Study of blade clearance effects on centrifugal pumps

A program of analysis, design, fabrication, and testing has been conducted to develop and experimentally verify analytical models to predict the effects of impeller blade clearance on centrifugal pumps. The effect of tip clearance on pump efficiency, and the relationship between the head coefficient and torque loss with tip clearance was established. Analysis were performed to determine the cost variation in design, manufacture, and test that would occur between unshrouded and shrouded impellers. An impeller, representative of typical rocket engine impellers, was modified by removing its front shroud to permit variation of its blade clearances. It was tested in water with special instrumentation to provide measurements of blade surface pressures during operation. Pump performance data were obtained from tests at various impeller tip clearances. Blade pressure data were obtained at the nominal tip clearance. Comparisons of predicted and measured data are given

Doctor of Philosophy

dissertationIndividuals who identify as Mormon-adherents to The Church of Jesus Christ of Latter-day Saints (Church), a distinct and peculiar form of Christianity-and who also identify as gay or lesbian face a unique challenge to their mental health as they wrestle with the integration of their faith and their sexuality. Compounding this matter is the commonly held belief that one cannot authentically be gay and Mormon nor can one be a practicing Mormon and gay. As academics and professionals gain a more nuanced understanding of the complexity of (a) those who identify as both Mormon and a sexual/gender minority, and (b) of the Church itself, they will begin to deconstruct their own biases and increase their multicultural competence, thus becoming better equipped to address the mental health concerns of this particular sexual-minority group. Cultural competence in this context involves an awareness that, under the modern gay rights movement, a troubling dominant discourse has emerged that-if taken to an extreme-is oppressive to the coexisting narrative of the LDS Church. For example, the LDS Church's doctrinal view on same-sex marriage contrasts sharply from the dominant, gay-affirming discourse and, as a result, has been stigmatized and marginalized. To examine this marginalization, I employ critical discourse analysis (CDA) in order to uncover the LDS Church's coexisting subordinate narrative and to further enable academics and professionals to deconstruct their own possible biases towards the Mormon religious minority group. Important to this deconstruction of bias is a realization that although cultural and societal values regarding sexuality, marriage, and family have rapidly evolved over this past decade, the fundamental doctrine of monogamous, heterosexual marriage espoused by LDS Church has not. Questions arise as to how orthodox Mormon families come to terms with their child coming out in light of the LDS Church's policy on same-sex marriage and families. To answer that question, I employ a case study method to explore the experience of one such orthodox Mormon family whose child came out as gay. The findings from my case study suggest that it is possible for families and individuals in these circumstances to develop and maintain loving and supportive relationships in spite of religious differences

Brain Areas Associated with Force Steadiness and Intensity During Isometric Ankle Dorsiflexion in Men and Women

Although maintenance of steady contractions is required for many daily tasks, there is little understanding of brain areas that modulate lower limb force accuracy. Functional magnetic resonance imaging was used to determine brain areas associated with steadiness and force during static (isometric) lower limb target-matching contractions at low and high intensities. Fourteen young adults (6 men and 8 women; 27.1 ± 9.1 years) performed three sets of 16-s isometric contractions with the ankle dorsiflexor muscles at 10, 30, 50, and 70 % of maximal voluntary contraction (MVC). Percent signal changes (PSCs, %) of the blood oxygenation level-dependent response were extracted for each contraction using region of interest analysis. Mean PSC increased with contraction intensity in the contralateral primary motor area (M1), supplementary motor area, putamen, pallidum cingulate cortex, and ipsilateral cerebellum (p \u3c 0.05). The amplitude of force fluctuations (standard deviation, SD) increased from 10 to 70 % MVC but relative to the mean force (coefficient of variation, CV %) was greatest at 10 % MVC. The CV of force was associated with PSC in the ipsilateral parietal lobule (r = −0.28), putamen (r = −0.29), insula (r = −0.33), and contralateral superior frontal gyrus (r = −0.33, p \u3c 0.05). There were minimal sex differences in brain activation across the isometric motor tasks indicating men and women were similarly motivated and able to activate cortical motor centers during static tasks. Control of steady lower limb contractions involves cortical and subcortical motor areas in both men and women and provides insight into key areas for potential cortical plasticity with impaired or enhanced leg function

An Agenda for the Obama Administration on Gender Equality: Lessons from Abroad

President Barack Obama came into office with a wealth of good will after winning the historic 2008 presidential election to become the first African-American commander-in-chief. Among the many daunting issues we hope he will tackle is one that Abigail Adams mentioned to her husband John in 1776: remember the ladies. How should our President and his new administration affect social justice for women

Force Steadiness During a Cognitively Challenging Motor Task Is Predicted by Executive Function in Older Adults

