Constant Particle Research Articles

FOAM STABILIZATION AND INTERACTIVE PROPERTIES OF KONO-BOUE CLAY NANOPARTICLES IN OIL RECOVERY

Different materials have been employed in chemical enhanced oil recovery (CEOR) to recover more residual oil from reservoir rock formations. Surfactants have been used though better recovery margin is expected when in conjunction with nanoparticles (NPs) (Silica and more recently clay). This combination reduces surfactant loss to the reservoir formation and enhances foam stability. The interactive properties and foam stability of locally available Kono Boue (KB) clay NPs were studied to establish its suitability for applications in CEOR. The KB clay NPs were synthesized using Sodium Dodecyl Sulphate (SDS) mediated (sol-gel) route and characterized with X-ray Diffraction (XRD), Energy Dispersive X-ray Fluorescence (EDXRF), Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FT-IR) spectroscopy, Wettability alteration, Interfacial Tension (IFT) and Foam stability. The XRD and EDXRF confirmed the clay as Kaolinite (Al > 16 %; Si > 30 %). Surface morphologies showed platy polycrystallites of different sizes on the SEM while characteristic vibrations of Si-O stretching (780 and 1056 cm-1) and Al-OH bending (698 cm-1) vibrations were obtained from the FT-IR. Control of particle sizes (85, 63, 66, 60, 66 and 90 nm) was achieved using different concentrations (0, 2.08, 6.25, 8.33, 10.42 and 14.58 mM) respectively of SDS at constant clay particles (10 g). The samples were calcined at 900 °C for 2 h. IFT reduction between the oil and the aqueous media at constant SDS concentration increased with decrease in particle sizes from 85 to 60 nm. Similarly, wettability alteration also showed changes from nearly neutral-wet towards more water-wet condition with particle size variation. The foam stability experiment confirmed that the clay NPs with the least particle size of 60 nm gave the most stable foam.

Modified Stability of microRNA-Loaded Nanoparticles.

microRNAs represent promising drugs to treat and prevent several diseases, such as diabetes mellitus. microRNA delivery brings many obstacles to overcome, and one strategy to bypass them is the manufacturing of self-assembled microRNA protein nanoparticles. In this work, a microRNA was combined with the cell-penetrating peptide protamine, forming so-called proticles. Previous studies demonstrated a lack of microRNA dissociation from proticles. Therefore, the goal of this study was to show the success of functionalizing binary proticles with citric acid in order to reduce the binding strength between the microRNA and protamine and further enable sufficient dissociation. Thus, we outline the importance of the present protons provided by the acid in influencing colloidal stability, achieving a constant particle size, and monodispersing the particle size distribution. The use of citric acid also provoked an increase in drug loading. Against all expectations, the AFM investigations demonstrated that our nanoparticles were loose complexes mainly consisting of water, and the addition of citric acid led to a change in shape. Moreover, a successful reduction in binding affinity and nanoparticulate stability are highlighted. Low cellular toxicity and a constant cellular uptake are demonstrated, and as uptake routes, active and passive pathways are discussed.

Flame structure and burning velocity of flames propagating in binary iron aerosols

A numerical study was performed for binary dispersed iron aerosols in air using different particle sizes with constant average particle size. The effects of particle size and density of the two aerosols on flame structure and speed are systematically investigated. Varying the amount of small and big particles results in separated and overlapped flame fronts. For higher values of particle size ratio (ratio between the size of big and small particles) and density of small particles, flame fronts are observed to overlap. The flame speed of the binary mixture is compared with the mono-dispersed case and the difference is analyzed for different particle size ratios. The addition of a small fraction of small particles in the binary mixture is found to result in a substantial increase in the flame speed if the particle size ratio is large. Detailed analyses on the variation of the total amount of fuel shows the particle size ratio determines the equivalence ratio at which the maximum flame speed occurs. The maximum flame speed as a function of equivalence ratio was observed to move from the lean to the rich side for particle size ratio sufficiently large enough.

