Focusing and Mobilization of Bacteria in Capillary Electrophoresis

An isotachophoretic method has been developed for mobilizing and focusing bacteria. This allows quantification and detection of bacteria in a narrow zone. Very good linearity was obtained for Micrococcus lysodeikticus (also called Micrococcus luteus, studied as a model of Gram+ bacteria) in the range of 0.4 × 10(8) cells/mL to 2.9 × 10(8) cells/mL, with correlation coefficients for peak height and peak area as a function of cell concentration of 0.999 and 0.998, respectively. This method is usable on both bare and hydroxypropyl cellulose-coated fused silica capillaries. The best results were obtained using 13.6 mM Tris, 150 mM boric acid as terminating electrolyte, and 4.5 mM Tris, 50 mM boric acid, and 3.31 mM HCl as leading electrolyte. With a 33.5 cm ×100 μm i.d. capillary, short migration times were obtained while maintaining very low electrical current in order to minimize any Joule heating and lysis of the bacteria. A UV area imaging detector (ActiPix D100, Paraytec) was used with a 109 cm × 100 μm i.d. capillary having three loops and four detection windows to monitor the migration behavior of M. luteus and to show the stability of the zone of the focused bacteria along the capillary. Similar results were obtained for Erwinia carotovora (a model of Gram- bacteria), and for Enterobacter cloacae and Vibrio splendidus.     

Solarthermal seawater desalination systems for decentralised use

The performance of a pilot solar Multi Effect Humidification (MEH) Desalination system in Fuerteventura, Canary Islands, had been measured and analysed in detail by the ZAE Bayern since 1992. The investigated distillation units showed constant performance over several years without extensive maintanance. However the efforts towards further efficiency improvement by economic means pointed out the need of supplementing the system with a thermal storage tank. The distillation unit being the most expensive part of a desalination system has to be run 24 hours a day in order to be economic. A cost estimation for storage implementation yields the result, that cost reduction for the produced water by more than a half is possible. In April 1997 a desalination system with 24 hour thermal storage was built up in Sfax / Tunisia. The results of a short term measuring campaign at this site are presented here.For optimizing the ratio of sizes of thermal storage, collector field and distillation module a simulation tool for collector field and storage is developed at the ZAE Bayern. The simulation results of a combined laboratory distillation unit and storage system are presented.     

Oil removal from water by sorption on hydrophobic cotton fibers. 2. Study of sorption properties in dynamic mode

The recovery of oil from an oil-in-water emulsion, during a flow through a bed of cotton rendered hydrophobic by acylation of cellulose was defined by sorption and coalescence phenomena. During percolation, the column "hold-up" (difference between injected and rejected oil) became constant at the equilibrium volume, i.e., as soon as the instant oil concentration in the effluent (C) was equal to the oil concentration in the initial emulsion (C0). This equilibrium permitted the measurement of the cotton sorption capacity (SC), which increased with C0 up to the cotton saturation. The oil-water separation improved at a lower temperature, lower flow, a deeper medium, and larger oil drops. The system was modeled as a piston flow-through in order to generalize the results.     

Theoretical and experimental studies of (In,Ga)As/GaP quantum dots

(In,Ga)As/GaP(001) quantum dots (QDs) are grown by molecular beam epitaxy and studied both theoretically and experimentally. The electronic band structure is simulated using a combination of k·p and tight-binding models. These calculations predict an indirect to direct crossover with the In content and the size of the QDs. The optical properties are then studied in a low-In-content range through photoluminescence and time-resolved photoluminescence experiments. It suggests the proximity of two optical transitions of indirect and direct types.     

Influence of the porosity gradient in cement paste matrix on the mechanical behavior of mortar

This paper is devoted to the study of the influence of the microstructure of mortar on its mechanical behavior. For this purpose, mechanical tests have been carried out on mortars and a mathematical model, the (n + 1)-phase model, has been used to take into account three variable parameters of the microstructure of mortar (the thickness of the interfacial transition zone, the porosity gradient in the cement paste matrix and the nature of the constituents of the Interfacial Transition Zone) for some given parameters (volume fraction of aggregates, porosity of the mortar and mechanical behavior of the aggregates and the cement paste). By fitting some measured moduli to the model predictions, we can estimate in a non-destructive manner, the possible distribution of porosity within the Interfacial Transition Zone. Our results provide information on the data such micromechanical models can deal with in order to predict the elastic behavior of mortars.     

