Increase In Number Of Particles Research Articles

Numerical investigation of coal particle stream ignition in oxy-atmosphere

The ignition of a stream of coal particles under oxy-fuel atmosphere is studied numerically in a laminar flow. Devolatilization of coal particles is modeled with the chemical percolation devolatilization (CPD) method coupled with a detailed chemistry model for homogeneous reactions. The particle and gas phase interactions are modeled with a fully coupled Euler-Lagrange code. A parametric study is performed to investigate the influence of particle number density, gas temperature, and velocity on ignition. We found that increasing particle number density delays the onset of ignition. Delayed ignition in denser streams is due to the lower gas temperature, which is caused by the higher energy required for particle heating. In addition, increasing particle number density leads to a more continuous and narrower flame front. Particle heating and ignition induce velocity variations in the gas phase through the coupling with particles. In the denser stream, velocity variations become significant and compromise the validity of a constant velocity assumption that is usually made in computing ignition delay time from the observed ignition location. It is also found that high particle slip velocities lead to a locally low volatile concentration and low temperature, and consequently increase ignition delay time.

Micro particles and microbial activity in Danish recirculating rainbow trout (Oncorhynchus mykiss) farms

Increasing intensities of water reuse in recirculating aquaculture systems (RAS) lead to a build-up of micro particles (< 20 μm) in the water. This build-up may have consequences for other water quality parameters and for the fish. This baseline study was carried out to determine the variation in micro particle levels (numbers, volume and surface area) and accompanying bacterial activity in commercially operated outdoor RAS, as well as the effects of different components in the recirculation loop on micro particle dynamics. Water samples were obtained during spring 2017 from 7 Danish Model Trout Farms (MTFs) producing rainbow trout (Oncorhynchus mykiss) in a total of 20 separate RAS units. Micro particle numbers and size distribution, bacterial activity, and inorganic and organic nutrient concentrations were analysed. Micro particle numbers ranged between 6.0·104 – 7.4·105 ml−1 and large variations were found between seemingly similarly operated RAS units within the same farm. There was a strong, positive correlation (p < 0.001) between micro particle levels and bacterial activity in the systems. Although not significant, biofilters generally seemed to trap particles whereas drum filters seemed to reduce particle volume while increasing particle numbers and surface area. The study sustains that bacterial activity in RAS is strongly associated with fine particle loading, and demonstrates for the first time the overall magnitude and level of variation in particle levels and bacterial activity that exists in commercially operated MTFs.

Freeze/thaw of IGG solutions

In this communication, the effect of mannitol and trehalose crystallization on the unfolding of IgG1, a monoclonal antibody, in the frozen state with repeat freeze/thaw under different pH conditions was explored. Formulations were annealed at −20 °C for 20 h five times (interrupted by freeze/thaw). This was done to induce excipient crystallization. Characterization of the frozen-thawed samples was performed by circular dichroism, particle analysis, and size exclusion chromatography. At a pH of 3, formation of insoluble and soluble aggregates was observed however, these could be reduced by the use of a surfactant. Cryoprotectant free formulations showed higher monomer content after freeze/thaw. At pH5, a single freeze/thaw cycle did not result in a significant increase in particle numbers. At pH range of 4–7 however, aggregate formation in the size range of 1–25 µm was observed after 5freeze/thaw cycles.

Optical rotational self-assembly at air-water surface by a single vortex beam

Abstract Self-assembly and relevant quantitative measurements of 4 um polystyrene microspheres at air-water surface were realized by utilizing optical tweezers with a low-numerical-aperture (NA) and long-working-distance (WD) microscope objective. It showed that the rotation velocity of a single microsphere varies with a nearly linear dependence on incident laser power with the existence of surface tension at air-water interface. The self-assembly experiments show that the rotation velocity of the bridging particle chain increases clearly as the particle number increases. This work would contribute to the related researches of micro granular structure fabrication and bio-printing of cell tissues.

Capillary Interaction and Self-Assembly of Tilted Magnetic Ellipsoidal Particles at Liquid Interfaces.

