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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 6585-6593 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new method which should have relatively general applicability for the identification and quantitative analysis of reactive adsorbed molecular intermediates in surface reactions will be described, and the first examples of its application will be presented. When a reactive intermediate is generated on a surface, it often has a tendency to dissociate before desorbing. Since dissociation generally requires additional free sites on the surface, dissociation can be suppressed and desorption correspondingly enhanced if the free sites on the surface can be properly poisoned. We have found that bismuth adatoms are very good inert site blockers, which can be postdosed to the surface of a transition metal containing a reactive adsorbed hydrocarbon without destroying the hydrocarbon. Whereas in the absence of bismuth, the hydrocarbon would completely dehydrogenate during thermal desorption spectroscopy (TDS) and liberate only H2 into the gas phase, after bismuth postdosing the reactive hydrocarbon desorbs intact for mass spectral identification and quantitative analysis. This method has been used to prove that adsorbed benzene is the initial product of the dehydrogenation of cyclohexane on Pt(111) at ∼235 K. In the absence of bismuth, this benzene all dissociates during TDS to liberate only H2, leaving graphitic carbon residue on the surface. When one-third monolayer of Bi is postdosed at 110 K, the dehydrogenation pathway is sterically poisoned and the adsorbed benzene quantitatively desorbs during TDS, where it is unambiguously identified by mass spectroscopy. By briefly heating the reactive adsorbed intermediate to increasing temperatures prior to Bi deposition, the thermal stability limits of the intermediate and the kinetic parameters for its dissociation can be established. This is demonstrated for the dehydrogenation reaction of adsorbed cyclopentene on Pt(111). Bismuth postdosing in thermal desorption mass spectroscopy (BPTDS) should be a very useful but inexpensive addition to surface analytical capabilities.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    International journal of cosmetic science 26 (2004), S. 0 
    ISSN: 1468-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Although the intensity and quality of fragrance perception is elicited by the physical mixture of volatile chemicals available to stimulate the olfactory system, the subjective experience and response an individual exhibits is often the product of those sensory or physiological signals and higher level psychological processes involved in perception, memory and judgment. For example, the frequency and duration of exposure to a fragrance can determine whether the subsequent perception is diminished (adaptation) or enhanced (sensitization), but an individual's memories of prior associations, the situational context or expectations, and their current emotional state are potent modifiers of the intensity and quality of the final chemosensory experience. Similarly, the context in which an irritant sensation is experienced (e.g., the product or situation) may determine whether it is perceived as an adverse or pleasurable sensation. Results from numerous laboratory studies have shown that these factors play a key role in the evaluation of odor and irritant sensations arising from the perception of fragrances. Importantly, cognitive and psychosocial factors appear to have significance for understanding reactions to fragrances in a variety of use situations, from consumer products to indoor environments.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Clinical & experimental allergy 33 (2003), S. 0 
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Many asthmatics report worsening of symptoms following exposure to odours and sensory irritants commonly found in household and cosmetic products. Despite this, little evidence exists to confirm the degree to which such subjective reports are correlated with localized, objective changes in the upper or lower airways following a fragranced product exposure.Objective Subjective symptom reports were compared to objective measures in mild asthmatics, moderate asthmatics and non-asthmatics following exposure to one of two fragranced household aerosol mixtures and a clean air control condition to determine if asthmatics reported greater subjective symptoms of nasal congestion or exhibited objective measures of elevated ocular irritation and nasal congestion following exposure than did healthy controls.Methods Measures of nasal mucosal swelling, using acoustic rhinometry, and photographic assessments of ocular hyperemia, using macro-photography, were taken before exposure, immediately after an initial 5-min exposure and again following a 30-min exposure to either of two, fragranced aerosol products and a clean air control. Self-reports of nasal patency at each time-point were also obtained.Results Although moderate asthmatics tended to report more nasal congestion following fragranced product exposure than did non-asthmatics, no exposure-related changes in ocular redness or nasal mucosal swelling were observed among the three groups. Spirometry readings also failed to show evidence of any exposure-related changes in pulmonary function.Conclusion Despite claims that exposure to fragranced products may trigger ocular and respiratory symptoms among asthmatics, we found no evidence that 30 min of exposure to one of two fragranced aerosols elicited objective adverse effects in the ocular or nasal mucosa of mild and moderate asthmatics. While physiological mechanisms of fragrance impact may yet be responsible for some of the adverse reports among asthmatics following fragrance exposure, such reports may also reflect a non-physiological locus of symptom perception triggered by other sensory cues.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Bulletin of economic research 37 (1985), S. 0 
    ISSN: 1467-8586
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Economics
    Notes: This article contributes to an established and growing literature in which a production function is estimated for educational institutions in order to investigate the relationship between school characteristics and performance.Existing studies in this area have generally met with only limited success. The present study, through its application of a statistical model to comprehensive data drawn from the UK private sector of education identifies a wide range of school characteristics which significantly influence performance.The article offers meaningful results and guidelines for further development of techniques in the investigation of a topic which is relevant to both producers and consumers of education.
