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Sample records for african magnetotelluric experiment

  1. Lithospheric structures and Precambrian terrane boundaries in northeastern Botswana revealed through magnetotelluric profiling as part of the Southern African Magnetotelluric Experiment

    NASA Astrophysics Data System (ADS)

    Miensopust, M. P.; Jones, A. G.; Muller, M. R.; Garcia, X.; Evans, R. L.

    2011-02-01

    Within the framework of the Southern African Magnetotelluric Experiment a focused study was undertaken to gain improved knowledge of the lithospheric geometries and structures of the westerly extension of the Zimbabwe craton (ZIM) into Botswana, with the overarching aim of increasing our understanding of southern African tectonics. The area of interest is located in northeastern Botswana, where Kalahari sands cover most of the geological terranes and very little is known about lithospheric structures and thicknesses. Some of the regional-scale terrane boundary locations, defined based on potential field data, are not sufficiently accurate for local-scale studies. Investigation of the NNW-SSE orientated, 600 km long ZIM line profile crossing the Zimbabwe craton, Magondi mobile belt, and Ghanzi-Chobe belt showed that the Zimbabwe craton is characterized by thick (˜220 km) resistive lithosphere, consistent with geochemical and geothermal estimates from kimberlite samples of the nearby Orapa and Letlhakane pipes (˜175 km west of the profile). The lithospheric mantle of the Ghanzi-Chobe belt is resistive, but its lithosphere is only about 180 km thick. At crustal depths a northward dipping boundary between the Ghanzi-Chobe and the Magondi belts is identified, and two middle to lower crustal conductors are discovered in the Magondi belt. The crustal terrane boundary between the Magondi and Ghanzi-Chobe belts is found to be located further to the north, and the southwestern boundary of the Zimbabwe craton might be further to the west, than previously inferred from the regional potential field data.

  2. Magnetotelluric experiment over the ROSE area

    SciTech Connect

    Filloux, J.H.

    1982-10-10

    Seafloor observations in natural electromagnetic fluctuations diffusing into the earth have been made in the vicinity of the Pacific Rise at 12/sup 0/N and 21/sup 0/N to gather information on the electrical conductivity structure of the oceanic basement near a spreading ridge. At 21/sup 0/N the close proximity of land (Baja California) introduces a noticeable distortion of the EM fields, and consequently the magnetotelluric sounding for this area must be interpreted with caution. At both locations the conductance of the upper 200 km appears exceptionally high and the conductivity rises rapidly below, reaching 1 S m/sup -1/ or more at 350 km. The statistical significance of a prominent conductivity increase near a depth of 22.5 km detected in the inverted data from 12/sup 0/N and of a less developed one at 30 km in the case of 21/sup 0/N is discussed. Records of the magnetic variations of 21/sup 0/N taken above the spreading center, compared to records from 40 and 120 km to the west, reveal a conspicuous enhancement of the high-frequency horizontal variations in a direction slightly west of magnetic north. We interpret this distinctive feature as the signature of an electric current sheet concentrated in an extremely high conductance, relatively shallow layer electrically bridging the two seafloor areas adjacent to the spreading center. An approximate calculation suggests a conductance in excess of 3000 S per meter of ridge crest in the close vicinity of the accretion center, equivalent to 1 to 8 km of molten basalt, depending on temperature (1000/sup 0/-1200/sup 0/C.) and depth (2-10 km.). This structure is consistent with seismic refraction information for the same area and with stratigraphic reconstruction of a fossil accretion center in Samail ophiolite. An interpretation in terms of a well-developed magma chamber is irresistable, although confirmation of the existence of this feature as well as improvement of its resolution by means of additional EM data would

  3. Canonical decomposition of magnetotelluric responses: Experiment on 1D anisotropic structures

    NASA Astrophysics Data System (ADS)

    Guo, Ze-qiu; Wei, Wen-bo; Ye, Gao-feng; Jin, Sheng; Jing, Jian-en

    2015-08-01

    Horizontal electrical heterogeneity of subsurface earth is mostly originated from structural complexity and electrical anisotropy, and local near-surface electrical heterogeneity will severely distort regional electromagnetic responses. Conventional distortion analyses for magnetotelluric soundings are primarily physical decomposition methods with respect to isotropic models, which mostly presume that the geoelectric distribution of geological structures is of local and regional patterns represented by 3D/2D models. Due to the widespread anisotropy of earth media, the confusion between 1D anisotropic responses and 2D isotropic responses, and the defects of physical decomposition methods, we propose to conduct modeling experiments with canonical decomposition in terms of 1D layered anisotropic models, and the method is one of the mathematical decomposition methods based on eigenstate analyses differentiated from distortion analyses, which can be used to recover electrical information such as strike directions, and maximum and minimum conductivity. We tested this method with numerical simulation experiments on several 1D synthetic models, which turned out that canonical decomposition is quite effective to reveal geological anisotropic information. Finally, for the background of anisotropy from previous study by geological and seismological methods, canonical decomposition is applied to real data acquired in North China Craton for 1D anisotropy analyses, and the result shows that, with effective modeling and cautious interpretation, canonical decomposition could be another good method to detect anisotropy of geological media.

  4. 2-D magnetotelluric experiment to investigate the Nassugtoqidian orogeny in South-East Greenland

    NASA Astrophysics Data System (ADS)

    Heincke, Björn; Chen, Jin; Riisager, Peter; Kolb, Jochen; Jørgensen, Asta F.

    2015-04-01

    The northwest-trending Palaeoproterozoic Nagssugtoqidian orogen extends over 250 km along the east coast of Greenland in the area around the village Tasiilaq. The geological evolution of this area closely compares with the ones of the Lewisian complex of Scotland and the Nagssugtoqidian orogen in western Greenland and, hence, leads to the suggestion that they belong to the same continental-scale orogenic belt. However, an accurate correlation across the inland ice is challenging and still ambiguous and therefore more detailed knowledge about the individual orogens might help to understand their relationship. Details about the large-scale tectonic evolution during the Nagssugtoqidian orogeny in this remote Arctic region are not known due to complex geology, relatively coarse geological mapping and the lack of extensive geophysical investigations. E.g. the vergence of the orogen, subduction-related magmatism and accretion history are matters of ongoing discussion (Kalsbeek et al., 1993; Nutman et al., 2008 and Kolb, 2013). We performed a 2-D magnetotelluric (MT) experiment across the southern part of the orogen along the Sermilik Fjord in order to improve our understanding of the orogenic process in general and to better constrain the location and vergence of the suture zone. However, because of the rough climate and the lack of infrastructure, this study is considered as a first test to investigate how MT surveys can be most efficiently performed in this remote part of the world. The NE-SW trending profile consists of eight MT stations and has a total length of ~70 km using long period LEMI-420 systems. The quality of the data is severely affected by polar electrojets that do not satisfy the plane wave assumptions, which is typical for regions close to the magnetic poles. In order to reduce the distortion from these signals onto the impedance estimates, we tested different advanced processing schemes. In addition to the more conventional robust response function

  5. Three-dimensional magnetotelluric inversion with distortion correction, practical experience and solution recipes

    NASA Astrophysics Data System (ADS)

    Moorkamp, Max; Avdeeva, Anna

    2016-04-01

    The static distortion of magnetotelluric (MT) impedances is a common problem that can prevent detailed imaging of the subsurface. The effect of distortion on the undistorted impedance Z can be described as a multiplication with an unknown, real-valued matrix C. Inverting the observed impedance Zobs = C ṡ Z without any consideration of distortion can result in strong artefacts, particularly in the near-surface. As a consequence, a variety of approaches have been developed to remove as much of the distortion effects as possible or compensate for them in the inversion. However, these either reduce the number of data and thus potentially reduce resolution, or make assumptions about the properties of the matrices C and Z which might not be generally valid. Recently we developed a new 3D inversion approach that includes the four unknown elements of C as parameters in the inversion and showed encouraging result with different synthetic test cases. In this presentation we will focus on the practical aspects of inverting real data with this approach. We will use a combined MT and transient electromagnetic (TEM) dataset acquired over the Kemaliye geothermal field in Turkey. We will demonstrate the improvements in imaging that can be obtained by incorporating distortion in the inversion. Having TEM data at each site, gives us some indication of the amount of distortion and we will compare our recovered distortion values with these measurements. Finally, we will also show in how far the inversion approach is robust in the presence of noise and present recipes for successful inversion with distortion correction.

  6. Cataloging the Pan-African Experience

    ERIC Educational Resources Information Center

    Hayes, Dianne

    2012-01-01

    Of all the honors and accolades bibliophile and noted authority on the Underground Railroad Charles Blockson has received, being bequeathed recently with some of Harriet Tubman's personal items by her great-niece is one of the most significant experiences of his life. A longtime collector of books and rare items by and about African-Americans,…

  7. The Lithospheric Structure of Southern Africa from Magnetotelluric Sounding

    NASA Astrophysics Data System (ADS)

    Evans, R. L.; Jones, A. G.; Atekwana, E. A.

    2014-12-01

    Measurements of mantle electrical conductivity, made through the magnetotelluric method, offer considerable insight into the structure of cratonic lithosphere. A particularly expansive data set has been collected in Southern Africa, started through the Southern Africa Magnetotelluric Experiment (SAMTEX) experiment, now continuing north through Zambia as part of the Project for Rift Initiation Development and Evolution (PRIDE) experiment. The combined data set highlights large variability in lithospheric structure that broadly correlates with surface geology: cratonic lithosphere is generally thick and electrically resistive, while much thinner lithosphere is seen beneath mobile belts. In areas of relatively uniform resistivity structure, we have constructed resistivity-depth profiles and use new laboratory data to place constraints on the water content of lithospheric mantle. Uncertainty in our estimates arises from differences between different laboratory results, but our data are generally consistent with a slightly damp upper lithospheric mantle above a dry and strong cratonic root. Other areas show complexity of structure that is difficult to understand using current knowledge of conductivity -the Bushveld complex, where the mantle is highly conductive, is one such example. In southwestern Zambia, the lithosphere is seen to be very thin (around 50km) beneath mobile belt terrain, as was inferred nearly 40 years ago on the basis of high heatflow. The mantle is highly conductive, most likely due to a combination of elevated temperatures, water content and perhaps a trace amount of melting. This anomalous structure may be linked to the southwest propagation of the East African Rift system.

  8. Electrical resistivity structure under the western Cosmonauts Sea at the continental margin of East Antarctica inferred via a marine magnetotelluric experiment

    NASA Astrophysics Data System (ADS)

    Matsuno, Tetsuo; Nogi, Yoshifumi; Seama, Nobukazu

    2015-06-01

    The western Cosmonauts Sea, off the coast of East Antarctica, was a site of rifting of the Gondwana supercontinent and subsequent early seafloor spreading. To improve our understanding of the breakup of Gondwana, we conducted a marine magnetotelluric experiment to determine the electrical resistivity structure within the uppermost several hundred kilometers beneath the western Cosmonauts Sea. Magnetotelluric response functions at two sites, obtained after considering possible influences of non-plane magnetic field sources, suggest that these responses include distortions by topographic variations and conductive anomalies around the observation sites. Three-dimensional forward modeling confirmed that these distortions due to topographic variations and a thin (∼2-km thick) conductive layer immediately under the sites (mostly sediments) are severe. Furthermore, three-dimensional forward modeling to investigate the resistivity structure at deeper depths revealed an upper resistive layer (≥300 Ω-m), with a thickness of <100 km, and an underlying conductive half-space (∼10 Ω-m). The upper resistive layer and the underlying conductive structure most likely represent dry and water/melt-rich oceanic upper mantle, respectively. The upper resistive layer may be thinner than anticipated under the old seafloor of the study area (likely >90 Ma), and may suggest a conductive anomaly in the upper mantle produced by mantle convection and/or upwelling.

  9. Constriant inversion of 2D magnetotelluric data with anisotropic conductivities

    NASA Astrophysics Data System (ADS)

    Chen, X.; Weckmann, U.

    2011-12-01

    Within the framework of the German - South African geo-scientific research initiative Inkaba yeAfrica a series of magnetotelluric (MT) field experiments were conducted along the Agulhas-Karoo Transect in South Africa. This transect crosses several continental collision zones between the Cape Fold Belt, the Namaqua Natal Mobile Belt and the Kaapvaal Craton. Along the Cape Fold Belt (CFB) profile we can identify areas (>10 km) where MT sites exhibit phases over 90°. This phenomenon usually occurs in presence of electrical anisotropy. Due to the dense site spacing we are able to observe this behaviour consistently at several sites. The anisotropy of electrical conductivity is essentially a scale effect: Even if the conductivity is isotropic on the micro scale, it will become anisotropic on a larger scale if, in the averaging volume, preferred orientation (e.g., layering or lamination) exist. Therefore, it is necessary to understand the electrical anisotropy in more details and furthermore electrical anisotropy offers new degrees of freedom, which should allow a better interpretation of data. In 2D MT case with considering of electrical anisotropy, computing of impedance tensor requires two independent electric field solutions computed for two different source polarisations. Based on the forward problem formulation and its numerical approximation we derive partial differential equations for the sensitivities of the magnetotelluric fields with respect to the elements of the conductivity tensor within the medium. For illustration a sensitivity study for a simple synthetic model is shown. We present an algorithm for the inversion of 2D magnetotelluric data with anisotropic conductivities which is a extension of the well-known NLCG minimization algorithm to anisotropic model. To constrain the structure complexity, a penalty function consists of datamisfit, standard model roughness and quadratic variation of the conductivity tensor elements is minimized. To demonstrate the

  10. Experiences of African American adolescent fathers.

    PubMed

    Dallas, C M; Chen, S P

    1998-04-01

    Social and cultural factors influence the experience of fatherhood. This descriptive focus-group study describes the lived experience of fatherhood from the perspectives of 5 unmarried, low-income, African American adolescent fathers in a Midwestern urban area. Naturalistic inquiry approach guided the study. Seven themes of fatherhood emerged: barriers to fatherhood, value of fatherhood, introduction to fatherhood, competencies of fatherhood, role-set relationships, social norms of fatherhood, and father-child contact. This study suggests that nurses should support the involvement of adolescent fathers with their children. Future study may determine the influence of adult female family members on the decisions of adolescent fathers to remain involved with their children. PMID:9550932

  11. South African TOPEX/Poseidon altimeter experiment

    NASA Technical Reports Server (NTRS)

    Gruendlingh, Marten L.; Shannon, L. V.; Lutjeharms, J. R.

    1991-01-01

    The area surrounding the southern tip of Africa contains a juxtaposition of a variety of interesting and climatically relevant features. On the Indian Ocean side, the Agulhas Current with its tributaries form a conduit through which much of the southern Indian Ocean surface flow is focused. South of the continent, this flow is fragmented and partially injected into the Atlantic Ocean and across the Subtropical Convergence into the Southern Ocean. To the west of the subcontinent, the circulation of the South Atlantic subtropical gyre in the Cape Basin interacts with the vigorous Benguela upwelling regime. The creation, transformation, and transport of water masses and the intra-annual and climatic importance of all these processes have been specifically recognized by the World Ocean Circulation Experiment (WOCE). The South African TOPEX/POSEIDON Altimeter Experiment addresses many of these issues through four mutually complementary and interrelated subprojects.

  12. Crustal structure of the southern margin of the African continent: Results from geophysical experiments

    NASA Astrophysics Data System (ADS)

    Stankiewicz, J.; Parsiegla, N.; Ryberg, T.; Gohl, K.; Weckmann, U.; Trumbull, R.; Weber, M.

    2008-10-01

    A number of geophysical onshore and offshore experiments were carried out along a profile across the southern margin of the African Plate in the framework of the Inkaba yeAfrica project. Refraction seismic experiments show that Moho depth decreases rapidly from over 40 km inland to around 30 km at the present coast before gently thinning out toward the Agulhas-Falkland Fracture Zone, which marks the transition zone between the continental and oceanic crust. In the region of the abruptly decreasing Moho depth, in the vicinity of the boundary between the Namaqua-Natal Mobile Belt and the Cape Fold Belt, lower crustal P-wave velocities up to 7.4 km/s are observed. This is interpreted as metabasic lithologies of Precambrian age in the Namaqua-Natal Mobile Belt, or mafic intrusions added to the base of the crust by younger magmatism. The velocity model for the upper crust has excellent resolution and is consistent with the known geological record. A joint interpretation of the velocity model with an electrical conductivity model, obtained from magnetotelluric studies, makes it possible to correlate a high-velocity anomaly north of the center of the Beattie magnetic anomaly with a highly resistive body.

  13. The college life experiences of African American women athletes.

    PubMed

    Sellers, R M; Kuperminc, G P; Damas, A

    1997-10-01

    The present study provides a descriptive analysis of four areas of African American women student athletes' college life experiences: academic performance; alienation and abuse; perceived social advantage as the result of athletics; and life satisfaction. Multivariate comparisons were made between the four areas of college life experiences of 154 African American women student athletes and 793 White women student athletes, 250 African American women nonathletes, and 628 African American men student athletes from a national sample of 39 NCAA Division I universities. Overall, African American women student athletes are performing adequately academically, integrating socially within the university, perceiving some social advantage as the result of being athletes, and are fairly satisfied with their life. Their experiences seem most consistent with African American women nonathletes. Results are discussed in the context of potential policy recommendations as well as the need for more research on this particular population. PMID:9485580

  14. Teaching Experiences of African American Educators in the Rural South

    ERIC Educational Resources Information Center

    Polidore, Ellene; Edmonson, Stacey L.; Slate, John R.

    2010-01-01

    A scarcity of research exists regarding the voices of African American teachers who taught in the rural South. In this study, we report the life experiences, perceptions, thoughts, and feelings of three female African American educators as they pertain to their experiences teaching before, during, and after desegregation. Three female African…

  15. Cancer and the African American Experience

    Cancer.gov

    The first plenary of the EPEC-O (Education in Palliative and End-of-Life Care for Oncology) Self-Study: Cultural Considerations When Caring for African Americans explores the many factors that lead to inequalities in cancer care outcomes for African Americans.

  16. Electrical signature of the Marrakech High Atlas: new insights from the TopoMed broad band magnetotelluric experiment.

    NASA Astrophysics Data System (ADS)

    Siniscalchi, A.; Romano, G.; Jones, A.; Ledo, J.; Campanyà, J.; Kiyan, D.

    2012-04-01

    In autumn 2009, a broadband magnetotelluric (BBMT) SSW-NNE striking profile crossing the Marrakech High Atlas was acquired as a part of the TopoMed Coordinated Research Project within the TOPO-EUROPE EUROCORES (http://www.esf.org/activities/eurocores/runningprogrammes/ topo-europe.html). The main purpose was to obtain information on the crustal structure in a poorly investigated area of the Atlas system [D. Frizon de Lamotte et al. 2008]. A total of 19 soundings were acquired allowing the estimation of the MT and the geomagnetic transfer function in the period range from 0.001 s to 1000 s. The data quality is not uniform along the profile and generally not as high as desired due to the combination of mainly two factors: low solar activity and the presence of strong cultural noise sources like those affecting the northern soundings, near Marrakech. Directionality analysis, made using all the soundings, indicates a strike direction NE-SW until periods of few hundred seconds (i.e., crust to upper mantle depths). The strike was determined from the geomagnetic transfer function and then, considering also the middle-low quality of the tipper data, confirmed by applying the distortion decomposition method of Groom and Bailey (1989) following the scheme of McNeice and Jones (2001). A preliminary analysis of subsurface resistivity distribution along the original profile was inferred by the so-called Niblett-Bostick (N-B) transform of the determinant apparent resistivity and phases, considering that they are rotationally invariant. This first stage data modeling shows a well distinct electrical signature among the Marrakech High Atlas with respect to the adjacent basins (Souss and Haouz) throughout the crust. Taking into account the electrical strike (NE-SW) the MT transfer functions were corrected for distortion and derived in the appropriate strike direction; sounding sites were projected on a transect line orthogonal to the strike (NW-SE). Joint TM and TE mode data were

  17. Geothermal and compositional variety of old oceanic upper mantle in northwestern Pacific: Insights from seafloor magnetotelluric experiments

    NASA Astrophysics Data System (ADS)

    Utada, H.; Baba, K.; Tada, N.; Shimizu, H.; Zhang, L.; Liang, P.

    2014-12-01

    Oceanic upper mantle beneath the northwestern Pacific has large-scale lateral heterogeneity that is impossible to attribute to just an age-dependency of the thermal structure based on a cooling of homogeneous mantle with age. This surprising fact was revealed from seafloor magnetotelluric (MT) data collected in three areas, northwest (Area A) and southeast (Area B) of the Shatsky Rise, and off the Bonin Trench (Area C), through the Normal Oceanic Mantle Project and the Stagnant Slab Project. One-dimensional structures of electrical conductivity representing each area show significant difference in the thickness of the upper resistive layer that may be interpreted as cool lithosphere. The thickness of the layer that is more resistive than 0.01 S m-1 is ~80 km for Area A, ~110 km for Area B, and ~180 km for Area C. The conductivity below the resistive layer is similar to ~0.03 S m-1 for Areas A and C but a slightly higher than it for Area B. The thermal structures for the lithospheric age representing the areas (130, 140, and 147 Ma for Areas A, B, and C, respectively) predicted from a simple plate cooling model are almost identical and thus cannot reproduce such variations in electrical conductivity. Then, in this study, thermal and compositional states of the mantle beneath the three areas were investigated to discuss the cause of the variations. Combination of five model parameters, electrical conductivity of crust, mantle potential temperature, thickness of thermally conductive plate, and H2O and CO2 contents in the asthenospheric mantle were searched by forward modeling and the χ2 misfit between the MT responses observed and predicted were assessed with 95% acceptable level. The possibility of partial melting was taken into account by comparing to the solidus of peridotite that is reduced by H2O and CO2. We assumed that the mantle conductivity may be represented by the mixture of hydrous olivine and hydrous carbonated melt. The results suggest a possible

  18. Mother Tongue Education: The West African Experience.

    ERIC Educational Resources Information Center

    Bamgbose, Ayo, Ed.

    In the rapidly changing political, economic, and social life of West Africa, there is a renewed interest in cultural identity. This book describes the developments and the difficulties experienced by different West African countries in the use of mother tongues in multi-lingual society. The book was commissioned to give scholars, educators, and…

  19. Crustal Structure of the Southern Margin of the African Continent: Results from Geophysical Experiments.

    NASA Astrophysics Data System (ADS)

    Stankiewicz, J.; Parsiegla, N.; Ryberg, T.; Gohl, K.; Weckmann, U.; Trumbull, R.; Weber, M.

    2009-04-01

    A number of geophysical onshore and offshore experiments were carried out along a profile across the southern margin of the African Plate in the framework of the Inkaba yeAfrica project. Refraction seismic experiments show that Moho depth decreases rapidly from over 40 km inland to around 30 km at the present coast, before gently thinning out towards the Agulhas-Falkland Fracture Zone, which marks the transition zone between continental and oceanic crust. In the region of the abruptly decreasing Moho depth, in the vicinity of the boundary between the Namaqua-Natal Mobile Belt and the Cape Fold Belt, lower crustal P-wave velocities up to 7.4 km/s are observed. This is interpreted as metabasic lithologies of Precambrian age in the Namaqua-Natal Mobile Belt, or mafic intrusions added to the base of the crust by younger magmatism. The velocity model for the upper crust has excellent resolution. It is consistent with the known geological record, and also reveals a number of new features. These include a high velocity anomaly north of the centre of the Beattie Magnetic Anomaly. A joint interpretation of the velocity model with an electrical conductivity model, obtained from magnetotelluric studies, makes it possible to correlate this feature with a highly resistive body. Furthermore, a synclinal low velocity feature was identified in the Mesoproterozoic basement beneath the front of the Cape Fold Belt, south of the above mentioned feature. The northern edge of this feature correlates with the second magnetic body necessary to account for the BMA's signature.

  20. African American Women's Breastfeeding Experiences: Cultural, Personal, and Political Voices.

    PubMed

    Spencer, Becky; Wambach, Karen; Domain, Elaine Williams

    2015-07-01

    The low rate of breastfeeding among African American women in the United States is a poorly understood, persistent disparity. Our purpose in this study was to gain an understanding of how African American women experience breastfeeding in the context of their day-to-day lives. The Sequential-Consensual Qualitative Design (SCQD), a 3-stage qualitative methodology aimed at exploring the cultural, personal, and political context of phenomena, was used to explore the experiences of African American women who felt successful with breastfeeding. An integration of qualitative content analysis and Black feminist theory was used to analyze the data. Themes that emerged from Stage-2 data analysis included self-determination, spirituality and breastfeeding, and empowerment. In Stage 3 of the study, participant recommendations regarding breastfeeding promotion and support initiatives for African American breastfeeding were categorized into three themes, including engaging spheres of influence, sparking breastfeeding activism, and addressing images of the sexual breast vs. the nurturing breast. PMID:25288408

  1. Experiences of undergraduate African health sciences students: A hermeneutic inquiry.

    PubMed

    Inyama, Davis; Williams, Allison; McCauley, Kay

    2015-06-01

    While efforts have been made to understand the experiences of African students in predominantly white environments, the experiences of African students in clinical placement areas have rarely been explored. This paper is a report on a study designed to address the gap in educational research on the experiences of African health sciences students in clinical placements in predominantly white environments. Interviews adopting an open approach to conversations were conducted with nine African students from three health disciplines at one metropolitan university in Australia between 2012 and 2013. Interview transcripts were analyzed using philosophical hermeneutics, where shared meanings were arrived at by employing key Gadamerian hermeneutic components. Findings revealed a number of factors that had a direct effect on the meaning students derived from their clinical placement experiences. These, as revealed in the interlinked domains of body, space, relationships, and time included difference, acceptance, resilience, and cultural sensitivity. Insights from this study may lead to the adoption of strategies designed to improve the experiences of African students studying health sciences in predominantly white environments. PMID:24942056

  2. African American Women's Sexual Objectification Experiences: A Qualitative Study

    ERIC Educational Resources Information Center

    Watson, Laurel B.; Robinson, Dawn; Dispenza, Franco; Nazari, Negar

    2012-01-01

    The purpose of our study was to investigate African American women's experiences with sexual objectification. Utilizing grounded theory methodology as well as Black feminist thought and objectification theory as the research lenses, the results of this study uncovered how racist, sexist, and classist ideologies contributed to sexual…

  3. Early Academic Experiences of Recently Incarcerated African American Males

    ERIC Educational Resources Information Center

    Jeffers, Adam R.

    2010-01-01

    This project examines the early educational experiences of 6 young African American males (ages 18-25) who attended urban schools in San Diego, California. All 6 men were incarcerated for at least 1-year before participating in a pre-release program. The participants were part of a pre-release program in San Diego, California, which was selected…

  4. Financing vaccinations - the South African experience.

    PubMed

    Blecher, Mark S; Meheus, Filip; Kollipara, Aparna; Hecht, Robert; Cameron, Neil A; Pillay, Yogan; Hanna, Luisa

    2012-09-01

    South Africa provides a useful country case study for financing vaccinations. It has been an early adopter of new vaccinations and has financed these almost exclusively from domestic resources, largely through general taxation. National vaccination policy is determined by the Department of Health, based on advice from a national advisory group on immunisation. Standard health economic criteria of effectiveness, cost-effectiveness, affordability and burden of disease are used to assess whether new vaccinations should be introduced. Global guidelines and the advice of local and international experts are also helpful in making the determination to introduce new vaccines. In terms of recent decisions to introduce new vaccines against pneumococcal disease and rotavirus diarrhoea in children, the evidence has proved unequivocal. Universal rollout has been implemented even though this has led to a fivefold increase in national spending on vaccines. The total cost to government remains below 1-1.5% of public expenditures for health, which is viewed by the South African authorities as affordable and necessary given the number of lives saved and morbidity averted. To manage the rapid increase in domestic spending, efforts have been made to scale up coverage over several years, give greater attention to negotiating price reductions and, in some cases, obtain initial donations or frontloaded deliveries to facilitate earlier universal rollout. There has been strong support from a wide range of stakeholders for the early introduction of new generation vaccines. PMID:22939027

  5. Oral submucous fibrosis. The South African experience.

    PubMed

    VanWyk, C W

    1997-01-01

    A review of research related to oral submucous fibrosis (OSF) among South Africans of Indian descent shows a certain uniqueness compared to other countries. In South Africa the betel habit is more common among women, only 60% of chewers prefer the betel quid while the rest like the nut by itself, the majority of chewers prefer the baked (black) nut variety and a minority add tobacco to their chew. This pattern reflects in the distribution of OSF and the practice of the habit by OSF subjects. Compared to chewers without OSF, OSF subjects are younger and have shorter histories of chewing. Yet the profile of systemic diseases were similar among subjects with and without OSF. The habit as practised in South Africa also determines the pattern of oral squamous carcinomas. They are more common in women, with buccal mucosa cancers being the most frequent. The latter are commonly found in subjects not using any tobacco, indicating the carcinogenicity of the areca nut. It was also shown that oral cancer can develop in chewers without an intermediate precancerous OSF phase. A follow-up of OSF cases after cessation of the habit revealed that once present the disease is permanent. An analysis of cultured OSF fibroblasts demonstrated a permanent shift to larger cells theoretically capable of producing larger amounts of collagen. Thus the agents in the nut could be the initiators of the disease and its permanent character the result of a phenotypic alteration in cells from changes in gene expression. PMID:9495135

  6. African Mask-Making Workshop: Professional Development Experiences of Diverse Participants

    ERIC Educational Resources Information Center

    Rule, Audrey C.; Montgomery, Sarah E.; Kirkland-Holmes, Gloria; Watson, Dwight C.; Ayesiga, Yvonne

    2015-01-01

    Diverse education professionals learned about African cultures in a workshop experience by making African masks using authentic symbolism. Analysis of reflections to evaluate the workshop for applicability to participants with and without African heritage showed that both groups expanded their cultural knowledge of traditional African ethnic…

  7. Older African American Women’s Lived Experiences with Depression

    PubMed Central

    Ward, Earlise C.; Mengesha, Maigenete; Issa, Fathiya

    2014-01-01

    Little is known about older African American women’s lived experiences with depression. What does depression mean to this group? What are they doing about their depression? Unfortunately, these questions are unanswered. This study examined older African American women’s lived experiences with depression and coping behaviours. The common sense model provided the theoretical framework for present study. Thirteen community-dwelling African American women aged 60 and older (M =71 years) participated. Using qualitative phenomenological data analysis, results showed the women held beliefs about factors that can cause depression including experiences of trauma, poverty, and disempowerment. Results also indicated the women believed that depression is a normal reaction to life circumstances and did not see the need to seek professional treatment for depression. They coped by use of culturally-sanctioned behaviours including religious practices and resilience. It appears these women’s beliefs about depression and use of culturally-sanctioned coping behaviours might potentially be a barrier to seeking professional mental health care, which could result in missed opportunities for early diagnosis and treatment of depression among this group. Implications for research, educational and clinical interventions are discussed. PMID:23742034

  8. An Examination of African American Female College Presidents' Professional Ascendancy and Mentoring Experiences

    ERIC Educational Resources Information Center

    Smith-Ligon, Pamela

    2011-01-01

    There is a large disparity in the number of African American women leaders in higher education, specifically in the presidency. Much of the literature negates the experiences of the African American woman, often fusing their experiences with those of all women, or those of African American men, which often disregards the challenges and successes…

  9. Pedagogies of Experience: A Case of the African American Male Teacher

    ERIC Educational Resources Information Center

    Brown, Anthony L.

    2011-01-01

    Numerous scholars have illustrated how African American teachers' past experiences provide them a philosophical vision committed to teaching for social and educational change for African American students. This article draws from this body of work by looking at the diverse ways five African American male teachers used their past experiences to…

  10. The lived experience of informal African American male caregivers.

    PubMed

    Weinland, Jo Ann

    2009-03-01

    Informal caregivers play a major role in providing care to loved ones within the home and demands for dependent care are likely to increase. Informal caregivers are likely to continue to be responsible for the majority of care for loved ones living well into late stages of life. This article describes the lived experience of African American men providing care to a relative within the home and explores their definition of caregiver distress. The phenomenological study was conducted using face-to-face interviews with 10 Christian African American men. Demographic data about the caregiver and the care recipient were collected. Common themes included: commitment, support (family support and formal health-related support), spirituality, and caregiver burden (stress, time strain and financial strain). Implications include the need for health care providers to expand their knowledge related to the diversity of caregivers and to use culturally relevant comprehensive assessments of caregivers and recipients, discharge planning tools, and community resources. PMID:19477717

  11. Experiences and Learning Needs of African American Family Dementia Caregivers.

    PubMed

    Samson, Zoe Blake; Parker, Monica; Dye, Clinton; Hepburn, Kenneth

    2016-09-01

    Dementia family caregivers display significant rates of psychological and physical symptoms. African Americans (AAs) are disproportionately affected by dementia. African American caregivers display unique patterns of symptomology and responses to interventions designed to promote caregiver well-being. This study analyzed qualitative focus group data from 32 AA caregivers to explore how issues of race and culture may be incorporated into a culturally sensitive intervention for AA dementia family caregivers. Caregivers were asked scripted questions about their caregiving experiences and to suggest alterations to an existing psychoeducation program. Analysis revealed 4 key themes: the tradition of family care, caregiving and caregiving issues, culturally appropriate care, and navigating without a map. Suggestions for an educational program included a focus on developing caregiver skills and knowledge for caregiving, promotion of self-care, and reflection on the AA family and community as resources for care. PMID:26953236

  12. The experiences of African American graduate students: A cultural transition

    NASA Astrophysics Data System (ADS)

    Joseph, Joretta

    Historically Black Colleges and Universities (HBCU) have long been an intellectual resource for the African American community. HBCUs have provided and continue to provide an educational pathway for many Black students, particularly women who seek graduate and advanced degrees. However, despite the overwhelmingly positive presence of HBCU in the African American community, the academic training of students who graduate from HBCUs may be perceived as insufficient by predominantly White graduate institutions (PWIs). As a result, African American students who are not well integrated into their respective departmental communities and cultures at PW/is are likely to leave graduate school. Thus the continuing loss of talented people, potential research, role models for society, and the next generation of African American students in the fields of math, engineering, and the sciences (STEM) create a segregated and limited university environment. Studies in the field that attempt to provide insight in to experiences of underrepresented students are ultimately beneficial. However, often such studies do not address the process of adapting to the culture of a predominantly white institution (PWI), particularly within white and male dominated fields such as mathematics and the sciences. Research has also indicated that the first two years at a predominantly white graduate institution is the crucial transitional period for students of color, and it is this transitional moment in time that is the focus of this study. I consider how students make the transition from HBCU to majority institutions, and what impact this transition has on their persistence and commitment to their discipline. The limited amount of research that does address the experiences of minority doctoral students in math and science is usually coupled with the experiences of women. However, race and gender are not linear or additive. It cannot be assumed that the same factors that effect the under representation

  13. Magnetotelluric Investigation of the South Aegean Volcanic Arc, Greece

    NASA Astrophysics Data System (ADS)

    Kalisperi, Despina; Romano, Gerardo; Smirnov, Maxim; Kouli, Maria; Perrone, Angela; Makris, John P.; Vallianatos, Filippos

    2014-05-01

    The South Aegean Volcanic Arc (SAVA) is a chain of volcanic islands in the South Aegean resulting from the subduction of the African tectonic plate beneath the Eurasian plate. It extends from Methana, northwest, to the Island of Nisyros southeast (450 km total length). SAVA comprises a series of dormant and historically active volcanoes, with the most prominent to be Aegina, Methana, Milos, Santorini, Kolumbo, Kos and Nisyros. The aim of the ongoing research project "MagnetoTellurics in studying Geodynamics of the hEllenic ARc (MT-GEAR)" is to contribute to the investigation of the geoelectric structure of Southern Aegean, and particularly to attempt to image the Hellenic Subduction Zone. In this context, onshore magnetotelluric (MT) measurements were recently carried out on the central and eastern part of SAVA (Milos, Santorini, Nisyros and Kos Islands). Data were collected using two MT systems running simultaneously plus a remote reference station installed in Omalos plateau (Western Crete). Robust MT data analysis of the broad-band MT soundings and the resulting model of the conductivity structure of the South Aegean Volcanic Arc is presented. The research is co-funded by the European Social Fund (ESF) and National Resources under the Operational Programme 'Education and Lifelong Learning (EdLL) within the context of the Action 'Supporting Postdoctoral Researchers' in the framework of the project title "MagnetoTellurics in studying Geodynamics of the hEllenic ARc (MT-GEAR)".

  14. The Meaning of KMT (Ancient Egyptian) History for Contemporary African American Experience.

    ERIC Educational Resources Information Center

    Hilliard, Asa G., III

    1992-01-01

    Explores the history of KMT (ancient Egypt) and its importance for contemporary African-American experience. Reviews evidence that ancient Egypt was a black African population bound by history and culture to the rest of Africa. The rescue of Kemetic history can restore a sense of heritage to African Americans. (SLD)

  15. Resiliency in Physics: The Lived Experiences of African-American Women Who Completed Doctoral Physics Programs

    ERIC Educational Resources Information Center

    Burnette, Samara Fleming

    2013-01-01

    Currently, little is known about African-American women with doctoral degrees in physics. This study examined the lived experiences of African-American women who completed doctoral programs in physics. Due to factors of race and gender, African-American women automatically enter a double-bind in science, technology, engineering, and mathematics…

  16. Multistation magnetotellurics. Final report, 1 January 1996--30 June 1997

    SciTech Connect

    Egbert, G.D.

    1997-12-31

    The author has developed the foundations of a practical multivariate approach to processing magnetotelluric array data. Compared to current standards for magnetotelluric data processing, the multivariate approach is unique in that all available data channels are used simultaneously. The approach is outlined in this report. Using Multmtrn, a program for multiple station analysis of magnetotelluric data, the author achieved significant improvements in apparent resistivity and phase estimates in initial tests. Examples of the use of this approach are given including: Carrizo Plain and Parkfield electromagnetic profiling data; sea floor magnetotelluric (MT) data from the Gulf of Mexico; MT survey in a culturally noisy area of Bavaria; and Parkfield/Hollister earthquake monitoring array data. Experience with these projects has resulted in an improved program. The new version of the code is available at http://www.cg.NRCan.gc.ca/mtnet/mtnet.html or by contacting egbert{at}oce.orst.edu. Appendices of this report present documentation for Multmtrn.

  17. Factors Influencing Dating Experiences Among African American Emerging Adults

    PubMed Central

    Hall, Naomi M.; Lee, Anna K.; Witherspoon, Daphne D.

    2014-01-01

    This study examined sociocultural factors that impact dating and sexual experiences of heterosexual African American undergraduate college students attending a historically Black institution in the Southeastern United States. Specifically, mate availability and relationship involvement were analyzed to document students’ experiences, and how these influences may be associated with sexual decision making and behavior. Data from nine focus groups (N = 57) were aggregated and four subthemes were identified: competition among women, acceptability of mates, high prevalence of casual relationships, and lowered expectations for commitment. Power dynamics emerged as a contributing factor to the types of relationship involvement, sexual decision-making, and behavior among participants. The importance of prevention programs focusing on situational and cultural variables is highlighted. Additionally, implications for professionals working with emerging adults to consider the impact of the gender ratio imbalance, and perceived power distributions on perceptions of dating relationships, and sexual decision making and behavior are addressed. PMID:25530924

  18. Achievement and Underachievement: The Experiences of African Caribbeans

    ERIC Educational Resources Information Center

    Rhamie, Jasmine

    2012-01-01

    The disproportionate representation of African Caribbeans in all the negative educational statistics has been well documented. Despite this, there are African Caribbeans who achieve academically but relatively few studies have explored this area. This study aimed to investigate the factors that contribute to African Caribbean academic success,…

  19. Diversifying the secondary school curriculum: The African experience

    NASA Astrophysics Data System (ADS)

    Sifuna, Daniel N.

    1992-01-01

    The paper discusses some African experiences in the diversification of secondary education, which is taken to mean curriculum change in a practical or vocational direction. This approach is intended to provide a wider set of future career options than is offered in the more uniform academic curriculum. The diversification policy has generally been seen as a solution to a number of economic and social problems facing the independent African countries, notably the increasing youth unemployment and the escalating costs of formal education. Studies which have so far been carried out have, however, revealed that diversification programmes have not met the intended objectives, although there is sustained interest in vocationalising formal education. Problems which commonly face these programmes include high unit costs, an absence of clarity in aims and objectives, a shortage of qualified teachers and the low status of vocational subjects as viewed by the students and the community. For future development, it is suggested that diversification programmes be reorganised to relate to more realistic goals through wider community participation and through the work-orientation of post-school training programmes.

  20. Cage experiments in an East African mangrove forest: a synthesis

    NASA Astrophysics Data System (ADS)

    Schrijvers, J.; Vincx, M.

    1997-12-01

    The impact of epibenthos on endobenthos has frequently been investigated for temperate saltmarsh regions by using cage exclusion experiments. Although the insight into the function of the endobenthos of mangrove forests is crucial for their management, very few cage experiments have so far been carried out in such areas. The present paper summaries the results of such experiments in a typical East African mangrove forest at Gazi Bay about 60 km south of Mombasa, Kenya. Epibenthic animals were excluded for one year in two mangrove zones which differed in forest morphology and intertidal position ( Ceriops tagal and Avicennia marina). Environmental factors and meiobenthic and macrobenthic densities were followed in a randomised block design, and procedural and exclusion effects were statistically detected. In confronting the separate responses of all faunal groups in the two mangrove zones, this synthesis gives a better insight into the tropho-dynamical interactions than the earlier separate reports on the same experiment. The ecosystem of the mangrove zones and the competitive interactions within this system provided an ideal opportunity to discover the existence of two food systems. This confirmed a strong involvement of the majority of the endobenthos in an isolated decompositional pathway in the mangrove sediment. It became clear that this exploitative competition was more important than the epibenthic predation in structuring and regulating the global endobenthic community. This synthesis therefore both demonstrates the decisive role of the endobenthos as regenators of mangrove material, and suggests that endobenthos plays a minor role as prey for the demersal or pelagic carnivores.

  1. Lithospheric structures and Precambrian terrane boundaries in northeastern Botswana revealed through magnetotelluric profiling

    NASA Astrophysics Data System (ADS)

    Miensopust, M. P.; Jones, A. G.; Muller, M. R.; Garcia, X. A.; Evans, R. L.; Khoza, D. T.

    2010-12-01

    Within the framework of the Southern African MagnetoTelluric EXperiment (SAMTEX) a focused study was undertaken to gain better knowledge of the lithospheric geometries and structures of the westerly extension of the Zimbabwe Craton into Botswana, with the overarching aim to increase our understanding of southern African tectonics. The area of interest is located in northeastern Botswana, where Kalahari sands cover most of the geological terranes, and little is known about lithospheric structures and thickness. Some of the regional scale terrane boundary locations, defined based on potential field data, may be not sufficiently accurate for local scale studies. Investigation of the NNW-SSE orientated, 600 km long ZIM line profile crossing the Zimbabwe craton, Magondi mobile belt and Ghanzi-Chobe belt showed that the Zimbabwe craton is characterized by thick ( ˜ 220 km) resistive lithosphere, consistent with geochemical and geothermal estimates from kimberlite samples of the Orapa and Letlhakane pipes ( ˜ 175 km west of the profile). The lithospheric mantle of the Ghanzi-Chobe belt is resistive but the lithosphere is only about 180 km thick. At crustal depths a northwards-dipping boundary between the Ghanzi-Chobe and the Magondi belts is identified, and two mid- to lower-crustal conductors are discovered in the Magondi belt. The crustal terrane boundary between the Magondi and Ghanzi-Chobe belts is found to be located further to the north, and the southwestern boundary of the Zimbabwe craton might be further to the west, than previously inferred from potential field data.

  2. Ogbu Revisited: Unpacking High-Achieving African American Girls' High School Experiences

    ERIC Educational Resources Information Center

    Archer-Banks, Diane A. M.; Behar-Horenstein, Linda S.

    2012-01-01

    How African American girls cope and excel amidst the discriminations and inequities they experience within U.S. educational systems has not been widely discussed in the body of research about African Americans' schooling experiences. In this study, the researchers examined the applicability of Ogbu's cultural-ecological theory to the…

  3. Representations of the Racialized Experiences of African Americans in Developmental Reading Textbooks

    ERIC Educational Resources Information Center

    Williams, Jeanine L.

    2013-01-01

    Race plays a major role in the lived experiences of African Americans. Consequently, race significantly impacts the identities and educational experiences of African American college students--many of whom require developmental reading courses. These courses, which are gateway courses in higher education, should address race along with reading…

  4. The Perceived Undergraduate Classroom Experiences of African American Women in Science, Technology, Engineering, and Mathematics (STEM)

    ERIC Educational Resources Information Center

    Holmes, Kimberly Monique

    2013-01-01

    The purpose of this dissertation study was to explore African-American women's perceptions of undergraduate STEM classroom experiences, and the ways in which those experiences have supported or hindered their persistence in physics majors. The major research question guiding this study was: How do African-American women perceive the climate and…

  5. Acculturative Experiences of Black-African International Students

    ERIC Educational Resources Information Center

    Boafo-Arthur, Susan

    2014-01-01

    There has been a significant increase in the number of international students pursuing higher education in the U.S. since 2001. Upon arrival, students are often beset with feelings of isolation and alienation, which are characteristic of adjusting to a new culture. African International students, specifically Black-African international students,…

  6. Experiences of African American Empowerment: A Jamesian Perspective on Agency

    ERIC Educational Resources Information Center

    Curtis-Tweed, Phyllis

    2003-01-01

    This essay draws from the work of William James and three African American pragmatists, W.E.B. Du Bois, Ralph Ellison and Cornel West, to explore the moral relevance of the self as an empowered agent among African American youth. The focus is on Jamesian agency as a function of the individual's awareness of options in context, the self-empowerment…

  7. Prospective Teachers Experiences Teaching Mathematics to African American Males

    ERIC Educational Resources Information Center

    Sheppard, Peter

    2009-01-01

    This paper describes an effort to provide prospective teachers opportunities to better understand African American male students and better focus on how they learn mathematics. Prospective teachers spent 15 hours over an eight week span mentoring and tutoring African American males without the guise of practicing teachers. Qualitative data drawn…

  8. Magnetotelluric pilot study in the Rio Grande Rift, southwest USA

    NASA Astrophysics Data System (ADS)

    Feucht, D. W.; Bedrosian, P. A.; Sheehan, A. F.

    2012-12-01

    A magnetotelluric (MT) pilot study consisting of approximately 25 stations distributed in and around the Rio Grande Rift of the southwest United States was carried out in the summer of 2012. Both broadband (100 Hz to 1000 s) and long-period (up to 10 000 s) MT data were collected across two profiles that run perpendicular to the rift axis near Denver, Colorado and Taos, New Mexico, respectively. Time-domain EM data was also collected at each site to account for galvanic distortion in the near-surface. The tectonic forces and rheologic properties behind the initiation and propagation of the rift are poorly understood. Surface mapping of volcanism, normal faulting and sedimentary basins reveals a narrow band of crustal deformation confined to a region in close proximity to the rift axis while geophysical results suggest that deformation is distributed across a much broader and deeper region of the lithosphere. In particular, seismic tomography shows low seismic wave speeds into the lower crust and upper mantle. The magnetotelluric technique is a well-proven passive electromagnetic method that allows for the detection of apparent resistivity at a wide range of depth scales. Complimenting the seismic results with MT data will provide important new information on the geologic and geophysical properties that control the rifting process in this low-strain rate environment. Properties to which the MT method is particular sensitive include temperature, fluid content, and mineral alteration. Preliminary results from this most recent survey are encouraging, showing good data quality up to 10 000 s. In an important precursor to full 2D modeling, the magnetotelluric phase tensor has been used to assess the dimensionality of the electrical resistivity structure at depth. This pilot study provides proof of concept for a much larger magnetotelluric experiment planned to take place in the Rio Grande Rift in 2013.

  9. The Perpetual Homelessness of College Experiences: Tensions between Home and Campus for African American Women

    ERIC Educational Resources Information Center

    Winkle-Wagner, Rachelle

    2009-01-01

    There is an ongoing debate about whether African American students need to sever ties with their families to be successful in college. Adding nuance to this debate, this ethnographic study examines African American women's experiences of navigating family relationships in a predominantly White institution. The women described multiple pressures…

  10. Exploring the Meaning African American PETE Teacher Candidates Ascribe to Their Aquatic Experiences

    ERIC Educational Resources Information Center

    Sato, Takahiro; Hodge, Samuel R.

    2012-01-01

    Physical Education Teacher Education (PETE) programs typically require their graduates to learn to swim proficiently. However, the research base is underdeveloped regarding the aquatic experiences of African Americans in PETE programs. The purpose of this study was to explore the meaning African American PETE teacher candidates ascribe to their…

  11. Help-Seeking Experiences and Attitudes among African American, Asian American, and European American College Students

    ERIC Educational Resources Information Center

    Masuda, Akihiko; Anderson, Page L.; Twohig, Michael P.; Feinstein, Amanda B.; Chou, Ying-Yi; Wendell, Johanna W.; Stormo, Analia R.

    2009-01-01

    The study examined African American, Asian American, and European American college students' previous direct and indirect experiences of seeking professional psychological services and related attitudes. Survey data were collected from 254 European American, 182 African American and 82 Asian American college students. Results revealed that fewer…

  12. Experiences of Chinese International Students Learning English at South African Tertiary Institutions

    ERIC Educational Resources Information Center

    Ayliff, D.; Wang, G.

    2006-01-01

    This article aims to provide insight into the experiences of Chinese international students in some South African tertiary institutions. The study investigates their successes and failures in endeavouring to learn English and the culture shock and "learning shock" they endure when registering to study in an African country with an essentially…

  13. Unheard and Unseen: How Housing Insecure African American Adolescents Experience the Education System

    ERIC Educational Resources Information Center

    Ellis, Addie Lucille; Geller, Kathy D.

    2016-01-01

    This narrative study is based on stories told by African American adolescents experiencing homelessness. It offers insights into their lived experiences and describes the challenges faced in negotiating the urban education system. African American youth are disproportionately represented in the adolescent homeless demographic. "Unheard and…

  14. Emerging from the Pipeline: African American Students, Socioeconomic Status, and College Experiences and Outcomes

    ERIC Educational Resources Information Center

    Walpole, MaryBeth

    2008-01-01

    This study focuses on how social class affects the college experiences and outcomes for African American students in 4-year colleges and universities. Using a national, longitudinal data base, the findings indicate that low SES African American students have less contact with faculty, study less, are less involved with student organizations, work…

  15. An Examination of the Lived Experiences of Successful African American Men Attending a Historically Black University

    ERIC Educational Resources Information Center

    Powell, Clark R.

    2013-01-01

    This phenomenological research explored the lived experiences of successful African American men attending a Historically Black College and University (HBCU) in the Midwest. The guiding questions for the study were (a) What positive characteristics do successful African American men demonstrate at HBCUs that offset major problems, concerns, and…

  16. Black African Parents' Experiences of an Educational Psychology Service

    ERIC Educational Resources Information Center

    Lawrence, Zena

    2014-01-01

    The evidence base that explores Black African parents' experiences of an Educational Psychology Service (EPS) is limited. This article describes an exploratory mixed methods research study undertaken during 2009-2011, that explored Black African parents' engagement with a UK EPS. Quantitative data were gathered from the EPS preschool…

  17. Experiences of african american parents following perinatal or pediatric death: a literature review.

    PubMed

    Boyden, Jackelyn Y; Kavanaugh, Karen; Issel, L Michele; Eldeirawi, Kamal; Meert, Kathleen L

    2014-01-01

    A child's death is one of life's most difficult experiences. Little is known about the unique factors that influence the grief experience for bereaved African American parents. Through an integrative review of 10 publications, the authors describe the grief responses, outcomes, and implications for African American parents who experience the death of a child. Four themes emerged: (a) emotional response to loss; (b) factors that added to the burden of loss; (c) coping strategies; and (d) health consequences of grief. Healthcare providers, administrators, and policymakers should be sensitive to the unique needs of African American parents following a child's death. PMID:24666143

  18. The Will to Achieve: A Phenomenological Study of the Experiences of African American High Achieving Students and Their Parents

    ERIC Educational Resources Information Center

    Spencer, Natalie Faye

    2012-01-01

    The purpose of this research study was to understand the experiences of high achieving African American students and their parents. The experiences of high achieving African American students and their parents have been missing from literature on the academic achievement of African American students. Much of the literature that has been published…

  19. The Soul of Leadership: African American Students' Experiences in Historically Black and Predominantly White Organizations

    ERIC Educational Resources Information Center

    Hotchkins, Bryan K.

    2013-01-01

    This study addresses African American students' leadership experiences at predominantly White institutions. Findings indicated participants utilized servant leadership in historically Black organizations and transformational leadership in predominantly White organizations. The differences displayed showed that participants' leadership perceptions…

  20. Continuous profiling of magnetotelluric fields

    SciTech Connect

    Verdin, C.T.

    1991-05-01

    The magnetotelluric (MT) method of mapping ground electrical conductivity is traditionally based on measurement of the surface impedance at widely spaced stations to infer models of the subsurface through a suitable pseudo 1-D inverse or with linearized least-squares inversion for 2- or 3-D geoelectric media. It is well known that small near-surface inhomogeneities can produce spatial discontinuities in the measured electric fields over a wide frequency range and may consequently bias the impedance on a very local scale. Inadequate station spacing effectively aliases the electric field measurements and results in distortions that cannot be removed in subsequent processing or modelling. In order to fully exploit the benefits of magnetotellurics in complex geological environments, closely spaced measurements must be used routinely. This thesis entertains an analysis of MT data taken along continuous profiles and is a first step that will allow more encompassing 2-D sampling techniques to become viable in the years to come. The developments presented here are to a large extent motivated by the physical insight gained from low-contrast solutions to the forward MT problem. These solutions describe the relationship between a perturbation in the electrical conductivity of the subsurface and the ensuing perturbation of the MT response as the output of a linear system. Albeit strictly accurate in a limited subset of practical exploration problems, the linearized solutions allow one to pursue a model independent study of the response characteristics of MT data. In fact, these solutions yield simple expressions for 1-,2-, and 3-D resistivity models which are here examined in progressive sequence.

  1. Solar quiet day ionospheric source current in the West African region

    PubMed Central

    Obiekezie, Theresa N.; Okeke, Francisca N.

    2012-01-01

    The Solar Quiet (Sq) day source current were calculated using the magnetic data obtained from a chain of 10 magnetotelluric stations installed in the African sector during the French participation in the International Equatorial Electrojet Year (IEEY) experiment in Africa. The components of geomagnetic field recorded at the stations from January–December in 1993 during the experiment were separated into the source and (induced) components of Sq using Spherical Harmonics Analysis (SHA) method. The range of the source current was calculated and this enabled the viewing of a full year’s change in the source current system of Sq. PMID:25685434

  2. Solar quiet day ionospheric source current in the West African region.

    PubMed

    Obiekezie, Theresa N; Okeke, Francisca N

    2013-05-01

    The Solar Quiet (Sq) day source current were calculated using the magnetic data obtained from a chain of 10 magnetotelluric stations installed in the African sector during the French participation in the International Equatorial Electrojet Year (IEEY) experiment in Africa. The components of geomagnetic field recorded at the stations from January-December in 1993 during the experiment were separated into the source and (induced) components of Sq using Spherical Harmonics Analysis (SHA) method. The range of the source current was calculated and this enabled the viewing of a full year's change in the source current system of Sq. PMID:25685434

  3. Leadership Development and the African American Male College Student Experience

    ERIC Educational Resources Information Center

    Oaks, D'Arcy John; Duckett, Kirstan; Suddeth, Todd; Kennedy-Phillips, Lance

    2013-01-01

    Qualitative interviews were employed to assess the effectiveness of a leadership program geared toward African American male personal and professional development, and to examine the relationship between program participation and connectedness. Elements of both social engagement (mentoring and being mentored, peer-to-peer relationships, and…

  4. Immersion and Identity: Experiences of an African American Preschool Child

    ERIC Educational Resources Information Center

    McCullough, Ruanda Garth; Reyes, Sharon Adelman

    2010-01-01

    This article explores the benefits and challenges of a Spanish language immersion preschool from the perspective of a non-Spanish speaking African American family. Data explored include the decision to enroll, reactions from peers and family, home-school communication issues, language development, and family involvement. In addition,…

  5. Exploration of the Lived Experiences of Illiterate African American Adults

    ERIC Educational Resources Information Center

    Waters, LaTonya Michell

    2009-01-01

    This phenomenological study examined the stories of illiterate African American adults to determine the factors that led to their illiteracy. Narrative techniques were utilized to discern themes from narrative accounts of eight participants. The participants were enrolled in one of two adult basic education programs referred to as ABE I and ABE…

  6. The South African Experience: Beyond the CIDA Model

    ERIC Educational Resources Information Center

    Bruton, John M.

    2008-01-01

    The Community and Individual Development Association (CIDA) City Campus is presented by Heaton as an innovative African alternative to traditional business education. However, he considers the model in isolation from the unique educational and economic circumstances of postapartheid South Africa. As a response, this article goes beyond the CIDA…

  7. Experiences of African American Young Women in Science, Technology, Engineering, and Mathematics (STEM) Education

    NASA Astrophysics Data System (ADS)

    Kolo, Yovonda Ingram

    African American women are underrepresented in science, technology, engineering, and mathematics (STEM) fields throughout the United States. As the need for STEM professionals in the United States increases, it is important to ensure that African American women are among those professionals making valuable contributions to society. The purpose of this phenomenological study was to describe the experiences of African American young women in relation to STEM education. The research question for this study examined how experiences with STEM in K-10 education influenced African American young women's academic choices in their final years in high school. The theory of multicontextuality was used to provide the conceptual framework. The primary data source was interviews. The sample was composed of 11 African American young women in their junior or senior year in high school. Data were analyzed through the process of open coding, categorizing, and identifying emerging themes. Ten themes emerged from the answers to research questions. The themes were (a) high teacher expectations, (b) participation in extra-curricular activities, (c) engagement in group-work, (d) learning from lectures, (e) strong parental involvement, (f) helping others, (g) self-efficacy, (h) gender empowerment, (i) race empowerment, and (j) strategic recruitment practices. This study may lead to positive social change by adding to the understanding of the experiences of African American young women in STEM. By doing so, these findings might motivate other African American young women to pursue advanced STEM classes. These findings may also provide guidance to parents and educators to help increase the number of African American women in STEM.

  8. Psychopathology, adversity, and creativity: diversifying experiences in the development of eminent African Americans.

    PubMed

    Damian, Rodica Ioana; Simonton, Dean Keith

    2015-04-01

    Symptoms associated with mental illness have been hypothesized to relate to creative achievement because they act as diversifying experiences. However, this theory has only been tested on predominantly majority-culture samples. Do tendencies toward mental illness still predict eminent creativity when they coexist with other diversifying experiences, such as early parental death, minority-status, or poverty? These alternative diversifying experiences can be collectively referred to as examples of developmental adversity. This conjecture was tested on a significant sample of 291 eminent African Americans who, by the nature of their status as long-term minorities, would experience more developmental adversity. Replicating majority-culture patterns, African American artists showed higher mental illness rates than African American scientists. Yet the absolute percentages were significantly lower for the African Americans, regardless of profession. Furthermore, mental illness predicted higher eminence levels only for the African American artists, an effect that diminished when controlling for developmental adversity. Because the latter predicted eminence for both artists and scientists, the "madness-to-genius" link probably represents just 1 of several routes by which diversifying experiences can influence eminence. The same developmental ends can be attained by different means. This inference warrants further research using other eminent creators emerging from minority culture populations. PMID:25090126

  9. The lithospheric architecture of a Neoproterozoic collision zone in Southern Africa inferred from deep probing magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Khoza, D. T.; Jones, A. G.; Muller, M. R.; Evans, R. L.; Miensopust, M. P.; Hamilton, M.; Garcia, X. A.; Cole, P.; Ngwisanyi, T.; Hutchins, D.; Fourie, S.; Jelsma, H.; Pettit, W.; Aravanis, T.; Webb, S. J.; Wasborg, J.

    2009-12-01

    Cratonic margins have played a major role in shaping the modern Southern African tectonic landscape, and central to our knowledge is information about the lithospheric-scale structures and geometries using geophysical methods. Understanding the evolution of the younger orogenic belts around Archean cratons using electrical resistivity data is one of the primary objectives of the Southern African Magnetotelluric Experiment (SAMTEX); the largest ever land-based magnetotelluric (MT) project. MT data were acquired along four profiles crossing the enigmatic Rehoboth Terrane, the Neo-Proterozoic Ghanzi-Chobe/Damara belts (collectively termed the Damara Mobile Belt, DMB) and the southern Angola craton. The extended Groom and Bailey distortion decomposition technique was applied to the MT data and analyses show significant depth and along-profile variations in geo-electric strike and dimensionality on all transects crossing these three tectonic units (i.e. Rehoboth Terrane, Angola craton and the DMB). Geo-electric strikes are generally parallel to the north-east trending tectonic fabric, as inferred from the magnetic data, but the significant strike variations with depth are expressions of heterogeneity in lithospheric structure. Electrical resistivity models derived from the data provide the first pseudo three-dimensional tectonic structure of the Damara orogen and adjacent terranes. Regional-scale resistivity models constructed from two-dimensional inversions of the MT data indicate significant variations in lithospheric resistivity structure along and across strike from the younger orogen to the older adjacent cratons. The Damara belt lithosphere, although generally more conductive and significantly thinner than adjacent Angola craton and Rehoboth terrane, exhibits upper resistive upper crustal features tentatively interpreted to be caused by igneous intrusions emplaced during Pan-African magmatic event. Upper crustal listric faults are imaged as conductive features and

  10. African American women's experiences with physical activity in their daily lives.

    PubMed

    Nies, M A; Vollman, M; Cook, T

    1999-02-01

    Sedentary behavior is a major public health problem for African American women. A qualitative study used focus groups to explore African American women's experiences with physical activity in their daily lives. Women aged 35-50 were recruited to participate in the focus groups. Transcripts from the focus groups were coded and analyzed. African American women's facilitators of physical activity were daily routine, practical and convenient activities, personal safety, child care, weight loss, stress reduction, knowledge and commitment, enjoyment, pets, family and peer support, home and work facilities, and daylight and climate conditions. Barriers to physical activity were lack of child care, no person to exercise with, competing responsibilities, lack of space in the home, inability to use exercise facilities at work, lack of motivation, fatigue, and unsafe neighborhood. This information will provide the basis for generating new strategies to increase physical activity for African American women in the community. PMID:10074819

  11. We fall down: the African American experience of coping with the homicide of a loved one.

    PubMed

    Sharpe, Tanya L; Boyas, Javier

    2011-01-01

    Rates of homicide among African Americans are much higher than those of other racial or ethnic groups. Research has demonstrated that homicide can be psychologically debilitating for surviving family members. Yet, exploring the experiences of homicide victims’ surviving loved ones has received little attention. This study examined the coping strategies of African American survivors of homicide. Qualitative interviews were conducted with 8 African American family members (ages 18-82) of homicide victims. Survivors were recruited from the Massachusetts Office of Victim Services and from homicide survivor support, school, and community groups throughout the New England area. Interviews were conducted using open-ended questions derived from coping, support network, grief, and bereavement literatures. Results indicate that the primary coping strategies utilized by African American survivors of homicide victims are spiritual coping and meaning making, maintaining a connection to the deceased, collective coping and caring for others, and concealment. Implications for research and practice are discussed. PMID:22073426

  12. The Lived Experiences of African American Women with Breast Cancer: Implications for Counselors

    ERIC Educational Resources Information Center

    Clay, LaTasha K.

    2013-01-01

    Qualitative phenomenological methodology was used to explore the lived experiences of African American women diagnosed with breast cancer. Phenomenology focuses on the meaning of the lived experiences of individuals experiencing a concept, structure, or phenomenon (Creswell, 2007). The purpose of phenomenological research is to identify phenomena…

  13. Discrimination at School: Latino and African American Male High School Students' Experiences

    ERIC Educational Resources Information Center

    Wakefield, W. David; Fajardo, Gabriela

    2005-01-01

    This study investigated male Latino and African American adolescents' experiences with racial discrimination at school. Participants (N = 85) were recruited from an urban public high school in southern California. Students completed paper and pencil measures assessing their experiences with racial discrimination. Overall, Latino and African…

  14. Caregiver Experiences of Discrimination and African American Adolescents' Psychological Health over Time

    ERIC Educational Resources Information Center

    Ford, Kahlil R.; Hurd, Noelle M.; Jagers, Robert J.; Sellers, Robert M.

