ABSTRACT
In the context of the circular economy, the sorting process during recycling of polymers is essential as regards the efficiency of the process itself and the quality of the so-obtained recycled materials. In this paper, the application of Hyperspectral Imaging (HSI) is proposed for this purpose, providing additional insight into the state of aging and the polymer quality. The underlying study comprises HSI in the wavelength range of 1115-1678 nm considering artificially aged Styrene-Butadiene-Styrene (SBS), where aging is performed for 2, 5, 10, 15 and 20 days in a forced-draft oven at a temperature of 105 °C. The obtained HSI spectra are normalized using the Standard Normal Variate (SNV) method, with the normalized spectra as well as their first and second derivative entering the modeling attempt for SBS aging. For the latter, different partial least squares regression (PLSR) models are evaluated, where the original spectra achieved a correlation of R2=0.94 and a root mean squared error of prediction (RMSEP) of 1.83 days, showing the suitability of HSI for the proper identification of the state of aging of SBS and its potential use for other polymers.
Subject(s)
Butadienes , Styrene , Hyperspectral Imaging , Least-Squares AnalysisABSTRACT
The aim of this work is to determine the influence of the bitumen chemistry on the rheological performance of bitumen and polymer modified bitumen (PmB), as well as the polymer distribution and storage stability. Six different bitumens and their 5 wt.% SBS mixtures are considered in this work. The bitumen composition was determined by SARA fractioning, which was then correlated with the glass transition temperature, complex modulus |G*|, and phase angle, which were obtained by parallel-plate dynamic shear rheology in the temperature range of -25 to 65 °C. The polymer distribution, which was derived from fluorescence microscopy images and the storage stability (determined by tube test) also correlated with the SARA fractions. It was found that the saturates decrease |G*| and Tg and increase the phase angle in crude bitumen, while the asphaltenes increase |G*| and the phase angle. For PmB, the amount of swelling was determined by the saturate content of bitumen. The glass transition temperature of PmBs increases for low saturate and decreases for high saturate contents. |G*| and the phase angle of PmBs correlates with the saturate content, with a varying influence depending on a high or low saturate content and the temperature range due to saturate depletion in the bitumen-rich phase and the varying vol% polymer-rich phase. The aromatic and resin fractions show no correlation in the considered bitumens and PmBs.
ABSTRACT
Antarctic cryoconite holes (CHs) are mostly perennially ice-lidded and sediment-filled depressions that constitute important features on glaciers and ice sheets. Once being hydrologically connected, these microbially dominated mini-ecosystems provide nutrients and biota for downstream environments. For example, the East Antarctic Anuchin Glacier gradually melts into the adjacent perennially ice-covered Lake Untersee, and CH biota from this glacier contribute up to one third of the community composition in benthic microbial mats within the lake. However, biogeochemical features of these CHs and associated spatial patterns across the glacier are still unknown. Here we hypothesized about the CH minerogenic composition between the different sources such as the medial moraine and other zones. Further, we intended to investigate if the depth of the CH mirrors the CH community composition, organic matter (OM) content and would support productivity. In this study we show that both microbial communities and biogeochemical parameters in CHs were significantly different between the zones medial moraine and the glacier terminus. Variations in microbial community composition are the result of factors such as depth, diameter, organic matter, total carbon, particle size, and mineral diversity. More than 90% of all ribosomal sequence variants (RSV) reads were classified as Proteobacteria, Cyanobacteria, Bacteroidetes, Actinobacteria, and Acidobacteria. Archaea were detected in 85% of all samples and exclusively belonged to the classes Halobacteria, Methanomicrobia, and Thermoplasmata. The most abundant genus was Halorubrum (Halobacteria) and was identified in nine RSVs. The core microbiome for bacteria comprised 30 RSVs that were affiliated with Cyanobacteria, Bacteroidetes, Actinobacteria, and Proteobacteria. The archaeal fraction of the core microbiome consisted of three RSVs belonging to unknown genera of Methanomicrobiales and Thermoplasmatales and the genus Rice_Cluster_I (Methanocellales). Further, mean bacterial carbon production in cryoconite was exceptionally low and similar rates have not been reported elsewhere. However, bacterial carbon production insignificantly trended toward higher rates in shallow CHs and did not seem to be supported by accumulation of OM and nutrients, respectively, in deeper holes. OM fractions were significantly different between shallower CHs along the medial moraine and deeper CHs at the glacier terminus. Overall, our findings suggest that wind-blown material originating south and southeast of the Anuchin Glacier and deposits from a nunatak are assumed to be local inoculation sources. High sequence similarities between samples from the Untersee Oasis and other Antarctic sites further indicate long-range atmospheric transport mechanisms that complement local inoculation sources.
ABSTRACT
Due to the influence of many environmental processes, a precise determination of the post-mortem interval (PMI) of skeletal remains is known to be very complicated. Although methods for the investigation of the PMI exist, there still remains much room for improvement. In this study the applicability of infrared (IR) microscopic imaging techniques such as reflection-, ATR- and Raman- microscopic imaging for the estimation of the PMI of human skeletal remains was tested. PMI specific features were identified and visualized by overlaying IR imaging data with morphological tissue structures obtained using light microscopy to differentiate between forensic and archaeological bone samples. ATR and reflection spectra revealed that a more prominent peak at 1042 cm-1 (an indicator for bone mineralization) was observable in archeological bone material when compared with forensic samples. Moreover, in the case of the archaeological bone material, a reduction in the levels of phospholipids, proteins, nucleic acid sugars, complex carbohydrates as well as amorphous or fully hydrated sugars was detectable at (reciprocal wavelengths/energies) between 3000 cm-1 to 2800 cm-1. Raman spectra illustrated a similar picture with less ν2PO43-at 450 cm-1 and ν4PO43- from 590 cm-1 to 584 cm-1, amide III at 1272 cm-1 and protein CH2 deformation at 1446 cm-1 in archeological bone material/samples/sources. A semi-quantitative determination of various distributions of biomolecules by chemi-maps of reflection- and ATR- methods revealed that there were less carbohydrates and complex carbohydrates as well as amorphous or fully hydrated sugars in archaeological samples compared with forensic bone samples. Raman- microscopic imaging data showed a reduction in B-type carbonate and protein α-helices after a PMI of 3 years. The calculated mineral content ratio and the organic to mineral ratio displayed that the mineral content ratio increases, while the organic to mineral ratio decreases with time. Cluster-analyses of data from Raman microscopic imaging reconstructed histo-anatomical features in comparison to the light microscopic image and finally, by application of principal component analyses (PCA), it was possible to see a clear distinction between forensic and archaeological bone samples. Hence, the spectral characterization of inorganic and organic compounds by the afore mentioned techniques, followed by analyses such as multivariate imaging analysis (MIAs) and principal component analyses (PCA), appear to be suitable for the post mortem interval (PMI) estimation of human skeletal remains.
