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  • 1
    Electronic Resource
    Electronic Resource
    Dissociative resonance activation of cyclopropane monolayers on copper: Evidence for CH and CC bond scission (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 8619-8626 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Energy selective electron beam modification of cyclopropane on Cu(110) and Cu(111) single crystal surfaces was performed using the electron beam intrinsic to a high resolution electron energy loss (HREELS) spectrometer. Vibrational spectra of the resulting adsorbed dissociation fragments were recorded using the same HREELS spectrometer. Electron irradiation in the range 10–18 eV of weakly adsorbed cyclopropane was found to lead to the formation of chemisorbed dissociation fragments. HREELS and complementary thermal desorption data were used to identify the chemisorbed products as metallacyclobutane and cyclopropyl groups. The formation of these two surface species implies the existence of two dissociation channels involving CC and CH bond scission, respectively. Variations in the cross section for electron induced modification indicates the presence of a dissociative attachment resonance centered at approximately 10 eV. Cyclopropyl formation and ring opening of cyclopropane at 10 eV are attributed to competition between two decay channels of a core-excited resonance. The cross section for metallacyclobutane formation, at 10 eV, was evaluated to be roughly 0.8×10−17 cm2. The ratio of cyclopropyl to metallacyclobutane surface species, formed at 10 eV, was found to be 4:1. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475014
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  • 2
    Electronic Resource
    Electronic Resource
    Current-induced local oxidation of metal films: Mechanism and quantum-size effects (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2173-2175 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel route is introduced for oxidizing thin metal films with nanometer-scale resolution. By locally subjecting Ti and Nb films to high in-plane current densities, metal-oxide tunneling barriers are formed in a self-limiting fashion. The oxidation is triggered by current-induced atomic rearrangements and local heating. At the final stages of the barrier formation, when only atomic-scale channels remain unoxidized, the oxidation rate decreases drastically while the conductance drops in steps of about 2e2/h. This behavior gives evidence of ballistic transport and a superior stability of such metallic nanowires against current-induced forces compared with the bulk metal. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122413
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  • 3
    Electronic Resource
    Electronic Resource
    Atomic force microscope tip-induced local oxidation of silicon: kinetics, mechanism, and nanofabrication (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 285-287 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Atomic force microscope induced local oxidation of silicon is a process with a strong potential for use in proximal probe nanofabrication. Here we examine its kinetics and mechanism and how such factors as the strength of the electric field, ambient humidity, and thickness of the oxide affect its rate and resolution. Detection of electrochemical currents proves the anodization character of the process. Initial very fast oxidation rates are shown to slow down dramatically as a result of a self-limiting behavior resulting from the build up of stress and a reduction of the electric field strength. The lateral resolution is determined by the defocusing of the electric field in a condensed water film whose extent is a function of ambient humidity. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119521
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  • 4
    Electronic Resource
    Electronic Resource
    Whey Changes during Processing Determined by Near Infrared Spectroscopy (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 62 (1997), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We assessed the potential application of near infrared (NIR) spectrophotometry using a remote optic fiber probe for the development of calibrations. We evaluated the heat denaturation of whey proteins, the chemical composition of a whey protein concentrate (WPC) during production, and the degree of hydrolysis (DH) of whey proteins during trypsin hydrolysis. Partial least square (PLS) calibrations were developed for these applications and were related to a variety of products and processing conditions, so as to increase their reliability. NIR has potential applications in real time analysis for whey processing lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1997.tb04409.x
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  • 5
    Electronic Resource
    Electronic Resource
    Residual Diesel Measurement in Sand Columns After Surfactant/Alcohol Washing (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 34 (1996), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: A new simple gravimetric technique has been designed to determine residual oil saturation of complex hydrocarbon mixtures (e.g., diesel) in sand column experiments because reliable methods are lacking. The He/N2 technique is based on drying of sand columns by circulating helium gas to drag oil droplets in a cold trap (liquid nitrogen). With this technique, residual diesel measurement can be performed easily immediately after alcohol/surfactant washing and in the same lab. For high residual diesel content in Ottawa sand (25 to 30 g/kg), the technique is much more accurate (± 2% or 600 mg/kg) than the standard analytical methods for the determination of mineral oil and grease. The average relative error on partial diesel dissolution in sand column estimated after alcohol/surfactant flooding (residual saturation of 10 to 15 g/kg) is as low as 5%. The precision of the He/N2 technique is adequate to compare relative efficiency of washing solutions when partial extraction of residual oil in Ottawa sand columns is performed. However, this technique is not adapted for determination of traces of oil in sediment or for environmental control of contaminated soils. Each diesel determination by the He/N2 technique costs less than 8 $US in chemical products (helium and liquid nitrogen). A simple laboratory drying setup can be built for less than 400 $US which makes this technique valuable for diesel analyses when a large number of tests are required.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1996.tb01876.x