Magnetic ellipsoidal particles adsorbed at a liquid interface provide exciting opportunities for creating switchable functional materials, where self-assembly can be switched on and off using an external field [Davies et al., Adv. Mater., 2014, 26, 6715]. In order to gain a deeper understanding of this novel system in the presence of an external field, we study the capillary interaction and self-assembly of tilted ellipsoids using analytical theory and finite element simulations. We derive an analytical expression for the dipolar capillary interaction between tilted ellipsoids in elliptical polar coordinates, which exhibits a 1/r2 power law dependence in the far field (i.e., large particle separations r) and correctly captures the orientational dependence of the capillary interactions in the near field. Using this dipole potential and finite element simulations, we further analyze the energy landscape of particle clusters consisting of up to eight tilted ellipsoids in contact. For clusters of two particles, we find that the side-to-side configuration is stable, whereas the tip-to-tip configuration is unstable. However, for clusters of more than three particles, we find that circular loops of side-to-side particles become globally stable, whereas linear chains of side-to-side particles become metastable. Furthermore, the energy barrier for the linear-to-loop transition decreases with increasing particle number. Our results explain both thermodynamically and kinetically why tilted ellipsoids assemble side-to-side locally but have a strong tendency to form loops on larger length scales.

The influence of humidity on the performance of a low-cost air particle mass sensor and the effect of atmospheric fog

Abstract. While low-cost particle sensors are increasingly being used in numerous applications, most of them have no heater or dryer at the inlet to remove water from the sample before measurement. Deliquescent growth of particles and the formation of fog droplets in the atmosphere can lead to significant increases in particle number concentration (PNC) and mass concentrations reported by such sensors. We carried out a detailed study using a Plantower PMS1003 low-cost particle sensor, both in the laboratory and under actual ambient field conditions, to investigate its response to increasing humidity and the presence of fog in the air. We found significant increases in particle number and mass concentrations at relative humidity above about 75 %. During a period of fog, the total PNC increased by 28 %, while the PNC larger than 2.5 µm increased by over 50 %. The PM10 concentration reported by the PMS1003 was 46 % greater than that on the standard monitor with a charcoal dryer at the inlet. While there is a causal link between particle pollution and adverse health effects, the presence of water on the particles is not harmful to humans. Therefore, air quality standards for particles are specifically limited to solid particles and standard particle monitoring instruments are fitted with a heater or dryer at the inlet to remove all liquid material from the sample before the concentrations are measured. This study shows that it is important to understand that the results provided by low-cost particle sensors, such as the PMS1003, cannot be used to ascertain if air quality standards are being met.

Manipulating the chemical affinity and kinetics of 3D silica particle network via the phase-separation technique

We developed a simple and versatile technique for a particle’s self-organizing-network based on a non-solvent induced micro-phase separation (NIPS). When a good solvent vaporizes from a particle dispersion in a ternary solution including the polymer, good solvent and non-solvent, the suspension is separated into the polymer network and non-solvent phase. If the affinity between the particles and polymer is sufficient enough, the particles are entrapped in the polymer network and particle network can be achieved. To expand this technique to particles with various physical properties, the surface of the particles was identified using the Hansen dispersibility parameter (HDP). From a comparison of the HDP of the unmodified and modified silica, an NH2 group is suitable for entrapment of the silica by cellulose acetate as the polymer. However, with an increase in number of the silica particles, entrapment of the silica in the polymer was prevented. Control of the phase separation rate by the lowering temperature leaded to entrapment of silica particles in the polymer network. The proposed technique is effective not only for spherical oxide particles, but also for non-oxides, various shapes and structures. Depending on particle characteristics, functional films and bulk materials for thermal insulation, light diffusion, and electro conductivity can be obtained.

Size-Resolved Surface-Active Substances of Atmospheric Aerosol: Reconsideration of the Impact on Cloud Droplet Formation.

