Mixing Homogeneity Research Articles

Hyperchaotic signal generation via DSP for efficient perturbations to liquid mixing

AbstractThis paper presents the design, simulation, hardware implementation and an application in liquid mixing of some hyperchaotic circuits, based on the digital signal processing (DSP) technology. The hyperchaotic Chen's system is used as an example to show the system discretization and variable renormalization in the design process. Numerical simulation is given to verify the hardware signal generator. The implemented hardware of Chen's system generates outputs in good agreement with the numerical simulation. The hyperchaotic signal output from the DSP is applied to generate complex perturbations in liquid mixing experiments. Dye dispersion experiments show that the induced hyperchaotic motion effectively helps enhance the mixing homogeneity in the stirred‐tank‐based mixer in our laboratory. Copyright © 2008 John Wiley & Sons, Ltd.

Pitt's inequality with sharp convolution estimates

Sharp $L^p$ extensions of Pitt’s inequality expressed as a weighted Sobolev inequality are obtained using convolution estimates and Stein-Weiss potentials. Optimal constants are obtained for the full Stein-Weiss potential as a map from $L^p$ to itself which in turn yield semi-classical Rellich inequalities on $\mathbb {R}^n$. Additional results are obtained for Stein-Weiss potentials with gradient estimates and with mixed homogeneity. New proofs are given for the classical Pitt and Stein-Weiss estimates.

Preparation and stabilization of nifedipine lipid nanoparticles

Design methods of nanoparticle formulations are divided into a break-down method and a build-up method. Furthermore, the former is further divided into dry and wet processes. For drug nanoparticle preparations, the wet process is generally employed, and organic solvents are used in most formulations. In this study, we investigated the preparation of nifedipine (NI) nanoparticles without using any organic solvent. NI nanoparticles with a mean particle size of approximately 50 nm could be prepared without organic solvent by a combination of roll mixing and high-pressure homogenization. The X-ray diffraction peak of the sample prepared by roll mixing was present at an identical position (2 θ) to that of NI crystals, showing that no peak shift was induced by interaction with lipid. These findings clarified that most NI remained as crystals in lipid. To maintain the particle size of the nanoparticles in suspension for a long time, a method of adding gelatin powder to the NI-lipid nanoparticle suspension, dissolving the mixture by heating, and then solidifying by cooling was investigated. The mean particle size of the sample was about 55 nm, and that after heat-liquefaction of the NI-lipid nanoparticle suspension gelated at 5 °C for 24 h was also about 55 nm, showing that the nanoparticle condition was retained.

Singular integral operators in Morrey spaces and interior regularity of solutions to systems of linear PDE’s

We obtain boundedness in Morrey spaces of singular integral operators with Calderon-Zygmund type kernel of mixed homogeneity. These estimates are used for the study of the interior regularity of the solutions of linear elliptic/parabolic systems. The proved Poincare-type inequality permits to describe the Holder, Morrey, and BMO regularity of the lower-order derivatives of the solutions.

Multidimensional integral operators with kernels of mixed homogeneity

Introduction. The role of integral operators with homogeneous kernels in mathematics and applications is well-known. Now we have a number of useful results concerning the operators, whose kernels are homogeneous of the degree (−n) and invariant with respect to the rotation group SO(n). Namely, the criteria of the invertibility and the Noether property are obtained; the Banach algebras generated by these operators are described; the conditions for the applicability of the projection method (see, for instance, [1]–[5] and references therein) are established. In this paper, we consider multidimensional integral operators, whose kernels have a mixed homogeneity: in a part of variables the kernel is homogeneous of the degree (−n), and in the rest variables the kernel is coordinate-wise homogeneous. For these operators below we prove the boundedness theorem and establish the invertibility criterion. Below we use the following notation: Rn is the n-dimensional Euclidean space; x = (x1, . . . , xn) ∈ Rn; |x| = √ x1 + · · · + xn; x′ = x/|x|; x · y = x1y1 + · · ·+ xnyn; x ◦ y = (x1y1, . . . , xnyn); e1 = (1, 0, . . . , 0); Sn−1 = {x ∈ Rn : |x| = 1}; R+ = {x ∈ Rn : xj > 0 ∀j = 1, 2, . . . , n}; Z+ is the set of all integer nonnegative numbers; Yνμ(σ) are spherical harmonics of the order ν (∈ Z+);

