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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.
21

Synthesis of zeolites from Tay Nguyen red mud and test of their adsorption ability

Pham, Thi Mai Hương, Tran, Hong Con, Le, Thi Phuong Quynh 16 January 2019 (has links)
Red mud is the waste from alumina production, contain high amount of residual alkaline, aluminate and some metals oxide such as iron oxide, silicon oxide, titanium oxide...; in which aluminum and silica proportions could be used for zeolite synthesis. The zeolite was synthesized by the hydrothermal method for obtaining RM-ZeO-Si which was signed for Si added and RM-ZeO- Si- Al for both Si and Al added. The obtained zeolites were then characterized by the XRD, EDX, SEM, BET and FT-IR methods. The results indicate that the synthesized zeolite is likely the new kind one with one surfur atom in the crystaline unit and has general formula of Na8(Al6Si6O24)S.4H2O. We tested the ability of ammonium and nitrite adsorption of the synthesized zeolites and found that the synthesized zeolites had very high adsorption capacity of both cation ammonium and anion nitrite; but the adsorption mechanism of each was different. Adsorption mechanism of ammonium was suggested as predominant ion exchange between ammonium cation in solution and sodium cation in zeolite crystals; while nitrite adsorbed on surface material by electrostatic attractive force between nitrite anion and electropositive surface of iron oxide particles. / Bùn đỏ là chất thải từ quá trình sản xuất nhôm, chứa lượng lớn kiểm, oxit nhôm và một số oxit khác như sắt oxit, silic oxit, titan oxit…trong đó tỷ lệ nhôm và silic có thể sử dụng để tổng hợp zeolit. Vật liệu zeolit được tổng hợp bằng phương pháp thủy nhiệt, thêm Si được ký hiệu là RMZeO- Si; vật liệu thêm đồng thời Si, Al được ký hiệu là RM- ZeO-Si/Al. Vật liệu zeolit tổng hợp được phân tích đặc trưng cấu trúc bằng các phương pháp XRD, EDX, SEM, BET và FT-IR. Các kết quả phân tích cho thấy vật liệu zeolit tổng hợp có điểm mới khác biệt so với các zeolit thông thường bởi trong cấu trúc phân tử có chứa nguyên tử S, công thức phân tử của zeolit là Na8(Al6Si6O24)S.4H2O. Kết quả khảo sát hấp phụ ban đầu cho thấy vật liệu có khả năng hấp phụ với cả ion amoni và nitrit, cơ chế hấp phụ khác nhau. Quá trình hấp phụ cation amoni là do quá trình trao đổi ion giữa cation amoni với cation natri trong tinh thể zeolit, còn quá trình hấp phụ nitrit trên bề mặt vật liệu do tương tác tĩnh điện giữa nitrit với các cấu tử oxit sắt.
22

Study on knowledge of medicinal plants used of Tay ethnic minority in Na Hang special-use forest, Tuyen Quang Province

