Separate detection of BTX mixture gas by a microfluidic device using a function of nanosized pores of mesoporous silica adsorbent

We achieved separate detection of the components of 10 ppm of a benzene, toluene, and o-xylene mixture gas by using mesoporous silica powder incorporated in our microfluidic device. The device consists of concentration and detection cells formed of 3 cm x 1 cm Pyrex plates. We first introduced the mixture gas into the concentration cell where it was adsorbed on an adsorbent in a channel formed in the cell. We then raised the temperature using a thin-film heater and introduced the desorbed gas into the detection cell. Here, we measured the changes in the absorption spectra of the mixture gas in the detection cell. We found that the mixture ratio of the compounds in the desorbed gas varies with time because the thermal desorption property of each compound is different from that of the adsorbent. We analyzed the thermal desorption mechanism by comparing two types of silica adsorbents with different pore structures. We found that an adsorbent that has pores with a periodic and uniform nanosized column shape provides better component separation. We concluded that the uniform pore structure might cause the adsorbate molecules to exhibit a homogeneous adsorption state thus revealing the desorption properties of the gas more clearly.     

有限混合体模型上的自动模型选择:一种崭新的数据建模方式

在数据建模和分析中,有限混合体模型被广泛地使用着。然而,如何仅仅针对一组来自于某个有限混合体模型的数据选择出分量或聚类的个数则依然是一个非常困难的问题。由于分量个数是混合体模型的规模度量,其选择问题被称为有限混合体的模型选择问题。最近,针对有限混合体模型,特别是高斯混合模型,一种自动模型选择学习机制逐步发展成熟起来。这种新的机制能够在学习参数的过程中自动地完成模型选择,为数据的建模与分析提供了一种新的思路与途径。本文将对于高斯混合模型或一般有限混合体模型的自动模型选择学习算法及其典型应用进行综述与总结。首先,我们综述了基于贝叶斯阴阳机和谐学习原则的自动模型选择学习算法。然后,我们描述了另一种基于熵惩罚的自动模型选择学习算法。最后,我们给出了自动模型选择学习算法的一些典型的应用。     

A method for quantification from composite spectra: application to the determination of isomeric DNA photoproducts by tandem mass spectrometry

Quantification of mixture components from their composite optical or mass spectra is a common need in analytical chemistry. We encountered the need when applying a combination of enzymatic digestion with nuclease P1 and tandem mass spectrometry to a mixture of isomeric photomodified oligodeoxynucleotides. In the procedure, we collisionally activated the [M - H]- or [M + Na - 2H]- ion of trinucleotide triphosphates, which were extricated enzymatically from the larger, damaged oligodeoxynucleotides, and we measured the relative abundances of characteristic fragment ions. The results sometimes yield curved calibrations for plots of the relative fragment ion abundances in the product ion spectra of isomers versus their relative amounts. We developed a normalized linear model, which brings understanding to the nonlinear plots and allows quantification of the mixture components from their composite spectra. The outcome demonstrates a general quantification procedure and shows that different yields for generating fragment ions from different constituents of the mixture cause the curved calibration lines.     

Analysis of quantitative proteomic data generated via multidimensional protein identification technology

We describe the analysis of quantitative proteomic samples via multidimensional protein identification technology (MudPIT). Ratio amounts of the soluble portion of the S. cerevisiae proteome from cultures of S. cerevisiae strain S288C grown in either 14N minimal media or 15N-enriched minimal media were mixed and digested into a complex peptide mixture. A 1 x 14N/1 x 15N complex peptide mixture was analyzed by single-dimensional reversed-phase chromatography and electrospray ionization quadrapole time-of-flight mass spectrometry in order to demonstrate the replacement of 14N by 15N under the growth conditions used. After conformation of the incorporation of 15N into the labeled sample, three separate samples consisting of a 1 x 14N/1 x 15N complex peptide mixture, a 5 x 14N/1 x 15N complex peptide mixture, and a 10 x 14N/1 x 15N complex peptide mixture were analyzed via MudPIT. We demonstrate the dynamic range of the system by analyzing a 1:1, 5:1, and 10:1 data set using the soluble portion from S. cerevisiae grown in either 14N or 15N-enriched minimal media. The method described provides an accurate way to undertake a large-scale quantitative proteomic study.     

