Science.gov

Sample records for african magnetotelluric experiment

  1. 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

  2. 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

  3. Practical Magnetotellurics

    NASA Astrophysics Data System (ADS)

    Simpson, Fiona; Bahr, Karsten

    2005-02-01

    The magnetotelluric (MT) method, a technique for probing the electrical conductivity structure of the Earth, is increasingly used both in applied geophysics and in basic research. This is the first book on the subject to go into detail on practical aspects of applying the MT technique. Beginning with the basic principles of electromagnetic induction in the Earth, this introduction to magnetotellurics aims to guide students and researchers in geophysics and other areas of earth science through the practical aspects of the MT method: from planning a field campaign, through data processing and modelling, to tectonic and geodynamic interpretation. The book will be of use to graduate-level students and researchers who are embarking on a research project involving MT; to lecturers preparing courses on MT; and to geoscientists involved in multi-disciplinary research projects who wish to incorporate MT results in their interpretations.

  4. 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.

  5. 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,…

  6. 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.

  7. 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.

  8. Magnetotelluric studies in East Africa

    NASA Astrophysics Data System (ADS)

    Whaler, K. A.

    2012-12-01

    Since its introduction just over half a century ago, the magnetotelluric method has been used in a wide range of environments, both onshore and submarine, at a large number of length scales, and to tackle a huge variety of problems in the earth sciences, both applied and curiosity-driven. Electromagnetic fields are induced in the sub-surface by passive magnetic field sources originating from lightning strikes trapped in the ionospheric waveguide and from the solar wind interacting with the magnetosphere, which enables information on the sub-surface resistivity distribution to be derived. Measuring the tiny induced signals depends on the careful deployment of very sensitive equipment. These time series are then subject to careful selection and processing techniques in the frequency domain to make robust estimates of the tensor quantity embodying the resistivity information as a function of depth. Further processing and assessment of the data allows the practitioner to assess the minimum dimension of the underlying resistivity distribution consistent with the data. As if this wasn't enough, the inverse problem is extremely non-linear, even in the simplest case of resistivity purely a function of depth. Most modelling and interpretation thus proceeds by a combination of forward modelling and regularised inversion, with tests to assess the resolving depth of the data, and their sensitivity to certain features of the model, for example. After introducing the method, I will illustrate it with examples of experiments carried out in East Africa with which I've been involved, concentrating on two substantial inter-disciplinary studies in Ethiopia, one of the northern Main Ethiopian rift, and the other an on-going project studying magmatic and tectonic processes associated with a current rifting episode in Afar. The main target for magnetotellurics in these projects has been imaging partial melt and magma in the sub-surface. I will aim to show how the interpretation of the

  9. 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.

  10. Magnetotelluric measurements in Antarctica

    NASA Astrophysics Data System (ADS)

    Trivedi, N. B.; Padilha, A. L.; Barbosa, M. J. F.

    1986-11-01

    In the period of 2/14/86 to 3/7/86, during the 4th Brazilian Scientific Expedition to Antarctica, organized through the CIRM (Comissao Interministerial para Recursos do Mar), Station Commander Ferraz, (62 deg 5 min S, 58 deg 23.5 min W), magnetotelluric measurements were accomplished in 120 second intervals for DC. This measurement complemented the former, accomplished in the preceeding year between 20 and 400 seconds and although it presented excellent agreement in the overlapping intervals, it was a difficult interpretation. A Hilbert transformation technique was utilized for solving this problem, which brought to mind similar obtained resistivity values. The preliminary results encountered were presented and discussed.

  11. Young Urban African American Adolescents' Experience of Discretionary Time Activities

    ERIC Educational Resources Information Center

    Bohnert, Amy M.; Richards, Maryse H.; Kolmodin, Karen E.; Lakin, Brittany L.

    2008-01-01

    This cross-sectional study examined the daily discretionary time experiences of 246 (107 boys, 139 girls) fifth through eighth grade urban African American adolescents using the Experience Sampling Method. Relations between the types of activities (i.e., active structured, active unstructured, passive unstructured) engaged in during discretionary…

  12. 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…

  13. 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

  14. African-American Women's Perceptions and Experiences About Breastfeeding.

    PubMed

    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

  15. Probability distributions for magnetotellurics

    SciTech Connect

    Stodt, John A.

    1982-11-01

    Estimates of the magnetotelluric transfer functions can be viewed as ratios of two complex random variables. It is assumed that the numerator and denominator are governed approximately by a joint complex normal distribution. Under this assumption, probability distributions are obtained for the magnitude, squared magnitude, logarithm of the squared magnitude, and the phase of the estimates. Normal approximations to the distributions are obtained by calculating mean values and variances from error propagation, and the distributions are plotted with their normal approximations for different percentage errors in the numerator and denominator of the estimates, ranging from 10% to 75%. The distribution of the phase is approximated well by a normal distribution for the range of errors considered, while the distribution of the logarithm of the squared magnitude is approximated by a normal distribution for a much larger range of errors than is the distribution of the squared magnitude. The distribution of the squared magnitude is most sensitive to the presence of noise in the denominator of the estimate, in which case the true distribution deviates significantly from normal behavior as the percentage errors exceed 10%. In contrast, the normal approximation to the distribution of the logarithm of the magnitude is useful for errors as large as 75%.

  16. 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…

  17. 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

  18. The Meaning of African American College Women's Experiences Attending a Predominantly White Institution: A Phenomenological Study

    ERIC Educational Resources Information Center

    Hannon, Christine R.; Woodside, Marianne; Pollard, Brittany L.; Roman, Jorge

    2016-01-01

    Because both race and gender are important to the development of African American women, student affairs professionals need to understand the unique experiences of African American women within the context of the college environment. In this phenomenological study, we examined African American women's lived experiences as college students at a…

  19. 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)".

  20. Experiences of HIV-positive African-American and African Caribbean childbearing women: a qualitative study.

    PubMed

    Njie-Carr, Veronica; Sharps, Phyllis; Campbell, Doris; Callwood, Gloria

    2012-07-01

    This qualitative study examined the experiences of HIV-positive African-American and African Caribbean childbearing women related to decisions about HIV testing, status disclosure, adhering to treatment, decisions about childbearing, and experiences in violent intimate relationships. Twenty-three women completed a 60-minute in-depth interview. Six themes emerged: perceived vulnerability to HIV infection; feelings about getting tested for HIV; knowledge, attitudes, and behaviors after HIV diagnosis; disclosure of HIV status; living with HIV (positivity, strength, and prayer); and, experiences with physical and sexual violence. Three women (13%) reported perinatal abuse and 10 women (n = 23, 43.4%) reported lifetime abuse. Positive experiences and resilience were gained from faith and prayer. Most important to the women were the perceived benefits of protecting the health of their baby. Findings suggest that policies supporting early identification of HIV-positive childbearing women are critical in order to provide counseling and education in forming their decisions for safety precautions in violent intimate partner relationships.

  1. 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.

  2. 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

  3. 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…

  4. 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)

  5. 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

  6. Going to School: The African-American Experience.

    ERIC Educational Resources Information Center

    Lomotey, Kofi, Ed.

    This volume presents the views of a range of African-American educators on questions related to African-American academic achievement. The concern in this volume is with the persistent, pervasive, and disproportionate underachievement of African-American students. The book is divided into four parts. Part 1, "Problem Identification," comprises the…

  7. 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.

  8. 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.

  9. 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…

  10. 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…

  11. 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…

  12. 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,…

  13. 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…

  14. 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.

  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. 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…

  17. 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…

  18. 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…

  19. 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…

  20. 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.

  1. The role of spirituality in the breast cancer experiences of African American women.

    PubMed

    Tate, Johnetta D

    2011-12-01

    Breast cancer is the most commonly diagnosed cancer type among African American women. African American women often use spirituality to overcome the physical, psychological, and emotional burdens that accompany a breast cancer diagnosis. Spirituality has been used over the years by African American women to bring hope when dealing with hardships. This integrative review seeks to explore the importance of spirituality to African American women throughout the breast cancer experience. Thirteen qualitative and quantitative studies that discussed how spirituality was used to cope with breast cancer from initial diagnosis to survivorship were reviewed. Spirituality was found to be the main coping mechanism used during all phases of the cancer experience. To provide holistic nursing care, nurses must understand that spirituality is an important coping strategy used by most African American women with breast cancer. The implications for nursing that were identified include the incorporation of spiritual interventions and the utilization of culturally appropriate assessment tools.

  2. 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…

  3. 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…

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

    NASA Astrophysics Data System (ADS)

    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.

  5. 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

  6. 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,…

  7. 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…

  8. 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…

  9. The Amistad Research Center: Documenting the African American Experience.

    ERIC Educational Resources Information Center

    Chepesiuk, Ron

    1993-01-01

    Describes the Amistad Research Center housed at Tulane University which is a repository of primary documents on African-American history. Topics addressed include the development and growth of the collection; inclusion of the American Missionary Association archives; sources of support; civil rights; and collecting for the future. (LRW)

  10. 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.

  11. 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.

  12. 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…

  13. 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…

  14. 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…

  15. 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

  16. Culturally specific interventions for African American smokers: an efficacy experiment.

    PubMed

    Webb, Monica S

    2009-09-01

    This pilot study sought to dismantle the efficacy of culturally specific print materials for smoking cessation. Two-hundred sixty-one African American smokers were randomized into 1 of 2 conditions: standard booklet or culturally specific booklet. The content and length of the interventions were identical yet varied in their degree of cultural specificity. Three-month follow-up assessments were completed by 70% (N = 183) of participants. Dependent variables included content evaluation, readiness to quit smoking, and actual behavior change. Evidence suggested that the culturally specific material was more effective at capturing attention, providing encouragement and gaining interest compared to standard materials; however, greater credibility was found for standard materials. In addition, greater readiness to quit and more 24-hour quit attempts were found in the standard condition. No differences were found in abstinence rates. In conclusion, culturally specific interventions may be preferred over standard approaches among African American smokers. Culturally specific approaches, however, may not result in greater behavior change. Implications for written interventions and cultural specificity are discussed. PMID:19806851

  17. 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

  18. Caregiver experiences of discrimination and african american adolescents' psychological health over time.

    PubMed

    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 were examined. It was found that caregiver discrimination experiences were positively related to adolescents' symptoms of depression and negatively related to their psychological well-being. Additional analysis revealed interactions between the effects of caregiver discrimination experiences and family income on all 3 outcomes. Greater caregiver discrimination experiences and lower family income were risk factors for the youth in the sample. These findings underscore the deleterious consequence of caregivers' discrimination experiences on African American youth's psychological health.

  19. Capacity development for health research in Africa: experiences managing the African Doctoral Dissertation Research Fellowship Program

    PubMed Central

    2010-01-01

    Africa's progress depends on her capacity to generate, adapt, and use scientific knowledge to meet regional health and development needs. Yet, Africa's higher education institutions that are mandated to foster this capacity lack adequate resources to generate and apply knowledge, raising the need for innovative approaches to enhance research capacity. In this paper, we describe a newly-developed program to support PhD research in health and population sciences at African universities, the African Doctoral Dissertation Research Fellowship (ADDRF) Program. We also share our experiences implementing the program. As health research capacity-strengthening in Africa continues to attract attention and as the need for such programs to be African-led is emphasized, our experiences in developing and implementing the ADDRF offer invaluable lessons to other institutions undertaking similar initiatives. PMID:20587016

  20. 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…

  1. 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…

  2. 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…

  3. 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…

  4. 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:…

  5. 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…

  6. Cooperative Policies and African International Students: Do Policy Spirits Match Experiences?

    ERIC Educational Resources Information Center

    McLellan, Carlton E.

    2009-01-01

    This paper explores the policy implications of experiences of African international students (AIS) studying at post-apartheid South Africa universities. It argues that given the spirit and tone of continental, regional, and domestic policies to which South Africa has committed that at the very least there is an implicit expectation of…

  7. 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…

  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. 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…

  10. 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,…

  11. 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…

  12. 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…

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

    PubMed

    Ramsay, Michèle; de Vries, Jantina; Soodyall, Himla; Norris, Shane A; Sankoh, Osman

    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.

  14. Sub-Saharan African Students and Their Experiences in American Higher Education

    ERIC Educational Resources Information Center

    Osikomaiya, Olujide

    2014-01-01

    The purpose of this research project is to study the experiences of Sub-Saharan African students, who have earned professional degrees from American institutions and are currently living in the United States. Acculturative stressors have been identified by researchers as predictors of loneliness, depression, homesickness, and poor mental health…

  15. 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,…

  16. 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…

  17. The Road Not Taken: Two African-American Girls' Experiences with School Mathematics

    ERIC Educational Resources Information Center

    Lim, Jae Hoon

    2008-01-01

    This article is a cross-case study exploring two young African-American adolescent girls' experiences with school mathematics and the impact of the socio-cultural context upon their motivation and mathematical identity. Based on repeated in-depth interviews and ethnographic observation of their mathematics classroom, the researcher portrays…

  18. 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.…

  19. 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…

  20. 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…

  1. 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…

  2. 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…

  3. 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…

  4. 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…

  5. Noma: experiences with a microvascular approach under West African conditions.

    PubMed

    Giessler, Goetz A; Schmidt, Andreas B

    2003-09-15

    Noma (cancrum oris) is a serious ulcerating disease that generally begins in the gingival sulcus of children. One of the main areas of prevalence today is West Africa. If noma is survived, it results in disfiguring midfacial defects and intense scarring. Oral incompetence is often combined with trismus resulting from scar formation or bony fusion between the maxilla and the mandible. Reconstructive approaches with pedicled flaps from the head or shoulder area for closure of the outer defects have been prone to donor-site complications or have not properly addressed the trismus, leading to high recurrence rates. During three West African Interplast missions, a single-stage procedure was developed for reconstruction of the inner and outer linings of the oral, nasal, and paranasal cavities, with restoration of jaw function. The procedure consists of radical scar excision, placement of an external distractor for mouth opening, and primary closure of the defect with a folded free parascapular flap for full-thickness coverage. Twenty-three patients with various noma-related defects were treated with this procedure; two cases are described in detail. This combined treatment can be a safe successful procedure for patients with noma, especially those with severe soft-tissue destruction and profound trismus, even under demanding surgical conditions.

  6. 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

  7. Coparenting experiences in African American families: an examination of single mothers and their nonmarital coparents.

    PubMed

    Gonzalez, Michelle; Jones, Deborah; Parent, Justin

    2014-03-01

    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 nonmarital coparents who participated in a study of African American single-mother families with an 11-16-year-old child. Specifically, the study examines: (a) the extent to which nonmarital coparents are involved in childrearing; (b) the relative levels of risk (i.e., depression, mother-coparent conflict) and protective (i.e., parenting) associated with maternal and coparent involvement; and (c) 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

  8. Racism experiences and psychological functioning in African American college freshmen: is racial socialization a buffer?

    PubMed

    Bynum, Mia Smith; Burton, E Thomaseo; Best, Candace

    2007-01-01

    Previous research has documented the negative effects of racism on the psychological health of African Americans. However, consideration of racial socialization as a potential buffer against racism experiences has received limited attention. The present study investigated whether two types of parental racial socialization messages reduced the impact of racism on psychological functioning in a sample of 247 African American college freshmen (M=18.30). Results indicated that students who reported more racism experiences also had poorer levels of psychological functioning as indicated by higher levels of psychological stress and psychological distress. Parental messages emphasizing the use of African American cultural resources to cope with racism reduced the impact of racism on psychological stress only. Cultural pride messages predicted less psychological distress while messages emphasizing the use of cultural resources predicted greater psychological distress. However, neither message type moderated the relationship between racism experiences and psychological distress. These results suggest that racial socialization messages have complex relations to psychological functioning in African American college students.

  9. 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

  10. Masculinities fathering and health: the experiences of African-Caribbean and white working class fathers.

    PubMed

    Williams, Robert Alan

    2007-01-01

    There is a developing body of research that investigates the links between masculinities and men's health experiences, but the links between masculinities and the health of fathers has been a neglected focus for research in the UK. This paper presents some of the findings drawn from a parent study which investigated African-Caribbean and white working class fathers' experiences of fathering, health and social connectedness. Data are drawn from interviews with 13 men (6 African-Caribbean and 7 White working class) living in a city in the West Midlands area of the UK. In this paper, I analyse and discuss African-Caribbean and white working class fathers' stories about the meaning of health, the influences upon their health, and their health practices. It was found that for the African-Caribbean fathers specifically, anticipated or perceived racist prejudice, abuse or discrimination influenced their health experiences. However, the meaning of health for both ethnic groups of fathers was as functional capacity, that is health was an asset that allowed fathers to meet the obligations of paid work and fathering. These obligations were also associated with a restricted sense of personal agency for the men interviewed, and the associated constraints were linked to transgressive consumption of alcohol, food and tobacco. In addition, fathers were also involved in solitary ways of dealing with their vulnerability, vulnerability that was associated with fathers' health concerns, and other difficult life experiences. Fathers' solitary experiences of vulnerability were also mediated by hegemonic forms of masculinity. Nevertheless, the experience of fathering within the lifecourse influenced men's health experiences: reflexivity and challenges to both transgressive consumption and solitary experiences were linked to fathers' perceived obligations to children. The significance of gender, ethnicity and social class for theory and future research with working class fathers and boys

  11. Freshman-year experiences for African-American students in engineering

    NASA Astrophysics Data System (ADS)

    Chapple, Bernadette Maria

    1998-12-01

    The purpose of this study was to discover (a) why African American students choose to persist as an engineering major and (b) why students choose to leave engineering as a major. A total of 17 students from a large land-grant university participated in this study that was both quantitative and qualitative in design. This research will assist both the College of Engineering and the University in understanding the educational experiences of the matriculating African American pre-engineering student. In an effort to provide reasons and rationale for why African American engineering students choose to stay in this major and why other African American engineering student majors choose to leave, the researcher examined an undergraduate engineering program at a large land-grant institution in the South. The College of Engineering at this institution was able to institute several programs designed to increase the number of African American students choosing engineering as a major. Although initiatives for pre-collegiate students are important in the retention of African American students, it is the retention of those students once accepted into a program of study that the institution focuses on most. It is the intent of this study to offer a better understanding of such a retention initiative. Due to the decline of African American students pursuing majors in science and mathematics in general and in engineering in particular, an important research concern is to offer more insight into the experiences of the freshman engineering student in an attempt to develop fundamental reasons for why students remain in engineering and why some students leave. To assist the College of Engineering and the University in understanding the educational experiences of the matriculating African American pre-engineering student the data were collected from both a quantitative and qualitative approach. Results indicated that (a) students who chose to persist in the engineering program where

  12. 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

  13. Correlates of coping with perceived discriminatory experiences among African American adolescents.

    PubMed

    Scott, Lionel D

    2004-04-01

    This study examined the relation of background and race-related factors to the use of approach and avoidance strategies to cope with perceived discriminatory experiences among a sample of African American adolescents of relative affluence ( n = 71). Results showed that gender, family structure, socioeconomic status (SES), perceived control over discriminatory experiences, discrimination distress, and racism-related socialization were significant correlates of coping with perceived discriminatory experiences. Results concerning gender, perceived control, and stress arousal were consistent with findings from the general adolescent stress and coping literature. Results concerning family structure, SES, and socialization suggest that certain factors may be very important for the positive adjustment of African American adolescents in the face of race-related adversity.

  14. 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.

  15. 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

  16. 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…

  17. 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…

  18. 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…

  19. "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…

  20. Evaluation of West African Monsoon Processes and Feedbacks: Second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II)

    NASA Astrophysics Data System (ADS)

    Xue, Y.; Lau, W. K.; Boone, A. A.; Seidou Sanda, I.; Thiaw, W. M.; Druyan, L.; Team, W.

    2013-12-01

    Despite recent progress in understanding of the West African monsoon (WAM), there are still many unanswered questions regarding to the impact of external forcings: oceans, land, and aerosols, on WAM variability, especially their roles in the Sahel drought. The West African Monsoon Modeling and Evaluation (WAMME) is a project comprised of both general circulation models (GCMs) and regional climate models (RCMs) with the objective to collectively provide best estimation of the relative importance of all those external forcing on WAM on seasonal to multi-decadal time scales. WAMME research activities are closely coordinated with those of AMMA, involving many African institutions. Observational evidence has shown strong decadal climate variabilities in the Sahel from the 1950s to the 2000s, not only in precipitation, but also in SST, vegetation cover, land use and land cover changes (LULCC), and aerosols. In WAMME-2, multi-model intercomparison experiments are designed to test how seasonal and decadal variabilities of WAM precipitation are associated with these forcings, and assess their relative contributions in producing/amplifying the WAM seasonal and decadal climate variability. The sensitivity of the WAM variability to those external forcings is also examined. The WAMME-2 strategy is to apply observational data-based anomaly forcing of SST, land surface and aerosols, i.e., "idealized but realistic" forcing, in GCM and RCM simulations with the specific purpose of estimating the relative impacts of each forcing and feedback mechanisms. In the SST experiment, in addition to the global SST effect, each ocean's role is also evaluated. The preliminary results from most GCMs consistently indicate that SST has a maximum impact on the WAM decadal variability compared with other forcings, and that the effect of the Pacific Ocean is most dominant. The models, however, differ in producing other oceans' contribution. Moreover, the models with specified maximum SST forcing are

  1. Racism and mental health: the African American experience.

    PubMed

    Williams, D R; Williams-Morris, R

    2000-01-01

    This paper provides an overview of United States-based research on the ways in which racism can affect mental health. It describes changes in racial attitudes over time, the persistence of negative racial stereotypes and the ways in which negative beliefs were incorporated into societal policies and institutions. It then reviews the available scientific evidence that suggests that racism can adversely affect mental health status in at least three ways. First, racism in societal institutions can lead to truncated socioeconomic mobility, differential access to desirable resources, and poor living conditions that can adversely affect mental health. Second, experiences of discrimination can induce physiological and psychological reactions that can lead to adverse changes in mental health status. Third, in race-conscious societies, the acceptance of negative cultural stereotypes can lead to unfavorable self-evaluations that have deleterious effects on psychological well-being. Research directions are outlined.

  2. 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

  3. 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…

  4. Magnetotellurics and radio-wave interference sounding

    NASA Astrophysics Data System (ADS)

    Khmelevskoy, V. K.; Petrukhin, B. P.; Pushkarev, P. Yu.

    2010-09-01

    The plane harmonic electromagnetic fields are considered in the theory of magnetotelluric methods in the range of frequencies from 0.0001 Hz to 20 kHz. These fields are natural by their origin and contain information on the depths from tens of meters up to 100 km and more. The magnetotelluric soundings, which use the fields of radio stations, expand the frequency band almost up to 1 MHz and make it possible to study the depths from the first few meters. The method of radio-wave interference sounding supplements geoelectric prospecting on plane waves into the range of even higher frequencies (up to 100 MHz). In this case, the conduction and displacement currents become comparable, which makes it possible to distinguish objects both by their electrical conductivity and by their dielectric permittivity. For the two-layered model of a medium, there exist simple kinematic methods of data interpretation of a radio-interferometry sounding. Within multilayer, and especially horizontally heterogeneous, media, methods for solving equations of electrodynamics and inverse problems of geophysics are required. In the present paper, the foundations of the theory of radio-interferometry sounding, the methodology, its role in geoelectric prospecting, and the opportunities for the solution of geological problems are discussed.

  5. 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).

  6. 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

  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.

  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. 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

  10. The perceived racism scale: a multidimensional assessment of the experience of white racism among African Americans.

    PubMed

    McNeilly, M D; Anderson, N B; Armstead, C A; Clark, R; Corbett, M; Robinson, E L; Pieper, C F; Lepisto, E M

    1996-01-01

    The experience of racism is a complex, multidimensional phenomenon. At present, there are few instruments that attempt to capture the experience of racism in all of its complexity. For this study, a new instrument, the Perceived Racism Scale, has been constructed to assess the experience of racism in African Americans in a multidimensional manner. The scale not only provides a measure of the frequency of exposure to many manifestations of racism (including individual and institutional, overt and covert, attitudinal, behavioral, and cultural), but takes a step forward in more comprehensively measuring the experience of racism by assessing emotional and behavioral coping responses to racism. These responses are measured with respect to exposure to racism in three situational domains: on the job, in academic settings, and in the public realm. Measurement of responses to a fourth domain, that of exposure to racist statements, is also included. It is hoped that the Perceived Racism Scale will facilitate a more comprehensive understanding of the experience of racism among African Americans and, through its use in research and clinical settings, will ultimately move us closer to reducing the prevalence and potentially untoward effects of racism.

  11. 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

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

    PubMed

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

    2011-12-01

    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.

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. Reflections on E. E. Just, Black Apollo of Science, and the experiences of African American scientists.

    PubMed

    Manning, Kenneth R

    2009-10-01

    The text below is a transcript of the keynote address Kenneth Manning gave at the symposium honoring E. E. Just that was held on the campus of Howard University on November 21, 2008. In his talk, Manning reflects on his experiences researching and writing Black Apollo of Science: The Life of Ernest Everett Just, his prize-winning biography published in 1983. In the process, he retells the fascinating story of the life of E. E. Just. Manning also discusses a number of other topics, including Just's legacy, the role of African Americans in science, and the importance of having minority representation on college campuses. PMID:19610070

  18. 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.

  19. 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

  20. 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

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

    PubMed

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

    2003-06-01

    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.

  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.

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. 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.

  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. Constraints From Deep-Imaging Magnetotellurics on the Lithospheric Structure and Evolution of the Enigmatic Okwa Terrane, Botswana

    NASA Astrophysics Data System (ADS)

    Muller, M. R.; Jones, A. G.; Evans, R. L.

    2009-12-01

    The Okwa Terrane, located in central Botswana, is perhaps one of the least understood terranes within the southern African Archean to Palaeoproterozoic tectonic framework. Thick Quaternary Kalahari sand-cover provides minimal crustal exposure with which to define the nature and evolution of the terrane: its potential affiliations and tectonic relationships with adjacent terranes remain speculative and largely unconstrained. The Okwa Terrane, as defined primarily in potential field images, is bounded to the west and north by the Early Proterozoic Rehoboth Terrane, to the south by the Archean Kaapvaal Craton, and to the east, across a poorly defined boundary, by the Palaeoproterozoic Magondi orogenic belt and the Archean Zimbabwe Craton. While the Okwa Terrane is inferred in some interpretations to constitute the northern-most portion of the Kaapvaal Craton, there is no direct evidence to support an Archean lithospheric stabilisation age for the terrane. The oldest recorded crustal ages, for intrusive granites located in the Okwa Inlier, are between 2.1 and 2.0 Ga. Gneissic deformation of the granites is recognised at ~1.8 Ga and, in alternative interpretations, is regarded as the accretion age of the Okwa Terrane with the Kaapvaal Craton along the major east-west trending Palala Shear Zone. A reported diamondiferous kimberlite pipe in the Gope cluster of the Okwa Terrane suggests a lithospheric thickness in excess of the depth of the diamond stability field (~160 km), at least at the time of kimberlite eruption at ~80 Ma. The multinational Southern African Magnetotelluric Experiment (SAMTEX) has acquired, during the period between 2003 and 2008, more than 730 magnetotelluric (MT) sites along 14,000 kilometers of profile length across southern Africa. In acquiring MT data on two orthogonal ~600 km-long profiles across the Okwa Terrane, SAMTEX provides the first deep crustal and lithospheric mantle images of the terrane. MT stations were installed at roughly 20 km

  10. 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…

  11. 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…

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. REGIONAL MAGNETOTELLURIC SURVEYS IN HYDROCARBON EXPLORATION, PARANA BASIN, BRAZIL.

    USGS Publications Warehouse

    Stanley, William D.; Saad, Antonio; Ohofugi, Walter

    1985-01-01

    The mangetotelluric 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 sounding 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. 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. Refs.

  17. 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.

  18. 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.

  19. Magnetotelluric Data, Southern San Luis Valley, Colorado

    USGS Publications Warehouse

    Williams, Jackie M.; Rodriguez, Brian D.

