•Automatic measurement of particle size distribution from micrographs.•The proposed algorithm is mainly based on local adaptive Canny edge detection and modified circular Hough transform.•The ...robustness and reliability of the algorithm were verified by several micrographs with different complexity.
To obtain size distribution of nanoparticles, scanning electron microscope (SEM) and transmission electron microscopy (TEM) have been widely adopted, but manual measurement of statistical size distributions from the SEM or TEM images is time-consuming and labor-intensive. Therefore, automatic detection methods are desirable. This paper proposes an automatic image processing algorithm which is mainly based on local adaptive Canny edge detection and modified circular Hough transform. The proposed algorithm can utilize the local thresholds to detect particles from the images with different degrees of complexity. Compared with the results produced by applying global thresholds, our algorithm performs much better. The robustness and reliability of this method have been verified by comparing its results with manual measurement, and an excellent agreement has been found. The proposed method can accurately recognize the particles with high efficiency.
Mixed‐Matrix Membranes Dechnik, Janina; Gascon, Jorge; Doonan, Christian J. ...
Angewandte Chemie International Edition,
August 1, 2017, Volume:
56, Issue:
32
Journal Article
Peer reviewed
Open access
Research into extended porous materials such as metal‐organic frameworks (MOFs) and porous organic frameworks (POFs), as well as the analogous metal‐organic polyhedra (MOPs) and porous organic cages ...(POCs), has blossomed over the last decade. Given their chemical and structural variability and notable porosity, MOFs have been proposed as adsorbents for industrial gas separations and also as promising filler components for high‐performance mixed‐matrix membranes (MMMs). Research in this area has focused on enhancing the chemical compatibility of the MOF and polymer phases by judiciously functionalizing the organic linkers of the MOF, modifying the MOF surface chemistry, and, more recently, exploring how particle size, morphology, and distribution enhance separation performance. Other filler materials, including POFs, MOPs, and POCs, are also being explored as additives for MMMs and have shown remarkable anti‐aging performance and excellent chemical compatibility with commercially available polymers. This Review briefly outlines the state‐of‐the‐art in MOF‐MMM fabrication, and the more recent use of POFs and molecular additives.
Challenging separations: The need for greater energy efficiency and the maximum use of limited resources has focused attention on improved separation technologies. For gas separations, mixed‐matrix membranes can provide enhanced separation performance and lead to more energy‐efficient, sustainable, and cost‐effective commercial applications.
•Clay content affects the size distribution of small soil microaggregates (<20 μm).•At <30% clay, free & occluded small microaggregates have similar size distribution.•At >30% clay, small ...microaggregates contained fine colloids (<1 μm).•Lower clay contents promote organic carbon enrichment in small microaggregates.
As soil microaggregates (<250 μm, SMA) usually withstand long-term tillage, we hypothesized that i) elevated clay contents in arable soil support aggregation already at microaggregate level, leading to ii) increasing organic carbon (SOC) enrichment in smaller SMA size fractions. To test these hypotheses we sampled the topsoil (5–20 cm) of Luvisols with a long history of agricultural management at the Scheyern experiment station (Germany) in quintuplicates from each of five subsites with different clay contents (19–34%). The field-fresh topsoil was fractionated into macroaggregates (8000–250 μm), large SMA (250–20 μm), and small SMA (<20 μm) and the mass distribution was recorded. In addition, the water stable macroaggregates (>250 μm) were dispersed ultrasonically to study occluded SMA and single building units. Finally, we analyzed the size distribution of the small SMA by laser diffraction analysis. The total mass distribution of free and occluded SMA grouped soils into those with small (19, 22, and 24%) and large (32 and 34%) clay contents. The finer textured soils exhibited larger portions of occluded SMA, with a gamma size distribution of small SMA peaking at 6 μm. Yet the occluded small SMA in the finer textured soils showed an additional enrichment of colloids <1 μm. The SOC was indeed enriched in finer fractions, but more in the small SMA of the coarse textured sites than in the finer textured ones, whereas the opposite was true for the large SMA. We conclude, therefore, that elevated contents of clay-sized particles promote SMA formation and stabilization, therewith shifting SOC enrichment from small to larger SMA.
