The growth inhibition of planktonic algae due to surfactants used in washing agents

A survey of inhibitory effects of nonionic and anionic surfactants, including a soap, used in washing agents, on the growth on three species of freshwater phytoplankton, Selenastrum capricornutum, Nitzschia fonticola and Microcystis aeruginosa was conducted. Based on the specific growth rate, μu estimated from a short period (2 or 3 days) cultivation of test algae, the growth inhibition was determined using EC₅₀ values where μu in the culture medium with surfactant decreased 50% of that without surfactant.The EC₅₀ values of nonionic and anionic surfactants tested here for S. capricornutum ranged from 2 to 50 mg l⁻¹ and from 10 to 100 mg l⁻¹, respectively. The tolerances of three species of algae tested with three surfactants, LAS, AE (EO:9) and soap, were different and the inhibitory effects were species specific. EC₅₀ values of LAS, AE (EO:9) and soap for S. capricornutum were 50–100, 4–8 and 10–50 mg l⁻¹, respectively. Those for N. fonticola were 20–50, 5–10 and 20–50 mg l⁻¹, and those for M. aeruginosa were 10–20, 10–50 and 10–20 mg l⁻¹, respectively.     

A new proxy for ground motion selection in seismic collapse assessment of tall buildings

Tall buildings are long‐period structures that are sensitive to the long‐period content of ground motions. Selection of appropriate ground motions is an important step in seismic collapse assessment of tall buildings using nonlinear dynamic analyses. Epsilon (ε_Sa) and eta (η) are two spectral shape indicators, which have been recently proposed for ground motion selection in the technical literature. In this study, a new parameter gamma (γ) is proposed, which has considerable correlation with the collapse capacity of long‐period structures having a fundamental period greater than 1 s. This parameter is a linear combination of ε_Sa and the displacement spectrum intensity epsilon (ε_DSI). The parameter γ is obtained and optimized by applying the particle swarm optimization algorithm. Since γ has significant correlation with the collapse capacity of long‐period structures, it can be used as an efficient proxy for ground motion selection in seismic collapse assessment of tall buildings. The results of this study show that ground motion selection considering the new proxy γ causes reduction in the dispersion of structural response and also decrease in the mean annual frequency of collapse, when compared with ground motion selection based on ε_Sa and η. Copyright © 2013 John Wiley & Sons, Ltd.     

Fatigue damage analysis of reinforced concrete column considering low‐cycle behavior of HRB400 steel

In this study, a damage model‐based fatigue behavior is proposed. To consider the fatigue behavior of steel in the damage model, the experimental research on reinforcing steel bar grades HRB400 was presented. The monotonic tension test and low‐cycle fatigue test were carried out. The plastic strain amplitude–fatigue cycle (ε_p–2N_f) curve and plastic strain amplitude–strength loss factor (ε_p–?_SR) curve were obtained. The fatigue parameters (C_f, C_d, and α) were proposed by nonlinear fitting. The specimens were simulated using the “Reinforcing Steel” material in “OpenSees” program. These fatigue parameters were proved to accurately describe the fatigue behavior of HRB400 rebar. Moreover, to verify the application of fatigue damage model in RC column, fiber‐based element models were established based on the quasi‐static cyclic test on RC columns. The calculated results agreed well with those of the tests. The damage degree of RC column was calculated by the recorded stress–strain curves of material. The proposed fatigue parameters could be referred in damage model based on material fatigue behavior.     

Incidence of heavy metal and antibiotic resistance in bacterial isolates from Blue Nile river water in Ethiopian region

Heavy metal pollution of river water has health implications. This study was aimed to test if bacteria that are heavy metal resistant can resist antibiotics. Heavy metal-resistant bacteria were isolated using Nutrient agar plates amended with 100?μg?ml^?1 of metal salts. Isolates were further screened to determine minimal inhibitory concentration against each metal. The isolates belonged to the genera of Neisseria, Bacillus, Pseudomonas, Staphylococcus, Streptococcus, Micrococcus, Corynebacterium and Proteus. Minimum inhibitory concentration of the isolates for heavy metals ranged from 200 to 2300?μg?ml^?1. Isolates of Pseudomonas, Neisseria, Bacillus, Protues, Streptococcus, Staphylococcus and Micrococcus spp. exhibited multiple antibiotic resistance. Statistically significant correlation between metal resistance and antibiotic resistance was observed among bacterial isolates. The present work suggests that some of the isolates could be hazardous to human beings as a result of natural selection of dual resistant mechanisms.     