Scrap computer keyboards a sustainable resource for silver (Ag) and low density oil (L D Oil)

Most neglected part of the scrap computers are the keyboards, which are generally incinerated by the informal recycling sectors creating environmental pollution and leads to the wastage of precious metallic contents present in it. Present paper is focused on a novel chemical processing technique developed to recover silver (Ag) as value added product and low density oil (L D Oil) from the computer keyboards. Initially, scrap keyboards were manually dismantled to separate Mylar sheets and the same were pyrolysed at 300 °C for 2 h to recover L D Oil. The obtained pyrolysed Mylar sheets was further crushed, milled and homogenized to reduce particle size (−100 mesh). The crushed sample was leached using 2 M HNO3 at 60 °C in mixing time of 20 min and pulp density of 100 g/L to achieve maximum dissolution of Ag. The leaching kinetics for Ag dissolution well fitted with chemical reaction control dense constant size cylindrical particles, 1-(1-X)1/2 = kct. The obtained leach liquor was put to cementation process using metallic copper (Cu). Almost 99% of Ag gets cemented as Ag powder in 15 min at a constant solution temperature of 60 °C and pH 1.1. The developed bench scale process has application orientation to the industry after piloting the process.

A novel magnetorheological braking system with variable magnetic particle volume fractioncontrolled by utilizing shape memory alloy

To address the shortcomings of decreasing shear yield stress of magnetorheological fluid due to temperature increase, magnetic saturation phenomenon under the action of a strong magnetic field, and decreasing performance of magnetorheological brake due to magnetic particle settling, a braking system of variable particle volume fraction of magnetorheological fluid modulated by shape memory alloy spring is proposed, which solves the shortcomings of constant particle volume fraction magnetorheological brakes. The brake temperature rises and automatically increases the volume fraction of magnetorheological fluid, leading to increase in the braking torque and ensuring stable braking performance at high temperatures. The magnetorheological fluid particle settling stability is enhanced, and energy consumption at idle is reduced. Based on the shape memory effect of shape memory alloy, the relationship between the output displacement of shape memory alloy spring and temperature, squeezing pressure and volume fraction of magnetic particles is established. Based on the microscopic body-centered tetragonal structure of magnetorheological fluid, the relationship between the volume fraction of magnetic particles and the magnetic permeability of magnetorheological fluid was established. Based on the rheological characteristics of magnetorheological fluid, the relationship between the braking torque of magnetorheological fluid and the magnetic permeability and the volume fraction of magnetic particles is established; and the finite element method was applied to simulate and analyze it. The results show that the magnetic permeability increases with the increase of the volume fraction of magnetic particles and the braking torque increase with the increase of the volume fraction of magnetic particles during the evolution of the magnetorheological fluid microstructure from single chain to body-centered tetragonal structure. When the volume fraction of magnetic particles in the magnetorheological fluid increased from 15% to 45%, the magnetorheological brake torque increased to 10.1N·m, and the braking performance of the magnetorheological brake improved by 14.3%. The experimental and theoretical analyses provide a theoretical basis for the design and manufacture of magnetorheological fluid brakes with variable particle volume fractions.

Phenylboronic acid conjugated mPEG-b-PCL micelles as DOX carriers for enhanced drug encapsulation and controlled drug release

Polymeric micelles represent an important delivery platform for hydrophobic drugs, but limited by unsatisfactory drug loading, micellar stability and controlled release. Herein, poly(ɛ-caprolactone) block copolymers with three different pendant groups (tert-butyl formate, carboxylate, and phenylboronic acid formate) were prepared by organocatalytic ring-opening polymerization and post modification. All three block polymers with different pendant groups can form micelles by self-assembly with uniform size of approximately 100 nm and narrow distribution. In particular, the DOX-loaded micelles with phenylboronic acid (PBA) conjugation exhibit high encapsulation efficiency (greater than95 %) and colloidal stability of constant basic particle size over a week. Besides, compared to the other two groups of drug-loaded micelles, the PBA-modified drug-loaded micelles can selectively release drugs by triggering with H2O2. After treatment with 100 μM H2O2, the cumulative drug release from micelles increased by 2.5 times in PBS solution at pH 7.4. More importantly, drug-loaded micelles of PBA modifying can be selectively released according to the high level of reactive oxygen species in cancer cells, which could improve anti-cancer efficacy and reduce toxic side effects. The micelle covalently modified by PBA was demonstrated as a promising drug carrier for DOX delivery.

