Biodegradation of chlorpyrifos and 3, 5, 6‐trichloro‐2‐pyridinol by a novel rhizobial strain Mesorhizobium sp. HN3

A chlorpyrifos (CP) and 3,5,6‐trichloro‐2‐pyridinol (TCP) degrading bacterial strain, Mesorhizobium sp. HN3, was isolated and characterized. Mesorhizobium sp. HN3 degraded CP efficiently up to 400 mg/L initial concentration at wide range of temperatures (30–40°C) and pH (6.0–8.0). However, optimal degradation of CP was achieved at 37°C and neutral pH (7.0) at an initial inoculum density 2 × 10⁷ colony forming unit/mL of culture medium. Kinetic parameters for CP degradation by Mesorhizobium sp. HN3 were estimated at different initial concentrations. Cultures exhibited significant variation (P ≤ 0.05) in the specific growth rate (μ), cell mass formation rate (Q_X) and the substrate uptake rate (Q_S) during degradation of CP. The values of kinetic parameters increased up to 100 mg/L CP and decreased at higher concentration. Investigation of degradation metabolites indicated that CP is converted to diethylthiophosphate and TCP that leads to the formation of 3,5,6‐trichloro‐2‐methoxypyridine.     

Spectrophotometric determination of nickel using a new chromogenic reagent in plant leaves

A Spectrophotometric method for the determination of nickel in plant leaves with new chromogenic reagent is presented. A new highly sensitive and selective chromogenic reagent dibromo‐p‐methyl‐carboxyazo was synthesized; in 0.25 M phosphoric acid medium, which greatly increases the selectivity. Nickel reacts with DBMCA to form a 1:2 mole‐ratio bluish red complex, having a sensitive absorption peak at 625 nm under optimal conditions. Beer's law is obeyed over the range from 0.01 to 0.79 µ mL^? Ni (II) and the apparent molar absorptivity is 1.038?×?10^??4 mol^??1 cm^??1. The detection limit and variation coefficient were found to be 2.12 ng mL^??1 and 1.0% respectively. It is found that, except for Ca (II) and Ba (II), all foreign ions studied do not interfere with determination. The interference caused by Ca(ll) and Ba(ll) can be easily eliminated by prior extraction with potassium iodide methyl isobutyl ketone. The method has been applied to the determination of nickel in plant leaves with good accuracy.     

Behaviour of uni‐axially loaded concrete‐filled‐steel‐tube columns confined by external rings

Concrete‐filled‐steel‐tube (CFST) columns have been widely adopted for column construction of tall buildings due to its superior strength and ductility performance contributed by the composite action. However, this beneficial composite action cannot be fully developed at early elastic stage as steel dilates more than concrete and thereby causing imperfect interface bonding. Hence, it reduces the elastic strength and stiffness of the CFST columns. To resolve the problem, external confinement in the form of steel rings is proposed in this study to restrict the lateral dilation of concrete and steel at initial elastic stage. In this paper, CFST columns of various dimensions cast with normal‐strength or high‐strength concrete and installed with external steel rings were tested under uni‐axial compression. From the results, it was evident that (a) the external steel rings could restrict the lateral dilation of CFST columns and improve the interface bonding condition and (b) externally confined CFST columns had uni‐axial strength and stiffness larger than those of unconfined CFST columns. With the experimental results, an analytical model taking into account the confining effects of steel tube and rings has been developed to predict the uni‐axial strength of ring‐confined CFST columns. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of in‐cycle strength degradation on collapse capacity of steel moment frames

In this study, the effects of in‐cycle strength degradation of steel moment connections are investigated on global behavior of multiple degree‐of‐freedom structures. Two types of degrading connection models are defined and compared with a bilinear non‐degrading model. Due to dispersion of the experimental test results on connections performance, two models are considered for each type. A probability assessment is carried out by implementation of incremental dynamic analysis to find the capacity of the structures for various performance levels. A sensitivity study is conducted on hysteresis parameters of connection models to investigate the effect of these parameters on global behavior of the structures. Due to increased dispersion of displacement demands observed in degrading cases, a reliability analysis is carried out to consider the effect of uncertainty on confidence level of the structures. Results show that in‐cycle strength degradation can lead to abrupt dynamic instability and as a consequence decrease in reliability of the system against collapse. Copyright © 2013 John Wiley & Sons, Ltd.     

