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  • 1
    ISSN: 1520-5002
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 40 (1996), S. 175-181 
    ISSN: 1572-879X
    Keywords: gold catalysis ; nano-size ; Debye function analysis ; TEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Using a Debye function analysis, the presence of icosahedral and face centered cuboctahedral gold in a 1 ∶ 1 ratio has been found in freshly prepared Au/Mg(OH)2 catalyst. The results support earlier studies which suggest the icosahedral form to be more stable at small nanometer sizes. Interactions between the gold and the Mg(OH)2 support appear to be weak, with the gold rapidly coagulating over a period of three months. Re-analysis of the aged sample shows the gold to be mainly in the form of truncated decahedra.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-879X
    Keywords: Co3O4 ; gold ; CO oxidation ; oscillation ; moisture effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of dry operating conditions upon the oxidation of CO over Co3O4 and Au/Co3O4 has been studied. Under dry conditions (with pretreatment and reaction gases dried at −76°C using molecular sieve traps) oxidation of CO over Co3O4 can be observed at temperatures as low as −54°C. However, without sufficient drying Co3O4 rapidly deactivates. On the other hand, the Au/Co3O4 catalyst is resistant to the presence of moisture even at low temperatures. For both the Co3O4 and Au/Co3O4 catalytic systems, strong and periodic oscillations in percentage conversion and catalyst bed temperature have been observed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of applied physiology 47 (1981), S. 113-122 
    ISSN: 1439-6327
    Keywords: Graded exercise testing ; jackieO2 max plateau ; Intra-individual variation ; Reliability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Eight boys aged 10–12 years performed three tests on each of three treadmill protocols. Each test was a continuous, progressively graded performance to exhaustion, but protocols differed in speed — (walk: 90 m·min−1, jog: 110 m·min−1, run: 130 m·min−1). The walk protocol was found inappropriate for jackeO2 max determination in children. Compared to the faster speeds, the walk test elicited a lower $$\dot VO_2 $$ at exhaustion, and had lower reliability (0.56) and a high coefficient of variation (8%). For the $$\dot VO_2 $$ at exhaustion on the jog and run protocols the coefficient of variation was 3–5% and the reliability coefficient averaged 0.90, comparable to values seen for repeated trials in adults. The usually accepted $$\dot VO_2 max$$ criterion of a plateau of $$\dot VO_2 $$ with increasing work levels was inappropriate for use with children. Attempts to derive plateau criteria suitable for use with children proved unsuccessful. Plateau criteria may be difficult to achieve with children in light of their apparently weaker glycolytic energy capacity. Nevertheless, the highest $$\dot VO_2 $$ measured at jog or run speeds has a consistency similar to that found for $$\dot VO_2 max$$ measurement in adults.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    European journal of applied physiology 57 (1988), S. 684-690 
    ISSN: 1439-6327
    Keywords: Muscle fatigue ; Aging ; Electrical stimulation ; Voluntary contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The 24 h recovery pattern of contractile properties of the triceps surae muscle, following a period of muscle fatigue, was compared in physically active young (25 years,n = 10) and elderly (66 years,n = 7) men. The fatigue test protocol consisted of 10 min of intermittent submaximal 20 Hz tetani. The maximal twitch (p t) and tetanic force at 3 frequencies (10, 20 and 50 Hz) were determined at baseline and at 15 min, 1, 4 and 24 h after fatiguing the muscle. Maximal voluntary contraction (MVC) and vertical jump (MVJ) were also assessed. The loss of force during the fatigue test was not significantly different between the young (18±13%) and elderly (22±15%). Both groups showed similar and significant reductions of Pt (15%), tetanic force (10 to 35%) and rate of force development (dp/dt) (20%) 15 min and 1 h into recovery. The loss of force was greater at the lower stimulation frequencies of 10 and 20 Hz. Time-to-peak tension was unchanged from baseline during recovery in either group. The average rate of relaxation of twitch force (−dPt/dt) was decreased (p〈0.05) and half-relaxation time significantly increased at 15 min and 1 h in the elderly but not the young. The findings indicate that after fatiguing contractions, elderly muscle demonstrates a slower return to resting levels of the rate and time course of twitch relaxation compared to the young.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European journal of applied physiology 55 (1986), S. 93-99 
    ISSN: 1439-6327
    Keywords: Anaerobic capacity ; Growth and development ; Maturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Nineteen boys were tested annually from age 11 to 15 years. Recovery O2 (or O2 debt in l and ml · kg−1) and blood lactate ([La], mmol · l−1) were measured following supramaximal treadmill tests (20% grade) designed to stress the anaerobic energy systems maximally. The purpose was to describe the rate of development of anaerobic capacity (AnC) from pre-puberty to adolescence. AnC improved from age 11 to 15 years, as indicated by a tripling of recovery O2 (l), 80% increase in recovery O2 per kg and 45% in [La]. Changes were similar from year to year with average yearly increments in recovery O2 of 0.81 or 9 ml · kg−1 and in [La] of 0.9 mmol · l−1. Individual data also were plotted in relation to age of peak height velocity (PHV, 12.9±1.2 years). Changes in the measures of AnC were not significantly different when related to biological rather than chronological age. Development of AnC did not show a growth function curve and was not closely correlated with size, nor was the development of AnC enhanced immediately following maturation. Thus, in this longitudinal study, recovery O2 and [La] as measures of AnC showed large increases from age 11 to 15 years, but the gains were similar year to year rather than related to size growth, per se, or hormonal influences at maturation postulated to induce qualitative changes in glycolytic potential of muscle.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European journal of applied physiology 58 (1989), S. 395-399 
