共查询到20条相似文献，搜索用时 15 毫秒
1.
The advent and dissemination of next-generation sequencing (NGS) technologies such as Illumina''s sequencing platforms has brought forth vast reductions in the cost, time, and technical difficulties associated with DNA and RNA sequencing. Despite this trend, the workflow required to generate nucleic acid libraries for sequencing remains time-consuming and laborious. The following research proposes a method for simplifying and streamlining this process by replacing the manual washing steps of the common magnetic bead-based cleanup with a novel microfluidic method by integrating magnetic separation and electrokinetic purification (MSEP). Requiring no pumps, pipette mixing, vortexing, or centrifugation, MSEP relies on selective adsorption of target DNA onto the magnetic beads with subsequent transport of beads through a microchannel undergoing an antiparallel electroosmotic flow. The synergetic flow conditions were optimized using a simple electrohydrodynamic flow model. This work demonstrates that MSEP is as effective in eliminating adapter-dimers from the post-ligation library mix as the manual method while also greatly reducing the hands-on time and amount of pipetting required. Although MSEP has been applied specifically toward NGS library preparation at this time, it has the potential to be adapted and employed for any bead-based separation scheme, namely, solid phase extraction, sequence-specific hybridization, and immunoprecipitation on a microscale. 相似文献
2.
We present dual-mode, on-demand droplet routing in a multiple-outlet microfluidic device using an oil-based magnetic fluid. Magnetite (Fe3O4) nanoparticle-contained oleic acid (MNOA) was used as a carrier phase for droplet generation and manipulation. The water-in-MNOA droplets were selectively distributed in a curved microchannel with three branches by utilizing both a hydrodynamic laminar flow pattern and an external magnetic field. Without the applied magnetic field, the droplets travelled along a hydrodynamic centerline that was displaced at each bifurcating junction. However, in the presence of a permanent magnet, they were repelled from the centerline and diverted into the desired channel when the repelled distance exceeded the minimum offset allocated to the channel. The repelled distance, which is proportional to the magnetic field gradient, was manipulated by controlling the magnet''s distance from the device. To evaluate routing performance, three different sizes of droplets with diameters of 63, 88, and 102 μm were directed into designated outlets with the magnet positioned at varying distances. The result demonstrated that the 102-μm droplets were sorted with an accuracy of ∼93%. Our technique enables on-demand droplet routing in multiple outlet channels by simply manipulating magnet positions (active mode) as well as size-based droplet separation with a fixed magnet position (passive mode). 相似文献
3.
《中国科学院院刊(英文版)》2005,19(1):14-14
A research team headed by Dr. Zhang Yongqing (Yong Q. Zhang) at the CAS Institute of Genetics & Developmental Biology recently received a financial grant from FRAXA, a US foundation supporting top-notch research of Fragile X Syndrome, a special hereditary disease of mental retardation. 相似文献
4.
Even though isoelectric focusing (IEF) is a very useful technique for sample concentration and
separation, it is challenging to extract separated samples for further processing. Moreover, the
continuous sample concentration and separation are not possible in the conventional IEF. To overcome
these challenges, free flow IEF (FFIEF) is introduced in which a flow field is applied in the
direction perpendicular to the applied electric field. In this study, a mathematical model is developed for FFIEF to understand
the roles of flow and
electric fields for
efficient design of microfluidic
chip for continuous separation of proteins from an initial well mixed solution. A finite volume based
numerical scheme is implemented to simulate two dimensional FFIEF in a microfluidic chip. Simulation results
indicate that a pH gradient forms as samples flow downstream and this pH profile agrees well with
experimental results validating our model. In addition, our simulation results predict the experimental behavior of
pI markers in a FFIEF microchip. This numerical model is used to predict the separation
behavior of two proteins
(serum albumin and cardiac troponin I) in a two-dimensional straight microchip. The effect of
electric field is
investigated for continuous separation of proteins. Moreover, a new channel design is presented to increase the separation
resolution by introducing cross-stream flow velocity. Numerical results indicate that the separation
resolution can be improved by three folds in this new design compare to the conventional straight
channel design. 相似文献
5.
