Effect of an additive TAB-1 on crystallization behaviors and tensile properties of iPB-1

The excellent high temperature performances of isotactic polybutene-1 (iPB-1) in form I are demanded by many thermoplastic products like hot water pipes. However, as iPB-1 melt is a strong liquid...

Longitudinal Associations of Substance Use Risk Profiles with the Use of Alternative Tobacco Products and Conventional Smoking among Adolescents

Although personality is associated with the onset of substance use (i.e., conventional smoking, alcohol use, and cannabis use) during adolescence, it is unclear whether personality traits are also associated with the onset of use of alternative tobacco products (ATPs), i.e., electronic cigarettes, shisha-pens, and water pipes. This study examines whether personality traits are associated with the onset of use of both conventional cigarettes and ATPs. Longitudinal data (baseline and 18-month follow-up) were used. The sample consisted of 1114 non-user adolescents (mean age = 13.36, SD = 0.93, 56% female) at baseline. To measure personality traits, the Substance Use Risk Profile Scale was used with four subscales: anxiety sensitivity, hopelessness, sensation seeking, and impulsivity. Structural equation models were conducted using Mplus 7.3. Results showed that both hopelessness and sensation seeking were associated with the onset of use of e-cigarettes and conventional cigarettes. Further, sensation seeking and impulsivity were associated with the onset of use of shisha-pens and water pipes. In conclusion, to prevent adolescents from using ATPs and/or conventional cigarettes, it is important to take their personality traits into account. More research on other (shared) risk factors and on more advanced stages of ATP use is needed before effective prevention strategies can be developed.

Investigating Bacterial and Free-Living Protozoa Diversity in Biofilms of Hot Water Pipes of Apartment Buildings in the City of Riga (Latvia)

Background: Biofilms, when formed on the surfaces of water pipes, can be responsible for a wide range of water quality and operational problems. We sought to assess the bacterial and free-living protozoa (FLP) diversity, in relation to the presence of Legionnaire's disease-causing bacteria Legionella pneumophila (L. pneumophila) in 45 biofilms of hot water distribution system pipes of apartment buildings in Riga, the capital city of Latvia.Results: 16S rRNA amplicon sequencing (metataxonomics) revealed that each biofilm contained 224 rather evenly distributed bacterial genera and that most common and most abundant were two genera, completely opposites in terms of their oxygen requirements: the obligately anaerobic Thermodesulfovibrio and the strictly aerobic Phenylobacterium. Water temperature and north-south axis (i.e., different primary water sources) displayed the most significant effect on the inter-sample variations, allowing us to re-construct three sub-networks (modules) of co-occurring genera, one involving (potentially FLP-derived) Legionella spp. Pangenome-based functional profile predictions suggested that all three may be dominated by pathways related to the development and maintenance of biofilms, including quorum sensing and nutrient transport, as well as the utilization of various energy sources, such as carbon and nitrogen. In our 18S rRNA amplicon sequencing data, potential hosts of L. pneumophila were detected in 11 out of 12 biofilm samples analyzed, however, in many cases, their relative abundance was very low (<1%). By validating our findings using culture-based methods, we detected L. pneumophila (serogroups 2, 3, 6 and 9) in nine (20%) biofilms, whereas FLP (mostly Acanthamoeba, Vahlkampfidae and Vermamoeba spp.) were present in six (~13%) biofilms. In two biofilms, L. pneumophila and its potential hosts were detected simultaneously, using culture-based methods.Conclusions: Overall, our study sheds light on the community diversity of hot water biofilms and predicts how several environmental factors, such as water temperature and source might shape it.

Teaching-Learning-Based Optimization of Neural Networks for Water Supply Pipe Condition Prediction

The bulk of water pipes experience major degradation and deterioration problems. This research aims at estimating the condition of water pipes in Shattora and Shaker Al-Bahery’s water distribution networks, in Egypt. The developed models involve training the Elman neural network (ENN) and feed-forward neural network (FFNN) coupled with particle swarm optimization (PSO), genetic algorithms (GA), the sine cosine algorithm (SCA), and the teaching-learning-based optimization (TLBO) algorithm. For the Shattora network, the inputs to these models are pipe characteristics such as length, wall thickness, diameter, material, lining and coating, surface type, traffic distribution, cathodic protection, flow velocity, and c-factor. For the Shaker Al-Bahery network, the data gathered include length, material, age, diameter, depth, and wall thickness. Three assessment criteria are used to evaluate the suggested machine learning models, namely index of agreement (IOA), correlation coefficient (R), and root mean squared error (RMSE). The results reveal that coupling FFNN with the TLBO algorithm outperforms other prediction models. Therefore, the FFNN-TLBO model can be a valuable tool for simulating the water network pipe condition. This study could help the water municipality allocate the available budget effectively and plan the required maintenance and rehabilitation actions.

Study on Optimization of Temperature Control Measures for Structure Concrete of Arc Dam

As the gate pier bracket of an arch dam are of complex structure which is characterized by use of high-grade concrete and more cement, higher adiabatic temperature rise, it is rather difficult to control temperature and vulnerable for cracking, and the cracks would absolutely affect the integrity, endurance and safety of pier gate bracket. It is necessary to take reasonable temperature control measures to reduce temperature stress during the construction and prevent cracking. This paper takes the gate pier bracket at the middle-hole dam section to perform simulation analysis of temperature field and stress field under different temperature control measures by 3D FEM. It proves that such measures as densifying water pipes, improving Phase I target cooling temperature appropriately, reducing Phase I cooling temperature falling variation and keeping insulation in low-temperature season can help reduce temperature stress and prevent cracking with good results.

Concentrations and Risk Assessment of Metals, Antifouling Paint Particles and Microplastics in Coastal Sediment of a Marina in Simon’s Town, South Africa

Maintenance of maritime vessels includes the removal of paint from hulls that ultimately ends up the aquatic environment. Coastal maritime vessel maintenance is a source of metals, antifouling paint particles (APPs) and microplastics (MPs) that ends up in the coastal environment. Simon’s Town is a small urban town in False Bay, Cape Town, South Africa, where maritime activities take place (there is a naval harbour, marina and boat maintenance facility). The aim of this study was to measure metals, APPs and MPs in Simon’s Town, to assess the impact of maritime activities and a storm water pipe in a protected marina. Sediment samples were collected from 6 sites during winter 2018. Sediment and extracted APPs were analysed for metal content and MPs characterised based on type (visual and polymer), colour and size. Metal and MP fragment concentrations were highest at the slipway of a boatyard / maintenance facility, decreasing with increased distance from the slipway. MP filaments were highest close to the storm water outfall pipe. Our results suggest that boating maintenance facilities are potential sources metals and MP APP fragments, with storm water pipes potential sources of MP filaments. Various indices applied to assessed the potential impacts of metals and MPs, suggests that these contaminants have the potential to severely adversely impact the intertidal ecosystem investigated.