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Sample records for oxygen uptake kinetics

  1. Muscular Oxygen Uptake Kinetics in Aged Adults.

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    Koschate, J; Drescher, U; Baum, K; Eichberg, S; Schiffer, T; Latsch, J; Brixius, K; Hoffmann, U

    2016-06-01

    Pulmonary oxygen uptake (V˙O2) kinetics and heart rate kinetics are influenced by age and fitness. Muscular V˙O2 kinetics can be estimated from heart rate and pulmonary V˙O2. In this study the applicability of a test using pseudo-random binary sequences in combination with a model to estimate muscular V˙O2 kinetics was tested. Muscular V˙O2 kinetics were expected to be faster than pulmonary V˙O2 kinetics, slowed in aged subjects and correlated with maximum V˙O2 and heart rate kinetics. 27 elderly subjects (73±3 years; 81.1±8.2 kg; 175±4.7 cm) participated. Cardiorespiratory kinetics were assessed using the maximum of cross-correlation functions, higher maxima implying faster kinetics. Muscular V˙O2 kinetics were faster than pulmonary V˙O2 kinetics (0.31±0.1 vs. 0.29±0.1 s; p=0.004). Heart rate kinetics were not correlated with muscular or pulmonary V˙O2 kinetics or maximum V˙O2. Muscular V˙O2 kinetics correlated with maximum V˙O2 (r=0.35; p=0.033). This suggests, that muscular V˙O2 kinetics are faster than estimates from pulmonary V˙O2 and related to maximum V˙O2 in aged subjects. In the future this experimental approach may help to characterize alterations in muscular V˙O2 under various conditions independent of motivation and maximal effort. © Georg Thieme Verlag KG Stuttgart · New York.

  2. OXYGEN UPTAKE KINETICS IN SPORT, EXERCISE AND MEDICINE

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    David C. Poole

    2005-03-01

    Full Text Available The objective of the book is to discuss the principal determinants of oxygen uptake dynamics which is essential to developing exercise performance and improving quality of life for patients, especially those with cardio-respiratory diseases. A broad review of the current knowledge about this relatively less studied field is provided by this book. Incidentally, it updates the reader about how a person can use his/her aerobic energy system more effectively in order to fatigue gradually and be able to endure more physical activity. It also discusses the effects of exercise training in speeding up oxygen uptake kinetics, and the effects of ageing and a selection of conditions in slowing oxygen dynamics and declining exercise capacity.

  3. Exertional oxygen uptake kinetics: a stamen of stamina?

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    Whipp, Brian J; Rossiter, H B; Ward, S A

    2002-04-01

    The fundamental pulmonary O(2) uptake (.VO(2)) response to moderate, constant-load exercise can be characterized as (d.VO(2)/dt)(tau)+Delta.VO(2) (t)=Delta.VO(2SS) where Delta.VO(2SS) is the steady-state response, and tau is the time constant, with the .VO(2) kinetics reflecting intramuscular O(2) uptake (.QO(2)) kinetics, to within 10%. The role of phosphocreatine (PCr) turnover in .QO(2) control can be explored using (31)P-MR spectroscopy, simultaneously with .VO(2). Although tau.VO(2) and tauPCr vary widely among subjects (approx. 20-65 s), they are not significantly different from each other, either at the on- or off-transient. A caveat to interpreting the "well-fit" exponential is that numerous units of similar Delta.VO(2SS) but with a wide tau distribution can also yield a .VO(2) response with an apparent single tau. This tau is, significantly, inversely correlated with lactate threshold and .VO(2max)(but is poorly predictive; a frail stamen, therefore), consistent with tau not characterizing a compartment with uniform kinetics. At higher intensities, the fundamental kinetics become supplemented with a slowly-developing phase, setting .VO(2)on a trajectory towards maximum .VO(2). This slow component is also demonstrable in Delta[PCr]: the decreased efficiency thereby reflecting a predominantly high phosphate-cost of force production rather than a high O(2)-cost of phosphate production. We also propose that the O(2)-deficit for the slow-component is more likely to reflect shifting Delta.VO(2SS) rather than a single one with a single tau.

  4. COMPARISON OF OXYGEN UPTAKE KINETICS AND OXYGEN DEFICIT IN SEVERELY OVERWEIGHT AND NORMAL WEIGHT ADOLESCENT FEMALES

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    Mark Loftin

    2005-12-01

    Full Text Available The purpose of this study was to determine if differences in oxygen uptake kinetics and oxygen deficit existed between normal weight and severely overweight adolescent girls. Subjects included 10 normal weight and 8 severely overweight girls. The participants performed a leg cycling VO2 peak test and a constant load leg cycling test at 80% of the ventilatory threshold (T-vent. In the constant workload test O2 kinetics as indicated by Phase I (VO2 L at 20 sec and Phase II time constants (t were determined. Also, the O2 deficit (VO2 L was measured. As expected significant differences were noted in body composition and VO2 peak relative to mass with normal weight body mass averaging 55.3 ± 7.0 kg, severely overweight 90.5 ± 18.0 kg, % fat normal weight 27.3 ± 3.9%, severely overweight 49.7 ± 4.9% and VO2 peak (ml·kg-1·min-1 normal weight 32.0 ± 2.7 and severely overweight 22.0 ± 5.3. VO2 peak (l·min-1 and T-vent (%VO2 max were similar between groups. Results revealed similar O2 kinetic responses between groups; phase I kinetics normal weight 0.72 ± 0.15 L; severely overweight 0.75 ± 0.13L, phase II (t normal weight 41.5 ± 21.3 sec; severely overweight 33.9 ± 22.7 sec. However, the O2 deficit was significantly higher in the severely overweight (0.75 ± 0.15L when compared to the normal weight group (0.34 ± 0.13L. Correlations ranged from r = -0.15 to 0.51 between VO2 peak (L·min-1 or fat weight and phase I, t and O2 deficit. These data generally support previous research concerning the independence of O2 uptake response and body size

  5. Influence of Prolonged Spaceflight on Heart Rate and Oxygen Uptake Kinetics

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    Hoffmann, U.; Moore, A.; Drescher, U.

    2013-02-01

    During prolonged spaceflight, physical training is used to minimize cardiovascular deconditioning. Measurement of the kinetics of cardiorespiratory parameters, in particular the kinetic analysis of heart rate, respiratory and muscular oxygen uptake, provides useful information with regard to the efficiency and regulation of the cardiorespiratory system. Practically, oxygen uptake kinetics can only be measured at the lung site (V’O2 resp). The dynamics of V’O2 resp, however, is not identical with the dynamics at the site of interest: skeletal muscle. Eight Astronauts were tested pre- and post-flight using pseudo random binary workload changes between 30 and 80 W. Their kinetic responses of heart rate, respiratory as well as muscular V’O2 kinetics were estimated by using time-series analysis. Statistical analysis revealed that the kinetic responses of respiratory as well as muscular V’O2 kinetics are slowed post-flight than pre-flight. Heart rate seems not to be influenced following flight. The influence of other factors (e. g. astronauts’ exercise training) may impact these parameters and is an area for future studies.

  6. Submaximal oxygen uptake kinetics, functional mobility, and physical activity in older adults with heart failure and reduced ejection fraction.

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    Hummel, Scott L; Herald, John; Alpert, Craig; Gretebeck, Kimberlee A; Champoux, Wendy S; Dengel, Donald R; Vaitkevicius, Peter V; Alexander, Neil B

    2016-07-01

    Submaximal oxygen uptake measures are more feasible and may better predict clinical cardiac outcomes than maximal tests in older adults with heart failure (HF). We examined relationships between maximal oxygen uptake, submaximal oxygen kinetics, functional mobility, and physical activity in older adults with HF and reduced ejection fraction. Older adults with HF and reduced ejection fraction (n = 25, age 75 ± 7 years) were compared to 25 healthy age- and gender-matched controls. Assessments included a maximal treadmill test for peak oxygen uptake (VO2peak), oxygen uptake kinetics at onset of and on recovery from a submaximal treadmill test, functional mobility testing [Get Up and Go (GUG), Comfortable Gait Speed (CGS), Unipedal Stance (US)], and self-reported physical activity (PA). Compared to controls, HF had worse performance on GUG, CGS, and US, greater delays in submaximal oxygen uptake kinetics, and lower PA. In controls, VO2peak was more strongly associated with functional mobility and PA than submaximal oxygen uptake kinetics. In HF patients, submaximal oxygen uptake kinetics were similarly associated with GUG and CGS as VO2peak, but weakly associated with PA. Based on their mobility performance, older HF patients with reduced ejection fraction are at risk for adverse functional outcomes. In this population, submaximal oxygen uptake measures may be equivalent to VO2 peak in predicting functional mobility, and in addition to being more feasible, may provide better insight into how aerobic function relates to mobility in older adults with HF.

  7. Submaximal oxygen uptake kinetics, functional mobility, and physical activity in older adults with heart failure and reduced ejection fraction

    OpenAIRE

    Hummel, Scott L; Herald, John; Alpert, Craig; Gretebeck, Kimberlee A; Champoux, Wendy S; Dengel, Donald R; Vaitkevicius, Peter V; Alexander, Neil B

    2016-01-01

    Background Submaximal oxygen uptake measures are more feasible and may better predict clinical cardiac outcomes than maximal tests in older adults with heart failure (HF). We examined relationships between maximal oxygen uptake, submaximal oxygen kinetics, functional mobility, and physical activity in older adults with HF and reduced ejection fraction. Methods Older adults with HF and reduced ejection fraction (n = 25, age 75 ? 7 years) were compared to 25 healthy age- and gender-matched cont...

  8. Effects of oxygen delivery, dietary nitrate, intensified training and prior exercise on oxygen uptake kinetics and performance in humans

    DEFF Research Database (Denmark)

    Christensen, Peter Møller

    benefits from supplementing with nitrate to improve exercise efficiency and performance in endurance trained subjects. Furthermore it appears difficult to improve VO2 kinetics with intensified training in trained athletes; however intense exercise can amplify the VO2 response during subsequent high......In response to an increase in the metabolic demand the oxygen uptake (VO2) increases in an exponential fashion in exercising muscles and stabilizes after 1-2 min eventually reaching a plateau or steady state where the energy demand is matched by the l vel of VO2. VO2 kinetics describes the distinct...... phases of the VO2 response at the onset of exercise. Fast VO2 kinetics are considered to be beneficial in intense endurance sports with competitions lasting ~2-8 min, whereas low VO2 at steady state (high efficiency) is considered beneficial especially in events of longer duration. To improve...

  9. Gymnasium-based unsupervised exercise maintains benefits in oxygen uptake kinetics obtained following supervised training in type 2 diabetes.

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    Macananey, Oscar; O'Shea, Donal; Warmington, Stuart A; Green, Simon; Egaña, Mikel

    2012-08-01

    Supervised exercise (SE) in patients with type 2 diabetes improves oxygen uptake kinetics at the onset of exercise. Maintenance of these improvements, however, has not been examined when supervision is removed. We explored if potential improvements in oxygen uptake kinetics following a 12-week SE that combined aerobic and resistance training were maintained after a subsequent 12-week unsupervised exercise (UE). The involvement of cardiac output (CO) in these improvements was also tested. Nineteen volunteers with type 2 diabetes were recruited. Oxygen uptake kinetics and CO (inert gas rebreathing) responses to constant-load cycling at 50% ventilatory threshold (V(T)), 80% V(T), and mid-point between V(T) and peak workload (50% Δ) were examined at baseline (on 2 occasions) and following each 12-week training period. Participants decided to exercise at a local gymnasium during the UE. Thirteen subjects completed all the interventions. The time constant of phase 2 of oxygen uptake was significantly faster (p exercise maintained benefits in oxygen uptake kinetics obtained during a supervised exercise in subjects with diabetes, and these benefits were associated with a faster dynamic response of heart rate after training.

  10. Training-induced acceleration of oxygen uptake kinetics in skeletal muscle: the underlying mechanisms.

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    Zoladz, J A; Korzeniewski, B; Grassi, B

    2006-11-01

    It is well known that the oxygen uptake kinetics during rest-to-work transition (V(O2) on-kinetics) in trained subjects is significantly faster than in untrained individuals. It was recently postulated that the main system variable that determines the transition time (t(1/2)) of the V(O2) on-kinetics in skeletal muscle, at a given moderate ATP usage/work intensity, and under the assumption that creatine kinase reaction works near thermodynamic equilibrium, is the absolute (in mM) decrease in [PCr] during rest-to-work transition. Therefore we postulate that the training-induced acceleration of the V(O2) on-kinetics is a marker of an improvement of absolute metabolic stability in skeletal muscles. The most frequently postulated factor responsible for enhancement of muscle metabolic stability is the training-induced increase in mitochondrial proteins. However, the mechanism proposed by Gollnick and Saltin (1982) can improve absolute metabolic stability only if training leads to a decrease in resting [ADP(free)]. This effect is not observed in many examples of training causing an acceleration of the V(O2) on-kinetics, especially in early stages of training. Additionally, this mechanism cannot account for the significant training-induced increase in the relative (expressed in % or as multiples of the resting values) metabolic stability at low work intensities, condition in which oxidative phosphorylation is not saturated with [ADP(free)]. Finally, it was reported that in the early stage of training, acceleration in the V(O2) on-kinetics and enhancement of muscle metabolic stability may precede adaptive responses in mitochondrial enzymes activities or mitochondria content. We postulate that the training-induced acceleration in the V(O2) on-kinetics and the improvement of the metabolite stability during moderate intensity exercise in the early stage of training is mostly caused by an intensification of the "parallel activation" of ATP consumption and ATP supply pathways

  11. A fast-start pacing strategy speeds pulmonary oxygen uptake kinetics and improves supramaximal running performance.

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    Tiago Turnes

    Full Text Available The focus of the present study was to investigate the effects of a fast-start pacing strategy on running performance and pulmonary oxygen uptake (VO2 kinetics at the upper boundary of the severe-intensity domain. Eleven active male participants (28±10 years, 70±5 kg, 176±6 cm, 57±4 mL/kg/min visited the laboratory for a series of tests that were performed until exhaustion: 1 an incremental test; 2 three laboratory test sessions performed at 95, 100 and 110% of the maximal aerobic speed; 3 two to four constant speed tests for the determination of the highest constant speed (HS that still allowed achieving maximal oxygen uptake; and 4 an exercise based on the HS using a higher initial speed followed by a subsequent decrease. To predict equalized performance values for the constant pace, the relationship between time and distance/speed through log-log modelling was used. When a fast-start was utilized, subjects were able to cover a greater distance in a performance of similar duration in comparison with a constant-pace performance (constant pace: 670 m±22%; fast-start: 683 m±22%; P = 0.029; subjects also demonstrated a higher exercise tolerance at a similar average speed when compared with constant-pace performance (constant pace: 114 s±30%; fast-start: 125 s±26%; P = 0.037. Moreover, the mean VO2 response time was reduced after a fast start (constant pace: 22.2 s±28%; fast-start: 19.3 s±29%; P = 0.025. In conclusion, middle-distance running performances with a duration of 2-3 min are improved and VO2 response time is faster when a fast-start is adopted.

  12. Oxygen Uptake Kinetics Is Slower in Swimming Than Arm Cranking and Cycling during Heavy Intensity

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    Sousa, Ana; Borrani, Fabio; Rodríguez, Ferran A.; Millet, Grégoire P.

    2017-01-01

    Oxygen uptake (V·O2) kinetics has been reported to be influenced by the activity mode. However, only few studies have compared V·O2 kinetics between activities in the same subjects in which they were equally trained. Therefore, this study compared the V·O2 kinetics response to swimming, arm cranking, and cycling within the same group of subjects within the heavy exercise intensity domain. Ten trained male triathletes (age 23.2 ± 4.5 years; height 180.8 ± 8.3 cm; weight 72.3 ± 6.6 kg) completed an incremental test to exhaustion and a 6-min heavy constant-load test in the three exercise modes in random order. Gas exchange was measured by a breath-by-breath analyzer and the on-transient V·O2 kinetics was modeled using bi-exponential functions. V·O2peak was higher in cycling (65.6 ± 4.0 ml·kg−1·min−1) than in arm cranking or swimming (48.7 ± 8.0 and 53.0 ± 6.7 ml·kg−1·min−1; P kinetics were slower in swimming (τ1 = 31.7 ± 6.2 s) than in arm cranking (19.3 ± 4.2 s; P = 0.001) and cycling (12.4 ± 3.7 s; P = 0.001). The amplitude of the primary component was lower in both arm cranking and swimming (21.9 ± 4.7 and 28.4 ± 5.1 ml·kg−1·min−1) compared with cycling (39.4 ± 4.1 ml·kg−1·min−1; P = 0.001). Although the gain of the primary component was higher in arm cranking compared with cycling (15.3 ± 4.2 and 10.7 ± 1.3 ml·min−1·W−1; P = 0.02), the slow component amplitude, in both absolute and relative terms, did not differ between exercise modes. The slower V·O2 kinetics during heavy-intensity swimming is exercise-mode dependent. Besides differences in muscle mass and greater type II muscle fibers recruitment, the horizontal position adopted and the involvement of trunk and lower-body stabilizing muscles could be additional mechanisms that explain the differences between exercise modalities. PMID:28919863

  13. The influence of different space-related physiological variations on exercise capacity determined by oxygen uptake kinetics

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    Stegemann, J.

    Oxygen uptake kinetics, following defined variations of work load changes allow to estimate the contribution of aerob and anaerob energy supply which is the base for determining work capacity. Under the aspect of long duration missions with application of adequate dosed countermeasures, a reliable estimate of the astronaut's work capacity is important to adjust the necessary inflight training. Since the kinetics of oxygen uptake originate in the working muscle group itself, while measurements are performed at the mouth, various influences within the oxygen transport system might disturb the determinations. There are not only detraining effects but also well-known other influences, such as blood- and fluid shifts induced by weightlessness. They might have an impact on the circulatory system. Some of these factors have been simulated by immersion, blood donation, and changing of the body position.

  14. Influence of oxygen uptake kinetics on physical performance in youth soccer.

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    Doncaster, Greg; Marwood, Simon; Iga, John; Unnithan, Viswanath

    2016-09-01

    To examine the relationship between oxygen uptake kinetics (VO2 kinetics) and physical measures associated with soccer match play, within a group of highly trained youth soccer players. Seventeen highly trained youth soccer players (age: 13.3 ± 0.4 year, self-assessed Tanner stage: 3 ± 1) volunteered for the study. Players initially completed an incremental treadmill protocol to exhaustion, to establish gaseous exchange threshold (GET) and VO2max (59.1 ± 5.4 mL kg(-1) min(-1)). On subsequent visits, players completed a step transition protocol from rest-moderate-intensity exercise, followed by an immediate transition, and from moderate- to severe-intensity exercise (moderate: 95 % GET, severe: 60 %∆), during which VO2 kinetics were determined. Physical soccer-based performance was assessed using a maximal Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1) and via GPS-derived measures of physical soccer performance during soccer match play, three 2 × 20 min, 11 v 11 matches, to gain measures of physical performance during soccer match play. Partial correlations revealed significant inverse relationships between the unloaded-to-moderate transition time constant (tau) and: Yo-Yo IR1 performance (r = -0.58, P = 0.02) and GPS variables [total distance (TD): r = -0.64, P = 0.007, high-speed running (HSR): r = -0.64, P = 0.008 and high-speed running efforts (HSReff): r = -0.66, P = 0.005]. Measures of VO2 kinetics are related to physical measures associated with soccer match play and could potentially be used to distinguish between those of superior physical performance, within a group of highly trained youth soccer players.

  15. OXYGEN UPTAKE KINETICS DURING INCREMENTAL- AND DECREMENTAL-RAMP CYCLE ERGOMETRY

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    Fadıl Özyener

    2011-09-01

    Full Text Available The pulmonary oxygen uptake (VO2 response to incremental-ramp cycle ergometry typically demonstrates lagged-linear first-order kinetics with a slope of ~10-11 ml·min-1·W-1, both above and below the lactate threshold (ӨL, i.e. there is no discernible VO2 slow component (or "excess" VO2 above ӨL. We were interested in determining whether a reverse ramp profile would yield the same response dynamics. Ten healthy males performed a maximum incremental -ramp (15-30 W·min-1, depending on fitness. On another day, the work rate (WR was increased abruptly to the incremental maximum and then decremented at the same rate of 15-30 W.min-1 (step-decremental ramp. Five subjects also performed a sub-maximal ramp-decremental test from 90% of ӨL. VO2 was determined breath-by-breath from continuous monitoring of respired volumes (turbine and gas concentrations (mass spectrometer. The incremental-ramp VO2-WR slope was 10.3 ± 0.7 ml·min-1·W-1, whereas that of the descending limb of the decremental ramp was 14.2 ± 1.1 ml·min-1·W-1 (p < 0.005. The sub-maximal decremental-ramp slope, however, was only 9. 8 ± 0.9 ml·min-1·W-1: not significantly different from that of the incremental-ramp. This suggests that the VO2 response in the supra-ӨL domain of incremental-ramp exercise manifest not actual, but pseudo, first-order kinetics

  16. Heart Rate and Oxygen Uptake Kinetics in Type 2 Diabetes Patients - A Pilot Study on the Influence of Cardiovascular Medication on Regulatory Processes.

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    Koschate, Jessica; Drescher, Uwe; Baum, Klaus; Brinkmann, Christian; Schiffer, Thorsten; Latsch, Joachim; Brixius, Klara; Hoffmann, Uwe

    2017-05-01

    The aim of this pilot study was to investigate whether there are differences in heart rate and oxygen uptake kinetics in type 2 diabetes patients, considering their cardiovascular medication. It was hypothesized that cardiovascular medication would affect heart rate and oxygen uptake kinetics and that this could be detected using a standardized exercise test. 18 subjects were tested for maximal oxygen uptake. Kinetics were measured in a single test session with standardized, randomized moderate-intensity work rate changes. Time series analysis was used to estimate kinetics. Greater maxima in cross-correlation functions indicate faster kinetics. 6 patients did not take any cardiovascular medication, 6 subjects took peripherally acting medication and 6 patients were treated with centrally acting medication. Maximum oxygen uptake was not significantly different between groups. Significant main effects were identified regarding differences in muscular oxygen uptake kinetics and heart rate kinetics. Muscular oxygen uptake kinetics were significantly faster than heart rate kinetics in the group with no cardiovascular medication (maximum in cross-correlation function of muscular oxygen uptake vs. heart rate; 0.32±0.08 vs. 0.25±0.06; p=0.001) and in the group taking peripherally acting medication (0.34±0.05 vs. 0.28±0.05; p=0.009) but not in the patients taking centrally acting medication (0.28±0.05 vs. 0.30±0.07; n.s.). It can be concluded that regulatory processes for the achievement of a similar maximal oxygen uptake are different between the groups. The used standardized test provided plausible results for heart rate and oxygen uptake kinetics in a single measurement session in this patient group. © Georg Thieme Verlag KG Stuttgart · New York.

  17. Physiological background of the change point in VO2 and the slow component of oxygen uptake kinetics.

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    Zoładź, J A; Korzeniewski, B

    2001-06-01

    It is generally believed that oxygen uptake during incremental exercise--until VO2max, increases linearly with power output (see eg. Astrand & Rodahl, 1986). On the other hand, it is well established that the oxygen uptake reaches a steady state only during a low power output exercise, but during a high power output exercise, performed above the lactate threshold (LT), the oxygen uptake shows a continuous increase until the end of the exercise. This effect has been called the slow component of VO2 kinetics (Whipp & Wasserman, 1972). The presence of a slow component in VO2 kinetics implies that during an incremental exercise test, after the LT has been exceeded, the VO2 to power output relationship has to become curvilinear. Indeed, it has recently been shown that during the incremental exercise, the exceeding of the power output, at which blood lactate begins to accumulate (LT), causes a non-proportional increase in VO2 (Zoladz et al. 1995) which indicates a drop in muscle mechanical efficiency. The power output at which VO2 starts to rise non-proportionally to the power output has been called "the change point in VO2" (Zoladz et al. 1998). In this paper, the significance of the factors most likely involved in the physiological mechanism responsible for the change point in oxygen uptake (CP-VO2) and for the slow component of VO2 kinetics, including: increase of activation of additional muscle groups, intensification of the respiratory muscle activity, recruitment of type II muscle fibres, increase of muscle temperature, increase of the basal metabolic rate, lactate and hydrogen ion accumulation, proton leak through the inner mitochondrial membrane, slipping of the ATP synthase and a decrease in the cytosolic phosphorylation potential, are discussed. Finally, an original own model describing the sequence of events leading to the non-proportional increase of oxygen cost of work at a high exercise intensity is presented.

  18. In vitro kinetic studies on the mechanism of oxygen-dependent cellular uptake of copper radiopharmaceuticals

    Energy Technology Data Exchange (ETDEWEB)

    Holland, Jason P; Bell, Stephen G; Wong, Luet-Lok; Dilworth, Jonathan R [Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA (United Kingdom); Giansiracusa, Jeffrey H [Department of Mathematics, Mathematical Institute, University of Oxford, 24-29 St Giles' , Oxford, OX1 3LB (United Kingdom)], E-mail: hollanj3@mskcc.org, E-mail: jasonpholland@gmail.com

    2009-04-07

    The development of hypoxia-selective radiopharmaceuticals for use as therapeutic and/or imaging agents is of vital importance for both early identification and treatment of cancer and in the design of new drugs. Radiotracers based on copper for use in positron emission tomography have received great attention due to the successful application of copper(II) bis(thiosemicarbazonato) complexes, such as [{sup 60/62/64}Cu(II)ATSM] and [{sup 60/62/64}Cu(II)PTSM], as markers for tumour hypoxia and blood perfusion, respectively. Recent work has led to the proposal of a revised mechanism of hypoxia-selective cellular uptake and retention of [Cu(II)ATSM]. The work presented here describes non-steady-state kinetic simulations in which the reported pO{sub 2}-dependent in vitro cellular uptake and retention of [{sup 64}Cu(II)ATSM] in EMT6 murine carcinoma cells has been modelled by using the revised mechanistic scheme. Non-steady-state (NSS) kinetic analysis reveals that the model is in very good agreement with the reported experimental data with a root-mean-squared error of less than 6% between the simulated and experimental cellular uptake profiles. Estimated rate constants are derived for the cellular uptake and washout (k{sub 1} = 9.8 {+-} 0.59 x 10{sup -4} s{sup -1} and k{sub 2} = 2.9 {+-} 0.17 x 10{sup -3} s{sup -1}), intracellular reduction (k{sub 3} = 5.2 {+-} 0.31 x 10{sup -2} s{sup -1}), reoxidation (k{sub 4} = 2.2 {+-} 0.13 mol{sup -1} dm{sup 3} s{sup -1}) and proton-mediated ligand dissociation (k{sub 5} = 9.0 {+-} 0.54 x 10{sup -5} s{sup -1}). Previous mechanisms focused on the reduction and reoxidation steps. However, the data suggest that the origins of hypoxia-selective retention may reside with the stability of the copper(I) anion with respect to protonation and ligand dissociation. In vitro kinetic studies using the nicotimamide adenine dinucleotide (NADH)-dependent ferredoxin reductase enzyme PuR isolated from the bacterium Rhodopseudomonas palustris have

  19. High-dose inhaled salbutamol has no acute effects on aerobic capacity or oxygen uptake kinetics in healthy trained men

    DEFF Research Database (Denmark)

    Elers, J; Mørkeberg, Jakob; Jansen, T

    2012-01-01

    enrolled nine healthy well-trained men in a randomized, blinded, placebo-controlled crossover study. Subjects were randomized to inhalation of 40 puffs of 0.2 mg salbutamol or two placebo tablets and performed an incremental test to exhaustion and three submaximal tests at 75% of peak power to determine...... oxygen uptake kinetics. During the incremental test, there were no effects of inhaled salbutamol on VO(2max) in absolute or relative terms, and no effect on peak power and lactate threshold. During the submaximal test, we found no effects on the time constant, time delay, the mean response time or O(2...

  20. Analysis of heart rate and oxygen uptake kinetics studied by two different pseudo-random binary sequence work rate amplitudes.

    Science.gov (United States)

    Drescher, U; Koschate, J; Schiffer, T; Schneider, S; Hoffmann, U

    2017-06-01

    The aim of the study was to compare the kinetics responses of heart rate (HR), pulmonary (V˙O 2 pulm) and predicted muscular (V˙O 2 musc) oxygen uptake between two different pseudo-random binary sequence (PRBS) work rate (WR) amplitudes both below anaerobic threshold. Eight healthy individuals performed two PRBS WR protocols implying changes between 30W and 80W and between 30W and 110W. HR and V˙O 2 pulm were measured beat-to-beat and breath-by-breath, respectively. V˙O 2 musc was estimated applying the approach of Hoffmann et al. (Eur J Appl Physiol 113: 1745-1754, 2013) considering a circulatory model for venous return and cross-correlation functions (CCF) for the kinetics analysis. HR and V˙O 2 musc kinetics seem to be independent of WR intensity (p>0.05). V˙O 2 pulm kinetics show prominent differences in the lag of the CCF maximum (39±9s; 31±4s; p<0.05). A mean difference of 14W between the PRBS WR amplitudes impacts venous return significantly, while HR and V˙O 2 musc kinetics remain unchanged. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Comparison of the oxygen uptake kinetics of club and olympic champion rowers.

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    Ingham, Stephen A; Carter, Helen; Whyte, Gregory P; Doust, Jonathan H

    2007-05-01

    To test the hypothesis that elite rowers would possess a faster, more economic oxygen uptake response than club standard rowers. Eight Olympic champion (ELITE) rowers were compared with a cohort of eight club standard (CLUB) rowers. Participants completed a progressive exercise test to exhaustion, repeated 6-min moderate and heavy square-wave transitions, and a maximal 2000-m ergometer time trial. The time constant (tau) of the primary component (PC) was faster for the ELITE group compared with CLUB for moderate-intensity (13.9 vs 19.4 s, P = 0.02) and heavy-intensity (18.7 vs 22.4 s, P = 0.005) exercise. ELITE rowers consumed less oxygen for moderate (14.2 vs 15.6 mL x min(-1) x W(-1); P = 0.009) and heavy (12.1 vs 13.7 mL x min(-1) x W(-1); P = 0.01) exercise. A greater absolute slow component was observed in the ELITE group (P = 0.009), but no differences were noted when the slow component was expressed relative to work rate performed (P = 0.14). Intergroup correlation with time trial performance speed was significant for tauPC during heavy-intensity exercise (r = -0.59, P = 0.02). Compared with CLUB rowers, the shorter time constant response and greater economy observed in ELITE rowers may suggest advantageous adjustment of oxidative processes from rest to work. Training status or performance level do not seem to be associated with a smaller slow component when comparing CLUB and ELITE oarsmen.

  2. Locomotor muscle fatigue does not alter oxygen uptake kinetics during high-intensity exercise

    Directory of Open Access Journals (Sweden)

    James Hopker

    2016-10-01

    Full Text Available The slow component (VO2sc that develops during high-intensity aerobic exercise is thought to be strongly associated with locomotor muscle fatigue. We sought to experimentally test this hypothesis by pre-fatiguing the locomotor muscles used during subsequent high-intensity cycling exercise. Over two separate visits, eight healthy male participants were asked to either perform a non-metabolically stressful 100 intermittent drop-jumps protocol (pre fatigue condition or rest for 33 minutes (control condition according to a random and counterbalanced order. Locomotor muscle fatigue was quantified with 6-second maximal sprints at a fixed pedaling cadence of 90 rev·min-1. Oxygen kinetics and other responses (heart rate, capillary blood lactate concentration and rating of perceived exertion, RPE were measured during two subsequent bouts of 6 min cycling exercise at 50% of the delta between the lactate threshold and VO2max determined during a preliminary incremental exercise test. All tests were performed on the same cycle ergometer. Despite significant locomotor muscle fatigue (P = 0.03, the VO2sc was not significantly different between the pre fatigue (464 ± 301 mL·min-1 and the control (556 ± 223 mL·min-1 condition (P = 0.50. Blood lactate response was not significantly different between conditions (P = 0.48 but RPE was significantly higher following the pre-fatiguing exercise protocol compared with the control condition (P < 0.01 suggesting higher muscle recruitment. These results demonstrate experimentally that locomotor muscle fatigue does not significantly alter the VO2 kinetic response to high intensity aerobic exercise, and challenge the hypothesis that the VO2sc is strongly associated with locomotor muscle fatigue.

  3. Locomotor Muscle Fatigue Does Not Alter Oxygen Uptake Kinetics during High-Intensity Exercise.

    Science.gov (United States)

    Hopker, James G; Caporaso, Giuseppe; Azzalin, Andrea; Carpenter, Roger; Marcora, Samuele M

    2016-01-01

    The [Formula: see text] slow component ([Formula: see text]) that develops during high-intensity aerobic exercise is thought to be strongly associated with locomotor muscle fatigue. We sought to experimentally test this hypothesis by pre-fatiguing the locomotor muscles used during subsequent high-intensity cycling exercise. Over two separate visits, eight healthy male participants were asked to either perform a non-metabolically stressful 100 intermittent drop-jumps protocol (pre-fatigue condition) or rest for 33 min (control condition) according to a random and counterbalanced order. Locomotor muscle fatigue was quantified with 6-s maximal sprints at a fixed pedaling cadence of 90 rev·min -1 . Oxygen kinetics and other responses (heart rate, capillary blood lactate concentration and rating of perceived exertion, RPE) were measured during two subsequent bouts of 6 min cycling exercise at 50% of the delta between the lactate threshold and [Formula: see text] determined during a preliminary incremental exercise test. All tests were performed on the same cycle ergometer. Despite significant locomotor muscle fatigue ( P = 0.03), the [Formula: see text] was not significantly different between the pre-fatigue (464 ± 301 mL·min -1 ) and the control (556 ± 223 mL·min -1 ) condition ( P = 0.50). Blood lactate response was not significantly different between conditions ( P = 0.48) but RPE was significantly higher following the pre-fatiguing exercise protocol compared with the control condition ( P locomotor muscle fatigue does not significantly alter the [Formula: see text] kinetic response to high intensity aerobic exercise, and challenge the hypothesis that the [Formula: see text] is strongly associated with locomotor muscle fatigue.

  4. Prior exercise speeds pulmonary oxygen uptake kinetics and increases critical power during supine but not upright cycling.

    Science.gov (United States)

    Goulding, Richie P; Roche, Denise M; Marwood, Simon

    2017-09-01

    What is the central question of this study? Critical power (CP) represents the highest work rate for which a metabolic steady state is attainable. The physiological determinants of CP are unclear, but research suggests that CP might be related to the time constant of phase II oxygen uptake kinetics (τV̇O2). What is the main finding and its importance? We provide the first evidence that τV̇O2 is mechanistically related to CP. A reduction of τV̇O2 in the supine position was observed alongside a concomitant increase in CP. This effect may be contingent on measures of oxygen availability derived from near-infrared spectroscopy. Critical power (CP) is a fundamental parameter defining high-intensity exercise tolerance and is related to the time constant of phase II pulmonary oxygen uptake kinetics (τV̇O2). To test the hypothesis that this relationship is causal, we determined the impact of prior exercise ('priming') on CP and τV̇O2 in the upright and supine positions. Seventeen healthy men were assigned to either upright or supine exercise groups, whereby CP, τV̇O2 and muscle deoxyhaemoglobin kinetics (τ [HHb] ) were determined via constant-power tests to exhaustion at four work rates with (primed) and without (control) priming exercise at ∼31%Δ. During supine exercise, priming reduced τV̇O2 (control 54 ± 18 s versus primed 39 ± 11 s; P exercise had no effect on τV̇O2 (control 37 ± 12 s versus primed 35 ± 8 s; P = 0.82), τ [HHb] (control 10 ± 5 s versus primed 14 ± 10 s; P = 0.10) or CP (control 235 ± 42 W versus primed 232 ± 35 W; P = 0.57) during upright exercise. The concomitant reduction of τV̇O2 and increased CP following priming in the supine group, effects that were absent in the upright group, provide the first experimental evidence that τV̇O2 is mechanistically related to critical power. The increased τ [HHb+Mb] suggests that this effect was mediated, at least in part, by improved oxygen

  5. Time Trials Versus Time-to-Exhaustion Tests: Effects on Critical Power, W', and Oxygen-Uptake Kinetics.

    Science.gov (United States)

    Karsten, Bettina; Baker, Jonathan; Naclerio, Fernando; Klose, Andreas; Bianco, Antonino; Nimmerichter, Alfred

    2018-02-01

    To investigate single-day time-to-exhaustion (TTE) and time-trial (TT) -based laboratory tests values of critical power (CP), W prime (W'), and respective oxygen-uptake-kinetic responses. Twelve cyclists performed a maximal ramp test followed by 3 TTE and 3 TT efforts interspersed by 60 min recovery between efforts. Oxygen uptake ( V ˙ O 2 ) was measured during all trials. The mean response time was calculated as a description of the overall [Formula: see text]-kinetic response from the onset to 2 min of exercise. TTE-determined CP was 279 ± 52 W, and TT-determined CP was 276 ± 50 W (P = .237). Values of W' were 14.3 ± 3.4 kJ (TTE W') and 16.5 ± 4.2 kJ (TT W') (P = .028). While a high level of agreement (-12 to 17 W) and a low prediction error of 2.7% were established for CP, for W' limits of agreements were markedly lower (-8 to 3.7 kJ), with a prediction error of 18.8%. The mean standard error for TTE CP values was significantly higher than that for TT CP values (2.4% ± 1.9% vs 1.2% ± 0.7% W). The standard errors for TTE W' and TT W' were 11.2% ± 8.1% and 5.6% ± 3.6%, respectively. The [Formula: see text] response was significantly faster during TT (~22 s) than TTE (~28 s). The TT protocol with a 60-min recovery period offers a valid, time-saving, and less error-filled alternative to conventional and more recent testing methods. Results, however, cannot be transferred to W'.

  6. Fitness Level and Not Aging per se, Determines the Oxygen Uptake Kinetics Response

    Directory of Open Access Journals (Sweden)

    Mitchell A. George

    2018-03-01

    Full Text Available Although aging has been associated to slower V˙O2 kinetics, some evidence indicates that fitness status and not aging per se might modulate this response. The main goal of this study was to examine the V˙O2, deoxygenated hemoglobin+myoglobin (deoxy-[Hb+Mb] kinetics, and the NIRS-derived vascular reperfusion responses in older compared to young men of different training levels (i.e., inactive, recreationally active, and endurance trained. Ten young inactive [YI; 26 ± 5 yrs.; peak V˙O2 (V˙O2peak, 2.96 ± 0.55 L·min−1], 10 young recreationally active (YR; 26 ± 6 yrs.; 3.92 ± 0.33 L·min−1, 10 young endurance trained (YT; 30 ± 4 yrs.; 4.42 ± 0.32 L·min−1, 7 older inactive (OI; 69 ± 4 yrs.; 2.50 ± 0.31 L·min−1, 10 older recreationally active (OR; 69 ± 5 yrs.; 2.71 ± 0.42 L·min−1, and 10 older endurance trained (OT; 66 ± 3 yrs.; 3.20 ± 0.35 L·min−1 men completed transitions of moderate intensity cycling exercise (MODS to determine V˙O2 and deoxy-[Hb+Mb] kinetics, and the deoxy-[Hb+Mb]/V˙O2 ratio. The time constant of V˙O2 (τV˙O2 was greater in YI (38.8 ± 10.4 s and OI (44.1 ± 10.8 s compared with YR (26.8 ± 7.5 s and OR (26.6 ± 6.5 s, as well as compared to YT (14.8 ± 3.4 s, and OT (17.7 ± 2.7 s (p < 0.05. τV˙O2 was greater in YR and OR compared with YT and OT (p < 0.05. The deoxy-[Hb+Mb]/V˙O2 ratio was greater in YI (1.23 ± 0.05 and OI (1.29 ± 0.08 compared with YR (1.11 ± 0.03 and OR (1.13 ± 0.06, as well as compared to YT (1.01 ± 0.03, and OT (1.06 ± 0.03 (p < 0.05. Similarly, the deoxy-[Hb+Mb]/ V˙O2 ratio was greater in YR and OR compared with YT and OT (p < 0.05. There was a main effect of training (p = 0.033, whereby inactive (p = 0.018 and recreationally active men (p = 0.031 had significantly poorer vascular reperfusion than endurance trained men regardless of age. This study demonstrated not only that age-related slowing of V˙O2 kinetics can be eliminated in endurance trained individuals

  7. Oxygen uptake kinetics during and after exercise are useful markers of coronary artery disease in patients with exercise electrocardiography suggesting myocardial ischemia

    International Nuclear Information System (INIS)

    Tajima, Akihiko; Ohkoshi, Nobuyuki; Kawara, Tokuhiro; Aizawa, Tadanori; Itoh, Haruki; Maeda, Tomoko; Osada, Naohiko; Omiya, Kazuto; Wasserman, K.

    2009-01-01

    The aim of the current study was to determine if the slowed exercise oxygen uptake (VO 2 ) kinetics, which is developed by myocardial ischemia, would be accompanied by delayed recovery VO 2 kinetics in patients with coronary artery disease (CAD). Thirty-seven patients with significant ST depression during treadmill exercise underwent cardiopulmonary exercise testing with cycle ergometer. Measurements performed are the ratios of change in increase in oxygen (O 2 ) uptake relative to increase in work rate (ΔVO 2 /ΔWR) across anaerobic threshold (AT) and 1 mm ST depression point (ST-dep), the time constants of VO 2 during recovery (T 1/2 VO 2 ), stress radio-isotope scintigraphy and coronary angiography. Patients were divided into CAD positive (CAD+) and CAD negative (CAD-) groups, based on coronary angiography. In CAD+, ΔVO 2 /ΔWR decreased above AT and ST-dep, in contrast to CAD- patients. The T 1/2 VO 2 in CAD+ (103.1±13.0 s) was greater than that of CAD- (76.5±8.7 s) and showed negative correlations to the ratios of ΔVO 2 /ΔWR across AT and ST-dep. These parameters improved in the patients who underwent coronary bypass surgery. Exercise and recovery VO 2 kinetics were slowed when myocardial ischemia was provoked by exercise. Measurement of exercise and recovery VO 2 kinetics improve the accuracy of the exercise electrocardiogram diagnosis of CAD. (author)

  8. Muscle glycogen reduction in man: relationship between surface EMG activity and oxygen uptake kinetics during heavy exercise.

    Science.gov (United States)

    Osborne, Mark A; Schneider, Donald A

    2006-01-01

    The purpose of this study was to determine whether muscle glycogen reduction prior to exercise would alter muscle fibre recruitment pattern and change either on-transient O2 uptake (VO2) kinetics or the VO2 slow component. Eight recreational cyclists (VO2peak, 55.6 +/- 1.3 ml kg (-1) min(-1)) were studied during 8 min of heavy constant-load cycling performed under control conditions (CON) and under conditions of reduced type I muscle glycogen content (GR). VO2 was measured breath-by-breath for the determination of VO2 kinetics using a double-exponential model with independent time delays. VO2 was higher in the GR trial compared to the CON trial as a result of augmented phase I and II amplitudes, with no difference between trials in the phase II time constant or the magnitude of the slow component. The mean power frequency (MPF) of electromyography activity for the vastus medialis increased over time during both trials, with a greater rate of increase observed in the GR trial compared to the CON trial. The results suggest that the recruitment of additional type II motor units contributed to the slow component in both trials. An increase in fat metabolism and augmented type II motor unit recruitment contributed to the higher VO2 in the GR trial. However, the greater rate of increase in the recruitment of type II motor units in the GR trial may not have been of sufficient magnitude to further elevate the slow component when VO2 was already high and approaching VO2peak .

  9. Modeling the oxygen uptake kinetics during exercise testing of patients with chronic obstructive pulmonary diseases using nonlinear mixed models

    DEFF Research Database (Denmark)

    Baty, Florent; Ritz, Christian; van Gestel, Arnoldus

    2016-01-01

    describe functionality of the R package medrc that extends the framework of the commonly used packages drc and nlme and allows fitting nonlinear mixed effects models for automated nonlinear regression modeling. The methodology was applied to a data set including 6MWT [Formula: see text]O2 kinetics from 61...... patients with chronic obstructive pulmonary disease (disease severity stage II to IV). The mixed effects approach was compared to a traditional curve-by-curve approach. RESULTS: A six-parameter nonlinear regression model was jointly fitted to the set of [Formula: see text]O2 kinetics. Significant...

  10. A short period of high-intensity interval training improves skeletal muscle mitochondrial function and pulmonary oxygen uptake kinetics

    DEFF Research Database (Denmark)

    Christensen, Peter Møller; Jacobs, Robert A; Bonne, Thomas Christian

    2016-01-01

    The aim of the present study was to examine whether improvements in pulmonary V̇O2 kinetics following a short period of high-intensity training (HIT) would be associated with improved skeletal muscle mitochondrial function. Ten untrained male volunteers (age: 26 ± 2; mean ± SD) performed six HIT...

  11. Insulin resistance and maximal oxygen uptake

    DEFF Research Database (Denmark)

    Seibaek, Marie; Vestergaard, Henrik; Burchardt, Hans

    2003-01-01

    BACKGROUND: Type 2 diabetes, coronary atherosclerosis, and physical fitness all correlate with insulin resistance, but the relative importance of each component is unknown. HYPOTHESIS: This study was undertaken to determine the relationship between insulin resistance, maximal oxygen uptake......, and the presence of either diabetes or ischemic heart disease. METHODS: The study population comprised 33 patients with and without diabetes and ischemic heart disease. Insulin resistance was measured by a hyperinsulinemic euglycemic clamp; maximal oxygen uptake was measured during a bicycle exercise test. RESULTS......: There was a strong correlation between maximal oxygen uptake and insulin-stimulated glucose uptake (r = 0.7, p = 0.001), and maximal oxygen uptake was the only factor of importance for determining insulin sensitivity in a model, which also included the presence of diabetes and ischemic heart disease. CONCLUSION...

  12. Lactate, Glucose and Oxygen Uptake in Human Brain During Recovery from Maximal Exercise

    DEFF Research Database (Denmark)

    Kojiro, I.; Schmalbruch, I.K.; Quistorff, B.

    1999-01-01

    Skeletal muscle, brain lactate uptake, brain oxygen uptake, energy metabolism, brain glucose uptake......Skeletal muscle, brain lactate uptake, brain oxygen uptake, energy metabolism, brain glucose uptake...

  13. 21 CFR 868.1730 - Oxygen uptake computer.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Oxygen uptake computer. 868.1730 Section 868.1730...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Diagnostic Devices § 868.1730 Oxygen uptake computer. (a) Identification. An oxygen uptake computer is a device intended to compute the amount of oxygen consumed by a...

  14. Uptake kinetics of arsenic by lettuce cultivars under hydroponics ...

    African Journals Online (AJOL)

    Arsenic (As) uptake ability based on kinetic parameters by two lettuce cultivars; Sijibaiye (SJBY) and Texuanyanlingsun (TXYLS) was investigated in nutrient solution containing eight levels of arsenic (As). Depletion of As from solution was monitored over a period of 24 h at regular time to estimate As uptake kinetics of the ...

  15. Uptake rate of cationic mitochondrial inhibitor MKT-077 determines cellular oxygen consumption change in carcinoma cells.

    Directory of Open Access Journals (Sweden)

    John L Chunta

    Full Text Available OBJECTIVE: Since tumor radiation response is oxygen-dependent, radiosensitivity can be enhanced by increasing tumor oxygenation. Theoretically, inhibiting cellular oxygen consumption is the most efficient way to increase oxygen levels. The cationic, rhodacyanine dye-analog MKT-077 inhibits mitochondrial respiration and could be an effective metabolic inhibitor. However, the relationship between cellular MKT-077 uptake and metabolic inhibition is unknown. We hypothesized that rat and human mammary carcinoma cells would take up MKT-077, causing a decrease in oxygen metabolism related to drug uptake. METHODS: R3230Ac rat breast adenocarcinoma cells were exposed to MKT-077. Cellular MKT-077 concentration was quantified using spectroscopy, and oxygen consumption was measured using polarographic electrodes. MKT-077 uptake kinetics were modeled by accounting for uptake due to both the concentration and potential gradients across the plasma and mitochondrial membranes. These kinetic parameters were used to model the relationship between MKT-077 uptake and metabolic inhibition. MKT-077-induced changes in oxygen consumption were also characterized in MDA-MB231 human breast carcinoma cells. RESULTS: Cells took up MKT-077 with a time constant of ∼1 hr, and modeling showed that over 90% of intracellular MKT-077 was bound or sequestered, likely by the mitochondria. The uptake resulted in a rapid decrease in oxygen consumption, with a time constant of ∼30 minutes. Surprisingly the change in oxygen consumption was proportional to uptake rate, not cellular concentration. MKT-077 proved a potent metabolic inhibitor, with dose-dependent decreases of 45-73% (p = 0.003. CONCLUSIONS: MKT-077 caused an uptake rate-dependent decrease in cellular metabolism, suggesting potential efficacy for increasing tumor oxygen levels and radiosensitivity in vivo.

  16. Oxygen regulation of nitrate uptake in denitrifying Pseudomonas aeruginosa.

    OpenAIRE

    Hernandez, D; Rowe, J J

    1987-01-01

    Oxygen had an immediate and reversible inhibitory effect on nitrate respiration by denitrifying cultures of Pseudomonas aeruginosa. Inhibition of nitrate utilization by oxygen appeared to be at the level of nitrate uptake, since nitrate reduction to nitrite in cell extracts was not affected by oxygen. The degree of oxygen inhibition was dependent on the concentration of oxygen, and increasing nitrate concentrations could not overcome the inhibition. The inhibitory effect of oxygen was maximal...

  17. Kinetics of oxygen uncoupling of a copper based oxygen carrier

    International Nuclear Information System (INIS)

    Hu, Wenting; Donat, Felix; Scott, S.A.; Dennis, J.S.

    2016-01-01

    Highlights: • The kinetics of a Cu-based oxygen carrier was determined using a TGA. • A diffusion model was applied to remove mass transfer effects from rate parameters. • Thermodynamics are separated from kinetics, usually difficult for the CLOU reaction. • The rate parameters correctly described the behaviour in a fluidised bed. • The rate parameters can be used to predict performance of large CLOU systems. - Abstract: Here, an oxygen carrier consisting of 60 wt% CuO supported on a mixture of Al_2O_3 and CaO (23 wt% and 17 wt% respectively) was synthesised by wet-mixing powdered CuO, Al(OH)_3 and Ca(OH)_2, followed by calcination at 1000 °C. Its suitability for chemical looping with oxygen uncoupling (CLOU) was investigated. After 25 repeated redox cycles in either a thermogravimetric analyser (TGA) or a laboratory-scale fluidised bed, (with 5 vol% H_2 in N_2 as the fuel, and air as the oxidant) no significant change in either the oxygen uncoupling capacity or the overall oxygen availability of the carrier was found. In the TGA, it was found that the rate of oxygen release from the material was controlled by intrinsic chemical kinetics and external transfer of mass from the surface of the particles to the bulk gas. By modelling the various resistances, values of the rate constant for the decomposition were obtained. The activation energy of the reaction was found to be 59.7 kJ/mol (with a standard error of 5.6 kJ/mol) and the corresponding pre-exponential factor was 632 m"3/mol/s. The local rate of conversion within a particle was assumed to occur either (i) by homogeneous chemical reaction, or (ii) in uniform, non-porous grains, each reacting as a kinetically-controlled shrinking core. Upon cross validation against a batch fluidised bed experiment, the homogeneous reaction model was found to be more plausible. By accurately accounting for the various artefacts (e.g. mass transfer resistances) present in both TGA and fluidised bed experiments, it was

  18. Nitrogen uptake kinetics of freshly isolated zooxanthellae

    Digital Repository Service at National Institute of Oceanography (India)

    Wafar, M.V.M.; Wafar, S.; Rajkumar, R.

    that for nitrate [2.8 nmol. ( mu chl-a)./1h/1] and urea [0.37 nmol. ( mu chl-a)./1h/1]. Half-saturation constants for uptake of the three nitrogen compounds were in the range of 10-15 mu mol.l/1. Generally, uptake of any one nitrogen substrate appears to be inhibit...

  19. Modeling uptake kinetics of cadmium by field-grown lettuce

    Energy Technology Data Exchange (ETDEWEB)

    Chen Weiping [Department of Environmental Sciences, University of California, 900 University Avenue, Riverside, CA 92521 (United States)], E-mail: chenweip@yahoo.com.cn; Li Lianqing [Institute of Resources, Ecosystem and Environment of Agriculture, Nanjing Agricultural University, Nanjing 210095 (China); Chang, Andrew C.; Wu Laosheng [Department of Environmental Sciences, University of California, 900 University Avenue, Riverside, CA 92521 (United States); Kwon, Soon-Ik [Agricultural Environmental and Ecology Division, National Institute of Agricultural Science and Technology, Suwon 441-707 (Korea, Republic of); Bottoms, Rick [Desert Research and Extension Center, 1004 East Holton Road, El Centro, CA 92243 (United States)

    2008-03-15

    Cadmium uptake by field grown Romaine lettuce treated with P-fertilizers of different Cd levels was investigated over an entire growing season. Results indicated that the rate of Cd uptake at a given time of the season can be satisfactorily described by the Michaelis-Menten kinetics, that is, plant uptake increases as the Cd concentration in soil solution increases, and it gradually approaches a saturation level. However, the rate constant of the Michaelis-Menten kinetics changes over the growing season. Under a given soil Cd level, the cadmium content in plant tissue decreases exponentially with time. To account for the dynamic nature of Cd uptake, a kinetic model integrating the time factor was developed to simulate Cd plant uptake over the growing season: C{sub Plant} = C{sub Solution} . PUF{sub max} . exp[-b . t], where C{sub Plant} and C{sub Solution} refer to the Cd content in plant tissue and soil solution, respectively, PUF{sub max} and b are kinetic constants. - A kinetic model was developed to evaluate the uptake of Cd under field conditions.

  20. Modeling uptake kinetics of cadmium by field-grown lettuce

    International Nuclear Information System (INIS)

    Chen Weiping; Li Lianqing; Chang, Andrew C.; Wu Laosheng; Kwon, Soon-Ik; Bottoms, Rick

    2008-01-01

    Cadmium uptake by field grown Romaine lettuce treated with P-fertilizers of different Cd levels was investigated over an entire growing season. Results indicated that the rate of Cd uptake at a given time of the season can be satisfactorily described by the Michaelis-Menten kinetics, that is, plant uptake increases as the Cd concentration in soil solution increases, and it gradually approaches a saturation level. However, the rate constant of the Michaelis-Menten kinetics changes over the growing season. Under a given soil Cd level, the cadmium content in plant tissue decreases exponentially with time. To account for the dynamic nature of Cd uptake, a kinetic model integrating the time factor was developed to simulate Cd plant uptake over the growing season: C Plant = C Solution . PUF max . exp[-b . t], where C Plant and C Solution refer to the Cd content in plant tissue and soil solution, respectively, PUF max and b are kinetic constants. - A kinetic model was developed to evaluate the uptake of Cd under field conditions

  1. Oxygen uptake during the γ-irradiation of fatty acids

    International Nuclear Information System (INIS)

    Metwally, M.M.K.; Moore, J.S.

    1987-01-01

    The radiation-induced oxidation of saturated and unsaturated fatty acids in aqueous solutions has been estimated by measurement of the continuous uptake of oxygen using an oxygen electrode. Chain reactions, initiated by HO radicals, are easily identified to be occurring in the case of unsaturated fatty acids. Other mild oxidation agents, namely (SCN)2 -anion radicals, Br 2 - anion radicals and N 3 -anion radicals, are also found to be capable of oxidizing the polyunsaturated fatty acids. Evidence is presented the O 2- anion radicals may also initiate peroxidation. The oxidation of the polyunsaturated fatty acids is dependent on dose rate, fatty acid concentration, temperature and the presence of antioxidant and other protective agents. Kinetic studies of the reaction of (SCN)2 - anion radicals and Br 2 - anion radicals with linoleic and linolenic acids have been carried out using pulse radiolysis. The bimolecular rate constants for both radical species with the lipids are approx 10 7 mol-? 1 dm 3 s -1 , below their critical micelle concentrations, and decrease at higher concentrations due to micelle formation. (author)

  2. Critical evaluation of oxygen-uptake assessment in swimming.

    Science.gov (United States)

    Sousa, Ana; Figueiredo, Pedro; Pendergast, David; Kjendlie, Per-Ludvik; Vilas-Boas, João P; Fernandes, Ricardo J

    2014-03-01

    Swimming has become an important area of sport science research since the 1970s, with the bioenergetic factors assuming a fundamental performance-influencing role. The purpose of this study was to conduct a critical evaluation of the literature concerning oxygen-uptake (VO2) assessment in swimming, by describing the equipment and methods used and emphasizing the recent works conducted in ecological conditions. Particularly in swimming, due to the inherent technical constraints imposed by swimming in a water environment, assessment of VO2max was not accomplished until the 1960s. Later, the development of automated portable measurement devices allowed VO2max to be assessed more easily, even in ecological swimming conditions, but few studies have been conducted in swimming-pool conditions with portable breath-by-breath telemetric systems. An inverse relationship exists between the velocity corresponding to VO2max and the time a swimmer can sustain it at this velocity. The energy cost of swimming varies according to its association with velocity variability. As, in the end, the supply of oxygen (whose limitation may be due to central-O2 delivery and transportation to the working muscles-or peripheral factors-O2 diffusion and utilization in the muscles) is one of the critical factors that determine swimming performance, VO2 kinetics and its maximal values are critical in understanding swimmers' behavior in competition and to develop efficient training programs.

  3. Tritium uptake kinetics in crayfish (Orconectes immunis)

    International Nuclear Information System (INIS)

    Patrick, P.H.

    1985-06-01

    Uptake of tritiated water (HTO) by Orconectes immunis was investigated under laboratory conditions. Tritium uptake in the tissue-free water fraction (TFWT) was described using an exponential model. When steady-state was reached, the ratio of TFWT to HTO was approximately 0.9. Uptake of tritium in the organically-bound fraction (OBT) proceeded slowly, and had not reached steady-state after 117 days of culture. Although steady-state was never reached, the maximum observed ration of OBT to TFWT in whole animals was approximately 0.6. However, this ratio exceeded unity in the exoskeleton. Specific activity ratios of OBT between crayfish and lettuce (food source) were less than or at unity for various test conditions

  4. Oxygen uptake during the exercise: temporal aspectos and adjustments of curves

    Directory of Open Access Journals (Sweden)

    Fernando Roberto de Oliveira

    2004-12-01

    Full Text Available The oxygen uptake has been considered as one of the most important physiological variables for exercise physiology. The first models relating oxygen uptake with performance emerged in the beginning of last century and it has been intensely discussed in the literature until today. This review discussed some topics about oxygen uptake, more specifically on aspects related with the kinetic and influences of the time response of this variable on the adjustment curve during an incremental test. Discussion on the level of aerobic condition and exercise intensity on the kinetics of oxygen uptake are also included in the text. Finally, verification on the slow component and on the physiological control of the oxygen uptake kinetics is also presented. RESUMO O consumo de oxigênio tem sido considerado uma das variáveis fisiológicas mais importantes para a fisiologia do exercício. Os primeiros modelos relacionando o consumo de oxigênio com o desempenho esportivo surgiram no inicio do século passado e continua sendo intensamente discutido na literatura atual. A presenterevisão discutiu alguns tópicos sobre consumo de oxigênio, mais especificamente sobre aspectos relacionados à cinética e a influencia do tempo de resposta dessa variável sobre os ajustes de curva em teste progressivo. Discussões relacionadas a influencia do nível de aptidão aeróbia e a intensidade do exercício sobre a cinética do consumo de oxigênio também estão inseridas no texto. Por fim, algumas constatações sobre componente lento e os controles fisiológicos da cinética do consumo de oxigênio são abordados.

  5. Uptake and elimination kinetics of heavy metals by earthworm ...

    African Journals Online (AJOL)

    Earthworm inoculation of petroleum hydrocarbon contaminated soil is thought to catalyze the bioremediation. Most bioremediation studies focus on the petroleum hydrocarbon content and not on the heavy metals. Here, the uptake kinetics of heavy metals by earthworm in used engine oil contaminated soil was investigated.

  6. A comparison of methods of predicting maximum oxygen uptake.

    OpenAIRE

    Grant, S; Corbett, K; Amjad, A M; Wilson, J; Aitchison, T

    1995-01-01

    The aim of this study was to compare the results from a Cooper walk run test, a multistage shuttle run test, and a submaximal cycle test with the direct measurement of maximum oxygen uptake on a treadmill. Three predictive tests of maximum oxygen uptake--linear extrapolation of heart rate of VO2 collected from a submaximal cycle ergometer test (predicted L/E), the Cooper 12 min walk, run test, and a multi-stage progressive shuttle run test (MST)--were performed by 22 young healthy males (mean...

  7. Kinetic Uptake Studies of Powdered Materials in Solution

    Directory of Open Access Journals (Sweden)

    Mohamed H. Mohamed

    2015-06-01

    Full Text Available Challenges exist for the study of time dependent sorption processes for heterogeneous systems, especially in the case of dispersed nanomaterials in solvents or solutions because they are not well suited to conventional batch kinetic experiments. In this study, a comparison of batch versus a one-pot setup in two variable configurations was evaluated for the study of uptake kinetics in heterogeneous (solid/solution systems: (i conventional batch method; (ii one-pot system with dispersed adsorbent in solution with a semi-permeable barrier (filter paper or dialysis tubing for in situ sampling; and (iii one-pot system with an adsorbent confined in a semi-permeable barrier (dialysis tubing or filter paper barrier with ex situ sampling. The sorbent systems evaluated herein include several cyclodextrin-based polyurethane materials with two types of phenolic dyes: p-nitrophenol and phenolphthalein. The one-pot kinetics method with in situ (Method ii or ex situ (Method iii sampling described herein offers significant advantages for the study of heterogeneous sorption kinetics of highly dispersed sorbent materials with particles sizes across a range of dimensions from the micron to nanometer scale. The method described herein will contribute positively to the development of advanced studies for heterogeneous sorption processes where an assessment of the relative uptake properties is required at different experimental conditions. The results of this study will be advantageous for the study of nanomaterials with significant benefits over batch kinetic studies for a wide range of heterogeneous sorption processes.

  8. Oxygen uptake rate (OUR) control strategy for improving avermectin B

    African Journals Online (AJOL)

    Glucose metabolism plays a crucial role in the process of avermectin B1a biosynthesis. Controlling glucose feeding based on oxygen uptake rate (OUR) was established to improve the efficiency of avermectin B1a production. The result showed that avermectin B1a production was greatly enhanced by OUR control strategy.

  9. Kinetic parameters of silicon uptake by rice cultivars

    Directory of Open Access Journals (Sweden)

    Priscila Oliveira Martins

    2012-02-01

    Full Text Available Silicon is considered an important chemical element for rice, because it can improve tolerance to biotic and abiotic stress. However, in many situations no positive effect of silicon was observed, probably due to genetic factors. The objective of this research was to monitor Si uptake kinetics and identify responses of rice cultivars in terms of Si uptake capacity and use. The experiment was carried out in a greenhouse of the São Paulo State University (UNESP, Brazil. The experiment was arranged in a completely randomized, factorial design with three replications. that consisted of two rice cultivars and two Si levels. Kinetic parameters (Vmax, Km, and Cmin, root morphology variables, dry matter yield, Si accumulation and levels in shoots and roots, uptake efficiency, utilization efficiency, and root/shoot ratio were evaluated. Higher Si concentrations in the nutrient solution did not increase rice dry matter. The development of the low-affinity silicon uptake system of the rice cultivar 'Caiapó' was better than of 'Maravilha'.

  10. Continuous ammonium enrichment of a woodland stream: uptake kinetics, leaf decomposition, and nitrification

    Energy Technology Data Exchange (ETDEWEB)

    Newbold, J D; Elwood, J W; Schulze, M S; Stark, R W; Barmeier, J C

    1983-01-01

    In order to test for nitrogen limitation and examine ammonium uptake by stream sediments, ammonium hydroxide was added continuously at concentrations averaging 100 /sup +/gl/sup -1/ for 70 days to a second-order reach of Walker Branch, an undisturbed woodland stream in Tennessee. Ammonium uptake during the first 4 h of addition corresponded to adsorption kinetics rather than to first-order uptake or to Michaelis-Menten kinetics. However, the calculated adsorption partition coefficient was two to four orders of magnitude greater than values reported for physical adsorption of ammonium, suggesting that the uptake was largely biotic. Mass balance indicated that the uptake of ammonium from the water could be accounted for by increased nitrogen content in benthic organic detritus. Nitrification, inferred from longitudinal gradients in NO/sub 3/, began soon after enrichment and increased dramatically near the end of the experiment. Both ammonium and nitrate concentrations dropped quickly to near background levels when input ceased, indicating little desorption or nitrification of excess nitrogen stored in the reach. There was no evidence of nitrogen limitation as measured by weight loss, oxygen consumption, phosphorus content, and macroinvertebrate density of red oak leaf packs, or by chlorophyll content and aufwuchs biomass on plexiglass slides. A continuous phosphorus enrichment 1 year earlier had demonstrated phosphorus limitation in Walker Branch. 38 references, 6 figures, 3 tables.

  11. Uptake kinetics of relatively insoluble particles by tracheobronchial lymph nodes

    International Nuclear Information System (INIS)

    Thomas, R.G.

    1976-01-01

    Tracheobronchial lymph nodes accumulate a portion of material deposited in the deep lung following inhalation of relatively insoluble particles. Experiments involving a variety of compounds, inhaled singly or repeatedly, indicate that the kinetics of lymph node uptake are fairly independent of particle characteristics and mammalian species. The buildup per unit weight of nodal tissue compared with that of lung tissue, with time, can be represented by a linear logarithmic function. However, since the scatter in experimental points may be large at any given time after inhalation exposure, a number of different kinetic descriptions of uptake can be derived. The logarithmic pattern of accumulation can be approximated over an extended time range (several years) by use of a combination of first-order kinetics of loss from the lung and of buildup in lymph nodes, but it is recognized that the processes are much more complicated than this treatment would indicate. Clearance (loss) from the lymph nodes is not well defined, but this aspect is discussed in light of the kinetic models presented

  12. Oxygen-18 as a tool for studying photorespiration. Oxygen uptake and incorporation into glycolate, glycine and serine

    International Nuclear Information System (INIS)

    Gerster, R.; Dimon, B.; Tournier, P.; Peybernes, A.

    1977-01-01

    The intensity of photosynthesis and photorespiration has been determined by measuring 16 O 2 evolvement and 18 O 2 uptake on algae and leaves. In the case of algae, there is still an important oxygen uptake even when ribulose diphosphate oxygenase is inhibited by 10 -3 M cyanide. Oxygen-18 incorporation into glycolate, glycine and serine of photorespiring algae and leaves exposed to atmospheres containing 18 O 2 has also been measured. Only one of the two atoms present in molecular oxygen was incorporated into the carboxyl group of the glycolate excreted from algae; the rate of 18 O incorporation was important (65 to 80% according to experimental conditions), even in the presence of 10 -3 M cyanide. Thus, oxidation of ribulose diphosphate is not the sole reaction leading to 18 O glycolate synthesis. In the case of maize, there was a rapid and important 18 O incorporation into the carboxyl group of glycine and serine, the kinetics of which was determined as a function of CO 2 presence in the atmosphere. These results suggest that photorespiration is also operating in C 4 species. Furthermore, in vitro experiments showed that phosphorylated ceto-acids of the Calvin cycle were very sensitive to H 2 O 2 ; the corresponding reaction can explain O 2 uptake and 18 O labelling of glycolate. (author)

  13. Embrittlement of zircaloy cladding due to oxygen uptake (CBRTTL)

    International Nuclear Information System (INIS)

    Reymann, G.A.

    1979-02-01

    A model for embrittlement of zircaloy due to oxygen uptake at high temperatures is described. The model defines limits for oxygen content and temperature which, if exceeded, give rise to zircaloy cladding which is sufficiently embrittled to cause failure either on quenching or normal handling following a transient. A significant feature of this model is that the onset of embrittlement is dependent on the cooling rate. A distinction is made between slow and fast cooling, with the boundary at 100 K/s. The material property correlations and computer subcodes described in MATPRO are developed for use in Light Water Reactor (LWR) codes

  14. Measuring oxygen uptake in fishes with bimodal respiration.

    Science.gov (United States)

    Lefevre, S; Bayley, M; McKenzie, D J

    2016-01-01

    Respirometry is a robust method for measurement of oxygen uptake as a proxy for metabolic rate in fishes, and how species with bimodal respiration might meet their demands from water v. air has interested researchers for over a century. The challenges of measuring oxygen uptake from both water and air, preferably simultaneously, have been addressed in a variety of ways, which are briefly reviewed. These methods are not well-suited for the long-term measurements necessary to be certain of obtaining undisturbed patterns of respiratory partitioning, for example, to estimate traits such as standard metabolic rate. Such measurements require automated intermittent-closed respirometry that, for bimodal fishes, has only recently been developed. This paper describes two approaches in enough detail to be replicated by the interested researcher. These methods are for static respirometry. Measuring oxygen uptake by bimodal fishes during exercise poses specific challenges, which are described to aid the reader in designing experiments. The respiratory physiology and behaviour of air-breathing fishes is very complex and can easily be influenced by experimental conditions, and some general considerations are listed to facilitate the design of experiments. Air breathing is believed to have evolved in response to aquatic hypoxia and, probably, associated hypercapnia. The review ends by considering what realistic hypercapnia is, how hypercapnic tropical waters can become and how this might influence bimodal animals' gas exchange. © 2015 The Fisheries Society of the British Isles.

  15. an improved solution of first order kinetics for biochemical oxygen ...

    African Journals Online (AJOL)

    DELL

    Accuracies of these methods were evaluated using relative error, Akaike ... Keywords: Wastewater, Environmental Engineering, Biochemical Oxygen Demand Kinetic Parameters,. Statistical ... evaluating organic pollution level and quality of wastewaters. ... compounds ...... method can be applied on electronic devices, and.

  16. An improved solution of first order kinetics for biochemical oxygen ...

    African Journals Online (AJOL)

    This paper evaluated selected Biochemical Oxygen Demand first order kinetics methods. Domesticinstitutional wastewaters were collected twice in a month for three months from the Obafemi Awolowo University, Ile-Ife waste stabilization ponds. Biochemical Oxygen Demand concentrations at different days were determined ...

  17. Determinants of maximal oxygen uptake in severe acute hypoxia

    DEFF Research Database (Denmark)

    Calbet, J A L; Boushel, Robert Christopher; Rådegran, G

    2003-01-01

    To unravel the mechanisms by which maximal oxygen uptake (VO2 max) is reduced with severe acute hypoxia in humans, nine Danish lowlanders performed incremental cycle ergometer exercise to exhaustion, while breathing room air (normoxia) or 10.5% O2 in N2 (hypoxia, approximately 5,300 m above sea......: 1) reduction of PiO2, 2) impairment of pulmonary gas exchange, and 3) reduction of maximal cardiac output and peak leg blood flow, each explaining about one-third of the loss in VO2 max....

  18. Factors determining the oxygen consumption rate (VO2) on-kinetics in skeletal muscles.

    OpenAIRE

    Korzeniewski, Bernard; Zoladz, Jerzy A

    2004-01-01

    Using a computer model of oxidative phosphorylation developed previously [Korzeniewski and Mazat (1996) Biochem. J. 319, 143-148; Korzeniewski and Zoladz (2001) Biophys. Chem. 92, 17-34], we analyse the effect of several factors on the oxygen-uptake kinetics, especially on the oxygen consumption rate (VO2) and half-transition time t(1/2), at the onset of exercise in skeletal muscles. Computer simulations demonstrate that an increase in the total creatine pool [PCr+/-Cr] (where Cr stands for c...

  19. Kinetic therapy improves oxygenation in critically ill pediatric patients.

    Science.gov (United States)

    Schultz, Theresa Ryan; Lin, Richard; Francis, Barbara A; Hales, Roberta L; Colborn, Shawn; Napoli, Linda A; Helfaer, Mark A

    2005-07-01

    To compare changes in oxygenation after manual turning and percussion (standard therapy) and after automated rotation and percussion (kinetic therapy). Randomized crossover trial. General and cardiac pediatric intensive care units. Intubated and mechanically ventilated pediatric patients who had an arterial catheter and no contraindications to using a PediDyne bed. Patients were placed on a PediDyne bed (Kinetic Concepts) and received 18 hrs blocks of standard and kinetic therapy in an order determined by randomization. Arterial blood gases were measured every 2 hrs during each phase of therapy. Oxygenation index and arterial-alveolar oxygen tension difference [P(A-a)O(2)] were calculated. Indexes calculated at baseline and after each 18-hr phase of therapy were analyzed. Fifty patients were enrolled. Data from 15 patients were either not collected or not used due to reasons that included violation of protocol and inability to tolerate the therapies in the study. Indexes of oxygenation were not normally distributed and were compared using Wilcoxon signed rank testing. Both therapies led to improvements in oxygenation, but only those from kinetic therapy achieved statistical significance. In patients receiving kinetic therapy first, median oxygenation index decreased from 7.4 to 6.19 (p = .015). The median P(A-a)O(2) decreased from 165.2 to 126.4 (p = .023). There were continued improvements in oxygenation after the subsequent period of standard therapy, with the median oxygenation index decreasing to 5.52 and median P(A-a)O(2) decreasing to 116.0, but these changes were not significant (p = .365 and .121, respectively). When standard therapy was first, the median oxygenation index decreased from 8.83 to 8.71 and the median P(a-a)o(2) decreased from 195.4 to 186.6. Neither change was significant. Median oxygenation index after the subsequent period of kinetic therapy was significantly lower (7.91, p = .044) and median P(A-a)O(2) trended lower (143.4, p = .077

  20. Can differences in phosphorus uptake kinetics explain the distribution of cattail and sawgrass in the Florida Everglades?

    Directory of Open Access Journals (Sweden)

    McKee Karen L

    2010-02-01

    Full Text Available Abstract Background Cattail (Typha domingensis has been spreading in phosphorus (P enriched areas of the oligotrophic Florida Everglades at the expense of sawgrass (Cladium mariscus spp. jamaicense. Abundant evidence in the literature explains how the opportunistic features of Typha might lead to a complete dominance in P-enriched areas. Less clear is how Typha can grow and acquire P at extremely low P levels, which prevail in the unimpacted areas of the Everglades. Results Apparent P uptake kinetics were measured for intact plants of Cladium and Typha acclimated to low and high P at two levels of oxygen in hydroponic culture. The saturated rate of P uptake was higher in Typha than in Cladium and higher in low-P acclimated plants than in high-P acclimated plants. The affinity for P uptake was two-fold higher in Typha than in Cladium, and two- to three-fold higher for low-P acclimated plants compared to high-P acclimated plants. As Cladium had a greater proportion of its biomass allocated to roots, the overall uptake capacity of the two species at high P did not differ. At low P availability, Typha increased biomass allocation to roots more than Cladium. Both species also adjusted their P uptake kinetics, but Typha more so than Cladium. The adjustment of the P uptake system and increased biomass allocation to roots resulted in a five-fold higher uptake per plant for Cladium and a ten-fold higher uptake for Typha. Conclusions Both Cladium and Typha adjust P uptake kinetics in relation to plant demand when P availability is high. When P concentrations are low, however, Typha adjusts P uptake kinetics and also increases allocation to roots more so than Cladium, thereby improving both efficiency and capacity of P uptake. Cladium has less need to adjust P uptake kinetics because it is already efficient at acquiring P from peat soils (e.g., through secretion of phosphatases, symbiosis with arbuscular mycorrhizal fungi, nutrient conservation growth

  1. First kinetic discrimination between carbon and oxygen reactivity of enols.

    Science.gov (United States)

    García-Río, Luis; Mejuto, Juan C; Parajó, Mercedes; Pérez-Lorenzo, Moisés

    2008-11-07

    Nitrosation of enols shows a well-differentiated behavior depending on whether the reaction proceeds through the carbon (nucleophilic catalysis is observed) or the oxygen atom (general acid-base catalysis is observed). This is due to the different operating mechanisms for C- and O-nitrosation. Nitrosation of acetylacetone (AcAc) shows a simultaneous nucleophilic and acid-base catalysis. This simultaneous catalysis constitutes the first kinetic evidence of two independent reactions on the carbon and oxygen atom of an enol. The following kinetic study allows us to determine the rate constants for both reaction pathways. A similar reactivity of the nucleophilic centers with the nitrosonium ion is observed.

  2. Kinetic study of the alkaline metals oxidation by dry oxygen

    International Nuclear Information System (INIS)

    Touzain, Ph.

    1967-06-01

    The oxidation of lithium, sodium, potassium, rubidium, cesium and sodium-potassium alloys by dry oxygen is studied at several temperatures and in the oxygen pressure range 40 to 400 mmHg. One distinguishes three different oxidation behaviours (inflammation, ignition and slow combustion) whose zones are precised in function of the temperature. The slow oxidation kinetic laws, the composition of oxides and the motive of oxides colorations are determined. At least, the experimental data are construed theoretically. (author) [fr

  3. Chloroform and trichloroethylene uptake from water into human skin in vitro: Kinetics and risk implications

    International Nuclear Information System (INIS)

    Bogen, K.T.; Keating, G.A.; Vogel, J.S.

    1995-03-01

    A model recently proposed by the US Environmental Protection Agency (EPA) predicts that short-term dermal uptakes of organic environmental water contaminants are proportional to the square root of exposure time. The model appears to underestimate dermal uptake, based on very limited in vivo uptake data obtained primarily using human subjects. To further assess this model, we examined in vitro dermal uptake kinetics for aqueous organic chemicals using accelerator mass spectrometry (AMS). Specifically, we examined the kinetics of in vitro dermal uptake of 14 C-labeled chloroform and trichloroethylene from dilute (5-ppb) aqueous solutions using full-thickness human cadaver skin exposed for (≤1 hr)

  4. Stoichiometry and kinetics of single and mixed substrate uptake in Aspergillus niger.

    Science.gov (United States)

    Lameiras, Francisca; Ras, Cor; Ten Pierick, Angela; Heijnen, Joseph J; van Gulik, Walter M

    2018-02-01

    In its natural environment, the filamentous fungus Aspergillus niger grows on decaying fruits and plant material, thereby enzymatically degrading the lignocellulosic constituents (lignin, cellulose, hemicellulose, and pectin) into a mixture of mono- and oligosaccharides. To investigate the kinetics and stoichiometry of growth of this fungus on lignocellulosic sugars, we carried out batch cultivations on six representative monosaccharides (glucose, xylose, mannose, rhamnose, arabinose, and galacturonic acid) and a mixture of these. Growth on these substrates was characterized in terms of biomass yields, oxygen/biomass ratios, and specific conversion rates. Interestingly, in combination, some of the carbon sources were consumed simultaneously and some sequentially. With a previously developed protocol, a sequential chemostat cultivation experiment was performed on a feed mixture of the six substrates. We found that the uptake of glucose, xylose, and mannose could be described with a Michaelis-Menten-type kinetics; however, these carbon sources seem to be competing for the same transport systems, while the uptake of arabinose, galacturonic acid, and rhamnose appeared to be repressed by the presence of other substrates.

  5. Determination of oxygen diffusion kinetics during thin film ruthenium oxidation

    NARCIS (Netherlands)

    Coloma Ribera, R.; van de Kruijs, Robbert Wilhelmus Elisabeth; Yakshin, Andrey; Bijkerk, Frederik

    2015-01-01

    In situ X-ray reflectivity was used to reveal oxygen diffusion kinetics for thermal oxidation of polycrystalline ruthenium thin films and accurate determination of activation energies for this process. Diffusion rates in nanometer thin RuO2 films were found to show Arrhenius behaviour. However, a

  6. Kinetics of oxygen species in an electrically driven singlet oxygen generator

    Science.gov (United States)

    Azyazov, V. N.; Torbin, A. P.; Pershin, A. A.; Mikheyev, P. A.; Heaven, M. C.

