通过能源替代确定满足碳排放约束的清洁能源量,最后以我国政府承诺的2020年碳减排目标为例,基于对2020年我国能源消费及碳排放量的预测,对我国整体能源结构优化进行实证分析。研究结果表明,2020年我国预测碳排放量高于碳减排目标,在清洁能源达到2 466.8万TJ~3 496.2万TJ时,能够实现2020年比2005年单位GDP减排40%~45%的碳排放目标。研究发现,碳排放约束下能源结构优化必须在一定的激励和约束措施下才能实现,且关键在于降低高碳能源的比重。能源结构的优化需依据能源的碳排放因子,按照由低向高的顺序通过清洁能源对高碳能源的替代来实现。清洁能源消费比重的提升是实现2020年碳减排目标的关键。中国经济步入以中高速增长为标志的"新常态"将有利于2020年能源消费总量的控制以及清洁能源消费比重的增加。 相似文献
6.
Yating Pan Yunyang Qian Xusheng Zheng Sheng-Qi Chu Yijun Yang Chunmei Ding Xi Wang Shu-Hong Yu Hai-Long Jiang 《国家科学评论(英文版)》2021,8(1)
While the surface charge state of co-catalysts plays a critical role for boosting photocatalysis, studies on surface charge regulation via their precise structure control remain extremely rare. Herein, metal-organic framework (MOF) stabilized bimetallic Pd@Pt nanoparticles, which feature adjustable Pt coordination environment and a controlled structure from core-shell to single-atom alloy (SAA), have been fabricated. Significantly, apart from the formation of a Mott-Schottky junction in a conventional way, we elucidate that Pt surface charge regulation can be alternatively achieved by changing its coordination environment and the structure of the Pd@Pt co-catalyst, where the charge between Pd and Pt is redistributed. As a result, the optimized Pd10@Pt1/MOF composite, which involves an unprecedented SAA co-catalyst, exhibits exceptionally high photocatalytic hydrogen production activity, far surpassing its corresponding counterparts. 相似文献
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《普罗米修斯》2012,30(3):241-257
Abstract Fifty years after the publication of Michael Polanyi's magnum opus, Personal Knowledge, the fashion for Knowledge Management (KM) has helped to institutionalise a redefinition of his distinction between tacit knowledge and explicit knowledge. But KM's redefinition of Polanyi's argument misrepresents his insights into the process of personal tacit ‘knowing’ and overlooks the implications of his faith in metaphysical ‘being’. This paper explores the significance of Polanyi's original concept of tacit knowledge, together with the consequences of assuming a ‘vertical’ connection between personal knowledge and faith in an unknowable absolute truth. By using faith to protect personal knowledge from the charge of subjectivism, Polanyi precluded the possibility that different people, who interact in different contexts and believe in different things, could develop viable modes of knowing and learning. However, rethinking Polanyi's philosophy with regard to Ernst von Glasersfeld's radical constructivism, which is derived from intersubjectively viable ‘horizontal’ communication, allows the virtues of tacit knowledge to be separated from the complications of metaphysical realism. 相似文献
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Walter Schrott Zdeněk Slouka Petr ?ervenka Ji?í Ston Marek Nebyla Michal P?ibyl Dalimil ?nita 《Biomicrofluidics》2009,3(4)
