Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Sources of Ground Water Salinization in Parts of West Texas (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water monitoring & remediation 7 (1987), S. 0 
    Details
    ISSN: 1745-6592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: AbstractDetermination of chemical constituent ratios allows distinction between two salinization mechanisms responsible for shallow saline ground water and vegetative-kill areas in parts of west Texas. Mixing of deep-basin (high Cl) salt water and shallow (low Cl) ground water results in saline waters with relatively low Ca/Cl, Mg/Cl, SO44/ Cl, Br/Cl, and NO3/Cl ratios. In scattergrams of major chemical constituents vs. chloride, plots of these waters indicate trends with deep-basin brines as high Cl end members. Evaporation of ground water from a shallow water table, in contrast, results in saline water that has relatively high Ca/Cl, Mg/Cl, SO4/Cl, and Br/CL ratios. Trends indicated by plots of this water type do not coincide with trends indicated by plots of sampled brines. Leaching of soil nitrate in areas with a shallow water table accounts for high NO3 concentrations in shallow ground water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6592.1987.tb00966.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Brine Discharge and Salinization, Concho River Watershed, West Texas (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 27 (1989), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Discharge of naturally occurring brine from the Southern Great Plains regional ground-water flow system significantly affects water quality in local aquifers in the Concho River watershed in West Texas. Aquifers in outcropping Permian rocks locally contain brine and hydrocarbons at depths as shallow as 135 ft (41 m). Maps of hydraulic head, salinity, and hydrochemical facies and graphs of ionic ratios and stable isotopic composition locate where brackish to saline ground water occurs naturally as a result of mixing between locally recharged meteoric water and subsurface brine in the regional flow system. Br/Cl, CI/SO4, Ca/Na, and δD/δ18O ratios distinguish between brine sources in the mixing zone. For example, chemical composition of brackish-to-saline shallow ground waters beneath the Concho River watershed more closely resembles the composition of Permian than of Pennsylvanian formation brines. Other possible salinity sources include (1) seepage of salt water from rocks beneath oil-field brine-disposal p ts, which ceased operation in the late 1960 s, and (2) upward flow of artesian salt water across confining beds through decades-old abandoned oil-exploration holes. These sources are superposed on the naturally occurring mixing zone between brine and fresh water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1989.tb00461.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Geochemistry of Salt Water Beneath the Rolling Plains, North-Central Texas (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 24 (1986), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Sodium-chloride brine underlies the shallow subsurface and discharges at numerous surface locations in the Rolling Plains of north-central Texas. According to the ratios of Na/Cl and Br/Cl, and supported by the contribution of other chemical constituents, two major brine types can be distinguished: (1) brine derived from dissolution of halite by fresh ground water, and (2) brine derived from discharge of deep-basin brine aquifers. All salt-spring brines as well as shallow subsurface brines in the northern and western parts of the Rolling Plains represent halite-dissolution brine, whereas deep-basin brine is represented by samples in the shallow subsurface in the south.The oxygen and hydrogen isotopic composition of the halite-dissolution brines indicates a local, meteoric origin for these brines. Shallow subsurface samples from the southeastern Rolling Plains graphically include deep-basin brine values and meteoric-water values as end points, suggesting mixing of deep-basin brine with local meteoric ground water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1986.tb01689.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Excitation energy transfer between molecular thin layers of poly(phenylene vinylene) and dye labeled poly(allylamine) in layer-by-layer self-assembled films (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 5191-5200 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Steady state Förster energy transfer is investigated in multilayer structures of self-assembled films prepared via the layer-by-layer deposition of oppositely charged polyelectrolytes. The samples consist of a single layer of the conjugated polymer poly(p- phenylene vinylene) (PPV) as a donor, several layers of poly(styrene sulfonate) (PSS), and poly(allylamine hydrochloride) (PAH) as a transparent spacer, and a single layer of dye labeled