    2015-12-01

    The kinetics of oxygen species in the gaseous medium of a discharge singlet oxygen generator has been revisited. Vibrationally excited ozone O3(υ) formed in O + O2 recombination is thought to be a significant agent in the deactivation of singlet oxygen O2(a1Δ), oxygen atom removal and ozone formation. It is shown that the process O3(υ ⩾ 2) + O2(a1Δ) → 2O2 + O is the main O2(a1Δ) deactivation channel in the post-discharge zone. If no measures are taken to decrease the oxygen atom concentration, the contribution of this process to the overall O2(a1Δ) removal is significant, even in the discharge zone. A simplified model for the kinetics of vibrationally excited ozone is proposed. Calculations based on this model yield results that are in good agreement with the experimental data.

  7. Uranium dioxide sintering Kinetics and mechanisms under controlled oxygen potentials

    International Nuclear Information System (INIS)

    Freitas, C.T. de.

    1980-06-01

    The initial, intermediate, and final sintering stages of uranium dioxide were investigated as a function of stoichiometry and temperature by following the kinetics of the sintering reaction. Stoichiometry was controlled by means of the oxygen potential of the sintering atmosphere, which was measured continuously by solid-state oxygen sensors. Included in the kinetic study were microspheres originated from UO 2 gels and UO 2 pellets produced by isostatic pressing ceramic grade powders. The microspheres sintering behavior was examined using hot-stage microscopy and a specially designed high-temperature, controlled atmosphere furnace. This same furnace was employed as part of an optical dilatometer, which was utilized in the UO 2 pellet sintering investigations. For controlling the deviations from stoichiometry during heat treatment, the oxygen partial pressure in the sintering atmosphere was varied by passing the gas through a Cu-Ti-Cu oxygen trap. The trap temperature determined the oxygen partial pressure of the outflowing mixture. Dry hydrogen was also used in some of the UO sub(2+x) sintering experiments. The determination of diametrial shrinkages and sintering indices was made utilizing high-speed microcinematography and ultra-microbalance techniques. It was observed that the oxygen potential has a substantial influence on the kinetics of the three sintering stages. The control of the sintering atmosphere oxygen partial pressure led to very fast densification of UO sub(2+x). Values in the interval 95.0 to 99.5% of theoretical density were reached in less than one minute. Uranium volume diffusion is the dominant mechanism in the initial and intermediate sintering stages. For the final stage, uranium grain boundary diffusion was found to be the main sintering mechanism. (Author) [pt

  8. Partitioning of oxygen uptake between the gills and skin in fish larvae: a novel method for estimating cutaneous oxygen uptake.

    Science.gov (United States)

    Rombough, P J

    1998-06-01

    The goal of this study was to develop an alternative to the traditional rubber dam method for measuring cutaneous oxygen uptake in bimodally respiring (skin + gills) fish larvae. The method tested involved using microelectrodes to measure the PO2 gradient in the diffusive boundary layer adjacent to seven positions on the skin surface (one on the head, two on the yolk sac, two on the trunk, one at the base of the dorsal fin-fold and one on the proximal portion of the caudal fin-fold) of rainbow trout (Oncorhynchus mykiss) larvae in still water. The PO2 gradient (deltaPO2/delta x, where x is the distance from the skin surface) was then used to calculate area-specific rate of O2 uptake (.MO2/A) according to the Fick equation, .MO2/A=Dbeta(deltaPO2/deltax), where A is the cross-sectional area of the boundary layer, D is the diffusion coefficient and beta is the capacitance coefficient for O2 in water. The accuracy of the method was assessed by comparing it with the rubber dam method. After correcting for differences in body mass, the two methods gave essentially identical results. According to the boundary layer method, the mean (+/-95 % CI) rate of O2 uptake across the skin of newly hatched rainbow trout at 10 degrees C is 3.13+/-0.18 microg O2 cm-2h-1 (N=265). The corresponding value obtained using the rubber dam method was 3. 36+/-0.35 microg O2 cm-2 h-1 (N=27). The advantages of the boundary layer method are that it can be used with smaller, more delicate larvae and that variables, such as flow rate, that can affect the efficiency of gas exchange can be regulated more precisely. The boundary layer method also permits examination of regional differences in exchange efficiency, although in still water such differences do not appear to be significant in trout larvae. The mean steepness of the PO2 gradient in the boundary layer and, hence, the mean rate of area-specific O2 uptake were essentially the same (P>0.05) at all seven locations tested in this study. The

  9. Comparison of specific oxygen uptake rates of two beach-scale ...

    African Journals Online (AJOL)

    The determined values of oxygen uptake rate during the endogenous reaction phase (between 0.1054 and 0.3564 mgO2/L.minute) and concentrations of mixed liquor suspended solids (between 1183 and 1957 mgMLSS/L) are comparable to those reported elsewhere in literature. Results of specific oxygen uptake rate of ...

  10. Response profiles of oxygen uptake efficiency during exercise in healthy children

    NARCIS (Netherlands)

    Bongers, Bart C.; Hulzebos, Erik H J; Helbing, Willem A.; Ten Harkel, Arend D J; Van Brussel, Marco; Takken, Tim

    2015-01-01

    Background Oxygen uptake efficiency (OUE), the relation between oxygen uptake (VO2) and minute ventilation (VE), differs between healthy children and children with heart disease. This study aimed to investigate the normal response profiles of OUE during a progressive cardiopulmonary exercise test.

  11. Heart Rate and Oxygen Uptake Recovery and the Level of Aerobic Capacity in Mountain Bikers

    Directory of Open Access Journals (Sweden)

    Michalik Kamil

    2017-12-01

    Full Text Available Introduction. Since mountain biking involves exercise of varying intensity, competitive performance may be affected by the rate of recovery. The aim of the current study was to determine whether maximal oxygen uptake is associated with the rate of heart rate and oxygen uptake recovery in mountain bike athletes.

  12. Recent advances in the kinetics of oxygen reduction

    Energy Technology Data Exchange (ETDEWEB)

    Adzic, R.

    1996-07-01

    Oxygen reduction is considered an important electrocatalytic reaction; the most notable need remains improvement of the catalytic activity of existing metal electrocatalysts and development of new ones. A review is given of new advances in the understanding of reaction kinetics and improvements of the electrocatalytic properties of some surfaces, with focus on recent studies of relationship of the surface properties to its activity and reaction kinetics. The urgent need is to improve catalytic activity of Pt and synthesize new, possibly non- noble metal catalysts. New experimental techniques for obtaining new level of information include various {ital in situ} spectroscopies and scanning probes, some involving synchrotron radiation. 138 refs, 18 figs, 2 tabs.

  13. Pediatric Exercise Testing: Value and Implications of Peak Oxygen Uptake

    Directory of Open Access Journals (Sweden)

    Paolo T. Pianosi

    2017-01-01

    Full Text Available Peak oxygen uptake (peak V ˙ O 2 measured by clinical exercise testing is the benchmark for aerobic fitness. Aerobic fitness, estimated from maximal treadmill exercise, is a predictor of mortality in adults. Peak V ˙ O 2 was shown to predict longevity in patients aged 7–35 years with cystic fibrosis over 25 years ago. A surge of exercise studies in young adults with congenital heart disease over the past decade has revealed significant prognostic information. Three years ago, the first clinical trial in children with pulmonary arterial hypertension used peak V ˙ O 2 as an endpoint that likewise delivered clinically relevant data. Cardiopulmonary exercise testing provides clinicians with biomarkers and clinical outcomes, and researchers with novel insights into fundamental biological mechanisms reflecting an integrated physiological response hidden at rest. Momentum from these pioneering observations in multiple disease states should impel clinicians to employ similar methods in other patient populations; e.g., sickle cell disease. Advances in pediatric exercise science will elucidate new pathways that may identify novel biomarkers. Our initial aim of this essay is to highlight the clinical relevance of exercise testing to determine peak V ˙ O 2 , and thereby convince clinicians of its merit, stimulating future clinical investigators to broaden the application of exercise testing in pediatrics.

  14. O2 uptake kinetics during exercise at peak O2 uptake.

    Science.gov (United States)

    Scheuermann, Barry W; Barstow, Thomas J

    2003-11-01

    Compared with moderate- and heavy-intensity exercise, the adjustment of O2 uptake (VO2) to exercise intensities that elicit peak VO2 has received relatively little attention. This study examined the VO2 response of 21 young, healthy subjects (25 +/- 6 yr; mean +/- SD) during cycle ergometer exercise to step transitions in work rate (WR) corresponding to 90, 100, and 110% of the peak WR achieved during a preliminary ramp protocol (15-30 W/min). Gas exchange was measured breath by breath and interpolated to 1-s values. VO2 kinetics were determined by use of a two- or three-component exponential model to isolate the time constant (tau2) as representative of VO2 kinetics and the amplitude (Amp) of the primary fast component independent of the appearance of any VO2 slow component. No difference in VO2 kinetics was observed between WRs (tau90 = 24.7 +/- 9.0; tau100 = 22.8 +/- 6.7; tau110 = 21.5 +/- 9.2 s, where subscripts denote percent of peak WR; P > 0.05); nor in a subgroup of eight subjects was tau2 different from the value for moderate-intensity (exercise (tau2 = 25 +/- 12 s, P > 0.05). As expected, the Amp increased with increasing WRs (Amp90 = 2,089 +/- 548; Amp100 = 2,165 +/- 517; Amp110 = 2,225 +/- 559 ml/min; Amp90 vs. Amp110, P exercise, the gain of the Vo2 response (as deltaVO2/DeltaWR) is reduced for exercise transitions in the severe-intensity domain, but the approach to this gain is well described by a common time constant that is invariant across work intensities. The lower deltaVO2/deltaWR may be due to an insufficient adjustment of the cardiovascular and/or pulmonary systems that determine O2 delivery to the exercising muscles or due to recruitment of motor units with lower oxidative capacity, after the onset of exercise in the severe-intensity domain.

  15. Peak oxygen uptake in a sprint interval testing protocol vs. maximal oxygen uptake in an incremental testing protocol and their relationship with cross-country mountain biking performance.

    Science.gov (United States)

    Hebisz, Rafał; Hebisz, Paulina; Zatoń, Marek; Michalik, Kamil

    2017-04-01

    In the literature, the exercise capacity of cyclists is typically assessed using incremental and endurance exercise tests. The aim of the present study was to confirm whether peak oxygen uptake (V̇O 2peak ) attained in a sprint interval testing protocol correlates with cycling performance, and whether it corresponds to maximal oxygen uptake (V̇O 2max ) determined by an incremental testing protocol. A sample of 28 trained mountain bike cyclists executed 3 performance tests: (i) incremental testing protocol (ITP) in which the participant cycled to volitional exhaustion, (ii) sprint interval testing protocol (SITP) composed of four 30 s maximal intensity cycling bouts interspersed with 90 s recovery periods, (iii) competition in a simulated mountain biking race. Oxygen uptake, pulmonary ventilation, work, and power output were measured during the ITP and SITP with postexercise blood lactate and hydrogen ion concentrations collected. Race times were recorded. No significant inter-individual differences were observed in regards to any of the ITP-associated variables. However, 9 individuals presented significantly increased oxygen uptake, pulmonary ventilation, and work output in the SITP compared with the remaining cyclists. In addition, in this group of 9 cyclists, oxygen uptake in SITP was significantly higher than in ITP. After the simulated race, this group of 9 cyclists achieved significantly better competition times (99.5 ± 5.2 min) than the other cyclists (110.5 ± 6.7 min). We conclude that mountain bike cyclists who demonstrate higher peak oxygen uptake in a sprint interval testing protocol than maximal oxygen uptake attained in an incremental testing protocol demonstrate superior competitive performance.

  16. Sex differences in the oxygen delivery, extraction, and uptake during moderate-walking exercise transition.

    Science.gov (United States)

    Beltrame, Thomas; Villar, Rodrigo; Hughson, Richard L

    2017-09-01

    Previous studies in children and older adults demonstrated faster oxygen uptake (V̇O 2 ) kinetics in males compared with females, but young healthy adults have not been studied. We hypothesized that young men would have faster aerobic system dynamics in response to the onset of exercise than women. Interactions between oxygen supply and utilization were characterized by the dynamics of V̇O 2 , deoxyhemoglobin (HHb), tissue saturation index (TSI), cardiac output (Q̇), and calculated arteriovenous O 2 difference (a-vO 2 diff ) in women and men. Eighteen healthy active young women and men (9 of each sex) with similar aerobic fitness levels volunteered for this study. Participants performed an incremental cardiopulmonary treadmill exercise test and 3 moderate-intensity treadmill exercise tests (at 80% V̇O 2 of gas exchange threshold). Data related to the moderate exercise were submitted to exponential data modelling to obtain parameters related to the aerobic system dynamics. The time constants of V̇O 2 , a-vO 2 diff , HHb, and TSI (30 ± 6, 29 ± 1, 16 ± 1, and 15 ± 2 s, respectively) in women were statistically (p < 0.05) faster than the time constants in men (42 ± 10, 49 ± 21, 19 ± 3, and 20 ± 4 s, respectively). Although Q̇ dynamics were not statistically different (p = 0.06) between groups, there was a trend to slower Q̇ dynamics in men corresponding with the slower V̇O 2 kinetics. These results indicated that the peripheral and pulmonary oxygen extraction dynamics were remarkably faster in women. Thus, contrary to the hypothesis, V̇O 2 dynamics measured at the mouth at the onset of submaximal treadmill walking were faster in women compared with men.

  17. Activation-induced resetting of cerebral oxygen and glucose uptake in the rat

    DEFF Research Database (Denmark)

    Madsen, P L; Linde, R; Hasselbalch, S G

    1998-01-01

    In the clinical setting it has been shown that activation will increase cerebral glucose uptake in excess of cerebral oxygen uptake. To study this phenomenon further, this study presents an experimental setup that enables precise determination of the ratio between cerebral uptake of glucose...... and oxygen in the awake rat. Global CBF was measured by the Kety-Schmidt technique, and the ratio between cerebral uptake rates for oxygen, glucose, and lactate was calculated from cerebral arterial-venous differences. During baseline conditions, rats were kept in a closed box designed to minimize...... interference. During baseline conditions CBF was 1.08 +/- 0.25 mL x g(-1) x minute(-1), and the cerebral oxygen to glucose uptake ratio was 5.5. Activation was induced by opening the sheltering box for 6 minutes. Activation increased CBF to 1.81 mL x g(-1) x minute(-1). During activation cerebral glucose...

  18. Oxygen uptake kinetics Of Pseudomonas sp. strain VB grown under ...

    African Journals Online (AJOL)

    Fred

    2004-07-22

    Jul 22, 2004 ... 1996). Its diverse uses makes the substance ubiquitous as an environmental xenobiotic which has considerable implications within the global biosphere. The microbial mixed cultural degradation of 2- methoxyethanol under anaerobic conditions has been reported (Tanaka et al., 1986; Tanaka and Pfennig,.

  19. Thromboxane plays a role in postprandial jejunal oxygen uptake and capillary exchange.

    Science.gov (United States)

    Alemayehu, A; Chou, C C

    1990-09-01

    The effects of a thromboxane A2 (TxA2)-endoperoxide receptor antagonist, SQ 29548, on jejunal blood flow, oxygen uptake, and capillary filtration coefficient (Kfc) were determined in anesthetized dogs under resting conditions and during the presence of predigested food in the jejunal lumen in three series of experiments. In series 1, 2.0 micrograms intra-arterial administration of SQ 29548 was found to abolish completely the vasoconstrictor action of graded doses (0.05-2.0 micrograms) of intra-arterial injection of a TxA2-endoperoxide analogue, U44069. SQ 29548 (2.0 micrograms ia) per se did not significantly alter resting jejunal blood flow, oxygen uptake, capillary pressure, or Kfc. Before SQ 29548, placement of food plus bile into the jejunal lumen increased blood flow +42 +/- 9%, oxygen uptake +28 +/- 7%, and Kfc +24 +/- 6%. After SQ 29548, the food placement increased blood flow +37 +/- 8%, oxygen uptake +52 +/- 11%, and Kfc +63 +/- 20%. The food-induced increases in oxygen uptake and Kfc after SQ 29548 were significantly greater than those induced before the blocking of TxA2-endoperoxide receptors by SQ 29548. Our study indicates that endogenous thromboxane does not play a role in regulating jejunal blood flow, capillary filtration, and oxygen uptake under resting conditions. However, it plays a role in limiting the food-induced increases in jejunal oxygen uptake and capillary exchange capacity without influencing the food-induced hyperemia.

  20. Estimation of maximal oxygen uptake without exercise testing in Korean healthy adult workers.

    Science.gov (United States)

    Jang, Tae-Won; Park, Shin-Goo; Kim, Hyoung-Ryoul; Kim, Jung-Man; Hong, Young-Seoub; Kim, Byoung-Gwon

    2012-08-01

    Maximal oxygen uptake is generally accepted as the most valid and reliable index of cardiorespiratory fitness and functional aerobic capacity. The exercise test for measuring maximal oxygen uptake is unsuitable for screening tests in public heath examinations, because of the potential risks of exercise exertion and time demands. We designed this study to determine whether work-related physical activity is a potential predictor of maximal oxygen uptake, and to develop a maximal oxygen uptake equation using a non-exercise regression model for the cardiorespiratory fitness test in Korean adult workers. Study subjects were adult workers of small-sized companies in Korea. Subjects with history of disease such as hypertension, diabetes, asthma and angina were excluded. In total, 217 adult subjects (113 men of 21-55 years old and 104 women of 20-64 years old) were included. Self-report questionnaire survey was conducted on study subjects, and maximal oxygen uptake of each subject was measured with the exercise test. The statistical analysis was carried out to develop an equation for estimating maximal oxygen uptake. The predictors for estimating maximal oxygen uptake included age, gender, body mass index, smoking, leisure-time physical activity and the factors representing work-related physical activity. The work-related physical activity was identified to be a predictor of maximal oxygen uptake. Moreover, the equation showed high validity according to the statistical analysis. The equation for estimating maximal oxygen uptake developed in the present study could be used as a screening test for assessing cardiorespiratory fitness in Korean adult workers.

  1. Effects of Iron-Oxide Nanoparticle Surface Chemistry on Uptake Kinetics and Cytotoxicity in CHO-K1 Cells

    Directory of Open Access Journals (Sweden)

    Camille C. Hanot

    2015-12-01

    Full Text Available Superparamagnetic iron-oxide nanoparticles (SPIONs show great promise for multiple applications in biomedicine. While a number of studies have examined their safety profile, the toxicity of these particles on reproductive organs remains uncertain. The goal of this study was to evaluate the cytotoxicity of starch-coated, aminated, and PEGylated SPIONs on a cell line derived from Chinese Hamster ovaries (CHO-K1 cells. We evaluated the effect of particle diameter (50 and 100 nm and polyethylene glycol (PEG chain length (2k, 5k and 20k Da on the cytotoxicity of SPIONs by investigating cell viability using the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT and sulforhodamine B (SRB assays. The kinetics and extent of SPION uptake by CHO-K1 cells was also studied, as well as the resulting generation of intracellular reactive oxygen species (ROS. Cell toxicity profiles of SPIONs correlated strongly with their cellular uptake kinetics, which was strongly dependent on surface properties of the particles. PEGylation caused a decrease in both uptake and cytotoxicity compared to aminated SPIONs. Interestingly, 2k Da PEG-modifed SPIONs displayed the lowest cellular uptake and cytotoxicity among all studied particles. These results emphasize the importance of surface coatings when engineering nanoparticles for biomedical applications.

  2. Kinetics of oxygen species in an electrically driven singlet oxygen generator

    International Nuclear Information System (INIS)

    Azyazov, V.N.; Torbin, A.P.; Pershin, A.A.; Mikheyev, P.A.; Heaven, M.C.

    2015-01-01

    Highlights: • Vibrational excitation of O_3 increases the rate constant for O_3 + O_2(a) → 2O_2(X) + O. • Vibrationally excited O_3 is produced by the O + O_2(X) + M → O_3 + M reaction. • Ozone concentrations are impacted by the reactions of vibrationally excited O_3. • Relevant to ozone concentrations in oxygen discharges and the upper atmosphere. - Abstract: The kinetics of oxygen species in the gaseous medium of a discharge singlet oxygen generator has been revisited. Vibrationally excited ozone O_3(υ) formed in O + O_2 recombination is thought to be a significant agent in the deactivation of singlet oxygen O_2(a"1Δ), oxygen atom removal and ozone formation. It is shown that the process O_3(υ ⩾ 2) + O_2(a"1Δ) → 2O_2 + O is the main O_2(a"1Δ) deactivation channel in the post-discharge zone. If no measures are taken to decrease the oxygen atom concentration, the contribution of this process to the overall O_2(a"1Δ) removal is significant, even in the discharge zone. A simplified model for the kinetics of vibrationally excited ozone is proposed. Calculations based on this model yield results that are in good agreement with the experimental data.

  3. Oxygen uptake efficiency slope and peak oxygen consumption predict prognosis in children with tetralogy of Fallot.

    Science.gov (United States)

    Tsai, Yun-Jeng; Li, Min-Hui; Tsai, Wan-Jung; Tuan, Sheng-Hui; Liao, Tin-Yun; Lin, Ko-Long

    2016-07-01

    Oxygen uptake efficiency slope (OUES) and peak oxygen consumption (VO2peak) are exercise parameters that can predict cardiac morbidity in patients with numerous heart diseases. But the predictive value in patients with tetralogy of Fallot is still undetermined, especially in children. We evaluated the prognostic value of OUES and VO2peak in children with total repair of tetralogy of Fallot. Retrospective cohort study. Forty tetralogy of Fallot patients younger than 12 years old were recruited. They underwent a cardiopulmonary exercise test during the follow-up period after total repair surgery. The results of the cardiopulmonary exercise test were used to predict the cardiac related hospitalization in the following two years after the test. OUES normalized by body surface area (OUES/BSA) and the percentage of predicted VO2peak appeared to be predictive for two-year cardiac related hospitalization. Receiver operating characteristic curve analysis demonstrated that the best threshold value for OUES/BSA was 1.029 (area under the curve = 0.70, p = 0.03), and for VO2peak was 74% of age prediction (area under the curve = 0.72, p = 0.02). The aforementioned findings were confirmed by Kaplan-Meier plots and log-rank test. OUES/BSA and VO2peak are useful predictors of cardiac-related hospitalization in children with total repair of tetralogy of Fallot. © The European Society of Cardiology 2015.

  4. Determination of oxygen diffusion kinetics during thin film ruthenium oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Coloma Ribera, R., E-mail: r.colomaribera@utwente.nl; Kruijs, R. W. E. van de; Yakshin, A. E.; Bijkerk, F. [MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands)

    2015-08-07

    In situ X-ray reflectivity was used to reveal oxygen diffusion kinetics for thermal oxidation of polycrystalline ruthenium thin films and accurate determination of activation energies for this process. Diffusion rates in nanometer thin RuO{sub 2} films were found to show Arrhenius behaviour. However, a gradual decrease in diffusion rates was observed with oxide growth, with the activation energy increasing from about 2.1 to 2.4 eV. Further exploration of the Arrhenius pre-exponential factor for diffusion process revealed that oxidation of polycrystalline ruthenium joins the class of materials that obey the Meyer-Neldel rule.

  5. Low blood flow at onset of moderate-intensity exercise does not limit muscle oxygen uptake

    DEFF Research Database (Denmark)

    Nyberg, Michael Permin; Mortensen, Stefan P; Saltin, Bengt

    2010-01-01

    The effect of low blood flow at onset of moderate-intensity exercise on the rate of rise in muscle oxygen uptake was examined. Seven male subjects performed a 3.5-min one-legged knee-extensor exercise bout (24 +/- 1 W, mean +/- SD) without (Con) and with (double blockade; DB) arterial infusion...... of inhibitors of nitric oxide synthase (N(G)-monomethyl-l-arginine) and cyclooxygenase (indomethacin) to inhibit the synthesis of nitric oxide and prostanoids, respectively. Leg blood flow and leg oxygen delivery throughout exercise was 25-50% lower (P ... +/- 12 vs. 262 +/- 39 ml/min). The present data demonstrate that muscle blood flow and oxygen delivery can be markedly reduced without affecting muscle oxygen uptake in the initial phase of moderate-intensity exercise, suggesting that blood flow does not limit muscle oxygen uptake at the onset...

  6. Kinetics of liquid lithium reaction with oxygen-nitrogen mixtures

    International Nuclear Information System (INIS)

    Gil, T.K.; Kazimi, M.S.

    1986-01-01

    A series of experiments have been conducted in order to characterize the kinetics of lithium chemical reaction with a mixture of oxygen and nitrogen. Three mixed gas compositions were used; 80% N 2 and 20% O 2 , 90% N 2 and 10% O 2 , and 95% N 2 and 5% O 2 . The reaction rate was obtained as a function of lithium temperature and the oxygen fraction. Liquid lithium temperature varied from 400 to 1100 0 C. By varying the composition, the degree of inhibition of the lithium-nitrogen reaction rate due to the presence of oxygen was observed. The results indicate that the lithium-nitrogen reaction rate depended on both the fraction of oxygen present and lithium temperature. The lithium nitride layer formed from the reaction also had a significant inhibition effect on the lithium-nitrogen reaction rate while the lithium-oxygen reaction rate was not as greatly hindered. LITFIRE, a computer code which simulates temperature and pressure history in a containment building following lithium spills, was modified by including (1) an improved model for the lithium-nitrogen reaction rate and (2) a model for the lithium-CO 2 reaction. LITFIRE was used to simulate HEDL's LC-2 and LA-5 experiments, and the predicted temperatures and pressures were in a reasonable agreement. Furthermore, LITFIRE was applied to a prototypical fusion reactor containment in order to simulate the consequences of a lithium spill accident. The result indicated that if nitrogen was used as containment building gas during the accident, the consequences of the accident would be less severe than those with air. The pressure rise in the building was found to be reduced by 50% and the maximum temperature of the combustion zone was limited to 900 0 C instead of 1200 0 C in the case of air

  7. Copper uptake kinetics and regulation in a marine fish after waterborne copper acclimation

    International Nuclear Information System (INIS)

    Dang Fei; Zhong Huan; Wang Wenxiong

    2009-01-01

    The uptake kinetics and regulation of copper in a marine predatory fish, the black sea bream Acanthopagrus schlegeli after acclimation to waterborne Cu were examined, using radiotracer techniques. The dissolved Cu uptake followed a linear pattern during the time of exposure, and the calculated uptake rate constant was 6.24 L kg -1 day -1 . The efflux rate constant was 0.091 day -1 following dietary uptake of Cu, and the dietary assimilation efficiency (AE) of Cu varied between 1.7% and 10.9% after the fish were fed with three types of prey (oysters, clams and brine shrimp). After the fish were acclimated at a nominal concentration of 50 μg Cu L -1 for 14 days, the Cu uptake rate and efflux rate constant did not change significantly, but the Cu body concentrations and metallothionein (MT) concentrations in fish tissues increased significantly. Subcellular Cu distributions were also modified. Significant MT induction was observed in response to increased Cu tissue concentrations, indicating that MT rather than the uptake kinetics may play a primary role in Cu regulation during waterborne Cu acclimation in this marine fish. Moreover, the high Cu efflux may also be important in Cu regulation during long-term exposure. Our modeling calculations indicated that dietary uptake was likely to be the main route for Cu bioaccumulation in the fish, and the relative contribution of waterborne and dietary uptake depended on the bioconcentration factor (BCF) of the prey and ingestion rate of fish.

  8. A comparative kinetic and mechanistic study between tetrahydrozoline and naphazoline toward photogenerated reactive oxygen species.

    Science.gov (United States)

    Criado, Susana; García, Norman A

    2010-01-01

    Kinetic and mechanistic aspects of the vitamin B2 (riboflavin [Rf])-sensitized photo-oxidation of the imidazoline derivates (IDs) naphazoline (NPZ) and tetrahydrozoline (THZ) were investigated in aqueous solution. The process appears as important on biomedical grounds, considering that the vitamin is endogenously present in humans, and IDs are active components of ocular medicaments of topical application. Under aerobic visible light irradiation, a complex picture of competitive interactions between sensitizer, substrates and dissolved oxygen takes place: the singlet and triplet ((3)Rf*) excited states of Rf are quenched by the IDs: with IDs concentrations ca. 5.0 mM and 0.02 mM Rf, (3)Rf* is quenched by IDs, in a competitive fashion with dissolved ground state oxygen. Additionally, the reactive oxygen species: O(2)((1)Delta(g)), O(2)(*-), HO(*) and H(2)O(2), generated from (3)Rf* and Rf(*-), were detected with the employment of time-resolved methods or specific scavengers. Oxygen uptake experiments indicate that, for NPZ, only H(2)O(2) was involved in the photo-oxidation. In the case of THZ, O(2)(*-), HO(*) and H(2)O(2) were detected, whereas only HO(*) was unambiguously identified as THZ oxidative agents. Upon direct UV light irradiation NPZ and THZ generate O(2)((1)Delta(g)), with quantum yields of 0.2 (literature value, employed as a reference) and 0.08, respectively, in acetonitrile.

  9. Kinetics of oxygen species in an electrically driven singlet oxygen generator

    Energy Technology Data Exchange (ETDEWEB)

    Azyazov, V.N., E-mail: azyazov@fian.smr.ru [Samara State Aerospace University, 443086 (Russian Federation); Lebedev Physical Institute of RAS, Samara 443011 (Russian Federation); Torbin, A.P.; Pershin, A.A. [Samara State Aerospace University, 443086 (Russian Federation); Lebedev Physical Institute of RAS, Samara 443011 (Russian Federation); Mikheyev, P.A., E-mail: mikheyev@fian.smr.ru [Samara State Aerospace University, 443086 (Russian Federation); Lebedev Physical Institute of RAS, Samara 443011 (Russian Federation); Heaven, M.C., E-mail: mheaven@emory.edu [Emory University, Atlanta, GA 30322 (United States)

    2015-12-16

    Highlights: • Vibrational excitation of O{sub 3} increases the rate constant for O{sub 3} + O{sub 2}(a) → 2O{sub 2}(X) + O. • Vibrationally excited O{sub 3} is produced by the O + O{sub 2}(X) + M → O{sub 3} + M reaction. • Ozone concentrations are impacted by the reactions of vibrationally excited O{sub 3}. • Relevant to ozone concentrations in oxygen discharges and the upper atmosphere. - Abstract: The kinetics of oxygen species in the gaseous medium of a discharge singlet oxygen generator has been revisited. Vibrationally excited ozone O{sub 3}(υ) formed in O + O{sub 2} recombination is thought to be a significant agent in the deactivation of singlet oxygen O{sub 2}(a{sup 1}Δ), oxygen atom removal and ozone formation. It is shown that the process O{sub 3}(υ ⩾ 2) + O{sub 2}(a{sup 1}Δ) → 2O{sub 2} + O is the main O{sub 2}(a{sup 1}Δ) deactivation channel in the post-discharge zone. If no measures are taken to decrease the oxygen atom concentration, the contribution of this process to the overall O{sub 2}(a{sup 1}Δ) removal is significant, even in the discharge zone. A simplified model for the kinetics of vibrationally excited ozone is proposed. Calculations based on this model yield results that are in good agreement with the experimental data.

  10. Real-time monitoring of specific oxygen uptake rates of embryonic stem cells in a microfluidic cell culture device.

    Science.gov (United States)

    Super, Alexandre; Jaccard, Nicolas; Cardoso Marques, Marco Paulo; Macown, Rhys Jarred; Griffin, Lewis Donald; Veraitch, Farlan Singh; Szita, Nicolas

    2016-09-01

    Oxygen plays a key role in stem cell biology as a signaling molecule and as an indicator of cell energy metabolism. Quantification of cellular oxygen kinetics, i.e. the determination of specific oxygen uptake rates (sOURs), is routinely used to understand metabolic shifts. However current methods to determine sOUR in adherent cell cultures rely on cell sampling, which impacts on cellular phenotype. We present real-time monitoring of cell growth from phase contrast microscopy images, and of respiration using optical sensors for dissolved oxygen. Time-course data for bulk and peri-cellular oxygen concentrations obtained for Chinese hamster ovary (CHO) and mouse embryonic stem cell (mESCs) cultures successfully demonstrated this non-invasive and label-free approach. Additionally, we confirmed non-invasive detection of cellular responses to rapidly changing culture conditions by exposing the cells to mitochondrial inhibiting and uncoupling agents. For the CHO and mESCs, sOUR values between 8 and 60 amol cell(-1) s(-1) , and 5 and 35 amol cell(-1) s(-1) were obtained, respectively. These values compare favorably with literature data. The capability to monitor oxygen tensions, cell growth, and sOUR, of adherent stem cell cultures, non-invasively and in real time, will be of significant benefit for future studies in stem cell biology and stem cell-based therapies. © 2016 The Authors. Biotechnology Journal published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Neuromuscular blockade of slow twitch muscle fibres elevates muscle oxygen uptake and energy turnover during submaximal exercise in humans

    DEFF Research Database (Denmark)

    Krustrup, Peter; Secher, Niels; Relu, Mihai U.

    2008-01-01

    We tested the hypothesis that a greater activation of fast-twitch (FT) fibres during dynamic exercise leads to a higher muscle oxygen uptake (VO2 ) and energy turnover as well as a slower muscle on-kinetics. Subjects performed one-legged knee-extensor exercise for 10 min at an intensity of 30 W...... without (CON) and with (CUR) arterial injections of the non-depolarizing neuromuscular blocking agent cisatracurium. In CUR, creatine phosphate (CP) was unaltered in slow twitch (ST) fibres and decreased (P fibres, whereas in CON, CP decreased (P ... at a contraction frequency of 1 Hz, and that the muscle VO2 kinetics is slowed by FT fibre activation....

  12. Factors determining the oxygen consumption rate (VO2) on-kinetics in skeletal muscles.

    Science.gov (United States)

    Korzeniewski, Bernard; Zoladz, Jerzy A

    2004-05-01

    Using a computer model of oxidative phosphorylation developed previously [Korzeniewski and Mazat (1996) Biochem. J. 319, 143-148; Korzeniewski and Zoladz (2001) Biophys. Chem. 92, 17-34], we analyse the effect of several factors on the oxygen-uptake kinetics, especially on the oxygen consumption rate (VO2) and half-transition time t(1/2), at the onset of exercise in skeletal muscles. Computer simulations demonstrate that an increase in the total creatine pool [PCr+/-Cr] (where Cr stands for creatine and PCr for phosphocreatine) and in glycolytic ATP supply lengthen the half-transition time, whereas increase in mitochondrial content, in parallel activation of ATP supply and ATP usage, in oxygen concentration, in proton leak, in resting energy demand, in resting cytosolic pH and in initial alkalization decrease this parameter. Theoretical studies show that a decrease in the activity of creatine kinase (CK) [displacement of this enzyme from equilibrium during on-transient (rest-to-work transition)] accelerates the first stage of the VO2 on-transient, but slows down the second stage of this transient. It is also demonstrated that a prior exercise terminated a few minutes before the principal exercise shortens the transition time. Finally, it is shown that at a given ATP demand, and under conditions where CK works near the thermodynamic equilibrium, the half-transition time of VO2 kinetics is determined by the amount of PCr that has to be transformed into Cr during rest-to-work transition; therefore any factor that diminishes the difference in [PCr] between rest and work at a given energy demand will accelerate the VO2 on-kinetics. Our conclusions agree with the general idea formulated originally by Easterby [(1981) Biochem. J. 199, 155-161] that changes in metabolite concentrations determine the transition times between different steady states in metabolic systems.

  13. Kinetic theory of oxygen isotopic exchange between minerals and water

    Science.gov (United States)

    Criss, R.E.; Gregory, R.T.; Taylor, H.P.

    1987-01-01

    Kinetic and mass conservation equations are used to describe oxygen isotopic exchange between minerals and water in "closed" and open hydrothermal systems. In cases where n coexisting mineral phases having different reaction rates are present, the exchange process is described by a system of n + 1 simultaneous differential equations consisting of n pseudo first-order rate equations and a conservation of mass equation. The simultaneous solutions to these equations generate curved exchange trajectories on ??-?? plots. Families of such trajectories generated under conditions allowing for different fluid mole fractions, different fluid isotopic compositions, or different fluid flow rates are connected by positive-sloped isochronous lines. These isochrons reproduce the effects observed in hydrothermally exchanged mineral pairs including 1) steep positive slopes, 2) common reversals in the measured fractionation factors (??), and 3) measured fractionations that are highly variable over short distances where no thermal gradient can be geologically demonstrated. ?? 1987.

  14. Ghost crabs on a treadmill: Oxygen Uptake and Haemocyanin ...

    African Journals Online (AJOL)

    Ghost crabs Ocypode ceratophthalmus were exercised on a specially constructed treadmill. At a running speed of 13,3 cm s-1, most crabs ran for 2 h before getting fatigued. At this speed the oxygen consumption rate (MO2) was measured in time intervals for a total of 52 min. For exercised crabs the MO2 values are about ...

  15. Land use/land cover and scale influences on in-stream nitrogen uptake kinetics

    Science.gov (United States)

    Covino, Tim; McGlynn, Brian; McNamara, Rebecca

    2012-06-01

    Land use/land cover change often leads to increased nutrient loading to streams; however, its influence on stream ecosystem nutrient transport remains poorly understood. Given the deleterious impacts elevated nutrient loading can have on aquatic ecosystems, it is imperative to improve understanding of nutrient retention capacities across stream scales and watershed development gradients. We performed 17 nutrient addition experiments on six streams across the West Fork Gallatin Watershed, Montana, USA, to quantify nitrogen uptake kinetics and retention dynamics across stream sizes (first to fourth order) and along a watershed development gradient. We observed that stream nitrogen (N) uptake kinetics and spiraling parameters varied across streams of different development intensity and scale. In more developed watersheds we observed a fertilization affect. This fertilization affect was evident as increased ash-free dry mass, chlorophylla, and ambient and maximum uptake rates in developed as compared to undeveloped streams. Ash-free dry mass, chlorophylla, and the number of structures in a subwatershed were significantly correlated to nutrient spiraling and kinetic parameters, while ambient and average annual N concentrations were not. Additionally, increased maximum uptake capacities in developed streams contributed to low in-stream nutrient concentrations during the growing season, and helped maintain watershed export at low levels during base flow. Our results indicate that land use/land cover change can enhance in-stream uptake of limiting nutrients and highlight the need for improved understanding of the watershed dynamics that control nutrient export across scales and development intensities for mitigation and protection of aquatic ecosystems.

  16. Multimodel inference applied to oxygen recovery kinetics after 6-min walk tests in patients with chronic obstructive pulmonary disease

    DEFF Research Database (Denmark)

    Baty, Florent; Ritz, Christian; Jensen, Signe Marie

    2017-01-01

    6-min walk tests (6MWT) are routinely performed in patients with chronic obstructive pulmonary disease (COPD). Oxygen uptake ([Formula: see text]) kinetics during 6MWT can be modeled and derived parameters provide indicators of patients' exercise capacity. Post-exercise [Formula: see text] recovery...... also provides important parameters of patients' fitness which has not been extensively investigated in COPD. Several nonlinear regression models with different underlying biological assumptions may be suitable for describing recovery kinetics. Multimodel inference (model averaging) can then be used...... to capture the uncertainty in considering several models. Our aim was to apply multimodel inference in order to better understand the physiological underpinnings of [Formula: see text] recovery after 6MWT in patients with COPD. 61 patients with COPD (stages 2 to 4) were included in this study. Oxygen...

  17. Thallium and potassium uptake kinetics and competition differ between durum wheat and canola.

    Science.gov (United States)

    Renkema, Heidi; Koopmans, Amy; Hale, Beverley; Berkelaar, Edward

    2015-02-01

    Thallium (Tl) is very toxic to mammals but little is known about its accumulation by plants, and it would be useful if prediction of Tl accumulation could be done using potassium (K) accumulation models. The objectives of this study were to compare the uptake kinetics of Tl(+) and K(+), and to determine how readily K(+) can inhibit Tl(+) uptake. Durum wheat (Triticum turgidum L.) and spring canola (Brassica napus L.) were grown hydroponically and exposed to 0-75 μM Tl or 0-250 μM K for up to 150 min (kinetics experiment), or to 0.1 or 10 μM Tl with Tl to K ratios of 1:1 to 1:10,000 for up to 300 min (competition experiment). The rate of uptake of Tl(+) by canola was about three to five times faster than by wheat, while the rate of Tl(+) uptake in wheat was the same as the rate of K(+) uptake by either species. Uptake of Tl(+) was more readily suppressed by K(+) in wheat than in canola. When exposed to 0.1 uM Tl for 300 min with 100 or 1,000 uM K(+), Tl(+) uptake by wheat was reduced by 20 % and 50 %, respectively, while Tl(+) uptake by canola was not reduced. Our results suggest that predicting Tl accumulation using a K accumulation model with a correction factor may be possible for canola, but would be much more difficult for wheat, since uptake of Tl(+) is very sensitive to levels of K(.)

  18. Influence of exercise intensity on skeletal muscle blood flow, O2 extraction and O2 uptake on-kinetics

    DEFF Research Database (Denmark)

    Jones, Andrew M; Krustrup, Peter; Wilkerson, Daryl P

    2012-01-01

    Key points Following the start of low-intensity exercise in healthy humans, it has been established that the kinetics of muscle O(2) delivery is faster than, and does not limit, the kinetics of muscle O(2) uptake. Direct data are lacking, however, on the question of whether O(2) delivery might...... limit O(2) uptake kinetics during high-intensity exercise. In this study, we made frequent measurements of muscle blood flow, arterial-to-venous O(2) difference (a- difference) and O(2) uptake following the onset of multiple transitions of both low-intensity and high-intensity knee-extension exercise...... in the same subjects. We show that although blood flow kinetics is slower for high-intensity compared with low-intensity exercise, this does not result in slower O(2) uptake kinetics. These results indicate that muscle O(2) delivery does not limit O(2) uptake during knee-extension exercise in healthy humans....

  19. Inhibition of total oxygen uptake by silica nanoparticles in activated sludge

    Energy Technology Data Exchange (ETDEWEB)

    Sibag, Mark [Department of Environment and Energy, Sejong University, 98 Gunja-Dong, Gwangjin-Gu, Seoul 143-747 (Korea, Republic of); Choi, Byeong-Gyu [School of Civil, Environmental and Architectural Engineering, Korea University, 145, Anam-ro, Sungbuk-ku, Seoul 136-701 (Korea, Republic of); Suh, Changwon [Energy Lab, Environment Group, Samsung Advanced Institute of Technology, 130 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 443-803 (Korea, Republic of); Lee, Kwan Hyung; Lee, Jae Woo [Department of Environmental Engineering and Program in Environmental Technology and Policy, Korea University, Sejong 339-700 (Korea, Republic of); Maeng, Sung Kyu [Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-Dong, Gwangjin-Gu, Seoul 143-747 (Korea, Republic of); Cho, Jinwoo, E-mail: jinwoocho@sejong.edu [Department of Environment and Energy, Sejong University, 98 Gunja-Dong, Gwangjin-Gu, Seoul 143-747 (Korea, Republic of)

    2015-02-11

    Highlights: • Silica nanoparticles (SNP) inhibit total oxygen uptake in activated sludge. • Relatively smaller SNP are inhibitorier than larger SNP. • SNP alters C15:0, C16:0 and C18:0 in activated sludge fatty acid methyl ester profile. - Abstract: Nanoparticle toxicity to biological activities in activated sludge is largely unknown. Among the widely used nanoparticles, silica nanoparticles (SNP) have a limited number of studies associated with inhibition to the activated sludge process (ASP). We demonstrated SNP inhibition of activated sludge respiration through oxygen uptake rate (OUR) measurement. Based on the percentage inhibition of total oxygen consumption (I{sub T}), we observed that smaller SNPs (12 nm, I{sub T} = 33 ± 3%; 151 nm, I{sub T} = 23 ± 2%) were stronger inhibitors than larger SNPs (442 and 683 nm, I{sub T} = 5 ± 1%). Transmission electron micrographs showed that some of the SNPs were adsorbed on and/or apparently embedded somewhere in the microbial cell membrane. Whether SNPs are directly associated with the inhibition of total oxygen uptake warrants further studies. However, it is clear that SNPs statistically significantly altered the composition of microbial membrane lipids, which was more clearly described by principal component analysis and weighted Euclidian distance (PCA-ED) of the fatty acid methyl ester (FAME) data. This study suggests that SNPs potentially affect the biological activity in activated sludge through the inhibition of total oxygen uptake.

  20. Copper uptake kinetics and regulation in a marine fish after waterborne copper acclimation

    Energy Technology Data Exchange (ETDEWEB)

    Dang Fei; Zhong Huan [AMCE and Department of Biology, Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon (Hong Kong); Wang Wenxiong, E-mail: wwang@ust.hk [AMCE and Department of Biology, Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon (Hong Kong)

    2009-09-14

    The uptake kinetics and regulation of copper in a marine predatory fish, the black sea bream Acanthopagrus schlegeli after acclimation to waterborne Cu were examined, using radiotracer techniques. The dissolved Cu uptake followed a linear pattern during the time of exposure, and the calculated uptake rate constant was 6.24 L kg{sup -1} day{sup -1}. The efflux rate constant was 0.091 day{sup -1} following dietary uptake of Cu, and the dietary assimilation efficiency (AE) of Cu varied between 1.7% and 10.9% after the fish were fed with three types of prey (oysters, clams and brine shrimp). After the fish were acclimated at a nominal concentration of 50 {mu}g Cu L{sup -1} for 14 days, the Cu uptake rate and efflux rate constant did not change significantly, but the Cu body concentrations and metallothionein (MT) concentrations in fish tissues increased significantly. Subcellular Cu distributions were also modified. Significant MT induction was observed in response to increased Cu tissue concentrations, indicating that MT rather than the uptake kinetics may play a primary role in Cu regulation during waterborne Cu acclimation in this marine fish. Moreover, the high Cu efflux may also be important in Cu regulation during long-term exposure. Our modeling calculations indicated that dietary uptake was likely to be the main route for Cu bioaccumulation in the fish, and the relative contribution of waterborne and dietary uptake depended on the bioconcentration factor (BCF) of the prey and ingestion rate of fish.

  1. Uptake and elimination kinetics of metals in soil invertebrates: a review.

    Science.gov (United States)

    Ardestani, Masoud M; van Straalen, Nico M; van Gestel, Cornelis A M

    2014-10-01

    Uptake and elimination kinetics of metals in soil invertebrates are a function of both soil and organism properties. This study critically reviewed metal toxicokinetics in soil invertebrates and its potential use for assessing bioavailability. Uptake and elimination rate constants of different metals are summarized. Invertebrates have different strategies for essential and non-essential metals. As a consequence, different types of models must be applied to describe metal uptake and elimination kinetics. We discuss model parameters for each metal separately and show how they are influenced by exposure concentrations and by physiological properties of the organisms. Soil pH, cation exchange capacity, clay and organic matter content significantly affect uptake rates of non-essential metals in soil invertebrates. For essential metals, kinetics is hardly influenced by soil properties, but rather prone to physiological regulation mechanisms of the organisms. Our analysis illustrates that toxicokinetics can be a valuable measurement to assess bioavailability of soil-bound metals. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Determination of kinetic parameters for 123-I thyroid uptake in healthy Japanese

    Science.gov (United States)

    Kusuhara, Hiroyuki; Maeda, Kazuya

    2017-09-01

    The purpose of this study was to compare the kinetic parameters for iodide thyroid accumulation in Japanese today with previously reported values. We determined the thyroid uptake of 123-I at 24 hours after the oral administration in healthy male Japanese without any diet restriction. The mean value was 16.1±5.4%, which was similar or rather lower than those previously reported in Japan (1958-1972). Kinetic model analysis was conducted to obtain the clearance for thyroid uptake from the blood circulation. The thyroid uptake clearance of 123-I was 0.540±0.073 ml/min, which was almost similar to those reported previously. There is no obvious difference in the thyroid uptake for 24 hours, and kinetic parameters in healthy Japanese for these 50 years. The fraction of distributed to the thyroid gland is lower than the ICRP reference man, and such difference must be taken into consideration to estimate the radiation exposure upon Fukushima accident in Japan.

  3. Kinetics of FeII-polyaminocarboxylate oxidation by molecular oxygen

    Science.gov (United States)

    Wilson, Jessica M.; Farley, Kevin J.; Carbonaro, Richard F.

    2018-03-01

    Complexation of iron by naturally-occurring and synthetic organic ligands has a large effect on iron oxidation and reduction rates which in turn affect the aqueous geochemistry of many other chemical constituents. In this study, the kinetics of FeII oxidation in the presence of the polyaminocarboxylate synthetic chelating agents ethylene glycol tetraacetic acid (EGTA) and trimethylenediamine-N,N,N‧,N‧-tetraacetic acid (TMDTA) was investigated over the pH range 5.50-8.53. Batch oxidation experiments in the presence of molecular oxygen were conducted using a 2:1 M concentration ratio of polyaminocarboxylate (ligand, L) to FeII. The experimental data resembled first order kinetics for the oxidation of FeII-L to FeIII-L and observed rate constants at pH 6.0 were comparable to rate constants for the oxidation of inorganic FeII. Similar to other structurally-similar FeII-polyaminocarboxylate complexes, oxidation rates of FeII-EGTA and FeII-TMDTA decrease with increasing pH, which is the opposite trend for the oxidation of FeII complexed with inorganic ligands. However, the oxidation rates of FeII complexed with EGTA and TMDTA were considerably lower (4-5 orders of magnitude) than FeII complexed to ethylenediaminetetraacetic acid (EDTA). The distinguishing feature of the slower-reacting complexes is that they have a longer backbone between diamine functional groups. An analytical equilibrium model was developed to determine the contributions of the species FeIIL2- and FeII(H)L- to the overall oxidation rate of FeII-L. Application of this model indicated that the protonated FeII(H)L species are more than three orders of magnitude more reactive than FeIIL2-. These rate constants were used in a coupled kinetic equilibrium numerical model where the ligand to iron ratio (TOTL:TOTFe) and pH were varied to evaluate the effect on the FeII oxidation rate. Overall, increasing TOTL:TOTFe for EGTA and TMDTA enhances FeII oxidation rates at lower pH and inhibits FeII oxidation

  4. Eddy correlation measurements of oxygen uptake in deep ocean sediments

    DEFF Research Database (Denmark)

    Berg, P.; Glud, Ronnie Nøhr; Hume, A.

    2010-01-01

    .62 +/- 0.23 (SE, n = 7), 1.65 +/- 0.33 (n = 2), and 1.43 +/- 0.15 (n = 25) mmol m(-2) d(-1). The very good agreement between the eddy correlation flux and the chamber flux serves as a new, important validation of the eddy correlation technique. It demonstrates that the eddy correlation instrumentation......Abstract: We present and compare small sediment-water fluxes of O-2 determined with the eddy correlation technique, with in situ chambers, and from vertical sediment microprofiles at a 1450 m deep-ocean site in Sagami Bay, Japan. The average O-2 uptake for the three approaches, respectively, was 1...... available today is precise and can resolve accurately even very small benthic O-2 fluxes. The correlated fluctuations in vertical velocity and O-2 concentration that give the eddy flux had average values of 0.074 cm s(-1) and 0.049 mu M. The latter represents only 0.08% of the 59 mu M mean O-2 concentration...

  5. Kinetics of photodissociated oxygen recombination to human oxyhemoglobin

    International Nuclear Information System (INIS)

    Bokut', S.B.; Syakhovich, V.E.; Parul', D.A.; Lepeshkevich, S.V.; Dzhagarov, B.M.

    2001-01-01

    Oxygen binding to the tetrameric hemoglobin (Hb) is a basic reaction for study of a cooperativity and allosteric homotropic and heterotropic interactions in proteins. In tetrameric hemoglobin the certain sites in the α 1 β 2 -interface have the precise geometry and chemical reactivity to bind 2,3-diphosphoglycerate, protons, chloride and hence shift the equilibrium away from the oxyconformation, thereby favoring O 2 release. Post-translational modifications of the major hemoglobin fraction Hb A 1 with sugar moiety in the Hb central cavity leads to differences in geometry of the effectors binding region providing a useful experimental tool to study the long range relationship in the tetramer molecule. Here we present the results of the nongeminate biomolecular association of Hb and O 2 obtained by nanosecond laser flash-photolysis. All measurements were carried out in 50 mM potassium-phosphate buffer pH 7.4 with the following samples Hb A 1 , HbA 1c , HbA 1b , and HbA 1 in the presence of the tenfold excess of inositol hexaphosphate (IHP). Our results show that oxygen recombination kinetics are characterized by two processes with different decay times and Hb-form-dependent contributions. This process can be described by the following expression: A(t)=A 1 exp(-t/τ 1 )+A 2 exp(-t/τ 2 ), where A(t) is a normalized number of the deoxy-Hb molecules. The short-live component has a lifetime τ 1 , which is Hb-type dependent and changes in the intervals 30-60 μs, the second component has a lifetime τ 2 around 100 μs, and also is sample-dependent value. A(t=0) is proportional to apparent quantum yields of the photodissociation and determines by geminate stages of oxygen binding to Fe from the protein matrix areas. These results show that post-translational modifications of the major hemoglobin component HbA 1 have influence on hemoglobin transport function via the long range relationship in the tetramer molecule

  6. Vasopressin and angiotensin II stimulate oxygen uptake in the perfused rat hindlimb

    DEFF Research Database (Denmark)

    Colquhoun, E Q; Hettiarachchi, M; Ye, J M

    1988-01-01

    Vasopressin and angiotensin II markedly stimulated oxygen uptake in the perfused rat hindlimb. The increase due to each agent approached 70% of the basal rate, and was greater than that produced by a maximal concentration of norepinephrine. Half-maximal stimulation occurred at 60 pM vasopressin, 0...

  7. Estimation of maximal oxygen uptake via submaximal exercise testing in sports, clinical, and home settings

    NARCIS (Netherlands)

    Sartor, F.; Vernillo, G.; de Morree, H.M.; Bonomi, A.G.; La Torre, A.; Kubis, H.P.; Veicsteinas, A.

    2013-01-01

    Assessment of the functional capacity of the cardiovascular system is essential in sports medicine. For athletes, the maximal oxygen uptake (V˙O2max) provides valuable information about their aerobic power. In the clinical setting, the V˙O2max provides important diagnostic and prognostic information

  8. Longitudinal Changes in Physical Activity Level, Body Mass Index, and Oxygen Uptake Among Norwegian Adolescents

    Directory of Open Access Journals (Sweden)

    Pål Lagestad

    2018-03-01

    Full Text Available Several studies have investigated activity levels among adolescents, but no study has examined longitudinal changes in physical activity (PA level, body mass, and oxygen uptake among the same adolescents from the age of 14 to 19 years. The present study examined data from a research project that included a group of randomly selected students (N = 116 with objective measurements of PA (accelerometer data, self-reported PA level, and body mass and oxygen uptake during a 5-year period. The results show a significant decrease in the accelerometer-based PA level over time, from age 14 to 19. At 14 years of age, the minutes of moderate and/or vigorous PA was 66.7 min·day−1, but was less than half, at only 24.4 min·day−1, at 19 years of age. The self-reported activity data show a decrease in girls’ general activity level over time, while boys’ activity level during school breaks decreased strongly during the period: at age 14, 61% of the boys were classified as active, while at age 19, only 11% were physically active. Furthermore, body mass index increased during the period for both genders, while oxygen uptake decreased. Since both BMI and maximal oxygen uptake are important risk factors for future CVD, these findings point toward the importance of maintaining a high activity level during childhood and adolescence, in order to keep fit later in life.

  9. Central Cardiovascular Responses of Quadriplegic Subjects to Arm Exercise at Varying Levels of Oxygen Uptake.

    Science.gov (United States)

    Figoni, Stephen F.

    The purpose of this study was to assess selected central cardiovascular functions of spinal cord injured, quadriplegic subjects at varying levels of oxygen uptake (VO sub 2). Subjects included 11 untrained, male college students with C5, C6, or C7 complete quadriplegia and 11 able-bodied reference subjects. Exercise was performed on a Monark cycle…

  10. Allometric scaling of peak oxygen uptake in male roller hockey players under 17 years old

    NARCIS (Netherlands)

    Valente-dos-Santos, J.; Sherar, L.; Coelho-e-Silva, MJ; Pereira, J.R.; Vaz, V.; Cupido-dos-Santos, A.; Baxter-Jones, A.; Visscher, C.; Elferink-Gemser, M.T.; Malina, R.M.

    Peak oxygen uptake ((V) over dotO(2peak)) is routinely expressed in litres per minute and by unit of body mass (mL.kg(-1).min(-1)) despite the theoretical and statistical limitations of using ratios. Allometric modeling is an effective approach for partitioning body-size effects in a performance

  11. Alterations in Strength and Maximal Oxygen Uptake Consequent to Nautilus Circuit Weight Training.

    Science.gov (United States)

    Messier, Stephen P.; Dill, Mary Elizabeth

    1985-01-01

    The study compared the effects on muscular strength and maximal oxygen uptake of a Nautilus circuit weight training program, a free weight strength training program, and a running program. Nautilus circuit weight training appears to be equally effective for a training period of short duration. (MT)

  12. Training-induced acceleration of O(2) uptake on-kinetics precedes muscle mitochondrial biogenesis in humans.

    Science.gov (United States)

    Zoladz, Jerzy A; Grassi, Bruno; Majerczak, Joanna; Szkutnik, Zbigniew; Korostyński, Michał; Karasiński, Janusz; Kilarski, Wincenty; Korzeniewski, Bernard

    2013-04-01

    The effects of 5 weeks of moderate-intensity endurance training on pulmonary oxygen uptake kinetics (V(O(2)) on-kinetics) were studied in 15 healthy men (mean ± SD: age 22.7 ± 1.8 years, body weight 76.4 ± 8.9 kg and maximal V(O(2)) 46.0 ± 3.7 ml kg(-1) min(-1)). Training caused a significant acceleration (P = 0.003) of V(O(2)) on-kinetics during moderate-intensity cycling (time constant of the 'primary' component 30.0 ± 6.6 versus 22.8 ± 5.6 s before and after training, respectively) and a significant decrease (P = 0.04) in the amplitude of the primary component (837 ± 351 versus 801 ± 330 ml min(-1)). No changes in myosin heavy chain distribution, muscle fibre capillarization, level of peroxisome proliferator-activated receptor γ coactivator 1α and other markers of mitochondrial biogenesis (mitochondrial DNA copy number, cytochrome c and cytochrome oxidase subunit I contents) in the vastus lateralis were found after training. A significant downregulation in the content of the sarcoplasmic reticulum ATPase 2 (SERCA2; P = 0.03) and a tendency towards a decrease in SERCA1 (P = 0.055) was found after training. The decrease in SERCA1 was positively correlated (P = 0.05) with the training-induced decrease in the gain of the V(O(2)) on-kinetics (ΔV(O(2)) at steady state/Δpower output). In the early stage of training, the acceleration in V(O(2)) on-kinetics during moderate-intensity cycling can occur without enhanced mitochondrial biogenesis or changes in muscle myosin heavy chain distribution and in muscle fibre capillarization. The training-induced decrease of the O(2) cost of cycling could be caused by the downregulation of SERCA pumps.

  13. Toxicological effects of multi-walled carbon nanotubes on Saccharomyces cerevisiae: The uptake kinetics and mechanisms and the toxic responses

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Song; Zhu, Bin; Huang, Aiguo [College of Animal Science and Technology, Northwest A& F University, Yangling 712100 (China); Hu, Yang [College of Science, Northwest A& F University, Yangling 712100 (China); Wang, Gaoxue, E-mail: wanggaoxue@126.com [College of Animal Science and Technology, Northwest A& F University, Yangling 712100 (China); Ling, Fei, E-mail: feiling@nwsuaf.edu.cn [College of Animal Science and Technology, Northwest A& F University, Yangling 712100 (China)

    2016-11-15

    Highlights: • MWCNTs (<100 mg/L) were not toxic to S. cerevisiae. • MWCNTs were internalized in S. cerevisiae cells by three pathways. • The uptake kinetics and the subcellular distribution of MWCNTs in S. cerevisiae cells were shown. • S. cerevisiae cells were undergoing apoptosis by mitochondrial impairment pathway. - Abstract: Using Saccharomyces cerevisiae as an experimental model, the potential toxicological effects of oxidized multi-walled carbon nanotubes (MWCNTs) were investigated following exposure to 0–600 mg/L for 24 h. Results indicated that MWCNTs (>100 mg/L) had adverse effects on the cell proliferation. MWCNTs were clearly visible in lysosome, vacuole, endosome, mitochondria, multivesicular body and localization in the perinuclear region. The uptake kinetics data demonstrated that the maximum MWCNTs content (209.61 mg/g) was reached at 3 h, and a steady state was reached after 18 h. Based on the combined results of transmission electron microscope, endocytosis inhibition experiments and endocytosis-related genes (END3, END6, Sla2 and Rsp5) expression analysis, we elucidated MWCNTs uptake mechanism: (i) via a direct penetration of single MWCNTs; (ii) via endocytosis of single MWCNTs; and (iii) via endocytosis of MWCNTs aggregates. The percentage of apoptosis was significant increased at 600 mg/L. The decrease of mitochondrial transmembrane potential and the leakage of cytochrome c shown dose-dependent manners. Interestingly, there was no significant increase of reactive oxygen species (ROS). The apoptosis-related genes (SOD1, SOD2, Yca1, Nma111 and Nuc1) were significant changed. These results obtained in our study demonstrated that oxidized MWCNTs induce Saccharomyces cerevisiae apoptosis via mitochondrial impairment pathway.

  14. Dynamics and Thermochemistry of Oxygen Uptake by a Mixed Ce-Pr Oxide

    Science.gov (United States)

    Sinev, M. Yu.; Fattakhova, Z. T.; Bychkov, V. Yu.; Lomonosov, V. I.; Gordienko, Yu. A.

    2018-03-01

    The dynamics of oxygen uptake by mixed Ce0.55Pr0.45O2-x oxide is studied in a pulsed oxygen supply mode using in situ high-temperature heat flow differential scanning calorimetry. It is stated that the oxidation proceeds in two regimes: a fast one at the beginning of the oxidation process, and a slow one, which is controlled by the diffusion of oxygen through the bulk of the solid at the later stages of the process. Analysis of the shape of calorimetric profiles reveals some processes, accompanied by heat release, that occur in the sample in the absence of oxygen in the gas phase. These could be due to both the redistribution of consumed oxygen in the oxide lattice and the lattice relaxation associated with the transformation of phases with different arrangements of oxygen vacancies in them. The heat effect (which diminishes from 60 to 40 kJ/mol in the course of oxygen uptake) associated with the oxidation of the reduced form of mixed Ce-Pr oxide, corresponds to the oxidation of praseodymium ions from (3+) to (4+).

  15. Oxygen reduction kinetics on mixed conducting SOFC model cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Baumann, F.S.

    2006-07-01

    The kinetics of the oxygen reduction reaction at the surface of mixed conducting solid oxide fuel cell (SOFC) cathodes is one of the main limiting factors to the performance of these promising systems. For ''realistic'' porous electrodes, however, it is usually very difficult to separate the influence of different resistive processes. Therefore, a suitable, geometrically well-defined model system was used in this work to enable an unambiguous distinction of individual electrochemical processes by means of impedance spectroscopy. The electrochemical measurements were performed on dense thin film microelectrodes, prepared by PLD and photolithography, of mixed conducting perovskite-type materials. The first part of the thesis consists of an extensive impedance spectroscopic investigation of La0.6Sr0.4Co0.8Fe0.2O3 (LSCF) microelectrodes. An equivalent circuit was identified that describes the electrochemical properties of the model electrodes appropriately and enables an unambiguous interpretation of the measured impedance spectra. Hence, the dependencies of individual electrochemical processes such as the surface exchange reaction on a wide range of experimental parameters including temperature, dc bias and oxygen partial pressure could be studied. As a result, a comprehensive set of experimental data has been obtained, which was previously not available for a mixed conducting model system. In the course of the experiments on the dc bias dependence of the electrochemical processes a new and surprising effect was discovered: It could be shown that a short but strong dc polarisation of a LSCF microelectrode at high temperature improves its electrochemical performance with respect to the oxygen reduction reaction drastically. The electrochemical resistance associated with the oxygen surface exchange reaction, initially the dominant contribution to the total electrode resistance, can be reduced by two orders of magnitude. This &apos

  16. Uptake kinetics of metals by the earthworm Eisenia fetida exposed to field-contaminated soils

    Energy Technology Data Exchange (ETDEWEB)

    Nahmani, Johanne, E-mail: nahmani@univ-metz.f [Laboratoire Interactions Ecotoxicite, Biodiversite, Ecosystemes, CNRS UMR 7146, Universite Paul Verlaine - Metz, Rue du General Delestraint, 57070 Metz (France); Department of Soil Science, School of Human and Environmental Sciences, University of Reading, Whiteknights, Reading, Berkshire RG6 6DW (United Kingdom); Hodson, Mark E. [Department of Soil Science, School of Human and Environmental Sciences, University of Reading, Whiteknights, Reading, Berkshire RG6 6DW (United Kingdom); Devin, Simon [Laboratoire Interactions Ecotoxicite, Biodiversite, Ecosystemes, CNRS UMR 7146, Universite Paul Verlaine - Metz, Rue du General Delestraint, 57070 Metz (France); Vijver, Martina G. [Leiden University, Institute of Environmental Sciences (CML), P.O. Box 9518, 2300 RA Leiden (Netherlands)

    2009-10-15

    It is well known that earthworms can accumulate metals. However, most accumulation studies focus on Cd-, Cu-, Pb- or Zn-amended soils, additionally few studies consider accumulation kinetics. Here we model the accumulation kinetics of 18 elements by Eisenia fetida, exposed to 8 metal-contaminated and 2 uncontaminated soils. Tissue metal concentration was determined after 3, 7, 14, 21, 28 and 42 days. Metal elimination rate was important in determining time to reach steady-state tissue metal concentration. Uptake flux to elimination rate ratios showed less variation and lower values for essential than for non-essential metals. In theory kinetic rate constants are dependent only on species and metal. Therefore it should be possible to predict steady-state tissue metal concentrations on the basis of very few measurements using the rate constants. However, our experiments show that it is difficult to extrapolate the accumulation kinetic constants derived using one soil to another. - Earthworm metal uptake and elimination constants derived from a one-compartment model show little systematic variation with soil properties.

  17. Oxygen microenvironment affects the uptake of nanoparticles in head and neck tumor cells

    Science.gov (United States)

    Chen, Eunice Y.; Hodge, Sasson; Tai, Katherine; Hou, Huagang; Khan, Nadeem; Hoopes, P. Jack; Samkoe, Kimberley S.

    2013-02-01

    Survival of head and neck cancer patients has not improved in several decades despite advances in diagnostic and therapeutic techniques. Tumor hypoxia in head and neck cancers is a critical factor that leads to poor prognosis, resistance to radiation and chemotherapies, and increased metastatic potential. Magnetic nanoparticle hyperthermia (mNPHT) is a promising therapy for hypoxic tumors because nanoparticles (NP) can be directly injected into, or targeted to, hypoxic tumor cells and exposed to alternating magnetic fields (AMF) to induce hyperthermia. Magnetic NPHT can improve therapeutic effectiveness by two modes of action: 1) direct killing of hypoxic tumor cells; and 2) increase in tumor oxygenation, which has the potential to make the tumor more susceptible to adjuvant therapies such as radiation and chemotherapy. Prior studies in breast cancer cells demonstrated that a hypoxic microenvironment diminished NP uptake in vitro; however, mNPHT with intratumoral NP injection in hypoxic tumors increased tumor oxygenation and delayed tumor growth. In this study, head and neck squamous cell carcinoma (HNSCC) cell lines were incubated in normoxic, hypoxic, and hyperoxic conditions with iron oxide NP for 4-72 hours. After incubation, the cells were analyzed for iron uptake by mass spectrometry, Prussian blue staining, and electron microscopy. In contrast to breast cancer cells, uptake of NPs was increased in hypoxic microenvironments as compared to normoxic conditions in HNSCC cells. In future studies, we will confirm the effect of the oxygen microenvironment on NP uptake and efficacy of mNPHT both in vitro and in vivo.

  18. Phosphate uptake kinetics for four species of submerged freshwater macrophytes measured by a 33P phosphate radioisotope technique

    DEFF Research Database (Denmark)

    Christiansen, Nina Høj; Andersen, Frede Østergaard; Jensen, Henning S.

    2016-01-01

    Phosphate (Pi) uptake kinetics were determined in shoot and root tissues for four freshwater macrophyte species, Littorella uniflora, Potamogeton perfoliatus, Myriophyllum alterniflorum and Elodea canadensis, using a radioactive 33P phosphate technique. Collection of plant material in the oligotr...

  19. Comparative kinetic analysis of89 Sr,60 Co and65 Zn Uptake by human bone powder

    International Nuclear Information System (INIS)

    Abdel-Fatah, A.T.A.; Essa, M.W.A.; Mohamed, S.A.; Molokhia, M.K.

    1990-01-01

    Human bone powder samples were prepared from recent femurs. The Bone particles range between 30 and 40 MU in diameter. One portion of this powder was prepared fat-free (FFB), the second portion as protein-free (PFB) and the last portion was left as raw bone powder-(RB). The sequence of uptake of 89 Sr by these types of bone powder is : FFB > RB > PFB, while that of 60 Co and 65 Zn is: PFB > FFB > RB. Kinetic analysis of the uptake curves of the 3 isotopes indicated that these processes proceed in 3 distinct steps; very fast initial, moderate intermediate and slow last step. The obtained rates of uptake indicated that : (1) the uptake by PEB is faster in its third step than the other types, (2) the most predominant step in case of 89 Sr and 60 Co is the third step (ion exchange step) while in case of 65 Zn it is the first step (physical adsorption), (3) defatenisation or deproteinisation, in general, inhances the uptake process

  20. Muscle oxygen kinetics at onset of intense dynamic exercise in humans

    DEFF Research Database (Denmark)

    Bangsbo, J; Krustrup, P; González-Alonso, J

    2000-01-01

    The present study examined the onset and the rate of rise of muscle oxidation during intense exercise in humans and whether oxygen availability limits muscle oxygen uptake in the initial phase of intense exercise. Six subjects performed 3 min of intense one-legged knee-extensor exercise [65.3 +/-...

  1. Toxicological effects of multi-walled carbon nanotubes on Saccharomyces cerevisiae: The uptake kinetics and mechanisms and the toxic responses

    International Nuclear Information System (INIS)

    Zhu, Song; Zhu, Bin; Huang, Aiguo; Hu, Yang; Wang, Gaoxue; Ling, Fei

    2016-01-01

    Highlights: • MWCNTs ( 100 mg/L) had adverse effects on the cell proliferation. MWCNTs were clearly visible in lysosome, vacuole, endosome, mitochondria, multivesicular body and localization in the perinuclear region. The uptake kinetics data demonstrated that the maximum MWCNTs content (209.61 mg/g) was reached at 3 h, and a steady state was reached after 18 h. Based on the combined results of transmission electron microscope, endocytosis inhibition experiments and endocytosis-related genes (END3, END6, Sla2 and Rsp5) expression analysis, we elucidated MWCNTs uptake mechanism: (i) via a direct penetration of single MWCNTs; (ii) via endocytosis of single MWCNTs; and (iii) via endocytosis of MWCNTs aggregates. The percentage of apoptosis was significant increased at 600 mg/L. The decrease of mitochondrial transmembrane potential and the leakage of cytochrome c shown dose-dependent manners. Interestingly, there was no significant increase of reactive oxygen species (ROS). The apoptosis-related genes (SOD1, SOD2, Yca1, Nma111 and Nuc1) were significant changed. These results obtained in our study demonstrated that oxidized MWCNTs induce Saccharomyces cerevisiae apoptosis via mitochondrial impairment pathway.

  2. The effects of capillary transit time heterogeneity (CTH on the cerebral uptake of glucose and glucose analogs:Application to FDG and comparison to oxygen uptake.

    Directory of Open Access Journals (Sweden)

    Hugo Angleys

    2016-10-01

    Full Text Available Glucose is the brain’s principal source of ATP, but the extent to which cerebral glucose consumption (CMRglc is coupled with its oxygen consumption (CMRO2 remains unclear. Measurements of the brain’s oxygen-glucose index OGI=CMRO2/CMRglc suggest that its oxygen uptake largely suffices for oxidative phosphorylation. Nevertheless, during functional activation and in some disease states, brain tissue seemingly produces lactate although cerebral blood flow (CBF delivers sufficient oxygen, so-called aerobic glycolysis. OGI measurements, in turn, are method-dependent in that estimates based on glucose analog uptake depend on the so-called lumped constant (LC to arrive at CMRglc. Capillary transit time heterogeneity (CTH, which is believed to change during functional activation and some disease states, affects the extraction efficacy of oxygen from blood. We developed a three-compartment model of glucose extraction to examine whether CTH also affects glucose extraction into brain tissue. We then combined this model with our previous model of oxygen extraction to examine whether differential glucose and oxygen extraction might favor nonoxidative glucose metabolism under certain conditions. Our model predicts that glucose uptake is largely unaffected by changes in its plasma concentration, while changes in CBF and CTH affect glucose and oxygen uptake to different extents. Accordingly, functional hyperemia facilitates glucose uptake more than oxygen uptake, favoring aerobic glycolysis during enhanced energy demands. Applying our model to glucose analogs, we observe that LC depends on physiological state, with a risk of overestimating relative increases in CMRglc during functional activation by as much as 50%.

  3. Low blood flow at onset of moderate intensity exercise does not limit muscle oxygen uptake

    DEFF Research Database (Denmark)

    Nyberg, Michael Permin; Mortensen, Stefan Peter; Saltin, Bengt

    2010-01-01

    The effect of low blood flow at onset of moderate intensity exercise on the rate of rise in muscle oxygen uptake was examined. Seven male subjects performed a 3.5 minute one-legged knee-extensor exercise bout (24+/-1 (+/-S.D.) W) without (CON) and with (double blockade; DB) arterial infusion of i....... Additionally, prostanoids and/or NO appear to play important roles in elevating skeletal muscle blood flow in the initial phase of exercise. Key words: Oxygen delivery, oxygen extraction, nitric oxide, prostanoids.......The effect of low blood flow at onset of moderate intensity exercise on the rate of rise in muscle oxygen uptake was examined. Seven male subjects performed a 3.5 minute one-legged knee-extensor exercise bout (24+/-1 (+/-S.D.) W) without (CON) and with (double blockade; DB) arterial infusion...... of inhibitors of nitric oxide synthase (NOS; L-NMMA) and cyclooxygenase (COX; indomethacin) in order to inhibit the synthesis of nitric oxide (NO) and prostanoids, respectively.. Leg blood flow and leg oxygen delivery throughout exercise was 25-50 % lower (P

  4. Oxygen discharge and post-discharge kinetics experiments and modeling for the electric oxygen-iodine laser system.

    Science.gov (United States)

    Palla, A D; Zimmerman, J W; Woodard, B S; Carroll, D L; Verdeyen, J T; Lim, T C; Solomon, W C

    2007-07-26

    Laser oscillation at 1315 nm on the I(2P1/2)-->I(2P3/2) transition of atomic iodine has been obtained by a near resonant energy transfer from O2(a1Delta) produced using a low-pressure oxygen/helium/nitric oxide discharge. In the electric discharge oxygen-iodine laser (ElectricOIL) the discharge production of atomic oxygen, ozone, and other excited species adds levels of complexity to the singlet oxygen generator (SOG) kinetics which are not encountered in a classic purely chemical O2(a1Delta) generation system. The advanced model BLAZE-IV has been introduced to study the energy-transfer laser system dynamics and kinetics. Levels of singlet oxygen, oxygen atoms, and ozone are measured experimentally and compared with calculations. The new BLAZE-IV model is in reasonable agreement with O3, O atom, and gas temperature measurements but is under-predicting the increase in O2(a1Delta) concentration resulting from the presence of NO in the discharge and under-predicting the O2(b1Sigma) concentrations. A key conclusion is that the removal of oxygen atoms by NOX species leads to a significant increase in O2(a1Delta) concentrations downstream of the discharge in part via a recycling process; however, there are still some important processes related to the NOX discharge kinetics that are missing from the present modeling. Further, the removal of oxygen atoms dramatically inhibits the production of ozone in the downstream kinetics.

  5. Meal-induced changes in splanchnic blood flow and oxygen uptake in middle-aged healthy humans

    DEFF Research Database (Denmark)

    Madsen, Jan Lysgård; Søndergaard, SB; Møller, Søren

    2006-01-01

    OBJECTIVE: For decades, the determination of changes in splanchnic blood flow and oxygen uptake after a meal has been used in the management of patients with suspected chronic intestinal ischaemia. However, little is known about the normal meal-induced responses. The aim of the present study...... was therefore to measure the splanchnic blood flow and oxygen uptake before and after a standardized meal in a group of middle-aged normal volunteers. MATERIAL AND METHODS: Splanchnic blood flow and oxygen uptake were determined at baseline and after a 3600-kJ mixed meal in 8 healthy women (50-70 years) and 10...... healthy men (52-76 years). Splanchnic blood flow was measured during hepatic vein catheterization by indirect Fick principle with indocyanine green as the indicator. Splanchnic oxygen uptake was calculated from splanchnic blood flow and the arteriovenous oxygen difference. RESULTS: The meal induced...

  6. Fast kinetics of the oxygen effect in irradiated mammalian cells

    International Nuclear Information System (INIS)

    Watts, M.E.; Maughan, R.L.; Michael, B.D.

    1978-01-01

    A technique using a fast gas transfer with a single pulse of electrons (the gas-explosion technique) has been used to investigate the time-dependence of the dose-modifying action of oxygen in irradiated V79 Chinese hamster cells. Oxygen did not significantly alter the shapes of the survival curves. The dose-modifying factor between the fully oxic and fully hypoxic (oxygen at 9000 ms) curve was 2.6. The dose-modifying factor for the survival curve drawn for oxygen contact at 0.3 ms after irradiation was 1.5 relative to the hypoxic curve. The duration of the post-effect (oxygen contact after irradiation) indicated that oxygen-dependent damage has a lifetime extending into the ms time-range. In the pre-effect time region (oxygen contact before irradiation) 1 to 2 ms oxygen contact was required to achieve the full sensitization. The results are discussed with reference to the diffusion time for oxygen to reach the sensitive site within the cell. (U.K.)

  7. 25(OHD3 Levels Relative to Muscle Strength and Maximum Oxygen Uptake in Athletes

    Directory of Open Access Journals (Sweden)

    Książek Anna

    2016-04-01

    Full Text Available Vitamin D is mainly known for its effects on the bone and calcium metabolism. The discovery of Vitamin D receptors in many extraskeletal cells suggests that it may also play a significant role in other organs and systems. The aim of our study was to assess the relationship between 25(OHD3 levels, lower limb isokinetic strength and maximum oxygen uptake in well-trained professional football players. We enrolled 43 Polish premier league soccer players. The mean age was 22.7±5.3 years. Our study showed decreased serum 25(OHD3 levels in 74.4% of the professional players. The results also demonstrated a lack of statistically significant correlation between 25(OHD3 levels and lower limb muscle strength with the exception of peak torque of the left knee extensors at an angular velocity of 150°/s (r=0.41. No significant correlations were found between hand grip strength and maximum oxygen uptake. Based on our study we concluded that in well-trained professional soccer players, there was no correlation between serum levels of 25(OHD3 and muscle strength or maximum oxygen uptake.

  8. Kinetic analysis of zinc uptake and serosal transfer by vascularly perfused rat intestine

    International Nuclear Information System (INIS)

    Hoadley, J.E.; Leinart, A.S.; Cousins, R.J.

