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Observations on some steels used in high performance gears are presented in this thesis. The object was to understand how microstructure and residual stress influenced mechanical properties, particularly fatigue strength. The investigations were carried out using fatigue testing, metallographic techniques, shot peening, hardness testing and Xray diffraction to determine residual stress and the amount of retained austenite. The work is divided into two main parts. In the first part, the opportunity was taken of investigating a batch of case-carburised gears manufactured from 17CrNiMo6 steel that contained an abnormally high level of retained austenite. . The benefits or otherwise of retained austenite is a matter of some controversy in the literature and this was an opportunity of testing the effect of high retained austenite in gears. In the second part, the properties of a recently formulated through hardening steel was investigated. The steel is inexpensive and capable of being fully hardened by air-cooling. It is believed that use of the material could reduce the cost of gear manufacture by eliminating the carburisation process, oil quenching and the subsequent need to correct distortions that arise from quenching. Gears were manufactured using l7CrNiMo6 steel. After carburization, one batch was found to have an abnormally high level of retained austenite (40 to 60%). Normally, gears with this level of retained austenite would be rejected. Nevertheless, gears from this batch were found to have surface and bending fatigue strengths that were not very different from those with much lower retained austenite contents. Despite the fact that the material is relatively soft, it was found that a very thin surface layer had hardened during back-to-back gear testing, probably by strain-induced transformation of the retained austenite. It was deduced that this thin layer of hardened material is sufficient to maintain a good level of surface contact fatigue strength. The second part of the work includes a basic study of the through-hardening steel. The study includes heat treatment and hardness, estimation of fracture toughness and the development of residual stress during heat treatment. Specialised standing contact fatigue (SCF) tests were also done using this material. The SCF test consists of cyclic loading of a hard ball in contact with the surface of the specimen, which is meant to simulate asperity contact in surface contact fatigue. Radial cracks or ring cracks or both are nucleated just outside the indentation circle in these tests, depending on the load and the development of plasticity. The stresses near the indentation were modelled using Finite Element analysis and were found to be consistent with the experimental results. Finally, the effect of residual compressive stress induced by shot peeing was studied using the SCF test. It was found that shot peening suppressed the formation of radial cracks.

Master of Science / Department of Agricultural Economics / Michael R. Langemeier / Retained ownership can generally be described as when a producer does not sell his or her calf crop immediately after weaning but keeps the calves for an extended period of time. This is a decision that is made by the cow-calf producer every year and may or may not change from year to year. For some, the decision is based on past practices while others will evaluate the market before making a decision. There are various levels of retained ownership that can be modified to fit a producer’s operation and can range from a preconditioning program to finishing the cattle in the feedlot. This study specified various retained ownership scenarios in order to be able to analyze the situations. Budgets were used to analyze the optimum phase of production at which to sell calves that is most profitable while taking risk into consideration. Specifically, budgets were developed for scenarios of four cow-calf herds, four backgrounding phases, two grazing phases, and six custom feedlot phases. These budgets were used to produce sixteen potential retained ownership scenarios. The scenarios range from selling the calves immediately after weaning to owning the cattle through finishing at the feedlot. Each scenario was then analyzed based on the net returns over a 10-year period. Additionally, the scenarios were analyzed based on net returns over feed costs. Target MOTAD was used to analyze the risk component of the scenarios. Although most of the net returns were negative for all scenarios, retained ownership showed a trend of improving net returns. However, along with the improved returns came a greater variability in returns which is unattractive to a risk adverse producer. Target MOTAD results on a net return basis selected the cow-calf only phase of production in all scenarios.

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Data from the 2001-2002 Texas A&M University Ranch to Rail Program-South were used to determine factors that influence cattle feedlot performance and profitability. Steers (n=860) were classified according to sire (SBIO) and dam (DBIO) biological groups, kill groups (KILL), and entry month (ENTRYMON). Biological groups were determined by predominant genetic make up of the sire or dam. Traits evaluated included net income (NI), feedlot average daily gain (ADG), slaughter weight (OUTWT), carcass weight (CW), fat thickness (FT), longissimus muscle area (LMA), marbling score (MS), yield grade, (YG), medicine costs (TOTMED), and carcass value (CVL). Analyses of covariance were performed to determine differences between SBIO and DBIO, KILL, and ENTRYMON, and the influence of initial feedlot weight (INWT). Sire biological type had a significant effect on NI, ADG, FT, LMA, MS, YG, and CVL. Dam biological type and KILL had significant effects on all traits excluding TOTMED. Entry month accounted for no differences. Among SBIO groups, British-sired steers exhibited greatest values for ADG (1.39 kg/d), MS (457), FT (1.45 cm), CVL ($891), and NI ($25.62). Continental-sired steers exhibited the largest LMA (97.65 cm) and lowest YG (2.51). Brahman-sired steers exhibited the lowest ADG (1.32kg/d), MS (405), CVL ($859), and NI ($-17.80). Multiple regression was performed to determine which traits had the greatest effect on CVL and NI. Independent categorical effects were SBIO, DBIO, KILL and ENTRYMON, while independent continuous effects were INWT, ADG, FT, LMA, MS and TOTMED. Both CVL and NI were influenced by CW, FT, LMA, and MS, but not by ADG, INWT, or TOTMED. Phenotypic correlation coefficients were determined among all traits. Highest correlations were present between CVL: and NI, CW, ADG, and LMA (0.80, 0.81, 0.54, and 0.49, respectively). Strong correlations were seen between ADG and CW (0.63), FT and YG (0.87) and YG and LMA (-0.51). Marbling score was moderately correlated to CVL (0.30) and NI (0.30). This study indicates that a wide variety of traits interact to determine CVL and NI in retained ownership programs, and that maximizing carcass value does not ensure increased profitability.

