Suspended Fraction Research Articles

A FRACTAL MODEL FOR NUCLEATE POOL BOILING OF NANOFLUIDS AT HIGH HEAT FLUX INCLUDING CHF

A fractal model for nucleate pool boiling of nanofluids at high heat flux and critical heat flux (CHF) is developed based on the fractal distribution of nanoparticles and nucleation sites on boiling surfaces in this paper. The formula of calculating high heat flux and CHF for nanofluids in nucleate pool boiling is given by taking into account heat convection between nanoparticles and liquids due to the Brownian motion of nanoparticles in fluids. The proposed model is expressed as a function of temperature of nanofluids, the effective thermal conductivity of nanofluids, the average size of nanoparticles, the fractal dimension of nanoparticles and nucleation sites, the nanoparticles volume fraction of suspension, and physical properties of fluids. No additional/new empirical constant is introduced in this fractal model. An agreement between the proposed model predictions and experimental data is found. The validity of the fractal model for nucleate pool boiling of nanofluids at high heat flux and CHF is thus verified.

Rheological properties of agar microgel suspensions prepared using water-in-oil emulsions

Agar microgel suspensions containing sugar fatty acid esters were prepared using a water-in-oil (w/o) emulsion system. The volume fraction of microgel particles was adjusted by centrifugation to obtain high volume fraction suspensions. The relationship between the apparent equilibrium shear modulus and the volume fraction was analyzed using a hard-sphere model. The rigidity of the microgel particles never affected the rheological property under the random close-packed-volume fraction, but it affected the fracture of the structure composed of packed microgel particles. The length of fatty acid emulsifiers also affected the rheological properties of the condensed suspensions. The stress growth under step shear flow was observed to study the lubrication effect of close-packed microgel particles containing ER-190 (C 22:1) or O-170 (C 18:1). Although both suspensions showed strain softening, the tendency was different in each. Such a w/o microgel suspension is a likely candidate for use in low-fat foods.

Contact Angle Hysteresis of Microbead Suspensions

Microbead suspensions are often used in microfluidic devices for transporting biomolecules. An experimental investigation on the wettability of microbead suspension is presented in this study. The variation in the surface tension and the equilibrium contact angle with the change in the volume fraction of the microbead is presented here. The surface tension of the microbead suspension is measured with the pendant drop technique, whereas the dynamic contact angle measurements, i.e., advancing and receding contact angles, are measured with the sessile drop technique. An equilibrium contact angle of a suspension with particular volume fraction is determined by computing an average over the measured advancing and receding contact angles. It is observed that the surface tension and the equilibrium contact angle determined from advancing and receding contact angles vary with the magnitude of the microbeads volume fraction in the suspension. A decrease in the surface tension with an increase in the volume fraction of the microbead suspension is observed. The advancement and the recession in contact line for dynamic contact angle measurements are achieved with the motorized dosing mechanism. For microbead suspensions, the advancement of the contact line is faster as compared to the recession of the contact line for the same flow rate. The presence of microbeads assists in the advancement and the recession of the contact line of the suspension. A decrease in the equilibrium contact angles with an increase in the microbead suspension volume fraction is observed. Inclusion of microbeads in the suspension increases the wetting capability for the considered combination of the microbead suspension and substrate. Finally, empirical correlations for the surface tension and the contact angle of the suspension as a function of microbead volume fraction are proposed. Such correlations can readily be used to develop mechanistic models for the capillary transport of microbead suspensions related to LOC applications.

Use of Spectra in the Visible and Near-Mid-Ultraviolet Range with Principal Component Analysis and Partial Least Squares Processing for Monitoring of Suspended Solids in Municipal Wastewater Treatment Plants

The present work assesses the possibility of using spectrophotometry in the near-mid-ultraviolet and visible wavelength ranges (282-790 nm) for the direct monitoring of treatment performance in municipal wastewater treatment plants (WWTPs). Principal component analysis (PCA) was used to analyze spectral data from samples collected along three WWTP process lines with different primary and secondary treatment units. The clustering observed in PCA score plots was mainly attributed to the suspended solids fraction present in the wastewater and highlighted differences in solids quality between plants and along the treatment lines. Thus, satisfactory partial least squares (PLS) calibration models to estimate total suspended solids (TSS) values from the acquired spectra could only be established per plant. The PLS models were established using 1-2 factors, with root mean error of cross-validation and coefficient of determination values in the 50-86 mg TSS L(-1) and 82-95% ranges, respectively.

