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  1. Examining African self-consciousness and Black racial identity as predictors of Black men's psychological well-being.

    Science.gov (United States)

    Pierre, Martin R; Mahalik, James R

    2005-02-01

    This study investigated African self-consciousness and Black racial identity as predictors of psychological distress and self-esteem for Black men. One hundred thirty Black men from a college and community sample completed the African Self-Consciousness Scale, the Racial Identity Attitude Scale-B, the Symptom Checklist 90-Revised, and the Coopersmith Self-Esteem Inventory. Canonical correlation analysis found 2 significant roots with the 1st root indicating that Black men whose attitudes reflected Preencounter and Immersion racial identity attitudes and who do not resist against anti-African/Black forces reported greater psychological distress and less esteem. Results from the 2nd root suggested that Black men whose attitudes reflect greater Internalization racial identity attitudes, greater resistance to anti-African/Black forces, and less identification with Blacks reported greater self-esteem. PMID:15727493

  2. Acculturative Experiences of Black-African International Students

    Science.gov (United States)

    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,…

  3. South African black generation Y students' perceptions of local black celebrity endorsers' credibility / Boitumelo Vincent Molelekeng

    OpenAIRE

    Molelekeng, Boitumelo Vincent

    2012-01-01

    The use of celebrity endorsers is a popular marketing strategy in many countries. Typically, many marketers believe that using celebrities is a viable marketing strategy for attracting customers, increasing market share and improving sales for their market offerings. The celebrity endorsement strategy using local celebrities is increasing in South Africa. Many South African marketers are now using popular local black celebrities in an attempt to attract the prosperous black emerging middle cl...

  4. The Self-Concept Level of Black Adolescents with and without African Names.

    Science.gov (United States)

    Terrell, Francis; And Others

    1988-01-01

    Explored the self-concept level of Black adolescents with and without African names, and of their parents, using the Terrell and Taylor Black Ideology Scale and the Coopersmith Self-Esteem Inventory. Adolescents with African names demonstrated significantly higher scores on the Black self-concept scales than did those without African names.…

  5. Black History Month 2005 to focus on "African Diaspora"

    OpenAIRE

    Felker, Susan B.

    2005-01-01

    "The African Diaspora" is the theme of the 2005 Black History Month observances at Virginia Tech, which will feature talks by noted scholars, films, theatrical performances, discussions, a formal dinner, and a beauty pageant. Programs, most of which are free and open to the public, actually begin with Martin Luther King Jr. Day commemorations and continue until the end of February.

  6. What do young black South Africans think about AIDS?

    Science.gov (United States)

    Spurgeon, D

    1992-07-01

    In South Africa, a fatalistic attitude prevails among young black youth toward prevention of HIV transmission. Many of the 3 million black migrant laborers in single-sex hostels have many partners who are prostitutes. Due to culture, race, and class, black women are so oppressed that they cannot even require sex partners to wear condoms. Blacks perceive condoms as a governmental means to control population growth. The Centre for Health and Social Studies has learned that 14-17 year old blacks have been sexually active for a long time, so it has decided to also market its AIDS prevention program to 11-13 year olds. AIDS has not yet reached epidemic proportions in South Africa, however, and a full scale intervention program implemented between the end of 1992 and mid-1993 could stem the epidemic. The Health and Refugee Trust has developed a data base about the attitudes of South African refugees toward AIDS and other sexually transmitted diseases. It plans to distribute educational materials to hostels, squatter settlements, and rural communities. The Transport and General Workers Union has also set up an AIDS prevention program since truckers are at high risk of HIV infection. At the end of 1991, 445,000 people in South Africa have been infected with HIV. Heterosexuality is the predominate mode of HIV transmission among blacks, but among whites, it is homosexuality. Educated, affluent whites tend to be knowledge about AIDS and practice safer sex. Among the working class whites, however, knowledge levels are high, but they do not necessarily practice safer sex. Awareness tends to be quite high among blacks, but they do not generally practice safer sex. South Africa and the US are the only 2 developed countries that do not provide health care for all. This weak system limits AIDS prevention efforts. 80% of whites have health insurance compared with only 7% of blacks. PMID:12317691

  7. Black to Black

    DEFF Research Database (Denmark)

    Langkjær, Michael Alexander

    2012-01-01

    Pop musicians performing in black stage costume take advantage of cultural traditions relating to matters black. Stylistically, black is a paradoxical color: although a symbol of melancholy, pessimism, and renunciation, black also expresses minimalist modernity and signifies exclusivity (as...

  8. Job-hopping amongst African Black senior management in South Africa

    Directory of Open Access Journals (Sweden)

    Khanyile C.C. Nzukuma

    2011-02-01

    Full Text Available Orientation: The study focuses on understanding labour turnover trends amongst African Black senior managers in South Africa. There is a perception that turnover amongst African Black senior managers is higher than average. There is also a perception that African Black senior managers are only motivated by financial rewards when considering job change.Research purpose: The study focused on understanding why African Black senior managers have a propensity to change jobs and how organisations can resolve the trend.Motivation for the study: To develop a better understanding of the push and pull factors for African Black senior managers in organisations.Research design, approach and method: The research was conducted in two phases, namely as part of a qualitative study and a quantitative study: Creswell (2003 refers to this approach as triangulation. The target population was African Black senior managers on the database of a large Human Resources Consultancy, The South African Rewards Association and the Association of Black Actuaries and Investment Professionals (ABSIP (n = 2600. A total of 208 usable responses were received.Main findings: The main findings and contribution to the field of study was that African Black senior managers do not trust organisations with their career development. They would rather take control of their own career development by moving from organisation to organisation to build their repertoire of skills and competence. They want to be in charge of their careers. This finding has profound implications for organisations employing African Black managers in the senior cadre.Practical/managerial implications: Managers of African Black senior managers need to create attractive employee value propositions that address the main findings. Contribution/value-add: The research shows that African Black senior managers generally seek corporate environments that encourage a sense of belonging and with a clear career growth plan.

  9. Black Americans, Africa and History: A Reassessment of the Pan-African and Identity Paradigms.

    Science.gov (United States)

    Adeleke, Tunde

    1998-01-01

    Examines the paradigm of Pan-Africanism and the identity construct in the historic and cultural contexts of blacks outside of Africa, critiquing theories on the African identity construct. Suggests that black American identity is too complex for this simplification and must be considered within the context of world acculturation. Contains 34…

  10. Adjustment of Black Students at a Historically White South African University.

    Science.gov (United States)

    Sennett, Justin; Finchilescu, Gillian; Gibson, Kerry; Strauss, Rosanna

    2003-01-01

    Examined the adjustment of African black and white freshman students(n=335) at a white South African university. Finds that the black students reported lower levels of social adjustment and personality adjustment, but not differences in academic adjustment or institutional commitment. Includes references. (CMK)

  11. Examining the Generalizability of Problem-Solving Appraisal in Black South Africans.

    Science.gov (United States)

    Heppner, P. Paul; Pretorius, T. B.; Wei, Meifen; Lee, Dong-gwi; Wang, Yu-Wei

    2002-01-01

    Examines the generalizability of the Problem Solving Inventory (PSI) through research with Black South African samples. The estimates of the factor structure as well as other reliability and validity estimates provided strong support for the generalizability of the PSI to South African Black college students. The results also provided partial…

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

    Science.gov (United States)

    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…

  13. Fibrinogen concentration and its role in CVD risk in black South Africans - effect of urbanisation

    NARCIS (Netherlands)

    Pieters, Marlien; De Maat, Moniek P. M.; Jerling, Johann C.; Hoekstra, Tiny; Kruger, Annamarie

    2011-01-01

    The aim of this study was to investigate correlates of fibrinogen concentration in black South Africans, as well as its association with cardiovascular disease (CVD) risk and whether urbanisation influences this association. A total of 1,006 rural and 1,004 urban black South Africans from the PURE s

  14. Leaving Home: The Challenges of Black-African International Students Prior to Studying Overseas

    Science.gov (United States)

    Caldwell, Elizabeth Frances; Hyams-Ssekasi, Denis

    2016-01-01

    Much of the literature on international students centres on their experiences once they arrive in their host countries. This study explores the preparations of Black-African students for leaving their home countries to study abroad. Semi-structured interviews were carried out with 50 Black-African students studying at one British university. The…

  15. [Conceptual parameters of the facial arc and articulators adapted for black Africans].

    Science.gov (United States)

    N'Dindin, A C; Djeredou, K B; N'Dindin-Guinan, B; Assi, K D

    2005-12-01

    Articulators and facial arc always used in dentistry are not adapted to African black people. Their use provokes many errors in the setting of models on articulators. In this work, authors propose facial arc and articulator parameters conceptions that are suited to black Africans.

  16. Patterns of autosomal dominant polycystic kidney diseases in black Africans

    Directory of Open Access Journals (Sweden)

    Fary Ka Elhadj

    2010-01-01

    Full Text Available Autosomal dominant polycystic kidney disease (ADPKD is not well described in black Africans while some data suggesting the disease is exceptional in this race. A retrospective study of patients with ADPKD followed in nephrology department of a teaching hospital in Dakar (January 1, 1995 to December 31, 2005 was therefore undertaken. Prevalence of ADPKD was one in 250. Mean age was 47 ± 5 years with a predominance of male (57%. High blood pressure (HBP was present in 68% of patients. Other renal manifestations were flank pain, hematuria and proteinuria. Majority of patients had impaired renal function at time of diagnosis. Extra-renal cysts were essentially found in liver (45.5%, pancreas and seminal vesicles. Main complications: ESRD (51% occurred within a 6 year mean period, urinary tract infection (13% and cerebral haemorrhage (2%. HBP control, in general needed 2 or more antihypertensive drugs. Fourteen patients died, ten patients had been on haemodialysis and four others died from uremic compli-cations. In conclusion, ADPKD in black African adults is not rare and probably underdiagnosed. Early HBP and ESRD are likely more frequent than in other races. Earlier ultrasound detection and strategies to preserve renal function should be offered to at-risk individuals to improve outcomes.

  17. Socially Responsible Leadership Capacity Development: Predictors among African American/Black Students at Historically Black Colleges and Universities and Predominantly White Institutions

    Science.gov (United States)

    Beazley, Michael Redmond

    2013-01-01

    This study examined the capacity and predictors of socially responsible leadership among African American/Black college students at HBCUs and PWIs using data from the Multi-institutional Study of Leadership. An independent sample t-test was used to test the hypothesis that African American/Black students at HBCUs would have higher leadership…

  18. Deconstructing Black History Month: Three African American Boys' Exploration of Identity

    Science.gov (United States)

    Landa, Melissa Hare

    2012-01-01

    Every February, schools celebrate Black History Month and teachers teach the grand narrative of famous African Americans such as Martin Luther King, Jr. While the stories communicate bravery, they are also about racism and violence. Here, through narrative inquiry, a teacher deconstructs Black History Month, inviting student responses to stories…

  19. Physical activity energy expenditure and sarcopenia in black South African urban women

    NARCIS (Netherlands)

    Kruger, Herculina S.; Havemann-Nel, Lize; Ravyse, Chrisna; Moss, Sarah J.; Tieland, Michael

    2016-01-01

    Background: Black women are believed to be genetically less predisposed to age-related sarcopenia. The objective of this study was to investigate lifestyle factors associated with sarcopenia in black South African (SA) urban women. Methods: In a cross-sectional study, 247 women (mean age 57 y) we

  20. African American Homeschool Parents' Motivations for Homeschooling and Their Black Children's Academic Achievement

    Science.gov (United States)

    Ray, Brian

    2015-01-01

    This study explores the motivations of African American parents for choosing homeschooling for their children and the academic achievement of their Black homeschool students. Their reasons for homeschooling are similar to those of homeschool parents in general, although some use homeschooling to help their children understand Black culture and…

  1. "Combing" through Representations of Black Girls' Hair in African American Children's Literature

    Science.gov (United States)

    Brooks, Wanda M.; McNair, Jonda C.

    2015-01-01

    In this article, we share findings from a content analysis of six picturebooks about hair. The picturebooks selected feature Black female protagonists and are written by African American females. Our content analysis examines the ways in which Black hair is theorized and represented to children (from diverse backgrounds) very early on in their…

  2. Private Sector Investment in Black Education and Training: Rescuing South African Capitalism from Apartheid's Crisis.

    Science.gov (United States)

    Kraak, Andre

    1989-01-01

    Discusses: (1) the factors contributing to increased involvement by South African business and industry in Black education and training; (2) the Urban Foundation's commitment to non-formal education in Black communities; (3) intervention by American corporations; and (4) the dramatic failure of capitalist initiatives. Contains 55 references. (SV)

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

    Science.gov (United States)

    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. Computer Cache. African American Websites for Black History Month and All Year Long

    Science.gov (United States)

    Byerly, Greg; Brodie, Carolyn S.

    2005-01-01

    February is Black History Month and time to celebrate the contributions of African Americans throughout history. This paper provides a selection of websites that can serve as starting points for learning and can be used all year long.

  5. FastStats: Health of Black or African American non-Hispanic Population

    Science.gov (United States)

    ... Health of Black or African American non-Hispanic Population Recommend on Facebook Tweet Share Compartir Data are ... Source: Summary Health Statistics Tables for the U.S. Population: National Health Interview Survey, 2014, Table P-1c [ ...

  6. Professor Bennie van der Walt: a bridge between white Afrikaners and black Africans

    OpenAIRE

    Y. Turaki

    2010-01-01

    This article honours Professor Bennie van der Walt as a bridge builder between white Afrikaners and black Africans as well as a renowned Christian scholar. Historical Western colonialism in South Africa divided its citizens against each other by means of white racism and apartheid. The whites in general were pitched against the blacks on the basis of white racism and its doctrine of apartheid. This doctrine of separation of races kept the white Afrikaners from the Bantu Africans. However, apa...

  7. The Black Arts Movement and African American Young Adult Literature: An Evaluation of Narrative Style

    Science.gov (United States)

    Henderson, Laretta

    2005-01-01

    In this article I question whether or not African American young adult literature serves as a primer for, and a version of, African American adult literature. Using the Black Aesthetic as my literary theory and the Coretta Scott King Award as the young adult canon, I note that while the content of adolescent literature is consistent with the…

  8. Rising diabetes prevalence among urban-dwelling black South Africans.

    Directory of Open Access Journals (Sweden)

    Nasheeta Peer

    Full Text Available OBJECTIVE: To examine the prevalence of and the association of psychosocial risk factors with diabetes in 25-74-year-old black Africans in Cape Town in 2008/09 and to compare the prevalence with a 1990 study. RESEARCH DESIGN AND METHODS: A randomly selected cross-sectional sample had oral glucose tolerance tests. The prevalence of diabetes (1998 WHO criteria, other cardiovascular risk factors and psychosocial measures, including sense of coherence (SOC, locus of control and adverse life events, were determined. The comparison of diabetes prevalence between this and a 1990 study used the 1985 WHO diabetes criteria. RESULTS: There were 1099 participants, 392 men and 707 women (response rate 86%. The age-standardised (SEGI prevalence of diabetes was 13.1% (95% confidence interval (CI 11.0-15.1, impaired glucose tolerance (IGT 11.2% (9.2-13.1 and impaired fasting glycaemia 1.2% (0.6-1.9. Diabetes prevalence peaked in 65-74-year-olds (38.6%. Among diabetic participants, 57.9% were known and 38.6% treated. Using 1985 WHO criteria, age-standardised diabetes prevalence was higher by 53% in 2008/09 (12.2% (10.2-14.2 compared to 1990 (8.0% (5.8-10.3 and IGT by 67% (2008/09: 11.7% (9.8-13.7; 1990: 7.0% (4.9-9.1. In women, older age (OR: 1.05, 95%CI: 1.03-1.08, p<0.001, diabetes family history (OR: 3.13, 95%CI: 1.92-5.12, p<0.001, higher BMI (OR: 1.44, 95%CI: 1.20-1.82, p = 0.001, better quality housing (OR: 2.08, 95%CI: 1.01-3.04, p = 0.047 and a lower SOC score (≤ 40 was positively associated with diabetes (OR: 2.57, 95%CI: 1.37-4.80, p = 0.003. Diabetes was not associated with the other psychosocial measures in women or with any psychosocial measure in men. Only older age (OR: 1.05, 95%CI: 1.02-1.08, p = 0.002 and higher BMI (OR: 1.10, 95%CI: 1.04-1.18, p = 0.003 were significantly associated with diabetes in men. CONCLUSIONS: The current high prevalence of diabetes in urban-dwelling South Africans, and the likelihood of further rises given the high

  9. Employers' perceptions of Black South African English usage / Henrietta Ntombi Tlaka

    OpenAIRE

    Tlaka, Henrietta Ntombi

    2001-01-01

    The common usage of Black South African English (BSAE) forms the main focus of this study. Its usage by members of the black population has caused a major debate on language standards and usage, and acceptance of BSAE as a variety of English. The purpose of this study was to establish employers' perceptions of BSAE usage by employees (and prospective employees). The employers' preferences, views on re-standardisation of English and the usage of English in South Africa were established. ...

  10. Understanding consumption patterns of the established and emerging South African black middle class

    OpenAIRE

    Ronelle Burger; Megan Louw; Brigitte Barbara Isabel de Oliveira Pegado; Servaas van der Berg

    2014-01-01

    Existing empirical research on consumption patterns of the South African black middle class leans either on the theory of conspicuous consumption or culture-specific utility functions. This paper departs from treatment of the black middle class as a homogenous group. By differentiating between a securely established group, with characteristics and consumption patterns similar to the white middle class, and an emerging group, often with weaker productive characteristics, it formally introduces...

  11. Developmental Characteristics of African American and Caribbean Black Adolescents’ Attributions Regarding Discrimination

    OpenAIRE

    Seaton, Eleanor K.; Caldwell, Cleopatra H.; Sellers, Robert M.; Jackson, James S.

    2010-01-01

    The present study examined discrimination attributions in the psychological well-being of Black adolescents. Findings are based on a representative sample of 810 African American and 360 Caribbean Black youth, aged 13 to 17, who participated in the National Survey of American Life (NSAL). Youth completed measures of perceived discrimination, discrimination attributions, depressive symptoms, self-esteem and life satisfaction. Approximately half the youth attributed discrimination to race/ethni...

  12. Rules of engagement: predictors of Black Caribbean immigrants' engagement with African American culture.

    Science.gov (United States)

    Joseph, Nancy; Watson, Natalie N; Wang, Zhenni; Case, Andrew D; Hunter, Carla D

    2013-10-01

    The cultural context in the United States is racialized and influences Black Caribbean immigrants' acculturation processes, but what role it plays in Black Caribbean immigrants' acculturation into specific facets of American society (e.g., African American culture) has been understudied in the field of psychology. The present study extends research on Black Caribbean immigrants' acculturative process by assessing how this group's experience of the racial context (racial public regard, ethnic public regard, and cultural race-related stress) influences its engagement in African American culture (i.e., adoption of values and behavioral involvement). Data were collected from 93 Black participants of Caribbean descent, ranging in age from 13 to 45 and analyzed using a stepwise hierarchical regression. The findings highlighted that when Black Caribbean-descended participants perceived that the public held a favorable view of their racial group they were more likely to engage in African American culture. In contrast, when participants perceived that the public held a favorable view of their ethnic group (e.g., Haitian) they were less likely to engage in African American culture. Furthermore, among participants experiencing low levels of cultural race-related stress, the associations between racial public regard and engagement with African American culture were amplified. However, for participants experiencing high cultural race-related stress, their engagement in African American culture did not change as a function of racial public regard. These findings may suggest that, for Black Caribbean immigrants, the experience of the racial context influences strategies that serve to preserve or bolster their overall social status and psychological well-being in the United States.

  13. The Black Black Woman and the Black Middle Class.

    Science.gov (United States)

    Jeffers, Trellie

    1981-01-01

    Reprint of a 1973 article that describes the discrimination that particularly dark-skinned Black women suffer, especially at the hands of a color-conscious Black middle class. Calls for dark women to look to the African appearance and working-class roots as sources of pride and strength. (GC)

  14. Black Consciousness

    Science.gov (United States)

    Hraba, Joseph; Siegman, Jack

    1974-01-01

    Black militancy is treated as an instance of class consciousness with criteria and scales developed to measure black consciousness and "self-placement" into black consciousness. These dimensions are then investigated with respect to the social and symbolic participation in the ideology of the black movement on the part of a sample of black…

  15. The Genetics of POAG in Black South Africans: A Candidate Gene Association Study

    OpenAIRE

    Williams, Susan E. I.; Carmichael, Trevor R.; Allingham, R. Rand; Hauser, Michael; Ramsay, Michele

    2015-01-01

    Multiple loci have been associated with either primary open angle glaucoma (POAG) or heritable ocular quantitative traits associated with this condition. This study examined the association of these loci with POAG, with central corneal thickness (CCT), vertical cup-to-disc ratio (VCDR) and with diabetes mellitus in a group of black South Africans (215 POAG cases and 214 controls). The population was homogeneous and distinct from other African and European populations. Single SNPs in the MYOC,...

  16. Systematic review of stigma reducing interventions for African/Black diasporic women

    OpenAIRE

    Mona Loutfy; Wangari Tharao; Carmen Logie; Muna A Aden; Chambers, Lori A.; Wei Wu; Marym Abdelmaseh; Liviana Calzavara

    2015-01-01

    Introduction: Literature indicates that racism, sexism, homophobia and HIV-related stigma have adverse impacts on health, well-being, and quality of life among HIV-positive women of African descent (African/Black diaspora). However, limited evidence exists on the effectiveness of interventions aimed at reducing stigma tailored for these women. This study systematically reviewed randomized controlled trials (RCTs), non-randomized observational and quasi-experimental studies evaluating the effe...

  17. Black Economic Empowerment Disclosures by South African Listed Corporations: The Influence of Ownership and Board Characteristics

    OpenAIRE

    Ntim, Collins G.; Soobaroyen, Teerooven

    2013-01-01

    This study investigates the extent to which South African listed corporations voluntarily disclose information on black economic empowerment (BEE) in their annual and sustainability reports using a sample of 75 listed corporations from 2003 to 2009. BEE is a form of socio-economic affirmative action championed by the African National Congress (ANC)-led government to address historical imbalances in business participation and ownership in South Africa. We find that block ownership and institut...

  18. Black economic empowerment in the South African coal industry

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-07-01

    South Africa has experienced great change and progress in the ten years since the end of apartheid and the inauguration of its first democratic government. Back in 1994, many were concerned about whether such a young and fragile democracy could survive. The new government needed to unify the country, while bringing about the significant change necessary to address the massive racial inequality at the heart of the apartheid system. The article explains actions and initiatives taken under the Black Economic Empowerment (BEE) programme, one of which is the establishment of Eyesizwe Coal. 2 figs., 1 photo.

  19. Plasma Clot Lysis Time and Its Association with Cardiovascular Risk Factors in Black Africans

    NARCIS (Netherlands)

    Z. de Lange (Zelda); M. Pieters (Marlien); J.C. Jerling (Johann); A. Kruger (Annamarie); D.C. Rijken (Dingeman)

    2012-01-01

    textabstractStudies in populations of European descent show longer plasma clot lysis times (CLT) in patients with cardiovascular disease (CVD) than in controls. No data are available on the association between CVD risk factors and fibrinolytic potential in black Africans, a group undergoing rapid ur

  20. Stress among Black Women in a South African Township: The Protective Role of Religion

    Science.gov (United States)

    Copeland-Linder, Nikeea

    2006-01-01

    Communities that have been exposed to high levels of stress and where religiosity is salient are ideal contexts in which to examine the role of religion in stress processes. The present study examines the protective function of religiosity among Black women in a South African township. The women (N = 172) were interviewed about sources of stress,…

  1. Black Tribal African Religion with Some Emphasis on Christianity and Islam in Africa.

    Science.gov (United States)

    Emmons, Marian

    This 6th grade social studies unit delves into the belief systems and external religious, cultural practices of Black Africans. It is part of a series of guides developed by the Public Education Religion Studies Center at Wright State University. Study is focused upon the Ashanti tribe of Ghana knowing that although the multiplicity of tribes have…

  2. Black Droplets

    CERN Document Server

    Santos, Jorge E

    2014-01-01

    Black droplets and black funnels are gravitational duals to states of a large N, strongly coupled CFT on a fixed black hole background. We numerically construct black droplets corresponding to a CFT on a Schwarzchild background with finite asymptotic temperature. We find two branches of such droplet solutions which meet at a turning point. Our results suggest that the equilibrium black droplet solution does not exist, which would imply that the Hartle-Hawking state in this system is dual to the black funnel constructed in \\cite{Santos:2012he}. We also compute the holographic stress energy tensor and match its asymptotic behaviour to perturbation theory.

  3. Black Eye

    Science.gov (United States)

    ... eyesight if not treated. If both eyes are black after a head injury, it could signify a skull fracture or other serious injury. Next Black Eye Symptoms Related Ask an Ophthalmologist Answers How ...

  4. Systematic review of stigma reducing interventions for African/Black diasporic women

    Directory of Open Access Journals (Sweden)

    Mona Loutfy

    2015-04-01

    Full Text Available Introduction: Literature indicates that racism, sexism, homophobia and HIV-related stigma have adverse impacts on health, well-being, and quality of life among HIV-positive women of African descent (African/Black diaspora. However, limited evidence exists on the effectiveness of interventions aimed at reducing stigma tailored for these women. This study systematically reviewed randomized controlled trials (RCTs, non-randomized observational and quasi-experimental studies evaluating the effectiveness of interventions aimed at reducing stigma experienced by this population. Methods: The Cochrane methodology was used to develop a search strategy in consultation with a librarian scientist. Databases searched included the Cochrane Library, Ovid EMBASE, PsycInfo, and 10 others. Two reviewers independently assessed the studies for potential relevance and conducted the Cochrane grading of RCTs to assess risk of bias and the Newcastle–Ottawa scale to assess the quality of non-randomized studies. Eligible papers were selected if they employed an intervention design with African/Black diasporic women living with HIV as the target population and had a primary outcome of stigma reduction. Results: Of the five studies that met all of the eligibility criteria, four demonstrated the effectiveness of interventions in reducing HIV-related stigma. Only two of the five studies were designed specifically for HIV-positive African/Black diasporic women. Limitations included the absence of interventions addressing other forms of stigma and discrimination (e.g. gender discrimination, racism, heterosexism. Conclusions: Our findings suggest that there are limited interventions designed to address multiple forms of stigma, including gender and racial discrimination, experienced by HIV-positive African/Black diasporic women.

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

    Science.gov (United States)

    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…

  6. Black-tailed Godwits in West African winter staging areas : habitat use and hunting-related mortality

    NARCIS (Netherlands)

    Kleijn, D.; Kamp, van der J.; Monteiro, H.; Ndiaye, I.; Wymenga, E.; Zwarts, L.

    2010-01-01

    The persistence of the Dutch Black-tailed Godwit population depends largely on high adult survival. Adult survival may be influenced by hunting pressure and land use change in the wintering area, the West African coastal zone. Here we examine hunting pressure on and habitat use of Black-tailed Godwi

  7. Common roots: a contextual review of HIV epidemics in black men who have sex with men across the African diaspora.

    Science.gov (United States)

    Millett, Gregorio A; Jeffries, William L; Peterson, John L; Malebranche, David J; Lane, Tim; Flores, Stephen A; Fenton, Kevin A; Wilson, Patrick A; Steiner, Riley; Heilig, Charles M

    2012-07-28

    Pooled estimates from across the African diaspora show that black men who have sex with men (MSM) are 15 times more likely to be HIV positive compared with general populations and 8·5 times more likely compared with black populations. Disparities in the prevalence of HIV infection are greater in African and Caribbean countries that criminalise homosexual activity than in those that do not criminalise such behaviour. With the exception of US and African epidemiological studies, most studies of black MSM mainly focus on outcomes associated with HIV behavioural risk rather than on prevalence, incidence, or undiagnosed infection. Nevertheless, black MSM across the African diaspora share common experiences such as discrimination, cultural norms valuing masculinity, concerns about confidentiality during HIV testing or treatment, low access to HIV drugs, threats of violence or incarceration, and few targeted HIV prevention resources. PMID:22819654

  8. The black Dutchmen: African soldiers in the Netherlands East Indies

    OpenAIRE

    Kessel, van, CGM

    2002-01-01

    Between 1831 and 1872 some 3000 African recruits sailed from Elmina (Gold Coast, now Ghana) to Batavia, the capital of the Netherlands East Indies. They had been recruited to serve in the Dutch colonial army, which throughout most of the 19th century experienced a chronic shortage of European manpower. The Africans counted as part of the European contingent of the army. After expiry of their contracts, some Africans returned to the Gold Coast, while others opted to settle in the East Indies. ...

  9. Black Holes

    Science.gov (United States)

    Luminet, Jean-Pierre

    1992-09-01

    Foreword to the French edition; Foreword to the English edition; Acknowledgements; Part I. Gravitation and Light: 1. First fruits; 2. Relativity; 3. Curved space-time; Part II. Exquisite Corpses: 4. Chronicle of the twilight years; 5. Ashes and diamonds; 6. Supernovae; 7. Pulsars; 8. Gravitation triumphant; Part III. Light Assassinated: 9. The far horizon; 10. Illuminations; 11. A descent into the maelstrom; 12. Map games; 13. The black hole machine; 14. The quantum black hole; Part IV. Light Regained: 15. Primordial black holes; 16. The zoo of X-ray stars; 17. Giant black holes; 18. Gravitational light; 19. The black hole Universe; Appendices; Bibliography; Name index; Subject index.

  10. Participation and Research of Astronomers and Astrophysicists of Black African Descent (1900–2005)

    Science.gov (United States)

    Oluseyi, Hakeem M.; Urama, Johnson

    The second half of the Twentieth Century witnessed the emergence of the first modern Astronomers and Astrophysicists of Black African descent. In this paper we enumerate these researchers and briefly describe their activities. We also describe the broader social and political contexts which have impacted their participation and research. We focus primarily on researchers in the United States of America (28) and in Nigeria (19) who have together produced over 90% of the astronomical researchers known to the authors. We briefly mention researchers from other countries including South Africa (3) and in Eurasia (2). We conclude by describing the pioneering researchers and disseminators of the Black African Diaspora's contribution of to the modern astronomical sciences.

  11. Participation and Research of Astronomers and Astrophysicists of Black African Descent (1900 2005)

    Science.gov (United States)

    Oluseyi, Hakeem M.; Urama, Johnson

    The second half of the Twentieth Century witnessed the emergence of the first modern Astronomers and Astrophysicists of Black African descent. In this paper we enumerate these researchers and briefly describe their activities. We also describe the broader social and political contexts which have impacted their participation and research. We focus primarily on researchers in the United States of America (28) and in Nigeria (19) who have together produced over 90% of the astronomical researchers known to the authors. We briefly mention researchers from other countries including South Africa (3) and in Eurasia (2). We conclude by describing the pioneering researchers and disseminators of the Black African Diaspora's contribution of to the modern astronomical sciences.

  12. Sex discrimination from the glenoid cavity in black South Africans: morphometric analysis of digital photographs.

    Science.gov (United States)

    Macaluso, P James

    2011-11-01

    Given that skeletal material recovered from medicolegal contexts is often incomplete or damaged, forensic anthropologists need to have a variety of techniques at their disposal in order to correctly determine the sex of unidentified human remains. The purpose of the present study, therefore, was to produce practical standards for discriminating the sex of black South Africans using measurements of the glenoid cavity of the scapula. Standardized digital photographs of the left glenoid fossa were taken for 60 males and 60 females drawn from the Pretoria Bone Collection. An image analysis software program was then used to collect height, breadth, area, and perimeter data from each digital photograph. All four dimensions of the glenoid cavity were highly sexually dimorphic in this population group (p Classification sex biases were below 5.0% for all equations. These results demonstrate that the analysis of glenoid cavity size provides a highly accurate method for discriminating the sex of black South Africans. PMID:20814691

  13. Hemoglobin levels and blood pressure are associated in rural black Africans

    DEFF Research Database (Denmark)

    Rasmussen, Jon Bjarke Jarløv; Mwaniki, David L; Kaduka, Lydia U;

    2016-01-01

    OBJECTIVES: The association between blood levels of hemoglobin (B-hgb) and blood pressure (BP) has been widely investigated in Caucasians and Asians but there is a paucity of data in rural black Africans. The objective was to investigate the association between B-hgb and BP in a rural black African...... test were obtained in each participant. RESULTS: Background characteristics among 1,167 participants showed that anemic and non-anemic participants differed significantly from each other as there were more women, lower body mass index and waist circumference (WC), lower degree of hepatic insulin...... resistance and plasma cholesterols among the anemic participants. Furthermore, anemic participants had significantly lower systolic and diastolic BP (P 

  14. Professor Bennie van der Walt: a bridge between white Afrikaners and black Africans

    Directory of Open Access Journals (Sweden)

    Y. Turaki

    2010-07-01

    Full Text Available This article honours Professor Bennie van der Walt as a bridge builder between white Afrikaners and black Africans as well as a renowned Christian scholar. Historical Western colonialism in South Africa divided its citizens against each other by means of white racism and apartheid. The whites in general were pitched against the blacks on the basis of white racism and its doctrine of apartheid. This doctrine of separation of races kept the white Afrikaners from the Bantu Africans. However, apartheid as a form of political, social, cultural and religious racism is now history in South Africa. The role which Professor Van der Walt played in bridging the gap between this racial divide is highly commendable and needs to be acknowledged and appreciated, hence the primary objective of this article in honour of his 71st birthday. Furthermore, the article discusses the immense contributions of Professor Bennie van der Walt to Christian scholarship in Africa.

  15. Heritage, blackness and Afro-cool: styling Africanness in Amsterdam

    NARCIS (Netherlands)

    M. de Witte

    2014-01-01

    This article focuses on the recent emergence of an "Afro-Dutch" category of self-identification among young people in Amsterdam. Dutch-born youth of different Afro-Caribbean and African backgrounds show a new sense of (and search for) a shared African heritage, and a growing desire for public exposu

  16. Cancer prevention: attitudes and practices among black South African university students

    Directory of Open Access Journals (Sweden)

    Karl Peltzer

    2001-02-01

    Full Text Available This study intended to investigate the attitudes and practices of cancer prevention among Black South African university students.

    Opsomming
    Die doelwit van hierdie navorsing was om die houdings en praktyke vir die voorkoming van kanker onder swart studente aan Universiteite in Suid Afrika na te vors. *Please note: This is a reduced version of the abstract. Please refer to PDF for full text.

  17. The State of Black Education: The Politics of Educating African American Students at Colleges and Universities

    OpenAIRE

    Earnest N. Bracey, Ph.D.

    2014-01-01

    In terms of higher education for African American students, the “school-to-prison pipeline” or Prison Industrial Complex must be totally dismantled in order to focus entirely on academic performance at colleges and universities and HBCUs. Additionally, mentors should be identified to tutor and guide and help black youngsters overcome their fear of learning and going to school, so that our whole society can benefit and improve academically. Finally, in this respect, we-the-people can move our ...

  18. Education services and resilience processes: Resilient Black South African students' experiences

    OpenAIRE

    Linda C. Theron; Adam M.C. Theron

    2014-01-01

    The resilience literature is increasingly drawing attention to formal service provision as a means for social ecologies to support children's and youths' positive adjustment to challenging life circumstances. This article interrogates the universality and simplicity of this argument. Using a secondary data analysis of the life stories of 16 resilient, Black South African students from impoverished families, we show that education services predominated students' childhood and youth experie...

  19. The New Black

    OpenAIRE

    Lettman-Hicks, Sharon

    2014-01-01

    The New Black is a documentary that tells the story of how the African American community is grappling with the gay rights issue in light of the recent gay marriage movement and the fight over Civil Rights. The film documents activities, families and clergy on both sides of the campaign to legalize gay marriage and examines homophobia in the Black community's institutional pillar, the Black church, and reveals the Christian right wing's strategy of exploiting this phenomenon in order to pursu...

  20. Black Culture

    Directory of Open Access Journals (Sweden)

    Angela Khristin Brown

    2013-07-01

    Full Text Available The migration of blacks in North America through slavery became united.  The population of blacks past downs a tradition of artist through art to native born citizens. The art tradition involved telling stories to each generation in black families. The black culture elevated by tradition created hope to determine their personal freedom to escape from poverty of enslavement and to establish a way of life through tradition. A way of personal freedoms was through getting a good education that lead to a better foundation and a better way of life. 

  1. Towards Producing Black Nobel Laureates Affiliated with ``African Universities''

    Science.gov (United States)

    Kenneth, Jude

    While Africa has produced a handful Nobel laureate in literature and peace, it has continued to shy away from producing any in the other categories. The reason is not farfetched; our university system is not up to standard. It is saddening that in this century, African countries place emphasis on certificates and not on knowledge. This has made the continent produce students that lack the intellectual capability, experimental ability, fundamental training, creativity, and motivation to excel except they get a foreign training. It is this backdrop that precipitated the research into the methods of teaching and research in universities across Africa. The study is designed to identify the problems and proffer solution to them. Two important questions immediately come to mind. (1) What factors account for the difficulty in producing Nobel laureates affiliated with African universities? (2) What strategies could be adopted to improve teaching and research in African universities? Several factors were investigated which revolve around funding, the competence of the lecturers, quality of students admitted, attitude of the students, parents and government. Nigerian universities were investigated and important deductions were made. During the study an inquiry was made on the method of instruction at various universities, from result obtained, the study therefore concluded that adequate funding, the presence of erudite scholars and brilliant minds will produce future Nobel laureate affiliated with the continent. The study therefore recommended admission and employment of only students and lecturers who have got a thing for academics into the universities and adequate funding of universities and research centres.

  2. Field Plot Techniques for Black Sigatoka Evaluation in East African Highland Bananas

    Directory of Open Access Journals (Sweden)

    Okoro, JU.

    1997-01-01

    Full Text Available Number of plants per experimental unit and number of replications for the efficient and precise assessment of black sigatoka leaf spot disease caused by Mycosphaerella fijiensis in East African Highland bananas were determined. Two representative cultivars were used. Host response to black sigatoka infection was measured by recording the youngest leaf with necrotic spots. The number of plants per experimental unit was determined, using the methods of maximum curvature and comparison of variances, while the number of replications was estimated by Hatheway's method. The optimum experimental plot size was 3 plants (18 m2 for the beer banana cultivar 'Igitsiri', and 30 plants (180 m2 for the cooking banana cultivar 'Igisahira Gisanzwe', using the comparison of variances method. However, the optimum plot size was 15 plants (90 m2 for both cultivars using the method of maximum curvature. The latter statistical method was preferred because of the low precision of the estimates in the former method. Unreplicated trials with plots of 15 plants could be adequate to assess black sigatoka response in East African bananas if uniform disease pressure exists.

  3. The genetics of POAG in black South Africans: a candidate gene association study.

    Science.gov (United States)

    Williams, Susan E I; Carmichael, Trevor R; Allingham, R Rand; Hauser, Michael; Ramsay, Michele

    2015-01-01

    Multiple loci have been associated with either primary open angle glaucoma (POAG) or heritable ocular quantitative traits associated with this condition. This study examined the association of these loci with POAG, with central corneal thickness (CCT), vertical cup-to-disc ratio (VCDR) and with diabetes mellitus in a group of black South Africans (215 POAG cases and 214 controls). The population was homogeneous and distinct from other African and European populations. Single SNPs in the MYOC, COL8A2, COL1A1 and ZNF469 gene regions showed marginal associations with POAG. No association with POAG was identified with tagging SNPs in TMCO1, CAV1/CAV2, CYP1B1, COL1A2, COL5A1, CDKN2B/CDKN2BAS-1, SIX1/SIX6 or the chromosome 2p16 regions and there were no associations with CCT or VCDR. However, SNP rs12522383 in WDR36 was associated with diabetes mellitus (p = 0.00008). This first POAG genetic association study in black South Africans has therefore identified associations that require additional investigation in this and other populations to determine their significance. This highlights the need for larger studies in this population if we are to achieve the goal of facilitating early POAG detection and ultimately preventing irreversible blindness from this condition. PMID:25669751

  4. Forced expiratory indices in normal black Southern African children aged 6-19 years

    OpenAIRE

    Shamssain, M H

    1991-01-01

    Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), forced expiratory ratio (FEV1/FVC x 100), forced mid expiratory flow (FMF), and peak expiratory flow (PEF) were measured in 2000 non-smoking black African schoolchildren aged 6-19 years from Umtata in the Republic of Transkei in Southern Africa. FVC, FEV1, FMF, and PEF were highly correlated with each other and all were highly correlated with age and standing height in both sexes. There was a significant negative corr...

  5. The State of Black Education: The Politics of Educating African American Students at Colleges and Universities

    Directory of Open Access Journals (Sweden)

    Earnest N. Bracey, Ph.D.

    2014-03-01

    Full Text Available In terms of higher education for African American students, the “school-to-prison pipeline” or Prison Industrial Complex must be totally dismantled in order to focus entirely on academic performance at colleges and universities and HBCUs. Additionally, mentors should be identified to tutor and guide and help black youngsters overcome their fear of learning and going to school, so that our whole society can benefit and improve academically. Finally, in this respect, we-the-people can move our nation forward by graduating people of color at higher institutions of learning, while providing them with a more productive life, and social advancement.

  6. NT-proBNP and potential vascular calcification in Black and Caucasian African men

    DEFF Research Database (Denmark)

    Kruger, Ruan; Schutte, Rudolph; Huisman, Hugo W;

    2012-01-01

    The N-terminal prohormone B-type natriuretic peptide (NT-proBNP) is a reliable marker of cardiac strain. In hypertensive heart disease, NT-proBNP levels increase and may lose its protective function. Simultaneously, the vasculature is also subject to hemodynamic stress, resulting in vascular matrix...... remodeling and stiffening which contribute to further cardiac alterations. Alkaline phosphatase (ALP) is a marker of osteoblast activity and is involved in vascular calcification. We explored the link between NT-proBNP and ALP in Black and Caucasian African men....

  7. The Association of Endothelin-1 with Markers of Arterial Stiffness in Black South African Women: The SABPA Study

    Directory of Open Access Journals (Sweden)

    Christine Susara du Plooy

    2015-01-01

    Full Text Available Background. Limited data exist regarding endothelin-1 (ET-1, a vasoactive contributor in vascular tone, in a population subjected to early vascular deterioration. We compared ET-1 levels and explored its association with markers of arterial stiffness in black and white South Africans. Methodology. This cross-sectional substudy included 195 black (men: n=99; women: n=95 and 197 white (men: n=99; women: n=98 South Africans. Serum ET-1 levels were measured as well as markers of arterial stiffness (blood pressure, pulse wave velocity, and arterial compliance. ET-1 levels were higher in black men and white women compared to their counterparts after adjusting for C-reactive protein. In both single and partial (adjusting for body mass index and gamma glutamyl transferase regression analyses ET-1 correlated with age, interleukin-6, high density lipoprotein cholesterol, systolic blood pressure, pulse pressure, and pulse wave velocity in black women. In multivariate regression analyses the independent association of ET-1 with systolic blood pressure (Adj. R2=0.13; β=0.28, p<0.01 and pulse pressure (Adj. R2=0.11; β=0.27, p<0.01 was confirmed in black women only. ET-1 additionally associated with interleukin-6 in black women (p<0.01. Conclusion. Our result suggests that ET-1 and its link with subclinical arteriosclerosis are potentially driven by low-grade inflammation as depicted by the association with interleukin-6 in the black female cohort.

  8. [Plummer-Vinson syndrome or related syndrome in 3 black African women].

    Science.gov (United States)

    Aubry, P; Oddes, B; Chazouillères, O; Lebourgeois, M; Delanoue, G; Seurat, P L

    1985-01-01

    The Plummer-Vinson syndrome or "sideropenic dysphagia" is exceptional among Blacks. One case was recently reported in a female patient from Guadeloupe. This study pertains to three cases observed in Senegalese Black women aged 28, 27, and 41 years. These three women were admitted for a dysphagia, in fact in evidence 10, 4, and 7 years respectively before the diagnosis was made. A clinical anemia was noted twice in addition to mucocutaneous disorders (cases 1 and 2). The laboratory tests showed in all three cases a hypochromic microcytic sideropenic anemia (serum iron levels at 32, 14, and 31 mcg 100 ml respectively). Barium swallow films showed esophageal rings in front of C5-C6 (case 1) of T2-T3 (case 2) and a web of fine mucosal folds in front of C5-C6 (case 3). These films were confirmed cineradiographically by esophagoscopy. The treatment consisted of blood transfusions (cases 1 and 2) and administration of iron by injections and or per os. The endoscopic exams were repeated two or three times. Medical treatment rapidly changed the course of disease for the better. No cause for bleeding was found. A chemical achlorhydria (case 1), a provoked hypoachlorhydria (cases 2 and 3) can be retained as associated factors. In light of the frequency of esophageal membranes in the general population and the incidence of sideropenic anemias among African women, the Plummer-Vinson syndrome should be more often detected in Black Africa.