Tandem Mass Spectrometry Analysis of N2-(trans-Isoestragol-3‘-yl)-2‘-deoxyguanosine as a Strategy to Study Species Differences in Sulfotransferase Conversion of the Proximate Carcinogen 1‘-Hydroxyestragole

To get more insight into possible species differences in the bioactivation of estragole, the kinetics for sulfonation of the proximate carcinogen 1'-hydroxyestragole were compared for male rat, male mouse, and mixed gender human liver S9 homogenates. In order to quantify sulfonation, 2'-deoxyguanosine was added to the incubation mixture in which sulfonation of 1'-hydroxyestragole was catalyzed to trap the reactive 1'-sulfooxyestragole. A method was developed with which the formation of the most abundant adduct with 2'-deoxyguanosine could be quantified using isotope dilution LC-ESI-MS/MS. Comparing the kinetics for sulfonation by liver S9 homogenates of male rat, male mouse, and humans revealed that sulfonation was about 30 times more efficient by male rat liver S9 than by human liver S9, whereas the catalytic efficiency by male mouse and human liver S9 was about the same. This indicates, as far as the bioactivation by sulfotransferase is concerned, that when extrapolating the cancer risk from laboratory animals to humans, using data from male rats may overestimate the cancer risk in humans, whereas using data from male mice may provide a better estimate of the cancer risk in humans.

Evaluation of the content homogeneity and dispersion properties of fluticasone DPI compositions

In dry powder formulations for inhalation, the micronized active substance is usually diluted with a mixture of coarse and fine carrier particles in order to increase its flowability and dispersion properties. Considering a selected DPI fluticasone propionate (Flp)-coarse (CL) and fine (FL) lactoses ([Pharmatose DCL 21/Microfine 80/20] 1:499 w/w) composition in terms of drug deposition, the aim of the present study was to establish the optimal blending conditions in three types of mixing equipment, and to determine the effects of FL on the mixing homogeneity and dispersibility of Flp. The Flp-lactose ternary mixtures were prepared by first premixing the two lactoses (CL/FL) in five different ratios: 100/0; 99/1; 90/10; 80/20; 0/100 (w/w). Then Flp was added and the blending was carried out at three rotational speeds (low, medium and high) in a three-dimensional motion mixer (Turbula 2C), a planetary mixer (Collette MP-20) and a high-shear (Mi-Pro) mixer. The incorporation of a large proportion of FL (20%) considerably improved the aerosol performance (FPD=87μg) but greatly reduced the content uniformity of Flp when the blending was performed in the Turbula mixer (relative standard deviation, RSD>20% after 20min irrespective of the selected speed). The achievement of a homogeneous mixture (RSD<3%) required the use of powerful shear mixers (Colette MP-20 or Mi-Pro) operating at moderated rotational speeds to avoid the phenomenon of powder segregation and dust generation.

