Growth by pulsed laser deposition and characterisation of zinc oxide thin films and nanostructures

This thesis describes the growth and characterisation of ZnO thin films and nanostructures grown using the pulsed laser deposition technique. In this technique, a solid state Nd:YAG laser operating at 266 nm and with a 6 ns pulse width was fired at a sintered, ceramic target to produce an expanding plume of ZnO into a vacuum chamber (pressures in the 10−1 mbar range). The plume material condenses on various substrates, chiefly sapphire, to form a thin film. The samples were analysed using a range of structural, optical, and surface analyses to determine the effects that varying pressures, temperatures, and laser energy fluence had on the growth modes of these thin films and nanostructures. Additionally, a study was carried out to determine the effects a mixed background gas (O2 and Ar) has on the nanostructured growth. A model for this case was proposed. Finally, a biomedical application of ZnO was investigated to determine the potential of ZnO thin films for the sterilisation of biofilms of the bacterium Staphylococcus epidermidis. It was found that such a biofilm grown atop a ZnO thin film is inactivated after exposure to UV light while submerged in an aqueous solution

The production of ultrafine fibres using variations of the centrifugal spinning technique

Centrifugal spinning uses high speed spinneret rotation to generate and elongate jets of polymeric material in to fine fibres. Variations of this basic technology has been used to form ultrafine fibres from: polypropylene (PP), ubiquitous in the nonwovens industry and a key material for nonwovens; polycaprolactone (PCL), a biocompatible polymer used previously as a biological scaffold; and polyvinylpyrrolidone with 1-triacontane (PVP/TA), a copolymer found in the cosmetics industry. This work demonstrated the melt centrifugal spinning of PP into sub-micron fibres ≤ 500 nm in diameter, and PCL fibres ≤900 nm in diameter. The influences of material properties and processing conditions on the fibre and webs properties were investigated and relationships established. For melt spinning, increasing the rotational speed will reduce the average fibre diameter and when solution spinning PCL a binary solvent produced finer fibres with increased surface textures. The spinning of PVP/TA into fibres demonstrated in this work has been previously unreported. PVP/TA fibres were created by centrifugal spinning at low temperatures were as fine as 1.5 µm on average. These fibres were used as an adsorbent and showed an affinity for the capture and retention of disperse dyes and hydrocarbons on the fibre surface. Carbon nanotube composite fibres were created by dispersing the nanotubes in both PP and PCL polymers using ultrasonic waves. The addition of carbon nanotubes significantly increased the level of beading during spinning in both PP and PCL as their presence causing an increase in Rayleigh instabilities. The addition of nanotubes did not improve web strength of the products compared to virgin polymer. Overall, centrifugal spinning has proven to be a highly versatile technique, capable of producing ultrafine fibres from a range of polymer feed materials which have potential to be utilised in a range of specialist applications

Centrifugally Spun PHBV Micro and Nanofibres

This paper reports the first study on centrifugal spinning of PHBV fibres. Fibres were spun from solution using a range of polymer concentrations, spin speeds and spinneret to collector distances. A PHBV polymer concentration of 25% w/v spun at 9000 r min⁻¹ produced the highest quality fibres, with fibre diameters predominantly in the 0.5-3 μm range. The rate at which fibre could be produced at the 9000 r min‾¹ spin speed and with a spinneret to collector distance of 39.2 cm was equivalent to 11 km of fibre per minute per needle. Average fibre strengths of 3 MPa were achieved, together with average moduli of 100 MPa, indicating that the fibres had higher strength but lower stiffness than electrospun PHBV. The productivity and mechanical properties achieved, together with the excellent biocompatibility of PHBV, means that these fibres have potential for application in a range of biomedical applications

Effect of Fibre Type on Mechanical Properties of Nonwoven Reinforced TPU Composites

Nonwoven-reinforced composites were produced using both low modulus fibres (lyocell, polyethylene terephthalate, and polyamide) and high modulus aramid fibres (polyphenylene terephthalamide) in thermoplastic polyurethane (TPU) matrix. Preferentially oriented web preforms were prepared by carding and pre-needling before impregnating the nonwovens in a thermoplastic polyurethane resin matrix. Composites were prepared by compression moulding and mechanical properties were evaluated. Scanning Electron Microscopy was employed to study the fibre-to-matrix interface in the nonwoven-reinforced composites. It was found that nonwoven reinforcement provided a range of mechanical properties, mainly linked to fibre properties and orientation of fibres in the web, apparently unaffected by the mechanical properties of the web. Furthermore, all studies fibres were thoroughly embedded in the matrix

Military Veterans and Their PTSD Service Dogs: Associations Between Training Methods, PTSD Severity, Dog Behavior, and the Human-Animal Bond

