Capillary electrochromatography-mass spectrometry of nonionic surfactants

The Triton X (TX)-series are alkylphenol polyethoxylates -type nonionic surfactants of varying numbers of ethylene oxide units. Applications include industrial and household detergent formulations as well as emulsifying agents. For analysis of these surfactants, capillary electrochromatography-electrospray ionization-mass spectrometry (CEC-ESI-MS) offers several unique advantages over the traditional hyphenation methods based on HPLC-MS. These include higher plate numbers attainable in CEC-MS, as well as more compatible flow rate (submicroliter) when coupled to ESI-MS and, perhaps most importantly, less consumption of toxic and costly organic solvents. In this work, different CEC-ESI-MS parameters such as mobile-phase composition, sheath liquid, and spray chamber parameters were optimized to provide suitable and sensitive analysis of short-, medium-, and long-chain length (e.g., n = 1-16) TX-series nonionic surfactants. The optimized CEC-ESI-MS conditions were mobile phase containing 90/10 ACN/2.5 mM Tris, pH 8, sheath liquid containing 50/50 MeOH/10 mM HCO(2)NH(4) delivered at 5 microL/min, spray chamber set to drying gas flow of 6 mL/min, nebulizer pressure of 5 psi, and drying gas temperature set to 200 degrees C. This optimization is followed by the more challenging separation of very long chain TX-series with a large number (n = 30-70) of ethoxy units, which were initially found to exhibit extreme retention using the developed method. It was observed that through the addition of small volume fraction of polar-aprotic tetrahydrofuran solvent to the running buffer, the retention time could be significantly reduced thus enhancing the feasibility for CEC-ESI-MS analysis of these very long chain nonionic surfactants for the first time. The detection limit was approximately 37 microg/mL total octylphenol ethoxylate for TX-45; acceptable precision of migration time (<1% RSD, n = 3) and peak area ( approximately 4% RSD, n = 3) were achieved.     

Solubilization of multi walled carbon nanotubes under a facile and mild condition

Multi-walled carbon nanotubes (MWCNTs) functionalized with amino groups was prepared via chemical modification of carboxyl groups introduced on the carbon nanotube surfaces. Oxidation of MWCNTs was performed with ozone in aqueous phase and amidation of generated carboxylic groups, was occurred with amines in the presence of HATU as a coupling agent. Obtained functionalized MWCNTs are soluble in many common organic solvents. The functionalized MWCNTs were characterized in detail using FTIR-ATR, Raman CHN and SEM methods.     

Equilibrium calculations for direct synthesis of dimethyl ether from syngas

Thermodynamic analysis of single‐step synthesis of dimethyl ether (DME) from syngas over a bi‐functional catalyst (BFC) in a slurry bed reactor has been investigated as a function of temperature (200–240°C), pressure (20–50 bar), and composition feed ratio (H₂/CO: 1–2). The BFC was prepared by physical mixing of CuO/ZnO/Al₂O₃ as a methanol synthesis catalyst and H‐ZSM‐5 as a methanol dehydration catalyst. The three reactions including methanol synthesis from CO and H₂, methanol dehydration to DME and water–gas shift reaction were chosen as the independent reactions. The equilibrium thermodynamic analysis includes a theoretical model predicting the behaviour and a comparison to experimental results. Theoretical model calculations of thermodynamic equilibrium constants of the reactions and equilibrium composition of all components at different reaction temperature, pressure, and H₂/CO ratio in feed are in good accordance with experimental values.     

Dowex50W-X树脂吸附硫酸溶液中的锶

In this study,strontium adsorption from sulfuric acid solution by different Dowex 50W-X ion exchange resins was investigated.Among these resins,Dowex 50W-X8 resin showed the maximum sorption of strontium from the aqueous solutions.The effect of pH,contact time,mass of resin,temperature,and concentration of interfering ions on strontium adsorption were evaluated to determine the optimum conditions of strontium sorption process.The kinetic models of sorption were analyzed using pseudo-first and pseudo-second order models.The results indicated that the pseudo-second order kinetic model was more appropriate than the other one.Moreover,the data obtained in this study were fitted into several sorption isotherm models and it was found that the Langmuir sorption isotherm shows the best fitting to the experimental data.     

Reliability-based optimization of trusses with random parameters under dynamic loads

In this work, a reliability-based optimization technique is addressed to obtain the minimum mean value of random mass of the structures with random parameters under stationary stochastic process excitation. The challenge of the problem lies in randomness involved from both structural parameters and dynamic load, which renders the structural reliability becoming the random dynamic reliability of the first passage problem. In order to obtain minimum mean value of random gross mass, element and system dynamic reliability constraints are constructed, respectively, and the structural sizing and shape optimization models based on the dynamic reliability are then presented. Moreover, among two optimal strategies proposed for optimization models, the second one can effectively reduce the workload by avoiding the computation of the variance of the dynamic response during the iterative process. Finally, the implementation of three examples is discussed to display the feasibility and validity of optimization technique given.     

