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  • 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.
181

Sustainability of dryland cropping systems in the Wimmera region of Victoria / y Yvonne L. Postlethwaite

Postlethwaite, Yvonne L., (Yvonne Lynette). January 1998 (has links) (PDF)
Bibliography: p. 283-313. Two systems of dryland cropping, one conventional and one conservation, were studied on the same farm over a period of 10 and 14 years respectively. The conventional cropping system was based on cultivated fallow which served to manage and conserve water, nitrified organic matter and controlled weeds. Stubble was burnt prior to cultivation for the fallow phase, with pasture and cropping phases rotated. The conservation farming system was based on the absence of soil tillage, stubble retention, rotation of a variety of crops and chemical control of weeds. Water conservation was achieved through increased infiltration by improved soil structure, avoidance of compaction, reduced water runoff and reduced evaporation by stubble retention. Overall, the conventional farming system was proven to be unsustainable. The conservation system was sustainable in terms of productivity, profitability and effect on the environmental resources of soil and water. The growing of sorghum as a summer grass in the Wimmera was also found to be an opportunity for improving productivity, profitability and sustainability by controlling winter weeds.
182

Enhancement of Dry Content in Coating Solution for Functional Packaging

Jonsson, Åsa January 2009 (has links)
<p>The main goal for a packaging is to protect the product inside. Typical packaging nowadays is made of layers of paper and barriers consisting of plastics or aluminum foil. A problem with the barrier used today is the environmental thinking. Xylophane® is an environmental friendly and biodegradable alternative to the current barrier material used in packaging. It consists of the natural carbohydrate xylan and additives. Xylophane® is an efficient barrier to oxygen, grease and aroma and can prolong the shelf life of sensitive food.</p><p>The raw material xylan is water soluble and Xylophane® can be coated on paper, board and plastics without using other solvents. A problem with the drying process is the amount of energy needed and the consumption needs to be decreased. Also, the drying capacity of the equipment to be used is often limited and the amount of water to be dried off is critical for the success of the coating process. By increasing the dry content of Xylophane® without increasing the viscosity too much, the drying process can be more effective. In this thesis, studies were made of using a filler as an additive to increase the dry content without destroying the barrier properties.</p><p>With an experimental design, a suitable relationship between the ingredients xylan (X), plasticizer (P) and filler (F) was found. Xylan is the main component and is needed to get a good oxygen barrier. The plasticizer decreases the oxygen barrier properties but is needed to make the material more flexible. The filler is positive for the barrier properties. The chosen composition was X:P = 7:3 and X:F = 1:1. Some extra experiments were made to find a reasonable value of the dry content. Dry contents around 18 % work well with temperatures at and above 45°C, but to manage to perform coating at room temperature the dry content needs to be lower.</p>
183

The suitability of optical particle counters for covariance estimates of the dry deposition velocity of particulate aerosols

Hubbe, John McBain 12 June 1984 (has links)
Experimental work at the 1982 Dry Deposition Intercomparison Experiment (DDIEx) involved the use of optical particle counters for covariance estimates of dry deposition velocities of accumulation mode aerosols. Meteorological and particle flux observations are presented. Deposition velocity estimates exhibit scatter about zero. A formulation of the standard error of the deposition velocity estimator is derived and examined. Using this formulation, the observed deposition velocities are shown to be marginally significant. Using a case study, the correlation coefficient is examined and presented as an important statistic to the work. Humidity effects on the measurements are briefly examined. Recommendations are made for improvements in the instrumentation. / Graduation date: 1985
184

Characterisation of microbial communities associated with hypolithic environments in Antarctic Dry Valley soils.

