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This contribution reports for the first time the possibility of using radiolysis to engineer stable efficient nanofluids which exhibit an enhanced thermal conductivity. The validation was confirmed on Ag-H2O and Ag-C2H6O2 nanofluids fabricated via g-radiolysis within the mild dose range of 0.95 × 103–2.45 × 103 Gray. The enhanced thermal conductivity of Ag-H2O and Ag-C2H6O2 nanofluids, was found to be g-radiations dose dependent. In the latter case of Ag-C2H6O2 nanofluid, the relative enhancement in the temperature range of 25–50 °C was found to be 8.89%, 11.54%, 18.69%, 23.57% and 18.45% for D1 = 0.95 × 103 Gray, D2 = 1.2 × 103 Gray, D3 = 1.54 × 103 Gray, D4 = 1.80 × 103 Gray and D5 = 2.45 × 103 Gray respectively. Yet not optimized, an enhancement of the effective thermal conductivity as much as 23.57% relatively to pure C2H6O2 was observed in stable Ag-C2H6O2 nanofluids. Equivalent results were obtained with Ag-H2O. [ABSTRACT FROM AUTHOR]

Context: Due to high protein concentrations in pastures, dairy cows offered a pasture-based diet often consume excess nitrogen (N), which leads to high ruminal ammonia concentrations and excessive urinary N excretion, thereby contributing to pasture N leaching. Aims: To study the effect of administration of natural zeolite on ruminal pH and ammonia production and N excretion in lactating cows offered an all-pasture herbage diet. Methods: In a metabolism stall trial using a crossover trial design, rumen-cannulated Friesian cows were administered either zero (Control, n = 16) or 400 g/day of zeolite (Zeolite; n = 16). Zeolite was divided into two equal portions and administered directly into the rumen before feeding fresh-cut ryegrass-clover herbage at 07:30 and 15:30 hours. Cows were kept in the metabolism stalls for two measurement periods of 5 days each, with each period preceded by an adaptation/washout period of 2 weeks. Feed intake, milk yield, total urine and faecal outputs were measured daily. During the last day of each measurement period ruminal fluid and blood were frequently sampled. Key results: Zeolite administered at 2.2% of dry matter intake (DMI) did not affect daily DMI. Moreover, milk yield and milk composition, including milk urea, were not affected by zeolite administration. In cows administered zeolite the mean 24-h ruminal ammonia concentration was reduced by 1.5 mmol/L (9%) and the ruminal pH pattern in zeolite-administered cows over 24 h was above that of Control cows, but the overall effect on pH was not significant. Zeolite had no effect on plasma urea, total urinary N excreted or faecal N. Of the total N excreted across the groups, 21.7, 50.6 and 27.7% was excreted into milk, urine and faeces respectively. Conclusions: Zeolite administration reduced ruminal ammonia concentration but this did not result in reduced urinary N excretion in dairy cows offered pasture. Implications: Dietary supplementation with zeolite may help to improve aspects of ruminal function in cows consuming pasture, but is unlikely to be an effective tool for reducing N leaching from pastures. [ABSTRACT FROM AUTHOR]

The dairy cow model 'Molly' is a mixed discrete event-continuous system model that simulates feeding, metabolism and lactation of dairy cows. Decades of model development have resulted in a valuable tool in dairy science. Due to the deprecation of the ACSL (Advanced Continuous Simulation Language) programming language, Molly has been translated into C++. This paper describes the translation process and discusses the advantages of the new implementation, one of which is the ability to run Molly within RStudio, a popular integrated development environment (IDE) for data science. [ABSTRACT FROM AUTHOR]