    2007-01-01

    Introduction The population of the San Luis Valley region is growing rapidly. The shallow unconfined and the deeper confined Santa Fe Group aquifer in the San Luis Basin is the main sources of municipal water for the region. Water shortfalls could have serious consequences. Future growth and land management in the region depend on accurate assessment and protection of the region's ground-water resources. An important issue in managing the ground-water 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 ground-water aquifers. The U.S. Geological Survey (USGS) is conducting a series of multidisciplinary studies of the San Luis Basin located in southern Colorado. 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 aquifer systems. The primary goal of the MT survey is to map changes in electrical resistivity with depth that are related to differences in rock type. These various rock types help control the properties of aquifers in the region. This report does not include any interpretation of the data. Its purpose is to release the MT data acquired at the 22 stations shown in figure 1.

  20. Magnetotelluric Data, San Luis Valley, Colorado

    USGS Publications Warehouse

    Rodriguez, Brian D.; Williams, Jackie M.

    2008-01-01

    The San Luis Valley region population 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 ground-water resources. An important issue in managing the ground-water 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 ground-water 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 located in southern Colorado. Detailed geologic mapping, high-resolution airborne magnetic surveys, gravity surveys, an electromagnetic survey (called magnetotellurics, or MT), and hydrologic and lithologic data are being used to better understand the aquifers. The MT survey primary goal is to map changes in electrical resistivity with depth that are related to differences in rock types. These various rock types help control the properties of aquifers. This report does not include any data interpretation. Its purpose is to release the MT data acquired at 24 stations. Two of the stations were collected near Santa Fe, New Mexico, near deep wildcat wells. Well logs from those wells will help tie future interpretations of this data with geologic units from the Santa Fe Group sediments to Precambrian basement.

  1. 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.

  2. Two and three dimensional magnetotelluric inversion

    NASA Astrophysics Data System (ADS)

    Booker, J. R.

    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 multidimensional, 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 multidimensional 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.

  3. 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.

  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.

  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. 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…

  7. 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…

  8. The stage-specific role of spirituality among African American Christian women throughout the breast cancer experience.

    PubMed

    Simon, Cassandra E; Crowther, Martha; Higgerson, Hyoun-Kyoung

    2007-01-01

    This study presents the results of semistructured interviews conducted with 18 African American Christian women regarding the role of spirituality throughout their breast cancer experiences. The spiritual themes relevant for phases of the breast cancer experience are identified. Analysis resulted in the identification of 11 codes and 5 subcodes that corresponded to the diagnosis, treatment, and posttreatment phases of the breast cancer experience. Most of the survivors indicated that their spirituality and faith assisted them throughout the breast cancer experience. Discussion focuses on the spiritual resources used by the participants at the different stages in the breast cancer experience. Attention is given to implications for how professionals can use these resources to assist African American women coping with breast cancer.

  9. Resistance and Assent: How Racial Socialization Shapes Black Students' Experience Learning African American History in High School

    ERIC Educational Resources Information Center

    Thornhill, Theodore E.

    2016-01-01

    African American history is often taught poorly in high school U.S. history courses. However, we know little about how Black students perceive and experience this situation. I use a refined racial socialization framework and interview data with 32 Black college students in the Northeast to investigate how familial racial socialization shapes their…

  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. A decade of experience with renal transplantation in African-Americans.

    PubMed

    Foster, Clarence E; Philosophe, Benjamin; Schweitzer, Eugene J; Colonna, John O; Farney, Alan C; Jarrell, Bruce; Anderson, Leslie; Bartlett, Stephen T

    2002-12-01

    OBJECTIVE To evaluate the strategies instituted by the authors' center to decrease the time to transplantation and increase the rate of transplantation for African-Americans, consisting of a formal education program concerning the benefits of living organ donation that is oriented to minorities; a laparoscopic living donation program; use of hepatitis C-positive donors in documented positive recipients; and encouraging vaccination for hepatitis B, allowing the use of hepatitis B core Ab-positive donors. SUMMARY BACKGROUND DATA The national shortage of suitable kidney donor organs has disproportional and adverse effects on African-Americans for several reasons. Type II diabetes mellitus and hypertension, major etiologic factors for end-stage renal disease, are more prevalent in African-Americans than in the general population. Once kidney failure has developed, African-Americans are disadvantaged for the following reasons: this patient cohort has longer median waiting times on the renal transplant list; African-Americans have higher rates of acute rejection, which affects long-term allograft survival; and once they are transplanted, the long-term graft survival rates are lower in this population than in other groups. METHODS From March 1990 to November 2001 the authors' center performed 2,167 renal transplants; 944 were in African-Americans (663 primary cadaver renal transplants and 253 primary Living donor renal transplants). The retransplants consisted of 83 cadaver transplants and 17 living donor transplants. Outcome measures of this retrospective analysis included median waiting time, graft and patient survival rates, and the rate of living donation in African-Americans and comparable non-African-Americans. Where applicable, data are compared to United Network for Organ Sharing national statistics. Statistical analysis employed appropriate SPSS applications. RESULTS One- and 5-year patient survival rates for living donor kidneys were 97.1% and 91.3% for non-African

  12. Establishing of cancer units in low or middle income african countries: angolan experience - a preliminary report

    PubMed Central

    Miguel, Fernando; Conceição, Ana Vaz; Lopes, Lygia Vieira; Bernardo, Dora; Monteiro, Fernando; Bessa, Fernanda; Santos, Cristina; Oliveira, João Blasques; Santos, Lúcio Lara

    2014-01-01

    Introduction The number of cancer cases and related deaths worldwide is expected to double over the next 20-30 years. African countries will be the most affected by the burden of cancer. The improving economic situation of Angola creates conditions for an increase in life expectancy which by itself is associated with an increased risk of oncological diseases. Because cancer therapy requires a multidisciplinary approach, trained health professionals, satisfactory infrastructure and appropriate facilities, the availability of effective cancer therapy is a difficult task that requires support. The aim of this article is to share our experience achieved in the establishment of cancer units in Angola and to validate our checklist for this action. Methods The survey method was a questionnaire addressed to Angolan cancer units, in order to evaluate the usefulness and feasibility of a checklist developed by the authors - The Cancer Units Assessment Checklist for low or middle income African countries - which was used previously in the establishment of those units. Afterwards, the crucial steps taken for the establishing of the main sites of each cancer unit considering, facilities, resources and professionals, were also recorded. Results All cancer units reported that the checklist was a useful tool in the development of the cancer program for the improvement of the unit or the establishing of cancer unit sites. This instrument helped identifying resources, defining the best practice and identifying barriers. Local experts, who know the best practices in oncology and who are recognized by the local heads, are also important and they proved to be the major facilitators. Conclusion The fight against cancer has just started in Angola. The training, education, advocacy and legislation are ongoing. According to our results, the assessment checklist for the establishment of cancer units is a useful instrument. PMID:25883719

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. "You learn to go last": perceptions of prenatal care experiences among African-American women with limited incomes.

    PubMed

    Salm Ward, Trina C; Mazul, Mary; Ngui, Emmanuel M; Bridgewater, Farrin D; Harley, Amy E

    2013-12-01

    African American infants die at higher rates and are at greater risk of adverse birth outcomes than White infants in Milwaukee. Though self-reported experiences of racism have been linked to adverse health outcomes, limited research exists on the impact of racism on women's prenatal care experiences. The purpose of this study was to examine the experiences of racial discrimination during prenatal care from the perspectives of African American women in a low income Milwaukee neighborhood. Transcripts from six focus groups with twenty-nine women and two individual interviews were analyzed to identify important emergent themes. Validity was maintained using an audit trail, peer debriefing, and two individual member validation sessions. Participants identified three areas of perceived discrimination based on: (1) insurance or income status, (2) race, and (3) lifetime experiences of racial discrimination. Women described being treated differently by support staff and providers based on type of insurance (public versus private), including perceiving a lower quality of care at clinics that accepted public insurance. While some described personally-mediated racism, the majority of women described experiences that fit within a definition of institutionalized racism-in which the system was designed in a way that worked against their attempts to get quality prenatal care. Women also described lifetime experiences of racial discrimination. Our findings suggest that African American women with limited incomes perceive many provider practices and personal interactions during prenatal care as discriminatory. Future studies could explore the relationship between perceptions of discrimination and utilization of prenatal care.

  18. 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.

  19. 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.

  20. 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…

  1. 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…

  2. 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…

  3. Experiences of High School Teachers and Administrators Regarding Suspension of African American Males

    ERIC Educational Resources Information Center

    Robinson, Corwin

    2014-01-01

    The large number of suspensions of African American high school males is one of the primary concerns facing high school administrators nationwide. At high schools in the southern United States, African American males are suspended at greater rates than their counterparts. Suspensions affect their levels of achievement, attitudes towards school,…

  4. In Their Own Words: African American Women Narrate Their Experiences to Leadership

    ERIC Educational Resources Information Center

    Choates, Ramelli

    2012-01-01

    This study employs a qualitative approach, using oral narratives to provide the life stories of five African American women administrators in higher education. The purpose of the study is to understand the impact of various influences, sources of support, and impact of mentorship on African American women who obtained senior administrative…

  5. 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…

  6. 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…

  7. 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…

  8. 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.

  9. 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…

  10. 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…

  11. 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…

  12. "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…

  13. 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…

  14. Experiences of African immigrant women living with HIV in the U.K.: implications for health professionals.

    PubMed

    Ndirangu, Eunice W; Evans, Catrin

    2009-04-01

    In the U.K. immigrant women from Africa constitute an increasingly large proportion of newly diagnosed cases of HIV. A significant minority of these are refugees and asylum seekers. Very little is known about their experiences of living with HIV/AIDS, their psychosocial needs or their views of health care provision. This paper reports the results of a qualitative study that explored these issues by interviewing eight African women living with HIV in the British city of Nottingham. Women's ability to live positively with HIV was found to be strongly shaped by their migration history, their legal status, their experience of AIDS-related stigma and their Christian faith. Significantly, health services were represented as a safe social space, and were highly valued as a source of advice and support. The findings indicate that non-judgemental, personalised health care plays a key role in encouraging migrant African women to access psychosocial support and appropriate HIV services.

  15. Health Care Experiences and Perceived Barriers to Health Care Access: A Qualitative Study Among African Migrants in Guangzhou, Guangdong Province, China

    PubMed Central

    Brown, Katherine B.; Yu, Fan; Yang, Jingqi; Wang, Jason; Schrock, Joshua M.; Bodomo, Adams B.; Yang, Ligang; Yang, Bin; Nehl, Eric J.; Tucker, Joseph D.; Wong, Frank Y.

    2014-01-01

    Guangzhou, one of China's largest cities and a main trading port in South China, has attracted many African businessmen and traders migrating to the city for financial gains. Previous research has explored the cultural and economic roles of this newly emerging population; however, little is known about their health care experiences while in China. Semi-structured interviews and focus groups were used to assess health care experiences and perceived barriers to health care access among African migrants in Guangzhou, China. Overall, African migrants experienced various barriers to accessing health care and were dissatisfied with local health services. The principal barriers to care reported included affordability, legal issues, language barriers, and cultural differences. Facing multiple barriers, African migrants have limited access to care in Guangzhou. Local health settings are not accustomed to the African migrant population, suggesting that providing linguistically and culturally appropriate services may improve access to care for the migrants. PMID:25294415

  16. Beyond magnetotelluric decomposition: Induction, current channeling, and magnetotelluric phases over 90°

    NASA Astrophysics Data System (ADS)

    Lezaeta, Pamela; Haak, Volker

    2003-06-01

    This paper presents a method to examine strong current channeling affecting the magnetotelluric (MT) impedances, going beyond existing tensor decomposition schemes. The method allows recognition of elongated conductors in the crust and is also useful for a qualitative recognition of general three-dimensional (3-D) high-conductivity anomalies. This has been tested with synthetic data from 3-D and 2-D anisotropic models. The current channeling analysis has been applied to MT data collected in the Andean subduction zone, where the Atacama megafault system close to the Pacific Ocean and oriented subparallel to the coast line is located. The analysis suggests the presence of vertical dike-like conductors of limited lateral extent along the fault zone. Several MT sites distributed along the faults have impedance phases of the electric field tangential to the local azimuth far exceeding 90° at longer periods. We are able to explain this as being the result of strong current channeling producing magnetic distortion due to an electromagnetic coupling between the conductive ocean and the continental elongated conductors.

  17. 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

  18. 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.

  19. 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

  20. Experiences and perspectives of African American, Latina/o, Asian American, and European American psychology graduate students: A national study.

    PubMed

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

    2011-01-01

    A national, Web-based survey of 1,219 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 within the academic environment, were also important predictors of satisfaction. Students of color perceived less fairness of representation of their ethnic group within psychology than European American students, and a greater linkage between aspects of the graduate school experience and their ethnicity. Limitations of the study and implications for future research and action are discussed.

  1. African American Women’s Limited Knowledge and Experiences with Genetic Counseling for Hereditary Breast Cancer

    PubMed Central

    Sheppard, Vanessa B.; Graves, Kristi D.; Christopher, Juleen; Hurtado-de-Mendoza, Alejandra; Talley, Costellia; Williams, Karen Patricia

    2014-01-01

    Genetic counseling and testing for hereditary breast cancer have the potential benefit of early detection and early interventions in African American women. However, African American women have low use of these services compared to White women. We conducted two focus groups with African American women diagnosed with breast cancer (affected group, n=13) and women with at least one first-degree relative with breast/ovarian cancer (unaffected group, n= 8). A content analysis approach was employed to analyze interview data. Breast cancer survivors had more knowledge about genetic counseling and testing than participants who were unaffected with cancer. However, knowledge about genetic counseling was limited in both groups. Barriers to pursuing genetic counseling and testing included poor understanding of the genetic counseling and testing process, fear of carrying the mutation, concerns about discrimination, and cost. Motivators to participate in genetic counseling and testing included desire to help family members, insurance coverage, and potential of benefiting the larger African American community. Education efforts are needed to increase genetic counseling and testing awareness in the African American community. PMID:24186304

  2. African American women's limited knowledge and experiences with genetic counseling for hereditary breast cancer.

    PubMed

    Sheppard, Vanessa B; Graves, Kristi D; Christopher, Juleen; Hurtado-de-Mendoza, Alejandra; Talley, Costellia; Williams, Karen Patricia

    2014-06-01

    Genetic counseling and testing for hereditary breast cancer have the potential benefit of early detection and early interventions in African American women. However, African American women have low use of these services compared to White women. We conducted two focus groups with African American women diagnosed with breast cancer (affected group, n = 13) and women with at least one first-degree relative with breast/ovarian cancer (unaffected group, n = 8). A content analysis approach was employed to analyze interview data. Breast cancer survivors had more knowledge about genetic counseling and testing than participants who were unaffected with cancer. However, knowledge about genetic counseling was limited in both groups. Barriers to pursuing genetic counseling and testing included poor understanding of the genetic counseling and testing process, fear of carrying the mutation, concerns about discrimination, and cost. Motivators to participate in genetic counseling and testing included desire to help family members, insurance coverage, and potential of benefiting the larger African American community. Education efforts are needed to increase genetic counseling and testing awareness in the African American community.

  3. 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

  4. 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

  5. Experiences of and responses to HIV among African and Caribbean communities in Toronto, Canada.

    PubMed

    Gardezi, F; Calzavara, L; Husbands, W; Tharao, W; Lawson, E; Myers, T; Pancham, A; George, C; Remis, R; Willms, D; McGee, F; Adebajo, S

    2008-07-01

    African and Caribbean communities in Canada and other developed countries are disproportionately affected by HIV/AIDS. This qualitative study of African and Caribbean communities in Toronto sought to understand HIV-related stigma, discrimination, denial and fear, and the effects of multiple intersecting factors that influence responses to the disease, prevention practices and access to treatment and support services. Semi-structured interviews were conducted with 30 HIV-positive men and women and focus groups were conducted with 74 men and women whose HIV status was negative or unknown. We identified a range of issues faced by African and Caribbean people that may increase the risk for HIV infection, create obstacles to testing and treatment and lead to isolation of HIV-positive people. Our findings suggest the need for greater sensitivity and knowledge on the part of healthcare providers; more culturally specific support services; community development; greater community awareness; and expanded efforts to tackle housing, poverty, racism and settlement issues.

  6. 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

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

    PubMed

    Moyi Okwaro, Ferdinand; Geissler, P W

    2015-12-01

    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.

  8. Development and validation of measures of religious involvement and the cancer experience among African Americans

    PubMed Central

    Holt, Cheryl L.; Caplan, Lee; Schulz, Emily; Blake, Victor; Southward, Vivian L.; Buckner, Ayanna V.

    2013-01-01

    Research indicates that African Americans diagnosed with cancer tend to use religion in coping, however less is known about the specific role that religion plays in the coping process. Based on previous qualitative work, five instruments were developed to assess the role of religious involvement in cancer coping: God as helper, God as healer, Faith in healing, Control over cancer, and New perspective. The instruments were administered to 100 African Americans with cancer. Each exhibited high internal reliability, and concurrent and discriminant validity. These instruments may have applied value for the development of church-based cancer support/survivorship interventions. PMID:19383653

  9. 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.

  10. 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.

  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 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,…

  13. 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…

  14. 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…

  15. A Vision to Serve: The Experiences of Five African American Urban Teacher Leaders

    ERIC Educational Resources Information Center

    Watson, Allyson

    2007-01-01

    History denotes a small number of African-Americans have held leadership roles in educational public and private school systems across the country. However, during the last decade black women have pioneered and forged new frontiers as educational as leaders within urban schools. Because of these contributions, more should be known regarding the…

  16. The Outdoor Recreation Experience: Factors Affecting Participation of African American Women.

    ERIC Educational Resources Information Center

    Roberts, Nina S.; Drogin, Ellen B.

    1993-01-01

    Discusses factors contributing to the nonparticipation of African-American women in outdoor recreation activities including (1) historical oppression and racism; (2) stereotyping by race and gender; (3) lack of role models; (4) insufficient exposure to activity options; (5) limited accessibility to outdoor recreation areas; and (6) oppressive…

  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. 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…

  19. 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…

  20. 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…

  1. 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…

  2. 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…

  3. "I Understand the Struggle": Leveraging the Lived Experiences of African American Teachers in TESOL

    ERIC Educational Resources Information Center

    Siefert, Bobbi; Salas, Spencer; D'amico, Mark M.

    2015-01-01

    Although TESOL in-service teacher education committed to "culturally sustaining pedagogy" (Paris, 2012) has underscored the critical role of teachers' professional subjectivities for student achievement, relatively few studies have attempted to capture the perspectives of African American classroom teachers working with English language…

  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.

  5. 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.

  6. Dry intrusions in the West African monsoon mid-troposphere during the AMMA experiment

    NASA Astrophysics Data System (ADS)

    Deme, A.; Roca, R.

    2009-04-01

    Mid-troposphere dry air patches (RH < 10%) have been recently detected over the African monsoon region and in particular over Sahel. At 500 hPa, these dry air features are thought to play a complex role onto convection: inhibition isolated convective cells but favouring already organized convection by feeding rear-inflow currents with dry air. The inhibiting action of the dry air onto convection comes from the temperature inversion induced by radiation at the bottom of the dry layer and/or by entrainment of dry air in ascending parcel that decreases its buoyancy. The organizing effect is associated to mesoscale currents within and around long lasting squall lines. This mid-tropospheric dry air has been shown to originate from the mid-latitudes upper level jets, therefore coined extra-tropical dry intrusions.Among all the forcings that control the dynamics of the West African monsoon, the role of a dry mid-troposphere needs to be clarified. The present study is dedicated to this objective and it is focused on extra-tropical dry air intrusions in the West African mid-troposphere during the AMMA campaign. The low level dynamics is documented (African Easterly Jet, African Easterly Wave) thanks to the NCEP operational analysis. It is completed by the radiosondes especially for the temperature and water vapor distribution. Back-trajectory are computed in order to highlight the origin of the tropospheric air mass. Finally Meteosat Second Generation derived water vapor and cloud and rainfall parameters are used to characterize the convective activity and its moist environment. Dry intrusions in the African mid troposphere during the summer 2006 have been shown to be associated with two major modes of occurrences: a 40-50 days mode and a 10-20 days mode. The long mode exhibits negative anomaly of the rainfall and a very large scale structure covering the whole West Africa region when occurring while the short mode is more restricted to the Sahelian longitude. Similarly

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. West Flank Coso FORGE Magnetotelluric 3D Data

    DOE Data Explorer

    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.

  12. 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…

  13. 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

  14. Masculinity and the body: how African American and White men experience cancer screening exams involving the rectum.

    PubMed

    Winterich, Julie A; Quandt, Sara A; Grzywacz, Joseph G; Clark, Peter E; Miller, David P; Acuña, Joshua; Arcury, Thomas A

    2009-12-01

    Past research on prostate and colorectal cancer disparities finds that barriers to screening, such as embarrassment and offensiveness, are often reported. Yet none of this literature investigates why. This study uses masculinity and health theory to examine how men experience two common screenings: digital rectal exams (DREs) and colonoscopies. In-depth interviews were conducted with 64 African American and White men from diverse backgrounds, aged 40 to 64, from North Carolina. Regardless of race or education, men experienced DREs more negatively than colonoscopies because penetration with a finger was associated with a gay sexual act. Some men disliked colonoscopies, however, because they associated any penetration as an affront to their masculinity. Because beliefs did not differ by race, future research should focus on structural issues to examine why disparities persist with prostate and colorectal cancer. Recommendations are provided for educational programs and physicians to improve men's experiences with exams that involve the rectum.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. The association between disaster-related experiences and mental health outcomes among drug using African American Hurricane Katrina evacuees.

    PubMed

    Cepeda, Alice; Saint Onge, Jarron M; Kaplan, Charles; Valdez, Avelardo

    2010-12-01

    This article provides a detailed examination of the relationship between disaster-related experiences and mental health outcomes among a sample of drug using African American Hurricane Katrina evacuees. Face-to-face structured interviews were administered to Hurricane Katrina evacuees (n = 350) residing in voucher assisted apartment complexes in Houston, Texas (2006-2007). We use Ordinary Least Squares and logistic regression models to examine both the relevance of disaster-related experiences and the interactive relationships between disaster-related experiences and post-disaster mental health outcomes including psychological distress, severe depression, somatic symptoms, and posttraumatic stress disorder. Results indicate that disaster-related experiences including negative life changes, disaster exposure, post-disaster stressors, and resource loss, have unique, inverse relationships with mental health. While resource loss has the strongest inverse relationship with mental health, disaster exposure has a negative interactive effect on psychological distress and anxiety. Although highly vulnerable populations report low levels of mental health nearly 2 years following a disaster experience, there is a convergence in mental health outcomes with high levels of disaster experiences and disaster exposure that suggests mental resiliency.

  3. "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…

  4. "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

  5. 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…

  6. 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

  7. Neighborhood Characteristics and Expectations of Racially Discriminatory Experiences Among African American Adolescents.

    PubMed

    Witherspoon, Dawn P; Seaton, Eleanor K; Rivas-Drake, Deborah

    2016-09-01

    This study examined how youth's neighborhood characteristics informed their expectations of racial discrimination concurrently and longitudinally. Secondary analyses were conducted on data from Waves 1, 3, 4, 5, and 6 of the Maryland Adolescent Development in Context Study, which permitted the examination of neighborhood influences among a socioeconomically diverse sample of African American parents and adolescents (n = 863; Mage  = 12.29). Youth exposed to more neighborhood disadvantage in seventh grade reported more negative concurrent neighborhood perceptions, which, in turn, predicted greater expectations of racial discrimination in eighth grade; youth's expectations remained stable into adulthood. Thus, support was found for the mediating role of youth's subjective neighborhood perceptions in the longitudinal relation between neighborhood structure and expectations of racial discrimination. PMID:27684392

  8. The Experience of Sexual Risk Communication in African American Families Living With HIV.

    PubMed

    Cederbaum, Julie A

    2012-09-01

    Mother-daughter communication plays an influential role in adolescent development. The impact of maternal HIV infection on family communication is not clear. This study explores how living with HIV impacts sexual risk communication between mothers and daughters and whether maternal HIV status influences adolescent choices about engagement in HIV risk behaviors. Data were collected from 12 African American women and 10 of their adolescent daughters through focus groups. Both mothers and daughters shared information about issues that promoted and inhibited communication and engagement in risk behaviors. Findings show that HIV status served as a mechanism for behavioral change related to communication and risk engagement behaviors. Therefore, HIV-infected mothers should be supported in communicating values and expectations to their daughters. PMID:23144530

  9. The Experience of Sexual Risk Communication in African American Families Living With HIV

    PubMed Central

    Cederbaum, Julie A.

    2012-01-01

    Mother-daughter communication plays an influential role in adolescent development. The impact of maternal HIV infection on family communication is not clear. This study explores how living with HIV impacts sexual risk communication between mothers and daughters and whether maternal HIV status influences adolescent choices about engagement in HIV risk behaviors. Data were collected from 12 African American women and 10 of their adolescent daughters through focus groups. Both mothers and daughters shared information about issues that promoted and inhibited communication and engagement in risk behaviors. Findings show that HIV status served as a mechanism for behavioral change related to communication and risk engagement behaviors. Therefore, HIV-infected mothers should be supported in communicating values and expectations to their daughters. PMID:23144530

  10. 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.

  11. 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

  12. The Estimation and Inversion of Magnetotelluric Data with Static Shift

    NASA Astrophysics Data System (ADS)

    Wang, X.; Zhou, J.; Zhang, J.; Min, G.; Xia, S.

    2015-12-01

    IntroductionIn magnetotelluric sounding data processing, the static shift correction is one of the most important steps. Due to the complexity of near-surface inhomogeneous bodies distribution, it is difficult to estimate the static shift of measured data. For this problem, we put forward on the basis of the inversion model for static shift estimation, and reconstructed the initial model with using the original data for 2D or 3D inversion. Estimation and Inversion methodThe magnetotelluric impedance phase has the characteristics of not influenced by the static shift in Two-dimensional electrical structure. The objective function for static shift estimation can be constructed based on impedance phase data. On the basis of normal inversion, utilizing one-dimensional linear search algorithm, combined with the forward modeling, the MT static shift can be estimated.Using estimation results for translation of anomaly measured curve. According to the inversion(1-D) of these translated curve, the initial model for two-dimensional or two-dimensional inversion can be reconstructed. On this basis, we do inversion for the original data, which not only can effectively eliminate the influence of static shift on the deep structure of inversion model, but also can get the right shallow electrical structure in the inversionConclusionThe estimation value of static shift based on impedance phase can be close to the true value. This estimation results can be used to modify the initial model, which makes the deep electric structure of the model more reasonable. On this basis, the inversion of the original data can ensure the correctness of the final inversion results (including shallow and deep).Acknowledgement This paper is supported by National Natural Science Foundation (41274078) and National 863 High Technology Research and Development Program (2014AA06A612).Reference[1] deGroot-Hedlin C. Removal of static shift in two dimensions by regularized inversion[J]. Geophysics, 1991, 56

  13. Physical activity among African American and Latino middle school girls: consistent beliefs, expectations, and experiences across two sites.

    PubMed

    Taylor, W C; Yancey, A K; Leslie, J; Murray, N G; Cummings, S S; Sharkey, S A; Wert, C; James, J; Miles, O; McCarthy, W J

    1999-01-01

    Physical inactivity is a major public health concern. Low levels of physical activity are reported in many subgroups of women including adolescent girls. More data are needed to better understand factors related to physical activity participation in adolescent girls. Therefore, we explored adolescent girls' reasons for participating and not participating in physical activity. Two independent samples were taken in California and Texas; the total sample included thirty-four African American and Latino girls. Six focus groups were conducted by trained facilitators. Based on independent qualitative analyses, six replicated themes emerged from the focus groups. Fun, social support, and concern with body image facilitated participation in activity. In contrast, negative experiences in physical education classes, concerns about appearance after activity, and lack of opportunity impeded participation in activity. Overall, the girls showed an interest in physical activity and identified activity motivators and barriers. We discuss the implications of our findings for future research.

  14. Enduring consequences of early experiences: 40 year effects on survival and success among African elephants (Loxodonta africana).