Nguyen, Thi Hai, Chu, Thi Thu Ha, Nguyen, The Cuong, Nguyen, Anh Tuan, Tran, Huy Thai 07 January 2019 (has links)
Tay ethnic minority using Tay - Thai language is the biggest population in Na Hang district (ca. 51.6%), Tuyen Quang province. Their knowledge and experience of using medicinal plants have been preserved and passed down through many generations. Medicinal plant resources in Na Hang special-use forests (SUF) have been contributing to the work of health care and treatment of communities in the region. Research results showed that the composition of medicinal plants used by Tay ethnic minority in Na Hang SUF included 223 vascular plant species, belonging to 4 phyla which were mainly belonging to Magnoliophyta, accounting for 90.0% of families; 94.97% of genera, and 95.92% of species. Among these 223 plant species, 9 species were ranked at different levels of endangered status. These are rare and precious gene sources that need to be strictly protected and conserved. 53 diseases/symptoms belonging to 7 groups of diseases can be treated with medicinal plants from Tay ethnic minority in Na Hang SUF. Particularly, 14 diseases to be treated by various medicinal herbs. / Dân tộc Tày là một cộng đồng thuộc ngôn ngữ Tày - Thái và có dân số đông nhất ở huyện Na Hang, tỉnh Tuyên Quang, chiếm 51,6% tổng dân số toàn huyện. Những tri thức và kinh nghiệm sử dụng những loài cây để chữa bệnh đã được người dân địa phương gìn giữ và lưu truyền lại qua nhiều đời, thế hệ sau. Nguồn tài nguyên cây thuốc ở rừng đặc dụng Na Hang đã và đang đóng góp vào công tác chăm sóc sức khoẻ và chữa bệnh của các cộng đồng trong khu vực. Kết quả điều tra cho thấy thành phần loài cây thuốc được người dân tộc Tày sử dụng gồm 223 loài thuộc 4 ngành thực vật bậc cao có mạch, chủ yếu thuộc ngành Mộc Lan (Magnoliophyta), chiếm 90,0% tổng số họ; 94,97% tổng số chi và 95,52% tổng số loài. Trong số 223 loài cây thuốc này, có 9 loài được xếp ở các cấp độ nguy cấp khác nhau. Đây là nguồn gien quý hiếm, cần có biện pháp bảo tồn nghiêm ngặt. Có 53 bệnh/triệu chứng bệnh thuộc 7 nhóm bệnh có thể chữa bằng cây thuốc tại rừng đặc dụng Na Hang từ người dân tộc Tày. Đặc biệt, 14 bệnh có thể chữa được bằng nhiều loại cây thuốc khác nhau.
23

From Watchman to Mockingbird: Tay Hohoff’s Editorial Influence on Harper Lee

Norris, Aine M 01 January 2016 (has links)
The 2015 publication of Harper Lee’s Go Set a Watchman (2015) raised questions and concerns when it was read in the context of the author’s first novel, To Kill a Mockingbird (1960), a text with strong, direct statements related to civil rights and social injustice. This thesis examines textual similarities and differences between Watchman and Mockingbird, suggesting the likely influence of editor Thèrése “Tay” von Hohoff in Mockingbird’s published version. Additionally, the thesis examines Hohoff’s 1959 biography, A Ministry to Man: The Life of John Lovejoy Elliott, as a plausible inspiration for Lee’s Mockingbird hero, Atticus Finch. Containing corroboration from available correspondence, biographical information, interviews, and historical records, this thesis documents Hohoff’s editorial influence on Lee as the two worked together to create a lasting contribution to American literary history and culture.
24

The Tay Salmon fisheries in the nineteenth century

Robertson, Iain Aitken January 1989 (has links)
At the beginning of the nineteenth century, new methods of preservation allowed Tay salmon to be sold on the London market for the entire fishing season. Such was the size and buoyancy of this market that it absorbed the entire produce of the Tay fisheries, though catches were at that time increasing due to the introduction of stake nets in the Firth. However, these beneficial developments created tensions among the participants in the fisheries. Stake nets took fish which would have ascended to the river, reducing the catches of river tacksmen and the rentals of river proprietors. An increasing number of tacksmen meant that management of the fisheries ceased, as formerly, to be in the hands of a single company and gave rise to more competitive exploitation of the existing salmon stock. A particular result of these developments was that all participants in the fisheries developed an abiding preoccupation with the threat of over-fishing. This was 'further enhanced by the introduction of stake nets on the coast after they were banned from the estuary, development of a series of stake net substitutes in the estuary, more efficient conventional methods of fishing at more stations, and a revival of poaching from mid-century onwards. The court case which led to stake nets being removed from the estuary formalised the animosity between the various proprietorial groups. Their subsequent adoption of entrenched positions eventually led to the tripartition of the Tay fisheries into estuarial, river and upper river factions. Successive inquiries and two Acts of Parliament failed to reconcile the enmities which were sustained by strongly held beliefs in property rights and the need to defend rental incomes. The impasse was ultimately resolved by a single company which, by doubling rental payments, was able to take all netting stations into its own hands and thus revive unified control of the Tay salmon fisheries.
25

