•BTEX were measured for the first time in the smoke of locally-available biomasses.•Benzene was detected in all investigated samples except for fresh plum endocarp.•PCA and CA shown how time and ...temperatures profiles during combustion and pyrolysis affected levels of BTEX in smoke.•Pelleting of plum endocarp with poplar sawdust can be used as an alternative fuel.
This paper reports the results of the level of benzene, toluene, ethylbenzene and p, m, o – xylenes (BTEX) compounds in smoke from combustion and pyrolysis of apricot endocarp, plum endocarp, the poplar wood pellets and sawdust of poplar clone I-214 (P. x euramericana cl. I-214 cultivated in Serbia). The total concentrations of BTEX, in the smoke produced by the combustion range from < LOD (fresh plum endocarp) to 1.74 mg kg−1 (apricot endocarp), while in the smoke produced by the pyrolysis, ranged from < LOD (poplar wood sawdust) to 1.99 mg kg−1 (apricot endocarp). Toluene, ethylbenzene and m ± p xylenes were detected during pyrolysis for all three plum endocarp samples, while during combustion only for fermented and distilled one. Additionally, this study was systematically investigated the application of cluster analysis CA and principal component analysis PCA in interpretation of origin and combustion and pyrolysis parameters; PCA and CA shown how time and temperatures profiles during combustion and pyrolysis affected levels of BTEX in smoke. The results of score plot demonstrated that PCA may be useful in discrimination between samples based on the combustion and pyrolysis properties and the emitted level of BTEX.
In this paper, a method for automatically solving a class of straightedge-and-compass construction problems is proposed. These are the problems where the goal is to construct a triangle given three ...located points. The method is based on identifying and systematising geometric knowledge, a specific, restricted search and handling redundant or locus-dependent instances. The proposed method is implemented and the current implementation can solve a large number of triangle construction problems. To our knowledge this is the first systematic automated construction solver focused on solving problems from the corpus given. This is also the first approach that considers proving correctness of generated constructions (using external automated theorem provers).
The paper presents a study of organochlorine compounds in street dust, an often forgotten aspect of urban environmental pollution. Six different polychlorinated biphenyls (PCBs) and eighteen ...organochlorine pesticides (OCPs) were monitored in terms of levels, distribution, seasonal variation and health risks. Street dust samples were collected from fifteen urban locations in Novi Sad including schools, recreational areas, residential and industrial zones. Street dust concentration of PCBs ranged from less than the limit of detection (<LOD) to 12.1 ng g−1 (mean = 0.58 ng g−1) in summer and from <LOD to 3.82 ng g−1 (mean = 0.45 ng g−1) in winter. Among the investigated OCPs, only dichlorodiphenyltrichloroethanes (DDTs) were detected - their concentration varied from <LOD to 34.7 ng g−1 (mean = 6.2 ng g−1 and median = 1.4 ng g−1) in summer to <LOD to 50.5 ng g−1 (mean = 7.1 ng g−1 and median = 2.0 ng g−1) in winter. Principal component analysis indicated a positive correlation among PCB 101, PCB 153 and pH as well as between PCB 138 and organic matter. Regression analysis revealed that distribution trends of DDTs between the soil and street dust samples are significantly correlated in the recreational areas. The average level of total lifetime carcinogenic risk (TLCR) for PCBs (3.7 × 10−9) and DDTs (3.6 × 10−9) found in Novi Sad street dust samples were well below the unacceptable level of 10−6, indicating that the lifetime cancer risk was acceptable. It was also found that the seasonal variations were not significant.
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•The first study on 6 PCBs and 18 OCPs in street dust from Serbia•The street dust was sampled from different functional areas.•Spatial and seasonal variation of PCBs and OCPs were estimated.•Human risk assessment shows that Novi Sad urban area is “suitable as residential”.•Spatial regression is used to account for correlation between soil and street dust.
We describe a system for automated ruler and compass triangle constructions in hyperbolic geometry. We discuss key differences between constructions in Euclidean and hyperbolic setting, compile a ...list of primitive constructions and lemmas used for constructions in hyperbolic geometry, build an automated system for solving construction problems, and test it on a corpus of triangle-construction problems. We extend the list of primitive constructions for hyperbolic geometry by several constructions that cannot be done by ruler and compass, but can be done by using algebraic calculations and show that such extended system solves more problems. We also use a dynamic geometry library to build an online compendium containing construction descriptions, illustrations, and step-by-step animations.
