Concentration Of Particles In Solution Research Articles

Effectiveness of ZnO Nano Particles against the Foodborne Microbial Pathogens E. coli and S. aureus

In this work, various concentrations of ZnO nano particles, prepared by the coprecipitation method with a size range of 47-68 nm, have been investigated as antimicrobial agents. Dilution antimicrobial susceptibility tests were carried out on two kinds of microbes (Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli) according to the standard method recommended by Clinical and Laboratory Standards Institute, CLSI-2015-M07-A10. The results showed that the antimicrobial effect is larger, the higher the concentration of ZnO nano particles in solution. It was also found that Gram-positive microbes are more sensitive to ZnO nano particles when compared with the Gram-negative ones. The minimum inhibitory concentration (MIC) for E. coli was found to be 50 mg/mL while that for S. aureus was 25 mg/mL. The minimum bactericidal concentration (MBC) was 1600 mg/mL for E. coli and 800 mg/mL for S. aureus.

Combining and comparing multiple serial dilution assays of particles in solution: application to brucellosis in elk of the Greater Yellowstone Ecosystem

The concentration detection threshold (CDT) is the concentration of particles in solution beyond which a (serial dilution) assay detects particle presence. By our account, CDTs typically are not estimated but are fixed at some value. Setting a CDT to zero (\(d=0\)) implies perfect detection, a common assumption, and setting \(d>0\) gives results that are “denominated” in units of \(d\), i.e., are relative to the choice of \(d\). Using multiple, different serial dilution assays, each with its own CDT, we choose a “reference assay,” to which we assign a fixed CDT value, to obtain relative estimates of the remaining assays’ CDTs and the underlying particle concentration. We present the CDTs as a novel way to account for or to compare different serial dilution assays, “sensitivities”. We apply our methodology to data from four assays of the presence of bacterial (B. abortus) antibodies in the serum of elk in the Greater Yellowstone Ecosystem, where transmission of brucellosis—the disease ensuing from infection—to commercial livestock is managed by the Wyoming Game and Fish Department to avoid the primary symptom of abnormal fetal abortion. Results agree qualitatively with the more traditional notion of sensitivity as the true positive rate.

Size-Dependent Nanoparticle Margination and Adhesion Propensity in a Microchannel

Intravenous injection of nanoparticles as drug delivery vehicles is a common practice in clinical trials of therapeutic agents to target specific cancerous or pathogenic sites. The vascular flow dynamics of nanocarriers (NCs) in human microcapillaries play an important role in the ultimate efficacy of this drug delivery method. This article reports an experimental study of the effect of nanoparticle size on their margination and adhesion propensity in microfluidic channels of a half-elliptical cross section. Spherical polystyrene particles ranging in diameter from 60 to 970 nm were flown in the microchannels and individual particles adhered to either the top or bottom wall of the channel were imaged using fluorescence microscopy. When the number concentration of particles in the flow was kept constant, the percentage of nanoparticles adhered to the top wall increased with decreasing diameter (d), with the number of particles adhered to the top wall following a d−3 trend. When the volume concentration of particles in solution was kept constant, no discernible trend was found. This experimental finding is explained by the competition between the Brownian force promoting margination and repulsive particle–particle electrostatic forces retarding adhesion to the wall. The 970 nm particles were found to adhere to the bottom wall much more than to the top wall for each of the three physiologically relevant shear rates tested, revealing the effect of gravitational force on the large particles. These findings on the flow behavior of spherical nanoparticles in artificial microcapillaries provide further insight for the rational design of NCs for targeted cancer therapeutics.

Interaction of Cocos nucifera cream casein with humic acid suspensions

Two caseins labelled as CaSMG (casein without fats) and CaMG (casein with fats) were extracted from coconut cream. Both caseins were used as coagulants for the aggregation of humic acid (HA) particles in synthetic water at pH = 6 during the jar-test essays. The optimum dosage of CaMG or CaSMG and the residual turbidities of treated water obtained depend on the type of used casein (CaMG or CaSMG) and the concentration of particles in solution. The optimal doses of CaMG and CaSMG are respectively 280 and 180 mg/L for solution S(1) (HA aqueous solution at 15 mg/L), and then 340 and 240 mg/L for solution S(2) (HA aqueous solution at 25 mg/L). The residual turbidities of treated water are respectively 6.88 and 3.85 NTU for solution S(1) and 4.52 and 2.53 NTU for solution S(2). The collected sediment volumes are respectively 1.2 and 1.5 mL for solutions S(1) and S(2). The electrophoretic mobility measurement and transmission electron microscopy images of flocs formed during the flocculation essays suggest that both caseins operate through both mechanisms (charge neutralisation and bridging process mechanism), this last one seems to be predominant. The aggregates formed are the large clusters and result from adsorption of HA particles by the casein molecules.

