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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Naturwissenschaften 85 (1998), S. 515-523 
    ISSN: 1432-1904
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Allgemeine Naturwissenschaft
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular medicine 71 (1993), S. 177-190 
    ISSN: 1432-1440
    Schlagwort(e): Adult respiratory distress syndrome ; Alveolar surfactant ; Surfactant phospholipids ; Surfactant apoproteins ; Surfactant inhibition ; Hyaline membranes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The adult respiratory distress syndrome (ARDS) is characterized by extended inflammatory processes in the lung microvascular, interstitial, and alveolar compartments, resulting in vasomotor disturbances, plasma leakage, cell injury, and complex gas exchange disturbances. Abnormalities in the alveolar surfactant system have long been implicated in the pathogenetic sequelae of this life-threatening syndrome. This hypothesis is supported by similarities in pulmonary failure between patients with ARDS and preterm babies with infant respiratory distress syndrome, known to be triggered primarily by lack of surfactant material. Mechanisms of surfactant alterations in ARDS include: (a) lack of surface-active compounds (phospholipids, apoproteins) due to reduced generation/release by diseased pneumocytes or to increased loss of material (this feature includes changes in the relative composition of the surfactant phospholipid and/or apoprotein profiles); (b) inhibition of surfactant function by plasma protein leakage (inhibitory potencies of different plasma proteins have been defined); (c) “incorporation” of surfactant phospholipids and apoproteins into polymerizing fibrin upon hyaline membrane formation; and (d) damage/inhibition of surfactant compounds by inflammatory mediators (proteases, oxidants, nonsurfactant lipids). Alterations in alveolar surfactant function may well contribute to a variety of pathophysiological key events encountered in ARDS. These include decrease in compliance, ventilation-perfusion mismatch including shunt flow due to altered gas flow distribution (atelectasis, partial alveolar collapse, small airway collapse), and lung edema formation. Moreover, more speculative at the present time, surfactant abnormalities may add to a reduction in alveolar host defense competence and an upregulation of inflammatory events under conditions of ARDS. Persistent atelectasis of surfactant-deficient and in particular fibrin-loaded alveoli may represent a key event to trigger fibroblast proliferation and fibrosis in late ARDS (“collapse induration”). Overall, the presently available data on surfactant abnormalities in ARDS lend credit to therapeutic trials with transbronchial surfactant administration. In addition to the classical goals of replacement therapy defined for preterm infants (rapid improvement in lung compliance and gas exchange), this approach will have to consider its impact on host defense competence and inflammatory and proliferative processes when applied in adults with respiratory failure.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1433-0474
    Schlagwort(e): Schlüsselwörter Herzerkrankung ; Thoraxschmerz ; Psychosomatische Störung ; Key words Heart disease ; Chest pain ; Psychosomatic disorder
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Summary Aims: Chest pain in children is often suspected to originate from cardiac disease. Aim of this study was to characterise the symptomatology of supposed cardiac chest pain in children and to investigate whether cardiac disease indeed underlies the pain or not. Furthermore, indications for a psychosomatic origin of the pain were searched for. Methods: The study involved 456 children referred to a pediatric cardiology outpatient department for chest pain. The patients were evaluated by ECG and echocardiogram. In selected cases, a chest radiograph, exercise ECG, or a 24-hour ECG monitoring was performed. A subgroup of 52 children and parents was interviewed on the basis of a questionnaire to evaluate the symptomatology of the pain, the family history, and psychosocial factors. Results: 15% of the children had diverse structural anomalies or arrhythmias usually of a low grade. The frequency of these findings did not differ from that of a control group without chest pain. Independent of the presence of these findings cardiac function was normal during exercise. The characteristic symptomatology (short, sharp, no radiation) did not correspond to that of ischemic heart disease, and was largely identical in children with and without cardiac findings. Factors typical of psychosomatic disorders were observed: a positive family history of „functional cardiac complaints” and other psychosomatic disorders particularly with regard to the mother, other somatic complaints prior to or along with the chest pain, and the presence of stressful life events. Conclusions: These data suggest that the described chest pain in children is a psychosomatic condition rather than caused by organic cardiac disease.
