A VLBA Search for a Stimulated Recombination Line from the Accretion Region in NGC1275

The radio source 3C84, in NGC1275, has a two sided structure on parsec scales. The northern feature, presumed to be associated with a jet moving away from the Earth, shows strong evidence for free-free absorption. The ionized gas responsible for that absorption would be a source of detectable stimulated recombination line emission for a wide range of physical conditions. The VLBA has been used to search for the H65$\alpha$ hydrogen recombination line. The line is only expected to be seen against the northern feature which contains a small fraction of the total radio flux density. This spatial discrimination significantly aids the search for a weak line. No line was seen, with upper limits of roughly 15% of the continuum over a velocity range of 1486 km/s with resolutions up to 6.6 km/s. In the absence of a strong radiation field, this would imply that the free-free absorbing gas has a wide velocity width, is moving rapidly relative to the systemic velocity, or is concentrated in a thin, high density structure. All of these possibilities are reasonably likely close to an AGN. However, in the intense radiation environment of the AGN, even considering only the radiation we actually observe passing through the free-free absorbing gas, the non-detection is probably assured by a combination of saturation and radiation damping.Comment: 14 pages with 4 postscript figures. Accepted for publication in the April 2003 Astronomical Journa

J06587-5558 -- A Very Unusual Polarised Radio Source

We have found a peculiar radio source in the field of one of the hottest known clusters of galaxies 1E0657-56. It is slightly extended, highly polarised (54% at 8.8GHz) and has a very steep spectrum, with alpha ~ -1 at 1.3 GHz, steepening to ~ -1.5 at 8.8GHz (S \propto nu^alpha). No extragalactic sources are known with such high integrated polarisation, and sources with spectra as steep as this are rare. In this paper, we report the unusual properties of the source J06587-5558 and speculate on its origin and optical identification.Comment: 5 pages, 6 figures, accepted by MNRAS letter

If I customize it, I will keep it longer? Segmenting mass customization consumers through the sustainability lens

2021 Spring.Includes bibliographical references.Mass customization (MC) refers to the manufacture of customized products on a mass basis at prices similar to mass-produced (MP) goods (Davis, 1996). Mass customized apparel (MCA) products can better address consumer needs through the consumer-centric process (Yang, Kincade & Chen-Yu, 2015). Additionally, MCA has been heralded for its ability to reduce waste throughout the supply chain, most notably through the elimination of deadstock (e.g., Boër, Redaelli, Boër, & Gatti, 2018), and is suggested to offer the potential for more sustainable consumer behavior through an emotional bond formed with the customized product (Mugge, Schoormans, & Schifferstein, 2009) that may lead to increased product longevity. The purpose of this thesis was to explore the current MCA consumer market and investigate potential connections among MCA consumer segments regarding sustainability related variables. Specifically, this study utilized actual MCA consumers' purchase patterns (i.e. frequency of MCA purchase, amount of MCA purchase, and duration of MCA purchase behavior) to identify consumer segments and profile this emerging market to better understand their MCA-specific motivations for MCA purchase and satisfaction with the MCA product and customization experience as well as demographic variables (i.e., income, education, and body mass index (BMI)). Additionally, this study aimed to uncover to what extent they may display sustainability-related variables (i.e., emotional product attachment and environmental attitudes) and behaviors (i.e., sustainable apparel behaviors and general sustainable behavior). To address this purpose, an online consumer survey was distributed in Spring 2019, and 318 usable responses were analyzed using the segmentation framework. Two clusters were identified who differed mainly on the duration of their MCA purchase behaviors; new customizers (n = 243) had an average of 2 years of experience as MCA consumers, while experienced customizers (n =75) had on average 9 years of experience purchasing MCA. T-test comparison, multiple regression, and correlation analyses were conducted to explore the characteristics of the clusters. Findings showed a general trend among experienced customizers for stronger motivations and satisfaction, as well as increased environmental attitudes, and more sustainable apparel behaviors and general sustainable behaviors. Interestingly, regression analysis revealed participants' who were interested in making sustainable pre-purchase apparel decisions, such as purchasing apparel made of organic materials were likely to be less satisfied with the MCA products and experience. Both new and experienced customizers reported intentions of keeping MCA products longer than MP apparel, and a significant difference between clusters found experienced customizers intended to keep their MCA product a year longer than new customizers; suggesting MCA maybe a sustainable alternative for consumers. This thesis concludes with a discussion of theoretical and managerial implications as well as suggestions for future research for this promising topic

Critical analysis of accumulated experimental data on filament-reinforced metal matric composites

Data analysis on filament reinforced metal matrix composite

A study of low density, high strength high modulus filaments and composites

Filament and whisker reinforcement of low density, high strength, high modulus composites - metallic and ceramic layers alternated in multilaminar composite

Prospects for Redshifted 21-cm observations of quasar HII regions

The introduction of low-frequency radio arrays over the coming decade is expected to revolutionize the study of the reionization epoch. Observation of the contrast in redshifted 21cm emission between a large HII region and the surrounding neutral IGM will be the simplest and most easily interpreted signature. We find that an instrument like the planned Mileura Widefield Array Low-Frequency Demonstrator (LFD) will be able to obtain good signal to noise on HII regions around the most luminous quasars, and determine some gross geometric properties, e.g. whether the HII region is spherical or conical. A hypothetical follow-up instrument with 10 times the collecting area of the LFD (MWA-5000) will be capable of mapping the detailed geometry of HII regions, while SKA will be capable of detecting very narrow spectral features as well as the sharpness of the HII region boundary. The MWA-5000 will discover serendipitous HII regions in widefield observations. We estimate the number of HII regions which are expected to be generated by quasars. Assuming a late reionization at z~6 we find that there should be several tens of quasar HII regions larger than 4Mpc at z~6-8 per field of view. Identification of HII regions in forthcoming 21cm surveys can guide a search for bright galaxies in the middle of these regions. Most of the discovered galaxies would be the massive hosts of dormant quasars that left behind fossil HII cavities that persisted long after the quasar emission ended, owing to the long recombination time of intergalactic hydrogen. A snap-shot survey of candidate HII regions selected in redshifted 21cm image cubes may prove to be the most efficient method for finding very high redshift quasars and galaxies.Comment: 14 pages, 8 figures. Submitted to Ap