Mean Equivalent Spherical Diameter Research Articles

Peaks, pores, and dragon eggs: Uncovering and quantifying the heterogeneity of treatment wetland biofilm matrices

Biofilms serve to house diverse microbial communities, which are responsible for the majority of wastewater constituent degradation and transformation in treatment wetlands (TWs). TW biofilm has been generally conceptualized as a relatively uniform film covering available surfaces. However, no studies attaining direct visual 3D representations of biofilm morphology have been conducted. This study focuses on imaging the morphology of detached, gravel-associated, and rhizospheric (Phalaris arundinacea) biofilms from subsurface TW mesocosms. Images obtained through both traditional light microscopy, environmental scanning electron microscopy (E-SEM) and Wet-SEM revealed that TW biofilms are structurally heterogeneous ranging from corrugated films to clusters of aggregates. Features such as water channels and pores were observed suggesting that pollutant transport inside biofilms is complex, and that the interfacial surface area between water and biofilm is much larger than previously understood. Biofilm thickness generally ranged between 170 and 240 μm, with internal biofilm porosities estimated as 34 ± 10 %, reaching a maximum of 50 %. Internal biofilm matrix pore diameters ranged from 1 to 205.2 μm, with a distribution that favored pores and channels smaller than 10 μm, and a mean equivalent spherical diameter of 8.6 μm. Based on the large variation in pore and channel sizes it is expected that a variety of flow regimes and therefore pollutant dynamics are likely to occur inside TW biofilm matrices. Based on the visual evidence and analysis, a new conceptual model was created to reflect the microscale TW biofilm dynamics and morphology. This new conceptual model will serve to inform future biokinetic modelling, microscale hydrology, microbial community assessment, and pollutant treatment studies.

Choline chloride-based deep eutectic solvent systems as a pretreatment for nanofibrillation of ramie fibers

As a new type of green solvents, deep eutectic solvents (DESs) were used as pretreatment media for the nanofibrillation of ramie fibers (RFs). Two DESs, choline chloride-oxalic acid dihydrate (CO) and choline chloride-urea (CU), were formed at 100 °C and then applied to decompose RFs. The DES-pretreated fibers were nanofibrillated using a planetary ball mill, and their properties were analyzed. During the DES pretreatment, CU DES could only dissolve some of hemicelluloses in raw RFs, while CO DES could degrade some oligosaccharides and a part of amorphous cellulose to loosen the fiber structure. Therefore, only the CO DES pretreatment could significantly enhance nanofibrillation of the RFs with a low hemicellulose content in this study, as indicated by the decrease of milling time (from 11 to 5 h) to obtain desirable cellulose nanofibrils (CNFs). After 7 h CO DES pretreatment at room temperature and a subsequent ball milling process, a turbid and gel-like CNF suspension with a mean equivalent spherical diameter of 262 nm was obtained from RFs, and the mass yield of CNFs reached 94.06%. The CNFs also showed a crystallinity index of 66.51% and a thermal stability with Tmax = 322.6 °C, and the produced CNF film had a tensile strength of 52 MPa. Overall, the CO DES pretreatment has great potential for use in the production of CNFs from RFs.

High photosynthetic rates associated with pico and nanophytoplankton communities and high stratification index in the North West Atlantic

The biological dynamics of pelagic marine ecosystems are strongly influenced by the size structure and ecological succession of phytoplankton, which in turn modifies photosynthetic efficiency. Variability in photosynthetic rates is closely coupled with changes in community structure, but it is difficult to obtain coincident data at high enough resolution to characterise these changes. In this study, we employ hierarchical cluster analysis on chlorophyll-normalised high performance liquid chromatography (HPLC) pigment concentrations from the North West Atlantic, to identify seasonal successional trends amongst phytoplankton populations. Changes in phytoplankton community were also analysed as a function of mean equivalent spherical diameter (MESD) derived from absorption measurements, photosynthetic rates, water-column stratification and temperature. Well-mixed conditions in spring to early summer were associated with populations of large cells containing high concentrations of fucoxanthin, chlorophyll-c1 and chlorophyll-c2 relative to chlorophyll-a (Chl a). As stratification increased over the course of the summer, these cells were replaced by populations dominated by chlorophyll-b, 19'-hexanoyloxyfucoxanthin, 19'-butanoyloxyfucoxanthin and divinyl chlorophyll-a, indicative of small picophytoplankton. As stratification decreased in autumn, MESD and alloxanthin increased, suggesting the presence of cryptophytes. Positive relationships were found between MESD and the quantum yield of photosynthesis (φm) for 7 out of the 8 phytoplankton clusters identified, while negative relationships between mean mixed layer photosynthetically active radiation and φm and the light limited slope of photosynthesis (αB) were observed for 4 clusters, as a result of nutrient limitation and photo-protection. The highest photosynthetic rates were associated with a pico & nanophytoplankton communities, which increased from spring to late summer as stratification intensified. By contrast, diatom communities had the lowest photosynthetic rates throughout the year. These successional patterns in the dominant phytoplankton size-class and phenology support Margalef's mandala in terms of the relationship between turbulence and community structure. The study sheds new light on assemblages dominated by smaller cells, under warm, stratified conditions, having higher photosynthetic efficiencies, which has implications for the carbon flux in the NW Atlantic.