Electrokinetic properties and morphology of PDMS microfluidic chips intended for bioassays are studied. The chips are fabricated by a casting method followed by polymerization bonding. Microchannels are coated with 1% solution of bovine serum albumin (BSA) in Tris buffer. Albumin passively adsorbs on the PDMS surface. Electrokinetic characteristics (electro-osmotic velocity, electro-osmotic mobility, and zeta potential) of the coated PDMS channels are experimentally determined as functions of the electric field strength and the characteristic electrolyte concentration. Atomic force microscopy (AFM) analysis of the surface reveals a “peak and ridge” structure of the protein layer and an imperfect substrate coating. On the basis of the AFM observation, several topologies of the BSA-PDMS surface are proposed. A nonslip mathematical model of the electro-osmotic flow is then numerically analyzed. It is found that the electrokinetic characteristics computed for a channel with the homogeneous distribution of a fixed electric charge do not fit the experimental data. Heterogeneous distribution of the fixed electric charge and the surface roughness is thus taken into account. When a flat PDMS surface with electric charge heterogeneities is considered, the numerical results are in very good agreement with our experimental data. An optimization analysis finally allowed the determination of the surface concentration of the electric charge and the degree of the PDMS surface coating. The obtained findings can be important for correct prediction and possibly for robust control of behavior of electrically driven PDMS microfluidic chips. The proposed method of the electro-osmotic flow analysis at surfaces with a heterogeneous distribution of the surface electric charge can also be exploited in the interpretation of experimental studies dealing with protein-solid phase interactions or substrate coatings. 相似文献
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我国设施蔬菜产地土壤环境质量问题及管理对策 总被引：3，自引：0，他引：3
由于设施蔬菜生产复种指数高、农用投入品投入量大、产地环境封闭等特点, 易造成污染物在土壤中积累及有效性增加, 带来生态环境风险。研究表明, 设施蔬菜土壤中农药、剩余养分、重金属、酞酸酯、抗生素等污染物积累明显高于一般大田蔬菜, 其环境与安全风险比常规农田明显要高。土壤性质改变和污染物积累, 可降低土壤的生态功能, 提高作物污染物含量, 影响水体质量, 给设施蔬菜生产系统生态环境安全和人体健康带来风险。其原因与农用投入品投入量过大、生产经营落后、法律法规和标准不适应管理需求、监管缺失等有关。未来需要加强农用投入品使用的监管和指导, 完善适应设施生产的环境质量评价标准体系, 建立设施蔬菜产地环境监管和指导机制, 加大环保科技投入, 以保证设施蔬菜生产得到可持续发展。 相似文献
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Surface charge is one of the most important properties of nanopores, which determines the nanopore performance in many practical applications. We report the surface charge densities of track-etched nanopores, which were obtained by measuring the streaming current and pore conductance, respectively. Experimental results reveal that surface charge densities depend significantly on the salt concentrations. In addition the values obtained with the pore conductance were always several times higher than those calculated with the streaming current, and the gel-like surface layer on the nanopore was considered to be responsible for this discrepancy. 相似文献
14.
碲锌镉单晶体是近年发展起来的一种性能优异的三元化合物晶体材料,具有良好的光电性质,被广泛用于制作核辐射探测器、红外探测器外延衬底等而引起了越来越多的研究者重视。研究碲锌镉晶体生长方法,对于低成本制备大体积、高质量的碲锌镉单晶体具有重要意义。数值模拟的发展,加深了对各种生长碲锌镉单晶体技术的认识,对加大碲锌镉单晶生长及应用的研究具有重要的意义。 相似文献
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电动汽车充电桩运营模式研究 总被引：2，自引：2，他引：0
以电动汽车民用充电桩为研究对象,在分析充电桩建设运营的政府主导模式、电网企业主导模式、汽车厂商主导模式等三种模式利弊的基础上,结合我国的实际情况,提出我国现阶段应实行汽车厂商与电网企业联盟建设充电桩的模式。建立一个考虑政府补助,建设成本和运行成本的充电桩利润函数模型,并提出充电桩运营的基本思路,为电动汽车充电桩在中国的长期发展提供思路和理论基础。 相似文献
16.
