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Sample records for black muntjac recapitulate

  1. Neo-sex chromosomes in the black muntjac recapitulate incipient evolution of mammalian sex chromosomes

    DEFF Research Database (Denmark)

    Zhou, Qi; Wang, Jun; Huang, Ling

    2008-01-01

    BACKGROUND: The regular mammalian X and Y chromosomes diverged from each other at least 166 to 148 million years ago, leaving few traces of their early evolution, including degeneration of the Y chromosome and evolution of dosage compensation. RESULTS: We studied the intriguing case of black...... muntjac, in which a recent X-autosome fusion and a subsequent large autosomal inversion within just the past 0.5 million years have led to inheritance patterns identical to the traditional X-Y (neo-sex chromosomes). We compared patterns of genome evolution in 35-kilobase noncoding regions and 23 gene...... pairs on the homologous neo-sex chromosomes. We found that neo-Y alleles have accumulated more mutations, comprising a wide variety of mutation types, which indicates cessation of recombination and is consistent with an ongoing neo-Y degeneration process. Putative deleterious mutations were observed...

  2. Characterization of muntjac DNA

    International Nuclear Information System (INIS)

    Davis, R.C.

    1981-01-01

    Sister chromatid exchange (SCE) in muntjac chromosomes is generally proportional to the chromosomal DNA content, but the SCE frequency is reduced in the heterochromatic neck region of the X chromosome. The physical properties of muntjac DNA and the kinetics of repair of UV damage in muntjac heterochromatin and euchromatin were examined and compared with the distribution of sister chromatid exchange

  3. Characterization of muntjac DNA

    Energy Technology Data Exchange (ETDEWEB)

    Davis, R.C.

    1981-05-27

    Sister chromatid exchange (SCE) in muntjac chromosomes is generally proportional to the chromosomal DNA content, but the SCE frequency is reduced in the heterochromatic neck region of the X chromosome. The physical properties of muntjac DNA and the kinetics of repair of UV damage in muntjac heterochromatin and euchromatin were examined and compared with the distribution of sister chromatid exchange.

  4. Chromosomal evolution of the Chinese muntjac (Muntiacus reevesi).

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    Yang, F; O'Brien, P C; Wienberg, J; Neitzel, H; Lin, C C; Ferguson-Smith, M A

    1997-06-01

    The aim of this study was to test the validity of the hypothesis that the 2n=46 karyotype of the Chinese muntjac (Muntiacus reevesi) could have evolved through 12 tandem fusions from a 2n=70 hypothetical ancestral karyotype, which is still retained in Chinese water deer (Hydropotes inermis) and brown-brocket deer (Mazama gouazoubira). Combining fluorescence-activated chromosomal sorting and degenerate oligonucleotide-primed polymerase chain reaction, we generated chromosome-specific DNA paint probes for 13 M. gouazoubira chromosomes and most of the M. reevesi chromosomes with the exception of 18, 19 and X. These paint probes were used for fluorescence in situ hybridisation to chromosomal preparations of M. reevesi, H. inermis and M. gouazoubira. Chromosome-specific paint probes from M. reevesi chromosomes 1-5 and 11 each delineated more than one homologous pair (18 pairs in total) on the metaphases of H. inermis and M. gouazoubira. All the other probes from M. reevesi and probes from M. gouazoubira each hybridised to one pair of homologous chromosomes or regions. The C5 probe, derived from centromeric satellite sequences of M. reevesi, hybridised to the centromeric regions of all chromosomes of these three species. Most interestingly, several non-random interstitial signals, which are apparently localised to the putative fusion points, were found on chromosomes 1-5 and 11 of M. reevesi. Both the reciprocal painting patterns and localisation of the C5 probe demonstrate that M. reevesi chromosomes 1-5 and 11 could have evolved from 18 different ancestral chromosomes through 12 tandem fusions, thus providing direct molecular cytogenetic support for the tandem fusion hypothesis of karyotype evolution in M. reevesi.

  5. Detection of a novel gammaherpesvirus (genus Rhadinovirus) in wild muntjac deer in Northern Ireland.

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    McKillen, John; Hogg, Kayleigh; Lagan, Paula; Ball, Cheryl; Doherty, Simon; Reid, Neil; Collins, Lisa; Dick, Jaimie T A

    2017-06-01

    This study represents the initial part of an investigation into the potential for non-native, wild, free-living muntjac deer (Muntiacus reevesi) to carry viruses that could be a threat to livestock. A degenerate PCR assay was used to screen a range of tissues from muntjac deer culled in Northern Ireland for the presence of herpesviral nucleic acids. This was followed by sequencing of PCR amplicons and phylogenetic analysis. We report the detection of a novel gammaherpesvirus most closely related to a type 2 ruminant rhadinovirus from mule deer. It remains to be determined if this new virus is pathogenic to deer or presents a risk to food security through the susceptibility of domestic livestock.

  6. Infectious Prions in the Pregnancy Microenvironment of Chronic Wasting Disease-Infected Reeves' Muntjac Deer.

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    Nalls, Amy V; McNulty, Erin; Hoover, Clare E; Pulscher, Laura A; Hoover, Edward A; Mathiason, Candace K

    2017-08-01

    Ample evidence exists for the presence of infectious agents at the maternal-fetal interface, often with grave outcomes to the developing fetus (i.e., Zika virus, brucella, cytomegalovirus, and toxoplasma). While less studied, pregnancy-related transmissible spongiform encephalopathies (TSEs) have been implicated in several species, including humans. Our previous work has shown that prions can be transferred from mother to offspring, resulting in the development of clinical TSE disease in offspring born to muntjac dams infected with chronic wasting disease (CWD) (1). We further demonstrated protein misfolding cyclic amplification (PMCA)-competent prions within the female reproductive tract and in fetal tissues harvested from CWD experimentally and naturally exposed cervids (1, 2). To assess whether the PMCA-competent prions residing at the maternal-fetal interface were infectious and to determine if the real-time quaking-induced conversion (RT-QuIC) methodology may enhance our ability to detect amyloid fibrils within the pregnancy microenvironment, we employed a mouse bioassay and RT-QuIC. In this study, we have demonstrated RT-QuIC seeding activity in uterus, placentome, ovary, and amniotic fluid but not in allantoic fluids harvested from CWD-infected Reeves' muntjac dams showing clinical signs of infection (clinically CWD-infected) and in some placentomes from pre-clinically CWD-infected dams. Prion infectivity was confirmed within the uterus, amniotic fluid, and the placentome, the semipermeable interface that sustains the developing fetus, of CWD-infected dams. This is the first report of prion infectivity within the cervid pregnancy microenvironment, revealing a source of fetal CWD exposure prior to the birthing process, maternal grooming, or encounters with contaminated environments. IMPORTANCE The facile dissemination of chronic wasting disease within captive and free-range cervid populations has led to questions regarding the transmission dynamics of this

  7. Mother to offspring transmission of chronic wasting disease in reeves' muntjac deer.

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    Amy V Nalls

    Full Text Available The horizontal transmission of prion diseases has been well characterized in bovine spongiform encephalopathy (BSE, chronic wasting disease (CWD of deer and elk and scrapie of sheep, and has been regarded as the primary mode of transmission. Few studies have monitored the possibility of vertical transmission occurring within an infected mother during pregnancy. To study the potential for and pathway of vertical transmission of CWD in the native cervid species, we used a small cervid model-the polyestrous breeding, indoor maintainable, Reeves' muntjac deer-and determined that the susceptibility and pathogenesis of CWD in these deer reproduce that in native mule and white-tailed deer. Moreover, we demonstrate here that CWD prions are transmitted from doe to fawn. Maternal CWD infection also appears to result in lower percentage of live birth offspring. In addition, evolving evidence from protein misfolding cyclic amplification (PMCA assays on fetal tissues suggest that covert prion infection occurs in utero. Overall, our findings demonstrate that transmission of prions from mother to offspring can occur, and may be underestimated for all prion diseases.

  8. Karyotype evolution of giraffes (Giraffa camelopardalis) revealed by cross-species chromosome painting with Chinese muntjac (Muntiacus reevesi) and human (Homo sapiens) paints.

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    Huang, L; Nesterenko, A; Nie, W; Wang, J; Su, W; Graphodatsky, A S; Yang, F

    2008-01-01

    Considering the giraffe (Giraffa camelopardalis, GCA, 2n = 30) as a primitive species, its comparative genomic data are critical for our understanding of the karyotype evolution of pecorans. Here, we have established genome-wide chromosomal homologies between giraffe, Chinese muntjac (Muntiacus reevesi, MRE, 2n = 46) and human (Homo sapiens, HSA, 2n = 46) with whole sets of chromosome-specific paints from Chinese muntjac and human, in addition to providing a high-resolution G-banding karyotype of giraffe. Chinese muntjac and human chromosome paints detected 32 and 45 autosomal homologs in the genome of giraffe, respectively. Our results suggest that it would require at least thirteen fissions, six fusions and three intrachromosomal rearrangements to 'transform' the 2n = 44 eutherian ancestral karyotype to the 2n = 58 pecoran ancestral karyotype. During giraffe evolution, some ancestral eutherian syntenies (i.e. association of HSA3/21, 4/8, 7/16, 14/15, 16/19 and two forms of 12/22) have been retained, while several derived syntenies (i.e. associations of human homologous segments 2/1, 2/9, 5/19, 4/12/22, 8/9, and 10/20) have been produced. The reduction of chromosome number in giraffe from the 2n = 58 pecoran ancestral karyotype could be primarily attributed to extensive Robertsonian translocations of ancestral chromosomal segments. More complex chromosomal rearrangements (including tandem fusion, centromere repositioning and pericentric inversion) have happened during the evolution of GCA2 and GCA8. Copyright 2008 S. Karger AG, Basel.

  9. Cerebral Organoids Recapitulate Epigenomic Signatures of the Human Fetal Brain

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    Chongyuan Luo

    2016-12-01

    Full Text Available Organoids derived from human pluripotent stem cells recapitulate the early three-dimensional organization of the human brain, but whether they establish the epigenomic and transcriptional programs essential for brain development is unknown. We compared epigenomic and regulatory features in cerebral organoids and human fetal brain, using genome-wide, base resolution DNA methylome and transcriptome sequencing. Transcriptomic dynamics in organoids faithfully modeled gene expression trajectories in early-to-mid human fetal brains. We found that early non-CG methylation accumulation at super-enhancers in both fetal brain and organoids marks forthcoming transcriptional repression in the fully developed brain. Demethylated regions (74% of 35,627 identified during organoid differentiation overlapped with fetal brain regulatory elements. Interestingly, pericentromeric repeats showed widespread demethylation in multiple types of in vitro human neural differentiation models but not in fetal brain. Our study reveals that organoids recapitulate many epigenomic features of mid-fetal human brain and also identified novel non-CG methylation signatures of brain development.

  10. Field migration rates of tidal meanders recapitulate fluvial morphodynamics.

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    Finotello, Alvise; Lanzoni, Stefano; Ghinassi, Massimiliano; Marani, Marco; Rinaldo, Andrea; D'Alpaos, Andrea

    2018-02-13

    The majority of tidal channels display marked meandering features. Despite their importance in oil-reservoir formation and tidal landscape morphology, questions remain on whether tidal-meander dynamics could be understood in terms of fluvial processes and theory. Key differences suggest otherwise, like the periodic reversal of landscape-forming tidal flows and the widely accepted empirical notion that tidal meanders are stable landscape features, in stark contrast with their migrating fluvial counterparts. On the contrary, here we show that, once properly normalized, observed migration rates of tidal and fluvial meanders are remarkably similar. Key to normalization is the role of tidal channel width that responds to the strong spatial gradients of landscape-forming flow rates and tidal prisms. We find that migration dynamics of tidal meanders agree with nonlinear theories for river meander evolution. Our results challenge the conventional view of tidal channels as stable landscape features and suggest that meandering tidal channels recapitulate many fluvial counterparts owing to large gradients of tidal prisms across meander wavelengths. Copyright © 2018 the Author(s). Published by PNAS.

  11. Field migration rates of tidal meanders recapitulate fluvial morphodynamics

    Science.gov (United States)

    Finotello, Alvise; Lanzoni, Stefano; Ghinassi, Massimiliano; Marani, Marco; Rinaldo, Andrea; D'Alpaos, Andrea

    2018-02-01

    The majority of tidal channels display marked meandering features. Despite their importance in oil-reservoir formation and tidal landscape morphology, questions remain on whether tidal-meander dynamics could be understood in terms of fluvial processes and theory. Key differences suggest otherwise, like the periodic reversal of landscape-forming tidal flows and the widely accepted empirical notion that tidal meanders are stable landscape features, in stark contrast with their migrating fluvial counterparts. On the contrary, here we show that, once properly normalized, observed migration rates of tidal and fluvial meanders are remarkably similar. Key to normalization is the role of tidal channel width that responds to the strong spatial gradients of landscape-forming flow rates and tidal prisms. We find that migration dynamics of tidal meanders agree with nonlinear theories for river meander evolution. Our results challenge the conventional view of tidal channels as stable landscape features and suggest that meandering tidal channels recapitulate many fluvial counterparts owing to large gradients of tidal prisms across meander wavelengths.

  12. Recapitulation of the forward nuclear auxin response pathway in yeast.

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    Pierre-Jerome, Edith; Jang, Seunghee S; Havens, Kyle A; Nemhauser, Jennifer L; Klavins, Eric

    2014-07-01

    Auxin influences nearly every aspect of plant biology through a simple signaling pathway; however, it remains unclear how much of the diversity in auxin effects is explained by variation in the core signaling components and which properties of these components may contribute to diversification in response dynamics. Here, we recapitulated the entire Arabidopsis thaliana forward nuclear auxin signal transduction pathway in Saccharomyces cerevisiae to test whether signaling module composition enables tuning of the dynamic response. Sensitivity analysis guided by a small mathematical model revealed the centrality of auxin/indole-3-acetic acid (Aux/IAA) transcriptional corepressors in controlling response dynamics and highlighted the strong influence of natural variation in Aux/IAA degradation rates on circuit performance. When the basic auxin response circuit was expanded to include multiple Aux/IAAs, we found that dominance relationships between coexpressed Aux/IAAs were sufficient to generate distinct response modules similar to those seen during plant development. Our work provides a new method for dissecting auxin signaling and demonstrates the key role of Aux/IAAs in tuning auxin response dynamics.

  13. Estradiol partially recapitulates murine pituitary cell cycle response to pregnancy.

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    Toledano, Yoel; Zonis, Svetlana; Ren, Song-Guang; Wawrowsky, Kolja; Chesnokova, Vera; Melmed, Shlomo

    2012-10-01

    Because pregnancy and estrogens both induce pituitary lactotroph hyperplasia, we assessed the expression of pituitary cell cycle regulators in two models of murine pituitary hyperplasia. Female mice were assessed during nonpregnancy, pregnancy, day of delivery, and postpartum. We also implanted estradiol (E(2)) pellets in female mice and studied them for 2.5 months. Pituitary weight in female mice increased 2-fold after E(2) administration and 1.4-fold at day of delivery, compared with placebo-treated or nonpregnant females. Pituitary proliferation, as assessed by proliferating cell nuclear antigen and/or Ki-67 staining, increased dramatically during both mid-late pregnancy and E(2) administration, and lactotroph hyperplasia was also observed. Pregnancy induced pituitary cell cycle proliferative and inhibitory responses at the G(1)/S checkpoint. Differential cell cycle regulator expression included cyclin-dependent kinase inhibitors, p21(Cip1), p27(Kip1), and cyclin D1. Pituitary cell cycle responses to E(2) administration partially recapitulated those effects observed at mid-late pregnancy, coincident with elevated circulating mouse E(2), including increased expression of proliferating cell nuclear antigen, Ki-67, p15(INK4b), and p21(Cip1). Nuclear localization of pituitary p21(Cip1) was demonstrated at mid-late pregnancy but not during E(2) administration, suggesting a cell cycle inhibitory role for p21(Cip1) in pregnancy, yet a possible proproliferative role during E(2) administration. Most observed cell cycle protein alterations were reversed postpartum. Murine pituitary meets the demand for prolactin during lactation associated with induction of both cell proliferative and inhibitory pathways, mediated, at least partially, by estradiol.

  14. Disregarding familiarity during recollection attempts: content-specific recapitulation as a retrieval orientation strategy.

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    Gray, Stephen J; Gallo, David A

    2015-01-01

    People can use a content-specific recapitulation strategy to trigger memories (i.e., mentally reinstating encoding conditions), but how people deploy this strategy is unclear. Is recapitulation naturally used to guide all recollection attempts, or is it only used selectively, after retrieving incomplete information that requires additional monitoring? According to a retrieval orientation model, people use recapitulation whenever they search memory for specific information, regardless of what information might come to mind. In contrast, according to a postretrieval monitoring model, people selectively engage recapitulation only after retrieving ambiguous information in order to evaluate this information and guide additional retrieval attempts. We tested between these models using a criterial recollection task, and by manipulating the strength of ambiguous information associated with to-be-rejected foils (i.e., familiarity or noncriterial information). Replicating prior work, foil rejections were greater when people attempted to recollect targets studied at a semantic level (deep test) compared to an orthographic level (shallow test), implicating more accurate retrieval monitoring. To investigate the role of a recapitulation strategy in this monitoring process, a final test assessed memory for the foils that were earlier processed on these recollection tests. Performance on this foil recognition test suggested that people had engaged in more elaborative content-specific recapitulation when initially tested for deep compared to shallow recollections, and critically, this elaboration effect did not interact with the experimental manipulation of foil strength. These results support the retrieval orientation model, whereby a recapitulation strategy was used to orient retrieval toward specific information during every recollection attempt. PsycINFO Database Record (c) 2015 APA, all rights reserved.

  15. Genome reactivation after the silence in mitosis: recapitulating mechanisms of development?

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    Zaret, Kenneth S

    2014-04-28

    Transcription is silenced during mitosis and reactivated at mitotic exit. The dynamics and identities of "bookmarking" transcription factors and chromatin marks that mediate reactivation often recapitulate those observed during cell identity establishment in development. Thus, features of postmitotic gene reactivation can provide insights into mechanisms of developmental cell fate establishment. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Translational control of TWIST1 expression in MCF-10A cell lines recapitulating breast cancer progression

    DEFF Research Database (Denmark)

    Nairismägi, Maarja-Liisa; Vislovukh, Andrii; Meng, Q

    2012-01-01

    TWIST1 is a highly conserved basic helix-loop-helix transcription factor that promotes epithelial–mesenchymal transition (EMT). Its misregulation has been observed in various types of tumors. Using the MCF-10A-series of cell lines that recapitulate the early stages of breast cancer formation...

  17. Black to Black

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    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 is hi...... suggested that appreciation of the highly personal motives of both Siouxsie Sioux and Janelle Monáe in wearing black may be achieved via analogies with the minimalist sublime of American artists Frank Stella’s and Ad Reinhardt’s black canvasses.......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...... is hinted by Rudyard Kipling’s illustration of ‘The [Black] Cat That Walked by Himself’ in his classic children’s tale). It was well understood by uniformed Anarchists, Fascists and the SS that there is an assertive presence connected with the black-clad figure. The paradox of black’s abstract elegance...

  18. A recapitulative three-dimensional model of breast carcinoma requires perfusion for multi-week growth

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    Kayla F Goliwas

    2016-07-01

    Full Text Available Breast carcinomas are complex, three-dimensional tissues composed of cancer epithelial cells and stromal components, including fibroblasts and extracellular matrix. In vitro models that more faithfully recapitulate this dimensionality and stromal microenvironment should more accurately elucidate the processes driving carcinogenesis, tumor progression, and therapeutic response. Herein, novel in vitro breast carcinoma surrogates, distinguished by a relevant dimensionality and stromal microenvironment, are described and characterized. A perfusion bioreactor system was used to deliver medium to surrogates containing engineered microchannels and the effects of perfusion, medium composition, and the method of cell incorporation and density of initial cell seeding on the growth and morphology of surrogates were assessed. Perfused surrogates demonstrated significantly greater cell density and proliferation and were more histologically recapitulative of human breast carcinoma than surrogates maintained without perfusion. Although other parameters of the surrogate system, such as medium composition and cell seeding density, affected cell growth, perfusion was the most influential parameter.

  19. [AN OVERALL SOUND PROCESS] Altered Dynamics and Instrumentation at the Onset of Recapitulation in the Nineteenth-Century Symphony

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    Steven Craig Cannon

    2016-01-01

    Full Text Available In standard sonata form, the onset of recapitulation exactly quotes the beginning of the exposition, preserving both “structural” parameters (melody, rhythm, harmony, key, as well as “secondary” ones (dynamics, instrumentation, register, tempo. In practice, however, composers may alter any aspect of the main theme upon its return. Most analysis of such recapitulatory alteration has focused on structural change, with other parameters receiving relatively little attention. This paper examines composers’ handling of two secondary parameters—dynamic markings and instrumental density—at the beginnings of recapitulations in the nineteenth-century symphonic repertoire. In order to analyse a large number of works, a system of classifications for recapitulatory alterations is necessary. The alterations fall into four broad types: “similar” recapitulations have few or no changes to dynamics and instrumentation, “intensified” recapitulations are louder or more fully orchestrated than the beginning of the exposition, “attenuated” recapitulations have quieter dynamics or sparser orchestration, and “contradictory” recapitulations have alterations to dynamics and instrumentation that work in opposite directions. After explaining this classification system in detail, with examples from specific symphonies, the paper then gives the results of an analytical survey of 483 sonata-form movements from 282 symphonies dating from the years 1800 to 1899. Similar and intensified recapitulations are most common, with preferences changing over time. Until about the 1840s, similar recapitulations were most common, but from around the 1860s on, intensified returns became the default choice. Attenuated and contradictory recapitulations, by contrast, are very rare throughout the century.

  20. Embryonic stem cell-derived embryoid bodies development in collagen gels recapitulates sprouting angiogenesis.

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    Feraud, O; Cao, Y; Vittet, D

    2001-12-01

    The formation of new blood vessels proceeds by both vasculogenesis and angiogenesis. The development of models, which fully recapitulate spatio-temporal events involved during these processes, are crucial to fully understand their mechanisms of regulation. In vitro differentiation of murine embryonic stem (ES) cells has been shown to be a useful tool to investigate factors and genes potentially involved in vasculogenesis (Hirashima et al, 1999; Risau et al, 1988; Vittet et al, 1996; Wang et al, 1992; Wartenberg et al, 1998). We asked here whether this model system can also recapitulate angiogenesis, which may offer new means to study mechanisms involved in this process. ES-derived embryoid bodies (EBs) obtained after 11 days of differentiation, in which a primitive vascular network had formed, were then subcultured into a type I collagen matrix. In the presence of angiogenic growth factors, EBs rapidly developed branching pseudopods. Whole mount immunostainings with a PECAM antibody revealed that more than 75% EBs displayed, within a few days, a large number of endothelial outgrowths that can give tube-like structures with concomitant differentiation of alpha-smooth muscle actin positive cells, thus evoking sprouting angiogenesis. High expression levels of flk1 (VEGFR2), flt1 (VEGFR1), tie-1, and tie-2 are also found, indicating that budding endothelial cells displayed an angiogenic phenotype. The endothelial sprouting response was specifically induced by angiogenic factors with a major contribution of vascular endothelial growth factor (VEGF). Known angiostatic agents, such as platelet factor 4 (PF4), angiostatin, and endostatin inhibited the formation of endothelial sprouts induced by angiogenic factors. Moreover, consistent with the in vivo phenotype, VE-cadherin deficient EBs failed to develop angiogenesis in this model. ES cell differentiation can then recapitulate, in addition to vasculogenesis, the early stages of sprouting angiogenesis. This model system

  1. Heterotypic mouse models of canine osteosarcoma recapitulate tumor heterogeneity and biological behavior

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    Milcah C. Scott

    2016-12-01

    Full Text Available Osteosarcoma (OS is a heterogeneous and rare disease with a disproportionate impact because it mainly affects children and adolescents. Lamentably, more than half of patients with OS succumb to metastatic disease. Clarification of the etiology of the disease, development of better strategies to manage progression, and methods to guide personalized treatments are among the unmet health needs for OS patients. Progress in managing the disease has been hindered by the extreme heterogeneity of OS; thus, better models that accurately recapitulate the natural heterogeneity of the disease are needed. For this study, we used cell lines derived from two spontaneous canine OS tumors with distinctly different biological behavior (OS-1 and OS-2 for heterotypic in vivo modeling that recapitulates the heterogeneous biology and behavior of this disease. Both cell lines demonstrated stability of the transcriptome when grown as orthotopic xenografts in athymic nude mice. Consistent with the behavior of the original tumors, OS-2 xenografts grew more rapidly at the primary site and had greater propensity to disseminate to lung and establish microscopic metastasis. Moreover, OS-2 promoted formation of a different tumor-associated stromal environment than OS-1 xenografts. OS-2-derived tumors comprised a larger percentage of the xenograft tumors than OS-1-derived tumors. In addition, a robust pro-inflammatory population dominated the stromal cell infiltrates in OS-2 xenografts, whereas a mesenchymal population with a gene signature reflecting myogenic signaling dominated those in the OS-1 xenografts. Our studies show that canine OS cell lines maintain intrinsic features of the tumors from which they were derived and recapitulate the heterogeneous biology and behavior of bone cancer in mouse models. This system provides a resource to understand essential interactions between tumor cells and the stromal environment that drive the progression and metastatic propensity of

  2. Recapitulation of Extracellular LAMININ Environment Maintains Stemness of Satellite Cells In Vitro

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    Kana Ishii

    2018-02-01

    Full Text Available Summary: Satellite cells function as precursor cells in mature skeletal muscle homeostasis and regeneration. In healthy tissue, these cells are maintained in a state of quiescence by a microenvironment formed by myofibers and basement membrane in which LAMININs (LMs form a major component. In the present study, we evaluated the satellite cell microenvironment in vivo and found that these cells are encapsulated by LMα2–5. We sought to recapitulate this satellite cell niche in vitro by culturing satellite cells in the presence of recombinant LM-E8 fragments. We show that treatment with LM-E8 promotes proliferation of satellite cells in an undifferentiated state, through reduced phosphorylation of JNK and p38. On transplantation into injured muscle tissue, satellite cells cultured with LM-E8 promoted the regeneration of skeletal muscle. These findings represent an efficient method of culturing satellite cells for use in transplantation through the recapitulation of the satellite cell niche using recombinant LM-E8 fragments. : In this study, examination of the satellite cell microenvironment in vivo revealed that these cells are encapsulated by LMα2–5. We find that reconstitution of the satellite cell niche with recombinant LM-E8 fragments promotes the proliferation and maintains satellite cells in an undifferentiated state. Keywords: Laminin, muscle stem cell, cell transplantation therapy, regeneration, muscle satellite cell, LM-E8

  3. Multiple congenital malformations of Wolf-Hirschhorn syndrome are recapitulated in Fgfrl1 null mice.

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    Catela, Catarina; Bilbao-Cortes, Daniel; Slonimsky, Esfir; Kratsios, Paschalis; Rosenthal, Nadia; Te Welscher, Pascal

    2009-01-01

    Wolf-Hirschhorn syndrome (WHS) is caused by deletions in the short arm of chromosome 4 (4p) and occurs in about one per 20,000 births. Patients with WHS display a set of highly variable characteristics including craniofacial dysgenesis, mental retardation, speech problems, congenital heart defects, short stature and a variety of skeletal anomalies. Analysis of patients with 4p deletions has identified two WHS critical regions (WHSCRs); however, deletions targeting mouse WHSCRs do not recapitulate the classical WHS defects, and the genes contributing to WHS have not been conclusively established. Recently, the human FGFRL1 gene, encoding a putative fibroblast growth factor (FGF) decoy receptor, has been implicated in the craniofacial phenotype of a WHS patient. Here, we report that targeted deletion of the mouse Fgfrl1 gene recapitulates a broad array of WHS phenotypes, including abnormal craniofacial development, axial and appendicular skeletal anomalies, and congenital heart defects. Fgfrl1 null mutants also display a transient foetal anaemia and a fully penetrant diaphragm defect, causing prenatal and perinatal lethality. Together, these data support a wider role for Fgfrl1 in development, implicate FGFRL1 insufficiency in WHS, and provide a novel animal model to dissect the complex aetiology of this human disease.

  4. Re-engaging with the past: recapitulation of encoding operations during retrieval

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    Alexa eMorcom

    2014-05-01

    Full Text Available Recollection of events is accompanied by selective reactivation of cortical regions which responded to specific sensory and cognitive dimensions of the original events. This reactivation is thought to reflect the reinstatement of stored memory representations and therefore to reflect memory content, but it may also reveal processes which support both encoding and retrieval. The present study used event-related functional magnetic resonance imaging (fMRI to investigate whether regions selectively engaged in encoding face and scene context with studied words are also re-engaged when the context is later retrieved. As predicted, encoding face and scene context with visually presented words elicited activity in distinct, context-selective regions. Retrieval of face and scene context also re-engaged some of the regions which had shown successful encoding effects. However, this recapitulation of encoding activity did not show the same context selectivity observed at encoding. Successful retrieval of both face and scene context re-engaged regions which had been associated with encoding of the other type of context, as well as those associated with encoding the same type of context. This recapitulation may reflect retrieval attempts which are not context-selective, but use shared retrieval cues to re-engage encoding operations in service of recollection.

  5. Recapitulation of Extracellular LAMININ Environment Maintains Stemness of Satellite Cells In Vitro.

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    Ishii, Kana; Sakurai, Hidetoshi; Suzuki, Nobuharu; Mabuchi, Yo; Sekiya, Ichiro; Sekiguchi, Kiyotoshi; Akazawa, Chihiro

    2018-02-13

    Satellite cells function as precursor cells in mature skeletal muscle homeostasis and regeneration. In healthy tissue, these cells are maintained in a state of quiescence by a microenvironment formed by myofibers and basement membrane in which LAMININs (LMs) form a major component. In the present study, we evaluated the satellite cell microenvironment in vivo and found that these cells are encapsulated by LMα2-5. We sought to recapitulate this satellite cell niche in vitro by culturing satellite cells in the presence of recombinant LM-E8 fragments. We show that treatment with LM-E8 promotes proliferation of satellite cells in an undifferentiated state, through reduced phosphorylation of JNK and p38. On transplantation into injured muscle tissue, satellite cells cultured with LM-E8 promoted the regeneration of skeletal muscle. These findings represent an efficient method of culturing satellite cells for use in transplantation through the recapitulation of the satellite cell niche using recombinant LM-E8 fragments. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  6. Black holes

    International Nuclear Information System (INIS)

    Feast, M.W.

    1981-01-01

    This article deals with two questions, namely whether it is possible for black holes to exist, and if the answer is yes, whether we have found any yet. In deciding whether black holes can exist or not the central role in the shaping of our universe played by the forse of gravity is discussed, and in deciding whether we are likely to find black holes in the universe the author looks at the way stars evolve, as well as white dwarfs and neutron stars. He also discusses the problem how to detect a black hole, possible black holes, a southern black hole, massive black holes, as well as why black holes are studied

  7. The Genetics of Mexico Recapitulates Native American Substructure and Affects Biomedical Traits

    Science.gov (United States)

    Moreno-Estrada, Andrés; Gignoux, Christopher R.; Fernández-López, Juan Carlos; Zakharia, Fouad; Sikora, Martin; Contreras, Alejandra V.; Acuña-Alonzo, Victor; Sandoval, Karla; Eng, Celeste; Romero-Hidalgo, Sandra; Ortiz-Tello, Patricia; Robles, Victoria; Kenny, Eimear E.; Nuño-Arana, Ismael; Barquera-Lozano, Rodrigo; Macín-Pérez, Gastón; Granados-Arriola, Julio; Huntsman, Scott; Galanter, Joshua M.; Via, Marc; Ford, Jean G.; Chapela, Rocío; Rodriguez-Cintron, William; Rodríguez-Santana, Jose R.; Romieu, Isabelle; Sienra-Monge, Juan José; Navarro, Blanca del Rio; London, Stephanie J.; Ruiz-Linares, Andrés; Garcia-Herrera, Rodrigo; Estrada, Karol; Hidalgo-Miranda, Alfredo; Jimenez-Sanchez, Gerardo; Carnevale, Alessandra; Soberón, Xavier; Canizales-Quinteros, Samuel; Rangel-Villalobos, Héctor; Silva-Zolezzi, Irma; Burchard, Esteban Gonzalez; Bustamante, Carlos D.

    2014-01-01

    Mexico harbors great cultural and ethnic diversity, yet fine-scale patterns of human genome-wide variation from this region remain largely uncharacterized. We studied genomic variation within Mexico from over 1,000 individuals representing 20 indigenous and 11 mestizo populations. We found striking genetic stratification among indigenous populations within Mexico at varying degrees of geographic isolation. Some groups were as differentiated as Europeans are from East Asians. Pre-Columbian genetic substructure is recapitulated in the indigenous ancestry of admixed mestizo individuals across the country. Furthermore, two independently phenotyped cohorts of Mexicans and Mexican Americans showed a significant association between sub-continental ancestry and lung function. Thus, accounting for fine-scale ancestry patterns is critical for medical and population genetic studies within Mexico, in Mexican-descent populations, and likely in many other populations worldwide. PMID:24926019

  8. Extrachromosomal recombination substrates recapitulate beyond 12/23 restricted VDJ recombination in nonlymphoid cells.

    Science.gov (United States)

    Jung, David; Bassing, Craig H; Fugmann, Sebastian D; Cheng, Hwei-Ling; Schatz, David G; Alt, Frederick W

    2003-01-01

    V(D)J recombination occurs efficiently only between gene segments flanked by recombination signals (RSs) containing 12 and 23 base pair spacers (the 12/23 rule). A further limitation "beyond the 12/23 rule" (B12/23) exists at the TCRbeta locus and ensures Dbeta usage. Herein, we show that extrachromosomal V(D)J recombination substrates recapitulate B12/23 restriction in nonlymphoid cells. We further demonstrate that the Vbeta coding flank, the 12-RS heptamer/nonamer, and the 23-RS spacer each can significantly influence B12/23 restriction. Finally, purified core RAG1 and RAG2 proteins (together with HMG2) also reproduce B12/23 restriction in a cell-free system. Our findings indicate that B12/23 restriction of V(D)J recombination is cemented at the level of interactions between the RAG proteins and TCRbeta RS sequences.

  9. Prolonged application of high fluid shear to chondrocytes recapitulates gene expression profiles associated with osteoarthritis.

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    Fei Zhu

    Full Text Available BACKGROUND: Excessive mechanical loading of articular cartilage producing hydrostatic stress, tensile strain and fluid flow leads to irreversible cartilage erosion and osteoarthritic (OA disease. Since application of high fluid shear to chondrocytes recapitulates some of the earmarks of OA, we aimed to screen the gene expression profiles of shear-activated chondrocytes and assess potential similarities with OA chondrocytes. METHODOLOGY/PRINCIPAL FINDINGS: Using a cDNA microarray technology, we screened the differentially-regulated genes in human T/C-28a2 chondrocytes subjected to high fluid shear (20 dyn/cm(2 for 48 h and 72 h relative to static controls. Confirmation of the expression patterns of select genes was obtained by qRT-PCR. Using significance analysis of microarrays with a 5% false discovery rate, 71 and 60 non-redundant transcripts were identified to be ≥2-fold up-regulated and ≤0.6-fold down-regulated, respectively, in sheared chondrocytes. Published data sets indicate that 42 of these genes, which are related to extracellular matrix/degradation, cell proliferation/differentiation, inflammation and cell survival/death, are differentially-regulated in OA chondrocytes. In view of the pivotal role of cyclooxygenase-2 (COX-2 in the pathogenesis and/or progression of OA in vivo and regulation of shear-induced inflammation and apoptosis in vitro, we identified a collection of genes that are either up- or down-regulated by shear-induced COX-2. COX-2 and L-prostaglandin D synthase (L-PGDS induce reactive oxygen species production, and negatively regulate genes of the histone and cell cycle families, which may play a critical role in chondrocyte death. CONCLUSIONS/SIGNIFICANCE: Prolonged application of high fluid shear stress to chondrocytes recapitulates gene expression profiles associated with osteoarthritis. Our data suggest a potential link between exposure of chondrocytes/cartilage to abnormal mechanical loading and the pathogenesis

  10. Novel mouse model recapitulates genome and transcriptome alterations in human colorectal carcinomas.

    Science.gov (United States)

    McNeil, Nicole E; Padilla-Nash, Hesed M; Buishand, Floryne O; Hue, Yue; Ried, Thomas

    2017-03-01

    Human colorectal carcinomas are defined by a nonrandom distribution of genomic imbalances that are characteristic for this disease. Often, these imbalances affect entire chromosomes. Understanding the role of these aneuploidies for carcinogenesis is of utmost importance. Currently, established transgenic mice do not recapitulate the pathognonomic genome aberration profile of human colorectal carcinomas. We have developed a novel model based on the spontaneous transformation of murine colon epithelial cells. During this process, cells progress through stages of pre-immortalization, immortalization and, finally, transformation, and result in tumors when injected into immunocompromised mice. We analyzed our model for genome and transcriptome alterations using ArrayCGH, spectral karyotyping (SKY), and array based gene expression profiling. ArrayCGH revealed a recurrent pattern of genomic imbalances. These results were confirmed by SKY. Comparing these imbalances with orthologous maps of human chromosomes revealed a remarkable overlap. We observed focal deletions of the tumor suppressor genes Trp53 and Cdkn2a/p16. High-level focal genomic amplification included the locus harboring the oncogene Mdm2, which was confirmed by FISH in the form of double minute chromosomes. Array-based global gene expression revealed distinct differences between the sequential steps of spontaneous transformation. Gene expression changes showed significant similarities with human colorectal carcinomas. Pathways most prominently affected included genes involved in chromosomal instability and in epithelial to mesenchymal transition. Our novel mouse model therefore recapitulates the most prominent genome and transcriptome alterations in human colorectal cancer, and might serve as a valuable tool for understanding the dynamic process of tumorigenesis, and for preclinical drug testing. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  11. Black Alcoholism.

    Science.gov (United States)

    Watts, Thomas D.; Wright, Roosevelt

    1988-01-01

    Examines some aspects of the problem of alcoholism among Blacks, asserting that Black alcoholism can best be considered in an ecological, environmental, sociocultural, and public health context. Notes need for further research on alcoholism among Blacks and for action to reduce the problem of Black alcoholism. (NB)

  12. Black Culture

    Science.gov (United States)

    Brown, Angela Khristin

    2013-01-01

    The migration of blacks in North America through slavery became united. The population of blacks passed down 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…

  13. Systematic Three-Dimensional Coculture Rapidly Recapitulates Interactions between Human Neurons and Astrocytes

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    Robert Krencik

    2017-12-01

    Full Text Available Summary: Human astrocytes network with neurons in dynamic ways that are still poorly defined. Our ability to model this relationship is hampered by the lack of relevant and convenient tools to recapitulate this complex interaction. To address this barrier, we have devised efficient coculture systems utilizing 3D organoid-like spheres, termed asteroids, containing pre-differentiated human pluripotent stem cell (hPSC-derived astrocytes (hAstros combined with neurons generated from hPSC-derived neural stem cells (hNeurons or directly induced via Neurogenin 2 overexpression (iNeurons. Our systematic methods rapidly produce structurally complex hAstros and synapses in high-density coculture with iNeurons in precise numbers, allowing for improved studies of neural circuit function, disease modeling, and drug screening. We conclude that these bioengineered neural circuit model systems are reliable and scalable tools to accurately study aspects of human astrocyte-neuron functional properties while being easily accessible for cell-type-specific manipulations and observations. : In this article, Krencik and colleagues show that high-density cocultures of pre-differentiated human astrocytes with induced neurons, from pluripotent stem cells, elicit mature characteristics by 3–5 weeks. This provides a faster and more defined alternative method to organoid cultures for investigating human neural circuit function. Keywords: human pluripotent stem cells, neurons, astrocytes, synapses, coculture, three-dimensional spheres, organoids, disease modeling

  14. Recapitulating physiological and pathological shear stress and oxygen to model vasculature in health and disease

    Science.gov (United States)

    Abaci, Hasan Erbil; Shen, Yu-I.; Tan, Scott; Gerecht, Sharon

    2014-05-01

    Studying human vascular disease in conventional cell cultures and in animal models does not effectively mimic the complex vascular microenvironment and may not accurately predict vascular responses in humans. We utilized a microfluidic device to recapitulate both shear stress and O2 levels in health and disease, establishing a microfluidic vascular model (μVM). Maintaining human endothelial cells (ECs) in healthy-mimicking conditions resulted in conversion to a physiological phenotype namely cell elongation, reduced proliferation, lowered angiogenic gene expression and formation of actin cortical rim and continuous barrier. We next examined the responses of the healthy μVM to a vasotoxic cancer drug, 5-Fluorouracil (5-FU), in comparison with an in vivo mouse model. We found that 5-FU does not induce apoptosis rather vascular hyperpermeability, which can be alleviated by Resveratrol treatment. This effect was confirmed by in vivo findings identifying a vasoprotecting strategy by the adjunct therapy of 5-FU with Resveratrol. The μVM of ischemic disease demonstrated the transition of ECs from a quiescent to an activated state, with higher proliferation rate, upregulation of angiogenic genes, and impaired barrier integrity. The μVM offers opportunities to study and predict human ECs with physiologically relevant phenotypes in healthy, pathological and drug-treated environments.

  15. Selective Activation of mTORC1 Signaling Recapitulates Microcephaly, Tuberous Sclerosis, and Neurodegenerative Diseases

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    Hidetoshi Kassai

    2014-06-01

    Full Text Available Mammalian target of rapamycin (mTOR has been implicated in human neurological diseases such as tuberous sclerosis complex (TSC, neurodegeneration, and autism. However, little is known about when and how mTOR is involved in the pathogenesis of these diseases, due to a lack of animal models that directly increase mTOR activity. Here, we generated transgenic mice expressing a gain-of-function mutant of mTOR in the forebrain in a temporally controlled manner. Selective activation of mTORC1 in embryonic stages induced cortical atrophy caused by prominent apoptosis of neuronal progenitors, associated with upregulation of HIF-1α. In striking contrast, activation of the mTORC1 pathway in adulthood resulted in cortical hypertrophy with fatal epileptic seizures, recapitulating human TSC. Activated mTORC1 in the adult cortex also promoted rapid accumulation of cytoplasmic inclusions and activation of microglial cells, indicative of progressive neurodegeneration. Our findings demonstrate that mTORC1 plays different roles in developmental and adult stages and contributes to human neurological diseases.

