• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 587
  • 556
  • 88
  • 59
  • 38
  • 18
  • 18
  • 18
  • 18
  • 18
  • 18
  • 13
  • 13
  • 12
  • 10
  • Tagged with
  • 1614
  • 557
  • 176
  • 167
  • 146
  • 136
  • 122
  • 117
  • 99
  • 92
  • 83
  • 82
  • 81
  • 76
  • 72
  • 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.
481

STUDY OF GENE SILENCING IN RICE: A ROOT PREFERENTIAL GENE RCG2

Shi, Xiangyu 2009 May 1900 (has links)
The RCg2 promoter was identified in a search for root-specific genes to combat the rice water weevil (RWW) but expressed at low frequency (~10%). Spatial expression of RCg2 was investigated using two reporter constructs YXA (RCg2-gus-ocs) and YXB (RCg2-gus-RCg2) that included 1.6 kb of the RCg2 5' sequence fused to the ?-glucuronidase (gus) coding region. YXB plants were generated via Agrobacterium-mediated transformation but only 8 of 158 plants analyzed showed strong GUS activity despite the presence of an intact construct. Reactivation of RCg2 gene in rice was investigated by treatment of R0 and R1 of YXB transgenic plants with 5-azacytidine. Reactivation of RCg2-gus was observed in some transgenic plants indicating different mechanisms involved in the gene silencing of the YXB lines. DNA methylation analysis, northern blotting, RT-PCR and small RNA analysis supported the conclusion that PTGS and TGS are present in the silenced plants. Promoter analysis in silico and using promoter deletion assays predicted that the RCg2 promoter contains a complex region that includes miRNA homologs, MITEs and repetitive sequences. The high frequency of promoter-related silencing suggests functional interactions of these elements of the transgene and the homologous endogenous gene. To identify key elements contributing to the root-preferential expression of RCg2 and the high frequency of silencing observed in transgenic (YXB) lines, several RCg2 promoter deletion constructs were designed. These include 5' deletions MC1, MC2, MC4, MC7 and MC8 and internal deletions MC5, MC11, MC12 and MC13. The frequency with which silencing was encountered in populations of the deletion mutants was used to characterize the effects of various promoter elements. Deletion of the region from -406 to -208 (compared MC11 to YXB, and MC13 to MC1) revealed that region contains a negative element. Among 36 independent transformants, 33% with MC11 expressed GUS and 85% with MC13 showed GUS expression. Comparing MC7 transgenic plants to MC1 revealed that the region ?888 to ?729 is another negative regulatory element, and comparing MC11 to MC12, the proportion of expression of transgenic plants indicated the region ?729 to ?406 is a positive regulatory element.
482

Queer as Vampires : A study of Anne Rice’s Interview With The Vampire through queer theory

Osap, Sonja January 2010 (has links)
This paper will focus on the homosexuality and homoeroticism that can be found in Anne Rice’s novel Interview With The Vampire using Queer theory. The paper is divided into four parts in which different aspects of the novel will be discussed. Firstly the discussion focuses on the homoeroticism which is abundant in Rice’s novel. The second part covers the subject of identity and Louis’ quest to find out what and why he is. Next the issue of family within the vampyric world is examined using the family unit that Louis, Lestat and Claudia make as its basis. Lastly the question of why the ‘gender-free’ love which is present in Interview With The Vampire is important to the vampire genre is answered.
483

Development of Self-consolidating High Performance Concrete Incorporating Rice Husk Ash

