The content of microplastics (MP) in the environment is constantly growing. Since the environmental relevance, particularly bioavailability, rises with decreasing particle size, the knowledge of the ...MP proportion in habitats and organisms is of gaining importance. The reliable recognition of MP particles is limited and underlies substantial uncertainties. Therefore spectroscopic methods are necessary to ensure the plastic nature of isolated particles, determine the polymer type and obtain particle count related quantitative data. In this study Curie-Point pyrolysis-gas chromatography–mass spectrometry combined with thermochemolysis is shown to be an excellent analytical tool to simultaneously identify and optionally quantify MP in environmental samples on a polymer specific mass related trace level. The method is independent of any mechanical preselection or particle appearance. For this purpose polymer characteristic pyrolysis products and their indicative fragment ions were used to analyze eight common types of plastics. Further aspects of calibration, recoveries, and potential matrix effects are discussed. The method is exemplarily applied on selected fish samples after an enzymatic-chemically pretreatment. This new approach with mass-related results is complementary to established FT-IR and Raman methods providing particle counts of individual polymer particles.
In this first mass-related survey of microplastics (MPs, <1 mm) in the German Bight (North Sea, 2.5 m water depth), spatial load, temporal variations, and potential sources were examined. Relevant ...plastic types were detected using pyrolysis–gas chromatography–mass spectrometry/thermochemolysis (Py-GC/MS). This suitable method provides qualitative and trace-level polymer or polymer cluster-specific mass quantitative MP data. Neither MP concentration (2–1396 μg m–3) nor type distribution was homogeneous. Concentrations appeared to be substantially influenced by meteorological and oceanographic conditions. The coastal MP-type composition showed an overprint indicating a packaging waste-related signal. Considerably different compositions were observed in central and estuarine areas. Here, a close relation to marine (antifouling) coating particles, i.e., abrased chlorinated rubber-, acryl-styrene-, and epoxide binder-containing particles are hypothesized as the main MP source, indicating ship “skid marks”. They represent a dominant, toxicologically relevant but underestimated marine-based MP share, inverting the widely cited 80% terrestrial- to 20% marine-based debris ratio for MPs. In consequence of the findings, polymer clusters attributed to the basic polymers polyethylene, polypropylene, polystyrene, poly(ethylene terephthalate), poly(vinyl chloride), poly(methyl methacrylate), and polycarbonate are proposed for Py-GC/MS MPs mass determination based on specific thermal decomposition products linked to related polymer structural units.
Context. Blazar flares provide a window onto the extreme physical processes occurring in relativistic outflows. Most numerical codes used for modelling blazar emission during flares use a simplified ...continuous-loss description of particle cooling due to the inverse Compton (IC) process, neglecting non-continuous (discrete) effects that arise in the Klein–Nishina (KN) regime. The significance of such effects has not yet been explored in detail. Aims. In this study, we investigate the importance of non-continuous Compton cooling losses and their impact on the electron spectrum and spectral energy distribution (SED) of blazars during high flux states (flares), as well as in the low state. Methods. We solve the full transport equation numerically, accounting for large relative jumps in energy by extending our existing blazar flare modelling code EMBLEM. We perform a detailed physical modelling of the brightest γ -ray flare of the archetypal flat-spectrum radio quasar (FSRQ) 3C 279 detected in June 2015. We then compare results obtained using the full cooling term and using the continuous-loss approximation. Results. We show that during flaring states of FSRQs characterised by high Compton dominance, the non-continuous cooling can lead to significant modification of the electron spectrum, introducing a range of distinct features, such as low-energy tails, hardening and/or softening, narrow and extended particle excesses, and shifts in the cooling break position. Such distortion translates to differences in the associated SED of up to ∼50%. This highlights the importance of non-continuous effects and the need to consider them in blazar emission models, particularly applied to extreme γ -ray flares.
Four common consumer plastic samples (polyethylene, polystyrene, polyethylene terephthalate, polyvinylchloride) were studied to investigate the impact of physical parameters such as turbulence, ...salinity and UV irradiance on leaching behavior of selected plastic components. Polymers were exposed to two different salinities (i.e. 0 and 35g/kg), UV radiation and turbulence. Additives (e.g. bisphenol A, phthalates, citrates, and Irgafos® 168 phosphate) and oligomers were detected in initial plastics and aqueous extracts. Identification and quantification was performed by GC–FID/MS. Bisphenol A and citrate based additives are leached easier compared to phthalates. The print highly contributed to the chemical burden of the analyzed polyethylene bag. The study underlines a positive relationship between turbulence and magnitude of leaching. Salinity had a minor impact that differs for each analyte. Global annual release of additives from assessed plastics into marine environments is estimated to be between 35 and 917tons, of which most are derived from plasticized polyvinylchloride.