Calculation of CO_2, CH_4 and H_2S Solubilities in Aqueous Electrolyte Solution at High Pressure and High Temperature

INTRODUCTIONPhasebehaviourinaqueouselectrolytesystemsisofinterestfornumerousindustrialapplicationssuchasscaleformationprediction,hydrometallurgy,distil-lation,gasstorage,waterpollutioncontrol.Becauseofeconomical,technicalandecologicalconsiderations,accuratepredictionofgassolubilitiesinelectrolyteso-latinnsoverawiderangeoftemperatures,pressures,andionicstrengthisneeded.Duringnilgration,production,transportandstock-ing,petroleumfluidsareincontactwithsaltedwa-ter(i.e.formationwater,seawateror…     

Chlorination of phenols: kinetics and formation of chloroform

The kinetics of chlorination of several phenolic compounds and the corresponding formation of chloroform were investigated at room temperature. For the chlorination of phenolic compounds, second-order kinetics was observed, first-order in chlorine, and first-order in the phenolic compound. The rate constants of the reactions of HOCl with phenol and phenolate anion and the rate constant of the acid-catalyzed reaction were determined in the pH range 1-11. The second-order rate constants for the reaction HOCl + phenol varied between 0.02 and 0.52 M(-1) s(-1), for the reaction HOCl and phenolate between 8.46 x 10(1) and 2.71 x 10(4) M(-1) s(-1). The rate constant for the acid-catalyzed reaction varied between 0.37 M(-2) s(-1) to 6.4 x 10(3) M(-2) s(-1). Hammett-type correlations were obtained for the reaction of HOCl with phenolate (log(k) = 4.15-3.00 x sigma sigma) and the acid-catalyzed reaction of HOCl with phenol (log(k) = 2.37-4.26 x sigma sigma). The formation of chloroform could be interpreted with a second-order model, first-order in chlorine, and first-order in chloroform precursors. The corresponding rate constants varied between k > 100 M(-1) s(-1) for resorcinol to 0.026 M(-1) s(-1) for p-nitrophenol at pH 8.0. It was found that the rate-limiting step of chloroform formation is the chlorination of the chlorinated ketones. Yields of chloroform formation depend on the type and position of the substituents and varied between 2 and 95% based on the concentration of the phenol.     

Bursting of shielded pressure vessels subject to hypervelocity impact

During the 30-year lifetime of the Space Station, NASA is concerned that a large piece of orbital debris could strike one of the inhabited or laboratory modules. The modules are basically cylindrical pressure vessels, 4.3 meters in diameter and 9.1 meters long, made of Al 2219-T87. There is a potential for unstable crack growth (“unzipping”) in these pressure vessels if a sufficiently-long crack were formed in the pressure vessel wall. The ragged hole generated when debris strikes an exterior shield and impulsively loads the pressure vessel wall could lead to such a crack. The central concern of this research is quantifying the minimum crack length (critical crack length) to initiate unstable crack growth. This paper reports on a two-part investigation into this problem: 1) fracture experiments and analyses aimed at determining the fracture resistance and critical crack length of the module walls, and 2) examination of impact data to determine the impact conditions that could cause the critical crack length to be exceeded. Al 2219-T87 was found to be a modestly rated sensitive material, exhibiting an increase in both ultimate strength and fracture toughness at high strain rates. The results of the conservative linear elastic fracture mechanics analyses indicate critical cracks at least 22.9 cm in length are required for unzipping (3.17-mm thick wall), and 45.7-cm length (for 4.83-mm thick wall). The dynamic analysis results indicate that the critical crack lengths are even longer, about 48.3 to 61.0 cm in length. Examination of the rather limited experimental database indicates that the dynamic analysis values are more realistic, and that under certain conditions of projectile size, wall stress, and shield design the critical crack length can be exceeded.