Mobile samplers of particulate matter - Flying omnivorous insects in detection of industrial contamination.

Flying insects are potential mobile samplers of airborne particulate matter (PM). However, current knowledge on their susceptibility to PM is limited to pollinators. Insects' capacity for particle surface accumulation depends on the lifestyle, structure of the body integuments, and behavioral patterns. Here, we investigate how two species of flying omnivorous insects from the genus Vespula, possessing direct interactions with air, soil, plants, and herbivores, indicate industrial pollution by accumulating coarse (PM10) and fine (PM2.5) particles on their bodies. The internal accumulation of particles in wasps' gut tissues is assessed considering heavy metals exposure to reveal and discuss the potential magnitude of ecotoxicological risks. Female individuals of Vespula vulgaris and V. germanica were sampled with a hand-netting near to Harjavalta Cu-Ni smelter and in the control areas in southwestern Finland. They were analyzed with light microscopy (LM), electron microscopy (SEM, TEM), and energy-dispersive X-ray spectroscopy (EDX) methods. Near to the smelter, wasps trapped significantly more particles, which were of bigger size and their surface optical density was higher. Vespula vulgaris accumulated larger particles than V. germanica, but that wasn't associated with morphological characteristics such as body size or hairiness. In both areas, accumulated surface PM carried clays and silicates. Only in polluted environments PM consistently contained metallic and nonmetallic particles (from high to moderate weight %) of Fe, Ni, Cu, and S - major pollutants emitted from the smelter. Wasps from industrially polluted areas carried significantly more granules in the columnar epithelial midgut cells. TEM-EDX analyses identified those structures were associated with metal ions such as Cr, Cu, Ni, and Fe. As epithelial gut cells accumulated metal particles, midgut confirmed as a barrier for metal exposure in wasps. External PM contamination in wasps is suggested as a qualitative, yet a natural and simple descriptor of local industrial emissions.

Submicron Plastic Adsorption by Peat, Accumulation in Sphagnum Mosses and Influence on Bacterial Communities in Peatland Ecosystems.

The smallest fraction of plastic pollution, submicron plastics (SMPs <1 µm) are expected to be ubiquitous in the environment. No information is available about SMPs in peatlands, which have a key role in sequestering carbon in terrestrial ecosystems. It is unknown how these plastic particles might behave and interact with (micro)organisms in these ecosystems. Here, we show that the chemical composition of polystyrene (PS) and poly(vinyl chloride) (PVC)-SMPs influenced their adsorption to peat. Consequently, this influenced the accumualtion of SMPs by Sphagnum moss and the composition and diversity of the microbial communities in peatland. Natural organic matter (NOM), which adsorbs from the surrounding water to the surface of SMPs, decreased the adsorption of the particles to peat and their accumulation by Sphagnum moss. However, the presence of NOM on SMPs significantly altered the bacterial community structure compared to SMPs without NOM. Our findings show that peatland ecosystems can potentially adsorb plastic particles. This can not only impact mosses themselves but also change the local microbial communities.

Influence of induction-annealing temperature on the morphology of barley-straw-derived Si@C and SiC@graphite for potential application in Li-ion batteries.

Silicon, a material with high theoretical energy density, holds great promise as a candidate material for anodes in lithium-ion batteries. However, due to an alloying mechanism the material undergoes volume expansion of up to 300%, which results in rapid capacity fading. The coating of silicon with carbon is done by using a biomass-based carbon precursor. The effects of annealing temperature on the morphology of the silicon-carbon structures is presented herein. The mechanically and chemically treated barley straw is mixed with silicon particles and induction annealed in argon atmosphere under different temperatures. The material transformation from carbon-coated silicon (Si@C) to graphite-coated silicon carbide (SiC@graphite) is studied. The Si@C displayed initial specific capacity of 1200 mAh g-1 at 0.1 A g-1, while the capacity retention analysis of Si@C revealed improved cycling stability compared to bare silicon.

Detection of amorphous-amorphous phase separation in small molecular co-amorphous mixtures with SEM-EDS.

