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  • Articles: DFG German National Licenses  (2)
  • Electronic Resource  (2)
  • 2000-2004  (2)
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  • Articles: DFG German National Licenses  (2)
Material
  • Electronic Resource  (2)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Pediatric allergy and immunology 13 (2002), S. 0 
    ISSN: 1399-3038
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The aim of our study was to determine the prevalence of asthma and related respiratory symptoms in school children from Costa Rica during the last 10 years, from 1989 to 1998. Using nationally representative samples of school children from Costa Rica during the last 10 years we have performed three studies. Altogether 9931 children were investigated. The age groups: study I, 5–17 years (n = 2682), study II, 6–7 years (n = 2944), 13–14 years (n = 3200) and study III, 10 years (n = 1105). The diagnostic criteria for asthma used in these studies was as follows: study I (1989), diagnosis by a doctor in combination with the presence of four kinds of respiratory symptoms; studies II (1995) and III (1998), history of wheeze in the past 12 months. The two latter were part of the International Study of Asthma and Allergies in Childhood (ISAAC).A very high prevalence of a history of wheezing was found in the three studies (46.8%, 42.9%, and 45.1%) as well as a diagnosis of asthma (23.4%, 27.7% and 27.1%). The physician's diagnosis of asthma reported in the first study (23%) increased from 23.1 in study II to 27.7% in study III (p = 0.004). This increment could be a real increase in asthma prevalence, or be due to a better awareness about asthma. In study II the group of 6–7-year-olds had respiratory symptoms significantly more often than 13–14-year-olds (p 〈 0.001). Boys more often had a history of wheezing (p = 0.001), wheeze during the previous 12 months (p = 0.01) and an asthma diagnosis at the age of 6–7 years (p = 0.002) than girls, but girls had more respiratory symptoms than boys at the age of 13–14 years (p 〈 0.005). Wheezing in the past 12 months was more common for those living in urban areas aged 6–7 years (p = 0.04), and there was an increase of wheeze after exercise (p = 0.01). For the 13–14-year-olds the risk of wheezing was higher during the previous 12 months if they lived in temperate areas (〈20°C) and at a high altitude (〉1000 m). Living in a rural area and in a warm region (〉20°C), increased the risk of dry cough during the previous 12 months in the group of 13–14-year-olds.In conclusion, Costa Rica is located in the tropics with a very high humidity, an enormous variety of flora and fauna and a very high prevalence of mite and cockroach allergens, which provide important risk factors that may explain the high prevalence of asthma and asthma-related symptoms. Further possible factors, such as the change towards a more Western life style, resulting in fewer infections and parasitic diseases in the first years of life and changes in bedding material, may also be unresolved. Increased environmental pollution may add to the very high prevalence of asthma and related respiratory symptoms. The very extensive exposure to mites and cockroaches in bed material and in homes with poor ventilation may be an important factor, but many asthmatic children behave as non atopic, with a viral respiratory infection as a major precipitating factor.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 217-224 
    ISSN: 1434-1948
    Keywords: Reaction mechanisms ; Cyclopalladation ; Acetic acid ; Pd-C bond stability ; Polynuclear species ; Palladium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The processes operating during the synthetic cyclopalladation reactions of imines in acetic acid have been studied from a kinetico-mechanistic point of view. These reactions include a fast initial coordination to the palladium through the N-donor atom of the imine, followed by the proper C-H bond activation to produce the acetato bridged dimeric species. At this point, the lability of the bridging acetato groups, the hydrolysis of the C-Pd bonds, and/or the hydrolysis of C=N exo bonds contribute to the generation of dark red polynuclear compounds. The processes occurring after the C-H activation have been followed kinetically, both from palladium acetate plus imine, and the synthetically pure isolated acetato dimers as starting materials. The kinetic and activation parameters have been found identical within experimental error whatever the starting material was (k323 = 1.5 × 10-4 s-1; ΔH# = 51 kJ mol-1; ΔS# = -163 JK-1 mol-1 ΔV# = +19 cm3 mol-1 for the 4-ClC6H4-CH=N-CH2-C6H5 imine derivative 1a). Acidolysis of C-Pd bonds has been found to occur in these polynuclear species. When alternative monomeric Cbenzylic-Pd bond-containing complexes are possible follow ups of the reactions produce them as final dead-end complexes (k323 = 2.2 × 10-5 s-1; ΔH# = 61 kJ mol-1; ΔS# = JK-1 mol-1 ΔV# ≈ 0 cm3 cm-1 for the [2,4,6-(CH3)3]C6H2-CH=N-CH2-[2-(CH3]C6[H4] imine derivative 3d). The same study has been carried out with primary amines in order to check the validity of the data if C=N bond hydrolysis is taking place in the imine derivatives with exo C=N bonds. For complexes with similar type of metallacycles, the results agree reasonably well with the proposed mechanism [k323 = 1.2·10-4 s-1, ΔH# = 46 kJ·mol-1, ΔS# = -180 J·K-1mol-1, ΔV# = -16 cm3·mol-1 for the polynuclear formation of the C6H5-CH2-NH2 derivative 4e; k323 = 3.0·10-4 s-1, ΔH# = 55 kJ·mol-1, ΔS
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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