    Notizen: Zusammenfassung Fragestellung: Thoraxschmerzen bei Kindern werden häufig mit Erkrankungen des Herzens in Zusammenhang gebracht. Im Rahmen dieser Studie sollten der Symptomkomplex kindlicher „Herzschmerzen” charakterisiert und seine Genese aus kardiologischer Sicht untersucht werden. Ein weiteres Ziel bestand darin, Hinweise auf psychogene Faktoren in der Schmerzgenese zu erhalten. Methode: In die Studie waren 456 Kinder einbezogen, die unter dem Verdacht von „Herzschmerzen” an kinderkardiologische Ambulanzen überwiesen worden waren. Die Basisdiagnostik umfaßte EKG und Echokardiographie. In vielen Fällen erfolgten zusätzlich Langzeit-EKG, Thoraxröntgen oder Belastungs-EKG. Zur Beschreibung der Symptomatik und zur Evaluierung familiärer und psychosozialer Faktoren wurde ein Fragebogen ausgearbeitet und damit eine Untergruppe von 52 Kindern untersucht. Ergebnisse: Bei 15% der Kinder wurden verschiedenartige und meist geringfügige strukturelle und funktionelle Abweichungen vom Normalbefund des Herzens beobachtet. Ihre Prävalenz war nicht höher als in einer Kontrollpopulation. Unabhängig vom Vorhandensein dieser Befunde war die kardiale Leistungsfähigkeit normal. Die typische Symptomatik (kurz, stechend, ohne Ausstrahlung) entsprach nicht der des ischämischen Herzschmerzes und war bei Kindern mit und ohne kardiale Veränderungen weitgehend identisch. Es wurden Faktoren beobachtet, die typisch für psychosomatische Erkrankungen sind: eine positive Familienanamnese für „funktionelle Herzbeschwerden” und andere psychosomatische Erkrankungen insbesondere hinsichtlich der Mutter, das gleichzeitige oder zeitlich versetzte Auftreten anderer Schmerzsyndrome und potentielle psychosoziale Belastungen. Schlußfolgerungen: Vermutlich spielen nicht manifeste organische Veränderungen am Herzen, sondern psychosomatische Faktoren in der Pathogenese des hier charakterisierten kindlichen Thoraxschmerzes eine Rolle.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1432-0630
    Schlagwort(e): 78.65 ; 68.55 ; 81.40
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The optical and structural properties of films deposited from laser sintered Zirconia (ZrO2), Hafnia (HfO2), and Yttria (Y2O3) and from the commercially available (unprocessed material) Zirconia, Hafnia and Yttria, were studied and compared. All the films had low absorption. Films deposited from the laser sintered material had very low optical inhomogeneity. ZrO2 films showed negative inhomogeneity for films deposited from the unprocessed material. The refractive index increased for ZrO2 films deposited from the laser sintered material. HfO2 and Y2O3 films showed positive inhomogeneity when deposited from the unprocessed material. The refractive index of the films of these materials decreased when deposited from the laser sintered material. The thin films of ZrO2 and Y2O3 prepared from laser sintered material had stable monoclinic and cubic structures respectively while HfO2 films were found to be amorphous.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Experiments in fluids 25 (1998), S. 503-511 
    ISSN: 1432-1114
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract A two-component laser Doppler velocimeter with high spatial and temporal resolution was used to obtain measurements for fully developed turbulent flow of water through a channel with an aspect ratio of 12 : 1 at Re=5700 (based on the centerline velocity and the half-height of the channel). Statistical quantities that were determined are the mean streamwise velocity, the root-mean-square of the fluctuations of the streamwise and the normal velocities, the Reynolds shear stress and higher order moments. Turbulence production is calculated from these quantities. Turbulence statistics obtained from experiments are compared with results from a direct numerical simulation at the same Reynolds number. The good agreement validates a recent DNS, at Re=5700, which is approximately twice as large as used in most previous studies.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1432-1939
    Schlagwort(e): Seasonal pattern ; Isoprene emission Nitrogen ; Temperature induction ; Biogenic emission inventory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Isoprene emission from plants represents one of the principal biospheric controls over the oxidative capacity of the continental troposphere. In the study reported here, the seasonal pattern of isoprene emission, and its underlying determinants, were studied for aspen trees growing in the Rocky Mountains of Colorado. The springtime onset of isoprene emission was delayed for up to 4 weeks following leaf emergence, despite the presence of positive net photosynthesis rates. Maximum isoprene emission rates were reached approximately 6 weeks following leaf