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  • 1
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    A possible close supermassive black-hole binary in a quasar with optical periodicity (2015)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2015-01-07
    Description: Quasars have long been known to be variable sources at all wavelengths. Their optical variability is stochastic and can be due to a variety of physical mechanisms; it is also well-described statistically in terms of a damped random walk model. The recent availability of large collections of astronomical time series of flux measurements (light curves) offers new data sets for a systematic exploration of quasar variability. Here we report the detection of a strong, smooth periodic signal in the optical variability of the quasar PG 1302-102 with a mean observed period of 1,884 +/- 88 days. It was identified in a search for periodic variability in a data set of light curves for 247,000 known, spectroscopically confirmed quasars with a temporal baseline of about 9 years. Although the interpretation of this phenomenon is still uncertain, the most plausible mechanisms involve a binary system of two supermassive black holes with a subparsec separation. Such systems are an expected consequence of galaxy mergers and can provide important constraints on models of galaxy formation and evolution.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Graham, Matthew J -- Djorgovski, S G -- Stern, Daniel -- Glikman, Eilat -- Drake, Andrew J -- Mahabal, Ashish A -- Donalek, Ciro -- Larson, Steve -- Christensen, Eric -- England -- Nature. 2015 Feb 5;518(7537):74-6. doi: 10.1038/nature14143. Epub 2015 Jan 7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA. ; Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, USA. ; Department of Physics, Middlebury College, Middlebury, Vermont 05753, USA. ; Lunar and Planetary Laboratory, Department of Planetary Sciences, University of Arizona, 1629 East University Boulevard, Tucson, Arizona 85721, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25561176" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    Science education. Increasing persistence of college students in STEM (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2013-09-28
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Graham, Mark J -- Frederick, Jennifer -- Byars-Winston, Angela -- Hunter, Anne-Barrie -- Handelsman, Jo -- 1R13GM090574-01/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- New York, N.Y. -- Science. 2013 Sep 27;341(6153):1455-6. doi: 10.1126/science.1240487.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for Scientific Teaching, Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24072909" target="_blank"〉PubMed〈/a〉
    Keywords: Engineering/*education ; Humans ; Mathematics/*education ; Research ; *Retention (Psychology) ; Science/*education ; Students/*psychology ; Technology/*education ; United States
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Social science. Scientific diversity interventions (2014)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2014-02-08
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Moss-Racusin, Corinne A -- van der Toorn, Jojanneke -- Dovidio, John F -- Brescoll, Victoria L -- Graham, Mark J -- Handelsman, Jo -- 1R13GM090574-01/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- New York, N.Y. -- Science. 2014 Feb 7;343(6171):615-6. doi: 10.1126/science.1245936.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Skidmore College, Saratoga Springs, NY 12866, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24503840" target="_blank"〉PubMed〈/a〉
    Keywords: *Cultural Diversity ; Female ; Humans ; Male ; *Racism ; Research Design ; Science/ethics/*manpower ; *Sexism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Identification of secreted bacterial proteins [Microbiology] (2014)
    National Academy of Sciences
    Details
    Publication Date: 2014-01-08
    Description: Pathogenic microbes have evolved complex secretion systems to deliver virulence factors into host cells. Identification of these factors is critical for understanding the infection process. We report a powerful and versatile approach to the selective labeling and identification of secreted pathogen proteins. Selective labeling of microbial proteins is accomplished via...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 5
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    Cell-specific proteomic analysis in C. elegans [Biochemistry] (2015)
    National Academy of Sciences
    Details
    Publication Date: 2015-03-04
    Description: Proteomic analysis of rare cells in heterogeneous environments presents difficult challenges. Systematic methods are needed to enrich, identify, and quantify proteins expressed in specific cells in complex biological systems including multicellular plants and animals. Here, we have engineered a Caenorhabditis elegans phenylalanyl-tRNA synthetase capable of tagging proteins with the reactive...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 6
    Electronic Resource
    Electronic Resource
    Structure of S on a passivated GaP(100) surface (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7567-7569 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray photoelectron spectroscopy (XPS), chemical state-specific photoelectron diffraction (XPD), and photoelectric polarization-dependent sulfur K-edge x-ray absorption near-edge structure (XANES) have been used to determine the structure of S on GaP(100) surfaces passivated in a (NH4)2S solution. XPS shows that S forms chemical bonds only with Ga. XPD and XANES measurements show that the Ga—S bond is a well-ordered bridge bond in the [011] azimuth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357032