Sodium dodecyl sulfate coated alumina modified with a new Schiff's base as a uranyl ion selective adsorbent

A simple and selective method was used for the preconcentration and determination of uranium(VI) by solid-phase extraction (SPE). In this method, a column of alumina modified with sodium dodecyl sulfate (SDS) and a new Schiff's base ligand was prepared for the preconcentration of trace uranyl(VI) from water samples. The uranium(VI) was completely eluted with HCl 2M and determined by a spectrophotometeric method with Arsenazo(III). The preconcentration steps were studied with regard to experimental parameters such as amount of extractant, type, volume and concentration of eluent, pH, flow rate of sample source and tolerance limit of diverse ions on the recovery of uranyl ion. A preconcentration factor more than 200 was achieved and the average recovery of uranyl(VI) was 99.5%. The relative standard deviation was 1.1% for 10 replicate determinations of uranyl(VI) ion in a solution with a concentration of 5 μg mL(-1). This method was successfully used for the determination of spiked uranium in natural water samples.     

Influence of polyethylene glycol on the excretion and digestibility of amino acids in casein and tannic acid‐fed broilers

Using the precision feeding technique, an experiment was conducted to evaluate the influence of tannic acid (TA) and polyethylene glycol (PEG) on the excretion of amino acids and the apparent and true digestibilities of casein protein in broilers. Seventy‐two 9‐week‐old broiler cockerels grouped in nine treatments of eight replicates were fed warm water (50 mL, control birds), casein alone (12 or 18 g) or casein (12 or 18 g) with TA solution (4.5 g per 10 mL) or/and PEG solution (2 g per 10 mL). Total excreta were collected for 48 h and freeze‐dried. The amino acid content of casein and excreta was determined by reverse phase high‐performance liquid chromatography. In the absence of TA the digestibility of casein was almost complete. TA increased the excretion of amino acids to a varying extent (P < 0.01). Although the digestibility of all essential and non‐essential amino acids was adversely affected by the presence of TA, raising the amount of casein from 12 to 18 g improved significantly (P < 0.05) the apparent and true digestibilities of all amino acids. PEG reduced significantly (P < 0.01) the excretion of amino acids and improved significantly (P < 0.01) the amino acid digestibility of casein in TA‐dosed birds. However, the improvement was greater when the lower level of casein (12 g) was fed. Thus PEG might play an important role in inactivating dietary tannins in the gastrointestinal tract of birds and improving protein digestibility and utilisation, particularly when the diet is low or intermediate in protein. Copyright © 2007 Society of Chemical Industry     

Robust adaptive vibration control of a flexible structure

Different types of L1 adaptive control systems show that using robust theories with adaptive control approaches has produced high performance controllers. In this study, a model reference adaptive control scheme considering robust theories is used to propose a practical control system for vibration suppression of a flexible launch vehicle (FLV). In this method, control input of the system is shaped from the dynamic model of the vehicle and components of the control input are adaptively constructed by estimating the undesirable vibration frequencies. Robust stability of the adaptive vibration control system is guaranteed by using the L1 small gain theorem. Simulation results of the robust adaptive vibration control strategy confirm that the effects of vibration on the vehicle performance considerably decrease without the loss of the phase margin of the system.     

Low interfacial tension liquid–liquid extraction with impinging-jets contacting method: Influencing parameters and relationship

Liquid–liquid extraction process with the recommended low interfacial tension chemical system of butanol–succinic acid–water was performed in a two impinging-jets contacting device (TIJCD), working continuously with opposed impinging jets. A range of extraction efficiency of 58–96% was achieved under different conditions. Overall volumetric mass transfer coefficient and specific power input criteria clearly indicate the great performance capability of TIJCD. An increase in nozzle diameter and/or jets force results an efficiency enhancement, while increase in inter-nozzle distance leads the efficiency diminish. The overall volumetric mass transfer coefficient was satisfactorily correlated in the form of ordinary and dimensionless correlations.     

Estimates of Transaction Costs in Transfer of Development Rights Programs

Problem, research strategy, and findings: Local jurisdictions in 36 states have implemented transfer of development rights (TDR) programs to provide a market-based approach to preserving farmlands and open space while redirecting future development to targeted areas. Participation in TDR programs involves transaction costs over and above paying for TDR credits. Planners know little about the magnitude of transaction costs; who, if anyone, incurs a disproportionate share of these costs; or how transaction costs affect TDR participation. In this study we estimate the magnitude and distribution of transaction costs incurred by participants in 4 countywide TDR programs in Maryland, a TDR pioneer, by interviewing multiple participants in these programs. We fi nd that total transaction costs were high and borne largely by private sector participants, although we exclude the initial public sector costs of establishing the programs. Total transaction costs range from 13% to 21% of total TDR costs per transaction. Our findings are based on data reported by participants and may not be scalable; transaction costs, however, might deter landowners from participating in TDR programs, thus thwarting the land use goals of planners.

Takeaway for practice: Planners should work to reduce transaction costs by better constructing TDR programs and providing greater information on TDR sale prices and potential buyers and sellers. Lowering and more fairly distributing transaction costs will make the TDR program a more successful approach to achieving land use goals and addressing the externalities arising from land use markets.