  9. Nonshaved cranial surgery in black Africans: technical report and a medium-term prospective outcome study.

    Science.gov (United States)

    Adeleye, Amos O

    2016-07-01

    Nonshaved neurosurgery, cranial or spinal, is well reported among Caucasians but hardly among native Africans. The ungroomed scalp hairs of black Africans have unique anthropological characteristics needing special attention for shaveless cranial surgery. A technical report of the execution of this surgical procedure among an indigenous patient population in a sub-Sahara African country is presented, as well as an outcome analysis in a prospective cohort over a 7-year period. A total of 303 patients (211 males, 70 %) fulfilled the criteria for this study. The surgical procedure was primary in 278 (92 %) and redo in 8 %. It was emergency surgery in 153 (51 %). They were trauma craniotomies or decompressive craniectomies in 95 cases (31 %), craniotomies for tumour resections in 86 (28 %), and the surgical dissections for other conditions in 122 (41 %). The duration of surgery ranged from 30 min to 8.5 h, mean 2.5 (SD, 1.6), median 2. In-hospital clinical outcome was good (normal status or moderate deficit on dichotomized Glasgow outcome scale (GOS)) in 273 (90.1 %) cases while surgical site infections occurred in only 10 cases (3.3 %). The type of surgery, redo or primary, did not have any significant association with the in-hospital outcome (p = 0.5), nor with the presence of surgical site infection (SSI) (p = 0.7). The length of follow-up ranged from 2 to 63 months (mean, 7) with no untoward complications reported so far. Medium-term outcome of nonshaved neurosurgery in this indigenous black Africans remains favourable with no attendant significant adverse after-effects. PMID:26873745

  10. Black psyllium

    Science.gov (United States)

    ... block your throat or esophagus and may cause choking. Do not take this product if you have ... take enough water. Otherwise, black psyllium might cause choking. Take at least 150 mL water for each ...

  11. Black tea

    Science.gov (United States)

    ... product containing black tea extract plus green tea extract, asparagus, guarana, kidney bean, and mate along with a combination of kidney bean pods, garcinia, and chromium yeast for 12 weeks does not reduce body weight ...

  12. Black tea

    Science.gov (United States)

    ... heartburn, dizziness, ringing in the ears, convulsions, and confusion. Also, people who drink black tea or other ... glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, pioglitazone (Actos), rosiglitazone (Avandia), chlorpropamide (Diabinese), glipizide (Glucotrol), tolbutamide ( ...

  13. Orthodontic probability tables for black patients of African descent: mixed dentition analysis.

    Science.gov (United States)

    Schirmer, U R; Wiltshire, W A

    1997-11-01

    Mixed dentition space analyses form an essential part of orthodontic diagnostic procedures to determine the amount of space available for the accommodation of permanent teeth. The Moyers' probability tables for computing the sizes of unerupted canines and premolars were formulated at the University of Michigan from a sample consisting of northern European white subjects and are currently used worldwide. Because tooth sizes vary significantly between different population groups, it was the purpose of this study to construct relevant probability tables that would be more applicable to black subjects. Data were collected from a series of 100 randomly selected study models of black patients. The sample was equally subdivided by gender and all subjects had Angle Class I molar relationships with only minor malocclusions such as minor crowding, rotations, or diastemas. Two investigators independently measured the teeth on the study casts with a Vernier gauge that had sharpened calliper tips. Intraexaminer and interexaminer reliability was determined at 0.2 mm. All teeth to and including the first molars were measured. These data were then utilized in regression equations for both maxillary and mandibular arches, to enable the prediction of the mesiodistal widths of the canines and two premolars. The equations and predicted values were compared with those of the Moyers' probability tables, and significant differences (p <0.05) were found (except for the prediction of maxillary canines and premolars in females at the 85 and 95 percentile probability level). New probability tables for black subjects were formulated. It is envisaged that the proposed probability tables would be more accurate for black patients of African ancestry. PMID:9387842

  14. Keloids: Assessment of effects and psychosocial- impacts on subjects in a black African population

    Directory of Open Access Journals (Sweden)

    Olaitan P

    2009-01-01

    Full Text Available Background: Keloids are vexatious swelling on the skin or the conjuctiva. The effects and impacts of these lesions have not been assessed in a keloid endemic environment like Nigeria. Aims: The purpose of this study is to assess the psychosocial impact as well as effects of keloids on the subjects in a black African population where lesions are commonly seen. Methods: This is a prospective study which assesses the impacts of keloid on keloid patients. Consented patients who presented to the Plastic Surgery Clinic of the Lautech Teaching Hospital, Osogbo, Nigeria were recruited into the study. A set of questionnaires were administered to all consented patients. The administered questionnaires were analyzed using SPSS version 10. Results: One hundred and thirty one patients were involved in this study. They comprised of 61 males and 70 females. Most (96.8% of them had the keloid lesion for more than one year. Sixteen (12.2% of the patients felt that keloids negatively affect their works, 64 (48.9% of the patients felt stigmatized by keloids, 28 (56.0% of them who had lesions in conspicuous parts while 24 (46.2% had lesions in non-conspicuous parts. Females (59.1% felt stigmatized than males. Only 47 (35.8% of the patients believed that keloid swelling limit their social interaction. Conclusion: Keloids do not appear to have significant negative impacts on keloid patients in a keloid-endemic community like a black African population.

  15. Pattern of skin infections in black Africans of Sierra Leone (West Africa

    Directory of Open Access Journals (Sweden)

    Bari Arfan ul

    2007-01-01

    Full Text Available Background: Physical differences among human populations may lead to variable prevalence of skin disorders in different ethnicities. Skin infections are one of the important curable and largely preventable categories of skin disorders in the communities. Aim: The purpose of the study was to see the patterns of skin infections in black Africans of Sierra Leone and to compare with other ethnic populations. Materials and Methods: Local blacks of all age groups presenting in Dermatology out patient department of Pak Field Hospital (established as a part of UN peacekeeping mission in Sierra Leone were included (from Nov 2004 to Oct 2005. Relevant clinical history and physical examination was done. Laboratory investigations were carried out when indicated. Skin diseases were broadly classified into two major categories i.e., infective and noninfective. Among infective, sexually transmitted infections were again separated. Nonblack settlers in the area and UN troops were not included in the study. Data was recorded and analyzed by Microsoft Excel program. Results: 3011 patients belonging to different local tribes having a variety of skin disorders were seen. Patients were of all ages and both sexes ranging from one month to 73 years of age. The Infective skin disorders were seen in 61.7% patients and most prevalent were superficial fungal infections (41.2% followed by, sexually transmitted infections (9.9% and parasitic infections (6.5%. Bacterial and viral infections were rare and so was the scabies. More than 90% parasitic infections were onchocerciasis with full spectrum of cutaneous manifestations. Conclusion: Pattern of skin infections in blacks varies considerably from other ethnic races. Environmental factors, geographical location and free existence of vector for onchocerciasis in West African region, possibly have a significant influence in this variable prevalence.

  16. Black holes

    CERN Document Server

    Chrúsciel, P T

    2002-01-01

    This paper is concerned with several not-quantum aspects of black holes, with emphasis on theoretical and mathematical issues related to numerical modeling of black hole space-times. Part of the material has a review character, but some new results or proposals are also presented. We review the experimental evidence for existence of black holes. We propose a definition of black hole region for any theory governed by a symmetric hyperbolic system of equations. Our definition reproduces the usual one for gravity, and leads to the one associated with the Unruh metric in the case of Euler equations. We review the global conditions which have been used in the Scri-based definition of a black hole and point out the deficiencies of the Scri approach. Various results on the structure of horizons and apparent horizons are presented, and a new proof of semi-convexity of horizons based on a variational principle is given. Recent results on the classification of stationary singularity-free vacuum solutions are reviewed. ...

  17. Importance of Religion and Spirituality in the Lives of African Americans, Caribbean Blacks and Non-Hispanic Whites

    Science.gov (United States)

    Taylor, Robert Joseph; Chatters, Linda M.

    2010-01-01

    This study examined the importance of spirituality and religion in daily life (i.e., only religion, only spirituality, both religion and spirituality, and neither religion nor spirituality) among a nationally representative sample of African Americans, Caribbean Blacks and non-Hispanic Whites. A majority in each group felt they were both important…

  18. Pan-Africanism, the Mystique of World Black Unity: An Afro-American Scholar's Sojourn in Africa.

    Science.gov (United States)

    Staples, Robert

    1977-01-01

    The author explores the ideology of Pan-Africanism in terms of the social and economic position of Blacks in the United States. He briefly describes his visit to Africa (Senegal and Nigeria) and the effects that this experience has had in forming his political viewpoint. (MC)

  19. Perspectives on Identity, Disclosure, and the Campus Environment among African American Gay and Bisexual Men at One Historically Black College

    Science.gov (United States)

    Patton, Lori D.

    2011-01-01

    This qualitative study examined how 6 African American men at one historically Black college made meaning of their gay or bisexual identity, made decisions about to whom they disclosed this identity, and how their sexual identity experiences were mediated given the context of the campus environment. The findings suggest although this particular…

  20. Factors Leading African Americans and Black Caribbeans to Use Social Work Services for Treating Mental and Substance Use Disorders

    Science.gov (United States)

    Cheng, Tyrone C.; Robinson, Michael A.

    2013-01-01

    This secondary analysis of 5,000 African Americans and black Caribbeans explored how their use of social work services to address mental and substance use disorders was associated with the disorder involved as well as their perceived need for services, belief system, family resources, proximity to services, social-structural factors, and…

  1. Triglyceride concentration and waist circumference influence alcohol-related plasminogen activator inhibitor-1 activity increase in black South Africans

    NARCIS (Netherlands)

    Pieters, Marlien; de Lange, Zelda; Hoekstra, Tiny; Ellis, Suria M.; Kruger, Annamarie

    2010-01-01

    We investigated the association between alcohol consumption and plasminogen activator inhibitor-1 activity (PAI-1(act)) and fibrinogen concentration in a black South African population presenting with lower PAI-1(act) and higher fibrinogen than what is typically observed in white populations. We, fu

  2. 'Just talking about it opens your heart': meaning-making among Black African migrants and refugees living with HIV.

    Science.gov (United States)

    Henrickson, Mark; Brown, Derek Brian; Fouché, Christa; Poindexter, Cynthia C; Scott, Kay

    2013-01-01

    Meaning-making has emerged as a core construct in addressing trauma, loss or crisis. This paper considers how diasporic Black Africans living with HIV, who come from interdependent collectivist cultures where the norm is one of implicit support, extend their meaning-making strategies when faced with a diagnosis of HIV. In this qualitative study, 13 Black African migrants and refugees living with HIV in New Zealand were interviewed and the transcripts analysed. After their diagnosis, participants began a journey of reconceptualising situational and global meaning. They extended their meaning-making strategies to include a community of like others to gain explicit support. Caregivers in host countries must understand the meaning-making processes of HIV-positive Black African migrants in order to provide competent services that lead to good social and health outcomes. All healthcare and social services workers should regularly assess Black African migrants and refugees living with HIV for positive social connectedness as well as medication adherence and more specific health concerns. PMID:23651201

  3. Racial and Athletic Identity of African American Football Players at Historically Black Colleges and Universities and Predominantly White Institutions

    Science.gov (United States)

    Steinfeldt, Jesse A.; Reed, Courtney; Steinfeldt, M. Clint

    2010-01-01

    This study examined racial and athletic identity among African American football players at historically Black colleges and universities (HBCUs) and predominantly White institutions (PWIs). Negotiating the dualism of racial and athletic identities can be problematic because both roles are subject to prejudice and discrimination, particularly for…

  4. [Protein C deficiency in black African with venous thromboembolism in Cotonou, Benin].

    Science.gov (United States)

    Houénassi, D M; Bigot, A; Tchabi, Y; Vehounkpé-Sacca, J; Akindes-Dossou Yovo, R; Gbaguidi, L; d'Almeida-Massougbodji, M; Agboton, H

    2013-02-01

    The aim of this study is to evaluate the frequency of protein C deficiency in venous thromboembolism in black African patients of Benin. It is a descriptive study. Inclusion criteria were: acceptance- having a venous thromboembolism. No exlusion criteria was retained. Protein C deficiency was diagnosed by quantitative technic with a Minividas materiel in the blood. Protein C dosage has been done before antivitamin k therapy and a second dosage has been done if the first one demonstrated a low level of protein C. Acuired aetiology have been research. For the 54 patients of this study mean age was 52.7±14.1 and sex-ratio 1.08. The frequency of protein C deficiency was 9.3% in all patients and 12.5% in those with clinical thrombophily (p=1). No acquired deficit has been found.

  5. [Determination of the average value of the condylar slope of black Africans].

    Science.gov (United States)

    Konaté, N Y; Djérédou, K B; Kamagaté, F S; Thiam, A; Pesson, D M; Assi, K D; Touré, S

    2008-09-01

    The objective of this work was to determinate the average value of the condylar slope of Black African subject and to set up its variation according to whether the localization of the hinge axis is real or arbitrary. With this intention, we made an axiographic study at 63 subjects presented complete natural teeth, with a normoclusion in class 1 of Angle. The results of this study reveal that the average value of the slope condylar is 44,28 degrees in arbitrary hinge axis and 45,7 degrees in hinge axis real; and this difference is not statistically significant. The graphic recording of condylar displacement by the "Quick-Axis" is thus possible without risk of error in the layout and the reproduction of the mandible movements which is of a great interest for the general practitioner taking into account the simplicity of handling of the FAG system.

  6. Tobacco use among black South African university students: attitudes, risk awareness and health locus of control

    Directory of Open Access Journals (Sweden)

    K Peltzer

    2001-09-01

    Full Text Available Objectives: To provide data on African/black South African university students’ tobacco use status, belief in the benefits to health of not smoking, risk awareness in terms of knowledge of the links between smoking and disease, health locus of control, value for health, subjective health status and well-being. Design: Cross sectional. Setting: University of the North Subjects: 793 Black University students from non-health courses chosen by random sampling, of these 370 (46.7% were males and 423 (53.3% were females in the age range of 18 to 25 years (M age 21.0 years, SD=3.48. Main Outcome Measures: A measure of smoking, the Multidimensional Health Locus of Control Scale, the Health as a Value Scale, and a measure for subjective health and subjective well-being. Results: The average prevalence of current tobacco use was 15% in men and 1% in women. The proportion of tobacco users who were classified as light users (1-10 per day averaged 10% in men and 1% in women. Age and being male were significantly positively associated with status and frequency of tobacco use. Awareness of the link between smoking and lung cancer was high (93%, but awareness of the role of smoking in heart disease was very low (16%. The importance to health of not smoking was associated with smoking status (non-smoking versus smoking. Overall, 75% of the current smokers stated that they would like to reduce the amount they smoked. Poor subjective health status and low subjective well-being was associated with smoking status. No significant differences were found among non-tobacco users and tobacco users in relation to the three subscales of the Health Locus of Control (Internal, Chance, and Powerful others and Value for health. Conclusion: For about 9% of the male students investigated, a high risk exists to become regular tobacco users for the next 30 years.

  7. Fischer Black

    OpenAIRE

    Robert C. Merton; Myron S. Scholes

    2013-01-01

    ReprintThis article was originally published by Wiley for the American Finance Association (Merton RC, Scholes MS. 1995. Fischer Black. J. Finance 50(5):1359–70). It is reprinted with permission from John Wiley and Sons © 1995. Reference formatting was updated to facilitate linking.

  8. The African American Read-In: Celebrating Black Writers and Supporting Youth

    Science.gov (United States)

    Carter, Stephanie Power

    2007-01-01

    Media subliminally bombard people with negative portrayals and stereotypes of Black people while doing little to represent the great contributions that Blacks have made in society and literature. This trend and lack of representation are also visible in schools, in particular the English classroom. Students are not often exposed to many writers of…

  9. The Frequency of Cytochrome P450 2E1 Polymorphisms in Black South Africans

    Directory of Open Access Journals (Sweden)

    Paul K. Chelule

    2006-01-01

    Full Text Available Polymorphisms in the promoter region of the Cytochrome P4502E1 (CYP2E1 gene reportedly modify the metabolic activity of CYP2E1 enzyme, and have been associated with increased susceptibility to squamous cell carcinoma (SCC of the oesophagus in high prevalence areas such as China. To assess the frequency of these polymorphisms in Black South Africans, a population with a high incidence of oesophageal SCC, this study examined genomic DNA from 331 subjects for restriction fragment length polymorphisms in the CYP2E1 (RsaI and PstI digestion. The frequency of the CYP2E1 c1/c1 and c1/c3 genotypes was 95% and 5% respectively. The frequency of the CYP2E1 allele distribution was found to be markedly different between Chinese and South African populations; hence it is important to place racial differences into consideration when proposing allelic variants as genetic markers for cancer.

  10. African Ancestry, Social Factors, and Hypertension Among Non-Hispanic Blacks in the Health and Retirement Study.

    Science.gov (United States)

    Marden, Jessica R; Walter, Stefan; Kaufman, Jay S; Glymour, M Maria

    2016-01-01

    The biomedical literature contains much speculation about possible genetic explanations for the large and persistent black-white disparities in hypertension, but profound social inequalities are also hypothesized to contribute to this outcome. Our goal is to evaluate whether socioeconomic status (SES) differences provide a plausible mechanism for associations between African ancestry and hypertension in a U.S. cohort of older non-Hispanic blacks. We included only non-Hispanic black participants (N = 998) from the Health and Retirement Study who provided genetic data. We estimated percent African ancestry based on 84,075 independent single nucleotide polymorphisms using ADMIXTURE V1.23, imposing K = 4 ancestral populations, and categorized into quartiles. Hypertension status was self-reported in the year 2000. We used linear probability models (adjusted for age, sex, and southern birth) to predict prevalent hypertension with African ancestry quartile, before and after accounting for a small set of SES measures. Respondents with the highest quartile of African ancestry had 8 percentage points' (RD = 0.081; 95% CI: -0.001, 0.164) higher prevalence of hypertension compared to the lowest quartile. Adjustment for childhood disadvantage, education, income, and wealth explained over one-third (RD = 0.050; 95% CI: -0.034, 0.135) of the disparity. Explanations for the residual disparity remain unspecified and may include other indicators of SES or diet, lifestyle, and psychosocial mechanisms. PMID:27050031

  11. black cat

    Institute of Scientific and Technical Information of China (English)

    杜铁梅

    2016-01-01

    The black cat is a masterpiece of short fiction of Poe. He successfully solved the problem of creating of the horror effect by using scene description, symbol, repetition and first-person narrative methods. And created a complete and unified mysterious terror, achieved the effect of shocking. This paper aims to discuss the mystery in-depth and to enrich the research system in Poe’s novels.

  12. Black African and Caribbean British Communities' Perceptions of Memory Problems: "We Don't Do Dementia.".

    Directory of Open Access Journals (Sweden)

    Sharne Berwald

    Full Text Available We aimed to identify and explore the barriers to help-seeking for memory problems, specifically within UK Black African and Caribbean communities.We purposively recruited participants from community groups and subsequent snowball sampling, to achieve a maximum variation sample and employed thematic analysis. Our qualitative semi-structured interviews used a vignette portraying a person with symptoms of dementia, and we asked what they or their family should do. We stopped recruiting when no new themes were arising.We recruited 50 people from a range of age groups, country of origin, time in the UK, religion and socio-economic background. Some of the barriers to presentation with dementia have been reported before, but others were specific to this group and newly identified. Many people recognised forgetfulness but neither that it could be indicative of dementia, nor the concept of dementia as applying to them. Dementia was viewed as a white person's illness. Participants felt there was little point in consulting a doctor for forgetfulness. Many thought that seeing a GP was only for severe problems. Some said that their culture was secretive and highly valued privacy of personal affairs and therefore did not want to discuss what they regarded as a private and stigmatising problem with a GP. Participants did not appreciate their GP could refer to memory services who have more time and expertise. They were concerned about harm from medication and compulsory institutionalisation. Care should be from the family. Any intervention should emphasise the legitimacy of seeing a doctor early for memory concerns, that dementia is a physical illness which also occurs in the Black community, that help and time are available from memory services whose role is to prolong independence and support families in caring.

  13. HIV-related stigma among African, Caribbean, and Black youth in Windsor, Ontario.

    Science.gov (United States)

    Mihan, Robert; Kerr, Jelani; Maticka-Tyndale, Eleanor

    2016-01-01

    HIV-related stigma has been shown to undermine prevention, care, treatment, and the well-being of people living with HIV. A disproportion burden of HIV infection, as well as elevated levels of HIV-related stigma, is evidenced in sub-Saharan African (SSA) and African-diasporic populations. This study explores factors that influence HIV-related stigma among 16- to 25-year-old youth residing in a Canadian city who identify as African, Caribbean, or Black. Stigma, as rooted in cultural norms and beliefs and related social institutions, combined with insights from research on stigma in SSA and African-diasporic populations, guided the development of a path analytic structural equation model predicting levels of HIV-related stigmatizing attitudes. The model was tested using survey responses of 510 youth to estimate the direct and indirect influences of ethno-religious identity, religious service attendance, time in Canada, HIV/AIDS knowledge, HIV-testing history, sexual health service contact, and gender on HIV-related stigma. Statistically significant negative associations were found between levels of stigma and knowledge and HIV-testing history. Ethno-religious identity and gender had both direct and indirect effects on stigma. African-Muslim participants had higher levels of stigma, lower knowledge, and were less likely to have been tested for HIV infection than other ethno-religious groups. Male participants had higher levels of stigma and lower knowledge than women. Time in Canada had only indirect effects on stigma, with participants in Canada for longer periods having higher knowledge and less likely to have been tested than more recent arrivals. While the strength of the effect of knowledge on stigmatizing attitudes in this research is consistent with other research on stigma and evaluations of stigma-reduction programs, the path analytic results provide additional information about how knowledge and HIV-testing function as mediators of non

  14. Predictors of success for african black physiotherapy students in South Africa

    Directory of Open Access Journals (Sweden)

    N. Mbambo-Kekana

    2011-02-01

    Full Text Available high school performance and aptitude tests are usually used to predict success at university, but this may not be applicable when the ethnic group of the student is considered. The aim of this study was to investigate factors  that  predict  success  of  African  black  students  in  physiotherapy programmes and whether these factors are influenced by race. A mixed methods approach was used. one hundred and twenty eight graduates who graduated between 2000 and 2005 from eight universities in South Africa and six heads of Physiotherapy Departments participated in the research. A  postal  questionnaire  comprising  closed  and  open-ended questions was used  for  graduate  and  in-depth  interviews  were conducted  with  heads  of Departments. Quantitative data were analyzed using descriptive analysis as well as inferential statistics using Chi square tests and logistic regression. Qualitative data was analysed using content analysis. of the participants, 59% of the African black students were successful compared to 90% of the white students.  A significant association was found between race and success with factors such as sharing a residence room, obtaining information about university support systems from classmates, feeling part of the group of classmates and choosing physiotherapy as the first choice of career being predictors of success. Students also highlighted determination to succeed and become a physiotherapist, financial and family support, and a favourable learning environment to contribute to success. HOD interviews associated adequate knowledge about the physiotherapy profession, proficiency in the language of instruction, academic discipline, relevant support and integration in the class with success. It is recommended that matriculation results should not be the only predictors of success but tertiary institutions should consider broader factors such as residential accommodation and a

  15. Demographic Correlates of Psychological Well-Being and Distress Among Older African Americans and Caribbean Black Adults

    OpenAIRE

    Lincoln, Karen D.; Taylor, Robert Joseph; Chae, David H.; Chatters, Linda M.

    2010-01-01

    This study examines the demographic correlates of psychological distress and psychological well-being among older African American and black Caribbean adults. Analysis of the National Survey of American Life revealed that psychological well-being and psychological distress are distinct concepts. Findings also identify distinct correlates of psychological well-being (e.g., happiness, life satisfaction, self-rated mental health) and psychological distress (e.g., depressive symptoms, serious psy...

  16. Being black in a white skin: Beliefs and stereotypes around albinism at a South African university

    Directory of Open Access Journals (Sweden)

    Relebohile Phatoli

    2015-02-01

    Full Text Available Background: Partly because of the legacy of apartheid, and despite being a constitutional democracy, South Africa continues to be a deeply divided society, particularly along racial lines. In this context many people with albinism do not fit neatly into black and white categories and are likely to experience social discrimination and marginalisation.Objectives: The study endeavoured to explore the beliefs and practices regarding albinism within a South African university, and the availability of support services. Method: The research was located within an interpretive qualitative paradigm and was framed within the theories of stigma, discrimination and ‘othering’. Interviews were conducted with five students with albinism and 10 students without albinism. Results: Findings confirmed the existence of myths and stereotypes regarding albinism. Students with albinism tended to exclude themselves from the rest of the student community to avoid discrimination and stereotypes around their condition. Conclusion: People with albinism can teach us about social constructions of race, colour and relations between minority groups and the majority culture. Results have implications for schools, disability units at universities, and albinism societies in terms of opening up channels of communication between people with albinism and the general public and fostering knowledge and awareness thereof.

  17. Satisfaction with personal and environmental quality of life: a black South African informal settlement perspective

    Directory of Open Access Journals (Sweden)

    MS Westaway

    2001-09-01

    Full Text Available A study was conducted with 487 black adult residents of a South African informal settlement (151 men and 336 women to ascertain satisfaction with personal and environmental quality of life. It was hypothesised that: (1 health status and life satisfaction were the underlying dimensions of personal quality of life (PQOL; (2 health status and life satisfaction were more strongly associated with PQOL than environmental quality of life (EQOL; and (3 life satisfaction and satisfaction with EQOL were positively related. Seventy per cent of respondents rated their health as good or better. Age, schooling and employment status were significantly related to health, life satisfaction and PQOL. Reliability (internal consistency coefficients were 0.77 for the 5-item life satisfaction scale and 0.82 for the 12-item EQOL measure. Factor analysis showed that safety and security was the major unmet service need. Health status and life satisfaction explained 38% of the variance in PQOL; health status explained only 4% of the variance in EQOL. Life satisfaction was significantly related to EQOL (r = 0.16, p = 0.01. The results provided support for all three hypotheses. It was concluded that the life satisfaction and EQOL measures had good reliability; there was a definite need for a safety and security programme; and good health was a more important predictor of PQOL than EQOL.

  18. Radionic nonuniform black strings

    Science.gov (United States)

    Tamaki, Takashi; Kanno, Sugumi; Soda, Jiro

    2004-01-01

    Nonuniform black strings in the two-brane system are investigated using the effective action approach. It is shown that the radion acts as a nontrivial hair of the black strings. From the brane point of view, the black string appears as the deformed dilatonic black hole which becomes a dilatonic black hole in the single brane limit and reduces to the Reissner-Nordström black hole in the close limit of two-branes. The stability of solutions is demonstrated using catastrophe theory. From the bulk point of view, the black strings are proved to be nonuniform. Nevertheless, the zeroth law of black hole thermodynamics still holds.

  19. Portraits of resilience : writing a socio-cultural history of a black South African location with the Ngilima photographic collection. Benoni, 1950s-1960s.

    NARCIS (Netherlands)

    Feyder, Sophie

    2016-01-01

    This thesis engages with the ongoing debate regarding how photographs can contribute to the writing of black South African history. In the field of South African visual history, a significant literature explores the “white gaze” that emanates from the administrative and missionary photographic archi

  20. Black Studies and Global Perspectives: An Essay.

    Science.gov (United States)

    Drake, St. Clair

    1984-01-01

    Relates the emergence of Black Studies programs in the 1960s to the interest of American Blacks in the African independence struggles. Observes a shift in Black Studies away from the militancy of its origins and calls for reconsideration of its purpose. Reviews related literature. (KH)

  1. Black Urine

    Directory of Open Access Journals (Sweden)

    Rahim Vakili

    2016-06-01

    Full Text Available A 2-year-old boy was born at term of healthy, non-consanguineous Iranian parents. His mother attended in the clinic with the history of sometimes discoloration of diapers after passing urine. She noticed that first at the age of one month with intensified in recent months. His Physical examination and growth parameters were normal. His mother denied taking any medication (sorbitol, nitrofurantoin, metronidazole, methocarbamol, sena and methyldopa (5. Qualitative urine examination showed dark black discoloration. By this history, alkaptonuria was the most clinical suspicious. A 24-hour-urine sample was collected and sent for quantitative measurements. The urine sample was highly positive for homogentisic acid and negative for porphyrin metabolites.

  2. Black Silicon Solar Cells with Black Ribbons

    DEFF Research Database (Denmark)

    Davidsen, Rasmus Schmidt; Tang, Peter Torben; Mizushima, Io;

    2016-01-01

    We present the combination of mask-less reactive ion etch (RIE) texturing and blackened interconnecting ribbons as a method for obtaining all-black solar panels, while using conventional, front-contacted solar cells. Black silicon made by mask-less reactive ion etching has total, average...... in the range 15.7-16.3%. The KOH-textured reference cell had an efficiency of 17.9%. The combination of black Si and black interconnecting ribbons may result in aesthetic, all-black panels based on conventional, front-contacted silicon solar cells....... reflectance below 0.5% across a 156x156 mm2 silicon (Si) wafer. Black interconnecting ribbons were realized by oxidizing copper resulting in reflectance below 3% in the visible wavelength range. Screen-printed Si solar cells were realized on 156x156 mm2 black Si substrates with resulting efficiencies...

  3. Noncommutative black holes

    International Nuclear Information System (INIS)

    We study noncommutative black holes, by using a diffeomorphism between the Schwarzschild black hole and the Kantowski-Sachs cosmological model, which is generalized to noncommutative minisuperspace. Through the use of the Feynman-Hibbs procedure we are able to study the thermodynamics of the black hole, in particular, we calculate Hawking's temperature and entropy for the 'noncommutative' Schwarzschild black hole

  4. Black Entrepreneurship in America.

    Science.gov (United States)

    Green, Shelley; Pryde, Paul

    The economic condition of black Americans is discussed, proceeding from the assumption that black economic progress does not depend on a renewed struggle for unobtained civil rights, but rather on the creative response of black Americans to economic opportunity and problems. In the long run, black economic development must rely on the…

  5. Interleukin-6 gene polymorphisms, dietary fat intake, obesity and serum lipid concentrations in black and white South African women.

    Science.gov (United States)

    Joffe, Yael T; van der Merwe, Lize; Evans, Juliet; Collins, Malcolm; Lambert, Estelle V; September, Alison V; Goedecke, Julia H

    2014-06-24

    This study investigated interactions between dietary fat intake and IL-6 polymorphisms on obesity and serum lipids in black and white South African (SA) women. Normal-weight and obese, black and white women underwent measurements of body composition, serum lipids and dietary fat intake, and were genotyped for the IL-6 -174 G>C, IVS3 +281 G>T and IVS4 +869 A>G polymorphisms. In black women the IVS4 +869 G allele was associated with greater adiposity, and with increasing dietary fat intake adiposity increased in the IVS3 +281 GT+GG and IVS4 +869 AA or AG genotypes. In white women, with increasing omega-3 (n-3) intake and decreasing n-6:n-3 ratio, body mass index (BMI) decreased in those with the -174 C allele, IVS3 +281 T allele and IVS4 +869 AG genotype. In the white women, those with the IVS3 +281 T allele had lower triglycerides. Further, with increasing n-3 polyunsaturated fatty acid (PUFA); triglyceride and total cholesterol:high-density lipoprotein cholesterol (T-C:HDL-C) ratio decreased in those with the -174 C allele. In black women, with increasing total fat intake, triglycerides and T-C:HDL-C ratio increased in those with the IVS4 +869 G allele. This study is the first to show that dietary fat intake modulates the relationship between the IL-6 -174 G>C, IVS3 +281 G>T and IVS4 +869 A>G polymorphisms on obesity and serum lipids in black and white SA women.

  6. A group of black South Africans' experience of telling their untold stories about the apartheid era / Jacques Vermeulen

    OpenAIRE

    Vermeulen, Jacques

    2006-01-01

    The aim or this research was to explore a group of black South Africans' experiences of telling their untold stories of survival about the apartheid era. The expectation was that if they did become more aware of these alternative stories, it could have a far-reaching effect on their lives. Research indicates that when attention is given to these narratives they may be a powerful tool in not only recovering the story but also in focusing on the survivors' own consciousness and g...

  7. Prostate cancer disparities in Black men of African descent: a comparative literature review of prostate cancer burden among Black men in the United States, Caribbean, United Kingdom, and West Africa

    Directory of Open Access Journals (Sweden)

    Reams R Renee

    2009-02-01

    Full Text Available Abstract Background African American men have the highest prostate cancer morbidity and mortality rates than any other racial or ethnic group in the US. Although the overall incidence of and mortality from prostate cancer has been declining in White men since 1991, the decline in African American men lags behind White men. Of particular concern is the growing literature on the disproportionate burden of prostate cancer among other Black men of West African ancestry in the Caribbean Islands, United Kingdom and West Africa. This higher incidence of prostate cancer observed in populations of African descent may be attributed to the fact that these populations share ancestral genetic factors. To better understand the burden of prostate cancer among men of West African Ancestry, we conducted a review of the literature on prostate cancer incidence, prevalence, and mortality in the countries connected by the Transatlantic Slave Trade. Results Several published studies indicate high prostate cancer burden in Nigeria and Ghana. There was no published literature for the countries Benin, Gambia and Senegal that met our review criteria. Prostate cancer morbidity and/or mortality data from the Caribbean Islands and the United Kingdom also provided comparable or worse prostate cancer burden to that of US Blacks. Conclusion The growing literature on the disproportionate burden of prostate cancer among other Black men of West African ancestry follows the path of the Transatlantic Slave Trade. To better understand and address the global prostate cancer disparities seen in Black men of West African ancestry, future studies should explore the genetic and environmental risk factors for prostate cancer among this group.

  8. The chimera of redistribution: 'Black Economic Empowerment' (BEE) in the South African fishing industry

    OpenAIRE

    Ponte, Stefano; van Sittert, Lance

    2006-01-01

    Redistributive processes do not belong to the pantheon of Neo-liberalism. In this framework, inequality of resources can only be addressed by equality of opportunity. Even in ‘softer’ impersonations of Neo-liberalism, corporate (mis)behaviour is tamed by corporate social responsibility, not by state disciplinary action. Yet, in the context of post-apartheid South Africa, the state can not ignore political pressure for redistribution, even if only rhetorically. The process of Black Economic Em...

  9. How is the epidemiology of heterosexually-acquired HIV infection evolving, particularly among black Africans, in England, Wales and Northern Ireland?

    OpenAIRE

    Rice, Brian

    2016-01-01

    In the United Kingdom (UK), an estimated 107,800 people were living with HIV in 2013, of whom 55% were heterosexual men and women. Black African men and women accounted for the majority of heterosexuals living with HIV in the UK in 2013. In this PhD by prospective publication my research question is “How is the epidemiology of heterosexually-acquired HIV infection evolving, particularly among black Africans, in England, Wales and Northern Ireland?”. I conducted a quantitative analysis of nati...

  10. Dietary Intake of the Urban Black Population of Cape Town: The Cardiovascular Risk in Black South Africans (CRIBSA Study

    Directory of Open Access Journals (Sweden)

    Nelia P. Steyn

    2016-05-01

    Full Text Available Introduction: To determine dietary intake of 19 to 64 years old urban Africans in Cape Town in 2009 and examine the changes between 1990 and 2009. Methods: A representative cross-sectional sample (n = 544, stratified by gender and age was randomly selected in 2009 from the same areas sampled in 1990. Socio-demographic data and a 24-h dietary recall were obtained by trained field workers. The associations of dietary data with an asset index and degree of urbanization were assessed. Results: Fat intakes were higher in 19–44-year-old men (32% energy (E and women (33.4%E in 2009 compared with 1990 (men: 25.9%E, women: 27.0%E while carbohydrate intakes were lower in 2009 (men 53.2%E, women: 55.5%E than in 1990 (men: 61.3%E; women: 62%E while sugar intake increased significantly (p < 0.01 in women. There were significant positive correlations between urbanization and total fat (p = 0.016, saturated fat (p = 0.001, monounsaturated fat (p = 0.002 and fat as a %E intake (p = 0.046. Urbanization was inversely associated with intake of carbohydrate %E (p < 0.001. Overall micronutrient intakes improved significantly compared with 1990. It should also be noted that energy and macronutrient intakes were all significant in a linear regression model using mean adequacy ratio (MAR as a measure of dietary quality in 2009, as was duration of urbanization. Discussion: The higher fat and lower carbohydrate %E intakes in this population demonstrate a transition to a more urbanized diet over last two decades. These dietary changes reflect the nutrition transitions that typically occur as a longer time is spent in urban centers.

  11. Black History, Inc! Investigating the Production of Black History through Walmart's Corporate Web Site

    Science.gov (United States)

    King, LaGarrett J.; Brown, Anthony L.

    2012-01-01

    Social and public sites are becoming a popular medium for intellectual consumption of Black history. Given the educational climate in which many students' exposure to Black history may come from outside of schools, the authors examine how Walmart's Black History Month Web site produced simplistic and safe narratives about African American history.

  12. Reconsidering the Freedom Charter, the black theology of liberation and the African proverb about the locust’s head in the context of poverty in South Africa

    Directory of Open Access Journals (Sweden)

    Ndikho Mtshiselwa

    2016-02-01

    Full Text Available While South Africa attained liberation from the apartheid rule in 1994, the legacy of colonialism and apartheid – in the form of poverty and economic inequality – continues to haunt black South Africans. The aim of this article is to make a case for the equitable sharing of South Africa’s mineral wealth amongst all its citizens with the view to alleviate poverty. Firstly, this article provides a reflection on the Freedom Charter and suggests that the values of the Charter, for instance, the sharing of resources and wealth, are relevant in South Africa today. Secondly, it is argued in the present article that the preferential option for the poor which is upheld in the black theology of liberation is equally relevant in post-apartheid South Africa where many black South Africans remain poor. Thirdly, this article argues that the African proverb, Bana ba motho ba ngwathelana hlogo ya tšie [The siblings share the head of a locust], also echoes the idea of equitable sharing of resources with a view to alleviate poverty. Lastly, the author submits that the idea of equitable sharing of resources and wealth that is echoed in the Freedom Charter, the black theology of liberation and the African wise saying support the equitable redistribution of the mineral wealth to the benefit of all South Africans.

  13. The Black Studies Boondoggle

    Science.gov (United States)

    Long, Richard A.

    1970-01-01

    Indicates tendencies dangerous to the basic purpose of Black Studies, and identifies four external challeges--imperialism, paternalism, nihilism, and materialism. An internal challenge is considered to be the use of European and Establishment constructs to analyze black reality. (DM)

  14. Dynamics of black holes

    OpenAIRE

    Hayward, Sean A.

    2008-01-01

    This is a review of current theory of black-hole dynamics, concentrating on the framework in terms of trapping horizons. Summaries are given of the history, the classical theory of black holes, the defining ideas of dynamical black holes, the basic laws, conservation laws for energy and angular momentum, other physical quantities and the limit of local equilibrium. Some new material concerns how processes such as black-hole evaporation and coalescence might be described by a single trapping h...

  15. Noncommutative black holes

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-DomInguez, J C [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico); Obregon, O [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico); RamIrez, C [Facultad de Ciencias FIsico Matematicas, Universidad Autonoma de Puebla, PO Box 1364, 72000 Puebla (Mexico); Sabido, M [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico)

    2007-11-15

    We study noncommutative black holes, by using a diffeomorphism between the Schwarzschild black hole and the Kantowski-Sachs cosmological model, which is generalized to noncommutative minisuperspace. Through the use of the Feynman-Hibbs procedure we are able to study the thermodynamics of the black hole, in particular, we calculate Hawking's temperature and entropy for the 'noncommutative' Schwarzschild black hole.

  16. Black holes without firewalls

    Science.gov (United States)

    Larjo, Klaus; Lowe, David A.; Thorlacius, Larus

    2013-05-01

    The postulates of black hole complementarity do not imply a firewall for infalling observers at a black hole horizon. The dynamics of the stretched horizon, that scrambles and reemits information, determines whether infalling observers experience anything out of the ordinary when entering a large black hole. In particular, there is no firewall if the stretched horizon degrees of freedom retain information for a time of the order of the black hole scrambling time.

  17. Black Nuns as Educators.

    Science.gov (United States)

    Rector, Theresa A.

    1982-01-01

    Traces the contributions of Black Roman Catholic nuns to Black education in the United States since the early 1800s. Also shows that, despite declining membership, the three existing religious orders continue to be active in Black education and social change. (GC)

  18. Marketing for Black Alums.

    Science.gov (United States)

    Harris, Tracy A.

    1994-01-01

    Considers need for colleges and universities to develop effective marketing plan for recruitment of black students. Highlights advantages of designing marketing plan for recruitment of black alumni to assist in recruitment and retention of black students. Identifies key indicators that often hinder institutions in their recruitment of black…

  19. Africans and Black Americans in the United States: Social Distance and Differential Acculturation.

    Science.gov (United States)

    Emoungu, Paul-Albert

    1992-01-01

    Presents an exploratory examination of the causes of social distance characterizing the association between Africans and African Americans. African American's perceptions about Africa and Africans are assessed through anecdotes and impressions, and thoughts and criticisms of Africans about African Americans are considered. A social science…

  20. 'Black Magic' and Diasporic Imagination

    OpenAIRE

    Raupach, Kirsten

    2002-01-01

    Within a colonial framework black diasporan thinking became most evident in the slaves' religious practices. Diasporic Imagination was displayed in terms of rituals of remembrance, social bonding across racial diversity, worship of African Gods, and imagined return to the homeland. These diasporic elements in African-Carribean slave religion, however, challenged white authority and conceptions of white superiority. A closer look at British colonial discourse of the late 18th century illustrat...

  1. REDUCED GLUTEAL EXPRESSION OF ADIPOGENIC AND LIPOGENIC GENES IN BLACK SOUTH AFRICAN WOMEN IS ASSOCIATED WITH OBESITY-RELATED INSULIN RESISTANCE

    Science.gov (United States)

    Goedecke, Julia H.; Evans, Juliet; Keswell, Dheshnie; Stimson, Roland H.; Livingstone, Dawn E.W.; Hayes, Philip; Adams, Kevin; Dave, Joel A.; Victor, Hendriena; Levitt, Naomi S.; Lambert, Estelle V.; Walker, Brian R.; Seckl, Jonathan R.; Olsson, Tommy; Kahn, Steven E.

    2014-01-01

    Context Black South African women are less insulin sensitive than their white counterparts, despite less central and greater peripheral fat deposition. We hypothesized that this paradox may be explained, in part, by differences in the adipogenic capacity of subcutaneous adipose tissue (SAT). Objective To measure adipogenic and lipogenic gene expression in abdominal and gluteal SAT depots, and determine their relationships with insulin sensitivity (SI) in South African women. Design Cross-sectional. Participants 14 normal-weight (BMI 30 kg/m2) black and 13 obese white premenopausal South African women. Main outcomes SI (frequently sampled intravenous glucose tolerance test) in relation to expression of adipogenic and lipogenic genes in abdominal and gluteal SAT depots. Results With increasing BMI, black women had less visceral fat (P=0.03) and more abdominal (P=0.017) and gynoid (P=0.041) SAT but had lower SI (P<0.01) than white women. The expression of adipogenic and lipogenic genes was proportionately lower with obesity in black, but not white women in the gluteal and deep SAT depots (P<0.05 for ethnicity x BMI effect). In black women only, the expression of these genes correlated positively with SI (all P<0.05), independently of age and fat mass. Conclusions Obese black women have reduced SAT expression of adipogenic and lipogenic genes compared to white women, which associates with reduced SI. These findings suggest that obesity in black women impairs SAT adipogenesis and storage, potentially leading to insulin resistance and increased risk of type 2 diabetes. PMID:21956425

  2. Racial Identity Attitudes, Womanist Identity Attitudes, and Self-Esteem in African American College Women Attending Historically Black Single-Sex and Coeducational Institutions

    Science.gov (United States)

    Watt, Sherry Kay

    2006-01-01

    This study examines racial identity attitudes, womanist identity attitudes, and self-esteem of 111 African American college women attending two historically Black higher educational institutions, one coeducational and one single-sex. The major findings indicate that pre-encounter and encounter attitudes of racial and womanist identity are…

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

    Science.gov (United States)

    Tedam, Prospera

    2014-01-01

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

  4. White South Africans' Reactions to Black Advancement: A Two-Sample Confirmatory Investigation of the Structure of Attitude Using an Analogy to the Multitrait-Multimethod Design.

