Artificial Particles Research Articles

Visualization and evaluation of flow during water filtration: Parameterization and sensitivity analysis

This paper deals with visualization and evaluation of flow during filtration of water seeded by artificial microscopic particles. Planar laser induced fluorescence (PLIF) is a wide spread method for visualization and non-invasive characterization of flow. However the method uses fluorescent dyes or fluorescent particles in special cases. In this article the flow is seeded by non-fluorescent monodisperse polystyrene particles with the diameter smaller than one micrometer. The monodisperse sub-micron particles are very suitable for testing of textile filtration materials. Nevertheless non-fluorescent particles are not useful for PLIF method. A water filtration setup with an optical access to the place, were a tested filter is mounted, was built and used for the experiments. Concentration of particles in front of and behind the tested filter in a laser light sheet measured is and the local filtration efficiency expressed is. The article describes further progress in the measurement. It was carried out sensitivity analysis, parameterization and performance of the method during several simulations and experiments.

Experimental Study of a Periodical Flapping Flag

A flag flapping in the wind is a classical fluid-structure interaction problem that concerns the interaction of elastic bodies with ambient fluid. The fluid-flag interaction can give rise to three self-sustained oscillation states under certain conditions, i.e., stretched-straight state, periodic state, and chaotic state. This paper reports an experimental study of a cantilevered polydimethylsiloxane (PDMS) flag flapping in a uniform flow at a periodic state. A heavy flag is well designed, with metal strips imbedded in the PDMS sheet. Immersing the elastic but self-sustaining flag into the water flow, we use the time-resolved particle image velocimetry (PIV) and visualization techniques to obtain the whole flow field around the midspan of the flapping flag. A unique PIV image processing method is used to measure the near-wall flow velocities around the flap-ping elastic flag at the periodic state. The image processing technique adopts a radon transform technology to determine the moving interface in the particle images. The interface velocity distribution is subsequently calculated. Artificial particles of uniform size with the interface velocity are added into the flag region. Therefore, the whole velocity field over a flapping period is accurately obtained, giving the basic data to analyze the flag flapping. It is found that there exists an inflection point in the envelope curve of the flag flapping. Based on the analyses of the flapping states and velocity fields, a unified flapping Strouhal number (St = 2Af/U) is proposed by choosing the amplitude of the inflection point as the characteristic length, which is similar to the Strouhal number of the flow around a circular cylinder over the same range of Reynolds number.

Direct contact between dust and HBCD-treated fabrics is an important pathway of source-to-dust transfer

Hexabromocyclododecanes (HBCDs) are a class of brominated flame retardant that have found extensive application in consumer products used widely in indoor environments. Although uncertainty remains about the human health impacts of HBCDs, ingestion of HBCD-contaminated indoor dust has been shown to be a particularly significant exposure pathway for young children. Despite this, understanding of the mechanisms via which HBCD transfer from products to indoor dust remains incomplete. In this study, an in-house test chamber was used to investigate transfer of HBCDs from a treated textile sample to indoor dust via direct textile:dust contact. Results were compared with previous data using the same test chamber to examine other pathways via which HBCDs transfer from products to dust, and highlighted HBCD transfer via direct source:dust contact as being particularly important. This novel finding was corroborated by complementary experiments that examined HBCD transfer via direct contact, from other treated textiles to three major components of indoor dust: artificial indoor dust, soil particles, and cotton linters.

Design of Surface‐Active Artificial Enzyme Particles to Stabilize Pickering Emulsions for High‐Performance Biphasic Biocatalysis

Surface-active artificial enzymes (SAEs) are designed and constructed by a general and novel strategy. These SAEs can simultaneously stabilize Pickering emulsions and catalyze biphasic biotransformation with superior enzymatic stability and good re-usability; for example, for the interfacial conversion of hydrophobic p-nitrophenyl butyrate into yellow water-soluble p-nitrophenolate catalyzed by esterase-mimic SAE.

Lipoprotein-Related and Apolipoprotein-Mediated Delivery Systems for Drug Targeting and Imaging.