    PubMed

    Lee, Phyllis C; Bussière, Luc F; Webber, C Elizabeth; Poole, Joyce H; Moss, Cynthia J

    2013-04-23

    Growth from conception to reproductive onset in African elephants (Loxodonta africana) provides insights into phenotypic plasticity, individual adaptive plastic responses and facultative maternal investment. Using growth for 867 and life histories for 2652 elephants over 40 years, we demonstrate that maternal inexperience plus drought in early life result in reduced growth rates for sons and higher mortality for both sexes. Slow growth during early lactation was associated with smaller adult size, later age at first reproduction, reduced lifetime survival and consequently limited reproductive output. These enduring effects of trading slow early growth against immediate survival were apparent over the very long term; delayed downstream consequences were unexpected for a species with a maximum longevity of 70+ years and unpredictable environmental experiences.

  15. 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

  16. Traditional healing, biomedicine and the treatment of HIV/AIDS: contrasting south african and native American experiences.

    PubMed

    Flint, Adrian

    2015-04-20

    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.

  17. 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.

  18. 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.

  19. Three-dimensional modelling in magnetotelluric and magnetic variational sounding

    NASA Technical Reports Server (NTRS)

    Reddy, I. K.; Phillips, R. J.; Rankin, D.

    1977-01-01

    The Galerkin finite-element method is used to obtain approximate solutions for the three-dimensional induction problem. A rectangular conductive prism is considered as an example, and solutions are obtained for linear and circularly polarized incident plane-wave fields. Magnetotelluric tensor impedances and magnetic transfer functions are computed. Polar diagrams of the tensor impedances and magnetic transfer functions along with their amplitude contour maps are presented. The dimensionality parameter, skew, is contoured at the surface of the earth. It is shown that the relative amplitudes and shapes of the additional and principal impedance polar diagrams can be used to determine the dimensionality of geoelectrical structures. Stations with skew values greater than 0.2 are significantly influenced by the three-dimensionality of the geoelectric structure. The amplitudes of the magnetic transfer function and the orientations of its polar diagrams exhibit large anomalies in the vicinity of the intersection of the lateral contacts.

  20. Magnetotelluric Response Function Estimation Based on Hilbert-Huang Transform

    NASA Astrophysics Data System (ADS)

    Cai, Jian-hua

    2013-11-01

    Magnetotelluric (MT) data series are non-stationary random signals that do not meet the basic requirements of conventional methods based on the Fourier transform. To minimize the estimation bias errors brought about by the non-stationary characteristics of MT data, a new method, based on the Hilbert-Huang transform (HHT), is proposed for the first time for estimating the MT response functions from a time series of electromagnetic field variations. With the HHT method, the amplitude of data series are expressed as a function of frequency and time and then response functions are estimated statistically from the time-frequency spectrum. Mathematical model and calculation processes are introduced and some simulated data are analyzed to verify the correctness of the method. Finally, the measured MT data is facilitated by applying the HHT to assess the ability of HHT method to quantify meaningful geologic information.

  1. Joint three-dimensional inversion of magnetotelluric and magnetovariational data

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

    The problem of quantitative three-dimensional interpretation of the magnetotelluric (MT) data ranks among the most difficult problems in electromagnetic (EM) geophysics. Our paper presents a new rigorous numerical method for MT inversion, based on the integral equations technique. An important feature of the proposed method is the calculation of the Frechet derivative with the aid of a quasi-analytical approximation with an inhomogeneous background. This approach simplifies the algorithm of inversion and requires only a single forward modeling on each iteration. We have also developed a method for a joint inversion of MT and magnetovariational (MV) data. We show in the present paper that the joint inversion of MT impedances and the Wiese-Parkinson vectors can automatically allow for the static shift in the observed data, which is caused by the geoelectric inhomogeneities contained in the near-surface layer.

  2. Magnetotelluric inversion for azimuthally anisotropic resistivities employing artificial neural networks

    NASA Astrophysics Data System (ADS)

    Montahaei, Mansoure; Oskooi, Behrooz

    2014-02-01

    An extension of an artificial neural network (ANN) approach to solve the magnetotelluric (MT) inverse problem for azimuthally anisotropic resistivities is presented and applied for a real dataset. Three different model classes, containing general 1-D and 2-D azimuthally anisotropic features, have been considered. For each model class, characteristics of three-layer feed forward ANNs trained through an error back propagation algorithm have been adjusted to approximate the inverse modeling function. It appears that, at least for synthetic models, reasonable results would be obtained by applying the amplitudes of the complex impedance tensor elements as inputs. Furthermore, the Levenberg-Marquart algorithm possesses optimal performance as a learning paradigm for this problem. The evaluation of applicability of the trained ANNs for unknown data sets excluded from the learning procedure reveals that the trained ANNs possess acceptable interpolation and extrapolation abilities to estimate model parameters accurately. This method was also successfully used for a field dataset wherein anisotropy had been previously recognized.

  3. "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…

  4. 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.…

  5. 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…

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

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

    PubMed

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

    2011-10-01

    We used Consensual Qualitative Research Methodology to analyze responses from 14 African American men (Mdn(Age) = 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.

  13. 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

  14. South African experience with asbestos related environmental mesothelioma: is asbestos fiber type important?

    PubMed

    White, Neil; Nelson, Gill; Murray, Jill

    2008-10-01

    South Africa (SA), a country in which all three commercially important asbestos minerals have been mined and milled, has retained proven cases of mesothelioma linked with environmental exposure to asbestos. This study illustrates the importance of fiber type in the occurrence of environmental mesothelioma. Four studies have reviewed the source of occupational or environmental asbestos exposure in 504 histologically proven cases of mesothelioma in South Africa. One hundred and eighteen cases (23%) were thought to be related to environmental exposure to asbestos. In the vast majority of these cases, exposure was linked to crocidolite mining activities in the Northern Cape Province. Two cases were thought to have occurred in relation to amosite and Transvaal crocidolite exposure in the Limpopo Province. In the balance of cases there was some uncertainty. No cases were reported with exposure to South African chrysotile. Consequently, in the vast majority of cases of mesothelioma, environmental exposure to asbestos occurred in the Northern Cape Province, in proximity to mines, mills and dumps where crocidolite was processed. Crocidolite appears to be far more mesotheliomagenic than amosite, and chrysotile has not been implicated in the disease. This is true for both occupationally and environmentally exposed individuals.

  15. 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.

  16. 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

  17. An Amphibious Magnetotelluric Investigation of the Cascadian Seismogenic and ETS zones.

    NASA Astrophysics Data System (ADS)

    Parris, B. A.; Livelybrooks, D.; Bedrosian, P.; Egbert, G. D.; Key, K.; Schultz, A.; Cook, A.; Kant, M.; Wogan, N.; Zeryck, A.

    2015-12-01

    The amphibious Magnetotelluric Observations of Cascadia using a Huge Array (MOCHA) experiment seeks to address unresolved questions about the seismogenic locked zone and down-dip transition zone where episodic tremor and slip (ETS) originates. The presence of free fluids is thought to be one of the primary controls on ETS behavior within the Cascadia margin. Since the bulk electrical conductivity in the crust and mantle can be greatly increased by fluids, magnetotelluric(MT) observations can offer unique insights on the fluid distribution and its relation to observed ETS behavior. Here we present preliminary results from the 146 MT stations collected for the MOCHA project. MOCHA is unique in that it is the first amphibious array of MT stations occupied to provide for 3-D interpretation of conductivity structure of a subduction zone. The MOCHA data set comprises 75 onshore stations and 71 offshore stations, accumulated over a two-year period, and located on an approximate 25km grid, spanning from the trench to the Eastern Willamette Valley, and from central Oregon into middle Washington. We present the results of a series of east-west (cross-strike) oriented, two-dimensional inversions created using the MARE2DEM software that provide an initial picture of the conductivity structure of the locked and ETS zones and its along strike variations. Our models can be used to identify correlations between ETS occurrence rates and inferred fluid concentrations. Our modeling explores the impact of various parameterizations on 2-D inversion results, including inclusion of a smoothness penalty reduction along the inferred slab interface. This series of 2-D inversions can then be used collectively to help make and guide an a priori 3-D inversion. In addition we will present a preliminary 3-D inversion of the onshore stations created using the ModEM software. We are currently working on modifying ModEM to support inversion of offshore data. The more computationally intensive 3-D

  18. 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

  19. 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…

  20. 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…

  1. 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…

  2. 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…

  3. 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…

  4. 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.

  5. Interpretation of EarthScope magnetotelluric data for Northwestern United States

    NASA Astrophysics Data System (ADS)

    Green, Alisa Marie

    In this dissertation, I present the results of large-scale three-dimensional magnetotelluric (MT) inversion, based on the nonlinear conjugate gradient algorithm and the contraction integral equation forward modeling method, applied to data collected in Northwestern United States for part of the EarthScope project. It is shown that the most noteworthy anomalies within the inverse geo-electrical model are resistive structures associated with oceanic lithosphere and cratons, and conductive features associated with mantle upwelling. Density estimations from seismic data analysis show upwelling phenomena in the upper mantle where Yellowstone is the present-day surface expression of the deep heat source. Comparison of MT results to approximately 400 km depth have reasonable correlation with P-wave and S-wave velocity models obtained from seismic tomography. The MT inversion demonstrates that strong resistive zones line up along the northwest coast correlating to recent seismic interpretations of old oceanic slabs at 100 km depth believed to be remnants of the Farrallon oceanic plate. This dissertation shows that access to multiple physical properties within the subsurface increases our ability to understand complexities in geological interpretations resulting from the interplay of transforming quanta at differing pressure and temperature regimes with depth. Therefore, EarthScope is proving true to the founding philosophy that the bold, new experiment will fundamentally change our view of the planet.

  6. 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…

  7. 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)…

  8. Examining the Cultural Adjustment Experiences of African International College Students: A Qualitative Analysis

    ERIC Educational Resources Information Center

    Constantine, Madonna G.; Anderson, Gregory M.; Berkel, LaVerne A.; Caldwell, Leon D.; Utsey, Shawn O.

    2005-01-01

    The authors examined the cultural adjustment experiences of 12 Kenyan, Nigerian, and Ghanaian international college students through semistructured interviews. Using consensual qualitative research methodology (C. E. Hill, B. J. Thompson, & E. N. Williams, 1997), 7 primary domains or themes related to these students' cultural adjustment…

  9. Life Experience of African Graduate Students in a Multi-Cultural Setting: A Case Study.

    ERIC Educational Resources Information Center

    Antwi, Ransford; Ziyati, Abdelali

    A study examined how international students from North and West Africa fit in, cope, manage, and respond to their experiences in American Universities that are in many cases set up in the context of Americans who constitute the majority. Assuming that the lives of international students outside their home countries and cultures are…

  10. 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

  11. 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

  12. Geophysical Studies of Irish Granites Using Magnetotelluric and Gravity Data

    NASA Astrophysics Data System (ADS)

    Farrell, T. F.; Muller, M. R.; Rath, V.; Feely, M.; Hogg, C.

    2014-12-01

    We present results of on-going geophysical studies of Caledonian radiothermal granite bodies in Ireland, which are being undertaken to investigate the volumetric depth extent and structural features of these granites. During three field seasons, magnetotelluric (MT) and audio-magnetotelluric (AMT) data were acquired at 156 sites targeting three separate granite bodies. These studies will contribute to a crustal-scale investigation of the geothermal energy potential of the granites and their contribution to the thermal field of the Irish crust. Across the calc-alkaline Galway granite, located on the Irish west coast, MT and AMT data were acquired at 75 sites distributed in a grid. Preliminary 3D inversion reveals the presence of a resistor, thickest beneath the central block of the granite where it extends to depths of 11 - 12 km. The greater depth of the resistor beneath the central block is in contrast to previous thinking that proposed the central block granites to have shallower depth extent than those of the western block, based on Bouguer anomaly maps of the area in which the western block exhibited a more pronounced negative Bouguer anomaly than the central block. At the S-type Leinster granite, in eastern Ireland and to the south of Dublin, MT and AMT data were acquired along two profiles (LGN - 27 sites and LGS - 32 sites). Preliminary 1D inversions of AMT data along profile LGN show the Northern Units of the Leinster granite to extend to a depth of 4.5 km and the Lugnaquilla pluton extending to 2.5 km depth. MT and AMT data were acquired at 22 sites along a profile across the buried Kentstown granite, 35 km to the NW of Dublin. The Kentstown granite was intersected by two mineral exploration boreholes at depths of 492 m and 663 m. Preliminary 2D inversions do not yet satisfactorily resolve the top of the buried granite. Inversion of MT and AMT data is continuing, with the electrical conductivity structures revealed by these inversions being used to

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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.

  18. 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

  19. 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

  20. 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

    2015-05-05

    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.

  1. New equipment and processing for magnetotelluric remote reference observations

    NASA Astrophysics Data System (ADS)

    Ritter, Oliver; Junge, Andreas; Dawes, Graham

    1998-03-01

    Robust estimates of magnetotelluric and geomagnetic response functions are determined using the coherency and expected uniformity of the magnetic source field as quality criteria. The method is applied on data sets of three simultaneously recording sites. For the data acquisition we used a new generation of geophysical equipment (S.P.A.M. MkIII), which comprises novel concepts of parallel computing and networked, digital data transmission. The data-processing results show that the amount of noise on the horizontal components of the magnetic field varies considerably in time, between sites and over the frequency range. The removal of such contaminated data beforehand is essential for most data-processing schemes, as the magnetic channels are usually assumed to be free of noise. The standard remote reference method is aimed at reducing bias in response function estimates. However, this does not necessarily improve their precision as our results clearly show. With our method, on the other hand, we can filter out source field irregularities, thereby providing suitable working conditions for the robust algorithm, and eventually obtain considerably improved results. Contrary to previous concepts, we suggest rejecting as much data as feasible in order to concentrate on the remaining parts of high-quality observations.

  2. An audio-magnetotelluric investigation in Terceira Island (Azores)

    NASA Astrophysics Data System (ADS)

    Monteiro Santos, Fernando A.; Trota, António; Soares, António; Luzio, Rafael; Lourenço, Nuno; Matos, Liliana; Almeida, Eugénio; Gaspar, João L.; Miranda, Jorge M.

    2006-08-01

    Ten audio-magnetotelluric soundings have been carried out along a profile crossing the Serra do Cume caldera in the eastern part of the Terceira Island (Azores). The main objectives of this investigation were to detect geoelectrical features related with tectonic structures and to characterize regional hydrological and hydrothermal aspects mainly those related to geothermal fluid dynamics. Three-dimensional numerical investigation showed that the data acquired at periods shorter than 1 s are not significantly affected by ocean effect. The data was analysed using the Smith's decomposition method in order to investigate possible distortions caused by superficial structures and to estimate a global regional strike. The results suggest that in general the soundings were not distorted. A regional N55°W strike was chosen for the two-dimensional data inversion. The low-resistivity zones (10-30 ohm-m) displayed in the central part of the 2-D geoelectrical model have been interpreted as caused by hydrothermal circulation. The low-resistivity anomalies at the ends of the profile might be attributed to alteration zones with interaction of seawater intrusion. High-resistivity (> 300 ohm-m) values have been related with less permeable zones in the SW of Cinco Picos and Guilherme Moniz caldera walls.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. First-Year Village: Experimenting with an African Model for First-Year Adjustment and Support in South Africa

    ERIC Educational Resources Information Center

    Speckman, McGlory

    2016-01-01

    Predicated on the principles of success and contextuality, this chapter shares an African perspective on a first-year adjustment programme, known as First-Year Village, including its potential and challenges in establishing it.

  9. 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.

  10. 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.

  11. Magnetotelluric data collected to characterize aquifers in the San Luis Basin, New Mexico

    USGS Publications Warehouse

    Ailes, Chad E.; Rodriguez, Brian D.

    2015-01-01

    The U.S. Geological Survey is conducting a series of multidisciplinary studies of the San Luis Basin as part of the Geologic Framework of Rio Grande Basins project. Detailed geologic mapping, high-resolution airborne magnetic surveys, gravity surveys, magnetotelluric surveys, and hydrologic and lithologic data are being used to better understand the aquifers in the San Luis Basin. This report describes one north-south and two east-west regional magnetotelluric sounding profiles, acquired in June of 2010 and July and August of 2011, across the San Luis Basin in northern New Mexico. No interpretation of the data is included.

  12. 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.

  13. 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.

  14. Photonics, Diversity and Mentoring -- 30 Years of Experiences and Strategies of an African-American Physicist

    NASA Astrophysics Data System (ADS)

    Johnson, Anthony M.

    2010-03-01

    As requested by our Session Chair, I hope to share a career that emphasizes cutting edge research in ultrafast optical phenomena, as well as outreach to women and underrepresented minorities that began over three decades ago at Bell Laboratories. My research career in Optical Physics owes it foundation and perspective to my mid-70s participation in the Bell Labs diversity programs the Summer Research Program for Minorities and Women (SRP) and the Cooperative Research Fellowship Program for Minorities (CRFP). In addition to striving to produce leading edge research, these programs made me a strong proponent of the recruitment and retention of women and underrepresented minorities into the scientific enterprise. Now approaching 15 years in academia, I have had the good fortune to continue the research tradition, where the majority of my graduate students are women and underrepresented minorities. Indeed, these students are out there, hungry for the experience, motivated to give their best effort, and thrive when given supportive and nurturing environments -- but you must expend the energy and resources to find them and I guarantee it will be worth it!

  15. Electronic data capture in a rural African setting: evaluating experiences with different systems in Malawi

    PubMed Central

    King, Carina; Hall, Jenny; Banda, Masford; Beard, James; Bird, Jon; Kazembe, Peter; Fottrell, Ed

    2014-01-01

    Background As hardware for electronic data capture (EDC), such as smartphones or tablets, becomes cheaper and more widely available, the potential for using such hardware as data capture tools in routine healthcare and research is increasing. Objective We aim to highlight the advantages and disadvantages of four EDC systems being used simultaneously in rural Malawi: two for Android devices (CommCare and ODK Collect), one for PALM and Windows OS (Pendragon), and a custom-built application for Android (Mobile InterVA – MIVA). Design We report on the personal field and development experience of fieldworkers, project managers, and EDC system developers. Results Fieldworkers preferred using EDC to paper-based systems, although some struggled with the technology at first. Highlighted features include in-built skip patterns for all systems, and specifically the ‘case’ function that CommCare offers. MIVA as a standalone app required considerably more time and expertise than the other systems to create and could not be customised for our specific research needs; however, it facilitates standardised routine data collection. CommCare and ODK Collect both have user-friendly web-interfaces for form development and good technical support. CommCare requires Internet to build an application and download it to a device, whereas all steps can be done offline with ODK Collect, a desirable feature in low connectivity settings. Pendragon required more complex programming of logic, using a Microsoft Access application, and generally had less technical support. Start-up costs varied between systems, and all were considered more expensive than setting up a paper-based system; however running costs were generally low and therefore thought to be cost-effective over the course of our projects. Conclusions EDC offers many opportunities for efficient data collection, but brings some issues requiring consideration when designing a study; the decision of which hardware and software to use

  16. 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

  17. 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

  18. Crosswell electromagnetic and magnetotelluric imaging of geothermal reservoirs - evaluation and case studies from Switzerland

    NASA Astrophysics Data System (ADS)

    Samrock, F.

    2015-12-01

    Geothermal energy resources are considered important contributors to any future energy mix, as they are renewable and can potentially provide a constant (i.e., baseload) and long-term energy output. However, most regions worldwide are lacking natural, convective hydrothermal resources. As a result, when relatively high subsurface temperatures exist in low-permeability rocks ("hot-dry" rocks), it has been suggested to artificially increase permeability to enable deep fluid circulation and associated advective heat transfer to a production well. One technique to enhance permeability, and thus the ability to extract geothermal heat, is hydraulic stimulation, creating (permeability) enhanced geothermal systems (EGS). In the "Deep Underground Geothermal (DUG)" laboratory in Switzerland, a meso-scale field experiment is planned, where pre-existing fault systems are hydraulically sheared. The aim of this experiment is to better understand the processes occurring during artificial reservoir creation. We present our 3D numerical modeling study evaluating the capability of low-frequency crosswell electromagnetic (EM) tomography using magnetic dipole sources to map stimulation-induced changes in electrical conductivity. This geophysical parameter is affected by several subsurface properties including temperature, interconnected porosity, permeability, and the presence of fluids. Electrical conductivity thus provides important information on the effectiveness of geothermal reservoir creation. Besides numerical modeling studies, we report on the current status of instrumentation and realization of crosswell EM measurements at the DUG laboratory. Furthermore, we present preliminary results of a magnetotelluric (MT) survey conducted at a prominent heat flow anomaly in Northern Switzerland. Here, we test methods to improve data quality of MT measurements in regions that exhibit substantial electromagnetic noise. We also discuss how information on the electrical conductivity

  19. 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

  20. Coupling Magnetotellurics and Hydrothermal Modeling to Further Understand Geothermal Resources

    NASA Astrophysics Data System (ADS)

    Folsom, M.; Pepin, J.; Kelley, S.; Person, M. A.; Blom, L.; Love, D.

    2015-12-01

    A comprehensive knowledge of the groundwater flow patterns associated with geothermal resources is critical to sustainable resource management and to discovering blind geothermal systems. Magnetotellurics (MT), which provides subsurface electrical conductivity information to substantial depths, has the ability to image geothermal reservoir features, such as conductive clay caps and hot, saline groundwater circulating within geothermal systems. We have used MT data along with 2D hydrothermal modeling, constrained by temperature, salinity and carbon-14 data, to explore possible deep groundwater circulation scenarios near the Sevilleta National Wildlife Refuge, in the Rio Grande Rift, central New Mexico. The area is underlain by a 100 to 150-m thick molten sill emplaced approximately 19 km below the surface. This sill is referred to locally as the Socorro Magma Body (SMB). Previous studies by Mailloux et al. (1999) and Pepin et al. (2015) suggest that the crystalline basement rocks in this region of the Rio Grande Rift can be significantly fractured to depths of 4-8 km and have permeabilities as high as 10-14 to 10-12 m2. The combination of high permeability conditions and the presence of the SMB makes this particular region a promising candidate for discovering a blind geothermal system at depth. We constructed a 2D hydrothermal model that traverses a 64-km zone of active uplift that is associated with the SMB. We also completed a 12-km long, 9-station MT transect across a portion of this profile, where land access was permitted and electromagnetic noise was minimal. Preliminary results suggest a deep convection-dominated system is a possibility, although further analysis of the MT data is necessary and ongoing. We hypothesize that using hydrothermal modeling in conjunction with MT surveys may prove to be an effective approach to discovering and managing deep regional hydrothermal resources.

  1. 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.

  2. 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

  3. MTpy - Python Tools for Magnetotelluric Data Processing and Analysis

    NASA Astrophysics Data System (ADS)

    Krieger, Lars; Peacock, Jared; Thiel, Stephan; Inverarity, Kent; Kirkby, Alison; Robertson, Kate; Soeffky, Paul; Didana, Yohannes

    2014-05-01

    We present the Python package MTpy, which provides functions for the processing, analysis, and handling of magnetotelluric (MT) data sets. MT is a relatively immature and not widely applied geophysical method in comparison to other geophysical techniques such as seismology. As a result, the data processing within the academic MT community is not thoroughly standardised and is often based on a loose collection of software, adapted to the respective local specifications. We have developed MTpy to overcome problems that arise from missing standards, and to provide a simplification of the general handling of MT data. MTpy is written in Python, and the open-source code is freely available from a GitHub repository. The setup follows the modular approach of successful geoscience software packages such as GMT or Obspy. It contains sub-packages and modules for the various tasks within the standard work-flow of MT data processing and interpretation. In order to allow the inclusion of already existing and well established software, MTpy does not only provide pure Python classes and functions, but also wrapping command-line scripts to run standalone tools, e.g. modelling and inversion codes. Our aim is to provide a flexible framework, which is open for future dynamic extensions. MTpy has the potential to promote the standardisation of processing procedures and at same time be a versatile supplement for existing algorithms. Here, we introduce the concept and structure of MTpy, and we illustrate the workflow of MT data processing, interpretation, and visualisation utilising MTpy on example data sets collected over different regions of Australia and the USA.

  4. 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

  5. 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.

  6. 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

  7. 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.

  8. 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.

  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. 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…

  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. 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…

  14. 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…

  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. 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…

  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. Influence of Kinship Social Support on the Parenting Experiences and Psychosocial Adjustment of African-American Adolescents.

    ERIC Educational Resources Information Center

    Taylor, Ronald D.; And Others

    1993-01-01

    Questionnaires assessed kinship support, psychosocial adjustment, and parenting practices for 125 African-American adolescents. Found that kinship support for adolescents was positively associated with adolescent adjustment and authoritative parenting practices in single- but not two-parent families and that parenting practices mediated the…

  19. Operating in the Middle: The Experiences of African American Female Transfer Students in STEM Degree Programs at HBCUs

    ERIC Educational Resources Information Center

    Smith, Dimitra Jackson

    2016-01-01

    Increasing the representation of African American females is essential to ensure the United States (U.S.) remains a viable competitor in the STEM (science, technology, engineering, and mathematics) workforce. With minorities anticipated to represent half of the resident U.S population by 2050, fostering STEM talent among this population is vital.…

  20. 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,…

  1. 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…

  2. 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…

  3. 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…

  4. 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

  5. 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.

  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. Noise Elimination Study for a Single Station Magnetotelluric Data

    NASA Astrophysics Data System (ADS)

    Şengül, Ebru; Uǧur Ulugergerli, Emin; Göktaş, Hilal

    2010-05-01

    Five components of the natural electromagnetic field relating to underground conductivity distribution on Earth are measured as a time series in the Magnetotelluric (MT) method. E (Ex, Ey) and H (Hx, Hy, Hz) components of the electromagnetic field suffers from noise contamination. The noise, in general, can be classified as random and systematic noise. Random noise disrupts the pattern of data such as sudden signal peaks and/or step structures called impulsive effect. This type of noise usually is dominant in some parts of the time series. The sources of random noise vary; some of the sources are instrumental problems and atmospheric events. On the other hand, systematic noise occurs at certain frequencies and is added to the data. Industrial activities cause such type of the noise and can corrupt all the data set. The estimation of the impedance tensor from single-station MT data is subject to this study. The proposed method uses statistical approaches focused on the noise elimination techniques. Noise elimination from MT time series is very important particularly to achieve repeatable impedance values using single station MT data. The conventional impedance estimation technique requires solution of a linear equation system (E = ZH) based on Gaussian statistical model which requires the noise of electric channels should obey Gaussian distribution and magnetic channels should be noise free. In fact, measured data never provides this ideal condition. Therefore, noise elimination techniques are very important step in data processing works in MT method. Random noise such as spikes makes deviations in impedance values, resistivity and phase curves. Random noise should be eliminated to correct of these deviations in the data. For this purpose firstly, all data are divided into time windows. Each window consists of 512 values. After that, spikes are removed and missing data are regenerated by using interpolation technique for each window in time domain. Then, data are

  8. 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

  9. EMT - Empirical-mode-decomposition-based Magneto-Telluric Processing

    NASA Astrophysics Data System (ADS)

    Neukirch, M.; Garcia, X.

    2012-04-01

    We present a new Magneto-Telluric (MT) data processing scheme based on an emerging non linear, non stationary time series analysis tool, called the Empirical Mode Decomposition (EMD) or Hilbert-Huang Transform (HHT), to transform data into a non-stationary frequency domain and a robust principal component regression to estimate the most likely MT transfer functions from the data with the 2-σ confidence intervals computed by a bootstrap algorithm. Optionally, data quality can be controlled by a physical coherence and a signal power filter. MT sources are assumed to be quasi stationary and therefore a (windowed) Fourier Transform is often applied to transform the time series into the frequency domain in which Transfer Functions (TF) are defined between the electromagnetic field components. This assumption can break down in the presence of noise or when the sources are non stationary, and then TF estimates can become unreliable when obtained through a stationary transform like the Fourier transform. Our TF estimation scheme naturally deals with non stationarity without introducing artifacts and, therefore, potentially can distinguish quasi-stationary sources and non-stationary noise. In contrast to previous works on using HHT for MT processing, we argue the necessity of a multivariate EMD to model the MT problem physically correctly and highlight the resulting possibility to use instantaneous parameters as independent and identically distributed variables. Furthermore, we define a homogenization between data channels of frequency discrepancies due to non stationarity and noise. The TF estimation in the frequency domain bases on a robust principal component analysis in order to find two source polarizations. These two principal components are used as predictor to regress robustly the data channels within a bootstrap algorithm to estimate the Earth's Transfer function with 2-σ confidence interval supplied by the measured data.The scheme can be used with and without

  10. 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

  11. Linking numerical models of lithospheric deformation and magnetotelluric images

    NASA Astrophysics Data System (ADS)

    Sobolev, S. V.