  16. Clinical challenges of chronic wounds: searching for an optimal animal model to recapitulate their complexity

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    Robert Nunan

    2014-11-01

    Full Text Available The efficient healing of a skin wound is something that most of us take for granted but is essential for surviving day-to-day knocks and cuts, and is absolutely relied on clinically whenever a patient receives surgical intervention. However, the management of a chronic wound – defined as a barrier defect that has not healed in 3 months – has become a major therapeutic challenge throughout the Western world, and it is a problem that will only escalate with the increasing incidence of conditions that impede wound healing, such as diabetes, obesity and vascular disorders. Despite being clinically and molecularly heterogeneous, all chronic wounds are generally assigned to one of three major clinical categories: leg ulcers, diabetic foot ulcers or pressure ulcers. Although we have gleaned much knowledge about the fundamental cellular and molecular mechanisms that underpin healthy, acute wound healing from various animal models, we have learned much less about chronic wound repair pathology from these models. This might largely be because the animal models being used in this field of research have failed to recapitulate the clinical features of chronic wounds. In this Clinical Puzzle article, we discuss the clinical complexity of chronic wounds and describe the best currently available models for investigating chronic wound pathology. We also assess how such models could be optimised to become more useful tools for uncovering pathological mechanisms and potential therapeutic treatments.

  17. Modeling the autistic cell: iPSCs recapitulate developmental principles of syndromic and nonsyndromic ASD.

    Science.gov (United States)

    Ben-Reuven, Lihi; Reiner, Orly

    2016-06-01

    The opportunity to model autism spectrum disorders (ASD) through generation of patient-derived induced pluripotent stem cells (iPSCs) is currently an emerging topic. Wide-scale research of altered brain circuits in syndromic ASD, including Rett Syndrome, Fragile X Syndrome, Angelman's Syndrome and sporadic Schizophrenia, was made possible through animal models. However, possibly due to species differences, and to the possible contribution of epigenetics in the pathophysiology of these diseases, animal models fail to recapitulate many aspects of ASD. With the advent of iPSCs technology, 3D cultures of patient-derived cells are being used to study complex neuronal phenotypes, including both syndromic and nonsyndromic ASD. Here, we review recent advances in using iPSCs to study various aspects of the ASD neuropathology, with emphasis on the efforts to create in vitro model systems for syndromic and nonsyndromic ASD. We summarize the main cellular activity phenotypes and aberrant genetic interaction networks that were found in iPSC-derived neurons of syndromic and nonsyndromic autistic patients. © 2016 Japanese Society of Developmental Biologists.

  18. Pathway-specific engineered mouse allograft models functionally recapitulate human serous epithelial ovarian cancer.

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    Ludmila Szabova

    Full Text Available The high mortality rate from ovarian cancers can be attributed to late-stage diagnosis and lack of effective treatment. Despite enormous effort to develop better targeted therapies, platinum-based chemotherapy still remains the standard of care for ovarian cancer patients, and resistance occurs at a high rate. One of the rate limiting factors for translation of new drug discoveries into clinical treatments has been the lack of suitable preclinical cancer models with high predictive value. We previously generated genetically engineered mouse (GEM models based on perturbation of Tp53 and Rb with or without Brca1 or Brca2 that develop serous epithelial ovarian cancer (SEOC closely resembling the human disease on histologic and molecular levels. Here, we describe an adaptation of these GEM models to orthotopic allografts that uniformly develop tumors with short latency and are ideally suited for routine preclinical studies. Ovarian tumors deficient in Brca1 respond to treatment with cisplatin and olaparib, a PARP inhibitor, whereas Brca1-wild type tumors are non-responsive to treatment, recapitulating the relative sensitivities observed in patients. These mouse models provide the opportunity for evaluation of effective therapeutics, including prediction of differential responses in Brca1-wild type and Brca1-deficient tumors and development of relevant biomarkers.

  19. Chemical polyglycosylation and nanolitre detection enables single-molecule recapitulation of bacterial sugar export

    Science.gov (United States)

    Kong, Lingbing; Almond, Andrew; Bayley, Hagan; Davis, Benjamin G.

    2016-05-01

    The outermost protective layer of both Gram-positive and Gram-negative bacteria is composed of bacterial capsular polysaccharides. Insights into the interactions between the capsular polysaccharide and its transporter and the mechanism of sugar export would not only increase our understanding of this key process, but would also help in the design of novel therapeutics to block capsular polysaccharide export. Here, we report a nanolitre detection system that makes use of the bilayer interface between two droplets, and we use this system to study single-molecule recapitulation of sugar export. A synthetic strategy of polyglycosylation based on tetrasaccharide monomers enables ready synthetic access to extended fragments of K30 oligosaccharides and polysaccharides. Examination of the interactions between the Escherichia coli sugar transporter Wza and very small amounts of fragments of the K30 capsular polysaccharide substrate reveal the translocation of smaller but not larger fragments. We also observe capture events that occur only on the intracellular side of Wza, which would complement coordinated feeding by adjunct biosynthetic machinery.

  20. Biomimetic strategies to recapitulate organ specific microenvironments for studying breast cancer metastasis.

    Science.gov (United States)

    Narkhede, Akshay A; Shevde, Lalita A; Rao, Shreyas S

    2017-09-15

    The progression of breast cancer from the primary tumor setting to the metastatic setting is the critical event defining Stage IV disease, no longer considered curable. The microenvironment at specific organ sites is known to play a key role in influencing the ultimate fate of metastatic cells; yet microenvironmental mediated-molecular mechanisms underlying organ specific metastasis in breast cancer are not well understood. This review discusses biomimetic strategies employed to recapitulate metastatic organ microenvironments, particularly, bone, liver, lung and brain to elucidate the mechanisms dictating metastatic breast cancer cell homing and colonization. These biomimetic strategies include in vitro techniques such as biomaterial-based co-culturing techniques, microfluidics, organ-mimetic chips, bioreactor technologies, and decellularized matrices as well as cutting edge in vivo techniques to better understand the interactions between metastatic breast cancer cells and the stroma at the metastatic site. The advantages and disadvantages of these systems are discussed. In addition, how creation of biomimetic models will impact breast cancer metastasis research and their broad utility is explored. © 2017 UICC.

  1. Per2 mutation recapitulates the vascular phenotype of diabetes in the retina and bone marrow.

    Science.gov (United States)

    Bhatwadekar, Ashay D; Yan, Yuanqing; Qi, Xiaoping; Thinschmidt, Jeffrey S; Neu, Matthew B; Li Calzi, Sergio; Shaw, Lynn C; Dominiguez, James M; Busik, Julia V; Lee, Choogon; Boulton, Michael E; Grant, Maria B

    2013-01-01

    In this study, we assessed whether Per2 clock gene-mutant mice exhibit a vascular phenotype similar to diabetes. Per2 (B6.129-Per2(tm1Drw)/J) or wild-type control mice 4 and 12 months of age were used. To evaluate diabetes-like phenotype in Per2 mutant mice, retina was quantified for mRNA expression, and degree of diabetic retinopathy was evaluated. Bone marrow neuropathy was studied by staining femurs for tyrosine hydroxylase (TH) and neurofilament 200 (NF-200). The rate of proliferation and quantification of bone marrow progenitor cells (BMPCs) was performed, and a threefold decrease in proliferation and 50% reduction in nitric oxide levels were observed in Per2 mutant mice. TH-positive nerve processes and NF-200 staining were reduced in Per2 mutant mice. Both retinal protein and mRNA expression of endothelial nitric oxide synthase were decreased by twofold. Other endothelial function genes (VEGFR2, VEGFR1) were downregulated (1.5-2-fold) in Per2 mutant retinas, whereas there was an upregulation of profibrotic pathway mediated by transforming growth factor-β1. Our studies suggest that Per2 mutant mice recapitulate key aspects of diabetes without the metabolic abnormalities, including retinal vascular damage, neuronal loss in the bone marrow, and diminished BMPC function.

  2. Preclinical platform of retinoblastoma xenografts recapitulating human disease and molecular markers of dissemination.

    Science.gov (United States)

    Pascual-Pasto, Guillem; Olaciregui, Nagore G; Vila-Ubach, Monica; Paco, Sonia; Monterrubio, Carles; Rodriguez, Eva; Winter, Ursula; Batalla-Vilacis, Mireia; Catala, Jaume; Salvador, Hector; Parareda, Andreu; Schaiquevich, Paula; Suñol, Mariona; Mora, Jaume; Lavarino, Cinzia; de Torres, Carmen; Chantada, Guillermo L; Carcaboso, Angel M

    2016-09-28

    Translational research in retinoblastoma - a pediatric tumor that originates during the development of the retina - would be improved by the creation of new patient-derived models. Using tumor samples from enucleated eyes we established a new battery of preclinical models that grow in vitro in serum-free medium and in vivo in immunodeficient mice. To examine whether the new xenografts recapitulate human disease and disseminate from the retina to the central nervous system, we evaluated their histology and the presence of molecular markers of dissemination that are used in the clinical setting to detect extraocular metastases. We evaluated GD2 synthase and CRX as such markers and generated a Taqman real-time quantitative PCR method to measure CRX mRNA for rapid, sensitive and specific quantification of local and metastatic tumor burden. This approach was able to detect 1 human retinoblastoma cell in 100.000 mouse brain cells. Our research adds novel preclinical tools for the discovery of new retinoblastoma treatments for clinical translation. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  3. Recapitulating the Structural Evolution of Redox Regulation in Adenosine 5'-Phosphosulfate Kinase from Cyanobacteria to Plants.

    Science.gov (United States)

    Herrmann, Jonathan; Nathin, David; Lee, Soon Goo; Sun, Tony; Jez, Joseph M

    2015-10-09

    In plants, adenosine 5'-phosphosulfate (APS) kinase (APSK) is required for reproductive viability and the production of 3'-phosphoadenosine 5'-phosphosulfate (PAPS) as a sulfur donor in specialized metabolism. Previous studies of the APSK from Arabidopsis thaliana (AtAPSK) identified a regulatory disulfide bond formed between the N-terminal domain (NTD) and a cysteine on the core scaffold. This thiol switch is unique to mosses, gymnosperms, and angiosperms. To understand the structural evolution of redox control of APSK, we investigated the redox-insensitive APSK from the cyanobacterium Synechocystis sp. PCC 6803 (SynAPSK). Crystallographic analysis of SynAPSK in complex with either APS and a non-hydrolyzable ATP analog or APS and sulfate revealed the overall structure of the enzyme, which lacks the NTD found in homologs from mosses and plants. A series of engineered SynAPSK variants reconstructed the structural evolution of the plant APSK. Biochemical analyses of SynAPSK, SynAPSK H23C mutant, SynAPSK fused to the AtAPSK NTD, and the fusion protein with the H23C mutation showed that the addition of the NTD and cysteines recapitulated thiol-based regulation. These results reveal the molecular basis for structural changes leading to the evolution of redox control of APSK in the green lineage from cyanobacteria to plants. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  4. Recapitulation of Human Retinal Development from Human Pluripotent Stem Cells Generates Transplantable Populations of Cone Photoreceptors

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    Anai Gonzalez-Cordero

    2017-09-01

    Full Text Available Transplantation of rod photoreceptors, derived either from neonatal retinae or pluripotent stem cells (PSCs, can restore rod-mediated visual function in murine models of inherited blindness. However, humans depend more upon cone photoreceptors that are required for daylight, color, and high-acuity vision. Indeed, macular retinopathies involving loss of cones are leading causes of blindness. An essential step for developing stem cell-based therapies for maculopathies is the ability to generate transplantable human cones from renewable sources. Here, we report a modified 2D/3D protocol for generating hPSC-derived neural retinal vesicles with well-formed ONL-like structures containing cones and rods bearing inner segments and connecting cilia, nascent outer segments, and presynaptic structures. This differentiation system recapitulates human photoreceptor development, allowing the isolation and transplantation of a pure population of stage-matched cones. Purified human long/medium cones survive and become incorporated within the adult mouse retina, supporting the potential of photoreceptor transplantation for treating retinal degeneration.

  5. Matrix-Bound Nanovesicles Recapitulate Extracellular Matrix Effects on Macrophage Phenotype.

    Science.gov (United States)

    Huleihel, Luai; Bartolacci, Joseph G; Dziki, Jenna L; Vorobyov, Tatiana; Arnold, Brooke; Scarritt, Michelle E; Pineda Molina, Catalina; LoPresti, Samuel T; Brown, Bryan N; Naranjo, Juan Diego; Badylak, Stephen F

    2017-11-01

    The early macrophage response to biomaterials has been shown to be a critical and predictive determinant of downstream outcomes. When properly prepared, bioscaffolds composed of mammalian extracellular matrix (ECM) have been shown to promote a transition in macrophage behavior from a proinflammatory to a regulatory/anti-inflammatory phenotype, which in turn has been associated with constructive and functional tissue repair. The mechanism by which ECM bioscaffolds promote this phenotypic transition, however, is poorly understood. The present study shows that matrix-bound nanovesicles (MBV), a component of ECM bioscaffolds, are capable of recapitulating the macrophage activation effects of the ECM bioscaffold from which they are derived. MBV isolated from two different source tissues, porcine urinary bladder and small intestinal submucosa, were found to be enriched in miRNA125b-5p, 143-3p, and 145-5p. Inhibition of these miRNAs within macrophages was associated with a gene and protein expression profile more consistent with a proinflammatory rather than an anti-inflammatory/regulatory phenotype. MBV and their associated miRNA cargo appear to play a significant role in mediating the effects of ECM bioscaffolds on macrophage phenotype.

  6. Advanced biomaterials and microengineering technologies to recapitulate the stepwise process of cancer metastasis.

    Science.gov (United States)

    Peela, Nitish; Truong, Danh; Saini, Harpinder; Chu, Hunghao; Mashaghi, Samaneh; Ham, Stephanie L; Singh, Sunil; Tavana, Hossein; Mosadegh, Bobak; Nikkhah, Mehdi

    2017-07-01

    Cancer is one of the leading causes of death globally according to the World Health Organization. Although improved treatments and early diagnoses have reduced cancer related mortalities, metastatic disease remains a major clinical challenge. The local tumor microenvironment plays a significant role in cancer metastasis, where tumor cells respond and adapt to a plethora of biochemical and biophysical signals from stromal cells and extracellular matrix (ECM) proteins. Due to these complexities, there is a critical need to understand molecular mechanisms underlying cancer metastasis to facilitate the discovery of more effective therapies. In the past few years, the integration of advanced biomaterials and microengineering approaches has initiated the development of innovative platform technologies for cancer research. These technologies enable the creation of biomimetic in vitro models with physiologically relevant (i.e. in vivo-like) characteristics to conduct studies ranging from fundamental cancer biology to high-throughput drug screening. In this review article, we discuss the biological significance of each step of the metastatic cascade and provide a broad overview on recent progress to recapitulate these stages using advanced biomaterials and microengineered technologies. In each section, we will highlight the advantages and shortcomings of each approach and provide our perspectives on future directions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Generation of a novel mouse model that recapitulates early and adult onset glycogenosis type IV

    Science.gov (United States)

    Akman, H. Orhan; Sheiko, Tatiana; Tay, Stacey K.H.; Finegold, Milton J.; DiMauro, Salvatore; Craigen, William J.

    2011-01-01

    Glycogen storage disease type IV (GSD IV) is a rare autosomal recessive disorder caused by deficiency of the glycogen branching enzyme (GBE). The diagnostic feature of the disease is the accumulation of a poorly branched form of glycogen known as polyglucosan (PG). The disease is clinically heterogeneous, with variable tissue involvement and age of disease onset. Absence of enzyme activity is lethal in utero or in infancy affecting primarily muscle and liver. However, residual enzyme activity (5–20%) leads to juvenile or adult onset of a disorder that primarily affects muscle as well as central and peripheral nervous system. Here, we describe two mouse models of GSD IV that reflect this spectrum of disease. Homologous recombination was used to insert flippase recognition target recombination sites around exon 7 of the Gbe1 gene and a phosphoglycerate kinase-Neomycin cassette within intron 7, leading to a reduced synthesis of GBE. Mice bearing this mutation (Gbe1neo/neo) exhibit a phenotype similar to juvenile onset GSD IV, with wide spread accumulation of PG. Meanwhile, FLPe-mediated homozygous deletion of exon 7 completely eliminated GBE activity (Gbe1−/−), leading to a phenotype of lethal early onset GSD IV, with significant in utero accumulation of PG. Adult mice with residual GBE exhibit progressive neuromuscular dysfunction and die prematurely. Differently from muscle, PG in liver is a degradable source of glucose and readily depleted by fasting, emphasizing that there are structural and regulatory differences in glycogen metabolism among tissues. Both mouse models recapitulate typical histological and physiological features of two human variants of branching enzyme deficiency. PMID:21856731

  8. Celiac Disease Histopathology Recapitulates Hedgehog Downregulation, Consistent with Wound Healing Processes Activation

    Science.gov (United States)

    Senger, Stefania; Sapone, Anna; Fiorentino, Maria Rosaria; Mazzarella, Giuseppe; Lauwers, Gregory Y.; Fasano, Alessio

    2015-01-01

    Background In celiac disease (CD), intestinal epithelium damage occurs secondary to an immune insult and is characterized by blunting of the villi and crypt hyperplasia. Similarities between Hedgehog (Hh)/BMP4 downregulation, as reported in a mouse model, and CD histopathology, suggest mechanistic involvement of Hh/BMP4/WNT pathways in proliferation and differentiation of immature epithelial cells in the context of human intestinal homeostasis and regeneration after damage. Herein we examined the nature of intestinal crypt hyperplasia and involvement of Hh/BMP4 in CD histopathology. Methods and Findings Immunohistochemistry, qPCR and in situ hybridization were used to study a cohort of 24 healthy controls (HC) and 24 patients with diagnosed acute celiac disease (A-CD) intestinal biopsies. In A-CD we observed an increase in cells positive for Leucin-rich repeat-containing G protein-coupled receptor 5 (LGR5), an epithelial stem cell specific marker and expansion of WNT responding compartment. Further, we observed alteration in number and distribution of mesenchymal cells, predicted to be part of the intestinal stem cells niche. At the molecular level we found downregulation of indian hedgehog (IHH) and other components of the Hh pathway, but we did not observe a concurrent downregulation of BMP4. However, we observed upregulation of BMPs antagonists, gremlin 1 and gremlin 2. Conclusions Our data suggest that acute CD histopathology partially recapitulates the phenotype reported in Hh knockdown models. Specifically, Hh/BMP4 paradigm appears to be decoupled in CD, as the expansion of the immature cell population does not occur consequent to downregulation of BMP4. Instead, we provide evidence that upregulation of BMP antagonists play a key role in intestinal crypt hyperplasia. This study sheds light on the molecular mechanisms underlying CD histopathology and the limitations in the use of mouse models for celiac disease. PMID:26649570

  9. Celiac Disease Histopathology Recapitulates Hedgehog Downregulation, Consistent with Wound Healing Processes Activation.

    Directory of Open Access Journals (Sweden)

    Stefania Senger

    Full Text Available In celiac disease (CD, intestinal epithelium damage occurs secondary to an immune insult and is characterized by blunting of the villi and crypt hyperplasia. Similarities between Hedgehog (Hh/BMP4 downregulation, as reported in a mouse model, and CD histopathology, suggest mechanistic involvement of Hh/BMP4/WNT pathways in proliferation and differentiation of immature epithelial cells in the context of human intestinal homeostasis and regeneration after damage. Herein we examined the nature of intestinal crypt hyperplasia and involvement of Hh/BMP4 in CD histopathology.Immunohistochemistry, qPCR and in situ hybridization were used to study a cohort of 24 healthy controls (HC and 24 patients with diagnosed acute celiac disease (A-CD intestinal biopsies. In A-CD we observed an increase in cells positive for Leucin-rich repeat-containing G protein-coupled receptor 5 (LGR5, an epithelial stem cell specific marker and expansion of WNT responding compartment. Further, we observed alteration in number and distribution of mesenchymal cells, predicted to be part of the intestinal stem cells niche. At the molecular level we found downregulation of indian hedgehog (IHH and other components of the Hh pathway, but we did not observe a concurrent downregulation of BMP4. However, we observed upregulation of BMPs antagonists, gremlin 1 and gremlin 2.Our data suggest that acute CD histopathology partially recapitulates the phenotype reported in Hh knockdown models. Specifically, Hh/BMP4 paradigm appears to be decoupled in CD, as the expansion of the immature cell population does not occur consequent to downregulation of BMP4. Instead, we provide evidence that upregulation of BMP antagonists play a key role in intestinal crypt hyperplasia. This study sheds light on the molecular mechanisms underlying CD histopathology and the limitations in the use of mouse models for celiac disease.

  10. 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.

  11. The Progressive BSSG Rat Model of Parkinson's: Recapitulating Multiple Key Features of the Human Disease.

    Directory of Open Access Journals (Sweden)

    Jackalina M Van Kampen

    Full Text Available The development of effective neuroprotective therapies for Parkinson's disease (PD has been severely hindered by the notable lack of an appropriate animal model for preclinical screening. Indeed, most models currently available are either acute in nature or fail to recapitulate all characteristic features of the disease. Here, we present a novel progressive model of PD, with behavioural and cellular features that closely approximate those observed in patients. Chronic exposure to dietary phytosterol glucosides has been found to be neurotoxic. When fed to rats, β-sitosterol β-d-glucoside (BSSG triggers the progressive development of parkinsonism, with clinical signs and histopathology beginning to appear following cessation of exposure to the neurotoxic insult and continuing to develop over several months. Here, we characterize the progressive nature of this model, its non-motor features, the anatomical spread of synucleinopathy, and response to levodopa administration. In Sprague Dawley rats, chronic BSSG feeding for 4 months triggered the progressive development of a parkinsonian phenotype and pathological events that evolved slowly over time, with neuronal loss beginning only after toxin exposure was terminated. At approximately 3 months following initiation of BSSG exposure, animals displayed the early emergence of an olfactory deficit, in the absence of significant dopaminergic nigral cell loss or locomotor deficits. Locomotor deficits developed gradually over time, initially appearing as locomotor asymmetry and developing into akinesia/bradykinesia, which was reversed by levodopa treatment. Late-stage cognitive impairment was observed in the form of spatial working memory deficits, as assessed by the radial arm maze. In addition to the progressive loss of TH+ cells in the substantia nigra, the appearance of proteinase K-resistant intracellular α-synuclein aggregates was also observed to develop progressively, appearing first in the

  12. Control of oxygen tension recapitulates zone-specific functions in human liver microphysiology systems.

    Science.gov (United States)

    Lee-Montiel, Felipe T; George, Subin M; Gough, Albert H; Sharma, Anup D; Wu, Juanfang; DeBiasio, Richard; Vernetti, Lawrence A; Taylor, D Lansing

    2017-10-01

    developed and present a method for computationally modeling and measuring oxygen that can easily be implemented in all MPS models. We have applied this method in a liver MPS in which we are then able to control oxygenation in separate devices and demonstrate that zonation-dependent hepatocyte functions in the MPS recapitulate what is known about in vivo liver physiology. We believe that this advance allows a deep experimental investigation on the role of zonation in liver metabolism and disease. In addition, modeling and measuring oxygen tension will be required as investigators migrate from PDMS to plastic and glass devices.

  13. Genetic inactivation of glutamate neurons in the rat sublaterodorsal tegmental nucleus recapitulates REM sleep behaviour disorder.

    Science.gov (United States)

    Valencia Garcia, Sara; Libourel, Paul-Antoine; Lazarus, Michael; Grassi, Daniela; Luppi, Pierre-Hervé; Fort, Patrice

    2017-02-01

    SEE SCHENCK AND MAHOWALD DOI101093/AWW329 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: Idiopathic REM sleep behaviour disorder is characterized by the enactment of violent dreams during paradoxical (REM) sleep in the absence of normal muscle atonia. Accumulating clinical and experimental data suggest that REM sleep behaviour disorder might be due to the neurodegeneration of glutamate neurons involved in paradoxical sleep and located within the pontine sublaterodorsal tegmental nucleus. The purpose of the present work was thus to functionally determine first, the role of glutamate sublaterodorsal tegmental nucleus neurons in paradoxical sleep and second, whether their genetic inactivation is sufficient for recapitulating REM sleep behaviour disorder in rats. For this goal, we first injected two retrograde tracers in the intralaminar thalamus and ventral medulla to disentangle neuronal circuits in which sublaterodorsal tegmental nucleus is involved; second we infused bilaterally in sublaterodorsal tegmental nucleus adeno-associated viruses carrying short hairpin RNAs targeting Slc17a6 mRNA [which encodes vesicular glutamate transporter 2 (vGluT2)] to chronically impair glutamate synaptic transmission in sublaterodorsal tegmental nucleus neurons. At the neuroanatomical level, sublaterodorsal tegmental nucleus neurons specifically activated during paradoxical sleep hypersomnia send descending efferents to glycine/GABA neurons within the ventral medulla, but not ascending projections to the intralaminar thalamus. These data suggest a crucial role of sublaterodorsal tegmental nucleus neurons rather in muscle atonia than in paradoxical sleep generation. In line with this hypothesis, 30 days after adeno-associated virus injections into sublaterodorsal tegmental nucleus rats display a decrease of 30% of paradoxical sleep daily quantities, and a significant increase of muscle tone during paradoxical sleep concomitant to a tremendous increase of abnormal motor dream

  14. Black Cohosh

    Science.gov (United States)

    ... who have had hormone-sensitive conditions such as breast cancer or for pregnant women or nursing mothers. Black cohosh should not be confused with blue cohosh (Caulophyllum thalictroides) , which has different effects and may not be safe. Black cohosh has ...

  15. Black Tea

    Science.gov (United States)

    ... leaves of the same plant, has some different properties. Black tea is used for improving mental alertness ... that slow blood clotting include aspirin, clopidogrel (Plavix), diclofenac (Voltaren, Cataflam, others), ibuprofen (Advil, Motrin, others), naproxen ( ...

  16. Targeting Hypoxia-Inducible Factor 1α in a New Orthotopic Model of Glioblastoma Recapitulating the Hypoxic Tumor Microenvironment.

    Science.gov (United States)

    Nigim, Fares; Cavanaugh, Jill; Patel, Anoop P; Curry, William T; Esaki, Shin-ichi; Kasper, Ekkehard M; Chi, Andrew S; Louis, David N; Martuza, Robert L; Rabkin, Samuel D; Wakimoto, Hiroaki

    2015-07-01

    Tissue hypoxia and necrosis represent pathophysiologic and histologic hallmarks of glioblastoma (GBM). Although hypoxia inducible factor 1α (HIF-1α) plays crucial roles in the malignant phenotypes of GBM, developing HIF-1α-targeted agents has been hampered by the lack of a suitable preclinical model that recapitulates the complex biology of clinical GBM. We present a new GBM model, MGG123, which was established from a recurrent human GBM. Orthotopic xenografting of stem-like MGG123 cells reproducibly generated lethal tumors that were characterized by foci of palisading necrosis, hypervascularity, and robust stem cell marker expression. Perinecrotic neoplastic cells distinctively express HIF-1α and are proliferative in both xenografts and the patient tissue. The xenografts contain scattered hypoxic foci that were consistently greater than 50 μm distant from blood vessels, indicating intratumoral heterogeneity of oxygenation. Hypoxia enhanced HIF-1α expression in cultured MGG123 cells, which was abrogated by the HIF-1α inhibitors digoxin or ouabain. In vivo, treatment of orthotopic MGG123 xenografts with digoxin decreased HIF-1α expression, vascular endothelial growth factor mRNA levels, and CD34-positive vasculature within the tumors, and extended survival of mice bearing the aggressive MGG123 GBM. This preclinical tumor model faithfully recapitulates the GBM-relevant hypoxic microenvironment and stemness and is a suitable platform for studying disease biology and developing hypoxia-targeted agents.

  17. Recapitulation of the cellular xeroderma pigmentosum-variant phenotypes using short interfering RNA for DNA polymerase H.

    Science.gov (United States)

    Laposa, Rebecca R; Feeney, Luzviminda; Cleaver, James E

    2003-07-15

    The lesion-specific DNA polymerase POLH gene is mutated in xeroderma pigmentosum variant (XP-V) patients who exhibit an increased skin cancer incidence from UV exposure. Normal cells in which POLH expression was reduced using short interfering RNAs (siRNAs) were compared with the XP-V cellular phenotype that results from naturally occurring inactivating mutations. Stable clones expressing siRNA had partially reduced POLH protein levels, and intermediate levels of UV sensitivity and S phase checkpoint activation, but similar levels of Mre11 foci as in XP-V cells. Therefore, suppression of POLH expression levels by siRNA recapitulates most of the phenotypes seen in cells from XP-V patients with inactivating mutations in POLH.

  18. A Novel Letrozole Model Recapitulates Both the Reproductive and Metabolic Phenotypes of Polycystic Ovary Syndrome in Female Mice1

    Science.gov (United States)

    Kauffman, Alexander S.; Thackray, Varykina G.; Ryan, Genevieve E.; Tolson, Kristen P.; Glidewell-Kenney, Christine A.; Semaan, Sheila J.; Poling, Matthew C.; Iwata, Nahoko; Breen, Kellie M.; Duleba, Antoni J.; Stener-Victorin, Elisabet; Shimasaki, Shunichi; Webster, Nicholas J.; Mellon, Pamela L.

    2015-01-01

    Polycystic ovary syndrome (PCOS) pathophysiology is poorly understood, due partly to lack of PCOS animal models fully recapitulating this complex disorder. Recently, a PCOS rat model using letrozole (LET), a nonsteroidal aromatase inhibitor, mimicked multiple PCOS phenotypes, including metabolic features absent in other models. Given the advantages of using genetic and transgenic mouse models, we investigated whether LET produces a similar PCOS phenotype in mice. Pubertal female C57BL/6N mice were treated for 5 wk with LET, which resulted in increased serum testosterone and normal diestrus levels of estradiol, similar to the hyperandrogenemia and follicular phase estrogen levels of PCOS women. As in PCOS, ovaries from LET mice were larger, polycystic, and lacked corpora lutea versus controls. Most LET females were acyclic, and all were infertile. LET females displayed elevated serum LH levels and higher Lhb mRNA in the pituitary. In contrast, serum FSH and Fshb were significantly reduced in LET females, demonstrating differential effects on gonadotropins, as in PCOS. Within the ovary, LET females had higher Cyp17, Cyp19, and Fsh receptor mRNA expression. In the hypothalamus, LET females had higher kisspeptin receptor mRNA expression but lower progesterone receptor mRNA levels. LET females also gained more weight than controls, had increased abdominal adiposity and adipocyte size, elevated adipose inflammatory mRNA levels, and impaired glucose tolerance, mirroring the metabolic phenotype in PCOS women. This is the first report of a LET paradigm in mice that recapitulates both reproductive and metabolic PCOS phenotypes and will be useful to genetically probe the PCOS condition. PMID:26203175

  19. Black Willow

    Science.gov (United States)

    R. M. Krinard

    1980-01-01

    Black willow and other species of Salix together comprise a majority of the stocking. Cottonwood is the chief associate, particularly in the early stages, but green ash, sycamore, pecan, persimmon, waterlocust, American elm, baldcypress, red maple, sugarberry, box-elder, and in some areas, silver maple are invaders preceding the next successional stage.

  20. Counseling Blacks

    Science.gov (United States)

    Vontress, Clemmont E.

    1970-01-01

    Blacks have developed unique environmental perceptions, values, and attitudes, making it difficult for counselors to establish and maintain positive rapport. This article examines attitudinal ingredients posited by Carl Rogers for relevance to this problem, and suggests in-service training to help counselors and other professionals relate…

  1. Black Psyllium

    Science.gov (United States)

    ... by mouth for up to 6 weeks reduces blood sugar in people with type 2 diabetes. Cancer. Diarrhea. Irritable bowel syndrome (IBS). Other conditions. ... with the dose. Diabetes: Black psyllium can lower blood sugar levels ... with type 2 diabetes by slowing down absorption of carbohydrates. Monitor blood ...

  2. Black hole astrophysics

    International Nuclear Information System (INIS)

    Blandford, R.D.; Thorne, K.S.

    1979-01-01

    Following an introductory section, the subject is discussed under the headings: on the character of research in black hole astrophysics; isolated holes produced by collapse of normal stars; black holes in binary systems; black holes in globular clusters; black holes in quasars and active galactic nuclei; primordial black holes; concluding remarks on the present state of research in black hole astrophysics. (U.K.)

  3. Quantum black holes

    CERN Document Server

    Calmet, Xavier; Winstanley, Elizabeth

    2014-01-01

    Written by foremost experts, this short book gives a clear description of the physics of quantum black holes. The reader will learn about quantum black holes in four and higher dimensions, primordial black holes, the production of black holes in high energy particle collisions, Hawking radiation, black holes in models of low scale quantum gravity and quantum gravitational aspects of black holes.

  4. Recapitulating cortical development with organoid culture in vitro and modeling abnormal spindle-like (ASPM related primary microcephaly disease

    Directory of Open Access Journals (Sweden)

    Rui Li

    2017-10-01

    Full Text Available Abstract The development of a cerebral organoid culture in vitro offers an opportunity to generate human brain-like organs to investigate mechanisms of human disease that are specific to the neurogenesis of radial glial (RG and outer radial glial (oRG cells in the ventricular zone (VZ and subventricular zone (SVZ of the developing neocortex. Modeling neuronal progenitors and the organization that produces mature subcortical neuron subtypes during early stages of development is essential for studying human brain developmental diseases. Several previous efforts have shown to grow neural organoid in culture dishes successfully, however we demonstrate a new paradigm that recapitulates neocortical development process with VZ, OSVZ formation and the lamination organization of cortical layer structure. In addition, using patient-specific induced pluripotent stem cells (iPSCs with dysfunction of the Aspm gene from a primary microcephaly patient, we demonstrate neurogenesis defects result in defective neuronal activity in patient organoids, suggesting a new strategy to study human developmental diseases in central nerve system.

  5. A Human Neural Crest Stem Cell-Derived Dopaminergic Neuronal Model Recapitulates Biochemical Abnormalities in GBA1 Mutation Carriers

    Directory of Open Access Journals (Sweden)

    Shi-Yu Yang

    2017-03-01

    Full Text Available Numerically the most important risk factor for the development of Parkinson's disease (PD is the presence of mutations in the glucocerebrosidase GBA1 gene. In vitro and in vivo studies show that GBA1 mutations reduce glucocerebrosidase (GCase activity and are associated with increased α-synuclein levels, reflecting similar changes seen in idiopathic PD brain. We have developed a neural crest stem cell-derived dopaminergic neuronal model that recapitulates biochemical abnormalities in GBA1 mutation-associated PD. Cells showed reduced GCase protein and activity, impaired macroautophagy, and increased α-synuclein levels. Advantages of this approach include easy access to stem cells, no requirement to reprogram, and retention of the intact host genome. Treatment with a GCase chaperone increased GCase protein levels and activity, rescued the autophagic defects, and decreased α-synuclein levels. These results provide the basis for further investigation of GCase chaperones or similar drugs to slow the progression of PD.

  6. Recapitulating the Structural Evolution of Redox Regulation in Adenosine 5′-Phosphosulfate Kinase from Cyanobacteria to Plants*

    Science.gov (United States)

    Herrmann, Jonathan; Nathin, David; Lee, Soon Goo; Sun, Tony; Jez, Joseph M.

    2015-01-01

    In plants, adenosine 5′-phosphosulfate (APS) kinase (APSK) is required for reproductive viability and the production of 3′-phosphoadenosine 5′-phosphosulfate (PAPS) as a sulfur donor in specialized metabolism. Previous studies of the APSK from Arabidopsis thaliana (AtAPSK) identified a regulatory disulfide bond formed between the N-terminal domain (NTD) and a cysteine on the core scaffold. This thiol switch is unique to mosses, gymnosperms, and angiosperms. To understand the structural evolution of redox control of APSK, we investigated the redox-insensitive APSK from the cyanobacterium Synechocystis sp. PCC 6803 (SynAPSK). Crystallographic analysis of SynAPSK in complex with either APS and a non-hydrolyzable ATP analog or APS and sulfate revealed the overall structure of the enzyme, which lacks the NTD found in homologs from mosses and plants. A series of engineered SynAPSK variants reconstructed the structural evolution of the plant APSK. Biochemical analyses of SynAPSK, SynAPSK H23C mutant, SynAPSK fused to the AtAPSK NTD, and the fusion protein with the H23C mutation showed that the addition of the NTD and cysteines recapitulated thiol-based regulation. These results reveal the molecular basis for structural changes leading to the evolution of redox control of APSK in the green lineage from cyanobacteria to plants. PMID:26294763

  7. Black holes

    International Nuclear Information System (INIS)

    Carter, B.

    1980-01-01

    In years 1920 as a result of quantum mechanics principles governing the structure of ordinary matter, a sudden importance for a problem raised a long time ago by Laplace: what happens when a massive body becomes so dense that even light cannot escape from its gravitational field. It is difficult to conceive how could be avoided in the actual universe the accumulation of important masses of cold matter having been submitted to gravitational breaking down followed by the formation of what is called to day a black hole [fr

  8. Making Blackness, Making Policy

    OpenAIRE

    Geller, Peter

    2012-01-01

    Too often the acknowledgment that race is a social construction ignores exactly how this construction occurs. By illuminating the way in which the category of blackness and black individuals are made, we can better see how race matters in America. Antidiscrimination policy, social science research, and the state's support of its citizens can all be improved by an accurate and concrete definition of blackness. Making Blackness, Making Policy argues that blackness and black people are literally...

  9. Black hole critical phenomena without black holes

    Indian Academy of Sciences (India)

    Black holes; numerical relativity; nonlinear sigma. Abstract. Studying the threshold of black hole formation via numerical evolution has led to the discovery of fascinating nonlinear phenomena. ... Theoretical and Computational Studies Group, Southampton College, Long Island University, Southampton, NY 11968, USA ...

  10. 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.

  11. Influenza A virus infection in zebrafish recapitulates mammalian infection and sensitivity to anti-influenza drug treatment

    Directory of Open Access Journals (Sweden)

    Kristin A. Gabor

    2014-11-01

    Full Text Available Seasonal influenza virus infections cause annual epidemics and sporadic pandemics. These present a global health concern, resulting in substantial morbidity, mortality and economic burdens. Prevention and treatment of influenza illness is difficult due to the high mutation rate of the virus, the emergence of new virus strains and increasing antiviral resistance. Animal models of influenza infection are crucial to our gaining a better understanding of the pathogenesis of and host response to influenza infection, and for screening antiviral compounds. However, the current animal models used for influenza research are not amenable to visualization of host-pathogen interactions or high-throughput drug screening. The zebrafish is widely recognized as a valuable model system for infectious disease research and therapeutic drug testing. Here, we describe a zebrafish model for human influenza A virus (IAV infection and show that zebrafish embryos are susceptible to challenge with both influenza A strains APR8 and X-31 (Aichi. Influenza-infected zebrafish show an increase in viral burden and mortality over time. The expression of innate antiviral genes, the gross pathology and the histopathology in infected zebrafish recapitulate clinical symptoms of influenza infections in humans. This is the first time that zebrafish embryos have been infected with a fluorescent IAV in order to visualize infection in a live vertebrate host, revealing a pattern of vascular endothelial infection. Treatment of infected zebrafish with a known anti-influenza compound, Zanamivir, reduced mortality and the expression of a fluorescent viral gene product, demonstrating the validity of this model to screen for potential antiviral drugs. The zebrafish model system has provided invaluable insights into host-pathogen interactions for a range of infectious diseases. Here, we demonstrate a novel use of this species for IAV research. This model has great potential to advance our

  12. In vitro recapitulation of functional microvessels for the study of endothelial shear response, nitric oxide and [Ca2+]i.

    Directory of Open Access Journals (Sweden)

    Xiang Li

    Full Text Available Microfluidic technologies enable in vitro studies to closely simulate in vivo microvessel environment with complexity. Such method overcomes certain constrains of the statically cultured endothelial monolayers and enables the cells grow under physiological range of shear flow with geometry similar to microvessels in vivo. However, there are still existing knowledge gaps and lack of convincing evidence to demonstrate and quantify key biological features of the microfluidic microvessels. In this paper, using advanced micromanufacturing and microfluidic technologies, we presented an engineered microvessel model that mimicked the dimensions and network structures of in vivo microvessels with a long-term and continuous perfusion capability, as well as high-resolution and real-time imaging capability. Through direct comparisons with studies conducted in intact microvessels, our results demonstrated that the cultured microvessels formed under perfused conditions recapitulated certain key features of the microvessels in vivo. In particular, primary human umbilical vein endothelial cells were successfully cultured the entire inner surfaces of the microchannel network with well-developed junctions indicated by VE-cadherin staining. The morphological and proliferative responses of endothelial cells to shear stresses were quantified under different flow conditions which was simulated with three-dimensional shear dependent numerical flow model. Furthermore, we successfully measured agonist-induced changes in intracellular Ca2+ concentration and nitric oxide production at individual endothelial cell levels using fluorescence imaging. The results were comparable to those derived from individually perfused intact venules. With in vivo validation of its functionalities, our microfluidic model demonstrates a great potential for biological applications and bridges the gaps between in vitro and in vivo microvascular research.

  13. Back to basics: the untreated rabbit reticulocyte lysate as a competitive system to recapitulate cap/poly(A) synergy and the selective advantage of IRES-driven translation.

    Science.gov (United States)

    Soto Rifo, Ricardo; Ricci, Emiliano P; Décimo, Didier; Moncorgé, Olivier; Ohlmann, Théophile

    2007-01-01

    Translation of most eukaryotic mRNAs involves the synergistic action between the 5' cap structure and the 3' poly(A) tail at the initiation step. The poly(A) tail has also been shown to stimulate translation of picornavirus internal ribosome entry sites (IRES)-directed translation. These effects have been attributed principally to interactions between eIF4G and poly(A)-binding protein (PABP) but also to the participation of PABP in other steps during translation initiation. As the rabbit reticulocyte lysate (RRL) does not recapitulate this cap/poly(A) synergy, several systems based on cellular cell-free extracts have been developed to study the effects of poly(A) tail in vitro but they generally exhibit low translational efficiency. Here, we describe that the non-nuclease-treated RRL (untreated RRL) is able to recapitulate the effects of poly(A) tail on translation in vitro. In this system, translation of a capped/polyadenylated RNA was specifically inhibited by either Paip2 or poly(rA), whereas translation directed by HCV IRES remained unaffected. Moreover, cleavage of eIF4G by FMDV L protease strongly stimulated translation directed by the EMCV IRES, thus recapitulating the competitive advantage that the proteolytic processing of eIF4G confers to IRES-driven RNAs.

