Microscale modelling of AISI 304 behaviour during hot deformation

This project aimed to model the microstructure evolution during and following hot deformation using a cellular automaton approach. The flow curves, softening kinetics and final microstructures were used as the input data for the post-deformation simulation to elucidate the effect of dynamic recrystallization on the post-deformation softening.

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

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 < 0.05) post-SE and post-UE compared with baseline at 50% V_T (17.3 ± 10.7 s and 17.5 ± 5.9 s vs. 29.9 ± 10.7 s), 80% V_T (18.9 ± 4.7 and 20.9 ± 8.4 vs. 34.3 ± 12.7s), and 50% Δ (20.4 ± 8.2 s and 20.2 ± 6.0 s vs. 27.6 ± 3.7 s). SE also induced faster heart rate kinetics at all 3 intensities and a larger increase in CO at 30 s in relation to 240 s at 80% V_T; and these responses were maintained post-UE. Unsupervised 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.

A clustered randomised trial examining the effect of social marketing and community mobilisation on the age of uptake and levels of alcohol consumption by Australian adolescents

Introduction
Throughout the world, alcohol consumption is common among adolescents. Adolescent alcohol use and misuse have prognostic significance for several adverse long-term outcomes, including alcohol problems, alcohol dependence, school disengagement and illicit drug use. The aim of this study was to evaluate whether randomisation to a community mobilisation and social marketing intervention reduces the proportion of adolescents who initiate alcohol use before the Australian legal age of 18, and the frequency and amount of underage adolescent alcohol consumption.
Method and analysis
The study comprises 14 communities matched with 14 non-contiguous communities on socioeconomic status (SES), location and size. One of each pair was randomly allocated to the intervention. Baseline levels of adolescent alcohol use were estimated through school surveys initiated in 2006 (N=8500). Community mobilisation and social marketing interventions were initiated in 2011 to reduce underage alcohol supply and demand. The setting is communities in three Australian states (Victoria, Queensland and Western Australia). Students (N=2576) will complete school surveys in year 8 in 2013 (average age 12). Primary outcomes: (1) lifetime initiation and (2) monthly frequency of alcohol use. Reports of social marketing and family and community alcohol supply sources will also be assessed. Point estimates with 95% CIs will be compared for student alcohol use in intervention and control communities. Changes from 2006 to 2013 will be examined; multilevel modelling will assess whether random assignment of communities to the intervention reduced 2013 alcohol use, after accounting for community level differences. Analyses will also assess whether exposure to social marketing activities increased the intervention target of reducing alcohol supply by parents and community members.

Respirometric techniques for assessment of biological kinetics in constructed wetland

The aim of this research was the development of a procedure to measure biological kinetics of organic matter oxidation and nitrification in constructed wetland, by using respirometric techniques. Columns simulating cores of vertical subsurface flow systems were investigated. The oxygen uptake rate (OUR) of the columns was calculated on the basis of the difference of DO concentrations measured continuously at the top and at the bottom of the column. From the respirogram, the following kinetic parameters have been evaluated: maximum rate of oxidation of readily biodegradable COD, maximum rate of nitrification, endogenous respiration of the biomass grown inside the bed. In order to improve the interpretation of the respirograms, additional respirometric tests were carried out on the wetland columns by using pure substrates, such as acetate (carbon source) and ammonium (substrate for nitrification). The kinetic parameters obtained from respirograms can be useful for control and design of constructed wetlands or for improving nutrient and carbon mass balances.

Muscle damage slows oxygen uptake kinetics during moderate-intensity exercise performed at high pedal rate

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Oxygen uptake kinetics and time to exhaustion in cycling and running: A comparison between trained and untrained subjects