The role of intertidal seagrass Zostera spp. in sediment deposition and coastal stability in the Tay Estuary, Scotland

Wilkie, Lorna January 2012 (has links)
The Tay estuary is situated on the east coast of Scotland. The estuary is dominated by sediment biotopes, including mudflats which support sparse beds of two nationally scarce seagrass species, Zostera marina var. angustfolia (Hornem.) and Z. noltii (Hornem.). Seagrasses have been described as ecosystem engineers, shaping their sediment environment, and this may increase sediment deposition and stability. In this thesis the ecosystem engineering characteristics of seagrass habitats are explored. In 2008, the distribution of Zostera spp. in the Tay estuary was surveyed and mapped for the first time. Sediments within beds of Z. marina and Z. noltii were compared to investigate the influence of seagrasses on sediment characteristics. To explore the role of seagrass in sediment deposition and erosion, and coastal stability, sediment depth measurements were made in patches of Z. noltii, Z. marina and bare sediment over one year. The role of the root/rhizome system on sediment retention over winter was also considered. Sediment deposition in Z. noltii beds, and the influence of the plants on near-bed flow dynamics was further explored in the laboratory, using an 8 m seawater flume. In the field the retention of particles over 2 and 14 tides was measured, and the results of this experiment led to a study of the influence of leaf and sediment biofilms on particle retention, using the novel method of magnetic particle induction (MagPI). The efficacy of artificial seagrass beds and Z. noltii transplantation as habitat restoration techniques were compared over one year. During the trial, sediment deposition and changes in sediment characteristics were determined, and the protection given to saltmarsh cliffs fringing the study plots was assessed. Mechanisms underlying the results are suggested and the findings discussed. This study provides an insight into the ecology of seagrass in the Tay estuary and its role as an ecosystem manager. It may offer valuable data which could be utilised for future conservation policies, habitat restoration schemes and management planning of the area.
26

An analysis of channel change on the Rivers Tay and Tummel, Scotland, using GIS and remote sensing techniques

Winterbottom, Sandra J. January 1995 (has links)
This thesis examines historical river channel change on a 12km study reach of the Rivers Tay and Tummel Scotland via the development of GIS and remote sensing techniques. Firstly, historical maps were combined using GIS rectification techniques in order to examine channel changes over the period 1755 to 1975. Secondly, also using GIS methodology, channel planforms as depicted in a series of aerial photographs were overlain to study recent channel change (1971 to 1994) including that caused by two major flood events. The study formed part of wider investigations into the hydrology and geomorphology of the River Tay, following the 1990 and 1993 flood events commissioned by organisations involved with management of the river. The study reach in 1863 and 1899 was shown to have alternating, highly divided sections with multiple mid-channel islands, and stable single-thread sections although, overall, the channel was less braided than depicted on 18th century maps. By 1975, the multi-channel sections had changed to a predominantly single-thread character and it is proposed that this had occurred in response to flood embankment construction and bank protection leading to channel narrowing and incision. This has wider implications for the management of the River Tay as channel instability supports diverse natural habitats with high conservation value. Once recent river planform changes on the study reach had been identified, stable and unstable reaches were defined allowing the determination of the degree and nature of instability using GIS methodology which included quantification of active channel widths and gravel area, braiding indices, sinuosity and channel occupancy indices. A number of unstable reaches were also studied in the field to examine the processes responsible for river bank erosion. In addition, the effect of in-channel morphology on river planform changes was examined by applying image analysis to bands 3, 5, 6 and 8 of airborne multi-spectral imagery (Daedalus ATM) to map channel bathymetry. The results showed that changes in channel planform and position occurred almost entirely in response to extreme flood events and that areas of greatest channel change were in zones of historical instability resulting from the presence of less cohesive sediments along the courses of former river channels. A meander-like alternation of pool-riffle sequences controlled the local distribution of bank erosion along most of these reaches by deflecting thalwegs against outer banks. The information derived from the study was used to construct an erosion hazard map. Using raster-based GIS techniques, these data were combined with measurements of distance from river channel and flood return periods, to create a model which enabled spatial mapping of river bank erosion probabilities. These probabilities were then mapped for hypothetical floods of 5, 10 and 25 year recurrence interval.
27