    2013-01-01

    The present study examined the effect of caregivers' experiences of racial discrimination on their adolescent children's psychological functioning among a sample of 264 African American dyads. Potential relations between caregiver discrimination experiences and a number of indicators of adolescents' (aged 12-17) psychological functioning over time…

  15. African American and European American Therapists' Experiences of Addressing Race in Cross-Racial Psychotherapy Dyads

    ERIC Educational Resources Information Center

    Knox, Sarah; Burkard, Alan W.; Johnson, Adanna J.; Suzuki, Lisa A.; Ponterotto, Joseph G.

    2003-01-01

    Using Consensual Qualitative Research, 12 licensed psychologists' overall experiences addressing race in psychotherapy were investigated, as were their experiences addressing race in a specific cross-racial therapy dyad. Results indicated that only African American psychologists reported routinely addressing race with clients of color or when race…

  16. The Experience of African Students Studying Nursing in the United States in Relation to Their Use of Critical Thinking

    ERIC Educational Resources Information Center

    Tyson, Donald Lee

    2012-01-01

    This qualitative study explores the critical thinking experiences of African nursing students enrolled in several universities in the U.S. Using a semi-structured interview approach, twelve African students discussed their experiences using and learning a western critical thinking approach, as well as described their educational experiences in…

  17. Experiences of African Students in Predominantly White Institutions: A Literature Overview.

    PubMed

    Inyama, Davis; Williams, Allison; McCauley, Kay

    2016-01-01

    The objective of this paper is to examine research conducted on the experiences of African health sciences students in predominantly white higher education institutions/environments. The main elements of cross-cultural adaptation models were adopted to discuss the amalgamated themes under the auspices of adjustment, integration, and conditioning. The overview revealed that African students encounter unique experiences, with isolation and "feeling different" being commonly mentioned. Recommendations for future research are presented, including programmatic implications for higher education and student affairs professionals. PMID:27525115

  18. Experiences of African Students in Predominantly White Institutions: A Literature Overview

    PubMed Central

    McCauley, Kay

    2016-01-01

    The objective of this paper is to examine research conducted on the experiences of African health sciences students in predominantly white higher education institutions/environments. The main elements of cross-cultural adaptation models were adopted to discuss the amalgamated themes under the auspices of adjustment, integration, and conditioning. The overview revealed that African students encounter unique experiences, with isolation and “feeling different” being commonly mentioned. Recommendations for future research are presented, including programmatic implications for higher education and student affairs professionals. PMID:27525115

  19. Academic attainment and the high school science experiences among high-achieving African American males

    NASA Astrophysics Data System (ADS)

    Trice, Rodney Nathaniel

    This study examines the educational experiences of high achieving African American males. More specifically, it analyzes the influences on their successful navigation through high school science. Through a series of interviews, observations, questionnaires, science portfolios, and review of existing data the researcher attempted to obtain a deeper understanding of high achieving African American males and their limitations to academic attainment and high school science experiences. The investigation is limited to ten high achieving African American male science students at Woodcrest High School. Woodcrest is situated at the cross section of a suburban and rural community located in the southeastern section of the United States. Although this investigation involves African American males, all of whom are successful in school, its findings should not be generalized to this nor any other group of students. The research question that guided this study is: What are the limitations to academic attainment and the high school science experiences of high achieving African American males? The student participants expose how suspension and expulsion, special education placement, academic tracking, science instruction, and teacher expectation influence academic achievement. The role parents play, student self-concept, peer relationships, and student learning styles are also analyzed. The anthology of data rendered three overarching themes: (1) unequal access to education, (2) maintenance of unfair educational structures, and (3) authentic characterizations of African American males. Often the policies and practices set in place by school officials aid in creating hurdles to academic achievement. These policies and practices are often formed without meaningful consideration of the unintended consequences that may affect different student populations, particularly the most vulnerable. The findings from this study expose that high achieving African American males face major

  20. Magnetotelluric Data, Stable Distributions and Stable Regression

    NASA Astrophysics Data System (ADS)

    Chave, A. D.

    2013-12-01

    The author has noted for many years that the residuals from robust or bounded influence estimates of the magnetotelluric response function are systematically long tailed compared to a Gaussian or Rayleigh distribution. Consequently, the standard statistical model of a Gaussian core contaminated by a fraction of outlying data is not really valid. However, the typical result is an improvement on ordinary least squares, and has become standard in the electromagnetic induction community. A recent re-evaluation of the statistics of magnetotelluric response function estimation has shown that, in almost all cases, the residuals are alpha stable rather than Gaussian. Alpha stable distributions are characterized by four parameters: a shape parameter lying on (0, 2], a skewness parameter, a scale parameter and a location parameter, and cannot be expressed in closed form except for a few special cases. When the shape parameter is 2, the result is Gaussian, but when it is smaller the resulting distribution has infinite variance. Typical magnetotelluric residuals are alpha stable with a shape parameter lying between 1 and 2. This suggests that robust methods improve response function estimates by eliminating data corresponding to the largest stable residuals while leaving the bulk of the population alone. A better statistical approach is based on stable regression that directly accommodates the actual residual distribution without eliminating the most extreme ones. This paper will introduce such an algorithm, and illustrate its functionality with a variety of magnetotelluric data. Further work remains to produce a robust stable regression algorithm that will eliminate real outliers such as lightning strikes or instrument problems without affecting the bulk stable population. Stable distributions are intimately associated with fractional derivative physical processes. Since the Maxwell equations and the constitutive relations pertaining to the earth do not contain any fractional

  1. Community among African American Students on Small, Predominantly White Campuses: The Unforeseen "Minority within a Minority" Experience.

    ERIC Educational Resources Information Center

    Littleton, Robert A.

    2003-01-01

    Describes the experiences of 16 African American students who attended four small, predominantly White colleges in the Southern Appalachian region of the United States. The African American community at these small colleges can sometimes be an unforeseen cultural experience especially for Black male and female nonathletes. Qualitative methodology…

  2. African American Women Coping with the Lived Experiences of Limited Mental Healthcare Access in Rural North Carolina

    ERIC Educational Resources Information Center

    Lesane, Everick S.

    2013-01-01

    This study examined the impact of lived experiences among African American women with limited mental healthcare access in rural North Carolina. The research examined how those lived experiences-due to limited transportation, low socioeconomic status, and limited healthcare access-further exacerbate emotional challenges among African American…

  3. The Lived Experience of the Adult African American Female Who Has Lived in Multiple Foster Care Placements

    ERIC Educational Resources Information Center

    Johnson, Avonda C.

    2012-01-01

    The purpose of the study was to examine and describe the lived experiences of the adult African American woman who had lived in multiple foster care placements. Eleven adult African American women ages 22-25 participated in semi-structured, face-to-face interviews to tell their stories and provide data of the memories of the experience. The…

  4. Striving to Be "in" the Profession and "of" It: The African American Experience in Physical Education and Kinesiology

    ERIC Educational Resources Information Center

    Wiggins, David K.; Wiggins, Brenda P.

    2011-01-01

    This study analyzes the experiences of African Americans in the physical education and kinesiology profession since the late 1850s. Using a variety of primary and secondary source material, we place special emphasis on the experiences of African American physical educators in higher education and in the American Alliance for Health, Physical…

  5. Resilience Post Tenure: The Experience of an African American Woman in a PWI

    ERIC Educational Resources Information Center

    Behar-Horenstein, Linda S.; West-Olatunji, Cirecie A.; Moore, Thomas E.; Houchen, Deidre F.; Roberts, Kellie W.

    2012-01-01

    The purpose of this study was: 1) to explore the pre-tenure experiences of an African American female faculty member in a counselor education program; and 2) to compare the themes that ascended from a precursor study to the current one. By using critical ethnography and case study format, this research gave voice to the participant by prompting…

  6. Racial Identity, Language Attitudes and Educational Experiences: The Voices of African American College Students

    ERIC Educational Resources Information Center

    Stewart, Gail A.

    2012-01-01

    The current study examines the language attitudes, racial identity and educational experiences of 75 African American university and community college students. This study is motivated by the hypothesis that the power of language attitudes dictates, to a large extent, the language one speaks, which is intimately tied to one's sense of…

  7. Personal, Professional, and Sociocultural Experiences of African American Female School Leaders

    ERIC Educational Resources Information Center

    Robinson, Armentress D.

    2014-01-01

    The purpose of this phenomenological study was to explore and gain an in-depth understanding of the personal, professional, and sociocultural experiences of ten African American female school leaders serving as assistant principals, principals, and central office administrators in four suburban school districts in the southeast region of the…

  8. Problematic Situations Associated with Dating Experiences and Relationships among Urban African American Adolescents: A Qualitative Study

    ERIC Educational Resources Information Center

    Sullivan, Terri N.; Erwin, Elizabeth H.; Helms, Sarah W.; Masho, Saba W.; Farrell, Albert D.

    2010-01-01

    This qualitative study focused on the identification of problem situations associated with adolescent dating experiences and relationships, including those that placed youth at risk for dating violence perpetration or victimization. Interviews were conducted with 44 African American middle and high school students in an urban school system.…

  9. Relationships between Discretionary Time Activities, Emotional Experiences, Delinquency and Depressive Symptoms among Urban African American Adolescents

    ERIC Educational Resources Information Center

    Bohnert, Amy M.; Richards, Maryse; Kohl, Krista; Randall, Edin

    2009-01-01

    Using the Experience Sampling Method (ESM), this cross-sectional study examined mediated and moderated associations between different types of discretionary time activities and depressive symptoms and delinquency among a sample of 246 (107 boys, 139 girls) fifth through eighth grade urban African American adolescents. More time spent in passive…

  10. Rearticulating the Leadership Experiences of African American Women in Midlevel Student Affairs Administration

    ERIC Educational Resources Information Center

    Clayborne, Hannah L.; Hamrick, Florence

    2007-01-01

    This qualitative study of African American women holding midlevel administrative positions sought to broaden and challenge conceptualizations of leadership by focusing on respondents' descriptions of their leadership experiences. Findings centered principally on the intensely relational qualities associated with leadership and leading, mentoring…

  11. A Phenomenological Investigation of African American Counselor Education Students' Challenging Experiences

    ERIC Educational Resources Information Center

    Henfield, Malik S.; Woo, Hongryun; Washington, Ahmad

    2013-01-01

    This study explored 11 African American doctoral students' perceptions of challenging experiences in counselor education programs. The authors identified the following themes using critical race theory: feelings of isolation, peer disconnection, and faculty misunderstandings and disrespect. Implications for counselor education programs and…

  12. Gay and Lesbian Youth Experiences of Homophobia in South African Secondary Education

    ERIC Educational Resources Information Center

    Butler, A. H.; Alpaslan, A. H.; Strumpher, J.; Astbury, G.

    2003-01-01

    In post-apartheid South Africa, the tenets of inclusivity, nondiscrimination, and tolerance are actively encouraged and legislated across all sectors of society, including education. However, in examining the coming out experiences of 18 South African gay and lesbian youth (1997-2000), it became apparent that they had all experienced…

  13. Ring of Silence: African American Women's Experiences Related to Their Breasts and Breast Cancer Screening

    ERIC Educational Resources Information Center

    Thomas, Eileen

    2006-01-01

    The purpose of this study was to explore women's memories and feelings concerning their breasts and breast cancer screening experiences in relation to their current breast cancer screening behaviors. Twelve African American women shared stories that were generated in written narratives and individual interviews. Two core themes emerged from the…

  14. Toddler Feeding: Expectations and Experiences of Low-Income African American Mothers

    ERIC Educational Resources Information Center

    Horodynski, Mildred A.; Brophy-Herb, Holly; Henry, Michelle; Smith, Katharine A.; Weatherspoon, Lorraine

    2009-01-01

    Objective: To ascertain maternal expectations and experiences with mealtimes and feeding of toddlers among low-income African American mothers in two mid- to large-size cities in the United States. Design: Qualitative focus group study. Setting: Two Early Head Start programme sites in a Midwestern state which serve low income families. Method:…

  15. Mathematically Successful Sons: The Roles Perceptions, and Experiences of African American Parents

    ERIC Educational Resources Information Center

    Berry, Robert Q., III.

    2008-01-01

    The stories of four mathematically successful middle schools African American boys are used to describe the roles, perceptions, and experiences of their parents. The parents of played multiple roles for their sons: (a) guardians of opportunities, (b) standard setters, (c) resources for mathematical knowledge, and (d) models of success. As…

  16. Black South Africans in the United States: An Analysis of Their Educational and Practical Training Experiences.

    ERIC Educational Resources Information Center

    Crawford, Beth S.; Kreidle, Ann M.

    A study was done of the experiences of Black South Africans who came to the United States for education and training. The research studied 140 individuals who participated in two programs between 1980 and 1991. Data were collected from the student files and from standard university data from "Profiles of American Colleges" by Barron's Educational…

  17. Ethical issues in genomic research on the African continent: experiences and challenges to ethics review committees

    PubMed Central

    2014-01-01

    This is a report on a workshop titled ‘Ethics for genomic research across five African countries: Guidelines, experiences and challenges’, University of the Witwatersrand, Johannesburg, South Africa, 10 and 11 December 2012. The workshop was hosted by the Wits-INDEPTH partnership, AWI-Gen, as part of the H3Africa Consortium. PMID:25145346

  18. Barriers to Persistence in Adult Basic Education: The Experiences of African American Learners

    ERIC Educational Resources Information Center

    Thomas, Simone

    2011-01-01

    One of the most pervasive issues facing educators and administrators in Adult Basic Education (ABE) is student persistence. The purposes of this qualitative study were 1) to identify the experiences that African American adult learners associated with their decisions to leave ABE programs; 2) to ascertain the impact of participants'…

  19. Illuminating the Experiences of African-American Nursing Faculty Seeking Employment in Higher Education in Nursing

    ERIC Educational Resources Information Center

    Loyd, Vanessa

    2015-01-01

    This study explored and described the experience of female African-American nursing faculty seeking employment in higher education in nursing. The lack of diversity in the nursing workforce has been attributed as a major underlying cause of disparity in healthcare in the United States. The importance of increasing the number of minority nursing…

  20. African American Students in Counselor Education Programs: Perceptions of Their Experiences

    ERIC Educational Resources Information Center

    Henfield, Malik S.; Owens, Delila; Witherspoon, Sheila

    2011-01-01

    The authors explored 11 African American doctoral students' perceptions of their experiences in counselor education programs, and their findings are presented. Using a phenomenological methodological framework, the authors investigated the various systems of support that students use as they navigate their respective programs. Human agency was the…

  1. African American Students' Perceptions of Their High School Career Counseling Experiences

    ERIC Educational Resources Information Center

    Byrd, Leah A.

    2013-01-01

    This study examined the perceptions of 10 African American 12th-grade students from one suburban high school regarding their high school career counseling experiences. The purpose was to better understand how students perceive their career counseling interactions and to ascertain what factors were relevant in the counseling relationship. An…

  2. The Intersection of Race and Class in the South African University: Student Experiences

    ERIC Educational Resources Information Center

    Soudien, C.

    2008-01-01

    The purpose of this article is to make a contribution to the discussion on the sociological features of higher education and the significant ways in which it comes to produce a particular version of the racial experience. While work has appeared which has begun to comment on fragmentation of identity in South African higher education there is…

  3. In Their Own Voices: Adolescent African American Males' Experiences of the Achievement Gap

    ERIC Educational Resources Information Center

    Moon, Natasha S.; Singh, Anneliese A.

    2015-01-01

    The authors use a phenomenological research tradition grounded in CRT tenets to describe the daily lived experiences that 12 male African American youth had in relation to the achievement gap. Researchers collected individual semi-structured interviews and focus group data related to the study phenomenon. There were five themes identified in…

  4. Missed Opportunities: Examining the Literacy Experiences of African American Students Displaced by Hurricane Katrina

    ERIC Educational Resources Information Center

    Pollard, Tamica McClarty

    2011-01-01

    The purpose of this study was to examine how five African American middle school students, who were displaced by Hurricane Katrina represent their literacy experiences before, during, and after their displacement. Specifically, the two research questions were: (a) What are the stories that these middle school students tell about their lives,…

  5. African American College Students' Experience of Racial Discrimination and the Role of College Hassles

    ERIC Educational Resources Information Center

    Banks, Kira Hudson

    2010-01-01

    The current study examines the relationship between racial discrimination and depressive symptoms. In particular, it investigated whether college hassles moderated or mediated the relationship. Participants included 194 African American students from a large, Midwestern, state university. Participants provided self-report of their experience of…

  6. On the Outside Looking in: An African American Family's Experience in an Individualized Education Plan Meeting

    ERIC Educational Resources Information Center

    Angelov, Azure D. S.; Anderson, Sheri L.

    2012-01-01

    The current laws that mandate special education originated through the advocacy of families (Turnbull & Turnbull, 1990). Over the years, families have challenged the system to provide free and appropriate public educations for their children. We share, through qualitative measures, the experiences of one African American family and the educators…

  7. Underserved, Underrepresented, Unprepared: Experiences of African American Females in Community College with Barriers to Academic Success

    ERIC Educational Resources Information Center

    Jobe, LaWanda D.

    2013-01-01

    African American women are enrolling and returning to college in large numbers across many community college campuses, especially those women who would be characterized as nontraditional students. This qualitative study examined and analyzed the experiences, stresses, and coping mechanisms of first generation, nontraditional, single parent,…

  8. African-American School Counselors in Majority School Districts: A Qualitative Perspective of Their Lived Experiences

    ERIC Educational Resources Information Center

    Wingate, Crystal Nicole

    2011-01-01

    This dissertation will focus on the lived experiences of African-American school counselors in majority school districts and the lack of retention among this population. The lack of retention and representation of ethnic minorities in the workforce has been the subject of much discussion throughout the United States (Ingersoll, 2004). The…

  9. Educational Change in Post-Conflict Contexts: Reflections on the South African Experience 20 Years Later

    ERIC Educational Resources Information Center

    Christie, Pam

    2016-01-01

    Reflecting on South African experience, this paper develops an analytical framework using the work of Henri Lefebvre and Nancy Fraser to understand why socially just arrangements may be so difficult to achieve in post-conflict reconstruction. The paper uses Lefebvre's analytic to trace three sets of entangled practices…

  10. Hand replantation: First experience in a sub-Saharan African country (Togo)

    PubMed Central

    Amouzou, Komla Sena; Amakoutou, Komla; Bakriga, Batarabadja; Abalo, Anani; Dossim, Assang

    2016-01-01

    Fifty years after Chen has performed the first forearm replantation, we report our first case of hand replantation in a sub-Saharan African country. The etiology of the amputation was machete due to interpersonal violence. The amputation was trans-carpal, guillotine-type, subtotal non-viable maintained with a small skin bridge. The replantation procedure was successful. At one year follow-up, the functional result according to Chen's criteria was excellent. Through this first experience, we can state that hand replantation can be performed successfully both in survival and function in a non-specialized hospital of a sub-Saharan African country. PMID:27274133

  11. African-American Women’s Perceptions and Experiences About Breastfeeding

    PubMed Central

    Obeng, Cecilia S.; Emetu, Roberta E.; Curtis, Terry J.

    2015-01-01

    There are health benefits to breastfeeding for both mothers and their children. The preventive health effects of breastfeeding continue into adulthood, lowering rate of various chronic illnesses. African-American women, especially of lower socioeconomic status, are less likely to breastfeed in comparison to their racial and ethnic counterparts. The purpose of this study is to explore how African-American women experience breastfeeding in the early stages of postpartum care. Two focus groups (N = 20, 10 in each group) were conducted with African-American mothers. Results revealed that participants felt that there were health benefits to breastfeeding, and organizations such as Women, Infants, and Children (WIC) provided support. However, participants stated that lack of information, negative perceptions, and unforeseen circumstances were barriers to breastfeeding. This study proposes support and interventions for this group to increase breastfeeding among this population. PMID:26734597

  12. Discriminatory Experiences and Depressive Symptoms among African American Women: Do Skin Tone and Mastery Matter?

    PubMed Central

    Lincoln, Karen D.; Taylor, Robert Joseph; Jackson, James S.

    2010-01-01

    We apply structural equation modeling techniques to data from the National Survey of American Life to investigate the relationship between perceived discrimination and depressive symptoms among African American women ages 18–98 years (N=2,299). In addition, we evaluate whether or not personal mastery accounts for the intensity of African American women’s psychological response to discrimination and whether or not exposure to discrimination varies by skin complexion. Findings reveal that discrimination is a major threat to African American women’s mental health. They are vulnerable to discrimination, in part, because discrimination undermines their beliefs in mastery making them less psychologically resilient. Experiences of discrimination do not differ by complexion. We conclude that complexion does not matter, but mastery does. PMID:21151821

  13. Tackling the African "poverty trap": the Ijebu-Ode experiment.

    PubMed

    Mabogunje, Akin L

    2007-10-23

    An experiment in poverty reduction began in 1998 in the city of Ijebu-Ode, Nigeria (estimated 1999 population 163,000), where, without the remittances from relatives abroad, an estimated 90% of the population lived below the poverty line of $1.00 (U.S.) per person per day. Central to the experiment was whether poverty can be dramatically reduced through a city consultation process that seeks to mobilize the entire community along with its diaspora. With 7 years of experience, the Ijebu-Ode experiment has been successful in many ways. There is increasing evidence that poverty in the city has been reduced significantly through the microfinancing of existing and new productive activities and the estimated >8,000 jobs these activities have created. Training based on both sustainability science and technology and indigenous practitioner knowledge has been a critical factor in the establishment of cooperatives and the development of new enterprises in specialty crops, small animal, and fish production. Much of this success has been possible as a result of harnessing social capital, especially through the dynamic leadership of the traditional authorities of the city and by the provision of ample loanable funds through the National Poverty Eradication Program of the federal government. The city consultation process itself engendered a participatory focus to the experiment from the beginning and has encouraged sustainability. Yet long-term sustainability is still in question as the initial leadership needs replacement, and credit, the heart of the experiment, lacks sufficient collateral. PMID:17942687

  14. African-American menthol and nonmenthol smokers: differences in smoking and cessation experiences.

    PubMed Central

    Okuyemi, Kolawole S.; Ebersole-Robinson, Maiko; Nazir, Niaman; Ahluwalia, Jasjit S.

    2004-01-01

    BACKGROUND: Despite smoking fewer cigarettes per day, African Americans have lower cessation rates and experience disproportionately higher rates of smoking-related health consequences. Because of their high preference for menthol cigarettes, it has been suggested that smoking menthol cigarettes may contribute to the excess smoking-related morbidity experienced by African Americans. Smoking menthol cigarettes could increase health risks from smoking if smokers of menthol cigarettes have lower cessation rates and thereby have longer duration of smoking compared to smokers of nonmentholated cigarettes. Few studies have examined associations between smoking of mentholated cigarettes and smoking cessation among African Americans. This study examined the smoking patterns of menthol cigarette smokers and their smoking cessation experiences. METHODS: A cross-sectional survey of 480 African-American smokers at an inner-city health center. Survey examined sociodemographics, smoking characteristics, and smoking cessation experiences of participants. Menthol smokers (n = 407) were compared to nonmenthol smokers (n = 73) in these characteristics. RESULTS: Menthol smokers were younger and more likely to smoke cigarettes with longer rod length, with filters, and those high in nicotine and tar. Although both groups did not differ by number of past quit attempts, time since most recent quit attempt was shorter for menthol smokers. The durations of most recent and longest-ever quit attempts were nonsignificantly shorter for menthol, compared to nonmenthol smokers. CONCLUSIONS: These data suggest that African-American menthol smokers are less successful with smoking cessation. Prospective studies are needed to confirm these findings and examine mechanisms underlying such differences. PMID:15481749

  15. Teacher and Parent Perceptions of Classroom Experiences of African American Male Students in a High School Alternative Program

    ERIC Educational Resources Information Center

    Johnson, Kimberly C.

    2013-01-01

    A major concern in the public schools is the low academic achievement of African American males. This mixed methods study examined the classroom experiences of African American male students in an alternative program. The dual purpose was to investigate the teachers' perceptions and their ability to provide best learning environments for…

  16. Community among African American Students on Small, Predominantly White Campuses: The Unforeseen "Minority within a Minority" Experience

    ERIC Educational Resources Information Center

    Journal of American College Health, 2005

    2005-01-01

    Sixteen African American students participated in semi-structured, open-ended interviews about their experiences at small, predominantly white colleges in the Appalachian region. Two main themes emerged from the interviews: community among minorities and minority within a minority. The students described community among African Americans on campus…

  17. "A Fly in the Ointment": African American Male Preservice Teachers' Experiences with Stereotype Threat in Teacher Education

    ERIC Educational Resources Information Center

    Scott, Sonya V.; Rodriguez, Louie F.

    2015-01-01

    This study draws from a larger phenomenological study on African American academic persistence and career aspirations in education. This article highlights three African American males' experiences with concentrated forms of stereotype threat in teacher education. Their voices revealed dimensions of how power and privilege operate in teacher…

  18. Not Merely a Matter of Academics: Student Experiences of a South African University as Study-Abroad Destination

    ERIC Educational Resources Information Center

    Paola, R. J.; Lemmer, E. M.

    2013-01-01

    Study abroad programmes attract considerable numbers of American college students; however, very few select an African country as their study-abroad destination. This article explores the experiences of American undergraduates who made the uncommon choice of a South African university as destination for a mid-length immersion type programme. The…

  19. How Religious Engagement Shapes the College Experience of African American Christian Males at a Predominantly White Institution: A Phenomenological Approach

    ERIC Educational Resources Information Center

    Rice, Stephen J.

    2012-01-01

    Understanding the different aspects of the college experience of African American males in a predominantly White institution is an important topic for researchers. This focus directly responds to the despairing statistics surrounding collegiate African American males, who often show lower graduation rates compared to other racial groups. The need…

  20. Race-ing through the School Day: African American Educators' Experiences with Race and Racism in Schools

    ERIC Educational Resources Information Center

    Jay, Michelle

    2009-01-01

    This article examines the ways African American educators experience themselves as raced individuals in their school settings and explores their perceptions of racial discrimination, subordination, and isolation. For this study, five African American educators participated in in-depth phenomenological interviews. Qualitative data analysis of their…

  1. Familial Factors in the Early Life Experiences of a Population of African American Crack-Cocaine Users: The Father Link?

    ERIC Educational Resources Information Center

    Dixon, Patricia

    1998-01-01

    Explored factors contributing to addiction in 140 African-American males in an inner-city homeless shelter. A common theme in their life stories is that of negative and painful experiences with father figures. Suggestions are made for research into this area and policy strategies to enhance the African-American father's role. (SLD)

  2. Diversifying the Secondary School Curriculum: The African Experience.

    ERIC Educational Resources Information Center

    Sifuna, Daniel N.

    1992-01-01

    Discusses the experiences of Tanzania, Botswana, Kenya, Sierra Leone, Zambia, and Zimbabwe in incorporating vocational education in secondary curricula by diversifying the whole formal educational system, creating parallel vocational systems, or injecting vocational components into the core curriculum. Discusses reasons that outcomes did not meet…

  3. Multi-dimensional Crustal and Lithospheric Structure of the Atlas Mountains of Morocco by Magnetotelluric Imaging

    NASA Astrophysics Data System (ADS)

    Kiyan, D.; Jones, A. G.; Fullea, J.; Ledo, J.; Siniscalchi, A.; Romano, G.

    2014-12-01

    The PICASSO (Program to Investigate Convective Alboran Sea System Overturn) project and the concomitant TopoMed (Plate re-organization in the western Mediterranean: Lithospheric causes and topographic consequences - an ESF EUROSCORES TOPO-EUROPE project) project were designed to collect high resolution, multi-disciplinary lithospheric scale data in order to understand the tectonic evolution and lithospheric structure of the western Mediterranean. The over-arching objectives of the magnetotelluric (MT) component of the projects are (i) to provide new electrical conductivity constraints on the crustal and lithospheric structure of the Atlas Mountains, and (ii) to test the hypotheses for explaining the purported lithospheric cavity beneath the Middle and High Atlas inferred from potential-field lithospheric modeling. We present the results of an MT experiment we carried out in Morocco along two profiles: an approximately N-S oriented profile crossing the Middle Atlas, the High Atlas and the eastern Anti-Atlas to the east (called the MEK profile, for Meknes) and NE-SW oriented profile through western High Atlas to the west (called the MAR profile, for Marrakech). Our results are derived from three-dimensional (3-D) MT inversion of the MT data set employing the parallel version of Modular system for Electromagnetic inversion (ModEM) code. The distinct conductivity differences between the Middle-High Atlas (conductive) and the Anti-Atlas (resistive) correlates with the South Atlas Front fault, the depth extent of which appears to be limited to the uppermost mantle (approx. 60 km). In all inverse solutions, the crust and the upper mantle show resistive signatures (approx. 1,000 Ωm) beneath the Anti-Atlas, which is the part of stable West African Craton. Partial melt and/or exotic fluids enriched in volatiles produced by the melt can account for the high middle to lower crustal and uppermost mantle conductivity in the Folded Middle Atlas, the High Moulouya Plain and the

  4. Three-Dimensional Forward Modeling of Magnetotelluric Data Over Cratonic Lithosphere and Attendent Geological Structures: Case Study of the Zimbabwe Craton

    NASA Astrophysics Data System (ADS)

    Miensopust, M. P.; Jones, A. G.; Farquharson, C. G.; MT Team

    2007-12-01

    The Southern African MagnetoTelluric Experiment (SAMTEX) is covering a huge area - containing parts of South Africa, Namibia and nearly the whole of Botswana - with acquisition of magnetotelluric (MT) data. The project's aim is to gain more information on the lithospheric geometries of the geological structures of this region which contains some of the oldest lithospheric pieces on Earth - the cratons (e.g. Kaapvaal and Zimbabwe cratons). Since the standard modeling of MT data is only in two-dimensions and the recently developed three-dimensional inversion programs require a lot of computation time and high speed computers with large memories, 3D forward modeling is a good compromise on the way to full 3D interpretation of MT data. Forward modeling of subsurface structures similar to the cratonic areas of study will give some indication of how the MT responses should look like and if they change significantly when the cratons have a different shape or extent or resistivity. The determined synthetic data then can be compared with the real data collected in the SAMTEX project. The area for the case study is the western edge of the Zimbabwe craton in eastern Botswana. The craton is surrounded by the Damara Mobile Belt and the Magondi Mobile Belt to the north and west and the Limpopo belt to the south. The giant northern Botswana dyke swarm is cross cutting the craton in about WNW to ESE direction. Based on this geological information, a 3D model was created to calculate synthetic MT responses using the forward modeling routine implemented in the 3D inversion program MT3Dinv (developed by the Geophysical Inversion Facility, University of British Columbia). We will show the results of this modeling exercise and compare them with the observations.

  5. An Intersectional Social Capital Analysis of the Influence of Historically Black Sororities on African American Women's College Experiences at a Predominantly White Institution

    ERIC Educational Resources Information Center

    Greyerbiehl, Lindsay; Mitchell, Donald, Jr.

    2014-01-01

    Research exploring the college experiences of African American women at predominantly White institutions (PWI) continues to be a necessity as African American women graduate at lower rates than their racial/ethnic peers. This qualitative study explored the influence historically Black sororities had on the college experiences of African American…

  6. The influences and experiences of African American undergraduate science majors at predominately White universities

    NASA Astrophysics Data System (ADS)

    Blockus, Linda Helen

    The purpose of this study is to describe and explore some of the social and academic experiences of successful African American undergraduate science majors at predominately White universities with the expectation of conceptualizing emerging patterns for future study. The study surveyed 80 upperclass African Americans at 11 public research universities about their perceptions of the influences that affect their educational experiences and career interests in science. The mailed survey included the Persistence/ voluntary Dropout Decision Scale, the Cultural Congruity Scale and the University Environment Scale. A variety of potential influences were considered including family background, career goals, psychosocial development, academic and social connections with the university, faculty relationships, environmental fit, retention factors, validation, participation in mentored research projects and other experiences. The students' sources of influences, opportunities for connection, and cultural values were considered in the context of a research university environment and investigated for emerging themes and direction for future research. Results indicate that performance in coursework appears to be the most salient factor in African American students' experience as science majors. The mean college gpa was 3.01 for students in this study. Challenging content, time demands, study habits and concern with poor grades all serve to discourage students; however, for most of the students in this study, it has not dissuaded them from their educational and career plans. Positive course performance provided encouragement. Science faculty provide less influence than family members, and more students find faculty members discouraging than supportive. Measures of faculty relations were not associated with academic success. No evidence was provided to confirm the disadvantages of being female in a scientific discipline. Students were concerned with lack of minority role models

  7. Striving to be in the profession and of It: the African American experience in physical education and kinesiology.

    PubMed

    Wiggins, David K; Wiggins, Brenda P

    2011-06-01

    This study analyzes the experiences of African Americans in the physical education and kinesiology profession since the late 1850s. Using a variety of primary and secondary source material, we place special emphasis on the experiences of African American physical educators in higher education and in the American Alliance for Health, Physical Education, Recreation and Dance and its southern, regional, and state chapters. Apparent from this examination is that African Americans have experienced various forms of racially discriminatory practices in physical education and kinesiology and have found it extraordinarily difficult to assume leader ship positions in the profession and be acknowledged for their scholarly and academic accomplishments. PMID:21699112

  8. African American eighth-grade female students' perceptions and experiences as learners of science literacy

    NASA Astrophysics Data System (ADS)

    Crim, Sharan R.

    The National Assessment of Educational Progress (2000) reports an achievement gap between male and female students and majority and minority students in science literacy. Rutherford and Algren (2000) describe a scientifically literate person as one who is aware that science, mathematics, and technology are interdependent human enterprises with strengths and limitations; understands key concepts and principles of science; is familiar with the natural world and recognizes both its diversity and unity; and uses scientific knowledge and scientific ways of thinking for individual and social purposes. The purpose of this qualitative case study research was to investigate African American eighth grade female students' perceptions and experiences as learners of science literacy. A social learning theory (Bandura, 1986) and constructivist theory (Vygotsky, 1977) served as a guide for the researcher. Two questions were explored: (1) What are African American eighth grade female students' perceptions and experiences as learners of science literacy? (2) In what ways do the perceptions and experiences of African American eighth grade female students influence their learning of science literacy? Purposeful sampling (Merriam, 1998) was used with four African American eighth grade female students selected as participants for the study. Data collection and analysis occurred between February and August in a single year. Data sources included an open-ended questionnaire, two in-depth interviews with each participant (Seidman, 1991); classroom observations, participant reflective journals, student artifacts, and a researcher's log. Data were analyzed through the constant comparative method (Glaser & Strauss, 1967), and richly descriptive participant portraits and qualitative case studies (Merriam, 1998) were used to report the findings. Three themes emerged from the study that positively affected the perceptions and experiences of African American eighth grade female students as

  9. Expecting the Unexpected: a Comparative Study of African-American Women's Experiences in Science during the High School Years

    NASA Astrophysics Data System (ADS)

    Hanson, Sandra L.; Johnson, Elizabeth Palmer

    Data from the National Educational Longitudinal Study (NELS) for the years 1988 to 1992 are used to explore the science experiences of young African-American women during the high school years. The comparison groups we use in trying to understand these experiences involve White women (for a race contrast) and African-American men (for a gender contrast). Within the context of a critical feminist perspective, it is argued that gender is constructed in a different way in White and African-American communities. Instead of expecting a disadvantage for young African-American women because of their gender and minority statuses, it is suggested that unique gender ideologies and work-family arrangements in the African-American community give these young women the resources and agency that allow them to compete with their White female counterparts and their African-American male counterparts in the science domain. Results from our analyses of the NELS data confirm these expectations. We find that on a majority of science measures, African-American women do as well as - and sometimes better than - White women and African-American men. For example, there are no differences between African-American women and men on attitudes toward science. And when compared with White women, African-American women tend to have more positive attitudes. When disadvantages appear for these young African-American women, they are more likely to be race effects then gender effects. The minimal gender effects in the science experiences of young African-Americans is in contrast to the more frequent male advantage in the White sample. A careful examination of family and individual resources shows that African-American families compensate for disadvantages on some resources (e.g., family socioeconomic status) by providing young women with an excess of other resources (e.g., unique gender ideologies, work expectations, and maternal expectations and involvement). And, unlike White parents, they sometimes

  10. From their own voices: the lived experience of African American registered nurses.

    PubMed

    Wilson, Deborah W

    2007-04-01

    This phenomenological study described the lived experience of African American registered nurses providing nursing care to individuals, families, and communities in southeast Louisiana. Data were collected from 13 African American registered nurses using semistructured interviews and a focus group. Analysis of the phenomenological data revealed two essential themes, (a) connecting with the patient and (b) proving yourself; and four incidental themes, (a) a fulfilling dream, (b) being invisible and voiceless, (c) surviving and persevering, and (d) mentoring and role modeling. The findings revealed that the general perception among participants was that they were not fully accepted as equal professionals by their Caucasian nurse colleagues, other health care providers, and sometimes patients. The findings of the study indicate the immediate need to address and resolve the issues of diversity within the nursing profession. Nursing will also have to reform its system and practices to embrace and support diversity. PMID:17416716

  11. Magnetotellurics as a multiscale geophysical exploration method

    NASA Astrophysics Data System (ADS)

    Carbonari, Rolando; D'Auria, Luca; Di Maio, Rosa; Petrillo, Zaccaria

    2016-04-01

    Magnetotellurics (MT) is a geophysical method based on the use of natural electromagnetic signals to define subsurface electrical resistivity structure through electromagnetic induction. MT waves are generated in the Earth's atmosphere and magnetosphere by a range of physical processes, such as magnetic storms, micropulsations, lightning activity. Since the underground MT wave propagation is of diffusive type, the longer is the wavelength (i.e. the lower the wave frequency) the deeper will be the propagation depth. Considering the frequency band commonly used in MT prospecting (10-4 Hz to 104 Hz), the investigation depth ranges from few hundred meters to hundreds of kilometers. This means that magnetotellurics is inherently a multiscale method and, thus, appropriate for applications at different scale ranging from aquifer system characterization to petroleum and geothermal research. In this perspective, the application of the Wavelet transform to the MT data analysis could represent an excellent tool to emphasize characteristics of the MT signal at different scales. In this note, the potentiality of such an approach is studied. In particular, we show that the use of a Discrete Wavelet (DW) decomposition of measured MT time-series data allows to retrieve robust information about the subsoil resistivity over a wide range of spatial (depth) scales, spanning up to 5 orders of magnitude. Furthermore, the application of DWs to MT data analysis has proven to be a flexible tool for advanced data processing (e.g. non-linear filtering, denoising and clustering).

  12. What makes African American health disparities newsworthy? An experiment among journalists about story framing

    PubMed Central

    Hinnant, Amanda; Oh, Hyun Jee; Caburnay, Charlene A.; Kreuter, Matthew W.

    2011-01-01

    News stories reporting race-specific health information commonly emphasize disparities between racial groups. But recent research suggests this focus on disparities has unintended effects on African American audiences, generating negative emotions and less interest in preventive behaviors (Nicholson RA, Kreuter MW, Lapka C et al. Unintended effects of emphasizing disparities in cancer communication to African-Americans. Cancer Epidemiol Biomarkers Prev 2008; 17: 2946–52). They found that black adults are more interested in cancer screening after reading about the progress African Americans have made in fighting cancer than after reading stories emphasizing disparities between blacks and whites. This study builds on past findings by (i) examining how health journalists judge the newsworthiness of stories that report race-specific health information by emphasizing disparities versus progress and (ii) determining whether these judgments can be changed by informing journalists of audience reactions to disparity versus progress framing. In a double-blind-randomized experiment, 175 health journalists read either a disparity- or progress-framed story on colon cancer, preceded by either an inoculation about audience effects of such framing or an unrelated (i.e. control) information stimuli. Journalists rated the disparity-frame story more favorably than the progress-frame story in every category of news values. However, the inoculation significantly increased positive reactions to the progress-frame story. Informing journalists of audience reactions to race-specific health information could influence how health news stories are framed. PMID:21911844

  13. Early life experiences linked to diabetes mellitus: a study of African-American migration.

    PubMed Central

    Schneider, D.; Greenberg, M.; Lu, L.

    1997-01-01

    African Americans experienced massive internal migrations that shifted more than 6 million Southern-born blacks to other sections of the United States over the past century, a trend that only recently has been reversed. Whenever mass migration takes place, there is an opportunity to examine the role of the native and relocated environments in the development of disease. This article examines those relationships for diabetes mellitus, a group of diseases that disproportionately affect African-Americans relative to other racial and ethnic groups in the United States. Age-specific and age-adjusted rates with 95% confidence intervals were calculated for males and females for combinations of five regions of birth and four regions of residence at time of death. Southern-born males had statistically significantly higher death rates from diabetes than did their counterparts who died in the same regions in 9 of 16 comparisons. For females, those born in the South had statistically significantly higher rates in 15 of 16 comparisons. The results of this study indicate that place of birth and early life experiences are statistically associated with diabetes mortality among African Americans regardless of place of residence at time of death. PMID:9002414

  14. The experience of African American women living with HIV: creating a prevention film for teens.

    PubMed

    Norris, Anne E; DeMarco, Rosanna

    2005-01-01

    The personal and social costs of HIV are well documented. What remains unknown is the effect of public disclosure of HIV status on the individual who is doing the disclosing. This study describes the experience of four African American women living with HIV who participated in the development of an intergenerational education intervention for African American adolescent girls. These women suggested that they be filmed discussing the "dark side" of HIV in an effort to create an intergenerational education intervention that would alter the risk-taking behavior that they observed in young women in their community. After a rough cut of the film was completed, these women viewed the film and participated in a focus group during which they discussed what it was like to reveal and revisit their own painful experiences associated with becoming infected and then living with HIV. Findings from content analysis of transcribed dialogue included the following positive themes: (a) self-acceptance by telling one's own story and hearing the stories of the other women, (b) a sense of liberation by disclosing publicly one's image and message and letting go of others' judgments, (c) feeling supported by meeting other women who share the same experience, (d) value of using the film to impact or save young people from the pain one has experienced. A negative theme emerged related to personal pain in reliving the individual's history with HIV. PMID:16438124

  15. Disability and Health: Exploring the Disablement Experience of Young Adult African Americans

    PubMed Central

    Harrison, Tracie

    2013-01-01

    Purpose The objective of this study was to examine disablement as experienced by young adult African American men and women with permanent mobility impairment. Methods This study included a sample of 5 male and 5 female participants ranging in age from 22 to 39. An exploratory descriptive design and qualitative methods, including interviews and fieldnotes, were used. Interview data was analyzed using the process of inductive qualitative content analysis. Results Basic desires for independence, shared intimacy, and psychological and physical health were not diminished by physical limitations. The disablement experience of this group is reflected in the themes of “Cumulative Losses” and “Sustained Desires.” The findings of this study describe the high level of motivation that young adult African American men and women with disabilities have to improve levels of health and well-being within the context of their impairments. Conclusion This study provides a better understanding of the contextual factors and experiences that may contribute to the development of further disability and subsequent health-related problems over time. Increased knowledge of the disablement experience of these young men and women may assist health care entities and social service providers in improving health care and rehabilitation efforts targeting this group. PMID:23745770

  16. Infected Lives: Lived Experiences of Young African American HIV-Positive Women.

    PubMed

    Peltzer, Jill N; Domian, Elaine W; Teel, Cynthia S

    2016-02-01

    This hermeneutic phenomenological study explored the lived experiences of young African American HIV-infected women. Eleven women between the ages of 21 and 35 participated. One pattern, Infected Lives, and three themes--Living Alone With HIV, Living With Unresolved Conflicts, and Living With Multiple Layers of Betrayal--emerged. The pattern and themes portray the very complex and challenging experiences faced by these young women living with HIV infection. They have experienced isolation, abandonment, betrayal, and discrimination in their interpersonal and social systems. They often dealt with conflicts of hope and anguish in the relationships with their children, and portraying strength, while feeling fragile. These complexities negatively influence the ability to fully engage in self-care activities. Implications for future research include further investigation about the experiences of psychological distress experienced post-diagnosis, development and evaluation of holistic nursing interventions, and evaluative research on mass media educational campaigns to reduce HIV-related stigma. PMID:25239137

  17. A study of the lived experiences of African American women STEM doctoral degree completers

    NASA Astrophysics Data System (ADS)

    Squires, Stephanie Michelle

    This study examined the lived experiences of African American women (AAW) who completed doctoral degrees in a STEM (science, technology, engineering, and mathematics) discipline in the United States. This study sought to fill the gap in the literature by examining how AAW described and made meaning of lived STEM educational experiences during doctoral degree completion in the context of the intersection of being African American and a woman. This study utilized a theoretical perspective based upon three theories: (a) critical race theory as a framework to gather AAW's narratives about STEM doctorate education, (b) Black feminist thought as a framework to view the intersection of being African American and a woman in the United States, and (c) the science identity model as a framework to view how women of color successfully complete scientific graduate degrees. Participants revealed that being an African American and a woman in a STEM doctoral program often complicated an already difficult process of completing the doctoral degree. The participants described the educational experience as challenging, particularly the writing of the dissertation. The challenges that the participants faced were due to various factors such as difficult advisor/advisee relationships, tedious writing and revision processes, politics, and lack of information regarding the doctoral degree process. The findings suggested that AAW participants confronted intrinsic bias while completing STEM doctoral degrees, which led to isolation and feelings of being an impostor---or feelings of not belonging in scientific studies. The findings also indicated that the women in this study ascribed success in dissertation writing and degree completion to one or more of the following attributes: (a) having a clear plan, (b) taking ownership of the writing process, (c) having an engaged advisor, (d) learning the writing style of the advisor, (e) understanding the temperament of the advisor, (f) personal will

  18. A MATLAB GUI based algorithm for modelling Magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Timur, Emre; Onsen, Funda

    2016-04-01

    The magnetotelluric method is an electromagnetic survey technique that images the electrical resistivity distribution of layers in subsurface depths. Magnetotelluric method measures simultaneously total electromagnetic field components such as both time-varying magnetic field B(t) and induced electric field E(t). At the same time, forward modeling of magnetotelluric method is so beneficial for survey planning purpose, for comprehending the method, especially for students, and as part of an iteration process in inverting measured data. The MTINV program can be used to model and to interpret geophysical electromagnetic (EM) magnetotelluric (MT) measurements using a horizontally layered earth model. This program uses either the apparent resistivity and phase components of the MT data together or the apparent resistivity data alone. Parameter optimization, which is based on linearized inversion method, can be utilized in 1D interpretations. In this study, a new MATLAB GUI based algorithm has been written for the 1D-forward modeling of magnetotelluric response function for multiple layers to use in educational studies. The code also includes an automatic Gaussian noise option for a demanded ratio value. Numerous applications were carried out and presented for 2,3 and 4 layer models and obtained theoretical data were interpreted using MTINV, in order to evaluate the initial parameters and effect of noise. Keywords: Education, Forward Modelling, Inverse Modelling, Magnetotelluric

  19. South Africans' experiences of being old and of care and caring in a transitional period.

    PubMed

    Bohman, Doris M; van Wyk, Neltjie C; Ekman, Sirkka-Liisa

    2011-09-01

    This focused ethnographic study aimed to illuminate a group of South Africans' experiences of being old and of care and caring in a transitional period. With a growing number of older people in Africa, studies on the individual experiences may help to develop care which is more sensitively based on the needs for older people in a changing Southern Africa context. Data were collected through group and individual in-depth interviews and participant observations which involved 16 individuals, aged 52-76. Data were analysed using a qualitative content analysis. The study showed two interrelated themes reflections on life and ubuntu - an orientation towards others. Findings were discussed from the viewpoint of the theory of gerotranscendence, showing similarities as well as differences, possibly due to societal and cultural differences. Shortage of formal care for older people living in poor conditions in Southern Africa, gave rise to the discussion for the need of a contextualized development of gerontological care. To enhance knowledge on the theory of gerotranscendence and develop guidelines for nursing in home-based care/community-based care in a South African context may be a first step to support older people in their process towards gerotranscendence. PMID:21631870

  20. Experiences of racist events are associated with negative health consequences for African American women.

    PubMed Central

    Kwate, Naa Oyo A.; Valdimarsdottir, Heiddis B.; Guevarra, Josephine S.; Bovbjerg, Dana H.

    2003-01-01

    This study investigated whether experiences of racist events were related to psychological distress, negative health behaviors, and health problems. Participants were 71 African American women (mean age 44.4) who were recruited from an urban cancer-screening clinic as part of a larger longitudinal study on familial risk of breast cancer. Participants completed three study assessments, approximately one month apart, and data were collected via self-report. Correlational analyses revealed that past year and lifetime racism were both related to psychological distress. Among smokers and drinkers, past year racism was positively correlated with number of cigarettes and drinks consumed. Lifetime racism was negatively related to perceived health, and positively related to lifetime history of physical disease and frequency of recent common colds. Analyses using a general linear model revealed that these relationships were largely unaccounted for by other variables. In addition, demographic variables such as income and education were not related to experiences of racism. The results suggest that racism can be detrimental to African American's well being and should be investigated in health disparities research. PMID:12856911

  1. Racism at the intersections: Gender and socioeconomic differences in the experience of racism among African Americans.

    PubMed

    Kwate, Naa Oyo A; Goodman, Melody S

    2015-09-01

    Several studies investigating the health effects of racism have reported gender and socioeconomic differences in exposures to racism, with women typically reporting lower frequencies, and individuals with greater resources reporting higher frequencies. This study used diverse measures of socioeconomic position and multiple measures and methods to assess experienced racism. Socioeconomic position included education and financial and employment status. Quantitative racism measures assessed individual experiences with day-to-day and with major lifetime incidents and perceptions of the extent to which African Americans as a group experience racism. A brief qualitative question asked respondents to describe a racist incident that stood out in recent memory. Participants comprised a probability sample of N = 144 African American adults aged 19 to 87 residing in New York City. Results suggested that women reported fewer lifetime incidents but did not differ from men on everyday racism. These differences appear to be partly because of scale content. Socioeconomic position as measured by years of education was positively associated with reported racism in the total sample but differently patterned across gender; subjective social status showed a negative association. Qualitative responses describing memorable incidents fell into 5 key categories: resources/opportunity structures, criminal profiling, racial aggression/assault, interpersonal incivilities, and stereotyping. In these narratives, men were more likely to offer accounts involving criminal profiling, and women encountered incivilities more often. The findings highlight the need for closer attention to the intersection of gender and socioeconomic factors in investigations of the health effects of racism. PMID:26460700

  2. African American women's preventative care usage: the role of social support and racial experiences and attitudes.

    PubMed

    Pullen, Erin; Perry, Brea; Oser, Carrie

    2014-09-01

    Research suggests that African Americans are less likely to utilise preventative care services than Americans of European descent, and that these patterns may contribute to racial health disparities in the United States. Despite the persistence of inequalities in preventative care utilisation, culturally relevant factors influencing the use of these gateway health services have been understudied among marginalised groups. Using a stratified sample of 205 low-income African American women, this research examines the predictors of receiving a physical exam, with a particular emphasis on how differing levels of social support from friend and family networks and experiences of racial discrimination and cultural mistrust shape utilisation. The findings underscore the importance of traditional predictors of utilisation, including insurance status and having a usual physician. However, they also indicate that supportive ties to friendship networks are associated with higher predicted rates of having an annual physical exam, while social support from family and sentiments of cultural mistrust are associated with lower rates of utilisation. Broadly, the findings indicate that even as traditional predictors of help-seeking become less relevant, it will be critical to explore how variations in discrimination experiences and social relationships across marginalised groups drive patterns of preventative care utilisation. PMID:24749849

  3. "I Want to Do the Right Thing but What Is It?": White Teachers' Experiences with African American Students

    ERIC Educational Resources Information Center

    Henfield, Malik S.; Washington, Ahmad R.

    2012-01-01

    This qualitative study examines 26 White middle school teachers' perceptions of their experiences in a predominantly White middle school with a growing African American student population. Utilizing in-depth focus group interviews, teachers elaborated on their experiences with navigating racial, ethnic and cultural boundaries as they attempted to…

  4. Stochastic Inversion of 2D Magnetotelluric Data

    2010-07-01

    The algorithm is developed to invert 2D magnetotelluric (MT) data based on sharp boundary parametrization using a Bayesian framework. Within the algorithm, we consider the locations and the resistivity of regions formed by the interfaces are as unknowns. We use a parallel, adaptive finite-element algorithm to forward simulate frequency-domain MT responses of 2D conductivity structure. Those unknown parameters are spatially correlated and are described by a geostatistical model. The joint posterior probability distribution function ismore » explored by Markov Chain Monte Carlo (MCMC) sampling methods. The developed stochastic model is effective for estimating the interface locations and resistivity. Most importantly, it provides details uncertainty information on each unknown parameter. Hardware requirements: PC, Supercomputer, Multi-platform, Workstation; Software requirements C and Fortan; Operation Systems/version is Linux/Unix or Windows« less

  5. Stochastic Inversion of 2D Magnetotelluric Data

    SciTech Connect

    Chen, Jinsong

    2010-07-01

    The algorithm is developed to invert 2D magnetotelluric (MT) data based on sharp boundary parametrization using a Bayesian framework. Within the algorithm, we consider the locations and the resistivity of regions formed by the interfaces are as unknowns. We use a parallel, adaptive finite-element algorithm to forward simulate frequency-domain MT responses of 2D conductivity structure. Those unknown parameters are spatially correlated and are described by a geostatistical model. The joint posterior probability distribution function is explored by Markov Chain Monte Carlo (MCMC) sampling methods. The developed stochastic model is effective for estimating the interface locations and resistivity. Most importantly, it provides details uncertainty information on each unknown parameter. Hardware requirements: PC, Supercomputer, Multi-platform, Workstation; Software requirements C and Fortan; Operation Systems/version is Linux/Unix or Windows

  6. New approaches to estimation of magnetotelluric parameters

    SciTech Connect

    Egbert, G.D.

    1991-01-01

    Fully efficient robust data processing procedures were developed and tested for single station and remote reference magnetotelluric (Mr) data. Substantial progress was made on development, testing and comparison of optimal procedures for single station data. A principal finding of this phase of the research was that the simplest robust procedures can be more heavily biased by noise in the (input) magnetic fields, than standard least squares estimates. To deal with this difficulty we developed a robust processing scheme which combined the regression M-estimate with coherence presorting. This hybrid approach greatly improves impedance estimates, particularly in the low signal-to-noise conditions often encountered in the dead band'' (0.1--0.0 hz). The methods, and the results of comparisons of various single station estimators are described in detail. Progress was made on developing methods for estimating static distortion parameters, and for testing hypotheses about the underlying dimensionality of the geological section.

  7. Victimization Experiences, Substance Misuse and Mental Health Problems in Relation to Risk for Lethality among African-American and African-Caribbean Women

    PubMed Central

    Sabri, Bushra; Stockman, Jamila K.; Betrand, Desiree; Campbell, Doris W.; Callwood, Gloria B.; Campbell, Jacquelyn C.

    2013-01-01

    The purpose of this study was to investigate the association of intimate partner victimization experiences, mental health, and substance misuse problems with the risk for lethality among women of African descent. Data for this cross-sectional study were derived from a large case-control study examining the relationship between abuse status and health consequences. Women were recruited from primary care, prenatal or family planning clinics in Baltimore and the US Virgin Islands. Logistic regression was used to generate the study findings. Among 543 abused women, physical and psychological abuse by intimate partners, comorbid PTSD and depression symptoms, and PTSD-only problems significantly increased the likelihood of lethality risk. However victims’ substance misuse and depression-only problems were not associated with the risk for lethality. Additionally, PTSD symptoms mediated the relationship between severe victimization experiences and risk for lethality. Practitioners should pay attention to victimization experiences and mental health issues when developing treatment and safety plans. Policies to fund integrated services for African-American and African-Caribbean women with victimization and related mental health issues, and training of providers to identify at-risk women may help reduce the risk for lethality in intimate partner relationships. PMID:23929602

  8. Magnetotelluric Study of the Southern Pamir, Tajikistan

    NASA Astrophysics Data System (ADS)

    Korolevski, W.; Ritter, O.; Weckmann, U.; Rybin, A.; Matiukov, V.

    2014-12-01

    The Pamir region at the western prolongation of the Tibet-Himalaya orogen is a high plateau which accommodated the India-Asia collision by crustal shortening and thickening. The same east-west-trending orogenic belts, corresponding to continental terranes which amalgamated with Asia prior to the collision with India, wrap around the Pamir and Tibet. The southern Pamir is equivalent to the Lhasa terrane in Tibet and consists of Paleozoic-Mesozoic meta-sedimentary rocks, rare Proterozoic gneisses, and voluminous Creaceous-Palaeogene granitoids. The Pamir, however, has been displaced northward by approximately 600km with respect to the Tarim Basin. Today, there is strong geophysical evidence that a slab of Asian lithosphere has been underthrust south-southeastward beneath the Pamir. In summer 2013 we installed 85 broad-band magnetotelluric (MT) stations in the southern Pamir covering a 200km wide and 100km long area between Murghab and Khorugh, with a site spacing of approximately 8km. MT data quality is excellent in the sparsely populated southeastern Pamir plateau and heterogeneous or even strongly disturbed by electromagnetic noise in the populated southwestern Pamir. The magnetotelluric survey was part of the interdisciplinary TIPTIMON (Tien-Shan-Pamir Monitoring Program) project. 3D inversion of the data reveals a prominent low-resistivity zone at a depth of approx. 10 km. This anomaly, with resistivities below 10 Ωm, extends across the entire southeastern Pamir and appears to be limited to the West by the Shakdara dome. The crystalline basement of the Shakdara dome is imaged as resistive material. We interpret the observed low resistivity of the southeastern Pamir is as partially molten felsic material at middle to lower crustal levels.

  9. On the statistics of magnetotelluric rotational invariants

    NASA Astrophysics Data System (ADS)

    Chave, Alan D.

    2014-01-01

    The statistical properties of the Swift skew, the phase-sensitive skew and the WAL invariants I1-I7 and Q are examined through analytic derivation of their probability density functions and/or simulation based on a Gaussian model for the magnetotelluric response tensor. The WAL invariants I1-I2 are shown to be distributed as a folded Gaussian, and are statistically well behaved in the sense that all of their moments are defined. The probability density functions for Swift skew, phase-sensitive skew and the WAL invariants I3-I4, I7 and Q are derived analytically or by simulation, and are shown to have no moments of order 2 or more. Since their support is semi-infinite or infinite, they cannot be represented trigonometrically, and hence are inconsistent with a Mohr circle interpretation. By contrast, the WAL invariants I5-I6 are supported on [ - 1, 1], and are inferred to have a beta distribution based on analysis and simulation. Estimation of rotational invariants from data is described using two approaches: as the ratio of magnetotelluric responses that are themselves averages, and as averages of section-by-section estimates of the invariant. Confidence intervals on the former utilize either Fieller's theorem, which is preferred because it is capable of yielding semi-infinite or infinite confidence intervals, or the less accurate delta method. Because section-by-section averages of most of the rotational invariants are drawn from distributions with infinite variance, the classical central limit theorem does not pertain. Instead, their averaging is accomplished using the median in place of the mean for location and an order statistic model to bound the confidence interval of the median. An example using real data demonstrates that the ratio of averages approach has serious systematic bias issues that render the result physically inconsistent, while the average of ratios result is a smooth, physically interpretable function of period, and is the preferred approach.

  10. It Just Couldn't Have Been Our School: A Phenomenological Study of the Schooling Experiences of African American Male Inmates.

    ERIC Educational Resources Information Center

    Terrell, Shandra R.

    The school experiences of African American male inmates are explored. Nine African American male inmates, ranging in age from 21 to 55, were interviewed regarding their schooling experiences. Interviews were recorded and transcribed to create a text, and themes were uncovered. Themes that describe their schooling experiences were identified. Four…

  11. Application of magnetotelluric in the modeling of underlying structure of Gour Oumelalen (Egere-Aleksod terrane, Central Hoggar, South of Algeria)

    NASA Astrophysics Data System (ADS)

    Boukhalfa, Zakaria; Abderrezak, Bouzid; Khadidja, Ouzegane; Abderrahmane, Bendaoud; Mohamed, Hamoudi; Abdeslam, Abtout; Abdelhamid, Bendekken; Sofiane Said, Bougchiche; Walid, Boukhlouf; Abdelgharfour, Boukar; Aboubakr, Deramchi; Mohamed, Bendali; Abdenaceur, Lemgharbi; Mohammed, Djeddi

    2016-04-01

    The results of a magnetotelluric experiment crossing Ounane granodiorite to the east until the Amadror Wadi to the West, passing through Adrar Ounane in our study area are presented. The magnetotelluric field survey was carried out in the Gour Oumelalen (GO) area during March 2015. We deployed 34 magnetotelluric sites along two parallel EW profiles of a hundred km long. Time series were collected using a V5 system 2000® of Phoenix Geophysics. The first profile located to the north is composed of 18 braodband measurement sites obtained from merging magnetotelluri with audio-magnetotelluric (AMT) data. The second one located 10 km south of the first, is composed of 15 MT sites. An inter-station distance of ~5 km provides good lateral resolution. The MT time series were recorded during about 20 hours which allows to reach a depth of 100 km or more and the AMT data 30 minutes. This allows to get broadband magnetotelluric soundings with good quality data in period range from 0.001 s to 3000 s. In this study we will use the south profile data for modeling the underlying structure of GO. The crustal part of the model shows a resistance bloc, divided by conductive parts which can be interpreted as faults, as regards the lithospheric part it less resistant the upper part, the transition crust / mantle corresponding to MOHO is estimated at more or less 35 km.