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  • 7
    Electronic Resource
    Electronic Resource
    Electrodeposition and characterization of magnetic Ni-Fe thin films on InP(100) surfaces (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5795-5799 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrodeposited magnetic Ni-Fe films are used in storage devices and are applicable as magnetic sensors. In this work, we demonstrate the electrochemical conditions for deposition of permalloy Ni-Fe nanocrystalline films onto InP(100) surfaces. The prepared Ni-Fe films were analyzed by scanning electron microscopy to determine surface morphology and by Auger electron spectroscopy for compositional depth profiling. Permalloy films with bulk composition of 81% Ni and 18% Fe were obtained by electrodeposition at −1.2 V (versus standard calomel electrode) in a bath of 0.5 M NiSO4, 0.02 M FeSO4, 0.4 M H3BO3, pH=3. Transmission electron microscopy measurements show that these films consist of fcc Ni-Fe nanocrystallites embedded in an amorphous matrix. The films also show good magnetic hysteresis loops, with low coercivity. The magnetic properties of these films are improved by an extended anneal at 100 °C. Interdiffusion occurred between Ni-Fe and the InP substrate after the sample was heated to 300 °C, and consequently a loss of ferromagnetic behavior was observed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359643
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  • 8
    Electronic Resource
    Electronic Resource
    Thin anodic oxides formed on GaAs in aqueous solutions (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7303-7311 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin (0–250 A(ring)) anodic oxides were formed on p-GaAs (100) in aqueous solutions (borate buffer, pH 8.4 and 0.3 M NH4H2PO4, pH 4.4). The thickness, composition, and electrochemical behavior were characterized by x-ray photoelectron spectroscopy, secondary ion mass spectrometry, ellipsometry, and electrochemical impedance spectroscopy. In borate buffer, oxide growth results in a two-layer structure with an outer As2O3-rich layer and ion transfer is mainly diffusion controlled. From the potential dependence of the film thickness a growth rate of 25 A(ring)/V was determined. Due to the formation of a Ga-phosphate precursor layer in NH4H2PO4, films grow under field control which results in a time dependence of oxide thickness and composition. Under pseudosteady state conditions a growth rate of 28 A(ring)/V was obtained. Films formed in NH4H2PO4 have, except for the outer phosphate layer, a fairly uniform composition in depth with a significant enrichment of Ga2O3, and show a 40 times higher specific charge transfer resistance than films formed in borate buffer. The superior quality of the oxide formed in NH4H2PO4 is also reflected in its high stability against H2O etch. In addition, substrate pretreatment and the effects of oxide washing on composition were investigated and the importance of an appropriate preparation of samples for ex situ analysis is demonstrated. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361524
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal oxide on CdSe (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 1632-1639 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray photoelectron spectroscopy (XPS) has been used to characterize the thin thermal oxide film grown on single crystal CdSe(0001) and polycrystalline CdSe by exposure to O2 (dry air) at 350 °C. SeOx species, where x=2,3, are clearly identified by a 5 eV shift of the Se 3d3/2,5/2 peaks to higher binding energy. A very weak shift to lower binding energy is observed for the Cd peaks. The positions of the Cd and O peaks do not match those found for the known cadmium oxides, CdO and CdO2. Instead, it is proposed that the Cd bound oxygen atoms occupy substitutional Se sites. The presence of Cd bound oxygen can also be inferred from the intensities of the SeOx, Cd, and O peaks. Raman spectroscopy confirms the existence of O in Se substitutional sites. Angle-resolved XPS is used to determine the thickness of the oxide and the relative amount of SeOx and Cd bound oxygen. The XPS data are consistent with an 8–9 Å thick oxide where ∼60% of the oxygen is bound to Se and ∼40 is bound to Cd. The data show that the oxide structure contains two layers; a passivation layer made of the SeOx species and, underneath, a layer containing oxygen in Se substitutional sites. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366263
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  • 10
    Electronic Resource
    Electronic Resource
    Structure of S on passivated GaAs (100) (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2932-2934 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray photoelectron spectroscopy (XPS) and E-polarization-dependent S K-edge x-ray absorption near-edge structure (XANES) are used to characterize the chemical structure and site location of S on the (NH4)2S-treated GaAs (100) surface. XPS studies show that S forms chemical bonds with both Ga and As on surfaces treated only with (NH4)2S. After receiving a sufficient water rinse, only Ga—S bonds remain on the surface. Photon E polarization-dependent XANES studies show that S is bridge bonded to Ga in the [011] azimuth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109201
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