Zhichang Qiu Long Tu Liang Huang Taoyuanmin Zhu Volker Nock Enchao Yu Xiao Liu Wenhui Wang 《Biomicrofluidics》2015,9(1)
Optogenetics has been recently applied to manipulate the neural circuits of Caenorhabditis elegans (C. elegans) to investigate its mechanosensation and locomotive behavior, which is a fundamental topic in model biology. In most neuron-related research, free C. elegans moves on an open area such as agar surface. However, this simple environment is different from the soil, in which C. elegans naturally dwells. To bridge up the gap, this paper presents integration of optogenetic illumination of C. elegans neural circuits and muscular force measurement in a structured microfluidic chip mimicking the C. elegans soil habitat. The microfluidic chip is essentially a ∼1 × 1 cm2 elastomeric polydimethylsiloxane micro-pillar array, configured in either form of lattice (LC) or honeycomb (HC) to mimic the environment in which the worm dwells. The integrated system has four key modules for illumination pattern generation, pattern projection, automatic tracking of the worm, and force measurement. Specifically, two optical pathways co-exist in an inverted microscope, including built-in bright-field illumination for worm tracking and pattern generation, and added-in optogenetic illumination for pattern projection onto the worm body segment. The behavior of a freely moving worm in the chip under optogenetic manipulation can be recorded for off-line force measurements. Using wild-type N2 C. elegans, we demonstrated optical illumination of C. elegans neurons by projecting light onto its head/tail segment at 14 Hz refresh frequency. We also measured the force and observed three representative locomotion patterns of forward movement, reversal, and omega turn for LC and HC configurations. Being capable of stimulating or inhibiting worm neurons and simultaneously measuring the thrust force, this enabling platform would offer new insights into the correlation between neurons and locomotive behaviors of the nematode under a complex environment. 相似文献
6.
中国早在20世纪20年代初就开始介绍玻尔的科学贡献。1929年,周培源最早访问了玻尔的研究所。1937年抗日战争前夕,玻尔应中国两所最高级的研究院和四所最重要的大学邀请,访问了上海、杭州、南京、北平,受到了最高规格的接待,会见了许多中国最重要的学术领导人、物理学家和学者。中国学者称玻尔是“现代科学思想的领袖”,“原子物理学的开拓者”,“世界今日最大的物理学家之一”。1938至1939年,张宗燧曾到玻尔的研究所工作,与玻尔一家建立了深厚的友谊。二次世界大战后,玻尔与中国学者断绝了来往。大战结束后,张宗燧恢复了与玻尔的通讯联系,胡宁访问了玻尔的研究所,哲学家罗忠恕在瑞典会见了玻尔。 相似文献
7.
8.
Linfeng Xu Hun Lee Mariana Vanderlei Brasil Pinheiro Phil Schneider Deekshitha Jetta Kwang W. Oh 《Biomicrofluidics》2015,9(1)
We propose a blood separation microfluidic device suitable for point-of-care (POC) applications. By utilizing the high gas permeability of polydimethylsiloxane (PDMS) and phaseguide structures, a simple blood separation device is presented. The device consists of two main parts. A separation chamber with the phaseguide structures, where a sample inlet, a tape-sealed outlet, and a dead-end ring channel are connected, and pneumatic chambers, in which manually operating syringes are plugged. The separation chamber and pneumatic chambers are isolated by a thin PDMS wall. By manually pulling out the plunger of the syringe, a negative pressure is instantaneously generated inside the pneumatic chamber. Due to the gas diffusion from the separation chamber to the neighboring pneumatic chamber through the thin permeable PDMS wall, low pressure can be generated, and then the whole blood at the sample inlets starts to be drawn into the separation chamber and separated through the phaseguide structures. Reversely, after removing the tape at the outlet and manually pushing in the plunger of the syringe, a positive pressure will be created which will cause the air to diffuse back into the ring channel, and therefore allow the separated plasma to be recovered at the outlet on demand. In this paper, we focused on the study of the plasma separation and associated design parameters, such as the PDMS wall thickness, the air permeable overlap area between the separation and pneumatic chambers, and the geometry of the phaseguides. The device required only 2 μl of whole blood but yielding approximately 0.38 μl of separated plasma within 12 min. Without any of the requirements of sophisticated equipment or dilution techniques, we can not only separate the plasma from the whole blood for on-chip analysis but also can push out only the separated plasma to the outlet for off-chip analysis. 相似文献
9.