Comparative study on organic constituents in polluted and unpolluted inland aquatic environments-I features of hydrocarbons for polluted and unpolluted waters

The constituents of hydrocarbons between highly polluted river waters collected from the Tokyo area and unpolluted river, brook, reservoir and pond waters obtained from the Ogasawara (Bonin) Islands were compared to characterize their features for polluted and unpolluted waters. n-Alkanes between the carbon chain length of C₁₂ and C₃₆, squalane and unresolved complex mixture of hydrocarbons (UCMH) were found in most of the river waters of the Tokyo area at the contents ranging from 0.026 to 14 μg 1⁻¹, from 0.004 to 1.7 μg 1⁻¹ and from less than 5 to 290 μg 1⁻¹, respectively, whereas in the waters of the Ogasawara Islands, only n-alkanes ranging from C₁₃ to C₃₇ were found with the great predominance of odd-carbon numbers at the contents varying from 0.042 to 4.0 μg 1⁻¹.It was indicated that the presence of squalane, UCMH and even-carbon numbered n-alkanes as the major constituents are intimately correlated with artificial hydrocarbon sources (fossil fuels and their products and both combustion products, and industrial products), while the great predominance of odd-carbon numbered n-alkanes for the unpolluted areas are mainly due to algae and higher plants. Besides, the major portion of n-alkanes, squalane and UCMH are thought to be present in polluted and unpolluted waters associated with particulate materials.     

Novel mold‐resistant building materials impregnated with thermally reduced nano‐silver

In this study, we evaluated the long‐term antifungal effectiveness of 3 types of interior building materials (gypsum board [GB], cement board [CB], and softwood plywood [S‐PW]) impregnated with thermally reduced silver nanoparticles supported by titanium dioxide (AgNPs/TiO₂) under 95% relative humidity for 4 weeks. AgNPs/TiO₂ was synthesized at 2 thermal reduction temperatures (TRTs, 120 and 200°C) with 2 different AgNP weight percentages (2 and 5 wt%). Four different silver‐loading levels (SLLs, 0.025, 0.05, and 0.5 μg/cm² and the critical concentration required to inhibit fungal growth on agar plates) and 3 fungal species (Aspergillus niger, Penicillium spinulosum, and Stachybotrys chartarum) were used in the experiments. Higher temperature reduced more ionic Ag⁺ to metallic Ag⁰ and increased the dispersion of Ag on TiO₂ surface. The 200°C thermally reduced AgNPs/TiO₂ demonstrated excellent antifungal efficiency: Mold growth was almost completely inhibited for 28 days at the low SLL of 0.5 μg/cm². Additionally, AgNPs/TiO₂ exhibited higher antifungal activity on GB and CB than on S‐PW. The stepwise regression results indicated that the TRT of AgNPs/TiO₂ (β = ?0.739 to ?0.51), the SLL (β = ?0.477 to ?0.269), and the Ag⁰ level in the AgNPs (β = ?0.379 to ?0.136) were the major factors influencing antifungal activity and TRT might be the most significant one.     

Growth responses of selected freshwater algae to trace elements and scrubber ash slurry generated by coal-fired power plants

In laboratory studies, the freshwater algae Ankistrodesmus falcatus, Scenedesmus obliquus, Selenastrum capricornutum, and Microcoleus vaginatus were exposed to potential pollutants from coal-fired power plants, and their growth responses were evaluated. Using a modification of the EPA Algal Assay Procedure Bottle Test, algae were incubated in media containing As(V) as Na₂HAsO₄ · 7H₂O, Cd(II) as CdSO₄, Hg(II) as HgSO₄, Se(VI) as Na₂SeO₄, in solution, and scrubber ash slurry generated at a western U.S. coal-fired power plant complex. First significant inhibition levels as well as algistatic-algicidal levels are reported. The median effective concentration (EC50) values for the potential pollutants ranged from 0.048–30.761 mg l⁻¹ (0.00064–0.41058 M) As(V), 0.005–0.019 mg l⁻¹ (0.00004–0.00017 M) Cd(II), 0.033–0.253 mg l⁻¹ (0.00016–0.00126 M) Hg(II), 0.033–8.511 mg l⁻¹ (0.00042–0.10779 M) Se(VI), and 3.048–15.417% scrubber ash slurry extract (SASE).     