Spectroscopic studies of the size and composition of single aerosol droplets

The characterization of aerosol properties and processes, non-intrusively and directly, poses a severe analytical challenge. In order to understand the role of aerosols in often complex environments, it is necessary to probe the particles in situ and without perturbation. Sampling followed by end-of-line analysis can lead to perturbations in particle composition, morphology and size, particularly when analysing liquid aerosol droplets containing volatile components. Optical spectroscopy can provide a strategy for the direct assessment of particle size, composition and phase. We review here the application of linear and non-linear Raman spectroscopies in the characterization of liquid aerosol droplets. Spontaneous Raman scattering can allow the unambiguous identification of chemical components and the determination of droplet composition. Stimulated Raman spectroscopy can allow the determination of droplet size with nanometre accuracy and can allow the characterization of near-surface composition. When combined, the mixing state and homogeneity in droplet composition can be investigated. We highlight some applications of these spectroscopic techniques in studies of the kinetics of particle transformation, the equilibrium composition of aqueous aerosol droplets, and the coagulation and mixing state of organic and aqueous aerosol components. Specifically, we examine the heat and mass transfer accompanying the evaporation of volatile components from liquid droplets, the equilibrium size of aqueous/sodium chloride droplets with varying relative humidity, and the mixing of the immiscible decane and water components during droplet coagulation. We conclude by considering the potential of these techniques for improving our understanding of aerosol properties and processes.

Numerical Simulation of Cloud–Clear Air Interfacial Mixing: Effects on Cloud Microphysics

This paper extends the previously published numerical study of Andrejczuk et al. on microscale cloud–clear air mixing. Herein, the primary interest is on microphysical transformations. First, a convergence study is performed—with well-resolved direct numerical simulation of the interfacial mixing in the limit—to optimize the design of a large series of simulations with varying physical parameters. The principal result is that all conclusions drawn from earlier low-resolution (Δx = 10−2 m) simulations are corroborated by the high-resolution (Δx = 0.25 × 10−2 m) calculations, including the development of turbulent kinetic energy (TKE) and the evolution of microphysical properties. This justifies the use of low resolution in a large set of sensitivity simulations, where microphysical transformations are investigated in response to variations of the initial volume fraction of cloudy air, TKE input, liquid water mixing ratio in cloudy filaments, relative humidity (RH) of clear air, and size of cloud droplets. The simulations demonstrate that regardless of the initial conditions the evolutions of the number of cloud droplets and the mean volume radius follow a universal path dictated by the TKE input, RH of clear air filaments, and the mean size of cloud droplets. The resulting evolution path only weakly depends on the progress of the homogenization. This is an important conclusion because it implies that a relatively simple rule can be developed for representing the droplet-spectrum evolution in cloud models that apply parameterized microphysics. For the low-TKE input, when most of the TKE is generated by droplet evaporation during mixing and homogenization, an inhomogeneous scenario is observed with approximately equal changes in the dimensionless droplet number and mean volume radius cubed. Consistent with elementary scale analysis, higher-TKE inputs, higher RH of cloud-free filaments, and larger cloud droplets enhance the homogeneity of mixing. These results are discussed in the context of observations of entrainment and mixing in natural clouds.

Quantifying water-stable soil aggregate turnover and its implication for soil organic matter dynamics in a model study

Recent studies have concluded that the dynamics of soil structure are central to the understanding of soil organic matter (SOM) cycling and the ensuing soil-water–nutrient relationships. Aggregate turnover directly controls the stabilization and physical protection of SOM. Therefore, quantifying aggregate dynamics will improve our ability to predict SOM behaviour as affected by ecosystem management and global change. We present an approach to directly quantify aggregate dynamics using rare-earth oxides as tracers. A 6-week laboratory incubation was set up to measure aggregate dynamics at different times. We made samples in which each different aggregate size-fraction contained a different tracer. By following the redistribution of these tracers into the other aggregate size-fractions, we could quantify all soil mass transfers between aggregate size-fractions. A comparison with a control soil showed that the tracer did not affect soil respiration or the aggregation process itself. Tracer mixing homogeneity, recovery and immobility were tested and validated. While initially macroaggregate formation occurred rapidly, microaggregate formation occurred more slowly during the experiment. Subsequent aggregate stabilization was more pronounced for the newly formed microaggregates than for the newly formed macroaggregates. Calculated turnover times were smaller for macroaggregates than for microaggregates (i.e. 30 vs. 88 days). Further research is needed to investigate to what extent these results can be extrapolated to the field. Our results confirmed existing qualitative views and concepts on aggregate dynamics in a quantitative way and will be valuable in directly linking aggregate turnover to the stabilization and protection of SOM.