Scaling up studies for mixing of granular materials in rotating drums

This study investigates the mixing of granular materials for rotating drums of different volumes which vary from 6.28 L to 402.12 L. Two groups of case studies are considered: Group I (constant particle diameter, d) and Group II (constant ratio of drum diameter to particle diameter, D/d). The results show that for Group I, the mixing performance deteriorates with drum size increasing. A correlation as a function of scale-up ratio and Froude number is proposed for mixing rate prediction. For Group II, at a constant Froude number, particle flow patterns and mixing performance are similar. The results also demonstrate that the scaled particle travel distances and displacements are affected by the ratio of D/d. For Group I, the scaled particle travel distances and displacements become more restricted as drums become larger, causing a delay in mixing. For Group II, similar particle travel distances and displacements are observed, hence the similar mixing performance.

Quantitative Analysis of Core Lipid Production in Methanothermobacter marburgensis at Different Scales.

Archaeal lipids have a high biotechnological potential, caused by their high resistance to oxidative stress, extreme pH values and temperatures, as well as their ability to withstand phospholipases. Further, methanogens, a specific group of archaea, are already well-established in the field of biotechnology because of their ability to use carbon dioxide and molecular hydrogen or organic substrates. In this study, we show the potential of the model organism Methanothermobacter marburgensis to act both as a carbon dioxide based biological methane producer and as a potential supplier of archaeal lipids. Different cultivation settings were tested to gain an insight into the optimal conditions to produce specific core lipids. The study shows that up-scaling at a constant particle number (n/n = const.) seems to be a promising approach. Further optimizations regarding the length and number of the incubation periods and the ratio of the interaction area to the total liquid volume are necessary for scaling these settings for industrial purposes.

Experimental Study on Factors Influencing Throughput Rate and Process of Polymer-Mineral Filler Mixing in a Twin Screw Extruder

Abstract The experimental study of mixing polymer (polypropylene, PP) with mineral filler (Talc) by both simultaneous and separate feed system in a twin screw extruder was described. In this study, melt flow rate (MFR) of PP, talc particle size and talc mixing ratio to PP were selected as parameters of interest. It was found that these parameters had influences on the maximum throughput rate of mixture. In the cases of constant talc particle size and mixing ratio while MFR of PP was varied from 1.8 to 33, it was observed that throughput rates of all mixtures with different MFR values increased as a function of screw speeds. Throughput rates of the mixture of lower MFR PP (MFR = 1.8) were slightly lower than those of the higher MFR mixture (MFR = 10, 33) for both simultaneous and separate feed systems. With regard to effects of talc particle size, compounds having fixed talc mixing ratio showed lower throughput rates when talc particle size was smaller. In the case where talc mixing ratio was varied, compounds with fixed MFR of PP and talc particle size showed lower throughput rates when talc mixing ratio was larger. The mixing state in the mixing zone was also observed. Based on the overall findings, the mechanisms of filler mixing were clearly understood. The observed mixing patterns were similar for both simultaneous and separate feed systems. It was found that the elimination of the air accompanying the filler when the filled polymer mixture passed down the extruder is important for mixing. Through the experimental observations, the schematic diagram, the model and the flow chart of the proper filler mixing process were proposed.

Evaluation of Isomotive Insulator-Based Dielectrophoretic Device by Measuring the Particle Velocity.

Many dielectrophoretic (DEP) devices for biomedical application have been suggested, such as the separation, concentration, and detection of biological cells or molecules. Most of these devices utilize the difference in their DEP properties. However, single-cell analysis is required to evaluate individual properties. Therefore, this paper proposed a modified isomotive insulator-based DEP (iDEP) creek-gap device for straightforward single-cell analysis, which is capable of measurement at a wide frequency band. The proposed iDEP device generates more constant particle velocity than the previous study. The insulator was fabricated using backside exposure for accurate forming. We measured the distribution of the particle velocity and frequency property, using homogeneous polystyrene particles to verify the effectiveness of the proposed device. The results show that the particle velocity distribution was consistent with the distribution of the numerically calculated electric field square (). Furthermore, the velocity measurement, at a wide frequency band, from 10 Hz to 20 MHz, was performed because of the long distance between electrodes. These results suggest that the prop-erties of various particles or cells can be obtained by simple measurement using the proposed device.

