A commercial retarding field analyzer is used to measure the time-averaged ion energy distributions of impacting ions at the powered electrode in a 13.56 MHz driven, capacitively coupled, parallel ...plate discharge operated at low pressure. The study is carried out in argon discharges at 10 mTorr where the sheaths are assumed to be collisionless. The analyzer is mounted flush with the powered electrode surface where the impacting ion and electron energy distributions are measured for a range of discharge powers. A circuit model of the discharge, in combination with analytical solutions for the ion energy distribution in radio-frequency sheaths, is used to calculate other important plasma parameters from the measured energy distributions. Radio-frequency compensated Langmuir probe measurements provide a comparison with the retarding field analyzer data. The time-resolved capability of the retarding field analyzer is also demonstrated in a separate pulsed dc magnetron reactor. The analyzer is mounted on the floating substrate holder and ion energy distributions of the impinging ions on a growing film, with 100 ns time resolution, are measured through a pulse period of applied magnetron power, which are crucial for the control of the microstructure and properties of the deposited films.
An experiment (3 × 4 factorial arrangement) was conducted to investigate the interaction between different levels of lactose (60 v. 150 v. 250 g/kg) and seaweed extract (0 v. 1 v. 2 v. 4 g/kg) ...containing both laminarin and fucoidan derived from Laminaria spp. on growth performance and nutrient digestibility of weanling pigs. In all, 384 piglets (24 days of age, 7.5 kg (s.d. 1 kg) live weight) were blocked on the basis of live weight and were assigned to one of 12 dietary treatments (eight replicates per treatment). Piglets were offered diets containing either low (60 g/kg), medium (150 g/kg) or high (250 g/kg) lactose levels with one of the following levels of seaweed extract additive: (1) 0 g/kg, (2) 1 g/kg, (3) 2 g/kg or (4) 4 g/kg seaweed extract. The pigs were offered the diets ad libitum for 21 days post weaning. There was a significant lactose × seaweed extract interaction (P < 0.05) in average daily gain (ADG) during the experimental period (days 0 to 21). At the low and medium levels of lactose, there was an increase in ADG as the level of seaweed extract increased to 2 g/kg (P < 0.05). However, at the high level of lactose there was no further response in ADG as the level of seaweed extract increased above 1 g/kg. There was a significant lactose × seaweed extract interaction during the experimental period (days 0 to 21) (P < 0.05) on the food conversion ratio (FCR). At the low level of lactose, there was a significant improvement in FCR as the levels of seaweed extract increased to 4 g/kg (P < 0.01). At the medium level of lactose, there was a significant improvement in FCR as seaweed extract increased to 2 g/kg. However, there was no significant effect of seaweed extract on FCR at the high levels of lactose (P > 0.05). There was a linear increase in average daily feed intake (ADFI) during the experimental period (days 0 to 21) (P < 0.05) as levels of seaweed extract increased. There was a linear increase in ash digestibility (P < 0.01) during the experimental period (days 0 to 21) as the level of lactose increased. There was a quadratic decrease (P < 0.01) in nitrogen (N) and neutral detergent fibre digestibility as the levels of lactose increased. In conclusion, pigs responded differently to the inclusion levels of seaweed extract at each level of lactose supplementation. The inclusion of a laminarin–fucoidan extract in piglet diets may alleviate the use for high-lactose diets (>60 g/kg) and would also alleviate some of the common problems that occur post weaning.
A retarding field energy analyzer is used to characterize an asymmetric, 13.56 MHz driven, capacitively coupled, parallel plate discharge operated at low pressure. The characterization is carried out ...in argon discharges at 10 and 20 mTorr where the sheaths are assumed to be collisionless. The analyzer is set in the powered electrode where the impacting ion and electron energy distributions are measured for a range of discharge powers. A circuit model of the discharge is used to infer important electrical parameters from the measured energy distributions, including electrode excitation voltages, plasma potential and sheath potentials. Analytical models of the ion energy distribution in a radio-frequency sheath are used to determine plasma parameters such as sheath width, ion transit time, electron temperature and ion flux. A radio-frequency compensated Langmuir probe is used for comparison with the retarding field analyzer measurements.
Ion energy distributions are investigated in an inductively coupled radio-frequency discharge at low pressures. A Langmuir probe is used to characterize the discharge and a retarding field energy ...analyzer measures the ion flux and energy distributions impacting a remote rf driven electrode. Comparisons are made between capacitive and direct coupling of the rf bias potential. The effects of ICP power, rf bias voltage (0-75 V amplitude), bias frequency (0.5-20 MHz) and discharge pressure (0.2-1.2 Pa) are presented. Results are shown for Ar, O2 and Ar-He discharges. A double layer was observed during source characterization measurements in an O2 discharge; however, the focus of this paper is on the behavior of ions through capacitively and directly coupled plasma sheaths.
