• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 256
  • 46
  • 20
  • 20
  • 20
  • 20
  • 20
  • 20
  • 3
  • Tagged with
  • 500
  • 500
  • 239
  • 165
  • 80
  • 80
  • 57
  • 52
  • 46
  • 41
  • 40
  • 36
  • 30
  • 30
  • 28
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
201

Effects of pure and impure carbon dioxide (CO2) on soil chemistry

Wei, Yang January 2013 (has links)
A cleaner use of fossil fuels supported by Carbon Capture and Storage (CCS) techniques is considered to be one of the main short-term strategies for addressing the global climate change problem. However, potential CO2 or CO2/SO2 seepage during some of the phases of a CCS project not only reduces its performing efficiency, but also impacts the local environment, which could have further impacts on human health. It is therefore essential to assess the potential risks and provide evidence that the impacts are well understood. Moreover, studying the effects of CO2 leakage is useful for identifying monitoring parameters if the leakage does happen, leading to the development of new approaches in detecting CO2 leaks. Accordingly, this research is carried out to assess the relevant impacts on the local environment of CO2 leakage, focusing on the environmental impacts caused by CO2 seepage associated with various soil types, mostly on the soil geochemical changes, which is currently lacked. As a cost effective approach, this research was carried out with two types of well controlled laboratory experiments: Stage I- Closed reactor experiments and Stage II- A flow through column system (designed by the author). As a supplementary study to the research of the ASGARD site, Stage I experiments were carried out with soil samples collected from the ASGARD site and gave directions for Stage II column system design. Stage II experiments were carried out with two contrasting mono-mineral sediments considering sensitivity to CO2 gas, Trucal 5 and Trucal 6 (limestone sand of different particle size) and silica sand. Certain limitations of this research have to be considered. Firstly, highly idealised samples were used in the experiments instead of true soils and there was no heterogeneity in the samples used, which is not representative of the full complexity of a natural system. Secondly, the scale limitation of the laboratory work would lead to a higher gas/mineral ratio compared with field conditions. Therefore, results from the laboratory work cannot simply represent all the soils in the field, except the specific soil related problem and the results are better to be used to demonstrate the conditions where the soils/sediments are surrounded by high levels of CO2, such as the ones nearby a leaking injection well or along a fracture/fault. Nevertheless, this study is believed to provide a step towards understanding the potential impacts of CO2 seepage in soil, and potentially to be useful as a mean of identifying indicators of related problems when applying to the full-scale design, leading to the development of new approaches in detecting CO2 leaks. Throughout the experiments, the experimental apparatus (the continuous column system) newly designed by the author was run successfully, providing an alternative way in respect to the majority of soil-column studies for assessing issues of CO2 seepage. The main impact of CO2 emissions on soil properties is to drop the pH which triggers metals mobilisation from soils (all within safety limits to plant growth). The change of pH associated with both limestone and silica sand indicates that pH is an excellent parameter to indicate the CO2 intrusion into sediments once the background is set. The response of calcium (Ca) to CO2 flux highlights that carbonate minerals are sensitive to CO2 increase and could possibly be used as a parameter to monitor CO2 leakage once the baseline for the pre-injection concentration is set.
202