    1987-01-01

    Transport kinetics were examined for uptake of 65 Zn from the lumen and for transport of mucosal 65 Zn subsequent to uptake in the isolated, vascularly perfused intestines of rats fed either a zinc-deficient or zinc-adequate diet. Zinc depletion influenced the intestinal transport of zinc by 1) stimulating a saturable uptake mechanisms, 2) reducing secretion of mucosal 65 Zn into the lumen, and 3) increasing the rate of 65 Zn turnover in a rapidly absorbed mucosal zinc compartment. Uptake of 65 Zn involved both saturable and nonsaturable processes. The saturable process was stimulated by zinc depletion with the apparent maximal transport rate for the saturable mechanism increasing from 60 to 180 nmol Zn x g -1 x 30 min -1 . Most of the 65 Zn taken up was not involved in the short-term secretion or absorption, and mucosal 65 Zn retention was independent of dietary zinc status. Absorption of mucosal 65 Zn was nonsaturable, involved a rapid exchanging zinc compartment, and was stimulated by zinc depletion. The half-life for 65 Zn in this mucosal zinc compartment was ∼ 24 min in the zinc-adequate group and 13 min in the zinc-depleted group

  9. Heavy and toxic metal uptake by mesoporous hypercrosslinked SMA beads: Isotherms and kinetics

    Directory of Open Access Journals (Sweden)

    Renuka Gonte

    2016-09-01

    Full Text Available Hypercrosslinked styrene-maleic acid copolymer beads were used for the removal of metal ions from mimicked industrial effluents. The polymer was characterized by SEM which revealed the presence of a porous network. Carboxyl acid groups of the polymer were identified as active sites for metal uptake. Highly porous surface enhanced metal ion uptake was achieved through a physicochemical process. Equilibrium sorption of metal ions was best described by the Freundlich and Temkin model with R2 > 0.99. Adsorption followed pseudo first and pseudo second order reaction kinetics. Intraparticle diffusion model suggested a three step equilibrium. Desorption was a fast process with ∼90% in 60 min.

  10. Application of Elovich equation on uptake kinetics of 137Cs by living freshwater macrophytes - a short duration laboratory study

    International Nuclear Information System (INIS)

    Jaison, T.J.; Patra, A.K.; Ravi, P.M.; Tripathi, R.M.

    2014-01-01

    Application of Elovich equation on uptake kinetics of 137 Cs by two living macrophytes during controlled experiments on short duration exposure is studied. Compliance to 2 nd order kinetics indicates the mechanism could be chemi-sorption, involving polar functional groups present on the extracelluar surface of the macrophytes. Data analysis suggests that Myriophyllum s. exhibits faster adsorption rate than Hydrilla v. As Myriophyllum s. exhibits better kinetics than Hydrilla v., former could be a better natural adsorbing media for 137 Cs. (author)

  11. Zirconium metal-water oxidation kinetics. III. Oxygen diffusion in oxide and alpha Zircaloy phases

    International Nuclear Information System (INIS)

    Pawel, R.E.

    1976-10-01

    The reaction of Zircaloy in steam at elevated temperature involves the growth of discrete layers of oxide and oxygen-rich alpha Zircaloy from the parent beta phase. The multiphase, moving boundary diffusion problem involved is encountered in a number of important reaction schemes in addition to that of Zircaloy-oxygen and can be completely (albeitly ideally) characterized through an appropriate model in terms of oxygen diffusion coefficients and equilibrium concentrations for the various phases. Conversely, kinetic data for phase growth and total oxygen consumption rates can be used to compute diffusion coefficients. Equations are developed that express the oxygen diffusion coefficients in the oxide and alpha phases in terms of the reaction rate constants and equilibrium solubility values. These equations were applied to recent experimental kinetic data on the steam oxidation of Zircaloy-4 to determine the effective oxygen diffusion coefficients in these phases over the temperature range 1000--1500 0 C

  12. Kinetics of zinc uptake and exchange by primary cultures of rat hepatocytes

    International Nuclear Information System (INIS)

    Pattison, S.E.; Cousins, R.J.

    1986-01-01

    The kinetics of 65 Zn 2+ uptake and exchange by hepatocytes in primary culture have been examined in detail to provide a basis for analyzing hormonal regulation of hepatic zinc metabolism. 65 Zn 2+ uptake was found to be a biphasic process. The slow phase represents an exchange between Zn 2+ in the medium and preexisting, intracellular zinc pools. This exchange rate was saturable with a medium zinc concentration of 9.5 microM eliciting one-half the maximum exchange rate and a maximum exchange rate of 9.9 pmol Zn 2+ . min-1 . mg protein-1 in the presence of bovine serum albumin. In the absence of albumin, a secondary, nonsaturable uptake rate was observed. The slow phase was relatively selective, and of the divalent transition metal ions tested, only Cd 2+ and Mn 2+ caused inhibition. The rate of exchange suggests total hepatocyte zinc has a turnover rate of approximately 30 h. The fast phase of 65 Zn 2+ reflects net Zn 2+ accumulation into a labile pool. The initial rates for this process were too fast to be measured accurately, but steady-state measurements allowed determination of the labile pool size. The pool dimensions saturated in the presence [Kapp = 28.6 microM; pool capacity = 0.44 nmol Zn 2+ /mg protein] and absence [Kapp = 11.8 microM; pool capacity = 0.34 nmol Zn 2+ /mg protein] of bovine serum albumin. Kinetics and equilibria of Zn 2+ uptake into the labile pool suggest that the latter acts as a source of Zn 2+ for the slow-exchange phase. Dexamethasone stimulated slow Zn 2+ exchange and also increased the labile pool size. The data suggest physiological factors alter hepatic zinc metabolism by influencing both intracellular Zn 2+ pools

  13. Neuromuscular blockade of slow twitch muscle fibres elevates muscle oxygen uptake and energy turnover during submaximal exercise in humans.

    Science.gov (United States)

    Krustrup, Peter; Secher, Niels H; Relu, Mihai U; Hellsten, Ylva; Söderlund, Karin; Bangsbo, Jens

    2008-12-15

    We tested the hypothesis that a greater activation of fast-twitch (FT) fibres during dynamic exercise leads to a higher muscle oxygen uptake (VO2 ) and energy turnover as well as a slower muscle on-kinetics. Subjects performed one-legged knee-extensor exercise for 10 min at an intensity of 30 W without (CON) and with (CUR) arterial injections of the non-depolarizing neuromuscular blocking agent cisatracurium. In CUR, creatine phosphate (CP) was unaltered in slow twitch (ST) fibres and decreased (P fibres, whereas in CON, CP decreased (P fibres, respectively. From 127 s of exercise, muscle VO2 was higher (P muscle VO2 response was slower (P muscle homogenate CP was lowered (P muscle lactate production was similar in CUR and CON (37.8 +/- 4.1 versus 35.2 +/- 6.2 mmol). Estimated total muscle ATP turnover was 19% higher (P fibres are less efficient than ST fibres in vivo at a contraction frequency of 1 Hz, and that the muscle VO2 kinetics is slowed by FT fibre activation.

  14. Persistent resetting of the cerebral oxygen/glucose uptake ratio by brain activation

    DEFF Research Database (Denmark)

    Madsen, P L; Hasselbalch, S G; Hagemann, L P

    1995-01-01

    fraction of the activation-induced excess glucose uptake. These data confirm earlier reports that brain activation can induce resetting of the cerebral oxygen/glucose consumption ratio, and indicate that the resetting persists for a long period after cerebral activation has been terminated and physiologic......Global cerebral blood flow (CBF), global cerebral metabolic rates for oxygen (CMRO2), and for glucose (CMRglc), and lactate efflux were measured during rest and during cerebral activation induced by the Wisconsin card sorting test. Measurements were performed in healthy volunteers using the Kety......-Schmidt technique. Global CMRO2 was unchanged during cerebral activation, whereas global CBF and global CMRglc both increased by 12%, reducing the molar ratio of oxygen to glucose consumption from 6.0 during baseline conditions to 5.4 during activation. Data obtained in the period following cerebral activation...

  15. Oxygen uptake from aquatic macrophyte decomposition from Piraju Reservoir (Piraju, SP, Brazil

    Directory of Open Access Journals (Sweden)

    I. Bianchini Jr.

    Full Text Available The kinetics of oxygen consumption related to mineralisation of 18 taxa of aquatic macrophytes (Cyperus sp, Azolla caroliniana, Echinodorus macrophyllus, Eichhornia azurea, Eichhornia crassipes, Eleocharis sp1, Eleocharis sp2, Hetereanthera multiflora, Hydrocotyle raniculoides, Ludwigia sp, Myriophyllum aquaticum, Nymphaea elegans, Oxycaryum cubense, Ricciocarpus natans, Rynchospora corymbosa, Salvinia auriculata, Typha domingensis and Utricularia foliosa from the reservoir of Piraju Hydroelectric Power Plant (São Paulo state, Brazil were described. For each species, two incubations were prepared with ca. 300.0 mg of plant (DW and 1.0 L of reservoir water sample. The incubations were maintained in the dark and at 20 ºC. Periodically the dissolved oxygen (DO concentrations were measured; the accumulated DO values were fitted to 1st order kinetic model and the results showed that: i high oxygen consumption was observed for Ludwigia sp (533 mg g-1 DW, while the lowest was registered for Eleocharis sp1 (205 mg g-1 DW mineralisation; ii the higher deoxygenation rate constants were verified in the mineralisation of A. caroliniana (0.052 day-1, H. raniculoides (0.050 day-1 and U. foliosa (0.049 day-1. The oxygen consumption rate constants of Ludwigia sp and Eleocharis sp2 mineralisation (0.027 day-1 were the lowest. The half-time of oxygen consumption varied from 9 to 26 days. In the short term, the detritus of E. macrophyllus, H. raniculoides, Ludwigia sp, N. elegans and U. foliosa were the critical resources to the reservoir oxygen demand; while in the long term, A. caroliniana, H. multiflora and T. domingensis were the resources that can potentially contribute to the benthic oxygen demand of this reservoir.

  16. Characterization of positron emission tomography hypoxia tracer uptake and tissue oxygenation via electrochemical modeling

    Energy Technology Data Exchange (ETDEWEB)

    Bowen, Stephen R., E-mail: srbowen@wisc.edu [University of Wisconsin School of Medicine and Public Health, Department of Medical Physics, Madison, WI 53706 (United States); Kogel, Albert J. van der [University Medical Centre St. Radboud, Nijmegen (Netherlands); Nordsmark, Marianne [Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus (Denmark); Bentzen, Soren M. [University of Wisconsin School of Medicine and Public Health, Department of Medical Physics, Madison, WI 53706 (United States); University of Wisconsin School of Medicine and Public Health, Department of Human Oncology, Clinical Sciences Center, Madison, WI 53792 (United States); Jeraj, Robert [University of Wisconsin School of Medicine and Public Health, Department of Medical Physics, Madison, WI 53706 (United States); University of Wisconsin School of Medicine and Public Health, Department of Human Oncology, Clinical Sciences Center, Madison, WI 53792 (United States); Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia)

    2011-08-15

    Purpose: Unique uptake and retention mechanisms of positron emission tomography (PET) hypoxia tracers make in vivo comparison between them challenging. Differences in imaged uptake of two common hypoxia radiotracers, [{sup 61}Cu]Cu-ATSM and [{sup 18}F]FMISO, were characterized via computational modeling to address these challenges. Materials and Methods: An electrochemical formalism describing bioreductive retention mechanisms of these tracers under steady-state conditions was adopted to relate time-averaged activity concentration to tissue partial oxygen tension (PO{sub 2}), a common metric of hypoxia. Chemical equilibrium constants of product concentration to reactant concentration ratios were determined from free energy changes and reduction potentials of pertinent reactions reported in the literature. Resulting transformation functions between tracer uptake and PO{sub 2} were compared against measured values in preclinical models. Additionally, calculated PO{sub 2} distributions from imaged Cu-ATSM tracer activity concentrations of 12 head and neck squamous cell carcinoma (HNSCC) patients were validated against microelectrode PO{sub 2} measurements in 69 HNSCC patients. Results: Both Cu-ASTM- and FMISO-modeled PO{sub 2} transformation functions were in agreement with preclinical measured values within single-deviation confidence intervals. High correlation (r{sup 2}=0.94, P<.05) was achieved between modeled PO{sub 2} distributions and measured distributions in the patient populations. On average, microelectrode hypoxia thresholds (2.5 and 5.0 mmHg) corresponded to higher Cu-ATSM uptake [2.5 and 2.0 standardized uptake value (SUV)] and lower FMISO uptake (2.0 and 1.4 SUV). Uncertainties in the models were dominated by variations in the estimated specific activity and intracellular acidity. Conclusions: Results indicated that the high dynamic range of Cu-ATSM uptake was representative of a narrow range of low oxygen tension whose values were dependent on

  17. Automated Determination of Oxygen-Dependent Enzyme Kinetics in a Tube-in-Tube Flow Reactor.

    Science.gov (United States)

    Ringborg, Rolf H; Toftgaard Pedersen, Asbjørn; Woodley, John M

    2017-09-08

    Enzyme-mediated oxidation is of particular interest to synthetic organic chemists. However, the implementation of such systems demands knowledge of enzyme kinetics. Conventionally collecting kinetic data for biocatalytic oxidations is fraught with difficulties such as low oxygen solubility in water and limited oxygen supply. Here, we present a novel method for the collection of such kinetic data using a pressurized tube-in-tube reactor, operated in the low-dispersed flow regime to generate time-series data, with minimal material consumption. Experimental development and validation of the instrument revealed not only the high degree of accuracy of the kinetic data obtained, but also the necessity of making measurements in this way to enable the accurate evaluation of high K MO enzyme systems. For the first time, this paves the way to integrate kinetic data into the protein engineering cycle.

  18. Study of oxygen mass transfer coefficient and oxygen uptake rate in a stirred tank reactor for uranium ore bioleaching

    International Nuclear Information System (INIS)

    Zokaei-Kadijani, S.; Safdari, J.; Mousavian, M.A.; Rashidi, A.

    2013-01-01

    Highlights: ► Mass transfer coefficient does not depend on biomass concentration. ► The pulp density has a negative effect on mass transfer coefficient. ► The pulp density is the unique factor that affects maximum OUR. ► In this work, Neale’s correlation is corrected for prediction of mass transfer coefficient. ► Biochemical reaction is a limiting factor in the uranium bioleaching process. - Abstract: In this work, the volumetric oxygen mass transfer coefficient and the oxygen uptake rate (OUR) were studied for uranium ore bioleaching process by Acidthiobacillus ferrooxidans in a stirred tank reactor. The Box-Bohnken design method was used to study the effect of operating parameters on the oxygen mass transfer coefficient. The investigated factors were agitation speed (rpm), aeration rate (vvm) and pulp density (% weight/volume) of the stirred tank reactor. Analysis of experimental results showed that the oxygen mass transfer coefficient had low dependence on biomass concentration but had higher dependence on the agitation speed, aeration rate and pulp density. The obtained biological enhancement factors were equal to ones in experiments. On the other hand, the obtained values for Damkohler number (Da < 0.468) indicated that the process was limited by the biochemical reaction rate. Experimental results obtained for oxygen mass transfer coefficient were correlated with the empirical relations proposed by Garcia-Ochoa and Gomez (2009) and Neale and Pinches (1994). Due to the high relative error in the correlation of Neale and Pinches, that correlation was corrected and the coefficient of determination was calculated to be 89%. The modified correlation has been obtained based on a wide range of operating conditions, which can be used to determine the mass transfer coefficient in a bioreactor

  19. Kinetics of radiolabelled silver uptake and depuration in the gills of rainbow trout (Oncorhynchus mykiss) and European eel (Anguilla anguilla)

    DEFF Research Database (Denmark)

    Wood, C.M.; Grosell, M.; Hogstrand, C.

    2002-01-01

    We examined the influence of speciation on the kinetics of silver uptake and deputation in the gills of two freshwater fish, the rainbow trout (Oncorhynchus mykiss) which has high branchial Na+ and Cl- uptake rates and is relatively sensitive to silver, and the European eel (Anguilla anguilla...... labile than from Ag+ exposures, with 1.6-1.8-fold greater loss rates during the fast phases in both species. Differences in branchial silver uptake between eel and trout correlate well with differences in acute toxicity, but are not as large as differences in ion uptake rates. The complex time...

  20. Changes in Peak Oxygen Uptake and Plasma Volume in Fit and Unfit Subjects Following Exposure to a Simulation of Microgravity

    National Research Council Canada - National Science Library

    Convertino, Victor

    1997-01-01

    To test the hypothesis that the magnitude of reduction in plasma volume and work capacity following exposure to simulated microgravity is dependent on the initial level of aerobic fitness, peak oxygen uptake (VO2peak...

  1. [Kinetics of uptake of phosphates and nitrates by marine multicellular algae Gelidium latifolium (Grev.) Born. et Thur].

    Science.gov (United States)

    Silkin, V A; Chubchikova, I N

    2007-01-01

    We studied nonstationary kinetics of the uptake of phosphates and nitrates by the red marine algae Gelidium latifolium (Grev.) Born et Thur. and calculated constants of the Michaelis-Menten equation for these elements. In the area of 0-3 microM, the kinetics of phosphate consumption had the following coefficients: maximum rate of uptake 0.8 micromol/(g x h), constant of half-saturation 1.745 microM. For nitrate nitrogen at 0-30 microM, an adaptive strategy of uptake kinetics was noted with change of the equation parameters with time: after 1 h, the maximum rate of uptake was 5.1 micromol/(g x h) and constant of half-saturation 19 gM, while within 2 h, the maximum rate of uptake significantly increased. This could be related to the synthesis of nitrate reductase. Coupled with the uptake of nitrates, nonstationary kinetics of the release of nitrates in the surrounding medium had a one-peak pattern: the maximum concentration of nitrites in the medium and the time of its achievement increased with the initial concentration of nitrates. The maximum concentration of nitrites was 6 to 14% of the initial concentration in the medium.

  2. Online Measurement of Oxygen-Dependent Enzyme Reaction Kinetics

    DEFF Research Database (Denmark)

    Meissner, Murray Peter; Nordblad, Mathias; Woodley, John M

    2018-01-01

    accurate measurement of the oxygen mass balance in the gas-phase of a reactor. The method was successfully validated and demonstrated using two model reactions: firstly the oxidation of glucose by glucose oxidase and secondly the Baeyer-Villiger oxidation of macrocyclic ketones to lactones. Initial...

  3. Uptake kinetics and nanotoxicity of silica nanoparticles are cell type dependent.

    Science.gov (United States)

    Blechinger, Julia; Bauer, Alexander T; Torrano, Adriano A; Gorzelanny, Christian; Bräuchle, Christoph; Schneider, Stefan W

    2013-12-09

    In this study, it is shown that the cytotoxic response of cells as well as the uptake kinetics of nanoparticles (NPs) is cell type dependent. We use silica NPs with a diameter of 310 nm labeled with perylene dye and 304 nm unlabeled particles to evaluate cell type-dependent uptake and cytotoxicity on human vascular endothelial cells (HUVEC) and cancer cells derived from the cervix carcinoma (HeLa). Besides their size, the particles are characterized concerning homogeneity of the labeling and their zeta potential. The cellular uptake of the labeled NPs is quantified by imaging the cells via confocal microscopy in a time-dependent manner, with subsequent image analysis via a custom-made and freely available digital method, Particle_in_Cell-3D. We find that within the first 4 h of interaction, the uptake of silica NPs into the cytoplasm is up to 10 times more efficient in HUVEC than in HeLa cells. Interestingly, after 10 or 24 h of interaction, the number of intracellular particles for HeLa cells by far surpasses the one for HUVEC. Inhibitor studies show that these endothelial cells internalize 310 nm SiO₂ NPs via the clathrin-dependent pathway. Remarkably, the differences in the amount of taken up NPs are not directly reflected by the metabolic activity and membrane integrity of the individual cell types. Interaction with NPs leads to a concentration-dependent decrease in mitochondrial activity and an increase in membrane leakage for HUVEC, whereas HeLa cells show only a reduced mitochondrial activity and no membrane leakage. In addition, silica NPs lead to HUVEC cell death while HeLa cells survive. These findings indicate that HUVEC are more sensitive than HeLa cells upon silica NP exposure. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Fermentation process using specific oxygen uptake rates as a process control

    Science.gov (United States)

    Van Hoek, Pim [Minnetonka, MN; Aristidou, Aristos [Maple Grove, MN; Rush, Brian [Minneapolis, MN

    2011-05-10

    Specific oxygen uptake (OUR) is used as a process control parameter in fermentation processes. OUR is determined during at least the production phase of a fermentation process, and process parameters are adjusted to maintain the OUR within desired ranges. The invention is particularly applicable when the fermentation is conducted using a microorganism having a natural PDC pathway that has been disrupted so that it no longer functions. Microorganisms of this sort often produce poorly under strictly anaerobic conditions. Microaeration controlled by monitoring OUR allows the performance of the microorganism to be optimized.

  5. Oxidation Kinetics of Chemically Vapor-Deposited Silicon Carbide in Wet Oxygen

    Science.gov (United States)

    Opila, Elizabeth J.

    1994-01-01

    The oxidation kinetics of chemically vapor-deposited SiC in dry oxygen and wet oxygen (P(sub H2O) = 0.1 atm) at temperatures between 1200 C and 1400 C were monitored using thermogravimetric analysis. It was found that in a clean environment, 10% water vapor enhanced the oxidation kinetics of SiC only very slightly compared to rates found in dry oxygen. Oxidation kinetics were examined in terms of the Deal and Grove model for oxidation of silicon. It was found that in an environment containing even small amounts of impurities, such as high-purity Al2O3 reaction tubes containing 200 ppm Na, water vapor enhanced the transport of these impurities to the oxidation sample. Oxidation rates increased under these conditions presumably because of the formation of less protective sodium alumino-silicate scales.

  6. The effect of 17-AAG on iodine uptake kinetics of NIS-transfected anaplastic thyroid cancer

    International Nuclear Information System (INIS)

    Wang Renfei; Tan Jian; Li Wei; Meng Zhaowei; Zheng Wei

    2012-01-01

    Objective: To investigate the effect of 17-allylamino-17-demethoxy geldanamycin (17-AAG) on iodine uptake kinetics of NIS-transfected anaplastic thyroid cancer (ATC) cells. Methods: Lipofection was used to transfect the recombinant plasmid, namely pcDNA3.1-NIS, into FRO cells (ATC cell line). A stable cell line NIS-FRO was obtained by G418 resistance selection. 125 I was added into the medium, and influx and efflux experiments were performed. Different time-radioactivity curves were drawn, and further analysis was performed between the non-transfected cells (the control group) and NIS-FRO cells treated with 1 μmol/L 17-AAG for 24 h. Student's t-test was used to analyze the data. Results: The iodine uptake ability of the NIS-FRO cells was significantly higher than that of the FRO cells (about 10.68 times, t=45.329, P<0.001). However, 125 I out-flowed rapidly when removed from the medium, and the retention rate of 125 I in the NIS-FRO cells was only 10.5% of the initial amount after 30 rin. After treatment with 1 μmol/L 17-AAG for 24 h, the 125 I uptake ability of NIS-FRO cells further increased. During the 20-60 min incubation with 125 I, the iodine uptake ability of 17-AAG treated NIS-FRO cells increased significantly with radioactive counts of 31771.8- 54815.5 per minute,which was much higher than that of the control group (24020.3-41293.8 per minute; t=3.096, 4.275, 3.055, 4.292 and 5.496, respectively, all P<0.05). The iodine uptake ability increased about 24.8%-35.5%. Furthermore, 5-30 min after removing the medium, the retention rates of 125 I in the 17-AAG treated NIS-FRO cells were significantly increased compared with those of the control group (32.7%-85.2% vs 10.5%-56.8%; t=22.801, 13.096, 19.631, 38.205, 43.519, 29.322, respectively, all P<0.01), and 125 I efflux was reduced. After 30 min, 125 I retention rate of the treatment group was 32.7%, which was 3.1 times higher than that of the control group. Conclusion: The iodine uptake ability can be

  7. Pain severity is associated with muscle strength and peak oxygen uptake in adults with fibromyalgia

    Directory of Open Access Journals (Sweden)

    Hooten WM

    2014-05-01

    Full Text Available W Michael Hooten,1,2 Jolene M Smith,3 Jason S Eldrige,1 David A Olsen,3 W David Mauck,1 Susan M Moeschler11Department of Anesthesiology, 2Department of Psychiatry and Psychology, Mayo Clinic College of Medicine, 3Mayo School of Graduate Medical Education, Rochester, MN, USABackground: The associations between pain, lower extremity strength, and aerobic conditioning have not been widely investigated in adults with fibromyalgia (FM. The principle objective of this study was to investigate the relationship between pain severity and knee strength in patients seeking treatment for FM. A secondary objective was to investigate the relationship between pain scores and aerobic conditioning.Methods: Three measures of knee strength (isokinetic extensor, isokinetic flexor, isometric extensor were quantified in the dominant leg of 69 adults with FM using a dynamometer at speeds of 60 degrees per second (60°/s and 180°/s. Peak oxygen uptake (VO2 was assessed using a cycle ergometer, and pain was assessed using the pain severity subscale of the Multidimensional Pain Inventory.Results: In univariable linear regression analyses using pain severity as the dependent variable, lesser values of isokinetic knee extensor strength at 60°/s (P=0.041 and 180°/s (P=0.010, isokinetic knee flexor strength at 60°/s (P=0.028 and 180°/s (P=0.003, and peak VO2 uptake (P=0.031 were predictive of greater pain severity scores. In multiple variable linear regression models adjusted for age, sex, body mass index, and opioid use, the following associations retained statistical significance; isokinetic knee extensor strength at 60°/s (P=0.020 and 180°/s (P=0.003, isokinetic knee flexor strength at 60°/s (P=0.015 and 180°/s (P=0.001, and peak VO2 uptake (P=0.014. However, no significant associations were found between pain severity and isometric knee extensor strength.Conclusion: The main findings from this study were that lesser values of isokinetic knee strength and peak VO

  8. Kinetic Monte Carlo Simulation of Oxygen and Cation Diffusion in Yttria-Stabilized Zirconia

    Science.gov (United States)

    Good, Brian

    2011-01-01

    Yttria-stabilized zirconia (YSZ) is of interest to the aerospace community, notably for its application as a thermal barrier coating for turbine engine components. In such an application, diffusion of both oxygen ions and cations is of concern. Oxygen diffusion can lead to deterioration of a coated part, and often necessitates an environmental barrier coating. Cation diffusion in YSZ is much slower than oxygen diffusion. However, such diffusion is a mechanism by which creep takes place, potentially affecting the mechanical integrity and phase stability of the coating. In other applications, the high oxygen diffusivity of YSZ is useful, and makes the material of interest for use as a solid-state electrolyte in fuel cells. The kinetic Monte Carlo (kMC) method offers a number of advantages compared with the more widely known molecular dynamics simulation method. In particular, kMC is much more efficient for the study of processes, such as diffusion, that involve infrequent events. We describe the results of kinetic Monte Carlo computer simulations of oxygen and cation diffusion in YSZ. Using diffusive energy barriers from ab initio calculations and from the literature, we present results on the temperature dependence of oxygen and cation diffusivity, and on the dependence of the diffusivities on yttria concentration and oxygen sublattice vacancy concentration. We also present results of the effect on diffusivity of oxygen vacancies in the vicinity of the barrier cations that determine the oxygen diffusion energy barriers.

  9. Exercise training induces similar elevations in the activity of oxoglutarate dehydrogenase and peak oxygen uptake in the human quadriceps muscle

    DEFF Research Database (Denmark)

    Blomstrand, Eva; Krustrup, Peter; Søndergaard, Hans

    2011-01-01

    During exercise involving a small muscle mass, peak oxygen uptake is thought to be limited by peripheral factors, such as the degree of oxygen extraction from the blood and/or mitochondrial oxidative capacity. Previously, the maximal activity of the Krebs cycle enzyme oxoglutarate dehydrogenase has...

  10. Microelectrode Studies of Seasonal Oxygen-Uptake in a Coastal Sediment - Role of Molecular-Diffusion

    DEFF Research Database (Denmark)

    RASMUSSEN, H.; JØRGENSEN, BB

    1992-01-01

    in the bay varied from 100 % air saturation during winter to 23 % during summer. The potentially higher O2 respiration during the summer months was counteracted by a lower O2 concentration in the bottom water, which led to a small seasonal variation in O2 uptake. Depth of the oxic sediment zone reached 5.1...... surface zone. The O2 consumption rates in the oxic surface layer, calculated from (b) and (c) using molecular diffusion coefficients of O2, closely agreed and accounted for 70 % of the total O2 uptake. The O2 uptake rates strongly depended on in situ O2 concentrations in the overlying seawater, which...... mm during winter, narrowed down rapidly to a few mm upon settling of a spring phytoplankton bloom, and was only 1.2 mm during summer. Modeling of O2 consumption from O2 microprofiles showed zero-order kinetics, i.e. constant O2 consumption rates throughout the oxic zone during winter. Enhanced O2...

  11. Kinetics of the Electric Discharge Pumped Oxygen-Iodine Laser

    Science.gov (United States)

    2011-09-01

    of the sustainer pulse is tailored to keep the discharge stable. In January 2007, OSU demonstrated a peak laser power of 0.28 W, using a pulser...controlled avalanche ionization, Applied Physics Letters, 22, p. 670, (1973). (57) Hill. A.E., The next generation of controlled avalanche discharge ...pressure oxygen pulsed discharge . Simple and quick method for temperature determination, J. Phys. D:Appl. Phys. 32, pp. 246-250, (1998). (71

  12. In-stream nutrient uptake kinetics along stream size and development gradients in a rapidly developing mountain resort watershed

    Science.gov (United States)

    Covino, T.; McGlynn, B.; McNamarra, R.; Gardner, K.

    2012-04-01

    Land use / land cover (LULC) change including mountain resort development often lead to increased nutrient loading to streams, however the potential influence on stream ecosystem nutrient uptake kinetics and transport remain poorly understood. Given the deleterious impacts elevated nutrient loading can have on aquatic ecosystems, it is imperative to improve understanding of nutrient retention capacities across stream scales and watershed development intensities. We performed seventeen nutrient addition experiments on six streams across the West Fork Gallatin Watershed, Montana, USA, to quantify nitrogen (N) uptake kinetics and retention dynamics across stream sizes (1st to 4th order) and along a mountain resort development gradient. We observed that stream N uptake kinetics and spiraling parameters varied across streams of different development intensity and scale. In more developed watersheds we observed a fertilization affect, however, none of the streams exhibited saturation with respect to N. Additionally, we observed that elevated loading led to increased biomass and retentive capacities in developed streams that helped maintain export at low levels during baseflow. Our results indicate that LULC can enhance in-stream uptake of limiting nutrients and highlight the value of characterizing uptake kinetic curves from ambient to saturation.

  13. Development of Singlet Oxygen Luminescence Kinetics during the Photodynamic Inactivation of Green Algae

    Directory of Open Access Journals (Sweden)

    Tobias Bornhütter

    2016-04-01

    Full Text Available Recent studies show the feasibility of photodynamic inactivation of green algae as a vital step towards an effective photodynamic suppression of biofilms by using functionalized surfaces. The investigation of the intrinsic mechanisms of photodynamic inactivation in green algae represents the next step in order to determine optimization parameters. The observation of singlet oxygen luminescence kinetics proved to be a very effective approach towards understanding mechanisms on a cellular level. In this study, the first two-dimensional measurement of singlet oxygen kinetics in phototrophic microorganisms on surfaces during photodynamic inactivation is presented. We established a system of reproducible algae samples on surfaces, incubated with two different cationic, antimicrobial potent photosensitizers. Fluorescence microscopy images indicate that one photosensitizer localizes inside the green algae while the other accumulates along the outer algae cell wall. A newly developed setup allows for the measurement of singlet oxygen luminescence on the green algae sample surfaces over several days. The kinetics of the singlet oxygen luminescence of both photosensitizers show different developments and a distinct change over time, corresponding with the differences in their localization as well as their photosensitization potential. While the complexity of the signal reveals a challenge for the future, this study incontrovertibly marks a crucial, inevitable step in the investigation of photodynamic inactivation of biofilms: it shows the feasibility of using the singlet oxygen luminescence kinetics to investigate photodynamic effects on surfaces and thus opens a field for numerous investigations.

  14. Effect of ship locking on sediment oxygen uptake in impounded rivers

    DEFF Research Database (Denmark)

    Lorke, A.; McGinnis, D. F.; Maeck, A.

    2012-01-01

    In the majority of large river systems, flow is regulated and/or otherwise affected by operational and management activities, such as ship locking. The effect of lock operation on sediment-water oxygen fluxes was studied within a 12.9 km long impoundment at the Saar River (Germany) using eddy....... Additional means by which the oxygen budget of the impoundment is affected by lock-induced flow variations are discussed. Citation: Lorke, A., D. F. McGinnis, A. Maeck, and H. Fischer (2012), Effect of ship locking on sediment oxygen uptake in impounded rivers, Water Resour. Res., 48, W12514, doi: 10....... These wave-induced flow variations cause variations in sediment-water oxygen fluxes. While the mean flux during time periods without lock operation was 0.5 +/- 0.1 g m(-2) d(-1), it increased by about a factor of 2 to 1.0 +/- 0.5 g m(-2) d(-1) within time periods with ship locking. Following the daily...

  15. Effects of Hemopure on maximal oxygen uptake and endurance performance in healthy humans.

    Science.gov (United States)

    Ashenden, M J; Schumacher, Y O; Sharpe, K; Varlet-Marie, E; Audran, M

    2007-05-01

    Haemoglobin-based oxygen carriers (HBOCs) such as Hemopure are touted as a tenable substitute for red blood cells and therefore potential doping agents, although the mechanisms of oxygen transport of HBOCs are incompletely understood. We investigated whether infusion of Hemopure increased maximal oxygen uptake (V.O 2max) and endurance performance in healthy subjects. Twelve male subjects performed two 4-minute submaximal exercise bouts equivalent to 60 % and 75 % of V.O (2max) on a cycle ergometer, followed by a ramped incremental protocol to elicit V.O (2max). A crossover design tested the effect of infusing either 30 g (6 subjects) or 45 g (6 subjects) of Hemopure versus a placebo. Under our study conditions, Hemopure did not increase V.O (2max) nor endurance performance. However, the infusion of Hemopure caused a decrease in heart rate of approximately 10 bpm (p=0.009) and an average increase in mean ( approximately 7 mmHg) and diastolic blood pressure ( approximately 8 mmHg) (p=0.046) at submaximal and maximal exercise intensities. Infusion of Hemopure did not bestow the same physiological advantages generally associated with infusion of red blood cells. It is conceivable that under exercise conditions, the hypertensive effects of Hemopure counter the performance-enhancing effect of improved blood oxygen carrying capacity.

  16. Reaction kinetics of oxygen on single-phase alloys, oxidation of nickel and niobium alloys

    International Nuclear Information System (INIS)

    Lalauze, Rene

    1973-01-01

    This research thesis first addresses the reaction kinetics of oxygen on alloys. It presents some generalities on heterogeneous reactions (conventional theory, theory of jumps), discusses the core reaction (with the influence of pressure), discusses the influence of metal self-diffusion on metal oxidation kinetics (equilibrium conditions at the interface, hybrid diffusion regime), reports the application of the hybrid diffusion model to the study of selective oxidation of alloys (Wagner model, hybrid diffusion model) and the study of the oxidation kinetics of an alloy forming a solid solution of two oxides. The second part reports the investigation of the oxidation of single phase nickel and niobium alloys (phase α, β and γ)

  17. Effect of ZnO nanoparticles in the oxygen uptake during aerobic wastewater treatment

    Energy Technology Data Exchange (ETDEWEB)

    Cervantes-Avilés, Pabel; Brito, Elcia M. S. [University of Guanajuato, Engineering Division, Department of Civil Engineering & Environmental Engineering (Mexico); Duran, Robert [Université de Pau et des Pays de l’Adour, Equipe Environment et Microbiologie (France); Martínez, Arodí Bernal; Cuevas-Rodríguez, Germán, E-mail: german28@ugto.mx [University of Guanajuato, Engineering Division, Department of Civil Engineering & Environmental Engineering (Mexico)

    2016-07-15

    The increased use of ZnO nanoparticles (NPs) in everyday products indicates the importance of studying NPs release to the wastewater and its possible effect on biological process for wastewater treatment. Therefore, the aim of this work was to study the effect of the presence of ZnO NPs in aerobic wastewater treatment. The results indicated that the oxygen uptake rate of microorganisms is inhibited for concentrations higher than 473 mg L{sup −1} of ZnO NPs. The diversity of microorganisms involved in wastewater treatment was reduced in presence of ZnO NPs. Related to morphological interaction between ZnO NPs and suspended biomass, physical damage in flocs structure were observed in presence of ZnO NPs. However, the internalization of Zn compounds in microorganisms not presented mechanical damage in the membrane cell. These findings suggest that inhibition in oxygen uptake was caused for negative effect that ZnO NPs induces in aerobic microorganisms involved in wastewater treatment.

  18. Photoluminescent Gold Nanoclusters in Cancer Cells: Cellular Uptake, Toxicity, and Generation of Reactive Oxygen Species.

    Science.gov (United States)

    Matulionyte, Marija; Dapkute, Dominyka; Budenaite, Laima; Jarockyte, Greta; Rotomskis, Ricardas

    2017-02-10

    In recent years, photoluminescent gold nanoclusters have attracted considerable interest in both fundamental biomedical research and practical applications. Due to their ultrasmall size, unique molecule-like optical properties, and facile synthesis gold nanoclusters have been considered very promising photoluminescent agents for biosensing, bioimaging, and targeted therapy. Yet, interaction of such ultra-small nanoclusters with cells and other biological objects remains poorly understood. Therefore, the assessment of the biocompatibility and potential toxicity of gold nanoclusters is of major importance before their clinical application. In this study, the cellular uptake, cytotoxicity, and intracellular generation of reactive oxygen species (ROS) of bovine serum albumin-encapsulated (BSA-Au NCs) and 2-(N-morpholino) ethanesulfonic acid (MES)capped photoluminescent gold nanoclusters (Au-MES NCs) were investigated. The results showed that BSA-Au NCs accumulate in cells in a similar manner as BSA alone, indicating an endocytotic uptake mechanism while ultrasmall Au-MES NCs were distributed homogeneously throughout the whole cell volume including cell nucleus. The cytotoxicity of BSA-Au NCs was negligible, demonstrating good biocompatibility of such BSA-protected Au NCs. In contrast, possibly due to ultrasmall size and thin coating layer, Au-MES NCs exhibited exposure time-dependent high cytotoxicity and higher reactivity which led to highly increased generation of reactive oxygen species. The results demonstrate the importance of the coating layer to biocompatibility and toxicity of ultrasmall photoluminescent gold nanoclusters.

  19. Photoluminescent Gold Nanoclusters in Cancer Cells: Cellular Uptake, Toxicity, and Generation of Reactive Oxygen Species

    Directory of Open Access Journals (Sweden)

    Marija Matulionyte

    2017-02-01

    Full Text Available In recent years, photoluminescent gold nanoclusters have attracted considerable interest in both fundamental biomedical research and practical applications. Due to their ultrasmall size, unique molecule-like optical properties, and facile synthesis gold nanoclusters have been considered very promising photoluminescent agents for biosensing, bioimaging, and targeted therapy. Yet, interaction of such ultra-small nanoclusters with cells and other biological objects remains poorly understood. Therefore, the assessment of the biocompatibility and potential toxicity of gold nanoclusters is of major importance before their clinical application. In this study, the cellular uptake, cytotoxicity, and intracellular generation of reactive oxygen species (ROS of bovine serum albumin-encapsulated (BSA-Au NCs and 2-(N-morpholino ethanesulfonic acid (MEScapped photoluminescent gold nanoclusters (Au-MES NCs were investigated. The results showed that BSA-Au NCs accumulate in cells in a similar manner as BSA alone, indicating an endocytotic uptake mechanism while ultrasmall Au-MES NCs were distributed homogeneously throughout the whole cell volume including cell nucleus. The cytotoxicity of BSA-Au NCs was negligible, demonstrating good biocompatibility of such BSA-protected Au NCs. In contrast, possibly due to ultrasmall size and thin coating layer, Au-MES NCs exhibited exposure time-dependent high cytotoxicity and higher reactivity which led to highly increased generation of reactive oxygen species. The results demonstrate the importance of the coating layer to biocompatibility and toxicity of ultrasmall photoluminescent gold nanoclusters.

  20. THE CONTRIBUTION OF 'RESTING' BODY MUSCLES TO THE SLOW COMPONENT OF PULMONARY OXYGEN UPTAKE DURING HIGH-INTENSITY CYCLING

    Directory of Open Access Journals (Sweden)

    Susan A. Ward

    2012-12-01

    Full Text Available Oxygen uptake (VO2 kinetics during moderate constant- workrate (WR exercise (>lactate-threshold (ӨL are well described as exponential. AboveӨL, these kinetics are more complex, consequent to the development of a delayed slow component (VO2sc, whose aetiology remains controversial. To assess the extent of the contribution to the VO2sc from arm muscles involved in postural stability during cycling, six healthy subjects completed an incremental cycle-ergometer test to the tolerable limit for estimation of ӨL and determination of peak VO2. They then completed two constant-WR tests at 90% of ӨL and two at 80% of ∆ (difference between ӨL and VO2peak. Gas exchange variables were derived breath-by-breath. Local oxygenation profiles of the vastus lateralis and biceps brachii muscles were assessed by near-infrared spectroscopy, with maximal voluntary contractions (MVC of the relevant muscles being performed post-exercise to provide a frame of reference for normalising the exercise-related oxygenation responses across subjects. Above supra-ӨL, VO2 rose in an exponential-like fashion ("phase 2, with a delayed VO2sc subsequently developing. This was accompanied by an increase in [reduced haemoglobin] relative to baseline (∆[Hb], which attained 79 ± 13 % (mean, SD of MVC maximum in vastus lateralis at end-exercise and 52 ± 27 % in biceps brachii. Biceps brachii ∆[Hb] was significantly correlated with VO2 throughout the slow phase. In contrast, for sub- L exercise, VO2 rose exponentially to reach a steady state with a more modest increase in vastus lateralis ∆[Hb] (30 ± 11 %; biceps brachii ∆[Hb] was minimally affected (8 ± 2 %. That the intramuscular O2 desaturation profile in biceps brachii was proportional to that for VO2sc during supra-ӨL cycle ergometry is consistent with additional stabilizing arm work contributing to the VO2sc

  1. Effects of vehicle on the uptake and elimination kinetics of capsaicinoids in human skin in vivo

    International Nuclear Information System (INIS)

    Pershing, Lynn K.; Reilly, Christopher A.; Corlett, Judy L.; Crouch, Dennis J.

    2004-01-01

    While the physiologic and molecular effects of capsaicinoids have been extensively studied in various model systems by a variety of administration routes, little is known about the uptake and elimination kinetic profiles in human skin following topical exposure. The present study evaluated the uptake and elimination kinetics of capsaicinoids in human stratum corneum following a single topical exposure to 3% solutions containing 55% capsaicin, 35% dihydrocapsaicin, and 10% other analogues prepared in three vehicles: mineral oil (MO), propylene glycol (PG), and isopropyl alcohol (IPA). Capsaicinoid solutions were evaluated simultaneously in a random application pattern on the volar forearms of 12 subjects using a small, single 150-μg dose. Capsaicin and dihydrocapsaicin were recovered from human skin using commercial adhesive discs to harvest stratum corneum from treated sites. Capsaicinoids were extracted from the stratum corneum-adhesive discs and quantified by liquid chromatography/mass spectroscopy (LC/MS). Both capsaicinoids were detected in stratum corneum 1 min after application with all vehicles and achieved a pseudo-steady state shortly thereafter. IPA delivered three times greater capsaicin and dihydrocapsaicin into the human stratum corneum than PG or MO at all time points investigated. The C max of capsaicin in IPA, PG, and MO was 16.1, 6.2, and 6.5 μg, respectively. The dihydrocapsaicin content was 60% of capsaicin with all vehicles. The estimated T half of capsaicin and dihydrocapsaicin in the three vehicles was similar (24 h). Thus, maximal cutaneous capsaicinoid concentrations were achieved quickly in the human stratum corneum and were concentration and vehicle dependent. In contrast, capsaicinoid half-life was long and vehicle independent

  2. EQUILIBRIUM AND KINETIC NITROGEN AND OXYGEN-ISOTOPE FRACTIONATIONS BETWEEN DISSOLVED AND GASEOUS N2O

    NARCIS (Netherlands)

    INOUE, HY; MOOK, WG

    1994-01-01

    Experiments were performed to determine the equilibrium as well as kinetic stable nitrogen and oxygen isotope fractionations between aqueous dissolved and gaseous N2O. The equilibrium fractionations, defined as the ratio of the isotopic abundance ratios (15R and 18R, respectively) of gaseous and

  3. Oxygen reduction kinetics on graphite cathodes in sediment microbial fuel cells.

    Science.gov (United States)

    Renslow, Ryan; Donovan, Conrad; Shim, Matthew; Babauta, Jerome; Nannapaneni, Srilekha; Schenk, James; Beyenal, Haluk

    2011-12-28

    Sediment microbial fuel cells (SMFCs) have been used as renewable power sources for sensors in fresh and ocean waters. Organic compounds at the anode drive anodic reactions, while oxygen drives cathodic reactions. An understanding of oxygen reduction kinetics and the factors that determine graphite cathode performance is needed to predict cathodic current and potential losses, and eventually to estimate the power production of SMFCs. Our goals were to (1) experimentally quantify the dependence of oxygen reduction kinetics on temperature, electrode potential, and dissolved oxygen concentration for the graphite cathodes of SMFCs and (2) develop a mechanistic model. To accomplish this, we monitored current on polarized cathodes in river and ocean SMFCs. We found that (1) after oxygen reduction is initiated, the current density is linearly dependent on polarization potential for both SMFC types; (2) current density magnitude increases linearly with temperature in river SMFCs but remains constant with temperature in ocean SMFCs; (3) the standard heterogeneous rate constant controls the current density temperature dependence; (4) river and ocean SMFC graphite cathodes have large potential losses, estimated by the model to be 470 mV and 614 mV, respectively; and (5) the electrochemical potential available at the cathode is the primary factor controlling reduction kinetic rates. The mechanistic model based on thermodynamic and electrochemical principles successfully fit and predicted the data. The data, experimental system, and model can be used in future studies to guide SMFC design and deployment, assess SMFC current production, test cathode material performance, and predict cathode contamination.

  4. Influence of dissolved oxygen on the nitrification kinetics in a circulating bed biofilm reactor

    Energy Technology Data Exchange (ETDEWEB)

    Nogueira, R.; Melo, L.F. [University of Minho, Braga (Portugal). Dept. Bioengineering; Lazarova, V.; Manem, J. [Centre of International Research for Water and Environment (CIRSEE), Lyonnaise des Eaux, Le Pecq (France)

    1998-12-01

    The influence of dissolved oxygen concentration on the nitrification kinetics was studied in the circulating bed reactor (CBR). The study was partly performed at laboratory scale with synthetic water, and partly at pilot scale with secondary effluent as feed water. The nitrification kinetics of the laboratory CBR as a function of the oxygen concentration can be described according to the half order and zero order rate equations of the diffusion-reaction model applied to porous catalysts. When oxygen was the rate limiting substrate, the nitrification rate was close to a half order function of the oxygen concentration. The average oxygen diffusion coefficient estimated by fitting the diffusion-reaction model to the experimental results was around 66% of the respective value in water. The experimental results showed that either the ammonia or the oxygen concentration could be limiting for the nitrification kinetics. The latter occurred for an oxygen to ammonia concentration ratio below 1.5-2 gO{sub 2}/gN-NH{sub 4}{sup +} for both laboratory and pilot scale reactors. The volumetric oxygen mass transfer coefficient (k{sub L}a) determined in the laboratory scale reactor was 0.017 s{sup -1} for a superficial air velocity of 0.02 m s{sup -1}, and the one determined in the pilot scale reactor was 0.040 s{sup -1} for a superficial air velocity of 0.031 m s{sup -1}. The k{sub L}a for the pilot scale reactor did not change significantly after biofilm development, compared to the value measured without biofilm. (orig.) With 7 figs., 5 tabs., 24 refs.

  5. Hydrogen uptake in alumina thin films synthesized from an aluminum plasma stream in an oxygen ambient

    International Nuclear Information System (INIS)

    Schneider, J.M.; Anders, A.; Hjoervarsson, B.; Petrov, I.; Macak, K.; Helmersson, U.; Sundgren, J.

    1999-01-01

    We describe the hydrogen uptake during the synthesis of alumina films from H 2 O present in the high vacuum gas background. The hydrogen concentration in the films was determined by the 1 H( 15 N,αγ) 12 C nuclear resonance reaction. Furthermore, we show the presence of hydrogen ions in the plasma stream by time-of-flight mass spectrometry. The hydrogen content increased in both the film and the plasma stream, as the oxygen partial pressure was increased. On the basis of these measurements and thermodynamic considerations, we suggest that an aluminum oxide hydroxide compound is formed, both on the cathode surface as well as in the film. The large scatter in the data reported in the literature for refractive index and chemical stability of alumina thin films can be explained on the basis of the suggested aluminum oxide hydroxide formation. copyright 1999 American Institute of Physics

  6. Influence of the temperature and oxygen exposure in red Port wine: A kinetic approach.

    Science.gov (United States)

    Oliveira, Carla Maria; Barros, António S; Silva Ferreira, António César; Silva, Artur M S

    2015-09-01

    Although phenolics are recognized to be related with health benefits by limiting lipid oxidation, in wine, they are the primary substrates for oxidation resulting in the quinone by-products with the participation of transition metal ions. Nevertheless, high quality Port wines require a period of aging in either bottle or barrels. During this time, a modification of sensory properties of wines such as the decrease of astringency or the stabilization of color is recognized to phenolic compounds, mainly attributed to anthocyanins and derived pigments. The present work aims to illustrate the oxidation of red Port wine based on its phenolic composition by the effect of both thermal and oxygen exposures. A kinetic approach toanthocyanins degradation was also achieved. For this purpose a forced red Port wine aging protocol was performed at four different storage temperatures, respectively, 20, 30, 35 and 40°C, and two adjusted oxygen saturation levels, no oxygen addition (treatment I), and oxygen addition (treatment II). Three hydroxycinnamic esters, three hydroxycinnamic acids, three hydroxybenzoic acids, two flavan-3-ols, and six anthocyanins were quantitated weekly during 63days, along with oxygen consumption. The most relevant phenolic oxidation markers were anthocyanins and catechin-type flavonoids, which had the highest decreases during the thermal and oxidative red Port wine process. Both temperature and oxygen treatments affected the rate of phenolic degradation. In addition, temperature seems to influence mostly the phenolics kinetic degradation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. THE KINETICS OF NH(4)+ AND NO3(-) UPTAKE BY DOUGLAS-FIR FROM SINGLE N-SOLUTIONS AND FROM SOLUTIONS CONTAINING BOTH NH(4)+ AND NO3(-)

    NARCIS (Netherlands)

    KAMMINGAVANWIJK, C; PRINS, HBA

    The kinetics of NH4+ and NO3- uptake in young Douglas fir trees (Pseudotsuga menziesii [Mirb.] Franco) were studied in solutions, containing either one or both N species. Using solutions containing a single N species, the V(max) of NH4+ uptake was higher than that of NO3- uptake. The K(m) of NH4+

  8. Commonly used reference values underestimate oxygen uptake in healthy, 50-year-old Swedish women.

    Science.gov (United States)

    Genberg, M; Andrén, B; Lind, L; Hedenström, H; Malinovschi, A

    2018-01-01

    Cardiopulmonary exercise testing (CPET) is the gold standard among clinical exercise tests. It combines a conventional stress test with measurement of oxygen uptake (V O 2 ) and CO 2 production. No validated Swedish reference values exist, and reference values in women are generally understudied. Moreover, the importance of achieved respiratory exchange ratio (RER) and the significance of breathing reserve (BR) at peak exercise in healthy individuals are poorly understood. We compared V O 2 at maximal load (peakV O 2 ) and anaerobic threshold (V O 2@ AT ) in healthy Swedish individuals with commonly used reference values, taking gender into account. Further, we analysed maximal workload and peakV O 2 with regard to peak RER and BR. In all, 181 healthy, 50-year-old individuals (91 women) performed CPET. PeakV O 2 was best predicted using Jones et al. (100·5%), while SHIP reference values underestimated peakV O 2 most: 112·5%. Furthermore, underestimation of peakV O 2 in women was found for all studied reference values (P 1·1 (2 328·7 versus 2 176·7 ml min -1 , P = 0·11). Lower BR (≤30%) related to significantly higher peakV O 2 (Pvalues underestimated oxygen uptake in women. No evidence for demanding RER > 1·1 in healthy individuals was found. A lowered BR is probably a normal response to higher workloads in healthy individuals. © 2016 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

  9. Kinetic of the Oxygen Control System (OCS) for stagnant lead-bismuth systems

    International Nuclear Information System (INIS)

    Lefhalm, C.H.; Knebel, J.U.; Mack, K.J.

    2001-09-01

    Within the framework of the HGF strategy fund project 99/16 ''Thermalhydraulic and Material Specific Investigations into the Realization of an accelerator driven system (ADS) to Transmute Minor Actinides'' at the institute for nuclear and energy technology (IKET) investigations on the cooling of thermally high-loaded surfaces with liquid lead bismuth (Pb-Bi) are carried out. To operate a Pb-Bi loop safety, for example in order to cool a spallation target or a blanket of an accelerator driven system (ADS), the control of the oxygen concentration within the liquid metal is an inalienable prerequisite to prevent or minimize corrosion at the structure material. In this report the kinetic behaviour of the oxygen control system (OCS), which was developed at Forschungszentrum Karlsruhe, is examined. The OCS controls the chemical potential of oxygen in the liquid metal by regulating the oxygen content in the gas phase which flows over the free surface of the liquid metal. In this work the experimental facility KOCOS (kinetics of oxygen control system) in the karlsruhe lead laboratory (KALLA) was built. A physical diffusion model was utilised and extended to describe the exchange of oxygen between the gas and the liquid metal. The theoretical calculations are in very good agreement to the experimental findings. The OCS allows to control reversibly the oxygen concentration in the liquid metal. According to the observed kinetics of the process one can extrapolate that the control of large volumes, as they are necessary to operate an ADS demonstrator, is possible. Therefore, further experiments in liquid metal loop systems are suggested. (orig.)

  10. Effects of hyperoxia on 18F-fluoro-misonidazole brain uptake and tissue oxygen tension following middle cerebral artery occlusion in rodents: Pilot studies.

    Directory of Open Access Journals (Sweden)

    Tim D Fryer

    Full Text Available Mapping brain hypoxia is a major goal for stroke diagnosis, pathophysiology and treatment monitoring. 18F-fluoro-misonidazole (FMISO positron emission tomography (PET is the gold standard hypoxia imaging method. Normobaric hyperoxia (NBO is a promising therapy in acute stroke. In this pilot study, we tested the straightforward hypothesis that NBO would markedly reduce FMISO uptake in ischemic brain in Wistar and spontaneously hypertensive rats (SHRs, two rat strains with distinct vulnerability to brain ischemia, mimicking clinical heterogeneity.Thirteen adult male rats were randomized to distal middle cerebral artery occlusion under either 30% O2 or 100% O2. FMISO was administered intravenously and PET data acquired dynamically for 3hrs, after which magnetic resonance imaging (MRI and tetrazolium chloride (TTC staining were carried out to map the ischemic lesion. Both FMISO tissue uptake at 2-3hrs and FMISO kinetic rate constants, determined based on previously published kinetic modelling, were obtained for the hypoxic area. In a separate group (n = 9, tissue oxygen partial pressure (PtO2 was measured in the ischemic tissue during both control and NBO conditions.As expected, the FMISO PET, MRI and TTC lesion volumes were much larger in SHRs than Wistar rats in both the control and NBO conditions. NBO did not appear to substantially reduce FMISO lesion size, nor affect the FMISO kinetic rate constants in either strain. Likewise, MRI and TTC lesion volumes were unaffected. The parallel study showed the expected increases in ischemic cortex PtO2 under NBO, although these were small in some SHRs with very low baseline PtO2.Despite small samples, the apparent lack of marked effects of NBO on FMISO uptake suggests that in permanent ischemia the cellular mechanisms underlying FMISO trapping in hypoxic cells may be disjointed from PtO2. Better understanding of FMISO trapping processes will be important for future applications of FMISO imaging.

  11. Acute toxicity, uptake and accumulation kinetics of nickel in an invasive copepod species: Pseudodiaptomus marinus.

    Science.gov (United States)

    Tlili, Sofiène; Ovaert, Julien; Souissi, Anissa; Ouddane, Baghdad; Souissi, Sami

    2016-02-01

    Pseudodiaptomus marinus is a marine calanoid copepod originating of the Indo-Pacific region, who has successfully colonized new areas and it was recently observed in the European side of the Mediterranean Sea as well as in the North Sea. Actually, many questions were posed about the invasive capacity of this copepod in several non-native ecosystems. In this context, the main aim of this study was to investigate the tolerance and the bioaccumulation of metallic stress in the invasive copepod P. marinus successfully maintained in mass culture at laboratory conditions since 2 years. In order to study the metallic tolerance levels of P. marinus, an emergent trace metal, the nickel, was chosen. First, lethal concentrations determination experiments were done for 24, 48, 72 and 96 h in order to calculated LC50% but also to select a relevant ecological value for the suite of experiments. Then, three types of experiments, using a single concentration of nickel (correspond the 1/3 of 96 h-LC50%) was carried in order to study the toxico-kinetics of nickel in P. marinus. Concerning lethal concentrations, we observed that P. marinus was in the same range of sensitivity compared to other calanoid copepods exposed to nickel in the same standardized experimental conditions. Results showed that the uptake of nickel in P. marinus depends from the pathways of entrance (water of food), but also that Isochrysis galbana, used as a food source, has an important bioaccumulation capacity and a rapid uptake of nickel. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. The oxygen-conserving potential of the diving response: A kinetic-based analysis.

    Science.gov (United States)

    Costalat, Guillaume; Coquart, Jeremy; Castres, Ingrid; Joulia, Fabrice; Sirost, Olivier; Clua, Eric; Lemaître, Frédéric

    2017-04-01

    We investigated the oxygen-conserving potential of the human diving response by comparing trained breath-hold divers (BHDs) to non-divers (NDs) during simulated dynamic breath-holding (BH). Changes in haemodynamics [heart rate (HR), stroke volume (SV), cardiac output (CO)] and peripheral muscle oxygenation [oxyhaemoglobin ([HbO 2 ]), deoxyhaemoglobin ([HHb]), total haemoglobin ([tHb]), tissue saturation index (TSI)] and peripheral oxygen saturation (SpO 2 ) were continuously recorded during simulated dynamic BH. BHDs showed a breaking point in HR kinetics at mid-BH immediately preceding a more pronounced drop in HR (-0.86 bpm.% -1 ) while HR kinetics in NDs steadily decreased throughout BH (-0.47 bpm.% -1 ). By contrast, SV remained unchanged during BH in both groups (all P > 0.05). Near-infrared spectroscopy (NIRS) results (mean ± SD) expressed as percentage changes from the initial values showed a lower [HHb] increase for BHDs than for NDs at the cessation of BH (+24.0 ± 10.1 vs. +39.2 ± 9.6%, respectively; P kinetic-based approach we used provides further credence to the concept of an "oxygen-conserving breaking point" in the human diving response.

  13. Effect of oral propranolol on splanchnic oxygen uptake and haemodynamics in patients with cirrhosis

    DEFF Research Database (Denmark)

    Bendtsen, Flemming; Henriksen, Jens Henrik; Becker, Povl Ulrik

    1987-01-01

    .01), azygos venous oxygen saturation (76 vs. 67%, P less than 0.05), ICG clearance (263 vs. 226 ml/min, P less than 0.01), wedged-to-free hepatic vein pressure (16 vs. 13.5 mm Hg, P less than 0.01), hepatic blood flow (1.18 vs. 0.78 l/min, P less than 0.01), cardiac index (3.42 vs. 2.53 l/min . min 2, P less...... mg propranolol. All patients underwent hepatic vein catheterization and had a primed continuous intravenous infusion of ICG. Azygos vein catheterization was performed in six patients. Splanchnic (hepatic-intestinal) oxygen uptake (median control 68 ml/min vs. beta-blockade 56 ml/min, P less than 0...... than 0.01), and heart rate (72 vs. 56 beats per min, P less than 0.01) decreased significantly after oral beta-blockade. The hepatic extraction ratio of ICG increased significantly (0.32 vs. 0.45, P less than 0.01), whereas estimated 'intrinsic' ICG clearance (289 vs. 300 ml/min, n.s.), arterial blood...

  14. A unified approach to model uptake kinetics of trace elements in complex aqueous – solid solution systems

    International Nuclear Information System (INIS)

    Thien, Bruno M.J.; Kulik, Dmitrii A.; Curti, Enzo

    2014-01-01

    Highlights: • There are several models able to describe trace element partitioning in growing minerals. • To describe complex systems, those models must be embedded in a geochemical code. • We merged two models into a unified one suitable for implementation in a geochemical code. • This unified model was tested against coprecipitation experimental data. • We explored how our model reacts to solution depletion effects. - Abstract: Thermodynamics alone is usually not sufficient to predict growth-rate dependencies of trace element partitioning into host mineral solid solutions. In this contribution, two uptake kinetic models were analyzed that are promising in terms of mechanistic understanding and potential for implementation in geochemical modelling codes. The growth Surface Entrapment Model (Watson, 2004) and the Surface Reaction Kinetic Model (DePaolo, 2011) were shown to be complementary, and under certain assumptions merged into a single analytical expression. This Unified Uptake Kinetics Model was implemented in GEMS3K and GEM-Selektor codes ( (http://gems.web.psi.ch)), a Gibbs energy minimization package for geochemical modelling. This implementation extends the applicability of the unified uptake kinetics model to accounting for non-trivial factors influencing the trace element partitioning into solid solutions, such as the changes in aqueous solution composition and speciation, or the depletion effects in closed geochemical systems

  15. UV-cured methacrylic-silica hybrids: Effect of oxygen inhibition on photo-curing kinetics

    International Nuclear Information System (INIS)

    Corcione, C. Esposito; Striani, R.; Frigione, M.

    2014-01-01

    Highlights: • The kinetic behavior of novel photopolymerizable organic–inorganic hybrid system was studied as a function of the composition and of the atmosphere for reactions. • The UV-curing reaction of the hybrid mixture was found fast and complete. • The combined presence of thiol monomer and nanostructured silica allows to reduce the effect of inhibition of oxygen towards the radical photopolymerization. - Abstract: The kinetic behavior of innovative photopolymerizable UV-cured methacrylic–silica hybrid formulations, previously developed, was studied and compared to that of a reference control system. The organic–inorganic (O–I) hybrids proposed in this study are obtained from organic precursors with a high siloxane content mixed with tetraethoxysilane (TEOS) in such a way to produce co-continuous silica nano-domains dispersed within a cross-linked organic phase, as a result of the hydrolysis and condensation reactions. The kinetics of the radical photopolymerization mechanism induced by UV-radiations, in presence of a suitable photoinitiator, was studied by calorimetric, FTIR and Raman spectroscopic analyses, by varying the composition of the mixtures and the atmosphere for reactions. The well known effect of oxygen on the kinetic mechanism of the free radical photopolymerization of the methacrylic–siloxane based monomers was found to be strongly reduced in the hybrid system, especially when a proper thiol was used. The experimental calorimetric data were fitted using a simple kinetic model for radical photopolymerization reactions, obtaining a good agreement between the experimental data and the theoretical model. From the comparison of the kinetic constants calculated for control and hybrid systems, it was possible to assess the effect of the composition, as well as of the atmosphere used during the photo-polymerization process, on the kinetic of photopolymerization reaction

  16. Machine learning and statistical methods for the prediction of maximal oxygen uptake: recent advances

    Directory of Open Access Journals (Sweden)

    Abut F

    2015-08-01

    Full Text Available Fatih Abut, Mehmet Fatih AkayDepartment of Computer Engineering, Çukurova University, Adana, TurkeyAbstract: Maximal oxygen uptake (VO2max indicates how many milliliters of oxygen the body can consume in a state of intense exercise per minute. VO2max plays an important role in both sport and medical sciences for different purposes, such as indicating the endurance capacity of athletes or serving as a metric in estimating the disease risk of a person. In general, the direct measurement of VO2max provides the most accurate assessment of aerobic power. However, despite a high level of accuracy, practical limitations associated with the direct measurement of VO2max, such as the requirement of expensive and sophisticated laboratory equipment or trained staff, have led to the development of various regression models for predicting VO2max. Consequently, a lot of studies have been conducted in the last years to predict VO2max of various target audiences, ranging from soccer athletes, nonexpert swimmers, cross-country skiers to healthy-fit adults, teenagers, and children. Numerous prediction models have been developed using different sets of predictor variables and a variety of machine learning and statistical methods, including support vector machine, multilayer perceptron, general regression neural network, and multiple linear regression. The purpose of this study is to give a detailed overview about the data-driven modeling studies for the prediction of VO2max conducted in recent years and to compare the performance of various VO2max prediction models reported in related literature in terms of two well-known metrics, namely, multiple correlation coefficient (R and standard error of estimate. The survey results reveal that with respect to regression methods used to develop prediction models, support vector machine, in general, shows better performance than other methods, whereas multiple linear regression exhibits the worst performance

  17. Kinetics of cellular uptake of viruses and nanoparticles via clathrin-mediated endocytosis

    Science.gov (United States)

    Banerjee, Anand; Berezhkovskii, Alexander; Nossal, Ralph

    2016-02-01

    Several viruses exploit clathrin-mediated endocytosis to gain entry into host cells. This process is also used extensively in biomedical applications to deliver nanoparticles (NPs) to diseased cells. The internalization of these nano-objects is controlled by the assembly of a clathrin-containing protein coat on the cytoplasmic side of the plasma membrane, which drives the invagination of the membrane and the formation of a cargo-containing endocytic vesicle. Current theoretical models of receptor-mediated endocytosis of viruses and NPs do not explicitly take coat assembly into consideration. In this paper we study cellular uptake of viruses and NPs with a focus on coat assembly. We characterize the internalization process by the mean time between the binding of a particle to the membrane and its entry into the cell. Using a coarse-grained model which maps the stochastic dynamics of coat formation onto a one-dimensional random walk, we derive an analytical formula for this quantity. A study of the dependence of the mean internalization time on NP size shows that there is an upper bound above which this time becomes extremely large, and an optimal size at which it attains a minimum. Our estimates of these sizes compare well with experimental data. We also study the sensitivity of the obtained results on coat parameters to identify factors which significantly affect the internalization kinetics.

  18. Kinetic Analysis of the Uptake and Release of Fluorescein by Metal-Organic Framework Nanoparticles

    Directory of Open Access Journals (Sweden)

    Tobias Preiß

    2017-02-01

    Full Text Available Metal-organic framework nanoparticles (MOF NPs are promising guest-host materials with applications in separation, storage, catalysis, and drug delivery. However, on- and off-loading of guest molecules by porous MOF nanostructures are still poorly understood. Here we study uptake and release of fluorescein by two representative MOF NPs, MIL-100(Fe and MIL-101(Cr. Suspensions of these MOF NPs exhibit well-defined size distributions and crystallinity, as verified by electron microscopy, dynamic light scattering, and X-ray diffraction. Using absorbance spectroscopy the equilibrium dissociation constants and maximum numbers of adsorbed fluorescein molecules per NP were determined. Time-resolved fluorescence studies reveal that rates of release and loading are pH dependent. The kinetics observed are compared to theoretical estimates that account for bulk diffusion into NPs, and retarded internal diffusion and adsorption rates. Our study shows that, rather than being simple volumetric carriers, MOF-NPs are dominated by internal surface properties. The findings will help to optimize payload levels and develop release strategies that exploit varying pH for drug delivery.

  19. Kinetics of pyrophosphate-driven proton uptake by acidocalcisomes of Leptomonas wallacei

    International Nuclear Information System (INIS)

    Moraes Moreira, Bernardo Luiz; Soares Medeiros, Lia Carolina A.; Miranda, Kildare; Souza, Wanderley de; Hentschel, Joachim; Plattner, Helmut; Barrabin, Hector

    2005-01-01

    In this work, we show the kinetics of pyrophosphate-driven H + uptake by acidocalcisomes in digitonin-permeabilized promastigotes of Leptomonas wallacei. The vacuolar proton pyrophosphatase activity was optimal in the pH range of 7.5-8.0, was inhibited by imidiodiphosphate, and was completely dependent on K + and PPi. H + was released with the addition of Ca 2+ , suggesting the presence of a Ca 2+ /H + antiport. In addition, X-ray elemental mapping associated with energy-filtering transmission electron microscopy showed that most of the Ca, Na, Mg, P, K, Fe, and Zn were located in acidocalcisomes. L. wallacei immunolabeled with antibodies against Trypanosoma cruzi pyrophosphatase show intense fluorescence in cytoplasmatic organelles of size and distribution similar to the acidocalcisomes. Altogether, the results show that L. wallacei acidocalcisomes possess a H + -pyrophosphatase with characteristics of type I V-H + -PPase. However, we did not find any evidence, either for the presence of H + -ATPases or for Na + /H + exchangers in these acidocalcisomes

  20. Cell respiration under hypoxia: facts and artefacts in mitochondrial oxygen kinetics.

    Science.gov (United States)

    Scandurra, Francesca M; Gnaiger, Erich

    2010-01-01

    When oxygen supply to tissues is limiting, mitochondrial respiration and ATP production are compromised. To assess the bioenergetic consequences under normoxia and hypoxia, quantitative evaluation of mitochondrial oxygen kinetics is required. Using high-resolution respirometry, the "apparent K (m)" for oxygen or p (50) of respiration in 32D cells was determined at 0.05 +/- 0.01 kPa (0.4 mmHg, 0.5 microM, 0.25% air saturation). Close agreement with p (50) of isolated mitochondria indicates that intracellular gradients are small in small cells at routine activity. At intracellular p (O2) respiration is limited by >2% with a p (50) of 0.05 kPa. Over-estimation of p (50) at 0.4 kPa (3 mmHg) would imply significant (>17%) oxygen limitation of respiration under intracellular normoxia. Based on a critical review, we conclude that p (50) ranges from 0.01 to 0.10 kPa in mitochondria and small cells in the absence of inhibitors of cytochrome c oxidase, whereas experimental artefacts explain the controversial >200-fold range of p (50) in the literature on mitochondrial oxygen kinetics.

  1. Dissociation kinetics of iodine in oxygen-containing electrical discharge plasmas

    International Nuclear Information System (INIS)

    Zakharov, A.I.; Klopovskii, K.S.; Rakhimova, T.V.; Samorodov, V.A.

    1993-01-01

    Studies of the kinetics of gaseous media containing oxygen and iodine molecules have been stimulated to a substantial degree by the search for ways of improving iodine-oxygen lasers and by the need for information on loss processes for atmospheric ozone. Results are presented from an experimental study and numerical simulations of the kinetics of the dissociation of iodine in self-sustained volume discharges in high-pressure O 2 :Ar:I 2 mixtures. It is shown that the well-studied mechanism for dissociation based on excitation of iodine molecules in successive collisions with singlet oxygen and excited iodine atoms is supplanted by a substantially different mechanism involving the creation and loss of 10 radicals when the densities of atomic oxygen and ozone are high enough. It is also shown that iodine fractions as low as ∼10 -3 in the mixture lead to rapid loss of ozone molecules while less than 18% of the discharge energy is expended in the production of singlet oxygen

  2. Aerobic composting of waste activated sludge: Kinetic analysis for microbiological reaction and oxygen consumption

    International Nuclear Information System (INIS)

    Yamada, Y.; Kawase, Y.

    2006-01-01

    In order to examine the optimal design and operating parameters, kinetics for microbiological reaction and oxygen consumption in composting of waste activated sludge were quantitatively examined. A series of experiments was conducted to discuss the optimal operating parameters for aerobic composting of waste activated sludge obtained from Kawagoe City Wastewater Treatment Plant (Saitama, Japan) using 4 and 20 L laboratory scale bioreactors. Aeration rate, compositions of compost mixture and height of compost pile were investigated as main design and operating parameters. The optimal aerobic composting of waste activated sludge was found at the aeration rate of 2.0 L/min/kg (initial composting mixture dry weight). A compost pile up to 0.5 m could be operated effectively. A simple model for composting of waste activated sludge in a composting reactor was developed by assuming that a solid phase of compost mixture is well mixed and the kinetics for microbiological reaction is represented by a Monod-type equation. The model predictions could fit the experimental data for decomposition of waste activated sludge with an average deviation of 2.14%. Oxygen consumption during composting was also examined using a simplified model in which the oxygen consumption was represented by a Monod-type equation and the axial distribution of oxygen concentration in the composting pile was described by a plug-flow model. The predictions could satisfactorily simulate the experiment results for the average maximum oxygen consumption rate during aerobic composting with an average deviation of 7.4%

  3. Strontium-free rare earth perovskite ferrites with fast oxygen exchange kinetics: Experiment and theory

    Science.gov (United States)

    Berger, Christian; Bucher, Edith; Windischbacher, Andreas; Boese, A. Daniel; Sitte, Werner

    2018-03-01

    The Sr-free mixed ionic electronic conducting perovskites La0.8Ca0.2FeO3-δ (LCF82) and Pr0.8Ca0.2FeO3-δ (PCF82) were synthesized via a glycine-nitrate process. Crystal structure, phase purity, and lattice constants were determined by XRD and Rietveld analysis. The oxygen exchange kinetics and the electronic conductivity were obtained from in-situ dc-conductivity relaxation experiments at 600-800 °C and 1×10-3≤pO2/bar≤0.1. Both LCF82 and PCF82 show exceptionally fast chemical surface exchange coefficients and chemical diffusion coefficients of oxygen. The oxygen nonstochiometry of LCF82 and PCF82 was determined by precision thermogravimetry. A point defect model was used to calculate the thermodynamic factors of oxygen and to estimate self-diffusion coefficients and ionic conductivities. Density Functional Theory (DFT) calculations on the crystal structure, oxygen vacancy formation as well as oxygen migration energies are in excellent agreement with the experimental values. Due to their favourable properties both LCF82 and PCF82 are of interest for applications in solid oxide fuel cell cathodes, solid oxide electrolyser cell anodes, oxygen separation membranes, catalysts, or electrochemical sensors.

  4. Kinetics of the high temperature oxygen exchange reaction on 238PuO2 powder

    International Nuclear Information System (INIS)

    Whiting, Christofer E.; Du, Miting; Felker, L. Kevin; Wham, Robert M.; Barklay, Chadwick D.; Kramer, Daniel P.

    2015-01-01

    Oxygen exchange reactions performed on PuO 2 suggest the reaction is influenced by at least three mechanisms: an internal chemical reaction, surface mobility of active species/defects, and surface exchange of gaseous oxygen with lattice oxygen. Activation energies for the surface mobility and internal chemical reaction are presented. Determining which mechanism is dominant appears to be a complex function including at least specific surface area and temperature. Thermal exposure may also impact the oxygen exchange reaction by causing reductions in the specific surface area of PuO 2 . Previous CeO 2 surrogate studies exhibit similar behavior, confirming that CeO 2 is a good qualitative surrogate for PuO 2 , in regards to the oxygen exchange reaction. Comparison of results presented here with previous work on the PuO 2 oxygen exchange reaction allows complexities in the previous work to be explained. These explanations allowed new conclusions to be drawn, many of which confirm the conclusions presented here. - Highlights: • PuO 2 Oxygen exchange kinetics can be influenced by at least 3 different mechanisms. • An internal chemical reaction controls the rate at high temperature and large SSA. • Surface mobility and surface exchange influence rate at lower temperatures and SSA. • Exchange temperatures may alter SSA and make data difficult to interpret.

  5. Estimation of peak oxygen uptake from maximal power output among 9-10 year-old children in Lhasa, Tibet

    DEFF Research Database (Denmark)

    Bianba, B; Berntsen, S; Andersen, Lars Bo

    2010-01-01

    with the equations from the present study. None of the three could accurately predict the direct measured V.O2peak, and predictions differed in an unsystematic manner, including over- or underestimation and no differentiation between genders. CONCLUSION: Peak oxygen uptake could be estimated from Wmax and sex...

  6. Allometric modelling of peak oxygen uptake in male soccer players of 8-18 years of age

    NARCIS (Netherlands)

    Valente-dos-Santos, Joao; Coelho-e-Silva, Manuel J.; Tavares, Oscar M.; Brito, Joao; Seabra, Andre; Rebelo, Antonio; Sherar, Lauren B.; Elferink-Gemser, Marije T.; Malina, Robert M.

    Background: Peak oxygen uptake (VO2peak) is routinely scaled as mL O-2 per kilogram body mass despite theoretical and statistical limitations of using ratios. Aim: To examine the contribution of maturity status and body size descriptors to ageassociated inter-individual variability in VO2peak and to

  7. Measuring oxygen surface exchange kinetics on mixed-conducting composites by electrical conductivity relaxation

    NARCIS (Netherlands)

    Hu, Bobing; Wang, Yunlong; Zhu, Zhuoying; Xia, Changrong; Bouwmeester, Henricus J.M.

    2015-01-01

    The oxygen release kinetics of mixed-conducting Sr2Fe1.5Mo0.5O6 d–Sm0.2Ce0.8O2 d (SFM–SDC) dualphase composites has been investigated, at 750 C, as a function of the SDC phase volume fraction using electrical conductivity relaxation (ECR) under reducing atmospheres, extending our previous work on

  8. Influence of exercise intensity on skeletal muscle blood flow, O2 extraction and O2 uptake on-kinetics

    Science.gov (United States)

    Jones, Andrew M; Krustrup, Peter; Wilkerson, Daryl P; Berger, Nicolas J; Calbet, José A; Bangsbo, Jens

    2012-01-01

    Following the start of low-intensity exercise in healthy humans, it has been established that the kinetics of skeletal muscle O2 delivery is faster than, and does not limit, the kinetics of muscle O2 uptake (). Direct data are lacking, however, on the question of whether O2 delivery might limit kinetics during high-intensity exercise. Using multiple exercise transitions to enhance confidence in parameter estimation, we therefore investigated the kinetics of, and inter-relationships between, muscle blood flow (), a– difference and following the onset of low-intensity (LI) and high-intensity (HI) exercise. Seven healthy males completed four 6 min bouts of LI and four 6 min bouts of HI single-legged knee-extension exercise. Blood was frequently drawn from the femoral artery and vein during exercise and , a– difference and were calculated and subsequently modelled using non-linear regression techniques. For LI, the fundamental component mean response time (MRTp) for kinetics was significantly shorter than kinetics (mean ± SEM, 18 ± 4 vs. 30 ± 4 s; P exercise intensities; however, the MRTp for a– difference was significantly shorter for HI compared with LI (17 ± 3 vs. 28 ± 4 s; P exercise and remained unaltered thereafter, with no differences between LI and HI. These results indicate that bulk O2 delivery does not limit kinetics following the onset of LI or HI knee-extension exercise. PMID:22711961

  9. Hydraulic Permeability of Resorcinol-Formaldehyde Ion-Exchange Resin - Effects of Oxygen Uptake and Radiation

    International Nuclear Information System (INIS)

    Taylor, Paul Allen

    2009-01-01

    An ion-exchange process, using spherical resorcinol-formaldehyde (RF) resin is the baseline process for removing cesium from the dissolved salt solution in the high-level waste tanks at the U.S. Department of Energy's (DOE) Hanford site in Washington State. The RF resin is also being evaluated for use in the proposed Small Column Ion Exchange (SCIX) system, which is an alternative treatment option at DOE's Savannah River Site (SRS)in South Carolina. Testing at ORNL will determine the impact of radiation exposure and oxygen uptake by the RF resin on the hydraulic permeability of the resin. Samples of the resin will be removed periodically to measure physical properties (bead size and compressibility) and cesium capacity. The proposed full-scale treatment system at Hanford, the Waste Treatment Plant (WTP), will use an ion-exchange column containing nominally 680 gal of resin, which will treat 30 gpm of waste solution. The ion-exchange column is designed for a typical pressure drop of 6 psig, with a maximum of 9.7 psig. The lab-scale column is 3-in. clear PVC pipe and is prototypic of the proposed Hanford column. The fluid velocity in the lab-scale test will be much higher than for the full-scale column, in order to generate the maximum pressure drop expected in that column (9.7 psig). The frictional drag from this high velocity will produce similar forces on the resin in the lab-scale column as would be expected at the bottom of the full-scale column. The chemical changes in the resin caused by radiation exposure and oxygen uptake are expected to cause physical changes in the resin that could reduce the bed porosity and reduce the hydraulic permeability of the resin bed. These changes will be monitored by measuring the pressure drop through the lab-scale column and by measuring the physical properties of samples of the resin. The test loop with the lab-scale column is currently being fabricated, and operation will start by late May. Testing will be completed by the

  10. Heart rate during basketball game play and volleyball drills accurately predicts oxygen uptake and energy expenditure.

