• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • Tagged with
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 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.
1

The Effects of Dietary Amino Acid Density in Broiler Feed on Carcass Characteristics and Meat Quality

Lilly, Reid Alexander 07 August 2010 (has links)
Research was conducted to evaluate the effect of dietary amino acid (AA) density (Deficient (D), Low (L), High (H), and Excessive (E)) on broiler breast and thigh meat quality. As expected, the feed conversion improved (P<0.05) as AA density increased. No differences (P>0.05) existed among treatments with regard to final pH, cooking loss, shear force, brine absorption proximate analysis, and average consumer acceptability of breast meat. The D AA diet yielded meat with less (P<0.05) moisture, less protein (P<0.05) and more fat (P<0.05) than all other treatments. Increasing AA density in the diet led to increased (P<0.05) concentrations of linoleic and linolenic acid in the thigh meat from the H and E treatments, thus making it more susceptible to oxidation (P<0.05) in comparison to the D and L treatments. Overall, data revealed that all four AA diets yielded high-quality breast and thigh meat with minimal product differences.
2

Mechanistic Investigation into the Conversion of Methanol to Hydrocarbons by Zeolite Catalysts

Liu, Zhaohui 10 1900 (has links)
Catalytic conversion of methanol to hydrocarbons (MTH) provides an alternative route to the production of fuels and important industrial chemicals that are currently mainly produced from the refinery of petroleum. The ability to control the product distribution of MTH according to the demands of specific applications is of crucial importance, which relies on the thorough understanding of the reaction pathways and mechanisms. Despite the significant research efforts devoted to zeolite-catalyzed MTH, it remains a challenge to establish a firm correlation between the physicochemical properties of zeolites and their catalytic activity and selectivity. In this dissertation, we designed a series of experiments to gain fundamental understanding of how the structural and compositional parameters of zeolites influence their catalytic performances in MTH. We investigated different types of zeolites, covering large-pore Beta, medium-pore ZSM-5, and small-pore DDR zeolites, and tune their crystallite size/diffusion length, hierarchical (mesoporous) structure, and Si/Al ratio (density of acid sites) by controlled synthesis or post-synthesis treatments. The influence of mesoporosity of a zeolite catalyst on its catalytic performance for MTH, with zeolite Beta, was first investigated. The shorter diffusion length associated with the hierarchical structure results in a lower ethylene selectivity but higher selectivity towards C4-C7 aliphatics. Then we investigated the correlation between the Al content and the ethylene selectivity by ZSM-5 zeolites with similar crystal sizes but varied Si/Al ratios. We realized that ethylene selectivity is promoted with the increase of aluminum content in the framework. These two observations can be explained by the same mechanistic reason: the ethylene selectivity is associated with the propagation degree of the aromatics catalytic cycle and essentially determined by the number of the acid sites that methylbenzenes would encounter before they exit the zeolite crystallite. Last we explored how to maximize the propylene selectivity by tuning the physicochemical properties of DDR zeolites. Due to the confined pore space in DDR, the propagation of olefins-based catalytic cycle can be preferentially promoted in a tunable manner, which cannot be realized with zeolites having larger pores. Thus, the propylene selectivity increases with increasing the Si/Al ratio and decreasing the crystallite size.

Page generated in 0.295 seconds