Application of superconducting coils to the NASA prototype magnetic balance

Application of superconducting coils to a general purpose magnetic balance was studied. The most suitable currently available superconducting cable for coils appears to be a bundle of many fine wires which are transposed and are mechanically confined. Sample coils were tested at central fields up to .5 Tesla, slewing rates up to 53 Tesla/ sec and frequencies up to 30 Hz. The ac losses were measured from helium boil-off and were approximately 20% higher than those calculated. Losses were dominated by hysteresis and a model for loss calculation which appears suitable for design purposes is presented along with computer listings. Combinations of two coils were also tested and interaction losses are reported. Two feasible geometries are also presented for prototype magnetic balance using superconductors

Expectant fears and racialized reproduction: African American women's lived experiences of pregnancy and motherhood

This study explores the lived experiences of pregnancy, childbirth and motherhood among African American women living in central North Carolina. Although there are many anthropological studies of reproduction, there is very little in the way of explorations of the lived experiences of pregnancy. This work was conducted between April 2002 and July 2003 with a group of 62 African American women who received prenatal care at a local OB-GYN office founded by two African American physicians and located in central North Carolina. An in-depth analysis of life history interviews with six of these women grounds the final analysis. I have used an overarching theoretical framework that examines pregnancy as a life process and a unique physiological event in order to understand the full range of life experiences that can come to bear on a woman's pregnancy. I have combined phenomenological understandings of perception and embodiment to explore the intersections of social, cultural and existential life in the contexts of pregnancy and motherhood. The women in this study have pointed to experiences of pregnancy that include experiencing pregnancy as fear of bearing a son and have developed a new way of understanding class experience in the context of a lived pregnancy. This study has pointed to experiences in African American women's lives that are positively, negatively, or neutrally felt that inform how they live their pregnancies. Those negatively felt experiences and perceptions that are related to being a pregnant African American woman emerged out of lived experiences in a racist U.S. culture whose histories, practices and ideologies of exclusion are still based on skin color. This work is informed by a Black Feminist perspective in which the researcher is compelled to engage in a "critical radical praxis" to effect change in African American women's lives. The goal of my research has been to provide information about those lived experiences of pregnancy in the lives of African American women that may help to address persistent and glaring inequalities in health

Education Reform for the Digital Era

Will the digital-learning movement repeat the mistakes of the charter-school movement? How much more successful might today's charter universe look if yesterday's proponents had focused on the policies and practices needed to ensure its quality, freedom, and resources over the long term? What mistakes might have been avoided? Damaging scandals forestalled? Missed opportunities seized

Octupole strength in the neutron-rich calcium isotopes

Low-lying excited states of the neutron-rich calcium isotopes $^{48-52}$Ca have been studied via $\gamma$-ray spectroscopy following inverse-kinematics proton scattering on a liquid hydrogen target using the GRETINA $\gamma$-ray tracking array. The energies and strengths of the octupole states in these isotopes are remarkably constant, indicating that these states are dominated by proton excitations.Comment: 15 pages, 3 figure

Excitable Scale Free Networks

When a simple excitable system is continuously stimulated by a Poissonian external source, the response function (mean activity versus stimulus rate) generally shows a linear saturating shape. This is experimentally verified in some classes of sensory neurons, which accordingly present a small dynamic range (defined as the interval of stimulus intensity which can be appropriately coded by the mean activity of the excitable element), usually about one or two decades only. The brain, on the other hand, can handle a significantly broader range of stimulus intensity, and a collective phenomenon involving the interaction among excitable neurons has been suggested to account for the enhancement of the dynamic range. Since the role of the pattern of such interactions is still unclear, here we investigate the performance of a scale-free (SF) network topology in this dynamic range problem. Specifically, we study the transfer function of disordered SF networks of excitable Greenberg-Hastings cellular automata. We observe that the dynamic range is maximum when the coupling among the elements is critical, corroborating a general reasoning recently proposed. Although the maximum dynamic range yielded by general SF networks is slightly worse than that of random networks, for special SF networks which lack loops the enhancement of the dynamic range can be dramatic, reaching nearly five decades. In order to understand the role of loops on the transfer function we propose a simple model in which the density of loops in the network can be gradually increased, and show that this is accompanied by a gradual decrease of dynamic range.Comment: 6 pages, 4 figure