The overall baseline (as received) moisture, protein and fat content of hybrid catfish (Ictalurus furcatus x Ictalurus punctatus) fillets were 77.8 +/- 1.38%, 16.7 +/- 0.50% and, 5.7 +/- 1.6%, respectively. Small fillets (111 +/- 19 g) had higher (P≤0.05) baseline moisture (78.6 +/- 0.87% vs 76.8 +/- 1.15%) and lower (P≤0.05) fat content (4.7 +/- 0.64% vs 6.8 +/- 1.72%) than large fillets (247 +/- 62 g), whereas protein content was similar (P>0.05) for both sizes. Retained water of the final fresh and frozen fillets was 1.2 +/- 2.03% and 3.1 +/- 1.02%, respectively, irrespective of fillet size. Psychrotrophic (PPC) and total coliform plate counts (TCC) of the baseline fillets were 4 log CFU/g and 1.6 log CFU/g, respectively and were not different between the process steps, except after injection which was higher (P>0.05) than baseline. Moisture-protein ratio and fat content were good (P≤0.05) predictors for retained water in catfish fillets during processing.

This dissertation demonstrates that substantial ductility improvement is possible for low-manganese transformation induced plasticity steel compositions through the quenching and partitioning heat treatment approach using a Gleeble thermo-mechanical simulator. Two investigated compositions had unique microstructures and mechanical behavior from an identical applied quenching and partitioning process. Electron backscattered diffraction analyses indicate that Comp-2 and Comp-5 both contained retained austenite which resulted in enhanced ductility. The face-centered cubic phase (austenite) more efficiently mitigates strain incompatibilities when located at martensitic grain boundaries known for hot spots and damage initiation. This location effect leads to enhanced ductility and improved toughness in a lean, transformation induced plasticity steel. However, the increase in ductility in Comp-2 and Comp-5 is limited; the partitioning of carbon cannot stabilize austenite to reach strength/ductility targets set by the Department of Energy. Comp-2 and Comp-5 lack sufficient manganese to stabilize austenite to a higher degree. Chem-2A will be explored to determine if the partitioning stage can stabilize austenite closer to the martensite finish temperature. Periodic intercritical annealing will be applied to Chem-1A to see if mechanical properties can be increased further than current research values. Ultimately, through literature, Manganese is proven to be a more effective austenite stabilizer than carbon, and with tailored heat-treatment, the DOE targets can be reached.

The aim was to explore the possibility to diagnose retained placental tissue and other placental complications with 3D ultrasound and to investigate the impact of previous caesarean section on placentation in forthcoming pregnancies. 3D ultrasound was used to measure the volumes of the uterine body and cavity in 50 women with uncomplicated deliveries throughout the postpartum period. These volumes were then used as reference, to diagnose retained placental tissue in 25 women with secondary postpartum haemorrhage. All but three of the 25 women had retained placental tissue confirmed at histopathology. The volume of the uterine cavity in women with retained placental tissue was larger than the reference in most cases, but even cavities with no retained placental tissue were enlarged (Studies I and II). Women with their first and second birth, recorded in the Swedish medical birth register, were studied in order to find an association between previous caesarean section and retained placenta. The risk of retained placenta with heavy bleeding (>1,000 mL) and normal bleeding (≤1,000 mL) was estimated for 19,459 women with first caesarean section delivery, using 239,150 women with first vaginal delivery as controls. There was an increased risk of retained placenta with heavy bleeding in women with previous caesarean section (adjusted OR 1.61; 95% CI 1.44-1.79). There was no increased risk of retained placenta with normal bleeding (Study III). Placental location, myometrial thickness and Vascularisation Index were recorded on 400 women previously delivered by caesarean section. The outcome was retained placenta and postpartum haemorrhage (≥1,000 mL). There was a trend towards increased risk of postpartum haemorrhage for women with anterior placentae. Women with placenta praevia had an increased risk of retained placenta and postpartum haemorrhage. Vascularisation Index and myometrial thickness did not associate (Study IV). In conclusion: 3D ultrasound can be used to measure the volume of the uterine body and cavity postpartum, but does not increase the diagnostic accuracy of retained placental tissue. Previous caesarean section increases the risk of retained placenta in subsequent pregnancy, and placenta praevia in women with previous caesarean section increases the risk for retained placenta and postpartum haemorrhage.