Our current understanding of the importance of surface-active substances (SAS) on atmospheric aerosol cloud-forming efficiency is limited, as explicit data on the content of size-resolved ambient aerosol SAS, which are responsible for lowering the surface tension (σ) of activating droplets, are not available. We report on the first data comprising seasonal variability of size-segregated SAS concentrations in ambient aerosol particulate matter (PM). To assess the impact of SAS distribution within PM on cloud droplet activation and growth, a concept of surfactant activity was adopted and a parametrization developed; i.e., surfactant activity factor (SAF) was defined, which allowed translation of experimental data for use in cloud parcel modeling. The results show that SAS-induced σ depression during cloud activation may affect droplet number ( Nd) as much as a 2-fold increase in particle number, whereas by considering also the size distribution of particulate SAS, Nd may increase for another 10%. This study underscores the importance of size-resolved SAS perspective on cloud activation, as data typically obtained from aqueous extracts of PM2.5 and PM10 may result in misleading conclusions about droplet growth due to large mass fractions of supermicron particles with SAS deficit and little or no influence on CCN and Nd.

Aging characteristics and properties of Fe-16Cr-2.5Mo-1.0Cu damping alloy

The precipitating behavior of Cu-riched particles during isothermally aging and its effect on hardness and damping capacity of Fe-16Cr-2.5Mo-1.0Cu damping alloy have been investigated by atom probe tomography (APT) and scanning transmission electron microscopy (STEM). The results show that aging at temperature range from 400 °C to 700 °C has minor influence on grain size. During aging at temperature below 400 °C, the supersaturated Cu dose not precipitate out. While aging temperature is 450 °C, a relatively small number of Cu-riched particles can be observed and the particle radius is small (1.5 ± 0.56 nm). With a further increasing aging temperature, the Cu-riched particles increase to 3.21 ± 0.52 nm at 550 °C and further grow to 12.88 ± 2.02 nm at 700 °C. As compared with 450 °C, the particle number increases significantly at 550 °C, and then decreases at 700 °C. Due to the stable grain size and no precipitate, the hardness keeps constant below 400 °C. With a further increasing aging temperature, the hardness increases gradually and reaches peak value aging at 600 °C due to the increase of Cu-riched particle number. The damping capacity significantly depends on particle. Once there appear Cu-riched particles, the damping capacity decreases obviously. During aging, both hardness and damping capacity of the alloy can keep stable when temperature is below 400 °C.

Slim Body Weight Is Highly Associated With Enhanced Lipoprotein Functionality, Higher HDL-C, and Large HDL Particle Size in Young Women.

There has been no information about the correlations between body weight distribution and lipoprotein metabolism in terms of high-density lipoproteins-cholesterol (HDL-C) and cholesteryl ester transfer protein (CETP). In this study, we analyzed the quantity and quality of HDL correlations in young women (21.5 ± 1.2-years-old) with a slim (n = 21, 46.2 ± 3.8 kg) or plump (n = 30, 54.6 ± 4.4 kg) body weight. Body weight was inversely correlated with the percentage of HDL-C in total cholesterol (TC). The plump group showed 40% higher body fat (26 ± 3 %) and 86% more visceral fat mass (VFM, 1.3 ± 0.3 kg) than the slim group, which showed 18 ± 2% body fat and 0.7 ± 0.2 kg of VFM. Additionally, the plump group showed 20% higher TC, 58% higher triglyceride (TG), and 12% lower HDL-C levels in serum. The slim group showed 34% higher apoA-I but 15% lower CETP content in serum compared to the plump group. The slim group showed a 13% increase in particle size and 1.9-fold increase in particle number with enhanced cholesterol efflux activity. Although the plump group was within a normal body mass index (BMI) range, its lipid profile and lipoprotein properties were distinctly different from those of the slim group in terms of CETP mass and activity, HDL functionality, and HDL particle size.

