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  • 1
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: The scattering of neutrons by a clean, type II superconductor in the mixed state is studied, using a quantized hydrodynamic theory for the superfluid vortex lattice. If the scattering amplitude is expanded in the number of quanta of vortex waves emitted or absorbed, the resulting inelastic cross section diverges at long wavelengths. Inclusion of inelastic effects to all orders removes this unphysical singularity and yields a differential cross section which differs only slightly from that predicted for elastic scattering.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Several targets are described that in simulations give yields of 1–30 MJ when indirectly driven by 0.9–2 MJ of 0.35 μm laser light. The article describes the targets, the modeling that was used to design them, and the modeling done to set specifications for the laser system in the proposed National Ignition Facility. Capsules with beryllium or polystyrene ablators are enclosed in gold hohlraums. All the designs utilize a cryogenic fuel layer; it is very difficult to achieve ignition at this scale with a noncryogenic capsule. It is necessary to use multiple bands of illumination in the hohlraum to achieve sufficiently uniform x-ray irradiation, and to use a low-Z gas fill in the hohlraum to reduce filling of the hohlraum with gold plasma. Critical issues are hohlraum design and optimization, Rayleigh–Taylor instability modeling, and laser–plasma interactions. © 1995 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Capillary GC ; Vacuum backflush ; Repetitive analysis ; Vapor stream analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A vacuum-pump-operated backflush system has been developed for applications involving high-speed, repetitive GC analysis of gas streams containing ppm and ppb levels of organic vapor. The system uses an injector capable of cryofocusing and a relatively short length of 0.25-mm i.d. fused silica column for the separation of relatively simple mixtures of volatile compounds. Analysis times typically are in the 5-10 s range, and backflush times are in the 2-5 s range. Gases from the flame ionization detector are used as the backflush carrier gas, and no modification of the detector is necessary. A procedure is described which allows the average gas velocity to be measured during backflush operation. The minimum backflush time is directly proportional to the analysis time and to the square of the column length, making this system most useful with short columns and short analysis times.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2020-01-18
    Type: Dataset
    Format: text/tab-separated-values, 192 data points
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  • 5
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    PANGAEA
    In:  Supplement to: Payeur, Amy L; Meyers, Philip A; Sacks, Richard D (2011): Evaluation of on-line pyrolysis two-dimensional gas chromatography time-of-flight mass spectrometry (Py–GC×GC–ToFMS) on whole sediments from a Mediterranean sapropel sequence. Organic Geochemistry, 42(10), 1263-1270, https://doi.org/10.1016/j.orggeochem.2011.07.008
    Publication Date: 2020-01-18
    Description: Analysis of the molecular composition of the organic matter (OM) from whole sediment samples can avoid analytical bias that might result from isolation of components from the sediment matrix, but has its own analytical challenges. We evaluated the use of GC * GC-ToFMS to analyze the pyrolysis products of six whole sediment samples obtained from above, within and below a 1 million year old OM-rich Mediterranean sapropel layer. We found differences in pyrolysis products 〈n-C22 between the OM-rich sapropel samples and the OM-poor background marls. The presence of alkyl pyrroles, probably derived from chlorophyll, in pyrolysates of the sapropels but not in those of the marls suggests that higher marine productivity and greater OM preservation accompanied deposition of the sapropels. Detection of tetramethyl benzenes considered to be pyrolysis products of isorenieratene in the sapropel samples is evidence that nitrogen-fixing green sulfur bacteria contributed to the high productivity. Greater abundances of shorter chain aliphatic hydrocarbons, pyrroles, furans and alkyl aromatics in the pyrolysates of sapropel samples relative to the marls confirm better preservation of marine OM in the sapropels. In addition, the presence of greater amounts of thiophenes in the sapropels than in the marls is consistent with the existence of euxinic conditions during sapropel deposition. The combination of whole sediment pyrolysis and GC × GC-ToFMS is promising, but the procedure requires careful selection of its multiple analytical variables, particularly the pyrolysis temperature and the operational features of the GC columns.
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 6
    ISSN: 0935-6304
    Keywords: High speed capillary GC ; Metal capillary cold traps ; Thermal decomposition of analytes ; Effect of carrier gas ; Quantitative analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal decomposition of some hydrocarbon and chlorinated hydrocarbon compounds in metal capillary tubes used in an inlet system for high speed gas chromatography has been investigated. The metal tube is cooled to about -75°C by a flow of cold nitrogen gas in order to focus a vapor sample cryogenically. A capacitive discharge power supply is then used to heat the metal tube resistively in order to revaporize the sample and introduce it to the separation column as a plug 5-10 ms wide. The effects of tube temperature, tube material, sample vapor residence time, and type of carrier gas on thermal cracking are described. Use of a copper-nickel alloy tube resulted in less cracking than either pure platinum or pure nickel. Cracking is more significant with hydrogen as carrier gas than with helium. Cracking also increases with increasing sample residence time in the hot tube. Quantitative sample injection with minimum decomposition can be obtained for a variety of aliphatic and aromatic hydrocarbons and chlorinated hydrocarbon compounds.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0935-6304
    Keywords: Tunable column ensembles ; high speed GC ; comprehensive two-dimensional GC ; time of flight ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A series-coupled ensemble of two capillary GC columns of different selectivity with an adjustable pressure at the column junction point is used to obtain tunable selectivity for high-speed GC and GC/TOFMS. An electronic pressure controller with a 0.1-psi step size is used to obtain numerous computer-selected unique selectivities. System configurations for conventional, atmospheric-pressure outlet operation with flame ionization detection and for vacuum-outlet operation with photoionization detection are described for GC-only experiments. Polydimethylsiloxane is used as the non-polar column and polyethylene glycol (atmospheric outlet) or triflouropropylpolysiloxane (vacuum outlet) is used as the polar column. For GC/TOFMS experiments, 5% phenyl polydimethylsiloxane was used as the non-polar column, and polyethylene glycol was used as the polar column. The time-of-flight mass spectrometer can acquire up to 500 complete mass spectra per second. Since spectral continuity is achieved across the entire chromatographic peak profile, severely overlapping peaks can be spectrally deconvoluted for high-speed characterization of completely unknown mixtures. For mixture components with significantly different fragmentation patterns, spectral deconvolution can be achieved for chromatographic peak separations of as little as 6.0 ms. This can result is very large peak capacity for time compressed (not completely resolved) chromatograms. The use of columns with tunable selectivity allows for precise peak-position control, which can result in more efficient utilization of available peak capacity and thus further time compression of chromatograms. The limits of tunability and deconvolution are tested for near co-elutions of different classes of hydrocarbon compounds as well as for more multi-functional mixtures.
    Additional Material: 9 Ill.
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  • 8
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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