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A mass of less than 15 solar masses for the black hole in an ultraluminous X-ray source

Nature - Wed, 10/08/2014 - 00:00

A mass of less than 15 solar masses for the black hole in an ultraluminous X-ray source

Nature 514, 7521 (2014). doi:10.1038/nature13730

Authors: C. Motch, M. W. Pakull, R. Soria, F. Grisé & G. Pietrzyński

Most ultraluminous X-ray sources have a typical set of properties not seen in Galactic stellar-mass black holes. They have luminosities of more than 3 × 1039 ergs per second, unusually soft X-ray components (with a typical temperature of less than about 0.3 kiloelectronvolts) and a characteristic downturn in their spectra above about 5 kiloelectronvolts. Such puzzling properties have been interpreted either as evidence of intermediate-mass black holes or as emission from stellar-mass black holes accreting above their Eddington limit, analogous to some Galactic black holes at peak luminosity. Recently, a very soft X-ray spectrum was observed in a rare and transient stellar-mass black hole. Here we report that the X-ray source P13 in the galaxy NGC 7793 is in a binary system with a period of about 64 days and exhibits all three canonical properties of ultraluminous sources. By modelling the strong optical and ultraviolet modulations arising from X-ray heating of the B9Ia donor star, we constrain the black hole mass to be less than 15 solar masses. Our results demonstrate that in P13, soft thermal emission and spectral curvature are indeed signatures of supercritical accretion. By analogy, ultraluminous X-ray sources with similar X-ray spectra and luminosities of up to a few times 1040 ergs per second can be explained by supercritical accretion onto massive stellar-mass black holes.

Categories: Literature

An ultraluminous X-ray source powered by an accreting neutron star

Nature - Wed, 10/08/2014 - 00:00

An ultraluminous X-ray source powered by an accreting neutron star

Nature 514, 7521 (2014). doi:10.1038/nature13791

Authors: M. Bachetti, F. A. Harrison, D. J. Walton, B. W. Grefenstette, D. Chakrabarty, F. Fürst, D. Barret, A. Beloborodov, S. E. Boggs, F. E. Christensen, W. W. Craig, A. C. Fabian, C. J. Hailey, A. Hornschemeier, V. Kaspi, S. R. Kulkarni, T. Maccarone, J. M. Miller, V. Rana, D. Stern, S. P. Tendulkar, J. Tomsick, N. A. Webb & W. W. Zhang

The majority of ultraluminous X-ray sources are point sources that are spatially offset from the nuclei of nearby galaxies and whose X-ray luminosities exceed the theoretical maximum for spherical infall (the Eddington limit) onto stellar-mass black holes. Their X-ray luminosities in the 0.5–10 kiloelectronvolt energy band range from 1039 to 1041 ergs per second. Because higher masses imply less extreme ratios of the luminosity to the isotropic Eddington limit, theoretical models have focused on black hole rather than neutron star systems. The most challenging sources to explain are those at the luminous end of the range (more than 1040 ergs per second), which require black hole masses of 50–100 times the solar value or significant departures from the standard thin disk accretion that powers bright Galactic X-ray binaries, or both. Here we report broadband X-ray observations of the nuclear region of the galaxy M82 that reveal pulsations with an average period of 1.37 seconds and a 2.5-day sinusoidal modulation. The pulsations result from the rotation of a magnetized neutron star, and the modulation arises from its binary orbit. The pulsed flux alone corresponds to an X-ray luminosity in the 3–30 kiloelectronvolt range of 4.9 × 1039 ergs per second. The pulsating source is spatially coincident with a variable source that can reach an X-ray luminosity in the 0.3–10 kiloelectronvolt range of 1.8 × 1040 ergs per second. This association implies a luminosity of about 100 times the Eddington limit for a 1.4-solar-mass object, or more than ten times brighter than any known accreting pulsar. This implies that neutron stars may not be rare in the ultraluminous X-ray population, and it challenges physical models for the accretion of matter onto magnetized compact objects.