Public choice for flood defence

Simpson, Katherine Hannah January 2015 (has links)
Why do we want to value the environment? Environmental assets provide a flow of goods and services over time which benefit mankind. Valuing these services contributes towards their protection and enhancement, however many of these benefits cannot be valued in traditional markets and as such rely on non-market valuation techniques. One of these is contingent valuation (CV) which directly asks respondents whether they are willing to pay for an improvement in the good or service. This thesis seeks to explore methodological issues associated with this method by undertaking a CV survey to elicit willingness to pay (WTP) for a new type of flood defence (managed realignment) on the Tay Estuary, Scotland. One challenge for survey designers is to provide high quality, readily understandable information to mitigate bias in WTP estimates. This thesis contributes to the information provision literature by examining whether prior knowledge or new information has a greater effect on the WTP estimate when controlling for respondent experience and familiarity with the good. A field experiment was designed to test for respondent’s prior knowledge; allow for varying levels of information to be presented to respondents and identify information acquisition for each respondent. Specifically tested was the notion that respondents who learn the most about the good during the survey process will have a more robust WTP estimate. Results were mixed: a causal relationship between information provision and learning was established with respondents in the higher treatment groups scoring higher in the second quiz. However, there was no relationship identified between prior knowledge, information provision and WTP. Personal motivations were the strongest predictors of WTP: those who were most concerned about flood risk and who lived closest to the proposed flood defence were willing to pay the most. A second issue in CV is consequentiality. Carson and Groves (2007) argue that for a survey to produce meaningful information about respondent’s preferences the respondent must view their responses as potentially influencing the supply of the public good. This thesis seeks add to this relatively new literature by exploring the observable factors which may influence respondents perceived consequentiality; specifically the effects of familiarity and information. Respondents were asked to state how confident they were that the results of the survey would be used by policy makers on a Likert scale ranging from “very unconfident” through to “very confident”. Results conformed to the Carson and Groves knife edge result: consequential respondents had significantly different WTP distributions compared to inconsequential and unsure respondents and were willing to pay significantly more towards the scheme. Consequential respondents also conformed the theoretical considerations of construct validity whilst inconsequential respondents did not. Respondents with more prior knowledge also appeared to be more likely to perceive the survey as consequential, although this was not consistent across all treatment groups. There is a concern that WTP and consequentiality are endogenous: respondents who want the policy to go ahead may be more likely to state the survey is consequential and state a high WTP in the hope these responses combined contribute to the policy maker’s decision. From a policy perspective the high level of support for the new scheme was encouraging and in contrast to previous findings on preferences for managed realignment. From a flood risk management perspective a “miss-match” between actual and perceived flood risk was highlighted, with many respondents stating they were not at risk from flooding when they in fact were. This is potentially concerning as respondents may not be taking adequate steps to protect their home from future flood risks. Overall it is recognised that values derived from the CV survey form one small part of the planning process and while informative, the decision for a scheme to take place should not be based on these values alone.
28

MECHANISMS OF NEURODEGENERATION IN A MOUSE MODEL OF SANDHOFF DISEASE: ROLES OF INFLAMMATION, EXCITOTOXICITY, AND APOPTOSIS / MECHANISMS OF NEURODEGENERATION IN A MOUSE MODEL OF SANDHOFF DISEASE

