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Acoustic radiation forces have been used to manipulate cells and bacteria in a number of recent microfluidic
applications. The net force on a cell has been subject to careful investigation over a number of decades. We
demonstrate that the radiation forces also act to deform
cells. An
ultrasonic standing
wave field is created in a
0.1 mm glass capillary at a frequency of 7.9 MHz. Using osmotically swollen red-blood cells, we show observable
deformations up to an aspect
ratio of 1.35, comparable to deformations created by optical tweezing. In contrast to optical technologies,
ultrasonic devices are
potentially capable of deforming thousands of cells simultaneously. We create a finite element model that includes both the acoustic
environment of the cell, and a model of the cell
membrane subject to forces resulting from the non-linear aspects of the acoustic
field. The model is found to
give reasonable agreement with the experimental results, and shows that the deformation is the result of variation in
an acoustic force that is directed outwards at all points on the cell membrane. We foresee applications in
diagnostic devices, and in the possibility of mechanically stimulating cells to promote differentiation and
physiological effects. 相似文献
4.
Red blood cells (RBCs) are important to dictate hemorheological properties of blood. The
shear-thinning effect of blood is mainly attributed to the characteristics of the RBCs. Variations
in hemorheological properties alter flow resistance and wall shear stress in blood vessels. Therefore, detailed
understanding of the relationship between the hemorheological and hemodynamic properties is of great
importance. In this study, blood viscosity and blood
flow were simultaneously measured in the same microfluidic device by monitoring the
flow-switching phenomenon. To investigate blood flows according to hemorheological variations, the flow rate of blood samples (RBCs
suspended in autologous plasma, dextran-treated plasma, and in phosphate buffered saline solution)
was precisely controlled with a syringe pump. Velocity profiles of blood flows were measured by using a micro-particle image
velocimetry technique. The
shape of velocity profiles
was quantified by using a curve-fitting equation. It is found that the shape of the velocity profiles is highly correlated with
blood viscosity. To
demonstrate the relationship under ex vivo conditions, biophysical properties and
velocity profiles were
measured in an extracorporeal rat bypass loop. Experimental results show that
increased blood viscosity seems to induce blunt velocity profile with high velocity component at the wall of the microchannel. Simultaneous
measurement of blood viscosity and velocity profile would be useful for understanding the effects of hemorheological
features on the hemodynamic
characteristics in capillary blood vessels. 相似文献
5.
Fangzhou Liu Xiang Li Muhua Zhao Mengjian Guo Kehong Han Xinxin Dong Jing Zhao Wanlun Cai Qifa Zhang Hongxia Hua 《国家科学评论(英文版)》2020,7(7):1181
Rice planthoppers, the most devastating rice pests, occur in two wing forms: the short-wing form for rapid population growth and long-wing form for long-distance migration, which together create the mechanism for outbreak. Here we show that Ultrabithorax (Ubx) is a key regulator for switching between the long- and short-wing forms of rice planthoppers. Ubx is expressed in both forewing and hindwing pads, which is different from the canonical model of Ubx expression. In brown planthoppers, expression of Ubx (NlUbx) is regulated by nutritional status of the rice host. High-quality young plants induce NlUbx expression leading to the short-wing form; low-quality ripe plants reduce NlUbx expression resulting in long-wing form. We also showed that NlUbx is regulated by the insulin receptors NlInR1 and NlInR2. The default expression of NlInR1 inhibits NlUbx resulting in long-wings, while high-quality hosts induce NlInR2 expression, which represses NlInR1 thus promoting NlUbx expression to produce short-wings. 相似文献
6.
Maedeh Roushan Parminder Kaur Alena Karpusenko Preston J. Countryman Carlos P. Ortiz Shuang Fang Lim Hong Wang Robert Riehn 《Biomicrofluidics》2014,8(3)
We present an analytic technique for probing protein-catalyzed transient DNA loops that is based on nanofluidic channels. In these nanochannels, DNA is forced in a linear configuration
that makes loops appear as folds whose size can easily be quantified. Using this technique, we study
the interaction between T4 DNA ligase and DNA. We find that T4 DNA ligase binding changes the physical characteristics of the DNA
polymer, in particular
persistence length and effective width. We find that the rate of DNA fold unrolling is significantly reduced
when T4 DNA ligase and ATP
are applied to bare DNA.