  12. Crustal and lithospheric imaging of the Atlas Mountains of Morocco inferred from magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Kiyan, D.; Jones, A. G.; Fullea, J.; Hogg, C.; Ledo, J.; Sinischalchi, A.; Campanya, J.; Picasso Phase II Team

    2010-12-01

    The Atlas System of Morocco is an intra-continental mountain belt extending for more than 2,000 km along the NW African plate with a predominant NE-SW trend. The System comprises three main branches: the High Atlas, the Middle Atlas, and the Anti Atlas. We present the results of a very recent multi-institutional magnetotelluric (MT) experiment across the Atlas Mountains region that started in September, 2009 and ended in February, 2010, comprising acquisition of broadband and long-period MT data. The experiment consisted of two profiles: (1) a N-S oriented profile crossing the Middle Atlas through the Central High Atlas to the east and (2) a NE-SW profile crossing the western High Atlas towards the Anti Atlas to the west. The MT measurements are part of the PICASSO (Program to Investigate Convective Alboran Sea System Overturn) and the concomitant TopoMed (Plate re-organization in the western Mediterranean: Lithospheric causes and topographic consequences - an ESF EUROCORES TOPO-EUROPE project) projects, to develop a better understanding of the internal structure and evolution of the crust and lithosphere of the Atlas Mountains. The MT data have been processed with robust remote reference methods and submitted to comprehensive strike and dimensionality analysis. Two clearly depth-differentiated strike directions are apparent for crustal (5-35 km) and lithospheric (50-150 km) depth ranges. These two orientations are roughly consistent with the NW-SE Africa-Eurasia convergence acting since the late Cretaceous, and the NNE-SSW Middle Atlas, where Miocene to recent Alkaline volcanism is present. Two-dimensional (2-D) smooth electrical resistivity models were computed independently for both 50 degrees and 20 degrees E of N strike directions. At the crustal scale, our preliminary results reveal a middle to lower-crustal conductive layer stretching from the Middle Atlas southward towards the High Moulouya basin. The most resistive (and therefore potentially thickest

  13. Crustal Scale Magnetotelluric Imaging of the Central Atlas in Moocco

    NASA Astrophysics Data System (ADS)

    Ledo, J.; Jones, A. G.; Sinischalchi, A.; Rouais, M.; Campanyà, J.; Kiyan, D.; Moretti, P.; Piña, P.; Hogg, C.; Romano, G.; Picasso Team

    2010-12-01

    The Central Atlas of Morocco is an intracontinental fold-thrust belt with an ENE-WSW main strike that extends about 2000 km and 100 km wide, located in the foreland of the Mediterranean Alpine belt. The structure of the Atlas resulted from the tectonic inversion of a Mesozoic extensional basin, due to compression related to convergence between Africa and Europe occurred from cenozoic to present times. Previous MT data models based on stitched 1D inversion or using only the phases and the induction vector data following and trial and error approach (Schwarz et al., 1992), therefore the overall geoelectrical structure is partly unresolved. In this paper we will expose and discuss the results of new magnetotelluric data acquired along a profile crossing the Atlas that allows imaging its electrical crustal structure.In the lower crust two conductive units appear. One below the Moulouya plains that coincides with a minimum of the Bouguer anomaly, less earthquakes than the adjacent Middle and High Atlas and a low velocity anomaly at lower crustal levels. Moreover, the Moulouya plain and the Middle Atlas to the north are host of the largest Neogene-Quaternary intraplate alkaline volcanic field in Morocco. This feature has been associated either to a Canary mantle plume flow beneath Africa or to the interplay between reactivation of inherited geological structures and the thermal erosion of the metasomatized lithosphere. In any case, all the authors agree that are originated by low degree partial melting of sublithospheric mantle sources. Another low resistivity anomaly appears at lower crustal depths below the Anti-Atlas, that could be either a remnant of tectonic processes in the pre-mesozoic or a more recent overprint of the lower crust due to mantle processes. Two main events during the Pan African orogeny may be the cause of this anomaly, a relic of a subduction process or a deep mineralization associated to magmatism. The Anti-Atlas consists of of a Precambrian

  14. Factors Associated with Partnership Experiences, Attitudes, and Perceptions: A Comparative Case Study of Two African Universities

    ERIC Educational Resources Information Center

    Chiteng Kot, Felly

    2011-01-01

    International partnerships have become an increasingly important trend in African higher education. The creation of partnerships with African universities has been on the rise in the last few years. Different factors (U.S., European, and African initiatives) suggest this trend will continue to increase. This study draws from a survey of a random…

  15. Contributions of College Experiences to African American and White Graduates' Careers.

    ERIC Educational Resources Information Center

    Nickols, Sharon Y.; And Others

    1996-01-01

    A survey of housing/consumer economics and social work alumni received responses from 38 African American and 50 white graduates. Likely sources of financial support for whites were parents, and for African Americans, grants. African Americans had significantly higher social support from churches, whites from sororities/fraternities. There were no…

  16. The South African Experience of Conservation and Social Forestry Outreach Nurseries

    NASA Astrophysics Data System (ADS)

    Botha, Jenny; Witkowski, Ed T. F.; Cock, Jacklyn

    2006-11-01

    Outreach nurseries are favored conservation and social forestry tools globally, but, as with many integrated conservation and development programs (ICDPs), they do not always produce anticipated results. A synopsis of the experience of South African practitioners is provided in this study of 65 outreach nurseries. South African outreach nurseries frequently include financial objectives, creating additional challenges in simultaneously attaining conservation and socioeconomic goals. Progress was hindered by biophysical problems (e.g., lack of water, poor soils, etc.) as well as the harsh socioeconomic conditions facing most communities in which nurseries had been established. Attaining financial viability was challenging. Business management skills were often restricted, and few viability studies included adequate market research. Costs to community participants were usually high, and benefits were limited. Conservation objectives were frequently lost in the struggle to attain financial viability. The management of social processes also proved challenging. Although small scale and relatively straightforward compared with many ICDPs, nurseries usually require substantial institutional support, including a range of technical, business, and development services. Project time frames need to be reconsidered, as practitioners estimate that it takes 5-10 years for nurseries to start meeting objectives, and donors and implementing agencies often operate on 2-3-year project cycles. Detailed viability studies are essential, incorporating a social probe and an assessment of potential impacts of projects on community participants. Progress needs to be continuously evaluated to enable institutions and community participants to adapt to changing conditions as well as ensure that the spectrum of objectives are being achieved.

  17. Comparison of Abuse Experiences of Rural and Urban African American Women During Perinatal Period

    PubMed Central

    Bhandari, Shreya; Bullock, Linda F. C.; Richardson, Jeanita W.; Kimeto, Pamela; Campbell, Jacquelyn C.; Sharps, Phyllis W.

    2015-01-01

    A subsample of 12 African American women (6 urban and 6 rural) were selected from a larger longitudinal, randomized control trial, Domestic Violence Enhanced Home Visitation (DOVE-R01 900903 National Institute of Nursing Research [NINR]/National Institutes of Health [NIH]). All African American women were chosen to control for any racial- and/or race-related cultural differences that may exist among women across geographical areas. The experiences of abuse during the perinatal period are drawn from in-depth interviews conducted at five points in time during pregnancy and the post-partum period. The analysis describes three major themes that highlight the similarities and differences among rural and urban women. The main themes found were (1) types of abuse, (2) location of abuse, and (3) response to abuse. In addition, two sub-themes (a) defiance and compliance and (b) role of children were also identified. Implications for universal screening for women of reproductive age, safer gun laws, and the need for further research are discussed. PMID:25315478

  18. Comparison of abuse experiences of rural and urban African American women during perinatal period.

    PubMed

    Bhandari, Shreya; Bullock, Linda F C; Richardson, Jeanita W; Kimeto, Pamela; Campbell, Jacquelyn C; Sharps, Phyllis W

    2015-07-01

    A subsample of 12 African American women (6 urban and 6 rural) were selected from a larger longitudinal, randomized control trial, Domestic Violence Enhanced Home Visitation (DOVE-R01 900903 National Institute of Nursing Research [NINR]/National Institutes of Health [NIH]). All African American women were chosen to control for any racial- and/or race-related cultural differences that may exist among women across geographical areas. The experiences of abuse during the perinatal period are drawn from in-depth interviews conducted at five points in time during pregnancy and the post-partum period. The analysis describes three major themes that highlight the similarities and differences among rural and urban women. The main themes found were (1) types of abuse, (2) location of abuse, and (3) response to abuse. In addition, two sub-themes (a) defiance and compliance and (b) role of children were also identified. Implications for universal screening for women of reproductive age, safer gun laws, and the need for further research are discussed. PMID:25315478

  19. Regulatory challenges for GM crops in developing economies: the African experience.

    PubMed

    Nang'ayo, Francis; Simiyu-Wafukho, Stella; Oikeh, Sylvester O

    2014-12-01

    Globally, transgenic or genetically modified (GM) crops are considered regulated products that are subject to regulatory oversight during trans-boundary movement, testing and environmental release. In Africa, regulations for transgenic crops are based on the outcomes of the historic Earth Summit Conference held in Rio, Brazil two decades ago, namely, the adoption of the Convention on Biological Diversity (CBD) and the subsequent adoption of the Cartagena Protocol on Biosafety. To exploit the potential benefits of transgenic crops while safeguarding the potential risks on human health and environment, most African countries have signed and ratified the CBD and the Cartagena Protocol on Biosafety. Consequently, these countries are required to take appropriate legal, administrative and other measures to ensure that the handling and utilization of living modified organisms are undertaken in a manner that reduces the risks to humans and the environment. These countries are also expected to provide regulatory oversight on transgenic crops through functional national biosafety frameworks (NBFs). While in principle this approach is ideal, NBFs in most African countries are steeped in a host of policy, legal and operational challenges that appear to be at cross-purposes with the noble efforts of seeking to access, test and deliver promising GM crops for use by resource-limited farmers in Africa. In this paper we discuss the regulatory challenges faced during the development and commercialization of GM crops based on experiences from countries in Sub-Saharan Africa. PMID:24821674

  20. Hydrogen Content Of The Mantle From Combined Magnetotelluric, Mineral Physics And Xenolith Data

    NASA Astrophysics Data System (ADS)

    Selway, K.; Karato, S.

    2012-12-01

    Determining the composition of the mantle is a significant challenge. The only direct measurements can be made from mantle xenoliths, which sample only a small fraction of the lithsopheric mantle and are unlikely to have strictly representative compositions. Therefore it is vital that geophysical data that image the mantle are also analysed and that their relationship to compositional factors is well understood. The geophysical techniques with the best resolution at mantle depths are seismic tomography and magnetotellurics (MT). MT is a passive electromagnetic method that relies on the fact that the Earth's time-varying magnetic field induces electrical currents in conductive bodies within the Earth and thus images the electrical resistivity structure of the Earth. Mineral physics experiments on the nominally anhydrous silicates that dominate the continental mantle have shown that, at a given temperature, their electrical conductivities are very sensitive to small amounts of hydrogen while being relatively insensitive to major element composition. The combination of MT data and experimental mineral physics data is therefore a powerful tool to constrain the hydration state of the mantle. However, in order to obtain reliable estimates of water content, the influence of other factors such as temperature and oxygen fugacity needs to be analysed with a great care. With this in mind, an MT survey was carried out in north-east Tanzania, crossing from the Tanzanian Craton over the East Africa Rift. The Tanzanian Craton has remained largely stable since the Archean whereas the adjacent lithosphere has been reworked during several major orogenic events including the Paleoproterozoic Usagaran Orogen, the Neoproterozoic East African Orogen and the current East Africa Rifting. The very different responses of the Tanzanian Craton and the adjacent lithosphere to these tectonothermal events suggests that there are significant compositional differences between them. Much of the

  1. Very long period magnetotellurics at Tucson observatory - Estimation of impedances

    NASA Astrophysics Data System (ADS)

    Egbert, Gary D.; Booker, John R.; Schultz, Adam

    1992-10-01

    Eleven years (1932-1942) of electric potential and magnetic measurements at the Tucson observatory represent a unique very long period magnetotelluric (MT) data set. We report here on a careful reanalysis of this data using modern processing techniques. We have developed and used novel methods of separating out the quasi-periodic daily variations fields and for cleaning up outliers and filling in missing data in the time domain. MT impedance tensors, estimated using the cleaned and filled data and using robust frequency domain methods, are well determined and smoothly varying for periods between 4 hours and 10 days. At longer periods the electric field data are swamped by large-amplitude incoherent noise, particularly after the third year of the experiment. Although we find no evidence for contamination of any field components by oceanic motional induction at tidal periods, the MT impedance do show evidence of small systematic biases due to finite spatial scale geomagnetic sources at harmonics of the daily variation period.

  2. On resolution of the method of directional magnetotelluric soundings

    NASA Astrophysics Data System (ADS)

    Savin, Mihail

    2015-12-01

    The problem is to examine the resolution of directional magnetotelluric soundings (DMTS). Abrupt changes of impedances Z^e,h of electrical and magnetic types in critical region of parameters R 0, Jωμσ where R=Re[(K_x)2+(K_y)2], J=Im[(K_x)2+(K_y)2] are shown to result in significantly higher resolution of the method as compared with the traditional interpretation using Tikhonov-Cagniard impedance Z^0. The stability of solution of DMTS method inverse problem is considered subject to field measurement errors limited the resolution. The minimum of the limits is determined for the conductivity Δσ/σ small variations. For studying DMTS resolution as applied to MT monitoring of earthquake site the mathematical experiment for three-layer geoelectric model was carried out. When changing the earthquake site conductivity of Δσ ∼ ±10 variations of reflection coefficient of electric mode ΔQe are in the range of 20% that is significantly more than the field measurement error. The possibility for prediction modeling in the context of obtained results is discussed.

  3. Problematic situations associated with dating experiences and relationships among urban African American adolescents: a qualitative study.

    PubMed

    Sullivan, Terri N; Erwin, Elizabeth H; Helms, Sarah W; Masho, Saba W; Farrell, Albert D

    2010-12-01

    This qualitative study focused on the identification of problem situations associated with adolescent dating experiences and relationships, including those that placed youth at risk for dating violence perpetration or victimization. Interviews were conducted with 44 African American middle and high school students in an urban school system. Qualitative analysis identified 18 individual themes representing six categories of problem situations: (a) approach and initiation; (b) conflict, conflict resolution, and break-ups; (c) communication, connection, and emotion; (d) aggression and victimization; (e) the role of others; and (f) media and technology. Identification of these problem situation themes has important implications for developing and evaluating prevention efforts designed to foster healthy adolescent dating relationships. PMID:20931286

  4. Early educational foundations for the development of civic responsibility: an African experience.

    PubMed

    Serpell, Robert; Mumba, Paul; Chansa-Kabali, Tamara

    2011-01-01

    An innovative curriculum designed to foster the development of social responsibility among pre-adolescent children was introduced at a rural Zambian primary school. The curriculum invoked Child-to-Child principles focusing on health education, advancing a synthesis of Western psychological theories and African cultural traditions. The teacher sought to democratize the educational process through cooperative learning in mixed-gender, mixed-social-class, and mixed-ability study groups. Learners engaged in community service activities and contributed to the nurturant care of younger children. Young adults interviewed seventeen years after completing the program recalled their experience and reflected on how it had promoted their personal agency, cooperative disposition, and civic responsibility in early adulthood. PMID:22147602

  5. “I thought we are safe”: Southern African lesbians' experiences of living with HIV

    PubMed Central

    Matebeni, Zethu; Reddy, Vasu; Sandfort, Theo; Southey-Swartz, Ian

    2013-01-01

    HIV prevention and service programmes have long either ignored or overlooked lesbians. The experiences of lesbians with HIV have similarly been unrecognised and unreported. This erasure has contributed to the invisibility of lesbians in relation to HIV and related health risks. This community participatory study, based on in-depth interviews with twenty-four self-identifying African lesbians living with HIV in South Africa, Zimbabwe and Namibia, focuses on their personal experiences and circumstances. Women's experiences shed light and challenge popular notions around lesbian risk. In particular among this group are lesbians who self-report exclusive sexual relationships with women. For these women, experiences of living with HIV are challenging as they struggle to understand the possibility of female-to-female transmission. While battling with their own perceptions of invulnerability and accepting their HIV positive status, they have to deal also with wide-ranging misconceptions about risk. The paper argues that within the context of HIV lesbians cannot be regarded as a `no-risk' group. Health services and health providers are encouraged to respond to the health needs of lesbians living with HIV. PMID:23627778

  6. A Case Study: How Do Social and Academic Experiences of African American Nontraditional Female Students on HBCU Campuses Influence Their Motivation to Graduate?

    ERIC Educational Resources Information Center

    Jackson-Golden, Cheryl D.

    2013-01-01

    Through a qualitative collective case study research design, the study captured the social and academic experiences of 13 African American nontraditional undergraduate female students enrolled in a historically Black college campus (HBCU) located in the southern United States. Experiences of 13 African American nontraditional undergraduate female…

  7. Schooling Experiences and Perceptions of Resettled Sub-Saharan African Refugee Middle School Students in a Southwest U.S. State

    ERIC Educational Resources Information Center

    Sallu, Adama

    2012-01-01

    This study examined the schooling experiences and perceptions of resettled sub-Saharan African middle school refugee students in a metropolitan area of the United States Southwest. The research questions underpinning this study included: What are the schooling experiences and perceptions of resettled sub-Saharan African middle school refugee…

  8. Introducing Python tools for magnetotellurics: MTpy

    NASA Astrophysics Data System (ADS)

    Krieger, L.; Peacock, J.; Inverarity, K.; Thiel, S.; Robertson, K.

    2013-12-01

    Within the framework of geophysical exploration techniques, the magnetotelluric method (MT) is relatively immature: It is still not as widely spread as other geophysical methods like seismology, and its processing schemes and data formats are not thoroughly standardized. As a result, the file handling and processing software within the academic community is mainly based on a loose collection of codes, which are sometimes highly adapted to the respective local specifications. Although tools for the estimation of the frequency dependent MT transfer function, as well as inversion and modelling codes, are available, the standards and software for handling MT data are generally not unified throughout the community. To overcome problems that arise from missing standards, and to simplify the general handling of MT data, we have developed the software package "MTpy", which allows the handling, processing, and imaging of magnetotelluric data sets. It is written in Python and the code is open-source. The setup of this package follows the modular approach of successful software packages like GMT or Obspy. It contains sub-packages and modules for various tasks within the standard MT data processing and handling scheme. Besides pure Python classes and functions, MTpy provides wrappers and convenience scripts to call external software, e.g. modelling and inversion codes. Even though still under development, MTpy already contains ca. 250 functions that work on raw and preprocessed data. However, as our aim is not to produce a static collection of software, we rather introduce MTpy as a flexible framework, which will be dynamically extended in the future. It then has the potential to help standardise processing procedures and at same time be a versatile supplement for existing algorithms. We introduce the concept and structure of MTpy, and we illustrate the workflow of MT data processing utilising MTpy on an example data set collected over a geothermal exploration site in South

  9. Moving Heaven and Earth: Administrative Search and Selection Processes and the Experience of an African American Woman Senior Administrator

    ERIC Educational Resources Information Center

    Barnett-Johnson, Kim R.

    2009-01-01

    The purpose of this case/phenomenological study was to examine a collegiate administrative search and selection process and the experience of an African American woman who was selected to the position of chancellor. A case concerning the search process of a regional campus of Ivy Tech Community College of Indiana was identified and chosen.…

  10. Sex-Role Egalitarian Attitudes and Gender Role Socialization Experiences of African American Men and Women: A Mixed Methods Paradigm

    ERIC Educational Resources Information Center

    Heard, Courtney Christian Charisse

    2013-01-01

    The purpose of this study was to assess the sex-role egalitarian attitudes and gender role socialization experiences of African American men and women. A sequential mixed-methods design was employed to research this phenomenon. The Sex-Role Egalitarianism Scale-Short Form BB (SRES-BB) was utilized to assess sex-role egalitarian attitudes (King…

  11. West Flank Coso, CA FORGE Magnetotelluric Inversion

    DOE Data Explorer

    Doug Blankenship

    2016-05-16

    The Coso Magnetotelluric (MT) dataset of which the West Flank FORGE MT data is a subset, was collected by Schlumberger / WesternGeco and initially processed by the WesternGeco GeoSolutions Integrated EM Center of Excellence in Milan, Italy. The 2011 data was based on 99 soundings that were centered on the West Flank geothermal prospect. The new soundings along with previous data from 2003 and 2006 were incorporated into a 3D inversion. Full impedance tensor data were inverted in the 1-3000 Hz range. The modelling report notes several noise sources, specifically the DC powerline that is 20,000 feet west of the survey area, and may have affected data in the 0.02 to 10 Hz range. Model cell dimensions of 450 x 450 x 65 feet were used to avoid computational instability in the 3D model. The fit between calculated and observed MT values for the final model run had an RMS value of 1.807. The included figure from the WesternGeco report shows the sounding locations from the 2011, 2006 and 2003 surveys.

  12. New approaches to estimation of magnetotelluric parameters

    SciTech Connect

    Egbert, G.D. . Coll. of Oceanography); Booker, J.R. )

    1990-01-01

    This document proposed the development and application of some new statistical techniques for improving the collection and analysis of wide-band magnetotelluric (MT) data. The principle goal of our work is to develop and implement fully automatic single station and remote reference impedance estimation schemes which are robust, unbiased and statistically efficient. The initial proposal suggested several extensions to the regression M-estimates to better allow for non-stationary and non-Gaussian noise in both electric and magnetic field channels (measured at one or more simultaneous stations). A second goal of the proposal was to develop formal, reliable procedures for estimating undistorted 2-d strike directions and to develop statistics for assessing the validity of the 2-d assumption that are unaffected by near surface static distortion effects. To test and validate the methods, working with data selected from a series of over 200 wide-band MT sites was proposed. For the current budget period, setting up a data base, and completing development and initial testing of the single station and remote reference methods outlined in the proposal is suggested. 8 refs., 13 figs.

  13. MTpy: A Python toolbox for magnetotellurics

    NASA Astrophysics Data System (ADS)

    Krieger, Lars; Peacock, Jared R.

    2014-11-01

    We present the software package MTpy that allows handling, processing, and imaging of magnetotelluric (MT) data sets. Written in Python, the code is open source, containing sub-packages and modules for various tasks within the standard MT data processing and handling scheme. Besides the independent definition of classes and functions, MTpy provides wrappers and convenience scripts to call standard external data processing and modelling software. In its current state, modules and functions of MTpy work on raw and pre-processed MT data. However, opposite to providing a static compilation of software, we prefer to introduce MTpy as a flexible software toolbox, whose contents can be combined and utilised according to the respective needs of the user. Just as the overall functionality of a mechanical toolbox can be extended by adding new tools, MTpy is a flexible framework, which will be dynamically extended in the future. Furthermore, it can help to unify and extend existing codes and algorithms within the (academic) MT community. In this paper, we introduce the structure and concept of MTpy. Additionally, we show some examples from an everyday work-flow of MT data processing: the generation of standard EDI data files from raw electric (E-) and magnetic flux density (B-) field time series as input, the conversion into MiniSEED data format, as well as the generation of a graphical data representation in the form of a Phase Tensor pseudosection.

  14. Motional magnetotellurics by long oceanic waves

    NASA Astrophysics Data System (ADS)

    Shimizu, Hisayoshi; Utada, Hisashi

    2015-04-01

    The observation of electromagnetic signals by ocean bottom electromagnetometers in association with the Tohoku tsunami of 2011 March 11 has raised the opportunity to re-examine the physics of motional induction due to oceanic long waves in the framework of 1-D magnetotellurics (MT). Although a propagating tsunami has a complex structure, the induced electromagnetic field can be simply approximated as a plane wave (though a simple thin-sheet approximation is not valid at higher frequencies). We found that the MT impedance due to a surface gravity wave (or the `motional impedance') is influenced largely by the dispersion of the wave if the period is sufficiently short or the electrical conductivity of the seabed is low. The tipper due to the motional induction (or the `motional tipper') and motional impedance are essentially identical if the underneath structure is 1-D. It would be possible to estimate the motional impedance and tipper from the observed ocean bottom electromagnetic field at the time of passing of a tsunami. The wave amplitude must be much greater than several tens of centimetres for the motional impedance and tipper estimation to be free from the effects of external sources. However, the obtained motional impedance and tipper will mostly represent the property of the wave and use of them may not be suitable to discuss the subseafloor conductivity structure.

  15. Two and three dimensional magnetotelluric inversion

    SciTech Connect

    Booker, J.R.

    1994-07-01

    Improved imaging of underground electrical structure has wide practical importance in exploring for groundwater, mineral and geothermal resources, and in characterizing oil fields and waste sites. Because the electromagnetic inverse problem for natural sources is generally multi-dimensional, most imaging algorithms saturate available computer power long before they can deal with complete data sets. We have developed an algorithm to directly invert large multi-dimensional magnetotelluric data sets that is orders of magnitude faster than competing methods. In the past year, we have extended the two- dimensional (2D) version to permit incorporation of geological constraints, have developed ways to assess model resolution and have completed work on an accurate and fast three-dimensional (3D) forward algorithm. We are proposing to further enhance the capabilities of the 2D code and to incorporate the 3D forward code in a fully 3D inverse algorithm. Finally, we will embark on an investigation of related EM imaging techniques which may have the potential for further increasing resolution.

  16. Magnetotelluric investigations at Mount Hood, Oregon

    SciTech Connect

    Mozley, E.C.; Goldstein, N.E.; Morrison, H.F.

    1986-10-01

    Magnetotelluric data, with both electric and magnetic field references for noise cancellation, were collected at accessible locations around and as close as possible to the Mount Hood andesite-dacite volcano. The purpose of the study was to identify and map conductive features and to relate them to the thermal regime of the region. Several conductors could be discerned. The shallowest, at a depth of around 500 m below the surface, was identified as a flow of heated water moving away from the summit: the deepest (--50 km) might be a melt zone in the upper mantle. Of particular interest is an elongate conductor that strikes N 10/sup 0/ W and extends from a depth of 12 km down to 22 km. Because the conductor strike is close to the trend of the chain of Cascade volcanoes and because of the high conductive thermal gradients reported for the area, this feature was initially believed to be a zone of partial melt following the volcanic axis. However, because no teleseismic P wave velocity anomaly has been found, the cause of the conductor is more problematic. While the existence of small zones of melt cannot be ruled out, it is possible that the conductor is caused by a large volume of intensely deformed rocks with brine-filled microfractures.

  17. Low Power Long Period Magnetotelluric System

    NASA Astrophysics Data System (ADS)

    Narod, B. B.; Bennest, J. R.; Booker, J. R.

    2001-12-01

    We have constructed a new MT system for periods longer than 1 second that uses substantially less power and is considerably easier to deploy than predecessors, such as the Geological Survey of Canada [GSC] Long Period Intelligent Magnetotelluric System [LIMS]. Technical aspects of these new systems include: Fully watertight; light weight [5 kg w/o magnetometer head], Eurocard card cage, 1.7 watt power consumption - 140mA @ 12vdc, built-in solar panel charge controller, GPS-disciplined timekeeping accurate to 1ms, 24-bit 8 Hz Analog to Digital conversion, data storage on a PCMCIA flash disk [85M and up], magnetic field: +/- 80,000 nT range with 10pT resolution, electric field ch: +/- 200 mv with sub-microvolt useful resolution. A setup program automatically handles most deployment tasks including recording site location and data start time. Data are logged in files that begin at hour marks and are of one-hour duration. They are thus automatically synchronous at an array of instruments. Data retrieval consists of moving a PCMCIA card from the data logger to a laptop computer. A revision of this system is already in progress. It will feature PC104 card formats and will be lighter, smaller and have even lower power consumption. Ten of these systems were deployed for the first time during August and September 2001, in Argentina. Sample data from these deployments will be shown.

  18. Coparenting Experiences in African American Families: An Examination of Single Mothers and their Non-Marital Coparents

    PubMed Central

    Gonzalez, Michelle; Jones, Deborah J.; Parent, Justin

    2015-01-01

    African American youth from single mother homes continue to be overrepresented in statistics on risk behavior and delinquency, a trend that many be attributed to father-absence, socioeconomic disadvantage, and compromises in parenting more typical of single than two-parent families. Yet, this risk-focused perspective ignores a long-standing strength of the African American community, the involvement and potential protective impact of extended family members in childrearing. This study describes the experiences of 95 African American single mothers and their non-marital coparents who participated in a study of African American single mother families with an 11 to 16 year old child. Specifically, the study examines: 1) the extent to which nonmarital coparents are involved in childrearing; 2) the relative levels of risk (i.e., depression, mother-coparent conflict) and protective (i.e., parenting) associated with maternal and coparent involvement; and 3) how similarly and/or differently coparent and mother variables operate with regard to youth externalizing problems. Findings reveal that a range of family members and other adults actively participate in childrearing in African American single mother families, coparents do not differ from mothers on certain study variables (i.e., depression and mother-coparent conflict) but do for others (parenting), and coparent involvement is associated with youth adjustment in ways that are similar to our more established understanding of maternal involvement. The potential clinical implications of the findings are discussed and future research directions are highlighted. PMID:24479612

  19. Experience of Consolidation Of Disused Sources In Developing Countries, An African Perspective

    SciTech Connect

    Kifanga, L.D.; Mompome, W.K.; Shao, D.

    2008-07-01

    Application of sealed sources in agriculture, medicine and industry was used in many African countries without having any arrangements in place for managing the sources when their useful life was over. In Tanzania a substantial use of such sources was utilized. In the early days source management was not an area that was given the required attention hence a legacy associated with sealed sources became evident in many African countries and Tanzania was one of them. In the 90's Tanzania Atomic Energy Commission (TAEC), realized the scope of the waste problem and began to participate in an International Atomic Energy Agency Regional (IAEA) project on waste management. Tanzania in cooperation with IAEA initiated activities under the IAEA Technical Cooperation and the Regional projects 'Strengthening Waste Management Infrastructure, RAF/4/015'; and 'Sustaining the Waste Management Infrastructure RAF/3/005' which played a significant role. The first outcome of the project was realized in 1999, as the first 'Temporary Radioactive Waste Storage Facility' began to operate. This particular Storage facility gave the first impact as well as the need to develop this particular infrastructure further. As the project carried on, more and more orphan sources were recovered, collected and safely stored at the facility. As the use of nuclear technology was expanding and the identification of the extent of sealed sources in the countries became more defined, the need to develop a 'Central Radioactive Waste Management Facility' (CRWMF) was becoming more desired. The central radioactive waste storage facility was constructed and commissioned in 2005. The facility was more advanced and could be used for much longer periods of time, as one of the most advanced storage facility in the Region. At present a large number of disused sources from various industries as well as from different activities are being stored at the facility. Tanzanian authorities are also planning to initiate a

  20. When Aspiration Meets Opportunity: Examining Transitional Experiences of African American Males in College Readiness Programs

    ERIC Educational Resources Information Center

    Baber, Lorenzo DuBois

    2014-01-01

    The lack of postsecondary success for African American males has garnered significant attention from academic scholars and public policy leaders. While this scholarship provides a strong portrait on issues related to African American males, there are still significant gaps to be addressed. Most notably, current research tends to focus on students…

  1. Gender and Racial Experiences in Executive School Leadership: Perceptions of African American Female Superintendents

    ERIC Educational Resources Information Center

    Colbert, Daveda Jean

    2009-01-01

    There is a leadership crisis that exists in our schools creating an urgent need for effective leadership. Even though African American women have made slight gains, throughout the country people of color and women are dramatically underrepresented in the superintendency. Therefore, the primary purpose of this study is to provide African American…

  2. Health Behaviors and Breast Cancer: Experiences of Urban African American Women

    ERIC Educational Resources Information Center

    Stolley, Melinda R.; Sharp, Lisa K.; Wells, Anita M.; Simon, Nolanna; Schiffer, Linda

    2006-01-01

    Breast-cancer survival rates are lower among African American women compared to White women. Obesity may contribute to this disparity. More than 77% of African American women are overweight or obese. Adopting health behaviors that promote a healthy weight status may be beneficial because obesity increases risk for recurrence. Studies among White…

  3. Faculty Perceptions of, and Experiences with, African American Male Students at a Community College

    ERIC Educational Resources Information Center

    Jenkins, Shantelle K.

    2013-01-01

    Many studies involving African American male students have focused on achievement gaps and student retention models of those attending four-year institutions. However, there are limited investigations of African American male students at the community college and very few that focus on faculty perceptions. This study employed a mixed Delphi…

  4. Jumping through Hoops: College Choice Experiences of African American Male Community College Club Basketball Players

    ERIC Educational Resources Information Center

    Ellis, Kimberly Carlotta

    2011-01-01

    This study aimed to learn what factors influenced the college choice decision-making process of African American male club basketball players in the community college. To understand how the participants determined their educational path, face-to-face interviews were conducted with 21 African American male students who were enrolled in at least six…

  5. Teaching White Students Black History: The African-American Experience in the Classroom

    ERIC Educational Resources Information Center

    Burrell, Leon F.; Walsh, Robert L.

    2001-01-01

    Many white students are barely exposed to African-American history throughout their schooling. When students do examine the other side of American history, the one not generally found in their textbooks, they often wonder why they have not learned this before. An understanding of African-American history is central to any effort to eliminate…

  6. Leading the Way: Inside the Experiences of High-Achieving African-American Male Students

    ERIC Educational Resources Information Center

    Harper, Shaun R.

    2005-01-01

    More than two-thirds of all African American males who begin college never finish. This and a legion of other discouraging facts about African American males are the usual headlines. Sharon Fries-Britt suggests that "the disproportionate focus on Black underachievement in the literature not only distorts the image of the community of Black…

  7. Reflections on Academic Development: What We Can Learn from the South African Experience. Technical Report.

    ERIC Educational Resources Information Center

    Epstein, Ruth

    A study examined academic literacy in high-risk South African students entering postsecondary education, and the relationship of academic literacy to instructional development. Data were gathered in discussions with academic staff at South African universities and technikons and at the University of Saskatchewan. The report begins with background…

  8. African-American Materials Project Experiment in Regional Cooperation. Final Report.

    ERIC Educational Resources Information Center

    Hall, Carol J.

    The African-American Materials Project was a three year venture in bibliographic control of African-American materials. It was a regional project, designed to locate and describe materials in six Southern states. The project was divided into three periods. Phase I was devoted to locating existing collections through the use of a questionnaire,…

  9. 3-D inversion of magnetotelluric Phase Tensor

    NASA Astrophysics Data System (ADS)

    Patro, Prasanta; Uyeshima, Makoto

    2010-05-01

    Three-dimensional (3-D) inversion of the magnetotelluric (MT) has become a routine practice among the MT community due to progress of algorithms for 3-D inverse problems (e.g. Mackie and Madden, 1993; Siripunvaraporn et al., 2005). While availability of such 3-D inversion codes have increased the resolving power of the MT data and improved the interpretation, on the other hand, still the galvanic effects poses difficulties in interpretation of resistivity structure obtained from the MT data. In order to tackle the galvanic distortion of MT data, Caldwell et al., (2004) introduced the concept of phase tensor. They demonstrated how the regional phase information can be retrieved from the observed impedance tensor without any assumptions for structural dimension, where both the near surface inhomogeneity and the regional conductivity structures can be 3-D. We made an attempt to modify a 3-D inversion code (Siripunvaraporn et al., 2005) to directly invert the phase tensor elements. We present here the main modification done in the sensitivity calculation and then show a few synthetic studies and its application to the real data. The synthetic model study suggests that the prior model (m_0) setting is important in retrieving the true model. This is because estimation of correct induction scale length lacks in the phase tensor inversion process. Comparison between results from conventional impedance inversion and new phase tensor inversion suggests that, in spite of presence of the galvanic distortion (due to near surface checkerboard anomalies in our case), the new inverion algorithm retrieves the regional conductivitity structure reliably. We applied the new inversion to the real data from the Indian sub continent and compared with the results from conventional impedance inversion.

  10. "Ain't Nobody Gonna Get Me down": An Examination of the Educational Experiences of Four African American Women Labeled with Disabilities

    ERIC Educational Resources Information Center

    Petersen, Amy J.

    2009-01-01

    This study used qualitative research methods to explore the educational experiences of four African American women with disabilities, revealing how each participant developed a critical consciousness in response to the dominant ideology surrounding the discourses of African American, woman, and disabled. The development of a critical consciousness…

  11. Exploring How African American Males from an Urban Community Navigate the Interracial and Intra-Racial Dimensions of Their Experiences at an Urban Jesuit High School

    ERIC Educational Resources Information Center

    Simmons, Robert W., III

    2012-01-01

    African American males from urban communities have been attending Jesuit high schools in urban spaces for many years, yet little to no literature exists that explores their experiences while attending these elite private schools. This qualitative study of 10 African American males from an urban community attending a similarly positioned Jesuit…

  12. A Hermeneutic Phenomenological Study of the Experiences of Female African American Undergraduate Engineering Students at a Predominantly White and an Historically Black Institution

    ERIC Educational Resources Information Center

    Frillman, Sharron Ann

    2011-01-01

    This phenomenological study examined the experiences of twelve female African Americans enrolled as fulltime undergraduate engineering students at North Carolina Agricultural and Technical State University, an historically Black university, and seven female African Americans enrolled as undergraduate engineering students at Purdue University in…

  13. Navigating Race and Cultural Identity: A Phenomenological Study of the Lived Experiences of African American Secondary Principals on the U.S.-Mexico Border of El Paso, Texas

    ERIC Educational Resources Information Center

    Hill, Natashia J.

    2013-01-01

    Presently the paucity of scholarship available is often unitary in nature and usually focuses on the lived experiences of African Americans principals in a predominately African American urban context and as well as emphasizes the necessity of same race principals for the purpose of mentorship and racial representation. Race and cultural identity…

  14. Negotiating Identity in a Bubble: A Critical Race Analysis of African American High School Students' Experiences in an Elite, Independent School

    ERIC Educational Resources Information Center

    DeCuir-Gunby, Jessica T.

    2007-01-01

    This study used critical race theory to examine how African American adolescents negotiated race and class identity at Wells Academy, a predominately white, independent school. Interviews were conducted, exploring the experiences of six African American high school students. Their counterstories were analyzed focusing on the critique of…

  15. Experimenting in Distance Education: The African Virtual University (AVU) and the Paradox of the World Bank in Kenya--A Rejoinder

    ERIC Educational Resources Information Center

    Munene, Ishmael I.

    2007-01-01

    This rejoinder is in response to criticism against the African Virtual University (AVU), an internet-based education modality, by Amutabi and Oketch [2003. Experimenting in distance education: the African Virtual University (AVU) and the Paradox of World Bank in Kenya. International Journal of Educational Development 23, 57-73]. By closely…

  16. Electrical conductivity of the Fennoscandian Shield margin from recent magnetotelluric profiles

    NASA Astrophysics Data System (ADS)

    Smirnov, M. Yu.; Korja, T.; Pedersen, L. B.

    2009-04-01

    During the last decade several magnetotelluric profiles extending from Proterozoic East European Craton into younger domains have been measured. Magnetotelluric TOR profile crosses the Sorgenfrei-Tornquist-Zone (STZ) in the southwestern part of the Fennoscandian Shield. The STZ marks the border between the intact shield in Sweden to the north and the reactivated Danish basin and the Ringkobing-Fyn High (RFH) to the south. The STZ manifests itself electrically very clearly in the lower crust and upper lithospheric mantle as a narrow zone of high conductivity. The thickness of the electric lithosphere decreases across the STZ from about 300 km in the Fennoscandian Shield to about 100 km in the Danish basin. Jämtland-Trondelag magnetotelluric profile crosses the Central Scandinavian Caledonides from Baltic to Norwegian Sea. The results of the data analysis reveal the following main features: (1) An electrically highly conducting layer beneath the Caledonides images alum shales, the autochthonous Cambrian carbon-bearing black shales on top of the Precambrian basement. (2) Beneath the eastern part of the profile in the Fennoscandian Shield, proper, the first upper mantle conductor is detected at the depth of more than 250-300 km. A region of enhanced conductivity is identified at the depth of c.100- 150 km under the Caledonides in the central part of the profile. Further to the west, however, the lithosphere seems to thicken to 150-200 km. A large-scale international electromagnetic experiment has been carried out in northwest Poland and northeast Germany across the Trans European Suture Zone (TESZ), which is the most prominent tectonic boundary in Europe and which constitutes a complex transition between the European Paleozoic Platform towards the southeast and the Precambrian Craton towards the northeast. The results show the presence of highly conductive Cenozoic-Mesozoic sedimentary cover reaching depths up to 3 km. The significant conductivity anomaly in the

  17. Regional magnetotelluric surveys in hydrocarbon exploration, Parana' Basin, Brazil

    SciTech Connect

    Stanley, W.D.; Ohofugi, W.; Saad, A.R.

    1985-03-01

    The magnetotelluric geophysical method has been used effectively as a hydrocarbon exploration tool in the intracratonic Parana basin of South America. The 1-2 km thick surface basalts and buried diabase sills pose no problem for the magnetotelluric method because the natural electromagnetic fields used as the energy source pass easily through the basalt. Data for the regional study were taken on six profiles with soundings spaced 8 to 15 km apart. The magnetotelluric sounding data outline a linear uplift known as the Ponta Grossa arch. This major structural feature cuts across the northeast-trending intracratonic basin almost perpendicularly, and is injected with numerous diabase dikes. In the survey area, MT interpretations show that basalts have aggregate thicknesses of as much as 2 km (6,600 ft), and basement may be as much as 6 km (20,000 ft) below the surface. Over most of the basin, the basalts are covered by Upper Cretaceous to Holocene continental sediments of a few hundred meters thickness and are underlain by 2 to 4 km (6,600 to 13,100 ft) thick Paleozoic sediments with possible hydrocarbon potential. Significant electrical contrasts occur between the Permian sediments and older units, so that magnetotelluric measurements can give an indication of the regional thickness of the Permian and younger sediments to aid in interpreting hydrocarbon migration patterns and possible trap areas.

  18. Magnetotelluric studies at the Cerro Prieto geothermal field

    SciTech Connect

    Goubau, W.M.; Goldstein, N.E.; Clarke, J.

    1981-01-01

    During three years of magnetotelluric surveying, data were acquired at 26 sites distributed over 190 km/sup 2/ around the production area. A relatively well-defined strike of N27W +- 1.5/sup 0/ (magnetic) was established. The simple model shown suggests a lateral discontinuity in the vicinity of Nueva Leon.

  19. Structure of the Tongariro Volcanic system: Insights from magnetotelluric imaging

    NASA Astrophysics Data System (ADS)

    Hill, Graham J.; Bibby, Hugh M.; Ogawa, Yasuo; Wallin, Erin L.; Bennie, Stewart L.; Caldwell, T. Grant; Keys, Harry; Bertrand, Edward A.; Heise, Wiebke

    2015-12-01

    The dynamics of magma reservoirs (the main repositories for eruptible magma) play a fundamental role in the style and behaviour of volcanic systems. A key first step in understanding these systems is to identify their location and size accurately. We present results from a broadband magnetotelluric study of the Tongariro Volcanic system and discuss how the results fit within current petrological models. The Tongariro Volcanic system is a composite andesitic cone complex, located at the southern end of the Taupo Volcanic Zone in the central North Island of New Zealand. We use data from 136 broadband magnetotelluric soundings within a 25 × 35 km area covering the volcanic system to construct a 3D image of the magmatic system of the Tongariro Volcanic Complex including Mount Ngauruhoe. The structure of the Tongariro magmatic system has been determined from 3D forward and inverse modelling of the magnetotelluric data and allowed for an estimation of the melt fraction present within the system. 3D inverse modelling of the magnetotelluric data shows: a well-developed shallow low resistivity zone outlining the geothermal system; a zone of even lower resistivity representing a shallow crustal magma accumulation zone located at a depth of ˜4-12 km offset to the east of the Tongariro vent system; and a zone with a slightly higher resistivity connecting these two components of the magmatic system providing the path for magmatic fluids from the deeper source region to reach the surface during eruptive events.

  20. Very long period magnetotellurics at Tucson Observatory: Estimation of impedances

    SciTech Connect

    Egbert, G.D.; Booker, J.R.; Schultz, A.

    1992-10-10

    Eleven years (1932-1942) of electric potential and magnetic measurements at the Tucson observatory represent a unique very long period magnetotelluric (MT) data set. The authors report on a careful reanalysis of this data using modern processing techniques. They have developed and used novel methods for separating out the quasi-periodic daily variation fields and for cleaning up outliers and filling in missing data in the time domain. MT impedance tensors, estimated using the cleaned and filled data and using robust frequency domain methods, are well determined and smoothly varying for periods between 4 hours and 10 days. At longer periods the electric field data are swamped by large-amplitude incoherent noise, particularly after the third year of the experiment. Although they find no evidence for contamination of any field components by oceanic motional induction at tidal periods, the MT impedance estimates do show evidence of small systematic biases due to finite spatial scale geomagnetic sources at harmonics of the daily variation period. These periods are thus removed from the time series and not used in further analysis. They show that the resulting impedance tensor is well modeled by a real, frequency-independent distortion of a scalar impedance, which is consistent with non-inductive distortion of the electric fields by local surface geology. To estimate the undetermined static shift of the MT impedance, the authors compare the long-period MT results to equivalent MT impedances determined from 46 years of geomagnetic data. Combining the geomagnetic and undistorted MT impedances results in scalar impedance estimates for periods 0.17 < T < 91 days of unprecedented precision. However, for periods less than one day, the phase and amplitude of this impedance, while individually consistent, are not mutually consistent with any one-dimensional conductivity distribution. 51 refs., 19 figs., 4 tabs.

  1. Dimensionality and geological implications of a sparse magnetotelluric dataset

    NASA Astrophysics Data System (ADS)

    Derosier, B.; Dennis, K. N.; Plata Martinez, R. O.; Montahaei, M.; Bedrosian, P.; Pellerin, L.

    2014-12-01

    High-quality broadband magnetotelluric (MT) data (0.01-1000 s period) were acquired at four stations in Borrego Canyon within the Santo Domingo Basin of the Rio Grande Rift, New Mexico, during the 2014 Summer of Applied Geophysical Experience (SAGE) field program. MT response functions along the 10-km long NW trending profile are nearly identical with all stations showing a distinct mode split at 10 s period, suggesting a significant conductivity contrast is located roughly 10-20 km away from the profile based on skin depth estimates. Audiomagnetotelluric, polar diagrams, impedance skew, induction vectors and phase tensor analysis all indicate one-dimensional (1-D) structure at periods <10 sec, a predominantly two-dimensional (2-D) structure at intermediate depths (10-100 s) with a 60° geoelectric strike, and three-dimensional (3-D) structure at the longest periods. Inverse modeling of the data from 0.01-10 s reveals a three-layer electrical structure: a moderately resistive sediments from the surface to ~750 m depth, a conductive layer (weathered volcanoclastics) to 4 km depth, and below 4 km a highly resistive basement of Mesozoic and Precambrian rocks. A 2-D inverse model converged, but resulted in physically unrealistic structure. Hence a 3-D forward model study was performed using the 2014 data together with three additional MT stations acquired further to the east during SAGE 2010. Models that include a NE-trending conductive structure to the north of the profile show broad consistency between the measured and synthetic phase tensors and impedances. We infer our MT data to be on the conductive side of this contact, with the resistive material to the NW attributed to a heavily intruded crust beneath the Jemez lineament, and possibly the edge of the thick lithosphere beneath the Colorado Plateau. 3-D inversion of this sparse data set is being carried out to determine whether this conceptual model is consistent with the full impedance tensor and tipper data.

  2. Probabilistic 3-D time-lapse inversion of magnetotelluric data: application to an enhanced geothermal system

    NASA Astrophysics Data System (ADS)

    Rosas-Carbajal, M.; Linde, N.; Peacock, J.; Zyserman, F. I.; Kalscheuer, T.; Thiel, S.

    2015-12-01

    Surface-based monitoring of mass transfer caused by injections and extractions in deep boreholes is crucial to maximize oil, gas and geothermal production. Inductive electromagnetic methods, such as magnetotellurics, are appealing for these applications due to their large penetration depths and sensitivity to changes in fluid conductivity and fracture connectivity. In this work, we propose a 3-D Markov chain Monte Carlo inversion of time-lapse magnetotelluric data to image mass transfer following a saline fluid injection. The inversion estimates the posterior probability density function of the resulting plume, and thereby quantifies model uncertainty. To decrease computation times, we base the parametrization on a reduced Legendre moment decomposition of the plume. A synthetic test shows that our methodology is effective when the electrical resistivity structure prior to the injection is well known. The centre of mass and spread of the plume are well retrieved. We then apply our inversion strategy to an injection experiment in an enhanced geothermal system at Paralana, South Australia, and compare it to a 3-D deterministic time-lapse inversion. The latter retrieves resistivity changes that are more shallow than the actual injection interval, whereas the probabilistic inversion retrieves plumes that are located at the correct depths and oriented in a preferential north-south direction. To explain the time-lapse data, the inversion requires unrealistically large resistivity changes with respect to the base model. We suggest that this is partly explained by unaccounted subsurface heterogeneities in the base model from which time-lapse changes are inferred.

  3. POLARIS Magnetotelluric Overview and Update - Spring 2004

    NASA Astrophysics Data System (ADS)

    Ferguson, I.; Samson, C.; Unsworth, M.; Asudeh, I.; Craven, J.; Atkinson, G.

    2004-05-01

    The Canadian POLARIS project includes an important component of electromagnetic studies. As part of this project, magnetotelluric (MT) equipment has been acquired to develop an infrastructure for electromagnetic soundings over depths ranging from the uppermost crust to depths of several hundreds kilometers into the asthenosphere. A key innovative feature of the POLARIS project is that MT instruments are being used in association with teleseismic techniques for imaging the Earth's structure, and for investigating seismogenic structures. MT soundings are in progress and, at the end of the project, will have been made at most of the 90 POLARIS observatory arrays on the Slave craton in the Northwest Territories, in the Casacadia region of southwestern British Columbia, and in the Precambrian Grenville Province in southern Ontario. MT equipment is also being used in studies of geomagnetically induced currents (GICs) on powerlines and pipelines. To carry out soundings at different target depths, the POLARIS MT equipment includes: audio-frequency (104 to 10 Hz) MT (AMT) systems for imaging the upper crust; broadband (102 to 10-3 Hz) MT (BBMT) systems for imaging the middle and lower crust; and long-period (1 to <10-4 Hz) MT (LMT) systems with specialized ring-core fluxgate magnetometers required for imaging at mantle depths and for geomagnetic hazard studies. More specifically, the AMT-BBMT equipment consists of six MTU-5A systems that have been procured from Phoenix Geophysics Ltd. and the LMT equipment of twenty-five ring-core NIMS systems on order from Narod Geophysics Ltd. A subset of the POLARIS MT equipment consisting of the AMT, BBMT, and fifteen of the LMT instruments is designed to be moved progressively through the POLARIS arrays providing MT responses over a broad frequency range. The remaining ten LMT instruments are to be deployed at carefully selected POLARIS sites in satellite-telemetered observatory configuration to provide ultra-deep imaging of the mantle

  4. Factors linking childhood experiences to adult romantic relationships among African Americans.

    PubMed

    Simons, Leslie Gordon; Simons, Ronald L; Landor, Antoinette M; Bryant, Chalandra M; Beach, Steven R H

    2014-06-01

    It is well known that a high-quality relationship with a romantic partner is related to a variety of positive outcomes associated with health and well-being. Establishing such relationships is an important developmental task for young adults, and past research indicates that there is a link between experiences in the family of origin and the success of later intimate relationships. It has been suggested that this association can be explained by the acquisition of social competencies (e.g., emotions, schemas, traits) that are acquired during childhood in the family of origin and, in turn, influence interaction with adult romantic partners. The current study builds on this foundation by identifying particular competencies expected to explain the association between childhood exposure to supportive and harsh parenting and later patterns of interaction with romantic partners. Specifically, we examine anger management, attachment style, hostile attribution bias, and self-control as potential mediators using prospective, longitudinal data from a sample of 345 African American young adults. Results from structural equation modeling indicate that each of the mediators in our study accounts for a significant portion of the effect of parenting on the quality of adult romantic relationships, although the constructs linking parenting to warm interactions with romantic partners are somewhat different from those that link parenting to hostile interactions with romantic partners. Even after accounting for the effect of the mediators, there is still a direct effect of parenting on both warm/loving and hostile/aggressive interactions with romantic partner. Implications for theory and practice are discussed. PMID:24730381

  5. Factors Linking Childhood Experiences to Adult Romantic Relationships among African Americans

    PubMed Central

    Simons, Leslie Gordon; Simons, Ronald L.; Landor, Antoinette M.; Bryant, Chalandra M.; Beach, Steven R.H.

    2014-01-01

    It is well known that a high quality relationship with a romantic partner is related to a variety of positive outcomes associated with health and well-being. Establishing such relationships is an important developmental task for young adults and past research indicates that there is a link between experiences in the family of origin and the success of later intimate relationships. It has been suggested that this association can be explained by the acquisition of social competencies (e.g., emotions, schemas, traits) that are acquired during childhood in the family of origin and, in turn, influence interaction with adult romantic partners. The current study builds on this foundation by identifying particular competencies expected to explain the association between childhood exposure to supportive and harsh parenting and later patterns of interaction with romantic partners. Specifically, we examine anger management, attachment style, hostile attribution bias, and self-control as potential mediators using prospective, longitudinal data from a sample of 345 African American young adults. Results from structural equation modeling indicate that each of the mediators in our study accounts for a significant portion of the effect of parenting on the quality of adult romantic relationships although the constructs linking parenting to warm interactions with romantic partners are somewhat different from those that link parenting to hostile interactions with romantic partners. Even after accounting for the effect of the mediators, there is still a direct effect of parenting on both warm/loving and hostile/aggressive interactions with romantic partner. Implications for theory and practice are discussed. PMID:24730381

  6. [Surgical treatment of priapism: experience of 56 cases in an African setting].

    PubMed

    Falandry, L; Berlizot, P; Fournier, R; Mechali, P; Thuret, R; Palascak, R; Houlgatte, A

    2000-01-01

    Since priapism is uncommon, treatment is controversial and difficult. In this article we describe a practical, well-documented approach for management of priapism in countries with a high incidence of sickle cell disease. This approach is based on our experience including a total of 56 black patients (49 adults and 7 children) as well as on the results reported in the literature. The patients in our series were examined and treated by the same physician over an 18 year period in various African countries, i.e., Burkina (n = 8), Chad (n = 12), Gabon (n = 19), and Niger (n = 17). Etiologies and pathophysiology are reviewed. In all cases, surgical treatment involved diversion from corpora cavernosa. In the 51 cases with follow-up periods of 3 months or longer, results were considered as excellent in 17 cases (33 p. 100), partial in 5 (9.8 p. 100), and unsuccessful in 29 (56.8). Since 1984, needle drainage with a unilateral transglandular cavernosal-spongiosum shunt based on the technique described by Al Ghorab's has led to better results with immediate detumescence in 80 p. 100 of cases and a long-term success rate of 52 p. 100 (13/25 cases with sufficient follow-up). Except in cases involving sickle cell anemia in which concomitant medical treatment of priapism can be useful, immediate surgical treatment is the only technique effective in avoiding secondary impotence, which was common in our series (58.6). Our p. 100 needle drainage technique appears to be the method of choice for simplified achievement of a unilateral transglandular cavernosal-spongiosum shunt. PMID:10989793

  7. Understanding the African American Research Experience (KAARE): Implications for HIV Prevention

    PubMed Central

    Kerkorian, Dara; Traube, Dorian E.; McKay, Mary M.

    2010-01-01

    SUMMARY Despite recognition that the African American population is underrepresented in studies of health and mental health treatment and prevention efforts, few investigations have systematically examined barriers to African American research participation. Without their participation, treatment and prevention strategies designed to curtail the spread of HIV in their communities will be bound to achieve less than optimal outcomes. Based on the assumption that successful recruitment of African Americans requires knowledge of (a) their beliefs about research, (b) their perceptions of the research process and researchers, (c) their motivations to participate, and (d) the historical and social factors that may be the source of at least some ambivalence, the current study undertook semi-structured interviews with 157 African American, low-income mothers residing in a large urban community where they and their children were at high risk for HIV. Given the sensitive nature of the research topic, members of the community were trained to conduct the interviews. Qualitative and quantitative analyses of the interview content suggest that despite having been consented, many participants (a) are not aware of their rights under informed consent and (b) lack knowledge of how the research will be used. Despite this and the subtle suspicion of White researchers held by some, many decide to participate for altruistic reasons. The implications for recruitment of participants in general and African Americans in particular into HIV prevention studies are discussed as are the implications for service providers directly or indirectly involved in the development and delivery of these interventions. PMID:20871788

  8. Sexual Decision Making in the Absence of Choice: The African American Female Dating Experience

    PubMed Central

    Andrasik, Michele P.; Nguyen, Hong V.; George, William H.; Kajumulo, Kelly F.

    2016-01-01

    Although links between low mate availability and increased HIV and STI risk for African American women have been documented in the literature, we know little about the impact of limited mate choices on the quality of relationships between Black men and women and how these relationship dynamics impact risk for young Black women. We conducted a qualitative study with African American female young adults (N=12) to explore the perceived impact of structural forces on African American female young adults’ dating and sexual behavior. Participants reported (1) perceptions of Black men as untrustworthy and manipulative, (2) the limited and often negative roles for Black men in the larger Black community, and (3) heterosexual relationships in the Black community as increasingly influenced by economics and commerce. Recommendations for HIV prevention interventions that include micro and macro level approaches are discussed. PMID:27182463

  9. In/dependent Collaborations: Perceptions and Experiences of African Scientists in Transnational HIV Research

    PubMed Central

    Moyi Okwaro, Ferdinand; Geissler, P. W.

    2015-01-01

    This article examines collaboration in transnational medical research from the viewpoint of African scientists working in partnerships with northern counterparts. It draws on ethnographic fieldwork in an HIV laboratory of an East African state university, with additional data from interviews with scientists working in related research institutions. Collaboration is today the preferred framework for the mechanisms by which northern institutions support research in the south. The concept signals a shift away from the legacy of unequal (post‐) colonial power relations, although, amid persisting inequalities, the rhetorical emphasis on equality might actually hinder critical engagement with conflicts of interest and injustice. To collaborate, African scientists engage various strategies: They establish a qualified but flexible, non‐permanent workforce, diversify collaborators and research areas, source complementary funding to assemble infrastructures, and maintain prospective research populations to attract transnational clinical trials. Through this labor of collaboration, they sustain their institutions under prevailing conditions of scarcity. PMID:25800667

  10. Quadratic function approaching method for magnetotelluric soundingdata inversion

    SciTech Connect

    Liangjun, Yan; Wenbao, Hu; Zhang, Keni

    2004-04-05

    The quadratic function approaching method (QFAM) is introduced for magnetotelluric sounding (MT) data inversion. The method takes the advantage of that quadratic function has single extreme value, which avoids leading to an inversion solution for local minimum and ensures the solution for global minimization of an objective function. The method does not need calculation of sensitivity matrix and not require a strict initial earth model. Examples for synthetic data and field measurement data indicate that the proposed inversion method is effective.

  11. Academically Successful African American Male Urban High School Students' Experiences of Mattering to Others at School

    ERIC Educational Resources Information Center

    Tucker, Catherine; Dixon, Andrea; Griddine, Ke'Shana

    2010-01-01

    Mattering to others has been shown to be a key construct of mental health and wellness. Emerging research links interpersonal mattering and school climate. In this study, the authors use transcendental phenomenology to explore how interpersonal mattering impacts the academic achievement of urban African American males who are academically…

  12. The Influence of Both Race and Gender on the Experiences of African American College Women.

    ERIC Educational Resources Information Center

    Jackson, Lisa R.

    1998-01-01

    At four colleges, 135 African American women students completed measures of self-concept, gender identity, and ethnic identity, and were interviewed. Results suggest that women's self-concepts of race and gender are experienced differently depending on their school's racial and gender composition. Colleges should reexamine diversity efforts to…

  13. What Makes African American Health Disparities Newsworthy? An Experiment among Journalists about Story Framing

    ERIC Educational Resources Information Center

    Hinnant, Amanda; Oh, Hyun Jee; Caburnay, Charlene A.; Kreuter, Matthew W.

    2011-01-01

    News stories reporting race-specific health information commonly emphasize disparities between racial groups. But recent research suggests this focus on disparities has unintended effects on African American audiences, generating negative emotions and less interest in preventive behaviors (Nicholson RA, Kreuter MW, Lapka C "et al." Unintended…

  14. Sense of Belonging and Student Success: An Analysis of Student Experiences in South African Universities

    ERIC Educational Resources Information Center

    Williams, Theresa

    2012-01-01

    Retention and graduation are major challenges in South African higher education institutions. These phenomena are especially troubling among Black and Colored (BC) students at both historically advantaged and historically disadvantaged institutions. The retention and graduation rates of these groups are disturbingly low compared to those of White…

  15. Towards a Meaningful Curriculum Implementation in South African Schools: Senior Phase Teachers' Experiences

    ERIC Educational Resources Information Center

    Taole, Matshidiso Joyce

    2015-01-01

    Different sectors of society register complaints about schooling in South Africa. Given that curriculum reform has such a poor record of implementation in the country, there is clearly a need for research that identifies factors that hinder or facilitate curriculum implementation in South African schools and identifies strategies to address the…

  16. Scaffolding the Home Reading Experiences of African-American First Graders

    ERIC Educational Resources Information Center

    Dunston, Yolanda L.; Patterson, Gerrelyn C.; Daniels, Kisha N.

    2010-01-01

    This study explored the feedback provided by sixty African American mothers as they listened to their first grade children read aloud from a grade level text. Maternal feedback fell into two distinct groups. Children with higher oral reading accuracy levels on the text had mothers who more frequently waited and permitted opportunities for the…

  17. African American Faculty Women Experiences of Underrepresentation in Computer Technology Positions in Higher Education

    ERIC Educational Resources Information Center

    King, Dolores

    2013-01-01

    African American women are underrepresented in computer technology disciplines in institutions of higher education throughout the United States. Although equitable gender representation is progressing in most fields, much less information is available on why institutions are still lagging in workforce diversity, a problem which can be lessened by…

  18. Till Death Do Us Part: Lived Experiences of HIV-Positive Married African American Women

    ERIC Educational Resources Information Center

    Edwards, Lorece V.; Irving, Shalon M.; Hawkins, Anita S.

    2011-01-01

    HIV/AIDS disease continues to be an escalating health problem, particularly among women. However, African American women are among the leading demographic groups for HIV prevalence in the United States. The typical woman with HIV/AIDS is young, in her late twenties, economically challenged, and of childbearing age. Participants were recruited from…

  19. Early Educational Foundations for the Development of Civic Responsibility: An African Experience

    ERIC Educational Resources Information Center

    Serpell, Robert; Mumba, Paul; Chansa-Kabali, Tamara

    2011-01-01

    An innovative curriculum designed to foster the development of social responsibility among pre-adolescent children was introduced at a rural Zambian primary school. The curriculum invoked Child-to-Child principles focusing on health education, advancing a synthesis of Western psychological theories and African cultural traditions. The teacher…

  20. The Experiences of African American Physical Education Teacher Candidates at Secondary Urban Schools

    ERIC Educational Resources Information Center

    Sato, Takahiro; Fisette, Jennifer; Walton, Theresa

    2013-01-01

    Presently, most physical education teachers in the United States are White Americans and from middle class families. In fact, 83% of all teachers in public schools are White Americans, whereas approximately 10% of all African American teachers are representative of all teachers in the United States. A student might feel cultural dissonance that…

  1. The Power of Peers: Influences on Postsecondary Education Planning and Experiences of African American Students

    ERIC Educational Resources Information Center

    Holland, Nicole E.

    2011-01-01

    This investigation demonstrates the effect that peers have on students' academic engagement and educational aspirations. Forty-nine African American university students retrospectively discuss the manner by which their friends influenced their academic commitment and activity while in high school; their postsecondary education aspirations,…

  2. A Dream Deferred: The Experience of an African American Student in a Doctoral Program in Science

    ERIC Educational Resources Information Center

    Green, Andre M.

    2008-01-01

    Due to a negative stigma that has been established about African Americans, many live their entire lives trying to "refute the degrading, humiliating and offensive racial images and stereotypes" that have plagued their race in scientific fields and in other areas of life. The images that are perpetuated have caused frustration as well as…

  3. A Bourdieusian Approach to Academic Reading: Reflections on a South African Teaching Experience

    ERIC Educational Resources Information Center

    Hill, Lloyd; Meo, Analía Inés

    2015-01-01

    As in many other parts of the world, "academic literacy" has emerged as both a concern and a contested concept in South African universities. In this article we focus specifically on academic reading, which we argue is a relatively underemphasized aspect of academic literacy. This article is the product of reflections on academic reading…

  4. A Survey of the Experiences of African Librarians in American Academic Libraries

    ERIC Educational Resources Information Center

    Ibraheem, Abiodun I.; Devine, Christopher

    2013-01-01

    A national research study was undertaken to identify and clarify issues related to the employment in academic settings of African librarians who have relocated to the United States. It examined, by means of a survey, employment issues concerned with education, credentialing, language skills and cultural bias from the perspective of those…

  5. The Stuff of Stereotypes: Toward Unpacking Identity Threats amid African American Students' Learning Experiences

    ERIC Educational Resources Information Center

    Larnell, Gregory V.; Boston, Denise; Bragelman, John

    2014-01-01

    The purpose of this article is to shed light on scenarios in which threatening stereotypes unfold, specifically in an institutional context in which African Americans are overrepresented. Drawing on data and findings from a recent study examining mathematics learning and identity in non-credit-bearing remedial math courses, we present three…

  6. The Invisible Wall: Exploring the Experiences of African-American Students at CCCU Institutions

    ERIC Educational Resources Information Center

    Young, Timothy Perry

    2013-01-01

    African-American students who attend a CCCU institution do not complete their degrees as frequently as other student groups. The average gap at CCCU institutions between "overall and Black graduation rates is more than 19%. This is greater than the gap at other private institutions" (Smith, 2009, p.80). While the six-year graduation rate…

  7. Examining Both Race and Gender in the Experiences of African American College Women.

    ERIC Educational Resources Information Center

    Jackson, Lisa R.