Fabrication of Large Ceramic Components with Controlled Microstructure by Powder Thermoset Molding

Thermoset molding in wet and dry state was successfully employed to fabricate high strength reaction bonded silicon carbide (RBSC) ceramics. Granule transfer molding (GCM) was developed to prevent segregation of component particles and binder phase in wet state, while granule compression molding was applied in dry state to fabricate green compact with significant variation of compaction ratio. Low-fill density granules with mixing homogeneity were critical for promoting lateral deformation of granules during consolidation. In addition, anodic performance of Ni-YSZ anode was significantly enhanced by replacing solid fugitive phase with viscoelastic fugitive phase used as binder in thermoset molding.

Rapid PCR amplification of DNA utilizing Coriolis effects

A novel polymerase chain reaction (PCR) method is presented that utilizes Coriolis and centrifugal effects, produced by rotation of the sample disc, in order to increase internal circulatory rates, and with them temperature homogenization and mixing speeds. A proof of concept has been presented by testing a rapid 45-cycle PCR DNA amplification protocol. During the repeated heating and cooling that constitutes a PCR process, the 100 microL samples were rotated at a speed equivalent to an effective acceleration of gravity of 7,000 g. A cycle time of 20.5 s gave a total process time of 15 min to complete the 45 cycles. A theoretical and numerical analysis of the resulting flow, which describes the increased mixing and temperature homogenization, is presented. The device gives excellent reaction speed efficiency, which is beneficial for rapid PCR.

Multilamination of flows in planar networks of rotating microchannels

We describe a new multilamination technique to accelerated mixing of centrifugally pumped flows through a simple network of preferentially radial, low-aspect-ratio microchannels. Mixing by multilamination is enforced by planar split-and-recombine structures, consisting of a common inlet for two concurrent centrifugal flows, and a transient region of parallel microchannels which merge again into one common outlet. A repatterning of flow is observed in each parallel channel which is induced by the Coriolis pseudo force. In a distinct regime of the parameter space spanned by the speed of rotation, the channel geometry as the viscosity (and density) of the liquids, a multilamination of flow is achieved at the entrance of the common outlet channel. We also present parallelization and cascading strategies to further enhance the homogeneity and throughput of mixing by multilamination.

Quantifying water‐stable soil aggregate turnover and its implication for soil organic matter dynamics in a model study

SummaryRecent studies have concluded that the dynamics of soil structure are central to the understanding of soil organic matter (SOM) cycling and the ensuing soil‐water–nutrient relationships. Aggregate turnover directly controls the stabilization and physical protection of SOM. Therefore, quantifying aggregate dynamics will improve our ability to predict SOM behaviour as affected by ecosystem management and global change. We present an approach to directly quantify aggregate dynamics using rare‐earth oxides as tracers. A 6‐week laboratory incubation was set up to measure aggregate dynamics at different times. We made samples in which each different aggregate size‐fraction contained a different tracer. By following the redistribution of these tracers into the other aggregate size‐fractions, we could quantify all soil mass transfers between aggregate size‐fractions. A comparison with a control soil showed that the tracer did not affect soil respiration or the aggregation process itself. Tracer mixing homogeneity, recovery and immobility were tested and validated. While initially macroaggregate formation occurred rapidly, microaggregate formation occurred more slowly during the experiment. Subsequent aggregate stabilization was more pronounced for the newly formed microaggregates than for the newly formed macroaggregates. Calculated turnover times were smaller for macroaggregates than for microaggregates (i.e. 30 vs. 88 days). Further research is needed to investigate to what extent these results can be extrapolated to the field. Our results confirmed existing qualitative views and concepts on aggregate dynamics in a quantitative way and will be valuable in directly linking aggregate turnover to the stabilization and protection of SOM.