The ability to separate and analyze chemical species with high resolution, sensitivity, and throughput is central to the development of microfluidics systems. Deterministic lateral displacement (DLD) is a continuous separation method based on the transport of species through an array of obstacles. In the case of force-driven DLD (f-DLD), size-based separation can be modelled effectively using a simple particle-obstacle collision model. We use a macroscopic model to study f-DLD and demonstrate, via a simple scaling, that the method is indeed predominantly a size-based phenomenon at low Reynolds numbers. More importantly, we demonstrate that inertia effects provide the additional capability to separate same size particles but of different densities and could enhance separation at high throughput conditions. We also show that a direct conversion of macroscopic results to microfluidic settings is possible with a simple scaling based on the size of the obstacles that results in a universal curve. 相似文献
10.
《Electronic Journal of Biotechnology》2014,17(6):262-267
BackgroundThe Tibetan pig is a pig breed with excellent grazing characteristics indigenous to the Qinghai–Tibet plateau in China. Under conditions of barn feeding, 90% of its diet consists of forage grass, which helps meet its nutritional needs. The present study aimed to isolate and identify a cellulolytic bacterium from the Tibetan pig's intestine and investigate cellulase production by this bacterium. The study purpose is to provide a basic theory for the research and development of herbivore characteristics and to identify a source of probiotics from the Tibetan pig.ResultsA cellulolytic bacterium was isolated from a Tibetan pig's intestine and identified based on morphological, physiological, and biochemical characteristics as well as 16S rRNA analysis; it was designated Bacillus subtilis BY-2. Examination of its growth characteristics showed that its growth curve entered the logarithmic phase after 8–12 h and the stable growth phase being between 20 and 40 h. The best carbon source for fermentation was 1% corn flour, while 2% peptone and yeast powder compound were the best nitrogen sources. The initial pH during fermentation was 5.5, with 4% inoculum, resulting in a high and stable amount of enzyme in 24–48 h.ConclusionsThe isolated BY-2 strain rapidly grew and produced cellulase. We believe that BY-2 cellulase can help overcome the shortage of endogenous animal cellulase, improve the utilization rate of roughage, and provide strain sources for research on porcine probiotics. 相似文献
11.
针对学者群体创办企业的微观过程,研究这类创业企业的成长路径。选取6家学者创业企业的发展历程作为研究案例,采用扎根理论方法提出技术路径、资源路径、补短路径、扬长路径、资本路径、人才路径6个主范畴及其对应的20个子范畴,构建学者创业企业成长三级动力火箭模型,归纳出学者创业企业在不同生命周期阶段的6条主要成长路径：在初创期可通过技术路径和资源路径打下生存基础;在成长期可通过补短路径和扬长路径取得快速发展;在成熟期可通过资本路径和人才路径持续迸发生命力。根据研究发现,建议创业的学者群体在自身擅长的技术领域开展创业,在筹备期积极争取课题或项目资源、在初创期重点加强校企合作、在成长期着力克服旧路径依赖并放大核心优势以及在成熟期预先储备资本运作技能。 相似文献
12.
Jin Liu Chenxu Wang Chaojia Lv Xiaowan Su Yijin Liu Ruilian Tang Jiuhua Chen Qingyang Hu Ho-Kwang Mao Wendy L Mao 《国家科学评论(英文版)》2021,8(4)
As the reaction product of subducted water and the iron core, FeO2 with more oxygen than hematite (Fe2O3) has been recently recognized as an important component in the D” layer just above the Earth''s core-mantle boundary. Here, we report a new oxygen-excess phase (Mg, Fe)2O3+δ (0 < δ < 1, denoted as ‘OE-phase’). It forms at pressures greater than 40 gigapascal when (Mg, Fe)-bearing hydrous materials are heated over 1500 kelvin. The OE-phase is fully recoverable to ambient conditions for ex situ investigation using transmission electron microscopy, which indicates that the OE-phase contains ferric iron (Fe3+) as in Fe2O3 but holds excess oxygen through interactions between oxygen atoms. The new OE-phase provides strong evidence that H2O has extraordinary oxidation power at high pressure. Unlike the formation of pyrite-type FeO2Hx which usually requires saturated water, the OE-phase can be formed with under-saturated water at mid-mantle conditions, and is expected to be more ubiquitous at depths greater than 1000 km in the Earth''s mantle. The emergence of oxygen-excess reservoirs out of primordial or subducted (Mg, Fe)-bearing hydrous materials may revise our view on the deep-mantle redox chemistry. 相似文献
13.