The objective of the present study was to compare pulmonary gas exchange kinetics (VO 2 kinetics) and time to exhaustion (Tlim) between trained and untrained individuals during severe exercise performed on a cycle ergometer and treadmill. Eleven untrained males in running (UR) and cycling (UC), nine endurance cyclists (EC), and seven endurance runners (ER) were submitted to the following tests on separate days: (i) incremental test for determination of maximal oxygen uptake (VO 2max) and the intensity associated with the achievement of VO 2max (IVO 2max) on a mechanical braked cycle ergometer (EC and UC) and on a treadmill (ER and UR); (ii) all-out exercise bout performed at IVO 2max to determine the time to exhaustion at IVO 2max (Tlim) and the time constant of oxygen uptake kinetics (τ). The τ was significantly faster in trained group, both in cycling (EC = 28.2 ± 4.7 s; UC = 63.8 ± 25.0 s) and in running (ER = 28.5 ± 8.5 s; UR = 59.3 ± 12.0 s). Tlim of untrained was significantly lower in cycling (EC = 384.4 ± 66.6 s vs. UC; 311.1 ± 105.7 s) and higher in running (ER = 309.2 ± 176.6 s vs. UR = 439.8 ± 104.2 s). We conclude that the VO 2 kinetic response at the onset of severe exercise, carried out at the same relative intensity is sensitive to endurance training, irrespective of the exercise type. The endurance training seems to differently influence Tlim during exercise at IVO 2max in running and cycling. © 2003 Taylor & Francis Ltd.

Pharmacokinetic and pharmacodynamic modelling of intravenous, intramuscular and subcutaneous buprenorphine in conscious cats

Objective To describe simultaneous pharmacokinetics (PK) and thermal antinociception after intravenous (IV), intramuscular (IM) and subcutaneous (SC) buprenorphine in cats. Study design Randomized, prospective, blinded, three period crossover experiment. Animals Six healthy adult cats weighing 4.1±0.5kg. Methods Buprenorphine (0.02mgkg-1) was administered IV, IM or SC. Thermal threshold (TT) testing and blood collection were conducted simultaneously at baseline and at predetermined time points up to 24hours after administration. Buprenorphine plasma concentrations were determined by liquid chromatography tandem mass spectrometry. TT was analyzed using anova (p<0.05). A pharmacokinetic-pharmacodynamic (PK-PD) model of the IV data was described using a model combining biophase equilibration and receptor association-dissociation kinetics. Results TT increased above baseline from 15 to 480minutes and at 30 and 60minutes after IV and IM administration, respectively (p<0.05). Maximum increase in TT (mean±SD) was 9.3±4.9°C at 60minutes (IV), 4.6±2.8°C at 45minutes (IM) and 1.9±1.9°C at 60minutes (SC). TT was significantly higher at 15, 60, 120 and 180minutes, and at 15, 30, 45, 60 and 120minutes after IV administration compared to IM and SC, respectively. IV and IM buprenorphine concentration-time data decreased curvilinearly. SC PK could not be modeled due to erratic absorption and disposition. IV buprenorphine disposition was similar to published data. The PK-PD model showed an onset delay mainly attributable to slow biophase equilibration (t1/2ke0=47.4minutes) and receptor binding (kon=0.011mL ng-1minute-1). Persistence of thermal antinociception was due to slow receptor dissociation (t1/2koff=18.2minutes). Conclusions and clinical relevance IV and IM data followed classical disposition and elimination in most cats. Plasma concentrations after IV administration were associated with antinociceptive effect in a PK-PD model including negative hysteresis. At the doses administered, the IV route should be preferred over the IM and SC routes when buprenorphine is administered to cats. © 2012 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.

Muscular and pulmonary O2 uptake kinetics during moderate- and high-intensity sub-maximal knee-extensor exercise in humans

