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  • 1
    Electronic Resource
    Electronic Resource
    Fluorobenzene and p-difluorobenzene microsolvated by methanol: An infrared spectroscopic and ab initio theoretical investigation (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1844-1858 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Laser spectroscopy, i.e., resonant two-photon ionization (R2PI), IR/R2PI ion depletion and hole burning spectroscopy have been applied in an experimental study of heterogenous clusters consisting of fluorobenzene (FB) or p-difluorobenzene (pDFB), respectively, microsolvated by up to three methanol molecules. Their infrared ion depletion spectra were taken in the region of the OH and CH stretches of methanol. In these complexes the methanol molecules form subclusters, which are weakly hydrogen bonded to either the aromatic π-system (πOH) or to the fluorine substituent (σF) and a CH group (σCH). In FB⋅(MeOH)1, pDFB⋅(MeOH)1, pDFB⋅(MeOH)2 and one isomer of FB⋅(MeOH)2 the methanol subunits exclusively exhibit σF and σCH H-bonds. A further isomer of FB⋅(MeOH)2 exhibits a πOH type interaction. For FB⋅(MeOH)3 and pDFB⋅(MeOH)3 (1:3) complexes the methanol subcluster may take on either a chainlike or a ringlike conformation. In the chainlike isomer of FB⋅(MeOH)3 the methanol trimer interacts with the chromophore via a πOH H-bond while with the corresponding pDFB cluster a σF H-bond is formed. High level ab initio calculations, still feasible for molecular clusters of this size, have also been carried out to supplement the experimental investigations. These calculations include complete geometry optimizations of FB⋅(MeOH)n (n=1–2) and pDFB⋅(MeOH)1 at the MP2/6-31+G* and B3LYP/6-31+G* levels of theory. The minimum energy structures of the microsolvates together with their harmonic vibrational spectra allow a reliable assignment of the experimentally observed spectra and the determination of structure of the complexes. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480748
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  • 2
    Electronic Resource
    Electronic Resource
    van der Waals isomers and ionic reactivity of the cluster system para-chlorofluorobenzene/methanol (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1170-1177 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This combined experimental and computational study is aimed at elucidating the structure and reactivity of heterogeneous molecular clusters. We report results for the system para-chlorofluorobenzene/methanol (pClFB/MeOH). Particularly, three different van der Waals (vdW) isomers of the neutral (1:1) aggregate (π,σF,σCl) have been assigned by comparison of experimental infrared frequencies in the O–H and C–H stretch regions measured by IR/R2PI depletion spectroscopy with calculated frequencies at MP2/6-31+G(d) and B3LYP/6-31+G(d) level. The isomers are weakly hydrogen-bonded complexes with methanol's OH group coordinated toward the aromatic π-electron cloud, the fluorine or the chlorine substituent, respectively. This assignment is corroborated by the UV and IR spectra of the corresponding monosubstituted benzene/methanol complexes. After resonant photoionization of pClFB⋅(MeOH)n, for n=1 besides vdW fragmentation, no chemical reactivity was observed for any isomer. The investigation of aggregates with n≥5 indicated a substitution reaction taking place to produce chloroanisole+, emphasizing the importance of neutral precursor cluster size over cluster structure for intracluster ion–molecule reactions. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480670
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  • 3
    Electronic Resource
    Electronic Resource
    On the microscopic interaction of para-chlorofluorobenzene with water (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 10045-10047 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The isolated (1:1) complex of para-chlorofluorobenzene with water has been investigated by IR/R2PI depletion spectroscopy and ab initio calculations on the geometry and IR spectra. Whereas three different isomers (σF, σCl, π) were located by theory, in the molecular beam experiments only the two σ isomers have been observed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1415457
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  • 4
    Electronic Resource
    Electronic Resource
    Shielding from instantaneously and adiabatically applied potential wells in collisionless plasmas (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 1091-1094 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The response of collisionless plasmas to an applied potential can differ from classic Debye shielding, and when the potential is rapidly applied ("instantaneous shielding"), the shielding can differ from when it is slowly applied ("adiabatic shielding"). Experiments demonstrate that when a test potential well is applied to a one-dimensional pure-electron plasma, instantaneous and adiabatic shielding are similar for small potentials, but that instantaneous shielding is weaker than adiabatic shielding for large potentials. These results have been confirmed with particle-in-cell computer simulations. Simulations also show that the peculiar distribution functions of instantaneously and adiabatically shielded plasmas agree with theoretical predictions. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1455633