Introduction: Psychiatric service dogs are increasingly being sought out by military veterans as a complementary intervention for posttraumatic stress disorder (PTSD). After receiving a service dog, many veterans continue training their service dog at home. Our objective was to explore the associations between training methods, PTSD severity, service dog behavior, and the veteran-service dog bond in a population of military veterans with PTSD.Methods: Post-9/11 military veterans with PTSD who had received a psychiatric service dog were recruited from a national service dog provider. A total of 111 veterans (M = 40.1 ± 8.3 years, 80% male) participated in an online survey regarding frequency of training methods, PTSD symptom severity, service dog behavior, and the human-animal bond. Service dogs were predominately Labrador Retriever purebreds or mixes of various breeds (66% male) and mostly obtained from shelters or rescues (58%). Training methods were divided into five categories: positive reinforcement (e.g., physical praise), negative punishment (e.g., ignoring the dog), positive punishment (e.g., verbal correction), dominance (e.g., alpha roll), and bond-based (e.g., co-sleeping). Data were analyzed using general linear models.Results: Veterans self-reported using all five categories of training methods at least once a month. More frequent use of positive punishment was associated with less closeness with their service dog (p = 0.02), more fear (p = 0.003), less eye contact (p < 0.0001), and less trainability (p = 0.04). More frequent use of positive reinforcement was associated with higher closeness to their service dog (p = 0.002) and perceived increased attachment behavior (p = 0.002) and playfulness (p = 0.002). More frequent use of bond-based methods was associated with higher closeness to their service dog (p = 0.02). PTSD severity was not significantly associated with reported dog behavior, temperament, or veteran-service dog closeness.Conclusion: Military veterans with PTSD service dogs reported using many training methods that were associated with different outcomes. In general, the reported use of positive reinforcement or bond-based training methods were associated with reporting more positive outcomes while the reported use of positive punishment was associated with reporting more negative outcomes. Educating service dog organizations and recipients about the impacts of training methods could be beneficial for service dog efficacy and welfare

Animal-assisted interventions: making better use of the human-animal bond

In the third of Veterinary Record’s series of articles promoting One Health, Daniel Mills and Sophie Hall discuss the therapeutic effects of companion animals, the influence of pets on childhood development and how researchers are elucidating the true value of animal companionship. IT has been proposed that the One Health initiative should be extended to ‘One Welfare’, in recognition of the diverse links between the welfare of human beings and other animals (Anon 2012). This is particularly true for companion animals, with a growing body of evidence indicating the diverse stress-ameliorating effects of the relationships between people and pets; however, their importance to mental and physical health from a developmental perspective(particularly for people) is perhaps not given the attention it deserves. This is potentially a serious oversight for ealthcare professionals, policymakers and government, at a time when there are concerns over the growing cost of public healthcare in the industrialised world. Indeed, in the current economic climate, there is perhaps a greater need than ever to consider novel approaches to preventive healthcare, such as the value of animal companionship, since such approaches are potentially more cost-effective and socially acceptable than technological solutions. Companion animals should not be considered a luxury or unnecessary indulgence, but rather, when cared for appropriately, they should be seen as valuable contributors to human health and wellbeing and, as a result, society and the broader economy

A Systematic Scoping Review: What is the Risk from Child-Dog Interactions to Dog Quality of Life?

There is growing interest in the value of assistance dogs, therapy dogs, and untrained pet dogs, for supporting children with specific needs. Research in this area focuses almost exclusively on the effect of dogs on child well-being and quality of life. The lack of research reporting the role of dog quality of life in this dynamic limits the development of best practice guidelines. Little attention has been paid to the risk from structured and unstructured exposures to children for dog quality of life to best protect the well-being of both parties and maximize the quality of interactions to enhance therapeutic effects. This systematic scoping review searched five databases to address the question ‘what is the risk from child-dog interactions to the quality of life of assistance, therapy and pet dogs?’ The review identified that there is limited specific scientific investment in understanding the relationship between child-dog interactions and dog quality of life. Of the five relevant articles that were identified specifically addressing this issue, two looked at aspects relating to quality of life of dogs living in family homes, (1=pet dogs, 1=trained assistance dogs). The remaining three papers reported factors relevant to quality of life of trained dogs working in structured therapy sessions. Specific child-dog interactions may be important risk factors to consider in relation to dog quality of life, specifically interactions involving unprovoked child attention (e.g., rough contact), interactions and environmental predictability (e.g., meltdowns and recreation time) and child initiated games (e.g., ‘dress up’). Identifying and monitoring the intensity and frequency of these interactions may be important for protecting dog quality of life in the therapeutic and home environment

Children reading to dogs: a systematic review of the literature

Background Despite growing interest in the value of human-animal interactions (HAI) to human mental and physical health the quality of the evidence on which postulated benefits from animals to human psychological health are based is often unclear. To date there exist no systematic reviews on the effects of HAI in educational settings specifically focussing on the perceived benefits to children of reading to dogs. With rising popularity and implementation of these programmes in schools, it is essential that the evidence base exploring the pedagogic value of these initiatives is well documented. Methods Using PRISMA guidelines we systematically investigated the literature reporting the pedagogic effects of reading to dogs. Because research in this area is in the early stages of scientific enquiry we adopted broad inclusion criteria, accepting all reports which discussed measurable effects related to the topic that were written in English. Multiple online databases were searched during January-March 2015; grey literature searches were also conducted. The search results which met the inclusion criteria were evaluated, and discussed, in relation to the Oxford Centre for Evidence Based Medicine levels of evidence; 27 papers were classified as Level 5, 13 as Level 4, 7 as Level 2c and 1 as Level 2b. Conclusion The evidence suggests that reading to a dog may have a beneficial effect on a number of behavioural processes which contribute to a positive effect on the environment in which reading is practiced, leading to improved reading performance. However, the evidence base on which these inferences are made is of low quality. There is a clear need for the use of higher quality research methodologies and the inclusion of appropriate controls in order to draw causal inferences on whether or how reading to dogs may benefit children’s reading practices. The mechanisms for any effect remain a matter of conjectur