During 1980-81, studies with crested wheatgrass (Agropyron desertorum) and fourwing saltbush (Atriplex canescens) were conducted in controlled environment growth chambers as well as under field conditions to achieve the following objectives: 1. To determine the effect of nitrogen fertilizer on the water use efficiency. 2. To determine the effects of various temperature, water stress and nitrogen treatments on the productivity, nitrogen content and carbohydrate reserves. 3. To determine the effects of N fertilization on fall and spring regrowth. Crested wheatgrass and fourwing saltbush plants were maintained in three growth chambers for 60 days under three temperature regimes (11/7, 19/7 and 27/7 C), two soil moisture stress regimes (-0.3 bars and -15 bars) and three N fertilizer levels (0, 50 and 100 kg of N/ha). During the study, tranpiration and plant biomass data were recorded. During the first week of September, 1980, crested wheatgrass and fourwing saltbush pastures at Nephi, Utah, were subjected to three nitrogen fertilizer levels (0, 50 and 100 kg N/ha). After 60 days the fall regrowth was clipped. In the first week of June 1981 spring regrowth of both species was measured. In the fall of 1981, a second experiment was laid out at Nephi where crested wheatgrass and fourwing saltbush plants were subjected to three soil moisture regimes (dry, medium and wet) and three nitrogen fertilizer levels. At the end of a 60 day study period, dry matter yield, root distribution, water content and soil samples at different incremental soil depths were collected. Under controlled environment conditions, the water use efficiency of both species was six percent more with the application of a moderate amount of nitrogen (50 kg/ha). A high temperature regime (27/7 C) and a high water stress regime (-15 bars) increased the water use efficiency of plants by eight and six percent respectively. Results of the growth chamber experiment revealed that nitrogen fertilization had a significant effect on plant biomass, nitrogen percent and total nonstructual carbohydrate reserves of crested wheatgrass and fourwing saltbush. The data further suggested that nitrogen fertilization can substitute for the adverse effects of low temperature and low soil moisture on plant growth. Nitrogen fertilization during fall increased plant biomass, nitrogen percent and total nonstructural carbohydrate reserves in crested wheatgrass and fourwing saltbush. Fall fertilization did not reduce spring regrowth. It is inferred that under limited soil moisture and low temperature during the fall growing season, a moderate amount of nitrogen fertilizer (50 kg N/ha) may increase the forage availability and water use efficiency of crested wheatgrass and fourwing saltbush to the level of plants maintained at moderate temperature and adequate soil moisture. Nitrogen fertilization (50 kg N/ha) of crested wheatgrass and fourwing saltbush during fall does not reduce plant nitrogen percent or carbohydrate reserves which may limit spring regrowth.

Falls are the leading cause of injuries among older adults (>65) and frequently result in reduced mobility, loss of independence, decreased quality of life, injury, and death.  Extensive research has been conducted regarding postural coordination and control, and other mechanisms/processes involved in maintaining postural stability.  However, there is relatively limited knowledge regarding the patterns of joint coordination, the underlying postural controller, and efficient methods to assess passive and active musculoskeletal properties relevant to balance.  In the current work, three new methods were developed to address these limitations and also to better understand the effects of localized ankle muscle fatigue, gender, and aging on postural coordination and control. First, two methods were used to evaluate postural coordination.  A wavelet coherence approach was developed and applied to assess the level and pattern of coordination between pairs of joints (i.e., ankle-knee, ankle-trunk, and ankle-head).  In addition, the uncontrolled manifold method was implemented for evaluation of potential whole-body coordination control goals.  Clear patterns of intermittent wavelet coherence were evident, indicating that joint coordination is intermittently executed.  Both in-phase and anti-phase coherence were detected over frequencies of 2.5 -- 4.0 Hz.  Shoulder and head kinematics appeared more likely than the whole-body center of mass as control goals for whole body coordination.  Both aging and ankle muscle fatigue led to a reduction of joint coordination. Second, an intermittent sliding mode controller was developed to model quiet upright stance.  In contrast to most previous postural controllers, which assume continuous control, an intermittent controller was considered more consistent with recent evidence on muscle activity and the results of the first study on postural coordination.  The sliding mode controller was able to accurately track kinematics and kinetics, and generated passive and active ankle torques comparable with previous results.  Ankle fatigue led to an increase in active ankle torque especially among young adults and males. Third, a new method was developed to estimate passive and active mechanical properties at the ankle (e.g., stiffness and damping).  This method was inspired from intermittent control theory, and the earlier results noted.  As opposed to conventional methods, this new method is computationally efficient and does not require external mechanical or sensory perturbations.  The method yielded a ratio of passive to active ankle torques consistent with earlier evidence, and larger passive and active ankle torques among males and older adults.  A post-fatigue increase of active ankle torque was estimated, especially among males and young adults. In addition to providing new analytical methods, the noted studies suggest that older adults have decreased joint coordination and increased ankle stiffness.  As a practical implication of this, fall prevention training programs may benefit from seeking to develop appropriate joint coordination strategies and ankle stiffness magnitudes.  To expand on the current work, future research should consider measuring muscle contraction characteristics at multiple joints and in different postures or activities. / Ph. D.