Dilution Technique To Determine the Hydrodynamic Volume Fraction of a Vesicle Suspension

A simple dilution method to determine the hydrodynamic volume fraction of vesicle suspensions is presented. The vesicle suspension is diluted with a solution containing a tracer Y, which is similar to a component X already present in the suspending fluid and which does not bind to or permeate through the vesicles. The concentrations of X and Y in the suspending fluid measured after dilution are used to determine the volume fraction. Using this technique, the volume fractions of vesicle suspensions comprising cationic vesicles prepared in solutions of CaCl(2) (X) were measured by dilution with MgCl(2) (Y) solutions. Various experimental parameters such as the concentration of the MgCl(2) diluents and the dilution volume ratio were studied and their effects optimized to arrive at a robust recipe for measuring the volume fraction. It is demonstrated that the technique can be applied to concentrated suspensions containing multilamellar and polydisperse vesicles.

Distribution of dimorphic yeast species in commercial extra virgin olive oil

Recent microbiological research has demonstrated the presence of a rich microflora mainly composed of yeasts in the suspended fraction of freshly produced olive oil. Some of the yeasts are considered useful as they improve the organoleptic characteristics of the oil during preservation, whereas others are considered harmful as they can damage the quality of the oil through the hydrolysis of the triglycerides. However, some dimorphic species can also be found among the unwanted yeasts present in the oil, considered to be opportunistic pathogens to man as they have often been isolated from immunocompromised hospital patients. Present research demonstrates the presence of dimorphic yeast forms in 26% of the commercial extra virgin olive oil originating from different geographical areas, where the dimorphic yeasts are represented by 3–99.5% of the total yeasts. The classified isolates belonged to the opportunistic pathogen species Candida parapsilosis and Candida guilliermondii, while among the dimorphic yeasts considered not pathogenic to man, the Candida diddensiae specie s was highlighted for the first time in olive oil. The majority of the studied yeast strains resulted lipase positive, and can consequently negatively influence the oil quality through the hydrolysis of the triglycerides. Furthermore, all the strains showed a high level of affinity with some organic solvents and a differing production of biofilm in “ vitro” corresponded to a greater or lesser hydrophobia of their cells. Laboratory trials indicated that the dimorphic yeasts studied are sensitive towards some components of the oil among which oleic acid, linoleic acid and triolein, whereas a less inhibiting effect was observed with tricaprilin or when the total polyphenols extracted from the oil were used. The observations carried out on a scanning electron microscope (SEM), demonstrated the production of long un-branched pseudohyphae in all the tested dimorphic yeasts when cultivated on nutrient-deficient substrates.

Fabricación y caracterización óptica de cristales coloidales de alta calidad formados por esferas de SiO2 de 225 nm de diámetro con empaquetamiento fcc crecidos por el método convectivo de auto-ensamblado de deposición vertical.

<p><strong>Objective:</strong> Fabrication and optical characterization of close-packed 225 nm SiO<sub>2</sub> -based colloidal crystals<strong>. Materials and methods:</strong> The vertical convective self-assembly method is used to grow high-quality 225 nm close-packed SiO<sub>2</sub>-based colloidal crystals. An annealing process (550°C) is made in order to improve the mechanical stability of the sample. Optical characterization is done by angle-resolved transmission spectroscopy (A-RTS) and structural characterization by Scanning Electron Microscopy (SEM). <strong>Results:</strong> Both, A-RTS and SEM, show that with the vertical convective self-assembly method, with the appropriate parameters of temperature of evaporation (60°C), volume fraction of the colloidal suspension (0.2% w/w) and acidity (pH=6), highly ordered close packed face centered cubic (fcc) SiO<sub>2</sub> based colloidal crystals are obtained. <strong>Conclusions:</strong> The growth of high-quality (long range order and defect-free) face centered cubic opal-based photonic crystals is reported.</p> <p><strong>Key words:</strong><em> </em>Photonic crystals, colloidal crystals, artificial opals, vertical convective deposition method, Bragg diffraction</p><br /><br />

