X-Ray scattering study of cellulosic arrangements in plant cell wall materials

Plant cell walls are the most important source of the polymer cellulose. The cell wall contains crystalline cellulose microfibrils embedded in a matrix of amorphous polymers. The most important of these amorphous polymers are the lignins and the hemi-celluloses. In this thesis we concentrate on the use of wide angle x-ray scattering as a tool to understand the important arrangements of cellulose in cell walls. Other experimental tools are used to supplement this information

Landscape Genetics of The Marbled Salamander, Ambystoma opacum, in a Nationally Protected Park

Landscape features may influence the patterns of migration and dispersal of amphibian species and create genetic structure. A primary goal of landscape genetics is to analyze these influences in order to make more informed management decisions. We sampled larvae from 50 breeding ponds within the boundaries of Mammoth Cave National Park and genotyped 12 individuals per pond at 10 microsatellite loci to estimate gene fl ow between ponds. We used GIS layers of habitat types to conduct a least-cost path analysis and determine the relative cost of movement through each habitat type. We were interested in answering two questions: does structure exist in this continuous landscape, and does a single pond equal a mating population? Preliminary data indicate that structure does exist at the park. Our results show that a landscape genetics approach is an appropriate mechanism for determining population structure and the size and locations of randomly mating populations

Making the MUVE to virtual education

Second Life, a 3D multi-user virtual environment (MUVE), is becoming an increasingly popular topic at educational technology conferences and in the media these days. What’s all the fuss about

The Survey of Lines in M31 (SLIM): The Drivers of the [CII]/TIR Variation

The ratio of the [CII] 158$\,\mu$m emission line over the total infrared emission (TIR) is often used as a proxy for the photoelectric (PE) heating efficiency ($\epsilon_{\rm PE}$) of the far-ultraviolet (FUV) photons absorbed by dust in the interstellar medium. In the nearby galaxy M31, we measure a strong radial variation of [CII]/TIR that we rule out as being due to an intrinsic variation in $\epsilon_{\rm PE}$. [CII]/TIR fails as a proxy for $\epsilon_{\rm PE}$, because the TIR measures all dust heating, not just the contribution from FUV photons capable of ejecting electrons from dust grains. Using extensive multiwavelength coverage from the FUV to far-infrared (FIR), we infer the attenuated FUV emission ($\rm UV_{att}$), and the total attenuated flux ($\rm TOT_{att}$). We find [CII]/TIR to be strongly correlated with $\rm UV_{att}$/$\rm TOT_{att}$, indicating that, in M31 at least, one of the dominant drivers for [CII]/TIR variation is the relative hardness of the absorbed stellar radiation field. We define $\rm{ \epsilon_{PE}^{UV}}$, [CII]/$\rm{ UV_{att}}$ which should be more closely related to the actual PE efficiency, which we find to be essentially constant ($1.85 \pm 0.8 \%$) in all explored fields in M31. This suggests that part of the observed variation of [CII]/TIR in other galaxies is likely due to a change in the relative hardness of the absorbed stellar radiation field, caused by a combination of variations in the stellar population, dust opacity and galaxy metallicity, although PE efficiency may also vary across a wider range of environments.Comment: 19 pages, 16 figures, accepted for publication in Ap

Total hip replacement: improving cement fixation of the acetabular component

The primary aim of this study was to propose fixation techniques that would improve the cement fixation of the acetabular cup. This was done by (1) studying current practice, (2) creating FE models of the reconstructed acetabulum to predict improved fixation techniques, (3) validating the FE models by laboratory investigations and (4) proposing designs of jigs and drill bit that would assist orthopaedic surgeons use the recommended techniques

Major Merger Galaxy Pairs at z = 0: Dust Properties and Companion Morphology

We present an analysis of dust properties of a sample of close major-merger galaxy pairs selected by K_s magnitude and redshift. The pairs represent the two populations of spiral–spiral (S+S) and mixed morphology spiral–elliptical (S+E). The Code Investigating GALaxy Emission software is used to fit dust models to the Two Micron All Sky Survey, Wide-Field Infrared Survey Explorer, and Herschel flux density measurements, and to derive the parameters describing the polycyclic aromatic hydrocarbons contribution, interstellar radiation field, and photodissociation regions. Model fits verify our previous Spitzer Space Telescope analysis that S+S and S+E pairs do not have the same level of enhancement of star formation and differ in dust composition. The spirals of mixed-morphology galaxy pairs do not exhibit the enhancements in interstellar radiation field and therefore dust temperature for spirals in S+S pairs in contrast to what would be expected according to standard models of gas redistribution due to encounter torques. This suggests the importance of the companion environment/morphology in determining the dust properties of a spiral galaxy in a close major-merger pair

Broadband Infrared Photodetection Using a Narrow Bandgap Conjugated Polymer

Photodetection spanning the short-, mid-, and long-wave infrared (SWIR-LWIR) underpins modern science and technology. Devices using state-of-the-art narrow bandgap semiconductors require complex manufacturing, high costs, and cooling requirements that remain prohibitive for many applications. We report high-performance infrared photodetection from a donor-acceptor conjugated polymer with broadband SWIR-LWIR operation. Electronic correlations within the π-conjugated backbone promote a high-spin ground state, narrow bandgap, long-wavelength absorption, and intrinsic electrical conductivity. These previously unobserved attributes enabled the fabrication of a thin-film photoconductive detector from solution, which demonstrates specific detectivities greater than 2.10 × 109 Jones. These room temperature detectivities closely approach those of cooled epitaxial devices. This work provides a fundamentally new platform for broadly applicable, low-cost, ambient temperature infrared optoelectronics

Angular clustering of galaxies at 3.6 microns from the Spitzer Wide-area Infrared Extragalactic (SWIRE) Survey

We present the first analysis of large-scale clustering from the Spitzer Wide-area Infrared Extragalactic legacy survey (SWIRE). We compute the angular correlation function of galaxies selected to have 3.6 m fluxes brighter than 32 Jy in three fields totaling 2 deg2 in area. In each field we detect clustering with a high level of significance. The amplitude and slope of the correlation function is consistent between the three fields and is modeled as w() ¼ A1 with A ¼ (0:6 0:3) ; 10 3; ¼ 2:03 0:10. With a fixed slope of ¼ 1:8, we obtain an amplitude of A ¼ (1:7 0:1) ; 10 3. Assuming an equivalent depth of K 18:7 mag we find that our errors are smaller but our results are consistent with existing clustering measurements in K-band surveys and with stable clustering models. We estimate our median redshift z ’ 0:75, and this allows us to obtain an estimate of the three-dimensional correlation function (r), for which we find r0 ¼ 4:4 0:1 h 1 Mpc