Stochastic model for simulating maize yield

Maize is one of the most important crops in the world. The products generated from this crop are largely used in the starch industry, the animal and human nutrition sector, and biomass energy production and refineries. For these reasons, there is much interest in figuring the potential grain yield of maize genotypes in relation to the environment in which they will be grown, as the productivity directly affects agribusiness or farm profitability. Questions like these can be investigated with ecophysiological crop models, which can be organized according to different philosophies and structures. The main objective of this work is to conceptualize a stochastic model for predicting maize grain yield and productivity under different conditions of water supply while considering the uncertainties of daily climate data. Therefore, one focus is to explain the model construction in detail, and the other is to present some results in light of the philosophy adopted. A deterministic model was built as the basis for the stochastic model. The former performed well in terms of the curve shape of the above-ground dry matter over time as well as the grain yield under full and moderate water deficit conditions. Through the use of a triangular distribution for the harvest index and a bivariate normal distribution of the averaged daily solar radiation and air temperature, the stochastic model satisfactorily simulated grain productivity, i.e., it was found that 10,604 kg ha(-1) is the most likely grain productivity, very similar to the productivity simulated by the deterministic model and for the real conditions based on a field experiment. © 2012 American Society of Agricultural and Biological Engineers.

Thin-Walled Timber Structures

Due to their efficiency, lightweight, ease of erection and low cost, steel and aluminium thin-walled structures have become very popular in the construction industry over the past few decades. Applications include roof and wall systems (purlins and girts), storage racks, and composite concrete and steel slabs. The effectiveness of these structures lies in the cross-sectional shape of the profiles which enhances their strength by controlling the three fundamental buckling modes: local, distortional, and global. However, despite the attractiveness of these structures, steel and aluminium are greenhouse gas intensive materials and do not produce sustainable structural products. This paper presents an investigation performed at the Griffith School of Engineering, Griffith University, which shows manufacturing these types of profiles in timber is possible. Short composite thinwalled timber Cee-sections (500 mm long) were fabricated by gluing together thin softwood (Araucaria cunninghamii) veneers (1 mm thick). Two types of Ceesections were considered, one with a web stiffener to increase the local buckling capacity of the profile and one without. The profiles were tested in compression and the test results are presented and discussed in the paper in terms of structural behaviour and performance. Further research directions are proposed in order to provide efficient and lightweight sustainable structural products to the timber industry. © RILEM 2014.

Hanging drop: An in vitro air toxic exposure model using human lung cells in 2D and 3D structures

Using benzene as a candidate air toxicant and A549 cells as an in vitro cell model, we have developed and validated a hanging drop (HD) air exposure system that mimics an air liquid interface exposure to the lung for periods of 1 h to over 20 days. Dose response curves were highly reproducible for 2D cultures but more variable for 3D cultures. By comparing the HD exposure method with other classically used air exposure systems, we found that the HD exposure method is more sensitive, more reliable and cheaper to run than medium diffusion methods and the CULTEX (R) system. The concentration causing 50% of reduction of cell viability (EC50) for benzene, toluene, p-xylene, m-xylene and o-xylene to A549 cells for 1 h exposure in the HD system were similar to previous in vitro static air exposure. Not only cell viability could be assessed but also sub lethal biological endpoints such as DNA damage and interleukin expressions. An advantage of the HD exposure system is that bioavailability and cell concentrations can be derived from published physicochemical properties using a four compartment mass balance model. The modelled cellular effect concentrations EC50(cell) for 1 h exposure were very similar for benzene, toluene and three xylenes and ranged from 5 to 15 mmol/kg(dry weight) which corresponds to the intracellular concentration of narcotic chemicals in many aquatic species, confirming the high sensitivity of this exposure method. (C) 2013 Elsevier B.V. All rights reserved.

Potential Animal and Environmental Sources of Q Fever Infection for Humans in Queensland

Q fever is a vaccine-preventable disease; despite this, high annual notification numbers are still recorded in Australia. We have previously shown seroprevalence in Queensland metropolitan regions is approaching that of rural areas. This study investigated the presence of nucleic acid from Coxiella burnetii, the agent responsible for Q fever, in a number of animal and environmental samples collected throughout Queensland, to identify potential sources of human infection. Samples were collected from 129 geographical locations and included urine, faeces and whole blood from 22 different animal species; 45 ticks were removed from two species, canines and possums; 151 soil samples; 72 atmospheric dust samples collected from two locations and 50 dust swabs collected from domestic vacuum cleaners. PCR testing was performed targeting the IS1111 and COM1 genes for the specific detection of C.burnetii DNA. There were 85 detections from 1318 animal samples, giving a detection rate for each sample type ranging from 2.1 to 6.8%. Equine samples produced a detection rate of 11.9%, whilst feline and canine samples showed detection rates of 7.8% and 5.2%, respectively. Native animals had varying detection rates: pooled urines from flying foxes had 7.8%, whilst koalas had 5.1%, and 6.7% of ticks screened were positive. The soil and dust samples showed the presence of C.burnetii DNA ranging from 2.0 to 6.9%, respectively. These data show that specimens from a variety of animal species and the general environment provide a number of potential sources for C.burnetii infections of humans living in Queensland. These previously unrecognized sources may account for the high seroprevalence rates seen in putative low-risk communities, including Q fever patients with no direct animal contact and those subjects living in a low-risk urban environment.