Investigating the transient response of a shear thickening fluid using the split Hopkinson pressure bar technique

The split Hopkinson pressure bar (SHPB) technique is implemented to evaluate the transient response of a colloidal suspension exhibiting shear thickening at strain rates and timescales never before explored in a laboratory instrument. These suspensions are shown to exhibit a discontinuous transition from fluid-like (shear thinning) to solid-like (shear thickening) behavior when evaluated using rotational rheometry. The effect of loading rate on this transition time is studied for a particle volume fraction of 0.54 using the SHPB technique. It is shown that the time required for transition to occur decreases logarithmically with loading rate. From these results, we conclude that transition is not triggered by a characteristic shear rate, but rather a critical shear strain is required. Results from SHPB experiments performed up to Peclet numbers of order 107 are presented and discussed for 0.50, 0.52, and 0.54 particle volume fraction suspensions.

Volumetric Filtration of Rainfall Runoff. II: Event-Based and Interevent Nutrient Fate

This study examines in situ phosphorus treatment using a combined unit operation and process, a volumetric clarifying filter (VCF). Urban rainfall-runoff transports phosphorus in dissolved and particulate phases with the latter phase distributed across the particulate matter (PM) gradation. From a clean initial condition, the VCF was monitored across 19 events without maintenance, to examine partitioning and phosphorus distribution on PM. For the monitoring period, site influent total phosphorus (TP) is 0.342 mg/L of which 0.081 mg/L is dissolved; and subsequently reduced to 0.095 and 0.031 mg/L, respectively, by the VCF. PM-bound phosphorus is categorized as suspended, settleable and sediment fractions based on PM size and separation behavior. Site influent PM-based concentrations (mg/g) are 0.22 for sediment, 0.42 for settleable and 3.27 for the suspended fraction with each fraction further enriched in the VCF, based on effluent monitoring. A categorical analysis and odds ratio testing of PM-based phosphorus specific capacities (mg/g) indicate that a significant fraction of phosphorus can bind to suspended PM preferentially over settleable and sediment PM as a PM-based concentration. At the end of the event-based monitoring the inter-event change in phosphorus and nitrogen, chemistry is examined as a function of runoff storage time. Runoff retention generates nitrate reduction and ammonia (NH3+NH4+) production; predominately as ammonium. Phosphorus partitioning is stable during runoff storage with a dissolved fraction between one fourth to one-third of TP. Predominant species are H2PO4− for a pH<7 and HPO42− for a pH>7.

Efficient degradation of rice straw in the reactors packed by carbon fiber textiles

We have reported for the first time that agricultural and cellulosic waste, i.e., rice straw was directly applied to methanogenic bioreactors containing carbon fiber textiles (CFT) as supporting material. Addition of CFT to the methanogenic bioreactors enhanced the conversion of dichromate chemical oxygen demand of the substrate to methane (41%) to a greater extent than bioreactors without CFT (9%). In addition, removal of rice straw as a suspended solid was increased from 31% (in bioreactors without CFT) to 57% (in those with CFT). Methanogenic 16S rRNA gene analysis showed that the abundance of acetoclastic methanogen, genus Methanosarcina, was about 11 times higher in bioreactors with CFT (suspended fraction plus retained fraction to CFT) than in bioreactors without CFT (suspended fraction), resulting in lower concentration of acetate in bioreactors with CFT (0.4 mM) than in those without CFT (29.7 mM). On the other hand, the abundance of hydrogenotrophic methanogen, genus Methanobacterium, in bioreactors with CFT was similar to those without CFT. Bacterial communities in bioreactors with CFT were different from those in bioreactors without CFT. Our results indicated that specific microbial community and cooperative relationships between microorganisms in reactors containing CFT facilitated efficient decomposition of rice straw and its conversion to methane.