  14. 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...... 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...... 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....

  15. 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...

  16. Black holes. Chapter 6

    International Nuclear Information System (INIS)

    Penrose, R.

    1980-01-01

    Conditions for the formation of a black hole are considered, and the properties of black holes. The possibility of Cygnus X-1 as a black hole is discussed. Einstein's theory of general relativity in relation to the formation of black holes is discussed. (U.K.)

  17. Black Eye: First Aid

    Science.gov (United States)

    First aid Black eye Black eye: First aid By Mayo Clinic Staff A black eye is caused by bleeding under the skin around the eye. Most injuries that cause a ... 13, 2018 Original article: http://www.mayoclinic.org/first-aid/first-aid-black-eye/basics/ART-20056675 . Mayo ...

  18. Search for black holes

    International Nuclear Information System (INIS)

    Cherepashchuk, Anatolii M

    2003-01-01

    Methods and results of searching for stellar mass black holes in binary systems and for supermassive black holes in galactic nuclei of different types are described. As of now (June 2002), a total of 100 black hole candidates are known. All the necessary conditions Einstein's General Relativity imposes on the observational properties of black holes are satisfied for candidate objects available, thus further assuring the existence of black holes in the Universe. Prospects for obtaining sufficient criteria for reliably distinguishing candidate black holes from real black holes are discussed. (reviews of topical problems)

  19. EMT/MET at the Crossroad of Stemness, Regeneration and Oncogenesis: The Ying-Yang Equilibrium Recapitulated in Cell Spheroids

    Directory of Open Access Journals (Sweden)

    Elvira Forte

    2017-07-01

    Full Text Available The epithelial-to-mesenchymal transition (EMT is an essential trans-differentiation process, which plays a critical role in embryonic development, wound healing, tissue regeneration, organ fibrosis, and cancer progression. It is the fundamental mechanism by which epithelial cells lose many of their characteristics while acquiring features typical of mesenchymal cells, such as migratory capacity and invasiveness. Depending on the contest, EMT is complemented and balanced by the reverse process, the mesenchymal-to-epithelial transition (MET. In the saving economy of the living organisms, the same (Ying-Yang tool is integrated as a physiological strategy in embryonic development, as well as in the course of reparative or disease processes, prominently fibrosis, tumor invasion and metastasis. These mechanisms and their related signaling (e.g., TGF-β and BMPs have been effectively studied in vitro by tissue-derived cell spheroids models. These three-dimensional (3D cell culture systems, whose phenotype has been shown to be strongly dependent on TGF-β-regulated EMT/MET processes, present the advantage of recapitulating in vitro the hypoxic in vivo micro-environment of tissue stem cell niches and their formation. These spheroids, therefore, nicely reproduce the finely regulated Ying-Yang equilibrium, which, together with other mechanisms, can be determinant in cell fate decisions in many pathophysiological scenarios, such as differentiation, fibrosis, regeneration, and oncogenesis. In this review, current progress in the knowledge of signaling pathways affecting EMT/MET and stemness regulation will be outlined by comparing data obtained from cellular spheroids systems, as ex vivo niches of stem cells derived from normal and tumoral tissues. The mechanistic correspondence in vivo and the possible pharmacological perspective will be also explored, focusing especially on the TGF-β-related networks, as well as others, such as SNAI1, PTEN, and EGR1. This

  20. Extensive Tonotopic Mapping across Auditory Cortex Is Recapitulated by Spectrally Directed Attention and Systematically Related to Cortical Myeloarchitecture.

    Science.gov (United States)

    Dick, Frederic K; Lehet, Matt I; Callaghan, Martina F; Keller, Tim A; Sereno, Martin I; Holt, Lori L

    2017-12-13

    diverse pathologies reduce quality of life by impacting such spectrally directed auditory attention, its neurobiological bases are unclear. We demonstrate that human primary and nonprimary auditory cortical activation is modulated by spectrally directed attention in a manner that recapitulates its tonotopic sensory organization. Further, the graded activation profiles evoked by single-frequency bands are correlated with attentionally driven activation when these bands are presented in complex soundscapes. Finally, we observe a strong concordance in the degree of cortical myelination and the strength of tonotopic activation across several auditory cortical regions. Copyright © 2017 Dick et al.

  1. Recapitulative list of the C.E.A. reports published by the French Atomic Energy Commission (n.757-1062, december 1957-december 1958) supplement to C.E.A. reports n. 593 and 756

    International Nuclear Information System (INIS)

    Schmiterlow, C.G.; Cohen, Y.

    1958-01-01

    Recapitulative list of the C.E.A. reports published by the French Atomic Energy Commission. (number 757-1062, december 1957 - december 1958). Supplement to C.E.A. reports number 593 and 756. (author) [fr

  2. Brane world black rings

    International Nuclear Information System (INIS)

    Sahay, Anurag; Sengupta, Gautam

    2007-01-01

    Five dimensional neutral rotating black rings are described from a Randall-Sundrum brane world perspective in the bulk black string framework. To this end we consider a rotating black string extension of a five dimensional black ring into the bulk of a six dimensional Randall-Sundrum brane world with a single four brane. The bulk solution intercepts the four brane in a five dimensional black ring with the usual curvature singularity on the brane. The bulk geodesics restricted to the plane of rotation of the black ring are constructed and their projections on the four brane match with the usual black ring geodesics restricted to the same plane. The asymptotic nature of the bulk geodesics are elucidated with reference to a bulk singularity at the AdS horizon. We further discuss the description of a brane world black ring as a limit of a boosted bulk black 2 brane with periodic identification

  3. Recapitulative list of the C.E.A. reports published by the French Atomic Energy Commission (n.757-1062, december 1957-december 1958) supplement to C.E.A. reports n. 593 and 756; Liste recapitulative des rapports C.E.A. publies par le Commissariat a l'Energie Atomique (du n.757 a 1062, decembre 1957-decembre 1958) complement aux rapports C.E.A. n. 593 et 756

    Energy Technology Data Exchange (ETDEWEB)

    Schmiterlow, C.G.; Cohen, Y. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1958-07-01

    Recapitulative list of the C.E.A. reports published by the French Atomic Energy Commission. (number 757-1062, december 1957 - december 1958). Supplement to C.E.A. reports number 593 and 756. (author) [French] Liste recapitulative des rapports C.E.A. publies par le Commissariat a l'Energie Atomique (du numero 757 au numero 1062, decembre 1957 - decembre 1958). Complement aux rapports C.E.A. numero 593 et 756. (auteur)

  4. Recapitulation of tumor heterogeneity and molecular signatures in a 3D brain cancer model with decreased sensitivity to histone deacetylase inhibition.

    Directory of Open Access Journals (Sweden)

    Stuart J Smith

    Full Text Available INTRODUCTION: Physiologically relevant pre-clinical ex vivo models recapitulating CNS tumor micro-environmental complexity will aid development of biologically-targeted agents. We present comprehensive characterization of tumor aggregates generated using the 3D Rotary Cell Culture System (RCCS. METHODS: CNS cancer cell lines were grown in conventional 2D cultures and the RCCS and comparison with a cohort of 53 pediatric high grade gliomas conducted by genome wide gene expression and microRNA arrays, coupled with immunohistochemistry, ex vivo magnetic resonance spectroscopy and drug sensitivity evaluation using the histone deacetylase inhibitor, Vorinostat. RESULTS: Macroscopic RCCS aggregates recapitulated the heterogeneous morphology of brain tumors with a distinct proliferating rim, necrotic core and oxygen tension gradient. Gene expression and microRNA analyses revealed significant differences with 3D expression intermediate to 2D cultures and primary brain tumors. Metabolic profiling revealed differential profiles, with an increase in tumor specific metabolites in 3D. To evaluate the potential of the RCCS as a drug testing tool, we determined the efficacy of Vorinostat against aggregates of U87 and KNS42 glioblastoma cells. Both lines demonstrated markedly reduced sensitivity when assaying in 3D culture conditions compared to classical 2D drug screen approaches. CONCLUSIONS: Our comprehensive characterization demonstrates that 3D RCCS culture of high grade brain tumor cells has profound effects on the genetic, epigenetic and metabolic profiles of cultured cells, with these cells residing as an intermediate phenotype between that of 2D cultures and primary tumors. There is a discrepancy between 2D culture and tumor molecular profiles, and RCCS partially re-capitulates tissue specific features, allowing drug testing in a more relevant ex vivo system.

  5. Black hole hair removal

    International Nuclear Information System (INIS)

    Banerjee, Nabamita; Mandal, Ipsita; Sen, Ashoke

    2009-01-01

    Macroscopic entropy of an extremal black hole is expected to be determined completely by its near horizon geometry. Thus two black holes with identical near horizon geometries should have identical macroscopic entropy, and the expected equality between macroscopic and microscopic entropies will then imply that they have identical degeneracies of microstates. An apparent counterexample is provided by the 4D-5D lift relating BMPV black hole to a four dimensional black hole. The two black holes have identical near horizon geometries but different microscopic spectrum. We suggest that this discrepancy can be accounted for by black hole hair - degrees of freedom living outside the horizon and contributing to the degeneracies. We identify these degrees of freedom for both the four and the five dimensional black holes and show that after their contributions are removed from the microscopic degeneracies of the respective systems, the result for the four and five dimensional black holes match exactly.

  6. 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)

  7. Black-Body Radiation

    Indian Academy of Sciences (India)

    Keywords. Black-body radiation; thermal radiation; heat; electromagnetic radiation; Stefan's Law; Stefan–Boltzmann Law; Wien's Law; Rayleigh–Jeans Law; black-body spectrum; ultraviolet catastrophe; zero point energy; photon.

  8. 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...

  9. Black holes are hot

    International Nuclear Information System (INIS)

    Gibbons, G.

    1976-01-01

    Recent work, which has been investigating the use of the concept of entropy with respect to gravitating systems, black holes and the universe as a whole, is discussed. The resulting theory of black holes assigns a finite temperature to them -about 10 -7 K for ordinary black holes of stellar mass -which is in complete agreement with thermodynamical concepts. It is also shown that black holes must continuously emit particles just like ordinary bodies which have a certain temperature. (U.K.)

  10. Monopole black hole skyrmions

    OpenAIRE

    Moss, I.G.; Shiiki, N.; Winstanley, E.

    2000-01-01

    Charged black hole solutions with pion hair are discussed. These can be\\ud used to study monopole black hole catalysis of proton decay.\\ud There also exist\\ud multi-black hole skyrmion solutions with BPS monopole behaviour.

  11. Alcoholism and Blacks.

    Science.gov (United States)

    Mosley, Bertha; And Others

    1988-01-01

    Notes that in America, knowledge base concerning alcoholism is concentrated on drinking patterns of Whites, and that Black Americans often differ in their drinking behavior, resulting in a need to clarify issues regarding alcoholism and Blacks. Provides theoretical information useful in better discerning drinking behavior of Blacks. (Author/NB)

  12. What is black hole?

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. What is black hole? Possible end phase of a star: A star is a massive, luminous ball of plasma having continuous nuclear burning. Star exhausts nuclear fuel →. White Dwarf, Neutron Star, Black Hole. Black hole's gravitational field is so powerful that even ...

  13. Genocide and Black Ecology

    Science.gov (United States)

    Sinnette, Calvin H.

    1972-01-01

    Contends that the survival of black people is in serious jeopardy as is evidenced in contemporary discussions on the worldwide plight of black people, and that an exhaustive study of the problem in its many dimensions is seriously lacking; the moral and ethical issues of genocide require examination from a black perspective. (JW)

  14. Black holes in binary stars

    NARCIS (Netherlands)

    Wijers, R.A.M.J.

    1996-01-01

    Introduction Distinguishing neutron stars and black holes Optical companions and dynamical masses X-ray signatures of the nature of a compact object Structure and evolution of black-hole binaries High-mass black-hole binaries Low-mass black-hole binaries Low-mass black holes Formation of black holes

  15. Ablation of fast-spiking interneurons in the dorsal striatum, recapitulating abnormalities seen post-mortem in Tourette syndrome, produces anxiety and elevated grooming.

    Science.gov (United States)

    Xu, M; Li, L; Pittenger, C

    2016-06-02

    Tic disorders, including Tourette syndrome (TS), are thought to involve pathology of cortico-basal ganglia loops, but their pathology is not well understood. Post-mortem studies have shown a reduced number of several populations of striatal interneurons, including the parvalbumin-expressing fast-spiking interneurons (FSIs), in individuals with severe, refractory TS. We tested the causal role of this interneuronal deficit by recapitulating it in an otherwise normal adult mouse using a combination transgenic-viral cell ablation approach. FSIs were reduced bilaterally by ∼40%, paralleling the deficit found post-mortem. This did not produce spontaneous stereotypies or tic-like movements, but there was increased stereotypic grooming after acute stress in two validated paradigms. Stereotypy after amphetamine, in contrast, was not elevated. FSI ablation also led to increased anxiety-like behavior in the elevated plus maze, but not to alterations in motor learning on the rotorod or to alterations in prepulse inhibition, a measure of sensorimotor gating. These findings indicate that a striatal FSI deficit can produce stress-triggered repetitive movements and anxiety. These repetitive movements may recapitulate aspects of the pathophysiology of tic disorders. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

  16. Black hole levitron

    International Nuclear Information System (INIS)

    Arsiwalla, Xerxes D.; Verlinde, Erik P.

    2010-01-01

    We study the problem of spatially stabilizing four dimensional extremal black holes in background electric/magnetic fields. Whilst looking for stationary stable solutions describing black holes placed in external fields we find that taking a continuum limit of Denef et al.'s multicenter supersymmetric black hole solutions provides a supergravity description of such backgrounds within which a black hole can be trapped within a confined volume. This construction is realized by solving for a levitating black hole over a magnetic dipole base. We comment on how such a construction is akin to a mechanical levitron.

  17. Interacting black holes

    International Nuclear Information System (INIS)

    Costa, Miguel S.; Perry, Malcolm J.

    2000-01-01

    We revisit the geometry representing l collinear Schwarzschild black holes. It is seen that the black holes' horizons are deformed by their mutual gravitational attraction. The geometry has a string like conical singularity that connects the holes but has nevertheless a well defined action. Using standard gravitational thermodynamics techniques we determine the free energy for two black holes at fixed temperature and distance, their entropy and mutual force. When the black holes are far apart the results agree with Newtonian gravity expectations. This analyses is generalized to the case of charged black holes. Then we consider black holes embedded in string/M-theory as bound states of branes. Using the effective string description of these bound states and for large separation we reproduce exactly the semi-classical result for the entropy, including the correction associated with the interaction between the holes

  18. Black silicon integrated aperture

    Science.gov (United States)

    Liu, Tianbo; Dickensheets, David L.

    2017-10-01

    This paper describes the incorporation of nanotextured black silicon as an optical absorbing material into silicon-based micro-optoelectromechanical systems devices to reduce stray light and increase optical contrast during imaging. Black silicon is created through a maskless dry etch process and characterized for two different etch conditions, a cold etch performed at 0°C and a cryogenic etch performed at -110°C. We measure specular reflection at visible wavelengths to be black velvet paint used to coat optical baffles and compare favorably with other methods to produce black surfaces from nanotextured silicon or using carbon nanotubes. We illustrate the use of this material by integrating a black silicon aperture around the perimeter of a deformable focus-control mirror. Imaging results show a significant improvement in contrast and image fidelity due to the effective reduction in stray light achieved with the self-aligned black aperture.

  19. 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.

  20. 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.

  1. Naked black holes

    International Nuclear Information System (INIS)

    Horowitz, G.T.; Ross, S.F.

    1997-01-01

    It is shown that there are large static black holes for which all curvature invariants are small near the event horizon, yet any object which falls in experiences enormous tidal forces outside the horizon. These black holes are charged and near extremality, and exist in a wide class of theories including string theory. The implications for cosmic censorship and the black hole information puzzle are discussed. copyright 1997 The American Physical Society

  2. Nonextremal stringy black hole

    International Nuclear Information System (INIS)

    Suzuki, K.

    1997-01-01

    We construct a four-dimensional BPS saturated heterotic string solution from the Taub-NUT solution. It is a nonextremal black hole solution since its Euler number is nonzero. We evaluate its black hole entropy semiclassically. We discuss the relation between the black hole entropy and the degeneracy of string states. The entropy of our string solution can be understood as the microscopic entropy which counts the elementary string states without any complications. copyright 1997 The American Physical Society

  3. 3D modeling of human cancer: A PEG-fibrin hydrogel system to study the role of tumor microenvironment and recapitulate the in vivo effect of oncolytic adenovirus.

    Science.gov (United States)

    Del Bufalo, Francesca; Manzo, Teresa; Hoyos, Valentina; Yagyu, Shigeki; Caruana, Ignazio; Jacot, Jeffrey; Benavides, Omar; Rosen, Daniel; Brenner, Malcolm K

    2016-04-01

    Interactions between malignant and stromal cells and the 3D spatial architecture of the tumor both substantially modify tumor behavior, including the responses to small molecule drugs and biological therapies. Conventional 2D culture systems cannot replicate this complexity. To overcome these limitations and more accurately model solid tumors, we developed a highly versatile 3D PEG-fibrin hydrogel model of human lung adenocarcinoma. Our model relevantly recapitulates the effect of oncolytic adenovirus; tumor responses in this setting nearly reproduce those observed in vivo. We have also validated the use of this model for complex, long-term, 3D cultures of cancer cells and their stroma (fibroblasts and endothelial cells). Both tumor proliferation and invasiveness were enhanced in the presence of stromal components. These results validate our 3D hydrogel model as a relevant platform to study cancer biology and tumor responses to biological treatments. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Black holes are warm

    International Nuclear Information System (INIS)

    Ravndal, F.

    1978-01-01

    Applying Einstein's theory of gravitation to black holes and their interactions with their surroundings leads to the conclusion that the sum of the surface areas of several black holes can never become less. This is shown to be analogous to entropy in thermodynamics, and the term entropy is also thus applied to black holes. Continuing, expressions are found for the temperature of a black hole and its luminosity. Thermal radiation is shown to lead to explosion of the black hole. Numerical examples are discussed involving the temperature, the mass, the luminosity and the lifetime of black mini-holes. It is pointed out that no explosions corresponding to the prediction have been observed. It is also shown that the principle of conservation of leptons and baryons is broken by hot black holes, but that this need not be a problem. The related concept of instantons is cited. It is thought that understanding of thermal radiation from black holes may be important for the development of a quantified gravitation theory. (JIW)

  5. 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…

  6. Black hole candidates

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Black hole candidates. In the case of X-ray sources such as Cyg X-1, the mass of the compact object inferred from combined optical and X-ray data, suggest M_compact object > 3.4 M_sun => Black Hole! A remarkable discovery!! Thus X-ray emitting binary systems ...

  7. Black hole Berry phase

    NARCIS (Netherlands)

    de Boer, J.; Papadodimas, K.; Verlinde, E.

    2009-01-01

    Supersymmetric black holes are characterized by a large number of degenerate ground states. We argue that these black holes, like other quantum mechanical systems with such a degeneracy, are subject to a phenomenon which is called the geometric or Berry’s phase: under adiabatic variations of the

  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. Black hole levitron

    NARCIS (Netherlands)

    Arsiwalla, X.D.; Verlinde, E.P.

    2010-01-01

    We study the problem of spatially stabilizing four dimensional extremal black holes in background electric/magnetic fields. Whilst looking for stationary stable solutions describing black holes placed in external fields we find that taking a continuum limit of Denef et al.’s multicenter

  10. Protecting Black Girls

    Science.gov (United States)

    Morris, Monique W.

    2016-01-01

    Statistics show that black girls in U.S. K-12 public schools are overrepresented among students who face disciplinary approaches (such as suspensions) that exclude or even criminalize them. Morris explains how black girls face conditions that make them vulnerable to a phenomenon she calls "school to confinement pathways"--conditions like…

  11. Black Hole Dynamic Potentials

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... 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 ...

  12. Black Boycott: Gainsville, Florida

    Science.gov (United States)

    White, Arthur O.

    1975-01-01

    A case study of the events precipitating a black student boycott in 1969 in Gainesville, Flordia, when school board manuevering to avoid school integration led to the threatened closing of Lincoln High School, a reputable black community school. Also described are the subsequent transformations of Lincoln into a vocational-technical school and…

  13. Neoliberalism and Black Education.

    Science.gov (United States)

    Rich, John Martin

    1986-01-01

    In contrast to traditional liberals, neoliberals share a commitment to greater economic risk-taking, support for entrepreneurism, a new industrial policy, and a different Federal Role. While New Deal and Great Society liberalism may have been more favorable to blacks, perhaps more balanced and equitable policies for blacks could be developed if…

  14. Lifshitz topological black holes

    International Nuclear Information System (INIS)

    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.

  15. Legitimizing Blacks in Philosophy

    Directory of Open Access Journals (Sweden)

    Jameliah Shorter-Bourhanou

    2017-12-01

    Full Text Available In its efforts toward improving diversity, the discipline of philosophy has tended to focus on increasing the number of black philosophers. One crucial issue that has received less attention is the extent to which black philosophers are delegitimized in the discipline because their philosophical contributions challenge the status quo. A systematic problem that bars black philosophers from equal and full participation, this delegitimization precludes the emergence of genuine diversity and reveals the importance of interrogating broader attitudes toward black philosophical contributions. In this essay, I argue for radical systematic changes to disciplinary hallmarks of professionalization such as pedagogy, mentoring, publishing, and hiring practices with the aim of legitimizing black philosophers and their contributions.

  16. Black hole critical phenomena without black holes

    Indian Academy of Sciences (India)

    as a star or dispersing altogether. Were we engineers with advanced technology, we might attempt to find that critical amount of energy necessary to form a black hole. However, despite some fears to the contrary, such technology does not exist, so instead we investigate this critical regime numerically. The first step is to pick ...

  17. Black hole critical phenomena without black holes

    Indian Academy of Sciences (India)

    denotes the partial derivatives of . The construction of a numerical method with which ... which configurations form black holes and which disperse (the only two options in this model). The problem in picturing such a space is that it is infinite ..... 4.1 The future: Less symmetry. The work described above all assumes spherical ...

  18. ULTRAMASSIVE BLACK HOLE COALESCENCE

    International Nuclear Information System (INIS)

    Khan, Fazeel Mahmood; Holley-Bockelmann, Kelly; 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 NGC 1277 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 NGC 1277 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, gravitational wave emission dominates, and the black holes coalesce in a mere few Myr. Curiously, these extremely massive binaries appear to nearly bypass the three-body scattering evolutionary phase. Our study suggests that in this extreme case, SMBH coalescence is governed by dynamical friction followed nearly directly by gravitational wave emission, resulting in a rapid and efficient SMBH coalescence timescale. We discuss the implications for gravitational wave event rates and hypervelocity star production

  19. "Black Like Me": Reframing Blackness for Decolonial Politics

    Science.gov (United States)

    Dei, George J. Sefa

    2018-01-01

    From a particular vantage point, as an African-born scholar with a politics to affirm my Black subjectivity and Indigeneity in a diasporic context, my article engages a (re)theorization of Blackness for decolonial politics. Building on existing works of how Black scholars, themselves, have theorized Blackness, and recognizing the fluid,…

  20. 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

  1. 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.

  2. Understanding the Black Aesthetic Experience.

    Science.gov (United States)

    Curtis, Marvin V.

    1988-01-01

    Discussing the importance of the Black aesthetic experience, Curtis examines Black cultural heritage and participatory style, the spiritual, and the creation and recreation of Black music. Advocating multicultural music education in teacher training, he suggests that Black music be studied for its value and contribution to society. Lists five ways…

  3. 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.

  4. Black Writers' Views of America.

    Science.gov (United States)

    Hairston, Loyle

    1979-01-01

    This article argues that the stagnation, pessimism, and self-pity evident in recent Black writing results in part from the alienation of Black writers from the mainstream of Black life, and in part from the illusions that they share with other Blacks who have embraced the American value system. (Author/EB)

  5. 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)

  6. Colliding black hole solution

    International Nuclear Information System (INIS)

    Ahmed, Mainuddin

    2005-01-01

    A new solution of Einstein equation in general relativity is found. This solution solves an outstanding problem of thermodynamics and black hole physics. Also this work appears to conclude the interpretation of NUT spacetime. (author)

  7. Black Sea aerosols

    International Nuclear Information System (INIS)

    Hacisalihoglu, G.; Eliyakut, F.; Anwari, M.A.; Ataman, O.Y.; Balkas, T.I.; Tuncel, G.; Olmez, I.

    1991-01-01

    Shipboard, high volume air particulate samples were collected from the Black Sea atmosphere and analyzed by instrumental neutron activation analysis, atomic absorption spectrophotometry and ion chromatography for about 40 elements and ions. Concentrations of elements in the eastern and western parts of the Black Sea are different at the 95% confidence level, with lower concentrations in the eastern Black Sea. Back-trajectories and concentrations of elements in trajectory groups show that Europe accounts for more than 70% of the anthropogenic elements in the atmosphere. The average sulfate concentration was 7 μg/m 3 , which is comparable with rural sulfate levels in western Europe. Fluxes of elements from the atmosphere to the Black Sea are in good agreement with the results of similar flux calculations for other regions

  8. Black Teenage Pregnancy

    Directory of Open Access Journals (Sweden)

    Loretta I. Winters

    2012-01-01

    Full Text Available This article examines the relative importance of race and socioeconomic status (SES in determining whether Black and White teenagers report having ever been pregnant. Data gathered from 1999 to 2006 by the National Center for Health Statistics of the Center for Disease Control and Prevention included 1,580 Black and White females aged 15 to 19 years. Results supported the effects of race and SES, with SES having the stronger effect. However, the effects of race and SES differ when controlling for the state of the economy. No difference between Blacks and Whites was found during better economic times. During 2003-2004, the period of greatest economic stress, race was determined to be the only predictor of teenage pregnancy. In particular, during 2005-2006, the reduction in pregnancy rates for Black minors (15-17 fell below those for White minors within their respective SES categories. Policy implications are discussed in light of these findings.

  9. Illuminating black holes

    Science.gov (United States)

    Barr, Ian A.; Bull, Anne; O'Brien, Eileen; Drillsma-Milgrom, Katy A.; Milgrom, Lionel R.

    2016-07-01

    Two-dimensional shadows formed by illuminating vortices are shown to be visually analogous to the gravitational action of black holes on light and surrounding matter. They could be useful teaching aids demonstrating some of the consequences of general relativity.

  10. Black holes with halos

    Science.gov (United States)

    Monten, Ruben; Toldo, Chiara

    2018-02-01

    We present new AdS4 black hole solutions in N =2 gauged supergravity coupled to vector and hypermultiplets. We focus on a particular consistent truncation of M-theory on the homogeneous Sasaki–Einstein seven-manifold M 111, characterized by the presence of one Betti vector multiplet. We numerically construct static and spherically symmetric black holes with electric and magnetic charges, corresponding to M2 and M5 branes wrapping non-contractible cycles of the internal manifold. The novel feature characterizing these nonzero temperature configurations is the presence of a massive vector field halo. Moreover, we verify the first law of black hole mechanics and we study the thermodynamics in the canonical ensemble. We analyze the behavior of the massive vector field condensate across the small-large black hole phase transition and we interpret the process in the dual field theory.

  11. Black Friday = Broget Branding?

    DEFF Research Database (Denmark)

    Hansen, Heidi

    2015-01-01

    Black Friday er et godt eksempel på, hvordan ikke kun produktbrands og corporate brands rejser på tværs af landegrænser, men også traditioner som Halloween, Valentines Day og i dette tilfælde den ultimative tilbuds-fredag, som i USA går under navnet Black Friday. Men hvad er Black Friday i Danmark......? 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...

  12. Mobilizing Black America

    Science.gov (United States)

    1993-04-01

    and financially for childbirth or parenting. - Adolescent Pregnancy Black female teenagers 15 to 19 years old were 140 percent more likely to have a...on adolescent pregnancy teenage sexual activity, and federally funded programs prevention. NATIONAL INSTITUTE OF CHILD HEALTH AND HUMAN DEVELOPMENT...communities? o Access to Health Care: Does everyone have equal access? o Poverty o Racism o Health Insurance o Black Physicians o Summary o Infant Mortality

  13. Black chrome outgassing study

    International Nuclear Information System (INIS)

    Beat, T.

    1979-01-01

    This report covers why black chrome is of interest, why its outgassing is relevant, how the study was conducted, examples of resultant data, and a conclusion. Black chrome is of interest in several areas of activity. Vacuum outgassing characteristics must be known to establish the pumping speed requirements. How much gas is evolved determines the pump speed required. The species of gas evolved determines the type of pump. The outgassing characteristics must be known to determine needed precleaning steps

  14. Quantum black holes

    International Nuclear Information System (INIS)

    't Hooft, G.

    1987-01-01

    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

  15. A zebrafish model of X-linked adrenoleukodystrophy recapitulates key disease features and demonstrates a developmental requirement for abcd1 in oligodendrocyte patterning and myelination.

    Science.gov (United States)

    Strachan, Lauren R; Stevenson, Tamara J; Freshner, Briana; Keefe, Matthew D; Miranda Bowles, D; Bonkowsky, Joshua L

    2017-09-15

    X-linked adrenoleukodystrophy (ALD) is a devastating inherited neurodegenerative disease caused by defects in the ABCD1 gene and affecting peripheral and central nervous system myelin. ABCD1 encodes a peroxisomal transmembrane protein required for very long chain fatty acid (VLCFA) metabolism. We show that zebrafish (Danio rerio) Abcd1 is highly conserved at the amino acid level with human ABCD1, and during development is expressed in homologous regions including the central nervous system and adrenal glands. We used TALENs to generate five zebrafish abcd1 mutant allele lines introducing premature stop codons in exon 1, as well as obtained an abcd1 allele from the Zebrafish Mutation Project carrying a point mutation in a splice donor site. Similar to patients with ALD, zebrafish abcd1 mutants have elevated VLCFA levels. Interestingly, we found that CNS development of the abcd1 mutants is disrupted, with hypomyelination in the spinal cord, abnormal patterning and decreased numbers of oligodendrocytes, and increased cell death. By day of life five abcd1 mutants demonstrate impaired motor function, and overall survival to adulthood of heterozygous and homozygous mutants is decreased. Expression of human ABCD1 in oligodendrocytes rescued apoptosis in the abcd1 mutant. In summary, we have established a zebrafish model of ALD that recapitulates key features of human disease pathology and which reveals novel features of underlying disease pathogenesis. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  16. Pipette-based Method to Study Embryoid Body Formation Derived from Mouse and Human Pluripotent Stem Cells Partially Recapitulating Early Embryonic Development Under Simulated Microgravity Conditions

    Science.gov (United States)

    Shinde, Vaibhav; Brungs, Sonja; Hescheler, Jürgen; Hemmersbach, Ruth; Sachinidis, Agapios

    2016-06-01

    The in vitro differentiation of pluripotent stem cells partially recapitulates early in vivo embryonic development. More recently, embryonic development under the influence of microgravity has become a primary focus of space life sciences. In order to integrate the technique of pluripotent stem cell differentiation with simulated microgravity approaches, the 2-D clinostat compatible pipette-based method was experimentally investigated and adapted for investigating stem cell differentiation processes under simulated microgravity conditions. In order to keep residual accelerations as low as possible during clinorotation, while also guaranteeing enough material for further analysis, stem cells were exposed in 1-mL pipettes with a diameter of 3.5 mm. The differentiation of mouse and human pluripotent stem cells inside the pipettes resulted in the formation of embryoid bodies at normal gravity (1 g) after 24 h and 3 days. Differentiation of the mouse pluripotent stem cells on a 2-D pipette-clinostat for 3 days also resulted in the formation of embryoid bodies. Interestingly, the expression of myosin heavy chain was downregulated when cultivation was continued for an additional 7 days at normal gravity. This paper describes the techniques for culturing and differentiation of pluripotent stem cells and exposure to simulated microgravity during culturing or differentiation on a 2-D pipette clinostat. The implementation of these methodologies along with -omics technologies will contribute to understand the mechanisms regulating how microgravity influences early embryonic development.

  17. Renin-angiotensin system transgenic mouse model recapitulates pathophysiology similar to human preeclampsia with renal injury that may be mediated through VEGF.

    Science.gov (United States)

    Denney, J Morgan; Bird, Cynthia; Gendron-Fitzpatrick, Annette; Sampene, Emmanuel; Bird, Ian M; Shah, Dinesh M

    2017-03-01

    Using a transgenic cross, we evaluated features of preeclampsia, renal injury and the sFlt1/VEGF changes. Transgenic hAGT and hREN, or wild-type (WT) C57Bl/6 mice were cross-bred: female hAGT × male hREN for preeclampsia (PRE) model and female WT × male WT for pregnant controls (WTP). Samples were collected for plasma VEGF, sFlt1, and urine albumin. Blood pressures (BP) were monitored by telemetry. Vascular reactivity was investigated by wire myography. Kidneys and placenta were immunostained for sFlt1 and VEGF. Eleven PRE and 9 WTP mice were compared. PRE more frequently demonstrated albuminuria, glomerular endotheliosis (80% vs. 11%; P = 0.02), and placental necrosis (60% vs. 0%; P preeclampsia recapitulates human preeclamptic state with high fidelity, and that, vascular adaptation to pregnancy is suggested by declining BPs and reduced vascular response to PE and increased response to acetylcholine. Placental damage with resultant increased release of sFlt1, proteinuria, deficient spiral artery remodeling, and glomerular endotheliosis were observed in this model of PRE. Increased VEGF binding to glomerular endothelial cells in this model of PRE is similar to human PRE and leads us to hypothesize that renal injury in preeclampsia may be mediated through local VEGF. Copyright © 2017 the American Physiological Society.

  18. Charged Galileon black holes

    International Nuclear Information System (INIS)

    Babichev, Eugeny; Charmousis, Christos; 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 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

  19. 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

  20. Surface geometry of 5D black holes and black rings

    International Nuclear Information System (INIS)

    Frolov, Valeri P.; Goswami, Rituparno

    2007-01-01

    We discuss geometrical properties of the horizon surface of five-dimensional rotating black holes and black rings. Geometrical invariants characterizing these 3D geometries are calculated. We obtain a global embedding of the 5D rotating black horizon surface into a flat space. We also describe the Kaluza-Klein reduction of the black ring solution (along the direction of its rotation) which, though it is nakedly singular, relates this solution to the 4D metric of a static black hole distorted by the presence of external scalar (dilaton) and vector ('electromagnetic') fields. The properties of the reduced black hole horizon and its embedding in E 3 are briefly discussed

  1. Mice long-term high-fat diet feeding recapitulates human cardiovascular alterations: an animal model to study the early phases of diabetic cardiomyopathy.

    Directory of Open Access Journals (Sweden)

    Sebastián D Calligaris

    Full Text Available BACKGROUND/AIM: Hypercaloric diet ingestion and sedentary lifestyle result in obesity. Metabolic syndrome is a cluster of clinical features secondary to obesity, considered as a pre-diabetic condition and recognized as an independent risk factor for cardiovascular diseases. To better understand the relationship between obesity, metabolic syndrome and cardiovascular disease as well as for the development of novel therapeutic strategies, animal models that reproduce the etiology, course and outcomes of these pathologies are required. The aim of this work was to characterize the long-term effects of high-fat diet-induced obesity on the mice cardiovascular system, in order to make available a new animal model for diabetic cardiomyopathy. METHODS/RESULTS: Male C57BL/6 mice were fed with a standardized high-fat diet (obese or regular diet (normal for 16 months. Metabolic syndrome was evaluated testing plasma glucose, triglycerides, cholesterol, insulin, and glucose tolerance. Arterial pressure was measured using a sphygmomanometer (non invasive method and by hemodynamic parameters (invasive method. Cardiac anatomy was described based on echocardiography and histological studies. Cardiac function was assessed by cardiac catheterization under a stress test. Cardiac remodelling and metabolic biomarkers were assessed by RT-qPCR and immunoblotting. As of month eight, the obese mice were overweight, hyperglycaemic, insulin resistant, hyperinsulinemic and hypercholesterolemic. At month 16, they also presented normal arterial pressure but altered vascular reactivity (vasoconstriction, and cardiac contractility reserve reduction, heart mass increase, cardiomyocyte hypertrophy, cardiac fibrosis, and heart metabolic compensations. By contrast, the normal mice remained healthy throughout the study. CONCLUSIONS: Mice fed with a high-fat diet for prolonged time recapitulates the etiology, course and outcomes of the early phases of human diabetic cardiomyopathy.

  2. Toward Personalized Medicine: Using Cardiomyocytes Differentiated From Urine-Derived Pluripotent Stem Cells to Recapitulate Electrophysiological Characteristics of Type 2 Long QT Syndrome.

    Science.gov (United States)

    Jouni, Mariam; Si-Tayeb, Karim; Es-Salah-Lamoureux, Zeineb; Latypova, Xenia; Champon, Benoite; Caillaud, Amandine; Rungoat, Anais; Charpentier, Flavien; Loussouarn, Gildas; Baró, Isabelle; Zibara, Kazem; Lemarchand, Patricia; Gaborit, Nathalie

    2015-09-01

    Human genetically inherited cardiac diseases have been studied mainly in heterologous systems or animal models, independent of patients' genetic backgrounds. Because sources of human cardiomyocytes (CMs) are extremely limited, the use of urine samples to generate induced pluripotent stem cell-derived CMs would be a noninvasive method to identify cardiac dysfunctions that lead to pathologies within patients' specific genetic backgrounds. The objective was to validate the use of CMs differentiated from urine-derived human induced pluripotent stem (UhiPS) cells as a new cellular model for studying patients' specific arrhythmia mechanisms. Cells obtained from urine samples of a patient with long QT syndrome who harbored the HERG A561P gene mutation and his asymptomatic noncarrier mother were reprogrammed using the episomal-based method. UhiPS cells were then differentiated into CMs using the matrix sandwich method.UhiPS-CMs showed proper expression of atrial and ventricular myofilament proteins and ion channels. They were electrically functional, with nodal-, atrial- and ventricular-like action potentials recorded using high-throughput optical and patch-clamp techniques. Comparison of HERG expression from the patient's UhiPS-CMs to the mother's UhiPS-CMs showed that the mutation led to a trafficking defect that resulted in reduced delayed rectifier K(+) current (IKr). This phenotype gave rise to action potential prolongation and arrhythmias. UhiPS cells from patients carrying ion channel mutations can be used as novel tools to differentiate functional CMs that recapitulate cardiac arrhythmia phenotypes. © 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

  3. Fukutin-related protein is essential for mouse muscle, brain and eye development and mutation recapitulates the wide clinical spectrums of dystroglycanopathies.

    Science.gov (United States)

    Chan, Yiumo Michael; Keramaris-Vrantsis, Elizabeth; Lidov, Hart G; Norton, James H; Zinchenko, Natalia; Gruber, Helen E; Thresher, Randy; Blake, Derek J; Ashar, Jignya; Rosenfeld, Jeffrey; Lu, Qi L

    2010-10-15

    Mutations in fukutin-related protein (FKRP) cause a common subset of muscular dystrophies characterized by aberrant glycosylation of alpha-dystroglycan (α-DG), collectively known as dystroglycanopathies. The clinical variations associated with FKRP mutations range from mild limb-girdle muscular dystrophy type 2I with predominantly muscle phenotypes to severe Walker-Warburg syndrome and muscle-eye-brain disease with striking structural brain and eye defects. In the present study, we have generated animal models and demonstrated that ablation of FKRP functions is embryonic lethal and that the homozygous-null embryos die before reaching E12.5. The homozygous knock-in mouse carrying the missense P448L mutation almost completely lacks functional glycosylation of α-DG in muscles and brain, validating the essential role of FKRP in the functional glycosylation of α-DG. However, the knock-in mouse survives and develops a wide range of structural abnormalities in the central nervous system, characteristics of neuronal migration defects. The brain and eye defects are highly reminiscent of the phenotypes seen in severe dystroglycanopathy patients. In addition, skeletal muscles develop progressive muscular dystrophy. Our results confirm that post-translational modifications of α-DG are essential for normal development of the brain and eyes. In addition, both the mutation itself and the levels of FKRP expression are equally critical for the survival of the animals. The exceptionally wide clinical spectrums recapitulated in the P448L mice also suggest the involvement of other factors in the disease progression. The mutant mouse represents a valuable model to further elucidate the functions of FKRP and develop therapies for FKRP-related muscular dystrophies.

  4. Merging Black Holes

    Science.gov (United States)

    Centrella, Joan

    2012-01-01

    The final merger of two black holes is expected to be the strongest source of gravitational waves for both ground-based detectors such as LIGO and VIRGO, as well as future. space-based detectors. Since the merger takes place in the regime of strong dynamical gravity, computing the resulting gravitational waveforms requires solving the full Einstein equations of general relativity on a computer. For many years, numerical codes designed to simulate black hole mergers were plagued by a host of instabilities. However, recent breakthroughs have conquered these instabilities and opened up this field dramatically. This talk will focus on.the resulting 'gold rush' of new results that is revealing the dynamics and waveforms of binary black hole mergers, and their applications in gravitational wave detection, testing general relativity, and astrophysics

  5. Pulsation of black holes

    Science.gov (United States)

    Gao, Changjun; Lu, Youjun; Shen, You-Gen; Faraoni, Valerio

    2018-01-01

    The Hawking-Penrose singularity theorem states that a singularity forms inside a black hole in general relativity. To remove this singularity one must resort to a more fundamental theory. Using a corrected dynamical equation arising in loop quantum cosmology and braneworld models, we study the gravitational collapse of a perfect fluid sphere with a rather general equation of state. In the frame of an observer comoving with this fluid, the sphere pulsates between a maximum and a minimum size, avoiding the singularity. The exterior geometry is also constructed. There are usually an outer and an inner apparent horizon, resembling the Reissner-Nordström situation. For a distant observer the horizon crossing occurs in an infinite time and the pulsations of the black hole quantum "beating heart" are completely unobservable. However, it may be observable if the black hole is not spherical symmetric and radiates gravitational wave due to the quadrupole moment, if any.

  6. 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.

  7. Bringing Black Holes Home

    Science.gov (United States)

    Furmann, John M.

    2003-03-01

    Black holes are difficult to study because they emit no light. To overcome this obstacle, scientists are trying to recreate a black hole in the laboratory. The article gives an overview of the theories of Einstein and Hawking as they pertain to the construction of the Large Hadron Collider (LHC) near Geneva, Switzerland, scheduled for completion in 2006. The LHC will create two beams of protons traveling in opposing directions that will collide and create a plethora of scattered elementary particles. Protons traveling in opposite directions at very high velocities may create particles that come close enough to each other to feel their compacted higher dimensions and create a mega force of gravity that can create tiny laboratory-sized black holes for fractions of a second. The experiments carried out with LHC will be used to test modern string theory and relativity.