    This study examined how African American women defined who they were in their respective college contexts, focusing on the roles of gender, race, and institutional type. A total of 20 women from a white coeducational institution, a predominantly white women's college, and a coeducational, historically black college participated in in-depth…

  8. Cooperative inversion of magnetotelluric and seismic data sets

    NASA Astrophysics Data System (ADS)

    Markovic, M.; Santos, F.

    2012-04-01

    Cooperative inversion of magnetotelluric and seismic data sets Milenko Markovic,Fernando Monteiro Santos IDL, Faculdade de Ciências da Universidade de Lisboa 1749-016 Lisboa Inversion of single geophysical data has well-known limitations due to the non-linearity of the fields and non-uniqueness of the model. There is growing need, both in academy and industry to use two or more different data sets and thus obtain subsurface property distribution. In our case ,we are dealing with magnetotelluric and seismic data sets. In our approach,we are developing algorithm based on fuzzy-c means clustering technique, for pattern recognition of geophysical data. Separate inversion is performed on every step, information exchanged for model integration. Interrelationships between parameters from different models is not required in analytical form. We are investigating how different number of clusters, affects zonation and spatial distribution of parameters. In our study optimization in fuzzy c-means clustering (for magnetotelluric and seismic data) is compared for two cases, firstly alternating optimization and then hybrid method (alternating optimization+ Quasi-Newton method). Acknowledgment: This work is supported by FCT Portugal

  9. Men of the Cloth: African-American Clergy's Knowledge and Experience in Providing Pastoral Care to African-American Elders with Late-Life Depression

    ERIC Educational Resources Information Center

    Stansbury, Kim L.

    2011-01-01

    African-American clergy's ability to recognize late-life depression and their capacity to provide support with this illness have been neglected in the literature. Using a mental health literacy framework, the purpose of this research was to explore African-American clergy's knowledge of and treatments for late-life depression. In-depth interviews…

  10. The IRETHERM Project: How Can We Characterize Geothermal Reservoirs in Ireland using Magnetotelluric Surveying?

    NASA Astrophysics Data System (ADS)

    Delhaye, R. P.; Jones, A. G.; Rath, V.; Brown, C.; Reay, D.

    2014-12-01

    We present results from two geophysical investigations of the north of Ireland, one of a concealed sedimentary basin and the other of an area of pre- to mid-Cambrian metasedimentary material with local microseismicity in Donegal. Magnetotelluric data have been acquired over each area as part of the IRETHERM Project in order to assess potential low-enthalpy geothermal resources. In addition, airborne frequency-domain EM response data have been used to assist in the definition of near-surface electrical structure and constraint of magnetotelluric modeling. The Rathlin Basin in Northern Ireland was identified as a potential geothermal resource due both an elevated geothermal gradient (observed in two deep boreholes) and favorable hydraulic properties in thick successions of Permian and Triassic sandstones (measured from core samples). Prior seismic experiments failed to fully image the sediments beneath the overlying flood basalt. A new experiment applying the magnetotelluric method has had more success, as the MT signal is not dissipated by the crystalline overburden. MT data were acquired at 69 sites across the north-eastern portion of the onshore Rathlin Basin and on nearby Rathlin Island in order to image the thickness, depth, and lateral continuity of the target sediments. Analyses and modeling of the data have determined a resistivity model that maps the variation in thickness of the sediment fill and the truncation of the sediments against the structurally-controlling Tow Valley Fault. Further testing of the model sensitivity to variations of the thickness of the Sherwood Sandstone Group within the sediment fill has also been performed, as the overlying sediments have lower porosities and permeabilities from core sampling. Microseismicity in a metasedimentary area of northern Donegal suggests that secondary porosity distributions along fracture planes may have been augmented, leading to elevated electrical conductivity. MT data were acquired over the epicenter

  11. Early sexual experience and later onset of illegal drug use among African American students on HBCU campuses.

    PubMed

    Wang, Yan; Storr, Carla; Browne, Dorothy C; Wagner, Fernando A

    2011-01-01

    Few studies examine whether early sexual experience is associated with subsequent illegal drug use among adolescents. A sample of 7,372 African American students who had not used illegal drugs before the age of 14 were identified in the dataset of the 2001 Historically Black Colleges and Universities (HBCU) Substance Use Survey. Using self-reported ages of onset, discrete-time survival models estimated the hazard of illegal drug use onset after age 13 subsequent to first sexual intercourse. Early sex was modestly associated with subsequent illegal drug initiation, particularly among females. Drug use prevention services should be provided to youth engaged in early sexual activity. PMID:20735190

  12. Deviant bodies, stigmatized identities, and racist acts: examining the experiences of African-American gamers in Xbox Live

    NASA Astrophysics Data System (ADS)

    Gray, K. L.

    2012-12-01

    The purpose of this article is to illustrate how minority gamers, particularly African-American males, are subject to the label of deviant within the virtual gaming community of Xbox Live. They are labeled deviant based on the stigma of their physical identity - blackness, through a process of linguistic profiling. By employing virtual ethnography, the author identifies a process that leads to racism based on how the black gamer sounds within the space. The act of racism emerges through a process involving questioning, provoking, instigating, and ultimately racism. Many black gamers have normalized these racist experiences and have accepted the label of deviant placed upon their bodies.

  13. The Impact of African American Parents' Racial Discrimination Experiences and Perceived Neighborhood Cohesion on their Racial Socialization Practices.

    PubMed

    Saleem, Farzana T; English, Devin; Busby, Danielle R; Lambert, Sharon F; Harrison, Aubrey; Stock, Michelle L; Gibbons, Frederick X

    2016-07-01

    Parental racial socialization is a parenting tool used to prepare African American adolescents for managing racial stressors. While it is known that parents' racial discrimination experiences affect the racial socialization messages they provide, little is known about the influence of factors that promote supportive and communal parenting, such as perceived neighborhood cohesion. In cohesive neighborhoods, neighbors may help parents address racial discrimination by monitoring youth and conveying racial socialization messages; additionally, the effect of neighborhood cohesion on parents' racial socialization may differ for boys and girls because parents socialize adolescents about race differently based on expected encounters with racial discrimination. Therefore, the current study examines how parents' perception of neighborhood cohesion and adolescents' gender moderate associations between parents' racial discrimination experiences and the racial socialization messages they deliver to their adolescents. Participants were a community sample of 608 African American adolescents (54 % girls; mean age = 15.5) and their primary caregivers (86 % biological mothers; mean age = 42.0). Structural equation modeling indicated that parental racial discrimination was associated with more promotion of mistrust messages for boys and girls in communities with low neighborhood cohesion. In addition, parental racial discrimination was associated with more cultural socialization messages about racial pride and history for boys in neighborhoods with low neighborhood cohesion. The findings suggest that parents' racial socialization messages are influenced by their own racial discrimination experiences and the cohesiveness of the neighborhood; furthermore, the content of parental messages delivered varies based on adolescents' gender. PMID:27189721

  14. Magnetotelluric imaging of a fossil paleozoic intraoceanic subduction zone in western Junggar, NW China

    NASA Astrophysics Data System (ADS)

    Xu, Yixian; Yang, Bo; Zhang, Sheng; Liu, Ying; Zhu, Lupei; Huang, Rong; Chen, Chao; Li, Yongtao; Luo, Yinhe

    2016-06-01

    The fate of subducted oceanic slabs can provide important clues to plate reconstruction through Earth history. Since oceanic slabs in continental collision zones are typically not well preserved, ancient subduction zones have rarely been imaged by geophysical techniques. Here we present an exception from the Darbut belt in the Junggar accretionary collage in the southern Altaids of Asia. We deployed a 182 km long magnetotelluric (MT) profile including 60 broadband sounding sites across the belt. Quality off-diagonal impedances were inverted by a three-dimensional scheme to image resistivities beneath the profile. The resistivity model along with MT impedance phase ellipses and induction vectors were tested and interpreted in detail. Combining geological and geophysical observations, mineral physical experiment, and geodynamic modeling results, the MT transect suggests a fossil intraoceanic subduction zone during the Late Paleozoic in the western Junggar that has been well preserved due to lack of significant subsequent tecto-thermal events.

  15. 3-D magnetotelluric image of offshore magmatism at the Walvis Ridge and rift basin

    NASA Astrophysics Data System (ADS)

    Jegen, Marion; Avdeeva, Anna; Berndt, Christian; Franz, Gesa; Heincke, Björn; Hölz, Sebastian; Neska, Anne; Marti, Anna; Planert, Lars; Chen, J.; Kopp, Heidrun; Baba, Kiyoshi; Ritter, Oliver; Weckmann, Ute; Meqbel, Naser; Behrmann, Jan

    2016-06-01

    The Namibian continental margin marks the starting point of the Tristan da Cunha hotspot trail, the Walvis Ridge. This section of the volcanic southwestern African margin is therefore ideal to study the interaction of hotspot volcanism and rifting, which occurred in the late Jurassic/early Cretaceous. Offshore magnetotelluric data image electromagnetically the landfall of Walvis Ridge. Two large-scale high resistivity anomalies in the 3-D resistivity model indicate old magmatic intrusions related to hot-spot volcanism and rifting. The large-scale resistivity anomalies correlate with seismically identified lower crustal high velocity anomalies attributed to magmatic underplating along 2-D offshore seismic profiles. One of the high resistivity anomalies (above 500 Ωm) has three arms of approximately 100 km width and 300 km to 400 km length at 120° angles in the lower crust. One of the arms stretches underneath Walvis Ridge. The shape is suggestive of crustal extension due to local uplift. It might indicate the location where the hot-spot impinged on the crust prior to rifting. A second, smaller anomaly of 50 km width underneath the continent ocean boundary may be attributed to magma ascent during rifting. We attribute a low resistivity anomaly east of the continent ocean boundary and south of Walvis Ridge to the presence of a rift basin that formed prior to the rifting.

  16. A population-based analysis of the health experience of African Nova Scotians

    PubMed Central

    Kisely, Steve; Terashima, Mikiko; Langille, Don

    2008-01-01

    Background People of African descent living in Britain and the United States have higher rates of morbidity from chronic disease than among the general population. We investigated whether the same applied to people of African descent living in a Canadian province. Methods We used administrative data to calculate 10-year cumulative incidence rate ratios for the period 1996–2005 for treated circulatory disease, diabetes mellitus and psychiatric disorders in Preston (population 2425), a community of predominantly African Nova Scotians. We used data for the province of Nova Scotia as a whole as the population reference standard. We also calculated 10-year incidence rate ratios for visits to family physicians and specialists and for admissions to hospital. We compared these findings with those in 7 predominantly white communities in Nova Scotia with otherwise similar socio-economic characteristics. Results In the province as a whole, we identified 787 787 incident cases for the 3 disease groups over the 10-year period. Incidence rate ratios for the community of interest relative to the provincial population were significantly elevated for the 3 diseases: circulatory disease (1.19, 95% CI 1.08–1.29), diabetes (1.43, 95% CI 1.21–1.64) and psychiatric disorders (1.13, 95% CI 1.06–1.20). Incidence rate ratios in the community of interest were also higher than those in the comparison communities. Visits to family physicians and specialists for circulatory disease and diabetes were similarly elevated, but the pattern was less clear for visits for psychiatric disorders and hospital admissions. Interpretation African Nova Scotians had higher morbidity levels associated with treated disease, which could not be explained by socio-economic characteristics, recent immigration or language. Apart from psychiatric disorders, use of specialist services was consistent with morbidity. Further study is needed to investigate the relative contribution of genetic, biological

  17. Rhythm experience and Africana culture trial (REACT!): A culturally salient intervention to promote neurocognitive health, mood, and well-being in older African Americans.

    PubMed

    Lukach, Alexis J; Jedrziewski, M Kathryn; Grove, George A; Mechanic-Hamilton, Dawn J; Williams, Shardae S; Wollam, Mariegold E; Erickson, Kirk I

    2016-05-01

    The Rhythm Experience and Africana Culture Trial (REACT!) is a multi-site randomized controlled intervention study designed to examine the efficacy of using African Dance as a form of moderate-intensity physical activity to improve cognitive function in older African Americans. African Americans are almost two times more likely than Caucasians to experience cognitive impairment in late adulthood. This increased risk may be attributed to lower level and quality of education, lower socioeconomic status, and higher prevalence of vascular diseases, type 2 diabetes, hypertension, and obesity, all of which are recognized as risk factors for dementia. Fortunately, interventions targeting cardiovascular health (i.e., physical activity) are associated with improved neurocognitive function and a reduced risk for dementia, so African Americans may be particularly suited for interventions targeting cardiovascular health and cognitive function. Here, we describe a randomized intervention protocol for increasing physical activity in older (65-75years) African Americans. Participants (n=80) at two study locations will be randomized into one of two groups. The treatment group will participate in African Dance three times per week for six months and the control group will receive educational training on Africana history and culture, as well as information about health behaviors, three times per week for six months. If successful, the REACT! study may transform community interventions and serve as a platform and model for testing other populations, age groups, and health outcomes, potentially identifying novel and creative methods for reducing or eliminating health disparities. PMID:27033674

  18. School Characteristics and Experiences of African American, Hispanic/Latino, and Native American Youth in Rural Communities: Relation to Educational Aspirations

    ERIC Educational Resources Information Center

    Irvin, Matthew J.; Byun, Soo-yong; Meece, Judith L.; Reed, Karla S.; Farmer, Thomas W.

    2016-01-01

    The primary purpose of this study was to examine differences in the school characteristics and experiences of African American, Hispanic/Latino, and Native American youth in rural high schools as well as their relation to educational aspirations. We also investigated the characteristics and experiences of students and their families given that…

  19. When Failing Doesn't Matter: A Narrative Inquiry into the Social Work Practice Learning Experiences of Black African Students in England

    ERIC Educational Resources Information Center

    Tedam, Prospera

    2014-01-01

    This paper reports the findings of a small-scale empirical study into the practice learning experiences of black African students of social work in England. Undertaken in the form of a pilot study, the findings reveal that practice learning experiences can be beneficial in enhancing skills and knowledge but can also cause distress, lower…

  20. Experiences and effects of psychiatric stigma: Monologues of the stigmatizers and the stigmatized in an African setting

    PubMed Central

    Egbe, Catherine O.

    2015-01-01

    People with mental illness (PWMI) are faced with a number of social and health-related challenges especially stigma and discrimination which tend to have negative effects on their lives. This paper presents narrative monologues portraying the experiences and effects of psychiatric stigma and discrimination on PWMI in South Africa. These narratives voice out the concerns of the stigmatizers (specifically family members and significant others of PWMI) and the stigmatized in a poetic fashion. The society is still not very sympathetic to the plights of PWMI and this affects their general health and well-being. Traditional beliefs and prejudice still drive public attitude towards PWMI especially in African settings. These narratives presented in a poetic fashion in this paper highlight some salient issues relating to the experience and effects of stigma and the desires of PWMI to be treated with love and respect and helped to lead healthy normal lives. PMID:26088367

  1. Experiences and effects of psychiatric stigma: Monologues of the stigmatizers and the stigmatized in an African setting.

    PubMed

    Egbe, Catherine O

    2015-01-01

    People with mental illness (PWMI) are faced with a number of social and health-related challenges especially stigma and discrimination which tend to have negative effects on their lives. This paper presents narrative monologues portraying the experiences and effects of psychiatric stigma and discrimination on PWMI in South Africa. These narratives voice out the concerns of the stigmatizers (specifically family members and significant others of PWMI) and the stigmatized in a poetic fashion. The society is still not very sympathetic to the plights of PWMI and this affects their general health and well-being. Traditional beliefs and prejudice still drive public attitude towards PWMI especially in African settings. These narratives presented in a poetic fashion in this paper highlight some salient issues relating to the experience and effects of stigma and the desires of PWMI to be treated with love and respect and helped to lead healthy normal lives. PMID:26088367

  2. Probabilistic 3-D time-lapse inversion of magnetotelluric data: Application to an enhanced geothermal system

    USGS Publications Warehouse

    Rosas-Carbajal, Marina; Linde, Nicolas; Peacock, Jared R.; Zyserman, F. I.; Kalscheuer, Thomas; Thiel, Stephan

    2015-01-01

    Surface-based monitoring of mass transfer caused by injections and extractions in deep boreholes is crucial to maximize oil, gas and geothermal production. Inductive electromagnetic methods, such as magnetotellurics, are appealing for these applications due to their large penetration depths and sensitivity to changes in fluid conductivity and fracture connectivity. In this work, we propose a 3-D Markov chain Monte Carlo inversion of time-lapse magnetotelluric data to image mass transfer following a saline fluid injection. The inversion estimates the posterior probability density function of the resulting plume, and thereby quantifies model uncertainty. To decrease computation times, we base the parametrization on a reduced Legendre moment decomposition of the plume. A synthetic test shows that our methodology is effective when the electrical resistivity structure prior to the injection is well known. The centre of mass and spread of the plume are well retrieved.We then apply our inversion strategy to an injection experiment in an enhanced geothermal system at Paralana, South Australia, and compare it to a 3-D deterministic time-lapse inversion. The latter retrieves resistivity changes that are more shallow than the actual injection interval, whereas the probabilistic inversion retrieves plumes that are located at the correct depths and oriented in a preferential north-south direction. To explain the time-lapse data, the inversion requires unrealistically large resistivity changes with respect to the base model. We suggest that this is partly explained by unaccounted subsurface heterogeneities in the base model from which time-lapse changes are inferred.

  3. Drawing the line: how African, Caribbean and White British women live out psychologically abusive experiences.

    PubMed

    Rivas, Carol; Kelly, Moira; Feder, Gene

    2013-09-01

    This study explores how African, Caribbean and White British women worked to hide psychological partner abuse as they experienced it, "do gender," and appear competent in social roles. They prioritized negotiated competencies as "good partners," actively setting socially and culturally embedded boundaries to their abuser's behaviors: an inner boundary encompassing normal behaviors and an outer one of "acceptable" behaviors projected as normal through remedial work. Behaviors breaching the outer boundary (e.g., if the women narrowed the bounds of the "acceptable") compromised the women's competence. This sometimes led them to actively use support services. Appropriate advice and support may change the boundaries. PMID:24142953

  4. Understanding the Breast Cancer Experience of Survivors: a Qualitative Study of African American Women in Rural Eastern North Carolina.

    PubMed

    Torres, Essie; Dixon, Crystal; Richman, Alice R

    2016-03-01

    The purpose of this study is to gain an in-depth understanding of African American breast cancer survivors' experiences, barriers and facilitators in accessing breast cancer treatment, and challenges in adherence to follow-up care. We conducted seven focus groups with 32 African American women with breast cancer in three rural counties in eastern North Carolina during August-November 2013. Surveys were also utilized to gather basic demographic and breast health history information. Thematic analysis was performed using the immersion crystallization approach. Several common areas of life affected by breast cancer included faith and support networks, psychosocial well-being, and quality of care issues. Faith in God was an important coping mechanism essential to all women in the study and a critical facilitator in survivorship. Support networks consisted of family, church-family, friends, and co-workers. The concept of fear included the discovery of breast cancer and fear of death, negative side effects of treatment, and social stigma of having breast cancer. Factors that influenced provider-patient relationship were age of provider, perceived lack of empathy, and providers leaving during treatment. Participants also expressed their lack of knowledge regarding a number of the side effects they were experiencing during and after their treatment. Results of this study contribute to the assessment of potential coping mechanisms used by African American breast cancer survivors (i.e., spirituality, positive attitudes, and support networks) that can potentially be effective and have a positive impact on the adjustment of life for survivors. PMID:25877467

  5. Diagnosing GCM errors over West Africa using relaxation experiments. Part II: intraseasonal variability and African easterly waves

    NASA Astrophysics Data System (ADS)

    Pohl, Benjamin; Douville, Hervé

    2011-10-01

    A near-global grid-point nudging of the Arpege-Climat atmospheric General Circulation Model towards ECMWF reanalyses is used to diagnose the regional versus remote origin of the summer model biases and variability over West Africa. First part of this study revealed a limited impact on the monsoon climatology compared to a control experiment without nudging, but a significant improvement of interannual variability, although the amplitude of the seasonal anomalies remained underestimated. Focus is given here on intraseasonal variability of monsoon rainfall and dynamics. The reproducible part of these signals is investigated through 30-member ensemble experiments computed for the 1994 rainy season, a year abnormally wet over the Sahel but representative of the model systematic biases. In the control experiment, Arpege-Climat simulates too few rainy days that are associated with too low rainfall amounts over the central and western Sahel, in line with the seasonal dry biases. Nudging the model outside Africa tends to slightly increase the number of rainy days over the Sahel, but has little effect on associated rainfall amounts. However, results do indicate that a significant part of the monsoon intraseasonal variability simulated by Arpege-Climat is controlled by lateral boundary conditions. Parts of the wet/dry spells over the Sahel occur in phase in the 30 members of the nudging experiment, and are therefore embedded in larger-scale variability patterns. Inter-member spread is however not constant across the selected summer season. It is partly controlled by African Easterly Waves, which show dissimilar amplitude from one member to another, but a coherent phasing in all members. A lowpass filtering of the nudging fields suggests that low frequency variations in the lateral boundary conditions can lead to eastward extensions of the African Easterly Jet, creating a favorable environment for easterly waves, while high frequency perturbations seem to control their

  6. Polarisation analysis of magnetotelluric time series using a wavelet-based scheme: A method for detection and characterisation of cultural noise sources

    NASA Astrophysics Data System (ADS)

    Escalas, M.; Queralt, P.; Ledo, J.; Marcuello, A.

    2013-05-01

    The identification and elimination of cultural noise that affects magnetotelluric (MT) time series presents a challenge in the vicinity of industrialised, urban or farming areas. Most noise sources are fixed in space and create a signal with certain polarisation properties. In this paper, we propose a new method for detection and characterisation of cultural noise sources in magnetotelluric time series based on polarisation analysis of the electromagnetic signal in the time-frequency domain using a wavelet scheme. We tested the proposed method with synthetic polarised signals and experimental time series corresponding to a field experiment with a controlled EM source and several MT real cases. The results demonstrated the difference between the polarisation properties of the natural MT signal and the signal contaminated by a controlled source or by cultural noise.

  7. Semiautomatic and Automatic Cooperative Inversion of Seismic and Magnetotelluric Data

    NASA Astrophysics Data System (ADS)

    Le, Cuong V. A.; Harris, Brett D.; Pethick, Andrew M.; Takam Takougang, Eric M.; Howe, Brendan

    2016-09-01

    Natural source electromagnetic methods have the potential to recover rock property distributions from the surface to great depths. Unfortunately, results in complex 3D geo-electrical settings can be disappointing, especially where significant near-surface conductivity variations exist. In such settings, unconstrained inversion of magnetotelluric data is inexorably non-unique. We believe that: (1) correctly introduced information from seismic reflection can substantially improve MT inversion, (2) a cooperative inversion approach can be automated, and (3) massively parallel computing can make such a process viable. Nine inversion strategies including baseline unconstrained inversion and new automated/semiautomated cooperative inversion approaches are applied to industry-scale co-located 3D seismic and magnetotelluric data sets. These data sets were acquired in one of the Carlin gold deposit districts in north-central Nevada, USA. In our approach, seismic information feeds directly into the creation of sets of prior conductivity model and covariance coefficient distributions. We demonstrate how statistical analysis of the distribution of selected seismic attributes can be used to automatically extract subvolumes that form the framework for prior model 3D conductivity distribution. Our cooperative inversion strategies result in detailed subsurface conductivity distributions that are consistent with seismic, electrical logs and geochemical analysis of cores. Such 3D conductivity distributions would be expected to provide clues to 3D velocity structures that could feed back into full seismic inversion for an iterative practical and truly cooperative inversion process. We anticipate that, with the aid of parallel computing, cooperative inversion of seismic and magnetotelluric data can be fully automated, and we hold confidence that significant and practical advances in this direction have been accomplished.

  8. Singular value decomposition in magnetotelluric sounding data processing

    SciTech Connect

    Shengjie, S. )

    1991-01-01

    In this paper singular value decomposition method, a method for magnetotelluric sounding data processing, is recommended minutely; and its real number operation process is derived. For analysis, this method decomposes data matrix into signal matrix and noise matrix. It may give least squares estimation of response function, performs quantitative analysis of signal and noise to calculate S/N ratio, and offers the estimated variance of the response function. Theoretical calculation shows that this method is reliable and effective in suppressing noise, estimating response function, and analyzing noise and variance.

  9. West Flank Coso FORGE Magnetotelluric 3D Data

    SciTech Connect

    Doug Blankenship

    2016-01-01

    This is the 3D version of the MT data for the West Flank FORGE area.The Coso geothermal field has had three Magnetotelluric (MT) datasets collected including surveys in 2003, 2006, and 2011. The final collection, in 2011, expanded the survey to the west and covers the West Flank of FORGE area.This most recent data set was collected by Schlumberger/WesternGeco and inverted by the WesternGeco GeoSolutions Integrated EM Center of Excellence in Milan, Italy; the 2003 and 2006 data were integrated for these inversions in the present study.

  10. Successfully Educating Our African-American Students

    ERIC Educational Resources Information Center

    Moncree-Moffett, Kareem

    2013-01-01

    The purpose of this empirical study was to explore the lived experiences of African American retired female teachers who have prior experience with educating urban African American students in public schools. Also explored are the experiences of active African American female teachers of urban African American students and comparisons are…

  11. "Are You Sure You Know What You Are Doing?"--The Lived Experiences of an African American Male Kindergarten Teacher

    ERIC Educational Resources Information Center

    Bryan, Nathaniel; Browder, Jamison K.

    2013-01-01

    As of 2012, data indicate that only one percent of public school teachers are African American males. Numerous reports urge decision makers and higher education professionals to aggressively recruit and retain African American males as teachers in an effort to improve the academic outcomes of African American children in our educational system…

  12. "She Told Them, Oh That Bitch Got AIDS": Experiences of Multilevel HIV/AIDS-Related Stigma Among African American Women Living with HIV/AIDS in the South.

    PubMed

    Fletcher, Faith; Ingram, Lucy Annang; Kerr, Jelani; Buchberg, Meredith; Bogdan-Lovis, Libby; Philpott-Jones, Sean

    2016-07-01

    African American women bear a disproportionate burden of HIV/AIDS in the United States. Although they constitute only 13% of the US population, African Americans account for nearly 65% of all new HIV infections among American women. In addition, this population suffers comparatively greater adverse health outcomes related to HIV status. African American women living with HIV in the South may be further burdened by HIV/AIDS stigma, which is comparatively more pronounced in this region. To further explore this burden, we used narrative data and the Social Ecological Model to explore how African American women living with HIV in the US South recount, conceptualize, and cope with HIV/AIDS stigma at interpersonal, community, and institutional levels. Our narrative analysis suggests that HIV-positive African American women living in the South are vulnerable to experiences of multilevel HIV stigma in various settings and contexts across multiple domains of life. Stigma subsequently complicated disclosure decisions and made it difficult for women to feel supported in particular social, professional and medical settings that are generally regarded as safe spaces for noninfected individuals. Findings suggest that the debilitating and compounded effect of multilevel HIV/AIDS stigma on HIV-positive African American women in the South warrants closer examination to tailor approaches that effectively address the unique needs of this population. PMID:27410498

  13. The experiences of African-American students majoring in engineering: Cognitive, non-cognitive and situational aspects

    NASA Astrophysics Data System (ADS)

    Hill, Gloria Pinckney

    1997-12-01

    To understand the causes for the disproportionately high rate of attrition among ethnic minority students, it is important to consider not only how they differ from the majority population, but what differences exist in personal qualities and academic preparation within groups at particular types of institutions, and within particular majors. The purpose of this study is to examine the experiences of African-American students enrolled in engineering at a predominately white, selective research university to determine which cognitive, non-cognitive and situational variables impact their progress towards graduation. The goal was to see how African-American students who meet or exceed the minimum criteria for admission perceive their experience on campus, and what strategies they use to manage their day-to-day existence. The study was conducted using personal interviews guided by an open-ended questionnaire. The qualitative methodology allowed students to assess the college experience through their own cultural lens, and to identify the cognitive, non-cognitive, and situational variables important to them. Responses were sorted by class and gender, tabulated and grouped into categories. Interpretation was primarily descriptive. Consistencies, inconsistencies, patterns and relationships to concepts in the literature and to the research questions were discussed. Findings indicate that well prepared students become less confident about their commitment to engineering and their ability to succeed academically after they begin matriculating rather than before, and that redefinition of what it means to be academically successful is an effective coping mechanism to sustain the effort required to master courses. The study suggests that the current focus on the impact of the freshman year transition on student retention should be expanded to include the sophomore year. This is particularly true for institutions where engineering students spend the first year in a core

  14. West African monsoon decadal variability and surface-related forcings: second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II)

    NASA Astrophysics Data System (ADS)

    Xue, Yongkang; De Sales, Fernando; Lau, William K.-M.; Boone, Aaron; Kim, Kyu-Myong; Mechoso, Carlos R.; Wang, Guiling; Kucharski, Fred; Schiro, Kathleen; Hosaka, Masahiro; Li, Suosuo; Druyan, Leonard M.; Sanda, Ibrah Seidou; Thiaw, Wassila; Zeng, Ning; Comer, Ruth E.; Lim, Young-Kwon; Mahanama, Sarith; Song, Guoqiong; Gu, Yu; Hagos, Samson M.; Chin, Mian; Schubert, Siegfried; Dirmeyer, Paul; Ruby Leung, L.; Kalnay, Eugenia; Kitoh, Akio; Lu, Cheng-Hsuan; Mahowald, Natalie M.; Zhang, Zhengqiu

    2016-06-01

    The second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II) is designed to improve understanding of the possible roles and feedbacks of sea surface temperature (SST), land use land cover change (LULCC), and aerosols forcings in the Sahel climate system at seasonal to decadal scales. The project's strategy is to apply prescribed observationally based anomaly forcing, i.e., "idealized but realistic" forcing, in simulations by climate models. The goal is to assess these forcings' effects in producing/amplifying seasonal and decadal climate variability in the Sahel between the 1950s and the 1980s, which is selected to characterize the great drought period of the last century. This is the first multi-model experiment specifically designed to simultaneously evaluate such relative contributions. The WAMME II models have consistently demonstrated that SST forcing is a major contributor to the twentieth century Sahel drought. Under the influence of the maximum possible SST forcing, the ensemble mean of WAMME II models can produce up to 60 % of the precipitation difference during the period. The present paper also addresses the role of SSTs in triggering and maintaining the Sahel drought. In this regard, the consensus of WAMME II models is that both Indian and Pacific Ocean SSTs greatly contributed to the drought, with the former producing an anomalous displacement of the Intertropical Convergence Zone before the WAM onset, and the latter mainly contributes to the summer WAM drought. The WAMME II models also show that the impact of LULCC forcing on the Sahel climate system is weaker than that of SST forcing, but still of first order magnitude. According to the results, under LULCC forcing the ensemble mean of WAMME II models can produces about 40 % of the precipitation difference between the 1980s and the 1950s. The role of land surface processes in responding to and amplifying the drought is also identified. The results suggest that catastrophic

  15. Surviving oppression under the Rock: The intersection of New York’s drug, welfare, and educational polices in the lived experiences of low-income African-Americans

    PubMed Central

    Windsor, Liliane Cambraia; Dunlap, Eloise; Armour, Marilyn

    2012-01-01

    Drawing on standpoint and intersectionality theories, this study explores the degree to which interactions among New York State’s Rockefeller Drug Laws, educational and welfare policies have contributed to the maintenance of a culture of surveillance in which the lives of impoverished African Americans are overseen and influenced by oppressive policies and governmental institutions. Qualitative secondary analysis of longitudinal ethnographic data was conducted. Findings demonstrate multiple disadvantages that impoverished African American families struggling with substance use and/or sale experience. These disadvantages accumulated intergenerationally, in a snowball effect making it difficult for participants to maintain stable lives. Findings explored the tension between participants’ experiences with oppression and the multiple ways they either assimilated or resisted their oppression. New sensitive policies informed by standpoint, intersectionality, and Afrocentric perspectives must be developed to increase the availability of meaningful employment and strengthening impoverished African American communities. PMID:23216440

  16. Good fit or chilly climate: An exploration of the persistence experiences of African-American women graduates of predominantly White college science programs

    NASA Astrophysics Data System (ADS)

    Justin-Johnson, Carolyn

    This qualitative study explored the persistence experiences of African-American women science graduates of a predominantly White institution (PWI). The purpose of the study was to promote a holistic understanding---complementing findings from quantitative studies---of how African-American women give meaning to their collegiate experiences. Eight recent graduates of two college science programs (biological sciences and chemistry) were selected to participate in the study because of their willingness to answer interview questions related to sensitive issues about their experiences. Data analysis included coding transcripts, creating a codebook, memo writing, and constructing a model single-case event-flow network and a conceptually clustered matrix. Participants in the study shared a common viewpoint about the unwelcoming and non-supportive environment that they navigated to persist to graduation. Specifically, they identified a combination of (1) non-supportive mechanisms that could have been deterrents to their persistence and (2) supportive mechanisms that were instrumental in helping them to cope with negative experiences on campus that made them feel "uncomfortable" and alienated as one of the few African-American women in science classes. Findings in this study suggest that it is imperative for predominantly White institutions to organize reform efforts around creating more welcoming and inclusive campus environments, especially in the sciences, for African-American women---thus promoting satisfying college experiences that lead to degree and career attainment.

  17. Improving of electrical channels for magnetotelluric sounding instrumentation

    NASA Astrophysics Data System (ADS)

    Prystai, A. M.; Pronenko, V. O.

    2015-07-01

    The study of the deep structure of the Earth's crust is of great interest for both applied (e.g. mineral exploration) and scientific research. For this the electromagnetic (EM) studies which enable one to construct the distribution of electrical conductivity in the Earth's crust are of great use. The most common method of EM exploration is magnetotelluric sounding (MT). This passive method of research uses a wide range of natural geomagnetic variations as a powerful source of electromagnetic induction in the Earth, producing telluric current variations there. It includes the measurements of variations of natural electric and magnetic fields in orthogonal directions at the surface of the Earth. By this, the measurements of electric fields are much more complicated metrological processes, and, namely, they limit the precision of MT prospecting. This is especially complicated at deep sounding when measurements of long periods are of interest. The increase in the accuracy of the electric field measurement can significantly improve the quality of MT data. Because of this, the development of a new version of an instrument for the measurements of electric fields at MT - both electric field sensors and the electrometer - with higher levels relative to the known instrument parameter level - was initiated. The paper deals with the peculiarities of this development and the results of experimental tests of the new sensors and electrometers included as a unit in the long-period magnetotelluric station LEMI-420 are given.

  18. Dimensionality imprint of electrical anisotropy in magnetotelluric responses

    NASA Astrophysics Data System (ADS)

    Martí, A.; Queralt, P.; Ledo, J.; Farquharson, C.

    2010-10-01

    Dimensionality analysis of magnetotelluric data is a common procedure for inferring the main properties of the geoelectric structures of the subsurface such as the strike direction or the presence of superficial distorting bodies, and enables the most appropriate modeling approach (1D, 2D or 3D) to be determined. Most of the methods currently used assume that the electrical conductivity of individual parts of a structure is isotropic, although some traces of anisotropy in data responses can be recognized. In this paper we investigate the imprints of anisotropic media responses in dimensionality analysis using rotational invariants of the magnetotelluric tensor. We show results for responses generated from 2D synthetic anisotropic models and for field data that have been interpreted as showing the effects of electrical anisotropy in parts of the subsurface structure. As a result of this study we extend the WAL dimensionality criteria to include extra conditions that allow anisotropic media to be distinguished from 2D isotropic ones. The new conditions require the analysis of the strike directions obtained and take into account the overall behavior of different sites in a survey.

  19. Inversion of magnetotelluric data in a sparse model domain

    NASA Astrophysics Data System (ADS)

    Nittinger, Christian G.; Becken, Michael

    2016-08-01

    The inversion of magnetotelluric data into subsurface electrical conductivity poses an ill-posed problem. Smoothing constraints are widely employed to estimate a regularized solution. Here, we present an alternative inversion scheme that estimates a sparse representation of the model in a wavelet basis. The objective of the inversion is to determine the few non-zero wavelet coefficients which are required to fit the data. This approach falls into the class of sparsity constrained inversion schemes and minimizes the combination of the data misfit in a least-squares ℓ2 sense and of a model coefficient norm in an ℓ1 sense (ℓ2-ℓ1 minimization). The ℓ1 coefficient norm renders the solution sparse in a suitable representation such as the multiresolution wavelet basis, but does not impose explicit structural penalties on the model as it is the case for ℓ2 regularization. The presented numerical algorithm solves the mixed ℓ2-ℓ1 norm minimization problem for the nonlinear magnetotelluric inverse problem. We demonstrate the feasibility of our algorithm on synthetic 2-D MT data as well as on a real data example. We found that sparse models can be estimated by inversion and that the spatial distribution of non-vanishing coefficients indicates regions in the model which are resolved.

  20. Magnetotelluric Data, Central Yucca Flat, Nevada Test Site, Nevada

    SciTech Connect

    J.M. Williams; B.D. Rodriguez, and T.H. Asch

    2005-11-23

    Nuclear weapons are integral to the defense of the United States. The U.S. Department of Energy, as the steward of these devices, must continue to gauge the efficacy of the individual weapons. This could be accomplished by occasional testing at the Nevada Test Site (NTS) in Nevada, northwest of Las Vegas. Yucca Flat Basin is one of the testing areas at the NTS. One issue of concern is the nature of the somewhat poorly constrained pre-Tertiary geology and its effects on ground-water flow in the area subsequent to a nuclear test. Ground-water modelers would like to know more about the hydrostratigraphy and geologic structure to support a hydrostratigraphic framework model that is under development for the Yucca Flat Corrective Action Unit (CAU). During 2003, the U.S. Geological Survey (USGS) collected and processed Magnetotelluric (MT) and Audio-magnetotelluric (AMT) data at the Nevada Test Site in and near Yucca Flat to help characterize this pre-Tertiary geology. That work will help to define the character, thickness, and lateral extent of pre-Tertiary confining units. In particular, a major goal has been to define the upper clastic confining unit (UCCU) in the Yucca Flat area. Interpretation will include a three-dimensional (3-D) character analysis and two-dimensional (2-D) resistivity model. The purpose of this report is to release the MT sounding data for Central Yucca Flat, Profile 1, as shown in figure 1. No interpretation of the data is included here.

  1. Magnetotelluric Data, Northern Frenchman Flat, Nevada Test Site Nevada

    SciTech Connect

    J.M. Williams; B.D. Rodriguez, and T. H. Asch

    2005-11-23

    Nuclear weapons are integral to the defense of the United States. The U.S. Department of Energy, as the steward of these devices, must continue to gauge the efficacy of the individual weapons. This could be accomplished by occasional testing at the Nevada Test Site (NTS) in Nevada, northwest of Las Vegas. Yucca Flat Basin is one of the testing areas at the NTS. One issue of concern is the nature of the somewhat poorly constrained pre-Tertiary geology and its effects on ground-water flow in the area subsequent to a nuclear test. Ground-water modelers would like to know more about the hydrostratigraphy and geologic structure to support a hydrostratigraphic framework model that is under development for the Yucca Flat Corrective Action Unit (CAU). During 2003, the U.S. Geological Survey (USGS) collected and processed Magnetotelluric (MT) and Audio-magnetotelluric (AMT) data at the Nevada Test Site in and near Yucca Flat to help characterize this pre-Tertiary geology. That work will help to define the character, thickness, and lateral extent of pre-Tertiary confining units. In particular, a major goal has been to define the upper clastic confining unit (UCCU) in the Yucca Flat area. Interpretation will include a three-dimensional (3-D) character analysis and two-dimensional (2-D) resistivity model. The purpose of this report is to release the MT sounding data for Frenchman Flat Profile 3, as shown in Figure 1. No interpretation of the data is included here.

  2. Magnetotelluric Data, Southern Yucca Flat, Nevada Test Site, Nevada

    SciTech Connect

    J.M. Williams; B.D. Rodriguez, and T.H. Asch

    2005-11-23

    Nuclear weapons are integral to the defense of the United States. The U.S. Department of Energy, as the steward of these devices, must continue to gauge the efficacy of the individual weapons. This could be accomplished by occasional testing at the Nevada Test Site (NTS) in Nevada, northwest of Las Vegas. Yucca Flat Basin is one of the testing areas at the NTS. One issue of concern is the nature of the somewhat poorly constrained pre-Tertiary geology and its effects on ground-water flow in the area subsequent to a nuclear test. Ground-water modelers would like to know more about the hydrostratigraphy and geologic structure to support a hydrostratigraphic framework model that is under development for the Yucca Flat Corrective Action Unit (CAU). During 2003, the U.S. Geological Survey (USGS) collected and processed Magnetotelluric (MT) and Audio-magnetotelluric (AMT) data at the Nevada Test Site in and near Yucca Flat to help characterize this pre-Tertiary geology. That work will help to define the character, thickness, and lateral extent of pre-Tertiary confining units. In particular, a major goal has been to define the upper clastic confining unit (UCCU) in the Yucca Flat area. Interpretation will include a three-dimensional (3-D) character analysis and two-dimensional (2-D) resistivity model. The purpose of this report is to release the MT sounding data for Southern Yucca Flat, Profile 4, as shown in Figure 1. No interpretation of the data is included here.

  3. Inversion of magnetotelluric data in a sparse model domain

    NASA Astrophysics Data System (ADS)

    Nittinger, Christian G.; Becken, Michael

    2016-06-01

    The inversion of magnetotelluric data into subsurface electrical conductivity poses an ill-posed problem. Smoothing constraints are widely employed to estimate a regularized solution. Here, we present an alternative inversion scheme that estimates a sparse representation of the model in a wavelet basis. The objective of the inversion is to determine the few non-zero wavelet coefficients which are required to fit the data. This approach falls into the class of sparsity constrained inversion schemes and minimizes the combination of the data misfit in a least squares ℓ2 sense and of a model coefficient norm in a ℓ1 sense (ℓ2-ℓ1 minimization). The ℓ1 coefficient norm renders the solution sparse in a suitable representation such as the multi-resolution wavelet basis, but does not impose explicit structural penalties on the model as it is the case for ℓ2 regularization. The presented numerical algorithm solves the mixed ℓ2-ℓ1 norm minimization problem for the non-linear magnetotelluric inverse problem. We demonstrate the feasibility of our algorithm on synthetic 2-D MT data as well as on a real data example. We found that sparse models can be estimated by inversion and that the spatial distribution of non-vanishing coefficients indicates regions in the model which are resolved.

  4. Fast and stable two-dimensional inversion of magnetotelluric data

    NASA Astrophysics Data System (ADS)

    de Lugao, Patricia Pastana

    1997-07-01

    The two-dimensional (2-D) magnetotelluric (MT) inverse problem still poses difficult challenges in spite of efforts to develop fast and efficient methods for its solution. In this work, a new approach based on regularization theory and the quasi-analytic calculation of the Frechet derivatives is presented. For the forward solution, a fast and efficient finite difference formulation to the solution of the MT equations in both transverse electric (TE) and transverse magnetic (TM) modes based on the balance method is used. The Frechet derivative matrix is obtained as a solution to simple forward and back substitution of the LU decomposed matrix of coefficients from the forward problem utilizing the principle of reciprocity. The magnetotelluric inverse problem is ill-posed. In order to constrain the solution to a set of acceptable models, Tikhonov regularization is applied based on the minimization of a parametric functional. The regularized cojugate gradient method is then utilized to minimize the parametric functional. Inversion results of a set of synthetic data and of a set of CSAMT data from Kennecott Exploration show that the method is fast, stable and produces geologically reasonable models.

  5. The experiences and coping strategies of United Kingdom-based African women following an HIV diagnosis during pregnancy.

    PubMed

    Treisman, Karen; Jones, Fergal W; Shaw, Elizabeth

    2014-01-01

    A qualitative investigation was conducted to explore the experience of African women living in the United Kingdom after being diagnosed with HIV during pregnancy. Participants (N = 12) completed a demographic questionnaire and participated in one-to-one semi-structured interviews. The interview addressed multiple personal, interpersonal, and systemic issues related to HIV, as well as HIV in the context of motherhood. Data were analyzed using interpretative phenomenological analysis. Themes that emerged included: (a) HIV being part of one's wider tapestry, (b) community and systemic influences and responses to HIV, (c) experiencing a different story of HIV, and (d) the mother-child relationship. Strikingly, the aspect of HIV these women reported finding most distressing was their inability to breastfeed, which seemed central to their cultural identity as mothers. Clinical recommendations and implications are made. PMID:23523367

  6. Undergraduate African American females in the sciences: A qualitative study of student experiences affecting academic success and persistence

    NASA Astrophysics Data System (ADS)

    Essien-Wood, Idara R.

    Given the lack of literature on Undergraduate African American females in the sciences (UAAFS), this study sought to explicate their experiences at one large, predominantly White, Research I institution in the southwestern United States. In particular, the purpose of this study was to identify factors that affect the academic success and persistence of Black females in the natural and physical sciences. Data was collected via in-depth, semi-structured interviews with 15 Black female science majors. Findings from this study identified several supportive mechanisms for academic success: family, religion, teaching assistants and friends. Also identified were seven barriers to academic success: employment, lack of diversity, cultural dissonance, unwelcoming Research I environment, faculty, advisors, classmates, and lab groups. Further, an analysis of students' responses revealed numerous instances of racial and gender micro-aggressions. Recommendations are provided to address factors identified as affecting student academic success and persistence as well as a culture of micro-aggressive behavior.

  7. Traditional Healing, Biomedicine and the Treatment of HIV/AIDS: Contrasting South African and Native American Experiences

    PubMed Central

    Flint, Adrian

    2015-01-01

    Traditional healing remains an important aspect of many people’s engagement with healthcare and, in this, responses to the treatment of HIV/AIDS are no different. However, given the gravity of the global HIV/AIDS pandemic, there has been much debate as to the value of traditional healing in this respect. Accordingly, this paper explores the extent to which meaningful accommodation between the biomedical and traditional sectors is possible (and/or even desirable). It does this through a consideration of Native American and South African experiences, looking at how the respective groups, in which medical pluralism is common, have addressed the issue of HIV/AIDS. The paper points to the importance of developing “culturally appropriate” forms of treatment that emphasise complementary rather than adversarial engagement between the traditional and biomedical systems and how policymakers can best facilitate this. PMID:25903057

  8. "We're Here Because We're Black": The Schooling Experiences of French-Speaking African-Canadian Students with Refugee Backgrounds

    ERIC Educational Resources Information Center

    Schroeter, Sara; James, Carl E.

    2015-01-01

    This article discusses the educational experiences of a group of French-speaking Black African-born students who entered Canada as refugees. They were attending a French school and were placed in a separate programme that was designed to meet their particular needs given their limited language skills and level of education. Drawing on critical…

  9. Low-Income African-American Caregivers' Experiences of Being Referred to Mental Health Services by the School Counselor: Implications for Best Practices

    ERIC Educational Resources Information Center

    Tucker, Catherine

    2009-01-01

    Referring students for mental health care is a core job function for school counselors, and one that is often stressful for all parties involved. In this phenomenological study, six low-income African-American caregivers were interviewed about their experiences of having a son or grandson referred for mental health care by the school counselor.…

  10. The Role of Race, Racism and Power in the Experiences and Perspectives of African American Males in the Context of Their Ascendence to the Superintendency

    ERIC Educational Resources Information Center

    George, Hughes B.

    2011-01-01

    Using the lens of Critical Race Theory, I present the experiences and perspectives of African American male superintendents in the context of their ascension to the superintendency. Participants in the study are chief executive officers of a school district. The primary question of this study is what are the contributing factors, particularly the…

  11. Life Experiences of People Who Stutter, and the Perceived Impact of Stuttering on Quality of Life: Personal Accounts of South African Individuals

    ERIC Educational Resources Information Center

    Klompas, Michelle; Ross, Eleanor

    2004-01-01

    The purpose of the study was to investigate the life experiences of a group of South African adults who stutter and the impact of stuttering on their quality of life. Participants were 16 adults with a mean age of 28.9 and ranging from 20 to 59 years. Methods involved individual interviews designed to explore the life domains of education; social…

  12. The Everyday Mathematical Experiences and Understandings of Three, 4-Year-Old, African-American Children from Working-Class Backgrounds

    ERIC Educational Resources Information Center

    Benigno, Grace Marie R.

    2012-01-01

    This qualitative study examined the everyday mathematical experiences and understandings of three, 4-year-old, African-American children from working-class backgrounds. The study drew on Street, Baker, and Tomlin's (2005) broad, ideological model of mathematics as "social" and their analytic concepts of mathematical events (units of…

  13. Rapid population growth and fragile environments: the sub-Saharan African and south Asian experience.

    PubMed

    Caldwell, J C; Caldwell, P

    1994-02-18

    Case studies of the world's two poorest regions, sub-Saharan Africa and South Asia, were used to illustrate the compromised standard of living of the poor and environmental damage due to continued rapid population growth. The conclusion was that the livelihoods of the poor should not be endangered for preserving the living standards of richer people. Nations must not ignore the challenges of reducing population growth as fast as can be achieved. The transitional period over the next 50 years is the main concern, because population growth rates will be slowing. Rural population growth is expected to decline from 60% of total population growth in South Asia to 7% between 2000 and 2025; similarly the decline in sub-Saharan Africa would be from 50% to 15%. Over the past 30 years, food production in South Asia has kept pace with population growth. Sub-Saharan Africa has adopted food importation to meet demand. African problems are a low resource base, faster population growth, and the fact that governments and individuals are too poor to maintain soil fertility. Long-term studies of how much soil depletion will occur are not available for these regions, and local area studies are not as pessimistic. Transition policies are needed to put "people first in terms of engineered or directed population and ecological change." The six main issues are the following: 1) the Brundtland Commission appropriately identified poverty as the main cause and effect of environmental degradation because of the threat to survival; 2) the verdict is still out about whether food production will keep pace with population growth through economic growth and investment in agriculture; 3) empirical research is needed to examine local social and regulatory institutions and the possibility of reinforcing these mechanisms rather than instituting central controls; 4) central coercion or modernizing economic policies can destroy local level controls; 5) famine is a complex ecological phenomenon and the

  14. The Electrical Structure of Upper Mantle Beneath 70Ma Pacific Seafloor Constrained by Seafloor Magnetotelluric Data

    NASA Astrophysics Data System (ADS)

    Tursack, E. K.; Evans, R. L.; Elsenbeck, J.; Lizarralde, D.; Collins, J. A.; Gaherty, J. B.; Hirth, G.

    2013-12-01

    The NOMELT experiment focused on understanding the structure of 70Ma oceanic lithosphere and underlying asthenosphere. The experiment used a combination of seismic and magnetotelluric (MT) techniques to image the lithosphere-asthenosphere boundary (LAB) and determine if partial melt is present beneath the lithosphere, or if another mechanism is responsible for the transition between lithosphere and asthenosphere at this intermediate plate age. We inverted the seafloor MT data from 4 stations to constrain the electrical structure of the LAB. We conducted two-dimensional regularized isotropic and anisotropic inversions. The resulting electrical resistivity model was then averaged into a one-dimensional profile and compared with data from the Marianas subduction zone [1], the Phillipine Sea [2], the MELT Experiment at 17°S on the EPR [3], and the Middle America Trench [4]. The preferred electrical resistivity model for the NOMELT region is isotropic and does not contain a highly conductive layer under the 70-80 km thick resistive lithosphere. This lack of a conductive layer suggests that partial melt is not present in a well-connected network within the lithosphere-asthenosphere boundary of 70Ma oceanic plate, in contrast to other regions [2, 4]. The lack of anisotropy within the upper asthenosphere is also in contrast to previous electromagnetic studies of oceanic settings that invoked a more hydrous asthenosphere [3, 5]. [1] Matsuno T, N Seama, RL Evans, AD Chave, K Baba, A White, T Goto, G Heinson, G Boren, A Yoneda, H Utada (2010) Upper mantle electrical resistivity structure beneath the central Mariana subduction system. Geochem. Geophys. Geosys., 11: Q09003, doi:10.1029/2010GC003101. [2] Baba K, H Utada, T Goto, T Kasaya, H Shimizu, N Tada (2010) Electrical conductivity imagine of the Philippine Sea upper mantle using seafloor magnetotelluric data. Phys. Earth and Planet. Int. 183: 44-62. [3] Evans RL, G Hirth, K Baba, D Forsyth, A Chave, R Mackie (2005

  15. The Subjective Experience of Social Class and Upward Mobility Among African American Men in Graduate School

    PubMed Central

    Sánchez, Francisco J.; Liu, William Ming; Leathers, Leslie; Goins, Joyce; Vilain, Eric

    2011-01-01

    We used Consensual Qualitative Research Methodology to analyze responses from 14 African American men (MdnAge = 25 years-old) in graduate school at a predominantly-White university in the Midwestern region of the United Sates regarding how they acquired awareness of their social-class status; how social class was related to their sense of masculinity; how social class was related to race and skin tone; and the role that education and a romantic partner could play in upward mobility. School peers were the main source for their early awareness of social class. Many believed that discrimination maintains social class stratification that disadvantages racial minorities and that one's race will always trump any personal characteristics—including having light-complected skin and an advanced degree. Finally many overcame several obstacles during their educational career, and most believed that a romantic relationship with a woman from a privileged background could facilitate upward mobility. Psychological scientists and practitioners are encouraged to consider the role that social class plays when examining men's well-being. PMID:22058659

  16. Factors affecting student success in a first-year mathematics course: a South African experience

    NASA Astrophysics Data System (ADS)

    Kizito, Rita; Munyakazi, Justin; Basuayi, Clement

    2016-01-01

    In spite of sustained efforts tertiary institutions implement to try and improve student academic performance, the number of students succeeding in first-year mathematics courses remains disturbingly low. For most students, the gap between their mathematical capability and the competencies they are expected and need to develop to function effectively in these courses persists even after course instruction. In this study, an instrument for identifying and examining factors affecting student performance and success in a first-year Mathematics university course was developed and administered to 86 students. The overall Cronbach's Alpha coefficient for the questionnaire was found to be 0.916. Having identified variables from prior research known to affect student performance, factor analysis was used to identify variables exhibiting the greatest impact on student performance. The variables included prior academic knowledge, workload, student approaches to learning, assessment, student support teaching quality, methods and resources. From the analysis, students' perceptions of their workload emerged as the factor having the greatest impact on student's performance, followed by the matriculation examination score. The findings are discussed and strategies that can be used to improve teaching and contribute to student success in a first-year mathematics course in a South African context are presented.

  17. Do experiences of racial discrimination predict cardiovascular disease among African American Men? The moderating role of internalized negative racial group attitudes

    PubMed Central

    Lincoln, Karen D; Adler, Nancy E; Syme, S. Leonard

    2010-01-01

    Studies examining associations between racial discrimination and cardiovascular health outcomes have been inconsistent, with some studies finding the highest risk of hypertension among African Americans who report no discrimination. A potential explanation of the latter is that hypertension and other cardiovascular problems are fostered by internalization and denial of racial discrimination. To explore this hypothesis, the current study examines the role of internalized negative racial group attitudes in linking experiences of racial discrimination and history of cardiovascular disease among African American men. We predicted a significant interaction between reported discrimination and internalized negative racial group attitudes in predicting cardiovascular disease. Weighted logistic regression analyses were conducted among 1216 African American men from the National Survey of American Life (NSAL; 2001– 2003). We found no main effect of racial discrimination in predicting history of cardiovascular disease. However, agreeing with negative beliefs about Blacks was positively associated with cardiovascular disease history, and also moderated the effect of racial discrimination. Reporting racial discrimination was associated with higher risk of cardiovascular disease among African American men who disagreed with negative beliefs about Blacks. However, among African American men who endorsed negative beliefs about Blacks, the risk of cardiovascular disease was greatest among those reporting no discrimination. Findings suggest that racial discrimination and the internalization of negative racial group attitudes are both risk factors for cardiovascular disease among African American men. Furthermore, the combination of internalizing negative beliefs about Blacks and the absence of reported racial discrimination appear to be associated with particularly poor cardiovascular health. Steps to address racial discrimination as well as programs aimed at developing a positive

  18. Terrain effects in resistivity and magnetotelluric surveys

    SciTech Connect

    Holcombe, H.T.

    1982-12-01

    A three-dimensional finite element computer algorithm which can accommodate arbitrarily complex topography and subsurface structure, has been developed to model the resistivity response of the earth. The algorithm has undergone extensive evaluation and is believed to provide accurate results for realistic earth models. Testing included comparison to scale model measurements, analytically calculated solutions, and results calculated numerically by other independent means. Computer modeling experiments have demonstrated that it is possible to remove the effect of topography on resistivity data under conditions where such effects dominate the response. This can be done without resorting to lengthy and costly trial and error computer modeling. After correction, the data can be interpreted with confidence that the anomalies are due only to subsurface structure. The results of case studies on resistivity field data measured in high relief topography are discussed.

  19. Overview of the Dust and Biomass-burning Experiment and African Monsoon Multidisciplinary Analysis Special Observing Period-0

    NASA Astrophysics Data System (ADS)

    Haywood, J. M.; Pelon, J.; Formenti, P.; Bharmal, N.; Brooks, M.; Capes, G.; Chazette, P.; Chou, C.; Christopher, S.; Coe, H.; Cuesta, J.; Derimian, Y.; Desboeufs, K.; Greed, G.; Harrison, M.; Heese, B.; Highwood, E. J.; Johnson, B.; Mallet, M.; Marticorena, B.; Marsham, J.; Milton, S.; Myhre, G.; Osborne, S. R.; Parker, D. J.; Rajot, J.-L.; Schulz, M.; Slingo, A.; Tanré, D.; Tulet, P.

    2008-12-01

    The African Monsoon Multidisciplinary Analysis (AMMA) is a major international campaign investigating far-reaching aspects of the African monsoon, climate and the hydrological cycle. A special observing period was established for the dry season (SOP0) with a focus on aerosol and radiation measurements. SOP0 took place during January and February 2006 and involved several ground-based measurement sites across west Africa. These were augmented by aircraft measurements made by the Facility for Airborne Atmospheric Measurements (FAAM) aircraft during the Dust and Biomass-burning Experiment (DABEX), measurements from an ultralight aircraft, and dedicated modeling efforts. We provide an overview of these measurement and modeling studies together with an analysis of the meteorological conditions that determined the aerosol transport and link the results together to provide a balanced synthesis. The biomass burning aerosol was significantly more absorbing than that measured in other areas and, unlike industrial areas, the ratio of excess carbon monoxide to organic carbon was invariant, which may be owing to interaction between the organic carbon and mineral dust aerosol. The mineral dust aerosol in situ filter measurements close to Niamey reveals very little absorption, while other measurements and remote sensing inversions suggest significantly more absorption. The influence of both mineral dust and biomass burning aerosol on the radiation budget is significant throughout the period, implying that meteorological models should include their radiative effects for accurate weather forecasts and climate simulations. Generally, the operational meteorological models that simulate the production and transport of mineral dust show skill at lead times of 5 days or more. Climate models that need to accurately simulate the vertical profiles of both anthropogenic and natural aerosols to accurately represent the direct and indirect effects of aerosols appear to do a reasonable job

  20. Unwanted sexual experiences among young men in four sub-Saharan African countries: prevalence and context.

    PubMed

    Moore, Ann M; Madise, Nyovani; Awusabo-Asare, Kofi

    2012-10-01

    Unwanted sexual experiences are most frequently examined from the woman's perspective, yet these experiences happen to men as well. Part of the reason for the paucity of studies on coerced sexual experiences among men is the difficulty in gathering information about such experiences. This study examines the prevalence of unwanted sexual experiences at sexual debut as well as ever among young men aged 12-19 years old in Burkina Faso, Ghana, Malawi and Uganda. The data come from nationally-representative surveys and in-depth interviews with approximately 50 young men in each country gathered around 2004. Between 4 and 12% of young men stated that they were 'not willing at all' at sexual debut and between 3 and 6% said that they had ever experienced unwanted sex. Narratives from in-depth interviews give insights into the context surrounding men's unwanted sexual experiences. The sometimes conflicting information provided by the respondents serve to confound rather than illuminate the contexts within which these unwanted sexual experiences occurred, demonstrating that coercion for young men looks extremely different than coercion for young women, spurring us to improve our measures of sexual coercion among men. PMID:22943657

  1. A new magnetotelluric inversion scheme using generalized RRI method

    NASA Astrophysics Data System (ADS)

    Yamane, Kazunobu; Takasugi, Shinji; Lee, Ki Ha

    1996-09-01

    A new two-dimensional (2-D) magnetotelluric (MT) inversion scheme is proposed in this paper. This scheme is based on a locally 2-D analysis in order to minimize computational time and computer memory. The MT governing equation is linearized in terms of the magnetic field and electrical conductivity for the perturbation analysis. The perturbed equation is then multiplied by a test function and integrated over the cross-section. Integrating by parts and then substituting this test function with local magnetic fields, a new equation is obtained that is a 2-D variational integral for the electrical conductivity. The new equation is general in the sense that it can explicitly include the horizontal derivative of the magnetic field. If the horizontal derivative term is eliminated, the new equation becomes identical to the Rapid Relaxation Inversion (RRI) scheme proposed by Smith and Booker (J. Geophys. Res., 96: 3905-3922, 1991).

  2. Magnetotelluric inversion via reverse time migration algorithm of seismic data

    SciTech Connect

    Ha, Taeyoung . E-mail: tyha@math.snu.ac.kr; Shin, Changsoo . E-mail: css@model.snu.ac.kr

    2007-07-01

    We propose a new algorithm for two-dimensional magnetotelluric (MT) inversion. Our algorithm is an MT inversion based on the steepest descent method, borrowed from the backpropagation technique of seismic inversion or reverse time migration, introduced in the middle 1980s by Lailly and Tarantola. The steepest descent direction can be calculated efficiently by using the symmetry of numerical Green's function derived from a mixed finite element method proposed by Nedelec for Maxwell's equation, without calculating the Jacobian matrix explicitly. We construct three different objective functions by taking the logarithm of the complex apparent resistivity as introduced in the recent waveform inversion algorithm by Shin and Min. These objective functions can be naturally separated into amplitude inversion, phase inversion and simultaneous inversion. We demonstrate our algorithm by showing three inversion results for synthetic data.

  3. Tackling the African “poverty trap”: The Ijebu-Ode experiment

    PubMed Central

    Mabogunje, Akin L.

    2007-01-01

    An experiment in poverty reduction began in 1998 in the city of Ijebu-Ode, Nigeria (estimated 1999 population 163,000), where, without the remittances from relatives abroad, an estimated 90% of the population lived below the poverty line of $1.00 (U.S.) per person per day. Central to the experiment was whether poverty can be dramatically reduced through a city consultation process that seeks to mobilize the entire community along with its diaspora. With 7 years of experience, the Ijebu-Ode experiment has been successful in many ways. There is increasing evidence that poverty in the city has been reduced significantly through the microfinancing of existing and new productive activities and the estimated >8,000 jobs these activities have created. Training based on both sustainability science and technology and indigenous practitioner knowledge has been a critical factor in the establishment of cooperatives and the development of new enterprises in specialty crops, small animal, and fish production. Much of this success has been possible as a result of harnessing social capital, especially through the dynamic leadership of the traditional authorities of the city and by the provision of ample loanable funds through the National Poverty Eradication Program of the federal government. The city consultation process itself engendered a participatory focus to the experiment from the beginning and has encouraged sustainabaility. Yet long-term sustainability is still in question as the initial leadership needs replacement, and credit, the heart of the experiment, lacks sufficient collateral. PMID:17942687

  4. Crustal structure beneath southern Norway imaged by magnetotellurics

    NASA Astrophysics Data System (ADS)

    Cherevatova, M.; Smirnov, M.; Korja, T.; Kaikkonen, P.; Pedersen, L. B.; Hübert, J.; Kamm, J.; Kalscheuer, T.