Limited resources in multi-lane stochastic transport system

The present study proposes a generalized mean-field approach to examine the significant effect of the finite supply of particles on multi-lane coupled system with non-conserving dynamics. The steady-state behavior is analyzed by exploring vital characteristics such as phase diagrams, density profiles, residence time and power spectra. Despite the fully asymmetrical coupling environment, symmetrical phases are identified along with asymmetrical phases. The emergence of shock results in the breaking of symmetry prevailing among the lanes for a critical value of the total number of particles in the system. Additionally, bulk induced phase transition results in the shifting from low density to high density regime. As expected, jamming length increases with increase in the total number of particles in the system. Particles follow the pseudo-Gaussian distribution with decreasing variance exhibiting the significant effect of limited resources on the system properties. For the lower values of the total number of particles, the current initially increases and then saturate beyond its critical value. Through power spectra damped oscillations are observed in the particles occupancy in one of the lanes while other lane and reservoir show undamped profile with non-conserving dynamics in the bulk.

Linking photons and ultra-light particles

Similarities between thermally equilibrated photons and an ideal gas composed of highly relativistic (ultra-light) particles have long been noted, as has the fact that the two systems appear to have different energy distribution functions. Here this connection is revisited to show that all the dynamical variable distribution functions of the two systems become identical when results obtained from ultra-light gas kinetic theory are required to be consistent with independently obtained results of thermodynamics and electromagnetic theory. Thus, classical ultra-light particles, whose rest mass approaches zero, are predicted to have equilibrium velocities that are practically indistinguishable from the speed of light, and the corresponding kinetic energy distribution functions are predicted to transform from a Wien distribution to a Planck distribution with increasing particle number density.

Evaluation of nanoparticle emissions from a laser printer in an experimental chamber and estimation of the human particle dose.

The aim of this study was to evaluate the nanoparticle emissions from a laser printer in a chamber in conjunction with emissions from printers in a print room (PR) and to characterize the processes that lead to increased nanoparticle concentrations, as well as to estimate the human particle dose of the printers' users. Measurements were conducted in a small stainless steel environmental chamber under controlled conditions, where the evolution of particle size distributions (PSDs) with time and printed pages was studied in detail. Printer was generating nanoparticles (vast majority ˂50nm with mode on ~ 15nm) primarily during cold startup. Previously, 1-week sampling was also done in a PR at the Technical University of Crete, where the tested laser printer is installed along with three other printers. Similarly, as it was observed in the chamber study, printers' startup on any given day was characterized by a sharp increase in particle number (PN) concentrations. Average measured PN concentrations during printing hours in PR (5.4 × 103 #/cm3) is similar to the one observed in chamber measurements (6.7 × 103 #/cm3). The ExDoM2 dosimetry model was further applied to calculate the deposition of particles in the human respiratory tract. More precisely, the increase in particle dose for an adult Caucasian male was 14.6- and 24.1-fold at printers' startup, and 1.2- and 5.2-fold during printing in the PR and experimental chamber, respectively, compared to the exposure dose at background concentrations (BCs).

The Impact of Inadequate Temperature Storage Conditions on Aggregate and Particle Formation in Drugs Containing Tumor Necrosis Factor-Alpha Inhibitors

PurposeTo measure aggregate and particle formation in tumor necrosis factor-alpha (TNF-α) inhibitors etanercept, adalimumab and certolizumab pegol product samples after exposure to freezing temperature conditions similar to storage conditions previously observed in patients’ homes.MethodsTNF-α inhibitors in their original primary and secondary packaging were exposed to 32 freeze-thaw cycles (−10°C for 120min/5°C for 60 min) or continuous low storage temperature (−20°C for 96 h) before thawing at 2–8°C. Non-stressed products were used as controls. The products were analyzed by high pressure size exclusion chromatography (HP-SEC), dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), micro-flow imaging (MFI) and second derivative ultraviolet (UV) spectroscopy.ResultsTen out of twenty-one stressed product samples (47.6%) showed increased particle numbers in the submicron and micron size range when compared to controls. For each product, DLS, MFI and NTA detected an increase in particle level in at least one stressed syringe (both continuous freezing and freeze-thaw), whereas HP-SEC and UV spectroscopy showed no differences between stressed and non-stressed products.ConclusionTNF-α inhibitors are relatively resistant to freezing temperatures similar to storage conditions previously observed in patients’ homes. However, almost half of the stressed product samples showed formation of particles in the submicron and micron size range.