Khan, Nuraan. January 2008 (has links)
<p>The Eastern Antarctic Dry Valley region is a polar desert, where conditions of extreme aridity, high temperature fluctuations and high irradiation levels make it one of the most extreme environments on earth. Despite the harsh environment, the soils in this region yield a wide range of bacterial and eukaryotic phylotypes in greater abundance than previously believed. In the Dry Valleys, highly localized niche communities colonise the underside of translucent quartz rocks and present macroscopic growth.</p>
185

Tolerance to sub-zero temperatures in <i>Phaseolus acutifolius</i> and interspecies hybrids between <i>Phaseolus vulgaris</i> and <i>P. acutifolius</i>

Martinez, Jocepascual 30 May 2011
Dry bean (Phaseolus vulgaris) is a sub-tropical crop severely affected by exposure to low temperatures during all of its growing stages. Cool spring temperatures and the risk of frost are major limiting factors for the early sowing of dry bean in Saskatchewan. Due to its economic importance; however, it has been introduced to Saskatchewan, but it needs to be made more cold tolerant to further expand acreage. The genes that can contribute some tolerance to low temperature stress in bean are not found within the primary gene pool, which limits the capability of breeders to generate a cultivar with such characteristics. Consequently studies have being done in order to find a possible source of genes that can induce tolerance to low temperature exposure. Phaseolus acutifolius is a relative of the domesticated dry bean and previous hybridizations with it have been successful. It is also known to be tolerant to abiotic stresses such as drought. For this reason the decision was taken to explore the level of resistance to low temperature stress exposure in several P. acutifolius accessions. Using whole plant freezing tests in controlled environment chambers, P. acutifolius W6 15578 was found to be more tolerant to exposure to sub-zero temperatures than were P. vulgaris genotypes. Interspecies hybrids were produced between P. vulgaris NY5-161 and W6 15578 and BC2 plants were produced using embryo rescue. The whole plant freezing test is a destructive method that cannot be used with unique F1 and BC2 genotypes, so an alternative methodology to evaluate the hybrids was explored. An electrolyte leakage test was used and showed similar results to the whole plant freezing test with the parent plant controls. The F1 hybrids had an intermediate tolerance to low temperature stress and the further generations (BC1 and BC2) had a better level of tolerance to this kind of stress than the cultivated parent (NY5-161). This suggests that the genes that confer tolerance to low temperature exposure are being maintained through several generations of backcrossing and that these interspecies hybrids may offer a chance for the development of improved dry bean cultivars for the Saskatchewan environment.
186

Multiscale mechanics and physics of nature’s dry adhesion systems

Karlsson, Nils January 2012 (has links)
Dry adhesion systems adhere via physical bonds without any significant contribution from a liquid medium. In nature, these systems are found among the footpads of spiders, lizards and many other small animals, with high adhesion force, low detachment force and elfcleaning properties. These features are highly interesting for biomimetic man-made adhesives. Heavy animals have an adhesion force much higher than its muscle force, and to enable detachment, they have evolved a functional surface with hair-like structures called setae. Each seta branches into numerous microcontact elements that interact with the contacting area. This thesis continue on previous work, analyzing the functional surface in terms of contact geometries and stress distribution, and considers, for the first time, the effect of thermal fluctuations. Numerical and analytical results show how the muscle force is concentrated to a small fraction of the adhesion area, where each microcontact element is trapped in a potential well. The rate of detachment depends on the maximal concentration of stress across the crocontacts. When a seta is axially loaded, the concentration of stress is minimized, whereas radial loading amplifies the concentration of stress by a factor of maximum 68 and enable detachment with the animal’s limited muscle force. The results give theoretical insight in the adhesion and detachment of a functional surface. This knowledge is valuable and can be considered when constructing man-made adhesives with inspiration from nature’s dry adhesion solutions.
187

Dry Versus Wet Aging of Beef: Retail Cutting Yields and Palatability Evaluations of Steaks Using Alternative Cutting Styles

