Estuarine habitat quality reflects urbanization at large spatial scales in South Carolina's coastal zone

Land cover patterns were evaluated in 29 estuarine watersheds of South Carolina to determine relationships between urban/suburban development and estuarine habitat quality. Principal components analysis and Pearson product moment correlation analyses were used to examine the relationships between ten land cover categories and selected measures of nutrient or bacterial enrichment in the water column and contaminant enrichment in sediments. These analyses indicated strong relationships between land cover categories representing upland development and a composite measure of 24 inorganic and organic contaminants using the Effect Range Median-Quotient (ERM-Q). Similar relationships also were observed for the summed concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), pesticides, and metals. Data obtained from tidal creeks generally showed stronger correlations between urban/suburban land use and pesticides and metals compared to data obtained from larger open water habitats. Correlations between PAH concentrations and the urban/suburban land cover categories were similar between creek and open water habitats. PCB concentrations generally showed very little relationship to any of the land cover categories. Measures of nutrient enrichment, which included total Kjeldahl nitrogen (TKN), nitrate-nitrite, phosphorus, chlorophyll-a, and total organic carbon, were generally not significantly correlated with any land cover categories, whereas fecal coliform bacteria were significantly and positively correlated with the urban/suburban land cover categories and negatively correlated with the non-urban land cover categories. Fecal coliform correlations were stronger using data from the open water sites than from the tidal creek sites. Both ERM-Q and fecal coliform concentrations were much greater and more pervasive in watersheds with relatively high (>50%) urban/suburban cover compared to watersheds with low (<30%) urban/suburban cover. These analyses support the hypotheses that estuarine habitat quality reflects upland development patterns at large spatial scales, and that upland urbanization can result in increased risk of biological degradation and reduced safe human use of South Carolina's coastal resources.     

Microstructural development and solidification cracking susceptibility of Cu deposits on steel: Part I

The tool and die industry is interested in depositing Cu onto steel using direct metal deposition techniques in order to improve thermal management of mold dies manufactured from steel alloys. However, Cu is a known promoter of solidification cracking in steel. The goal of this work was to identify the range of Cu compositions in steel that cause cracking and understand the cracking susceptibility through analysis and modeling of microstructural development. A wide range of steel–Cu deposits, from approximately 3 to 97 wt% Cu, were fabricated using the gas tungsten arc welding (GTAW) process with cold wire feed. The deposits were found to be crack free when the concentration of Cu was below approximately 5 wt% or above approximately 52 wt%. Cracking was observed in deposits with Cu concentration between approximately 5 and 43 wt%. Thus, to ensure crack free deposition of Cu onto Steel, the concentration of the first layer must be about 52 wt% Cu or greater. The corresponding volume fraction of terminal Cu in samples that cracked was between approximately 0.1 and 27%. The resultant microstructures were characterized by various microscopy techniques to understand the influence of Cu on solidification cracking. Additionally, solidification modeling was undertaken to determine the amount of terminal Cu rich liquid that would form under equilibrium and non-equilibrium solidification conditions.     

Discovery of extreme events-related communities in contrasting groups of physical system networks

The latent behavior of a physical system that can exhibit extreme events such as hurricanes or rainfalls, is complex. Recently, a very promising means for studying complex systems has emerged through the concept of complex networks. Networks representing relationships between individual objects usually exhibit community dynamics. Conventional community detection methods mainly focus on either mining frequent subgraphs in a network or detecting stable communities in time-varying networks. In this paper, we formulate a novel problem—detection of predictive and phase-biased communities in contrasting groups of networks, and propose an efficient and effective machine learning solution for finding such anomalous communities. We build different groups of networks corresponding to different system’s phases, such as higher or low hurricane activity, discover phase-related system components as seeds to help bound the search space of community generation in each network, and use the proposed contrast-based technique to identify the changing communities across different groups. The detected anomalous communities are hypothesized (1) to play an important role in defining the target system’s state(s) and (2) to improve the predictive skill of the system’s states when used collectively in the ensemble of predictive models. When tested on the two important extreme event problems—identification of tropical cyclone-related and of African Sahel rainfall-related climate indices—our algorithm demonstrated the superior performance in terms of various skill and robustness metrics, including 8–16 % accuracy increase, as well as physical interpretability of detected communities. The experimental results also show the efficiency of our algorithm on synthetic datasets.     

