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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 25 (1998), S. 503-511 
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: Key words Chronic hypoxia ; Atrial natriuretic peptide ; Right ventricular hypertrophy ; ANP gene expression ; β/α-Myosin gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 85 (1998), S. 515-523 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1433-0474
    Keywords: Schlüsselwörter Herzerkrankung ; Thoraxschmerz ; Psychosomatische Störung ; Key words Heart disease ; Chest pain ; Psychosomatic disorder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: 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.
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-0662
    Keywords: arctic air pollution ; precursor substances ; vertical profiles ; ozone ; PAN ; SO2 ; gaseous HNO3 ; particulate nitrate ; sulfate ; ammonium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Environmental monitoring and assessment 44 (1997), S. 375-382 
    ISSN: 1573-2959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0006-3592
    Keywords: nitrification ; immobilized cells ; activation energy ; diffusion limitation ; temperature ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Activation energies of suspended and immobilized nitrifying bacteria were determined and compared to determine if diffusion limitation results in decreased sensitivity for temperature. The activation energy for the respiration activity of suspended Nitrosomonas europaea and Nitrobacter agilis was found to be 86.4 and 58.4 kJ mol-1, respectively. The activation energy for oxygen diffusion in the support material, κ-carrageenan, determined from the effect of temperature on the effective diffusion coefficient (D), was 17.2 kJ mol-1. Consequently, the apparent actvation energy of diffusion limited cells should be lower. It was indeed shown that due to the effect of diffusion limitation and to temperature effects on the Monod constant Ks, the immobilized-cell activity was less sensitive to temperature. The apparent activation energy for immobilized Ns. europaea was between 28.6 and 94.2 kJ mol-1 and for immobilized Nb. agilis between 1.4 and 72.9 kJ mol-1, depending on the oxygen concentration and temperature. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 25 (1995), S. XVI 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 61 (1922), S. 354-355 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 29 (1995), S. XVI 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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