Amorphicity is one possible way to increase the solubility of poorly water soluble drugs. However, amorphous solids are thermodynamically unstable and tend to recrystallize with material-specific kinetics. Crystallization is not the prime phenomenon in the whole process, although it is the easiest to measure. The primary phenomenon prior to the crystallization of glass is phase separation, the detection of which is very rarely reported among small molecular compounds. In the present study, a scanning electron microscope with energy dispersive X-ray spectrometer (SEM-EDS) was used to detect very early stage amorphous-amorphous phase separation in co-amorphous drug mixtures. Miscibility was calculated for five studied mixtures based on the Flory-Huggins method and four immiscible pairs and one partial miscible pair were selected for the laboratory experiments. Co-amorphous samples (n = 3) were prepared by melt-quench method and stored at the elevated temperature to induce the separation of amorphous phases. Each sample was stored at the same relative percentage temperature between glass transition temperature Tg and melting temperature Tm. Immediately after the sample preparation, the full amorphousness was verified with polarizing light microscopy. Before SEM-EDS analysis, the samples were fractured into two pieces and measurements were done from cross-section (from the bulk sample). All five pairs phase separated during two days of storage at the elevated temperature. The study proved that SEM-EDS was able to detect a very small phase separated regions in the amorphous sample, as amorphous-amorphous phase separation was detected in four out of five pairs. However, the surface roughness could affect the analysis and give a false indication of phase separation. SEM-EDS also supported calculation results, since every studied pair showed phase separation during study, as was predicted on the grounds of Flory-Huggins miscibility calculation.

Physicochemical Characterization of Aerosol Generated in the Gas Tungsten Arc Welding of Stainless Steel.

OBJECTIVES: Exposure to stainless steel (SS) welding aerosol that contain toxic heavy metals, chromium (Cr), manganese (Mn), and nickel (Ni), has been associated with numerous adverse health effects. The gas tungsten arc welding (GTAW) is commonly applied to SS and produces high number concentration of substantially smaller particles compared with the other welding techniques, although the mass emission rate is low. Here, a field study in a workshop with the GTAW as principal welding technique was conducted to determine the physicochemical properties of the airborne particles and to improve the understanding of the hazard the SS welding aerosols pose to welders. METHODS: Particle number concentration and number size distribution were measured near the breathing zone (50cm from the arc) and in the middle of the workshop with condensation particle counters and electrical mobility particle sizers, respectively. Particle morphology and chemical composition were studied using scanning and transmission electron microscopy and energy-dispersive X-ray spectroscopy. RESULTS: In the middle of the workshop, the number size distribution was unimodal with the geometric mean diameter (GMD) of 46nm. Near the breathing zone the number size distribution was multimodal, and the GMDs of the modes were in the range of 10-30nm. Two different agglomerate types existed near the breathing zone. The first type consisted of iron oxide primary particles with size up to 40nm and variable amounts of Cr, Mn, and Ni replacing iron in the structure. The second type consisted of very small primary particles and contained increased proportion of Ni compared to the proportion of (Cr + Mn) than the first agglomerate type. CONCLUSIONS: The alterations in the distribution of Ni between different welding aerosol particles have not been reported previously.

Release and characteristics of fungal fragments in various conditions.

Intact spores and submicrometer size fragments are released from moldy building materials during growth and sporulation. It is unclear whether all fragments originate from fungal growth or if small pieces of building materials are also aerosolized as a result of microbial decomposition. In addition, particles may be formed through nucleation from secondary metabolites of fungi, such as microbial volatile organic compounds (MVOCs). In this study, we used the elemental composition of particles to characterize the origin of submicrometer fragments released from materials contaminated by fungi. Particles from three fungal species (Aspergillus versicolor, Cladosporium cladosporioides and Penicillium brevicompactum), grown on agar, wood and gypsum board were aerosolized using the Fungal Spore Source Strength Tester (FSSST) at three air velocities (5, 16 and 27 m/s). Released spores (optical size, dp ≥ 0.8 µm) and fragments (dp ≤ 0.8 µm) were counted using direct-reading optical aerosol instruments. Particles were also collected on filters, and their morphology and elemental composition analyzed using scanning electron microscopes (SEMs) coupled with an Energy-Dispersive X-ray spectroscopy (EDX). Among the studied factors, air velocity resulted in the most consistent trends in the release of fungal particles. Total concentrations of both fragments and spores increased with an increase in air velocity for all species whereas fragment-spore (F/S) ratios decreased. EDX analysis showed common elements, such as C, O, Mg and Ca, for blank material samples and fungal growth. However, N and P were exclusive to the fungal growth, and therefore were used to differentiate biological fragments from non-biological ones. Our results indicated that majority of fragments contained N and P. Because we observed increased release of fragments with increased air velocities, nucleation of MVOCs was likely not a relevant process in the formation of fungal fragments. Based on elemental composition, most fragments originated from fungi, but also fragments from growth material were detected.

