Use Of Small Particles Research Articles

Efficient and high-quality absorption enhancement using epsilon-near-zero cylindrical nano-shells constructed by graphene

This paper presents a detailed scattering analysis of a hollow-core plasmonic-shell cylindrical wire to design an efficient, compact, narrowband, and reconfigurable optical absorber. The shell is formed by a thin graphene material, investigated in its epsilon-near-zero (ENZ) plasmonic region. Compared to the graphene plasmonic resonances in the terahertz(THz)/far-infrared (FIR) frequencies, the ENZ plasmonic resonances offer a blue shift in the operating frequency of the second-order plasmonic resonances by increasing the geometrical dimensions. This feature is successfully used to design efficient optical wave absorbers with absorption cross-sections much larger than geometrical and scattering cross-sections. The observed blue shift in the resonance spectrum, which is the key point of the design, is further verified by defining each particle with its polarizability and fulfilling the resonant scattering condition in the framework of Mie’s theory. Furthermore, graphene relaxation time and chemical potential can be used to manipulate the absorption rate. Observed resonances have narrow widths, achieved with simple geometry. To consider more practical scenarios, the one-dimensional arrangement of the cylindrical elements as a dense and sparse array is also considered and the design key point regarding graphene quality is revealed. The quality factor of the sparse array resonance is 2272.8 and it demands high-quality graphene material in design. It is also observed that due to the use of small particles in the design, the near-field and cooperative effects are not visible in the absorption cross-section of the array and a clear single peak is attained. This polarization-insensitive absorber can tolerate a wide range of incident angles with an absorption rate above 90%.

Elasticity and Viscoelasticity Imaging Based on Small Particles Exposed to External Forces

Particle-mediated elasticity/viscoelasticity imaging has the potential to expand the elasticity imaging field, as it can provide accurate and local tissue elastic properties as well as density and viscosity. Here, we investigated elasticity imaging based on small particles located within the tissue and at the tissue interface exposed to static/dynamic external loads. First, we discuss elasticity/viscoelasticity imaging methods based on the use of particles (bubbles and rigid spheres) placed within the tissue. Elasticity/viscoelasticity imaging techniques based on the use of particles (bubbles, rigid, and soft spheres) located at the tissue interface are then presented. Based on new advances, we updated some of the models for the responses of the particles placed within the tissue and at the tissue interface available in the literature. Finally, we compared the mathematical models for the particles located within the tissue and at the tissue interface and evaluated the elasticity/viscoelasticity imaging methods based on the use of small particles. This review summarized the methods for measuring the elasticity and viscosity of material using particles exposed to external forces. Remote viscoelasticity imaging can be used to improve material characterization in both medical and industrial applications and will have a direct impact on our understanding of tissue properties or material defects.

Effect of nano-carbon decorated Ti particle on powder feeding behavior of directed energy deposition

The use of small particles to decorate alloy surfaces to prepare powder materials for directed energy deposition (DED) of composites has received significant attention; however, minimal research has been conducted on how this decorative effect influences powder delivery behavior, despite the powder delivery behavior being an important factor in dictating the quality of the composites’ deposition. This work outlines the result of an investigation into the effect of the decorative effect of nanoparticles (nano-carbon) on the feeding behavior of metal powder (pure titanium). The experimental and simulation results show that nano-carbon decreases the collision recovery coefficient of the powder by 31.6%, which weakens the collision behavior between the powder and the nozzle wall, enhancing the convergence of the composite powder and increasing the velocity of the composite powder by 7.8% (experimental value). This study can serve as a foundation for improving the process development of DED-formed composites.

Improvement of the Water Absorbency of Softener-treated Fabric: Addition of a New Hydrophilic Surface.

Softening agents, when applied in appropriate amounts, can impart softness to fabrics, particularly cotton towels, such that improved comfort and feel can be achieved when using the fabrics. On the other hand, water absorbency, which is commonly regarded as the mark of high-quality cotton products, significantly decreases when any of the currently existing softeners is used. To date, when a softener is used on cotton fabrics, there is a trade-off between excellent softness and high-water absorbency. In our research, we introduced a new sensory evaluation indicator called the "water wiping-off feeling ratio" which looks primitive but shows high correlation with our actual feel over any other existing indicators. Furthermore, we developed a new method and model to overcome the above-mentioned trade-off, involving the use of small particles with a hydrophilic surface together with the softener. Inspired by the theory of fractal geometry and the combination of models/equations by Cassie, Baxter, and Wenzel, the idea of adding new convex hydrophilic domains onto the surface of cotton fibers along with the softening agent was conceived. Finally, we successfully improved the wiping-off feel without decreasing the softness, i.e., we developed a strategy to overcome the above-mentioned trade-off in softener-treated fabrics that has proven challenging thus far.