Categories: Literature

An ultraluminous X-ray source powered by an accreting neutron star

Nature - Wed, 10/08/2014 - 00:00

An ultraluminous X-ray source powered by an accreting neutron star

Nature 514, 7521 (2014). doi:10.1038/nature13791

Authors: M. Bachetti, F. A. Harrison, D. J. Walton, B. W. Grefenstette, D. Chakrabarty, F. Fürst, D. Barret, A. Beloborodov, S. E. Boggs, F. E. Christensen, W. W. Craig, A. C. Fabian, C. J. Hailey, A. Hornschemeier, V. Kaspi, S. R. Kulkarni, T. Maccarone, J. M. Miller, V. Rana, D. Stern, S. P. Tendulkar, J. Tomsick, N. A. Webb & W. W. Zhang

The majority of ultraluminous X-ray sources are point sources that are spatially offset from the nuclei of nearby galaxies and whose X-ray luminosities exceed the theoretical maximum for spherical infall (the Eddington limit) onto stellar-mass black holes. Their X-ray luminosities in the 0.5–10 kiloelectronvolt energy band range from 1039 to 1041 ergs per second. Because higher masses imply less extreme ratios of the luminosity to the isotropic Eddington limit, theoretical models have focused on black hole rather than neutron star systems. The most challenging sources to explain are those at the luminous end of the range (more than 1040 ergs per second), which require black hole masses of 50–100 times the solar value or significant departures from the standard thin disk accretion that powers bright Galactic X-ray binaries, or both. Here we report broadband X-ray observations of the nuclear region of the galaxy M82 that reveal pulsations with an average period of 1.37 seconds and a 2.5-day sinusoidal modulation. The pulsations result from the rotation of a magnetized neutron star, and the modulation arises from its binary orbit. The pulsed flux alone corresponds to an X-ray luminosity in the 3–30 kiloelectronvolt range of 4.9 × 1039 ergs per second. The pulsating source is spatially coincident with a variable source that can reach an X-ray luminosity in the 0.3–10 kiloelectronvolt range of 1.8 × 1040 ergs per second. This association implies a luminosity of about 100 times the Eddington limit for a 1.4-solar-mass object, or more than ten times brighter than any known accreting pulsar. This implies that neutron stars may not be rare in the ultraluminous X-ray population, and it challenges physical models for the accretion of matter onto magnetized compact objects.

Categories: Literature

Vibrational spectroscopy in the electron microscope

Nature - Wed, 10/08/2014 - 00:00

Vibrational spectroscopy in the electron microscope

Nature 514, 7521 (2014). doi:10.1038/nature13870

Authors: Ondrej L. Krivanek, Tracy C. Lovejoy, Niklas Dellby, Toshihiro Aoki, R. W. Carpenter, Peter Rez, Emmanuel Soignard, Jiangtao Zhu, Philip E. Batson, Maureen J. Lagos, Ray F. Egerton & Peter A. Crozier

Vibrational spectroscopies using infrared radiation, Raman scattering, neutrons, low-energy electrons and inelastic electron tunnelling are powerful techniques that can analyse bonding arrangements, identify chemical compounds and probe many other important properties of materials. The spatial resolution of these spectroscopies is typically one micrometre or more, although it can reach a few tens of nanometres or even a few ångströms when enhanced by the presence of a sharp metallic tip. If vibrational spectroscopy could be combined with the spatial resolution and flexibility of the transmission electron microscope, it would open up the study of vibrational modes in many different types of nanostructures. Unfortunately, the energy resolution of electron energy loss spectroscopy performed in the electron microscope has until now been too poor to allow such a combination. Recent developments that have improved the attainable energy resolution of electron energy loss spectroscopy in a scanning transmission electron microscope to around ten millielectronvolts now allow vibrational spectroscopy to be carried out in the electron microscope. Here we describe the innovations responsible for the progress, and present examples of applications in inorganic and organic materials, including the detection of hydrogen. We also demonstrate that the vibrational signal has both high- and low-spatial-resolution components, that the first component can be used to map vibrational features at nanometre-level resolution, and that the second component can be used for analysis carried out with the beam positioned just outside the sample—that is, for ‘aloof’ spectroscopy that largely avoids radiation damage.

Categories: Literature

Vibrational spectroscopy in the electron microscope

Nature - Wed, 10/08/2014 - 00:00

Vibrational spectroscopy in the electron microscope

Nature 514, 7521 (2014). doi:10.1038/nature13870

Authors: Ondrej L. Krivanek, Tracy C. Lovejoy, Niklas Dellby, Toshihiro Aoki, R. W. Carpenter, Peter Rez, Emmanuel Soignard, Jiangtao Zhu, Philip E. Batson, Maureen J. Lagos, Ray F. Egerton & Peter A. Crozier