Safiuddin, Md. January 2008 (has links)
The work presented in this thesis deals with the development of self-consolidating high performance concrete (SCHPC) incorporating rice husk ash (RHA) as a supplementary cementing material. Various SCHPCs were produced using the water-binder (W/B) ratios of 0.30, 0.35, 0.40 and 0.50, and RHA content in the range of 0 to 30% of cement by weight. In addition, a number of pastes and mortars formulated from the concretes were prepared and tested for the filling ability. The paste and mortar filling abilities were tested with respect to flow time and flow spread, respectively, at various dosages of high-range water reducer (HRWR). Also, the mortars were tested for the air content at various dosages of air-entraining admixture (AEA). It was observed that the flow time of the pastes increased with lower W/B ratio and higher RHA content, whereas the flow spread of the mortars decreased with higher W/B ratio and greater RHA content. Both paste and mortar filling abilities increased with higher HRWR dosages. In addition, the air content of the mortars decreased with lower W/B ratio and higher RHA content for given AEA dosages. The fresh SCHPCs were tested for filling ability, passing ability, air-void stability, segregation resistance, unit weight and air content. The filling ability was determined with respect to slump and slump flow, inverted slump cone flow time and spread, and orimet flow time and spread. The passing ability was measured with regard to slump and slump flow with J-ring, inverted slump cone flow spread with J-ring, and orimet flow spread with J-ring. The air-void stability in several fresh SCHPC mixtures was investigated with respect to re-mixing of concrete and subsequent measurement of air content at different test stages. The test results obtained for the fresh properties showed that the inverted slump cone and orimet flow times increased with lower W/B ratio and greater RHA content. In addition, the slump flow, inverted slump cone flow spread, and orimet flow spread with and without J-ring increased considerably with lower W/B ratio and greater RHA content. However, the increases in slump with and without J-ring at lower W/B ratio and higher RHA content were not significant. The unit weight of concrete slightly decreased with higher W/B ratio and greater RHA content, and with higher air content. Achieving the target air content required greater AEA dosages for lower W/B ratio and higher RHA content. However, the presence of RHA had no adverse effect on the air-void stability of concrete. The segregation resistance of various SCHPCs was investigated by visual inspection of concrete in mixer pan, and during and after different flow tests. Slight bleeding and a thick layer of paste were noticed in mixer pan for several concretes. The dynamic segregation in the form of discontinuity or blockage of flow did not occur during the orimet and inverted slump cone flow tests for any concrete. No aggregate pile appeared in the slump flow, and orimet and inverted slump cone flow spreads of any concrete. But minor to severe mortar halos were noticed in the periphery of the flow spread of several concretes, particularly in the presence of high RHA content. The results of visual inspection suggest that both lower W/B ratio and greater RHA content improved the dynamic segregation resistance of concrete. In contrast, the higher RHA content resulted in a lower static segregation resistance, which was overcome in the presence of viscosity-enhancing admixture (VEA). The static segregation resistance of several SCHPCs was quantitatively determined by sieve and column apparatus. The segregation index given by the sieve increased with lower W/B ratio and higher RHA content, thus indicating a reduced static segregation resistance. In contrast, the segregation factor given by the column apparatus decreased with lower W/B ratio suggesting an increased static segregation resistance. However, the segregation factor increased with higher RHA content, and thus revealed a reduction in static segregation resistance. In the presence of VEA, both segregation index and segregation factor decreased significantly, indicating an improvement in the static segregation resistance of concrete. The hardened SCHPCs were tested for compressive strength, ultrasonic pulse velocity, water absorption, total porosity and electrical resistivity. Test results revealed that the compressive strength, ultrasonic pulse velocity and true electrical resistivity increased, whereas the water absorption and total porosity decreased with lower W/B ratio and higher RHA content. The entrained air-voids decreased the compressive strength, ultrasonic pulse velocity, water absorption and total porosity, but slightly increased the electrical resistivity of concrete. In general, the hardened properties indicated good durability of the concretes. The empirical models for the filling ability (slump flow) and compressive strength of SCHPC were derived and verified with test data from this study and other data taken from the literature. The slump flow and compressive strength computed from the models were coherent with the measured values. Both filling ability and strength models were useful to develop a mixture design method for SCHPC with and without RHA.
484