Role of particle size on the multicycle calcium looping activity of limestone for thermochemical energy storage

The calcium looping process, based on the reversible reaction between CaCO3 and CaO, is recently attracting a great deal of interest as a promising thermochemical energy storage system to be integrated in Concentrated Solar Power plants (CaL-CSP). The main drawbacks of the system are the incomplete conversion of CaO and its sintering-induced deactivation. In this work, the influence of particle size in these deactivation mechanisms has been assessed by performing experimental multicycle tests using standard limestone particles of well-defined and narrow particle size distributions. The results indicate that CaO multicycle conversion benefits from the use of small particles mainly when the calcination is carried out in helium at low temperature. Yet, the enhancement is only significant for particles below 15 μm. On the other hand, the strong sintering induced by calcining in CO2 at high temperatures makes particle size much less relevant for the multicycle performance. Finally, SEM imaging reveals that the mechanism responsible for the loss of activity is mainly pore-plugging when calcination is performed in helium, whereas extensive loss of surface area due to sintering is responsible for the deactivation when calcination is carried out in CO2 at high temperature.

Material Removal Mechanism of Additively Manufactured Components Finished using Magnetic Abrasive Finishing

This paper describes the effects of tool deformability, by changing the size of magnetic particles mixed with abrasive, and abrasive type (magnetic abrasive or conventional abrasive) on the material removal mechanism and resulting surface profiles of 316L stainless steel components made by selective laser melting (SLM). The use of large particles (rigid tool) facilitated the removal of material from the peaks of the target surface geometry of the SLM-produced workpiece. The use of small particles (flexible tool) facilitated the removal of material from the target surface along the surface features. The magnetic abrasive gradually removed material from the peaks of the surface features according to the magnetic abrasive contact against the target surface. In contrast, conventional abrasive freely contacted the target surface and removed material from surface according to the magnetic particle contact against the target surface. Magnetic abrasive finishing produces a surface dominated by valleys. In particular, the surface made by the magnetic abrasive showed higher skewness and lower kurtosis than the one made by the conventional abrasive.

Creation and validation of a simulator for corneal rust ring removal

ObjectiveTo create and validate a simulation model for corneal rust ring removal. MethodsRust rings were created on cadaveric eyes with the use of small particles of metal. The eyes were mounted on suction plates at slit lamps and the trainees practiced rust ring removal. An inexperienced cohort of medical students and first year ophthalmology residents (n=11), and an experienced cohort of senior residents and faculty (n=11) removed the rust rings from the eyes with the use of a burr. Rust ring removal was evaluated based on removal time, percentage of rust removed and incidence of corneal perforation. A survey was administered to participants to determine face validity. ResultsTime for rust ring removal was longer in the inexperienced group at 187±93 seconds (range of 66-408 seconds), compared to the experienced group at 117±54 seconds (range of 55-240 seconds) (p=0.046). Removal speed was similar between groups, at 4847±4355 pixels/minute and 7206±5181 pixels/minute in the inexperienced and experienced groups, respectively (p=0.26). Removal percentage values were similar between groups, at 61±15% and 69±18% (p=0.38). There were no corneal perforations. 100% (22/22) of survey respondents believed the simulator would be a valuable practice tool, and 89% (17/19) felt the simulation was a valid representation of the clinical correlate. ConclusionThe corneal rust ring simulator presented here is a valid training tool that could be used by early trainees to gain greater comfort level before attempting rust ring removal on a live patient.

