Particle Size Spectra Research Articles

Seasonal dynamics in bacterial communities of closed-cage broiler houses.

The bacteria contained in air aerosols from poultry houses are closely connected to animal health and production. This study aimed to investigate the seasonal factors on microbial aerosol concentration, particle size and bacterial spectrum composition inside a closed-cage broiler house. Then, 16S rDNA sequencing technology was applied to analyze the characteristics of bacterial abundance and diversity. The results indicated that the concentration of bacterial aerosol in the broiler house varied significantly in different seasons, with a concentration range of 5.87-15.77 × 103 CFU/m3, and the highest and lowest concentrations in the summer and winter, respectively. Microbiological analysis showed that the proportion of Gram-negative bacteria in autumn was significantly higher than that in summer (P < 0.05). In addition, the floral structure of potential pathogenic bacterial genera also differed by season. Escherichia-Shigella, Streptococcus, Acinetobacter, Pseudomonas were identified in the bacterial aerosols. Importantly, the relative abundance of Firmicutes in spring and autumn was much higher. In contrast, the relative abundance of Proteobacteria in spring and autumn was lower than that in summer and winter. Altogether, results revealed the effects of seasonal factors on the diversity and abundance of bacteria and the distribution characteristics of major opportunistic pathogens in the air of closed-cage broiler houses. These results will provide important information for exploring the potential risk of aerosols from poultry houses all four seasons.

Comparisons of macrofaunal communities occupying shores across the full particle-size spectrum reveals pebble beaches to be a distinct coastal habitat type

Intertidal research has focused primarily on very fine to coarse sandy beaches (grain size <1 mm) and on rocky shores, while shores with grain sizes of 1-256+ mm have rarely been studied. Within South Africa, few published accounts describe the biota of very coarse sand (1-<2 mm), granule (2-<4 mm), pebble (4-<64 mm) or cobble (64-<256 mm) shores, and only one reports on boulder (256+ mm) shores. The objective here was to determine how many distinct habitat types occur across the full spectrum of particle sizes within this region, and what taxa characterise the biota of each habitat type. Biota from 14 shores of grain sizes 1-256 mm within the Western Cape Province (southeastern Atlantic Ocean) were sampled and compared with similar published data from 32 other regional sites with either finer or coarser grain size. Three main groupings emerged from a similarity analysis: sandy shores (of particle size <1 mm); pebble (4-<64 mm) shores; and boulder (256+ mm) plus rocky shores, with cobbles serving as a transition between those two. Sandy shores were characterised by various burrowing taxa, and boulder (>256 mm) and rocky shores mostly by grazing gastropods. Shores of 4-<64 mm particle grain size were colonised by a distinctive but previously unrecognised macrofaunal community characterised by an impoverished fauna dominated by small, mobile, mostly air-breathing arthropod taxa.

Effect of Internal Decay Power and Surface Cooling on Nuclear Fuel Droplet Solidification During MFCI in a SFR—A Numerical Study

Melting of the nuclear core is one of the severe accident scenarios in a Sodium-cooled Fast Reactor (SFR). During such an event, molten corium may come into contact with the coolant sodium. This interaction of the molten fuel and the coolant is commonly termed molten fuel–coolant interaction (MFCI) in the nuclear industry. In this study, a numerical analysis is carried out to study the solidification of a molten fuel droplet in the liquid sodium pool. In the first part of the study, the effect of constant internal heat generation on the solidification of the droplet is evaluated with convective heat dissipation prescribed at the droplet surface. The internal heat generation (decay power) and the heat transfer coefficient are varied as parameters, and the time required for complete solidification of the molten droplet is obtained. Based on the results, the freezing of the droplet is categorized into three regimes: conduction limited, transition, and internal heat generation dominated regimes. It is observed that the solidification process of nuclear fuel droplets generated during MFCI is not influenced by internal heat generation and lies in a conduction-limited regime for decay power level prevailing in a medium-sized SFR. Hence, in the next part of the study, the numerical analysis is carried out by incorporating the time-dependent decay power and the temperature-dependent heat transfer coefficient in the computational model by developing user-defined subroutines depicting a realistic scenario of an accident. The results of the analysis show that because of the high subcooling of sodium, film boiling is ruled out; nucleate boiling with a maximum heat transfer rate occurs briefly. The heat transfer coefficient then declines as the interface temperature between the droplet and the sodium decreases rapidly until the natural convective regime is reached. A parametric study on the droplet diameter is also carried out by varying the diameter from 0.5 to 10 mm, spanning the typical particle size spectrum expected during MFCI.