Mixing Time, Homogenization Energy and Residence Time Distribution in a Gas-Induced Contactor

Mixing time, homogenization energy and residence time distribution (RTD) experiments have been carried out in a gas-induced contactor in order to determine mixing characteristics of the vessel. Effects of sensor location, impeller speed, gas induction, and gassing on mixing time have been studied. Experiments on a semi-technical scale vessel have identified optimal mixing time conditions and optimal impeller speeds for most efficient homogenization energy. The effects of liquid flow rate and impeller speed on liquid phase RTD have also been investigated. The contactor mixing behaviour was modelled by a continuous stirred tank reactor (CSTR) with dead zones and bypassing. Good agreement between experimental and model results was observed. Analysis shows that contactor performance is close to that of an ideal CSTR; however, dead zones (as large as 16.7%) at low liquid flow rates and bypassing (as large as 10%) at high liquid rates need to be considered.

An original image-processing technique for obtaining the mixing time: The box-counting with erosions method

This study shows an original method to follow the blending of two powders and of these two powders and one viscous liquid in a classical reactor, under different agitation conditions. This technique takes a series of images and analyses them. It is a non-intrusive method which avoids sampling and therefore process interruption and sample preparation necessary otherwise. However, the image analysis is not evident and needs several steps. The simple application of the box-counting method on the synthetic on real images did not lead to good results because of the lack of variation of the fractal dimension between different images with a variable homogeneity. The box-counting method was then associated with an erosion treatment, leading to a useful parameter to characterise the mixture homogeneity. This parameter is the variation of the fractal dimension of the image, from the initial crude image to the final completely eroded one. The first results showed that the mixing is completely homogeneous after 100 s of agitation. In fact, a pseudo-homogeneity is achieved much more rapidly ( t < 40 s) but subsequent images show that aggregates still remain in the reactor. The method is then applied to the mixing of the two powders under different operating conditions and also to the blend of the two powders and one viscous liquid to simulate the chemical reaction evolution. The results obtained are satisfactory. They allow determination of the mixing time and quantification of the degree of homogeneity of the blend. For the solid/liquid mixture, the poor affinities between oil and solid have modified the characteristics of the mixture and made it difficult to produce. The final aim is to link these results on the mixing homogeneity and the solid/solid contact times with the reaction kinetics.

Stimulation of the synthesis of ribosomal proteins in regenerating rat liver with special reference to the increase in the amounts of effective mRNAs for ribosomal proteins.

1 Normal and partially hepatectomized rats were pulse labeled for 15 min with [14C]leucine and [3H]leucine respectively. Both kinds of liver homogenates were mixed and the ribosomal protein fraction was purified from the mixed homogenate by chromatographic procedures. The 3H/14C ratio of this fraction was about three times higher than that of total protein, indicating that the synthesis of ribosomal proteins is selectively increased in regenerating rat liver. 2 The free polysomes from normal or regenerating rat livers were incubated with [3H]leucine in the presence of regenerating rat liver supernatant. Ribosomal proteins were then purified, finally by two-dimensional acrylamide gel electrophoresis. Biosyntheses of most of ribosomal proteins by regenerating rat liver polysomes were about 2.5 to 3.6 times higher than those by normal rat liver polysomes. 3 Using a wheat germ cell-free system, the template activities of poly(A)-containing mRNAs for ribosomal proteins were compared between normal and regenerating rat livers. The template activities at 6, 12, 18, 24 and 48 h after partial hepatectomy were about 1.3, 1.8, 2.4, 1.5 and 1.3 times higher, respectively, than the activity of normal rat liver. The extents of increase in the template activity of poly(A)-containing mRNAs for most of individual ribosomal proteins separated by two-dimensional gel electrophoresis were not so different at 18 h after the operation and the average template activity was 2.8 times higher than that of normal rat liver. The enhanced activity of regenerating rat liver for ribosomal protein synthesis is mainly caused by the increase in the apparent concentrations of mRNAs for ribosomal proteins.