A systematic review of the risk factors for cervical artery dissection

BACKGROUND AND PURPOSE: Cervical artery dissection (CAD) is a recognized cause of ischemic stroke among young and middle-aged individuals. The pathogenesis of dissections is unknown, although numerous constitutional and environmental risk factors have been postulated. To better understand the quality and nature of the research on the pathogenesis of CAD, we performed a systematic review of its risk factors. METHODS: PubMed [MEDLINE (1966 to February 22, 2005)] and Embase (1980 to February 22, 2005) were searched to identify studies fulfilling the inclusion criteria. Two reviewers independently assessed methodological quality of the primary studies. Relevant data were extracted, including the risk factor(s) investigated, characteristics of the study population, and strength of the association(s). RESULTS: Thirty-one case-control studies were included for analysis. Selection bias, lack of control for confounding, and inadequate method of data analysis were the most common identified methodological shortcomings. Strong associations were reported from individual studies for the following risk factors: aortic root diameter >34 mm (odds ratio [OR=14.2; 95% confidence interval [CI], 3.2 to 63.6), migraine (ORadj, 3.6; 95% CI, 1.5 to 8.6), relative diameter change (>11.8%) during the cardiac cycle of the common carotid artery (ORadj, 10.0; 95% CI, 1.8 to 54.2), and trivial trauma (in the form of manipulative therapy of the neck) (ORadj, 3.8; 95% CI, 1.3 to 11). A weak association was found for homocysteine (2 studies: ORcrude, unknown; 95% CI, 1.05 to 1.52; ORcrude, 1.3; 95% CI, 1.0 to 1.7), and recent infection (ORadj, 1.60; 95% CI, 0.67 to 3.80). Two studies had conflicting findings for low levels of alpha1-antitrypsin, with the methodologically stronger study suggesting no association with CAD. CONCLUSIONS: CAD is a multi-factorial disease. Many of the reviewed studies contained 2 or more major sources of bias commonly found in case-control studies. Only one study (of homocysteine) used healthy controls, a robust sample size, and had a low risk of biased results. The relationship between atherosclerosis and CAD has been insufficiently examine

Barriers to truck drivers’ healthy eating: Environmental influences and health promotion strategies.

This article presents an assessment of 25 trucking work settings designed to examine whether the environmental attributes of these settings influence eating patterns of truckers who are at risk for excess weight gain. Findings corroborate evidence that these work settings represent healthy food deserts. From restaurants and vending machines to the social/information environments and their surrounding communities, only meager opportunities exist for healthful eating practices. This article aims to place underserved truckers and warehousing-sector employees firmly within the discourse of workplace health promotion and calls for multistakeholder wellness strategies that encompass the intertwined risk factors linked with the transportation work environment

Active Living in the Trucking Sector: Environmental Barriers and Health Promotion Strategies.

Background: As one of the most underserved segments of the U.S. labor force, truck drivers have been associated with a series of morbid conditions intimately linked to their occupational milieux, their mostly unhealthful nutritional intake and sedentary lifestyles, and their resulting excess weight-gain. Methods: This paper reports data from a baseline assessment of 25 trucking work settings located around interstate highways I-40 and I-85 in North Carolina. It examines how the environmental attributes of these work settings influence the physical and recreational activity behaviors of truckers, compares findings with those from other occupational environments, and brings to the fore a new health promotion paradigm for trucking worksites. Results: Findings support growing empirical and anecdotal evidence that trucking work settings remain not only active-living deserts, but overall unhealthful places. A scan of physical, social, and information environments within trucking worksites as well as physical environments of surrounding communities reveal only meager opportunities for physical and recreational activity for truckers. Conclusion: This paper places the highly underserved population of truckers firmly within the discourse of worksite health promotion, and calls for comprehensive multistakeholder wellness strategies that address a multitude of risk factors linked to the occupational context

SPECT/CT imaging of the lumbar spine in chronic low back pain: a case report

Mechanical low back pain is a common indication for Nuclear Medicine imaging. Whole-body bone scan is a very sensitive but poorly specific study for the detection of metabolic bone abnormalities. The accurate localisation of metabolically active bone disease is often difficult in 2D imaging but single photon emission computed tomography/computed tomography (SPECT/CT) allows accurate diagnosis and anatomic localisation of osteoblastic and osteolytic lesions in 3D imaging. We present a clinical case of a patient referred for evaluation of chronic lower back pain with no history of trauma, spinal surgery, or cancer. Planar whole-body scan showed heterogeneous tracer uptake in the lumbar spine with intense localisation to the right lateral aspect of L3. Integrated SPECT/CT of the lumbar spine detected active bone metabolism in the right L3/L4 facet joint in the presence of minimal signs of degenerative osteoarthrosis on CT images, while a segment demonstrating more gross degenerative changes was more quiescent with only mild tracer uptake. The usefulness of integrated SPECT/CT for anatomical and functional assessment of back pain opens promising opportunities both for multi-disciplinary clinical assessment and treatment for manual therapists and for research into the effectiveness of manual therapies