The characteristics of particulate matter during an air pollution process revealed by joint observation of multiple equipments

During a particle pollution in Hefei, Anhui Province from November 25 to December 9, 2018, we used a set of particle monitoring devices with different principles installed on the top floor of a 5-story experimental building to observe the mass concentration, particle diameter distribution and chemical composition. The results show that this pollution process can be divided into three stages: accumulation, outbreak and dissipation. At the beginning of pollution outbreak, it can be observed through the lidar that particulate matter first appears in the upper part of the boundary layer, and then accumulates downward and develops into ground pollution. During the pollution outbreak, particulate matter with an equivalent diameter of 0.8–1.6 μm increases significantly, with an average increase of more than 50%. In the particle size spectrum, the full width at half maximum also increases, and the particle diameter at the peak is about 0.76 μm. Furthermore, the change in particle size over time shows that the number concentration of particles with smaller size grows before those with larger size. By identifying and comparing characteristic ions, we found that the increase in the number of sulfate particles and the increase of their size correspond well to the outbreak of pollution, and the rapid decline in the fraction of sulfate corresponds well to the dissipation of pollution too. Sulfate is the most sensitive factor in the pollution process. The EC is the main component throughout the pollution process, but EC responds more slowly to pollution changes than sulfate, it is important but less sensitive.

Role of gas–molecular cluster–aerosol dynamics in atmospheric new-particle formation

New-particle formation from vapors through molecular cluster formation is a central process affecting atmospheric aerosol and cloud condensation nuclei numbers, and a significant source of uncertainty in assessments of aerosol radiative forcing. While advances in experimental and computational methods provide improved assessments of particle formation rates from different species, the standard approach to implement these data in aerosol models rests on highly simplifying assumptions concerning gas–cluster–aerosol dynamics. To quantify the effects of the simplifications, we develop an open-source tool for explicitly simulating the dynamics of the complete particle size spectrum from vapor molecules and molecular clusters to larger aerosols for multi-compound new-particle formation. We demonstrate that the simplified treatment is a reasonable approximation for particle formation from weakly clustering chemical compounds, but results in overprediction of particle numbers and of the contribution of new-particle formation to cloud condensation nuclei for strongly clustering, low-concentration trace gases. The new explicit approach circumvents these issues, thus enabling robust model–measurement comparisons, improved assessment of the importance of different particle formation agents, and construction of optimal simplifications for large-scale models.

On numerical broadening of particle-size spectra: a condensational growth study using PyMPDATA 1.0

Abstract. This work discusses the numerical aspects of representing the condensational growth of particles in models of aerosol systems such as atmospheric clouds. It focuses on the Eulerian modelling approach, in which fixed-bin discretisation is used for the probability density function describing the particle-size spectrum. Numerical diffusion is inherent to the employment of the fixed-bin discretisation for solving the arising transport problem (advection equation describing size spectrum evolution). The focus of this work is on a technique for reducing the numerical diffusion in solutions based on the upwind scheme: the multidimensional positive definite advection transport algorithm (MPDATA). Several MPDATA variants are explored including infinite-gauge, non-oscillatory, third-order terms and recursive antidiffusive correction (double-pass donor cell, DPDC) options. Methodologies for handling coordinate transformations associated with both particle-size spectrum coordinate choice and with numerical grid layout choice are expounded. Analysis of the performance of the scheme for different discretisation parameters and different settings of the algorithm is performed using (i) an analytically solvable box-model test case and (ii) the single-column kinematic driver (“KiD”) test case in which the size-spectral advection due to condensation is solved simultaneously with the advection in the vertical spatial coordinate, and in which the supersaturation evolution is coupled with the droplet growth through water mass budget. The box-model problem covers size-spectral dynamics only; no spatial dimension is considered. The single-column test case involves a numerical solution of a two-dimensional advection problem (spectral and spatial dimensions). The discussion presented in the paper covers size-spectral, spatial and temporal convergence as well as computational cost, conservativeness and quantification of the numerical broadening of the particle-size spectrum. The box-model simulations demonstrate that, compared with upwind solutions, even a 10-fold decrease in the spurious numerical spectral broadening can be obtained by an apt choice of the MPDATA variant (maintaining the same spatial and temporal resolution), yet at an increased computational cost. Analyses using the single-column test case reveal that the width of the droplet size spectrum is affected by numerical diffusion pertinent to both spatial and spectral advection. Application of even a single corrective iteration of MPDATA robustly decreases the relative dispersion of the droplet spectrum, roughly by a factor of 2 at the levels of maximal liquid water content. Presented simulations are carried out using PyMPDATA – a new open-source Python implementation of MPDATA based on the Numba just-in-time compilation infrastructure.

