Development of an uncompensated diagnostic for the measurement of phase-resolved characteristics in radio-frequency plasmas

In recent years, plasma technology has found its way into a wide and diveme array of manufacturing techniques and facilities, ranging from biomedical applications to microprocessor fabrication. In all cases, greater overall efficiency and usefulness can be improved by understanding the fundamentals of how and why plasmas behave the way they do. In order to achieve this understanding, we use a wide variety of plasma diagnostics to perform measurements of all the Important plasma parameters. The work presented in this thesis is focused on electrostatic probes, in particular, the Langmuir probe, which is arguably the most common diagnostic in the world of experimental plasma physics. Eventhough the Langmuir probe was invented over 80 years ago and was the first diagnostic tool used for studying plasmas in detail, it is still widely used today. The reason it has survived, even in the presence of more accurate and advanced methods, is because no other diagnostic can obtain so many of the important parameters in such a relatively simple way. However, in many cases the Langmuir probe can only be used as an estimator of plasma parameters, as its accuracy is questionable, particularly in radio frequency(rf) discharges. The inaccuracies are caused by the non-linear dynamics of the plasma sheath, which result in an extra dc current component being measured. This extra component, AI, results in a difference between the time average I-V characteristic and the effective dc I-V characteristic. In 'normal' operation, the Langmuir probe only measures time averaged values, and so, errors result, such as, over-estimation of electron temperature, Te. Compensated Langmuir probes have been developed to try and eliminate the distortion effect of the plasma potential oscillation on the probe measurements RF compensation usually involves high impedance inductors placed near the tip and a large compensation electrode, both des~gnedt o make the probe tip follow the plasma voltage oscillation, thus reducing it impact on the measurements. Many semiconductor processing tools use capacitively coupled plasma discharges (CCP's) for etching, deposition and sputtering. CCP's generally have a large voltage oscillation so the ability to accurately measure the plasma parameters under these conditions is highly desirable. Unfortunately, even highly compensated probes have difficulty in providing accurate measurements under most CCP conditions. This 1s because, in practice, it is very difficult to achieve sufficient probe impedance relative to the sheath impedance and also probe construction can be difficult, especially for commercial discharges. For these reasons, and others, even compensated probes do not give reliable results in plasmas with large voltage oscillations. This was the main motivation for the work presented in this thesis - to design a probe capable of accurately measuring the I-V characteristics and plasma potential oscillations without the need for complex compensation techniques. To achieve this goal, a simple uncompensated Langmuir probe was mvestigated. A computer model was constructed in MatLab to aid in the understanding. A technique was developed in which the dzstortzon-free I-V characteristic is obtained from the time-averaged (distorted) I-V trace by utilizing the rf data measured through a capacitively-coupled, synchronized rf current sensor. This allows phase dependant characteristics to be obtained and also allows reconstruction of the plasma potential oscillation, complex sheath Impedance and other important properties. The probe deslgn and circu~try are relatively simple, thus providing a useful diagnostic for probing radio-frequency plasmas

Spatial variation of heart failure and air pollution in Warwickshire, UK : an investigation of small scale variation at the ward-level

Objectives To map using geospatial modelling techniques the morbidity and mortality caused by heart failure within Warwickshire to characterise and quantify any influence of air pollution on these risks. Design Cross-sectional. Setting Warwickshire, UK. Participants Data from all of the 105 current Warwickshire County wards were collected on hospital admissions and deaths due to heart failure. Results In multivariate analyses, the presence of higher mono-nitrogen oxide (NOx) in a ward (3.35:1.89, 4.99), benzene (Ben) (31.9:8.36, 55.85) and index of multiple deprivation (IMD; 0.02: 0.01, 0.03), were consistently associated with a higher risk of heart failure morbidity. Particulate matter (Pm; −12.93: −20.41, −6.54) was negatively associated with the risk of heart failure morbidity. No association was found between sulfur dioxide (SO2) and heart failure morbidity. The risk of heart failure mortality was higher in wards with a higher NOx (4.30: 1.68, 7.37) and wards with more inhabitants 50+ years old (1.60: 0.47, 2.92). Pm was negatively associated (−14.69: −23.46, −6.50) with heart failure mortality. SO2, Ben and IMD scores were not associated with heart failure mortality. There was a prominent variation in heart failure morbidity and mortality risk across wards, the highest risk being in the regions around Nuneaton and Bedworth. Conclusions This study showed distinct spatial patterns in heart failure morbidity and mortality, suggesting the potential role of environmental factors beyond individual-level risk factors. Air pollution levels should therefore be taken into account when considering the wider determinants of public health and the impact that changes in air pollution might have on the health of a population