Humane mechanical methods for killing poultry on-farm

Martin, Jessica E. January 2015 (has links)
Worldwide, an estimated 9.1 billion birds may need to be killed on farm each year. As of January 2013 the use of manual cervical dislocation (MCD) as a killing method for poultry on-farm has been heavily restricted through new EU legislation (EC 1099/2009) on the Welfare of Animals at the Time of Killing, following reported welfare concerns. The method by which birds are killed on farm is crucial to poultry welfare on a large scale. The overall aim of this project was to design a mechanical device conforming to the new legislation to kill poultry humanely on-farm and provide a competitive replacement for MCD. Following a survey and a literature review, four mechanical devices were designed and prototyped: Modified Armadillo (MARM); Modified Pliers (MPLI); Modified Rabbit Zinger (MZIN) and a Novel mechanical cervical dislocation glove (NMCD). The devices were tested for killing efficacy in three laboratory experiments, assessing their performance in poultry cadavers (Study 1), anaesthetised birds (Study 2) and live conscious birds (Study 3). The reliability and welfare impact of the devices, along with comparisons with a control method (MCD) were evaluated via post-mortem analysis, reflex and behaviour durations, and characteristics of electroencephalography (EEG) analysis. Due to consistently high kill success rates and rapid loss of reflexes, as well as short durations of EEG activity indicating consciousness across three laboratory experiments, the NMCD device was shown to have the most promise as a mechanical device to be used as an alternative to MCD for poultry stock-workers and keepers. The final experiment explored the user-reliability and practicality of the NMCD device in two relevant commercial environments (a layer hen farm and a broiler farm). When applied by multiple users, the NMCD device did not match the killing performance of MCD, however it did show promise and the study highlighted the need for further refinement in the training protocol in order to encompass the wide variation in MCD techniques and experience. The result of this project is a novel on-farm mechanical killing device, which shows great potential in laboratory experiments and competed with the traditional MCD method in commercial environments. Further training refinements are required in order to develop the device into a marketable product which any individual could purchase and use as a humane method for killing poultry.
203

Environmental genetics of root system architecture

Kellermeier, Fabian January 2013 (has links)
The root system is the plant’s principal organ for water and mineral nutrient supply. Root growth follows an endogenous, developmental programme. Yet, this programme can be modulated by external cues which makes root system architecture (RSA), the spatial configuration of all root parts, a highly plastic trait. Presence or absence of nutrients such as nitrate (N), phosphate (P), potassium (K) and sulphate (S) serve as environmental signals to which a plant responds with targeted proliferation or restriction of main or lateral root growth. In turn, RSA serves as a quantitative reporter system of nutrient starvation responses and can therefore be used to study nutrient sensing and signalling mechanisms. In this study, I have analysed root architectural responses of various Arabidopsis thaliana genotypes (wildtype, mutants and natural accessions) to single and multiple nutrient deficiency treatments. A comprehensive analysis of combinatorial N, P, K an S supply allowed me to dissect the effect of individual nutrients on individual root parameters. It also highlighted the existence of interactive effects arising from simultaneous environmental stimuli. Quantification of appropriate RSA parameters allowed for targeted testing of known regulatory genes in specific nutritional settings. This revealed, for example, a novel role for CIPK23, AKT1 and NRT1.1 in integrating K and N effects on higher order lateral root branching and main root angle. A significant contribution to phenotypic variation also arose from P*K interactions. I could show that the iron (Fe) concentration in the external medium is an important driving force of RSA responses to low-P and low-K. In fact, P and K deprivation caused Fe accumulation in distinct parts of the root system, as demonstrated by Fe staining and synchrotron X-Ray fluorescence. Again, selected K, P and Fe transport and signalling mutants were tested for aberrant low-K and/or low-P phenotypes. Most notably, the two paralogous ER-localised multicopper oxidases LPR1 and LPR2 emerged as important signalling components of P and K deprivation, potentially integrating Fe homeostasis with meristematic activity under these conditions. In addition to the targeted characterisation of specific genotype-environment interactions, I investigated novel RSA responses to low-K via a non-targeted approach based on natural variation. A morphological gradient spanned the entire genotype set, linking two extreme strategies of low-K responses. Strategy I accessions responded to low-K with a moderate reduction of main root growth but a severe restriction of lateral root elongation. In contrast, strategy II genotypes ceded main root growth in favour of lateral root proliferation. The genetic basis of these low-K responses was then subsequently mapped onto the A. thaliana genome via quantitative trait loci (QTL) analysis using recombinant inbred lines derived from parental accessions that either adopt strategy I (Col-0) or II (Ct-1). In sum, this study addresses the question how plants incorporate environmental signals to modulate developmental programmes that underly RSA formation. I present evidence for novel phenotypic responses to nutrient deprivation and for novel genetic regulators involved in nutrient signalling and crosstalk.
204

Mapping the language of landownership : discourses of property, management and rurality

