Gas hydrates are solid compounds that form under high-pressure and low-temperature conditions, posing a major threat to oil and gas operations because of their tendency to agglomerate and block pipelines. One mitigation strategy is to allow hydrates to form under controlled conditions, enabling their transport as a slurry within the liquid phase. However, limited research on how such particles affect key multiphase flow parameters has been conducted. This study investigates the influence of particle concentration on slug flow characteristics, a common flow regime in oil and gas production. Experiments using air–water and air–oil systems with model polyethylene particles mimicking hydrate density were performed in a flow loop. The test section was composed of 50-mm ID, 34-m long horizontal pipe. Four particle concentrations were tested: 0%, 5%, 10% and 20% v/v. Except under flow conditions near the stratified–slug transition line, which lead to long elongated bubbles and low slug frequencies, particles were effectively dispersed and transported in both the film and slug regions. The presence of particles had a weak effect on the slug flow topology – structure lengths, flow frequency, bubble velocity and phase fraction remained almost unchanged. This was attributed to the minimal impact of the particles on the thermophysical properties of the mixture. In contrast, particles significantly increased the pressure drops in the oil system because of a higher mixture density and a particle size comparable to the viscous sublayer, what affects the apparent viscosity. An empirical correlation for pressure drop prediction was proposed, achieving deviations of about 5% compared to experimental data.
Bottles (∼180 mL) were produced by three-dimensional (3D) printing using food-grade glycol-modified poly (ethylene terephthalate) (PETG) as an alternative packaging for olive oil. Internal surfaces were functionalized with polydimethylsiloxane (PDMS) coatings containing either freeze-dried powder or freeze-dried aqueous extract powder from cv. ‘Cobrançosa’ olive leaf (0.92 ± 0.10 and 0.80 ± 0.13 mg GAE/mLPDMS, respectively), aiming to reduce oil oxidation while promoting olive leaf valorization. Functionalized bottles were compared with non-functionalized 3D-printed and conventional glass bottles. Olive oil quality was evaluated before and after accelerated storage (30 days, 40 °C, dark) using free acidity, peroxide value (PV), UV extinction coefficients (K232, K268), total phenolics, antioxidant activity, oxidative stability (OS), and sensory analysis. All samples suffered oxidation and quality downgrade from extra virgin to lampante (K232 > 2.60). However, oils stored under accelerated conditions in functionalized bottles showed significantly (P-value < 0.05) lower PV and K268, higher OS, better phenolic retention and lower rancidity (3.0–3.1 vs. 4.3) than glass-stored oils. Overall, functionalized bottles provided the greatest protection against oil sensory degradation, followed by non-functionalized and conventional glass bottles. This suggests that PETG/PDMS material itself exhibits a protective effect, enhanced by functionalization, although this empirical interpretation requires mechanistic confirmation. Unsupervised and supervised multivariate analysis confirmed the active packaging protective effect, with oils in functionalized bottles clustering closer to unstored samples. Both coatings were effective, though freeze-dried olive leaf powder being less technically-demanding is more practical. Thus, functionalized 3D-printed bottles emerge as a sustainable and active solution to reduce olive oil oxidation and support by-product valorization.
Microplastics are emerging pollutants that have raised great concerns to the fish community and are present in most freshwater aquatic ecosystems. These pollutants can cause physical damage and accumulate in the gastrointestinal tract, leading to intestinal obstruction. Thus, the objective of this study was to evaluate the presence of microplastics in the gastrointestinal content of the fish community in the Jaguariaíva River, considered an important tributary of the Itararé River, upper Paraná River basin, Brazil. To this end, we tested whether (i) microplastic ingestion varies among fish from different trophic guilds (detritivores, omnivores, herbivores, insectivores, and piscivores) and (ii) whether ingestion is associated with habitat use (demersal, benthopelagic, and pelagic). The fishes were collected from March 2013 to December 2014 at seven points along the Jaguariaíva River and had their gastrointestinal tracts removed and analyzed in the laboratory. Microplastics were analyzed with a micro Fourier transform infrared spectrometer. In general, fibers and fragments were found in 13 fish species, with their composition being polyvinyl alcohol and polydimethylsiloxane. Furthermore, the consumption of these microplastics was not associated with trophic groups or the types of habitats used by the species analyzed. The presence of microplastics in fish provides insights into the current pollution in the Jaguariaíva River. These findings reinforce the need for mitigation measures to reduce plastic pollution and minimize its impact on aquatic biodiversity.
How species abundance distributions vary along gradients of climatic seasonality remains unclear, particularly in subtropical forests where macroecological structure is poorly understood. Here, we analyzed species abundance distributions (SADs) of tree assemblages across three forest zones in southern Brazil—the Semi-deciduous Forest (SDF), Serra Geral Deciduous Forest (SGD), and Upper Uruguay Deciduous Forest (AUD)—to assess their agreement with statistical models and predictions from the maximum entropy theory of ecology (METE). We compared the fit of the Zipf–Mandelbrot and lognormal models with METE predictions derived from species richness and total abundance. Assemblages differed in dominance structure and model fit, with SDF showing closer agreement with METE, AUD showing greater deviation, and SGD exhibiting intermediate patterns. The Zipf–Mandelbrot model provided the best fit across all forest zones. Despite these differences, Kullback–Leibler (KL) divergence did not differ significantly among forest zones, indicating similar magnitudes of deviation from METE predictions. Assemblages that more closely matched METE predictions exhibited stronger dominance, whereas increased evenness was associated with greater deviation. Overall, these findings suggest that METE provides a statistical baseline for species abundance distributions, while observed patterns reflect ecological processes that modify this expectation along environmental gradients.
Covering schemes were recently introduced as a generalization of both difference matrices and difference schemes, providing an efficient method for building covering arrays with a certain degree of symmetry. On the other hand, Tang and Woo (1983) showed that sets of constant-weight tuples yield several upper bounds on covering arrays. However, these sets usually do not have enough symmetry to induce good covering schemes. In this work, we derive a classification of invariant sets of constant-weight tuples under the action of the diagonal group of ℤ_q^k . This classification enables us to obtain new upper bounds on covering scheme numbers, including the exact class for binary covering scheme numbers with k columns and strength k-2.