The objective of the current experiment was to evaluate the influence of dietary cereal sources of β(1,3)(1,4)-D-glucan (β-glucan) and enzyme supplementation on indices of environmental pollution ...from finisher pigs. An experiment with a 2 x 2 factorial arrangement of treatments was initiated to investigate the effect of dietary source of β-glucan (barley vs. oats) and enzyme supplementation (no vs. yes) on nutrient digestibility, N utilization, intestinal fermentation, and manure odor and ammonia emissions from finisher boars (n = 4; BW = 73.9 kg; SD = 4.7). Sixteen boars were assigned to 1 of 4 dietary treatments (n = 4/treatment): 1) barley-based diet, 2) barley-based diet + exogenous enzyme, 3) oat-based diet, and 4) oat-based diet + enzyme. The enzyme supplement used contained endo-1,3(4)-β-glucanase and endo-1,4-β-xylanase. Experimental diets were formulated to contain similar concentrations of DE (13.5 MJ/kg) and digestible lysine (8.8 g/kg). Pigs offered oat-based diets had reduced digestibility of DM (0.795 vs. 0.849; SEM 0.007; P = 0.001), OM (0.808 vs. 0.865; SEM 0.007; P = 0.001), GE (0.806 vs. 0.845; SEM 0.006; P = 0.002), and NDF (0.233 vs. 0.423; SEM 0.033; P < 0.003) compared with those offered barley-based diets. Oat-based diets increased populations of Bifidobacterium spp. (7.26 vs. 6.38 log cfu/g of digesta; SEM 0.201; P = 0.005) and Lactobacillus spp. (6.99 vs. 6.18 log cfu/g of digesta; SEM 0.234; P = 0.022) in the proximal colon and decreased manure odor emissions 2,179.6 vs. 4,984.6 OuE/m³ (where OuE refers to European odor units); SEM 653.7; P < 0.011 compared with barley-based diets. There was an interaction between cereal type and enzyme inclusion on manure ammonia emissions from 0 to 96 h (P = 0.050). Pigs offered barley-based diets containing an enzyme supplement had increased manure ammonia emissions compared with those offered unsupplemented barley-based diets. However, there was no effect of enzyme inclusion on oat-based diets. In conclusion, pigs offered oat-based diets harbored increased Bifidobacterium spp. and Lactobacillus spp. populations in the proximal colon and had decreased manure odor emissions compared with those offered barley-based diets. Enzyme inclusion had no effect on manure ammonia emissions from pigs offered oat-based diets.
Two experiments were conducted to investigate the effects of cereal type, β-glucan type and exogenous enzyme supplementation (ES) on microbial populations, volatile fatty acid (VFA) concentrations, ...nutrient digestibility, indole and skatole levels in the digesta and mineral metabolism in pigs. In Experiment 1, 28 boars (59
±
2
kg; 119
±
2 days of age) were used in a 2
×
2 factorial arrangement and were assigned to one of 4 dietary treatments (
n
=
7): T1) barley-based diet; T2) barley-based diet plus ES; T3) oat-based diet and T4) oat-based diet plus ES. The ES used in both experiments contained endo-1,3-β-glucanase and endo-1,4-β-xylanase. In Experiment 2, 28 boars (60
±
1.9
kg; 119
±
2 days of age) were assigned to one of 4 dietary treatments (
n
=
7): T1) oat-based diet containing endogenous (non-purified) β-glucans; T2) oat-based diet containing endogenous β-glucans plus ES; T3) wheat-based diet and exogenous (laboratory purified) β-glucans and T4) wheat-based diet and exogenous β-glucans plus ES. The laboratory purified exogenous β-glucans used in Experiment 2 were oat-derived β-glucans. The diets were equalised to have similar amount of total β-glucan and arabinoxylan. In Experiment 1, pigs offered barley-based diets had higher (P<0.001) coefficient of total tract apparent digestibility (CTTAD) of organic matter (OM) and gross energy (GE) and lower CTTAD (P<0.05) of nitrogen compared to oat-based diets. Pigs offered barley-based diets had higher (P<0.001) molar proportions of butyric and propionic acids and higher total VFA concentrations in the caecum (P<0.01) and colon (P<0.001) than pigs fed oat-based diets. Pigs offered oat-based diets had higher populations of
Bifidobacteria in the ileum (P<0.05) and colon (P<0.01), and
Lactobacilli in the colon (P<0.05) compared with pigs fed barley-based diets. In Experiment 2, pigs offered diets containing endogenous β-glucans without ES had higher populations of
Bifidobacteria (P<0.01) compared to pigs offered diets supplemented with exogenous β-glucans without ES. Diets containing endogenous β-glucans without ES had a lower (P<0.001) CTTAD of OM and GE compared to diets supplemented with exogenous β-glucans without ES. In conclusion, barley-based diets have more beneficial effects on parameters related to gut health than oat-based diets; however oat-based diets exhibit higher potential to enhance beneficial microbial populations. Endogenous β-glucans show better prebiotic properties than exogenous β-glucans.