Wright, Nick January 2004 (has links)
Hegemonic categorisations have been used to examine rural landownership'. including non-farmer/farmer, production/consumption and productive/postproductive. Evocative in the abstract, a shared dichotomy is unsuitable for examining the complexity of how meaning is given to rural land. To arrive at a more finegrained understanding, transcripts of interviews undertaken with landowners, centred around the Cotswolds in Gloucestershire, were analysed using a methodology of discourse analysis. The data was conceptualised in terms of discourses of property, management and rurality. 'Discourse' is here understood to mean vivid images often evoked in metaphor. This discourse analytic approach was useful in examining the way meanings of rural land vary across the course of an interview. Discourses were found adapted according to circumstance, rather than deployed in their entirely 'traditional' form. Discourse analysis allowed exploration and explanation of the processes involved in constructing meaning. For example the use of the part-whole metonymy allowed landowners to talk about part of their property, including management as stewardship, while referring to landownership as a whole. This type of discourse use was strategic. Landowners variously used discourses of stewardship of the environment, farming as a business and accommodation between the two, in different situations within talk to achieve specific, localised effects. It was found that discourses of townies, country people, 'no difference between townies and country people' and townie farmers, constitute a cultural repertoire from which landowners draw. When deployed in talk they create different effects because they relate in various ways to social representations of the rural idyll and urban dystopia. Understanding how meanings of land are constructed in talk is a critical step towards a more informed debate over the future shape of rural landownership.
205

The practice of local partnership in rural development : the cases of Newent (UK) and Sault (France)

James, Marie-Eva January 2001 (has links)
This research is concerned with the practice of local partnerships in the promotion of rural development with particular reference to two case study areas, Newent in the UK and Sault in France. In recent years, local partnership working has become increasingly common in the promotion of rural development. It is presented by academics, politicians, policy makers and practitioners as 'inherent' and 'imperative' to the preparation and implementation of rural development programmes today. However, there still exists limited understanding and knowledge about local partnership working in practice and the validity and importance of such statements. To advance this understanding the present research had four main objectives organised around the identification and the exploration of four main issues: the reasons, the processes, the outcomes and the implications of the local partnership practice in rural development. The author has sought to elucidate the subject by means of a detailed exploratory study involving the longitudinal observation of two particular examples of local partnerships. Two case study areas were selected, both with an active history of rural development initiatives and partnership working at parish or commune level. Newent is a small town in the Forest of Dean, which has sought to address growing socio-economic decline in recent years by preparing and implementing a regeneration strategy through local partnership working. Sault is a village in Provence, which has had to respond to depopulation and various economic difficulties as well as the closure in 1996-98 of the military base of Albion. Qualitative data on local partnership evolution and operation, collected in both areas between 1998 and 2001, was assembled from documentary research, semi structured interviews and direct observation at meetings. This investigation has allowed the identification of various explanations for the recent increase in the practice of local partnership in rural development, explanations which are mainly associated with the underlying context of the rural development process today and with the meaning of the partnership concept itself. From this investigation local partnership working in rural development has emerged as a long-term, progressive, comprehensive and pragmatic process that is organised over time. Its existence and longevity depend primarily on the local context, the existence of opportunities, the issues to be addressed, a broad mobilisation of local/rural actors, a flexible local space, some local re-organisation as well as regular and concrete achievements. In this respect, the most commonly reported outcomes of local partnership working pertain to the process of partnership working more than to the tangible outputs that may have resulted from it. These meet the initial expected benefits from such a practice as for example broader participation, greater reciprocity between rural development actors and territories, and an increase in local capacity for development action.
206

Worker injuries involving the interaction of cattle, cattle handlers, and farm structures or equipment