    Type of Medium: Electronic Resource
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  • 5
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Women's Studies International Quarterly 1 (1978), S. 279-280 
    ISSN: 0148-0685
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Sociology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Women's Studies International Quarterly 3 (1980), S. 55-57 
    ISSN: 0148-0685
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Sociology
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Despite previous unsuccessful attempts to use hydrated poly(2-hydroxyethyl methacrylate) sponges as implantable biomaterials, recently these materials became important as peripheral components in an artificial cornea of the core-and-skirt design. The low mechanical strength of sponges prompted this study on possible improvement of tensile properties by the use of a variety of crosslinking agents. Three vinylic (dimethacrylates) and two allylic compounds were used at different concentrations (0.1 to 2% (mol)) as crosslinking agents in the production of sponges. Their influence on the mechanical properties, porous morphology and swelling behavior of resulting sponges was evaluated. The onset of phase separation during polymerization was also measured by visible spectrophotometry. The results suggested an inherent heterogeneity of sponges, i.e. pores of non-uniform size and structural inhomogeneities. While the effects of changes in the nature and concentration of crosslinking agents on the equilibrium water content of sponges were ambiguous, some of the mechanical properties, such as toughness and elasticity, were improved by crosslinking with allylic agents. Scanning electron microscopic examination suggested that the mechanical effect is related to the variation of size of the polymer particles constituting the sponge structure, which was proved to be dependent upon the onset of phase separation during polymerization. ©2000 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    International archives of occupational and environmental health 69 (1997), S. 407-417 
    ISSN: 1432-1246
    Keywords: Key words Olfaction ; Irritation ; Response bias ; Health symptoms ; Acetone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective: Responses to volatile chemicals are often subjective and variable, both over time and across individuals. Although variability can derive from differences in individual olfactory sensitivity, the response to a chemical stimulus is also influenced by the complex environment surrounding the exposure, which can include the perceiver’s cognitive state. To explore the role of cognitive bias in chemical exposures, we evaluated whether information about the consequences of exposure to acetone could influence ratings of odor and irritation during exposure and/or the frequency or intensity of reported health symptoms following exposure. Methods: Ninety adults (mean age 33.7, range 25–64) with no history of occupational exposure to solvents, were exposed to 800 ppm acetone in a chamber for 20 min. To control for non-specific responses to the odor of acetone, the subjects were also exposed for 20 min to 200 ppm phenylethyl alcohol (PEA), a nonirritant volatile chemical that produces a distinct odor but does not elicit irritation in the vapor phase. Subjects were assigned to one of three groups (n=30/group); each group was given either a positive, negative or neutral bias towards the consequences of exposure to the chemicals in the study. During exposure, subjects rated the intensity of odor and irritation; following exposure, they completed symptom questionnaires. Results: During the 20-min exposure to acetone, the positive bias group exhibited the most adaptation to its odor and the lowest perceived irritation; following exposure they reported the fewest health symptoms. In contrast, the negative bias group rated higher levels of odor intensity and, on average, reported the most overall irritation; following exposure they reported significantly more health symptoms than the other groups. None of the demographic variables studied (e.g., age, gender, race, smoking status) were predictive of the response to odor or irritation. The perceived irritancy of acetone was well predicted by a linear combination of the perceived odor of acetone and the perceived irritation from PEA (the nonirritant), r 2=0.73. Conclusions: The results provide strong evidence that both the perceived odor and cognitive expectations about a chemical can significantly affect how individuals respond to it. Moreover, because naive control subjects appear to exhibit extreme variation in their cognitive evaluations of chemical effects, there may be limited value in using non-exposed controls to assess the irritancy of chemicals for worker populations.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Turner's syndrome is a sporadic disorder of human females in which all or part of one X chromosome is deleted. Intelligence is usually normal but social adjustment problems are common. Here we report a study of 80 females with Turner's syndrome and a single X chromosome, in 55 of which the X ...
    Type of Medium: Electronic Resource
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