Vibrational spectroscopies using infrared radiation, Raman scattering, neutrons, low-energy electrons and inelastic electron tunnelling are powerful techniques that can analyse bonding arrangements, identify chemical compounds and probe many other important properties of materials. The spatial resolution of these spectroscopies is typically one micrometre or more, although it can reach a few tens of nanometres or even a few ångströms when enhanced by the presence of a sharp metallic tip. If vibrational spectroscopy could be combined with the spatial resolution and flexibility of the transmission electron microscope, it would open up the study of vibrational modes in many different types of nanostructures. Unfortunately, the energy resolution of electron energy loss spectroscopy performed in the electron microscope has until now been too poor to allow such a combination. Recent developments that have improved the attainable energy resolution of electron energy loss spectroscopy in a scanning transmission electron microscope to around ten millielectronvolts now allow vibrational spectroscopy to be carried out in the electron microscope. Here we describe the innovations responsible for the progress, and present examples of applications in inorganic and organic materials, including the detection of hydrogen. We also demonstrate that the vibrational signal has both high- and low-spatial-resolution components, that the first component can be used to map vibrational features at nanometre-level resolution, and that the second component can be used for analysis carried out with the beam positioned just outside the sample—that is, for ‘aloof’ spectroscopy that largely avoids radiation damage.

Categories: Literature

Pleistocene cave art from Sulawesi, Indonesia

Nature - Wed, 10/08/2014 - 00:00

Pleistocene cave art from Sulawesi, Indonesia

Nature 514, 7521 (2014). doi:10.1038/nature13422

Authors: M. Aubert, A. Brumm, M. Ramli, T. Sutikna, E. W. Saptomo, B. Hakim, M. J. Morwood, G. D. van den Bergh, L. Kinsley & A. Dosseto

Archaeologists have long been puzzled by the appearance in Europe ∼40–35 thousand years (kyr) ago of a rich corpus of sophisticated artworks, including parietal art (that is, paintings, drawings and engravings on immobile rock surfaces) and portable art (for example, carved figurines), and the absence or scarcity of equivalent, well-dated evidence elsewhere, especially along early human migration routes in South Asia and the Far East, including Wallacea and Australia, where modern humans (Homo sapiens) were established by 50 kyr ago. Here, using uranium-series dating of coralloid speleothems directly associated with 12 human hand stencils and two figurative animal depictions from seven cave sites in the Maros karsts of Sulawesi, we show that rock art traditions on this Indonesian island are at least compatible in age with the oldest European art. The earliest dated image from Maros, with a minimum age of 39.9 kyr, is now the oldest known hand stencil in the world. In addition, a painting of a babirusa (‘pig-deer’) made at least 35.4 kyr ago is among the earliest dated figurative depictions worldwide, if not the earliest one. Among the implications, it can now be demonstrated that humans were producing rock art by ∼40 kyr ago at opposite ends of the Pleistocene Eurasian world.

Categories: Literature

Pleistocene cave art from Sulawesi, Indonesia

Nature - Wed, 10/08/2014 - 00:00

Pleistocene cave art from Sulawesi, Indonesia

Nature 514, 7521 (2014). doi:10.1038/nature13422

Authors: M. Aubert, A. Brumm, M. Ramli, T. Sutikna, E. W. Saptomo, B. Hakim, M. J. Morwood, G. D. van den Bergh, L. Kinsley & A. Dosseto

Archaeologists have long been puzzled by the appearance in Europe ∼40–35 thousand years (kyr) ago of a rich corpus of sophisticated artworks, including parietal art (that is, paintings, drawings and engravings on immobile rock surfaces) and portable art (for example, carved figurines), and the absence or scarcity of equivalent, well-dated evidence elsewhere, especially along early human migration routes in South Asia and the Far East, including Wallacea and Australia, where modern humans (Homo sapiens) were established by 50 kyr ago. Here, using uranium-series dating of coralloid speleothems directly associated with 12 human hand stencils and two figurative animal depictions from seven cave sites in the Maros karsts of Sulawesi, we show that rock art traditions on this Indonesian island are at least compatible in age with the oldest European art. The earliest dated image from Maros, with a minimum age of 39.9 kyr, is now the oldest known hand stencil in the world. In addition, a painting of a babirusa (‘pig-deer’) made at least 35.4 kyr ago is among the earliest dated figurative depictions worldwide, if not the earliest one. Among the implications, it can now be demonstrated that humans were producing rock art by ∼40 kyr ago at opposite ends of the Pleistocene Eurasian world.