  8. Coiffured black rings

    Science.gov (United States)

    Bena, Iosif; Ross, Simon F.; Warner, Nicholas P.

    2014-08-01

    We describe a new type of hair on supersymmetric black string and black ring solutions, which produces the largest known violation of black hole uniqueness, parameterized by an arbitrary function and hence an infinite number of continuous parameters. The new solutions can have non-trivial density profiles for the electric fields along the horizon, and yet have a geometry that is regular, although generically not infinitely differentiable, at the horizon. Both neutral and charged probes can cross the horizon without experiencing divergent forces. We also find restricted examples, parameterized by a few arbitrary continuous parameters, where the charge densities fluctuate but the metric does not and hence is completely differentiable. Our new class of solutions owes its existence to a mechanism reminiscent of the Q-ball: in the simplest examples the metric has more symmetry than the matter that supports it.

  9. Black hole gravitohydromagnetics

    CERN Document Server

    Punsly, Brian

    2008-01-01

    Black hole gravitohydromagnetics (GHM) is developed from the rudiments to the frontiers of research in this book. GHM describes plasma interactions that combine the effects of gravity and a strong magnetic field, in the vicinity (ergosphere) of a rapidly rotating black hole. This topic was created in response to the astrophysical quest to understand the central engines of radio loud extragalactic radio sources. The theory describes a "torsional tug of war" between rotating ergospheric plasma and the distant asymptotic plasma that extracts the rotational inertia of the black hole. The recoil from the struggle between electromagnetic and gravitational forces near the event horizon is manifested as a powerful pair of magnetized particle beams (jets) that are ejected at nearly the speed of light. These bipolar jets feed large-scale magnetized plasmoids on scales as large as millions of light years (the radio lobes of extragalactic radio sources). This interaction can initiate jets that transport energy fluxes exc...

  10. Slowly balding black holes

    International Nuclear Information System (INIS)

    Lyutikov, Maxim; McKinney, Jonathan C.

    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 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 N B =eΦ ∞ /(πc(ℎ/2π)), where Φ ∞ ≅2π 2 B NS R NS 3 /(P NS c) 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.

  11. Black widow spider envenomation.

    Science.gov (United States)

    Peterson, Michael E

    2006-11-01

    Black widow spiders are found throughout the continental United States and north into the southern Canadian provinces. Male black widow spiders are of little medical importance. Female black widow spiders can be 20 times larger than males. The female can be identified by the hourglass pattern, red or orange in color, on the ventral aspect of her shiny, globose black abdomen. Black widow spiders control the amount of venom they inject; an estimated 15% of bites to humans are non-envenomating. Cats are very sensitive to the venom and deaths are common. Dogs have severe clinical signs but are considered more resistant than cats. A single bite is capable of delivering a lethal dose of venom to companion animals. There are several toxic components consisting of five or six biologically active proteins. These include a potent mammalian neurotoxin called alpha-latrotoxin, which induces neurotransmitter release from nerve terminals. Acetylcholine, noradrenalin, dopamine, glutamate, and enkephalin systems are all susceptible to the toxin. Onset of clinical signs usually occurs during the first 8 hours post envenomation. The condition is extremely painful in moderate to severe envenomations. Abdominal rigidity without tenderness is a hallmark sign of Latrodectus envenomation. In cats, paralytic signs may occur early and are particularly marked. Hypertension is a significant threat. First aid is of no value in the treatment. The primary treatment for black widow spider envenomation is the administration of specific antivenin, which provides the most permanent and quickest relief of the envenomation syndrome, usually within 30 minutes of infusion. The prognosis of Latrodectus envenomation is uncertain of several days, and complete recovery may take weeks.

  12. Characterizing Black Hole Mergers

    Science.gov (United States)

    Baker, John; Boggs, William Darian; Kelly, Bernard

    2010-01-01

    Binary black hole mergers are a promising source of gravitational waves for interferometric gravitational wave detectors. Recent advances in numerical relativity have revealed the predictions of General Relativity for the strong burst of radiation generated in the final moments of binary coalescence. We explore features in the merger radiation which characterize the final moments of merger and ringdown. Interpreting the waveforms in terms of an rotating implicit radiation source allows a unified phenomenological description of the system from inspiral through ringdown. Common features in the waveforms allow quantitative description of the merger signal which may provide insights for observations large-mass black hole binaries.

  13. Superfluid Black Holes.

    Science.gov (United States)

    Hennigar, Robie A; Mann, Robert B; Tjoa, Erickson

    2017-01-13

    We present what we believe is the first example of a "λ-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 anti-de Sitter 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.

  14. Are black holes springlike?

    Science.gov (United States)

    Good, Michael R. R.; Ong, Yen Chin

    2015-02-01

    A (3 +1 )-dimensional asymptotically flat Kerr black hole angular speed Ω+ can be used to define an effective spring constant, k =m Ω+2. Its maximum value is the Schwarzschild surface gravity, k =κ , 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 π T =κ -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.

  15. Bulletproof Black Man

    DEFF Research Database (Denmark)

    Højer, Henrik

    2016-01-01

    Netflix’ kommende serie om den sorte Marvel-helt Luke Cage lander snart – midt i de aktuelle racekonflikter i USA. I GIF-anatomien "Bulletproof Black Man" sætter Henrik Højer serien ind i dens amerikanske kontekst.......Netflix’ kommende serie om den sorte Marvel-helt Luke Cage lander snart – midt i de aktuelle racekonflikter i USA. I GIF-anatomien "Bulletproof Black Man" sætter Henrik Højer serien ind i dens amerikanske kontekst....

  16. Virtual Black Holes

    OpenAIRE

    Hawking, Stephen W.

    1995-01-01

    One would expect spacetime to have a foam-like structure on the Planck scale with a very high topology. If spacetime is simply connected (which is assumed in this paper), the non-trivial homology occurs in dimension two, and spacetime can be regarded as being essentially the topological sum of $S^2\\times S^2$ and $K3$ bubbles. Comparison with the instantons for pair creation of black holes shows that the $S^2\\times S^2$ bubbles can be interpreted as closed loops of virtual black holes. It is ...

  17. Better Physician's 'Black Bags'

    Science.gov (United States)

    1976-01-01

    The "black bag" is outgrowth of astronaut monitoring technology from NASA's Johnson Space Center. Technically known as the portable medical status system, a highly advanced physician's "black bag" weighs less than 30 pounds, yet contains equipment for monitoring and recording vital signs, electrocardiograms, and electroencephalograms. Liquid crystal displays are used to present 15 digits of data simultaneously for long periods of time without excessive use of battery power. Single printed circuit card contains all circuitry required to measure and display vital signs such as heart and respiration rate, temperature, and blood pressure.

  18. Partons and black holes

    International Nuclear Information System (INIS)

    Susskind, L.; Griffin, P.

    1994-01-01

    A light-front renormalization group analysis is applied to study matter which falls into massive black holes, and the related problem of matter with transplankian energies. One finds that the rate of matter spreading over the black hole's horizon unexpectedly saturates the causality bound. This is related to the transverse growth behavior of transplankian particles as their longitudinal momentum increases. This growth behavior suggests a natural mechanism to implement 't Hooft's scenario that the universe is an image of data stored on a 2 + 1 dimensional hologram-like projection

  19. Black Elite: The New Market for Highly Educated Black Americans.

    Science.gov (United States)

    Freeman, Richard B.

    This examination of the collapse in traditional discriminatory patterns in the market for highly qualified black Americans documents the World War II gain of college trained and related high level black workers, investigates the response of black college students and qualified personnel to the new market setting, and explores the factors that…

  20. Black strings ending on horizons

    Science.gov (United States)

    Haddad, Nidal

    2012-12-01

    We construct an approximate static gravitational solution of the Einstein equations, with negative cosmological constant, describing a test black string stretching from the boundary of the Schwarzschild-AdS5 black brane toward the horizon. The construction builds on a derivative expansion method, assuming that the black brane metric changes slowly along the black string direction. We provide a solution up to second order in derivatives, and it implies, in particular, that the black string must shrink to zero size at the horizon of the black brane. In the near-horizon region of the black brane, where the two horizons intersect, we provide an exact solution of a cone that describes two intersecting horizons at different temperatures. Moreover, we show that this solution equally describes a thin and long black droplet.

  1. Reflections on a Black Mirror

    OpenAIRE

    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. Black Musicians Leading the Way.

    Science.gov (United States)

    Music Educators Journal, 1982

    1982-01-01

    Describes the careers and musical achievements of Blacks who were forerunners in jazz, blues, gospel, music, spirituals, band music, classical music, ragtime, and opera. The list was compiled to provide teachers with historical background information for "Black History Month." (AM)

  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. 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...

  5. 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.

  6. Aspects of hairy black holes

    Energy Technology Data Exchange (ETDEWEB)

    Anabalón, Andrés, E-mail: andres.anabalon-at@uai.cl [Departamento de Ciencias, Facultad de Artes Liberales y Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Viña del Mar (Chile); Astefanesei, Dumitru [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla 4059, Valparaíso (Chile)

    2015-03-26

    We review the existence of exact hairy black holes in asymptotically flat, anti-de Sitter and de Sitter space-times. We briefly discuss the issue of stability and the charging of the black holes with a Maxwell field.

  7. 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.

  8. 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…

  9. 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.

  10. Scholarly Black Market.

    Science.gov (United States)

    Sorooshian, Shahryar

    2017-04-01

    Fake and unethical publishers' activities are known by most of the readers of Science and Engineering Ethics. This letter tries to draw the readers' attention to the hidden side of some of these publishers' business. Here the black market of scholarly articles, which negatively affects the validity and reliability of research in higher education, as well as science and engineering, will be introduced.

  11. Twistors and Black Holes

    NARCIS (Netherlands)

    Neitzke, A.; Pioline, B.; Vandoren, S.

    2007-01-01

    Motivated by black hole physics in N = 2,D = 4 supergravity, we study the geometry of quaternionic-K¨ahler manifolds Mobtained by the c-map construction from projective special Kähler manifolds Ms. Improving on earlier treatments, we compute the Käahler potentials on the twistor space Z and Swann

  12. on black ironbark (Eucalyptus

    African Journals Online (AJOL)

    (Eucalyptus sideroxylon). B. Buys. Plant Protection Research Institute, Private Bag X5017,. Stellenbosch, 7600 Republic of South Africa. Received May /984; accepted 28 November /986. Black ironbark trees secrete nectar during the night. Argentine ants collected 42% of the nectar before honeybees started foraging in the ...

  13. 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.

  14. Suburban Black Lives Matter

    Science.gov (United States)

    Lewis-McCoy, R. L'Heureux

    2018-01-01

    This article explores the range of experiences and meanings of Black life in suburban space. Drawing from educational, historical, and sociological literatures, I argue that an underconsideration of suburban space has left many portraits of educational inequality incomplete. The article outlines the emergence of American suburbs and the formation…

  15. Black Psychology. Third Edition.

    Science.gov (United States)

    Jones, Reginald L., Ed.

    This book is the third edition of a resource for advanced students and professionals in black psychology in the form of 41 papers organized under 5 subheadings. The "overview" section includes one classic article and offers a new, world view paper. A "perspectives" section treats Afrocentric, humanistic, historical,…

  16. [Reinvesting in Black Communities].

    Science.gov (United States)

    Shipp, James

    Some of the issues involved in promoting home ownership among blacks and investment in inner city communities are discussed in this paper. The experiences of the Bedford Stuyvesant Restoration Corporation in revitalizing Bedford Stuyvesant are described. Economic barriers to prospective home ownership are identified and strategies and programs…

  17. Black Holes and Entanglement

    International Nuclear Information System (INIS)

    Borsten, L.

    2011-01-01

    An unexpected interplay between the seemingly disparate fields of M-theory and Quantum Information has recently come to light. We summarise these developments, culminating in a classification of 4-qubit entanglement from the physics of STU black holes. Based on work done in collaboration with D. Dahanayake, M. J. Duff, H. Ebrahim, A. Marrani and W. Rubens.

  18. Black Holes and Entanglement

    Science.gov (United States)

    Borsten, L.

    2011-07-01

    An unexpected interplay between the seemingly disparate fields of M-theory and Quantum Information has recently come to light. We summarise these developments, culminating in a classification of 4-qubit entanglement from the physics of STU black holes. Based on work done in collaboration with D. Dahanayake, M. J. Duff, H. Ebrahim, A. Marrani and W. Rubens.

  19. Watchable Wildlife: The Black Bear

    Science.gov (United States)

    Lynn L. Rogers

    1992-01-01

    Black bears are the bears people most often encounter. Black bears live in forests over much of North America, unlike grizzlies that live only in Alaska, northern and western Canada, and the northern Rocky Mountains. This brochure presents the latest information on black bear life and how this species responds to an ever-increasing number of campers, hikers, and...

  20. Health Issues Facing Black Women.

    Science.gov (United States)

    Reid, Inez Smith

    Black women in the United States experience a high incidence of serious health problems and, as a group, receive insufficient and inadequate medical care. The death rate for black women suffering from breast cancer has increased substantially since 1950. Also of great concern is the high incidence of cervical cancer in low income black women…

  1. Uncovering Black Womanhood in Engineering

    Science.gov (United States)

    Gibson, Sheree L.; Espino, Michelle M.

    2016-01-01

    Despite the growing research that outlines the experiences of Blacks and women undergraduates in engineering, little is known about Black women in this field. The purpose of this qualitative study was to uncover how eight Black undergraduate women in engineering understood their race and gender identities in a culture that can be oppressive to…

  2. Warped products and black holes

    International Nuclear Information System (INIS)

    Hong, Soon-Tae

    2005-01-01

    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

  3. Reading Black Literature With Understanding.

    Science.gov (United States)

    Alexander, Jean A.

    This paper is a broad study of the field of black American Literature which outlines the important movements, stereotypes, and trends that have had significant influence upon the literature. The changing stereotypes and archetypes of blacks depicted in American literature from the early concept of blacks as "chattels" to the contemporary concept…

  4. Queering Black Racial Identity Development

    Science.gov (United States)

    Johnson, Alandis A.; Quaye, Stephen John

    2017-01-01

    We used queer theory to encourage readers to think differently about previous theories about Black racial identity development. Queer theory facilitates new and deeper understandings of how Black people develop their racial identities, prompting more fluidity and nuance. Specifically, we present a queered model of Black racial identity development…

  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. Looking for the invisible universe - Black matter, black energy, black holes

    International Nuclear Information System (INIS)

    Elbaz, David

    2016-01-01

    As the discovery of the expansion of the universe and of black holes put the study of cosmology into question again because it now refers to invisible things such as black holes, black energy and black matter, the author proposes an other view on the universe within such a context. He first discusses these three enigmas of black matter, black energy and black holes. In a second part, he addresses, discusses and comments five illusions: the Uranian illusion (questions of the existence of an anti-world, of black matter temperature), the Mercurian illusion (quantum gravity, the string theory), the Martian illusion (a patchwork universe, the illusion of the infinite), the cosmic Maya (the John Wheeler's cup, the holographic universe), and the narcissistic illusion

  7. Black Strings, Black Rings and State-space Manifold

    CERN Document Server

    Bellucci, Stefano

    2011-01-01

    State-space geometry is considered, for diverse three and four parameter non-spherical horizon rotating black brane configurations, in string theory and $M$-theory. We have explicitly examined the case of unit Kaluza-Klein momentum $D_1D_5P$ black strings, circular strings, small black rings and black supertubes. An investigation of the state-space pair correlation functions shows that there exist two classes of brane statistical configurations, {\\it viz.}, the first category divulges a degenerate intrinsic equilibrium basis, while the second yields a non-degenerate, curved, intrinsic Riemannian geometry. Specifically, the solutions with finitely many branes expose that the two charged rotating $D_1D_5$ black strings and three charged rotating small black rings consort real degenerate state-space manifolds. Interestingly, arbitrary valued $M_5$-dipole charged rotating circular strings and Maldacena Strominger Witten black rings exhibit non-degenerate, positively curved, comprehensively regular state-space con...

  8. Computational cell model based on autonomous cell movement regulated by cell-cell signalling successfully recapitulates the "inside and outside" pattern of cell sorting

    Directory of Open Access Journals (Sweden)

    Ajioka Itsuki

    2007-09-01

    Full Text Available Abstract Background Development of multicellular organisms proceeds from a single fertilized egg as the combined effect of countless numbers of cellular interactions among highly dynamic cells. Since at least a reminiscent pattern of morphogenesis can be recapitulated in a reproducible manner in reaggregation cultures of dissociated embryonic cells, which is known as cell sorting, the cells themselves must possess some autonomous cell behaviors that assure specific and reproducible self-organization. Understanding of this self-organized dynamics of heterogeneous cell population seems to require some novel approaches so that the approaches bridge a gap between molecular events and morphogenesis in developmental and cell biology. A conceptual cell model in a computer may answer that purpose. We constructed a dynamical cell model based on autonomous cell behaviors, including cell shape, growth, division, adhesion, transformation, and motility as well as cell-cell signaling. The model gives some insights about what cellular behaviors make an appropriate global pattern of the cell population. Results We applied the model to "inside and outside" pattern of cell-sorting, in which two different embryonic cell types within a randomly mixed aggregate are sorted so that one cell type tends to gather in the central region of the aggregate and the other cell type surrounds the first cell type. Our model can modify the above cell behaviors by varying parameters related to them. We explored various parameter sets with which the "inside and outside" pattern could be achieved. The simulation results suggested that direction of cell movement responding to its neighborhood and the cell's mobility are important for this specific rearrangement. Conclusion We constructed an in silico cell model that mimics autonomous cell behaviors and applied it to cell sorting, which is a simple and appropriate phenomenon exhibiting self-organization of cell population. The model

  9. Statistical mechanics of black holes

    International Nuclear Information System (INIS)

    Harms, B.; Leblanc, Y.

    1992-01-01

    We analyze the statistical mechanics of a gas of neutral and charged black holes. The microcanonical ensemble is the only possible approach to this system, and the equilibrium configuration is the one for which most of the energy is carried by a single black hole. Schwarzschild black holes are found to obey the statistical bootstrap condition. In all cases, the microcanonical temperature is identical to the Hawking temperature of the most massive black hole in the gas. U(1) charges in general break the bootstrap property. The problems of black-hole decay and of quantum coherence are also addressed

  10. 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.

  11. 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.

  12. 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

  13. f(R) Black holes

    OpenAIRE

    Moon, Taeyoon; Myung, Yun Soo; Son, Edwin J.

    2011-01-01

    We study the $f(R)$-Maxwell black hole imposed by constant curvature and its all thermodynamic quantities, which may lead to the Reissner-Nordstr\\"om-AdS black hole by redefining Newtonian constant and charge. Further, we obtain the $f(R)$-Yang-Mills black hole imposed by constant curvature, which is related to the Einstein-Yang-Mills black hole in AdS space. Since there is no analytic black hole solution in the presence of Yang-Mills field, we obtain asymptotic solutions. Then, we confirm th...

  14. Rotating black hole and quintessence

    International Nuclear Information System (INIS)

    Ghosh, Sushant G.

    2016-01-01

    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 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 E ), which corresponds to an extremal black hole with degenerate horizons, while for a < a E , it describes a nonextremal black hole with Cauchy and event horizons, and no black hole for a > a E . We find that the extremal value a E is also influenced by the parameter ω and so is the ergoregion. (orig.)

  15. Internal structure of black holes

    International Nuclear Information System (INIS)

    Cvetic, Mirjam

    2013-01-01

    Full text: We review recent progress that sheds light on the internal structure of general black holes. We first summarize properties of general multi-charged rotating black holes both in four and five dimensions. We show that the asymptotic boundary conditions of these general asymptotically flat black holes can be modified such that a conformal symmetry emerges. These subtracted geometries preserve the thermodynamic properties of the original black holes and are of the Lifshitz type, thus describing 'a black hole in the asymptotically conical box'. Recent efforts employ solution generating techniques to construct interpolating geometries between the original black hole and their subtracted geometries. Upon lift to one dimension higher, these geometries lift to AdS 3 times a sphere, and thus provide a microscopic interpretation of the black hole entropy in terms of dual two-dimensional conformal field theory. (author)

  16. Caged black holes: Black holes in compactified spacetimes. I. Theory

    International Nuclear Information System (INIS)

    Kol, Barak; Sorkin, Evgeny; Piran, Tsvi

    2004-01-01

    In backgrounds with compact dimensions there may exist several phases of black objects including a black hole and a black string. The phase transition between them raises questions and touches on fundamental issues such as topology change, uniqueness, and cosmic censorship. No analytic solution is known for the black hole, and moreover one can expect approximate solutions only for very small black holes, while phase transition physics happens when the black hole is large. Hence we turn to numerical solutions. Here some theoretical background to the numerical analysis is given, while the results will appear in a subsequent paper. The goals for a numerical analysis are set. The scalar charge and tension along the compact dimension are defined and used as improved order parameters which put both the black hole and the black string at finite values on the phase diagram. The predictions for small black holes are presented. The differential and the integrated forms of the first law are derived, and the latter (Smarr's formula) can be used to estimate the 'overall numerical error'. Field asymptotics and expressions for physical quantities in terms of the numerical values are supplied. The techniques include the 'method of equivalent charges', free energy, dimensional reduction, and analytic perturbation for small black holes

  17. 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.

  18. Forging a Black identity

    Directory of Open Access Journals (Sweden)

    Barry Chevannes

    1992-07-01

    Full Text Available [First paragraph] The Rastafarians: sounds of cultural dissonance [revised and updated editionj. LEONARD E. BARRETT, SR. Boston: Beacon Press, 1988. xviii + 302 pp. (Paper US$ 11.95 Rasta and resistance: from Marcus Garvey to Walter Rodney. HORACE CAMPBELL. Trenton NJ: Africa World Press, 1987. xiii + 236 pp. (Cloth US$32.95, Paper US$ 10.95 Garvey's children: the legacy of Marcus Garvey. TONY SEWELL. London: Macmillan Caribbean, 1990. 128 pp. (Paper £ 17.95 The central theme linking these three titles is the evolution of a black identity among English-speaking Caribbean peoples, in particular Jamaicans. Consequently all three authors cover the two most important historical phenomena in Caribbean black nationalism, namely Garveyism and Rastafari, one focusing on the former and the other two focusing on the latter.

  19. 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.

  20. Mobilizing Black America

    Science.gov (United States)

    1992-04-01

    or just for a walk in the park. They offer an ear if the youngster simply needs someone to talk to. When it comes to a discussion of economic...neighborhoods and making it unsafe for decent people to walk the streets. One method that several schools have used to support the community in this...children with their studies. By their very presence these men show that education is not sissy .’ 3 6 Once we have succeeded in keeping black Americans

  1. Beyond the black hole

    International Nuclear Information System (INIS)

    Boslough, J.

    1985-01-01

    This book is about the life and work of Stephen Hawking. It traces the development of his theories about the universe and particularly black holes, in a biographical context. Hawking's lecture 'Is the end in sight for theoretical physics' is presented as an appendix. In this, he discusses the possibility of achieving a complete, consistent and unified theory of the physical interactions which would describe all possible observations. (U.K.)

  2. Black Sea challenges

    International Nuclear Information System (INIS)

    Drevet, J.F.

    2008-01-01

    In this month's European column, Jean-Francois Drevet examines the issues that arise for Europe from the Black Sea region. The Black Sea is increasingly becoming a crucial place of transit for hydrocarbon imports from the Caspian and Russia into the European Union. The considerable increase in this traffic raises both environmental problems (the risk of oil slicks) and issues of security of supply, on account of the economic and political fragility of some of the bordering or neighbouring states (Ukraine, Georgia, Armenia, Azerbaijan, Russia/Chechnya etc.). This is why, as Jean-Francois Drevet stresses, the European Union has been trying since the mid-1990's to claim a role in the management of the affairs of the region. With two bordering states (Rumania and Bulgaria) joining the EU in 2007, cooperation in the Black Sea has become a priority within the framework of the European Neighbourhood Policy, and this column delineates a number of the obstacles that still have to be surmounted. (author)

  3. 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....

  4. 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

  5. Black holes in realistic branes: Black string-like objects?

    Energy Technology Data Exchange (ETDEWEB)

    Bazeia, D., E-mail: bazeia@fisica.ufpb.br [Instituto de Física, Universidade de São Paulo, 05314-970, São Paulo, SP (Brazil); Departamento de Física, Universidade Federal da Paraíba, 58051-970, João Pessoa, PB (Brazil); Hoff da Silva, J.M., E-mail: hoff@feg.unesp.br [Departamento de Física e Química, Universidade Estadual Paulista, Av. Dr. Ariberto Pereira da Cunha, 333, Guaratinguetá, SP (Brazil); Rocha, Roldão da, E-mail: roldao.rocha@ufabc.edu.br [Centro de Matemática, Computação e Cognição, Universidade Federal do ABC (UFABC), 09210-170, Santo André, SP (Brazil)

    2013-04-25

    A realistic model describing a black string-like object in an expanding Universe is analyzed in the context of the McVittie's solution of the Einstein field equations. The bulk metric near the brane is provided analogously to previous solutions for black strings. In particular, we show that at least when the Hubble parameter on the brane is positive, a black string-like object seems to play a fundamental role in the braneworld scenario, generalizing the standard black strings in the context of a dynamical brane.

  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

    ... Bear Hydro Partners, LLC and Black Bear Development Holdings, LLC and Black Bear SO, LLC; Notice of..., 2012, Black Bear Hydro Partners, LLC, sole licensee (transferor) and Black Bear Development Holdings, LLC and Black Bear SO, LLC (transferees) filed an application for the partial the transfer of licenses...

  7. Black Father Involvement in Gifted Education: Thoughts from Black Fathers on Increasing/Improving Black Father-Gifted Teacher Partnerships

    Science.gov (United States)

    Grantham, Tarek C.; Henfield, Malik S.

    2011-01-01

    Black fathers are important advocates in addressing the underrepresentation of Black students in gifted programs, as well as the achievement gaps between Black and White students. Black fathers increasingly understand the important role that Black mothers have traditionally played in supporting their gifted children's school experiences. As a…

  8. 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.

  9. Quantum effects in black holes

    International Nuclear Information System (INIS)

    Frolov, V.P.

    1979-01-01

    A strict definition of black holes is presented and some properties with regard to their mass are enumerated. The Hawking quantum effect - the effect of vacuum instability in the black hole gravitational field, as a result of shich the black hole radiates as a heated body is analyzed. It is shown that in order to obtain results on the black hole radiation it is sufficient to predetermine the in-vacuum state at a time moment in the past, when the collapsing body has a large size, and its gravitational field can be neglected. The causes and the place of particle production by the black hole, and also the space-time inside the black hole, are considered

  10. Particle creation by black holes

    International Nuclear Information System (INIS)

    Hawking, S.W.

    1975-01-01

    In the classical theory black holes can only absorb and not emit particles. However it is shown that quantum mechanical effects cause black holes to create and emit particles. This thermal emission leads to a slow decrease in the mass of the black hole and to its eventual disappearance: any primordial black hole of mass less than about 10 15 g would have evaporated by now. Although these quantum effects violate the classical law that the area of the event horizon of a black hole cannot decrease, there remains a Generalized Second Law: S + 1/4 A never decreases where S is the entropy of matter outside black holes and A is the sum of the surface areas of the event horizons. This shows that gravitational collapse converts the baryons and leptons in the collapsing body into entropy. It is tempting to speculate that this might be the reason why the Universe contains so much entropy per baryon. (orig.) [de

  11. 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...

  12. Destroying extremal magnetized black holes

    Science.gov (United States)

    Siahaan, Haryanto M.

    2017-07-01

    The gedanken experiment by Wald to destroy a black hole using a test particle in the equatorial plane is adapted to the case of extremal magnetized black holes. We find that the presence of external magnetic fields resulting from the "Ernst magnetization" permits a test particle to have strong enough energy to destroy the black hole. However, the corresponding effective potentials show that such particles would never reach the horizon.

  13. Statistical Hair on Black Holes

    International Nuclear Information System (INIS)

    Strominger, A.

    1996-01-01

    The Bekenstein-Hawking entropy for certain BPS-saturated black holes in string theory has recently been derived by counting internal black hole microstates at weak coupling. We argue that the black hole microstate can be measured by interference experiments even in the strong coupling region where there is clearly an event horizon. Extracting information which is naively behind the event horizon is possible due to the existence of statistical quantum hair carried by the black hole. This quantum hair arises from the arbitrarily large number of discrete gauge symmetries present in string theory. copyright 1996 The American Physical Society

  14. On black hole horizon fluctuations

    International Nuclear Information System (INIS)

    Tuchin, K.L.

    1999-01-01

    A study of the high angular momentum particles 'atmosphere' near the Schwarzschild black hole horizon suggested that strong gravitational interactions occur at invariant distance of the order of 3 √M [2]. We present a generalization of this result to the Kerr-Newman black hole case. It is shown that the larger charge and angular momentum black hole bears, the larger invariant distance at which strong gravitational interactions occur becomes. This invariant distance is of order 3 √((r + 2 )/((r + - r - ))). This implies that the Planckian structure of the Hawking radiation of extreme black holes is completely broken

  15. Black holes and the multiverse

    Energy Technology Data Exchange (ETDEWEB)

    Garriga, Jaume [Departament de Fisica Fonamental i Institut de Ciencies del Cosmos, Universitat de Barcelona, Marti i Franques, 1, Barcelona, 08028 Spain (Spain); Vilenkin, Alexander; Zhang, Jun, E-mail: jaume.garriga@ub.edu, E-mail: vilenkin@cosmos.phy.tufts.edu, E-mail: jun.zhang@tufts.edu [Institute of Cosmology, Tufts University, 574 Boston Ave, Medford, MA, 02155 (United States)

    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.

  16. Thermodynamics of Accelerating Black Holes.

    Science.gov (United States)

    Appels, Michael; Gregory, Ruth; Kubizňák, David

    2016-09-23

    We address a long-standing problem of describing the thermodynamics of an 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.

  17. Braneworld Black Hole Gravitational Lensing

    International Nuclear Information System (INIS)

    Liang Jun

    2017-01-01

    A class of braneworld black holes, which I called as Bronnikov–Melnikov–Dehen (BMD) black holes, are studied as gravitational lenses. I obtain the deflection angle in the strong deflection limit, and further calculate the angular positions and magnifications of relativistic images as well as the time delay between different relativistic images. I also compare the results with those obtained for Schwarzschild and two braneworld black holes, i.e., the tidal Reissner-Nordström (R-N) and the Casadio–Fabbri–Mazzacurati (CFM) black holes. (paper)

  18. Black report up-date

    International Nuclear Information System (INIS)

    1988-12-01

    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)

  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. Nariai black holes with quintessence

    OpenAIRE

    Fernando, Sharmanthie

    2014-01-01

    In this paper we study the properties of Schwarzschild black hole surrounded by quintessence matter. The main objective of the paper is to show the existence of Nariai type black hole for special values of the parameters in the theory. The Nariai black hole with the quintessence has the topology $dS_2 \\times S_2$ with $dS_2$ with a different scalar curvature than what would be expected for the Schwarzschild-de Sitter degenerate black hole. Temperature and the entropy for the Schwarzschild-de ...

  1. Children's Reactions to T.V. Blacks

    Science.gov (United States)

    Greenberg, Bradley S.

    1972-01-01

    An assessment of the frequency of exposure of young children, both black and white, to TV series which regularly featured blacks, degree of identification with black performers, attitudes towards blacks on TV and blacks outside of television, among other behaviors. (Author/JM)

  2. Artificial black holes

    CERN Document Server

    Visser, Matt; Volovik, Grigory E

    2009-01-01

    Physicists are pondering on the possibility of simulating black holes in the laboratory by means of various "analog models". These analog models, typically based on condensed matter physics, can be used to help us understand general relativity (Einstein's gravity); conversely, abstract techniques developed in general relativity can sometimes be used to help us understand certain aspects of condensed matter physics. This book contains 13 chapters - written by experts in general relativity, particle physics, and condensed matter physics - that explore various aspects of this two-way traffic.

  3. Magnonic Black Holes.

    Science.gov (United States)

    Roldán-Molina, A; Nunez, Alvaro S; Duine, R A

    2017-02-10

    We show that the interaction between the spin-polarized current and the magnetization dynamics can be used to implement black-hole and white-hole horizons for magnons-the quanta of oscillations in the magnetization direction in magnets. We consider three different systems: easy-plane ferromagnetic metals, isotropic antiferromagnetic metals, and easy-plane magnetic insulators. Based on available experimental data, we estimate that the Hawking temperature can be as large as 1 K. We comment on the implications of magnonic horizons for spin-wave scattering and transport experiments, and for magnon entanglement.

  4. 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

  5. Drifting black aurorae?

    International Nuclear Information System (INIS)

    Schoute-Vanneck, H.; Scourfield, M.W.J.; Nielsen, E.

    1990-01-01

    Characteristics of eastward drifting forms, previously described in the literature as black aurorae, have been identified in low-light level TV camera data. The TV field of view was within the field of view of STARE and that of an all-sky camera. On the basis of these observations the authors propose that these auroral forms are a manifestation of folds or waves on the borders of auroral bands propagating along the dark regions between neighboring auroral bands. Conditions under which the folds or waves occur are compatible with their formation by the Kelvin-Helmholtz electrostatic instability

  6. Black lung disease

    Energy Technology Data Exchange (ETDEWEB)

    Ramani, R.V.; Frantz, R.L. [Pennsylvania State University, University Park, PA (United States)

    1995-12-31

    Coal workers` pneumoconiosis (CWP), often called Black Lung Disease is a occupational disease which results from inhalation of coal mine dust which usually contains small amounts of free crystalline silica. This chapter reviews the current knowledge of the epidemiology and clinical aspects of CWP and how it has been controlled in the USA through the 1969 Coal Mine Act and dust level standards. It describes the sampling methods used. Medical control methods and engineering control of the disease is discussed. Work of the Generic Mineral Technology Center for Respirable Dust is described. 28 refs., 6 figs.

  7. Black American and Nigerian Pentecostalism: A Black Religious ...

    African Journals Online (AJOL)

    Black American and Nigerian Pentecostalism: A Black Religious Schizophrenia, 1910-2010. ... in American and African Pentecostalism as is related to social crisis, the dislocation of masses brought on by economic deprivation, urbanization, the break up of traditional society and consequence loss of traditional values.

  8. Black Interpretation, Black American Literature, and Grey Audiences.

    Science.gov (United States)

    Washington, Earl M.

    1981-01-01

    Defines and illustrates language techniques used by Black authors writing to and for Blacks in the 1960s and 1970s. Suggests how language and theme barriers of such literature might be overcome in a contemporary integrated oral interpretation classroom. (PD)

  9. Black holes and holography

    International Nuclear Information System (INIS)

    Mathur, Samir D

    2012-01-01

    The idea of holography in gravity arose from the fact that the entropy of black holes is given by their surface area. The holography encountered in gauge/gravity duality has no such relation however; the boundary surface can be placed at an arbitrary location in AdS space and its area does not give the entropy of the bulk. The essential issues are also different between the two cases: in black holes we get Hawking radiation from the 'holographic surface' which leads to the information issue, while in gauge/gravity duality there is no such radiation. To resolve the information paradox we need to show that there are real degrees of freedom at the horizon of the hole; this is achieved by the fuzzball construction. In gauge/gravity duality we have instead a field theory defined on an abstract dual space; there are no gravitational degrees of freedom at the holographic boundary. It is important to understand the relations and differences between these two notions of holography to get a full understanding of the lessons from the information paradox.

  10. 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.

  11. Teaching Black History after Obama

    Science.gov (United States)

    Sotiropoulos, Karen

    2017-01-01

    This article is a reflection on the teaching of black history after the Obama presidency and at the dawn of the Trump era. It is both an analysis of the state of the academic field and a primer on how to integrate the past few decades of scholarship in black history broadly across standard K-12 curriculum. It demonstrates the importance of…

  12. Black Holes in Our Universe

    Indian Academy of Sciences (India)

    most sensitive scientific instrument ever ... sion, expelling a lot of the mass, but leaving behind a black hole that is at least ... hole, and indeed such a phenomenon may explain the disappear- ance of a star in the galaxy N6946 [21]. The collapse of stars into black holes might account for some of the extraordinarily powerful ...

  13. COMPOSITION OF BLACK BEAR MILK.

    Science.gov (United States)

    An analysis of black bear ( Ursus americanus Pallas) milk showed that the total solids, fat and protein were much higher and the lactose lower than...either cow or human milk. In comparison with polar bear (Thalarcotos maritimus ), the black bear milk was lower in fat, protein and total calories. (Author)

  14. 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.

  15. Black Holes in Our Universe

    Indian Academy of Sciences (India)

    was discovered in the constellation Cygnus; a bright X-ray emit- ter associated with a twin-star system, and christened Cygnus X-. 1. It has a massive star and a black hole orbiting each other. With an optical telescope it is the companion star of the black hole which is visible, which produces stellar winds blowing away from.

  16. Black holes and quantum mechanics

    NARCIS (Netherlands)

    t Hooft, G.|info:eu-repo/dai/nl/074127888

    2010-01-01

    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

  17. 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....

  18. 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).

  19. Motor neuron disease in blacks

    African Journals Online (AJOL)

    1989-08-19

    Aug 19, 1989 ... A series of 86 black, Indian and white patients with motor neuron disease were analysed retrospectively. Although the material does not allow statistically valid conclusions, there are sufficient cases among blacks to allow two prima facie observations in this population group: (~ motor neuron disease.

  20. Black Music: A Financial Perspective.

    Science.gov (United States)

    Ashburne, Michael R.

    1977-01-01

    The financial relationships among artists, record companies, and music publishers in the recording industry are examined. It is shown that, although Black talent in the recording field has produced millions of dollars annually since the turn of the century, Black artists have been grossly underpaid. (Author/GC)

  1. Resource recovery from black water

    NARCIS (Netherlands)

    Graaff, de M.S.

    2010-01-01

    New sanitation systems based on separation at source offer a large potential for resource recovery from wastewater, e.g. energy and nutrients from black water and irrigation water from grey water. This review focuses on the components in source separated black water. The treatment options for the

  2. Black Youths and Illegal Drugs.

    Science.gov (United States)

    Joseph, Janice; Pearson, Patricia G.

    2002-01-01

    Examines the effect of drugs on black youths, discussing different types of drug involvement, reasons for drug involvement, extent and nature of involvement, drugs and crime, drugs and health issues, drug control strategies, and prevention. Policy implications include prioritizing drug prevention among black youths, providing alternatives to drug…

  3. What, no black hole evaporation

    International Nuclear Information System (INIS)

    Hajicek, P.; Israel, W.

    1980-01-01

    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.)

  4. Statistical black-hole thermodynamics

    International Nuclear Information System (INIS)

    Bekenstein, J.D.

    1975-01-01

    Traditional methods from statistical thermodynamics, with appropriate modifications, are used to study several problems in black-hole thermodynamics. Jaynes's maximum-uncertainty method for computing probabilities is used to show that the earlier-formulated generalized second law is respected in statistically averaged form in the process of spontaneous radiation by a Kerr black hole discovered by Hawking, and also in the case of a Schwarzschild hole immersed in a bath of black-body radiation, however cold. The generalized second law is used to motivate a maximum-entropy principle for determining the equilibrium probability distribution for a system containing a black hole. As an application we derive the distribution for the radiation in equilibrium with a Kerr hole (it is found to agree with what would be expected from Hawking's results) and the form of the associated distribution among Kerr black-hole solution states of definite mass. The same results are shown to follow from a statistical interpretation of the concept of black-hole entropy as the natural logarithm of the number of possible interior configurations that are compatible with the given exterior black-hole state. We also formulate a Jaynes-type maximum-uncertainty principle for black holes, and apply it to obtain the probability distribution among Kerr solution states for an isolated radiating Kerr hole

  5. Marital Happiness of Black Women.

    Science.gov (United States)

    Rutledge, Essie M.

    According to a study of 256 black married women between the ages of 26 and 60 living with their spouses, marital happiness is more common among black women than marital unhappiness. This finding is based on the secondary analysis of a sample of data collected in Detroit in 1968-1969. Variables statistically significant to the marital happiness of…

  6. 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...

  7. Black hole decay as geodesic motion

    International Nuclear Information System (INIS)

    Gupta, Kumar S.; Sen, Siddhartha

    2003-01-01

    We show that a formalism for analyzing the near-horizon conformal symmetry of Schwarzschild black holes using a scalar field probe is capable of describing black hole decay. The equation governing black hole decay can be identified as the geodesic equation in the space of black hole masses. This provides a novel geometric interpretation for the decay of black holes. Moreover, this approach predicts a precise correction term to the usual expression for the decay rate of black holes

  8. Black holes and quantum processes in them

    International Nuclear Information System (INIS)

    Frolov, V.P.

    1976-01-01

    The latest achievements in the physics of black holes are reviewed. The problem of quantum production in a strong gravitational field of black holes is considered. Another parallel discovered during investigation of interactions between black holes and between black holes and surrounding media, is also drawn with thermodynamics. A gravitational field of rotating black holes is considered. Some cosmological aspects of evaporation of small black holes are discussed as well as possibilities to observe them

  9. String-Corrected Black Holes

    Energy Technology Data Exchange (ETDEWEB)

    Hubeny, V.

    2005-01-12

    We investigate the geometry of four dimensional black hole solutions in the presence of stringy higher curvature corrections to the low energy effective action. For certain supersymmetric two charge black holes these corrections drastically alter the causal structure of the solution, converting seemingly pathological null singularities into timelike singularities hidden behind a finite area horizon. We establish, analytically and numerically, that the string-corrected two-charge black hole metric has the same Penrose diagram as the extremal four-charge black hole. The higher derivative terms lead to another dramatic effect--the gravitational force exerted by a black hole on an inertial observer is no longer purely attractive. The magnitude of this effect is related to the size of the compactification manifold.

  10. The search for black holes

    International Nuclear Information System (INIS)

    Torn, K.

    1976-01-01

    Conceivable experimental investigations to prove the existence of black holes are discussed. Double system with a black hole turning around a star-satellite are in the spotlight. X-radiation emmited by such systems and resulting from accretion of the stellar gas by a black hole, and the gas heating when falling on the black hole might prove the model suggested. A source of strong X-radiation observed in the Cygnus star cluster and referred to as Cygnus X-1 may be thus identified as a black hole. Direct registration of short X-ray pulses with msec intervals might prove the suggestion. The lack of appropriate astrophysic facilities is pointed out to be the major difficulty on the way of experimental verifications

  11. Compressibility of rotating black holes

    International Nuclear Information System (INIS)

    Dolan, Brian P.