Protective Action of Phosphate and Calcium-Containing Pigments under the Conditions of the Stress Corrosion Fracture of Steels

We have established that strontium chromate and a mixture of modified zinc phosphate and calcium-containing pigment inhibit substantially the corrosion of low-carbon steel in slightly acid rain solution. We observed mainly the anodic control of corrosion in the extract of chromate pigment and mixed control in the extract of a mixture of nonchromate pigments. Zinc ions in corrosive media enhance significantly the protective action of this pigment mixture. Here, a crystal-like protective film, consisting of calcium and zinc phosphates, is formed on the surface of steel. The extracts of chromate pigment and a mixture of nonchromate pigments in a slightly acid medium increase the resistance of low-carbon steel to corrosion fatigue in the stages of crack initiation and growth. Thus, the necessary prerequisites are created for enhancing the service life of steel constructions with organic coatings, containing inhibiting pigments, under conditions of the joint action of a corrosive medium and cyclic loading.__________Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 5, pp. 31–36, September–October, 2004.     

Effect of additives on the pore structure of ceramics based on crystalline SiO<Subscript>2</Subscript>

We have studied a method of controlling the pore structure of ceramics based on crystalline silica by introducing different burnable additives into the starting mixture. We have developed mathematical models in the form of best fit equations, which adequately represent the relationships between the burnable additive content of the starting mixture, the porosity of the ceramic samples, and their mechanical strength.     

The effect of diborane additive on the plasma-chemical properties of deposited carbon films

We present the results of studies of the optical, electrical, and mechanical properties of diamondlike carbon films prepared by plasma-chemical vapor deposition from a mixture of methane and diborane in various proportions. Upon reaching the threshold concentration (~12%) of diborane in the mixture, inclusions of a new phase start to form in the structure of the films. This leads to nonlinear dependence of the interior stresses and the surface resistance of coatings on the composition of the mixture with minimum values corresponding to a diborane concentration of about 12%.

     

Resolution of multicomponent fluorescence emission using frequency-dependent phase angle and modulation spectra

We describe a new fluorescence method that allows the resolution of both the decay times and emission spectra of mixtures of fluorophores. This method is completely general and does not require any assumptions or knowledge of the decay times or emission spectra of the individual fluorophores. We use the phase angle spectra and modulation spectra of the mixture, measured over a range of suitable light modulation frequencies and emission wavelengths. These data are analyzed by nonlinear least-squares analysis to recover the emission spectra and the associated decay times. The principle of the method and the nature of the data are illustrated by using two-component mixtures with increasing spectral overlap. We then demonstrate the recovery of minor components, of structure emission spectra, and of a three-component mixture with completed overlapping emission spectra. And finally, we describe the resolution of a two-component mixture with decay times of 0.8 and 1.4 ns using modulation frequencies up to 774 MHz.     

Estimating the segregation of a granular bed subjected to vibration in various modes

We present in this paper a DEM study on the segregation behavior of vibrated binary mixture, by focusing on the influence of vibration modes. The numerical simulation program includes a number of vibration tests on a binary mixture in a cylindrical bed, which are performed under different vibration velocity modes, frequencies and amplitudes. We utilize a novel segregation index, namely, the graphic segregation index (GPSI), to characterize the segregation behavior and trace the segregation evolution for binary mixtures. The numerical simulations reveal that the influence of velocity mode is coupled with that resulting from vibration frequency. The binary mixture tends to segregate at a low frequency, with little influence exerted by the velocity mode, whereas it does not fulfill complete segregation at a relatively high frequency, with the vibration frequency having some limited impact on the segregation behavior. Given an intermediate frequency the segregation behavior of the mixture is a little mixed for various velocity modes. It is also found that increasing vibration amplitude enhances the segregation degree of binary mixture. The operation of percolation mechanism in the broad sense is assumed to be primarily responsible for the occurrence of segregation in this study, and this alleged percolation mechanism, as an overall effect, is a result of three effects: the random gap effect, the size-and-mass dependent acceleration and the intrusion and expulsion effect.     