The aim of this paper was to determine spatial and seasonal variation of 6 indicator polychlorinated biphenyls (PCBs) and 18 organochlorine pesticides (OCPs) in urban soils of Novi Sad, Serbia. Sixty ...surface soil samples were collected during both winter and summer season, from different types of locations: schools, recreational areas, residential and industrial zones. Samples were treated using the method of accelerated solvent extraction, which allows simultaneous extraction and clean up of PCBs and OCPs. Targeted compounds were analyzed by GC-μECD and confirmed by GC-MS. The total concentrations of studied PCBs varied from <LOD to 18.9 ng g−1 (mean 2.84 ng g−1 and median value of 1.21 ng g−1) in winter and from <LOD to 24.6 ng g−1 (mean 3.27 ng g−1 and median value of 1.60 ng g−1) in summer. Regarding the OCPs analyzed, dichlorodiphenyltrichloroethanes (DDTs) were only detected in both seasons. The total concentration of DDTs ranging from <LOD to 86.3 ng g−1 (mean 7.57 ng g−1 and median value of 1.87 ng g−1) in summer and from <LOD to 182 ng g−1 (mean 15.6 ng g−1 and median value of 3.15 ng g−1) in winter. There were no significant difference between seasons for studied PCBs and DDTs. Spatial distribution of PCBs and DDTs were also evaluated using Arc GIS. Additional, principle component analysis was performed to evaluate relationships between PCBs, DDTs and soil characteristics. Positive correlation was observed among p,p′-DDE, p,p′-DDD and organic matter. The total lifetime carcinogenic risk indicated that the lifetime cancer risk was acceptable.
•Novel method of pressurized liquid extraction for PCBs and OCPs in soil was developed.•The results revealed that the seasonal variation of PCBs and DDTs was rather stable.•Health risk assessment suggested that Novi Sad is suitable as residential.•Profiles of DDTs indicated aged residues.•OCPs residues and PCBs in soil are not a serious public health threat in Novi Sad.
The aim of this paper is to determine the level and distribution of the sixteen polycyclic aromatic hydrocarbons (PAHs) listed by the US Environmental Protection Agency (US-EPA) in smoke from poplar ...wood pellets and sawdust combustion and thermal decomposition, respectively. Namely, the growth of selected poplar plantations, wood cultivation and production in the north part of the Republic of Serbia, Vojvodina Province, considerably increased. However, mechanical wood processing creates a lot of sawdust, which causes an occupational and environmental risk and also poses a fire hazard. Furthermore, in order to protect the environment and provide additional energy sources, sawdust is commonly pelletized and further used as a fuel. Thus, the assessment of environmental impact of its use becomes an important issue. Therefore, the intention of the authors was to determine the level and profile of PAHs emitted by combustion and thermal decomposition under atmospheric conditions of poplar wood pellets and sawdust. The 16 US-EPA PAHs were analyzed by gas chromatograph with mass selective detector. The level of total US-EPA 16 PAHs formed during combustion of wood pellets was 4.7mgkg−1, whereas during the sawdust combustion it was 3.8mgkg−1, while the resulting total PAHs concentration during thermal degradation under atmospheric conditions of pellets and sawdust was 3.4mgkg−1 and 3.7mgkg−1, respectively. The most common PAHs present in smoke from the combustion and thermal decomposition under atmospheric conditions of poplar wood pellets were phenanthrene, fluorene and naphthalene, while from the sawdust were phenanthrene, naphthalene, acenaphthylene and fluorene, respectively. BaPeq value obtained during the combustion of wood pellets was 0.081mg kg−1, whereas from the combustion of sawdust it was 0.047mgkg−1, while the resulting BaPeq value during the thermal degradation under atmospheric conditions of pellets and sawdust was 0.057mgkg−1 and 0.049mgkg−1, respectively. Biomass densification process did not affect PAHs emission neither during the combustion process nor the thermal decomposition process. To the best of our knowledge, it is the first study which considers the level and profile of PAHs found in smoke from the combustion and thermal decomposition of poplar clone I-214 (P. x euramericana cl. I-214) cultivated in the Republic of Serbia.
•PAHs were determined in smoke from poplar wood pellets and sawdust of poplar clone I-214.•Level of PAHs found in this study would be a baseline for further monitoring campaigns.•Biomass densification process did not affect PAHs emission.•The obtained data for BaPeq values indicated that poplar wood pellets and sawdust could be used as an eco-friendly fuel.
Human milk is a biofluid with a unique composition among mammalian milks. Besides this milk's major components, its bioactive compounds, like hormones, immune factors, and oligosaccharides, are ...unique and important for infant growth and development. The best form of nutrition for term and preterm infants is the mother's own milk. However, in the absence of the mother's own milk, donor milk should be made available. Milk banks support neonatal intensive care units by providing preterm infants with human milk that generally has reasonable nutritive value for this sensitive population. However, neither mother's own milk nor donor milk has sufficient energy content for the growth of preterm babies, so adequate human milk supplementation is crucial for their progress. Due to the different characteristics of human breast milk, as well as ubiquitous environmental pollutants, such as microplastics, new methods are required for monitoring the quality and characteristics of human milk, which will lay a solid foundation for the further development and progress of human milk research.
Dynamic Geometry Software (DGS) is present for more than three decades: it found its way to classrooms worldwide and it is now an irreplaceable component of mathematical education. From the very ...beginning and still, DGS tools are built around one central scenario: the user chooses several (free) points and, using them, constructs some other points and other geometric objects. Then, the user can move (“drag”) a chosen free point and explore how the constructed points and other constructed objects change. In this paper we describe one new DGS scenario: the user can move the constructed points and explore how the free points and the constructed objects change accordingly. This scenario uses a solver for geometry construction problems. We implemented this DGS feature within our prototype tool Touch&Drag, developed for touch-based devices. The presented feature can be implemented in other DGS tools, too.