    2014-07-01

    We use data from two magnetotelluric profiles, ToSca10 and ToSca'09, over the Scandinavian Mountains to study the crustal structure in southern Norway. The profiles cross the major tectonic structures of the Caledonian orogen as well as the western margin of the Precambrian Baltica. Dimensionality and strike analyses indicate generally 3-D behavior of the data. However, the majority of the used data distinguishes a preferable strike direction, which is supported by the geology of the region. Hence, we employ 2-D inversion and choose to invert the determinant of the impedance tensor to mitigate 3-D effects in the data on our 2-D models. Magnetotelluric data from both profiles are inverted using a damped least squares solution based on a singular value decomposition. We improved the solution by defining the inverse model covariance matrix through gradient or Laplacian smoothing operators. The two-dimensional inversion models of the ToSca'09 and ToSca'10 field data from southern Norway derived from the damped least squares scheme with the Laplacian inverse model covariance matrix are presented. Resistive rocks, extending to the surface, image the autochthonous Southwest Scandinavian Domain and the allochthonous Western Gneiss Region. Near-surface conductors, which are located between the resistive Caledonian nappes and Precambrian basement, delineate highly conductive shallow-sea sediments, so called alum shales. They exhibit a decollement along which the Caledonian nappes were overthrust. A deeper, upper to mid-crustal conducting layer in the Southwest Scandinavian Domain may depict the remnants of closed ocean basins formed during the accretions and collisions of various Sveconorwegian terranes. In ToSca'10, the Caledonian nappes, the conducting alum shales and the deeper conductor are terminated in the west by the Faltungsgraben shear complex which represents a crustal scale boundary between the Western Gneiss Region in the west and the Southwest Scandinavian

  5. Magnetotelluric Data, North Central Yucca Flat, Nevada Test Site, Nevada

    SciTech Connect

    J.M. Williams; B.D. Rodriguez, and T.H. Asch

    2005-11-23

    Nuclear weapons are integral to the defense of the United States. The U.S. Department of Energy, as the steward of these devices, must continue to gauge the efficacy of the individual weapons. This could be accomplished by occasional testing at the Nevada Test Site (NTS) in Nevada, northwest of Las Vegas. Yucca Flat Basin is one of the testing areas at the NTS. One issue of concern is the nature of the somewhat poorly constrained pre-Tertiary geology and its effects on ground-water flow in the area subsequent to a nuclear test. Ground-water modelers would like to know more about the hydrostratigraphy and geologic structure to support a hydrostratigraphic framework model that is under development for the Yucca Flat Corrective Action Unit (CAU). During 2003, the U.S. Geological Survey (USGS) collected and processed Magnetotelluric (MT) and Audio-magnetotelluric (AMT) data at the Nevada Test Site in and near Yucca Flat to help characterize this pre-Tertiary geology. That work will help to define the character, thickness, and lateral extent of pre-Tertiary confining units. In particular, a major goal has been to define the upper clastic confining unit (UCCU) in the Yucca Flat area. Interpretation will include a three-dimensional (3-D) character analysis and two-dimensional (2-D) resistivity model. The purpose of this report is to release the MT sounding data for north central Yucca Flat, Profile 7, as shown in Figure 1. No interpretation of the data is included here.

  6. Magnetotelluric Data, Northern Yucca Flat, Nevada Test Site, Nevada

    SciTech Connect

    J.M. Williams; B.D. Rodriguez, and T.H. Asch

    2005-11-23

    Nuclear weapons are integral to the defense of the United States. The U.S. Department of Energy, as the steward of these devices, must continue to gauge the efficacy of the individual weapons. This could be accomplished by occasional testing at the Nevada Test Site (NTS) in Nevada, northwest of Las Vegas. Yucca Flat Basin is one of the testing areas at the NTS. One issue of concern is the nature of the somewhat poorly constrained pre-Tertiary geology and its effects on ground-water flow in the area subsequent to a nuclear test. Ground-water modelers would like to know more about the hydrostratigraphy and geologic structure to support a hydrostratigraphic framework model that is under development for the Yucca Flat Corrective Action Unit (CAU). During 2003, the U.S. Geological Survey (USGS) collected and processed Magnetotelluric (MT) and Audio-magnetotelluric (AMT) data at the Nevada Test Site in and near Yucca Flat to help characterize this pre-Tertiary geology. That work will help to define the character, thickness, and lateral extent of pre-Tertiary confining units. In particular, a major goal has been to define the upper clastic confining unit (UCCU) in the Yucca Flat area. Interpretation will include a three-dimensional (3-D) character analysis and two-dimensional (2-D) resistivity model. The purpose of this report is to release the MT sounding data for Profile 2, (fig. 1), located in the northern Yucca Flat area. No interpretation of the data is included here.

  7. Magnetotelluric Data, Across Quartzite Ridge, Nevada Test Site, Nevada

    SciTech Connect

    J.M. Williams; B.D. Rodriguez, and T.H. Asch

    2005-11-23

    Nuclear weapons are integral to the defense of the United States. The U.S. Department of Energy, as the steward of these devices, must continue to gauge the efficacy of the individual weapons. This could be accomplished by occasional testing at the Nevada Test Site (NTS) in Nevada, northwest of Las Vegas. Yucca Flat Basin is one of the testing areas at the NTS. One issue of concern is the nature of the somewhat poorly constrained pre-Tertiary geology and its effects on ground-water flow in the area subsequent to a nuclear test. Ground-water modelers would like to know more about the hydrostratigraphy and geologic structure to support a hydrostratigraphic framework model that is under development for the Yucca Flat Corrective Action Unit (CAU). During 2003, the U.S. Geological Survey (USGS) collected and processed Magnetotelluric (MT) and Audio-magnetotelluric (AMT) data at the Nevada Test Site in and near Yucca Flat to help characterize this pre-Tertiary geology. That work will help to define the character, thickness, and lateral extent of pre-Tertiary confining units. In particular, a major goal has been to define the upper clastic confining unit (UCCU) in the Yucca Flat area. Interpretation will include a three-dimensional (3-D) character analysis and two-dimensional (2-D) resistivity model. The purpose of this report is to release the MT soundings across Quartzite Ridge, Profiles 5, 6a, and 6b, as shown in Figure 1. No interpretation of the data is included here.

  8. A magnetotelluric model of the Mana Pools basin, northern Zimbabwe

    NASA Astrophysics Data System (ADS)

    Bailey, D.; Whaler, K. A.; Zengeni, T.; Jones, P. C.; Gwavava, O.

    2000-05-01

    The Mana Pools sedimentary basin lies within the Zambezi mobile belt in northern Zimbabwe. New and preexisting magnetotelluric data and the available seismic reflection data are used to constrain the basin structure and the depth to the electrical basement. Long-period magnetotelluric (LMT) data were collected at five stations along a 60 km north-south profile across the Mana Pools basin and onto the southern escarpment. These data augment an existing audiofrequency (AMT) data set from 11 sites in the same area. The subsurface apparent resistivities measured at periods sampling the basin are very low (a few Ωm). After processing both data sets, the estimated impedance tensor is decomposed, showing that the resistivity structure of the Mana Pools basin can be modeled two dimensionally. The ρ+ algorithm is used to show that there is no systematic offset in magnitude between the AMT and LMT data sets before they are combined. Minimum structure resistivity models of the Mana Pools basin compare well with the information from reflection seismic data and support its previous description as a half graben basin of ˜7 km depth. The excellent conductor in the Mana Pools basin is quite different to those seen elsewhere in the orogenic belt in that it is a feature of the sedimentary fill rather than the basement. The resistivity of the basement is low but no localized good conductor is observed; these low resistivities may result from a high degree of either chemical or tectonic alteration to the underlying rocks due to metamorphic processes and tectonic disruption during rift formation.

  9. Magnetotelluric array data analysis from north-west Fennoscandia

    NASA Astrophysics Data System (ADS)

    Cherevatova, M.; Smirnov, M. Yu.; Jones, A. G.; Pedersen, L. B.; Becken, M.; Biolik, M.; Cherevatova, M.; Ebbing, J.; Gradmann, S.; Gurk, M.; Hübert, J.; Jones, A. G.; Junge, A.; Kamm, J.; Korja, T.; Lahti, I.; Löwer, A.; Nittinger, C.; Pedersen, L. B.; Savvaidis, A.; Smirnov, M.

    2015-06-01

    New magnetotelluric (MT) data in north-west Fennoscandia were acquired within the framework of the project "Magnetotellurics in the Scandes" (MaSca). The project focuses on the investigation of the crustal and upper mantle lithospheric structure in the transition zone from stable Precambrian cratonic interior to passive continental margin beneath the Caledonian orogen and the Scandinavian Mountains in western Fennoscandia. An array of 59 synchronous long period and 220 broad-band MT sites was occupied in the summers of 2011 to 2013. We estimated MT transfer functions in the period range from 0.003 to 105 s. The Q-function multi-site multi-frequency analysis and the phase tensor were used to estimate strike and dimensionality of MT data. Dimensionality and strike analyses indicate generally 2-D behaviour of the data with 3-D effects at some sites and period bands. In this paper we present 2-D inversion of the data, 3-D inversion models are shown in the parallel paper. We choose to invert the determinant of the impedance tensor to mitigate 3-D effects in the data on our 2-D models. Seven crustal-scale and four lithospheric-scale 2-D models are presented. The resistive regions are images of the Archaean and Proterozoic basement in the east and thin Caledonian nappes in the west. The middle and lower crust of the Svecofennian province is conductive. The southern end of the Kittilä Greenstone Belt is seen in the models as a strong upper to middle crustal conductor. In the Caledonides, the highly conductive alum shales are observed along the Caledonian Thrust Front. The thickest lithosphere is in the Palaeoproterozioc Svecofennian Domain, not in the Archaean. The thickness of the lithosphere is around 200 km in the north and 300 km in the south-west.

  10. A new method to compensate for bias in magnetotellurics

    NASA Astrophysics Data System (ADS)

    Müller, A.

    2000-07-01

    Error estimates from statistical regression analysis are often obviously too small, leading to doubts about the given equations, the statistical method itself and finally, with resignation, to the conclusion that mathematical equations and reality never agree. However, for magnetotelluric data we have found an almost perfect fit between observed scattering and predicted confidence limits of regression coefficients after accounting for a systematic error-the bias. Different methods to compensate for bias in magnetotelluric impedance estimation have been described using additional data from a reference station. However, sufficiently accurate reference data are often not available. A new method has been developed that enables bias compensation without additional data. For the new method we derive a linear relationship between the effect of bias and an expression depending on the data fit. From this we extrapolate the solution for the unbiased impedance. The new method assumes a special model of uncorrelated noise as well as an approximation for the structure of the impedance tensor. From each pair of components of the unrotated impedance tensor corresponding to the same output channel, one of the pair can be compensated if its magnitude is large compared to that of the other. The method has been successfully applied in many cases. We claim that the solution is closer to the true impedance than any solution based on the selection of events. It gives a measure of the partitioning of noise between the electric and magnetic channels. We applied the method to measurements from the North Anatolian Fault Zone (Turkey) and from the Merapi volcano (Central Java) in the period range 10-2500s. Different instrumentation was used for the two sets of measurements, but in both cases we used fluxgate magnetometers to measure the magnetic variations.

  11. A practical, low-noise coil system for magnetotellurics

    USGS Publications Warehouse

    Stanley, William D.; Tinkler, Richard D.

    1983-01-01

    Magnetotellurics is a geophysical technique which was developed by Cagnaird (1953) and Tikhonov (1950) and later refined by other scientists worldwide. The technique is a method of electromagnetic sounding of the Earth and is based upon the skin depth effect in conductive media. The electric and magnetic fields arising from natural sources are measured at the surface of the earth over broad frequency bands. An excellent review of the technique is provided in the paper by Vozoff (1972). The sources of the natural fields are found in two basic mechanisms. At frequencies above a few hertz, most of the energy arises from lightning in thunderstorm belts around the equatorial regions. This energy is propagated in a wave-guide formed by the earthionospheric cavity. Energy levels are higher at fundamental modes for this cavity, but sufficient energy exists over most of the audio range to be useful for sounding at these frequencies, in which case the technique is generally referred to as audio-magnetotellurics or AMT. At frequencies lower than audio, and in general below 1 Hz, the source of naturally occuring electromagnetic energy is found in ionospheric currents. Current systems flowing in the ionosphere generate EM waves which can be used in sounding of the earth. These fields generate a relatively complete spectrum of electromagnetic energy that extends from around 1 Hz to periods of one day. Figure 1 shows an amplitude spectrum characteristic of both the ionospheric and lightning sources, covering a frequency range from 0.0001 Hz to 1000 Hz. It can be seen that there is a minimum in signal levels that occurs at about 1 Hz, in the gap between the two sources, and that signal level increases with a decrease in frequency.

  12. A Grounded Theory of the College Experiences of African American Males in Black Greek-Letter Organizations

    ERIC Educational Resources Information Center

    Ford, David Julius, Jr.

    2014-01-01

    Studies have shown that involvement in a student organization can improve the academic and psychosocial outcomes of African American male students (Harper, 2006b; Robertson & Mason, 2008; Williams & Justice, 2010). Further, Harper, Byars, and Jelke (2005) stated that African American fraternities and sororities (i.e., Black Greek-letter…

  13. Understanding the Relationships and Experiences That Contribute to African Americans' Decision to Enroll in Doctoral Education

    ERIC Educational Resources Information Center

    McCallum, Carmen Michelle

    2012-01-01

    African Americans have made great advancements in postsecondary education. Over the last thirty years, enrollment and degree attainment has increased over 65% at undergraduate and graduate degree levels (National Center for Education Statistics, 2008). Yet despite these gains, African Americans continue to severely trail behind other racial and…

  14. Experiences of Reentry and Nontraditional African American Women and Their Support Networks: A Journey in Pursuit of a College Degree

    ERIC Educational Resources Information Center

    Denson, Janet L.

    2010-01-01

    This research study reports the findings of how support networks impact the success of African American women in completing their college degree. A phenomenological research methodology of 10 African American women participants of in-depth face-to-face interviews was used to collect the data. Fifty percent of the women completed their degree and…

  15. Cultural Self Meets Cultural Other in the African American Experience: Teachers' Responses to a Curriculum Content Reform.

    ERIC Educational Resources Information Center

    Shujaa, Mwalimu J.

    1995-01-01

    Discusses certain complexities of personal transformation among people implementing African and African American curriculum content reform in the Buffalo (New York) public schools, highlighting individual teachers' understanding of and responses to the reform and noting that attitudes about their own and other people's ethnicity proved important…

  16. Exploring the Lived Experiences of African American and White Female Faculty toward Tenure-Granting and Promotion Processes

    ERIC Educational Resources Information Center

    Oliver, Ralphilia C.

    2010-01-01

    Purpose:The purpose of this study was to explore African American and White female faculty members' perceptions about tenure and promotion processes at research universities. As more women enter the ranks of academia, the difficulties encountered toward attainment of tenure continue to prevail, specifically for African American women. It is hoped…

  17. Religion and Spirituality in the Meaning-Making and Coping Experiences of African American Women: A Qualitative Analysis

    ERIC Educational Resources Information Center

    Mattis, Jacqueline S.

    2002-01-01

    This qualitative study examines the ways in which African American women use religion/spirituality to cope and to construct meaning in times of adversity. Content analysis of the narratives of a sample of African American women respondents (n = 23) revealed a set of eight nonoverlapping themes that explicate religiosity/spirituality's role in…

  18. The Black Body as a Counterspace: The Experiences of African American Students at a Predominantly White Institution

    ERIC Educational Resources Information Center

    Jones-Malone, Dionne LaShell

    2011-01-01

    This qualitative study examines the use of counterspaces by eight upperclassman African American students at a predominantly White institution. This study sought to identify how counterspaces were used by African American students and how those counterspaces foster a sense of belonging for students. Field observations and semi-structured, in-depth…

  19. Behind the Miracle: Emerging Insights from South African Business Leadership Experiences

    ERIC Educational Resources Information Center

    Lynham, Susan A.; Taylor, Robert K.; Dooley, Larry M.

    2005-01-01

    The decade preceding the end of apartheid in South Africa (SA) represents a period of remarkable national leadership, and atypical business leadership. Insights from these extraordinary business leadership experiences largely remain in the form of uncaptured oral histories. Yet they are inspiring stories of practices and principles of truly…

  20. Racial Ideological Beliefs and Racial Discrimination Experiences as Predictors of Academic Engagement among African American Adolescents

    ERIC Educational Resources Information Center

    Smalls, Ciara; White, Rhonda; Chavous, Tabbye; Sellers, Robert

    2007-01-01

    Adolescents' understandings of their social identities and related personal experiences influence their adaptations and responses within domains in which those identities are salient. The authors explore associations of racial identity beliefs regarding how Blacks should act, think, and behave (racial ideologies) and racial discrimination…

  1. Predicting Substance Use Behavior among South African Adolescents: The Role of Leisure Experiences across Time

    ERIC Educational Resources Information Center

    Sharp, Erin Hiley; Coffman, Donna L.; Caldwell, Linda L.; Smith, Edward A.; Wegner, Lisa; Vergnani, Tania; Mathews, Catherine

    2011-01-01

    Using seven waves of data, collected twice a year from the 8th through the 11th grades in a low-resource community in Cape Town, South Africa, we aimed to describe the developmental trends in three specific leisure experiences (leisure boredom, new leisure interests, and healthy leisure) and substance use (cigarettes, alcohol, and marijuana)…

  2. Experiences of forced sex among female patrons of alcohol-serving venues in a South African township

    PubMed Central

    Watt, Melissa H.; Sikkema, Kathleen J.; Abler, Laurie; Velloza, Jennifer; Eaton, Lisa A.; Kalichman, Seth C.; Skinner, Donald; Pieterse, Desiree

    2014-01-01

    South Africa has among the highest rates of forced sex worldwide, and alcohol use has consistently been associated with risk of forced sex in South Africa. However, methodological challenges impact the accuracy of forced sex measurements. This study explored the assessment of forced sex among South African women attending alcohol-serving venues and identified factors associated with reporting recent forced sex. Women (n=785) were recruited from 12 alcohol-serving venues in a peri-urban township in Cape Town. Brief self-administered surveys included questions about lifetime and recent experiences of forced sex. Surveys included a single question about forced sex and detailed questions about sex by physical force, threats, verbal persuasion, trickery, and spiked drinks. We first compared the single question about forced sex to a composite variable of forced sex as unwanted sex by physical force, threats or spiked drinks. We then examined potential predictors of recent forced sex (demographics, drinking behavior, relationship to the venue, abuse experiences). The single question about forced sex had low sensitivity (0.38); over half of the respondents who reported on the detailed questions that they had experienced forced sex by physical force, threats or spiked drinks reported on the single question item that they had not experienced forced sex. Using our composite variable, 18.6% of women reported lifetime and 10.8% reported recent experiences of forced sex. In our adjusted logistic regression model, recent forced sex using the composite variable was significantly associated with hazardous drinking (OR=1.92), living farther from the venue (OR=1.81), recent intimate partner violence (OR=2.53), and a history of childhood sexual abuse (OR=4.35). The findings support the need for additional work to refine the assessment of forced sex. Efforts to prevent forced sex should target alcohol-serving venues, where norms and behaviors may present particular risks for women who

  3. Experiences of forced sex among female patrons of alcohol-serving venues in a South African township.

    PubMed

    Watt, Melissa H; Sikkema, Kathleen J; Abler, Laurie; Velloza, Jennifer; Eaton, Lisa A; Kalichman, Seth C; Skinner, Donald; Pieterse, Desiree

    2015-05-01

    South Africa has among the highest rates of forced sex worldwide, and alcohol use has consistently been associated with risk of forced sex in South Africa. However, methodological challenges affect the accuracy of forced sex measurements. This study explored the assessment of forced sex among South African women attending alcohol-serving venues and identified factors associated with reporting recent forced sex. Women (n = 785) were recruited from 12 alcohol-serving venues in a peri-urban township in Cape Town. Brief self-administered surveys included questions about lifetime and recent experiences of forced sex. Surveys included a single question about forced sex and detailed questions about sex by physical force, threats, verbal persuasion, trickery, and spiked drinks. We first compared the single question about forced sex to a composite variable of forced sex as unwanted sex by physical force, threats, or spiked drinks. We then examined potential predictors of recent forced sex (demographics, drinking behavior, relationship to the venue, abuse experiences). The single question about forced sex had low sensitivity (0.38); more than half of the respondents who reported on the detailed questions that they had experienced forced sex by physical force, threats, or spiked drinks reported on the single question item that they had not experienced forced sex. Using our composite variable, 18.6% of women reported lifetime and 10.8% reported recent experiences of forced sex. In our adjusted logistic regression model, recent forced sex using the composite variable was significantly associated with hazardous drinking (OR = 1.92), living farther from the venue (OR = 1.81), recent intimate partner violence (OR = 2.53), and a history of childhood sexual abuse (OR = 4.35). The findings support the need for additional work to refine the assessment of forced sex. Efforts to prevent forced sex should target alcohol-serving venues, where norms and behaviors may present particular

  4. Using diaries to explore the work experiences of primary health care nursing managers in two South African provinces

    PubMed Central

    Munyewende, Pascalia O.; Rispel, Laetitia C.

    2014-01-01

    Background South Africa is on the brink of another wave of major health system reforms that underscore the centrality of primary health care (PHC). Nursing managers will play a critical role in these reforms. Objective The aim of the study was to explore the work experiences of PHC clinic nursing managers through the use of reflective diaries, a method hitherto under-utilised in health systems research in low- and middle-income countries. Design During 2012, a sub-set of 22 PHC nursing managers was selected randomly from a larger nurses’ survey in two South African provinces. After informed consent, participants were requested to keep individual diaries for a period of 6 weeks, using a clear set of diary entry guidelines. Reminders consisted of weekly short message service reminders and telephone calls. Diary entries were analysed using thematic content analysis. A diary feedback meeting was held with all the participants to validate the findings. Results Fifteen diaries were received, representing a 68% response rate. The majority of respondents (14/15) were female, each with between 5 and 15 years of nursing experience. Most participants made their diary entries at home. Diaries proved to be cathartic for individual nursing managers. Although inter-related and not mutually exclusive, the main themes that emerged from the diary analysis were health system deficiencies; human resource challenges; unsupportive management environment; leadership and governance; and the emotional impact of clinic management. Conclusions Diaries are an innovative method of capturing the work experiences of managers at the PHC level, as they allow for confidentiality and anonymity, often not possible with other qualitative research methods. The expressed concerns of nursing managers must be addressed to ensure the success of South Africa's health sector reforms, particularly at the PHC level. PMID:25537937

  5. Drinking before and after pregnancy recognition among South African women: the moderating role of traumatic experiences

    PubMed Central

    2014-01-01

    Background South Africa has one of the world’s highest rates of fetal alcohol spectrum disorder (FASD) and interpersonal trauma. These co-occurring public health problems raise the need to understand alcohol consumption among trauma-exposed pregnant women in this setting. Since a known predictor of drinking during pregnancy is drinking behavior before pregnancy, this study explored the relationship between women’s drinking levels before and after pregnancy recognition, and whether traumatic experiences – childhood abuse or recent intimate partner violence (IPV) – moderated this relationship. Methods Women with incident pregnancies (N = 66) were identified from a longitudinal cohort of 560 female drinkers in a township of Cape Town, South Africa. Participants were included if they reported no pregnancy at one assessment and then reported pregnancy four months later at the next assessment. Alcohol use was measured by the Alcohol Use Disorders Identification Test (AUDIT), and traumatic experiences of childhood abuse and recent IPV were also assessed. Hierarchical linear regressions controlling for race and age examined childhood abuse and recent IPV as moderators of the effect of pre-pregnancy recognition drinking on post-pregnancy recognition AUDIT scores. Results Following pregnancy recognition, 73% of women reported drinking at hazardous levels (AUDIT ≥ 8). Sixty-four percent reported early and/or recent exposure to trauma. While drinking levels before pregnancy significantly predicted drinking levels after pregnancy recognition, t(64) = 3.50, p < .01, this relationship was moderated by experiences of childhood abuse, B = -.577, t(60) = -2.58, p = .01, and recent IPV, B = -.477, t(60) = -2.16, p = .04. Pregnant women without traumatic experiences reported drinking at levels consistent with levels before pregnancy recognition. However, women with traumatic experiences tended to report elevated AUDIT scores following pregnancy recognition, even if low

  6. XML Storage for Magnetotelluric Transfer Functions: Towards a Comprehensive Online Reference Database

    NASA Astrophysics Data System (ADS)

    Kelbert, A.; Blum, C.

    2015-12-01

    Magnetotelluric Transfer Functions (MT TFs) represent most of the information about Earth electrical conductivity found in the raw electromagnetic data, providing inputs for further inversion and interpretation. To be useful for scientific interpretation, they must also contain carefully recorded metadata. Making these data available in a discoverable and citable fashion would provide the most benefit to the scientific community, but such a development requires that the metadata is not only present in the file but is also searchable. The most commonly used MT TF format to date, the historical Society of Exploration Geophysicists Electromagnetic Data Interchange Standard 1987 (EDI), no longer supports some of the needs of modern magnetotellurics, most notably accurate error bars recording. Moreover, the inherent heterogeneity of EDI's and other historic MT TF formats has mostly kept the community away from healthy data sharing practices. Recently, the MT team at Oregon State University in collaboration with IRIS Data Management Center developed a new, XML-based format for MT transfer functions, and an online system for long-term storage, discovery and sharing of MT TF data worldwide (IRIS SPUD; www.iris.edu/spud/emtf). The system provides a query page where all of the MT transfer functions collected within the USArray MT experiment and other field campaigns can be searched for and downloaded; an automatic on-the-fly conversion to the historic EDI format is also included. To facilitate conversion to the new, more comprehensive and sustainable, XML format for MT TFs, and to streamline inclusion of historic data into the online database, we developed a set of open source format conversion tools, which can be used for rotation of MT TFs as well as a general XML <-> EDI converter (https://seiscode.iris.washington.edu/projects/emtf-fcu). Here, we report on the newly established collaboration between the USGS Geomagnetism Program and the Oregon State University to gather

  7. Building effective public-private partnerships: experiences and lessons from the African Comprehensive HIV/AIDS Partnerships (ACHAP).

    PubMed

    Ramiah, Ilavenil; Reich, Michael R

    2006-07-01

    This paper examines the processes for building highly collaborative public-private partnerships for public health, with a focus on the efforts to manage the complex relationships that underlie these partnerships. These processes are analyzed for the African Comprehensive HIV/AIDS Partnerships (ACHAP), a 5-year partnership (2001-2005) between the government of Botswana, Merck & Co., Inc. (and its company foundation), and the Bill & Melinda Gates Foundation. ACHAP is a highly collaborative initiative. The ACHAP office in Botswana engages intensively (on a daily basis) with the government of Botswana (an ACHAP partner and ACHAP's main grantee) to support HIV/AIDS control in that country, which had an adult prevalence of 38.5% HIV infection in 2000 when ACHAP was being established. The paper discusses the development of ACHAP in four stages: the creation of ACHAP, the first year, the second and third years, and the fourth year. Based on ACHAP's experiences over these four years, the paper identifies five lessons for managing relationships in highly collaborative public-private partnerships for public health. PMID:16487640

  8. Measuring conditions and trends in ecosystem services at multiple scales: the Southern African Millennium Ecosystem Assessment (SAfMA) experience.

    PubMed

    van Jaarsveld, A S; Biggs, R; Scholes, R J; Bohensky, E; Reyers, B; Lynam, T; Musvoto, C; Fabricius, C

    2005-02-28

    The Southern African Millennium Ecosystem Assessment (SAfMA) evaluated the relationships between ecosystem services and human well-being at multiple scales, ranging from local through to sub-continental. Trends in ecosystem services (fresh water, food, fuel-wood, cultural and biodiversity) over the period 1990-2000 were mixed across scales. Freshwater resources appear strained across the continent with large numbers of people not securing adequate supplies, especially of good quality water. This translates to high infant mortality patterns across the region. In some areas, the use of water resources for irrigated agriculture and urban-industrial expansion is taking place at considerable cost to the quality and quantity of freshwater available to ecosystems and for domestic use. Staple cereal production across the region has increased but was outstripped by population growth while protein malnutrition is on the rise. The much-anticipated wood-fuel crisis on the subcontinent has not materialized but some areas are experiencing shortages while numerous others remain vulnerable. Cultural benefits of biodiversity are considerable, though hard to quantify or track over time. Biodiversity resources remain at reasonable levels, but are declining faster than reflected in species extinction rates and appear highly sensitive to land-use decisions. The SAfMA sub-global assessment provided an opportunity to experiment with innovative ways to assess ecosystem services including the use of supply-demand surfaces, service sources and sink areas, priority areas for service provision, service 'hotspots' and trade-off assessments. PMID:15814355

  9. Measuring conditions and trends in ecosystem services at multiple scales: the Southern African Millennium Ecosystem Assessment (SAfMA) experience

    PubMed Central

    van Jaarsveld, A.S; Biggs, R; Scholes, R.J; Bohensky, E; Reyers, B; Lynam, T; Musvoto, C; Fabricius, C

    2005-01-01

    The Southern African Millennium Ecosystem Assessment (SAfMA) evaluated the relationships between ecosystem services and human well-being at multiple scales, ranging from local through to sub-continental. Trends in ecosystem services (fresh water, food, fuel-wood, cultural and biodiversity) over the period 1990–2000 were mixed across scales. Freshwater resources appear strained across the continent with large numbers of people not securing adequate supplies, especially of good quality water. This translates to high infant mortality patterns across the region. In some areas, the use of water resources for irrigated agriculture and urban–industrial expansion is taking place at considerable cost to the quality and quantity of freshwater available to ecosystems and for domestic use. Staple cereal production across the region has increased but was outstripped by population growth while protein malnutrition is on the rise. The much-anticipated wood-fuel crisis on the subcontinent has not materialized but some areas are experiencing shortages while numerous others remain vulnerable. Cultural benefits of biodiversity are considerable, though hard to quantify or track over time. Biodiversity resources remain at reasonable levels, but are declining faster than reflected in species extinction rates and appear highly sensitive to land-use decisions. The SAfMA sub-global assessment provided an opportunity to experiment with innovative ways to assess ecosystem services including the use of supply–demand surfaces, service sources and sink areas, priority areas for service provision, service ‘hotspots’ and trade-off assessments. PMID:15814355

  10. Effects of mammalian herbivore declines on plant communities: observations and experiments in an African savanna

    PubMed Central

    Young, Hillary S; McCauley, Douglas J; Helgen, Kristofer M; Goheen, Jacob R; Otárola-Castillo, Erik; Palmer, Todd M; Pringle, Robert M; Young, Truman P; Dirzo, Rodolfo

    2013-01-01

    1. Herbivores influence the structure and composition of terrestrial plant communities. However, responses of plant communities to herbivory are variable and depend on environmental conditions, herbivore identity and herbivore abundance. As anthropogenic impacts continue to drive large declines in wild herbivores, understanding the context dependence of herbivore impacts on plant communities becomes increasingly important. 2. Exclosure experiments are frequently used to assess how ecosystems reorganize in the face of large wild herbivore defaunation. Yet in many landscapes, declines in large wildlife are often accompanied by other anthropogenic activities, especially land conversion to livestock production. In such cases, exclosure experiments may not reflect typical outcomes of human-driven extirpations of wild herbivores. 3. Here, we examine how plant community responses to changes in the identity and abundance of large herbivores interact with abiotic factors (rainfall and soil properties). We also explore how effects of wild herbivores on plant communities differ between large-scale herbivore exclosures and landscape sites where anthropogenic activity has caused wildlife declines, often accompanied by livestock increases. 4. Abiotic context modulated the responses of plant communities to herbivore declines with stronger effect sizes in lower-productivity environments. Also, shifts in plant community structure, composition and species richness following wildlife declines differed considerably between exclosure experiments and landscape sites in which wild herbivores had declined and were often replaced by livestock. Plant communities in low wildlife landscape sites were distinct in both composition and physical structure from both exclosure and control sites in experiments. The power of environmental (soil and rainfall) gradients in influencing plant response to herbivores was also greatly dampened or absent in the landscape sites. One likely explanation for

  11. Effects of mammalian herbivore declines on plant communities: observations and experiments in an African savanna.

    PubMed

    Young, Hillary S; McCauley, Douglas J; Helgen, Kristofer M; Goheen, Jacob R; Otárola-Castillo, Erik; Palmer, Todd M; Pringle, Robert M; Young, Truman P; Dirzo, Rodolfo

    2013-07-01

    1. Herbivores influence the structure and composition of terrestrial plant communities. However, responses of plant communities to herbivory are variable and depend on environmental conditions, herbivore identity and herbivore abundance. As anthropogenic impacts continue to drive large declines in wild herbivores, understanding the context dependence of herbivore impacts on plant communities becomes increasingly important. 2. Exclosure experiments are frequently used to assess how ecosystems reorganize in the face of large wild herbivore defaunation. Yet in many landscapes, declines in large wildlife are often accompanied by other anthropogenic activities, especially land conversion to livestock production. In such cases, exclosure experiments may not reflect typical outcomes of human-driven extirpations of wild herbivores. 3. Here, we examine how plant community responses to changes in the identity and abundance of large herbivores interact with abiotic factors (rainfall and soil properties). We also explore how effects of wild herbivores on plant communities differ between large-scale herbivore exclosures and landscape sites where anthropogenic activity has caused wildlife declines, often accompanied by livestock increases. 4. Abiotic context modulated the responses of plant communities to herbivore declines with stronger effect sizes in lower-productivity environments. Also, shifts in plant community structure, composition and species richness following wildlife declines differed considerably between exclosure experiments and landscape sites in which wild herbivores had declined and were often replaced by livestock. Plant communities in low wildlife landscape sites were distinct in both composition and physical structure from both exclosure and control sites in experiments. The power of environmental (soil and rainfall) gradients in influencing plant response to herbivores was also greatly dampened or absent in the landscape sites. One likely explanation for

  12. Long regional magnetotelluric profile crossing geotectonic structures of central Poland

    NASA Astrophysics Data System (ADS)

    Stefaniuk, M.; Pokorski, J.; Wojdyla, M.

    2009-04-01

    Introduction The magnetotelluric survey was made along a regional profile, which runs across Poland from south-west to north-east during 2005-2006 years. The profile crosses major geological structures of Central Poland, including the Variscan Externides and Variscan foredeep, the Transeuropean Suture Zone and the marginal zone of East European Craton. The main objectives of the project include identification of sub-Zechstein sedimentary structures and evaluation of resistivity distribution within the deep crust, especially at the contact of East European Precambrian Craton and Central Europe Paleozoic structures. The length of the profile is about 700 km; 161 deep magnetotelluric sounding sites were made with a medium spacing of about 4 km. Data acquisition and processing The recording of the components of natural electromagnetic field was made with a broad range of frequencies, varying from 0.0003 Hz up to 575 Hz with use of MT-1 system of Electromagnetic Instruments Incorporation. This frequency band allowed obtaining the information about geology ranging from a few dozen meters to approximately 100 km, depending on the vertical distribution of the resistivity inside geological medium. To reduce the electromagnetic noise, magnetic and electric remote reference was applied. A remote reference site was located at a distance of over 100 km of field sites. Processing of the recorded data included the estimation of the components of impedance tensor (Zxx, Zxy, Zyx and Zyy ), with use of robust type procedures. The components of the impedance tensor allowed in a subsequent step for calculation of field curves for two orientations of the measurement system (XY - described further as the TM mode and YX - TE mode) and additional parameters of the medium like skew, strike, pole diagrams etc. Recording of the vertical component of electromagnetic field (Hz) allowed calculation of tipper parameter T. Magnetotelluric soundings interpretation Geophysical interpretation of MT

  13. Challenges associated with tracking resources allocation for reproductive health in sub-Saharan African countries: the UNFPA/NIDI resource flows project experience.

    PubMed

    Sidze, Estelle M; Beekink, Erik; Maina, Beatrice W

    2015-01-01

    Universal access to reproductive health services entails strengthening health systems, but requires significant resource commitments as well as efficient and effective use of those resources. A number of international organizations and governments in developing countries are putting efforts into tracking the flow of health resources in order to inform resource mobilization and allocation, strategic planning, priority setting, advocacy and general policy making. The UNFPA/NIDI-led Resource Flows Project ("The UNFPA/NIDI RF Project") has conducted annual surveys since 1997 to monitor progress achieved by developing countries in implementing reproductive health financial targets. This commentary summarizes the Project experiences and challenges in gathering data on allocation of resources for reproductive health at the domestic level in sub-Saharan African countries. One key lesson learnt from the Project experience is the need for strengthening tracking mechanisms in sub-Saharan African countries and making information on reproductive health resources and expenditures available, in particular the private sector resources. PMID:26012472

  14. Pathways to success in science: A phenomenological study, examining the life experiences of African-American women in higher education

    NASA Astrophysics Data System (ADS)

    Giscombe, Claudette Leanora

    This study is a qualitative investigation in which five African American women science faculty, in higher education, within the age range of 45--60, were the participants. The data that was collected, over twelve months, was primarily obtained from the in-depth phenomenological interviewing method (Seidman, 1991). The interpretation of the data was the result of ongoing cross analysis of the participants' life experiences, perceptions, and beliefs of the how they navigated and negotiated pathways to careers in the natural sciences, and the meanings they attach to these experiences. The software Ethnograph (V5.0) was used to organize the participants' responses into patterns and emergent themes. The Black women in this study articulated several themes that were critical determinants of their successes and achievements in science careers. From the analysis of the data set, four major findings were identified: (1) "Black Intentional Communities" acted as social agencies for the positive development of the participants; (2) "My World Reality" which was described by the participants as their acceptance of their segregated worlds, not being victims of inequities and injustices, but being resilient and determined to forge on to early academic successes. Early academic successes were identified as precursors and external motivational stimuli to their interests and achievements in science; (3) Their experiences of "Tensions and Double Consciousness" from race and gender negative images and career stereotypes, required the women to make "intra-cultural deviations" from stereotypic career roles and to develop "pragmatic coping strategies" to achieve in science careers and; (4) "Meaning-making"---Significant to the meaning of their journey was the fact that the participants grounded their experiences in a social context rather than in a scientific context and that they ended their journey with expressions of personal satisfactions about their journey and their unique drive and

  15. Results of the South African Cloud-Seeding Experiments Using Hygroscopic Flares.

    NASA Astrophysics Data System (ADS)

    Mather, G. K.; Terblanche, D. E.; Steffens, F. E.; Fletcher, L.

    1997-11-01

    A new method of seeding convective clouds for the purpose of augmenting rainfall is being developed in South Africa. Flares that produce small salt particles (0.5-m mean diameter) are attached to the trailing edge of the wings of seeding aircraft and ignited in updrafts below the cloud base of convective storms. This method of delivery overcomes most of the difficulties encountered in the handling and the use of hygroscopic materials, difficulties that made seeding with ice nuclei (AgI) a more attractive option.The research that has led to the development of this new technique was prompted by an encounter with a storm with dramatically altered microphysics that was growing over a Kraft paper mill in the research area. Hygroscopic seeding flares were subsequently developed, and seeding trials began in October 1990. Successful seeding trials quickly led to the design and execution of a randomized convective cloud-seeding experiment, the results of which show convincing evidence of increases in the radar-measured rain mass from seeded storms when compared to the control or unseeded storms.Heightened reflectivities aloft seen by the real-time storm-tracking software and observed in the exploratory analysis raises the possibility of developing a radar-measured seeding algorithm that can recognize in almost real time a successful convective seeding event. The implications of such a development would have far-reaching effects on the conduct of future convective cloud-seeding experiments and operations.The authors' seeding hypothesis postulates that the hygroscopic seeding at cloud base accelerates the growth of large hydrometeors in the treated clouds, which harvest more of the available supercooled water before it is expelled into the anvils by the strong updrafts that are a characteristic of the local storms, thereby increasing the efficiency of the rainfall process. The validity of this hypothesis is supported by microphysical measurements made from an instrumented

  16. Magnetotelluric monitoring of a fluid injection: Example from an enhanced geothermal system

    NASA Astrophysics Data System (ADS)

    Peacock, J. R.; Thiel, S.; Reid, P.; Heinson, G.

    2012-09-01

    Enhanced geothermal systems (EGS) are on the verge of becoming commercially viable for power production, where advancements in subsurface characterization are imperative to develop EGS into a competitive industry. Theory of an EGS is simple, pump fluids into thermally enhanced lithology and extract the hot fluids to produce energy. One significant complication in EGS development is estimating where injected fluids flow in the subsurface. Micro-seismic surveys can provide information about where fractures opened, but not fracture connectivity nor fluid inclusion. Electromagnetic methods are sensitive to conductivity contrasts and can be used as a supplementary tool to delineate reservoir boundaries. In July, 2011, an injection test for a 3.6 km deep EGS at Paralana, South Australia was continuously monitored by both micro-seismic and magnetotellurics (MT). Presented are the first results from continuous MT measurements suggesting transient variations in subsurface conductivity structure generated from the introduction of fluids at depth can be measured. Furthermore, phase tensor representation of the time dependent MT response suggests fluids migrated in a NE direction from the injection well. Results from this experiment supports the extension of MT to a monitoring tool for not only EGS but other hydraulic stimulations.

  17. Salt, Sediments and Seawater: Marine Magnetotellurics in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Weiss, C.; Key, K.; Constable, S.

    2002-12-01

    The Smackover and Louann salt formations are distinguishing features of the Gulf of Mexico which not only provide clues to the tectonic evolution of the Gulf, but also play a critical role in the formation of traps for hydrocarbon reservoirs. However, the challenge of mapping these features is only partially met by existing seismic methods: the top of salt (TOS) is usually well resolved while the base of salt (BOS) is remarkably less so. Owing to the high contrast in electrical conductivity between salt and the surrounding sediments, electromagnetic methods such as magnetotellurics (MT) are promising techniques for minimizing the uncertainty in mapping allocthonous salt structures. Futhermore, the high conductivity of the seawater invites speculation on the usefulness of vertical electric field measurements in TOS/BOS characterization. Thus, we present results from a series of 3D numerical modeling experiments of electromagnetic induction over a ``realistic'' salt body: a 3D seismic--derived volume representing the Gemini salt structure, located beneath 1000m of water in the Mississippi Canyon, Gulf of Mexico. Results are compared to a collection of 34 broadband (T= 1--5000 s) MT datasets collected in three surveys over the structure between 1998 and 2001. Previously obtained 2D inversion results of the observed data are validated by 2D inversion of the fully 3D synthetic model response.

  18. Magnetotelluric Data, Mid Valley, Nevada Test Site, Nevada.

    SciTech Connect

    Jackie M. Williams; Erin L. Wallin; Brian D. Rodriguez; Charles R. Lindsay; and Jay A. Sampson

    2007-08-15

    The United States Department of Energy (DOE) and the National Nuclear Security Administration (NNSA) at their Nevada Site Office (NSO) are addressing ground-water contamination resulting from historical underground nuclear testing through the Environmental Management (EM) program and, in particular, the Underground Test Area (UGTA) project. One issue of concern is the nature of the somewhat poorly constrained pre-Tertiary geology and its effects on ground-water flow. Ground-water modelers would like to know more about the hydrostratigraphy and geologic structure to support a hydrostratigraphic framework model that is under development for the Rainier Mesa/Shoshone Mountain Corrective Action Unit (CAU) (Bechtel Nevada, 2006). During 2003, the U.S. Geological Survey (USGS), in cooperation with the DOE and NNSA-NSO, collected and processed data at the Nevada Test Site in and near Yucca Flat (YF) to help define the character, thickness, and lateral extent of the pre-tertiary confining units. We collected 51 magnetotelluric (MT) and audio-magnetotelluric (AMT), stations for that research (Williams and others, 2005a, 2005b, 2005c, 2005d, 2005e, 2005f). In early 2005 we extended that research with 26 additional MT data stations (Williams and others, 2006), located on and near Rainier Mesa and Shoshone Mountain (RM-SM). The new stations extended the area of the hydrogeologic study previously conducted in Yucca Flat. This work was done to help refine what is known about the character, thickness, and lateral extent of pre-Tertiary confining units. In particular, a major goal was to define the upper clastic confining unit (UCCU). The UCCU is comprised of late Devonian to Mississippian siliciclastic rocks assigned to the Eleana Formation and Chainman Shale. The UCCU underlies the Yucca Flat area and extends westward towards Shoshone Mountain, southward to Buckboard Mesa, and northward to Rainier Mesa. Late in 2005 we collected another 14 MT stations in Mid Valley and in

  19. Magnetotelluric Data, Mid Valley, Nevada Test Site, Nevada

    USGS Publications Warehouse

    Williams, Jackie M.; Wallin, Erin L.; Rodriguez, Brian D.; Lindsey, Charles R.; Sampson, Jay A.

    2007-01-01

    Introduction The United States Department of Energy (DOE) and the National Nuclear Security Administration (NNSA) at their Nevada Site Office (NSO) are addressing ground-water contamination resulting from historical underground nuclear testing through the Environmental Management (EM) program and, in particular, the Underground Test Area (UGTA) project. One issue of concern is the nature of the somewhat poorly constrained pre-Tertiary geology and its effects on ground-water flow. Ground-water modelers would like to know more about the hydrostratigraphy and geologic structure to support a hydrostratigraphic framework model that is under development for the Rainier Mesa/Shoshone Mountain Corrective Action Unit (CAU). During 2003, the U.S. Geological Survey (USGS), in cooperation with the DOE and NNSA-NSO, collected and processed data at the Nevada Test Site in and near Yucca Flat (YF) to help define the character, thickness, and lateral extent of the pre-Tertiary confining units. We collected 51 magnetotelluric (MT) and audio-magnetotelluric (AMT), stations for that research. In early 2005 we extended that research with 26 additional MT data stations, located on and near Rainier Mesa and Shoshone Mountain (RM-SM). The new stations extended the area of the hydrogeologic study previously conducted in Yucca Flat. This work was done to help refine what is known about the character, thickness, and lateral extent of pre-Tertiary confining units. In particular, a major goal was to define the upper clastic confining unit (UCCU). The UCCU is comprised of late Devonian to Mississippian siliciclastic rocks assigned to the Eleana Formation and Chainman Shale. The UCCU underlies the Yucca Flat area and extends westward towards Shoshone Mountain, southward to Buckboard Mesa, and northward to Rainier Mesa. Late in 2005 we collected another 14 MT stations in Mid Valley and in northern Yucca Flat basin. That work was done to better determine the extent and thickness of the UCCU near

  20. Blockage and flow: intimate experiences of condoms and microbicides in a South African clinical trial.

    PubMed

    Stadler, Jonathan; Saethre, Eirik

    2011-01-01

    Based on qualitative research undertaken during a phase-three microbicide gel trial, this paper explores female participants' experiences and perceptions of gel and condom use and the opinions of their male partners and community members. Participants were aware that condoms were effective in preventing HIV infection and that the efficacy of the microbicide was unproven. Yet, in narratives about gel and condom use, participants ascribed improvements to their reproductive health and intimate relationships with men to gel use. In contrast, condoms were believed to prevent disease, yet also embodied mistrust, were believed to contain dangerous substances and were felt to block the womb. These apparently contradictory views about condoms and gels are explored in the light of conceptions of flow and blockage. Health is achieved by maintaining a steady balance of substances within the body, while preventing fluid flow results in illness. We argue that women enrolled in the trial broadened the meaning of the gel beyond its primary intended effect of preventing HIV. Through their accounts of gel use, women 'reinvented' the gel as a substance that transformed their bodies and sexual relations. This has implications for understanding how local knowledge of health and illness intersects with biomedical knowledge. PMID:20960355

  1. The spectrum of injuries resulting from posterior abdominal stab wounds: a South African experience

    PubMed Central

    Oosthuizen, GV; Clarke, DL

    2015-01-01

    Introduction The spectrum of injury associated with anterior abdominal stab wounds (SWs) is well established. The literature on the spectrum of organ injury associated with SWs to the posterior abdomen, however, is limited. Methods We reviewed our experience of 105 consecutive patients who had established indications for laparotomy managed over a 4-year period in a high volume trauma service in South Africa. Results Of the 105 patients, 97 (92%) were male and the overall mean age was 24 years. Fifty-seven patients (54%) had immediate indications for laparotomy. The remaining 48 patients (46%) initially underwent active clinical observation and the indications for laparotomy became apparent during the observation period. Of the 105 laparotomies performed, 94 (90%) were positive and 11 (10%) were negative. Of the 94 positive laparotomies, 92 were therapeutic and 2 were non-therapeutic. A total of 176 organ injuries were identified: 50 (53%) of the 94 patients sustained a single organ injury while the remaining 44 (47%) sustained multiple organ injuries. The most commonly injured organs were the colon (n=63), spleen (n=21) and kidney (n=19). Conclusions The pattern of intra-abdominal injuries secondary to SWs to the posterior abdomen is different to that seen with the anterior abdomen. Colonic injury is most commonly encountered, followed by injuries to the spleen and kidney. Clinicians must remain vigilant because of the potential for occult injuries. PMID:26263933

  2. Crustal properties in the continuum Baltic Shield-Scandinavian Mountains from seismic ambient noise and magnetotelluric analysis

    NASA Astrophysics Data System (ADS)

    Ben Mansour, Walid; England, Richard W.; Fishwick, Stewart; Köhler, Andreas; Moorkamp, Max; Ottemøller, Lars; Smirnov, Maxim

    2016-04-01

    The Scandinavian passive margin is a good example of a region where a Precambrian shield is directly in contact with a younger mountain belt. Located along the Atlantic coast, the Scandinavian mountains, formed 440 Ma ago, show high peaks (> 1 km from the sea level) due to an uplift event 12 Ma ago. This topography contrasts strongly with the low topography of the Baltic shield (around 500 m from the sea level). If the mountain shows high topography compared to the shield, P-receiver functions analysis indicates that the Moho is deeper beneath the shield than beneath the orogenic belt. This result is surprising, as simple crustal isostasy would produce the opposite result. It is therefore likely that there is further variation in crustal and lithospheric properties between the shield and the mountain belt. In this perspective, several geophysical experiments (SCANLIPS2, POLENET-LAPNET, SCANLIPS3D, Norwegian National Seismic Network) have been deployed in the region in order to better understand the lateral variation in the crustal properties. From these different seismic arrays, we used the technique of ambient noise cross correlation in order to reconstruct the Rayleigh wave Green's function (R-R and Z-Z components) and produced a new Vs model of the upper crust in the transition between the Scandinavian mountains and Baltic Shield. In addition of this study, a magnetotelluric survey was done in the framework of MaSCa (MAgnetotellurics in the SCandes) project between 2011 and 2013 in the same area of broadband seismic network (Northern Scandinavia Mountains and the Baltic Shield). This project shows higher resistivity in the crust beneath the Baltic shield than beneath the orogenic belt. The results of this study are used in a joint inversion with seismic ambient noise in order to improve existing models. We used the multi objective genetic algorithms (GA) to inverse in the same time seismological data (receiver functions and dispersion curves from seismic ambient

  3. Involving lay community researchers in epidemiological research: experiences from a seroprevalence study among sub-Saharan African migrants

    PubMed Central

    Nöstlinger, Christiana; Loos, Jasna

    2016-01-01

    ABSTRACT Community-based participatory research (CBPR) has received considerable attention during past decades as a method to increase community ownership in research and prevention. We discuss its application to epidemiological research using the case of second-generation surveillance conducted among sub-Saharan African (SSA) migrants in Antwerp city. To inform evidence-based prevention planning for this target group, this HIV-prevalence study used two-stage time-location sampling preceded by formative research. Extensive collaborative partnerships were built with community organizations, a Community Advisory Board provided input throughout the project, and community researchers were trained to participate in all phases of the seroprevalence study. Valid oral fluid samples for HIV testing were collected among 717 SSA migrants and linked to behavioural data assessed through an anonymous survey between December 2013 and August 2014. A qualitative content analysis of various data sources (extensive field notes, minutes of intervision, and training protocols) collected at 77 data collection visits in 51 settings was carried out to describe experiences with challenges and opportunities inherent to the CBPR approach at three crucial stages of the research process: building collaborative partnerships; implementing the study; dissemination of findings including prevention planning. The results show that CBPR is feasible in conducting scientifically sound epidemiological research, but certain requirements need to be in place. These include among others sufficient resources to train, coordinate, and supervise community researchers; continuity in the implementation; transparency about decision-taking and administrative procedures, and willingness to share power and control over the full research process. CBPR contributed to empowering community researchers on a personal level, and to create greater HIV prevention demand in the SSA communities. PMID:26885938

  4. Involving lay community researchers in epidemiological research: experiences from a seroprevalence study among sub-Saharan African migrants.

    PubMed

    Nöstlinger, Christiana; Loos, Jasna

    2016-01-01

    Community-based participatory research (CBPR) has received considerable attention during past decades as a method to increase community ownership in research and prevention. We discuss its application to epidemiological research using the case of second-generation surveillance conducted among sub-Saharan African (SSA) migrants in Antwerp city. To inform evidence-based prevention planning for this target group, this HIV-prevalence study used two-stage time-location sampling preceded by formative research. Extensive collaborative partnerships were built with community organizations, a Community Advisory Board provided input throughout the project, and community researchers were trained to participate in all phases of the seroprevalence study. Valid oral fluid samples for HIV testing were collected among 717 SSA migrants and linked to behavioural data assessed through an anonymous survey between December 2013 and August 2014. A qualitative content analysis of various data sources (extensive field notes, minutes of intervision, and training protocols) collected at 77 data collection visits in 51 settings was carried out to describe experiences with challenges and opportunities inherent to the CBPR approach at three crucial stages of the research process: building collaborative partnerships; implementing the study; dissemination of findings including prevention planning. The results show that CBPR is feasible in conducting scientifically sound epidemiological research, but certain requirements need to be in place. These include among others sufficient resources to train, coordinate, and supervise community researchers; continuity in the implementation; transparency about decision-taking and administrative procedures, and willingness to share power and control over the full research process. CBPR contributed to empowering community researchers on a personal level, and to create greater HIV prevention demand in the SSA communities. PMID:26885938

  5. Magnetotelluric measurements on the Methana Peninsula (Greece): modelling and interpretation

    NASA Astrophysics Data System (ADS)

    Volti, Theodora K.

    1999-01-01

    As a first deep geophysical survey, thirteen magnetotelluric and magnetovariation soundings in the period range of 0.0085-6000 s have been carried out in the Methana Peninsula and Trizina area (Greece), which form the western part of the active Hellenic Volcanic Arc. Data have been processed using robust techniques and further analysed using decomposition methods in order to find the regional azimuth. By using the smooth inverse of Smith and Booker (J. Geophys. Res. 96, 3905-3922, 1991), the 2-D modelling has resolved a low-resistivity area (<30 Ω m) at depths of 2-3 km beneath the volcanics, whereas elsewhere the resistivity is much higher (>100 Ω m). Parkinson induction arrows also at the range 0.01-0.1 s point towards the centre of the peninsula. The conductivity anomaly is interpreted as being connected with the volcanic history of Methana, as a cooler remnant of former magmatic activity. The contrast with the much higher resistivities suggested at depths >5 km, is discussed in terms of fluid mobility, limitation of the MT method and extensional processes in the southern Aegean.

  6. Characterization of Clastic Dikes Using Controlled Source Audio Magnetotellurics

    NASA Astrophysics Data System (ADS)

    Persichetti, J. A.; Alumbaugh, D.

    2001-12-01

    A site consisting of 3D geology on the Hanford Reservation in Hanford, Washington, has been surveyed using Controlled Source Audio Magnetotellurics (CSAMT) to determine the method's ability to detect clastic dikes. The dikes are fine-grained, soft-sediment intrusions, formed by the buoyant rise of buried, unconsolidated, water rich mud into overlying unconsolidated sediment. The dikes are of major importance because they may act as natural barriers inhibiting the spread of contaminants, or as conduits, allowing the contaminants to be quickly wicked away from the contaminant storage tanks that may be located in close vicinity of the dikes. The field setup consisted of a 33 meter by 63 meter receiver grid with 3 meter spacing in all directions with the transmitter positioned 71.5 meters from the center of the receiver grid. A total of 12 frequencies were collected from 1.1kHz to 66.2kHz. The CSAMT data is being analyzed using a 2D CSAMT RRI code (Lu, Unsworth and Booker, 1999) and a 2D MT RRI code (Smith and Booker, 1991). Of interest is examining how well the 2D codes are able to map 3D geology, the level of resolution that is obtained, and how important it is to include the 3D source in the solution. The ultimate goal is to determine the applicability of using CSAMT for mapping these types of features at the Hanford Reservation site.

  7. Ophiolite emplacement in NE Oman: constraints from magnetotelluric sounding

    NASA Astrophysics Data System (ADS)

    Thiel, S.; Heinson, G.; Gray, D. R.; Gregory, R. T.

    2009-03-01

    Magnetotelluric (MT) data have been acquired across the Samail Ophiolite, Oman mountains, along a 115km transect in January 2005. Twenty-five MT stations were deployed approximately every 4km along a profile perpendicular to the coastline near Muscat. The profile extends from the Huw'l/Meeh subwindow in the northwestern part of the profile and crosses the Saih Hatat window, a Tertiary domal culmination that folds a major NE-facing recumbent fold nappe, and ends along the southern boundary between the Dasir and Ibra ophiolite blocks. The survey aimed to investigate the tectonic evolution of the emplacement of the Samail Ophiolite by delineating major faults and geological boundaries on a crustal scale. The data shows complex behaviour with the influence of static shift effects and anomalously high phases exceeding 90°. Phase tensor analysis and 3-D forward modelling hint that the upper plate-lower plate (UP-LP) shear zone has a 3-D effect on the data in the northern part of the profile. Rotated MT impedances were inverted using a 2-D code. Major resistivity interfaces coincide with the location of the UP-LP shear zone near the surface, and dip towards the Arabian margin suggesting a southwest orientated underthrusting prior to the ophiolite emplacement. The para-autochthonous and less deformed upper plate is a resistor, whereas the strongly deformed lower plate is more conductive.

  8. A magnetotelluric survey in the northern Bolivian Altiplano

    SciTech Connect

    Ritz, M. ); Bondoux, F. ); Herail, G.; Sempere, T. )

    1991-03-01

    Magnetotelluric (MT) measurements were performed at 9 sites on the northern Bolivian Altiplano in an attempt to determine thicknesses of the Cainozoic sedimentary infill and to characterize the underlying crust. At some of the sites the MT soundings show complications due to static shift effects caused by local, surficial heterogeneities. Preliminary one-dimensional (1D) modeling of the data based on the impedance tensor determinant parameters was undertaken for sites considered to be free of static effects, and was followed by 2D modeling. The model obtained indicates, from the surface downward, three important geoelectrical units, namely (1) a very low-resistivity layer (1-6 ohm-m) consisting of late Cainozoic volcanic rocks and/or Tertiary-Cretaceous sedimentary rocks 1-4 km in thickness, (2) a crustal resistive zone (about 200 ohm-m), and (3) a lower crustal or uppermost mantle conductor (less than 10 ohm-m) at depths of 40-45 km which might be related to partial melting. This model is consistent with the geological model according to which the Altiplano formed as a synorogenic basin showing abrupt changes in depositional thicknesses across thrust faults.

  9. Magnetotelluric models of the Roosevelt Hot Springs thermal area, Utah

    SciTech Connect

    Wannamaker, P.E.; Ward, S.H.; Hohmann, G.W.; Sill, W.R.

    1980-09-01

    The Roosevelt Hot Springs (RHS) thermal area, which includes a hotwater-dominated fracture zone prospect, near the eastern margin of the Basin-Range tectonic province, conceivably possesses a whole family of resistivity structures that includes the following: deep hot brine reservoirs, deep-seated partially molten heat sources in the crust or upper mantle that drive the convective system, near-surface hydrothermal alteration zones, wet sedimentary fill in valleys, and a regional, apparently one-dimensional resistivity profile of the crust and upper mantle. This complex resistivity makeup, particular to RHS but probably similar to that at other geothermal areas in the Great Basin, must be treated as being fully three-dimensional (3-D). In an attempt to understand these structures, broadband (10/sup -3/ to 10/sup -2/ Hz) tensor magnetotelluric (MT) data were obtained including apparent resistivities (rho/sub a/), impedance phases (phi) and vertical magnetic field transfer functions for 93 sites in the vicinity of this resource area.

  10. Magnetotelluric investigation in the High Agri Valley (southern Apennine, Italy)

    NASA Astrophysics Data System (ADS)

    Balasco, M.; Giocoli, A.; Piscitelli, S.; Romano, G.; Siniscalchi, A.; Stabile, T. A.; Tripaldi, S.

    2015-04-01

    In this paper we present the result of a magnetotelluric (MT) investigation carried out across the High Agri Valley (HAV), southern Italy. Several MT soundings were carried out in order to obtain a ~15 km long 2-D resistivity model with an investigation depth of ~10 km. The main aim was to provide valuable data on the geological and structural setting of the HAV. The MT model was compared with pre-existing geological, geophysical and seismic data. The MT model can be schematized as a superposition of three stack lateral varying layers with different thickness and resistivity values: a surficial low-medium resistivity layer associated with the Quaternary deposits and to the allochthonous units; and a deeper high resistivity layer related to the Apulia Platform, separated by a thin layer connected to the mélange zone and to the Pliocene terrigenous marine deposits. Sharp lateral resistivity variations are interpreted as faults that, on the basis of accurate focal mechanism computations, display normal-faulting kinematics.

  11. Magnetotelluric investigation in the High Agri Valley (southern Apennine, Italy)

    NASA Astrophysics Data System (ADS)

    Balasco, M.; Giocoli, A.; Piscitelli, S.; Romano, G.; Siniscalchi, A.; Stabile, T. A.; Tripladi, S.

    2014-11-01

    In this paper we present the result of a Magnetotelluric (MT) investigation carried out across the High Agri Valley (HAV), southern Italy. Several MT soundings were carried out in order to obtain a ~15 km long 2-D resistivity model with an investigation depth of ~10 km. The main aim was to provide valuable data on the geological and structural setting of the HAV. The MT model was compared with pre-existing geological, geophysical and seismic data. The MT model can be schematized as a superposition of three stack lateral varying layers with different thickness and resistivity values: a surficial low-medium resistivity layer, associated to the Quaternary deposits and to the allochthonous units, and a deeper high resistivity layer, related to the Apulia Platform, separated by a thin layer connected to the mélange zone and to the Pliocene terrigenous marine deposits. Sharp lateral resistivity variations are interpreted as faults that, on the basis of accurate focal mechanism computations, display normal-faulting kinematics.

  12. Magnetotelluric data, Taos Plateau Volcanic Field, New Mexico

    USGS Publications Warehouse

    Ailes, Chad E.; Rodriguez, Brian D.

    2010-01-01

    The population of the San Luis Basin region of northern New Mexico is growing. Water shortfalls could have serious consequences. Future growth and land management in the region depend on accurate assessment and protection of the region's groundwater resources. An important issue in managing the groundwater resources is a better understanding of the hydrogeology of the Santa Fe Group and the nature of the sedimentary deposits that fill the Rio Grande rift, which contain the principal groundwater aquifers. The shallow unconfined aquifer and the deeper confined Santa Fe Group aquifer in the San Luis Basin are the main sources of municipal water for the region. The U.S. Geological Survey (USGS) is conducting a series of multidisciplinary studies of the San Luis Basin. Detailed geologic mapping, high-resolution airborne magnetic surveys, gravity surveys, an electromagnetic survey called magnetotellurics (MT), and hydrologic and lithologic data are being used to better understand the aquifers. This report describes a regional east-west MT sounding profile acquired in late July 2009 across the Taos Plateau Volcanic Field where drillhole data are sparse. Resistivity modeling of the MT data can be used to help map changes in electrical resistivity with depths that are related to differences in rock types. These various rock types help control the properties of aquifers. The purpose of this report is to release the MT sounding data collected along the east-west profile. No interpretation of the data is included.