Together with evidence of T4 DNA ligase bridging two different segments of DNA based on AFM imaging, we thus conclude that ligase
can transiently stabilize folded
DNA configurations by coordinating genetically distant DNA stretches. 相似文献
7.
太湖流域主要河道浮游植物类群对比研究 总被引:7,自引:0,他引:7
2010年春季(4月13日-4月22日)和夏季(7月10日-7月19日)对太湖流域主要入湖河道进行了两次调查。对不同河道浮游植物群落结构进行了对比分析。入湖河流优势属主要有针杆藻(Synedra sp.)、隐藻(Cryptomonas sp.)、直链硅藻(Aulacoseira sp.)、脆杆藻属(Fragilaria sp.)和舟形藻(Navicula sp.)等;出湖河道主要优势属有直链硅藻(Aulacoseira sp.)、栅藻(Scenedesmus sp.)、隐藻(Cryptomonas sp.)等。夏季入湖河道优势属有针杆藻(Synedra sp.)、十字藻(Crucigenia sp.)、隐藻(Cryptomonas sp.)、裸藻(Euglena sp.)和微囊藻(Microcystis sp.)等;出湖河道优势属有直链硅藻(Aulacoseira sp.)、栅藻(Scenedesmus sp.)、隐藻(Cryptomonas sp.)、针杆藻(Synedra sp.)等。太湖流域河道浮游植物物种多样性春季要高于夏季,电导率、总磷、总氮、总悬浮物浓度、高锰酸钾指数和硝态氮与河道内浮游植物物种多样性显著相关。典范对应分析(CCA)结果显示影响春季浮游植物群落结构的关键因子有总悬浮物浓度、总氮和电导率,夏季则主要是高锰酸钾指数、硝态氮和总氮浓度。 相似文献
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Irving Langmuir 《Journal of The Franklin Institute》1934,217(5):543-569
The rate of evaporation of electrons, νe, from a thoriated tungsten filament depends on the temperature T and on θ, the fraction of the surface covered by thorium atoms. The relation of νe to θ and T has been given by Brattain and Becker. From νe the change in contact potential V of the filament surface produced by the adsorbed thorium can be calculated by the Boltzmann equation. Knowing σ the number of thorium atoms per cm.3, the dipole moment M of each is given by V = 2τσM. By an equation already used for Cs films on tungsten, the 2-dimensional equation of state of the adsorbed film can be calculated from M. Then by Gibbs' adsorption equation the relation of the atom evaporation rate νa to θ and T can be determined. It is thus calculated that in the range from θ = 0.2 to θ = 0.6, νa varies in proportion to ?Hθ where H = 8.1 in good agreement with the value H = 7.8 given by Brattain and Becker's measurements. A recalculation of the data of numerous experiments in 1921–1923, using the new relations of νe to θ1 gives data on νa as a function of T and θ in good agreement with the values of νa calculated from νe.The diffusion coefficients of Th through tungsten crystals, along grain boundaries and over the free filament surface, are calculated. A theory is given for the cause of the variation in the surface diffusion coefficient with σ. The probable mechanism of the production of the metallic thorium within the filament is discussed. At 2400° the thorium which arrives at the surface along grain boundaries, for some unknown reason, does not spread out over the surface as it does at lower temperatures (1900–2100°). 相似文献
10.
Using data generated by progressive nucleation mechanism on the cumulative fraction of citations of individual papers published successively by a hypothetical author, an expression for the time dependence of the cumulative number Lsum(t) of citations of progressively published papers is proposed. It was found that, for all nonzero values of constant publication rate ΔN, the cumulative citations Lsum(t) of the cumulative N papers published by an author in his/her entire publication career spanning over T years may be represented in distinct regions: (1) in the region 0 < t < Θ0 (where Θ0 ≈ T/3), Lsum(t) slowly increases proportionally to the square of the citation time t, and (2) in the region t > Θ0, Lsum(t) approaches a constant Lsum(max) at T. In the former region, the time dependence of Lsum(t) of an author is associated with three parameters, viz. the citability parameter λ0, the publication rate ΔN and his/her publication career t. Based on the predicted dependence of Lsum(t) on t, a useful scientometric age-independent measure, defined as citation acceleration a = Lsum(t)/t2, is suggested to analyze and compare the scientific activities of different authors. Confrontation of the time dependence of cumulative number Lsum(t) of citations of papers with the theoretical equation reveals one or more citation periods during the publication careers of different authors. 相似文献
11.