Biopolymer self-assembly pathways are complicated by the ability of their monomeric subunits to adopt different conformational states. This means nucleation often involves a two-step mechanism where ...the monomers first condense to form a metastable intermediate, which then converts to a stable polymer by conformational rearrangement of constituent monomers. Nucleation intermediates play a causative role in amyloid diseases such as Alzheimer's and Parkinson's. While existing mathematical models neglect the conversion dynamics, experiments show that conversion events frequently occur on comparable timescales to the condensation of intermediates and growth of mature polymers and thus cannot be ignored. We present a model that explicitly accounts for simultaneous assembly and conversion. To describe conversion, we propose an experimentally motivated initiation-propagation mechanism in which the stable phase arises locally within the intermediate and then spreads by nearest-neighbor interactions, in a manner analogous to one-dimensional Glauber dynamics. Our analysis shows that the competing timescales of assembly and conversion result in a nonequilibrium critical point, separating a regime where intermediates are kinetically unstable from one where conformationally mixed intermediates accumulate. This strongly affects the accumulation rate of the stable biopolymer phase. Our model is uniquely able to explain experimental phenomena such as the formation of mixed intermediates and abrupt changes in the scaling exponent γ, which relates the total monomer concentration to the accumulation rate of the stable phase. This provides a first step toward a general model of two-step biopolymer nucleation, which can quantitatively predict the concentration and composition of biologically crucial intermediates.
Accurate measurement of ion current density and ion energy distributions (IEDs) is often critical for plasma processes in both industrial and research settings. Retarding field energy analysers ...(RFEAs) have been used to measure IEDs because they are considered accurate, relatively simple and cost effective. However, their usage for critical measurement of ion current density is less common due to difficulties in estimating the proportion of incident ion current reaching the current collector through the RFEA retarding grids. In this paper an RFEA has been calibrated to measure ion current density from an ion beam at pressures ranging from 0.5 to 50.0 mTorr. A unique method is presented where the currents generated at each of the retarding grids and the RFEA upper face are measured separately, allowing the reduction in ion current to be monitored and accounted for at each stage of ion transit to the collector. From these
I
–
V
measurements a physical model is described. Subsequently, a mathematical description is extracted which includes parameters to account for grid transmissions, upper face secondary electron emission and collisionality. Pressure-dependent calibration factors can be calculated from least mean square best fits of the collector current to the model allowing quantitative measurement of ion current density.
Consumption of barley-based diets has been demonstrated to reduce manure odour and ammonia emissions generated from pig production, but is associated with depressed nutrient digestibility when ...compared with wheat-based formulations. It was hypothesised that supplementation of a wheat-based diet with purified mixed-linkage β (1,3) (1,4)-D-glucan (β-glucans) to levels comparable with a barley-based diet may beneficially ameliorate manure odour and ammonia emissions, without depressing nutrient digestibility. A complete randomized design experiment was conducted to investigate the effect of dietary β-glucans source and an enzyme composite containing β-glucanase and β-xylanase on energy and nutrient digestibility, distal gastrointestinal tract (dGIT) fermentation, manure odour and ammonia emissions from finishing boars. Twenty-eight boars (74.2kg SD 3.6) were assigned to one of four dietary treatments (n =7); (1) a barley-based diet (B), (2) a barley-based diet+enzyme composite (BE), (3) a wheat-based diet+purified β-glucans (WG) and (4) a wheat-based diet+purified β-glucans+enzyme composite (WGE). The wheat-based diets containing purified β-glucans were formulated to contain concentrations of total β-glucans comparable with the barley-based diets. Consumption of the WG diet increased the coefficient of total tract apparent digestibility (CTTAD) of gross energy (P=0.001) and N (P=0.001) compared with the B diet. Pigs offered the WG diet had increased manure ammonia emissions (P=0.042) compared with the B diet. There was no significant difference between consumption of the WG diet and the B diet on subsequent manure odour emissions. In summary, the current study demonstrates that β-glucans may be added to a wheat-based diet without depressing nutrient digestibility as compared with a barley-based diet. Furthermore, manure odour from pigs offered a wheat-based diet containing β-glucans may be improved to levels comparable with a barley-based diet. However β-glucan supplementation was ineffectual at attenuating manure ammonia emissions comparable with consumption of a barley-based diet.
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