    2011-01-01

    Interpreting the cosmological constant as a pressure, whose thermodynamically conjugate variable is a volume, modifies the first law of black hole thermodynamics. Properties of the resulting thermodynamic volume are investigated: the compressibility and the speed of sound of the black hole are derived in the case of nonpositive cosmological constant. The adiabatic compressibility vanishes for a nonrotating black hole and is maximal in the extremal case--comparable with, but still less than, that of a cold neutron star. A speed of sound v s is associated with the adiabatic compressibility, which is equal to c for a nonrotating black hole and decreases as the angular momentum is increased. An extremal black hole has v s 2 =0.9 c 2 when the cosmological constant vanishes, and more generally v s is bounded below by c/√(2).

  12. Are LIGO's Black Holes Made From Smaller Black Holes?

    Science.gov (United States)

    Kohler, Susanna

    2017-05-01

    The recent successes of the Laser Interferometer Gravitational-Wave Observatory (LIGO) has raised hopes that several long-standing questions in black-hole physics will soon be answerable. Besides revealing how the black-hole binary pairs are built, could detections with LIGO also reveal how the black holes themselves form?Isolation or HierarchyThe first detection of gravitational waves, GW150914, was surprising for a number of reasons. One unexpected result was the mass of the two black holes that LIGO saw merging: they were a whopping 29 and 36 solar masses.On the left of this schematic, two first-generation (direct-collapse) black holes form a merging binary. The right illustrates a second-generation hierarchical merger: each black hole in the final merging binary was formed by the merger of two smaller black holes. [Adapted fromGerosa et al., a simultaneously published paper that also explores the problem of hierarchical mergers and reaches similar conclusions]How do black holes of this size form? One possibility is that they form in isolation from the collapse of a single massive star. In an alternative model, they are created through the hierarchical merger of smaller black holes, gradually building up to the size we observed.A team of scientists led by Maya Fishbach (University of Chicago) suggests that we may soon be able to tell whether or not black holes observed by LIGO formed hierarchically. Fishbach and collaborators argue that hierarchical formation leaves a distinctive signature on the spins of the final black holes and that as soon as we have enough merger detections from LIGO, we can use spin measurements to statistically determine if LIGO black holes were formed hierarchically.Spins from Major MergersWhen two black holes merge, both their original spins and the angular momentum of the pair contribute to the spin of the final black hole that results. Fishbach and collaborators calculate the expected distribution of these final spins assuming that

  13. Regular phantom black holes.

    Science.gov (United States)

    Bronnikov, K A; Fabris, J C

    2006-06-30

    We study self-gravitating, static, spherically symmetric phantom scalar fields with arbitrary potentials (favored by cosmological observations) and single out 16 classes of possible regular configurations with flat, de Sitter, and anti-de Sitter asymptotics. Among them are traversable wormholes, bouncing Kantowski-Sachs (KS) cosmologies, and asymptotically flat black holes (BHs). A regular BH has a Schwarzschild-like causal structure, but the singularity is replaced by a de Sitter infinity, giving a hypothetic BH explorer a chance to survive. It also looks possible that our Universe has originated in a phantom-dominated collapse in another universe, with KS expansion and isotropization after crossing the horizon. Explicit examples of regular solutions are built and discussed. Possible generalizations include k-essence type scalar fields (with a potential) and scalar-tensor gravity.

  14. Complicated Contradictions Amid Black Feminism and Millennial Black Women Teachers Creating Curriculum for Black Girls

    Science.gov (United States)

    Nyachae, Tiffany M.

    2016-01-01

    Millennial Black women teachers wrestle with two simultaneous burdens: disrupting the racist and sexist status quo of schooling through curriculum, and employing tactics to survive school politics among their majority White women colleagues. This article describes how the "Sisters of Promise" (SOP) curriculum aligned with Black feminism…

  15. Black Lives Matter of Black Identity Extremist? : The FBI, Black Activists and the Struggle for Victimhood

    NARCIS (Netherlands)

    Mutsaers, Paul

    2017-01-01

    The question 'who is the victim?' is an important social directive that shapes the struggles for victimhood in which Black Lives Matters, U.S. police forces and their various (counter)publics are currently engaging. This column begins with a controversial FBI report on so-called Black Identity

  16. Magnetic fields around black holes

    Science.gov (United States)

    Garofalo, David A. G.

    Active Galactic Nuclei are the most powerful long-lived objects in the universe. They are thought to harbor supermassive black holes that range from 1 million solar masses to 1000 times that value and possibly greater. Theory and observation are converging on a model for these objects that involves the conversion of gravitational potential energy of accreting gas to radiation as well as Poynting flux produced by the interaction of the rotating spacetime and the electromagnetic fields originating in the ionized accretion flow. The presence of black holes in astrophysics is taking center stage, with the output from AGN in various forms such as winds and jets influencing the formation and evolution of the host galaxy. This dissertation addresses some of the basic unanswered questions that plague our current understanding of how rotating black holes interact with their surrounding magnetized accretion disks to produce the enormous observed energy. Two magnetic configurations are examined. The first involves magnetic fields connecting the black hole with the inner accretion disk and the other involves large scale magnetic fields threading the disk and the hole. We study the effects of the former type by establishing the consequences that magnetic torques between the black hole and the inner accretion disk have on the energy dissipation profile. We attempt a plausible explanation to the observed "Deep Minimum" state in the Seyfert galaxy MCG-6- 30-15. For the latter type of magnetic geometry, we study the effects of the strength of the magnetic field threading the black hole within the context of the cherished Blandford & Znajek mechanism for black hole spin energy extraction. We begin by addressing the problem in the non-relativistic regime where we find that the black hole-threading magnetic field is stronger for greater disk thickness, larger magnetic Prandtl number, and for a larger accretion disk. We then study the problem in full relativity where we show that our

  17. A nonsingular rotating black hole

    International Nuclear Information System (INIS)

    Ghosh, Sushant G.

    2015-01-01

    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.)

  18. The renaissance of black phosphorus.

    Science.gov (United States)

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

    2015-04-14

    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.

  19. A Lovelock black hole bestiary

    International Nuclear Information System (INIS)

    Camanho, Xián O; Edelstein, José D

    2013-01-01

    We revisit the study of (A)dS black holes in Lovelock theories. We present a new tool that allows to attack this problem in full generality. In analyzing maximally symmetric Lovelock black holes with non-planar horizon topologies, many distinctive and interesting features are observed. Among them, the existence of maximally symmetric vacua does not support black holes in vast regions of the space of gravitational couplings, multi-horizon black holes and branches of solutions that suggest the existence of a rich diagram of phase transitions. The appearance of naked singularities seems unavoidable in some cases, raising the question about the fate of the cosmic censorship conjecture in these theories. There is a preferred branch of solutions for planar black holes, as well as for non-planar black holes with high enough mass or temperature. Our study clarifies the role of all branches of solutions, including asymptotically dS black holes, and whether they should be considered when studying these theories in the context of AdS/CFT. (paper)

  20. Phase transition for black holes with scalar hair and topological black holes

    OpenAIRE

    Myung, Yun Soo

    2008-01-01

    We study phase transitions between black holes with scalar hair and topological black holes in asymptotically anti-de Sitter spacetimes. As the ground state solutions, we introduce the non-rotating BTZ black hole in three dimensions and topological black hole with hyperbolic horizon in four dimensions. For the temperature matching only, we show that the phase transition between black hole with scalar hair (Martinez-Troncoso-Zanelli black hole) and topological black hole is second-order by usi...

  1. 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.

  2. Tunnelling from Goedel black holes

    International Nuclear Information System (INIS)

    Kerner, Ryan; Mann, R. B.

    2007-01-01

    We consider the spacetime structure of Kerr-Goedel black holes, analyzing their parameter space in detail. We apply the tunnelling method to compute their temperature and compare the results to previous calculations obtained via other methods. We claim that it is not possible to have the closed timelike curve (CTC) horizon in between the two black hole horizons and include a discussion of issues that occur when the radius of the CTC horizon is smaller than the radius of both black hole horizons

  3. Black Holes: A Traveler's Guide

    Science.gov (United States)

    Pickover, Clifford A.

    1998-03-01

    BLACK HOLES A TRAVELER'S GUIDE Clifford Pickover's inventive and entertaining excursion beyond the curves of space and time. "I've enjoyed Clifford Pickover's earlier books . . . now he has ventured into the exploration of black holes. All would-be tourists are strongly advised to read his traveler's guide." -Arthur C. Clarke. "Many books have been written about black holes, but none surpass this one in arousing emotions of awe and wonder towards the mysterious structure of the universe." -Martin Gardner. "Bucky Fuller thought big. Arthur C. Clarke thinks big, but Cliff Pickover outdoes them both." -Wired. "The book is fun, zany, in-your-face, and refreshingly addictive." -Times Higher Education Supplement.

  4. 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.

  5. Quantum mechanics of black holes.

    Science.gov (United States)

    Witten, Edward

    2012-08-03

    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.

  6. Vacuum metastability with black holes

    International Nuclear Information System (INIS)

    Burda, Philipp; Gregory, Ruth; Moss, Ian G. annd

    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 evaporation process. Finally, we comment on the application of these results to vacuum decay seeded by black holes produced in particle collisions.

  7. Black holes from fluid mechanics

    Science.gov (United States)

    Lahiri, Subhaneil

    2009-12-01

    We use the AdS/CFT correspondence in a regime where the field theory is well described by fluid mechanics to study large black holes in asymptotically locally anti de Sitter spaces. In particular, we use the fluid description to study the thermodynamics of the black holes and the existence of exotic horizon topologies in higher dimensions. First we test this method by comparing large rotating black holes in global AdSD spaces to stationary solutions of the relativistic Navier-Stokes equations on SD-2. Reading off the equation of state of this fluid from the thermodynamics of non-rotating black holes, we proceed to construct the nonlinear spinning solutions of fluid mechanics that are dual to rotating black holes. In all known examples, the thermodynamics and the local stress tensor of our solutions are in precise agreement with the thermodynamics and boundary stress tensor of the spinning black holes. Our results yield predictions for the thermodynamics of all large black holes in all theories of gravity on AdS spaces, for example, IIB string theory on AdS5 x S 5 and M theory on AdS4 x S7 and AdS7 x S 4. We then construct solutions to the relativistic Navier-Stokes equations that describe the long wavelength collective dynamics of the deconfined plasma phase of N = 4 Yang Mills theory compactified down to d = 3 on a Scherk-Schwarz circle. Our solutions are stationary, axially symmetric spinning balls and rings of plasma. These solutions, which are dual to (yet to be constructed) rotating black holes and black rings in Scherk-Schwarz compactified AdS 5, and have properties that are qualitatively similar to those of black holes and black rings in flat five dimensional gravity. We also study the stability of these solutions to small fluctuations, which provides an indirect method for studying Gregory-Laflamme instabilities. We also extend the construction to higher dimensions, allowing one to study the existence of new black hole topologies and their phase diagram.

  8. 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.

  9. Gravitational polarizability of black holes

    International Nuclear Information System (INIS)

    Damour, Thibault; Lecian, Orchidea Maria

    2009-01-01

    The gravitational polarizability properties of black holes are compared and contrasted with their electromagnetic polarizability properties. The 'shape' or 'height' multipolar Love numbers h l of a black hole are defined and computed. They are then compared to their electromagnetic analogs h l EM . The Love numbers h l give the height of the lth multipolar 'tidal bulge' raised on the horizon of a black hole by faraway masses. We also discuss the shape of the tidal bulge raised by a test-mass m, in the limit where m gets very close to the horizon.

  10. Black holes and Higgs stability

    CERN Document Server

    Tetradis, Nikolaos

    2016-09-20

    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.

  11. Black layers on historical architecture.

    Science.gov (United States)

    Toniolo, Lucia; Zerbi, Carlotta M; Bugini, Roberto

    2009-03-01

    The external surface of any building in urban polluted environment is unavoidably destined to be covered with layers that assume a grey to black colour and are generally called 'black crusts'. These, according to standard protocols and glossary, are deteriorated surface layers of stone material; they can have variable thickness, are hard and fragile and can detach spontaneously from the substrate, which, in general, is quite decayed. Plain visual examination may lead to consider 'black crusts' all similar, whilst only a careful diagnostic investigation can distinguish 'black crusts' and the consequences of their formation on stone substrates. In this paper, various black layers on marble are studied and compared and the morphological and compositional characteristics discussed according to the related mechanisms of formation. Differences between old (hundred years) and recent crusts (30 years) are investigated and pointed out. Samples of black crusts collected from the Milan Cathedral façade (Candoglia Marble) have been studied and compared with the careful and synergic employ of traditional techniques: optical (transmission and reflected VIS light) and electron microscopy, X-ray spectrometry and micro-Fourier transform infrared spectroscopy. Visual examination of loose fragments does not allow to point out outstanding differences amongst the various samples; black layers have similar main mineral components, gypsum and airborne particles, with different spatial distribution. The microscopic studies allowed to point out the porosity differences, the gypsum crystallisation habit, different amount of embedded particles, level and progress of marble decay. The observations lead to define three main types of black crusts: black crust deriving from marble sulphation, compact deposit and encrustation due to exogenic materials deposition. Black crusts show evidence of sulphation in progress, without a clear continuity solution between crust and marble; the lack of

  12. Cryo-Etched Black Silicon for Use as Optical Black

    Science.gov (United States)

    Yee, Karl Y.; White, Victor E.; Mouroulis, Pantazis; Eastwood, Michael L.

    2011-01-01

    Stray light reflected from the surface of imaging spectrometer components in particular, the spectrometer slit degrade the image quality. A technique has been developed for rapid, uniform, and cost-effective black silicon formation based on inductively coupled plasma (ICP) etching at cryogenic temperatures. Recent measurements show less than 1-percent total reflectance from 350 2,500 nm of doped black silicon formed in this way, making it an excellent option for texturing of component surfaces for reduction of stray light. Oxygen combines with SF6 + Si etch byproducts to form a passivation layer atop the Si when the etch is performed at cryogenic temperatures. Excess flow of oxygen results in micromasking and the formation of black silicon. The process is repeatable and reliable, and provides control over etch depth and sidewall profile. Density of the needles can be controlled to some extent. Regions to be textured can be patterned lithographically. Adhesion is not an issue as the nanotips are part of the underlying substrate. This is in contrast to surface growth/deposition techniques such as carbon nanotubes (CNTs). The black Si surface is compatible with wet processing, including processing with solvents, the textured surface is completely inorganic, and it does not outgas. In radiometry applications, optical absorbers are often constructed using gold black or CNTs. This black silicon technology is an improvement for these types of applications.

  13. 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

  14. The Black Man in American Society.

    Science.gov (United States)

    Framingham Public Schools, MA.

    GRADE OR AGES: Junior high school. SUBJECT MATTER: The black man in American society. ORGANIZATION AND PHYSICAL APPEARANCE: There are four major parts each with an overview. The four parts concern a) the African heritage of the black man, b) the American exploitation of the black man, c) the black man's contribution to American society, d) the…

  15. Black Hole Complementary Principle and Noncommutative Membrane

    International Nuclear Information System (INIS)

    Wei Ren

    2006-01-01

    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.

  16. Accretion, primordial black holes and standard cosmology

    Indian Academy of Sciences (India)

    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 ...

  17. The Black Journalist in South Africa.

    Science.gov (United States)

    Hachten, William A.

    The role of the black journalist in South Africa is contradictory, precarious, and permeated with politics. There is little freedom of expression for blacks in South Africa, yet white-owned newspapers have expanded their coverage of black news, and some have special editions for black readers. As a result, the English language press is using more…

  18. 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,…

  19. Then and Now: Black Boycott in Waterloo.

    Science.gov (United States)

    Anderson, Ruth B.

    1983-01-01

    Discusses events following the desegregation of Waterloo, Iowa, schools. Describes the 1978 Black boycott of Hoover Junior High, which led to improvements in the treatment of Black students. Lists administrative responses to each Black grievance, and presents interviews with ten Black students three years after the boycott. (KH)

  20. Black Sprayable Molecular Adsorber Coating

    Data.gov (United States)

    National Aeronautics and Space Administration — The main objective of this technology project is to develop, optimize, and flight qualify a black version of the molecular adsorber coating and a conductive version...

  1. 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.

  2. Black hole evaporation: a paradigm

    International Nuclear Information System (INIS)

    Ashtekar, Abhay; Bojowald, Martin

    2005-01-01

    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

  3. 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.

  4. "Be Real Black for Me": Imagining BlackCrit in Education

    Science.gov (United States)

    Dumas, Michael J.; ross, kihana miraya

    2016-01-01

    The authors put forward a theorization of a Black Critical Theory, or what might be called BlackCrit, within, and in response to, Critical Race Theory, and then outline ways that BlackCrit in education helps us to more incisively analyze how the specificity of (anti)blackness matters in explaining how Black bodies become marginalized, disregarded,…

  5. A radiant black market

    International Nuclear Information System (INIS)

    Roser, T.

    1993-01-01

    On the 13 October the Bavarian police seized 2.2kg of uranium and arrested a group of seven people who had offered to sell it for $500.000. The existence of a black market for uranium may be a proliferation risk but it is not a serious health hazard - even if the material is negligently packed, as it seems to have been in all the recent cases. The situation is quite different when it comes to dealing with highly radioactive materials such as fission productions. Two such cases have been reported this summer involving Cs-137 and Sr-90, both emitters of hard beta rays. Little is known about the provenance of the radioactive and fissile material discovered. Obviously it originates from the ex-USSR, and the absence of highly enriched material suggests a civil rather than a military source. The governments of ex-Soviet states have apparently tried to intercept smugglers at their western frontiers, but have so far been unable to pinpoint the breaches in their security. It is also uncertain whether the occurrences discovered and reported are merely the tip of an iceberg. (author)

  6. Black holes in astrophysics

    International Nuclear Information System (INIS)

    Narayan, Ramesh

    2005-01-01

    This paper reviews the current status of black hole (BH) astrophysics, focusing on topics of interest to a physics audience. Astronomers have discovered dozens of compact objects with masses greater than 3M o-dot , the likely maximum mass of a neutron star. These objects are identified as BH candidates. Some of the candidates have masses ∼5M o-dot -20M o-dot and are found in x-ray binaries, while the rest have masses ∼10 6 M o-dot -10 9.5 M o-dot and are found in galactic nuclei. A variety of methods are being tried to estimate the spin parameters of the candidate BHs. There is strong circumstantial evidence that many of the objects have event horizons, so there is good reason to believe that the candidates are true BHs. Recent MHD simulations of magnetized plasma accreting on rotating BHs seem to hint that relativistic jets may be produced by a magnetic analogue of the Penrose process

  7. Black coal. Annual report 1997

    International Nuclear Information System (INIS)

    1997-01-01

    An overview is given of the situation of the world energy industry with regard to all energy carriers. Then energy-political conclusions are drawn for German black coal and the resulting prospects are detailed. Finally, some socio-political aspects are considered with regard to German black-coal mining: Workforce policy, tariff policy, social security and social safeguards for the adaptation process. (orig.) [de

  8. Black strings and classical hair

    International Nuclear Information System (INIS)

    Horowitz, G.T.; Yang, H.

    1997-01-01

    We examine the geometry near the event horizon of a family of black string solutions with traveling waves. It has previously been shown that the metric is continuous there. Contrary to expectations, we find that the geometry is not smooth, and the horizon becomes singular whenever a wave is present. Both five-dimensional and six-dimensional black strings are considered with similar results. copyright 1997 The American Physical Society

  9. Black holes from extended inflation

    International Nuclear Information System (INIS)

    Hsu, S.D.H.; Lawrence Berkeley Lab., CA

    1990-01-01

    It is argued that models of extended inflation, in which modified Einstein gravity allows a graceful exit from the false vacuum, lead to copious production of black holes. The critical temperature of the inflationary phase transition must be >10 8 GeV in order to avoid severe cosmological problems in a universe dominated by black holes. We speculate on the possibility that the interiors of false vacuum regions evolve into baby universes. (orig.)

  10. Black Holes as Dark Matter

    OpenAIRE

    Frampton, Paul H.

    2009-01-01

    While the energy of the universe has been established to be about 0.04 baryons, 0.24 dark matter and 0.72 dark energy, the cosmological entropy is almost entirely, about $(1 - 10^{-15})$, from black holes and only $10^{-15}$ from everything else. This identification of all dark matter as black holes is natural in statistical mechanics. Cosmological history of dark matter is discussed.

  11. Black holes in the universe

    International Nuclear Information System (INIS)

    Camenzind, M.

    2005-01-01

    While physicists have been grappling with the theory of black holes (BH), as shown by the many contributions to the Einstein year, astronomers have been successfully searching for real black holes in the Universe. Black hole astrophysics began in the 1960s with the discovery of quasars and other active galactic nuclei (AGN) in distant galaxies. Already in the 1960s it became clear that the most natural explanation for the quasar activity is the release of gravitational energy through accretion of gas onto supermassive black holes. The remnants of this activity have now been found in the centers of about 50 nearby galaxies. BH astrophysics received a new twist in the 1970s with the discovery of the X-ray binary (XRB) Cygnus X-1. The X-ray emitting compact object was too massive to be explained by a neutron star. Today, about 20 excellent BH candidates are known in XRBs. On the extragalactic scale, more than 100.000 quasars have been found in large galaxy surveys. At the redshift of the most distant ones, the Universe was younger than one billion year. The most enigmatic black hole candidates identified in the last years are the compact objects behind the Gamma-Ray Bursters. The formation of all these types of black holes is accompanied by extensive emission of gravitational waves. The detection of these strong gravity events is one of the biggest challenges for physicists in the near future. (author)

  12. Black Hole Spin Measurement Uncertainty

    Science.gov (United States)

    Salvesen, Greg; Begelman, Mitchell C.

    2018-01-01

    Angular momentum, or spin, is one of only two fundamental properties of astrophysical black holes, and measuring its value has numerous applications. For instance, obtaining reliable spin measurements could constrain the growth history of supermassive black holes and reveal whether relativistic jets are powered by tapping into the black hole spin reservoir. The two well-established techniques for measuring black hole spin can both be applied to X-ray binaries, but are in disagreement for cases of non-maximal spin. This discrepancy must be resolved if either technique is to be deemed robust. We show that the technique based on disc continuum fitting is sensitive to uncertainties regarding the disc atmosphere, which are observationally unconstrained. By incorporating reasonable uncertainties into black hole spin probability density functions, we demonstrate that the spin measured by disc continuum fitting can become highly uncertain. Future work toward understanding how the observed disc continuum is altered by atmospheric physics, particularly magnetic fields, will further strengthen black hole spin measurement techniques.

  13. Atomic structure in black hole

    International Nuclear Information System (INIS)

    Nagatani, Yukinori

    2006-01-01

    We propose that any black hole has atomic structure in its inside and has no horizon as a model of black holes. Our proposal is founded on a mean field approximation of gravity. The structure of our model consists of a (charged) singularity at the center and quantum fluctuations of fields around the singularity, namely, it is quite similar to that of atoms. Any properties of black holes, e.g. entropy, can be explained by the model. The model naturally quantizes black holes. In particular, we find the minimum black hole, whose structure is similar to that of the hydrogen atom and whose Schwarzschild radius is approximately 1.1287 times the Planck length. Our approach is conceptually similar to Bohr's model of the atomic structure, and the concept of the minimum Schwarzschild radius is similar to that of the Bohr radius. The model predicts that black holes carry baryon number, and the baryon number is rapidly violated. This baryon number violation can be used as verification of the model. (author)

  14. 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.

  15. Thermodynamics of Horava-Lifshitz black holes

    International Nuclear Information System (INIS)

    Myung, Yun Soo; Kim, Yong-Wan

    2010-01-01

    We study black holes in the Horava-Lifshitz gravity with a parameter λ. For 1/3≤λ 3, 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.)

  16. Detecting Black Hole Binaries by Gaia

    OpenAIRE

    Yamaguchi, Masaki S.; Kawanaka, Norita; Bulik, Tomasz; Piran, Tsvi

    2017-01-01

    We study the prospect of the Gaia satellite to identify black hole binary systems by detecting the orbital motion of the companion stars. Taking into account the initial mass function, mass transfer, common envelope phase, interstellar absorption and identifiability of black holes, we estimate the number of black hole binaries detected by Gaia and their distributions with respect to the black hole mass for several models with different parameters. We find that $\\sim 300-6000$ black hole binar...

  17. Black holes, qubits and octonions

    International Nuclear Information System (INIS)

    Borsten, L.; Dahanayake, D.; Duff, M.J.; Ebrahim, H.; Rubens, W.

    2009-01-01

    We review the recently established relationships between black hole entropy in string theory and the quantum entanglement of qubits and qutrits in quantum information theory. The first example is provided by the measure of the tripartite entanglement of three qubits (Alice, Bob and Charlie), known as the 3-tangle, and the entropy of the 8-charge STU black hole of N=2 supergravity, both of which are given by the [SL(2)] 3 invariant hyperdeterminant, a quantity first introduced by Cayley in 1845. Moreover the classification of three-qubit entanglements is related to the classification of N=2 supersymmetric STU black holes. There are further relationships between the attractor mechanism and local distillation protocols and between supersymmetry and the suppression of bit flip errors. At the microscopic level, the black holes are described by intersecting D3-branes whose wrapping around the six compact dimensions T 6 provides the string-theoretic interpretation of the charges and we associate the three-qubit basis vectors, |ABC>(A,B,C=0 or 1), with the corresponding 8 wrapping cycles. The black hole/qubit correspondence extends to the 56 charge N=8 black holes and the tripartite entanglement of seven qubits where the measure is provided by Cartan's E 7 contains [SL(2)] 7 invariant. The qubits are naturally described by the seven vertices ABCDEFG of the Fano plane, which provides the multiplication table of the seven imaginary octonions, reflecting the fact that E 7 has a natural structure of an O-graded algebra. This in turn provides a novel imaginary octonionic interpretation of the 56=7x8 charges of N=8: the 24=3x8 NS-NS charges correspond to the three imaginary quaternions and the 32=4x8 R-R to the four complementary imaginary octonions. We contrast this approach with that based on Jordan algebras and the Freudenthal triple system. N=8 black holes (or black strings) in five dimensions are also related to the bipartite entanglement of three qutrits (3-state systems

  18. Black hole quantum spectrum

    Science.gov (United States)

    Corda, Christian

    2013-12-01

    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.

  19. Violent flickering in Black Holes

    Science.gov (United States)

    2008-10-01

    Unique observations of the flickering light from the surroundings of two black holes provide new insights into the colossal energy that flows at their hearts. By mapping out how well the variations in visible light match those in X-rays on very short timescales, astronomers have shown that magnetic fields must play a crucial role in the way black holes swallow matter. Flickering black hole ESO PR Photo 36/08 Flickering black hole Like the flame from a candle, light coming from the surroundings of a black hole is not constant -- it flares, sputters and sparkles. "The rapid flickering of light from a black hole is most commonly observed at X-ray wavelengths," says Poshak Gandhi, who led the international team that reports these results. "This new study is one of only a handful to date that also explore the fast variations in visible light, and, most importantly how these fluctuations relate to those in X-rays." The observations tracked the shimmering of the black holes simultaneously using two different instruments, one on the ground and one in space. The X-ray data were taken using NASA's Rossi X-ray Timing Explorer satellite. The visible light was collected with the high speed camera ULTRACAM, a visiting instrument at ESO's Very Large Telescope (VLT), recording up to 20 images a second. ULTRACAM was developed by team members Vik Dhillon and Tom Marsh. "These are among the fastest observations of a black hole ever obtained with a large optical telescope," says Dhillon. To their surprise, astronomers discovered that the brightness fluctuations in the visible light were even more rapid than those seen in X-rays. In addition, the visible-light and X-ray variations were found not to be simultaneous, but to follow a repeated and remarkable pattern: just before an X-ray flare the visible light dims, and then surges to a bright flash for a tiny fraction of a second before rapidly decreasing again. None of this radiation emerges directly from the black hole, but from the

  20. Black holes: a slanted overview

    International Nuclear Information System (INIS)

    Vishveshwara, C.V.

    1988-01-01

    The black hole saga spanning some seventy years may be broadly divided into four phases, namely, (a) the dark ages when little was known about black holes even though they had come into existence quite early through the Schwarzschild solution, (b) the age of enlightenment bringing in deep and prolific discoveries, (c) the age of fantasy that cast black holes in all sorts of extraordinary roles, and (d) the golden age of relativistic astrophysics - to some extent similar to Dirac's characterisation of the development of quantum theory - in which black holes have been extensively used to elucidate a number of astrophysical phenomena. It is impossible to give here even the briefest outline of the major developments in this vast area. We shall only attempt to present a few aspects of black hole physics which have been actively pursued in the recent past. Some details are given in the case of those topics that have not found their way into text books or review articles. (author)

  1. Cosmology with primordial black holes

    International Nuclear Information System (INIS)

    Lindley, D.

    1981-09-01

    Cosmologies containing a substantial amount of matter in the form of evaporating primordial black holes are investigated. A review of constraints on the numbers of such black holes, including an analysis of a new limit found by looking at the destruction of deuterium by high energy photons, shows that there must be a negligible population of small black holes from the era of cosmological nucleosynthesis onwards, but that there are no strong constraints before this time. The major part of the work is based on the construction of detailed, self-consistent cosmological models in which black holes are continually forming and evaporating The interest in these models centres on the question of baryon generation, which occurs via the asymmetric decay of a new type of particle which appears as a consequence of the recently developed Grand Unified Theories of elementary particles. Unfortunately, there is so much uncertainty in the models that firm conclusions are difficult to reach; however, it seems feasible in principle that primordial black holes could be responsible for a significant part of the present matter density of the Universe. (author)

  2. Black holes: the membrane paradigm

    International Nuclear Information System (INIS)

    Thorne, K.S.; Price, R.H.; Macdonald, D.A.

    1986-01-01

    The physics of black holes is explored in terms of a membrane paradigm which treats the event horizon as a two-dimensional membrane embedded in three-dimensional space. A 3+1 formalism is used to split Schwarzschild space-time and the laws of physics outside a nonrotating hole, which permits treatment of the atmosphere in terms of the physical properties of thin slices. The model is applied to perturbed slowly or rapidly rotating and nonrotating holes, and to quantify the electric and magnetic fields and eddy currents passing through a membrane surface which represents a stretched horizon. Features of tidal gravitational fields in the vicinity of the horizon, quasars and active galalctic nuclei, the alignment of jets perpendicular to accretion disks, and the effects of black holes at the center of ellipsoidal star clusters are investigated. Attention is also given to a black hole in a binary system and the interactions of black holes with matter that is either near or very far from the event horizon. Finally, a statistical mechanics treatment is used to derive a second law of thermodynamics for a perfectly thermal atmosphere of a black hole

  3. Why Blue-Collar Blacks Help Less

    OpenAIRE

    Smith, Sandra Susan; Young, Kara Alexis

    2013-01-01

    Why are blue-collar blacks less likely to help jobseekers than jobholders from other ethnoracial groups or even than more affluent blacks? Drawing from in-depth, semi-structured interviews with 97 black and Latino workers at one large, public sector employer, we find that blue-collar black workers both helped less proactively and rejected more requests for assistance than did blue-collar Latino and white-collar black workers. We attribute blue-collar blacks’ more passive engagement to their...

  4. Black holes a very short introduction

    CERN Document Server

    Blundell, Katherine

    2015-01-01

    Black holes are a constant source of fascination to many due to their mysterious nature. Black Holes: A Very Short Introduction addresses a variety of questions, including what a black hole actually is, how they are characterized and discovered, and what would happen if you came too close to one. It explains how black holes form and grow—by stealing material that belongs to stars—as well as how many there may be in the Universe. It also explores the large black holes found in the centres of galaxies, and how black holes power quasars and lie behind other spectacular phenomena in the cosmos.

  5. Black Hole Blows Big Bubble

    Science.gov (United States)

    2010-07-01

    Combining observations made with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. This object, also known as a microquasar, blows a huge bubble of hot gas, 1000 light-years across, twice as large and tens of times more powerful than other known microquasars. The discovery is reported this week in the journal Nature. "We have been astonished by how much energy is injected into the gas by the black hole," says lead author Manfred Pakull. "This black hole is just a few solar masses, but is a real miniature version of the most powerful quasars and radio galaxies, which contain black holes with masses of a few million times that of the Sun." Black holes are known to release a prodigious amount of energy when they swallow matter. It was thought that most of the energy came out in the form of radiation, predominantly X-rays. However, the new findings show that some black holes can release at least as much energy, and perhaps much more, in the form of collimated jets of fast moving particles. The fast jets slam into the surrounding interstellar gas, heating it and triggering an expansion. The inflating bubble contains a mixture of hot gas and ultra-fast particles at different temperatures. Observations in several energy bands (optical, radio, X-rays) help astronomers calculate the total rate at which the black hole is heating its surroundings. The astronomers could observe the spots where the jets smash into the interstellar gas located around the black hole, and reveal that the bubble of hot gas is inflating at a speed of almost one million kilometres per hour. "The length of the jets in NGC 7793 is amazing, compared to the size of the black hole from which they are launched," says co-author Robert Soria [1]. "If the black hole were shrunk to the size of a soccer ball, each jet would extend from the Earth to beyond the orbit of Pluto." This research will help

  6. 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.

  7. Massive Black Holes and Galaxies

    CERN Multimedia

    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.

  8. The black hole quantum atmosphere

    Science.gov (United States)

    Dey, Ramit; Liberati, Stefano; Pranzetti, Daniele

    2017-11-01

    Ever since the discovery of black hole evaporation, the region of origin of the radiated quanta has been a topic of debate. Recently it was argued by Giddings that the Hawking quanta originate from a region well outside the black hole horizon by calculating the effective radius of a radiating body via the Stefan-Boltzmann law. In this paper we try to further explore this issue and end up corroborating this claim, using both a heuristic argument and a detailed study of the stress energy tensor. We show that the Hawking quanta originate from what might be called a quantum atmosphere around the black hole with energy density and fluxes of particles peaked at about 4 MG, running contrary to the popular belief that these originate from the ultra high energy excitations very close to the horizon. This long distance origin of Hawking radiation could have a profound impact on our understanding of the information and transplanckian problems.

  9. The black hole quantum atmosphere

    Directory of Open Access Journals (Sweden)

    Ramit Dey

    2017-11-01

    Full Text Available Ever since the discovery of black hole evaporation, the region of origin of the radiated quanta has been a topic of debate. Recently it was argued by Giddings that the Hawking quanta originate from a region well outside the black hole horizon by calculating the effective radius of a radiating body via the Stefan–Boltzmann law. In this paper we try to further explore this issue and end up corroborating this claim, using both a heuristic argument and a detailed study of the stress energy tensor. We show that the Hawking quanta originate from what might be called a quantum atmosphere around the black hole with energy density and fluxes of particles peaked at about 4MG, running contrary to the popular belief that these originate from the ultra high energy excitations very close to the horizon. This long distance origin of Hawking radiation could have a profound impact on our understanding of the information and transplanckian problems.

  10. 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)

  11. Geometric inequalities for black holes

    International Nuclear Information System (INIS)

    Dain, Sergio

    2013-01-01

    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)

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

    Energy Technology Data Exchange (ETDEWEB)

    Bambi, Cosimo [Center for Field Theory and Particle Physics and Department of Physics, Fudan University,200433 Shanghai (China); Theoretical Astrophysics, Eberhard-Karls Universität Tübingen,72076 Tübingen (Germany); Malafarina, Daniele [Department of Physics, Nazarbayev University,010000 Astana (Kazakhstan); Modesto, Leonardo [Center for Field Theory and Particle Physics and Department of Physics, Fudan University,200433 Shanghai (China)

    2016-04-22

    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.

  13. Black Psychology and Black Personality: Some Issues for Considerations

    Science.gov (United States)

    Baldwin, Joseph A.

    1976-01-01

    Discusses an emerging body of psychological literature by black behavioral scientists assumed to represent a radical departure in its conceptual orientation from the social pathology tradition advanced primarily by white behavioral scientists; and focuses on the construct of Self-Extension Orientation, a dynamic process which is assumed to…

  14. Black Students, Black Colleges: An African American College Choice Model.

    Science.gov (United States)

    McDonough, Patricia M.; Antonio, Anthony Lising; Trent, James W.

    1997-01-01

    Explores African Americans' college choice decisions, based on a national sample of 220,757 freshmen. Independent of gender, family income, or educational aspiration, the most powerful predictors for choosing historically black colleges and universities are geography, religion, the college's academic reputation, and relatives' desires. The top…

  15. 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

  16. Interior structure of rotating black holes. III. Charged black holes

    International Nuclear Information System (INIS)

    Hamilton, Andrew J. S.

    2011-01-01

    This paper extends to the case of charged rotating black holes the conformally stationary, axisymmetric, conformally separable solutions presented for uncharged rotating black holes in a companion paper. In the present paper, the collisionless fluid accreted by the black hole may be charged. The charge of the black hole is determined self-consistently by the charge accretion rate. As in the uncharged case, hyper-relativistic counterstreaming between ingoing and outgoing streams drives inflation at (just above) the inner horizon, followed by collapse. If both ingoing and outgoing streams are charged, then conformal separability holds during early inflation, but fails as inflation develops. If conformal separability is imposed throughout inflation and collapse, then only one of the ingoing and outgoing streams can be charged: the other must be neutral. Conformal separability prescribes a hierarchy of boundary conditions on the ingoing and outgoing streams incident on the inner horizon. The dominant radial boundary conditions require that the incident ingoing and outgoing number densities be uniform with latitude, but the charge per particle must vary with latitude such that the incident charge densities vary in proportion to the radial electric field. The subdominant angular boundary conditions require specific forms of the incident number- and charge-weighted angular motions. If the streams fall freely from outside the horizon, then the prescribed angular conditions can be achieved by the charged stream, but not by the neutral stream. Thus, as in the case of an uncharged black hole, the neutral stream must be considered to be delivered ad hoc to just above the inner horizon.

  17. Black hole entropy, curved space and monsters

    International Nuclear Information System (INIS)

    Hsu, Stephen D.H.; Reeb, David

    2008-01-01

    We investigate the microscopic origin of black hole entropy, in particular the gap between the maximum entropy of ordinary matter and that of black holes. Using curved space, we construct configurations with entropy greater than the area A of a black hole of equal mass. These configurations have pathological properties and we refer to them as monsters. When monsters are excluded we recover the entropy bound on ordinary matter S 3/4 . This bound implies that essentially all of the microstates of a semiclassical black hole are associated with the growth of a slightly smaller black hole which absorbs some additional energy. Our results suggest that the area entropy of black holes is the logarithm of the number of distinct ways in which one can form the black hole from ordinary matter and smaller black holes, but only after the exclusion of monster states

  18. Atypical features of hyperthyroidism in Blacks

    International Nuclear Information System (INIS)

    Kalk, W.J.

    1980-01-01

    Hyperthyroidism is reportedly uncommon in the indigenous populations of Africa. The presenting symptoms volunteered, the symptoms elicited by direct questioning, and the results of physical examination were therefore prospectively compared in 60 Black and 56 White patients with thyrotoxicosis attending a single thyroid clinic. Fewer Blacks than Whites volunteered information about weight loss, while more Blacks complained only of the presence of a goitre. A 'chance' diagnosis of hyperthyroidism was made more frequently in Blacks. Symptomatology elicited by direct questioning and findings on physical examination were generally similar in each group, except that Blacks presented more frequently with complicated disease (cardiac failure and overt myopathy) and infiltrative ophthalmopathy. The frequency with which hyperthyroidism presents 'atypically' in Black compared with White patients may reflect educational, socio-economic and cultural differences in the Black and White populations, and may partly explain the infrequency with which this disease is diagnosed in Blacks

  19. Black Adolescent Fathers: Issues for Service Provision.

    Science.gov (United States)

    Smith, Linda Anderson

    1988-01-01

    Claims black adolescent fathers deserve attention of social work profession because they are a vulnerable population. Describes costs of adolescent parenthood, help seeking behavior of the black adolescent father, historical restriction of opportunities, and implications for social work practice. (ABL)

  20. Entropy of black holes with multiple horizons

    Science.gov (United States)

    He, Yun; Ma, Meng-Sen; Zhao, Ren

    2018-05-01

    We examine the entropy of black holes in de Sitter space and black holes surrounded by quintessence. These black holes have multiple horizons, including at least the black hole event horizon and a horizon outside it (cosmological horizon for de Sitter black holes and "quintessence horizon" for the black holes surrounded by quintessence). Based on the consideration that the two horizons are not independent each other, we conjecture that the total entropy of these black holes should not be simply the sum of entropies of the two horizons, but should have an extra term coming from the correlations between the two horizons. Different from our previous works, in this paper we consider the cosmological constant as the variable and employ an effective method to derive the explicit form of the entropy. We also try to discuss the thermodynamic stabilities of these black holes according to the entropy and the effective temperature.

  1. Black and White Differentials in Mortality.

    Science.gov (United States)

    Rene, Antonio A.; Clifford, Patrick R.

    1986-01-01

    Overviews vital statistics data, emphasizing differences in health status between the Black and White populations with respect to specific diseases and mortality. Discusses major causes of death among US Blacks. (GC)

  2. Bosonic instability of charged black holes

    International Nuclear Information System (INIS)

    Gaina, A.B.; Ternov, I.M.

    1986-01-01

    The processes of spontaneous and induced production and accumulation of charged bosons on quasibound superradiant levels in the field of Kerr-Newman black hole is analysed. It is shown that bosonic instability may be caused exclusively by the rotation of the black hole. Particulary, the Reissner-Nordstrom configuration is stable. In the case of rotating and charged black hole the bosonic instability may cause an increase of charge of the black hole

  3. Black hole holography and mean field evolution

    Science.gov (United States)

    Lowe, David A.; Thorlacius, Larus

    2018-01-01

    Holographic theories representing black holes are expected to exhibit quantum chaos. We argue if the laws of quantum mechanics are expected to hold for observers inside such black holes, then such holographic theories must have a mean field approximation valid for typical black hole states, and for timescales approaching the scrambling time. Using simple spin models as examples, we examine the predictions of such an approach for observers inside black holes, and more speculatively inside cosmological horizons.

  4. Black holes and traversible wormholes: a synthesis

    OpenAIRE

    Hayward, Sean A.