Study on pressure distribution of pump chamber and axial force in particle-laden flow of centrifugal pump

To explore the pressure distribution characteristics of pump chambers, and the law governing the axial force in a particle-laden flow centrifugal pump, a semi-open impeller centrifugal pump was selected as the research object. The particle model and heterogeneous model were used to develop the numerical calculations of the particle-laden flow field within the centrifugal pump. For the liquid phase we adopted the shear–stress–transport (SST) turbulence model, while for the solid phase we adopted the discrete phase zero equation model. The external characteristics, pressure distribution and axial forces were compared and analyzed (1) for a constant solid particle diameter, d, of 0.1 mm and particle volume fractions, Cv, of 0, 1, 5, and 10%, and (2) for a constant particle volume fraction, Cv, of 10% and solid particle diameters, d, of 0, 0.01, 0.1, and 0.5 mm. The correlations between the particle volume fractions and solid particle diameters with the pump chamber pressure distributions and axial forces were obtained. The results show that when Cv increased from 1–10%, or d from 0.01–0.5 mm, the pump head and efficiency decreased continuously under the same flow rate. At the same time, larger particle volume fractions resulted in larger pressures at the same radius, while for larger solid particle diameters, smaller pressures were obtained at the same radius. Under the same flow rate, when Cv increased from 1–10%, the total axial force of the centrifugal pump increased, but it was smaller than what was achieved under the clean-water condition. When d increased from 0.01 to 0.5 mm, the total axial force of the centrifugal pump decreased. This study provides a reference for the calculation and balance of the total axial force in a particle-laden flow centrifugal pump.

Modeling Snow Saltation: The Effect of Grain Size and Interparticle Cohesion

AbstractThe surface of the Earth is snow‐covered at least seasonally over large areas. This snow surface is highly dynamic, particularly under the influence of strong winds. The motion of snow particles driven by the wind not only changes the snow cover but has important consequences for the atmosphere in that it adds mass and moisture and extracts heat. Large scale meteorological and climatological models neglect these surface dynamics or produce conflicting results from too simplified process representation. With recent progress in the detailed understanding of the saltation process, in particular with respect to sand saltation, and the advancement of numerical models, we can systematically investigate the influence of snow properties on saltation. This contribution uses a Large Eddy Simulation model with full surface particle dynamics to investigate how snow cohesion and size distribution influence saltation dynamics and in particular the total mass flux. The model reproduces some known characteristics of the saltation system such as a focus point or a constant near surface particle speed. An interesting result is that cohesion and grain size heterogeneity can increase the overall saltation mass flux at high friction velocities. Moreover, some simplified models agree reasonably well with the simulations for given bed characteristics, while others clearly do not. These results are valid for continuous saltation while intermittent saltation, which often occurs in nature, needs further investigation. In order to successfully parameterize saltation in large scale models, progress must be made in correctly representing snow surface properties in these models, in particular cohesion.

Influence of Particle Size and Shapes on the Antifungal Activities of Greener Nanostructured Copper against Penicillium italicum

