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  • 1
    ISSN: 1432-1238
    Keywords: Key words Sepsis ; Endotoxin ; Nitric oxide ; Pulmonary surfactant ; Acute respiratory distress syndrome ; Respiratory therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective: To evaluate the efficacy of surfactant and inhaled nitric oxide (iNO) in endotoxin-induced acute lung injury (ALI).¶Design: Prospective, randomised, controlled experimental study.¶Setting: A medical university hospital research laboratory.¶Intervention: Twenty-nine adult rabbits (2.4–3.4 kg) were given two doses of intravenous endotoxin (Escherichia coli) (0.01 mg/kg and, 12 h later, 0.1 mg/kg), and then subjected to mechanical ventilation. After 8 h these animals were allocated to four treatment groups: (1) control, (2) iNO at 20 ppm (NO), (3) surfactant at 100 mg/kg (Surf) and (4) both surfactant and iNO as in groups 2 and 3 (SNO), and ventilated for a further 6 h followed by broncho-alveolar lavage (BAL), analysis of surfactant contents in BAL fluid and histological examination of the lungs.¶Measurements and results: All the animals had developed ALI with respiratory failure 8 h after the second dose of endotoxin as evidenced by a decrease of PaO2/FIO2 from 520 ± 30 to 395 ± 19 mmHg and dynamic compliance (Cdyn) from 1.20 ± 0.11 to 0.73 ± 0.05 ml/cmH2O × kg, and an increase of intrapulmonary shunting (Qs/Qt) from 7.5 ± 0.8 % to 12.9 ± 1.0 % (all measurements p 〈 0.01 versus baseline). In the SNO group, values for PaO2/FIO2, Cdyn and Qs/Qt after 6 h were 301 ± 15 mmHg, 0.67 ± 0.05 ml/cmH2O × kg and 16.5 ± 0.8 %, compared to 224 ± 26 mmHg, 0.53 ± 0.04 ml/cmH2O × kg and 24.1 ± 2.0 %, respectively, in the control group (all measurements p 〈 0.01). Both Surf and NO groups showed intermediate levels of these parameters. In both Surf and SNO groups, the minimum surface tension of BAL fluid was lower, and the content of disaturated phosphatidylcholine/total protein higher, than in the control and NO groups (p 〈 0.01). Histological features of lung injury were less prominent and wet/dry lung weight ratio lower in the NO, Surf and SNO groups. Decreased surfactant protein A (SP-A) and its mRNA expression were found in all endotoxin-exposed groups, but the SP-A content of the SNO group was moderately improved in comparison to the control group. Surfactant aggregate size was not affected.¶Conclusion: Early application of surfactant and iNO moderately mitigated ALI as reflected by improvement of lung mechanics, pulmonary perfusion and morphology.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 12 (1983), S. 153-162 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Cross-sections for bremsstrahlung production in thin films may be derived theoretically only if certain approximations are made or if there is recourse to numerical techniques. In this paper, two approximate equations, one based on the Sommerfeld theory and the other on the Bethe-Heitler theory, are assessed for their accuracy in predicting cross-sections differential in photon energy and emergence angle when a thin foil target is bombarded with electrons with energies between 40 and 100 keV. Experimental data are presented from eight different target materials and these are processed initially to make comparisons between experimental and theoretical spectral shapes and subsequently to compare observed and predicted absolute cross-section values. Except for the heaviest target material (Au), the Bethe-Heitler theory provided a satisfactory description of all experimental observations. In contrast, the Sommerfeld theory provided a significantly inferior description of spectral shapes and consistently overestimated absolute cross-sections by 15-20%.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Two approximate theories are considered for the production of characteristic x-rays when thin foil targets are bombarded with electrons with energies between 40 and 100 keV. One, due to Kolbenstvedt, is semi-classical in nature whilst the other, due to Bethe, contains two parameters which are normally adjusted empirically. Data from six different target materials are presented, but because errors in experimentally derived absolute cross-sections are large, a comparison is made between theoretical and observed ratios of characteristic Kα photons to bremsstrahlung photons in a 20 eV channel directly beneath the peak. By adjusting the Bethe parameters and using a modified Bethe-Heitler theory to predict the bremsstrahlung, agreement between experiment and theory of typically 10% is recorded. Finally, a means of simplifying the equations used to enable rapid calculation of x-ray spectra with a pocket calculator is indicated.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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