On the characteristics of substructure development through dynamic recrystallization

Substructure development in an austenitic Ni-30%Fe model alloy was investigated within a dynamic recrystallization (DRX) regime. The substructure characteristics of the deformed matrix and DRX grains were markedly different regardless of the grain size and orientation. The former largely displayed 'organized', banded subgrain arrangements with alternating misorientations, resulting from a limited number of active slip systems. In contrast, the substructure of DRX grains was generally more 'random' and exhibited complex subgrain/cell arrangements characterized by local accumulation of misorientations, suggesting multiple slip. The proposed mechanism of the unique substructure development within DRX grains suggests that the DRX nuclei, forming along pre-existing grain boundaries and triple points, essentially represent grain boundary regions, which experience multiple slip to preserve the compatibility with neighbouring deformed grains. This results in the formation of a complex cell/subgrain structure, which progressively extends as the grain boundary regions expand outwards during DRX growth.

Study on the oriented recrystallization of carbon-coated polyethylene oriented ultrathin films

It is confirmed that a layer of vacuum-evaporated carbon on the surface of a preoriented ultrathin polymer film can lead to an oriented recrystallization of the polymer film. This has been attributed to a strong fixing effect of vacuum-evaporated carbon layer on the film surface of the polymer. To study the origin of the strong fixing effect of vacuum-evaporated carbon layer on the polymer films, the melting and recrystallization behaviors of the preoriented ultrathin PE film with a vacuum-evaporated carbon layer were studied by using atomic force microscopy, electron diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. We found that there exists some extent of chain orientation of carbon-coated polyethylene (PE) preoriented ultrathin film above its melting temperature. These oriented PE chain sequences act as nucleation sites and induce the oriented recrystallization of preoriented PE film from melt. Raman spectroscopy results suggest that new carbon-carbon bonds between the carbon layer and the oriented PE film are created during the process of vacuum carbon evaporation. As a result, some of the PE chain stems are fixed to the coated carbon substrate via covalent bond. Such a bonding has retarded the relaxation of the PE chains at the spot and, therefore, preserves the original orientation of the PE stems at high temperature, which in turn derives the recrystallization of the PE chains in an oriented structure.

RiboSys, a high-resolution, quantitative approach to measure the in vivo kinetics of pre-mRNA splicing and 3'-end processing in Saccharomyces cerevisiae

We describe methods for obtaining a quantitative description of RNA processing at high resolution in budding yeast. As a model gene expression system, we constructed tetON (for induction studies) and tetOFF (for repression, derepression, and RNA degradation studies) yeast strains with a series of reporter genes integrated in the genome under the control of a tetO7 promoter. Reverse transcription and quantitative real-time-PCR (RT-qPCR) methods were adapted to allow the determination of mRNA abundance as the average number of copies per cell in a population. Fluorescence in situ hybridization (FISH) measurements of transcript numbers in individual cells validated the RT-qPCR approach for the average copy-number determination despite the broad distribution of transcript levels within a population of cells. In addition, RT-qPCR was used to distinguish the products of the different steps in splicing of the reporter transcripts, and methods were developed to map and quantify 3′-end cleavage and polyadenylation. This system permits pre-mRNA production, splicing, 3′-end maturation and degradation to be quantitatively monitored with unprecedented kinetic detail, suitable for mathematical modeling. Using this approach, we demonstrate that reporter transcripts are spliced prior to their 3′-end cleavage and polyadenylation, that is, cotranscriptionally.

Evaluation of chlorine decay kinetics expressions for drinking water distribution systems modelling

The decay of chlorine in drinking water involves a complex set of reactions that is usually simplified to first order kinetics in models of water quality in distribution systems. However, to be useful in optimising chlorine dosing regimes, the kinetics expression should accurately describe the shape of the chlorine decay curve for different chlorine doses and be able to simulate re-chlorination. After considering the nature of the reactions involved in chlorine decay, five simplified reaction schemes were evaluated for their suitability to describe chlorine concentration in bulk water. Each scheme was fitted to a sample of experimental data of chlorine decay in raw water obtained from Warragamba Dam (the major source of water supplied to Sydney, Australia). A scheme involving two parallel reactions of organic carbon compounds with chlorine is both necessary and sufficient to satisfy the requirements of modelling chlorine decay accurately.

Microstructural characterization of the austenite behaviour during metadynamic recrystallization

The work discusses the recent findings obtained from the microstructural characterization of an austenitic Ni-30%Fe model alloy during metadynamic recrystallization (MDRX) using both EBSD and TEM techniques. The characterization of the grain structure, texture and dislocation substructure evolution of the fully dynamically recrystallized (DRX) microstructure during post deformation annealing revealed a novel softening mechanism occurring under the current experimental conditions. It is proposed that the initial softening stage involves rapid growth of the dynamically formed nuclei and migration of the mobile boundaries in correspondence with the well-established MDRX mechanism. However, the sub-boundaries within DRX grains progressively disintegrate through dislocation climb and dislocation annihilation, which ultimately leads to the formation of dislocation-free grains. Consequently, the DRX texture largely remains preserved throughout the annealing process.

On the characteristics of substructure development through dynamic recrystallization

This body of data is the result of an investigation into the effect of grain boundary movement on the characteristics of substructure development in an austenitic Ni-30%Fe model alloy within the DRX regime. Different thermo-mechanical processing routes were employed to produce a range of DRX grain sizes at a given deformation temperature. The development of dislocation substructure was investigated using electron back-scattered diffraction (EBSD) in conjunction with transmission electron microscopy (TEM).