Uncertain response of ocean biological carbon export in a changing world

The transfer of organic carbon from the upper to the deep ocean by particulate export flux is the starting point for the long-term storage of photosynthetically fixed carbon. This ‘biological carbon pump’ is a critical component of the global carbon cycle, reducing atmospheric CO2 levels by ~200 ppm relative to a world without export flux. This carbon flux also fuels the productivity of the mesopelagic zone, including important fisheries. Here we show that, despite its importance for understanding future ocean carbon cycling, Earth system models disagree on the projected response of the global export flux to climate change, with estimates ranging from −41% to +1.8%. Fundamental constraints to understanding export flux arise because a myriad of interconnected processes make the biological carbon pump challenging to both observe and model. Our synthesis prioritizes the processes likely to be most important to include in modern-day estimates (particle fragmentation and zooplankton vertical migration) and future projections (phytoplankton and particle size spectra and temperature-dependent remineralization) of export. We also identify the observations required to achieve more robust characterization, and hence improved model parameterization, of export flux and thus reduce uncertainties in current and future estimates in the overall cycling of carbon in the ocean. A synthesis of recent work on marine carbon export fluxes finds that many processes that are key to understanding the effects of a warming climate on ocean carbon cycling are missing from current climate models.

Phytoplankton and particle size spectra indicate intense mixotrophic dinoflagellates grazing from summer to winter.

Mixotrophic dinoflagellates (MTD) are a diverse group of organisms often responsible for the formation of harmful algal blooms. However, the development of dinoflagellate blooms and their effects on the plankton community are still not well explored. Here we relate the species succession of MTD with parallel changes of phytoplankton size spectra during periods of MTD dominance. We used FlowCAM analysis to acquire size spectra in the range 2–200 μm every one or two weeks from July to December 2007 at Helgoland Roads (Southern North Sea). Most size spectra of dinoflagellates were bimodal, whereas for other groups, e.g. diatoms and autotrophic flagellates, the spectra were unimodal, which indicates different resource use strategies of autotrophs and mixotrophs. The biomass lost in the size spectrum correlates with the potential grazing pressure of MTD. Based on size-based analysis of trophic linkages, we suggest that mixotrophy, including detritivory, drives species succession and facilitates the formation of bimodal size spectra. Bimodality in particular indicates niche differentiation through grazing of large MTD on smaller MTD. Phagotrophy of larger MTD may exceed one of the smaller MTD since larger prey was more abundant than smaller prey. Under strong light limitation, a usually overlooked refuge strategy may derive from detritivory. The critical role of trophic links of MTD as a central component of the plankton community may guide future observational and theoretical research.

Aquatic macrophyte fluctuations since the 1900s in the third largest Chinese freshwater lake (Lake Taihu): Evidences, drivers and management implications