    Science.gov (United States)

    Scribbans, T D; Berg, K; Narazaki, K; Janssen, I; Gurd, B J

    2015-09-01

    There is currently little information regarding the ability of metabolic prediction equations to accurately predict oxygen uptake and exercise intensity from heart rate (HR) during intermittent sport. The purpose of the present study was to develop and, cross-validate equations appropriate for accurately predicting oxygen cost (VO2) and energy expenditure from HR during intermittent sport participation. Eleven healthy adult males (19.9±1.1yrs) were recruited to establish the relationship between %VO2peak and %HRmax during low-intensity steady state endurance (END), moderate-intensity interval (MOD) and high intensity-interval exercise (HI), as performed on a cycle ergometer. Three equations (END, MOD, and HI) for predicting %VO2peak based on %HRmax were developed. HR and VO2 were directly measured during basketball games (6 male, 20.8±1.0 yrs; 6 female, 20.0±1.3yrs) and volleyball drills (12 female; 20.8±1.0yrs). Comparisons were made between measured and predicted VO2 and energy expenditure using the 3 equations developed and 2 previously published equations. The END and MOD equations accurately predicted VO2 and energy expenditure, while the HI equation underestimated, and the previously published equations systematically overestimated VO2 and energy expenditure. Intermittent sport VO2 and energy expenditure can be accurately predicted from heart rate data using either the END (%VO2peak=%HRmax x 1.008-17.17) or MOD (%VO2peak=%HRmax x 1.2-32) equations. These 2 simple equations provide an accessible and cost-effective method for accurate estimation of exercise intensity and energy expenditure during intermittent sport.

  11. Pedaling rate is an important determinant of human oxygen uptake during exercise on the cycle ergometer.

    Science.gov (United States)

    Formenti, Federico; Minetti, Alberto E; Borrani, Fabio

    2015-09-01

    Estimation of human oxygen uptake (V˙o2) during exercise is often used as an alternative when its direct measurement is not feasible. The American College of Sports Medicine (ACSM) suggests estimating human V˙o2 during exercise on a cycle ergometer through an equation that considers individual's body mass and external work rate, but not pedaling rate (PR). We hypothesized that including PR in the ACSM equation would improve its V˙o2 prediction accuracy. Ten healthy male participants' (age 19-48 years) were recruited and their steady-state V˙o2 was recorded on a cycle ergometer for 16 combinations of external work rates (0, 50, 100, and 150 W) and PR (50, 70, 90, and 110 revolutions per minute). V˙o2 was calculated by means of a new equation, and by the ACSM equation for comparison. Kinematic data were collected by means of an infrared 3-D motion analysis system in order to explore the mechanical determinants of V˙o2. Including PR in the ACSM equation improved the accuracy for prediction of sub-maximal V˙o2 during exercise (mean bias 1.9 vs. 3.3 mL O2 kg(-1) min(-1)) but it did not affect the accuracy for prediction of maximal V˙o2 (P > 0.05). Confirming the validity of this new equation, the results were replicated for data reported in the literature in 51 participants. We conclude that PR is an important determinant of human V˙o2 during cycling exercise, and it should be considered when predicting oxygen consumption. © 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

  12. Machine learning and statistical methods for the prediction of maximal oxygen uptake: recent advances.

    Science.gov (United States)

    Abut, Fatih; Akay, Mehmet Fatih

    2015-01-01

    Maximal oxygen uptake (VO2max) indicates how many milliliters of oxygen the body can consume in a state of intense exercise per minute. VO2max plays an important role in both sport and medical sciences for different purposes, such as indicating the endurance capacity of athletes or serving as a metric in estimating the disease risk of a person. In general, the direct measurement of VO2max provides the most accurate assessment of aerobic power. However, despite a high level of accuracy, practical limitations associated with the direct measurement of VO2max, such as the requirement of expensive and sophisticated laboratory equipment or trained staff, have led to the development of various regression models for predicting VO2max. Consequently, a lot of studies have been conducted in the last years to predict VO2max of various target audiences, ranging from soccer athletes, nonexpert swimmers, cross-country skiers to healthy-fit adults, teenagers, and children. Numerous prediction models have been developed using different sets of predictor variables and a variety of machine learning and statistical methods, including support vector machine, multilayer perceptron, general regression neural network, and multiple linear regression. The purpose of this study is to give a detailed overview about the data-driven modeling studies for the prediction of VO2max conducted in recent years and to compare the performance of various VO2max prediction models reported in related literature in terms of two well-known metrics, namely, multiple correlation coefficient (R) and standard error of estimate. The survey results reveal that with respect to regression methods used to develop prediction models, support vector machine, in general, shows better performance than other methods, whereas multiple linear regression exhibits the worst performance.

  13. Kinetics of the exchange of oxygen between carbon dioxide and carbonate in aqueous solution

    International Nuclear Information System (INIS)

    Tu, C.K.; Silverman, D.N.

    1975-01-01

    A kinetic analysis of the exchange of oxygen between carbon dioxide and carbonate ion in alkaline, aqueous solutions is presented. The exchange was observed by placing 18 O-labeled carbonate, not enriched in 13 C, into solution with 13 C-enriched carbonate, not enriched in 18 O. The rate of depletion of 18 O from the 12 C-containing species and the rate of appearance of 18 O in the 13 C-containing species was measured by mass spectrometry. From these data, the second-order rate constant for the reaction between carbon dioxide and carbonate which results in the exchange of oxygen at 25 0 is 114 +- 11 M -1 sec -1 . It is emphasized that this exchange of oxygen between species of CO 2 in solution must be recognized in studies using 18 O labels to determine the fate of CO 2 in biochemical and physiological processes. (auth)

  14. Study on kinetics of glucose uptake by some species of plankton

    Science.gov (United States)

    Li, Wenquan; Wang, Xian; Zhang, Yaohua

    1993-03-01

    The rates of glucose uptake by some species of plankton were determined by3H-glucose tracer method. Experimental results indicated that the observed glucose uptake at natural seawater concentrations by Platymonas subcordiformis and Brachionus plicatilis was principally a metabolic process fitted with the Michaelis-Menten equation in the range of adaptive temperatures. Heterotrophic uptake by Platymonas subcordiformis was mainly dependent on diffusion at high glucose levels. The uptake by Brachionus plicatilis showed active transport even at high glucose levels, indicating its high heterotrophic activity. The uptake rate by Artemia salina was lower, and its V m/K ratio was lower than those of the other two species of plankton.

  15. Root-exuded acid phosphatase and 32Pi-uptake kinetics of wheat, rye and triticale under phosphorus starvation

    International Nuclear Information System (INIS)

    Pandey, Renu

    2006-01-01

    A nutrient culture experiment was conducted with cereal species viz., wheat (Triticum aestivum L.) cv. PBW-343), rye (Secale cereale L cv. R-308) and triticale (Triticale octoploide L. cv. DT-46), a hybrid of wheat and rye, to examine the genetic variation in root-exuded acid phosphatase (ACPase) activity and kinetics of 32 Pi-uptake under P deficient condition. The ACPase activity was assayed in the extract (intra-) and on surface (extra-cellular) or root, using p-nitrophenyl phosphate as substrate. Significantly higher ACPase activity was observed in wheat followed by rye and triticale both on the root surface and in root extract. In general, root surface ACPase activity was 2.2-fold higher than that in root extract. A strong correlation (r 2 = 0.87**) between extra and intra-cellular ACPase activity was observed. In terms of kinetic parameters, it was observed that 32 Pi uptake and I max values were significantly higher in rye while C min and K m were lowest compared to wheat and triticale. The dry weights of shoot, root and total plant were significantly higher in rye compared to wheat and triticale. Rye also had higher amount of total plant P content The superiority of rye over wheat and triticale in P uptake was observed mainly due to efficient Pi-uptake system, which needs further studies to ascertain the enhancement of Pi-induced high-affinity P transporter in these cereals. (author)

  16. Artifacts in measuring aerosol uptake kinetics: the roles of time, concentration and adsorption

    Directory of Open Access Journals (Sweden)

    L. H. Renbaum

    2011-07-01

    Full Text Available In laboratory studies of organic aerosol particles reacting with gas-phase oxidants, high concentrations of radicals are often used to study on the timescale of seconds reactions which may be occurring over days or weeks in the troposphere. Implicit in this approach is the assumption that radical concentration and time are interchangeable parameters, though this has not been established. Here, the kinetics of OH- and Cl-initiated oxidation reactions of model single-component liquid (squalane and supercooled (brassidic acid and 2-octyldodecanoic acid organic aerosols are studied by varying separately the radical concentration and the reaction time. Two separate flow tubes with residence times of 2 and 66 s are used, and [OH] and [Cl] are varied by adjusting either the laser photolysis fluence or the radical precursor concentration ([O3] or [Cl2], respectively used to generate the radicals. It is found that the rates measured by varying the radical concentration and the reaction time are equal only if the precursor concentrations are the same in the two approaches. Further, the rates depend on the concentrations of the precursor species with a Langmuir-type functional form suggesting that O3 and Cl2 saturate the surface of the liquid particles. It is believed that the presence of O3 inhibits the rate of OH reaction, perhaps by reacting with OH radicals or by O3 or intermediate species blocking surface sites, while Cl2 enhances the rate of Cl reaction by participating in a radical chain mechanism. These results have important implications for laboratory experiments in which high concentrations of gas-phase oxidants are used to study atmospheric reactions over short timescales and may explain the variability in recent measurements of the reactive uptake of OH on squalane particles in reactor systems used in this and other laboratories.

  17. Kinetics and mechanism of oxygen reduction reaction at CoPd system synthesized on XC72

    International Nuclear Information System (INIS)

    Tarasevich, M.R.; Chalykh, A.E.; Bogdanovskaya, V.A.; Kuznetsova, L.N.; Kapustina, N.A.; Efremov, B.N.; Ehrenburg, M.R.; Reznikova, L.A.

    2006-01-01

    Studies are presented of the kinetics and mechanism of oxygen electroreduction reaction on CoPd catalysts synthesized on carbon black XC72. As shown both in model conditions and in the tests within the cathodes of hydrogen-oxygen fuel cells with proton conducting electrolyte, CoPd/C system features a higher activity, as compared to Co/C. The highest activity in the oxygen reduction reaction is demonstrated by the catalysts with the Pd:Co atomic ratio being 7:3 and 4:1. The structural studies (XPS and XRD, and also the data of CO desorption measurements) evidence the CoPd alloy formation, which is reflected in the negative shift of the bonding energy maximum as compared to Pd/C and in the appearance of the additional CO desorption maximums on the voltammograms. It is found by means of structural research that CoPd alloy is formed in the course of the catalyst synthesis which features a higher catalytic activity of the binary systems. Besides, CoPd/C catalyst is more stable in respect to corrosion than Pd supported on carbon black. The measurements on the rotating disc electrode and rotating ring-disc electrode evidence that CoPd/C system provides the predominant oxygen reduction to water in the practically important range of potentials (E > 0.7 V). The proximity of kinetic parameters of the oxygen reduction reaction on CoPd/C and Pt/C catalysts points to the similar reaction mechanism. The slow step of the reaction is the addition of the first electron to the adsorbed and previously protonated O 2 molecule. The assumptions are offered about the reasons causing the higher activity and selectivity of the binary catalyst towards oxygen reduction to water, as compared to Co/C. The studies of the most active catalysts within the fuel cell cathodes are performed

  18. Relative contributions of copper oxide nanoparticles and dissolved copper to Cu uptake kinetics of Gulf killifish (Fundulus grandis) embryos

    Science.gov (United States)

    Jiang, Chuanjia; Castellon, Benjamin T.; Matson, Cole W.; Aiken, George R.; Hsu-Kim, Heileen

    2017-01-01

    The toxicity of soluble metal-based nanomaterials may be due to the uptake of metals in both dissolved and nanoparticulate forms, but the relative contributions of these different forms to overall metal uptake rates under environmental conditions are not quantitatively defined. Here, we investigated the linkage between the dissolution rates of copper(II) oxide (CuO) nanoparticles (NPs) and their bioavailability to Gulf killifish (Fundulus grandis) embryos, with the aim of quantitatively delineating the relative contributions of nanoparticulate and dissolved species for Cu uptake. Gulf killifish embryos were exposed to dissolved Cu and CuO NP mixtures comprising a range of pH values (6.3–7.5) and three types of natural organic matter (NOM) isolates at various concentrations (0.1–10 mg-C L–1), resulting in a wide range of CuO NP dissolution rates that subsequently influenced Cu uptake. First-order dissolution rate constants of CuO NPs increased with increasing NOM concentration and for NOM isolates with higher aromaticity, as indicated by specific ultraviolet absorbance (SUVA), while Cu uptake rate constants of both dissolved Cu and CuO NP decreased with NOM concentration and aromaticity. As a result, the relative contribution of dissolved Cu and nanoparticulate CuO species for the overall Cu uptake rate was insensitive to NOM type or concentration but largely determined by the percentage of CuO that dissolved. These findings highlight SUVA and aromaticity as key NOM properties affecting the dissolution kinetics and bioavailability of soluble metal-based nanomaterials in organic-rich waters. These properties could be used in the incorporation of dissolution kinetics into predictive models for environmental risks of nanomaterials.

  19. Do individuals with intellectual disability have a lower peak heart rate and maximal oxygen uptake?

    Science.gov (United States)

    Hilgenkamp, Thessa Irena Maria; Baynard, Tracy

    2017-12-12

    Individuals with intellectual disability (ID) have very low physical activity and low peak oxygen uptake (VO 2peak ), potentially explained by physiologically lower peak heart rates (HR peak ). The present authors performed a retrospective analysis of a large data set of individuals with intellectual disability (n = 100), with Down syndrome (DS) (n = 48) and without intellectual disability (n = 224) using multiple linear regression analyses, to determine if individuals with intellectual disability exhibit lower HR peak and VO 2peak than individuals without intellectual disability, controlling for age, sex and body mass index (BMI). Individuals with intellectual disability on average have significantly lower HR peak and VO 2peak than individuals without intellectual disability, even when controlling VO 2peak for the lower HR peak . This study suggests potential physiological differences in individuals with intellectual disability and warrants further investigation to determine their relevance to physical activity promotion and exercise testing in individuals with intellectual disability. © 2017 John Wiley & Sons Ltd.

  20. Relationship between changes in haemoglobin mass and maximal oxygen uptake after hypoxic exposure.

    Science.gov (United States)

    Saunders, Philo U; Garvican-Lewis, Laura A; Schmidt, Walter F; Gore, Christopher J

    2013-12-01

    Endurance athletes have been using altitude training for decades to improve near sea-level performance. The predominant mechanism is thought to be accelerated erythropoiesis increasing haemoglobin mass (Hb(mass)) resulting in a greater maximal oxygen uptake (VO₂(max)). Not all studies have shown a proportionate increase in VO₂(max) as a result of increased Hb(mass). The aim of this study was to determine the relationship between the two parameters in a large group of endurance athletes after altitude training. 145 elite endurance athletes (94 male and 51 female) who participated in various altitude studies as altitude or control participants were used for the analysis. Participants performed Hb(mass) and VO₂(max) testing before and after intervention. For the pooled data, the correlation between per cent change in Hb(mass) and per cent change in VO₂(max) was significant (pstatistical power, we conclude that altitude training of endurance athletes will result in an increase in VO₂(max) of more than half the magnitude of the increase in Hb(mass), which supports the use of altitude training by athletes. But race performance is not perfectly related to relative VO₂(max), and other non-haematological factors altered from altitude training, such as running economy and lactate threshold, may also be beneficial to performance.

  1. Root porosity and radial oxygen loss related to arsenic tolerance and uptake in wetland plants

    International Nuclear Information System (INIS)

    Li, H.; Ye, Z.H.; Wei, Z.J.; Wong, M.H.

    2011-01-01

    The rates of radial oxygen loss (ROL), root porosity, concentrations of arsenic (As), iron (Fe) and manganese (Mn) in shoot and root tissues and on root surfaces, As tolerances, and their relationships in different wetland plants were investigated based on a hydroponic experiment (control, 0.8, 1.6 mg As L -1 ) and a soil pot trail (control, 60 mg As kg -1 ). The results revealed that wetland plants showed great differences in root porosity (9-64%), rates of ROL (55-1750 mmo1 O 2 kg -1 root d.w. d -1 ), As uptake (e.g., 8.8-151 mg kg -1 in shoots in 0.8 mg As L -1 treatment), translocation factor (2.1-47% in 0.8 mg As L -1 ) and tolerance (29-106% in 0.8 mg As L -1 ). Wetland plants with higher rates of ROL and root porosity tended to form more Fe/Mn plaque, possess higher As tolerance, higher concentrations of As on root surfaces and a lower As translocation factor so decreasing As toxicity. - Research highlights: → There is significant correlation between the porosity of roots and rates of ROL. → The rates of ROL are significantly correlated with tolerance indices and concentrations of As, Fe, Mn on root surface. → The rates of ROL is negatively correlated with As translocation factor. - Wetland plants with high rates of ROL tended to form more Fe plaque on root surfaces and possess higher As tolerance.

  2. Effect of maximal oxygen uptake and different forms of physical training on serum lipoproteins.

    Science.gov (United States)

    Schnabel, A; Kindermann, W

    1982-01-01

    260 well trained male sportsmen between 17 and 30 years of age participating in a variety of events were examined for total serum cholesterol and lipoprotein cholesterol and compared with 37 moderately active leisure-time sportsmen and 20 sedentary controls of similar ages and sex. Lipoprotein cholesterol distribution was determined by quantitative electrophoresis. Mean HDL-cholesterol increased progressively from the mean of the sedentary control to the mean of the long-distance runners, indicating a graded effect of physical activity on HDL-cholesterol. In all sporting groups mean LDL-cholesterol tended to be lower than in the controls, no association between LDL-cholesterol and form of training being apparent. Except for the long-distance runners, all sporting groups tended to be lower in total cholesterol than the controls. The HDL-/total cholesterol and LDL/HDL ratios yielded a better discrimination between the physically active and inactive than the HDL-cholesterol alone. Significant positive correlations with maximal oxygen uptake and roentgenologically determined heart volume were found for HDL-cholesterol and HDL-/total cholesterol, and negative ones for LDL/HDL. Differences in the regressions among subsets made up of sporting groups under different physical demands suggest a positive relationship between lipoprotein distribution and the magnitude of the trained muscle mass.

  3. The effect of caffeine on maximal oxygen uptake and vertical jump performance in male basketball players.

    Science.gov (United States)

    Tucker, Matthew A; Hargreaves, Jill M; Clarke, Jenny C; Dale, Darren L; Blackwell, Gavin J

    2013-02-01

    This study investigated whether performance enhancement from caffeine described by other researchers transfers to male basketball players. The effects of caffeine ingestion were studied in a maximal-effort test on a treadmill that was followed by a vertical-jump test. Five elite-level male basketball players completed a graded treadmill test that measured maximal oxygen uptake, blood lactate profiles, respiratory exchange ratio, and rating of perceived exertion at each 3-minute stage. After a 15-minute warm-down, the subjects performed 10 vertical rebound jumps. Each subject completed the test twice--once with a 3 mg·kg(-1) of body weight dose of caffeine and once with a placebo, with the dosage administered 60 minutes before commencement of exercise. The test was thus administered according to a double-blind protocol. No substantial trends were found between caffeine and control trials, regardless of trial order. The study showed that the specified dosage had negligible effects on the players' power and endurance performance and had no efficacy as an ergogenic aid for male basketball players.

  4. The Impact of Firefighter Personal Protective Equipment and Treadmill Protocol on Maximal Oxygen Uptake

    Science.gov (United States)

    Lee, Joo-Young; Bakri, Ilham; Kim, Jung-Hyun; Son, Su-Young; Tochihara, Yutaka

    2015-01-01

    This study investigated the effects of firefighter personal protective equipment (PPE) on the determination of maximal oxygen uptake (VO2max) while using two different treadmill protocols: a progressive incline protocol (PIP) and a progressive speed protocol (PSP), with three clothing conditions (Light-light clothing; Boots-PPE with rubber boots; Shoes-PPE with running shoes). Bruce protocol with Light was performed for a reference test. Results showed there was no difference in VO2max between Bruce Light, PIP Light, and PSP Light. However, VO2max was reduced in Boots and Shoes with shortened maximal performance time (7 and 6 min reduced for PIP Boots and Shoes, respectively; 11 and 9 min reduced for PSP Boots and Shoes, respectively), whereas the increasing rate of VO2 in Boots and Shoes during submaximal exercise was greater compared with Light. Wearing firefighter boots compared with wearing running shoes also significantly affected submaximal VO2 but not VO2max. These results suggest that firefighters’ maximal performance determined from a typical VO2max test without wearing PPE may overestimate the actual performance capability of firefighters wearing PPE. PMID:23668854

  5. Chromium and zinc uptake by algae Gelidium and agar extraction algal waste: kinetics and equilibrium.

    Science.gov (United States)

    Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

    2007-11-19

    Biosorption of chromium and zinc ions by an industrial algal waste, from agar extraction industry has been studied in a batch system. This biosorbent was compared with the algae Gelidium itself, which is the raw material for agar extraction, and the industrial waste immobilized with polyacrylonitrile (composite material). Langmuir and Langmuir-Freundlich equilibrium models describe well the equilibrium data. The parameters of Langmuir equilibrium model at pH 5.3 and 20 degrees C were for the algae, q(L)=18 mg Cr(III)g(-1) and 13 mgZn(II)g(-1), K(L) = 0.021l mg(-1)Cr(III) and 0.026l mg(-1) Zn(II); for the algal waste, q(L)=12 mgCr(III)g(-1) and 7mgZn(II)g(-1), K(L)=0.033lmg(-1) Cr(III) and 0.042l mg(-1) Zn(II); for the composite material, q(L) = 9 mgCr(III)g(-1) and 6 mgZn(II)g(-1), K(L)=0.032l mg(-1)Cr(III) and 0.034l mg(-1)Zn(II). The biosorbents exhibited a higher preference for Cr(III) ions and algae Gelidium is the best one. The pseudo-first-order Lagergren and pseudo-second-order models fitted well the kinetic data for the two metal ions. Kinetic constants and equilibrium uptake concentrations given by the pseudo-second-order model for an initial Cr(III) and Zn(II) concentration of approximately 100 mgl(-1), at pH 5.3 and 20 degrees C were k(2,ads)=0.04 g mg(-1)Cr(III)min(-1) and 0.07 g mg(-1)Zn(II)min(-1), q(eq)=11.9 mgCr(III)g(-1) and 9.5 mgZn(II)g(-1) for algae; k(2,ads)=0.17 g mg(-1)Cr(III)min(-1) and 0.19 g mg(-1)Zn(II)min(-1), q(eq)=8.3 mgCr(III)g(-1) and 5.6 mgZn(II)g(-1) for algal waste; k(2,ads)=0.01 g mg(-1)Cr(III)min(-1) and 0.18 g mg(-1)Zn(II)min(-1), q(eq)=8.0 mgCr(III)g(-1) and 4.4 mgZn(II)g(-1) for composite material. Biosorption was modelled using a batch adsorber mass transfer kinetic model, which successfully predicts Cr(III) and Zn(II) concentration profiles. The calculated average homogeneous diffusivities, D(h), were 4.2 x 10(-8), 8.3 x 10(-8) and 1.4 x 10(-8)cm(2)s(-1) for Cr(III) and 4.8 x 10(-8), 9.7 x 10(-8) and 6.2 x 10(-8)cm(2)s(-1

  6. Isotopic exchange between CO2 and H2O and labelling kinetics of photosynthetic oxygen

    International Nuclear Information System (INIS)

    Gerster, Richard

    1971-01-01

    The reaction of carbon dioxide with water has been studied by measuring the rate of oxygen exchange between C 18 O 2 and H 2 16 O. The mathematical treatment of the kinetics allows to determine with accuracy the diffusion flow between the gas and the liquid phase, in the same way as the CO 2 hydration rate. The velocity constant of this last process, whose value gives the in situ enzymatic activity of carbonic anhydrase, has been established in the case of chloroplast and Euglena suspensions and of aerial leaves. The study of the isotopic exchange between C 18 O 2 and a vegetable submitted to alternations of dark and light has allowed to calculate the isotopic abundance of the metabolized CO 2 whose value has been compared to that of the intracellular water and that of photosynthetic oxygen. In addition, a new method using 13 C 18 O 2 gives the means to measure with accuracy eventual isotopic effects. The labelling kinetics of the oxygen evolved by Euglena suspensions whose water has been enriched with 18 O have been established at different temperatures. (author) [fr

  7. Cinética do consumo de oxigênio e tempo limite na vvo2max: comparação entre homens e mulheres Oxygen uptake kinetics and threshold time at the vVO2max: tomparison between men and women

    Directory of Open Access Journals (Sweden)

    Paulo Henrique Silva Marques de Azevedo

    2010-08-01

    Full Text Available Foi investigada a influência do gênero no tempo limite (Tlim e na cinética do VO2 durante corrida na velocidade associada ao VO2max (vVO2max em nove homens e nove mulheres, todos adultos, jovens e sedentários, com idades entre 20 e 30 anos. Homens e mulheres realizaram dois testes em esteira rolante, sendo um teste incremental para determinar VO2max (42,66 ± 4,50 vs. 32,92 ± 6,03mL.kg-1.min-1 e vVO2max (13.2 ± 1.5 vs. 10,3 ± 2,0km.h-1, respectivamente. Um segundo teste com carga constante na vVO2max até a exaustão. O Tlim e a cinética do VO2 foram determinados. Não houve diferença significante entre homens e mulheres para constante de tempo (τ (35,76 ± 21,03 vs. 36,5 ± 6,21s, respectivamente; P = 0,29; Tlim (308 ± 84,3 vs. 282,11 ± 57,19s, respectivamente; P = 0,68, tempo para atingir o VO2max (TAVO2max (164,48 ± 96,73 vs. 167,88 ± 28,59s, respectivamente; P = 0,29, tempo para atingir o VO2max em percentual do Tlim (%Tlim (50,24 ± 16,93 vs. 62,63 ± 16,60%, respectivamente; P = 0,19, tempo mantido no VO2max (TMVO2max (144,08 ± 42,55 vs. 114,23 ± 76,96s, respectivamente; P = 0,13. Estes resultados sugerem que a cinética do VO2 e o Tlim são similares entre homens e mulheres sedentários na vVO2max.The aim of this study was to investigate the influence of gender on Tthre and VO2 response during running exercise performed at vVO2max. Therefore, eighteen untrained individuals (9 male and 9 female with normal weight and aged between 20 - 30 years (VO2max = 42.66 ± 4.50 vs 32.92 ± 6.03 mL.kg-1.min-1 and vVO2max = 13.2 ± 1.5 vs 10.3 ± 2.0 km.h-1, for male and female, respectively were assessed. Subjects performed two exercise tests on treadmill. First one was an incremental test to determine VO2max, velocity at VO2max (vVO2max and second test was performed at steady velocity - vVO2max - until exhaustion. The threshold time (Tthre and VO2 kinetics response was determined. No significant differences were observed between men

  8. Oxygen uptake during Wingate tests for arms and legs in swimmers and water polo players

    Directory of Open Access Journals (Sweden)

    Colantonio Emilson

    2003-01-01

    Full Text Available OBJECTIVE: The aim of the present study is to compare the values of the maximal oxygen uptake (O2 max during two consecutive bouts in Wingate tests for arms and legs in swimmers (S and water polo players (WP. METHODS: Sample - seven national level athletes (4 S and 3 WP, age 17,90 ± 2,14 years, body mass 71,41 ± 6,84 kg, height 176,65 ± 7,02 cm, % body fat 13,23 ± 4,18. Two Wingate bouts with 30 sec each with 3 min interval between them, for arms and legs in alternated days. Oxygen uptake: breath-by-breath using the gas analysis system K4 b² Cosmed. Statistical analysis: Wilcoxon test for dependent variables and Kolmogorov-Smirnov test for independent variables. RESULTS: The mean values found at the O2 peak (PO2, mean power (MP and peak power (PP for each bout of the Wingate test, for arms and legs. For Arms: PO2 = 55.16 ± 5.72 ml.kg-1.min-1, MP = 5.28 ± 0.59 watts.kg-1 and PP = 6.71 ± 0.88 watts.kg-1 got in the first bout (1st Arms and PO2 = 60.12 ± 6.10 ml.kg-1.min-1, MP = 5.03 ± 0.40 watts.kg-1 and PP = 6.25 ± 0.51 watts.kg-1, got in the second bout (2nd Arms. For legs: PO2 = 55.66 ± 6.85 ml.kg-1.min-1, MP = 4.75 ± 1.79 watts.kg-1 and PP = 7.44 ± 1.96 watts.kg-1 got in the first bout (1st Legs and PO2 = 62.09 ± 5.99 ml.kg-1.min-1, MP = 4.28 ± 1.47 watts.kg-1 and PP = 6.68 ± 1.63 watts.kg-1 got in the second bout (2nd Legs. DISCUSSION AND CONCLUSION: All variables studied did not present significant difference among arms and legs, as much the first as the second bout for arms for PO2 (p < 0.05. There was no difference between the PM mean values of the first and the second bout. But the mean of the second bout of legs was significant smaller than the first bout (p < 0.05. For the PP variable there was no difference among the mean values to the first and second bout as much for arms as for legs. It looks like to exist larger magnitude to O2 adjustment for arms than legs, that could be associated to specific demands to which S

  9. Opposite effects of WR-2721 and WR-1065 on radiation-induced hypothermia: possible correlation with oxygen uptake

    International Nuclear Information System (INIS)

    Kandasamy, S.B.; Kumar, K.S.; Hunt, W.A.; Weiss, J.F.

    1988-01-01

    Ionizing radiation induces hypothermia in guinea pigs. While systemic injection of the radioprotectant S-2-(3-aminopropylamino)ethylphosphorothioic acid (WR-2721) did not block hyperthermia induced by exposure to 10 Gy of gamma radiation, central administration did attenuate it. The dephosphorylated metabolite of WR-2721, N-(2-mercaptoethyl)-1,3-diaminopropane (WR-1065), accentuated radiation-induced hypothermia by both routes of administration. In brain homogenates, oxygen uptake was inhibited by WR-2721 but elevated by WR-1065. These results suggest that the antagonism of radiation-induced hypothermia found only after central administration of WR-2721 is due to its direct actions and not to its dephosphorylated metabolite and that this effect may be correlated with the inhibition by WR-2721 of oxygen uptake

  10. Uptake of vaporized molybdenum and cesium tracers by molten oxide mixtures as function of free oxygen ion activity

    International Nuclear Information System (INIS)

    Carmon, B.

    1975-11-01

    Molten mixtures of oxides containing Ca, Fe, Al, Na and Si were exposed to vaporized Mo-99 and Cs-137 tracers at 1100 and 1300 deg C. Uptake values at 1300 deg C were extrapolated to short heating times. The obtained ''attachment coefficients'' for that temperature are shown to have the relationship (Mo) approximately equal to (Cs)sup(-1/2). The chemical composition of the melts and their oxygen to metal ratio found to affect the uptake of both tracers. This is associated with the cationic field strengths and the free oxygen ion activities in the mixtures. Molybdenum and cesium apparently behave like glass-network forming and glass-network modifying species, respectively. (author)

  11. EFFECTS OF IMMOBILIZATION IN Ba-ALGINATE ON NITRILE-DEPENDENT OXYGEN UPTAKE RATES OF CANDIDA GUILLIERMONDII

    Directory of Open Access Journals (Sweden)

    Dias João Carlos Teixeira

    2001-01-01

    Full Text Available Yeast cells immobilized by entrapment in Ba-alginate gel were investigated for growth pattern and respiratory activity. The oxygen uptake rates (OUR of cells entrapped in gels with 4% alginate were 5.2 and 23% lower than the OUR of 2% alginate and free cells, respectively. The mass-transfer resistance offered by the matrix and growth of the entrapped cells determine a gradient of nutrients throughout the gel which is responsible for both a lower specific growth rate of immobilized cells with respect to that of free ones, and a heterogeneous biomass distribution, with progressively increasing cellular density from the inside to the outside of the matrix. Gel-matrix polymer concentration affected the maximum oxygen uptake of immobilized growing yeast cells.

  12. Peak Exercise Oxygen Uptake Predicts Recurrent Admissions in Heart Failure With Preserved Ejection Fraction.

    Science.gov (United States)

    Palau, Patricia; Domínguez, Eloy; Núñez, Eduardo; Ramón, José María; López, Laura; Melero, Joana; Sanchis, Juan; Bellver, Alejandro; Santas, Enrique; Bayes-Genis, Antoni; Chorro, Francisco J; Núñez, Julio

    2018-04-01

    Heart failure with preserved ejection fraction (HFpEF) is a highly prevalent syndrome with an elevated risk of morbidity and mortality. To date, there is scarce evidence on the role of peak exercise oxygen uptake (peak VO 2 ) for predicting the morbidity burden in HFpEF. We sought to evaluate the association between peak VO 2 and the risk of recurrent hospitalizations in patients with HFpEF. A total of 74 stable symptomatic patients with HFpEF underwent a cardiopulmonary exercise test between June 2012 and May 2016. A negative binomial regression method was used to determine the association between the percentage of predicted peak VO 2 (pp-peak VO 2 ) and recurrent hospitalizations. Risk estimates are reported as incidence rate ratios. The mean age was 72.5 ± 9.1 years, 53% were women, and all patients were in New York Heart Association functional class II to III. Mean peak VO 2 and median pp-peak VO 2 were 10 ± 2.8mL/min/kg and 60% (range, 47-67), respectively. During a median follow-up of 276 days [interquartile range, 153-1231], 84 all-cause hospitalizations in 31 patients (41.9%) were registered. A total of 15 (20.3%) deaths were also recorded. On multivariate analysis, accounting for mortality as a terminal event, pp-peak VO 2 was independently and linearly associated with the risk of recurrent admission. Thus, and modeled as continuous, a 10% decrease of pp-peak VO 2 increased the risk of recurrent hospitalizations by 32% (IRR, 1.32; 95%CI, 1.03-1.68; P = .028). In symptomatic elderly patients with HFpEF, pp-peak VO 2 predicts all-cause recurrent admission. Copyright © 2017 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.

  13. Application of the allometric scale for the submaximal oxygen uptake in runners and rowers

    Directory of Open Access Journals (Sweden)

    M.P. Tartaruga

    2010-12-01

    Full Text Available Background: The aim of the current study was to determine the allometric exponents for runners and rower’s metabolic cost, while also verifying the relation of performance with and without the allometric application. Methods: Eleven runners (age: 22.3±10.4 years; height: 174±8.8 cm; body mass: 61.7±9.3 kg; maximum oxygen uptake ( •VO2max: 56.3±3.9 ml.kg[sup]-1[/sup].min[sup]-1[/sup] and fifteen rowers (age: 24±5.4 years; height: 185.5±6.5 cm; body mass: 83.5±7.2 kg; •VO2max: 61.2±3.4 ml.kg[sup]-1[/sup].min[sup]-1[/sup] carried out a specific progressive maximum test. The allometric exponent was determined from the logarithmic equation Log y = Log b Log x, where x is the mass, y is the VO2max (l.min[sup]-1[/sup], a is one constant and b is the allometric exponent. The data were analyzed using descriptive and comparative statistics (independent T test of the Student, with p<0.05 (SPSS version 13.0. Results: The allometric exponent of the rowers was 0.70 and that of the runners was 1.00. Significant differences were found between the fat mass percentage, with higher value for rowers, suggesting that this variable may influence the behavior of the allometric exponent and consequently of the basal metabolic rate. Conclusions: Scaling may help in understanding variation in aerobic power and in defining the physiological limitations of work capacity.

  14. Physical activity as a long-term predictor of peak oxygen uptake: the HUNT Study.

    Science.gov (United States)

    Aspenes, Stian Thoresen; Nauman, Javaid; Nilsen, Tom Ivar Lund; Vatten, Lars Johan; Wisløff, Ulrik

    2011-09-01

    A physically active lifestyle and a relatively high level of cardiorespiratory fitness are important for longevity and long-term health. No population-based study has prospectively assessed the association of physical activity levels with long-term peak oxygen uptake (VO(2peak)). 1843 individuals (906 women and 937 men) who were between 18 and 66 yr at baseline and were free from known lung or heart diseases at both baseline (1984-1986) and follow-up (2006-2008) were included in the study. Self-reported physical activity was recorded at both occasions, and VO(2peak) was measured at follow-up. The association of physical activity levels and VO(2peak) was adjusted for age, level of education, smoking status, and weight change from baseline to follow-up, using ANCOVA statistics. The level of physical activity at baseline was strongly associated with VO(2peak) at follow-up 23 yr later in both men and women (Ptrends active at baseline had higher (3.3 and 4.6 mL·kg(-1)·min(-1)) VO(2peak) at follow-up. Women who were inactive at baseline but highly active at follow-up had 3.7 mL·kg(-1)·min(-1) higher VO(2peak) compared with women who were inactive both at baseline and at follow-up. The corresponding comparison in men showed a difference of 5.2 mL·kg(-1)·min(-1) (95% confidence interval = 3.1-7.3) in VO(2peak). Physical activity level at baseline was positively associated with directly measured cardiorespiratory fitness (VO(2peak)) 23 yr later. People who changed from low to high activity during the observation period had substantially higher V˙O(2peak) at follow-up compared with people whose activity remained low.

  15. Effect of wearing clothes on oxygen uptake and ratings of perceived exertion while swimming.

    Science.gov (United States)

    Choi, S W; Kurokawa, T; Ebisu, Y; Kikkawa, K; Shiokawa, M; Yamasaki, M

    2000-07-01

    For a comparative study between swimming in swimwear (control-sw) and swimming in clothes (clothes-sw), oxygen uptake (VO2) and ratings of perceived exertion (RPE) were measured. The subjects were six male members of a university swimming team. Three swimming strokes--the breaststroke, the front crawl stroke and the elementary backstroke--were applied. With regards to clothes-sw, swimmers wore T-shirts, sportswear (shirt and pants) over swimwear and running shoes. In both cases of control-sw and clothes-sw, the VO2 was increased exponentially with increased swimming speed. The VO2 of the subjects during the clothed tests did not exceed 1.4 times of that in the case of control-sw at swimming speeds below 0.3 m/s. As swimming speeds increased, VO2 difference in both cases increased. Consequently, VO2 in the clothed tests was equal to 1.5-1.6 times and 1.5-1.8 times of that in the swimwear tests at speeds of 0.5 and 0.7 m/s, respectively. At speeds below 0.6 m/s in clothes-sw, the breaststroke showed lower VO2 than the front crawl stroke, and the elementary backstroke showed higher VO2 than the other two swimming strokes. RPE increased linearly with %peak VO2. In addition, any RPE differences among the three swimming strokes were not shown in the control-sw tests. At an exercise intensity above 60 %peak VO2, clothed swimmers showed slightly higher RPE in the front crawl stroke compared to that in the two other swimming strokes.

  16. Root porosity and radial oxygen loss related to arsenic tolerance and uptake in wetland plants

    Energy Technology Data Exchange (ETDEWEB)

    Li, H. [State Key Laboratory for Bio-control, and School of Life Sciences, Sun Yat-sen University, Guangzhou 510006 (China); Croucher Institute for Environmental Sciences, and Department of Biology, Hong Kong Baptist University, Kowloon Tong (Hong Kong); Ye, Z.H., E-mail: lssyzhh@mail.sysu.edu.c [State Key Laboratory for Bio-control, and School of Life Sciences, Sun Yat-sen University, Guangzhou 510006 (China); Wei, Z.J. [School of Information and Technology, Guangdong University of Foreign Studies, Guangzhou 510275 (China); Wong, M.H., E-mail: mhwong@hkbu.edu.h [Croucher Institute for Environmental Sciences, and Department of Biology, Hong Kong Baptist University, Kowloon Tong (Hong Kong)

    2011-01-15

    The rates of radial oxygen loss (ROL), root porosity, concentrations of arsenic (As), iron (Fe) and manganese (Mn) in shoot and root tissues and on root surfaces, As tolerances, and their relationships in different wetland plants were investigated based on a hydroponic experiment (control, 0.8, 1.6 mg As L{sup -1}) and a soil pot trail (control, 60 mg As kg{sup -1}). The results revealed that wetland plants showed great differences in root porosity (9-64%), rates of ROL (55-1750 mmo1 O{sub 2} kg{sup -1} root d.w. d{sup -1}), As uptake (e.g., 8.8-151 mg kg{sup -1} in shoots in 0.8 mg As L{sup -1} treatment), translocation factor (2.1-47% in 0.8 mg As L{sup -1}) and tolerance (29-106% in 0.8 mg As L{sup -1}). Wetland plants with higher rates of ROL and root porosity tended to form more Fe/Mn plaque, possess higher As tolerance, higher concentrations of As on root surfaces and a lower As translocation factor so decreasing As toxicity. - Research highlights: There is significant correlation between the porosity of roots and rates of ROL. The rates of ROL are significantly correlated with tolerance indices and concentrations of As, Fe, Mn on root surface. The rates of ROL is negatively correlated with As translocation factor. - Wetland plants with high rates of ROL tended to form more Fe plaque on root surfaces and possess higher As tolerance.

  17. Kinetics of oxygen reduction reaction at electrochemically fabricated tin-palladium bimetallic electrocatalyst in acidic media

    Energy Technology Data Exchange (ETDEWEB)

    Miah, Md. Rezwan, E-mail: mrmche@yahoo.co [Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Mail Box G1-5, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan); Masud, Jahangir [Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Mail Box G1-5, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan); Ohsaka, Takeo, E-mail: ohsaka@echem.titech.ac.j [Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Mail Box G1-5, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan)

    2010-12-15

    In the present article, oxygen reduction reaction (ORR) at electrochemically fabricated tin-palladium (Sn-Pd) bimetallic electrocatalyst-modified glassy carbon (GC) electrode (Sn-Pd/GC electrode) in acidic media is addressed. Hydrodynamic voltammetric measurements were employed with a view to evaluating various kinetic parameters of the ORR at the Sn-Pd/GC electrode. The obtained results obviously demonstrated that the Sn-Pd bimetallic electrocatalyt substantially promoted the activity of the GC electrode and drove the ORR through an exclusive one-step four-electron pathway forming H{sub 2}O as the final product.

  18. Kinetics of oxygen reduction reaction at tin-adatoms-modified gold electrodes in acidic media

    International Nuclear Information System (INIS)

    Miah, Md. Rezwan; Ohsaka, Takeo

    2009-01-01

    In the present report, oxygen reduction reaction (ORR) at polycrystalline gold (Au (poly)) electrode in situ modified by the underpotential deposition (upd) of Sn-adatoms is addressed. The ORR was investigated at the Sn-adatoms-modified Au (poly) electrode by the hydrodynamic voltammetric technique with a view to evaluating the various related kinetic parameters. The results demonstrated that the underpotential deposited Sn-adatoms on the Au (poly) electrode substantially promoted the activity of the electrode towards an exclusive one-step four-electron ORR forming H 2 O as the final product.

  19. Kinetics of oxygen reduction reaction at electrochemically fabricated tin-palladium bimetallic electrocatalyst in acidic media

    International Nuclear Information System (INIS)

    Miah, Md. Rezwan; Masud, Jahangir; Ohsaka, Takeo

    2010-01-01

    In the present article, oxygen reduction reaction (ORR) at electrochemically fabricated tin-palladium (Sn-Pd) bimetallic electrocatalyst-modified glassy carbon (GC) electrode (Sn-Pd/GC electrode) in acidic media is addressed. Hydrodynamic voltammetric measurements were employed with a view to evaluating various kinetic parameters of the ORR at the Sn-Pd/GC electrode. The obtained results obviously demonstrated that the Sn-Pd bimetallic electrocatalyt substantially promoted the activity of the GC electrode and drove the ORR through an exclusive one-step four-electron pathway forming H 2 O as the final product.

  20. Kinetics of oxygen reduction reaction at tin-adatoms-modified gold electrodes in acidic media

    Energy Technology Data Exchange (ETDEWEB)

    Miah, Md. Rezwan [Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Mail Box G1-5, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan)], E-mail: mrmche@yahoo.com; Ohsaka, Takeo [Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Mail Box G1-5, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan)], E-mail: ohsaka@echem.titech.ac.jp

    2009-10-01

    In the present report, oxygen reduction reaction (ORR) at polycrystalline gold (Au (poly)) electrode in situ modified by the underpotential deposition (upd) of Sn-adatoms is addressed. The ORR was investigated at the Sn-adatoms-modified Au (poly) electrode by the hydrodynamic voltammetric technique with a view to evaluating the various related kinetic parameters. The results demonstrated that the underpotential deposited Sn-adatoms on the Au (poly) electrode substantially promoted the activity of the electrode towards an exclusive one-step four-electron ORR forming H{sub 2}O as the final product.

  1. Kinetics of oxygen adsorption on ZnS nanoparticles synthesized by precipitation process

    Directory of Open Access Journals (Sweden)

    Ahmadi Reza

    2016-06-01

    Full Text Available ZnS nanoparticles were synthesized through a one-step precipitation process. Effect of time and temperature on the formation reaction was investigated. The synthesized samples were characterized by X-ray diffraction (XRD, ultraviolet (UV visible absorption and photoluminescence (PL spectrophotometry. Based on XRD and UV-Vis data, the particles produced at 70 °C had a mean particle size of about 5 nm. Increasing time and temperature of the synthesis reaction resulted in photoluminescence intensification. PL spectroscopy helped understanding the adsorption kinetics of oxygen on ZnS nanoparticles during the precipitation synthesis process. Fabrication of ZnS structures with appropriate oxygen adsorption capacity was suggested as a means of PL emission intensity control.

  2. FET PET for the evaluation of untreated gliomas: correlation of FET uptake and uptake kinetics with tumour grading

    International Nuclear Information System (INIS)

    Poepperl, Gabriele; Koch, Walter; Gildehaus, Franz J.; Tatsch, Klaus; Kreth, Friedrich W.; Mehrkens, Jan H.; Tonn, Joerg C.; Herms, Jochen; Kretzschmar, Hans A.; Seelos, Klaus

    2007-01-01

    Treatment and prognosis of gliomas depend on their histological tumour grade. The aim of the study was to evaluate the potential of [ 18 F]fluoroethyltyrosine (FET) PET for non-invasive tumour grading in untreated patients. Dynamic FET PET studies were performed in 54 patients who, based on MRI, were estimated to have low grade (LG; n = 20), intermediate (WHO II-III; n = 4) or high grade (HG; n = 30) tumours. For standard evaluation, tumour SUV max and the ratio to background (SUV max /BG) were calculated (sum image: 20-40 min). For dynamic evaluation, mean SUV values within a 90% isocontour ROI (SUV90) and the SUV90/BG ratios were determined for each time frame to evaluate the course of FET uptake. Results were correlated with histopathological findings from PET-guided stereotactic biopsies. Histology revealed gliomas in all patients. Using the standard method a statistically significant difference (p = 0.001) was found between LG (n = 20; SUV max /BG: 2.16 ± 0.98) and HG (n = 34; SUV max /BG: 3.29 ± 1.06) gliomas (opt. threshold 2.58: SN71%/SP85%/area under ROC curve [AUC]:0.798), however, with a marked overlap between WHO II to IV tumours. Time activity curves showed slight increase in LG, whereas HG tumours presented with an early peak (10-20 min) followed by a decrease. Dynamic evaluation successfully separated LG from HG gliomas with higher diagnostic accuracy (SN94%/SP100%/AUC:0.967). Based on the ratio-based method, a statistically significant difference was found between LG and HG gliomas. Due to the interindividual variability, however, no reliable individual grading was possible. In contrast, dynamic evaluation allowed LG and HG gliomas to be differentiated with high diagnostic power and, thus, should supplement the conventional method. (orig.)

  3. Tritiated water uptake kinetics in tissue-free water and organically-bound fractions of tomato plants

    International Nuclear Information System (INIS)

    Spencer, F.S.

    1984-03-01

    The kinetics of tritiated water (HTO) vapour uptake into tissue-free water tritium (TFWT) and organically bound tritium (OBT) fractions of tomato, Lycopersicon esculentum Mill., cv Vendor, were investigated under controlled growing conditions. Most uptake data fitted a first-order kinetic model, C t = C ∞ (1-e -kt ), where C t is the tritium concentration at time t, Ca the steady-state concentration and k the uptake rate constant. During atmospheric-HTO exposure with clean-water irrigation in open pots the TFWT k values were 0.024 ± 0.023 h -1 for new foliage, 0.104 ± 0.067 h -1 for old foliage and 0.042 ± to 0.136 h -1 for new green fruit. OBT uptake rate constants were 20 percent less for new foliage and 76 percent less for new green fruit. Under steady-state conditions the ratio of tritium specific activities of TWFT to atmospheric HTO were 0.43 in new foliage, 0.46 in old foliage and 0.19 in green fruit. Within the plant, OBT and TFWT ratios were 0.70 for new foliage, 0.63 for old foliage (maximum) and between 0.72 and 1.92 for green fruit. The greater than unity tritium specific activity ratios in green fruit were not attributed to tritium enrichment but rather to the translocation of foliar OBT to the growing fruit which contained lower specific activity TFWT derived from soil water

  4. Evaluation of Optimum Moisture Content for Composting of Beef Manure and Bedding Material Mixtures Using Oxygen Uptake Measurement

    Directory of Open Access Journals (Sweden)

    Eunjong Kim

    2016-05-01

    Full Text Available Moisture content influences physiological characteristics of microbes and physical structure of solid matrices during composting of animal manure. If moisture content is maintained at a proper level, aerobic microorganisms show more active oxygen consumption during composting due to increased microbial activity. In this study, optimum moisture levels for composting of two bedding materials (sawdust, rice hull and two different mixtures of bedding and beef manure (BS, Beef cattle manure+sawdust; BR, Beef cattle manure+rice hull were determined based on oxygen uptake rate measured by a pressure sensor method. A broad range of oxygen uptake rates (0.3 to 33.3 mg O2/g VS d were monitored as a function of moisture level and composting feedstock type. The maximum oxygen consumption of each material was observed near the saturated condition, which ranged from 75% to 98% of water holding capacity. The optimum moisture content of BS and BR were 70% and 57% on a wet basis, respectively. Although BS’s optimum moisture content was near saturated state, its free air space kept a favorable level (above 30% for aerobic composting due to the sawdust’s coarse particle size and bulking effect.

  5. Evaluation of Optimum Moisture Content for Composting of Beef Manure and Bedding Material Mixtures Using Oxygen Uptake Measurement.

    Science.gov (United States)

    Kim, Eunjong; Lee, Dong-Hyun; Won, Seunggun; Ahn, Heekwon

    2016-05-01

    Moisture content influences physiological characteristics of microbes and physical structure of solid matrices during composting of animal manure. If moisture content is maintained at a proper level, aerobic microorganisms show more active oxygen consumption during composting due to increased microbial activity. In this study, optimum moisture levels for composting of two bedding materials (sawdust, rice hull) and two different mixtures of bedding and beef manure (BS, Beef cattle manure+sawdust; BR, Beef cattle manure+rice hull) were determined based on oxygen uptake rate measured by a pressure sensor method. A broad range of oxygen uptake rates (0.3 to 33.3 mg O2/g VS d) were monitored as a function of moisture level and composting feedstock type. The maximum oxygen consumption of each material was observed near the saturated condition, which ranged from 75% to 98% of water holding capacity. The optimum moisture content of BS and BR were 70% and 57% on a wet basis, respectively. Although BS's optimum moisture content was near saturated state, its free air space kept a favorable level (above 30%) for aerobic composting due to the sawdust's coarse particle size and bulking effect.

  6. Uptake of phosphorus from surfactant solutions by wheat leaves: spreading kinetics, wetted area, and drying time.

    Science.gov (United States)

    Peirce, Courtney A E; Priest, Craig; McBeath, Therese M; McLaughlin, Mike J

    2016-01-07

    The delivery and uptake of nutrients at the surface of plant leaves is an important physicochemical phenomenon that depends on leaf surface morphology and chemistry, fertilizer formulation chemistry (including adjuvant and associated surfactants), wetting dynamics, and many other physical, chemical and biological factors. In this study, the role of spreading dynamics in determining uptake of the macronutrient phosphorus from phosphoric acid fertilizer solution in combination with three different adjuvants was measured in the absence of droplet run-off and splashing. When run-off and splashing losses were zero, spreading and drying rates had a small to negligible effect on the uptake efficiency. The results suggest that uptake may be much less sensitive to the specific choice of adjuvant and long time-scale spreading behaviour than one might intuitively expect.

  7. Characterization of positron emission tomography hypoxia tracer uptake and tissue oxygenation via electrochemical modeling

    NARCIS (Netherlands)

    Bowen, S.R.; Kogel, A.J. van der; Nordsmark, M.; Bentzen, S.M.; Jeraj, R.

    2011-01-01

    PURPOSE: Unique uptake and retention mechanisms of positron emission tomography (PET) hypoxia tracers make in vivo comparison between them challenging. Differences in imaged uptake of two common hypoxia radiotracers, [(61)Cu]Cu-ATSM and [(18)F]FMISO, were characterized via computational modeling to

  8. Spatiotemporal variation of nitrate uptake kinetics within the maize (Zea mays L.) root system is associated with greater nitrate uptake and interactions with architectural phenes.

    Science.gov (United States)

    York, Larry M; Silberbush, Moshe; Lynch, Jonathan P

    2016-06-01

    Increasing maize nitrogen acquisition efficiency is a major goal for the 21st century. Nitrate uptake kinetics (NUK) are defined by I max and K m, which denote the maximum uptake rate and the affinity of transporters, respectively. Because NUK have been studied predominantly at the molecular and whole-root system levels, little is known about the functional importance of NUK variation within root systems. A novel method was created to measure NUK of root segments that demonstrated variation in NUK among root classes (seminal, lateral, crown, and brace). I max varied among root class, plant age, and nitrate deprivation combinations, but was most affected by plant age, which increased I max, and nitrate deprivation time, which decreased I max K m was greatest for crown roots. The functional-structural simulation SimRoot was used for sensitivity analysis of plant growth to root segment I max and K m, as well as to test interactions of I max with root system architectural phenes. Simulated plant growth was more sensitive to I max than K m, and reached an asymptote near the maximum I max observed in the empirical studies. Increasing the I max of lateral roots had the largest effect on shoot growth. Additive effects of I max and architectural phenes on nitrate uptake were observed. Empirically, only lateral root tips aged 20 d operated at the maximum I max, and simulations demonstrated that increasing all seminal and lateral classes to this maximum rate could increase plant growth by as much as 26%. Therefore, optimizing I max for all maize root classes merits attention as a promising breeding goal. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  9. KINETICS OF CATHODIC REDUCTION OF OXYGEN ON NI-CR-MO-W ALLOY

    International Nuclear Information System (INIS)

    NA

    2006-01-01

    Ni-Cr-Mo-W alloys (C-group alloys) are well known as materials with very high Corrosion resistance in very aggressive environments, an asset that has motivated the selection of Alloy 22 as a waste package material in the Yucca Mountain Project for the long-term geologic disposal of spent nuclear fuel and other high-level radioactive wastes. The aim of this project is to elucidate the corrosion performance of Alloy 22 under aggressive conditions and to provide a conceptual understanding and parameter data base that could act as a basis for modeling the corrosion performance of waste packages under Yucca Mountain conditions. A key issue in any corrosion process is whether or not the kinetics of the cathodic reactions involved can support a damaging rate of anodic metal (alloy) dissolution. Under Yucca Mountain conditions the primary oxidant available to drive corrosion (most likely in the form of crevice, or under-deposit, corrosion) will be oxygen. Here, we present results on the kinetics of oxygen reduction at the Alloy 22/solution interface

  10. Kinetics of irreversible thermal decomposition of dissociating nitrogen dioxide with nitrogen oxide or oxygen additions

    International Nuclear Information System (INIS)

    Gvozdev, A.A.

    1987-01-01

    The effect of NO or O 2 admixtures on kinetics of the irreversible thermal decomposition of nitrogen dioxide at temperatures 460-520 deg C and pressures 4-7 MPa has been studied. It follows from experimental data that the rate of N 2 O 4 formation reduces with the increase of partial pressure of oxygen or decrease of partial pressure of nitrogen oxide. The same regularity is seen for the rate of nitrogen formation. The rate constants of N 2 O formation in dissociating nitrogen tetroxide with oxygen or nitrogen oxide additions agree satisfactorily with previously published results, obtained in stoichiometric mixtures. The appreciable discrepancy at 520 deg C is bind with considerable degree of nitrogen oxide transformation which constitutes approximately 14%. It is determined that the kinetics of formation of the products of irreversible N 2 O and N 2 decomposition in stoichiometric and non-stoichiometric 2NO 2 ↔ 2NO+O 2 mixtures is described by identical 3NO → N 2 O+NO 2 and N 2 O+NO → N 2 +NO 2 reactions

  11. Removal of copper by oxygenated pyrolytic tire char: kinetics and mechanistic insights.

    Science.gov (United States)

    Quek, Augustine; Balasubramanian, Rajashekhar

    2011-04-01

    The kinetics of copper ion (Cu(II)) removal from aqueous solution by pyrolytic tire char was modeled using five different conventional models. A modification to these models was also developed through a modified equation that accounts for precipitation. Conventional first- and second-order reaction models did not fit the copper sorption kinetics well, indicating a lack of simple rate-order dependency on solute concentration. Instead, a reversible first-order rate reaction showed the best fit to the data, indicating a dependence on surface functional groups. Due to the varying solution pH during the sorption process, modified external and internal mass transfer models were employed. Results showed that the sorption of copper onto oxygenated chars was limited by external mass transfer and internal resistance with and without the modification. However, the modification of the sorption process produced very different results for unoxygenated chars, which showed neither internal nor external limitation to sorption. Instead, its slow sorption rate indicates a lack of surface functional groups. The sorption of Cu(II) by oxygenated and unoxygenated chars was also found to occur via three and two distinct stages, respectively. Copyright © 2010 Elsevier Inc. All rights reserved.

  12. Endocytosis of the major yolk proteins of the silkmoth, Hyalophora cecropia: Uptake kinetics and interactions

    International Nuclear Information System (INIS)

    Kulakosky, P.C.

    1989-01-01

    The oocytes of Lepidopteran insects take up several yolk proteins in defined proportions even though their relative availability in the hemolymph changes during the several days required to complete yolk formation in all the eggs. There are three hemolymph yolk precursors, vitellogenin, microvitellogenin and lipophorin; one precursor, paravitellogenin is produced in the ovary. The control mechanism for their proportional endocytosis is not known. In this thesis, the author describe the purification of all four proteins and the radiolabeling of the hemolymph precursors. The radiolabeled proteins were tested with an in vitro incubation system to assess the biological activity of the proteins and the reliability of the incubation methods. All of the labeled probes were transferred from the incubation medium to yolk spheres within the oocyte in a saturable, energy-dependent, and stage-specific manner. The rates of uptake were similar to the estimated rates of uptake in situ. The concentration dependence of in vitro uptake was investigated and found to be consistent with in situ concentrations and the composition of yolk in mature eggs. Two precursors, vitellogenin and lipophorin, competed for uptake indicating that they share a common binding site while the third, microvitellin, did not compete with the others. Though vitellogenin and lipophorin competed for uptake, only vitellogenin displayed the unique ability to increase the uptake rate of microvitellin and fluid in vitro

  13. Estimation of maximal oxygen uptake via submaximal exercise testing in sports, clinical, and home settings.

    Science.gov (United States)

    Sartor, Francesco; Vernillo, Gianluca; de Morree, Helma M; Bonomi, Alberto G; La Torre, Antonio; Kubis, Hans-Peter; Veicsteinas, Arsenio

    2013-09-01

    Assessment of the functional capacity of the cardiovascular system is essential in sports medicine. For athletes, the maximal oxygen uptake [Formula: see text] provides valuable information about their aerobic power. In the clinical setting, the (VO(2max)) provides important diagnostic and prognostic information in several clinical populations, such as patients with coronary artery disease or heart failure. Likewise, VO(2max) assessment can be very important to evaluate fitness in asymptomatic adults. Although direct determination of [VO(2max) is the most accurate method, it requires a maximal level of exertion, which brings a higher risk of adverse events in individuals with an intermediate to high risk of cardiovascular problems. Estimation of VO(2max) during submaximal exercise testing can offer a precious alternative. Over the past decades, many protocols have been developed for this purpose. The present review gives an overview of these submaximal protocols and aims to facilitate appropriate test selection in sports, clinical, and home settings. Several factors must be considered when selecting a protocol: (i) The population being tested and its specific needs in terms of safety, supervision, and accuracy and repeatability of the VO(2max) estimation. (ii) The parameters upon which the prediction is based (e.g. heart rate, power output, rating of perceived exertion [RPE]), as well as the need for additional clinically relevant parameters (e.g. blood pressure, ECG). (iii) The appropriate test modality that should meet the above-mentioned requirements should also be in line with the functional mobility of the target population, and depends on the available equipment. In the sports setting, high repeatability is crucial to track training-induced seasonal changes. In the clinical setting, special attention must be paid to the test modality, because multiple physiological parameters often need to be measured during test execution. When estimating VO(2max), one has

  14. A prospective population study of resting heart rate and peak oxygen uptake (the HUNT Study, Norway.

    Directory of Open Access Journals (Sweden)

    Javaid Nauman

    Full Text Available OBJECTIVES: We assessed the prospective association of resting heart rate (RHR at baseline with peak oxygen uptake (VO(2peak 23 years later, and evaluated whether physical activity (PA could modify this association. BACKGROUND: Both RHR and VO(2peak are strong and independent predictors of cardiovascular morbidity and mortality. However, the association of RHR with VO(2peak and modifying effect of PA have not been prospectively assessed in population studies. METHODS: In 807 men and 810 women free from cardiovascular disease both at baseline (1984-86 and follow-up 23 years later, RHR was recorded at both occasions, and VO(2peak was measured by ergospirometry at follow-up. We used Generalized Linear Models to assess the association of baseline RHR with VO(2peak, and to study combined effects of RHR and self-reported PA on later VO(2peak. RESULTS: There was an inverse association of RHR at baseline with VO(2peak (p<0.01. Men and women with baseline RHR greater than 80 bpm had 4.6 mL.kg(-1.min(-1 (95% confidence interval [CI], 2.8 to 6.3 and 1.4 mL.kg(-1.min(-1 (95% CI, -0.4 to 3.1 lower VO(2peak at follow-up compared with men and women with RHR below 60 bpm at baseline. We found a linear association of change in RHR with VO(2peak (p=0.03, suggesting that a decrease in RHR over time is likely to be beneficial for cardiovascular fitness. Participants with low RHR and high PA at baseline had higher VO(2peak than inactive people with relatively high RHR. However, among participants with relatively high RHR and high PA at baseline, VO(2peak was similar to inactive people with relatively low RHR. CONCLUSION: RHR is an important predictor of VO(2peak, and serial assessments of RHR may provide useful and inexpensive information on cardiovascular fitness. The results suggest that high levels of PA may compensate for the lower VO(2peak associated with a high RHR.

  15. Kinetics and autoradiography of high affinity uptake of serotonin by primary astrocyte cultures

    International Nuclear Information System (INIS)

    Katz, D.M.; Kimelberg, H.K.

    1985-01-01

    Primary astrocyte cultures prepared from the cerebral cortices of neonatal rats showed significant accumulation of serotonin (5-hydroxytryptamine; [ 3 H]-5-HT). At concentrations in the range of 0.01 to 0.7 microM [ 3 H]-5-HT, this uptake was 50 to 85% Na+ dependent and gave a Km of 0.40 +/- 0.11 microM [ 3 H]-5-HT and a Vmax of 6.42 +/- 0.85 (+/- SEM) pmol of [ 3 H]-5-HT/mg of protein/4 min for the Na+-dependent component. In the absence of Na+ the uptake was nonsaturable. Omission of the monoamine oxidase inhibitor pargyline markedly reduced the Na+-dependent component of [ 3 H]-5-HT uptake but had a negligible effect on the Na+-independent component. This suggest significant oxidative deamination of serotonin after it has been taken up by the high affinity system, followed by release of its metabolite. The authors estimated that this system enabled the cells to concentrate [ 3 H]-5-HT up to 44-fold at an external [ 3 H]-5-HT concentration of 10(-7) M. Inhibition of [ 3 H]-5-HT uptake by a number of clinically effective antidepressants was also consistent with a specific high affinity uptake mechanism for 5-HT, the order of effectiveness of inhibition being chlorimipramine greater than fluoxetine greater than imipramine = amitriptyline greater than desmethylimipramine greater than iprindole greater than mianserin. Uptake of [ 3 H]-5-HT was dependent on the presence of Cl- as well as Na+ in the medium, and the effect of omission of both ions was nonadditive. Varying the concentration of K+ in the media from 1 to 50 mM had a limited effect on [ 3 H]-5-HT uptake

  16. The role of oxygen in the uptake of deuterium in lithiated graphite

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, C. N.; Luitjohan, K. E. [School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Dadras, J. [Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37998 (United States); Allain, J. P. [School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, West Lafayette, Indiana 47907 (United States); Krstic, P. S. [Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37998 (United States); Joint Institute of Computational Sciences, University of Tennessee, Knoxville, Tennessee 37998 (United States); Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Skinner, C. H. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

    2013-12-14

    We investigate the mechanism of deuterium retention by lithiated graphite and its relationship to the oxygen concentration through surface sensitive experiments and atomistic simulations. Deposition of lithium on graphite yielded 5%–8% oxygen surface concentration and when subsequently irradiated with D ions at energies between 500 and 1000 eV/amu and fluences over 10{sup 16} cm{sup −2} the oxygen concentration rose to between 25% and 40%. These enhanced oxygen levels were reached in a few seconds compared to about 300 h when the lithiated graphite was allowed to adsorb oxygen from the ambient environment under equilibrium conditions. Irradiating graphite without lithium deposition, however, resulted in complete removal of oxygen to levels below the detection limit of XPS (e.g., <1%). These findings confirm the predictions of atomistic simulations, which had concluded that oxygen was the primary component for the enhanced hydrogen retention chemistry on the lithiated graphite surface.

  17. Leg oxygen uptake in the initial phase of intense exercise is slowed by a marked reduction in oxygen delivery

    DEFF Research Database (Denmark)

    Christensen, Peter Møller; Nyberg, Michael Permin; Mortensen, Stefan Peter

    2013-01-01

    -extensor exercise (60±3 W) for 4 min in a control setting (CON) and with arterial infusion of L-NMMA and indomethacin in the working leg to reduce blood flow by inhibiting formation of nitric oxide and prostanoids (double blockade; DB). In DB leg blood flow (LBF) and oxygen delivery during the first minute...

  18. Surface coverage of Pt atoms on PtCo nanoparticles and catalytic kinetics for oxygen reduction

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Rongzhong, E-mail: rongzhong.jiang@us.army.mi [Sensors and Electron Devices Directorate, U.S. Army Research Laboratory, 2800 Powder Mill Road, Adelphi, MD 20783-1197 (United States); Rong, Charles; Chu, Deryn [Sensors and Electron Devices Directorate, U.S. Army Research Laboratory, 2800 Powder Mill Road, Adelphi, MD 20783-1197 (United States)

    2011-02-01

    The surface coverage of Pt atoms on PtCo nanoparticles and its effect on catalytic kinetics for oxygen reduction were investigated. The PtCo nanoparticles with different surface coverage of Pt atoms were synthesized with various methods, including normal chemical method, microemulsion synthesis, and ultrasound-assisted microemulsion. A model of Pt atoms filling into a spherical nanoparticle was proposed to explain the relationship of surface metal atoms and nanoparticle size. The catalytic activity of the PtCo nano-particles is highly dependent on the synthetic methods, even if they have the same chemical composition. The PtCo nano-particles synthesized with ultrasound-assisted microemulsion showed the highest activity, which is attributed to an increase of active surface coverage of Pt atoms on the metal nanoparticles. The rate of oxygen reduction at 0.5 V (vs. SCE) catalyzed by the PtCo synthesized with ultrasound-assisted micro-emulsion was about four times higher than that of the PtCo synthesized with normal chemical method. As demonstrated with rotating-ring disk electrode measurement, the PtCo nano-particles can catalyze oxygen 4-electron reduction to water without intermediate H{sub 2}O{sub 2} detected.

  19. Effects of dipyridamole-induced vasodilation on myocardial uptake and clearance kinetics of thallium-201

    International Nuclear Information System (INIS)

    Beller, G.A.; Holzgrefe, H.H.; Watson, D.D.

    1983-01-01

    Myocardial thallium-201 (201Tl) uptake and clearance after intravenous administration of dipyridamole (150 micrograms/kg) were determined in 12 open-chest anesthetized dogs with a partial coronary artery stenosis. 201Tl (1.5 mCi) was injected intravenously and myocardial biopsy specimens were obtained 10 min, 60 min, and 2 hr after injection. Serial changes in 201Tl activity in the normal zone and in the zone of partial stenosis were correlated with microsphere-determined regional blood flow and distal coronary pressure. Another nine dogs with equivalent stenosis not given dipyridamole before 201Tl served as controls. Data indicate that dipyridamole-induced vasodilation in the presence of a partial stenosis results in diminished uptake and delayed clearance compared with increased uptake and more rapid clearance in normally perfused myocardium producing an initial 201Tl defect with delayed redistribution

  20. Uptake and kinetics of 226Ra, 210Pb and 210Po in big sage brush

    International Nuclear Information System (INIS)

    Simon, S.L.

    1985-01-01

    Root uptake of 226 Pb and 210 Po by mature sage brush was studied using a soil injection method for spiking the soil with minimal root disturbance. The main objective was to measure vegetation concentrations and determine concentration ratios (CR's) due to root uptake as a function of time in mature big sage brush. Concentration ratios obtained in mature vegetation and in steady-state situations may be valuable in assessing the impact of uranium mining and milling. The vegetation was sampled approximately every 3 mo for A 2 y period. Significant levels of activity were detected in the vegetation beginning at the first sampling (81 d after soil injection for 226 Ra, 28 d for 210 Pb and 210 Po). There was an exponential decrease in concentration to an apparent steady state value. Mean values (geometric) of the data pooled over the second year period indicated that steady-state Cr's for 226 Ra, 210 Pb and 210 Po, as determined in mature sage brush, were 0.04, 0.009, and 0.08, respectively. Investigations were also carried out to verify the suitability of soil injection for uptake studies and to evaluate the time dependence of 226 Ra leaching from sage brush leaves. The soil injection method was determined to produce, on the average, uptake equivalent to that produce by a uniform soil distribution, however, the variety of uptake for plants growing in injected soil was higher than for plants growing in uniformly contaminated soil. A three compartment mathematical model was formulated to help understand mechanisms of plant uptake and to predict, if possible, the concentration of 226 Ra, 210 Po in vegetation as a function of time after soil spiking

  1. Non-invasive differentiation of pancreatic lesions: is analysis of FDG kinetics superior to semiquantitative uptake value analysis?

    International Nuclear Information System (INIS)

    Nitzsche, E.U.; Hoegerle, S.; Mix, M.; Brink, I.; Otte, A.; Moser, E.

    2002-01-01

    The diagnostic utility of fluorine-18 2-deoxy-D-glucose positron emission tomography (FDG PET) for the non-invasive differentiation of focal pancreatic lesions originating from cancer or chronic pancreatitis by combined visual image interpretation and semiquantitative uptake value analysis has been documented. However, in clinical routine some misdiagnosis is still observed. This is because there is potential overlap between the semiquantitative uptake values obtained for active inflammatory lesions and cancer. Therefore, this prospective study was undertaken to test the hypothesis that analysis of dynamic kinetics of focal pancreatic lesions based on FDG PET may more accurately determine the benign or malignant nature of such lesions. Thirty patients (56±17 years) were studied dynamically with FDG PET for a period of 60-90 min. Patients were assigned to one of four groups: control, acute pancreatitis, chronic pancreatitis or pancreatic cancer. Two observers, blinded to the clinical data, analysed the time-activity curves of FDG kinetics based on region of interest analysis. The diagnosis predicted by FDG PET was compared with the result of histological examination of the surgical specimen. Analysis of FDG kinetics revealed significant differences in the shape of the time-activity curve for controls, pancreatic cancer and inflammatory disease. Surprisingly, there was no significant difference in the time-activity curve shape for chronic pancreatitis and acute pancreatitis; this is, however, not a clinical issue. Furthermore, acquisition time (60 min vs 90 min) did not affect interpretation of the time-activity curve, so that scanning time may be regularly shortened to 60 min. Interobserver agreement was 1. Based on these findings, non-invasive differentiation between pancreatic cancer and chronic pancreatitis was correctly predicted in all cases, as confirmed by histology. In addition, the specificity was increased compared with that obtained from standardised

  2. A kinetic study of cation release from a mixed mineral assemblage: implications for determination of uranium uptake

    International Nuclear Information System (INIS)

    Fenton, B.R.; Waite, T.D.

    1996-01-01

    The uptake of U(VI) as UO 2+ 2 on a natural complex mineral assemblage has been studied using batch selective chemical extraction techniques and secondary ion mass spectroscopy (SIMS). Sediments used in the study consisted of a quartz/mica schist collected from the locale of the Koongarra Uranium ore body, Alligator Rivers Uranium Province, Northern Territory, Australia. The bulk sediment was gravity separated into four size fractions, with attention focused on the nominally <25 μm and 250-1000 μm fractions of the bulk sample, in order to assess the effects of particle size on uranium uptake. Investigation of the kinetics of elemental release in the presence of selective extractants show that uranium is bound largely within the iron and aluminium oxyhydroxides of the assemblage, with a highly mobile fraction of this associated with aluminol sites. SIMS analysis of the natural substrate confirms that significant quantities of aluminium are present in surface layers. The effect of particle size on the uptake of uranium indicates very little change with respect to particle size. This finding may be attributed to the presence of highly porous surface coatings. (orig.)

  3. Understanding the in vivo uptake kinetics of a phosphatidylethanolamine-binding agent 99mTc-Duramycin

    International Nuclear Information System (INIS)

    Audi, Said; Li Zhixin; Capacete, Joseph; Liu Yu; Fang, Wei; Shu, Laura G.; Zhao Ming

    2012-01-01

    Introduction: 99m Tc-Duramycin is a peptide-based molecular probe that binds specifically to phosphatidylethanolamine (PE). The goal was to characterize the kinetics of molecular interactions between 99m Tc-Duramycin and the target tissue. Methods: High level of accessible PE is induced in cardiac tissues by myocardial ischemia (30 min) and reperfusion (120 min) in Sprague–Dawley rats. Target binding and biodistribution of 99m Tc-duramycin were captured using SPECT/CT. To quantify the binding kinetics, the presence of radioactivity in ischemic versus normal cardiac tissues was measured by gamma counting at 3, 10, 20, 60 and 180 min after injection. A partially inactivated form of 99m Tc-Duramycin was analyzed in the same fashion. A compartment model was developed to quantify the uptake kinetics of 99m Tc-Duramycin in normal and ischemic myocardial tissue. Results: 99m Tc-duramycin binds avidly to the damaged tissue with a high target-to-background radio. Compartment modeling shows that accessibility of binding sites in myocardial tissue to 99m Tc-Duramycin is not a limiting factor and the rate constant of target binding in the target tissue is at 2.2 ml/nmol/min/g. The number of available binding sites for 99m Tc-Duramycin in ischemic myocardium was estimated at 0.14 nmol/g. Covalent modification of D15 resulted in a 9-fold reduction in binding affinity. Conclusion: 99m Tc-Duramycin accumulates avidly in target tissues in a PE-dependent fashion. Model results reflect an efficient uptake mechanism, consistent with the low molecular weight of the radiopharmaceutical and the relatively high density of available binding sites. These data help better define the imaging utilities of 99m Tc-Duramycin as a novel PE-binding agent.

  4. Gill structural change in response to turbidity has no effect on the oxygen uptake of a juvenile sparid fish.

    Science.gov (United States)

    Cumming, H; Herbert, N A

    2016-01-01

    Turbidity as a result of increased suspended sediments in coastal waters is an environmental stress of worldwide concern. Recent research on fish suggests that detrimental changes to gill structure can occur in turbid waters, with speculation that these alterations diminish fitness variables, such as growth and development, by negatively impacting the O 2 uptake capacity (respiration) of fish. Specifically to address this unknown, the impact of turbid water on the gill structure, somatic growth rate and O 2 uptake rates of a juvenile sparid species ( Pagrus auratus ) was addressed following exposure to five different turbidity treatments (turbidity units) for 30 days. Significant gill structural change was apparent with a progressive increase in turbidity and was quantified as a reduction in lamellar density, as well as an increase in basal hyperplasia, epithelial lifting and increased oxygen diffusion distance across the lamellae. The weight of control fish did not change throughout the experiment, but all fish exposed to turbid waters lost weight, and weight loss increased with nephelometric turbidity units, confirming that long-term turbidity exposure is detrimental to growth productivity. The growth of fish could be impacted in a variety of ways, but the specific hypothesis that structural alteration of the gills impairs O 2 uptake across the gills and limits growth fitness was not supported because there was no measurable difference in the standard metabolic rate, maximal metabolic rate, aerobic metabolic scope or critical oxygen saturation limit of fish measured in clear water after 30 days of exposure. Although impaired O 2 uptake as a result of structurally adjusted gills is unlikely to be the cause of poor fish growth, the exact mechanism by which growth productivity is affected in turbid conditions remains unclear and warrants further investigation.

  5. Usefulness of decrease in oxygen uptake efficiency to identify gas exchange abnormality in patients with idiopathic pulmonary arterial hypertension.

    Directory of Open Access Journals (Sweden)

    Xiaoyue Tan

    Full Text Available BACKGROUND: Decline in oxygen uptake efficiency (OUE, especially during exercise, is found in patients with chronic heart failure. In this study we aimed to test the validity and usefulness of OUE in evaluating gas exchange abnormality of patients with idiopathic pulmonary arterial hypertension (IPAH. METHODS: We retrospectively investigated the cardiopulmonary exercise test (CPET with gas exchange measurements in 32 patients with confirmed IPAH. All patients also had resting hemodynamic measurements and pulmonary function test (PFT. Sixteen healthy subjects, matched by age, sex, and body size were used as controls, also had CPET and PFT measurements. RESULTS: In IPAH patients, the magnitude of absolute and percentage of predicted (%pred oxygen uptake efficiency slope (OUES and oxygen uptake efficiency plateau (OUEP, as well as several other CPET parameters, were strikingly worse than healthy subjects (P<0.0001. Pattern of changes in OUE in patients is similar to that in controls, In IPAH patients, OUE values at rest, warming up, anaerobic threshold and peak exercise were all significantly lower than in normal (P<0.0001. OUEP%pred, better than OUES%pred, correlated significantly with New York Heart Association (NYHA functional Class (r = -0.724, P<0.005, Total Pulmonary Vascular Resistance (TPVR (r = -0.694, P<0.005, diffusing capacity for carbon monoxide (DLCO (r = 0.577, P<0.05, and the lowest ventilation versus CO2 output ratio during exercise (LowestV˙E/V˙CO2 (r = -0.902, P<0.0001. In addition, the coefficient of variation (COV of OUEP was lower (20.9% markedly than OUES (34.3% (P<0.0001. CONCLUSIONS: In patients with IPAH, OUES and OUEP are both significantly lower than the healthy subjects. OUEP is a better physiological parameter than OUES in evaluating the gas exchange abnormality of patients with IPAH.