Impact of Microscale and Pilot-Scale Freeze-Drying on Protein Secondary Structures: Sucrose Formulations of Lysozyme and Catalase.

Microscale (MS) freeze-drying offers rapid process cycles for early-stage formulation development. The effects of the MS approach on the secondary structures of two model proteins, lysozyme and catalase, were compared with pilot-scale (PS) vial freeze-drying. The secondary structures were assessed by attenuated total reflection Fourier transformed infrared spectroscopy. Formulations were made with increasing sucrose-protein ratios. Freeze-drying protocols involved regular cooling without thermal treatment and annealing with MS and PS equipment, and cooling rate variations with the MS. Principal component analysis of smoothed second-derivative amide I spectra revealed sucrose-protein ratio-dependent shifts toward α-helical structures. Transferability of sucrose-protein formulations from MS to PS vial freeze-drying was evidenced at regular cooling rates. Local differences in protein secondary structures between the bottom and top of sucrose-catalase samples could be detected at the sucrose-catalase ratios of 1 and 2, this being related to the initial filling height and ice crystal morphology. Annealing revealed temperature, protein, formulation, and sample location-dependent effects influencing surface morphology at the top, or causing protein secondary structure perturbation at the bottom. With the MS approach, protein secondary structure differences at different cooling rates could be detected for sucrose-lysozyme samples at the sucrose-lysozyme ratio of 1.

Real-time tablet formation monitoring with ultrasound measurements in eccentric single station tablet press.

A real-time ultrasound measurement system for tablet compression monitoring is introduced. The measurement system was tested in actual manufacturing environment and found to be capable of measuring the ultrasound response of the tabletting process from bulk to tablet. The tablet sets were compressed and the ultrasound measurements were conducted as implemented in eccentric single station tabletting apparatus in through transmission geometry. The speed of sound and ultrasound spectrum was measured during dynamic compression for microcrystalline cellulose/paracetamol tablets. The ultrasound system introduced in this study was found to be suitable for tabletting process monitoring as the mechanical properties of compressed tablets can be estimated during compression using the ultrasound system. In addition, it was found that the ultrasound was sensitive to the mixing time of magnesium stearate and the concentration of paracetamol. Thus, ultrasound measurements made during the compression can be used to monitor the tablet formation process.

Monitoring of swelling of hydrophilic polymer matrix tablets by ultrasound techniques.

The aim of this study was to investigate the ability of ultrasound (US) techniques to monitor the swelling behaviour of hydrophilic polymer matrix tablets. Tablets were prepared from hydroxypropyl methylcellulose (HPMC) and polyethylene oxide (PEO) polymers. The movement of the eroding front was investigated with ultrasound scanning techniques on each tablet's outer interface during tablet immersion in phosphate buffer (PB). In addition, a US window technique was utilized to simultaneously evaluate eroding and swelling front movements during the tablet dissolution process. An optical monitoring was used as the reference method. The focused pulsed echo ultrasound method was found to be applicable for evaluating the swelling process of hydrophilic polymer matrix tablets. Furthermore, it was noted that the sensitivity to follow hydrogel formation and thickening by US monitoring varied depending on the polymer under study. Thus, multifront detection is challenging since the hydrogels formed by different polymers may have totally different acoustic properties. It was found that the microbubbles formed inside the hydrogel were acting as a "contrast agent", characteristic of some polymers during immersion. In spite of these challenges, the US window technique introduced in this study was proven to be a promising method for simultaneous multifront detection.

In-line ultrasound measurement system for detecting tablet integrity.

An ultrasound measurement system for tablet defect detection is introduced. The measurement system was implemented in an eccentric single station tabletting apparatus, where ultrasound transducers were placed inside the upper and lower punches. These instrumented punches were then used to measure the speed of sound and ultrasound attenuation values in both intact and defective tablets made from dibasic calcium phosphate, microcrystalline cellulose and lactose monohydrate. Ultrasound attenuation was found to be a very sensitive method to discriminate defective tablets from intact ones. In addition, it was found that the determined ultrasound attenuation was different between all three materials used in this study, which indicates that different materials could be distinguished from one another by this detection method.