Untersuchungen zur Drehbettung von biegedrillknickgefährdeten Trägern durch Sandwichelemente

Investigation of the torsional restraint of sandwich panels against lateral torsional buckling of beams. Experimental investigations and parametric FE‐analyses show that the torsional restraint of sandwich panels against lateral torsional buckling of beams can be expressed by a tri‐linear moment‐rotation‐relationship. Formulae are given for different profile types combined with sandwich panels for roof and wall for calculation of the parameters of this relationship. From this moment‐rotation‐relationship, which depends on the lateral load of the beam, the rotational stiffness c_{ϑ A} of the connection is obtained as secant stiffness. The rotational stiffness c_ϑ required for the design against lateral torsional buckling according to DIN 18800 part 2 is governed by c_{ϑ A}. The rotational stiffness values c_{ϑ A} of the connection, which so far were only known for two types of elements, can be calculated with this method for all common types of sandwich panels and different types of constructions.     

Modified method for predicting lateral displacement of PVD-improved ground under combined vacuum and surcharge loading

A modified method is proposed to predict the lateral displacement (δ) of prefabricated vertical drains (PVDs) improved ground under combined vacuum and surcharge loads, which is derived based on a few modified triaxial tests and a series of finite element analyses of PVD unit cells. It is observed that reducing the surcharge load (p_s) and loading rate (LR) and increasing the vacuum pressure (p_v), pre-vacuum consolidation period (t_v), and initial undrained shear strength (s_u0) could be effective in controlling the outward δ. Variations of the effective stress ratio (K_e) that controlling the δ with p_s, p_v, LR, t_v, and s_u0 are then presented. A synthetic relationship between the normalized horizontal strain (ε_h) by a reference one-dimensional vertical strain (ε_v1) and the normalized K_e by the at-rest earth pressure coefficient (K₀) is proposed for cases with and without t_v. Further, a modified index parameter (β₁) is introduced for quantitatively considering the effect of p_s, p_v, LR, t_v, s_u0, and consolidation properties of the soil, a relationship between K_e and β₁ is then established for evaluating the value of K_e. Combinations of the ε_h/ε_v1–K_e/K₀ and K_e–β₁ relationships enable modified predictions of the δ from basic preloading conditions and soil parameters.     

Influence of pH,salinity, and selenium on the growth of Aeromonas veronii in evaporation agricultural drainage water

Aeromonas veronii was isolated from seleniferous agricultural drainage water and characterized in terms of growth kinetics under changing environmental parameters [i.e. pH, selenium (Se) and salinity (electrical conductivity, EC)] that simulated evaporation. Aeromonas veronii metabolized peptone and was active in volatilizing Se, principally as dimethyl selenide (DMSe). Other volatile products produced included dimethyl disulfide, methyl selenol, dimethyl selenosulfide and dimethyl diselenide. The rate of Se volatilization correlated with the growth of A. veronii, with the highest levels of DMSe released during the exponential phase of growth. The C assimilated was primarily respired as CO₂ or incorporated into cell biomass with a small fraction used in the alkylation of Se. The maximum growth rate (μ_max) for A. veronii was 0.23 h⁻¹ at pH 7.94, 10 μg Se 1⁻¹, and EC of 3.9 dS m⁻¹ and decreased to 0.06 h⁻¹ with increasing salt content (40.2 dS m⁻¹), pH (8.53) and Se (500 μg l⁻¹). Salinity appeared to be the dominant inhibitory factor as observed by a decrease in growth rate and mass of cells. The range in salt content that was most inhibitory to the growth rate of A. veronii was from EC 11.7 to 40.2 dS m⁻¹. As drainage waters evaporate in holding facilities, salinity tends to increase having serious ecological effects on the growth of A. veronii.     