Apprehension and interest: Therapist and student views of the role emerging placement model in the Republic of Ireland

Purpose - Role-emerging placements have been used internationally within occupational therapy education but are relatively new to Ireland. At times, there has been a debate in the profession regarding the use of this placement model. This paper aims to generate views from both occupational therapists and occupational therapy students on the use of role-emerging placements in the Republic of Ireland. Design/methodology/approach - Electronic surveys were administered to occupational therapy students and occupational therapists in Ireland. Quantitative data were analysed using the SPSS Statistics software package and the content of the open question responses were analysed into themes. Findings - Occupational therapists (n = 60) and occupational therapy students (n = 45) indicated that there were inconsistent views surrounding role-emerging placements. It is deemed as an effective method for student learning, but apprehension exists around inclusion within occupational therapy programmes in the Republic of Ireland. Preference was indicated towards inclusion of role-emerging placements on a part-time basis within formal occupational therapy education. Originality/value - Both respondent groups viewed that role-emerging placements can positively influence new areas of occupational therapy practice and concern over the use of the placement model requires further exploration and debate. This study is from an Irish context, although there are similarities with other countries’ use of the placement model. There is a need for research through an in-depth exploration of the learning experience of undertaking role-emerging placements from the students’ perspective and identification of supports required to promote an optimal learning experience

TB84: Controlling the Saratoga Spittlebug in Young Red Pine Plantations by Removal of Alternate Hosts

The Saratoga spittlebug, Aphrophora saratogensis (Fitch), is a major pest of young red pine (Pinus resinosa Ait. ) and jack pine (Pinus banksiana Lamb. ) plantations in the Lake States, Ontario, and more recently in the Northeast. Although insecticides are successful in controlling the Saratoga spittlebug, the biology of the insect raises the possibility of an alternative method of control. The spittlebug requires an alternate host to complete its nymphal development. The objective of this study was to investigate the feasibility of using herbicides to control nymphal host plants of the spittlebug in red pine plantations.https://digitalcommons.library.umaine.edu/aes_techbulletin/1113/thumbnail.jp

Increasing intake by the development of optimal grazing management in relation to animal behaviour at pasture.

End of Project ReportIn each month from July to December, grazing activity for each of 12 animals was recorded over a number of days continuously using vibrarecorders. The work was done at Killarney National Park and the animals were heifers of the Kerry breed living under semi-natural conditions with abundant pasture available. In July (16 hour day-length) - all animals began grazing at dawn and grazed for about 2.5 hours. This first bout was followed at intervals of about 2 hours by shorter bouts each about one hour in duration. In late afternoon another bout commenced which continued for 4 to 5 hours through until after dusk. During darkness, about midnight, there was a short bout of grazing. All of the animals behaved thus and the pattern was repeated each day. Total grazing time was near 11 hours each day. By October day-length had decreased. There was still a bout at dawn and a bout at sunset. As in July there were three smaller bouts but all occurred during darkness. The total grazing time was close to 11 hours as before. The pattern of grazing was consistent between animals and days. In August-September-October and November there were always two major bouts of grazing related to dawn and dusk. Grazing total time was always near 11 hours. As day-length decreased the smaller daylight bouts were progressively replaced by bouts during darkness. Similar patterns were also found in studies of grazing Holstein/Friesian heifers and of housed non-lactating cows at Moorepark. The primary feature of the grazing pattern is the bout. The bout implies that there is a control that determines when grazing commences and ends. Rumen capacity plays a part but does not explain why minor bouts are only one hour and major bouts are more than 4 hours. The rigid association of the two major bouts with dawn and dusk implies that light also plays a part. That the total grazing time is constant suggests that yet another control is operating that is related to the state of the animal relative to a target state. And this control relates to a 24-hour period. Domestic bovines do not display any patterns of behaviour related to seasonal or lunar cycles. The patterns appear to be circadian and in that case it would not be surprising to find that the suggested light cue was present as a means of measuring the day.EU Structural Funds (EAGGF