Evaluation of Halftone Images by Modulation Transfer

This paper concerns an investigation for determining the feasibility of employing methods, similar to those used in conventional continuous tone photography, for determining the modulation transfer of variable area images on lithographic films. It deals with some of the special problems of separating the signal (the image) from the noise (the pattern of the screen), and describes the instruments and approaches to data read-out

Genetic insights into climate-driven range expansion of a coastal foundation species

In this thesis, I address gaps in our understanding of how climate-driven range expansion can shape genetic variation within a coastal foundation species and how the resulting genetic changes may have broader ecological consequences. To do this, I study the neotropical black mangrove (Avicennia germinans) across its distribution in the United States, and then I focus on its expanding Atlantic Florida range margin. First, in Chapter 2, I find that genetic variation within A. germinans declines towards three range margins in the United States, but that this reduction may not constrain adaptation within this species as range-margin A. germinans exhibit shifts in functional traits consistent with greater cold tolerance. Leveraging these insights and genetic data, I then document patterns in mating system and dispersal, factors that can shape intraspecific genetic variation and influence expansion success, towards the Atlantic Florida range margin. In Chapter 3, I find evidence for plastic shifts towards greater self-fertilisation at this sparsely-populated range margin, a mechanism that can facilitate colonisation of new areas. In Chapter 4, I show how extreme storm events may facilitate poleward expansion of A. germinans and how this form of episodic dispersal can shape genetic variation within newly-colonised populations. Finally, I evaluate potential ecological consequences of the unique genetic variation found within these Atlantic Florida A. germinans. In Chapter 5, at the scale of a range-margin population, I find that genetically-similar A. germinans harboured similar fungal communities, a relationship that may have implications for the fitness of these mangrove hosts. In Chapter 6, using a greenhouse common garden, I demonstrate a genetic basis to adaptative trait shifts within these range-margin A. germinans that may facilitate future range expansion of this species. These novel insights should improve our ability to predict how mangrove range margins may respond to climate change and help inform future mangrove restoration initiatives

Effects of Diet during the First Winter on Replacement Heifer Weight Gain and Body Condition Score during the Subsequent Grazing Season

In seasonal calving dairy production systems it is important that heifers attain puberty in an appropriate timeframe especially when they are bred to calve at 2 years of age and in systems that impose restricted breeding periods (Ferrell, 1982). Achieving target weights at key time points is critical because, for example, the onset of puberty usually occurs in dairy heifers at 30-40% of their expected mature BW (Heinrichs 1993) which corresponds to approximately 240-320 kg in Holstein heifers. Furthermore, heifers should be managed to achieve 55% to 60% of mature bodyweight (BW) at mating start date (MSD; Patterson et al. 1992). Archbold et al. (2012) has shown that both heifer BW and body condition score (BCS) at MSD are positively associated with calving date and potential milk fat plus milk protein yield when they enter the lactating herd. Heifer rearing is the second largest expense in the dairy system, accounting for approximately 20% of total costs (Gabler et al. 2000). Therefore, it is necessary to focus on reducing costs of production, particularly feed costs, as they account for approximately 80% of total variable costs (Shalloo et al., 2004). One of the methods of reducing feed costs in particular, is by sourcing lower cost feeds. Finneran et al. (2010) reported that kale grazed in-situ ranked as the cheapest alternative to grazed grass and was considerably cheaper than grass silage. Kale has higher crude protein (CP) content than grass silage (Keogh et al. 2009) and may be suitable for inclusion in the diet of replacement dairy heifers. However, kale also tends to have a low neutral-detergent fibre (NDF) concentration (Keogh et al. 2009) suggesting that feeds with a higher NDF concentration (\u3e 500 g/kg DM), such as silage may need to be offered in order to avoid acidosis. The objectives of this study were to i) investigate five contrasting winter feeding regimes on heifer bodyweight (BW) gain and body condition score (BCS), ii) establish if similar BW gain is achieved from a kale only diet compared to a kale + grass silage diet and iii) determine if compensatory growth during the following grazing season exists in replacement heifer rearing systems

Cultivar Influences Milk Production of Grazing Dairy Cows

Perennial ryegrass is considered one of the most important forage grass species used in temperate ruminant animal production systems. Maximizing milk production from grazed grass is a major objective of pastoral-based dairy systems. While DM yield is an important trait, it fails to define the ultimate value of a grass cultivar, which is its potential to improve animal performance from a pasture sward (Reed 1994). The majority of cultivar evaluation trials are conducted under cutting, so therefore inferior cultivars from an animal production perspective may not be identified until commercialisation when animals graze a pasture sward. Reed (1978) reported that ryegrass pastures of similar digestibility can have different animal production responses depending on the season. Without exposure to animal production trials, practical differences between cultivars under field conditions may not be detected. The objective of the current study was to evaluate the effect of four perennial ryegrass cultivars with different sward characteristics on milk yield, milk composition and dry matter intake (DMI) of lactating dairy cows during the spring and mid-season period