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  • 6
    Electronic Resource
    Electronic Resource
    Kinetic study of Maillard reactions in milk powder by photoacoustic spectroscopy (1988)
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 36 (1988), S. 497-501 
    Details
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jf00081a023
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  • 7
    Electronic Resource
    Electronic Resource
    Surfactant Solutions Developed for NAPL Recovery in Contaminated Aquifers (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 34 (1996), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Phase diagrams can be used to select surfactant solutions for diesel dissolution and extraction in contaminated aquifers. They indicate the active matter concentrations which can be injected into an aquifer. Due to surfactant precipitation or fine particles dispersion in sediments, surfactant solutions concentration greater than 5% and less than their solubility limit can be used for injections. Surfactant solution effects on interfacial tension (IFT) are consistent with predictions from phase diagrams. For similar active matter concentrations, IFT are lower for surfactant solutions that dissolve more diesel. IFT values between equilibrated diesel and surfactant solutions and observation of the oil-in-water microemulsions in column effluents confirm that solubilization of oil can occur in a Winsor type I system without oil mobilization. More than 50 sand column experiments were done for this study and a good agreement is observed between diesel dissolved in sand column experiments (with downward injection) and diesel dissolution predicted from phase diagrams. However, sand columns experiments showed significant decrease in efficiency with a drop in temperature from 25° C to 8° C (phase diagrams predict no change) and they are essential to check efficiencies of washing solution selected by phase diagrams. Optimal injection concentration of solutions decreases as the alcohols ratio (n-AmOH:n-BuOH) increases and as the temperature decreases. In columns, optimal concentration of surfactant solutions has a maximum efficiency of 0.4 (dissolved diesel/active matter). This limited performance is explained by: (1) the use of water to push a slug of washing solution creates dilution and thus demixing of the oil-in-water microemulsion in the column; (2) the limited interfacial area between diesel and washing solution in the porous media; (3) surface effects on the solid phase. Diesel extraction in sand columns is strongly influenced by the flow direction (up/down), the volume of the solution, and to a lesser extent by water salinity. Small modifications of flow velocity (three times faster) do not have a significant effect on diesel dissolution. Efficiency of diesel dissolution by surfactant solutions decreases as washing progresses because interfacial area (diesel/surfactant solution) decreases. The selection of a surfactant for diesel recovery is not based on efficiency alone but must also consider the costs of the ingredients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1996.tb01874.x
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  • 8
    Electronic Resource
    Electronic Resource
    Phase Diagrams to Optimize Surfactant Solutions for Oil and DNAPL Recovery in Aquifers (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 31 (1993), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Phase diagrams can be used to optimize the composition of surfactant solutions (cosurfactant/surfactant) designed for the recovery of DNAPLs at residual saturation in aquifer formations. The study also shows that the combination of cosurfactant (alcohol) and surfactant is more effective than the use of alcohols or surfactants separately. The suggested approach is based on miscible oil displacement using surfactant solutions at high concentrations. Most of the recent projects using surfactants for aquifer cleanup use low-concentration solutions that promote immiscible oil displacement. The goal of the present study is to demonstrate the potential of optimized surfactant solutions to restore oil and DNAPL-contaminated sites such as the one in Ville Mercier, Quebec (site contaminated with a mixture of petroleum and chlorinated solvents). The results show that alcohol/surfactant systems can be used to solubilize chlorinated solvents (TCE, PCE) and light oils (gasoline, diesel). For the dissolution of heavy and viscous oils (motor oil, ATF, creosote, Ville Mercier oil), an organic solvent must be added to the alcohol/surfactant system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1993.tb00852.x
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  • 9
    Electronic Resource
    Electronic Resource
    Rings of single-walled carbon nanotubes (1999)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 398 (1999), S. 299-299 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Among the most studied processes of self-organization, are the coiling and ring formation of biopolymers such as DNA and proteins. These processes are complex, involving several different types of interaction. We have found that single-walled carbon nanotubes (SWNTs), which are renowned for ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/18589
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  • 10
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    Current-induced local oxidation of metal films: Mechanism and quantum-size effects (1998)
    American Institute of Physics
    Details
    Publication Date: 1998-10-12
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics
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