Breaking the black-body limit with resonant surfaces

The speed with which electromagnetic energy can be wirelessly transferred from a source to the user is a crucial indicator for the performance of a large number of electronic and photonic devices. We expect that energy transfer can be enhanced using special materials. In this paper, we determine the constituent parameters of a medium which can support theoretically infinite energy concentration close to its boundary; such a material combines properties of Perfectly Matched Layers (PML) and Double-Negative (DNG) media. It realizes conjugate matching with free space for every possible mode including, most importantly, all evanescent modes; we call this medium Conjugate Matched Layer (CML). Sources located outside such layer deliver power to the conjugate-matched body exceptionally effectively, impressively overcoming the black-body absorption limit which takes into account only propagating waves. We also expand this near-field concept related to the infinitely fast absorption of energy along the air-medium interface to enhance the far-field radiation. This becomes possible with the use of small particles randomly placed along the boundary; the induced currents due to the extremely high-amplitude resonating fields can play the role of emission “vessels”, by sending part of the theoretically unlimited near-field energy far away from the CML structure.

Biodegradable microsphere-mediated cell perforation in microfluidic channel using femtosecond laser.

The use of small particles has expanded the capability of ultrashort pulsed laser optoinjection technology toward simultaneous treatment of multiple cells. The microfluidic platform is one of the attractive systems that has obtained synergy with laser-based technology for cell manipulation, including optoinjection. We have demonstrated the delivery of molecules into suspended-flowing cells in a microfluidic channel by using biodegradable polymer microspheres and a near-infrared femtosecond laser pulse. The use of polylactic-co-glycolic acid microspheres realized not only a higher optoinjection ratio compared to that with polylactic acid microspheres but also avoids optical damage to the microfluidic chip, which is attributable to its higher optical intensity enhancement at the localized spot under a microsphere. Interestingly, optoinjection ratios to nucleus showed a difference for adhered cells and suspended cells. The use of biodegradable polymer microspheres provides high throughput optoinjection; i.e., multiple cells can be treated in a short time, which is promising for various applications in cell analysis, drug delivery, and ex vivo gene transfection to bone marrow cells and stem cells without concerns about residual microspheres.

Biosensors in clinical chemistry: An overview

Biosensors are small devices that employ biological/biochemical reactions for detecting target analytes. Basically, the device consists of a biocatalyst and a transducer. The biocatalyst may be a cell, tissue, enzyme or even an oligonucleotide. The transducers are mainly amperometric, potentiometric or optical. The classification of biosensors is based on (a) the nature of the recognition event or (b) the intimacy between the biocatalyst and the transducer. Bioaffinity and biocatalytic devices are examples for the former and the first, whereas second and third generation instruments are examples for the latter. Cell-based biosensors utilizing immobilized cells, tissues as also enzyme immunosensors and DNA biosensors find variegated uses in diagnostics. Enzyme nanoparticle-based biosensors make use of small particles in the nanometer scale and are currently making a mark in laboratory medicine. Nanotechnology can help in optimizing the diagnostic biochips, which would facilitate sensitive, rapid, accurate and precise bedside monitoring. Biosensors render themselves as capable diagnostic tools as they meet most of the above-mentioned criteria.

J043024 低圧コールドスプレー法を用いた色素増感太陽電池用T102皮膜の開発([J043-02]厚膜形成技術と厚膜の機械特性評価(2))

In order to make a dye-sensitized solar (DSC) cell, a Low-pressure Cold Spray (LCS) technique is used to make Ti02 film in this study. In our previous study, it was successful that dense and more than 15μm thick TiO_2 film can be obtained by the LCS. However, in the case of the DSC, the dense film is not good for power generation. It is better to obtain films with pores, high cohesive force, and suitable thickness. Therefore, the aim of this study is to make the porous and thick film, which was controlled by mixture TiO_2 powder with large and small diameters. It was made that several mixture TiO_2 powders with different proportion of large and small powders, and then a film was coated by the LCS. Moreover, the influence on the deposition efficiency and the film thickness in repetition film coating were evaluated. As a result, it is successful to make porous TiO_2 films controlled by proportion of large and small powder contents. And, it was made clear that use of small particles indicated high deposition efficiency. On the other hand, use of large particles indicated low deposition efficiency. Finally, the battery properties of the film made by the LCS was evaluated. As a result, conversion efficiencies of the film made by the LCS were less than 1% in any mixture ratio, because of inhomogeneous porosity. However, the LCS becomes an effective tool for making films for the DSC.

