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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 117 (1995), S. 6994-7002 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 117 (1995), S. 9740-9748 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1430-4171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An environmentally friendly redox laboratory for the determination of Fe(II) in an acid aqueous medium is presented. This laboratory exercise is an appropriate substitute for the traditional dichromate titration, which is environmentally problematic. This titration method uses the periodate ion as the oxidizing agent and yields results which are as accurate as the dichromate titration. Student success rate in quantitative analysis is better than 80% in two separate laboratory-based trials. This method requires a fairly high degree of operator skill to yield good results, making this a viable laboratory exercise at the sophomore or junior level.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1430-4171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Polarity of molecules is one of the central concepts that is used for predicting or rationalizing a wide array of concepts in the undergraduate chemistry curriculum. These concepts include the physical properties of molecules at the freshman level, structure-reactivity relationships in organic and inorganic chemistry, and selection rules in spectroscopy. In all of the freshman chemistry textbooks that we examined, bond dipoles are assigned based on electronegativity differences, which are then added vectorially (sometimes implicitly) to obtain the net dipole moment for a given molecule. We have found that this approach, which relies on the students’ familiarity and comfort level with vector addition in three dimensions, works well only for a small fraction of our students. We present an alternative pedagogical method for conveying this important concept. This method does not invoke vector addition, relying instead on a simple, pictorial approach that is transparent to a majority of our students. This method applies not only to species with a clearly defined central atom but to substituted alkenes and substituted benzenes as well. In addition, it can also be extended to paramagnetic species, whose polarity is not generally discussed in most freshman chemistry textbooks.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    The chemical educator 5 (2000), S. 113-119 
    ISSN: 1430-4171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The Dirac (bracket) notation is ubiquitous in the chemical literature, but it is rarely introduced in the undergraduate chemistry curriculum. In this article we present a pictorial approach to the bracket notation that we have successfully used for the past three years in a junior-senior-level physical chemistry course. We have found that it requires roughly 75 minutes to introduce this topic, and, upon integration into subsequent discussions, it prepares our undergraduate students to routinely use this powerful tool in the study of chemical bonding and spectroscopy. We believe that this approach, when introduced after the traditional integral treatment, enhances student learning of the abstract subject of quantum mechanics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 59 (1987), S. 453-455 
    ISSN: 1432-0738
    Keywords: DDT ; Uterine leiomyoma ; DDE ; DDD ; Gas-liquid chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Residues of dichlorodiphenyltrichloroethane (DDT) and its metabolites were monitored in leiomyomatous and normal human uterine tissue by gas-liquid chromatography (GLC). The metabolites detected were: 2,2-bis-(p-chlorophenyl)-1,1-dichloroethylene (p,p′-DDE), 2-(o-chlorophenyl)-2-(p-chlorophenyl)-1,1,1-trichloroethane (o,p′-DDT), 2,2-bis-(p-chlorophenyl)-1,1-dichloroethane (p,p′-DDD) and 2,2-bis-(p-chlorophenyl)-1,1,1-trichloroethane (p,p′-DDT). Total DDT ranged from 0.245 to 1.982 ppm, with a mean value of 0.845 ppm in leiomyomatous tissue. In normal human uterine tissue, total DDT ranged from 0.030 to 0.282 ppm, with a mean value of 0.103 ppm. Significantly higher levels of DDT and its metabolites in leiomyomatous tissue as compared to normal uterine tissue suggest their involvement in uterine leiomyomas. The data is discussed in the light of existing knowledge on estrogenic activity of DDT analogs and estrogeninfluenced growth of uterine leiomyomas.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 347-357 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: State-to-state integral cross sections for rovibrationally inelastic collisions between CO2 and hot hydrogen atoms are obtained by inversion of rotationally resolved population measurements of CO2 (0001). The inversion/fitting procedure is based upon the infinite order sudden (IOS) scaling law and employs a spline interpolating model to reduce the amount of information to be extracted. The experimental data used in the analysis was obtained using time domain tunable diode laser absorption spectroscopy to measure rotationally resolved excitation in CO2 (0001) following the generation of translationally hot H atoms via H2S photolysis at 193 nm. The analysis utilizes data acquired at two temperatures, 292 and 223 K, in order to acquire additional information about the temperature independent scattering cross sections. Sensitivity analysis is employed to gauge the sensitivity of the extracted cross sections to uncertainties in the experimental data, and also to estimate the effect of additional measurements at different temperatures. The final extracted cross sections exhibit strong rotational inelasticity, with a propensity for scattering from 0000; J' to both 0001; J=J' and 0001; J=||J'±41||. The largest state-to-state collision cross section corresponds to the (0000; J'=0) to (0001; J=41) transition and has a magnitude of (2.0±0.4)×10−3 A(ring)2.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4876-4886 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time-domain tunable diode laser absorption spectroscopy has been used to measure rotationally resolved transient absorption line shapes and nascent rotational populations for CO2 molecules excited into the (0001) vibrational state by collisions with translationally hot hydrogen atoms. High-accuracy measurements were made at both 292 and 223 K, providing information about the initial-state dependence of the collision dynamics and about the (temperature-independent) state–to–state scattering cross sections. The nascent rotational population distribution is found to be nearly independent of temperature, indicating broad rotational inelasticity in the 0000→0001 scattering process. The nascent populations and transient linewidths are interpreted in terms of two separate theoretical models which lend substantial insight into the H–CO2 collision dynamics.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time domain tunable diode laser absorption spectroscopy has been used to measure rotationally resolved transient absorption line shapes and nascent rotational populations for CO2 molecules excited into the (0111) vibrational state by collisions with translationally hot hydrogen atoms. The even rotational levels are more heavily populated than the odd levels, in agreement with propensity rules derived earlier by Alexander and Clary. The nascent populations and transient linewidths are interpreted in terms of a theoretical model that lends insight into the H–CO2 collision dynamics. The cross section for exciting (0111) is ∼0.23 times the cross section for exciting (0001), and ∼0.38 times the cross section for exciting (1000).
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 251 (2005), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Nutrition influenced growth, sporulation and virulence of the insect pathogenic fungus, Metarhizium anisopliae. Virulent conidia were produced on susceptible insect hosts, 1% yeast extract, 2% peptone, osmotic stress medium (OSM) and CN 10:1 medium. Several strain independent markers were identified that could be used to predict the virulence of M. anisopliae conidia. Virulent conidia typically had high levels of spore bound Pr1, an important cuticle degrading protease, and high germination rates. We also show for the first time that virulent conidia have an endogenous CN ratio below 5.2:1. Real Time PCR revealed that virulent conidia from insects contained significantly higher levels of transcripts of pr1 A and other pathogenicity-related genes than inoculum from artificial media. Of the artificial media studied, 1% yeast extract medium yielded the most virulent conidia, these had higher levels of transcripts of these pathogenicity-related genes than the least virulent conidia from the high conidia yielding CN 35:1 medium (= SDA), however, the levels were significantly lower than those in insect-derived conidia. Our study shows for the first time that the passaged inoculum is virulent irrespective of the original culture medium or insect host. Virulent conidia were consistently produced on OSM even though growth and sporulation were poor. We postulate that starvation conditions, whether in vivo or in vitro, results in de-repression of Pr1 and that elevated levels of this enzyme enhance fungal virulence.
    Type of Medium: Electronic Resource
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