Smith, Amanda 1987- 14 March 2013 (has links)
Boneless ribeye rolls (n = 12) and boneless top sirloin butts (n = 12) were obtained from heavy weight carcasses (mean = 407.8 kg), assigned to one of two aging treatments (dry or wet) and aged for 35 days at a commercial aging facility. Cutting tests were performed at the end of the aging period to determine retail yields. Subprimals were fabricated using the Beef Alternative Merchandising cutting styles, isolating four specific muscles: M. spinalis thoracis, M. longissimus thoracis, M. gluteobiceps, and M. gluteus medius. Retail cutting tests showed wet-aged subprimals had higher (P < 0.0001) total saleable yield percentages with decreased cooler shrink and gross cut loss percentages. This resulted in wet-aged ribeye rolls and top sirloin butts yielding 1.5 times and 1.3 times more saleable product than dry-aged counterparts, respectively. In order to determine palatability characteristics, consumer sensory evaluations and trained panel evaluations were preformed. Palatability related to aging and muscle type resulted in significant differences. From a consumer standpoint, aging treatment influenced OLIKE, FLAV, FLEVEL, and BEEFLIKE but only through the interaction of aging treatment x muscle. Clearly, consumers rated the wet-aged, M. spinalis thoracis highest in each of the previously stated attributes. Aging also affected JUIC, whereas muscle type had a significant (P < 0.0001) effect on FLVBF, TEND, LEVTEND, JUIC, and LEVJUIC. As far as trained sensory attributes were concerned, a more concrete flavor profile of aged beef was obtained. In addition, dry-aged steaks had greater (P < 0.0001) cooking yield percentages when compared to wet-aged steaks.
188

Learning through Farmer Field Schools: a case study of the Taita Hills, Kenya

Najjar, Dina 17 September 2008 (has links)
This research explores transformative learning occurring through the Farmer Field Schools of the Taita Hills, Kenya using a qualitative, case study approach. The findings reveal that cultural roles and premises profoundly impacted learning and that a mixed-group setting could contribute to closing the gap between gender inequalities, leading to a more just and sustainable type of agriculture. / February 2009
189

Vulkanisk svaveldimma : Risken att det drabbar Sverige

Andersson, Emmelie January 2011 (has links)
In the year 1783 a fissure eruption from Laki in the southern part of Iceland produced a large amount of volcanic gases during a period of eight months. The volcanic gases and aerosols spread across the northern hem sphere due to ideal weather conditions and had a substantial impact on the environment, human health and also climate effects. This, so called dry fog, caused severe health problems, which led to death casualties, killing animals, crops and other vegetation. The consequence was a widespread famine which was aggravated by a hard and long winter in 1783/84. Analysis shows that the Icelandic volcanoes are the primary risk to produce dry fog that can affect Sweden. The fog will most likely cause severe health effects, such as respiratory and cardiovascular problems. It will also cause damage to the vegetation, especially coniferous trees, and it may affect the water by acid chock. The fog may have great impact on the critical infrastructure in Sweden, depending on magnitude and duration. These types of volcanic hazards are difficult to predict and evaluate due to their sporadic nature and the sparse amount of data that is available. It is therefore important to focus on the consequences and develop the Swedish community preparedness on a general basis to handle this type of event.
190

Enhancement of Dry Content in Coating Solution for Functional Packaging

Jonsson, Åsa January 2009 (has links)
The main goal for a packaging is to protect the product inside. Typical packaging nowadays is made of layers of paper and barriers consisting of plastics or aluminum foil. A problem with the barrier used today is the environmental thinking. Xylophane® is an environmental friendly and biodegradable alternative to the current barrier material used in packaging. It consists of the natural carbohydrate xylan and additives. Xylophane® is an efficient barrier to oxygen, grease and aroma and can prolong the shelf life of sensitive food. The raw material xylan is water soluble and Xylophane® can be coated on paper, board and plastics without using other solvents. A problem with the drying process is the amount of energy needed and the consumption needs to be decreased. Also, the drying capacity of the equipment to be used is often limited and the amount of water to be dried off is critical for the success of the coating process. By increasing the dry content of Xylophane® without increasing the viscosity too much, the drying process can be more effective. In this thesis, studies were made of using a filler as an additive to increase the dry content without destroying the barrier properties. With an experimental design, a suitable relationship between the ingredients xylan (X), plasticizer (P) and filler (F) was found. Xylan is the main component and is needed to get a good oxygen barrier. The plasticizer decreases the oxygen barrier properties but is needed to make the material more flexible. The filler is positive for the barrier properties. The chosen composition was X:P = 7:3 and X:F = 1:1. Some extra experiments were made to find a reasonable value of the dry content. Dry contents around 18 % work well with temperatures at and above 45°C, but to manage to perform coating at room temperature the dry content needs to be lower.

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