  6. The effects of radial oxygen loss on arsenic tolerance and uptake in rice and on its rhizosphere

    International Nuclear Information System (INIS)

    Mei, X.Q.; Wong, M.H.; Yang, Y.; Dong, H.Y.; Qiu, R.L.; Ye, Z.H.

    2012-01-01

    Understanding the complex biotic and abiotic interactions invoked by the rice root system in oxygen-depleted soil is an important step in screening genotypes for low toxic metal or metalloid accumulation. A hydroponic and a rhizobox experiment have been conducted to explore the effects of varying root oxygen release on chemical changes, As fractionation in rhizosphere soil and Fe plaque formation, As uptake and tolerance by different rice genotypes. The results showed that rice genotypes with higher rates of radial oxygen loss (ROL) and at the bolting stage, tended to have greater effects on rhizosphere Eh, pH, Fe 3+ /Fe 2+ quotients, As fractionation and mobility and also on Fe plaque formation compared to those with lower ROL and at the tillering stage. Genotypes with higher ROL have a strong ability to reduce As accumulation in shoots and increase As tolerance by reducing As mobilization in the rhizosphere and by limiting As translocation. - Highlights: ► We investigate the effects of ROL on As tolerance, uptake, and changes in rhizosphere of rice genotypes and their correlation. ► Indices of As tolerance of genotypes are positively correlated with their rates of ROL. ► Genotypes with higher rates of ROL have greater effects on rhizosphere. ► Genotypes with higher rates of ROL have a strong ability to reduce As uptake by immobilizing As on roots and in rhizosphere. - Rice genotypes with high ROL and at the bolting stage have greater effects on their rhizosphere than others with lower ROL and at tillering stage and also have lower shoot As and higher As tolerance.

  7. Age-related changes in oxygen and nutrient uptake by hindquarters in newborn pigs during cold-induced shivering.

    Science.gov (United States)

    Lossec, G; Lebreton, Y; Hulin, J C; Fillaut, M; Herpin, P

    1998-11-01

    Newborn pigs rely essentially on shivering thermogenesis in the cold. In order to understand the rapid postnatal enhancement of thermogenic capacities in piglets, the oxygen and nutrient uptake of hindquarters was measured in vivo in 1- (n = 6) and 5-day-old (n = 6) animals at thermal neutrality and during cold exposure. The hindquarters were considered to represent a skeletal muscle compartment. Indirect calorimetry and arterio-venous techniques were used. The cold challenge (23 C at 1 day old and 15 C at 5 days old for 90 min) induced a similar increase (+90 %) in regulatory heat production at both ages. Hindquarters blood flow was higher at 5 days than 1 day old at thermal neutrality (26 +/- 3 vs. 17 +/- 1 ml min-1 (100 g hindquarters)-1) and its increase in the cold was much more marked (+65 % at 5 days old vs. +25 % at 1 day old). Oxygen extraction by the hindquarters rose from 30-35 % at thermal neutrality to 65-70 % in the cold at both ages. The calculated contribution of skeletal muscle to total oxygen consumption averaged 34-40 % at thermal neutrality and 50-64 % in the cold and skeletal muscle was the major contributor to regulatory thermogenesis. Based on hindquarters glucose uptake and lactate release, carbohydrate appeared to be an important fuel for shivering. However, net uptake of fatty acids increased progressively during cold exposure at 5 days old. The enhancement in muscular blood supply and fatty acid utilization during shivering is probably related to the postnatal improvement in the thermoregulatory response of the piglet.

  8. O2(a1Δ) vibrational kinetics in oxygen-iodine laser

    Science.gov (United States)

    Torbin, A. P.; Pershin, A. A.; Heaven, M. C.; Azyazov, V. N.; Mebel, A. M.

    2018-04-01

    Kinetics of vibrationally-excited singlet oxygen O2(a1Δ,ν) in gas mixture O3/N2/CO2 was studied using a pulse laser technique. Molecules O2(a1Δ,ν) were produced by laser photolysis of ozone at 266 nm. The O3 molecules number density was followed using time-resolved absorption spectroscopy. It was found that an upper bound for the rate constant of chemical reaction O2(a1Δ,ν)+ O3 is about 10-15 cm3/s. The rate constants of O2(a1Δ,ν= 1, 2 and 3) quenching by CO2 are presented.

  9. Pulmonary O2 uptake on-kinetics in endurance- and sprint-trained master athletes.

    Science.gov (United States)

    Berger, N J A; Rittweger, J; Kwiet, A; Michaelis, I; Williams, A G; Tolfrey, K; Jones, A M

    2006-12-01

    The purpose of this study was to characterise the VO2 kinetic response to moderate intensity cycle exercise in endurance-trained (END) and sprint or power-trained (SPR) track and field master athletes ranging in age from 45 to 85 years. We hypothesised that the time constant (tau) describing the Phase II VO2 on-response would be smaller in the END compared to the SPR athletes, and that the tau would become greater with increasing age in both groups. Eighty-four master athletes who were competing at either the British or European Veteran Athletics Championships acted as subjects, and were classified as either END (800 m - marathon; n = 41), or SPR (100 - 400 m and field events; n = 43) specialists. Subjects completed two 6 minute "step" transitions to a work rate of moderate intensity on a cycle ergometer and pulmonary gas exchange was measured breath-by-breath. Analysis of variance revealed that SPR athletes had slower VO2 on-kinetics (i.e., greater tau) compared to END athletes at each of the age groups studied: 46 - 55 yrs (END: 25 +/- 6 vs. SPR: 36 +/- 9 s; p kinetics became slower with advancing age in the SPR athletes (p kinetics in SPR compared to END master athletes is consistent both with differences in physiology (e.g., muscle fibre type, oxidative/glycolytic capacity) and training between these specialist athletes. Master END athletes have similar tau values to their younger counterparts (approximately 25 s) suggesting that participation in endurance exercise training limits the slowing of VO2 on-kinetics with age in this population.

  10. Uptake and kinetics of 226Ra, 210Pb and 210Po in big sagebrush

    International Nuclear Information System (INIS)

    Simon, S.L.

    1985-01-01

    Root uptake of 226 Ra, 210 Pb and 210 Po by mature sagebrush was studied using a soil injection method for spiking the soil with minimal root disturbance. The main objective was to measure vegetation concentrations and determine concentration ratios (CR's) due to root uptake as a function of time in mature big sagebrush. Concentration ratios obtained in mature vegetation and in steady-state situations may be valuable in assessing the impact of uranium mining and milling. The vegetation was sampled approximately every 3 months for a 2 year period. Significant levels of activity were detected in the vegetation beginning at the first sampling (81 days after soil injection for 226 Ra, 28 days for 210 Pb and 210 Po). There was an exponential decrease in concentration to an apparent steady-state value. Mean values (geometric) of the data pooled over the second year period indicated that the steady-state CR's for 226 Ra, 210 Pb and 210 Po, as determined in mature sagebrush, were 0.04, 0.009, and 0.08, respectively. A three compartment mathematical model was formulated to help understand mechanisms of plant uptake and to predict, if possible, the concentration of 226 Ra, 210 Pb and 210 Po in vegetation as a function of time after soil spiking. A numerical solution was determined by 'calibrating' the general model solution with constants determined from regressions of concentrations in vegetation, soil leaching and leaf leaching data. Validation of the model is currently not possible because of an absence of similar time-dependent uptake studies. 168 refs., 19 figs., 18 tabs

  11. Dynamic Model of Basic Oxygen Steelmaking Process Based on Multi-zone Reaction Kinetics: Model Derivation and Validation

    Science.gov (United States)

    Rout, Bapin Kumar; Brooks, Geoff; Rhamdhani, M. Akbar; Li, Zushu; Schrama, Frank N. H.; Sun, Jianjun

    2018-04-01

    A multi-zone kinetic model coupled with a dynamic slag generation model was developed for the simulation of hot metal and slag composition during the basic oxygen furnace (BOF) operation. The three reaction zones (i) jet impact zone, (ii) slag-bulk metal zone, (iii) slag-metal-gas emulsion zone were considered for the calculation of overall refining kinetics. In the rate equations, the transient rate parameters were mathematically described as a function of process variables. A micro and macroscopic rate calculation methodology (micro-kinetics and macro-kinetics) were developed to estimate the total refining contributed by the recirculating metal droplets through the slag-metal emulsion zone. The micro-kinetics involves developing the rate equation for individual droplets in the emulsion. The mathematical models for the size distribution of initial droplets, kinetics of simultaneous refining of elements, the residence time in the emulsion, and dynamic interfacial area change were established in the micro-kinetic model. In the macro-kinetics calculation, a droplet generation model was employed and the total amount of refining by emulsion was calculated by summing the refining from the entire population of returning droplets. A dynamic FetO generation model based on oxygen mass balance was developed and coupled with the multi-zone kinetic model. The effect of post-combustion on the evolution of slag and metal composition was investigated. The model was applied to a 200-ton top blowing converter and the simulated value of metal and slag was found to be in good agreement with the measured data. The post-combustion ratio was found to be an important factor in controlling FetO content in the slag and the kinetics of Mn and P in a BOF process.

  12. Calculation of hydrogen and oxygen uptake in fuel rod cladding during severe accidents using the integral diffusion method -- Preliminary design report

    International Nuclear Information System (INIS)

    Siefken, L.J.

    1999-01-01

    Preliminary designs are described for models of hydrogen and oxygen uptake in fuel rod cladding during severe accidents. Calculation of the uptake involves the modeling of seven processes: (1) diffusion of oxygen from the bulk gas into the boundary layer at the external cladding surface, (2) diffusion from the boundary layer into the oxide layer, (3) diffusion from the inner surface of the oxide layer into the metallic part of the cladding, (4) uptake of hydrogen in the event that the cladding oxide layer is dissolved in a steam-starved region, (5) embrittlement of cladding due to hydrogen uptake, (6) cracking of cladding during quenching due to its embrittlement and (7) release of hydrogen from the cladding after cracking of the cladding. An integral diffusion method is described for calculating the diffusion processes in the cladding. Experimental results are presented that show a rapid uptake of hydrogen in the event of dissolution of the oxide layer and a rapid release of hydrogen in the event of cracking of the oxide layer. These experimental results are used as a basis for calculating the rate of hydrogen uptake and the rate of hydrogen release. The uptake of hydrogen is limited to the equilibrium solubility calculated by applying Sievert's law. The uptake of hydrogen is an exothermic reaction that accelerates the heatup of a fuel rod. An embrittlement criteria is described that accounts for hydrogen and oxygen concentration and the extent of oxidation. A design is described for implementing the models for hydrogen and oxygen uptake and cladding embrittlement into the programming framework of the SCDAP/RELAP5 code. A test matrix is described for assessing the impact of the proposed models on the calculated behavior of fuel rods in severe accident conditions. This report is a revision and reissue of the report entitled; ''Preliminary Design Report for Modeling of Hydrogen Uptake in Fuel Rod Cladding During Severe Accidents.''

  13. Genetic variants of uncoupling proteins-2 and -3 in relation to maximal oxygen uptake in different sports.

    Science.gov (United States)

    Holdys, Joanna; Gronek, Piotr; Kryściak, Jakub; Stanisławski, Daniel

    2013-01-01

    Uncoupling proteins 2 and 3 (UCP2 and UCP3) as mitochondrial electron transporters are involved in regulation of ATP production and energy dissipation as heat. Energy efficiency plays an important role in physical performance, especially in aerobic fitness. The aim of this study was to examine the association between maximal oxygen uptake and genetic variants of the UCP2 and UCP3 genes. The studies were carried out in a group of 154 men and 85 women, professional athletes representing various sports and fitness levels and students of the University of Physical Education in Poznań. Physiological and molecular procedures were used, i.e. direct measurement of maximum oxygen uptake (VO₂max) and analysis of an insertion/deletion (I/D) polymorphism in the 3'untranslated region of exon 8 of the UCP2 gene and a C>T substitution in exon 5 (Y210Y) of the UCP3 gene. No statistically significant associations were found, only certain trends. Insertion allele (I) of the I/D UCP2 and the T allele of the UCP3 gene were favourable in obtaining higher VO₂max level and might be considered as endurance-related alleles.

  14. Endurance training decreases the non-linearity in the oxygen uptake-power output relationship in humans.

    Science.gov (United States)

    Majerczak, Joanna; Korostynski, Michal; Nieckarz, Zenon; Szkutnik, Zbigniew; Duda, Krzysztof; Zoladz, Jerzy A

    2012-03-01

    In this study, we hypothesized that 5 weeks of cycling endurance training can decrease the magnitude of the non-proportional increase in oxygen uptake (V(O(2))) to power output relationship (V(O(2)) 'excess') at exercise intensities exceeding the lactate threshold (LT). Ten untrained, physically active men performed a bout of incremental cycling exercise until exhaustion before and after training. The mitochondrial DNA copy number, myosin heavy chain composition and content of uncoupling protein 3 and sarcoplasmic reticulum Ca(2+)-ATPases (SERCAs) were analysed in muscle biopsies taken from vastus lateralis before and after training. The training resulted in an enhancement of the power-generating capabilities at maximal oxygen uptake (V(O(2)max)) by ∼7% (P = 0.002) despite there being no changes in V(O(2)max) (P = 0.49). This effect was due to a considerable reduction in the magnitude of the V(O(2)) 'excess' (P 0.05) were found after training. We conclude that the training-induced increase in power-generating capabilities at V(O(2)max) was due to attenuation of the V(O(2)) 'excess' above the LT. This adaptive response seems to be related to the improvement of muscle metabolic stability, as judged by a lowering of plasma ammonia concentration. The enhancement of muscle metabolic stability after training could be caused by a decrease in ATP usage at a given power output owing to downregulation of SERCA2 pumps.

  15. Quantification of atmospheric oxygen levels during the Paleoproterozoic using paleosol compositions and iron oxidation kinetics

    Science.gov (United States)

    Murakami, Takashi; Sreenivas, Bulusu; Sharma, Subrata Das; Sugimori, Hirokazu

    2011-07-01

    The increase in atmospheric oxygen during the Precambrian is a key to understand the co-evolution of life and environment and has remained as a debatable topic. Among various proxies for the estimation of atmospheric oxygen levels, paleosols, ancient weathering profiles, can provide a quantitative pattern of atmospheric oxygen increase during the Precambrian period of Earth history. We have re-evaluated the chemical compositions of paleosols, and presented a new method of applying Fe 2+ oxidation kinetics to the Fe 2+ and Fe 3+ concentrations in paleosols to decipher the quantitative partial pressure of atmospheric oxygen ( P) between 2.5 and 2.0 Ga. We first estimated the compaction factor ( CF, the fraction of original thickness) using the immobile elements such as Ti, Al and Zr on equal volume basis, which was then used to calculate retention fractions ( M R), a mass ratio of paleosol to parent rock, of redox-sensitive elements. The CF and Fe R values were evaluated for factors such as homogeneity of immobile elements, erosion, and formation time of weathering. Fe R increased gradually within the time window of ˜2.5-2.1 Ga and remained close to 1.0 since ˜2.1 Ga onwards. Mn R also increased gradually similar to Fe R but at a slower rate and near complete retention was observed ˜1.85 Ga, suggesting an almost continuous increase in the oxidation of Fe 2+ and Mn 2+ in paleosols ranging in age between ˜2.5 and 1.9 Ga. We have modeled P variations during the Paleoproterozoic by applying Fe 2+ oxidation kinetics to the Fe 2+ and Fe 3+ concentrations in paleosols, which enabled us to derive an Fe 2+ oxidation term referred to as ψ. Possible changes in temperature and P during this time window and their effects on resulting models of P evolution have been also considered. We assumed four cases for the calculations of P variations between 2.5 and 2.0 Ga: no change in either temperature or P, long-term change in only P, long-term changes in both temperature and P

  16. Seasonal variability in nitrate and phosphate uptake kinetics in a forested headwater stream using pulse nutrient additions

    Science.gov (United States)

    Griffiths, N. A.; Mulholland, P. J.

    2011-12-01

    We used the Tracer Additions for Spiraling Curve Characterization (TASCC) approach to quantify seasonal variability in ambient nutrient spiraling metrics and nutrient uptake kinetics in the West Fork of Walker Branch, a forested headwater stream in eastern Tennessee, USA. We performed instantaneous additions of nitrate (NO3-) and phosphate (PO4-3) separately with a conservative tracer (chloride, Cl-) during the following biologically-important time periods: autumn (during leaf fall, high organic matter [OM] standing stocks), winter (low OM standing stocks), spring (prior to canopy closure), and summer (closed canopy). We predicted that nutrient demand would be highest during autumn and spring, as OM inputs fuel heterotrophic respiration and high light availability stimulates autotrophic production, respectively. The measured ambient PO4-3 uptake rates (Vf-amb) followed our predictions, with the highest Vf-amb rates in autumn (Vf-amb = 2.8 mm/min) and spring (Vf-amb = 2.9 mm/min), and undetectable uptake in winter. Further, maximum areal PO4-3 uptake rates (Umax) were higher in autumn (Umax = 297 μg/m2/min) than spring (Umax = 106 μg/m2/min), possibly due to greater nutrient demand of heterotrophs on leaf litter accumulations. Contrary to our predictions, ambient NO3- uptake rates were highest in autumn and winter (autumn: Vf-amb = 2.8 mm/min, winter: Vf-amb = 2.4 mm/min), and lowest in spring (Vf-amb = 1.0 mm/min). The higher than expected Vf-amb rate in winter may be due to higher stream metabolism rates and thus greater nitrogen demand; the lower than expected Vf-amb rate in spring may reflect an alleviation of nitrogen demand due to high ammonium concentrations during this time. As the demand for both nitrogen and phosphorus in Walker Branch is greatest in autumn, future work will characterize how nutrient metrics change during this dynamic time period (i.e., before, during, and after leaf fall).

  17. COMBINED THEORETICAL AND EXPERIMENTAL INVESTIGATION OF MECHANISMS AND KINETICS OF VAPOR-PHASE MERCURY UPTAKE BY CARBONACEOUS SURFACES; ANNUAL

    International Nuclear Information System (INIS)

    Radisav D. Vidic; Eric V. Borguet; Karl J. Johnson

    2000-01-01

    The overall goal of this research program is to gain fundamental understanding of the important chemistry and physics involved in mercury adsorption on carbonaceous surfaces. This knowledge will then be used to optimize adsorption processes and operating conditions to maximize the uptake of mercury within the required contact time. An additional long-term benefit of this research is the basic understanding of the Hg adsorption process, which may facilitate the design of new adsorbents for more efficient and cost-effective removal of Hg from a variety of effluent streams. Molecular modeling of the adsorption of Hg on carbonaceous surfaces will greatly increase the insight into the physics of the adsorption process and combined with in situ rate measurements of mercury adsorption and desorption (conventional and pulsed laser) on graphite using linear and nonlinear optical probes with real time optical resolution have the potential to provide fundamental insight into the process of mercury uptake by carbonaceous surfaces. Besides accurate assessment of key parameters influencing adsorption equilibrium, fundamental understanding of the kinetics of mercury adsorption, desorption, and diffusion will be developed in this study. These key physical and chemical processes postulated through molecular modeling efforts and verified by in situ measurements will be utilized to select (or develop) promising sorbents for mercury control, which will be tested under dynamic conditions using simulated flue gas

  18. Uptake and Loss Kinetics of 57Co, 85Sr and 134Cs on Blood Cockle Anadara granosa

    International Nuclear Information System (INIS)

    Srisuksawad, K; Prasertchiewchan, N.; Tungkitjanukij, S.; Pakkong, P.

    2005-02-01

    Adult blood cockle (A. granosa) were exposed in the laboratory to 57 Co, 85 Sr, and 134 Cs in seawater at average +- s.e. stable activities of 0.725+-0.010 Bq/ml, 0.917+-0.066 Bq/ml and 1.37+-0.105 Bq/ml, respectively. The study aims to determine key contaminant bioaccumulation, retention and loss parameters for bio-indicator organisms used in assessment of the impact of the effluent discharge from nuclear and non-nuclear facilities on coastal area. Natural coastal water conditions in dry season with a salinity of 30 ppt, at 30οC and p H 8.1+-0.1 of the study area (Bang Pa Kong river basin) were simulated as far as practicable. 19 d uptake of radiotracers showed that blood cockle did not accumulate 134 Cs and 85 Sr but considerably accumulated 57 Co. Non-linear regression model fitting of a 1-compartment exponential uptake model derived overall weight concentration factors for the whole cockle at saturation of 687.6+-6.23 ml/g for 57 Co. 22 d loss experiment showed that 57 Co is tightly bounded in blood cockle and 63.2+-15.2% retained in the whole body. Loss of 57 Co displayed 2-compartment loss kinetic. The calculated half time for the short and long components of loss model was estimated 1.4 dand 41 d, respectively

  19. Kinetic of magnetic nanoparticles uptake evaluated by morphometry of mice peritoneal cells

    International Nuclear Information System (INIS)

    Silva, L.P.; Kuckelhaus, S.; Guedes, M.H.A.; Lacava, Z.G.M.; Tedesco, A.C.; Morais, P.C.; Azevedo, R.B.

    2005-01-01

    The development of magnetic fluids (MFs) has led to a wide range of new biomedical applications. Nevertheless, few studies have examined the kinetics of the magnetic nanoparticles (MNPs) internalization by phagocytes. In this study, we present morphometry as a method to quantify the cell surface covered by MNPs. The maximum cell surface covered by MNPs aggregates was 32.5% (8.5 min), 18.3% (24.1 min), and 18.0% (20.2 min) in DMSA, citric acid and dextran-coated MNPs, respectively. We concluded that the phagocytosis process of MNPs is strongly dependent upon the coating species

  20. An in silico analysis of oxygen uptake of a mild COPD patient during rest and exercise using a portable oxygen concentrator

    Directory of Open Access Journals (Sweden)

    Katz I

    2016-09-01

    Full Text Available Ira Katz,1,2 Marine Pichelin,1 Spyridon Montesantos,1 Min-Yeong Kang,3 Bernard Sapoval,3,4 Kaixian Zhu,5 Charles-Philippe Thevenin,5 Robert McCoy,6 Andrew R Martin,7 Georges Caillibotte1 1Medical R&D, Air Liquide Santé International, Centre de Recherche Paris-Saclay, Les Loges-en-Josas, France; 2Department of Mechanical Engineering, Lafayette College, Easton, PA, USA; 3Physique de la Matière Condensée, CNRS, Ecole Polytechnique, Palaiseau, 4Centre de Mathématiques et de leurs Applications, CNRS, UniverSud, Cachan, 5Centre Explor!, Air Liquide Healthcare, Gentilly, France; 6Valley Inspired Products, Inc, Apple Valley, MN, USA; 7Department of Mechanical Engineering, University of Alberta, Edmonton, AB, Canada Abstract: Oxygen treatment based on intermittent-flow devices with pulse delivery modes available from portable oxygen concentrators (POCs depends on the characteristics of the delivered pulse such as volume, pulse width (the time of the pulse to be delivered, and pulse delay (the time for the pulse to be initiated from the start of inhalation as well as a patient’s breathing characteristics, disease state, and respiratory morphology. This article presents a physiological-based analysis of the performance, in terms of blood oxygenation, of a commercial POC at different settings using an in silico model of a COPD patient at rest and during exercise. The analysis encompasses experimental measurements of pulse volume, width, and time delay of the POC at three different settings and two breathing rates related to rest and exercise. These experimental data of device performance are inputs to a physiological-based model of oxygen uptake that takes into account the real dynamic nature of gas exchange to illustrate how device- and patient-specific factors can affect patient oxygenation. This type of physiological analysis that considers the true effectiveness of oxygen transfer to the blood, as opposed to delivery to the nose (or mouth, can be

  1. Kinetics of highly vibrationally excited O2(X) molecules in inductively-coupled oxygen plasmas

    Science.gov (United States)

    Annušová, Adriana; Marinov, Daniil; Booth, Jean-Paul; Sirse, Nishant; Lino da Silva, Mário; Lopez, Bruno; Guerra, Vasco

    2018-04-01

    The high degree of vibrational excitation of O2 ground state molecules recently observed in inductively coupled plasma discharges is investigated experimentally in more detail and interpreted using a detailed self-consistent 0D global kinetic model for oxygen plasmas. Additional experimental results are presented and used to validate the model. The vibrational kinetics considers vibrational levels up to v = 41 and accounts for electron impact excitation and de-excitation (e-V), vibration-to-translation relaxation (V-T) in collisions with O2 molecules and O atoms, vibration-to-vibration energy exchanges (V-V), excitation of electronically excited states, dissociative electron attachment, and electron impact dissociation. Measurements were performed at pressures of 10–80 mTorr (1.33 and 10.67 Pa) and radio frequency (13.56 MHz) powers up to 500 W. The simulation results are compared with the absolute densities in each O2 vibrational level obtained by high sensitivity absorption spectroscopy measurements of the Schumann–Runge bands for O2(X, v = 4–18), O(3 P) atom density measurements by two-photon absorption laser induced fluorescence (TALIF) calibrated against Xe, and laser photodetachment measurements of the O‑ negative ions. The highly excited O2(X, v) distribution exhibits a shape similar to a Treanor-Gordiets distribution, but its origin lies in electron impact e-V collisions and not in V-V up-pumping, in contrast to what happens in all other molecular gases known to date. The relaxation of vibrational quanta is mainly due to V-T energy-transfer collisions with O atoms and to electron impact dissociation of vibrationally excited molecules, e+O2(X, v)→O(3P)+O(3P).

  2. Enhanced kinetics of hole transfer and electrocatalysis during photocatalytic oxygen evolution by cocatalyst tuning

    KAUST Repository

    Nurlaela, Ela; Wang, Hai; Shinagawa, Tatsuya; Flanagan, Sean; Ould-Chikh, Samy; Qureshi, Muhammad; Mics, Zoltan; Sautet, Philippe; Le Bahers, Tangui; Canovas, Enrique; Bonn, Mischa; Takanabe, Kazuhiro

    2016-01-01

    Understanding photophysical and electrocatalytic processes during photocatalysis in a powder suspension system is crucial for developing efficient solar energy conversion systems. We report a substantial enhancement by a factor of 3 in photocatalytic effi-ciency for the oxygen evolution reaction (OER) by adding trace amounts (~0.05 wt%) of noble metals (Rh or Ru) to a 2 wt% cobalt oxide-modified Ta3N5 photocatalyst particulate. The optimized system exhibited high quantum efficiencies (QEs) of up to 28 and 8.4% at 500 and 600 nm in 0.1 M Na2S2O8 at pH 14. By isolating the electrochemical components to generate doped cobalt oxide electrodes, the electrocatalytic activity of cobalt oxide when doped with Ru or Rh was improved compared with cobalt oxide, as evidenced by the onset shift for electrochemical OER. Density functional theory (DFT) calculation shows that the ef-fects of a second metal addition perturbs the electronic structure and redox properties in such a way that both hole transfer kinetics and electrocatalytic rates improve. Time resolved terahertz spectroscopy (TRTS) measurement provides evidence of long-lived electron populations (>1 ns; with mobilities μe ~0.1-3 cm2 V-1 s-1), which are not perturbed by the addition of CoOx-related phases. Furthermore, we find that Ta3N5 phases alone suffer ultrafast hole trapping (within 10 ps); the CoOx and M-CoOx decorations most likely induce a kinetic competition between hole transfer toward the CoOx-related phases and trapping in the Ta3N5 phase, which is consistent with the improved OER rates. The present work not only provides a novel way to improve electrocatalytic and photocatalytic performance but also gives additional tools and insight to understand the characteristics of photocatalysts that can be used in a suspension system.

  3. Enhanced kinetics of hole transfer and electrocatalysis during photocatalytic oxygen evolution by cocatalyst tuning

    KAUST Repository

    Nurlaela, Ela

    2016-05-23

    Understanding photophysical and electrocatalytic processes during photocatalysis in a powder suspension system is crucial for developing efficient solar energy conversion systems. We report a substantial enhancement by a factor of 3 in photocatalytic effi-ciency for the oxygen evolution reaction (OER) by adding trace amounts (~0.05 wt%) of noble metals (Rh or Ru) to a 2 wt% cobalt oxide-modified Ta3N5 photocatalyst particulate. The optimized system exhibited high quantum efficiencies (QEs) of up to 28 and 8.4% at 500 and 600 nm in 0.1 M Na2S2O8 at pH 14. By isolating the electrochemical components to generate doped cobalt oxide electrodes, the electrocatalytic activity of cobalt oxide when doped with Ru or Rh was improved compared with cobalt oxide, as evidenced by the onset shift for electrochemical OER. Density functional theory (DFT) calculation shows that the ef-fects of a second metal addition perturbs the electronic structure and redox properties in such a way that both hole transfer kinetics and electrocatalytic rates improve. Time resolved terahertz spectroscopy (TRTS) measurement provides evidence of long-lived electron populations (>1 ns; with mobilities μe ~0.1-3 cm2 V-1 s-1), which are not perturbed by the addition of CoOx-related phases. Furthermore, we find that Ta3N5 phases alone suffer ultrafast hole trapping (within 10 ps); the CoOx and M-CoOx decorations most likely induce a kinetic competition between hole transfer toward the CoOx-related phases and trapping in the Ta3N5 phase, which is consistent with the improved OER rates. The present work not only provides a novel way to improve electrocatalytic and photocatalytic performance but also gives additional tools and insight to understand the characteristics of photocatalysts that can be used in a suspension system.

  4. Gender differences in residual effect of prior drop jumps on oxygen uptake during heavy cycling exercise

    Directory of Open Access Journals (Sweden)

    Neringa Baranauskienė

    2017-12-01

    Conclusions: Prior eccentric–concentric exercise of thigh muscles (100 drop jumps accelerates VO2 kinetics at the start and increases VO2 during steady state of heavy cycling only in the male group. So, prior exercise of such type has a higher negative impact on cycling economy in men than in women and this might be related to greater muscle damage and fatigue in physically active male persons after plyometric exercise.

  5. Polycaprolactone/maltodextrin nanocarrier for intracellular drug delivery: formulation, uptake mechanism, internalization kinetics, and subcellular localization.

    Science.gov (United States)

    Korang-Yeboah, Maxwell; Gorantla, Yamini; Paulos, Simon A; Sharma, Pankaj; Chaudhary, Jaideep; Palaniappan, Ravi

    2015-01-01

    Prostate cancer (PCa) disease progression is associated with significant changes in intracellular and extracellular proteins, intracellular signaling mechanism, and cancer cell phenotype. These changes may have direct impact on the cellular interactions with nanocarriers; hence, there is the need for a much-detailed understanding, as nanocarrier cellular internalization and intracellular sorting mechanism correlate directly with bioavailability and clinical efficacy. In this study, we report the differences in the rate and mechanism of cellular internalization of a biocompatible polycaprolactone (PCL)/maltodextrin (MD) nanocarrier system for intracellular drug delivery in LNCaP, PC3, and DU145 PCa cell lines. PCL/MD nanocarriers were designed and characterized. PCL/MD nanocarriers significantly increased the intracellular concentration of coumarin-6 and fluorescein isothiocyanate-labeled bovine serum albumin, a model hydrophobic and large molecule, respectively. Fluorescence microscopy and flow cytometry analysis revealed rapid internalization of the nanocarrier. The extent of nanocarrier cellular internalization correlated directly with cell line aggressiveness. PCL/MD internalization was highest in PC3 followed by DU145 and LNCaP, respectively. Uptake in all PCa cell lines was metabolically dependent. Extraction of endogenous cholesterol by methyl-β-cyclodextrin reduced uptake by 75%±4.53% in PC3, 64%±6.01% in LNCaP, and 50%±4.50% in DU145, indicating the involvement of endogenous cholesterol in cellular internalization. Internalization of the nanocarrier in LNCaP was mediated mainly by macropinocytosis and clathrin-independent pathways, while internalization in PC3 and DU145 involved clathrin-mediated endocytosis, clathrin-independent pathways, and macropinocytosis. Fluorescence microscopy showed a very diffused and non-compartmentalized subcellular localization of the PCL/MD nanocarriers with possible intranuclear localization and minor colocalization in

  6. Investigations on the kinetics of the oxygen reduction in high temperature fuel cells

    International Nuclear Information System (INIS)

    Erning, J.W.

    1998-07-01

    Lanthan-Strontium-Manganite perowskites are the most widespread materials in use for solid oxide fuel cell cathodes. The electrode reaction taking place, i.e. the reduction of oxygen supplied by air, was investigated by electrochemical means to obtain further knowledge about the electrode processes. The high activation energy of this reaction (200 kJ/mol), preventing lower operation temperatures of the SOFC, was the starting point for the investigation. Quasi steady state current voltage measurements and impedance spectroscopy were performed in a three electrode configuration. The electrodes were of circular shape with a diameter of 10 mm. The preparation was made by screen printing as well as wet powder spraying onto plates made of Yttria-stabilized zirconia. Perowskite powders of varying chemical and stoichiometric composition were used. To obtain higher power densities and, more important, lower apparent activation energies, catalytic layers were added at the interface electrode/electrolyte. Additionally, a less complex system, a model electrode/electrolyte setup made from single-crystal YSZ as electrolyte and gold in liquid and solid state as electrode was developed to create a better defined system. This setup was used to investigate the behaviour of the electrode/electrolyte interface. Reliable, reproducible results could be obtained using either setup. The experimental conditions i.e. oxygen partial pressure, temperature and overpotential were varied in order to determine the kinetic properties of the electrodes. Apparent activation energies, pre-exponential factors, apparent charge-transfer coefficients and electrochemical orders of reaction were calculated from the current-voltage data in order to propose possible reaction steps. (orig.)

  7. Numerical simulation of kinetic demixing and decomposition in a LaCoO3-δ oxygen membrane under an oxygen potential gradient

    DEFF Research Database (Denmark)

    Ta, Na; Chen, Ming; Zhang, Lijun

    2018-01-01

    A composition- and temperature-dependent mobility database of all ionic species in the LaCoO3-δ phase was developed and combined with a La-Co-O thermodynamic database to simulate kinetic demixing and partial decomposition in LaCoO3-δ oxygen membranes operated under a 0.0001/0.21 bar oxygen partial...... pressure difference at 1073 K for 1 year. Formation of La2O3, Co3O4 and CoO phases across the membrane is predicted. The kinetic demixing process can be divided into two stages, namely, establishment of the oxygen potential gradient (fast) and demixing of the cations (slow); the former is controlled...... by the mobility of oxygen ions, and the latter is determined by the higher mobility of Co ions as compared to the La ion in the ABO3-type perovskite. A drift motion of both oxide surfaces towards the high PO2 side occurs with the movement of cations....

  8. Organic N cycling in Arctic ecosystems: Quantifying root uptake kinetics and temporal variability of soil amino acids.

    Science.gov (United States)

    Homyak, P. M.; Iverson, S. L.; Slessarev, E.; Marchus, K.; Schimel, J.

    2017-12-01

    Arctic ecosystems are undergoing shifts in plant community composition with increased warming. How these changes may alter ecosystem function is not well constrained, owing in part to uncertainties on how plant-soil feedbacks influence nutrient cycling. For nitrogen (N), in particular, understanding how these feedbacks may alter cycling rates is challenging because i) Arctic plants take up organic N (i.e., amino acids; AA) when inorganic N is limiting, yet ii) it has never been quantified, for any plant species growing in the wild, how much of its N demand is actually met by taking up AA. To advance fundamental understanding of plant-soil feedbacks as the Arctic warms, we are integrating field measurements of AA availability in N-limited tussock tundra (E. vaginatum) and a comparably less N-limited birch shrub tundra (Betula nana and Salix spp.) with a root uptake model. We used soil microdialysis to determine available AA concentrations in the soil solution and potential rates of AA diffusion and mass flow to roots at the Toolik Field Station in Alaska. These measurements are being combined with AA root uptake kinetic experiments using E. vaginatum to establish actual AA root uptake rates. We found that in the early growing season (June), total AA concentrations in the soil solution averaged 104 µg N L-1 and were similar to NH4+ across sites. In the late growing season (August), AA were the dominant form of N averaging 75 µg N L-1 while NH4+ decreased to 13 µg N L-1. In the early growing season AA diffusion rates in the soil averaged 200 ng N cm-2 s-1 and declined to 150 ng N cm-2 s-1 in the late growing season. Lysine, serine, and arginine were the most abundant AA and differences in the N status of sites did not affect total AA concentrations. Amino acids made up at least half of the N diffusing through the soil solution, suggesting they can subsidize the N demand of arctic plants. Ongoing field experiments at Toolik will be used to constrain actual AA root

  9. Oxygen in the deep-sea: The challenge of maintaining uptake rates in a changing ocean

    Science.gov (United States)

    Hofmann, A. F.; Peltzer, E. T.; Brewer, P. G.

    2011-12-01

    Although focused on recently, ocean acidification is not the only effect of anthropogenic CO2 emissions on the ocean. Ocean warming will reduce dissolved oxygen concentrations and at the hypoxic limit for a given species this can pose challenges to marine life. The limit is traditionally reported simply as the static mass concentration property [O2]; here we treat it as a dynamic gas exchange problem for the animal analogous to gas exchange at the sea surface. The diffusive limit and its relationship to water velocity is critical for the earliest stages of marine life (eggs, embryos), but the effect is present for all animals at all stages of life. We calculate the external limiting O2 conditions for several representative metabolic rates and their relationship to flow of the bulk fluid under different environmental conditions. Ocean O2 concentrations decline by ≈ 14 μmol kg-1 for a 2 °C rise in temperature. At standard 1000 m depth conditions in the Pacific, flow over the surface would have to increase by ≈ 60% from 2.0 to 3.2 cm s-1 to compensate for this change. The functions derived allow new calculations of depth profiles of limiting O2 concentrations, as well as maximal diffusively sustainable metabolic oxygen consumption rates at various places around the world. Our treatment shows that there is a large variability in the global ocean in terms of facilitating aerobic life. This variability is greater than the variability of the oxygen concentration alone. It becomes clear that temperature and pressure dependencies of diffusion and partial pressure create a region typically around 1000 m depth where a maximal [O2] is needed to sustain a given metabolic rate. This zone of greatest physical constriction on the diffusive transport in the boundary layer is broadly consistent with the oxygen minimum zone, i.e., the zone of least oxygen concentration supply, resulting in a pronounced minimum of maximal diffusively sustainable metabolic oxygen consumption

  10. Factors influencing photo curing kinetics of novel UV-cured siloxane-modified acrylic coatings: Oxygen inhibition and composition

    International Nuclear Information System (INIS)

    Esposito Corcione, Carola; Frigione, Mariaenrica

    2012-01-01

    Highlights: ► The inhibition effect of oxygen on the kinetic behaviour of photopolymerizable siloxane acrylic formulations was analyzed by thermal analysis. ► The addition of a thiol in the mixtures allows to obtain higher conversion, to reduce the content of the UV initiator and to increase the T g . ► The data found in air were fitted as a function of the presence of the thiol monomer obtaining a good agreement. - Abstract: An experimental study was carried out for the development and characterization of innovative photopolymerizable siloxane-modified acrylic formulations for possible use as protective coatings of stone substrates. The kinetics of the radical photopolymerization mechanism induced by UV radiations in presence of a suitable photoinitiator was studied by a calorimetric analysis by varying the atmosphere (oxygen or nitrogen) and the composition of the mixtures, in particular of the UV photoinitiator. The reactivity, expressed in terms of both heat developed and rate of reaction, was generally found to decrease when the photopolymerization was carried out in air, due the inhibiting action of the oxygen towards the free radical polymerization. The addition of a proper thiol to the acrylic modified resin was found to reduce the adverse effect of oxygen on the kinetic reaction and on the degree of conversion. This result allowed to reduce the content of the photoinitiator and to increase the content of the siloxane in the acrylic based mixtures. The effect of the change of the composition of the formulations on the kinetic behaviour of the acrylic based resins was also analysed by calorimetric analysis. Calorimetric experimental data were fitted to a simple kinetic model for radical photopolymerization reactions. Finally, a proper relationship between the glass transition temperature and the total extent of reaction was applied to the experimental data. A good agreement between the experimental data and both the theoretical models was generally

  11. Oxygen Reduction Kinetics Enhancement on a Heterostructured Oxide Surface for Solid Oxide Fuel Cells

    KAUST Repository

    Crumlin, Ethan J.

    2010-11-04

    Heterostructured interfaces of oxides, which can exhibit transport and reactivity characteristics remarkably different from those of bulk oxides, are interesting systems to explore in search of highly active cathodes for the oxygen reduction reaction (ORR). Here, we show that the ORR of ∼85 nm thick La0.8Sr0.2CoO3-δ (LSC113) films prepared by pulsed laser deposition on (001)-oriented yttria-stabilized zirconia (YSZ) substrates is dramatically enhanced (∼3-4 orders of magnitude above bulk LSC113) by surface decorations of (La 0.5Sr0.5)2CoO4±δ (LSC214) with coverage in the range from ∼0.1 to ∼15 nm. Their surface and atomic structures were characterized by atomic force, scanning electron, and scanning transmission electron microscopy, and the ORR kinetics were determined by electrochemical impedance spectroscopy. Although the mechanism for ORR enhancement is not yet fully understood, our results to date show that the observed ORR enhancement can be attributed to highly active interfacial LSC113/LSC214 regions, which were shown to be atomically sharp. © 2010 American Chemical Society.

  12. Oxygen Reduction Kinetics Enhancement on a Heterostructured Oxide Surface for Solid Oxide Fuel Cells

    KAUST Repository

    Crumlin, Ethan J.; Mutoro, Eva; Ahn, Sung-Jin; la O’ , Gerardo Jose; Leonard, Donovan N.; Borisevich, Albina; Biegalski, Michael D.; Christen, Hans M.; Shao-Horn, Yang

    2010-01-01

    Heterostructured interfaces of oxides, which can exhibit transport and reactivity characteristics remarkably different from those of bulk oxides, are interesting systems to explore in search of highly active cathodes for the oxygen reduction reaction (ORR). Here, we show that the ORR of ∼85 nm thick La0.8Sr0.2CoO3-δ (LSC113) films prepared by pulsed laser deposition on (001)-oriented yttria-stabilized zirconia (YSZ) substrates is dramatically enhanced (∼3-4 orders of magnitude above bulk LSC113) by surface decorations of (La 0.5Sr0.5)2CoO4±δ (LSC214) with coverage in the range from ∼0.1 to ∼15 nm. Their surface and atomic structures were characterized by atomic force, scanning electron, and scanning transmission electron microscopy, and the ORR kinetics were determined by electrochemical impedance spectroscopy. Although the mechanism for ORR enhancement is not yet fully understood, our results to date show that the observed ORR enhancement can be attributed to highly active interfacial LSC113/LSC214 regions, which were shown to be atomically sharp. © 2010 American Chemical Society.

  13. Hepatic encephalopathy is associated with decreased cerebral oxygen metabolism and blood flow, not increased ammonia uptake

    DEFF Research Database (Denmark)

    Dam, Gitte; Keiding, Susanne; Munk, Ole Lajord

    2013-01-01

    Studies have shown decreased cerebral oxygen metabolism (CMRO(2)) and blood flow (CBF) in patients with cirrhosis with hepatic encephalopathy (HE). It remains unclear, however, whether these disturbances are associated with HE or with cirrhosis itself and how they may relate to arterial blood...... associated with HE rather than the liver disease as such. The changes in CMRO(2) and CBF could not be linked to blood ammonia concentration or CMRA....

  14. Deciphering relationships between in-stream travel times, nutrient concentrations, and uptake through analysis of hysteretic and non-hysteretic kinetic behavior

    Science.gov (United States)

    Covino, T. P.; Bowden, W. B.; Gooseff, M. N.; Wollheim, W. M.; McGlynn, B. L.; Whittinghill, K. A.; Wlostowski, A. N.; Herstand, M. R.

    2012-12-01

    Understanding the relationship between solute travel time, concentration, and nutrient uptake remains a central question in watershed hydrology and biogeochemistry. Theoretical understanding predicts that nutrient uptake should increase as in-stream solute travel time lengthens and/or as concentration increases; however, results from field-based studies have been contradictory. We used a newly developed approach, Tracer Additions for Spiraling Curve Characterization (TASCC), to investigate relationships between solute travel time, nutrient concentration, and nutrient uptake across a range of stream types. This approach allows us to quantify in-stream nutrient uptake across a range of travel times and nutrient concentrations using single instantaneous injections (slugs) of conservative and non-conservative tracers. In some systems we observed counter-clockwise hysteresis loops in the relationship between nutrient uptake and concentration. Greater nutrient uptake on the falling limb of tracer breakthrough curves indicates stronger uptake for a given concentration at longer travel times. However, in other systems we did not observe hysteresis in these relationships. Lack of hysteresis indicates that nutrient uptake kinetics were not influenced by travel time travel time. Here we investigate the potential roles of travel time and in-stream flowpaths that could be responsible for hysteretic behavior.

  15. The role of radial oxygen loss and root anatomy on zinc uptake and tolerance in mangrove seedlings

    International Nuclear Information System (INIS)

    Cheng, H.; Liu, Y.; Tam, N.F.Y.; Wang, X.; Li, S.Y.; Chen, G.Z.; Ye, Z.H.

    2010-01-01

    Root anatomy, radial oxygen loss (ROL) and zinc (Zn) uptake and tolerance in mangrove plants were investigated using seedlings of Aegiceras corniculatum, Bruguiera gymnorrhiza and Rhizophora stylosa. The results revealed that B. gymnorrhiza, which possessed the 'tightest barrier' in ROL spatial patterns among the three species studied, took up the least Zn and showed the highest Zn tolerance. Furthermore, zinc significantly decreased the ROL of all three plants by inhibition of root permeability, which included an obvious thickening of outer cortex and significant increases of lignification in cell walls. The results of SEM X-ray microanalysis further confirmed that such an inducible, low permeability of roots was likely an adaptive strategy to metal stress by direct prevention of excessive Zn entering into the root. The present study proposes new evidence of structural adaptive strategy on metal tolerance by mangrove seedlings. - Mangrove seedlings with a 'tighter barrier' in ROL spatial pattern exhibit higher Zn tolerance.

  16. The role of radial oxygen loss and root anatomy on zinc uptake and tolerance in mangrove seedlings

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, H. [State Key Laboratory for Bio-control, and School of Life Sciences, Sun Yat-sen University, Guangzhou 510006 (China); Liu, Y. [Ministry of Agriculture Key Laboratory of Mariculture Ecology and Products Quality and Safety, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510300 (China); Tam, N.F.Y. [Department of Biology and Chemistry, City University of Hong Kong (Hong Kong); Wang, X. [State Key Laboratory for Bio-control, and School of Life Sciences, Sun Yat-sen University, Guangzhou 510006 (China); Li, S.Y.; Chen, G.Z. [School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Ye, Z.H., E-mail: lssyzhh@mail.sysu.edu.c [State Key Laboratory for Bio-control, and School of Life Sciences, Sun Yat-sen University, Guangzhou 510006 (China)

    2010-05-15

    Root anatomy, radial oxygen loss (ROL) and zinc (Zn) uptake and tolerance in mangrove plants were investigated using seedlings of Aegiceras corniculatum, Bruguiera gymnorrhiza and Rhizophora stylosa. The results revealed that B. gymnorrhiza, which possessed the 'tightest barrier' in ROL spatial patterns among the three species studied, took up the least Zn and showed the highest Zn tolerance. Furthermore, zinc significantly decreased the ROL of all three plants by inhibition of root permeability, which included an obvious thickening of outer cortex and significant increases of lignification in cell walls. The results of SEM X-ray microanalysis further confirmed that such an inducible, low permeability of roots was likely an adaptive strategy to metal stress by direct prevention of excessive Zn entering into the root. The present study proposes new evidence of structural adaptive strategy on metal tolerance by mangrove seedlings. - Mangrove seedlings with a 'tighter barrier' in ROL spatial pattern exhibit higher Zn tolerance.

  17. Biomass characterization by dielectric monitoring of viability and oxygen uptake rate measurements in a novel membrane bioreactor.

    Science.gov (United States)

    Shariati, Farshid Pajoum; Heran, Marc; Sarrafzadeh, Mohammad Hossein; Mehrnia, Mohammad Reza; Sarzana, Gabriele; Ghommidh, Charles; Grasmick, Alain

    2013-07-01

    The application of permittivity and oxygen uptake rate (OUR) as biological process control parameters in a wastewater treatment system was evaluated. Experiments were carried out in a novel airlift oxidation ditch membrane bioreactor under different organic loading rates (OLR). Permittivity as representative of activated sludge viability was measured by a capacitive on-line sensor. OUR was also measured as a representative for respirometric activity. Results showed that the biomass concentration increases with OLR and all biomass related measurements and simulators such as MLSS, permittivity, OUR, ASM1 and ASM3 almost follow the same increasing trends. The viability of biomass decreased when the OLR was reduced from 5 to 4 kg COD m(-3)d(-1). During decreasing of OLR, biomass related parameters generally decreased but not in a similar manner. Also, protein concentration in the system during OLR decreasing changed inversely with the activated sludge viability. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. The relationship between skeletal muscle mitochondrial citrate synthase activity and whole body oxygen uptake adaptations in response to exercise training

    DEFF Research Database (Denmark)

    Vigelsø, Andreas; Andersen, Nynne B; Dela, Flemming

    2014-01-01

    Citrate synthase (CS) activity is a validated biomarker for mitochondrial density in skeletal muscle. CS activity is also used as a biochemical marker of the skeletal muscle oxidative adaptation to a training intervention, and a relationship between changes in whole body aerobic capacity and chan......Citrate synthase (CS) activity is a validated biomarker for mitochondrial density in skeletal muscle. CS activity is also used as a biochemical marker of the skeletal muscle oxidative adaptation to a training intervention, and a relationship between changes in whole body aerobic capacity...... and changes in CS activity is often assumed. However, this relationship and absolute values of CS and maximal oxygen uptake (V.O2max) has never been assessed across different studies. A systematic PubMed search on literature published from 1983 to 2013 was performed. The search profile included: citrate...... and CS activity. 70 publications with 97 intervention groups were included. There was a positive (r = 0.45) correlation (P

  19. Oxygen uptake by excised gills of Procambarus clarkii (Girard) from Albufera Lake of Valencia, Spain, under heavy metal treatments

    Energy Technology Data Exchange (ETDEWEB)

    Diaz-Mayans, J.; Torreblanca, A.; Del Ramo, J.; Nunez, A.

    1986-06-01

    The American red crayfish Procambarus clarkii, originally from Louisiana (USA) was introduced in Spain in the 70's in the Guadalquivir River swamps. It appeared first randomly and in a more regular basis afterwards since 1978 in the Albufera Lake south of Valencia and in the surrounding rice fields. Albufera lake and surrounding rice fields waters are being subject since the last three decades to very heavy load of sewage, toxic industrial residues including heavy metals and pesticides from the many urban and industrial settlements in the zone. In the present study, the authors have investigated the effect that heavy metals (Chromium, Cadmium and Mercury) have on the oxygen uptake by excised bills of Procambarus clarkii (Girard) coming from the Albufera Lake (Valencia).

  20. Clinical safety and parameters of maximum oxygen uptake (Vo/sub 2/ max) testing in pakistani patients with heart failure

    International Nuclear Information System (INIS)

    Hussain, S.; Kayani, A.M.

    2015-01-01

    To determine the parameters of maximum oxygen uptake (VO2 max) in a Pakistani systolic heart failure cohort and its safety in a clinical setting. Study Design: Descriptive study. Place and Duration of Study: Armed Forces Institute of Cardiology, National Institute of Heart Diseases, Rawalpindi, from June 2011 to January 2013. Methodology: Maximum oxygen uptake test was performed in patients with severe heart failure, who could perform the VO2 max treadmill test. Age, Body Mass Index (BMI) ejection fraction, VO2 max and respiratory exchange ratios and their correlations were determined. Results: Out of 135 patients, 77% (n=104) were males, with a mean age of 45.9 ± 15.7 years. Weight of patients ranged from 30 kg to 107 kg (mean 63.29 ± 13.6 kg); mean BMI was 23.16 ± 4.56 kg/m2. All patients presented with either NYHA class of III (50.3%; n=68) or IV (49.7%; n=67); mean ejection fraction was 22.54 ± 5.7% (10 - 35%, IQ:20 - 25). The VO2 max of the patients ranged from 3 to 32 ml/kg/minute (mean 12.85 ± 4.49 ml/kg/minute). Respiratory exchange ratio was over 1 for all patients (1.12 - 1.96, mean = 1.36 ± 0.187). There was a negative correlation with age (r = -0.204; p = 0.028) whereas a positive correlation was found with exercise time (r = 0.684; p = 0.000), hemoglobin (r = 0.190; p = 0.047) and ejection fraction (r = 0.187 ; p = 0.044). Conclusion: Cardiopulmonary exercise testing in a high-risk heart failure cohort is safe and provides information beyond the routine clinical evaluation of heart failure patients. (author)

  1. Skeletal muscle blood flow and oxygen uptake at rest and during exercise in humans: a PET study with nitric oxide and cyclooxygenase inhibition

    DEFF Research Database (Denmark)

    Heinonen, Ilkka; Saltin, Bengt; Kemppainen, Jukka

    2011-01-01

    The aim of the present study was to determine the effect of nitric oxide and prostanoids on microcirculation and oxygen uptake specifically in the active skeletal muscle by use of positron emission tomography (PET). Healthy males performed 3 five min bouts of light knee-extensor exercise. Skeletal...... muscle blood flow and oxygen uptake were measured at rest and during the exercise using PET with H(2)O(15) and (15)O(2) during: 1) control conditions; 2) nitric oxide synthase (NOS) inhibition by arterial infusion of L-NMMA and 3) combined NOS and cyclooxygenase (COX) inhibition by arterial infusion of L...

  2. Pulse radiolysis study of reaction of bull serum albumin electron adduct with oxygen. Polychromatic kinetics of reaction with adsorbed oxygen

    International Nuclear Information System (INIS)

    Pribush, A.G.

    1986-01-01

    By the method of pulse radiolysis the reaction of bull serum albumin electron adduct with oxygen is investigated. As pulsed radiation source electron linear accelerators with particle energy of 8.0 and 4.5 MeV and pulse time of 40 ns and 2.2 μs, respectively have been used. It is assumed that the disappearance of protein electron adduct occurs in the course of its interaction with oxygen adsorbed on protein globular molecule

  3. Kinetics of oxygen exchange between bisulfite ion and water as studied by oxygen-17 nuclear magnetic resonance spectroscopy

    International Nuclear Information System (INIS)

    Horner, D.A.

    1984-08-01

    The nuclear magnetic relaxation times of oxygen-17 have been measured in aqueous sodium bisulfite solutions in the pH range from 2.5 to 5 as a function of temperature, pH, and S(IV) concentration, at an ionic strength of 1.0 m. The rate law for oxygen exchange between bisulfite ion and water was obtained from an analysis of the data, and is consistent with oxygen exchange occurring via the reaction SO 2 + H 2 O right reversible H + + SHO 3 - . The value of k/sub -1/ is in agreement with relaxation measurements. Direct spectroscopic evidence was found for the existence of two isomers of bisulfite ion: one with the proton bonded to the sulfur (HSO 3 - ) and the other with the proton bonded to an oxygen (SO 3 H - ). (The symbol SHO 3 - in the above chemical equation refers to both isomeric forms of bisulfite ion.) The relative amounts of the two isomers were determined as a function of temperature, and the rate and mechanism of oxygen exchange between the two was investigated. One of the two isomers, presumably SO 3 H - , exchanges oxygens with water much more rapidly than does the other. A two-pulse sequence was developed which greatly diminished the solvent peak in the NMR spectrum

  4. The uptake kinetics and immunotoxic effects of microcystin-LR in human and chicken peripheral blood lymphocytes in vitro

    International Nuclear Information System (INIS)

    Lankoff, Anna; Carmichael, Wayne W.; Grasman, Keith A.; Yuan, Moucun

    2004-01-01

    Microcystin-LR is a cyanobacterial heptapeptide that presents acute and chronic hazards to animal and human health. We investigated the influence of this toxin on human and chicken immune system modulation in vitro. Peripheral blood lymphocytes were treated with microcystin-LR at environmentally relevant doses of 1, 10 and 25 μg/ml for 12, 24, 48, 72 h (for proliferation assay cells were treated for 72 h). T-cell and B-cell proliferation as well as apoptosis and necrosis were determined in human and chicken samples. IL-2 and IL-6 production by human lymphocytes also was measured. In addition, uptake kinetics of microcystin-LR into human and chicken peripheral blood lymphocytes were calculated by Liquid Chromatography (LS) /Mass Spectrometry (MS) analysis. At the highest dose microcystin-LR decreased T-cell proliferation and all doses of microcystin-LR inhibited B-cell proliferation. The frequency of apoptotic and necrotic cells increased in a dose and time-dependent manner. Human lymphocytes responded to stimulation with microcystin-LR by increased production of IL-6 and decreased production of IL-2. Human lymphocytes were able to uptake from 0.014 to 1.663 μg/ml and chicken lymphocytes from 0.035 to 1.733 μg/ml of the microcystin-LR added to the cultures, depending on the treatment time and dose. In conclusion, microcystin-LR acted as an immunomodulator in cytokine production and down-regulated lymphocyte functions by induction of apoptosis and necrosis. However, further studies dealing with the influence of microcystin-LR on expression cytokine genes and transcription factors are necessary to confirm these hypotheses

  5. Uptake, transfer and elimination kinetics of paralytic shellfish toxins in common octopus (Octopus vulgaris).

    Science.gov (United States)

    Lopes, Vanessa M; Baptista, Miguel; Repolho, Tiago; Rosa, Rui; Costa, Pedro Reis

    2014-01-01

    Marine phycotoxins derived from harmful algal blooms are known to be associated with mass mortalities in the higher trophic levels of marine food webs. Bivalve mollusks and planktivorous fish are the most studied vectors of marine phycotoxins. However, field surveys recently showed that cephalopod mollusks also constitute potential vectors of toxins. Thus, here we determine, for the first time, the time course of accumulation and depuration of paralytic shellfish toxins (PSTs) in the common octopus (Octopus vulgaris). Concomitantly, the underlying kinetics of toxin transfer between tissue compartments was also calculated. Naturally contaminated clams were used to orally expose the octopus to PSTs during 6 days. Afterwards, octopus specimens were fed with non-contaminated shellfish during 10 days of depuration period. Toxins reached the highest concentrations in the digestive gland surpassing the levels in the kidney by three orders of magnitude. PSTs were not detected in any other tissue analyzed. Net accumulation efficiencies of 42% for GTX5, 36% for dcSTX and 23% for C1+2 were calculated for the digestive gland. These compounds were the most abundant toxins in both digestive gland and the contaminated shellfish diet. The small differences in relative abundance of each toxin observed between the prey and the cephalopod predator indicates low conversion rates of these toxins. The depuration period was better described using an exponential decay model comprising a single compartment - the entire viscera. It is worth noting that since octopuses' excretion and depuration rates are low, the digestive gland is able to accumulate very high toxin concentrations for long periods of time. Therefore, the present study clearly shows that O. vulgaris is a high-potential vector of PSTs during and even after the occurrence of these toxic algal blooms. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Heterogeneous oxidation of saturated organic aerosols by hydroxyl radicals: uptake kinetics, condensed-phase products, and particle size change

    Directory of Open Access Journals (Sweden)

    I. J. George

    2007-08-01

    Full Text Available The kinetics and reaction mechanism for the heterogeneous oxidation of saturated organic aerosols by gas-phase OH radicals were investigated under NOx-free conditions. The reaction of 150 nm diameter Bis(2-ethylhexyl sebacate (BES particles with OH was studied as a proxy for chemical aging of atmospheric aerosols containing saturated organic matter. An aerosol reactor flow tube combined with an Aerodyne time-of-flight aerosol mass spectrometer (ToF-AMS and scanning mobility particle sizer (SMPS was used to study this system. Hydroxyl radicals were produced by 254 nm photolysis of O3 in the presence of water vapour. The kinetics of the heterogeneous oxidation of the BES particles was studied by monitoring the loss of a mass fragment of BES with the ToF-AMS as a function of OH exposure. We measured an initial OH uptake coefficient of γ0=1.3 (±0.4, confirming that this reaction is highly efficient. The density of BES particles increased by up to 20% of the original BES particle density at the highest OH exposure studied, consistent with the particle becoming more oxidized. Electrospray ionization mass spectrometry analysis showed that the major particle-phase reaction products are multifunctional carbonyls and alcohols with higher molecular weights than the starting material. Volatilization of oxidation products accounted for a maximum of 17% decrease of the particle volume at the highest OH exposure studied. Tropospheric organic aerosols will become more oxidized from heterogeneous photochemical oxidation, which may affect not only their physical and chemical properties, but also their hygroscopicity and cloud nucleation activity.

  7. Cs-134 transfer from water or food to the Ciprinid Tinca tinca Linnaeus: uptake and loss kinetics

    International Nuclear Information System (INIS)

    Corisco, J.A.G.; Carreiro, M.C.V.

    1991-01-01

    Experiments with 134 Cs and the fish Tinca tinca Linnaeus (fam. Cyprinidae), as a part of a more extensive work, concerning a simplified freshwater trophic chain using water from Fratel dam, (at Tejo River), were undertaken. Direct uptake from water, during a period of about 30 days, leads to a kinetics expressed by the power function: CF (t) = 0.58 t 0.781 (t in days), the concentration factor (CF) referred to wet weight. Retention study, showed the existence of two biological half-lives, Tb 1 = 7 days and Tb 2 = 87 days, which might concern respectively, the 134 Cs desorption from the transit organs and the loss of the assimilated isotope from the storage organs. In the accumulation through the food chain, using planktonic crustacean Daphnia magna Straus (Cladocera) as prey, a transfer factor (TF) related to wet weight of both fish and prey, is estimated through the power function: TF (t) = 0.022 t 0.578 (t in days). Finally, the retention study following the food pathway contamination, stresses the existence of one long term component, with half-life Tb = 61 days. The transfer factor kinetics seems to point out to a rather slow process, leading to lower 134 Cs concentration values, than the contamination through the water. The loss of the assimilated 134 Cs, uptaken through both pathways, water or food, is a slow process. The longer biological half-life is very important in Radiological Protection, once it may be attributed to the radionuclide loss from the muscular mass. (author)

  8. Pulmonary O2 uptake and leg blood flow kinetics during moderate exercise are slowed by hyperventilation-induced hypocapnic alkalosis

    Science.gov (United States)

    Chin, Lisa M. K.; Heigenhauser, George J. F.; Paterson, Donald H.

    2010-01-01

    The effect of hyperventilation-induced hypocapnic alkalosis (Hypo) on the adjustment of pulmonary O2 uptake (V̇o2p) and leg femoral conduit artery (“bulk”) blood flow (LBF) during moderate-intensity exercise (Mod) was examined in eight young male adults. Subjects completed four to six repetitions of alternate-leg knee-extension exercise during normal breathing [Con; end-tidal partial pressure of CO2 (PetCO2) ∼40 mmHg] and sustained hyperventilation (Hypo; PetCO2 ∼20 mmHg). Increases in work rate were made instantaneously from baseline (3 W) to Mod (80% estimated lactate threshold). V̇o2p was measured breath by breath by mass spectrometry and volume turbine, and LBF (calculated from mean femoral artery blood velocity and femoral artery diameter) was measured simultaneously by Doppler ultrasound. Concentration changes of deoxy (Δ[HHb])-, oxy (Δ[O2Hb])-, and total hemoglobin-myoglobin (Δ[HbTot]) of the vastus lateralis muscle were measured continuously by near-infrared spectroscopy (NIRS). The kinetics of V̇o2p, LBF, and Δ[HHb] were modeled using a monoexponential equation by nonlinear regression. The time constants for the phase 2 V̇o2p (Hypo, 49 ± 26 s; Con, 28 ± 8 s) and LBF (Hypo, 46 ± 16 s; Con, 23 ± 6 s) were greater (P alkalosis is associated with slower convective (i.e., slowed femoral artery and microvascular blood flow) and diffusive (i.e., greater fractional O2 extraction for a given ΔV̇o2p) O2 delivery, which may contribute to the hyperventilation-induced slowing of V̇o2p (and muscle O2 utilization) kinetics. PMID:20339012

  9. Surface defect chemistry and oxygen exchange kinetics in La2-xCaxNiO4+δ

    Science.gov (United States)

    Tropin, E. S.; Ananyev, M. V.; Farlenkov, A. S.; Khodimchuk, A. V.; Berenov, A. V.; Fetisov, A. V.; Eremin, V. A.; Kolchugin, A. A.

    2018-06-01

    Surface oxygen exchange kinetics and diffusion in La2-xCaxNiO4+δ (x = 0; 0.1; 0.3) have been studied by the isotope exchange method with gas phase equilibration in the temperature range of 600-800 °C and oxygen pressure range 0.13-2.5 kPa. Despite an enhanced electrical conductivity of La2-xCaxNiO4+δ theirs oxygen surface exchange (k*) and oxygen tracer diffusion (D*) coefficients were significantly lower in comparison with La2NiO4+δ. The rates of the elementary stages of oxygen exchange have been calculated. Upon Ca doping the change of the rate-determining stage was observed. The surface of the oxides was found to be inhomogeneous towards oxygen exchange process according to the recently developed model. The reasons of such inhomogeneity are discussed as well as Ca influence on the surface defect chemistry and oxygen surface exchange and diffusivity.

  10. Kinetics of the high temperature oxygen exchange reaction on {sup 238}PuO{sub 2} powder

    Energy Technology Data Exchange (ETDEWEB)

    Whiting, Christofer E., E-mail: chris.whiting@udri.udayton.edu [University of Dayton – Research Institute, 300 College Park, Dayton, OH 45469-0172 (United States); Du, Miting; Felker, L. Kevin; Wham, Robert M. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831 (United States); Barklay, Chadwick D.; Kramer, Daniel P. [University of Dayton – Research Institute, 300 College Park, Dayton, OH 45469-0172 (United States)

    2015-12-15

    Oxygen exchange reactions performed on PuO{sub 2} suggest the reaction is influenced by at least three mechanisms: an internal chemical reaction, surface mobility of active species/defects, and surface exchange of gaseous oxygen with lattice oxygen. Activation energies for the surface mobility and internal chemical reaction are presented. Determining which mechanism is dominant appears to be a complex function including at least specific surface area and temperature. Thermal exposure may also impact the oxygen exchange reaction by causing reductions in the specific surface area of PuO{sub 2}. Previous CeO{sub 2} surrogate studies exhibit similar behavior, confirming that CeO{sub 2} is a good qualitative surrogate for PuO{sub 2}, in regards to the oxygen exchange reaction. Comparison of results presented here with previous work on the PuO{sub 2} oxygen exchange reaction allows complexities in the previous work to be explained. These explanations allowed new conclusions to be drawn, many of which confirm the conclusions presented here. - Highlights: • PuO{sub 2} Oxygen exchange kinetics can be influenced by at least 3 different mechanisms. • An internal chemical reaction controls the rate at high temperature and large SSA. • Surface mobility and surface exchange influence rate at lower temperatures and SSA. • Exchange temperatures may alter SSA and make data difficult to interpret.

  11. Electrostimulation improves muscle perfusion but does not affect either muscle deoxygenation or pulmonary oxygen consumption kinetics during a heavy constant-load exercise.

    Science.gov (United States)

    Layec, Gwenael; Millet, Grégoire P; Jougla, Aurélie; Micallef, Jean-Paul; Bendahan, David

    2008-02-01

    Electromyostimulation (EMS) is commonly used as part of training programs. However, the exact effects at the muscle level are largely unknown and it has been recently hypothesized that the beneficial effect of EMS could be mediated by an improved muscle perfusion. In the present study, we investigated rates of changes in pulmonary oxygen consumption (VO(2p)) and muscle deoxygenation during a standardized exercise performed after an EMS warm-up session. We aimed at determining whether EMS could modify pulmonary O(2) uptake and muscle deoxygenation as a result of improved oxygen delivery. Nine subjects performed a 6-min heavy constant load cycling exercise bout preceded either by an EMS session (EMS) or under control conditions (CONT). VO(2p) and heart rate (HR) were measured while deoxy-(HHb), oxy-(HbO(2)) and total haemoglobin/myoglobin (Hb(tot)) relative contents were measured using near infrared spectroscopy. EMS significantly increased (P < 0.05) the Hb(tot) resting level illustrating a residual hyperaemia. The EMS priming exercise did not affect either the HHb time constant (17.7 +/- 14.2 s vs. 13.1 +/- 2.3 s under control conditions) or the VO(2p) kinetics (time-constant = 18.2 +/- 5.2 s vs. 15.4 +/- 4.6 s under control conditions). Likewise, the other VO(2p) parameters were unchanged. Our results further indicated that EMS warm-up improved muscle perfusion through a residual hyperaemia. However, neither VO(2p) nor [HHb] kinetics were modified accordingly. These results suggest that improved O(2) delivery by residual hyperaemia induced by EMS does not accelerate the rate of aerobic metabolism during heavy exercise at least in trained subjects.

  12. Influence of Chironomus riparius (Diptera, Chironomidae) and Tubifex tubifex (Annelida, Oligochaeta) on oxygen uptake by sediments. Consequences of uranium contamination

    Energy Technology Data Exchange (ETDEWEB)

    Lagauzere, S. [Laboratoire de Radioecologie et d' Ecotoxicologie, Institut de Radioprotection et de Surete Nucleaire (IRSN), DEI/SECRE/LRE, Cadarache 186, BP 3, F-13115 Cedex, Saint Paul Lez Durance (France)], E-mail: lagauzere@gmail.com; Pischedda, L.; Cuny, P. [Laboratoire de Microbiologie, Geochimie et Ecologie Marines, UMR 6117 CNRS/COM/Universite de la Mediterranee, Campus de Luminy, Case 901, F-13288 Cedex 09, Marseille (France); Gilbert, F. [EcoLab, Laboratoire d' Ecologie Fonctionnelle, UMR 5245 CNRS/INP/Universite Paul Sabatier, 29 Rue Jeanne Marvig, F-31055 Cedex 4, Toulouse (France); Stora, G. [Laboratoire de Microbiologie, Geochimie et Ecologie Marines, UMR 6117 CNRS/COM/Universite de la Mediterranee, Campus de Luminy, Case 901, F-13288 Cedex 09, Marseille (France); Bonzom, J.-M. [Laboratoire de Radioecologie et d' Ecotoxicologie, Institut de Radioprotection et de Surete Nucleaire (IRSN), DEI/SECRE/LRE, Cadarache 186, BP 3, F-13115 Cedex, Saint Paul Lez Durance (France)

    2009-04-15

    The diffusive oxygen uptake (DOU) of sediments inhabited by Chironomus riparius and Tubifex tubifex was investigated using a planar oxygen optode device, and complemented by measurements of bioturbation activity. Additional experiments were performed within contaminated sediments to assess the impact of uranium on these processes. After 72 h, the two invertebrate species significantly increased the DOU of sediments (13-14%), and no temporal variation occurred afterwards. Within contaminated sediments, it was already 24% higher before the introduction of the organisms, suggesting that uranium modified the sediment biogeochemistry. Although the two species firstly reacted by avoidance of contaminated sediment, they finally colonized it. Their bioturbation activity was reduced but, for T. tubifex, it remained sufficient to induce a release of uranium to the water column and an increase of the DOU (53%). These results highlight the necessity of further investigations to take into account the interactions between bioturbation, microbial metabolism and pollutants. - This study highlights the ecological importance of bioturbation in metal-contaminated sediments.

  13. Influence of Chironomus riparius (Diptera, Chironomidae) and Tubifex tubifex (Annelida, Oligochaeta) on oxygen uptake by sediments. Consequences of uranium contamination

    International Nuclear Information System (INIS)

    Lagauzere, S.; Pischedda, L.; Cuny, P.; Gilbert, F.; Stora, G.; Bonzom, J.-M.

    2009-01-01

    The diffusive oxygen uptake (DOU) of sediments inhabited by Chironomus riparius and Tubifex tubifex was investigated using a planar oxygen optode device, and complemented by measurements of bioturbation activity. Additional experiments were performed within contaminated sediments to assess the impact of uranium on these processes. After 72 h, the two invertebrate species significantly increased the DOU of sediments (13-14%), and no temporal variation occurred afterwards. Within contaminated sediments, it was already 24% higher before the introduction of the organisms, suggesting that uranium modified the sediment biogeochemistry. Although the two species firstly reacted by avoidance of contaminated sediment, they finally colonized it. Their bioturbation activity was reduced but, for T. tubifex, it remained sufficient to induce a release of uranium to the water column and an increase of the DOU (53%). These results highlight the necessity of further investigations to take into account the interactions between bioturbation, microbial metabolism and pollutants. - This study highlights the ecological importance of bioturbation in metal-contaminated sediments

  14. A COMPARISON BETWEEN VENTILATION AND HEART RATE AS INDICATOR OF OXYGEN UPTAKE DURING DIFFERENT INTENSITIES OF EXERCISE

    Directory of Open Access Journals (Sweden)

    Jacques Prioux

    2010-03-01

    Full Text Available The aim of this study is to compare the relation between ventilation (VE and oxygen uptake (VO2 [VO2=ƒ(VE] and between heart rate (HR and VO2 [VO2=ƒ(HR]. Each one of the subjects performed three types of activities of different intensities (walking without load, walking with load and intermittent work. VO2, VE, and HR were measured continuously by using indirect calorimetry and an electrocardiogram. Linear regressions and coefficients of determination (r² were calculated to compare the relation VO2 =ƒ(VE and VO2 =ƒ(HR for two different regroupings: by session duration (r²session and by subject (r²subject. Results showed that r²session of the relation VO2 =ƒ(VE were significantly higher than those of the relation VO2 =ƒ(HR for steady state activities (walking with or without load during 3 or 6 min, p < 0.01 and for activities without oxygen consumption steady state (walking with or without load during 1 min, p < 0.01 and intermittent work, p < 0.05. VE is more strongly correlated with VO2 than with HR. This is a very promising approach to develop a new method to estimate energy expenditure

  15. Increased cardiac output and maximal oxygen uptake in response to ten sessions of high intensity interval training.

    Science.gov (United States)

    Astorino, Todd A; Edmunds, Ross M; Clark, Amy; King, Leesa; Gallant, Rachael M; Namm, Samantha; Fischer, Anthony; Wood, Kimi A

    2018-01-01

    Increases in maximal oxygen uptake (VO2max) are widely reported in response to completion of high intensity interval training (HIIT), yet the mechanism explaining this result is poorly understood. This study examined changes in VO2max and cardiac output (CO) in response to 10 sessions of low-volume HIIT. Participants included 30 active men and women (mean age and VO2max=22.9±5.4 years and 39.6±5.6 mL/kg/min) who performed HIIT and 30 men and women (age and VO2max=25.7±4.5 years and 40.7±5.2 mL/kg/min) who served as non-exercising controls (CON). High intensity interval training consisted of 6-10 s bouts of cycling per session at 90-110 percent peak power output (PPO) interspersed with 75 s recovery. Before and after training, progressive cycling to exhaustion was completed during which CO, stroke volume (SV), and heart rate (HR) were estimated using thoracic impedance. To confirm VO2max attainment, a verification test was completed after progressive cycling at a work rate equal to 110%PPO. Data demonstrated significant improvements in VO2max (2.71±0.63 L/min to 2.86±0.63 L/min, Psessions of HIIT is due to improvements in oxygen delivery.

  16. Bulk chlorine uptake by polyamide active layers of thin-film composite membranes upon exposure to free chlorine-kinetics, mechanisms, and modeling.

    Science.gov (United States)

    Powell, Joshua; Luh, Jeanne; Coronell, Orlando

    2014-01-01

    We studied the volume-averaged chlorine (Cl) uptake into the bulk region of the aromatic polyamide active layer of a reverse osmosis membrane upon exposure to free chlorine. Volume-averaged measurements were obtained using Rutherford backscattering spectrometry with samples prepared at a range of free chlorine concentrations, exposure times, and mixing, rinsing, and pH conditions. Our volume-averaged measurements complement previous studies that have quantified Cl uptake at the active layer surface (top ≈ 7 nm) and advance the mechanistic understanding of Cl uptake by aromatic polyamide active layers. Our results show that surface Cl uptake is representative of and underestimates volume-averaged Cl uptake under acidic conditions and alkaline conditions, respectively. Our results also support that (i) under acidic conditions, N-chlorination followed by Orton rearrangement is the dominant Cl uptake mechanism with N-chlorination as the rate-limiting step; (ii) under alkaline conditions, N-chlorination and dechlorination of N-chlorinated amide links by hydroxyl ion are the two dominant processes; and (iii) under neutral pH conditions, the rates of N-chlorination and Orton rearrangement are comparable. We propose a kinetic model that satisfactorily describes Cl uptake under acidic and alkaline conditions, with the largest discrepancies between model and experiment occurring under alkaline conditions at relatively high chlorine exposures.

  17. Benthic Oxygen Uptake in the Arctic Ocean Margins - A Case Study at the Deep-Sea Observatory HAUSGARTEN (Fram Strait.

    Directory of Open Access Journals (Sweden)

    Cecile Cathalot

    Full Text Available The past decades have seen remarkable changes in the Arctic, a hotspot for climate change. Nevertheless, impacts of such changes on the biogeochemical cycles and Arctic marine ecosystems are still largely unknown. During cruises to the deep-sea observatory HAUSGARTEN in July 2007 and 2008, we investigated the biogeochemical recycling of organic matter in Arctic margin sediments by performing shipboard measurements of oxygen profiles, bacterial activities and biogenic sediment compounds (pigment, protein, organic carbon, and phospholipid contents. Additional in situ oxygen profiles were performed at two sites. This study aims at characterizing benthic mineralization activity along local bathymetric and latitudinal transects. The spatial coverage of this study is unique since it focuses on the transition from shelf to Deep Ocean, and from close to the ice edge to more open waters. Biogeochemical recycling across the continental margin showed a classical bathymetric pattern with overall low fluxes except for the deepest station located in the Molloy Hole (5500 m, a seafloor depression acting as an organic matter depot center. A gradient in benthic mineralization rates arises along the latitudinal transect with clearly higher values at the southern stations (average diffusive oxygen uptake of 0.49 ± 0.18 mmol O2 m-2 d-1 compared to the northern sites (0.22 ± 0.09 mmol O2 m-2 d-1. The benthic mineralization activity at the HAUSGARTEN observatory thus increases southward and appears to reflect the amount of organic matter reaching the seafloor rather than its lability. Although organic matter content and potential bacterial activity clearly follow this gradient, sediment pigments and phospholipids exhibit no increase with latitude whereas satellite images of surface ocean chlorophyll a indicate local seasonal patterns of primary production. Our results suggest that predicted increases in primary production in the Arctic Ocean could induce a larger

  18. Electrodeposited ultrafine TaOx/CB catalysts for PEFC cathode application: Their oxygen reduction reaction kinetics

    KAUST Repository

    Seo, Jeongsuk

    2014-12-01

    Ultrafine TaOx nanoparticles were electrodeposited on carbon black (CB) powder in a nonaqueous Ta complex solution at room temperature, and the resultant TaOx/CB catalysts were assessed as oxygen reduction reaction (ORR) electrocatalysts for polymer electrolyte fuel cell (PEFC) cathodes. The Ta electrodeposition process was scaled up using a newly designed working electrode containing a CB dense layer, without introducing any binder such as the ionomer Nafion in the electrode for electrodeposition. The electrodeposited TaOx/CB powders were removed from the deposition electrode and subsequent H2 treatment at varying temperatures between 523 and 1073 K was attempted to increase the ORR performance. The TaOx/CB samples were characterized by SEM, STEM, XPS, and EELS measurements. XPS and EELS results indicated the reduced nature of the Ta species caused by the high-temperature treatment in H2, while STEM images clearly revealed that the TaOx particles aggregated as the treatment temperature increased. When the TaOx/CB catalyst, which was treated at 873 K for 2 h, was deposited on a glassy carbon substrate with Nafion ionomer, it resulted in the highest activity among the samples investigated, giving an onset potential of 0.95 VRHE at -2 μA cm-2 in a 0.1 M H2SO4 solution. Moreover, the long-term stability test with 10,000 cycles of the voltammetry only led to a 6% loss in the ORR currents, demonstrating the high stability of the TaOx/CB catalysts. Kinetic analysis by R(R)DE indicated that the four-electron transfer pathway in the ORR process was dominant for this TaOx/CB catalyst, and Tafel plots showed a slope corresponding to a one-electron reaction for the rate-determining step.