[EN] The purpose of this investigation was to determine the contribution of muscle O(2) consumption (mVO2) to pulmonary O(2) uptake (pVO2) during both low-intensity (LI) and high-intensity (HI) knee-extension exercise, and during subsequent recovery, in humans. Seven healthy male subjects (age 20-25 years) completed a series of LI and HI square-wave exercise tests in which mVO2 (direct Fick technique) and pVO2 (indirect calorimetry) were measured simultaneously. The mean blood transit time from the muscle capillaries to the lung (MTTc-l) was also estimated (based on measured blood transit times from femoral artery to vein and vein to artery). The kinetics of mVO2 and pVO2 were modelled using non-linear regression. The time constant (tau) describing the phase II pVO2 kinetics following the onset of exercise was not significantly different from the mean response time (initial time delay + tau) for mVO2 kinetics for LI (30 +/- 3 vs 30 +/- 3 s) but was slightly higher (P < 0.05) for HI (32 +/- 3 vs 29 +/- 4 s); the responses were closely correlated (r = 0.95 and r = 0.95; P < 0.01) for both intensities. In recovery, agreement between the responses was more limited both for LI (36 +/- 4 vs 18 +/- 4 s, P < 0.05; r = -0.01) and HI (33 +/- 3 vs 27 +/- 3 s, P > 0.05; r = -0.40). MTTc-l was approximately 17 s just before exercise and decreased to 12 and 10 s after 5 s of exercise for LI and HI, respectively. These data indicate that the phase II pVO2 kinetics reflect mVO2 kinetics during exercise but not during recovery where caution in data interpretation is advised. Increased mVO2 probably makes a small contribution to during the first 15-20 s of exercise.

Process-based modelling of lichens and bryophytes and their role in global biogeochemical cycles

This thesis presents a process-based modelling approach to quantify carbon uptake by lichens and bryophytes at the global scale. Based on the modelled carbon uptake, potential global rates of nitrogen fixation, phosphorus uptake and chemical weathering by the organisms are estimated. In this way, the significance of lichens and bryophytes for global biogeochemical cycles can be assessed. The model uses gridded climate data and key properties of the habitat (e.g. disturbance intervals) to predict processes which control net carbon uptake, namely photosynthesis, respiration, water uptake and evaporation. It relies on equations used in many dynamical vegetation models, which are combined with concepts specific to lichens and bryophytes, such as poikilohydry or the effect of water content on CO2 diffusivity. To incorporate the great functional variation of lichens and bryophytes at the global scale, the model parameters are characterised by broad ranges of possible values instead of a single, globally uniform value. The predicted terrestrial net uptake of 0.34 to 3.3 Gt / yr of carbon and global patterns of productivity are in accordance with empirically-derived estimates. Based on the simulated estimates of net carbon uptake, further impacts of lichens and bryophytes on biogeochemical cycles are quantified at the global scale. Thereby the focus is on three processes, namely nitrogen fixation, phosphorus uptake and chemical weathering. The presented estimates have the form of potential rates, which means that the amount of nitrogen and phosphorus is quantified which is needed by the organisms to build up biomass, also accounting for resorption and leaching of nutrients. Subsequently, the potential phosphorus uptake on bare ground is used to estimate chemical weathering by the organisms, assuming that they release weathering agents to obtain phosphorus. The predicted requirement for nitrogen ranges from 3.5 to 34 Tg / yr and for phosphorus it ranges from 0.46 to 4.6 Tg / yr. Estimates of chemical weathering are between 0.058 and 1.1 km³ / yr of rock. These values seem to have a realistic order of magnitude and they support the notion that lichens and bryophytes have the potential to play an important role for global biogeochemical cycles.

Cerium oxide nanoparticle uptake kinetics from the gas-phase into lung cells in vitro is transport limited

Nowadays, aerosol processes are widely used for the manufacture of nanoparticles (NPs), creating an increased occupational exposure risk of workers, laboratory personnel and scientists to airborne particles. There is evidence that possible adverse effects are linked with the accumulation of NPs in target cells, pointing out the importance of understanding the kinetics of particle internalization. In this context, the uptake kinetics of representative airborne NPs over 30 min and their internalization after 24 h post-exposure were investigated by the use of a recently established exposure system. This system combines the production of aerosolized cerium oxide (CeO(2)) NPs by flame spray synthesis with its simultaneous particle deposition from the gas-phase onto A549 lung cells, cultivated at the air-liquid interface. Particle uptake was quantified by mass spectrometry after several exposure times (0, 5, 10, 20 and 30 min). Over 35% of the deposited mass was found internalized after 10 min exposure, a value that increased to 60% after 30 min exposure. Following an additional 24 h post-incubation, a time span, after which adverse biological effects were observed in previous experiments, over 80% of total CeO(2) could be detected intracellularly. On the ultrastructural level, focal cerium aggregates were present on the apical surface of A549 cells and could also be localized intracellularly in vesicular structures. The uptake behaviour of aerosolized CeO(2) is in line with observations on cerium suspensions, where particle mass transport was identified as the rate-limiting factor for NP internalization.