•None of the analyzed consumer plastics (PE, PET, PS and PVC) was chemically inert. Leaching was observed in all cases.•Turbulence strongly increases leaching of additives and PS oligomers.•Salinity alone, or combined with UV, while having an impact for each individual analyte, did not show a distinct, general trend on additive release.•Prints (here from PE) strongly contribute to the chemical burden of plastics.•Estimated from resulting data, between 35 and 917tons of additives are potentially leached into the oceans every year.
Summary
Background
Early colonization with bifidobacteria and lactobacilli is postulated to protect children from allergy, while Clostridium (C.) difficile colonization might be associated with ...allergic disease. Previous studies of infant gut microbiota in relation to subsequent allergy development have mostly employed culture‐dependent techniques, studied genera of bacteria and the follow‐up period was limited to 2 years.
Objective
To relate gut microbiota in early infancy, notably bifidobacteria and lactobacilli at species level, to allergy development during the first 5 years of life and study if environmental factors influence the early infant gut microbiota.
Methods
Fecal samples were collected at 1 week, 1 month and 2 months after birth from 47 Swedish infants, followed prospectively to 5 years of age. Bacterial DNA was analysed with real‐time PCR and related to allergy development, family size as well as endotoxin and Fel d 1 levels in house dust samples. Primers binding to C. difficile, four species of bifidobacteria, two lactobacilli groups and Bacteroides fragilis were used. Children regarded as allergic manifested allergic symptoms and were skin prick test positive during their first 5 years while non‐allergic children were neither.
Results
Children who developed allergy were significantly less often colonized with lactobacilli group I (Lactobacillus (L.) rhamnosus, L. casei, L. paracasei), Bifidobacterium adolescentis and C. difficile during their first 2 months. Infants colonized with several Bifidobacterium species had been exposed to higher amounts of endotoxin and grew up in larger families than infants harbouring few species.
Conclusion
A more diverse gut microbiota early in life might prevent allergy development and may be related to the previously suggested inverse relationship between allergy, family size and endotoxin exposure.
Summary
Introduction
Among sensitized infants, those with high, as compared with low levels, of salivary secretory IgA (SIgA) are less likely to develop allergic symptoms. Also, early colonization ...with certain gut microbiota, e.g. Lactobacilli and Bifidobacterium species, might be associated with less allergy development. Although animal and in vitro studies emphasize the role of the commensal gut microbiota in the development of the immune system, the influence of the gut microbiota on immune development in infants is unclear.
Objective
To assess whether early colonization with certain gut microbiota species associates with mucosal and systemic immune responses i.e. salivary SIgA and the spontaneous Toll‐like receptor (TLR) 2 and TLR4 mRNA expression and lipopolysaccharide (LPS)‐induced cytokine/chemokine responses in peripheral blood mononuclear cells (PBMCs).
Methods
Fecal samples were collected at 1 week, 1 month and 2 months after birth from 64 Swedish infants, followed prospectively up to 5 years of age. Bacterial DNA was analysed with real‐time PCR using primers binding to Clostridium difficile, four species of bifidobacteria, two lactobacilli groups and Bacteroides fragilis. Saliva was collected at age 6 and 12 months and at 2 and 5 years and SIgA was measured with ELISA. The PBMCs, collected 12 months after birth, were analysed for TLR2 and TLR4 mRNA expression with real‐time PCR. Further, the PBMCs were stimulated with LPS, and cytokine/chemokine responses were measured with Luminex.
Results
The number of Bifidobacterium species in the early fecal samples correlated significantly with the total levels of salivary SIgA at 6 months. Early colonization with Bifidobacterium species, lactobacilli groups or C. difficile did not influence TLR2 and TLR4 expression in PBMCs. However, PBMCs from infants colonized early with high amounts of Bacteroides fragilis expressed lower levels of TLR4 mRNA spontaneously. Furthermore, LPS‐induced production of inflammatory cytokines and chemokines, e.g. IL‐6 and CCL4 (MIP‐1β), was inversely correlated to the relative amounts of Bacteroides fragilis in the early fecal samples.
Conclusion
Bifidobacterial diversity may enhance the maturation of the mucosal SIgA system and early intense colonization with Bacteroides fragilis might down‐regulate LPS responsiveness in infancy.