HELPING COGNITIVE RADIO IN THE SEARCH FOR FREE SPACE

Gonzales Fuentes, Lee January 2012 (has links)
Spectrum sensing is an essential pre-processing step of cognitive radio technology for dynamic radio spectrum management. One of the main functions of Cognitive radios is to detect the unused spectrum and share it without harmful interference with other users. The detection of signal components present within a determined frequency band is an important requirement of any sensing technique. Most methods are restricted to the detection of the spectral lines. However, these methods may not comply with the needs imposed by practical applications.  This master thesis work presents a novel method to detect significant spectral components in measured non-flat spectra by classifying them in two groups: signal and noise frequency lines. The algorithm based on Fisher’s discriminant analysis, aside from the detection of spectral lines, estimates the magnitude of the spectral lines and provides a measure of the quality of classification to determine if a spectral line was incorrectly classified. Furthermore, the frequency lines with higher probability of misclassification are regrouped and the validation process recomputed, which results in lower probabilities of misclassification. The proposed automatic detection algorithm requires no user interaction since any prior knowledge about the measured signal and the noise power is needed. The presence or absence of a signal regardless of the shape of the spectrum can be detected. Hence, this method becomes a strong basis for high-quality operation mode of cognitive radios. Simulation and measurement results prove the advantages of the presented technique. The performance of the technique is evaluated for different signal-to-noise ratios (SNR) ranging from 0 to -21dB as required by the IEEE standard for smart radios. The method is compared with previous signal detection methods.
485

Cost – Benefit Analysis of Different Rice Cropping systems in Thailand

ARAYAPHONG, SUPISRA January 2012 (has links)
System of Rice Intensification (SRI) has been introduced and practiced throughout Thailand. However, the conventional transplanting system is well-accepted among Thai farmers over the country. This paper quantifies and compares costs and benefits of SRI and the conventional system of rice cultivation in Thailand to find the best system for a farmer, the environment and a society. The scope of this paper includes a farmer’s profit, the environmental damages and a society’s net benefits categorized in clay soil and sandy loam conditions. The farmer’s profit consists of a production cost and income. The amount of fertilizer application, level of lethal dose and climate change cost are regarded as environmental damage components. The society has concerned over the farmer’s profit and the environmental cost in a decision. The study uses cost-benefit analysis to investigate mean and variation of profit and cost in monetary term. Monte Carlo simulation is utilized for quantifying risk in each scenario. The study finds that SRI saves the production input and increases yield gain significantly. The most impressive results are a reduction in water consumption and number of seeds. Also, the environmental damage caused by this system is lower due to less amount of chemical fertilizer and pesticide applications as well as a low rate of methane gas emission. Sensitivity analysis shows that SRI has better performance under best and worst case scenarios for both types of soil (clay soil and sandy loam). However, the system contains the highest risk of the farmer’s profit. In conclusion, SRI is more beneficial and efficient than conventional system. Still, risk aspects should be considered in decision making. This study can be employed as a framework for government or any parties, who are interested or have willingness to conduct a field study of SRI and the conventional rice cropping system or for the further study about the integrated system (a combination between SRI and conventional system).
486

Development of Self-consolidating High Performance Concrete Incorporating Rice Husk Ash