The toxic effects of trinitrotoluene (TNT) and its primary degradation products on two species of algae and the fathead minnow

The effects of alpha trinitrotoluene (alpha TNT) and its primary degradation product (TNTcc), commonly referred to as “pink water”, were determined on members of two trophic levels. The growth responses of the algae Selenastrum capricornutum and Microcystis aeruginosa were examined through static bioassays. Death and behavioral responses of the fathead minnow (Pimephales promelas) were determined using a proportional diluter. Alpha TNT and TNTcc were both more toxic to the fathead minnow than to either species of alga. Five and 15 mg l⁻¹ alpha TNT inhibited S. capricornutum and M. aeruginosa growth, respectively. TNTcc inhibited S. capricornutum growth at concentrations above 9 mg l⁻¹; it was lethal to M. aeruginosa at 50 mg l⁻¹, but stimulated growth at lower concentrations. The 96-h lc₅₀ values based on the death response of the fathead minnow to alpha TNT and TNTcc were 2.58 and 1.60 mg l⁻¹, respectively. The 96-h ec₅₀ values based on the behavioral responses were 0.46 and 0.64 mg l⁻¹, respectively. There was no response to concentrations of 0.05 mg l⁻¹ alpha TNT and 0.07 mg l⁻¹ TNTcc.     

Effects of copper, zinc and cadmium on Selanastrum Capricornutum

The algicidal and algistatic effects of copper, zinc and cadmium on Selanastrum capricornutum, a unicellular green algae were analyzed by using a modification of the Algal Assay Procedures Bottle Test.Algicidal concentrations of copper, zinc and cadmium were 0.30, 0.70, and 0.65 mg 1⁻¹. Treatment of Selanastrum with various concentrations of the metals resulted in similar growth rates characterized by extended lag growth phases.Combinations of copper, zinc and cadmium were similar in toxicity to equal concentrations of zinc. Combinations of copper and cadmium resulted in a greater growth rate than equal concentrations of copper suggesting that cadmium inhibits copper toxicity.Selanastrum was able to exist in waters from the upper South Fork and North Fork of the Coeur d'Alene River where zinc and other metals were in low concentration. However, the algae was not able to tolerate zinc concentrations greater than 0·5 mg 1⁻¹ from waters of other parts of the drainage. These observations were consistent with laboratory findings where 0.7 mg 1⁻¹ zinc was algicidal and 0.1 mg 1⁻¹ inhibited the growth of Selanastrum.     

Treatment of wastewater in sewer by Spirogyra sp. green algae: effects of light and carbon sources

The aim of this study is to evaluate the use of Spirogyra sp. green algae for wastewater treatment process in sewer. The effects of light and carbon sources were investigated on growth of the algae Spirogyra sp, removal of nitrate, nitrite, phosphate, chemical oxygen demand (COD) and pH changes. Samples 1 & 4 were grown in autotroph form, while samples 2 & 5 and 3 & 6 were grown in media containing 100 and 200 mg/L of glucose, respectively. Samples 1 up to 3 were grown in cycling light but samples 4 up to 6 were grown in continuous light. Results indicated that algal growth, levels of nitrites and pH and removal of nitrate and phosphate were increased in continuous illumination and carbon sources availability (100 and 200 mg/L of glucose). It can be recommended to apply Spirogyra sp. for wastewater treatment proces s in sewer collection system.     

The impact of wastewater irrigation on the chemical quality of groundwater

The purpose of this investigation was to assess the groundwater impact of irrigation with industrial wastewater (baker's yeast wastewater, BYW) and to determine if agricultural reuse can be considered as an efficient wastewater treatment method. The impact of the irrigation and the status of the groundwater quality were determined using chemical parameters that are typical contaminants of BYW and characterise the content of total suspended solids (TSSs), organic matter (biochemical and chemical oxygen demands), nutrients (N_org, N‐NH₄, N‐NO₃, N_total, P_total and K), salts (Cl, SO₄ and Na) and pH. The study revealed that BYW irrigation did not cause a significant increase in the content of these parameters in groundwater at a low water table region (WTR). However, at a high WTR, the irrigation had an extremely significant (P < 0.001) impact on the chemical status of groundwater that has been demonstrated by substantially high values of COD, N‐NH₄, Cl, SO₄ and Na.     