Visualization Approaches for Evaluating Ridge Regression Estimators in Mixture and Mixture‐Process Experiments

When the component proportions in mixture experiments are restricted by lower and upper bounds, the input space of a designed experiment space can become an irregular region that can induce multicollinearity problems when estimating the component proportion parameters. Thus, ridge regression provides a beneficial means of stabilizing the coefficient estimates in the fitted model. Previous research has focused on using prediction variance as a metric for determining an appropriate value of the ridge constant, k. We use visualization techniques to illustrate and evaluate ridge regression estimators and the robustness of estimation with respect to the variance and the bias. The addition of bias allows better balancing between the stability of the estimators and minimally changing the estimates. We illustrate the graphical methods with mixture and mixture‐process examples from the literature. Copyright © 2014 John Wiley & Sons, Ltd.     

Leung-Griffiths model for the thermodynamic properties of mixtures of CO2 and C2H6 near the gas-liquid critical line

Leung and Griffiths have proposed a fundamental thermodynamic equation for a binary mixture near the critical line and have successfully applied it to the mixture of He³ and He⁴ in which the critical line is a nearly linear function of composition. We have used a Leung-Griffiths type equation of state to describe the thermodynamic properties of the mixture of carbon dioxide and ethane. The critical line of this mixture is, unlike that of He³ and He⁴, a nonlinear function of composition, and the azeotropic line extends to the critical line. Comparison of the predictions of the equation to experimental data shows a good agreement for the mixture of CO₂ and C₂H₆.     

Development of a micro thermal sensor for real-time monitoring of lubricating oil concentration

We report development of a micro thermal sensor and sensing techniques for monitoring the oil concentration in a refrigeration system. The sensor acquires the thermal response of the mixture to ac heating and then the concentration can be determined using one of the two different methods. In the first method, the thermal conductivity of the mixture is obtained using the three-omega method and the concentration is determined using the correlation between the mixture concentration and thermal conductivity. In the alternative fast-detection method, the concentration is determined by directly calibrating the sensor output signal to the mixture concentration. The performance of the sensor was tested using the R410A/polyvinyl ether (PVE) oil mixture. The uncertainty of the oil concentration measurement was estimated to be 5.8-7.3 wt.%, depending on the sensing scheme. Especially, the simple structure of the sensor makes the technique cost effective and adequate for miniaturization, i.e., for installation in a limited space.     

Boundary conditions for the slippage of a binary mixture of gases and their application in the dynamics of aerosols. I. Flow of a mixture of gases along a solid plane wall

We investigate the flow of a thermally and concentrationally inhomogeneous binary mixture of gases near a solid nonevaporating surface. Using the method of half-space moments to solve the kinetic equation with the Boltzmann collision intergral, we determine the velocity distribution function of the molecules of the mixture components. The slip velocity of the mixture is calculated.Moscow Pedagogical Institute, Moscow. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 4, pp. 421–426, April, 1994.     