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
12.
n-grams have been used widely and successfully for approximate string matching in many areas. s-grams have been introduced recently as an n-gram based matching technique, where di-grams are formed of both adjacent and non-adjacent characters. s-grams have proved successful in approximate string matching across language boundaries in Information Retrieval (IR). s-grams however lack precise definitions. Also their similarity comparison lacks precise definition. In this paper, we give precise definitions for both. Our definitions are developed in a bottom-up manner, only assuming character strings and elementary mathematical concepts. Extending established practices, we provide novel definitions of s-gram profiles and the L1 distance metric for them. This is a stronger string proximity measure than the popular Jaccard similarity measure because Jaccard is insensitive to the counts of each n-gram in the strings to be compared. However, due to the popularity of Jaccard in IR experiments, we define the reduction of s-gram profiles to binary profiles in order to precisely define the (extended) Jaccard similarity function for s-grams. We also show that n-gram similarity/distance computations are special cases of our generalized definitions. 相似文献
13.
J.L. Finck 《Journal of The Franklin Institute》1940,229(2):201-221
This paper is a continuation of a previous paper published in this JOURNAL. The basic idea in the two papers is to enlarge the assemblage of thermodynamic states by including the so-called “metastable” states. Considering a system, in one or two phases, which has a single type of transformation, the writer develops an equation of state of the form η = a + by + cp + dpv + (e + fv + gp + hpv) In T, where p, v, T are three independent variables, and a, b, c, etc. are constants.The latent heat at p, T = constant is λP,T = I (v2 -v1) [b+db+(f+hp) InT), which is derived from the equation of state.The available thermodynamic data on ammonia and steam are used to check these equations. It is found that within the saturated region the agreement is quite satis factory, whereas for the superheated region the agreement is not so good. 相似文献
14.
Shih-Feng YangChyi Hwang 《Journal of The Franklin Institute》2002,339(2):129-144
In this paper we present a method for testing the Hurwitz property of a segment of polynomials (1−λ)p0(s)+λp1(s), where λ∈[0,1] and p0(s) and p1(s) are nth-degree polynomials with complex coefficients. The method consists in constructing a parametric Routh-like array with polynomial entries and generating Sturm sequences for checking the absence of zeros of two real λ-polynomials of degrees 2 and 2n in the interval (0,1). The presented method is easy to implement. Moreover, it accomplishes the test in a finite number of arithmetic operations because it does not invoke any numerical root-finding procedure. 相似文献
15.
I. Malkin 《Journal of The Franklin Institute》1942,234(4):355-369
Introduction: a. The vibration problem in its actual aspects in the steam turbine design; b. The fundamental conception of the solution used in the steam turbine practice as derived from the Rayleigh Ritz method substituted for the original Kirchhoff theory; c. Illustration of the actual problem by an example taken from the one-dimensional theory of vibrations; d. The “Wheel Vibrations” of the disk; e. The blade vibrations with the disk proper entirely at rest; f. Asymptotical representation of the actual (“Disk Blade”) vibrations of the disk; g. Simplifications used in the procedure of frequency computation; h. The disk with heavy rim. 相似文献
16.
Montgomery multiplication over rings 总被引:1,自引:0,他引:1
Montgomery multiplication of two elements a and b of a finite field Fq is defined as abr-1 where r is a fixed field element in . In this paper we define Montgomery multiplication of elements a(x) and b(x) in a polynomial ring modulo the ideal generated by a reducible polynomial f(x). We then show that Montgomery multiplication over a field represented by a polynomial ring modulo an irreducible pentanomial can be performed more efficiently in terms of time delay by embedding the field in a quotient of a polynomial ring modulo a reducible trinomial. The trinomial has a degree that is slightly higher than that of the pentanomial, thereby increasing the number of gates in the multiplier by a small amount. 相似文献
17.
