In vitro activities of antimicrobial agents, alone and in combination, against Acinetobacter baumannii isolated from blood

In vitro activities of 15 antimicrobial agents against 90 strains of Acinetobacter baumannii isolated from blood cultures from hospitalized patients were determined using the agar dilution method. Imipenem, ofloxacin, and ciprofloxacin had the best antimicrobial activity with minimum inhibitory concentrations (MIC50s) of 0.25 mu g/ml and MIC90s of 0.5-1 mu g/ml. beta-lactam antibiotics other than imipenem had poor activity, with MIC50s ranging from 8 to 64 mu g/ml and MIC90s from 32 to > or = 256 mu g/ml. The checkerboard titration method was used to study the effects of combination of two antimicrobial agents. Combinations of ceftazidime, aztreonam, imipenem, or ciprofloxacin with amikacin showed either synergistic effects or partial synergistic effects for 40.9%-86.4% of 22 tested strains. The best in vitro activity was observed with the combination of imipenem and amikacin. No antagonistic effects were observed with the combination of imipenem and amikacin. Synergistic effects were confirmed by time-kill curve studies. In conclusion, imipenem, ofloxacin, and ciprofloxacin were the three most active agents against human blood isolates of A. baumannii. The combination of a beta-lactam or ciprofloxacin with amikacin was synergistic for some of the isolates.     

Solvent sublation for waste minimization in a process water stream - a pilot-scale study

Solvent sublation, an adsorptive bubble separation process, was carried out on a pilot scale to separate dilute concentrations (30-100ppmw) of naphthalene from a process water stream at a temperature of 140 degrees F. The test was conducted at the Borden Chemicals and Plastics (BCP) acetylene plant site located in Geismar, Louisiana. A carbon steel column of 6" i.d. and 17' high was constructed. White mineral oil supplied by Texaco Inc., was used as the organic solvent for solvent sublation. A special annular shear sparger was used for nitrogen gas sparging into the vessel. The process was conducted in two-phase continuous and three-phase continuous modes. The naphthalene recovery from the process water was independent of the oil flow rate, but depended on the nitrogen-to-water flow rate ratio. The release of naphthalene to the overhead gas space during the solvent sublation process was substantially less than that during conventional gas stripping. The improved performance of solvent sublation over both conventional gas stripping and solvent extraction operations was apparent.     

Sediment-air equilibrium partitioning of semi-volatile hydrophobic organic compounds part 2. Saturated vapor pressures, and the effects of sediment moisture content and temperature on the partitioning of polyaromatic hydrocarbons

A gas saturation methodology was used to determine the sediment/air partition coefficient (K(SA)) for phenanthrene and dibenzofuran on a local sediment from the Campus Lake, Baton Rouge. The effects of sediment moisture content, air relative humidity and temperature on K(SA) for phenanthrene were ascertained. The saturated vapor pressures of the compounds were also measured. The sediment moisture content had a striking effect on K(SA); increasing sediment moisture content decreased K(SA). Temperature also had a dramatic effect on K(SA). The variation with temperature was used to evaluate the heats of adsorption on both 'dry' (< 0.8% by mass of water) and 'wet' (> 6% by mass of water) sediments. The heat of adsorption for phenanthrene normalized to unit molecular surface area indicated for the physically adsorbed organic compound was seven times smaller than that for a water molecule. The experimental value of K(SA) was used to test a proposed theoretical model. A good agreement was observed for both phenanthrene and dibenzofuran. The model can be extended to other compounds and sediment types for prediction of air emissions from exposed sediment and dredged materials.     

An experimental study on solar distillation in a single slope basin still by surface heating the water mass

An experimental study was conducted in a single slope basin solar still after introducing a floating perforated and folded aluminium sheet over the water surface, which concentrates heat energy at the surface layer, prevents the whole water mass from getting heated up by convection (by preventing/reducing transmission of radiation through the water body to the bottom liner) and allows evaporated water particles from the covered segments to escape out into the air gap through the holes on it. The distillate yield was found to have improved considerably, especially when the water depth was high. The study also indicated some design features that would further enhance the improvement in output due to the modification made.     

A Dantzig‐Wolfe Decomposition‐Based Heuristic for Off‐line Capacity Calibration of Dynamic Traffic Assignment

Abstract: One of the critical elements in considering any real‐time traffic management strategy requires assessing network traffic dynamics. Traffic is inherently dynamic, since it features congestion patterns that evolve over time and queues that form and dissipate over a planning horizon. Dynamic traffic assignment (DTA) is therefore gaining wider acceptance among agencies and practitioners as a more realistic representation of traffic phenomena than static traffic assignment. Though it is imperative to calibrate the DTA model such that it can accurately reproduce field observations and avoid erroneous flow predictions when evaluating traffic management strategies, DTA calibration is an onerous task due to the large number of variables that can be modified and the intensive computational resources required. To compliment other research on behavioral and trip table issues, this work focuses on DTA capacity calibration and presents an efficient Dantzig‐Wolfe decomposition‐based heuristic that decomposes the problem into a restricted master problem and a series of pricing problems. The restricted master problem is a capacity manipulation problem, which can be solved by a linear programming solver. The pricing problem is the user optimal DTA which can be optimally solved by an existing combinatorial algorithm. In addition, the proposed set of dual variable approximation techniques is one of a very limited number of approaches that can be used to estimate network‐wide dual information in facilitating algorithmic designs while maintaining scalability. Two networks of various sizes are empirically tested to demonstrate the efficiency and efficacy of the proposed heuristic. Based on the results, the proposed heuristic can calibrate the network capacity and match the counts within a 1% optimality gap.