Effect of external factors on segregation of different granular mixtures

Segregation is a common problem faced by different pharmaceutical, chemical, and food processing industries due to non-uniformity in the end-products. Our aim is to minimize the segregation of binary granular mixture by changing the external chute-related factors rather than internal factors like material properties which is often not possible in industries. We investigate the effect of inclination angle, friction, fill volume and channel geometry in a steady, gravity driven flow of granular mixture in an inclined plane. We perform the numerical simulation using an open-source Discrete Element Method code - LIGGGHTS. We observe that the segregation of dry granular particles in stream-wise direction of the chute is minimum at low stream-wise velocity i.e. by keeping the chute at a low inclination and adding the wall roughness. The segregation in cross-stream and vertical direction is at a minimum when the chute is filled to at least 40% of its height. We also investigated the optimal conditions for minimum segregation in different granular mixtures and found that a mixture with size or density ratio up to 4 can have minimum segregation, if we fill the chute to 75% height. For a greater size or density ratio, it is difficult to minimize the segregation. The optimal segregation conditions for mixtures with different elastic modulus ratio were generally constant.     

Orientational Ordering of ortho–para Mixtures of Crystals of Homonuclear Diatomic Molecules: Theoretical Evidence for Reentrance

We have developed a theoretical formalism to calculate the orientational phase diagram of ortho–para (or odd-J/even-J) mixtures of homonuclear diatomic molecules in the low-pressure solid phases. In particular, our formalism allows for the explicit disorder present in such mixtrues. While the formalism is general, here we apply it to the quantum anisotropic planar rotor model, a two-dimensional model of coupled rotors. Our calculated phase diagram, separating phases of disorder and short-range order is reentrant, when an equilibrium mixture of odd-J/even-J species is considered. A reentrant phase diagram separating states of disorder and long-range order is known to exist in all-J species in both two and three dimensions. The phase diagram we find for the thermal mixture of odd-J/even-J species exhibits reentrance over a wider range of coupling constants than the corresponding all-J species. We also investigate systems where the odd-J fraction is fixed as a function of temperature. We find that even 1% odd-J mixture exhibits a phase diagram different from the pure even-J case, indicating that the even-J molecules play important role in orientational ordering.     

Raman investigation of the supercritical mixture He-H2

We investigated the vibrational Raman spectrum of H₂ in the binary mixture He-H₂. The Q₁-line was measured between 150 and 350 K for two isobars in the gigapascal region in a mixture of critical composition. The results indicate a broadening of the spectrum due to critical concentration fluctuations.     

The Influence of an External Magnetic Field on the Burning of a High-Speed Air-Carbon Mixture

We present the experimental results on the influence of a non-uniform magnetic field on the processes of burning an air-propane mixture in a high-speed flow; the burning is initiated by a longitudinaltransverse DC discharge. From the experiments, it follows that by varying the value and the orientation of the magnetic-induction vector with respect to the direction of the discharge current we may be able to govern the process of burning an air-propane mixture in a high-speed flow.     

Use of optimal mixture-process designs and response-surface models to study properties of calcium silicate units

Calcium silicate units are versatile and widely used construction materials for edifices. Their production process involves several factors that concern either the mixture of the raw materials or the curing process. The understanding of how raw materials and process variables interact in achieving the compressive strength of the final product enables a cost- and energy-efficient layout of the production process. In this paper, we use mixture-process experiments to derive a prediction model for compressive strength. We compare computer-generated D-optimal designs with different numbers of center points by various criteria and by their prediction variance throughout the design space. In contrast to traditional mixture designs, these designs take additional constraints on the mixture components into account and can include process variables. We review suitable response-surface models, which combine mixture and process variables. Based on results from 72 experimental runs, a model for the mean compressive strength is built, combining expert knowledge with statistical model-selection strategies. The resulting model covers not only linear effects of mixture components and process variables but also interactions and quadratic terms. For example, the influence of the lime share on compressive strength differs among the use of various sand mixtures. For desired values of predicted compressive strength, factor settings can thereby be found reducing costs and energy emission.     

Theory of Thermophoresis of Moderately Large Drops of Concentrated Solutions in Binary Gaseous Mixtures

We have derived a formula for the rate of thermophoresis of a volatile drop of a concentrated solution in a binary gaseous mixture with allowance for known effects that are associated with all types of slipping of the gaseous mixture along the drop surface and jumps of temperature and concentrations. An analysis of this formula has been performed for a number of limiting cases.