    Science.gov (United States)

    Taylor, Terence R.; Chemel, Charles S.

    1991-01-01

    A questionnaire measuring affective, conative, and cognitive responses to 3 aspects of Black advancement in the workplace was administered to 128 White English-speaking and 140 Afrikaans-speaking South Africans. Results of confirmatory, single-group, and multigroup analyses of the data indicate that the structures were very similar across the…

  5. Gender nonconformity, discrimination, and mental health among Black South African men who have sex with men: A further exploration of unexpected findings

    NARCIS (Netherlands)

    T. Sandfort; H. Bos; J. Knox; V. Reddy

    2015-01-01

    Using data from a study about HIV risk among Black South African MSM, we aimed to ascertain whether unexpected findings about the relationship between gender nonconformity, discrimination, and mental health in this population, as reported by Cook, Sandfort, Nel, and Rich (2013), could be replicated,

  6. Racial and Ethnic-Related Stressors as Predictors of Perceived Stress and Academic Performance for African American Students at a Historically Black College and University

    Science.gov (United States)

    Greer, Tawanda M.

    2008-01-01

    The purpose of this investigation was to determine whether racial and ethnic-related stressors were associated with overall levels of perceived stress and academic performance among African American students at a historically Black college and university (HBCU). Hierarchical regression analyses were used to test racial and ethnic-related stressors…

  7. In black south africans from rural and urban communities, the 4G/5G PAI-1 polymorphism influences PAI-1 activity, but not plasma clot lysis time

    NARCIS (Netherlands)

    Z. de Lange (Zelda); D.C. Rijken (Dingeman); T. Hoekstra (Tiny); K.R. Conradie (Karin); J.C. Jerling (Johann); M. Pieters (Marlien)

    2013-01-01

    textabstractData on genetic and environmental factors influencing PAI-1 levels and their consequent effect on clot lysis in black African populations are limited. We identified polymorphisms in the promoter area of the PAI-1 gene and determined their influence on PAI-1act levels and plasma clot lysi

  8. Black English in New York.

    Science.gov (United States)

    Dillard, J. L.

    1971-01-01

    Black English has existed for a considerable length of time in the North as well as in the South. West African slaves who came to New York in 1625 found a contact language useful and mandatory in order to function in the slave community. The earliest slaves in the New York area may have used Pidgin English, Pidgin Portuguese, or Pidgin French…

  9. Stuffed Black Holes

    CERN Document Server

    Arbona, A; Carot, J; Mas, L; Massó, J; Stela, J

    1998-01-01

    Initial data corresponding to spacetimes containing black holes are considered in the time symmetric case. The solutions are obtained by matching across the apparent horizon different, conformally flat, spatial metrics. The exterior metric is the vacuum solution obtained by the well known conformal imaging method. The interior metric for every black hole is regular everywhere and corresponds to a positive energy density. The resulting matched solutions cover then the whole initial (Cauchy) hypersurface, without any singularity, and can be useful for numerical applications. The simpler cases of one black hole (Schwarzschild data) or two identical black holes (Misner data) are explicitly solved. A procedure for extending this construction to the multiple black hole case is also given, and it is shown to work for all time symmetric vacuum solutions obtained by the conformal imaging method. The numerical evolution of one such 'stuffed' black hole is compared with that of a pure vacuum or 'plain' black hole in the...

  10. Child-Pugh-Turcott versus Meld score for predicting survival in a retrospective cohort of black African cirrhotic patients

    Institute of Scientific and Technical Information of China (English)

    KA Attia; KC Ackoundou-N'guessan; AT N'dri-yoman; AK Mahassadi; E Messou; YF Bathaix; YH Kissi

    2008-01-01

    AIM: To compare the performance of the Child-Pugh-Turcott (CPT) score to that of the model for end-stage liver disease (MELD) score in predicting survival of a retrospective cohort of 172 Black African patients with cirrhosis on a short and mid-term basis.METHODS: Univariate and multivariate (Cox model)analyses were used to identify factors related to mortality. Relationship between the two scores was appreciated by calculating the correlation coefficient.The Kaplan Meier method and the log rank test were used to elaborate and compare survival respectively.The Areas Under the Curves were used to compare the performance between scores at 3, 6 and 12 mo.RESULTS: The study population comprised 172 patients, of which 68.9% were male. The mean age of the patient was 47.5 ± 13 years. Hepatitis B virus infection was the cause of cirrhosis in 70% of the cases.The overall mortality was 31.4% over 11 years of follow up. Independent factors significantly associated with mortality were: CPT score (HR = 3.3, 95% CI [1.7-6.2])(P 1.5 mg/dL versus serum creatine 21 vs MELD < 21). The area under the curves (AUC)that predict survival was 0.72 and 0.75 at 3 mo (P = 0.68),0.64 and 0.62 at 6 mo (P = 0.67), 0.69 and 0.64 at 12 mo (P = 0.38) respectively for the CPT score and the MELD score.CONCLUSION: The CPT score displays the same prognostic significance as does the MELD score in black African patients with cirrhosis. Moreover, its handling appears less cumbersome in clinical practice as compared to the latter.

  11. Black Essentialism: The Art of Jazz Rap.

    Science.gov (United States)

    Stewart, Earl; Duran, Jane

    1999-01-01

    Establishes a black essentialist aesthetic for jazz rap, showing its relation to an African-derived history and other black traditions. Examines newer lines of argument in aesthetics about contemporary recordings focusing on Theodore Gracyk. Argues that jazz rap is defined by actual, not recorded, performance. (CMK)

  12. Stimulated Black Hole Evaporation

    CERN Document Server

    Spaans, Marco

    2016-01-01

    Black holes are extreme expressions of gravity. Their existence is predicted by Einstein's theory of general relativity and is supported by observations. Black holes obey quantum mechanics and evaporate spontaneously. Here it is shown that a mass rate $R_f\\sim 3\\times 10^{-8} (M_0/M)^{1/2}$ $M_0$ yr$^{-1}$ onto the horizon of a black hole with mass $M$ (in units of solar mass $M_0$) stimulates a black hole into rapid evaporation. Specifically, $\\sim 3 M_0$ black holes can emit a large fraction of their mass, and explode, in $M/R_f \\sim 3\\times 10^7 (M/M_0)^{3/2}$ yr. These stimulated black holes radiate a spectral line power $P \\sim 2\\times 10^{39} (M_0/M)^{1/2}$ erg s$^{-1}$, at a wavelength $\\lambda \\sim 3\\times 10^5 (M/M_0)$ cm. This prediction can be observationally verified.

  13. Extremal Hairy Black Holes

    CERN Document Server

    Gonzalez, P A; Saavedra, Joel; Vasquez, Yerko

    2014-01-01

    We consider a gravitating system consisting of a scalar field minimally coupled to gravity with a self-interacting potential and an U(1) electromagnetic field. Solving the coupled Einstein-Maxwell-scalar system we find exact hairy charged black hole solutions with the scalar field regular everywhere. We go to the zero temperature limit and we study the effect of the scalar field on the near horizon geometry of an extremal black hole. We find that except a critical value of the charge of the black hole there is also a critical value of the charge of the scalar field beyond of which the extremal black hole is destabilized. We study the thermodynamics of these solutions and we find that if the space is flat then at low temperature the Reissner-Nordstr\\"om black hole is thermodynamically preferred, while if the space is AdS the hairy charged black hole is thermodynamically preferred at low temperature.

  14. Astrophysical black holes

    CERN Document Server

    Gorini, Vittorio; Moschella, Ugo; Treves, Aldo; Colpi, Monica

    2016-01-01

    Based on graduate school lectures in contemporary relativity and gravitational physics, this book gives a complete and unified picture of the present status of theoretical and observational properties of astrophysical black holes. The chapters are written by internationally recognized specialists. They cover general theoretical aspects of black hole astrophysics, the theory of accretion and ejection of gas and jets, stellar-sized black holes observed in the Milky Way, the formation and evolution of supermassive black holes in galactic centers and quasars as well as their influence on the dynamics in galactic nuclei. The final chapter addresses analytical relativity of black holes supporting theoretical understanding of the coalescence of black holes as well as being of great relevance in identifying gravitational wave signals. With its introductory chapters the book is aimed at advanced graduate and post-graduate students, but it will also be useful for specialists.

  15. Cosmic Black Holes

    OpenAIRE

    Ahn, Eun-Joo; Cavaglia, Marco

    2003-01-01

    Production of high-energy gravitational objects is a common feature of gravitational theories. The primordial universe is a natural setting for the creation of black holes and other nonperturbative gravitational entities. Cosmic black holes can be used to probe physical properties of the very early universe which would usually require the knowledge of the theory of quantum gravity. They may be the only tool to explore thermalisation of the early universe. Whereas the creation of cosmic black ...

  16. Perturbations around black holes

    CERN Document Server

    Wang, B

    2005-01-01

    Perturbations around black holes have been an intriguing topic in the last few decades. They are particularly important today, since they relate to the gravitational wave observations which may provide the unique fingerprint of black holes' existence. Besides the astrophysical interest, theoretically perturbations around black holes can be used as testing grounds to examine the proposed AdS/CFT and dS/CFT correspondence.

  17. Black Branes as Piezoelectrics

    CERN Document Server

    Armas, Jay; Obers, Niels A

    2012-01-01

    We find a realization of linear electroelasticity theory in gravitational physics by uncovering a new response coefficient of charged black branes, exhibiting their piezoelectric behavior. Taking charged dilatonic black strings as an example and using the blackfold approach we measure their elastic and piezolectric moduli. We also use our results to draw predictions about the equilibrium condition of charged dilatonic black rings in dimensions higher than six.

  18. Black branes as piezoelectrics.

    Science.gov (United States)

    Armas, Jay; Gath, Jakob; Obers, Niels A

    2012-12-14

    We find a realization of linear electroelasticity theory in gravitational physics by uncovering a new response coefficient of charged black branes, exhibiting their piezoelectric behavior. Taking charged dilatonic black strings as an example and using the blackfold approach we measure their elastic and piezolectric moduli. We also use our results to draw predictions about the equilibrium condition of charged dilatonic black rings in dimensions higher than six. PMID:23368298

  19. Ten shades of black

    CERN Document Server

    Hod, Shahar

    2015-01-01

    The holographic principle has taught us that, as far as their entropy content is concerned, black holes in $(3+1)$-dimensional curved spacetimes behave as ordinary thermodynamic systems in flat $(2+1)$-dimensional spacetimes. In this essay we point out that the opposite behavior can also be observed in black-hole physics. To show this we study the quantum Hawking evaporation of near-extremal Reissner-Nordstr\\"om black holes. We first point out that the black-hole radiation spectrum departs from the familiar radiation spectrum of genuine $(3+1)$-dimensional perfect black-body emitters. In particular, the would be black-body thermal spectrum is distorted by the curvature potential which surrounds the black hole and effectively blocks the emission of low-energy quanta. Taking into account the energy-dependent gray-body factors which quantify the imprint of passage of the emitted radiation quanta through the black-hole curvature potential, we reveal that the $(3+1)$-dimensional black holes effectively behave as p...

  20. Evidence for black holes.

    Science.gov (United States)

    Begelman, Mitchell C

    2003-06-20

    Black holes are common objects in the universe. Each galaxy contains large numbers-perhaps millions-of stellar-mass black holes, each the remnant of a massive star. In addition, nearly every galaxy contains a supermassive black hole at its center, with a mass ranging from millions to billions of solar masses. This review discusses the demographics of black holes, the ways in which they interact with their environment, factors that may regulate their formation and growth, and progress toward determining whether these objects really warp spacetime as predicted by the general theory of relativity. PMID:12817138

  1. Asymptotic Black Holes

    CERN Document Server

    Ho, Pei-Ming

    2016-01-01

    Following earlier works on the KMY model of black-hole formation and evaporation, we construct the metric for a matter sphere in gravitational collapse, with the back-reaction of pre-Hawking radiation taken into consideration. The mass distribution and collapsing velocity of the matter sphere are allowed to have an arbitrary radial dependence. We find that a generic gravitational collapse asymptote to a universal configuration which resembles a black hole but without horizon. This approach clarifies several misunderstandings about black-hole formation and evaporation, and provides a new model for black-hole-like objects in the universe.

  2. Black stain - a review.

    Science.gov (United States)

    Ronay, Valerie; Attin, Thomas

    2011-01-01

    The purpose of this review was to summarise the fundamentals about black stain, its diagnosis and possible differential diagnoses as well as its microbiology and therapy. In addition, various studies investigating the relationship between black stain and dental caries are examined. Many studies report lower caries prevalence in children with black stain, but this finding could not be confirmed by all authors. Also, a negative relation between degree of staining and caries severity has been described. Reasons for these results are not yet clear but it was speculated that they are related to the specific oral microflora described in black stain-affected individuals. PMID:21594205

  3. A Black Hole Levitron

    CERN Document Server

    Arsiwalla, Xerxes D

    2009-01-01

    We study the problem of spatially stabilising four dimensional extremal black holes in background electric/magnetic fields. Whilst looking for stationary stable solutions describing black holes kept in external fields we find that taking a continuum limit of Denef et al's multi-center solutions provides a supergravity description of such backgrounds within which a black hole can be trapped in a given volume. This is realised by levitating a black hole over a magnetic dipole base. We comment on how such a construction resembles a mechanical Levitron.

  4. Deforming regular black holes

    CERN Document Server

    Neves, J C S

    2015-01-01

    In this work, we have deformed regular black holes which possess a general mass term described by a function which generalizes the Bardeen and Hayward mass terms. Using linear constraints in the energy-momentum tensor, the solutions are either regular or singular. That is, with this approach, it is possible to generate singular black holes from regular black holes and vice versa. Moreover, contrary to the Bardeen and Hayward regular solutions, the regular deformed metrics may violate the weak energy condition despite the presence of the spherical symmetry. Some comments on accretion of deformed black holes in cosmological scenarios are made.

  5. Black holes and beyond

    International Nuclear Information System (INIS)

    Belief in the existence of black holes is the ultimate act of faith for a physicist. First suggested by the English clergyman John Michell in the year 1784, the gravitational pull of a black hole is so strong that nothing - not even light - can escape. Gravity might be the weakest of the fundamental forces but black-hole physics is not for the faint-hearted. Black holes present obvious problems for would-be observers because they cannot, by definition, be seen with conventional telescopes - although before the end of the decade gravitational-wave detectors should be able to study collisions between black holes. Until then astronomers can only infer the existence of a black hole from its gravitational influence on other matter, or from the X-rays emitted by gas and dust as they are dragged into the black hole. However, once this material passes through the 'event horizon' that surrounds the black hole, we will never see it again - not even with X-ray specs. Despite these observational problems, most physicists and astronomers believe that black holes do exist. Small black holes a few kilometres across are thought to form when stars weighing more than about two solar masses collapse under the weight of their own gravity, while supermassive black holes weighing millions of solar masses appear to be present at the centre of most galaxies. Moreover, some brave physicists have proposed ways to make black holes - or at least event horizons - in the laboratory. The basic idea behind these 'artificial black holes' is not to compress a large amount of mass into a small volume, but to reduce the speed of light in a moving medium to less than the speed of the medium and so create an event horizon. The parallels with real black holes are not exact but the experiments could shed new light on a variety of phenomena. The first challenge, however, is to get money for the research. One year on from a high-profile meeting on artificial black holes in London, for instance, the UK

  6. Evolution of massive black holes

    OpenAIRE

    Volonteri, Marta

    2007-01-01

    Supermassive black holes are nowadays believed to reside in most local galaxies. Accretion of gas and black hole mergers play a fundamental role in determining the two parameters defining a black hole: mass and spin. I briefly review here some of the physical processes that are conducive to the evolution of the massive black hole population. I'll discuss black hole formation processes that are likely to place at early cosmic epochs, and how massive black hole evolve in a hierarchical Universe...

  7. Carbon black recovery

    International Nuclear Information System (INIS)

    A process and apparatus for recovering carbon black from hot smoke which comprises passing the smoke through a cyclone separation zone following cooling, then through aggregate filter beds and regeneration of filter beds with clean off-gas which is recycled to the carbon black reaction zone as quench

  8. Black holes matter

    DEFF Research Database (Denmark)

    Kragh, Helge Stjernholm

    2016-01-01

    Review essay, Marcia Bartusiak, Black Hole: How an Idea Abandoned by Newtonians, Hated by Einstein, and Gambled On by Hawking Became Loved (New Haven: Yale University Press, 2015).......Review essay, Marcia Bartusiak, Black Hole: How an Idea Abandoned by Newtonians, Hated by Einstein, and Gambled On by Hawking Became Loved (New Haven: Yale University Press, 2015)....

  9. Scattering by Black Holes

    CERN Document Server

    Andersson, N

    2000-01-01

    This is a chapter on Black-hole Scattering that was commissioned for an Encyclopaedia on Scattering edited by Pike and Sabatier, to be published by Academic Press. The chapter surveys wave propagation in black-hole spacetimes, diffraction effects in wave scattering, resonances, quasinormal modes and related topics.

  10. Arbitrators, Blacks and Discipline

    Science.gov (United States)

    Jennings, Kenneth

    1975-01-01

    A discussion of the handling of disciplinary problems of black employees concludes that management should be concerned because of the effect that grievance resolution may have on the company's overall employee discipline program and the additional appeal alternatives available to the black employee. (Author/EA)

  11. Noncommutative Singular Black Holes

    International Nuclear Information System (INIS)

    In this paper, applying the method of coordinate coherent states to describe a noncommutative model of Vaidya black holes leads to an exact (t - r) dependence of solution in terms of the noncommutative parameter σ. In this setup, there is no black hole remnant at long times.

  12. Noncommutative Singular Black Holes

    Science.gov (United States)

    Hamid Mehdipour, S.

    2010-11-01

    In this paper, applying the method of coordinate coherent states to describe a noncommutative model of Vaidya black holes leads to an exact (t — r) dependence of solution in terms of the noncommutative parameter σ. In this setup, there is no black hole remnant at long times.

  13. Black Hole Dynamic Potentials

    Indian Academy of Sciences (India)

    Koustubh Ajit Kabe

    2012-09-01

    In the following paper, certain black hole dynamic potentials have been developed definitively on the lines of classical thermodynamics. These potentials have been refined in view of the small differences in the equations of the laws of black hole dynamics as given by Bekenstein and those of thermodynamics. Nine fundamental black hole dynamical relations have been developed akin to the four fundamental thermodynamic relations of Maxwell. The specific heats , and , have been defined. For a black hole, these quantities are negative. The d equation has been obtained as an application of these fundamental relations. Time reversible processes observing constancy of surface gravity are considered and an equation connecting the internal energy of the black hole , the additional available energy defined as the first free energy function , and the surface gravity , has been obtained. Finally as a further application of the fundamental relations, it has been proved for a homogeneous gravitational field in black hole space times or a de Sitter black hole that $C_{\\Omega,\\Phi}-C_{J,Q}=\\kappa \\left[\\left(\\dfrac{\\partial J}{\\partial \\kappa}\\right)_{\\Omega,\\Phi}\\left(\\dfrac{\\partial \\Omega}{\\partial \\kappa}\\right)_{J,Q}+\\left(\\dfrac{\\partial Q}{\\partial \\kappa}\\right)_{\\Omega,\\Phi}\\left(\\dfrac{\\partial\\Phi}{\\partial \\kappa}\\right)_{J,Q}\\right]$. This is dubbed as the homogeneous fluid approximation in context of the black holes.

  14. Black Craftsmen Through History.

    Science.gov (United States)

    Myers, Robin

    This report traces the evolution of the black craftsmen from ancient Egypt to the present. Special attention is given to the restricted use of black craftsmen under slavery, and the added problems they faced after being freed. Business and union discimination is described, along with recent government and private efforts to achieve equal…

  15. Fluctuating Black Hole Horizons

    CERN Document Server

    Mei, Jianwei

    2013-01-01

    In this paper we treat the black hole horizon as a physical boundary to the spacetime and study its dynamics following from the Gibbons-Hawking-York boundary term. Using the Kerr black hole as an example we derive an effective action that describes, in the large wave number limit, a massless Klein-Gordon field living on the average location of the boundary. Complete solutions can be found in the small rotation limit of the black hole. The formulation suggests that the boundary can be treated in the same way as any other matter contributions. In particular, the angular momentum of the boundary matches exactly with that of the black hole, suggesting an interesting possibility that all charges (including the entropy) of the black hole are carried by the boundary. Using this as input, we derive predictions on the Planck scale properties of the boundary.

  16. Lifshitz Topological Black Holes

    CERN Document Server

    Mann, R B

    2009-01-01

    I find a class of black hole solutions to a (3+1) dimensional theory gravity coupled to abelian gauge fields with negative cosmological constant that has been proposed as the dual theory to a Lifshitz theory describing critical phenomena in (2+1) dimensions. These black holes are all asymptotic to a Lifshitz fixed point geometry and depend on a single parameter that determines both their area (or size) and their charge. Most of the solutions are obtained numerically, but an exact solution is also obtained for a particular value of this parameter. The thermodynamic behaviour of large black holes is almost the same regardless of genus, but differs considerably for small black holes. Screening behaviour is exhibited in the dual theory for any genus, but the critical length at which it sets in is genus-dependent for small black holes.

  17. Young, black, and connected: Facebook usage among African American college students.

    Science.gov (United States)

    Lee, E Bun

    2012-01-01

    This article examines the extent and intensity of Facebook usage among African American college students and investigates their reasons for using Facebook. As expected, 98% of students in the survey had a Facebook account, and a large number of Facebook “friends.” Younger users spent significantly more time on Facebook than older ones. Our findings underscore the importance of cultural influence for African American online users. Displaying photographs and personal interests on Facebook signals racial identity among African American college students. Personality traits, such as self-esteem, trust in people, satisfaction with university life, and racial identity, were not significant predictors on the time spent on Facebook. PMID:22536626

  18. Black Youth Unemployment and the Black Family.

    Science.gov (United States)

    Hoskins, Linus A.

    This paper analyzes the results of a survey conducted to ascertain the attitudes of 400 employers, youth, and academic/community professionals in Los Angeles, Chicago and Washington, D.C., toward an approach to Black youth unemployment centered on the creation of jobs and training among minority businesses in selected metropolitan areas. Minority…

  19. Black Hole Critical Phenomena Without Black Holes

    CERN Document Server

    Liebling, S L

    2000-01-01

    Studying the threshold of black hole formation via numerical evolution has led to the discovery of fascinating nonlinear phenomena. Power-law mass scaling, aspects of universality, and self-similarity have now been found for a large variety of models. However, questions remain. Here I briefly review critical phenomena, discuss some recent results, and describe a model which demonstrates similar phenomena without gravity.

  20. Undoing Racism in America: Help from the Black Church.

    Science.gov (United States)

    Vora, Erika; Vora, Jay A.

    2002-01-01

    Investigated whether a planned engagement of white college students, which had very little contact with African Americans, with members of a black community in a safe, welcoming environment (a black church) would significantly reduce racism. Participant surveys indicated that positive interactions between Blacks and Whites resulted in positive…

  1. Uncovering Black/African American and Latina/o students' motivation to learn science: Affordances to science identity development

    Science.gov (United States)

    Mahfood, Denise Marcia

    The following dissertation reports on a qualitative exploration that serves two main goals: (1) to qualitatively define and highlight science motivation development of Black/African American and Latina/o students as they learn science in middle school, high school, and in college and (2) to reveal through personal narratives how successful entry and persistence in science by this particular group is linked to the development of their science identities. The targeted population for this study is undergraduate students of color in science fields at a college or university. The theoretical frameworks for this study are constructivist theory, motivation theory, critical theory, and identity theories. The methodological approach is narrative which includes students' science learning experiences throughout the course of their academic lives. I use The Science Motivation Questionnaire II to obtain baseline data to quantitatively assess for motivation to learn science. Data from semi-structured interviews from selected participants were collected, coded, and configured into a story, and emergent themes reveal the important role of science learning in both informal and formal settings, but especially in informal settings that contribute to better understandings of science and the development of science identities for these undergraduate students of color. The findings have implications for science teaching in schools and teacher professional development in science learning.

  2. Evaluation of serum chemistry values associated with avian malaria infections in African black-footed penguins (Spheniscus demersus).

    Science.gov (United States)

    Graczyk, T K; Cranfield, M R; Bicknese, E J

    1995-01-01

    The value profiles of 5 intracellular enzymes, 15 metabolites (with 2 associated ratios), and 3 electrolytes were monitored over time in 9 captive-reared African black-footed penguins (Spheniscus demersus) with different avian malaria clinical status: uninfected, subclinically infected, and clinically infected with fatal outcome. Fatal infections were caused by Plasmodium relictum. Numerous schizonts were visible in the lungs, liver, spleen, and interstitial tissue of the kidneys. The reference ranges of 23 serum clinical chemistry parameters and 2 ratios were established for S. demersus. The mean values obtained for 8 of 23 parameters of the infected penguins were significantly different from those recorded for the uninfected birds, indicating impaired renal function, hepatic dysfunction, and nonspecific tissue damage related to the infestation with exoerythrocytic schizonts. Analysis of sensitivity, specificity, and negative and positive predictive values (PPVs) showed that gamma-glutamyltranspeptidase (GGTP), alanine aminotransferase (ALT), and creatinine reached PPVs and a specificity over 57% for avian malaria infections in penguins. Creatinine, ALT, and GGTP values should be consulted in evaluation of the clinical malaria status of S. demersus. PMID:7624290

  3. Gatekeeping and its impact on father involvement among Black South Africans in rural KwaZulu-Natal.

    Science.gov (United States)

    Makusha, Tawanda; Richter, Linda

    2016-01-01

    Involved and caring fatherhood contributes to the health and wellbeing of children, women and men. The corollary is also true - men, women and children are affected when fathers are not involved or supportive of their children. Many factors affect fathers' involvement, including women's attitudes, the history and nature of the relationship between mother and father, and the cultural context. This study explores gatekeeping and its impact on father involvement among Black South Africans in rural KwaZulu-Natal. Among married couples, gatekeeping occurs with respect to childcare and housework through women's attempts to validate their maternal identity according to socially and culturally constructed gender roles. Among unmarried, non-resident parents, women control father-child contact and involvement, with mothers and/or their families either facilitating or inhibiting father involvement. In this context, we found that cultural gatekeeping had a huge impact on father involvement, with the non-payment of inhlawulo or lobola regulating father-child involvement. In a country like South Africa, where there is high non-marital fertility and father-child non-residence, future research, parenting and family programmes should focus on strategies that encourage positive paternal involvement as well as maternal and cultural support for father involvement, regardless of parental relationship and residence status. PMID:26501893

  4. On the Charter Question: Black Marxism and Black Nationalism

    Science.gov (United States)

    Stern, Mark; Hussain, Khuram

    2015-01-01

    This article brings two black intellectual traditions to bear on the question of charter schools: black Marxism and black nationalism. The authors examine the theoretical and rhetorical devices used to talk about charters schools by focusing on how notions of "black liberation" are deployed by the charter movement, and to what end. The…

  5. Scalarized Hairy Black Holes

    CERN Document Server

    Kleihaus, Burkhard; Yazadjiev, Stoytcho

    2015-01-01

    In the presence of a complex scalar field scalar-tensor theory allows for scalarized rotating hairy black holes. We exhibit the domain of existence for these scalarized black holes, which is bounded by scalarized rotating boson stars and ordinary hairy black holes. We discuss the global properties of these solutions. Like their counterparts in general relativity, their angular momentum may exceed the Kerr bound, and their ergosurfaces may consist of a sphere and a ring, i.e., form an ergo-Saturn.

  6. Noncommutative Solitonic Black Hole

    CERN Document Server

    Chang-Young, Ee; Lee, Daeho; Lee, Youngone

    2012-01-01

    We investigate solitonic black hole solutions in three dimensional noncommutative spacetime. We do this in gravity with negative cosmological constant coupled to a scalar field using the Moyal product expanded up to first order in the noncommutativity parameter in the two noncommutative spatial directions. By numerical simulation we look for black hole solutions by increasing the non- commutativity parameter value starting from regular solutions with vanishing noncommutativity. We find that even a regular soliton solution in the commutative case becomes a black hole solution when the noncommutativity parameter reaches a certain value.

  7. Scalarized hairy black holes

    Energy Technology Data Exchange (ETDEWEB)

    Kleihaus, Burkhard, E-mail: b.kleihaus@uni-oldenburg.de [Institut für Physik, Universität Oldenburg, Postfach 2503, D-26111 Oldenburg (Germany); Kunz, Jutta [Institut für Physik, Universität Oldenburg, Postfach 2503, D-26111 Oldenburg (Germany); Yazadjiev, Stoytcho [Department of Theoretical Physics, Faculty of Physics, Sofia University, Sofia 1164 (Bulgaria)

    2015-05-11

    In the presence of a complex scalar field scalar–tensor theory allows for scalarized rotating hairy black holes. We exhibit the domain of existence for these scalarized black holes, which is bounded by scalarized rotating boson stars and hairy black holes of General Relativity. We discuss the global properties of these solutions. Like their counterparts in general relativity, their angular momentum may exceed the Kerr bound, and their ergosurfaces may consist of a sphere and a ring, i.e., form an ergo-Saturn.

  8. Scalarized hairy black holes

    Directory of Open Access Journals (Sweden)

    Burkhard Kleihaus

    2015-05-01

    Full Text Available In the presence of a complex scalar field scalar–tensor theory allows for scalarized rotating hairy black holes. We exhibit the domain of existence for these scalarized black holes, which is bounded by scalarized rotating boson stars and hairy black holes of General Relativity. We discuss the global properties of these solutions. Like their counterparts in general relativity, their angular momentum may exceed the Kerr bound, and their ergosurfaces may consist of a sphere and a ring, i.e., form an ergo-Saturn.

  9. Black holes new horizons

    CERN Document Server

    Hayward, Sean Alan

    2013-01-01

    Black holes, once just fascinating theoretical predictions of how gravity warps space-time according to Einstein's theory, are now generally accepted as astrophysical realities, formed by post-supernova collapse, or as supermassive black holes mysteriously found at the cores of most galaxies, powering active galactic nuclei, the most powerful objects in the universe. Theoretical understanding has progressed in recent decades with a wider realization that local concepts should characterize black holes, rather than the global concepts found in textbooks. In particular, notions such as trapping h

  10. Scalarized hairy black holes

    International Nuclear Information System (INIS)

    In the presence of a complex scalar field scalar–tensor theory allows for scalarized rotating hairy black holes. We exhibit the domain of existence for these scalarized black holes, which is bounded by scalarized rotating boson stars and hairy black holes of General Relativity. We discuss the global properties of these solutions. Like their counterparts in general relativity, their angular momentum may exceed the Kerr bound, and their ergosurfaces may consist of a sphere and a ring, i.e., form an ergo-Saturn

  11. The Price of "Black Dominance."

    Science.gov (United States)

    Hoberman, John

    2000-01-01

    Discusses the harmful effects of stereotyping black males as athletes, noting that over-identification with athletes and the world of physical performance limits black children's development by discouraging academic achievement. Examines the negative influence of mass media focus on black athletes, rappers, and stylized ghetto blackness. Discusses…

  12. On Noncommutative Black Holes Thermodynamics

    CERN Document Server

    Faizal, Mir; Ulhoa, S C

    2015-01-01

    In this paper, we will analyze noncommutative deformation of the Schwarzschild black holes and Kerr black holes. We will perform our analysis by relating the commutative and the noncommutative metrics using an Moyal product. We will also analyze the thermodynamics of these noncommutative black hole solutions. We will explicitly derive expression for the corrected entropy and temperature of these black hole solutions.

  13. The Thermodynamics of Black Holes

    Directory of Open Access Journals (Sweden)

    Wald Robert M.

    2001-01-01

    Full Text Available We review the present status of black hole thermodynamics. Our review includes discussion of classical black hole thermodynamics, Hawking radiation from black holes, the generalized second law, and the issue of entropy bounds. A brief survey also is given of approaches to the calculation of black hole entropy. We conclude with a discussion of some unresolved open issues.

  14. Black-White Health Inequalities in Canada.

    Science.gov (United States)

    Veenstra, Gerry; Patterson, Andrew C

    2016-02-01

    Little is known about Black-White health inequalities in Canada or the applicability of competing explanations for them. To address this gap, we used nine cycles of the Canadian Community Health Survey to analyze multiple health outcomes in a sample of 3,127 Black women, 309,720 White women, 2,529 Black men and 250,511 White men. Adjusting for age, marital status, urban/rural residence and immigrant status, Black women and men were more likely than their White counterparts to report diabetes and hypertension, Black women were less likely than White women to report cancer and fair/poor mental health and Black men were less likely than White men to report heart disease. These health inequalities persisted after controlling for education, household income, smoking, physical activity and body-mass index. We conclude that high rates of diabetes and hypertension among Black Canadians may stem from experiences of racism in everyday life, low rates of heart disease and cancer among Black Canadians may reflect survival bias and low rates of fair/poor mental health among Black Canadian women represent a mental health paradox similar to the one that exists for African Americans in the United States. PMID:25894533

  15. Topics in black hole evaporation

    International Nuclear Information System (INIS)

    Two major aspects of particle creation by gravitational fields of black holes are studied: the neutrino emission from rotating black holes; and interactions between scalar particles emitted by a black hole. Neutrino emission is investigated under three topics: The asymmetry of the angular dependence of neutrino emission from rotating black holes; the production of a local matter excess by rotating black holes in a baryon symmetric universe; and cosmological magnetic field generation by neutrinos from evaporating black holes. Finally the author studies the effects of interactions on the black hole evaporation process

  16. Black Holes in Higher Dimensions

    International Nuclear Information System (INIS)

    In four space-time dimensions black holes of Einstein-Maxwell theory satisfy a number of theorems. In more than four space-time dimensions, however, some of the properties of black holes can change. In particular, uniqueness of black holes no longer holds. In five and more dimensions black rings arise. Thus in a certain region of the phase diagram there are three black objects with the same global charges present. Here we discuss properties of higher-dimensional vacuum and charged black holes, which possess a spherical horizon topology, and of vacuum and charged black rings, which have a ringlike horizon topology

  17. Introducing the Black Hole

    Science.gov (United States)

    Ruffini, Remo; Wheeler, John A.

    1971-01-01

    discusses the cosmology theory of a black hole, a region where an object loses its identity, but mass, charge, and momentum are conserved. Include are three possible formation processes, theorized properties, and three way they might eventually be detected. (DS)

  18. Janus black holes

    Science.gov (United States)

    Bak, Dongsu; Gutperle, Michael; Janik, Romuald A.

    2011-10-01

    In this paper Janus black holes in A dS 3 are considered. These are static solutions of an Einstein-scalar system with broken translation symmetry along the horizon. These solutions are dual to interface conformal field theories at finite temperature. An approximate solution is first constructed using perturbation theory around a planar BTZ blackhole. Numerical and exact solutions valid for all sets of parameters are then found and compared. Using the exact solution the thermodynamics of the system is analyzed. The entropy associated with the Janus black hole is calculated and it is found that the entropy of the black Janus is the sum of the undeformed black hole entropy and the entanglement entropy associated with the defect.

  19. Black Widow Spider

    Science.gov (United States)

    ... dling boxes, firewood, lumber, and rocks, etc. The black widow is commonly found in the following places: • Outdoors - woodpiles, rubble piles, under stones, in hol- low stumps, and in rodent burrows, privies, sheds ...

  20. Cosmological Black Holes

    OpenAIRE

    Stornaiolo, Cosimo

    2001-01-01

    In this paper we propose a model for the formation of the cosmological voids. We show that cosmological voids can form directly after the collapse of extremely large wavelength perturbations into low-density black holes or cosmological black holes (CBH). Consequently the voids are formed by the comoving expansion of the matter that surrounds the collapsed perturbation. It follows that the universe evolves, in first approximation, according to the Einstein-Straus cosmological model. We discuss...

  1. Quantum black holes

    International Nuclear Information System (INIS)

    No particle theory can be complete without gravity. Einstein's theory of gravity is of the Euler-Lagrange form, but standard quantization procedure fails. In quantum gravity the higher order interactions have a dimensionality different form the fundamental ones, because Newton's constant G has dimensions and the renormalization procedure fails. Another problem with quantum gravity is even more mysterious. Suppose that we had regularized the gravitational forces at the small distance end in the way that the weak intermediate vector boson regularized the fundamental 4-fermion interaction vertex of the weak interactions. Then what we discover is that the gravitational forces are unstable. Given sufficiently large amount of matter, it can collapse under its own weight. Classical general relativity tells us what will happen: a black hole is formed. But how is this formulated in quantum theory. S. Hawking observed that when a field theory is quantized in the background metric of a black hole, the black hole actually emits particles in a completely random thermal way. Apparently black holes are just another form of matter unstable against Hawking decay. Unfortunately this picture cannot be complete. The problem is that the quantum version of black holes has infinite phase space, and other symptoms of a run-away solution. Black holes are the heaviest and most compact forms of matter that can be imagined. A complete particle theory can have nothing but a spectrum of black-hole like objects at it high-energy end. This is why it is believed that a resolution of the black hole problem will in time disclose the complete small-distance structure of our world. 6 references

  2. Black Is Cool!

    Institute of Scientific and Technical Information of China (English)

    Dorine; Houston

    1997-01-01

    Do you remember the colors the college freshmen dyed their hair when you were here? Turquoise, orange, bright yellow.... Things have changed. Black has (?)ome the color of choice among the young people. Young men and women alike dye their hair coal black. The women let their hair grow very long. and it hangs straight and stringy down their backs. The young men leave it long on

  3. Modelling quantum black hole

    CERN Document Server

    Govindarajan, T R

    2016-01-01

    Novel bound states are obtained for manifolds with singular potentials. These singular potentials require proper boundary conditions across boundaries. The number of bound states match nicely with what we would expect for black holes. Also they serve to model membrane mechanism for the black hole horizons in simpler contexts. The singular potentials can also mimic expanding boundaries elegantly, there by obtaining appropriately tuned radiation rates.

  4. Cosmic censorship inside black holes

    CERN Document Server

    Thorlacius, L

    2006-01-01

    A simple argument is given that a traversable Cauchy horizon inside a black hole is incompatible with unitary black hole evolution. The argument assumes the validity of black hole complementarity and applies to a generic black hole carrying angular momentum and/or charge. In the second part of the paper we review recent work on the semiclassical geometry of two-dimensional charged black holes.

  5. Black hole critical phenomena without black holes

    Indian Academy of Sciences (India)

    Steven L Liebling

    2000-10-01

    Studying the threshold of black hole formation via numerical evolution has led to the discovery of fascinating nonlinear phenomena. Power-law mass scaling, aspects of universality, and self-similarity have now been found for a large variety of models. However, questions remain. Here I briefly review critical phenomena, discuss some recent results, and describe a model which demonstrates similar phenomena without gravity.

  6. Charged Galileon black holes

    Science.gov (United States)

    Babichev, Eugeny; Charmousis, Christos; Hassaine, Mokhtar

    2015-05-01

    We consider an Abelian gauge field coupled to a particular truncation of Horndeski theory. The Galileon field has translation symmetry and couples non minimally both to the metric and the gauge field. When the gauge-scalar coupling is zero the gauge field reduces to a standard Maxwell field. By taking into account the symmetries of the action, we construct charged black hole solutions. Allowing the scalar field to softly break symmetries of spacetime we construct black holes where the scalar field is regular on the black hole event horizon. Some of these solutions can be interpreted as the equivalent of Reissner-Nordstrom black holes of scalar tensor theories with a non trivial scalar field. A self tuning black hole solution found previously is extended to the presence of dyonic charge without affecting whatsoever the self tuning of a large positive cosmological constant. Finally, for a general shift invariant scalar tensor theory we demonstrate that the scalar field Ansatz and method we employ are mathematically compatible with the field equations. This opens up the possibility for novel searches of hairy black holes in a far more general setting of Horndeski theory.

  7. Ultramassive Black Hole Coalescence

    CERN Document Server

    Khan, Fazeel; Berczik, Peter

    2015-01-01

    Although supermassive black holes (SMBHs) correlate well with their host galaxies, there is an emerging view that outliers exist. Henize 2-10, NGC 4889, and NGC1277 are examples of SMBHs at least an order of magnitude more massive than their host galaxy suggests. The dynamical effects of such ultramassive central black holes is unclear. Here, we perform direct N-body simulations of mergers of galactic nuclei where one black hole is ultramassive to study the evolution of the remnant and the black hole dynamics in this extreme regime. We find that the merger remnant is axisymmetric near the center, while near the large SMBH influence radius, the galaxy is triaxial. The SMBH separation shrinks rapidly due to dynamical friction, and quickly forms a binary black hole; if we scale our model to the most massive estimate for the NGC1277 black hole, for example, the timescale for the SMBH separation to shrink from nearly a kiloparsec to less than a parsec is roughly 10 Myr. By the time the SMBHs form a hard binary, gr...

  8. Identité et marchandisation : Le cas des black memorabilia et black collectibles Identity and Commodification: The Case of Black Memorabilia and Black Collectibles

    OpenAIRE

    Eliane Elmaleh

    2009-01-01

    The aim of this article is to raise the issue of the commodification of African American culture, mainly through a certain form of art that has re-emerged with Black memorabilia which paradoxically fit into a black-driven market. However, these items penetrated American culture from 1920 to the 1950s to convey images of black people as lazy, stupid, childlike and happy. This condition of permanent happiness, typified by a broad smile and white teeth, was a fundamental component of this racist...

  9. Functional anatomy of the lacrimal gland in African black ostrich Struthio camelus domesticus in the embryonic and postnatal period

    Directory of Open Access Journals (Sweden)

    Joanna Klećkowska-Nawrot

    2015-02-01

    Full Text Available The aim of the present study was morphological and histochemical analysis of the lacrimalgland (LG in African black ostrich Struthio camelus domesticus in the embryonic and postnatalperiod. Studies were conducted on 50 ostriches aged between the 28th day of incubation until7 months old. Tissue sections were stained with haematoxylin and eosin, Azan trichrome,periodic acid-Schiff, Alcian blue pH 2.5, aldehyde fuchsin and Hale’s dialysed iron. The LGin ostrich was classified as a tubulo-acinar type. The primordia of the lobes were determinedin the LG structure on the 28th day of incubation, whilst the weakly visible lobes with aciniand tubules were observed on the 40th day of incubation. Morphometric studies of the LGshowed steady growth, characterised by an increase in both length and width. Histometricmeasurements of lobe size showed little difference between the first, second and third agegroups, whilst in the fourth age group a marked increase in size of lobes was observed.The study showed that, apart from morphological changes, during the growth of the LGthe character of acid mucopolysaccharides changed. Sulphated acid mucopolysaccharideswere indicated, particularly with aldehyde fuchsin (AF staining in the fourth age group.The Hale’s dialysed iron (HDI staining showed a low concentration of carboxylated acidmucopolysaccharides in the first and second age groups and a higher concentration in thethird and fourth age groups. Periodic acid-Schiff staining (PAS-positive cells were observedin each age group, but only a small number of cells with a weakly PAS-positive reaction weredemonstrated in the first age group.

  10. Generating Conflict for Greater Good: Utilizing Contingency Theory to Assess Black and Mainstream Newspapers as Public Relations Vehicles to Promote Better Health among African Americans.

    Science.gov (United States)

    Lumpkins, Crystal Y; Bae, Jiyang; Cameron, Glen T

    2010-03-01

    The potential use of strategic conflict management ( Wilcox and Cameron, 2006; Cameron, Wilcox, Reber and Shin ( in press) as a health advocacy tool in US African-American and mainstream newspapers, arguing that escalation of conflict can increase effectiveness of health-related news releases. For health communicators focusing on at-risk populations with poor health outcomes, such goals would include increased awareness of health problems and solutions, along with increased motivation arising from indignation over health disparities. Content analysis of 1,197 stories in 24 Black and 12 mainstream newspapers showed that more conflict factors were present in Black vs. mainstream newspapers, suggesting a way to strategically place health messages in news releases disseminated to newspapers that motivate at-risk publics to better health. The findings suggest that conflict factors such as racial disparity data regarding health issues may enhance media advocacy. PMID:22822291

  11. Generating Conflict for Greater Good: Utilizing Contingency Theory to Assess Black and Mainstream Newspapers as Public Relations Vehicles to Promote Better Health among African Americans.

    Science.gov (United States)

    Lumpkins, Crystal Y; Bae, Jiyang; Cameron, Glen T

    2010-03-01

    The potential use of strategic conflict management ( Wilcox and Cameron, 2006; Cameron, Wilcox, Reber and Shin ( in press) as a health advocacy tool in US African-American and mainstream newspapers, arguing that escalation of conflict can increase effectiveness of health-related news releases. For health communicators focusing on at-risk populations with poor health outcomes, such goals would include increased awareness of health problems and solutions, along with increased motivation arising from indignation over health disparities. Content analysis of 1,197 stories in 24 Black and 12 mainstream newspapers showed that more conflict factors were present in Black vs. mainstream newspapers, suggesting a way to strategically place health messages in news releases disseminated to newspapers that motivate at-risk publics to better health. The findings suggest that conflict factors such as racial disparity data regarding health issues may enhance media advocacy.