Evaluation of cassava peel waste as lowcost biosorbent for Ni-sorption : equilibrium, kinetics, thermodynamics and mechanism

The feasibility of cassava peel waste for Ni-sorption is evaluated in this work. The biosorbents are characterized by Boehm titration, Fourier transform-infra red (FTIR) spectroscopy, Nitrogen sorption, scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis (e.g. elemental mapping) and X-ray photoelectron spectroscopy (XPS). Adsorption experiments are performed in batch mode at 30 °C (303.15 K), 45 °C (318.15 K) and 60 °C (333.15 K). The performance of several temperature dependence forms of isotherm models e.g. Langmuir, Freundlich, Sips and Toth to represent the adsorption equilibrium data is evaluated and contrasted. Sips model demonstrates the best fitting with the maximum uptake capacity for Ni(II) ions of 57 mg/g (0.971 mmol/g) at pH 4.5. For kinetic data correlation, pseudo-second order model shows the best representation. The chemisorption mechanism and thermodynamics aspect are also discussed.

Effect of adrenaline on glucose kinetics during exercise in adrenalectomised humans

1. The role of adrenaline in regulating hepatic glucose production and muscle glucose uptake during exercise was examined in six adrenaline deficient, bilaterally adrenalectomised humans. Six sex and age matched healthy individuals served as controls (CON).

2. Adrenalectomised subjects cycled for 45 min at 68 ± 1% maximum pulmonary Oμ uptake (VOμ,max), followed by 15 min at 84 ± 2% VOμ,max without (−ADR) or with (+ADR) adrenaline infusion, which elevated plasma adrenaline levels (45 min, 4·49 ± 0·69 nmol l¢; 60 min, 12·41 ± 1·80 nmol l¢; means ± s.e.m.). Glucose kinetics were measured using [3_ÅH]glucose.

3. Euglycaemia was maintained during exercise in CON and −ADR, whilst in +ADR plasma glucose was elevated. The exercise induced increase in hepatic glucose production was similar in +ADR and −ADR; however, adrenaline infusion augmented the rise in hepatic glucose production early in exercise. Glucose uptake increased during exercise in +ADR and −ADR, but was lower and metabolic clearance rate was reduced in +ADR.

4. During exercise noradrenaline and glucagon concentrations increased, and insulin and cortisol concentrations decreased, but plasma levels were similar between trials. Adrenaline infusion suppressed growth hormone and elevated plasma free fatty acids, glycerol and lactate. Alanine and â_hydroxybutyrate levels were similar between trials.

5. The results demonstrate that glucose homeostasis was maintained during exercise in adrenalectomised subjects. Adrenaline does not appear to play a major role in matching hepatic glucose production to the increase in glucose clearance. In contrast, adrenaline infusion results in a mismatch by simultaneously enhancing hepatic glucose production and inhibiting glucose clearance.

Effect of increased blood glucose availability on glucose kinetics during exercise

This study examined the effect of increased blood glucose availability on glucose kinetics during exercise. Five trained men cycled for 40 min at 77 ± 1% peak oxygen uptake on two occasions. During the second trial (Glu), glucose was infused at a rate equal to the average hepatic glucose production (HGP) measured during exercise in the control trial (Con). Glucose kinetics were measured by a primed continuous infusion ofd-[3-3H]glucose. Plasma glucose increased during exercise in both trials and was significantly higher in Glu. HGP was similar at rest (Con, 11.4 ± 1.2; Glu, 10.6 ± 0.6 μmol ⋅ kg−1 ⋅ min−1). After 40 min of exercise, HGP reached a peak of 40.2 ± 5.5 μmol ⋅ kg−1 ⋅ min−1in Con; however, in Glu, there was complete inhibition of the increase in HGP during exercise that never rose above the preexercise level. The rate of glucose disappearance was greater (P < 0.05) during the last 15 min of exercise in Glu. These results indicate that an increase in glucose availability inhibits the rise in HGP during exercise, suggesting that metabolic feedback signals can override feed-forward activation of HGP during strenuous exercise.

Effect of heat stress on glucose kinetics during exercise

To identify the mechanism underlying the exaggerated hyperglycemia during exercise in the heat, six trained men were studied during 40 min of cycling exercise at a workload requiring 65% peak pulmonary oxygen uptake (V˙o 2 peak) on two occasions at least 1 wk apart. On one occasion, the ambient temperature was 20°C [control (Con)], whereas on the other, it was 40°C [high temperature (HT)]. Rates of glucose appearance and disappearance were measured by using a primed continuous infusion of [6,6-2H]glucose. No differences in oxygen uptake during exercise were observed between trials. After 40 min of exercise, heart rate, rectal temperature, respiratory exchange ratio, and plasma lactate were all higher in HT compared with Con (P < 0.05). Plasma glucose levels were similar at rest (Con, 4.54 ± 0.19 mmol/l; HT, 4.81 ± 0.19 mmol/l) but increased to a greater extent during exercise in HT (6.96 ± 0.16) compared with Con (5.45 ± 0.18;P < 0.05). This was the result of a higher glucose rate of appearance in HT during the last 30 min of exercise. In contrast, the glucose rate of disappearance and metabolic clearance rate were not different at any time point during exercise. Plasma catecholamines were higher after 10 and 40 min of exercise in HT compared with Con (P < 0.05), whereas plasma glucagon, cortisol, and growth hormone were higher in HT after 40 min. These results indicate that the hyperglycemia observed during exercise in the heat is caused by an increase in liver glucose output without any change in whole body glucose utilization.

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.