Experimental study of across‐wind aerodynamic damping of super high‐rise buildings with aerodynamically modified square cross‐sections

Across‐wind aerodynamic damping ratios are determined from the wind‐induced acceleration responses of 10 aeroelastic models of square super high‐rise buildings in an urban flow condition (exposure category C in the Chinese code) using the random decrement technique. Moreover, the influences of amplitude‐dependent structural damping ratio on the estimation of aerodynamic damping ratio are discussed. The validity of estimated damping is examined through a comparison with previous research achievements. On the basis of the estimated results, the characteristics of the across‐wind aerodynamic damping ratios of modified square high‐rise buildings are studied. The effects of aerodynamically modified cross‐sections, such as chamfered, slotted and tapered cross‐section, on the across‐wind aerodynamic damping ratio are investigated. The results indicate that modifications of cross‐sections are not always effective in suppressing the aeroelastic effects of super high‐rise buildings. Low corner‐cut ratios (chamfer ratios from 5% to 20% and slot ratios from 5% to 10%) and low taper ratio (1%) significantly decrease the magnitudes of absolute aerodynamic damping ratios. However, large modifications of cross‐sections (slot ratio of 20% and taper ratios from 3% to 5%) increase wind‐induced responses by changing the aerodynamic damping ratios. According to the database, empirical aerodynamic damping function parameters are fitted for high‐rise buildings with aerodynamically modified square cross‐sections. Copyright © 2013 John Wiley & Sons, Ltd.     

Valuation of multi‐stage BOT projects involving dedicated asset investments: a sequential compound option approach

The valuation of multi‐stage build‐operate‐transfer projects is not a trivial task. It needs to deal with uncertain project values in future expansions and the possibility of expansions or abandonment in the presence of project risks. The valuation problem becomes more difficult when multi‐stage projects require upfront and intermediate dedicated asset investments for future expansions. Dedicated asset investments may or may not create project values, depending on whether future expansions could be justified and realized. A sequential compound option model is proposed to tackle these important valuation issues.     

Variations in isotopic composition of desalinated water

Variations in isotopic ratios of water samples collected from three plants functioning on two different desalination processes were evaluated by comparing their measured δ¹⁸O, δ¹⁷O and the δ²H isotopic ratios before and after desalination using a system based on tunable off‐axis integrated‐cavity‐output diode laser spectroscopy (OA‐ICOS). The δ¹⁸O, δ¹⁷O and the δ²H isotopic ratio measurements for water samples collected before desalination are compared against their peers of desalinated water from two desalination plants on the Arabian Gulf that are operating under the Multistage Flash (MSF) process. Also, variations in the δ¹⁸O, δ¹⁷O and the δ²H isotopic ratio measurements due to desalination from a Reversal Osmosis (RO) facility in Dhahran, Saudi Arabia were also reported and compared against variations in isotopic composition of water desalinated in two MSF plants.     

Verbunddecken aus Stahlfaserbeton und Holz

Composite Floors made of Steel Fibre Reinforced Concrete and Timber For many years the timber‐concrete composite construction is known and approved particularly with regard to the revaluation and strengthening of timber beam ceilings. The benefits are an obvious increase of the load bearing capacity, a reduction of the deflection, a better vibration behaviour of the ceiling and an improvement of building physical properties like sound insulation and fire resistance. The reinforcement of the concrete slab is necessary, but leads to a large slab thickness in connection with the necessity of a sufficient concrete cover and to disadvantages during the execution of construction work. Therefore it is reasonable to replace the conventional reinforcement by steel fibres. This paper reports on two building projects and their associated experimental pre‐tests, in which steel fibre reinforced concrete was applied for the strengthening of timber beam ceilings.