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Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 21, 2007) Includes bibliographical references.

The total water uptake, rate of water uptake, extract release volume and maximum shear force were measured on a series of samples of irradiated freeze-dried beef. Forty seven pieces of round steak (2.5 cm x 2.5 cm x 10.4 cm or 1" x 1" x 4") were irradiated at one, three and five megarad. The control samples were not irradiated. Half of the samples were irradiated when fresh, and the other half were irradiated after freeze drying. This procedure has been defined as the "fresh-dry" irradiation sequence throughout the report. The samples were frozen in an air blast at two temperatures (-22.2°C and -56.1°C). Freeze-drying was carried out below 300 microns of Hg and a maximum shelf temperature of 15.6°C (60°F). There appears to be three phases of water uptake: 1) A very rapid, almost instantaneous, absorption. 2) A more gradual uptake (called Part.1 in the report). 3) A relatively slow asymptotic approach to an equilibrium condition (Part 2). These two last phases are shown to be straight lines when the logarithm of the water uptake is plotted against the logarithm of the immersion time. Irradiation level has no significant effect on the final water content or on the slow asymptotic absorption (Part 2) or the extract release volume, but has a significant effect on the gradual water uptake (Part 1) and on the shear press force. Fresh-dry irradiation sequence (and freezing rate) have a significant effect on the total water uptake and on the slow asymptotic water (Part 2) uptake, but not on the gradual water uptake (Part 1), or on the extract release volume or on the shear press forces. Freezing rates have a significant effect on the total water uptake, but not on the slow asymptotic water uptake (Part 2), on the gradual water uptake (Part 1), on the extract release volume or on the shear press forces. The highest total water uptake was found for the meat irradiated when fresh, and slow frozen at -2 2.2°C. The mechanism of the gradual absorption appears to follow a phenomena of water flow, as evidenced by the straight line relationship found in the plots of logarithm water uptake versus logarithm immersion time. / Land and Food Systems, Faculty of / Graduate

Thesis. 1975. M.S.--Massachusetts Institute of Technology. Dept. of Nutrition and Food Science. / Bibliography: leaves 109-112. / M.S.

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No description available.

Segmental retaining walls (SRW), typically constructed along highways, have grown in popularity over the past decade. Manufacturers of SRW blocks have estimated the service life of a properly constructed wall to be approximately 75 years. However, there have been reports of SRW systems failing after only five years in service. Suspected causes of the SRW failures are freeze-thaw damage while exposed to deicing salts sprayed by snow plows from highways. The current standard test method used for evaluating the freeze-thaw durability of SRW blocks has several drawbacks and does not accurately replicate environmental exposure field conditions. The objective of this research is to develop and assess a new standard test method for evaluating the freeze-thaw durability of SRW blocks that obtains reproducible results and offers sufficient information on the freeze-thaw performance for SRW block manufacturers and state highway agencies (SHAs). The research completed a preliminary proof of concept test for the new freezethaw test method developed using small, commercially available SRW blocks to mitigate potential problems and establish appropriate test parameters. The testing produced results of freeze-thaw degradation that followed the same modes of failure that has been discovered during field evaluations. After the proof of concept test was completed, a series of freeze-thaw tests were conducted using sets of SHA approved and non-SHA approved SRW blocks. Three different manufacturers’ SRW blocks were evaluated. There was no significant freezethaw degradation of any of the blocks after 200 freeze-thaw cycles, so for two blocks, experiments were extended to 400 cycles using a twelve-hour freeze-thaw cycle. The modification of the test did not result in more rapid deterioration of the SRW blocks. The researchers found that the freeze-thaw durability test method developed herein is beneficial for determining the freeze-thaw performance of the lower quality specified blocks. The test method gives realistic results, which match typical deterioration modes that are common in field settings, in a timely manner. However, the test method for testing SHA quality SRW blocks takes longer times and may not be a reasonable test for such products.

The purpose of this study is to develop, evaluate, and apply a CRISSP-2D river ice model for a highly complex reach of the Nelson River upstream of the Jenpeg Generating Station in northern Manitoba. The calibrated model is applied in a backcasting scenario to evaluate its potential of predicting the river ice regime associated with specific hydraulic and meteorologic conditions. Secondly, a real-time application is conducted in collaboration with Manitoba Hydro to forecast overnight ice conditions as part of the 2011 Ice Stabilization Program. The model is shown to be fully capable of predicting the onset and type of ice regime that occurs. Spatial variation in ice generation across the study region is accurately captured, including locations of thermal bridging and initial ice front advance. Several modelling limitations associated with parameterization limit model accuracy during the latter stages of freeze-up and are identified as enhancement opportunities.

Quality Control (QC) reference materials are widely used in microbiology to demonstrate the efficacy of testing methods and culture media. The current method for preparation of QC materials is by serial dilution of a microbial broth culture to obtain a suspension that contains an estimated number of colony forming units (cfu). Commercial reference material products are available with dried microbial cells, however, the numbers of cells are variable between batches as the production processes are reliant on cell suspensions of estimated cell number. This study developed a method to produce precise microbial reference materials with a accurate number of viable cells. Flow cytometry was used to count and dispense precise numbers of cells into a single droplet of fluid. The droplets were then mixed with a lyoprotectant solution and subjected to freeze-drying. The resultant freeze-dried pellets showed consistent average cfu counts between 28-33 cfu with a standard deviation < 3 cfu. The freeze-drying methodology and developed conditions of cell growth enabled > 90% of the cells to survive freeze-drying and remain viable for one year at a storage temperature below -18??C. The methodology for the production of freeze-dried pellet was applied to a range of genera including, different E. coli strains, Gram positive bacteria such as Listeria and Staphylococcus, the yeast Candida albicans and a spore-producing Bacillus cereus. The precision of cell numbers was comparable between different microbial genera and strains and a consistent standard deviation below 3 cfu was achieved. The same freeze-dried pellet method was used for the different micro-organisms, except for changes to preparation of cell suspensions. Different methods of broth culture were developed to ensure freeze-dried cell survival. A measurement of method reproducibility was obtained when 99 batches of pellets were produced, and within batch and between batch variation was determined.

Quality Control (QC) reference materials are widely used in microbiology to demonstrate the efficacy of testing methods and culture media. The current method for preparation of QC materials is by serial dilution of a microbial broth culture to obtain a suspension that contains an estimated number of colony forming units (cfu). Commercial reference material products are available with dried microbial cells, however, the numbers of cells are variable between batches as the production processes are reliant on cell suspensions of estimated cell number. This study developed a method to produce precise microbial reference materials with a accurate number of viable cells. Flow cytometry was used to count and dispense precise numbers of cells into a single droplet of fluid. The droplets were then mixed with a lyoprotectant solution and subjected to freeze-drying. The resultant freeze-dried pellets showed consistent average cfu counts between 28-33 cfu with a standard deviation < 3 cfu. The freeze-drying methodology and developed conditions of cell growth enabled > 90% of the cells to survive freeze-drying and remain viable for one year at a storage temperature below -18??C. The methodology for the production of freeze-dried pellet was applied to a range of genera including, different E. coli strains, Gram positive bacteria such as Listeria and Staphylococcus, the yeast Candida albicans and a spore-producing Bacillus cereus. The precision of cell numbers was comparable between different microbial genera and strains and a consistent standard deviation below 3 cfu was achieved. The same freeze-dried pellet method was used for the different micro-organisms, except for changes to preparation of cell suspensions. Different methods of broth culture were developed to ensure freeze-dried cell survival. A measurement of method reproducibility was obtained when 99 batches of pellets were produced, and within batch and between batch variation was determined.