Quantitative and sensitive detection of rare mutations using droplet-based microfluidics

Somatic mutations within tumoral DNA can be used as highly specific biomarkers to distinguish cancer cells from their normal counterparts. These DNA biomarkers are potentially useful for the diagnosis, prognosis, treatment and follow-up of patients. In order to have the required sensitivity and specificity to detect rare tumoral DNA in stool, blood, lymph and other patient samples, a simple, sensitive and quantitative procedure to measure the ratio of mutant to wild-type genes is required. However, techniques such as dual probe TaqMan(?) assays and pyrosequencing, while quantitative, cannot detect less than ～1% mutant genes in a background of non-mutated DNA from normal cells. Here we describe a procedure allowing the highly sensitive detection of mutated DNA in a quantitative manner within complex mixtures of DNA. The method is based on using a droplet-based microfluidic system to perform digital PCR in millions of picolitre droplets. Genomic DNA (gDNA) is compartmentalized in droplets at a concentration of less than one genome equivalent per droplet together with two TaqMan(?) probes, one specific for the mutant and the other for the wild-type DNA, which generate green and red fluorescent signals, respectively. After thermocycling, the ratio of mutant to wild-type genes is determined by counting the ratio of green to red droplets. We demonstrate the accurate and sensitive quantification of mutated KRAS oncogene in gDNA. The technique enabled the determination of mutant allelic specific imbalance (MASI) in several cancer cell-lines and the precise quantification of a mutated KRAS gene in the presence of a 200,000-fold excess of unmutated KRAS genes. The sensitivity is only limited by the number of droplets analyzed. Furthermore, by one-to-one fusion of drops containing gDNA with any one of seven different types of droplets, each containing a TaqMan(?) probe specific for a different KRAS mutation, or wild-type KRAS, and an optical code, it was possible to screen the six common mutations in KRAS codon 12 in parallel in a single experiment.     

Penetration height correlations for non-aerated and aerated transverse liquid jets in supersonic cross flow

Experimental results on the mixing of non-aerated and aerated transverse liquid jet in supersonic cross flow (M = 1.5) are presented in this paper. The goal of this study is to investigate the effect of the gas/liquid mass ratio on the penetration and atomization of an aerated liquid jet in high speed cross flow and to develop correlations for the penetration heights. High speed imaging system was used in this study for the visualization of the injection of aerated liquid jet. The results show the effect of jet/cross flow momentum flux ratio, the gas/liquid mass ratio and the Ohnesorge number on the penetration of aerated liquid jet in supersonic cross-flow. New correlations of the spray penetration height for the non-aerated liquid jet (GLR = 0) and the net gain in spray penetration height for the aerated liquid jet (GLR > 0) are presented.     

Multi-group grey wolf optimizer (MG-GWO) for estimating photovoltaic solar cell model

Journal of Thermal Analysis and Calorimetry - The use of photovoltaic (PV) solar systems as a direct convertor of electricity is increasing on daily basis at industrial and domestic scales. Such...     

Measurements of soot volume fraction in pulsed diffusion flame by laser induced incandescence

Laser induced incandescence (LII) is used in this study to measure soot volume fractions in steady and pulsed laminar diffusion flame. The main objective of this study is to investigate the effect of flame pulsing on soot formation inside the flame region. Phase-locked soot images were obtained for flame pulsing frequency between 10 and 200 Hz. The phase-locked soot images revealed the entire motion process of the soot field during one pulsation period. The results showed that the total soot volume fraction in the flame region increased by 45% when the pulsing frequency was increased from 10 to 200 Hz.     

Global exponential stability of pseudo almost automorphic solutions for delayed Cohen-Grosberg neural networks with measure

Applications of Mathematics - We investigate the Cohen-Grosberg differential equations with mixed delays and time-varying coefficient: Several useful results on the functional space of such...     

IMPROVEMENT OF FLUIDIZABILITY OF FINE POWDERS ——A COMPUTER STUDY

Simulations of the gas fluidization of a cohesive powder were performed using the Stokesian Dynamics method and an agglomeration-deagglomeration model to investigate methods of improving the fluidizability of fine powders. Three techniques (a) high gas velocity (b) vibration-assisted fluidization and (c) tapered fluidizer were used in the simulations which provided detailed information on the bed microscopy such as the motion of 1 O0 particles in a fluidizing vessel along with the formation and destruction of cohesive bonds dudng collisions. While all three techniques were found to effectively improve the fluidizability of a strongly cohesive powder, we suggest a combination of high velocity fluidization assisted by extemal vibration of the fluidized bed to minimize entrainment of particles.     

Polymerization Compounding on the Surface of Zirconia Nanoparticles

Zirconia nanoparticles were encapsulated by polyethylene via a polymerization compounding method using a Ziegler-Natta catalyst. The chemical reaction was carried out in an organic solvent under moderate pressure of ethylene monomer. Transmission electron microscopy (TEM) indicated the presence of a thin layer of polymer, about 6 nm, uniformly applied around the particles. However, the thickness of coating layer can be controlled as a function of time and operating conditions of the process. The morphology study using scanning electron microscopy (SEM) as well as TEM revealed that although the nanoparticles seem to be coated individually, some agglomerates, encapsulated by a polymer film, could be observed. The grafting of the catalyst to the original surface of particles was further confirmed by X-ray photoelectron spectroscopy (XPS).     

Inhibition of acid corrosion of mild steel by Anacyclus pyrethrum L. extracts

Inhibition of the corrosion of mild steel in sulfuric acid by extracts of Anacyclus pyrethrum L. (leaves and stems, AP-LS; flowers AP-F; roots, AP-R) has been studied by use of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. Anacyclus pyrethrum L. inhibited the corrosion of mild steel in 0.5 M H₂SO₄ solution. Polarization curves show that the different parts of plants act as anodic type inhibitors. Changes in impedance data (charge transfer resistance, R _t, and double layer capacitance, C _dl) were indicative of adsorption of the extracts on the metal surface, leading to the formation of protective films. The extent of surface coverage by the inhibitors was determined by measurement of ac impedance; it was found that adsorption of these inhibitors on the mild steel surface obeys the Langmuir adsorption isotherm. Activation energies in the presence and absence of AP-LS and AP-F were obtained by measuring the temperature dependence of the corrosion current.     

Using S-statistic for investigating the effect of temperature on hydrodynamics of gas–solid fluidization

The influence of temperature on fluidization was investigated by a statistical chaotic attractor comparison test known as S-statistic. After calibration of the variables used in this method, the S-test was applied to the radioactive particle tracking (RPT) data obtained from a lab-scale fluidized bed. Experiments were performed with sand as fluidized particles and in temperatures from ambient up to 600 °C with superficial gas velocities of 0.29, 0.38 and 0.52 m/s. Considering the behavior of bubbles and comparing with frequency domain analysis, it was concluded that S-statistic is a reliable method for characterization of fluidization process behavior at different temperatures.     

INTERPARTICLE FORCES IN HIGH TEMPERATURE FLUIDIZATION OF GELDART A PARTICLES

Previous reports and current studies show that fluidization of some Geldart A particles is enhanced by in-creasing bed temperature.Both the averaged local particle concentration and the particle concentration in the dense phase decrease with increasing bed temperature,at constant superficial gas velocities.However,conventional models fail to predict these changes,because the role of interparticle forces is usually neglected at different bed temperatures.Here.the temperature increases,the interparticle attractive forces decrease while the interparticle repulsive forces increase.Consequently.fluidization behaviors of some Geldart A particles seem to increasingly shift from typical Geldart A towards B with increasing temperature.