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  • 1
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Cytochemical detection of ascorbic acid in cultured root tips of Zea mays shows that dividing cells accumulate ascorbic acid in the cytoplasm. The localization pattern alters in the root tip as the cells begin to elongate. In elongating cells ascorbic acid is distinctly localized on cell walls. Ascorbic acid content per cell inreases with the onset of cell elongation. Fully elongated cells contain fivefold more ascorbic acid than meristematic cells. Cytophotometric analysis reveals a sharp and positive correlation (r=+0.93) between percentage increase in content of ascorbic acid per cell and corresponding increase in cell size at different phases of cell elongation. IAA treatment to the roots raises the content of ascorbic acid per cell with a parallel increase in size of cell. Involvement of ascorbic acid in IAA induced cell elongation is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1741-0444
    Keywords: Airway model ; In vivo air temperature ; Respiratory convective heat transfer ; Respiratory heat loss
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Airway cooling and drying has been proposed as a mechanism of exercise-induced asthma. Of interest in understanding the role of respiratory heat loss are the airway zones enduring the principal cooling and drying stresses. We have compared the axial rise in air temperature in the upper respiratory tract of asthmatics with that occurring in a laminar airflow steady-state model of convective heat transfer. The latter allowed an assessment of the contribution of airway geometry to the overall air warming process and gave some indication of the likely in vivo air temperature during hyperventilation, which due to the nature of our patients we could not measure directly. In vivo measurements were performed during a fibre-optic bronchoscopy. Eleven patients (67 years ±0·76) inhaled ambient air (23·2°C) and cold air (−17·5°C) nasally at a ventilation of 10 l min−1. During cold air inhalation the air temperature of the pharynx was 32·7°C (1·0) and at the third-generation bronchi 37°C (0·5), whereas with ambient air these were 35·8°C (0·8) and 37·7°C (0·6), respectively. For the same inspired ambient air condition the corresponding air temperatures in the thermodynamic model were approximately 27°C and 32°C. The axial rise in air temperature in both the model and in vivo state were characterised by a rapid early warming phase regardless of airflow rate. We conclude that the region proximal to the pharynx will endure the most severe cooling during a hyperventilation challenge.
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  • 3
    ISSN: 1436-5073
    Keywords: molybdenum ; AAS ; solvent extraction of Mo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A selective and sensitive method for the extraction and microgram determination of molybdenum (VI) with hydroxamic acid as yellow molybdenum-hydroxamate complex from acidic medium is described. The molybdenum-PCPPSAHA complex has λmax 388 nm, molar absorptivity 5.0 × 103l mol−1 cm−1. The system obeys Beer's law in the range of 1–28 μg/ml of molybdenum(VI). Sandell's sensitivity is 0.0192 μg cm2 and stoichiometry of the complex is 1∶2, molybdenum: PCPPSAHA while mixed complex molybdenum-PCPPSAHA-morin has λmax 400 nm and molar absorptivity 5.9 × 103lmo1−1 cm−1 and stoichiometry of the complex is 1∶2∶1. The molybdenum is determined by graphite furnace atomic absorption spectrophotometry after directly pipetted the extract into the furnace which increases the sensitivity 20 fold.
    Type of Medium: Electronic Resource
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