Interleukin-10 as a prognostic factor in patients treated with autologous melanoma cell vaccine.

8588 Background: Interleukin-10 (IL-10) downregulates the T cell-mediated immune response. We studied the association between IL10 production by freshly isolated melanoma cell suspensions in vitro and overall survival in patients who were treated with cancer vaccine consisting of the same autologous melanoma cells modified with a hapten, dinitrophenyl (DNP). It was assumed that production of IL-10 in tumor cell suspensions reflect the degree of IL-10 in tumor microenvironment. Methods: Tumor cells were extracted from metastatic tissues and cryopreserved until vaccine production. Small fraction of melanoma cell suspensions were separated prior to vaccine production and cultured overnight for the production of IL-10 in the culture supernatants. After inactivation with radiation and modification with DNP, autologous melanoma cells were injected to patients as a cancer vaccine. The final vaccine products did not produce IL-10. Forty four patients including 29 stage III and 15 stage IV disease were evaluated. The cut-off of 200 pg/mL was used to differentiate high versus low IL-10 producers based on scattergram. Cox regression model was used for multivariate analysis. Overall survival was calculated using Kaplan and Meier method and survival curves were compared with log-rank tests. Results: Out of 44 patients, 29 were low and 15 were high IL-10 producers. The overall survival (OS) was significantly longer for low versus high IL-10 producers (median OS 42 vs. 10.5 months, p = 0.02). In stage III patients, median OS for low and high IL-10 producers was 84 months and 9.7 months respectively (p = 0.07). In stage IV patients, the corresponding values were 13.7 months and 10.5 months (0.62). In multivariate analysis, the hazard ratios for stage III and stage IV patients were 2.92 (1.04-8.20) and 0.92 (0.28-3.00). Conclusions: Our study suggests that high IL-10 production in tumor cells is associated with worse prognosis in stage III melanoma patients receiving autologous vaccine. It has been shown that delayed-type hypersensitivity to autologous tumor cells is associated with longer OS. By downregulating the T cell mediated immune response, IL-10 in tumor microenvironment may decrease the effectiveness of the vaccine. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration AVAX

Particle migration in oscillatory torsional flows of concentrated suspensions

This study presents an experimental investigation into particle migration behavior of concentrated suspensions of noncolloidal spheres in oscillatory torsional flows between parallel plates. Video imaging of the radial drift velocity of dyed tracer particles in a monodisperse, 0.4 bulk particle volume fraction suspension was performed during flow evolution. In conjunction with simultaneous rheological measurements, particle tracking provided insight into migration phenomena. For all of the cases studied, the average displacement of the tracer particles per cycle was directed radially outward and was approximately a linear function of the oscillatory strain amplitude while also varying with the frequency of oscillation in a nearly inverse square relationship. The measured radial migration velocity exceeded that estimated from the suspension balance continuum model for a corresponding steady flow, likely due to the increased microstructural mobility developed during oscillatory flow. Generally, the oscillatory torque increased as the flow evolved, while local minima in the torque ratio and radial drift velocity were detected at intermediate strain values, in agreement with recent studies of oscillatory flow. The results suggest the competition between radial shear-induced particle migration driven by the overall particle stress balance and rearrangement of particles into an ordered microstructure driven by local interactions.

Efficient treatment of garbage slurry in methanogenic bioreactor packed by fibrous sponge with high porosity

Adding a supporting material to a methanogenic bioreactor treating garbage slurry can improve efficiency of methane production. However, little is known on how characteristics (e.g., porosity and hydrophobicity) of the supporting material affect the bioreactor degrading garbage slurry. We describe the reactor performances and microbial communities in bioreactors containing hydrophilic or hydrophobic sheets, or fibrous hydrophilic or hydrophobic sponges. The porosity affected the efficiency of methane production and solid waste removal more than the hydrophilic or hydrophobic nature of the supporting material. When the terminal restriction fragment length polymorphism technique was used at a lower organic loading rate (OLR), microbial diversities in the suspended fraction were retained on the hydrophobic, but not the hydrophilic, sheets. Moreover, real-time quantitative polymerase chain reaction (PCR) performed at a higher OLR revealed that the excellent performance of reactors containing fibrous sponges with high porosity (98%) was supported by a clear increase in the numbers of methanogens on these sponges, resulting in larger total numbers of methanogens in the reactors. In addition, the bacterial communities in fractions retained on both the hydrophobic and hydrophilic fibrous sponges differed from those in the suspended fraction, thus increasing bacterial diversity in the reactor. Thus, higher porosity of the supporting material improves the bioreactor performance by increasing the amount of methanogens and bacterial diversity; surface hydrophobicity contributes to maintaining the suspended microbial community.