Paddock selection is an important component of grazing management and is based on either an estimate of herbage mass, or the interval since last grazing for each paddock. Obtaining estimates of herbage mass to guide grazing management can be a time consuming task. A value proposition could therefore assist farmers in deciding whether to invest resources in obtaining such information. A farm-scale simulation exercise was designed to estimate the effect of three levels of knowledge of individual paddock herbage mass on profitability of two typical pasture-based dairy systems in New Zealand; a medium input system stocked at 3.2 Friesian-Jersey cross bred cows/ha with ~15% imported feed, and a high input system stocked at 4.5 Friesian cows/ha with ~40% imported feed. The three levels of knowledge were: (1) 'perfect knowledge', where herbage mass per paddock is known with perfect accuracy, (2) 'imperfect knowledge', where herbage mass per paddock is estimated with an average error of 15%, (3) 'low knowledge', where herbage mass is not known, and paddocks are selected based on longest time since last grazing. In both systems, grazing management based on imperfect knowledge increased farm operating profit by ~NZ$385/ha at a milk price of NZ$6.33/kg milksolids (fat + protein) compared with low knowledge. Perfect knowledge added a further NZ$155/ha to profit. The main driver of these results is the level of accuracy in daily feed allocation, which increases with improved knowledge of herbage availability. This allows feed supply and demand to be better matched, resulting in less incidence of under- and over-feeding, higher milk production, and more optimal post-grazing residual herbage mass to maximise herbage regrowth. Knowledge of herbage mass per paddock is important for managing rotational grazing on pasture-based dairy farms. The aim of the present study was to model a value proposition for collecting and using this information, with a value estimated at NZ$385/ha versus a cost of collecting of NZ$20-40/ha. This result can help farmers evaluate the effort of collecting the data versus the opportunity to improve the profitability of their businesses. [ABSTRACT FROM AUTHOR]

Measurements of the dose equivalent at different distances from the isocenter of the proton therapy center at iThemba LABS were previously performed with a tissue-equivalent proportional counter (TEPC). These measurements showed that the scattered radiation levels were one or two orders of magnitude higher in comparison to other passive scattering delivery systems. In order to reduce these radiation levels, additional shielding was installed shortly after the measurements were done. Therefore, the aim of this work is to quantify and assess the reduction of the secondary doses delivered in the proton therapy room at iThemba LABS after the installation of the additional shielding. This has been performed by measuring microdosimetric spectra with a TEPC at 11 locations around the isocenter when a clinical modulated beam of 200 MeV proton was impinging onto a water phantom placed at the isocenter. [ABSTRACT FROM AUTHOR]

Detailed representation of ingesta inflow to and digesta outflow from the rumen is critical for improving the modelling of rumen function and herbage intake of grazing ruminants. The objective of the current work was to extend a mechanistic model of a grazing ruminant, MINDY, to simulate the dynamic links between ingestive and digestive processes as affected by forage and sward features (e.g. sward structure, herbage chemical composition) as well as the internal state of the animal. The work integrates existing aspects of forage ingestion, oral physiology and rumen digestion that influence ingesta characteristics and digesta outflows from the rumen, respectively. The paper describes the structure and function of the new development, assessing the new model in terms of dynamic changes of oral processing of ingesta and rumen dilution rate under different grazing contexts. MINDY reproduces characteristics of ingesta inflow to and digesta outflow from the rumen of grazing ruminants, achieving temporal patterns of occurrence within and between meals, similar to those for grazing animals reported in the literature. The model realistically simulates changes in particle size distribution of the ingestive bolus, bolus weight and rumen dilution rate in response to contrasting grazing management regimes. The new concepts encoded in MINDY capture the underlying biological mechanisms that drive the dynamic link between ingestion and digestion patterns. This development advances in the understanding and modelling of grazing and digestive behaviour patterns of free-ranging ruminants. [ABSTRACT FROM AUTHOR]

Measurement of water consumption and urinary nitrogen (UN) excretion of individual grazing ruminants is difficult, time-consuming and expensive. Therefore, prediction and modelling are critical for research to improve N and water use efficiency. The objective of the current work was to use a mechanistic model of a grazing ruminant, MINDY, to represent drinking and urination diurnal patterns, and the resulting pattern of UN excretion. This work is primarily an integration of existing knowledge of basic urination physiology and water dynamics in ruminants. MINDY reproduces observed patterns of urination achieving the correct temporal occurrence, relative volumes and nitrogen (N) concentration of individual urination events for a grazing dairy cow, comparable with those reported in the literature. The model simulates daily water imbibed and UN realistically, as well as ingestion rates for herbages with different protein content and contrasting grazing managements. Results of a cross-validation indicate that the root mean square prediction error and mean absolute error as % of the observed mean, respectively, were 26 and 23% for daily water imbibed, 26 and 27% for urination volume, and 25 and 19% for the frequency of urination. Although further parameterization and validation are needed, for a new development in an exploratory model like MINDY, these numbers are encouraging and reflect that the concepts encoded capture many of the underlying biological mechanisms that drive the diurnal pattern and daily UN excretion, as well as thirst, acceptable. [ABSTRACT FROM PUBLISHER]

