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81.
This paper presents a protocol using theoretical methods and free software to design and analyze multivolume digital PCR (MV digital PCR) devices; the theory and software are also applicable to design and analysis of dilution series in digital PCR. MV digital PCR minimizes the total number of wells required for "digital" (single molecule) measurements while maintaining high dynamic range and high resolution. In some examples, multivolume designs with fewer than 200 total wells are predicted to provide dynamic range with 5-fold resolution similar to that of single-volume designs requiring 12,000 wells. Mathematical techniques were utilized and expanded to maximize the information obtained from each experiment and to quantify performance of devices and were experimentally validated using the SlipChip platform. MV digital PCR was demonstrated to perform reliably, and results from wells of different volumes agreed with one another. No artifacts due to different surface-to-volume ratios were observed, and single molecule amplification in volumes ranging from 1 to 125 nL was self-consistent. The device presented here was designed to meet the testing requirements for measuring clinically relevant levels of HIV viral load at the point-of-care (in plasma, <500 molecules/mL to >1,000,000 molecules/mL), and the predicted resolution and dynamic range was experimentally validated using a control sequence of DNA. This approach simplifies digital PCR experiments, saves space, and thus enables multiplexing using separate areas for each sample on one chip, and facilitates the development of new high-performance diagnostic tools for resource-limited applications. The theory and software presented here are general and are applicable to designing and analyzing other digital analytical platforms including digital immunoassays and digital bacterial analysis. It is not limited to SlipChip and could also be useful for the design of systems on platforms including valve-based and droplet-based platforms. In a separate publication by Shen et al. (J. Am. Chem. Soc., 2011, DOI: 10.1021/ja2060116), this approach is used to design and test digital RT-PCR devices for quantifying RNA. 相似文献
82.
83.
Nguyen Van Toan Chuen‐How Ng Kyaw Nyein Aye Trung Si Trang Willem F. Stevens 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2006,81(7):1113-1118
Chitin and chitosan with improved characteristics were produced from shrimp shell waste preconditioned by limited decay or by treatment with 0.016 mol L?1 benzoic acid. Preconditioned shrimp shells were transparent, had a clean surface and were susceptible to demineralization and deproteinization using 0.68 mol L?1 HCl and 0.62 mol L?1 NaOH, respectively. The ash and protein residues in the final chitosan were about 0.2% and 0.4%, respectively, the viscosity was up to 7000 cps, and the solubility and transparency nearly 100%. In comparison with treatment at ambient temperature (30 °C) without preconditioning, the chemical consumption, the duration of the treatment, ash and protein residues was reduced to 75–25%, whereas viscosity and absence of insolubles improved by a factor of 2–3. Copyright © 2006 Society of Chemical Industry 相似文献
84.
This article researches nonlinear response of imperfect eccentrically stiffened symmetric FGM thin circular cylindrical shells with ceramic-metal-ceramic layers, which are symmetric through the middle surface by Sigmoid-law distribution (S-FGM) and have stiffeners surrounded on elastic foundations under uniform radial load. The Donnell classical shell theory, stress function, and Galerkin method are used for investigation of the nonlinear stability of the S-FGM shell. The obtained results show the effects of the stiffeners, elastic foundations, mechanical load, and material parameters on the nonlinear buckling response of symmetric S-FGM circular cylindrical shells. 相似文献
85.
C. Thang Nguyen Toan Vu-Khanh Patricia I. Dolez Jaime Lara 《International Journal of Fracture》2009,155(1):83-91
Resistance to puncture by medical needles is becoming one of the most critical mechanical properties of rubber membranes,
which are heavily used in protective gloves. Yet the intrinsic material parameters controlling the process of puncture by
medical needles are still unknown. In a first paper presenting this two-part study, it has been shown that puncture by medical
needles proceeds gradually as the needle cuts through the rubber membrane. The phenomenon of puncture by medical needles was
revealed to involve contributions both from friction and fracture energy, in a similar way as for cutting. The use of a lubricant
was not successful for removing the friction contribution for the determination of the material fracture energy corresponding
to puncture by medical needles. This paper describes an alternative approach based on the application of a prestrain to the
sample in a similar way as the work of Lake and Yeoh on cutting. A theoretical formulation for the tearing energy is derived
from the theory of Rivlin and Thomas on the rupture of rubber. It is validated with a model extending expressions provided
by the linear elastic fracture mechanics (LEFM) to include the non-linear stress–strain behavior displayed by rubber. For
low values of the tearing energy, the total fracture energy, i.e. the sum of the puncture and tearing energies, is constant;
the material fracture energy is obtained by extrapolation at zero tearing energy. This prestrain method allowed a complete
removal of the friction contribution. The value obtained for the fracture energy corresponding to puncture by medical needles
is found to be larger than the energy associated to cutting and smaller than that obtained for tearing. This can be related
to the value of the crack tip diameter, which is, in that case, given by the needle cutting edge diameter. 相似文献
86.