We show, via three-dimensional immersed-boundary-finite-element-lattice-Boltzmann simulations, that deformability-based red blood cell (RBC) separation in deterministic lateral displacement (DLD) devices is possible. This is due to the deformability-dependent lateral extension of RBCs and enables us to predict a priori which RBCs will be displaced in a given DLD geometry. Several diseases affect the deformability of human cells. Malaria-infected RBCs, for example, tend to become stiffer than their healthy counterparts. It is therefore desirable to design microfluidic devices which can detect diseases based on the cells'' deformability fingerprint, rather than preparing samples using expensive and time-consuming biochemical preparation steps. Our findings should be helpful in the development of new methods for sorting cells and particles by deformability. 相似文献
14.
We present a microfluidic technique that generates asymmetric giant unilamellar vesicles (GUVs) in the size range of 2–14 μm. In our method, we (i) create water-in-oil emulsions as the precursors to build synthetic vesicles, (ii) deflect the emulsions across two oil streams containing different phospholipids at high throughput to establish an asymmetric architecture in the lipid bilayer membranes, and (iii) direct the water-in-oil emulsions across the oil–water interface of an oscillating oil jet in a co-flowing confined geometry to encapsulate the inner aqueous phase inside a lipid bilayer and complete the fabrication of GUVs. In the first step, we utilize a flow-focusing geometry with precisely controlled pneumatic pressures to form monodisperse water-in-oil emulsions. We observed different regimes in forming water-in-oil multiphase flows by changing the applied pressures and discovered a hysteretic behavior in jet breakup and droplet generation. In the second step of GUV fabrication, an oil stream containing phospholipids carries the emulsions into a separation region where we steer the emulsions across two parallel oil streams using active dielectrophoretic and pinched-flow fractionation separations. We explore the effect of applied DC voltage magnitude and carrier oil stream flow rate on the separation efficiency. We develop an image processing code that measures the degree of mixing between the two oil streams as the water-in-oil emulsions travel across them under dielectrophoretic steering to find the ideal operational conditions. Finally, we utilize an oscillating co-flowing jet to complete the formation of asymmetric giant unilamellar vesicles and transfer them to an aqueous phase. We investigate the effect of flow rates on properties of the co-flowing jet oscillating in the whipping mode (i.e., wavelength and amplitude) and define the phase diagram for the oil-in-water jet. Assays used to probe the lipid bilayer membrane of fabricated GUVs showed that membranes were unilamellar, minimal residual oil remained trapped between the two lipid leaflets, and 83% asymmetry was achieved across the lipid bilayers of GUVs. 相似文献
15.
Weijie Zhao 《国家科学评论(英文版)》2021,8(11)
On 17 June 2021, China''s spacecraft Shenzhou 12 took three Chinese astronauts into the Earth''s orbit and docked with the assembly of Tianhe and Tianzhou, the core module and cargo ship of the Chinese Space Station (CSS), which had been launched and assembled in orbit earlier this year. The three astronauts became the first visitors of the CSS and would stay in orbit for about three months. In 2022, two laboratory cabin modules, Wentian and Mengtian, will be launched and assembled into Tianhe, completing the basic structure of the CSS. The CSS is designed to be used for at least 10 years, and will provide an outer space experimental platform for researchers from multiple disciplines.On 23 July 2021, National Science Review (NSR) interviewed Professor Ming Gao (高铭), the Commander-in-Chief of the Space Utilizaiton System of the China Manned Space Program, Director General of the Technology and Engineering Center for Space Utilization (CSU) of the Chinese Academy of Sciences and an Academician of the International Academy of Astronautics. The Space Utilizaiton System is the scientific part of the CSS project, responsible for the design and organization of the onboard research programs. Gao has been involved in China''s Manned Space Program since 1994, and has experienced the whole development process from the Shenzhou spacecraft to the CSS. In this interview, she introduces the scientific goals, plans and aspirations of the CSS. 相似文献
16.