    2002-01-01

    A unified framework for black holes and traversible wormholes is described, where both are locally defined by outer trapping horizons, two-way traversible for wormholes and one-way traversible for black or white holes. In a two-dimensional dilaton gravity model, examples are given of: construction of wormholes from black holes; operation of wormholes for transport, including back-reaction; maintenance of an operating wormhole; and collapse of wormholes to black holes. In spherically symmetric...

  5. Will black holes eventually engulf the Universe?

    International Nuclear Information System (INIS)

    Martin-Moruno, Prado; Jimenez Madrid, Jose A.; Gonzalez-Diaz, Pedro F.

    2006-01-01

    The Babichev-Dokuchaev-Eroshenko model for the accretion of dark energy onto black holes has been extended to deal with black holes with non-static metrics. The possibility that for an asymptotic observer a black hole with large mass will rapidly increase and eventually engulf the Universe at a finite time in the future has been studied by using reasonable values for astronomical parameters. It is concluded that such a phenomenon is forbidden for all black holes in quintessential cosmological models

  6. Building blocks of a black hole

    OpenAIRE

    Bekenstein, Jacob D.; Gour, Gilad

    2002-01-01

    What is the nature of the energy spectrum of a black hole ? The algebraic approach to black hole quantization requires the horizon area eigenvalues to be equally spaced. As stressed long ago by by Mukhanov, such eigenvalues must be exponentially degenerate with respect to the area quantum number if one is to understand black hole entropy as reflecting degeneracy of the observable states. Here we construct the black hole states by means of a pair of "creation operators" subject to a particular...

  7. Radiation from the LTB black hole

    OpenAIRE

    Firouzjaee, J. T.; Mansouri, Reza

    2011-01-01

    Does a dynamical black hole embedded in a cosmological FRW background emit Hawking radiation where a globally defined event horizon does not exist? What are the differences to the Schwarzschild black hole? What about the first law of black hole mechanics? We face these questions using the LTB cosmological black hole model recently published. Using the Hamilton-Jacobi and radial null geodesic-methods suitable for dynamical cases, we show that it is the apparent horizon which contributes to the...

  8. Re-Examining the Black on Black Crime Issue: A Theoretical Essay.

    Science.gov (United States)

    Perry, Robert L.

    1989-01-01

    Discusses Black on Black crime and provides evidence that it is directly linked to American societal problems. Covers the following historical and societal influences: (1) the legacy of slavery and Jim Crow; (2) Black migration and disorder in cities; (3) the use of alcohol and drugs; and (4) policing of the Black ghetto. (JS)

  9. Black Studies, Rap and the Academy. Black Literature and Culture Series.

    Science.gov (United States)

    Baker, Houston A., Jr.

    The relationships among Black Studies as an intellectual discipline and rap music are explored. It is argued that black urban culture has provided much of the impetus for Black Studies, and that the academy and those involved in the black studies discipline should feel a responsibility to take rap music seriously as the expression of urban youth,…

  10. The Growth of Public Schools for Blacks, and the Emergence of Professional Black Savannahians.

    Science.gov (United States)

    Perdue, Robert E.

    The history of the growth of public education for the black masses, including topics such as racial attitudes toward black education, the financial problems facing black schools, and the political pressures that led to the development of a system of education for blacks, is traced and discussed in this paper -- specifically as it concerns…

  11. Language and Stylistic Influences of the Black Folk Tradition of Black Literature.

    Science.gov (United States)

    Anderson, Edward

    Because the style and language of the black folk tradition have contributed significantly to the development of the English language, an analysis of black persuasive techniques and black communication systems can enhance the teaching of composition, rhetoric, and literature for both black and white students. Some of the persuasive techniques of…

  12. "No Cosby Show": Single Black Mother Homes and How Black Men Build Romantic Relationships

    Science.gov (United States)

    Moore, Maia Niguel

    2016-01-01

    This qualitative study explored the lives of 11 Black men to better understand how Black men who were raised in single Black mother homes build romantic relationships with Black women. One focus group and a series of individual in-person interviews were conducted with the participants who ranged between 23 and 43 years of age. Participants were…

  13. Black English: A Strength Analysis of Non-Standard English in Black Dialect.

    Science.gov (United States)

    Bousquet, Robert J.

    Many black students speak a nonprestige dialect called black English, which places them at a disadvantage academically and socially. This monograph describes the features of black English, defines its use, discusses several theories of its origin, and offers some methods for teaching black students standard spoken usage as another style of speech.…

  14. Black Hawkid harjutasid Pakri poolsaarel

    Index Scriptorium Estoniae

    2014-01-01

    USA 173. õhudessantbrigaadi Eestis viibiv kompanii ja Scoutspataljoni C-kompanii jalaväerühma kaitseväelased alustasid eile ühisõppust, mille käigus harjutatakse kahe Black Hawk UH-60 helikopteriga nelja Pakri poolsaarel asuva õppeobjekti ründamist

  15. Black Holes in Our Universe

    Indian Academy of Sciences (India)

    Current technologies have enabled glimpses at the many facetsof black holes, which we know to be plentiful in our cosmos.A panoramic view of the evidence for them is presented hereacross the large range of masses that they span. Author Affiliations. Prajval Shastri. Resonance – Journal of Science Education.

  16. The Award Winning Black Suns

    Science.gov (United States)

    Holbrook, Jarita

    2018-01-01

    Black Suns: An Astrophysics Adventure is a documentary film focusing on the annular and total solar eclipses of 2012. We made a different kind of astronomy documentary showing the human aspects rather than just focusing on pretty astronomy pictures. The film combines personal stories with science. Our heroes are Hakeem Oluseyi and Alphonse Sterling, who valiantly travel to study the solar corona during total solar eclipses. The goals of the film included presenting three dimensional scientists, to show their paths to becoming astrophysicists, and to show them as they collect data and work as scientists. Drama and tension surround taking data during the small window of time during totality. The Black Suns was filmed in Tokyo, Cairns, Tucson, and Melbourne Florida. Uniquely, the film began through a Kickstarter campaign to fund travel and filming in Tokyo. Many American Astronomical Society members donated to the film! Black Suns won the Jury Prize at the 2017 Art of Brooklyn Film Festival. Black Suns will be screening in full on ???.

  17. Satellite monitoring of black bear.

    Science.gov (United States)

    Craighead, J. J.; Craighead, F. C., Jr.; Varney, J. R.; Cote, C. E.

    1971-01-01

    Description of a feasibility experiment recently performed to test the use of a satellite system for telemetering environmental and physiological data from the winter den of a 'hibernating' black bear, Ursus americanus. The instrumentation procedure and evaluations of the equipment performance and sensory data obtained are discussed in detail.

  18. ECONOMIC CRISIS SUSTAINS BLACK MARKET

    Directory of Open Access Journals (Sweden)

    Dicoi Daniel -Ioan

    2012-12-01

    Full Text Available The purpose of this research is to bring out the fact that during the periods of economic crisis, the black market finds a warm place to develop and even to diversify the ways of expressing. Based on some data of the National Institute of Statistics and the Organization for Economic Co-operation and Development (OECD1 , I’m trying to prove the fact that during the last two years while the world economic crisis has occurred, the black market has been increasing and there have been new forms of expressing this phenomenon. Although there are some positive ways of this phenomenon, on the whole, the increasing of the black market percent of GDP represents a wound within a healthy economy, which if it cannot be stopped at least to be reduced. This work intends to make radiography of the present economic society, a period of economic crisis, during which the black market has found a warm place to express and extend, in most of the countries, including the developed ones, this phenomenon has reached alarming limits.

  19. '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. © 2013, The Society of Analytical Psychology.

  20. Stellar dynamics and black holes

    Indian Academy of Sciences (India)

    Stellar dynamics and black holes. DAVID MERRITT. Department of Physics, Rochester Institute of Technology, 78 Lomb Memorial Drive, Rochester,. NY 14623, USA. E-mail: merritt@astro.rit.edu. Abstract. Chandrasekhar's most important contribution to stellar dynamics was the concept of dynamical friction. I briefly review ...

  1. 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.

  2. 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.

  3. [The black death in Norway].

    Science.gov (United States)

    Oeding, P

    1990-06-30

    The old Icelandic annals tell that the Black Death came to Bergen, Norway, in 1349 with a ship from England. This was probably at the beginning of September. From Bergen the plague spread rapidly northwards and southwards along the coast and over land to Eastern Norway. The Black Death remained in Norway for approximately six months. The epidemic must have been started by infected black rats and rat fleas in the grain cargo of the ship. The account in the annals, and experiences from other countries, indicate that pneumonic plague was dominant in Bergen at the start of the epidemic. After that the Black Death must have spread partly as pneumonic plague but mainly probably as bubonic plague, transmitted via human fleas from person to person. The rats cannot have played a part except in the initial phase. The annals say that 2/3 of Norway's population died. This is probably a big exaggeration. The mortality in Norway can hardly have been more than 40-50%. Even this is high compared with an estimated mortality of approximately 33% in England and on the continent.

  4. Transracial Adoption of Black Children

    Science.gov (United States)

    Chimezie, Amuzie

    1975-01-01

    The author discusses the advantages and disadvantages of the adoption of black children by white parents. He concludes that until empirical studies are made, placements should not proceed as if it had already been ascertained that transracial adoption is beneficial. (Author/BW)

  5. Why Black Officers Still Fail

    Science.gov (United States)

    2010-03-01

    National Endowment of the Arts reported that Whites were three times as likely as Blacks to attend a classical music performance, opera or ballet ...Conclusion Although one would like to believe that the Army has progressed to a point in its history where race is no longer a factor in the success or

  6. The Migration Experience of Blacks

    Science.gov (United States)

    Long, Larry

    1975-01-01

    This testimony, before a public hearing of the New York City Commission on Human Rights, concludes that in many ways northern cities seem to be characterized not so much by excessive migration of blacks from the south, but by inadequate migration from one northern metropolitan area to another. (Author/JM)

  7. 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.

  8. Black Hole Macro-Quantumness

    CERN Document Server

    Dvali, Gia

    2014-01-01

    It is a common wisdom that properties of macroscopic bodies are well described by (semi)classical physics. As we have suggested this wisdom is not applicable to black holes. Despite being macroscopic, black holes are quantum objects. They represent Bose-Einstein condensates of N-soft gravitons at the quantum critical point, where N Bogoliubov modes become gapless. As a result, physics governing arbitrarily-large black holes (e.g., of galactic size) is a quantum physics of the collective Bogoiliubov modes. This fact introduces a new intrinsically-quantum corrections in form of 1/N, as opposed to exp(-N). These corrections are unaccounted by the usual semiclassical expansion in h and cannot be recast in form of a quantum back-reaction to classical metric. Instead the metric itself becomes an approximate entity. These 1/N corrections abolish the presumed properties of black holes, such as non existence of hair, and are the key to nullifying the so-called information paradox.

  9. Eerste bevindingen onderzoek Black Mold

    NARCIS (Netherlands)

    Werd, de H.A.E.

    2008-01-01

    In de zomer van 2007 veroorzaakte de ziekte Black Mold grote schade in de rozenteelt. Omdat er weinig bekend is over preventie en bestrijding hebben PPO Bomen en Cultus Agro Advies een onderzoeksproject gestart, waarvan de eerste resultaten inmiddels bekend zijn.

  10. Black Womanhood and Feminist Standpoints.

    Science.gov (United States)

    Allen, Brenda J.

    1998-01-01

    Discusses challenges and consequences of being a member of two historically oppressed groups in the United States--Blacks and females. Relies on feminist standpoint theory--a distinctive element of contemporary feminist thought about how knowledge is constructed. Focuses on academe as a discursive site for constructing identity. (PA)

  11. Body Image Satisfaction among Blacks

    Science.gov (United States)

    Gustat, Jeanette; Carton, Thomas W.; Shahien, Amir A.; Andersen, Lori

    2017-01-01

    Satisfaction with body image is a factor related to health outcomes. The purpose of this study is to examine the relationship between body image satisfaction and body size perception in an urban, Black community sample in New Orleans, Louisiana. Only 42.2% of respondents were satisfied with their body image and 44.1% correctly perceived their body…

  12. 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…

  13. Motor neuron disease in blacks

    African Journals Online (AJOL)

    1989-08-19

    Aug 19, 1989 ... We reported earlier that motor neuron disease occurs more commonly among blacks than Parkinson's disease, which is relatively rare in this race group.! The hypothesis that these conditions, and other neuronal abiotrophies, are the result of previous subclinical neuronal insult and subsequent age-related.

  14. Wands of the Black Ring

    Czech Academy of Sciences Publication Activity Database

    Pravda, Vojtěch; Pravdová, Alena

    2005-01-01

    Roč. 37, č. 7 (2005), s. 1277-1287 ISSN 0001-7701 R&D Projects: GA ČR GP202/03/P017; GA AV ČR KJB1019403 Institutional research plan: CEZ:AV0Z10190503 Keywords : algebraic classification * Petrov classification * black ring Subject RIV: BA - General Mathematics Impact factor: 1.550, year: 2005

  15. A Black Hole Spectral Signature

    Science.gov (United States)

    Titarchuk, Lev; Laurent, Philippe

    2000-03-01

    An accreting black hole is, by definition, characterized by the drain. Namely, the matter falls into a black hole much the same way as water disappears down a drain matter goes in and nothing comes out. As this can only happen in a black hole, it provides a way to see ``a black hole'', an unique observational signature. The accretion proceeds almost in a free-fall manner close to the black hole horizon, where the strong gravitational field dominates the pressure forces. In this paper we present analytical calculations and Monte-Carlo simulations of the specific features of X-ray spectra formed as a result of upscattering of the soft (disk) photons in the converging inflow (CI) into the black hole. The full relativistic treatment has been implemented to reproduce these spectra. We show that spectra in the soft state of black hole systems (BHS) can be described as the sum of a thermal (disk) component and the convolution of some fraction of this component with the CI upscattering spread (Greens) function. The latter boosted photon component is seen as an extended power-law at energies much higher than the characteristic energy of the soft photons. We demonstrate the stability of the power spectral index over a wide range of the plasma temperature 0 - 10 keV and mass accretion rates (higher than 2 in Eddington units). We also demonstrate that the sharp high energy cutoff occurs at energies of 200-400 keV which are related to the average energy of electrons mec2 impinging upon the event horizon. The spectrum is practically identical to the standard thermal Comptonization spectrum when the CI plasma temperature is getting of order of 50 keV (the typical ones for the hard state of BHS). In this case one can see the effect of the bulk motion only at high energies where there is an excess in the CI spectrum with respect to the pure thermal one. Furthermore we demonstrate that the change of spectral shapes from the soft X-ray state to the hard X-ray state is clearly to be

  16. On black holes and gravitational waves

    CERN Document Server

    Loinger, Angelo

    2002-01-01

    Black holes and gravitational waves are theoretical entities of today astrophysics. Various observed phenomena have been associated with the concept of black hole ; until now, nobody has detected gravitational waves. The essays contained in this book aim at showing that the concept of black holes arises from a misinterpretation of general relativity and that gravitational waves cannot exist.

  17. 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…

  18. 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…

  19. Hawking radiation of black rings from anomalies

    International Nuclear Information System (INIS)

    Chen Bin; He Wei

    2008-01-01

    We derive Hawking radiation of five-dimensional black rings from gauge and gravitational anomalies using the method proposed by Robinson and Wilczek. We find, as in the black hole case, that the problem could reduce to a (1+1)-dimensional field theory and the anomalies result in correct Hawking temperature for neutral, dipole and charged black rings

  20. On Being an Angry Black Man

    Science.gov (United States)

    Quaye, Stephen John

    2017-01-01

    Black men are often seen as problems, threats, and thugs. The mere existence of a Black body is often met with fear. Using autoethnographic mystory, I blend personal stories, poetry, song lyrics, and analysis to subvert the angry Black man mantra and explore the productive use of anger to stimulate change.

  1. The Decline of Black Farming in America.

    Science.gov (United States)

    Browning, Pamela; And Others

    The rapid decline in the number of farms operated by blacks in the United States, and the consequences of this decline on the conditions of black farmers are the focus of this report. Chapter 1 compares the rate of agricultural land loss from 1900 to 1978 among blacks and whites. Chapter 2 outlines historical conditions, such as racism, lack of…

  2. The State of Black America, 1978.

    Science.gov (United States)

    Anderson, Bernard E.; And Others

    In this report seven scholars (Bernard Anderson, James Dumpson, Charles Hamilton, Robert Hill, Vernon Jordan, Jr., Bernard Watson and Robert Weaver) appraise the social, economic, political, and educational status of blacks and black families. Minimal gains and poor prospects for black female heads of families in the current recession job market…

  3. Area spectra of near extremal black holes

    International Nuclear Information System (INIS)

    Chen, Deyou; Yang, Haitang; Zu, Xiaotao

    2010-01-01

    Motivated by Maggiore's new interpretation of quasinormal modes, we investigate area spectra of a near extremal Schwarzschild-de Sitter black hole and a higher-dimensional near extremal Reissner-Nordstrom-de Sitter black hole. The result shows that the area spectra are equally spaced and irrelevant to the parameters of the black holes. (orig.)

  4. 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),

  5. 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.

  6. Black Hole Monodromy and Conformal Field Theory

    NARCIS (Netherlands)

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

    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

  7. Transracial Adoption: The Black Community Perspective

    Science.gov (United States)

    Howard, Alicia; And Others

    1977-01-01

    How does a cross section of the black community feel about white parents adopting black children? This study suggests that the majority of blacks do not support the militant position against transracial adoption and, in fact, favor such adoption when the alternative is institutionalization. (Author)

  8. Blacks on TV: Adjusting the Image.

    Science.gov (United States)

    Bayles, Martha

    1985-01-01

    The stereotyping of Blacks on television has changed in nature but continues despite the networks' awkward efforts to avoid accusation of racism. Today, situation comedies and detective shows include Blacks in positive roles, but very few portray Blacks as realistically or authentically as Whites are portrayed. (KH)

  9. The Chicano and the Black Legend.

    Science.gov (United States)

    Sanchez, Porfirio

    An historical overview traces the Black Legend about persons of Spanish descent and seeks to demonstrate the influence of the Black Legend on Anglo attitudes towards Mexican Americans. The beginnings of the Black Legend are found in the sixteenth century when European countries in conflict with Spain used Spanish actions during the Sack of Rome,…

  10. Accretion, primordial black holes and standard cosmology

    Indian Academy of Sciences (India)

    loops [8]. In 1974, Hawking discovered that the black holes emit thermal radiation due to quantum effects [9]. So the black holes get evaporated depending upon their masses. Smaller the masses of the PBHs, quicker they evaporate. But the density of a black hole varies inversely with its mass. So high density is needed for ...

  11. White holes and eternal black holes

    International Nuclear Information System (INIS)

    Hsu, Stephen D H

    2012-01-01

    We investigate isolated white holes surrounded by vacuum, which correspond to the time reversal of eternal black holes that do not evaporate. We show that isolated white holes produce quasi-thermal Hawking radiation. The time reversal of this radiation, incident on a black hole precursor, constitutes a special preparation that will cause the black hole to become eternal. (paper)

  12. Black holes under external influence

    Indian Academy of Sciences (India)

    In particular we pay attention to the effect of the expulsion of the flux of external fields across charged and rotating black holes which are approaching extremal states. Recently this effect has been shown to occur for black hole solutions in string theory. We also discuss black holes surrounded by rings and disks and rotating ...

  13. The fuzzball proposal for black holes

    NARCIS (Netherlands)

    Skenderis, K.; Taylor, M.

    2008-01-01

    The fuzzball proposal states that associated with a black hole of entropy S, there are expS horizon-free non-singular solutions that asymptotically look like the black hole but generically differ from the black hole up to the horizon scale. These solutions, the fuzzballs, are considered to be the

  14. IQ Tests and the Black Culture

    Science.gov (United States)

    McNiel, Nathaniel D.

    1975-01-01

    On a test (Black Intelligence Test of Cultural Homogeneity) oriented toward the language, attitudes, and life-styles of Afro-Americans, white students perform more poorly than blacks do on tests oriented toward white middle-class values, indicating that there are important dissimilarities in the cultural backgrounds of blacks and whites.…

  15. Therapeutic Dimensions of the Black Aesthetic

    Science.gov (United States)

    Toldson, Ivory L.; Pasteur, Alfred B.

    1976-01-01

    The authors of this article see the black aesthetic largely in terms of the affective component. Emotional oneness which is foreign to the white world view is the means by which the black man can achieve optimal mental health and development. The therapeutic implications of the black aesthetic are outlined. (NG)

  16. Accretion, primordial black holes and standard cosmology

    Indian Academy of Sciences (India)

    Abstract. 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 con- jecture that the primordial ...

  17. Shapes and Positions of Black Hole Shadows in Accretion Disks and Spin Parameters of Black Holes

    OpenAIRE

    Takahashi, Rohta

    2004-01-01

    Can we determine a spin parameter of a black hole by observation of a black hole shadow in an accretion disk? In order to answer this question, we make a qualitative analysis and a quantitative analysis of a shape and a position of a black hole shadow casted by a rotating black hole on an optically thick accretion disk and its dependence on an angular momentum of a black hole. We have found black hole shadows with a quite similar size and a shape for largely different black hole spin paramete...

  18. Black holes, qubits and octonions

    Energy Technology Data Exchange (ETDEWEB)

    Borsten, L. [Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BZ (United Kingdom)], E-mail: leron.borsten@imperial.ac.uk; Dahanayake, D. [Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BZ (United Kingdom)], E-mail: duminda.dahanayake@imperial.ac.uk; Duff, M.J. [Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BZ (United Kingdom)], E-mail: m.duff@imperial.ac.uk; Ebrahim, H. [Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BZ (United Kingdom); Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Theory Group, Martin Fisher School of Physics, Brandeis University, MS057, 415 South Street, Waltham, MA 02454 (United States)], E-mail: hebrahim@brandeis.edu; Rubens, W. [Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BZ (United Kingdom)], E-mail: william.rubens06@imperial.ac.uk

    2009-02-15

    We review the recently established relationships between black hole entropy in string theory and the quantum entanglement of qubits and qutrits in quantum information theory. The first example is provided by the measure of the tripartite entanglement of three qubits (Alice, Bob and Charlie), known as the 3-tangle, and the entropy of the 8-charge STU black hole of N=2 supergravity, both of which are given by the [SL(2)]{sup 3} invariant hyperdeterminant, a quantity first introduced by Cayley in 1845. Moreover the classification of three-qubit entanglements is related to the classification of N=2 supersymmetric STU black holes. There are further relationships between the attractor mechanism and local distillation protocols and between supersymmetry and the suppression of bit flip errors. At the microscopic level, the black holes are described by intersecting D3-branes whose wrapping around the six compact dimensions T{sup 6} provides the string-theoretic interpretation of the charges and we associate the three-qubit basis vectors, |ABC>(A,B,C=0 or 1), with the corresponding 8 wrapping cycles. The black hole/qubit correspondence extends to the 56 charge N=8 black holes and the tripartite entanglement of seven qubits where the measure is provided by Cartan's E{sub 7} contains [SL(2)]{sup 7} invariant. The qubits are naturally described by the seven vertices ABCDEFG of the Fano plane, which provides the multiplication table of the seven imaginary octonions, reflecting the fact that E{sub 7} has a natural structure of an O-graded algebra. This in turn provides a novel imaginary octonionic interpretation of the 56=7x8 charges of N=8: the 24=3x8 NS-NS charges correspond to the three imaginary quaternions and the 32=4x8 R-R to the four complementary imaginary octonions. We contrast this approach with that based on Jordan algebras and the Freudenthal triple system. N=8 black holes (or black strings) in five dimensions are also related to the bipartite entanglement of

  19. Phase transition for black holes with scalar hair and topological black holes

    International Nuclear Information System (INIS)

    Myung, Yun Soo

    2008-01-01

    We study phase transitions between black holes with scalar hair and topological black holes in asymptotically anti-de Sitter spacetimes. As the ground state solutions, we introduce the non-rotating BTZ black hole in three dimensions and topological black hole with hyperbolic horizon in four dimensions. For the temperature matching only, we show that the phase transition between black hole with scalar hair (Martinez-Troncoso-Zanelli black hole) and topological black hole is second-order by using differences between two free energies. However, we do not identify what order of the phase transition between scalar and non-rotating BTZ black holes occurs in three dimensions, although there exists a possible decay of scalar black hole to non-rotating BTZ black hole

  20. Chandra Catches "Piranha" Black Holes

    Science.gov (United States)

    2007-07-01

    Supermassive black holes have been discovered to grow more rapidly in young galaxy clusters, according to new results from NASA's Chandra X-ray Observatory. These "fast-track" supermassive black holes can have a big influence on the galaxies and clusters that they live in. Using Chandra, scientists surveyed a sample of clusters and counted the fraction of galaxies with rapidly growing supermassive black holes, known as active galactic nuclei (or AGN). The data show, for the first time, that younger, more distant galaxy clusters contained far more AGN than older, nearby ones. Galaxy clusters are some of the largest structures in the Universe, consisting of many individual galaxies, a few of which contain AGN. Earlier in the history of the universe, these galaxies contained a lot more gas for star formation and black hole growth than galaxies in clusters do today. This fuel allows the young cluster black holes to grow much more rapidly than their counterparts in nearby clusters. Illustration of Active Galactic Nucleus Illustration of Active Galactic Nucleus "The black holes in these early clusters are like piranha in a very well-fed aquarium," said Jason Eastman of Ohio State University (OSU) and first author of this study. "It's not that they beat out each other for food, rather there was so much that all of the piranha were able to really thrive and grow quickly." The team used Chandra to determine the fraction of AGN in four different galaxy clusters at large distances, when the Universe was about 58% of its current age. Then they compared this value to the fraction found in more nearby clusters, those about 82% of the Universe's current age. The result was the more distant clusters contained about 20 times more AGN than the less distant sample. AGN outside clusters are also more common when the Universe is younger, but only by factors of two or three over the same age span. "It's been predicted that there would be fast-track black holes in clusters, but we never

  1. Modified dispersion relations and black hole physics

    International Nuclear Information System (INIS)

    Ling Yi; Li Xiang; Hu Bo

    2006-01-01

    A modified formulation of the 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 a 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 approaches the Planck scale. It can prevent black holes from total evaporation, as a result providing a plausible mechanism to treat the remnant of black holes as a candidate for dark matter

  2. Dyonic black hole in heterotic string theory

    International Nuclear Information System (INIS)

    Jatkar, D.P.; Mukherji, S.

    1997-01-01

    We study some features of the dyonic black hole solution in heterotic string theory on a six-torus. This solution has 58 parameters. Of these, 28 parameters denote the electric charge of the black hole, another 28 correspond to the magnetic charge, and the other two parameters are the mass and the angular momentum of the black hole. We discuss the extremal limit and show that in various limits it reduces to the known black hole solutions. The solutions saturating the Bogomolnyi bound are identified. An explicit solution is presented for the non-rotating dyonic black hole. (orig.)

  3. Black-hole creation in quantum cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Zhong Chao, Wu [Rome, Univ. `La Sapienza` (Italy). International Center for Relativistic Astrophysics]|[Specola Vaticana, Vatican City State (Vatican City State, Holy See)

    1997-11-01

    It is proven that the probability of a black hole created from the de Sitter space-time background, at the Wkb level, is the exponential of one quarter of the sum of the black hole and cosmological horizon areas, or the total entropy of the universe. This is true not only for the spherically symmetric cases of the Schwarzschild or Reissner-Nordstroem black holes, but also for the rotating cases of the Kerr black hole and the rotating charged case of the Newman black hole. The de Sitter metric is the most probable evolution at the Planckian era of the universe.

  4. Few-layer black phosphorus nanoparticles.

    Science.gov (United States)

    Sofer, Zdenek; Bouša, Daniel; Luxa, Jan; Mazanek, Vlastimil; Pumera, Martin

    2016-01-28

    Herein, black phosphorus quantum dots and nanoparticles of a few layer thickness were prepared and characterized using STEM, AFM, dynamic light scattering, X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy and photoluminescence. Impact electrochemistry of the induvidual black phosphorus nanoparticles allows their size determination. The centrifugation of colloidal black phosphorus nanoparticles allowed separation of quantum dots with sizes up to 15 nm. These black phosphorus nanoparticles exhibit a large band gap and are expected to find a wide range of applications from semiconductors to biomolecule tags. The use of black phosphorus nanoparticles for vapour sensing was successfully demonstrated.

  5. Black hole entropy and quantum information

    CERN Document Server

    Duff, M J

    2006-01-01

    We review some recently established connections between the mathematics of black hole entropy in string theory and that of multipartite entanglement in quantum information theory. In the case of N=2 black holes and the entanglement of three qubits, the quartic [SL(2)]^3 invariant, Cayley's hyperdeterminant, provides both the black hole entropy and the measure of tripartite entanglement. In the case of N=8 black holes and the entanglement of seven qubits, the quartic E_7 invariant of Cartan provides both the black hole entropy and the measure of a particular tripartite entanglement encoded in the Fano plane.

  6. Black Holes Shed Light on Galaxy Formation

    Science.gov (United States)

    2000-01-01

    This videotape is comprised of several segments of animations on black holes and galaxy formation, and several segments of an interview with Dr. John Kormendy. The animation segments are: (1) a super massive black hole, (2) Centarus A active black hole found in a collision, (3) galaxy NGC-4261 (active black hole and jet model), (4) galaxy M-32 (orbits of stars are effected by the gravity of the black hole), (5) galaxy M-37 (motion of stars increases as mass of black hole increases), (6) Birth of active galactic nuclei, (7) the collision of two galaxy leads to merger of the black holes, (8) Centarus A and simulation of the collision of 2 galaxies. There are also several segments of an interview with John Kormendy. In these segments he discusses the two most important aspects of his recent black hole work: (1) the correlations between galaxies speed and the mass of the black holes, and (2) the existence of black holes and galactic formation. He also discusses the importance of the Hubble Space Telescope and the Space Telescope Imaging Spectrograph to the study of black holes. He also shows the methodology of processing images from the spectrograph in his office.

  7. Extremal vacuum black holes in higher dimensions

    International Nuclear Information System (INIS)

    Figueras, Pau; Lucietti, James; Rangamani, Mukund; Kunduri, Hari K.

    2008-01-01

    We consider extremal black hole solutions to the vacuum Einstein equations in dimensions greater than five. We prove that the near-horizon geometry of any such black hole must possess an SO(2,1) symmetry in a special case where one has an enhanced rotational symmetry group. We construct examples of vacuum near-horizon geometries using the extremal Myers-Perry black holes and boosted Myers-Perry strings. The latter lead to near-horizon geometries of black ring topology, which in odd spacetime dimensions have the correct number of rotational symmetries to describe an asymptotically flat black object. We argue that a subset of these correspond to the near-horizon limit of asymptotically flat extremal black rings. Using this identification we provide a conjecture for the exact 'phase diagram' of extremal vacuum black rings with a connected horizon in odd spacetime dimensions greater than five.

  8. Slow relaxation of rapidly rotating black holes

    International Nuclear Information System (INIS)

    Hod, Shahar

    2008-01-01

    We study analytically the relaxation phase of perturbed, rapidly rotating black holes. In particular, we derive a simple formula for the fundamental quasinormal resonances of near-extremal Kerr black holes. The formula is expressed in terms of the black hole physical parameters: ω=mΩ-i2πT BH (n+(1/2)), where T BH and Ω are the temperature and angular velocity of the black hole, and m is the azimuthal harmonic index of a corotating equatorial mode. This formula implies that the relaxation period τ∼1/ω of the black hole becomes extremely long as the extremal limit T BH →0 is approached. The analytically derived formula is shown to agree with direct numerical computations of the black hole resonances. We use our results to demonstrate analytically the fact that near-extremal Kerr black holes saturate the recently proposed universal relaxation bound.

  9. Quantum information erasure inside black holes

    International Nuclear Information System (INIS)

    Lowe, David A.; Thorlacius, Larus

    2015-01-01

    An effective field theory for infalling observers in the vicinity of a quasi-static black hole is given in terms of a freely falling lattice discretization. The lattice model successfully reproduces the thermal spectrum of outgoing Hawking radiation, as was shown by Corley and Jacobson, but can also be used to model observations made by a typical low-energy observer who enters the black hole in free fall at a prescribed time. The explicit short distance cutoff ensures that, from the viewpoint of the infalling observer, any quantum information that entered the black hole more than a scrambling time earlier has been erased by the black hole singularity. This property, combined with the requirement that outside observers need at least of order the scrambling time to extract quantum information from the black hole, ensures that a typical infalling observer does not encounter drama upon crossing the black hole horizon in a theory where black hole information is preserved for asymptotic observers.

  10. Quantum information erasure inside black holes

    Energy Technology Data Exchange (ETDEWEB)

    Lowe, David A. [Department of Physics, Brown University,Providence, RI, 02912 (United States); Thorlacius, Larus [University of Iceland, Science Institute,Dunhaga 3, IS-107 Reykjavik (Iceland); The Oskar Klein Centre for Cosmoparticle Physics, Department of Physics,Stockholm University, AlbaNova University Centre, 10691 Stockholm (Sweden)

    2015-12-15

    An effective field theory for infalling observers in the vicinity of a quasi-static black hole is given in terms of a freely falling lattice discretization. The lattice model successfully reproduces the thermal spectrum of outgoing Hawking radiation, as was shown by Corley and Jacobson, but can also be used to model observations made by a typical low-energy observer who enters the black hole in free fall at a prescribed time. The explicit short distance cutoff ensures that, from the viewpoint of the infalling observer, any quantum information that entered the black hole more than a scrambling time earlier has been erased by the black hole singularity. This property, combined with the requirement that outside observers need at least of order the scrambling time to extract quantum information from the black hole, ensures that a typical infalling observer does not encounter drama upon crossing the black hole horizon in a theory where black hole information is preserved for asymptotic observers.

  11. Black hole with quantum potential

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Ahmed Farag, E-mail: ahmed.ali@fsc.bu.edu.eg [Department of Physics, Faculty of Science, Benha University, Benha 13518 (Egypt); Khalil, Mohammed M., E-mail: moh.m.khalil@gmail.com [Department of Electrical Engineering, Alexandria University, Alexandria 12544 (Egypt)

    2016-08-15

    In this work, we investigate black hole (BH) physics in the context of quantum corrections. These quantum corrections were introduced recently by replacing classical geodesics with quantal (Bohmian) trajectories and hence form a quantum Raychaudhuri equation (QRE). From the QRE, we derive a modified Schwarzschild metric, and use that metric to investigate BH singularity and thermodynamics. We find that these quantum corrections change the picture of Hawking radiation greatly when the size of BH approaches the Planck scale. They prevent the BH from total evaporation, predicting the existence of a quantum BH remnant, which may introduce a possible resolution for the catastrophic behavior of Hawking radiation as the BH mass approaches zero. Those corrections also turn the spacelike singularity of the black hole to be timelike, and hence this may ameliorate the information loss problem.

  12. Black hole with quantum potential

    Directory of Open Access Journals (Sweden)

    Ahmed Farag Ali

    2016-08-01

    Full Text Available In this work, we investigate black hole (BH physics in the context of quantum corrections. These quantum corrections were introduced recently by replacing classical geodesics with quantal (Bohmian trajectories and hence form a quantum Raychaudhuri equation (QRE. From the QRE, we derive a modified Schwarzschild metric, and use that metric to investigate BH singularity and thermodynamics. We find that these quantum corrections change the picture of Hawking radiation greatly when the size of BH approaches the Planck scale. They prevent the BH from total evaporation, predicting the existence of a quantum BH remnant, which may introduce a possible resolution for the catastrophic behavior of Hawking radiation as the BH mass approaches zero. Those corrections also turn the spacelike singularity of the black hole to be timelike, and hence this may ameliorate the information loss problem.

  13. Lifetime of a black hole

    International Nuclear Information System (INIS)

    Carlitz, R.D.; Willey, R.S.

    1987-01-01

    We study the constraints placed by quantum mechanics upon the lifetime of a black hole. In the context of a moving-mirror analog model for the Hawking radiation process, we conclude that the period of Hawking radiation must be followed by a much longer period during which the remnant mass (of order m/sub P/) may be radiated away. We are able to place a lower bound on the time required for this radiation process, which translates into a lower bound for the lifetime of the black hole. Particles which are emitted during the decay of the remnant, like the particles which comprise the Hawking flux, may be uncorrelated with each other. But each particle emitted from the decaying remnant is correlated with one particle emitted as Hawking radiation. The state which results after the remnant has evaporated is one which locally appears to be thermal, but which on a much larger scale is marked by extensive correlations

  14. From Black Holes to Quivers

    CERN Document Server

    Manschot, Jan; Sen, Ashoke

    2012-01-01

    Middle cohomology states on the Higgs branch of supersymmetric quiver quantum mechanics - also known as pure Higgs states - have recently emerged as possible microscopic candidates for single-centered black hole micro-states, as they carry zero angular momentum and appear to be robust under wall-crossing. Using the connection between quiver quantum mechanics on the Coulomb branch and the quantum mechanics of multi-centered black holes, we propose a general algorithm for reconstructing the full moduli-dependent cohomology of the moduli space of an arbitrary quiver, in terms of the BPS invariants of the pure Higgs states. We analyze many examples of quivers with loops, including all cyclic Abelian quivers and several examples with two loops or non-Abelian gauge groups, and provide supporting evidence for this proposal. We also develop methods to count pure Higgs states directly.

  15. Black Orpheus and Aesthetic Historicism

    Directory of Open Access Journals (Sweden)

    Marina Paola Banchetti-Robino

    2011-11-01

    Full Text Available This essay offers a novel approach for understanding the poetry of negritude and its role in the struggle for black liberation by appealing to Giambattista Vico’s insights on the historical, cultural, and myth-making function of poetry and of the mythopoetic imagination.  The essay begins with a discussion of Vico’s aesthetic historicism and of his ideas regarding the role of imagination, poetry, and myth-making and then brings these ideas to bear on the discussion of the function of negritude poetry, focusing primarily on the writings of Aimé Césaire and on Jean-Paul Sartre’s essay, Black Orpheus.

  16. The Black Death in England.

    Science.gov (United States)

    Sloan, A W

    1981-04-25

    From 1348 to 1350 Europe was devastated by an epidemic of plague, called at the time the Great Mortality and later the Black Death. The epidemic reached southern Europe from the Middle East and spread northward, reaching England in June 1348. Contemporary descriptions leave no doubt of the diagnosis, but estimates of the mortality differ widely owing to lack of contemporary statistics; in England it was probably between one-third and one-half of the population. The Black Death and subsequent plague epidemics in the 14th century had marked social and economic effects, reduced the prestige of the Church and off the medical profession, and were a factor in the social unrest which led to the Renaissance of the Reformation.

  17. Black holes in magnetic monopoles

    Science.gov (United States)

    Lee, Kimyeong; Nair, V. P.; Weinberg, Erick J.

    1991-01-01

    We study magnetically charged classical solutions of a spontaneously broken gauge theory interacting with gravity. We show that nonsingular monopole solutions exist only if the Higgs field vacuum expectation value v is less than or equal to a critical value v sub cr, which is of the order of the Planck mass. In the limiting case, the monopole becomes a black hole, with the region outside the horizon described by the critical Reissner-Nordstrom solution. For v less than v sub cr, we find additional solutions which are singular at f = 0, but which have this singularity hidden within a horizon. These have nontrivial matter fields outside the horizon, and may be interpreted as small black holes lying within a magnetic monopole. The nature of these solutions as a function of v and of the total mass M and their relation to the Reissner-Nordstrom solutions is discussed.

  18. Accelerating and rotating black holes

    International Nuclear Information System (INIS)

    Griffiths, J B; Podolsky, J

    2005-01-01

    An exact solution of Einstein's equations which represents a pair of accelerating and rotating black holes (a generalized form of the spinning C-metric) is presented. The starting point is a form of the Plebanski-Demianski metric which, in addition to the usual parameters, explicitly includes parameters which describe the acceleration and angular velocity of the sources. This is transformed to a form which explicitly contains the known special cases for either rotating or accelerating black holes. Electromagnetic charges and a NUT parameter are included, the relation between the NUT parameter l and the Plebanski-Demianski parameter n is given, and the physical meaning of all parameters is clarified. The possibility of finding an accelerating NUT solution is also discussed

  19. The phase structure of higher-dimensional black rings and black holes

    International Nuclear Information System (INIS)

    Emparan, Roberto; Harmark, Troels; Niarchos, Vasilis; Obers, Niels A.; RodrIguez, Maria J.

    2007-01-01

    We construct an approximate solution for an asymptotically flat, neutral, thin rotating black ring in any dimension D ≥ 5 by matching the near-horizon solution for a bent boosted black string, to a linearized gravity solution away from the horizon. The rotating black ring solution has a regular horizon of topology S 1 x S D-3 and incorporates the balancing condition of the ring as a zero-tension condition. For D = 5 our method reproduces the thin ring limit of the exact black ring solution. For D ≥ 6 we show that the black ring has a higher entropy than the Myers-Perry black hole in the ultra-spinning regime. By exploiting the correspondence between ultra-spinning black holes and black membranes on a two-torus, we take steps towards qualitatively completing the phase diagram of rotating blackfolds with a single angular momentum. We are led to propose a connection between MP black holes and black rings, and between MP black holes and black Saturns, through merger transitions involving two kinds of 'pinched' black holes. More generally, the analogy suggests an infinite number of pinched black holes of spherical topology leading to a complicated pattern of connections and mergers between phases

  20. Black ringoids: spinning balanced black objects in d≥5 dimensions — the codimension-two case

    International Nuclear Information System (INIS)

    Kleihaus, Burkhard; Kunz, Jutta; Radu, Eugen

    2015-01-01

    We propose a general framework for the study of asymptotically flat black objects with k+1 equal magnitude angular momenta in d≥5 spacetime dimensions (with 0≤k≤[((d−5)/2)]). In this approach, the dependence on all angular coordinates but one is factorized, which leads to a codimension-two problem. This framework can describe black holes with spherical horizon topology, the simplest solutions corresponding to a class of Myers-Perry black holes. A different set of solutions describes balanced black objects with S n+1 ×S 2k+1 horizon topology. The simplest members of this family are the black rings (k=0). The solutions with k>0 are dubbed black ringoids. Based on the nonperturbative numerical results found for several values of (n,k), we propose a general picture for the properties and the phase diagram of these solutions and the associated black holes with spherical horizon topology: n=1 black ringoids repeat the k=0 pattern of black rings and Myers-Perry black holes in 5 dimensions, whereas n>1 black ringoids follow the pattern of higher dimensional black rings associated with ‘pinched’ black holes and Myers-Perry black holes.