Diverse aquatic macrophyte communities represent an essential component of healthy shallow lake ecosystems, and information on changes in macrophytes abundance and composition is crucial for restoration initiatives and management. However, the long-term dynamics of aquatic macrophyte communities are poorly understood for most subtropical freshwater lakes. This study used macrophyte surveys from 1960 to 2014 alongside plant macrofossil and pollen remains deposited in the sediment to reconstruct, macrophyte community change over the two centuries in the southeastern bay of Lake Taihu, China. Plant macrofossils efficiently captured the main historical recorded macrophyte species, including four unrecorded submerged taxa (Vallisneria spinulosa, Zannichellia palustris, Nitella sp., and Chara sp.) by the monitoring surveys. Aquatic pollen failed to reflect the main species composition in the bay, but provided additional information on species with no macrofossils and few seeds, especially the floating-leaved and free-floating taxa (e.g., Nymphoides and Azolla). We conducted a constrained incremental sum of squares cluster analysis and a multiple factor analysis (MFA) to the macrophyte community in the core and identified three major changes over the past century, with a shift from Potamogeton malaianus (pre-1960), to Vallisneria natans, P. malaianus, Potamogeton maackianus, and charophyte species (1960–1998), followed by the proliferation of pollutant-resistant species Ceratophyllum demersum and Myriophyllum spicatum, as well as the floating-leaved plant Nymphoides (post-1998). MFA also clearly elucidated the relationships between macrophyte shifts and changes in various environmental stressors (i.e., cladocerans, particle size spectra and geochemical data). The results confirmed our hypothesis, which stated that hydrological alterations and increased nutrient inputs, driven by the increasing anthropogenic pressures were likely the main drivers of the alteration in the macrophyte composition and succession in the bay. Our study provides a unique perspective on the pre-disturbance macrophyte community composition of Eastern Lake Taihu, thereby offering useful information not only for lake managers in the Yangtze region, but also for the global decision-making for the eutrophication and restoration of large shallow lakes.

Synthesis mechanisms and effects of BaTiO3 doping on the optical properties of Bi0.5Na0.5TiO3 lead-free ceramics

Research in (1-x)Bi0.5Na0.5TiO3-xBaTiO3, (x ​= ​0.01 to 0.09), (known as BNT-BT) perovskite materials ranges from fundamental scientific analysis like crystal structure, optical and electrical properties to technologies for advanced energy storage batteries, low-power electronics, sensors, and energy conversion devices. The properties observed in this versatile materials class originate, in part, from the ability to connect crystallographic structures with several applications. The aim of this review article is the emerging technologies in BNT-BT materials by several syntheses aimed to reach unexplored portions of the crystallographic structure with optical property for rational materials design. The four chemistry dependent strategies have been reviewed: crystal structure with the domain-super lattice, synthesis routes, comparison of particle size, microstructure and Raman spectra. Finally, this article touches on the new functionalities of BNT-BT that the material could attain through external applications and highlight unresolved problems.

Synthetic Mechanism of UiO‐66‐NH2/BiVO4/BiOBr Spherical and Lamellar Dual Z‐scheme Heterojunction and Efficient Photocatalytic Degradation of Tetracycline Under Visible Light

AbstractIn order to solve antibiotic pollution, it is necessary to design photocatalysts with high specific surface area and efficient electron transfer performance. In this study, we report that two‐dimensional (2D) BiVO4/BiOBr flakes were anchored on the smooth surface of UIO‐66‐NH2 using a two‐step solvothermal‐hydrothermal approach, which forms the dual Z‐scheme mechanism and has rich specific surface area (306.5 m2/g), uniform particle size (2.05 nm) and wide absorption spectrum (2.76 eV). It shows 89.56 % tetracycline (TC) degradation efficiency within 180 min under visible light illumination due to the excellent adsorption properties and ample active sites. This work provides an effective strategy for designing a novel ternary photocatalyst to the degradation of refractory organic pollutants.

Slow Particle Remineralization, Rather Than Suppressed Disaggregation, Drives Efficient Flux Transfer Through the Eastern Tropical North Pacific Oxygen Deficient Zone

AbstractModels and observations suggest that particle flux attenuation is lower across the mesopelagic zone of anoxic environments compared to oxic environments. Flux attenuation is controlled by microbial metabolism as well as aggregation and disaggregation by zooplankton, all of which shape the relative abundance of differently sized particles. Observing and modeling particle spectra can provide information about the contributions of these processes. We measured particle size spectrum profiles at one station in the oligotrophic Eastern Tropical North Pacific Oxygen Deficient Zone (ETNP ODZ) using an underwater vision profiler (UVP), a high‐resolution camera that counts and sizes particles. Measurements were taken at different times of day, over the course of a week. Comparing these data to particle flux measurements from sediment traps collected over the same time‐period allowed us to constrain the particle size to flux relationship, and to generate highly resolved depth and time estimates of particle flux rates. We found that particle flux attenuated very little throughout the anoxic water column, and at some time points appeared to increase. Comparing our observations to model predictions suggested that particles of all sizes remineralize more slowly in the ODZ than in oxic waters, and that large particles disaggregate into smaller particles, primarily between the base of the photic zone and 500 m. Acoustic measurements of multiple size classes of organisms suggested that many organisms migrated, during the day, to the region with high particle disaggregation. Our data suggest that diel‐migrating organisms both actively transport biomass and disaggregate particles in the ODZ core.