Synthesis and characterization of cellulose nanocrystals derived from walnut shell agricultural residues

Cellulose nanocrystals (CNCs) have novel and diversified applications in different fields including packaging and nanodelivery systems. This study was dedicated to fabricate CNCs from walnut shell as an abundant source of agricultural byproducts using alkali/acidic hydrolysis method. Moreover, homogenizer and ultrasound devices were applied to produce the CNCs with minimum hazardous solvents in the preparation steps. The physicochemical characteristics of CNCs, such as color, size, yield, and swelling capacity plus their characterization using X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR) were studied. The mean equivalent spherical diameter of the fabricated CNCs was about 130 nm and the production efficiency was 91.5%. Besides, the swelling capacity of CNCs was 1.5-fold of cellulose with a swelling of 400%. The crystallinity degree of the cellulose obtained from walnut shell was 49%, which was improved following acidic and alkali hydrolysis (60%). TGA analysis revealed that the thermal stability of the CNCs was lower than cellulose; moreover, the FTIR results demonstrated that there is not a considerable difference between normal cellulose and CNCs. Overall, it was concluded that walnut shell-derived CNCs have the potential to be employed as promising nanocarriers in different sectors, especially in the food and drug delivery sectors.

Ambient fine particles (PM2.5 ) attenuate collagen-induced platelet activation through interference of the PLCγ2/Akt/GSK3β signaling pathway.

It has been proven that carbon nanoparticles or diesel exhaust particles stimulate platelet activation. However, the effect of fine particle matter (PM2.5 ) on platelet activation remains unknown, which motivates this study. PM2.5 samples were collected in an urban area of Zhengzhou, China. To study the morphological characteristics and the mass concentrations of trace elements of PM2.5 samples, a filed-emission scanning electron microscope, the Image-J software, and an inductively coupled plasma mass spectrometry were used. Washed human platelets or platelet-rich-plasma were used to study the effect of PM2.5 on platelet aggregation, P-selectin expression, or platelet signaling pathways. The cytotoxicity in platelets exposed to PM2.5 was evaluated by a lactate dehydrogenase assay kit. In addition, platelet adhesion and spreading were studied on collagen-coated surfaces in stable conditions. The filed-emission scanning electron microscope scanning showed that PM2.5 samples varied in shape and size distributions. The mean equivalent spherical diameter of these particles was 1.97 ± 0.04 μm, of which 82.40% were particles with equivalent spherical diameters of less than 2.5 μm. The mass concentration of Ca was higher than that of other elements. The other elements followed the trend of Al>Fe>Zn>Mg>Pb>K>Mn>Cu>Ti>Ba>As>Sr>Sn>Sb>Cd>B>Se>Mo>Ag>Ni>TI>V>Co. Furthermore, pretreatment of PM2.5 significantly inhibited rather than potentiated collagen-induced platelet aggregation and P-selectin expression, whereas it had no significant effect on ADP-induced platelet aggregation and P-selectin expression. The lactate dehydrogenase analysis showed trivial cytotoxic effect of PM2.5 exposure on platelets. Pretreatment of PM2.5 inhibited platelet adhesion on immobilized collagen-coated surfaces; however, it almost did not impact the platelet spreading. Immunoblotting analysis indicated that PM2.5 reduced collagen-induced phosphorylation of phospholipase C gamma-2 (PLCγ2) at Tyr759, Akt at Ser473, and glycogen synthase kinase 3β (GSK3β) at Ser9. PM2.5 attenuated collagen-induced platelet aggregation, α-granule secretion and adhesion, with the potential mechanism of impairing PLCγ2, Akt, and GSK3β signaling. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 530-540, 2017.