Motivated by the work in [1] of Abualrub and Siap (2009), we investigate (1+λu)-constacyclic codes over Fp[u]/〈um〉 of an arbitrary length, where λ is a nonzero element of Fp. We find the generator polynomials of (1+λu)-constacyclic codes over Fp[u]/〈um〉, and determine the number of (1+λu)-constacyclic codes over Fp[u]/〈um〉 for a given length, as well as the number of codewords in each such code. Some optimal linear codes over F3 and F5 are constructed from (1+λu)-constacyclic codes over Fp+uFp under a Gray map. 相似文献
18.
Jinshan Zhang Zhenyu Zhou Jinjuan Bai Xiaoping Tao Ling Wang Hui Zhang Jian-Kang Zhu 《国家科学评论(英文版)》2020,7(1):102
The microRNA miR396 directly represses GROWTH-REGULATING FACTORs (OsGRFs) and has been implicated in regulating rice yield and in nitrogen assimilation. Overexpressing the miR396 targets OsGRF4 and OsGRF6 improves rice yield via increased grain size and panicle branching, respectively. Here, we used CRISPR/Cas9 to assess the function of miR396 genes in rice. Knockout of MIR396ef (MIR396e and MIR396f), but not other isoforms, enhanced both grain size and panicle branching, resulting in increased grain yield. Importantly, under nitrogen-deficient conditions, mir396ef mutants showed an even higher relative increase in grain yield as well as elevated above-ground biomass. Furthermore, we identified OsGRF8 as a new target of miR396, in addition to the known targets OsGRF4 and OsGRF6. Disruption of the miR396-targeting site in OsGRF8 was sufficient to both enlarge grain size and elongate panicles. Our results suggest that rice-seed and panicle development are regulated by miR396ef-GRF4/6/8-GIF1/2/3 modules and that miR396ef are promising targets of genome editing for breeding environmentally friendly rice varieties that require less nitrogen fertilization. 相似文献
19.
BackgroundMemecylon species are commonly used in Indian ethnomedical practices. The accurate identification is vital to enhance the drug's efficacy and biosafety. In the present study, PCR based techniques like RAPD, ISSR and DNA barcoding regions, such as 5s, psbA-trnH, rpoC1, ndh and atpF-atpH, were used to authenticate and analyze the diversity of five Memecylon species collected from Western Ghats of India.ResultsPhylogenetic analysis clearly distinguished Memecylon malabaricum from Memecylon wightii and Memecylon umbellatum from Memecylon edule and clades formed are in accordance with morphological keys. In the RAPD and ISSR analyses, 27 accessions representing five Memecylon species were distinctly separated into three different clades. M. malabaricum and M. wightii grouped together and M. umbellatum, M. edule and Memecylon talbotianum grouped in the same clade with high Jaccard dissimilarity coefficient and bootstrap support between each node, indicating that these grouped species are phylogenetically similar.ConclusionData from the present study reveals that chloroplast psbA-trnH region could be used as a potential candidate region for identifying Memecylon species, and ISSR marker system could be used for estimating genetic diversity since it has high percent polymorphism compared to RAPD marker. 相似文献
20.
Arthur K. Doolittle 《Journal of The Franklin Institute》1976,301(3):241-251
The work reported in Ref. (1), carried out on n-heptane from 273·16K to the critical point (under moderate pressures), is extended to five n-alkanes, benzene, mercury and water under saturation pressures and extended to much lower temperatures.Forty calculations of various thermodynamic quantities pertaining to the liquids here studied (648 points) are presented in Tables II-IV. All parameters and physical constants involved are presented in Table V. The Standard Percentage Errors (SPE) for all the calculations and the temperature ranges are given in Table VI. The grand average SPE for the 648 points is about one-third of 1%. Only one calculation (the temperature of water from 393·16 to 563·16 K) had an error greater than 1% (18 points). 相似文献