Pathogenic microorganisms cause diseases that play a limiting role in food production. The growth of blue mold rot on citrus fruits caused by Penicillium italicum poses postharvest economic loss due to food decay. The control of P. italicum using toxic synthetic fungicide raises serious concerns about food safety and quality. There is a need to develop safe fungi management techniques to prevent economic loss in the agro-industry. Copper nanoparticles (CuNPs) are typically prepared at elevated temperatures (200 °C) using toxic surfactants such as cetyltrimethylammonium bromide (CTAB) and harsh organic solvents. We hereby report, for the first time, a novel greener and eco-friendly one-pot aqueous method for synthesizing copper nanospheres (CuNS) and well-defined copper nanocubes (CuNCs) with controlled shape and size using copper(II) sulfate (CuSO4) precursor and water-soluble quercetin diphosphate (QDP) as a bio-reducing and capping agent at room temperature. The CuNPs were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, and X-ray diffraction (XRD). CuNCs with average edge lengths of 150–250 and 80–180 nm were designed using QDP and CuSO4 in the ratio of 3:1, respectively. The metrics of sustainability obtained include atom economy (73.56%), molar efficiency (0.9019), and environmental factor (3.429). The antifungal activity of CuNCs and CuNSs was tested against P. italicum using the Kirby–Bauer method. This study demonstrated the comparative effect of CuNCs and CuNSs on the growth of P. italicum spores in a dose-dependent manner. The results indicated that CuNCs and CuNSs showed antifungal activity against the growth of P. italicum, with the minimum inhibitory concentration (MIC) of 100 and 200 μg/mL, respectively. At a constant particle size, it was evident that CuNCs showed significant inhibitory activity of P. italicum at a low-dose treatment (100 μg/mL) in comparison to CuNS. The particle size and shape effect of CuNCs played a vital role in its antifungal activity. QDP-mediated synthesis of CuNC and CuNS could serve as a potent biocide for the natural remediation of citrus-based fungal diseases.

Repulsive torques alone trigger crystallization of constant speed active particles

We investigate the possibility for self-propelled particles to crystallize without reducing their intrinsic speed. We illuminate how, in the absence of any force, the competition between self-propulsion and repulsive torques determines the macroscopic phases of constant-speed active particles. This minimal model expands upon existing approaches for an improved understanding of crystallization of active matter.

MICROSPHERES: A NOVEL DRUG DELIVERYSYSTEM

Microspheres are freeflowing powders that are made up of proteins or synthetic polymers. They are little spherical particles with diameters ranging from a few millimetres to a few millimetres (typically from 1 to 100 micrometer). Microspheres are microparticles that are employed in applications that require a predictable and constant particle surface area.To achieve the desired impact, the drug should be delivered in an ideal amount at the right time to the target tissue with the least degree of adverse effects and maximal therapeutic efficacy. The microspheres drew a lot of attention because of their long-lasting release and ability to target anticancermedications to the tumor.Microspheres will play a key role in innovative medication delivery in the future, particularly in sick cell sorting, diagnostics, gene & genetic materials, and safe, targeted and precise delivery.

STATISTICAL MODEL FOR GROUNDNUT OIL EXTRACTION FOR FOOD SUSTAINABILITY

Groundnut oil was extracted using solvent extraction method, the process of extraction was investigated to check the effect of moisture content, extraction temperature and extraction time on the percentage oil yield obtained from groundnut seeds. The experiment carried out was designed with the aid of central composite design of response surface methodology while maintaining a constant particle size of 0.6mm throughout the experiment. The optimum percentage oil yield of 50.85% was obtained at moisture content, extraction temperature and extraction time of 6% (wet basis), 600C and extraction time of 8hr respectively. While, the least value of 32.37% was obtained at moisture content, extraction temperature and extraction time of 18% (wet basis), 400C and 4hr respectively. The data obtained were used to investigate the effect of moisture content, extraction temperature and extraction time on percentage oil yield. A quadratic model was developed to predict the percentage oil yield at a given combination of the process factors. All the factors under investigated has a significant effect on the percentage oil yield obtained from groundnut seeds. The validation results of the developed model showed that there is good agreement between the experiment and predicted values.

Effect of hydrophilic silica nanoparticles on hydrate formation during methane gas migration in a simulated wellbore