  19. Electrodeposited ultrafine TaOx/CB catalysts for PEFC cathode application: Their oxygen reduction reaction kinetics

    KAUST Repository

    Seo, Jeongsuk; Anjum, Dalaver H.; Takanabe, Kazuhiro; Kubota, Jun; Domen, Kazunari

    2014-01-01

    Ultrafine TaOx nanoparticles were electrodeposited on carbon black (CB) powder in a nonaqueous Ta complex solution at room temperature, and the resultant TaOx/CB catalysts were assessed as oxygen reduction reaction (ORR) electrocatalysts for polymer electrolyte fuel cell (PEFC) cathodes. The Ta electrodeposition process was scaled up using a newly designed working electrode containing a CB dense layer, without introducing any binder such as the ionomer Nafion in the electrode for electrodeposition. The electrodeposited TaOx/CB powders were removed from the deposition electrode and subsequent H2 treatment at varying temperatures between 523 and 1073 K was attempted to increase the ORR performance. The TaOx/CB samples were characterized by SEM, STEM, XPS, and EELS measurements. XPS and EELS results indicated the reduced nature of the Ta species caused by the high-temperature treatment in H2, while STEM images clearly revealed that the TaOx particles aggregated as the treatment temperature increased. When the TaOx/CB catalyst, which was treated at 873 K for 2 h, was deposited on a glassy carbon substrate with Nafion ionomer, it resulted in the highest activity among the samples investigated, giving an onset potential of 0.95 VRHE at -2 μA cm-2 in a 0.1 M H2SO4 solution. Moreover, the long-term stability test with 10,000 cycles of the voltammetry only led to a 6% loss in the ORR currents, demonstrating the high stability of the TaOx/CB catalysts. Kinetic analysis by R(R)DE indicated that the four-electron transfer pathway in the ORR process was dominant for this TaOx/CB catalyst, and Tafel plots showed a slope corresponding to a one-electron reaction for the rate-determining step.

  20. Peroxone mineralization of chemical oxygen demand for direct potable water reuse: Kinetics and process control.

    Science.gov (United States)

    Wu, Tingting; Englehardt, James D

    2015-04-15

    Mineralization of organics in secondary effluent by the peroxone process was studied at a direct potable water reuse research treatment system serving an occupied four-bedroom, four bath university residence hall apartment. Organic concentrations were measured as chemical oxygen demand (COD) and kinetic runs were monitored at varying O3/H2O2 dosages and ratios. COD degradation could be accurately described as the parallel pseudo-1st order decay of rapidly and slowly-oxidizable fractions, and effluent COD was reduced to below the detection limit (<0.7 mg/L). At dosages ≥4.6 mg L(-1) h(-1), an O3/H2O2 mass ratio of 3.4-3.8, and initial COD <20 mg/L, a simple first order decay was indicated for both single-passed treated wastewater and recycled mineral water, and a relationship is proposed and demonstrated to estimate the pseudo-first order rate constant for design purposes. At this O3/H2O2 mass ratio, ORP and dissolved ozone were found to be useful process control indicators for monitoring COD mineralization in secondary effluent. Moreover, an average second order rate constant for OH oxidation of secondary effluent organics (measured as MCOD) was found to be 1.24 × 10(7) ± 0.64 × 10(7) M(-1) S(-1). The electric energy demand of the peroxone process is estimated at 1.73-2.49 kW h electric energy for removal of one log COD in 1 m(3) secondary effluent, comparable to the energy required for desalination of medium strength seawater. Advantages/disadvantages of the two processes for municipal wastewater reuse are discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Characterization of hydroxybenzoic acid chelating resins: equilibrium, kinetics, and isotherm profiles for Cd(II and Pb(II uptake

    Directory of Open Access Journals (Sweden)

    BHAVNA A. SHAH

    2011-06-01

    Full Text Available Chelating ion-exchange resins were synthesized by polycondensation of ortho/para hydroxybenzoic acid with resorcinol/catechol employing formaldehyde as cross-linking agent at 80±5 °C in DMF. The resins were characterized by FTIR and XRD. The uptake behaviour of synthesized resins for Cd(II and Pb(II ions have been studied depending on contact time, pH, metal ion concentration and temperature. The sorption data obtained at optimized conditions were analyzed by the Langmuir and Freundlich isotherms. Experimental data of all metal–resin system were best represented by the Freundlich isotherm. The maximum obtained sorption capacity for cadmium was 69.53 mg g-1 and 169.32 mg g-1 for Lead. The adsorption process follows first order kinetics and the specific rate constant Kr was obtained by the application of the Lagergan equation. Thermodynamic parameters ∆Gads, ∆Sads and ∆Hads were calculated for the metal–resin systems. The external diffusion rate constant (KS and the intra-particle diffusion rate constant (Kid were calculated by the Spahn–Schlunder and Weber–Morris models, respectively. The sorption process was found to follow an intra-particle diffusion phenomenon.

  2. EMG and oxygen uptake responses during slow and fast ramp exercise in humans.

    Science.gov (United States)

    Scheuermann, Barry W; Tripse McConnell, Joyce H; Barstow, Thomas J

    2002-01-01

    This study examined the relationship between muscle recruitment patterns using surface electromyography (EMG) and the excess O(2) uptake (Ex.V(O(2))) that accompanies slow (SR, 8 W min(-1)) but not fast (FR, 64 W min(-1)) ramp increases in work rate (WR) during exercise on a cycle ergometer. Nine subjects (2 females) participated in this study (25 +/- 2 years, +/- S.E.M.). EMG was obtained from the vastus lateralis and medialis and analysed in the time (root mean square, RMS) and frequency (median power frequency, MDPF) domain. Results for each muscle were averaged to provide an overall response and expressed relative to a maximal voluntary contraction (%MVC). Delta.V(O(2))/DeltaWR was calculated for exercise below (S(1)) and above (S(2)) the lactate threshold (LT) using linear regression. The increase in RMS relative to the increase in WR for exercise below the LT (DeltaRMS/DeltaWR-S(1)) was determined using linear regression. Due to non-linearities in RMS above the LT, DeltaRMS/DeltaWR-S(2) is reported as the difference in RMS (DeltaRMS) and the difference in WR (DeltaWR) at end-exercise and the LT. SR was associated with a higher (P exercise is not associated with the recruitment of additional motor units since Ex.V(O(2)) was observed during SR only. Compared to the progressive decrease in MDPF observed during FR, the MDPF remained relatively constant during SR suggesting that either (i) there was no appreciable recruitment of the less efficient type II muscle fibres, at least in addition to those recruited initially at the onset of exercise, or (ii) the decrease in MDPF associated with fatigue was offset by the addition of a higher frequency of type II fibres recruited to replace the fatigued motor units.

  3. Carbon and nitrogen uptake of calcareous benthic foraminifera along a depth-related oxygen gradient in the OMZ of the Arabian Sea

    Directory of Open Access Journals (Sweden)

    Annekatrin Julie Enge

    2016-02-01

    Full Text Available Foraminifera are an important faunal element of the benthos in oxygen-depleted settings such as Oxygen Minimum Zones (OMZs where they can play a relevant role in the processing of phytodetritus. We investigated the uptake of phytodetritus (labeled with 13C and 15N by cal-careous foraminifera in the 0-1 cm sediment horizon under different oxygen concentrations within the OMZ in the eastern Arabian Sea. The in situ tracer experiments were carried out along a depth transect on the Indian margin over a period of 4 to 10 days. The uptake of phy-todetrital carbon within 4 days by all investigated species shows that phytodetritus is a rele-vant food source for foraminifera in OMZ sediments. The decrease of total carbon uptake from 540 to 1100 m suggests a higher demand for carbon by species in the low-oxygen core region of the OMZ or less food competition with macrofauna. Especially Uvigerinids showed high uptake of phytodetrital carbon at the lowest oxygenated site. Variation in the ratio of phytodetrital carbon to nitrogen between species and sites indicates that foraminiferal carbon and nitrogen use can be decoupled and different nutritional demands are found between spe-cies. Lower ratio of phytodetrital carbon and nitrogen at 540 m could hint for greater demand or storage of food-based nitrogen, ingestion or hosting of bacteria under almost anoxic condi-tions. Shifts in the foraminiferal assemblage structure (controlled by oxygen or food availabil-ity and in the presence of other benthic organisms account for observed changes in the pro-cessing of phytodetritus in the different OMZ habitats. Foraminifera dominate the short-term processing of phytodetritus in the OMZ core but are less important in the lower OMZ bounda-ry region of the Indian margin as biological interactions and species distribution of foraminif-era change with depth and oxygen levels.

  4. Electrophysiological approach to determine kinetic parameters of sucrose uptake by single sieve elements or phloem parenchyma cells in intact Vicia faba plants.

    Science.gov (United States)

    Hafke, Jens B; Höll, Sabina-Roxana; Kühn, Christina; van Bel, Aart J E

    2013-01-01

    Apart from cut aphid stylets in combination with electrophysiology, no attempts have been made thus far to measure in vivo sucrose-uptake properties of sieve elements. We investigated the kinetics of sucrose uptake by single sieve elements and phloem parenchyma cells in Vicia faba plants. To this end, microelectrodes were inserted into free-lying phloem cells in the main vein of the youngest fully-expanded leaf, half-way along the stem, in the transition zone between the autotrophic and heterotrophic part of the stem, and in the root axis. A top-to-bottom membrane potential gradient of sieve elements was observed along the stem (-130 mV to -110 mV), while the membrane potential of the phloem parenchyma cells was stable (approx. -100 mV). In roots, the membrane potential of sieve elements dropped abruptly to -55 mV. Bathing solutions having various sucrose concentrations were administered and sucrose/H(+)-induced depolarizations were recorded. Data analysis by non-linear least-square data fittings as well as by linear Eadie-Hofstee (EH) -transformations pointed at biphasic Michaelis-Menten kinetics (2 MM, EH: K m1 1.2-1.8 mM, K m2 6.6-9.0 mM) of sucrose uptake by sieve elements. However, Akaike's Information Criterion (AIC) favored single MM kinetics. Using single MM as the best-fitting model, K m values for sucrose uptake by sieve elements decreased along the plant axis from 1 to 7 mM. For phloem parenchyma cells, higher K m values (EH: K m1 10 mM, K m2 70 mM) as compared to sieve elements were found. In preliminary patch-clamp experiments with sieve-element protoplasts, small sucrose-coupled proton currents (-0.1 to -0.3 pA/pF) were detected in the whole-cell mode. In conclusion (a) K m values for sucrose uptake measured by electrophysiology are similar to those obtained with heterologous systems, (b) electrophysiology provides a useful tool for in situ determination of K m values, (c) As yet, it remains unclear if one or two uptake systems are involved in sucrose

  5. Kinetic study of the alkaline metals oxidation by dry oxygen; Etude cinetique de l'oxydation des metaux alcalins par l'oxygene sec

    Energy Technology Data Exchange (ETDEWEB)

    Touzain, Ph. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1967-06-15

    The oxidation of lithium, sodium, potassium, rubidium, cesium and sodium-potassium alloys by dry oxygen is studied at several temperatures and in the oxygen pressure range 40 to 400 mmHg. One distinguishes three different oxidation behaviours (inflammation, ignition and slow combustion) whose zones are precised in function of the temperature. The slow oxidation kinetic laws, the composition of oxides and the motive of oxides colorations are determined. At least, the experimental data are construed theoretically. (author) [French] L'oxydation du lithium, du sodium, du potassium, du rubidium, du cesium et des alliages sodium-potassium par l'oxygene sec est etudiee a diverses temperatures et a des pressions comprises entre 40 et 400 mmHg d'oxygene. On distingue trois processus d'oxydation differents (l'inflammation, l'ignition et la combustion lente) dont les domaines en fonction de la temperature sont precises. Les lois cinetiques d'oxydation lente, la nature des oxydes formes ainsi que les causes des colorations de ces oxydes sont determinees. Enfin les resultats obtenus sont interpretes theoriquement. (auteur)

  6. Kinetic study of the alkaline metals oxidation by dry oxygen; Etude cinetique de l'oxydation des metaux alcalins par l'oxygene sec

    Energy Technology Data Exchange (ETDEWEB)

    Touzain, Ph [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1967-06-15

    The oxidation of lithium, sodium, potassium, rubidium, cesium and sodium-potassium alloys by dry oxygen is studied at several temperatures and in the oxygen pressure range 40 to 400 mmHg. One distinguishes three different oxidation behaviours (inflammation, ignition and slow combustion) whose zones are precised in function of the temperature. The slow oxidation kinetic laws, the composition of oxides and the motive of oxides colorations are determined. At least, the experimental data are construed theoretically. (author) [French] L'oxydation du lithium, du sodium, du potassium, du rubidium, du cesium et des alliages sodium-potassium par l'oxygene sec est etudiee a diverses temperatures et a des pressions comprises entre 40 et 400 mmHg d'oxygene. On distingue trois processus d'oxydation differents (l'inflammation, l'ignition et la combustion lente) dont les domaines en fonction de la temperature sont precises. Les lois cinetiques d'oxydation lente, la nature des oxydes formes ainsi que les causes des colorations de ces oxydes sont determinees. Enfin les resultats obtenus sont interpretes theoriquement. (auteur)

  7. Relationship between work rate and oxygen uptake in mitochondrial myopathy during ramp-incremental exercise

    Directory of Open Access Journals (Sweden)

    A.C. Gimenes

    2011-04-01

    Full Text Available We determined the response characteristics and functional correlates of the dynamic relationship between the rate (Δ of oxygen consumption ( O2 and the applied power output (work rate = WR during ramp-incremental exercise in patients with mitochondrial myopathy (MM. Fourteen patients (7 males, age 35.4 ± 10.8 years with biopsy-proven MM and 10 sedentary controls (6 males, age 29.0 ± 7.8 years took a ramp-incremental cycle ergometer test for the determination of the O2 on-exercise mean response time (MRT and the gas exchange threshold (GET. The ΔO2/ΔWR slope was calculated up to GET (S1, above GET (S2 and over the entire linear portion of the response (S T. Knee muscle endurance was measured by isokinetic dynamometry. As expected, peak O2 and muscle performance were lower in patients than controls (P O2/ΔWR than controls, especially the S2 component (6.8 ± 1.5 vs 10.3 ± 0.6 mL·min-1·W-1, respectively; P O2/ΔWR (S T and muscle endurance, MRT-O2, GET and peak O2 in MM patients (P O2/ΔWR below 8 mL·min-1·W-1 had severely reduced peak O2 values (O2 had lower ΔO2/ΔWR (P O2/ΔWR is typically reduced in patients with MM, being related to increased functional impairment and higher cardiopulmonary stress.

  8. The Effects of Hypobaric Hypoxia on Erythropoiesis, Maximal Oxygen Uptake and Energy Cost of Exercise Under Normoxia in Elite Biathletes

    Directory of Open Access Journals (Sweden)

    Milosz Czuba

    2014-12-01

    Full Text Available The aim of the present study was to evaluate the effects of 3 weeks altitude training according to the HiHiLo (live high-base train high-interval train low procedure as described by Chapman et al. (1998, on erythropoiesis, maximal oxygen uptake and energy cost of exercise under normoxia in elite biathletes. Fifteen male elite biathletes randomly divided into an experimental (H group (n = 7; age 27.1 ± 4.6 years; maximal oxygen uptake (VO2max 66.9 ± 3.3 ml·kg–1·min–1; body height (BH 1.81 ± 0.06 m; body mass (BM 73.1 ± 5.4kg, and a control (C group (n = 8; age 23.2 ± 0.9 years; VO2max 68.2 ± 4.1 ml·kg–1·min–1; BH 1.75 ± 0.03 m; BM 63.1 ± 1.5 kg took part in the study. The H group stayed for 3 weeks at an altitude of 2015 m and performed endurance training on skis four times per week at 3000 m. Additionally, the training protocol included three high-intensity interval sessions at an altitude of 1000 m. The C group followed the same training protocol with skirollers in normoxia at an altitude of 600 m. The HiHiLo protocol applied in our study did not change VO2max or maximal workload (WRmax significantly during the incremental treadmill test in group H. However, the energy cost for selected submaximal workloads in group H was significantly (p < 0.01 reduced compared to group C (-5.7%, -4.4%, -6% vs. -3.5%, -2.1%, -2.4%. Also a significant (p < 0.001 increase in serum EPO levels during the first two weeks of HiHiLo training at 2015 m was observed, associated with a significant (p < 0.05 increase in hemoglobin mass, number of erythrocytes, hematocrit value and percent of reticulocytes compared with initial values (by 6.4%, 5%, 4.6% and 16,6%, respectively. In group C, changes in these variables were not observed. These positive changes observed in our study led to a conclusion that the HiHiLo training method could improve endurance in normoxia, since most of the biathlon competitions are performed at submaximal intensities.

  9. Effect of caffeine on maximal oxygen uptake in wheelchair rugby players: A randomized, placebo-controlled, double-blind study

    Directory of Open Access Journals (Sweden)

    Iva Klimešová

    2017-03-01

    Full Text Available Background: The positive effects of caffeine supplementation on strength-power and endurance performance in healthy athletes have been demonstrated in many studies. A possible mechanism for its ergogenic effect relates to its influence on the central nervous system. Post-traumatic complications in cervical spinal cord injury affect almost all body systems including the nervous system. For this reason, we expect that caffeine will have a different effect of performance in the group of athletes with spinal cord injuries. Objective: To examine the effects of caffeine supplementation on maximal aerobic power in elite wheelchair rugby players. Methods: Seven elite male wheelchair rugby players with complete cervical-level SCI (C4-Th1 were recruited (mean age: 28 ± 5.42 years; mean body mass index: 26 ± 2.84 kg/m2. The effect of caffeine was assessed by an incremental arm ergometer test until volitional exhaustion. The maximal oxygen uptake (VO2max/kg, maximum power (W max/kg, peak heart rate (HR peak, and intensity of perceived exertion (RPE were measured. Participants performed the test twice with a two-week washout period. One hour before each exercise test subjects ingested a capsule of placebo or caffeine (3 mg per kg of body weight. The tests were applied in a double-blind, randomized, repeated-measures, and cross-over design. Wheelchair rugby players were chosen because of the expected high homogeneity of participants - in terms of the type and degree of disability, gender, and age of the players. Results: The monitored parameters were not significantly influenced by caffeine intervention as compared to placebo: VO2max/kg (p = .40, W max/kg (p = .34, HR peak (p = .50 and RPE (p = .50. Conclusions: The current findings suggest that a caffeine dose of 3 mg/kg body mass does not improve oxygen uptake and maximal power in elite wheelchair rugby players.

  10. Comparison of oxygen uptake during and after the execution of resistance exercises and exercises performed on ergometers, matched for intensity

    Directory of Open Access Journals (Sweden)

    Vilaça-Alves José

    2016-12-01

    Full Text Available The aim of this study was to compare the values of oxygen uptake (VO2 during and after strength training exercises (STe and ergometer exercises (Ee, matched for intensity and exercise time. Eight men (24 ± 2.33 years performed upper and lower body cycling Ee at the individual’s ventilatory threshold (VE/VCO2. The STe session included half squats and the bench press which were performed with a load at the individual blood lactate concentration of 4 mmol/l. Both sessions lasted 30 minutes, alternating 50 seconds of effort with a 10 second transition time between upper and lower body work. The averaged overall VO2 between sessions was significantly higher for Ee (24.96 ± 3.6 ml·kg·min-1 compared to STe (21.66 ± 1.77 ml·kg·min-1 (p = 0.035, but this difference was only seen for the first 20 minutes of exercise. Absolute VO2 values between sessions did not reveal differences. There were more statistically greater values in Ee compared to STe, regarding VO2 of lower limbs (25.44 ± 3.84 ml·kg·min-1 versus 21.83 ± 2·24 ml·kg·min-1; p = 0.038 and upper limbs (24.49 ± 3.84 ml·kg·min-1 versus 21.54 ± 1.77 ml·kg·min-1; p = 0.047. There were further significant differences regarding the moment effect (p<0.0001 of both STe and Ee sessions. With respect to the moment × session effect, only VO2 5 minutes into recovery showed significant differences (p = 0.017. In conclusion, although significant increases in VO2 were seen following Ee compared to STe, it appears that the load/intensity, and not the material/equipment used for the execution of an exercise, are variables that best influence oxygen uptake.

  11. Automated Determination of Oxygen-Dependent Enzyme Kinetics in a Tube-in-Tube Flow Reactor

    DEFF Research Database (Denmark)

    Ringborg, Rolf Hoffmeyer; Pedersen, Asbjørn Toftgaard; Woodley, John

    2017-01-01

    revealed not only the high degree of accuracy of the kinetic data obtained, but also the necessity of making measurements in this way to enable the accurate evaluation of high KMO enzyme systems. For the first time, this paves the way to integrate kinetic data into the protein engineering cycle....

  12. Kinetics of Several Oxygen-Containing Carbon-Centered Free Radical Reactions with Nitric Oxide.

    Science.gov (United States)

    Rissanen, Matti P; Ihlenborg, Marvin; Pekkanen, Timo T; Timonen, Raimo S

    2015-07-16

    Kinetics of four carbon-centered, oxygen-containing free radical reactions with nitric oxide (NO) were investigated as a function of temperature at a few Torr pressure of helium, employing flow tube reactors coupled to a laser-photolysis/resonance-gas-discharge-lamp photoionization mass spectrometer (LP-RPIMS). Rate coefficients were directly determined from radical (R) decay signals under pseudo-first-order conditions ([R]0 ≪ [NO]). The obtained rate coefficients showed negative temperature dependences, typical for a radical-radical association process, and can be represented by the following parametrizations (all in units of cm(3) molecule(-1) s(-1)): k(CH2OH + NO) = (4.76 × 10(-21)) × (T/300 K)(15.92) × exp[50700/(RT)] (T = 266-363 K, p = 0.79-3.44 Torr); k(CH3CHOH + NO) = (1.27 × 10(-16)) × (T/300 K)(6.81) × exp[28700/(RT)] (T = 241-363 K, p = 0.52-3.43 Torr); k(CH3OCH2 + NO) = (3.58 ± 0.12) × 10(-12) × (T/300 K)(-3.17±0.14) (T = 221-363 K, p = 0.50-0.80 Torr); k(T)3 = 9.62 × 10(-11) × (T/300 K)(-5.99) × exp[-7100/(RT)] (T = 221-473 K, p = 1.41-2.95 Torr), with the uncertainties given as standard errors of the fits and the overall uncertainties estimated as ±20%. The rate of CH3OCH2 + NO reaction was measured in two density ranges due to its observed considerable pressure dependence, which was not found in the studied hydroxyalkyl reactions. In addition, the CH3CO + NO rate coefficient was determined at two temperatures resulting in k298K(CH3CO + NO) = (5.6 ± 2.8) × 10(-13) cm(3) molecule(-1) s(-1). No products were found during these experiments, reasons for which are briefly discussed.

  13. Depuration and uptake kinetics of I, CS, MN, ZN and CD by the earthworm (lumbricus terrestris) in radiotracer-spiked litter

    International Nuclear Information System (INIS)

    Sheppard, S.C.; Evenden, W.G.; Cornwell, T.C.

    1997-01-01

    The relative depuration and uptake kinetics of contaminants should be known to interpret appropriately the use of organisms such as earthworms in environmental bioassays and monitoring. For example, 14-d earthworm bioassays should be interpreted with the knowledge that some contaminants will continue to accumulate in tissues for months. The radiotracers 125 I, 134 Cs, 54 Mn, 65 Zn, and 109 Cd were applied to deciduous litter and specimens of Lumbricus terrestris were exposed, either to litter alone or to litter on the top of soil columns. Depuration was monitored for 120 d and uptake, in a separate experiment, for 20 d. Both depuration and uptake were described using two-phase, first-order statistical models. Gut clearance had a mean half-time of 1.4 d. The mean half-time for physiological depuration decreased from I (210 d) > Cd (150 d) > Zn (69 d) > Mn (40 d) > Cs (24 d). Both the deputation and the uptake experiments were necessary to resolve even partially the multiphase processes. Earthworm/soil dry weight concentration ratios decreased from Cd > Zn > I ≥ Cs ≥ Mn. The very slow kinetics indicate that tissue concentrations will increase continuously for a long time, with important implications for subsequent food-chain transfers. (author)

  14. Oxygen uptake response to cycle ergometry in post-acute stroke patients with different severity of hemiparesis.

    Science.gov (United States)

    Chen, Chun-Kai; Weng, Ming-Cheng; Chen, Tien-Wen; Huang, Mao-Hsiung

    2013-11-01

    This study evaluated the impact of severity of hemiparesis on oxygen uptake (VO2) response in post-acute stroke patients. Sixty-four patients with a mean poststroke interval of 8.6 ± 3.8 days underwent a ramp cardiopulmonary exercise test on a cycling ergometer to volitional termination. Mean peak VO2 (VO2peak) and work efficiency (ΔVO2/ΔWR) were measured by open-circuit spirometry during standard upright ergometer cycling. Severity of the hemiparetic lower limb was assessed by Brunnstrom's motor recovery stages lower extremity (BMRSL). VO2peak was 10% lower in hemiparetic leg with BMRSL V than in that with BMRSL VI, 20% lower in BMRSL IV, and 50% lower in BMRSL III. ΔVO2/ΔWR was higher for the group with increased BMRSL. The relations were consistent after adjustment for age, sex, body mass index, stroke type, hemiparetic side, modified Ashworth Scale, time poststroke, comorbidities, and medications. Our findings revealed that O2peak is dependent on the severity of hemiparesis in leg, and along with ΔO2/ΔWR closely related to the severity of hemiparesis in post-acute stroke patients, regardless of the types and locations of lesion after stroke, as well as the differences in comorbidities and medications. Copyright © 2013. Published by Elsevier B.V.

  15. Influence of silicon treatment on antimony uptake and translocation in rice genotypes with different radial oxygen loss.

    Science.gov (United States)

    Zhang, Liping; Yang, Qianqian; Wang, Shiliang; Li, Wanting; Jiang, Shaoqing; Liu, Yan

    2017-10-01

    Antimony (Sb) pollution in soil may have a negative impact on the health of people consuming rice. This study investigated the effect of silicon (Si) application on rice biomass, iron plaque formation, and Sb uptake and speciation in rice plants with different radial oxygen loss (ROL) using pot experiments. The results demonstrated that Si addition increased the biomass of straw and grain, but had no obvious impact on the root biomass. Indica genotypes with higher ROL underwent greater iron plaque formation and exhibited more Sb sequestration in iron plaque. Silicon treatments increased iron levels in iron plaque from the different genotypes but decreased the total Sb concentration in root, straw, husk, and grain. In addition, Si treatment reduced the inorganic Sb concentrations but slightly increased the trimethylantimony (TMSb) concentrations in rice straw. Moreover, rice straw from hybrid genotypes accumulated higher concentrations of TMSb and inorganic Sb than that from indica genotypes. The conclusions from this study indicate that Sb contamination in rice can be efficiently reduced by applying Si treatment and selecting genotypes with high ROL. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Cardiorespiratory Responses and Prediction of Peak Oxygen Uptake during the Shuttle Walking Test in Healthy Sedentary Adult Men

    Science.gov (United States)

    Neves, Camila D. C.; Lacerda, Ana Cristina Rodrigues; Lage, Vanessa K. S.; Lima, Liliana P.; Fonseca, Sueli F.; de Avelar, Núbia C. P.; Teixeira, Mauro M.; Mendonça, Vanessa A.

    2015-01-01

    Background The application of the Shuttle Walking Test (SWT) to assess cardiorespiratory fitness and the intensity of this test in healthy participants has rarely been studied. This study aimed to assess and correlate the cardiorespiratory responses of the SWT with the cardiopulmonary exercise testing (CEPT) and to develop a regression equation for the prediction of peak oxygen uptake (VO2 peak) in healthy sedentary adult men. Methods In the first stage of this study, 12 participants underwent the SWT and the CEPT on a treadmill. In the second stage, 53 participants underwent the SWT twice. In both phases, the VO2 peak, respiratory exchange ratio (R), and heart rate (HR) were evaluated. Results Similar results in VO2 peak (P>0.05), R peak (P>0.05) and predicted maximum HR (P>0.05) were obtained between the SWT and CEPT. Both tests showed strong and significant correlations of VO2 peak (r = 0.704, P = 0.01) and R peak (r = 0.737, P0.05) was found. Conclusions The SWT produced maximal cardiorespiratory responses comparable to the CEPT, and the developed equation showed viability for the prediction of VO2 peak in healthy sedentary men. PMID:25659094

  17. Effect of high-intensity training versus moderate training on peak oxygen uptake and chronotropic response in heart transplant recipients

    DEFF Research Database (Denmark)

    Dall, C H; Snoer, M; Christensen, S

    2014-01-01

    In heart transplant (HTx) recipients, there has been reluctance to recommend high-intensity interval training (HIIT) due to denervation and chronotropic impairment of the heart. We compared the effects of 12 weeks' HIIT versus continued moderate exercise (CON) on exercise capacity and chronotropic...... response in stable HTx recipients >12 months after transplantation in a randomized crossover trial. The study was completed by 16 HTx recipients (mean age 52 years, 75% males). Baseline peak oxygen uptake (VO2peak ) was 22.9 mL/kg/min. HIIT increased VO2peak by 4.9 ± 2.7 mL/min/kg (17%) and CON by 2.6 ± 2.......2 mL/kg/min (10%) (significantly higher in HIIT; p HIIT, systolic blood pressure decreased significantly (p = 0.037) with no significant change in CON (p = 0.241; between group difference p = 0.027). Peak heart rate (HRpeak ) increased significantly by 4.3 beats per minute (p = 0...

  18. Oxygen uptake in water polo, comparison and agreement in cycle ergometer and eggbeater kick: A pilot study

    Directory of Open Access Journals (Sweden)

    Ligia Ignêz Engelmann

    Full Text Available Abstract The aim of this study was to compare and verify the agreement of maximal oxygen uptake (VO2 max values obtained from tests on land and in water. Twelve recreational water polo players (30.5 ± 7.7 years; 79.2 ± 7.2 kg body mass; 179.1 ± 5.9 cm height were assessed in two phases: (1 in laboratory with maximal test on a cycle ergometer and (2 in a swimming pool with maximal test in eggbeater kick. Maximum values obtained in the two tests (respectively, cycle ergometer, and eggbeater kick: VO2 max = 40.2 ± 2.7 ml.kg-1.min-1 and 38.4 ± 5.7 ml.kg-1.min-1; RER = 1.17 ± 0.08 and 1.19 ± 0.12; HR max = 181.4 ± 11.7 bpm and 179 ± 11.7 bpm; IEP = 20 and 20 did not show significant differences. According to the Bland-Altman analyses, there were acceptable limits of agreement between the two tests (land and water. Therefore, it can be concluded that the eggbeater kick test is a specific and valid protocol to asses VO2 max in water polo players.

  19. Relationship between oxygen uptake slow component and surface EMG during heavy exercise in humans: influence of pedal rate.

    Science.gov (United States)

    Vercruyssen, Fabrice; Missenard, Olivier; Brisswalter, Jeanick

    2009-08-01

    The aim of this study was to test the hypothesis that extreme pedal rates contributed to the slow component of oxygen uptake (VO(2) SC) in association with changes in surface electromyographic (sEMG) during heavy-cycle exercise. Eight male trained cyclists performed two square-wave transitions at 50 and 110 rpm at a work rate that would elicit a VO(2) corresponding to 50% of the difference between peak VO(2) and the ventilatory threshold. Pulmonary gas exchange was measured breath-by-breath and sEMG was obtained from the vastus lateralis and medialis muscles. Integrated EMG flow (QiEMG) and mean power frequency (MPF) were computed. The relative amplitude of the VO(2) SC was significantly higher during the 110-rpm bout (556+/-186 ml min(-1), Pexercise only during the 110-rpm bout and were associated with the greater amplitude of the VO(2) SC observed for this condition (Pmotor units recruitment pattern, muscle energy turnover and muscle temperature have been suggested to explain the different VO(2) SC to heavy pedal rate bouts.

  20. 18F-FLT uptake kinetics in head and neck squamous cell carcinoma: A PET imaging study

    International Nuclear Information System (INIS)

    Liu, Dan; Fenwick, John D.; Chalkidou, Anastasia; Landau, David B.; Marsden, Paul K.

    2014-01-01

    Purpose: To analyze the kinetics of 3 ′ -deoxy-3 ′ -[F-18]-fluorothymidine (18F-FLT) uptake by head and neck squamous cell carcinomas and involved nodes imaged using positron emission tomography (PET). Methods: Two- and three-tissue compartment models were fitted to 12 tumor time-activity-curves (TACs) obtained for 6 structures (tumors or involved nodes) imaged in ten dynamic PET studies of 1 h duration, carried out for five patients. The ability of the models to describe the data was assessed using a runs test, the Akaike information criterion (AIC) and leave-one-out cross-validation. To generate parametric maps the models were also fitted to TACs of individual voxels. Correlations between maps of different parameters were characterized using Pearson'sr coefficient; in particular the phosphorylation rate-constants k 3-2tiss and k 5 of the two- and three-tissue models were studied alongside the flux parameters K FLT-2tiss and K FLT of these models, and standardized uptake values (SUV). A methodology based on expectation-maximization clustering and the Bayesian information criterion (“EM-BIC clustering”) was used to distil the information from noisy parametric images. Results: Fits of two-tissue models 2C3K and 2C4K and three-tissue models 3C5K and 3C6K comprising three, four, five, and six rate-constants, respectively, pass the runs test for 4, 8, 10, and 11 of 12 tumor TACs. The three-tissue models have lower AIC and cross-validation scores for nine of the 12 tumors. Overall the 3C6K model has the lowest AIC and cross-validation scores and its fitted parameter values are of the same orders of magnitude as literature estimates. Maps ofK FLT and K FLT-2tiss are strongly correlated (r = 0.85) and also correlate closely with SUV maps (r = 0.72 for K FLT-2tiss , 0.64 for K FLT ). Phosphorylation rate-constant maps are moderately correlated with flux maps (r = 0.48 for k 3-2tiss vs K FLT-2tiss and r = 0.68 for k 5 vs K FLT ); however, neither phosphorylation

  1. Fast kinetics of the oxygen effe4ct for DNA double-strand breakage and cell killing in irradiated yeast

    Energy Technology Data Exchange (ETDEWEB)

    Frankenberg, D; Frankenberg-Schwager, M; Harbich, R [Gesellschaft fuer Strahlen- und Umweltforschung mbH, Frankfurt/Main (Germany, F.R.). Inst. fuer Biophysikalische Strahlenforschung; Michael, B D [Mount Vernon Hospital, Northwood (UK). Gray Lab.

    1990-03-01

    The most important result of dsb kinetic data presented here is that lifetimes of the oxygen-dependent precursors are dose-dependent. This seems mainly to be caused by increased depletion of GSH at high doses. Therefore, shorter lifetimes of the oxygen-dependent precursors of dsb as measured by the inactivation of rad54-3 cells at 36{sup 0}C (t{sub 1/2}=0.25ms), or of stationary haploid GSH{sup +} cells (t{sub 1/2}=0.37 ms) are considered to be more relevant values, especially at low doses than those obtained by direct measurements (t{sub 1/2}=2.18 ms). Rejoining of dsb complicates the kinetics of the oxygen effect as measured at the survival level at the permissive temperature for dsb rejoining. When rejoining of dsb is allowed, besides the fast component a slow component becomes detectable. It is speculated that dsb having such long-living precursors are less readily susceptible for enzymatic rejoining, or are even irreparable. (author).

  2. Aspects of the uptake of dissolved oxygen in Cabiúnas and Imboassica Lagoons (Macaé, RJ

    Directory of Open Access Journals (Sweden)

    Paulo R. Brum

    1999-01-01

    Full Text Available In this work, we describe qualitative and quantitative aspects of the cycling of detritus of aquatic macrophytes and carbohydrates in two coastal lagoons of the northeastern part of the State of Rio de Janeiro. Samples of water of the Imboassica and Cabiúnas lagoons were enriched with sucrose. Samples of water of the Cabiúnas lagoon were also utilized to arrange mineralization chambers with fragments of three species of aquatic macrophytes found in these lagoons (Typha domingensis, Potamogeton stenostachys and Nymphaea ampla. Following that, the bottles were aerated and incubated (in the laboratory for a period of 8 days. The concentrations of dissolved oxygen, the pH, the electrical conductivity and the temperature were daily measured. The anaerobic processes were inhibited by periodical aeration of the bottles. The results suggested that the mineralization process in Imboassica lagoon was more efficient; in Cabiúnas lagoon the process of immobilization of the organic matter was dominant. In the short term, maximum oxygen uptake occurred in the mineralization of N. ampla, followed by the mineralization of P. stenostachys and of T. domingensis. However, it was estimated that in long term the mineralization of P. stenostachys showed a greater oxygen uptake.Nesta pesquisa, descrevemos aspectos qualitativos e quantitativos da ciclagem de detritos de macrófitas aquáticas e carboidratos em duas lagoas costeiras do nordeste do Estado do Rio de Janeiro. Amostras de água das lagoas Imboassica e Cabiúnas foram enriquecidas com sacarose. Amostras de água da lagoa Cabiúnas foram também utilizadas para a montagem de câmaras de mineralização com fragmentos de três espécies de macrófitas aquáticas encontradas nestas lagoas (Typha domingensis, Potamogeton stenostachys e Nymphaea ampla. Em seguida, as garrafas foram aeradas e incubadas (no laboratório por um período de 8 dias. As concentrações de oxigênio dissolvido, o pH, a condutividade

  3. Kinetic bottlenecks to chemical exchange rates for deep-sea animals - Part 1: Oxygen

    Science.gov (United States)

    Hofmann, A. F.; Peltzer, E. T.; Brewer, P. G.

    2012-10-01

    Ocean warming will reduce dissolved oxygen concentrations which can pose challenges to marine life. Oxygen limits are traditionally reported simply as a static concentration thresholds with no temperature, pressure or flow rate dependency. Here we treat the oceanic oxygen supply potential for heterotrophic consumption as a dynamic molecular exchange problem analogous to familiar gas exchange processes at the sea surface. A combination of the purely physico-chemical oceanic properties temperature, hydrostatic pressure, and oxygen concentration defines the ability of the ocean to supply oxygen to any given animal. This general oceanic oxygen supply potential is modulated by animal specific properties such as the diffusive boundary layer thickness to define and limit maximal oxygen supply rates. Here we combine all these properties into formal, mechanistic equations defining novel oceanic properties that subsume various relevant classical oceanographic parameters to better visualize, map, comprehend, and predict the impact of ocean deoxygenation on aerobic life. By explicitly including temperature and hydrostatic pressure into our quantities, various ocean regions ranging from the cold deep-sea to warm, coastal seas can be compared. We define purely physico-chemical quantities to describe the oceanic oxygen supply potential, but also quantities that contain organism-specific properties which in a most generalized way describe general concepts and dependencies. We apply these novel quantities to example oceanic profiles around the world and find that temperature and pressure dependencies of diffusion and partial pressure create zones of greatest physical constriction on oxygen supply typically at around 1000 m depth, which coincides with oxygen concentration minimum zones. In these zones, which comprise the bulk of the world ocean, ocean warming and deoxygenation have a clear negative effect for aerobic life. In some shallow and warm waters the enhanced diffusion and

  4. The relative importance of skin oxygen uptake in the naturally buried plaice, Pleuronectes platessa, exposed to graded hypoxia

    DEFF Research Database (Denmark)

    Steffensen, J F; Lomholt, J P; Johansen, K

    1981-01-01

    Cutaneous O2-uptake has been estimated in plaice, Pleuronectes platessa, naturally buried in sediment as the difference between total O2-uptake, measured in a flow-through respirometer, and branchial O2-uptake calculated from direct and continuous recordings of gill water flow and O2-extraction...

  5. Using Argo-O2 data to examine the impact of deep-water formation events on oxygen uptake in the Labrador Sea

    Science.gov (United States)

    Wolf, M. K.; Hamme, R. C.; Gilbert, D.; Yashayaev, I.

    2016-02-01

    Deep-water formation allows the deep ocean to communicate with the atmosphere, facilitating exchanges of heat as well as important gases such as CO2 and oxygen. The Labrador Sea is the most studied location of deep convection in the North Atlantic Ocean and a strong contributor to the global thermohaline circulation. Since there are no internal sources of oxygen below the euphotic zone, deep-water formation is vital for oxygen transport to the deep ocean. Recent studies document large interannual variability in the strength and depth of convection in the Labrador Sea, from mixed layers of 100m to greater than 1000m. A weakening of this deep convection starves the deep ocean of oxygen, disrupting crucial deep sea biological processes, as well as reducing oceanic CO2 uptake and ocean circulation. We used data from the extensive Argo float network to examine these deep-water formation events in the Labrador Sea. The oxygen optodes onboard many Argo floats suffer from biases whose amplitude must be determined; therefore we investigated and applied various optode calibration methods. Using calibrated vertical profiles of oxygen, temperature, and salinity, we observed the timing, magnitude, and location of deep convection, restratification, and spring phytoplankton blooms. In addition, we used surface oxygen values along with NCEP wind speeds to calculate the air-sea oxygen flux using a range of air-sea gas exchange parameterizations. We then compared this oxygen flux to the rate of change of the measured oxygen inventory. Where the inventory and flux did not agree, we identified other oceanic processes such as biological activity or lateral advection of water masses occurring, or advection of the float itself into a new area. The large role that horizontal advection of water or the float has on oxygen uptake and cycling leads us to conclude that this data cannot be easily interpreted as a 1-D system. Oxygen exchanges with the atmosphere at a faster rate than CO2, is

  6. Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

    Directory of Open Access Journals (Sweden)

    Nicola H. Perry

    2016-10-01

    Full Text Available Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface oxygen exchange, fast bulk transport (electronic and ionic, and thermo-chemo-mechanical stability of oxygen electrodes will require increased understanding of the impact of both bulk and surface chemistry on these properties. This review highlights selected work at the International Institute for Carbon-Neutral Energy Research (I2CNER, Kyushu University, set in the context of work in the broader community, aiming to characterize and understand relationships between bulk and surface composition and oxygen electrode performance. Insights into aspects of bulk point defect chemistry, electronic structure, crystal structure, and cation choice that impact carrier concentrations and mobilities, surface exchange kinetics, and chemical expansion coefficients are emerging. At the same time, an understanding of the relationship between bulk and surface chemistry is being developed that may assist design of electrodes with more robust surface chemistries, e.g., impurity tolerance or limited surface segregation. Ion scattering techniques (e.g., secondary ion mass spectrometry, SIMS, or low energy ion scattering spectroscopy, LEIS with high surface sensitivity and increasing lateral resolution are proving useful for measuring surface exchange kinetics, diffusivity, and corresponding outer monolayer chemistry of electrodes exposed to typical operating conditions. Beyond consideration of chemical composition, the use of strain and/or a high density of active interfaces also show promise for enhancing performance.

  7. Kinetics of adsorption and uptake of Cu2+ by Chlorella vulgaris: influence of pH, temperature, culture age, and cations.

    Science.gov (United States)

    Mehta, S K; Singh, Alpana; Gaur, J P

    2002-03-01

    Adsorption and uptake of Cu2+ by Chlorella vulgaris were distinguished by extracting the surface-bound Cu2+ with EDTA. The uptake of Cu2+ followed Michaelis Menten kinetics. The maximum rate of Cu2+ uptake (0.362fmolcell(-1) h(-1)) was obtained at pH 6.0. The rate of Cu2+ uptake was greater for cultures in the exponential phase of growth, and increased with a rise in temperature from 6 to 25 degrees C, thus pointing towards an active mechanism. The maximum number of Cu2+ binding sites was 3.245 fmol cell(-1) at pH 4.5. Adsorption of Cu2+ was strongly pH-dependent thereby indicating that the number and nature of metal binding sites on the cell surface change with changing chemistry of the solution. Unlike uptake, the adsorption remained unaffected by small changes in temperature. Older cultures displayed a higher Cu2+ adsorption capacity than the exponentially growing ones thus suggesting generation of new and/or additional Cu2+ binding sites on older cells of C. vulgaris. By pH titration, the cation-exchange capacity of Chlorella, measured in terms of H+/ Na+ exchange, was about 17 fmol cell(-1) at pH 10.5. Negligible cation exchange capacity at and below pH 5.0 indicated that ion exchange was not the sole mechanism of Cu2+ adsorption by Chlorella. The uptake and adsorption of Cu2+ were inhibited by 100 microM of various cations including other heavy metal ions. The general concept that cations competitively inhibit accumulation of metals in living organisms does not hold for C. vulgaris. Non-competitive, uncompetitive and mixed inhibition of Cu2+ uptake and adsorption by various cations were more common than competitive inhibition.

  8. Effects of grain boundaries at the electrolyte/cathode interfaces on oxygen reduction reaction kinetics of solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Min Gi; Koo, Ja Yang; Ahn, Min Woo; Lee, Won Young [Dept. of Mechanical Engineering, Sungkyunkwan University, Suwon (Korea, Republic of)

    2017-04-15

    We systematically investigated the effects of grain boundaries (GBs) at the electrolyte/cathode interface of two conventional electrolyte materials, i.e., yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC). We deposited additional layers by pulsed laser deposition to control the GB density on top of the polycrystalline substrates, obtaining significant improvements in peak power density (two-fold for YSZ and three-fold for GDC). The enhanced performance at high GB density in the additional layer could be ascribed to the accumulation of oxygen vacancies, which are known to be more active sites for oxygen reduction reactions (ORR) than grain cores. GDC exhibited a higher enhancement than YSZ, due to the easier formation, and thus higher concentration, of oxygen vacancies for ORR. The strong relation between the concentration of oxygen vacancies and the surface exchange characteristics substantiated the role of GBs at electrolyte/cathode interfaces on ORR kinetics, providing new design parameters for highly performing solid oxide fuel cells.

  9. Reassessment of FDG uptake in tumor cells: High FDG uptake as a reflection of oxygen-independent glycolysis dominant energy production

    Energy Technology Data Exchange (ETDEWEB)

    Waki, A.; Fujibayashi, Y.; Yonekura, Y.; Sadato, N.; Ishii, Y.; Yokoyama, A

    1997-10-01

    To determine appropriate use of 2-[{sup 18}F]-fluoro-2-deoxy-D-glucose (FDG) in the diagnosis of malignant tumors, the mechanism of enhanced FDG uptake in tumor cells was reassessed using in vitro cultured cell lines and {sup 3}H-deoxyglucose (DG), in combination with possible parameters of aerobic and anaerobic energy production. The high DG uptake in the tumor cells reflected the dependency of energy production on anaerobic glycolysis, and paradoxically on low levels of aerobic oxidative phosphorylation in mitochondria. We discuss here factors underlying anaerobic glycolysis in tumor cells.

  10. Oxygen self-diffusion mechanisms in monoclinic Zr O2 revealed and quantified by density functional theory, random walk analysis, and kinetic Monte Carlo calculations

    Science.gov (United States)

    Yang, Jing; Youssef, Mostafa; Yildiz, Bilge

    2018-01-01

    In this work, we quantify oxygen self-diffusion in monoclinic-phase zirconium oxide as a function of temperature and oxygen partial pressure. A migration barrier of each type of oxygen defect was obtained by first-principles calculations. Random walk theory was used to quantify the diffusivities of oxygen interstitials by using the calculated migration barriers. Kinetic Monte Carlo simulations were used to calculate diffusivities of oxygen vacancies by distinguishing the threefold- and fourfold-coordinated lattice oxygen. By combining the equilibrium defect concentrations obtained in our previous work together with the herein calculated diffusivity of each defect species, we present the resulting oxygen self-diffusion coefficients and the corresponding atomistically resolved transport mechanisms. The predicted effective migration barriers and diffusion prefactors are in reasonable agreement with the experimentally reported values. This work provides insights into oxygen diffusion engineering in Zr O2 -related devices and parametrization for continuum transport modeling.

  11. Oxygen Reduction Kinetics of La2-xSrxNiO 4+delta Electrodes for Solid Oxide Fuel Cells

    Science.gov (United States)

    Guan, Bo

    In the development of intermediate temperature solid oxide fuel cell (IT-SOFC), mixed ionic-electronic conductors (MIEC) have drawn big interests due to their both ionic and electronic species transport which can enlarge the 3-dimension of the cathode network. This thesis presents an investigation of MIEC of Ruddlesden-popper (RP) phases like K2NiF4 type La2NiO4+delta (LNO)-based oxides which have interesting transport, catalytic properties and suitable thermal expansion coefficients. The motivation of this present work is to further understand the fundamental of the effect of Sr doing on the oxygen reduction reaction (ORR) kinetics of LNO cathode. Porous symmetrical cells of La2-xSrxNiO4+delta (0≤x≤0.4) were fabricated and characterized by electrochemical impedance spectroscopy (EIS) in different PO2 from temperature range of 600˜800°C. The spectra were analyzed based on the impedance model introduced by Adler et al. The rate determining steps (RDS) for ORR were proposed and the responsible reasons were discussed. The overall polarization resistances of doped samples increase with Sr level. Surface oxygen exchange and bulk ionic diffusion co-control the ORR kinetics. With high Sr content (x=0.3, 0.4), oxygen ion transfer resistance between nickelate/electrolyte is observed. However for porous symmetrical cells it is hard to associate the resistance from EIS directly to each ORR elementary processes because of the difficulty in describing the microstructure of the porous electrode. The dense electrode configuration was adopted in this thesis. By using the dense electrode, the surface area, the thickness of electrode, the interface between electrode and electrolyte and lastly the 3PB are theoretically well-defined. Through this method, there is a good chance to distinguish the contribution of surface exchange from other processes. Dense and thin electrode layers in thickness of ˜40 mum are fabricated by using a novel spray modified pressing method. Negligible

  12. The effects of high-Dk rigid contact lens center thickness, material permeability, and blinking on the oxygen uptake of the human cornea.

    Science.gov (United States)

    Gardner, Hope Patterson; Fink, Barbara A; Mitchell, Lynn G; Hill, Richard M

    2005-06-01

    The human corneal oxygen uptake responses associated with the static (nonblinking) and dynamic (blinking) wear of five rigid gas-permeable materials with high oxygen permeabilities were determined for three different center thicknesses and compared with the responses for the normal open eye and severe hypoxic stress (static wear of polymethylmethacrylate). Corneal oxygen uptake rates were measured with a Clark-type polarographic electrode during two sessions with each of 10 human subjects. Measurements were made on the right eye for the normal open eye (air) and after 5 minutes of static and dynamic wear of polymethylmethacrylate and five rigid gas-permeable contact lens materials: Fluoroperm 92 (paflufocon A, Dk = 92), Fluoroperm 151 (paflufocon D, Dk = 151), 1992 Menicon SF-P (melafocon A, Dk = 102), 1995 Menicon SF-P (melafocon A, Dk = 159), and Menicon Z (tisilfocon A, Dk = 163-250). Lenses were manufactured in three different center thicknesses (0.12, 0.16, and 0.20 mm), with all other parameters remaining constant. Repeated-measures analysis of variance was used and included lens material (five levels), blinking condition (two levels), and lens thickness (three levels) as within-subject effects. Significant differences were found in corneal oxygen responses to lens material (p Dk rigid lens materials studied here, moderate changes in lens thickness or material permeability may result in modest differences in corneal hypoxic relief, whereas blinking results in no significant improvement to corneal oxygenation.

  13. Oxygen uptake and body composition after aquatic physical training in women with fibromyalgia: a randomized controlled trial.

    Science.gov (United States)

    Andrade, Carolina P; Zamunér, Antonio R; Forti, Meire; França, Thalita F; Tamburús, Nayara Y; Silva, Ester

    2017-10-01

    Aquatic physical training (APT) has been strongly recommended to improve symptoms in fibromyalgia syndrome (FMS). However, its effects on body composition and whether lean body mass (LBM) directly influences the aerobic functional capacity of this population are still not clear. To investigate whether APT can help improve body composition and increase the aerobic functional capacity in women with FMS, and whether oxygen uptake (VO2) related to LBM can better quantify the functional capacity of this population. Randomized controlled trial. The Federal University of São Carlos, São Paulo, Brazil. Fifty-four women with FMS were randomly assigned to trained group (TG, N.=27) or control group (CG, N.=27). All women underwent cardiopulmonary exercise test (CPET) to assess oxygen consumption at ventilatory anaerobic threshold (VAT) and at peak exercise, and also to assess body composition. The TG was submitted to APT program, held twice a week for 16 weeks. The exercise intensity was adapted throughout the sessions in order to keep heart rate and ratings of perceived exertion achieved at VAT. After APT, body composition was not significantly different between groups (TG and CG). In VAT only TG showed increased VO2 related to LBM, since in peak CPET, VO2 in absolute units, VO2 related to total body mass (TBM), VO2 related to LBM and power showed significant differences. Significant difference between VO2 related to TBM and VO2 related to baseline LBM and after 16 weeks of follow-up, both in VAT as in peak CPET in both groups. Significant difference between VO2 related to TBM and VO2 related to LBM at VAT and at peak CPET in both groups at baseline and after 16 weeks of follow-up was observed. APT with standardized intensities did not cause significant changes in body composition, but was effective in promoting increased VO2 at peak CPET in women with FMS. However, VO2 related to LBM more accurately reflected changes in aerobic functional capacity at VAT level after to

  14. Seasonal variations in body composition, maximal oxygen uptake, and gas exchange threshold in cross-country skiers.

    Science.gov (United States)

    Polat, Metin; Korkmaz Eryılmaz, Selcen; Aydoğan, Sami

    2018-01-01

    In order to ensure that athletes achieve their highest performance levels during competitive seasons, monitoring their long-term performance data is crucial for understanding the impact of ongoing training programs and evaluating training strategies. The present study was thus designed to investigate the variations in body composition, maximal oxygen uptake (VO 2max ), and gas exchange threshold values of cross-country skiers across training phases throughout a season. In total, 15 athletes who participate in international cross-country ski competitions voluntarily took part in this study. The athletes underwent incremental treadmill running tests at 3 different time points over a period of 1 year. The first measurements were obtained in July, during the first preparation period; the second measurements were obtained in October, during the second preparation period; and the third measurements were obtained in February, during the competition period. Body weight, body mass index (BMI), body fat (%), as well as VO 2max values and gas exchange threshold, measured using V-slope method during the incremental running tests, were assessed at all 3 time points. The collected data were analyzed using SPSS 20 package software. Significant differences between the measurements were assessed using Friedman's twoway variance analysis with a post hoc option. The athletes' body weights and BMI measurements at the third point were significantly lower compared with the results of the second measurement ( p exchange threshold, running speed at the gas exchange threshold, VO 2max , amount of oxygen consumed at gas exchange threshold level (VO 2GET ), maximal heart rate (HR max ), and heart rate at gas exchange threshold level (HR GET ) values did not significantly differ between the measurement time points ( p >0.05). VO 2max and gas exchange threshold values recorded during the third measurements, the timing of which coincided with the competitive season of the cross-country skiers

  15. CLA supplementation and aerobic exercise lower blood triacylglycerol, but have no effect on peak oxygen uptake or cardiorespiratory fatigue thresholds.

    Science.gov (United States)

    Jenkins, Nathaniel D M; Buckner, Samuel L; Cochrane, Kristen C; Bergstrom, Haley C; Goldsmith, Jacob A; Weir, Joseph P; Housh, Terry J; Cramer, Joel T

    2014-09-01

    This study examined the effects of 6 weeks of conjugated linoleic acid (CLA) supplementation and moderate aerobic exercise on peak oxygen uptake (VO2 peak), the gas exchange threshold (GET), the respiratory compensation point (RCP), and serum concentrations of cholesterol, triacylglycerol, and glucose in humans. Thirty-four untrained to moderately trained men (mean ± SD; age = 21.5 ± 2.8 years; mass = 77.2 ± 9.5 kg) completed this double-blind, placebo controlled study and were randomly assigned to either a CLA (Clarinol A-80; n = 18) or placebo (PLA; sunflower oil; n = 16) group. Prior to and following 6 weeks of aerobic training (50% VO2 peak for 30 min, twice per week) and supplementation (5.63 g of total CLA isomers [of which 2.67 g was c9, t11 and 2.67 g was t10, c12] or 7.35 g high oleic sunflower oil per day), each participant completed an incremental cycle ergometer test to exhaustion to determine their [Formula: see text] peak, GET, and RCP and fasted blood draws were performed to measure serum concentrations of cholesterol, triacylglycerol, and glucose. Serum triacylglycerol concentrations were lower (p interactions (p 0.05) between the CLA and PLA groups. GET and RCP increased (p < 0.05) from pre- to post-training for both the CLA and PLA groups. Overall, these data suggested that CLA and aerobic exercise may have synergistic, blood triacylglycerol lowering effects, although CLA may be ineffective for enhancing aerobic exercise performance in conjunction with a 6-week aerobic exercise training program in college-age men.

  16. Non-linear relationship between oxygen uptake and power output in the Astrand nomogram-old data revisited.

    Science.gov (United States)

    Zoladz, J A; Szkutnik, Z; Majerczak, J; Duda, K; Pedersen, P K

    2007-06-01

    For the last decade there have been considerable discussion concerning the linearity / non-linearity of the oxygen uptake (V(O2)) - power output (W) relationship with strong experimental evidence of non-linearity provided mainly by breath-by-breath measurements. In this study, we attempted to answer the question whether the V(O2) - W relationship in the Astrand nomogram, as presented in the Textbook of Work Physiology, P.-O. Astrand et al. (2003), page 281, based on the Douglas bag method, is indeed linear, as stated by the authors before, or if a change point in V(O2), described by Zoladz et al. (1998) Eur J Appl Physiol 78: 369-377, can possibly be detected in those data. The V(O2) - W data were taken from the Astrand nomogram referenced above and from the Table 9.5 on page 282 in the same reference and tested for the presence of the change point in V(O2), using our two-phase model (see the reference above). In the first phase, a linear V(O2) - W relationship was assumed, whereas in the second one (above the so-called change point) an additional increase in V(O2) above the values expected from the linear model was allowed. It was found that in the data taken from the Astrand nomogram (data for men), as well as in the data taken from the Table 9.5, statistically significant change points in V(O2) were present at the power output of 150 W. The documentation of the presence of a change point in the V(O2) - W relationship in the Astrand data provides further evidence for the existence of a non-linearity in the V(O2) - W relationship in incremental exercise tests of humans, also in V(O2) data based upon the Douglas bag method.

  17. The correlation between running economy and maximal oxygen uptake: cross-sectional and longitudinal relationships in highly trained distance runners.

    Science.gov (United States)

    Shaw, Andrew J; Ingham, Stephen A; Atkinson, Greg; Folland, Jonathan P

    2015-01-01

    A positive relationship between running economy and maximal oxygen uptake (V̇O2max) has been postulated in trained athletes, but previous evidence is equivocal and could have been confounded by statistical artefacts. Whether this relationship is preserved in response to running training (changes in running economy and V̇O2max) has yet to be explored. This study examined the relationships of (i) running economy and V̇O2max between runners, and (ii) the changes in running economy and V̇O2max that occur within runners in response to habitual training. 168 trained distance runners (males, n = 98, V̇O2max 73.0 ± 6.3 mL∙kg-1∙min-1; females, n = 70, V̇O2max 65.2 ± 5.9 mL kg-1∙min-1) performed a discontinuous submaximal running test to determine running economy (kcal∙km-1). A continuous incremental treadmill running test to volitional exhaustion was used to determine V̇O2max 54 participants (males, n = 27; females, n = 27) also completed at least one follow up assessment. Partial correlation analysis revealed small positive relationships between running economy and V̇O2max (males r = 0.26, females r = 0.25; Peconomy and V̇O2max in response to habitual training (r = 0.35; Peconomy and V̇O2max in highly trained distance runners. With >85% of the variance in these parameters unexplained by this relationship, these findings reaffirm that running economy and V̇O2max are primarily determined independently.

  18. Oxygen and Perfusion Kinetics in Response to Fractionated Radiation Therapy in FaDu Head and Neck Cancer Xenografts Are Related to Treatment Outcome

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Fangyao [Department of Biomedical Engineering, Duke University, Durham, North Carolina (United States); Vishwanath, Karthik [Department of Physics, Miami University, Oxford, Ohio (United States); Salama, Joseph K. [Department of Radiation Oncology, Duke University, Durham, North Carolina (United States); Division of Radiation Oncology, Veterans Administration Medical Center, Durham, North Carolina (United States); Erkanli, Alaattin; Peterson, Bercedis [Department of Biostatistics and Bioinformatics, Duke University Medical Center, Durham, North Carolina (United States); Oleson, James R. [Department of Radiation Oncology, Duke University, Durham, North Carolina (United States); Division of Radiation Oncology, Veterans Administration Medical Center, Durham, North Carolina (United States); Lee, Walter T. [Department of Radiation Oncology, Duke University, Durham, North Carolina (United States); Division of Head and Neck Surgery and Communicative Sciences, Duke University Medical Center, Durham, North Carolina (United States); Section of Otolaryngology Head and Neck Surgery, Veterans Administration Medical Center, Durham, North Carolina (United States); Brizel, David M. [Department of Radiation Oncology, Duke University, Durham, North Carolina (United States); Division of Head and Neck Surgery and Communicative Sciences, Duke University Medical Center, Durham, North Carolina (United States); Ramanujam, Nimmi [Department of Biomedical Engineering, Duke University, Durham, North Carolina (United States); Dewhirst, Mark W., E-mail: mark.dewhirst@duke.edu [Department of Radiation Oncology, Duke University, Durham, North Carolina (United States)

    2016-10-01

    Purpose: To test whether oxygenation kinetics correlate with the likelihood for local tumor control after fractionated radiation therapy. Methods and Materials: We used diffuse reflectance spectroscopy to noninvasively measure tumor vascular oxygenation and total hemoglobin concentration associated with radiation therapy of 5 daily fractions (7.5, 9, or 13.5 Gy/d) in FaDu xenografts. Spectroscopy measurements were obtained immediately before each daily radiation fraction and during the week after radiation therapy. Oxygen saturation and total hemoglobin concentration were computed using an inverse Monte Carlo model. Results: First, oxygenation kinetics during and after radiation therapy, but before tumor volumes changed, were associated with local tumor control. Locally controlled tumors exhibited significantly faster increases in oxygenation after radiation therapy (days 12-15) compared with tumors that recurred locally. Second, within the group of tumors that recurred, faster increases in oxygenation during radiation therapy (day 3-5 interval) were correlated with earlier recurrence times. An area of 0.74 under the receiver operating characteristic curve was achieved when classifying the local control tumors from all irradiated tumors using the oxygen kinetics with a logistic regression model. Third, the rate of increase in oxygenation was radiation dose dependent. Radiation doses ≤9.5 Gy/d did not initiate an increase in oxygenation, whereas 13.5 Gy/d triggered significant increases in oxygenation during and after radiation therapy. Conclusions: Additional confirmation is required in other tumor models, but these results suggest that monitoring tumor oxygenation kinetics could aid in the prediction of local tumor control after radiation therapy.

  19. Oxygen and Perfusion Kinetics in Response to Fractionated Radiation Therapy in FaDu Head and Neck Cancer Xenografts Are Related to Treatment Outcome

    International Nuclear Information System (INIS)

    Hu, Fangyao; Vishwanath, Karthik; Salama, Joseph K.; Erkanli, Alaattin; Peterson, Bercedis; Oleson, James R.; Lee, Walter T.; Brizel, David M.; Ramanujam, Nimmi; Dewhirst, Mark W.

    2016-01-01

    Purpose: To test whether oxygenation kinetics correlate with the likelihood for local tumor control after fractionated radiation therapy. Methods and Materials: We used diffuse reflectance spectroscopy to noninvasively measure tumor vascular oxygenation and total hemoglobin concentration associated with radiation therapy of 5 daily fractions (7.5, 9, or 13.5 Gy/d) in FaDu xenografts. Spectroscopy measurements were obtained immediately before each daily radiation fraction and during the week after radiation therapy. Oxygen saturation and total hemoglobin concentration were computed using an inverse Monte Carlo model. Results: First, oxygenation kinetics during and after radiation therapy, but before tumor volumes changed, were associated with local tumor control. Locally controlled tumors exhibited significantly faster increases in oxygenation after radiation therapy (days 12-15) compared with tumors that recurred locally. Second, within the group of tumors that recurred, faster increases in oxygenation during radiation therapy (day 3-5 interval) were correlated with earlier recurrence times. An area of 0.74 under the receiver operating characteristic curve was achieved when classifying the local control tumors from all irradiated tumors using the oxygen kinetics with a logistic regression model. Third, the rate of increase in oxygenation was radiation dose dependent. Radiation doses ≤9.5 Gy/d did not initiate an increase in oxygenation, whereas 13.5 Gy/d triggered significant increases in oxygenation during and after radiation therapy. Conclusions: Additional confirmation is required in other tumor models, but these results suggest that monitoring tumor oxygenation kinetics could aid in the prediction of local tumor control after radiation therapy.

  20. Kinetics of the oxygen effect in yeast irradiated in dry and wet conditions

    International Nuclear Information System (INIS)

    Kiefer, J.; Schoepfer, F.; Luggen-Hoelscher, J.

    1981-01-01

    There are indications that the radiobiological oxygen-effect consists of more than one component: in dry bacterial spores three different classes can be separated depending on exposure- and after-treatment conditions, the dependence of the oxygen-enhancement ratio (OER) on oxygen concentration shows breaks in various systems, and it has been suggested that type O and type N damage are localized in different parts of the cells. These questions were studied in the simple eucaryote Saccharomyces cerevisiae using two approaches: the dependence of OER on oxygen tension was determined both for survivial and mutation induction. Since a forward mutation was used a haploid strain had to be employed in this case. In order to assess whether also in yeast cells more than one component may exist, the techniques originally developed for bacterial spores were adapted for dried diploid yeast cells. The results show that the dependence on oxygen concentration is the same for survival and mutation within error limits, implicating DNA as the main target and that also in our system three classes of oxygen dependent damage exist

  1. Reversible uptake of molecular oxygen by heteroligand Co(II)-L-α-amino acid-imidazole systems: equilibrium models at full mass balance.

    Science.gov (United States)

    Pająk, Marek; Woźniczka, Magdalena; Vogt, Andrzej; Kufelnicki, Aleksander

    2017-09-19

    The paper examines Co(II)-amino acid-imidazole systems (where amino acid = L-α-amino acid: alanine, asparagine, histidine) which, when in aqueous solutions, activate and reversibly take up dioxygen, while maintaining the structural scheme of the heme group (imidazole as axial ligand and O 2 uptake at the sixth, trans position) thus imitating natural respiratory pigments such as myoglobin and hemoglobin. The oxygenated reaction shows higher reversibility than for Co(II)-amac systems with analogous amino acids without imidazole. Unlike previous investigations of the heteroligand Co(II)-amino acid-imidazole systems, the present study accurately calculates all equilibrium forms present in solution and determines the [Formula: see text]equilibrium constants without using any simplified approximations. The equilibrium concentrations of Co(II), amino acid, imidazole and the formed complex species were calculated using constant data obtained for analogous systems under oxygen-free conditions. Pehametric and volumetric (oxygenation) studies allowed the stoichiometry of O 2 uptake reaction and coordination mode of the central ion in the forming oxygen adduct to be determined. The values of dioxygen uptake equilibrium constants [Formula: see text] were evaluated by applying the full mass balance equations. Investigations of oxygenation of the Co(II)-amino acid-imidazole systems indicated that dioxygen uptake proceeds along with a rise in pH to 9-10. The percentage of reversibility noted after acidification of the solution to the initial pH ranged within ca 30-60% for alanine, 40-70% for asparagine and 50-90% for histidine, with a rising tendency along with the increasing share of amino acid in the Co(II): amino acid: imidazole ratio. Calculations of the share of the free Co(II) ion as well as of the particular complex species existing in solution beside the oxygen adduct (regarding dioxygen bound both reversibly and irreversibly) indicated quite significant values for the

  2. Measuring Steady-State Oxygen Uptake during the 6-Min Walk Test in Adults with Cerebral Palsy: Feasibility and Construct Validity

    Science.gov (United States)

    Maltais, Desiree B.; Robitaille, Nancy-Michelle; Dumas, Francine; Boucher, Normand; Richards, Carol L.

    2012-01-01

    This study evaluated the feasibility of measuring steady-state oxygen uptake (V[Combining Dot Above]O[subscript 2]) during the 6-min walk test (6MWT) in adults with cerebral palsy (CP) who walk without support and whether there is construct validity for net 6MWT V[Combining Dot Above]O[subscript 2] as a measure of their walking ability.…

  3. Thermochemical conversion of biomass in smouldering combustion across scales: The roles of heterogeneous kinetics, oxygen and transport phenomena.

    Science.gov (United States)

    Huang, Xinyan; Rein, Guillermo

    2016-05-01

    The thermochemical conversion of biomass in smouldering combustion is investigated here by combining experiments and modeling at two scales: matter (1mg) and bench (100g) scales. Emphasis is put on the effect of oxygen (0-33vol.%) and oxidation reactions because these are poorly studied in the literature in comparison to pyrolysis. The results are obtained for peat as a representative biomass for which there is high-quality experimental data published previously. Three kinetic schemes are explored, including various steps of drying, pyrolysis and oxidation. The kinetic parameters are found using the Kissinger-Genetic Algorithm method, and then implemented in a one-dimensional model of heat and mass transfer. The predictions are validated with thermogravimetric and bench-scale experiments and then analyzed to unravel the role of heterogeneous reaction. This is the first time that the influence of oxygen on biomass smouldering is explained in terms of both chemistry and transport phenomena across scales. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  4. Kinetics and mechanisms of the reactions of alkyl radicals with oxygen and with complexes of Co(III), Ru(III), and Ni(III)

    International Nuclear Information System (INIS)

    Kelley, D.

    1990-01-01

    The kinetics of the reactions of C 2 H 5 radical with Co(NH 3 ) 5 X 2+ , Ru(NH 3 ) 5 X 2+ , and Co(dmgH) 2 (X) (Y) (X = Br, Cl, N 3 , SCN; Y = H 2 O, CH 3 CN) complexes were studied using laser flash photolysis of ethylcobalt complexes. The kinetics were obtained by the kinetic probe method. Some relative rate constants were also determined by a competition method based on ethyl halide product ratios. The kinetics of colligation reactions of a series of alkyl radicals with β-Ni(cyclam) 2+ were studied using flaser flash photolysis of alkylcobalt complexes. Again, the kinetics were obtained by employing the kinetic probe competition method. The kinetics of the unimolecular homolysis of a series of RNi(cyclam)H 2 O 2+ were studied. Activation parameters were obtained for the unimolecular homolysis of C 2 H 5 Ni(cyclam)H 2 O 2+ . Kinetic and thermodynamic data obtained from these reactions were compared with those for the σ-bonded organometallic complexes. The kinetics of the unimolecular homolysis of a series of RNi(cyclam)H 2 O 2+ complexes were studied by monitoring the formation of the oxygen insertion product RO 2 Ni(cyclam)H 2 O 2+ . The higher rate constants for the reactions of alkyl radicals with oxygen in solution, as compared with those measured in the gas phase, were discussed. 30 refs

  5. The electrode kinetics of the evolution and dissolution of oxygen at the urania-zirconia interfaces

    International Nuclear Information System (INIS)

    Badwal, S.P.S.; Bevan, D.J.M.; Bockris, J.O'M.

    1980-01-01

    In order to assess the potential of urania-yttria fluorite-type solid solutions as electrodes for high-temperature electrolysis of steam, oxygen evolution and dissolution reactions have been studied at the (Usub(0.7)Ysub(0.3))Osub (2+x)/YSZ interface. A current-interruption technique was used to separate overpotential and resistive potential drop. In oxygen and air the overpotential-current curves obey the Tafel law, suggesting that a charge-transfer process is rate determining. Activation energies of 120 kJ mole -1 and 165 kJ mole -1 were obtained for the cathodic reaction in oxygen and air respectively. The capacitance obtained from galvanostatic transients varied with potential, temperature, and oxygen partial pressure. The average value of n, the number of electrons involved in the overall charge-transfer reaction, was determined to be 4.01 from reversible potential measurements. The overpotential losses are small for porous electrodes at high psub(O 2 ). A mechanism for the oxygen transfer reaction has been proposed and its limitations discussed. (author)

  6. Dynamic Model of Basic Oxygen Steelmaking Process Based on Multizone Reaction Kinetics: Modeling of Decarburization

    Science.gov (United States)

    Rout, Bapin Kumar; Brooks, Geoffrey; Akbar Rhamdhani, M.; Li, Zushu; Schrama, Frank N. H.; Overbosch, Aart

    2018-03-01

    In a previous study by the authors (Rout et al. in Metall Mater Trans B 49:537-557, 2018), a dynamic model for the BOF, employing the concept of multizone kinetics was developed. In the current study, the kinetics of decarburization reaction is investigated. The jet impact and slag-metal emulsion zones were identified to be primary zones for carbon oxidation. The dynamic parameters in the rate equation of decarburization such as residence time of metal drops in the emulsion, interfacial area evolution, initial size, and the effects of surface-active oxides have been included in the kinetic rate equation of the metal droplet. A modified mass-transfer coefficient based on the ideal Langmuir adsorption equilibrium has been proposed to take into account the surface blockage effects of SiO2 and P2O5 in slag on the decarburization kinetics of a metal droplet in the emulsion. Further, a size distribution function has been included in the rate equation to evaluate the effect of droplet size on reaction kinetics. The mathematical simulation indicates that decarburization of the droplet in the emulsion is a strong function of the initial size and residence time. A modified droplet generation rate proposed previously by the authors has been used to estimate the total decarburization rate by slag-metal emulsion. The model's prediction shows that about 76 pct of total carbon is removed by reactions in the emulsion, and the remaining is removed by reactions at the jet impact zone. The predicted bath carbon by the model has been found to be in good agreement with the industrially measured data.

  7. Dynamic Model of Basic Oxygen Steelmaking Process Based on Multizone Reaction Kinetics: Modeling of Decarburization

    Science.gov (United States)

    Rout, Bapin Kumar; Brooks, Geoffrey; Akbar Rhamdhani, M.; Li, Zushu; Schrama, Frank N. H.; Overbosch, Aart

    2018-06-01

    In a previous study by the authors (Rout et al. in Metall Mater Trans B 49:537-557, 2018), a dynamic model for the BOF, employing the concept of multizone kinetics was developed. In the current study, the kinetics of decarburization reaction is investigated. The jet impact and slag-metal emulsion zones were identified to be primary zones for carbon oxidation. The dynamic parameters in the rate equation of decarburization such as residence time of metal drops in the emulsion, interfacial area evolution, initial size, and the effects of surface-active oxides have been included in the kinetic rate equation of the metal droplet. A modified mass-transfer coefficient based on the ideal Langmuir adsorption equilibrium has been proposed to take into account the surface blockage effects of SiO2 and P2O5 in slag on the decarburization kinetics of a metal droplet in the emulsion. Further, a size distribution function has been included in the rate equation to evaluate the effect of droplet size on reaction kinetics. The mathematical simulation indicates that decarburization of the droplet in the emulsion is a strong function of the initial size and residence time. A modified droplet generation rate proposed previously by the authors has been used to estimate the total decarburization rate by slag-metal emulsion. The model's prediction shows that about 76 pct of total carbon is removed by reactions in the emulsion, and the remaining is removed by reactions at the jet impact zone. The predicted bath carbon by the model has been found to be in good agreement with the industrially measured data.

  8. Kinetics of 13N-ammonia uptake in myocardial single cells indicating potential limitations in its applicability as a marker of myocardial blood flow

    International Nuclear Information System (INIS)

    Rauch, B.; Helus, F.; Grunze, M.; Braunwell, E.; Mall, G.; Hasselbach, W.; Kuebler, W.

    1985-01-01

    To study kinetics and principles of cellular uptake of 13 N-ammonia, a marker of coronary perfusion in myocardial scintigraphy, heart muscle cells of adult rats were isolated by perfusion with collagenase and hyaluronidase. Net uptake of 13 N, measured by flow dialysis, reached equilibrium within 20 sec in the presence of sodium bicarbonate and carbon dioxide (pH 7.4, 37 degrees C). Total extraction, 80 sec after the reaction start, was 786 +/- 159 mumol/ml cell volume. Cells destroyed by calcium overload were unable to extract 13 N-ammonia. Omission of bicarbonate and carbon dioxide reduced total extraction to 36% of control. 13 N-Ammonia uptake could also be reduced by 50 muM 4,4' diisothiocyanostilbene 2,2' disulfonic acid, by 100 micrograms/ml 1-methionine sulfoximine, and by preincubation with 5 muM free oleic acid. These results indicate that in addition to metabolic trapping by glutamine synthetase, the extraction of 13 N-ammonia by myocardial cells is influenced by cell membrane integrity, intracellular-extracellular pH gradient, and possibly an anion exchange system for bicarbonate. For this reason, the uptake of 13 N-ammonia may not always provide a valid measurement of myocardial perfusion

  9. Nitrogen nutrition of Salvinia natans: Effects of inorganic nitrogen form on growth, morphology, nitrate reductase activity and uptake kinetics of ammonium and nitrate

    DEFF Research Database (Denmark)

    Jampeetong, Arunothai; Brix, Hans

    2009-01-01

    In this study we assessed the growth, morphological responses, and N uptake kinetics of Salvinia natans when supplied with nitrogen as NO3-, NH4+, or both at equimolar concentrations (500 μM). Plants supplied with only NO3- had lower growth rates (0.17 ± 0.01 g g-1 d-1), shorter roots, smaller...... leaves with less chlorophyll than plants supplied with NH4+ alone or in combination with NO3- (RGR = 0.28 ± 0.01 g g-1 d-1). Ammonium was the preferred form of N taken up. The maximal rate of NH4+ uptake (Vmax) was 6-14 times higher than the maximal uptake rate of NO3- and the minimum concentration...... for uptake (Cmin) was lower for NH4+ than for NO3-. Plants supplied with NO3- had elevated nitrate reductase activity (NRA) particularly in the roots showing that NO3- was primarily reduced in the roots, but NRA levels were generally low (NH4...

  10. Kinetics of 3H-serotonin uptake by platelets in infantile autism and developmental language disorder (including five pairs of twins)

    International Nuclear Information System (INIS)

    Katsui, T.; Okuda, M.; Usuda, S.; Koizumi, T.

    1986-01-01

    The kinetics of 5-HT uptake by platelets was studied in cases of infantile autism and developmental language disorder (DLD) and normal subjects. Two patients of the autism group were twins, and the seven patients of the DLD group were members of four pairs of twins. The Vmax values (means +/- SD) for autism and DLD were 6.46 +/- .90 pmol 5-HT/10(7) cells/min and 4.85 +/- 1.50 pmol 5-HT/10(7) cells/min, respectively. These values were both significantly higher than that of 2.25 +/- .97 pmole 5-HT/10(7) cells/min for normal children. The Km values of the three groups were not significantly different. Data on the five pairs of twins examined suggested that the elevated Vmax of 5-HT uptake by platelets was determined genetically

  11. Kinetics of 3H-serotonin uptake by platelets in infantile autism and developmental language disorder (including five pairs of twins)

    Energy Technology Data Exchange (ETDEWEB)

    Katsui, T.; Okuda, M.; Usuda, S.; Koizumi, T.