Fox, Shannon January 1900 (has links)
Master of Science / Department of Animal Sciences and Industry / J. Ernest Minton / Mitchell Ricketts / Cattle and other livestock have been identified as leading sources of injuries to workers in agriculture. Cattle handling injuries can be serious and often appear to be under-reported [superscript]3,[superscript]4. Many of these injuries involve predictable patterns of interactions among victims, animals, and fixed farmstead structures or gates. There has been some progress toward developing safer facility designs and work procedures, but continuing reports of injuries suggest further efforts are still needed. The present study focused on worker injuries that involved the interaction of three elements: (a) cattle, (b) cattle handlers, and (c) farm structures or equipment—including swinging gates and stationary barriers. The goal of the study was to identify opportunities for injury prevention. The source of injury cases was the Consumer Product Safety Commission’s National Electronic Injury Surveillance System (NEISS)[superscript]29,[superscript]45. We believe this is the first report of cattle related injuries based on NEISS data. We selected the NEISS database for this investigation because it includes product codes for many farmstead barriers such as fences, walls, and doors. The database was also selected because it contains brief narratives that help to describe the circumstances of each incident. Predictable interactions between humans, animals, and farm structures led to many of the cattle handling injuries reported in the NEISS database. In almost 30% of cases, cattle pushed workers into structures such as fences, gates, posts, and walls. In another 16-19% of injuries, cattle struck gates and other objects, propelling them at the victims. These percentages are similar to findings reported in previous studies that drew on data from New York hospitals[superscript]10, news reports in the central United States[superscript]5, and workers compensation cases in Colorado[superscript]3,[superscript]4. In all, gates and other physical barriers contributed to about 45% of cattle handling injuries in the present study.
207

Effects of fresh-cow diseases on reproduction in a large commercial dairy herd

Tollefsrud, Ryan Peder January 1900 (has links)
Master of Science / Department of Clinical Sciences / Bob L. Larson / The 2007 NAHMS (National Animal Health Monitoring System) survey indicated that early lactation health issues are major factors influencing reproduction and culling on U.S. dairy herds. The objective of this study was to evaluate fresh-cow health during the first 30 days in milk, and its association with days to pregnancy in the concurrent lactation. Data were collected on cattle that calved over a two month period (July and August 2009) on a dairy farm located in the Upper Midwest region of the U.S. Health and production data were collected daily for each cow from the beginning of lactation until the majority of the study population was confirmed pregnant. Both a competing risk analysis and a semi-parametric Cox regression model were used to test the association between specific health-related events and days to pregnancy and the outcomes of the two models were compared. These analyses showed metritis and dystocia in the first 30 days of lactation were associated with greater days to pregnancy. The only difference noted between parities was that lactation-five and greater cows were significantly associated with greater days to pregnancy. The two analyses showed conflicting significance of association between retained placenta, ketosis, twinning, lameness, and other non-specific illnesses with days to pregnancy. This study found that a competing risk analysis and a semi-parametric regression model were appropriate methods to analyze time sensitive data such as reproductive efficiency. This study supports the evidence that parity, metritis, retained placenta, ketosis, dystocia, twinning, lameness, and other non-specific illnesses can have an impact on reproductive efficiency.
208

Fundamental bases for the improving action of novel enzyme-oxidant combinations in frozen dough

Oshikiri, Reona January 1900 (has links)
Master of Science / Department of Grain Science and Industry / J.M. Faubion / The market for frozen goods is expanding and the frozen dough goods sector still has potential to expand its market. It is well known that deterioration in bread quality occurs during frozen dough/bread production. In addition, it is known that dough rheology influences bread quality. To prevent deterioration of bread quality, many additives have been used and researched. Combinations of oxidants (potassium bromate and ascorbic acid) are widely used worldwide. However, potassium bromate may be carcinogenic to humans, and it has been detected in bread after baking. Since it has been prohibited or strictly limited in many countries, many researchers have tried to find a replacement. Ascorbic acid is safe for human intake, and does not persist in bread. However, it is not as effective as potassium bromate. Possible replacements in frozen doughs include oxidant (ascorbic acid)-enzyme combinations. This study evaluated the effects of ascorbic acid-specific enzyme combinations as a replacement for the potassium bromate in frozen dough and related the effects to dough behavior (gluten network strength) as evaluated by dynamic oscillation rheometry. Bread quality was evaluated by test baking. Based on the results from fresh baking studies, potassium bromate can be replaced by an optimum level combination of ascorbic acid and hemicellulase/endo-xylanase. This combination clearly improved loaf volume, and crumb grain over both control and potassium bromate containing doughs. For frozen dough/bread production, the addition of all additives improved bread quality, but ascorbic acid and endo-xylanase containing dough resulted in higher volume, and better crumb structure than did dough containing potassium bromate. Dough rheology experiments show that rheology was affected by both the process and additives. Strain sweeps gave the information about dough stability. Both the additives and proofing improved dough stability. Dough behavior (gluten network strength) was assessed by frequency sweeps. Dough containing ascorbic acid and endoxylanase was most stable during frozen dough processing.
209