Quantum droplet of one-dimensional bosons with a three-body attraction

Ultracold atoms offer valuable opportunities where interparticle interactions can be controlled at will. In particular, by extinguishing the two-body interaction, one can realize unique systems governed by the three-body interaction, which is otherwise hidden behind the two-body interaction. Here we study one-dimensional bosons with a weak three-body attraction and show that they form few-body bound states as well as a many-body droplet stabilized by the quantum mechanical effect. Their binding energies relative to that of three bosons are all universal and the ground-state energy of the dilute droplet is found to grow exponentially as $E_N/E_3\to\exp(8N^2/\sqrt3\pi)$ with increasing particle number $N\gg1$. The realization of our system with coupled two-component bosons in an optical lattice is also discussed.

An efficient virus aerosol sampler enabled by adiabatic expansion

Protection of public health against pathogenic viruses transmitted through the airborne route requires effective sampling of airborne viruses for determination of their concentration and distribution. However, sampling viable airborne viruses is challenging as conventional bioaerosol sampling devices operate on inertia-based mechanisms that inherently have low sampling efficiency for virus aerosols in the ultrafine size range (< 100nm). Herein, a Batch Adiabatic-expansion for Size Intensification by Condensation (BASIC) approach was developed for efficient sampling of virus aerosols. The BASIC utilizes adiabatic expansion in a supersaturated container to activate condensation of water vapor onto virus aerosol particles, thus amplifying the size of the particles by orders of magnitude. Using aerosolized MS2 bacteriophage, the BASIC's performance was evaluated and optimized both from the perspectives of physical size amplification as well as preservation of the viability of the MS2 bacteriophage. Experimental results show that one compression/expansion (C/E) cycle under a compression pressure of 103.5kPa and water temperature of 25°C was sufficient to increase the particle diameter from < 100nm to > 1µm; further increases in the number of C/E cycles neither increased particle number concentration nor diameter. An increase in compression pressure was associated with physical size amplification and a higher concentration of collected viable MS2. Water temperature of 40°C was found to be the optimal for size amplification as well as viability preservation. No significant effect on particle size enlargement was observed by changing the dwell time after expansion. The results illustrate the BASIC's capability as a simple, quick and inexpensive tool for rapid sampling of viable airborne viruses.

Effects of adding Ti on microstructure and properties of Al-Bi immiscible alloy

Immiscible alloy, as a kind of special metallurgy characteristic alloy, has been investigated for decades. The fabrication of immiscible alloy with a homogeneous microstructure remains a challenge due to the liquid-liquid phase separation. The microstructure and the properties of Al-Bi immiscible alloy with an addition of Ti are investigated, and the effect of adding Ti on mechanical behavior for self-lubricating performance is measured. The pure Al and Ti are first melted in graphite crucible under argon gas protection. An appropriate amount of Bi is added into the melt. After melting and homogenizing the immiscible alloy, the melt is maintained at 1150 ℃ for 10 min, and then it is quenched. The scanning electron microscope analysis results show that the addition of Ti leads to a significant reduction of Bi-rich droplet size and an increase of particle number. The Bi-rich droplets of the ternary Al-Bi-Ti alloy are more homogeneously distributed throughout the Al matrix than the microstructure of binary Al-Bi alloy. The results from X-ray diffraction and energy disspersive spectrometer indicate that Al3Ti compounds, which are the transformation products between Al and Ti elements, disperse in the Al matrix. The needle-like Al3Ti compounds suspend in Al-Bi melt and impede the Bi phase in the liquid miscibility gap from being segregated. This is conducible to refining the microstructure of Al-Bi alloy. The Al3Ti compounds form before the initial nucleation of the Bi phase in the Al matrix, and impede the Bi phase from being segregated. Al-Bi immiscible alloy is effectively fabricated with dispersed fine second phase droplets by the addition of Ti. For the Al-Bi alloy, the coarse and non-uniform distribution of Bi-rich droplets can be easily broken. The improvement in the wear resistance of Al-Bi immiscible alloy by adding Ti can be attributed not only to the dispersion and size of the Bi soft phase but also to the in-situ formation of Al3Ti compounds. The addition of Ti is effective for refining the microstructure and improving the wear properties, which simultaneously improves the practical applications of self-lubrication bearing material with low coefficient of friction i.e., reducing the energy loss.