《Information processing & management》2019,56(3):823-843
A vast number of user opinions are available from reviews posted on e-commerce websites. Although these opinions are a valuable source of knowledge for both manufacturers and customers, they provide volumes of information that exceeds the human cognitive processing capacity, which can be a major bottleneck for their effective use. To address this problem, a number of opinion-summarization methods have been proposed to organize these opinions by grouping them around aspects. However, these methods tend to generate an excessive number of aspect groups that are frequently overly generic and difficult to interpret. We argue that a superior alternative would be to organize opinions around product attributes as defined in a product catalog. Typically, product attributes correspond to the most important characteristics of the products. Furthermore, they are common to all products in a given category and thus, form a more stable set than aspects. In this paper, we propose a novel approach called OpinionLink to products in a catalog at the attribute granularity level with opinions extracted from product reviews. The proposed approach is divided into two phases. In the first phase, OpinionLink uses a classifier to identify opinionated sentences in the reviews on a particular product. In the second phase, another classifier is used to map the opinions that were previously extracted from the user reviews to the attributes of the products in the product catalog. We performed a series of experiments on these phases. For the first phase, our experiments indicated that using classifiers with the proposed features achieved an average of 0.87 in terms of F1 measure for the task of identifying opinionated sentences. In the second phase, the method we proposed for the opinion-mapping task achieved an average of 0.85 in terms of F1. Further, we verified the effectiveness of the proposed approach as a realistic end-to-end application, indicating that we can use OpinionLink in a real setting. Finally, we empirically demonstrate the feasibility of using the proposed approach with an extremely large volume of opinions available in a collection of more than 600,000 real reviews. We also set forth a number of directions for future research. 相似文献
17.
章学诚,作为一名杰出的史学理论家,他拥有丰富而独特的史学理论：作为一名杰出的方志学家,他不仅建立了一整套完善的方志理论．同时也修著了不少地方志著作。章学诚将吏学理论与方志修著实践相结合,首创了“方志学”。本文将从章学诚方志学的角度出发,深入研究、探讨章学诚的史学理论。同时,通过对章学诚方志学和史学理论的探讨．总结章学诚在史学领域的成就。 相似文献
18.
Weiran Liu Weixing Chen Ran Liu Yuan Ou Haoran Liu Lan Xie Ying Lu Caixia Li Bin Li Jing Cheng 《Biomicrofluidics》2015,9(4)
In sexual assault cases, forensic samples are a mixture of sperm from the perpetrator and epithelial cells from the victim. To obtain an independent short tandem repeat (STR) profile of the perpetrator, sperm cells must be separated from the mixture of cells. However, the current method used in crime laboratories, namely, differential extraction, is a time-consuming and labor-intensive process. To achieve a rapid and automated sample pretreatment process, we fabricated a microdevice for hydrodynamic and size-based separation of sperm and epithelial cells. When cells in suspension were introduced into the device''s microfluidic channels, they were forced to flow along different streamlines and into different outlets due to their different diameters. With the proposed microdevice, sperm can be separated within a short period of time (0.5 h for a 50-μl mock sample). The STR profiles of the products in the sperm outlet reservoir demonstrated that a highly purified male DNA fraction could be obtained (94.0% male fraction). This microdevice is of low-cost and can be easily integrated with other subsequent analysis units, providing great potential in the process of analyzing sexual assault evidence as well as in other areas requiring cell sorting. 相似文献
19.
文章实验通过高效磨矿分级技术、铅锑浮选新药剂、高效锌硫分离技术、细泥锡石回收新技术的研究,研究出了更适合105号矿体矿石的工艺流程和新技术,解决了过去100号矿选矿存在的磨矿锡石过粉碎、铅锑精矿含锌较高、锌硫分离精矿质量难保证、作业回收率低、矿泥锡石选别指标差等长期存在的技术难题。 相似文献
20.
国际一流智库影响力的取得有很多决定因素,但关键是其战略研究与政策咨询报告的高质量,而高质量又取决于其研究成果的高标准与质量管理机制。文章通过对一些国际一流智库高质量研究标准或指南、研究成果的严格独立同行评审的质量管理机制和流程的梳理,总结了研究成果质量管理机制的有益经验和启示。文章指出,我国新型智库建设中,尚未将高质量分析与研究的质量管理机制作为智库建设的重要环节来抓,既缺乏研究成果的相关高质量管理理念,也缺乏管理的制度规范,更缺乏质量管理控制的严格流程。为此,文章提出了我国新型智库建设的高质量分析与研究标准及质量管理机制建议。 相似文献