Comparison of ultra-high performance supercritical fluid chromatography and ultra-high performance liquid chromatography for the analysis of pharmaceutical compounds

Currently, columns packed with sub-2μm particles are widely employed in liquid chromatography but are scarcely used in supercritical fluid chromatography. The goal of the present study was to compare the performance, possibilities and limitations of both ultra-high performance liquid chromatography (UHPLC) and ultra-high performance supercritical fluid chromatography (UHPSFC) using columns packed with sub-2μm particles. For this purpose, a kinetic evaluation was first performed, and van Deemter curves and pressure plots were constructed and compared for columns packed with hybrid silica stationary phases composed of 1.7 and 3.5μm particles. As expected, the kinetic performance of the UHPSFC method was significantly better than that of the UHPLC. Indeed, the hmin values were in the same range with both strategies and were between 2.2 and 2.8, but uopt was increased by a factor of >4 in UHPSFC conditions. Another obvious advantage of UHPSFC over UHPLC is related to the generated backpressure, which is significantly lower in the presence of a supercritical or subcritical fluid. However, the upper pressure limit of the UHPSFC system was only ∼400bar vs. ∼1000bar in the UHPLC system, which prevents the use of highly organic mobile phases at high flow rates in UHPSFC. Second, the impact of reducing the particle size (from 3.5 to 1.7μm) was evaluated in both UHPLC and UHPSFC conditions. The effect of frictional heating on the selectivity was demonstrated in UHPLC and that of fluid density or decompression cooling was highlighted in UHPSFC. However, in both cases, a change in selectivity was observed for only a limited number of compounds. Third, various types of column chemistries packed with 1.7μm particles were evaluated in both UHPLC and UHPSFC conditions using a model mixture of acidic, neutral and basic compounds. It has been shown that more drastic changes in selectivity were obtained using UHPSFC columns compared to those obtained by changing UHPLC columns. In addition, there was a good complementarity between the two separation modes. Finally, by combining the use of small particles with supercritical fluids as a mobile phase, it was possible to achieve the analysis of pharmaceutical compounds in less than 1min or to attain a peak capacity of more than 250 in approximately 40min, both with a high degree of repeatability.

Mercury removal by thiol‐functionalized metal oxide–carbon black sorbent and mixed‐matrix membranes

Aqueous mercury sorption is achieved using a novel thiol‐functionalized metal oxide‐coated carbon sorbent. The material is hydrolytically and thermally stable (up to 250°C) because of the formation of covalent siloxane bonds on functionalization and increased hydrophobicity. The particles were synthesized with a variety of morphologies; the base particles are ∼80 nm and a nonuniform metal oxide (including silica) coating less than 5 nm thick. This sorbent material has a high equilibrium capacity for mercury (∼60 mg/g) at concentrations up to ∼150 mg/L. The Langmuir constant for equilibrium sorption (ka/kd) is K = 16.9 L/mol. Packed column experiments using real water reduced mercury levels to below detectable limits. Mixed‐matrix membranes (sorbent particles and polysulfone) were synthesized to combine the ease of surface functionalization on particles with advantages of polymer membranes. Membranes with up to 50 wt % particles were synthesized, with sorption capacities at 200 mg/g sorbent or greater due to dispersion of particles in the matrix and the use of small particles, which are impractical in packed column operations. A regeneration scheme is proposed using multifunctional particles (thiol and sulfonate moieties). Initial experiments showed that mild regeneration conditions (dilute HCl at pH 4) partially regenerated the sorbent particles. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 705–714, 2013

Microfibrous entrapped catalysts for low temperature CO oxidation in humid air

CO oxidation on Pt-CeO 2 /SiO 2 catalyst was found to be diffusion controlled at ambient conditions ( T < 50 °C; RH: 10–90%), so the use of small particles was imperative to optimize Pt utilization. Packed beds (PBs) of small particles cause channeled flow, axial dispersion due to cluster formation and they are susceptible to vibrations and changes in orientation. Nickel microfibers (4–8 μm) entrapped catalysts (MFECs) were developed to avoid these problems with PBs. These MFECs improved heat transfer within the reactor and minimized flow maldistribution thereby improving the activity. MFECs outperformed the PBs over a wide range of CO concentrations exhibiting greater stability and performance (CO conv. > 99% for > 10 hrs). ► Impact of internal diffusion limitation on Pt-CeO2/SiO2 catalyst activity was studied. ► Entrapment of catalysts in Ni fibers resulted in greater activity for CO Oxidation at ambient conditions. ► Impact of heat and mass transport properties on catalyst performance was investigated. ► Stability of Ni microfibers entrapped catalysts was studied.