A remarkable feature of active matter is the propensity to self-organize. One striking instance of this ability to generate spatial structures is the cluster phase, where clusters broadly distributed ...in size constantly move and evolve through particle exchange, breaking or merging. Here we propose an exhaustive description of the cluster dynamics in apolar active matter. Exploiting large statistics gathered on thousands of Janus colloids, we measure the aggregation and fragmentation rates and rationalize the resulting cluster size distribution and fluctuations. We also show that the motion of individual clusters is entirely consistent with a model positing random orientation of colloids. Our findings establish a simple, generic model of cluster phase, and pave the way for a thorough understanding of clustering in active matter.
Display omitted
•Large aggregates deeply modify electromagnetic energy absorbed by photocatalysts.•Photodegradation rate was proportional to quantum efficiency at lower TiO2 loadings.•For larger TiO2 ...loadings, photoactivity was mostly related to aggregation particle.•Photocatalytic responses are fundamentally controlled by the absorbed radiation.
This work examines the important role of light power absorbed by TiO2 on the photocatalytic degradation of dichloroacetic acid (DCA) in a semi-continuous slurry photoreactor with UV–Vis radiation. This system is an excellent model for understanding the light matter interaction, because DCA is transparent and the acid pH of the solution prevents the formation of large TiO2 aggregates. Under these conditions, the light power absorbed by four different commercial Titania photocatalysts, along the whole volume of the reactor, has been quantitatively calculated by assuming a Mie scattering model on a distribution of different particle sizes. Although the different chemical nature of the four considered samples (three of them provided by the Evonik Company, P25, P25/20 and P90, together with Hombikat UV 100), and the different catalytic efficiency based on weight, we have found that all the catalytic responses are fundamentally controlled by the absorbed radiation in the four samples. Therefore, in the studied samples, any difference in the catalytic behavior is only due to the light-matter interaction being of lesser importance other mechanisms, as space-charge blocking.
In a comprehensive study of microplastic contamination in southern Germany, 1167 individual fish of 22 different species were sampled from 11 rivers and 6 lakes across the state. The microplastic ...burden of investigated fish was analyzed on the basis of habitat type, location, and a number of abiotic and biotic factors. A particle size distribution analysis of the detected microplastics was carried out. The results showed a relatively low plastic prevalence of 18.8%, with significant differences between rivers (20.6%) and lakes (16.5%). The number of ingested plastic particles ranged between 1 and 4 particles per fish. The majority of abiotic and biotic factors seem to play little or no role in the ingestion of microplastics, suggesting that in most cases uptake is passive or accidental. It is notable that piscivorous fish appeared significantly less burdened, suggesting a low transfer rate and no accumulation in the food web. However, size distribution analysis identified a power law growth fit in particle numbers at the smallest end of the distribution. This carries a worrying implication, that >95% of particles are likely to be smaller than 40 μm and thereby beyond the detection range of this and most other microplastic surveys conducted so far. When the frequency development of small particles is taken into account, the likely microplastic prevalence in the present study increases to 100%, with an average intensity of around 23 predominantly small particles per fish. A striking 70% of those particles would be smaller than 5 μm and therefore eligible for translocation into tissues, with critical implications for fish health and consumer exposure. This raises a question as to whether current estimates of microplastic burden in fishes generally might be overlooking a majority of potential contamination within the critical smaller particle size classes.
Display omitted
•A comprehensive study to examine microplastic burden in fishes was carried out•Ingested microplastics were detected in around one fifth of examined fishes•Piscivorous fish were significantly less burdened, indicating a excretory effect•Models indicate a hyperbolic increase of particle number with decreasing size•95% of particles are <40 μm and thus not detectable by current methods.
Group C particles possess great potential in gas-phase catalytic reactions due to the large specific surface area. This work focuses on the effects of particle size distribution (PSD), average ...particle diameter, and addition of nano-additive on the flowability and fluidization quality of Group C and Group A powders. Virgin Group C powders are hard to fluidize, but with the so-called nano-modulation, Group C powders exhibit readily detectable minimum fluidization velocity (Umf), high bed expansion and large dense-phase voidage. After nano-modulation, Group C particles with a wider PSD show higher bed expansion, indicating better gas-solid contact. On the other hand, a narrower PSD contributes to better flowability, higher normalized pressure drop, and lower Umf. For Group C particles with the same span, a smaller particle size improves bed expansion. Comparative studies also show that the influence of PSD is more significant for Group C particles than for Group A particles.
