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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.
251

Will the Timing of Temperate Deciduous Trees' Budburst and Leaf Senescence Keep up with a Warming Climate?

Salk, Carl F. January 2011 (has links)
<p>Recent changes in the timing of annual events are a sign that climate change is already impacting ecosystems. Carbon sequestration by forests increases with longer growing seasons. Biodiversity can be affected by mis-timing of events through shading interactions and frost damage. Projecting forests' ability to provide these ecosystem services in the future requires an understanding of trees' phenological responses to a new climate. I begin by proposing a first order definition of an `optimal' phenological response to warming: that the mean temperature following budburst should remain essentially constant. Analogously, the temperature preceding senescence can serve the same role. </p><p>To understand which environmental cues will drive future changes in phenology, I assimilate clues from observational and experimental literature. For budburst in woody plants, spring warmth, over-winter chilling and light drive nearly all behavior, but species' responses vary widely. Species using chilling or light as safety mechanisms against budburst during mid-winter thaws are thought to be less able to phenologically track a warming climate. However, I show that even species cued solely by spring warmth are likely to under-track temperature changes. Fall cues are more idiosyncratic, and a plant's driver of senescence is likely to vary from year to year. </p><p>Models are a tempting method to untangle species budburst cues and forecast phenology under warmer climate scenarios. I tested two models' ability to recover parameters used to simulate budburst data. The simpler model was cued only by spring warmth while the complex one modulated warmth requirements with chilling exposure. For the simple model, parameters could be recovered consistently from some, but not all, regions of parameter space. The complex model's parameters were largely unrecoverable. To understand the consequences of parameter uncertainty, I applied both models to an 18 year phenological record of 13 deciduous tree species. While a few species fell into identifiable regions of the simple model's parameter space, most did not, and projected budburst dates had wide parameter-derived uncertainty intervals. These bands were wider still under a 5°C warming scenario. Even greater uncertainty resulted from the complex model.</p><p>To better understand plants' potential for growing season extension I subjected seedlings to warmer climates in a series of open-topped chambers in sites at each end of the eastern deciduous biome. Soil and air were heated to 3 or 5°C above ambient, or left unheated. For nearly all species, warming hastened budburst and germination and delayed senescence. However, these events failed to track temperature changes, happening at warmer temperatures in hotter chambers. Individual species showed a remarkable variability of all events' dates within treatments, and even within chambers. Because phenological traits are heritable, this offers a potential for evolutionary response to climate change.</p><p>This research has shown that while individual trees extend their growing seasons under warmer temperatures, they typically under-respond to the magnitude of warming, suggesting forests' capacity for increased carbon sequestration may reach a limit. However, within populations, trees vary substantially in their phenological responses, forming a possibility for evolutionarily adaptation to changing cues.</p> / Dissertation
252

A Guide to the Pomona College Organic Farm: An Introduction to the Farm’s History and Basic Gardening Skills and Techniques

Long, Adam J 01 April 2013 (has links)
It was almost four years ago when I first visited the Pomona College Organic Farm and since then I have learned everything from the basics of gardening to the complex steps required to organize students for events and activities. As I learned more and saw so many students come and go, I saw a need for written documentation that would allow future generations of students to benefit from the skills that my peers and I have learned in our time at the Farm. The value of the Farm is grounded in having a vibrant physical space, and right now the knowledge to maintain and improve this space is only passed down from person to person. I hope to eventually combine the disparate bits of knowledge that I have accumulated over the years into a single guidebook. This thesis project, which is the first major section of that guidebook, covers the Farm’s history and basic technical skills like soil preparation, planting, plant maintenance, weeding, pest control, and tool use. This is a living document and will be constantly updated as the Farm changes and grows and as new information comes to light. Although the Farm has come a long way over the years, it still has a lot of unrealized potential, and I hope that this document both facilitates and records the great changes that are soon to come.
253

Automatic segmentation of wall structures from cardiac images

zHu, LiangJia 18 December 2012 (has links)
One important topic in medical image analysis is segmenting wall structures from different cardiac medical imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI). This task is typically done by radiologists either manually or semi-automatically, which is a very time-consuming process. To reduce the laborious human efforts, automatic methods have become popular in this research. In this thesis, features insensitive to data variations are explored to segment the ventricles from CT images and extract the left atrium from MR images. As applications, the segmentation results are used to facilitate cardiac disease analysis. Specifically, 1. An automatic method is proposed to extract the ventricles from CT images by integrating surface decomposition with contour evolution techniques. In particular, the ventricles are first identified on a surface extracted from patient-specific image data. Then, the contour evolution is employed to refine the identified ventricles. The proposed method is robust to variations of ventricle shapes, volume coverages, and image quality. 2. A variational region-growing method is proposed to segment the left atrium from MR images. Because of the localized property of this formulation, the proposed method is insensitive to data variabilities that are hard to handle by globalized methods. 3. In applications, a geometrical computational framework is proposed to estimate the myocardial mass at risk caused by stenoses. In addition, the segmentation of the left atrium is used to identify scars for MR images of post-ablation.
254