Categories: Literature

Protein competition switches the function of COP9 from self-renewal to differentiation

Nature - Wed, 10/08/2014 - 00:00

Protein competition switches the function of COP9 from self-renewal to differentiation

Nature 514, 7521 (2014). doi:10.1038/nature13562

Authors: Lei Pan, Su Wang, Tinglin Lu, Changjiang Weng, Xiaoqing Song, Joseph K. Park, Jin Sun, Zhi-Hao Yang, Junjing Yu, Hong Tang, Dennis M. McKearin, Daniel A. Chamovitz, Jianquan Ni & Ting Xie

The balance between stem cell self-renewal and differentiation is controlled by intrinsic factors and niche signals. In the Drosophila melanogaster ovary, some intrinsic factors promote germline stem cell (GSC) self-renewal, whereas others stimulate differentiation. However, it remains poorly understood how the balance between self-renewal and differentiation is controlled. Here we use D. melanogaster ovarian GSCs to demonstrate that the differentiation factor Bam controls the functional switch of the COP9 complex from self-renewal to differentiation via protein competition. The COP9 complex is composed of eight Csn subunits, Csn1–8, and removes Nedd8 modifications from target proteins. Genetic results indicated that the COP9 complex is required intrinsically for GSC self-renewal, whereas other Csn proteins, with the exception of Csn4, were also required for GSC progeny differentiation. Bam-mediated Csn4 sequestration from the COP9 complex via protein competition inactivated the self-renewing function of COP9 and allowed other Csn proteins to promote GSC differentiation. Therefore, this study reveals a protein-competition-based mechanism for controlling the balance between stem cell self-renewal and differentiation. Because numerous self-renewal factors are ubiquitously expressed throughout the stem cell lineage in various systems, protein competition may function as an important mechanism for controlling the self-renewal-to-differentiation switch.

Categories: Literature

Protein competition switches the function of COP9 from self-renewal to differentiation

Nature - Wed, 10/08/2014 - 00:00

Protein competition switches the function of COP9 from self-renewal to differentiation

Nature 514, 7521 (2014). doi:10.1038/nature13562

Authors: Lei Pan, Su Wang, Tinglin Lu, Changjiang Weng, Xiaoqing Song, Joseph K. Park, Jin Sun, Zhi-Hao Yang, Junjing Yu, Hong Tang, Dennis M. McKearin, Daniel A. Chamovitz, Jianquan Ni & Ting Xie

The balance between stem cell self-renewal and differentiation is controlled by intrinsic factors and niche signals. In the Drosophila melanogaster ovary, some intrinsic factors promote germline stem cell (GSC) self-renewal, whereas others stimulate differentiation. However, it remains poorly understood how the balance between self-renewal and differentiation is controlled. Here we use D. melanogaster ovarian GSCs to demonstrate that the differentiation factor Bam controls the functional switch of the COP9 complex from self-renewal to differentiation via protein competition. The COP9 complex is composed of eight Csn subunits, Csn1–8, and removes Nedd8 modifications from target proteins. Genetic results indicated that the COP9 complex is required intrinsically for GSC self-renewal, whereas other Csn proteins, with the exception of Csn4, were also required for GSC progeny differentiation. Bam-mediated Csn4 sequestration from the COP9 complex via protein competition inactivated the self-renewing function of COP9 and allowed other Csn proteins to promote GSC differentiation. Therefore, this study reveals a protein-competition-based mechanism for controlling the balance between stem cell self-renewal and differentiation. Because numerous self-renewal factors are ubiquitously expressed throughout the stem cell lineage in various systems, protein competition may function as an important mechanism for controlling the self-renewal-to-differentiation switch.

Categories: Literature

Corrigendum: A global strategy for road building

Nature - Wed, 10/08/2014 - 00:00

Corrigendum: A global strategy for road building

Nature 514, 7521 (2014). doi:10.1038/nature13876

Authors: William F. Laurance, Gopalasamy Reuben Clements, Sean Sloan, Christine S. O’Connell, Nathan D. Mueller, Miriam Goosem, Oscar Venter, David P. Edwards, Ben Phalan, Andrew Balmford, Rodney Van Der Ree & Irene Burgues Arrea

Nature513, 229–232 (2014); doi:10.1038/nature13717In this Letter, as a result of an inadvertent spreadsheet error, four values presented in Table 1 were slightly inflated. These relate to the proportions of Earth’s total land surface located within the ‘conserve’,

Categories: Literature

Corrigendum: Comprehensive molecular profiling of lung adenocarcinoma

Nature - Wed, 10/08/2014 - 00:00

Corrigendum: Comprehensive molecular profiling of lung adenocarcinoma

Nature 514, 7521 (2014). doi:10.1038/nature13879

Author:

Nature511, 543–550 (2014); doi:10.1038/nature13385In this Article, the surname of author Kristen Rodgers was incorrectly spelled Rogers. This error has been corrected in the HTML and PDF of the original paper.