    1986-03-01

    The kinetics of 5-HT uptake by platelets was studied in cases of infantile autism and developmental language disorder (DLD) and normal subjects. Two patients of the autism group were twins, and the seven patients of the DLD group were members of four pairs of twins. The Vmax values (means +/- SD) for autism and DLD were 6.46 +/- .90 pmol 5-HT/10(7) cells/min and 4.85 +/- 1.50 pmol 5-HT/10(7) cells/min, respectively. These values were both significantly higher than that of 2.25 +/- .97 pmole 5-HT/10(7) cells/min for normal children. The Km values of the three groups were not significantly different. Data on the five pairs of twins examined suggested that the elevated Vmax of 5-HT uptake by platelets was determined genetically.

  12. Tracking of cell nuclei for assessment of in vitro uptake kinetics in ultrasound-mediated drug delivery using fibered confocal fluorescence microscopy.

    Science.gov (United States)

    Derieppe, Marc; de Senneville, Baudouin Denis; Kuijf, Hugo; Moonen, Chrit; Bos, Clemens

    2014-10-01

    Previously, we demonstrated the feasibility to monitor ultrasound-mediated uptake of a cell-impermeable model drug in real time with fibered confocal fluorescence microscopy. Here, we present a complete post-processing methodology, which corrects for cell displacements, to improve the accuracy of pharmacokinetic parameter estimation. Nucleus detection was performed based on the radial symmetry transform algorithm. Cell tracking used an iterative closest point approach. Pharmacokinetic parameters were calculated by fitting a two-compartment model to the time-intensity curves of individual cells. Cells were tracked successfully, improving time-intensity curve accuracy and pharmacokinetic parameter estimation. With tracking, 93 % of the 370 nuclei showed a fluorescence signal variation that was well-described by a two-compartment model. In addition, parameter distributions were narrower, thus increasing precision. Dedicated image analysis was implemented and enabled studying ultrasound-mediated model drug uptake kinetics in hundreds of cells per experiment, using fiber-based confocal fluorescence microscopy.

  13. Kinetics and mechanisms of the oxidation of alcohols and hydroxylamines by hydrogen peroxide, catalyzed by methyltrioxorhenium, MTO, and the oxygen binding properties of cobalt Schiff base complexes

    Energy Technology Data Exchange (ETDEWEB)

    Zauche, Timothy [Iowa State Univ., Ames, IA (United States)

    1999-02-12

    Catalysis is a very interesting area of chemistry, which is currently developing at a rapid pace. A great deal of effort is being put forth by both industry and academia to make reactions faster and more productive. One method of accomplishing this is by the development of catalysts. Enzymes are an example of catalysts that are able to perform reactions on a very rapid time scale and also very specifically; a goal for every man-made catalyst. A kinetic study can also be carried out for a reaction to gain a better understanding of its mechanism and to determine what type of catalyst would assist the reaction. Kinetic studies can also help determine other factors, such as the shelf life of a chemical, or the optimum temperature for an industrial scale reaction. An area of catalysis being studied at this time is that of oxygenations. Life on this earth depends on the kinetic barriers for oxygen in its various forms. If it were not for these barriers, molecular oxygen, water, and the oxygenated materials in the land would be in a constant equilibrium. These same barriers must be overcome when performing oxygenation reactions on the laboratory or industrial scale. By performing kinetic studies and developing catalysts for these reactions, a large number of reactions can be made more economical, while making less unwanted byproducts. For this dissertation the activation by transition metal complexes of hydrogen peroxide or molecular oxygen coordination will be discussed.

  14. Investigation of the relevant kinetic processes in the initial stage of a double-arcing instability in oxygen plasmas

    Science.gov (United States)

    Mancinelli, B.; Prevosto, L.; Chamorro, J. C.; Minotti, F. O.; Kelly, H.

    2018-05-01

    A numerical investigation of the kinetic processes in the initial (nanosecond range) stage of the double-arcing instability was developed. The plasma-sheath boundary region of an oxygen-operated cutting torch was considered. The energy balance and chemistry processes in the discharge were described. It is shown that the double-arcing instability is a sudden transition from a diffuse (glow-like) discharge to a constricted (arc-like) discharge in the plasma-sheath boundary region arising from a field-emission instability. A critical electric field value of ˜107 V/m was found at the cathodic part of the nozzle wall under the conditions considered. The field-emission instability drives in turn a fast electronic-to-translational energy relaxation mechanism, giving rise to a very fast gas heating rate of at least ˜109 K/s, mainly due to reactions of preliminary dissociation of oxygen molecules via the highly excited electronic state O2(B3Σu-) populated by electron impact. It is expected that this fast oxygen heating rate further stimulates the discharge contraction through the thermal instability mechanism.

  15. Maximum Plant Uptakes for Water, Nutrients, and Oxygen Are Not Always Met by Irrigation Rate and Distribution in Water-based Cultivation Systems.

    Science.gov (United States)

    Blok, Chris; Jackson, Brian E; Guo, Xianfeng; de Visser, Pieter H B; Marcelis, Leo F M

    2017-01-01

    Growing on rooting media other than soils in situ -i.e., substrate-based growing- allows for higher yields than soil-based growing as transport rates of water, nutrients, and oxygen in substrate surpass those in soil. Possibly water-based growing allows for even higher yields as transport rates of water and nutrients in water surpass those in substrate, even though the transport of oxygen may be more complex. Transport rates can only limit growth when they are below a rate corresponding to maximum plant uptake. Our first objective was to compare Chrysanthemum growth performance for three water-based growing systems with different irrigation. We compared; multi-point irrigation into a pond (DeepFlow); one-point irrigation resulting in a thin film of running water (NutrientFlow) and multi-point irrigation as droplets through air (Aeroponic). Second objective was to compare press pots as propagation medium with nutrient solution as propagation medium. The comparison included DeepFlow water-rooted cuttings with either the stem 1 cm into the nutrient solution or with the stem 1 cm above the nutrient solution. Measurements included fresh weight, dry weight, length, water supply, nutrient supply, and oxygen levels. To account for differences in radiation sum received, crop performance was evaluated with Radiation Use Efficiency (RUE) expressed as dry weight over sum of Photosynthetically Active Radiation. The reference, DeepFlow with substrate-based propagation, showed the highest RUE, even while the oxygen supply provided by irrigation was potentially growth limiting. DeepFlow with water-based propagation showed 15-17% lower RUEs than the reference. NutrientFlow showed 8% lower RUE than the reference, in combination with potentially limiting irrigation supply of nutrients and oxygen. Aeroponic showed RUE levels similar to the reference and Aeroponic had non-limiting irrigation supply of water, nutrients, and oxygen. Water-based propagation affected the subsequent

  16. Basic microscopic theory of the distribution, transfer and uptake kinetics of dissolved radionuclides by suspended particulate matter - Part I; Theory development

    International Nuclear Information System (INIS)

    Abril, J.M.

    1998-01-01

    Recently much experimental effort has been focused on determining those factors which affect the kinetics and the final equilibrium conditions for the uptake of radionuclides from the aqueous phase by particulate matter. At present, some of these results appear to be either surprising or contradictory and introduce some uncertainty in which parameter values are most appropriate for environmental modelling. In this paper, we study the ionic exchange between the dissolved phase and suspended particles from a microscopic viewpoint, developing a mathematical description of the kinetic transfer and the k d distribution coefficients. The most relevant contribution is the assumption that the exchange of radionuclides occurs in a specific surface layer on the particles, with a non-zero thickness. A wide range of experimental findings can be explained with this theory. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  17. On the mechanism controlling the redox kinetics of Cu-based oxygen carriers

    NARCIS (Netherlands)

    San Pio Bordeje, M.A.; Gallucci, F.; Roghair, I.; van Sint Annaland, M.

    2017-01-01

    Copper oxide on alumina is often used as oxygen carrier for chemical looping combustion owing to its very high reduction rates at lower temperatures and its very good mechanical and chemical stability at temperatures below 1000 °C. In this work, the redox behaviour of CuO/Al2O3 has been studied in

  18. [{sup 14}C]Serotonin uptake and [O-methyl-{sup 11}C]venlafaxine kinetics in porcine brain

    Energy Technology Data Exchange (ETDEWEB)

    Smith, D.F. E-mail: dfsmith@inet.uni2.dk; Hansen, S.B.; Oestergaard, L.; Gee, A.D.; Danielsen, E.; Ishizu, K.; Bender, D.; Poulsen, P.H.; Gjedde, A

    2001-08-01

    As part of our program of developing PET tracers for neuroimaging of psychotropic compounds, venlafaxine, an antidepressant drug, was evaluated. First, we measured in vitro rates of serotonin uptake in synaptosomes prepared from selected regions of porcine brain. Then, we determined the pharmacokinetics of venlafaxine, [O-methyl-{sup 11}C]-labeled for PET. Synaptosomal studies showed that the active uptake of [{sup 14}C]5-HT differed markedly between brain regions, with highest rates in hypothalamus, raphe region, and thalamus, and lowest rates in cortex and cerebellum. PET studies showed that the unidirectional rate of uptake of [O-methyl-{sup 11}C]venlafaxine from blood to brain was highest in the hypothalamus, raphe region, thalamus and basal ganglia and lowest in the cortex and cerebellum. Under normal physiological conditions, the capillary permeability-surface area (PS) product for [O-methyl-{sup 11}C]venlafaxine could not be estimated, because of complete flow-limitation of the cerebral uptake. Nevertheless, a correlation occurred between the apparent partition volume of the radiotracer and the rate of active uptake of 5-HT in selected regions of the porcine brain. During hypercapnia, limitations of blood-brain transfer were observed, giving PS-products for water that were only ca. 50% higher than those of venlafaxine. Thus, under normal physiological conditions, the rate of uptake of venlafaxine from blood into brain is completely flow-limited.

  19. Skeletal muscle bioenergetics during all-out exercise: mechanistic insight into the oxygen uptake slow component and neuromuscular fatigue.

    Science.gov (United States)

    Broxterman, Ryan M; Layec, Gwenael; Hureau, Thomas J; Amann, Markus; Richardson, Russell S

    2017-05-01

    and skeletal muscle bioenergetics underlying all-out exercise performance are unclear. This study revealed an increase in oxidative ATP synthesis rate gain and the ATP cost of contraction during all-out exercise. Furthermore, peripheral fatigue was related to the perturbation in pH and deprotonated phosphate ion. These findings support the concept that the oxygen uptake slow component arises from within active skeletal muscle and that skeletal muscle force generating capacity is linked to the intramuscular metabolic milieu.

  20. Thermodynamics and Kinetics of Sulfide Oxidation by Oxygen: A Look at Inorganically Controlled Reactions and Biologically Mediated Processes in the Environment

    Science.gov (United States)

    Luther, George W.; Findlay, Alyssa J.; MacDonald, Daniel J.; Owings, Shannon M.; Hanson, Thomas E.; Beinart, Roxanne A.; Girguis, Peter R.

    2011-01-01

    The thermodynamics for the first electron transfer step for sulfide and oxygen indicates that the reaction is unfavorable as unstable superoxide and bisulfide radical ions would need to be produced. However, a two-electron transfer is favorable as stable S(0) and peroxide would be formed, but the partially filled orbitals in oxygen that accept electrons prevent rapid kinetics. Abiotic sulfide oxidation kinetics improve when reduced iron and/or manganese are oxidized by oxygen to form oxidized metals which in turn oxidize sulfide. Biological sulfur oxidation relies on enzymes that have evolved to overcome these kinetic constraints to affect rapid sulfide oxidation. Here we review the available thermodynamic and kinetic data for H2S and HS• as well as O2, reactive oxygen species, nitrate, nitrite, and NOx species. We also present new kinetic data for abiotic sulfide oxidation with oxygen in trace metal clean solutions that constrain abiotic rates of sulfide oxidation in metal free solution and agree with the kinetic and thermodynamic calculations. Moreover, we present experimental data that give insight on rates of chemolithotrophic and photolithotrophic sulfide oxidation in the environment. We demonstrate that both anaerobic photolithotrophic and aerobic chemolithotrophic sulfide oxidation rates are three or more orders of magnitude higher than abiotic rates suggesting that in most environments biotic sulfide oxidation rates will far exceed abiotic rates due to the thermodynamic and kinetic constraints discussed in the first section of the paper. Such data reshape our thinking about the biotic and abiotic contributions to sulfide oxidation in the environment. PMID:21833317

  1. Mechanism and kinetics of Fe, Cr, Mo and Mn atom interaction with molecular oxygen

    International Nuclear Information System (INIS)

    Akhmadov, U.S.; Zaslonko, I.S.; Smirnov, V.N.

    1988-01-01

    Rate constants of atomic interaction of some transition metals (Fe, Cr, Mo, Mn) with molecular oxygen are measured in shock waves using the resonance atomic-absorption method. A new method for determination of the parameter γ in the modified Lambert-Beer law D=ε(lN)γ is suggested and applied. Bond strength in CrO and MoO molecules is estimated

  2. Kinetics of caesium and potassium absorption by roots of three grass pastures and competitive effects of potassium on caesium uptake in Cynodon sp.

    Science.gov (United States)

    Ayub, J. Juri; Valverde, L. Rubio; Garcia-Sanchez, M. J.; Fernandez, J. A.; Velasco, R. H.

    2008-08-01

    Caesium uptake by plant roots has been normally associated with the uptake of potassium as the potassium transport systems present in plants have also the capacity to transport caesium. Three grass species (Eragrostis curvula, Cynodon sp and Distichlis spicata) growing in seminatural grassland of central Argentina were selected to study their capability to incorporate Cs+ (and K+) using electrophysiological techniques. Although the 137Cs soil inventory ranged between 328-730 Bq m-2 in this region, no 137Cs activity was detected in these plants. However, all the species, submitted previously to K+ starvation, showed the uptake of both Cs+ and K+ when micromolar concentrations of these cations were present in the medium. The uptake showed saturation kinetics for both cations that could be fitted to the Michelis-Menten model. KM values were smaller for K+ than for Cs+, indicating a higher affinity for the first cation. The presence of increasing K+ concentrations in the assay medium inhibited Cs+ uptake in Cynodon sp., as expected if both cations are transported by the same transport systems. This effect is due to the competition of both ions for the union sites of the high affinity potassium transporters. In field situation, where soil concentration of Cs+ is smaller than K+ concentration, is then expectable that caesium activity in plants is not detectable. Nevertheless, the studied plants would have the capacity to incorporate caesium if its availability in soil solution increases. In addition, studies of Cs/K interaction can help us to understand the variability in transfer factors.

  3. Kinetics of caesium and potassium absorption by roots of three grass pastures and competitive effects of potassium on caesium uptake in Cynodon sp

    International Nuclear Information System (INIS)

    Ayub, J. Juri; Velasco, R. H.; Valverde, L. Rubio; Garcia-Sanchez, M. J.; Fernandez, J. A.

    2008-01-01

    Caesium uptake by plant roots has been normally associated with the uptake of potassium as the potassium transport systems present in plants have also the capacity to transport caesium. Three grass species (Eragrostis curvula, Cynodon sp and Distichlis spicata) growing in seminatural grassland of central Argentina were selected to study their capability to incorporate Cs + (and K + ) using electrophysiological techniques. Although the 137 Cs soil inventory ranged between 328-730 Bq m -2 in this region, no 137 Cs activity was detected in these plants. However, all the species, submitted previously to K + starvation, showed the uptake of both Cs + and K + when micromolar concentrations of these cations were present in the medium. The uptake showed saturation kinetics for both cations that could be fitted to the Michelis-Menten model. K M values were smaller for K + than for Cs + , indicating a higher affinity for the first cation. The presence of increasing K + concentrations in the assay medium inhibited Cs + uptake in Cynodon sp., as expected if both cations are transported by the same transport systems. This effect is due to the competition of both ions for the union sites of the high affinity potassium transporters. In field situation, where soil concentration of Cs + is smaller than K + concentration, is then expectable that caesium activity in plants is not detectable. Nevertheless, the studied plants would have the capacity to incorporate caesium if its availability in soil solution increases. In addition, studies of Cs/K interaction can help us to understand the variability in transfer factors

  4. Effect of thyroxine on cellular oxygen-consumption and glucose uptake: evidence of an effect of total T4 and not "free T4"

    DEFF Research Database (Denmark)

    Kvetny, J; Matzen, L E

    1990-01-01

    Recent studies of cellular T4 and T3 uptake have indicated active transport of the hormones into the cell rather than passive diffusion of the non-protein bound fraction. In order to study the significance of the extracellular environment, oxygen consumption and glucose uptake were examined...... in human mononuclear blood cells. Cells were incubated in protein free medium and in human serum totally depleted of thyroid hormones by resin treatment and fixed amounts of T4 (total T4 = 0-50-100-5000 nmol/l; free T4 = 0-5-11-5600 pmol/l) were added. Thyroxine stimulated glucose uptake and oxygen......-consumption in a dose dependent manner but the T4 stimulation was dependent on the total concentration of T4 and did not differ between serum incubation or non-protein containing medium. Addition of ANS (100 mg/l) which inhibits binding of T4 to TBG, did not increase T4 effect in serum. Inhibition of the Na...

  5. Kinetics of oxygen reduction in perovskite cathodes for solid oxide fuel cells: A combined modeling and experimental approach

    Science.gov (United States)

    Miara, Lincoln James

    Solid oxide fuel cells (SOFCs) have the potential to replace conventional stationary power generation technologies; however, there are major obstacles to commercialization, the most problematic of which is poor cathode performance. Commercialization of SOFCs will follow when the mechanisms occurring at the cathode are more thoroughly understood and adapted for market use. The catalytic reduction of oxygen occurring in SOFC cathodes consists of many elementary steps such as gas phase diffusion, chemical and/or electrochemical reactions which lead to the adsorption and dissociation of molecular oxygen onto the cathode surface, mass transport of oxygen species along the surface and/or through the bulk of the cathode, and full reduction and incorporation of the oxygen at the cathode/electrolyte two or three phase boundary. Electrochemical impedance spectroscopy (EIS) is the main technique used to identify the occurrence of these different processes, but when this technique is used without an explicit model describing the kinetics it is difficult to unravel the interdependence of each of these processes. The purpose of this dissertation is to identify the heterogeneous reactions occurring at the cathode of an SOFC by combining experimental EIS results with mathematical models describing the time dependent behavior of the system. This analysis is performed on two different systems. In the first case, experimental EIS results from patterned half cells composed of Ca-doped lanthanum manganite (LCM)| yttria-doped ZrO2 (YSZ) are modeled to investigate the temperature and partial pressure of oxygen, pO2, dependence of oxygen adsorption/dissociation onto the LCM surface, surface diffusion of atomic oxygen, and electrochemical reduction and incorporation of the oxygen into the electrolyte in the vicinity of the triple phase boundary (TPB). This model determines the time-independent state-space equations from which the Faradaic admittance transfer function is obtained. The

  6. Temperature dependence of the oxygen reduction kinetics on Ru{sub x}Se{sub y}/C catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Leveratto, D.; Racz, A.; Savinova, E.R.; Stimming, U. [Technische Universitaet Muenchen, Department of Physics E19, James-Franck-Str. 1, D-85748 Garching (Germany)

    2006-07-15

    The temperature dependence of the oxygen reduction kinetics on carbon-supported Ru{sub x}Se{sub y} catalysts is studied using a rotating disc electrode in 0.5 M H{sub 2}SO{sub 4} in the temperature interval from 25 C to 65 C. When the absolute value of the overpotential is below ca. 0.65 V, the reaction is limited by a one-electron charge transfer step, where the transfer coefficient is independent of the temperature and equal to 0.44. The apparent activation enthalpy at zero overpotential is 0.49 eV and the pre-exponential factor is independent of the temperature. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  7. Kinetics of phosphate uptake, growth, and accumulation of cyclic diphosphoglycerate in a phosphate-limited continuous culture of Methanobacterium thermoautotrophicum.

    Science.gov (United States)

    Krueger, R D; Harper, S H; Campbell, J W; Fahrney, D E

    1986-07-01

    The archaebacterium Methanobacterium thermoautotrophicum was grown in continuous culture at 65 degrees C in a phosphate-limited medium at specific growth rates from 0.06 to 0.28 h-1 (maximum growth rate [mu max] = 0.36 h-1). Cyclic-2,3-diphosphoglycerate (cyclic DPG) levels ranged from 2 to 20 mM in Pi-limited cells, compared with about 30 mM in batch-grown cells. The Monod constant for Pi-limited growth was 5 nM. Pi uptake rates were determined by following the disappearance of 32Pi from the medium. Interrupting the H2 supply stopped the uptake of Pi and the release of organic phosphates. Little or no efflux of Pi occurred in the presence or absence of H2. Pi uptake of cells adapted to nanomolar Pi concentrations could be accounted for by the operation of one uptake system with an apparent Km of about 25 nM and a Vmax of 58 nmol of Pi per min per g (dry weight). Uptake curves at 30 microM Pi or above were biphasic due to a sevenfold decrease in Vmax after an initial phase of rapid movement of Pi into the cell. Under these conditions the growth rate slowed to zero and the cyclic DPG pool expanded before growth resumed. Thus, three properties of M. thermoautotrophicum make it well adapted to live in a low-P environment: the presence of a low-Km, high-Vmax uptake system for Pi; the ability to accumulate cyclic DPG rapidly; and a growth strategy in which accumulation of Pi and cyclic DPG takes precedence over a shift-up in growth rate when excess Pi becomes available.

  8. Kinetics of phosphate uptake, growth, and accumulation of cyclic diphosphoglycerate in a phosphate-limited continuous culture of Methanobacterium thermoautotrophicum.

    Science.gov (United States)

    Krueger, R D; Harper, S H; Campbell, J W; Fahrney, D E

    1986-01-01

    The archaebacterium Methanobacterium thermoautotrophicum was grown in continuous culture at 65 degrees C in a phosphate-limited medium at specific growth rates from 0.06 to 0.28 h-1 (maximum growth rate [mu max] = 0.36 h-1). Cyclic-2,3-diphosphoglycerate (cyclic DPG) levels ranged from 2 to 20 mM in Pi-limited cells, compared with about 30 mM in batch-grown cells. The Monod constant for Pi-limited growth was 5 nM. Pi uptake rates were determined by following the disappearance of 32Pi from the medium. Interrupting the H2 supply stopped the uptake of Pi and the release of organic phosphates. Little or no efflux of Pi occurred in the presence or absence of H2. Pi uptake of cells adapted to nanomolar Pi concentrations could be accounted for by the operation of one uptake system with an apparent Km of about 25 nM and a Vmax of 58 nmol of Pi per min per g (dry weight). Uptake curves at 30 microM Pi or above were biphasic due to a sevenfold decrease in Vmax after an initial phase of rapid movement of Pi into the cell. Under these conditions the growth rate slowed to zero and the cyclic DPG pool expanded before growth resumed. Thus, three properties of M. thermoautotrophicum make it well adapted to live in a low-P environment: the presence of a low-Km, high-Vmax uptake system for Pi; the ability to accumulate cyclic DPG rapidly; and a growth strategy in which accumulation of Pi and cyclic DPG takes precedence over a shift-up in growth rate when excess Pi becomes available. PMID:3722128

  9. Oxidative vaporization kinetics of Cr2O3 in oxygen from 1000 to 1300 C

    Science.gov (United States)

    Stearns, C. A.; Kohl, F. J.; Fryburg, G. C.

    1974-01-01

    Rates of oxidative vaporization of Cr2O3 on preoxidized resistively heated chromium were determined in flowing oxygen at a pressure of 0.115 Torr for temperatures from 1000 to 1300 C. Reaction controlled rates were obtained from experimental rates by a gold calibration technique, and these rates were shown to agree with those predicted by thermochemical analysis. The activation energy obtained for the oxidative vaporization reaction corresponded numerically with the thermochemical enthalpy of the reaction. A theoretical equation is given for calculating the rate from thermodynamic data using boundary-layer theory.

  10. Oxidative vaporization kinetics of chromium (III) oxide in oxygen from 1270 to 1570 K

    Science.gov (United States)

    Stearns, C. A.; Kohl, F. J.; Fryburg, G. C.

    1974-01-01

    Rates of oxidative vaporization of Cr2O3 on preoxidized resistively heated chromium were determined in flowing oxygen at 0.115 torr for temperatures from 1270 to 1570 K. Reaction controlled rates were obtained from experimental rates by a gold calibration technique. These rates were shown to agree with those predicted by thermochemical analysis. The activation energy obtained for the oxidative vaporation reaction corresponded numerically with the thermochemical enthalpy of the reaction. A theoretical equation is given for calculating the rate from thermodynamic data by using boundary layer theory.

  11. Phosphorus Uptake Kinetics of Different Types of Duckweed.%不同品种浮萍磷素吸收动力学特征

    Institute of Scientific and Technical Information of China (English)

    蔡树美; 刘文桃; 张震; 柏彦超; 钱晓晴

    2011-01-01

    以长江三角洲地区常见的3种浮萍--稀脉浮萍(Lemna aequinoctialis)、少根紫萍(Spirodela oligorrhiza)和紫萍(Spriodela polyrrhiza)为对象,研究不同品种浮萍对HPO42-的吸收动力学影响.结果表明,3种浮萍对无机磷的吸收动力学特征基本可采用Michaelis-Menten方程描述,3种浮萍无机磷吸收速率V对磷浓度S双倒数曲线的拟合关系均在α=0.01水平上显著.稀脉浮萍对无机磷的亲和力较强,适宜应用于对低磷浓度污水的净化;紫萍对无机磷的最大吸收速率Vmax较高,适宜应用于对高磷浓度污水的净化.%An increasing attention has been paid to the use of duckweed in treating eutrophicated water as a tool of bio-remediation of domestic wastewater.Phosphorus uptake kinetics was studied,of different species of duckweeds, i.e.Lemna aequinoctialis, Spirodela oligorrhiza and Spriodela polyrrhiza, which are common in the Yangtze River Delta area.Results show that the phosphorus uptake kinetics of the duckweeds could be expressed with the Michaelis-Menten equation; and the relation between phosphorus uptake rate (V) of the duckweeds and inorganic phosphorus(Pi) concentration (S), was well fitted with a double-reciprocal curve with at =0.01; the Km value for Pi uptake of Lemna aequinoctialis was lower than that of Spirodela oligorrhiza and Spriodela polyrrhiza, making it a better candidate for treating wastewater low in Pi concentration.The maximum phosphorus uptake rate of Spriodela polyrrhiza was higher than that of the other two species, which allows Spriodela polyrrhiza better performance in purifying wastewater higher in Pi concentration.

  12. Technical note: Influence of surface roughness and local turbulence on coated-wall flow tube experiments for gas uptake and kinetic studies

    Directory of Open Access Journals (Sweden)

    G. Li

    2018-02-01

    Full Text Available Coated-wall flow tube reactors are frequently used to investigate gas uptake and heterogeneous or multiphase reaction kinetics under laminar flow conditions. Coating surface roughness may potentially distort the laminar flow pattern, induce turbulence and introduce uncertainties in the calculated uptake coefficient based on molecular diffusion assumptions (e.g., Brown/Cooney–Kim–Davis (CKD/Knopf–Pöschl–Shiraiwa (KPS methods, which has not been fully resolved in earlier studies. Here, we investigate the influence of surface roughness and local turbulence on coated-wall flow tube experiments for gas uptake and kinetic studies. According to laminar boundary theory and considering the specific flow conditions in a coated-wall flow tube, we derive and propose a critical height δc to evaluate turbulence effects in the design and analysis of coated-wall flow tube experiments. If a geometric coating thickness δg is larger than δc, the roughness elements of the coating may cause local turbulence and result in overestimation of the real uptake coefficient (γ. We further develop modified CKD/KPS methods (i.e., CKD-LT/KPS-LT to account for roughness-induced local turbulence effects. By combination of the original methods and their modified versions, the maximum error range of γCKD (derived with the CKD method or γKPS (derived with the KPS method can be quantified and finally γ can be constrained. When turbulence is generated, γCKD or γKPS can bear large difference compared to γ. Their difference becomes smaller for gas reactants with lower uptake (i.e., smaller γ and/or for a smaller ratio of the geometric coating thickness to the flow tube radius (δg ∕ R0. On the other hand, the critical height δc can also be adjusted by optimizing flow tube configurations and operating conditions (i.e., tube diameter, length, and flow velocity, to ensure not only unaffected laminar flow patterns but also other specific requirements for an

  13. Uptake, translocation and biotransformation kinetics of BDE-47, 6-OH-BDE-47 and 6-MeO-BDE-47 in maize (Zea mays L.).

    Science.gov (United States)

    Xu, Xuehui; Wen, Bei; Huang, Honglin; Wang, Sen; Han, Ruixia; Zhang, Shuzhen

    2016-01-01

    This study presents a detailed kinetic investigation on the uptake, acropetal translocation and transformation of BDE-47, 6-OH-BDE-47 and 6-MeO-BDE-47 in maize (Zea mays L.) by hydroponic exposure. Root uptake followed the order: BDE-47 > 6-MeO-BDE-47 > 6-OH-BDE-47, while 6-OH-BDE-47 was the most prone to acropetal translocation. Debromination rates of BDE-47 were 1.31 and 1.46 times greater than the hydroxylation and methoxylation rates, respectively. Transformation from BDE-47 to lower brominated OH/MeO-PBDEs occurred mainly through debromination first followed by hydroxylation or methoxylation. There was no transformation from 6-OH-BDE-47 or 6-MeO-BDE-47 to PBDEs. Methylation rate of 6-OH-BDE-47 was twice as high as that of 6-MeO-BDE-47 hydroxylation, indicating methylation of 6-OH-BDE-47 was easier and more rapid than hydroxylation of 6-MeO-BDE-47. Debromination and isomerization were potential metabolic pathways for 6-OH-BDE-47 and 6-MeO-BDE-47 in maize. This study provides important information for better understanding the mechanism on plant uptake and transformation of PBDEs. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Kinetics of phosphorus and potassium release from rock phosphate and waste mica enriched compost and their effect on yield and nutrient uptake by wheat (Triticum aestivum).

    Science.gov (United States)

    Nishanth, D; Biswas, D R

    2008-06-01

    An attempt was made to study the efficient use of rice straw and indigenous source of phosphorus and potassium in crop production through composting technology. Various enriched composts were prepared using rice straw, rock phosphate (RP), waste mica and bioinoculant (Aspergillus awamori) and kinetics of release of phosphorus and potassium from enriched composts and their effect on yield and nutrient uptake by wheat (Triticum aestivum) were carried out. Results showed sharp increases in release in water-soluble P and K from all the composts at 8th to 12th day of leaching, thereafter, it decreased gradually. Maximum release of water-soluble P and K were obtained in ordinary compost than enriched composts during the initial stages of leaching, but their differences narrowed down at latter stages. Data in pot experiments revealed that enriched composts performed poorly than diammonium phosphate during initial stages of crop growth, but they out yielded at the latter stages, particularly at maturity stage, as evident from their higher yield, uptake, nutrient recoveries and fertility status of P and K in soils. Moreover, enriched composts prepared with RP and waste mica along with A. awamori resulted in significantly higher biomass yield, uptake and recoveries of P and K as well as available P and K in soils than composts prepared without inoculant. Results indicated that enriched compost could be an alternate technology for the efficient management of rice straw, low-grade RP and waste mica in crop production, which could help to reduce the reliance on costly chemical fertilizers.

  15. Competition between organics and bromide at the aqueous solution-air interface as seen from ozone uptake kinetics and X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Lee, Ming-Tao; Brown, Matthew A; Kato, Shunsuke; Kleibert, Armin; Türler, Andreas; Ammann, Markus

    2015-05-14

    A more detailed understanding of the heterogeneous chemistry of halogenated species in the marine boundary layer is required. Here, we studied the reaction of ozone (O3) with NaBr solutions in the presence and absence of citric acid (C6H8O7) under ambient conditions. Citric acid is used as a proxy for oxidized organic material present at the ocean surface or in sea spray aerosol. On neat NaBr solutions, the observed kinetics is consistent with bulk reaction-limited uptake, and a second-order rate constant for the reaction of O3 + Br(-) is 57 ± 10 M(-1) s(-1). On mixed NaBr-citric acid aqueous solutions, the uptake kinetics was faster than that predicted by bulk reaction-limited uptake and also faster than expected based on an acid-catalyzed mechanism. X-ray photoelectron spectroscopy (XPS) on a liquid microjet of the same solutions at 1.0 × 10(-3)-1.0 × 10(-4) mbar was used to obtain quantitative insight into the interfacial composition relative to that of the bulk solutions. It revealed that the bromide anion becomes depleted by 30 ± 10% while the sodium cation gets enhanced by 40 ± 20% at the aqueous solution-air interface of a 0.12 M NaBr solution mixed with 2.5 M citric acid in the bulk, attributed to the role of citric acid as a weak surfactant. Therefore, the enhanced reactivity of bromide solutions observed in the presence of citric acid is not necessarily attributable to a surface reaction but could also result from an increased solubility of ozone at higher citric acid concentrations. Whether the acid-catalyzed chemistry may have a larger effect on the surface than in the bulk to offset the effect of bromide depletion also remains open.

  16. Reproducibility of O-(2-{sup 18}F-fluoroethyl)-L-tyrosine uptake kinetics in brain tumors and influence of corticoid therapy: an experimental study in rat gliomas

    Energy Technology Data Exchange (ETDEWEB)

    Stegmayr, Carina; Schoeneck, Michael; Oliveira, Dennis; Willuweit, Antje [Institute of Neuroscience and Medicine, Research Center Juelich, Juelich (Germany); Filss, Christian; Coenen, Heinz H.; Langen, Karl-Josef [Institute of Neuroscience and Medicine, Research Center Juelich, Juelich (Germany); University of Aachen, Department of Nuclear Medicine and Neurology, Aachen (Germany); Galldiks, Norbert [Institute of Neuroscience and Medicine, Research Center Juelich, Juelich (Germany); University of Cologne, Department of Neurology, Cologne (Germany); Shah, N. Jon [Institute of Neuroscience and Medicine, Research Center Juelich, Juelich (Germany); University of Aachen, Department of Nuclear Medicine and Neurology, Aachen (Germany); Juelich-Aachen Research Alliance (JARA) - Section JARA-Brain, Juelich (Germany)

    2016-06-15

    Positron emission tomography (PET) using O-(2-{sup 18}F-fluoroethyl)-L-tyrosine ({sup 18}F-FET) is a well-established method for the diagnostics of brain tumors. This study investigates reproducibility of {sup 18}F-FET uptake kinetics in rat gliomas and the influence of the frequently used dexamethasone (Dex) therapy. F98 glioma or 9L gliosarcoma cells were implanted into the striatum of 31 Fischer rats. After 10-11 days of tumor growth, the animals underwent dynamic PET after injection of {sup 18}F-FET (baseline). Thereafter, animals were divided into a control group and a group receiving Dex injections, and all animals were reinvestigated 2 days later. Tumor-to-brain ratios (TBR) of {sup 18}F-FET uptake (18-61 min p.i.) and the slope of the time-activity-curves (TAC) (18-61 min p.i.) were evaluated using a Volume-of-Interest (VOI) analysis. Data were analyzed by two-way repeated measures ANOVA and reproducibility by the intraclass correlation coefficient (ICC). The slope of the tumor TACs showed high reproducibility with an ICC of 0.93. A systematic increase of the TBR in the repeated scans was noted (3.7 ± 2.8 %; p < 0.01), and appeared to be related to tumor growth as indicated by a significant correlation of TBR and tumor volume (r = 0.77; p < 0.0001). After correction for tumor growth TBR showed high longitudinal stability with an ICC of 0.84. Dex treatment induced a significant decrease of the TBR (-8.2 ± 6.1 %; p < 0.03), but did not influence the slope of the tumor TAC. TBR of {sup 18}F-FET uptake and tracer kinetics in brain tumors showed high longitudinal stability. Dex therapy may induce a minor decrease of the TBR; this needs further investigation. (orig.)

  17. Carbon Dioxide Hydrogenation into Higher Hydrocarbons and Oxygenates: Thermodynamic and Kinetic Bounds and Progress with Heterogeneous and Homogeneous Catalysis.

    Science.gov (United States)

    Prieto, Gonzalo

    2017-03-22

    Under specific scenarios, the catalytic hydrogenation of CO 2 with renewable hydrogen is considered a suitable route for the chemical recycling of this environmentally harmful and chemically refractory molecule into added-value energy carriers and chemicals. The hydrogenation of CO 2 into C 1 products, such as methane and methanol, can be achieved with high selectivities towards the corresponding hydrogenation product. More challenging, however, is the selective production of high (C 2+ ) hydrocarbons and oxygenates. These products are desired as energy vectors, owing to their higher volumetric energy density and compatibility with the current fuel infrastructure than C 1 compounds, and as entry platform chemicals for existing value chains. The major challenge is the optimal integration of catalytic functionalities for both reductive and chain-growth steps. This Minireview summarizes the progress achieved towards the hydrogenation of CO 2 to C 2+ hydrocarbons and oxygenates, covering both solid and molecular catalysts and processes in the gas and liquid phases. Mechanistic aspects are discussed with emphasis on intrinsic kinetic limitations, in some cases inevitably linked to thermodynamic bounds through the concomitant reverse water-gas-shift reaction, which should be considered in the development of advanced catalysts and processes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Kinetic and mechanisms of methanimine reactions with singlet and triplet molecular oxygen: Substituent and catalyst effects

    Science.gov (United States)

    Asgharzadeh, Somaie; Vahedpour, Morteza

    2018-06-01

    Methanimine reaction with O2 on singlet and triplet potential energy surfaces are investigated using B3PW91, M06-2X, MP2 and CCSD(T) methods. Thermodynamic and kinetic parameters are calculated at M06-2X method. The most favorable channel involves H-abstraction of CH2NH+O2 to the formation of HCN + H2O2 products via low level energy barrier. The catalytic effect of water molecule on HCN + H2O2 products pathway are investigated. Result shows that contribution of water molecule using complex formation with methanimine can decreases barrier energy of transition state and the reaction rate increases. Also, substituent effect of fluorine atom as deactivating group are investigated on the main reaction pathway.

  19. Growth kinetics of vertically aligned carbon nanotube arrays in clean oxygen-free conditions.

    Science.gov (United States)

    In, Jung Bin; Grigoropoulos, Costas P; Chernov, Alexander A; Noy, Aleksandr

    2011-12-27

    Vertically aligned carbon nanotubes (CNTs) are an important technological system, as well as a fascinating system for studying basic principles of nanomaterials synthesis; yet despite continuing efforts for the past decade many important questions about this process remain largely unexplained. We present a series of parametric ethylene chemical vapor deposition growth studies in a "hot-wall" reactor using ultrapure process gases that reveal the fundamental kinetics of the CNT growth. Our data show that the growth rate is proportional to the concentration of the carbon feedstock and monotonically decreases with the concentration of hydrogen gas and that the most important parameter determining the rate of the CNT growth is the production rate of active carbon precursor in the gas phase reaction. The growth termination times obtained with the purified gas mixtures were strikingly insensitive to variations in both hydrogen and ethylene pressures ruling out the carbon encapsulation of the catalyst as the main process termination cause.

  20. An experimental and kinetic investigation of premixed furan/oxygen/argon flames.

    Science.gov (United States)

    Tian, Zhenyu; Yuan, Tao; Fournet, Rene; Glaude, Pierre-Alexandre; Sirjean, Baptiste; Battin-Leclerc, Frédérique; Zhang, Kuiwen; Qi, Fei

    2011-04-01

    The detailed chemical structures of three low-pressure (35 Torr) premixed laminar furan/oxygen/argon flames with equivalence ratios of 1.4, 1.8 and 2.2 have been investigated by using tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry. About 40 combustion species including hydrocarbons and oxygenated intermediates have been identified by measurements of photoionization efficiency spectra. Mole fraction profiles of the flame species including reactants, intermediates and products have been determined by scanning burner position with some selected photon energies near ionization thresholds. Flame temperatures have been measured by a Pt-6%Rh/Pt-30%Rh thermocouple. A new mechanism involving 206 species and 1368 reactions has been proposed whose predictions are in reasonable agreement with measured species profiles for the three investigated flames. Rate-of-production and sensitivity analyses have been performed to track the key reaction paths governing furan consumption for different equivalence ratios. Both experimental and modeling results indicate that few aromatics could be formed in these flames. Furthermore, the current model has been validated against previous pyrolysis results of the literature obtained behind shock waves and the agreement is reasonable as well.

  1. The Kinetics of Oxygen Atom Recombination in the Presence of Carbon Dioxide

    Science.gov (United States)

    Jamieson, C. S.; Garcia, R. M.; Pejakovic, D.; Kalogerakis, K.

    2009-12-01

    Understanding processes involving atomic oxygen is crucial for the study and modeling of composition, energy transfer, airglow, and transport dynamics in planetary atmospheres. Significant gaps and uncertainties exist in the understanding of these processes and often the relevant input from laboratory measurements is missing or outdated. We are conducting laboratory experiments to measure the rate coefficient for O + O + CO2 recombination and investigating the O2 excited states produced following the recombination. These measurements will provide key input for a quantitative understanding and reliable modeling of the atmospheres of the CO2 planets and their airglow. An excimer laser providing pulsed output at either 193 nm or 248 nm is employed to produce O atoms by dissociating carbon dioxide, nitrous oxide, or ozone. In an ambient-pressure background of CO2, O atoms recombine in a time scale of a few milliseconds. Detection of laser-induced fluorescence at 845 nm following two-photon excitation near 226 nm monitors the decay of the oxygen atom population. From the temporal evolution of the signal the recombination rate coefficient is extracted. Fluorescence spectroscopy is used to detect the products of O-atom recombination and subsequent relaxation in CO2. This work is supported by the US National Science Foundation’s (NSF) Planetary Astronomy Program. Rosanne Garcia’s participation was funded by the NSF Research Experiences for Undergraduates (REU) Program.

  2. Peak oxygen uptake in Paralympic sitting sports: A systematic literature review, meta- and pooled-data analysis.

    Science.gov (United States)

    Baumgart, Julia Kathrin; Brurok, Berit; Sandbakk, Øyvind

    2018-01-01

    Peak oxygen uptake (VO2peak) in Paralympic sitting sports athletes represents their maximal ability to deliver energy aerobically in an upper-body mode, with values being influenced by sex, disability-related physiological limitations, sport-specific demands, training status and how they are tested. To identify VO2peak values in Paralympic sitting sports, examine between-sports differences and within-sports variations in VO2peak and determine the influence of sex, age, body-mass, disability and test-mode on VO2peak. Systematic literature review and meta-analysis. PubMed, CINAHL, SPORTDiscusTM and EMBASE were systematically searched in October 2016 using relevant medical subject headings, keywords and a Boolean. Studies that assessed VO2peak values in sitting sports athletes with a disability in a laboratory setting were included. Data was extracted and pooled in the different sports disciplines, weighted by the Dersimonian and Laird random effects approach. Quality of the included studies was assessed with a modified version of the Downs and Black checklist by two independent reviewers. Meta-regression and pooled-data multiple regression analyses were performed to assess the influence of sex, age, body-mass, disability, test mode and study quality on VO2peak. Of 6542 retrieved articles, 57 studies reporting VO2peak values in 14 different sitting sports were included in this review. VO2peak values from 771 athletes were used in the data analysis, of which 30% participated in wheelchair basketball, 27% in wheelchair racing, 15% in wheelchair rugby and the remaining 28% in the 11 other disciplines. Fifty-six percent of the athletes had a spinal cord injury and 87% were men. Sports-discipline-averaged VO2peak values ranged from 2.9 L∙min-1 and 45.6 mL∙kg-1∙min-1 in Nordic sit skiing to 1.4 L∙min-1 and 17.3 mL∙kg-1∙min-1 in shooting and 1.3 L∙min-1 and 18.9 mL∙kg-1∙min-1 in wheelchair rugby. Large within-sports variation was found in sports with few

  3. Peak oxygen uptake in Paralympic sitting sports: A systematic literature review, meta- and pooled-data analysis.

    Directory of Open Access Journals (Sweden)

    Julia Kathrin Baumgart

    Full Text Available Peak oxygen uptake (VO2peak in Paralympic sitting sports athletes represents their maximal ability to deliver energy aerobically in an upper-body mode, with values being influenced by sex, disability-related physiological limitations, sport-specific demands, training status and how they are tested.To identify VO2peak values in Paralympic sitting sports, examine between-sports differences and within-sports variations in VO2peak and determine the influence of sex, age, body-mass, disability and test-mode on VO2peak.Systematic literature review and meta-analysis.PubMed, CINAHL, SPORTDiscusTM and EMBASE were systematically searched in October 2016 using relevant medical subject headings, keywords and a Boolean.Studies that assessed VO2peak values in sitting sports athletes with a disability in a laboratory setting were included.Data was extracted and pooled in the different sports disciplines, weighted by the Dersimonian and Laird random effects approach. Quality of the included studies was assessed with a modified version of the Downs and Black checklist by two independent reviewers. Meta-regression and pooled-data multiple regression analyses were performed to assess the influence of sex, age, body-mass, disability, test mode and study quality on VO2peak.Of 6542 retrieved articles, 57 studies reporting VO2peak values in 14 different sitting sports were included in this review. VO2peak values from 771 athletes were used in the data analysis, of which 30% participated in wheelchair basketball, 27% in wheelchair racing, 15% in wheelchair rugby and the remaining 28% in the 11 other disciplines. Fifty-six percent of the athletes had a spinal cord injury and 87% were men. Sports-discipline-averaged VO2peak values ranged from 2.9 L∙min-1 and 45.6 mL∙kg-1∙min-1 in Nordic sit skiing to 1.4 L∙min-1 and 17.3 mL∙kg-1∙min-1 in shooting and 1.3 L∙min-1 and 18.9 mL∙kg-1∙min-1 in wheelchair rugby. Large within-sports variation was found in

  4. Peak oxygen uptake in Paralympic sitting sports: A systematic literature review, meta- and pooled-data analysis

    Science.gov (United States)

    Brurok, Berit; Sandbakk, Øyvind

    2018-01-01

    Background Peak oxygen uptake (VO2peak) in Paralympic sitting sports athletes represents their maximal ability to deliver energy aerobically in an upper-body mode, with values being influenced by sex, disability-related physiological limitations, sport-specific demands, training status and how they are tested. Objectives To identify VO2peak values in Paralympic sitting sports, examine between-sports differences and within-sports variations in VO2peak and determine the influence of sex, age, body-mass, disability and test-mode on VO2peak. Design Systematic literature review and meta-analysis. Data sources PubMed, CINAHL, SPORTDiscusTM and EMBASE were systematically searched in October 2016 using relevant medical subject headings, keywords and a Boolean. Eligibility criteria Studies that assessed VO2peak values in sitting sports athletes with a disability in a laboratory setting were included. Data synthesis Data was extracted and pooled in the different sports disciplines, weighted by the Dersimonian and Laird random effects approach. Quality of the included studies was assessed with a modified version of the Downs and Black checklist by two independent reviewers. Meta-regression and pooled-data multiple regression analyses were performed to assess the influence of sex, age, body-mass, disability, test mode and study quality on VO2peak. Results Of 6542 retrieved articles, 57 studies reporting VO2peak values in 14 different sitting sports were included in this review. VO2peak values from 771 athletes were used in the data analysis, of which 30% participated in wheelchair basketball, 27% in wheelchair racing, 15% in wheelchair rugby and the remaining 28% in the 11 other disciplines. Fifty-six percent of the athletes had a spinal cord injury and 87% were men. Sports-discipline-averaged VO2peak values ranged from 2.9 L∙min-1 and 45.6 mL∙kg-1∙min-1 in Nordic sit skiing to 1.4 L∙min-1 and 17.3 mL∙kg-1∙min-1 in shooting and 1.3 L∙min-1 and 18.9 mL∙kg-1

  5. Abolition of reflex bradycardia by cardiac vagotomy has no effect on the regulation of oxygen uptake by Atlantic cod in progressive hypoxia

    DEFF Research Database (Denmark)

    McKenzie, David; Skov, Peter Vilhelm; Taylor, E.W.T.

    2009-01-01

    The functional significance of chemoreflexive hypoxic bradycardia was explored in Atlantic cod Gadus morhua L. (mean mass similar to 800 g, acclimated to a seawater temperature of 11 degrees C) by investigating responses to progressive hypoxia following section of the cardiac branches of cranial...... nerve X Cardiac denervation had no effect on oxygen uptake rate (M-O2), gill ventilation rate (f(G)) or opercular pressure amplitude (P-OP) under normoxic conditions, but caused a significant increase in heart rate (f(H)), to 50 +/- 1 beats min(-1) by comparison to 40 +/- 2 beats min(-1) in sham...

  6. Kinetics and Mechanisms of Oxygen Surface Exchange on La0.6Sr0.4FeO3-delta Thin Films

    OpenAIRE

    Mosleh, Majid; Søgaard, Martin; Hendriksen, Peter Vang

    2009-01-01

    The thermodynamic properties as well as oxygen exchange kinetics were examined on mixed ionic and electronic conducting (La0.6Sr0.4)0.99FeO3− (LSF64) thin films deposited on MgO single crystals. It is found that thin films and bulk material have the same oxygen stoichiometry for a given temperature and oxygen partial pressure [i.e., the incorporation reaction has the same reaction enthalpy (H0=−105 KJ/mol) and entropy (S0=−75.5 J/mol/K) as found for bulk material]. The thin film shows smaller...

  7. The Effect of Non-equilibrium Kinetics on Oxygen Chemistry in the Interstellar Medium

    Science.gov (United States)

    Naduvalath, Balakrishnan

    2006-01-01

    It has been suggested that in photon-dominated regions, oxygen chemistry is initiated by the O+H2 yields OH+H reaction. The reaction has an energy barrier of about 0.4 eV with ground state reactants and it is slow at low temperatures. There is strong experimental evidence that vibrational excitation of the H2 molecule increases the reactivity significantly. We present extensive quantum calculations of cross sections and rate coefficients for the O+H2(v) reaction for v = 0 - 3 of the H2 molecule and show that the vibrational excitation of the molecule has a significant effect on reactivity, especially at low temperatures.

  8. Hydrogen/Oxygen Reactions at High Pressures and Intermediate Temperatures: Flow Reactor Experiments and Kinetic Modeling

    DEFF Research Database (Denmark)

    Hashemi, Hamid; Christensen, Jakob Munkholt; Glarborg, Peter

    A series of experimental and numerical investigations into hydrogen oxidation at high pressures and intermediate temperatures has been conducted. The experiments were carried out in a high pressure laminar flow reactor at 50 bar pressure and a temperature range of 600–900 K. The equivalence ratio......, the mechanism is used to simulate published data on ignition delay time and laminar burning velocity of hydrogen. The flow reactor results show that at reducing, stoichiometric, and oxidizing conditions, conversion starts at temperatures of 750–775 K, 800–825 K, and 800–825 K, respectively. In oxygen atmosphere......, ignition occurs at the temperature of 775–800 K. In general, the present model provides a good agreement with the measurements in the flow reactor and with recent data on laminar burning velocity and ignition delay time....

  9. Uptake, translocation and biotransformation kinetics of BDE-47, 6-OH-BDE-47 and 6-MeO-BDE-47 in maize (Zea mays L.)

    International Nuclear Information System (INIS)

    Xu, Xuehui; Wen, Bei; Huang, Honglin; Wang, Sen; Han, Ruixia; Zhang, Shuzhen

    2016-01-01

    This study presents a detailed kinetic investigation on the uptake, acropetal translocation and transformation of BDE-47, 6-OH-BDE-47 and 6-MeO-BDE-47 in maize (Zea mays L.) by hydroponic exposure. Root uptake followed the order: BDE-47 > 6-MeO-BDE-47 > 6-OH-BDE-47, while 6-OH-BDE-47 was the most prone to acropetal translocation. Debromination rates of BDE-47 were 1.31 and 1.46 times greater than the hydroxylation and methoxylation rates, respectively. Transformation from BDE-47 to lower brominated OH/MeO-PBDEs occurred mainly through debromination first followed by hydroxylation or methoxylation. There was no transformation from 6-OH-BDE-47 or 6-MeO-BDE-47 to PBDEs. Methylation rate of 6-OH-BDE-47 was twice as high as that of 6-MeO-BDE-47 hydroxylation, indicating methylation of 6-OH-BDE-47 was easier and more rapid than hydroxylation of 6-MeO-BDE-47. Debromination and isomerization were potential metabolic pathways for 6-OH-BDE-47 and 6-MeO-BDE-47 in maize. This study provides important information for better understanding the mechanism on plant uptake and transformation of PBDEs. - Highlights: • Uptake and translocation of BDE-47 and 6-OH/MeO-BDE-47 were analog-specific. • Debromination was the fast and dominant metabolic reaction of BDE-47 in maize. • Metabolic pathways of BDE-47, 6-OH/MeO-BDE-47 in maize were discussed. • Metabolic processes should be considered in exploring phytoremediation strategy. - This article provides direct in vivo evidences of bioaccumulation and biotransformation of PBDEs, OH-PBDEs and MeO-PBDEs in plants.

  10. Oxidation of D-glucose and D-fructose with oxygen in aqueous, alkaline solutions. III. Kinetic approach to the product distribution

    NARCIS (Netherlands)

    de Wilt, H.G.J.; Kuster, Ben

    1972-01-01

    Based on a previously reported, integral reaction-scheme for the homogeneous oxidation of -glucose and -fructose with oxygen in aqueous, alkaline solutions, a kinetic model covering the product distribution has been developed. The model consists of a repeated set of reactions with constant rate

  11. 99Tcm-N(NOEt2 Uptake Kinetics Difference among KMB17 Human Embryonic Lung Diploid Fibroblast and Different Human Lung Cancer Cells

    Directory of Open Access Journals (Sweden)

    Wei JIA

    2010-04-01

    Full Text Available Background and objective PET/CT imaging is expensive, so searching the tumor imaging agent for SPECT/CT is necessary. 99Tcm-N(NOEt2 [bis (N-ethoxy-N-ethyl dithiocarbamato nitrido99Tcm (V] can be uptaken by lung cancer cells and other cells alike. The aim of this study is to evaluate the distinctive value in lung tumor with 99Tcm-N(NOEt2, the difference in its uptake kinetics in human embryonic lung diploid fibroblasts KMB17 and several kinds of lung cancer cells lines. Methods Firstly, six different cell culture medium which contained YTMLC Gejiu human lung squamous carcinoma cell, SPC-A1 human lung adenocarcinoma cell, AGZY low metastatic human lung adenocarcinoma, 973 high metastatic human lung adenocarcinoma cell, GLC-82 Gejiu human lung adenocarcinoma cell, and KMB17 human embryonic lung diploid fibroblast, respectively with equal cell density of 1×106/mL and the same volume were prepared; secondly, the same radioactive dose of 99Tcm-N(NOEt2 was added into each sample and then 300 μL mixed sample was taken out respectively and cultured in 37 oC culture box; Finally, 5 min, 15 min, 30 min, 45 min, 60 min, 75 min, 90 min after cultivation, centrifuged each cultured sample and determined the intracellular radiocounts of each sample, calculated each cell sample’s uptake rate of 99Tcm-N(NOEt2 at different time. Results Statistical difference was found among six cell samples, and the uptake rate sequence from high to low is 973 and SPC-A1>YTMLC>GLC-82>AGZY>KMB17 respectively; furthermore, 30 min-45 min after culture, the uptake rate reached stability, and the 45 min uptake rate of each sample was higher than its 96.7% uptake peak. Conclusion Based on the results above mentioned, it is supposed that there are discriminative clinical value when using 99Tcm-N(NOEt2 as a tumor targeting imaging agent, and 30 min or so after injection may be the best imaging time in the early imaging stage.

  12. Fish embryos on land: terrestrial embryo deposition lowers oxygen uptake without altering growth or survival in the amphibious fish Kryptolebias marmoratus.

    Science.gov (United States)

    Wells, Michael W; Turko, Andy J; Wright, Patricia A

    2015-10-01

    Few teleost fishes incubate embryos out of water, but the oxygen-rich terrestrial environment could provide advantages for early growth and development. We tested the hypothesis that embryonic oxygen uptake is limited in aquatic environments relative to air using the self-fertilizing amphibious mangrove rivulus, Kryptolebias marmoratus, which typically inhabits hypoxic, water-filled crab burrows. We found that adult mangrove rivulus released twice as many embryos in terrestrial versus aquatic environments and that air-reared embryos had accelerated developmental rates. Surprisingly, air-reared embryos consumed 44% less oxygen and possessed larger yolk reserves, but attained the same mass, length and chorion thickness. Water-reared embryos moved their opercula ∼2.5 more times per minute compared with air-reared embryos at 7 days post-release, which probably contributed to the higher rates of oxygen uptake and yolk utilization we observed. Genetically identical air- and water-reared embryos from the same parent were raised to maturity, but the embryonic environment did not affect growth, reproduction or emersion ability in adults. Therefore, although aspects of early development were plastic, these early differences were not sustained into adulthood. Kryptolebias marmoratus embryos hatched out of water when exposed to aerial hypoxia. We conclude that exposure to a terrestrial environment reduces the energetic costs of development partly by reducing the necessity of embryonic movements to dispel stagnant boundary layers. Terrestrial incubation of young would be especially beneficial to amphibious fishes that occupy aquatic habitats of poor water quality, assuming low terrestrial predation and desiccation risks. © 2015. Published by The Company of Biologists Ltd.

  13. Kinetics of sodium borohydride direct oxidation and oxygen reduction in sodium hydroxide electrolyte

    International Nuclear Information System (INIS)

    Chatenet, Marian; Micoud, Fabrice; Roche, Ivan; Chainet, Eric

    2006-01-01

    The direct oxidation of sodium borohydride in concentrated sodium hydroxide medium has been studied by cyclic and linear voltammetry, chronoamperometry and chronopotentiometry for silver and gold electrocatalysts, either bulk and polycrystalline or nanodispersed over high area carbon blacks. Gold and silver yield rather complete utilisation of the reducer: around 7.5 electrons are delivered on these materials, versus 4 at the most for platinum as a result of the BH 4 - non-negligible hydrolysis taking place on this latter material. The kinetic parameters for the direct borohydride oxidation are better for gold than for silver. A strong influence of the ratio of sodium hydroxide versus sodium borohydride is found: whereas the theoretical stoichiometry does forecast that eight hydroxide ions are needed for each borohydride ion, our experimental results prove that a larger excess hydroxide ion is necessary in quasi-steady state conditions. When the above-mentioned ratio is unity (1 M NaOH and 1 M NaBH 4 ), the tetrahydroborate ions direct oxidation is limited by the hydroxide concentration, and their hydrolysis is no longer negligible. The hydrolysis products are probably BH 3 OH - ions, for which gold displays a rather good oxidation activity. Additionally, silver, which is a weak BH 4 - oxidation electrocatalyst, exhibits the best activity of all the studied materials towards the BH 3 OH - direct oxidation. Finally, carbon-supported gold nanoparticles seem promising as anode material to be used in direct borohydride fuel cells

  14. Effect of an insect juvenile hormone analogue, Fenoxycarb on development and oxygen uptake by larval lobsters Homarus gammarus (L.).

    Science.gov (United States)

    Arnold, Katie E; Wells, Colin; Spicer, John I

    2009-04-01

    Little attention has been focused on the effect of anthropogenic compounds that disrupt the endocrine systems in crustaceans. Consequently, this study investigated the effects of the juvenile hormone analogue (JHA), Fenoxycarb on selected physiological and developmental processes of the zoeal stages in the European lobster, Homarus gammarus. Chronic exposure to Fenoxycarb (50microg L(-1)) resulted in a significant (p < 0.05) reduction in moult frequency and size at moult. Fenoxycarb exposure extended zoeal duration between zoea I to II (p<0.05) and resulted in total inhibition of the moult from zoea II to III. Significantly greater rates of O2 uptake were observed in Fenoxycarb-exposed larvae in comparison with controls (p<0.05). All rates of O2 uptake decreased significantly between 7 and 12d of exposure (p<0.05). At 12d, exposure to the solvent control no longer influenced rates of O2 uptake, but it was not possible to attribute increased O2 uptake to Fenoxycarb exposure directly, as treated individuals did not moult beyond zoea III. The low exposure concentrations of Fenoxycarb, comparable to those used in plant protection, resulted in endocrine disrupted responses in H. gammarus (albeit with little clear, demonstrable effect on metabolism) a finding that could have important ecological and commercial implications.

  15. Blood gas analyzer utility in evaluating oxygen kinetics of the aqueous humor

    Directory of Open Access Journals (Sweden)

    Ismail Ersan

    2015-04-01

    Full Text Available Purpose: To measure the partial pressure of oxygen (PO2 and carbon dioxide (PCO2 and the pH of aqueous humor (AH and arterial blood samples from rabbits using a blood gas analyzer. Methods: Twenty New Zealand rabbits were anesthetized intramuscularly with ketamine and xylazine and were then allowed to breathe room air. Using a gas blood analyzer, arterial blood and AH samples were analyzed for PO2, PCO2, and pH. Results: The mean arterial blood pressure was 87.14 ± 15.0 mmHg. The mean blood and AH PO2 were 95.18 ± 11.76 mmHg and 88.83 ± 9.92 mmHg, the mean blood and AH PCO2 were 25.86 ± 5.46 mmHg and 29.50 ± 5.36 mmHg, and the mean blood and AH pH were 7.38 ± 0.06 and 7.33 ± 0.09, respectively. Conclusion: Conclusions: The blood gas analyzer was easily employed to evaluate the aqueous humor in rabbits. When comparing the results of studies evaluating aqueous PO2, care should be taken to determine the methods used in these studies.

  16. Oxygen kinetics and mechanism at electrocatalysts on the base of palladium-iron system

    International Nuclear Information System (INIS)

    Tarasevich, M.R.; Zhutaeva, G.V.; Bogdanovskaya, V.A.; Radina, M.V.; Ehrenburg, M.R.; Chalykh, A.E.

    2007-01-01

    Binary nanodispersed carbon XC72 supported PdFe catalysts with different atomic palladium-to-iron ratios are synthesized and studied in oxygen reduction reaction in acid solution at 60 o C. The Pd:Fe ratio was well controlled by the initial concentrations of Pd and Fe in the precursor solutions. The nanoparticles were characterized by transmission electron microscopy, X-ray diffractometry and X-ray photoelectron spectroscopy. The optimum Pd:Fe ratio for this reaction was determined to be 3:1. The comparison of activities of the catalysts with component ratios equaled 3:1 and 10:1 is shown that the activities are differed from each other by 10-15 times in advantage of catalyst with lesser content of palladium. This phenomenon can be related to the different particle size of both catalysts and different distribution of particles by size discovered by TEM method. The achievement of maximum activity near the ratio of Pd:Fe = 3:1 is due to as effect of alloy-forming and the influence of binary system component ratio and synthesis conditions on dispersity degree of metallic phase nanoparticles. Under optimal conditions of precursor mixture high-temperature pyrolysis, iron produces the stabilizing effect palladium. It gives rise to obtaining the uniform and finely divided (7-8 nm) metallic particles

  17. VO2 OFF TRANSIENT KINETICS IN EXTREME INTENSITY SWIMMING

    Directory of Open Access Journals (Sweden)

    Ana Sousa

    2011-09-01

    Full Text Available Inconsistencies about dynamic asymmetry between the on- and off- transient responses in oxygen uptake are found in the literature. Therefore, the purpose of this study was to characterize the oxygen uptake off-transient kinetics during a maximal 200-m front crawl effort, as examining the degree to which the on/off regularity of the oxygen uptake kinetics response was preserved. Eight high level male swimmers performed a 200-m front crawl at maximal speed during which oxygen uptake was directly measured through breath-by-breath oxymetry (averaged every 5 s. This apparatus was connected to the swimmer by a low hydrodynamic resistance respiratory snorkel and valve system. Results: The on- and off-transient phases were symmetrical in shape (mirror image once they were adequately fitted by a single-exponential regression models, and no slow component for the oxygen uptake response was developed. Mean (± SD peak oxygen uptake was 69.0 (± 6.3 mL·kg-1·min-1, significantly correlated with time constant of the off- transient period (r = 0.76, p < 0.05 but not with any of the other oxygen off-transient kinetic parameters studied. A direct relationship between time constant of the off-transient period and mean swimming speed of the 200-m (r = 0.77, p < 0.05, and with the amplitude of the fast component of the effort period (r = 0.72, p < 0.05 were observed. The mean amplitude and time constant of the off-transient period values were significantly greater than the respective on- transient. In conclusion, although an asymmetry between the on- and off kinetic parameters was verified, both the 200-m effort and the respectively recovery period were better characterized by a single exponential regression model

  18. Functional High-Intensity Circuit Training Improves Body Composition, Peak Oxygen Uptake, Strength, and Alters Certain Dimensions of Quality of Life in Overweight Women.

    Science.gov (United States)

    Sperlich, Billy; Wallmann-Sperlich, Birgit; Zinner, Christoph; Von Stauffenberg, Valerie; Losert, Helena; Holmberg, Hans-Christer

    2017-01-01

    The effects of circuit-like functional high-intensity training (Circuit HIIT ) alone or in combination with high-volume low-intensity exercise (Circuit combined ) on selected cardio-respiratory and metabolic parameters, body composition, functional strength and the quality of life of overweight women were compared. In this single-center, two-armed randomized, controlled study, overweight women performed 9-weeks (3 sessions·wk -1 ) of either Circuit HIIT ( n = 11), or Circuit combined ( n = 8). Peak oxygen uptake and perception of physical pain were increased to a greater extent ( p body mass, body-mass-index, waist-to-hip ratio, fat mass, and enhanced fat-free mass; decreased ratings of perceived exertion during submaximal treadmill running; improved the numbers of push-ups, burpees, one-legged squats, and 30-s skipping performed, as well as the height of counter-movement jumps; and improved physical and social functioning, role of physical limitations, vitality, role of emotional limitations, and mental health to a similar extent (all p training can be employed to improve body composition, selected variables of functional strength, and certain dimensions of quality of life in overweight women. However, Circuit HIIT improves peak oxygen uptake to a greater extent, but with more perception of pain, whereas Circuit combined results in better perception of general health.

  19. Kinetics and Mechanism of Bioactivation via S-Oxygenation of Anti-Tubercular Agent Ethionamide by Peracetic Acid.

    Science.gov (United States)

    Chipiso, Kudzanai; Logan, Isabelle E; Eskew, Matthew W; Omondi, Benard; Simoyi, Reuben H

    2016-10-11

    The kinetics and mechanism of the oxidation of the important antitubercular agent, ethionamide, ETA (2-ethylthioisonicotinamide), by peracetic acid (PAA) have been studied. It is effectively a biphasic reaction with an initial rapid first phase of the reaction which is over in about 5 s and a second slower phase of the reaction which can run up to an hour. The first phase involves the addition of a single oxygen atom to ethionamide to form the S-oxide. The second phase involves further oxidation of the S-oxide to desulfurization of ETA to give 2-ethylisonicotinamide. In contrast to the stability of most organosulfur compounds, the S-oxide of ETA is relatively stable and can be isolated. In conditions of excess ETA, the stoichiometry of the reaction was strictly 1:1: CH 3 CO 3 H + Et(C 5 H 4 )C(═S)NH 2 → CH 3 CO 2 H + Et(C 5 H 4 )C(═NH)SOH. In this oxidation, it was apparent that only the sulfur center was the reactive site. Though ETA was ultimately desulfurized, only the S-oxide was stable. Electrospray ionization (ESI) spectral analysis did not detect any substantial formation of the sulfinic and sulfonic acids. This suggests that cleavage of the carbon-sulfur bond occurs at the sulfenic acid stage, resulting in the formation of an unstable sulfur species that can react further to form more stable sulfur species. In this oxidation, no sulfate formation was observed. ESI spectral analysis data showed a final sulfur species in the form of a dimeric sulfur monoxide species, H 3 S 2 O 2 . We derived a bimolecular rate constant for the formation of the S-oxide of (3.08 ± 0.72) × 10 2 M -1 s -1 . Oxidation of the S-oxide further to give 2-ethylisonicotinamide gave zero order kinetics.

  20. Genetic characterization, nickel tolerance, biosorption, kinetics, and uptake mechanism of a bacterium isolated from electroplating industrial effluent.

    Science.gov (United States)

    Nagarajan, N; Gunasekaran, P; Rajendran, P

    2015-04-01

    Electroplating industries in Madurai city produce approximately 49,000 L of wastewater and 1200 L of sludge every day revealing 687-5569 ppm of nickel (Ni) with other contaminants. Seventeen Ni-tolerant bacterial strains were isolated from nutrient-enriched effluents. Among them one hyper Ni accumulating strain was scored and identified as Bacillus cereus VP17 on the basis of morphology, biochemical tests, 16S rDNA gene sequencing, and phylogenetic analysis. Equilibrium data of Ni(II) ions using the bacterium as sorbent at isothermal conditions (37 °C) and pH 6 were best adjusted by Langmuir (R(2) = 0.6268) and Freundlich models (R(2) = 0.9505). Experimental validation reveals Ni sorption takes place on a heterogeneous surface of the biosorbent, and predicted metal sorption capacity is 434 ppm. The pseudo-second-order kinetic model fitted the biosorption kinetic data better than the pseudo-first-order kinetic model (R(2) = 0.9963 and 0.3625). Scanning electron microscopy, energy dispersive X-ray, and Fourier transform infrared spectroscopy studies of the bacterial strain with and without Ni(II) ion reveals the biosorption mechanism. The results conclude possibilities of using B. cereus VP17 for Ni bioremediation.

  1. Study on biofiltration capacity and kinetics of nutrient uptake by Gracilaria cervicornis (Turner J. Agardh (Rhodophyta, Gracilariaceae

    Directory of Open Access Journals (Sweden)

    Marcella A. A. Carneiro

    2011-04-01

    Full Text Available The absorption efficiency and kinetic parameters (Vmax, Ks and Vmax:Ks of the seaweed Gracilaria cervicornis for the nutrients NH4+, NO3- and PO4(3- were evaluated. Absorption efficiency was measured by monitoring nutrient concentrations for 5 h in culture media with initial concentrations of 5, 10, 20 and 30µM. Kinetic parameters were determined by using the Michaelis-Menten formula. Absorption efficiencies for this algae were greater in treatments with lower concentrations, as evidenced by a reduction of 85.3, 97.5 and 81.2% for NH4+, NO3- and PO4(3-, respectively. Kinetic parameters show that G. cervicornis exhibits greater ability to take up high concentrations of NH4+ (Vmax=158.5µM g dw-1 h-1 and low concentrations of PO4(3- (Ks=5µM and Vmax:Ks=10.3. These results suggest that this algal species has good absorption capacity for the nutrients tested and may be a promising candidate as a bioremediator of eutrophized environments.

  2. Uptake and release kinetics of 134Cs by goldfish (Carassius auratus) and 137Cs by zebra fish (Brachydanio rerio) in controlled aquatic environment

    International Nuclear Information System (INIS)

    Srivastava, A.; Reddy, S.J.; Kelber, O.; Urich, K.; Denschlag, H.O.

    1994-01-01

    The uptake and release kinetics of 134 Cs by Goldfish (Carassius auratus) and 137 Cs by Zebra Fish (Brachydanio rerio) from aquatic media of different ionic compositions and temperature was studied in controlled laboratory conditions. The accumulation of radiocesium in the case of Brachydanio rerio is observed to be strongly dependent on the potassium ion concentration of the aquatic medium, but in the case of Carassius auratus this dependence is quite weak. The biological half-lives of the cesium isotopes incorporated into the fish investigated in the present work vary from 19 to 80 days and are influenced by the temperature and the ionic composition of the aquatic medium. (author) 19 refs.; 1 fig.; 3 tabs

  3. Iodine capsules in thyroid therapy: An individually controlled study of I-131 uptake kinetics as compared to liquid administration

    International Nuclear Information System (INIS)

    von Schulthess, G.K.; Seelentag, W.W.; Pfeiffer, G.; Blauenstein, P.; Bekier, A.

    1984-01-01

    The aim of this study was to determine the additional radiation dose sustained by parts of the patients gastric mucosa when given I-131 therapy in capsular rather than liquid form, and thus to establish the safety of this procedure. 16 patients with benign thyroid disease were studied by measuring serum radioactivity at 0, 5, 10, 20, 40, and 80 min. after administration of the capsule (120-200 MBq I131). These serum uptake values were compared to the uptake after administration of a liquid diagnostic dose of I-131 (2 MBq). From the resulting uptake curves the delay due to capsular dissolution was determined. The average dissolution time was found to be 12 min. with a large standard deviation of 7 min. Also, a theoretical curve was computed to indicate the dose rate as a function of the distance from the surface of the capsule. Based on this information the maximum dose to the gastric mucosa is of the order of 250 cGy for a therapeutic activity of 185 MBq, which is the maximum dose which may be given as single application to outpatients in Switzerland. By having the patient swallow some liquid during the first ten minutes, the capsule can be made to move around, and hence, the local radiation dose can be reduced substantially. The authors conclude, that I-131 in capsular form is a safe galenic form for therapeutic use in patients with thyroid disease. When large doses are given, administration of the dose in several capsules may be advisable

  4. Effects of exercise mode on the peak oxygen uptake and blood lactate response in boys aged 11-12 years

    Directory of Open Access Journals (Sweden)

    Fabiana Andrade Machado

    2006-09-01

    Full Text Available The objective of this study was to analyze the effects of exercise mode (running x cycling on the indexesrelated to aerobic fitness (VO2peak and blood lactate response to exercise in children. Participated of this study 20 active boys apparently healthy (age = 11.48 + 0.41 yr.; body mass = 41.38 + 10.45 kg; stature = 147.45 + 6.56 cm, with sexual maturational level 1 and 2 (pubic hair, which performed two incremental tests, with stages of 3 minutes until voluntary exhaustion, in treadmill (TR and cycle ergometer (CE, to the determination of peak oxygen uptake (VO2peak and lactate threshold (LT. The VO2peak was determined through the higher value obtained at intervals of 15 seconds. The LT was determined as the exercise intensity where the first and sustained increase of blood lactate above rest level occurred. The VO2peak (45.16 + 5.98 x 42.93 + 7.51 ml/kg/min, maximal heart rate (196.5 + 6.98 x 187.3 + 9.27 bpm, VO2 at LL (31.82 + 10.09 x 25.19 + 7.36 ml/kg/min and HR at LL (150.5 + 17.75 x 131.3 + 12.98 bpm were significantly higher in TR than CE, respectively. Thus, similar to adults, boys of 11 to 12 years present higher aerobic indexes (submaximal and maximal in running than cycling, which can haveimportant implications for healthy professionals that utilize exercise for the healthy promotion, rehabilitation and experimental designs. RESUMO O objetivo deste estudo foi analisar os efeitos do modo de exercício (corrida x ciclismo sobre os índices relacionados com a aptidão aeróbia (VO2pico e resposta de lactato ao exercício em crianças. Participaram doestudo 20 meninos, aparentemente saudáveis e ativos (idade = 11,48 + 0,41 anos; massa corporal = 41,38 + 10,45 kg; estatura = 147,45 + 6,56 cm, com níveis de maturação sexual 1 e 2 (pilosidade pubiana, que realizaram dois testes incrementais, com estágios de 3 minutos até a exaustão voluntária, em esteira rolante (ER e bicicleta ergométrica (BE, para a determinação do pico do

  5. Kinetics of phosphate uptake, growth, and accumulation of cyclic diphosphoglycerate in a phosphate-limited continuous culture of Methanobacterium thermoautotrophicum.

    OpenAIRE

    Krueger, R D; Harper, S H; Campbell, J W; Fahrney, D E

    1986-01-01

    The archaebacterium Methanobacterium thermoautotrophicum was grown in continuous culture at 65 degrees C in a phosphate-limited medium at specific growth rates from 0.06 to 0.28 h-1 (maximum growth rate [mu max] = 0.36 h-1). Cyclic-2,3-diphosphoglycerate (cyclic DPG) levels ranged from 2 to 20 mM in Pi-limited cells, compared with about 30 mM in batch-grown cells. The Monod constant for Pi-limited growth was 5 nM. Pi uptake rates were determined by following the disappearance of 32Pi from the...

  6. Kinetics of several oxygenated carbon-centered free radical reactions with NO2.

    Science.gov (United States)

    Rissanen, Matti P; Arppe, Suula L; Timonen, Raimo S

    2013-05-16

    Five oxygenated carbon-centered free radical reactions with nitrogen dioxide (NO2) have been studied in direct time-resolved measurements. Experiments were conducted in a temperature-controlled flow tube reactor coupled to a 193 nm exciplex laser photolysis and a resonance gas lamp photoionization mass spectrometer. Reactions were investigated under pseudofirst-order conditions, with the NO2 concentrations of the experiments in great excess over the initial radical concentrations ([R]0 CH3CO radical reactions with NO2 and, hence, includes the three smallest hydroxyalkyl radical species (CH2OH, CH2CH2OH, and CH3CHOH). The obtained rate coefficients are high with the temperature-dependent rate coefficients given by a formula k(T) = k300K × (T/300 K)(-n) as (in units of cm(3) molecule(-1) s(-1)): k(CH2OH + NO2) = (8.95 ± 2.70) × 10(-11) × (T/300 K)(-0.54±0.27) (T = 298-363 K), k(CH2CH2OH + NO2) = (5.99 ± 1.80) × 10(-11) × (T/300 K)(-1.49±0.45)(T = 241-363 K), k(CH3CHOH + NO2) = (7.48 ± 2.24) × 10(-11) × (T/300 K)(-1.36±0.41) (T = 266-363 K), k(CH3OCH2 + NO2) = (7.85 ± 2.36) × 10(-11) × (T/300 K)(-0.93±0.28) (T = 243-363 K), and k(CH3CO + NO2) = (2.87 ± 0.57) × 10(-11) × (T/300 K)(-2.45±0.49) (T = 241-363 K), where the uncertainties refer to the estimated overall uncertainties of the values obtained. The determined rate coefficients show negative temperature dependence with no apparent bath gas pressure dependence under the current experimental conditions (241-363 K and about 1-3 Torr helium). This behavior is typical for a radical-radical addition mechanism with no potential energy barrier above the energy of the separated reactants in the entrance channel of the reaction. Unfortunately the absence of detected product signals prevented gaining deeper insight into the reaction mechanism.

  7. Denitrifying bacterial community composition changes associated with stages of denitrification in oxygen minimum zones

    Digital Repository Service at National Institute of Oceanography (India)

    Jayakumar, D.A; O'Mullan, G.D.; Naqvi, S.W.A.; Ward, B.B.

    in the ocean. Nature 445:163–167 11. Devol AH (1978) Bacterial oxygen uptake kinetics as related to biological processes in oxygen deficient zones of the oceans. Deep-Sea Res 25:137–146 12. Devol AH, Uhlenhopp AG, Naqvi SWA, Brandes JA, Jayakumar DA, Naik H...

  8. Kinetic box models for the uptake of radionuclides and heavy metals by suspended particulate matter: equivalence between models and its implications

    International Nuclear Information System (INIS)

    Barros, H.; Abril, J.M.