emergence. During this initial developmental phase, isoprene emission rates were negatively correlated with leaf nitrogen concentrations. During the autumnal decline in isoprene emission, rates were positively correlated with leaf nitrogen concentration. Given past studies that demonstrate a correlation between leaf nitrogen concentration and isoprene emission rate, we conclude that factors other than the amount of leaf nitrogen determine the early-season initiation of isoprene emission. The late-season decline in isoprene emission rate is interpreted as due to the autumnal breakdown of metabolic machinery and loss of leaf nitrogen. In potted aspen trees, leaves that emerged in February and developed under cool, springtime temperatures did not emit isoprene until 23 days after leaf emergence. Leaves that emrged in July and developed in hot, midsummer temperatures emitted isoprene within 6 days. Leaves that had emerged during the cool spring, and had grown for several weeks without emitting isoprene, could be induced to emit isoprene within 2 h of exposure to 32°C. Continued exposure to warm temperatures resulted in a progressive increase in the isoprene emission rate. Thus, temperature appears to be an important determinant of the early season induction of isoprene emission. The seasonal pattern of isoprene emission was examined in trees growing along an elevational gradient in the Colorado Front Range (1829–2896 m). Trees at different elevations exhibited staggered patterns of bud-break and initiation of photosynthesis and isoprene emission in concert with the staggered onset of warm, springtime temperatures. The springtime induction of isoprene emission could be predicted at each of the three sites as the time after bud break required for cumulative temperatures above 0°C to reach approximately 400 degree days. Seasonal temperature acclimation of isoprene emission rate and photosynthesis rate was not observed. The temperature dependence of isoprene emission rate between 20 and 35°C could be accurately predicted during spring and summer using a single algorithm that describes the Arrhenius relationship of enzyme activity. From these results, it is concluded that the early season pattern of isoprene emission is controlled by prevailing temperature and its interaction with developmental processes. The late-season pattern is determined by controls over leaf nitrogen concentration, especially the depletion of leaf nitrogen during senescence. Following early-season induction, isoprene emission rates correlate with photosynthesis rates. During the season there is little acclimation to temperature, so that seasonal modeling simplifies to a single temperature-response algorithm.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    ISSN: 1432-2013
    Schlagwort(e): Key words Chronic hypoxia ; Atrial natriuretic peptide ; Right ventricular hypertrophy ; ANP gene expression ; β/α-Myosin gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  It is unclear whether the increase in plasma atrial natriuretic peptide (ANP) concentration during hypoxia is due to direct, hypoxia-induced upregulation of ANP secretion in the heart, or to pressure overload of the right ventricle (RV) following hypoxia-induced pulmonary hypertension. To test the hypothesis that hypoxia leads to an early upregulation of the ANP gene, we examined the influence of acute and prolonged inspiratory hypoxia (6 h, 1 or 3 weeks) on the expression of ANP messenger ribonucleic acid (mRNA) in rat heart and compared the results with the expression of the ANP gene after acute pressure overload induced by experimental coarctation of the main pulmonary artery. As a molecular marker for hypertrophy we determined the ratio of α- and β-myosin gene expression. Hypoxia increased systolic RV pressure from 20.0 ± 1.6 mmHg to 27.8 ± 1.6 mmHg (P 〈 0.01) and 41.6 ± 2.1 mmHg (P 〈 0.05) after 1 and 3 weeks hypoxia respectively. The ANP plasma concentration did not change significantly after 6 h or 1 week: 232 ± 21 pg/ml (control), 246 ± 25 pg/ml (6 h), 268 ± 25 pg/ml (1 week), but increased significantly after 3 weeks hypoxia (446.8 ± 99.56 pg/ml; P 〈 0.05). ANP mRNA levels in different regions of the heart did not change after 6 h or 1 week hypoxia. After 3 weeks hypoxia ANP mRNA had increased 2.7-fold in the RV (P 〈 0.05), 4.2-fold in the left ventricle (LV, P 〈 0.05), 3.5-fold in the septum (S, P 〈 0.05) and about 1.4-fold in the right (n.s.) and left atrium (n.s.). Relative ventricular masses increased significantly only for the RV (190%, P 〈 0.05) during hypoxia. The β/α-myosin mRNA ratio did not change after 6 h hypoxia but, contrary to ANP gene expression, increased after just 1 week (6.1-fold in RV, 7.8-fold in LV, 6-fold in S; P 〈 0.05) and was more pronounced in the RV after 3 