Model of Toner Impaction and Developer Failure

High definition digital imaging is enabled in printers by using small micron and nano toner particles. Use of small particles in a housing presents challenges in particle flow as small particles tend to aggregate, clog and impact either on the wall of the housing or on other surfaces. Solids are known to undergo brittle-ductile transition depending on the size of a particle, elastic plastic behavior and strain rates under which they are deformed.In macromolecules, polymer chain flexibility and shear flow of uniformly sized, spherical particles can be analyzed. Inter-particle attractive forces are considered to influence flow of small particles. Simulations performed for different strengths of cohesion, shear rates, particle stiffnesses, particle volume fractions and coefficients of friction show interesting results. From each simulation, the average normal and shear stresses and the average coordination number have been extracted. Generally small particles are externally mixed with nano-sized particles to improve flow. Hard nano-sized particles reduce cohesiveness of toner particles and reduce its aggregation.Particulate flow can some time result in jamming and has been analyzed using Lattice-Boltzmann (LB) or DEM (Discrete Element Methods) involving deformation from collisions resulting from hydrodynamic forces. Consequence of particle impaction on surfaces is a reduction in particle charge with wider distribution causing shortfalls in electro-photographic development and image quality. A rate equation model is developed for impaction in a cylindrical cavity that depends on the impact parameter, rate of volumetric flow, yield stress (modulus) of the elastic-plastic particle, size of the particle and dynamic coefficient of friction. The model predictions are compared with experimental data on the particle (toner) impaction

Integrated risk assessment of a hydroxyapatite–protein-composite for use in oral care products: A weight-of-evidence case study

Risk assessment of cosmetic ingredients represents a regulatory standard requirement in Europe and other regions. An integrated approach was designed to assess the safety of HPC, a particulate composite of hydroxyapatite and protein (gelatin) for use in oral care products, employing a weight-of-evidence assessment and considering specific physico-chemical properties and exposure conditions. An initial evaluation of the constituents suggested that their chemical nature does not represent a particular health hazard per se. Hydroxyapatite is the main component of teeth and bones in mammals; gelatin is used in food and assumed to be safe once a BSE/TSE risk has been excluded. In vitro screening tests were chosen to further evaluate the biocompatibility: Hen’s egg test-chorioallantoic membrane (HET-CAM) to assess irritating effects towards mucous membranes; MTT cytotoxicity test with 3T3 fibroblasts; human corneal epithelial models to investigate inflammatory mediators and cytotoxicity; macrophage assays to measure cytotoxicity, inflammatory mediators and oxidative stress. Together with results from clinical studies, exposure estimates and analyses of kinetic properties, the presented information provides sound evidence to support the safe use of HPC. This is an example of a risk assessment for cosmetic use of small particles without the need for additional animal studies.

Silicon/organic semiconductor heterojunctions for solar cells

AbstractUsing current–voltage measurements, photocurrent spectroscopy, and light‐induced electron spin resonance (LESR), we have investigated hybrid solar cells consisting of composites of silicon nanocrystals (Si‐ncs) and poly‐3(hexylthiophene) (P3HT). For a more detailed understanding of the inorganic/organic interface, we have also studied the properties of crystalline silicon (c‐Si)/P3HT heterostructures. Current–voltage characteristics of Si‐ncs/P3HT blends show an open‐circuit voltage of up to 0.76 V. Photocurrent spectroscopy measurements give a strong indication that both, the Si‐ncs and P3HT, contribute to the photo‐induced current. Further, we directly demonstrate a light‐induced charge transfer between the Si‐ncs and P3HT via LESR. Current–voltage measurements of c‐Si/P3HT heterojunctions were performed under illumination with high power light emitting diodes (LEDs) of different wavelengths, which allow a selective excitation of charge carriers in P3HT, silicon, or both materials. We have observed a disadvantageous energy band alignment of the valence band of silicon and the highest occupied molecular orbital (HOMO) level of P3HT which favors the use of small particles with a larger band gap due to quantum confinement.