    2012-12-01

    Efficient modeling of geodynamic processes requires constraints from different fields of geosciences. Frequently used are data on crustal structure and composition and their evolution constrained by seismic, gravity and petrological/geochemical studies. However, links between geodynamic modeling and rapidly developing field of magnetotelluric (MT) studies are still insufficient. I'll consider two recent examples of MT observations and geodynamic modeling demonstrating that joint analyses of thermomechanical models of lithospheric deformation and MT images may be useful to understand geodynamic processes. One set of observations is MT data for San Andreas Fault (SAF) in the region close to the SAFOD Site (Becken et al., 2011) that shows high conductivity anomalies in the mantle, that are interpreted as fluid flow feeding creeping part of SAF south of the SAFOD Site. Interestingly, zones of high conductivity do not coincide with the expected zones of the recent active deformation (SAF), but are located to the west of it. Based on thermomechanical model of the evolution of the SAFS in Central and Northern California during the last 20 Mln. years (Popov et al., 2012), I'll demonstrate that high conductivity anomalies precisely coincide with the expected zones of the highest accumulated shear strain. Possible interpretation of this coincidence is that strong preferred orientation of olivine crystals in the highly deformed mantle shear zone causes high permeability of fluids. Another set of observations is MT data showing high conductivity anomalies in the crust of Tibet (Unsworh et al., 2005, Bai et al., 2010) and Pamirs (Sass et al., 2011) that are often interpreted as an evidence for the widely spread partially molten crust. Using 2D thermomechanical models of the collision between India and Eurasia, I'll demonstrate that such structures in the crust cannot appear without delamination of the mantle lithosphere during tectonic shortening. Internal heating of the

  12. Magnetotelluric soundings on the Idaho National Engineering Laboratory Facility, Idaho

    NASA Astrophysics Data System (ADS)

    Stanley, William D.

    1982-04-01

    The magnetotelluric (MT) method was used as one of several geophysical tools to study part of the Idaho Engineering Laboratory (INEL) facility. The purpose of the geophysical study on INEL was to investigate the facility for a possible site to drill a geothermal exploration well. A successful geothermal well would be used to provide hot water for a chemical processing plant. The MT method was employed to map any large-scale structures or conductivity anomalies that might prove interesting as geothermal exploration targets. In addition to the MT data, direct current resistivity soundings, gravity data, aeromagnetic data, and seismic refraction data were obtained in the course of the geophysical study. In the MT survey described in this paper, an additional goal was to provide a better understanding of the electrical units mapped in the regional study of the Snake River Plain (SNRP) by Stanley et al. (1977). It was thought that a widespread conductive layer found beneath surface basalts in the 1977 study could be categorized petrologically by a deep well and additional MT soundings done nearby. Also, INEL is located on the margin of the SNRP, and it was desired to have MT data in the area to study the electrical nature of the margin of the plain. The MT sounding interpretations did not indicate any conductivity anomalies or significant structures near the chemical processing plant which could be used to guide the location of the proposed geothermal well to be drilled to a depth of 3 km. The initial interpretation of the MT sounding data was done with one-dimensional models consisting of four or five layers, the minimum number required to fit the data. After the test well (INEL-1) was completed, the electric log was used to guide an improved one-dimensional ID interpretation of the MT sounding data. Profile models derived from the well log provided good agreement with velocity models derived from refraction seismic data. A resolution study using generalized inverse

  13. The Skellefte Ore District as seen with magnetotellurics

    NASA Astrophysics Data System (ADS)

    de los Ángeles García Juanatey, María; Hübert, Juliane; Tryggvason, Ari; Juhlin, Christopher; Pedersen, Laust B.; Bauer, Tobias E.; Dehghannejad, Mahdieh; Weihed, Pär

    2013-04-01

    The Skellefte District is one of the richest metallogenic mining areas in Sweden. The main deposits consist of volcanic-hosted massive sulphides (VHMS) rich in zinc, copper, lead, gold and silver, that have been explored and mined for more than a century. Considering that technological advancements allow deeper mining, and that today new discoveries occur less often, new efforts have been directed at locating targets at greater depths. Thus, current exploration strategies need to be adjusted, and a better understanding of regional scale structures is necessary. Following this approach the project "VINNOVA 4D modeling of the Skellefte District" was launched. Its main purpose was to unravel the regional structures and tectonic setting of the Skellefte District and construct a 3D geological model of two key localities within the district. To help accomplish this, magnetotelluric (MT) data were acquired throughout the district together with seismic reflection, geoelectric (ERT and IP) and potential field data. The MT data set consists of 120 stations that were mainly acquired along existing seismic lines. Time series processing yielded MT transfer functions in the frequency range between 700 Hz and 200 s. These data were inverted into 2D resistivity depth sections and subsequently analyzed to identify robust features. Additionally, 3D inversions were computed and compared with the standard 2D results to assess their reliability and better locate conductive bodies. The resistivity features deemed trustworthy were then interpreted in geological terms. For this task, results from the other geophysical methods were considered. The achieved penetration depth varied between 10 and 20 km. The main findings include: (1) conductive hydrothermally altered zones are present within the otherwise resistive rocks of the ore-bearing volcanic units, (2) the depth extension of early and post-orogenic intrusions are depicted as high resistivity features, (3) several prominent conductive

  14. “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

  15. 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.

  16. Magnetotelluric Phase Tensor Applications to Geothermal Assessment in New Zealand and New Mexico

    NASA Astrophysics Data System (ADS)

    Jiracek, G. R.; Feucht, D. W.; Brown, D.; Castro, B.; Chang, J.; Goff, D.; Hardwick, C.; Hollingshaus, B.; Bowles-martinez, E.; Nakai, J.; Wilson, C.; Bertrand, E. A.; Bennie, S.; Caldwell, G.; Hill, G. J.; Wallin, E.; Bedrosian, P. A.; Hasterok, D. P.; Pellerin, L.

    2012-12-01

    Magnetotelluric (MT) phase tensor analysis preserves the background (regional) phase response irrespective of galvanic distortion even if distorting inhomogeneities change between multiple MT deployments. This characteristic is the basis for repeat MT monitoring of the South Karapiti, New Zealand region near the Wairakei Power Station where 1-2 km-deep reinjection of spent geothermal fluids will commence soon. Deep electrical conductivity changes caused by this injection may be detected by background phase tensor changes independent of possible surficial changes, e.g., from drilling operations, or from differing sensor alignments during the multi-MT occupations. In 2010-2012 twenty MT sites within 1.5 km of a newly-drilled injection well were reoccupied by New Zealand GNS scientists and US students from NSF's International Research Experiences for Students program. Maps of phase tensor ellipses at various frequencies have identified frequency bands exhibiting good repeatability, therefore, they are potentially useful for detection of future brine injection. Final reoccupation of the MT sites is scheduled in 2013 after a large brine injection. In New Mexico, the 2012 SAGE program (Summer of Applied Geophysical Experience) applied phase tensor analysis to 8 MT soundings aimed at understanding the occurrence of anomalously high vertical and horizontal temperature gradients located approximately 25 km NW of Santa Fe. Plots of phase tensor ellipses allowed unique, distortion-free visualization of the dimensionality and directions of background geoelectric variations. Analysis of the plots as functions of frequency and location revealed a nearly one-dimensional (1-D) upper conductive (sedimentary) section. Variations in the orientations of the principal axes of phase tensor ellipses exposed an overall, deeper three-dimensional (3-D) geoelectric structure in the region. However, two sequential frequency bands revealed dominantly two-dimensional (2-D) regional features

  17. 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.

  18. 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.

  19. African and African Caribbean users' perceptions of inpatient services.

    PubMed

    Secker, J; Harding, C

    2002-04-01

    It has been suggested that well-documented differences in African and African Caribbean people's contact with mental health services may stem from the organization, processes and practices of services themselves. This article presents the findings of a qualitative study which explored the inpatient experiences of a sample of African and African Caribbean people. Although some positive experiences were described, in the main, participants' accounts revolved around a sense of loss of control and around experiences of overt and implicit racism. Underpinning these experiences were relationships with staff that were perceived to be unhelpful. On the basis of both the positive and negative experiences described, we draw conclusions about the changes required to ensure that inpatient services more effectively meet the needs of this group.

  20. "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…

  1. 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

  2. Experiences of racial discrimination and relation to sexual risk for HIV among a sample of urban black and African American men.

    PubMed

    Reed, E; Santana, M C; Bowleg, L; Welles, S L; Horsburgh, C R; Raj, A

    2013-04-01

    This study aimed to examine racial discrimination and relation to sexual risk for HIV among a sample of urban black and African American men. Participants of this cross-sectional study were black and African American men (N = 703) between the ages of 18 and 65 years, recruited from four urban clinical sites in the northeast. Multivariate logistic regression models were used to analyze the relation of reported racial discrimination to the following: (1) sex trade involvement, (2) recent unprotected sex, and (3) reporting a number of sex partners in the past 12 months greater than the sample average. The majority of the sample (96%) reported racial discrimination. In adjusted analyses, men reporting high levels of discrimination were significantly more likely to report recent sex trade involvement (buying and/or selling) (adjusted odds ratio (AOR) range = 1.7-2.3), having recent unprotected vaginal sex with a female partner (AOR = 1.4, 95% confidence interval (CI), 1.1-2.0), and reporting more than four sex partners in the past year (AOR = 1.4, 95% CI, 1.1-1.9). Findings highlight the link between experiences of racial discrimination and men's sexual risk for HIV.

  3. Very Long Period Magnetotelluric Data Across the India-Asia Collision Zone

    NASA Astrophysics Data System (ADS)

    Spratt, J. E.; Jones, A. G.; Nelson, K. D.; Unsworth, M. J.

    2002-12-01

    The collision of the Indian subcontinent with Asia is unparalleled - it offers the holy grail for interpreting the cryptic rock record of ancient collisional orogens, and provides a benchmark for testing evolutionary theories of tectonic processes. But, despite its importance, it remains poorly studied. Project INDEPTH was initiated in 1992 to advance our knowledge of the Tibetan Plateau, and magnetotelluric surveying was added during INDEPTH II in 1995. Broadband and long period data were acquired in 1995 along a N-S transect crossing the India-Asia collision zone, the Indus-Zangbo suture, at ~90° E longitude. However, these data failed to penetrate to mantle depths due to:\\ (1) Sunspot activity was at its lowest in the last 11-year solar cycle,\\ (2) Tibetan crust is doubly-thickened, with Moho depth estimates of >70 km, and\\ (3) Crustal conductivity is high at depths below about 20 km, and penetration beyond ~40 km was not possible.Mantle information is key for this region to provide a test of the model of subcretion to southern Tibet by the stiff Indian mantle lid. In order to obtain deep crustal and upper mantle information, an ultra-long period experiment was performed across the suture in 2001 as a component of a second Indus-Zangbo-crossing profile. It was planned to acquire two months of data at each of the five ultra-long period sites, but a series of problems resulted in inadequate data for most sites, with the exception of reasonable data at one site just north of the suture. Preliminary processing of the data from that site indicates upward-trending \\rhoa curves beyond 2,000 s, suggestive of an upper mantle resistive layer than could be the subcreted Indian mantle lid. Further processing and modeling will be shown. This second profile also permits comparison of possible along-strike variation of the Indus-Zangbo suture by comparing the results obtained from this survey with those obtained in 1995.

  4. A new seafloor electromagnetic station with an Overhauser magnetometer, a magnetotelluric variograph and an acoustic telemetry modem

    NASA Astrophysics Data System (ADS)

    Toh, Hiroaki; Goto, Tadanori; Hamano, Yozo

    1998-11-01

    A new type of SeaFloor ElectroMagnetic Station (SFEMS) has been newly developed by adding a magnetotelluric (MT) variograph to its prototype built previously (Toh and Hamano, 1997). New SFEMS is able to conduct long-term electromagnetic (EM) observations at the seafloor, which is one of the principal goals of the Ocean Hemisphere Project (OHP). Long-term seafloor EM observations enable us to probe into the deep Earth (both the mantle and the core) by improving the spatial coverage of the existing EM observation network. The SFEMS has been tested in three sea experiments to yield 3 components of the geomagnetic field, 2 horizontal components of the geoelectric field and 2 components of tilts in addition to the absolute geomagnetic total force. The SFEMS is designed for measuring these EM signals at the seafloor continuously for as long as 2 yrs. The SFEMS mainly consists of the following three parts: (1) An Overhauser proton precession magnetometer for the absolute measurements of the geomagnetic total force with a possible bias of less than 10 nT. (2) An MT variograph that measures the rest of the EM components and tilt. (3) An Acoustic Telemetry Modem (ATM) that allows us to control/monitor the seafloor instrument as well as data transmission at the maximum rate of 1200 baud. Construction of seafloor EM observatories in regions where significant EM data have never been collected is now quite feasible by development of the SFEMS.

  5. 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)

  6. "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

  7. "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.

  8. 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.

  9. The potential impact of pneumococcal conjugate vaccine in Africa: Considerations and early lessons learned from the South African experience

    PubMed Central

    Madhi, Shabir A; Nunes, Marta C

    2016-01-01

    The introduction of pneumococcal conjugate vaccine (PCV) into the South African public immunization program since 2009 adopted a novel vaccination schedule of 3 doses at 6, 14 and 40 weeks of age. Over the past 5 y it has been shown that infant PCV immunization in South Africa is effective in reducing the burden of invasive pneumococcal disease (IPD) among HIV-infected and HIV-uninfected children. Furthermore, indirect protection of unvaccinated age-groups (including high risk groups such as HIV-infected adults) against IPD was demonstrated despite the absence of any substantial catch-up campaign of older children. This indirect effect against IPD is corroborated by the temporal reduction in vaccine-serotype colonization among age-groups targeted for PCV immunization as well as unvaccinated HIV-infected and HIV-uninfected adults, which was evident within 2 y of PCV introduction into the immunization program. Vaccine effectiveness has also been demonstrated in children against presumed bacterial pneumonia. The evaluation of the impact of PCV in South Africa, however, remains incomplete. The knowledge gaps remaining include the evaluation of PCV on the incidence of all-cause pneumonia hospitalization among vaccinated and unvaccinated age-groups. Furthermore, ongoing surveillance is required to determine whether there is ongoing replacement disease by non-vaccine serotypes, which could offset the early gains associated with the immunization program in the country. PMID:26317537

  10. Adolescent experiences of violence and relation to violence perpetration beyond young adulthood among an urban sample of Black and African American males.

    PubMed

    Reed, Elizabeth; Lawrence, Danielle A; Santana, M C; Welles, C Seth L; Horsburgh, C Robert; Silverman, Jay G; Rich, John A; Raj, Anita

    2014-02-01

    The purpose of this study is to determine if experiences of physical violence during early and late adolescence (12-21 years) places urban Black males at increased risk for interpersonal violence perpetration beyond young adulthood (30 years and older). Participants of this cross-sectional study were Black and African American men (N = 455) between the ages of 30 and 65 years, recruited from four urban clinical sites in the Northeast. Multivariate logistic regression models were used to analyze the relation of adolescent experiences of violence to: (1) past 6 month street violence involvement and (2) past year intimate partner violence perpetration. Ten percent of the sample reported that they experienced adolescent victimization. Men reporting adolescent victimization were significantly more likely to report past 6-month street violence involvement (Adjusted Odds Ratio (AOR) = 3.2, 95 % CI = 1.7-6.3) and past 6 month intimate partner violence perpetration (AOR = 2.8, 95 % CI = 1.8-5.4) compared to men who did not report such victimization. Study findings suggest that in order to prevent adulthood perpetration of violence, more work is needed to address experiences of victimization among young Black males, particularly violence experienced during adolescence.

  11. 1D and 2D Occam's Inversion of Magnetotelluric Data Applied in Volcano-Geothermal Area In Central Java, Indonesia

    NASA Astrophysics Data System (ADS)

    Ariani, Elsi; Srigutomo, Wahyu

    2016-08-01

    One-dimensional (1D) and two-dimensional (2D) magnetotelluric data inversion were conducted to reveal the subsurface resistivity structure beneath the eastern part of a volcano in Central Java, Indonesia. Fifteen magnetotelluric sounding data spanning two lines of investigation were inverted using Occam's inversion scheme. The result depict that there are extensively conductive layer (2-10 ohm meter) below the volcanic overburden. This conductive layer is interpreted as the clay cap resulted from thermal alteration. A higher resistivity layer (10-80 ohm meter) underlies the clay cap and is interpreted as the reservoir whose top boundaries vary between 1000 m above and 2000 m below sea level.

  12. 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

  13. 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.

  14. 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…

  15. 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

  16. 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

  17. Testing the Accuracy of Aerial Surveys for Large Mammals: An Experiment with African Savanna Elephants (Loxodonta africana)

    PubMed Central

    Schlossberg, Scott; Chase, Michael J.; Griffin, Curtice R.

    2016-01-01

    Accurate counts of animals are critical for prioritizing conservation efforts. Past research, however, suggests that observers on aerial surveys may fail to detect all individuals of the target species present in the survey area. Such errors could bias population estimates low and confound trend estimation. We used two approaches to assess the accuracy of aerial surveys for African savanna elephants (Loxodonta africana) in northern Botswana. First, we used double-observer sampling, in which two observers make observations on the same herds, to estimate detectability of elephants and determine what variables affect it. Second, we compared total counts, a complete survey of the entire study area, against sample counts, in which only a portion of the study area is sampled. Total counts are often considered a complete census, so comparing total counts against sample counts can help to determine if sample counts are underestimating elephant numbers. We estimated that observers detected only 76% ± SE of 2% of elephant herds and 87 ± 1% of individual elephants present in survey strips. Detectability increased strongly with elephant herd size. Out of the four observers used in total, one observer had a lower detection probability than the other three, and detectability was higher in the rear row of seats than the front. The habitat immediately adjacent to animals also affected detectability, with detection more likely in more open habitats. Total counts were not statistically distinguishable from sample counts. Because, however, the double-observer samples revealed that observers missed 13% of elephants, we conclude that total counts may be undercounting elephants as well. These results suggest that elephant population estimates from both sample and total counts are biased low. Because factors such as observer and habitat affected detectability of elephants, comparisons of elephant populations across time or space may be confounded. We encourage survey teams to

  18. 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,…

  19. 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…

  20. 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.

  1. Electrical conductivity structure of north-west Fennoscandia from three-dimensional inversion of magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Cherevatova, M.; Smirnov, M. Yu.; Korja, T.; Pedersen, L. B.; Ebbing, J.; Gradmann, S.; Becken, 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 simultaneous long period and 220 broad-band MT sites were occupied in the summers of 2011 to 2013. The 3-D inversion of the MaSca data was obtained using the ModEM 3-D code. The full impedance and tipper data were used for the inversion. The rocks of Archaean and Proterozoic basement towards east and the Caledonian nappes towards west are modelled as resistive structures. In the central and southern parts, the whole crust is resistive and reflects the Trans-Scandinavian Igneous Belt granitoids. The middle to lower crust of the Svecofennian province is conductive. An uppermost crustal conductor is revealed in the Skellefteå Ore District. The south 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. A map of the crustal conductance for the north-west Fennoscandian Shield is presented.

  2. Magnetotelluric evidence for crustal suture zones bounding the southern Great Valley, California

    SciTech Connect

    Park, S.K.; Biasi, G.P. ); Mackie, R.L.; Madden T.R. )

    1991-01-10

    A geoelectric section inferred from a regional magnetotelluric study across the Coast Ranges, the Great Valley, and the Sierra Nevada reveals significant variations in electrical resistivity. Zones of lower resistivity interpreted at depths from 10 km to at least 30 km lie near mapped geologic boundaries between the Coast Ranges and the Great Valley and beneath the eastern side of the Great Valley. The former boundary is inferred by others to separate the subduction complex of the Coast Ranges from the mafic basement of the Great Valley. The lower resistivities are most likely associated with metasediments trapped between the Coast Ranges ophiolite and the former oceanic crust beneath the Great Valley. The latter boundary is problematic, but may be evidence for a deep metasedimentary section trapped between the ophiolites beneath the Great Valley and granitic rocks of the Sierra Nevada. The lack of change in the magnetotelluric phase across the Great Valley indicates that a suture zone marked by lower resistivities is unlikely to be present beneath the valley. However, this does not preclude the existence of a resistive suture zone.

  3. 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.

  4. Deep Magnetotelluric survey on Crete Island across the Hellenic Subduction Zone

    NASA Astrophysics Data System (ADS)

    Kalisperi, D.; Smirnov, M.; Kokologiannakis, A.; Pentes, G.; Makris, J. P.

    2013-12-01

    Crete Island is located in a prominent position at the fore-arc of the Hellenic Subduction Zone (HSZ), thus enabling onshore study of the Earth's deep structure. The area is characterized by a complicated geological and geotectonic setting as well as by intense geodynamics that manifests itself in high seismicity. 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 try to image the Hellenic Subduction Zone. In this context, onshore magnetotelluric (MT) measurements were carried out in July 2013 on Crete Island, comprising three parallel profiles aligned to the North-South (NS) direction, yielding a site spacing of about 5 to 10 km. In total, 21 broad-band MT soundings were conducted in the period range of 0.003-1000 s organized in the three 36Km, 30Km and 42Km long NS trending profiles. Data were collected using two different types of MT instruments (an EMI MT24LF and two Uppsala type MTU2000 systems) which were running simultaneously. We present the resulting model of the conductivity structure of the HSZ in the area of Crete.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Two dimension magnetotelluric modeling using finite element method, incomplete lu preconditioner and biconjugate gradient stabilized technique

    NASA Astrophysics Data System (ADS)

    Zukir, Muhammad; Srigutomo, Wahyu

    2016-08-01

    Magnetotelluric (MT) method is a passive geophysical exploration technique utilizing natural electromagnetic source to obtain variation of the electric field and magnetic field on the surface of the earth. The frequency range used in this modeling is 10-4 Hz to 102 Hz. The two-dimensional (2D) magnetotelluric modeling is aimed to determine the value of electromagnetic field in the earth, the apparent resistivity, and the impedance phase. The relation between the geometrical and physical parameters used are governed by the Maxwell's equations. These equations are used in the case of Transverse Electric polarization (TE) and Transverse Magnetic polarization (TM). To calculate the solutions of electric and magnetic fields in the entire domain, the modeling domain is discretized into smaller elements using the finite element method, whereas the assembled matrix of equation system is solved using the Biconjugate Gradient Stabilized (BiCGStab) technique combined with the Incomplete Lower - Upper (ILU) preconditioner. This scheme can minimize the iteration process (computational cost) and is more effective than the Biconjugate Gradient (BiCG) technique with LU preconditions and Conjugate Gradient Square (CGS).

  10. "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…

  11. Differences in African-American and European-American Students' Engagement with Nanotechnology Experiences: Perceptual Position or Assessment Artifact?

    ERIC Educational Resources Information Center

    Jones, M. Gail; Tretter, Thomas; Paechter, Manuela; Kubasko, Dennis; Bokinsky, Alexandra; Andre, Thomas; Negishi, Atsuko

    2007-01-01

    This study examined middle and high school students' perceptions of a weeklong science experience with nanotechnology and atomic force microscopy. Through an examination of student self assessments and their writing, the study allowed us to examine some of the issues that may contribute to discrepancies that are seen between European-American and…

  12. Joint Interpretation of Magnetotellurics and Airborne Electromagnetics in the Rathlin Basin, Northern Ireland

    NASA Astrophysics Data System (ADS)

    Delhaye, Robert; Rath, Volker; Jones, Alan G.; Reay, Derek; The Iretherm Team

    2015-04-01

    In this study we present results from geophysical investigation of the sedimentary Rathlin Basin in Northern Ireland in order to assess the potential for low-to-medium enthalpy geothermal aquifers within the porous Permian and Triassic sandstone groups. The area and groups were identified as a potential geothermal resource due to the presence of both an elevated geothermal gradient (observed in two deep boreholes onshore) and favourable hydraulic properties (measured on core samples in the offshore part of the basin). Previous seismic experiments were not able to fully characterise the sediments beneath the overlying flood basalt. Complementing these earlier results, magnetotelluric data were acquired on a grid of 56 sites across the north-eastern portion of the onshore Rathlin Basin, and an additional 12 sites on the nearby Rathlin Island, in order to image the thickness, depth, and lateral continuity of the target sediments. Analysis and 3D modelling, including the effects of the highly conducting ocean, has been successful in deriving a resistivity model that maps the variation in the top of the sediments (base of the basalts) and the truncation of the basin sediments against the Tow Valley Fault, and gives a reasonable estimate of the thickness of the sediment fill. However, the resulting models show significant effects from distortion caused by near-surface inhomogeneities in the responses that cannot be resolved using the given frequency range and site density. Fortunately, for the area of Rathlin Basin, airborne electromagnetic data from the TELLUS project (http://www.bgs.ac.uk/gsni/tellus/contact/index.html) are available. These data were measured at four frequencies between 0.9 kHz and 25 kHz in a verical-coplanar loop configuration, with the dipole axis in flight direction. The spatial sampling distance was less than 25 m, with about 200 m distance between flight lines. Survey altitudes vary between 56 m and 244 m. Thus, for the top ˜100 m penetrated by

  13. 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.

  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. 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…

  16. "African Connection."

    ERIC Educational Resources Information Center

    Adelman, Cathy; And Others

    This interdisciplinary unit provides students in grades kindergarten through seventh grade an opportunity to understand diversity through a study of Africa as a diverse continent. The project is designed to provide all elementary students with cultural enrichment by exposing them to African music, art, storytelling, and movement. This project can…

  17. 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

  18. 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

  19. '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

  20. Synthesize function for describing distorted 2-D magnetotelluric responses caused by topography

    NASA Astrophysics Data System (ADS)

    Promdee, Ninrat; Sarakorn, Weerachai

    2016-04-01

    In this research, the distortions of 2-D magnetotelluric responses caused by topographies are described by an appropriated synthesize functions. The damping wave equations and the considered topographic curves are used as the kernel of selected synthesize functions. The parameters of those functions are estimated by using the randomized neighborhood search method. The validity of functions is tested on half-space and COMMEMI2D-1 models with cosinusoidal, Gaussian and logistic topographic curves. The obtained results indicate that distorted apparent resistivity are well described by the selected synthesize functions with an acceptable root mean square errors. The obtained values of parameters are varied on both periods of EM wave and height of topographies.

  1. Indication of meta-anthracite by magnetotellurics in the Köszeg-Rechnitz Penninic window

    NASA Astrophysics Data System (ADS)

    Novák, Attila; Ádám, Antal; Prácser, Ernő

    2013-04-01

    In the Eastern end of the Eastern Alps - at the Austrian-Hungarian border - there are Pennninic Nappes among them the Köszeg-Rechnitz tectonic window having complicated metamorphic history from the Jurassic time. The organic material of the Penninic Ocean transformed to meta-anthracite. Its amount in the calc-phyllite has been estimated by the geochemists to 0.2 percent. Magnetotelluric soundings have been carried out to determine: - the resistivity decrease due to the above amount of conductive material, - the different EM distortions in E and B polarization caused by the conductor near and far from it, - the asthenospheric depth in the area of the tectonic window stepping out from the shallow asthenosphere of the Pannonian Basin, - looking for relation between geoelectric and seismic crustal structures.

  2. Analytical investigations of the magnetotelluric directionality estimation in 1-D anisotropic layered media

    NASA Astrophysics Data System (ADS)

    Okazaki, T.; Oshiman, N.; Yoshimura, R.

    2016-11-01

    Inferring geoelectric dimensionality (1D, 2D or 3D) and directionality (strike directions) from the impedance tensor is a basic procedure in magnetotelluric data processing. Given that electrical anisotropy is increasingly recognized in observations, it is valuable to understand the imprint of anisotropy in these analyses. In this paper, we analytically investigate the estimation of strike directions based on rotational invariants in 1D anisotropic layered media. We first show that if anisotropy axes are identical in all anisotropic layers, the estimated strike coincides with that direction. We then derive an analytical formula of the strike angle at long periods for general anisotropic layers with an isotropic basement. This formula shows a clear physical interpretation that the strike angle points where the conductance integrated along depth takes a maximum value.