The Underwater Vision Profiler 6: an imaging sensor of particle size spectra and plankton, for autonomous and cabled platforms.

Autonomous and cabled platforms are revolutionizing our understanding of ocean systems by providing 4D monitoring of the water column, thus going beyond the reach of ship‐based surveys and increasing the depth of remotely sensed observations. However, very few commercially available sensors for such platforms are capable of monitoring large particulate matter (100–2000 μm) and plankton despite their important roles in the biological carbon pump and as trophic links from phytoplankton to fish. Here, we provide details of a new, commercially available scientific camera‐based particle counter, specifically designed to be deployed on autonomous and cabled platforms: the Underwater Vision Profiler 6 (UVP6). Indeed, the UVP6 camera‐and‐lighting and processing system, while small in size and requiring low power, provides data of quality comparable to that of previous much larger UVPs deployed from ships. We detail the UVP6 camera settings, its performance when acquiring data on aquatic particles and plankton, their quality control, analysis of its recordings, and streaming from in situ acquisition to users. In addition, we explain how the UVP6 has already been integrated into platforms such as BGC‐Argo floats, gliders and long‐term mooring systems (autonomous platforms). Finally, we use results from actual deployments to illustrate how UVP6 data can contribute to addressing longstanding questions in marine science, and also suggest new avenues that can be explored using UVP6‐equipped autonomous platforms.

Size-Fractionated Filtration Combined with Molecular Methods Reveals the Size and Diversity of Picophytoplankton.

Simple SummaryIn order to accurately characterize the composition of the picophytoplankton community by size in the marine environment, we used a size-fractionated filtration plus a high-throughput sequencing molecular method. The results showed that this method can detect the composition of picophytoplankton in different particle size ranges in detail, and it is accurate in assessing the vertical distribution patterns and size of phytoplankton. This method can enrich the study of phytoplankton communities with diameters of less than 2 μm.In this study, flow cytometry (FCM) and size-fractionated filtration, together with high-throughput molecular sequencing methods (SM), were used to investigate picophytoplankton. A particle separation filter and a higher-throughput sequencing method were used to evaluate the composition of a euphotic zone of picophytoplankton—especially picoeukaryotic phytoplankton—in the Western Pacific, and the results of flow cytometry, which is a classic way to detect picophytoplankton, were used as a standard to evaluate the reliability of the results of the SMs. Within a water column of 200 m, six water depths (5, 25, 50, 113 (DCM), 150, and 200 m) were established. In order to further study the particle size spectra of the picophytoplankton, size-fractionated filtration was used to separate water samples from each water depth into three particle size ranges: 0.2–0.6, 0.6–1.2, and 1.2–2 μm. A total of 36 (6 × 3 × 2) samples were obtained through PCR amplification of the 18S rRNA V4 hypervariable region and 16S rRNA, which were biased toward phytoplankton plastids, and then high-throughput sequencing was performed. The estimation of the picophytoplankton diameter relied on forward scattering (FSC) through FCM. The estimation of the vertical distribution and diameter of the picophytoplankton using the SM was consistent with the results with FCM; thus, we believe that the estimation of picophytoplankton composition with the SM has value as a reference, although the size-fractionated filtration seemed to cause some deviations. In addition to Prochlorococcus and Synechococcus, the SM was used to evaluate the composition of picoeukaryotic phytoplankton, which mainly included Prymnesiophycea (Haptophyta) (38.15%), Cryptophyceae (Cryptophyta) (22.36%), Dictyochophyceae (Chrysophyta) (12.22%), and Mamiellophyceae (Chlorophyta) (3.31%). In addition, the SM also detected Dinophyceae (Dinoflagellata) (11.69%) sequences and a small number of Bacillariophyceae (Diatom) (1.64%) sequences, which are generally considered to have large particle sizes. The results of the SM also showed that the picoeukaryotic phytoplankton were not evenly distributed in the euphotic layer, and the vertical distributions of the different picoeukaryotic phytoplankton were different. An analysis of correlations with environmental factors showed that temperature was the main environmental factor controlling the vertical distribution of picophytoplankton.