Effect of Surface Charge and Elemental Composition on the Swelling and Delamination of Montmorillonite Nanoclays Using Sedimentation Field-flow Fractionation and Mass Spectroscopy

AbstractThe swelling properties of smectite-type clay particles (including montmorillonite) are of interest in various industries. A fundamental understanding of the surface properties of smectite particles at the sub-micron level would facilitate investigation of the effect of distributed properties such as charge and elemental composition. Swelling and delamination of SWy-2 Na-montmorillonite (Na-Mnt) nano-clay particles were studied here using size distributions obtained by sedimentation field-flow fractionation (SdFFF). Fractions were examined by electron microscopy and inductively-coupled optical emission spectroscopy (ICP-OES). Two distinct populations were observed in the size distribution of SWy-2 Na-Mnt particles (bimodal size distribution), with mean equivalent spherical diameters of ~60 nm and 250 nm, respectively. In contrast, the size distribution of STx-1 Ca-montmorillonite (Ca-Mnt) particles showed only one peak with a mean equivalent spherical diameter of ~410 nm, which changed to 440 nm after 4 days of hydration. Analyses of the fractions by ICP-OES obtained along the size distribution of Na-Mnt showed an abundance of Ca and Mg in the fractions below 250 nm, and confirmed the presence of Fe and Mg as isomorphous substituents. Electron micrographs of the fractions obtained from Na-Mnt size distributions were used to calculate the thickness of the clay particles. Bridging forces between pure orMgsubstituted montmorillonite and either Ca2+ or Na+ were calculated using semi-empirical methods. The results demonstrated that swelling and delamination of Na-Mnt clay particles are dictated by properties such as elemental composition and surface charge which are distributed along the size distribution.

Production and Characterization of Encapsulated Potassium Permanganate for Sustained Release as an in Situ Oxidant

Potassium permanganate (KMnO4) has been widely applied as an oxidant for in situ remediation of contaminated groundwater and soil. This study describes the creation and characterization of encapsulated KMnO4 particles, the purpose of which is to serve as a material that can be specifically targeted and delivered to a contaminant source zone for optimal oxidative destruction of the contaminant. Multinuclear particulate KMnO4 with a mean equivalent spherical diameter of 15 (± 8.6) μm was incorporated into a paraffin wax matrix and then pulverized, resulting in completely or partially encapsulated particles with a mean equivalent spherical diameter of 874 (± 377) μm. Paraffin wax is biodegradable and insoluble in water, and yet is very soluble in most hydrophobic contaminants, including chlorinated solvents such as perchloroethylene (PCE). Thus, KMnO4 is released very slowly into water from the encapsulating matrix, but the oxidant is rapidly released into PCE. The release kinetics of KMnO4 from the encapsul...

Preliminary studies of airborne particulate emmisions from the Ampellum S.A. copper smelter, Zlatna, Romania

Preliminary studies have been carried on the characterization of particulate emissions from the Ampellum S.A. copper smelter in the town of Zlatna, Romania. The particulates studied were collected on polycarbonate filters using air pump apparatus and on the surfaces of lichens. Mass of total suspended particulates (TSP) and PM10 varied from 19 to 230 μg/m3 and 3 to 146 μg/m3, respectively (PM10/TSP = 0.14 to 1.0), depending on wind direction and proximity to the smelter. Particulates on collection filters from a site directly downwind from the smelter have a mean equivalent spherical diameter (ESD) of 0.94 μm (s.d. 1.1) and are dominantly made up of material with the composition of anglesite (PbSO4). The remainder of the material is a heterogeneous mixture of silicates and Fe-, Pb- and Cu-bearing phases. Particulates > 5 μm ESD are rare on the TSP filters, mainly due to the restricted sampling durations possible with the equipment used (<3 hours). Particulates have therefore been studied in the lichen Acarospora smaragdula, which was growing on posts downwind from the smelter and which was found to contain high levels and a broader range of particulates compared with the filters (<5 to 100 μm in diameter). Larger particles include 20-30 μm diameter Fe-rich spherules, which occasionally have Pb- and S-rich encrustations on their surfaces. The nature and possible health effects of the particulates are discussed and recommendations made for future studies.

Removal efficiency of the dinoflagellate Heterocapsa triquetra by phosphatic clay, and implications for the mitigation of harmful algal blooms