  12. Black holes and beyond

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-02-01

    Belief in the existence of black holes is the ultimate act of faith for a physicist. First suggested by the English clergyman John Michell in the year 1784, the gravitational pull of a black hole is so strong that nothing - not even light - can escape. Gravity might be the weakest of the fundamental forces but black-hole physics is not for the faint-hearted. Black holes present obvious problems for would-be observers because they cannot, by definition, be seen with conventional telescopes - although before the end of the decade gravitational-wave detectors should be able to study collisions between black holes. Until then astronomers can only infer the existence of a black hole from its gravitational influence on other matter, or from the X-rays emitted by gas and dust as they are dragged into the black hole. However, once this material passes through the 'event horizon' that surrounds the black hole, we will never see it again - not even with X-ray specs. Despite these observational problems, most physicists and astronomers believe that black holes do exist. Small black holes a few kilometres across are thought to form when stars weighing more than about two solar masses collapse under the weight of their own gravity, while supermassive black holes weighing millions of solar masses appear to be present at the centre of most galaxies. Moreover, some brave physicists have proposed ways to make black holes - or at least event horizons - in the laboratory. The basic idea behind these 'artificial black holes' is not to compress a large amount of mass into a small volume, but to reduce the speed of light in a moving medium to less than the speed of the medium and so create an event horizon. The parallels with real black holes are not exact but the experiments could shed new light on a variety of phenomena. The first challenge, however, is to get money for the research. One year on from a high-profile meeting on artificial black holes in London, for

  13. The Black Cultural Ethos and science teachers' practices: A case study exploring how four high school science teachers meet their African American students' needs in science

    Science.gov (United States)

    Strachan, Samantha L.

    The underachievement of African American students in science has been a persistent problem in science education. The achievement patterns of African American students indicate that researchers must take a closer look at the types of practices that are being used to meet these students' needs in science classrooms. Determining why science teachers decide to employ certain practices in their classrooms begins with a careful examination of teachers' beliefs as well as their instructional approaches. The purpose of this study was to explore four urban high school science teachers' beliefs about their African American students' learning needs and to investigate how these teachers go about addressing students' needs in science classrooms. This research study also explored the extent to which teachers' practices aligned with the nine dimensions of an established cultural instructional theory, namely the Black Cultural Ethos. Qualitative research methods were employed to gather data from the four teachers. Artifact data were collected from the teachers and they were interviewed and observed. Believing that their students had academic-related needs as well as needs tied to their learning preferences, the four science teachers employed a variety of instructional strategies to meet their students where they were in learning. Overall, the instructional strategies that the teachers employed to meet their students' needs aligned with five of the nine tenets of the Black Cultural Ethos theory.

  14. Black Thyroid Associated with Thyroid Carcinoma

    Directory of Open Access Journals (Sweden)

    Emad Kandil

    2010-01-01

    Full Text Available Objective. Black thyroid is a rare pigmented change seen almost exclusively in patients upon minocycline ingestion, and the process has previously been thought to be generally benign. There have been 61 reported cases of black thyroid. We are aware of 13 cases previously reported in association with thyroid carcinoma. This paper reports six patients with black thyroid pigmentation in association with thyroid carcinoma. Design. The medical records of six patients who were diagnosed with black thyroid syndrome, all of whom underwent thyroid surgery, were reviewed. Data on age, gender, race, preoperative fine needle aspiration biopsy (FNA, thyroid function levels, and pathology reports were collected. Main Outcome. The mean age was 60 years. There were 5 females, 4 of whom were African American. All patients were clinically and biochemically euthyroid. Black pigmentation was not diagnosed in preoperative FNA, and only one patient had a preoperative diagnosis of papillary thyroid carcinoma. The other patients underwent surgery and were found to have black pigmentation of the thyroid associated with carcinoma. Conclusions. FNA does not diagnose black thyroid, which is associated with thyroid carcinoma. Thyroid glands with black pigmentation deserve thorough pathologic examination, including several sections of each specimen.

  15. Life "Inside the Shell" A Needs Survey of Spinal Cord-Injured Wheelchair Users in a Black South African Township.

    Science.gov (United States)

    Cock, Jacklyn

    1989-01-01

    The paper describes experiences of 88 Black spinal cord-injured and wheelchair bound adults living in Soweto, South Africa. Discrimination in the areas of income, education, housing, transport, social attitudes, family life, and social participation are reported by the respondents. (DB)

  16. Charged Galileon black holes

    CERN Document Server

    Babichev, Eugeny; Hassaine, Mokhtar

    2015-01-01

    We consider an Abelian gauge field coupled to a particular truncation of Horndeski theory. The Galileon field has translation symmetry and couples non minimally both to the metric and the gauge field. When the gauge-scalar coupling is zero the gauge field reduces to a standard Maxwell field. By taking into account the symmetries of the action, we construct charged black hole solutions. Allowing the scalar field to softly break symmetries of spacetime we construct black holes where the scalar field is regular on the black hole event horizon. Some of these solutions can be interpreted as the equivalent of Reissner-Nordstrom black holes of scalar tensor theories with a non trivial scalar field. A self tuning black hole solution found previously is extended to the presence of dyonic charge without affecting whatsoever the self tuning of a large positive cosmological constant. Finally, for a general shift invariant scalar tensor theory we demonstrate that the scalar field Ansatz and method we employ are mathematic...

  17. Black Afrikaans: An alternative use

    Directory of Open Access Journals (Sweden)

    Anna P. Maritz

    2016-09-01

    Full Text Available This article provides a first look at the nature of the alternative functions of Black Afrikaans. These functions realise when Black Afrikaans is imitated by Afrikaans mother-tongue speakers. The functions of the alternative use of Black Afrikaans centre on: the social nature of the variety, sensitivity as a deciding role-player, identity, humour, inclusivity and exclusivity, language repertoire and similar variety. Furthermore, because of the direct relationship between Black Afrikaans, Pidginised Afrikaans and the imitation of Black Afrikaans, these varieties are compared to establish a starting point description for the imitation of Black Afrikaans, as the variety has not yet been described.

  18. Secondary sexual characteristics of stunted and non-stunted Black South African Boys living in a township in the North West Province

    OpenAIRE

    Kruger, Herculina Salome; Mamabolo, Ramoteme Lesley; Monyeki, Makama Andries; Pienaar, Anita Elizabeth; Toriola, Abel; Van Ridder, Johannes Hendrik

    2012-01-01

    It is known that sexual maturation is dependent on genetic and environmental factors and socio-economic status. The purpose of this study was to describe secondary sexual characteristics of stunted and non-stunted black South African boys from a low socio-economic status living in a township in the North West Province. A total of 129 boys aged 12 to 16 years participated in the study. Height and weight were measured according to the standard protocol suggested by the International Society of ...

  19. Incidence of prostatic calcification in blacks in Washington, D.C., and selected African cities. Correlation of specimen roentgenographs and pathologic findings. Cooperative Prostatic Research Group.

    Science.gov (United States)

    Kovi, J; Rao, M S; Heshmat, M Y; Akberzie, M E; Jackson, M A; Ogunmuyiwa, T A

    1979-10-01

    The incidence of calcification in the prostate gland of black men from Washington, D.C., and from Ibadan, Nigeria, and Accra, Ghana, West Africa, was assessed in a total of 874 consecutive, unselected prostate specimens removed at autopsy during a five-year period (1973--1978). In the combined series there was a significant positive association between prostatic calcification and age (p less than 0.001). The frequency of calcification was significantly higher in the Washington, D.C. series than in the West African series at all age levels (p less than 0.001). This difference most likely reflects the different dietary patterns of the two population groups.

  20. Turbulent black holes.

    Science.gov (United States)

    Yang, Huan; Zimmerman, Aaron; Lehner, Luis

    2015-02-27

    We demonstrate that rapidly spinning black holes can display a new type of nonlinear parametric instability-which is triggered above a certain perturbation amplitude threshold-akin to the onset of turbulence, with possibly observable consequences. This instability transfers from higher temporal and azimuthal spatial frequencies to lower frequencies-a phenomenon reminiscent of the inverse cascade displayed by (2+1)-dimensional fluids. Our finding provides evidence for the onset of transitory turbulence in astrophysical black holes and predicts observable signatures in black hole binaries with high spins. Furthermore, it gives a gravitational description of this behavior which, through the fluid-gravity duality, can potentially shed new light on the remarkable phenomena of turbulence in fluids.

  1. Black hole entropy quantization

    CERN Document Server

    Corichi, A; Fernandez-Borja, E; Corichi, Alejandro; Diaz-Polo, Jacobo; Fernandez-Borja, Enrique

    2006-01-01

    Ever since the pioneer works of Bekenstein and Hawking, black hole entropy has been known to have a quantum origin. Furthermore, it has long been argued by Bekenstein that entropy should be quantized in discrete (equidistant) steps given its identification with horizon area in (semi-)classical general relativity and the properties of area as an adiabatic invariant. This lead to the suggestion that black hole area should also be quantized in equidistant steps to account for the discrete black hole entropy. Here we shall show that loop quantum gravity, in which area is not quantized in equidistant steps can nevertheless be consistent with Bekenstein's equidistant entropy proposal in a subtle way. For that we perform a detailed analysis of the number of microstates compatible with a given area and show that an observed oscillatory behavior in the entropy-area relation, when properly interpreted yields an entropy that has discrete, equidistant values that are consistent with the Bekenstein framework.

  2. Photon Black Holes

    CERN Document Server

    Hernández, X; Mendoza, S; Sussman, R A

    2005-01-01

    We study the relationship between the energy and entropy of a black body photon gas, within an idealised spherical adiabatic enclosure of radius R, as this is compressed into a self-gravitating regime. We show that this regime approximately coincides with the black hole regime for the system, i.e., R ~ R_{s}, where R_{s} denotes the Schwarzschild radius of the system. The entropy of this system is always below the suggested Holographic bound, even as R \\to R_{s}. A plausible quantum configuration for the photon gas at R \\to R_{s} is suggested, which satisfies all energy, entropy and temperature black hole conditions. Finally we examine our results from the point of view of recent Loop Quantum Gravity ideas.

  3. Black Hole Bose Condensation

    Science.gov (United States)

    Vaz, Cenalo; Wijewardhana, L. C. R.

    2013-12-01

    General consensus on the nature of the degrees of freedom responsible for the black hole entropy remains elusive despite decades of effort dedicated to the problem. Different approaches to quantum gravity disagree in their description of the microstates and, more significantly, in the statistics used to count them. In some approaches (string theory, AdS/CFT) the elementary degrees of freedom are indistinguishable, whereas they must be treated as distinguishable in other approaches to quantum gravity (eg., LQG) in order to recover the Bekenstein-Hawking area-entropy law. However, different statistics will imply different behaviors of the black hole outside the thermodynamic limit. We illustrate this point by quantizing the Bañados-Teitelboim-Zanelli (BTZ) black hole, for which we argue that Bose condensation will occur leading to a "cold", stable remnant.

  4. Turbulent black holes.

    Science.gov (United States)

    Yang, Huan; Zimmerman, Aaron; Lehner, Luis

    2015-02-27

    We demonstrate that rapidly spinning black holes can display a new type of nonlinear parametric instability-which is triggered above a certain perturbation amplitude threshold-akin to the onset of turbulence, with possibly observable consequences. This instability transfers from higher temporal and azimuthal spatial frequencies to lower frequencies-a phenomenon reminiscent of the inverse cascade displayed by (2+1)-dimensional fluids. Our finding provides evidence for the onset of transitory turbulence in astrophysical black holes and predicts observable signatures in black hole binaries with high spins. Furthermore, it gives a gravitational description of this behavior which, through the fluid-gravity duality, can potentially shed new light on the remarkable phenomena of turbulence in fluids. PMID:25768746

  5. Noncommutative black hole thermodynamics

    International Nuclear Information System (INIS)

    We give a general derivation, for any static spherically symmetric metric, of the relation Th=(K/2π) connecting the black hole temperature (Th) with the surface gravity (K), following the tunneling interpretation of Hawking radiation. This derivation is valid even beyond the semi-classical regime, i.e. when quantum effects are not negligible. The formalism is then applied to a spherically symmetric, stationary noncommutative Schwarzschild space-time. The effects of backreaction are also included. For such a black hole the Hawking temperature is computed in a closed form. A graphical analysis reveals interesting features regarding the variation of the Hawking temperature (including corrections due to noncommutativity and backreaction) with the small radius of the black hole. The entropy and tunneling rate valid for the leading order in the noncommutative parameter are calculated. We also show that the noncommutative Bekenstein-Hawking area law has the same functional form as the usual one

  6. Tunneling Through Black Rings

    Institute of Scientific and Technical Information of China (English)

    ZHAO Liu

    2007-01-01

    Hawking radiation of black ring solutions to 5-dimensional Einstein-Maxwell-dilaton theory is analyzed by use of the Parikh-Wilczek tunneling method. To get the correct tunneling amplitude and emission rate, we adopt and develop the Angheben-Nadalini-Vanzo-Zerbini covariant approach to cover the effects of rotation and electronic discharge all at once, and the effect of back reaction is also taken into account. This constitutes a unified approach to the tunneling problem. Provided the first law of thermodynamics for black rings holds, the emission rate is proportional to the exponential of the change of Bekenstein-Hawking entropy. Explicit calculation for black ring temperatures agrees exactly with the results obtained via the classical surface gravity method and the quasi-local formalism.

  7. Black doctors and discrimination under South Africa's apartheid regime.

    Science.gov (United States)

    Digby, Anne

    2013-04-01

    This article discusses an under-researched group and provides an analytical overview of the comparative experiences of African, Indian and Coloured doctors at South African universities during the apartheid era. It probes diversity of experience in training and practice as well as gendered differentiation amongst black students before going on to discuss the careers and political activism of black doctors as well as the impact of recent transformational change on their position. It briefly assesses how singular this South African experience was.

  8. Slowly balding black holes

    International Nuclear Information System (INIS)

    The 'no-hair' theorem, a key result in general relativity, states that an isolated black hole is defined by only three parameters: mass, angular momentum, and electric charge; this asymptotic state is reached on a light-crossing time scale. We find that the no-hair theorem is not formally applicable for black holes formed from the collapse of a rotating neutron star. Rotating neutron stars can self-produce particles via vacuum breakdown forming a highly conducting plasma magnetosphere such that magnetic field lines are effectively ''frozen in'' the star both before and during collapse. In the limit of no resistivity, this introduces a topological constraint which prohibits the magnetic field from sliding off the newly-formed event horizon. As a result, during collapse of a neutron star into a black hole, the latter conserves the number of magnetic flux tubes NB=eΦ∞/(πc(ℎ/2π)), where Φ∞≅2π2BNSRNS3/(PNSc) is the initial magnetic flux through the hemispheres of the progenitor and out to infinity. We test this theoretical result via 3-dimensional general relativistic plasma simulations of rotating black holes that start with a neutron star dipole magnetic field with no currents initially present outside the event horizon. The black hole's magnetosphere subsequently relaxes to the split-monopole magnetic field geometry with self-generated currents outside the event horizon. The dissipation of the resulting equatorial current sheet leads to a slow loss of the anchored flux tubes, a process that balds the black hole on long resistive time scales rather than the short light-crossing time scales expected from the vacuum no-hair theorem.

  9. Slowly balding black holes

    Science.gov (United States)

    Lyutikov, Maxim; McKinney, Jonathan C.

    2011-10-01

    The “no-hair” theorem, a key result in general relativity, states that an isolated black hole is defined by only three parameters: mass, angular momentum, and electric charge; this asymptotic state is reached on a light-crossing time scale. We find that the no-hair theorem is not formally applicable for black holes formed from the collapse of a rotating neutron star. Rotating neutron stars can self-produce particles via vacuum breakdown forming a highly conducting plasma magnetosphere such that magnetic field lines are effectively “frozen in” the star both before and during collapse. In the limit of no resistivity, this introduces a topological constraint which prohibits the magnetic field from sliding off the newly-formed event horizon. As a result, during collapse of a neutron star into a black hole, the latter conserves the number of magnetic flux tubes NB=eΦ∞/(πcℏ), where Φ∞≈2π2BNSRNS3/(PNSc) is the initial magnetic flux through the hemispheres of the progenitor and out to infinity. We test this theoretical result via 3-dimensional general relativistic plasma simulations of rotating black holes that start with a neutron star dipole magnetic field with no currents initially present outside the event horizon. The black hole’s magnetosphere subsequently relaxes to the split-monopole magnetic field geometry with self-generated currents outside the event horizon. The dissipation of the resulting equatorial current sheet leads to a slow loss of the anchored flux tubes, a process that balds the black hole on long resistive time scales rather than the short light-crossing time scales expected from the vacuum no-hair theorem.

  10. A high burden of hypertension in the urban black population of Cape Town: the cardiovascular risk in Black South Africans (CRIBSA study.

    Directory of Open Access Journals (Sweden)

    Nasheeta Peer

    Full Text Available OBJECTIVE: To determine the prevalence, associations and management of hypertension in the 25-74-year-old urban black population of Cape Town and examine the change between 1990 and 2008/09 in 25-64-year-olds. METHODS: In 2008/09, a representative cross-sectional sample, stratified for age and sex, was randomly selected from the same townships sampled in 1990. Cardiovascular disease risk factors were determined by administered questionnaires, clinical measurements and fasting biochemical analyses. Logistic regression models evaluated the associations with hypertension. RESULTS: There were 1099 participants, 392 men and 707 women (response rate 86% in 2008/09. Age-standardised hypertension prevalence was 38.9% (95% confidence interval (CI: 35.6-42.3 with similar rates in men and women. Among 25-64-year-olds, hypertension prevalence was significantly higher in 2008/09 (35.6%, 95% CI: 32.3-39.0 than in 1990 (21.6%, 95% CI: 18.6-24.9. In 2008/09, hypertension odds increased with older age, family history of hypertension, higher body mass index, problematic alcohol intake, physical inactivity and urbanisation. Among hypertensive participants, significantly more women than men were detected (69.5% vs. 32.7%, treated (55.7% vs. 21.9% and controlled (32.4% vs. 10.4% in 2008/09. There were minimal changes from 1990 except for improved control in 25-64-year-old women (1990∶14.1% vs. 2008/09∶31.5%. CONCLUSIONS: The high and rising hypertension burden in this population, its association with modifiable risk factors and the sub-optimal care provided highlight the urgent need to prioritise hypertension management. Innovative solutions with efficient and cost-effective healthcare delivery as well as population-based strategies are required.

  11. When Lions Write History: Black History Textbooks, African-American Educators, & the Alternative Black Curriculum in Social Studies Education, 1890-1940

    Science.gov (United States)

    King, LaGarrett J.

    2014-01-01

    The African proverb, "Until the lions have their historians, tales of the hunt shall always glorify the hunter," is used to metaphorically describe how dominant groups inscribe power through historical narrative. In this article the author discusses how African-American educators between the years of 1890-1940 conceptualized citizenship…

  12. Are Black Holes Springy?

    CERN Document Server

    Good, Michael R R

    2014-01-01

    A $(3+1)$-dimensional asymptotically flat Kerr black hole angular speed $\\Omega_+$ can be used to define an effective spring constant, $k=m\\Omega_+^2$. Its maximum value is the Schwarzschild surface gravity, $k = \\kappa $, which rapidly weakens as the black hole spins down and the temperature increases. The Hawking temperature is expressed in terms of the spring constant: $2\\pi T = \\kappa - k$. Hooke's law, in the extremal limit, provides the force $F = 1/4$, which is consistent with the conjecture of maximum force in general relativity.

  13. Noncommutative solitonic black hole

    International Nuclear Information System (INIS)

    We investigate solitonic black hole solutions in three-dimensional noncommutative spacetime. We do this in gravity with a negative cosmological constant coupled to a scalar field. Noncommutativity is realized with the Moyal product which is expanded up to first order in the noncommutativity parameter in two spatial directions. With numerical simulation we study the effect of noncommutativity by increasing the value of the noncommutativity parameter starting from commutative solutions. We find that even a regular soliton solution in the commutative case becomes a black hole solution when the noncommutativity parameter reaches a certain value. (paper)

  14. Noncommutative solitonic black hole

    Science.gov (United States)

    Chang-Young, Ee; Kimm, Kyoungtae; Lee, Daeho; Lee, Youngone

    2012-05-01

    We investigate solitonic black hole solutions in three-dimensional noncommutative spacetime. We do this in gravity with a negative cosmological constant coupled to a scalar field. Noncommutativity is realized with the Moyal product which is expanded up to first order in the noncommutativity parameter in two spatial directions. With numerical simulation we study the effect of noncommutativity by increasing the value of the noncommutativity parameter starting from commutative solutions. We find that even a regular soliton solution in the commutative case becomes a black hole solution when the noncommutativity parameter reaches a certain value.

  15. Horndeski black hole geodesics

    CERN Document Server

    Tretyakova, D A

    2016-01-01

    We examine geodesics for the scalar-tensor black holes in the Horndeski-Galileon framework. Our analysis shows that first kind relativistic orbits may not be present within some model parameters range. This is a highly pathological behavior contradicting to the black hole accretion and Solar System observations. We also present a new (although very similar to those previously known) solution, which contains the orbits we expect from a compact object, admits regular scalar field at the horizon and and can fit into the known stability criteria.

  16. Dancing with black holes

    CERN Document Server

    Aarseth, Sverre J

    2007-01-01

    We describe efforts over the last six years to implement regularization methods suitable for studying one or more interacting black holes by direct N-body simulations. Three different methods have been adapted to large-N systems: (i) Time-Transformed Leapfrog, (ii) Wheel-Spoke, and (iii) Algorithmic Regularization. These methods have been tried out with some success on GRAPE-type computers. Special emphasis has also been devoted to including post-Newtonian terms, with application to moderately massive black holes in stellar clusters. Some examples of simulations leading to coalescence by gravitational radiation will be presented to illustrate the practical usefulness of such methods.

  17. Modeling black hole evaporation

    CERN Document Server

    Fabbri, Alessandro

    2005-01-01

    The scope of this book is two-fold: the first part gives a fully detailed and pedagogical presentation of the Hawking effect and its physical implications, and the second discusses the backreaction problem, especially in connection with exactly solvable semiclassical models that describe analytically the black hole evaporation process. The book aims to establish a link between the general relativistic viewpoint on black hole evaporation and the new CFT-type approaches to the subject. The detailed discussion on backreaction effects is also extremely valuable.

  18. Black-pigmented sputum

    Directory of Open Access Journals (Sweden)

    Rafael Martínez-Girón

    2013-01-01

    Full Text Available Black-pigmented sputum, also called "melanoptysis," is a symptom that may be observed in certain pathologies such us coal workers′ pneumoconiosis (anthracosis. The cavitation and liquefaction of a fibrosed mass by an infectious process (tuberculosis, infections by anaerobes, etc. or by ischemic necrosis may cause expectoration of a blackish secretion. We report the case of a patient with labor precedents as a coal worker, from whom abundant black sputum was obtained in the course of an incidental expectoration. Cyto-histological findings are shown and a differential diagnosis is established.

  19. Superfluid Black Holes

    CERN Document Server

    Hennigar, Robie A; Tjoa, Erickson

    2016-01-01

    We present what we believe is the first example of a "$\\lambda$-line" phase transition in black hole thermodynamics. This is a line of (continuous) second order phase transitions which in the case of liquid $^4$He marks the onset of superfluidity. The phase transition occurs for a class of asymptotically AdS hairy black holes in Lovelock gravity where a real scalar field is conformally coupled to gravity. We discuss the origin of this phase transition and outline the circumstances under which it (or generalizations of it) could occur.

  20. In search of genetic markers for nonsyndromic deafness in Africa: a study in Cameroonians and Black South Africans with the GJB6 and GJA1 candidate genes.

    Science.gov (United States)

    Bosch, Jason; Lebeko, Kamogelo; Nziale, Jean Jacques Noubiap; Dandara, Collet; Makubalo, Nomlindo; Wonkam, Ambroise

    2014-07-01

    Deafness is the most common sensory disability in the world and has a variety of causes. Globally, mutations in GJB2 have been shown to play a major role in nonsyndromic deafness, but this has not been seen in Africans. Two other connexin genes, GJB6 and GJA1, have been implicated in hearing loss but have seldom been investigated in African populations. We set out to investigate the role of genetic variation in GJB6 and GJA1 in a group of Cameroonian and South African Blacks with nonsyndromic recessive hearing loss. A subset of 100 patients, affected with nonsyndromic hearing loss, from a cohort that was previously shown not to have GJB2 mutation, was analyzed by Sanger sequencing of the entire coding regions of GJB6 and GJA1. In addition, the large-scale GJB6-D3S1830 deletion was also investigated. No pathogenic mutation was detected in either GJB6 or GJA1, nor was the GJB6-D3S1830 deletion detected. There were no statistically significant differences in sequence variants between patients and controls. Mutations in GJB6 and GJA1 are not a major cause of nonsyndromic deafness in this group of Africans from Cameroon and South Africa. Currently, there is no sufficient evidence to support their testing in a clinical setting for individuals of African ancestry.

  1. Reflections on a Black Mirror

    CERN Document Server

    Good, Michael R R

    2016-01-01

    A black mirror is an accelerated boundary that produces particles in an exact correspondence to an evaporating black hole. We investigate the spectral dynamics of the particle creation during the formation process.

  2. The black hole final state

    OpenAIRE

    Horowitz, Gary T.; Maldacena, Juan

    2003-01-01

    We propose that in quantum gravity one needs to impose a final state boundary condition at black hole singularities. This resolves the apparent contradiction between string theory and semiclassical arguments over whether black hole evaporation is unitary.

  3. Quantum aspects of black holes

    CERN Document Server

    2015-01-01

    Beginning with an overview of the theory of black holes by the editor, this book presents a collection of ten chapters by leading physicists dealing with the variety of quantum mechanical and quantum gravitational effects pertinent to black holes. The contributions address topics such as Hawking radiation, the thermodynamics of black holes, the information paradox and firewalls, Monsters, primordial black holes, self-gravitating Bose-Einstein condensates, the formation of small black holes in high energetic collisions of particles, minimal length effects in black holes and small black holes at the Large Hadron Collider. Viewed as a whole the collection provides stimulating reading for researchers and graduate students seeking a summary of the quantum features of black holes.

  4. Meer bekend over Black Mold

    NARCIS (Netherlands)

    Duyvesteijn, R.G.E.; Kohrman, E.

    2008-01-01

    In de vollegrondsrozenteelt zorgde Black Mold in 2007 voor een groot aantal mislukte oculaties. In 2008 waren er aanzienlijk minder problemen. Uit onderzoek is meer bekend over de oorzaak en bestrijding van Black Mold.

  5. Conquering the Black Girl Blues.

    Science.gov (United States)

    Jones, Lani Valencia; Guy-Sheftall, Beverly

    2015-10-01

    An examination of the literature on epidemiology, etiology, and use of services for this population reveals an insufficient application of culturally congruent approaches to intervening with black women. An exploration of the social work practice literature and other relevant fields indicate that black feminist perspectives offer the opportunity to gain a clearer understanding of the intersection and influence of oppression among black women struggling with psychiatric issues and provide a useful framework for mental health practice with this population. This article discusses the evolving black feminist thought and summarizes the scholarship on black women's mental health services needs and utilization issues. The article includes a discussion of black feminisms as an emerging mental health perspective, arguing that black feminist perspectives in therapy provide an ideal framework for services that are responsive to the values and health needs of black women. The article concludes with a case vignette that illustrates some of its points.

  6. Conquering the Black Girl Blues.

    Science.gov (United States)

    Jones, Lani Valencia; Guy-Sheftall, Beverly

    2015-10-01

    An examination of the literature on epidemiology, etiology, and use of services for this population reveals an insufficient application of culturally congruent approaches to intervening with black women. An exploration of the social work practice literature and other relevant fields indicate that black feminist perspectives offer the opportunity to gain a clearer understanding of the intersection and influence of oppression among black women struggling with psychiatric issues and provide a useful framework for mental health practice with this population. This article discusses the evolving black feminist thought and summarizes the scholarship on black women's mental health services needs and utilization issues. The article includes a discussion of black feminisms as an emerging mental health perspective, arguing that black feminist perspectives in therapy provide an ideal framework for services that are responsive to the values and health needs of black women. The article concludes with a case vignette that illustrates some of its points. PMID:26489355

  7. Black Sea Bass genetic connectivity

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Microsatellite analysis of black sea bass was undertaken to determine magnitude and direction of mixing of black seabass across the Hatteras boundary, as well as...

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

    Science.gov (United States)

    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.

  9. Antibodies against six human herpesviruses in relation to seven cancers in black South Africans: A case control study

    Directory of Open Access Journals (Sweden)

    Ruff P

    2006-09-01

    Full Text Available Abstract Background Infections with certain human herpesviruses have been established as risk factors for some cancer types. For example, Epstein-Barr Virus is considered a cause of Burkitt's lymphoma and other immunosuppression related lymphomas, Hodgkin lymphoma, and nasopharyngeal cancer. Several other human herpesviruses have been linked to cancers but the totality of evidence is inconclusive. Methods We conducted a systematic sub-study from within an ongoing case control study of adult black South Africans to investigate the relationship between antibodies to six human herpesviruses and seven cancer groups that may be caused by infectious agents. Subjects had incident cancers of the oral cavity(n = 88, the cervix(n = 53, the prostate(n = 66, Hodgkin lymphoma(n = 83, non-Hodgkin lymphoma(n = 80, multiple myeloma(n = 94 or leukaemia(n = 203. For comparison, patients with other cancers(n = 95 or cardiovascular disease(n = 101 were randomly selected from within the study. Patients were interviewed and their blood was tested for IgG antibodies against HSV-1, HSV-2, VZV, EBV-EBNA, CMV and HHV-6 using enzyme linked immunosorbent assays. Because these viruses are highly prevalent in this population, optical density results from the assays were used as an indirect, quantitative measure of antibody level. Results There was significant variation in the mean log antibody measures for HSV-2, VZV, CMV and HHV-6 between the disease groups. However, none of the specific cancer groups had significantly higher mean log antibody measures for any of the viruses compared to either control group. In a more detailed examination of seven associations between cancers and herpesviruses for which there had been prior reports, two statistically significant associations were found: a decreasing risk of myeloid leukaemia and an increasing risk of oral cancer with increasing tertiles of antibodies against HHV-6 compared to all other patients (p-trend = 0.03 and 0

  10. Third molar maturity index (I3M) for assessing age of majority in a black African population in Botswana.

    Science.gov (United States)

    Cavrić, Jelena; Galić, Ivan; Vodanović, Marin; Brkić, Hrvoje; Gregov, Jelena; Viva, Serena; Rey, Laura; Cameriere, Roberto

    2016-07-01

    Assessment of legal age, also known as age of majority, is a controversial issue as there are few body biomarkers or evidence during late adolescence differentiating a subject from being a minor or adult. The third molar was recognized as a suitable site for age examination in late adolescence. We analyzed the development of the left mandibular third molar by the third molar maturity index (I3M) and a specific cut-off value of I3M = 0.08, established by Cameriere et al. in 2008 and used it for discriminating between minors and adult black Africans from Gaborone, Botswana. A final sample of panoramic radiographs (OPTs) of 1294 people (582 males and 712 females) aged between 13 and 23 years was evaluated. The real age decreased as I3M gradually increased. There was no statistically significant difference in the third molar development evaluated using I3M between males and females (p > 0.05) across different I3M classes. Results of 2 × 2 contingency tables for different cut-off values indicated that I3M = 0.08 was useful in discriminating between adults and minors. Precisely, for I3M = 0.08, the values of accuracy or overall fraction of correctly classified were 0.91 in males with a 95 % confidence interval (95 % CI) of 0.88 to 0.93 and 0.92 (95 % CI, 0.90 to 0.93) in females. Values of sensitivity of the test or the proportion of participants being 18 years and older were 0.88 (95 % CI, 0.87 to 0.90) in males and 0.88 (95 % CI, 0.90 to 0.93) in females, while values of specificity or proportion of individuals younger than 18 who have I3M age of 18 years in Botswana. Further studies should address the usefulness of this method and specific cut-off for different adolescent populations.

  11. Effect of Expectation of Care on Adherence to Antihypertensive Medications Among Hypertensive Blacks: Analysis of the Counseling African Americans to Control Hypertension (CAATCH) Trial.

    Science.gov (United States)

    Grant, Andrea Barnes; Seixas, Azizi; Frederickson, Keville; Butler, Mark; Tobin, Jonathan N; Jean-Louis, Girardin; Ogedegbe, Gbenga

    2016-07-01

    Novel ideas are needed to increase adherence to antihypertensive medication. The current study used data from the Counseling African Americans to Control Hypertension (CAATCH) study, a sample of 442 hypertensive African Americans, to investigate the mediating effects of expectation of hypertension care, social support, hypertension knowledge, and medication adherence, adjusting for age, sex, number of medications, diabetes, education, income, employment, insurance status, and intervention. Sixty-six percent of patients had an income of $20,000 or less and 56% had a high school education or less, with a mean age of 57 years. Greater expectation of care was associated with greater medication adherence (P=.007), and greater social support was also associated with greater medication adherence (P=.046). Analysis also showed that expectation of care mediated the relationship between hypertension knowledge and medication adherence (Psocial support are important factors for developing interventions to increase medication adherence among blacks. PMID:26593105

  12. Black Hole Evaporation. A Survey

    OpenAIRE

    Benachenhou, Farid

    1994-01-01

    This thesis is a review of black hole evaporation with emphasis on recent results obtained for two dimensional black holes. First, the geometry of the most general stationary black hole in four dimensions is described and some classical quantities are defined. Then, a derivation of the spectrum of the radiation emitted during the evaporation is presented. In section four, a two dimensional model which has black hole solutions is introduced, the so-called CGHS model. These two dimensional blac...

  13. Black Hole: The Interior Spacetime

    CERN Document Server

    Ong, Yen Chin

    2016-01-01

    The information loss paradox is often discussed from the perspective of the observers who stay outside of a black hole. However, the interior spacetime of a black hole can be rather nontrivial. We discuss the open problems regarding the volume of a black hole, and whether it plays any role in information storage. We also emphasize the importance of resolving the black hole singularity, if one were to resolve the information loss paradox.

  14. Black Holes in Higher Dimensions

    Directory of Open Access Journals (Sweden)

    Reall Harvey S.

    2008-09-01

    Full Text Available We review black-hole solutions of higher-dimensional vacuum gravity and higher-dimensional supergravity theories. The discussion of vacuum gravity is pedagogical, with detailed reviews of Myers–Perry solutions, black rings, and solution-generating techniques. We discuss black-hole solutions of maximal supergravity theories, including black holes in anti-de Sitter space. General results and open problems are discussed throughout.

  15. Towards noncommutative quantum black holes

    International Nuclear Information System (INIS)

    In this paper we study noncommutative black holes. We use a diffeomorphism between the Schwarzschild black hole and the Kantowski-Sachs cosmological model, which is generalized to noncommutative minisuperspace. Through the use of the Feynman-Hibbs procedure we are able to study the thermodynamics of the black hole, in particular, we calculate the Hawking's temperature and entropy for the noncommutative Schwarzschild black hole

  16. Towards Noncommutative Quantum Black Holes

    OpenAIRE

    Lopez-Dominguez, J. C.; Obregon, O.; Ramirez, C.; Sabido, M.

    2006-01-01

    In this paper we study noncommutative black holes. We use a diffeomorphism between the Schwarzschild black hole and the Kantowski-Sachs cosmological model, which is generalized to noncommutative minisuperspace. Through the use of the Feynman-Hibbs procedure we are able to study the thermodynamics of the black hole, in particular, we calculate the Hawking's temperature and entropy for the noncommutative Schwarzschild black hole.

  17. The Black Ring is Unstable

    CERN Document Server

    Santos, Jorge E

    2015-01-01

    We study non-axisymmetric linearised gravitational perturbations of the Emparan-Reall black ring using numerical methods. We find an unstable mode whose onset lies within the "fat" branch of the black ring and continues into the "thin" branch. Together with previous results using Penrose inequalities that fat black rings are unstable, this provides numerical evidence that the entire black ring family is unstable.

  18. 'Black Magic' and Diasporic Imagination

    Directory of Open Access Journals (Sweden)

    Raupach, Kirsten

    2002-01-01

    Full Text Available Within a colonial framework black diasporan thinking became most evident in the slaves' religious practices. Diasporic Imagination was displayed in terms of rituals of remembrance, social bonding across racial diversity, worship of African Gods, and imagined return to the homeland. These diasporic elements in African-Carribean slave religion, however, challenged white authority and conceptions of white superiority. A closer look at British colonial discourse of the late 18th century illustrates the colonialist's obsession with the slaves' display of their Africaness in religious ceremonies and the struggle to come to terms with the unsettling implications of slave magic. Moreover, these literary productions reflect white anxieties as to the stability of the imperial situation and reveal the white man's growing awareness regarding the limitations of imperial power.

  19. Warped products and black holes

    International Nuclear Information System (INIS)

    We apply the warped product space-time scheme to the Banados-Teitelboim-Zanelli black holes and the Reissner-Nordstroem-anti-de Sitter black hole to investigate their interior solutions in terms of warped products. It is shown that there exist no discontinuities of the Ricci and Einstein curvatures across event horizons of these black holes

  20. Blacks and the Women's Movement.

    Science.gov (United States)

    Loiacono, Stephanie

    1989-01-01

    Although Black female leaders were influential in creating the modern women's movement, feminism has evolved differently for both Black and White women. Suggests that, although Black women have struggled largely against racial and economic inequalities, women of all colors and backgrounds should embrace their diversity and unite to oppose racism…

  1. Black carbon in marine sediments

    NARCIS (Netherlands)

    Middelburg, J.J.; Nieuwenhuize, J.; Van Breugel, P.

    1999-01-01

    Concentrations of black carbon were determined for a number of marine sediments. A comparison of black carbon based on thermal oxidation and hot concentrated nitric acid pretreatments revealed that the latter significantly overestimates combustion derived carbon phases. Black carbon accounts for abo

  2. Warped products and black holes

    CERN Document Server

    Hong, S T

    2005-01-01

    We apply the warped product spacetime scheme to the Banados-Teitelboim-Zanelli black holes and the Reissner-Nordstr\\"om-anti-de Sitter black hole to investigate their interior solutions in terms of warped products. It is shown that there exist no discontinuities of the Ricci and Einstein curvatures across event horizons of these black holes.

  3. Black Progress: Convergence or Cleavage?

    Science.gov (United States)

    Hill, Robert B.

    1982-01-01

    The popular view of a permanent Black underclass falling farther behind an expanding Black middle class is disputed by empirical evidence that the underclass is experiencing upward mobility. The discrepancy stems from social scientists' overreliance on cross-sectional data rather than longitudinal data in analyzing economic change among Blacks.…

  4. The professional identity of black South African teachers : personal and professional struggles in a disjunction between policy and practice

    OpenAIRE

    2008-01-01

    Problem area for discussion This thesis sets out to describe and deliberate on the concept of the professional identity of black teachers in South Africa. The historical and cultural context of South Africa stretching from apartheid rule to the first years of democratisation creates a frame around this study, within which I have investigated the life and work of this professional group who performs a very significant job in the process of developing a young democracy. Although this study ...

  5. Black silicon with black bus-bar strings

    DEFF Research Database (Denmark)

    Davidsen, Rasmus Schmidt; Tang, Peter Torben; Mizushima, Io;

    2016-01-01

    We present the combination of black silicon texturing and blackened bus-bar strings as a potential method for obtaining all-black solar panels, while using conventional, front-contacted solar cells. Black silicon was realized by mask-less reactive ion etching resulting in total, average reflectance...... below 0.5% across a 156x156 mm2 silicon wafer. Black bus-bars were realized by oxidized copper resulting in reflectance below 3% in the entire visible wavelength range. The combination of these two technologies may result in aesthetic, all-black panels based on conventional, front-contacted solar cells...

  6. Empowering Young Black Males

    Science.gov (United States)

    Kafele, Baruti K.

    2012-01-01

    Of all the challenges we face in education today, the author can think of none greater than the challenge of motivating, educating, and empowering black male learners. The fact that this group of students is in crisis is evident on multiple levels, starting with graduation rates. According to the Schott Foundation (2008), the U.S. high school…

  7. Black History Speech

    Science.gov (United States)

    Noldon, Carl

    2007-01-01

    The author argues in this speech that one cannot expect students in the school system to know and understand the genius of Black history if the curriculum is Eurocentric, which is a residue of racism. He states that his comments are designed for the enlightenment of those who suffer from a school system that "hypocritically manipulates Black…

  8. Black holes and qubits

    CERN Document Server

    Duff, M J

    2012-01-01

    Quantum entanglement lies at the heart of quantum information theory, with applications to quantum computing, teleportation, cryptography and communication. In the apparently separate world of quantum gravity, the Hawking effect of radiating black holes has also occupied centre stage. Despite their apparent differences, it turns out that there is a correspondence between the two.

  9. Trichomicosis pubis: black variety.

    OpenAIRE

    Neri, I.; Frassetto, A; Pasquinelli, G.; Patrizi, A.

    1994-01-01

    A case of a 25 year old man with the black variety of trichomicosis pubis is presented on account of its extreme rareity. Scanning electron microscopy confirms that trichomicosis pubis is caused by bacterial colonisation of the pubic hair and shows that bacteria are able to penetrate cuticular horny cells directly through their free plasma membrane.

  10. Rotating regular black holes

    Energy Technology Data Exchange (ETDEWEB)

    Bambi, Cosimo, E-mail: bambi@fudan.edu.cn; Modesto, Leonardo, E-mail: lmodesto@fudan.edu.cn

    2013-04-25

    The formation of spacetime singularities is a quite common phenomenon in General Relativity and it is regulated by specific theorems. It is widely believed that spacetime singularities do not exist in Nature, but that they represent a limitation of the classical theory. While we do not yet have any solid theory of quantum gravity, toy models of black hole solutions without singularities have been proposed. So far, there are only non-rotating regular black holes in the literature. These metrics can be hardly tested by astrophysical observations, as the black hole spin plays a fundamental role in any astrophysical process. In this Letter, we apply the Newman–Janis algorithm to the Hayward and to the Bardeen black hole metrics. In both cases, we obtain a family of rotating solutions. Every solution corresponds to a different matter configuration. Each family has one solution with special properties, which can be written in Kerr-like form in Boyer–Lindquist coordinates. These special solutions are of Petrov type D, they are singularity free, but they violate the weak energy condition for a non-vanishing spin and their curvature invariants have different values at r=0 depending on the way one approaches the origin. We propose a natural prescription to have rotating solutions with a minimal violation of the weak energy condition and without the questionable property of the curvature invariants at the origin.

  11. Moulting Black Holes

    Science.gov (United States)

    Bena, Iosif; Chowdhury, Borun D.; de Boer, Jan; El-Showk, Sheer; Shigemori, Masaki

    2012-03-01

    We find a family of novel supersymmetric phases of the D1-D5 CFT, which in certain ranges of charges have more entropy than all known ensembles. We also find bulk BPS configurations that exist in the same range of parameters as these phases, and have more entropy than a BMPV black hole; they can be thought of as coming from a BMPV black hole shedding a "hair" condensate outside of the horizon. The entropy of the bulk configurations is smaller than that of the CFT phases, which indicates that some of the CFT states are lifted at strong coupling. Neither the bulk nor the boundary phases are captured by the elliptic genus, which makes the coincidence of the phase boundaries particularly remarkable. Our configurations are supersymmetric, have non-Cardy-like entropy, and are the first instance of a black hole entropy enigma with a controlled CFT dual. Furthermore, contrary to common lore, these objects exist in a region of parameter space (between the "cosmic censorship bound" and the "unitarity bound") where no black holes were thought to exist.

  12. When Black Holes Collide

    Science.gov (United States)

    Baker, John

    2010-01-01

    Among the fascinating phenomena predicted by General Relativity, Einstein's theory of gravity, black holes and gravitational waves, are particularly important in astronomy. Though once viewed as a mathematical oddity, black holes are now recognized as the central engines of many of astronomy's most energetic cataclysms. Gravitational waves, though weakly interacting with ordinary matter, may be observed with new gravitational wave telescopes, opening a new window to the universe. These observations promise a direct view of the strong gravitational dynamics involving dense, often dark objects, such as black holes. The most powerful of these events may be merger of two colliding black holes. Though dark, these mergers may briefly release more energy that all the stars in the visible universe, in gravitational waves. General relativity makes precise predictions for the gravitational-wave signatures of these events, predictions which we can now calculate with the aid of supercomputer simulations. These results provide a foundation for interpreting expect observations in the emerging field of gravitational wave astronomy.