SiC Particles Concentration Dependent the Properties of Electroless Ni-P-SiC Coatings

In this study, Ni-P-SiC composite coatings were prepared by adding different amount of SiC particles into electroless Ni-P plating solution. The effects of SiC particles concentration in solution on depositing rate and composition of the coatings were investigated. The different SiC contents in coatings could be obtained by adjusting the amount of SiC particle concentration in electroless plating solution. Scanning electron microscopy (SEM) results indicate that SiC particles are dispersed in the composite coating and Ni-P alloy is mainly as a bond metal envelope with SiC particles. At the same time, the microhardness became increased and the wear resistance improved with the increasing of SiC content.

SiC Particles Concentration Dependent the Properties of Electroless Ni-P-SiC Coatings

In this study, Ni-P-SiC composite coatings were prepared by adding different amount of SiC particles into electroless Ni-P plating solution. The effects of SiC particles concentration in solution on depositing rate and composition of the coatings were investigated. The different SiC contents in coatings could be obtained by adjusting the amount of SiC particle concentration in electroless plating solution. Scanning electron microscopy (SEM) results indicate that SiC particles are dispersed in the composite coating and Ni-P alloy is mainly as a bond metal envelope with SiC particles. At the same time, the microhardness became increased and the wear resistance improved with the increasing of SiC content.

Effect of Colloidal Particle Size on Adsorbed Monodisperse and Bidisperse Monolayers

Coating hydrogel films or microspheres by an adsorbed colloidal shell is one synthesis method for forming colloidosomes. The colloidal shell allows control of the release rate of encapsulated materials, as well as selective transport. Previous studies found that the packing density of self-assembled, adsorbed colloidal monolayers is independent of the colloidal particle size. In this paper we develop an equilibrium model that correlates the packing density of charged colloidal particles in an adsorbed shell to the particle dimensions in monodisperse and bidisperse systems. In systems where the molar concentration in solution is fixed, the increase in adsorption energy with increasing particle size leads to a monotonic increase in the monolayer packing density with particle radius. However, in systems where the mass fraction of the particles in the adsorbing solutions is fixed, increasing particle size also reduces the molar concentration of particles in solution, thereby reducing the probability of adsorption. The result is a nonmonotonic dependence of the packing density in the adsorbed layer on the particle radius. In bidisperse monolayers composed of two particle sizes, the packing density in the layer increases significantly with size asymmetry. These results may be utilized to design the properties of colloidal shells and coatings to achieve specific properties such as transport rate and selectivity.

KINETIC STUDY OF WC PARTICLES INCORPORATION IN NICKEL COMPOSITE PLATING

The particles, suspended in the electrolyte, can be co-deposited with metal. The co-deposition behaviors of WC and Co-coated WC particles on nickel matrix were investigated. Many operating parameters that influence on the quantity of incorporated particles, including current density, bath agitation and electrolyte composition were investigated. The co-deposition of particles during electroplating depends on the rate of metal deposition and on the flux of particles to the film surface. The growth rate of the metal film is determined by the current density, whereas the flux of particles to the electrode surface is dependent on the particle size, particle concentration in solution, the electrode rotation rate, the particle diffusion coefficient, and the electrode geometry. The kinetic parameters in the co-deposition were calculated from the experimental results. Co-coated WC particles were easily incorporated in the matrix than WC particles from the calculated and experimental results.

Covalent Nanoparticle Assembly onto Random Copolymer Films

We present a novel class of nanoparticle-decorated surfaces: amine-functionalized silica nanoparticles covalently attached to poly(styrene-random-acrylic acid) films and carboxylic acid-terminated self-assembled monolayers (SAMs). The dependence of the particle attachment kinetics on the concentration of particles in solution and acrylic acid moieties in the polymer backbone was investigated and was compared to the observed kinetics with SAM substrates. The kinetics on the polymer films included three distinct stages, which were governed by the acrylic acid concentration-dependent morphological changes of the films under the reaction conditions. The first stage was an induction period with little change in the particle coverage with time, followed by a rapid rise in the coverage, and finally a plateau. The maximum coverage achieved for the polymer films, 70%, was nearly twice that of the SAM substrates, which followed diffusion-limited coverage kinetics prior to reaching saturation. This enhanced coverage is attributed to the swelling of the acrylic acid groups at the film surface in the reaction solvent, which increases the surface area and roughness of the substrate. This approach is a reproducible way of preparing nanoparticle-decorated, chemically robust surfaces with controlled coverages and have potential applications for controlling surface wettability, optical properties, and cellular adhesion.