The integration of lipoprotein-related or apolipoprotein-targeted nanoparticles as pharmaceutical carriers opens new therapeutic and diagnostic avenues in nanomedicine. The concept is to exploit the intrinsic characteristics of lipoprotein particles as being the natural transporter of apolar lipids and fat in human circulation. Discrete lipoprotein assemblies and lipoprotein-based biomimetics offer a versatile nanoparticle platform that can be manipulated and tuned for specific medical applications. This article reviews the possibilities for constructing drug loaded, reconstituted or artificial lipoprotein particles. The advantages and limitations of lipoprotein-based delivery systems are critically evaluated and potential future challenges, especially concerning targeting specificity, concepts for lipoprotein rerouting and design of innovative lipoprotein mimetic particles using apolipoprotein sequences as targeting moieties are discussed. Finally, the review highlights potential medical applications for lipoprotein-based nanoparticle systems in the fields of cardiovascular research, cancer therapy, gene delivery and brain targeting focusing on representative examples from literature.

Tribochemical Component of Oxidative Stress Development at Artificial Joints Implantation. Part 5. Pro-oxidative Properties and Interrelation of Titanium and Non-Metallic Orthopaedic Material Wear Particles with Antioxidants

Radical-forming ability of artificial wear particles of BT6 titanium alloy and nonmetallic materials was studied using modelling reaction of cumene oxidation. It was stated that alloy particles initiate formation of radicals and consecutive repeated cumene oxidation by metallic particles took place with significantly higher rate of radicals’ formation. Particles of nonmetallic materials (polyethylene, corundum ceramics, carbon nanocomposite) are inert and do not possess radical-forming ability that ensures their advantage in prevention of possible development of adverse free radical reactions in surrounding implant tissues.

Tribochemical Component of Oxidative Stress Development at Artificial Joints Implantation. Part 5. Pro-oxidative Properties and Interrelation of Titanium and Non-Metallic Orthopaedic Material Wear Particles with Antioxidants

Radical-forming ability of artificial wear particles of BT6 titanium alloy and nonmetallic materials was studied using modelling reaction of cumene oxidation. It was stated that alloy particles initiate formation of radicals and consecutive repeated cumene oxidation by metallic particles took place with significantly higher rate of radicals’ formation. Particles of nonmetallic materials (polyethylene, corundum ceramics, carbon nanocomposite) are inert and do not possess radical-forming ability that ensures their advantage in prevention of possible development of adverse free radical reactions in surrounding implant tissues.

The deposition and imaging of silica sub-micron particles in dentine

ObjectivesSub-micron particles may assist in the delivery of compounds into dentine tubules. The surface interactions of the particles with dentine may prevent them from entering the tubules. The aim of this study is to investigate whether silica particles, treated with surfactants improves dentine tubules occlusion using both artificial and human tooth models MethodsSpherical silica particles (size 130–810nm) bearing an encapsulated ruthenium luminescent complex were coated with the following surfactants: Zonyl® FSA, Triton® X-100 and Tween20®. The particles were prepared as 0.004% w/v and 0.04% w/v solutions with deionized water and were applied to the surface of; (1) in vitro model of PET ThinCert™ cell culture inserts; (2) 0.1mm thick sections of human molar teeth. ResultsScanning electron and confocal fluorescence microscopy images show that particles without any coating and with TritonX-100 coating had the highest aggregation. Particles with Tween-20 are less aggregated on the surface and show inclusion in the tubules. Particles coated with fluorosurfactant Zonyl show a preference for aggregation at the tubule. With the ThinCert™ membranes high aggregation within the artificial tubules was increased by particle concentration. ConclusionsThe use of silica sub-micron particles on hard dental tissues is dependent on the modification of the surface chemistry of both the particle and the dentine and the employment of the fluorοsurfactant may improve tubule occlusion. The use of ThinCerts™ membrane is useful in vitro model to mimic dentinal tubules and observe the ability of particles to occlude small channels. Clinical significanceThe use of silica sub-micron particles on hard dentine tissues is dependent on the modification of the surface coating of the particles. This may influence how particles are incorporated in potential delivery vehicles applied to the dentine surface with the employment of a fluorosurfactant showing promise.

Hysteretic dynamics of active particles in a periodic orienting field.