Ways of Optimizing the Preparation of Sintering-Machine Charges

Studies that were performed led the the following recommendations on optimizing the preparation of charges for sintering: improve the mixing (homogenization) of the charge, possibly by using high-speed paddle mixers, screw-driven pan-type mixers, or large mixing drums with a mixing coefficient of 0.95; intensify the balling of the charge in balling drums (high-intensity-rumbling regime); optimize moistening by using fine-spray water nozzles that employ compressed air; introduce automation systems at the stages of primary mixing and balling (high-intensity-rumbling regime), as well as moistening.

Characterization of gana-1, a Caenorhabditis elegans gene encoding a single ortholog of vertebrate α-galactosidase and α-N-acetylgalactosaminidase

BackgroundHuman α-galactosidase A (α-GAL) and α-N-acetylgalactosaminidase (α-NAGA) are presumed to share a common ancestor. Deficiencies of these enzymes cause two well-characterized human lysosomal storage disorders (LSD) – Fabry (α-GAL deficiency) and Schindler (α-NAGA deficiency) diseases. Caenorhabditis elegans was previously shown to be a relevant model organism for several late endosomal/lysosomal membrane proteins associated with LSDs. The aim of this study was to identify and characterize C. elegans orthologs to both human lysosomal luminal proteins α-GAL and α-NAGA.ResultsBlastP searches for orthologs of human α-GAL and α-NAGA revealed a single C. elegans gene (R07B7.11) with homology to both human genes (α-galactosidase and α-N-acetylgalactosaminidase) – gana-1. We cloned and sequenced the complete gana-1 cDNA and elucidated the gene organization.Phylogenetic analyses and homology modeling of GANA-1 based on the 3D structure of chicken α-NAGA, rice α-GAL and human α-GAL suggest a close evolutionary relationship of GANA-1 to both human α-GAL and α-NAGA.Both α-GAL and α-NAGA enzymatic activities were detected in C. elegans mixed culture homogenates. However, α-GAL activity on an artificial substrate was completely inhibited by the α-NAGA inhibitor, N-acetyl-D-galactosamine.A GANA-1::GFP fusion protein expressed from a transgene, containing the complete gana-1 coding region and 3 kb of its hypothetical promoter, was not detectable under the standard laboratory conditions. The GFP signal was observed solely in a vesicular compartment of coelomocytes of the animals treated with Concanamycin A (CON A) or NH4Cl, agents that increase the pH of the cellular acidic compartment.Immunofluorescence detection of the fusion protein using polyclonal anti-GFP antibody showed a broader and coarsely granular cytoplasmic expression pattern in body wall muscle cells, intestinal cells, and a vesicular compartment of coelomocytes.Inhibition of gana-1 by RNA interference resulted in a decrease of both α-GAL and α-NAGA activities measured in mixed stage culture homogenates but did not cause any obvious phenotype.ConclusionsGANA-1 is a single C. elegans ortholog of both human α-GAL and α-NAGA proteins. Phylogenetic, homology modeling, biochemical and GFP expression analyses support the hypothesis that GANA-1 has dual enzymatic activity and is localized in an acidic cellular compartment.

Color mixing in the metering zone of a single screw extruder: Numerical simulations and experimental validation

We present numerical simulations for an acrylonitrile-butadiene-styrene copolymer (ABS) resin extrusion in an industrial conventional single-screw extruder. Based upon the flow field patterns obtained in the simulations, a particle tracking procedure was employed to obtain information about the spatial distribution of particle tracers of two colors. Results of the simulation were compared with experimental data obtained under similar extrusion conditions. To evaluate the degree of color mixing and color homogeneity for the system, we employ a specific index calculated based upon the Shannon entropy for two species populations. POLYM. ENG. SCI., 45:1011–1020, 2005. © 2005 Society of Plastics Engineers