  3. 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.

  4. 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.

  5. 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.

  6. High-resolution lithosphere viscosity and dynamics revealed by magnetotelluric imaging

    NASA Astrophysics Data System (ADS)

    Liu, Lijun; Hasterok, Derrick

    2016-09-01

    An accurate viscosity structure is critical to truthfully modeling lithosphere dynamics. Here, we report an attempt to infer the effective lithospheric viscosity from a high-resolution magnetotelluric (MT) survey across the western United States. The high sensitivity of MT fields to the presence of electrically conductive fluids makes it a promising proxy for determining mechanical strength variations throughout the lithosphere. We demonstrate how a viscosity structure, approximated from electrical resistivity, results in a geodynamic model that successfully predicts short-wavelength surface topography, lithospheric deformation, and mantle upwelling beneath recent volcanism. We further show that this viscosity is physically consistent with and better constrained than that derived from laboratory-based rheology. We conclude that MT imaging provides a practical observational constraint for quantifying the dynamic evolution of the continental lithosphere.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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 ...

  12. 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…

  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. South African Education Program: An Evaluation Report.

    ERIC Educational Resources Information Center

    Ladd, Florence C.

    Consequences of participation in the South African Education Program, which enabled 290 South Africans to study in the United States between 1979 and 1985, were evaluated. Attention was directed to outcomes of participation and the educational experience and intellectual and social growth experienced by the students and alumni, who were Black…

  15. Problems of Transition for African Students in an American University.

    ERIC Educational Resources Information Center

    Adelegan, Francis O.; Parks, David J.

    1985-01-01

    Surveyed Black East African, Black West African and Arabic North African students (N=33) enrolled in an American university to identify their problems and personal attributes and environmental conditions influencing their experience. Discusses social, transportation, food, loneliness, and other problems. (MCF)

  16. 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

  17. Exploring the Experiences of African American Women in an Undergraduate Summer Research Program Designed to Address the Underrepresentation of Women and Minorities in Neuroscience: A Qualitative Analysis

    ERIC Educational Resources Information Center

    Reid, Ericka L.

    2010-01-01

    African American women compose a critical proportion of the potential science, technology, engineering, and mathematics (STEM) workforce of the future, yet are disproportionately represented and largely underutilized. While various programs and initiatives have been designed and implemented to target women and underrepresented minorities, the…

  18. 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,…

  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. 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…

  1. Therapy with African Families.

    ERIC Educational Resources Information Center

    Nwadiora, Emeka

    1996-01-01

    Informs helping professionals about the unique history and challenges of African families to guide them toward providing ethnically sensitive psychological services to African immigrant families in need. African families undergo great stress when faced with the alienation of being Black and African in a Euro-American culture. (SLD)

  2. 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…

  3. 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…

  4. 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.

  5. 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

  6. New explanation of an old magnetotelluric observation: source rock of the Transdanubian Range Conductivity Anomaly ascertained

    NASA Astrophysics Data System (ADS)

    Németh, Viktória; Horváth, Frank; Tari, Gabor; Wesztergom, Viktor

    2014-05-01

    The so-called Transdanubian Conductivity Anomaly (TCA) at the Hungarian part of the NW Pannonian Basin has been well known for nearly four decades. Hungarian research institutions carried out several magnetotelluric soundings and exceptionally low resistivity (i.e. 1-2 Ohmm) zones were found with a large areal extent (on the order of few thousand square km). The low resistivity bodies are situated in the depth range of 4 to 10 km and no surface outcrops of such a highly conducting rock mass can be found in Hungary. This enigmatic geophysical anomaly was explained in a number of ways by different authors, invoking sub-horizontal Alpine nappe contacts to subvertical dikes with graphite and/or saline fluid content. Only one possible outcrop area of the high conductivity anomaly was considered so far, in the Drauzug/Gailtal area of the Eastern Alps in Austria, some 300 km to the West from the anomaly area. Whereas there were previous attempts to find correspondence between the TCA and prominent seismic reflectors seen on 2D seismic reflection profiles, in this study we have systematically correlated, for the first time, the TCA with modern 2D and 3D industry seismic reflection data. Our results show a very strong correlation between the subsurface extent and position of TCA and various sub-horizontal Cretaceous Alpine nappe surfaces. In addition, we drew on the latest structural correlation of the Alpine nappe stack of the Transdanubian Central Range with its proper tectonic counterpart in the Eastern Alps. At the southern edge of the Upper Austroalpine units in northern Styria, in the Veitsch Nappe of the Greywacke Zone, numerous graphite localities are known historically. We propose that the best explanation for the observed extent and geometry of the TCA is the presence of graphite in subhorizontal, tectonically thinned detachment surfaces in the Upper Austroalpine nappe edifice of NW Hungary. This explanation is supported by reinterpretation of old magnetotelluric

  7. 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

  8. 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

  9. 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

  10. 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

  11. (An)isotropic 3D Array Magnetotelluric Modeling of the South Western Vogelsberg Area

    NASA Astrophysics Data System (ADS)

    Junge, A.; Löwer, A.

    2013-12-01

    The Vogelsberg is the largest volcanic region in Central Europe with an area of 2100sqkm. It covers the Phyllitzone, which marks the border between the Rhenoherzynikum and the Moldanubikum. The structural fabric in this zone is predominantly arranged NW-SE and correlated with the variscan strike direction. Because of huge basalt layers the exact extension of the Phyllitzone in the Vogelsberg region could not be verified by drillings. Another fault is the Horloff-Graben, which crosses the Phyllitzone with a NNW-SSE strike direction and is an extension of the Upper-Rhine-Graben to the north. Recent seismicity signifies a weak active fault zone which is reaching the middle crust. In the southwest Vogelsberg area plenty mineral and thermal waters appear whose origin is under controversial discussion. The conductivity structure beneath the Vogelsberg area was investigated with the magnetotelluric method. This method uses natural time depending variations of the earth's electric and magnetic field, their sources originate e.g. in electric currents in the ionosphere for low-frequencies and lightning for high-frequencies. The method responds to conductivity contrasts beneath the surface which might be graphite, free fluids and/or partial melts. The Phyllitzone is supposed to have an anisotropic conductivity structure and should therefore be differentiable from the bedrock of the mid-German crystalline rise and the sediment covering of the Horloff Graben. The targets of these studies are the differentiation and search for the extension of the geological structures beneath the Vogelsberg basalt, particularly those from the Phyllitzone, the mid-German crystalline rise and the Horloff-Graben, and also their importance for the exploration of hydrological and geothermal resources. A 3D array with 25 broadband magnetotelluric stations was set up during winter 2010/11 and 2011/12 in an area of about 300 square miles south west of the Vogelsberg. Thus it is covering the Horloff

  12. 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

  13. 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…

  14. 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…

  15. An Ambivalent Community: International African Students in Residence at a South African University

    ERIC Educational Resources Information Center

    Weber, Everard

    2016-01-01

    This is a qualitative case study of the experiences and perceptions of South African and especially international, African students living in university residences in South Africa. The concept, community, is used to interpret interview data. This community was characterised by ambivalent social relations: There was discrimination by South Africans…

  16. 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…

  17. 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.

  18. 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.

  19. Web-based application for inverting one-dimensional magnetotelluric data using Python

    NASA Astrophysics Data System (ADS)

    Suryanto, Wiwit; Irnaka, Theodosius Marwan

    2016-11-01

    One-dimensional modeling of magnetotelluric (MT) data has been performed using an online application on a web-based virtual private server. The application was developed with the Python language using the Django framework with HTML and CSS components. The input data, including the apparent resistivity and phase as a function of period or frequency with standard deviation, can be entered through an interactive web page that can be freely accessed at https://komputasi.geofisika.ugm.ac.id. The subsurface models, represented by resistivity as a function of depth, are iteratively improved by changing the model parameters, such as the resistivity and the layer depth, based on the observed apparent resistivity and phase data. The output of the application displayed on the screen presents resistivity as a function of depth and includes the RMS error for each iteration. Synthetic and real data were used in comparative tests of the application's performance, and it is shown that the application developed accurate subsurface resistivity models. Hence, this application can be used for practical one-dimensional modeling of MT data.

  20. Application of Mixture of Gaussian Clustering on Joint Facies Interpretation of Seismic and Magnetotelluric Sections

    NASA Astrophysics Data System (ADS)

    Shahrabi, Mohammad Ali; Hashemi, Hosein; Hafizi, Mohammad Kazem

    2016-02-01

    Seismic and magnetotelluric (MT) methods are the most applicable geophysical methods in exploration of hydrocarbon resources. In this paper, mixture of Gaussian clustering is used to combine seismic and MT images under the scheme of Expectation/Maximization (EM) algorithm. Pre-Stack Depth Migration (PSDM) velocity, Root Mean Square (RMS) velocity and vertical gradient of RMS velocity of seismic and resistivity model of MT along 19.3 km MUN-21 profile in Munir Block that has been located in Southwest of Iran in Dezful embayment over the Seh-Qanat anticline are applied. The anticline is the most important oil trap of this area. The Expectation/Maximization (EM) method that has been applied includes: (1) creation of data vectors from the seismic and MT images using image processing techniques, (2) normalizing and mapping using Principal Component Analysis (PCA) procedure (3) unsupervised learning of dataset matrix, (4) setting the matrix in Expectation/Maximization (EM) iteration algorithm (5) remapping to physical space. The final model consists fof six classes which could be given to eight formations that belong to Eocene to Neocomian geological age. Pre-Stack Depth Migration (PSDM) velocity model obtained from seismic study on Seh-Qanat anticline only detected 2 horizons of formations, Asmari and Sarvak Formations; however, the current methodology introduces subdivision anticline into six classes by matching it to the log information of Seh-Qanat Deep-1 (SQD-1) borehole where it was excavated over the anticline with total depth of 2876 m.

  1. Three-dimensional Magnetotelluric Modeling of the Pohukuloa Training Area, Hawaii Island

    NASA Astrophysics Data System (ADS)

    Thomas, D. M.; Lienert, B. R.; Wallin, E.

    2015-12-01

    We report the results of 3D modeling of magnetotelluric (MT) data collected in the Pohakuloa Training Area (PTA) on the saddle between Mauna Loa and Mauna Kea volcanoes on Hawaii Island. We have previously used lower frequency MT data to construct 1D and 2D resistivity profiles in this area and confirmed the presence of a low-resistivity region at depths of about 2 km. One of our drill holes in PTA had previously encountered temperatures of 150 C at a similar depth. However, our 1D and 2D models were unable to fit features of the data that we suspected were due to 3D variations in subsurface resistivity. For the 3D modeling, we reprocessed the higher frequency data (1 kHz sampling rate) which were available at all 20 sites. We were then able to obtain complex impedances at frequencies of 0.5-500 Hz to use for the 3D inversion. We used Siripunvaraporn's 3D inversion method to obtain resistivities in a rectangular array of 0.5x0.5x0.25 km blocks spanning the areal extent of the stations down to a depth of 2.5 km. The results confirmed that much of the anomalous data could be explained by near-surface 3D variations in resistivity. The underlying conductor of 5-10 ohm-m at 2 km depth now appears to extend over the entire survey area.

  2. Preliminary Results of a Magnetotelluric Survey in the Center of Hawaii Island

    NASA Astrophysics Data System (ADS)

    Lienert, B. R.; Thomas, D. M.; Wallin, E.

    2014-12-01

    From 2013 up to the present we have been recording magnetotelluric (MT) data at 25 sites in a 35x25 km region (elev. 1943 m) on the saddle between the active volcano of Mauna Loa (4169 m) and the dormant volcano of Mauna Kea (4205 m) on Hawai'i Island. The MT data, particularly the electric fields, are frequently contaminated by spurious components that are not due to the plane-wave magnetic signals required for derivation of the MT impedance tensor. We therefore developed interactive graphical software (MTPlot) to plot and analyze the MT signals in the field. MTPlot allows us to quickly examine records in both the time and frequency domain to in order to judge their quality. It also transforms the data into estimates of apparent resistivity and their error in the frequency range 0.001-500 Hz. This has proved very useful for selecting suitable records for subsequent analysis. We then use multi-taper remote reference processing to obtain our final apparent resistivity estimates and their errors. We present preliminary results of one and two dimensional modeling of these estimates to obtain the three-dimensional distribution of subsurface resistivities down to depths of 5 km. The results are compared to temperatures and properties of cores obtained when we drilled a research hole to a depth of 1760 m in this same region. We shall discuss how our results relate to the extent of the fresh-water and geothermal energy reservoirs that we discovered during drilling.

  3. A method of synthesis magnetotelluric time-series combining interstation transfer functions and a reference site

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Campanyà, Joan

    2016-04-01

    A new method to Synthesis magnetotelluric (MT) data is proposed whereby the MT Time-series of local site are derived using an Inverse Fourier transform of electric and magnetic fields spectrum of local site, which are computed by Combining Interstation transfer functions and a Reference horizontal magnetic time series (STICIR). The method is based on the stability of interstation transfer function, assuming that the geoelectrical structures of the subsurface independent of time. Applying the suggested method, two interstation transfer functions need to be estimated: the quasi-MT impedance tensor and the interstation geomagnetic transfer functions, which are used to compute the horizontal electric fields and the vertical magnetic field at the local site, respectively. The interstation transfer functions can be estimated by single site robust or remote reference (RR) method if another reference site existed. STICIR provides a new way to synthesis MT time-series at the local site combining interstation transfer functions and the magnetic fields at a reference site. Due to this property, STICIR provides significant improvements processing MT data when time-series at the local site are affected by local noise or are truncated. A test with good quality of MT data shows that synthetic time-series are similar to natural electric and magnetic time series. For contaminated data example, when this method is used to remove noise present at the local site, the scatter of MT sounding curves are clear reduced, and the low frequency data quality are improved.

  4. 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.

  5. 2-D magnetotelluric inversion of the central part of Paraná Basin

    NASA Astrophysics Data System (ADS)

    Santos, E. B.; Santos, H. B.; Vitorello, I.; Pádua, M. B.

    2013-12-01

    The Paraná Basin is a large sedimentary basin in central-eastern South America that extends through Brazil, Paraguay, Uruguay and Argentina. Evolved completely over the South American continental crust, this Paleozoic basin is filled with sedimentary and volcanic rocks deposited from the Silurian to the Cretaceous, when a significant basaltic effusion covered almost the entire area of the basin. A series of superposed sedimentary and volcanic rock layers were laid down under the influence of different tectonic settings, probably originated from distant collisional dynamics of continental boards that led to the amalgamation of Gondwanaland. The current boundaries of the basin can be the result of issuing erosional or of tectonic origin, such as the building up of large arches and faults. To evaluate the deep structural architecture of the lithosphere under a sedimentary basin is a great challenge, requiring the integration of different geophysical and geological studies. In this paper, we present the resulting Paraná Basin lithospheric model, obtained from processing and inversion of broadband and long-period magnetotelluric soundings along an E-W profile across the central part of the basin, complemented by a qualitative joint interpretation of gravimetric data, in order to obtain a more precise geoelectric model of the deep structure of the region.

  6. Joint Interpretation of Magnetotelluric and Gravimetric Data from the South American Paraná Basin

    NASA Astrophysics Data System (ADS)

    Santos, E. B.; Santos, H. B.; Vitorello, I.; Pádua, M. B.

    2013-05-01

    The Paraná Basin is a large sedimentary basin in central-eastern South America that extends through Brazil, Paraguay, Uruguay and Argentina. Evolved completely over the South American continental crust, this Paleozoic basin is filled with sedimentary and volcanic rocks deposited from the Silurian to the Cretaceous, when a significant basaltic effusion covered almost the entire area of the basin. A series of superposed sedimentary and volcanic rock layers were laid down under the influence of different tectonic settings, probably originated from distant collisional dynamics of continental boards that led to the amalgamation of Gondwanaland. The current boundaries of the basin can be the result of issuing erosional or of tectonic origin, such as the building up of large arches and faults. To evaluate the deep structural architecture of the lithosphere under a sedimentary basin is a great challenge, requiring the integration of different geophysical and geological studies. In this paper, we present the resulting Paraná Basin lithospheric model, obtained from processing and inversion of broadband and long-period magnetotelluric soundings along an E-W profile across the central part of the basin, complemented by a qualitative joint interpretation of gravimetric data, in order to obtain a more precise geoelectric model of the deep structure of the region.

  7. Bootstrap resampling as a tool for uncertainty analysis in 2-D magnetotelluric inversion modelling

    NASA Astrophysics Data System (ADS)

    Schnaidt, Sebastian; Heinson, Graham

    2015-10-01

    Uncertainty estimation is a vital part of geophysical numerical modelling. There exist a variety of methods aimed at uncertainty estimation, which are often complicated and difficult to implement. We present an inversion technique that produces multiple solutions, based on bootstrap resampling, to create a qualitative uncertainty measure for 2-D magnetotelluric inversion models. The approach is easy to implement, can be used with almost any inversion code, and does not require access to the inversion software's source code. It is capable of detecting the effect of data uncertainties on the model result rather than just analysing the effect of model variations on the model response. To obtain uncertainty estimates for an inversion model, the original data set is resampled repeatedly and alternate data set realizations are created and inverted. This ensemble of solutions is then statistically analysed to determine the variability between the different solutions. The process yields interpretable uncertainty maps for the inversion model and we demonstrate its effectiveness to qualitatively quantify uncertainty in synthetic model tests and a case study.

  8. The Use of Direct Solver in Vector Finite Element Modeling for Calculating 3-D Magnetotelluric Responses

    NASA Astrophysics Data System (ADS)

    Prihantoro, Rudy; Sutarno, Doddy; Nurhasan

    2016-08-01

    In this work, we seek numerical solution of 3-D Magnetotelluric (MT) using edge- based finite element method. This approach is a variant of standard finite element method and commonly referred as vector finite-element (VFE) method. Nonphysical solutions usually occurred when the solution is sought using standard finite element which is a node based element. Vector finite element attempt to overcome those nonphysical solutions by using the edges of the element as vector basis. The proposed approach on solving second order Maxwell differential equation of 3-D MT is using direct solver rather than iterative method. Therefore, divergence correction to accelerate the rate of convergence for its iterative solution is no longer needed. The utilization of direct solver has been verified previously for correctness by comparing the resulting solution to those given by analytical solution, as well as the solution come from the other numerical methods, for earth layered model, 2-D models and COMMEMI 3D-2 model. In this work, further verification resulted from recent comparison model of Dublin Test Model 1 (DTM1) is presented.

  9. Joint Geophysical Characterization of Geothermal System in Menengai, Kenya Using Magnetotelluric and Gravity

    NASA Astrophysics Data System (ADS)

    Wamalwa, A. M.; Serpa, L. F.

    2010-12-01

    Geothermal exploration typically focuses on the identification of the heat source and defining the plumbing system that allows fluid flow at depths of 1-5 km where production of geothermal energy is feasible. The faults and fracture systems that make up the plumbing systems for hydrothermal fluids are often offset from their source and may be entirely hidden beneath basin fill or volcanic flows. Thus, a variety of different geophysical methods are used to detect the fracture zones and heat sources, including electrical, electromagnetic, seismic, and potential field techniques, each not giving a unique interpretation. Therefore a careful qualitative and quantitative joint analysis of these data based on common/shared geology may improve the overall understanding of the study area. To determine the extent of geothermal system as the target for development around Menengai volcano in the southern region of the Kenya rift valley, Magnetotelluric (MT) and gravity data were analysed. Subsurface conductivity and density distribution were used to infer the possible geological structures that relate to permeability and the heat source. Density gradient in the NW and NE north of the Menengai caldera defines the rift faults. A low resistivity layer at about 500 m and 1 km is interpreted as alteration clay minerals and overlays a relatively resistive zone. A low resistivity region at a depth of about 5-6 km is inferred to be a cooling magmatic body.

  10. 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.

  11. Deep crustal structure of the Cascade Range and surrounding regions from seismic refraction and magnetotelluric data

    USGS Publications Warehouse

    Stanley, W.D.; Mooney, W.D.; Fuis, G.S.

    1990-01-01

    Several regional seismic refraction and magnetotelluric (MT) profiles have been completed across the Cascade Range and surrounding geologic provinces in California, Oregon, and Washington. Analysis of three MT and two seismic refraction profiles in Oregon and a coincident MT and refraction profile in northern California show a high degree of correlation between resistivity and velocity models. The main feature that is evident in both data sets is a highly conductive (2-20 ohm m) zone that occurs at depths of 6-20 km and largely within a midcrustal velocity layer of 6.4-6.6 km/s, overlying a lower crust with velocities of 7.0-7.4 km/s. Accretionary structures in the southern Washington Cascades have been shown to be related to stress release in the area of Mount St. Helens. In order to explain the similar structures in the MT and refraction models for Oregon and California, a model is proposed involving the effects of metamorphic zonation to produce the velocity structure, combined with metamorphically produced fluids and partial melt to produce the deep conductor. -from Authors

  12. 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.

  13. 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.

  14. 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.

  15. Lassen Known Geothermal Resource Area, California: audio-magnetotelluric, telluric profiling, and self-potential studies

    SciTech Connect

    Christopherson, K.R.; Hoover, D.B.; Lewis, V.; Radtke, B.; Senterfit, R.M.

    1980-01-01

    During the summer of 1979, geophysical work was done in the Lassen KGRA in northeastern California to assess the geothermal potential of the area. As part of the study, 68 audio-magnetotelluric (AMT) soundings were made and 2 telluric and self-potential (SP) profiles were done. The AMT station locations are shown. The scalar resistivities were contoured for 7.5 and 27 hertz data at north-south and east-west E-line orientations. The contour maps are complex, reflecting both lateral changes in geology and geothermal activity. The locations of the telluric and self-potential traverses are given. The profiles for traverse 1 show varied SP and telluric responses. The variations are probably geologically related with the drop in SP voltage and telluric resistivity on the east end of the traverse caused by a lateral lithology change. The profiles for traverse 2 show a sharp drop in SP voltage combined with a sharp increase in telluric resistivity near station 6. This could be associated with large-scale intrusive features (a ring dike) which trend to the northwest.

  16. Extensional extrusion: Insights into south-eastward expansion of Tibetan Plateau from magnetotelluric array data

    NASA Astrophysics Data System (ADS)

    Dong, Hao; Wei, Wenbo; Jin, Sheng; Ye, Gaofeng; Zhang, Letian; Jing, Jian'en; Yin, Yaotian; Xie, Chengliang; Jones, Alan G.

    2016-11-01

    Despite extensive effort over many decades to understand the tectonic evolution of the Tibetan Plateau, the geodynamic processes creating the iconic south-eastward expansion of the plateau at the Eastern Himalayan Syntaxis (EHS) are still unclear and are hotly debated. Two popular (but not necessarily exclusive) geodynamic models, namely crustal flow at mid-to-lower crustal depths and coherent deformation between the crust and lithospheric mantle, are commonly invoked to explain the expansion mechanism. However, neither of these is able to reconcile all of the abundant geological and geophysical data. Here we present a three-dimensional (3D) geo-electrical model, derived from new SINOPROBE magnetotelluric (MT) array data, that reveals the geo-electrical, and by inference rheological, structure of southeast Tibet. Instead of NW-SE conductive channels proposed in prior two-dimensional (2D) MT studies, distinct NNE-SSW directed quasi-linear conductive anomalies are identified in the mid-to-lower crust, which are separated by a large-scale electrically resistive structure that extends from the crust to the upper mantle. This argues against the prior proposed model of south-eastward conductive anomalies, and hence against the southeast lower crust flow of material. To interpret our observations and resultant model, a new mechanism of "extensional extrusion" is proposed to address the lithospheric deformation of the south-eastward expansion of Tibetan Plateau.

  17. Three-dimensional controlled-source electromagnetic and magnetotelluric joint inversion

    SciTech Connect

    Commer, M.; Newman, G.A.

    2009-02-15

    The growing use of the controlled-source electromagnetic method (CSEM) and magnetotellurics (MT) for exploration applications has been driving the development of data acquisition technologies, and three-dimensional (3-D) modeling and imaging techniques. However, targeting increasingly complex geological environments also further enhances the problems inherent in large-scale inversion, such as non-uniqueness and resolution issues. In this paper, we report on two techniques to mitigate these problems. We use 3-D joint CSEM and MT inversion to improve the model resolution. To avoid the suppression of the resolution capacities of one data type, and thus to balance the use of inherent, and ideally complementary information content, different data reweighting schemes are proposed. Further, a hybrid model parameterization approach is presented, where traditional cell-based model parameters are used simultaneously within a parametric inversion. The idea is to limit the non-uniqueness problem, typical for 3-D imaging problems, in order to allow for a more focusing inversion. The methods are demonstrated using synthetic data generated from models with a strong practical relevance.

  18. 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.

  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. Weighted Least Squares Estimates of the Magnetotelluric Transfer Functions from Nonstationary Data

    SciTech Connect

    Stodt, John A.

    1982-11-01

    Magnetotelluric field measurements can generally be viewed as sums of signal and additive random noise components. The standard unweighted least squares estimates of the impedance and tipper functions which are usually calculated from noisy data are not optimal when the measured fields are nonstationary. The nonstationary behavior of the signals and noises should be exploited by weighting the data appropriately to reduce errors in the estimates of the impedances and tippers. Insight into the effects of noise on the estimates is gained by careful development of a statistical model, within a linear system framework, which allows for nonstationary behavior of both the signal and noise components of the measured fields. The signal components are, by definition, linearly related to each other by the impedance and tipper functions. It is therefore appropriate to treat them as deterministic parameters, rather than as random variables, when analyzing the effects of noise on the calculated impedances and tippers. From this viewpoint, weighted least squares procedures are developed to reduce the errors in impedances and tippers which are calculated from nonstationary data.

  1. Perspectives of African-American women on infant mortality.

    PubMed

    Barnes, Glenna L

    2008-01-01

    Twice as many African-American infants die each year when compared to White infants. This study explores the lived experiences of African-American women to identify factors related to this racial gap in infant mortality. Thirteen African-American women from two Virginia towns participated in either a focus group or in-depth interviews. Content and interpretive analysis revealed several themes. Participants indicated that the experiences of stress and racism are constant factors in African-American women's lives and are inseparable from their pregnancy experiences. Participants noted the importance of social support and the health care provider-client relationship for positive pregnancy outcomes.

  2. Prostate cancer in men of African origin.

    PubMed

    McGinley, Kathleen F; Tay, Kae Jack; Moul, Judd W

    2016-02-01

    Men of African origin are disproportionately affected by prostate cancer: prostate cancer incidence is highest among men of African origin in the USA, prostate cancer mortality is highest among men of African origin in the Caribbean, and tumour stage and grade at diagnosis are highest among men in sub-Saharan Africa. Socioeconomic, educational, cultural, and genetic factors, as well as variations in care delivery and treatment selection, contribute to this cancer disparity. Emerging data on single-nucleotide-polymorphism patterns, epigenetic changes, and variations in fusion-gene products among men of African origin add to the understanding of genetic differences underlying this disease. On the diagnosis of prostate cancer, when all treatment options are available, men of African origin are more likely to choose radiation therapy or to receive no definitive treatment than white men. Among men of African origin undergoing surgery, increased rates of biochemical recurrence have been identified. Understanding differences in the cancer-survivorship experience and quality-of-life outcomes among men of African origin are critical to appropriately counsel patients and improve cultural sensitivity. Efforts to curtail prostate cancer screening will likely affect men of African origin disproportionately and widen the racial disparity of disease.