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrafast optical nonlinearity of low-temperature-grown GaInAs/AlInAs quantum wells at wavelengths around 1.55 μm (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 1936-1938 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ultrafast optical response of low-temperature-grown GaInAs/AlInAs multiple quantum wells is studied in pump-probe experiments with a femtosecond Er:fiber laser. As-grown samples doped with beryllium (concentration of 8×1017 cm−3) display a nonlinear transmission change, which decays by carrier trapping with a time constant of 230 fs. Experiments with pairs of ultrashort pulses separated by 1.5 ps demonstrate a fast modulation of transmission and very small accumulation effects, making this material highly promising for all-optical switching. Substantially longer recovery times are found in annealed, Be-doped samples and in undoped samples. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1461429
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  • 6
    Electronic Resource
    Electronic Resource
    Association of α-amylase and the R1 protein with starch granules precedes the initiation of net starch degradation in turions of Spirodela polyrhiza (2002)
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 114 (2002), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In turions of Spirodela polyrhiza (L.) Schleiden, net degradation of storage starch is controlled by a special low fluence response of phytochrome requiring illumination for several days. This light effect has been used to study protein–starch interactions that occur prior to and during net degradation of starch. Following various pretreatments on S. polyrhiza turions, native starch granules were isolated and two fractions of starch-related proteins were distinguished: proteins enclosed within the starch particles (starch-internalized proteins) and those attached to the surface (starch-associated proteins). The pattern of starch-associated proteins as resolved by SDS-PAGE was more complex than that of starch-internalized proteins and varied depending upon the pretreatment of the turions. Two starch associated proteins were identified immunochemically as α-amylase (EC 3.2.1.1) and the R1 protein (Lorberth et al. (1998) Nature Biotechnology 16: 473–477). Dark-pretreatment of non-dormant turions does not induce starch net degradation. Under these conditions, α-amylase and R1 were bound to the surface of the starch granules. Continuous illumination with red light induces a rapid degradation of starch. Within the first 24 h of illumination the level of starch-associated α-amylase transiently increased and subsequently decreased rapidly. Similarly, the amount of the starch-associated R1 also decreased during illumination. The dissociation of both α-amylase and R1 from the starch granules preceded the decrease in starch content. However, binding of the two proteins to starch granules remained unchanged when the turions did not perform net starch degradation (as observed during continuous darkness, orthophosphate deficiency, or dormancy of the turions). Thus, during net starch degradation, so far unidentified changes are postulated to occur at the surface of the starch particles that are relevant for protein binding. This conclusion was supported by in vitro studies in which the binding of purified β-amylase (EC 3.2.1.2) to starch granules isolated from turions following various pretreatments was monitored. The enzyme did bind to starch granules prepared from dark-stored turions (in which starch degradation had not been initiated), but not to those isolated from illuminated (starch degrading) turions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2002.1140102.x
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  • 7
    Electronic Resource
    Electronic Resource
    Food allergy and non-allergic food hypersensitivity in children and adolescents (2004)
    Oxford, UK : Blackwell Science Ltd
    Clinical & experimental allergy 34 (2004), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Previous studies have shown a 10-fold discrepancy of self-reported food-induced symptoms and physician-diagnosed food hypersensitivity. Little information is available on the prevalence of food hypersensitivity in unselected paediatric populations. No data were available for German children.Objective To study the perception of food-induced symptoms in the paediatric population, to investigate the allergens accused, to objectify patients' reports, and to identify subgroups at risk of having food-induced allergy (FA) or non-allergic food hypersensitivity (NAFH) reactions.Methods This paper presents the data of the paediatric group (0–17 years) of a representative, randomly sampled, cross-sectional population-based survey studying 13 300 inhabitants of the German capital city Berlin regarding food-related symptoms. Instruments included mailed questionnaires, structured telephone interviews, physical examination, skin-prick tests, specific serum IgE and standardized, controlled and blinded oral food challenges.Results Two thousand three hundred and fifty-four individuals were contacted by mailed questionnaire, 739 (31.4%) responses could be fully evaluated. Four hundred and fifty-five (61.5%) participants reported symptoms related to food ingestion, 284 (38.4%) affirmed reproducible symptoms in the standardized telephone interview. One hundred and eighty-four (24.8%) individuals were fully examined. Reproducible symptoms to food were found in 31 (4.2%) children and adolescents: 26 (3.5%) showed symptoms of FA and five (0.7%) of NAFH. The oral allergy syndrome was most often observed. Foods most commonly identified by oral challenges were apple, hazelnut, soy, kiwi, carrot and wheat.Conclusion: The perception of food-related symptoms is common among children and adolescents from the general population. Self-reports could be confirmed in around one out of 10 individuals, still resulting in 4.2% of proven clinical symptoms. However, most reactions were mild and mainly because of pollen-associated FA, while NAFH reactions were less common. Severe IgE-mediated FA was observed in individuals with pre-existing atopic disease, who should be fully investigated for clinically relevant FA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2222.2004.02080.x