Odour, dust and non-methane volatile organic-compound emissions from tunnel-ventilated layer-chicken sheds: a case study of two farms

An observational study was undertaken to measure odour and dust (PM10 and PM2.5) emission rates and identify non-methane volatile organic compounds (NMVOCs) and odorants in the exhaust air from two tunnel-ventilated layer-chicken sheds that were configured with multi-tiered cages and manure belts. The study sites were located in south-eastern Queensland and the West Gippsland region of Victoria, Australia. Samples were collected in summer and winter on sequential days across the manure-belt cleaning cycle. Odour emissions ranged from 58 to 512 ou/s per 1000 birds (0.03-0.27 ou/s.kg) and dust emission rates ranged 0.014-0.184 mg/s per 1000 birds for PM10 and 0.001-0.190 mg/s per 1000 birds for PM2.5. Twenty NMVOCs were identified, including three that were also identified as odorants using thermal desorption-gas chromatography-mass spectrometry/olfactometry analysis. Odour emission rates were observed to vary with the amount of manure accumulation on the manure belts, being lowest 2-4 days after removing manure. Odour emission rates were also observed to vary with diurnal and seasonal changes in ventilation rate. Dust emissions were observed to increase with ventilation rate but not with manure accumulation. Some NMVOCs were identified at both farms and in different seasons whereas others were observed only at one farm or in one season, indicating that odorant composition was influenced by farm-specific practices and season.

Demographic and functional responses of wild dogs to poison baiting

Lethal control of wild dogs - that is Dingo (Canis lupus dingo) and Dingo/Dog (Canis lupus familiaris) hybrids - to reduce livestock predation in Australian rangelands is claimed to cause continental-scale impacts on biodiversity. Although top predator populations may recover numerically after baiting, they are predicted to be functionally different and incapable of fulfilling critical ecological roles. This study reports the impact of baiting programmes on wild dog abundance, age structures and the prey of wild dogs during large-scale manipulative experiments. Wild dog relative abundance almost always decreased after baiting, but reductions were variable and short-lived unless the prior baiting programme was particularly effective or there were follow-up baiting programmes within a few months. However, age structures of wild dogs in baited and nil-treatment areas were demonstrably different, and prey populations did diverge relative to nil-treatment areas. Re-analysed observations of wild dogs preying on kangaroos from a separate study show that successful chases that result in attacks of kangaroos by wild dogs occurred when mean wild dog ages were higher and mean group size was larger. It is likely that the impact of lethal control on wild dog numbers, group sizes and age structures compromise their ability to handle large difficult-to-catch prey. Under certain circumstances, these changes sometimes lead to increased calf loss (Bos indicus/B. taurus genotypes) and kangaroo numbers. Rangeland beef producers could consider controlling wild dogs in high-risk periods when predation is more likely and avoid baiting at other times.

Evaluation and histological examination of a Campylobacter fetus subsp. venerealis small animal infection model

Bovine genital campylobacteriosis (BGC), caused by Campylobacter fetus subsp. venerealis, is associated with production losses in cattle worldwide. This study aimed to develop a reliable BGC guinea pig model to facilitate future studies of pathogenicity, abortion mechanisms and vaccine efficacy. Seven groups of five pregnant guinea pigs (1 control per group) were inoculated with one of three strains via intra-peritoneal (IP) or intra-vaginal routes. Samples were examined using culture, PCR and histology. Abortions ranged from 0 to 100 and re-isolation of causative bacteria from sampled sites varied with strain, dose of bacteria and time to abortion. Histology indicated metritis and placentitis, suggesting that the bacteria induce inflammation, placental detachment and subsequent abortion. Variation of virulence between strains was observed and determined by culture and abortion rates. IP administration of C. fetus subsp. venerealis to pregnant guinea pigs is a promising small animal model for the investigation of BGC abortion.

The Ethics of a Co-regulatory Model for Farm Animal Welfare Research

Standards for farm animal welfare are variously managed at a national level by government-led regulatory control, by consumer-led welfare economics and co-regulated control in a partnership between industry and government. In the latter case the control of research to support animal welfare standards by the relevant industry body may lead to a conflict of interest on the part of researchers, who are dependent on industry for continued research funding. We examine this dilemma by reviewing two case studies of research published under an Australian co-regulated control system. Evidence of unsupported conclusions that are favourable to industry is provided, suggesting that researchers do experience a conflict of interest that may influence the integrity of the research. Alternative models for the management of research are discussed, including the establishment of an independent research management body for animal welfare because of its public good status and the use of public money derived from taxation, with representation from government, industry, consumers, and advocacy groups.

A promising and simple method to quantify soil/manure mixing on beef feedlot pens

On beef cattle feed pen surfaces, fresh and decayed manure is mixed with base rock or soil (base). Quantifying this mixing has beneficial applications for aspects including nutrient and greenhouse gas budgeting. However, no practical methods exist to quantify mixing. We investigated if measuring element concentrations in: (A) fresh manure, (B) base material, and (C) pen manure offers a promising method to quantify manure/base mixing on pen surfaces. Using three operational beef feedlots as study sites, we targeted carbon (C), and silicon (Si), which are the two most abundant and easily measurable organic and inorganic elements. Our results revealed that C concentrations were strongly (>15 times) and significantly (P < 0.05) higher whereas Si concentrations strongly (>10 times) and significantly (P < 0.01) lower in fresh manure than base material at all three sites. These relative concentrations were not significantly impacted by manure decay, as determined by an 18-week incubation experiment. This suggested that both of these elements are suitable markers for quantifying base/manure mixing on pens. However, due to the chemical change of manure during decay, C was shown to be an imprecise marker of base/manure mixing. By contrast, using Si to estimate base/manure mixing was largely unaffected by manure decay. These findings were confirmed by measuring C and Si concentrations in stockpiled pen surface manure from one of the sites. Using Si concentrations is a promising approach to quantify base/manure mixing on feed pens given that this element is abundantly concentrated in soils and rocks.