Complications of Particle Embolization of Meningiomas: Frequency, Risk Factors, and Outcome: Fig 1.

Particle embolization is widely used in the treatment of meningiomas. We assessed the frequency and outcome of complications of embolization of meningiomas and tried to identify risk factors. Between 1994 and 2009, a total of 198 patients with 201 meningiomas underwent embolization. Indication for embolization was preoperative in 165 meningiomas and adjunctive to radiosurgery in 8. In the remaining 28 meningiomas, embolization was initially offered as a sole therapy. There were 128 women and 70 men with a mean age of 54.4 years (median age, 54 years; range, 15-90 years). Complications were defined as any neurologic deficit or death that occurred during or after embolization. Logistic regression was used to identify the following possible risk factors: age above median, female sex, tumor size above median, meningioma location in 5 categories, use of small particle size (45-150 microm), the presence of major peritumoral edema, and arterial supply in 3 categories. Complications occurred in 11 patients (5.6%; 95% confidence interval [CI], 3.0%-9.8%). Ten complications were hemorrhagic, and 1 was ischemic. Six of 10 patients with hemorrhagic complications underwent emergency surgery with removal of the hematoma and meningioma. Complications of embolization resulted in death in 2 and dependency in 5 patients (7/198, 3.5%; 95% CI, 1.6%-2.0%). The use of small particles (45-150 mum) was the only risk factor for complications (odds ratio [OR], 10.21; CI, 1.3-80.7; P = .028). In this series, particle embolization of meningiomas had a complication rate of 5.6%. We believe that the use of small polyvinyl alcohol (PVA) particles (45-150 microm) should be discouraged.

Particle size influence in an impaction bone grafting model. Comparison of fresh-frozen and freeze-dried allografts

BackgroundImpaction bone grafting with large particles is considered as mechanically superior to smaller morsels. Interest of freeze-dried irradiated bone for impaction bone grafting has been observed with small particles. Influence of bone process on other particle sizes still needed to be assessed. Material and methodsTwenty-four osteoarthrotic femoral heads were used to prepare fresh-frozen and freeze-dried irradiated cancellous bone. Each group was divided into four batches of different particle sizes, each batch containing 18 samples. The different particle sizes were obtained with a Retsch Cross Beater Mill SK 100, Noviomagus rotating bone mills with two sizes of rasps and a Luer bone rongeur. Bone grafts were impacted in a contained cylinder. Stiffness was monitored during impaction. ResultsFreeze-dried irradiated grafts showed higher stiffness than fresh-frozen bone whatever the size of the particles. Large particles obtained with the rongeur and the large rasp from the Noviomagus bone mill were mechanically superior than small particles up to 30 impactions. InterpretationLarge particles offer better mechanical performance as a greater magnitude of force would be required to deform and break the particles. Freeze-dried irradiated bone brittleness reduces this advantage after 30 impactions. Large particles embrittlement leads to similar mechanical results as small particles at higher impaction rate. This may account for partial collapse of the graft layer in clinical situation when impaction rate is lower. This model supports the use of small particles obtained with thin rasp bone mill when freeze-dried irradiated bone for impaction bone grafting and large particles obtained with the Rongeur when fresh-frozen bone is available.

Study on nonspecificity of an immuoassay using Eu-doped polystyrene nanoparticle labels

Nanoparticle labels have been shown to improve the sensitivity of a sandwich immunoassay significantly. Further improvement in sensitivity is limited by nonspecific binding of the nanoparticle labels. Here, an experimental characterization of assay performance was carried out using clinically important analytes thyroid stimulating hormone and prostate-specific antigen. Particular attention was paid to characterization of nonspecific binding properties of nanoparticle labels. Therefore, different particle sizes and high affinity monoclonal antibodies (Mab) and their Fab and scFv recombinant antibody fragments were investigated. Combination of Fab fragment as a capture antibody and Mab as a detector antibody on a nanoparticle label resulted in high signal-to-background ratio consistently. Against the expectations no significant difference in nonspecific binding was found using fragmented antibodies compared to Mabs. The results also suggested that nonspecific binding was independent of the particle size. The particle size had a significant effect on the specific signal favouring the use of small particles giving a high specific signal. This study indicated that nonspecific binding is not readily affected by the physical size of the nanoparticle label or antibodies used in the assay.