Safiuddin, Md. January 2008 (has links)
The work presented in this thesis deals with the development of self-consolidating high performance concrete (SCHPC) incorporating rice husk ash (RHA) as a supplementary cementing material. Various SCHPCs were produced using the water-binder (W/B) ratios of 0.30, 0.35, 0.40 and 0.50, and RHA content in the range of 0 to 30% of cement by weight. In addition, a number of pastes and mortars formulated from the concretes were prepared and tested for the filling ability. The paste and mortar filling abilities were tested with respect to flow time and flow spread, respectively, at various dosages of high-range water reducer (HRWR). Also, the mortars were tested for the air content at various dosages of air-entraining admixture (AEA). It was observed that the flow time of the pastes increased with lower W/B ratio and higher RHA content, whereas the flow spread of the mortars decreased with higher W/B ratio and greater RHA content. Both paste and mortar filling abilities increased with higher HRWR dosages. In addition, the air content of the mortars decreased with lower W/B ratio and higher RHA content for given AEA dosages. The fresh SCHPCs were tested for filling ability, passing ability, air-void stability, segregation resistance, unit weight and air content. The filling ability was determined with respect to slump and slump flow, inverted slump cone flow time and spread, and orimet flow time and spread. The passing ability was measured with regard to slump and slump flow with J-ring, inverted slump cone flow spread with J-ring, and orimet flow spread with J-ring. The air-void stability in several fresh SCHPC mixtures was investigated with respect to re-mixing of concrete and subsequent measurement of air content at different test stages. The test results obtained for the fresh properties showed that the inverted slump cone and orimet flow times increased with lower W/B ratio and greater RHA content. In addition, the slump flow, inverted slump cone flow spread, and orimet flow spread with and without J-ring increased considerably with lower W/B ratio and greater RHA content. However, the increases in slump with and without J-ring at lower W/B ratio and higher RHA content were not significant. The unit weight of concrete slightly decreased with higher W/B ratio and greater RHA content, and with higher air content. Achieving the target air content required greater AEA dosages for lower W/B ratio and higher RHA content. However, the presence of RHA had no adverse effect on the air-void stability of concrete. The segregation resistance of various SCHPCs was investigated by visual inspection of concrete in mixer pan, and during and after different flow tests. Slight bleeding and a thick layer of paste were noticed in mixer pan for several concretes. The dynamic segregation in the form of discontinuity or blockage of flow did not occur during the orimet and inverted slump cone flow tests for any concrete. No aggregate pile appeared in the slump flow, and orimet and inverted slump cone flow spreads of any concrete. But minor to severe mortar halos were noticed in the periphery of the flow spread of several concretes, particularly in the presence of high RHA content. The results of visual inspection suggest that both lower W/B ratio and greater RHA content improved the dynamic segregation resistance of concrete. In contrast, the higher RHA content resulted in a lower static segregation resistance, which was overcome in the presence of viscosity-enhancing admixture (VEA). The static segregation resistance of several SCHPCs was quantitatively determined by sieve and column apparatus. The segregation index given by the sieve increased with lower W/B ratio and higher RHA content, thus indicating a reduced static segregation resistance. In contrast, the segregation factor given by the column apparatus decreased with lower W/B ratio suggesting an increased static segregation resistance. However, the segregation factor increased with higher RHA content, and thus revealed a reduction in static segregation resistance. In the presence of VEA, both segregation index and segregation factor decreased significantly, indicating an improvement in the static segregation resistance of concrete. The hardened SCHPCs were tested for compressive strength, ultrasonic pulse velocity, water absorption, total porosity and electrical resistivity. Test results revealed that the compressive strength, ultrasonic pulse velocity and true electrical resistivity increased, whereas the water absorption and total porosity decreased with lower W/B ratio and higher RHA content. The entrained air-voids decreased the compressive strength, ultrasonic pulse velocity, water absorption and total porosity, but slightly increased the electrical resistivity of concrete. In general, the hardened properties indicated good durability of the concretes. The empirical models for the filling ability (slump flow) and compressive strength of SCHPC were derived and verified with test data from this study and other data taken from the literature. The slump flow and compressive strength computed from the models were coherent with the measured values. Both filling ability and strength models were useful to develop a mixture design method for SCHPC with and without RHA.
487