PAH as an acceptor. The dyes are rhodamine B and fluorescein, whereas the molar ratio with respect to the PAH monomers is less than 0.2% for both systems. The steady state fluorescence intensity of the PPV is measured for a series of samples with different spacer thicknesses. The spacer thicknesses are evaluated from x-ray reflectivity measurements. At large thickness of the spacer the donor intensity I versus distance d follows the 1/(1+(d0/d)4) law as theoretically predicted for the case of ideal two-dimensional layers. At short distances a different behavior is observed which is explained first, by the low lateral density of the acceptor molecules and second, by a distribution of the dyes normal to the layer plane. Good agreement between the experimental data and computer simulations is obtained under the assumption of a Gaussian distribution of both donor and acceptor molecules, in the direction normal to the film plane with a width of 25–30 Å. However, a mismatch is observed between the Förster radius derived from the spectroscopic properties and that obtained from the layer-to-layer energy transfer. This is discussed under the consideration of a nonperfect layer structure and the photophysics of the PPV. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479773
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Optisch aktive, aromatische Spirane, 9. Mitt.: Überprüfung eines Näherungsansatzes für Chiralitätsfunktionen bei 5,5′,6′-trisubstituierten 2,2′-Spirobiindanen (1979)
    Springer
    Monatshefte für Chemie 110 (1979), S. 931-946 
    Details
    ISSN: 1434-4475
    Keywords: Ligand parameters ; chirality function ; 2,2′-Spirobiindanes ; 5,5′-disubstituted
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In order to test the semiempirical value of chirality functions in their mathematically most simple form 23 new optically active 5,5′-disubstituted 2,2′-spirobiindanes1 of known chirality and enantiomeric purity were prepared. Thus a set of about hundred compounds is now available with altogether sixteen types of ligands (i.e. substituents including hydrogen); the experimental molar rotation of fifteen compounds is used to determine the value of a ligandspecific parameter occuring in the used chirality polynomial. According to theory this polynomial is an approximation for the total rotation of derivatives with ligands of three different types and it approximates an experimentally separable part of the rotation as far as compounds with four different ligands are concerned. The additional chirality component, occurring exclusively in the case of derivatives with four different types of ligands turns out to be relatively small but not vanishing. Accordingly, the molar rotation predicted by our method is very good for disubstituted spirobiindanes of type1 and rather good for others with three different types of ligands but is distinctly worse for those with four different ligands. The numerical trend, however, is clearly represented even in cases where our calculation in principle refers to a part of the phenomenon only and the predicted absolute configuration is in call cases in agreement with the experiment. An adequate criterion to judge the quality of our approximation is introduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00906690
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Synthese von Cotarnin-Iodid (1989)
    Springer
    Monatshefte für Chemie 120 (1989), S. 765-769 
    Details
    ISSN: 1434-4475
    Keywords: Croweacinaldehyde ; Isoquinoline ; Cotarnin iodide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Starting from 4-methoxy-1,3-benzodioxol-5-carbaldehyde (croweacin aldehyde,3) a six-step synthesis of cotarnin iodide (9, 67% total yield) is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809970
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Novel Ring Systems in Morphinoides II [1]: C8,17-Ethano-Bridged 4,5-Epoxyhasubanans (2000)
    Springer
    Monatshefte für Chemie 131 (2000), S. 997-1009 
    Details
    ISSN: 1434-4475
    Keywords: Keywords. Codeine; Claisen-Eschenmoser rearrangement; Hasubanan; N-Demethylation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary.  Claisen-Eschenmoser rearrangement of the 9,10-saturated derivative of 4,5-epoxyhasubanan-6β-ol affords the 8β-substituted amide which can be converted to the polycyclic quaternary ammonium salt 7 with an indolizidine substructure. An N-demethylation step with triethylborohydride leads to three products in accordance with the different possible positions of attack of the hydride ion to the strained ring system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007060070056
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Induktive Systeme in der Kombinatorik (1974)
    Springer
    Archiv der Mathematik 25 (1974), S. 329-336 
    Details
    ISSN: 1420-8938
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01238682