Categories: Literature

Erratum: Haematopoietic stem cells and early lymphoid progenitors occupy distinct bone marrow niches

Nature - Wed, 10/08/2014 - 00:00

Erratum: Haematopoietic stem cells and early lymphoid progenitors occupy distinct bone marrow niches

Nature 514, 7521 (2014). doi:10.1038/nature13880

Authors: Lei Ding & Sean J. Morrison

Nature495, 231–235 (2013); doi:10.1038/nature11885The y axis in Fig. 3h of this Letter was mislabelled owing to a production error. The ticks on the axis should have been labelled ‘0.04’ and ‘0.08’ instead of ‘0.4’ and ‘0.8’,

Categories: Literature

Deep Ocean Heat Storage Not Behind Global Warming Pause, Study Finds

Yale Environment 360 - Tue, 10/07/2014 - 09:59

The deepest reaches of earth's oceans have not warmed significantly over the last decade, according to scientists at NASA's Jet Propulsion Laboratory in California — a finding that undermines a leading theory as to why the pace of global warming has slowed over the last 15 years. Scientists have speculated that the recent slowdown in rising surface air temperatures was a result of heat accumulating in the deep ocean. But in a paper published in the journal Nature Climate Change, the NASA researchers concluded that the vast majority of sea level rise since 2005 was attributable to just two sources: upper ocean heat expansion and glacial melting. From this they inferred that the deep ocean was not also warming. In a separate paper published in the same journal, however, scientists from the Lawrence Livermore Laboratory noted that the upper ocean was absorbing between 24 and 58 percent more heat than was previously thought. That's not enough to account for the pause in surface air warming, but the researchers suggest it is evidence that more accurate data on ocean warming is needed.

Categories: Environmental News

Out of Africa

Nature - Tue, 10/07/2014 - 00:00

Out of Africa

Nature 514, 7521 (2014). doi:10.1038/514139a

The Ebola outbreak in West Africa must be shut down now, or the disease will continue to spread.

Categories: Literature

Holy cows

Nature - Tue, 10/07/2014 - 00:00

Holy cows

Nature 514, 7521 (2014). doi:10.1038/514140a

A mass beaching of walruses in Alaska is a sign of things to come.

Categories: Literature

US plans upgrade for ageing Greenland research station

Nature - Tue, 10/07/2014 - 00:00

US plans upgrade for ageing Greenland research station

Nature 514, 7521 (2014). http://www.nature.com/doifinder/10.1038/514147a

Author: Alexandra Witze

But proposals spur concern that development will pollute the nearly pristine site.

Categories: Literature

Nobel for blue LED that revolutionized lighting

Nature - Tue, 10/07/2014 - 00:00

Nobel for blue LED that revolutionized lighting

Nature 514, 7521 (2014). http://www.nature.com/doifinder/10.1038/514152a

Author: Elizabeth Gibney

Physics prize recognizes potential of invention with power to reduce global electricity consumption.

Categories: Literature

Number of Megacities Has Nearly Tripled Since 1990, UN Report Says

Yale Environment 360 - Mon, 10/06/2014 - 11:27

The number of urban areas with more than 10 million inhabitants — sometimes called "megacities" — has

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Urban footprint of Tokyo nearly tripled in the last 24 years, jumping from 10 in 1990 to 28 in 2014, according to the latest UN report on world urbanization. The total number of people living in megacities has grown from 153 million to 453 million during that period, the report says, and such areas now account for 15 percent of global GDP. Although densely populated urban areas can be environmental blights, innovations in efficient transportation have arisen from some major cities in Asia and Lagos, Nigeria, because those cities have invested heavily in public transit infrastructure, researchers say.

Categories: Environmental News

With the Boom in Oil and Gas, Pipelines Proliferate in the U.S.

Yale Environment 360 - Mon, 10/06/2014 - 07:33

The rise of U.S. oil and gas production has spurred a dramatic expansion of the nation's pipeline infrastructure. As the lines reach into new communities and affect more property owners, concerns over the environmental impacts are growing. BY PETER MOSKOWITZ

Categories: Environmental News

Nobel prize for decoding brain’s sense of place

Nature - Mon, 10/06/2014 - 00:00

Nobel prize for decoding brain’s sense of place

Nature 514, 7521 (2014). http://www.nature.com/doifinder/10.1038/514153a

Authors: Alison Abbott & Ewen Callaway

Discoverers of brain’s navigation system get physiology Nobel.

Categories: Literature

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