Active motion of living organisms and artificial self-propelling particles has been an area of intense research at the interface of biology, chemistry and physics. Significant progress in understanding these phenomena has been related to the observation that dynamic self-organization in active systems has much in common with ordering in equilibrium condensed matter such as spontaneous magnetization in ferromagnets. The velocities of active particles may behave similar to magnetic dipoles and develop global alignment, although interactions between the individuals might be completely different. In this work, we show that the dynamics of active particles in external fields can also be described in a way that resembles equilibrium condensed matter. It follows simple general laws, which are independent of the microscopic details of the system. The dynamics is revealed through hysteresis of the mean velocity of active particles subjected to a periodic orienting field. The hysteresis is measured in computer simulations and experiments on unicellular organisms. We find that the ability of the particles to follow the field scales with the ratio of the field variation period to the particles' orientational relaxation time, which, in turn, is related to the particle self-propulsion power and the energy dissipation rate. The collective behaviour of the particles due to aligning interactions manifests itself at low frequencies via increased persistence of the swarm motion when compared with motion of an individual. By contrast, at high field frequencies, the active group fails to develop the alignment and tends to behave like a set of independent individuals even in the presence of interactions. We also report on asymptotic laws for the hysteretic dynamics of active particles, which resemble those in magnetic systems. The generality of the assumptions in the underlying model suggests that the observed laws might apply to a variety of dynamic phenomena from the motion of synthetic active particles to crowd or opinion dynamics.

A versatile nano display platform from bacterial spore coat proteins.

Dormant bacterial spores are encased in a thick protein shell, the ‘coat', which contains ∼70 different proteins. The coat protects the spore from environmental insults, and is among the most durable static structures in biology. Owing to extensive cross-linking among coat proteins, this structure has been recalcitrant to detailed biochemical analysis, so molecular details of how it assembles are largely unknown. Here, we reconstitute the basement layer of the coat atop spherical membranes supported by silica beads to create artificial spore-like particles. We report that these synthetic spore husk-encased lipid bilayers (SSHELs) assemble and polymerize into a static structure, mimicking in vivo basement layer assembly during sporulation in Bacillus subtilis. In addition, we demonstrate that SSHELs may be easily covalently modified with small molecules and proteins. We propose that SSHELs may be versatile display platforms for drugs and vaccines in clinical settings, or for enzymes that neutralize pollutants for environmental remediation.

Characterization of particulate matter in attic and settled dusts collected from two buildings in Budapest, Hungary

Abstract We have investigated two buildings covered with Zsolnay glazed architectural ceramics in Budapest (Hungary), one located in the densely built-up area of the city centre with a high traffic rate and one in a city quarter with moderate traffic and more open space. A black crust layer, containing a large amount of artificial particulate matter with different size and chemical composition, was observed on the ceramic material of both buildings, whereas weathered glaze was detected only on the ceramics of the building situated in the city centre. In this paper, our goal is to reveal the role of the particulate matter in the degradation of architectural ceramics. For this reason the attic dust and settled dust from the roofs of the studied buildings were collected. In the attic dust, besides the natural particles of geological origin, three types of artificial particles typically with spherical shape (spherules) were also distinguished: aluminosilicate (two subtypes), carbonaceous, and iron-rich fly-ash. The appearance of gypsum crystallites around the particulate matter in association with all spherule types suggests that the particulate matter greatly contributes to the degradation process.

Organic compounds in circumstellar and interstellar environments.

Recent research has discovered that complex organic matter is prevalent throughout the Universe. In the Solar System, it is found in meteorites, comets, interplanetary dust particles, and planetary satellites. Spectroscopic signatures of organics with aromatic/aliphatic structures are also found in stellar ejecta, diffuse interstellar medium, and external galaxies. From space infrared spectroscopic observations, we have found that complex organics can be synthesized in the late stages of stellar evolution. Shortly after the nuclear synthesis of the element carbon, organic gas-phase molecules are formed in the stellar winds, which later condense into solid organic particles. This organic synthesis occurs over very short time scales of about a thousand years. In order to determine the chemical structures of these stellar organics, comparisons are made with particles produced in the laboratory. Using the technique of chemical vapor deposition, artificial organic particles have been created by injecting energy into gas-phase hydrocarbon molecules. These comparisons led us to believe that the stellar organics are best described as amorphous carbonaceous nanoparticles with mixed aromatic and aliphatic components. The chemical structures of the stellar organics show strong similarity to the insoluble organic matter found in meteorites. Isotopic analysis of meteorites and interplanetary dust collected in the upper atmospheres have revealed the presence of pre-solar grains similar to those formed in old stars. This provides a direct link between star dust and the Solar System and raises the possibility that the early Solar System was chemically enriched by stellar ejecta with the potential of influencing the origin of life on Earth.