  13. Newborn Black Holes

    Science.gov (United States)

    Science Teacher, 2005

    2005-01-01

    Scientists using NASA's Swift satellite say they have found newborn black holes, just seconds old, in a confused state of existence. The holes are consuming material falling into them while somehow propelling other material away at great speeds. "First comes a blast of gamma rays followed by intense pulses of x-rays. The energies involved are much…

  14. The logic of Black Economic Empowerment

    OpenAIRE

    Southall, Roger

    2006-01-01

    The policies relating to Black Economic Empowerment (BEE) in South Africa constitute a logical unfolding of a strategy which has been largely dictated by the history of the ruling African National Congress (ANC), the nature of the democratic settlement of 1994, and the structure of the South African economy. From this perspective, the logic of BEE can be pursued through ten propositions which argue that the ANC has sought control of the state to ‘internally decolonise’ South Africa. This incl...

  15. Harvard, Harvard: He's Perfect and He's Black.

    Science.gov (United States)

    Barrett, Paul M.

    1999-01-01

    Describes the higher educational experiences of Lawrence Mungin, an African American who attended Harvard University and Harvard Law School. Mungin believed that working hard and being the good Black would lead to success in the White world. Despite his credentials, he was given trivial work at the law firm that hired him and that he later sued.…

  16. The Black Consciousness Movement in South Africa: A Product of The Entire Black World

    Directory of Open Access Journals (Sweden)

    Mgwebi Snail

    2009-12-01

    Full Text Available El trabajo ilustra cómo el surgimiento del Movimiento de Conciencia Negra en Sudáfrica puede estar diametralmente unido a la emergencia de los movimientos de Conciencia Negra y Black Power en América. Pretende demostrar además cómo, en el contexto africano, el Movimiento de Conciencia Negra fue impulsado por el nacionalismo africano y cómo ese nacionalismo fue moldeado y transformado por pensadores africanos de la década de los 50 y 60 en el Panafricanismo. El artículo también mostrará similitudes y diferencias entre la Negritud Africana y el Movimiento de Conciencia Negra. El texto de nuevo explicará de manera cronológica cómo el Garveyismo, la Conciencia Negra en América y el nacionalismo africano, la personalidad africana y la Negritud en África contribuyeron al surgimiento del Movimiento de Conciencia Negra en Sudáfrica. El estudio advierte de que la falta de comprensión de estos antecedentes, podría llevar a la confusión y a una mala interpretación de concepto vital en la historia de África. Finalmente, este trabajo busca hacer hincapié en la historización del desarrollo del por qué el Movimiento de Conciencia Negra en Sudáfrica no puede estar divorciado del contexto global.____________________ABSTRACT:The paper illustrates how the rise of the Black Consciousness Movement in South Africa can be diametrically tied up with the emergence of the Black Consciousness and Black-Power Movements in America. It goes further to demonstrate how, in the African context, the Black Consciousness Movement was given impetus by African nationalism and how that nationalism was later moulded and shaped by African thinkers of the 1950’s and 1960’s into Pan Africanism. The paper, will also try to show similarities and the disparities between Negritude African personality and the Black Consciousness Movement. The paper will again explain in a chronological manner how Garveyism, Black Consciousness in America and African Nationalism in

  17. Observational Evidence for Black Holes

    OpenAIRE

    Narayan, Ramesh; McClintock, Jeffrey E.

    2013-01-01

    Astronomers have discovered two populations of black holes: (i) stellar-mass black holes with masses in the range 5 to 30 solar masses, millions of which are present in each galaxy in the universe, and (ii) supermassive black holes with masses in the range 10^6 to 10^{10} solar masses, one each in the nucleus of every galaxy. There is strong circumstantial evidence that all these objects are true black holes with event horizons. The measured masses of supermassive black hole are strongly corr...

  18. BlackBerry For Dummies

    CERN Document Server

    Kao, Robert

    2010-01-01

    Get the most juice out of your BlackBerry handheld!. Feature-rich and complex, the BlackBerry is the number one smartphone in the corporate world is among the most popular handhelds for business users. This new and updated edition includes all the latest and greatest information on new and current BlackBerry mobile devices. Covering a range of valuable how-to topics, this helpful guide explores the BlackBerry's most useful features, techniques for getting the most out of your BlackBerry, and practical information about power usage.: Covers all aspects of the number one smartphone in the corpor

  19. Over spinning a black hole?

    Energy Technology Data Exchange (ETDEWEB)

    Bouhmadi-Lopez, Mariam; Cardoso, Vitor; Nerozzi, Andrea; Rocha, Jorge V, E-mail: mariam.bouhmadi@ist.utl.pt, E-mail: vitor.cardoso@ist.utl.pt, E-mail: andrea.nerozzi@ist.utl.pt, E-mail: jorge.v.rocha@ist.utl.pt [CENTRA, Department de Fisica, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049 Lisboa (Portugal)

    2011-09-22

    A possible process to destroy a black hole consists on throwing point particles with sufficiently large angular momentum into the black hole. In the case of Kerr black holes, it was shown by Wald that particles with dangerously large angular momentum are simply not captured by the hole, and thus the event horizon is not destroyed. Here we reconsider this gedanken experiment for black holes in higher dimensions. We show that this particular way of destroying a black hole does not succeed and that Cosmic Censorship is preserved.

  20. Growth of Primordial Black Holes

    Science.gov (United States)

    Harada, Tomohiro

    Primordial black holes have important observational implications through Hawking evaporation and gravitational radiation as well as being a candidate for cold dark matter. Those black holes are assumed to have formed in the early universe typically with the mass scale contained within the Hubble horizon at the formation epoch and subsequently accreted mass surrounding them. Numerical relativity simulation shows that primordial black holes of different masses do not accrete much, which contrasts with a simplistic Newtonian argument. We see that primordial black holes larger than the 'super-horizon' primordial black holes have decreasing energy and worm-hole like struture, suggesting the formation through quamtum processes.

  1. Identité et marchandisation : Le cas des black memorabilia et black collectibles

    OpenAIRE

    Elmaleh, Eliane

    2009-01-01

    The aim of this article is to raise the issue of the commodification of African American culture, mainly through a certain form of art that has re-emerged with Black memorabilia which paradoxically fit into a black-driven market. However, these items penetrated American culture from 1920 to the 1950s to convey images of black people as lazy, stupid, childlike and happy. This condition of permanent happiness, typified by a broad smile and white teeth, was a fundamental component of this racist...

  2. Prisons of light : black holes

    Science.gov (United States)

    Ferguson, Kitty

    What is a black hole? Could we survive a visit to one -- perhaps even venture inside? Have we yet discovered any real black holes? And what do black holes teach us about the mysteries of our Universe? These are just a few of the tantalizing questions examined in this tour-de-force, jargon-free review of one of the most fascinating topics in modern science. In search of the answers, we trace a star from its birth to its death throes, take a hypothetical journey to the border of a black hole and beyond, spend time with some of the world's leading theoretical physicists and astronomers, and take a whimsical look at some of the wild ideas black holes have inspired. Prisons of Light - Black Holes is comprehensive and detailed. Yet Kitty Ferguson's lightness of touch and down-to-earth analogies set this book apart from all others on black holes and make it a wonderfully stimulating and entertaining read.

  3. Point mass Cosmological Black Holes

    CERN Document Server

    Firouzjaee, Javad T

    2016-01-01

    Real black holes in the universe are located in the expanding accelerating background which are called the cosmological black holes. Hence, it is necessary to model these black holes in the cosmological background where the dark energy is the dominant energy. In this paper, we argue that most of the dynamical cosmological black holes can be modeled by point mass cosmological black holes. Considering the de Sitter background for the accelerating universe, we present the point mass cosmological background in the cosmological de Sitter space time. Our work also includes the point mass black holes which have charge and angular momentum. We study the mass, horizons, redshift structure and geodesics properties for these black holes.

  4. Philosophical Issues of Black Holes

    CERN Document Server

    Romero, Gustavo E

    2014-01-01

    Black holes are extremely relativistic objects. Physical processes around them occur in a regime where the gravitational field is extremely intense. Under such conditions, our representations of space, time, gravity, and thermodynamics are pushed to their limits. In such a situation philosophical issues naturally arise. In this chapter I review some philosophical questions related to black holes. In particular, the relevance of black holes for the metaphysical dispute between presentists and eternalists, the origin of the second law of thermodynamics and its relation to black holes, the problem of information, black holes and hypercomputing, the nature of determinisim, and the breakdown of predictability in black hole space-times. I maintain that black hole physics can be used to illuminate some important problems in the border between science and philosophy, either epistemology and ontology.

  5. An analysis of stereotype threat in African American engineering students at predominantly White, ethnically diverse, and historically Black colleges and universities

    Science.gov (United States)

    Sparks, David M.

    The purpose of this research was to distinguish the similarities and differences in coping strategies of African American engineering students by analyzing their perceptions of stereotype threat at three academic institution types, Predominantly White Institutions (PWI), ethnically diverse, and Historically Black Colleges and Universities (HBCUs). The researcher collected demographic and survey data using the Stereotype Vulnerability Scale (SVS). The study was offered to the entire population of African American engineering students at each college using an online survey. Results were analyzed using MANOVA and Pearson's correlational statistical analyses to test the hypotheses. Findings revealed that little differences exist between students' scores on an assessment of stereotype vulnerability, with a few areas showing that HBCUs and ethnically diverse universities are doing a similar job in addressing perceptions of their African American engineering students. Finding also revealed that the percentage of African American students at a university did not correlate with the scores on the SVS accept on questions related to the personal feelings students have about their race. The strongest findings related to the differences in male and female students across the universities. African American female engineering students appeared to perceive more stereotype threat than did their male counterparts; although, this fining was not statistically significant. Overall, no statistically significant differences were found between students' perceptions of stereotype threat at the three types of universities. Future research should expand the number of survey participants at the current universities, add more HBCUs to the study population, run similar experiments in different parts of the country, compare stereotype threat in private and elite universities, use ethnically diverse universities as models for minority student development, and use new or improved survey instruments

  6. Black Holes and Fourfolds

    CERN Document Server

    Bena, Iosif; Vercnocke, Bert

    2012-01-01

    We establish the relation between the structure governing supersymmetric and non-supersymmetric four- and five-dimensional black holes and multicenter solutions and Calabi-Yau flux compactifications of M-theory and type IIB string theory. We find that the known BPS and almost-BPS multicenter black hole solutions can be interpreted as GKP compactifications with (2,1) and (0,3) imaginary self-dual flux. We also show that the most general GKP compactification leads to new classes of BPS and non-BPS multicenter solutions. We explore how these solutions fit into N=2 truncations, and elucidate how supersymmetry becomes camouflaged. As a necessary tool in our exploration we show how the fields in the largest N=2 truncation fit inside the six-torus compactification of eleven-dimensional supergravity.

  7. Shape of black holes

    CERN Document Server

    Clement, María E Gabach

    2015-01-01

    It is well known that celestial bodies tend to be spherical due to gravity and that rotation produces deviations from this sphericity. We discuss what is known and expected about the shape of black holes' horizons from their formation to their final, stationary state. We present some recent results showing that black hole rotation indeed manifests in the widening of their central regions, limits their global shapes and enforces their whole geometry to be close to the extreme Kerr horizon geometry at almost maximal rotation speed. The results depend only on the horizon area and angular momentum. In particular they are entirely independent of the surrounding geometry of the spacetime and of the presence of matter satisfying the strong energy condition. We also discuss the the relation of this result with the Hoop conjecture.

  8. Presentism meets black holes

    CERN Document Server

    Romero, Gustavo E

    2014-01-01

    Presentism is, roughly, the metaphysical doctrine that maintains that whatever exists, exists in the present. The compatibility of presentism with the theories of special and general relativity was much debated in recent years. It has been argued that at least some versions of presentism are consistent with time-orientable models of general relativity. In this paper we confront the thesis of presentism with relativistic physics, in the strong gravitational limit where black holes are formed. We conclude that the presentist position is at odds with the existence of black holes and other compact objects in the universe. A revision of the thesis is necessary, if it is intended to be consistent with the current scientific view of the universe.

  9. Asymmetric black dyonic holes

    Directory of Open Access Journals (Sweden)

    I. Cabrera-Munguia

    2015-04-01

    Full Text Available A 6-parametric asymptotically flat exact solution, describing a two-body system of asymmetric black dyons, is studied. The system consists of two unequal counterrotating Kerr–Newman black holes, endowed with electric and magnetic charges which are equal but opposite in sign, separated by a massless strut. The Smarr formula is generalized in order to take into account their contribution to the mass. The expressions for the horizon half-length parameters σ1 and σ2, as functions of the Komar parameters and of the coordinate distance, are displayed, and the thermodynamic properties of the two-body system are studied. Furthermore, the seven physical parameters satisfy a simple algebraic relation which can be understood as a dynamical scenario, in which the physical properties of one body are affected by the ones of the other body.

  10. Black-hole astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Bender, P. [Univ. of Colorado, Boulder, CO (United States); Bloom, E. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Cominsky, L. [Sonoma State Univ., Rohnert Park, CA (United States). Dept. of Physics and Astronomy] [and others

    1995-07-01

    Black-hole astrophysics is not just the investigation of yet another, even if extremely remarkable type of celestial body, but a test of the correctness of the understanding of the very properties of space and time in very strong gravitational fields. Physicists` excitement at this new prospect for testing theories of fundamental processes is matched by that of astronomers at the possibility to discover and study a new and dramatically different kind of astronomical object. Here the authors review the currently known ways that black holes can be identified by their effects on their neighborhood--since, of course, the hole itself does not yield any direct evidence of its existence or information about its properties. The two most important empirical considerations are determination of masses, or lower limits thereof, of unseen companions in binary star systems, and measurement of luminosity fluctuations on very short time scales.

  11. Black Holes and Firewalls

    Science.gov (United States)

    Polchinski, Joseph

    2015-04-01

    Our modern understanding of space, time, matter, and even reality itself arose from the three great revolutions of the early twentieth century: special relativity, general relativity, and quantum mechanics. But a century later, this work is unfinished. Many deep connections have been discovered, but the full form of a unified theory incorporating all three principles is not known. Thought experiments and paradoxes have often played a key role in figuring out how to fit theories together. For the unification of general relativity and quantum mechanics, black holes have been an important arena. I will talk about the quantum mechanics of black holes, the information paradox, and the latest version of this paradox, the firewall. The firewall points to a conflict between our current theories of spacetime and of quantum mechanics. It may lead to a new understanding of how these are connected, perhaps based on quantum entanglement.

  12. Noncommutative Black Holes

    CERN Document Server

    Bastos, C; Dias, N C; Prata, J N

    2010-01-01

    One considers phase-space noncommutativity in the context of a Kantowski-Sachs cosmological model to study the interior of a Schwarzschild black hole. It is shown that the potential function of the corresponding quantum cosmology problem has a local minimum. One deduces the thermodynamics and show that the Hawking temperature and entropy exhibit an explicit dependence on the momentum noncommutativity regime and it is shown that the wave function vanishes in this limit.

  13. Noncommutative Solitonic Black Hole

    OpenAIRE

    Chang-Young, Ee; Kimm, Kyoungtae; Lee, Daeho; Lee, Youngone

    2011-01-01

    We investigate solitonic black hole solutions in three dimensional noncommutative spacetime. We do this in gravity with negative cosmological constant coupled to a scalar field. Noncommutativity is realized with the Moyal product which is expanded up to first order in the noncommutativity parameter in two spatial directions. With numerical simulation we study the effect of noncommutativity by increasing the value of the noncommutativity parameter starting from commutative solutions. We find t...

  14. Black Friday = Broget Branding?

    DEFF Research Database (Denmark)

    Hansen, Heidi

    2015-01-01

    ? Essensen ved Black Friday er lave priser, og det er der ved første øjekast ikke mange brandingmuligheder forbundet ved, hvis man forstår branding som en måde at skabe ekstra værdi omkring sit produkt eller sin virksomhed. Som brand bliver man dog alligevel nødt til at forholde sig til konceptet, da det er...

  15. Slowly balding black holes

    CERN Document Server

    Lyutikov, Maxim

    2011-01-01

    The "no hair" theorem, a key result in General Relativity, states that an isolated black hole is defined by only three parameters: mass, angular momentum, and electric charge; this asymptotic state is reached on a light-crossing time scale. We find that the "no hair" theorem is not formally applicable for black holes formed from collapse of a rotating neutron star. Rotating neutron stars can self-produce particles via vacuum breakdown forming a highly conducting plasma magnetosphere such that magnetic field lines are effectively "frozen-in" the star both before and during collapse. In the limit of no resistivity, this introduces a topological constraint which prohibits the magnetic field from sliding off the newly-formed event horizon. As a result, during collapse of a neutron star into a black hole, the latter conserves the number of magnetic flux tubes $N_B = e \\Phi_\\infty /(\\pi c \\hbar)$, where $\\Phi_\\infty \\approx 2 \\pi^2 B_{NS} R_{NS}^3 /(P_{\\rm NS} c)$ is the initial magnetic flux through the hemisphere...

  16. Thermal corpuscular black holes

    Science.gov (United States)

    Casadio, Roberto; Giugno, Andrea; Orlandi, Alessio

    2015-06-01

    We study the corpuscular model of an evaporating black hole consisting of a specific quantum state for a large number N of self-confined bosons. The single-particle spectrum contains a discrete ground state of energy m (corresponding to toy gravitons forming the black hole), and a gapless continuous spectrum (to accommodate for the Hawking radiation with energy ω >m ). Each constituent is in a superposition of the ground state and a Planckian distribution at the expected Hawking temperature in the continuum. We first find that, assuming the Hawking radiation is the leading effect of the internal scatterings, the corresponding N -particle state can be collectively described by a single-particle wave function given by a superposition of a total ground state with energy M =N m and a Planckian distribution for E >M at the same Hawking temperature. From this collective state, we compute the partition function and obtain an entropy which reproduces the usual area law with a logarithmic correction precisely related with the Hawking component. By means of the horizon wave function for the system, we finally show the backreaction of modes with ω >m reduces the Hawking flux. Both corrections, to the entropy and to the Hawking flux, suggest the evaporation properly stops for vanishing mass, if the black hole is in this particular quantum state.

  17. Moulting Black Holes

    CERN Document Server

    Bena, Iosif; de Boer, Jan; El-Showk, Sheer; Shigemori, Masaki

    2011-01-01

    We find a family of novel supersymmetric phases of the D1-D5 CFT, which in certain ranges of charges have more entropy than all known ensembles. We also find bulk BPS configurations that exist in the same range of parameters as these phases, and have more entropy than a BMPV black hole; they can be thought of as coming from a BMPV black hole shedding a "hair" condensate outside of the horizon. The entropy of the bulk configurations is smaller than that of the CFT phases, which indicates that some of the CFT states are lifted at strong coupling. Neither the bulk nor the boundary phases are captured by the elliptic genus, which makes the coincidence of the phase boundaries particularly remarkable. Our configurations are supersymmetric, have non-Cardy-like entropy, and are the first instance of a black hole entropy enigma with a controlled CFT dual. Furthermore, contrary to common lore, these objects exist in a region of parameter space (between the "cosmic censorship bound" and the "unitarity bound") where no b...

  18. Attractors in Black

    CERN Document Server

    Bellucci, S; Marrani, A

    2008-01-01

    We review recent results in the study of attractor horizon geometries (with non-vanishing Bekenstein-Hawking entropy) of dyonic extremal d=4 black holes in supergravity. We focus on N=2, d=4 ungauged supergravity coupled to a number n_{V} of Abelian vector multiplets, outlining the fundamentals of the special Kaehler geometry of the vector multiplets' scalar manifold (of complex dimension n_{V}), and studying the 1/2-BPS attractors, as well as the non-BPS (non-supersymmetric) ones with non-vanishing central charge. For symmetric special Kaehler geometries, we present the complete classification of the orbits in the symplectic representation of the classical U-duality group (spanned by the black hole charge configuration supporting the attractors), as well as of the moduli spaces of non-BPS attractors (spanned by the scalars which are not stabilized at the black hole event horizon). Finally, we report on an analogous classification for N>2-extended, d=4 ungauged supergravities, in which also the 1/N-BPS attrac...

  19. Black silicon solar cells with black bus-bar strings

    DEFF Research Database (Denmark)

    Davidsen, Rasmus Schmidt; Tang, Peter Torben; Mizushima, Io;

    2016-01-01

    We present the combination of black silicon texturing and blackened bus-bar strings as a potential method for obtaining all-black solar panels, while using conventional, front-contacted solar cells. Black silicon was realized by maskless reactive ion etching resulting in total, average reflectance...... below 0.5% across a 156x156 mm2 silicon wafer. Four different methods to obtain blackened bus-bar strings were compared with respect to reflectance, and two of these methods (i.e., oxidized copper and etched solder) were used to fabricate functional allblack solar 9-cell panels. The black bus-bars (e.......g., by oxidized copper) have a reflectance below 3% in the entire visible wavelength range. The combination of black silicon cells and blackened bus-bars results in aesthetic, all-black panels based on conventional, front-contacted solar cells without compromising efficiency....

  20. Non-Abelian magnetic black strings versus black holes

    Science.gov (United States)

    Mazharimousavi, S. Habib; Halilsoy, M.

    2016-05-01

    We present d+1 -dimensional pure magnetic Yang-Mills (YM) black strings (or 1-branes) induced by the d -dimensional Einstein-Yang-Mills-Dilaton black holes. The Born-Infeld version of the YM field makes our starting point which goes to the standard YM field through a limiting procedure. The lifting from black holes to black strings (with less number of fields) is done by adding an extra, compact coordinate. This amounts to the change of horizon topology from S^{d-2} to a product structure. Our black string in 5 dimensions is a rather special one, with uniform Hawking temperature and non-asymptotically flat structure. As the YM charge becomes large the string gets thinner to tend into a breaking point and transform into a 4-dimensional black hole.

  1. Familial influences on poverty among young children in black immigrant, U.S.-born black, and nonblack immigrant families.

    Science.gov (United States)

    Thomas, Kevin J A

    2011-05-01

    This study examines how familial contexts affect poverty disparities between the children of immigrant and U.S.-born blacks, and among black and nonblack children of immigrants. Despite lower gross child poverty rates in immigrant than in U.S.-born black families, accounting for differences in family structure reveals that child poverty risks among blacks are highest in single-parent black immigrant families. In addition, within two-parent immigrant families, child poverty declines associated with increasing assimilation are greater than the respective declines in single-parent families. The heads of black immigrant households have more schooling than those of native-black households. However, increased schooling has a weaker negative association with child poverty among the former than among the latter. In terms of racial disparities among the children of immigrants, poverty rates are higher among black than nonblack children. This black disadvantage is, however, driven by the outcomes of first-generation children of African and Hispanic-black immigrants. The results also show that although children in refugee families face elevated poverty risks, these risks are higher among black than among nonblack children of refugees. In addition, the poverty-reducing impact associated with having an English-proficient household head is about three times lower among black children of immigrants than among non-Hispanic white children of immigrants. PMID:21491186

  2. How Black Are Black Hole Candidates?

    CERN Document Server

    Robertson, S L; Robertson, Stanley L.; Leiter, Darryl J.

    2002-01-01

    In previous work we found that many of the spectral properties of x-ray binaries, including both galactic black hole candiates (GBHC) and neutron stars, were consistent with the existence of intrinsically magnetized central objects. Here we review and extend the observational evidence for the existence of intrinsically magnetized GBHC and show that their existence is consistent with a new class of solutions of the Einstein field equations of General Relativity. These solutions are based on a strict adherence to the Principle of Equivalence, which prevents the time-like geodesics of physical matter from becoming null on trapped surfaces of infinite red shift. The new solutions emerge from the fact that the structure and radiation transfer properties of the energy-momentum tensor on the right hand side of the Einstein field equations must have a form that is consistent with this Principle of Equivalence requirement. In this context, we show that the Einstein field equations allow the existence of highly red shi...

  3. Development of Onchocerca volvulus (Filarioidea: Onchocercidae) in the West African black fly Simulium yahense (Diptera: Simuliidae) in Liberia.

    Science.gov (United States)

    Trpis, M; Wergin, W P; Murphy, C A

    2001-12-01

    Simulium yahense black flies infected with microfilaria of Onchocerca volvulus were kept in a defined insectary environment in Liberia, West Africa. A daily sample of infected flies was dissected for larvae developing in the thoracic muscles and examined for growth in stadial development. Microfilariae ingested by black flies transformed to the L1 larval stage without molting. Successive larval development included molting to the L2 stage and, finally, to the L3 stage, which was infective in humans. The cephalic cap, consisting of a laterally located hook and central stoma, occurs in the first larval stage. The caudal appendix and the laterally located anal opening are apparent in the L1 larva. In the L2 stage, the cephalic cap is lost and the large circular stoma becomes surrounded with elevated flaps. The caudal appendix was lost after larvae molted to the L3 stage, and in its place, 3 terminal papillae developed. Sense organs, such as 2 opposing phasmids and 8 papillae that were arranged into 2 circles, developed in the cephalic region of the L3 larva. The evidence of pathological consequences due to the presence of the L3 larva in the fly host are illustrated and discussed. PMID:11780809

  4. Adapting an Evidence-Based HIV Intervention for At-Risk African American College Women at Historically Black Colleges and Universities Who Use Alcohol and Drugs

    Directory of Open Access Journals (Sweden)

    Kyla Marie Sawyer-Kurian

    2012-11-01

    Full Text Available The convergence of the high prevalence of HIV incidence among African American adolescent and adult women along with substance use and risky sexual behavior among university students necessitates the development of a HIV intervention specifically addressing culture, gender, and college factors for female African American university students. The woman-focused HIV intervention was chosen for adaptation because it has been shown to be efficacious with reducing risk for African American women who use alcohol and drugs, and has been successfully adapted 7 times. The target population was African American college women enrolled at a historically Black university who use alcohol and other drugs, and who engaged in risky sex behaviors. To understand and assess the needs of this population, we conducted four focus groups with African American college women, two in-depth interviews with faculty, and a combination of in-depth interviews and focus groups with student affairs and health staff that were analyzed using content analysis. From this analysis, several themes emerged that were used to adapt the intervention. Emerging themes included challenges related to identity and societal stereotypes, lack of knowledge about sexual health (i.e., negotiating safer sex and the function of female and male anatomies, high incidents of pregnancy, negative consequences related to alcohol and marijuana use, and the need to incorporate testimonies from college students, media enhancements, and role-plays to convey intervention messages. After the preliminary adaptation, 11 college women reviewed the adapted intervention and provided positive feedback. Plans for future research are discussed.

  5. Black Swan Tropical Cyclones

    Science.gov (United States)

    Emanuel, K.; Lin, N.

    2012-12-01

    Virtually all assessments of tropical cyclone risk are based on historical records, which are limited to a few hundred years at most. Yet stronger TCs may occur in the future and at places that have not been affected historically. Such events lie outside the realm of historically based expectations and may have extreme impacts. Their occurrences are also often made explainable after the fact (e.g., Hurricane Katrina). We nickname such potential future TCs, characterized by rarity, extreme impact, and retrospective predictability, "black swans" (Nassim Nicholas Taleb, 2007). As, by definition, black swan TCs have yet to happen, statistical methods that solely rely on historical track data cannot predict their occurrence. Global climate models lack the capability to predict intense storms, even with a resolution as high as 14 km (Emanuel et al. 2010). Also, most dynamic downscaling methods (e.g., Bender et al. 2010) are still limited in horizontal resolution and are too expensive to implement to generate enough events to include rare ones. In this study, we apply a simpler statistical/deterministic hurricane model (Emanuel et al. 2006) to simulate large numbers of synthetic storms under a given (observed or projected) climate condition. The method has been shown to generate realistic extremes in various basins (Emanuel et al. 2008 and 2010). We also apply a hydrodynamic model (ADCIRC; Luettich et al. 1992) to simulate the storm surges generated by these storms. We then search for black swan TCs, in terms of the joint wind and surge damage potential, in the generated large databases. Heavy rainfall is another important TC hazard and will be considered in a future study. We focus on three areas: Tampa Bay in the U.S., the Persian Gulf, and Darwin in Australia. Tampa Bay is highly vulnerable to storm surge as it is surrounded by shallow water and low-lying lands, much of which may be inundated by a storm tide of 6 m. High surges are generated by storms with a broad

  6. In and out of love with hip-hop: saliency of sexual scripts for young adult African American women in hip-hop and Black-oriented television.

    Science.gov (United States)

    Coleman, M Nicole; Butler, Ebony O; Long, Amanda M; Fisher, Felicia D

    2016-10-01

    Hip-hop media and Black-oriented reality television are powerful mechanisms for conveying and promoting stereotypes of Black women. Black women's sexuality is frequently presented as highly-salient in each medium. However, little is known about the impact of those images on Black women's sexuality and identity. The current study uses focus-group methodology to engage young adult Black in critical discussion of two predominant sexual scripts found in hip-hop music and Black-oriented reality television - the Freak and the Gold Digger. Analyses revealed shared and distinct aspects of each sexual script represented in both media and the impact of those scripts on participants' experiences. Implications for future research are discussed. PMID:27188876

  7. In and out of love with hip-hop: saliency of sexual scripts for young adult African American women in hip-hop and Black-oriented television.

    Science.gov (United States)

    Coleman, M Nicole; Butler, Ebony O; Long, Amanda M; Fisher, Felicia D

    2016-10-01

    Hip-hop media and Black-oriented reality television are powerful mechanisms for conveying and promoting stereotypes of Black women. Black women's sexuality is frequently presented as highly-salient in each medium. However, little is known about the impact of those images on Black women's sexuality and identity. The current study uses focus-group methodology to engage young adult Black in critical discussion of two predominant sexual scripts found in hip-hop music and Black-oriented reality television - the Freak and the Gold Digger. Analyses revealed shared and distinct aspects of each sexual script represented in both media and the impact of those scripts on participants' experiences. Implications for future research are discussed.

  8. Geometry of black hole spacetimes

    CERN Document Server

    Andersson, Lars; Blue, Pieter

    2016-01-01

    These notes, based on lectures given at the summer school on Asymptotic Analysis in General Relativity, collect material on the Einstein equations, the geometry of black hole spacetimes, and the analysis of fields on black hole backgrounds. The Kerr model of a rotating black hole in vacuum is expected to be unique and stable. The problem of proving these fundamental facts provides the background for the material presented in these notes. Among the many topics which are relevant for the uniqueness and stability problems are the theory of fields on black hole spacetimes, in particular for gravitational perturbations of the Kerr black hole, and more generally, the study of nonlinear field equations in the presence of trapping. The study of these questions requires tools from several different fields, including Lorentzian geometry, hyperbolic differential equations and spin geometry, which are all relevant to the black hole stability problem.

  9. Hidden Structures of Black Holes

    CERN Document Server

    Vercnocke, Bert

    2010-01-01

    This thesis investigates two main topics concerning black holes in extensions of general relativity inspired by string theory. First, the structure of the equations of motion underlying black hole solutions is considered, in theories of D-dimensional gravity coupled to scalars and vectors. For solutions preserving supersymmetry, the equations of motion have a dramatic simplification: they become first-order instead of the second-order equations one would expect. Recently, it was found that this is a feature some non-supersymmetric black hole solutions exhibit as well. We investigate if this holds more generally, by examining what the conditions are to have first-order equations for the scalar fields of non-supersymmetric black holes, that mimic the form of their supersymmetric counterparts. This is illustrated in examples. Second, the structure of black holes themselves is investigated. String theory has been successful in explaining the Bekenstein-Hawking entropy for (mainly supersymmetric) black holes from ...

  10. Small black holes on cylinders

    International Nuclear Information System (INIS)

    We find the metric of small black holes on cylinders, i.e. neutral and static black holes with a small mass in d-dimensional Minkowski space times a circle. The metric is found using an ansatz for black holes on cylinders proposed in J. High Energy Phys. 05, 032 (2002). We use the new metric to compute corrections to the thermodynamics which is seen to deviate from that of the (d+1)-dimensional Schwarzschild black hole. Moreover, we compute the leading correction to the relative binding energy which is found to be non-zero. We discuss the consequences of these results for the general understanding of black holes and we connect the results to the phase structure of black holes and strings on cylinders

  11. Black Hole's 1/N Hair

    CERN Document Server

    Dvali, Gia

    2013-01-01

    According to the standard view classically black holes carry no hair, whereas quantum hair is at best exponentially weak. We show that suppression of hair is an artifact of the semi-classical treatment and that in the quantum picture hair appears as an inverse mass-square effect. Such hair is predicted in the microscopic quantum description in which a black hole represents a self-sustained leaky Bose-condensate of N soft gravitons. In this picture the Hawking radiation is the quantum depletion of the condensate. Within this picture we show that quantum black hole physics is fully compatible with continuous global symmetries and that global hair appears with the strength B/N, where B is the global charge swallowed by the black hole. For large charge this hair has dramatic effect on black hole dynamics. Our findings can have interesting astrophysical consequences, such as existence of black holes with large detectable baryonic and leptonic numbers.

  12. The Experience of Antiretroviral Treatment for Black West African Women who are HIV Positive and Living in London: An Interpretative Phenomenological Analysis.

    Science.gov (United States)

    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.

  13. Information Storage in Black Holes

    OpenAIRE

    Maia, M. D.

    2005-01-01

    The information loss paradox for Schwarzschild black holes is examined, using the ADS/CFT correspondence extended to the $M_6 (4,2)$ bulk. It is found that the only option compatible with the preservation of the quantum unitarity is when a regular remnant region of the black hole survives to the black hole evaporation process, where information can be stored and eventually retrieved.

  14. Origin of supermassive black holes

    OpenAIRE

    Dokuchaev, V. I.; Eroshenko, Yu. N.; Rubin, S. G.

    2007-01-01

    The origin of supermassive black holes in the galactic nuclei is quite uncertain in spite of extensive set of observational data. We review the known scenarios of galactic and cosmological formation of supermassive black holes. The common drawback of galactic scenarios is a lack of time and shortage of matter supply for building the supermassive black holes in all galaxies by means of accretion and merging. The cosmological scenarios are only fragmentarily developed but propose and pretend to...

  15. Brane-world black holes

    International Nuclear Information System (INIS)

    In this talk, I present and discuss a number of attempts to construct black hole solutions in models with Warped Extra Dimensions. Then, a contact is made with models with Large Extra Dimensions, where black-hole solutions are easily constructed - here the focus will be on the properties of microscopic black holes and the possibility of using phenomena associated with them, such as the emission of Hawking radiation, to discover fundamental properties of our spacetime.

  16. A preliminary factor analytic investigation into the firstorder factor structure of the Fifteen Factor Plus (15FQ+ on a sample of Black South African managers

    Directory of Open Access Journals (Sweden)

    Seretse Moyo

    2011-03-01

    Full Text Available Orientation: The Fifteen Factor Questionnaire Plus (15FQ+ is a prominent personality questionnaire that organisations frequently use in personnel selection in South Africa.Research purpose: The primary objective of this study was to undertake a factor analytic investigation of the first-order factor structure of the 15FQ+.Motivation for the study: The construct validity of the 15FQ+, as a measure of personality, is necessary even though it is insufficient to justify its use in personnel selection.Research design, approach and method: The researchers evaluated the fit of the measurement model, which the structure and scoring key of the 15FQ+ implies, in a quantitative study that used an ex post facto correlation design through structural equation modelling. They conducted a secondary data analysis. They selected a sample of 241 Black South African managers from a large 15FQ+ database.Main findings: The researchers found good measurement model fit. The measurement model parameter estimates were worrying. The magnitude of the estimated model parameters suggests that the items generally do not reflect the latent personality dimensions the designers intended them to with a great degree of precision. The items are reasonably noisy measures of the latent variables they represent.Practical/managerial implications: Organisations should use the 15FQ+ carefully on Black South African managers until further local research evidence becomes available.Contribution/value-add: The study is a catalyst to trigger the necessary additional research we need to establish convincingly the psychometric credentials of the 15FQ+ as a valuable assessment tool in South Africa.

  17. In black South Africans from rural and urban communities, the 4G/5G PAI-1 polymorphism influences PAI-1 activity, but not plasma clot lysis time.

    Directory of Open Access Journals (Sweden)

    Zelda de Lange

    Full Text Available Data on genetic and environmental factors influencing PAI-1 levels and their consequent effect on clot lysis in black African populations are limited. We identified polymorphisms in the promoter area of the PAI-1 gene and determined their influence on PAI-1act levels and plasma clot lysis time (CLT. We also describe gene-environment interactions and the effect of urbanisation. Data from 2010 apparently healthy urban and rural black participants from the South African arm of the PURE study were cross-sectionally analysed. The 5G allele frequency of the 4G/5G polymorphism was 0.85. PAI-1act increased across genotypes in the urban subgroup (p = 0.009 but not significantly in the rural subgroup, while CLT did not differ across genotypes. Significant interaction terms were found between the 4G/5G polymorphism and BMI, waist circumference and triglycerides in determining PAI-1act, and between the 4G/5G polymorphism and fibrinogen and fibrinogen gamma prime in determining CLT. The C428T and G429A polymorphisms did not show direct relationships with PAI-1act or CLT but they did influence the association of other environmental factors with PAI-1act and CLT. Several of these interactions differed significantly between rural and urban subgroups, particularly in individuals harbouring the mutant alleles. In conclusion, although the 4G/5G polymorphism significantly affected PAI-1act, it contributed less than 1% to the PAI-1act variance. (Central obesity was the biggest contributor to PAI-1act variance (12.5%. Urbanisation significantly influenced the effect of the 4G/5G polymorphism on PAI-1act as well as gene-environment interactions for the C428T and G429A genotypes in determining PAI-1act and CLT.

  18. Black holes and the multiverse

    Science.gov (United States)

    Garriga, Jaume; Vilenkin, Alexander; Zhang, Jun

    2016-02-01

    Vacuum bubbles may nucleate and expand during the inflationary epoch in the early universe. After inflation ends, the bubbles quickly dissipate their kinetic energy; they come to rest with respect to the Hubble flow and eventually form black holes. The fate of the bubble itself depends on the resulting black hole mass. If the mass is smaller than a certain critical value, the bubble collapses to a singularity. Otherwise, the bubble interior inflates, forming a baby universe, which is connected to the exterior FRW region by a wormhole. A similar black hole formation mechanism operates for spherical domain walls nucleating during inflation. As an illustrative example, we studied the black hole mass spectrum in the domain wall scenario, assuming that domain walls interact with matter only gravitationally. Our results indicate that, depending on the model parameters, black holes produced in this scenario can have significant astrophysical effects and can even serve as dark matter or as seeds for supermassive black holes. The mechanism of black hole formation described in this paper is very generic and has important implications for the global structure of the universe. Baby universes inside super-critical black holes inflate eternally and nucleate bubbles of all vacua allowed by the underlying particle physics. The resulting multiverse has a very non-trivial spacetime structure, with a multitude of eternally inflating regions connected by wormholes. If a black hole population with the predicted mass spectrum is discovered, it could be regarded as evidence for inflation and for the existence of a multiverse.

  19. How black holes saved relativity

    Science.gov (United States)

    Prescod-Weinstein, Chanda

    2016-02-01

    While there have been many popular-science books on the historical and scientific legacy of Albert Einstein's general theory of relativity, a gap exists in the literature for a definitive, accessible history of the theory's most famous offshoot: black holes. In Black Hole, the science writer Marcia Bartusiak aims for a discursive middle ground, writing solely about black holes at a level suitable for both high-school students and more mature readers while also giving some broader scientific context for black-hole research.

  20. Black report up-date

    International Nuclear Information System (INIS)

    In 1984, the Black Report published its results on the incidence of cancer and leukaemia in under 25-year olds in the village of Seascale and the surrounding area near the Sellafield nuclear reprocessing plant. Since then the pressure group core, as a result of their own independent research, has discovered ten additional cases of childhood cancer which should have been included in the Black Report and a Further two cases since the Black Report was written. This represents an additional 31% over the initial numbers considered and a review of the Black Report is sought. (UK)

  1. Pyrolytic carbon coated black silicon.

    Science.gov (United States)

    Shah, Ali; Stenberg, Petri; Karvonen, Lasse; Ali, Rizwan; Honkanen, Seppo; Lipsanen, Harri; Peyghambarian, N; Kuittinen, Markku; Svirko, Yuri; Kaplas, Tommi

    2016-01-01

    Carbon is the most well-known black material in the history of man. Throughout the centuries, carbon has been used as a black material for paintings, camouflage, and optics. Although, the techniques to make other black surfaces have evolved and become more sophisticated with time, carbon still remains one of the best black materials. Another well-known black surface is black silicon, reflecting less than 0.5% of incident light in visible spectral range but becomes a highly reflecting surface in wavelengths above 1000 nm. On the other hand, carbon absorbs at those and longer wavelengths. Thus, it is possible to combine black silicon with carbon to create an artificial material with very low reflectivity over a wide spectral range. Here we report our results on coating conformally black silicon substrate with amorphous pyrolytic carbon. We present a superior black surface with reflectance of light less than 0.5% in the spectral range of 350 nm to 2000 nm. PMID:27174890

  2. Thermodynamics of Accelerating Black Holes

    CERN Document Server

    Appels, Michael; Kubiznak, David

    2016-01-01

    We address a long-standing problem of describing the thermodynamics of a charged accelerating black hole. We derive a standard first law of black hole thermodynamics, with the usual identification of entropy proportional to the area of the event horizon -- even though the event horizon contains a conical singularity. This result not only extends the applicability of black hole thermodynamics to realms previously not anticipated, it also opens a possibility for studying novel properties of an important class of exact radiative solutions of Einstein equations describing accelerated objects. We discuss the thermodynamic volume, stability and phase structure of these black holes.

  3. Acceleration of black hole universe

    Science.gov (United States)

    Zhang, T. X.; Frederick, C.

    2014-01-01

    Recently, Zhang slightly modified the standard big bang theory and developed a new cosmological model called black hole universe, which is consistent with Mach's principle, governed by Einstein's general theory of relativity, and able to explain all observations of the universe. Previous studies accounted for the origin, structure, evolution, expansion, and cosmic microwave background radiation of the black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This paper investigates acceleration of the black hole universe and provides an alternative explanation for the redshift and luminosity distance measurements of type Ia supernovae. The results indicate that the black hole universe accelerates its expansion when it accretes the ambient matter in an increasing rate. In other words, i.e., when the second-order derivative of the mass of the black hole universe with respect to the time is positive . For a constant deceleration parameter , we can perfectly explain the type Ia supernova measurements with the reduced chi-square to be very close to unity, χ red˜1.0012. The expansion and acceleration of black hole universe are driven by external energy.

  4. Excessive daytime sleepiness and adherence to antihypertensive medications among Blacks: analysis of the counseling African Americans to control hypertension (CAATCH trial

    Directory of Open Access Journals (Sweden)

    Williams NJ

    2014-03-01

    Full Text Available Natasha J Williams,1 Girardin Jean-Louis,1 Abhishek Pandey,2 Joseph Ravenell,1 Carla Boutin-Foster,3 Gbenga Ogedegbe1 1Center for Healthful Behavior Change, Division of Internal Medicine, NYU Medical Center, New York, 2Department of Family Medicine, SUNY Downstate Medical Center, Brooklyn, 3Center of Excellence in Disparities Research, Weill Cornell Medical College, New York, NY, USA Background: Excessive daytime sleepiness (EDS often occurs as a result of insufficient sleep, sleep apnea, illicit substance use, and other medical and psychiatric conditions. This study tested the hypothesis that blacks exhibiting EDS would have poorer self-reported adherence to hypertensive medication using cross-sectional data from the Counseling African-Americans to Control Hypertension (CAATCH trial. Methods: A total of 1,058 hypertensive blacks (average age 57±12 years participated in CAATCH, a randomized controlled trial evaluating the effectiveness of a multilevel intervention for participants who receive care from community health centers in New York City. Data analyzed in this study included baseline sociodemographics, medical history, EDS, and medication adherence. We used the Epworth Sleepiness Scale, with a cutoff score of ≥10, to define EDS. Medication adherence was measured using an abbreviated Morisky Medication Adherence scale, with a score >0 indicating nonadherence. Results: Of the sample, 71% were female, 72% received at least a high school education, 51% reported a history of smoking, and 33% had a history of alcohol consumption. Overall, 27% of the participants exhibited EDS, and 44% of those who exhibited EDS were classified as adherent to prescribed antihypertensive medications. Multivariable logistic regression analysis, adjusting for effects of age, body mass index, sex, education, and smoking and drinking history indicated that participants who exhibited EDS were more than twice as likely to be nonadherent (odds ratio 2.28, 95

  5. Identité et marchandisation : Le cas des black memorabilia et black collectibles Identity and Commodification: The Case of Black Memorabilia and Black Collectibles

    Directory of Open Access Journals (Sweden)

    Eliane Elmaleh

    2009-07-01

    Full Text Available The aim of this article is to raise the issue of the commodification of African American culture, mainly through a certain form of art that has re-emerged with Black memorabilia which paradoxically fit into a black-driven market. However, these items penetrated American culture from 1920 to the 1950s to convey images of black people as lazy, stupid, childlike and happy. This condition of permanent happiness, typified by a broad smile and white teeth, was a fundamental component of this racist and stereotyped imagery. Thus, this article focuses on the thin border between racism and the denunciation of racism, commodification and denunciation of commodification, art and its by-products being always co-opted in the specific logic of private productivity.