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  • 8
    Electronic Resource
    Electronic Resource
    Oxidative and premature skin ageing (2003)
    Oxford, UK : Munksgaard International Publishers
    Experimental dermatology 12 (2003), S. 0 
    Details
    ISSN: 1600-0625
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract:  To elucidate the scientific state of the art with respect to the role of nutrition in skin ageing, nine experts from different disciplines discussed the role of micronutrients on ‘oxidative and premature skin ageing’. In this 25th Hohenheim Consensus Meeting, 13 questions were discussed and, based on published valid data, answered by mutual agreement. The consensus answers achieved during the meeting are justified by a scientific background text. The importance of in vitro and in vivo models regarding oxidative and premature skin ageing was critically evaluated. There was a special focus on prevention and intervention of skin ageing with nutrition. Finally, the paper summarizes the scientific background from different areas related to oxidative and premature skin ageing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0906-6705.2003.00148.x
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  • 9
    Electronic Resource
    Electronic Resource
    DNA vaccines expressing antigens with a stress protein-capturing domain display enhanced immunogenicity (2004)
    Oxford, UK; Malden, USA : Munksgaard International Publishers
    Immunological reviews 199 (2004), S. 0 
    Details
    ISSN: 1600-065X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary:  An expression system for DNA vaccines is described, in which a fusion protein with an N-terminal, viral J-domain that captures heat-shock proteins (Hsps) is translated in-frame with C-terminal antigen-encoding sequences (of various lengths and origins). The system supports enhanced expression of chimeric antigens (of 〉800 residues in length) with an extended half life (〉8 h). When used as a DNA vaccine, it delivers antigen together with the intrinsic adjuvant activity provided by bound Hsps. We describe the design of vectors for DNA vaccination that support the expression of different immunogenic domains of different origins as large, Hsp-capturing chimeric fusion antigens. The immunogenicity of the antigens produced by this expression system (when it is built into DNA vaccines) has been characterized in detail, with particular emphasis on priming CD8+ T-cell responses. We also discuss areas of vaccine research to which the new technology may provide useful contributions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0105-2896.2004.00136.x
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  • 10
    Electronic Resource
    Electronic Resource
    Prevalence of adverse reactions to food in Germany – a population study (2004)
    Oxford, UK : Munksgaard International Publishers
    Allergy 59 (2004), S. 0 
    Details
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective:  A population study was performed to identify the prevalence of all kinds of adverse reactions to food.Methods:  In a representative cross-sectional survey performed in 1999 and 2000 in Berlin, 13 300 inhabitants of all ages were addressed by questionnaire. This questionnaire was answered by 4093 persons. All respondents mentioning any sign of food intolerance or the existence of allergic diseases (n = 2298) were followed up by telephone and, in case food intolerance could not be ruled out by patient history, were invited to attend to the clinic for personal investigation including double-blind, placebo-controlled food challenge tests (DBPCFC).Results:  The self-reported lifetime prevalence of any adverse reaction to food in the Berlin population (mean age 41 years) was 34.9%. Eight hundred and fourteen individuals were personally investigated according to the guidelines. The point prevalence of adverse reactions to food confirmed by DBPCFC tests in the Berlin population as a mean of all age groups was 3.6% (95% confidence interval [3.0–4.2%]) and 3.7% in the adult population (18–79 years, 95% confidence interval [3.1–4.4.%]). Two and a half percent were IgE-mediated and 1.1% non-IgE-mediated, females were more frequently affected (60.6%). Based on a statistical comparison with available data of adults from the nationwide German Health Survey from 1998, adverse reactions to food in the adult population of Germany (age 18–79) were calculated with 2.6% [2.1–3.2%]).Conclusions:  The study gives for the first time information about the point prevalence of both immunological and nonimmunological adverse reactions to food and underlines the relevance of this issue in public health. The data also show that an individualized stepwise approach including provocation tests is mandatory to confirm the diagnosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1398-9995.2003.00403.x
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