Variability of plankton size distribution and controlling factors across a coastal frontal zone

Strong temperature fronts are commonly formed in the coastal northern South China Sea (NSCS) by mixing of the nearshore mesotrophic cold waters with the offshore oligotrophic warm waters. To understand community response to the rapid environmental change across the frontal system, a field survey was conducted during March 2019 focusing on the spatial and vertical variations of plankton size structure, including chlorophyll-a size-fractionation, picoplankton composition and biomass via flow cytometry, as well as the normalized biovolume size spectrum (NBSS) of nano- and microplankton by Flow Image Microscopy (FlowCAM). In the surface layer, we observed a substantial loss of chain-forming diatoms from the nearshore to the frontal zone. In contrast, a rapid decline of small phytoplankton including Synechococcus, picoeukaryotes, and small nanoplankton (mainly Chaetoceros) was documented from the frontal zone to the offshore. The sharp change in surface plankton community had resulted in a large spatial variation of the mean NBSS slope from −0.37 in the nearshore, to −0.78 at the frontal zone, and −0.62 in the offshore. The cross-frontal change of plankton size composition could be explained by the varying physical and biogeochemical settings given the significant correlations of the NBSS slope and intercept with both nutrient and temperature in the surface waters. In the bottom layer of the temperature front, the resuspension of sediment detrital particles was found to substantially affect the particle size spectra with the steepest NBSS slope (−0.94) but the highest NBSS intercept (18.92) appearing at the bottom of the frontal zone. When the sediment signals were removed, the spatial change in abundance of microplankton from FlowCAM showed a general agreement with that from the micro-phytoplankton chlorophyll-a revealing the importance of phytoplankton dynamics and sediment resuspension in controlling the cross-frontal distribution of plankton size structure in the bottom layer. Finally, we found a significant negative correlation of the NBSS slope with the transparent exopolymer particles (TEP) in the bottom waters, which is different from the positive correlation observed in the surface waters. This result may be related to various roles of TEP on particle size structure in different layers of the frontal system.

The effects of different parameters and interaction angles of a 532 nm pulsed Nd: YAG laser on the properties of laser-ablated silver nanoparticles

Laser ablation in liquids (LAL) is being used to create contaminant-free colloidal nanoparticles with unique properties. The absorbance of a substance to incident laser light, which results in the formation of a nanoparticle, as well as the control of size and shape, are all affected by many factors. Among these are laser energy, laser wavelength, ablation time, laser polarization, angle of incidence, and material properties. In this paper, we present the results of producing silver nanoparticles’ colloids in distilled water by laser ablation from a bulk silver metal using the 2nd harmonic of Nd: YAG laser. The effects on the nanoparticles due to different ablation times, energies, and laser incidence angles have been studied. The particle size, morphology, and absorption spectrum of the nanoparticles colloids are derived from the transmission electron microscopy (TEM) and ultraviolet–visible (UV–Vis) spectrophotometer. The silver nanoparticles TEM image shows a spherical-like shape at different ablation time, different energies, while showing different nano shapes at ablation laser pulse energy ≥100 mJ, and when the angle between the laser beam and the silver bulk was changed from 90°to 60°. The size distribution of the nanoparticles was found to be shifted to the quantum size range (<10 nm) with increase of the laser ablation time and reach an average size of 7.5 nm at 30 min ablation time with laser pulse energy at 100 mJ. Also, in the case of 30 min ablation time and laser pulse energy of 100 mJ, the obtained nanoparticles have a size distribution falling into two ranges of 1–10 nm (55%) and 10–20 nm (45%).

The construction of gold hybrid supramolecular hydrogels for doxorubicin delivery

ABSTRACT Currently, drug delivery systems with low toxicity and high efficacy are urgently needed to suppress cancer cells. Herein, a non-toxic and biocompatible drug carrier (mPEG-luteolin-AuNPs) was prepared, which was characteristic by SEM, FT-IR, XRD, average particle size, zeta potential and UV-Vis spectra, respectively. Considering that the morphology of supramolecular hydrogel was porous which was good for storage of drugs, a stable supramolecular hydrogel self-assembly formed based on mPEG-luteolin-AuNPs and α-cyclodextrin (α-CD) was reported. Then, supramolecular hydrogel loaded doxorubicin hydrochloride (DOX) and sustained DOX release. Meanwhile, in vitro experiments clearly demonstrated that DOX of hydrogel (mPEG-luteolin-AuNPs/DOX) was biologically active, similar to free DOX, but with better cytotoxicity to human glioblastoma cells (U-87 MG) because of its controllable release. Our findings indicated that mPEG-luteolin-AuNPs/DOX might be promising delivery systems for anticancer chemotherapy.