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Longitudinale Untersuchung zur Ausscheidung von 1-Hydroxypyren im Urin nach externer Behandlung mit Steinkohlenteer (1997)
    Springer
    Der Hautarzt 48 (1997), S. 240-245 
    Details
    ISSN: 1432-1173
    Keywords: Schlüsselwörter Steinkohlenteer ; Polyzyklische aromatische Kohlenwasserstoffe ; Externe Therapie ; 1-Hydroxypyren ; Renale Ausscheidung ; Key words Coal tar ; Polycyclic aromatic hydrocarbons ; Topical treatment ; 1-Hydroxypyrene ; Urinary excretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In order to study the dermal uptake, time course, and urinary excretion of polycyclic aromatic hydrocarbons, the concentration of 1-hydroxypyrene in urine was determined by means of high performance liquid chromatography with fluorescence detection before, during, and after the topical treatment with coal tar in 19 patients suffering from prurigo simplex subacuta, microbial eczema, atopic dermatitis, eczematization after scabies, exanthematous lichen ruber, pityriasis lichenoides and cutaneous sarcoidosis. Beginning with a value of 6.04±2.06 µg 1-hydroxypyrene/g creatinine before treatment, the urinary excretion significantly increased during the therapy with coal tar (p〈0.0001 at 3rd, 5th, and 6th day of therapy). A maximum was reached at day 8 of topical treatment with a value of 584.35± 191.96 µg 1-hydroxypyrene/g creatinine (p〈0.002). Already during treatment at day 10 there was a beginning decrease of 1-hydroxypyrene to 361.63±170.13 µg/g creatinine. After the end of treatment, the excretion further decreased reaching a value of 5.31±2.85 µg 1-hydroxypyrene/g creatinine at the 10th day after therapy. Skin carcinomas due to therapeutical use of coal tar occur extremely rarely and only after vergoten, non-controlled use. We suggest that the duration of exposure is the most important factor for the carcinogenic effect of coal tar.
    Notes: Zusammenfassung Bei insgesamt 19 Patienten mit Prurigo simplex subacuta, mikrobiellem, atopischem sowie postskabiösem Ekzem, Lichen ruber exanthematicus, Pityriasis lichenoides and Hautsarkoidose wurde die 1-Hydroxypyren-Konzentration im Urin vor, während und nach einer externen Steinkohlenteerbehandlung mittels Hochleistungsflüssigkeitschromatographie mit Fluoreszenzdetektion bestimmt, um so einen Rückschluß auf die dermale Aufnahme und den zeitlichen Verlauf der renalen Exkretion der potentiell kanzerogenen polyzyklischen aromatischen Kohlenwasserstoffe aus dem Teer zu erhalten. Ausgehend von einem prätherapeutischen Wert von 6,04±2,06 µg 1-Hydroxypyren/g Kreatinin steigt die renale Ausscheidung während der Teerbehandlung signifikant an (p〈0,0001 am 3., 5. und 6. Tag der Therapie), um am achten Tag das Maximum von 584,35±191,96 µg 1-Hydroxypyren/g Kreatinin zu erreichen (p〈0,002). Noch unter der Teerbehandlung ist am Tag 10 ein erster Abfall von 1-Hydroxypyren auf 361,63± 170,17 µg/g Kreatinin zu verzeichnen. Nach Absetzen der Teerbehandlung sinkt die Ausscheidung weiter steil ab, um am 10. Tag nach Therapie mit einem Wert von 5,31± 2,86 µg 1-Hydroxypyren/g Kreatinin wieder Ausgangsniveau zu erreichen. Da Hautkarzinome durch eine therapeutische Teeranwendung extrem selten auftreten und auf eine unkontrollierte und jahrzehntelange Anwendung zurückzuführen sind, wird gefolgert, daß die Expositionsdauer für die kanzerogene Wirkung des Teers anscheinend eine entscheidende Rolle spielt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001050050576
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Doppelnebenklassen als Klassenbegriff und Nomenklaturprinzip für Isomere und ihre AbzÄhlung (1970)
    Springer
    Theoretical chemistry accounts 19 (1970), S. 288-300 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Das allgemeine Prinzip, Moleküle gleicher Bruttoformel nach „Konfigurationen“ zu klassifizieren, beruht auf der Kombination zweier Abstraktionsprozesse in der Menge starrer Molekülmodelle zu einem gemeinsamen Molekülgerüst mit bezifferten PlÄtzen für Liganden und bezifferten Liganden. Es wird gezeigt, da\ die möglichen Klassifizierungsgesichtspunkte den möglichen Einteilungen von Permutationen einer Gruppe $$\mathfrak{A}$$ in Doppelnebenklassen des Produkts zweier entsprechend ausgewÄhlten Untergruppen $$\mathfrak{B}$$ und $$\mathfrak{S}$$ entsprechen. Ähnlich wie die irreduziblen Darstellungen der Symmetriegruppe einer Observablen die Nomenklatur für die Rassen der Eigenfunktion liefern, stellen die Doppelnebenklassen eine Nomenklatur für Konfigurationen. Das spezielle Klassifizierungsprinzip drückt sich in der Wahl der Gruppen $$\mathfrak{A}$$ , $$\mathfrak{B}$$ und $$\mathfrak{S}$$ aus. Die AbzÄhlung von Konfigurationen führt damit auf das verallgemeinerte Problem der AbzÄhlung von Doppelnebenklassen. Dafür werden drei Formeln abgeleitet. Im Falle der speziellen Gruppe $$\mathfrak{S} = \mathfrak{S}_n $$ ist von G. Pólya eine Anzahlformel entwickelt worden, die im Anhang auf unsere Formeln zurückgeführt wird.