Mobility safety, especially fall prevention, plays a significant role in successful aging for older adults. Fall preventive programs aim to reduce risks for mortality from fall-related injuries among older adults. However, the covariation between personal perceptions of falls and factors and confidence of self-management in falls (CSMoF) is still under-studied despite its importance to fall prevention. Using the International Classification of Functioning, Disability, and Health (ICF) model, this dissertation aimed to investigate the relative contribution of CSMoF in relation to fall risk self-perceptions while controlling for demographics and self-reported health and functioning. Participants were 691 older adults recruited from Area Agency on Aging at Arlington, Texas. They completed measures of physical functioning, CSMoF, fall risk perceptions and fear of falls. Regression analyses indicated that fear of falls was the most predictive factor of CSMoF among older persons. Physical function measures of age, chronic illnesses of metabolism, sensory impairment, and health status were also significant predictors of the CSMoF. The interaction of perception of falls and fall experience attenuated CSMoF, with physical functioning limitations. Fear of falls served as a mediator through which demographic predictors influence CSMoF. The joint effects of perception of falls and fear of falls likely explain CSMoF among older adults more than physical functional indicators. Fall prevention programs for older adults should prioritize to address modifiable subjective factors of fall perceptions, fear of falls, and CSMoF across health and functioning statuses. Fear of falls should be the center of CSMoF enhancement.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18107号 / 理博第3985号 / 新制||理||1575(附属図書館) / 30965 / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 朝倉 彰, 講師 宮崎 勝己, 教授 疋田 努 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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Glyphosate-resistant (GR) horseweed has become a major problem in many row crop production systems in the United States. Horseweed is a winter annual weed common in no-till production systems. Fall-applied herbicides were compared with spring-applied treatments for the control of horseweed. In cotton, fall-applied trifloxysulfuron provided similar or greater control of horseweed when compared to spring-applied treatments of glyphosate + dicamba. Cotton yields with fall-applied trifloxysulfuron, clomazone, and flumioxazin were comparable to or better than spring-applied glyphosate + dicamba both years. Fall-applied cloransulam-methyl, flumetsulam, sulfentrazone, and the combination of chlorimuron-ethyl + metribuzin resulted in horseweed control and soybean yields comparable to spring-applied glyphosate + 2,4-D both years. Multiple-resistance to glyphosate and paraquat exists in a horseweed population from Mississippi. Herbicide rates of 0.066 kg ae/ha glyphosate and 0.078 kg ai/ha paraquat were required to reduce susceptible horseweed biomass 50%; whereas, rates of 0.78 kg/ha glyphosate and 0.67 kg/ha paraquat were required to reduce biomass of resistant horseweed to a similar intent. This is the first broadleaf weed species reported as exhibiting multiple-resistance to glyphosate and paraquat. The addition of metribuzin to paraquat improved control of paraquat-resistant horseweed. Paraquat at 0.84 kg/ha plus all rates of metribuzin controlled 15-cm tall horseweed at least 90% both years compared to 73% with 0.84 kg/ha paraquat alone. The addition of 1 and 2% methylated seed oil (MSO) to saflufenacil controlled horseweed 91 and 93%, respectively compared to 78% control with saflufenacil alone. The addition of saflufenacil to glyphosate improved control of GR horseweed from 50% to 100% at 21 d after treatment; control of horseweed with the combination of saflufenacil + glyphosate was additive. Saflufenacil did not affect absorption of glyphosate in glyphosate-susceptible horseweed; however, absorption increased in GR horseweed from 36 to 44% at 48 h after treatment with the addition of saflufenacil when compared to glyphosate alone treatments. Overall, the addition of saflufenacil reduced glyphosate translocation in horseweed at least 6%; however, due to the exceptional efficacy of saflufenacil on horseweed these reductions did not reduce control of GR horseweed.

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Fall risk among older adult is a worldwide public health problem. As the older adult population is continuing to increase, addressing this issue is critical. Several fall risk assessment tools have been designed to help predict various risk factors. Among these assessment tools is the Hendrich II Fall Risk Model (HIIFRM). This tool uses evidence-based risk factors including mental status, sex, functional status, and whether the patient is taking antileptics and/or benzodiazepines. The purpose of this paper is to validate the HFRM, explore additional variables that increase the likelihood of falling including both past falls and the number of prescription medications a patient is taking. Our findings validate the HFRM; with each additional point on the HFRM score, holding all other explanatory variables constant, the odds of having multiple previous fall-related admissions increased by 38.3% (P < 0.001). The strongest predictor of future falls was previous falls. With confounders held constant, each additional previous fall predicted a 3.9-fold increase in the odds of experiencing a future fall (p < 0.001; 95% CI of OR: 3.131 to 4.961). When looking at prescription medications, for each additional increase in prescription medications, we observe a 11.8% increase in the number of falls experienced during the tracking period (p<0.001; 95% CI of IRR: 1.084 to 1.170). Although a validated tool, our research indicates additional variables that could further enhance its effectiveness.

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