This study used the DairyNZ Whole Farm Model to assess the cost–benefit of duration-controlled grazing (DCG) to reduce the time dairy cows spend on pastures with high soil water content. Within the model, grazing duration was reduced from 21 hours down to 17, 13 or 0 hours when soil moisture was above a critical water content. Scenario farms encompassed four climatic regions of New Zealand and two soil types. Regardless of region, soil type or grazing duration, implementation of DCG was not profitable except in one single instance. Furthermore, increased pasture production in response to DCG was minimal due to poor pasture management. Farms located on poorly drained soils experienced more wet days per year, thereby increasing the frequency of standoff pad use and higher operational costs. Results indicate that any financial benefit that was gained from protecting imperfectly drained and poorly drained soils through DCG was diminished by a high capital repayment and operational cost associated with the off-paddock facility. [ABSTRACT FROM PUBLISHER]

We report on the optical performances of laccaic acid dye in solution at different concentrations and dye-poly(methyl methacrylate) composite thin films. The linear spectral characteristics including optical constants, i.e. refractive index ( n) and extinction coefficient ( k), were carried out in a comprehensive way through absorbance, fluorescence and ellipsometric studies. The nonlinear optical parameters such as nonlinear absorption coefficient β (or β), the imaginary third-order susceptibility (Im[ χ]) and the imaginary part of second-order hyperpolarizability ( γ) of the samples were evaluated using the open-aperture Z-scan technique with a laser pulse duration of 10 ns at 532 nm wavelength. The corresponding numerical values of these parameters were of 10, 10 and 10 order, respectively. Two-photon absorption was revealed to be the main driving physical mechanism in the nonlinear response. This suggests that laccaic acid dye can be a potential candidate for NLO materials application. [ABSTRACT FROM AUTHOR]

The work presented here represents additions to the mechanistic and dynamic model of a grazing dairy cow (MINDY). The additions include a module representing preference and selection, based on two theories, namely, post-ingestive feedback and discomfort. The model was evaluated by assessing its ability to simulate patterns of preference and selection in response to a variety of feeding management. The improvements detailed here enable a realistic simulation of patterns of food selection by grazing ruminants, based on a range of feeding situations from different studies with cattle and sheep. These simulations indicate that the concepts encoded in MINDY capture several of the underlying biological mechanisms that drive preferences and selective behaviour. Thus, simulations using MINDY allow prediction of daily and diurnal patterns of selection based on preference, derived from some post-ingestive feedbacks and total discomfort. Estimates of herbage intake and parallel measurements of ingestive behaviour, rumen function and metabolism in grazing ruminants pose experimental and technical difficulties, and matching these processes to animal preference and selective behaviour is a greater challenge. As a consequence, advances in knowledge of foraging behaviour and dietary choice are slow and costly. On completion of more thorough testing, MINDY can be used as a tool for exploratory mechanistic research, to design and organise experimental programs to address a range of factors that control intake and its ecology, helping advance knowledge faster and at a low cost. In this paper, we describe a new development of MINDY, a model of the diurnal grazing pattern of a dairy cow. This development integrates a theory of dietary choice, based on post-ingestive feedbacks and total discomfort. The new MINDY simulates daily and diurnal patterns of selective grazing behaviour of ruminants from several studies. The ability to model preference and selective behaviour is useful for mechanistic research on foraging behaviour, intake and design of feeding managements for grazing ruminants. [ABSTRACT FROM AUTHOR]