  13. Comparison study of magnetotelluric inversion using different transfer functions

    NASA Astrophysics Data System (ADS)

    Bierman, David Frank

    Near-surface inhomogeneities (NSI) are a major problem that distorts magnetotelluric (MT) data. In this thesis, I have developed a method of 3D inversion of MT data based on the phase-tensor approach. Theoretically, unlike conventional MT apparent resistivities, the phase-tensor data are not distorted by the near-surface inhomogeneities and thus should provide more reliable information about deep geoelectrical structures. I have derived the relationships between Frechet derivatives of the phase tensor and those of the MT impedance components. Once the sensitivities are known, the method closely follows Consortium for Electromagnetic Modeling and Inversion's (CEMI's) 3D MT inversion algorithm, which is based on the integral equation (IE) formulation of EM field equations and receiver footprint approach. In this thesis, I conduct a comparison study of 3D MT inversions, using impedance tensor and phase tensor methods. I present a case study using the MT data from the McArthur River area. The results from the impedance tensor compared well with the results from other publications. The phase tensor results did not compare well with any other results. This indicates that the phase tensor method, being theoretically very robust to near-surface distortions, in practice does not work as well as one would expect. I explain this phenomenon by the significant effects of noise in the field MT data on the components of the phase tensor.

  14. Three-dimensional inversion for Network-Magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Siripunvaraporn, W.; Uyeshima, M.; Egbert, G.

    2004-09-01

    Three-dimensional inversion of Network-Magnetotelluric (MT) data has been implemented. The program is based on a conventional 3-D MT inversion code (Siripunvaraporn et al., 2004), which is a data space variant of the OCCAM approach. In addition to modifications required for computing Network-MT responses and sensitivities, the program makes use of Massage Passing Interface (MPI) software, with allowing computations for each period to be run on separate CPU nodes. Here, we consider inversion of synthetic data generated from simple models consisting of a 1 W-m conductive block buried at varying depths in a 100 W-m background. We focus in particular on inversion of long period (320-40,960 seconds) data, because Network-MT data usually have high coherency in these period ranges. Even with only long period data the inversion recovers shallow and deep structures, as long as these are large enough to affect the data significantly. However, resolution of the inversion depends greatly on the geometry of the dipole network, the range of periods used, and the horizontal size of the conductive anomaly.

  15. Comparing multiple 3D magnetotelluric inversions of the same dataset

    NASA Astrophysics Data System (ADS)

    Walter, C.; Jones, A. G.

    2013-12-01

    The Taupo Volcanic Zone (TVZ) hosts the majority of the geothermal systems in New Zealand and is a valuable source for power generation and tourism. It is important for the sustainable exploitation of this area to fully understand the processes and structures in the TVZ. As part of the 'Hotter and Deeper' project of the Foundation for Research, Science and Technology (FRST), a dataset of 200 broadband magnetotelluric (MT) stations has been collected in the TVZ of New Zealand in 2009 and 2010. Combined with a smaller dataset from Reporoa, a total of 230 stations are available for 3D inversion to image the deeper structures of the TVZ. For the study presented in this paper, multiple 3D inversions of this dataset using different control parameters have been undertaken to study the influence of the choice of parameters on the inversion result. The parameters that have been varied include; the type of responses used in the inversion, the use of topography and bathymetry, and varying vertical grid spacings. All inversions commenced with a uniform half-space so that there was no preconceived structures to begin with. The results show that the main structures in the model are robust in that they are independent of the choice of parameters and become introduced in every inversion. The only differences are in the shape and exact location of the structures, which vary between the models. Furthermore, different ways to get a measure for the differences between models have been explored.

  16. 3D magnetotelluric inversion with full distortion matrix

    NASA Astrophysics Data System (ADS)

    Gribenko, A. V.; Zhdanov, M. S.

    2014-12-01

    Distortion of regional electric fields by local structures represent one of the major problems facing three-dimensional magnetotelluric (MT) interpretation. Effect of 3D local inhomogenities on MT data can be described by a real 2x2 distortion matrix. In this project we develop a method of simultaneous inversion of the full MT impedance data for 3D conductivity distribution and for the distortion matrix. Tikhonov regularization is employed to solve the resulting inverse problem. Integral equations method is used to compute MT responses. Minimization of the cost functional is achieved via conjugate gradient method. The inversion algorithm is tested on the synthetic data from Dublin Secret Model II (DSM 2) for which multiple inversion solutions are available for comparison. Inclusion of the distortion matrix provides faster convergence and allows coarser discretization of the near-surface while achievingsimilar or better data fits as inversion for the conductivity only with finely discretized shallow regions. As a field data example we chose a subset of the EarthScope MT dataset covering Great Basin and adjacent areas of the Western United States. Great Basin data inversion identified several prominent conductive zones which correlate well with areas of tectonic and geothermal activity.

  17. Experiences and Perspectives of African-American, Latina/o, Asian-American and European-American Psychology Graduate Students: A National Study

    PubMed Central

    Maton, Kenneth I.; Wimms, Harriette E.; Grant, Sheila K.; Wittig, Michele A.; Rogers, Margaret R.; Vasquez, Melba J. T.

    2013-01-01

    A national, web-based survey of 1,222 African-American, Latina/o, Asian-American and European-American psychology graduate students revealed both similarities and differences in experiences and perspectives. Mentoring was found to be the strongest predictor of satisfaction across groups. Academic supports and barriers, along with perceptions of diversity were also important predictors of satisfaction. Students of color differed from European-American students in perceptions of fairness of representation of their ethnic group within psychology, and in aspects of the graduate school experience perceived as linked to ethnicity. Limitations of the study and implications for future research and action are discussed. PMID:21341899

  18. Building capacity for the assessment of HIV drug resistance: experiences from the PharmAccess African Studies to Evaluate Resistance network.

    PubMed

    Hamers, Raph L; Straatsma, Elske; Kityo, Cissy; Wallis, Carole L; Stevens, Wendy S; Sigaloff, Kim C E; Siwale, Margaret; Conradie, Francesca; Botes, Mariette E; Mandaliya, Kishor; Wellington, Maureen; Osibogun, Akin; van Vugt, Michèle; Rinke de Wit, Tobias F

    2012-05-01

    The PharmAccess African Studies to Evaluate Resistance (PASER) network was established as a collaborative partnership of clinical sites, laboratories, and research groups in 6 African countries; its purpose is to build research and laboratory capacity in support of a coordinated effort to assess population-level acquired and transmitted human immunodeficiency virus type-1 drug resistance (HIVDR), thus contributing to the goals of the World Health Organization Global HIV Drug Resistance Network. PASER disseminates information to medical professionals and policy makers and conducts observational research related to HIVDR. The sustainability of the network is challenged by funding limitations, constraints in human resources, a vulnerable general health infrastructure, and high cost and complexity of molecular diagnostic testing. This report highlights experiences and challenges in the PASER network from 2006 to 2010. PMID:22544185

  19. A hermeneutic phenomenological study of the experiences of female African American undergraduate engineering students at a predominantly White and an historically Black institution

    NASA Astrophysics Data System (ADS)

    Frillman, Sharron Ann

    2011-12-01

    This phenomenological study examined the experiences of twelve female African Americans enrolled as fulltime undergraduate engineering students at North Carolina Agricultural and Technical State University, an historically Black university, and seven female African Americans enrolled as undergraduate engineering students at Purdue University in West Lafayette, Indiana, a traditionally White institution. Interviews provided insights into the "lived" experiences of these young women and the factors they believe have contributed to their success in their respective engineering programs. Data analysis involved coding each participant's responses to interview questions using Atlas.ti, a powerful qualitative data analysis tool. This generated 181 codes that were further categorized into nine emergent themes, indicating the potential for extensive associations among the variables. The emergent themes are as follows: (1) Demographic information/special circumstances, (2) Personal attributes and characteristics, (3) Personal insights, (4) Sense of mission, (5) Sources of negative stress, (6) Success strategies, (7) Various forms of support, (8) Would/would not have made it to where she is now, and (9) Being African American and female in engineering. Analysis of these themes and their relationships led to the development of the Frillman Model of Emergent Themes in Female African American Engineering Students. Success. In addressing similarities and differences, three overriding theme categories emerged. These were: (1) Four personhood themes and dual social identity theme; (2) Environmental input and response theme; and (3) Outcome emergent theme of Would/Would not have made it to where she is now. Recommendations were made for future research to expand upon this exploratory study.

  20. A final report on computed magneto-telluric curves for hypothetical models of crustal structure

    USGS Publications Warehouse

    Pritchard, J.I.

    1965-01-01

    Several mathematical models were investigated to determine the capa-bilities of the magneto-telluric method for determining the resistivity structure of the earth's crust. The model parameters were based on the crust model proposed by Keller (1963). The mathematical technique used was developed by Cagniard (1953). The investigations indicate that a three-layer model approximation of the crust and mantle is the most detailed model warranted in inter-preting the information provided by the magneto-telluric method about the lower crust. Only the thickness of the lower crust can be determined, and not the resistivity.

  1. Audio-magnetotelluric survey to characterize the Sunnyside porphyry copper system in the Patagonia Mountains, Arizona

    USGS Publications Warehouse

    Sampson, Jay A.; Rodriguez, Brian D.

    2010-01-01

    The Sunnyside porphyry copper system is part of the concealed San Rafael Valley porphyry system located in the Patagonia Mountains of Arizona. The U.S. Geological Survey is conducting a series of multidisciplinary studies as part of the Assessment Techniques for Concealed Mineral Resources project. To help characterize the size, resistivity, and skin depth of the polarizable mineral deposit concealed beneath thick overburden, a regional east-west audio-magnetotelluric sounding profile was acquired. The purpose of this report is to release the audio-magnetotelluric sounding data collected along that east-west profile. No interpretation of the data is included.

  2. Magnetotelluric survey to characterize the Sunnyside porphyry copper system in the Patagonia Mountains, Arizona

    USGS Publications Warehouse

    Rodriguez, Brian D.; Sampson, Jay A.

    2010-01-01

    The Sunnyside porphyry copper system is part of the concealed San Rafael Valley porphyry system located in the Patagonia Mountains of Arizona. The U.S. Geological Survey is conducting a series of multidisciplinary studies as part of the Assessment Techniques for Concealed Mineral Resources project. To help characterize the size and resistivity of the mineralized area beneath overburden, a regional east-west magnetotelluric sounding profile was acquired. This is a data release report of the magnetotelluric sounding data collected along the east-west profile; no interpretation of the data is included.

  3. UNDERSTANDING THE BREAST CANCER EXPERIENCE OF WOMEN: A QUALITATIVE STUDY OF AFRICAN AMERICAN, ASIAN AMERICAN, LATINA AND CAUCASIAN CANCER SURVIVORS

    PubMed Central

    ASHING-GIWA, KIMLIN TAM; PADILLA, GERALDINE; TEJERO, JUDITH; KRAEMER, JANET; WRIGHT, KAREN; COSCARELLI, ANNE; CLAYTON, SHEILA; WILLIAMS, IMANI; HILLS, DAWN

    2006-01-01

    Breast cancer is the most common form of cancer in American women across most ethnic groups. Although the psychosocial impact of breast cancer is being studied, there is little information on women from diverse ethnic and socioeconomic backgrounds. We conducted a qualitative study with breast cancer survivors (BCS) of various ethnicities. A total of 102 BCS participated in focus group interviews (24 African Americans, 34 Asians, 26 Latinas and 18 Caucasians); 20 health professionals participated in key informant interviews. Important ethnic differences in type of treatment were noted, Asians and Latinas were more likely to receive mastectomies and African American BCS were least likely to receive adjuvant therapies, including radiation and chemotherapy. These BCS enjoyed a fairly good overall health-related quality of life (HRQOL) with some persistent concerns. The prevailing concerns among all women included overall health, moderate physical concerns, cancer recurrence or metastases, psychosocial concerns related to worry about children and burdening the family, and body image and sexual health concerns. Additional challenges included: lack of knowledge about breast cancer; medical care issues such as insurance, cost and amount of time spent with physician; cultural sensitivity of providers, language barriers, cultural factors related to beliefs about illness, gender role and family obligations (e.g. self-sacrifice). These BCS, particularly the women of color, voiced that their spiritual beliefs and practices are central to their coping. This study accomplishes two goals; it adds to the sparse literature concerning the psychosocial sequelae of breast cancer among women of color, and it increases our knowledge of specific cultural influences (e.g. dietary practices, coping) and socio-ecological factors on HRQOL. More importantly, the study addressed areas that have not been studied before, specifically, an in-depth study on BCS QOL comparing multiple ethnic groups

  4. African American Preschoolers' Language, Emergent Literacy Skills, and Use of African American English: A Complex Relation

    ERIC Educational Resources Information Center

    Connor, Carol McDonald; Craig, Holly K.

    2006-01-01

    Purpose: This study examined the relation between African American preschoolers' use of African American English (AAE) and their language and emergent literacy skills in an effort to better understand the perplexing and persistent difficulties many African American children experience learning to read proficiently. Method: African American…

  5. WALDIM: A code for the dimensionality analysis of magnetotelluric data using the rotational invariants of the magnetotelluric tensor

    NASA Astrophysics Data System (ADS)

    Martí, A.; Queralt, P.; Ledo, J.

    2009-12-01

    In the magnetotelluric (MT) method, the analysis of geoelectric dimensionality has acquired special importance in the last years, because numerical codes have made it possible to model and invert data using either one-dimensional (1D), two-dimensional (2D) or three-dimensional (3D) approaches. We present a FORTRAN code termed WALDIM to perform the dimensionality analysis of a set of MT data, according to the WAL rotational invariants criteria. These criteria are based on the possible annulment of the invariants of the MT tensor, which allow retrieval of as much information as possible from this tensor, without taking any a priori dimensionality assumption. When determining the dimensionality of real and therefore noisy data, two problems arise. The first is due to the data errors, which propagate into the invariants values, and therefore, to the determination of the dimensionality. The second is the fact that the invariants are rarely precisely zero, and the definition of a threshold is necessary. To solve these problems, WALDIM takes into account the data errors. Additionally, the dimensionality results can be grouped into frequency bands. Thus, we provide a software utility that allows providing a robust description of the dimensionality, and the parameters necessary for data correction prior to modeling. Given its completeness at analyzing the MT tensor for both individual and bands of frequencies, this code is meant to be a practical tool for MT data analysis.

  6. A magnetotelluric study of the sensitivity of an area to seismoelectric signals

    USGS Publications Warehouse

    Balasis, G.; Bedrosian, P.A.; Eftaxias, K.

    2005-01-01

    During recent years, efforts at better understanding the physical properties of precursory ultra-low frequency pre-seismic electric signals (SES) have been intensified. Experiments show that SES cannot be observed at all points of the Earth's surface but only at certain so-called sensitive sites. Moreover, a sensitive site is capable of collecting SES from only a restricted number of seismic areas (selectivity effect). Tberefore the installation of a permanent station appropriate for SES collection should necessarily be preceded by a pilot study over a broad area and for a long duration. In short, a number of temporary stations are installed and, after the occurrence of several significant earthquakes (EQs) from a given seismic area, the most appropriate (if any) of these temporary stations, in the sense that they happen to collect SES, can be selected as permanent. Such a long experiment constitutes a serious disadvantage in identifying a site as SES sensitive. However, the SES sensitivity of a site should be related to the geoelectric structure of the area that hosts the site as well as the regional geoelectric structure between the station and the seismic focal area. Thus, knowledge of the local and regional geoelectric structure can dramatically reduce the time involved in identifying SES sites. hi this paper the magnetotelluric method is used to investigate the conductivity structure of an area where a permanent SES station is in operation. Although general conclusions cannot be drawn, the area surrounding an SES site near Ioannina, Greece is characterized by: (1) major faults in the vicinity; (2) highly resistive structure flanked by abrupt conductivity contrasts associated with large-scale geologic contacts, and (3) local inhomogeneities in conductivity structure. The above results are consistent with the fact that electric field amplitudes from remotely-generated signals should be appreciably stronger at such sites when compared to neighboring sites

  7. Experimenting in Distance Education: The African Virtual University (AVU) and the Paradox of the World Bank in Kenya

    ERIC Educational Resources Information Center

    Amutabi, M. N.; Oketch, M. O.

    2003-01-01

    This article seeks to accomplish three objectives. The first is to interrogate the efficacy of the African Virtual University (AVU), which is a satellite and information technology (IT)-based distance education system, sponsored by the World Bank in Kenya. The second is to demonstrate the failures of the AVU and the reasons why this has been the…

  8. From Victory to Freedom: The African American Experience. Curriculum Guide: Elementary and Middle School Course of Study.

    ERIC Educational Resources Information Center

    Ohio Historical Society, Columbus.

    This elementary and middle school curriculum guide contains three sections of instructional materials about three areas of African American life. The section "Community Life" includes detailed lessons on family, the church, education, business, and organizations. The section "Public Life" provides in-depth lessons on media, science and medicine,…

  9. The African Experience. Volume I: Syllabus Lectures; Volume II: Bibliographic References; Volume IIIA: Introductory Essays; Volume IIIB: Introductory Essays.

    ERIC Educational Resources Information Center

    Paden, John N.; Soja, Edward W.

    In response to demands for more and better teaching about Africa in American higher education, the US Office of Education requested that the Program of African Studies at Northwestern University generate a set of teaching materials which could be used in introductory undergraduate courses. Included in these volumes, these materials provide…

  10. Inclusive Education and Training in South African Higher Education: Mapping the Experiences of a Student with Physical Disability at University

    ERIC Educational Resources Information Center

    Ntombela, Sithabile

    2013-01-01

    The South African Constitution upholds and entrenches the human right of all citizens. Similarly, the Higher Education Act of 1997 promotes equality of access for all, especially for those previously marginalised or excluded. The study reported in this article explored challenges experienced by students with disabilities at his university. Using…

  11. Ethnic Identity, Neighborhood Risk, and Adolescent Drug and Sex Attitudes and Refusal Efficacy: The Urban African American Girls' Experience

    ERIC Educational Resources Information Center

    Corneille, Maya A.; Belgrave, Faye Z.

    2007-01-01

    This study examined the impact of ethnic identity and neighborhood risk on drug and sex attitudes and refusal efficacy among early adolescent urban African American females (n = 175). The model also predicted a moderating relationship of ethnic identity on neighborhood risk for drug and sex attitudes and refusal efficacy. Data were collected as…

  12. Interactive Reading Experiences of African American Fathers and Social Fathers and Their 4- and 5-Year-Old Children

    ERIC Educational Resources Information Center

    Jackson, Clarissa R.

    2012-01-01

    The purpose of this mixed-methods study was to investigate the patterns of book choice and interaction during book reading sessions of six African American fathers and social fathers and their 4- to 5-year-old children. The fathers/social fathers selected and read aloud expository text, narrative text, and poetry to their children while…

  13. Building the Capacity of First Year Social Work Students: Experiences from a South African Tertiary Education Institution

    ERIC Educational Resources Information Center

    Drower, Sandra J.; Kleijn, Amelia A.

    2008-01-01

    A three part Building Capacity Program developed for social work students in a South African tertiary education institution is described. The primary purpose of the Program was to build the capacity of social work students considered to be at risk of not completing their studies. The Program is located within the socio-political context of South…

  14. Retaining and Reclaiming Ourselves: Reflections on a Peer Mentoring Group Experience for New African American Women Professors

    ERIC Educational Resources Information Center

    Packer-Williams, Catherine L.; Evans, Kathy M.

    2011-01-01

    This article reports on the results of a qualitative study of new African American female professors' participation in a peer mentoring group. Three key themes that emerged from the data included peer mentoring as a vehicle to process and cope effectively with microaggressions, increase positive self-identity and self-efficacy as a scholar, and…

  15. A Peculiar Sensation: Double Consciousness and the Lived Experiences of African American Art Historians at Predominately White Institutions

    ERIC Educational Resources Information Center

    Swaidan, Christina Michelle

    2010-01-01

    Double consciousness is the identity conflict of being Black and being an American (Du Bois, 1903). Double consciousness leads to "identity confusion and inherent contradictions in the collective psyche of people of African descent" (Benjamin, 2005, p. 21.). This study employed grounded theory to collect and analyze the data that emerged from the…

  16. Executive University Managers' Experiences of Strike and Protest Activity: A Qualitative Case Study of a South African University

    ERIC Educational Resources Information Center

    Dominguez-Whitehead, Y.

    2011-01-01

    Strike and protest activity at South African universities continues to be prevalent nearly two decades after the dismantling of apartheid, although there has been a shift away from directing strikes and protests against the government (during the apartheid era), to directing them against higher education institutions and management (since the…

  17. Narratives of Agency: The Experiences of Braille Literacy Practitioners in the "Kha Ri Gude" South African Mass Literacy Campaign

    ERIC Educational Resources Information Center

    McKay, Veronica I.; Romm, Norma R. A.

    2015-01-01

    In this article, we locate the "Kha Ri Gude" South African Mass Literacy Campaign within the context of the problem of illiteracy and exclusion in South Africa, while concentrating on various post-apartheid initiatives designed to give visually challenged adults the opportunity to become literate. We shall provide a detailed account of…

  18. Technical Consulting: The African-American Perspective

    ERIC Educational Resources Information Center

    Whitfield, Tracy N.

    2010-01-01

    The qualitative research study explored the organizational characteristics necessary in addressing the low concentration of African American technical consultants employed in the information technology industry. Using research participants' professional experience, participants responded to a developed questionnaire. African American technical…

  19. Cooperation between scientists, NGOs and industry in support of sustainable fisheries: the South African hake Merluccius spp. trawl fishery experience.

    PubMed

    Field, J G; Attwood, C G; Jarre, A; Sink, K; Atkinson, L J; Petersen, S

    2013-10-01

    This paper examines the increasingly close interaction between natural and social scientists, non-governmental organizations (NGO) and industry, in pursuit of responsible ecosystem-based management of fisheries. South Africa has committed to implementing an ecosystem approach to fisheries management. Management advice stems from multi-stakeholder representation on government-led scientific and management working groups. In the hake Merluccius capensis and Merluccius paradoxus fishery, the primary management measure is an annual total allowable catch (TAC), the level of which is calculated using a management procedure (MP) that is revised approximately every 4 years. Revision of the MP is a consultative process involving most stakeholders, and is based on simulation modelling of projected probable scenarios of resource and fishery dynamics under various management options. NGOs, such as the Worldwide Fund for Nature in South Africa (WWF-SA), have played an important role in influencing consumers, the fishing industry and government to develop responsible fishing practices that minimize damage to marine ecosystems. Cooperation between industry, government and scientists has helped to improve sustainability and facilitated the meeting of market-based incentives for more responsible fisheries. Research includes ecosystem modelling, spatial analysis and ecosystem risk assessment with increasing research focus on social and economic aspects of the fishery. A four-year cooperative experiment to quantify the effect of trawling on benthic community structure is being planned. The food requirements of top predators still need to be included in the TAC-setting formulae and more social and economic research is needed. This paper also demonstrates how NGO initiatives such as Marine Stewardship Council certification and the Southern African Sustainable Seafood Initiative, a traffic light system of classifying seafood for consumers, have contributed to responsible fishing

  20. Two-dimensional magnetotelluric inversion of the EMSLAB Lincoln Line

    NASA Astrophysics Data System (ADS)

    Jiracek, George R.; Curtis, Jeffrey H.; Ramirez, Jorge; Martinez, Mario; Romo, Jose

    1989-10-01

    Two-dimensional, Backus-Gilbert inversion of the EMSLAB land magnetotelluric (MT) data along the 200-km-long Lincoln Line has yielded optimally smooth geoelectric sections. Inversions were performed on the apparent resistivity and impedance phase data approximating the transverse magnetic (TM) mode. The land portion of the Lincoln Line traverses the edge of the North American plate that is being underthrust by the Juan de Fuca plate system. The inversion reveals three centralized conductive zones in the depth range of 20-40 km. A slightly conducting (<100 S) zone is centered at 30-35 km depth under the Oregon Coast Range; this feature may be the top of the subducting Juan de Fuca plate since there is complementary evidence here from Consortium for Continental Reflection Profiling seismic data. A prominent conduction zone of several hundred Siemens (S) is also detected at 30-35 km depth under the very resistive (>1000 ohm m) Western Cascades. Here the depth is too shallow for the zone to be the subducting plate. There is also evidence for a highly conducting (>1000 S) lower crust east of the High Cascades on the east end of the Lincoln Line. Two vertical conductive regions are also exposed in the inversion model. One occurs at 70-80 km from the coast under the Willamette Valley where a postulated Eocene trench may have left a suture zone. The second region is coincident with surface hydrothermal activity along the Western-High Cascades boundary. There are ample sources of water in the crust, e.g., in subducted sediments, from dehydration reactions along the upper plate boundary, and in volcanic arc magmas, to lead us to believe that hot, saline water is the major source of the conductive occurrences along the Lincoln Line. However, the various zones appear to be distinct, and the water may be trapped by different mechanisms.

  1. 3D Magnetotelluric characterization of the COSO GeothermalField

    SciTech Connect

    Newman, Gregory A.; Hoversten, Michael; Gasperikova, Erika; Wannamaker, Philip E.

    2005-01-01

    Knowledge of the subsurface electrical resistivity/conductivity can contribute to a better understanding of complex hydrothermal systems, typified by Coso geothermal field, through mapping the geometry (bounds and controlling structures) over existing production. Three-dimensional magnetotelluric (MT) inversion is now an emerging technology for characterizing the resistivity structures of complex geothermal systems. The method appears to hold great promise, but histories exploiting truly 3D inversion that demonstrate the advantages that can be gained by acquiring and analyzing MT data in three dimensions are still few in number. This project will address said issue, by applying 3D MT forward modeling and inversion to a MT data set acquired over the Coso geothermal field. The goal of the project is to provide the capability to image large geothermal reservoirs in a single self-consistent model. Initial analysis of the Coso MT data has been carried out using 2D MT imaging technology to construct an initial 3D resistivity model from a series of 2D resistivity images obtained using the inline electric field measurements (Zxy impedance elements) along different measurement transects. This model will be subsequently refined through a 3D inversion process. The initial 3D resistivity model clearly shows the controlling geological structures possibly influencing well production at Coso. The field data however, also show clear three dimensionality below 1 Hz, demonstrating the limitations of 2D resistivity imaging. The 3D MT predicted data arising from this starting model show good correspondence in dominant components of the impedance tensor (Zxy and Zyx) above 1Hz. Below 1 Hz there is significant differences between the field data and the 2D model data.

  2. Magnetotelluric Investigation of Melt Storage Beneath Okmok Caldera, Alaska

    NASA Astrophysics Data System (ADS)

    Bennington, N. L.; Bedrosian, P.; Key, K.; Zelenak, G.

    2015-12-01

    Alaska accounts for nearly 99% of the seismic moment release within the US. Much of this is associated with the Aleutian volcanic arc, the most tectonically active region in North America, and an ideal location for studying arc magmatism. Okmok is an active volcano located in the central Aleutian arc, defined by a pair of nested, 10 km diameter calderas. The subdued topography of Okmok, relative to other Aleutian volcanoes, improves access and permits dense sampling within the caldera closer to the underlying magmatic system. Okmok volcano was selected as the site of study for this project due to frequent volcanic activity and the presence of a crustal magma reservoir as inferred from previous coarse resolution seismic studies. In June-July 2015, we carried out an amphibious geophysical field deployment at Okmok. Onshore work in and around the volcano included collection of an array of magnetotelluric (MT) stations and installation of a temporary, year-long seismic array. A ring of 3D offshore MT deployments made around the island augments the onshore array. An additional 2D tectonic-scale profile spans the trench, volcanic arc, and backarc. This new geophysical data will be used to gain a greater understanding of Aleutian arc melt generation, migration, and storage beneath an active caldera. We present results from the analysis of the newly collected amphibious 3D MT data. This data will be used to model the distribution and migration of melt within Okmok's crustal magma reservoir. Initial processing of the data shows strong MT signal levels, in particular from a geomagnetic storm that occurred from June 21-23, 2015. A companion abstract discussing the 2D tectonic scale MT profile, which constrains the mantle and deep crust beneath Okmok volcano, is discussed by Zelenak et al.

  3. Using Empirical Mode Decomposition to process Marine Magnetotelluric Data

    NASA Astrophysics Data System (ADS)

    Chen, J.; Jegen, M. D.; Heincke, B. H.; Moorkamp, M.

    2014-12-01

    The magnetotelluric (MT) data always exhibits nonstationarities due to variations of source mechanisms causing MT variations on different time and spatial scales. An additional non-stationary component is introduced through noise, which is particularly pronounced in marine MT data through motion induced noise caused by time-varying wave motion and currents. We present a new heuristic method for dealing with the non-stationarity of MT time series based on Empirical Mode Decomposition (EMD). The EMD method is used in combination with the derived instantaneous spectra to determine impedance estimates. The procedure is tested on synthetic and field MT data. In synthetic tests the reliability of impedance estimates from EMD-based method is compared to the synthetic responses of a 1D layered model. To examine how estimates are affected by noise, stochastic stationary and non-stationary noise are added on the time series. Comparisons reveal that estimates by the EMD-based method are generally more stable than those by simple Fourier analysis. Furthermore, the results are compared to those derived by a commonly used Fourier-based MT data processing software (BIRRP), which incorporates additional sophisticated robust estimations to deal with noise issues. It is revealed that the results from both methods are already comparable, even though no robust estimate procedures are implemented in the EMD approach at present stage. The processing scheme is then applied to marine MT field data. Testing is performed on short, relatively quiet segments of several data sets, as well as on long segments of data with many non-stationary noise packages. Compared to BIRRP, the new method gives comparable or better impedance estimates, furthermore, the estimates are extended to lower frequencies and less noise biased estimates with smaller error bars are obtained at high frequencies. The new processing methodology represents an important step towards deriving a better resolved Earth model to

  4. Magnetotelluric signature of anticlines in Iran's Sehqanat oil field

    NASA Astrophysics Data System (ADS)

    Mansoori, Isa; Oskooi, Behrooz; Pedersen, Laust B.

    2015-07-01

    The magnetotelluric (MT) method has proved to be an effective tool in hydrocarbon exploration especially in areas with geological structures/formations where seismic reflection provides neither good quality data nor images. The Sehqanat oil field located in the sedimentary zone of Zagros in SW of Iran is a typical example. It is covered by the high velocity and heterogeneous formation of Gachsaran, which is exposed at the surface and has a thickness varying from 500 m to more than 2 km in the region. Gachsaran is composed mainly of salt and evaporites overlying, as a cap rock, the Asmari limestone formation which is the main reservoir in all oil fields of Iran along the Zagros range. The main geological interface which is targeted to be imaged with the MT method is the contact between the highly conductive evaporites of the Gachsaran formation and the underlying more resistive carbonates of the Asmari formation. MT data at more than 600 stations along five parallel SW-NE profiles crossing the main geological trend of the study area and transient electromagnetic data over 400 stations to be used for static shift corrections of the MT data were available. Dimensionality and strike analysis of the MT data show dominant two-dimensional (2-D) conditions in almost all sites and periods. The 2-D resistivity models resolved the boundary between Gachsaran and Asmari formations as a transition zone from highly conductive to resistive structures. The Sehqanat anticline has also been delineated throughout the 2-D resistivity sections as a resistive dome-shaped body located in the middle part of the MT profiles. There is a considerable correlation between the 2-D resistivity models and the adjacent 2-D reflection seismic sections so that a more reliable interpretation on the hydrocarbon trap of the Sehqanat anticline can be obtained.

  5. Non-linearity in Bayesian 1-D magnetotelluric inversion

    NASA Astrophysics Data System (ADS)

    Guo, Rongwen; Dosso, Stan E.; Liu, Jianxin; Dettmer, Jan; Tong, Xiaozhong

    2011-05-01

    This paper applies a Bayesian approach to examine non-linearity for the 1-D magnetotelluric (MT) inverse problem. In a Bayesian formulation the posterior probability density (PPD), which combines data and prior information, is interpreted in terms of parameter estimates and uncertainties, which requires optimizing and integrating the PPD. Much work on 1-D MT inversion has been based on (approximate) linearized solutions, but more recently fully non-linear (numerical) approaches have been applied. This paper directly compares results of linearized and non-linear uncertainty estimation for 1-D MT inversion; to do so, advanced methods for both approaches are applied. In the non-linear formulation used here, numerical optimization is carried out using an adaptive-hybrid algorithm. Numerical integration applies Metropolis-Hastings sampling, rotated to a principal-component parameter space for efficient sampling of correlated parameters, and employing non-unity sampling temperatures to ensure global sampling. Since appropriate model parametrizations are generally not known a priori, both under- and overparametrized approaches are considered. For underparametrization, the Bayesian information criterion is applied to determine the number of layers consistent with the resolving power of the data. For overparametrization, prior information is included which favours simple structure in a manner similar to regularized inversion. The data variance and/or trade-off parameter regulating data and prior information are treated in several ways, including applying fixed optimal estimates (an empirical Bayesian approach) or including them as hyperparameters in the sampling (hierarchical Bayesian). The latter approach has the benefit of accounting for the uncertainty in the hyperparameters in estimating model parameter uncertainties. Non-linear and linearized inversion results are compared for synthetic test cases and for the measured COPROD1 MT data by considering marginal probability

  6. Using climate model experiments to explore difference between degrees of global warming: lessons from a study of African precipitation

    NASA Astrophysics Data System (ADS)

    James, Rachel; Washington, Richard

    2015-04-01

    A 2°C increase in global mean temperature (ΔTg) has been widely adopted as a benchmark for dangerous climate change, and is currently being reviewed under the United Nations Framework Convention on Climate Change. However, there has been relatively little research into the implications of 2°C, or any other degree of global warming, for regional climate. This lack of research is particularly pressing in the case of vulnerable regions, including many in Africa. In recognition of this research gap, we conducted an in depth study of changes in African temperature and precipitation associated with 1°C, 1.5°C, 2°C, 3°C, 4°C, and beyond, using output from almost 400 climate model experiments: simulations from international modelling centres (CMIP3 and CMIP5), two perturbed physics ensembles, and a group of five regional models. The implications of global warming are different depending on which models are consulted, but each model consistently shows that temperature and precipitation anomalies are enhanced progressively with global warming. At 1°C, there is little significant change, but from 1.5°C or 2°C anomalies develop which grow in magnitude and spatial extent with global temperature, for example drying over Angola, and wetting in East Africa. The main difference between ΔTg intervals is in the magnitude and spatial extent of change. There do not appear to be rapid accelerations in the rate of change or trend reversals. This is not only true for lower levels of anthropogenic forcing, but also at higher degrees of warming up to 6°C. This finding has potential implications for policy. Given that larger changes in climate are likely to generate greater challenges for society, it suggests that global temperature should be limited to the lowest level possible. It does not imply that 2°C, or any other ΔTg increment, should be a preferred target from the perspective of regional climate. However, it is important to consider whether the approximately linear

  7. MT+, integrating magnetotellurics to determine earth structure, physical state, and processes

    USGS Publications Warehouse

    Bedrosian, P.A.

    2007-01-01

    As one of the few deep-earth imaging techniques, magnetotellurics provides information on both the structure and physical state of the crust and upper mantle. Magnetotellurics is sensitive to electrical conductivity, which varies within the earth by many orders of magnitude and is modified by a range of earth processes. As with all geophysical techniques, magnetotellurics has a non-unique inverse problem and has limitations in resolution and sensitivity. As such, an integrated approach, either via the joint interpretation of independent geophysical models, or through the simultaneous inversion of independent data sets is valuable, and at times essential to an accurate interpretation. Magnetotelluric data and models are increasingly integrated with geological, geophysical and geochemical information. This review considers recent studies that illustrate the ways in which such information is combined, from qualitative comparisons to statistical correlation studies to multi-property inversions. Also emphasized are the range of problems addressed by these integrated approaches, and their value in elucidating earth structure, physical state, and processes. ?? Springer Science+Business Media B.V. 2007.

  8. Audio-magnetotelluric data collected in the area of Beatty, Nevada

    SciTech Connect

    Williams, J.M.

    1998-11-01

    In the summer of 1997, electrical geophysical data was collected north of Beatty, Nevada. Audio-magnetotellurics (AMT) was the geophysical method used to collect 16 stations along two profiles. The purpose of this data collection was to determine the depth to the alluvial basement, based upon the needs of the geologists requesting the data.

  9. SAGE 2010 Magnetotelluric Soundings Provide New Constraints on Rio Grande Rift Mid-Crustal Conductor

    NASA Astrophysics Data System (ADS)

    Strader, A. E.; Martin, C. L.; Thomas, T.; Bedrosian, P. A.; Pellerin, L.; Jiracek, G. R.

    2010-12-01

    Since the inception of the Summer of Applied Geophysical Experience (SAGE) program in 1983, long-period magnetotelluric (MT) soundings have imaged a pronounced mid-crustal conductor at 10-20 km depth within the central Rio Grande rift. Wideband MT soundings (0.01 to over 1000 s period) collected in 2010 extended the detection of this feature to nearly 100 km length along the rift axis in the vicinity of Santa Fe, New Mexico. The conductive anomaly is clearly defined in the longest periods of the mode identified as the transverse electric (TE) in the recently acquired MT data. The spatially-limited 2010 soundings in the Santo Domingo Basin do not allow two-dimensional (2-D) inversions; however, one-dimensional (1-D) inversion of TE mode measurements in conductive rift basins can yield good depth estimates of deep conductive layers as has been shown by 2-D rift MT modeling. Such 1-D inversions of the 2010 MT soundings yield ~20 km depth to the top of the mid-crustal conductor, 5-10 km deeper than 90 km to the north if 3-D effects are negligible. Estimated conductance of the Santo Domingo basin conductor is 2000 S with resistivities in the range of 2-10 ohm-m. An interpretation of the ubiquitous, mid-crustal conductor in the Rio Grande rift is interconnected, saline, aqueous fluid trapped in the ductile crust below the ~10 km-deep seismogenic zone after fluid release and upward ascent from an upwarped mantle.

  10. Gravity and Magnetotelluric Modeling of the Santo Domingo Basin, Northern New Mexico

    NASA Astrophysics Data System (ADS)

    Zamudio, K. D.; Keithline, N.; Blum, C.; Cunningham, E.; Fromont, A.; Jorgensen, M.; Lee, R.; McBride, K.; Saez Berrios, P.; Harper, C.; Pellerin, L.; McPhee, D.; Ferguson, J. F.

    2015-12-01

    The Santo Domingo Basin, one of a series of basins within the Rio Grande Rift, is located between Santa Fe and Albuquerque, NM, and has been the focus of research by the Summer of Geophysical Experience (SAGE) program since 2000. Gravity, magnetotelluric (MT), and seismic data have been collected throughout the region, although we are concentrating on gravity and MT data collected during SAGE 2014 and 2015. The study area is located in the center of the Santo Domingo basin, an extensional, Miocene age, rift basin, in an area that was minimally involved in the preceding local Laramide orogenic activity. Rift sediments (~3.5 km thick) are underlain by Eocene age sediments that were shed from adjacent uplifts. Up to 3 km of Mesozoic and Paleozoic sediments are preserved above the Precambrian basement. Geologic outcrop, borehole and seismic reflection data, and known density values were used in the construction of a ~100 km-long, generalized geologic cross section from which a gravity response was calculated. The modeled gravity response makes fairly definitive predictions about the geometry of the basin as well as the stratigraphy and faulting within and bounding the basin. MT data was collected at ten stations within the basin. The MT sounding curves exhibit one-dimensional behavior at short periods (<10 s), not surprisingly considering the relatively flat local structure in the area. Layered-earth MT models, without geologic constraints, show a conductive (<10 ohm-m) layer at ~1.5 km above a more resistive layer (>1000 ohm-m) at ~ 3.5-4 km. Conductivities of the major stratigraphic units have been determined from well logs and previous MT modeling. Forward and inverse MT models constrained by the gravity-modeled geologic cross section are used to develop a conductivity model consistent with the geology, and are a step towards a better unified treatment of MT, seismic and gravity data.

  11. An efficient modified hierarchical domain decomposition for two-dimensional magnetotelluric forward modelling

    NASA Astrophysics Data System (ADS)

    Rung-Arunwan, Tawat; Siripunvaraporn, Weerachai

    2010-11-01

    We use 2-D magnetotelluric (MT) problems as a feasibility study to demonstrate that 3-D MT problems can be solved with a direct solver, even on a standard single processor PC. The scheme used is a hierarchical domain decomposition (HDD) method in which a global computational domain is uniformly split into many smaller non-overlapping subdomains. To make it more efficient, two modifications are made to the standard HDD method. Instead of three levels as in the standard HDD method, we classify the unknowns into four classes: the interiors, the horizontal interfaces, the vertical interfaces and the intersections. Four sets of smaller systems of equations are successively solved with a direct method (an LU factorization). The separation significantly reduces the large memory requirements of a direct solver. It also reduces the CPU time to almost half that of the standard HDD method although it is still slower than the conventional finite difference (FD) method. To further enhance the speed of the code, a red-black ordering is applied to solve the horizontal and vertical interface reduced systems. Numerical experiments on a 2-D MT problem of a given size running on a single processor machine shows that CPU time and memory used are almost constant for any resistivity models, frequencies and modes. This is a clear advantage of our algorithm and is of particular importance if the method is applied to 3-D problems. We show that our new method results in reductions in both memory usage and CPU time for large enough domains when compared to the standard FD and HDD schemes. In addition, we also introduce a `memory minimization map', a graphical tool we can use instead of trial-and-error to pre-select the optimal size of subdomains, which yield the best performance in both CPU time and memory even running on a serial machine.

  12. A layer stripping approach for monitoring resistivity variations using surface magnetotelluric responses

    NASA Astrophysics Data System (ADS)

    Ogaya, Xènia; Ledo, Juanjo; Queralt, Pilar; Jones, Alan G.; Marcuello, Álex

    2016-09-01

    The resolution of surface-acquired magnetotelluric data is typically not sufficiently high enough in monitoring surveys to detect and quantify small resistivity variations produced within an anomalous structure at a given depth within the subsurface. To address this deficiency we present an approach, called "layer stripping", based on the analytical solution of the one-dimensional magnetotelluric problem to enhance the sensitivity of surface magnetotelluric responses to such subtle subsurface temporal variations in resistivity within e.g. reservoirs. Given a well-known geoelectrical baseline model of a reservoir site, the layer stripping approach aims to remove the effect of the upper, unchanging structures in order to simulate the time-varying magnetotelluric responses at depth. This methodology is suggested for monitoring all kinds of reservoirs, e.g. hydrocarbons, gas, geothermal, compress air storage, etc., but here we focus on CO2 geological storage. We study one-dimensional and three-dimensional resistivity variations in the reservoir layer and the feasibility of the method is appraised by evaluating the error of the approach and defining different detectability parameters. The geoelectrical baseline model of the Hontomín site (Spain) for CO2 geological storage in a deep saline aquifer is taken as our exemplar for studying the validity of the 1D assumption in a real scenario. We conclude that layer stripping could help detect resistivity variations and locate them in the space, showing potential to also sense unforeseen resistivity variations at all depths. The proposed approach constitutes an innovative contribution to take greater advantage of surface magnetotelluric data and to use the method as a cost-effective permanent monitoring technique in suitable geoelectrical scenarios.

  13. Shallow water radio-magnetotelluric (RMT) measurements in urban environment: A case study from Stockholm city

    NASA Astrophysics Data System (ADS)

    Mehta, Suman; Bastani, Mehrdad; Malehmir, Alireza; Wang, Shunguo; Pedersen, Laust

    2014-05-01

    of the impedance tensor were obtained by the parametric representation combined with a Truncated Singular Value Decomposition (TSVD) regularization of Bastani and Pedersen (2001). The processed data were then inverted to obtain 2D resistivity models. The resulting models along 23 lines correlate well and image variation of water depth, thickness of subaqueous sediments as well as the depth to crystalline bedrock. Low resistivity zones observed in the bedrock coincide well with the low velocity zones identified in refraction seismic surveys available along the RMT lines, indicating the presence of possible fracture zones in the bedrock. The experiment illustrates that the RMT methods can be well adapted to this type of environment; it is fast and cost-effective in shallow water especially in urban settings. Acknowledgments: Formas, SGU, BeFo, SBUF, Skanska, Boliden, FQM and NGI References: Bastani, M., 2001, EnviroMT - a new Controlled Source/Radio Magnetotelluric System: Ph.D. thesis, ISBN 91-554-5051-2, Uppsala University. Bastani, M. and Pedersen, L. B., 2001, Estimation of magnetotelluric transfer functions from radio transmitters. GEOPHYSICS, 66, 1038-1051.

  14. Magnetotelluric data, stable distributions and impropriety: an existential combination

    NASA Astrophysics Data System (ADS)

    Chave, Alan D.

    2014-07-01

    The robust statistical model of a Gaussian core contaminated by outlying data that underlies robust estimation of the magnetotelluric (MT) response function has been re-examined. The residuals from robust estimators are systematically long tailed compared to a distribution based on the Gaussian, and hence are inconsistent with the robust model. Instead, MT data are pervasively described by the alpha stable distribution family whose variance and sometimes mean are undefined. A maximum likelihood estimator (MLE) that exploits the stable nature of MT data is formulated, and its two-stage implementation in which stable parameters are first fit to the data and then the MT responses are solved for is described. The MLE is shown to be inherently robust, but differs from the conventional robust estimator because it is based on a model derived from the data, while robust estimators are ad hoc, being based on the robust model that is inconsistent with actual data. Propriety versus impropriety of the complex MT response was investigated, and a likelihood ratio test for propriety and its null distribution was established. The Cramér-Rao lower bounds for the covariance matrix of proper and improper MT responses were specified. The MLE was applied to exemplar long period and broad-band data sets from South Africa. Both are shown to be significantly stably distributed using the Kolmogorov-Smirnov goodness of fit and Ansari-Bradley non-parametric dispersion tests. Impropriety of the MT responses at both sites is pervasive, hence the improper Cramér-Rao bound was used to estimate the MLE covariance. The MLE is shown to be nearly unbiased and well described by a Gaussian distribution based on bootstrap simulation. The MLE was compared to a conventional robust estimator, establishing that the standard errors of the former are systematically smaller than for the latter and that the standardized differences between them exhibit excursions that are both too frequent and too large to

  15. Anisotropic magnetotelluric inversion using a mutual information constraint

    NASA Astrophysics Data System (ADS)

    Mandolesi, E.; Jones, A. G.

    2012-12-01

    In recent years, several authors pointed that the electrical conductivity of many subsurface structures cannot be described properly by a scalar field. With the development of field devices and techniques, data quality improved to the point that the anisotropy in conductivity of rocks (microscopic anisotropy) and tectonic structures (macroscopic anisotropy) cannot be neglected. Therefore a correct use of high quality data has to include electrical anisotropy and a correct interpretation of anisotropic data characterizes directly a non-negligible part of the subsurface. In this work we test an inversion routine that takes advantage of the classic Levenberg-Marquardt (LM) algorithm to invert magnetotelluric (MT) data generated from a bi-dimensional (2D) anisotropic domain. The LM method is routinely used in inverse problems due its performance and robustness. In non-linear inverse problems -such the MT problem- the LM method provides a spectacular compromise betwee quick and secure convergence at the price of the explicit computation and storage of the sensitivity matrix. Regularization in inverse MT problems has been used extensively, due to the necessity to constrain model space and to reduce the ill-posedness of the anisotropic MT problem, which makes MT inversions extremely challenging. In order to reduce non-uniqueness of the MT problem and to reach a model compatible with other different tomographic results from the same target region, we used a mutual information (MI) based constraint. MI is a basic quantity in information theory that can be used to define a metric between images, and it is routinely used in fields as computer vision, image registration and medical tomography, to cite some applications. We -thus- inverted for the model that best fits the anisotropic data and that is the closest -in a MI sense- to a tomographic model of the target area. The advantage of this technique is that the tomographic model of the studied region may be produced by any

  16. Using empirical mode decomposition to process marine magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Chen, Jin; Heincke, Bjoern; Jegen, Marion; Moorkamp, Max

    2012-07-01

    A major step in processing magnetotelluric (MT) data is the calculation of an impedance tensor as function of frequency from recorded time-varying electromagnetic fields. Common signal processing techniques such as Fourier transform based procedures assume that the signals are stationary over the record length, which is not necessarily the case in MT, due to the possibility of sudden spatial and temporal variations in the naturally occurring source fields. In addition, noise in the recorded electric and magnetic field data may also be non-stationary. Many modern MT processing techniques can handle such non-stationarities through strategies such as windowing of the time-series. However, it is not completely clear how extreme non-stationarity may affect the resulting impedances. As a possible alternative, we examine a heuristic method called empirical mode decomposition (EMD) that is developed to handle arbitrary non-stationary time-series. EMD is a dynamic time series analysis method, in which complicated data sets can be decomposed into a finite number of simple intrinsic mode functions. In this paper, we use the EMD method on real and synthetic MT data. To determine impedance tensor estimates we first calculate instantaneous frequencies and spectra from the intrinsic mode functions and apply the impedance formula proposed by Berdichevsky to the instantaneous spectra. We first conduct synthetic tests where we compare the results from our EMD method to analytically determined apparent resistivities and phases. Next, we compare our strategy to a simple Fourier derived impedance formula and the frequently used robust processing technique bounded-influence remote reference processing (BIRRP) for different levels of stochastic noise. All results show that apparent resistivities and phases which are calculated from EMD derived impedance tensors are generally more stable than those determined from simple Fourier analysis and only slightly worse than those from the robust

  17. Experiences of Discrimination and Their Impact on the Mental Health Among African American, Asian and Pacific Islander, and Latino Men Who Have Sex With Men

    PubMed Central

    Paul, Jay; Ayala, George; Boylan, Ross; Gregorich, Steven E.

    2013-01-01

    Objectives. We examined the associations between specific types and sources of discrimination and mental health outcomes among US racial/ethnic minority men who have sex with men (MSM) and how these associations varied by race/ethnicity. Methods. A chain-referral sample of 403 African American, 393 Asian and Pacific Islander (API), and 400 Latino MSM recruited in Los Angeles County, California completed a standardized questionnaire. Data were obtained from the Ethnic Minority Men’s Health Study from May 2008 to October 2009. Results. Past-year experiences of racism within the general community and perceived homophobia among heterosexual friends were positively associated with depression and anxiety. Past-year homophobia experienced within the general community was also positively associated with anxiety. These statistically significant associations did not vary across racial/ethnic groups. The positive association of perceived racism within the gay community with anxiety differed by race/ethnicity, and was statistically significant only for APIs. Perceived homophobia within the family was not associated with either depression or anxiety. Conclusions. Higher levels of experiences of discrimination were associated with psychological distress among MSM of color. However, specific types and sources of discrimination were differentially linked to negative mental health outcomes among African American, API, and Latino MSM. PMID:23488483

  18. EXPERIENCES OF HIV/AIDS STIGMA OF PERSONS LIVING WITH HIV/AIDS AND NURSES INVOLVED IN THEIR CARE FROM FIVE AFRICAN COUNTRIES

    PubMed Central

    Greeff, Minrie; Uys, Leana R; Holzemer, William L; Makoae, Lucia N; Dlamini, Priscilla S; Kohi, Thecla W; Chirwa, Maureen L; Naidoo, Joanne R; Phetlhu, Rene D.

    2009-01-01

    The concept of stigma has received significant attention in recent years in the HIV/AIDS literature. Although there is some change towards the positive, AIDS still remains a significantly stigmatized condition. AIDS stigma and discrimination continue to influence people living with and affected by HIV (PLWA), as well as their health-care providers. Unless stigma is conquered, the illness will not be defeated. Due to the burden that HIV/AIDS places on people living in Africa, a five-year project entitled Perceived AIDS Stigma: A Multinational African Study was undertaken. The focus of the first phase of this project was on exploring and describing the meaning and effect of stigma on PLWA from the experiences of PLWA and the nurses involved in their care in five African countries: Lesotho, Swaziland, Malawi, South Africa and Tanzania. An exploratory descriptive qualitative research design was used to explore and describe the experience of stigma through the critical incident method. Purposive voluntary sampling was utilized. Forty-three focus group discussions were held with respondents to relate incidences which they themselves observed, as well as those that they themselves experienced in the community and in families. The transcribed data was analyzed through the technique of open coding using the NVivo 2.0 analysis package. Three types of stigma (received stigma, internal stigma and associated stigma) and several dimensions for each of these types of stigma emerged from the data. Recommendations were made to pursue these findings further. PMID:20052299

  19. EXPERIENCES OF HIV/AIDS STIGMA OF PERSONS LIVING WITH HIV/AIDS AND NURSES INVOLVED IN THEIR CARE FROM FIVE AFRICAN COUNTRIES.

    PubMed

    Greeff, Minrie; Uys, Leana R; Holzemer, William L; Makoae, Lucia N; Dlamini, Priscilla S; Kohi, Thecla W; Chirwa, Maureen L; Naidoo, Joanne R; Phetlhu, Rene D

    2008-01-01

    The concept of stigma has received significant attention in recent years in the HIV/AIDS literature. Although there is some change towards the positive, AIDS still remains a significantly stigmatized condition. AIDS stigma and discrimination continue to influence people living with and affected by HIV (PLWA), as well as their health-care providers. Unless stigma is conquered, the illness will not be defeated. Due to the burden that HIV/AIDS places on people living in Africa, a five-year project entitled Perceived AIDS Stigma: A Multinational African Study was undertaken. The focus of the first phase of this project was on exploring and describing the meaning and effect of stigma on PLWA from the experiences of PLWA and the nurses involved in their care in five African countries: Lesotho, Swaziland, Malawi, South Africa and Tanzania. An exploratory descriptive qualitative research design was used to explore and describe the experience of stigma through the critical incident method. Purposive voluntary sampling was utilized. Forty-three focus group discussions were held with respondents to relate incidences which they themselves observed, as well as those that they themselves experienced in the community and in families. The transcribed data was analyzed through the technique of open coding using the NVivo 2.0 analysis package. Three types of stigma (received stigma, internal stigma and associated stigma) and several dimensions for each of these types of stigma emerged from the data. Recommendations were made to pursue these findings further. PMID:20052299

  20. Crustal architecture and deep structure of the Namibian continental shelf and adjacent oceanic basins around the landfall of Walvis Ridge from wide-angle seismic and marine magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Planert, L.; Behrmann, J.; Jegen, M.; Heincke, B.; Jokat, W.; Bialas, J.; Marti, A.

    2012-12-01

    The opening of the South Atlantic ocean basin resulted in voluminous magmatism on the conjugate continental margins of Africa and South America, including the formation of the Parana and Entendeka large igneous provinces (LIPs), the formation of up to 100 km wide volcanic wedges characterized by seaward dipping reflector sequences (SDRs), as well as the formation of paired hotspot tracks on the rifted African and South American plates, the Walvis Ridge and the Rio Grande Rise. Hence, the passive margins bordering the South Atlantic are today considered as type examples for models involving hotspot related continental break-up. However, the presence of volcanic features (SDRs, LIPs) appears to be limited south of the hotspot trails. The resulting segmentation of the margins offers a prime opportunity to study the magmatic signal in space and time, and investigate the interrelation with rift-related deformation. A globally significant question to be adressed here is whether magmatism is the driving force for continental break-up, or whether even rifting with abundant hotspot related magmatism is in principle in response to crustal and lithospheric stretching. In 2010/11, a combination of on-/offshore wide-angle seismic, marine magnetotelluric and on-/offshore seismological data were acquired around the landfall of Walvis Ridge at the Namibian passive continental margin. The set of experiments was designed to provide crustal velocity and conductivity information and to investigate the structure of the upper mantle. In particular, we aimed at identifying deep fault zones and variations in Moho depth, the presence of interleaved sediment layers in SDR sequences as well as magmatic intrusions and underplated material near the continent-ocean transition. The sedimentary portions down to the igneous basement were additionally constrained by coincident single-channel reflection seismic data. Here, we present preliminary results for two wide-angle seismic transects and first

  1. “It's The Skin You're In”: African-American Women Talk About Their Experiences of Racism. An Exploratory Study to Develop Measures of Racism for Birth Outcome Studies

    PubMed Central

    Nuru-Jeter, Amani; Dominguez, Tyan Parker; Hammond, Wizdom Powell; Leu, Janxin; Skaff, Marilyn; Egerter, Susan; Jones, Camara P.; Braveman, Paula

    2011-01-01

    Objectives Stress due to experiences of racism could contribute to African-American women's adverse birth outcomes, but systematic efforts to measure relevant experiences among childbearing women have been limited. We explored the racism experiences of childbearing African-American women to inform subsequent development of improved measures for birth outcomes research. Methods Six focus groups were conducted with a total of 40 socioeconomically diverse African-American women of childbearing age in four northern California cities. Results Women reported experiencing racism (1) throughout the lifecourse, with childhood experiences seeming particularly salient and to have especially enduring effects (2) directly and vicariously, particularly in relation to their children; (3) in interpersonal, institutional, and internalized forms; (4) across different life domains; (5) with active and passive responses; and (6) with pervasive vigilance, anticipating threats to themselves and their children. Conclusions This exploratory study's findings support the need for measures reflecting the complexity of childbearing African-American women's racism experiences. In addition to discrete, interpersonal experiences across multiple domains and active/passive responses, which have been measured, birth outcomes research should also measure women's childhood experiences and their potentially enduring impact, perceptions of institutionalized racism and internalized negative stereotypes, vicarious experiences related to their children, vigilance in anticipating future racism events, as well as the pervasiveness and chronicity of racism exposure, all of which could be sources of ongoing stress with potentially serious implications for birth outcomes. Measures of racism addressing these issues should be developed and formally tested. PMID:18463971

  2. Magnetotelluric measurements across the southern Barberton greenstone belt, South Africa: data improving strategies and 2-D inversion results

    NASA Astrophysics Data System (ADS)

    Kutter, S.; Chen, X.; Weckmann, U.

    2011-12-01

    Magnetotelluric (MT) measurements in areas with electromagnetic (EM) noise sources such as electric fences, power and railway lines pose severe challenges to the standard processing procedures. In order to significantly improve the data quality advanced filtering and processing techniques need to be applied. The presented 5-component MT data set from two field campaigns in 2009 and 2010 in the Barberton/Badplaas area, South Africa, was acquired within the framework of the German-South African geo-scientific research initiative Inkaba yeAfrica. Approximately 200 MT sites aligned along six profiles provide a good areal coverage of the southern part of the Barberton Greenstone Belt (BGB). Since it is one of the few remaining well-preserved geological formations from the Archean, it presents an ideal area to study the tectonic evolution and the role of plate tectonics on Early Earth. Comparing the electric properties, the surrounding high and low grade metamorphic rocks are characteristically resistive whereas mineralized shear zones are possible areas of higher electrical conductivity. Mapping their depth extension is a crucial step towards understanding the formation and the evolution of the BGB. Unfortunately, in the measurement area numerous noise sources were active, producing severe spikes and steps in the EM fields. These disturbances mainly affect long periods which are needed for resolving the deepest structures. The Remote Reference technique as well as two filtering techniques are applied to improve the data in different period ranges. Adjusting their parameters for each site is necessary to obtain the best possible results. The improved data set is used for two-dimensional inversion studies for the six profiles applying the RLM2DI algorithm by Rodi and Mackie (2001, implemented in WinGlink). In the models, areas with higher conductivity can be traced beneath known faults throughout the entire array along different profiles. Resistive zones seem to correlate

  3. The Experience of Antiretroviral Treatment for Black West African Women who are HIV Positive and Living in London: An Interpretative Phenomenological Analysis.

    PubMed

    Spiers, Johanna; Smith, Jonathan A; Poliquin, Elizabeth; Anderson, Jane; Horne, Rob

    2016-09-01

    Antiretroviral therapy (ART) offers a powerful intervention in HIV but effectiveness can be compromised by inadequate adherence. This paper is a detailed examination of the experience of medication in a purposively selected group of people living with HIV. In-depth interviews were conducted with 10 HIV positive, West African women of black heritage living in London, UK. This group was of interest since it is the second largest group affected by HIV in the UK. Interviews were subjected to interpretative phenomenological analysis, an idiographic, experiential, qualitative approach. The paper details the women's negative experience of treatment. ART can be considered difficult and unrelenting and may be disconnected from the women's sense of health or illness. Participants' social context often exacerbated the difficulties. Some reported an improvement in their feelings about the medication over time. These findings point to some intrinsic and social motivators which could act as spurs to adherence. PMID:26767539

  4. Broadband Marine Magnetotelluric Exploration of the East Pacific Rise at 9 N

    NASA Astrophysics Data System (ADS)

    Myer, D. G.; Key, K.; Constable, S.

    2005-12-01

    In February 2004, we conducted the world's largest academic broadband marine magnetotelluric (MT) experiment at the RIDGE2000 integrated study site (ISS) on the East Pacific Rise (EPR). Forty broadband EM receivers were deployed a total of 72 times to yield 69 sites of data. Twenty instruments were deployed in a small aperture (30 km) transect of densely spaced MT sites across the ridge at the ISS ``bull's eye'' focus area at 9°50' N. Further south, 40 sites were collected along a 200 km aperture transect at 9°30'} N. This larger aperture transect was positioned to avoid 3D structure associated with the Lamont seamounts and the Clipperton transform. The site density in the middle 30 km of the longer transect matches the density of the smaller transect, providing two separate data sets for shallow imaging. Twelve additional MT sites were collected in a grid along the ridge axis just north of the longer transect. Robust multi-station MT processing has provided good quality MT impedance responses for most of the data. Eigenvalue analysis of the robustly estimated spectral density matrix for arrays of 3 to 4 MT sites show high signal-to-noise ratios for periods between about 20 s to 5000 s. Based on our earlier pilot MT experiment of 4 sites (Key and Constable, 2000), this bandwidth of data is sensitive to structures from the near surface to about 300 km depth. We will present pseudo-sections of both MT transects as well as 2D conductivity models computed using a new adaptive finite-element modeling technique. Key issues of the ridge magmatic and hydrothemal systems to be addressed by this experiment are: 1. The distribution, vertical extent and volume fraction of melt present in the mid to lower crust. 2. The extent that hydrothermal circulation plays a role in heat removal from the crust as well as the linkages between hydrothermal activity and crustal magma. 3. The extent of melt accumulation at the base of the crust. Does a relatively thin layer of concentrated

  5. "Give a Brotha a Break!": The Experiences and Dilemmas of Middle-Class African American Male Students in White Suburban Schools

    ERIC Educational Resources Information Center

    Gordon, Beverly M.

    2012-01-01

    Background/Context: Today, in the era of the first African American president, approximately one third of all African Americans live in suburban communities, and their children are attending suburban schools. Although most research on the education of African American students, particularly males, focuses on their plight in urban schooling, what…

  6. Oncology pharmacy units: a safety policy for handling hazardous drugs and related waste in low- and middle-income African countries—Angolan experience

    PubMed Central

    da Conceição, Ana Vaz; Bernardo, Dora; Lopes, Lygia Vieira; Miguel, Fernando; Bessa, Fernanda; Monteiro, Fernando; Santos, Cristina; Oliveira, Blasques; Santos, Lúcio Lara

    2015-01-01

    In African countries, higher rates of late-stage cancers at the time of first diagnosis are a reality. In this context, hazardous drugs (HDs), such as chemotherapy, play an important role and have immense benefits for patients’ treatment. HDs should be handled under specific conditions. At least a class 5 environment primary engineering control (PEC), physically located in an appropriate buffer area, is mandatory for sterile HDs compounding, as well as administrative control, personal protective equipment, work practices and other engineering and environmental controls, in order to protect the environment, patient, and worker. The aim of this study is to describe the Angolan experience regarding the development of oncology pharmacy units and discuss international evidence-based guidelines on handling HDs and related waste. Measures to incorporate modern and economical solutions to upgrade or build adequate and safe facilities and staff training, in order to comply with international guidelines in this area, are crucial tasks for African countries of low and middle income. PMID:26557873

  7. Magnetotelluric study of the Xuefeng mountain area, Hu'nan Province, China

    NASA Astrophysics Data System (ADS)

    Chen, Musen; Xue, Lingxiang; Wang, Yousheng; Zhu, Shengjun

    2016-04-01

    A magnetotelluric study was carried out in the Xuefeng mountain uplift belt and its western margins. A detailed investigation was made of the resistivity of the formations, and reliable data were obtained. The sedimentary cover and basement structure of the Xuefeng mountain area and the deep geological structure were analyzed in detail using magnetotelluric data from the two-dimensional inversion of the resistivity profile data in combination with regional gravity and magnetic data. It was concluded that the tectonic movements were characterized by basement detachment, and north-south ramp. The study area can be divided into a southern uplift zone, a southern thrust-faulted zone, a central uplift zone, and a northern depression zone. This work has provided geophysical evidence that can be used in future studies of the tectonics and petroleum geology of this region.