Walking performance, oxygen uptake kinetics and resting muscle pyruvate dehydrogenase complex activity in peripheral arterial disease

In the present study, we tested the hypothesis that walking intolerance in intermittent claudication (IC) is related to both slowed whole body oxygen uptake (Vo(2)) kinetics and altered activity of the active fraction of the pyruvate dehydrogenase complex (PDCa) in skeletal muscle. Ten patients with IC and peripheral arterial disease [ankle/brachial index (ABI) = 0.73 +/- 0.13] and eight healthy controls (ABI = 1. 17 +/- 0.13) completed three maximal walking tests. From these tests, averaged estimates of walking time, peak Vo(2) and the time constant of Vo(2) (tau) during submaximal walking were obtained. A muscle sample was taken from the gastrocnemius medialis muscle at rest and analysed for PDCa and several other biochemical variables. Walking time and peak Vo(2) were approx. 50 % lower in patients with IC than controls, and tau was 2-fold higher (P < 0.05). r was significantly correlated with walking time (r = -0.72) and peak Vo(2) (r = -0.66) in patients with IC, but not in controls. PDCa was not significantly lower in patients with IC than controls; however, PDCa tended to be correlated with tau (r = -0.56, P = 0.09) in patients with IC, but not in controls (r = -0.14). A similar correlation was observed between resting ABI and tau (r = -0.63, P = 0.05) in patients with IC. These data suggest that the impaired Vo(2) kinetics contributes to walking intolerance in IC and that, within a group of patients with IC, differences in Vo(2) kinetics might be partly linked to differences in muscle carbohydrate oxidation.

The influence of substrate kinetics on the microbial community structure in granular anaerobic biomass

The development of a strong, active granular sludge bed is necessary for optimal operation of upflow anaerobic sludge blanket reactors. The microbial and mechanical structure of the granules may have a strong influence on desirable properties such as growth rate, settling velocity and shear strength. Theories have been proposed for granule microbial structure based on the relative kinetics of substrate degradation, but contradict some observations from both modelling and microscopic studies. In this paper, the structures of four granule types were examined from full-scale UASB reactors, treating wastewater from a cannery, a slaughterhouse, and two breweries. Microbial structure was determined using fluorescence in situ hybridisation probing with 16S rRNA-directed oligonucleotide probes, and superficial structure and microbial density (volume occupied by cells and microbial debris) assessed using scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The granules were also modelled using a distributed parameter biofilm model, with a previously published biochemical model structure, biofilm modelling approach, and model parameters. The model results reflected the trophic structures observed, indicating that the structures were possibly determined by kinetics. Of particular interest were results from simulations of the protein grown granules, which were predicted to have slow growth rates, low microbial density, and no trophic layers, the last two of which were reflected by microscopic observations. The primary cause of this structure, as assessed by modelling, was the particulate nature of the wastewater, and the slow rate of particulate hydrolysis, rather than the presence of proteins in the wastewater. Because solids hydrolysis was rate limiting, soluble substrate concentrations were very low (below Monod half saturation concentration), which caused low growth rates. (C) 2003 Elsevier Ltd. All rights reserved.

CFD modelling of the fast pyrolysis of an in-flight cellulosic particle subjected to convective heat transfer

The pyrolysis of a freely moving cellulosic particle inside a 41.7mgs -1 source continuously fed fluid bed reactor subjected to convective heat transfer is modelled. The Lagrangian approach is adopted for the particle tracking inside the reactor, while the flow of the inert gas is treated with the standard Eulerian method for gases. The model incorporates the thermal degradation of cellulose to char with simultaneous evolution of gases and vapours from discrete cellulosic particles. The reaction kinetics is represented according to the Broido–Shafizadeh scheme. The convective heat transfer to the surface of the particle is solved by two means, namely the Ranz–Marshall correlation and the limit case of infinitely fast external heat transfer rates. The results from both approaches are compared and discussed. The effect of the different heat transfer rates on the discrete phase trajectory is also considered.