Electro-active nanofibres electrospun from blends of poly-vinyl cinnamate and a cholesteric liquid crystalline silicone polymer

Electrospinning was used to generate polymer nanofibres from blends of poly-vinyl cinnamate (PVCN) and a cholesteric silicone polymer. Only blends that contained at least 40 % of PVCN produced fibres. Both differential scanning calorimetry and electron dispersion spectroscopy data indicate that the samples are miscible over a wide temperature interval. The variation of fibre diameter with concentration is nonlinear with a well-defined minimum corresponding to an 80 % PVCN blend. The fibres are birefringent with Kerr constants similar to that of cholesteric liquid crystals. Although not significant, the Kerr constant increases with increasing silicone polymer concentration.     

Synthesis and properties of bio‐based poly(pentamethylene oxamide)

A novel bio‐based polyamide, poly(pentamethylene oxamide) (PA52), with high molecular weight has been prepared from dibutyl oxalate and renewable monomer of 1,5‐pentanediamine by a two‐step polymerization procedure. The chemical structures are analyzed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy while the properties are evaluated by differential scanning calorimetry, thermogravimetric analysis, and water uptake measurements for the obtained PA52. The results reveal that PA52 possesses distinguished properties such as high temperature resistance, excellent crystallizability and low water absorption. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

Solvent-extractable polycyclic aromatic hydrocarbons in biochar: influence of pyrolysis temperature and feedstock

Despite the increasing agricultural use of biochar as a way of combining the utilization of biomass for energy production with the removal of CO(2) from the atmosphere, it is not known how variations in pyrolysis temperature and feedstock type affect concentration and composition of polycyclic aromatic hydrocarbons (PAHs) that inevitably form and associate with biochar. To close this knowledge gap, we quantified 11 unsubstituted three- to five-ring PAHs as well as alkylated forms of phenanthrene and anthracene in grass and wood chars produced in 100 °C increments across a temperature range (100 to 700 °C). Our results show that solvent-extractable PAH concentrations in biochars produced at heat treatment temperatures (HTTs) of 400 and 500 °C greatly exceed those observed at higher and lower temperature, supporting a low HTT solid-phase formation mechanism operable at temperatures commonly used for industrial biochar production. The maximum extractable yield of 'pyrolytic' unsubstituted PAHs for grass (22 μg g(-1) at HTT = 500 °C) greatly exceeds the value for wood (5.9 μg g(-1)). Moreover, PAH signatures (e.g., total monomethylphenanthrene to phenanthrene ratios, MP/P ～2-3) at intermediate temperatures (400 °C) resemble those of fossil oils rather than that commonly attributed to pyrolytic products. Further research is needed to characterize the PAH evolution in modern pyrolysis reactors and assess the fate of biochar-bound PAHs in soils and sediments. Various commonly applied PAH ratios and indicator compounds show promise as markers for specific feedstock materials and pyrolysis conditions of biochars in environmental systems.     

Intrinsic and extrinsic sources of phosphorus loading into the Nyando River,Kenya

The Nyando River supports a large human population and an enriched biodiversity. The basin has undergone extreme modification over the last century through changes in hydrological changes and land‐use activities. The impacts of the changes have severely shifted the ecology of the river from desirable to less desirable. Of all the major rivers draining into Lake Victoria‐Kenya, the Nyando River is consistently the most turbid and exhibits the greatest phosphorus load. The present study investigated the present limnological status and sources of phosphorus loads between 2015 and 2016 through water and sediment sampling during high and low flow regimes. The samples were analysed for various phosphorus fractions, including soluble reactive phosphorus (SRP), total phosphorus in water (TP_w), non‐apatite inorganic phosphorus (NAIP), apatite phosphorus (AP), inorganic phosphorus (IP), organic phosphorus (OP), total phosphorus in sediments (TP_s) and elemental compositions. The measured SRP and TP_w concentrations indicated hypertrophic conditions, with means for both high and low flows ranging from 79.3 to 165.7 μg P/L, and 200.0 to 243.9 μg P/L, respectively. The AP concentrations were high, with mean measurements for high and low flows being 766.9 and 790.5 mg/kg, respectively. The sources of high phosphorus loads were established to be both natural and anthropogenic, with major drivers being the industrial establishments along the river basin. Erosion of the catchment phosphorus‐enriched carbonatite rocks and river banks also contributed significant phosphorus loads. Enhanced effluent treatment, quarry dust containment, improved forest cover and regeneration of riverine buffer strips are recommended to restore the river's ecosystems.     

