A titanium alloy (Ti-6Al-4V STOA) plate material was provided by the University of Dayton Research Institute from a previous U.S. Air Force high-cycle fatigue study. Fatigue-crack-growth tests on compact, C(T), specimens have been previously performed at Mississippi State University on the same material over a wide range in rates from threshold to near fracture for several load ratios (R = Pmin/Pmax). These tests used the compression pre-cracking method to generate fatigue-crack-growth-rate data in the near-threshold regime. Current load-reduction procedures were found to give elevated thresholds compared to compression pre-cracking methods. A crack-closure model was then used to determine crackront constraint and a plasticity-corrected effective stress-intensityactor-range relation over a wide range in rates and load ratios. Some engineering estimates were made for extremely slow rates (small-crack behavior), below the commonly defined threshold rate. Single-edge-notch-bend, SEN(B), fatigue specimens were machined from titanium alloy plates and were fatigue tested at two constant-amplitude load ratios (R = 0.1 and 0.5) and a modified Cold-Turbistan engine spectrum. Calculated fatigue lives from FASTRAN, a fatigue-life-prediction code, using small-crack theory with an equivalent-initiallaw-size (semi-circular surface flaw) of 9 µm in radius at the center of the semi-circular edge notch fit the constant-amplitude test data fairly well, but underpredicted the spectrum loading results by about a factor of 2 to 3. Life predictions made with linear-cumulative damage (LCD) calculations agreed fairly well with the spectrum tests.

Although there is an abundance of research investigating the effects of exercise on cognitive function, few studies have investigated acute effects of exercise on performance of tasks involving executive function. Furthermore, the effects of different exercise intensities on multiple tests of executive function have received little attention. The purpose of this study was to examine the acute effects of 20-minutes of stationary cycling exercise at varying exercise intensities on executive function performance and to determine these acute effects immediately following exercise as well as after 10 and 30-minute delays following exercise. University students (N = 88) completed baseline measures of executive function (stop-signal task [SST] and Stroop task [ST]) and a graded cardiovascular exercise test on Visit 1. On Visit 2, participants were stratified by gender and fitness level and randomized to one of four conditions: high-intensity interval training (HIT), high, moderate or low-intensity steady-state exercise performed on a cycle ergometer. The ST and SST were performed immediately following exercise and again at 10- and 30-minutes post-exercise. Immediately following exercise, ST response times were significantly different (p < .05), demonstrating faster response times for the high and moderate intensity exercise (p < .05), while improvements in SST response inhibition were revealed for the HIT (p < .01) condition. At 10-minutes post-exercise, moderate and low-intensity conditions revealed improvements in ST response times (p <.05), with enhanced SST response inhibition evident in the HIT, moderate and low-intensity conditions (p < .05). At 30-minutes post-exercise, ST response times continued to show improvements from baseline for the moderate and low-intensity conditions (p < .05), while SST response inhibition trended back towards baseline levels (p > .05). The present outcomes demonstrate beneficial effects of exercise, regardless of intensity, for up to 38 minutes post-exercise. Future research should focus on mechanisms that would account for these effects and factors that support enhanced executive function performance with exercise training. / Thesis / Master of Science (MSc)

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24488号 / 医博第4930号 / 新制||医||1063(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 花川 隆, 教授 渡邉 大, 教授 村井 俊哉 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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As researchers explore the benefits of using pedometers to assess physical activity they are discovering that intensity of physical activity may be estimated from steps per minute (SPM). The purpose of this study was to determine the SPM and kilocalories (kcals) expended associated with moderate physical activity in middle school students (12 - 14 years old). Methods: Ninety-three (49 boys, 44 girls) middle school youth between the ages of 12 and 14, walked on a treadmill at four different speeds (4.0, 4.8, 5.64, and 6.4 km/h) for three minutes at each speed. Each participant wore a pedometer in order to obtain their steps per minute and a heart rate monitor to record their heart rate level during each test speed. Results: Moderate physical activity was reached, on average, by girls and boys at 122 SPM (5.64 km/h) and 115 SPM (4.8 km/h), respectively. At this SPM rate boys and girls expended 232.55 kcals and 176.66 kcals per hour. This study augments previous studies that explored ways to assess activity levels using SPM calculations.

In order to facilitate the acquisition and accurate interpretation of intensity and energy density data in high-amplitude pressure fields, the expressions for intensity and energy density are examined to ascertain the impact of nonlinear processes on the standard expressions. Measurement techniques for estimating acoustic particle velocity are presented. The finite-difference method is developed in an alternate manner and presented along with bias and confidence estimates. Additionally, two new methods for estimating the local particle velocity are presented. These methods appears to eliminate the errors and bias associated with the finite-difference technique for certain cases.

Key aspects of prosody have been studied in adults for a number of years; however, less attention has been paid to the acoustic patterns of prosody in children. Thus, the purpose of the present study was to evaluate how a group of 20 pre-adolescent children use prosody to mark contrastive stress compared to a control group of adult speakers. It was of interest to investigate whether the children's use of prosody differed between boys and girls or the part of speech being emphasized. The prosodic patterns of contrastive stress were evaluated in terms of duration, fundamental frequency, and intensity change relative to a baseline production of the same sentence. In addition, a perceptual experiment was conducted to determine if listeners could reliably identify the gender of the child speakers when listening to sentence length utterances. Statistical analysis indicated that there were some differences in the duration and fundamental frequency change as a function of speaker age and the part of speech being emphasized, with relatively minor differences between genders. However it remains unclear if the acoustic differences found in this study were substantial enough to cause a salient perceptual difference. Although previous studies have identified increases in frequency, intensity, and duration as cues of contrastive stress, the present findings revealed patterns that did not consistently conform to these expectations. Limitations in the task design, individual speaker characteristics, and also the type of acoustic measure used may have contributed to these results.