  3. Magnetotelluric deep soundings, gravity and geoid in the south São Francisco craton: Geophysical indicators of cratonic lithosphere rejuvenation and crustal underplating

    NASA Astrophysics Data System (ADS)

    Pinto, Luis Gustavo Rodrigues; de Pádua, Marcelo Banik; Ussami, Naomi; Vitorello, Ícaro; Padilha, Antonio Lopes; Braitenberg, Carla

    2010-09-01

    In the south São Francisco craton a circular and 8-m amplitude geoid anomaly coincides with the outcropping terrain of an Archean-Paleoproterozoic basement. Broadband magnetotelluric (MT) data inversions of two radial profiles within the positive geoid and Bouguer gravity anomaly yield geo-electrical crustal sections, whereby the lower crust is locally more conductive (10 to 100 Ωm) in spatial coincidence with a denser lower crust modeled by the gravity data. This anomalous lower crust may have resulted from magmatic underplating, associated with Mesoarchean and Proterozoic episodes of tholeiitic dike intrusion. Long-period MT soundings reveal a low electrical resistivity mantle (20 to 200 Ωm) from depths beyond 120 km. Forward geoid modeling, using the scope of the low electrical resistivity region within the mantle as a constraint, entails a density increase (40 to 50 kg/m 3) possibly due to Fe enrichment of mantle minerals. However, this factor alone does not explain the observed resistivity. A supplemented presence of small amounts of percolated carbonatite melting (~ 0.005 vol.%), dissolved water and enhanced oxygen fugacity within the peridotitic mantle are viable agents that could explain the less resistive upper mantle. We propose that metasomatic processes confined in the sub-continental lithospheric mantle foster the conditions for a low degree melting with variable CO 2, H 2O and Fe content. Even though the precise age of this metasomatism is unknown it might be older than the Early Cretaceous based on the evidence that a high-degree of melting in a lithospheric mantle impregnated with carbonatites originated the tholeiitic dike intrusions dispersed from the southeastern border of the São Francisco craton, during the onset of the lithosphere extension and break-up of the western Gondwana. The proxies are the NE Paraná and Espinhaço (130 Ma, Ar/Ar ages) tholeiitic dikes, which contain (~ 3%) carbonatites in their composition. The occurrence of a

  4. Racism: perceptions of distress among African Americans.

    PubMed

    Thompson, Vetta L Sanders

    2002-04-01

    Some scholars have suggested that stressful living conditions are a major source of mental disorder among African Americans (Krieger, 1999; Neighbors, 1990; Kessler & Neighbors, 1986). There has, however, been debate as to whether this higher level of distress is due to racism or the fact that African Americans are more often of lower socioeconomic status. Stressors that play a significant role in mental disorder might be expected to occur more frequently among African Americans than the general population. This paper attempts to provide empirical support for the notion that racism is a separate and unique source of stress for African Americans. Specifically, it was hypothesized that African Americans would report more experiences of (1) daily stress and (2) racism than other groups and (3) the impact of racial stress would be greater among African Americans. One hundred and fifty six participants completed the Daily Stress Inventory and the Experience of Discrimination questionnaire. Multivariate analysis of variance indicated that African Americans reported higher impact of discrimination scores than European Americans. There were no gender or ethnicity differences in daily stress or the number of racial incidents reported. The implications of the data are discussed.

  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. 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…

  7. 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…

  8. Linguistic Imperialism: African Perspectives.

    ERIC Educational Resources Information Center

    Phillipson, Robert

    1996-01-01

    Responds to an article on aspects of African language policy and discusses the following issues: multilingualism and monolingualism, proposed changes in language policy from the Organization for African Unity and South African initiatives, the language of literature, bilingual education, and whose interests English-language teaching is serving.…

  9. 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

  10. 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.

  11. High resolution imaging of the Methana volcanic complex, Greece, with magnetotelluric and aeromagnetic data

    NASA Astrophysics Data System (ADS)

    Efstathiou, A.; Tzanis, A.; Chailas, S.; Lagios, E.; Stamatakis, M.

    2012-04-01

    The Methana calc-alkaline volcanic complex is located off the NE coast of Argolis Peninsula (Peloponnesus, Greece) at the NW terminus of the Hellenic Volcanic Arc (HVA). It consists of approximately 32 domes, with the most recent eruptive episodes dated to 258 BCE and 1700 CE. Herein, we report the results an attempt to investigate the volcano's interior with joint interpretation of Magnetotelluric and Aeromagnetic data. The aeromagnetic data was inverted with the UBC-GIF 3D magnetic inversion suite, constrained by several in-situ susceptibility measurements. At depths to 2 km, the inversion resolves individual intrusions corresponding to known phases of volcanic activity (domes), with susceptibilities >0.1. At depths greater than 4.5 km, a more weakly magnetized domain is detected (~0.025); its ceiling is well resolved; its floor cannot be placed with certainty but extends to at least 7 km. The depths are comparable to those of magma chambers. Based on the palaeomagnetic analysis of nearby volcanic rocks, it may be safely suggested that its temperature should not be higher than 550-600°C, but also not considerably lower. It may comprise a magma chamber, inasmuch as it compares well with the temperatures and locations of known magma chambers along the HVA. Finally, there's exists evidence of the location of the vents through which the extrusive activity has taken place. A Magnetotelluric survey comprising 14 stations was conducted IN 1992, as part of a geothermal project. Herein, this data is reevaluated with modern analysis methods and re-interpreted with 2D inversion. The results indicate the presence of conductors at depths of 1500-2500 m beneath the centre of the Peninsula, extensive horizontal conductors at, or just below sea level and conductive protrusions above sea level. The joint interpretation of the susceptibility and geoelectric images is based on the premise that they both are generated by hydrothermal circulation which depresses resistivity and

  12. 3D inversion based on multi-grid approach of magnetotelluric data from Northern Scandinavia

    NASA Astrophysics Data System (ADS)

    Cherevatova, M.; Smirnov, M.; Korja, T. J.; Egbert, G. D.

    2012-12-01

    In this work we investigate the geoelectrical structure of the cratonic margin of Fennoscandian Shield by means of magnetotelluric (MT) measurements carried out in Northern Norway and Sweden during summer 2011-2012. The project Magnetotellurics in the Scandes (MaSca) focuses on the investigation of the crust, upper mantle and lithospheric structure in a transition zone from a stable Precambrian cratonic interior to a passive continental margin beneath the Caledonian Orogen and the Scandes Mountains in western Fennoscandia. Recent MT profiles in the central and southern Scandes indicated a large contrast in resistivity between Caledonides and Precambrian basement. The alum shales as a highly conductive layers between the resistive Precambrian basement and the overlying Caledonian nappes are revealed from this profiles. Additional measurements in the Northern Scandes were required. All together data from 60 synchronous long period (LMT) and about 200 broad band (BMT) sites were acquired. The array stretches from Lofoten and Bodo (Norway) in the west to Kiruna and Skeleftea (Sweden) in the east covering an area of 500x500 square kilometers. LMT sites were occupied for about two months, while most of the BMT sites were measured during one day. We have used new multi-grid approach for 3D electromagnetic (EM) inversion and modelling. Our approach is based on the OcTree discretization where the spatial domain is represented by rectangular cells, each of which might be subdivided (recursively) into eight sub-cells. In this simplified implementation the grid is refined only in the horizontal direction, uniformly in each vertical layer. Using multi-grid we manage to have a high grid resolution near the surface (for instance, to tackle with galvanic distortions) and lower resolution at greater depth as the EM fields decay in the Earth according to the diffusion equation. We also have a benefit in computational costs as number of unknowns decrease. The multi-grid forward

  13. Three-dimensional inversion of magnetotelluric data from the Central Andean continental margin

    NASA Astrophysics Data System (ADS)

    Kühn, Christine; Küster, Jonas; Brasse, Heinrich

    2014-12-01

    Magnetotelluric data were collected in the late 1990s in the Central Andes of Chile and Bolivia, with the aim to delineate the electrical conductivity distribution in the subsurface and its relations to subduction processes. In previous studies, these data were interpreted based on 2-D models. The principal result was a vast conductivity zone beneath the Altiplano high plateau at mid and lower crustal depths and a much smaller, though significant conductor associated with the Precordillera Fault System. However, there are some significant 3-D effects in the investigation area, in particular near the coast and on the eastern Altiplano. The aim of this work is to give a reinterpretation based on new 3-D inversion of these data. The 3-D inversion not only provides a better fit to the data compared to 2-D results but furthermore allows to include sites with strong telluric distortion which were ignored in previous studies. We are now able to explain anomalous phases above 90° and induction arrows pointing subparallel to the coast as observed at several sites in the Coastal Cordillera. These strongly distorted data are caused by highly conductive near-surface structures that are partly connected to the Pacific Ocean, forcing currents to flow around the sites. The lower crust beneath the Coastal Cordillera resembles a poorly conductive, nearly homogeneous half-space and is electrically unremarkable. Besides, we can now image the Precordillera conductor as a continuous, elongated feature. The volcanic arc of the Western Cordillera is highly resistive with the exception of a few conductive spots which may be associated with certain individual volcanoes or geothermal resources, respectively. The Altiplano conductor is again the dominant electrical feature in the Central Andes, indicating widespread melting of the middle and lower back-arc crust.

  14. Crustal Structure at the vicinity of Nigde Massif and Central Anatolian Fault Zone from Magnetotelluric Data

    NASA Astrophysics Data System (ADS)

    Tank, B.; Sandvol, E. A.; Karas, M.; Ozaydin, S.

    2015-12-01

    Three magnetotelluric (MT) profiles were constructed to examine the electrical resistivity strucuture of a metamorphic core complex renown as Niğde massif and a northeast - southwest aligned fault zone (Central Anatolian Fault Zone, CAFZ) bounding this massif on the east in Central Anatolia. Nigde massif is a crystalline dome close to Inner-Tauride suture at the southern part of Central Anatolian Crystalline Complex. The sinistral CAFZ (in the south it is called Ecemis fault) is a ~700 km long, 2 to 80 km wide zone with an offset of 60 to 80 km. Northwest-southeast aligned Tuz Gölü (Salt Lake) and Derinkuyu faults are other major features that shape up the study area. A three-dimensional numerical modeling routine based on data-space modeling (WSINV3DMT) was used to invert the MT data collected at 85 high quality soundings. A mesh with 76 x 74 x 40 (7 layers for air) cells was used during the inversions. The resulting models suggest that (i) there is a low conductivity dome-like anomaly that coincides with the Nigde massif (presumably matches with Uckapili granite). (ii) Beneath this low conductivity anomaly there is a deeper (>20 km) high conductivity zone caused by partial melting (iii) Ecemis fault near Pozanti appears as a low to high conductivity interface. (iv) Likewise, Tuz Gölü and Derinkuyu faults appear as a low to high conductivity interfaces representing barriers for fluid flow (v) Adana basin sediments show high conductivity values (vi) Mt. Hasan and Mt. Karaca and the volcanic complexes in between them show highly conductive features in their roots, but (vi) older Mt. Erciyes lacks such a deep conductor.

  15. Analysis and 3D inversion of magnetotelluric crooked profile data from central Svalbard for geothermal application

    NASA Astrophysics Data System (ADS)

    Beka, Thomas I.; Smirnov, Maxim; Birkelund, Yngve; Senger, Kim; Bergh, Steffen G.

    2016-08-01

    Broadband (0.001-1000 s) magnetotelluric (MT) data along a crooked profile collected to investigate the geothermal potential on Spitsbergen could not be fully explained by two-dimensional (2D) models; hence we interpret the data with three-dimensional (3D) inversion herein. To better accommodate 3D features and nearby off profile resistivity structures, the full MT impedance tensor data together with the tipper were inverted. As a model control, a detailed bathymetry is systematically incorporated in the inversion. Our results from testing different inversion settings emphasised that appropriately choosing and tuning the starting model, data error floor and the model regularization together are crucial to obtain optimum benefit from MT field data. Through the 3D inversion, we reproduced out of quadrant impedance components and obtained an overall satisfactory data fit (RMS = 1.05). The final 3D resistivity model displays a complex geology of the near surface region (< 1.5 km), which suggests fractures, localized and regional fault systems and igneous intrusions in the Mesozoic platform cover deposits. The Billefjorden fault zone is revealed as a consistent and deep rooted (> 2 km) conductive anomaly, confirming the regional nature of the fault. The fault zone is positioned between two uplifted basement blocks (> 1000 Ωm) of presumably pre-Devonian (Caledonian) metamorphic rocks, and the fault may have been responsible for deformation in the overlying Paleozoic-Mesozoic unit. Upper crustal conductive anomalies (< 10 Ωm) below the Paleozoic-Mesozoic succession in the western part of the 3D model are interpreted as part of a Devonian basin fill. These conductors are laterally and vertically bounded by resistive rocks, suggesting a conducive environment for deep geothermal heat storage. Having this scenario in an area of a known high heat-flow, deep faults and a thinned lithosphere makes the hypothesis on finding a technologically exploitable geothermal resource

  16. A magnetotelluric sounding across Vancouver Island detects the subducting Juan de Fuca plate

    NASA Astrophysics Data System (ADS)

    Kurtz, R. D.; Delaurier, J. M.; Gupta, J. C.

    1986-06-01

    Magnetotelluric1 (MT) and geomagnetic2 depth-sounding measurements have been made at 18 sites (7 with remote reference3) across Vancouver Island (Fig. 1), beneath which the Juan de Fuca plate is underthrusting4,5. Vancouver Island is part of the old accretionary Wrangellia terrane6 and is located in the central portion of a 350-km forearc region that extends from the sediment-filled trench7 to the Garibaldi volcanic belt8. Gravity9 and seismic refraction studies10 suggest that the descending plate has a shallow northeasterly dip of 8°-16° with perhaps higher dips beneath northeastern Vancouver Island. A high-resolution seismic reflection survey11 along lines 1 and 3 (Fig. 1) located a zone of strong acoustic reflections (the E-horizon11) near the top of the subducting Juan de Fuca plate at depths of 23-34 km. Our model of the broad-band MT data defines a sloping, highly conducting zone also near the top of the subducting plate at the same depths as the seismic E-horizon. The high electrical conductivity in this zone (the E-conductor) is the result of saline fluid within the pore spaces of sedimentary and mafic materials of the upper oceanic crust that have been subducted to those depths beneath Vancouver Island. These are the first data which clearly define a dipping conductive layer associated with the boundary region between converging plates; they have significant implications for thrust earthquakes and metamorphic reactions that occur in subduction zones.

  17. Magnetotelluric investigation of the Vestfold Hills and Rauer Group, East Antarctica

    USGS Publications Warehouse

    Peacock, Jared R.; Selway, Katherine

    2016-01-01

    The Vestfold Hills and Rauer Group in East Antarctica have contrasting Archean to Neoproterozoic geological histories and are believed to be juxtaposed along a suture zone that now lies beneath the Sørsdal Glacier. Exact location and age of this suture zone are unknown, as is its relationship to regional deformation associated with the amalgamation of East Gondwana. To image the suture zone, magnetotelluric (MT) data were collected in Prydz Bay, East Antarctica, mainly along a profile crossing the Sørsdal Glacier and regions inland of the Vestfold Hills and Rauer Group islands. Time-frequency analysis of the MT time series yielded three important observations: (1) Wind speeds in excess of ∼8 m/s reduce coherence between electric and magnetic fields due to charged wind-blown particles of ice and snow. (2) Estimation of the MT transfer function is best between 1000 and 1400 UT when ionospheric Hall currents enhance the magnetic source field. (3) Nonplanar source field effects were minimal but detectable and removed from estimation of the MT transfer function. Inversions of MT data in 2-D and 3-D produce similar resistivity models, where structures in the preferred 3-D resistivity model correlate strongly with regional magnetic data. The electrically conductive Rauer Group is separated from the less conductive Vestfold Hills by a resistive zone under the Sørsdal Glacier, which is interpreted to be caused by oxidation during suturing. Though a suture zone has been imaged, no time constrains on suturing can be made from the MT data.

  18. Imaging the magmatic and hydrothermal systems of Long Valley Caldera, California with magnetotellurics

    NASA Astrophysics Data System (ADS)

    Peacock, J.; Mangan, M.; McPhee, D.; Ponce, D. A.

    2015-12-01

    Long Valley Caldera (LVC) in Eastern California contains active hydrothermal systems, areas of episodic seismicity, and areas of elevated gas emissions, all of which are related to a deeper magmatic system that is not well characterized. To better image the Long Valley magmatic system, 60 full-tensor broadband magnetotelluric (MT) stations were collected in LVC and modeled in three-dimensions to constrain the subsurface electrical resistivity structure down to 30 km. Three conductive zones are imaged in the preferred resistivity model. The most prominent conductive zone (<7 Ohm-m) is located 5 km beneath the resurgent dome (near the center of Long Valley Caldera), where it elongates in a north-south direction, and has westward connection to the surface close to well 44-16 near Deer Mountan. This conductive zone is interpreted to be an accumulation zone of hydrothermal fluids originating from a deeper magmatic source. The shape of the conductive body suggests that the fluids pool under the resurgent dome and migrate westward, upwelling just south of well 44-16 to feed the near surface geothermal system. A second conductive zone (<10 Ohm-m) is 4 km southeast of the resurgent dome and 5 km deep and coincident with the seismic swarm of 2014. This is another zone of fluid accumulation, where the source could be the fluid accumulation zone to the west or an independent deeper source. The third conductive anomaly (<10 Ohm-m) is a few kilometers south of the resurgent dome below a depth of 15 km, and collocated with a low p- and s-wave velocity zone, and directly beneath a GPS inflation area, all of which advocate for a magma mush zone of as much as 30% interstitial melt. The preferred resistivity model suggests an accumulation of hydrothermal fluids 5 km below the resurgent dome that originates from a deeper magmatic source at 15 km depth.

  19. Lithospheric structure of the Yukon, northern Canadian Cordillera, obtained from magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Ledo, Juanjo; Jones, Alan G.; Ferguson, Ian J.; Wolynec, Lisa

    2004-04-01

    Two goals of Lithoprobe's geoscientific studies in the Phanerozoic accretionary cordillera of western North America were to define the subsurface geometries of the terranes and to infer the physical conditions of the crust. These questions were addressed in Canada's southern cordillera a decade ago and have more recently been addressed in the northern cordillera, of which one component of the new studies is magnetotelluric (MT) profiling from ancestral North American rocks to the coast. We present a resistivity cross section, and its interpretation, of the northern cordillera derived from modeling data from 42 MT sites along a 470-km-long NE-SW profile. Beneath the Coast Belt (southwestern end of the profile) a deep crustal low-resistivity layer dips inland; we interpret the crustal part of this conductor as being due to metasedimentary rocks emplaced and metamorphosed during Paleocene Kula plate subduction. A strong lateral transition in lithospheric mantle resistivity exists below the Intermontane Belt that is spatially coincident with changes in chemical and isotopic characteristics of Tertiary to recent alkaline lavas, suggesting that isotopically enriched lithosphere related to the Coast Belt basalts extends partly beneath the Intermontane Belt. The unusually high lower crustal resistivity in the Intermontane and Omineca Belts, similar in value to the resistivity found in the unextended part of central British Columbia, excludes the presence of fluids or conducting metasediments. Finally, our resistivity model displays strong lateral variation of the middle and lower crust between different terranes within the same belt, as a result of the complex structural evolution of the lithosphere.

  20. 3D magnetotelluric modelling of the Alnö alkaline and carbonatite ring complex, central Sweden

    NASA Astrophysics Data System (ADS)

    Yan, Ping; Andersson, Magnus; Kalscheuer, Thomas; García Juanatey, María A.; Malehmir, Alireza; Shan, Chunling; Pedersen, Laust B.; Almqvist, Bjarne S. G.

    2016-06-01

    Thirty-four broadband magnetotelluric stations were deployed across the Alnö alkaline and carbonatite ring intrusion in central Sweden. The measurements were designed such that both 2D models along existing seismic profiles and a 3D model can be constructed. Alnö Island and surrounding areas are densely populated and industrialized and in order to reduce the effect of noise, the remote reference technique was utilized in time series processing. Strike and dimensionality analyses together with the induction arrows show that there is no homogeneous regional strike direction in this area. Therefore, only the determinant of the impedance tensor was used for 2D inversion whereas all elements of the impedance tensor were used for 3D inversion. Representative rock samples were collected from existing outcrops and their resistivities were measured in the laboratory to facilitate interpretation of the inversion models. The results from these measurements show that coarse-grained (sövite, white color) and fine-grained (dark color) carbonatites are the most conductive and resistive rock types, respectively. In accordance with the interpretation of the reflection seismic images, the 2D and 3D resistivity models depict the caldera-related ring-type fault system and updoming faulted and fractured systems as major 10-500 Ωm conductors, extending down to about 3 km depth. A central ~ 4000 Ωm resistive unit at about 3 km depth appears to correspond to a solidified fossil magma chamber as speculated from the reflection seismic data and earlier field geological studies.

  1. Using seismically constrained magnetotelluric inversion to recover velocity structure in the shallow lithosphere

    NASA Astrophysics Data System (ADS)

    Moorkamp, M.; Fishwick, S.; Jones, A. G.

    2015-12-01

    Typical surface wave tomography can recover well the velocity structure of the upper mantle in the depth range between 70-200km. For a successful inversion, we have to constrain the crustal structure and assess the impact on the resulting models. In addition,we often observe potentially interesting features in the uppermost lithosphere which are poorly resolved and thus their interpretationhas to be approached with great care.We are currently developing a seismically constrained magnetotelluric (MT) inversion approach with the aim of better recovering the lithospheric properties (and thus seismic velocities) in these problematic areas. We perform a 3D MT inversion constrained by a fixed seismic velocity model from surface wave tomography. In order to avoid strong bias, we only utilize information on structural boundaries to combine these two methods. Within the region that is well resolved by both methods, we can then extract a velocity-conductivity relationship. By translating the conductivitiesretrieved from MT into velocities in areas where the velocity model is poorly resolved, we can generate an updated velocity model and test what impactthe updated velocities have on the predicted data.We test this new approach using a MT dataset acquired in central Botswana over the Okwa terrane and the adjacent Kaapvaal and Zimbabwe Cratons togetherwith a tomographic models for the region. Here, both datasets have previously been used to constrain lithospheric structure and show some similarities.We carefully asses the validity of our results by comparing with observations and petrophysical predictions for the conductivity-velocity relationship.

  2. Broadband signal generator for the approximation of a magnetotelluric source for indoor testing

    NASA Astrophysics Data System (ADS)

    Ge, Shuang-chao; Deng, Ming; Chen, Kai; Shi, Xin-yu

    2016-08-01

    To test the frequency response of a magnetotelluric (MT) receiver, a broadband source, especially white noise is more efficient and intuitive than single frequency signals. In view of the absence of an appropriate source generator for MT receiver indoor testing, we designed a broadband signal generator based on a pseudo-random binary sequence (PRBS). Firstly, we divided the whole MT band into two segments to avoid data redundancy and simplify calculation in data processing and designed a generator composed of several modules: a clock module, a PRBS logic module, and a voltage level conversion module. We conducted a detailed analysis of the optimal parameter selection methods for each module, and key parameters including clock frequency, order, the primitive polynomial and the original states of the linear registers were determined. The generator provides four-channel PRBS signals with two effective bandwidths of 5  ×  10‑4–714 Hz and 0.1 Hz–14 kHz which are broad enough to cover the frequency range for different MT methods. These four-channel signals were used to simulate two modes of sources (xy and yx) with strong auto-correlation and weak cross-correlation. The power spectral density is quite stable in the whole passband. The new generator is characterized by broadband output in low-frequency bands, low power consumption, simple operation and reliable performance. Indoor and field tests indicated that the generator can provide an analog MT source and is a practical tool for MT receiver indoor testing.

  3. Mapping Electrical Structures in the Jarud Basin, Northeast China through Magnetotelluric Sounding

    NASA Astrophysics Data System (ADS)

    Zhao, W.

    2015-12-01

    In recent years, China Geological Survey (CGS) has launched 3D geological mapping programs from regional to local scales. The project Deep geological survey at the periphery of the Songliao Basin funded by CGS was implemented from 2012 to 2014. Its main goals are to reveal the tectonic framework of the Jarud Basin (JB) as well as to identify the strata distribution of Permian Linxi Formation by integrating new electromagnetic data with existing geophysical and geological data since black mudstones in the Linxi Formation have shown the potential of shale gas. The study area covered dominantly with Cretaceous-Jurassic igneous rocks with exception of the southeast part is situated in Jarud Banner and Ar Horqin Banner, Inner Mongolia, China. It tectonically lies in the southern Great Khingan Range, western margin of the Songliao Basin, and north of Xar Moron Fault. Over the period of 2012 to 2014, a magnetotelluric survey was carried out at the JB. A total of 926 MT sites with nominal spacing 1 km was acquired in the effective frequency range of 0.01 Hz ~ 300 Hz on six NW and five NE profiles, covering area that exceeds 10, 000 km2. After dimensionality analysis and static shift removal, the nonlinear conjugate algorithm was used to conduct 2D inversion for TM and TE modes. The resistivity models underwent examination using sensitivity tests. The optimal resistivity models revealed numerous large faults, some of which constitute the boundaries of the JB, and modified the tectonic framework. Integrated with well logging and geological mapping data, the strata of Linxi Formation were identified and classified into three depressions: Depressions Arituguri, Gadasu and Wufen. Attention should be paid to Depression Gadasu with area of around 500 km2 since it contains reasonably thick conductive sediments exceeding 4 km in depth which are inferred to be black mudstones pertaining to shale gas.

  4. 3-D analysis and interpretation of magnetotelluric data from the Aluto-Langano geothermal field, Ethiopia

    NASA Astrophysics Data System (ADS)

    Samrock, F.; Kuvshinov, A.; Bakker, J.; Jackson, A.; Fisseha, S.

    2015-09-01

    The Main Ethiopian Rift Valley encompasses a number of volcanoes, which are known to be actively deforming with reoccurring periods of uplift and setting. One of the regions where temporal changes take place is the Aluto volcanic complex. It hosts a productive geothermal field and the only currently operating geothermal power plant of Ethiopia. We carried out magnetotelluric (MT) measurements in early 2012 in order to identify the source of unrest. Broad-band MT data (0.001-1000 s) have been acquired at 46 sites covering the expanse of the Aluto volcanic complex with an average site spacing of 1 km. Based on this MT data it is possible to map the bulk electrical resistivity of the subsurface down to depths of several kilometres. Resistivity is a crucial geophysical parameter in geothermal exploration as hydrothermal and magmatic reservoirs are typically related to low resistive zones, which can be easily sensed by MT. Thus by mapping the electrical conductivity one can identify and analyse geothermal systems with respect to their temperature, extent and potential for production of energy. 3-D inversions of the observed MT data from Aluto reveal the typical electrical conductivity distribution of a high-enthalpy geothermal system, which is mainly governed by the hydrothermal alteration mineralogy. The recovered 3-D conductivity models provide no evidence for an active deep magmatic system under Aluto. Forward modelling of the tippers rather suggest that occurrence of melt is predominantly at lower crustal depths along an off-axis fault zone a few tens of kilometres west of the central rift axis. The absence of an active magmatic system implies that the deforming source is most likely situated within the shallow hydrothermal system of the Aluto-Langano geothermal field.

  5. Lithospheric electrical structure of South China imaged by magnetotelluric data and its tectonic implications

    NASA Astrophysics Data System (ADS)

    Zhang, Letian; Jin, Sheng; Wei, Wenbo; Ye, Gaofeng; Jing, Jianen; Dong, Hao; Xie, Chengliang

    2015-02-01

    The region of South China mainly consists of the Yangtze block in the northwest, the Cathaysia block in the southeast and the Jiangnan orogen in between these two major Precambrian continental blocks. The Yangtze block borders the North China Craton in the north and the eastern margin of the Tibetan Plateau in the west. The Cathaysia block adjoins the Pacific tectonic domain in the east. The study of tectonics in this region is of great significance given its important role in understanding the formation of the Asia continent. Under the auspices of SinoProbe Project, new magnetotelluric (MT) data were collected along a ∼1200 km long profile starting from central Sichuan Basin near Suining, extending southeastward, passing through the Yangtze Block, Jiangnan Orogen, and terminating within the western Cathaysia Block near Ganzhou. Based on data analysis results, 2D inversions were conducted on the dataset. Resulting model shows that the lithospheric electrical structure of South China is generally resistive which is consistent with the basic feature of stable Precambrian tectonic setting. The resistive western Yangtze block represents the stable, Archean aged cratonic region of the Yangtze basement. While the electrically conductive eastern Yangtze block is characterized by lithospheric shearing of the strike-slip fault system and extensional process that is probably caused by slab roll-back of a flatly subducted plate. The Jiangshao fault performs as a northwestward dipping conductive layer, which indicates the lithospheric underthrusting of Cathaysia block beneath Yangtze block with its frontal edge reaching the area of Jishou in the upper mantle. To the west of Jiangshao fault, eastern flank of the Xuefengshan Mountain marks the overthrusting frontier of the Yangtze block, as well as its southeastern boundary. To the east of Jiangshao fault, the northwestern boundary of the Cathaysia block displays the pattern of wedging tectonics, which is characterized by a

  6. MT Alcudia: a magnetotelluric profile across the south-eastern part of the Central Iberian Zone

    NASA Astrophysics Data System (ADS)

    Pous, J.; Monteiro Santos, F.; Galindo, J.; Ibarra, P.; Plancha, J.; Gonçalves, R.; Almeida, E.; Pedrera, A.; Ruiz-Constan, A.; Anahnah, F.