Ho Sang Jung Sang Yul Yang Kyeong Ho Cho Min Geun Song Canh Toan Nguyen Hoa Phung Uikyum Kim Hyungpil Moon Ja Choon Koo Jae-Do Nam Hyouk Ryeol Choi 《International Journal of Control, Automation and Systems》2017,15(1):25-35
This paper presents a novel design of dielectric elastomer actuator (DEA), called single body dielectric elastomer actuator (SDEA), to improve the performance of existing DEAs. The DEA is typically configured with stacking multiple dielectric elastomer film and linearly contracted according to the applied voltage. SDEA is fabricated monolithically without external frame and has the advantages of flexibility and light weight. Thus, it is applicable to various configurations of actuators such as twisting or bending, etc. By exploiting the advantages of SDEA, we propose a new 2-ply design of SDEA. The design is configured with plying couples of monolithically fabricated SDEA. We explain how it can amplify the stroke with its basic principles of operations. In addition, its fabrication method is addressed. Finally, the results of performance evaluations are included with respect to stroke, force, speed, etc. 相似文献
87.
Experimental results are presented for attenuation measurements performed on cylindrical-shaped forest components. Microwave propagation in simulated canopies composed of bare deciduous twigs and leafy coniferous branches was investigated at 9 GHz. In order to account for the influence of natural component parameters, the experiments were carried out under laboratory conditions where those parameters could be easily and fully controlled. The influence of the physical parameters (number density of scatterers and gravimetric water content) and the geometrical parameters (dimensions and orientation of the scatterers) on the angular and polarization attenuation behaviors is pointed out. These results supplement previous attenuation observations obtained with natural cylindrical elements 相似文献
88.
Methyl sulfide production by Aerobacter aerogenes in milk 总被引:1,自引:0,他引:1
89.
Rana Al-Sadi Viszwapriya Dharmaprakash Prashant Nighot Shuhong Guo Meghali Nighot Toan Do Thomas Y. Ma 《International journal of molecular sciences》2021,22(15)
Defective intestinal tight junction (TJ) barrier is a hallmark in the pathogenesis of inflammatory bowel disease (IBD). To date, there are no effective therapies that specifically target the intestinal TJ barrier. Among the various probiotic bacteria, Bifidobacterium, is one of the most widely studied to have beneficial effects on the intestinal TJ barrier. The main purpose of this study was to identify Bifidobacterium species that cause a sustained enhancement in the intestinal epithelial TJ barrier and can be used therapeutically to target the intestinal TJ barrier and to protect against or treat intestinal inflammation. Our results showed that Bifidobacterium bifidum caused a marked, sustained enhancement in the intestinal TJ barrier in Caco-2 monolayers. The Bifidobacterium bifidum effect on TJ barrier was strain-specific, and only the strain designated as BB1 caused a maximal enhancement in TJ barrier function. The mechanism of BB1 enhancement of intestinal TJ barrier required live bacterial cell/enterocyte interaction and was mediated by the BB1 attachment to Toll-like receptor-2 (TLR-2) at the apical membrane surface. The BB1 enhancement of the intestinal epithelial TJ barrier function was mediated by the activation of the p38 kinase pathway, but not the NF-κB signaling pathway. Moreover, the BB1 caused a marked enhancement in mouse intestinal TJ barrier in a TLR-2-dependent manner and protected against dextran sodium sulfate (DSS)-induced increase in mouse colonic permeability, and treated the DSS-induced colitis in a TJ barrier-dependent manner. These studies show that probiotic bacteria BB1 causes a strain-specific enhancement of the intestinal TJ barrier through a novel mechanism involving BB1 attachment to the enterocyte TLR-2 receptor complex and activation of p38 kinase pathway. 相似文献
90.
Branching model for vegetation 总被引:3,自引:0,他引:3
Yueh S.H. Kong J.A. Jao J.K. Shin R.T. Le Toan T. 《Geoscience and Remote Sensing, IEEE Transactions on》1992,30(2):390-402
A branching model is proposed for the remote sensing of vegetation. The frequency and angular responses of a two-scale cylinder cluster are calculated to demonstrate the significance of vegetation architecture. The results indicate that the architecture of vegetation plays an important role in determining the observed coherent effects. A two-scale branching model is implemented for soybean with its internal structure and the resulting clustering effects considered. At the scale of soybean fields, the relative location of soybean plants is described by a pair distribution function. The polarimetric backscattering coefficients are obtained in terms of the scattering properties of soybean plants and the pair distribution function. Theoretical backscattering coefficients evaluated using the hole-correction pair distribution are in good agreement with extensive data from soybean fields. The hole-correction approximation, which prevents two soybean plants from overlapping each other, is more realistic and improves the agreement between the model calculation and experimental data near normal incidence 相似文献