  8. Magnetotelluric study of the Xuefeng mountain area, Hu'nan Province, China

    NASA Astrophysics Data System (ADS)

    Chen, Musen; Xue, Lingxiang; Wang, Yousheng; Zhu, Shengjun

    2016-03-01

    A magnetotelluric study was carried out in the Xuefeng mountain uplift belt and its western margins. A detailed investigation was made of the resistivity of the formations, and reliable data were obtained. The sedimentary cover and basement structure of the Xuefeng mountain area and the deep geological structure were analyzed in detail using magnetotelluric data from the two-dimensional inversion of the resistivity profile data in combination with regional gravity and magnetic data. It was concluded that the tectonic movements were characterized by basement detachment, and north-south ramp. The study area can be divided into a southern uplift zone, a southern thrust-faulted zone, a central uplift zone, and a northern depression zone. This work has provided geophysical evidence that can be used in future studies of the tectonics and petroleum geology of this region.

  9. Geothermal exploration using audio-magnetotelluric in Pariangan Tanah Datar, West Sumatra

    NASA Astrophysics Data System (ADS)

    Saputra, Andriyan; Widodo, Kholid, Muhammad

    2015-04-01

    The existence of Mt. Marapi in Pariangan Tanah Datar has a big potential of geothermal energy resource. The study area is located in southeastern Mt. Marapi. The geological elements correspond to lava granitic, sandstone quartz, quartzite and conglomerate. The aim of this research is to investigate the geothermal system in this area. Measurements of audio-magnetotelluric (AMT) long line are 10 km with two profiles. The audio-magnetotelluric (AMT) data carried out during July 2014. The models result were done by using 1-D inversion technique. The 1-D inversion was done with Occam and Marquadt algoritm. We assumed that for the first layer indicates as the conductive zone (±10 Ωm), the second layer as the reservoir geothermal system (±100 Ωm) that contains with sandstone quartz, and the third layer can be interpreted as volcanic rock (±1000 - 10000 Ωm) which is the basement of geothermal system.

  10. The African-American History of Martha's Vineyard.

    ERIC Educational Resources Information Center

    Weintraub, Elaine

    1993-01-01

    Reports on research into African American history and experiences in Martha's Vineyard (Massachusetts). Examines primary sources and oral traditions of African American cultural and social history from 1703 to the present. Discusses African American sailors, race relations, and contributions by African American individuals to the community. (CFR)

  11. Two-dimensional magnetotelluric characterization of the El Hito Anticline (Loranca Basin, Spain)

    NASA Astrophysics Data System (ADS)

    Piña-Varas, Perla; Ledo, Juanjo; Queralt, Pilar; Roca, Eduard; García-Lobón, Jose L.; Ibarra, Pedro; Biete, Cristina

    2013-08-01

    Magnetotelluric surveys were conducted to investigate the structure in the El Hito Anticline in the southern Loranca Basin, Spain. The structure of this anticline is partly known from nearby data (geological cross sections, geological maps, well-logs) from vintage geophysical and geological basin-scale surveys. Unfortunately, these surveys do not have the appropriate resolution to determine certain characteristics of the anticline accurately, such as the thickness or geometry of geological units. To address this deficiency, magnetotelluric data were acquired at 51 sites along three profiles to image the electrical resistivity of the anticline. To identify a geologically reasonable resistivity model, a conceptual model based on previous geological and geophysical information (cross sections and well-log data) was generated. Several inversions were performed using the conceptual model, which played a key role in the interpretation of the magnetotelluric data, and the construction of a suitable initial model was essential in producing geologically meaningful models. Using these results, we obtained 2-D resistivity models that provide information on the main geological units and structures. We also performed sensitivity tests to understand the morphology and structure of the resistive basement better. The results indicate the presence of basement highs that show different structural styles for the basement and its cover, and an increase in the basement depth towards the south. The final 2-D resistivity models provide new information regarding the structure of the anticline and demonstrate a clear correlation between the main geological units and resistivity, as well as correlations with mapped surface faults.

  12. Hydrothermal System of the Lastarria Volcano (Central Andes) Imaged by Magnetotellurics

    NASA Astrophysics Data System (ADS)

    Diaz, D.

    2015-12-01

    Lazufre volcanic complex, located in the central Andes, is recently undergoing an episode of uplift, conforming one of the most extensive deforming volcanic systems worldwide. Recent works have focused on the subsurface of this volcanic system at different scales, using surface deformation data, seismic noise tomography and magnetotellurics. Here we image the electrical resistivity structure of the Lastarria volcano, one of the most important features in the Lazufre area, using broadband magnetotelluric data at 30 locations around the volcanic edifice. Results from 3-D modeling show a conductive zone at 6 km depth south of the Lastarria volcano interpreted as a magmatic heat source, which is connected to a shallower conductive area beneath the volcanic edifice and its close vicinity. This shallow highly conductive zone fits with geochemical analysis results of thermal fluid discharges, related to fumaroles present in this area, in terms of depth extent and possible temperatures of fluids, and presents also a good correlation with seismic tomography results. The horizontal extension of this shallow conductive zone, related to the hydrothermal system of Lastarria, suggests that it has been draining one of the lagoons in the area (Laguna Azufrera), forming a sulfur rich area which can be observed at the southern side of this lagoon. Joint modeling of the hydrothermal system using magnetotellurics and seismic data is part of the current work.

  13. "Come on Baby. You Know I Love You": African American Women's Experiences of Communication with Male Partners and Disclosure in the Context of Unwanted Sex.

    PubMed

    Gutzmer, Kyle; Ludwig-Barron, Natasha T; Wyatt, Gail E; Hamilton, Alison B; Stockman, Jamila K

    2016-05-01

    We examined African American women's experiences of communication with their male intimate partners a couple of hours before and after an incident of unwanted sex. We also examined women's experiences of disclosure following an incident of unwanted sex. Semi-structured qualitative interviews were conducted with a community-based sample of sexually active African American women (n = 19) reporting at least one incident of sexual coercion (i.e., being pressured into unwanted sex without consent) by an intimate male partner since the age of 18. Our analysis was guided by "the sexual division of power" from Connell's (1987) theory of gender and power. Data were analyzed inductively by examining the interviews for common themes in the following domains: communication before the unwanted sex, communication after the unwanted sex, and disclosure to others. Men pressured partners for unwanted sex through verbal and non-verbal tactics, ranging from pestering and blunt requests for sex to verbal bullying and violence. Many women responded by clearly saying no. However, many women also described eventually ceasing to resist their partners and engaging in unwanted sex. After the unwanted sex, men actively and passively avoided discussing the incident. Although many women discussed the unwanted sex with family and friends, less women disclosed to trained professionals. In some cases, women did not discuss the incident with anyone at all. These findings indicate that, when addressing sexual violence against women, there is a need to target men as well as the norms of masculinity that underpin physical and sexual violence against women. PMID:26892099

  14. Three-Dimensional Resistivity Model of the Mono Craters Region in Eastern California from Magnetotellurics

    NASA Astrophysics Data System (ADS)

    Peacock, J.; Mangan, M.; McPhee, D.; Ponce, D. A.

    2014-12-01

    The Long Valley volcanic region in eastern California contains three magmatic foci; Long Valley Caldera (760-50 ka), Mammoth Mountain (120-8 ka), and Mono-Inyo Craters (60-0.3 ka). Zones of partial melt and/or hydrothermal fluids are known to exist under all three systems, but are not well constrained. In 2013-2014, we collected 110 magnetotelluric stations within a 40km x 45km grid, from Mono Craters through Long Valley Caldera. To date, a 3-D resistivity model has been created for Mono Craters showing three distinct features. Best constrained is a 150±50 km3, near vertical conductive anomaly (0.1-3 Ω·m) located under the southeast margin of Mono Craters at depths from 10km to >35km, which may reflect the deep, partially molten source region for Holocene eruptions. Electrical resistivity calculations suggest temperatures of 775°C±50 and a partial melt fraction 0.2 ±0.1. The location, melt fraction, and volume estimated in this study are consistent with those from teleseismic experiments conducted by Archauer (1986) and Dawson et al. (1990). A second conductive anomaly (0.5-5 Ω·m) at 12km to >35km depths was found 10km west of the Mono Craters near the eastern front of the Sierra Nevada. This anomaly coincides with a zone of sporadic, long-period earthquakes interpreted as "fluid-driven" by Pitt et al. (1994). This anomaly may reflect a zone of hydrothermal fluid infiltration originating from the aforementioned magmatic region. The third feature identified in this study is a resistive anomaly (103-104 Ω·m) under Aeolian Buttes, a Cretaceous quartz monzanite outcropping within the Bishop Tuff between Mono Craters and the Sierran front. The anomaly, which fills a crustal volume of 1500 ±500 km3, balloons upward from a deep root at >30 km to within 2 km of the surface and is interpreted as a cold, granitic pluton as supported by gravity and magnetic data. Future work will extend our three-dimensional resistivity model southwards to Inyo Craters and Long

  15. African Green Monkeys Recapitulate the Clinical Experience with Replication of Live Attenuated Pandemic Influenza Virus Vaccine Candidates

    PubMed Central

    Matsuoka, Yumiko; Suguitan, Amorsolo; Orandle, Marlene; Paskel, Myeisha; Boonnak, Kobporn; Gardner, Donald J.; Feldmann, Friederike; Feldmann, Heinz; Marino, Michael; Jin, Hong; Kemble, George

    2014-01-01

    ABSTRACT Live attenuated cold-adapted (ca) H5N1, H7N3, H6N1, and H9N2 influenza vaccine viruses replicated in the respiratory tract of mice and ferrets, and 2 doses of vaccines were immunogenic and protected these animals from challenge infection with homologous and heterologous wild-type (wt) viruses of the corresponding subtypes. However, when these vaccine candidates were evaluated in phase I clinical trials, there were inconsistencies between the observations in animal models and in humans. The vaccine viruses did not replicate well and immune responses were variable in humans, even though the study subjects were seronegative with respect to the vaccine viruses before vaccination. Therefore, we sought a model that would better reflect the findings in humans and evaluated African green monkeys (AGMs) as a nonhuman primate model. The distribution of sialic acid (SA) receptors in the respiratory tract of AGMs was similar to that in humans. We evaluated the replication of wt and ca viruses of avian influenza (AI) virus subtypes H5N1, H6N1, H7N3, and H9N2 in the respiratory tract of AGMs. All of the wt viruses replicated efficiently, while replication of the ca vaccine viruses was restricted to the upper respiratory tract. Interestingly, the patterns and sites of virus replication differed among the different subtypes. We also evaluated the immunogenicity and protective efficacy of H5N1, H6N1, H7N3, and H9N2 ca vaccines. Protection from wt virus challenge correlated well with the level of serum neutralizing antibodies. Immune responses were slightly better when vaccine was delivered by both intranasal and intratracheal delivery than when it was delivered intranasally by sprayer. We conclude that live attenuated pandemic influenza virus vaccines replicate similarly in AGMs and human subjects and that AGMs may be a useful model to evaluate the replication of ca vaccine candidates. IMPORTANCE Ferrets and mice are commonly used for preclinical evaluation of influenza

  16. Experiences and Perceptions of Interpersonal, Environmental, and Institutional Racism among African-American Students in Psychology Graduate Training.

    ERIC Educational Resources Information Center

    Burrell, Tracey

    Racist incidents that graduate students in psychology may experience can be reflective of Eurocentric values and forces which permeate present institutions. To better understand these forces, the experiences and perceptions of racism as experienced by minority graduate students are explored. Seventeen doctoral students in psychology, who…

  17. Experiences and conceptualizations of sexual debut from the narratives of South African men and women in the context of HIV/AIDS.

    PubMed

    Stern, Erin; Cooper, Diane

    2014-01-01

    Given the pivotal role of first sex in the development of sexual and reproductive health (SRH) practices, there is a need for more contextualised and nuanced understandings of young people's early sexual debut experiences. This study used sexual history narratives to investigate how South African men and women experience and attribute meaning to their sexual debut, and their SRH practices. In light of the gendered disparities among young people's SRH awareness and risk, differences between men and women's narratives of sexual debut were assessed. Fifty sexual history interviews were conducted with men and 25 sexual history interviews with women, with participants purposively sampled from three age categories, a range of cultural and racial backgrounds and urban and rural sites across five provinces. Narrative interviews were designed to elicit stories around participants' early knowledge of sex and sexual experimentation, their range of sexual relationships and SRH practices. The data were analysed using a thematic approach. Participants generally reflected on their early sexual experiences with feelings of inadequacy and disappointment. While men appeared to hold greater decision-making power than women at sexual debut, descriptions of men's early sexual experiences were often characterised by respect, intimacy and vulnerability. Many men attributed the timing of their sexual debut to peer pressure, which typically generated higher social status and rarely included consideration of the need to practice safer sex. Several women felt pressured by their partner to sexually debut, which could have informed their perceptions of men being sexually controlling and aggressive. The study demonstrates the value of a narrative approach for generating insights on young people's sexual debut experiences and SRH practices, and the underlying gendered norms and expectations that shape these. The findings indicate the need for gender transformative HIV interventions to take into

  18. Analytic magnetotelluric responses to a two-segment model with axially anisotropic conductivity structures overlying a perfect conductor

    NASA Astrophysics Data System (ADS)

    Qin, Linjiang; Yang, Changfu

    2016-06-01

    The rocks in the crust and the upper mantle of the Earth are believed to exhibit electrical anisotropy to some extent. It is beneficial to further understand and recognize the propagation of the electromagnetic waves in the Earth by investigating the magnetotelluric (which is one of the main geophysical techniques to probe the deep structures in the Earth) responses of the media with anisotropic conductivity structures. In this study, we examine the magnetotelluric fields over an idealized 2-D model consisting of two segments with axially anisotropic conductivity structures overlying a perfect conductor basement by a quasi-static analytic approach. The resulting analytic solution could not only contribute to the electromagnetic induction theory in the anisotropic Earth but also serve as at least an initial standard solution which could be used to validate the reliability and accuracy of the numerical algorithms developed for modelling the magnetotelluric responses of the 2-D media with much more general anisotropic conductivity.

  19. Analytic magnetotelluric responses to a two-segment model with axially anisotropic conductivity structures overlying a perfect conductor

    NASA Astrophysics Data System (ADS)

    Linjiang, QIN; Changfu, YANG

    2016-03-01

    The rocks in the crust and the upper mantle of the Earth are believed to exhibit electrical anisotropy to some extent. It is beneficial to further understand and recognize the propagation of the electromagnetic waves in the Earth by investigating the magnetotelluric (which is one of the main geophysical techniques to probe the deep structures in the Earth) responses of the media with anisotropic conductivity structures. In the present study, we examine the magnetotelluric fields over an idealized 2-D model consisting of two segments with axially anisotropic conductivity structures overlying a perfect conductor basement by a quasi-static analytic approach. The resulting analytic solution could not only contribute to the electromagnetic induction theory in the anisotropic Earth but also serve as at least an initial standard solution which could be used to validate the reliability and accuracy of the numerical algorithms developed for modeling the magnetotelluric responses of the 2-D media with much more general anisotropic conductivity.

  20. The Underrepresentation of African American Women Faculty: A Phenomenological Study Exploring the Experiences of McKnight Doctoral Fellow Alumna Serving in the Professoriate

    ERIC Educational Resources Information Center

    Ferguson, Dionne J.

    2013-01-01

    While African American women have been participating in higher education for more than a century, they remain significantly underrepresented among college and university professors in America. This study was pursued in an attempt to address the underrepresentation of African American women faculty at public and private universities within the…

  1. Am I "That Jew"? North African Jewish Experiences in the Toronto Jewish Day School System and the Establishment of or Haemet Sephardic School

    ERIC Educational Resources Information Center

    Train, Kelly Amanda

    2013-01-01

    This article explores the North African Jewish community's establishment of Or Haemet Sephardic School as a response to the forced "Ashkenazification" of Sephardic students in the Orthodox Jewish day school system. The establishment of the school signifies the North African Jewish community's refusal and resistance to an essentialist Jewish…

  2. Diagnosed but Not Defeated: The Experiences of African-American Males with Past Histories of Enrollment in Special Education Who Successfully Attend Community College

    ERIC Educational Resources Information Center

    Strickland-Dixon, Kennedi

    2013-01-01

    African-American males are disappearing at alarming rates before our eyes through racially driven practices that secure their position in the penal system and special education. Though many scholars in the field of education have highlighted alarming rates of incarceration and overrepresentation in special education for African-American males,…

  3. African American Single Mothers Raising Sons: Implications for Family Therapy

    ERIC Educational Resources Information Center

    Gantt, Ann L.; Greif, Geoffrey L.

    2009-01-01

    Being raised by a single mother is one factor that has been suggested as contributing to the plight of African American males. Yet few studies have focused specifically on African American single mothers' experiences with raising sons. This qualitative study explored the following questions: (1) What are the experiences of African American single…

  4. Joint interpretation of seismic tomography and new magnetotelluric results provide evidence for support of high topography in the Southern Rocky Mountains and High Plains of eastern Colorado, USA

    NASA Astrophysics Data System (ADS)

    Feucht, D. W.; Sheehan, A. F.; Bedrosian, P.

    2015-12-01

    A recent magnetotelluric (MT) survey in central Colorado, USA, when interpreted alongside existing seismic tomography, reveals potential mechanisms of support for high topography both regionally and locally. Broadband and long period magnetotelluric data were collected at twenty-three sites along a 330 km E-W profile across the Southern Rocky Mountains and High Plains of central North America as part of the Deep RIFT Electrical Resistivity (DRIFTER) experiment. Remote-reference data processing yielded high quality MT data over a period range of 100 Hz to 10,000 seconds. A prominent feature of the regional geo-electric structure is the Denver Basin, which contains a thick package of highly conductive shales and porous sandstone aquifers. One-dimensional forward modeling was performed on stations within the Denver Basin to estimate depth to the base of this shallow conductor. Those estimates were then used to place a horizontal penalty cut in the model mesh of a regularized two-dimensional inversion. Two-dimensional modeling of the resistivity structure reveals two major anomalous regions in the lithosphere: 1) a high conductivity region in the crust under the tallest peaks of the Rocky Mountains and 2) a lateral step increase in lithospheric resistivity beneath the plains. The Rocky Mountain crustal anomaly coincides with low seismic wave speeds and enhanced heat flow and is thus interpreted as evidence of partial melt and/or high temperature fluids emplaced in the crust by tectonic activity along the Rio Grande Rift. The lateral variation in the mantle lithosphere, while co-located with a pronounced step increase in seismic velocity, appears to be a gradational boundary in resistivity across eastern Colorado and could indicate a small degree of compositional modification at the edge of the North American craton. These inferred conductivity mechanisms, namely crustal melt and modification of mantle lithosphere, likely contribute to high topography locally in the

  5. Race, health, and the African Diaspora.

    PubMed

    Spigner, Clarence

    Health inequalities exist throughout the African Diaspora and are viewed in this article as largely color-coded. In developed, developing, and undeveloped nations today, "racial" stratification is consistently reflected in an inability to provide adequate health regardless of national policy or ideology. For instance, African Americans experience less than adequate health care very similar to Blacks in Britain, in spite of each nations differing health systems. Latin America's Africana Negra communities experience poorer health similar to Blacks throughout the Caribbean. The African continent itself is arguably the poorest on earth. A common history of racism correlates with health disparities across the African Diaspora. PMID:18364304

  6. Magnetotellurics with long distance remote reference to reject DC railway noise

    NASA Astrophysics Data System (ADS)

    Hanstein, T.; Jiang, J.; Strack, K.; Ritter, O.

    2014-12-01

    Some parts of railway network in Europe is electrified by DC current. The return current in the ground is varying in space, time and power when the train is moving. Since the train traffic is active 24 hours, there is no quite time. The train signal is dominating for periods longer than 1 s and is a near field source. The transfer function of the magnetotelluric sounding (MT) is influenced by this near field source, the phase is going to zero and amplitude increase with slope 1 for longer periods. Since this dominating noise is present all day robust magnetotelluric processing technique to identify and remove outliers are not applicable and sufficient. The remote reference technique has successfully been applied for magnetotelluric soundings Combining an disturbed local MT data set with the data of the remote station, which is recording simultaneously the horizontal magnetic fields, can improve the data quality. Finding a good remote station during field survey is difficult and expensive. There is a permanent MT remote reference station in Germany. The set up and maintance is done by the GFZ - Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences. The location is near Wittstock and has good signal-to-noise-ratio with low cutural noise, the ground is almost lD and recording since May 2010. The electric and magnetic field is continously recorded with 250 Hz sampling and induction coils. The magnetic field is also recorded with fluxgate magnetometers and 5 Hz sampling. The distance to the local MT site is about 600 km.

  7. African Aesthetics

    ERIC Educational Resources Information Center

    Abiodun, Rowland

    2001-01-01

    No single traditional discipline can adequately supply answers to the many unresolved questions in African art history. Because of the aesthetic, cultural, historical, and, not infrequently, political biases, already built into the conception and development of Western art history, the discipline of art history as defined and practiced in the West…

  8. Perceptions of Online Learning Experiences: Voices of African American Women at a Historically Black College and University

    ERIC Educational Resources Information Center

    Yee Chief, Irene Mary

    2012-01-01

    An increasing number of higher education learners are using online learning. The purpose of this exploratory study was to examine non-traditional learners' perceptions and experiences of online learning at a public Historically Black College or University (HBCU). This study examined learners' interactivity with peers, teachers,…

  9. "I'm Used to It Now": Experiences of Homophobia among Queer Youth in South African Township Schools

    ERIC Educational Resources Information Center

    Msibi, Thabo

    2012-01-01

    This paper explores how sexually marginalised black high-school students from conservative schooling contexts in KwaZulu-Natal, South Africa, experience schooling. It draws on queer theories through life narratives in presenting findings from a small-scale interventionist project designed by the author. The project involved 14 participants…

  10. MT3D: a 3 dimensional magnetotelluric modeling program (user's guide and documentation for Rev. 1)

    SciTech Connect

    Nutter, C.; Wannamaker, P.E.

    1980-11-01

    MT3D.REV1 is a non-interactive computer program written in FORTRAN to do 3-dimensional magnetotelluric modeling. A 3-D volume integral equation has been adapted to simulate the MT response of a 3D body in the earth. An integro-difference scheme has been incorporated to increase the accuracy. This is a user's guide for MT3D.REV1 on the University of Utah Research Institute's (UURI) PRIME 400 computer operating under PRIMOS IV, Rev. 17.

  11. Correction of magnetotelluric static shift by analysis of 3D forward modelling and measured test data

    NASA Astrophysics Data System (ADS)

    Zhang, Kun; Wei, Wenbo; Lu, Qingtian; Wang, Huafeng; Zhang, Yawei

    2016-06-01

    To solve the problem of correction of magnetotelluric (MT) static shift, we quantise factors that influence geological environments and observation conditions and study MT static shift according to 3D MT numerical forward modelling and field tests with real data collection. We find that static shift distortions affect both the apparent resistivity and the impedance phase. The distortion results are also related to the frequency. On the basis of synthetic and real data analysis, we propose the concept of generalised static shift resistivity (GSSR) and a new method for correcting MT static shift. The approach is verified by studying 2D inversion models using synthetic and real data.

  12. Two-dimensional magnetotelluric and gravity models of the Tuzgle volcano zone (Jujuy province, Argentina)

    NASA Astrophysics Data System (ADS)

    Sainato, Claudia M.; Pomposiello, Maria C.

    1997-07-01

    The Tuzgle volcano (24 ° 03'S, 66 ° 29'W) is situated in the southern part of the South American Andean Altiplano (Puna). The region has several geothermal manifestations. A 2-D magnetotelluric model of resistivity distribution and a 3-D gravity anomaly of the area have been proposed. A highly conductive and low density body is probably associated with a magma chamber surrounded by free saline fluids with its top at about 8 km depth. The release of fluids might be caused by the chemical reactions generated at the subduction plate of Nazca in contact with the South American plate.

  13. New facilities for magnetotelluric sounding and electromagnetic sounding with active sources

    NASA Astrophysics Data System (ADS)

    Klymovych, Y.; Rakhlin, L.; Tregubenko, V.

    2003-04-01

    Magnetotelluric (MT) sounding and investigations that use electromagnetic sounding with active sources (SAS) are wide spread in many branch of geophysics. The main goal of their application is Earth geoelectric cross-section parameters definition. For MT sounding it was possible to carry out it mostly till the time intervals less, than 10000 sec, that does not permitted to get the sections for the depth more than some first kilometres. Last years in LCISR the new generation of MT and facilities for deep electromagnetic sounding in ultra-low frequencies periods up to 200,000 sec were designed. It became possible after the development of highly stable devices for DC magnetic and telluric measurements. The long term stability of newly created magnetometers now is better than 0.5 nT per month and temperature stability about 0.1 nT/oC. For telluric currents measurements highly stable non-polarized electrodes with long term stability better than 60 mV per month, and temperature stability about 10 mV/oC were designed. Implementation of such facilities made it possible to realize the magnetotelluric sounding to the depth 400-600 km and the experimental results have good agreement with global magnetotelluric curve. Such MT stations (LEMI-404 model) were used in BEAR (Baltic Electromagnetic Array Research) and several others projects. Their use made it possible also to prove with very high probability the existence of low-depth astenosphere in Dnepre-Donetsk Basin (Ukraine). Now a batch of these MT stations is manufactured and used in Ukrainian magnetotelluric net. This net was intended firstly for investigation of electromagnetic earthquake precursors, but after its further development - for geoelectric section circular changes too. Recently two new MT stations are developed. First one low-frequency (DC 1 Hz) inexpensive station LEMI-411 which, having as high metrological parameters as the wide-band one, costs considerebly lower. Second one is multifunctional SAS station

  14. First Generation U.S.-Born Africans and the Expanded Nigrescence Theory: The Stretching of a Theory for a "Different" African American Experience at a Predominantly White Institution of Higher Education

    ERIC Educational Resources Information Center

    De Walt, Patrick S.

    2009-01-01

    This dissertation explores the applicability of a "stretched" Expanded Nigrescence theory (Cross and Vandiver 2001; NT-E) to the racial identities/attitudes of six First Generation U.S.-Born Africans (FGAs) at a predominantly White institution (PWI). This instrumental case study blended ethnographic techniques and surveys to tell the stories of…

  15. [Restoration of continuity after rectosigmoidectomy by colorectal intubation and transproctoanal anastomosis. An African experience with 10 cases].

    PubMed

    Ribault, L; Veillard, J M; Sarre, B; Diouf, B; Diagne, L; Vayre, P

    1990-01-01

    On the basis of 10 cases (8 cases of rectosigmoid cancer and 2 of sigmoid volvulus), the authors report about their experience in the restoration of GI tract continuity using colorectal intubation into the rectal lumen and a transproctoanal anastomosis. This technique helps avoiding subperitoneal sutures, which are a cause of fistulae and shrinkage. It is simple enough to be performed by younger surgeons. This technique was initially developed for anterior resections for rectosigmoid cancer, and it can be utilized as an emergency procedure with single-piece resection without untwisting the sphacelous sigmoid loops, so that neither a temporary left iliostomy nor a second operation are needed. PMID:2279439

  16. Magnetotelluric survey to locate the Archean-Proterozoic suture zone in the northeastern Great Basin, Nevada, Utah, and Idaho

    USGS Publications Warehouse

    Sampson, Jay A.; Rodriguez, Brian D.

    2013-01-01

    North-central Nevada contains a large amount of gold in linear belts, the origin of which is not fully understood. During July 2008, September 2009, and August 2010, the U.S. Geological Survey, as part of the Assessment Techniques for Concealed Mineral Resources project, collected twenty-three magnetotelluric soundings along two profiles in Box Elder County, Utah; Elko County, Nevada; and Cassia, Minidoka, and Blaine Counties, Idaho. The main twenty-sounding north-south magnetotelluric profile begins south of Wendover, Nev., but north of the Deep Creek Range. It continues north of Wendover and crosses into Utah, with the north profile terminus in the Snake River Plain, Idaho. A short, three-sounding east-west segment crosses the main north-south profile near the northern terminus of the profile. The magnetotelluric data collected in this study will be used to better constrain the location and strike of the concealed suture zone between the Archean crust and the Paleoproterozoic Mojave province. This report releases the magnetotelluric sounding data that was collected. No interpretation of the data is included.

  17. 3-D Magnetotelluric Exploration of Tenerife Geothermal System (Canary Islands, Spain)

    NASA Astrophysics Data System (ADS)

    Piña-Varas, P.; Ledo, J.; Queralt, P.; Marcuello, A.; Bellmunt, F.; Hidalgo, R.; Messeiller, M.

    2014-07-01

    The resistivity structure of the Tenerife geothermal system has been determined by the 3-D inversion of data from different magnetotelluric surveys. In this paper, the ocean and topography effects on the magnetotelluric data were investigated by constructing a 3-D conceptual geoelectrical model of the island. The study showed that these effects should be taken into account in order to obtain a reliable subsurface model of the island. Data from 148 sites were used during three-dimensional inversion. The most interesting feature in the final geoelectrical model of the geothermal system is a low resistivity structure (<10 Ωm) above the resistive core of the system. The low resistivity structure has been interpreted as a hydrothermal clay alteration cap typically generated in the conventional geothermal systems. The resistivity model has been correlated with a recent seismic velocity model, showing that a low resistivity structure surrounds an area with high P wave velocity and medium-high resistivity. This medium-high resistivity area can be associated with a slowly solidified magma and, therefore, with a hotter part of the geothermal system.

  18. Magnetotelluric Evidence of Regional Lithospheric Modification in Ordos Block, North China

    NASA Astrophysics Data System (ADS)

    Dong, H.; Wei, W.; Ye, G.; Jin, S.; Jones, A. G.

    2013-12-01

    The Ordos Block (OB), which is located in the western part of the North China Craton (NCC), is one of the oldest and most stable cratonic blocks in Asia. To study the electrical structure of Ordos block, long period magnetotelluric (MT) array data from project SINOPROBE were acquired and modeled using three-dimensional (3D) MT inversion method. For the first time a high resolution 3D resistivity model of the lithosphere is acquired in the region. The lithosphere beneath the northern part of the OB and Hetao Graben is revealed to be geo-electrically distinct from that beneath the middle and southern Ordos. Contrary to what would be expected for a stable cratonic block, compelling evidence is presented of a large scale conductive complex in the lower crust and upper mantle beneath north Ordos and Hetao Graben. The abnormally conductive structure indicates the presence of aqueous fluids and/or inter-connected sulphides, possibly resulting from an upwelling of mantle material beneath the region. Correlating well with results of seismic studies, the evidence from independent magnetotelluric data supports a regional modification and thinning of the lithosphere, which might contribute to the extension of Hetao Graben started in late Miocene to Pliocene, as well as the uplifting of the north the Ordos Block since Neogene.

  19. Water exploration using Magnetotelluric and gravity data analysis; Wadi Nisah, Riyadh, Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Aboud, Essam; Saud, Ramzi; Asch, Theodore; Aldamegh, Khaled; Mogren, Saad

    2014-12-01

    Saudi Arabia is a desert country with no permanent rivers or lakes and very little rainfall. Ground water aquifers are the major source of water in Saudi Arabia. In the Riyadh region, several Wadies including Wadi Nisah store about 14 × 106 m3 of water, which is extracted for local irrigation purposes. In such areas, the water wells are as shallow as 200-300 m in depth. The importance of Wadi Nisah is because the subsurface water aquifers that are present there could support the region for many years as a water resource. Accordingly, in this study, we performed a Magnetotelluric survey using a portable broadband sounding system (MT24/LF) to evaluate the ground water aquifer at great depths. We collected 10 broadband Magnetotelluric sounding stations (1 station/day) with an interval of about 2-3 km reaching a profile length of about 25-30 km along Wadi Nisah. Additionally, we used available gravity data to image the subsurface structure containing the aquifer. MT results indicated a low resistivity layer, associated with alluvium deposits, which was defined at a depth of about 1-2 km and extended horizontally about 15 km. Gravity data analysis was used to model this resistivity layer indicating a basement surface at 3-4 km depth.

  20. New application of wavelets in magnetotelluric data processing: reducing impedance bias

    NASA Astrophysics Data System (ADS)

    Larnier, Hugo; Sailhac, Pascal; Chambodut, Aude

    2016-04-01

    Magnetotelluric (MT) data consist of the sum of several types of natural sources including transient and quasiperiodic signals and noise sources (instrumental, anthropogenic) whose nature has to be taken into account in MT data processing. Most processing techniques are based on a Fourier transform of MT time series, and robust statistics at a fixed frequency are used to compute the MT response functions, but only a few take into account the nature of the sources. Moreover, to reduce the influence of noise in the inversion of the response functions, one often sets up another MT station called a remote station. However, even careful setup of this remote station cannot prevent its failure in some cases. Here, we propose the use of the continuous wavelet transform on magnetotelluric time series to reduce the influence of noise even for single site processing. We use two different types of wavelets, Cauchy and Morlet, according to the shape of observed geomagnetic events. We show that by using wavelet coefficients at clearly identified geomagnetic events, we are able to recover the unbiased response function obtained through robust remote processing algorithms. This makes it possible to process even single station sites and increase the confidence in data interpretation.

  1. Crustal rheology of the Himalaya and Southern Tibet inferred from magnetotelluric data

    USGS Publications Warehouse

    Unsworth, M.J.; Jones, A.G.; Wei, W.; Marquis, G.; Gokarn, S.G.; Spratt, J.E.; Bedrosian, P.; Booker, J.; Leshou, C.; Clarke, G.; Shenghui, L.; Chanhong, L.; Ming, D.; Sheng, J.; Solon, K.; Handong, T.; Ledo, J.; Roberts, B.

    2005-01-01

    The Cenozoic collision between the Indian and Asian continents formed the Tibetan plateau, beginning about 70 million years ago. Since this time, at least 1,400 km of convergence has been accommodated by a combination of underthrusting of Indian and Asian lithosphere, crustal shortening, horizontal extrusion and lithospheric delamination. Rocks exposed in the Himalaya show evidence of crustal melting and are thought to have been exhumed by rapid erosion and climatically forced crustal flow. Magnetotelluric data can be used to image subsurface electrical resistivity, a parameter sensitive to the presence of interconnected fluids in the host rock matrix, even at low volume fractions. Here we present magnetotelluric data from the Tibetan-Himalayan orogen from 77??E to 92??E, which show that low resistivity, interpreted as a partially molten layer, is present along at least 1,000 km of the southern margin of the Tibetan plateau. The inferred low viscosity of this layer is consistent with the development of climatically forced crustal flow in Southern Tibet. ?? 2005 Nature Publishing Group.

  2. Magnetotelluric Data, Rainier Mesa/Shoshone Mountain, Nevada Test Site, Nevada

    USGS Publications Warehouse

    Williams, Jackie M.; Sampson, Jay A.; Rodriguez, Brian D.; Asch, Theodore H.

    2006-01-01

    Introduction: The United States Department of Energy (DOE) and the National Nuclear Security Administration (NNSA) at their Nevada Site Office (NSO) are addressing ground-water contamination resulting from historical underground nuclear testing through the Environmental Management (EM) program and, in particular, the Underground Test Area (UGTA) project. During 2005, the U.S. Geological Survey (USGS), in cooperation with the DOE and NNSA-NSO, collected and processed data from twenty-six magnetotelluric (MT) and audio-magnetotelluric (AMT) sites at the Nevada Test Site. The 2005 data stations were located on and near Rainier Mesa and Shoshone Mountain to assist in characterizing the pre-Tertiary geology in those areas. These new stations extend the area of the hydrogeologic study previously conducted in Yucca Flat. The MT data presented in this report will help refine what is known about the character, thickness, and lateral extent of pre Tertiary confining units. Subsequent interpretation will include a three dimensional (3 D) character analysis and a two-dimensional (2 D) resistivity model. The purpose of this report is to release the MT sounding data. No interpretation of the data is included here.

  3. Detection of Deep Fluid Flow in Subduction Zones with Magnetotelluric Monitoring

    NASA Astrophysics Data System (ADS)

    Ritter, O.; Araya, J.

    2014-12-01

    After the 1995 Mw 8 Antofagasta earthquake, Husen and Kissling (2001) interpreted alterations observed in the seismic velocity structure as large-scale fluid distribution changes, deep within the subduction zone. Such large scale fluid relocation would cause similar modifications of the associated deep electrical resistivity structure. In this paper, we examine feasibility to detect such changes in the deep hydraulic system with magnetotelluric monitoring. Continuous magnetotelluric (MT) data have been recorded above the subduction zone in northern Chile as part of the Integrated Plate Boundary Observatory Chile (IPOC) with an array of 9 stations since 2007. With the MT method, electrical resistivity and lateral changes of the resistivity structure are estimated from so called transfer functions (TF). If the subsurface resistivity structure is stable, these TFs vary only within their statistical significance intervals over time. Any statistically significant deviations, particularly when observed over the network of sites, must be originated from a change in the subsurface resistivity structure. We simulate the effects of such changes on the TFs using 3D forward modelling studies. The background model is based on 3D inversion of the IPOC MT stations. The results show that detectable differences in the TFs are obtained if the resistivity decreases by 5 times of its original value in the lower continental crust over the rupture zone. The implications of these results are compared with observed changes in the TFs after the 2007 Mw 7.7 Tocopilla and 2014 Mw 8.2 Pisagua earthquakes.

  4. Interpretation of magnetotelluric measurements over an electrically dispersive one-dimensional earth

    SciTech Connect

    Patella, D.

    1987-01-01

    Frequency dispersion of electromagnetic parameters of earth materials has been widely documented in recent years. It is claimed that magnetotellurics (MT)may be significantly affected by dispersion. This paper studies the MT plane-wave interpretative problem for a one-dimensional earth characterized by the presence of dispersive layers. The theoretical properties of the MT field under the dispersion hypothesis, and the main features of the dispersion phenomenon are synthetically reviewed. The examination of previously published MT curve responses over some models of dispersive earth section shows that ambiguity can arise when interpreting MT data with no other source of information. Thus it maybe almost impossible to distinguish between the response of a dispersive section and an equally probable dispersion-free section. The dispersion magnetotelluric (DMT) method is proposed as a means to resolve the ambiguity. The DMT method is based on the execution, at the same site, of an MT sounding and of an always dispersion-free dc geoelectric deep sounding.

  5. "Out of All of this Mess, I Got a Blessing": Perceptions and Experiences of Reproduction and Motherhood in African American Women Living With HIV.

    PubMed

    Fletcher, Faith; Ingram, Lucy Annang; Kerr, Jelani; Buchberg, Meredith; Richter, Donna L; Sowell, Richard

    2016-01-01

    HIV disproportionately impacts African American women of childbearing age residing in the southern United States. Antiretroviral therapy has increased the quantity and quality of life for people living with HIV and produced viable and safe reproduction possibilities for women living with HIV. However, little is known about reproductive decision-making processes for African American women living with HIV. The overall goal of our study was to qualitatively explore perspectives related to reproduction and motherhood in HIV-infected African American women of childbearing capacity. HIV-infected African American women of childbearing capacity in South Carolina (N = 42) participated in in-depth interviews. Our respondents held positive views about pregnancy and motherhood, despite nonsupportive pregnancy messages from interpersonal influences, including health care providers. Study findings uncovered the need for programs and interventions to support women's reproductive autonomy and focus on reducing conception- and pregnancy-related transmission risks to infants and uninfected sexual partners. PMID:26781931

  6. Simulation of magnetotelluric fields at Stromboli volcano using unstructured grid finite element techniques together with digital topography and bathymetry data

    NASA Astrophysics Data System (ADS)

    Kütter, Sissy; Franke-Börner, Antje; Börner, Ralph-Uwe; Spitzer, Klaus

    2010-05-01

    Marine volcanoes are particularly demanding when it comes to applying electric or electromagnetic methods to investigate their interiors. First, the surrounding highly conductive sea water represents a significant difference in conductivity with respect to the volcanic edifice, second, the volcano's topography has great impact on the electromagnetic response, and, third, the surrounding sea bed topography heavily distorts electromagnetic fields in frequency bands that interfere with a certain spatial wavelength and amplitude of the bathymetry. By neglecting these issues severe misinterpretations are the inevitable consequence. We present different approaches to 3D vector finite element simulation on unstructured grids which are able to compute plain-wave magnetotelluric fields for models including arbitrary surface and sea bed topography. As an example, we consider Stromboli volcano. One major issue is the incorporation of the Stromboli topography using a digital terrain model so that nearly all geometric features affecting the electromagnetic response are considered and an electromagnetic view on Stromboli's interior becomes possible. By carrying out a number of different synthetic experiments it has become obvious that not only the topography of Stromboli island itself is influencing the behavior of the fields but, even stronger, the topography of the surrounding sea bed within a radius of several tens of kilometers. The experiment therefore comprises three steps which gradually approach the complex setting of the target and map the entire volcanic environment with increasing accuracy. The first step outlines the volcano as a resistive geometric frustum surrounded by conductive sea water and underlain by a resistive substratum. This model already gives fundamental answers concerning the principal frequency-dependent current flow pattern within the edifice and the surrounding sea. For this purpose, the MT response was calculated at the earth/sea and the earth

  7. Magnetotelluric images of the crustal structure of Chyulu Hills volcanic field, Kenya

    NASA Astrophysics Data System (ADS)

    Sakkas, V.; Meju, M. A.; Khan, M. A.; Haak, V.; Simpson, F.

    2002-03-01

    Electromagnetic experiments were conducted in 1995 as part of a multidisciplinary research project to investigate the deep structure of the Chyulu Hills volcanic chain on the eastern flank of the Kenya Rift in East Africa. Transient electromagnetic (TEM) and broadband (120-0.0001 Hz) magnetotelluric (MT) soundings were made at eight stations along a seismic survey line and the data were processed using standard techniques. The TEM data provided effective correction for static shifts in MT data. The MT data were inverted for the structure in the upper 20 km of the crust using a 2-D inversion scheme and a variety of starting models. The resulting 2-D models show interesting features but the wide spacing between the MT stations limited model resolution to a large extent. These models suggest that there are significant differences in the physical state of the crust between the northern and southern parts of the Chyulu Hills volcanic field. North of the Chyulu Hills, the resistivity structure consists of a 10-12-km-thick resistive (up to 4000 Ω m) upper crustal layer, ca. 10-km-thick mid-crustal layer of moderate resistivity (˜50 Ω m), and a conductive substratum. The resistive upper crustal unit is considerably thinner over the main ridge (where it is ca. 2 km thick) and further south (where it may be up to 5 km thick). Below this cover unit, steep zones of low resistivity (0.01-10 Ω m) occur underneath the main ridge and at its NW and SE margins (near survey positions 100 and 150-210 km on seismic line F of Novak et al. [Novak, O., Prodehl, C., Jacob, A.W.B., Okoth, W., 1997. Crustal structure of the southern flank of the Kenya Rift deduced from wide-angle P-wave data. In: Fuchs, K., Altherr, R., Muller, B., Prodehl, C. (Eds.), Structure and Dynamic Processes in the Lithosphere of the Afro-Arabian Rift System. Tectonophysics, vol. 278, 171-186]). These conductors appear to be best developed in upper crustal (1-8 km) and middle crustal (9-18 km) zones in the areas

  8. Multiple Intimate Partner Violence Experiences: Knowledge, Access, Utilization and Barriers to Utilization of Resources by Women of the African Diaspora

    PubMed Central

    Sabri, Bushra; Huerta, Julia; Alexander, Kamila A.; St.Vil, Noelle M.; Campbell, Jacquelyn C.; Callwood, Gloria B.

    2016-01-01

    Objective This study examined knowledge, access, utilization, and barriers to use of resources among Black women exposed to multiple types of intimate partner violence in Baltimore, Maryland and the U.S. Virgin Islands (USVI). Methods We analyzed quantitative survey data collected by 163 women recruited from primary care, prenatal or family planning clinics in Baltimore and the USVI. In addition we analyzed qualitative data from in-depth interviews with 11 women. Quantitative data were analyzed using descriptive statistics and qualitative data were analyzed using thematic analysis. Results A substantial proportion of Black women with multiple types of violence experiences lacked knowledge of, did not have access to, and did not use resources. Barriers to resource use were identified at the individual, relationship, and community levels. Conclusion There is need for programs to develop awareness, promote access and utilization of resources, and eliminate barriers to resource use among abused Black women. PMID:26548679

  9. Perception, experience, and indigenous knowledge of climate change and variability: the case of Accra, a sub-Saharan African city

    USGS Publications Warehouse

    Codjoe, Samuel N.A.; Owusu, George; Burkett, Virginia

    2014-01-01

    Several recent international assessments have concluded that climate change has the potential to reverse the modest economic gains achieved in many developing countries over the past decade. The phenomenon of climate change threatens to worsen poverty or burden populations with additional hardships, especially in poor societies with weak infrastructure and economic well-being. The importance of the perceptions, experiences, and knowledge of indigenous peoples has gained prominence in discussions of climate change and adaptation in developing countries and among international development organizations. Efforts to evaluate the role of indigenous knowledge in adaptation planning, however, have largely focused on rural people and their agricultural livelihoods. This paper presents the results of a study that examines perceptions, experiences, and indigenous knowledge relating to climate change and variability in three communities of metropolitan Accra, which is the capital of Ghana. The study design is based on a three-part conceptual framework and interview process involving risk mapping, mental models, and individual stressor cognition. Most of the residents interviewed in the three communities of urban Accra attributed climate change to the combination of deforestation and the burning of firewood and rubbish. None of the residents associated climate change with fossil fuel emissions from developed countries. Numerous potential adaptation strategies were suggested by the residents, many of which have been used effectively during past drought and flood events. Results suggest that ethnic residential clustering as well as strong community bonds in metropolitan Accra have allowed various groups and long-settled communities to engage in the sharing and transmission of knowledge of weather patterns and trends. Understanding and building upon indigenous knowledge may enhance the design, acceptance, and implementation of climate change adaptation strategies in Accra and

  10. Obesity and African Americans

    MedlinePlus

    ... Data > Minority Population Profiles > Black/African American > Obesity Obesity and African Americans African American women have the ... ss6304.pdf [PDF | 3.38MB] HEALTH IMPACT OF OBESITY More than 80 percent of people with type ...

  11. 'We are despised in the hospitals': sex workers' experiences of accessing health care in four African countries.

    PubMed

    Scorgie, Fiona; Nakato, Daisy; Harper, Eric; Richter, Marlise; Maseko, Sian; Nare, Prince; Smit, Jenni; Chersich, Matthew

    2013-01-01

    Sex workers in east and southern Africa are exposed to multiple occupational health and safety risks. Detailed understanding of barriers to accessing care would optimise design of improved services for this population. In this study, trained sex workers conducted 55 in-depth interviews and 12 focus group discussions with 106 female, 26 male and 4 transgender sex workers across 6 urban sites in Kenya, Zimbabwe, Uganda and South Africa. Data were analysed thematically, following an interpretive framework. Participants cited numerous unmet health needs, including diagnosis and treatment for sexually transmitted infections and insufficient access to condoms and lubricant. Denial of treatment for injuries following physical assault or rape and general hostility from public-sector providers was common. Resources permitting, many sex workers attended private services, citing higher quality and respect for dignity and confidentiality. Sex workers in southern Africa accessed specialised sex worker clinics, reporting mostly positive experiences. Across sites, participants called for additional targeted services, but also sensitisation and training of public-sector providers. Criminalisation of sex workers and associated stigmatisation, particularly of transgender and male sex workers, hinder HIV-prevention efforts and render access to mainstream healthcare precarious. Alongside law reform, sex worker-led peer outreach work should be strengthened and calls by sex workers for additional targeted services heeded. PMID:23414116

  12. African Sojourn: Two Narratives of African American Women Educators' Educational Philosophy.

    ERIC Educational Resources Information Center

    Pollard, Mignonne Y.

    This paper examines how the educational philosophies of two representative African American women university professors were influenced by multiple sojourns between Africa and North America. Two African American women born in the 1940s were interviewed about their early educational experiences, racial identity, and experiences in Africa. Each…

  13. A Mirror Image African American Student Reflections

    ERIC Educational Resources Information Center

    Cannon Dawson, Candice

    2012-01-01

    This dissertation is a narrative inquiry research project that focuses on the collegiate experiences of African American students at both historically black colleges and universities (HBCUs) and predominantly white institutions (PWIs). I look at how African American college students who engage in race or culturally specific activities, the degree…

  14. African American Undergraduates and the Academic Library

    ERIC Educational Resources Information Center

    Whitmire, Ethelene

    2006-01-01

    This study examines the academic library experiences of African American undergraduates attending a research university in the Midwest. Data collection techniques included questionnaires and ethnographic observations. The results indicated that African American undergraduates are using the academic library primarily to read and to study with their…

  15. High-resolution magnetotelluric studies of the Archaean-Proterozoic border zone in the Fennoscandian Shield, Finland

    NASA Astrophysics Data System (ADS)

    Vaittinen, K.; Korja, T.; Kaikkonen, P.; Lahti, I.; Smirnov, M. Yu.

    2012-03-01

    The Archaean-Proterozoic collisional zone is a complex mixture of the Archaean complexes [e.g. Iisalmi Complex (IC)], Proterozoic supracrustal belts [e.g. Kainuu Belt (KB) and Savo Belt (SB)] and oceanic arc lithologies in the central Fennoscandian Shield. The zone was formed in the Savo orogeny when the Keitele microcontinent collided with the Archaean Karelian craton in the Palaeoproterozoic time. The crustal architecture of this palaeosuture is studied using new broad-band magnetotelluric data from 104 sites. 2-D conductivity models across the border zone between the Palaeoproterozoic Svecofennian Domain and the Archaean Karelian province are constrained using the recent, partly collocated reflection seismic data from the Finnish Reflection Experiment (FIRE). Dimensionality analyses, in particular the Q-function analysis, show that magnetotelluric data represent reasonably well regional 2-D structure at periods <100 s, which is the longest period used in this study. Strike determinations gave a stable strike of N15W. For the inversions, the data are projected into three parallel profiles with an azimuth of N75E. The determinant inversion is selected as the most suitable method for the data set. Especially the phase data are useable only from the determinant since one of the polarizations have the out-of-quadrant phase at several sites. The interpreted final, geological more appropriate models, where smoother thick conductive areas are replaced by thinner layers, are constructed from the results of the unconstrained smooth inversions with the help of forward modelling, synthetic and prior model inversions and reflection seismic models. The two major sets of crustal conductors are identified. They have an opposite dip and together they form a bowl-shaped conductor. In the west, the eastward dipping SB conductors are located at the bottom of the formation underlain by the Keitele microcontinent. The SB conductors extend to the east possibly cutting the westward

  16. Non-operative management of renal trauma in very young children: experiences from a dedicated South African paediatric trauma unit.

    PubMed

    Tsui, Alex; Lazarus, John; Sebastian van As, A B

    2012-09-01

    Blunt abdominal trauma results in renal injury in 10% of paediatric cases. Over the last twenty years, the management of paediatric renal trauma has shifted towards a primarily non-operative approach that is now well-established for children up to 18 years old. This retrospective study reviews our experiences of non-operatively managing blunt renal trauma in a very young cohort of patients up to 11 years old. Between June 2006 and June 2010, 118 children presented to the Red Cross War Memorial Children's Hospital in Cape Town with blunt abdominal trauma. 16 patients shown to have sustained renal injury on abdominal computed tomography (CT) scanning were included in this study. Medical records were reviewed for the mechanism of injury, severity of renal injury, clinical presentation, associated injuries, management method and clinical outcomes. All renal injuries were graded (I-V) according to the American Association for the Surgery of Trauma Organ Injury Severity Scale. All renal trauma patients included in this study were aged between 1 and 11 years (mean of 6.5 years). 1 patient sustained grade V injuries; 2 grade IV, 6 grade III and 7 grade I injuries. The majority of injuries (9/16) were caused by motor vehicle crashes, whilst 5 children fell from height, 1 was struck by a falling tree and 1 hit by a moving train. 1 of 16 patients was haemodynamically unstable on presentation as a result of multiple splenic and hepatic lacerations. He was resuscitated and underwent immediate laparotomy. However, his renal injuries were not indications for surgical management. 15 haemodynamically stable patients were non-operatively managed for their renal injuries. Following lengths of admissions ranging from 4 to 132 days, all 16 patients were successfully discharged with no mortalities. No significant complications of renal trauma, such as new-onset hypertension, were detected during their first follow up outpatient appointments. Our findings successfully extend non

  17. A framework for process-based assessment of regional climate model experiments: applied to projections of southern African precipitation

    NASA Astrophysics Data System (ADS)

    James, Rachel; Washington, Richard; Jones, Richard

    2015-04-01

    There is a demand from adaptation planners for regional climate change projections, particularly the finer resolution data delivered by regional models. However, climate models are subject to important uncertainties, and their projections diverge substantially, particularly for precipitation. So how should decision makers know which futures to consider and which to disregard? Model evaluation is clearly a priority. The majority of studies seeking to assess the validity of projections are based on comparison of the models' twentieth century climatologies with observations or reanalysis. Whilst this work is very important, examination of the modelled mean state it is not sufficient to assess the credibility of modelled changes. Direct investigation of the mechanisms for change is also vital. In this study, a framework for process-based analysis of projections is presented, whereby circulation changes accompanying future responses are examined, and then compared to atmospheric dynamics during historical years in models and reanalyses. This framework has previously been applied to investigate a drying signal in West Africa, and will here be used to examine projected precipitation change in southern Africa. An ensemble of five global and regional model experiments will be employed, consisting of five perturbed versions of HadCM3 and five corresponding runs of HadRM3P (PRECIS), run over the CORDEX Africa domain. The global and regional model runs show contrasting future responses: there is a strong drying in the global models over southern Africa during the rainy season, but the regional models show drying over Madagascar and the south west Indian Ocean. Circulation changes associated with these projections will be presented as a first step towards understanding the mechanisms for change and the reasons for difference between the global and regional models. The interannual variability will also be examined and compared to reanalysis to explore how well the models

  18. Sexual experiences and condom use of heterosexual, low-income African American and Hispanic youth practicing relative monogamy, serial monogamy, and nonmonogamy.

    PubMed

    Norris, A E; Ford, K

    1999-01-01

    An understanding of differences in contraceptive use patterns among monogamous, serially monogamous, and nonmonogamous adolescents is essential to the design and targeting of condom promotion interventions. Interviews were conducted in Detroit, Michigan (US), in 1991 with a probability sample of 1062 heterosexual, low-income, African American and Hispanic youth 15-24 years of age. 577 were categorized as relatively monogamous, 171 as serially monogamous, and 278 as nonmonogamous. Monogamous youth were most likely to be female, Hispanic, married, and to have engaged in unprotected intercourse. Those who practiced serial monogamy were likely to be younger and to have used condoms at last intercourse. Nonmonogamous youth initiated intercourse earlier, were most likely to have experienced oral and anal intercourse, tended not to use contraception, and had the highest use rates of alcohol and marijuana. Condom use at last intercourse was reported by 38.6% of monogamous youth, 57.3% of the serially monogamous, and 38.2% of nonmonogamous youth; consistent condom use during the past year was reported by only 3.0%, 3.1%, and 2.5%, respectively. Discriminant analysis indicated that age at first intercourse, experience with oral sex, and number of partners best distinguished monogamous youth from serial and nonmonogamous youth. The 3 groups differed significantly in their perceived susceptibility to HIV; 11.0%, 17.8%, and 23.6%, respectively, had ever worried about contracting HIV from a partner. Risk reduction programs should be tailored to accommodate the different needs of these 3 subgroups. For example, nonmonogamous youth tend to be sensation seekers and may be more responsive to condom promotion campaigns that emphasize pleasure enhancement than to fear-based interventions. PMID:9918319

  19. Empowerment Groups for Urban African American Girls: A Response

    ERIC Educational Resources Information Center

    Holcomb-McCoy, Cheryl C.

    2005-01-01

    Although the author wanted to read Bemak, Chung, and Siroskey-Sabdo's article in an objective sense, her response to their article is most likely influenced by her own experiences as an African American female and mother of an African American daughter. To her, the paramount issue facing African American females is the double and sometimes triple…

  20. Response Function Estimation of Marine Magnetotelluric Data Measured at Tristan de Cunha Hot Spot

    NASA Astrophysics Data System (ADS)

    Chen, J.; Jegen, M. D.; Baba, K.; Utada, H.

    2015-12-01

    According to classical plume theory, the Tristan da Cunha hotspot is thought to have played a major role in the rifting of the South Atlantic margins and the creation of the aseismic Walvis Ridge by impinging at the base of the continental lithosphere shortly before or during the breakup of the South Atlantic margins. To understand the tectonic processes of the opening of the South Atlantic, the formation of the Walvis ridge and to understand, whether Tristan da Cunha is the cause or the consequence of the rifting, a network of 26 ocean-bottom magnetotelluric stations (OBMT) (cooperation between GEOMAR Germany and the Earthquake Research Institute at the University of Tokyo) and 24 broadband ocean-bottom seismometers was in operation during February 2012 and January 2013 within the framework of the project ISOLDE during the second phase of the SPP 1375. To complement the ocean-bottom network and the existing stations on Tristan da Cunha, one magnetotelluric land station and two land seismometers were installed on Nightingale Island. Marine magnetotelluric data is often contaminated with different levels of non-stationary noise originating from water waves, passing ships and tilt movements of the instruments. In traditional data processing, such noisy segments are removed from the time series before processing. As a consequence only a portion of data remains for response function estimation and accordingly no information about longer periods (deeper structure) remains. However, since the focus of this study is melt anomalies in the upper mantle, long period estimators of the response function are vital. To investigate which processing method yields the more reliable estimates between tens to 100 000 seconds (i.e. penetration depth from a few kilometers to approximately 600 to 800 km) for our recorded data, we applied and compared different sophisticated preprocessing and processing methods (e.g., pre-whitening, one-stage BIRRP, advanced two-stage BIRRP and

  1. Receiver function and magnetotelluric analysis to understand the first stage of a continental lithospheric break-up : case of the North Tanzanian Rift

    NASA Astrophysics Data System (ADS)

    Plasman, M.; Tiberi, C.; Tarits, P.; Hautot, S.; Gautier, S.; Ebinger, C. J.; Mulibo, G. D.; Khalfan, M.

    2015-12-01

    First stage of continental break-up, though intensively studied, is yet poorly understood. This is partly because actual rifting areas are either too mature (more than 10 My) or not easily accessible (thick sediment cover or under water). The North Tanzania part of the East African Rift is the place of a lithosphere's early break-up (less than 5My) in response to a combination of regional pulling forces and mantle upwelling. Deformation there results from complex interactions between magmatic intrusions, faulting, asthenospheric dynamics and far field stresses. CoLiBrEA (ANR) and CRAFTI (NSF) are two multidisciplinary projects which collaboratively focus on this area to understand the interactions between faults and magma, the role of inherited structures and rheological heterogeneities of the lithosphere. For that purpose, we deployed 38 broadband seismic stations in the Natron and Ngorongoro areas from January 2013 to December 2014 and carried out a 120 km East-West magnetotelluric (MT) profile to image the crustal and mantle structures. The 3D resistivity model, obtained from the inversion of the MT data along the profile, shows an highly heterogeneous crust with three-dimensional structures over a more homogeneous upper mantle. The first inversion result from the receiver function (RF) by the Zhu and Kanamori's inversion method show a thick crust (~35 km) with important variations (maximum 15km) especially in the Ngorongoro area, and an average Vp/Vs ratio of 1.75. We then completed this study by combining the MT data and the RF at the 11 sites of the EW profile. For each site, we built a 1D velocity model (Vs and VpVs) obtained by combining the Sambridge forward solution with a non linear descent research algorithm and constrained by the resistivity structure. The inversion shows an heterogeneous crust obviously dominated by the Moho interface at different depths, with low velocity layers mainly corresponding to low resistivity features.

  2. Two and three-dimensional magnetotelluric inversion. Technical report, December 1, 1991--May 31, 1994

    SciTech Connect

    Booker, J.R.

    1994-06-27

    Our overall goal is to develop efficient techniques for high resolution imaging of the electrical structure of the Earth`s subsurface. We have focussed on natural source techniques. Such as magnetotellurics (MT). The main accomplishment under our past DOE funding has been to implement a new algorithm to invert MT data for multi-dimensional structure which is orders of magnitude faster and more memory efficient than competing algorithms. In our most recent work, we have substantially extended the capability of our two-dimensional code: completed basic implementation of a three-dimensional code and investigated holographic techniques able to rapidly extract images without solving for material properties. The principal new goal of our proposed research is to extend our methods to the controlled source electromagnetic (CSEM) techniques used in many industrial applications.

  3. Electrical resistivity image of the South Atlantic continental margin derived from onshore and offshore magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Kapinos, G.; Weckmann, U.; Jegen-Kulcsar, M.; Meqbel, N.; Neska, A.; Katjiuongua, T. T.; Hoelz, S.; Ritter, O.

    2016-01-01

    We present a deep electrical resistivity image from the passive continental margin in Namibia. The approximately 700 km long magnetotelluric profile follows the Walvis Ridge offshore, continues onshore across the Kaoko Mobile Belt and reaches onto the Congo Craton. Two-dimensional inversion reveals moderately resistive material offshore, atypically low for oceanic lithosphere, reaching depths of 15-20 km. Such moderate resistivities are consistent with seismic P wave velocity models, which suggest up to 35 km thick crust. The Neoproterozoic rocks of the Kaoko Mobile Belt are resistive, but NNW-striking major shear-zones are imaged as subvertical, conductive structures in the upper and middle crust. Since the geophysical imprint of the shear zones is intact, opening of the South Atlantic in the Cretaceous did not alter the middle crust. The transition into the cratonic region coincides with a deepening of the high-resistive material to depths of more than 60 km.

  4. Application of Modified Differential Evolution Algorithm to Magnetotelluric and Vertical Electrical Sounding Data

    NASA Astrophysics Data System (ADS)

    Mingolo, Nusharin; Sarakorn, Weerachai

    2016-04-01

    In this research, the Modified Differential Evolution (DE) algorithm is proposed and applied to the Magnetotelluric (MT) and Vertical Electrical sounding (VES) data to reveal the reasonable resistivity structure. The common processes of DE algorithm, including initialization, mutation and crossover, are modified by introducing both new control parameters and some constraints to obtain the fitting-reasonable resistivity model. The validity and efficiency of our developed modified DE algorithm is tested on both synthetic and real observed data. Our developed DE algorithm is also compared to the well-known OCCAM's algorithm for real case of MT data. For the synthetic case, our modified DE algorithm with appropriate control parameters can reveal the reasonable-fitting models when compared to the original synthetic models. For the real data case, the resistivity structures revealed by our algorithm are closed to those obtained by OCCAM's inversion, but our obtained structures reveal layers more apparently.

  5. Crustal structure of the Chicxulub Impact crater imaged with magnetotelluric exploration

    NASA Astrophysics Data System (ADS)

    Unsworth, Martyn; Enriquez, Oscar Campos; Belmonte, Salvador; Arzate, Jorge; Bedrosian, Paul

    2002-08-01

    The electrical resistivity structure of the Chicxulub Impact crater has been imaged using broadband magnetotelluric exploration. A 1-2 km thick sequence of conductive Tertiary sedimentary rocks was imaged within the crater. The shallow resistivity of this layer increases across the cenote ring. This is primarily due to a decrease in porosity, although the groundwater composition may have some effect. While this layer reduces the sensitivity of MT, several features can be discerned beneath it. In the center of the crater the structural high is imaged as a region of high resistivity. In the outer part of the crater, lower resistivities in the upper crust may be due to mineralization or hydrothermal alteration.

  6. Seismic and magneto-telluric imaging for geothermal exploration at Jemez pueblo in New Mexico

    SciTech Connect

    Huang, Lianjie; Albrecht, Michael

    2011-01-25

    A shallow geothermal reservoir in the Pueblo of Jemez in New Mexico may indicate a commercial-scale geothermal energy potential in the area. To explore the geothermal resource at Jemez Pueblo, seismic surveys are conducted along three lines for the purpose of imaging complex subsurface structures near the Indian Springs fault zone. A 3-D magneto-telluric (MT) survey is also carried out in the same area. Seismic and MT imaging can provide complementary information to reveal detailed geologic formation properties around the fault zones. The high-resolution seismic images will be used together with MT images, geologic mapping, and hydrogeochemistry, to explore the geothermal resource at Jemez Pueblo, and to determine whether a conunercial-scale geothermal resource exists for power generation or direct use applications after drilling and well testing.