The largest contributor to nitrogen (N) leaching from ryegrass-clover pasture based dairy farms is the surplus feed N excreted as urinary N (UN) onto pastures. Pastures consisting of mixtures of ryegrass, herbs and legumes (diverse pastures) have shown potential to yield similar DM, but with a lower N content and a higher water soluble carbohydrate : crude protein ratio compared with standard ryegrass-clover pastures. These diverse pastures have shown the potential to lower the UN excreted by dairy cows in short-term, late-lactation studies. This modelling study was designed to scale the results from component studies up to farm and over a full season to evaluate the potential of diverse pastures to become a suitable strategy for reducing N leaching on New Zealand dairy farms. The Molly cow model was tested against observed data from one indoor and one outdoor study where feeding diverse pasture resulted in UN (N excreted in urine g/day) reductions of 50% and 17%, respectively. The model predicted UN reductions of 23% and 17%. Farm-scale model scenarios, where 20% or 50% of the farm was sown with diverse pastures, resulted in 2% and 6% reductions in UN deposited onto paddocks. This reduction was smaller than expected with some system interactions related to seasonal feed supply, diet composition and total N intake being likely to play a role. The reduction in UN onto paddocks, together with a dilution effect from larger urine volumes per cow per day as a result of lower DM% of diverse pastures, resulted in N leaching reductions of 11% and 19% for the two scenarios, respectively. This potential to reduce N leaching needs to be evaluated further in the context of farm profitability when other aspects of diverse pastures such as yield, persistency, drought resistance and ability to extract N from the soil becomes part of the farm-system analysis. We used models in an attempt to scale the results from component studies up to farm and over a full season to evaluate the potential of diverse pastures (mixtures of ryegrass, herbs and legumes) to reducing nitrogen leaching. The combined reduction in urinary nitrogen load and concentration in farm systems with 20% or 50% of the land in diverse pastures has the potential to reduce nitrogen leaching by 11% or 19%. [ABSTRACT FROM AUTHOR]

Abstract Possible constraints on the passive recovery of bare areas in the Karoo, a semiarid region in South Africa, include inadequate supply of seed, availability of suitable microsites for plant establishment, altered soil properties, and the truncation of key soil biotic processes. Here we investigate the possibility of initiating the restoration of bare areas by soil surface treatments with gypsum (CaSO4 ) and/or organic mulch. We also apply an exogenous seed source to test the hypothesis that seed availability limits autogenic recovery. Both gypsum and mulch improved rain water infiltration, gypsum more so than mulch, and both treatments resulted in significantly higher numbers of reseeded seedlings compared with controls. Gypsum also improved the survival of the cohorts of seedlings of the larger seeded Tripteris sinuata . Tripteris showed the highest number of seedlings (maximum count of 150 seedlings/1,000 viable seeds sown) and surviving plants of the three reseeded species, which included two small-seeded species, Ruschia spinosa and Chaetobromus dregeanus . Throughout the study period significantly higher plant volumes of naturally seeded annuals and perennials were recorded in the gypsum and/or mulch treatments compared with the controls. Germination and emergence of reseeded and naturally seeded plants appears to be determined by the availability of cool season (autumn to spring ) soil moisture, whereas follow-up rainfall during this time is important for plant survival. Mulching of bare areas in the Succulent Karoo has the potential to re-create vegetated areas that will further capture and conserve water, soil, and nutrients. Gypsum also showed positive results but might not be a cost-effective option because of transport costs to these remote arid areas. [ABSTRACT FROM AUTHOR]

The article focuses on a study concerning the selenium content of tooth enamel. It states that epidemiologic studies suggest there is a positive association between the consumption of small amounts of dietary selenium during the tooth formation period and an increased risk of dental caries. It comments that animal studies corroborated this and that selenium was incorporated into the organic fraction of dentin and dental enamel, replacing sulfur in methionine and cystine, and might interfere with apatite growth and nucleation. It states that a study of the dental caries incidence of black and white South African high school students was determined in an urban area, with neutron activation analysis used on the enamel of extracted sound permanent teeth.