  1. Working with young black people.

    OpenAIRE

    Sallah, Momodou; Howson, Carlton

    2007-01-01

    This is an important collection, integrating research with messages for practitioners in an area where there has as yet been insufficient material published. This book also formed the focal point for a major international conference in the Summer of 2006. As well as jointly editing the publication, the author contributed a chapter to it. Bringing together this work's different dimensions and perspectives, this book seeks to challenge both the accepted status quo of Black young people s neg...

  2. A black-hole cosmology

    International Nuclear Information System (INIS)

    Debney, G.; Farnsworth, D.

    1983-01-01

    Motivated by the fact that 2m/r is of the order of magnitude unity for the observable universe, we explore the possibility that a Schwarzschild or black hole cosmological model is appropriate. Luminosity distance and frequency shifts of freely-falling, standard, monochromatic objects are viewed by a freely-falling observer. The observer is inside r=2m. The observer in such a world does not see the same universe as do astronomers. (author)

  3. Gravitating discs around black holes

    Czech Academy of Sciences Publication Activity Database

    Karas, Vladimír; Huré, J.-M.; Semerák, O.

    2004-01-01

    Roč. 21, č. 7 (2004), R1-R5 ISSN 0264-9381 R&D Projects: GA ČR GA205/03/0902; GA AV ČR KSK1048102 Institutional research plan: CEZ:AV0Z1003909 Keywords : black holes * accretion discs * general relativity Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.941, year: 2004

  4. Van der Waals black hole

    Directory of Open Access Journals (Sweden)

    Aruna Rajagopal

    2014-10-01

    Full Text Available In the context of extended phase space, where the negative cosmological constant is treated as a thermodynamic pressure in the first law of black hole thermodynamics, we find an asymptotically AdS metric whose thermodynamics matches exactly that of the Van der Waals fluid. We show that as a solution of Einstein's equations, the corresponding stress energy tensor obeys (at least for certain range of metric parameters all three weak, strong, and dominant energy conditions.

  5. Aspirin Recapitulates Features of Caloric Restriction

    Directory of Open Access Journals (Sweden)

    Federico Pietrocola

    2018-02-01

    Full Text Available The age-associated deterioration in cellular and organismal functions associates with dysregulation of nutrient-sensing pathways and disabled autophagy. The reactivation of autophagic flux may prevent or ameliorate age-related metabolic dysfunctions. Non-toxic compounds endowed with the capacity to reduce the overall levels of protein acetylation and to induce autophagy have been categorized as caloric restriction mimetics (CRMs. Here, we show that aspirin or its active metabolite salicylate induce autophagy by virtue of their capacity to inhibit the acetyltransferase activity of EP300. While salicylate readily stimulates autophagic flux in control cells, it fails to further increase autophagy levels in EP300-deficient cells, as well as in cells in which endogenous EP300 has been replaced by salicylate-resistant EP300 mutants. Accordingly, the pro-autophagic activity of aspirin and salicylate on the nematode Caenorhabditis elegans is lost when the expression of the EP300 ortholog cpb-1 is reduced. Altogether, these findings identify aspirin as an evolutionary conserved CRM.

  6. Soft Hair on Black Holes.

    Science.gov (United States)

    Hawking, Stephen W; Perry, Malcolm J; Strominger, Andrew

    2016-06-10

    It has recently been shown that Bondi-van der Burg-Metzner-Sachs supertranslation symmetries imply an infinite number of conservation laws for all gravitational theories in asymptotically Minkowskian spacetimes. These laws require black holes to carry a large amount of soft (i.e., zero-energy) supertranslation hair. The presence of a Maxwell field similarly implies soft electric hair. This Letter gives an explicit description of soft hair in terms of soft gravitons or photons on the black hole horizon, and shows that complete information about their quantum state is stored on a holographic plate at the future boundary of the horizon. Charge conservation is used to give an infinite number of exact relations between the evaporation products of black holes which have different soft hair but are otherwise identical. It is further argued that soft hair which is spatially localized to much less than a Planck length cannot be excited in a physically realizable process, giving an effective number of soft degrees of freedom proportional to the horizon area in Planck units.

  7. What caused the Black Death?

    Science.gov (United States)

    Duncan, C J; Scott, S

    2005-05-01

    For the whole of the 20th century it was believed that the Black Death and all the plagues of Europe (1347-1670) were epidemics of bubonic plague. This review presents evidence that this view is incorrect and that the disease was a viral haemorrhagic fever, characterised by a long incubation period of 32 days, which allowed it to be spread widely even with the limited transport of the Middle Ages. It is suggested that haemorrhagic plague emerged from its animal host in Ethiopia and struck repeatedly at European/Asian civilisations, before appearing as the Black Death. The CCR5-Delta32 mutation confers protection against HIV-1 in an average of 10% of the people of European origin today. It is suggested that all the Deltaccr5 alleles originated from a single mutation event that occurred before 1000 BC and the subsequent epidemics of haemorrhagic plague gently forced up its frequency to 5 x 10(-5) at the time of the Black Death. Epidemics of haemorrhagic plague over the next three centuries then steadily raised the frequency in Europe (but not elsewhere) to present day values.

  8. Entanglement Entropy of Black Holes

    Directory of Open Access Journals (Sweden)

    Sergey N. Solodukhin

    2011-10-01

    Full Text Available The entanglement entropy is a fundamental quantity, which characterizes the correlations between sub-systems in a larger quantum-mechanical system. For two sub-systems separated by a surface the entanglement entropy is proportional to the area of the surface and depends on the UV cutoff, which regulates the short-distance correlations. The geometrical nature of entanglement-entropy calculation is particularly intriguing when applied to black holes when the entangling surface is the black-hole horizon. I review a variety of aspects of this calculation: the useful mathematical tools such as the geometry of spaces with conical singularities and the heat kernel method, the UV divergences in the entropy and their renormalization, the logarithmic terms in the entanglement entropy in four and six dimensions and their relation to the conformal anomalies. The focus in the review is on the systematic use of the conical singularity method. The relations to other known approaches such as ’t Hooft’s brick-wall model and the Euclidean path integral in the optical metric are discussed in detail. The puzzling behavior of the entanglement entropy due to fields, which non-minimally couple to gravity, is emphasized. The holographic description of the entanglement entropy of the black-hole horizon is illustrated on the two- and four-dimensional examples. Finally, I examine the possibility to interpret the Bekenstein-Hawking entropy entirely as the entanglement entropy.

  9. Glory scattering by black holes

    International Nuclear Information System (INIS)

    Matzner, R.A.; DeWitte-Morette, C.; Nelson, B.; Zhang, T.

    1985-01-01

    We present a physically motivated derivation of the JWKB backward glory-scattering cross section of massless waves by Schwarzschild black holes. The angular dependence of the cross section is identical with the one derived by path integration, namely, dsigma/dΩ = 4π 2 lambda -1 B/sub g/ 2 (dB mWπ, where lambda is the wavelength, B(theta) is the inverse of the classical deflection function CTHETA(B), B/sub g/ is the glory impact parameter, s is the helicity of the scattered wave, and J/sub 2s/ is the Bessel function of order 2s. The glory rings formed by scalar waves are bright at the center; those formed by polarized waves are dark at the center. For scattering of massless particles by a spherical black hole of mass M, B(theta)/Mapprox.3 √3 + 3.48 exp(-theta), theta > owigπ. The numerical values of dsigma/dΩ for this deflection function are found to agree with earlier computer calculations of glory cross sections from black holes

  10. The stable problem of the black-hole connected region in the Schwarzschild black hole

    OpenAIRE

    Tian, Guihua

    2005-01-01

    The stability of the Schwarzschild black hole is studied. Using the Painlev\\'{e} coordinate, our region can be defined as the black-hole-connected region(r>2m, see text) of the Schwarzschild black hole or the white-hole-connected region(r>2m, see text) of the Schwarzschild black hole. We study the stable problems of the black-hole-connected region. The conclusions are: (1) in the black-hole-connected region, the initially regular perturbation fields must have real frequency or complex frequen...

  11. Charged spinning black holes as particle accelerators

    International Nuclear Information System (INIS)

    Wei Shaowen; Liu Yuxiao; Guo Heng; Fu Chune

    2010-01-01

    It has recently been pointed out that the spinning Kerr black hole with maximal spin could act as a particle collider with arbitrarily high center-of-mass energy. In this paper, we will extend the result to the charged spinning black hole, the Kerr-Newman black hole. The center-of-mass energy of collision for two uncharged particles falling freely from rest at infinity depends not only on the spin a but also on the charge Q of the black hole. We find that an unlimited center-of-mass energy can be approached with the conditions: (1) the collision takes place at the horizon of an extremal black hole; (2) one of the colliding particles has critical angular momentum; (3) the spin a of the extremal black hole satisfies (1/√(3))≤(a/M)≤1, where M is the mass of the Kerr-Newman black hole. The third condition implies that to obtain an arbitrarily high energy, the extremal Kerr-Newman black hole must have a large value of spin, which is a significant difference between the Kerr and Kerr-Newman black holes. Furthermore, we also show that, for a near-extremal black hole, there always exists a finite upper bound for center-of-mass energy, which decreases with the increase of the charge Q.

  12. BSW process of the slowly evaporating charged black hole

    OpenAIRE

    Wang, Liancheng; He, Feng; Fu, Xiangyun

    2015-01-01

    In this paper, we study the BSW process of the slowly evaporating charged black hole. It can be found that the BSW process will also arise near black hole horizon when the evaporation of charged black hole is very slow. But now the background black hole does not have to be an extremal black hole, and it will be approximately an extremal black hole unless it is nearly a huge stationary black hole.

  13. Boosting jet power in black hole spacetimes.

    Science.gov (United States)

    Neilsen, David; Lehner, Luis; Palenzuela, Carlos; Hirschmann, Eric W; Liebling, Steven L; Motl, Patrick M; Garrett, Travis

    2011-08-02

    The extraction of rotational energy from a spinning black hole via the Blandford-Znajek mechanism has long been understood as an important component in models to explain energetic jets from compact astrophysical sources. Here we show more generally that the kinetic energy of the black hole, both rotational and translational, can be tapped, thereby producing even more luminous jets powered by the interaction of the black hole with its surrounding plasma. We study the resulting Poynting jet that arises from single boosted black holes and binary black hole systems. In the latter case, we find that increasing the orbital angular momenta of the system and/or the spins of the individual black holes results in an enhanced Poynting flux.

  14. Escape of Black Holes from the Brane

    International Nuclear Information System (INIS)

    Flachi, Antonino; Tanaka, Takahiro

    2005-01-01

    TeV-scale gravity theories allow the possibility of producing small black holes at energies that soon will be explored at the CERN LHC or at the Auger observatory. One of the expected signatures is the detection of Hawking radiation that might eventually terminate if the black hole, once perturbed, leaves the brane. Here, we study how the 'black hole plus brane' system evolves once the black hole is given an initial velocity that mimics, for instance, the recoil due to the emission of a graviton. The results of our dynamical analysis show that the brane bends around the black hole, suggesting that the black hole eventually escapes into the extra dimensions once two portions of the brane come in contact and reconnect. This gives a dynamical mechanism for the creation of baby branes

  15. Hidden conformal symmetry of extremal black holes

    International Nuclear Information System (INIS)

    Chen Bin; Long Jiang; Zhang Jiaju

    2010-01-01

    We study the hidden conformal symmetry of extremal black holes. We introduce a new set of conformal coordinates to write the SL(2,R) generators. We find that the Laplacian of the scalar field in many extremal black holes, including Kerr(-Newman), Reissner-Nordstrom, warped AdS 3 , and null warped black holes, could be written in terms of the SL(2,R) quadratic Casimir. This suggests that there exist dual conformal field theory (CFT) descriptions of these black holes. From the conformal coordinates, the temperatures of the dual CFTs could be read directly. For the extremal black hole, the Hawking temperature is vanishing. Correspondingly, only the left (right) temperature of the dual CFT is nonvanishing, and the excitations of the other sector are suppressed. In the probe limit, we compute the scattering amplitudes of the scalar off the extremal black holes and find perfect agreement with the CFT prediction.

  16. Black holes are almost optimal quantum cloners

    Science.gov (United States)

    Adami, Christoph; Ver Steeg, Greg

    2015-06-01

    If black holes were able to clone quantum states, a number of paradoxes in black hole physics would disappear. However, the linearity of quantum mechanics forbids exact cloning of quantum states. Here we show that black holes indeed clone incoming quantum states with a fidelity that depends on the black hole’s absorption coefficient, without violating the no-cloning theorem because the clones are only approximate. Perfectly reflecting black holes are optimal universal ‘quantum cloning machines’ and operate on the principle of stimulated emission, exactly as their quantum optical counterparts. In the limit of perfect absorption, the fidelity of clones is only equal to what can be obtained via quantum state estimation methods. But for any absorption probability less than one, the cloning fidelity is nearly optimal as long as ω /T≥slant 10, a common parameter for modest-sized black holes.

  17. Black-hole bomb and superradiant instabilities

    International Nuclear Information System (INIS)

    Cardoso, Vitor; Dias, Oscar J.C.; Lemos, Jose P.S.; Yoshida, Shijun

    2004-01-01

    A wave impinging on a Kerr black hole can be amplified as it scatters off the hole if certain conditions are satisfied, giving rise to superradiant scattering. By placing a mirror around the black hole one can make the system unstable. This is the black-hole bomb of Press and Teukolsky. We investigate in detail this process and compute the growing time scales and oscillation frequencies as a function of the mirror's location. It is found that in order for the system black hole plus mirror to become unstable there is a minimum distance at which the mirror must be located. We also give an explicit example showing that such a bomb can be built. In addition, our arguments enable us to justify why large Kerr-AdS black holes are stable and small Kerr-AdS black holes should be unstable

  18. Black Feminism: An Integrated Review of Literature.

    Science.gov (United States)

    Love, Katie L

    2016-01-01

    This study presents a systematic literature review exploring the uses and potential benefits of Black Feminism in nursing research. Black Feminism may benefit knowledge development for nursing in a variety of ways, such as illuminating the multifaceted factors of Black women's identities in helping scholars move away from generalization of experiences, to improve understanding of health disparities, and making such changes by broadening the social consciousness of the nurse researchers, who are predominantly White. Discrimination in health disparities may be deconstructed if the focus is placed on asking different research questions and offering different interventions with the social structures that contributes to such actions. When Black Feminism guides the research method (including research questions and analysis), the accuracy of representing the experiences of Black women is increased. In this research, Black Feminism highlights experience, coping mechanisms, spiritual values, a tradition of strength, and a holistic view of identity.

  19. Charged black holes with scalar hair

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Zhong-Ying; Lü, H. [Center for Advanced Quantum Studies, Department of Physics,Beijing Normal University, Beijing 100875 (China)

    2015-09-10

    We consider a class of Einstein-Maxwell-Dilaton theories, in which the dilaton coupling to the Maxwell field is not the usual single exponential function, but one with a stationary point. The theories admit two charged black holes: one is the Reissner-Nordstrøm (RN) black hole and the other has a varying dilaton. For a given charge, the new black hole in the extremal limit has the same AdS{sub 2}×Sphere near-horizon geometry as the RN black hole, but it carries larger mass. We then introduce some scalar potentials and obtain exact charged AdS black holes. We also generalize the results to black p-branes with scalar hair.

  20. Information Retention by Stringy Black Holes

    CERN Document Server

    Ellis, John

    2015-01-01

    Building upon our previous work on two-dimensional stringy black holes and its extension to spherically-symmetric four-dimensional stringy black holes, we show how the latter retain information. A key r\\^ole is played by an infinite-dimensional $W_\\infty$ symmetry that preserves the area of an isolated black-hole horizon and hence its entropy. The exactly-marginal conformal world-sheet operator representing a massless stringy particle interacting with the black hole necessarily includes a contribution from $W_\\infty$ generators in its vertex function. This admixture manifests the transfer of information between the string black hole and external particles. We discuss different manifestations of $W_\\infty$ symmetry in black-hole physics and the connections between them.

  1. Black-hole thermodynamics and Riemann surfaces

    International Nuclear Information System (INIS)

    Krasnov, Kirill

    2003-01-01

    We use the analytic continuation procedure proposed in our earlier works to study the thermodynamics of black holes in 2 + 1 dimensions. A general black hole in 2 + 1 dimensions has g handles hidden behind h horizons. The result of the analytic continuation of a black-hole spacetime is a hyperbolic 3-manifold having the topology of a handlebody. The boundary of this handlebody is a compact Riemann surface of genus G = 2g + h - 1. Conformal moduli of this surface encode in a simple way the physical characteristics of the black hole. The moduli space of black holes of a given type (g, h) is then the Schottky space at genus G. The (logarithm of the) thermodynamic partition function of the hole is the Kaehler potential for the Weil-Peterson metric on the Schottky space. The Bekenstein bound on the black-hole entropy leads us to conjecture a new strong bound on this Kaehler potential

  2. Shaping Globular Clusters with Black Holes

    Science.gov (United States)

    Kohler, Susanna

    2018-03-01

    How many black holes lurk within the dense environments of globular clusters, and how do these powerful objects shape the properties of the cluster around them? One such cluster, NGC 3201, is now helping us to answer these questions.Hunting Stellar-Mass Black HolesSince the detection of merging black-hole binaries by the Laser Interferometer Gravitational-Wave Observatory (LIGO), the dense environments of globular clusters have received increasing attention as potential birthplaces of these compact binary systems.The central region of the globular star cluster NGC 3201, as viewed by Hubble. The black hole is in orbit with the star marked by the blue circle. [NASA/ESA]In addition, more and more stellar-mass black-hole candidates have been observed within globular clusters, lurking in binary pairs with luminous, non-compact companions. The most recent of these detections, found in the globular cluster NGC 3201, stands alone as the first stellar-mass black hole candidate discovered via radial velocity observations: the black holes main-sequence companion gave away its presence via a telltale wobble.Now a team of scientists led by Kyle Kremer (CIERA and Northwestern University) is using models of this system to better understand the impact that black holes might have on their host clusters.A Model ClusterThe relationship between black holes and their host clusters is complicated. Though the cluster environment can determine the dynamical evolution of the black holes, the retention rate of black holes in a globular cluster (i.e., how many remain in the cluster when they are born as supernovae, rather than being kicked out during the explosion) influences how the host cluster evolves.Kremer and collaborators track this complex relationship by modeling the evolution of a cluster similar to NGC 3201 with a Monte Carlo code. The code incorporates physics relevant to the evolution of black holes and black-hole binaries in globular clusters, such as two-body relaxation

  3. Seeding black holes in cosmological simulations

    Science.gov (United States)

    Taylor, P.; Kobayashi, C.

    2014-08-01

    We present a new model for the formation of black holes in cosmological simulations, motivated by the first star formation. Black holes form from high density peaks of primordial gas, and grow via both gas accretion and mergers. Massive black holes heat the surrounding material, suppressing star formation at the centres of galaxies, and driving galactic winds. We perform an investigation into the physical effects of the model parameters, and obtain a `best' set of these parameters by comparing the outcome of simulations to observations. With this best set, we successfully reproduce the cosmic star formation rate history, black hole mass-velocity dispersion relation, and the size-velocity dispersion relation of galaxies. The black hole seed mass is ˜103 M⊙, which is orders of magnitude smaller than that which has been used in previous cosmological simulations with active galactic nuclei, but suggests that the origin of the seed black holes is the death of Population III stars.

  4. What does a black hole look like?

    CERN Document Server

    Bailyn, Charles D

    2014-01-01

    Emitting no radiation or any other kind of information, black holes mark the edge of the universe--both physically and in our scientific understanding. Yet astronomers have found clear evidence for the existence of black holes, employing the same tools and techniques used to explore other celestial objects. In this sophisticated introduction, leading astronomer Charles Bailyn goes behind the theory and physics of black holes to describe how astronomers are observing these enigmatic objects and developing a remarkably detailed picture of what they look like and how they interact with their surroundings. Accessible to undergraduates and others with some knowledge of introductory college-level physics, this book presents the techniques used to identify and measure the mass and spin of celestial black holes. These key measurements demonstrate the existence of two kinds of black holes, those with masses a few times that of a typical star, and those with masses comparable to whole galaxies--supermassive black holes...

  5. Charged topological black hole pair creation

    International Nuclear Information System (INIS)

    Mann, R.B.

    1998-01-01

    I examine the pair creation of black holes in space-times with a cosmological constant of either sign. I consider cosmological C-metrics and show that the conical singularities in this metric vanish only for three distinct classes of black hole metric, two of which have compact event horizons on each spatial slice. One class is a generalization of the Reissner-Nordstroem (anti-)de Sitter black holes in which the event horizons are the direct product of a null line with a 2-surface with topology of genus g. The other class consists of neutral black holes whose event horizons are the direct product of a null conoid with a circle. In the presence of a domain wall, black hole pairs of all possible types will be pair created for a wide range of mass and charge, including even negative mass black holes. I determine the relevant instantons and Euclidean actions for each case. (orig.)

  6. Reversible Carnot cycle outside a black hole

    International Nuclear Information System (INIS)

    Xi-Hao, Deng; Si-Jie, Gao

    2009-01-01

    A Carnot cycle outside a Schwarzschild black hole is investigated in detail. We propose a reversible Carnot cycle with a black hole being the cold reservoir. In our model, a Carnot engine operates between a hot reservoir with temperature T 1 and a black hole with Hawking temperature T H . By naturally extending the ordinary Carnot cycle to the black hole system, we show that the thermal efficiency for a reversible process can reach the maximal efficiency 1 – T H /T 1 . Consequently, black holes can be used to determine the thermodynamic temperature by means of the Carnot cycle. The role of the atmosphere around the black hole is discussed. We show that the thermal atmosphere provides a necessary mechanism to make the process reversible. (general)

  7. Hawking temperature of constant curvature black holes

    International Nuclear Information System (INIS)

    Cai Ronggen; Myung, Yun Soo

    2011-01-01

    The constant curvature (CC) black holes are higher dimensional generalizations of Banados-Teitelboim-Zanelli black holes. It is known that these black holes have the unusual topology of M D-1 xS 1 , where D is the spacetime dimension and M D-1 stands for a conformal Minkowski spacetime in D-1 dimensions. The unusual topology and time-dependence for the exterior of these black holes cause some difficulties to derive their thermodynamic quantities. In this work, by using a globally embedding approach, we obtain the Hawking temperature of the CC black holes. We find that the Hawking temperature takes the same form when using both the static and global coordinates. Also, it is identical to the Gibbons-Hawking temperature of the boundary de Sitter spaces of these CC black holes.

  8. Superradiance by mini black holes with mirror

    OpenAIRE

    Lee, Jong-Phil

    2011-01-01

    The superradiant scattering of massive scalar particles by a rotating mini black hole is investigated. Imposing the mirror boundary condition, the system becomes the so called black-hole bomb where the rotation energy of the black hole is transferred to the scattered particle exponentially with time. Bulk emissions as well as brane emissions are considered altogether. It is found that the largest effects are expected for the brane emission of lower angular modes with lighter mass and larger a...

  9. Geometrothermodynamics of higher dimensional black holes

    Science.gov (United States)

    Bravetti, Alessandro; Momeni, Davood; Myrzakulov, Ratbay; Quevedo, Hernando

    2013-08-01

    We study the thermodynamics and geometrothermodynamics of different black hole configurations in more than four spacetime dimensions. We use the response functions to find the conditions under which second order phase transitions occur in higher-dimensional static Reissner-Nordström and stationary Kerr black holes. Our results indicate that the equilibrium manifold of all these black hole configurations is in general curved and that curvature singularities appear exactly at those places where second order phase transitions occur.

  10. Effective Stringy Description of Schwarzschild Black Holes

    OpenAIRE

    Krasnov , Kirill; Solodukhin , Sergey N.

    2004-01-01

    We start by pointing out that certain Riemann surfaces appear rather naturally in the context of wave equations in the black hole background. For a given black hole there are two closely related surfaces. One is the Riemann surface of complexified ``tortoise'' coordinate. The other Riemann surface appears when the radial wave equation is interpreted as the Fuchsian differential equation. We study these surfaces in detail for the BTZ and Schwarzschild black holes in four and higher dimensions....

  11. Observability of Quantum State of Black Hole

    CERN Document Server

    David, J R; Mandal, G; Wadia, S R; David, Justin R.; Dhar, Avinash; Mandal, Gautam; Wadia, Spenta R.

    1997-01-01

    We analyze terms subleading to Rutherford in the $S$-matrix between black hole and probes of successively high energies. We show that by an appropriate choice of the probe one can read off the quantum state of the black hole from the S-matrix, staying asymptotically far from the BH all the time. We interpret the scattering experiment as scattering off classical stringy backgrounds which explicitly depend on the internal quantum numbers of the black hole.

  12. Black hole mergers in the universe

    OpenAIRE

    Zwart, Simon Portegies; McMillan, Stephen

    1999-01-01

    Mergers of black-hole binaries are expected to release large amounts of energy in the form of gravitational radiation. However, binary evolution models predict merger rates too low to be of observational interest. In this paper we explore the possibility that black holes become members of close binaries via dynamical interactions with other stars in dense stellar systems. In star clusters, black holes become the most massive objects within a few tens of millions of years; dynamical relaxation...

  13. A New Model of Black Hole Formation

    Directory of Open Access Journals (Sweden)

    Thayer G. D.

    2013-10-01

    Full Text Available The formation of a black hole and its event horizon are described. Conclusions, which are the result of a thought experiment, show that Schwarzschild [1] was correct: A singularity develops at the event horizon of a newly-formed black hole. The intense gravitational field that forms near the event horizon results in the mass-energy of the black hole accumulating in a layer just inside the event horizon, rather than collapsing into a central singularity.

  14. Gravitational lensing by a Horndeski black hole

    Energy Technology Data Exchange (ETDEWEB)

    Badia, Javier [Instituto de Astronomia y Fisica del Espacio (IAFE, CONICET-UBA), Buenos Aires (Argentina); Eiroa, Ernesto F. [Instituto de Astronomia y Fisica del Espacio (IAFE, CONICET-UBA), Buenos Aires (Argentina); Universidad de Buenos Aires, Ciudad Universitaria Pabellon I, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina)

    2017-11-15

    In this article we study gravitational lensing by non-rotating and asymptotically flat black holes in Horndeski theory. By adopting the strong deflection limit, we calculate the deflection angle, from which we obtain the positions and the magnifications of the relativistic images. We compare our results with those corresponding to black holes in General Relativity. We analyze the astrophysical consequences in the case of the nearest supermassive black holes. (orig.)

  15. Unified geometric description of black hole thermodynamics

    International Nuclear Information System (INIS)

    Alvarez, Jose L.; Quevedo, Hernando; Sanchez, Alberto

    2008-01-01

    In the space of thermodynamic equilibrium states we introduce a Legendre invariant metric which contains all the information about the thermodynamics of black holes. The curvature of this thermodynamic metric becomes singular at those points where, according to the analysis of the heat capacities, phase transitions occur. This result is valid for the Kerr-Newman black hole and all its special cases and, therefore, provides a unified description of black hole phase transitions in terms of curvature singularities.

  16. Measuring the spins of accreting black holes

    International Nuclear Information System (INIS)

    McClintock, Jeffrey E; Narayan, Ramesh; Gou, Lijun; Kulkarni, Akshay; Penna, Robert F; Steiner, James F; Davis, Shane W; Orosz, Jerome A; Remillard, Ronald A

    2011-01-01

    A typical galaxy is thought to contain tens of millions of stellar-mass black holes, the collapsed remnants of once massive stars, and a single nuclear supermassive black hole. Both classes of black holes accrete gas from their environments. The accreting gas forms a flattened orbiting structure known as an accretion disk. During the past several years, it has become possible to obtain measurements of the spins of the two classes of black holes by modeling the x-ray emission from their accretion disks. Two methods are employed, both of which depend upon identifying the inner radius of the accretion disk with the innermost stable circular orbit, whose radius depends only on the mass and spin of the black hole. In the Fe Kα method, which applies to both classes of black holes, one models the profile of the relativistically broadened iron line with a special focus on the gravitationally redshifted red wing of the line. In the continuum-fitting (CF) method, which has so far only been applied to stellar-mass black holes, one models the thermal x-ray continuum spectrum of the accretion disk. We discuss both methods, with a strong emphasis on the CF method and its application to stellar-mass black holes. Spin results for eight stellar-mass black holes are summarized. These data are used to argue that the high spins of at least some of these black holes are natal, and that the presence or absence of relativistic jets in accreting black holes is not entirely determined by the spin of the black hole.

  17. Low-mass black holes as the remnants of primordial black hole formation.

    Science.gov (United States)

    Greene, Jenny E

    2012-01-01

    Bridging the gap between the approximately ten solar mass 'stellar mass' black holes and the 'supermassive' black holes of millions to billions of solar masses are the elusive 'intermediate-mass' black holes. Their discovery is key to understanding whether supermassive black holes can grow from stellar-mass black holes or whether a more exotic process accelerated their growth soon after the Big Bang. Currently, tentative evidence suggests that the progenitors of supermassive black holes were formed as ∼10(4)-10(5) M(⊙) black holes via the direct collapse of gas. Ongoing searches for intermediate-mass black holes at galaxy centres will help shed light on this formation mechanism.

  18. Spin One Hawking Radiation from Dirty Black Holes

    OpenAIRE

    Petarpa Boonserm; Tritos Ngampitipan; Matt Visser

    2013-01-01

    A “clean” black hole is a black hole in vacuum such as the Schwarzschild black hole. However in real physical systems, there are matter fields around a black hole. Such a black hole is called a “dirty black hole”. In this paper, the effect of matter fields on the black hole and the greybody factor is investigated. The results show that matter fields make a black hole smaller. They can increase the potential energy to a black hole to obstruct Hawking radiation to propagate. This causes the gre...

  19. New geometries for black hole horizons

    Energy Technology Data Exchange (ETDEWEB)

    Armas, Jay [Physique Théorique et Mathématique,Université Libre de Bruxelles and International Solvay Institutes, ULB-Campus Plaine CP231, B-1050 Brussels (Belgium); Blau, Matthias [Albert Einstein Center for Fundamental Physics, University of Bern,Sidlerstrasse 5, 3012 Bern (Switzerland)

    2015-07-10

    We construct several classes of worldvolume effective actions for black holes by integrating out spatial sections of the worldvolume geometry of asymptotically flat black branes. This provides a generalisation of the blackfold approach for higher-dimensional black holes and yields a map between different effective theories, which we exploit by obtaining new hydrodynamic and elastic transport coefficients via simple integrations. Using Euclidean minimal surfaces in order to decouple the fluid dynamics on different sections of the worldvolume, we obtain local effective theories for ultraspinning Myers-Perry branes and helicoidal black branes, described in terms of a stress-energy tensor, particle currents and non-trivial boost vectors. We then study in detail and present novel compact and non-compact geometries for black hole horizons in higher-dimensional asymptotically flat space-time. These include doubly-spinning black rings, black helicoids and helicoidal p-branes as well as helicoidal black rings and helicoidal black tori in D≥6.

  20. On the thermodynamics of hairy black holes

    Energy Technology Data Exchange (ETDEWEB)

    Anabalón, Andrés [Departamento de Ciencias, Facultad de Artes Liberales y Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Viña del Mar (Chile); Astefanesei, Dumitru [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla 4059, Valparaíso (Chile); Choque, David, E-mail: brst1010123@gmail.com [Universidad Técnica Federico Santa María, Av. España 1680, Valparaiso (Chile)

    2015-04-09

    We investigate the thermodynamics of a general class of exact 4-dimensional asymptotically Anti-de Sitter hairy black hole solutions and show that, for a fixed temperature, there are small and large hairy black holes similar to the Schwarzschild–AdS black hole. The large black holes have positive specific heat and so they can be in equilibrium with a thermal bath of radiation at the Hawking temperature. The relevant thermodynamic quantities are computed by using the Hamiltonian formalism and counterterm method. We explicitly show that there are first order phase transitions similar to the Hawking–Page phase transition.

  1. Black hole evaporation in conformal gravity

    Energy Technology Data Exchange (ETDEWEB)

    Bambi, Cosimo; Rachwał, Lesław [Center for Field Theory and Particle Physics and Department of Physics, Fudan University, 220 Handan Road, 200433 Shanghai (China); Modesto, Leonardo [Department of Physics, Southern University of Science and Technology, 1088 Xueyuan Road, Shenzhen 518055 (China); Porey, Shiladitya, E-mail: bambi@fudan.edu.cn, E-mail: lmodesto@sustc.edu.cn, E-mail: shilp@iitk.ac.in, E-mail: rachwal@fudan.edu.cn [Department of Physics, Indian Institute of Technology, 208016 Kanpur (India)

    2017-09-01

    We study the formation and the evaporation of a spherically symmetric black hole in conformal gravity. From the collapse of a spherically symmetric thin shell of radiation, we find a singularity-free non-rotating black hole. This black hole has the same Hawking temperature as a Schwarzschild black hole with the same mass, and it completely evaporates either in a finite or in an infinite time, depending on the ensemble. We consider the analysis both in the canonical and in the micro-canonical statistical ensembles. Last, we discuss the corresponding Penrose diagram of this physical process.

  2. Strings, black holes, and quantum information

    International Nuclear Information System (INIS)

    Kallosh, Renata; Linde, Andrei

    2006-01-01

    We find multiple relations between extremal black holes in string theory and 2- and 3-qubit systems in quantum information theory. We show that the entropy of the axion-dilaton extremal black hole is related to the concurrence of a 2-qubit state, whereas the entropy of the STU black holes, Bogomol'nyi-Prasad-Sommerfield (BPS) as well as non-BPS, is related to the 3-tangle of a 3-qubit state. We relate the 3-qubit states with the string theory states with some number of D-branes. We identify a set of large black holes with the maximally entangled Greenberger, Horne, Zeilinger (GHZ) class of states and small black holes with separable, bipartite, and W states. We sort out the relation between 3-qubit states, twistors, octonions, and black holes. We give a simple expression for the entropy and the area of stretched horizon of small black holes in terms of a norm and 2-tangles of a 3-qubit system. Finally, we show that the most general expression for the black hole and black ring entropy in N=8 supergravity/M theory, which is given by the famous quartic Cartan E 7(7) invariant, can be reduced to Cayley's hyperdeterminant describing the 3-tangle of a 3-qubit state

  3. Micro black holes and the democratic transition

    International Nuclear Information System (INIS)

    Dvali, Gia; Pujolas, Oriol

    2009-01-01

    Unitarity implies that the evaporation of microscopic quasiclassical black holes cannot be universal in different particle species. This creates a puzzle, since it conflicts with the thermal nature of quasiclassical black holes, according to which all of the species should see the same horizon and be produced with the same Hawking temperatures. We resolve this puzzle by showing that for the microscopic black holes, on top of the usual quantum evaporation time, there is a new time scale which characterizes a purely classical process during which the black hole loses the ability to differentiate among the species and becomes democratic. We demonstrate this phenomenon in a well-understood framework of large extra dimensions, with a number of parallel branes. An initially nondemocratic black hole is the one localized on one of the branes, with its high-dimensional Schwarzschild radius being much shorter than the interbrane distance. Such a black hole seemingly cannot evaporate into the species localized on the other branes that are beyond its reach. We demonstrate that in reality the system evolves classically in time, in such a way that the black hole accretes the neighboring branes. The end result is a completely democratic static configuration, in which all of the branes share the same black hole and all of the species are produced with the same Hawking temperature. Thus, just like their macroscopic counterparts, the microscopic black holes are universal bridges to the hidden sector physics.

  4. Black Hole Universe Model and Dark Energy

    Science.gov (United States)

    Zhang, Tianxi

    2011-01-01

    Considering black hole as spacetime and slightly modifying the big bang theory, the author has recently developed a new cosmological model called black hole universe, which is consistent with Mach principle and Einsteinian general relativity and self consistently explains various observations of the universe without difficulties. According to this model, the universe originated from a hot star-like black hole and gradually grew through a supermassive black hole to the present universe by accreting ambient material and merging with other black holes. The entire space is infinitely and hierarchically layered and evolves iteratively. The innermost three layers are the universe that we lives, 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 zero limits for both the mass density and absolute temperature. All layers or universes are governed by the same physics, the Einstein general relativity with the Robertson-Walker metric of spacetime, and tend to expand outward physically. When one universe expands out, a new similar universe grows up from its inside black holes. The origin, structure, evolution, expansion, and cosmic microwave background radiation of black hole universe have been presented in the recent sequence of American Astronomical Society (AAS) meetings and published in peer-review journals. This study will show how this new model explains the acceleration of the universe and why dark energy is not required. We will also compare the black hole universe model with the big bang cosmology.

  5. Charged black holes in phantom cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Jamil, Mubasher; Qadir, Asghar; Rashid, Muneer Ahmad [National University of Sciences and Technology, Center for Advanced Mathematics and Physics, Rawalpindi (Pakistan)

    2008-11-15

    In the classical relativistic regime, the accretion of phantom-like dark energy onto a stationary black hole reduces the mass of the black hole. We have investigated the accretion of phantom energy onto a stationary charged black hole and have determined the condition under which this accretion is possible. This condition restricts the mass-to-charge ratio in a narrow range. This condition also challenges the validity of the cosmic-censorship conjecture since a naked singularity is eventually produced due to accretion of phantom energy onto black hole. (orig.)

  6. Destroying black holes with test bodies

    Energy Technology Data Exchange (ETDEWEB)

    Jacobson, Ted [Center for Fundamental Physics, University of Maryland, College Park, MD 20742-4111 (United States); Sotiriou, Thomas P, E-mail: jacobson@umd.ed, E-mail: T.Sotiriou@damtp.cam.ac.u [Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA (United Kingdom)

    2010-04-01

    If a black hole can accrete a body whose spin or charge would send the black hole parameters over the extremal limit, then a naked singularity would presumably form, in violation of the cosmic censorship conjecture. We review some previous results on testing cosmic censorship in this way using the test body approximation, focusing mostly on the case of neutral black holes. Under certain conditions a black hole can indeed be over-spun or over-charged in this approximation, hence radiative and self-force effects must be taken into account to further test cosmic censorship.

  7. Light geodesics near an evaporating black hole

    Energy Technology Data Exchange (ETDEWEB)

    Guerreiro, Thiago, E-mail: thiago.barbosa@unige.ch; Monteiro, Fernando, E-mail: fernando.monteiro@unige.ch

    2015-10-16

    Quantum effects imply that an infalling observer cannot cross the event horizon of an evaporating black hole, even in her proper time. The Penrose diagram of an evaporating black hole is different from the one usually reported in the literature. We show that before the observer can cross the horizon the black hole disappears. Possible observational consequences are discussed. - Highlights: • We calculate the in-falling light geodesics in an evaporating black hole. • For our calculation we use a non-static metric called Vaydia metric. • We show that in-falling light cannot cross the event horizon. • In this case there is no information paradox.

  8. Noncommutative Black Holes at the LHC

    Science.gov (United States)

    Villhauer, Elena Michelle

    2017-12-01

    Based on the latest public results, 13 TeV data from the Large Hadron Collider at CERN has not indicated any evidence of hitherto tested models of quantum black holes, semiclassical black holes, or string balls. Such models have predicted signatures of particles with high transverse momenta. Noncommutative black holes remain an untested model of TeV-scale gravity that offers the starkly different signature of particles with relatively low transverse momenta. Considerations for a search for charged noncommutative black holes using the ATLAS detector will be discussed.

  9. Hawking radiation and strong gravity black holes

    International Nuclear Information System (INIS)

    Qadir, A.; Sayed, W.A.

    1979-01-01

    It is shown that the strong gravity theory of Salam et al. places severe restrictions on black hole evaporation. Two major implications are that: mini blck holes (down to masses approximately 10 -16 kg) would be stable in the present epoch; and that some suggested mini black hole mechanisms to explain astrophysical phenomena would not work. The first result implies that f-gravity appears to make black holes much safer by removing the possibility of extremely violent black hole explosions suggested by Hawking. (Auth.)

  10. Tidal interactions with Kerr black holes

    International Nuclear Information System (INIS)

    Hiscock, W.A.

    1977-01-01

    The tidal deformation of an extended test body falling with zero angular momentum into a Kerr black hole is calculated. Numerical results for infall along the symmetry axis and in the equatorial plane of the black hole are presented for a range of values of a, the specific angular momentum of the black hole. Estimates of the tidal contribution to the gravitational radiation are also given. The tidal contribution in equatorial infall into a maximally rotating Kerr black hole may be of the same order as the center-of-mass contribution to the gravitational radiation

  11. Particle accelerators inside spinning black holes.

    Science.gov (United States)

    Lake, Kayll

    2010-05-28

    On the basis of the Kerr metric as a model for a spinning black hole accreting test particles from rest at infinity, I show that the center-of-mass energy for a pair of colliding particles is generically divergent at the inner horizon. This shows not only that classical black holes are internally unstable, but also that Planck-scale physics is a characteristic feature within black holes at scales much larger that the Planck length. The novel feature of the divergence discussed here is that the phenomenon is present only for black holes with rotation, and in this sense it is distinct from the well-known Cauchy horizon instability.

  12. Schwarzschild black holes can wear scalar wigs.

    Science.gov (United States)

    Barranco, Juan; Bernal, Argelia; Degollado, Juan Carlos; Diez-Tejedor, Alberto; Megevand, Miguel; Alcubierre, Miguel; Núñez, Darío; Sarbach, Olivier

    2012-08-24

    We study the evolution of a massive scalar field surrounding a Schwarzschild black hole and find configurations that can survive for arbitrarily long times, provided the black hole or the scalar field mass is small enough. In particular, both ultralight scalar field dark matter around supermassive black holes and axionlike scalar fields around primordial black holes can survive for cosmological times. Moreover, these results are quite generic in the sense that fairly arbitrary initial data evolve, at late times, as a combination of those long-lived configurations.

  13. Rotating black holes and Coriolis effect

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Chia-Jui, E-mail: agoodmanjerry.ep02g@nctu.edu.tw [Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan, ROC (China); Wu, Xiaoning, E-mail: wuxn@amss.ac.cn [Institute of Mathematics, Academy of Mathematics and System Science, CAS, Beijing, 100190 (China); Yang, Yi, E-mail: yiyang@mail.nctu.edu.tw [Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan, ROC (China); Yuan, Pei-Hung, E-mail: phyuan.py00g@nctu.edu.tw [Institute of Physics, National Chiao Tung University, Hsinchu, Taiwan, ROC (China)

    2016-10-10

    In this work, we consider the fluid/gravity correspondence for general rotating black holes. By using the suitable boundary condition in near horizon limit, we study the correspondence between gravitational perturbation and fluid equation. We find that the dual fluid equation for rotating black holes contains a Coriolis force term, which is closely related to the angular velocity of the black hole horizon. This can be seen as a dual effect for the frame-dragging effect of rotating black hole under the holographic picture.