Verbesserung der Lagerqualität von Äpfeln

Amani, Ricarda, Krieghoff, Olaf 26 September 2013 (has links) (PDF)
Das Standardverfahren ULO (Ultra Low Oxygene) zur Lagerung von Äpfeln wurde mit zwei neuen DCA-Lagerverfahren (Dynamic Controlled Atmosphere) verglichen. Ziel des Projektes war, die Wettbewerbsfähigkeit der sächsischen Erzeuger durch eine Verbesserung der Qualität und der zeitlichen Verfügbarkeit von Äpfeln zu erhöhen. Im dreijährigen Versuch mit den Sorten Gala und Shampion zeigten sich Unterschiede in der Fruchtfleischfestigkeit. Sie blieb bei der DCA-Lagerung besser und länger erhalten als bei der Standard ULO-Lagerung. Bei der DCA-Lagerung und der ULO-Lagerung mit Ethylenreduktion entstehen im Vergleich zur normalen ULO-Lagerung höhere Kosten.
255

Role of Computer Mediated Communication (CMC) in growing trading organization in Pakistan

Shahzad, Eram, Khan, Junaid January 2012 (has links)
In third world countries like Pakistan, companies are growing their trading business with remarkable pace. Increase in business volume has raised the challenges to keep growth sustainable. Communication is one of the biggest challenges for most of small size trading and marketing companies in the region. Face-to-face communication is only type of communication available in companies for inter departmental and intra departmental communication. Although face-to-face is one of the best type of communication but it is not possible to have face-to-face communication all the time with all employees especially when volume of company is growing with remarkable pace. In result company faces challenges like information delay, information lost or communication handicap. These challenges affect efficiency and effectiveness of company. We performed qualitative survey with directors and employees of Abuzar Marketing and Trading Company to develop deep understanding with communication problem to eliminate it. Analyzing empirical data and literature, it is found that Computer Mediated Communication (CMC) provides synchronous and asynchronous types of communication, which could help the company to overcome communication challenges with several other potential benefits e.g. knowledge sharing, employees training, democracy in batter manners.  Since every company in region is facing similar problem, general recommendation and precautions are made to introduce computer mediated communication (CMC).
256

Management Training at Cypress Security : A Case Study Application

Lindahl, Olof, Hasanogullari, Yusuf January 2007 (has links)
Many Small and Medium-sized Enterprises (SMEs) today face problems with growth and profitability due to lack of management training within the managerial staff. This study aims to create a holistic model for how to construct a Management Training Plan for such companies and test this model on a case company. The study found four main phases in the creation of a training plan, and thus, the model consists of four parts. The first part deals with the motivation of the trainees to go through with the training. The second part deals with deciding the content of the training plan. The third part looks at how the training plan should be designed. The fourth part looks at how to evaluate the training after it has been conducted. The main findings are that the most interesting areas of training for the managers at Cypress Security are customer communication and financial management. The training should be a mixture between group discussions and self-study material. We believe the results in this study should prove useful when constructing training programs for other companies since the model can be applied to almost any type of company. By providing specialized management training of this kind, SMEs reduce the need for hiring and recruiting managers with academic background and allows them to recruit from within.
257

The effect of activated carbon on the organic and elemental composition of plant tissue culture medium

Van Winkle, Stephen C. 05 1900 (has links)
No description available.
258

Lipid Metabolism, Gene Expression, Substrate Oxidation, and Meat Quality of Growing-finishing Pigs Supplemented with Conjugated Linoleic Acid and Arginine