  6. stu Black Holes Unveiled

    Directory of Open Access Journals (Sweden)

    Armen Yeranyan

    2008-10-01

    Full Text Available The general solutions of the radial attractor flow equations for extremal black holes, both for non-BPS with non-vanishing central charge Z and for Z = 0, are obtained for the so-called stu model, the minimal rank-3 N = 2 symmetric supergravity in d = 4 space-time dimensions. Comparisons with previous partial results, as well as the fake supergravity (first order formalism and an analysis of the marginal stability of corresponding D-brane configurations, are given.

  7. Black luminescent silicon

    Energy Technology Data Exchange (ETDEWEB)

    Pezoldt, Joerg [FG Nanotechnologie, Institut fuer Mikro- und Nanotechnologie, TU Ilmenau, Postfach 100565, 98684 Ilmenau (Germany); Kups, Thomas [FG Werkstoffe der Elektrotechnik, Institut fuer Mikro- und Nanotechnologien, TU Ilmenau, Postfach 1005765, 98684 Ilmenau (Germany); Stubenrauch, Mike [FG Mikromechanische Systeme, Institut fuer Mikro- und Nanotechnologien, TU Ilmenau, Postfach 1005765, 98684 Ilmenau (Germany); Fischer, Michael [FG Elektroniktechnologie, Institut fuer Mikro- und Nanotechnologien, TU Ilmenau, Postfach 1005765, 98684 Ilmenau (Germany)

    2011-03-15

    Black silicon is a fascinating multipurpose modification of bulk silicon which can be fabricated in a selforganized structure formation process during dry etching of bare silicon wafer leading to the formation of a high density of silicon needles. The smallest dimension of the tips approaches values between 1 and 2 nm. The silicon nanostructure exhibits an extremely low diffuse reflectivity. The nanosized tips and their coating with fluorine doped nonstoichiometric silicon dioxide are responsible for cathodoluminescence in the blue-green and red regions of the visible spectra (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Noncommutative black holes

    Science.gov (United States)

    Bastos, C.; Bertolami, O.; Dias, N. C.; Prata, J. N.

    2010-04-01

    One considers phase-space noncommutativity in the context of a Kantowski-Sachs cosmological model to study the interior of a Schwarzschild black hole. It is shown that the potential function of the corresponding quantum cosmology problem has a local minimum. One deduces the thermodynamics and show that the Hawking temperature and entropy exhibit an explicit dependence on the momentum noncommutativity parameter, η. Furthermore, the t = r = 0 singularity is analysed in the noncommutative regime and it is shown that the wave function vanishes in this limit.

  9. Noncommutative black holes

    Energy Technology Data Exchange (ETDEWEB)

    Bastos, C; Bertolami, O [Departamento de Fisica, Instituto Superior Tecnico, Avenida Rovisco Pais 1, 1049-001 Lisboa (Portugal); Dias, N C; Prata, J N, E-mail: cbastos@fisica.ist.utl.p, E-mail: orfeu@cosmos.ist.utl.p, E-mail: ncdias@mail.telepac.p, E-mail: joao.prata@mail.telepac.p [Departamento de Matematica, Universidade Lusofona de Humanidades e Tecnologias, Avenida Campo Grande, 376, 1749-024 Lisboa (Portugal)

    2010-04-01

    One considers phase-space noncommutativity in the context of a Kantowski-Sachs cosmological model to study the interior of a Schwarzschild black hole. It is shown that the potential function of the corresponding quantum cosmology problem has a local minimum. One deduces the thermodynamics and show that the Hawking temperature and entropy exhibit an explicit dependence on the momentum noncommutativity parameter, {eta}. Furthermore, the t = r = 0 singularity is analysed in the noncommutative regime and it is shown that the wave function vanishes in this limit.

  10. Noncommutative black holes

    International Nuclear Information System (INIS)

    One considers phase-space noncommutativity in the context of a Kantowski-Sachs cosmological model to study the interior of a Schwarzschild black hole. It is shown that the potential function of the corresponding quantum cosmology problem has a local minimum. One deduces the thermodynamics and show that the Hawking temperature and entropy exhibit an explicit dependence on the momentum noncommutativity parameter, η. Furthermore, the t = r = 0 singularity is analysed in the noncommutative regime and it is shown that the wave function vanishes in this limit.

  11. Thermal BEC Black Holes

    Directory of Open Access Journals (Sweden)

    Roberto Casadio

    2015-10-01

    Full Text Available We review some features of Bose–Einstein condensate (BEC models of black holes obtained by means of the horizon wave function formalism. We consider the Klein–Gordon equation for a toy graviton field coupled to a static matter current in a spherically-symmetric setup. The classical field reproduces the Newtonian potential generated by the matter source, while the corresponding quantum state is given by a coherent superposition of scalar modes with a continuous occupation number. An attractive self-interaction is needed for bound states to form, the case in which one finds that (approximately one mode is allowed, and the system of N bosons can be self-confined in a volume of the size of the Schwarzschild radius. The horizon wave function formalism is then used to show that the radius of such a system corresponds to a proper horizon. The uncertainty in the size of the horizon is related to the typical energy of Hawking modes: it decreases with the increasing of the black hole mass (larger number of gravitons, resulting in agreement with the semiclassical calculations and which does not hold for a single very massive particle. The spectrum of these systems has two components: a discrete ground state of energy m (the bosons forming the black hole and a continuous spectrum with energy ω > m (representing the Hawking radiation and modeled with a Planckian distribution at the expected Hawking temperature. Assuming the main effect of the internal scatterings is the Hawking radiation, the N-particle state can be collectively described by a single-particle wave-function given by a superposition of a total ground state with energy M = Nm and Entropy 2015, 17 6894 a Planckian distribution for E > M at the same Hawking temperature. This can be used to compute the partition function and to find the usual area law for the entropy, with a logarithmic correction related to the Hawking component. The backreaction of modes with ω > m is also shown to reduce

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

    Science.gov (United States)

    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.

  13. Area spectrum of slowly rotating black holes

    OpenAIRE

    Myung, Yun Soo

    2010-01-01

    We investigate the area spectrum for rotating black holes which are Kerr and BTZ black holes. For slowly rotating black holes, we use the Maggiore's idea combined with Kunstatter's method to derive their area spectra, which are equally spaced.

  14. Spacetime Duality of BTZ Black Hole

    OpenAIRE

    Ho, Jeongwon; Kim, Won T.; Park, Young-Jai

    1999-01-01

    We consider the duality of the quasilocal black hole thermodynamics, explicitly the quasilocal black hole thermodynamic first law, in BTZ black hole solution as a special one of the three-dimensional low energy effective string theory.

  15. Empowering Young Black Males--III: A Systematic Modular Training Program for Black Male Children & Adolescents.

    Science.gov (United States)

    Lee, Courtland C.

    This series of five interrelated modules is an update and revision of "Saving the Native Son: Empowerment Strategies for Young Black Males (1996)." It offers specific strategies for empowering young African American males to help them achieve optimal educational and social success. Empowerment is a developmental process by which people who are…

  16. Noted black American psychologist to deliver keynote address during Black History Month

    OpenAIRE

    Felker, Susan B.

    2005-01-01

    A pioneer in the development of an African-centered approach to modern psychology, the noted clinical psychologist and author Na'im Akbar of Florida State University, will deliver the keynote address for Virginia Tech's Black History Month observances at 7 p.m. Thursday, Feb. 3, in the Haymarket Theatre, Squires Student Center.

  17. A Repository of Hope for Social Justice: Black Women Leaders at Historically Black Colleges and Universities

    Science.gov (United States)

    Jean-Marie, Gaetane; Normore, Anthony H.

    2006-01-01

    The 1954 ruling of "Brown v. Board of Education" by the U.S. Supreme Court impacted the social lives of African Americans. The primary purpose of this research was to examine the experiences and struggles for social justice in education and educational institutions as viewed from the context of historically Black colleges and universities (HBCU)…

  18. Twistors and Black Holes

    CERN Document Server

    Neitzke, A; Vandoren, S; Neitzke, Andrew; Pioline, Boris; Vandoren, Stefan

    2007-01-01

    Motivated by black hole physics in N=2, D=4 supergravity, we study the geometry of quaternionic-Kahler manifolds M obtained by the c-map construction from projective special Kahler manifolds M_s. Improving on earlier treatments, we compute the Kahler potentials on the twistor space Z and Swann space S in the complex coordinates adapted to the Heisenberg symmetries. The results bear a simple relation to the Hesse potential \\Sigma of the special Kahler manifold M_s, and hence to the Bekenstein-Hawking entropy for BPS black holes. We explicitly construct the ``covariant c-map'' and the ``twistor map'', which relate real coordinates on M x CP^1 (resp. M x R^4/Z_2) to complex coordinates on Z (resp. S). As applications, we solve for the general BPS geodesic motion on M, and provide explicit integral formulae for the quaternionic Penrose transform relating elements of H^1(Z,O(-k)) to massless fields on M annihilated by first or second order differential operators. Finally, we compute the exact radial wave function ...

  19. Transient Black Hole Binaries

    CERN Document Server

    Belloni, T M

    2016-01-01

    The last two decades have seen a great improvement in our understand- ing of the complex phenomenology observed in transient black-hole binary systems, especially thanks to the activity of the Rossi X-Ray Timing Explorer satellite, com- plemented by observations from many other X-ray observatories and ground-based radio, optical and infrared facilities. Accretion alone cannot describe accurately the intricate behavior associated with black-hole transients and it is now clear that the role played by different kinds of (often massive) outflows seen at different phases of the outburst evolution of these systems is as fundamental as the one played by the accretion process itself. The spectral-timing states originally identified in the X-rays and fundamentally based on the observed effect of accretion, have acquired new importance as they now allow to describe within a coherent picture the phenomenology observed at other wave- length, where the effects of ejection processes are most evident. With a particular focu...

  20. Quantum black hole evaporation

    CERN Document Server

    Schoutens, K; Verlinde, Erik; Schoutens, Kareljan; Verlinde, Erik; Verlinde, Herman

    1993-01-01

    We investigate a recently proposed model for a full quantum description of two-dimensional black hole evaporation, in which a reflecting boundary condition is imposed in the strong coupling region. It is shown that in this model each initial state is mapped to a well-defined asymptotic out-state, provided one performs a certain projection in the gravitational zero mode sector. We find that for an incoming localized energy pulse, the corresponding out-going state contains approximately thermal radiation, in accordance with semi-classical predictions. In addition, our model allows for certain acausal strong coupling effects near the singularity, that give rise to corrections to the Hawking spectrum and restore the coherence of the out-state. To an asymptotic observer these corrections appear to originate from behind the receding apparent horizon and start to influence the out-going state long before the black hole has emitted most of its mass. Finally, by putting the system in a finite box, we are able to deriv...

  1. Thermal BEC black holes

    CERN Document Server

    Casadio, Roberto; Micu, Octavian; Orlandi, Alessio

    2015-01-01

    We review some features of BEC models of black holes obtained by means of the HWF formalism. We consider the KG equation for a toy graviton field coupled to a static matter current in spherical symmetry. The classical field reproduces the Newtonian potential generated by the matter source, while the corresponding quantum state is given by a coherent superposition of scalar modes with continuous occupation number. An attractive self-interaction is needed for bound states to form, so that (approximately) one mode is allowed, and the system of N bosons can be self-confined in a volume of the size of the Schwarzschild radius. The HWF is then used to show that the radius of such a system corresponds to a proper horizon. The uncertainty in the size of the horizon is related to the typical energy of Hawking modes: it decreases with the increasing of the black hole mass (larger number of gravitons), in agreement with semiclassical calculations and different from a single very massive particle. The spectrum contains a...

  2. Thermal corpuscular black holes

    CERN Document Server

    Casadio, Roberto; Orlandi, Alessio

    2015-01-01

    We study the corpuscular model of an evaporating black hole consisting of a specific quantum state for a large number $N$ of self-confined bosons. The single-particle spectrum contains a discrete ground state of energy $m$ (corresponding to toy gravitons forming the black hole), and a gapless continuous spectrum (to accommodate for the Hawking radiation with energy $\\omega>m$). Each constituent is in a superposition of the ground state and a Planckian distribution at the expected Hawking temperature in the continuum. We first find that, assuming the Hawking radiation is the leading effect of the internal scatterings, the corresponding $N$-particle state can be collectively described by a single-particle wave-function given by a superposition of a total ground state with energy $M=N\\,m$ and a Planckian distribution for $E>M$ at the same Hawking temperature. From this collective state, we compute the partition function and obtain an entropy which reproduces the usual area law with a logarithmic correction preci...

  3. Black hairy tongue syndrome.

    Science.gov (United States)

    Gurvits, Grigoriy E; Tan, Amy

    2014-08-21

    Black hairy tongue (BHT) is a benign medical condition characterized by elongated filiform lingual papillae with typical carpet-like appearance of the dorsum of the tongue. Its prevalence varies geographically, typically ranging from 0.6% to 11.3%. Known predisposing factors include smoking, excessive coffee/black tea consumption, poor oral hygiene, trigeminal neuralgia, general debilitation, xerostomia, and medication use. Clinical presentation varies but is typically asymptomatic, although aesthetic concerns are common. Differential diagnosis includes pseudo-BHT, acanthosis nigricans, oral hairy leukoplakia, pigmented fungiform papillae of the tongue, and congenital melanocytic/melanotic nevi/macules. Clinical diagnosis relies on visual observation, detailed history taking, and occasionally microscopic evaluation. Treatment involves identification and discontinuation of the offending agent, modifications of chronic predisposing factors, patient's re-assurance to the benign nature of the condition, and maintenance of adequate oral hygiene with gentle debridement to promote desquamation. Complications of BHT (burning mouth syndrome, halitosis, nausea, gagging, dysgeusia) typically respond to therapy. Prognosis is excellent with treatment of underlying medical conditions. BHT remains an important medical condition which may result in additional burden on the patient and health care system and requires appropriate prevention, recognition and treatment.

  4. Supersymmetric black holes in string theory

    OpenAIRE

    Mohaupt, T.

    2007-01-01

    We review recent developments concerning supersymmetric black holes in string theory. After a general introduction to the laws of black hole mechanics and to black hole entropy in string theory, we discuss black hole solutions in N=2 supergravity, special geometry, the black hole attractor equations and the underlying variational principle. Special attention is payed to the crucial role of higher derivative corrections. Finally we discuss black hole partition functions and their relation to t...

  5. What, no black hole evaporation

    International Nuclear Information System (INIS)

    Tipler has claimed that the inward flux of negative energy across the horizon which (according to the semi-classical approximation) accompanies the evaporation of a black hole would cause a solar mass black hole to evaporate in less than a second. It is shown that this claim is in error. (orig.)

  6. Nonlinear Electrodynamics and black holes

    CERN Document Server

    Breton, N; Breton, Nora; Garcia-Salcedo, Ricardo

    2007-01-01

    It is addressed the issue of black holes with nonlinear electromagnetic field, focussing mainly in the Born-Infeld case. The main features of these systems are described, for instance, geodesics, energy conditions, thermodynamics and isolated horizon aspects. Also are revised some black hole solutions of alternative nonlinear electrodynamics and its inconveniences.

  7. Black-Hole Mass Measurements

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2004-01-01

    The applicability and apparent uncertainties of the techniques currently available for measuring or estimating black-hole masses in AGNs are briefly summarized.......The applicability and apparent uncertainties of the techniques currently available for measuring or estimating black-hole masses in AGNs are briefly summarized....

  8. Black Component of Dark Matter

    Directory of Open Access Journals (Sweden)

    A. V. Grobov

    2014-01-01

    Full Text Available A mechanism of primordial black hole formation with specific mass spectrum is discussed. It is shown that these black holes could contribute to the energy density of dark matter. Our approach is elaborated in the framework of universal extra dimensions.

  9. ATLAS simulated black hole event

    CERN Multimedia

    Pequenão, J

    2008-01-01

    . The simulated collision event shown is viewed along the beampipe. The event is one in which a microscopic-black-hole was produced in the collision of two protons (not shown). The microscopic-black-hole decayed immediately into many particles. The colors of the tracks show different types of particles emerging from the collision (at the center).

  10. Educating Black Males with Dyslexia

    Science.gov (United States)

    Robinson, Shawn Anthony

    2013-01-01

    Much of the scholarship on Black males in the educational literature focuses on the achievement gap; their underrepresentation in gifted and advanced placement programs; their overrepresentation in special education programs and their high rates of school suspensions and expulsions. Although overrepresented in special education, Black males with…

  11. Black holes in brane worlds

    Indian Academy of Sciences (India)

    M S Modgil; S Panda; S Sengupta

    2004-03-01

    A Kerr metric describing a rotating black hole is obtained on the three brane in a five-dimensional Randall-Sundrum brane world by considering a rotating five-dimensional black string in the bulk. We examine the causal structure of this space-time through the geodesic equations.

  12. Reconceptualizing Retirement for Black Americans.

    Science.gov (United States)

    Gibson, Rose C.

    1987-01-01

    Examined subsample of nonworking older Black Americans (N=295) from the National Survey of Black Americans sample. Found four factors contributed significantly to respondents' unretired-retired status: indistinct line between lifetime and old age work patterns, view that occasional work is necessary, income from other than private pensions, and…

  13. Black raspberry: Korean vs. American

    Science.gov (United States)

    This fact sheet shows Korean black raspberry (Rubus coreanus) fruit, flower, and leaf features that distinguish them from their Rubus relatives, black raspberry (R. occidentalis) native to America. Common names with fruit characteristics, including berry size and pigment fingerprints, are summarized...

  14. The Christian church’s role in the escalating mob justice system in our black townships – An African pastoral view

    Directory of Open Access Journals (Sweden)

    Elijah Baloyi

    2015-02-01

    Full Text Available Among the crimes in the South African black townships, mob justice has become a growing concern. Some questions that need to be asked are: Is our police force doing enough to protect the ordinary citizens of this country? If the situation continues, will all suspects be killed in the same manner or will there be a solution to change the situation? What is the impact of mob justice on the families of the victims and the witnesses of the brutal acts? How long are we going to live as a traumatised nation as a result of these violent acts? Is there any hope that our nation will ever have the peace it deserves in the context of democracy? This article intends to investigate the impact of the mob justice system and find out what the role of the Christian church should be in the midst of this escalating violence. This study aims to unveil the negative impact of mob justice on the lives of many township South Africans and giving pastoral-biblical suggestions of the church’s role in the elimination of this kind of brutality.

  15. Prisons of Light - Black Holes

    Science.gov (United States)

    Ferguson, Kitty

    1998-05-01

    In this jargon-free review of one of the most fascinating topics in modern science, acclaimed science writer Kitty Ferguson examines the discovery of black holes, their nature, and what they can teach us about the mysteries of the universe. In search of the answers, we trace a star from its birth to its death throes, take a hypothetical journey to the border of a black hole and beyond, spend time with some of the world's leading theoretical physicists and astronomers, and take a whimsical look at some of the wild ideas black holes have inspired. Prisons of Light--Black Holes is comprehensive and detailed. Yet Kitty Ferguson's lightness of touch and down-to-earth analogies set this book apart from all others on black holes and make it a wonderfully stimulating and entertaining read.

  16. Black Hole Final State Conspiracies

    CERN Document Server

    McInnes, Brett

    2008-01-01

    The principle that unitarity must be preserved in all processes, no matter how exotic, has led to deep insights into boundary conditions in cosmology and black hole theory. In the case of black hole evaporation, Horowitz and Maldacena were led to propose that unitarity preservation can be understood in terms of a restriction imposed on the wave function at the singularity. Gottesman and Preskill showed that this natural idea only works if one postulates the presence of "conspiracies" between systems just inside the event horizon and states at much later times, near the singularity. We argue that some AdS black holes have unusual internal thermodynamics, and that this may permit the required "conspiracies" if real black holes are described by some kind of sum over all AdS black holes having the same entropy.

  17. Black holes and the multiverse

    CERN Document Server

    Garriga, Jaume; Zhang, Jun

    2015-01-01

    Vacuum bubbles may nucleate and expand during the inflationary epoch in the early universe. After inflation ends, the bubbles quickly dissipate their kinetic energy; they come to rest with respect to the Hubble flow and eventually form black holes. The fate of the bubble itself depends on the resulting black hole mass. If the mass is smaller than a certain critical value, the bubble collapses to a singularity. Otherwise, the bubble interior inflates, forming a baby universe, which is connected to the exterior FRW region by a wormhole. A similar black hole formation mechanism operates for spherical domain walls nucleating during inflation. As an illustrative example, we studied the black hole mass spectrum in the domain wall scenario, assuming that domain walls interact with matter only gravitationally. Our results indicate that, depending on the model parameters, black holes produced in this scenario can have significant astrophysical effects and can even serve as dark matter or as seeds for supermassive blac...

  18. When Charged Black Holes Merge

    Science.gov (United States)

    Kohler, Susanna

    2016-08-01

    Most theoretical models assume that black holes arent charged. But a new study shows that mergers of charged black holes could explain a variety of astrophysical phenomena, from fast radio bursts to gamma-ray bursts.No HairThe black hole no hair theorem states that all black holes can be described by just three things: their mass, their spin, and their charge. Masses and spins have been observed and measured, but weve never measured the charge of a black hole and its widely believed that real black holes dont actually have any charge.That said, weve also never shown that black holes dont have charge, or set any upper limits on the charge that they might have. So lets suppose, for a moment, that its possible for a black hole to be charged. How might that affect what we know about the merger of two black holes? A recent theoretical study by Bing Zhang (University of Nevada, Las Vegas) examines this question.Intensity profile of a fast radio burst, a sudden burst of radio emission that lasts only a few milliseconds. [Swinburne Astronomy Productions]Driving TransientsZhangs work envisions a pair of black holes in a binary system. He argues that if just one of the black holes carries charge possibly retained by a rotating magnetosphere then it may be possible for the system to produce an electromagnetic signal that could accompany gravitational waves, such as a fast radio burst or a gamma-ray burst!In Zhangs model, the inspiral of the two black holes generates a global magnetic dipole thats perpendicular to the plane of the binarys orbit. The magnetic flux increases rapidly as the separation between the black holes decreases, generating an increasingly powerful magnetic wind. This wind, in turn, can give rise to a fast radio burst or a gamma-ray burst, depending on the value of the black holes charge.Artists illustration of a short gamma-ray burst, thought to be caused by the merger of two compact objects. [ESO/A. Roquette]Zhang calculates lower limits on the charge

  19. The Dialectics of African Education and Western Discourses: Counter-Hegemonic Perspectives. Black Studies and Critical Thinking. Volume 21

    Science.gov (United States)

    Wright, Handel Kashope, Ed.; Abdi, Ali A., Ed.

    2012-01-01

    "The Dialectics of African Education and Western Discourses" addresses how continental Africans who have worked or are currently working in the Canadian academy address their dual legacy of African and Euro-American knowledge paradigms. Reflecting a range of approaches to hegemonic Euro-American paradigms that can be summarized as "appropriation,…

  20. Switching on After Nine: Black gay-identified men's perceptions of sexual identities and partnerships in South African towns.

    Science.gov (United States)

    Mantell, Joanne E; Tocco, Jack Ume; Osmand, Thomas; Sandfort, Theo; Lane, Tim

    2016-01-01

    There is considerable diversity, fluidity and complexity in the expressions of sexuality and gender among men who have sex with men (MSM). Some non-gay identified MSM are known colloquially by gay-identified men in Mpumalanga, Province, South Africa, as 'After-Nines' because they do not identify as gay and present as straight during the day but also have sex with other men at night. Based on, key informant interviews and focus group discussions in two districts in Mpumalanga, we explored Black gay-identified men's perceptions of and relationships with After-Nine men, focusing on sexual and gender identities and their social consequences. Gay-identified men expressed ambivalence about their After-Nine partners, desiring them for their masculinity, yet often feeling dissatisfied and exploited in their relationships with them. The exchange of sex for commodities, especially alcohol, was common. Gay men's characterisation of After-Nines as men who ignore them during the day but have sex with them at night highlights the diversity of how same-sex practicing men perceive themselves and their sexual partners. Sexual health promotion programmes targeting 'MSM' must understand this diversity to effectively support the community in developing strategies for reaching and engaging different groups of gay and non-gay identified men. PMID:26878380

  1. Picture Books about Blacks: An Interview with Opal Moore.

    Science.gov (United States)

    MacCann, Donnarae; Richard, Olga

    1991-01-01

    Presents an interview with Opal Moore, who discusses Black imagery in picture books published in the last four years and the institutions that circulate that imagery. Topics discussed include the issue of race pride; interracial themes; appropriate illustrations; African versus African-American books; and the roles of publishers, books reviewers,…

  2. Slicing black hole spacetimes

    CERN Document Server

    Bini, Donato; Geralico, Andrea; Jantzen, Robert T

    2015-01-01

    A general framework is developed to investigate the properties of useful choices of stationary spacelike slicings of stationary spacetimes whose congruences of timelike orthogonal trajectories are interpreted as the world lines of an associated family of observers, the kinematical properties of which in turn may be used to geometrically characterize the original slicings. On the other hand properties of the slicings themselves can directly characterize their utility motivated instead by other considerations like the initial value and evolution problems in the 3-plus-1 approach to general relativity. An attempt is made to categorize the various slicing conditions or "time gauges" used in the literature for the most familiar stationary spacetimes: black holes and their flat spacetime limit.

  3. Postoperative Morbidity and Mortality of Perforated Peptic Ulcer: Retrospective Cohort Study of Risk Factors among Black Africans in Côte d'Ivoire

    Science.gov (United States)

    Gona, Soro Kountele; Marcellin, Koffi Gnangoran; Adama, Coulibaly; Toussaint, Assohoun; Manuela, Ehua Adjoba; Sylvain, Seu Gagon; Anthony, Afum-Adjei Awuah; Francis, Ehua Somian

    2016-01-01

    Introduction. Surgical treatment of perforated peptic ulcer (PPU) is a challenge for surgeons in Africa. Aim. To determine risk factors of postoperative complications or mortality among black Ivoirian patients with PPU. Methods. All 161 patients (median age = 34 years, 90.7 male) operated on for PPU in the visceral and general surgery unit were enrolled in a retrospective cohort study. Variables were studied with Kaplan Meier and Cox proportional hazard models. Results. Among 161 patients operated on for PPU, 36 (27.5%) experienced complications and 31 (19.3%) died. Follow-up results were the incidence of complications and mortality of 6.4 (95% CI: 4.9–8.0) per 100 person-days and 3.0 (95% CI: 1.9–4.0) per 100 person-days for incidence of mortality. In multivariate analysis, risk factors of postoperative complications or mortality were comorbidities (HR = 2.1, P = 0.03), tachycardia (pulse rate > 100/minutes) (HR = 2.4, P = 0.02), purulent intra-abdominal fluid collection (HR = 2.1, P = 0.04), hyponatremia (median value ≤ 134 mEq/L) (HR = 2.3, P = 0.01), delayed time of hospital admission > 72 hours (HR = 2.6, P < 0.0001), and delayed time of surgical intervention between 24 and 48 hours (HR = 3.8, P < 0.0001). Conclusion. The delayed hospital admission or surgical intervention and hyponatremia may be considered as additional risk of postoperative complications or mortality in Black African patients with PPU. PMID:26925099

  4. Postoperative Morbidity and Mortality of Perforated Peptic Ulcer: Retrospective Cohort Study of Risk Factors among Black Africans in Côte d’Ivoire

    Directory of Open Access Journals (Sweden)

    Soro Kountele Gona

    2016-01-01

    Full Text Available Introduction. Surgical treatment of perforated peptic ulcer (PPU is a challenge for surgeons in Africa. Aim. To determine risk factors of postoperative complications or mortality among black Ivoirian patients with PPU. Methods. All 161 patients (median age = 34 years, 90.7 male operated on for PPU in the visceral and general surgery unit were enrolled in a retrospective cohort study. Variables were studied with Kaplan Meier and Cox proportional hazard models. Results. Among 161 patients operated on for PPU, 36 (27.5% experienced complications and 31 (19.3% died. Follow-up results were the incidence of complications and mortality of 6.4 (95% CI: 4.9–8.0 per 100 person-days and 3.0 (95% CI: 1.9–4.0 per 100 person-days for incidence of mortality. In multivariate analysis, risk factors of postoperative complications or mortality were comorbidities (HR = 2.1, P=0.03, tachycardia (pulse rate > 100/minutes (HR = 2.4, P=0.02, purulent intra-abdominal fluid collection (HR = 2.1, P=0.04, hyponatremia (median value ≤ 134 mEq/L (HR = 2.3, P=0.01, delayed time of hospital admission > 72 hours (HR = 2.6, P<0.0001, and delayed time of surgical intervention between 24 and 48 hours (HR = 3.8, P<0.0001. Conclusion. The delayed hospital admission or surgical intervention and hyponatremia may be considered as additional risk of postoperative complications or mortality in Black African patients with PPU.

  5. Tyrosinase-positive oculocutaneous albinism in Southern African blacks: P gene-associated haplotypes suggest a major mutation in the 5{prime} region of the gene

    Energy Technology Data Exchange (ETDEWEB)

    Ramsay, M.; Stevens, G.; Beukering, J. van [Univ. of the Witwatersrand, Johannesburg (South Africa)] [and others

    1994-09-01

    Tyrosinase-positive oculocutaneous albinism (ty-pos OCA) occurs with a prevalence of 1 in 3900 among Southern African (SA) blacks. The major contributors to morbidity and mortality are skin cancer and decreased visual acuity. Two distinct phenotypes occur, namely individuals with ephelides (darkly pigmented patches) and those without. There is complete concordance with regard to ephelus status among siblings. The disorder is linked to markers on chromosome 15q11.2-q12, and no obligatory cross-overs were observed with polymophic markers at the human homolog, P, of the mouse pink eyed dilute gene, p. Contrary to what has been shown for Caucasoid ty-pos OCA, this condition shows locus homogeneity among SA blacks. The P gene is an excellent candidate for ty-pos OCA and mutations in this gene will confirm its role in causing the common form of albinism in SA. Numerous P gene mutations have been described in other populations. In an attempt to detect mutations, the P gene cDNA was used to search for structural rearrangements or polymorphisms. Six polymorphisms (plR10/Scal, 912/Xbal, 912/HincII, 912/TaqI, 1412/TaqI [two systems] and 1412/HindIII) were detected with subclones of the P cDNA and haplotypes were determined in each family. None were clearly associated with an albinism-related rearrangement. However, strong linkage disequilibrium was observed with alleles at loci toward the 5{prime} region of the gene ({triangle}=0.65, 0.57 and 0.80 for the three polymorphisms detected with the 912 subclone), suggesting a major ty-pos OCA mutation in this region. Haplotype analysis provides evidence for a major mutation associated with the same haplotype in individuals with ephelides (8/12 OCA chromosomes) and those without ephelides (24:30). The presence of other ty-pos OCA associated haplotypes indicates several other less common mutations.

  6. 77 FR 70423 - Black Bear Hydro Partners, LLC and Black Bear Development Holdings, LLC and Black Bear SO, LLC...

    Science.gov (United States)

    2012-11-26

    ... Energy Regulatory Commission Black Bear Hydro Partners, LLC and Black Bear Development Holdings, LLC and Black Bear SO, LLC; Notice of Application for Partial Transfer of Licenses, and Soliciting Comments and Motions To Intervene On October 25, 2012, Black Bear Hydro Partners, LLC, sole licensee (transferor)...

  7. The renaissance of black phosphorus

    Science.gov (United States)

    Ling, Xi; Wang, Han; Huang, Shengxi; Xia, Fengnian; Dresselhaus, Mildred S.

    2015-04-01

    One hundred years after its first successful synthesis in the bulk form in 1914, black phosphorus (black P) was recently rediscovered from the perspective of a 2D layered material, attracting tremendous interest from condensed matter physicists, chemists, semiconductor device engineers, and material scientists. Similar to graphite and transition metal dichalcogenides (TMDs), black P has a layered structure but with a unique puckered single-layer geometry. Because the direct electronic band gap of thin film black P can be varied from 0.3 eV to around 2 eV, depending on its film thickness, and because of its high carrier mobility and anisotropic in-plane properties, black P is promising for novel applications in nanoelectronics and nanophotonics different from graphene and TMDs. Black P as a nanomaterial has already attracted much attention from researchers within the past year. Here, we offer our opinions on this emerging material with the goal of motivating and inspiring fellow researchers in the 2D materials community and the broad readership of PNAS to discuss and contribute to this exciting new field. We also give our perspectives on future 2D and thin film black P research directions, aiming to assist researchers coming from a variety of disciplines who are desirous of working in this exciting research field.

  8. Rotating black hole and quintessence

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Sushant G. [Jamia Millia Islamia, Centre for Theoretical Physics, New Delhi (India); University of KwaZulu-Natal, Astrophysics and Cosmology Research Unit, School of Mathematics, Statistics and Computer Science, Private Bag 54001, Durban (South Africa)

    2016-04-15

    We discuss spherically symmetric exact solutions of the Einstein equations for quintessential matter surrounding a black hole, which has an additional parameter (ω) due to the quintessential matter, apart from the mass (M). In turn, we employ the Newman-Janis complex transformation to this spherical quintessence black hole solution and present a rotating counterpart that is identified, for α = -e{sup 2} ≠ 0 and ω = 1/3, exactly as the Kerr-Newman black hole, and as the Kerr black hole when α = 0. Interestingly, for a given value of parameter ω, there exists a critical rotation parameter (a = a{sub E}), which corresponds to an extremal black hole with degenerate horizons, while for a < a{sub E}, it describes a nonextremal black hole with Cauchy and event horizons, and no black hole for a > a{sub E}. We find that the extremal value a{sub E} is also influenced by the parameter ω and so is the ergoregion. (orig.)

  9. A nonsingular rotating black hole

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Sushant G. [Jamia Millia Islamia, Centre for Theoretical Physics, New Delhi (India); University of KwaZulu-Natal, Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, Durban (South Africa)

    2015-11-15

    The spacetime singularities in classical general relativity are inevitable, as predicated by the celebrated singularity theorems. However, it is a general belief that singularities do not exist in Nature and that they are the limitations of the general relativity. In the absence of a welldefined quantum gravity, models of regular black holes have been studied. We employ a probability distribution inspired mass function m(r) to replace the Kerr black hole mass M to represent a nonsingular rotating black hole that is identified asymptotically (r >> k, k > 0 constant) exactly as the Kerr-Newman black hole, and as the Kerr black hole when k = 0. The radiating counterpart renders a nonsingular generalization of Carmeli's spacetime as well as Vaidya's spacetime, in the appropriate limits. The exponential correction factor changing the geometry of the classical black hole to remove the curvature singularity can also be motivated by quantum arguments. The regular rotating spacetime can also be understood as a black hole of general relativity coupled to nonlinear electrodynamics. (orig.)

  10. Black powder in gas pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Sherik, Abdelmounam [Saudi Aramco, Dhahran (Saudi Arabia)

    2009-07-01

    Despite its common occurrence in the gas industry, black powder is a problem that is not well understood across the industry, in terms of its chemical and physical properties, source, formation, prevention or management of its impacts. In order to prevent or effectively manage the impacts of black powder, it is essential to have knowledge of its chemical and physical properties, formation mechanisms and sources. The present paper is divided into three parts. The first part of this paper is a synopsis of published literature. The second part reviews the recent laboratory and field work conducted at Saudi Aramco Research and Development Center to determine the compositions, properties, sources and formation mechanisms of black powder in gas transmission systems. Microhardness, nano-indentation, X-ray Diffraction (XRD), X-ray Fluorescence (XRF) and Scanning Electron Microscopy (SEM) techniques were used to analyze a large number of black powder samples collected from the field. Our findings showed that black powder is generated inside pipelines due to internal corrosion and that the composition of black powder is dependent on the composition of transported gas. The final part presents a summary and brief discussion of various black powder management methods. (author)

  11. A nonsingular rotating black hole

    International Nuclear Information System (INIS)

    The spacetime singularities in classical general relativity are inevitable, as predicated by the celebrated singularity theorems. However, it is a general belief that singularities do not exist in Nature and that they are the limitations of the general relativity. In the absence of a welldefined quantum gravity, models of regular black holes have been studied. We employ a probability distribution inspired mass function m(r) to replace the Kerr black hole mass M to represent a nonsingular rotating black hole that is identified asymptotically (r >> k, k > 0 constant) exactly as the Kerr-Newman black hole, and as the Kerr black hole when k = 0. The radiating counterpart renders a nonsingular generalization of Carmeli's spacetime as well as Vaidya's spacetime, in the appropriate limits. The exponential correction factor changing the geometry of the classical black hole to remove the curvature singularity can also be motivated by quantum arguments. The regular rotating spacetime can also be understood as a black hole of general relativity coupled to nonlinear electrodynamics. (orig.)

  12. Acceleration of Black Hole Universe

    Science.gov (United States)

    Zhang, Tianxi

    2012-05-01

    An alternative cosmological model called black hole universe has been recently proposed by the author. According to this model, the universe originated from a hot star-like black hole, and gradually grew up through a supermassive black hole to the present state by accreting ambient materials and merging with other black holes. The entire space is structured with an infinite number of layers hierarchically. The innermost three layers are the universe that we live, the outside space called mother universe, and the inside star-like and supermassive black holes called child universes. The outermost layer has an infinite radius and limits to zero for both the mass density and absolute temperature. All layers or universes are governed by the same physics, the Einstein general theory of relativity with the Robertson-Walker metric of space-time, and tend to expand outward physically. The evolution of the space structure is iterative. When one universe expands out, a new similar universe grows up from its inside. In this study. we will analyze the acceleration of black hole universe that accretes its ambient matter in an increasing rate. We will also compare the result obtained from the black hole universe model with the measurement of type Ia supernova and the result from the big bang cosmology.

  13. Quantum mechanics of black holes.

    Science.gov (United States)

    Witten, Edward

    2012-08-01

    The popular conception of black holes reflects the behavior of the massive black holes found by astronomers and described by classical general relativity. These objects swallow up whatever comes near and emit nothing. Physicists who have tried to understand the behavior of black holes from a quantum mechanical point of view, however, have arrived at quite a different picture. The difference is analogous to the difference between thermodynamics and statistical mechanics. The thermodynamic description is a good approximation for a macroscopic system, but statistical mechanics describes what one will see if one looks more closely.

  14. Thermodynamics of Lifshitz black holes

    Science.gov (United States)

    Devecioǧlu, Deniz Olgu; Sarıoǧlu, Özgür

    2011-06-01

    We apply the recently extended conserved Killing charge definition of Abbott-Deser-Tekin formalism to compute, for the first time, the energies of analytic Lifshitz black holes in higher dimensions. We then calculate the temperature and the entropy of this large family of solutions, and study and discuss the first law of black hole thermodynamics. Along the way we also identify the possible critical points of the relevant quadratic curvature gravity theories. Separately, we also apply the generalized Killing charge definition to compute the energy and the angular momentum of the warped AdS3 black hole solution of the three-dimensional new massive gravity theory.

  15. Black holes and Higgs stability

    CERN Document Server

    Tetradis, Nikolaos

    2016-01-01

    We study the effect of primordial black holes on the classical rate of nucleation of AdS regions within the standard electroweak vacuum. We find that the energy barrier for transitions to the new vacuum, which characterizes the exponential suppression of the nucleation rate, can be reduced significantly in the black-hole background. A precise analysis is required in order to determine whether the the existence of primordial black holes is compatible with the form of the Higgs potential at high temperature or density in the Standard Model or its extensions.

  16. Static-Fluid Black Holes

    CERN Document Server

    Cho, Inyong

    2016-01-01

    We investigate black holes formed by static perfect fluid with $p=-\\rho/3$. These represent the black holes in $S_3$ and $H_3$ spatial geometries. There are three classes of black-hole solutions, two $S_3$ types and one $H_3$ type. The interesting solution is the one of $S_3$ type which possesses two singularities. The one is at the north pole behind the horizon, and the other is naked at the south pole. The observers, however, are free from falling to the naked singularity. There are also nonstatic cosmological solutions in $S_3$ and $H_3$, and a singular static solution in $H_3$.

  17. Quantum black hole without singularity

    CERN Document Server

    Kiefer, Claus

    2015-01-01

    We discuss the quantization of a spherical dust shell in a rigorous manner. Classically, the shell can collapse to form a black hole with a singularity. In the quantum theory, we construct a well-defined self-adjoint extension for the Hamilton operator. As a result, the evolution is unitary and the singularity is avoided. If we represent the shell initially by a narrow wave packet, it will first contract until it reaches the region where classically a black hole would form, but then re-expands to infinity. In a way, the state can be interpreted as a superposition of a black hole with a white hole.

  18. Orbital resonances around black holes.

    Science.gov (United States)

    Brink, Jeandrew; Geyer, Marisa; Hinderer, Tanja

    2015-02-27

    We compute the length and time scales associated with resonant orbits around Kerr black holes for all orbital and spin parameters. Resonance-induced effects are potentially observable when the Event Horizon Telescope resolves the inner structure of Sgr A*, when space-based gravitational wave detectors record phase shifts in the waveform during the resonant passage of a compact object spiraling into the black hole, or in the frequencies of quasiperiodic oscillations for accreting black holes. The onset of geodesic chaos for non-Kerr spacetimes should occur at the resonance locations quantified here. PMID:25768747

  19. The Black Hole Information Problem

    CERN Document Server

    Polchinski, Joseph

    2016-01-01

    The black hole information problem has been a challenge since Hawking's original 1975 paper. It led to the discovery of AdS/CFT, which gave a partial resolution of the paradox. However, recent developments, in particular the firewall puzzle, show that there is much that we do not understand. I review the black hole, Hawking radiation, and the Page curve, and the classic form of the paradox. I discuss AdS/CFT as a partial resolution. I then discuss black hole complementarity and its limitations, leading to many proposals for different kinds of `drama.' I conclude with some recent ideas.

  20. Can Black Hole Relax Unitarily?

    CERN Document Server

    Solodukhin, S N

    2004-01-01

    We review the way the BTZ black hole relaxes back to thermal equilibrium after a small perturbation and how it is seen in the boundary (finite volume) CFT. The unitarity requires the relaxation to be quasi-periodic. It is preserved in the CFT but is not obvious in the case of the semiclassical black hole the relaxation of which is driven by complex quasi-normal modes. We discuss two ways of modifying the semiclassical black hole geometry to maintain unitarity: the (fractal) brick wall and the worm-hole modification. In the latter case the entropy comes out correctly as well.

  1. Orbital resonances around black holes.

    Science.gov (United States)

    Brink, Jeandrew; Geyer, Marisa; Hinderer, Tanja

    2015-02-27

    We compute the length and time scales associated with resonant orbits around Kerr black holes for all orbital and spin parameters. Resonance-induced effects are potentially observable when the Event Horizon Telescope resolves the inner structure of Sgr A*, when space-based gravitational wave detectors record phase shifts in the waveform during the resonant passage of a compact object spiraling into the black hole, or in the frequencies of quasiperiodic oscillations for accreting black holes. The onset of geodesic chaos for non-Kerr spacetimes should occur at the resonance locations quantified here.

  2. Can Black Hole Relax Unitarily?

    Science.gov (United States)

    Solodukhin, S. N.

    2005-03-01

    We review the way the BTZ black hole relaxes back to thermal equilibrium after a small perturbation and how it is seen in the boundary (finite volume) CFT. The unitarity requires the relaxation to be quasi-periodic. It is preserved in the CFT but is not obvious in the case of the semiclassical black hole the relaxation of which is driven by complex quasi-normal modes. We discuss two ways of modifying the semiclassical black hole geometry to maintain unitarity: the (fractal) brick wall and the worm-hole modification. In the latter case the entropy comes out correctly as well.

  3. Accretion, Primordial Black Holes and Standard Cosmology

    OpenAIRE

    Nayak, Bibekananda; Singh, Lambodar Prasad

    2009-01-01

    Primordial Black Holes evaporate due to Hawking radiation. We find that the evaporation time of primordial black holes increase when accretion of radiation is included.Thus depending on accretion efficiency more and more number of primordial black holes are existing today, which strengthens the idea that the primordial black holes are the proper candidate for dark matter.