weeks (9.4-fold in RV, 7.6-fold in LV, 9.1-fold in S; P 〈 0.05). The increase in the β/α-myosin mRNA ratio in the LV contrasts with a lack of increase in relative ventricular mass. Acute pressure overload in the RV after pulmonary arterial banding significantly increased ANP-mRNA and the β/α-myosin mRNA ratio after 1 day in the RV. In the LV ANP mRNA was unchanged. The delayed upregulation of the ANP gene suggests that hypoxia per se is not a significant stimulus for ANP gene expression in the heart and that hypoxia-induced ANP-gene expression in the heart is regulated predominantly by the increase in RV afterload due to hypoxia-induced increased pulmonary pressure. The upregulation of ANP and β-myosin mRNA in the LV during chronic hypoxia has yet to be elucidated.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Journal of atmospheric chemistry 14 (1992), S. 315-337 
    ISSN: 1573-0662
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract Emissions of sulfur gases from both natural and anthropogenic sources strongly influence the chemistry of the atmosphere. To assess the relative importance of these sources we have combined the measurements of sulfur gases and fluxes during the past decade to create a global emission inventory. The inventory, which is divided into 12 latitude belts, takes into account the seasonal dependence of sulfur emissions from biogenic sources. The total emissions of sulfur gases from natural sources are approximately 0.79 Tmol S/a. These emissions are 16% of the total sulfur emissions in the Northern Hemisphere and 58% in the Southern Hemisphere. The inventory clearly shows the impact of anthropogenic sulfur emissions in the region between 35° and 50°N.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1573-0662
    Schlagwort(e): arctic air pollution ; precursor substances ; vertical profiles ; ozone ; PAN ; SO2 ; gaseous HNO3 ; particulate nitrate ; sulfate ; ammonium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract During two measuring campaigns in early spring 1994 and 1995 (March/April) and one campaign in summer 1994, measurements of ozone, PAN, sulfur dioxide, nitric acid, and particulate nitrate, sulfate, and ammonium (only 1995) were recorded in the Arctic. Observations were made by aircraft at various sites in the eastern and western Arctic. Ozone concentrations showed a steady increase with altitude both in spring and summer. During five flights in springtime, low ozone events (LOEs) could be observed near the surface and up to altitudes of 2000 m. SO2 background concentrations, ranging from detection limit (0.5 nmol/m3) to 5 nmol/m3, were observed during both spring and summer. Distinct maxima up to 55 nmol/m3 in lower altitudes were only obtained in springtime. Concentrations of the organic nitrate PAN were within a similar range as those of the inorganic nitrate HNO3 during spring campaigns. In contrast, concentrations of particulate nitrate were one half an order of magnitude lower. HNO3 concentrations increased significantly with altitude. Evidently, HNO3 was intruded from the stratosphere into the troposphere. Sulfate concentrations ranged between 5 and 30 nmol/m3; ammonium concentrations were obtained within a range from 10 to 50 nmol/m3.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Environmental monitoring and assessment 44 (1997), S. 375-382 
    ISSN: 1573-2959
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract A flow injection analysis (FIA) system using immobilized acetylcholinesterase (AChE) has been used for the detection of methamidophos in vegetable extracts. Methamidophos is one of the most commonly used organophosphate insecticides in South East Asia. AChE was immobilized onto magnetic particles; using a magnetic reactor, the particles could easily be separated from the test sample. Results show that complex matrices such as vegetable extracts have no inhibitory effect on AChE activity in the FIA system. The presence of methamidophos in the extracts caused AChE inhibition. The response could be followed as an inhibition curve and the inhibition constant calculated. Results show that using 85% AChE residual activity as the detection limit, methamidophos could be detected in lettuce and cabbage at 12 and 3 mg/kg vegetable material respectively. In a simulated field situation, cabbage leaves were spiked with 20 to 40 mg/kg methamidophos, homogenized and tested in the FIA system. The corresponding methamidophos levels predicted by the experimental results came very close to the known calculated values. Data presented here suggest that it is feasible to use this system to supplement the traditional chromatographic analysis methods for methamidophos analysis.
    Materialart: Digitale Medien
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