OBJECTIVE: The aim of this in-vitro study is to assess the effect of cyclic loading fatigue on failure load of CAD/CAM cement-retained implant crowns and screw-retained implant crowns with screw access holes sealed with composite or Enamic inlay. MATERIALS AND METHODS: For the screw-retained implant crowns, Ivoclar e.max and Vita Enamic CAD/CAM (n=44 for each material) and Enamic inlays (n=44) were designed using Sirona in-Lab software system (SW4 4.2.5) and milled using CEREC in-Lab MC XL. All the prepared e.max and Enamic crowns were cemented to Sirona TiBase (B O 4.1 L) using Ivoclar hybrid multilink cement. The access holes were sealed either by using composite or and Enamic inlay (n=22 for each group). For cement-retained implant crowns, Ivoclar e.max, Vita Enamic, and Vita Mark II CAD/CAM (n=20 for each material) and Enamic and Zirconia abutments (n=40 for each group) were designed using Sirona in-Lab software system (SW4 4.2.5) and milled using CEREC in-Lab MC XL. All the prepared zirconia and Enamic abutments were cemented to Sirona TiBase (B O 4.1 L) using Ivoclar hybrid multilink cement. Then, all prepared Ivoclar e.max, Vita Enamic, and Vita Mark II crowns were cemented to the abutments using Multilink Automix cement. After cementation, 10-12 specimens from each group (both screw and cement-retained) were subjected to a static load to failure test in a universal mechanical testing machine (Instron 5566A). The mean failure load for each group was calculated. The other 10 specimens for each group were subjected to cyclic loading fatigue under 40% of static failure load for 50,000 and 100,000 cycles. After cyclic loading, the surviving specimens were tested for static failure load. The comparison of failure load between tested groups was analyzed by one-way ANOVA using JMP Pro 13 with α=0.05. RESULTS: For IPS e-max CAD screw-retained implant crowns, there was a significant difference in the failure load at static and after cyclic fatigue for 50,000 cycles, but no significant difference between static and after cyclic fatigue for 100,000 cycles. For Vita Enamic crowns, there was no significant difference in the failure load at static and after cyclic fatigue for 50,000 cycles and 100,000 cycles. There was a significant difference in the failure load between screw-retained implant crowns sealed with composite and those sealed with Enamic inlay. For IPS e-max CAD /Zr abutment and Vita Mark II/ Enamic abutment cement-retained implant crowns, there was a significant difference in the failure load at static and after cyclic fatigue for 100,000 cycles. For Vita Enamic /Zr abutment cement-retained implant crowns, there was no significant difference in the failure load at static and after cyclic fatigue for 100,000 cycles. CONCLUSION: The screw-retained implant crowns sealed with composite had higher failure load than those sealed with Enamic inlay. The cyclic fatigue has an effect on IPS e.max CAD screw-retained implant crowns, IPS e-max CAD /Zr abutment and Vita Mark II/ Enamic abutment cement-retained implant crowns. The cyclic fatigue has no effect on Vita Enamic screw-retained implant crowns and Vita Enamic/ Zr abutment cement-retained implant crowns.

With the price of corn now over $6 per bushel, and with feedlot total cost per pound of gain now approaching $1.00 per pound of gain there are new incentives to try and add weight to calves outside of feedlots. The question then arises of how to add weight to a calf in the most economical manner. There are many different feeding programs to consider. However, with few exceptions, the cheapest way to add weight outside of a feedlot usually involves the calf grazing for an extended period of time. Winter pasture grazing, wheat pasture grazing and corn stalk grazing followed by summer pasture grazing are examples of these programs. However, with the exception of California, most of the area west of the Great Plains lacks the resources and climate for most of these winter grazing programs. For those states, cattle producers can background calves through the winter and then allow them to graze pastures in the summer. Backgrounding calves is essentially taking calves at weaning and feeding them to heavier weights without placing them directly in a feedlot on a finishing ration. The overall objective of this research is to evaluate the level and variability of returns to several background feeding alternatives. The returns will be evaluated in an expected value-variance analysis and ranked using stochastic dominance procedures. It appears that there are several different background alternatives that producers could utilize to increase returns with an acceptable level of risk and add additional value to their calves.