  14. Rotating black holes and Coriolis effect

    Directory of Open Access Journals (Sweden)

    Chia-Jui Chou

    2016-10-01

    Full Text Available In this work, we consider the fluid/gravity correspondence for general rotating black holes. By using the suitable boundary condition in near horizon limit, we study the correspondence between gravitational perturbation and fluid equation. We find that the dual fluid equation for rotating black holes contains a Coriolis force term, which is closely related to the angular velocity of the black hole horizon. This can be seen as a dual effect for the frame-dragging effect of rotating black hole under the holographic picture.

  15. Planar domain walls in black hole spacetimes

    Science.gov (United States)

    Ficek, Filip; Mach, Patryk

    2018-02-01

    We investigate the behavior of low-mass, planar domain walls in the so-called ϕ4 model of the scalar field on the Schwarzschild and Kerr backgrounds. We focus on a transit of a domain wall through a black hole and solve numerically the equations of motion for a range of parameters of the domain wall and the black hole. We observe a behavior resembling an occurrence of ringing modes. Perturbations of domain walls vanish during latter evolution, suggesting their stability against a passage through the black hole. The results obtained for Kerr and Reissner-Nordström black holes are also compared.

  16. Entropy evaporated by a black hole

    International Nuclear Information System (INIS)

    Zurek, W.H.

    1982-01-01

    It is shown that the entropy of the radiation evaporated by an uncharged, nonrotating black hole into vacuum in the course of its lifetime is approximately (4/3) times the initial entropy of this black hole. Also considered is a thermodynamically reversible process in which an increase of black-hole entropy is equal to the decrease of the entropy of its surroundings. Implications of these results for the generalized second law of thermodynamics and for the interpretation of black-hole entropy are pointed out

  17. Traversable Wormholes and Black Hole Complementarity

    OpenAIRE

    Gottesman, Daniel

    1994-01-01

    Black hole complementarity is incompatible with the existence of traversable wormholes. In fact, traversable wormholes cause problems for any theory where information comes out in the Hawking radiation.

  18. Black hole thermodynamics from Euclidean horizon constraints.

    Science.gov (United States)

    Carlip, S

    2007-07-13

    To explain black hole thermodynamics in quantum gravity, one must introduce constraints to ensure that a black hole is actually present. I show that for a large class of black holes, such "horizon constraints" allow the use of conformal field theory techniques to compute the density of states, reproducing the Bekenstein-Hawking entropy in a nearly model-independent manner. One standard string theory approach to black hole entropy arises as a special case, lending support to the claim that the mechanism may be "universal." I argue that the relevant degrees of freedom are Goldstone-boson-like excitations arising from the weak breaking of symmetry by the constraints.

  19. Quantum black hole: What is that?

    International Nuclear Information System (INIS)

    Berezin, Victor

    2000-01-01

    In this paper we are trying to explain our point of view on what a quantum black hole is. The ideas are based on the previous works by the author and his collaborators where the concrete models of quantum black holes were constructed. It is argued that the main feature of quantum black holes that would allow us to distinguish them from other quantum object is some specific quantum radiation. Such a radiation in the quasiclassical limit is just the Hawking evaporation if the change in the black hole mass due to radiation can be neglected

  20. Do black holes really evaporate thermally

    International Nuclear Information System (INIS)

    Tipler, F.J.

    1980-01-01

    The Raychaudhuri equation is used to analyze the effect of the Hawking radiation back reaction upon a black-hole event horizon. It is found that if the effective stress-energy tensor of the Hawking radiation has negative energy density as expected, then an evaporating black hole initially a solar mass in size must disappear in less than a second. This implies that either the evaporation process, if it occurs at all, must be quite different from what is commonly supposed, or else black-hole event horizons: and hence black holes: do not exist

  1. On algebraically special perturbations of black holes

    International Nuclear Information System (INIS)

    Chandrasekhar, S.

    1984-01-01

    Algebraically special perturbations of black holes excite gravitational waves that are either purely ingoing or purely outgoing. Solutions, appropriate to such perturbations of the Kerr, the Schwarzschild, and the Reissner-Nordstroem black-holes, are obtained in explicit forms by different methods. The different methods illustrate the remarkable inner relations among different facets of the mathematical theory. In the context of the Kerr black-hole they derive from the different ways in which the explicit value of the Starobinsky constant emerges, and in the context of the Schwarzschild and the Reissner-Nordstroem black-holes they derive from the potential barriers surrounding them belonging to a special class. (author)

  2. Causticizing for Black Liquor Gasifiers

    Energy Technology Data Exchange (ETDEWEB)

    Scott Sinquefeld; James Cantrell; Xiaoyan Zeng; Alan Ball; Jeff Empie

    2009-01-07

    The cost-benefit outlook of black liquor gasification (BLG) could be greatly improved if the smelt causticization step could be achieved in situ during the gasification step. Or, at a minimum, the increase in causticizing load associated with BLG could be mitigated. A number of chemistries have been proven successful during black liquor combustion. In this project, three in situ causticizing processes (titanate, manganate, and borate) were evaluated under conditions suitable for high temperature entrained flow BLG, and low temperature steam reforming of black liquor. The evaluation included both thermodynamic modeling and lab experimentation. Titanate and manganate were tested for complete direct causticizing (to thus eliminate the lime cycle), and borates were evaluated for partial causticizing (to mitigate the load increase associated with BLG). Criteria included high carbonate conversion, corresponding hydroxide recovery upon hydrolysis, non process element (NPE) removal, and economics. Of the six cases (three chemistries at two BLG conditions), only two were found to be industrially viable: titanates for complete causticizing during high temperature BLG, and borates for partial causticizing during high temperature BLG. These two cases were evaluated for integration into a gasification-based recovery island. The Larsen [28] BLG cost-benefit study was used as a reference case for economic forecasting (i.e. a 1500 tpd pulp mill using BLG and upgrading the lime cycle). By comparison, using the titanate direct causticizing process yielded a net present value (NPV) of $25M over the NPV of BLG with conventional lime cycle. Using the existing lime cycle plus borate autocausticizing for extra capacity yielded a NPV of $16M.

  3. Ten Myths, Half-Truths and Misunderstandings About Black History.

    Science.gov (United States)

    Ruffins, Paul

    1997-01-01

    Common myths and misconceptions about Blacks in American history and evidence that refutes them are presented. Issues addressed include Black enslavement patterns, social status within the Black community based on skin color, the legality of slaves learning to read, resistance to slavery, African influences in modern Black culture, Black names and…

  4. 75 FR 1421 - BlackRock, Inc.; Notice of Application

    Science.gov (United States)

    2010-01-11

    ... attempting to influence or control BlackRock, and imposes a number of other limitations governing the Black... BlackRock and Merrill Lynch is readily apparent to the public and the market at large. 8. BlackRock... COMMISSION BlackRock, Inc.; Notice of Application January 4, 2010. AGENCY: Securities and Exchange Commission...

  5. The Films of Oscar Micheaux: America's First Fabulous Black Filmmaker.

    Science.gov (United States)

    Peterson, Bernard L., Jr.

    1979-01-01

    Although Oscar Micheaux was not the first Black American filmmaker, he was undoubtedly the most prolific Black American movie producer. He is credited with making the first full-length, all-Black silent film produced by a Black company, as well as the first full-length, all-Black sound film. (Author/MC)

  6. Black Sea coastal forecasting system

    Directory of Open Access Journals (Sweden)

    A. I. Kubryakov

    2012-03-01

    Full Text Available The Black Sea coastal nowcasting and forecasting system was built within the framework of EU FP6 ECOOP (European COastalshelf sea OPerational observing and forecasting system project for five regions: the south-western basin along the coasts of Bulgaria and Turkey, the north-western shelf along the Romanian and Ukrainian coasts, coastal zone around of the Crimea peninsula, the north-eastern Russian coastal zone and the coastal zone of Georgia. The system operates in the real-time mode during the ECOOP project and afterwards. The forecasts include temperature, salinity and current velocity fields. Ecosystem model operates in the off-line mode near the Crimea coast.

  7. Extremal Black Holes and Attractors

    CERN Document Server

    Ferrara, S

    2010-01-01

    These lectures give an elementary introduction to the subject of four dimensional black holes (BHs) in supergravity and the Attractor Mechanism in the extremal case. Some thermodynamical properties are discussed and some relevant formula for the critical points of the BH effective potential are given. The case of Maxwell-Einstein-axion-dilaton (super)gravity is discussed in detail. Analogies among BH entropy and multipartite entanglement of qubits in quantum information theory, as well moduli spaces of extremal BH attractors, are also discussed.

  8. REFRACTORY FOR BLACK LIQUOR GASIFIERS

    Energy Technology Data Exchange (ETDEWEB)

    William L. Headrick Jr; Musa Karakus; Jun Wei

    2005-03-01

    The University of Missouri-Rolla will identify materials that will permit the safe, reliable and economical operation of combined cycle gasifiers by the pulp and paper industry. The primary emphasis of this project will be to resolve the material problems encountered during the operation of low-pressure high-temperature (LPHT) and low-pressure low-temperature (LPLT) gasifiers while simultaneously understanding the materials barriers to the successful demonstration of high-pressure high-temperature (HPHT) black liquor gasifiers. This study will define the chemical, thermal and physical conditions in current and proposed gasifier designs and then modify existing materials and develop new materials to successfully meet the formidable material challenges. Resolving the material challenges of black liquor gasification combined cycle technology will provide energy, environmental, and economic benefits that include higher thermal efficiencies, up to three times greater electrical output per unit of fuel, and lower emissions. In the near term, adoption of this technology will allow the pulp and paper industry greater capital effectiveness and flexibility, as gasifiers are added to increase mill capacity. In the long term, combined-cycle gasification will lessen the industry's environmental impact while increasing its potential for energy production, allowing the production of all the mill's heat and power needs along with surplus electricity being returned to the grid. An added benefit will be the potential elimination of the possibility of smelt-water explosions, which constitute an important safety concern wherever conventional Tomlinson recovery boilers are operated. Developing cost-effective materials with improved performance in gasifier environments may be the best answer to the material challenges presented by black liquor gasification. Refractory materials may be selected/developed that either react with the gasifier environment to form protective

  9. Black Officer Accession and Retention

    Science.gov (United States)

    1980-05-15

    W CO Te im -xinn in dd pepw w dus of drn wdsw aM do 110 rmm nbell ct ts vim of th Depnanmt of Ddna i m y of ift oipmin. Thso0 11m o enmd6 opec...All Don’. Blacks Bla "k Know 1 2 3 4 5 6 7 9 0% 1-197. 20-397. 40-597Z 60-79Y, 80--991, 100Y. 68. COMBINED JUNIOR-SENIOR HIGH (ONE IN WHICH YOU SPENT

  10. Retaining Black Teachers: An Examination of Black Female Teachers' Intentions to Remain in K-12 Classrooms

    Science.gov (United States)

    Farinde, Abiola A.; Allen, Ayana; Lewis, Chance W.

    2016-01-01

    Sixty years after "Brown v. Board of Education," retention trends indicate that there is a Black teacher shortage. Research shows that Black teachers' retention rates are often lower than the retention rates of White teachers. Black teachers report low salaries, lack of administrative support, and other school variables as reasons for…

  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. "Styled by Their Perceptions": Black Adolescent Girls Interpret Representations of Black Females in Popular Culture

    Science.gov (United States)

    Muhammad, Gholnecsar E.; McArthur, Sherell A.

    2015-01-01

    Identity formation is a critical process shaping the lives of adolescents and can present distinct challenges for Black adolescent girls who are positioned in society to negotiate ideals of self when presented with false and incomplete images representing Black girlhood. Researchers have found distorted images of Black femininity derived from…

  13. Exploring the Perceptions of Study Abroad among Black Undergraduates at Historically Black Colleges and Universities

    Science.gov (United States)

    Gaines, Nykia Dionne

    2012-01-01

    International education helps students become more engaged within the United States and abroad. Black undergraduates continue to be underrepresented in study abroad despite two decades of increased enrollment by Black students in higher education in the United States. This study had three purposes: (1) to explore how Black undergraduates attending…

  14. From Black Power to Black Studies: How a Radical Social Movement became an Academic Discipline

    Science.gov (United States)

    Rojas, Fabio

    2007-01-01

    The black power movement helped redefine African Americans' identity and establish a new racial consciousness in the 1960s. As an influential political force, this movement in turn spawned the academic discipline known as Black Studies. Today there are more than a hundred Black Studies degree programs in the United States, many of them located in…

  15. NASA Observatory Confirms Black Hole Limits

    Science.gov (United States)

    2005-02-01

    The very largest black holes reach a certain point and then grow no more, according to the best survey to date of black holes made with NASA's Chandra X-ray Observatory. Scientists have also discovered many previously hidden black holes that are well below their weight limit. These new results corroborate recent theoretical work about how black holes and galaxies grow. The biggest black holes, those with at least 100 million times the mass of the Sun, ate voraciously during the early Universe. Nearly all of them ran out of 'food' billions of years ago and went onto a forced starvation diet. Focus on Black Holes in the Chandra Deep Field North Focus on Black Holes in the Chandra Deep Field North On the other hand, black holes between about 10 and 100 million solar masses followed a more controlled eating plan. Because they took smaller portions of their meals of gas and dust, they continue growing today. "Our data show that some supermassive black holes seem to binge, while others prefer to graze", said Amy Barger of the University of Wisconsin in Madison and the University of Hawaii, lead author of the paper describing the results in the latest issue of The Astronomical Journal (Feb 2005). "We now understand better than ever before how supermassive black holes grow." One revelation is that there is a strong connection between the growth of black holes and the birth of stars. Previously, astronomers had done careful studies of the birthrate of stars in galaxies, but didn't know as much about the black holes at their centers. DSS Optical Image of Lockman Hole DSS Optical Image of Lockman Hole "These galaxies lose material into their central black holes at the same time that they make their stars," said Barger. "So whatever mechanism governs star formation in galaxies also governs black hole growth." Astronomers have made an accurate census of both the biggest, active black holes in the distance, and the relatively smaller, calmer ones closer by. Now, for the first

  16. Spacetime and orbits of bumpy black holes

    International Nuclear Information System (INIS)

    Vigeland, Sarah J.; Hughes, Scott A.

    2010-01-01

    Our Universe contains a great number of extremely compact and massive objects which are generally accepted to be black holes. Precise observations of orbital motion near candidate black holes have the potential to determine if they have the spacetime structure that general relativity demands. As a means of formulating measurements to test the black hole nature of these objects, Collins and Hughes introduced ''bumpy black holes'': objects that are almost, but not quite, general relativity's black holes. The spacetimes of these objects have multipoles that deviate slightly from the black hole solution, reducing to black holes when the deviation is zero. In this paper, we extend this work in two ways. First, we show how to introduce bumps which are smoother and lead to better behaved orbits than those in the original presentation. Second, we show how to make bumpy Kerr black holes--objects which reduce to the Kerr solution when the deviation goes to zero. This greatly extends the astrophysical applicability of bumpy black holes. Using Hamilton-Jacobi techniques, we show how a spacetime's bumps are imprinted on orbital frequencies, and thus can be determined by measurements which coherently track the orbital phase of a small orbiting body. We find that in the weak field, orbits of bumpy black holes are modified exactly as expected from a Newtonian analysis of a body with a prescribed multipolar structure, reproducing well-known results from the celestial mechanics literature. The impact of bumps on strong-field orbits is many times greater than would be predicted from a Newtonian analysis, suggesting that this framework will allow observations to set robust limits on the extent to which a spacetime's multipoles deviate from the black hole expectation.

  17. Wavy strings: Black or bright?

    International Nuclear Information System (INIS)

    Kaloper, N.; Myers, R.C.; Roussel, H.

    1997-01-01

    Recent developments in string theory have brought forth considerable interest in time-dependent hair on extended objects. This novel new hair is typically characterized by a wave profile along the horizon and angular momentum quantum numbers l,m in the transverse space. In this work, we present an extensive treatment of such oscillating black objects, focusing on their geometric properties. We first give a theorem of purely geometric nature, stating that such wavy hair cannot be detected by any scalar invariant built out of the curvature and/or matter fields. However, we show that the tidal forces detected by an infalling observer diverge at the open-quotes horizonclose quotes of a black string superposed with a vibration in any mode with l≥1. The same argument applied to longitudinal (l=0) waves detects only finite leading-order tidal forces. We also provide an example with a manifestly smooth metric, proving that at least a certain class of these longitudinal waves have regular horizons. copyright 1997 The American Physical Society

  18. Gravitating discs around black holes

    International Nuclear Information System (INIS)

    Karas, V; Hure, J-M; Semerak, O

    2004-01-01

    Fluid discs and tori around black holes are discussed within different approaches and with the emphasis on the role of disc gravity. First reviewed are the prospects of investigating the gravitational field of a black hole-disc system using analytical solutions of stationary, axially symmetric Einstein equations. Then, more detailed considerations are focused to the middle and outer parts of extended disc-like configurations where relativistic effects are small and the Newtonian description is adequate. Within general relativity, only a static case has been analysed in detail. Results are often very inspiring. However, simplifying assumptions must be imposed: ad hoc profiles of the disc density are commonly assumed and the effects of frame-dragging are completely lacking. Astrophysical discs (e.g. accretion discs in active galactic nuclei) typically extend far beyond the relativistic domain and are fairly diluted. However, self-gravity is still essential for their structure and evolution, as well as for their radiation emission and the impact on the surrounding environment. For example, a nuclear star cluster in a galactic centre may bear various imprints of mutual star-disc interactions, which can be recognized in observational properties, such as the relation between the central mass and stellar velocity dispersion. (topical review)

  19. Superluminality, black holes and EFT

    Energy Technology Data Exchange (ETDEWEB)

    Goon, Garrett [Department of Applied Mathematics and Theoretical Physics,Cambridge University, Cambridge, CB3 0WA (United Kingdom); Hinterbichler, Kurt [CERCA, Department of Physics, Case Western Reserve University,10900 Euclid Ave, Cleveland, OH 44106 (United States)

    2017-02-27

    Under the assumption that a UV theory does not display superluminal behavior, we ask what constraints on superluminality are satisfied in the effective field theory (EFT). We study two examples of effective theories: quantum electrodynamics (QED) coupled to gravity after the electron is integrated out, and the flat-space galileon. The first is realized in nature, the second is more speculative, but they both exhibit apparent superluminality around non-trivial backgrounds. In the QED case, we attempt, and fail, to find backgrounds for which the superluminal signal advance can be made larger than the putative resolving power of the EFT. In contrast, in the galileon case it is easy to find such backgrounds, indicating that if the UV completion of the galileon is (sub)luminal, quantum corrections must become important at distance scales of order the Vainshtein radius of the background configuration, much larger than the naive EFT strong coupling distance scale. Such corrections would be reminiscent of the non-perturbative Schwarzschild scale quantum effects that are expected to resolve the black hole information problem. Finally, a byproduct of our analysis is a calculation of how perturbative quantum effects alter charged Reissner-Nordstrom black holes.

  20. Quantum criticality and black holes.

    Science.gov (United States)

    Sachdev, Subir; Müller, Markus

    2009-04-22

    Many condensed matter experiments explore the finite temperature dynamics of systems near quantum critical points. Often, there are no well-defined quasiparticle excitations, and so quantum kinetic equations do not describe the transport properties completely. The theory shows that the transport coefficients are not proportional to a mean free scattering time (as is the case in the Boltzmann theory of quasiparticles), but are completely determined by the absolute temperature and by equilibrium thermodynamic observables. Recently, explicit solutions of this quantum critical dynamics have become possible via the anti-de Sitter/conformal field theory duality discovered in string theory. This shows that the quantum critical theory provides a holographic description of the quantum theory of black holes in a negatively curved anti-de Sitter space, and relates its transport coefficients to properties of the Hawking radiation from the black hole. We review how insights from this connection have led to new results for experimental systems: (i) the vicinity of the superfluid-insulator transition in the presence of an applied magnetic field, and its possible application to measurements of the Nernst effect in the cuprates, (ii) the magnetohydrodynamics of the plasma of Dirac electrons in graphene and the prediction of a hydrodynamic cyclotron resonance.

  1. Emissions & Measurements - Black Carbon | Science ...

    Science.gov (United States)

    Emissions and Measurement (EM) research activities performed within the National Risk Management Research Lab NRMRL) of EPA's Office of Research and Development (ORD) support measurement and laboratory analysis approaches to accurately characterize source emissions, and near source concentrations of air pollutants. They also support integrated Agency research programs (e.g., source to health outcomes) and the development of databases and inventories that assist Federal, state, and local air quality managers and industry implement and comply with air pollution standards. EM research underway in NRMRL supports the Agency's efforts to accurately characterize, analyze, measure and manage sources of air pollution. This pamphlet focuses on the EM research that NRMRL researchers conduct related to black carbon (BC). Black Carbon is a pollutant of concern to EPA due to its potential impact on human health and climate change. There are extensive uncertainties in emissions of BC from stationary and mobile sources. Emissions and Measurement (EM) research activities performed within the National Risk Management Research Lab NRMRL) of EPA's Office of Research and Development (ORD)

  2. Black branes in flux compactifications

    Energy Technology Data Exchange (ETDEWEB)

    Torroba, Gonzalo; Wang, Huajia

    2013-10-01

    We construct charged black branes in type IIA flux compactifications that are dual to (2 + 1)-dimensional field theories at finite density. The internal space is a general Calabi-Yau manifold with fluxes, with internal dimensions much smaller than the AdS radius. Gauge fields descend from the 3-form RR potential evaluated on harmonic forms of the Calabi-Yau, and Kaluza-Klein modes decouple. Black branes are described by a four-dimensional effective field theory that includes only a few light fields and is valid over a parametrically large range of scales. This effective theory determines the low energy dynamics, stability and thermodynamic properties. Tools from flux compactifications are also used to construct holographic CFTs with no relevant scalar operators, that can lead to symmetric phases of condensed matter systems stable to very low temperatures. The general formalism is illustrated with simple examples such as toroidal compactifications and manifolds with a single size modulus. We initiate the classification of holographic phases of matter described by flux compactifications, which include generalized Reissner-Nordstrom branes, nonsupersymmetric AdS2×R2 and hyperscaling violating solutions.

  3. Refractory for Black Liquor Gasifiers

    Energy Technology Data Exchange (ETDEWEB)

    William L. Headrick Jr; Alireza Rezaie; Xiaoting Liang; Musa Karakus; Jun Wei

    2005-12-01

    The University of Missouri-Rolla identified materials that permit the safe, reliable and economical operation of combined cycle gasifiers by the pulp and paper industry. The primary emphasis of this project was to resolve the material problems encountered during the operation of low-pressure high-temperature (LPHT) and low-pressure low-temperature (LPLT) gasifiers while simultaneously understanding the materials barriers to the successful demonstration of high-pressure high-temperature (HPHT) black liquor gasifiers. This study attempted to define the chemical, thermal and physical conditions in current and proposed gasifier designs and then modify existing materials and develop new materials to successfully meet the formidable material challenges. Resolving the material challenges of black liquor gasification combined cycle technology will provide energy, environmental, and economic benefits that include higher thermal efficiencies, up to three times greater electrical output per unit of fuel, and lower emissions. In the near term, adoption of this technology will allow the pulp and paper industry greater capital effectiveness and flexibility, as gasifiers are added to increase mill capacity. In the long term, combined-cycle gasification will lessen the industry's environmental impact while increasing its potential for energy production, allowing the production of all the mill's heat and power needs along with surplus electricity being returned to the grid. An added benefit will be the potential elimination of the possibility of smelt-water explosions, which constitute an important safety concern wherever conventional Tomlinson recovery boilers are operated. Developing cost-effective materials with improved performance in gasifier environments may be the best answer to the material challenges presented by black liquor gasification. Refractory materials were selected or developed that reacted with the gasifier environment to form protective surfaces in

  4. Refractory for Black Liquor Gasifiers

    Energy Technology Data Exchange (ETDEWEB)

    William L. Headrick Jr; Musa Karakus; Xiaoting Liang

    2005-10-01

    The University of Missouri-Rolla identified materials that permit the safe, reliable and economical operation of combined cycle gasifiers by the pulp and paper industry. The primary emphasis of this project was to resolve the material problems encountered during the operation of low-pressure high-temperature (LPHT) and low-pressure low-temperature (LPLT) gasifiers while simultaneously understanding the materials barriers to the successful demonstration of high-pressure high-temperature (HPHT) black liquor gasifiers. This study attempted to define the chemical, thermal and physical conditions in current and proposed gasifier designs and then modify existing materials and develop new materials to successfully meet the formidable material challenges. Resolving the material challenges of black liquor gasification combined cycle technology will provide energy, environmental, and economic benefits that include higher thermal efficiencies, up to three times greater electrical output per unit of fuel, and lower emissions. In the near term, adoption of this technology will allow the pulp and paper industry greater capital effectiveness and flexibility, as gasifiers are added to increase mill capacity. In the long term, combined-cycle gasification will lessen the industry's environmental impact while increasing its potential for energy production, allowing the production of all the mill's heat and power needs along with surplus electricity being returned to the grid. An added benefit will be the potential elimination of the possibility of smelt-water explosions, which constitute an important safety concern wherever conventional Tomlinson recovery boilers are operated. Developing cost-effective materials with improved performance in gasifier environments may be the best answer to the material challenges presented by black liquor gasification. Refractory materials were selected/developed that either react with the gasifier environment to form protective surfaces in

  5. Refractory for Black Liquor Gasifiers

    Energy Technology Data Exchange (ETDEWEB)

    William L. Headrick; Musa Karakus; Alireza Rezaie

    2004-03-30

    The University of Missouri-Rolla will identify materials that will permit the safe, reliable and economical operation of combined cycle gasifiers by the pulp and paper industry. The primary emphasis of this project will be to resolve the material problems encountered during the operation of low-pressure high-temperature (LPHT) and low-pressure low-temperature (LPLT) gasifiers while simultaneously understanding the materials barriers to the successful demonstration of high-pressure high-temperature (HPHT) black liquor gasifiers. This study will define the chemical, thermal and physical conditions in current and proposed gasifier designs and then modify existing materials and develop new materials to successfully meet the formidable material challenges. Resolving the material challenges of black liquor gasification combined cycle technology will provide energy, environmental, and economic benefits that include higher thermal efficiencies, up to three times greater electrical output per unit of fuel, and lower emissions. In the near term, adoption of this technology will allow the pulp and paper industry greater capital effectiveness and flexibility, as gasifiers are added to increase mill capacity. In the long term, combined-cycle gasification will lessen the industry's environmental impact while increasing its potential for energy production, allowing the production of all the mill's heat and power needs along with surplus electricity being returned to the grid. An added benefit will be the potential elimination of the possibility of smelt-water explosions, which constitute an important safety concern wherever conventional Tomlinson recovery boilers are operated. Developing cost-effective materials with improved performance in gasifier environments may be the best answer to the material challenges presented by black liquor gasification. Refractory materials may be selected/developed that either react with the gasifier environment to form protective

  6. REFRACTORY FOR BLACK LIQUOR GASIFIERS

    Energy Technology Data Exchange (ETDEWEB)

    William L. Headrick Jr; Musa Karakus; Xiaoting Liang; Alireza Rezaie

    2004-07-01

    The University of Missouri-Rolla will identify materials that will permit the safe, reliable and economical operation of combined cycle gasifiers by the pulp and paper industry. The primary emphasis of this project will be to resolve the material problems encountered during the operation of low-pressure high-temperature (LPHT) and low-pressure low-temperature (LPLT) gasifiers while simultaneously understanding the materials barriers to the successful demonstration of high-pressure high-temperature (HPHT) black liquor gasifiers. This study will define the chemical, thermal and physical conditions in current and proposed gasifier designs and then modify existing materials and develop new materials to successfully meet the formidable material challenges. Resolving the material challenges of black liquor gasification combined cycle technology will provide energy, environmental, and economic benefits that include higher thermal efficiencies, up to three times greater electrical output per unit of fuel, and lower emissions. In the near term, adoption of this technology will allow the pulp and paper industry greater capital effectiveness and flexibility, as gasifiers are added to increase mill capacity. In the long term, combined-cycle gasification will lessen the industry's environmental impact while increasing its potential for energy production, allowing the production of all the mill's heat and power needs along with surplus electricity being returned to the grid. An added benefit will be the potential elimination of the possibility of smelt-water explosions, which constitute an important safety concern wherever conventional Tomlinson recovery boilers are operated. Developing cost-effective materials with improved performance in gasifier environments may be the best answer to the material challenges presented by black liquor gasification. Refractory materials may be selected/developed that either react with the gasifier environment to form protective

  7. REFRACTORY FOR BLACK LIQUOR GASIFIERS

    Energy Technology Data Exchange (ETDEWEB)

    William L. Headrick Jr; Musa Karakus; Xiaoting Liang; Alireza Rezaie

    2004-10-01

    The University of Missouri-Rolla will identify materials that will permit the safe, reliable and economical operation of combined cycle gasifiers by the pulp and paper industry. The primary emphasis of this project will be to resolve the material problems encountered during the operation of low-pressure high-temperature (LPHT) and low-pressure low-temperature (LPLT) gasifiers while simultaneously understanding the materials barriers to the successful demonstration of high-pressure high-temperature (HPHT) black liquor gasifiers. This study will define the chemical, thermal and physical conditions in current and proposed gasifier designs and then modify existing materials and develop new materials to successfully meet the formidable material challenges. Resolving the material challenges of black liquor gasification combined cycle technology will provide energy, environmental, and economic benefits that include higher thermal efficiencies, up to three times greater electrical output per unit of fuel, and lower emissions. In the near term, adoption of this technology will allow the pulp and paper industry greater capital effectiveness and flexibility, as gasifiers are added to increase mill capacity. In the long term, combined-cycle gasification will lessen the industry's environmental impact while increasing its potential for energy production, allowing the production of all the mill's heat and power needs along with surplus electricity being returned to the grid. An added benefit will be the potential elimination of the possibility of smelt-water explosions, which constitute an important safety concern wherever conventional Tomlinson recovery boilers are operated. Developing cost-effective materials with improved performance in gasifier environments may be the best answer to the material challenges presented by black liquor gasification. Refractory materials may be selected/developed that either react with the gasifier environment to form protective

  8. REFRACTORY FOR BLACK LIQUOR GASIFIERS

    Energy Technology Data Exchange (ETDEWEB)

    William L. Headrick Jr; Musa Karakus; Xiaoting Liang; Jun Wei

    2005-01-01

    The University of Missouri-Rolla will identify materials that will permit the safe, reliable and economical operation of combined cycle gasifiers by the pulp and paper industry. The primary emphasis of this project will be to resolve the material problems encountered during the operation of low-pressure high-temperature (LPHT) and low-pressure low-temperature (LPLT) gasifiers while simultaneously understanding the materials barriers to the successful demonstration of high-pressure high-temperature (HPHT) black liquor gasifiers. This study will define the chemical, thermal and physical conditions in current and proposed gasifier designs and then modify existing materials and develop new materials to successfully meet the formidable material challenges. Resolving the material challenges of black liquor gasification combined cycle technology will provide energy, environmental, and economic benefits that include higher thermal efficiencies, up to three times greater electrical output per unit of fuel, and lower emissions. In the near term, adoption of this technology will allow the pulp and paper industry greater capital effectiveness and flexibility, as gasifiers are added to increase mill capacity. In the long term, combined-cycle gasification will lessen the industry's environmental impact while increasing its potential for energy production, allowing the production of all the mill's heat and power needs along with surplus electricity being returned to the grid. An added benefit will be the potential elimination of the possibility of smelt-water explosions, which constitute an important safety concern wherever conventional Tomlinson recovery boilers are operated. Developing cost-effective materials with improved performance in gasifier environments may be the best answer to the material challenges presented by black liquor gasification. Refractory materials may be selected/developed that either react with the gasifier environment to form protective

  9. REFRACTORY FOR BLACK LIQUOR GASIFIERS

    Energy Technology Data Exchange (ETDEWEB)

    William L. Headrick Jr; Musa Karakus; Xiaoting Liang; Jun Wei

    2005-04-01

    The University of Missouri-Rolla will identify materials that will permit the safe, reliable and economical operation of combined cycle gasifiers by the pulp and paper industry. The primary emphasis of this project will be to resolve the material problems encountered during the operation of low-pressure high-temperature (LPHT) and low-pressure low-temperature (LPLT) gasifiers while simultaneously understanding the materials barriers to the successful demonstration of high-pressure high-temperature (HPHT) black liquor gasifiers. This study will define the chemical, thermal and physical conditions in current and proposed gasifier designs and then modify existing materials and develop new materials to successfully meet the formidable material challenges. Resolving the material challenges of black liquor gasification combined cycle technology will provide energy, environmental, and economic benefits that include higher thermal efficiencies, up to three times greater electrical output per unit of fuel, and lower emissions. In the near term, adoption of this technology will allow the pulp and paper industry greater capital effectiveness and flexibility, as gasifiers are added to increase mill capacity. In the long term, combined-cycle gasification will lessen the industry's environmental impact while increasing its potential for energy production, allowing the production of all the mill's heat and power needs along with surplus electricity being returned to the grid. An added benefit will be the potential elimination of the possibility of smelt-water explosions, which constitute an important safety concern wherever conventional Tomlinson recovery boilers are operated. Developing cost-effective materials with improved performance in gasifier environments may be the best answer to the material challenges presented by black liquor gasification. Refractory materials may be selected/developed that either react with the gasifier environment to form protective

  10. REFRACTORY FOR BLACK LIQUOR GASIFIERS

    Energy Technology Data Exchange (ETDEWEB)

    William L. Headrick Jr; Musa Karakus; Xiaoting Liang

    2005-07-01

    The University of Missouri-Rolla will identify materials that will permit the safe, reliable and economical operation of combined cycle gasifiers by the pulp and paper industry. The primary emphasis of this project will be to resolve the material problems encountered during the operation of low-pressure high-temperature (LPHT) and low-pressure low-temperature (LPLT) gasifiers while simultaneously understanding the materials barriers to the successful demonstration of high-pressure high-temperature (HPHT) black liquor gasifiers. This study will define the chemical, thermal and physical conditions in current and proposed gasifier designs and then modify existing materials and develop new materials to successfully meet the formidable material challenges. Resolving the material challenges of black liquor gasification combined cycle technology will provide energy, environmental, and economic benefits that include higher thermal efficiencies, up to three times greater electrical output per unit of fuel, and lower emissions. In the near term, adoption of this technology will allow the pulp and paper industry greater capital effectiveness and flexibility, as gasifiers are added to increase mill capacity. In the long term, combined-cycle gasification will lessen the industry's environmental impact while increasing its potential for energy production, allowing the production of all the mill's heat and power needs along with surplus electricity being returned to the grid. An added benefit will be the potential elimination of the possibility of smelt-water explosions, which constitute an important safety concern wherever conventional Tomlinson recovery boilers are operated. Developing cost-effective materials with improved performance in gasifier environments may be the best answer to the material challenges presented by black liquor gasification. Refractory materials may be selected/developed that either react with the gasifier environment to form protective

  11. REFRACTORY FOR BLACK LIQUOR GASIFIERS

    Energy Technology Data Exchange (ETDEWEB)

    William L. Headrick Jr.; Alireza Rezaie

    2004-04-01

    The University of Missouri-Rolla will identify materials that will permit the safe, reliable and economical operation of combined cycle gasifiers by the pulp and paper industry. The primary emphasis of this project will be to resolve the materials problems encountered during the operation of low-pressure high-temperature (LPHT) and low-pressure low-temperature (LPLT) gasifiers while simultaneously understanding the materials barriers to the successful demonstration of high-pressure high-temperature (HPHT) black liquor gasifiers. This study will define the chemical, thermal and physical conditions in current and proposed gasifier designs and then modify existing materials and develop new materials to successfully meet the formidable material challenges. Resolving the material challenges of black liquor gasification combined cycle technology will provide energy, environmental, and economic benefits that include higher thermal efficiencies, up to three times greater electrical output per unit of fuel, and lower emissions. In the near term, adoption of this technology will allow the pulp and paper industry greater capital effectiveness and flexibility, as gasifiers are added to increase mill capacity. In the long term, combined-cycle gasification will lessen the industry's environmental impact while increasing its potential for energy production, allowing the production of all the mill's heat and power needs along with surplus electricity being returned to the grid. An added benefit will be the potential elimination of the possibility of smelt-water explosions, which constitute an important safety concern wherever conventional Tomlinson recovery boilers are operated. Developing cost-effective materials with improved performance in gasifier environments may be the best answer to the material challenges presented by black liquor gasification. Refractory materials may be selected/developed that either react with the gasifier environment to form protective

  12. REFRACTORY FOR BLACK LIQUOR GASIFIERS

    Energy Technology Data Exchange (ETDEWEB)

    William L. Headrick Jr.; Alireza Rezaie

    2003-12-01

    The University of Missouri-Rolla will identify materials that will permit the safe, reliable and economical operation of combined cycle gasifiers by the pulp and paper industry. The primary emphasis of this project will be to resolve the materials problems encountered during the operation of low-pressure high-temperature (LFHT) and low-pressure low-temperature (LPLT) gasifiers while simultaneously understanding the materials barriers to the successful demonstration of high-pressure high-temperature (HPHT) black liquor gasifiers. This study will define the chemical, thermal and physical conditions in current and proposed gasifier designs and then modify existing materials and develop new materials to successfully meet the formidable material challenges. Resolving the material challenges of black liquor gasification combined cycle technology will provide energy, environmental, and economic benefits that include higher thermal efficiencies, up to three times greater electrical output per unit of fuel, and lower emissions. In the near term, adoption of this technology will allow the pulp and paper industry greater capital effectiveness and flexibility, as gasifiers are added to increase mill capacity. In the long term, combined-cycle gasification will lessen the industry's environmental impact while increasing its potential for energy production, allowing the production of all the mill's heat and power needs along with surplus electricity being returned to the grid. An added benefit will be the potential elimination of the possibility of smelt-water explosions, which constitute an important safety concern wherever conventional Tomlinson recovery boilers are operated. Developing cost-effective materials with improved performance in gasifier environments may be the best answer to the material challenges presented by black liquor gasification. Refractory materials may be selected/developed that either react with the gasifier environment to form protective

  13. Short communications: The Southern Black Tit Melaniparus niger in ...

    African Journals Online (AJOL)

    Short communications: The Southern Black Tit Melaniparus niger in Tanzania with comments on the Northern Black Tit M. leucomelas , White-shouldered Black Tit M. guineensis and the White-bellied Tit M. albiventris.

  14. Rotating embedded black holes: Entropy and Hawking's radiation

    OpenAIRE

    Ibohal, Ng

    2004-01-01

    In this paper we derive a class of rotating embedded black holes. Then we study Hawking's radiation effects on these embedded black holes. The surface gravity, entropy and angular velocity are given for each of these black holes.

  15. Low-mass black holes as the remnants of primordial black hole formation

    OpenAIRE

    Greene, Jenny E.

    2012-01-01

    This article documents our ongoing search for the elusive "intermediate-mass" black holes. These would bridge the gap between the approximately ten solar mass "stellar-mass" black holes that are the end-product of the life of a massive star, and the "supermassive" black holes with masses of millions to billions of solar masses found at the centers of massive galaxies. The discovery of black holes with intermediate mass is the key to understanding whether supermassive black holes can grow from...

  16. How Black women make sense of 'White' and 'Black' fashion magazines: a qualitative think aloud study.

    Science.gov (United States)

    Ogden, Jane; Russell, Sheriden

    2013-12-01

    This qualitative think aloud study explored how Black women (n = 32) processed information from a White or Black fashion magazine. Comments to the 'White' magazine were characterised by rejection, being critical of the media and ambivalence, whereas they responded to the 'Black' magazine with celebration, identification and a search for depth. Transcending these themes was their self-identity of being a Black woman that was brought to the fore either by a sense of exclusion (White magazine) or engagement (Black magazine). Such an identity provides resilience against the media's thin ideals by minimising the processes of social comparison and internalisation.

  17. Rholography, black holes and Scherk-Schwarz

    NARCIS (Netherlands)

    Gaddam, Nava; Gnecchi, Alessandra; Vandoren, Stefan; Varela, Oscar

    2015-01-01

    We present a construction of a class of near-extremal asymptotically flat black hole solutions in four (or five) dimensional gauged supergravity with R-symmetry gaugings obtained from Scherk-Schwarz reductions on a circle. The entropy of these black holes is counted holographically by the well known

  18. Blacks in Pop Music: A Short Story.

    Science.gov (United States)

    Rickelman, Melinda

    1991-01-01

    A short history of black pop music includes artists who have changed pop music or culture and highlights from the 1920s into the 1980s, from Fats Waller to Michael Jackson. In black pop music, there is a direct line of influence from the sharecropper to the current Top 40. (SLD)

  19. Messinian events in the Black Sea

    NARCIS (Netherlands)

    van Baak, Christiaan G C; Radionova, Eleanora P.; Golovina, Larisa A.; Raffi, Isabella; Kuiper, Klaudia F.; Vasiliev, Iuliana; Krijgsman, Wout

    2015-01-01

    Past hydrological interactions between the Mediterranean Sea and Black Sea are poorly resolved due to complications in establishing a high-resolution time frame for the Black Sea. We present a new greigite-based magnetostratigraphic age model for the Mio-Pliocene deposits of DSDP Hole 380/380A,

  20. Nonisolated dynamic black holes and white holes

    International Nuclear Information System (INIS)

    McClure, M. L.; Anderson, Kaem; Bardahl, Kirk

    2008-01-01

    Modifying the Kerr-Schild transformation used to generate black and white hole spacetimes, new dynamic black and white holes are obtained using a time-dependent Kerr-Schild scalar field. Physical solutions are found for black holes that shrink with time and for white holes that expand with time. The black hole spacetimes are physical only in the vicinity of the black hole, with the physical region increasing in radius with time. The white hole spacetimes are physical throughout. Unlike the standard Schwarzschild solution the singularities are nonisolated, since the time dependence introduces a mass-energy distribution. The surfaces in the metrics where g tt =g rr =0 are dynamic, moving inward with time for the black holes and outward for the white holes, which leads to a question of whether these spacetimes truly have event horizons--a problem shared with Vaidya's cosmological black hole spacetimes. By finding a surface that shrinks or expands at the same rate as the null geodesics move, and within which null geodesics move inward or outward faster than the surfaces shrink or expand, respectively, it is verified that these do in fact behave like black and white holes