Incidence and spread of insects from bucket elevator leg boots

Tilley, Dennis Ray January 1900 (has links)
Doctor of Philosophy / Department of Grain Science / Bhadriraju Subramanyam / Mark E. Casada / In commercial grain elevators and feed mills, the boot and pit areas contribute to commingling of insects with grain that moves through the elevator leg. A pilot-scale bucket elevator leg with a modified removable boot, or slip-boot, was used to measure the magnitude of commingling as a function of stored-product insect density and boot holding time in tests with wheat and corn. Pilot-scale tests showed that clean grain transferred over infested boots was infested with about 1 insect/kg when transferred immediately after the boot was infested; this increased to 2 insects/kg after incubating the boot for 8 wk. Larger numbers of kernels with internal infestations were picked up by clean grain during transfer compared with externally infesting insects, because the mobility of the latter enabled them to move away from buckets during transfer. Monthly surveys over two years at elevators and feed mills revealed several stored-product insects in grain residues from the boot and pit areas and bulk load-out samples. Insect densities in the boot and pit areas were impacted by seasonal temperatures and facility sanitation practices. Recommended sanitation guidelines for the boot and pit areas include: (1) boot residual grain clean-out every 30 d, (2) removal of grain spillage and floor sweepings from the pit area, and (3) proper disposal of boot and pit residual grain. Facilities following these sanitation guidelines could avoid costly grain discounts, increase income of the business operation and minimize or prevent cross contamination of clean grain by infested grain in the boot and pit areas.
210

Determinants of adoption of genetically modified maize by smallholders in KwaZulu-Natal, South Africa

Manes, Rebecca January 1900 (has links)
Master of Science / Department of Agricultural Economics / Timothy Dalton / Previous research on small-scale farmers in KwaZulu-Natal, South Africa indicates that certain genetically modified maize seed types improve production efficiencies and increase net returns (Regier 2012). Yet despite the substantiated advantages, not all farmers have adopted genetically modified maize. The purpose of this research is to identify the determinants of adopting certain types of genetically modified maize over traditional or conventional hybrid maize for 184 small-holders in two villages in KwaZulu-Natal, South Africa. Previous adoption studies use socioeconomic characteristics of the farmer as well as farm-level production characteristics to determine the probability that a farmer will implement an improved agricultural technology. While many studies employ a binomial approach to adoption, this study tests the probability of adopting three different GM varieties—the insect resistant Bt maize, the herbicide tolerant Roundup Ready® maize, and the stacked trait BR maize. Furthermore, the model is enhanced by farmers’ open-ended explanations of their perceptions on genetically modified maize and of the major production constraints they face. Following results from previous adoption studies, this research tests three hypotheses in a three different model structures. The first hypothesis tests whether farmers are more likely to adopt if they have greater financial means to cover higher expected production costs. This is tested by variables measuring off-farm employment and expected production costs. The second hypothesis tests whether farmers with less labor availability are more likely to choose maize with the herbicide tolerant technology, either the Roundup Ready® or stacked BR maize, which reduce the need for weeding. The final hypothesis is whether there are differences in the determinants of adoption that differentiate GM adopters into three distinct categories. These hypotheses are tested in three model structures that test the binary probability of adopting GM maize over non-GM, the probabilities of adopting each maize variety separately, and the intensity of adoption. The first finding is that many non-adopters have greater access to income and are more likely to sell a portion of their yield than are many farmers who adopted, especially in comparison to those who plant RR maize. Also, BR farmers are more likely to report input expenses as a major constraint in their adoption decision. Results for the second hypothesis show that those who planted either RR or BR maize did in fact have less family labor available, used less total labor, and used a greater proportion of family to hired labor. Finally, there are differences in the determinants for geographic site, education, self-sufficiency in maize supply, number of family members working off-farm, and whether households planned to sell any of their maize yields. This indicates that adoption should be considered according to each genetically modified trait.

Page generated in 0.0459 seconds