Light-scattering of tracer particles for liquid flow measurements

A variety of modern flow measurement techniques use tracer particles that should accurately follow fluid motions and should scatter sufficient light to be detectable by imagining systems. These two requirements are at odds if they are to be full-filled by varying the tracer size. For this reason, other particle properties such as material, structure, and coating are also considered. While the effect of these properties on the particle response time can be estimated, it is challenging to quantify their effect on the scattered light using the Mie scattering theory. To address this issue, we investigated the light scattering properties of several commercially available tracer particles and provided simple guidelines for selecting appropriate particles. The investigations were carried out using particle images recorded in forward, side, and backward-scatter angles that are typically used in 3D-particle tracking velocimetry. The selected particles represent a wide spectrum of particle sizes and included glass, polymer, and fluorescent particles used in liquid flows. Other properties such as hollow structures and metallic coatings were also investigated. The results showed that glass particles had greater light scattering in the forward-scatter direction, while the polystyrene particles scattered more light in the back-scatter direction. The fluorescent particles had a relatively narrow intensity distribution with a strong side-scatter. We found that silver-coated glass particles had two to four times higher image intensity in the side and back-scatter cameras when compared with uncoated glass particles. The hollow glass particles had a higher forward-scatter compared with the solid glass particles. The recorded images were also used to obtain 3D particle tracks. A large intensity variation was observed along the 3D tracks that was mainly associated with the discretization of particle images on the camera sensor.

A model to estimate the effect of variables causing erosion in wind turbine blades

AbstractThe quantification of the severity of erosion in wind turbine blades is challenging due to the many aspects involved, including meteorology, aerodynamics, materials science, and wind turbine dynamics. A complete model relies on several building blocks, which cover the characterization of precipitation and aerosols, the trajectories of droplets and particles, the operational settings of the wind turbine, and finally the structural response of the leading edge to the large number of impacts across a spectrum of particle sizes and impacts speeds. This paper presents a multidisciplinary model, defining magnitudes representative of erosion severity and formulating their dependencies. The method uses the formula for the erosion incubation time as defined by Springer. The model incorporates the effect of wind velocity and density, particle size, and erosion intensity, and it allows four erosion mechanisms to be considered: rainfall, snowfall, sea spray, and fog. Comparison of the predicted erosion incubation time versus blade inspections shows good qualitative agreement. The equations from the model suggest that the characterization of atmospheric conditions at the site is essential for an accurate estimation of the severity of erosion. Equally important are the material properties, and the impingement process at the leading edge.

Stability of plankton community structure in a long-term biomanipulated eutrophic shallow lake in southeast China: Evidence from particle size spectra

To characterize the plankton size structure and evaluate plankton community stability in Longhu Lake, a shallow eutrophic lake in southeast China that has been biomanipulated for ~20 years, the biomass-size spectra of the plankton were seasonally studied from August 2017 to November 2018. The plankton-size spectra revealed a typical bimodal structure in all seasons. The higher peak consisted of small-sized phytoplankton ranging from 10 to 30 μm, while the lower peak consisted mainly of rotifers and ciliates ranging from 66 to 83 μm. Compared with other eutrophic lakes, the size classes of the bimodal structure in Longhu Lake were relatively smaller, indicating individual miniaturization in the lake's plankton community. There was also a trough in the 90 to 370 μm region of the size spectra, indicating a low biomass for crustacean zooplankton in the lake. The slope (b = −1.27 ± 0.04) of the normalized size spectra was lower than that of the theoretical equilibrium state (b = −1), suggesting high energy transfer from the large phytoplankton (>30 μm) and zooplankton (>90 μm) to the planktivorous silver and bighead carps via filter feeding. Although the seasonal size spectra fluctuated with the water temperature (positively) and nutrients (negatively) in Longhu Lake, their patterns and coefficients of determination did not significantly vary with the seasons (R2 = 0.98 ± 0.01, p < 0.05), indicating the plankton community is stable in this long-term biomanipulated eutrophic lake.