    2009-04-01

    The western part of the Iberian Peninsula (Iberian Massif) is the best exposed fragment of the Variscan orogen in Europe. Its southern half was generated by an oblique collision between three continental terranes belonging to the margins of Laurassia (Avalonia) - the South Portuguese Zone- and Godwana - the Ossa Morena Zone (OMZ) and the Central Iberian Zone (CIZ). The boundaries between them are considered to be sutures. A 210 km long magnetotelluric profile across the eastern part of the Central Iberian Zone is presented. The profile crosses the boundary between the Ossa Morena and Central Iberian zones and spans up to the Tajo basin, crossing the Sierra de Alcudia and the Toledo Mountains. The main structures investigated are: the Los Pedroches batholit, the Alcudia anticline - Domo Extremeño, the Almadén syncline, the fold structures located to the north and the Toledo fault. We present the results of this profile, which consists of 33 MT sites, with the five components of the electromagnetic field and period ranging from 1000 Hz to 1000 s. In each MT site a TEM sounding was carried out in order to characterize the shallow electrical resistivity and to control the galvanic distortion (static shift). The results of two-dimensional inversion reveal a high conductivity zone with the transition OMZ/CIZ. Apart from the sallow structure, the most striking feature is a high conductive layer at middle to lower crust in the whole CIZ, confirming the prolongation of the same layer detected in the OMZ in previous studies.

  7. Broadband signal generator for the approximation of a magnetotelluric source for indoor testing

    NASA Astrophysics Data System (ADS)

    Ge, Shuang-chao; Deng, Ming; Chen, Kai; Shi, Xin-yu

    2016-08-01

    To test the frequency response of a magnetotelluric (MT) receiver, a broadband source, especially white noise is more efficient and intuitive than single frequency signals. In view of the absence of an appropriate source generator for MT receiver indoor testing, we designed a broadband signal generator based on a pseudo-random binary sequence (PRBS). Firstly, we divided the whole MT band into two segments to avoid data redundancy and simplify calculation in data processing and designed a generator composed of several modules: a clock module, a PRBS logic module, and a voltage level conversion module. We conducted a detailed analysis of the optimal parameter selection methods for each module, and key parameters including clock frequency, order, the primitive polynomial and the original states of the linear registers were determined. The generator provides four-channel PRBS signals with two effective bandwidths of 5  ×  10-4-714 Hz and 0.1 Hz-14 kHz which are broad enough to cover the frequency range for different MT methods. These four-channel signals were used to simulate two modes of sources (xy and yx) with strong auto-correlation and weak cross-correlation. The power spectral density is quite stable in the whole passband. The new generator is characterized by broadband output in low-frequency bands, low power consumption, simple operation and reliable performance. Indoor and field tests indicated that the generator can provide an analog MT source and is a practical tool for MT receiver indoor testing.

  8. Three-dimensional conductivity image of the Society hotspot using marine magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Tada, Noriko; Tarits, Pascal; Baba, Kiyoshi; Utada, Hisashi; Kasaya, Takafumi; Suetsugu, Daisuke

    2016-04-01

    The mantle upwellings are one of the most important features for understanding the mantle dynamics. A large-scale mantle upwelling beneath the French Polynesia region in the South Pacific has been suggested from seismic studies, which is called the South Pacific superplume, and a slow velocity anomaly continues from the core mantle boundary to the upper mantle just beneath the Society hotspot (e.g., Suetsugu et al., 2009). However, the previous studies are not enough to understand the geometry, temperature, and composition of the Society hotspot. Then, we carried out the TIARES project that composed of multi-sensor stations that include broadband ocean bottom seismometers, ocean bottom electromagnetometers (OBEMs), and differential pressure gauges from 2009 to 2010 (Suetsugu et al., 2012). In this study, we will present the results of observed data obtained from OBEMs. In order to obtain three-dimensional (3-D) image of the upwelling of the Society hotspot in terms of electrical conductivity, we newly settled eleven OBEMs. In addition to these data, the old data obtained by Nolasco et al. (1998) was reanalyzed, and we obtained magnetotelluric (MT) responses at 20 sites totally. A 3-D marine MT inversion program (Tada et al., 2012; Baba et al., 2013), which can treat topographic change distorting EM data, was applied to these MT responses to estimate 3-D electrical conductivity image beneath the seafloor. The result detected a 3-D shaped high conductive anomaly, like a thumb, elongating from the mantle transition zone to the uppermost upper mantle just below the Society hotspot. With regard to interpretations, we will make a presentation at another session (GD3.3/EMRP4.3/GMPV3.3/SM6.11).

  9. Structure and tectonics of the northwestern United States from EarthScope USArray magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Bedrosian, Paul A.; Feucht, Daniel W.

    2014-09-01

    The magnetotelluric component of the EarthScope USArray program has covered over 35% of the continental United States. Resistivity tomography models derived from these data image lithospheric structure and provide constraints on the distribution of fluids and melt within the lithosphere. We present a three-dimensional resistivity model of the northwestern United States which provides new insight into the tectonic assembly of western North America from the Archean to present. Comparison with seismic tomography models reveals regions of correlated and anti-correlated resistivity and velocity that help identify thermal and compositional variations within the lithosphere. Recent (Neogene) tectonic features reflected in the model include the subducting Juan de Fuca-Gorda plate which can be traced beneath the forearc to more than 100 km depth, high lithospheric conductivity along the Snake River Plain, and pronounced lower-crustal and upper-mantle conductivity beneath the Basin and Range. The latter is abruptly terminated to the northwest by the Klamath-Blue Mountains Lineament, which we interpret as an important structure during and since the Mesozoic assembly of the region. This boundary is interpreted to separate hot extended lithosphere from colder, less extended lithosphere. The western edge of Proterozoic North America, as indicated by the Cretaceous initial 87Sr/86Sr = 0.706 contour, is clearly reflected in the resistivity model. We further image an Archean crustal block (“Pend Oreille block”) straddling the Washington/Idaho border, which we speculate separated from the Archean Medicine Hat block in the Proterozoic. Finally, in the modern Cascades forearc, the geometry and internal structure of the Eocene Siletz terrane is reflected in the resistivity model. The apparent eastern edge of the Siletz terrane under the Cascades arc suggests that pre-Tertiary rocks fill the Washington and Oregon back-arc.

  10. Imaging the conductivity anomalies at the vicinity of Ganos Fault, northwest Turkey by magnetotellurics

    NASA Astrophysics Data System (ADS)

    Karaş, Mustafa; Tank, Bülent; Özaydın, Sinan

    2016-04-01

    Audio-frequency magnetotelluric (AMT: 10400 Hz. - 1 Hz.) data were collected across Ganos Fault, near Mürefte, at the western part of North Anatolian Fault, Turkey. The twelve observation points were densely distributed to form a north - south aligned continuous profile that aims to reveal the electrical resisitivity structure to a depth of 1500 m. Ganos Fault is inactive since 1912 Mürefte Earthquake (Ms: 7.4) and acts as a locked segment with the potential to generate a significant event in the near future. Preliminary dimensionality analyses of the AMT data were performed by using three approaches; strike angle determination following Groom and Bailey decomposition (N70°E), phase tensor analyses (N70°E) and induction vectors (N60°E). All of these methods gave results that are in good agreement with present geological (N70°E) and seismological (N70°E) values. Following the dimensionality analyses, two- and three- dimensional numerical modeling routines were utilized to perform inverse modeling. The inversions were performed by different methods such as Rodi and Mackie, WinGLink, (2001) and Ogawa and Uchida, ABIC, (1996) for 2D and Siripunvaraporn et al., WSINV3DMT (2005) and Egbert and Kelbert, ModEM (2012) for 3D. All modeling attempts ended up with similar models suggesting that: (i) A significant low resistivity anomaly was detected just below the fault's trace representing the so-called "fault zone conductor" with 400 m width and 500 m depth, (ii) An asymmetric damage zone is present involving the fault's core concentrated to the south, (iii) A resistivity contrast between the two sides of the fault, representing a geological boundary between Eocene aged Keşan Formation in the north and Miocene aged Çengelli Formation in the south (iv) Opiholitic basement appears as a high resistivity block at a depth of 800 m.

  11. Inversion of Magnetotelluric Data in Anisotropic Media Using Maximization of Mutual Information

    NASA Astrophysics Data System (ADS)

    Mandolesi, E.; Jones, A. G.

    2011-12-01

    Regularization in inverse geophysics problems has been used extensively, due to the necessity to constrain the model space and to reduce the ill-posedness of several problems. Magnetotelluric (MT) problems suffer from severe non-linearity and ill-posedness, which makes MT inversions extremely challenging. The use of a reference model has been used by many authors in order to drive the inversion process to converge on a model that shares features with the reference, as a result reducing non-uniqueness and improving the model resolution. In our work the reference model drives the inversion keeping the conductivity distribution close to that of the velocity using variation of information as measure of distance between the two pictures. In this way the electrical conductivity and seismic velocity can be compared from a statistical point of view, without the necessity of a common parameterization or a strict geometrical similarity. Our work involves the inversion of MT long-period data, which are sensitive to electrical conductivity, using shear wave velocity maps as reference model in a 1D anisotropic domain. Computation of variation of information is performed through the generation of the joint probability distribution, which allows exploration of the relation between models that fit seismic data and models that fit electrical properties. An approximate agreement between geoelectric strike direction and seismic fast axis have been recognized in different continental lithospheric areas, suggesting a common cause for both the seismic and electric anisotropic behavior. We present an application of this inversion approach to a real dataset from Central Germany, discussing pros and cons of this approach in relation to similar studies on the same area. Due to the minimal assumptions required by this approach, it highlights the possibility of application to different tomography techniques.

  12. Pattern recognition and lithological interpretation of collocated seismic and magnetotelluric models using self-organizing maps

    NASA Astrophysics Data System (ADS)

    Bauer, K.; Muñoz, G.; Moeck, I.

    2012-05-01

    Joint interpretation of models from seismic tomography and inversion of magnetotelluric (MT) data is an efficient approach to determine the lithology of the subsurface. Statistical methods are well established but were developed for only two types of models so far (seismic P velocity and electrical resistivity). We apply self-organizing maps (SOMs), which have no limitations in the number of parameters considered in the joint interpretation. Our SOM method includes (1) generation of data vectors from the seismic and MT images, (2) unsupervised learning, (3) definition of classes by algorithmic segmentation of the SOM using image processing techniques and (4) application of learned knowledge to classify all data vectors and assign a lithological interpretation for each data vector. We apply the workflow to collocated P velocity, vertical P-velocity gradient and resistivity models derived along a 40 km profile around the geothermal site Groß Schönebeck in the Northeast German Basin. The resulting lithological model consists of eight classes covering Cenozoic, Mesozoic and Palaeozoic sediments down to 5 km depth. There is a remarkable agreement between the litho-type distribution from the SOM analysis and regional marker horizons interpolated from sparse 2-D industrial reflection seismic data. The most interesting features include (1) characteristic properties of the Jurassic (low P-velocity gradients, low resistivity values) interpreted as the signature of shales, and (2) a pattern within the Upper Permian Zechstein layer with low resistivity and increased P-velocity values within the salt depressions and increased resistivity and decreased P velocities in the salt pillows. The latter is explained in our interpretation by flow of less dense salt matrix components to form the pillows while denser and more brittle evaporites such as anhydrite remain in place during the salt mobilization.

  13. Structure and Tectonics of the Pacific Northwest from EarthScope Magnetotelluric Data

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Though largely covered by thick volcanic sequences, the northwestern US preserves a record of the Mesozoic to present tectonic evolution of North America. Three-dimensional inversion of Earthscope Transportable Array magnetotelluric data provides important constraints on lithospheric structure as well as the distribution of fluids and melt within the crust and mantle. Resistivity models image a first-order change in the upper mantle across the Klamath-Blue Mountains lineament. Southeast of this boundary, high upper-mantle conductivity is characteristic of the extended Basin and Range province, and is attributed to elevated temperatures and a small percentage of melt. An incursion of this conductive zone to 45 degrees north within the Oregon arc and backarc separates arc segments with distinct isotopic and heat-flow character. The lithosphere is resistive to at least 200 km beneath Idaho and eastern Washington. Correspondence of the western edge of this deep resistor with the Sr 0.706 line suggests this represents the western edge of cratonic North America. Resistive lithosphere is also observed beneath the Hearne and Wyoming cratons and the Colorado Plateau. The geometry and extent of the Eocene Siletz Terrane is also imaged, shows close correspondence with magnetic-field data, and has an eastern boundary roughly coincident with the modern arc. The geometry of the Snake River Plain is clearly reflected within the resistivity model. High crustal resistivity suggests a heavily intruded crustal column, whereas high conductivity in the mantle lithosphere indicates elevated temperatures and partial melt. No indication of the Newberry volcanic progression is evident in the models. Though generally resistive, a modest enhancement in conductivity near the top of the subducting Juan de Fuca slab at of 30-40 km depth may reflect fluid release from metamorphic reactions or pore collapse. At greater depth, a pronounced lateral conductivity contrast projects to the magmatic arc

  14. Imaging Ancient Sutures with EarthScope Transportable Array Magnetotelluric Data

    NASA Astrophysics Data System (ADS)

    Egbert, G. D.

    2014-12-01

    Magnetotellurics (MT) provides a powerful geophysical tool for imaging of ancient suture zones, which are frequently marked by elongated zones of very low resistivity. These conductive anomalies, which can extend to great depths and have apparently persisted for several billion years, most likely result from graphite and sulfides deeply emplaced and remobilized, through subduction, accretion and orogenesis. The Earthscope MT transportable array provides a unique broad-scale view of sutures in the continental US. In the northwestern US subvertical conductive features bound all of the major cratonic blocks. These can be identified with the Cheyenne Belt between the Wyoming Craton (WC) and Yavapai Terranes (YT), the Great Falls Tectonic Zone between WC and the Medicine Hat Block (MHB), and the Vulcan Structure of southern Alberta between MHB and the Hearne Craton. In all cases the conductive anomalies extend well into the mantle lithosphere. The more recent MT TA footprint in the north-central US (surrounding the Mid-Continent Rift (MCR)) also reveals conductive signatures of ancient sutures. The most prominent lies south of Lake Superior, just north of the Niagara Fault (NF), and can be associated with the Penokean Orogeny (~1.85 Ga). A second, further south beneath Iowa and western Wisconsin, just south of the Spirit Lake tectonic zone (SLtz), can be identified with YT accretion (~1.75 Ga). Both of these sutures are cleanly cut by the MCR. The break in the anomalies is narrow (comparable to the surface expression of the MCR) indicating that rifting impacts on the entire crustal section were highly localized. The south-dipping NF conductive anomaly extends from surface outcrop to at least the Moho. The SLtz anomaly is north-dipping, extending from mid-crust through the Moho. In both cases there is some evidence for a modestly conductive layer (likely carbon) thrust to mid-lithospheric depths within the overriding terrane.

  15. Magnetotelluric investigation of the Vestfold Hills and Rauer Group, East Antarctica

    NASA Astrophysics Data System (ADS)

    Peacock, J. R.; Selway, K.

    2016-04-01

    The Vestfold Hills and Rauer Group in East Antarctica have contrasting Archean to Neoproterozoic geological histories and are believed to be juxtaposed along a suture zone that now lies beneath the Sørsdal Glacier. Exact location and age of this suture zone are unknown, as is its relationship to regional deformation associated with the amalgamation of East Gondwana. To image the suture zone, magnetotelluric (MT) data were collected in Prydz Bay, East Antarctica, mainly along a profile crossing the Sørsdal Glacier and regions inland of the Vestfold Hills and Rauer Group islands. Time-frequency analysis of the MT time series yielded three important observations: (1) Wind speeds in excess of ˜8 m/s reduce coherence between electric and magnetic fields due to charged wind-blown particles of ice and snow. (2) Estimation of the MT transfer function is best between 1000 and 1400 UT when ionospheric Hall currents enhance the magnetic source field. (3) Nonplanar source field effects were minimal but detectable and removed from estimation of the MT transfer function. Inversions of MT data in 2-D and 3-D produce similar resistivity models, where structures in the preferred 3-D resistivity model correlate strongly with regional magnetic data. The electrically conductive Rauer Group is separated from the less conductive Vestfold Hills by a resistive zone under the Sørsdal Glacier, which is interpreted to be caused by oxidation during suturing. Though a suture zone has been imaged, no time constrains on suturing can be made from the MT data.

  16. Multi-site magnetotelluric measurement system with real-time data analysis. Final technical report No. 210

    SciTech Connect

    Becker, J.D.; Bostick, F.X. Jr.; Smith, H.W.

    1981-09-01

    A magnetotelluric measurement system has been designed to provide a more cost effective electrical method for geothermal and mineral exploration. The theoretical requirements and sensitivities of the magnetotelluric inversion process were specifically addressed in determining system performance requirements. Significantly reduced instrument noise levels provide improved data quality, and simultaneous measurement at up to six locations provides reduced cost per site. Remotely located, battery powered, instrumentation packages return data to a central controlling site through a 2560 baud wire-line or radio link. Each remote package contains preamplifiers, data conditioning filters, and a 12-bit gain ranging A-D converter for frequencies from 0.001 Hz to 8 Hz. Data frequencies above 8 Hz are processed sequentially by a heterodyne receiver to reduce bandwidth to within the limits of the 2560 baud data link. The central data collection site provides overall control for the entire system. The system operator interacts with the system through a CRT terminal, and he receives hard copy from a matrix graphics printer. Data from the remote packages may be recorded in time sequence on a magnetic tape cartridge system, or an optional Hewlett-Packard 21MX minicomputer can be used to perform real-time frequency analysis. The results of this analysis provide feedback to the operator for improved evaluation of system performance and for selection of future measurement sites.

  17. Two-dimensional magnetotelluric model of deep resistivity structure in the Bodie-Aurora district of California

    USGS Publications Warehouse

    Sampson, Jay A.

    2006-01-01

    Introduction: Magnetotelluric data were acquired during October 2001 by the U.S. Geological Survey (USGS) as part of a study to examine the structural nature of basins in the transition zone between the Sierra Nevada Mountains of California and the Basin and Range province of Nevada. Magnetotelluric (MT) geophysical studies assist the mapping of geologic structure and the inference of lithologic packages that are concealed beneath the Earth's surface. The Basin and Range province has a complicated geologic history, which includes extension and compression of the Earth's crust to form the basins and ranges that blanket much of Nevada. The basins and ranges in the vicinity of this study trend northeastward and are bounded by steeply dipping strike slip faults. Interestingly, deep east-west magnetic trends occur in the aeromagnetic data of this study area indicating that the northeast-trending basins and ranges represent only thin-skinned deformation at the surface with an underlying east-west structure. To investigate this issue, MT data were acquired at seven stations in eastern California, 20 km east of Mono Lake. The purpose of this report is to present a two-dimensional apparent resistivity model of the MT data acquired for this study.

  18. The Making of the Second Diaspora: On the Recent African Immigrant Community in the United States of America.

    ERIC Educational Resources Information Center

    Takyi, Baffour K.

    2002-01-01

    Documents the experiences of recent African immigrants using data from the 1990 U.S. Census. Results indicate that emigration from Africa to the United States is a recent phenomenon, the African immigrant community is not very large, and eight main countries provide the bulk of African immigrants. Significant numbers of African immigrants have…

  19. MARE2DEM: a 2-D inversion code for controlled-source electromagnetic and magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Key, Kerry

    2016-08-01

    This work presents MARE2DEM, a freely available code for 2-D anisotropic inversion of magnetotelluric (MT) data and frequency-domain controlled-source electromagnetic (CSEM) data from onshore and offshore surveys. MARE2DEM parameterizes the inverse model using a grid of arbitrarily shaped polygons, where unstructured triangular or quadrilateral grids are typically used due to their ease of construction. Unstructured grids provide significantly more geometric flexibility and parameter efficiency than the structured rectangular grids commonly used by most other inversion codes. Transmitter and receiver components located on topographic slopes can be tilted parallel to the boundary so that the simulated electromagnetic fields accurately reproduce the real survey geometry. The forward solution is implemented with a goal-oriented adaptive finite element method that automatically generates and refines unstructured triangular element grids that conform to the inversion parameter grid, ensuring accurate responses as the model conductivity changes. This dual-grid approach is significantly more efficient than the conventional use of a single grid for both the forward and inverse meshes since the more detailed finite element meshes required for accurate responses do not increase the memory requirements of the inverse problem. Forward solutions are computed in parallel with a highly efficient scaling by partitioning the data into smaller independent modeling tasks consisting of subsets of the input frequencies, transmitters and receivers. Non-linear inversion is carried out with a new Occam inversion approach that requires fewer forward calls. Dense matrix operations are optimized for memory and parallel scalability using the ScaLAPACK parallel library. Free parameters can be bounded using a new non-linear transformation that leaves the transformed parameters nearly the same as the original parameters within the bounds, thereby reducing non-linear smoothing effects. Data

  20. MARE2DEM: a 2-D inversion code for controlled-source electromagnetic and magnetotelluric data

    NASA Astrophysics Data System (ADS)

    Key, Kerry

    2016-10-01

    This work presents MARE2DEM, a freely available code for 2-D anisotropic inversion of magnetotelluric (MT) data and frequency-domain controlled-source electromagnetic (CSEM) data from onshore and offshore surveys. MARE2DEM parametrizes the inverse model using a grid of arbitrarily shaped polygons, where unstructured triangular or quadrilateral grids are typically used due to their ease of construction. Unstructured grids provide significantly more geometric flexibility and parameter efficiency than the structured rectangular grids commonly used by most other inversion codes. Transmitter and receiver components located on topographic slopes can be tilted parallel to the boundary so that the simulated electromagnetic fields accurately reproduce the real survey geometry. The forward solution is implemented with a goal-oriented adaptive finite-element method that automatically generates and refines unstructured triangular element grids that conform to the inversion parameter grid, ensuring accurate responses as the model conductivity changes. This dual-grid approach is significantly more efficient than the conventional use of a single grid for both the forward and inverse meshes since the more detailed finite-element meshes required for accurate responses do not increase the memory requirements of the inverse problem. Forward solutions are computed in parallel with a highly efficient scaling by partitioning the data into smaller independent modeling tasks consisting of subsets of the input frequencies, transmitters and receivers. Non-linear inversion is carried out with a new Occam inversion approach that requires fewer forward calls. Dense matrix operations are optimized for memory and parallel scalability using the ScaLAPACK parallel library. Free parameters can be bounded using a new non-linear transformation that leaves the transformed parameters nearly the same as the original parameters within the bounds, thereby reducing non-linear smoothing effects. Data

  1. The upper crust of the Scandinavian Caledonides as seen by Magnetotellurics

    NASA Astrophysics Data System (ADS)

    Yan, Ping; Garcia Juanatey, Maria A.; Kalscheuer, Thomas; Juhlin, Christopher

    2015-04-01

    As part of the Collisional Orogeny in the Scandinavian Caledonides (COSC) project, broadband magnetotelluric (MT) data were acquired along a 60 km long profile following recent seismic reflection surveys. In total, 78 MT sites were installed with an inter-site spacing varying between 600 and 1000 m. The aims of this study are to provide resistivity information on the upper crust of the mountain belt and, together with other geophysical investigations, to better delineate the structures of the orogen and the processes that shaped it. Additionally, the MT data are expected to help determine the location of a future borehole, COSC-2. COSC-2 is planned to drill through the décollement zone associated to the graphitic rich alum shales. Since these shales are highly conductive, they are an excellent target for the MT method. Besides the long MT profile, one short profile with 5 stations was acquired nearby the already existing COSC-1 drill site to increase areal coverage and better constrain 3D resistivity structures. The new 3D information improves the existing 3D geological model around the borehole, that has been interpreted from seismic reflection and potential field data. The impedance functions were calculated using a robust statistical procedure and the remote reference technique. MT data from Norway recorded at the same time in a field campaign by Oulu University were used for remote referencing. The data quality of the obtained transfer functions varies along the profile, being very good in remote areas, but quite noisy close to cities. Thus, a careful selection of the data set was necessary prior to analysis and modelling. 2D resistivity models of the 60 km long profile were estimated through inversion using the determinant of the impedance tensor, the TE mode, the TM mode, and the combination of TE and TM modes. The main features shared by the models are a resistor lying beneath COSC-1 extending down to about 2 km depth, a shallow resistor further to the east

  2. Magnetotelluric investigation of the Alnö alkaline and carbonatite ring complex, central Sweden

    NASA Astrophysics Data System (ADS)

    Yan, Ping; Andersson, Magnus; Garcia Juanatey, Maria A.; Shan, Chunling; Malehmir, Alireza; Pedersen, Laust B.

    2014-05-01

    Alnö complex, 553-590 Ma, located in central Sweden, is one of the largest of few known alkaline and carbonatite ring intrusions in the world. The complex primarily consists of alkaline silicate rocks (ijolite, nepheline-syenite and pyroxenite) and a wide range of carbonatite dykes with different compositions (e.g., sövite). To better understand the intrusion mechanism(s) and the deeper structure of the intrusion, three high-resolution reflection seismic, gravity and magnetic profiles, crossing the main intrusion, were acquired in winter 2010. Together with these, petrophysical measurements on various rock samples have also been carried out. These data not only successfully showed the lateral extension of the intrusion at depth but also suggested a solidified saucer-shaped magma chamber at about 3 km depth that is associated with caldera-related ring-type fault systems. To further elucidate these interpretations, magnetotelluric (MT) data were acquired in summer 2013. The MT data were measured at 34 stations across the intrusion and designed so that a 3D conductivity model can be obtained. Most of the sites are located along the seismic profiles, while the rest is distributed over the intrusion area, to provide lateral and off-profile information. The time series were recorded with four broadband MT instruments simultaneously. The used sampling rates were 1000 Hz (two hours after midnight) and 20 Hz (a full day). The collected MT data are highly influenced by noise from cultural sources. Luckily, higher frequencies are less influenced providing a good coverage of the interest depth of about 5 km. Therefore, the data processing and analysis focused solely on the high frequency data. To decrease the effect of noise, the best quality site in one day was chosen for remote referencing the other three. Even if the sites were only 500 to 1000 m apart, better results were obtained, indicating very localized noise sources in the area. The strike analysis of the obtained

  3. The IRETHERM project: Magnetotelluric assessment of the Rathlin Basin as a possible geothermal aquifer

    NASA Astrophysics Data System (ADS)

    Delhaye, Robert; Jones, Alan; Reay, Derek

    2014-05-01

    IRETHERM (www.iretherm.ie) is a collaborative, SFI-funded research project to identify and evaluate sites within Ireland possessing the greatest potential for deep, low-enthalpy, geothermal energy provision. Possible areas for geothermal potential include the Permian and Triassic sedimentary basins in Northern Ireland, which contain groups with relatively high primary porosity, with viability depending largely on the permeability distribution, which controls fluid flow and heat-exchange. The most promising of these is the Triassic Sherwood Sandstone Group, which has measured porosities and permeabilities of 8-24% and 2-1000 mD respectively from borehole core samples. The subject of the work presented here, the Rathlin Basin in County Antrim, is one of three onshore basins in Northern Ireland, where measurements in two independent boreholes show geothermal gradients of between 36 and 43 °C/km to depths of 1481 m. Previously published interpretations of gravity models across the basin attribute a thickness of 2000 m to the Sherwood Sandstone Group, with a maximum depth to the Permo-Triassic basement of 4000 m. Magnetotelluric data were acquired onshore in June 2012 across a 2-D grid of 57 sites with a 2 km site spacing, and on the nearby Rathlin Island on two profiles totalling 12 sites with an 800 m site spacing in April 2013 in order to image the thickness and continuity of the sediments in the north-eastern portion of the basin. In the modelling results presented here, the Permo-Triassic sediment fill has a well-imaged resistivity contrast to the surrounding basal Dalradian metasediments. The data have been analysed and modelled to determine a resistivity model that maps the variation in thickness of the sediment fill and the truncation of the basin sediments against the Tow Valley Fault. Further synthetic testing of the model sensitivity to variation of the thickness of the Sherwood Sandstone Group within the sediment fill has also been performed, as the

  4. Magnetotelluric survey to locate the Archean/Proterozoic suture zone north of Wells, Nevada

    USGS Publications Warehouse

    Williams, Jackie M.; Rodriguez, Brian D.