Hooper, Alexander William Maurice January 2016 (has links)
Lysosomal storage disorders are a group of rare neurodegenerative diseases that are collectively common, sharing many aspects with other neurodegenerative disorders, including substrate build-up and neuroinflammation. The GM2 Gangliosidoses, Tay-Sachs disease and Sandhoff disease, are pathologically overlapping lysosomal storage disorders, with high prevalence within specific ethnicities. Their effects are neurologically devastating and often fatal at young ages. Current treatments only slow or stall an inevitable decline in health. Novel treatment targets are needed for these disorders, and others with similar pathologies. In these works we demonstrate the negative effect the inflammatory cytokine tumour necrosis factor-alpha has on survival of a model of Sandhoff disease. We demonstrate its role in the upregulation of astrogliosis, and apoptosis, and we present evidence that this effect on astrogliosis occurs through an upregulation of the JAK-2/STAT3 pathway. Though fruitful, a singular focus on inflammation/gliosis in these diseases has left a vacuum in the research into neuron specific molecular processes. We observe the development of inflammation, astrogliosis and neuronal processes in our model, and demonstrate a bi-phasic disease progression, in which early onset microgliosis precedes terminal astrogliosis, apoptosis, and a decline in excitatory glutamate receptors, suggesting neuron-specific malfunction. Furthermore, we show that knockout of the synaptic protein neuronal pentraxin 1 retards neurodegeneration and extends the lifespan of Sandhoff disease mice, independent of inflammation or astrogliosis. Through electrophysiology, we provide evidence of dysregulation of glutamate receptors in Sandhoff disease, and show that knockout of neuronal pentraxin 1 provides rescue from this dysregulation. This work expands on research into gliosis in GM2 gangliosidoses, presents the finding of a novel protein isoform, and presents a new focus on non-glial disease mechanisms and treatments for these and other neurodegenerative disorders. / Thesis / Doctor of Philosophy (PhD) / Lysosomal storage disorders are a group of neurological diseases that are debilitating, and often fatal at a young age. Two diseases of this group- Tay-Sachs disease and Sandhoff disease – are similar in their causes and symptoms. Current treatments for these diseases only slow or stall an inevitable decline in health. New targets for treatment are required, and we provide data suggesting several proteins that may fit this criterion. We also provide evidence of the discovery of a new form of one of these proteins, which is found in high levels in the disease, indicating it may be important in these and other neurodegenerative diseases. Finally, we provide findings indicating that a certain cell type, which is largely ignored in current research for these diseases, may be important in the disease progress. These findings increase our knowledge of Tay-Sachs disease and Sandhoff disease, and open new avenues for medicinal intervention.
29

Tay-Sachs Disease: Mechanisms of Neuropathology and Potential Therapeutic Strategies Utilizing Human Lysosomal Sialidase

Egier, David A. 04 1900 (has links)
<p>GM2 gangliosidoses encompass a group of chronic neurodegenerative disorders characterized by metabolic defects in ganglioside catabolism and marked intralysosomal accumulation of GM2 in central nervous system (CNS)-resident neurons. Included in this group are Tay-Sachs and Sandhoff disease. Human cases of Tay-Sachs and Sandhoff disease present with devastating neurological deterioration; however, murine models display drastically divergent phenotypes. Tay-Sachs mice avoid pathology via a sialidase-mediated bypass of β-hexosaminidase A (HEXA) deficiency, though the precise mechanism of avoidance is not fully elucidated. The following work aimed to: i) determine if the murine sialidase-mediated bypass could be potentiated in human cells, and ii) help clarify the mechanism of disease avoidance in Tay-Sachs animals.</p> <p>Adenoviral overexpression of truncated CCAAT displacement protein (CDP<sup>831-1505</sup>) in human Tay-Sachs neuroglia augmented neuraminidase 1/lysosomal sialidase (NEU1) protein levels, which reduced intralysosomal GM2 accumulations. Chromatin immunoprecipitation revealed binding of CDP<sup>831-1505</sup> to the human <em>NEU1</em> promoter in Tay-Sachs neuroglia. These results provide mechanistic and functional evidence supporting therapeutic exploitation of <em>NEU1</em> for Tay-Sachs disease.</p> <p>Comparison of immunological responses of bone marrow-derived macrophages (BMDMs) to pathogen associated molecular patterns (PAMPs) or GM2 demonstrated that Sandhoff macrophages secrete increased TNF and reduced IL-10 following lipopolysaccharide stimulation. GM2 treatment failed to stimulate an immune response. Such behaviour occurred in the absence of clearly observable intralysosomal ganglioside accumulations. Altered LAMP2 protein size, potentially due to aberrant glycosylation, is hypothesized to disrupt autophagosomal/lysosomal fusion. Subsequent autophagosomal accumulation could result in inherent macrophage hypersensitivity and immunologic irritability. Downstream interleukin-10 (IL-10)/signal transducer and activator of transcription 3 (Stat3) axis, mitogen activated protein kinase (MAPK), and glycogen synthase kinase 3-beta (GSK3β) signaling pathways were affected in Sandhoff BMDMs. These data indicate inherent differences in immunological responses of BMDMs from Sandhoff mice, presumably related to their β-hexosaminidase B (HEXB) deficiency.</p> <p>Data presented here provides evidence to suggest a paradigm shift in the neurodegenerative model of Tay-Sachs and Sandhoff Diseases towards one that places immune cells as an initiating factor for widespread neuroinflammation.</p> / Master of Science (MSc)
30