Exchange between suspended and sinking particles in the northwest Mediterranean as inferred from the organic composition of in situ pump and sediment trap samples

The extent to which sinking particles disaggregate and exchange with surrounding material affects the efficiency of particulate organic carbon export to the deep sea. In 2003 and 2005, we compared the pigment and amino acid compositions of sediment trap and in situ pump samples collected in the northwest Mediterranean Sea to assess exchange between sinking and suspended particles. While sediment traps collected only sinking particles, in situ pumps collected both larger (&gt; 70‐µm) particles, believed to represent the sinking fraction, as well as smaller (1–70‐µm) particles, believed to represent the suspended fraction. The organic compound compositions of sinking and suspended particles were very different and remained consistently so with depth, suggesting that exchange between them was limited. This difference was particularly pronounced during the high flux periods in spring. Sinking particles appeared to be composed of many fecal pellets and a few phytoplankton aggregates, and were enriched in diatom indicators. Suspended particles appeared to be more enriched in fresh phytoplankton and contained indicators of calcium carbonate‐bearing organisms. During the low‐flux summer period, the contribution of fecal pellet indicators to sinking particles was lower, whereas the contribution of microbial degradation products in both particle types was higher, possibly indicating greater exchange during periods of low flux when fecal pellets were not as abundant. Results from this study suggest that fecal pellets, although already degraded upon formation, are more robust than phytoplankton aggregates and, therefore, more likely to resist disaggregation and further decomposition during transit through the water column.

Effect of composition and different fractions of hay dust suspension on inflammation in lungs of heaves-affected horses: MMP-9 and MMP-2 as indicators of tissue destruction

Airway matrix metalloproteinases (MMPs) increase following inhalation of organic dust. The relative contribution of dust components to this elevation is unknown. To identify components of organic dust responsible for elevated MMP levels in equine airways. Bronchoalveolar lavage (BALF) from 7 heaves-susceptible horses, collected 6 h following inhalation challenges with saline, 2 different hay dust suspensions (HDS-1 and -2) and soluble and particulate fractions of HDS-1, were analysed for MMP-2 and -9 using SDS-page gelatin zymography. HDS-1 challenge increased BALF proMMP-9 and total MMP-9. HDS-1 fractions, or the particulate fraction with added lipopolysaccharide, increased BALF proMMP-9 and total MMP-9 in combination, but not when inhaled separately. HDS-2 inhalation elevated BALF complex forms, proMMP-9, active MMP-9, total MMP-9 and total MMP-2. The results suggest synergistic action of soluble and particulate organic dust components. The fact that HDS-1 and HDS-2 had different glucan concentrations supports a role for moulds in the activation of MMP-9. Activation and release of MMPs in response to inhaled moulds are involved in the aetiopathogenesis of heaves. Endotoxin contributes to the synergistic action of the dust components, but the overall MMP response to organic dust inhalation in heaves-susceptible horses largely reflects the mould content of the dust. In the future, inhibition of MMP production and release may offer therapeutic means for treatment and prevention of heaves and recommendations for acceptable dust levels can be given.

Influence of clays on the rheology of cement pastes

The fresh state of concrete is becoming increasingly important in furthering the types of applications of today's construction world. Processing techniques have resulted in technologies such as self-consolidating concrete and depend on the microstructural changes that take place during and immediately after mixing and placing. These changes to the microstructure reflect the flocculation behavior between the particles in suspension. The ability to modify this behavior allows control over the balance among flowability and shape-stability of concrete. This study investigates how clay admixtures affect the microstructure of cement pastes from a rheological stand point. Shear and compressive rheology techniques are used to measure how the solids volume fraction of suspensions with different admixtures evolves with stress. Based on these relationships, the effectiveness of clays on the balance between flowability and shape-stability is measured. Results are consistent with green strength tests performed on concrete mixes derived from the cement paste mixes.