    2006-01-01

    , three regional north-south magnetotelluric (MT) sounding profiles were acquired in western Utah and northeastern Nevada (Williams and Rodriguez, 2003; 2004; 2005), and one east-west MT sounding profile (fig. 1) MT sounding profile was acquired in northeastern Nevada. Resistivity modeling of the MT data can be used to investigate buried structures or sutures that may have influenced subsequent regional fluid flow and localized mineralization. The purpose of this report is to release the MT sounding data collected along the east-west profile in northeastern Nevada; no interpretation of the data is included.

  5. Magnetotelluric study of the Pahute Mesa and Oasis Valley regions, Nye County, Nevada

    USGS Publications Warehouse

    Schenkel, Clifford J.; Hildenbrand, Thomas G.; Dixon, Gary L.

    1999-01-01

    Magnetotelluric data delineate distinct layers and lateral variations above the pre-Tertiary basement. On Pahute Mesa, three resistivity layers associated with the volcanic rocks are defined: a moderately resistive surface layer, an underlying conductive layer, and a deep resistive layer. Considerable geologic information can be derived from the conductive layer which extents from near the water table down to a depth of approximately 2 km. The increase in conductivity is probably related to zeolite zonation observed in the volcanic rock on Pahute Mesa, which is relatively impermeable to groundwater flow unless fractured. Inferred faults within this conductive layer are modeled on several profiles crossing the Thirsty Canyon fault zone. This fault zone extends from Pahute Mesa into Oasis Valley basin. Near Colson Pond where the basement is shallow, the Thirsty Canyon fault zone is several (~2.5) kilometers wide. Due to the indicated vertical offsets associated with the Thirsty Canyon fault zone, the fault zone may act as a barrier to transverse (E-W) groundwater flow by juxtaposing rocks of different permeabilities. We propose that the Thirsty Canyon fault zone diverts water southward from Pahute Mesa to Oasis Valley. The electrically conductive nature of this fault zone indicates the presence of abundant alteration minerals or a dense network of open and interconnected fractures filled with electrically conductive groundwater. The formation of alteration minerals require the presence of water suggesting that an extensive interconnected fracture system exists or existed at one time. Thus, the fractures within the fault zone may be either a barrier or a conduit for groundwater flow, depending on the degree of alteration and the volume of open pore space. In Oasis Valley basin, a conductive surface layer, composed of alluvium and possibly altered volcanic rocks, extends to a depth of 300 to 500 m. The underlying volcanic layer, composed mostly of tuffs, fills the

  6. Amphibious Magnetotelluric Investigation of the Aleutian Arc: Mantle Melt Generation and Migration beneath Okmok Caldera

    NASA Astrophysics Data System (ADS)

    Zelenak, G.; Key, K.; Bennington, N. L.; Bedrosian, P.

    2015-12-01

    Understanding the factors controlling the release of volatiles from the downgoing slab, the subsequent generation of melt in the overlying mantle wedge, the migration of melt to the crust, and its evolution and emplacement within the crust are important for advancing our understanding of arc magmatism and crustal genesis. Because melt and aqueous fluids are a few orders of magnitude more electrically conductive than unmelted peridotite, the conductivity-mapping magnetotelluric (MT) method is well-suited to imaging fluids and melt beneath arc volcanoes. Here we present conductivity results from an amphibious MT profile crossing Okmok volcano in the central Aleutian arc. The Aleutian arc is one of the most volcanically active regions in North America, making it an ideal location for studying arc magnetism. Okmok volcano, located on the northeastern portion of Umnak Island, is among the most active volcanoes in the Aleutian chain. In addition to two caldera-forming events in the Holocene, numerous eruptions in the past century indicate a robust magmatic supply. Previous coarse resolution seismic studies have inferred a crustal magma reservoir. In order to investigate the role fluids play in melting the mantle wedge, how melts ascend through the corner flow regime of the mantle wedge, how melt migrates and is stored within the upper mantle and crust, and how this impacts explosive caldera forming eruptions, we carried out an amphibious geophysical survey across the arc in June-July 2015. Twenty-nine onshore MT stations and 10 offshore stations were collected in a 3D array covering Okmok, and 43 additional offshore MT stations completed a 300 km amphibious profile starting at the trench, crossing the forearc, arc and backarc. Thirteen onshore passive seismic stations were also installed and will remain in place for one year to supplement the twelve permanent stations on the island. Data collected by this project will be used to map seismic velocity and electrical

  7. Geoelectric structure estimated from magnetotelluric data from the Uttarakhand Himalaya, India

    NASA Astrophysics Data System (ADS)

    Miglani, Rohit; Shahrukh, M.; Israil, M.; Gupta, Pravin K.; Varshney, S. K.; Elena, Sokolova

    2014-12-01

    Geoelectric strike and resistivity structure of the crust have been estimated from 37 magnetotelluric (MT) data sites along a profile from Roorkee to Gangotri in Uttarakhand Himalaya. Impedance decomposition schemes based on Bahr's, Groom Bailey and Phase tensor were implemented in a MATLAB code for the average strike estimation. Geoelectric strike direction varies with period as well as in different litho-tectonic units along the profile. In the period band from 1 to 100 s average geoelectric strike in the southern end of the profile (Indo-Gangetic Plains) is N79°W, which is slightly rotated to the north in the Lesser Himalayan region and becomes N68°W whereas it is N81°W in the Higher Himalayan region. However, average strike is stabilized to N77°W for the entire profile in the long period band (100-1000 s). Geoelectrical structure of the crust has been obtained along the profile by 2D inversion of MT data. Major features of 2D resistivity model are: (i) southern part of the model is a low resistivity (<50 Om) zone at shallow depth (5-7 km) representing the loose sediments of the Indo-Gangetic Plains (IGP), whose thickness increases in the south; (ii) highly resistive (>1000 Om) layer below the IGP sediments is the basement rock, representing the resistivity of the top of the subducting Indian Plate; (iii) the Main Boundary Thrust (MBT) and the Main Central Thrust (MCT) zones can be seen in the electrical image. However, the Himalayan Frontal Thrust (HFT) could not be resolved and (iv) a low resistivity (<10 Om) feature in the MCT zone extending to the depth of 30 km is delineated. This low resistivity could be due to fluid-filled fractured rock matrix or partial melt zone. Hypocenters of many earthquakes are concentrated along the boundary of this low resistivity zone and relatively high resistivity blocks around it. The resulted model supports flat-ramp-flat geometry of the Main Himalayan Thrust along which the Indian Plate is subducting.

  8. Identification of kimberlite bodies in Brazil from a 3D audio-magnetotelluric survey

    NASA Astrophysics Data System (ADS)

    De Lugao, P. P.; Eric, C. D. O.; Loureiro, F. O.; Arantes, P. R.; Pastana, A. F.

    2015-12-01

    We report on a succesfull identification of kimberlite bodies in Brazil through the use of the electromagnetic technique audio-magnetotelluric (AMT). Macnae (1979) writes that "In one large survey in South Africa, electromagnetic (EM) techniques have proven to be remarkably effective in detecting the presence of weathered clays or epiclastic kimberlite contained within the pipes." Full tensor AMT data were acquired at 65 points (stations) in a 3D configuration with frequencies ranging from 10kHz to 1Hz. The survey was located in the NW portion of the Mato Grosso state, Brazil, in na area of thick jungle coverage. During the AMT survey, few outcrops were seen because of the dense forest cover. Usually, the occurrences found were of sand deposits, indicating the occurence of Fazenda Casa Branca and Utiariti Formations and gravel from Salto das Nuvens Formation, widely used in paving trails n this region. In the area of the survey, three main targets were confirmed/identified: Kimberlite Area 1 - a classic kimberlite in the region, with the crater facies with different clasts and distinct size. We noted the occurrence of a red-brown soil and an unusual vegetation in this area. The resistivity model provided confirmed the presence of Kimberlite Area 1 and was used to identify other two areas. Area of Interest 1 - area with atypical vegetation along a trail. There is an excavation that displays soil of white color with several blocks present, there are small quartz crystal agglomerates in these blocks. The resistivity model cleary shows a conductive body here, indicative of the presence of a kimberlite. Area of Interest 2 - the presence of a kimberlite was confirmed, not exactly where the targeted Area 2 was, but the southwest of it. Close to this area, there was a very fine rock and a few blocks of pure silica, probably indicating a kimberlitic intrusion. In summary, the 3D resistivity model in depth obtained from inversion of the AMT data confirmed and identified

  9. Imaging the magmatic system of Mono Basin, California with magnetotellurics in three--dimensions

    USGS Publications Warehouse

    Peacock, Jared R.; Mangan, Margaret T.; McPhee, Darcy K.; Ponce, David A.

    2015-01-01

    A three–dimensional (3D) electrical resistivity model of Mono Basin in eastern California unveils a complex subsurface filled with zones of partial melt, fluid–filled fracture networks, cold plutons, and regional faults. In 2013, 62 broadband magnetotelluric (MT) stations were collected in an array around southeastern Mono Basin from which a 3D electrical resistivity model was created with a resolvable depth of 35 km. Multiple robust electrical resistivity features were found that correlate with existing geophysical observations. The most robust features are two 300 ± 50 km3 near-vertical conductive bodies (3–10 Ω·m) that underlie the southeast and north-eastern margin of Mono Craters below 10 km depth. These features are interpreted as magmatic crystal–melt mush zones of 15 ± 5% interstitial melt surrounded by hydrothermal fluids and are likely sources for Holocene eruptions. Two conductive east–dipping structures appear to connect each magma source region to the surface. A conductive arc–like structure (< 0.9 Ω·m) links the northernmost mush column at 10 km depth to just below vents near Panum Crater, where the high conductivity suggests the presence of hydrothermal fluids. The connection from the southernmost mush column at 10 km depth to below South Coulée is less obvious with higher resistivity (200 Ω·m) suggestive of a cooled connection. A third, less constrained conductive feature (4–10 Ω·m) 15 km deep extending to 35 km is located west of Mono Craters near the eastern front of the Sierra Nevada escarpment, and is coincident with a zone of sporadic, long–period earthquakes that are characteristic of a fluid-filled (magmatic or metamorphic) fracture network. A resistive feature (103–105 Ω·m) located under Aeolian Buttes contains a deep root down to 25 km. The eastern edge of this resistor appears to structurally control the arcuate shape of Mono Craters. These observations have been combined to form a new conceptual model

  10. Physical properties of volcanic lightning: Constraints from magnetotelluric and video observations at Sakurajima volcano, Japan

    NASA Astrophysics Data System (ADS)

    Aizawa, Koki; Cimarelli, Corrado; Alatorre-Ibargüengoitia, Miguel A.; Yokoo, Akihiko; Dingwell, Donald B.; Iguchi, Masato

    2016-06-01

    The lightning generated by explosive volcanic eruptions is of interest not only as a promising technique for monitoring volcanic activity, but also for its broader implications and possible role in the origin of life on Earth, and its impact on the atmosphere and biosphere of the planet. However, at present the genetic mechanisms and physical properties of volcanic lightning remain poorly understood, as compared to our understanding of thundercloud lightning. Here, we present joint magnetotelluric (MT) data and video imagery that were used to investigate the physical properties of electrical discharges generated during explosive activity at Sakurajima volcano, Japan, and we compare these data with the characteristics of thundercloud lightning. Using two weeks of high-sensitivity, high-sample-rate MT data recorded in 2013, we detected weak electromagnetic signals radiated by volcanic lightning close to the crater. By carefully inspecting all MT waveforms that synchronized with visible flashes, and comparing with high-speed (3000 frame/s) and normal-speed (30 frame/s) videos, we identified two types of discharges. The first type consists of impulses (Type A) and is interpreted as cloud-to-ground (CG) lightning. The second type is characterized by weak electromagnetic variations with multiple peaks (Type B), and is interpreted as intra-cloud (IC) lightning. In addition, we observed a hybrid MT event wherein a continuous weak current accompanied Type A discharge. The observed features of volcanic lightning are similar to thunderstorm lightning, and the physical characteristics show that volcanic lightning can be treated as a miniature version of thunderstorm lightning in many respects. The overall duration, length, inter-stroke interval, peak current, and charge transfer all exhibit values 1-2 orders of magnitude smaller than those of thunderstorm lightning, thus suggesting a scaling relation between volcanic and thunderstorm lightning parameters that is independent of

  11. Magnetotelluric imaging of the subducting slab in Cascadia with constraints from seismology

    NASA Astrophysics Data System (ADS)

    Yang, B.; Egbert, G. D.; Kelbert, A.; Humphreys, E.

    2015-12-01

    We present results from three-dimensional (3D) inversion of long-period magnetotelluric (MT) data from Cascadia, using seismological constraints on plate geometry and back-arc structure, to refine 3D images of electrical resistivity across this subduction zone. For this study we employed the impedances and vertical transfer functions from 144 sites from the EarthScope Transportable Array, along with data from previous higher density MT profiles from Cascadia (EMSLAB, CAFE-MT etc.). Morphological parameters for the subducting Juan de Fuca and Gorda plates (e.g. upper boundary and thickness) were extracted from McCrory et al (2012) and Schmandt and Humphreys (2010) seismological models and used to define a resistive subducting slab structure in 3D. This was then either used as a prior model, or fixed (both resistivity and geometry) during the MT inversion. By imposing constraints on the geometry of the slab (which is otherwise imaged as an amorphous broad resistive zone) we improve recovery and resolution of subduction related conductivity features. The constrained inversions also allowed us to test sensitivity of the MT data to variants on slab geometry, such as the proposed slab "tear" near the Oregon-Washington border suggested by some seismic tomography models, and to explore consistency of the MT data with seismic models, which suggest segmentation of back-arc upwelling. Three zones of substantially reduced resistivity were found, all exhibiting significant along-strike variability. In the forearc, an N-S stripe of high conductivity (10 ohm-m or less) was found just above the plate interface, near the tip of the mantle wedge. This conductive feature is spatially coincident with mapped locations of episodic tremor and slip, and likely represents aqueous fluids associated with slab dehydration. To the east, a second, clearly separated, N-S elongate zone of similarly high conductivity occurs in the mid-lower crust and upper mantle beneath the modern arc, again

  12. Three-dimensional magnetotelluric exploration of Tenerife geothermal field (Canary Islands, Spain).

    NASA Astrophysics Data System (ADS)

    Piña-Varas, Perla; Ledo, Juanjo; Queralt, Pilar; Marcuello, Alex; Bellmunt, Fabián; Hidalgo, Raúl

    2013-04-01

    Several magnetotelluric (MT) surveys have been carried out to investigate the geothermal system in Tenerife Island (Canary Islands, Spain). These data have been acquired since 1987 till 2012 by different agencies and institutions. In 1987 and 1991, two MT surveys were carried out by the Spanish Geological Survey (IGME). These data in paper format (129 MT sites in total) were collected and digitized. In October 2009, 83 stations were acquired for Petratherm Ltd., and 25 stations in March 2012 by the University of Barcelona. In total, 237 MT stations distributed around the island center are available for this study. A simplified conceptual model of the island using known geological and geophysical data has been created to identify the ocean and topography effects on the MT data. The typical conceptual model of a generic high temperature volcanic geothermal system (Cumming, 2009a; Pellerin, 1996) and the 1D models from the MT data have played a key role for the correct construction of this conceptual model. Synthetic forward modeling was performed on a set of models to determine the effect of topography and of the conductive Atlantic Ocean. Finally, a 3D resistivity model of Tenerife Island has been computed with modEM code (Egbert and Kelbert, 2012). Out of the 237 MT sites available, 87 stations were discarded because of computational capability problems. Thus, for this new 3D model, 150 MT sites have been taking into account from the different field surveys. The model is discrtized on 94x65x133-layer grid and the inversions are undertaken using the off-diagonal components (Zxy, Zyx) of the impedance tensor for 16 periods in the frequency range from 1000 to 0.1 Hz. In the inversion processing we assumed a 5% error floor in the impedance components and the final RMS is 3.5. The 3D inversion model shows the typical layered pattern expected from a volcanic complex (andesite, basalt) with a possible geothermal overprint; a resistive fresh volcanic structure near the

  13. Magnetotelluric Studies of the Laguna del Maule Volcanic Field, Central Chile

    NASA Astrophysics Data System (ADS)

    Cordell, D. R.; Unsworth, M. J.; Diaz, D.; Pavez, M.; Blanco, B.

    2015-12-01

    Geodetic data has shown that the surface of the Laguna del Maule (LdM) volcanic field in central Chile has been moving upwards at rates >20 cm/yr since 2007 over a 200 km2 area. It has been hypothesized that this ground deformation is due to the inflation of a magma body at ~5 km depth beneath the lake (2.8 km b.s.l.). This magma body is a likely source for the large number of rhyolitic eruptions at this location over the last 25 ka. A dense broadband magnetotelluric (MT) array was collected from 2009 to 2015 and included data from a geothermal exploration project. MT phase tensor analysis indicates that the resistivity structure of the region is largely three-dimensional for signals with periods longer than 1 s, which corresponds to depths >5 km. The MT data were inverted using the ModEM inversion algorithm to produce a three-dimensional electrical resistivity model which included topography. Four primary features were identified in the model: 1) A north-south striking, 10 km by 5 km, low-resistivity zone (<5 Ωm) northwest of the inflation centre at a depth of ~5 km (2.8 km b.s.l.) is interpreted as a zone of partial melt which may be supplying material via conduits to account for the observed ground deformation; 2) A shallow low-resistivity feature ~400 m beneath the lake surface (1.8 km a.s.l.) and spatially coincident with the inflation centre is interpreted to be a zone of hydrothermal alteration; 3) A thin, low-resistivity feature to the west of LdM at a depth of ~250 m (2.2 km a.s.l.) is interpreted to be the clay cap of a potential geothermal prospect; 4) A large, low-resistivity zone beneath the San Pedro-Tatara Volcanic Complex to the west of LdM at a depth of ~10 km (8 km b.s.l.) is interpreted to be a zone of partial melt. Further MT data collection is planned for 2016 which will expand the current grid of MT stations to better constrain the lateral extent of the observed features and give greater insight into the dynamics of this restless magma system.

  14. 3-D inversion of magnetotelluric data using unstructured tetrahedral elements: applicability to data affected by topography

    NASA Astrophysics Data System (ADS)

    Usui, Yoshiya

    2015-08-01

    A 3-D magnetotelluric (MT) inversion code using unstructured tetrahedral elements has been developed in order to correct the topographic effect by directly incorporating it into computational grids. The electromagnetic field and response functions get distorted at the observation sites of MT surveys because of the undulating surface topography, and without correcting this distortion, the subsurface structure can be misinterpreted. Of the two methods proposed to correct the topographic effect, the method incorporating topography explicitly in the inversion is applicable to a wider range of surveys. For forward problems, it has been shown that the finite element method using unstructured tetrahedral elements is useful for the incorporation of topography. Therefore, this paper shows the applicability of unstructured tetrahedral elements in MT inversion using the newly developed code. The inversion code is capable of using the impedance tensor, the vertical magnetic transfer function (VMTF), and the phase tensor as observational data, and it estimates the subsurface resistivity values and the distortion tensor of each observation site. The forward part of the code was verified using two test models, one incorporating topographic effect and one without, and the verifications showed that the results were almost the same as those of previous works. The developed inversion code was then applied to synthetic data from a MT survey, and was verified as being able to recover the resistivity structure as well as other inversion codes. Finally, to confirm its applicability to the data affected by topography, inversion was performed using the synthetic data of the model that included two overlapping mountains. In each of the cases using the impedance tensor, the VMTF and the phase tensor, by including the topography in the mesh, the subsurface resistivity was determined more proficiently than in the case using the flat-surface mesh. Although the locations of the anomalies were

  15. [Clinical experience and comparison of ketamine-medetomidine with ketamine-xylazine anesthesia in the African wild dog (Lycaon pictus) in captivity].

    PubMed

    Váhala, J

    1993-01-01

    The effects of two mixtures, ketamine-xylazine and ketamine-medetomidine, were compared in anesthesia of African wild dog (Lycaon pictus) in the Zoo park at Dvůr Králové; the effects of these combinations were also investigated on the triad values and on the basic hematological (red blood counts, hematocrit, hemoglobin content, derived parameters MCM, MCHC, MCV, white blood counts, differential blood counting) and biochemical (total proteins, glucose, creatinine, urea, cholesterol, magnesium, calcium, phosphorus, chlorides, sodium, potassium, alkaline phosphatase, gamma-glutamyl transferase, alanine transferase, aspartate transaminase) parameters of blood and blood serum in anesthesia. Tab. I shows the reasons for anesthesia in 68 individuals of African wild dog in the years 1980-1990. As for both mixtures, application of drugs with a blowpipe was used. In the anesthetized animals, the outset of ataxia, laying down and the outset of sleep were followed (Tab. II), as well as the time of wakening up without and with antidote administration (Tabs. IV and V). The outset of ataxia was fast 1.5 +/- 0.6 min) in the ketamine-xylazine mixture administered at doses of 5.07 +/- 1.16 mg/kg ketamine and 2.11 +/- 0.53 mg/kg xylazine, similarly like lying down (3.2 +/- 1.0 min) and loosing sensation (6.3 +/- 1.6 min). At the start of the drug action, vomiting was often observed, and sometimes in the first ten minutes after drug harpooning short clonic convulsions of the limbs or the whole body occurred. In further course, immobilization and anesthesia were complete and satisfactory in all cases. The first reactions to outer stimuli during wakening up without antidote administration were observed in 135 +/- 11.9 minutes while the animals stood up in 210 +/- 44.5 minutes after drug harpooning (Tab. IV). When the nonspecific antidote xylazine-yohimbine was used, the first reactions after i.m. instillation at a dose of 0.31 +/- 0.02 mg/kg appeared in 20.3 +/- 0.57 min, after i

  16. Laboratory capacity building for the International Health Regulations (IHR[2005]) in resource-poor countries: the experience of the African Field Epidemiology Network (AFENET).

    PubMed

    Masanza, Monica Musenero; Nqobile, Ndlovu; Mukanga, David; Gitta, Sheba Nakacubo

    2010-12-03

    Laboratory is one of the core capacities that countries must develop for the implementation of the International Health Regulations (IHR[2005]) since laboratory services play a major role in all the key processes of detection, assessment, response, notification, and monitoring of events. While developed countries easily adapt their well-organized routine laboratory services, resource-limited countries need considerable capacity building as many gaps still exist. In this paper, we discuss some of the efforts made by the African Field Epidemiology Network (AFENET) in supporting laboratory capacity development in the Africa region. The efforts range from promoting graduate level training programs to building advanced technical, managerial and leadership skills to in-service short course training for peripheral laboratory staff. A number of specific projects focus on external quality assurance, basic laboratory information systems, strengthening laboratory management towards accreditation, equipment calibration, harmonization of training materials, networking and provision of pre-packaged laboratory kits to support outbreak investigation. Available evidence indicates a positive effect of these efforts on laboratory capacity in the region. However, many opportunities exist, especially to support the roll-out of these projects as well as attending to some additional critical areas such as biosafety and biosecuity. We conclude that AFENET's approach of strengthening national and sub-national systems provide a model that could be adopted in resource-limited settings such as sub-Saharan Africa.

  17. Viewpoint: Cultural competence and the African American experience with health care: The case for specific content in cross-cultural education.

    PubMed

    Eiser, Arnold R; Ellis, Glenn

    2007-02-01

    Achieving cultural competence in the care of a patient who is a member of an ethnic or racial minority is a multifaceted project involving specific cultural knowledge as well as more general skills and attitude adjustments to advance cross-cultural communication in the clinical encounter. Using the important example of the African American patient, the authors examine relevant historical and cultural information as it relates to providing culturally competent health care. The authors identify key influences, including the legacy of slavery, Jim Crow discrimination, the Tuskegee syphilis study, religion's interaction with health care, the use of home remedies, distrust, racial concordance and discordance, and health literacy. The authors propose that the awareness of specific information pertaining to ethnicity and race enhances cross-cultural communication and ways to improve the cultural competence of physicians and other health care providers by providing a historical and social context for illness in another culture. Cultural education, modular in nature, can be geared to the specific populations served by groups of physicians and provider organizations. Educational methods should include both information about relevant social group history as well as some experiential component to emotively communicate particular cultural needs. The authors describe particular techniques that help bridge the cross-cultural clinical communication gaps that are created by patients' mistrust, lack of cultural understanding, differing paradigms for illness, and health illiteracy.

  18. The African superswell

    NASA Technical Reports Server (NTRS)

    Nyblade, Andrew A.; Robinson, Scott W.

    1994-01-01

    Maps of residual bathymetry in the ocean basins around the African continent reveal a broad bathymetric swell in the southeastern Atlantic Ocean with an amplitude of about 500 m. We propose that this region of anomalously shallow bathymetry, together with the contiguous eastern and southern African plateaus, form a superswell which we refer to as the African superswell. The origin of the African superswell is uncertain. However, rifting and volcanism in eastern Africa, as well as heat flow measurements in southern Africa and the southeastern Atlantic Ocean, suggest that the superswell may be attributed, at least in part, to heating of the lithosphere.

  19. School and Peer Influences on the Academic Outcomes of African American Adolescents

    PubMed Central

    Estrada-Martinez, Lorena; Colin, Rosa J.; Jones, Brittni D.

    2015-01-01

    Little scholarship explores how adolescents’ beliefs about school and peers influence the academic outcomes of African American boys and girls. The sample included 612 African American boys (N=307, Mage=16.84) and girls (N=305, Mage=16.79). Latent class analysis (LCA) revealed unique patterns for African American boys and girls. Findings indicate that for African American boys, school attachment was protective, despite having peers who endorsed negative achievement values. Furthermore, socio-economic (SES) status was associated with higher grade point averages (GPA) for African American girls. Overall, these findings underscore the unique role of school, peer, and gendered experiences in lives of African American adolescents. PMID:26277404

  20. In vitro permeation of platinum through African and Caucasian skin.

    PubMed

    Franken, A; Eloff, F C; du Plessis, J; Badenhorst, C J; Du Plessis, J L

    2015-02-01

    The majority of the South African workforce are Africans, therefore potential racial differences should be considered in risk and exposure assessments in the workplace. Literature suggests African skin to be a superior barrier against permeation and irritants. Previous in vitro studies on metals only included skin from Caucasian donors, whereas this study compared the permeation of platinum through African and Caucasian skin. A donor solution of 0.3 mg/ml of potassium tetrachloroplatinate (K₂PtCl₄) dissolved in synthetic sweat was applied to the vertical Franz diffusion cells with full thickness abdominal skin. Skin from three female African and three female Caucasian donors were included (n=21). The receptor solution was removed at various intervals during the 24 h experiment, and analysed with high resolution inductively coupled plasma-mass spectrometry (ICP-MS). Skin was digested and analysed by inductively coupled plasma-optical emission spectrometry (ICP-OES). Significantly higher permeation of platinum through intact African skin (p=0.044), as well as a significantly higher mass of platinum retention in African skin in comparison with Caucasian skin (p=0.002) occurred. Significant inter-donor variation was found in both racial groups (p<0.02). Results indicate that African workers have increased risk of dermal permeation and therefore possible sensitisation caused by dermal exposure to platinum salts. These results are contradictory to limited literature suggesting a superior barrier in African skin and further investigation is necessary to explain the higher permeation through African skin.