  7. Numerical solution of 3-D magnetotelluric using vector finite element method

    NASA Astrophysics Data System (ADS)

    Prihantoro, Rudy; Sutarno, Doddy; Nurhasan

    2015-09-01

    Magnetotelluric (MT) is a passive electromagnetic (EM) method which measure natural variations of electric and magnetic vector fields at the Earth surface to map subsurface electrical conductivity/resistivity structure. In this study, we obtained numerical solution of three-dimensional (3-D) MT using vector finite element method by solving second order Maxwell differential equation describing diffusion of plane wave through the conductive earth. Rather than the nodes of the element, the edges of the element is used as a vector basis to overcome the occurrence of nonphysical solutions that usually faced by scalar (node based) finite element method. Electric vector fields formulation was used and the resulting system of equation was solved using direct solution method to obtain the electric vector field distribution throughout the earth resistivity model structure. The resulting MT response functions was verified with 1-D layered Earth and 3-D2 COMMEMI outcropping structure. Good agreement is achieved for both structure models.

  8. Magnetotelluric/audiomagnetotelluric study of the Zuni Hot Dry Rock Geothermal Prospect, New Mexico

    SciTech Connect

    Ander, M.E.; Goss, R.; Strangway, D.; Hillebrand, C.; Laughlin, A.W.; Hudson, C.

    1980-01-01

    The Los Alamos Scientific Laboratory has been investigating a large area in New Mexico for Hot Dry Rock geothermal potential. The area includes parts of the Jemez volcanic lineament and the central Rio Grande rift. LASL has completed a detailed magnetotelluric/audiomagnetotelluric survey covering 161 square km over an area of high heat flow, south of Zuni, NM. The data collection was collected and preliminary analysis phases of a regional MT survey which suggest the Jemez lineament is associated with a crustal structure of anomalously high electrical conductivity. The detailed MT shows an average tipper strike of N60/sup 0/E above 100 sec period, representing the structural trend within Precambrian basement. The Jemez lineament strikes approximately N55/sup 0/E; this suggests a relationship between the Precambrian structure beneath the Zuni area and the Jemez lineament.

  9. APPLICATION OF AUDIO-MAGNETOTELLURIC SURVEYS ON SAO MIGUEL ISLAND, AZORES PORTUGAL.

    USGS Publications Warehouse

    Hoover, Donald; Rodrigues Da Silva, A.; Pierce, Herbert A.; Amaral, Roberto

    1984-01-01

    Geothermal exploration and development has been under way on Sao Miguel Island, Azores since 1975. This work had been restricted to the Fogo volcano, one of three dormant silicic volcanic centers on the island. The USGS in 1982 and 1983 conducted reconnaissance natural-source audio-magnetotelluric (AMT) surveys of all three silicic centers to evaluate the potential for geothermal systems at each and to demonstrate the utility of the method in areas of difficult terrain. Results on Fogo showed a low resistivity trend extending from the present production area upslope to the caldera boundary. The upper part of this trend is the upwelling zone of a thermal plume which supplies the production area. Further exploration and drilling are now planned for this area.

  10. Broadband Marine Magnetotelluric Exploration of the Crust at a Petroleum Prospect and a Mid-Ocean RIdge

    NASA Astrophysics Data System (ADS)

    Key, K. W.; Constable, S. C.

    2004-12-01

    Broadband marine magnetotelluric (MT) instrumentation developed at Scripps Institution of Oceanography enables resolution of electrical resistivity structure at much shallower depths than previously attainable. While marine seismic reflection surveys have routinely surveyed crustal structure on the continental shelves and mid-ocean ridges, traditional marine MT sensors were only capable of measuring long period fields and so MT experiments were limited to studying mantle structure. The introduction of low-noise sensors allows the broadband MT instrument to now measure the shorter period fields that contain information about crustal resistivity structure. We present two case studies of using the broadband MT system at areas previously surveyed with seismic methods. The joint interpretation of both seismic and MT models for these case studies leads to an improved geological interpretation. At Gemini Prospect in the northern Gulf of Mexico we have collected 42 MT sites in a grid over a three-dimensional (3D) resistive salt structure associated with the petroleum prospect. Depth migrated seismic reflection profiles from a 3D seismic survey at Gemini allow for the verification of two-dimensional (2D) MT inversion models. Combined images of the MT resistivity and seismic reflection profiles show that 2D MT can recover that salt body despite its 3D shape. A steeply dipping and overhanging resistive feature correlates with a previously uninterpreted strong reflection and illustrates how MT can constrain structure in regions where the seismic method performs poorly. A thin and shallow resistive feature shown outside the seismic salt volume may indicate a change in porosity or pore fluids associated with a natural trap in the sediments. At the East Pacific Rise near 9{o50'}N, a pilot survey using the broadband instruments shows sensitivity to structure at shallower depths than previous ridge MT experiments. Two-dimensional inversion of data from 4 MT sites shows a high

  11. Africans in America.

    ERIC Educational Resources Information Center

    Hart, Ayanna; Spangler, Earl

    This book introduces African-American history and culture to children. The first Africans in America came from many different regions and cultures, but became united in this country by being black, African, and slaves. Once in America, Africans began a long struggle for freedom which still continues. Slavery, the Civil War, emancipation, and the…

  12. African Outreach Workshop 1974.

    ERIC Educational Resources Information Center

    Schmidt, Nancy J.

    This report discusses the 1974 African Outreach Workshop planned and coordinated by the African Studies Program at the University of Illinois at Urbana-Champaign. Its major aim was to assist teachers in developing curriculum units on African using materials available in their local community. A second aim was for the African Studies Program to…

  13. Magnetotelluric investigations of the lithosphere beneath the central Rae craton, mainland Nunavut, Canada

    NASA Astrophysics Data System (ADS)

    Spratt, Jessica E.; Skulski, Thomas; Craven, James A.; Jones, Alan G.; Snyder, David B.; Kiyan, Duygu

    2014-03-01

    New magnetotelluric soundings at 64 locations throughout the central Rae craton on mainland Nunavut constrain 2-D resistivity models of the crust and lithospheric mantle beneath three regional transects. Responses determined from colocated broadband and long-period magnetotelluric recording instruments enabled resistivity imaging to depths of > 300 km. Strike analysis and distortion decomposition on all data reveal a regional trend of 45-53°, but locally the geoelectric strike angle varies laterally and with depth. The 2-D models reveal a resistive upper crust to depths of 15-35 km that is underlain by a conductive layer that appears to be discontinuous at or near major mapped geological boundaries. Surface projections of the conductive layer coincide with areas of high grade, Archean metasedimentary rocks. Tectonic burial of these rocks and thickening of the crust occurred during the Paleoproterozoic Arrowsmith (2.3 Ga) and Trans-Hudson orogenies (1.85 Ga). Overall, the uppermost mantle of the Rae craton shows resistivity values that range from ~3000 Ω m in the northeast (beneath Baffin Island and the Melville Peninsula) to ~10,000 Ω m beneath the central Rae craton, to >50,000 Ω m in the south near the Hearne Domain. Near-vertical zones of reduced resistivity are identified within the uppermost mantle lithosphere that may be related to areas affected by mantle melt or metasomatism associated with emplacement of Hudsonian granites. A regional decrease in resistivities to values of ~500 Ω m at depths of 180-220 km, increasing to 300 km near the southern margin of the Rae craton, is interpreted as the lithosphere-asthenosphere boundary.

  14. Eastern termination of the Altyn Tagh Fault, western China: Constraints from a magnetotelluric survey

    NASA Astrophysics Data System (ADS)

    Xiao, Qibin; Shao, Guihang; Liu-Zeng, Jing; Oskin, Michael E.; Zhang, Jin; Zhao, Guoze; Wang, Jijun

    2015-05-01

    The left-lateral Altyn Tagh Fault forms the northern boundary of the Tibetan Plateau. The strike-slip rate of the active Altyn Tagh Fault decreases northeastward and reduces close to zero as it passes north of the Qilian Shan. This geometry raises controversies on whether and how the fault terminates or extends further east. To address these controversies, wide-band magnetotelluric data were collected along four profiles across the Altyn Tagh Fault ranging from 135 to 261 km in length. All four profiles are located in the foreland of the Qilian Shan Ranges and are oriented perpendicular to the inferred fault zone that could be the continuation of Altyn Tagh Fault. Both the two-dimensional and three-dimensional electrical resistivity models derived from our magnetotelluric data show that the Hexi Corridor crust is generally of low resistivity, whereas the crust of the Huahai-Jinta basin is, in general, of high resistivity with a local and isolated low-resistivity anomaly within the mid-lower crust. The generally high-resistivity crust of the Huahai-Jinta basin may be rheologically unfavorable for the Altyn Tagh Fault passing through the basin toward the northeast. The entirely different electrical structure between the Hexi Corridor and its northern neighbors indicates the existence of a tectonic boundary that coincides with the Altyn Tagh Fault in the west and reverse faults in the east. The two-dimensional electrical conductivity models suggest that the Altyn Tagh Fault transfers from a single fault in the west to a branching set of mainly dip-slip faults in the east.

  15. Internal structure of the Chicxulub Impact crater imaged with magnetotelluric exploration

    NASA Astrophysics Data System (ADS)

    Campos, O.; Unsworth, M.; Bedrosian, P.; Belmonte, S.; Arzate, J.; Lazorek, M.; Zimmer, U.

    2001-12-01

    The magnetotelluric technique allows remote sensing of the Earth's subsurface structure using natural, low frequency radio waves. It measures the electrical resistivity, a parameter that contains information about the lithology and fluid content of subsurface rock units. In January 2001, magnetotelluric (MT) data were collected on two radial profiles across the Chicxulub impact crater in Yucatan, Mexico. Each profile extended from the centre of the crater near Puerto Chicxulub to beyond the cenote ring. The MT data were processed and then combined with data collected in previous years by UNAM. The combined data set was then inverted to give a two-dimensional image of the subsurface resistivity structure of the crater. The following features can be resolved in the subsurface resistivity model. The Tertiary sedimentary sequence that fills the crater has a resistivity of 1-3 ohm-m and is approximately 2 km deep. In the basement a zone of high resistivity is imaged from the centre of the impact structure to a radius of approximately 45 km. This high resistivity at shallow depth can be interpreted as uplifted basement rocks of the structural high in the centre of the crater. Between radial distances of 50 and 70 km is a zone of lower resistivities in the upper 5-10 km of the crust. This coincides with the observed low in the Bouguer gravity anomaly. The coincidence of these two anomalies suggests a common origin. This is most probably due to a region of breccia that exhibits both low electrical resistivity and density.

  16. A data variance technique for automated despiking of magnetotelluric data with a remote reference

    SciTech Connect

    Kappler, K.

    2011-02-15

    The magnetotelluric method employs co-located surface measurements of electric and magnetic fields to infer the local electrical structure of the earth. The frequency-dependent 'apparent resistivity' curves can be inaccurate at long periods if input data are contaminated - even when robust remote reference techniques are employed. Data despiking prior to processing can result in significantly more reliable estimates of long period apparent resistivities. This paper outlines a two-step method of automatic identification and replacement for spike-like contamination of magnetotelluric data; based on the simultaneity of natural electric and magnetic field variations at distant sites. This simultaneity is exploited both to identify windows in time when the array data are compromised, and to generate synthetic data that replace observed transient noise spikes. In the first step, windows in data time series containing spikes are identified via intersite comparison of channel 'activity' - such as the variance of differenced data within each window. In the second step, plausible data for replacement of flagged windows is calculated by Wiener filtering coincident data in clean channels. The Wiener filters - which express the time-domain relationship between various array channels - are computed using an uncontaminated segment of array training data. Examples are shown where the algorithm is applied to artificially contaminated data, and to real field data. In both cases all spikes are successfully identified. In the case of implanted artificial noise, the synthetic replacement time series are very similar to the original recording. In all cases, apparent resistivity and phase curves obtained by processing the despiked data are much improved over curves obtained from raw data.

  17. Melt detected at the oceanic LAB with magnetotelluric data: Where else could it exist? (Invited)

    NASA Astrophysics Data System (ADS)

    Naif, S.; Key, K.; Constable, S.; Evans, R. L.

    2013-12-01

    We carried out a 280 km electromagnetic (EM) profile across the Middle America Trench offshore Nicaragua in order to image the electrical resistivity structure of the incoming oceanic plate and the underlying mantle. A total of 50 EM instruments were deployed to record magnetotelluric (MT) and controlled-source electromagnetic (CSEM) data. Results from the CSEM data discussing the structure of the topmost 20 km will be presented in session GP017; here we focus on results from the magnetotelluric data. Two-dimensional anisotropic inversions of the MT data reveal a laterally extensive low-resistivity layer (4-6 ohm-m) that is 25 km thick beneath the incoming oceanic plate at depths consistent with the seismically observed lithosphere-asthenosphere boundary. This low resistivity signature cannot be explained by melt-free hydrous olivine, as it requires unrealistically large water concentrations that would induce melting. Hence, a low degree of hydrated partial melt provides the simplest inference. The layer is anisotropic with 1.5-2 times lower resistivity in the plate motion parallel direction than the trench parallel direction, whereas the deeper mantle is isotropic and more resistive (10-20 ohm-m). We posit that this observed anisotropy is evidence that the layer is being actively sheared by the overlying lithosphere, such that the depth at which the model returns to an isotropic state is indicative of the extent over which the lithosphere and asthenosphere are coupled. In light of these observations, we use a plate-cooling model and models for the volatile influenced peridotite solidus for various mantle states to predict where a similar melt rich asthenosphere may be detected by geophysical observations.

  18. Annotated Selected Bibliography & Index for Teaching African-American Learners: Culturally Responsive Pedagogy Project.

    ERIC Educational Resources Information Center

    Hilliard, Asa G.

    This annotated bibliography and index presents nearly 2,000 references that are substantially unique to African or African American teaching and learning. Designed to support teacher education, the bibliography features references that were chosen if they were culturally relevant, recognized the African or African American experience, and drew…

  19. Walking on the Red Brick Path: A Portrait of African-American Women's Experiences with the Built Environment of a Predominantly White Institution

    ERIC Educational Resources Information Center

    Krusemark, Stephanie L.

    2010-01-01

    "Space, like language, is socially constructed; and like the syntax of language, the spatial arrangements of our buildings and communities reflect and reinforce the nature of gender, race, and class relations in society" (Weisman, 1992, p. 2). While institutions of higher education have granted physical access to African-American women over the…

  20. Black in White America: Historical Perspectives. The African Experience: Exploring What was Lost to a Man Enslaved and Brought to the New World.

    ERIC Educational Resources Information Center

    Dollase, Richard; And Others

    This volume is the first of a three-part course of study for secondary students. The entire course is designed to take six to eight weeks. This unit is concerned with life as Africans knew it in their homeland, before the incursions of the slave traders. While the introductory section describes the traumatic process of being uprooted and enslaved,…

  1. Faith in Counseling: A Qualitative Examination of the Experiences of African American College Students with the Integration of Religion and Spirituality into Counseling

    ERIC Educational Resources Information Center

    Blash, Daniel L.

    2010-01-01

    This qualitative study explored the integration of religion and spirituality in counseling among six African American Christian college students ranging from age 26-48. Specifically, attention was given to the circumstances that either facilitated or discouraged the student's willingness to include their faith system in counseling. Thematic…

  2. 3D structures of the crust and upper mantle in Atlas Mountains of Morocco from magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Kiyan, D.; Jones, A.; Ledo, J.; Fullea, J.; Sinischalchi, A.; Romano, G.; Campanya, J.

    2012-04-01

    As a part of the PICASSO (Program to Investigate Convective Alboran Sea System Overturn) and concomitant TopoMed (Plate re-organization in the western Mediterranean: Lithospheric causes and topographic consequences - an ESF EUROCORES TOPO-EUROPE project) projects, a multi-institutional magnetotelluric (MT) experiment across the Atlas Mountains initiated in September 2009 and ended in February 2010. The overarching objective of the project is to provide new constrains on the lithospheric structure of the Atlas Mountains, and to aid in discriminating between competing models describing the tectonics of the region. The experiment comprised acquisition of broad-band (crustal probing) and long period (mantle probing) MT data along two profiles: a N-S oriented profile crossing the Middle Atlas through the Central High Atlas to the east (profile MEK) and a NE-SW oriented profile crossing the western High Atlas towards the Anti Atlas in the west (profile MAR). Our MT inversion results from the MEK profile (Ledo et al., 2011), assuming that the Earth can be validly represented by two-dimensional (2D) structures, reveal two major mid- to lower crustal scale conductive features. The first anomaly is stretching from the Middle Atlas southward towards the High Moulouya basin and the second one is located beneath the Anti Atlas. There is a gradual increase in mantle resistivity to the south which may indicate a thickening lithosphere beneath the Anti Atlas. To validate the 2D inversion results, the MT data on the same profile were inverted for 3D electrical resistivity structure using both WSINV3DMT (Siripunvaraporn et al., 2005a) and ModEM (Egbert et al., 2011). We ran inversions with the full impedance tensor and also with only the off-diagonal components. Following the paper of Patro and Egbert (2011), we are testing the effect of using different length scales in the along-strike and across strike directions. As expected, the 3D inversion results provide a better fit to the

  3. Crustal resistivity structure from magnetotelluric soundings in the Colorado Plateau-Basin and Range provinces, central and western Arizona

    USGS Publications Warehouse

    Klein, D.P.

    1991-01-01

    Resistivity structure to about 25 km depth is defined from two-dimensional modeling of 29 magnetotelluric (MT) soundings (0.002-5 Hz) that traverse 280 km of the southwestern Colorado Plateau, transition zone, and Basin and Range provinces in Arizona. From the surface to 5 km depth, the MT model suggests structural relationships between low-resistivity sedimentary and volcanic rocks (50-300 ohm m) and high-resistivity granitic and gneissic basement (500-9000 ohm m). -from Author

  4. Research with African Americans: Lessons Learned about Recruiting African American Women

    ERIC Educational Resources Information Center

    Coker, Angela D.; Huang, Hsin-Hsin; Kashubeck-West, Susan

    2009-01-01

    The authors briefly explore literature related to recruiting African American research participants, reflect on their experiences conducting body image research with a sample of African American college women in an earlier study (S. Kashubeck-West et al., 2008), and discuss some methodological and cultural challenges that they encountered during…

  5. Changing Fatherhood: An Exploratory Qualitative Study with African and African Caribbean Men in England

    ERIC Educational Resources Information Center

    Williams, Robert; Hewison, Alistair; Wildman, Stuart; Roskell, Carolyn

    2013-01-01

    This paper presents findings from a qualitative study undertaken with 46 African and African Caribbean men exploring their experiences of fatherhood. Data analysis was informed by Connell's theoretical work on changing gender relations. Findings indicate that fathers' lives were mediated by masculinities, racism, gender, migration and…

  6. Teaching African American Youth: Learning from the Lives of Three African American Social Studies Teachers

    ERIC Educational Resources Information Center

    McBride, Chantee Earl

    2010-01-01

    This study examines the life histories of three African American social studies teachers, focusing on the evolution and changes in their identities, perspectives, and attitudes related to their profession and instructional practice. In addition, the study addresses the significance of the teachers' racialized experiences as African Americans and…

  7. Are the geoelectric structures of the Betics lithosphere anisotropic? Insights from a complete dimensionality analysis of magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Martí, A.; Rosell, O.; Queralt, P.; Ledo, J.; Marcuello, A.; Roca, E.

    2012-04-01

    Magnetotelluric (MT) exploration in orogenic zones has provided valuable information on the sructures and processes that can be correlated with other geophysical observations. In the Betic Chain (SE Spain), an extensive broadband and long period MT dataset allowed the charaterization of the geoelectric structure of the lithosphere using 3D modelling, in agreement with the 3D character of the data. The model revealed the presence of a low conductivity zone at lithospheric mantle depths that was identified as asthenospheric intruding material related to the westwards roll-back of a lithospheric subduction. As an advancing step in the understanding of the Betics lithospheric structure we present the results of a new dimensionality analysis of the magnetotelluric data with the goal of identifying the possible presence of electrical anisotropy. In the last years, electrical anisotropy within the Earth has been included in geoelectric models and has been related to tectonic structures and geodynamic processes. However, given the amount of information contained in the magnetotelluric impedance tensor and induction arrows, it is not a routine task to uniquely identify the presence and nature of anisotropy, given that it can occur within different types of structures and at different scales. Thus, our analysis is based on a previous methodological work, which established the relationship between the dimensionality pattern obtained at different sites and periods and the possible presence of anisotropy. Additionally, we use the information contained in the induction arrows to constrain the results and compare them with other geophysical data.

  8. Three-dimensional magnetotelluric imaging of crustal and uppermost mantle structures of the Atlas Mountains of Morocco

    NASA Astrophysics Data System (ADS)

    Kiyan, Duygu; Jones, Alan G.; Fullea, Javier; Ledo, Juanjo; Siniscalchi, Agata; Romano, Gerardo

    2013-04-01

    The primary goal of TopoMed (Plate re-organization in the western Mediterranean: Lithospheric causes and topographic consequences - an ESF EUROCORES TOPO-EUROPE Collaborative Research Project) project, is to define the geometries and determine the nature of the major crustal and upper mantle boundaries, through imaging electric structures, that provide information on understanding the tectonic evolution of the Atlas Mountains of Morocco. A multi-institutional magnetotelluric (MT) experiment across the Atlas Mountains region comprises the acquisition of broadband and long period MT data along two profiles: a N-S oriented profile through Middle Atlas to the east and a NE-SW profile through Marrakech to the west. The preliminary results of two-dimensional (2-D) interpretation of the MT data collected over the first profile were presented in the paper by Ledo et al. (2011). In this study, we present the results from three-dimensional (3-D) MT inversion using the codes WSINV3DMT (Siripunvaraporn et al., 2005) and Modular system for Electromagnetic Inversion (ModEM; Egbert & Kelbert, 2012). There is a general good agreement between the main features obtained from the 2-D models and the new results of the 3-D modelling. Models inverting for only off-diagonal tensor components showed a distinct conductivity contrast between Middle-High Atlas and Anti Atlas correlates with the South Atlas Front fault, the depth extent of which appears to be limited to uppermost mantle (approximately 55 km). The eastern Anti-Atlas is characterized by a resistive (i.e. cold) lithosphere. Beside this, a prominent conducting anomaly at the lower crust/uppermost mantle is imaged west of the profile in the junction between the High and Middle Atlas (Moulouya plain). The conductive body, which extends from northern boundary of Middle Atlas to the northern boundary of High Atlas, is interpreted as due to the presence of partial melt and/or migrated fluids. We can correlate this conductivity anomaly

  9. Deep-crustal magma reservoirs beneath the Nicaraguan volcanic arc, revealed by 2-D and semi 3-D inversion of magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Brasse, Heinrich; Schäfer, Anja; Díaz, Daniel; Alvarado, Guillermo E.; Muñoz, Angélica; Mütschard, Lutz

    2015-11-01

    A long-period magnetotelluric (MT) experiment was conducted in early 2009 in western Nicaragua to study the electrical resistivity and thus fluid/melt distribution at the Central American continental margin where the Cocos plate subducts beneath the Caribbean plate. Strike analysis yields a preference direction perpendicular to the profile, with moderate deviation from two-dimensionality, however. Two-dimensional modeling maps the sediments of the Nicaraguan Depression and a high-conductivity zone in the mid-crust, slightly offset from the arc. Further conductors are modeled in the backarc. However, these features are probably artifacts when a 2-D program is applied to data which show moderate 3-D characteristics. 3-D inversion clarifies the situation, and the major remaining conductive structure is now quasi directly beneath the volcanic chain and interpreted as a deep-seated magma deposit. Conductivity in the backarc is also relatively high and may either be caused by still existing partial melts beneath the Paleocene to Miocene volcanic arcs or by related metallic deposits in the aureoles of hydrothermal alteration.

  10. Engaging Depressed African American Adolescents in Treatment: Lessons From The AAKOMA PROJECT

    PubMed Central

    Breland-Noble, Alfiee M.; Burriss, Antoinette; Poole, H. Kathy

    2013-01-01

    The authors describe and illustrate means of engaging depressed African American adolescents in treatment. Twenty-eight youth participated in focus groups or individual interviews. Using grounded theory and transcript based analysis, they derived 5 themes describing African American adolescents’ experience of depression and suggested mechanisms for improving African American youth treatment engagement. Practitioners can educate African American youth about depression as a medical disorder, build trust, and apply innovative approaches to recognizing differential manifestations of depression in African American youth. PMID:20564682

  11. Joint interpretation of magnetotelluric, seismic, and well-log data in Hontomín (Spain)

    NASA Astrophysics Data System (ADS)

    Ogaya, Xènia; Alcalde, Juan; Marzán, Ignacio; Ledo, Juanjo; Queralt, Pilar; Marcuello, Alex; Martí, David; Saura, Eduard; Carbonell, Ramon; Benjumea, Beatriz

    2016-06-01

    Hontomín (N of Spain) hosts the first Spanish CO2 storage pilot plant. The subsurface characterization of the site included the acquisition of a 3-D seismic reflection and a circumscribed 3-D magnetotelluric (MT) survey. This paper addresses the combination of the seismic and MT results, together with the available well-log data, in order to achieve a better characterization of the Hontomín subsurface. We compare the structural model obtained from the interpretation of the seismic data with the geoelectrical model resulting from the MT data. The models correlate well in the surroundings of the CO2 injection area with the major structural differences observed related to the presence of faults. The combination of the two methods allowed a more detailed characterization of the faults, defining their geometry, and fluid flow characteristics, which are key for the risk assessment of the storage site. Moreover, we use the well-log data of the existing wells to derive resistivity-velocity relationships for the subsurface and compute a 3-D velocity model of the site using the 3-D resistivity model as a reference. The derived velocity model is compared to both the predicted and logged velocity in the injection and monitoring wells, for an overall assessment of the computed resistivity-velocity relationships. The major differences observed are explained by the different resolution of the compared geophysical methods. Finally, the derived velocity model for the near surface is compared with the velocity model used for the static corrections in the seismic data. The results allowed extracting information about the characteristics of the shallow unconsolidated sediments, suggesting possible clay and water content variations. The good correlation of the velocity models derived from the resistivity-velocity relationships and the well-log data demonstrate the potential of the combination of the two methods for characterizing the subsurface, in terms of its physical properties

  12. Magnetotelluric investigation of the geothermal anomaly in Hailin, Mudanjiang, northeastern China

    NASA Astrophysics Data System (ADS)

    Zhang, Lili; Hao, Tianyao; Xiao, Qibin; Wang, Jie; Zhou, Liang; Qi, Min; Cui, Xiangpan; Cai, Ningxiao

    2015-07-01

    To study the occurrence conditions and locations of geothermal bodies in Hailin, Mudanjiang, northeastern China, we conducted a magnetotelluric investigation to delineate the electrical conductivity structure of the area on three parallel profiles. The area to the west of the Mudanjiang Fault lies in the Hailang sag of the Ning'an Basin. The data were processed using the mutual reference technique, static shift correction, and structural strike and dimensionality analysis based on tensor decomposition. Moreover, a modified anisotropic-diffusion-based method was used to suppress noise for the magnetotelluric time series data. This method retains the advantages of conventional anisotropic diffusion and is superior in its discrimination ability. The method is characteristic not only of the inherited features such as intra-region smoothing and edge preservation, but also of the adaptive selection of the diffusion coefficient. Data analysis revealed that the electrical resistivity structure can be approximated by a two-dimensional characterization. Two-dimensional inversion and rendering visualization show that a highly resistive granite basement is covered with conductive sedimentary layers and that a relatively low-resistivity anomalous structure with a resistivity of approximately 100-600 Ω·m is imbedded in the high-resistivity background. The anomalous structure has a narrow top and a wide bottom (the bottom depth is at least 3500 m). The shape and electrical features of the structure indicate favorable storage space for hot subsurface water. Fault activities and magma intrusion may result in the fractures of the basement, which are filled with hot water and thus produce the relatively low resistivity. Based on a comprehensive analysis, we infer that the structure is indicative of a geothermal reservoir. An exploratory well drilled near the structure confirms the occurrence of high temperatures. Several geological factors (cap rock, basement, and major faults

  13. INTERPRETATION OF SHALLOW ELECTRICAL FEATURES FROM ELECTROMAGNETIC AND MAGNETOTELLURIC SURVEYS AT MOUNT HOOD, OREGON

    SciTech Connect

    Wilt, M.; Goldstein, N.E.; Mozley, E.

    1981-04-01

    A magnetotelluric survey, with a reference magnetometer for noise cancellation, was conducted at accessible locations around Mount Hood, Oregon. Thirty-eight tensor magnetotelluric (MT) and remote telluric stations were set up in clusters around the volcano except for the northwest quadrant, a wilderness area. Because of limited access, station locations were restricted to elevations below 1829 m, or no closer than 5 km from the 3424-m summit. On the basis of the MT results, three areas were later investigated in more detail using a large-moment, controlled-source electromagnetic (EM) system developed at Lawrence Berkeley Laboratory and the University of California at Berkeley. One-dimensional interpretations of EM and MT data on the northeast flank of the mountain near the Cloud Cap eruptive center and on the south flank near Timberline Lodge show a similar subsurface resistivity pattern: a resistive surface layer 400-700 m thick, underlain by a conductive layer with variable thickness and resistivity of <20 ohm m. It is speculated that the surface layer consists of volcanics partially saturated with cold meteoric water. The underlying conductive zone is presumed to be volcanics saturated with water heated within the region of the central conduit and, possibly, at the Cloud Cap side vent. This hypothesis is supported by the existence of warm springs at the base of the mountain, most notably Swim Warm Springs on the south flank, and by several geothermal test wells, one of which penetrates the conductor south of Timberline Lodge. The MT data typically gave a shallower depth to the conductive zone than did the EM data. This is attributed, in part, to the error inherent in one-dimensional MT interpretations of geologically or topographically complex areas. On the other hand, MT was better for resolving the thickness of the conductive layer and deeper structure. The MT data show evidence for a moderately conductive north-south structure on the south flank below the

  14. Efficient computational methods for electromagnetic imaging with applications to 3D magnetotellurics

    NASA Astrophysics Data System (ADS)

    Kordy, Michal Adam

    The motivation for this work is the forward and inverse problem for magnetotellurics, a frequency domain electromagnetic remote-sensing geophysical method used in mineral, geothermal, and groundwater exploration. The dissertation consists of four papers. In the first paper, we prove the existence and uniqueness of a representation of any vector field in H(curl) by a vector lying in H(curl) and H(div). It allows us to represent electric or magnetic fields by another vector field, for which nodal finite element approximation may be used in the case of non-constant electromagnetic properties. With this approach, the system matrix does not become ill-posed for low-frequency. In the second paper, we consider hexahedral finite element approximation of an electric field for the magnetotelluric forward problem. The near-null space of the system matrix for low frequencies makes the numerical solution unstable in the air. We show that the proper solution may obtained by applying a correction on the null space of the curl. It is done by solving a Poisson equation using discrete Helmholtz decomposition. We parallelize the forward code on multicore workstation with large RAM. In the next paper, we use the forward code in the inversion. Regularization of the inversion is done by using the second norm of the logarithm of conductivity. The data space Gauss-Newton approach allows for significant savings in memory and computational time. We show the efficiency of the method by considering a number of synthetic inversions and we apply it to real data collected in Cascade Mountains. The last paper considers a cross-frequency interpolation of the forward response as well as the Jacobian. We consider Pade approximation through model order reduction and rational Krylov subspace. The interpolating frequencies are chosen adaptively in order to minimize the maximum error of interpolation. Two error indicator functions are compared. We prove a theorem of almost always lucky failure in the

  15. Joint Audio-Magnetotelluric and Passive Seismic Imaging of the Cerdanya Basin

    NASA Astrophysics Data System (ADS)

    Gabàs, A.; Macau, A.; Benjumea, B.; Queralt, P.; Ledo, J.; Figueras, S.; Marcuello, A.

    2016-09-01

    The structure of Cerdanya Basin (north-east of Iberian Peninsula) is partly known from geological cross sections, geological maps and vintage geophysical data. However, these data do not have the necessary resolution to characterize some parts of Cerdanya Basin such as the thickness of soft soil, geometry of bedrock or geometry of geological units and associated faults. For all these reasons, the main objective of this work is to improve this deficiency carrying out a detailed study in this Neogene basin applying jointly the combination of passive seismic methods ( H/V spectral ratio and seismic array) and electromagnetic methods (audio-magnetotelluric and magnetotelluric method). The passive seismic techniques provide valuable information of geometry of basement along the profile. The maximum depth is located near Alp village with a bedrock depth of 500 m. The bedrock is located in surface at both sites of profile. The Neogene sediments present a shear-wave velocity between 400 and 1000 m/s, and the bedrock basement presents a shear-wave velocity values between 1700 and 2200 m/s. These results are used as a priori information to create a 2D resistivity initial model which constraints the inversion process of electromagnetic data. We have obtained a 2D resistivity model which is characterized by (1) a heterogeneous conductivity zone (<40 Ohm m) that corresponds to shallow part of the model up to 500 m depth in the centre of the profile. These values have been associated with Quaternary and Neogene sediments formed by silts, clays, conglomerates, sandstones and gravels, and (2) a deeper resistive zone (1000-3000 Ohm m) interpreted as Palaeozoic basement (sandstones, limestones and slates at NW and conglomerates and microconglomerates at SE). The resistive zone is truncated by a discontinuity at the south-east of the profile which is interpreted as the Alp-La Tet Fault. This discontinuity is represented by a more conductive zone (600 Ohm m approx.) and is explained

  16. The application of artificial neural networks to magnetotelluric time-series analysis

    NASA Astrophysics Data System (ADS)

    Manoj, C.; Nagarajan, Nandini

    2003-05-01

    Magnetotelluric (MT) signals are often contaminated with noise from natural or man-made processes that may not fit a normal distribution or are highly correlated. This may lead to serious errors in computed MT transfer functions and result in erroneous interpretation. A substantial improvement is possible when the time-series are presented as clean as possible for further processing. Cleaning of MT time-series is often done by manual editing. Editing of magnetotelluric time-series is subjective in nature and time consuming. Automation of such a process is difficult to achieve by statistical methods. Artificial neural networks (ANNs) are widely used to automate processes that require human intelligence. The objective here is to automate MT long-period time-series editing using ANN. A three-layer feed-forward artificial neural network (FANN) was adopted for the problem. As ANN-based techniques are computationally intensive, a novel approach was made, which involves editing of five simultaneously measured MT time-series that have been subdivided into stacks (a stack=5 × 256 data points). Neural network training was done at two levels. Signal and noise patterns of individual channels were taught first. Five channel parameters along with interchannel correlation and amplitude ratios formed the input for a final network, which predicts the quality of a stack. A large database (5000 traces for pattern training and 900 vectors for interchannel training) was prepared to train the network. There were two error parameters to minimize while training: training error and testing error. Training was stopped when both errors were below an acceptable level. The sensitivity of the neural network to the signal-to-noise ratio and the relative significance of its inputs were tested to ensure that the training was correct. MT time-series from four stations with varying degrees of noise contamination were used to demonstrate the application of the network. The application brought out

  17. Magnetotelluric Data, Rainier Mesa/Shoshone Mountain, Nevada Test Site, Nevada.

    SciTech Connect

    Jackie M. Williams; Jay A. Sampson; Brian D. Rodriguez; and Theodore H. Asch.

    2006-11-03

    The United States Department of Energy (DOE) and the National Nuclear Security Administration (NNSA) at their Nevada Site Office (NSO) are addressing ground-water contamination resulting from historical underground nuclear testing through the Environmental Management (EM) program and, in particular, the Underground Test Area (UGTA) project. From 1951 to 1992, 828 underground nuclear tests were conducted at the Nevada Test Site northwest of Las Vegas. Most of these tests were conducted hundreds of feet above the ground-water table; however, more than 200 of the tests were near or within the water table. This underground testing was limited to specific areas of the Nevada Test Site, including Pahute Mesa, Rainier Mesa/Shoshone Mountain, Frenchman Flat, and Yucca Flat. One issue of concern is the nature of the somewhat poorly constrained pre-Tertiary geology, and its effects on ground-water flow. Ground-water modelers would like to know more about the hydrostratigraphy and geologic structure to support a hydrostratigraphic framework model that is under development for the Rainier Mesa/Shoshone Mountain Corrective Action Unit (Bechtel Nevada, 2006). During 2005, the U.S. Geological Survey (USGS), in cooperation with the DOE and NNSA-NSO, collected and processed data from twenty-six magnetotelluric (MT) and audio-magnetotelluric (AMT) sites at the Nevada Test Site. The 2005 data stations were located on and near Rainier Mesa and Shoshone Mountain to assist in characterizing the pre-Tertiary geology in those areas. These new stations extend the area of the hydrogeologic study previously conducted in Yucca Flat. This work will help refine what is known about the character, thickness, and lateral extent of pre-Tertiary confining units. In particular, a major goal has been to define the upper clastic confining unit (UCCU – late Devonian to Mississippian-age siliciclastic rocks assigned to the Eleana Formation and Chainman Shale) from the Yucca Flat area and west towards

  18. Characterization of the Pyrenean lithosphere using new long period magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Campanyà, Joan; Ledo, Juanjo; Queralt, Pilar; Marcuello, Alex; Muñoz, Josep Anton; Liesa, Montserrat

    2010-05-01

    New magnetotelluric (MT) data has been acquired along a N-S profile of 180 km length that cross the Pyrenean range. The new MT data are complemented with old MT data registered at the same profile 15 years ago. In this work we have 15 old MT data with periods ranging from 0.0128 s to 2000 s and 8 new MT data with periods ranging from 0.001 s to 20000 s. The new data allows us to arrive deeper and determine the lithosphere resistivity structure with more precision up to 150 km depth. Moreover, the final geoelectric model has been obtained using 2D inversion procedures. The previous model was obtained by direct modelling, following a trial and error approach. Analyses of the MT data using the Groom and Bailey decomposition method, as well as the use of the tensor invariants corroborate the validity of assuming regional 2D structures. The strike direction of the electrical structures is E-W, parallel to the Pyrenean range. The final model obtained shows a deep large structure with low electrical resistivity values between Iberian and European plates that can be associated to the subduction of the Iberian plate. We suggest, that the cause of this low resistivity values is the existence of partial melting of the Iberian lower crust below the European one. Sensitivity tests prove that resistivity in this structure is not homogeneous. A vertical gradient is observed between the top and the bottom of the structure, having the top low electrical resistivity values, around 3 Ohm•m, than the bottom that present values between 10 Ohm•m and 56 Ohm•m. At the base of the model appears another low resistivity zone associated with the asthenosphere. The lithosphere asthenosphere boundary depth is different for the two plates studied. The sensitivity tests show that the depth for Iberian plate is 80 ± 20 km and 120 ± 15 km for the European plate. The different depths of these limits show that European plate is thicker. The geoelectric model is compared with several

  19. Joint Audio-Magnetotelluric and Passive Seismic Imaging of the Cerdanya Basin

    NASA Astrophysics Data System (ADS)

    Gabàs, A.; Macau, A.; Benjumea, B.; Queralt, P.; Ledo, J.; Figueras, S.; Marcuello, A.

    2016-06-01

    The structure of Cerdanya Basin (north-east of Iberian Peninsula) is partly known from geological cross sections, geological maps and vintage geophysical data. However, these data do not have the necessary resolution to characterize some parts of Cerdanya Basin such as the thickness of soft soil, geometry of bedrock or geometry of geological units and associated faults. For all these reasons, the main objective of this work is to improve this deficiency carrying out a detailed study in this Neogene basin applying jointly the combination of passive seismic methods (H/V spectral ratio and seismic array) and electromagnetic methods (audio-magnetotelluric and magnetotelluric method). The passive seismic techniques provide valuable information of geometry of basement along the profile. The maximum depth is located near Alp village with a bedrock depth of 500 m. The bedrock is located in surface at both sites of profile. The Neogene sediments present a shear-wave velocity between 400 and 1000 m/s, and the bedrock basement presents a shear-wave velocity values between 1700 and 2200 m/s. These results are used as a priori information to create a 2D resistivity initial model which constraints the inversion process of electromagnetic data. We have obtained a 2D resistivity model which is characterized by (1) a heterogeneous conductivity zone (<40 Ohm m) that corresponds to shallow part of the model up to 500 m depth in the centre of the profile. These values have been associated with Quaternary and Neogene sediments formed by silts, clays, conglomerates, sandstones and gravels, and (2) a deeper resistive zone (1000-3000 Ohm m) interpreted as Palaeozoic basement (sandstones, limestones and slates at NW and conglomerates and microconglomerates at SE). The resistive zone is truncated by a discontinuity at the south-east of the profile which is interpreted as the Alp-La Tet Fault. This discontinuity is represented by a more conductive zone (600 Ohm m approx.) and is explained as

  20. Black African Traditional Mathematics

    ERIC Educational Resources Information Center

    Zaslavsky, Claudia

    1970-01-01

    Discusses the traditional number systems and the origin of the number names used by several African peoples living south of the Sahara. Also included are limitations in African mathematical development, and possible topics for research. (RP)

  1. The African Connection

    ERIC Educational Resources Information Center

    Oguntoyinbo, Lekan

    2012-01-01

    From student and faculty exchanges to joint research projects, U.S. universities maintain a broad spectrum of collaborative relationships with African universities. It's unclear how many U.S. colleges and universities have partnerships with African universities. The African Studies Association, an organization of scholars, doesn't keep that kind…

  2. Bioenergy and African transformation.

    PubMed

    Lynd, Lee R; Sow, Mariam; Chimphango, Annie Fa; Cortez, Luis Ab; Brito Cruz, Carlos H; Elmissiry, Mosad; Laser, Mark; Mayaki, Ibrahim A; Moraes, Marcia Afd; Nogueira, Luiz Ah; Wolfaardt, Gideon M; Woods, Jeremy; van Zyl, Willem H

    2015-01-01

    Among the world's continents, Africa has the highest incidence of food insecurity and poverty and the highest rates of population growth. Yet Africa also has the most arable land, the lowest crop yields, and by far the most plentiful land resources relative to energy demand. It is thus of interest to examine the potential of expanded modern bioenergy production in Africa. Here we consider bioenergy as an enabler for development, and provide an overview of modern bioenergy technologies with a comment on application in an Africa context. Experience with bioenergy in Africa offers evidence of social benefits and also some important lessons. In Brazil, social development, agricultural development and food security, and bioenergy development have been synergistic rather than antagonistic. Realizing similar success in African countries will require clear vision, good governance, and adaptation of technologies, knowledge, and business models to myriad local circumstances. Strategies for integrated production of food crops, livestock, and bioenergy are potentially attractive and offer an alternative to an agricultural model featuring specialized land use. If done thoughtfully, there is considerable evidence that food security and economic development in Africa can be addressed more effectively with modern bioenergy than without it. Modern bioenergy can be an agent of African transformation, with potential social benefits accruing to multiple sectors and extending well beyond energy supply per se. Potential negative impacts also cut across sectors. Thus, institutionally inclusive multi-sector legislative structures will be more effective at maximizing the social benefits of bioenergy compared to institutionally exclusive, single-sector structures. PMID:25709714

  3. Counseling Groups for African American Women: A Focus on Spirituality.

    ERIC Educational Resources Information Center

    Williams, Carmen Braun; Frame, Marsha Wiggins; Green, Evelyn

    1999-01-01

    Explains cultural and spiritual traditions within African American women's experience that form the foundation for group counseling strategies. Reviews literature regarding African American women's experience in groups. Explains group interventions such as art, music, dance, imagery, journaling, and rituals that can help transcend, empower, and…

  4. Parental Attachments and Psychological Distress among African American College Students

    ERIC Educational Resources Information Center

    Love, Keisha McGhee

    2008-01-01

    African American college students attending predominately White institutions often encounter stressors that their Caucasian peers do not experience. Because of these unique stressors, African American students are more prone to experience psychological distress. Identifying factors that counteract psychological distress among these students is…

  5. “I just start crying for no reason”: The experience of stress and depression in pregnant urban African American adolescents and their perception of yoga as a management strategy

    PubMed Central

    Kinser, Patricia; Masho, Saba

    2015-01-01

    Purpose Perinatal health disparities are of particular concern with pregnant urban African American adolescents who have high rates of stress and depression during pregnancy, higher rates of adverse pregnancy and neonatal outcomes, and many barriers to effective treatment. The purpose of this study was to explore pregnant urban African American teenagers’ experience of stress and depression and examine their perceptions of adjunctive non-pharmacologic management strategies, such as yoga. Methods This community-based qualitative study utilized non-therapeutic focus groups to allow for exploration of attitudes, concerns, beliefs and values regarding stress and depression in pregnancy and non-pharmacologic management approaches, such as mind-body therapies and other prenatal activities. Findings The sample consisted of pregnant African-American low-income adolescents (n=17) who resided in a large urban area in the United States. The themes that arose in the focus group discussions were: (1) stress and depression symptoms are pervasive in daily life; (2) participants felt a generalized sense of isolation; (3) stress/depression-management techniques should be group-based, interactive, and focused on the specific needs of teenagers; (4) yoga is an appealing stress-management technique to this population. Conclusions The findings from this study suggest that pregnant urban adolescents are highly stressed, they interpret depression-like symptoms to be signs of stress, they desire group-based, interactive activities, and they are interested in yoga classes for stress/depression management and relationship-building. It is imperative that healthcare providers and researchers focus on these needs, particularly when designing prevention and intervention strategies. PMID:25648492

  6. Spatial and temporal characterization of CO2 storage sites using magnetotellurics

    NASA Astrophysics Data System (ADS)

    Ledo, J.; Queralt, P.; Marcuello, A.; Roca, E.; Rubinat, M.

    2009-04-01

    Integration of different geophysical, geological and geochemical methods will play a key role for the spatial and temporal characterization of underground CO2 storage sites. Among the geophysical techniques the magnetotelluric method (MT) may help on both, site characterization and monitoring of the CO2 plume, mainly on deep saline reservoirs. In this work we present the characterization of a salt diapir in southern Spain using MT data. This diaper does not satisfy the conditions to be a future reservoir due to the absence of a good lithological seal, but can be use as a natural analog to determine the validity of different geophysical methods. In total 34 MT sites were acquired along a 15 km profile. Once the data has been analyzed, inverted and integrated with surface geological data a simulated investigation for monitoring the CO2 has been carried out. In this simulation the CO2 has been located at the base of the Jurassic to Turonnian carbonates and marls increasing the resistivity of the model. Several tests varying the resistivity and the amount of the CO2 as well as the number of MT sites used will be show.

  7. Geodynamic implications for the formation of the Betic-Rif orogen from magnetotelluric studies

    NASA Astrophysics Data System (ADS)

    Martí, A.; Queralt, P.; Roca, E.; Ledo, J.; Galindo-ZaldíVar, J.

    2009-01-01

    Magnetotelluric data from the central Betics mountains (Spain) have been used to determine the electrical resistivity of the crust after a three-dimensional (3D) interpretive approach. At shallow levels (<2 km), the resulting model shows good correlation between the geoelectric structures and the geologic units. At greater depths (>3 km), the most striking and well-resolved feature of the model is an upper-middle crust conductive body, located at the core of the Internal Betics antiform. This approximately 14-km-thick body is interpreted as basic or ultrabasic rocks containing a conducting mineral phase. Its structural location above the sole thrust of the Betic orogen and beneath the Nevado-Filábride complex confirms the presence of a major suture zone between this complex and the autochthonous Iberian plate. This suture may correspond to an ancient oceanic or transitional domain developed between Iberia and the Alboran Domain during the opening of the Tethys Ocean, partially subducted and closed during the development of the Betic orogen. The possible geodynamic scenarios for the Betics have been reconsidered, taking into account this new constraint.

  8. Evidence of a North-trending lithospheric detachment beneath the Betic Cordillera revealed by magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Rosell, O.; Marti, A.; Marcuello, A.; Ledo, J.; Queralt, P.; Roca, E.; Campanya, J.

    2010-12-01

    Several and contradictory geodynamic models have been proposed to explain the opening of the Alboran Sea during the Oligocene - Miocene based on different geological and geophysical data, which do not allow to unequivocally distinguish between them. Using broad band and long period magnetotelluric data, we constructed a 3D model of the lithospheric electrical resistivity distribution beneath the Betic Cordillera. The model depicts the lithosphere - asthenosphere boundary, located deeper under the Iberian plate and the Betic Cordillera (160 km) than under the Alboran Basin (110 km). However, the main feature of the model is a N-S oriented conductive body in the lithospheric mantle located East of the 4W meridian. This conductive body coincides with a low velocity anomaly in an area without earthquake hypocenter locations. We interpret this N-S conductive body as asthenospheric material that has been intruded due to a lithospheric tearing process and the breaking-off of the East directed subducting slab. These new constraints, added to the available geodynamic models proposed, allow us to reconstruct a plausible geometry of the subduction and slab break-off of the Ligurian oceanic lithosphere under the Alboran Domain.

  9. Two and three dimensional inversion of magnetotelluric data: Annual report No. 2

    SciTech Connect

    Booker, J.R.

    1988-02-01

    We have developed an efficient iterative inversion method applicable to both 2 and 3-D magnetotelluric data. The method approximates horizontal derivative terms with their values calculated from the fields of the previous iteration. The equations at each horizontal coordinate then become uncoupled and 1-D with an added term containing the effects of the horizontal derivatives. At each iteration this allows separate 1-D inversions for the conductivity profile beneath each measurement site. Resultant profiles are interpolated to form a new multi-dimensional model for which the fields are calculated. Residuals to this new model are used in the next iteration. The method is very fast, as partial derivatives are calculated for 1-D problems only and computation time grows only linearly with the number of sites of data inverted. Preliminary tests with 2-D data show very promising results. Some practial problems remain in application of the algorithm to real 2-D data. We are requesting continued support to resolve these questions and to extend the method to 3-D.

  10. Midcontinent Rift and Remnants of Initiating Mantle Plume Imaged With Magnetotellurics

    NASA Astrophysics Data System (ADS)

    Bowles-martinez, E.; Schultz, A.

    2015-12-01

    Geologic evidence has long suggested that the Midcontinent Rift (MCR) was initiated by a mantle plume 1.1 Ga in the western Lake Superior region. EarthScope magnetotelluric data has been inverted to create a 3D resistivity model that shows remnants of the plume to depths of at least 150 km. The mantle plume remnants are imaged as a body of highly conductive material in the lithosphere. It is focused below western Lake Superior and northwestern Wisconsin, and elongated in a NW-SE direction, consistent with plate motion vectors. Recent seismic velocity models from EarthScope data also show an anomaly at this location. The presence of a plume after so much time has passed invites many questions regarding the long-term stability of conductive materials, the thickness of the lithosphere, and the stability of sub-craton mantle over long time periods. The resistivity model also shows features defining the length of the MCR as well as the Grenville orogeny. New data being collected this summer is incorporated into the model, extending it southeast across Grenville.

  11. Focused time-lapse inversion of radio and audio magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Rosas Carbajal, Marina; Linde, Niklas; Kalscheuer, Thomas

    2012-09-01

    Geoelectrical techniques are widely used to monitor groundwater processes, while surprisingly few studies have considered audio (AMT) and radio (RMT) magnetotellurics for such purposes. In this numerical investigation, we analyze to what extent inversion results based on AMT and RMT monitoring data can be improved by (1) time-lapse difference inversion; (2) incorporation of statistical information about the expected model update (i.e., the model regularization is based on a geostatistical model); (3) using alternative model norms to quantify temporal changes (i.e., approximations of l1 and Cauchy norms using iteratively reweighted least-squares), (4) constraining model updates to predefined ranges (i.e., using Lagrange Multipliers to only allow either increases or decreases of electrical resistivity with respect to background conditions). To do so, we consider a simple illustrative model and a more realistic test case related to seawater intrusion. The results are encouraging and show significant improvements when using time-lapse difference inversion with non l2 model norms. Artifacts that may arise when imposing compactness of regions with temporal changes can be suppressed through inequality constraints to yield models without oscillations outside the true region of temporal changes. Based on these results, we recommend approximate l1-norm solutions as they can resolve both sharp and smooth interfaces within the same model.

  12. Distribution of melt beneath Mount St Helens and Mount Adams inferred from magnetotelluric data

    USGS Publications Warehouse

    Hill, G.J.; Caldwell, T.G.; Heise, W.; Chertkoff, D.G.; Bibby, H.M.; Burgess, M.K.; Cull, J.P.; Cas, Ray A.F.

    2009-01-01

    Three prominent volcanoes that form part of the Cascade mountain range in Washington State (USA)Mounts StHelens, Adams and Rainierare located on the margins of a mid-crustal zone of high electrical conductivity1,5. Interconnected melt can increase the bulk conductivity of the region containing the melt6,7, which leads us to propose that the anomalous conductivity in this region is due to partial melt associated with the volcanism. Here we test this hypothesis by using magnetotelluric data recorded at a network of 85 locations in the area of the high-conductivity anomaly. Our data reveal that a localized zone of high conductivity beneath thisvolcano extends downwards to join the mid-crustal conductor. As our measurements were made during the recent period of lava extrusion at Mount St Helens, we infer that the conductivity anomaly associated with the localized zone, and by extension with the mid-crustal conductor, is caused by the presence of partial melt. Our interpretation is consistent with the crustal origin of silicic magmas erupting from Mount St Helens8, and explains the distribution of seismicity observed at the time of the catastrophic eruption in 1980 (refs9, 10). ?? 2009 Macmillan Publishers Limited. All rights reserved.

  13. Regularized inversion of controlled source audio-frequency magnetotelluric data in horizontally layered transversely isotropic media

    NASA Astrophysics Data System (ADS)

    Zhou, Jianmei; Wang, Jianxun; Shang, Qinglong; Wang, Hongnian; Yin, Changchun

    2014-04-01

    We present an algorithm for inverting controlled source audio-frequency magnetotelluric (CSAMT) data in horizontally layered transversely isotropic (TI) media. The popular inversion method parameterizes the media into a large number of layers which have fixed thickness and only reconstruct the conductivities (e.g. Occam's inversion), which does not enable the recovery of the sharp interfaces between layers. In this paper, we simultaneously reconstruct all the model parameters, including both the horizontal and vertical conductivities and layer depths. Applying the perturbation principle and the dyadic Green's function in TI media, we derive the analytic expression of Fréchet derivatives of CSAMT responses with respect to all the model parameters in the form of Sommerfeld integrals. A regularized iterative inversion method is established to simultaneously reconstruct all the model parameters. Numerical results show that the inverse algorithm, including the depths of the layer interfaces, can significantly improve the inverse results. It can not only reconstruct the sharp interfaces between layers, but also can obtain conductivities close to the true value.

  14. Testing Magnetotelluric Constraints on the Physical State of the Yellowstone Plume

    NASA Astrophysics Data System (ADS)

    Murphy, B. S.; Egbert, G. D.; Humphreys, E.

    2015-12-01

    Recent inversions of long-period magnetotelluric (MT) datasets (Kelbert et al., 2012; Meqbel et al., 2014) have suggested that the mantle lithosphere directly beneath the modern Yellowstone caldera is electrically resistive. This observation implies that the uppermost mantle does not contain significant quantities of melt and therefore seems to contradict seismic tomography studies that find a major low-velocity plume-like feature directly beneath Yellowstone. Our ongoing investigation of the long-period Earthscope MT data suggests that these data are relatively insensitive to the conductivity structure in the upper mantle due to screening of deeper features by the modern electrically conductive magma chamber(s). Hence, at present we cannot conclude that the uppermost mantle directly beneath Yellowstone is electrically resistive. However, we do resolve a major electrically conductive anomaly that dips generally to the west at approximately 30 degrees from the vicinity of the seismically imaged magma reservoir(s) beneath the Yellowstone. The MT data therefore may indicate that the flow of melt is at least partially influenced by structures to the west of the modern caldera, specifically ancient (Paleoproterozoic) structures at the edge of the Wyoming Craton. While the geochemistry of Yellowstone eruptive products remains ambiguous with regards to source, radiogenic isotope model ages could be interpreted as supporting this possibility.

  15. Subduction of the Rivera Plate Beneath the Jalisco Block as Imaged by Magnetotelluric Data

    NASA Astrophysics Data System (ADS)

    Alvarez, R.; Corbo, F.; Arzate, J.

    2013-05-01

    Two magnetotelluric profiles perpendicular to the trench provide information on the subduction of the Rivera plate under the Jalisco Block (JB). The geometry of the subducting slab is inferred by the anomalous conductor on the top of the profile in the central part of the JB. High-conductivity zones (< 50 ohm-m) at depths shallower than 10 km are associated to dewatering of the oceanic crust below the accretion prism in the SW portion of the profile. Away from the coast, observed upper crustal conductors (< 10 km) are interpreted as partial melt related to the Central Jalisco Volcanic Lineament. The source of the crustal conductor in the central part of the MT profile, ~150 km inland and down to depths of 40 km is interpreted as a region of interconnected fluids associated with the metamorphic dehydration of the oceanic plate. Contrasting resistivity at the mantle wedge at depths below 40 km suggest to us that hot mantle material may be migrating upwards, mixing with dehydration reaction products. Across Bahia de Banderas fault (BBF) zone subduction appears to stop or to occur closer to the trench at a steeper angle. The conductivity image at the NW edge of JB reveals no downwards dipping plate but an extended conductor apparently rising from depths > 40 km. Our results supports the mantle upwelling theory as an explanation to the reported 1.5 km uplift of the central part of the Jalisco Block, and the Rivera plate discontinuity across the BBF zone as suggested by seismicity data.

  16. Three-dimensional inversion of magnetotelluric impedance tensor data and full distortion matrix

    NASA Astrophysics Data System (ADS)

    Avdeeva, A.; Moorkamp, M.; Avdeev, D.; Jegen, M.; Miensopust, M.

    2015-07-01

    Galvanic distortion of magnetotelluric (MT) data due to small-scale surficial bodies or due to topography is one of the major factors that prevents accurate imaging of the subsurface. We present a 3-D algorithm for joint inversion of MT impedance tensor data and a frequency-independent full distortion matrix that circumvents this problem. We perform several tests of our algorithm on synthetic data affected by different amounts of distortion. These tests show that joint inversion leads to a better conductivity model compared to the inversion of the MT impedance tensor without any correction for distortion effects. For highly distorted data, inversion without any distortion correction results in strong artefacts and we cannot fit the data to the specified noise level. When the distortion is reduced, we can fit the data to an RMS of one, but still observe artefacts in the shallow part of the model. In contrast, in both cases our joint inversion can fit the data within the assumed noise level and the resulting models are comparable to the inversion of undistorted data. In addition, we show that the elements of the full distortion matrix can be well resolved by our algorithm. Finally, when inverting undistorted data, including the distortion matrix in the inversion only results in a minor loss of resolution. We therefore consider our new approach a promising tool for the general analysis of field MT data.

  17. Advances in applications of magnetotellurics to hydrocarbon exploration in Papua New Guinea

    SciTech Connect

    Christopherson, K.R.

    1995-06-01

    More than 800 Magnetotelluric (MT) stations and EMAP dipoles have been acquired in Papua New Guinea (PNG) since 1988. The use and understanding of this non-seismic method has developed because the lucrative petroleum province of the Highlands Fold Belt. Exploration in this area precludes conventional seismic acquisition owing to outcropping limestone which is karstified and more than 3000 feet (1 km) thick in most areas. MT acquisition has expanded from acquiring single-site or dual-site data using standard wire-link communication to acquiring five stations simultaneously, with communications via radio telemetry. This has resulted in higher production rates, better quality data, and more flexible emplacement of station locations. Design modifications to acquisition equipment has resulted in lighter gear which acquires data with higher signal-to-noise ratio, leading to more reliable interpretations. Advances in computer modeling, primarily through Geotools software, along with better understanding of the structural province and integration with geologists` information, have improved the usability of the interpreted data. The last seven years have seen several wells drilled of which many are now in production. MT has been acquired at many of these locations, and continues to be a advanced exploration tool. Case histories will demonstrate the effectiveness of exploration using MT and other electrical methods.

  18. Magnetotelluric imaging of upper crustal partial melt at Tendaho graben in Afar, Ethiopia

    NASA Astrophysics Data System (ADS)

    Didana, Yohannes Lemma; Thiel, Stephan; Heinson, Graham

    2014-05-01

    We report on a recent magnetotelluric (MT) survey across the Manda Hararo magmatic segment (MHMS) within the Tendaho graben in the Afar Depression in northeastern Ethiopia. Twenty-two broadband MT sites with ˜1 km station spacing were deployed along a profile with the recorded data covering a period range from 0.003 s to 1000 s. A two-dimensional (2-D) resistivity model reveals an upper crustal fracture zone (fault) and partial melt with resistivity of 1-10Ωm at a depth of >1 km. The partial melt has a maximum horizontal width of 15 km and extends to a depth of 15 km within the Afar Stratoid Series basalts. We estimate a melt fraction of about 13% based on geochemical and borehole data, and bulk resistivity from the 2-D MT inversion model. The interpreted upper crustal partial melt may have been formed by either a magma intrusion from mantle sources or a large volume of continental crust that has been fluxed by a small amount of mantle melt and heat. Within the MHMS and Tendaho graben, a magma intrusion is a plausible explanation for the upper crustal conductor. The inferred presence of a conductive fracture zone or fault with hydrothermal fluid and shallow heat sourcing magma reservoir also makes the Tendaho graben a promising prospect for the development of conventional hydrothermal geothermal energy.

  19. Preliminary magnetotelluric results across Dalma Volcanics, Eastern India: Inferences on metallogeny

    NASA Astrophysics Data System (ADS)

    Maurya, Ved P.; Shalivahan; Bhattacharya, B. B.; Adhikari, P. K.; Das, L. K.

    2015-04-01

    The regional magnetotelluric (MT) survey across Dalma Volcanics (DVs) in North Singhbhum Mobile Belt (NSMB) was carried out to obtain the conductivity model and to understand the metallogeny. The structure in general is 2-D and the average strike is N60°W. 2-D inversions using TE + TM and TE + TM + Tzy were carried out. Both inversions derived models with similar features but with modified shape. The TE + TM + Tzy inversion brings up two conducting zones enveloping three anomalous conducting bodies. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis of the samples collected from 8 to 10 m pit from different stratigraphic units of Dalma volcano-sedimentary belt indicates the presence of gold, silver, uranium and copper. The study area is a felsic dominated rifted margin and shows high conductivity contrast along with high gravity, magnetic and significant radiometric anomaly. Thus, the conducting zones indicate the presence of volcanogenic massive sulfide (VMS) or volcano hosted gold deposit (Au-VMS) in NSMB.

  20. Lithology-derived structure classification from the joint interpretation of magnetotelluric and seismic models

    USGS Publications Warehouse

    Bedrosian, P.A.; Maercklin, N.; Weckmann, U.; Bartov, Y.; Ryberg, T.; Ritter, O.

    2007-01-01

    Magnetotelluric and seismic methods provide complementary information about the resistivity and velocity structure of the subsurface on similar scales and resolutions. No global relation, however, exists between these parameters, and correlations are often valid for only a limited target area. Independently derived inverse models from these methods can be combined using a classification approach to map geologic structure. The method employed is based solely on the statistical correlation of physical properties in a joint parameter space and is independent of theoretical or empirical relations linking electrical and seismic parameters. Regions of high correlation (classes) between resistivity and velocity can in turn be mapped back and re-examined in depth section. The spatial distribution of these classes, and the boundaries between them, provide structural information not evident in the individual models. This method is applied to a 10 km long profile crossing the Dead Sea Transform in Jordan. Several prominent classes are identified with specific lithologies in accordance with local geology. An abrupt change in lithology across the fault, together with vertical uplift of the basement suggest the fault is sub-vertical within the upper crust. ?? 2007 The Authors Journal compilation ?? 2007 RAS.