    ISSN: 1439-6327
    Keywords: Aging ; Physical fitness ; Muscle contraction ; Strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The capacity for twitch potentiation in the gastrocnemius muscle was determined following maximal voluntary contractions (MVC) in 11 elderly (¯x±SD; 66.9±5.3 years) and 12 young (25.7±3.8 years) men. Potentiation was observed by applying selective stimulation to the muscle belly, 2 s after a 5 s MVC. With this procedure, both groups showed significant (P〈0.05) increases in twitch tension in the gastrocnemius (ratios of potentiated twitch to baseline were ¯x=1.68±0.40 for young vs ¯x=1.40±0.20 for the elderly,P〈0.001). Time to peak tension of the twitch decreased from ¯x=101.5±17.9 ms to ¯x=88.0±15.8 ms in the young men following po tentiation; the respective values for the older men were 136.7±17.9 ms and 133.1±28.6 ms. These changes resulted in a greater rate of tension development in the potentiated state. The elderly gastrocnemius thus showed qualitatively similar changes in the isometric twitch following potentiation, but reduced and prolonged responses in comparison to young adults. Slowed muscle contraction and reduced capacity for potentiation may be physiological correlates of the reported morphological changes in aged skeletal muscle.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1439-6327
    Keywords: Cardiac output ; Children ; Intra-individual variability ; Arterial $$P_{aCO_2 } $$
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Exercise cardiac output ( $$\dot Q$$ ) was determined using the CO2 rebreathing equilibrium method. Five repeat tests in 12 boys and two tests over a 4 month interval in 47 boys were performed. Regression equations to predict $$\dot Q$$ from $$\dot V$$ O2 were in close agreement with dye dilution studies in boys (Eriksson and Koch 1973). Group mean data were reproducible from trial to trial. The day-to-day variability of $$\dot Q$$ , with a coefficient of variation of 7–8%, was found to be higher than when the CO2 method has been applied in adults. This greater variability was related, in part, to a larger biological variation in children as depicted in such relatively simple measures as submaximal exercise heart rate. The larger variability was also related to inaccuracies in the methods of $$P_{aCO_2 } $$ estimation in children. Estimation from end-tidal CO2 concentrations requires further research to establish a correction for the alveolar-arterial gradient during exercise in children. Estimation of the child's dead space in exercise, with subsequent derivation of $$P_{aCO_2 } $$ from the Bohr equation, also could be improved. Nevertheless, $$\dot Q$$ estimates in children exercising above $$\dot V$$ O2 1.01·min−1 showed a day-to-day and long term stability acceptable for use in research and clinical studies.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    European journal of applied physiology 56 (1987), S. 24-29 
    ISSN: 1439-6327
    Keywords: Maximum oxygen uptake ; Ageing and strength ; Speed of movement and strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Isokinetic torques (Cybex II) of the plantar flexors in 25 healthy men were compared at 5 angular velocities (30, 60, 90, 120 and 180° · s−1). The purposes were to compare plantar flexion torques in young and old subjects, and to determine whether the expected decrease was significantly associated with age, physical activity, or aerobic fitness. Four groups were studied: young (21.7±2.0 years) and older (63.3±2.8 years), active and sedentary. Measurements of height, weight, % body fat, $$\dot V_{{\text{O}}_{{\text{2 max}}} } $$ and daily leisure energy expenditure (questionnaire) were determined for each subject. Statistical measures of analysis of variance were used to determine significant differences among groups; product moment correlation and stepwise regression analysis were used to describe the degree of association between the dependent variable of plantar flexion torque and the independent variables at each velocity. A decline in torque was observed as the isokinetic velocity of angular motion increased. Age alone was a significant determinant of plantar flexion torque, whereas at the slowest speed, when $$\dot V_{{\text{O}}_{{\text{2 max}}} } $$ was used as an explanatory variable, age was not a significant determinant of torque. At 30° · s−1 47% of the variance in torque was explained by $$\dot V_{{\text{O}}_{{\text{2 max}}} } $$ while at 180° · s−1 49% of the variance was explained by age.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    European journal of applied physiology 52 (1983), S. 115-119 
    ISSN: 1439-6327
    Keywords: Self-paced walking ; Oxygen uptake ; Prediction of oxygen uptake ; Age and energy expenditure ; Body composition and oxygen uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Oxygen uptake-velocity regression equations were developed for floor and level treadmill walking by having two groups of men, aged 19–29 years (n=20) and 55–66 years (n=22), walk at four self-selected paces, from “rather slowly” to “as fast as possible”. A two-variable quadratric model relating VO2 (ml·kg−1·min−1) to velocity (m·s−1) was adopted for prediction purposes. However, age and fatness significantly (p〈0.05) interacted with treadmill walking speed, while age alone significantly interacted with floor speed. In addition, a significant difference was found between the energy cost of floor and treadmill walking. For example at the normal walking speed of 1.33 m·s−1, the energy cost for the treadmill (age 55–66 years) was 10.58 ml·kg−1·min−1 and for the floor, 11.04 ml·kg−1·min−1 (p〈0.05). Four quadratic equations are therefore presented, one each for floor and treadmill in each of the two age-groups. The percent variance explained was between 87 and 95% for each of these equations.
    Type of Medium: Electronic Resource
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