Temperature effect on the stability of bentonite colloids in water

The stability of natural bentonite suspensions has been investigated as a function of temperature at pH 9 and ionic strength 10 −3 M. The sedimentation rate of the particles is directly related to their stability. The sedimentation kinetics was determined by examining the variation of particle concentration in solution with time. The observed kinetics for sedimentation is discussed quantitatively in terms of the potential energy between particles. The ζ-potential of the particles was measured and the DLVO theory was used to calculate attractive and repulsive potentials. Experimental observations are consistent with DLVO model predictions and show that the stability of bentonite colloids increases with temperature. Differences with other colloidal systems can be attributed to the temperature dependence of the surface charge of bentonite particles.

Single and Multiple‐Step Dip‐Coating of Colloidal Maghemite (γ‐Fe2O3) Nanoparticles onto Si, Si3N4, and SiO2 Substrates

AbstractThe adsorption behavior of colloidal maghemite (γ‐Fe2O3) nanoparticles, passivated by oleic acid and dispersed in octane solution, onto three different substrates (Si, Si3N4, and SiO2) is investigated. The average nanoparticle size is 10 nm, with a size variation (σ) less than 5 %. The adsorption of particles is strongly dependent on both the type of substrate and the particle concentration in solution. By a single‐dipping process, we have obtained a maximum coverage of 0.45 on a Si substrate, but much less on other substrates (0.19 on Si3N4 and 0.14 on SiO2). The particle coverage was drastically increased by the multiple‐adsorption process, where the process of dipping and drying was repeated multiple times. With this process, we can obtain a maximum particle coverage of about 0.76 on a Si substrate and 0.61 on a thermally grown SiO2 substrate.

Statistical properties of surfaces covered by deposited particles

The statistical properties of surfaces covered by irreversibly adsorbed colloidal particles are studied as a function of the Péclet number (or equivalently as a function of their rescaled radius R*). More precisely, the radial distribution function g(r) is determined as a function of the coverage θ for five systems corresponding to different values of R*. Also measured is the reduced variance σ2/〈n〉 of the number n of adsorbed particles on surfaces of given area out of the adsorption plane. Finally, the evolution of 〈n〉 with the concentration of particles in solution during the deposition process is determined for the different systems. This allows us to obtain information on the available surface function Φ. All these parameters are compared to their expected behavior according to the random sequential adsorption (RSA) model and to the ballistic model (BM). It is found that the radial distribution function of the system of particles characterized by R*<1 is well predicted by the RSA model whereas for R*≳3 the BM can serve as a good first approximation. On the other hand, one finds surprisingly that the available surface function Φ and the reduced variance σ2/〈n〉 vary with the coverage θ in a similar way for all the systems over the range of value of R* investigated. Their behavior corresponds, in first approximation, to the expectations from the BM. In particular, the reduced variance σ2/〈n〉 exhibits a horizontal tangent at low coverage whereas the RSA model predicts an initial slope of −4. This result is the more intriguing that σ2/〈n〉 is directly related to the radial distribution function g(r), which does vary with R*. Finally, higher order moments of the distribution of the number of particles n adsorbed on our surfaces are also determined as a function of the coverage. They behave, within experimental errors, like those of a Gaussian distribution as predicted by the central limit theorem.

Amino acids as CH acids

1. The formation of protonated and free Schiff's bases from S-alanine and salicylaldehyde was studied quantitatively by the PMR method in the interval of pD 9.0–12.0. 2. The rate constants of the racemization of S-alanine and its Schiffs base with salicylaldehyde protonated at the nitrogen were determined, and they were compared with the analogous constants for N-salicyl-idene-S-alaninate complexes of Cr(III), Rh(III), and Co(III) and the Schiffs base from pyridoxal and S-alanine. 3. The basic role of the metal in the model reactions consists of increasing the concentration of reactive particles in solution as a result of coordination of the Schiffs base with the metal ion.