An increased incidence of harmful algal blooms (HABs) has been reported in nearshore coastal waters, including economically important aquaculture sites worldwide. This has generated interest in using ecologically inert clays as a means of mitigating HABs at relatively shallow enclosed mariculture sites. This proposed mitigation measure assumes that flocculation and accelerated sedi- mentation of large algal cells (dinoflagellates) occurs with the application of clays. The objective of the current research was to characterize suspended clay-algal interactions and in situ particle size in a laboratory application of the phosphatic clay IMC-P (1.8 µm mean equivalent spherical diameter, ESD) to a simulated Heterocapsa triquetra (14.7 µm mean ESD) bloom. Flow speed was adjusted to provide 2 contrasting regimes (mimicking possible field conditions). This research was conducted in a recirculating flume and used a novel in situ device, the small volume particle microsampler (SVPM), for particle size characterization. Results indicated that 100% of the thecate dinoflagellate H. triquetra was removed in 48 h by IMC-P in a low-flow ( 13 cm s -1 ) regime. The mechanism for algal removal is equivocal since SVPM filter photographs indicated that clay aggregated to form particles >3 µm, but did not aggregate with algal cells under the experimental conditions tested. At this particle size, the clay aggregates become available for retention with 100% efficiency on the gills of suspension-feeding bivalves, which could be seriously affected by the increased particle flux to the bottom. The mecha- nism of cell removal by clays has not been identified; however, it may occur via direct effects of clay on cell surface properties and swimming ability. Further investigations on the removal mechanism are required to predict the fate of cells in a field application of clay.

Planktonic ciliates of the North American Great Lakes: Lakes Superior, Huron, Erie, and Ontario

Lakewide information about the planktonic ciliates of the North American Great Lakes has been lacking. Previously published data are limited spatially and temporally and based on few samples. This article focuses on ciliates sampled in lakewide longitudinal surveys conducted by Fisheries and Oceans Canada in four of the Great Lakes. Extensive sampling (n = 442) was conducted at stations distributed across Lakes Superior, Huron, Erie, and Ontario in various years from 1979–2000. The study focuses on abundance, biomass, and size spectrum. Our data demonstrate that ciliates contribute significantly to the planktonic communities of the Great Lakes. Mean abundance ranged from &amp;lt;1.0 to &amp;gt;14,000 l−1. Mean biomass ranged from &amp;lt;1.0 to &amp;gt;680 mg m-3. The mean abundance and biomass values are comparable to those reported earlier by other investigators from Great Lakes and other temperate lakes. Abundance and biomass differences, between the upper and lower Great Lakes, decreased from the 1980s compared to 1990s sampling when four- to ten-fold and two-fold decreases were recorded for the lower and upper Great Lakes, respectively. The six most common genera in these samples were Askenasia, Halteria, Balanion, Strobilidium, Strombidium, and Urotricha. The ciliate community was dominated by cells &amp;lt;30 μm equivalent spherical diameter. Pre- and post-zebra mussel size spectra of ciliates were compared for Lakes Erie and Ontario. The mean equivalent spherical diameter was significantly greater in Lake Erie in the post years compared to pre-mussel period. On the other hand, in Lake Ontario the mean diameter was significantly greater in the pre-mussel period than the post. It is likely that shifts in these distributions may be due to shifts in the relative abundance of the prey species of the ciliates. Among other factors, zebra mussels may be indirectly influencing the size-frequency distribution of the ciliate community.

Ciliated protozoa in Lake Nakuru, a shallow alkaline-saline lake in Kenya: Seasonal variation, potential production and role in the food web

Six sampling sites in Lake Nakuru were sampled monthly for 8 months spanning rainy and dry seasons, and including an interval when Spirulina-dominated the phytoplankton community. A total of 33 species in 29 genera were observed. Small bacterivorous ciliates, especially Cyclidium, were numerically dominant, but the greatest biomass was due to the large ciliate Condylostoma. Abundance ranged from 10.4 to 14,200 ciliates mL -1 (mean ± SE = 1,150 ± 309 ciliates mL -1 ) while biomass ranged from 0.017 to 500 mg C.L -1 (mean 18.2 ± 10.8 mg C.L -1 ). Ciliates were generally large (mean equivalent spherical diameter 43 μm) compared to previous studies of marine or freshwater plankton. Using published maximum growth rates for the species, we calculated that ciliate production could be as much as 6.4 ± 2.3 mg C L -1 , which is higher than previous estimates of primary production, and indicates that ciliates probably play a major role in energy flow in this system. Most of the estimated production was by large ciliates, the algivorous Frontonia (58 %) and the predacious Condylostoma (33 %), while the more numerous bacterivores contributed only 4%.