  4. Accretion, primordial black holes and standard cosmology

    Indian Academy of Sciences (India)

    B Nayak; P Singh

    2011-01-01

    Primordial black holes evaporate due to Hawking radiation. We find that the evaporation times of primordial black holes increase when accretion of radiation is included. Thus, depending on accretion efficiency, more primordial black holes are existing today, which strengthens the conjecture that the primordial black holes are the proper candidates for dark matter.

  5. Black Hole Complementary Principle and Noncommutative Membrane

    International Nuclear Information System (INIS)

    In the spirit of black hole complementary principle, we have found the noncommutative membrane of Scharzchild black holes. In this paper we extend our results to Kerr black hole and see the same story. Also we make a conjecture that spacetimes are noncommutative on the stretched membrane of the more general Kerr-Newman black hole.

  6. Towards a Theory of Quantum Black Hole

    OpenAIRE

    Berezin, V.

    2001-01-01

    We describe some specific quantum black hole model. It is pointed out that the origin of a black hole entropy is the very process of quantum gravitational collapse. The quantum black hole mass spectrum is extracted from the mass spectrum of the gravitating source. The classical analog of quantum black hole is constructed.

  7. The Core Journal Concept in Black Studies

    Science.gov (United States)

    Weissinger, Thomas

    2010-01-01

    Black Studies scholars have shown interest in the core journal concept. Indeed, the idea of core journals for the study of the Black experience has changed several times since 1940. While Black Studies scholars are citing Black Studies journals with frequency, they also cite traditional disciplinary journals a great deal of the time. However,…

  8. Erratic Black Hole Regulates Itself

    Science.gov (United States)

    2009-03-01

    New results from NASA's Chandra X-ray Observatory have made a major advance in explaining how a special class of black holes may shut off the high-speed jets they produce. These results suggest that these black holes have a mechanism for regulating the rate at which they grow. Black holes come in many sizes: the supermassive ones, including those in quasars, which weigh in at millions to billions of times the mass of the Sun, and the much smaller stellar-mass black holes which have measured masses in the range of about 7 to 25 times the Sun's mass. Some stellar-mass black holes launch powerful jets of particles and radiation, like seen in quasars, and are called "micro-quasars". The new study looks at a famous micro-quasar in our own Galaxy, and regions close to its event horizon, or point of no return. This system, GRS 1915+105 (GRS 1915 for short), contains a black hole about 14 times the mass of the Sun that is feeding off material from a nearby companion star. As the material swirls toward the black hole, an accretion disk forms. This system shows remarkably unpredictable and complicated variability ranging from timescales of seconds to months, including 14 different patterns of variation. These variations are caused by a poorly understood connection between the disk and the radio jet seen in GRS 1915. Chandra, with its spectrograph, has observed GRS 1915 eleven times since its launch in 1999. These studies reveal that the jet in GRS 1915 may be periodically choked off when a hot wind, seen in X-rays, is driven off the accretion disk around the black hole. The wind is believed to shut down the jet by depriving it of matter that would have otherwise fueled it. Conversely, once the wind dies down, the jet can re-emerge. "We think the jet and wind around this black hole are in a sort of tug of war," said Joseph Neilsen, Harvard graduate student and lead author of the paper appearing in the journal Nature. "Sometimes one is winning and then, for reasons we don

  9. Homophobia, hypermasculinity and the US black church.

    Science.gov (United States)

    Ward, Elijah G

    2005-01-01

    Black churches in the USA constitute a significant source of the homophobia that pervades black communities. This theologically-driven homophobia is reinforced by the anti-homosexual rhetoric of black nationalism. Drawing on a variety of sources, this paper discusses the sources of homophobia within black communities, and its impact upon self-esteem, social relationships and physical health. Religion-based homophobia and black nationalism point to wider structures which have influenced their emergence, including racism, patriarchy and capitalism. It is vital for US black churches and communities to understand and transcend their longstanding resistance to openly addressing complex, painful issues of sexuality and embrace healthier definitions of black manhood.

  10. Thermodynamics of Horava-Lifshitz black holes

    Energy Technology Data Exchange (ETDEWEB)

    Myung, Yun Soo; Kim, Yong-Wan [Inje University, Institute of Basic Science and School of Computer Aided Science, Gimhae (Korea)

    2010-07-15

    We study black holes in the Horava-Lifshitz gravity with a parameter {lambda}. For 1/3{<=}{lambda}<3, the black holes behave the Lifshitz black holes with dynamical exponent 03, the black holes behave the Reissner-Nordstroem type black hole in asymptotically flat spacetimes. Hence, these all are quite different from the Schwarzschild-AdS black hole of Einstein gravity. The temperature, mass, entropy, and heat capacity are derived for investigating thermodynamic properties of these black holes. (orig.)

  11. How objective is black hole entropy?

    CERN Document Server

    Lau, Y K

    1994-01-01

    The objectivity of black hole entropy is discussed in the particular case of a Schwarzchild black hole. Using Jaynes' maximum entropy formalism and Euclidean path integral evaluation of partition function, it is argued that in the semiclassical limit when the fluctutation of metric is neglected, the black hole entropy of a Schwarzchild black hole is equal to the maximal information entropy of an observer whose sole knowledge of the black hole is its mass. Black hole entropy becomes a measure of number of its internal mass eigenstates in accordance with the Boltzmann principle only in the limit of negligible relative mass fluctutation. {}From the information theoretic perspective, the example of a Schwarzchild black hole seems to suggest that black hole entropy is no different from ordinary thermodynamic entropy. It is a property of the experimental data of a black hole, rather than being an intrinsic physical property of a black hole itself independent of any observer. However, it is still weakly objective in...

  12. 'Black holes': escaping the void.

    Science.gov (United States)

    Waldron, Sharn

    2013-02-01

    The 'black hole' is a metaphor for a reality in the psyche of many individuals who have experienced complex trauma in infancy and early childhood. The 'black hole' has been created by an absence of the object, the (m)other, so there is no internalized object, no (m)other in the psyche. Rather, there is a 'black hole' where the object should be, but the infant is drawn to it, trapped by it because of an intrinsic, instinctive need for a 'real object', an internalized (m)other. Without this, the infant cannot develop. It is only the presence of a real object that can generate the essential gravity necessary to draw the core of the self that is still in an undeveloped state from deep within the abyss. It is the moving towards a real object, a (m)other, that relativizes the absolute power of the black hole and begins a reformation of its essence within the psyche.

  13. Space, time, and black holes

    Energy Technology Data Exchange (ETDEWEB)

    Darling, D.

    1980-10-01

    A discussion of Einstein's General Relativity and how it can explain black holes is included. The key idea of general relativity being that gravitational forces are a direct outcome of local curvature of space-time. The more mass something has the deeper the depression or well it causes in space-time. Black holes are supermassive objects, hence their gravity well is so steep even light can't escape. The three properties associated with a black hole are mass angular momentum, and electric charge. Non-rotating, Schwarzchild, and rotating, Kerr, black holes are studied. A Kruskal-Szekeres diagram for each type is given and explained. (SC)

  14. Black hole accretion disc impacts

    Science.gov (United States)

    Pihajoki, P.

    2016-04-01

    We present an analytic model for computing the luminosity and spectral evolution of flares caused by a supermassive black hole impacting the accretion disc of another supermassive black hole. Our model includes photon diffusion, emission from optically thin regions and relativistic corrections to the observed spectrum and time-scales. We test the observability of the impact scenario with a simulated population of quasars hosting supermassive black hole binaries. The results indicate that for a moderate binary mass ratio of 0.3, and impact distances of 100 primary Schwarzschild radii, the accretion disc impacts can be expected to equal or exceed the host quasar in brightness at observed wavelength λ = 510 nm up to z = 0.6. We conclude that accretion disc impacts may function as an independent probe for supermassive black hole binaries. We release the code used for computing the model light curves to the community.

  15. Black hole accretion disc impacts

    CERN Document Server

    Pihajoki, Pauli

    2015-01-01

    We present an analytic model for computing the luminosity and spectral evolution of flares caused by a supermassive black hole impacting the accretion disc of another supermassive black hole. Our model includes photon diffusion, emission from optically thin regions and relativistic corrections to the observed spectrum and time-scales. We test the observability of the impact scenario with a simulated population of quasars hosting supermassive black hole binaries. The results indicate that for a moderate binary mass ratio of 0.3, and impact distances of 100 primary Schwarzschild radii, the accretion disc impacts can be expected to equal or exceed the host quasar in brightness at observed wavelength {\\lambda} = 510 nm up to z = 0.6. We conclude that accretion disc impacts may function as an independent probe for supermassive black hole binaries. We release the code used for computing the model light curves to the community.

  16. Black hole evaporation: a paradigm

    International Nuclear Information System (INIS)

    A paradigm describing black hole evaporation in non-perturbative quantum gravity is developed by combining two sets of detailed results: (i) resolution of the Schwarzschild singularity using quantum geometry methods and (ii) time evolution of black holes in the trapping and dynamical horizon frameworks. Quantum geometry effects introduce a major modification in the traditional spacetime diagram of black hole evaporation, providing a possible mechanism for recovery of information that is classically lost in the process of black hole formation. The paradigm is developed directly in the Lorentzian regime and necessary conditions for its viability are discussed. If these conditions are met, much of the tension between expectations based on spacetime geometry and structure of quantum theory would be resolved

  17. Switching off black hole evaporation

    International Nuclear Information System (INIS)

    The inclusion of the back-reaction in the Hawking effect leads to the result that, if vector boson fields predominate in nature, then black holes stop evaporating when their mass reaches a non-vanishing limiting value. (author)

  18. Recoiling Black Holes in Quasars

    CERN Document Server

    Bonning, E W; Salviander, S

    2007-01-01

    Recent simulations of merging black holes with spin give recoil velocities from gravitational radiation up to several thousand km/s. A recoiling supermassive black hole can retain the inner part of its accretion disk, providing fuel for a continuing QSO phase lasting millions of years as the hole moves away from the galactic nucleus. One possible observational manifestation of a recoiling accretion disk is in QSO emission lines shifted in velocity from the host galaxy. We have examined QSOs from the Sloan Digital Sky Survey with broad emission lines substantially shifted relative to the narrow lines. We find no convincing evidence for recoiling black holes carrying accretion disks. We place an upper limit on the incidence of recoiling black holes in QSOs of 4% for kicks greater than 500 km/s and 0.35% for kicks greater than 1000 km/s line-of-sight velocity.

  19. Black holes and quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Hooft, G. ' t, E-mail: g.thooft@uu.n [Institute for Theoretical Physics, Utrecht University and Spinoza Institute, P.O. Box 80.195, 3508 TD Utrecht (Netherlands)

    2010-07-15

    After a brief review of quantum black hole physics, it is shown how the dynamical properties of a quantum black hole may be deduced to a large extent from Standard Model Physics, extended to scales near the Planck length, and combined with results from perturbative quantum gravity. Together, these interactions generate a Hilbert space of states on the black hole horizon, which can be investigated, displaying interesting systematics by themselves. To make such approaches more powerful, a study is made of the black hole complementarity principle, from which one may deduce the existence of a hidden form of local conformal invariance. Finally, the question is raised whether the principles underlying Quantum Mechanics are to be sharpened in this domain of physics as well. There are intriguing possibilities.

  20. Black Liquid Solar Collector Demonstrator.

    Science.gov (United States)

    Weichman, F. L.; Austen, D. J.

    1979-01-01

    Describes the details of constructing, and use of, a solar collector. Uses a black liquid to absorb the energy, the thermosyphon effect to drive the liquid through the collector, and a floodlamp as a surrogate sun. (GA)

  1. Formation of Supermassive Black Holes

    CERN Document Server

    Volonteri, Marta

    2010-01-01

    Evidence shows that massive black holes reside in most local galaxies. Studies have also established a number of relations between the MBH mass and properties of the host galaxy such as bulge mass and velocity dispersion. These results suggest that central MBHs, while much less massive than the host (~ 0.1%), are linked to the evolution of galactic structure. In hierarchical cosmologies, a single big galaxy today can be traced back to the stage when it was split up in hundreds of smaller components. Did MBH seeds form with the same efficiency in small proto-galaxies, or did their formation had to await the buildup of substantial galaxies with deeper potential wells? I briefly review here some of the physical processes that are conducive to the evolution of the massive black hole population. I will discuss black hole formation processes for `seed' black holes that are likely to place at early cosmic epochs, and possible observational tests of these scenarios.

  2. Wire Jewelry/Black History.

    Science.gov (United States)

    Daniel, Robert A.; Robinson, Charles C.

    1984-01-01

    Described is a project which made the study of Black history more real to fifth graders by having them make wire jewelry, smaller versions of the ornate filigreed ironwork produced by slave blacksmiths. (RM)

  3. Black hole information vs. locality

    CERN Document Server

    Itzhaki, N

    1996-01-01

    We discuss the limitations on space time measurement in Schwarzchild metric. We find that near the horizon the limitations on space time measurement are of the order of the black hole radius. We suggest that it indicates that a large mass black hole can not be described by means of local field theory even at macroscopic distances and that any attempt to describe black hole formation and evaporation by means of an effective local field theory will necessarily lead to information loss. We also present a new interpretation of the black hole entropy which leads to S=cA , where c is a constant of order 1 which does not depend on the number of fields.

  4. Wormholes as Black Hole Foils

    CERN Document Server

    Damour, Thibault

    2007-01-01

    We study to what extent wormholes can mimic the observational features of black holes. It is surprisingly found that many features that could be thought of as ``characteristic'' of a black hole (endowed with an event horizon) can be closely mimicked by a globally static wormhole, having no event horizon. This is the case for: the apparently irreversible accretion of matter down a hole, no-hair properties, quasi-normal-mode ringing, and even the dissipative properties of black hole horizons, such as a finite surface resistivity equal to 377 Ohms. The only way to distinguish the two geometries on an observationally reasonable time scale would be through the detection of Hawking's radiation, which is, however, too weak to be of practical relevance for astrophysical black holes. We point out the existence of an interesting spectrum of quantum microstates trapped in the throat of a wormhole which could be relevant for storing the information ``lost'' during a gravitational collapse.

  5. The Black Hole Universe Model

    Science.gov (United States)

    Zhang, Tianxi

    2014-06-01

    The black hole universe model is a multiverse model of cosmology recently developed by the speaker. According to this new model, our universe is a fully grown extremely supermassive black hole, which originated from a hot star-like black hole with several solar masses, and gradually grew up from a supermassive black hole with million to billion solar masses to the present state with trillion-trillion solar masses by accreting ambient matter or merging with other black holes. The entire space is structured with infinite layers or universes hierarchically. The innermost three layers include the universe that we live, the inside star-like and supermassive black holes called child universes, and the outside space called mother universe. The outermost layer is infinite in mass, radius, and entropy without an edge and limits to zero for both the matter density and absolute temperature. All layers are governed by the same physics and tend to expand physically in one direction (outward or the direction of increasing entropy). The expansion of a black hole universe decreases its density and temperature but does not alter the laws of physics. The black hole universe evolves iteratively and endlessly without a beginning. When one universe expands out, a new similar one is formed from inside star-like and supermassive black holes. In each of iterations, elements are resynthesized, matter is reconfigurated, and the universe is renewed rather than a simple repeat. The black hole universe is consistent with the Mach principle, observations, and Einsteinian general relativity. It has only one postulate but is able to explain all phenomena occurred in the universe with well-developed physics. The black hole universe does not need dark energy for acceleration and an inflation epoch for flatness, and thus has a devastating impact on the big bang model. In this talk, I will present how this new cosmological model explains the various aspects of the universe, including the origin

  6. Vacuum metastability with black holes.

    OpenAIRE

    Burda, Philipp; Gregory, Ruth; Moss, Ian

    2015-01-01

    We consider the possibility that small black holes can act as nucleation seeds for the decay of a metastable vacuum, focussing particularly on the Higgs potential. Using a thin-wall bubble approximation for the nucleation process, which is possible when generic quantum gravity corrections are added to the Higgs potential, we show that primordial black holes can stimulate vacuum decay. We demonstrate that for suitable parameter ranges, the vacuum decay process dominates over the Hawking evapor...

  7. Energy Extraction from Black Holes

    OpenAIRE

    Straumann, Norbert

    2007-01-01

    In this lecture I give an introduction to the rotational energy extraction of black holes by the electromagnetic Blandford-Znajek process and the generation of relativistic jets. After some basic material on the electrodynamics of black hole magnetospheres, we derive the most important results of Blandford and Znajek by making use of Kerr-Schild coordinates, which are regular on the horizon. In a final part we briefly describe results of recent numerical simulations of accretion flows on rota...

  8. Dynamic black-hole entropy

    OpenAIRE

    Hayward, Sean A.; Mukohyama, Shinji; Ashworth, M. C.

    1998-01-01

    We consider two non-statistical definitions of entropy for dynamic (non-stationary) black holes in spherical symmetry. The first is analogous to the original Clausius definition of thermodynamic entropy: there is a first law containing an energy-supply term which equals surface gravity times a total differential. The second is Wald's Noether-charge method, adapted to dynamic black holes by using the Kodama flow. Both definitions give the same answer for Einstein gravity: one-quarter the area ...

  9. Black Holes and String Theory

    CERN Document Server

    Myers, R C

    2001-01-01

    This is a short summary of my lectures given at the Fourth Mexican School on Gravitation and Mathematical Physics. These lectures gave a brief introduction to black holes in string theory, in which I primarily focussed on describing some of the recent calculations of black hole entropy using the statistical mechanics of D-brane states. The following overview will also provide the interested students with an introduction to the relevant literature.

  10. Charged rotating noncommutative black holes

    International Nuclear Information System (INIS)

    In this paper we complete the program of the noncomutative geometry inspired black holes, providing the richest possible solution, endowed with mass, charge and angular momentum. After providing a prescription for employing the Newman-Janis algorithm in the case of nonvanishing stress tensors, we find regular axisymmetric charged black holes in the presence of a minimal length. We study also the new thermodynamics and we determine the corresponding higher-dimensional solutions. As a conclusion we make some consideration about possible applications.

  11. Charged rotating noncommutative black holes

    Science.gov (United States)

    Modesto, Leonardo; Nicolini, Piero

    2010-11-01

    In this paper we complete the program of the noncomutative geometry inspired black holes, providing the richest possible solution, endowed with mass, charge and angular momentum. After providing a prescription for employing the Newman-Janis algorithm in the case of nonvanishing stress tensors, we find regular axisymmetric charged black holes in the presence of a minimal length. We study also the new thermodynamics and we determine the corresponding higher-dimensional solutions. As a conclusion we make some consideration about possible applications.

  12. Charged rotating noncommutative black holes

    CERN Document Server

    Modesto, Leonardo

    2010-01-01

    In this paper we complete the program of the Noncomutative Geometry inspired black holes, providing the richest possible solution, endowed with mass, charge and angular momentum. After providing a prescription for employing the Newmann-Janis algorithm in case of nonvanishing stress tensors, we find regular axisymmetric charged black holes in the presence of a minimal length. We study also the new thermodynamics and we determine the corresponding higher-dimensional solutions. As a conclusion we make some consideration about possible applications.

  13. Geometric inequalities for black holes

    CERN Document Server

    Dain, Sergio

    2014-01-01

    It is well known that the three parameters that characterize the Kerr black hole (mass, angular momentum and horizon area) satisfy several important inequalities. Remarkably, some of these inequalities remain valid also for dynamical black holes. This kind of inequalities play an important role in the characterization of the gravitational collapse. They are closed related with the cosmic censorship conjecture. In this article recent results in this subject are reviewed.

  14. Tensor Network and Black Hole

    CERN Document Server

    Matsueda, Hiroaki; Hashizume, Yoichiro

    2012-01-01

    A tensor network formalism of thermofield dynamics is introduced. The formalism relates the original Hilbert space with its tilde space by a product of two copies of a tensor network. Then, their interface becomes an event horizon, and the logarithm of the tensor rank corresponds to the black hole entropy. Eventually, multiscale entanglement renormalization anzats (MERA) reproduces an AdS black hole at finite temperature. Our finding shows rich functionalities of MERA as efficient graphical representation of AdS/CFT correspondence.

  15. Comments on Black Holes in Matrix Theory

    OpenAIRE

    Horowitz, Gary T.; Martinec, Emil J.

    1997-01-01

    The recent suggestion that the entropy of Schwarzschild black holes can be computed in matrix theory using near-extremal D-brane thermodynamics is examined. It is found that the regime in which this approach is valid actually describes black strings stretched across the longitudinal direction, near the transition where black strings become unstable to the formation of black holes. It is argued that the appropriate dynamics on the other (black hole) side of the transition is that of the zero m...

  16. Massive Black Holes: formation and evolution

    OpenAIRE

    Rees, Martin J.; Volonteri, Marta

    2007-01-01

    Supermassive black holes are nowadays believed to reside in most local galaxies. Observations have revealed us vast information on the population of local and distant black holes, but the detailed physical properties of these dark massive objects are still to be proven. Accretion of gas and black hole mergers play a fundamental role in determining the two parameters defining a black hole: mass and spin. We briefly review here the basic properties of the population of supermassive black holes,...

  17. Rotating Black Holes in Higher Dimensions

    CERN Document Server

    Kleihaus, Burkhard; Navarro-Lerida, Francisco

    2007-01-01

    The properties of higher-dimensional black holes can differ significantly from those of black holes in four dimensions, since neither the uniqueness theorem, nor the staticity theorem or the topological censorship theorem generalize to higher dimensions. We first discuss black holes of Einstein-Maxwell theory and Einstein-Maxwell-Chern-Simons theory with spherical horizon topology. Here new types of stationary black holes are encountered. We then discuss nonuniform black strings and present evidence for a horizon topology changing transition.

  18. Rotating Black Holes in Higher Dimensions

    Science.gov (United States)

    Kleihaus, Burkhard; Kunz, Jutta; Navarro-Lérida, Francisco

    2008-03-01

    The properties of higher-dimensional black holes can differ significantly from those of black holes in four dimensions, since neither the uniqueness theorem, nor the staticity theorem or the topological censorship theorem generalize to higher dimensions. We first discuss black holes of Einstein-Maxwell theory and Einstein-Maxwell-Chern-Simons theory with spherical horizon topology. Here new types of stationary black holes are encountered. We then discuss nonuniform black strings and present evidence for a horizon topology changing transition.

  19. Regular black hole in three dimensions

    OpenAIRE

    Myung, Yun Soo; Yoon, Myungseok

    2008-01-01

    We find a new black hole in three dimensional anti-de Sitter space by introducing an anisotropic perfect fluid inspired by the noncommutative black hole. This is a regular black hole with two horizons. We compare thermodynamics of this black hole with that of non-rotating BTZ black hole. The first-law of thermodynamics is not compatible with the Bekenstein-Hawking entropy.

  20. Regular black hole in three dimensions

    International Nuclear Information System (INIS)

    We find a new black hole in three-dimensional anti-de Sitter space by introducing an anisotropic perfect fluid inspired by the noncommutative black hole. This is a regular black hole with two horizons. We compare the thermodynamics of this black hole with that of a non-rotating BTZ black hole. The first-law of thermodynamics is not compatible with the Bekenstein-Hawking entropy. (orig.)

  1. Regular black hole in three dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Myung, Yun Soo [Inje University, Institute of Basic Science and School of Computer Aided Science, Gimhae (Korea); Yoon, Myungseok [Sogang University, Center for Quantum Spacetime, Seoul (Korea)

    2009-07-15

    We find a new black hole in three-dimensional anti-de Sitter space by introducing an anisotropic perfect fluid inspired by the noncommutative black hole. This is a regular black hole with two horizons. We compare the thermodynamics of this black hole with that of a non-rotating BTZ black hole. The first-law of thermodynamics is not compatible with the Bekenstein-Hawking entropy. (orig.)

  2. The Black Box QGP

    CERN Document Server

    Tawfik, A

    2006-01-01

    According to the extensive ab initio calculations of lattice QCD, the much large energy density available in the heavy-ion collisions at SPS and now at RHIC should be enough to create the quark-gluon plasma (QGP); a new state of matter in form plasma of free quarks and gluons. The new matter discovered at RHIC is a ''nearly perfect'' fluid rather than a plasma. The shear viscosity is too small. We should then ask about the theoretical and phenomenological consequences and why we simply assumed that the deconfined hadronic matter should be an ideal gas. Finally, I will address five questions; about the properties of the new phases at high temperatures and the orders of phase transitions. Before we clarify such questions, the QGP will remain a kind of black box. One sends a signal via new experiments or simulations and gets another one out if it. Then one try to explain what is going on. I will show that some promising ideas already have been suggested long time ago, but it seems that community didn't care. Is ...

  3. Black Box QGP

    CERN Document Server

    Tawfik, A

    2006-01-01

    According to extensive ab initio calculations of lattice QCD, the very large energy density available in heavy-ion collisions at SPS and now at RHIC must be sufficient to generate quark-gluon plasma (QGP), a new state of matter in the form of plasma of free quarks and gluons. The new state of matter discovered at RHIC seems to be perfect fluid rather than free plasma. Its shear viscosity is assumed to be almost zero. In this work, I first considered the theoretical and phenomenological consequences of this discovery and finally asked questions about the nature of phase transition and properties of matter. It is important to answer these questions, otherwise QGP will remain a kind of black box; one sends a signal via new experiments or simulations or models and gets another one from it. I will show that some promising ideas have already been suggested a long time ago. I will also suggest a new phase diagram with separated deconfinement and freeze-out boundaries and a mixed state of thermal quark matter and bub...

  4. Black Hole Meiosis

    CERN Document Server

    Van Herck, Walter

    2009-01-01

    The enumeration of BPS bound states in string theory needs refinement. Studying partition functions of particles made from D-branes wrapped on algebraic Calabi-Yau 3-folds, and classifying states using split attractor flow trees, we extend the method for computing a refined BPS index, arXiv:0810.4301. For certain D-particles, a finite number of microstates, namely polar states, exclusively realized as bound states, determine an entire partition function (elliptic genus). This underlines their crucial importance: one might call them the `chromosomes' of a D-particle or a black hole. As polar states also can be affected by our refinement, previous predictions on elliptic genera are modified. This can be metaphorically interpreted as `crossing-over in the meiosis of a D-particle'. Our results improve on hep-th/0702012, provide non-trivial evidence for a strong split attractor flow tree conjecture, and thus suggest that we indeed exhaust the BPS spectrum. In the D-brane description of a bound state, the necessity...

  5. Black hole meiosis

    Science.gov (United States)

    van Herck, Walter; Wyder, Thomas

    2010-04-01

    The enumeration of BPS bound states in string theory needs refinement. Studying partition functions of particles made from D-branes wrapped on algebraic Calabi-Yau 3-folds, and classifying states using split attractor flow trees, we extend the method for computing a refined BPS index, [1]. For certain D-particles, a finite number of microstates, namely polar states, exclusively realized as bound states, determine an entire partition function (elliptic genus). This underlines their crucial importance: one might call them the ‘chromosomes’ of a D-particle or a black hole. As polar states also can be affected by our refinement, previous predictions on elliptic genera are modified. This can be metaphorically interpreted as ‘crossing-over in the meiosis of a D-particle’. Our results improve on [2], provide non-trivial evidence for a strong split attractor flow tree conjecture, and thus suggest that we indeed exhaust the BPS spectrum. In the D-brane description of a bound state, the necessity for refinement results from the fact that tachyonic strings split up constituent states into ‘generic’ and ‘special’ states. These are enumerated separately by topological invariants, which turn out to be partitions of Donaldson-Thomas invariants. As modular predictions provide a check on many of our results, we have compelling evidence that our computations are correct.

  6. African and African American Children's and Adolescent Literature in the Classroom: A Critical Guide. Black Studies and Critical Thinking. Volume 11

    Science.gov (United States)

    Yenika-Agbaw, Vivian, Ed.; Napoli, Mary, Ed.

    2011-01-01

    The essays in this collection discuss multicultural issues in children's and adolescent literature, focusing particularly on African and African American cultures. They challenge everyone's understanding of what, in an age of globalization, multicultural texts really are. Cumulatively, these essays illustrate multicultural literature's power to…

  7. Black hole quantum spectrum

    International Nuclear Information System (INIS)

    Introducing a black hole (BH) effective temperature, which takes into account both the non-strictly thermal character of Hawking radiation and the countable behavior of emissions of subsequent Hawking quanta, we recently re-analysed BH quasi-normal modes (QNMs) and interpreted them naturally in terms of quantum levels. In this work we improve such an analysis removing some approximations that have been implicitly used in our previous works and obtaining the corrected expressions for the formulas of the horizon's area quantization and the number of quanta of area and hence also for Bekenstein-Hawking entropy, its subleading corrections and the number of micro-states, i.e. quantities which are fundamental to realize the underlying quantum gravity theory, like functions of the QNMs quantum ''overtone'' number n and, in turn, of the BH quantum excited level. An approximation concerning the maximum value of n is also corrected. On the other hand, our previous results were strictly corrected only for scalar and gravitational perturbations. Here we show that the discussion holds also for vector perturbations. The analysis is totally consistent with the general conviction that BHs result in highly excited states representing both the ''hydrogen atom'' and the ''quasi-thermal emission'' in quantum gravity. Our BH model is somewhat similar to the semi-classical Bohr's model of the structure of a hydrogen atom. The thermal approximation of previous results in the literature is consistent with the results in this paper. In principle, such results could also have important implications for the BH information paradox. (orig.)

  8. Black hole quantum spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Corda, Christian [Institute for Theoretical Physics and Advanced Mathematics (IFM) Einstein-Galilei, Prato (Italy); Istituto Universitario di Ricerca ' ' Santa Rita' ' , Prato (Italy); International Institute for Applicable Mathematics and Information Sciences (IIAMIS), Hyderabad (India)

    2013-12-15

    Introducing a black hole (BH) effective temperature, which takes into account both the non-strictly thermal character of Hawking radiation and the countable behavior of emissions of subsequent Hawking quanta, we recently re-analysed BH quasi-normal modes (QNMs) and interpreted them naturally in terms of quantum levels. In this work we improve such an analysis removing some approximations that have been implicitly used in our previous works and obtaining the corrected expressions for the formulas of the horizon's area quantization and the number of quanta of area and hence also for Bekenstein-Hawking entropy, its subleading corrections and the number of micro-states, i.e. quantities which are fundamental to realize the underlying quantum gravity theory, like functions of the QNMs quantum ''overtone'' number n and, in turn, of the BH quantum excited level. An approximation concerning the maximum value of n is also corrected. On the other hand, our previous results were strictly corrected only for scalar and gravitational perturbations. Here we show that the discussion holds also for vector perturbations. The analysis is totally consistent with the general conviction that BHs result in highly excited states representing both the ''hydrogen atom'' and the ''quasi-thermal emission'' in quantum gravity. Our BH model is somewhat similar to the semi-classical Bohr's model of the structure of a hydrogen atom. The thermal approximation of previous results in the literature is consistent with the results in this paper. In principle, such results could also have important implications for the BH information paradox. (orig.)

  9. Virtual Black Spaces: An Anthropological Exploration of African American Online Communities' Racial and Political Agency amid Virtual Universalism

    Science.gov (United States)

    Heyward, Kamela S.

    2012-01-01

    This dissertation examines the strategic practice of virtual racial embodiment, as a case study of African Americans attempting to complicate current constructions of race and social justice in new media. I suggest that dominant racial constructions online teeter between racial stereotypes and the absence of race. Virtual racial classification and…

  10. Defensive Localism in White and Black: A Comparative History of European-American and African-American Youth Gangs.

    Science.gov (United States)

    Adamson, Christopher

    2000-01-01

    Compares European American and African American youth gangs in four historical periods (seaboard, immigrant, racially changing, and hypersegregated cities), showing that differences can be traced to race-specific effects of labor, housing, and consumer markets, government policies, local politics, and organized crime on their communities.…

  11. Kraft black liquor delivery systems

    Energy Technology Data Exchange (ETDEWEB)

    Adams, T.N.; Empie, H.L.; Obuskovic, N.; Spielbauer, T.M.

    1990-02-01

    Improvement of spray nozzles for black liquor injection into kraft recovery furnaces is expected to result from obtaining a controlled, well-defined droplet size distribution. Work this year has centered on defining the capabilities of commercial black liquor nozzles currently in use. Considerations of the observed mechanism of droplet formation suggest a major revision is needed in the theory of how droplets form from these nozzles. High resolution, high sensitivity video has been shown to be superior to flash x-ray as a technique for measuring the droplet size distribution as well as the formation history. An environmentally sound spray facility capable of spraying black liquor at temperatures up to normal firing conditions is being constructed before data acquisition continues. Preliminary correlations have been developed between liquor properties, nozzle design, and droplet size. Three aspects of nozzle design have been investigated: droplet size distribution, fluid sheet thickness, and flow and pressure drop characteristics. The standard deviation about the median droplet size for black liquor is nearly the same as the for a wide variety of other fluids and nozzle types. Preliminary correlation for fluid sheet thickness on the plate of a splashplate nozzle show the strong similarities of black liquor to other fluids. The flow and pressure drop characteristic of black liquor nozzle, follow a simple two-term relationship similar to other flow devices. This means that in routine mill operation of black liquor nozzles only the fluid acceleration in the nozzle is important, viscous losses are quiet small. 21 refs., 53 figs., 10 tabs.

  12. New Horizons for Black Holes and Branes

    CERN Document Server

    Emparan, Roberto; Niarchos, Vasilis; Obers, Niels A

    2009-01-01

    We initiate a systematic scan of the landscape of black holes in any spacetime dimension using the recently proposed blackfold effective worldvolume theory. We focus primarily on asymptotically flat stationary vacuum solutions, where we uncover large classes of new black holes. These include helical black strings and black rings, black odd-spheres, for which the horizon is a product of a large and a small sphere, and non-uniform black cylinders. More exotic possibilities are also outlined. The blackfold description recovers correctly the ultraspinning Myers-Perry black holes as ellipsoidal even-ball configurations where the velocity field approaches the speed of light at the boundary of the ball. Helical black ring solutions provide the first instance of asymptotically flat black holes in more than four dimensions with a single spatial U(1) isometry. They also imply infinite rational non-uniqueness in ultraspinning regimes, where they maximize the entropy among all stationary single-horizon solutions. Moreove...

  13. Resource Letter BH-2: Black Holes

    CERN Document Server

    Gallo, Elena

    2008-01-01

    This resource letter is designed to guide students, educators, and researchers through (some of) the literature on black holes. Both the physics and astrophysics of black holes are discussed. Breadth has been emphasized over depth, and review articles over primary sources. We include resources ranging from non-technical discussions appropriate for broad audiences to technical reviews of current research. Topics addressed include classification of stationary solutions, perturbations and stability of black holes, numerical simulations, collisions, the production of gravity waves, black hole thermodynamics and Hawking radiation, quantum treatments of black holes, black holes in both higher and lower dimensions, and connections to nuclear and condensed matter physics. On the astronomical end, we also cover the physics of gas accretion onto black holes, relativistic jets, gravitationally red-shifted emission lines, evidence for stellar-mass black holes in binary systems and super-massive black holes at the centers...

  14. Urban–rural and gender differences in tobacco and alcohol use, diet and physical activity among young black South Africans between 1998 and 2003

    Directory of Open Access Journals (Sweden)

    Nasheeta Peer

    2013-01-01

    Full Text Available Background: Non-communicable chronic diseases (NCDs have increased in South Africa over the past 15 years. While these usually manifest during mid-to-late adulthood, the development of modifiable risk factors that contribute to NCDs are usually adopted early in life. Objective: To describe the urban–rural and gender patterns of NCD risk factors in black adolescents and young adults (15- to 24-year-olds from two South African Demographic and Health Surveys conducted 5 years apart. Design: An observational study based on interviews and measurements from two cross-sectional national household surveys. Changes in tobacco and alcohol use, dietary intake, physical inactivity, and overweight/obesity among 15- to 24-year-olds as well as urban–rural and gender differences were analysed using logistic regression. The ‘Surveyset’ option in Stata statistical software was used to allow for the sampling weight in the analysis. Results: Data from 3,186 and 2,066 black 15- to 24-year-old participants in 1998 and 2003, respectively, were analysed. In males, the prevalence of smoking (1998: 21.6%, 2003: 19.1% and problem drinking (1998: 17.2%, 2003: 15.2% were high and increased with age, but in females were much lower (smoking – 1998: 1.0%, 2003: 2.1%; problem drinking – 1998: 4.2%, 2003: 5.8%. The predominant risk factors in females were overweight/obesity (1998: 29.9%, 2003: 31.1% and physical inactivity (2003: 46%. Urban youth, compared to their rural counterparts, were more likely to smoke (odds ratio (OR: 1.39, 95% confidence interval (CI: 1.09–1.75, have high salt intake (OR: 1.75, 95% CI: 1.12–2.78, be overweight/obese (OR: 1.39, 95% CI: 1.14–1.69, or be physically inactive (OR: 1.45, 95% CI: 1.12–1.89. However, they had lower odds of inadequate micronutrient intake (OR: 0.46, 95% CI 0.34–0.62, and there was no overall significant urban– rural difference in the odds for problem drinking but among females the odds were higher in

  15. Massless black holes as black diholes and quadruholes

    CERN Document Server

    Ortín, Tomas

    1996-01-01

    Massless black holes can be understood as bound states of a (positive mass) extreme a=\\sqrt{3} black hole and a singular object with opposite ({\\it i.e.}~negative) mass with vanishing ADM (total) mass but non-vanishing gravitational field. Supersymmetric balance of forces is crucial for the existence of this kind of bound states and explains why the system does not move at the speed of light in spite of being massless. We also explain how supersymmetry allows for negative mass as long as it is never isolated but in bound states of total non-negative mass. The known massless black-hole solutions should then be considered particular cases of ``gravitational dipoles''. We also present ``gravitational quadrupoles'' and comment on the possible role of all these objects in string phase transitions.

  16. Hedonic and utilitarian shopping motivations among South African black Generation Y students / Riané Cherylise Zeeman

    OpenAIRE

    Zeeman, Riané Cherylise

    2013-01-01

    With the South African retail industry being a major and attractive industry, marketers and retailers are pressured to obtain and maintain a competitive advantage by developing marketing strategies that appeal to various consumers. Retailers need to focus on satisfying consumers’ needs, as well as offering a full shopping experience. Shopping entails more than the mere selection of products. Consumers’ motivation or driving force behind the act of shopping is embedded in satisfying internal n...

  17. Information locking in black holes

    CERN Document Server

    Smolin, J; Smolin, John; Oppenheim, Jonathan

    2005-01-01

    The black hole information loss paradox has plagued physicists since Hawking's discovery that black holes evaporate. The calculation suggests that information thrown into a black hole is evaporated away as thermal radiation, and is destroyed: either the unitary laws of quantum theory break down, or we must modify the laws of general relativity. Here we show that one of the central presumptions of the debate is incorrect. Ensuring that information not escape during the semi-classical evaporation process does not require that all the information remain in the black hole until the final stages of evaporation. By taking into account recent results in quantum information theory, we find that the amount of information that must remain in the black hole until the final stages of evaporation can be very small, even though the amount of information which has already radiated away is negligible. Quantum effects mean that information need not be additive: a small number of quanta can lock a large amount of information, ...

  18. Black lenses in string theory

    Science.gov (United States)

    Kunduri, Hari K.; Lucietti, James

    2016-09-01

    We present a new supersymmetric, asymptotically flat, black hole solution to five-dimensional U (1 )3 supergravity which is regular on and outside an event horizon of lens space topology L (2 ,1 ). The solution has seven independent parameters and uplifts to a family of 1 /8 -supersymmetric D1-D5-P black brane solutions to type IIB supergravity. The decoupling limit is asymptotically AdS3×S3×T4 , with a near-horizon geometry that is a twisted product of the near-horizon geometry of the extremal Bañados-Teitelboim-Zanelli black hole and L (2 ,1 )×T4, although it is not (locally) a product space in the bulk. We show that the decoupling limit of a special case of the black lens is related to that of a black ring by spectral flow, thereby supplying an account of its entropy. Analogous solutions of U (1 )N supergravity are also presented.

  19. Time dependent black holes and scalar hair

    International Nuclear Information System (INIS)

    We show how to correctly account for scalar accretion onto black holes in scalar field models of dark energy by a consistent expansion in terms of a slow roll parameter. At leading order, we find an analytic solution for the scalar field within our Hubble volume, which is regular on both black hole and cosmological event horizons, and compute the back reaction of the scalar on the black hole, calculating the resulting expansion of the black hole. Our results are independent of the relative size of black hole and cosmological event horizons. We comment on the implications for more general black hole accretion, and the no hair theorems. (paper)

  20. Implementing black hole as efficient power plant

    OpenAIRE

    Wei, Shao-Wen; Liu, Yu-Xiao

    2016-01-01

    Treating the black hole molecules as working substance and considering its phase structure, we study the black hole heat engine by a charged anti-de Sitter black hole. In the reduced temperature-entropy chart, it is found that the work, heat, and efficiency of the engine are independent of the black hole charge. Applying the Rankine cycle with or without a back pressure mechanism to the black hole heat engine, the efficiency is numerically solved. The result shows that the black hole engine w...

  1. Astrophysical Black Holes: Evidence of a Horizon?

    Science.gov (United States)

    Colpi, Monica

    In this Lecture Note we first follow a short account of the history of the black hole hypothesis. We then review on the current status of the search for astrophysical black holes with particular attention to the black holes of stellar origin. Later, we highlight a series of observations that reveal the albeit indirect presence of supermassive black holes in galactic nuclei, with mention to forthcoming experiments aimed at testing directly the black hole hypothesis. We further focus on evidences of a black hole event horizon in cosmic sources.

  2. Radionic Non-uniform Black Strings

    OpenAIRE

    Tamaki, Takashi; Kanno, Sugumi; Soda, Jiro

    2003-01-01

    Non-uniform black strings in the two-brane system are investigated using the effective action approach. It is shown that the radion acts as a non-trivial hair of the black strings. From the brane point of view, the black string appears as the deformed dilatonic black hole which becomes dilatonic black hole in the single brane limit and reduces to the Reissner-Nordstr\\"om black hole in the close limit of two-branes. The stability of solutions is demonstrated using the catastrophe theory. From ...

  3. Macroscopic black holes, microscopic black holes and noncommutative membrane

    Energy Technology Data Exchange (ETDEWEB)

    Li Miao [Institute of Theoretical Physics, Academia Sinica, PO Box 2735, Beijing 100080 (China)

    2004-07-21

    We study the stretched membrane of a black hole as consisting of a perfect fluid. We find that the pressure of this fluid is negative and the specific heat is also negative. A surprising result is that if we are to assume the fluid to be composed of some quanta, then the dispersion relation of the fundamental quantum is E = m{sup 2}/k, with m at the scale of the Planck mass. There are two possible interpretations of this dispersion relation. One is the noncommutative spacetime on the stretched membrane and the other is that the fundamental quanta are microscopic black holes.

  4. Macroscopic black holes, microscopic black holes and noncommutative membrane

    International Nuclear Information System (INIS)

    We study the stretched membrane of a black hole as consisting of a perfect fluid. We find that the pressure of this fluid is negative and the specific heat is also negative. A surprising result is that if we are to assume the fluid to be composed of some quanta, then the dispersion relation of the fundamental quantum is E = m2/k, with m at the scale of the Planck mass. There are two possible interpretations of this dispersion relation. One is the noncommutative spacetime on the stretched membrane and the other is that the fundamental quanta are microscopic black holes

  5. National Black HIV/AIDS Awareness Day

    Centers for Disease Control (CDC) Podcasts

    2012-02-01

    In observance of National Black HIV/AIDS Awareness Day, Dr. Kevin Fenton, Director of CDC’s National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, talks about the HIV/AIDS among African Americans and what steps can be taken on the national, state, local, and individual levels to address this epidemic.  Created: 2/1/2012 by National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention (NCHHSTP).   Date Released: 2/1/2012.

  6. Scrambling with matrix black holes

    Science.gov (United States)

    Brady, Lucas; Sahakian, Vatche

    2013-08-01

    If black holes are not to be dreaded sinks of information but rather fully described by unitary evolution, they must scramble in-falling data and eventually leak it through Hawking radiation. Sekino and Susskind have conjectured that black holes are fast scramblers; they generate entanglement at a remarkably efficient rate, with the characteristic time scaling logarithmically with the entropy. In this work, we focus on Matrix theory—M-theory in the light-cone frame—and directly probe the conjecture. We develop a concrete test bed for quantum gravity using the fermionic variables of Matrix theory and show that the problem becomes that of chains of qubits with an intricate network of interactions. We demonstrate that the black hole system evolves much like a Brownian quantum circuit, with strong indications that it is indeed a fast scrambler. We also analyze the Berenstein-Maldacena-Nastase model and reach the same tentative conclusion.

