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Master of Science

The main objective of this study was twofold: 1. To determine the effect of freezing and thawing on the loss in strength of lime-soil mixture. 2. To investigate the effect of the addition of an air entraining agent on the freezing and thawing durability of lime-soil mixtures. For the first part, twelve specimens were prepared for each of 0, 5, 10, 15 and 20 percent combination of lime-clay mixture, giving a total of 60 specimens. For the second part, twelve specimens were prepared for each of 0, 5 and 10 percent of lime, giving a total of 36 specimens. Those containing five percent were treated with 4, 6, 8, 10 and 12 drops of air entraining agent for each two specimen batch, while those containing 0 and 10 percent were treated with 4, 7, 10, 15 and 20 drops. All specimens were wrapped with aluminum foil and immediately sealed with paraffin and cured for two days at 120°F. Control specimens were placed in the 70°F environment for ten days while companion specimens underwent five and ten cycles of freezing and thawing. The results of this study indicated the following: 1. Addition of lime increases the strength of clay soil. 2. Maximum percent increase in durability of clay soil found to occur with addition of ten pero.ent lime. 3. The decrease in strength due to freezing and thawing mainly occurred during the first five cycles. 4. Seven drops of air entraining agent gave maximum strength of air entrained specimens. / Master of Science

The relationship between soil temperature and CO₂ flux from undisturbed soil cores was examined during freeze-up of arctic tundra. Three habitats which dominate tundra topography, polygon trough, ridge and basin, produced significantly different amounts of CO₂ when soil temperatures were above 0 C. A significant positive correlation between soil temperatures between 10 to -7 C and CO₂ flux from each habitat was established. Substantial quantities of CO₂ were produced during freeze-up period when soil temperatures remained near 0 C for an extended period, and the CO₂ production continued at reduced levels as the soil temperature dropped below 0 C. When soil temperatures reached -7 C and the study was terminated, the CO₂ flux was reduced to a low level, but did not reach extinction. A maximum CO₂ flux of 2925 mg CO₂/m²/day from the trough habitat was observed when the soil temperature was 10 C, and the minimum CO₂ flux of 131 mg/m²/day was observed when the soil temperature was -7 C. These data are consistant with the hypothesis that soil microorganisms in arctic tundra are capable of physiological activity in the range of 0 to -7 C. / Master of Science

Motor vehicle collisions can result in life threatening liver injuries. Dummies are utilized to study injury in motor vehicle collisions; however, no crash test dummies are currently equipped to represent individual solid organs. This has increased the use of finite element models to help reduce these injuries; however, accurate material models need to be established to have accurate injury assessment using these models. This thesis presents a total of 4 studies that explore the biomechanical response of liver. The research on bovine liver is geared to understanding whether or not liver tissue can be frozen prior to testing and what environmental temperature the liver should be tested at. The first study utilized two bovine livers that were each divided in half and one half was tested at 75°F while the other half was tested at 98°F. A total of 24 tensile failure tests were performed on the parenchyma. It was determined that there were no statically significant differences between failure stresses and strains between the testing temperatures. To test the effects of freezing, tensile tests were performed on the parenchyma of a single bovine liver that was divided in half. One half was frozen and then thawed prior to tensile testing while the other was tested fresh. It was determined that freezing reduces average failure strain by 50%. The research on human liver was geared toward understanding the rate dependence during uniaxial tension tests and unconfined compression tests. Samples were constructed of only the parenchyma. A total of 7 livers were used to create the 51 tensile specimens and a total of 6 livers were used to obtain the 36 unconfined compression specimens. For the uniaxial tensile tests, average failure stresses ranged from 40.21 to 61.02 kPa while average failure strain ranged from 24% to 34%. For the unconfined compression tests, average failure stresses ranged from -165 to -203 kPa while average failure strain ranged from -46% to -61%. It is expected that the results presented in this thesis will: 1) Help establish correct transportation and procurement methodology for soft tissue mechanical testing. 2) Provide tension and compression material response of the human liver at multiple strain rates for use as material properties and injury tolerance values to validate finite element models. / Master of Science

Parkinsons sjukdom drabbar 15 av 10 000 personer. Sjukdomen kan påverka gången genom freezing, då individen stannar upp och är oförmögen att fortsätta att gå. Detta är ett mycket besvärande symtom som kan behandlas med olika cueingstrategier. Även gånghastighet kan förbättras med hjälp av cueingstrategier. I den senaste litteraturstudien var evidensen för cueing oenig. Syftet med litteraturöversikten var att undersöka om evidensen för auditiv och visuell cueings effekt på freezing och gånghastighet har stärkts sedan den senaste litteraturstudiens kartläggning. En deskriptiv design valdes för litteraturöversikten. Sju artiklar från databaserna PubMed, Amed, PEDro och Cinahl uppfyllde inklusionskrierierna och granskades enligt PEDro scale. Auditiva och visuella cueingstrategier minskade freezing och hade varierande effekt på gånghastighet. Flera studier kombinerade båda cueingstrategierna tillsammans eller med annan träning. Vidare studier där enbart en cueingstrategi används behöver göras för att fastställa vilken cueingstrategi som ger vilken effekt. / Parkinson’s disease affects 15 of 10 000 people. The disease can affect gait through freezing, which is when the individual stagnates, unable to continue walking. This disabling symptom can be managed with cueing strategies. Gait speed can also improve with cueing. The latest literature review that examined cueing showed disagreeing results. The aim of this literature review was to investigate if the evidence for the effect of auditory and visual cueing on freezing and gait speed has improved since the latest review. A descriptive design was chosen. Seven articles from the databases PubMed, Amed, PEDro and Cinahl met the inclusion criteria and were analyzed with PEDro scale. Auditory and visual cueing decreased freezing and showed varying results on gait speed. Several studies combined both cueing strategies with each other and other training. Future research that only uses one cueing strategy is needed to determine the effects of each strategy.