Go, Gwang-Woong, 1979- 2010 December 1900 (has links)
We hypothesized that supplementation of dietary conjugated linoleic acid (CLA) and arginine singly or in combination would increase animal performance and meat quality by decreasing adiposity and increasing lean mass in growing-finishing pigs. Sixteen pigs (80 kg) were assigned to four treatments in a 2 x 2 factorial design, differing in dietary fatty acid and amino acid composition [control: 2.05% alanine (isonitrogenous control) plus 1% canola oil (lipid control); CLA: 2.05% alanine + 1% CLA; arginine: 1% arginine + 1% canola oil; arginine + CLA: 1% arginine + 1 CLA]. Preliminary tests indicated that up to 2% arginine was acceptable without interfering with lysine absorption. Pigs were allowed to feed free choice until reaching 110 kg. There were no significant differences across treatments in feed intake, weight gain, or feed efficiency. CLA tended to decrease carcass length (P = 0.06), whereas backfat thickness tended to be greater in pigs supplemented with arginine (P = 0.08). Arginine decreased muscle pH at 45 min postmortem (P = 0.001) and tended to increase lightness of muscle at 24 h postmortem (P = 0.07). CLA supplementation increased the concentrations of trans-isomers of 18:1 (P = 0.001) and SFA (P = 0.01) in s.c. and r.p. adipose tissue. CLA supplementation increased palmitate incorporation into total lipids in longissimus muscle (P = 0.01). Glucose oxidation to CO₂ in r.p. and s.c. adipose tissue were greater in pigs supplemented with CLA in the absence or presence of arginine (P = 0.03 and P = 0.04, respectively). The volume of s.c. adipocytes in s.c. and r.p. adipose tissues was greater in pigs supplemented with CLA, arginine, or CLA plus arginine than in control pigs (P = 0.001). Neither CLA nor arginine affected the expression of PGC-1[alpha],AMPK, mTOR, CPT-1A, FAS, or SCD (P > 0.05) in any tissues. We conclude that there was no significant interaction between arginine and CLA. Supplementary CLA or arginine to finishing-growing pigs did not modulate growth performance and did not reduce adiposity. CLA increased intramuscular fat content without deteriorating meat quality traits and increased saturated fatty acids and substrate oxidation in adipose tissues. In the presence of 1% of canola oil or CLA in the diet, arginine has the potential to deteriorate meat quality by reducing early postmortem pH and by increasing carcass fatness.
259

Segmentation Of Torso Ct Images

Demirkol, Onur Ali 01 July 2006 (has links) (PDF)
Medical imaging modalities provide effective information for anatomic or metabolic activity of tissues and organs in the body. Therefore, medical imaging technology is a critical component in diagnosis and treatment of various illnesses. Medical image segmentation plays an important role in converting medical images into anatomically, functionally or surgically identifiable structures, and is used in various applications. In this study, some of the major medical image segmentation methods are examined and applied to 2D CT images of upper torso for segmentation of heart, lungs, bones, and muscle and fat tissues. The implemented medical image segmentation methods are thresholding, region growing, watershed transformation, deformable models and a hybrid method / watershed transformation and region merging. Moreover, a comparative analysis is performed among these methods to obtain the most efficient segmentation method for each tissue and organ in torso. Some improvements are proposed for increasing accuracy of some image segmentation methods.
260

Paleolimnological Assessment Of Past Aquatic Vegetation Dynamics And Ecosytem State In Turkish Shallow Lakes

Levi, Eti Ester 01 September 2009 (has links) (PDF)
Since submerged macrophytes are a key primary producer of shallow lakes and are sensitive to environmental changes, macrofossils of them can be used in investigations of past environmental conditions, to infer human introduced environmental impacts (e.g. eutrophication) and to determine past macrophyte communities. The present study includes twenty six shallow lakes, which were chosen along a latitudinal gradient ranging from the North (41&deg / 52&acute / N, 27&deg / 58&acute / E) to the South (37&deg / 06&acute / N, 29&deg / 36&acute / E) in Turkey. Sampling for environmental variables and sediment was carried out using a snap-shot sampling protocol (developed within the framework of the EU FP6 project &lsquo / Eurolimpacs&rsquo / ) during the summers of three consecutive years (2006-2008). Surface sediment, short core and long core samples were retrieved from the lakes. The aims of this study were i. to compare the surface sediment plant macrofossils with present day macrophyte taxa of the lakes, ii. to determine the environmental variables potentially influencing the temporal changes in macrophyte communities, and iii. to assess vegetation community dynamics in dated short and long cores. Comparison of plant macrofossil assemblages in surface sediment with present day macrophyte coverage revealed that approximately 41% of the modern taxa were represented among the surface sediment macrofossils. Redundancy analysis (RDA) was carried out for surface macrofossil data with corresponding environmental data. RDA revealed relation of plant species and environmental variables (e.g. Salinity and Najas marina L.). Changes in plant species assemblages in short and long cores from eight lakes chosen along a latitudinal gradient ranging from North to South Turkey is discussed in relation to the RDA results.

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