Genome packaging of reovirus is mediated by the scaffolding property of the microtubule network.

Reovirus replication occurs in the cytoplasm of the host cell, in virally induced mini-organelles called virus factories. On the basis of the serotype of the virus, the virus factories can manifest as filamentous (type 1 Lang strain) or globular structures (type 3 Dearing strain). The filamentous factories morphology is dependent on the microtubule cytoskeleton; however, the exact function of the microtubule network in virus replication remains unknown. Using a combination of fluorescent microscopy, electron microscopy, and tomography of high-pressure frozen and freeze-substituted cells, we determined the ultrastructural organisation of reovirus factories. Cells infected with the reovirus microtubule-dependent strain display paracrystalline arrays of progeny virions resulting from their tiered organisation around microtubule filaments. On the contrary, in cells infected with the microtubule-independent strain, progeny virions lacked organisation. Conversely to the microtubule-dependent strain, around half of the viral particles present in these viral factories did not contain genomes (genome-less particles). Complementarily, interference with the microtubule filaments in cells infected with the microtubule-dependent strain resulted in a significant increase of genome-less particle number. This decrease of genome packaging efficiency could be rescued by rerouting viral factories on the actin cytoskeleton. These findings demonstrate that the scaffolding properties of the microtubule, and not biochemical nature of tubulin, are critical determinants for reovirus efficient genome packaging. This work establishes, for the first time, a functional correlation between ultrastructural organisation of reovirus factories with genome packaging efficiency and provides novel information on how viruses coordinate assembly of progeny particles.

Using in-situ viscosimetry and morphogranulometry to explore hydrolysis mechanisms of filter paper and pretreated sugarcane bagasse under semi-dilute suspensions

The relationship between in-situ viscosimetry, in- and ex-situ morphogranulometry, and biochemistry has been investigated during enzymatic hydrolysis of pretreated sugarcane bagasse (SCB, 3% w/v) and filter paper (FP, 1.5% w/v) at various enzyme dosages (0.3–25FPU/g cellulose). Semi-dilute conditions (1.5–2 times higher than critical concentrations) were considered in order to generate non-Newtonian rheological behaviors and to avoid neglecting particle–particle interactions in opposition to dilute conditions. Observed phenomena as well as hydrolysis mechanisms including solvation, separation, fragmentation, and solubilization appeared to depend strongly on initial substrate properties. For both FP and SCB, suspension viscosities were correlated with particle size distributions and volume fractions during hydrolysis, but they exhibited strongly different trends. With SCB, a viscosity overtaking was clearly observed at enzyme loading ≤10FPU/g cellulose. This phenomenon is explained by the separation of agglomerates into individual fragments, leading to an increase in the total number of particles and a morphological shift of particles from sphere-like into fiber-like. With FP, the viscosity collapsed at the initial stage in relation to the volume reduction of coarse particles and the number increase of fine particles. Suspension viscosity was strongly dependent on the fraction of coarse population and nearly independent from the glucose conversion yield.

Semiclassical Identification of Periodic Orbits in a Quantum Many-Body System

While a wealth of results has been obtained for chaos in single-particle quantum systems, much less is known about chaos in quantum many-body systems. We contribute to recent efforts to make a semiclassical analysis of such systems feasible, which is nontrivial due to the exponential proliferation of orbits with increasing particle number. Employing a recently discovered duality relation, we focus on the collective, coherent motion that together with the also present incoherent one typically leads to a mixture of regular and chaotic dynamics. We investigate a kicked spin chain as an example of a presently experimentally and theoretically much studied class of systems.