Display omitted
•Group C particles is more sensitive to PSD compared with Group A particles.•A narrow PSD leads to good flowability, high normalized pressure drop, and low Umf.•For Group C particles, a wider PSD generally brings higher bed expansion.•Addition of nanoparticles develops the gas-holding ability of Group C powders.
This study aimed to evaluate the potential of β-cyclodextrin combination with different wall materials (gum arabic and sodium caseinate) in the microencapsulation of refined kenaf seed oil by spray ...drying. Three models of microcapsules were developed, including protein-based (β-cyclodextrin/sodium caseinate), carbohydrate-based (β-cyclodextrin/gum arabic) and mixed-based (β-cyclodextrin/gum arabic/sodium caseinate). The characteristics of the obtained microcapsules including moisture content, water activity, wettability, solubility, density, flowability, cohesiveness, bulk porosity, microencapsulation efficiency, particle size, surface morphology, and possible interactions between the oil and wall materials were evaluated. The moisture content and water activity were in the range of 2.7–3.9% and 0.2 to 0.3, respectively, which is suitable for long-term storage. The obtained microcapsules showed a particle size distribution (D4,3) of 25.4–37.3 μm. Scanning electron micrographs of microcapsules showed spherical shapes without any apparent cracking on the surfaces. Fourier transform infrared spectroscopy revealed that the oil was well encapsulated in the microcapsules. The highest microencapsulation efficiency was achieved for the carbohydrate-based microcapsule (95.3%), followed by the protein-based microcapsule (93.1%) and mixed-based microcapsule (90.0%). Three formulations offered high microencapsulation efficiency to encapsulate the refined kenaf seed oil in this study.
Display omitted
•Three different formulations (β-cyclodextrin/gum arabic/sodium caseinate) were developed for encapsulation.•Different combinations of wall materials were significantly affected the physical characteristics.•Three formulations offered a higher microencapsulation efficiency to encapsulate the refined kenaf seed oil.
Over the past few decades, metal nanoparticles less than 100 nm in diameter have made a substantial impact across diverse biomedical applications, such as diagnostic and medical devices, for ...personalized healthcare practice. In particular, silver nanoparticles (AgNPs) have great potential in a broad range of applications as antimicrobial agents, biomedical device coatings, drug-delivery carriers, imaging probes, and diagnostic and optoelectronic platforms, since they have discrete physical and optical properties and biochemical functionality tailored by diverse size- and shape-controlled AgNPs. In this review, we aimed to present major routes of synthesis of AgNPs, including physical, chemical, and biological synthesis processes, along with discrete physiochemical characteristics of AgNPs. We also discuss the underlying intricate molecular mechanisms behind their plasmonic properties on mono/bimetallic structures, potential cellular/microbial cytotoxicity, and optoelectronic property. Lastly, we conclude this review with a summary of current applications of AgNPs in nanoscience and nanomedicine and discuss their future perspectives in these areas.
Understanding the particle size distribution in the air and patterns of environmental contamination of SARS-CoV-2 is essential for infection prevention policies. Here we screen surface and air ...samples from hospital rooms of COVID-19 patients for SARS-CoV-2 RNA. Environmental sampling is conducted in three airborne infection isolation rooms (AIIRs) in the ICU and 27 AIIRs in the general ward. 245 surface samples are collected. 56.7% of rooms have at least one environmental surface contaminated. High touch surface contamination is shown in ten (66.7%) out of 15 patients in the first week of illness, and three (20%) beyond the first week of illness (p = 0.01, χ
test). Air sampling is performed in three of the 27 AIIRs in the general ward, and detects SARS-CoV-2 PCR-positive particles of sizes >4 µm and 1-4 µm in two rooms, despite these rooms having 12 air changes per hour. This warrants further study of the airborne transmission potential of SARS-CoV-2.
PDF