Particle size and morphology of UHMWPE wear debris in failed total knee arthroplasties––a comparison between mobile bearing and fixed bearing knees

Osteolysis induced by ultrahigh molecular weight polyethylene wear debris has been recognized as the major cause of long-term failure in total joint arthroplasties. In a previous study, the prevalence of intraoperatively identified osteolysis during primary revision surgery was much higher in mobile bearing knee replacements (47%) than in fixed bearing knee replacements (13%). We postulated that mobile bearing knee implants tend to produce smaller sized particles. In our current study, we compared the particle size and morphology of polyethylene wear debris between failed mobile bearing and fixed bearing knees. Tissue specimens from interfacial and lytic regions were extracted during revision surgery of 10 mobile bearing knees (all of the low contact stress (LCS) design) and 17 fixed bearing knees (10 of the porous-coated anatomic (PCA) and 7 of the Miller/Galante design). Polyethylene particles were isolated from the tissue specimens and examined using both scanning electron microscopy and light-scattering analyses. The LCS mobile bearing knees produced smaller particulate debris (mean equivalent spherical diameter: 0.58 μm in LCS, 1.17 μm in PCA and 5.23 μm in M/G) and more granular debris (mean value: 93% in LCS, 77% in PCA and 15% in M/G).

The small volume particle microsampler (SVPM): a new approach to particle size distribution and composition

The characterization of trophically and geochemically important suspended particulate matter (SPM) has traditionally relied on bottle sampling and subsequent analysis with Coulter Multisizers and other instruments, which are not sufficient in preserving the in situ size, shape and composition of aggregated particles. The small volume particle microsampler (SVPM) is a sampling device that captures individual particles on filters with minimal disturbance for microscope image analysis of size distribution and composition. Sand grains, microalga ( Dunaliella tertiolecta) and laboratory cultivated flocs were used to test the SVPM's ability to determine particle size. For statistical analysis of the SVPM's capabilities, sand grain and algal size distribution, calculated as equivalent spherical diameter (ESD), were compared to Multisizer data while video images provided a comparison for the flocs. Non-aggregated sand particles sampled by the SVPM showed a size distribution that was similar to that of the Multisizer. Aggregated D. tertiolecta flocs were broken up by the Multisizer, and SVPM data indicated a significantly greater mean ESD. The SVPM showed significantly smaller mean ESDs than the video images because of the higher resolution of the sampler for small particles. In terms of particle concentration, the microsampler measured values similar to those of the Multisizer and video camera. The most important feature of the SVPM is its ability to capture aggregates for the analysis of composition, by histological stains or other means. The SVPM is an alternative method of sampling that is more effective in preserving aggregates for laboratory analyses and is less complicated and expensive than in situ optical sampling techniques, especially in documenting the lower end of the particle size spectrum.

Influence of aggregate architecture and minerals on living habitats and soil organic matter

We used an integrated approach to determine the effects of soil particle architecture and minerals on living habitats and soil organic matter (SOM). Macroaggregate (&gt; 250 µm), microaggregate 1 (50–250 µm), and microaggregate 2 (&lt; 50 µm) fractions of adjacent forested and cultivated Gleysolic soil were obtained by wet sieving. The forested site was used as a reference to evaluate the effects of cultivation on soil particle architecture. Aggregates and respective clay fractions were characterized using optical, chemical, physical and microbial methods. Microaggregates 1 had primary particles with the largest mean equivalent spherical diameter (ESD) and void volume of all aggregate fractions. These physical characteristics were paralleled by the highest SOM and microbial biomass content, and number of microorganisms. Cultivation increased the weathering of primary particles and SOM loss, and decreased the content of microbial pools, suggesting deteriorated living habitats. Soil organic C content in aggregates correlated significantly with the amount of ammonium oxalate extractable Al, chloritized vermiculite, and vermiculite, and was inversely associated with the total clay content. The mean ESD of primary particles and expandable phyllosilicates of aggregates influenced living habitats by supplying substrates, and providing different void and protective space for soil microorganisms. Key words: Aggregate, mean equivalent spherical diameter, bacteria, fungi, actinomycetes, microbial biomasss, organic carbon, vermiculite, non-crystalline inorganic soil components

Benoxaprofen, a New Anti-Inflammatory Agent: Particle-Size Effect on Dissolution Rate and Oral Absorption in Humans

The particle-size effect of benoxaprofen, a new nonsteroidal anti-inflammatory agent, on the in vitro dissolution rate and oral absorption in humans was evaluated. Ten normal subjects participated in a randomized crossover-designed absorption study with two sieved particle-size formulations: one with crystals larger than 60 mesh (mean equivalent spherical diameter = 640 μ) and the other with crystals smaller than 100 mesh (mean equivalent spherical diameter = 67 μ). Plasma drug concentrations and urinary drug excretion were used to determine the relative absorption of the two formulations. The standard USP procedure was used for the dissolution study. Particle size had a dramatic effect on both the in vitro drug dissolution and its oral absorption in humans. In vitro, the smaller crystals dissolved more rapidly and more efficiently than the larger crystals. In vivo, the smaller crystals produced higher plasma concentrations, more rapid peak concentration attainment, and more drug excreted in the urine.