Context. The neutrino event IceCube−170922A appears to originate from the BL Lac object TXS 0506+056. To understand the neutrino creation process and to localize the emission site, we studied the ...radio images of the jet at 15 GHz. Aims. Other BL Lac objects show properties similar to those of TXS 0506+056, such as multiwavelength variability or a curved jet. However, to date only TXS 0506+056 has been identified as neutrino emitter. The aim of this paper is to determine what makes the parsec-scale jet of TXS 0506+056 specific in this respect. Methods. We reanalyzed and remodeled 16 VLBA 15 GHz observations between 2009 and 2018. We thoroughly examined the jet kinematics and flux-density evolution of individual jet components during the time of enhanced neutrino activity between September 2014 and March 2015, and in particular before and after the neutrino event. Results. Our results suggest that the jet is very strongly curved and most likely observable under a special viewing angle of close to zero. We may observe the interaction between jet features that cross each other’s paths. We find subsequent flux-density flaring of six components passing the likely collision site. In addition, we find a strong indication for precession of the inner jet, and model a precession period of about 10 yr via the Lense-Thirring effect. We discuss an alternative scenario, which is the interpretation of observing the signature of two jets within TXS 0506+056, again hinting toward a collision of jetted material. We essentially suggest that the neutrino emission may result from the interaction of jetted material in combination with a special viewing angle and jet precession. Conclusions. We propose that the enhanced neutrino activity during the neutrino flare in 2014–2015 and the single EHE neutrino IceCube-170922A could have been generated by a cosmic collision within TXS 0506+056. Our findings seem capable of explaining the neutrino generation at the time of a low gamma-ray flux and also indicate that TXS 0506+056 might be an atypical blazar. It seems to be the first time that a potential collision of two jets on parsec scales has been reported and that the detection of a cosmic neutrino might be traced back to a cosmic jet-collision.
Magnetic skyrmions are localized, topologically protected spin structures that have been proposed for storing or processing information due to their intriguing dynamical and transport properties. ...Important in terms of applications is the recent discovery of interface stabilized skyrmions as evidenced in ultra-thin transition-metal films. However, so far only skyrmions at interfaces with a single atomic layer of a magnetic material were reported, which greatly limits their potential for application in devices. Here we predict the emergence of skyrmions in 4d/Fe2/5dn multilayers, that is, structures composed of Fe biatomic layers sandwiched between 4d and 5d transition-metal layers. In these composite structures, the exchange and the Dzyaloshinskii-Moriya interactions that control skyrmion formation can be tuned separately by the two interfaces. This allows engineering skyrmions as shown based on density functional theory and spin dynamics simulations.
Thermal methods are of increased relevance in the field of microplastics (MP) analysis. The presented method improvements emphasize the potential of pyrolysis gas-chromatography mass-spectrometry ...(Py-GCMS) methods for mass-related MP quantification in environmental samples. A previously established Curie-Point (CP)-pyrolyzer is compared to a micro furnace (MF) pyrolyzer of higher sample capacity. The two Py-GCMS systems are examined in terms of calibration aspects like dynamic range, linearity, process standard deviation and overall sensitivity. Here, MF-PyGCMS provided advantages. Depending on the samples and their residual organic matrix content, the related pyrolysis products may interact with relevant indicator ions of interesting polymers. This can hamper or even impede any calibration and quantification of MP in the given sample. An internal standard mixture added just before the pyrolysis process (ISTD py ) mimics these interactions to a certain extent. Based on selected peak ratios, ISTD py offers a possible quantification option in those cases. The application in selected environmental samples (sea salt, surface water and muddy sediment) after adequate preconcentration illustrates the capability and sensitivity of MF-Py-GCMS for MP-quantification regarding the encountered concentrations (ppt–ppm).
The paper presents the results of isothermal and transient oxidation experiments of the advanced cladding alloys M5® and ZIRLO™ in comparison to Zircaloy-4 in air at temperatures from 973 to 1853
K.
...Generally, oxidation in air leads to a strong degradation of the cladding material. The main mechanism of this process is the formation of zirconium nitride and its re-oxidation. From the point of view of safety, the barrier effect of the fuel cladding is lost much earlier than during accident transients with a steam atmosphere only.
Comparison of the three alloys investigated reveals a qualitatively similar, but quantitatively varying oxidation behavior in air. The mainly parabolic oxidation kinetics, where applicable, is comparable for the three alloys. Strong differences of up to 500% in oxidation rates were observed after transition to linear kinetics at temperatures below 1300
K.
The paper presents kinetic rate constants as well as critical times and oxide scale thicknesses at the point of transition from parabolic to linear kinetics.
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