Bacterial suppression of chlorella by hydroxylamine production

An actively nitrifying Arthrobacter sp. isolated from a lake inhibited the growth of Chlorella vulgaris. This was found to be due to hydroxylamine released by the bacterium during the oxidation of ammonium or other reduced nitrogen compounds. Plates containing Plate Count Agar streaked with Arthrobacter, accumulated 5 μg ml⁻¹ hydroxylamine-N. Chlorella was sensitive to less than 0.24 μg ml⁻¹ hydroxylamine-N. Non-nitrifying bacterial isolates of lacustrine origin did not demonstrate inhibiting activity. Our results indicate that nitrifying microorganisms may thus affect the population dynamics of algae in eutrophic lakes.     

Guidelines to unbraced frame design with LRFD

This paper reviews the unbraced frame design procedures in LRFD to highlight the particular difficulties associated with the member capacity checks. Clear guidelines are provided on how the K‐factors and the member forces in sway and non‐sway cases be correctly used for the calculation of several other factors such as B₁, B₂ factors and the column strength calculation P_n. A step‐by‐step design procedure is then outlined to provide a systematic approach to check columns in framed structures. Case studies of columns in two unbraced frames made using the procedure are presented to clarify some possible confusion associated with the LRFD implementation. Copyright © 1999 John Wiley & Sons, Ltd.     

Comparison of the toxicity thresholds of water pollutants to bacteria, algae, and protozoa in the cell multiplication inhibition test

Using analogous methods of the cell multiplication inhibition test, the toxicity threshold (TT) of 156 potential water pollutants was determined for model organisms of biological self-purification, i.e. bacteria of the species Pseudomonas putida, green algae of the species Scenedesmus quadricauda, and flagellate protozoa of the species Entosiphon sulcatum. From the number of 156 inorganic and organic pollutants tested, 23 exhibited a pronounced selective toxic action on bacteria of the species Pseudomonas putida, 47 on algae of the species Scenedesmus quadricauda, and 43 on flagellate protozoa of the species Entosiphon sulcatum. It is seen from the ratios found that a determination of the toxicity threshold of potential water pollutants for these three model organisms from the microbiological spectrum would provide a broader basis for assessing the damaging action of water pollutants to model organisms active in the biological self-purification of water. Ecotoxicological testing of potential water pollutants to evaluate their toxicity involving only one model organism of biological self-purification would give an incomplete and biased picture of the effects of pollutants.     

Empirical evaluation of ductility factors for the special steel moment‐resisting frames in view of soil condition

It is well known that the response modification factor (R) takes into account the ductility, over‐strength, redundancy and damping of structural systems. The ductility factor has played an important role in seismic design, as it is a key component of R. In this study, the ductility factors (R_μ,MDOF) of special steel moment‐resisting frames are calculated by multiplying the ductility factor of single degree of freedom (SDOF) systems (R_μ,SDOF) with the multi‐degree of freedom (MDOF) modification factors (R_M). The ductility factors (R_μ,SDOF) of SDOF systems are computed from non‐linear dynamic analysis undergoing different levels of displacement ductility demands and periods when subjected to a large number of recorded earthquake ground motions. To compute the R_μ,SDOF, a group of 1,860 ground motions recorded from 47 earthquakes were considered. R_M factors are proposed to account for the MDOF systems, based on previous studies. A total of 108 prototype steel frames were designed to investigate the ductility factors, considering design parameters such as the number of stories (4, 8 and 16), framing systems (perimeter frames and distributed frames), failure mechanisms (strong column‐weak beam and weak column‐strong beam), soil profiles (S_A, S_C and S_E in Uniform Building Code 1997) and seismic zone factors (Z = 0·075, 0·2, and 0·4 in UBC 1997). The effects of these design parameters on the R_μ,MDOF of special steel‐moment‐resisting frames were investigated. Copyright © 2009 John Wiley & Sons, Ltd.