Aquatic vegetation processes in a floodplain-river system and the influence of lateral dynamics and connectivity

Keruzoré, Antoine January 2012 (has links)
In river ecology the description and understanding of near-natural ecosystem functionality is a difficult task to achieve as the majority of river floodplains have been intensively impacted by human activities. This work addresses ecological functionality of a relatively unimpacted large river system, focussing on the lateral dynamic and connectivity mechanisms driving aquatic vegetation processes. Macrophytes were found to be very patchily distributed at the riverscape scale, being mainly confined to low energy lateral habitats in the floodplain, such as backwaters. Backwaters provided favourable conditions for plants to colonise and recruit and contributed highly to species diversity and productivity at the floodplain scale. Differences between backwaters were attributed to the frequency of connectivity with the main channel during flood events. Nevertheless, the ecological mechanism driving diversity through flooding appears not to be related to flow disturbance. Biomass produced in backwaters was found to remain stable after potentially scouring floods. Therefore the hypothesis that flood disturbances promote species diversity through the removal and destruction of biomass and rejuvenate communities such that species coexistence is increased was rejected. Rather, it appears that diversity in backwaters increases along a temporal gradient as a response to the input of colonists and their accumulation overtime through successive flood inputs. Despite the apparently non-destructive effect of floods on macrophyte biomass, backwaters appear to have a significant role in exporting large amounts of plant propagules from the site of production. Backwaters represented a net source of propagules which highly enriched the main channel pool of potential colonists. However, whereas propagules could be dispersed for long distances in flood flows the probability for them to reach a suitable downstream habitat was extremely low. This work showed that dispersal at baseflow and entry to backwaters through the downstream end after short dispersal drift provided a greater chance of successful colonisation despite the individually much shorter distance moved. Backwaters were demonstrated to be rather isolated aquatic habitats, even though they experience hydrological connectivity, suggesting that primary colonisation of these sites is a limiting step. Instead, colonisation was shown to rely primarily on propagules generated internally by established plants. Whereas colonisation could occur via internal re-organisation of existing plant propagules, the backwater seed bank could also contribute to the macrophytes species established in backwaters. Such contribution was consistently low to medium along a gradient of disturbances and connectivity and showed independence from such river flow processes. Species richness was found to be higher in the established species than in the seed bank, suggesting that asexual reproduction is prioritised by aquatic vegetation in riverine backwaters. The occurrence or persistence of macrophyte species in backwaters depends upon rhizome and plant shoot regeneration. The lack of influence of connectivity revealed that plants may originate from both in situ and externally waterborne vegetative propagules derived from other upstream backwaters. This research demonstrated that the lateral dynamic and associated connectivity are major components of river floodplain ecology which generate a wide spectrum of habitats and have a controlling effect on vegetation processes. Therefore a naturally dynamic ecological state is required to support ecosystem functionality in large river floodplains and especially to maintain a high level of species diversity, productivity and colonisation of backwaters by macrophytes.

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