Natural gas hydrates are mostly formed in low-permeability and fractured muddy sedimentary formations. Adding suitable nanoparticles to the drilling fluid system can improve its filtrate resistance and fracture plugging, and effectively weaken the invasion of drilling fluid into the reservoir. However, it is likely that nanoparticles promote hydrate formation and accumulation in wellbores which will induce accidents. Therefore, this study investigated the effect of hydrophilic silica nanoparticles with particle sizes of 30 nm, 60 nm, and 80 nm and concentrations of 0.5–4.0 wt% on hydrate formation during upward migration of methane gas using a dynamic simulation system for hydrate formation in a wellbore. The experimental results show that under the condition of methane gas migration, hydrophilic silica nanoparticles inhibit hydrate formation. The inhibition effect increased with the growth in the particle size under a constant concentration, whereas it first increased and then decreased with increasing nanoparticle concentration under a constant particle size. The strongest inhibition effect was observed at a hydrophilic silica nanoparticle concentration of 2.0 wt%. The influence of hydrophilic silica nanoparticles on hydrate formation may be mainly determined by their hydrophilic properties, heat and mass transfer, and gas migration in the wellbore. Our research indicates that hydrophilic silica nanoparticles can be added to hydrate drilling fluid systems if their concentration can be properly controlled.

Experimental study on the parameter optimization and application of a packed-bed dielectric barrier discharge reactor in diesel particulate filter regeneration

To compensate for the shortcomings of the thermal and catalytic regeneration of the diesel particulate filter (DPF), a self-designed packed-bed dielectric barrier discharge (DBD) reactor for DPF regeneration was developed. The DBD reactor with the main active substance of nonthermal plasma (NTP) as the target parameter was optimized by adjusting the feed gas, packing particles (material or size), and cooling water temperature. Moreover, a set of optimal working parameters (gas source, O2; packing particles, 1.2–1.4 mm ZrO2; and cooling water temperature, 20 °C) was selected to evaluate the effect of different O3 concentrations on DPF regeneration. The research results showed that selecting packing particles with high dielectric constant and large particles, as well as reducing the cooling water temperature, with oxygen as the feed gas, contributed to an increase in O3 concentration. During DPF regeneration, the following changes were observed: the power of the NTP reactor decreased to lower than 100 W, the O3 concentration increased from 15 g m−3 to 45 g m−3, the CO and CO2 volume fractions of the particulate matter decomposition products increased, and the peak regeneration temperature increased to 173.4 °C. The peak temperature arrival time was 60 min earlier, indicating that the regeneration rate of DPF increased with the increase in O3 concentration. However, the O3 utilization rate (the amount of carbon deposit removed per unit volume O3) initially increased and then decreased; when the O3 concentration was set to 25 g m−3, the highest O3 utilization rate was reached. The packed-bed DBD technology contributed to the increase in the concentration of NTP active substances and the regeneration efficiency of DPF. It provides a theoretical and experimental basis for high-efficiency regeneration of DPF at low temperatures (<200 °C).

Signatures of extended radio emission from escaping electrons in the Lighthouse Nebula

Several supersonic runaway pulsar wind nebulae (sPWNe) with jet-like extended structures have been recently discovered in X-rays. If these structures are the product of electrons escaping the system and diffusing into the surrounding interstellar medium, they can produce a radio halo extending for several arcmins around the source. We model the expected radio emission in this scenario in the Lighthouse Nebula sPWN. We assume a constant particle injection rate during the source lifetime, and isotropic diffusion into the surrounding medium. Our predictions strongly depend on the low- and high-energy cutoffs given in the particle distribution. Our results indicate that extended radio emission can be detected from the Lighthouse Nebula without the need to invoke extreme values for the model parameters. We provide synthetic synchrotron maps that can be used to constrain these results with observations by current highly sensitive radio instruments.

Multifluid modeling of coal pyrolysis in a coupled downer-hopper reactor

In the coal pyrolysis process, the diameter of particles normally changes with the process of reaction, which not only affects the hydrodynamic behavior but also influences the heat generation and yield of the products. However, most of the previous simulation work assumes a constant diameter in the model, which may disobey the law of mass conservation at the particle scale. In this work, a multifluid framework is developed to simulate the coal pyrolysis in a coupled downer-hopper reactor. The advanced kinetic theory for particulate phase stress and particle-particle drag force, the cluster behavior modified gas-particle drag force and gas-particle heat transfer have been considered in the present study. Based on the default constant particle diameter model, the expression of coal particle size and density changing with the reaction process is derived according to the mass conservation of a single particle. Results show that the flow and reaction characteristics, including the particle density and velocity distribution, temperature behavior, pyrolysis rate and yield are significantly affected by the variable particle diameter.