Contract farming and organic rice production in Laos : a transformation analysis

Erikson, Gustaf January 2011 (has links)
As in many least developed countries the farmers in Laos are heavily dependent on subsistence based agriculture production for their livelihood. A key for increased welfare for the rural population inLaosis to increase their profits of small scale farmers and generate a higher income per capita. One possible way to increase the profits and income for smallholder farmers may be to convert in to organic rice production for the export market, since the international market for organic rice is growing, consumers are prepared to pay a premium prise for organic products and conditions for organic rice production are favourable in Laos. Organic rice farming has grown in Laos during the last decade as greater volumes of organic rice are produced and exported. Organic rice is mainly produced by smallholders in donor projects or by contract farmers supplying contract farming companies. In this thesis I try to determine the causes behind this structural transformation by incorporating evolutionary economic theory (Schumpeter, 1911; Dahmén, 1950 and Marmefelt, 1998) which focuses on entrepreneurial innovations and creditors as the basis for changes in the economy. By performing a Dahménian transformation analysis of the transition from conventional- to organic rice production within the development block around rice production in Laos, I try to determine the transformation pressure causing the transformation to take place. Emphasis is in particular given to the role of contract farming in this process. I investigate to what extent the contract farming firm can be regarded as a Schumpeterian banker, a concept introduced by Marmefelt (1998), that can coordinate the development block around rice production by providing credits to the entrepreneurs within the development block. The analysis shows that two types of transformation pressures are likely to have caused the farmers to convert to organic rice production. First of all it is likely that the relatively higher price paid for organic rice (42 percent higher than conventional rice) has convinced farmers to make the transition. This type of transformation pressure can be seen as a market pull type, as it originates from an increased demand in the international market, which in turn increases the relative price for the product. The analysis further shows that a production method innovation had taken place by the introduction of new inputs, made available by the contract farming firm. This has led to an increased productivity which, combined with the premium price, generated higher profits for the organic contract farmers. The production method innovation can be seen as a market push type of transformation pressure originating from the supply side. In this thesis I argue that it is unlikely that the transformation would have occurred without the involvement of the contract farming firm. On their own, farmers did neither have the means to grow the organic rice, nor the proper market channels to process and sell the organic rice on the international market. I argue that the contract farming firm’s ability to facilitate price signal information from the international market to farmers, provide access to the new market thru market links, and provide credits for new inputs as well as technical assistance essentially made the transition to organic rice possible. However the analysis also shows that the contract farming firm had a limited ability to fulfil its role as a coordinator in the evolvement of the organic rice production, in terms of a Schumpeterian banker, because of limited abilities to solve bottlenecks in the value chain. The reason for this is mainly limited financial resources to finance complementary investments in other parts of the development block.
488

STUDY OF GENE SILENCING IN RICE: A ROOT PREFERENTIAL GENE RCG2

Shi, Xiangyu 2009 May 1900 (has links)
The RCg2 promoter was identified in a search for root-specific genes to combat the rice water weevil (RWW) but expressed at low frequency (~10%). Spatial expression of RCg2 was investigated using two reporter constructs YXA (RCg2-gus-ocs) and YXB (RCg2-gus-RCg2) that included 1.6 kb of the RCg2 5' sequence fused to the ?-glucuronidase (gus) coding region. YXB plants were generated via Agrobacterium-mediated transformation but only 8 of 158 plants analyzed showed strong GUS activity despite the presence of an intact construct. Reactivation of RCg2 gene in rice was investigated by treatment of R0 and R1 of YXB transgenic plants with 5-azacytidine. Reactivation of RCg2-gus was observed in some transgenic plants indicating different mechanisms involved in the gene silencing of the YXB lines. DNA methylation analysis, northern blotting, RT-PCR and small RNA analysis supported the conclusion that PTGS and TGS are present in the silenced plants. Promoter analysis in silico and using promoter deletion assays predicted that the RCg2 promoter contains a complex region that includes miRNA homologs, MITEs and repetitive sequences. The high frequency of promoter-related silencing suggests functional interactions of these elements of the transgene and the homologous endogenous gene. To identify key elements contributing to the root-preferential expression of RCg2 and the high frequency of silencing observed in transgenic (YXB) lines, several RCg2 promoter deletion constructs were designed. These include 5' deletions MC1, MC2, MC4, MC7 and MC8 and internal deletions MC5, MC11, MC12 and MC13. The frequency with which silencing was encountered in populations of the deletion mutants was used to characterize the effects of various promoter elements. Deletion of the region from -406 to -208 (compared MC11 to YXB, and MC13 to MC1) revealed that region contains a negative element. Among 36 independent transformants, 33% with MC11 expressed GUS and 85% with MC13 showed GUS expression. Comparing MC7 transgenic plants to MC1 revealed that the region ?888 to ?729 is another negative regulatory element, and comparing MC11 to MC12, the proportion of expression of transgenic plants indicated the region ?729 to ?406 is a positive regulatory element.
489