Liquid-to-solid transition of concentrated suspensions under complex transient shear histories

Suspensions containing noncolloidal aluminum particles in a Newtonian carrier liquid and the effects of shear history on the rheological properties of suspensions are investigated showing a critical concentration phi(c), which is close to the "freezing" packing fraction of spherical particle suspensions. An apparent liquid-to-solid transition was clearly found for suspensions below phi(c) via transient step shear after long shear history as well as via the large amplitude oscillatory shear flow with controlled shear stress. The microstructures or the local flow characteristics of suspensions with phi<phi(c) and with phi>phi(c) are still different according to the Fourier Transform Rheological analysis. Although suspensions with phi<phi(c) show solidlike behaviors after long shear history, the flow behaviors keep unchanged as shear stress increases, and typically show solidlike, liquid-solid coexistence, liquidlike, and jamming behaviors, successively. However, liquidlike regime of concentrated suspensions with phi>phi(c) disappears after preshear.

Fractionation of non-Brownian rod-like particle suspensions in a viscoplastic fluid

In this work we explore a fractionation technique for non-Brownian rod-like particle suspensions based upon the control of the threshold for motion in a yield stress fluid. The principle is demonstrated by observing the motion of particles under the influence of a centrifugal force in a weak gel. Here we develop calibration curves of the force required to initiate motion in a gel under numerous configurations of the particles. Demonstration separations of bidisperse suspensions are reported. Here we achieve complete separation of dilute suspensions based upon length, diameter, or density. The method is then applied to an industrially important suspension, that is a polydispersed papermaking fibre suspension, in which a length-based fractionation is reported.

Sorption of Estrogens onto Different Fractions of Sediment and Its Effect on Vitellogenin Expression in Male Japanese Medaka

This study investigated the sorption capacity of estrogenic compounds-such as estrone (E1), 17beta-estradiol (E2), and 17alpha-ethynylestradiol (EE2)-of different sediment particle fractions. Two-sized fractions of sediment were used in the experiments, with a particle size <1 microm (mostly from 450 to 800 nm) and >1 microm up to 50 microm. Sorption kinetics were followed using a two-step reaction in which the major amount of chemicals was sorbed rapidly within minutes and then gradually increased until equilibrium was reached after 48 h. The sorption capacity of the fine particle fraction (particle size <1 microm) was shown to be significantly higher than that of the large fraction (1 microm < particle size < 50 microm). The sorption kinetics and isotherm were adequately predicted by using a pseudo second-order model and the Freundlich equation, respectively. Total organic carbon (TOC) content and surface area of particle fractions were also measured. Although the effects of TOC on the sorption of estrogens could not be verified, a higher surface area of fine particle fractions may significantly increase sorption capacity to target compounds. Sorption of estrogens onto sediment particles could be used to explain the differences of estrogenic activity of E2 spiked into different size fractions of particle suspensions.

Growth kinetics of 2- and 3-D cell models as influenced by the microenvironment

The noncontact cocultivation system was developed for the study of the paracrine interactions between MCF-7 (breast carcinoma cells) and MT-4 (a line of human T-cell leukemia). Viability and proliferation rates were determined in the adhesion and suspension fractions of MCF-7 cells sampled from two model systems: monolayer culture and multicellular tumor spheroids (MTS). Cocultivation with MT-4 reduced the number of MCF-7 cells in the adhesion fraction and had no effect upon the suspension fraction, despite an increase in the total population of MCF-7 cells. The two model systems displayed a substantial difference in cell viability, alone and in the presence of MT-4 cells — the fraction of viable cells in the monolayers was greater than in the spheroids. It is suggested that cocultivation with MT-4 stimulates proliferation of MCF-7 cells via a paracrine mechanism, reduces adhesion to the substrate, and leads to MTS formation.