    2008-01-01

    In recent years an increasing experimental effort has been paid to the study of the sorption process of radionuclides and heavy metals by particulate matter in aquatic environments. This has led to the development of different kinetic box models. Most of them are variations of two basic approaches: one containing several (up to three) parallel reactions while the other involves consecutive reactions. All the reactions are reversible (irreversibility is contained as a particular case) with concentration independent coefficients. The present work provides analytical solutions and demonstrates that both approaches are mathematically equivalent. That is, both models produce the same analytical solution for the uptake curve (time course of the concentrations in the dissolved phase), which is illustrated using literature data. This result unifies the description of the observed behaviour, but it brings up the question of the physical meaning of the involved coefficients. Finally, the mathematical relationship developed here serves to discuss some limitations found in recent attempts in literature devoted to distinguish the actual uptake mechanism

  9. Differentiation of Glioblastomas from Metastatic Brain Tumors by Tryptophan Uptake and Kinetic Analysis: A Positron Emission Tomographic Study with Magnetic Resonance Imaging Comparison

    Directory of Open Access Journals (Sweden)

    David O. Kamson

    2013-07-01

    Full Text Available Differentiating high-grade gliomas from solitary brain metastases is often difficult by conventional magnetic resonance imaging (MRI; molecular imaging may facilitate such discrimination. We tested the accuracy of α[11C]methyl-L-tryptophan (AMT–positron emission tomography (PET to differentiate newly diagnosed glioblastomas from brain metastases. AMT-PET was performed in 36 adults with suspected brain malignancy. Tumoral AMT accumulation was measured by standardized uptake values (SUVs. Tracer kinetic analysis was also performed to separate tumoral net tryptophan transport (by AMT volume of distribution [VD] from unidirectional uptake rates using dynamic PET and blood input function. Differentiating the accuracy of these PET variables was evaluated and compared to conventional MRI. For glioblastoma/metastasis differentiation, tumoral AMT SUV showed the highest accuracy (74% and the tumor/cortex VD ratio had the highest positive predictive value (82%. The combined accuracy of MRI (size of contrast-enhancing lesion and AMT-PET reached up to 93%. For ring-enhancing lesions, tumor/cortex SUV ratios were higher in glioblastomas than in metastatic tumors and could differentiate these two tumor types with > 90% accuracy. These results demonstrate that evaluation of tryptophan accumulation by PET can enhance pretreatment differentiation of glioblastomas and metastatic brain tumors. This approach may be particularly useful in patients with a newly diagnosed solitary ring-enhancing mass.

  10. Arm Crank and Wheelchair Ergometry Produce Similar Peak Oxygen Uptake but Different Work Economy Values in Individuals with Spinal Cord Injury

    Directory of Open Access Journals (Sweden)

    Tom Tørhaug

    2016-01-01

    Full Text Available Objective. To study whether values for peak oxygen uptake (VO2peak and work economy (WE at a standardized workload are different when tested by arm crank ergometry (ACE and wheelchair ergometry (WCE. Methods. Twelve paraplegic men with spinal cord injury (SCI in stable neurological condition participated in this cross-sectional repeated-measures study. We determined VO2peak and peak power output (POpeak values during ACE and WCE in a work-matched protocol. Work economy was tested at a standardized workload of 30 Watts (W for both ACE and WCE. Results. There were no significant differences in VO2peak (mL·kg−1·min−1 between ACE (27.3±3.2 and WCE (27.4±3.8 trials, and a Bland-Altman plot shows that findings are within 95% level of agreement. WE or oxygen consumption at 30 W (VO2-30W was significantly lower during WCE compared to ACE (P<0.039. Mean (95% CI POpeak (W were 130 (111–138 and 100 (83–110 during ACE and WCE, respectively. Conclusion. The findings in the present study support the use of both ACE and WCE for testing peak oxygen uptake. However, WE differed between the two test modalities, meaning that less total energy is used to perform external work of 30 W during wheelchair exercise when using this WCE (VP100 Handisport ergometer. Clinical Trials Protocol Record is NCT00987155/4.2007.2271.

  11. Relation of oxygen uptake to work rate in prepubertal healthy children - reference for VO2/W-slope and effect on cardiorespiratory fitness assessment.

    Science.gov (United States)

    Tompuri, Tuomo; Lintu, Niina; Laitinen, Tomi; Lakka, Timo A

    2017-08-09

    Exercise testing by cycle ergometer allows to observe the interaction between oxygen uptake (VO 2 ) and workload (W), and VO 2 /W-slope can be used as a diagnostic tool. Respectively, peak oxygen uptake (VO 2 PEAK ) can be estimated by maximal workload. We aim to determine reference for VO 2 /W-slope among prepubertal children and define agreement between estimated and measured VO 2 PEAK . A total of 38 prepubertal children (20 girls) performed a maximal cycle ergometer test with respiratory gas analysis. VO 2 /W-slopes were computed using linear regression. Agreement analysis by Bland and Altman for estimated and measured VO 2 PEAK was carried out including limits of agreement (LA). Determinants for VO 2 /W-slopes and estimation bias were defined. VO2/W-slope was in both girls and boys ≥9·4 and did not change with exercise level, but the oxygen cost of exercise was higher among physically more active children. Estimated VO 2 PEAK had 6·4% coefficient of variation, and LA varied from 13% underestimation to 13% overestimation. Bias had a trend towards underestimation along lean mass proportional VO 2 PEAK . The primary determinant for estimation bias was VO2/W-slope (β = -0·65; PW-slope among healthy prepubertal children were similar to those published for adults and among adolescents. Estimated and measured VO 2 PEAK should not be considered to be interchangeable because of the variation in the relationship between VO 2 and W. On other hand, variation in the relationship between VO 2 and W enables that VO 2 /W-slope can be used as a diagnostic tool. © 2017 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

  12. Electrochemical kinetics and X-ray absorption spectroscopy investigations of select chalcogenide electrocatalysts for oxygen reduction reaction applications

    International Nuclear Information System (INIS)

    Ziegelbauer, Joseph M.; Murthi, Vivek S.; O'Laoire, Cormac; Gulla, Andrea F.; Mukerjee, Sanjeev

    2008-01-01

    Transition metal-based chalcogenide electrocatalysts exhibit a promising level of performance for oxygen reduction reaction applications while offering significant economic benefits over the state of the art Pt/C systems. The most active materials are based on Ru x Se y clusters, but the toxicity of selenium will most likely limit their embrace by the marketplace. Sulfur-based analogues do not suffer from toxicity issues, but suffer from substantially less activity and stability than their selenium brethren. The structure/property relationships that result in these properties are not understood due to ambiguities regarding the specific morphologies of Ru x S y -based chalcogenides. To clarify these properties, an electrochemical kinetics study was interpreted in light of extensive X-ray diffraction, scanning electron microscopy, and in situ X-ray absorption spectroscopy evaluations. The performance characteristics of ternary M x Ru y S z /C (M = Mo, Rh, or Re) chalcogenide electrocatalysts synthesized by the now-standard low-temperature nonaqueous (NA) route are compared to commercially available (De Nora) Rh- and Ru-based systems. Interpretation of performance differences is made in regards to bulk and surface properties of these systems. In particular, the overall trends of the measured activation energies in respect to increasing overpotential and the gross energy values can be explained in regards to these differences

  13. Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O3-x thin film case study.

    Science.gov (United States)

    Perry, Nicola H; Kim, Jae Jin; Tuller, Harry L

    2018-01-01

    We compare approaches to measure oxygen surface exchange kinetics, by simultaneous optical transmission relaxation (OTR) and AC-impedance spectroscopy (AC-IS), on the same mixed conducting SrTi 0.65 Fe 0.35 O 3-x film. Surface exchange coefficients were evaluated as a function of oxygen activity in the film, controlled by gas partial pressure and/or DC bias applied across the ionically conducting yttria-stabilized zirconia substrate. Changes in measured light transmission through the film over time (relaxations) resulted from optical absorption changes in the film corresponding to changes in its oxygen and oxidized Fe (~Fe 4+ ) concentrations; such relaxation profiles were successfully described by the equation for surface exchange-limited kinetics appropriate for the film geometry. The k chem values obtained by OTR were significantly lower than the AC-IS derived k chem values and k q values multiplied by the thermodynamic factor (bulk or thin film), suggesting a possible enhancement in k by the metal current collectors (Pt, Au). Long-term degradation in k chem and k q values obtained by AC-IS was also attributed to deterioration of the porous Pt current collector, while no significant degradation was observed in the optically derived k chem values. The results suggest that, while the current collector might influence measurements by AC-IS, the OTR method offers a continuous, in situ , and contact-free method to measure oxygen exchange kinetics at the native surfaces of thin films.

  14. Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O3-x thin film case study

    Science.gov (United States)

    Perry, Nicola H.; Kim, Jae Jin; Tuller, Harry L.

    2018-01-01

    Abstract We compare approaches to measure oxygen surface exchange kinetics, by simultaneous optical transmission relaxation (OTR) and AC-impedance spectroscopy (AC-IS), on the same mixed conducting SrTi0.65Fe0.35O3-x film. Surface exchange coefficients were evaluated as a function of oxygen activity in the film, controlled by gas partial pressure and/or DC bias applied across the ionically conducting yttria-stabilized zirconia substrate. Changes in measured light transmission through the film over time (relaxations) resulted from optical absorption changes in the film corresponding to changes in its oxygen and oxidized Fe (~Fe4+) concentrations; such relaxation profiles were successfully described by the equation for surface exchange-limited kinetics appropriate for the film geometry. The kchem values obtained by OTR were significantly lower than the AC-IS derived kchem values and kq values multiplied by the thermodynamic factor (bulk or thin film), suggesting a possible enhancement in k by the metal current collectors (Pt, Au). Long-term degradation in kchem and kq values obtained by AC-IS was also attributed to deterioration of the porous Pt current collector, while no significant degradation was observed in the optically derived kchem values. The results suggest that, while the current collector might influence measurements by AC-IS, the OTR method offers a continuous, in situ, and contact-free method to measure oxygen exchange kinetics at the native surfaces of thin films. PMID:29511391

  15. Selective oxidation of methyl {alpha}-D-glucopyranoside with oxygen over supported platinum: Kinetic modeling in the presence of deactivation by overoxidation of the catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Vleeming, J.H.; Kuster, B.F.M.; Marin, G.B. [Eindhoven Univ. of Technology (Netherlands)

    1997-09-01

    The selective oxidation of alcohols and carbohydrates with molecular oxygen in aqueous media is an industrial and environmental attractive process. A kinetic model is presented, which describes the platinum-catalyzed selective oxidation of methyl {alpha}-D-glucopyranoside to sodium methyl {alpha}-D-glucuronate with molecular oxygen in the presence of deactivation by overoxidation. Overoxidation is completely reversible and most adequately described by a reversible transformation of oxygen adatoms into inactive subsurface oxygen. A clear distinction is made between the rapid establishment of the steady-state degree of coverage by the reaction intermediates at the platinum surface and the much slower reversible process of overoxidation. This clear distinction is reflected in the rate equation, which can be written as the product of an initial rate and a deactivation function. The deactivation function is given as a function of the degree of coverage by inactive subsurface oxygen. The rate-determining step in the selective oxidation consists of the reaction between dissociatively chemisorbed oxygen and physisorbed methyl {alpha}-D-glucopyranoside. The corresponding standard activation entropy and enthalpy amount to respectively {minus}111 {+-} 12 J/mol K and 51 {+-} 4 kJ/mol. The standard reaction entropy for the transformation of oxygen atoms into subsurface oxygen amounts to {minus}35 {+-} 16 J/mol K and the standard reaction enthalpy to {minus}36 {+-} 15 kJ/mol.

  16. Kinetic study of phytotoxicity induced by foliar lead uptake for vegetables exposed to fine particles and implications for sustainable urban agriculture.

    Science.gov (United States)

    Xiong, TianTian; Austruy, Annabelle; Pierart, Antoine; Shahid, Muhammad; Schreck, Eva; Mombo, Stéphane; Dumat, Camille

    2016-08-01

    At the global scale, foliar metal transfer occurs for consumed vegetables cultivated in numerous urban or industrial areas with a polluted atmosphere. However, the kinetics of metal uptake, translocation and involved phytotoxicity was never jointly studied with vegetables exposed to micronic and sub-micronic particles (PM). Different leafy vegetables (lettuces and cabbages) cultivated in RHIZOtest® devices were, therefore, exposed in a greenhouse for 5, 10 and 15days to various PbO PM doses. The kinetics of transfer and phytotoxicity was assessed in relation to lead concentration and exposure duration. A significant Pb accumulation in leaves (up to 7392mg/kg dry weight (DW) in lettuce) with translocation to roots was observed. Lead foliar exposure resulted in significant phytotoxicity, lipid composition change, a decrease of plant shoot growth (up to 68.2% in lettuce) and net photosynthesis (up to 58% in lettuce). The phytotoxicity results indicated plant adaptation to Pb and a higher sensitivity of lettuce in comparison with cabbage. Air quality needs, therefore, to be considered for the health and quality of vegetables grown in polluted areas, such as certain megacities (in China, Pakistan, Europe, etc.) and furthermore, to assess the health risks associated with their consumption. Copyright © 2016. Published by Elsevier B.V.

  17. The uptake of NO3-, NO2-, and NH4+ by intact wheat (Triticum aestivum) seedlings. I. Induction and kinetics of transport systems

    Science.gov (United States)

    Goyal, S. S.; Huffaker, R. C.

    1986-01-01

    The inducibility and kinetics of the NO3-, NO2-, and NH4+ transporters in roots of wheat seedlings (Triticum aestivum cv Yercora Rojo) were characterized using precise methods approaching constant analysis of the substrate solutions. A microcomputer-controlled automated high performance liquid chromatography system was used to determine the depletion of each N species (initially at 1 millimolar) from complete nutrient solutions. Uptake rate analyses were performed using computerized curve-fitting techniques. More precise estimates were obtained for the time required for the extent of the induction of each transporter. Up to 10 and 6 hours, respectively, were required to achieve apparent full induction of the NO3- and NO2- transporters. Evidence for substrate inducibility of the NH4+ transporters requiring 5 hours is presented. The transport of NO3- was mediated by a dual system (or dual phasic), whereas only single systems were found for transport of NO2- and NH4+. The Km values for NO3-, NO2-, and NH4+ were, respectively, 0.027, 0.054, and 0.05 millimolar. The Km for mechanism II of NO3- transport could not be defined in this study as it exhibited only apparent first order kinetics up to 1 millimolar.

  18. Influence of priming exercise on pulmonary O2 uptake kinetics during transitions to high-intensity exercise from an elevated baseline.

    Science.gov (United States)

    DiMenna, Fred J; Wilkerson, Daryl P; Burnley, Mark; Jones, Andrew M

    2008-08-01

    It has been suggested that the slower O2 uptake (VO2) kinetics observed when exercise is initiated from an elevated baseline metabolic rate are linked to an impairment of muscle O2 delivery. We hypothesized that "priming" exercise would significantly reduce the phase II time constant (tau) during subsequent severe-intensity cycle exercise initiated from an elevated baseline metabolic rate. Seven healthy men completed exercise transitions to 70% of the difference between gas exchange threshold (GET) and peak VO2 from a moderate-intensity baseline (90% GET) on three occasions in each of the "unprimed" and "primed" conditions. Pulmonary gas exchange, heart rate, and the electromyogram of m. vastus lateralis were measured during all tests. The phase II VO2 kinetics were slower when severe exercise was initiated from a baseline of moderate exercise compared with unloaded pedaling (mean+/-SD tau, 42+/-15 vs. 33+/-8 s; P0.05). The amplitude of the VO2 slow component and the change in electromyogram from minutes 2 to 6 were both significantly reduced following priming exercise (VO2 slow component: from 0.47+/-0.09 to 0.27+/-0.13 l/min; change in integrated electromyogram between 2 and 6 min: from 51+/-35 to 26+/-43% of baseline; Pchanges in muscle fiber activation.

  19. Kinetics and equilibrium modelling of lead uptake by algae Gelidium and algal waste from agar extraction industry.

    Science.gov (United States)

    Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

    2007-05-08

    Pb(II) biosorption onto algae Gelidium, algal waste from agar extraction industry and a composite material was studied. Discrete and continuous site distribution models were used to describe the biosorption equilibrium at different pH (5.3, 4 and 3), considering competition among Pb(II) ions and protons. The affinity distribution function of Pb(II) on the active sites was calculated by the Sips distribution. The Langmuir equilibrium constant was compared with the apparent affinity calculated by the discrete model, showing higher affinity for lead ions at higher pH values. Kinetic experiments were conducted at initial Pb(II) concentrations of 29-104 mgl(-1) and data fitted to pseudo-first Lagergren and second-order models. The adsorptive behaviour of biosorbent particles was modelled using a batch mass transfer kinetic model, which successfully predicts Pb(II) concentration profiles at different initial lead concentration and pH, and provides significant insights on the biosorbents performance. Average values of homogeneous diffusivity, D(h), are 3.6 x 10(-8); 6.1 x 10(-8) and 2.4 x 10(-8)cm(2)s(-1), respectively, for Gelidium, algal waste and composite material. The concentration of lead inside biosorbent particles follows a parabolic profile that becomes linear near equilibrium.

  20. Kinetics and equilibrium modelling of lead uptake by algae Gelidium and algal waste from agar extraction industry

    International Nuclear Information System (INIS)

    Vilar, Vitor J.P.; Botelho, Cidalia M.S.; Boaventura, Rui A.R.

    2007-01-01

    Pb(II) biosorption onto algae Gelidium, algal waste from agar extraction industry and a composite material was studied. Discrete and continuous site distribution models were used to describe the biosorption equilibrium at different pH (5.3, 4 and 3), considering competition among Pb(II) ions and protons. The affinity distribution function of Pb(II) on the active sites was calculated by the Sips distribution. The Langmuir equilibrium constant was compared with the apparent affinity calculated by the discrete model, showing higher affinity for lead ions at higher pH values. Kinetic experiments were conducted at initial Pb(II) concentrations of 29-104 mg l -1 and data fitted to pseudo-first Lagergren and second-order models. The adsorptive behaviour of biosorbent particles was modelled using a batch mass transfer kinetic model, which successfully predicts Pb(II) concentration profiles at different initial lead concentration and pH, and provides significant insights on the biosorbents performance. Average values of homogeneous diffusivity, D h , are 3.6 x 10 -8 ; 6.1 x 10 -8 and 2.4 x 10 -8 cm 2 s -1 , respectively, for Gelidium, algal waste and composite material. The concentration of lead inside biosorbent particles follows a parabolic profile that becomes linear near equilibrium

  1. Kinetics and equilibrium modelling of lead uptake by algae Gelidium and algal waste from agar extraction industry

    Energy Technology Data Exchange (ETDEWEB)

    Vilar, Vitor J.P. [Laboratory of Separation and Reaction Engineering (LSRE), Departamento de Engenharia Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal); Botelho, Cidalia M.S. [Laboratory of Separation and Reaction Engineering (LSRE), Departamento de Engenharia Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal); Boaventura, Rui A.R. [Laboratory of Separation and Reaction Engineering (LSRE), Departamento de Engenharia Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal)]. E-mail: bventura@fe.up.pt

    2007-05-08

    Pb(II) biosorption onto algae Gelidium, algal waste from agar extraction industry and a composite material was studied. Discrete and continuous site distribution models were used to describe the biosorption equilibrium at different pH (5.3, 4 and 3), considering competition among Pb(II) ions and protons. The affinity distribution function of Pb(II) on the active sites was calculated by the Sips distribution. The Langmuir equilibrium constant was compared with the apparent affinity calculated by the discrete model, showing higher affinity for lead ions at higher pH values. Kinetic experiments were conducted at initial Pb(II) concentrations of 29-104 mg l{sup -1} and data fitted to pseudo-first Lagergren and second-order models. The adsorptive behaviour of biosorbent particles was modelled using a batch mass transfer kinetic model, which successfully predicts Pb(II) concentration profiles at different initial lead concentration and pH, and provides significant insights on the biosorbents performance. Average values of homogeneous diffusivity, D {sub h}, are 3.6 x 10{sup -8}; 6.1 x 10{sup -8} and 2.4 x 10{sup -8} cm{sup 2} s{sup -1}, respectively, for Gelidium, algal waste and composite material. The concentration of lead inside biosorbent particles follows a parabolic profile that becomes linear near equilibrium.

  2. Peak oxygen uptake and left ventricular ejection fraction, but not depressive symptoms, are associated with cognitive impairment in patients with chronic heart failure

    Directory of Open Access Journals (Sweden)

    Steinberg G

    2011-12-01

    Full Text Available Gerrit Steinberg1,2*, Nicole Lossnitzer2*, Dieter Schellberg2, Thomas Mueller-Tasch2, Carsten Krueger3, Markus Haass4, Karl Heinz Ladwig5, Wolfgang Herzog2, Jana Juenger21University Hospital of Psychiatry, University of Bern, Bern, Switzerland; 2Department of Psychosomatic and General Internal Medicine, Medical Hospital, University of Heidelberg, Heidelberg, 3Department of Cardiology, Josefs Hospital, Heidelberg, 4Department of Cardiology, Theresien Hospital, Mannheim, 5Institute of Epidemiology, German Research Center for Environmental Health, Munich, Germany*both authors contributed equally to this paperBackground: The aim of the present study was to assess cognitive impairment in patients with chronic heart failure (CHF and its associations with depressive symptoms and somatic indicators of illness severity, which is a matter of controversy.Methods and results: Fifty-five patients with CHF (mean age 55.3 ± 7.8 years; 80% male; New York Heart Association functional class I–III underwent assessment with an expanded neuropsychological test battery (eg, memory, complex attention, mental flexibility, psychomotor speed to evaluate objective and subjective cognitive impairment. Depressive symptoms were assessed using the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (SCID and a self-report inventory (Hospital Anxiety and Depression Scale [HADS]. A comprehensive clinical dataset, including left ventricular ejection fraction, peak oxygen uptake, and a 6-minute walk test, was obtained for all patients. Neuropsychological functioning revealed impairment in 56% of patients in at least one measure of our neuropsychological test battery. However, the Mini Mental State Examination (MMSE could only detect cognitive impairment in 1.8% of all patients, 24% had HADS scores indicating depressive symptoms, and 11.1% met SCID criteria for a depressive disorder. No significant association was found

  3. Effects of administration route, dietary condition, and blood glucose level on kinetics and uptake of 18F-FDG in mice.

    Science.gov (United States)

    Wong, Koon-Pong; Sha, Wei; Zhang, Xiaoli; Huang, Sung-Cheng

    2011-05-01

    The effects of dietary condition and blood glucose level on the kinetics and uptake of (18)F-FDG in mice were systematically investigated using intraperitoneal and tail-vein injection. Dynamic PET was performed for 60 min on 23 isoflurane-anesthetized male C57BL/6 mice after intravenous (n = 11) or intraperitoneal (n = 12) injection of (18)F-FDG. Five and 6 mice in the intravenous and intraperitoneal groups, respectively, were kept fasting overnight (18 ± 2 h), and the others were fed ad libitum. Serial blood samples were collected from the femoral artery to measure (18)F-FDG and glucose concentrations. Image data were reconstructed using filtered backprojection with CT-based attenuation correction. The standardized uptake value (SUV) was estimated from the 45- to 60-min image. The metabolic rate of glucose (MRGlu) and (18)F-FDG uptake constant (K(i)) were derived by Patlak graphical analysis. In the brain, SUV and K(i) were significantly higher in fasting mice with intraperitoneal injection, but MRGlu did not differ significantly under different dietary states and administration routes. Cerebral K(i) was inversely related to elevated blood glucose levels, irrespective of administration route or dietary state. In myocardium, SUV, K(i), and MRGlu were significantly lower in fasting than in nonfasting mice for both routes of injection. Myocardial SUV and K(i) were strongly dependent on the dietary state, and K(i) did not correlate with the blood glucose level. Similar results were obtained for skeletal muscle, although the differences were not as pronounced. Intraperitoneal injection is a valid alternative route, providing pharmacokinetic data equivalent to data from tail-vein injection for small-animal (18)F-FDG PET. Cerebral K(i) varies inversely with blood glucose level, but the measured cerebral MRGlu does not correlate with blood glucose level or dietary condition. Conversely, the K(i) values of the myocardium and skeletal muscle are strongly dependent on

  4. Kinetic, Thermodynamic and Equilibrium Studies on Uptake of Rhodamine B onto ZnCl2 Activated Low Cost Carbon

    Directory of Open Access Journals (Sweden)

    N. Bhadusha

    2012-01-01

    Full Text Available A carbonaceous adsorbent prepared from biomass waste like wood apple outer shell (Limonia acidissima by ZnCl2 treatment was investigated for its efficiency in removing Rhodamine B (RDB. Influence of agitation time, adsorbent dose, dye concentration, pH and temperature were explored. Two theoretical adsorption isotherms namely Langmuir and Freundlich were used to describe the experimental results. The Langmuir adsorption capacity (Qo was found to be 46.7 mg/g and the equilibrium parameter (RL values indicate favourable adsorption. The experimental data were well fitted with Langmuir isotherm model and pseudo second order kinetic model. Desorption studies showed that ion exchange mechanism might be involved in the adsorption process.

  5. Evaluation of Optimum Moisture Content for Composting of Beef Manure and Bedding Material Mixtures Using Oxygen Uptake Measurement

    OpenAIRE

    Eunjong Kim; Dong-Hyun Lee; Seunggun Won; Heekwon Ahn

    2016-01-01

    Moisture content influences physiological characteristics of microbes and physical structure of solid matrices during composting of animal manure. If moisture content is maintained at a proper level, aerobic microorganisms show more active oxygen consumption during composting due to increased microbial activity. In this study, optimum moisture levels for composting of two bedding materials (sawdust, rice hull) and two different mixtures of bedding and beef manure (BS, Beef cattle manure+sawdu...

  6. High temperature mechanisms and kinetics of SiC oxidation under low partial pressures of oxygen: application to the fuel cladding of gas fast reactors

    International Nuclear Information System (INIS)

    Hun, N.

    2011-01-01

    Gas Fast Reactor (GFR) is one of the different Generation IV concepts under investigation for energy production. SiC/SiC composites are candidates of primary interest for a GFR fuel cladding use, thanks to good corrosion resistance among other properties. The mechanisms and kinetics of SiC oxidation under operating conditions have to be identified and quantified as the corrosion can decrease the mechanical properties of the composite. An experimental device has been developed to study the oxidation of silicon carbide under high temperature and low oxygen partial pressure. The results pointed out that not only parabolic oxidation, but also interfacial reactions and volatilization occur under such conditions. After determining the kinetics of each mechanism, as functions of oxygen partial pressure and temperature, the data are used for the modeling of the composites oxidation. The model will be used to predict the lifetime of the composite in operating conditions. (author) [fr

  7. Myosin heavy chain composition in the vastus lateralis muscle in relation to oxygen uptake and heart rate during cycling in humans.

    Science.gov (United States)

    Majerczak, J; Nieckarz, Z; Karasinski, J; Zoladz, J A

    2014-04-01

    In this study we examined the relationship between fast myosin heavy chain (MyHC2) content in the vastus lateralis and the rate of oxygen uptake (VO2) and heart rate (HR) increase during an incremental exercise in 38, young, healthy men. Prior to the exercise test, muscle biopsies were taken in order to evaluate the MyHC composition. It was found that during cycling performed below the lactate threshold (LT), a positive relationship between MyHC2 and the intercept of the oxygen uptake and power output (VO2-PO) relationship existed (r=0.49, P=0.002), despite no correlation between MyHC2 and the slope value of the VO2-PO relationship (r= -0.18, P=0.29). During cycling performed above the LT, MyHC2 correlated positively with the magnitude of the nonlinearity in the VO2-PO relationship; i.e. with the accumulated VO2'excess' (r=0.44, P=0.006) and peak VO2'excess' (r=0.44, P=0.006), as well as with the slope of the HR-PO relationship (r=0.49, P=0.002). We have concluded that a greater MyHC2 content in the vastus lateralis is accompanied by a higher oxygen cost of cycling during exercise performed below the LT. This seems to be related to the higher energy cost of the non-cross-bridge activities in the muscles possessing a greater proportion of MyHC2 content. In the case of heavy-intensity exercise, a higher MyHC2 content in the vastus lateralis is accompanied by greater non-linearity in the VO2-PO relationship, as well as a steeper increase in HR in the function of an increase of PO. This relationship can be explained by greater disturbances in metabolic stability in type II muscle fibres during exercise, resulting in a decrease of muscle mechanical efficiency and greater increase of heart rate at a given power output. Therefore, MyHC composition has an impact on the oxygen cost of cycling both below and above the LT.

  8. An experimental study on the effect of carbonic anhydrase on the oxygen isotope exchange kinetics and equilibrium in the carbonic acid system

    Science.gov (United States)

    Uchikawa, J.; Zeebe, R. E.

    2011-12-01

    Stable oxygen isotopes of marine biogenic carbonates are often depleted in 18O relative to the values expected for thermodynamic equilibrium with ambient seawater. One possibility is that 18O-depletion in carbonates is kinetically controlled. The kinetic isotope effect associated with the hydration of CO2 results in 18O-depleted HCO3-. If the HCO3- is utilized before re-establishing equilibrium with ambient water under rapid calcification, the 18O-depletion will be recorded in carbonates. But one caveat in this kinetic model is the fact that many marine calcifiers posses carbonic anhydrase, a zinc-bearing enzyme that catalyzes the CO2 hydration reaction. It is expected that this enzyme accelerates 18O-equilibration in the carbonic acid system by facilitating direct oxygen isotope exchange between HCO3- and H2O via CO2 hydration. Clearly this argues against the conceptual framework of the kinetic model. Yet the critical variable here is the effectiveness of the carbonic anhydrase, which is likely to depend on its concentration and the carbonate chemistry of the aqueous medium. It is also hitherto unknown whether the presence of carbonic anhydrase alters the equilibrium oxygen isotope fractionations between dissolved carbonate species and water. We performed a series of quantitative inorganic carbonate precipitation experiments to examine the changes in the oxygen isotope equilibration time as a function of carbonic anhydrase concentrations. We conducted experiments at pH 8.3 and 8.9. These pH values are similar to the average surface ocean pH and the elevated pH levels observed within calcification microenvironments of certain corals and planktonic foraminifera. A summary of our new experimental results will be presented.

  9. Peak oxygen uptake and left ventricular ejection fraction, but not depressive symptoms, are associated with cognitive impairment in patients with chronic heart failure.

    Science.gov (United States)

    Steinberg, Gerrit; Lossnitzer, Nicole; Schellberg, Dieter; Mueller-Tasch, Thomas; Krueger, Carsten; Haass, Markus; Ladwig, Karl Heinz; Herzog, Wolfgang; Juenger, Jana

    2011-01-01

    The aim of the present study was to assess cognitive impairment in patients with chronic heart failure (CHF) and its associations with depressive symptoms and somatic indicators of illness severity, which is a matter of controversy. Fifty-five patients with CHF (mean age 55.3 ± 7.8 years; 80% male; New York Heart Association functional class I-III) underwent assessment with an expanded neuropsychological test battery (eg, memory, complex attention, mental flexibility, psychomotor speed) to evaluate objective and subjective cognitive impairment. Depressive symptoms were assessed using the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (SCID) and a self-report inventory (Hospital Anxiety and Depression Scale [HADS]). A comprehensive clinical dataset, including left ventricular ejection fraction, peak oxygen uptake, and a 6-minute walk test, was obtained for all patients. Neuropsychological functioning revealed impairment in 56% of patients in at least one measure of our neuropsychological test battery. However, the Mini Mental State Examination (MMSE) could only detect cognitive impairment in 1.8% of all patients, 24% had HADS scores indicating depressive symptoms, and 11.1% met SCID criteria for a depressive disorder. No significant association was found between depressive symptoms and cognitive impairment. Left ventricular ejection fraction was related to subjective cognitive impairment, and peak oxygen uptake was related to objective cognitive impairment. Cognitive functioning was substantially reduced in patients with CHF and should therefore be diagnosed and treated in routine clinical practice. Caution is advised when the MMSE is used to identify cognitive impairment in patients with CHF.

  10. Changes in cardiac activity, oxygen uptake and perfusion indices in Carcinus maenas (L. ) exposed to crude oil and dispersant

    Energy Technology Data Exchange (ETDEWEB)

    Depledge, M.H.

    1984-01-01

    Cardiac activity and oxygen consumption increased when C. maenas were exposed to a 20% solution of the water-soluble fraction of Fortes crude oil, a 10% solution of the dispersant BP1100WD or a combination of both. Normal feeding behaviour was disrupted. Perfusion indices (Q/VO2) decreased as locomotor activity increased following exposure to crude oil. However, exposure to dispersant or dispersant + crude oil resulted in elevation of perfusion index despite crabs becoming active. All test animals survived for at least 6 weeks following exposure to the pollutants. The acute, sublethal effects of dispersant and dispersant + crude oil were more severe than the effects of crude oil alone.

  11. Comparison of the Danish step test and the watt-max test for estimation of maximal oxygen uptake

    DEFF Research Database (Denmark)

    Aadahl, Mette; Zacho, Morten; Linneberg, Allan René

    2013-01-01

    . Altogether, 795 eligible participants (response rate 35.8%) performed the watt max and the Danish step test. Correlation and agreement between the two VO(2max) test results was explored by Pearson's rho, Bland-Altman plots, Kappa(w), and gamma coefficients.Results: The correlation between VO(2max) (ml......Introduction: There is a need for simple and feasible methods for estimation of cardiorespiratory fitness (CRF) in large study populations, as existing methods for valid estimation of maximal oxygen consumption are generally time consuming and relatively expensive to administer. The Danish step...

  12. Pulse radiolysis investigation of the reaction of the electronic adduct of bovine serum albumin with oxygen. Polychromatic kinetics of the reaction with adsorbed oxygen

    International Nuclear Information System (INIS)

    Pribush, A.G.

    1986-01-01

    The method of pulse radiolysis was used to investigate the reaction of the electronic adduct of bovine serum albumin with oxygen. It was suggested that the disappearance of the electronic adduct of the protein occurs in the course of its interaction with oxygen adsorbed on the globular protein molecule

  13. Characterizing nutrient uptake kinetics for efficient crop production during Solanum lycopersicum var. cerasiforme Alef. growth in a closed indoor hydroponic system.

    Science.gov (United States)

    Lee, Ju Yeon; Rahman, Arifur; Azam, Hossain; Kim, Hyung Seok; Kwon, Man Jae

    2017-01-01

    A balanced nutrient supply is essential for the healthy growth of plants in hydroponic systems. However, the commonly used electrical conductivity (EC)-based nutrient control for plant cultivation can provide amounts of nutrients that are excessive or inadequate for proper plant growth. In this study, we investigated the kinetics of major and minor nutrient uptake in a nutrient solution during the growth of tomato (Solanum lycopersicum var. cerasiforme Alef.) in a closed hydroponic system. The concentrations of major and minor ions in the nutrient solution were determined by various analytical methods including inductively coupled plasma-optical emission spectroscopy (ICP-OES), ion chromatography (IC), ion specific electrodes, and/or colorimetric methods. The concentrations of the individual nutrient ions were compared with changes in the EC. The EC of the nutrient solution varied according to the different growth stages of tomato plants. Variation in the concentrations of NO3-, SO42-, Mg2+, Ca2+, and K+ was similar to the EC variation. However, in the cases of PO43-, Na+, Cl-, dissolved Fe and Mn, Cu2+, and Zn2+, variation did not correspond with that of EC. These ions were generally depleted (to 0 mg L-1) during tomato growth, suggesting that these specific ions should be monitored individually and their supply increased. Nutrient uptake rates of major ions increased gradually at different growth stages until harvest (from 15 mg L-1 d-1). Saturation indices determined by MINEQL+ simulation and a mineral precipitation experiment demonstrated the potential for amorphous calcium phosphate precipitation, which may facilitate the abiotic adsorptive removal of dissolved Fe, dissolved Mn, Cu2+, and Zn2+.

  14. Diffusion and Monod kinetics model to determine in vivo human corneal oxygen-consumption rate during soft contact lens wear

    Directory of Open Access Journals (Sweden)

    Luis F. Del Castillo

    2015-01-01

    Conclusion: Present results are relevant for the calculation on the partial pressure of oxygen, available at different depths into the corneal tissue behind contact lenses of different oxygen transmissibility.

  15. Twin-domain size and bulk oxygen in-diffusion kinetics of YBa 2Cu 3O 6+x studied by neutron powder diffraction and gas volumetry

    Science.gov (United States)

    Poulsen, H. F.; Andersen, N. H.; Lebech, B.

    1991-02-01

    We report experimental results of twin-domain size and bulk oxygen in-diffusion kinetics of YBa 2Cu 3O 6+ x, which supplement a previous and simultaneous study of the structural phase diagram and oxygen equilibrium partial pressure. Analysis of neutron powder diffraction peak broadening show features which are identified to result from temperature independent twin-domain formation in to different orthorhombic phases with domain sizes and 250 and 350Å, respectively. The oxygen in-diffusion flow shows simple relaxation type behaviour J=J 0 exp( {-t}/{τ}) despite a rather broad particle size distribution. At higher temperatures, τ is activated with activation energies 0.55 and 0.25 eV in the tetragonal and orthorhombic phases, respectively. Comparison between twin-domain sizes and bulk oxygen in-diffusion time constants indicates that the twin-domain boundaries may contribute to the effective bulk oxygen in-diffusion. All our results may be interpreted in terms of the 2D ASYNNNI model description of the oxygen basal plane ordering, and they suggest that recent first principles interaction parameters should be modified.

  16. Effect of pedal rate on primary and slow-component oxygen uptake responses during heavy-cycle exercise.

    Science.gov (United States)

    Pringle, Jamie S M; Doust, Jonathan H; Carter, Helen; Tolfrey, Keith; Jones, Andrew M

    2003-04-01

    We hypothesized that a higher pedal rate (assumed to result in a greater proportional contribution of type II motor units) would be associated with an increased amplitude of the O(2) uptake (Vo(2)) slow component during heavy-cycle exercise. Ten subjects (mean +/- SD, age 26 +/- 4 yr, body mass 71.5 +/- 7.9 kg) completed a series of square-wave transitions to heavy exercise at pedal rates of 35, 75, and 115 rpm. The exercise power output was set at 50% of the difference between the pedal rate-specific ventilatory threshold and peak Vo(2), and the baseline power output was adjusted to account for differences in the O(2) cost of unloaded pedaling. The gain of the Vo(2) primary component was significantly higher at 35 rpm compared with 75 and 115 rpm (mean +/- SE, 10.6 +/- 0.3, 9.5 +/- 0.2, and 8.9 +/- 0.4 ml. min(-1). W(-1), respectively; P exercise at the same relative intensity, presumably by altering motor unit recruitment patterns.

  17. Partial neuromuscular blockade in humans enhances muscle blood flow during exercise independently of muscle oxygen uptake and acetylcholine receptor blockade

    DEFF Research Database (Denmark)

    Hellsten, Ylva; Krustrup, Peter; Iaia, F Marcello

    2009-01-01

    This study examined the role of acetylcholine for skeletal muscle blood flow during exercise by use of the competitive neuromuscular blocking agent cisatracurium in combination with the acetylcholine receptor blocker glycopyrrone. Nine healthy male subjects performed a 10-min bout of one-legged k......This study examined the role of acetylcholine for skeletal muscle blood flow during exercise by use of the competitive neuromuscular blocking agent cisatracurium in combination with the acetylcholine receptor blocker glycopyrrone. Nine healthy male subjects performed a 10-min bout of one...... conductance during exercise, events that are not associated with either acetylcholine or an increased oxygen demand. The results do not support an essential role for acetylcholine, released form the neuromuscular junction, in exercise hyperaemia or for the enhanced blood flow during neuromuscular blockade....... The enhanced exercise hyperemia during partial neuromuscular blockade may be related to a greater recruitment of fast-twitch muscle fibres. Key words: blood flow, neuromuscular blockade, exercise, skeletal muscle....

  18. Oxygen-Dependent Transcriptional Regulator Hap1p Limits Glucose Uptake by Repressing the Expression of the Major Glucose Transporter Gene RAG1 in Kluyveromyces lactis▿

    Science.gov (United States)

    Bao, Wei-Guo; Guiard, Bernard; Fang, Zi-An; Donnini, Claudia; Gervais, Michel; Passos, Flavia M. Lopes; Ferrero, Iliana; Fukuhara, Hiroshi; Bolotin-Fukuhara, Monique

    2008-01-01

    The HAP1 (CYP1) gene product of Saccharomyces cerevisiae is known to regulate the transcription of many genes in response to oxygen availability. This response varies according to yeast species, probably reflecting the specific nature of their oxidative metabolism. It is suspected that a difference in the interaction of Hap1p with its target genes may explain some of the species-related variation in oxygen responses. As opposed to the fermentative S. cerevisiae, Kluyveromyces lactis is an aerobic yeast species which shows different oxygen responses. We examined the role of the HAP1-equivalent gene (KlHAP1) in K. lactis. KlHap1p showed a number of sequence features and some gene targets (such as KlCYC1) in common with its S. cerevisiae counterpart, and KlHAP1 was capable of complementing the hap1 mutation. However, the KlHAP1 disruptant showed temperature-sensitive growth on glucose, especially at low glucose concentrations. At normal temperature, 28°C, the mutant grew well, the colony size being even greater than that of the wild type. The most striking observation was that KlHap1p repressed the expression of the major glucose transporter gene RAG1 and reduced the glucose uptake rate. This suggested an involvement of KlHap1p in the regulation of glycolytic flux through the glucose transport system. The ΔKlhap1 mutant showed an increased ability to produce ethanol during aerobic growth, indicating a possible transformation of its physiological property to Crabtree positivity or partial Crabtree positivity. Dual roles of KlHap1p in activating respiration and repressing fermentation may be seen as a basis of the Crabtree-negative physiology of K. lactis. PMID:18806211

  19. Exploring the kinetic and thermodynamic aspects of four-electron electrochemical reactions: electrocatalysis of oxygen evolution by metal oxides and biological systems.

    Science.gov (United States)

    Wang, Vincent C-C

    2016-08-10

    Finding fundamental and general mechanisms for electrochemical reactions, such as the oxygen evolution reaction (OER) from water and reduction of CO2, plays vital roles in developing the desired electrocatalysts for facilitating solar fuel production. Recently, density functional theory (DFT) calculations have shown that there is a universal scaling relation of adsorption energy between key intermediate species, HO(ad) and HOO(ad), on the surface of metal oxides as OER electrocatalysts. In this paper, a kinetic and thermodynamic model for the four-electron electrochemical reaction based on previous OER mechanisms proposed by DFT calculations is developed to further investigate the electrocatalytic properties over a wide range of metal oxides and photosystem II. The OER activity of metal oxides (i.e. electrocatalytic current) calculated from the DFT-calculated equilibrium potentials with kinetic properties, such as the rate constants for interfacial electron transfer and catalytic turnover, can lead to a volcano-shaped trend that agrees with the results observed in experiments. In addition, the kinetic aspects of the impact on the electrocatalysts are evaluated. Finally, comparing the results of metal oxides and photosystem II, and fitting experimental voltammograms give further insights into kinetic and thermodynamic roles. Here, the general guidelines for designing OER electrocatalysts with unified kinetic and thermodynamic properties are presented.

  20. COMBINED THEORETICAL AND EXPERIMENTAL INVESTIGATION OF MECHANISMS AND KINETICS OF VAPOR-PHASE MERCURY UPTAKE BY CARBONACOUES SURFACES

    Energy Technology Data Exchange (ETDEWEB)

    Radisav D. Vidic

    2002-05-01

    The first part of this study evaluated the application of a versatile optical technique to study the adsorption and desorption of model adsorbates representative of volatile polar (acetone) and non-polar (propane) organic compounds on a model carbonaceous surface under ultra high vacuum (UHV) conditions. The results showed the strong correlation between optical differential reflectance (ODR) and adsorbate coverage determined by temperature programmed desorption (TPD). ODR technique was proved to be a powerful tool to investigate surface adsorption and desorption from UHV to high pressure conditions. The effects of chemical functionality and surface morphology on the adsorption/desorption behavior of acetone, propane and mercury were investigated for two model carbonaceous surfaces, namely air-cleaved highly oriented pyrolytic graphite (HOPG) and plasma-oxidized HOPG. They can be removed by thermal treatment (> 500 K). The presence of these groups almost completely suppresses propane adsorption at 90K and removal of these groups leads to dramatic increase in adsorption capacity. The amount of acetone adsorbed is independent of surface heat treatment and depends only on total exposure. The effects of morphological heterogeneity is evident for plasma-oxidized HOPG as this substrate provides greater surface area, as well as higher energy binding sites. Mercury adsorption at 100 K on HOPG surfaces with and without chemical functionalities and topological heterogeneity created by plasma oxidation occurs through physisorption. The removal of chemical functionalities from HOPG surface enhances mercury physisorption. Plasma oxidation of HOPG provides additional surface area for mercury adsorption. Mercury adsorption by activated carbon at atmospheric pressure occurs through two distinct mechanisms, physisorption below 348 K and chemisorption above 348 K. No significant impact of oxygen functionalities was observed in the chemisorption region. The key findings of this study

  1. A hybrid multibreath wash-in wash-out lung function quantification scheme in human subjects using hyperpolarized 3 He MRI for simultaneous assessment of specific ventilation, alveolar oxygen tension, oxygen uptake, and air trapping.

    Science.gov (United States)

    Hamedani, Hooman; Kadlecek, Stephen; Xin, Yi; Siddiqui, Sarmad; Gatens, Heather; Naji, Joseph; Ishii, Masaru; Cereda, Maurizio; Rossman, Milton; Rizi, Rahim

    2017-08-01

    To present a method for simultaneous acquisition of alveolar oxygen tension (P A O 2 ), specific ventilation (SV), and apparent diffusion coefficient (ADC) of hyperpolarized (HP) gas in the human lung, allowing reinterpretation of the P A O 2 and SV maps to produce a map of oxygen uptake (R). An imaging scheme was designed with a series of identical normoxic HP gas wash-in breaths to measure ADC, SV, P A O 2 , and R in less than 2 min. Signal dynamics were fit to an iterative recursive model that regionally solved for these parameters. This measurement was successfully performed in 12 subjects classified in three healthy, smoker, and chronic obstructive pulmonary disease (COPD) cohorts. The overall whole lung ADC, SV, P A O 2 , and R in healthy, smoker, and COPD subjects was 0.20 ± 0.03 cm 2 /s, 0.39 ± 0.06,113 ± 2 Torr, and 1.55 ± 0.35 Torr/s, respectively, in healthy subjects; 0.21 ± 0.03 cm 2 /s, 0.33 ± 0.06, 115.9 ± 4 Torr, and 0.97 ± 0.2 Torr/s, respectively, in smokers; and 0.25 ± 0.06 cm 2 /s, 0.23 ± 0.08, 114.8 ± 6.0Torr, and 0.94 ± 0.12 Torr/s, respectively, in subjects with COPD. Hetrogeneity of SV, P A O 2 , and R were indicators of both smoking-related changes and disease, and the severity of the disease correlated with the degree of this heterogeneity. Subjects with symptoms showed reduced oxygen uptake and specific ventilation. High-resolution, nearly coregistered and quantitative measures of lung function and structure were obtained with less than 1 L of HP gas. This hybrid multibreath technique produced measures of lung function that revealed clear differences among the cohorts and subjects and were confirmed by correlations with global lung measurements. Magn Reson Med 78:611-624, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  2. Oxygen exchange at gas/oxide interfaces: how the apparent activation energy of the surface exchange coefficient depends on the kinetic regime.

    Science.gov (United States)

    Fielitz, Peter; Borchardt, Günter

    2016-08-10

    In the dedicated literature the oxygen surface exchange coefficient KO and the equilibrium oxygen exchange rate [Fraktur R] are considered to be directly proportional to each other regardless of the experimental circumstances. Recent experimental observations, however, contradict the consequences of this assumption. Most surprising is the finding that the apparent activation energy of KO depends dramatically on the kinetic regime in which it has been determined, i.e. surface exchange controlled vs. mixed or diffusion controlled. This work demonstrates how the diffusion boundary condition at the gas/solid interface inevitably entails a correlation between the oxygen surface exchange coefficient KO and the oxygen self-diffusion coefficient DO in the bulk ("on top" of the correlation between KO and [Fraktur R] for the pure surface exchange regime). The model can thus quantitatively explain the range of apparent activation energies measured in the different regimes: in the surface exchange regime the apparent activation energy only contains the contribution of the equilibrium exchange rate, whereas in the mixed or in the diffusion controlled regime the contribution of the oxygen self-diffusivity has also to be taken into account, which may yield significantly higher apparent activation energies and simultaneously quantifies the correlation KO ∝ DO(1/2) observed for a large number of oxides in the mixed or diffusion controlled regime, respectively.

  3. Photodynamic Inactivation of Candida albicans with Imidazoacridinones: Influence of Irradiance, Photosensitizer Uptake and Reactive Oxygen Species Generation.

    Directory of Open Access Journals (Sweden)

    Aleksandra Taraszkiewicz

    Full Text Available The increasing applicability of antifungal treatments, the limited range of available drug classes and the emergence of drug resistance in Candida spp. suggest the need for new treatment options. To explore the applicability of C. albicans photoinactivation, we examined nine structurally different imidazoacridinone derivatives as photosensitizing agents. The most effective derivatives showed a >10(4-fold reduction of viable cell numbers. The fungicidal action of the three most active compounds was compared at different radiant powers (3.5 to 63 mW/cm2, and this analysis indicated that 7 mW/cm2 was the most efficient. The intracellular accumulation of these compounds in fungal cells correlated with the fungicidal activity of all 9 derivatives. The lack of effect of verapamil, an inhibitor targeting Candida ABC efflux pumps, suggests that these imidazoacridinones are not substrates for ABC transporters. Thus, unlike azoles, a major class of antifungals used against Candida, ABC transporter-mediated resistance is unlikely. Electron paramagnetic resonance (EPR-spin trapping data suggested that the fungicidal light-induced action of these derivatives might depend on the production of superoxide anion. The highest generation rate of superoxide anion was observed for 1330H, 1610H, and 1611. Singlet oxygen production was also detected upon the irradiation of imidazoacridinone derivatives with UV laser light, with a low to moderate yield, depending on the type of compound. Thus, imidazoacridinone derivatives examined in the present study might act via mixed type I/type II photodynamic mechanism. The presented data indicate lack of direct correlation between the structures of studied imidazoacridinones, cell killing ability, and ROS production. However, we showed for the first time that for imidazoacridinones not only intracellular accumulation is necessary prerequisite of lethal photosensitization of C. albicans, but also localization within particular

  4. Increased Tumor Oxygenation and Drug Uptake During Anti-Angiogenic Weekly Low Dose Cyclophosphamide Enhances the Anti-Tumor Effect of Weekly Tirapazamine

    Science.gov (United States)

    Doloff, J.C.; Khan, N.; Ma, J.; Demidenko, E.; Swartz, H.M.; Jounaidi, Y.

    2010-01-01

    Metronomic cyclophosphamide treatment is associated with anti-angiogenic activity and is anticipated to generate exploitable hypoxia using hypoxia-activated prodrugs. Weekly administration of tirapazamine (TPZ; 5 mg/kg body weight i.p.) failed to inhibit the growth of 9L gliosarcoma tumors grown s.c. in scid mice. However, the anti-tumor effect of weekly cyclophosphamide (CPA) treatment (140 mg/kg BW i.p.) was substantially enhanced by weekly TPZ administration. An extended tumor free period and increased frequency of tumor eradication without overt toxicity were observed when TPZ was given 3, 4 or 5 days after each weekly CPA treatment. Following the 2nd CPA injection, Electron Paramagnetic Resonance (EPR) Oximetry indicated significant increases in tumor pO2, starting at 48 hr, which further increased after the 3rd CPA injection. pO2 levels were, however, stable in growing untreated tumors. A strong negative correlation (−0.81) between tumor pO2 and tumor volume during 21 days of weekly CPA chemotherapy was observed, indicating increasing tumor pO2 with decreasing tumor volume. Furthermore, CPA treatment resulted in increased tumor uptake of activated CPA. CPA induced increases in VEGF RNA, which reached a maximum on day 1, and in PLGF RNA which was sustained throughout the treatment, while anti-angiogenic host thrombospondin-1 increased dramatically through day 7 post-CPA treatment. Weekly cyclophosphamide treatment was anticipated to generate exploitable hypoxia. However, our findings suggest that weekly CPA treatment induces a functional improvement of tumor vasculature, which is characterized by increased tumor oxygenation and drug uptake in tumors, thus counter-intuitively, benefiting intratumoral activation of TPZ and perhaps other bioreductive drugs. PMID:19754361

  5. Comparison of actual oxygen delivery kinetics to those predicted by mathematical modeling following stage 1 palliation just prior to superior cavopulmonary anastomosis.

    Science.gov (United States)

    Yuki, Koichi; DiNardo, James A

    2015-02-01

    Optimizing systemic oxygen delivery (DO2) and hemodynamics in children with hypoplastic left heart syndrome (HLHS) is a clinical challenge. Mathematical modeling of the HLHS circulation has been used to determine the relationship between oxygen kinetic parameters and DO2 and to determine how DO2 might be optimized. The model demonstrates that neither arterial oxygen saturation (SaO2) nor mixed venous oxygen saturation (SvO2) alone accurately predicts DO2. Oxygen delivery kinetics predicted by previously described mathematical modeling were compared with actual patients' hemodynamic data. We sought to determine which patient derived parameters correlated best with DO2. Patients with HLHS who underwent cardiac catheterization prior to surgery to create a superior cavopulmonary anastomosis from 2007 to 2011 were identified. Hemodynamic data obtained were compared with the data derived from the mathematical model. Correlations between SaO2, SvO2, SaO2-SvO2, SaO2/(SaO2-SvO2), pulmonary-to-systemic blood flow ratio (Qp/Qs), and DO2 were evaluated using both linear and nonlinear analyses, and R(2) was calculated. Patients' data fit most aspects of the mathematical model. DO2 had the best correlation with SaO2/(SaO2-SvO2; R(2) = 0.8755) followed by SaO2 -SvO2 (R(2) = 0.8063), while SaO2 or SvO2 alone did not demonstrate a significant correlation as predicated by the mathematical model (R(2) = 0.09564 and 0.4831, respectively). SaO2/(SaO2 -SvO2) would be useful clinically to track changes in DO2 that occur with changes in patient condition or with interventions. © 2014 John Wiley & Sons Ltd.

  6. Irradiation of cells by single and double pulses of high intensity radiation: oxygen sensitization and diffusion kinetics

    International Nuclear Information System (INIS)

    Epp, E.R.; Ling, C.C.; Weiss, H.

    1976-01-01

    This paper discusses advances made on both experimental and theoretical approaches involving single and double pulses of high intensity ionizing radiation delivered to cultured bacterial and mammalian cells where the effect of oxygen is concerned. Information gained on the lifetime of oxygen-sensitive species suspected to be produced in critical molecules in irradiated cells and perhaps intimately related to the still unknown mechanisms of oxygen sensitization is described. The diffusion characteristics of oxygen at the cellular level obtained from experimental data are discussed. Current knowledge on intracellular radiolytic oxygen depletion is also presented. Future work on the use of high intensity pulsed radiation as a tool in cellular radiobiological research is outlined. It is expected that obtaining knowledge of the time available for damaged molecules to enter into chemical reactions may lead to insights into the mechanisms of radiation injury in cells, such as those involved in the oxygen effect. (Auth.)

  7. Assessment of peak oxygen uptake during handcycling: Test-retest reliability and comparison of a ramp-incremented and perceptually-regulated exercise test.

    Science.gov (United States)

    Hutchinson, Michael J; Paulson, Thomas A W; Eston, Roger; Goosey-Tolfrey, Victoria L

    2017-01-01

    To examine the reliability of a perceptually-regulated maximal exercise test (PRETmax) to measure peak oxygen uptake ([Formula: see text]) during handcycle exercise and to compare peak responses to those derived from a ramp-incremented protocol (RAMP). Twenty recreationally active individuals (14 male, 6 female) completed four trials across a 2-week period, using a randomised, counterbalanced design. Participants completed two RAMP protocols (20 W·min-1) in week 1, followed by two PRETmax in week 2, or vice versa. The PRETmax comprised five, 2-min stages clamped at Ratings of Perceived Exertion (RPE) 11, 13, 15, 17 and 20. Participants changed power output (PO) as often as required to maintain target RPE. Gas exchange variables (oxygen uptake, carbon dioxide production, minute ventilation), heart rate (HR) and PO were collected throughout. Differentiated RPE were collected at the end of each stage throughout trials. For relative [Formula: see text], coefficient of variation (CV) was equal to 4.1% and 4.8%, with ICC(3,1) of 0.92 and 0.85 for repeated measures from PRETmax and RAMP, respectively. Measurement error was 0.15 L·min-1 and 2.11 ml·kg-1·min-1 in PRETmax and 0.16 L·min-1 and 2.29 ml·kg-1·min-1 during RAMP for determining absolute and relative [Formula: see text], respectively. The difference in [Formula: see text] between PRETmax and RAMP was tending towards statistical significance (26.2 ± 5.1 versus 24.3 ± 4.0 ml·kg-1·min-1, P = 0.055). The 95% LoA were -1.9 ± 4.1 (-9.9 to 6.2) ml·kg-1·min-1. The PRETmax can be used as a reliable test to measure [Formula: see text] during handcycle exercise in recreationally active participants. Whilst PRETmax tended towards significantly greater [Formula: see text] values than RAMP, the difference is smaller than measurement error of determining [Formula: see text] from PRETmax and RAMP.

  8. Skeletal muscle-specific expression of PGC-1α-b, an exercise-responsive isoform, increases exercise capacity and peak oxygen uptake.

    Directory of Open Access Journals (Sweden)

    Miki Tadaishi

    Full Text Available Maximal oxygen uptake (VO(2max predicts mortality and is associated with endurance performance. Trained subjects have a high VO(2max due to a high cardiac output and high metabolic capacity of skeletal muscles. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α, a nuclear receptor coactivator, promotes mitochondrial biogenesis, a fiber-type switch to oxidative fibers, and angiogenesis in skeletal muscle. Because exercise training increases PGC-1α in skeletal muscle, PGC-1α-mediated changes may contribute to the improvement of exercise capacity and VO(2max. There are three isoforms of PGC-1α mRNA. PGC-1α-b protein, whose amino terminus is different from PGC-1α-a protein, is a predominant PGC-1α isoform in response to exercise. We investigated whether alterations of skeletal muscle metabolism by overexpression of PGC-1α-b in skeletal muscle, but not heart, would increase VO(2max and exercise capacity.Transgenic mice showed overexpression of PGC-1α-b protein in skeletal muscle but not in heart. Overexpression of PGC-1α-b promoted mitochondrial biogenesis 4-fold, increased the expression of fatty acid transporters, enhanced angiogenesis in skeletal muscle 1.4 to 2.7-fold, and promoted exercise capacity (expressed by maximum speed by 35% and peak oxygen uptake by 20%. Across a broad range of either the absolute exercise intensity, or the same relative exercise intensities, lipid oxidation was always higher in the transgenic mice than wild-type littermates, suggesting that lipid is the predominant fuel source for exercise in the transgenic mice. However, muscle glycogen usage during exercise was absent in the transgenic mice.Increased mitochondrial biogenesis, capillaries, and fatty acid transporters in skeletal muscles may contribute to improved exercise capacity via an increase in fatty acid utilization. Increases in PGC-1α-b protein or function might be a useful strategy for sedentary subjects to perform exercise

  9. Dopamine in human follicular fluid is associated with cellular uptake and metabolism-dependent generation of reactive oxygen species in granulosa cells: implications for physiology and pathology.

    Science.gov (United States)

    Saller, S; Kunz, L; Berg, D; Berg, U; Lara, H; Urra, J; Hecht, S; Pavlik, R; Thaler, C J; Mayerhofer, A

    2014-03-01

    Is the neurotransmitter dopamine (DA) in the human ovary involved in the generation of reactive oxygen species (ROS)? Human ovarian follicular fluid contains DA, which causes the generation of ROS in cultured human granulosa cells (GCs), and alterations of DA levels in follicular fluid and DA uptake/metabolism in GCs in patients with polycystic ovary syndrome (PCOS) are linked to increased levels of ROS. DA is an important neurotransmitter in the brain, and the metabolism of DA results in the generation of ROS. DA was detected in human ovarian homogenates, but whether it is present in follicular fluid and plays a role in the follicle is not known. We used human follicular fluid from patients undergoing in vitro fertilization (IVF), GCs from patients with or without PCOS and also employed mathematical modeling to investigate the presence of DA and its effects on ROS. DA in follicular fluid and GCs was determined by enzyme-linked immunosorbent assay. GC viability, apoptosis and generation of ROS were monitored in GCs upon addition of DA. Inhibitors of DA uptake and metabolism, an antioxidant and DA receptor agonists, were used to study cellular uptake and the mechanism of DA-induced ROS generation. Human GCs were examined for the presence and abundance of transcripts of the DA transporter (DAT; SLC6A3), the DA-metabolizing enzymes monoamine oxidases A/B (MAO-A/B) and catechol-O-methyltransferase and the vesicular monoamine transporter. A computational model was developed to describe and predict DA-induced ROS generation in human GCs. We found DA in follicular fluid of ovulatory follicles of the human ovary and in GCs. DAT and MAO-A/B, which are expressed by GCs, are prerequisites for a DA receptor-independent generation of ROS in GCs. Blockers of DAT and MAO-A/B, as well as an antioxidant, prevented the generation of ROS (P human follicular compartment, functions of DA could only be studied in IVF-derived GCs, which can be viewed as a cellular model for the

  10. Diffusion of Oxygen in Alginate Gels Related to the Kinetics of Methanol Oxidation by Immobilized Hansenula polymorpha Cells

    NARCIS (Netherlands)

    Hiemstra, Harry; Dijkhuizen, Lubbert; Harder, Willem

    1983-01-01

    In the yeast Hansenula polymorpha an oxygen-requiring enzyme, alcohol oxidase, catalyzes the conversion of methanol into formaldehyde. After growth on methanol cells of the organism were harvested and entrapped in barium-alginate gels. The diffusion of oxygen towards these cells is seriously

  11. Oxygen diffusion kinetics and reactive lifetimes in bacterial and mammalian cells irradiated with nanosecond pulses of high intensity electrons

    International Nuclear Information System (INIS)

    Epp, E.R.; Weiss, H.; Ling, C.C.; Djordjevic, B.; Kessaris, N.D.

    1975-01-01

    Experiaments have been designed to gain information on the lifetime of oxygen-sensitive species suspected to be produced in critical molecules in irradiated cells and on the time-diffusion of oxygen in cells. An approach developed in this laboratory involves the delivery of two high intensity electron pulses each of 3 ns duration to a thin layer of cells equilibrated with a known concentration of oxygen. The first pulse serves to render the cells totally anoxic by the radiochemical depletion of oxygen; the second is delivered at a time electronically delayed after the first allowing for diffusion of oxygen during this time. Under these conditions the radiosensitivity of E coli B/r has been measured over six decades of interpulse time. Cellular time-diffusion curves constructed from the measurements show that oxygen establishes its sensitizing effect within 10 -4 s after the creation of intracellular anoxia establishing this time as an upper limit to the lifetime of the species. Unusual behaviour of the diffusion curve observed for longer delay times can be explained by a model wherein it is postulated that a radiation-induced inhibiting agent slows down diffusion. Application of this model to the experimental data yields a value of 0.4x10 -5 cm 2 s -1 for the cellular oxygen diffusion coefficient. Similar experiments recently carried out for Serratia marcescens will also be described. The oxygen effect in cultured HeLa cells exposed to single short electron pulses has been examined over a range of oxygen concentrations. A family of breaking survival curves was obtained similar to those previously measured for E coli B/r by this laboratory. The data appear to be reasonably consistent with a physicochemical mechanism involving the radiochemical depletion of oxygen previously invoked for bacteria. (author)

  12. Effect of Aerobic Training on Peak Oxygen Uptake Among Seniors Aged 70 or Older: A Meta-Analysis of Randomized Controlled Trials.

    Science.gov (United States)

    Bouaziz, Walid; Kanagaratnam, Lukshe; Vogel, Thomas; Schmitt, Elise; Dramé, Moustapha; Kaltenbach, Georges; Geny, Bernard; Lang, Pierre Olivier

    2018-01-02

    Older adults undergo a progressive decline in cardiorespiratory fitness and functional capacity. This lower peak oxygen uptake (VO 2peak ) level is associated with increased risk of frailty, dependency, loss of autonomy, and mortality from all causes. Regular physical activity and particularly aerobic training (AT) have been shown to contribute to better and healthy aging. We conducted a meta-analysis to measure the exact benefit of AT on VO 2peak in seniors aged 70 years or older. A comprehensive, systematic database search for articles was performed in Embase, Medline, PubMed Central, Science Direct, Scopus, and Web of Science using key words. Two reviewers independently assessed interventional studies for potential inclusion. Ten randomized controlled trials (RCTs) were included totaling 348 seniors aged 70 years or older. Across the trials, no high risk of bias was measured and all considered open-label arms for controls. With significant heterogeneity between the RCTs (all p seniors were, respectively, 1.72 (95% CI: 0.34-3.10) and 1.47 (95% CI: 0.60-2.34). This meta-analysis confirms the AT-associated benefits on VO 2peak in healthy and unhealthy seniors.

  13. Response of the oxygen uptake efficiency slope to orthotopic heart transplantation: lack of correlation with changes in central hemodynamic parameters and resting lung function.

    Science.gov (United States)

    Van Laethem, Christophe; Goethals, Marc; Verstreken, Sofie; Walravens, Maarten; Wellens, Francis; De Proft, Margot; Bartunek, Jozef; Vanderheyden, Marc

    2007-09-01

    Recently, a new linear measure of ventilatory response to exercise, the oxygen uptake efficiency slope (OUES), was proposed in the evaluation of heart failure patients. No data are available on the response of the OUES after orthotopic heart transplantation (HTx). Thirty patients who underwent HTx between 1999 and 2003 were included in the study. Data from maximal cardiopulmonary exercise test, resting pulmonary function and hemodynamic assessment were collected before the transplant at time of screening and 1 year after HTx. During the first year after HTx, OUES and normalized OUES for body weight (OUES/kg) increased significantly from 15.6 +/- 4.9 to 19.7 +/- 4.8 (p volumes or capacities and measures of central hemodynamic function after HTx. OUES improved significantly after HTx, but, similar to other exercise parameters, remained considerably impaired. The changes in OUES were highly correlated with the improvements in other exercise variables, but did not correlate with marked improvements in central hemodynamics or resting lung function.

  14. Maximum oxygen uptake and objectively measured physical activity in Danish children 6-7 years of age: the Copenhagen school child intervention study

    DEFF Research Database (Denmark)

    Eiberg, Stig; Hasselstrøm, Henriette; Grønfeldt, Vivian

    2005-01-01

    Objectives: To provide normative data on maximum oxygen uptake (V·O2MAX) and physical activity in children 6-7 years of age and analyse the association between these variables. Methods: VO2MAX was measured in 366 boys (mean (SD) 6.8 (0.4) years of age) and 332 girls (6.7 (0.4) years of age) from.......5 (6.0) v 44.8 (5.6) ml/kg/min (+8%); pgirls. The difference in VO2MAX between boys and girls decreased to +2% when expressed relative to lean body mass (LBM). Absolute VO2MAX was related to LBM, body mass, and stature (all pBoys were more physically active than girls (mean counts...... +9.4%, pboys and girls with the same VO2MAX were compared, boys were more active. The difference in physical activity between the sexes was higher when sustained activity of higher intensity was compared. Conclusions: VO2MAX is higher in boys than girls (+11%), even when...

  15. Oxygen uptake during peak graded exercise and single-stage fatigue tests of wheelchair propulsion in manual wheelchair users and the able-bodied.

    Science.gov (United States)

    Keyser, R E; Rodgers, M M; Gardner, E R; Russell, P J

    1999-10-01

    To determine if a single-stage, submaximal fatigue test on a wheelchair ergometer would result in higher than expected energy expenditure. An experimental survey design contrasting physiologic responses during peak graded exercise tests and fatigue tests. A rehabilitation science laboratory that included a prototypical wheelchair ergometer, open-circuit spirometry system, and heart rate monitor. Nine able-bodied non-wheelchair users (the NWC group: 6 men and 3 women, mean +/- SD age 30 +/- 7yrs) and 15 manual wheelchair users (the WC group: 12 men and 3 women, age 40 +/- 9yrs, time in wheelchair 16 +/- 9yrs). No subject had any disease, medication regimen, or upper body neurologic, orthopedic, or other condition that would limit wheelchair exercise. Peak oxygen uptake (VO2) for graded exercise testing and during fatigue testing, using a power output corresponding to 75% peak aerobic capacity on graded exercise test. In the WC group, VO2 at 6 minutes of fatigue testing was not significantly different from peak VO2. In the NWC group, VO2 was similar to the expected level throughout fatigue testing. Energy expenditure was higher than expected in the WC group but not in the NWC group. Fatigue testing may provide a useful evaluation of cardiorespiratory status in manual wheelchair users.

  16. Effects of prior short multiple-sprint exercises with different intersprint recoveries on the slow component of oxygen uptake during high-intensity exercise.

    Science.gov (United States)

    Lanzi, Stefano; Borrani, Fabio; Wolf, Martin; Gojanovic, Boris; Malatesta, Davide

    2012-12-01

    This study compares the effects of two short multiple-sprint exercise (MSE) (6 × 6 s) sessions with two different recovery durations (30 s or 180 s) on the slow component of oxygen uptake ([Formula: see text]O(2)) during subsequent high-intensity exercise. Ten male subjects performed a 6-min cycling test at 50% of the difference between the gas exchange threshold and [Formula: see text]O(2peak) (Δ50). Then, the subjects performed two MSEs of 6 × 6 s separated by two intersprint recoveries of 30 s (MSE(30)) and 180 s (MSE(180)), followed 10 min later by the Δ50 (Δ50(30) and Δ50(180), respectively). Electromyography (EMG) activities of the vastus medialis and lateralis were measured throughout each exercise bout. During MSE(30), muscle activity (root mean square) increased significantly (p ≤ 0.04), with a significant leftward-shifted median frequency of the power density spectrum (MDF; p ≤ 0.01), whereas MDF was significantly rightward-shifted during MSE(180) (p = 0.02). The mean [Formula: see text]O(2) value was significantly higher in MSE(30) than in MSE(180) (p motor units recruitment profile (i.e., change in the type of muscle fibers recruited) and (or) an improved muscle O(2) delivery during subsequent exercise.

  17. Oxygen uptake and haemocyanin oxygen affinity

    African Journals Online (AJOL)

    1990-04-17

    Apr 17, 1990 ... reni showed that the two different gas exchange processes operating in water and in .... CaCl2 20 mmol rl; MgC~ 10 mmol rl; flow rate 7 ml h-I) at different pH values. ... on the moving canvas. In their behaviour on the treadmill,.

  18. Kinetics of [123I]iodide uptake and discharge by perchlorate in studies of inhibition of iodide binding by antithyroid drugs

    International Nuclear Information System (INIS)

    McCruden, D.C.; Connell, J.M.C.; Alexander, W.D.; Hilditch, T.E.

    1985-01-01

    Thyroidal binding of iodide was studied by kinetic analysis of [ 123 ]iodide uptake and its discharge by perchlorate in 80 hyperthyroid subjects receiving antithyroid drug therapy. Five dosage regimens ranging from 5 mg carbimazole twice daily to 15 mg methimazole twice daily were studied. Binding inhibition was estimated at 5-7 h after drug as an index of the mean effect of the 12 hourly regimen. In all cases, except one in the lowest dose group, binding was found to be markedly reduced with mean binding rates ranging from 0.002 to 0.020 min -1 (normal > 0.15 min -1 ). The net clearance of iodide in the lowest dose group was reduced to a mean value near the upper limit of the euthyroid range, whereas in the highest dose group it lay at the lower limit of the euthyroid range. These results were reflected in the serum thyroid hormone response. There was a reducing incidence of inadequate control of hyperthyroidism and an increasing incidence of hypothyroidism with increasing thiourylene dose. The exit rate constant of free iodide for the various doses showed values from 0.048 to 0.055 min -1 . Correpsonding mean values for the discharge rate constant after perchlorate were 0.087 to 0.105 min -1 . This suggests that perchlorate increases the rate of iodide release from the thyroid gland. Studies at a later interval after drug (12-14 h) showed no change in discharge rate constant. This leads to the conclusion that perchlorate may further inhibit iodide binding in subjects receiving antithyroid drug therapy. (author)

  19. Oxygen reduction kinetics and transport properties of (Ba,Sr)(Co,Fe)O3-δ solid oxide fuel cell cathode materials

    International Nuclear Information System (INIS)

    Wang, Lei; Merkle, Rotraut; Baumann, Frank S.; Maier, Joachim; Fleig, Juergen

    2007-01-01

    Full text: The oxygen reduction at the surface of cathode materials is crucial for the performance of solid oxide fuel cells (SOFC), but a detailed understanding of the mechanism is not available yet. (Ba x Sr 1-x )(Co 1-y Fe y )O 3-δ shows strongly improved oxygen reduction rates compared to previously applied perovskite cathode materials. In this work, surface rate constants as well as bulk transport properties are studied. (Ba x Sr 1-x )(Co 1-y Fe y )O 3-δ with 0≤x≤0.5, 0.2≤y≤1 was synthesized by the Pechini method. Oxygen stoichoimetry was obtained from thermo-gravimetric analysis, confirming that Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ has an exceptionally low oxygen content which is generally smaller than 2.5. Dense thin films were grown by pulsed laser deposition (PLD) and patterned into circular microelectrodes by photolithography. The surface resistance R s , which dominate the overall electrode resistance, were measured by impedance spectroscopy on individual microelectrodes at different T, pO 2 and applied electrical bias. PLD technique greatly helps to study the oxygen reduction kinetics since only measurements on dense thin films allow to record absolute R s values without interference from morphology effects. These R s values were found to be much lower than those for (La,Sr)(Co,Fe)O 3-δ . The variation of the surface reaction rates with A-site and B-site composition was studied and correlations with bulk materials properties such as oxygen nonstoichiometry, ionic mobility or oxidation enthalpy were examined. Plausible reaction mechanisms as well as possible reasons for the high absolute surface reaction rates will be discussed

  20. Dissolution kinetics of small amounts of oxygen in tantalum alloy T-111 and internal oxide displacement reactions during annealing

    Science.gov (United States)

    Stecura, S.

    1976-01-01

    Oxygen was added to T-111 (Ta-8W-2Hf, wt. %) at 820 and 990 C at an oxygen pressure of about 0.0003 torr. The technique employed permitted predetermined and reproducible doping of T-111 up to 3.0 at. % oxygen. Based on the temperature dependence of the doping reaction, it is concluded that the initial rates of oxygen pickup are probably controlled by solution of oxygen into the T-111 lattice. Although hafnium oxides are more stable than those of tantalum or tungsten, analyses of extracted residues indicate that the latter oxides predominate in the as-doped specimens, presumably because of the higher concentrations of tantalum and tungsten in the alloy. However, high-temperature annealing promotes gettering of dissolved oxygen and of other oxides to form hafnium oxides. Small amounts of tantalum and tungsten oxides were still present after high-temperature annealing. Tungsten oxide (WO3) volatilizes slightly from the surface of T-111 at 990 C. The vaporization of WO3 has no apparent affect on the doping reaction.

  1. Batch culture of Azotobacter vinelandii under oxygen limitation conditionS

    Energy Technology Data Exchange (ETDEWEB)

    Camacho Rubio, F.; Martinez Nieto, L.; Fernandez Serrano, M.; Jimenez Moleon, M.C. [Departamento de Ingenieria Quimica, Universidad de Granada, Granada (Spain)

    1996-12-01

    The batch culture of Azotobacter vinealandii on glucose under nitrogen-fixing conditions, seeking oxygen limitation conditions, has been studied in order to use it as a Biological Test System for the experimental study of oxygen transfer enhancement methods in aerobic fermenters. overall kinetic parameters for exponential growth and for linear growth (under oxygen limitation) have been determined. It was noted an appreciable influence of the oxygen transfer rate on glucose and oxygen uptake, which seems to be due to alginate production, excreted as a nitrogenase protection mechanisms. (Author) 12 refs.

  2. Evaluation of thermodynamic and kinetic stability of P-type transparent conducting oxide, SrCu2O2 under various oxygen partial pressures

    International Nuclear Information System (INIS)

    Sugimoto, Takayuki; Yanagawa, Atsumi; Hashimoto, Takuya

    2012-01-01

    Highlights: ▶ Thermodynamic and kinetic stabilities of SrCu 2 O 2 under various P(O 2 ) was estimated. ▶ The reaction rate for decomposition decreased with decreasing temperature and P(O 2 ). ▶ The activation energy for decomposition of SrCu 2 O 2 was estimated to be 66 kJ/mol. ▶ SrCu 2 O 2 showed less stability than those of other transparent p-type semiconductors. - Abstract: Kinetic stability of transparent p-type conducting oxide, SrCu 2 O 2 , has been evaluated by using X-ray diffraction measurement and thermogravimetry. It was revealed that SrCu 2 O 2 decomposed to mixture of CuO and Sr 14 Cu 24 O 41 in air at temperatures above 300 °C. The decomposition reaction rate can be successfully explained by kinetic model assuming first-order chemical reaction. The rate constant can be suppressed with decreasing temperature and oxygen partial pressure. The activation energy for decomposition reaction of SrCu 2 O 2 calculated from Arrhenius plot was 66 kJ/mol, which was lower than those of other transparent p-type semiconductors such as CuAlO 2 and CuGaO 2 . The low decomposition temperature and activation energy for decomposition indicate that chemical stability of SrCu 2 O 2 is far lower than those of other p-type conducting oxides.

  3. Low- and high-volume of intensive endurance training significantly improves maximal oxygen uptake after 10-weeks of training in healthy men.

    Directory of Open Access Journals (Sweden)

    Arnt Erik Tjønna

    Full Text Available Regular exercise training improves maximal oxygen uptake (VO2max, but the optimal intensity and volume necessary to obtain maximal benefit remains to be defined. A growing body of evidence suggests that exercise training with low-volume but high-intensity may be a time-efficient means to achieve health benefits. In the present study, we measured changes in VO2max and traditional cardiovascular risk factors after a 10 wk. training protocol that involved three weekly high-intensity interval sessions. One group followed a protocol which consisted of 4×4 min at 90% of maximal heart rate (HRmax interspersed with 3 min active recovery at 70% HRmax (4-AIT, the other group performed a single bout protocol that consisted of 1×4 min at 90% HRmax (1-AIT. Twenty-six inactive but otherwise healthy overweight men (BMI: 25-30, age: 35-45 y were randomized to either 1-AIT (n = 11 or 4-AIT (n = 13. After training, VO2max increased by 10% (∼5.0 mL⋅kg(-1⋅min(-1 and 13% (∼6.5 mL⋅kg(-1⋅min(-1 after 1-AIT and 4-AIT, respectively (group difference, p = 0.08. Oxygen cost during running at a sub-maximal workload was reduced by 14% and 13% after 1-AIT and 4-AIT, respectively. Systolic blood pressure decreased by 7.1 and 2.6 mmHg after 1-AIT and 4-AIT respectively, while diastolic pressure decreased by 7.7 and 6.1 mmHg (group difference, p = 0.84. Both groups had a similar ∼5% decrease in fasting glucose. Body fat, total cholesterol, LDL-cholesterol, and ox-LDL cholesterol only were significantly reduced after 4-AIT. Our data suggest that a single bout of AIT performed three times per week may be a time-efficient strategy to improve VO2max and reduce blood pressure and fasting glucose in previously inactive but otherwise healthy middle-aged individuals. The 1-AIT type of exercise training may be readily implemented as part of activities of daily living and could easily be translated into programs designed to improve public health

  4. Nicotinic receptors modulate the onset of reactive oxygen species production and mitochondrial dysfunction evoked by glutamate uptake block in the rat hypoglossal nucleus.

    Science.gov (United States)

    Tortora, Maria; Corsini, Silvia; Nistri, Andrea

    2017-02-03

    In several neurodegenerative diseases, glutamate-mediated excitotoxicity is considered to be a major process to initiate cell degeneration. Indeed, subsequent to excessive glutamate receptor stimulation, reactive oxygen species (ROS) generation and mitochondrial dysfunction are regarded as two major gateways leading to neuron death. These processes are mimicked in an in vitro model of rat brainstem slice when ex