Impact of Two Water Management Systems on Arsenic Speciation and Microbial Populations in Rice Rhizosphere

Somenahally, Anil Kumar C. 2010 December 1900 (has links)
Arsenic (As) is a problem with rice production systems throughout the world as high As concentrations are reported in rice grains originating from several parts of the world. This characteristic is mainly due to the flooded conditions utilized in rice culture. We hypothesized that the soluble As concentrations in the rice rhizosphere can be decreased by growing rice more aerobically through intermittent flooding. Intermittent water management practices might also change microbial populations in the rice rhizosphere that might potentially impact As chemistry and bioavailability. Two field-scale experiments were conducted over two years to study the impact of intermittent and continuous flooding on As speciation and microbial populations in the rice rhizosphere. As levels and speciation in the rhizosphere soil, root-plaque and pore-water were determined using a high performance liquid chromatography-inductively coupled plasmamass spectroscopy (HPLC-ICP-MS). The microbial populations were assessed from the rhizosphere soil and root-plaque samples using quantitative polymerase chain reaction (qPCR) and 16S rRNA sequencing. Pore-water and root-plaque total-As concentrations significantly decreased in the intermittent compared to the continuous flood plots. Inorganic arsenite (iAsIII) was predominant in pore-water and inorganic arsenate (iAsV) in root-plaque and soil. Rootplaque sequestered significantly higher levels of As (almost tenfold higher) than the adjacent rhizosphere soil. Grain As concentrations also decreased by 35 to 45 percent in the intermittent compared to the continuously flooded plots. Organic As species, monomethyl and dimethyl arsenate were detected in the rhizosphere with relative increases and decreases among the treatments. Bacteria were the predominant group (91 to 94 percent and 48 to 78 percent of total community in root-plaque and rhizosphere soils, respectively). Archaea were also a major component of rhizosphere soil with their populations being higher under continuous flooding. The relative abundance of iron-reducing bacteria was around 3 to 6 percent of the total community in root-plaque and around 6 to 6 percent in soil, with significantly lower abundance in the intermittent compared to the continuously flooded plots. Results of these studies demonstrated that intermittent flooding could be a potential management option to reduce grain As in rice cultivated on fields with moderate to high As concentrations.
490

The Analysis of Rice Policy Reform in Taiwan since Its Accession to WTO

Lee, Ju-lung 19 June 2006 (has links)
After its accession to the WTO, under the open market for agricultural products and reducing domestic support, Taiwan needs to import brown rice of at least 144,000 metric tons, following the rule of minimum access in order to meet the requirements¡¦ of the WTO. To protect farmer¡¦s interest and agriculturalecology, the Taiwan government continues to implement paddy land utilization adjustment policy and price guarantee policy, which sustains government supplement to rice but it fails to reach the good of price stability in the market. This means all related policies still have room for improvement. In recent years, new rounds of negotiation for agriculture under the WTO framework have begun and, due to the pressure of negotiation, it is unavoidable to implement import tariff for rice. Thus, Taiwan¡¦s agricultural sectors are under the threat of a collapse, and to maintain the development of rice farming industry under the WTO regulations will be a very important issue. Also, the government should take more aggressive and prospective measures to overcome the current difficulties of the rice industry. This paper will explore rice policies in Taiwan and propose on improvement with consideration for a long term agricultural policy. Taiwan implements paddy land utilization adjustment policy for the preparation of tariff systems. Although this will meet the WTO regulation in the short term, it would experience risks and challenge, in the future. Currently, alternative plans are not available and what is suggested in this paper basically follows the American FSRIA and Japanese rice stability policies to reach a balance between government and farmers under the WTO regulation, trying to eliminate market intervention and reduce government¡¦s financial burden. With the decline of rice price and rent, the rice industry will develop towards a large scale of management and rice competitiveness will be upgraded, which will then increase farmer¡¦s revenue even when subsidies are reduced.

Page generated in 0.081 seconds