酸性 Fe（II） 水溶液の空気酸化による人工鉄さび粒子の構造および形態に対するアニオンの影響

In order to simulate the atmospheric corrosion of steel, artificial steel rust particles were synthesized by aerial oxidation of aqueous solutions containing FeCl2, FeSO4 and NaNO3, and the structure and morphology of the obtained particles were characterized by XRD and TEM. Needle-like SO42− containing Schwertmannite (Fe8O8(OH)6(SO4)) particles were mainly formed in FeCl2–FeSO4, FeSO4–NaNO3, FeCl2–FeSO4–NaNO3 systems, and the crystallization and particle growth of this material were not influenced by added Cl− and NO3−. The rod-shaped β-FeOOH particles were formed from in only FeCl3-NaNO3 system, though no marked change in crystallite and particle sizes of the β-FeOOH was recognized by adding NO3−. Accordingly, it can be suggested that the corrosive SOX gas and air-borne chloride strongly affect the rust formation in atmospheric corrosion of the steels.

人工鉄さび粒子を用いた鋼材の大気腐食機構の解明

In order to clarify the atmospheric corrosion process of steel in different exposure environments, various methods such as exposure test, salt spray test, accelerated corrosion test, combined wet-dry cyclic corrosion test have been used. Our group has proposed that the rust formation by atmospheric corrosion in thin film water and/or adsorbed water on the steels regards as the reaction of metal ions eluted from steel and anions generated by dissolution of corrosive gasses such as NaCl, SOx and NOx. Therefore, simulating study using the artificial iron rust particles is effective to understand the rust formation process on the steels. In this review, influence of cations and anions on the structure, composition and morphology of artificially synthesized iron rust particles was described centering on our researches.

챔버 내 발생 입자를 이용한 CPC 수농도 비교 평가

Abstract Two butanol-based Condensation Particle Counters(CPC 3022, CPC 3025), three water-based CPCs(CPC3781,CPC3785×2), a Gardner Counter, a Fast Mobility Particle Sizer (FMPS), and an Aerosol Electrometer (AE) weredeployed to measure the number concentrations from atomized aerosol under six different conditions. Comparisonsof particle number concentrations measured by the CPCs, FMPS, and AE were conducted to evaluate the perfor-mance of the each CPCs using laboratory generated artificial particles such as NaCl, succinic acid (C 4 H 6 O 4 ), andparticles generated by propane torch & heat gun in the chamber. Good correlation between the CPC3025 and FMPSwas observed for the total particle number concentrations in the size range 15 nm to 90 nm. In addition, this papersuggests that photometric mode in water-based CPC3785 could not be used as quantitative of number concentra-tions for CPC3785. Key words : CPC, FMPS, Aerosol Electrometer, Size distribution, Comparison *Corresponding author.Tel : +82-(0)61-450-2485, E-mail : minsbae@hotmail.com

Molecular dynamics and finite elements: an approach to couple different worlds

AbstractThe procedure proposed here couples a continuum with a particle region by introducing an overlapping bridging domain where both regions exchange information. Beyond existing methods, the particle region is computed by Molecular Dynamics (MD) at finite temperature, using a code that has been developed by our co‐workers of the Theoretical Physical Chemistry Group at TU Darmstadt. It is also used in the wide field of physical chemistry for various approaches. In contrast to MD procedures employing periodic boundary conditions (PBC), stochastic boundary conditions (SBC) allow for the definition of static anchor points. These additional artificial particles are coupled to the continuum part and serve as information transmitter. The continuum is treated classically by the Finite Element Method (FEM) which has been adapted based on the Arlequin and the bridging domain method. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Three-dimensional ordered particulate structures: Method to retrieve characteristics from photonic band gap data

A method to retrieve characteristics of ordered particulate structures, such as photonic crystals, is proposed. It is based on the solution of the inverse problem using data on the photonic band gap (PBG). The quasicrystalline approximation (QCA) of the theory of multiple scattering of waves and the transfer matrix method (TMM) are used. Retrieval of the refractive index of particles is demonstrated. Refractive indices of the artificial opal particles are estimated using the published experimental data.