Kynurenine pathway metabolism and the microbiota-gut-brain axis

It has become increasingly clear that the gut microbiota influences not only gastrointestinal physiology but also central nervous system (CNS) function by modulating signalling pathways of the microbiota-gut-brain axis. Understanding the neurobiological mechanisms underpinning the influence exerted by the gut microbiota on brain function and behaviour has become a key research priority. Microbial regulation of tryptophan metabolism has become a focal point in this regard, with dual emphasis on the regulation of serotonin synthesis and the control of kynurenine pathway metabolism. Here, we focus in detail on the latter pathway and begin by outlining the structural and functional dynamics of the gut microbiota and the signalling pathways of the brain-gut axis. We summarise preclinical and clinical investigations demonstrating that the gut microbiota influences CNS physiology, anxiety, depression, social behaviour, cognition and visceral pain. Pertinent studies are drawn from neurogastroenterology demonstrating the importance of tryptophan and its metabolites in CNS and gastrointestinal function. We outline how kynurenine pathway metabolism may be regulated by microbial control of neuroendocrine function and components of the immune system. Finally, preclinical evidence demonstrating direct and indirect mechanisms by which the gut microbiota can regulate tryptophan availability for kynurenine pathway metabolism, with downstream effects on CNS function, is reviewed. Targeting the gut microbiota represents a tractable target to modulate kynurenine pathway metabolism. Efforts to develop this approach will markedly increase our understanding of how the gut microbiota shapes brain and behaviour and provide new insights towards successful translation of microbiota-gut-brain axis research from bench to bedside

Developmental Neurotoxicity of Fluoride: A Quantitative Risk Analysis Toward Establishing a Safe Dose for Children

A meta-analysis showed that children with higher fluoride exposure have lower IQs than similar children with lower exposures. Circulating levels of fluoride in blood and urine in children have also been linked quantitatively to significantly lower IQ. Other human and animal studies indicate that fluoride is a developmental neurotoxicant and that it operates in utero. Economic impacts of IQ loss have been quantified. The objective was to use data from the meta-analysis and other studies to estimate a daily dose of fluoride that would protect all children from lowered IQ, and to estimate economic impacts. We used two methods: traditional lowest-observed-adverse-effect (LOAEL)/no-observed-adverse-effect level (NOAEL); and benchmark dose (BMD). We used 3 mg/L in drinking water as an “adverse effect concentration,” with reported fluoride intakes from food, in the LOAEL/NOAEL method. We used the available dose–response data for the BMD analysis. Arsenic, iodine, and lead levels were controlled for in studies we used. BMD analysis shows the possible safe dose to protect against a five-point IQ loss is between 0.0014 and 0.050 mg/day. The LOAEL/NOAEL safe dose range estimate is 0.0042–0.16 mg/day. The economic impact for IQ loss among US children is loss of tens of billions of dollars

Multiplex microsatellite PCR panels for the neotropical mangrove Rhizophora mangle: combining efforts towards a cost-effective and modifiable tool to better inform conservation and management

Better-informed mangrove conservation and management practices are needed as the ecosystem services provided by these intertidal forests continue to be threatened by increasing anthropogenic pressures and climate change. Multiple layers of knowledge are required to achieve this goal, including insights into population genetics of mangrove species. Understanding the importance of population-genetic insights to conservation, multiple research groups have developed microsatellite loci for the widespread, neotropical red mangrove, Rhizophora mangle. However, although a wealth of genetic markers exist, empirical research is limited in the number of these loci employed. Here, we designed two multiplex PCR panels that combine seven novel loci developed for this work and eight previously-developed loci from three research groups to generate 15-locus genotypes, more than twice the average number of loci used in previous research, in only two PCR. We demonstrated utility in R. mangle from four sites across ~2500 km near this species’ northern latitudinal limits, and that these multiplex panels were better able to delineate populations than data subsets with numbers of loci comparable to previous research. We focus our discussion on how this tool is a more-informative, efficient (both in terms of time and resources), and easily-modifiable alternative to address many pressing conservation and management issues, such as the generation of baseline genetic data for areas not yet studied, better defining management units, and monitoring genetic effects of restoration projects. We also provide a quick protocol that outlines each step in this procedure to facilitate the use of this tool by others