    Abstract: Résumé Les propriétés pseudoscalaires des molécules chirales sont l'object d'une théorie algébrique après une définition convenable des classes de molécules. L'analyse du phénomène de chiralité sur ces classes conduit à des aspects particuliers de la théorie de la représentation des fonctions de chiralité, à une nouvelle structure de réseau des partitions, à des propriétés des groupes de permutation qui y sont liés et donne finalement un aperÇu sur la structure des points de vue approchés pour les fonctions de chiralité. Ainsi le présent article contient des aspects purement mathématiques. Les théorèmes mathématiques qui seront énoncés et prouvés sans référence essentielle à la physique se trouveront dans l'appendice. L'article lui-mÊme présente en premier lieu le phénomène physique; les concepts proposés par le formalisme mathématique tels que: ordre de chiralité, indice de chiralité, nombres de chiralité, complétude qualitative, hypothèse brève, partitions active et inactive des ligands, etc... donnent lieu à une systématisation et à une étude concernant la measure des propriétés liées à la chiralité des molécules. Par example, les points de vue co- et contravariant pour le comportement des fonctions par transformation nozs deux interprétations possibles des fonctions par transformation nous donne deux interprétations possibles des fonctions de chiralité. Nous pouvons considérer les composantes des fonctions appartenant à des représentations irréductibles comme des fonctions de chiralité pour des mélanges d'isomères. De là les opérateurs de projection sont dotés d'une interprétation physique d'opérateurs d'ensemble pour les mélanges d'isomères. Le chapitre 10 esquisse des applications de la théorie de cet article. Les premières comparaisons convaincantes des données expérimentales pour le pouvoir rotatoire des dérivés alléniques avec les valeurs théoriques basées sur les approximations des méthodes présentées aux chapitres 8 et 10 sont disponibles et en voie de publication. Les conséquences mathématiques de la définition du réseau de partition donnée au chapitre 6 seront développées par ailleurs.
    Notes: Abstract The general principle of classifying molecules of a common gross formula according to “configurations” is founded on the combination of two abstractions among rigid molecular models with a common molecular frame, numbered places for ligands, and numbered ligands. It is shown that the various points of view, which can be taken for the classification are determined by two accordingly chosen subgroups $$\mathfrak{A}$$ and $$\mathfrak{B}$$ of a permutation group $$\mathfrak{S}$$ , the configurations being defined by the double cosets of the product $$\mathfrak{A}\mathfrak{B}$$ . Just as the irreducible representations of the symmetry group of an observable furnish the nomenclature for different types of eingenfunctions the double cosets here provide a nomenclature for the configurations. The special principle of classification is given by the choice of $$\mathfrak{A}$$ , $$\mathfrak{B}$$ and $$\mathfrak{S}$$ . Thus, the enumeration of configuration leads to the generalised problem of enumerating double cosets. For this, three formulas are derived. In case of the special group $$\mathfrak{S} = \mathfrak{S}_n $$ G. Pólya found a formula of enumeration which is shown to reduce to our formulas in the appendix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00532233
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...