Dynamic cluster in particle swarm optimization algorithm

Particle swarm optimization is an optimization method based on a simulated social behavior displayed by artificial particles in a swarm, inspired from bird flocks and fish schools. An underlying component that influences the exchange of information between particles in a swarm, is its topological structure. Therefore, this property has a great influence on the comportment of the optimization method. In this study, we propose DCluster: a dynamic topology, based on a combination of two well-known topologies viz. Four-cluster and Fitness. The proposed topology is analyzed, and compared to six other topologies used in the standard PSO algorithm using a set of benchmark test functions and several well-known constrained and unconstrained engineering design problems. Our comparisons demonstrate that DCluster outperforms the other tested topologies and leads to satisfactory performance while avoiding the problem of premature convergence.

Chemical Properties of the Individual Asian Dust Particles Clarified by Micro-PIXE Analytical System

The present study was undertaken to evaluate the chemical characteristics of Asian dust (hereafter called “AD”) particles with the aid of the most advanced micro-PIXE (Particle-induced X-ray emission) analytical technique. To this end, size-selected particles were sampled on a rural peninsula of Korea (Byunsan, 35.37N; 126.27E) during AD and non-AD periods in 2004. The coarse particle (>2 μm) number density during an AD event were 170 times higher than those of the non-AD counterpart. The average net-count of silica in individual particles collected on AD event was roughly 11 times higher than that of non-AD counterpart. The X-ray net-counts of trace elements (Zn, Co, Mn, and V) were also considerably high in AD relative to the non-AD day. Particle classification based on the inter ratio analysis of elemental net-count suggests that a large portion of the coarse particles collected during AD event underwent chemical transformation to a certain degree. The visual interpretation of micro-PIXE elemental maps and elemental localization data in and/or on individual AD particles clarified the internal mixture of AD particles with sea-salt and artificial metallic particles.

Up-Cycling Waste Glass to Minimal Water Adsorption/Absorption Lightweight Aggregate by Rapid Low Temperature Sintering: Optimization by Dual Process-Mixture Response Surface Methodology

Mixed color waste glass extracted from municipal solid waste is either not recycled, in which case it is an environmental and financial liability, or it is used in relatively low value applications such as normal weight aggregate. Here, we report on converting it into a novel glass-ceramic lightweight aggregate (LWA), potentially suitable for high added value applications in structural concrete (upcycling). The artificial LWA particles were formed by rapidly sintering (<10 min) waste glass powder with clay mixes using sodium silicate as binder and borate salt as flux. Composition and processing were optimized using response surface methodology (RSM) modeling, and specifically (i) a combined process-mixture dual RSM, and (ii) multiobjective optimization functions. The optimization considered raw materials and energy costs. Mineralogical and physical transformations occur during sintering and a cellular vesicular glass-ceramic composite microstructure is formed, with strong correlations existing between bloating/shrinkage during sintering, density and water adsorption/absorption. The diametrical expansion could be effectively modeled via the RSM and controlled to meet a wide range of specifications; here we optimized for LWA structural concrete. The optimally designed LWA is sintered in comparatively low temperatures (825-835 °C), thus potentially saving costs and lowering emissions; it had exceptionally low water adsorption/absorption (6.1-7.2% w/wd; optimization target: 1.5-7.5% w/wd); while remaining substantially lightweight (density: 1.24-1.28 g.cm(-3); target: 0.9-1.3 g.cm(-3)). This is a considerable advancement for designing effective environmentally friendly lightweight concrete constructions, and boosting resource efficiency of waste glass flows.