Motor performance and cognitive function both decline with aging. Older adults for example are usually less steady for a constant-force task than young adults when performing low-intensity contractions with limb muscles. Healthy older adults can also show varying degrees of cognitive decline, particularly in executive function skills. It is not known, however, whether age-related changes in steadiness of low-force tasks and cognitive function are independent of one another. In this study, we determined if executive function skills in aging are associated with the steadiness during a low-force muscle contraction performed with and without the imposition of a cognitive challenge. We recruited 60 older adults (60–85 years old, 34 women, 26 men) and 48 young adults (19–30 years old, 24 women, 24 men) to perform elbow flexor muscle contractions at 5% of maximal voluntary contraction (MVC) force in the presence and absence of a difficult mental-math task (counting backward by 13 from a four-digit number). Force steadiness was quantified as the coefficient of variation (CV) of force and executive function was estimated with the Trail-making Test part A and B. The cognitive challenge increased the CV of force (i.e., decreased force steadiness) with greater changes in older adults than young adults (5.2 vs. 1.3%, respectively, cognitive challenge × age: P \u3c 0.001). Older adults were 35% slower in both parts A and B of the Trail-making Test (P \u3c 0.001), and to eliminate the effects of age and education on this variable, all further analyses were performed with the age-corrected z-scores for each individual using established normative values. Hierarchical regression models indicated that decreased force steadiness during a cognitive challenge trial was in part, explained by the performance in the Trail-making Test part A and B in older (r = 0.53 and 0.50, respectively, P \u3c 0.05), but not in young adults (P \u3e 0.05). Thus, healthy community-dwelling older adults, who have poorer executive function skills, exhibit reduced force steadiness during tasks when also required to perform a high cognitive demand task, and are likely at risk of reduced capacity to perform daily activities that involve cognitively challenging motor tasks

Finite-Time Disentanglement via Spontaneous Emission

We show that under the influence of pure vacuum noise two entangled qubits become completely disentangled in a finite time, and in a specific example we find the time to be given by $\ln \Big(\frac{2 +\sqrt 2}{2}\Big)$ times the usual spontaneous lifetime.Comment: revtex, 4 pages, 2 figure

Sex Differences in Arm Muscle Fatigability With Cognitive Demand in Older Adults

Background Muscle fatigability can increase when a stressful, cognitively demanding task is imposed during a low-force fatiguing contraction with the arm muscles, especially in women. Whether this occurs among older adults (\u3e 60 years) is currently unknown. Questions/purposes We aimed to determine if higher cognitive demands, stratified by sex, increased fatigability in older adults (\u3e 60 years). Secondarily, we assessed if varying cognitive demand resulted in decreased steadiness and was explained by anxiety or cortisol levels. Methods Seventeen older women (70 ± 6 years) and 13 older men (71 ± 5 years) performed a sustained, isometric, fatiguing contraction at 20% of maximal voluntary contraction until task failure during three sessions: high cognitive demand (high CD = mental subtraction by 13); low cognitive demand (low CD = mental subtraction by 1); and control (no subtraction). Results Fatigability was greater when high and low CD were performed during the fatiguing contraction for the women but not for the men. In women, time to failure with high CD was 16 ± 8 minutes and with low CD was 17 ± 4 minutes, both of which were shorter than time to failure in control contractions (21 ± 7 minutes; high CD mean difference: 5 minutes [95% confidence interval {CI}, 0.78–9.89], p = 0.02; low CD mean difference: 4 minutes [95% CI, 0.57–7.31], p = 0.03). However, in men, no differences were detected in time to failure with cognitive demand (control: 13 ± 5 minutes; high CD mean difference: −0.09 minutes [95% CI, −2.8 to 2.7], p = 1.00; low CD mean difference: 0.75 minutes [95% CI, −1.1 to 2.6], p = 0.85). Steadiness decreased (force fluctuations increased) more during high CD than control. Elevated anxiety, mean arterial pressure, and salivary cortisol levels in both men and women did not explain the greater fatigability during high CD. Conclusions Older women but not men showed marked increases in fatigability when low or high CD was imposed during sustained static contractions with the elbow flexor muscles and contrasts with previous findings for the lower limb. Steadiness decreased in both sexes when high CD was imposed. Clinical Relevance Older women are susceptible to greater fatigability of the upper limb with heightened mental activity during sustained postural contractions, which are the foundation of many work-related tasks

A handbook for the determination of radon attenuation through cover materials

Radon emissions from bare and covered uranium mill tailings can be estimated by diffusion theory if appropriate diffusion coefficients are known. The mathematical basis for the diffusion theory expressions are herein presented, as is a general survey of previous and present research, as well as technological developments associated with randon transport through tailing cover systems. Research is presently being conducted to define more clearly the influences of moisture, porosity, pore size distribution and other factors, on the attenuative properties of cover materials. The results of these present investigations will be incorporated in a subsequent addendum to this handbook. The radon fluxes or cover thicknesses can be calculated by hand or by available computer programs. The equations and procedure for the hand calculations is in direct support of the methodology contained in Appendix P of the Generic Environmental Impact Statement on Uranium Milling. Several examples are given to demonstrate the methodology