《普罗米修斯》2012,30(2):213-230
Each Australian state and the Australian Capital Territory has signed a 'whole of education department' contract with the Microsoft® Corporation for the provision of operating systems and other software. This contracted use of Microsoft® products is one story where the purchase of specific commodities is directly connected to the provision of public schooling. It is argued that through these contracts Microsoft® exercises a hegemonic relationship with the schooling systems in Australia. The legal relationships that exist between Microsoft® Corporation and the respective Australian states and territories schooling systems seem to mutually maintain and reinforce the monopolistic, or at best, oligopolistic position of Microsoft® Corporation and its hegemony over Australian public schooling. Further, it is argued that Microsoft's® hegemonic position in part is maintained by both establishing a 'commonsense' about its products and by receiving legitimation and authority through the State for its products used in Australian schools. 相似文献
17.
“三本”院校英语精读课程学生自主学习能力培养对策研究 总被引：1，自引：0，他引：1
英语精读课程是英语专业学生在大学一、二年级的专业主修课程,集培养学生英语听、说、读、写、译五种能力的目标为一体。课程的性质与定位要求学生具备较强的自主学习意识与能力。本文将结合“三本”院校英语专业学生的特点与英语精读课程的课程性质,提出一种培养学生在英语精读课程自主学习能力的方法,进而促进英语精读课程教学活动的开展与进行。 相似文献
18.
The cell''s micro-environment plays an important role in various physiological and pathological phenomena. To better investigate in vivo cellular behaviors, researchers have expended great effort in building controlled in vitro biophysical and biochemical environments. Because a cell''s gaseous environment affects properties such as its division, metastasis, and differentiation, we developed a zero-flow based platform for studying mammalian cell chemotaxis behavior in different oxygen environments. This platform can construct a linear range of oxygen tensions within one chip (i.e., from 1.4% to 3.6% or 5.5% to 14.5%). To study cell chemotaxis behavior under varying oxygen environments, the chemical gradient direction is established perpendicularly to oxygen change within an observation area. Because the observation area is not subject to flow, shear force is of no concern. In addition, water flow around the cell chambers greatly reduces evaporation and makes long-term microscope imaging possible. In this study, we precisely measure the chemotaxis velocity of MCF-7 human breast cancer cells under different oxygen tension conditions towards CXCL12, which is a stromal cell-derived factor. We find that cell migration rates are not equivalent, even under two close oxygen tensions. We also observed that cells move faster towards high concentrations of chemoattractant when the oxygen tension is below 3% due to the increased expression of HIF-1 (hypoxia-inducible factor 1), which promotes a transition to the amoeboid rather than mesenchymal mode of movement. Our experiments demonstrate that this new microfluidic platform is useful for the quantitative study of mammalian cell chemotaxis under different oxygen conditions in the absence of shear force. We also shed light on the study of chemotaxis under other gaseous environments. 相似文献
19.
Sunghoon Cho Young Jin Choi Shaohui Zheng Jiwon Han Seong Young Ko Jong-Oh Park Sukho Park 《Biomicrofluidics》2015,9(5)
The bacteria-based microrobot (Bacteriobot) is one of the most effective vehicles for drug delivery systems. The bacteriobot consists of a microbead containing therapeutic drugs and bacteria as a sensor and an actuator that can target and guide the bacteriobot to its destination. Many researchers are developing bacteria-based microrobots and establishing the model. In spite of these efforts, a motility model for bacteriobots steered by chemotaxis remains elusive. Because bacterial movement is random and should be described using a stochastic model, bacterial response to the chemo-attractant is difficult to anticipate. In this research, we used a population-scale approach to overcome the main obstacle to the stochastic motion of single bacterium. Also known as Keller-Segel''s equation in chemotaxis research, the population-scale approach is not new. It is a well-designed model derived from transport theory and adaptable to any chemotaxis experiment. In addition, we have considered the self-propelled Brownian motion of the bacteriobot in order to represent its stochastic properties. From this perspective, we have proposed a new numerical modelling method combining chemotaxis and Brownian motion to create a bacteriobot model steered by chemotaxis. To obtain modeling parameters, we executed motility analyses of microbeads and bacteriobots without chemotactic steering as well as chemotactic steering analysis of the bacteriobots. The resulting proposed model shows sound agreement with experimental data with a confidence level <0.01. 相似文献