Competition often requires teams that reside at sea level to compete against opponents whose residence is at a moderate altitude. This may pose a potential competitive disadvantage considering that moderate altitude may cause decrements in VO2max, distance covered, and time to exhaustion in endurance athletes. The purpose of this study was to examine the effect of altitude on game performance measures. Six NCAA Division I female soccer players (20.33 ± 1.21 y; 168 ± 6.45 cm; 62.5 ± 6.03 kg) were retrospectively examined. Comparisons were made between two competitions that were played at sea level (SL) within two weeks of a game played at a moderate altitude (1840 m) on game characteristics including high intensity running (HIR) and total distance covered (TDC). Analysis was performed on these six players who met a threshold of playing sixty or more minutes in each competition. A 10-Hz global positioning system (GPS) was used to measure distance and velocity. The rate of TDC and HIR during the game (m?min-1) and percentage of time at HIR during competition were evaluated. The two games at SL were averaged to establish baseline performance and the mean results were compared with the single game played at altitude. Paired samples t-tests were performed to determine if any mean differences existed between performance at altitude and sea level. Significant differences (p < 0.05) were seen in minutes played between the games at SL (74.23 ± 2.93 min) versus altitude (83.24 ± 5.27 min). The relative distance rate during the game at altitude was lower at altitude (105.77 ± 10.19 m?min-1) than at SL (120.55 ± 8.26 m?min-1). HIR rate was greater at SL (27.65 ± 9.25 m?min-1) compared to altitude (25.07 ± 7.66 m?min-1). The percent of time spent at high intensity was not significantly different (p = 0.064), yet tended to be greater at sea level (10.4 ± 3.3%) than when they performed at altitude (9.1 ±2.2%). Soccer performance at a moderate altitude appears to reduce the rate at which players run throughout the competition, as well as their rate at a high intensity. Results suggest that teams that reside at SL may be at a competitive disadvantage when competing at altitude.

The mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway appears to be the primary regulator of protein synthesis and growth. While resistance exercise paradigms are often divided into hypertrophy (HYP) and strength (STR) protocols, it is unknown whether these protocols differentially stimulate mTORC1 signaling. The purpose of this study was to examine mTORC1 signaling in conjunction with circulating hormone concentrations following a typical lower-body HYP and STR resistance exercise protocol. Ten resistance-trained men (24.7±3.4y; 90.1±11.3kg; 176.0±4.9cm) performed each resistance exercise protocol in a random, counterbalanced order. Blood samples were obtained at baseline (BL), immediately (IP), 30 minutes (30P), 1 hour (1H), 2 hours (2H), and 5 hours (5H) post-exercise. Fine needle muscle biopsies were completed at BL, 1H, and 5H. Electromyography of the vastus lateralis was also recorded during each protocol. HYP and STR produced a similar magnitude of muscle activation across sets. Myoglobin and lactate dehydrogenase concentrations were significantly greater following STR compared to HYP (p=0.01-0.02), whereas the lactate response was significantly higher following HYP compared to STR (p=0.003). The GH, cortisol, and insulin responses were significantly greater following HYP compared to STR (p=0.0001-0.04). No significant differences between protocols were observed for the IGF-1 or testosterone response. Intramuscular anabolic signaling analysis revealed a significantly greater (p=0.03) phosphorylation of IGF-1 receptor at 1H following HYP compared to STR. Phosphorylation status of all other signaling proteins including mTOR (mammalian target of rapamycin), p70S6k (ribosomal S6 kinase 1), and RPS6 (ribosomal protein S6) were not significantly different between trials. Despite significant differences in markers of muscle damage and the endocrine response following STR and HYP, both protocols appeared to elicit similar mTORC1 activation in resistance-trained men.

When high strength aluminum alloys are subjected to liquid metals, physical and chemical reactions ensue resulting in what is known as liquid metal embrittlement (LME). A subset of environmentally-assisted cracking, LME is exhibited when a liquid metal, e.g. Hg or Ga, comes into intimate contact with a solid metal having significant susceptibility. As mechanical loads are applied, the interaction between the two metals results in a reduction in the flow properties of the solid metal. Several theories have been proposed to identify the underlying microstructural failure mechanism; however, none have been widely accepted, as failures can typically incorporate features common to several failure theories. In an effort to confirm, extend or replace the physically-based theories, fracture mechanics experiments on Al 7075-T651 in liquid mercury have been conducted. Experiments were conducted in a custom environmental chamber capable of exposing specimens to liquid environments while applying a mechanical load. Through both plane-strain fracture and stress intensity factor-dependent (SIF) tests, fracture toughness values along with incubation periods were analyzed and provided data for a load-based theory of LME. These mechanical test data, along with metallographic analysis, show that the phenomena of LME is both strongly time- and SIF-dependent.