Browsing by Subject "satellite"
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Item Genomic organization of chromosomal centromeres in the cultivated rice, Oryza sativa L., and its wild progenitor, O. rufipogon Griff.(Texas A&M University, 2004-11-15) Uhm, TaesikCentromeres are responsible for sister-chromatid cohesion, kinetochore formation, and accurate transmission of chromosomes. Rice provides an excellent model for organizational and functional studies of centromeres since several of its chromosomes contain limited amounts of satellite and other repetitive sequences in their centromeres. To facilitate molecular characterization of the centromeres, we screened several BIBAC and BAC libraries of japonica and indica rice, using several centromere-specific repeat elements as probes. The positive clones were identified, fingerprinted and integrated into our whole genome physical map databases of the two rice subspecies. BAC/BIBACbased physical maps were constructed for the centromeric regions of the subspecies. To determine whether the genomic organization of the centromeres has changed since the cultivated rice split from its progenitor and to identify the sequences potentially playing an important role in centromere functions, we constructed a large-insert BIBAC library for the wild progenitor of Asian cultivated rice, O. rufipogon. The library contains 24,192 clones, has an average insert size of 163 kb, and covers 5 x haploid genome of wild rice. We screened the wild rice library with two centromere 8-specific overgo probes designed from the sequences flanking centromere 8 of japonica rice. A BIBACbased map was constructed for wild rice centromere 8. Two of the clones, B43P04 and B15E04, were found to span the entire region of the wild rice centromere and thus selected for sequencing the centromere. By sequencing the B43P09 clone, a 95% genomic sequence of the long arm side of wild rice centromere 8 was obtained. Comparative analysis revealed that the centromeric regions of wild rice have a similar gene content to japonica rice, but the centromeric regions of japonica rice have undergone chromosomal rearrangements at both large scale and nucleotide levels. In addition, although the 155-bp satellite repeats showed dramatic changes at the middle region, they are conserved at the 5' and 3' ends of satellite monomers, suggesting that those regions might have important functional roles for centromeres. These results provide not only new insights into genomic organization and evolution, but also a platform for functional analysis of plant centromeres.Item Satellite Remote Sensing of Mid-level Clouds(2012-11-07) Jin, Hongchun 1980-This dissertation aims to study the mid-level clouds using satellite observations. It consists of two major parts: characteristics (including cloud top/base heights, cloud top pressure and temperature, and cloud thickness) and thermodynamic phase of mid-level clouds. Each part devotes to a particular issue of significant importance for satellite-based remote sensing of mid-level clouds. The first part of this dissertation focuses on the impacts of three definitions of the mid-level clouds based on cloud top pressure, cloud top height, and cloud base height on mid-level cloud characteristics. The impacts of multi-layer clouds on satellite-based global statistics of clouds at different levels, particularly for mid- level clouds, are demonstrated. Mid-level clouds are found to occur more frequently than underlying upper-level clouds. Comparisons of cloud amounts between a merged CALIPSO, CloudSat, CERES, and MODIS (CCCM) dataset and International Satellite Cloud Climatology Project (ISCCP) climatology are made between July 2006 and December 2009. Midlevel cloud characteristics are shown to be sensitive to perturbations in midlevel boundary pressures and heights. The second part focuses on the thermodynamic phase of mid-level clouds. A new algorithm to detect cloud phase using Atmospheric Infrared Sounder (AIRS) high spectral measurements is introduced. The AIRS phase algorithm is based on the newly developed High-spectral-resolution cloudy-sky Radiative Transfer Model (HRTM). The AIRS phase algorithm is evaluated using the CALIPSO cloud phase products for single-layer, heterogeneous, and multi-layer scenes. The AIRS phase algorithm has excellent performance (>90%) in detecting ice clouds compared to the CALIPSO ice clouds. It is capable of detecting optically thin ice clouds in tropics and clouds in the mid-temperature range. Thermodynamic phase of mid-level clouds are investigated using the spatially collocated AIRS phase and CALIPSO phase products between December 2007 and November 2008. Overall, the statistics show that ice, liquid water, and mixed-phase of the mid-level clouds are approximately 20%, 40%, and 40%, globally.