  7. Life under a black sun

    CERN Document Server

    Opatrný, Tomáš; Bakala, Pavel

    2016-01-01

    Life is dependent on the income of energy with low entropy and the disposal of energy with high entropy. On Earth, the low-entropy energy is provided by solar radiation and the high-entropy energy is disposed as infrared radiation emitted into the cold space. Here we turn the situation around and assume cosmic background radiation as the low-entropy source of energy for a planet orbiting a black hole into which the high-entropy energy is disposed. We estimate the power that can be produced by thermodynamic processes on such a planet, with a particular interest in planets orbiting a fast rotating Kerr black hole as in the science fiction movie {\\em Interstellar}. We also briefly discuss a reverse Dyson sphere absorbing cosmic background radiation from the outside and dumping waste energy to a black hole inside.

  8. Liouvillian perturbations of black holes

    Science.gov (United States)

    Couch, W. E.; Holder, C. L.

    2007-10-01

    We apply the well-known Kovacic algorithm to find closed form, i.e., Liouvillian solutions, to the differential equations governing perturbations of black holes. Our analysis includes the full gravitational perturbations of Schwarzschild and Kerr, the full gravitational and electromagnetic perturbations of Reissner-Nordstrom, and specialized perturbations of the Kerr-Newman geometry. We also include the extreme geometries. We find all frequencies ω, in terms of black hole parameters and an integer n, which allow Liouvillian perturbations. We display many classes of black hole parameter values and their corresponding Liouvillian perturbations, including new closed-form perturbations of Kerr and Reissner-Nordstrom. We also prove that the only type 1 Liouvillian perturbations of Schwarzschild are the known algebraically special ones and that type 2 Liouvillian solutions do not exist for extreme geometries. In cases where we do not prove the existence or nonexistence of Liouvillian perturbations we obtain sequences of Diophantine equations on which decidability rests.

  9. Black holes and galaxy formation

    CERN Document Server

    Propst, Raphael J

    2010-01-01

    Galaxies are the basic unit of cosmology. The study of galaxy formation is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning. The physics of galaxy formation is complicated because it deals with the dynamics of stars, thermodynamics of gas and energy production of stars. A black hole is a massive object whose gravitational field is so intense that it prevents any form of matter or radiation to escape. It is hypothesized that the most massive galaxies in the universe- "elliptical galaxies"- grow simultaneously with the supermassive black holes at their centers, giving us much stronger evidence that black holes control galaxy formation. This book reviews new evidence in the field.

  10. Energy on black hole spacetimes

    CERN Document Server

    Corichi, Alejandro

    2012-01-01

    We consider the issue of defining energy for test particles on a background black hole spacetime. We revisit the different notions of energy as defined by different observers. The existence of a time-like isometry allows for the notion of a total conserved energy to be well defined, and subsequently the notion of a gravitational potential energy is also meaningful. We then consider the situation in which the test particle is adsorbed by the black hole, and analyze the energetics in detail. In particular, we show that the notion of horizon energy es defined by the isolated horizons formalism provides a satisfactory notion of energy compatible with the particle's conserved energy. As another example, we comment a recent proposal to define energy of the black hole as seen by an observer at rest. This account is intended to be pedagogical and is aimed at the level of and as a complement to the standard textbooks on the subject.

  11. Disrupting Entanglement of Black Holes

    CERN Document Server

    Leichenauer, Stefan

    2014-01-01

    We study entanglement in thermofield double states of strongly coupled CFTs by analyzing two-sided Reissner-Nordstrom solutions in AdS. The central object of study is the mutual information between a pair of regions, one on each asymptotic boundary of the black hole. For large regions the mutual information is positive and for small ones it vanishes; we compute the critical length scale, which goes to infinity for extremal black holes, of the transition. We also generalize the butterfly effect of Shenker and Stanford to a wide class of charged black holes, showing that mutual information is disrupted upon perturbing the system and waiting for a time of order $\\log E/\\delta E$ in units of the temperature. We conjecture that the parametric form of this timescale is universal.

  12. Constraints on Black Hole Remnants

    CERN Document Server

    Giddings, Steven B

    1994-01-01

    One possible fate of information lost to black holes is its preservation in black hole remnants. It is argued that a type of effective field theory describes such remnants (generically referred to as informons). The general structure of such a theory is investigated and the infinite pair production problem is revisited. A toy model for remnants clarifies some of the basic issues; in particular, infinite remnant production is not suppressed simply by the large internal volumes as proposed in cornucopion scenarios. Criteria for avoiding infinite production are stated in terms of couplings in the effective theory. Such instabilities remain a problem barring what would be described in that theory as a strong coupling conspiracy. The relation to euclidean calculations of cornucopion production is sketched, and potential flaws in that analysis are outlined. However, it is quite plausible that pair production of ordinary black holes (e.g. Reissner Nordstrom or others) is suppressed due to strong effective couplings....

  13. Edge phonons in black phosphorus.

    Science.gov (United States)

    Ribeiro, H B; Villegas, C E P; Bahamon, D A; Muraca, D; Castro Neto, A H; de Souza, E A T; Rocha, A R; Pimenta, M A; de Matos, C J S

    2016-01-01

    Black phosphorus has recently emerged as a new layered crystal that, due to its peculiar and anisotropic crystalline and electronic band structures, may have important applications in electronics, optoelectronics and photonics. Despite the fact that the edges of layered crystals host a range of singular properties whose characterization and exploitation are of utmost importance for device development, the edges of black phosphorus remain poorly characterized. In this work, the atomic structure and behaviour of phonons near different black phosphorus edges are experimentally and theoretically studied using Raman spectroscopy and density functional theory calculations. Polarized Raman results show the appearance of new modes at the edges of the sample, and their spectra depend on the atomic structure of the edges (zigzag or armchair). Theoretical simulations confirm that the new modes are due to edge phonon states that are forbidden in the bulk, and originated from the lattice termination rearrangements. PMID:27412813

  14. Massive Black Holes and Galaxies

    CERN Document Server

    CERN. Geneva

    2016-01-01

    Evidence has been accumulating for several decades that many galaxies harbor central mass concentrations that may be in the form of black holes with masses between a few million to a few billion time the mass of the Sun. I will discuss measurements over the last two decades, employing adaptive optics imaging and spectroscopy on large ground-based telescopes that prove the existence of such a massive black hole in the Center of our Milky Way, beyond any reasonable doubt. These data also provide key insights into its properties and environment. Most recently, a tidally disrupting cloud of gas has been discovered on an almost radial orbit that reached its peri-distance of ~2000 Schwarzschild radii in 2014, promising to be a valuable tool for exploring the innermost accretion zone. Future interferometric studies of the Galactic Center Black hole promise to be able to test gravity in its strong field limit.

  15. Calabi-Yau black holes

    Science.gov (United States)

    Shmakova, Marina

    1997-07-01

    We find the entropy of N=2 extreme black holes associated with general Calabi-Yau moduli space and the prepotential F=dABC(XAXBXC/X0). We show that for arbitrary dABC and black hole charges p and q the entropy-area formula depends on combinations of these charges and parameters dABC. These combinations are the solutions of a simple system of algebraic equations. We give a few examples of particular Calabi-Yau moduli spaces for which this system has an explicit solution. For the special case when one of the black hole charges is equal to zero (p0=0) the solution always exists.

  16. Black holes with vector hair

    Science.gov (United States)

    Fan, Zhong-Ying

    2016-09-01

    In this paper, we consider Einstein gravity coupled to a vector field, either minimally or non-minimally, together with a vector potential of the type V = 2{Λ}_0+1/2{m}^2{A}^2 + {γ}_4{A}^4 . For a simpler non-minimally coupled theory with Λ0 = m = γ4 = 0, we obtain both extremal and non-extremal black hole solutions that are asymptotic to Minkowski space-times. We study the global properties of the solutions and derive the first law of thermodynamics using Wald formalism. We find that the thermodynamical first law of the extremal black holes is modified by a one form associated with the vector field. In particular, due to the existence of the non-minimal coupling, the vector forms thermodynamic conjugates with the graviton mode and partly contributes to the one form modifying the first law. For a minimally coupled theory with Λ0 ≠ 0, we also obtain one class of asymptotically flat extremal black hole solutions in general dimensions. This is possible because the parameters ( m 2 , γ4) take certain values such that V = 0. In particular, we find that the vector also forms thermodynamic conjugates with the graviton mode and contributes to the corresponding first law, although the non-minimal coupling has been turned off. Thus all the extremal black hole solutions that we obtain provide highly non-trivial examples how the first law of thermodynamics can be modified by a either minimally or non-minimally coupled vector field. We also study Gauss-Bonnet gravity non-minimally coupled to a vector and obtain asymptotically flat black holes and Lifshitz black holes.

  17. Associations between HIV-related stigma, racial discrimination, gender discrimination, and depression among HIV-positive African, Caribbean, and Black women in Ontario, Canada.

    Science.gov (United States)

    Logie, Carmen; James, Llana; Tharao, Wangari; Loutfy, Mona

    2013-02-01

    Abstract African, Caribbean, and Black (ACB) women are greatly overrepresented in new HIV infections in comparison with Canada's general population. Social and structural factors such as HIV-related stigma, gender discrimination, and racial discrimination converge to increase vulnerability to HIV infection among ACB women by reducing access to HIV prevention services. Stigma and discrimination also present barriers to treatment, care, and support and may contribute to mental health problems. We administered a cross-sectional survey to HIV-positive ACB women (n=173) across Ontario in order to examine the relationships between HIV-related stigma, gender discrimination, racial discrimination, and depression. One-third of participants reported moderate/severe depression scores using the Beck Depression Inventory Fast-Screen guidelines. Hierarchical block regression, moderation, and mediation analyses were conducted to measure associations between independent (HIV-related stigma, gender discrimination, racial discrimination), moderator/mediator (social support, resilient coping), and dependent (depression) variables. Findings included: (1) HIV-related stigma was associated with increased depression; (2) resilient coping was associated with reduced depression but did not moderate the influence of HIV-related stigma on depression; and (3) the effects of HIV-related stigma on depression were partially mediated through resilient coping. HIV-related stigma, gender discrimination, and racial discrimination were significantly correlated with one another and with depression, highlighting the salience of examining multiple intersecting forms of stigma. Generalizability of findings may be limited due to nonrandom sampling. Findings emphasize the importance of multi-component interventions, including building resilient coping skills, mental health promotion and assessment, and stigma reduction programs.

  18. Foraging ecology of an endemic shorebird, the African Black Oystercatcher ( Haematopus moquini) on the south-east coast of South Africa

    Science.gov (United States)

    Kohler, Sophie; Bonnevie, Bo; McQuaid, Christopher; Jaquemet, Sébastien

    2009-09-01

    We investigated small-medium (1-300 km) scale variation in the foraging ecology of the African Black Oystercatcher during its breeding season, using traditional diet analysis coupled with carbon and nitrogen stable isotope analysis. Fieldwork was conducted between January and March 2006 and 2007, on rocky shores on the south-east coast of South Africa at East London, Kenton and Port Elizabeth. Middens of shelled prey left by adults feeding their chicks were collected from five territories and the abundances of the collected prey on the foraging areas were estimated using quadrats. Blood samples from 45 birds (16 females, 10 males and 19 chicks) and tissues from the predominant prey species on the territory of each breeding pair were collected for isotope analysis. The Manly-Chesson selectivity index revealed that adults feed their chicks preferentially with the limpet Scutellastra cochlear and the Mediterranean mussel Mytilus galloprovincialis, if available. A slight enrichment in the 15N stable-carbon isotope signature was observed towards the west in both prey and oystercatchers. Differences in isotope signatures between males and females from the same breeding pair indicate sex-related differences in the diet. Both had signatures indicating a mixed diet, but with males exhibiting a signature closer to that of limpets and females closer to that of mussels. In the single case where mussels were rare on the feeding territory, the two members of a pair showed carbon signatures which were identical and very similar to that of limpets. These results indicate dietary partitioning between genders in breeding pairs.

  19. Control of black hole evaporation?

    International Nuclear Information System (INIS)

    Contradiction between Hawking's semi-classical arguments and the string theory on the evaporation of a black hole has been one of the most intriguing problems in fundamental physics. A final-state boundary condition inside the black hole was proposed by Horowitz and Maldacena to resolve this contradiction. We point out that the original Hawking effect can also be regarded as a separate boundary condition at the event horizon for this scenario. Here, we found that the change of the Hawking boundary condition may affect the information transfer from the initial collapsing matter to the outgoing Hawking radiation during the evaporation process and as a result the evaporation process itself, significantly

  20. Black holes and warped spacetime

    International Nuclear Information System (INIS)

    Black holes (BHs) and their warping effect on spacetime are described, beginning with a discussion on stellar evolution that includes white dwarfs, supernovas and neutron stars. The structure of static, rotating, and electrically charged BHs are considered, as well as the general theory of relativity, quantum mechanics, the Einstein-Rosen bridge, and wormholes in spacetime. Attention is also given to gravitational lenses, various space geometries, quasars, Seyfert galaxies, supermassive black holes, the evaporation and particle emission of BHs, and primordial BHs, including their temperature and lifetime

  1. Black diholes in five dimensions

    CERN Document Server

    Teo, E

    2003-01-01

    Using a generalized Weyl formalism, we show how stationary, axisymmetric solutions of the four-dimensional vacuum Einstein equation can be turned into static, axisymmetric solutions of five-dimensional dilaton gravity coupled to a two-form gauge field. This procedure is then used to obtain new solutions of the latter theory describing pairs of extremal magnetic black holes with opposite charges, known as black diholes. These diholes are kept in static equilibrium by membrane-like conical singularities stretching along two different directions. We also present solutions describing diholes suspended in a background magnetic field, and with unbalanced charges.

  2. Geometric inequalities for black holes

    Energy Technology Data Exchange (ETDEWEB)

    Dain, Sergio [Universidad Nacional de Cordoba (Argentina)

    2013-07-01

    Full text: A geometric inequality in General Relativity relates quantities that have both a physical interpretation and a geometrical definition. It is well known that the parameters that characterize the Kerr-Newman black hole satisfy several important geometric inequalities. Remarkably enough, some of these inequalities also hold for dynamical black holes. This kind of inequalities, which are valid in the dynamical and strong field regime, play an important role in the characterization of the gravitational collapse. They are closed related with the cosmic censorship conjecture. In this talk I will review recent results in this subject. (author)

  3. Asymptotic black hole quasinormal frequencies

    OpenAIRE

    Motl, Lubos; Neitzke, Andrew

    2003-01-01

    We give a new derivation of the quasinormal frequencies of Schwarzschild black holes in d greater than or equal to 4 and Reissner-Nordstrom black holes in d = 4, in the limit of infinite damping. For Schwarzschild in d greater than or equal to 4 we find that the asymptotic real part is THawkinglog(3) for scalar perturbations and for some gravitational perturbations; this confirms a result previously obtained by other means in the case d = 4. For Reissner-Nordstrom in d = 4 w...

  4. Black supernovae and black holes in non-local gravity

    Science.gov (United States)

    Bambi, Cosimo; Malafarina, Daniele; Modesto, Leonardo

    2016-04-01

    In a previous paper, we studied the interior solution of a collapsing body in a non-local theory of gravity super-renormalizable at the quantum level. We found that the classical singularity is replaced by a bounce, after which the body starts expanding. A black hole, strictly speaking, never forms. The gravitational collapse does not create an event horizon but only an apparent one for a finite time. In this paper, we solve the equations of motion assuming that the exterior solution is static. With such an assumption, we are able to reconstruct the solution in the whole spacetime, namely in both the exterior and interior regions. Now the gravitational collapse creates an event horizon in a finite comoving time, but the central singularity is approached in an infinite time. We argue that these black holes should be unstable, providing a link between the scenarios with and without black holes. Indeed, we find a non catastrophic ghost-instability of the metric in the exterior region. Interestingly, under certain conditions, the lifetime of our black holes exactly scales as the Hawking evaporation time.

  5. Moodulitest komplekteeritav diivan Black = A modular sofa called Black

    Index Scriptorium Estoniae

    2007-01-01

    Autor Tiina Mang pälvis diivanikomplekti Black eest Eesti Sisearhitektide Liidu 2006. a. esemepreemia. T. Mangist, objektid, kuhu on valitud T. Mangi projekteeritud mööblit, näitused. 3 värv. vaadet, foto T. Mangist

  6. Irreversible gravitational collapse: black stars or black holes?

    CERN Document Server

    Corda, Christian

    2011-01-01

    It is well known that the concept of black hole has been considered very fascinating by scientists even before the introduction of Einstein's general relativity. They should be the final result of an irreversible gravitational collapse of very massive bodies. However, an unsolved problem concerning such objects is the presence of a space-time singularity in their core. Such a problem was present starting by the first historical papers concerning black holes. It is a common opinion that this problem could be solved when a correct quantum gravity theory will be, finally, constructed. In this work we review a way to remove black hole singularities at a classical level i.e. without arguments of quantum gravity. By using a particular non-linear electrodynamics Lagrangian, an exact solution of Einstein field equations is shown. The solution prevents the collapsing object to reach the gravitational radius, thus the final result becomes a black star, i.e. an astrophysical object where both of singularities and event ...

  7. Regular Black Holes with Cosmological Constant

    Institute of Scientific and Technical Information of China (English)

    MO Wen-Juan; CAI Rong-Gen; SU Ru-Keng

    2006-01-01

    We present a class of regular black holes with cosmological constant Λ in nonlinear electrodynamics. Instead of usual singularity behind black hole horizon, all fields and curvature invariants are regular everywhere for the regular black holes. Through gauge invariant approach, the linearly dynamical stability of the regular black hole is studied. In odd-parity sector, we find that the Λ term does not appear in the master equations of perturbations, which shows that the regular black hole is stable under odd-parity perturbations. On the other hand, for the even-parity sector, the master equations are more complicated than the case without the cosmological constant. We obtain the sufficient conditions for stability of the regular black hole. We also investigate the thermodynamic properties of the regular black hole, and find that those thermodynamic quantities do not satisfy the differential form of first law of black hole thermodynamics. The reason for violating the first law is revealed.

  8. A Perspective for Assertiveness Training for Blacks

    Science.gov (United States)

    Minor, Billy Joe

    1978-01-01

    This article discussess assertiveness in the Black-White encounter. The author delineates the assertive options available to Blacks, distortions in interpretation of assertive messages, and strategies for more effective and efficient assertions. (Author)

  9. Implementing black hole as efficient power plant

    CERN Document Server

    Wei, Shao-Wen

    2016-01-01

    Treating the black hole molecules as working substance and considering its phase structure, we study the black hole heat engine by a charged anti-de Sitter black hole. In the reduced temperature-entropy chart, it is found that the work, heat, and efficiency of the engine are independent of the black hole charge. Applying the Rankine cycle with or without a back pressure mechanism to the black hole heat engine, the efficiency is numerically solved. The result shows that the black hole engine working along the Rankine cycle with a back pressure mechanism has a higher efficiency. This provides a novel and efficient mechanism to produce the useful mechanical work with black hole, and such heat engine may act as a possible energy source for the high energy astrophysical phenomena near the black hole.

  10. Black humor in O.Henry's novels

    Institute of Scientific and Technical Information of China (English)

    冯静楠

    2013-01-01

      Black humor is a kind of literary style rose in American and O .Henry's novels used it to express the satire to society and show the sympathy to the lower class .The most typical works contain black humor two are The Cop and the Anthem and The Gift of the Magi.By using black humor, he created his unique endings .This article is trying to analysis the use of black humor in his novels and the effect.

  11. Modified dispersion relations and black hole physics

    OpenAIRE

    Ling, Yi; Hu, Bo; Li, Xiang

    2005-01-01

    A modified formulation of energy-momentum relation is proposed in the context of doubly special relativity. We investigate its impact on black hole physics. It turns out that such modification will give corrections to both the temperature and the entropy of black holes. In particular this modified dispersion relation also changes the picture of Hawking radiation greatly when the size of black holes approaching the Planck scale. It can prevent black holes from total evaporation, as a result pr...

  12. The coalescence rates of double black holes

    OpenAIRE

    Belczynski, Krzysztof; Bulik, Tomasz; Dominik, Michal; Prestwich, Andrea

    2011-01-01

    We present the summary of the recent investigations of double black hole binaries in context of their formation and merger rates. In particular we discuss the spectrum of black hole masses, the formation scenarios in the local Universe and the estimates of detection rates for gravitational radiation detectors like LIGO and VIRGO. Our study is based on observed properties of known Galactic and extra-galactic stellar mass black holes and evolutionary predictions. We argue that the binary black ...

  13. Black-hole formation from stellar collapse

    International Nuclear Information System (INIS)

    I review the end-state of massive stellar evolution, following the evolution of these massive stars from the onset of collapse through the formation of a compact remnant and the possible supernova or hypernova explosion. In particular, I concentrate on the formation of black holes from stellar collapse: the fraction of stars that form black holes, the black-hole mass distribution and the velocities these black-hole remnants may receive during their formation process

  14. Black Thyroid Associated with Thyroid Carcinoma

    OpenAIRE

    Emad Kandil; Mohamed Abdel Khalek; Haytham Alabbas; Philip Daroca; Tina Thethi; Paul Friedlander; Ryan Leblanc; Obai Abdullah; Bernard Jaffe; Byron Crawford

    2010-01-01

    Objective. Black thyroid is a rare pigmented change seen almost exclusively in patients upon minocycline ingestion, and the process has previously been thought to be generally benign. There have been 61 reported cases of black thyroid. We are aware of 13 cases previously reported in association with thyroid carcinoma. This paper reports six patients with black thyroid pigmentation in association with thyroid carcinoma. Design. The medical records of six patients who were diagnosed with black ...

  15. BLACK POLYPROPYLENE MULCH TEXTILE IN ORGANIC AGRICULTURE

    OpenAIRE

    Dvorak, Petr; Hajšlová, Jana; Hamouz, Karel; Schulzová, Věra; Kuchtova, Perla; Tomasek, Jaroslav

    2010-01-01

    Black polyethylene mulch is used for weed control in a range of crops under the organic system. The use of black polypropylene mulch is usually restricted to perennial crops. The trial was conducted at Experimental station of Department of Crop Production of the Czech University of Life Science Prague-Uhříněves in Czech Republic. For the experiments were used black polypropylene woven mulch (comparison wit bare soil), two varieties of early potatoes Finka and Katka. Black polypropylene textil...

  16. Supermassive Black Holes and Their Environments

    OpenAIRE

    Colberg, Joerg M.; Di Matteo, Tiziana

    2008-01-01

    We make use of the first high--resolution hydrodynamic simulations of structure formation which self-consistently follows the build up of supermassive black holes introduced in Di Matteo et al. (2007) to investigate the relation between black holes (BH), host halo and large--scale environment. There are well--defined relations between halo and black hole masses and between the activities of galactic nuclei and halo masses at low redshifts. A large fraction of black holes forms anti--hierarchi...

  17. Black hole growth in hierarchical galaxy formation.

    OpenAIRE

    Malbon, R. K.; Baugh, C M; Frenk, C. S.; Lacey, C. G.

    2007-01-01

    We incorporate a model for black hole growth during galaxy mergers into the semi-analytical galaxy formation model based on Lambda-CDM proposed by Baugh et al. (2005). Our black hole model has one free parameter, which we set by matching the observed zeropoint of the local correlation between black hole mass and bulge luminosity. We present predictions for the evolution with redshift of the relationships between black hole mass and bulge properties. Our simulations reproduce the evolution of ...

  18. Energy conservation for dynamical black holes

    OpenAIRE

    Hayward, Sean A.

    2004-01-01

    An energy conservation law is described, expressing the increase in mass-energy of a general black hole in terms of the energy densities of the infalling matter and gravitational radiation. For a growing black hole, this first law of black-hole dynamics is equivalent to an equation of Ashtekar & Krishnan, but the new integral and differential forms are regular in the limit where the black hole ceases to grow. An effective gravitational-radiation energy tensor is obtained, providing measures o...

  19. Noncommutative geometry inspired Schwarzschild black hole

    OpenAIRE

    Nicolini, Piero; Smailagic, Anais; Spallucci, Euro

    2005-01-01

    We investigate the behavior of a noncommutative radiating Schwarzschild black hole. It is shown that coordinate noncommutativity cures usual problems encountered in the description of the terminal phase of black hole evaporation. More in detail, we find that: the evaporation end-point is a zero temperature extremal black hole even in the case of electrically neutral, non-rotating, objects; there exists a finite maximum temperature that the black hole can reach before cooling down to absolute ...

  20. Recommendations to Public Speaking Instructors for the Negotiation of Code-Switching Practices among Black English-Speaking African American Students

    Science.gov (United States)

    Greene, Deric M.; Walker, Felicia R.

    2004-01-01

    Six recommendations that instructors can employ to encourage effective classroom code-switching practices among Black English-speaking students in the basic communication course are discussed. These include reconsidering attitudes, communicating expectations, demonstrating model language behavior, affirming students' language, creating culturally…

  1. Signatures of black holes at the LHC

    OpenAIRE

    Cavaglia, Marco; Godang, Romulus; Cremaldi, Lucien M.; Summers, Donald J.

    2007-01-01

    Signatures of black hole events at CERN's Large Hadron Collider are discussed. Event simulations are carried out with the Fortran Monte Carlo generator CATFISH. Inelasticity effects, exact field emissivities, color and charge conservation, corrections to semiclassical black hole evaporation, gravitational energy loss at formation and possibility of a black hole remnant are included in the analysis.

  2. Micro black holes in the laboratory

    CERN Document Server

    Bleicher, Marcus; Sprenger, Martin; Winstanley, Elizabeth

    2011-01-01

    The possibility of creating microscopic black holes is one of the most exciting predictions for the LHC, with potentially major consequences for our current understanding of physics. We briefly review the theoretical motivation for micro black hole production, and our understanding of their subsequent evolution. Recent work on modelling the radiation from quantum-gravity-corrected black holes is also discussed.

  3. Pure states don't wear black

    CERN Document Server

    Myers, R C

    1997-01-01

    Recently, string theory has provided some remarkable new insights into the microphysics of black holes. I argue that a simple and important lesson is also provided with regards to the information loss paradox, namely, pure quantum states do not form black holes! Thus it seems black hole formation, as well as evaporation, must be understood within the framework of quantum decoherence.

  4. The Institutional Decimation of Black American Males.

    Science.gov (United States)

    Stewart, James B.; Scott, Joseph W.

    1978-01-01

    In 1970, there were 85 Black men for every 100 Black women in major American cities. Factors which produced this imbalance in the sex ratio of Blacks include educational, health care, public assistance, and penal correction systems, labor market mechanisms, and the military. (Author/MC)

  5. Scalar field radiation from dilatonic black holes

    Science.gov (United States)

    Gohar, H.; Saifullah, K.

    2012-12-01

    We study radiation of scalar particles from charged dilaton black holes. The Hamilton-Jacobi method has been used to work out the tunneling probability of outgoing particles from the event horizon of dilaton black holes. For this purpose we use WKB approximation to solve the charged Klein-Gordon equation. The procedure gives Hawking temperature for these black holes as well.

  6. Extremal black holes in N=2 supergravity

    NARCIS (Netherlands)

    Katmadas, S.

    2011-01-01

    An explanation for the entropy of black holes has been an outstanding problem in recent decades. A special case where this is possible is that of extremal black holes in N=2 supergravity in four and five dimensions. The best developed case is for black holes preserving some supersymmetry (BPS), whic

  7. Radionic Non-uniform Stable Black Strings

    OpenAIRE

    Tamaki, Takashi; Kanno, Sugumi; Soda, Jiro

    2003-01-01

    Non-uniform black strings in the two-brane system are investigated using the effective action approach. It is shown that the radion acts as a non-trivial hair of black strings. The stability of solutions is demonstrated using the catastrophe theory. The black strings are shown to be non-uniform.

  8. Troubling Success: Interviews with Black Female Faculty

    Science.gov (United States)

    Edwards, Nivischi N.; Beverly, Monifa Green; Alexander-Snow, Mia

    2011-01-01

    This study explores the complexity of success for Black female faculty members based on six Black women at a public research oriented university in the Southeast. All women shared the challenges they experience as Black female faculty members. Findings indicate that while these women seemingly have attained professional success, they are leery of…

  9. Rising Expectations, Black Anger, and the Future

    Science.gov (United States)

    Cogdell, Roy T.; McLemore, William P.

    1977-01-01

    The societal paradox of abundant opportunities and numerous constraints affects black people's expectations, frustrations, and anger. Specific questions that this paper examines are: What are some possible causes of anger? How have black people reacted to anger-provoking situations? And what are future prospects for black people? (Author/JM)

  10. Event horizons of two Schwarzchild black holes

    Energy Technology Data Exchange (ETDEWEB)

    Bishop, N.T.

    1988-06-01

    The problem of two Schwarzchild black holes, one much smaller than the other, is investigated by an approximate analytic method. The critical separation between the black holes at which their event horizons join is found for two cases, (2) time-symmetric initial data, and (b) the small black hole falls from rest at infinity.

  11. Black Frontier Settlements in Spanish Colonial Florida.

    Science.gov (United States)

    Landers, Jane

    1988-01-01

    Addresses the much neglected area of Black frontier experience in the Spanish colonies. Concentrates on the role played by Black settlers and one Black township in defending the Spanish frontier in colonial Florida against the threat of growing English settlements to the north. Provides an introduction to the 18th century Southeastern Spanish…

  12. Radionic Non-Uniform Black Strings

    Science.gov (United States)

    Tamaki, T.; Kanno, S.; Soda, J.

    Non-uniform black strings in the two-brane system are investigated using the effective action approach. It is shown that the radion acts as a non-trivial hair of black strings. The stability of solutions is demonstrated using the catastrophe theory. The black strings are shown to be non-uniform.

  13. Black Editors' Responses to Power and Propaganda.

    Science.gov (United States)

    Kreiling, Albert

    Two leading black newspapers were very outspoken during the black American's struggle for equality following the Civil War of the 1860s. The Chicago-based "Conservator" and "Appeal" actively encouraged blacks to enter the nationwide power struggle among warring interests on their own behalf, and on a cultural level they attempted to elevate the…

  14. On Quantum Contributions to Black Hole Growth

    NARCIS (Netherlands)

    Spaans, M.

    2013-01-01

    The effects of Wheeler’s quantum foam on black hole growth are explored from an astrophysical per- spective. Quantum fluctuations in the form of mini (10−5 g) black holes can couple to macroscopic black holes and allow the latter to grow exponentially in mass on a time scale of 109 years. Consequent

  15. A Black Hole in Our Galactic Center

    Science.gov (United States)

    Ruiz, Michael J.

    2008-01-01

    An introductory approach to black holes is presented along with astronomical observational data pertaining to the presence of a supermassive black hole at the center of our galaxy. Concepts of conservation of energy and Kepler's third law are employed so students can apply formulas from their physics class to determine the mass of the black hole…

  16. Compensating Scientism through "The Black Hole."

    Science.gov (United States)

    Roth, Lane

    The focal image of the film "The Black Hole" functions as a visual metaphor for the sacred, order, unity, and eternal time. The black hole is a symbol that unites the antinomic pairs of conscious/unconscious, water/fire, immersion/emersion, death/rebirth, and hell/heaven. The black hole is further associated with the quest for transcendent…

  17. Black Hole Monodromy and Conformal Field Theory

    NARCIS (Netherlands)

    A. Castro; J.M. Lapan; A. Maloney; M.J. Rodriguez

    2013-01-01

    The analytic structure of solutions to the Klein-Gordon equation in a black hole background, as represented by monodromy data, is intimately related to black hole thermodynamics. It encodes the "hidden conformal symmetry" of a nonextremal black hole, and it explains why features of the inner event h

  18. Resource Letter BH-1: Black Holes.

    Science.gov (United States)

    Detweiler, Steven

    1981-01-01

    Lists resources on black holes, including: (1) articles of historical interest; (2) books and journal articles on elementary expositions; (3) elementary and advanced textbooks; and (4) research articles on analytic structure of black holes, black hole dynamics, and astrophysical processes. (SK)

  19. Black weathering of Bentheim and Obernkirchen sandstone

    NARCIS (Netherlands)

    Nijland, T.G.; Dubelaar, C.W.; Hees, R.P.J. van; Linden, T.J.M. van der

    2003-01-01

    Black weathering of sandstone in monuments is widespread. Some obiects owe their name to it, like the Porta Nigra in Triet (Germany). Other than the black gypsum crusts common on limestone, the black weathering layer on sandstone is rather thin and well adhe¡ent. Formation of such layers on Bentheim

  20. Scattering by regular black holes: Planar massless scalar waves impinging upon a Bardeen black hole

    CERN Document Server

    Macedo, Caio F B; Crispino, Luís C B

    2015-01-01

    Singularities are common features of general relativity black holes. However, within general relativity, one can construct black holes that present no singularities. These regular black hole solutions can be achieved by, for instance, relaxing one of the energy conditions on the stress energy tensor sourcing the black hole. Some regular black hole solutions were found in the context of non-linear electrodynamics, the Bardeen black hole being the first one proposed. In this paper, we consider a planar massless scalar wave scattered by a Bardeen black hole. We compare the scattering cross section computed using a partial-wave description with the classical geodesic scattering of a stream of null geodesics, as well as with the semi-classical glory approximation. We obtain that, for some values of the corresponding black hole charge, the scattering cross section of a Bardeen black hole has a similar interference pattern of a Reissner-Nordstr\\"om black hole.

  1. Teacher Education and Black Male Students in the United States

    Directory of Open Access Journals (Sweden)

    H. Richard Milner

    2013-10-01

    Full Text Available Teacher education programs in the United States (U.S. struggle to prepare teachers to meet the complex needs of elementary and secondary students in public schools - especially those of color, those living in poverty, and those whose first language is not English. In this article, we argue for focused attention on preparing educators to teach African American male students as these students face particular institutional challenges in successfully navigating the U.S. public school system. Drawing from the significant body of research on teacher education and teacher learning for equity and social justice, four Black teacher educators discuss challenges they have faced in classes designed to prepare teachers to teach Black male students. Through an analysis of commonalities in their experiences, they propose means for teacher educators to foster greater understandings of the heterogeneity found among Black male students so that teachers can craft more responsive and responsible educational experiences for Black males.

  2. The first massive black holes

    OpenAIRE

    Volonteri, Marta

    2012-01-01

    I briefly outline recent theoretical developments on the formation of the first massive black holes (MBHs) that may grow into the population of MBHs powering quasars and inhabiting galactic centers today. I also touch upon possible observational tests that may give insights on what the properties of the first MBHs were.

  3. Sexuality Attitudes of Black Adults.

    Science.gov (United States)

    Timberlake, Constance A.; Carpenter, Wayne D.

    1990-01-01

    Assessed sexuality attitudes of black middle-class sample (N=124) concerning communication regarding sexuality information, adolescent contraception, adolescent pregnancy, nonmarital intercourse, responsibility for contraception and pregnancy, abortion, pornography, and masturbation. Results suggest that participants were well-informed, moderate,…

  4. From Pinholes to Black Holes

    Energy Technology Data Exchange (ETDEWEB)

    Fenimore, Edward E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-10-06

    Pinhole photography has made major contributions to astrophysics through the use of “coded apertures”. Coded apertures were instrumental in locating gamma-ray bursts and proving that they originate in faraway galaxies, some from the birth of black holes from the first stars that formed just after the big bang.

  5. Extremal Higher Spin Black Holes

    CERN Document Server

    Bañados, Máximo; Faraggi, Alberto; Jottar, Juan I

    2015-01-01

    The gauge sector of three-dimensional higher spin gravities can be formulated as a Chern-Simons theory. In this context, a higher spin black hole corresponds to a flat connection with suitable holonomy (smoothness) conditions which are consistent with the properties of a generalized thermal ensemble. Building on these ideas, we discuss a definition of black hole extremality which is appropriate to the topological character of 3d higher spin theories. Our definition can be phrased in terms of the Jordan class of the holonomy around a non-contractible (angular) cycle, and we show that it is compatible with the zero-temperature limit of smooth black hole solutions. While this notion of extremality does not require nor implies the existence of supersymmetry, we exemplify its consequences in the context of sl(3|2) + sl(3|2) Chern-Simons theory. Remarkably, while as usual not all extremal solutions preserve supersymmetries, we find that the higher spin setup allows for non-extremal supersymmetric black hole solutio...

  6. Black Physical Educators and Utilitarianism.

    Science.gov (United States)

    Coursey, Leon N.

    The contributions of black professional personnel to the field of physical education are enumerated and described. The careers of Anita J. Turner, Edwin B. Henderson, and Albert J. Overly in particular are examined. The ability of a minority group to provide significant leadership in an educational field is discussed, and the challenge still…

  7. Black Holes and Exotic Spinors

    Directory of Open Access Journals (Sweden)

    J. M. Hoff da Silva

    2016-05-01

    Full Text Available Exotic spin structures are non-trivial liftings, of the orthogonal bundle to the spin bundle, on orientable manifolds that admit spin structures according to the celebrated Geroch theorem. Exotic spin structures play a role of paramount importance in different areas of physics, from quantum field theory, in particular at Planck length scales, to gravity, and in cosmological scales. Here, we introduce an in-depth panorama in this field, providing black hole physics as the fount of spacetime exoticness. Black holes are then studied as the generators of a non-trivial topology that also can correspond to some inequivalent spin structure. Moreover, we investigate exotic spinor fields in this context and the way exotic spinor fields branch new physics. We also calculate the tunneling probability of exotic fermions across a Kerr-Sen black hole, showing that the exotic term does affect the tunneling probability, altering the black hole evaporation rate. Finally we show that it complies with the Hawking temperature universal law.

  8. [Nuptiality among Brazil's black population].

    Science.gov (United States)

    Berquo, E

    1987-08-01

    Data from a three percent sample of the 1980 census of Brazil are used to analyze nuptiality trends by ethnic group. The focus is on the homogamy of marriage by color and age and on the marriage patterns of the black population.

  9. Black Youth, Identity, and Ethics

    Science.gov (United States)

    Duncan, Garrett Albert

    2005-01-01

    This article examines stage models of racial identity that researchers and educators use to explain the subjective processes that influence how black youth navigate school. Despite the explicit challenge that most models of racial identity have posed to racist discourses in the research literature, the underlying ethics of their developmental…

  10. Android for the Beaglebone Black

    CERN Document Server

    Henderson, Andrew

    2015-01-01

    If you are an Android app developer who wants to experiment with the hardware capabilities of the BeagleBone Black platform, then this book is ideal for you. You are expected to have basic knowledge of developing Android apps but no prior hardware experience is required.

  11. Information retrieval from black holes

    CERN Document Server

    Lochan, Kinjalk; Padmanabhan, T

    2016-01-01

    It is generally believed that, when matter collapses to form a black hole, the complete information about the initial state of the matter cannot be retrieved by future asymptotic observers, through local measurements. This is contrary to the expectation from a unitary evolution in quantum theory and leads to (a version of) the black hole information paradox. Classically, nothing else, apart from mass, charge and angular momentum is expected to be revealed to such asymptotic observers after the formation of a black hole. Semi-classically, black holes evaporate after their formation through the Hawking radiation. The dominant part of the radiation is expected to be thermal and hence one cannot know anything about the initial data from the resultant radiation. However, there can be sources of distortions which make the radiation non-thermal. Although the distortions are not strong enough to make the evolution unitary, these distortions carry some part of information regarding the in-state. In this work, we show ...

  12. Wormholes as black hole foils

    Science.gov (United States)

    Damour, Thibault; Solodukhin, Sergey N.

    2007-07-01

    We study to what extent wormholes can mimic the observational features of black holes. It is surprisingly found that many features that could be thought of as “characteristic” of a black hole (endowed with an event horizon) can be closely mimicked by a globally static wormhole, having no event horizon. This is the case for the apparently irreversible accretion of matter down a hole, no-hair properties, quasi-normal-mode ringing, and even the dissipative properties of black hole horizons, such as a finite surface resistivity equal to 377 Ohms. The only way to distinguish the two geometries on an observationally reasonable time scale would be through the detection of Hawking’s radiation, which is, however, too weak to be of practical relevance for astrophysical black holes. We point out the existence of an interesting spectrum of quantum microstates trapped in the throat of a wormhole which could be relevant for storing the information lost during a gravitational collapse.

  13. Graduate Opportunities for Black Students.

    Science.gov (United States)

    Paynter, Julie, Ed.

    This document catalogues graduate opportunities specifically for black students in 1969-70 at 42 universities, 96 additional graduate departments (social sciences, natural sciences, mathematics, and humanities), and 111 additional professional schools (particularly social work, education, law, medicine, theology, business, and library science).…

  14. Electroelasticity of Charged Black Branes

    CERN Document Server

    Armas, Jay; Obers, Niels A

    2013-01-01

    We present the first order corrected dynamics of fluid branes carrying higher-form charge by obtaining the general form of their equations of motion to pole-dipole order. Assuming linear response theory, we characterize the corresponding effective theory of stationary bent charged (an)isotropic fluid branes in terms of two sets of response coefficients, the Young modulus and the piezoelectric moduli. We subsequently find large classes of examples in gravity of this effective theory, by constructing stationary strained charged black brane solutions to first order in a derivative expansion. Using solution generating techniques and bent neutral black branes as a seed solution, we obtain a class of charged black brane geometries carrying smeared Maxwell charge in Einstein-Maxwell-dilaton gravity. In the specific case of ten-dimensional space-time we furthermore use T-duality to generate bent black branes with higher-form charge, including smeared D-branes of type II string theory. By subsequently measuring the be...

  15. Force-feeding Black Holes

    CERN Document Server

    Begelman, Mitchell C

    2012-01-01

    We propose that the growth of supermassive black holes is associated mainly with brief episodes of highly super-Eddington infall of gas ("hyperaccretion"). This gas is not swallowed in real time, but forms an envelope of matter around the black hole that can be swallowed gradually, over a much longer timescale. However, only a small fraction of the black hole mass can be stored in the envelope at any one time. We argue that any infalling matter above a few per cent of the hole's mass is ejected as a result of the plunge in opacity at temperatures below a few thousand degrees K, corresponding to the Hayashi track. The speed of ejection of this matter, compared to the velocity dispersion (sigma) of the host galaxy's core, determines whether the ejected matter is lost forever or returns eventually to rejoin the envelope, from which it can be ultimately accreted. The threshold between matter recycling and permanent loss defines a relationship between the maximum black hole mass and sigma that resembles the empiri...

  16. Close encounters of black holes

    CERN Document Server

    Giulini, D

    2003-01-01

    This is an introduction into the problem of how to set up black hole initial-data for the matter-free field equations of General Relativity. The approach is semi-pedagogical and addresses a more general audience of astrophysicists and students with no specialized training in General Relativity beyond that of an introductory lecture.

  17. Black yeasts in cold habitats

    NARCIS (Netherlands)

    L. Selbmann; G.S. de Hoog; L. Zucconi; D. Isola; S. Onofri

    2014-01-01

    Black yeasts have already been known since the end of the nineteenth century, but for a number of reasons, only few workers were familiar with them. That was since recently, until the wealth of biodiversity, stunning ecologies and potential applications have become apparent. Some remote and extreme

  18. Black Holes: A Selected Bibliography.

    Science.gov (United States)

    Fraknoi, Andrew

    1991-01-01

    Offers a selected bibliography pertaining to black holes with the following categories: introductory books; introductory articles; somewhat more advanced articles; readings about Einstein's general theory of relativity; books on the death of stars; articles on the death of stars; specific articles about Supernova 1987A; relevant science fiction…

  19. 'Black Athena' and Africa's contribution to global cultural history

    OpenAIRE

    Binsbergen, van, W.M.J.

    1996-01-01

    Martin Bernal's 'Black Athena' has evoked three kinds of reaction: scholarly evaluation of the historical evidence for Bernal's claims, both of Ancient Europe's indebtedness to West Asia and Northeast Africa, and of the construction in recent centuries of the Greek miracle as a Eurocentric, racialist myth; appropriation of the Bernal thesis by African-American and African intellectuals in the process of identity construction and in the politics of global knowledge production as a counterforce...

  20. The External Effects of Black-Male Incarceration on Black Females

    OpenAIRE

    Stéphane Mechoulan

    2006-01-01

    We examine how the rising incarceration of Black men and the sex ratio imbalance it induces shapes young Black women’s behavior during their late teens and early twenties. Combining data from the BJS and the CPS to match incarceration rates with individual observations, we show that Black male incarceration lowers the odds of non-marital teenage fertility and increases single Black women’s school attainment and early employment. We do not find consistent evidence that high Black male incarcer...