Laser-induced spark for measurements of the fuel-to-air ratio of a combustible mixture

This work investigates the use of the laser-induced gas breakdown for fuel-to-air ratio measurements. In essence, we examine the late time behavior of the line radiation at the wavelength of the H_α-lines and the O I triplet emitted from the laser-induced spark in CH₄-air mixtures. Sparks were produced using a single-mode, Q-switched Nd-YAG laser. The laser produced a beam of 6 mm in diameter at the wavelength of 1064 nm and a pulse duration of 5.5 ns. For the equivalence ratio from 0.1 to 5.0, the radiation intensity ratio of the H_α-lines to the O I triplet increased linearly with the equivalence ratio. For the laser energy from 10 to 50 mJ it was independent of the laser energy when the laser energy was higher than 20 mJ. The technique, therefore, has a potential for measuring the fuel-to-air ratio of a combustible flow environment.     

Utilization of lignocellulosic waste for ethanol production : Enzymatic digestibility and fermentation of pretreated shea tree sawdust

Enzymatic hydrolysis and fermentation methods were evaluated on alkaline peroxide pretreated shea tree sawdust conversion to ethanol. Optimum pretreatment conditions of 120 °C reaction temperature, 30 min reaction time, and 20 mL L^?1 of water hydrogen peroxide concentration (1%(v/v)H₂O₂) solubilized 679 g kg^?1 of hemicellulose and 172 g kg^?1 of lignin. 617 g kg^?1 cellulose was retained in the solid fraction. The maximum yield of reducing sugar with optimized enzyme loadings by two enzyme preparations (cellulase and β-glucosidase) was 165 g kg^?1 of dry biomass. The ethanol yield was 7.35 g L^?1 after 72 h incubation period under the following conditions: 2% cellulose loading, enzyme concentration was 25 FPU (g cellulose)^?1 loading, yeast inoculums was 10% (v/v), 32 oC, and pH 4.8. The pretreatments gave information about the hindrances caused by lignin presence in lignocellulosic materials and that hemicelluloses are better hydrolyzed than lignin, thereby enhancing enzymatic digestibility of the sawdust material.     

The responses of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) in Lake Wamala (Uganda) to changing climatic conditions

Changes in the catches of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758), in Lake Wamala (Uganda) have been observed since its introduction. The factors contributing to these changes, however, are not well understood. This study examined changes in species composition, size structure, size at first maturity, length–weight relationship and condition factor of Nile tilapia in Lake Wamala, in relation to changes in temperature, rainfall and lake depth, to provide a better understanding of the possible role of changing climatic conditions. There was an increase in the minimum, maximum and average temperatures since 1980, but only the minimum (0.021 °C year^?1) and average temperatures (0.018 °C year^?1) exhibited a significant trend (P < 0.05). Rainfall increased by 8.25 mm year^?1 since 1950 and accounted for 79.5% of the water input into the lake during the period 2011–2013, while evaporation accounted for 86.2% of the water loss from the lake. The lake depth was above 4 m during the years when the rainfall exceeded the average of 1180 mm, except after 2000. The contribution of Nile tilapia to total fish catch and catch per unit effort (CPUE) increased with rainfall and lake depth up to the year 2000, after which they decreased, despite an increased rainfall level. The lake depth was positively correlated with the average total length and length at 50% maturity (r = 0.991 and 0.726, respectively), while the slopes of the length–weight relationships differed significantly between high and low lake depths [t₍₆₎ = 3.225, P < 0.05]. Nile tilapia shifted from an algal‐dominated diet during the wet season to include more insects during the dry season. The results of this study indicate Nile tilapia in Lake Wamala displays a typical r‐selected reproductive strategy, by growing to a small size, maturing faster and feeding on different food types, in order to survive high mortality rates under unfavourable conditions attributable to higher temperatures, low rainfall and low lake water levels.